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Sample records for schottky contact formation

  1. Influence of the Interaction Between Graphite and Polar Surfaces of ZnO on the Formation of Schottky Contact

    Science.gov (United States)

    Yatskiv, R.; Grym, J.

    2018-03-01

    We show that the interaction between graphite and polar surfaces of ZnO affects electrical properties of graphite/ZnO Schottky junctions. A strong interaction of the Zn-face with the graphite contact causes interface imperfections and results in the formation of laterally inhomogeneous Schottky contacts. On the contrary, high quality Schottky junctions form on the O-face, where the interaction is significantly weaker. Charge transport through the O-face ZnO/graphite junctions is well described by the thermionic emission model in both forward and reverse directions. We further demonstrate that the parameters of the graphite/ZnO Schottky diodes can be significantly improved when a thin layer of ZnO2 forms at the interface between graphite and ZnO after hydrogen peroxide surface treatment.

  2. Schottky contacts to In2O3

    Directory of Open Access Journals (Sweden)

    H. von Wenckstern

    2014-04-01

    Full Text Available n-type binary compound semiconductors such as InN, InAs, or In2O3 are especial because the branch-point energy or charge neutrality level lies within the conduction band. Their tendency to form a surface electron accumulation layer prevents the formation of rectifying Schottky contacts. Utilizing a reactive sputtering process in an oxygen-containing atmosphere, we demonstrate Schottky barrier diodes on indium oxide thin films with rectifying properties being sufficient for space charge layer spectroscopy. Conventional non-reactive sputtering resulted in ohmic contacts. We compare the rectification of Pt, Pd, and Au Schottky contacts on In2O3 and discuss temperature-dependent current-voltage characteristics of Pt/In2O3 in detail. The results substantiate the picture of oxygen vacancies being the source of electrons accumulating at the surface, however, the position of the charge neutrality level and/or the prediction of Schottky barrier heights from it are questioned.

  3. Formation and Schottky barrier height of Au contacts to CuInSe2

    International Nuclear Information System (INIS)

    Nelson, A.J.; Gebhard, S.; Kazmerski, L.L.; Colavita, E.; Engelhardt, M.; Hoechst, H.

    1991-01-01

    Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Au/CuInSe 2 interface. Au overlayers were deposited in steps on single-crystal p and n-type CuInSe 2 at ambient temperature. Reflection high-energy electron diffraction analysis before and during growth of the Au overlayers indicated that the Au overlayer was amorphous. Photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the In 4d and Se 3d core lines. The results were used to correlate the interface chemistry with the electronic structure at these interfaces and to directly determine the Au/CuInSe 2 Schottky barrier height

  4. Schottky-contact plasmonic rectenna for biosensing

    Science.gov (United States)

    Alavirad, Mohammad; Siadat Mousavi, Saba; Roy, Langis; Berini, Pierre

    2013-10-01

    We propose a plasmonic gold nanodipole array on silicon, forming a Schottky contact thereon, and covered by water. The behavior of this array under normal excitation has been extensively investigated. Trends have been found and confirmed by identification of the mode propagating in nanodipoles and its properties. This device can be used to detect infrared radiation below the bandgap energy of the substrate via internal photoelectric effect (IPE). Also we estimate its responsivity and detection limit. Finally, we assess the potential of the structure for bulk and surface (bio) chemical sensing. Based on modal results an analytical model has been proposed to estimate the sensitivity of the device. Results show a good agreement between numerical and analytical interpretations.

  5. Silicide Schottky Contacts to Silicon: Screened Pinning at Defect Levels

    Energy Technology Data Exchange (ETDEWEB)

    Drummond, T.J.

    1999-03-11

    Silicide Schottky contacts can be as large as 0.955 eV (E{sub v} + 0.165 eV) on n-type silicon and as large as 1.05 eV (E{sub c} {minus} 0.07 eV) on p-type silicon. Current models of Schottky barrier formation do not provide a satisfactory explanation of occurrence of this wide variation. A model for understanding Schottky contacts via screened pinning at defect levels is presented. In the present paper it is shown that most transition metal silicides are pinned approximately 0.48 eV above the valence band by interstitial Si clusters. Rare earth disilicides pin close to the divacancy acceptor level 0.41 eV below the conduction band edge while high work function silicides of Ir and Pt pin close to the divacancy donor level 0.21 eV above the valence band edge. Selection of a particular defect pinning level depends strongly on the relative positions of the silicide work function and the defect energy level on an absolute energy scale.

  6. Organic modification of metal / semiconductor Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Mendez Pinzon, H.A.

    2006-07-10

    In the present work a Metal / organic / inorganic semiconductor hybrid heterostructure (Ag / DiMe-PTCDI / GaAs) was built under UHV conditions and characterised in situ. The aim was to investigate the influence of the organic layer in the surface properties of GaAs(100) and in the electrical response of organic-modified Ag / GaAs Schottky diodes. The device was tested by combining surface-sensitive techniques (Photoemission spectroscopy and NEXAFS) with electrical measurements (current-voltage, capacitance-voltage, impedance and charge transient spectroscopies). Core level examination by PES confirms removal of native oxide layers on sulphur passivated (S-GaAs) and hydrogen plasma treated GaAs(100) (H+GaAs) surfaces. Additional deposition of ultrathin layers of DiMe-PTCDI may lead to a reduction of the surface defects density and thereby to an improvement of the electronic properties of GaAs. The energy level alignment through the heterostructure was deduced by combining UPS and I-V measurements. This allows fitting of the I-V characteristics with electron as majority carriers injected over a barrier by thermionic emission as a primary event. For thin organic layers (below 8 nm thickness) several techniques (UPS, I-V, C-V, QTS and AFM) show non homogeneous layer growth, leading to formation of voids. The coverage of the H+GaAs substrate as a function of the nominal thickness of DiMe-PTCDI was assessed via C-V measurements assuming a voltage independent capacitance of the organic layer. The frequency response of the device was evaluated through C-V and impedance measurements in the range 1 kHz-1 MHz. The almost independent behaviour of the capacitance in the measured frequency range confirmed the assumption of a near geometrical capacitor, which was used for modelling the impedance with an equivalent circuit of seven components. From there it was found a predominance of the space charge region impedance, so that A.C. conduction can only takes place through the

  7. Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts

    KAUST Repository

    Hu, Youfan

    2010-05-31

    A Schottky barrier can be formed at the interface between a metal electrode and a semiconductor. The current passing through the metal-semiconductor contact is mainly controlled by the barrier height and barrier width. In conventional nanodevices, Schottky contacts are usually avoided in order to enhance the contribution made by the nanowires or nanotubes to the detected signal. We present a key idea of using the Schottky contact to achieve supersensitive and fast response nanowire-based nanosensors. We have illustrated this idea on several platforms: UV sensors, biosensors, and gas sensors. The gigantic enhancement in sensitivity of up to 5 orders of magnitude shows that an effective usage of the Schottky contact can be very beneficial to the sensitivity of nanosensors. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Schottky contact analysis of photovoltaic chalcopyrite thin film absorbers

    International Nuclear Information System (INIS)

    Schlenker, E.; Mertens, V.; Parisi, J.; Reineke-Koch, R.; Koentges, M.

    2007-01-01

    Current-voltage and capacitance-voltage measurements serve to analyze thermally evaporated Al Schottky contacts on Cu(In, Ga)Se 2 based photovoltaic thin film devices, either taken as grown or etched in a bromine-methanol solution. The characteristics of the Schottky contacts on the as-grown films give evidence for some dielectric layer developing between the metal and the semiconductor. Etching the semiconductor surface prior to evaporation of the Al front contact yields a pure metal-semiconductor behavior, including effects that can be attributed to an additional diode at the Mo contact. Simulations confirm the experimental results

  9. Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor

    KAUST Repository

    Wei, Te-Yu

    2009-12-09

    A new single nanowire based nanosensor is demonstrated for illustrating its ultrahigh sensitivity for gas sensing. The device is composed of a single ZnO nanowire mounted on Pt electrodes with one end in Ohmic contact and the other end in Schottky contact. The Schottky contact functions as a "gate" that controls the current flowing through the entire system. By tuning the Schottky barrier height through the responsive variation of the surface chemisorbed gases and the amplification role played by the nanowire to Schottky barrier effect, an ultrahigh sensitivity of 32 000% was achieved using the Schottky contacted device operated in reverse bias mode at 275 °C for detection of 400 ppm CO, which is 4 orders of magnitude higher than that obtained using an Ohmic contact device under the same conditions. In addition, the response time and reset time have been shortened by a factor of 7. The methodology and principle illustrated in the paper present a new sensing mechanism that can be readily and extensively applied to other gas sensing systems. © 2009 American Chemical Society.

  10. Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor

    KAUST Repository

    Wei, Te-Yu; Yeh, Ping-Hung; Lu, Shih-Yuan; Wang, Zhong Lin

    2009-01-01

    A new single nanowire based nanosensor is demonstrated for illustrating its ultrahigh sensitivity for gas sensing. The device is composed of a single ZnO nanowire mounted on Pt electrodes with one end in Ohmic contact and the other end in Schottky contact. The Schottky contact functions as a "gate" that controls the current flowing through the entire system. By tuning the Schottky barrier height through the responsive variation of the surface chemisorbed gases and the amplification role played by the nanowire to Schottky barrier effect, an ultrahigh sensitivity of 32 000% was achieved using the Schottky contacted device operated in reverse bias mode at 275 °C for detection of 400 ppm CO, which is 4 orders of magnitude higher than that obtained using an Ohmic contact device under the same conditions. In addition, the response time and reset time have been shortened by a factor of 7. The methodology and principle illustrated in the paper present a new sensing mechanism that can be readily and extensively applied to other gas sensing systems. © 2009 American Chemical Society.

  11. Process for preparing schottky diode contacts with predetermined barrier heights

    Science.gov (United States)

    Chang, Y. Austin; Jan, Chia-Hong; Chen, Chia-Ping

    1996-01-01

    A process is provided for producing a Schottky diode having a preselected barrier height .phi..sub.Bn. The substrate is preferably n-GaAs, the metallic contact is derived from a starting alloy of the Formula [.SIGMA.M.sub..delta. ](Al.sub.x Ga.sub.1-x) wherein: .SIGMA.M is a moiety which consists of at least one M, and when more than one M is present, each M is different, M is a Group VIII metal selected from the group consisting of nickel, cobalt, ruthenium, rhodium, indium and platinum, .delta. is a stoichiometric coefficient whose total value in any given .SIGMA.M moiety is 1, and x is a positive number between 0 and 1 (that is, x ranges from greater than 0 to less than 1). Also, the starting alloy is capable of forming with the substrate a two phase equilibrium reciprocal system of the binary alloy mixture [.SIGMA.M.sub..delta. ]Ga-[.SIGMA.M.sub..delta. ]Al-AlAs-GaAs. When members of an alloy subclass within this Formula are each preliminarily correlated with the barrier height .phi..sub.Bn of a contact producable therewith, then Schottky diodes of predetermined barrier heights are producable by sputtering and annealing. Further provided are the product Schottky diodes that are produced according to this process.

  12. The nature of electrical interaction of Schottky contacts

    International Nuclear Information System (INIS)

    Torkhov, N. A.

    2011-01-01

    Electrical interaction between metal-semiconductor contacts combined in a diode matrix with a Schottky barrier manifests itself in an appreciable variation in their surface potentials and static current-volt-characteristics. The necessary condition for appearance of electrical interaction between such contacts consists in the presence of a peripheral electric field (a halo) around them; this field propagates to a fairly large distances ( i,j ), concentration of doping impurities in the semiconductor N D , and physical nature of a metal-semiconductor system with a Schottky barrier (with the barrier height φ b ). It is established that bringing the contacts closer leads to a relative decrease in the threshold value of the “dead” zone in the forward current-voltage characteristics, an increase in the effective height of the barrier, and an insignificant increase in the nonideality factor. An increase in the total area of contacts (a total electric charge in the space charge region) in the matrix brings about an increase in the threshold value of the “dead” zone, a relative decrease in the effective barrier height, and an insignificant increase in the ideality factor.

  13. All-back-Schottky-contact thin-film photovoltaics

    Science.gov (United States)

    Nardone, Marco

    2016-02-01

    The concept of All-Back-Schottky-Contact (ABSC) thin-film photovoltaic (TFPV) devices is introduced and evaluated using 2D numerical simulation. Reach-through Schottky junctions due to two metals of different work functions in an alternating, side-by-side pattern along the non-illuminated side generate the requisite built-in field. It is shown that our simulation method quantitatively describes existing data for a recently demonstrated heterojunction thin-film cell with interdigitated back contacts (IBCs) of one metal type. That model is extended to investigate the performance of ABSC devices with bimetallic IBCs within a pertinent parameter space. Our calculations indicate that 20% efficiency is achievable with micron-scale features and sufficient surface passivation. Bimetallic, micron-scale IBCs are readily fabricated using photo-lithographic techniques and the ABSC design allows for optically transparent surface passivation layers that need not be electrically conductive. The key advantages of the ABSC-TFPV architecture are that window layers, buffer layers, heterojunctions, and module scribing are not required because both contacts are located on the back of the device.

  14. Electrical characterisation of ruthenium Schottky contacts on n-Ge (1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Chawanda, Albert, E-mail: albert.chawanda@up.ac.za [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa); Department of Physics, Midlands State University, Bag 9055, Gweru (Zimbabwe); Nyamhere, Cloud [Department of Physics, Nelson Mandela Metropolitan University, Box 7700, Port Elizabeth 6031 (South Africa); Auret, Francois D.; Nel, Jacqueline M.; Mtangi, Wilbert; Diale, Mmatsae [Department of Physics, University of Pretoria, Pretoria 0002 (South Africa)

    2012-05-15

    Ruthenium (Ru) Schottky contacts were fabricated on n-Ge (1 0 0) by electron beam deposition. Current-voltage (I-V), deep level transient spectroscopy (DLTS), and Laplace-DLTS techniques were used to characterise the as-deposited and annealed Ru/n-Ge (1 0 0) Schottky contacts. The variation of the electrical properties of the Ru samples annealed between 25 Degree-Sign C and 575 Degree-Sign C indicates the formation of two phases of ruthenium germanide. After Ru Schottky contacts fabrication, an electron trap at 0.38 eV below the conduction band with capture cross section of 1.0 Multiplication-Sign 10{sup -14} cm{sup -2} is the only detectable electron trap. The hole traps at 0.09, 0.15, 0.27 and 0.30 eV above the valence band with capture cross sections of 7.8 Multiplication-Sign 10{sup -13} cm{sup -2}, 7.1 Multiplication-Sign 10{sup -13} cm{sup -2}, 2.4 Multiplication-Sign 10{sup -13} cm{sup -2} and 6.2 Multiplication-Sign 10{sup -13} cm{sup -2}, respectively, were observed in the as-deposited Ru Schottky contacts. The hole trap H(0.30) is the prominent single acceptor level of the E-centre, and H(0.09) is the third charge state of the E-centre. H(0.27) shows some reverse annealing and reaches a maximum concentration at 225 Degree-Sign C and anneals out after 350 Degree-Sign C. This trap is strongly believed to be V-Sb{sub 2} complex formed from the annealing of V-Sb defect centre.

  15. Alternative current source based Schottky contact with additional electric field

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2017-07-01

    Additional electric field (AEF) in the Schottky contacts (SC) that covered the peripheral contact region wide and the complete contact region narrow (as TMBS diode) SC. Under the influence of AEF is a redistribution of free electrons produced at certain temperatures of the semiconductor, and is formed the space charge region (SCR). As a result of the superposition of the electric fields SCR and AEF occurs the resulting electric field (REF). The REF is distributed along a straight line perpendicular to the contact surface, so that its intensity (and potential) has a minimum value on the metal surface and the maximum value at a great distance from the metal surface deep into the SCR. Under the influence of AEF as a sided force the metal becomes negative pole and semiconductor - positive pole, therefore, SC with AEF becomes an alternative current source (ACS). The Ni-nSi SC with different diameters (20-1000 μm) under the influence of the AEF as sided force have become ACS with electromotive force in the order of 0.1-1.0 mV, which are generated the electric current in the range of 10-9-10-7 A, flowing through the external resistance 1000 Ohm.

  16. Explanation of the barrier heights of graphene Schottky contacts by the MIGS-and-electronegativity concept

    Science.gov (United States)

    Mönch, Winfried

    2016-09-01

    Graphene-semiconductor contacts exhibit rectifying properties and, in this respect, they behave in exactly the same way as a "conventional" metal-semiconductor or Schottky contacts. It will be demonstrated that, as often assumed, the Schottky-Mott rule does not describe the reported barrier heights of graphene-semiconductor contacts. With "conventional" Schottky contacts, the same conclusion was reached already in 1940. The physical reason is that the Schottky-Mott rule considers no interaction between the metal and the semiconductor. The barrier heights of "conventional" Schottky contacts were explained by the continuum of metal-induced gap states (MIGSs), where the differences of the metal and semiconductor electronegativities describe the size and the sign of the intrinsic electric-dipoles at the interfaces. It is demonstrated that the MIGS-and-electronegativity concept unambiguously also explains the experimentally observed barrier heights of graphene Schottky contacts. This conclusion includes also the barrier heights reported for MoS2 Schottky contacts with "conventional" metals as well as with graphene.

  17. Schottky-contact plasmonic dipole rectenna concept for biosensing.

    Science.gov (United States)

    Alavirad, Mohammad; Mousavi, Saba Siadat; Roy, Langis; Berini, Pierre

    2013-02-25

    Nanoantennas are key optical components for several applications including photodetection and biosensing. Here we present an array of metal nano-dipoles supporting surface plasmon polaritons (SPPs) integrated into a silicon-based Schottky-contact photodetector. Incident photons coupled to the array excite SPPs on the Au nanowires of the antennas which decay by creating "hot" carriers in the metal. The hot carriers may then be injected over the potential barrier at the Au-Si interface resulting in a photocurrent. High responsivities of 100 mA/W and practical minimum detectable powers of -12 dBm should be achievable in the infra-red (1310 nm). The device was then investigated for use as a biosensor by computing its bulk and surface sensitivities. Sensitivities of ∼ 250 nm/RIU (bulk) and ∼ 8 nm/nm (surface) in water are predicted. We identify the mode propagating and resonating along the nanowires of the antennas, we apply a transmission line model to describe the performance of the antennas, and we extract two useful formulas to predict their bulk and surface sensitivities. We prove that the sensitivities of dipoles are much greater than those of similar monopoles and we show that this difference comes from the gap in dipole antennas where electric fields are strongly enhanced.

  18. Influence of Asymmetric Contact Form on Contact Resistance and Schottky Barrier, and Corresponding Applications of Diode.

    Science.gov (United States)

    Zhao, Yudan; Xiao, Xiaoyang; Huo, Yujia; Wang, Yingcheng; Zhang, Tianfu; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan; Li, Qunqing

    2017-06-07

    We have fabricated carbon nanotube and MoS 2 field-effect transistors with asymmetric contact forms of source-drain electrodes, from which we found the current directionality of the devices and different contact resistances under the two current directions. By designing various structures, we can conclude that the asymmetric electrical performance was caused by the difference in the effective Schottky barrier height (Φ SB ) caused by the different contact forms. A detailed temperature-dependent study was used to extract and compare the Φ SB for both contact forms of CNT and MoS 2 devices; we found that the Φ SB for the metal-on-semiconductor form was much lower than that of the semiconductor-on-metal form and is suitable for all p-type, n-type, or ambipolar semiconductors. This conclusion is meaningful with respect to the design and application of nanomaterial electronic devices. Additionally, using the difference in barrier height caused by the contact forms, we have also proposed and fabricated Schottky barrier diodes with a current ratio up to 10 4 ; rectifying circuits consisting of these diodes were able to work in a wide frequency range. This design avoided the use of complex chemical doping or heterojunction methods to achieve fundamental diodes that are relatively simple and use only a single material; these may be suitable for future application in nanoelectronic radio frequency or integrated circuits.

  19. A strained silicon cold electron bolometer using Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Brien, T. L. R., E-mail: tom.brien@astro.cf.ac.uk; Ade, P. A. R.; Barry, P. S.; Dunscombe, C.; Morozov, D. V.; Sudiwala, R. V. [School of Physics and Astronomy, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Leadley, D. R.; Myronov, M.; Parker, E. H. C.; Prest, M. J.; Whall, T. E. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Prunnila, M. [VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo (Finland); Mauskopf, P. D. [School of Physics and Astronomy, Cardiff University, Queen' s Buildings, The Parade, Cardiff CF24 3AA (United Kingdom); Department of Physics and School of Earth and Space Exploration, Arizona State University, 650 E. Tyler Mall, Tempe, Arizona 85287 (United States)

    2014-07-28

    We describe optical characterisation of a strained silicon cold electron bolometer (CEB), operating on a 350 mK stage, designed for absorption of millimetre-wave radiation. The silicon cold electron bolometer utilises Schottky contacts between a superconductor and an n{sup ++} doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to 160 GHz and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of 50% for radiation coupled into the device by the planar antenna and an overall noise equivalent power, referred to absorbed optical power, of 1.1×10{sup −16} W Hz{sup −1/2} when the detector is observing a 300 K source through a 4 K throughput limiting aperture. Even though this optical system is not optimized, we measure a system noise equivalent temperature difference of 6 mK Hz{sup −1/2}. We measure the noise of the device using a cross-correlation of time stream data, measured simultaneously with two junction field-effect transistor amplifiers, with a base correlated noise level of 300 pV Hz{sup −1/2} and find that the total noise is consistent with a combination of photon noise, current shot noise, and electron-phonon thermal noise.

  20. Tuning the Schottky contacts in the phosphorene and graphene heterostructure by applying strain.

    Science.gov (United States)

    Liu, Biao; Wu, Li-Juan; Zhao, Yu-Qing; Wang, Lin-Zhi; Caii, Meng-Qiu

    2016-07-20

    The structures and electronic properties of the phosphorene and graphene heterostructure are investigated by density functional calculations using the hybrid Heyd-Scuseria-Ernzerhof (HSE) functional. The results show that the intrinsic properties of phosphorene and graphene are preserved due to the weak van der Waals contact. But the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure can be tuned from p-type to n-type by the in-plane compressive strains from -2% to -4%. After analyzing the total band structure and density of states of P atom orbitals, we find that the Schottky barrier height (SBH) is determined by the P-pz orbitals. What is more, the variation of the work function of the phosphorene monolayer and the graphene electrode and the Fermi level shift are the nature of the transition of Schottky barrier from n-type Schottky contact to p-type Schottky contact in the phosphorene and graphene heterostructure under different in-plane strains. We speculate that these are general results of tuning of the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure by controlling the in-plane compressive strains to obtain a promising method to design and fabricate a phosphorene-graphene based field effect transistor.

  1. Schottky contacts to polar and nonpolar n-type GaN

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hogyoung [Hanbat National University, Daejeon (Korea, Republic of); Phark, Soohyon [Max-Planck-Institut fur Mikrostrukturphysik, Halle (Germany); Song, Keunman [Korea Advanced Nano Fab Center, Suwon (Korea, Republic of); Kim, Dongwook [Ewha Woman' s University, Seoul (Korea, Republic of)

    2012-01-15

    Using the current-voltage measurements, we observed the barrier heights of c-plane GaN in Pt and Au Schottky contacts to be higher than those of a-plane GaN. However, the barrier height of c-plane GaN was lower than that of a-plane GaN in the Ti Schottky contacts. The N/Ga ratio calculated by integrating the X-ray photoelectron spectroscopy (XPS) spectra of Ga 3d and N 1s core levels showed that c-plane GaN induced more Ga vacancies near the interface than a-plane GaN in the Ti Schottky contacts, reducing the effective barrier height through an enhancement of the tunneling probability.

  2. Annealing effects on structural and electrical properties of Ru/Au on n-GaN Schottky contacts

    International Nuclear Information System (INIS)

    Reddy, V. Rajagopal; Rao, P. Koteswara; Ramesh, C.K.

    2007-01-01

    Thermal annealing effects on electrical and structural properties of Ru/Au Schottky contact to n-type GaN (n d = 4.07 x 10 17 cm -3 ) have been investigated using current-voltage (I-V), capacitance-voltage (C-V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD). The Schottky barrier height of the as-deposited sample was found to be 0.75 eV (I-V) and 0.93 eV (C-V), respectively. It is noted that the barrier height increased when the contact was annealed at 300 deg. C and slightly decreased upon annealing at temperatures of 400 deg. C and 500 deg. C. The extracted Schottky barrier heights are 0.99 eV (I-V), 1.34 eV (C-V) for 300 deg. C, 0.88 eV (I-V), 1.20 eV (C-V) for 400 deg. C and 0.72 eV (I-V), 1.08 eV (C-V) for 500 deg. C annealed contacts, respectively. Further it is observed that annealing results in the improvement of electrical properties of Ru/Au Schottky contacts. Based on Auger electron spectroscopy and X-ray diffraction studies, the formation of gallide phases at the Ru/Au/n-GaN interface could be the reason for the improvement of electrical characteristics upon annealing at elevated temperatures

  3. Electrical characterization of Au/ZnO/Si Schottky contact

    International Nuclear Information System (INIS)

    Asghar, M; Mahmood, K; Faisal, M; Hasan, M A

    2013-01-01

    In this study, temperature dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements have been performed on Au/ZnO/Si Schottky barrier diode in the range 150 – 400K. The room temperature values for ideality factor and barrier height found to be 2.68 and 0.68 eV respectively. From the temperature dependence of I–V, the ideality factor was observed to decrease with increasing temperature and barrier height increased with increasing temperature. The observed barrier height trend was disagreeing with the negative temperature coefficient for semiconductor. A deep defect with activation energy 0.57 eV below the conduction band was observed using the saturation current plot and deep level transient spectroscopy.

  4. Carrier velocity effect on carbon nanotube Schottky contact

    Energy Technology Data Exchange (ETDEWEB)

    Fathi, Amir, E-mail: fathi.amir@hotmail.com [Urmia University, Department of Electrical Engineering, Microelectronic Research Laboratory (Iran, Islamic Republic of); Ahmadi, M. T., E-mail: mt.ahmadi@urmia.ac.ir; Ismail, Razali, E-mail: Razali@fke.utm.my [University Technology Malaysia, Department of Electronic Engineering (Malaysia)

    2016-08-15

    One of the most important drawbacks which caused the silicon based technologies to their technical limitations is the instability of their products at nano-level. On the other side, carbon based materials such as carbon nanotube (CNT) as alternative materials have been involved in scientific efforts. Some of the important advantages of CNTs over silicon components are high mechanical strength, high sensing capability and large surface-to-volume ratio. In this article, the model of CNT Schottky transistor current which is under exterior applied voltage is employed. This model shows that its current has a weak dependence on thermal velocity corresponding to the small applied voltage. The conditions are quite different for high bias voltages which are independent of temperature. Our results indicate that the current is increased by Fermi velocity, but the I–V curves will not have considerable changes with the variations in number of carriers. It means that the current doesn’t increase sharply by voltage variations over different number of carriers.

  5. Hydrogen peroxide treatment on ZnO substrates to investigate the characteristics of Pt and Pt oxide Schottky contacts

    International Nuclear Information System (INIS)

    Tsai, Chia-Hung; Hung, Chen-I; Yang, Cheng-Fu; Houng, Mau-Phon

    2010-01-01

    We utilize hydrogen peroxide (H 2 O 2 ) treatment on (0 0 0 1) ZnO substrates to investigate the characteristics of Pt and Pt oxide Schottky contacts (SCs). X-ray rocking curves show the mosaicity structure becomes larger after H 2 O 2 treatment. Photoluminescence (PL) spectra show the yellow-orange emission peaking at ∼576-580 nm with respect to deep level of oxygen interstitials introduced by H 2 O 2 treatment. The threshold formation of ZnO 2 resistive layer on H 2 O 2 -treated ZnO for 45 min is observed from grazing-incidence X-ray diffraction. The better electrical characteristic is performed by Pt oxide SC with the larger barrier height (1.09 eV) and the lower leakage current (9.52 x 10 -11 A/cm 2 at -2 V) than Pt SC on the H 2 O 2 -treated ZnO for 60 min. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometer (SIMS) examinations indicate the promoted interface oxide bonding and Zn outdiffusion for Pt oxide contact, different from Pt contact. Based on current-voltage, capacitance-voltage, X-ray diffraction, PL spectra, XPS, and SIMS results, the possible mechanism for effective rectifying characteristic and enhanced Schottky fbehavior is given.

  6. Canonical Schottky barrier heights of transition metal dichalcogenide monolayers in contact with a metal

    Science.gov (United States)

    Szcześniak, Dominik; Hoehn, Ross D.; Kais, Sabre

    2018-05-01

    The transition metal dichalcogenide (M X2 , where M =Mo , W and X =S , Se, Te) monolayers are of high interest for semiconducting applications at the nanoscale level; this interest is due to both their direct band gaps and high charge mobilities. In this regard, an in-depth understating of the related Schottky barrier heights, associated with the incorporation of M X2 sheets into novel low-dimensional metal-semiconductor junctions, is of crucial importance. Herein, we generate and provide analysis of the Schottky barrier heights behavior to account for the metal-induced gap states concept as its explanation. In particular, the present investigations concentrate on the estimation of the charge neutrality levels directly by employing the primary theoretical model, i.e., the cell-averaged Green's function formalism combined with the complex band structure technique. The results presented herein place charge neutrality levels in the vicinity of the midgap; this is in agreement with previous reports and analogous to the behavior of three-dimensional semiconductors. The calculated canonical Schottky barrier heights are also found to be in agreement with other computational and experimental values in cases where the difference between electronegativities of the semiconductor and metal contact is small. Moreover, the influence of the spin-orbit effects is herein considered and supports that Schottky barrier heights have metal-induced gap state-derived character, regardless whether spin-orbit coupling interactions are considered. The results presented within this report constitute a direct and vital verification of the importance of metal-induced gap states in explaining the behavior of observed Schottky barrier heights at M X2 -metal junctions.

  7. Comparison of nickel, cobalt, palladium, and tungsten Schottky contacts on n-4H-silicon carbide

    Science.gov (United States)

    Gora, V. E.; Chawanda, A.; Nyamhere, C.; Auret, F. D.; Mazunga, F.; Jaure, T.; Chibaya, B.; Omotoso, E.; Danga, H. T.; Tunhuma, S. M.

    2018-04-01

    We have investigated the current-voltage (I-V) characteristics of nickel (Ni), cobalt (Co), tungsten (W) and palladium (Pd) Schottky contacts on n-type 4H-SiC in the 300-800 K temperature range. Results extracted from I-V measurements of Schottky barrier diodes showed that barrier height (ФBo) and ideality factor (n) were strongly dependent on temperature. Schottky barrier heights for contacts of all the metals showed an increase with temperature between 300 K and 800 K. This was attributed to barrier inhomogeneities at the interface between the metal and the semiconductor, which resulted in a distribution of barrier heights at the interface. Ideality factors of Ni, Co and Pd decreased from 1.6 to 1.0 and for W the ideality factor decreased from 1.1 to 1.0 when the temperature was increased from 300 K to 800 K respectively. The device parameters were compared to assess advantages and disadvantages of the metals for envisaged applications.

  8. Out-of-plane strain and electric field tunable electronic properties and Schottky contact of graphene/antimonene heterostructure

    Science.gov (United States)

    Phuc, Huynh V.; Hieu, Nguyen N.; Hoi, Bui D.; Phuong, Le T. T.; Hieu, Nguyen V.; Nguyen, Chuong V.

    2017-12-01

    In this paper, the electronic properties of graphene/monolayer antimonene (G/m-Sb) heterostructure have been studied using the density functional theory (DFT). The effects of out-of-plane strain (interlayer coupling) and electric field on the electronic properties and Schottky contact of the G/m-Sb heterostructure are also investigated. The results show that graphene is bound to m-Sb layer by a weak van-der-Waals interaction with the interlayer distance of 3.50 Å and the binding energy per carbon atom of -39.62 meV. We find that the n-type Schottky contact is formed at the G/m-Sb heterostructure with the Schottky barrier height (SBH) of 0.60 eV. By varying the interlayer distance between graphene and the m-Sb layer we can change the n-type and p-type SBH at the G/m-Sb heterostructure. Especially, we find the transformation from n-type to p-type Schottky contact with decreasing the interlayer distance. Furthermore, the SBH and the Schottky contact could be controlled by applying the perpendicular electric field. With the positive electric field, electrons can easily transfer from m-Sb to graphene layer, leading to the transition from n-type to p-type Schottky contact.

  9. Effect of the periphery of metal-semiconductor contacts with Schottky barriers on their static current-voltage characteristic

    International Nuclear Information System (INIS)

    Torkhov, N. A.

    2010-01-01

    Kelvin probe atomic-force microscopy of the electrostatic surface potential of gold Schottky contacts on n-GaAs showed that there is an extended transition area (halo) (tens of micrometers) around contacts in which the surface potential varies from the n-GaAs free surface potential to the gold contact surface potential. The contact potential and its distribution in the surrounding halo are controlled by the contact structure. The study of spreading currents showed that there is a high-conductance area (periphery) around the contact perimeter due to strong electric fields of the halo, which causes leakage currents. The conductivity of the main contact area is caused by 100- to 200-nm local areas with higher and lower conducting abilities. Mesa formation around contacts causes a decrease in the work function, a decrease in the halo extent and electric field strength, which is accompanied by spreading and decreasing of the peripheral area conductance. This results in disappearance of leakage currents and a decrease in the ideality index. In contrast, protection of the peripheral area by a SiO 2 insulating film 0.5 μm thick increases the work function, which is accompanied by the formation of potential lobes around the contact in two mutually perpendicular crystallographic directions. A stronger penetration of halo electric fields into the contact area results in an increase in the ideality index and disappearance of high-conductance peripheral area and leakage currents. The difference between the electrical properties of the periphery, gold grains, and their boundaries controls the contact switching mechanism when applying forward or reverse biases.

  10. A graphene barristor using nitrogen profile controlled ZnO Schottky contacts.

    Science.gov (United States)

    Hwang, Hyeon Jun; Chang, Kyoung Eun; Yoo, Won Beom; Shim, Chang Hoo; Lee, Sang Kyung; Yang, Jin Ho; Kim, So-Young; Lee, Yongsu; Cho, Chunhum; Lee, Byoung Hun

    2017-02-16

    We have successfully demonstrated a graphene-ZnO:N Schottky barristor. The barrier height between graphene and ZnO:N could be modulated by a buried gate electrode in the range of 0.5-0.73 eV, and an on-off ratio of up to 10 7 was achieved. By using a nitrogen-doped ZnO film as a Schottky contact material, the stability problem of previously reported graphene barristors could be greatly alleviated and a facile route to build a top-down processed graphene barristor was realized with a very low heat cycle. This device will be instrumental when implementing logic functions in systems requiring high-performance logic devices fabricated with a low temperature fabrication process such as back-end integrated logic devices or flexible devices on soft substrates.

  11. Film thickness degradation of Au/GaN Schottky contact characteristics

    International Nuclear Information System (INIS)

    Wang, K.; Wang, R.X.; Fung, S.; Beling, C.D.; Chen, X.D.; Huang, Y.; Li, S.; Xu, S.J.; Gong, M.

    2005-01-01

    Electrical characteristics of Au/n-GaN Schottky contacts with different Au film thicknesses up to 1300 A, have been investigated using current-voltage (I-V) and capacitance-voltage (C-V) techniques. Results show a steady decrease in the quality of the Schottky diodes for increasing Au film thickness. I-V measurements indicate that thin ( 500 A). Depth profiling Auger electron spectroscopy (AES) shows that the width of the Au/GaN junction interface increases with increasing Au thickness, suggesting considerable inter-mixing of Au, Ga and N. The results have been interpreted in terms of Ga out-diffusion from the GaN giving rise to gallium vacancies that in turn act as sites for electron-hole pair generation within the depletion region. The study supports the recent suggestion that gallium vacancies associated with threaded dislocations are playing an important role in junction breakdown

  12. Experimental and numerical investigation of contact-area-limited doping for top-contact pentacene thin-film transistors with Schottky contact.

    Science.gov (United States)

    Noda, Kei; Wada, Yasuo; Toyabe, Toru

    2015-10-28

    Effects of contact-area-limited doping for pentacene thin-film transistors with a bottom-gate, top-contact configuration were investigated. The increase in the drain current and the effective field-effect mobility was achieved by preparing hole-doped layers underneath the gold contact electrodes by coevaporation of pentacene and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), confirmed by using a thin-film organic transistor advanced simulator (TOTAS) incorporating Schottky contact with a thermionic field emission (TFE) model. Although the simulated electrical characteristics fit the experimental results well only in the linear regime of the transistor operation, the barrier height for hole injection and the gate-voltage-dependent hole mobility in the pentacene transistors were evaluated with the aid of the device simulation. This experimental data analysis with the simulation indicates that the highly-doped semiconducting layers prepared in the contact regions can enhance the charge carrier injection into the active semiconductor layer and concurrent trap filling in the transistor channel, caused by the mitigation of a Schottky energy barrier. This study suggests that both the contact-area-limited doping and the device simulation dealing with Schottky contact are indispensable in designing and developing high-performance organic thin-film transistors.

  13. Effect of hydrogen on ZnO films and Au/ZnO Schottky contacts

    International Nuclear Information System (INIS)

    Tsiarapas, C; Girginoudi, D; Georgoulas, N

    2014-01-01

    The structural, optical and electrical properties of ZnO films for different amounts of incorporated hydrogen (H), as well as the electrical characteristics of Au Schottky contacts based on these ZnO layers have been investigated. The films were deposited with the dc-magnetron sputtering technique, varying the H flow rate in the Ar/H sputtering gas. We found a significant improvement of the crystallinity (as obtained from x-ray diffraction spectra), Hall mobility and resistivity as the H concentration per vol. [H 2 ] (during deposition) increases from 0% to 33.3%, which is followed by degradation for further [H 2 ] increase. A high dependence of the carrier mobility on the grain size is also noted. The Schottky diodes were characterized through current–voltage (I–V) and capacitance–voltage (C–V) measurements at room temperature. In correlation with the basic film properties, we obtained the best results for the Schottky diodes with [H 2 ] = 33.3%, in terms of higher rectification ratio, lower ideality factor (η) and series resistance (R s ). Both the electron concentration n and the ionized donors' concentration N D (obtained from C–V curves) increase constantly with [H 2 ] increase, and that seems to be consistent with our suggestion that H acts as a donor in ZnO. (paper)

  14. Schottky and Ohmic Au contacts on GaAs: Microscopic and electrical investigation

    International Nuclear Information System (INIS)

    Liliental-Weber, Z.; Gronsky, R.; Washburn, J.; Newman, N.; Spicer, W.E.; Weber, E.R.

    1986-01-01

    We report here a systematic study which uses electrical device measurements and transmission electron microscopy (TEM) methods to investigate the electrical, morphological, and structural properties of Au/GaAs Schottky diodes. The electrical characteristics of Au diodes formed on atomically clean and air-exposed GaAs(110) surfaces are found to change from rectifying to Ohmic behavior after annealing above the Au--Ga eutectic temperature (360 0 C). This change is shown to be due to an Ohmic-like contact at the periphery of the device. TEM studies of these structures indicate that the Ohmic peripheral current pathway can be correlated with the formation of near surface Ga-rich Au crystallites at the diode circumference upon annealing. Further evidence of the correlation of the Ohmic electrical characteristics with the morphology of the periphery comes from data which indicate that the removal of these Au crystallites by mesa etching is also accompanied with the elimination of the Ohmic current. The morphology of the overlayer was found to depend strongly on annealing and surface treatment. TEM indicates that the interface is flat and abrupt for all unannealed diodes, as well as for annealed diodes formed on atomically clean surfaces. For annealed diodes formed on the air-exposed surfaces, the metal--semiconductor interface contains large metallic protrusions extending up to several hundred angstroms into the semiconductor. For comparison to practical structures, the morphology of annealed diodes formed using typical commercial processing technology [i.e., formed on chemically prepared (100) surfaces annealed in forming gas] was also investigated using TEM. The interface for these structures is more complex than interfaces formed on the atomically clean and air-exposed cleaved (110) surfaces

  15. Electronic Transport Mechanism for Schottky Diodes Formed by Au/HVPE a-Plane GaN Templates Grown via In Situ GaN Nanodot Formation

    Directory of Open Access Journals (Sweden)

    Moonsang Lee

    2018-06-01

    Full Text Available We investigate the electrical characteristics of Schottky contacts for an Au/hydride vapor phase epitaxy (HVPE a-plane GaN template grown via in situ GaN nanodot formation. Although the Schottky diodes present excellent rectifying characteristics, their Schottky barrier height and ideality factor are highly dependent upon temperature variation. The relationship between the barrier height, ideality factor, and conventional Richardson plot reveals that the Schottky diodes exhibit an inhomogeneous barrier height, attributed to the interface states between the metal and a-plane GaN film and to point defects within the a-plane GaN layers grown via in situ nanodot formation. Also, we confirm that the current transport mechanism of HVPE a-plane GaN Schottky diodes grown via in situ nanodot formation prefers a thermionic field emission model rather than a thermionic emission (TE one, implying that Poole–Frenkel emission dominates the conduction mechanism over the entire range of measured temperatures. The deep-level transient spectroscopy (DLTS results prove the presence of noninteracting point-defect-assisted tunneling, which plays an important role in the transport mechanism. These electrical characteristics indicate that this method possesses a great throughput advantage for various applications, compared with Schottky contact to a-plane GaN grown using other methods. We expect that HVPE a-plane GaN Schottky diodes supported by in situ nanodot formation will open further opportunities for the development of nonpolar GaN-based high-performance devices.

  16. Determination of the Schottky barrier height of ferromagnetic contacts to few-layer phosphorene

    Energy Technology Data Exchange (ETDEWEB)

    Anugrah, Yoska; Robbins, Matthew C.; Koester, Steven J. [Department of Electrical and Computer Engineering, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455 (United States); Crowell, Paul A. [School of Physics and Astronomy, University of Minnesota-Twin Cities, Minneapolis, Minnesota 55455 (United States)

    2015-03-09

    Phosphorene, the 2D analogue of black phosphorus, is a promising material for studying spin transport due to its low spin-orbit coupling and its ½ nuclear spin, which could allow the study of hyperfine effects. In this work, the properties of permalloy (Py) and cobalt (Co) contacts to few-layer phosphorene are presented. The Schottky barrier height was extracted and determined as a function of gate bias. Flat-band barrier heights, relative to the valence band edge, of 110 meV and 200 meV were determined for Py and Co, respectively. These results are important for future studies of spin transport in phosphorene.

  17. Thermal stability of TaN Schottky contacts on n-GaN

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, J.R.; Kim, D-W.; Meidia, H.; Mahajan, S

    2003-02-07

    The thermal stability and electrical characteristics of tantalum-nitrogen alloy Schottky contacts on n-GaN were investigated. Non-stoichiometric {delta}-phase (40 atomic percent nitrogen) tantalum nitride contacts exhibited good electrical properties up to an annealing temperature of 600 deg. C. However, they degrade rapidly above this temperature due to outward diffusion of Ga and presumably nitrogen into the {delta}-phase tantalum nitride. It is surmised that excess Ta reacts with N at the GaN surface, freeing Ga which then diffuses into the TaN layer. Stoichiometric TaN Schottky contacts were stable at temperatures as high as 800 deg. C and had far superior electrical performance. This stems from the thermodynamic stability of the stoichiometric TaN/GaN interface. {delta}-phase TaN had I-V and C-V barrier heights of 0.55 eV and 0.8 eV respectively. On the other hand, TaN had an I-V barrier height near 0.7 eV and a C-V barrier height near 1.2 eV. The ideality factors for both {delta}-phase TaN and TaN were above 1.8 at all annealing temperatures, suggesting tunneling contributes significantly to current transport.

  18. The modulation of Schottky barriers of metal-MoS2 contacts via BN-MoS2 heterostructures.

    Science.gov (United States)

    Su, Jie; Feng, Liping; Zhang, Yan; Liu, Zhengtang

    2016-06-22

    Using first-principles calculations within density functional theory, we systematically studied the effect of BN-MoS2 heterostructure on the Schottky barriers of metal-MoS2 contacts. Two types of FETs are designed according to the area of the BN-MoS2 heterostructure. Results show that the vertical and lateral Schottky barriers in all the studied contacts, irrespective of the work function of the metal, are significantly reduced or even vanish when the BN-MoS2 heterostructure substitutes the monolayer MoS2. Only the n-type lateral Schottky barrier of Au/BN-MoS2 contact relates to the area of the BN-MoS2 heterostructure. Notably, the Pt-MoS2 contact with n-type character is transformed into a p-type contact upon substituting the monolayer MoS2 by a BN-MoS2 heterostructure. These changes of the contact natures are ascribed to the variation of Fermi level pinning, work function and charge distribution. Analysis demonstrates that the Fermi level pinning effects are significantly weakened for metal/BN-MoS2 contacts because no gap states dominated by MoS2 are formed, in contrast to those of metal-MoS2 contacts. Although additional BN layers reduce the interlayer interaction and the work function of the metal, the Schottky barriers of metal/BN-MoS2 contacts still do not obey the Schottky-Mott rule. Moreover, different from metal-MoS2 contacts, the charges transfer from electrodes to the monolayer MoS2, resulting in an increment of the work function of these metals in metal/BN-MoS2 contacts. These findings may prove to be instrumental in the future design of new MoS2-based FETs with ohmic contact or p-type character.

  19. Contribution to the study of rectification at the metal-semiconductor contact: analysis of aging in silicon Schottky diodes

    International Nuclear Information System (INIS)

    Ponpon, J.-P.

    1979-01-01

    The formation of the barrier height and the aging of metal-semiconductor contacts during exposure to air have been studied. The evolution of the electrical characteristics, especially the barrier height, of silicon Schottky diodes results from the diffusion of oxygen through the electrode and its accumulation at the interface. The diffusion coefficient of oxygen has been deduced for each metal used. In a first step the oxygen neutralize a fixed positive charge which remains at the semiconductor surface after etching; then, as silicon is oxidized, a MIS device is formed. Similar results have been obtained in the case of germanium, while no aging appears with cadmium telluride. In this case the barrier height seems to be determined by chemical reactions at the interface [fr

  20. Strong Schottky barrier reduction at Au-catalyst/GaAs-nanowire interfaces by electric dipole formation and Fermi-level unpinning.

    Science.gov (United States)

    Suyatin, Dmitry B; Jain, Vishal; Nebol'sin, Valery A; Trägårdh, Johanna; Messing, Maria E; Wagner, Jakob B; Persson, Olof; Timm, Rainer; Mikkelsen, Anders; Maximov, Ivan; Samuelson, Lars; Pettersson, Håkan

    2014-01-01

    Nanoscale contacts between metals and semiconductors are critical for further downscaling of electronic and optoelectronic devices. However, realizing nanocontacts poses significant challenges since conventional approaches to achieve ohmic contacts through Schottky barrier suppression are often inadequate. Here we report the realization and characterization of low n-type Schottky barriers (~0.35 eV) formed at epitaxial contacts between Au-In alloy catalytic particles and GaAs-nanowires. In comparison to previous studies, our detailed characterization, employing selective electrical contacts defined by high-precision electron beam lithography, reveals the barrier to occur directly and solely at the abrupt interface between the catalyst and nanowire. We attribute this lowest-to-date-reported Schottky barrier to a reduced density of pinning states (~10(17) m(-2)) and the formation of an electric dipole layer at the epitaxial contacts. The insight into the physical mechanisms behind the observed low-energy Schottky barrier may guide future efforts to engineer abrupt nanoscale electrical contacts with tailored electrical properties.

  1. Polycrystalline silicon carbide dopant profiles obtained through a scanning nano-Schottky contact

    Energy Technology Data Exchange (ETDEWEB)

    Golt, M. C.; Strawhecker, K. E.; Bratcher, M. S. [U.S. Army Research Laboratory, WMRD, Aberdeen Proving Ground, Maryland 21005 (United States); Shanholtz, E. R. [ORISE, Belcamp, Maryland 21017 (United States)

    2016-07-14

    The unique thermo-electro-mechanical properties of polycrystalline silicon carbide (poly-SiC) make it a desirable candidate for structural and electronic materials for operation in extreme environments. Necessitated by the need to understand how processing additives influence poly-SiC structure and electrical properties, the distribution of lattice defects and impurities across a specimen of hot-pressed 6H poly-SiC processed with p-type additives was visualized with high spatial resolution using a conductive atomic force microscopy approach in which a contact forming a nano-Schottky interface is scanned across the sample. The results reveal very intricate structures within poly-SiC, with each grain having a complex core-rim structure. This complexity results from the influence the additives have on the evolution of the microstructure during processing. It was found that the highest conductivities localized at rims as well as at the interface between the rim and the core. The conductivity of the cores is less than the conductivity of the rims due to a lower concentration of dopant. Analysis of the observed conductivities and current-voltage curves is presented in the context of nano-Schottky contact regimes where the conventional understanding of charge transport to diode operation is no longer valid.

  2. Polycrystalline silicon carbide dopant profiles obtained through a scanning nano-Schottky contact

    International Nuclear Information System (INIS)

    Golt, M. C.; Strawhecker, K. E.; Bratcher, M. S.; Shanholtz, E. R.

    2016-01-01

    The unique thermo-electro-mechanical properties of polycrystalline silicon carbide (poly-SiC) make it a desirable candidate for structural and electronic materials for operation in extreme environments. Necessitated by the need to understand how processing additives influence poly-SiC structure and electrical properties, the distribution of lattice defects and impurities across a specimen of hot-pressed 6H poly-SiC processed with p-type additives was visualized with high spatial resolution using a conductive atomic force microscopy approach in which a contact forming a nano-Schottky interface is scanned across the sample. The results reveal very intricate structures within poly-SiC, with each grain having a complex core-rim structure. This complexity results from the influence the additives have on the evolution of the microstructure during processing. It was found that the highest conductivities localized at rims as well as at the interface between the rim and the core. The conductivity of the cores is less than the conductivity of the rims due to a lower concentration of dopant. Analysis of the observed conductivities and current-voltage curves is presented in the context of nano-Schottky contact regimes where the conventional understanding of charge transport to diode operation is no longer valid.

  3. Development of high temperature stable Ohmic and Schottky contacts on n-gallium nitride

    Science.gov (United States)

    Khanna, Rohit

    In this work the effort was made to towards develop and investigate high temperature stable Ohmic and Schottky contacts for n type GaN. Various borides and refractory materials were incorporated in metallization scheme to best attain the desired effect of minimal degradation of contacts when placed at high temperatures. This work focuses on achieving a contact scheme using different borides which include two Tungsten Borides (namely W2B, W2B 5), Titanium Boride (TiB2), Chromium Boride (CrB2) and Zirconium Boride (ZrB2). Further a high temperature metal namely Iridium (Ir) was evaluated as a potential contact to n-GaN, as part of continuing improved device technology development. The main goal of this project was to investigate the most promising boride-based contact metallurgies on GaN, and finally to fabricate a High Electron Mobility Transistor (HEMT) and compare its reliability to a HEMT using present technology contact. Ohmic contacts were fabricated on n GaN using borides in the metallization scheme of Ti/Al/boride/Ti/Au. The characterization of the contacts was done using current-voltage measurements, scanning electron microscopy (SEM) and Auger Electron Spectroscopy (AES) measurements. The contacts formed gave specific contact resistance of the order of 10-5 to 10-6 Ohm-cm2. A minimum contact resistance of 1.5x10-6 O.cm 2 was achieved for the TiB2 based scheme at an annealing temperature of 850-900°C, which was comparable to a regular ohmic contact of Ti/Al/Ni/Au on n GaN. When some of borides contacts were placed on a hot plate or in hot oven for temperature ranging from 200°C to 350°C, the regular metallization contacts degraded before than borides ones. Even with a certain amount of intermixing of the metallization scheme the boride contacts showed minimal roughening and smoother morphology, which, in terms of edge acuity, is crucial for very small gate devices. Schottky contacts were also fabricated and characterized using all the five boride

  4. GaAs detectors with an ultra-thin Schottky contact for spectrometry of charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Chernykh, S.V., E-mail: chsv_84@mail.ru [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Chernykh, A.V. [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Didenko, S.I.; Baryshnikov, F.M. [National University of Science and Technology “MISIS”, Moscow (Russian Federation); Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Burtebayev, N. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Institute of Nuclear Physics, Almaty (Kazakhstan); Britvich, G.I. [Institute of High Energy Physics, Protvino, Moscow region (Russian Federation); Chubenko, A.P. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow (Russian Federation); Guly, V.G.; Glybin, Yu.N. [LLC “SNIIP Plus”, Moscow (Russian Federation); Zholdybayev, T.K.; Burtebayeva, J.T.; Nassurlla, M. [Research Institute of Experimental and Theoretical Physics, Almaty (Kazakhstan); Institute of Nuclear Physics, Almaty (Kazakhstan)

    2017-02-11

    For the first time, samples of particle detectors based on high-purity GaAs epilayers with an active area of 25 and 80 mm{sup 2} and an ultra-thin Pt Schottky barrier were fabricated for use in the spectrometry of charged particles and their operating characteristics were studied. The obtained FWHM of 14.2 (for 25 mm{sup 2} detector) and 15.5 keV (for 80 mm{sup 2} detector) on the 5.499 MeV line of {sup 238}Pu is at the level of silicon spectrometric detectors. It was found that the main component that determines the energy resolution of the detector is a fluctuation in the number of collected electron–hole pairs. This allows us to state that the obtained energy resolution is close to the limit for VPE GaAs. - Highlights: • VPE GaAs particle detectors with an active area of 25 and 80 mm{sup 2} were fabricated. • 120 Å ultra-thin Pt Schottky barrier was used as a rectifying contact. • The obtained FWHM of 14.2 keV ({sup 238}Pu) is at the level of Si spectrometric detectors. • Various components of the total energy resolution were analyzed. • It was shown that obtained energy resolution is close to its limit for VPE GaAs.

  5. Characterization technique for inhomogeneous 4H-SiC Schottky contacts: A practical model for high temperature behavior

    Science.gov (United States)

    Brezeanu, G.; Pristavu, G.; Draghici, F.; Badila, M.; Pascu, R.

    2017-08-01

    In this paper, a characterization technique for 4H-SiC Schottky diodes with varying levels of metal-semiconductor contact inhomogeneity is proposed. A macro-model, suitable for high-temperature evaluation of SiC Schottky contacts, with discrete barrier height non-uniformity, is introduced in order to determine the temperature interval and bias domain where electrical behavior of the devices can be described by the thermionic emission theory (has a quasi-ideal performance). A minimal set of parameters, the effective barrier height and peff, the non-uniformity factor, is associated. Model-extracted parameters are discussed in comparison with literature-reported results based on existing inhomogeneity approaches, in terms of complexity and physical relevance. Special consideration was given to models based on a Gaussian distribution of barrier heights on the contact surface. The proposed methodology is validated by electrical characterization of nickel silicide Schottky contacts on silicon carbide (4H-SiC), where a discrete barrier distribution can be considered. The same method is applied to inhomogeneous Pt/4H-SiC contacts. The forward characteristics measured at different temperatures are accurately reproduced using this inhomogeneous barrier model. A quasi-ideal behavior is identified for intervals spanning 200 °C for all measured Schottky samples, with Ni and Pt contact metals. A predictable exponential current-voltage variation over at least 2 orders of magnitude is also proven, with a stable barrier height and effective area for temperatures up to 400 °C. This application-oriented characterization technique is confirmed by using model parameters to fit a SiC-Schottky high temperature sensor's response.

  6. Influence of B doping on the carrier transport mechanism and barrier height of graphene/ZnO Schottky contact

    Science.gov (United States)

    Li, Yapeng; Li, Yingfeng; Zhang, Jianhua; Tong, Ting; Ye, Wei

    2018-03-01

    The ZnO films were fabricated on the surface of n-Si(1 1 1) substrate using the sol-gel method, and the graphene was then transferred to its surface for the fabrication of the graphene/ZnO Schottky contact. The results showed that ZnO films presented a strong (0 0 2) preferred direction, and that the particle sizes on the surface decreased as the doping concentration of B ions increased. The electrical properties of the graphene/ZnO Schottky contact were measured by using current-voltage measurements. It was found that the graphene/ZnO Schottky contact showed a fine rectification behavior when the doping concentration of B ions was increased. However, when the doping concentration of the B ions increased to 0.15 mol l-1, the leakage current increased and rectification behavior weakened. This was due to the Fermi level pinning caused by the presence of the O vacancy at the interface of the graphene/ZnO Schottky contact.

  7. Experimental analysis of the Schottky barrier height of metal contacts in black phosphorus field-effect transistors

    Science.gov (United States)

    Chang, Hsun-Ming; Fan, Kai-Lin; Charnas, Adam; Ye, Peide D.; Lin, Yu-Ming; Wu, Chih-I.; Wu, Chao-Hsin

    2018-04-01

    Compared to graphene and MoS2, studies on metal contacts to black phosphorus (BP) transistors are still immature. In this work, we present the experimental analysis of titanium contacts on BP based upon the theory of thermionic emssion. The Schottky barrier height (SBH) is extracted by thermionic emission methods to analyze the properties of Ti-BP contact. To examine the results, the band gap of BP is extracted followed by theoretical band alignment by Schottky-Mott rule. However, an underestimated SBH is found due to the hysteresis in electrical results. Hence, a modified SBH extraction for contact resistance that avoids the effects of hysteresis is proposed and demonstrated, showing a more accurate SBH that agrees well with theoretical value and results of transmission electron microscopy and energy-dispersive x-ray spectroscopy.

  8. Schottky Barrier Height of Pd/MoS2 Contact by Large Area Photoemission Spectroscopy.

    Science.gov (United States)

    Dong, Hong; Gong, Cheng; Addou, Rafik; McDonnell, Stephen; Azcatl, Angelica; Qin, Xiaoye; Wang, Weichao; Wang, Weihua; Hinkle, Christopher L; Wallace, Robert M

    2017-11-08

    MoS 2 , as a model transition metal dichalcogenide, is viewed as a potential channel material in future nanoelectronic and optoelectronic devices. Minimizing the contact resistance of the metal/MoS 2 junction is critical to realizing the potential of MoS 2 -based devices. In this work, the Schottky barrier height (SBH) and the band structure of high work function Pd metal on MoS 2 have been studied by in situ X-ray photoelectron spectroscopy (XPS). The analytical spot diameter of the XPS spectrometer is about 400 μm, and the XPS signal is proportional to the detection area, so the influence of defect-mediated parallel conduction paths on the SBH does not affect the measurement. The charge redistribution by Pd on MoS 2 is detected by XPS characterization, which gives insight into metal contact physics to MoS 2 and suggests that interface engineering is necessary to lower the contact resistance for the future generation electronic applications.

  9. Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact.

    Science.gov (United States)

    Gorji, Mohammad Saleh; Razak, Khairunisak Abdul; Cheong, Kuan Yew

    2013-10-15

    Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. The influence of thermal annealing on the characteristics of Au/Ni Schottky contacts on n-type 4 H-SiC

    Science.gov (United States)

    Omotoso, E.; Auret, F. D.; Igumbor, E.; Tunhuma, S. M.; Danga, H. T.; Ngoepe, P. N. M.; Taleatu, B. A.; Meyer, W. E.

    2018-05-01

    The effects of isochronal annealing on the electrical, morphological and structural characteristics of Au/Ni/4 H-SiC Schottky barrier diodes (SBDs) have been studied. Current-voltage ( I- V), capacitance-voltage ( C- V), deep-level transient spectroscopy, scanning electron microscope (SEM) and X-ray diffraction measurements were employed to study the thermal effect on the characteristics of the SBDs. Prior to thermal annealing of Schottky contacts, the I- V measurements results confirmed the good rectification behaviour with ideality factor of 1.06, Schottky barrier height of 1.20 eV and series resistance of 7 Ω. The rectification properties after annealing was maintained up to an annealing temperature of 500 °C, but deviated slightly above 500 °C. The uncompensated ionized donor concentration decreased with annealing temperature, which could be attributed to out-diffusion of the 4 H-SiC into the Au/Ni contacts and decrease in bonding due to formation of nickel silicides. We observed the presence of four deep-level defects with energies 0.09, 0.11, 0.16 and 0.65 eV below the conduction band before and after the isochronal annealing up to 600 °C. The conclusion drawn was that annealing did not affect the number of deep-level defects present in Au/Ni/4 H-SiC contacts. The variations in electrical properties of the devices were attributed to the phase transformations and interfacial reactions that occurred after isochronal annealing.

  11. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong; Cheng, Yingchun; Schwingenschlö gl, Udo; Zhang, Qingyun

    2013-01-01

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  12. Two-dimensional ferromagnet/semiconductor transition metal dichalcogenide contacts: p-type Schottky barrier and spin-injection control

    KAUST Repository

    Gan, Liyong

    2013-09-26

    We study the ferromagnet/semiconductor contacts formed by transition metal dichalcogenide monolayers, focusing on semiconducting MoS2 and WS2 and ferromagnetic VS2. We investigate the degree of p-type doping and demonstrate tuning of the Schottky barrier height by vertical compressive pressure. An analytical model is presented for the barrier heights that accurately describes the numerical findings and is expected to be of general validity for all transition metal dichalcogenide metal/semiconductor contacts. Furthermore, magnetic proximity effects induce a 100% spin polarization at the Fermi level in the semiconductor where the spin splitting increases up to 0.70 eV for increasing pressure.

  13. Barrier characteristics of Pt/Ru Schottky contacts on n-type GaN ...

    Indian Academy of Sciences (India)

    Pt/Ru Schottky rectifiers; n-type GaN; temperature–dependent electrical properties; inhomogeneous barrier heights .... a 2 μm thick Si-doped GaN films which were grown by .... ted values of ap using (9) for two Gaussian distributions of bar-.

  14. Characterization and Reliability of Vertical N-Type Gallium Nitride Schottky Contacts

    Science.gov (United States)

    2016-09-01

    ACKNOWLEDGMENTS Foremost, I would like to thank my wife, Melissa, with whom I have three wonderful children. Without her endless love , unwavering...conducting research in the lab and studying in the library, she cared for our children and created a loving home for our family. Her strength, passion...Online]. Available: http://ecee.colorado.edu/~bart/book/book/title.htm 78 [12] R. T. Tung, “The physics and chemistry of the Schottky barrier

  15. Improved Pt/Au and W/Pt/Au Schottky contacts on n-type ZnO using ozone cleaning

    International Nuclear Information System (INIS)

    Ip, K.; Gila, B.P.; Onstine, A.H.; Lambers, E.S.; Heo, Y.W.; Baik, K.H.; Norton, D.P.; Pearton, S.J.; Kim, S.; LaRoche, J.R; Ren, F.

    2004-01-01

    UV-ozone cleaning prior to metal deposition of either e-beam Pt contacts or sputtered W contacts on n-type single-crystal ZnO is found to significantly improve their rectifying characteristics. Pt contacts deposited directly on the as-received ZnO surface are Ohmic but show rectifying behavior with ozone cleaning. The Schottky barrier height of these Pt contacts was 0.70 eV, with ideality factor of 1.5 and a saturation current density of 6.2x10 -6 A cm -2 . In contrast, the as-deposited W contacts are Ohmic, independent of the use of ozone cleaning. Postdeposition annealing at 700 deg. C produces rectifying behavior with Schottky barrier heights of 0.45 eV for control samples and 0.49 eV for those cleaned with ozone exposure. The improvement in rectifying properties of both the Pt and W contacts is related to removal of surface carbon contamination from the ZnO

  16. A comparative study of the electrical properties of Pd/ZnO Schottky contacts fabricated using electron beam deposition and resistive/thermal evaporation techniques

    International Nuclear Information System (INIS)

    Mtangi, W.; Auret, F. D.; Janse van Rensburg, P. J.; Coelho, S. M. M.; Legodi, M. J.; Nel, J. M.; Meyer, W. E.; Chawanda, A.

    2011-01-01

    A systematic investigation to check the quality of Pd Schottky contacts deposited on ZnO has been performed on electron beam (e-beam) deposited and resistively/thermally evaporated samples using current-voltage, IV, and conventional deep level transient spectroscopy (DLTS) measurements. Room temperature IV measurements reveal the dominance of pure thermionic emission on the resistively evaporated contacts, while the e-beam deposited contacts show the dominance of generation recombination at low voltages, -10 A at a reverse voltage of 1.0 V whereas the e-beam deposited contacts have reverse currents of the order of 10 -6 A at 1.0 V. Average ideality factors have been determined as (1.43 ± 0.01) and (1.66 ± 0.02) for the resistively evaporated contacts and e-beam deposited contacts, respectively. The IV barrier heights have been calculated as (0.721 ± 0.002) eV and (0.624 ± 0.005) eV for the resistively evaporated and e-beam deposited contacts, respectively. Conventional DLTS measurements reveal the presence of three prominent defects in both the resistive and e-beam contacts. Two extra peaks with energy levels of 0.60 and 0.81 eV below the conduction band minimum have been observed in the e-beam deposited contacts. These have been explained as contributing to the generation recombination current that dominates at low voltages and high leakage currents. Based on the reverse current at 1.0 V, the degree of rectification, the dominant current transport mechanism and the observed defects, we conclude that the resistive evaporation technique yields better quality Schottky contacts for use in solar cells and ultraviolet detectors compared to the e-beam deposition technique. The 0.60 eV has been identified as possibly related to the unoccupied level for the doubly charged oxygen vacancy, V o 2+ .

  17. Influence of He-ion irradiation on the characteristics of Pd/n-Si{sub 0.90}Ge{sub 0.10}/Si Schottky contacts

    Energy Technology Data Exchange (ETDEWEB)

    Mamor, M; Sellai, A; Bouziane, K; Harthi, S H Al; Busaidi, M Al; Gard, F S [Physics Department, Sultan Qaboos University, PO Box 36 Muscat 123, Sultanate of (Oman)

    2007-03-07

    Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of He-ion irradiated Pd/n-Si{sub 09}Ge{sub 0.10} Schottky contacts have been measured in the temperature range from 100 to 300 K. Schottky barrier properties such as the Schottky barrier height ({phi}{sub bn}) and ideality factor (n) have been studied as a function of temperature. The degree to which their characteristics deviated from the ideal case increased as the temperature decreased. A decrease in {phi}{sub bn} and an increase in n with decreasing temperature are observed. Additionally, linear dependence between the so-called temperature factor T{sub 0} and temperature as well as between {phi}{sub bn} and n are shown. This type of strong temperature dependence indicates the presence of a large degree of lateral inhomogeneities of the barrier height, resulting from the He-ion irradiation induced defects and traps which produce a variation in the number of free carriers. The presence of electrically active defects introduced by He-ion irradiation at and below the Si{sub 0.90}Ge{sub 0.10} surface support this interpretation.

  18. Contact nuclei formation in aqueous dextrose solutions

    Science.gov (United States)

    Cerreta, Michael K.; Berglund, Kris A.

    1990-06-01

    A laser Raman microprobe was used in situ to observe the growth of alpha dextrose monohydrate on alpha anhydrous dextrose crystals. The Raman spectra indicate growth of the monohydrate below 28.1°C, but the presence of only the anhydrous form above 40.5°C. Contact nucleation experiments with parent anhydrous crystals yielded only monohydrate nuclei below 28.1°C, while contacts in solutions between 34.5 and 41.0°C produced both crystalline forms, and contacts in solutions above 43.5°C produced only anhydrous nuclei. The inability of the monohydrate to grow on anhydrous crystals in the same solution that forms the two crystalline phases with a single contact precludes a simple attrition mechanism of nuclei formation. For the same reason, the hypothetical mechanism involving parent crystal stabilization of pre-crystalline clusters, allowing the clusters to grow into nuclei, is also contradicted. A third, mechanism, which may be a combination of the two, is believed to apply.

  19. Phase formation in contact of dissimilar metals

    Energy Technology Data Exchange (ETDEWEB)

    Savvin, V S; Kazachkova, Yu A; Povzner, A A [Ural State Technical University-UPI, Mira st., 19, A-203, Yekaterinburg 620002 (Russian Federation)], E-mail: savvin-vs@yandex.ru

    2008-02-15

    Formation and growth of intermediate phases in contact of the crystalline samples forming a two-component eutectic system is considered. It is shown that during the competition to a growing liquid phase the intermediate solid phases cannot grow by diffusion. The alternative is formation of metastable areas of a liquid phase. Measurements of liquid layers extent in Pb-Bi and In-Bi systems have allowed to define the composition of liquid on interface where formation of metastable liquid is possible. The results show that the concentration interval of a liquid layer corresponds to a stable constitution diagram. In order to explain the experimental results the hypothesis according to which the intermediate solid phases are formed as a result of precipitation from metastable melt is considered. The experimental confirmation of formation and crystallization of a metastable liquid is the fact that intergrowth of the samples forming system with an intermetallic phase at temperatures below the temperature of fusion of the most low-melting eutectic is observed. The possibility of the processes concerned with the occurrence of metastable areas of a liquid is showed by means of computer imitation.

  20. Tuning of Schottky Barrier Height at NiSi/Si Contact by Combining Dual Implantation of Boron and Aluminum and Microwave Annealing

    Directory of Open Access Journals (Sweden)

    Feng Sun

    2018-03-01

    Full Text Available Dopant-segregated source/drain contacts in a p-channel Schottky-barrier metal-oxide semiconductor field-effect transistor (SB-MOSFET require further hole Schottky barrier height (SBH regulation toward sub-0.1 eV levels to improve their competitiveness with conventional field-effect transistors. Because of the solubility limits of dopants in silicon, the requirements for effective hole SBH reduction with dopant segregation cannot be satisfied using mono-implantation. In this study, we demonstrate a potential solution for further SBH tuning by implementing the dual implantation of boron (B and aluminum (Al in combination with microwave annealing (MWA. By using such a method, not only has the lowest hole SBH ever with 0.07 eV in NiSi/n-Si contacts been realized, but also the annealing duration of MWA was sharply reduced to 60 s. Moreover, we investigated the SBH tuning mechanisms of the dual-implanted diodes with microwave annealing, including the dopant segregation, activation effect, and dual-barrier tuning effect of Al. With the selection of appropriate implantation conditions, the dual implantation of B and Al combined with the MWA technique shows promise for the fabrication of future p-channel SB-MOSFETs with a lower thermal budget.

  1. Structural, microstructural, and electrical properties of gold films and Schottky contacts on remote plasma-cleaned, n-type ZnO{0001} surfaces

    International Nuclear Information System (INIS)

    Coppa, B.J.; Fulton, C.C.; Kiesel, S.M.; Davis, R.F.; Pandarinath, C.; Burnette, J.E.; Nemanich, R.J.; Smith, D.J.

    2005-01-01

    Current-voltage measurements of Au contacts deposited on ex situ cleaned, n-type ZnO(0001) [(0001)] surfaces showed reverse bias leakage current densities of ∼0.01 (∼0.1) A/cm 2 at 4.6 (3.75) V reverse bias and ideality factors >2 (both surfaces) before sharp, permanent breakdown (soft breakdown). This behavior was due primarily to the presence of (1.6-2.0)±0.1 [(0.7-2.6)±0.1] monolayers (ML) of hydroxide, which forms an electron accumulation layer and increases the surface conductivity. In situ remote plasma cleaning of the (0001) [(0001)] surfaces using a 20 vol % O 2 /80 vol % He mixture for the optimized temperatures, times, and pressure of 550±20 deg. C (525±20 deg. C), 60 (30) min, and 0.050 Torr reduced the thickness of the hydroxide layer to ∼0.4±0.1 ML and completely eliminated all detectable hydrocarbon contamination. Subsequent cooling of both surfaces in the plasma ambient resulted in the chemisorption of oxygen and a change from 0.2 eV of downward band bending for samples cooled in vacuum to 0.3 eV of upward band bending indicative of the formation of a depletion layer of lower surface conductivity. Cooling in either ambient produced stoichiometric ZnO{0001} surfaces having an ordered crystallography as well as a step-and-terrace microstructure on the (0001) surface; the (0001) surface was without distinctive features. Sequentially deposited, unpatterned Au films, and presumably the rectifying gold contacts, initially grew on both surfaces cooled in the plasma ambient via the formation of islands that subsequently coalesced, as indicated by calculations from x-ray photoelectron spectroscopy data and confirmed by transmission electron microscopy. Calculations from the current-voltage data of the best contacts revealed barrier heights on the (0001) [(0001)] surfaces of 0.71±0.05 (0.60±0.05) eV, a saturation current density of (4±0.5)x10 -6 A/cm 2 (2.0±0.5x10 -4 A/cm 2 ), a lower value of n=1.17±0.05 (1.03±0.05), a significantly lower

  2. From Schottky to Ohmic graphene contacts to AlGaN/GaN heterostructures: Role of the AlGaN layer microstructure

    International Nuclear Information System (INIS)

    Fisichella, G.; Greco, G.; Roccaforte, F.; Giannazzo, F.

    2014-01-01

    The electrical behaviour of graphene (Gr) contacts to Al x Ga 1−x N/GaN heterostructures has been investigated, focusing, in particular, on the impact of the AlGaN microstructure on the current transport at Gr/AlGaN interface. Two Al 0.25 Ga 0.75 N/GaN heterostructures with very different quality in terms of surface roughness and defectivity, as evaluated by atomic force microscopy (AFM) and transmission electron microscopy, were compared in this study, i.e., a uniform and defect-free sample and a sample with a high density of typical V-defects, which locally cause a reduction of the AlGaN thickness. Nanoscale resolution current voltage (I-V) measurements by an Au coated conductive AFM tip were carried out at several positions both on the bare and Gr-coated AlGaN surfaces. Rectifying contacts were found onto both bare AlGaN surfaces, but with a more inhomogeneous and lower Schottky barrier height (Φ B  ≈ 0.6 eV) for AlGaN with V-defects, with respect to the case of the uniform AlGaN (Φ B  ≈ 0.9 eV). Instead, very different electrical behaviours were observed in the presence of the Gr interlayer between the Au tip and AlGaN, i.e., a Schottky contact with reduced barrier height (Φ B ≈ 0.4 eV) for the uniform AlGaN and an Ohmic contact for the AlGaN with V-defects. Interestingly, excellent lateral uniformity of the local I-V characteristics was found in both cases and can be ascribed to an averaging effect of the Gr electrode over the AlGaN interfacial inhomogeneities. Due to the locally reduced AlGaN layer thickness, V defect act as preferential current paths from Gr to the 2DEG and can account for the peculiar Ohmic behaviour of Gr contacts on defective AlGaN

  3. Mechanism of improving forward and reverse blocking voltages in AlGaN/GaN HEMTs by using Schottky drain

    International Nuclear Information System (INIS)

    Zhao Sheng-Lei; Mi Min-Han; Luo Jun; Wang Yi; Dai Yang; Zhang Jin-Cheng; Ma Xiao-Hua; Hao Yue; Hou Bin

    2014-01-01

    In this paper, we demonstrate that a Schottky drain can improve the forward and reverse blocking voltages (BVs) simultaneously in AlGaN/GaN high-electron mobility transistors (HEMTs). The mechanism of improving the two BVs is investigated by analysing the leakage current components and by software simulation. The forward BV increases from 72 V to 149 V due to the good Schottky contact morphology. During the reverse bias, the buffer leakage in the Ohmicdrain HEMT increases significantly with the increase of the negative drain bias. For the Schottky-drain HEMT, the buffer leakage is suppressed effectively by the formation of the depletion region at the drain terminal. As a result, the reverse BV is enhanced from −5 V to −49 V by using a Schottky drain. Experiments and the simulation indicate that a Schottky drain is desirable for power electronic applications. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  4. Tuning of Schottky barrier height of Al/n-Si by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vali, Indudhar Panduranga [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Shetty, Pramoda Kumara, E-mail: pramod.shetty@manipal.edu [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Mahesha, M.G. [Manipal Institute of Technology, Manipal University, Manipal 576104 (India); Petwal, V.C.; Dwivedi, Jishnu [Raja Ramanna Centre for Advanced Technology, Department of Atomic Energy, Government of India, Indore 452012 (India); Choudhary, R.J. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India)

    2017-06-15

    Highlights: • Tuning of Schottky barrier height has been achieved by electron beam irradiation at different doses on n-Si wafer prior to the fabrication of Schottky contact. • The XPS analyses have shown irradiation induced defects and the formation of several localized chemical states in Si/SiOx interface that influences the Schottky barrier height. • High ideality factor indicates metal-insulator-semiconductor configuration of the Schottky diode and the inhomogeneous nature of the Schottky barrier height. • The modifications in I–V characteristics have been observed as a function of electron dose. This is caused due to changes in the Schottky diode parameters and different transport mechanisms. - Abstract: The effect of electron beam irradiation (EBI) on Al/n-Si Schottky diode has been studied by I–V characterization at room temperature. The behavior of the metal-semiconductor (MS) interface is analyzed by means of variations in the MS contact parameters such as, Schottky barrier height (Φ{sub B}), ideality factor (n) and series resistance (R{sub s}). These parameters were found to depend on the EBI dose having a fixed incident beam of energy 7.5 MeV. At different doses (500, 1000, 1500 kGy) of EBI, the Schottky contacts were prepared and extracted their contact parameters by applying thermionic emission and Cheung models. Remarkably, the tuning of Φ{sub B} was observed as a function of EBI dose. The improved n with increased Φ{sub B} is seen for all the EBI doses. As a consequence of which the thermionic emission is more favored. However, the competing transport mechanisms such as space charge limited emission, tunneling and tunneling through the trap states were ascribed due to n > 1. The analysis of XPS spectra have shown the presence of native oxide and increased radiation induced defect states. The thickness variation in the MS interface contributing to Schottky contact behavior is discussed. This study explains a new technique to tune

  5. Formation and Evolution of Contact Binaries

    Directory of Open Access Journals (Sweden)

    Peter P. Eggleton

    2012-06-01

    Full Text Available describe a series of processes, including hierarchical fragmentation, gravitational scattering, Kozai cycles within triple systems, tidal friction and magnetic braking, that I believe are responsible for producing the modest but significant fraction of stars that are observed as contact binaries. I also discuss further processes, namely heat transport, mass transport, nuclear evolution, thermal relaxation oscillations, and further magnetic braking with tidal friction, that influence the evolution during contact. The endpoint, for contact, is that the two components merge into a single star, as recently was observed in the remarkable system V1309 Sco. The single star probably throws off some mass and rotates rapidly at first, and then slows by magnetic braking to become a rather inconspicuous but normal dwarf or subgiant. If however the contact binary was part of a triple system originally–as I suggested above was rather likely–then the result could be a widish binary with apparently non-coeval components. There are several such known.

  6. Spatial fluctuations in barrier height at the graphene-silicon carbide Schottky junction.

    Science.gov (United States)

    Rajput, S; Chen, M X; Liu, Y; Li, Y Y; Weinert, M; Li, L

    2013-01-01

    When graphene is interfaced with a semiconductor, a Schottky contact forms with rectifying properties. Graphene, however, is also susceptible to the formation of ripples upon making contact with another material. Here we report intrinsic ripple- and electric field-induced effects at the graphene semiconductor Schottky junction, by comparing chemical vapour-deposited graphene transferred on semiconductor surfaces of opposite polarization-the hydrogen-terminated silicon and carbon faces of hexagonal silicon carbide. Using scanning tunnelling microscopy/spectroscopy and first-principles calculations, we show the formation of a narrow Schottky dipole barrier approximately 10 Å wide, which facilitates the observed effective electric field control of the Schottky barrier height. We further find atomic-scale spatial fluctuations in the Schottky barrier that directly follow the undulation of ripples on both graphene-silicon carbide junctions. These findings reveal fundamental properties of the graphene/semiconductor Schottky junction-a key component of vertical graphene devices that offer functionalities unattainable in planar device architecture.

  7. Formation of a contact binary star system

    International Nuclear Information System (INIS)

    Mullen, E.F.F.

    1974-01-01

    The process of forming a contact binary star system is investigated in the light of current knowledge of the W Ursae Majoris type eclipsing binaries and the current rotational braking theories for contracting stars. A preliminary stage of mass transfer is proposed and studied through the use of a computer program which calculates evolutionary model sequences. The detailed development of both stars is followed in these calculations, and findings regarding the internal structure of the star which is receiving the mass are presented. Relaxation of the mass-gaining star is also studied; for these stars of low mass and essentially zero age, the star eventually settles to a state very similar to a zero-age main sequence star of the new mass. A contact system was formed through these calculations; it exhibits the general properties of a W Ursae Majoris system. The initial masses selected for the calculation were 1.29 M/sub solar mass/ and 0.56 M/sub solar mass/. An initial mass transfer rate of about 10 -10 solar masses per year gradually increased to about 10 -8 solar masses per year. After about 2.5 x 10 7 years, the less massive star filled its Roche lobe and an initial contact system was obtained. The final masses were 1.01359 M/sub solar mass/ and 0.83641 M/sub solar mass/. The internal structure of the secondary component is considerably different from that of a main sequence star of the same mass

  8. The importance of the neutral region resistance for the calculation of the interface state in Pb/p-Si Schottky contacts

    International Nuclear Information System (INIS)

    Aydin, M.E.; Akkilic, K.; Kilicoglu, T.

    2004-01-01

    We have fabricated H-terminated Pb/p-type Si Schottky contacts with and without the native oxide layer to explain the importance of the fact that the neutral region resistance value is considered in calculating the interface state density distribution from the nonideal forward bias current-voltage (I-V) characteristics. The diodes with the native oxide layer (metal-insulating layer-semiconductor (MIS)) showed nonideal I-V behavior with an ideality factor value of 1.310 and the barrier height value of 0.746eV. An ideality factor value of 1.065 and a barrier height value of 0.743eV were obtained for the diodes without the native oxide layer (MS). At the same energy position near the top of the valance band, the calculated interface states density (Nss) values, obtained without taking into account the series resistance of the devices (i.e. without subtracting the voltage drop across the series resistance from the applied voltage values V) is almost one order of magnitude larger than Nss values obtained by taking into account the series resistance

  9. Numerical Study on Open-Circuit Voltage of Single Layer Organic Solar Cells with Schottky Contacts: Effects of Molecular Energy Levels, Temperature and Thickness

    International Nuclear Information System (INIS)

    Rong-Hua, Li; Ying-Quan, Peng; Chao-Zhu, Ma; Run-Sheng, Wang; Hong-Wei, Xie; Ying, Wang; Wei-Min, Meng

    2010-01-01

    We numerically investigate the effects of the exciton generation rate G, temperature T, the active layer thickness d and the position of LUMO level E L related to the cathode work function W c at a given energy gap on the open-circuit voltage V oc of single layer organic solar cells with Schottky contact. It is demonstrated that open-circuit voltage increases concomitantly with the decreasing cathode work function W c for given anode work functions and exciton generation rates. In the case of given cathode and anode work functions, the open-circuit voltage first increases with the exciton generation rate and then reaches a saturation value, which equals to the built-in voltage. Additionally, it is worth noting that a significant improvement to V oc could be made by selecting an organic material which has a relative high LUMO level (low |E L | value). However, V oc decreases as the temperature increases, and the decreasing rate reduces with the enhancement of exciton generation rate. Our study also shows that it is of no benefit to improve the open-circuit voltage by increasing the device thickness because of an enhanced charge recombination in thicker devices. (cross-disciplinary physics and related areas of science and technology)

  10. Influence of impurities on silicide contact formation

    International Nuclear Information System (INIS)

    Kazdaev, Kh.R.; Meermanov, G.B.; Kazdaev, R.Kh.

    2002-01-01

    Research objectives of this work are to investigate the influence of light impurities implantation on peculiarities of the silicides formation in molybdenum monocrystal implanted by silicon, and in molybdenum films sputtered on silicon substrate at subsequent annealing. Implantation of the molybdenum samples was performed with silicon ions (90 keV, 5x10 17 cm -2 ). Phase identification was performed by X ray analysis with photographic method of registration. Analysis of the results has shown the formation of the molybdenum silicide Mo 3 Si at 900 deg. C. To find out the influence of impurities present in the atmosphere (C,N,O) on investigated processes we have applied combined implantation. At first, molybdenum was implanted with ions of the basic component (silicon) and then -- with impurities ions. Acceleration energies (40keV for C, 45 keV for N and 50 keV for O) were chosen to obtain the same distribution profiles for basic and impurities ions. Ion doses were 5x10 17 cm -2 for Si-ions and 5x10 16 cm -2 - for impurities. The most important results are reported here. The first, for all three kinds of impurities the decreased formation temperatures of the phase Mo 3 Si were observed; in the case of C and N it was ∼100 deg. and in the case of nitrogen - ∼200 deg. Further, simultaneously with the Mo 3 Si phase, the appearance of the rich-metal phase Mo 5 Si 3 was registered (not observed in the samples without additional implantation). In case of Mo/Si-structure, the implantation of the impurities (N,O) was performed to create the peak concentration (∼4at/%) located in the middle of the molybdenum film (∼ 150nm) deposited on silicon substrate. Investigation carried out on unimplanted samples showed the formation of the silicide molybdenum MoSi 2 , observed after annealing at temperatures 900/1000 deg. C, higher than values 500-600 deg. C reported in other works. It is discovered that electrical conductivity of Mo 5 Si 3 -films synthesized after impurities

  11. (001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni{sub 2}Si formation and the resulting barrier height changes

    Energy Technology Data Exchange (ETDEWEB)

    Tengeler, Sven, E-mail: stengeler@surface.tu-darmstadt.de [Institute of Material Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Univ. Grenoble Alpes, CNRS, LMGP, F-38000 Grenoble (France); Kaiser, Bernhard [Institute of Material Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany); Chaussende, Didier [Univ. Grenoble Alpes, CNRS, LMGP, F-38000 Grenoble (France); Jaegermann, Wolfram [Institute of Material Science, Technische Universität Darmstadt, 64287 Darmstadt (Germany)

    2017-04-01

    Highlights: • Schottky behavior (Φ{sub B} = 0.41 eV) and Fermi level pining were found pre annealing. • Ni{sub 2}Si formation was confirmed for 5 min at 850 °C. • 3C/Ni{sub 2}Si Fermi level alignment is responsible for ohmic contact behavior. • Wet chemical etching (Si–OH/C–H termination) does not impair Ni{sub 2}Si formation. - Abstract: The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a Ni{sub 2}Si layer and a reversal of the band bending to 0.06 eV downward. Thus explaining the ohmic contact behaviour frequently reported for annealed n-type 3C SiC/Ni contacts.

  12. (001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni_2Si formation and the resulting barrier height changes

    International Nuclear Information System (INIS)

    Tengeler, Sven; Kaiser, Bernhard; Chaussende, Didier; Jaegermann, Wolfram

    2017-01-01

    Highlights: • Schottky behavior (Φ_B = 0.41 eV) and Fermi level pining were found pre annealing. • Ni_2Si formation was confirmed for 5 min at 850 °C. • 3C/Ni_2Si Fermi level alignment is responsible for ohmic contact behavior. • Wet chemical etching (Si–OH/C–H termination) does not impair Ni_2Si formation. - Abstract: The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a Ni_2Si layer and a reversal of the band bending to 0.06 eV downward. Thus explaining the ohmic contact behaviour frequently reported for annealed n-type 3C SiC/Ni contacts.

  13. Thermal annealing behaviour of Pd Schottky contacts on melt-grown single crystal ZnO studied by IV and CV measurements

    International Nuclear Information System (INIS)

    Mtangi, W.; Auret, F.D.; Chawanda, A.; Janse van Rensburg, P.J.; Coelho, S.M.M.; Nel, J.M.; Diale, M.; Schalkwyk, L. van; Nyamhere, C.

    2012-01-01

    Highlights: ► Highly rectifying Pd/ZnO contacts have been fabricated. ► The rectification behaviour decrease with annealing temperature. ► The surface donor concentration increases with increase in annealing temperature. ► The depletion layer width at a specific reverse voltage decreases with increase in annealing temperature. - Abstract: Current–voltage (IV) and capacitance–voltage (CV) measurement techniques have successfully been employed to study the effects of annealing highly rectifying Pd/ZnO Schottky contacts. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at −1.5 V. An average barrier height of (0.77 ± 0.02) eV has been calculated by assuming pure thermionic emission for the as-deposited material and as (0.56 ± 0.03) eV after annealing at 550 °C. The reverse current has been measured as (2.10 ± 0.01) × 10 −10 A for the as-deposited and increases by 5 orders of magnitude after annealing at 550 °C to (1.56 ± 0.01) × 10 −5 A. The depletion layer width measured at −2.0 V has shown a strong dependence on thermal annealing as it decreases from 1.09 μm after annealing at 200 °C to 0.24 μm after annealing at 500 °C, resulting in the modification of the dopant concentration within the depletion region and hence the current flowing through the interface from pure thermionic emission to thermionic field emission with the donor concentrations increasing from 6.90 × 10 15 cm −3 at 200 °C to 6.06 × 10 16 cm −3 after annealing at 550 °C. This increase in the volume concentration has been explained as an effect of a conductive channel that shifts closer to the surface after sample annealing. The series resistance has been observed to decrease with increase in annealing temperature. The Pd contacts have shown high stability up to an annealing temperature of 250 °C as revealed by the IV

  14. Thermal annealing behaviour of Pd Schottky contacts on melt-grown single crystal ZnO studied by IV and CV measurements

    Energy Technology Data Exchange (ETDEWEB)

    Mtangi, W., E-mail: wilbert.mtangi@up.ac.za [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Auret, F.D.; Chawanda, A.; Janse van Rensburg, P.J.; Coelho, S.M.M.; Nel, J.M.; Diale, M.; Schalkwyk, L. van [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Nyamhere, C. [Department of Physics, P.O. Box 77000, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Highly rectifying Pd/ZnO contacts have been fabricated. Black-Right-Pointing-Pointer The rectification behaviour decrease with annealing temperature. Black-Right-Pointing-Pointer The surface donor concentration increases with increase in annealing temperature. Black-Right-Pointing-Pointer The depletion layer width at a specific reverse voltage decreases with increase in annealing temperature. - Abstract: Current-voltage (IV) and capacitance-voltage (CV) measurement techniques have successfully been employed to study the effects of annealing highly rectifying Pd/ZnO Schottky contacts. IV results reveal a decrease in the contact quality with increasing annealing temperature as confirmed by a decrease in the zero bias barrier height and an increase in the reverse current measured at -1.5 V. An average barrier height of (0.77 {+-} 0.02) eV has been calculated by assuming pure thermionic emission for the as-deposited material and as (0.56 {+-} 0.03) eV after annealing at 550 Degree-Sign C. The reverse current has been measured as (2.10 {+-} 0.01) Multiplication-Sign 10{sup -10} A for the as-deposited and increases by 5 orders of magnitude after annealing at 550 Degree-Sign C to (1.56 {+-} 0.01) Multiplication-Sign 10{sup -5} A. The depletion layer width measured at -2.0 V has shown a strong dependence on thermal annealing as it decreases from 1.09 {mu}m after annealing at 200 Degree-Sign C to 0.24 {mu}m after annealing at 500 Degree-Sign C, resulting in the modification of the dopant concentration within the depletion region and hence the current flowing through the interface from pure thermionic emission to thermionic field emission with the donor concentrations increasing from 6.90 Multiplication-Sign 10{sup 15} cm{sup -3} at 200 Degree-Sign C to 6.06 Multiplication-Sign 10{sup 16} cm{sup -3} after annealing at 550 Degree-Sign C. This increase in the volume concentration has been explained as an effect of a conductive channel

  15. Role of photocurrent in low-temperature photoemission studies of Schottky-barrier formation

    International Nuclear Information System (INIS)

    Hecht, M.H.

    1990-01-01

    Photoelectron spectroscopy is frequently used to study band bending in semiconductors due to charge stored in surface or interface states. This paper examines how such experimental results are modified by photovoltages generated within the band-bending region not only by ambient light sources, but by the incident x rays themselves. Recent experiments which have suggested dopant-dependent and reversible temperature-dependent band bending in the initial stages of formation of the metal-GaAs(110) interface are used as an example. It is shown here that the reported dependence derives from a photovoltaic effect

  16. Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts

    International Nuclear Information System (INIS)

    Lü Yuan-Jie; Lin Zhao-Jun; Zhang Yu; Meng Ling-Guo; Cao Zhi-Fang; Luan Chong-Biao; Chen Hong; Wang Zhan-Guo

    2011-01-01

    Ni Schottky contacts on AlGaN/GaN heterostructures were fabricated. Some samples were thermally treated in a furnace with N 2 ambience at 600 °C for different times (0.5 h, 4.5 h, 10.5 h, 18 h, 33 h, 48 h, and 72 h), the others were thermally treated for 0.5 h at different temperatures (500 °C, 600 °C, 700 °C, and 800 °C). With the measured current—voltage (I—V) and capacitance—voltage (C—V) curves and by self-consistently solving Schrodinger's and Poisson's equations, we found that the relative permittivity of the AlGaN barrier layer was related to the piezoelectric and the spontaneous polarization of the AlGaN barrier layer. The relative permittivity was in proportion to the strain of the AlGaN barrier layer. The relative permittivity and the strain reduced with the increased thermal stress time until the AlGaN barrier totally relaxed (after 18 h at 600 °C in the current study), and then the relative permittivity was almost a constant with the increased thermal stress time. When the sample was treated at 800 °C for 0.5 h, the relative permittivity was less than the constant due to the huge diffusion of the contact metal atoms. Considering the relation between the relative permittivity of the AlGaN barrier layer and the converse piezoelectric effect, the conclusion can be made that a moderate thermal stress can restrain the converse piezoelectric effect and can improve the stability of AlGaN/GaN heterostructure devices. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. X-ray photoelectron spectroscopy study of Schottky barrier formation and thermal stability of the LaB6/GaAs(001) c (4 x 4) interface

    International Nuclear Information System (INIS)

    Yokotsuka, T.; Narusawa, T.; Uchida, Y.; Nakashima, H.

    1987-01-01

    Schottky barrier formation and thermal stability of the LaB 6 /GaAs(001) c (4 x 4) interface were investigated by x-ray photoelectron spectroscopy. Results show an excellent thermal stability without any appreciable interface reactions such as interdiffusion. Band bending induced by LaB 6 deposition is found to depend on the evaporation condition. However, the Fermi level pinning position does not change due to heat treatments between 300 and 700 0 C. This indicates that LaB 6 is a promising gate material for GaAs integrated circuits

  18. Effects of fluorine-based plasma treatment and thermal annealing on high-Al content AlGaN Schottky contact

    International Nuclear Information System (INIS)

    Liu Fang; Qin Zhixin

    2016-01-01

    Fluorine plasma treatment was used prior to the Schottky metal deposition on the undoped Al 0.45 Ga 0.55 N, which aimed at the solar-blind wavelength. After fluorine plasma treatment and before depositing the Ni/Au Schottky, the samples were thermal annealed in the N 2 gas at 400 °C. The reverse leakage current density of Al 0.45 Ga 0.55 N Schottky diode was reduced by 2 orders of magnitude at −10 V. The reverse leakage current density was reduced by 3 orders of magnitude after thermal annealing. Further capacitance–frequency analysis revealed that the fluorine-based plasma treatment reduces the surface states of AlGaN by one order of magnitude at different surface state energies. The capacitance–frequency analysis also proved that the concentration of carriers in AlGaN top is reduced through fluorine plasma treatment. (paper)

  19. (001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni2Si formation and the resulting barrier height changes

    Science.gov (United States)

    Tengeler, Sven; Kaiser, Bernhard; Chaussende, Didier; Jaegermann, Wolfram

    2017-04-01

    The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a Ni2Si layer and a reversal of the band bending to 0.06 eV downward. Thus explaining the ohmic contact behaviour frequently reported for annealed n-type 3C SiC/Ni contacts.

  20. Schottky junctions on perovskite single crystals: light-modulated dielectric constant and self-biased photodetection

    KAUST Repository

    Shaikh, Parvez Abdul Ajij; Shi, Dong; Duran Retamal, Jose Ramon; Sheikh, Arif D.; Haque, Mohammed; Kang, Chen-Fang; He, Jr-Hau; Bakr, Osman; Wu, Tao

    2016-01-01

    Schottky junctions formed between semiconductors and metal contacts are ubiquitous in modern electronic and optoelectronic devices. Here we report on the physical properties of Schottky-junctions formed on hybrid perovskite CH3NH3PbBr3 single

  1. Formation of a quasi-neutral region in Schottky diodes based on semi-insulating GaAs and the influence of the compensation mechanism on the particle detector performance

    CERN Document Server

    Rogalla, M

    1999-01-01

    A model for the electric field distribution beneath the Schottky contact in semi-insulating (SI) GaAs particle detectors is developed. The model is based on a field-enhanced electron capture of the EL2-defect. The influence of the compensation mechanism in SI-GaAs on the field distribution, leakage current density and charge collection properties of the detectors will be discussed. The detailed understanding allows then a device optimization. (author)

  2. Spatial inhomogeneity in Schottky barrier height at graphene/MoS2 Schottky junctions

    Science.gov (United States)

    Tomer, D.; Rajput, S.; Li, L.

    2017-04-01

    Transport properties of graphene semiconductor Schottky junctions strongly depend on interfacial inhomogeneities due to the inherent formation of ripples and ridges. Here, chemical vapor deposited graphene is transferred onto multilayer MoS2 to fabricate Schottky junctions. These junctions exhibit rectifying current-voltage behavior with the zero bias Schottky barrier height increases and ideality factor decreases with increasing temperature between 210 and 300 K. Such behavior is attributed to the inhomogeneous interface that arises from graphene ripples and ridges, as revealed by atomic force and scanning tunneling microscopy imaging. Assuming a Gaussian distribution of the barrier height, a mean value of 0.96  ±  0.14 eV is obtained. These findings indicate a direct correlation between temperature dependent Schottky barrier height and spatial inhomogeneity in graphene/2D semiconductor Schottky junctions.

  3. Spatial inhomogeneity in Schottky barrier height at graphene/MoS2 Schottky junctions

    International Nuclear Information System (INIS)

    Tomer, D; Rajput, S; Li, L

    2017-01-01

    Transport properties of graphene semiconductor Schottky junctions strongly depend on interfacial inhomogeneities due to the inherent formation of ripples and ridges. Here, chemical vapor deposited graphene is transferred onto multilayer MoS 2 to fabricate Schottky junctions. These junctions exhibit rectifying current–voltage behavior with the zero bias Schottky barrier height increases and ideality factor decreases with increasing temperature between 210 and 300 K. Such behavior is attributed to the inhomogeneous interface that arises from graphene ripples and ridges, as revealed by atomic force and scanning tunneling microscopy imaging. Assuming a Gaussian distribution of the barrier height, a mean value of 0.96  ±  0.14 eV is obtained. These findings indicate a direct correlation between temperature dependent Schottky barrier height and spatial inhomogeneity in graphene/2D semiconductor Schottky junctions. (paper)

  4. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    International Nuclear Information System (INIS)

    Cheng, Chiu-Ping; Chen, Wan-Sin; Lin, Keng-Yung; Wei, Guo-Jhen; Cheng, Yi-Ting; Lin, Yen-Hsun; Wan, Hsien-Wen; Pi, Tun-Wen; Tung, Raymond T.; Kwo, Jueinai; Hong, Minghwei

    2017-01-01

    Highlights: • The interaction of Ag on a p-type α2 GaAs(001)-2 × 4 surface has been studied. • The dipole formation mechanism of the Ag/GaAs(001)-2 × 4 interface is proposed. • Determination of the SBH prior to metal formation is found. • Inadequacy of the metal-induced gap-state model for explaining the SBH is evident. - Abstract: The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  5. Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Chiu-Ping, E-mail: cpcheng@mail.ncyu.edu.tw [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Chen, Wan-Sin [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Lin, Keng-Yung [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Wei, Guo-Jhen; Cheng, Yi-Ting [Department of Electrophysics, National Chiayi University, Chiayi, 60004, Taiwan, ROC (China); Lin, Yen-Hsun; Wan, Hsien-Wen [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China); Pi, Tun-Wen, E-mail: pi@nsrrc.org.tw [National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan, ROC (China); Tung, Raymond T. [Department of Physics, Brooklyn College, CUNY, NY 11210 (United States); Kwo, Jueinai, E-mail: raynien@phys.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 30013, Taiwan, ROC (China); Hong, Minghwei, E-mail: mhong@phys.ntu.edu.tw [Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei, 10617, Taiwan, ROC (China)

    2017-01-30

    Highlights: • The interaction of Ag on a p-type α2 GaAs(001)-2 × 4 surface has been studied. • The dipole formation mechanism of the Ag/GaAs(001)-2 × 4 interface is proposed. • Determination of the SBH prior to metal formation is found. • Inadequacy of the metal-induced gap-state model for explaining the SBH is evident. - Abstract: The Interface of Ag with p-type α2 GaAs(001)-2 × 4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26 eV; a SBH of 0.38 eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08 eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25 Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.

  6. Electronic Properties of Graphene-PtSe2 Contacts.

    Science.gov (United States)

    Sattar, Shahid; Schwingenschlögl, Udo

    2017-05-10

    In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe 2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe 2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe 2 and a p-type Schottky contact with bilayer PtSe 2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

  7. Electronic Properties of Graphene–PtSe2 Contacts

    KAUST Repository

    Sattar, Shahid

    2017-04-26

    In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

  8. Electronic Properties of Graphene–PtSe2 Contacts

    KAUST Repository

    Sattar, Shahid; Schwingenschlö gl, Udo

    2017-01-01

    In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

  9. Local Schottky contacts of embedded Ag nanoparticles in Al2O3/SiNx:H stacks on Si: a design to enhance field effect passivation of Si junctions.

    Science.gov (United States)

    Ibrahim Elmi, Omar; Cristini-Robbe, Odile; Chen, Minyu; Wei, Bin; Bernard, Rémy; Okada, Etienne; Yarekha, Dmitri A; Ouendi, Saliha; Portier, Xavier; Gourbilleau, Fabrice; Xu, Tao; Stievenard, Didier

    2018-04-26

    This paper describes an original design leading to the field effect passivation of Si n+-p junctions. Ordered Ag nanoparticle (Ag-NP) arrays with optimal size and coverage fabricated by means of nanosphere lithography and thermal evaporation, were embedded in ultrathin-Al2O3/SiNx:H stacks on the top of implanted Si n+-p junctions, to achieve effective surface passivation. One way to characterize surface passivation is to use photocurrent, sensitive to recombination centers. We evidenced an improvement of photocurrent by a factor of 5 with the presence of Ag nanoparticles. Finite-difference time-domain (FDTD) simulations combining with semi-quantitative calculations demonstrated that such gain was mainly due to the enhanced field effect passivation through the depleted region associated with the Ag-NPs/Si Schottky contacts. © 2018 IOP Publishing Ltd.

  10. Improvements in DC Current-Ioltage (I-V) Characteristics of n-GaN Schottky Diode using Metal Overlap Edge Termination

    International Nuclear Information System (INIS)

    Munir, T.; Aziz, A. A.; Abdullah, M. J.; Ain, M. F.

    2010-01-01

    Practical design of GaN Schottky diodes incorporating a field plate necessitates an understanding of how the addition of such plate affects the diode performance. In this paper, we investigated the effects on DC current-voltage (I-V) characteristics of n-GaN schottky diode by incorporating metal overlap edge termination. The thickness of the oxide film varies from 0.001 to 1 micron. Two-dimensional Atlas/Blaze simulations revealed that severe electric field crowding across the metal semiconductor contact will cause reliability concern and limit device breakdown voltage. DC current-voltage (I-V) measurements indicate that the forward currents are higher for thinner oxide film schottky diodes with metal overlap edge termination than those of unterminated schottky diodes. The forward current increased due to formation of an accumulation layer underneath the oxide layer. Extending the field plate to beyond periphery regions of schottky contact does not result in any significant increase in forward current. The new techniques of ramp oxide metal overlap edge termination have been implemented to increase the forward current of n-GaN schottky diode. In reverse bias, breakdown voltage increased with edge termination oxide up to a certain limit of oxide thickness.

  11. Carbon nanotube Schottky diode: an atomic perspective

    International Nuclear Information System (INIS)

    Bai, P; Li, E; Kurniawan, O; Koh, W S; Lam, K T

    2008-01-01

    The electron transport properties of semiconducting carbon nanotube (SCNT) Schottky diodes are investigated with atomic models using density functional theory and the non-equilibrium Green's function method. We model the SCNT Schottky diode as a SCNT embedded in the metal electrode, which resembles the experimental set-up. Our study reveals that the rectification behaviour of the diode is mainly due to the asymmetric electron transmission function distribution in the conduction and valence bands and can be improved by changing metal-SCNT contact geometries. The threshold voltage of the diode depends on the electron Schottky barrier height which can be tuned by altering the diameter of the SCNT. Contrary to the traditional perception, the metal-SCNT contact region exhibits better conductivity than the other parts of the diode

  12. Flexible IGZO Schottky diodes on paper

    Science.gov (United States)

    Kaczmarski, Jakub; Borysiewicz, Michał A.; Piskorski, Krzysztof; Wzorek, Marek; Kozubal, Maciej; Kamińska, Eliana

    2018-01-01

    With the development of novel device applications, e.g. in the field of robust and recyclable paper electronics, came an increased demand for the understanding and control of IGZO Schottky contact properties. In this work, a fabrication and characterization of flexible Ru-Si-O/IGZO Schottky barriers on paper is presented. It is found that an oxygen-rich atomic composition and microstructure of Ru-Si-O containing randomly oriented Ru inclusions with diameter of 3-5 nm embedded in an amorphous SiO2 matrix are effective in preventing interfacial reactions in the contact region, allowing to avoid pre-treatment of the semiconductor surface and fabricate reliable diodes at room temperature characterized by Schottky barrier height and ideality factor equal 0.79 eV and 2.13, respectively.

  13. Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors

    Science.gov (United States)

    Mao, Ling-Feng; Ning, Huansheng; Huo, Zong-Liang; Wang, Jin-Yan

    2015-12-01

    A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs.

  14. Physical Modeling of Gate-Controlled Schottky Barrier Lowering of Metal-Graphene Contacts in Top-Gated Graphene Field-Effect Transistors.

    Science.gov (United States)

    Mao, Ling-Feng; Ning, Huansheng; Huo, Zong-Liang; Wang, Jin-Yan

    2015-12-17

    A new physical model of the gate controlled Schottky barrier height (SBH) lowering in top-gated graphene field-effect transistors (GFETs) under saturation bias condition is proposed based on the energy conservation equation with the balance assumption. The theoretical prediction of the SBH lowering agrees well with the experimental data reported in literatures. The reduction of the SBH increases with the increasing of gate voltage and relative dielectric constant of the gate oxide, while it decreases with the increasing of oxide thickness, channel length and acceptor density. The magnitude of the reduction is slightly enhanced under high drain voltage. Moreover, it is found that the gate oxide materials with large relative dielectric constant (>20) have a significant effect on the gate controlled SBH lowering, implying that the energy relaxation of channel electrons should be taken into account for modeling SBH in GFETs.

  15. Phosphorylcholine impairs susceptibility to biofilm formation of hydrogel contact lenses.

    Science.gov (United States)

    Selan, Laura; Palma, Stefano; Scoarughi, Gian Luca; Papa, Rosanna; Veeh, Richard; Di Clemente, Daniele; Artini, Marco

    2009-01-01

    To compare silicone-hydrogel, poly(2-hydroxyethyl methacrylate) (pHEMA), and phosphorylcholine-coated (PC-C) contact lenses in terms of their susceptibility to biofilm formation by Staphylococcus epidermidis and Pseudomonas aeruginosa. Laboratory investigation. Biofilm formation on colonized test lenses was evaluated with confocal microscopy and in vitro antibiotic susceptibility assays. The results of the latter assays were compared with those performed on planktonic cultures of the same organism. For both microorganisms, sessile colonies on silicone-hydrogel and pHEMA lenses displayed lower antibiotic susceptibility than their planktonic counterparts. In contrast, the susceptibility of cultures growing on PC-C lenses was comparable with that for planktonic cultures. In particular, minimum inhibitory concentration for Tazocin (piperacillin plus tazobactam; Wyeth Pharmaceuticals, Aprilia, Italy; S. epidermidis) and gentamicin (P. aeruginosa) was identical, either in the presence of PC-C support or in planktonic cultures (Tazocin, aeruginosa) was two-fold higher for PC-C lenses (0.4 mug/ml) with respect to planktonic cultures (0.2 mug/ml). Confocal microscopy of lenses colonized for 24 hours with P. aeruginosa green fluorescent protein-expressing cells revealed a sessile colonization on silicone-hydrogel lens and a few isolated bacterial cells scattered widely over the surface of the PC-C lens. An increase in antibiotic susceptibility of bacterial cultures was associated with diminished bacterial adhesion. Our results indicate that PC-C lenses seem to be more resistant than silicone-hydrogel and pHEMA lenses to bacterial adhesion and colonization. This feature may facilitate their disinfection.

  16. The current–voltage and capacitance–voltage characteristics at high temperatures of Au Schottky contact to n-type GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Özerli, Halil; Karteri, İbrahim [Department of Materials Science And Engineering, Kahramanmaraş Sütçü İmam University, 46100 Kahramanmaraş (Turkey); Karataş, Şükrü, E-mail: skaratas@ksu.edu.tr [Department of Materials Science And Engineering, Kahramanmaraş Sütçü İmam University, 46100 Kahramanmaraş (Turkey); Department of Physics, Kahramanmaraş Sütçü İmam University, 46100 Kahramanmaraş (Turkey); Altindal, Şemsettin [Department of Physics, Gazi University, 06100 Ankara (Turkey)

    2014-05-01

    Highlights: • The electronic parameters of the diode under temperature were investigated. • The barrier heights have a Gaussian distribution. • Au/n-GaAs diode exhibits a rectification behavior. - Abstract: We have investigated the temperature-dependent current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Au/n-GaAs Schottky barrier diodes (SBDs) in the temperature range of 280–415 K. The barrier height for the Au/n-type GaAs SBDs from the I–V and C–V characteristics have varied from 0.901 eV to 0.963 eV (I–V) and 1.234 eV to 0.967 eV (C–V), and the ideality factor (n) from 1.45 to 1.69 in the temperature range 280–415 K. The conventional Richardson plots are found to be linear in the temperature range measured. Both the ln(I{sub 0}/T{sup 2}) versus (kT){sup −1} and ln(I{sub 0}/T{sup 2}) versus (nkT){sup −1} plots gives a straight line corresponding to activation energies 0.773 eV and 0.870 eV, respectively. A Φ{sub b0} versus 1/T plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ{sup ¯}{sub b0} = 1.071 eV and σ{sub 0} = 0.094 V for the mean BH and zero-bias standard deviation have been obtained from this plot.

  17. The current–voltage and capacitance–voltage characteristics at high temperatures of Au Schottky contact to n-type GaAs

    International Nuclear Information System (INIS)

    Özerli, Halil; Karteri, İbrahim; Karataş, Şükrü; Altindal, Şemsettin

    2014-01-01

    Highlights: • The electronic parameters of the diode under temperature were investigated. • The barrier heights have a Gaussian distribution. • Au/n-GaAs diode exhibits a rectification behavior. - Abstract: We have investigated the temperature-dependent current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Au/n-GaAs Schottky barrier diodes (SBDs) in the temperature range of 280–415 K. The barrier height for the Au/n-type GaAs SBDs from the I–V and C–V characteristics have varied from 0.901 eV to 0.963 eV (I–V) and 1.234 eV to 0.967 eV (C–V), and the ideality factor (n) from 1.45 to 1.69 in the temperature range 280–415 K. The conventional Richardson plots are found to be linear in the temperature range measured. Both the ln(I 0 /T 2 ) versus (kT) −1 and ln(I 0 /T 2 ) versus (nkT) −1 plots gives a straight line corresponding to activation energies 0.773 eV and 0.870 eV, respectively. A Φ b0 versus 1/T plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ ¯ b0 = 1.071 eV and σ 0 = 0.094 V for the mean BH and zero-bias standard deviation have been obtained from this plot

  18. On the junction physics of Schottky contact of (10, 10) MX{sub 2} (MoS{sub 2}, WS{sub 2}) nanotube and (10, 10) carbon nanotube (CNT): an atomistic study

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Amretashis [Hanse-Wissenschaftskolleg (HWK), Delmenhorst (Germany); Universitaet Bremen, Bremen Center for Computational Materials Science (BCCMS), Bremen (Germany)

    2017-04-15

    Armchair nanotubes of MoS{sub 2} and WS{sub 2} offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX{sub 2} (MoS{sub 2}, WS{sub 2}) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) can be useful for nanoelectronics and photonics applications. In this work, atomistic simulations of MoS{sub 2} NT-CNT and WS{sub 2} NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX{sub 2} NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Green's function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS{sub 2} NT-CNT junction and 1.2526 for the WS{sub 2} NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697-0.664 eV for MoS{sub 2} NT-CNT and 0.669-0.610 eV for the WS{sub 2} NT-CNT, respectively. (orig.)

  19. Photoemission study on the formation of Mo contacts to CuInSe2

    International Nuclear Information System (INIS)

    Nelson, A.J.; Niles, D.W.; Kazmerski, L.L.; Rioux, D.; Patel, R.; Hoechst, H.

    1992-01-01

    Synchrotron radiation soft-x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Mo/CuInSe 2 interface. Mo overlayers were e-beam deposited in steps on single-crystal n-type CuInSe 2 at ambient temperature. Photoemission measurements were acquired after each growth in order to observe changes in the valence-band electronic structure as well as changes in the In 4d, Se 3d, and Mo 4d core lines. Photoemission measurements on the valence-band and core lines were also obtained after annealing. The results were used to correlate the interface chemistry with the electronic structure at this interface and to directly determine the maximum possible Schottky barrier height φ b to be ≤0.2 eV at the Mo/CuInSe 2 junction before annealing, thus showing that this contact is essentially ohmic

  20. Role of Firing Temperature, Sheet Resistance, and Contact Area in Contact Formation on Screen-Printed Metal Contact of Silicon Solar Cell

    Science.gov (United States)

    Ahmad, Samir Mahmmod; Leong, Cheow Siu; Sopian, K.; Zaidi, Saleem H.

    2018-03-01

    Formation of an Ohmic contact requires a suitable firing temperature, appropriate doping profile, and contact dimensions within resolution limits of the screen-printing process. In this study, the role of the peak firing temperature in standard rapid thermal annealing (RTA) six-zone conveyor belt furnace (CBF) and two inexpensive alternate RTA systems [a custom-designed, three-zone, 5″-diameter quartz tube furnace (QTF) and a tabletop, 3″-diameter rapid thermal processing (RTP)] has been investigated. In addition, the role of sheet resistance and contact area in achieving low-resistance ohmic contacts has been examined. Electrical measurements of ohmic contacts between silver paste/ n +-emitter layer with varying sheet resistances and aluminum paste/ p-doped wafer were carried out in transmission line method configuration. Experimental measurements of the contact resistivity ( ρ c) exhibited the lowest values for CBF at 0.14 mΩ cm2 for Ag and 100 mΩ cm2 for Al at a peak firing temperature of 870°C. For the QTF configuration, lowest measured contact resistivities were 3.1 mΩ cm2 for Ag and 74.1 mΩ cm2 for Al at a peak firing temperature of 925°C. Finally, for the RTP configuration, lowest measured contact resistivities were 1.2 mΩ cm2 for Ag and 68.5 mΩ cm2 for Al at a peak firing temperature of 780°C. The measured contact resistivity exhibits strong linear dependence on sheet resistance. The contact resistivity for Ag decreases with contact area, while for Al the opposite behavior is observed.

  1. Contact Burn with Blister Formation in Children Treated with Sennosides.

    Science.gov (United States)

    Cogley, Kimberly; Echevarria, Andrea; Correa, Catalina; De la Torre-Mondragón, Luis

    2017-03-01

    Eight children treated for severe constipation with sennosides unexpectedly developed contact burns with blisters secondary to the use of these laxatives. All patients wore diapers, and the injuries occurred overnight. To avoid this side effect, we recommend that patients treated with sennosides, especially those in diapers, receive the medication at a time that allows for bowel movements to occur during the day and not overnight. © 2017 Wiley Periodicals, Inc.

  2. High-temperature current conduction through three kinds of Schottky diodes

    International Nuclear Information System (INIS)

    Fei, Li; Xiao-Ling, Zhang; Yi, Duan; Xue-Song, Xie; Chang-Zhi, Lü

    2009-01-01

    Fundamentals of the Schottky contacts and the high-temperature current conduction through three kinds of Schottky diodes are studied. N-Si Schottky diodes, GaN Schottky diodes and AlGaN/GaN Schottky diodes are investigated by I–V–T measurements ranging from 300 to 523 K. For these Schottky diodes, a rise in temperature is accompanied with an increase in barrier height and a reduction in ideality factor. Mechanisms are suggested, including thermionic emission, field emission, trap-assisted tunnelling and so on. The most remarkable finding in the present paper is that these three kinds of Schottky diodes are revealed to have different behaviours of high-temperature reverse currents. For the n-Si Schottky diode, a rise in temperature is accompanied by an increase in reverse current. The reverse current of the GaN Schottky diode decreases first and then increases with rising temperature. The AlGaN/GaN Schottky diode has a trend opposite to that of the GaN Schottky diode, and the dominant mechanisms are the effects of the piezoelectric polarization field and variation of two-dimensional electron gas charge density. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  3. Polycrystalline Diamond Schottky Diodes and Their Applications.

    Science.gov (United States)

    Zhao, Ganming

    In this work, four-hot-filament CVD techniques for in situ boron doped diamond synthesis on silicon substrates were extensively studied. A novel tungsten filament shape and arrangement used to obtain large-area, uniform, boron doped polycrystalline diamond thin films. Both the experimental results and radiative heat transfer analysis showed that this technique improved the uniformity of the substrate temperature. XRD, Raman and SEM studies indicate that large area, uniform, high quality polycrystalline diamond films were obtained. Schottky diodes were fabricated by either sputter deposition of silver or thermal evaporation of aluminum or gold, on boron doped diamond thin films. High forward current density and a high forward-to-reverse current ratio were exhibited by silver on diamond Schottky diodes. Schottky barrier heights and the majority carrier concentrations of both aluminum and gold contacted diodes were determined from the C-V measurements. Furthermore, a novel theoretical C-V-f analysis of deep level boron doped diamond Schottky diodes was performed. The analytical results agree well with the experimental results. Compressive stress was found to have a large effect on the forward biased I-V characteristics of the diamond Schottky diodes, whereas the effect on the reverse biased characteristics was relatively small. The stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. This result shows that CVD diamond device has potential for mechanical transducer applications. The quantitative photoresponse characteristics of the diodes were studied in the spectral range of 300 -1050 nm. Semi-transparent gold contacts were used for better photoresponse. Quantum efficiency as high as 50% was obtained at 500 nm, when a reverse bias of over 1 volt was applied. The Schottky barrier heights between either gold or

  4. Calculation of force and time of contact formation at diffusion metal joining

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanov, V E [Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR); Grushevskij, A V [Moskovskij Stankoinstrumental' nyj Inst., Moscow (USSR); Surovtsev, A P

    1989-03-01

    An analytical model of contact for mation at diffusion joining is suggested. It is based on the introduction of a rough surface with roughnesses in the form of absolutely rigid spherical segnunts into a smooth laminar body. Mathematical expressions, permitting to calculate maximum welding force (pressure) providing close contact of the surfaces welded and time for contact formation between rough surfaces joined, are obtained. Divergence of calculational and experimental data does not exceed 20%. It is confirmed that the most intensive formation of joining occurs in the initial period of welding -the stage of formation of a physical contact, when deformation processes proceed in tensively. Finite formation of a strength joint occurs at the stage of diffusion interaction.

  5. Schottky Barriers in Bilayer Phosphorene Transistors.

    Science.gov (United States)

    Pan, Yuanyuan; Dan, Yang; Wang, Yangyang; Ye, Meng; Zhang, Han; Quhe, Ruge; Zhang, Xiuying; Li, Jingzhen; Guo, Wanlin; Yang, Li; Lu, Jing

    2017-04-12

    It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the Fermi-level pinning. Here, we report the first systematical study of bilayer (BL) phosphorene FETs in contact with a series of metals with a wide work function range (Al, Ag, Cu, Au, Cr, Ti, Ni, and Pd) by using both ab initio electronic band calculations and quantum transport simulation (QTS). Different from only one type of Schottky barrier (SB) identified in the ML phosphorene FETs, two types of SBs are identified in BL phosphorene FETs: the vertical SB between the metallized and the intact phosphorene layer, whose height is determined from the energy band analysis (EBA); the lateral SB between the metallized and the channel BL phosphorene, whose height is determined from the QTS. The vertical SBHs show a better consistency with the lateral SBHs of the ML phosphorene FETs from the QTS compared than that of the popular WFA. Therefore, we develop a better and more general method than the WFA to estimate the lateral SBHs of ML semiconductor transistors with strongly interacted electrodes based on the EBA for its BL counterpart. In terms of the QTS, n-type lateral Schottky contacts are formed between BL phosphorene and Cr, Al, and Cu electrodes with electron SBH of 0.27, 0.31, and 0.32 eV, respectively, while p-type lateral Schottky contacts are formed between BL phosphorene and Pd, Ti, Ni, Ag, and Au electrodes with hole SBH of 0.11, 0.18, 0.19, 0.20, and 0.21 eV, respectively. The theoretical polarity and SBHs are in good agreement with available experiments. Our study provides an insight into the BL phosphorene-metal interfaces that are crucial for designing the BL phosphorene device.

  6. High-Performance Schottky Diode Gas Sensor Based on the Heterojunction of Three-Dimensional Nanohybrids of Reduced Graphene Oxide-Vertical ZnO Nanorods on an AlGaN/GaN Layer.

    Science.gov (United States)

    Minh Triet, Nguyen; Thai Duy, Le; Hwang, Byeong-Ung; Hanif, Adeela; Siddiqui, Saqib; Park, Kyung-Ho; Cho, Chu-Young; Lee, Nae-Eung

    2017-09-13

    A Schottky diode based on a heterojunction of three-dimensional (3D) nanohybrid materials, formed by hybridizing reduced graphene oxide (RGO) with epitaxial vertical zinc oxide nanorods (ZnO NRs) and Al 0.27 GaN 0.73 (∼25 nm)/GaN is presented as a new class of high-performance chemical sensors. The RGO nanosheet layer coated on the ZnO NRs enables the formation of a direct Schottky contact with the AlGaN layer. The sensing results of the Schottky diode with respect to NO 2 , SO 2 , and HCHO gases exhibit high sensitivity (0.88-1.88 ppm -1 ), fast response (∼2 min), and good reproducibility down to 120 ppb concentration levels at room temperature. The sensing mechanism of the Schottky diode can be explained by the effective modulation of the reverse saturation current due to the change in thermionic emission carrier transport caused by ultrasensitive changes in the Schottky barrier of a van der Waals heterostructure between RGO and AlGaN layers upon interaction with gas molecules. Advances in the design of a Schottky diode gas sensor based on the heterojunction of high-mobility two-dimensional electron gas channel and highly responsive 3D-engineered sensing nanomaterials have potential not only for the enhancement of sensitivity and selectivity but also for improving operation capability at room temperature.

  7. New GaN Schottky barrier diode employing a trench on AlGaN/GaN heterostructure

    Science.gov (United States)

    Ha, Min-Woo; Lee, Seung-Chul; Choi, Young-Hwan; Kim, Soo-Seong; Yun, Chong-Man; Han, Min-Koo

    2006-10-01

    A new GaN Schottky barrier diode employing a trench structure, which is proposed and fabricated, successfully decreases a forward voltage drop without sacrificing any other electric characteristics. The trench is located in the middle of Schottky contact during a mesa etch. The Schottky metal of Pt/Mo/Ti/Au is e-gun evaporated on the 300 nm-deep trench as well as the surface of the proposed GaN Schottky barrier diode. The trench forms the vertical Au Schottky contact and lateral Pt Schottky contact due to the evaporation sequence of Schottky metal. The forward voltage drops of the proposed diode and conventional one are 0.73 V and 1.25 V respectively because the metal work function (5.15 eV) of the vertical Au Schottky contact is considerably less than that of the lateral Pt Schottky contact (5.65 eV). The proposed diode exhibits the low on-resistance of 1.58 mΩ cm 2 while the conventional one exhibits 8.20 mΩ cm 2 due to the decrease of a forward voltage drop.

  8. Laser-fired contact formation on metallized and passivated silicon wafers under short pulse durations

    Science.gov (United States)

    Raghavan, Ashwin S.

    The objective of this work is to develop a comprehensive understanding of the physical processes governing laser-fired contact (LFC) formation under microsecond pulse durations. Primary emphasis is placed on understanding how processing parameters influence contact morphology, passivation layer quality, alloying of Al and Si, and contact resistance. In addition, the research seeks to develop a quantitative method to accurately predict the contact geometry, thermal cycles, heat and mass transfer phenomena, and the influence of contact pitch distance on substrate temperatures in order to improve the physical understanding of the underlying processes. Finally, the work seeks to predict how geometry for LFCs produced with microsecond pulses will influence fabrication and performance factors, such as the rear side contacting scheme, rear surface series resistance and effective rear surface recombination rates. The characterization of LFC cross-sections reveals that the use of microsecond pulse durations results in the formation of three-dimensional hemispherical or half-ellipsoidal contact geometries. The LFC is heavily alloyed with Al and Si and is composed of a two-phase Al-Si microstructure that grows from the Si wafer during resolidification. As a result of forming a large three-dimensional contact geometry, the total contact resistance is governed by the interfacial contact area between the LFC and the wafer rather than the planar contact area at the original Al-Si interface within an opening in the passivation layer. By forming three-dimensional LFCs, the total contact resistance is significantly reduced in comparison to that predicted for planar contacts. In addition, despite the high energy densities associated with microsecond pulse durations, the passivation layer is well preserved outside of the immediate contact region. Therefore, the use of microsecond pulse durations can be used to improve device performance by leading to lower total contact resistances

  9. Effects of internal friction on contact formation dynamics of polymer chain

    Science.gov (United States)

    Bian, Yukun; Li, Peng; Zhao, Nanrong

    2018-04-01

    A theoretical framework is presented to study the contact formation dynamics of polymer chains, in accompany with an electron-transfer quenching. Based on a non-Markovian Smoluchowski equation supplemented with an exponential sink term, we derive the mean time of contact formation under Wilemski-Fixman approximation. Our particular attentions are paid to the effect of internal friction. We find out that internal friction induces a novel fractional viscosity dependence, which will become more remarkable as internal friction increases. Furthermore, we clarify that internal friction inevitably promotes a diffusion-controlled mechanism by slowing the chain relaxation. Finally, we apply our theory to rationalise the experimental investigation for contact formation of a single-stranded DNA. The theoretical results can reproduce the experimental data very well with quite reasonable estimation for the intrinsic parameters. Such good agreements clearly demonstrate the validity of our theory which has appropriately addressed the very role of internal friction to the relevant dynamics.

  10. SCHOTTKY MEASUREMENTS DURING RHIC 2000

    International Nuclear Information System (INIS)

    CAMERON, P.; CUPOLO, J.; DEGEN, C.; HAMMONS, L.; KESSELMAN, M.; LEE, R.; MEYER, A.; SIKORA, R.

    2001-01-01

    The 2GHz Schottky system was a powerful diagnostic during RHIC 2000 commissioning. A continuous monitor without beam excitation, it provided betatron tune, chromaticity, momentum spread relative emittance, and synchrotron tune. It was particularly useful during transition studies. In addition, a BPM was resonated at 230MHz for Schottky measurements

  11. Graphite based Schottky diodes formed semiconducting substrates

    Science.gov (United States)

    Schumann, Todd; Tongay, Sefaattin; Hebard, Arthur

    2010-03-01

    We demonstrate the formation of semimetal graphite/semiconductor Schottky barriers where the semiconductor is either silicon (Si), gallium arsenide (GaAs) or 4H-silicon carbide (4H-SiC). The fabrication can be as easy as allowing a dab of graphite paint to air dry on any one of the investigated semiconductors. Near room temperature, the forward-bias diode characteristics are well described by thermionic emission, and the extracted barrier heights, which are confirmed by capacitance voltage measurements, roughly follow the Schottky-Mott relation. Since the outermost layer of the graphite electrode is a single graphene sheet, we expect that graphene/semiconductor barriers will manifest similar behavior.

  12. High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes.

    Science.gov (United States)

    Ye, Yu; Dai, Yu; Dai, Lun; Shi, Zujin; Liu, Nan; Wang, Fei; Fu, Lei; Peng, Ruomin; Wen, Xiaonan; Chen, Zhijian; Liu, Zhongfan; Qin, Guogang

    2010-12-01

    High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ∼0.15 V, a short circuit current of ∼275.0 pA, and an energy conversion efficiency of up to ∼1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.

  13. The formation mechanism for printed silver-contacts for silicon solar cells.

    Science.gov (United States)

    Fields, Jeremy D; Ahmad, Md Imteyaz; Pool, Vanessa L; Yu, Jiafan; Van Campen, Douglas G; Parilla, Philip A; Toney, Michael F; van Hest, Maikel F A M

    2016-04-01

    Screen-printing provides an economically attractive means for making Ag electrical contacts to Si solar cells, but the use of Ag substantiates a significant manufacturing cost, and the glass frit used in the paste to enable contact formation contains Pb. To achieve optimal electrical performance and to develop pastes with alternative, abundant and non-toxic materials, a better understanding the contact formation process during firing is required. Here, we use in situ X-ray diffraction during firing to reveal the reaction sequence. The findings suggest that between 500 and 650 °C PbO in the frit etches the SiNx antireflective-coating on the solar cell, exposing the Si surface. Then, above 650 °C, Ag(+) dissolves into the molten glass frit - key for enabling deposition of metallic Ag on the emitter surface and precipitation of Ag nanocrystals within the glass. Ultimately, this work clarifies contact formation mechanisms and suggests approaches for development of inexpensive, nontoxic solar cell contacting pastes.

  14. On the external relations of Purepecha : an investigation into classification, contact and patterns of word formation

    NARCIS (Netherlands)

    Bellamy, K.R.

    2018-01-01

    This thesis considers Purepecha from the perspectives of genealogy and contact, as well as offering insight into word formation processes. The genealogy study re-visits the most prominent classification proposals for Purepecha, concluding on the basis of a quantitative lexical comparison and

  15. Facet formation and ohmic contacts for laser diodes on non- and semipolar GaN

    Energy Technology Data Exchange (ETDEWEB)

    Rass, Jens; Ploch, Simon; Vogt, Patrick [Technische Universitaet Berlin (Germany). Institute of Solid State Physics; Wernicke, Tim; Redaelli, Luca; Einfeldt, Sven [Ferdinand- Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany); Kneissl, Michael [Technische Universitaet Berlin (Germany). Institute of Solid State Physics; Ferdinand- Braun-Institut fuer Hoechstfrequenztechnik, Berlin (Germany)

    2009-07-01

    Group-III-Nitride heterostructures grown on nonpolar and semipolar planes allow the realization of highly efficient devices such as laser diodes and LEDs due to the reduction or elimination of the quantum confined Stark effect. However, the realization of these devices poses a number of challenges, in particular the formation of smooth laser facets and the fabrication of ohmic contacts. In this talk optimized schemes for facet formation and contact resistance reduction for nitride based devices on non- and semipolar planes are presented, and various concepts are discussed. We discuss a laser scribing process that allows the cleaving of facets along the c- and a-plane for devices grown on nonpolar substrates. For semipolar planes there is no low-index cleavage plane in order to form resonators along the projection of the c-axis. Therefore we have investigated etching techniques in order to produce flat facets perpendicular to the plane of growth. For the challenging formation of p-type contacts to GaN we discuss different methods such as chemical treatments, different metallization schemes and capping layers to reduce the contact resistivity.

  16. Tuning the Schottky barrier in the arsenene/graphene van der Waals heterostructures by electric field

    Science.gov (United States)

    Li, Wei; Wang, Tian-Xing; Dai, Xian-Qi; Wang, Xiao-Long; Ma, Ya-Qiang; Chang, Shan-Shan; Tang, Ya-Nan

    2017-04-01

    Using density functional theory calculations, we investigate the electronic properties of arsenene/graphene van der Waals (vdW) heterostructures by applying external electric field perpendicular to the layers. It is demonstrated that weak vdW interactions dominate between arsenene and graphene with their intrinsic electronic properties preserved. We find that an n-type Schottky contact is formed at the arsenene/graphene interface with a Schottky barrier of 0.54 eV. Moreover, the vertical electric field can not only control the Schottky barrier height but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the interface. Tunable p-type doping in graphene is achieved under the negative electric field because electrons can transfer from the Dirac point of graphene to the conduction band of arsenene. The present study would open a new avenue for application of ultrathin arsenene/graphene heterostructures in future nano- and optoelectronics.

  17. Schottky spectra and crystalline beams

    International Nuclear Information System (INIS)

    Pestrikov, D.V.

    1996-01-01

    In this paper we revise the current dependence of the Schottky noise power of a cooled proton beam previously measured at NAP-M. More careful study of experimental data indicates a linear decrease in the inverse Schottky noise power with an increase in the beam intensity (N). The root of this function determines a threshold current which occurs at N = N th ≅1.2 x 10 8 particles. The inspection of measured Schottky spectra shows that this threshold does not correspond to some collective instability of the measured harmonic of the linear beam density. The found value of N th does not depend on the longitudinal beam temperature. For the case of NAP-M lattice, the study of the spectral properties of the Schottky noise in the crystalline string predicts the current dependence of the equilibrium momentum spread of the beam, which qualitatively agrees with that, recalculated from the NAP-M data. (orig.)

  18. Contact in Adoption and Adoptive Identity Formation: The Mediating Role of Family Conversation

    Science.gov (United States)

    Korff, Lynn Von; Grotevant, Harold D.

    2012-01-01

    The present study examined adoption-related family conversation as a mediator of the association between adoptive parents’ facilitation of contact with birth relatives and adolescent adoptive identity formation. The sample consisted of 184 adoptive families. Data were collected in two waves from adoptive mothers and fathers, and adoptees (M = 15.68 years at adolescence; M = 24.95 years at emerging adulthood) using semistructured interviews and questionnaires. Structural equation models showed a good fit to sample data, and analyses supported the hypothesized mediation model. Contact with birth relatives is associated with more frequent adoption-related family conversation, which in turn is associated with the development of adoptive identity. These results highlight the importance of supporting activities such as contact that lead to adoption-related family conversation. PMID:21517175

  19. Contact in adoption and adoptive identity formation: the mediating role of family conversation.

    Science.gov (United States)

    Von Korff, Lynn; Grotevant, Harold D

    2011-06-01

    The present study examined adoption-related family conversation as a mediator of the association between adoptive parents' facilitation of contact with birth relatives and adolescent adoptive identity formation. The sample consisted of 184 adoptive families. Data were collected in two waves from adoptive mothers and fathers, and adoptees (M = 15.68 years at adolescence; M = 24.95 years at emerging adulthood) using semistructured interviews and questionnaires. Structural equation models showed a good fit to sample data, and analyses supported the hypothesized mediation model. Contact with birth relatives is associated with more frequent adoption-related family conversation, which in turn is associated with the development of adoptive identity. These results highlight the importance of supporting activities such as contact that lead to adoption-related family conversation. 2011 APA, all rights reserved

  20. Sub 20 meV Schottky barriers in metal/MoTe2 junctions

    Science.gov (United States)

    Townsend, Nicola J.; Amit, Iddo; Craciun, Monica F.; Russo, Saverio

    2018-04-01

    The newly emerging class of atomically-thin materials has shown a high potential for the realisation of novel electronic and optoelectronic components. Amongst this family, semiconducting transition metal dichalcogenides (TMDCs) are of particular interest. While their band gaps are compatible with those of conventional solid state devices, they present a wide range of exciting new properties that is bound to become a crucial ingredient in the future of electronics. To utilise these properties for the prospect of electronics in general, and long-wavelength-based photodetectors in particular, the Schottky barriers formed upon contact with a metal and the contact resistance that arises at these interfaces have to be measured and controlled. We present experimental evidence for the formation of Schottky barriers as low as 10 meV between MoTe2 and metal electrodes. By varying the electrode work functions, we demonstrate that Fermi level pinning due to metal induced gap states at the interfaces occurs at 0.14 eV above the valence band maximum. In this configuration, thermionic emission is observed for the first time at temperatures between 40 K and 75 K. Finally, we discuss the ability to tune the barrier height using a gate electrode.

  1. Contact in Adoption and Adoptive Identity Formation: The Mediating Role of Family Conversation

    OpenAIRE

    Korff, Lynn Von; Grotevant, Harold D.

    2011-01-01

    The present study examined adoption-related family conversation as a mediator of the association between adoptive parents’ facilitation of contact with birth relatives and adolescent adoptive identity formation. The sample consisted of 184 adoptive families. Data were collected in two waves from adoptive mothers and fathers, and adoptees (M = 15.68 years at adolescence; M = 24.95 years at emerging adulthood) using semistructured interviews and questionnaires. Structural equation models showed...

  2. Electronic parameters of high barrier Au/Rhodamine-101/n-Inp Schottky diode with organic ınterlayer

    International Nuclear Information System (INIS)

    Güllü, Ö.; Aydoğan, S.; Türüt, A.

    2012-01-01

    In this work, we present that Rhodamine-101 (Rh-101) organic molecules can control the electrical characteristics of conventional Au/n-InP metal–semiconductor contacts. An Au/n-InP Schottky junction with Rh-101 interlayer has been formed by using a simple cast process. A potential barrier height as high as 0.88 eV has been achieved for Au/Rh-101/n-InP Schottky diodes, which have good current–voltage (I–V) characteristics. This good performance is attributed to the effect of formation of interfacial organic thin layer between Au and n-InP. By using capacitance-voltage measurement of the Au/Rh-101/n-InP Schottky diode the diffusion potential and the barrier height have been calculated as 0.78 V and 0.88 eV, respectively. From the I–V measurement of the diode under illumination, short circuit current and open circuit voltage have been extracted as 1.70 μA and 240 mV, respectively.

  3. Bacterial and fungal biofilm formation on contact lenses and their susceptibility to lens care solutions

    Directory of Open Access Journals (Sweden)

    Siddharth Kackar

    2017-01-01

    Full Text Available Background: Microbial biofilm formation on contact lenses and lens storage cases may be a risk factor for contact lens-associated corneal infections. Various types of contact lens care solutions are used to reduce microbial growths on lenses. Objectives: The present study aimed at comparing the growths of biofilms on the different contact lenses and lens cases. The study also aimed at determining the effect of lens care solutions and bacteriophage on these biofilms. Materials and Methods: One type of hard lens and two types of soft lenses were used for the study. The organisms used were Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Candida albicans ATCC 60193 and Escherichia coli ATCC 25922. Biofilm production was performed by modified O'Toole and Kolter method and effect of lens cleaning solutions and a crude coliphage on biofilms was also studied. Results were visualised using scanning electron microscopy and quantitated by colony counting method and spectrophotometric measurement of optical density (OD. Statistical analysis was done by SPSS 11.5, Kruskal–Wallis test and Chi-square test. Results: Soft lens cleaning solutions had a significant inhibitory effect (P = 0.020 on biofilm formation on soft lenses and also lens cases (P < 0.001. Soft lens cleaning solution 2 was more efficient than solution 1. However, no such inhibitory effect was observed with regard to hard lens cleaning solution, but for a significant reduction in the OD values (P < 0.001. There was no significant inhibitory effect by bacteriophages. Conclusion: This study showed the importance of selecting the appropriate lens cleaning solution to prevent biofilm production on contact lenses.

  4. Current Transport Properties of Monolayer Graphene/n-Si Schottky Diodes

    Science.gov (United States)

    Pathak, C. S.; Garg, Manjari; Singh, J. P.; Singh, R.

    2018-05-01

    The present work reports on the fabrication and the detailed macroscopic and nanoscale electrical characteristics of monolayer graphene/n-Si Schottky diodes. The temperature dependent electrical transport properties of monolayer graphene/n-Si Schottky diodes were investigated. Nanoscale electrical characterizations were carried out using Kelvin probe force microscopy and conducting atomic force microscopy. Most the values of ideality factor and barrier height are found to be in the range of 2.0–4.4 and 0.50–0.70 eV for monolayer graphene/n-Si nanoscale Schottky contacts. The tunneling of electrons is found to be responsible for the high value of ideality factor for nanoscale Schottky contacts.

  5. Effect of surface microgeometry on the physical contact formation during pressure welding

    Energy Technology Data Exchange (ETDEWEB)

    Karakozov, E S; Grigor' evskii, V I; Orlova, L M

    1976-01-01

    Methods are discussed to analyse both qualitatively and quantitatively the physical contact formation depending upon a microprotrusion height in case of pressure welding. For this purpose VT14 two-phase titanium alloy and in some cases OT4 alloy (for comparison) have been used. Those alloys are of a fine-grained polyhedral structure with a grain size of 8-10 ..mu..m for OT4 alloy and 2-3 ..mu..m for VT14 alloy. The tests have been performed with round specimens with a dia. of 16 mm and a height of 30 mm. The contact surface of one of the samples has been polished, that of the other one had triangular notched microprotrusions with a constant angle ..beta.. equalling 15 deg and a pitch varying in different samples. The specimens have been butt-welded. The surface of the contact formed has been assessed after a break-down of welded joints depending upon the imprint area of the specimen with a polished surface. An assessment of the physical contact surface as well as fractographic and metallographic studies of the break-down surface have been performed with MMI-2, MBS-2 and MIM-8 microscopes. The paper describes results of studies at a welding temperature of 850-950 deg C, with a duration of 20 min specific pressure of 0.2 kgf/sq.mm.

  6. Effect of surface microgeometry on the physical contact formation during pressure welding

    International Nuclear Information System (INIS)

    Karakozov, Eh.S.; Grigor'evskij, V.I.; Orlova, L.M.

    1976-01-01

    Methods are discussed to analyse both qualitatively and quantitatively the physical contact formation depending upon a microprotrusion height in case of pressure welding. For this purpose VT14 two-phase titanium alloy and in some cases OT4 alloy (for comparison) have been used. Those alloys are of a fine-grained polyhedral structure with a grain size of 8-10 μm for OT4 alloy and 2-3 μm for VT14 alloy. The tests have been performed with round specimens with a dia. of 16 mm and a height of 30 mm. The contact surface of one of the samples has been polished, that of the other one had triangular notched microprotrusions with a constant angle β equalling 15 deg and a pitch varying in different samples. The specimens have been butt-welded. The surface of the contact formed has been assessed after a break-down of welded joints depending upon the imprint area of the specimen with a polished surface. An assessment of the physical contact surface as well as fractographic and metallographic studies of the break-down surface have been performed with MMI-2, MBS-2 and MIM-8 microscopes. The paper describes results of studies at a welding temperature of 850-950 deg C, with a duration of 20 min specific pressure of 0.2 kgf/sq.mm

  7. Barrier Height Variation in Ni-Based AlGaN/GaN Schottky Diodes

    NARCIS (Netherlands)

    Hajlasz, Marcin; Donkers, Johan J.T.M.; Pandey, Saurabh; Hurkx, Fred; Hueting, Raymond J.E.; Gravesteijn, Dirk J.

    2017-01-01

    In this paper, we have investigated Ni-based AlGaN/GaN Schottky diodes comprising capping layers with silicon-Technology-compatible metals such as TiN, TiW, TiWN, and combinations thereof. The observed change in Schottky barrier height of a Ni and Ni/TiW/TiWN/TiW contact can be explained by stress

  8. Effect of thermal contact resistances on fast charging of large format lithium ion batteries

    International Nuclear Information System (INIS)

    Ye, Yonghuang; Saw, Lip Huat; Shi, Yixiang; Somasundaram, Karthik; Tay, Andrew A.O.

    2014-01-01

    Highlights: • The effect of thermal contact resistance on thermal performance of large format lithium ion batteries. • The effect of temperature gradient on electrochemical performance of large format batteries during fast charging. • The thermal performance of lithium ion battery utilizing pulse charging protocol. • Suggestions on battery geometry design optimization to improve thermal performance. - Abstract: A two dimensional electrochemical thermal model is developed on the cross-plane of a laminate stack plate pouch lithium ion battery to study the thermal performance of large format batteries. The effect of thermal contact resistance is taken into consideration, and is found to greatly increase the maximum temperature and temperature gradient of the battery. The resulting large temperature gradient would induce in-cell non-uniformity of charging-discharging current and state of health. Simply increasing the cooling intensity is inadequate to reduce the maximum temperature and narrow down the temperature difference due to the poor cross-plane thermal conductivity. Pulse charging protocol does not help to mitigate the temperature difference on the bias of same total charging time, because of larger time-averaged heat generation rate than constant current charging. Suggestions on battery geometry optimizations for both prismatic/pouch battery and cylindrical battery are proposed to reduce the maximum temperature and mitigate the temperature gradient within the lithium ion battery

  9. Thermal Diffusion Processes in Metal-Tip-Surface Interactions: Contact Formation and Adatom Mobility

    DEFF Research Database (Denmark)

    Sørensen, Mads Reinholdt; Jacobsen, Karsten Wedel; Jonsson, Hannes

    1996-01-01

    and the surface can occur by a sequence of atomic hop and exchange processes which become active on a millisecond time scale when the tip is about 3-5 Angstrom from the surface. Adatoms on the surface are stabilized by the presence of the tip and energy barriers for diffusion processes in the region under the tip......We have carried out computer simulations to identify and characterize various thermally activated atomic scale processes that can play an important role in room temperature experiments where a metal tip is brought close to a metal surface. We find that contact formation between the tip...

  10. Temperature dependent current transport of Pd/ZnO nanowire Schottky diodes

    Science.gov (United States)

    Gayen, R. N.; Bhattacharyya, S. R.; Jana, P.

    2014-09-01

    Zinc oxide (ZnO) nanowire based Schottky barrier diodes are fabricated by depositing Pd metal contact on top of vertically well-aligned ZnO nanowire arrays. A vertical array of ZnO nanowires on indium tin oxide (ITO) coated glass substrates is synthesized by hybrid wet chemical route. Scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) measurement confirm the formation of stoichiometric well-aligned hexagonal (h-ZnO) nanowire arrays with wurtzite structure. Temperature dependent current-voltage (I-V) measurements on palladium-ZnO (Pd/ZnO) nanowire Schottky junctions in the temperature range 303-383 K exhibit excellent rectifying character. From these nonlinear I-V plots, different electrical parameters of diode-like reverse saturation current, barrier height and ideality factor are determined as a function of temperature assuming pure thermionic emission model. The ideality factor is found to decrease while the barrier height increases with the increase in temperature. The series resistance values calculated from Cheung’s functions also show temperature dependency. Such behavior can be attributed to the presence of defects that traps carriers, and barrier height inhomogeneity at the interface of the barrier junction. After barrier height inhomogeneity correction, considering a Gaussian distributed barrier height fluctuation across the Pd/ZnO interface, the estimated values of mean barrier height and modified Richardson constant are more closely matched to the theoretically predicted value for Pd/ZnO Schottky barrier diodes. The variation of density of interface states as a function of interface state energy is also calculated.

  11. The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, I.H.; Davids, P.S.; Smith, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico87545 (United States); Barashkov, N.N.; Ferraris, J.P. [The University of Texas at Dallas, Richardson, Texas75083 (United States)

    1998-04-01

    We present device model calculations of the current{endash}voltage (I{endash}V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I{endash}V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I{endash}V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited. {copyright} {ital 1998 American Institute of Physics.}

  12. The Schottky energy barrier dependence of charge injection in organic light-emitting diodes

    Science.gov (United States)

    Campbell, I. H.; Davids, P. S.; Smith, D. L.; Barashkov, N. N.; Ferraris, J. P.

    1998-04-01

    We present device model calculations of the current-voltage (I-V) characteristics of organic diodes and compare them with measurements of structures fabricated using MEH-PPV. The structures are designed so that all of the current is injected from one contact. The I-V characteristics are considered as a function of the Schottky energy barrier to charge injection from the contact. Experimentally, the Schottky barrier is varied from essentially zero to more than 1 eV by using different metal contacts. A consistent description of the device I-V characteristics is obtained as the Schottky barrier is varied from small values, less than about 0.4 eV, where the current flow is space-charge limited to larger values where it is contact limited.

  13. Biofilm formation on materials into contact with water: hygienic and technical aspects

    International Nuclear Information System (INIS)

    Bonadonna, L; Memoli, G.; Chiaretti, G.

    2008-01-01

    Biofilm formation in man-made water systems has a hygienic concern when it is considered that the continuous detachment of this structure in the water flow, condition representing a potential source of contamination of plumbing and a risk for health, allows also pathogen microorganisms to reach consumers. The trend of biofilm formation was evaluated through series of microbiological analyses performed, under controlled conditions, on pipes made of materials that come into contact with drinking water according to the Decree of Ministry of Health n. 174. The investigation showed that, respect to the other materials, the reticulated polyethylene allows to sustain higher microorganisms concentrations. This characteristic was also observed in biofilms developed in condition of water stagnation compared to biofilm risen on surfaces of pipes under water flow [it

  14. Development of Schottky diode detectors at Research Institute of Electrical Communication, Tohoku University

    International Nuclear Information System (INIS)

    Mizuno, K.; Ono, S.; Suzuki, T.; Daiku, Y.

    1982-01-01

    Schottky diode detectors are widely used as fast, sensitive submillimeter detectors in plasma physics, radio astronomy, frequency standards and so on. In this paper, the research on submillimeter Schottky diodes at Tohoku University is described. A brief description is given on the theoretical examination of diode parameters for video detection in design and on the fabrication of n/n + GaAs Schottky diode chips. Antennas for Schottky barrier diodes are discussed. Three types of antenna structures have been proposed, and used for whisker-contacted Schottky diodes so far. These are compared with each other for their frequency response and gain. The bicone type antenna is promising because of its larger frequency response, but the optimum design for this type of antenna has not yet sufficiently been obtained. As the application of Schottky barrier diodes, the intensity modulation of submillimeter laser and a quasi-optically coupled harmonic mixer have been studied. The modulation degree of about 4 % for HCN laser output has been so far obtained at the maximum modulation frequency of 2 GHz. Since 1976, a quasi-optically coupled harmonic mixer has been used with a Schottky diode in harmonic mixing between microwaves, millimeter waves, and submillimeter waves. (Wakatsuki, Y.)

  15. Fluctuations in Schottky barrier heights

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1984-01-01

    A double Schottky barrier is often formed at the grain boundary in polycrystalline semiconductors. The barrier height is shown to fluctuate in value due to the random nature of the impurity positions. The magnitude of the fluctuations is 0.1 eV, and the fluctuations cause the barrier height measured by capacitance to differ from the one measured by electrical conductivity

  16. The properties of transparent TiO2 films for Schottky photodetector

    Directory of Open Access Journals (Sweden)

    Sung-Ho Park

    2017-08-01

    Full Text Available In this data, the properties of transparent TiO2 film for Schottky photodetector are presented for the research article, entitled as “High-performing transparent photodetectors based on Schottky contacts” (Patel et al., 2017 [1]. The transparent photoelectric device was demonstrated by using various Schottky metals, such as Cu, Mo and Ni. This article mainly shows the optical transmittance of the Ni-transparent Schottky photodetector, analyzed by the energy dispersive spectroscopy and interfacial TEM images for transparency to observe the interface between NiO and TiO2 film. The observation and analyses clearly show that no pinhole formation in the TiO2 film by Ni diffusion. The rapid thermal process is an effective way to form the quality TiO2 film formation without degradation, such as pinholes (Qiu et al., 2015 [2]. This thermal process may apply to form functional metal oxide layers for solar cells and photodetectors.

  17. Contact Line Instability Caused by Air Rim Formation under Nonsplashing Droplets.

    Science.gov (United States)

    Pack, Min; Kaneelil, Paul; Kim, Hyoungsoo; Sun, Ying

    2018-05-01

    Drop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray-coating technologies. The recent discovery of the role of air entrainment between the droplet and the impacting surface has produced numerous works, uncovering the unique physics that correlates the air film dynamics with the drop impact outcomes. In this study, we focus on the post-failure air entrainment dynamics for We numbers well below the splash threshold under different ambient pressures and elucidate the interfacial instabilities formed by air entrainment at the wetting front of impacting droplets on perfectly smooth, viscous films of constant thickness. A high-speed total internal reflection microscopy technique accounting for the Fresnel reflection at the drop-air interface allows for in situ measurements of an entrained air rim at the wetting front. The presence of an air rim is found to be a prerequisite to the interfacial instability which is formed when the capillary pressure in the vicinity of the contact line can no longer balance the increasing gas pressure near the wetting front. A critical capillary number for the air rim formation is experimentally identified above which the wetting front becomes unstable where this critical capillary number inversely scales with the ambient pressure. The contact line instabilities at relatively low We numbers ( We ∼ O(10)) observed in this study provide insight into the conventional understanding of hydrodynamic instabilities under drop impact which usually require We ≫ 10.

  18. Investigation of biofilm formation on contact eye lenses caused by methicillin resistant Staphylococcus aureus.

    Science.gov (United States)

    Khalil, M A; Sonbol, F I

    2014-01-01

    The objective was to investigate the biofilm-forming capacity of methicillin resistant Staphylococcus aureus (MRSA) isolated from eye lenses of infected patients. A total of 32 MRSA isolated from contact lenses of patients with ocular infections were screened for their biofilm-forming capacity using tube method (TM), Congo red agar (CRA), and microtiter plate (MtP) methods. The effect of some stress factor on the biofilm formation was studied. The biofilm-forming related genes, icaA, icaD and 10 microbial surface components that recognize adhesive matrix molecule (MSCRAMM), of the selected MRSA were also detected using polymerase chain reaction. Of 32 MRSA isolates, 34.37%, 59.37%, and 81.25% showed positive results using CRA, TM or MtP, respectively. Biofilm production was found to be reduced in the presence of ethanol or ethylenediaminetetraacetic acid and at extreme pH values. On the other hand, glucose or heparin leads to a concentration dependent increase of biofilm production by the isolates. The selected biofilm producing MRSA isolate was found to harbor the icaA, icaD and up to nine of 10 tested MSCRAMM genes, whereas the selected non biofilm producing MRSA isolate did not carry any of the tested genes. The MtP method was found to be the most effective phenotypic screening method for detection of biofilm formation by MRSA. Furthermore, the molecular approach should be taken into consideration for the rapid and correct diagnosis of virulent bacteria associated with contact eye lenses.

  19. Metal-oxide-semiconductor capacitors and Schottky diodes studied with scanning microwave microscopy at 18 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Kasper, M. [Christian Doppler Laboratory for Nanoscale Methods in Biophysics, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz (Austria); Gramse, G. [Biophysics Institute, Johannes Kepler University of Linz, Gruberstrasse 40, 4020 Linz (Austria); Hoffmann, J. [METAS, National Metrology Institute of Switzerland, Lindenweg 50, 3003 Bern-Wabern (Switzerland); Gaquiere, C. [MC2 technologies, 5 rue du Colibri, 59650 Villeneuve D' ascq (France); Feger, R.; Stelzer, A. [Institute for Communications Engineering and RF-Systems, Johannes Kepler University, Altenberger Str. 69, 4040 Linz (Austria); Smoliner, J. [Vienna University of Technology, Institute for Solid State Electronics, Floragasse 7, 1040 Vienna (Austria); Kienberger, F., E-mail: ferry-kienberger@keysight.com [Keysight Technologies Austria, Measurement Research Lab, Gruberstrasse 40, 4020 Linz (Austria)

    2014-11-14

    We measured the DC and RF impedance characteristics of micrometric metal-oxide-semiconductor (MOS) capacitors and Schottky diodes using scanning microwave microscopy (SMM). The SMM consisting of an atomic force microscopy (AFM) interfaced with a vector network analyser (VNA) was used to measure the reflection S11 coefficient of the metallic MOS and Schottky contact pads at 18 GHz as a function of the tip bias voltage. By controlling the SMM biasing conditions, the AFM tip was used to bias the Schottky contacts between reverse and forward mode. In reverse bias direction, the Schottky contacts showed mostly a change in the imaginary part of the admittance while in forward bias direction the change was mostly in the real part of the admittance. Reference MOS capacitors which are next to the Schottky diodes on the same sample were used to calibrate the SMM S11 data and convert it into capacitance values. Calibrated capacitance between 1–10 fF and 1/C{sup 2} spectroscopy curves were acquired on the different Schottky diodes as a function of the DC bias voltage following a linear behavior. Additionally, measurements were done directly with the AFM-tip in contact with the silicon substrate forming a nanoscale Schottky contact. Similar capacitance-voltage curves were obtained but with smaller values (30–300 aF) due to the corresponding smaller AFM-tip diameter. Calibrated capacitance images of both the MOS and Schottky contacts were acquired with nanoscale resolution at different tip-bias voltages.

  20. Rapakivi texture formation via disequilibrium melting in a contact partial melt zone, Antarctica

    Science.gov (United States)

    Currier, R. M.

    2017-12-01

    In the McMurdo Dry Valleys of Antarctica, a Jurassic aged dolerite sill induced partial melting of granite in the shallow crust. The melt zone can be traced in full, from high degrees of melting (>60%) along the dolerite contact, to no apparent signs of melting, 10s of meters above the contact. Within this melt zone, the well-known rapakivi texture is found, arrested in various stages of development. High above the contact, and at low degrees of melting, K-feldspar crystals are slightly rounded and unmantled. In the lower half of the melt zone, mantles of cellular textured plagioclase appear on K-feldspar, and thicken towards the contact heat source. At the highest degrees of melting, cellular-textured plagioclase completely replaces restitic K-feldspar. Because of the complete exposure and intact context, the leading models of rapakivi texture formation can be tested against this system. The previously proposed mechanisms of subisothermal decompression, magma-mixing, and hydrothermal exsolution all fail to adequately describe rapakivi generation in this melt zone. Preferred here is a closed system model that invokes the production of a heterogeneous, disequilibrium melt through rapid heating, followed by calcium and sodium rich melt reacting in a peritectic fashion with restitic K-feldspar crystals. This peritectic reaction results in the production of plagioclase of andesine-oligoclase composition—which is consistent with not just mantles in the melt zone, but globally as well. The thickness of the mantle is diffusion limited, and thus a measure of the diffusive length scale of sodium and calcium over the time scale of melting. Thermal modeling provides a time scale of melting that is consistent with the thickness of observed mantles. Lastly, the distribution of mantled feldspars is highly ordered in this melt zone, but if it were mobilized and homogenized—mixing together cellular plagioclase, mantled feldspars, and unmantled feldspars—the result would be

  1. Very low Schottky barrier height at carbon nanotube and silicon carbide interface

    Energy Technology Data Exchange (ETDEWEB)

    Inaba, Masafumi, E-mail: inaba-ma@ruri.waseda.jp; Suzuki, Kazuma; Shibuya, Megumi; Lee, Chih-Yu [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Masuda, Yoshiho; Tomatsu, Naoya; Norimatsu, Wataru; Kusunoki, Michiko [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603 (Japan); Hiraiwa, Atsushi [Institute for Nanoscience and Nanotechnology, Waseda University, 513 Waseda-tsurumaki, Shinjuku, Tokyo 162-0041 (Japan); Kawarada, Hiroshi [Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Institute for Nanoscience and Nanotechnology, Waseda University, 513 Waseda-tsurumaki, Shinjuku, Tokyo 162-0041 (Japan); The Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, 2-8-26 Nishiwaseda, Shinjuku, Tokyo 169-0051 (Japan)

    2015-03-23

    Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3 × 10{sup 18 }cm{sup −3} was estimated to be ∼1.3 × 10{sup −4} Ω cm{sup 2} and the Schottky barrier height of the CNT/SiC contact was in the range of 0.40–0.45 eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices.

  2. Monte Carlo modelling of Schottky diode for rectenna simulation

    Science.gov (United States)

    Bernuchon, E.; Aniel, F.; Zerounian, N.; Grimault-Jacquin, A. S.

    2017-09-01

    Before designing a detector circuit, the electrical parameters extraction of the Schottky diode is a critical step. This article is based on a Monte-Carlo (MC) solver of the Boltzmann Transport Equation (BTE) including different transport mechanisms at the metal-semiconductor contact such as image force effect or tunneling. The weight of tunneling and thermionic current is quantified according to different degrees of tunneling modelling. The I-V characteristic highlights the dependence of the ideality factor and the current saturation with bias. Harmonic Balance (HB) simulation on a rectifier circuit within Advanced Design System (ADS) software shows that considering non-linear ideality factor and saturation current for the electrical model of the Schottky diode does not seem essential. Indeed, bias independent values extracted in forward regime on I-V curve are sufficient. However, the non-linear series resistance extracted from a small signal analysis (SSA) strongly influences the conversion efficiency at low input powers.

  3. Research of formation of deposits in technological devices and corrosion of contact devices from stainless steel

    Directory of Open Access Journals (Sweden)

    KATAMANOV Vladimir Leonidovich

    2017-11-01

    Full Text Available The paper shows that for majority of technological plants used to process hydrocarbon raw materials when operating a problem of formation of deposits in still-head pipes after the rectifying and stabilization columns, furnaces and other technology devices in oil processing is still of great importance. The structure of still-head deposits of furnace coils and rectifying columns has been studied by the example of small technological plant (STP of JSC Kondensat (Aksay, the Republic of Kazakhstan. It was determined that key components of these deposits are sulfides of iron and copper as well as elementary sulfur. It is shown that the surface of contact devices of STP – grids made of stainless steel of brand 12X18H10T, is substantially subject to corrosion. These samples are the structures which are still keeping geometry of initial grids, but lost their functional properties and characteristics. When mechanical influence is applied such samples easily transform into gray high-disperse powder. During operation period of STP various corrosion inhibitors and deemulgators (for example, TAL-25-13-R have been tested. At the same time practically all tested brands of corrosion inhibitors couldn't decrease corrosion of stainless steel and formation of firm deposits in still-head pipes of technological devices. The existing corrosion inhibitors create protection on the boundary of phases metallic surface – liquid, but they aren't efficient on the boundary of phases metallic surface – liquid – steam-gas phase (at the temperature of 150–250оC. The authors propose the mechanism of formation of these compounds based on result of corrosion of metal gauzes made of stainless steels brand X6CrNiTi18-10in the presence of sulphurous compounds.An active method of corrosion prevention is recommended to apply. The method is based on creation of nanodimensional anticorrosion coatings from binary compounds (such as titanium nitride or pure metals (Ni, Cr, Ti

  4. Schottky signal analysis: tune and chromaticity computation

    CERN Document Server

    Chanon, Ondine

    2016-01-01

    Schottky monitors are used to determine important beam parameters in a non-destructive way. The Schottky signal is due to the internal statistical fluctuations of the particles inside the beam. In this report, after explaining the different components of a Schottky signal, an algorithm to compute the betatron tune is presented, followed by some ideas to compute machine chromaticity. The tests have been performed with offline and/or online LHC data.

  5. Longitudinal Schottky noise of intense beam

    International Nuclear Information System (INIS)

    Pestrikov, D.V.

    1990-01-01

    Some phenomena, which can be observed in the longitudinal Schottky spectra in storage ring with electron cooling as well as some technical details, which can be useful for the models of fitting are reviewed. Results shows that both the spectra and the power of the Schottky noise of the coasting beam are very sensitive to collective behaviour of the beam. This can be used for fitting of Schottky noise measurements and recalculation of beam parameters, parameters of cooling device. 9 refs.; 4 figs

  6. Conduction mechanism in electron beam irradiated Al/n-Si Schottky diode

    International Nuclear Information System (INIS)

    Vali, Indudhar Panduranga; Shetty, Pramoda Kumara; Mahesha, M.G.; Petwal, V.C.

    2016-01-01

    In the high energy physics experiments, silicon based diodes are used to fabricate radiation detector to detect the charged particles. The Schottky barrier diodes have been studied extensively to understand the behavior of metal semiconductor interface, since such interfaces have been utilized as typical contacts in silicon devices. Because of surface states, interfacial layer, microscopic clusters of metal-semiconductor phases and other effects, it is difficult to fabricate junctions with barriers near the ideal values predicted from the work functions of the two isolated materials, therefore measured barrier heights are used in the device design. In this work, the Al/n-Si Schottky contacts are employed to study the diode parameters (Schottky barrier height and ideality factor), where the Schottky contacts were fabricated on electron beam irradiated silicon wafers. The interface behavior between electron irradiated Si wafer and post metal deposition is so far not reported. This method could be an alternative way to tailor the Schottky barrier height (SBH) without subjecting semiconductor sample to pre chemical and/or post heat treatments during fabrication

  7. Research on the electrical characteristics of the Pt/CdS Schottky diode

    Science.gov (United States)

    Ding, Jia-xin; Zhang, Xiang-feng; Yao, Guansheng

    2013-08-01

    With the development of technology, the demand for semiconductor ultraviolet detector is increasing day by day. Compared with the traditional infrared detector in missile guidance, ultraviolet/infrared dual-color detection can significantly improve the anti-interference ability of the missile. According to the need of missile guidance and other areas of the application of ultraviolet detector, the paper introduces a manufacture of the CdS Schottky barrier ultraviolet detector. By using the radio frequency magnetron sputtering technology, a Pt thin film layer is sputtered on CdS basement to form a Schottky contact firstly. Then the indium ohmic contact electrode is fabricated by thermal evaporation method, and eventually a Pt/CdS/In Schottky diode is formed. The I-V characteristic of the device was tested at room temperature, its zero bias current and open circuit voltage is -0.578nA and 130mV, respectively. Test results show that the the Schottky contact has been formed between Pt and CdS. The device has good rectifying characteristics. According to the thermionic emission theory, the I-V curve fitting analysis of the device was studied under the condition of small voltage. The ideality factor and Schottky barrier height is 1.89 and 0.61eV, respectively. The normalized spectral responsivity at zero bias has been tested. The device has peak responsivity at 500nm, and it cutoff at 510nm.

  8. Tuning the electronic properties and Schottky barrier height of the vertical graphene/MoS2 heterostructure by an electric gating

    Science.gov (United States)

    Nguyen, Chuong V.

    2018-04-01

    In this paper, the electronic properties and Schottky contact in graphene/MoS2 (G/MoS2) heterostructure under an applied electric field are investigated by means of the density functional theory. It can be seen that the electronic properties of the G/MoS2 heterostructure are preserved upon contacting owing to the weak van der Waals interaction. We found that the n-type Schottky contact is formed in the G/MoS2 heterostructure with the Schottky barrier height of 0.49 eV. Furthermore, both Schottky contact and Schottky barrier height in the G/MoS2 heterostructure could be controlled by the applied electric field. If a positive electric field of 4 V/nm is applied to the system, a transformation from the n-type Schottky contact to the p-type one was observed, whereas the system keeps an n-type Schottky contact when a negative electric field is applied. Our results may provide helpful information to design, fabricate, and understand the physics mechanism in the graphene-based two-dimensional van der Waals heterostructures like as G/MoS2 heterostructure.

  9. Tuning the Schottky rectification in graphene-hexagonal boron nitride-molybdenum disulfide heterostructure.

    Science.gov (United States)

    Liu, Biao; Zhao, Yu-Qing; Yu, Zhuo-Liang; Wang, Lin-Zhi; Cai, Meng-Qiu

    2018-03-01

    It was still a great challenge to design high performance of rectification characteristic for the rectifier diode. Lately, a new approach was proposed experimentally to tune the Schottky barrier height (SBH) by inserting an ultrathin insulated tunneling layer to form metal-insulator-semiconductor (MIS) heterostructures. However, the electronic properties touching off the high performance of these heterostructures and the possibility of designing more efficient applications for the rectifier diode were not presently clear. In this paper, the structural, electronic and interfacial properties of the novel MIS diode with the graphene/hexagonal boron nitride/monolayer molybdenum disulfide (GBM) heterostructure had been investigated by first-principle calculations. The calculated results showed that the intrinsic properties of graphene and MoS 2 were preserved due to the weak van der Waals contact. The height of interfacial Schottky barrier can be tuned by the different thickness of hBN layers. In addition, the GBM Schottky diode showed more excellent rectification characteristic than that of GM Schottky diode due to the interfacial band bending caused by the epitaxial electric field. Based on the electronic band structure, we analyzed the relationship between the electronic structure and the nature of the Schottky rectifier, and revealed the potential of utilizing GBM Schottky diode for the higher rectification characteristic devices. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Electrical transport measurements and degradation of graphene/n-Si Schottky junction diodes

    International Nuclear Information System (INIS)

    Park, No-Won; Lee, Won-Yong; Lee, Sang-Kwon; Koh, Jung-Hyuk; Kim, Dong-Joo; Kim, Gil-Sung; Hyung, Jung-Hwan; Hong, Chang-Hee; Kim, Keun-Soo

    2015-01-01

    We report on the electrical properties, such as the ideality factors and Schottky barrier heights, that were obtained by using current density - voltage (J - V ) and capacitance - voltage (C - V ) characteristics. To fabricate circularly- and locally-contacted Au/Gr/n-Si Schottky diode, we deposited graphene through the chemical vapor deposition (CVD) growth technique, and we employed reactive ion etching to reduce the leakage current of the Schottky diodes. The average values of the barrier heights and the ideality factors from the J .V characteristics were determined to be ∼0.79 ± 0.01 eV and ∼1.80 ± 0.01, respectively. The Schottky barrier height and the doping concentration from the C - V measurements were ∼0.85 eV and ∼1.76 x 10 15 cm -3 , respectively. From the J - V characteristics, we obtained a relatively low reverse leakage current of ∼2.56 x 10 -6 mA/cm -2 at -2 V, which implies a well-defined rectifying behavior. Finally, we found that the Gr/n-Si Schottky diodes that were exposed to ambient conditions for 7 days exhibited a ∼3.2-fold higher sheet resistance compared with the as-fabricated Gr/n-Si diodes, implying a considerable electrical degradation of the Gr/n-Si Schottky diodes.

  11. High Voltage GaN Schottky Rectifiers

    Energy Technology Data Exchange (ETDEWEB)

    CAO,X.A.; CHO,H.; CHU,S.N.G.; CHUO,C.-C.; CHYI,J.-I.; DANG,G.T.; HAN,JUNG; LEE,C.-M.; PEARTON,S.J.; REN,F.; WILSON,R.G.; ZHANG,A.P.

    1999-10-25

    Mesa and planar GaN Schottky diode rectifiers with reverse breakdown voltages (V{sub RB}) up to 550V and >2000V, respectively, have been fabricated. The on-state resistance, R{sub ON}, was 6m{Omega}{center_dot} cm{sup 2} and 0.8{Omega}cm{sup 2}, respectively, producing figure-of-merit values for (V{sub RB}){sup 2}/R{sub ON} in the range 5-48 MW{center_dot}cm{sup -2}. At low biases the reverse leakage current was proportional to the size of the rectifying contact perimeter, while at high biases the current was proportional to the area of this contact. These results suggest that at low reverse biases, the leakage is dominated by the surface component, while at higher biases the bulk component dominates. On-state voltages were 3.5V for the 550V diodes and {ge}15 for the 2kV diodes. Reverse recovery times were <0.2{micro}sec for devices switched from a forward current density of {approx}500A{center_dot}cm{sup -2} to a reverse bias of 100V.

  12. Electrical and structural properties of a stacked metal layer contact to n-InP

    International Nuclear Information System (INIS)

    Huang, Wen-Chang; Horng, Chia-Tsung

    2011-01-01

    In this study, we found that the double metal contact structure in Pt/Al/n-InP diodes provides better rectification characteristics than conventional single-metal/n-InP Schottky diodes. The effective barrier height was measured to be 0.67 eV for a 400 deg. C-annealed Pt/Al/n-InP diode sample. The increase in the barrier height is attributed to the formation of Al 2 O 3 at the metal/n-InP contact interface during thermal annealing. The formation of the phase Al 2 O 3 phase was monitored by X-ray diffraction (XRD) analysis. The corresponding element profiles of Al and O were also confirmed at the metal/n-InP contact interface using secondary ion mass spectrum (SIMS) analysis. The lowering of the Schottky barrier height due to the inhomogeneity at the metal/n-InP junction is also discussed on the basis of the TE theory. The distribution of local effective Schottky barrier heights was explained by a model incorporating the existence of double Gaussian barrier heights, which represent the high barrier and low barrier of the full distribution in the temperature ranges of 83-198 and 198-300 K.

  13. Analytical modeling of trilayer graphene nanoribbon Schottky-barrier FET for high-speed switching applications.

    Science.gov (United States)

    Rahmani, Meisam; Ahmadi, Mohammad Taghi; Abadi, Hediyeh Karimi Feiz; Saeidmanesh, Mehdi; Akbari, Elnaz; Ismail, Razali

    2013-01-30

    Recent development of trilayer graphene nanoribbon Schottky-barrier field-effect transistors (FETs) will be governed by transistor electrostatics and quantum effects that impose scaling limits like those of Si metal-oxide-semiconductor field-effect transistors. The current-voltage characteristic of a Schottky-barrier FET has been studied as a function of physical parameters such as effective mass, graphene nanoribbon length, gate insulator thickness, and electrical parameters such as Schottky barrier height and applied bias voltage. In this paper, the scaling behaviors of a Schottky-barrier FET using trilayer graphene nanoribbon are studied and analytically modeled. A novel analytical method is also presented for describing a switch in a Schottky-contact double-gate trilayer graphene nanoribbon FET. In the proposed model, different stacking arrangements of trilayer graphene nanoribbon are assumed as metal and semiconductor contacts to form a Schottky transistor. Based on this assumption, an analytical model and numerical solution of the junction current-voltage are presented in which the applied bias voltage and channel length dependence characteristics are highlighted. The model is then compared with other types of transistors. The developed model can assist in comprehending experiments involving graphene nanoribbon Schottky-barrier FETs. It is demonstrated that the proposed structure exhibits negligible short-channel effects, an improved on-current, realistic threshold voltage, and opposite subthreshold slope and meets the International Technology Roadmap for Semiconductors near-term guidelines. Finally, the results showed that there is a fast transient between on-off states. In other words, the suggested model can be used as a high-speed switch where the value of subthreshold slope is small and thus leads to less power consumption.

  14. Metal-semiconductor Schottky barrier junctions and their applications

    CERN Document Server

    1984-01-01

    The present-day semiconductor technology would be inconceivable without extensive use of Schottky barrier junctions. In spite of an excellent book by Professor E.H. Rhoderick (1978) dealing with the basic principles of metal­ semiconductor contacts and a few recent review articles, the need for a monograph on "Metal-Semiconductor Schottky Barrier Junctions and Their Applications" has long been felt by students, researchers, and technologists. It was in this context that the idea of publishing such a monograph by Mr. Ellis H. Rosenberg, Senior Editor, Plenum Publishing Corporation, was considered very timely. Due to the numerous and varied applications of Schottky barrier junctions, the task of bringing it out, however, looked difficult in the beginning. After discussions at various levels, it was deemed appropriate to include only those typical applications which were extremely rich in R&D and still posed many challenges so that it could be brought out in the stipulated time frame. Keeping in view the la...

  15. Schottky junction photovoltaic devices based on CdS single nanobelts.

    Science.gov (United States)

    Ye, Y; Dai, L; Wu, P C; Liu, C; Sun, T; Ma, R M; Qin, G G

    2009-09-16

    Schottky junction photovoltaic (PV) devices were fabricated on single CdS nanobelts (NBs). Au was used as the Schottky contact, and In/Au was used as the ohmic contact to CdS NB. Typically, the Schottky junction exhibits a well-defined rectifying behavior in the dark with a rectification ratio greater than 10(3) at +/- 0.3 V; and the PV device exhibits a clear PV behavior with an open circuit photovoltage of about 0.16 V, a short circuit current of about 23.8 pA, a maximum output power of about 1.6 pW, and a fill factor of 42%. Moreover, the output power can be multiplied by connecting two or more of the Schottky junction PV devices, made on a single CdS NB, in parallel or in series. This study demonstrates that the 1D Schottky junction PV devices, which have the merits of low cost, easy fabrication and material universality, can be an important candidate for power sources in nano-optoelectronic systems.

  16. Enhancement in performance of polycarbazole-graphene nanocomposite Schottky diode

    International Nuclear Information System (INIS)

    Pandey, Rajiv K.; Singh, Arun Kumar; Prakash, Rajiv

    2013-01-01

    We report formation of polycarbazole (PCz)–graphene nanocomposite over indium tin oxide (ITO) coated glass substrate using electrochemical technique for fabrication of high performance Schottky diodes. The synthesized nanocomposite is characterized before fabrication of devices for confirmation of uniform distribution of graphene nanosheets in the polymer matrix. Pure PCz and PCz-graphene nanocomposites based Schottky diodes are fabricated of configuration Al/PCz/ITO and Al/PCz-graphene nanocomposite/ITO, respectively. The current density–voltage (J-V) characteristics and diode performance parameters (such as the ideality factor, barrier height, and reverse saturation current density) are compared under ambient condition. Al/PCz-graphene nanocomposite/ITO device exhibits better ideality factor in comparison to the device formed using pure PCz. It is also observed that the Al/PCz-graphene nanocomposite/ITO device shows large forward current density and low turn on voltage in comparison to Al/PCz/ITO device

  17. Al-Si alloy point contact formation and rear surface passivation for silicon solar cells using double layer porous silicon

    International Nuclear Information System (INIS)

    Moumni, Besma; Ben Jaballah, Abdelkader; Bessais, Brahim

    2012-01-01

    Lowering the rear surface recombination velocities by a dielectric layer has fascinating advantages compared with the standard fully covered Al back-contact silicon solar cells. In this work the passivation effect by double layer porous silicon (PS) (wide band gap) and the formation of Al-Si alloy in narrow p-type Si point contact areas for rear passivated solar cells are analysed. As revealed by Fourier transform infrared spectroscopy, we found that a thin passivating aluminum oxide (Al 2 O 3 ) layer is formed. Scanning electron microscopy analysis performed in cross sections shows that with bilayer PS, liquid Al penetrates into the openings, alloying with the Si substrate at depth and decreasing the contact resistivity. At the solar cell level, the reduction in the contact area and resistivity leads to a minimization of the fill factor losses.

  18. Chemical trends of Schottky barrier behavior on monolayer hexagonal B, Al, and Ga nitrides

    Science.gov (United States)

    Lu, Haichang; Guo, Yuzheng; Robertson, John

    2016-08-01

    The Schottky Barrier Heights (SBH) of metal layers on top of monolayer hexagonal X-nitrides (X = B, Al, Ga, and h-XN) are calculated using supercells and density functional theory so as to understand the chemical trends of contact formation on graphene and the 2D layered semiconductors such as the transition metal dichalcogenides. The Fermi level pinning factor S of SBHs on h-BN is calculated to be nearly 1, indicating no pinning. For h-AlN and h-GaN, the calculated pinning factor is about 0.63, less than for h-BN. We attribute this to the formation of stronger, chemisorptive bonds between the nitrides and the contact metal layer. Generally, the h-BN layer remains in a planar sp2 geometry and has weak physisorptive bonds to the metals, whereas h-AlN and h-GaN buckle out of their planar geometry which enables them to form the chemisorptive bonds to the metals.

  19. In vitro reestablishment of cell-cell contacts in adult rat cardiomyocytes. Functional role of transmembrane components in the formation of new intercalated disk-like cell contacts.

    Science.gov (United States)

    Eppenberger, H M; Zuppinger, C

    1999-01-01

    Primary adult rat cardiomyocytes (ARC)in culture are shown to be a model system for cardiac cell hypertrophy in vitro. ARC undergo a process of morphological transformation and grow only by increase in cell size, however, without loss of the cardiac phenotype. The isolated cells spread and establish new cell-cell contacts, eventually forming a two-dimensional heart tissue-like synchronously beating cell sheet. The reformation of specific cell contacts (intercalated disks) is shown also between ventricular and atrial cardiomyocytes by using antibodies against the gap junction protein connexin-43 and after microinjection into ARC of N-cadherin cDNA fused to reporter green fluorescent protein (GFP) cDNA. The expressed fusion protein allowed the study of live cell cultures and of the dynamics of the adherens junction protein N-cadherin during the formation of new cell-cell contacts. The possible use of the formed ARC cell-sheet cells under microgravity conditions as a test system for the reformation of the cytoskeleton of heart muscle cells is proposed.

  20. Electrical characterization of organic-on-inorganic semiconductor Schottky structures

    International Nuclear Information System (INIS)

    Guellue, Oe; Tueruet, A; Asubay, S

    2008-01-01

    We prepared a methyl red/p-InP organic-inorganic (OI) Schottky device formed by evaporation of an organic compound solution directly to a p-InP semiconductor wafer. The value of the optical band gap energy of the methyl red organic film on a glass substrate was obtained as 2.0 eV. It was seen that the Al/methyl red/p-InP contacts showed a good rectifying behavior. An ideality factor of 2.02 and a barrier height (Φ b ) of 1.11 eV for the Al/methyl red/p-InP contact were determined from the forward bias I-V characteristics. It was seen that the value of 1.11 eV obtained for Φ b for the Al/methyl red/p-InP contact was significantly larger than the value of 0.83 eV for conventional Al/p-InP Schottky diodes. Modification of the interfacial potential barrier for the Al/p-InP diode was achieved using a thin interlayer of the methyl red organic semiconductor. This ascribed to the fact that the methyl red interlayer increases the effective Φ b by influencing the space charge region of InP

  1. Schottky Noise and Beam Transfer Functions

    Energy Technology Data Exchange (ETDEWEB)

    Blaskiewicz M.; Blaskiewicz M.

    2016-12-01

    Beam transfer functions (BTF)s encapsulate the stability properties of charged particle beams. In general one excites the beam with a sinusoidal signal and measures the amplitude and phase of the beam response. Most systems are very nearly linear and one can use various Fourier techniques to reduce the number of measurements and/or simulations needed to fully characterize the response. Schottky noise is associated with the finite number of particles in the beam. This signal is always present. Since the Schottky current drives wakefields, the measured Schottky signal is influenced by parasitic impedances.

  2. Evolution of Electrically Active Defects in n-GaN During Heat Treatment Typical for Ohmic Contact Formation

    DEFF Research Database (Denmark)

    Boturchuk, Ievgen; Scheffler, Leopold Julian; Larsen, Arne Nylandsted

    2018-01-01

    Ohmic contact formation to n-type GaN often involves high temperature steps, for example sintering at about 800 °C in the case of Ti-based contacts. Such processing steps might cause changes in the distribution, concentration, and properties of the defects. The present work aims at contributing...... to the knowledge about defect evolution in GaN upon processing at different temperatures. The processing temperatures are selected according to fabrication procedures for commonly used ohmic contacts to n-GaN: 300 °C (In-based), 550 °C (Ta-based), and 800 °C (Ti-based). Properties and concentration of the defects...

  3. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy

    Science.gov (United States)

    Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-01

    To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.

  4. Schottky-Gated Probe-Free ZnO Nanowire Biosensor

    KAUST Repository

    Yeh, Ping-Hung

    2009-12-28

    (Figure Presented) A nanowire-based nanosensor for detecting biologically and chemically charged molecules that is probe-free and highly sensitive is demonstrated. The device relies on the nonsymmetrical Schottky contact under reverse bias (see figure) and is much more sensitive than the device based on the symmetric ohmic contact. This approach serves as a guideline for designing more practical chemical and biochemical sensors. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

  5. Indium gallium zinc oxide (IGZO)-based Ohmic contact formation on n-type gallium antimony (GaSb)

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Jeong-Hun; Jung, Hyun-Wook [Samsung-SKKU Graphene Center and School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Park, Jin-Hong, E-mail: jhpark9@skku.edu [Samsung-SKKU Graphene Center and School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-02-14

    In this paper, Ohmic-like contact on n-type GaSb with on/off-current ratio of 1.64 is presented, which is formed at 500 °C by inserting IGZO between metal (Ni) and GaSb. The resulting Ohmic contact is systematically investigated by TOF-SIMS, HSC chemistry simulation, XPS, TEM, AFM, and J–V measurements. Two main factors contributing to the Ohmic contact formation are (1) InSb (or InGaSb) with narrow energy bandgap (providing low electron and hole barrier heights) formed by In diffusion from IGZO and Sb released by Ga oxidation, and (2) free Sb working as traps that induces tunneling current. - Highlights: • We demonstrate Ohmic-like contact on n-type GaSb with on/off-current ratio of 1.64. • The reverse current is increased by low electron barrier height and high TAT current. • The low electron barrier height is achieved by the formation of InGaSb. • Free Sb atoms also work as traps inducing high TAT current.

  6. Contact ion pair formation between hard acids and soft bases in aqueous solutions observed with 2DIR spectroscopy.

    Science.gov (United States)

    Sun, Zheng; Zhang, Wenkai; Ji, Minbiao; Hartsock, Robert; Gaffney, Kelly J

    2013-12-12

    The interaction of charged species in aqueous solution has important implications for chemical, biological, and environmental processes. We have used 2DIR spectroscopy to study the equilibrium dynamics of thiocyanate chemical exchange between free ion (NCS(-)) and contact ion pair configurations (MNCS(+)), where M(2+) = Mg(2+) or Ca(2+). Detailed studies of the influence of anion concentration and anion speciation show that the chemical exchange observed with the 2DIR measurements results from NCS(-) exchanging with other anion species in the first solvation shell surrounding Mg(2+) or Ca(2+). The presence of chemical exchange in the 2DIR spectra provides an indirect, but robust, determinant of contact ion pair formation. We observe preferential contact ion pair formation between soft Lewis base anions and hard Lewis acid cations. This observation cannot be easily reconciled with Pearson's acid-base concept or Collins' Law of Matching Water Affinities. The anions that form contact ion pairs also correspond to the ions with an affinity for water and protein surfaces, so similar physical and chemical properties may control these distinct phenomena.

  7. Fire-through Ag contact formation for crystalline Si solar cells using single-step inkjet printing.

    Science.gov (United States)

    Kim, Hyun-Gang; Cho, Sung-Bin; Chung, Bo-Mook; Huh, Joo-Youl; Yoon, Sam S

    2012-04-01

    Inkjet-printed Ag metallization is a promising method of forming front-side contacts on Si solar cells due to its non-contact printing nature and fine grid resolution. However, conventional Ag inks are unable to punch through the SiN(x) anti-reflection coating (ARC) layer on emitter Si surfaces. In this study, a novel formulation of Ag ink is examined for the formation of fire-through contacts on a SiN(x)-coated Si substrate using the single-step printing of Ag ink, followed by rapid thermal annealing at 800 degrees C. In order to formulate Ag inks with fire-through contact formation capabilities, a liquid etching agent was first formulated by dissolving metal nitrates in an organic solvent and then mixing the resulting solution with a commercial Ag nanoparticle ink at various volume ratios. During the firing process, the dissolved metal nitrates decomposed into metal oxides and acted in a similar manner to the glass frit contained in Ag pastes for screen-printed Ag metallization. The newly formulated ink with a 1 wt% loading ratio of metal oxides to Ag formed finely distributed Ag crystallites on the Si substrate after firing at 800 degrees C for 1 min.

  8. Power Conversion Efficiency of AlGaAs/GaAs Schottky Diode for Low-Power On-Chip Rectenna Device Application

    International Nuclear Information System (INIS)

    Mustafa, Farahiyah; Hashim, Abdul Manaf; Rahman, Shaharin Fadzli Abd; Osman, Mohd Nizam

    2011-01-01

    A Schottky diode has been designed and fabricated on n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences of Schottky barrier height from theoretical value are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are well rectified by the fabricated Schottky diodes and stable DC output voltage is obtained. Power conversion efficiency up to 50% is obtained at 1 GHz with series connection between diode and load. The fabricated the n-AlGaAs/GaAs Schottky diode provide conduit for breakthrough designs for ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  9. Liftoff process for exfoliation of thin film photovoltaic devices and back contact formation

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Richard A.; Hannon, James B.; Oida, Satoshi

    2018-04-03

    A method for forming a back contact on an absorber layer in a photovoltaic device includes forming a two dimensional material on a first substrate. An absorber layer including Cu--Zn--Sn--S(Se) (CZTSSe) is grown over the first substrate on the two dimensional material. A buffer layer is grown on the absorber layer on a side opposite the two dimensional material. The absorber layer is exfoliated from the two dimensional material to remove the first substrate from a backside of the absorber layer opposite the buffer layer. A back contact is deposited on the absorber layer.

  10. Fabrication and characteristics of a 4H-SiC junction barrier Schottky diode

    International Nuclear Information System (INIS)

    Chen Fengping; Zhang Yuming; Lue Hongliang; Zhang Yimen; Guo Hui; Guo Xin

    2011-01-01

    4H-SiC junction barrier Schottky (JBS) diodes with four kinds of design have been fabricated and characterized using two different processes in which one is fabricated by making the P-type ohmic contact of the anode independently, and the other is processed by depositing a Schottky metal multi-layer on the whole anode. The reverse performances are compared to find the influences of these factors. The results show that JBS diodes with field guard rings have a lower reverse current density and a higher breakdown voltage, and with independent P-type ohmic contact manufacturing, the reverse performance of 4H-SiC JBS diodes can be improved effectively. Furthermore, the P-type ohmic contact is studied in this work. (semiconductor devices)

  11. Charge conduction process and photovoltaic effects in thiazole yellow (TY) thin film based Schottky devices

    Energy Technology Data Exchange (ETDEWEB)

    Roy, M.S. [Defence Lab., Jodhpur (India). Camouflage Div.; Sharma, G.D.; Gupta, S.K. [Department of Physics, J.N.V. University, Jodhpur (Raj.) (India)

    1997-11-21

    The charge generation and photovoltaic effects observed with thin films of TY in the form of sandwich structures, were analysed by J-V, C-V and photoaction spectra. These measurements were explained in terms of n-type semiconductivity of TY thin film and by the formation of a Schottky barrier with ITO while Ohmic contact with an Al or In electrode. The existence of thermionic emission over the ITO-TY barrier has been observed in low voltage region, whereas at high voltages, the process is dominant by the series resistance of TY layer. Various electrical parameters were calculated from the analysis of J-V and C-V characteristics of the devices and discussed in details. The diode quality factor is higher for Al/TY/ITO than In/TY/ITO device which can be attributed to the formation of thin layer of Al{sub 2}O{sub 3} between Al and TY. The photoaction spectra of the devices reveal that the fraction of light which is absorbed near the ITO-TY interface, to the depth of 180 A, is responsible for producing the charge carriers. The photovoltaic parameters were also calculated from the J-V characteristics of the devices, under illumination and described in detail. (orig.) 21 refs.

  12. Simulation studies of current transport in metal-insulator-semiconductor Schottky barrier diodes

    International Nuclear Information System (INIS)

    Chand, Subhash; Bala, Saroj

    2007-01-01

    The current-voltage characteristics of Schottky diodes with an interfacial insulator layer are analysed by numerical simulation. The current-voltage data of the metal-insulator-semiconductor Schottky diode are simulated using thermionic emission diffusion (TED) equation taking into account an interfacial layer parameter. The calculated current-voltage data are fitted into ideal TED equation to see the apparent effect of interfacial layer parameters on current transport. Results obtained from the simulation studies shows that with mere presence of an interfacial layer at the metal-semiconductor interface the Schottky contact behave as an ideal diode of apparently high barrier height (BH), but with same ideality factor and series resistance as considered for a pure Schottky contact without an interfacial layer. This apparent BH decreases linearly with decreasing temperature. The effects giving rise to high ideality factor in metal-insulator-semiconductor diode are analysed. Reasons for observed temperature dependence of ideality factor in experimentally fabricated metal-insulator-semiconductor diodes are analysed and possible mechanisms are discussed

  13. Low Temperature Hydrothermal Growth of ZnO Nanorod Films for Schottky Diode Application

    International Nuclear Information System (INIS)

    Singh, Shaivalini; Park, Si-Hyun

    2016-01-01

    The purpose of this research is to report on the fabrication and characterizations of Pd/ZnO nanorod-based Schottky diodes for optoelectronic applications. ZnO nanorods (NRs) were grown on silicon (Si) substrates by a two step hydrothermal method. In the first step, a seed layer of pure ZnO was deposited from a solution of zinc acetate and ethyl alcohol, and then in the second step, the main growth of the ZnO NRs was done over the seed layer. The structural morphology and optical properties of the ZnO NR films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis spectroscopy. The electrical characterization of the Pd/ZnO NR contacts was studied using a current-voltage (I-V) tool. The ZnO NR films exhibited a wurtzite ZnO structure,and the average length of the ZnO NRs were in the range of 750 nm to 800 nm. The values of ideality factor, turn-on voltage and reverse saturation current were calculated from the I-V characteristics of Pd/ZnO NR-based Schottky diodes. The study demonstrates that Pd/ZnO NR Schottky contacts fabricated by a simple and inexpensive method can be used as a substitute for conventional Schottky diodes for optoelectronic applications.

  14. Investigation of Thermostressed State of Coating Formation at Electric Contact Surfacing of “Shaft” Type Parts

    Directory of Open Access Journals (Sweden)

    Olena V. Berezshnaya

    2016-01-01

    Full Text Available The forming of coating at electric contact surfacing is considered. The mathematical model of the coating formation is developed. The method of numerical recurrent solution of the finite-difference form of static equilibrium conditions of the selected elementary volume of coating is used. This model considers distribution of thermal properties and geometric parameters along the thermal deformation zone during the process of electric contact surfacing by compact material. It is found that the change of value of speed asymmetry factor leads to increasing of the friction coefficient in zone of surfacing. This provides the forming of the coating of higher quality. The limitation of the technological capabilities of equipment for electric contact surfacing is related to the size of recoverable parts and application of high electromechanical powers. The regulation of the speed asymmetry factor allows for expanding the technological capabilities of equipment for electric contact surfacing. The nomograms for determination of the stress on the roller electrode and the finite thickness of the coating as the function of the initial thickness of the compact material and the deformation degree are shown.

  15. Transport mechanisms in low-resistance ohmic contacts to p-InP formed by rapid thermal annealing

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1993-01-01

    process is related to interdiffusion and compound formation between the metal elements and the InP. The onset of low specific contact resistance is characterized by a change in the dominant transport mechanism; from predominantly a combination of thermionic emission and field emission to purely thermionic......Thermionic emission across a very small effective Schottky barrier (0-0.2 eV) are reported as being the dominant transport process mechanism in very low-resistance ohmic contacts for conventional AuZn(Ni) metallization systems top-InP formed by rapid thermal annealing. The barrier modulation...

  16. Comparison of electrical characteristic between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes

    International Nuclear Information System (INIS)

    Lü Yuan-Jie; Feng Zhi-Hong; Gu Guo-Dong; Dun Shao-Bo; Yin Jia-Yun; Han Ting-Ting; Cai Shu-Jun; Lin Zhao-Jun

    2014-01-01

    Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current—voltage and capacitance—voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an AlGaN/GaN diode by self-consistently solving Schrödinger's and Poisson's equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostructure results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an AlGaN/GaN diode. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. Prediction of barrier inhomogeneities and carrier transport in Ni-silicided Schottky diode

    International Nuclear Information System (INIS)

    Saha, A.R.; Dimitriu, C.B.; Horsfall, A.B.; Chattopadhyay, S.; Wright, N.G.; O'Neill, A.G.; Maiti, C.K.

    2006-01-01

    Based on Quantum Mechanical (QM) carrier transport and the effects of interface states, a theoretical model has been developed to predict the anomalous current-voltage (I-V) characteristics of a non-ideal Ni-silicided Schottky diode at low temperatures. Physical parameters such as barrier height, ideality factor, series resistance and effective Richardson constant of a silicided Schottky diode were extracted from forward I-V characteristics and are subsequently used for the simulation of both forward and reverse I-V characteristics using a QM transport model in which the effects of interface state and bias dependent barrier reduction are incorporated. The present analysis indicates that the effects of barrier inhomogeneity caused by incomplete silicide formation at the junction and the interface states may change the conventional current transport process, leading to anomalous forward and reverse I-V characteristics for the Ni-silicided Schottky diode

  18. Schottky barrier measurements on individual GaAs nanowires by X-ray photoemission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Di Mario, Lorenzo [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Turchini, Stefano, E-mail: stefano.turchini@cnr.it [ISM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Zamborlini, Giovanni; Feyer, Vitaly [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Tian, Lin [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy); Schneider, Claus M. [Peter Grünberg Institute (PGI-6) and JARA-FIT, Research Center Jülich, 52425 Jülich (Germany); Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CENIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany); Rubini, Silvia [IOM-CNR, TASC Laboratory, Basovizza 34149, Trieste (Italy); Martelli, Faustino, E-mail: faustino.martelli@cnr.it [IMM-CNR, via del Fosso del Cavaliere 100, 00133 Rome (Italy)

    2016-11-15

    Highlights: • The Schottky barrier at the interface between Cu and GaAs nanowires was measured. • Individual nanowires were investigated by X-ray Photoemission Microscopy. • The Schottky barrier at different positions along the nanowire was evaluated. - Abstract: We present measurements of the Schottky barrier height on individual GaAs nanowires by means of x-ray photoelectron emission microscopy (XPEEM). Values of 0.73 and 0.51 eV, averaged over the entire wires, were measured on Cu-covered n-doped and p-doped GaAs nanowires, respectively, in agreement with results obtained on bulk material. Our measurements show that XPEEM can become a feasible and reliable investigation tool of interface formation at the nanoscale and pave the way towards the study of size-dependent effects on semiconductor-based structures.

  19. Ultra-low leakage and high breakdown Schottky diodes fabricated on free-standing GaN substrate

    International Nuclear Information System (INIS)

    Wang, Yaqi; Alur, Siddharth; Sharma, Yogesh; Tong, Fei; Thapa, Resham; Gartland, Patrick; Issacs-Smith, Tamara; Ahyi, Claude; Williams, John; Park, Minseo; Johnson, Mark; Paskova, Tanya; Preble, Edward A; Evans, Keith R

    2011-01-01

    Vertical Schottky diodes were fabricated on the bulk GaN substrate with decreasing impurity concentration from N-face to Ga-face. An array of circular Pt Schottky contacts and a full backside Ti/Al/Ni/Au ohmic contact were prepared on the Ga-face and the N-face of the n-GaN substrate, respectively. The Schottky diode exhibits a minimum specific on-state resistance of 1.3 mΩ cm 2 and a maximum breakdown voltage of 600 V, resulting in a figure-of- merit of 275 MW cm −2 . An ultra-low reverse leakage current density of 3.7 × 10 −4 A cm −2 at reverse bias of 400 V was observed. Temperature-dependent I–V measurements were also carried out to study the forward and reverse transportation mechanisms. (fast track communication)

  20. AlGaN-Based Solar-Blind Schottky Photodetectors Fabricated on AlN/Sapphire Template

    International Nuclear Information System (INIS)

    Li-Wen, Sang; Zhi-Xin, Qin; Long-Bin, Cen; Bo, Shen; Guo-Yi, Zhang; Shu-Ping, Li; Hang-Yang, Chen; Da-Yi, Liu; Jun-Yong, Kang; Cai-Jing, Cheng; Hong-Yan, Zhao; Zheng-Xiong, Lu; Jia-Xin, Ding; Lan, Zhao; Jun-Jie, Si; Wei-Guo, Sun

    2008-01-01

    We report AlGaN-based back-illuminated solar-blind Schottky-type ultraviolet photodetectors with the cutoff-wavelength from 280nm to 292nm without bias. The devices show low dark current of 2.1 × 10 −6 A/cm 2 at the reverse bias of 5 V. The specific detectivity D* is estimated to be 3.3 × 10 12 cmHz 1/2 W −1 . To guarantee the performance of the photodetectors, the optimization of AlGaN growth and annealing condition for Schottky contacts were performed. The results show that high-temperature annealing method for Ni/Pt Schottky contacts is effective for the reduction of leakage current

  1. Effect of annealing temperature on electrical properties of Au/polyvinyl alcohol/n-InP Schottky barrier structure

    International Nuclear Information System (INIS)

    Reddy, V. Rajagopal; Reddy, M. Siva Pratap; Kumar, A. Ashok; Choi, Chel-Jong

    2012-01-01

    In the present work, thin film of polyvinyl alcohol (PVA) is fabricated on n-type InP substrate as an interfacial layer for electronic modification of Au/n-InP Schottky contact. The electrical characteristics of Au/PVA/n-InP Schottky diode are determined at annealing temperature in the range of 100–300 °C by current–voltage (I-V) and capacitance–voltage (C-V) methods. The Schottky barrier height and ideality factor (n) values of the as-deposited Au/PVA/n-InP diode are obtained at room temperature as 0.66 eV (I-V), 0.82 eV (C-V) and 1.32, respectively. Upon annealing at 200 °C in nitrogen atmosphere for 1 min, the barrier height value increases to 0.81 eV (I-V), 0.99 eV (C-V) and ideality factor decreases to 1.18. When the contact is annealed at 300 °C, the barrier height value decreases to 0.77 eV (I-V), 0.96 eV (C-V) and ideality factor increases to 1.22. It is observed that the interfacial layer of PVA increases the barrier height by the influence of the space charge region of the Au/n-InP Schottky junction. The discrepancy between Schottky barrier heights calculated from I-V and C-V measurements is also explained. Further, Cheung's functions are used to extract the series resistance of Au/PVA/n-InP Schottky diode. The interface state density as determined by Terman's method is found to be 1.04 × 10 12 and 0.59 × 10 12 cm −2 eV −1 for the as-deposited and 200 °C annealed Au/PVA/n-InP Schottky diodes. Finally, it is seen that the Schottky diode parameters changed with increase in the annealing temperature. - Highlights: ► Electrical properties of Au/polyvinyl alcohol (PVA)/n-InP structure have been studied. ► The Au/PVA/n-InP Schottky structure showed a good rectifying behavior. ► A maximum barrier height is obtained when the contact is annealed at 200 °C. ► Interface state density found to be 0.59 × 10 12 cm −2 eV −1 for 200 °C annealed contact. ► Significant effect of interface state density and series resistance on electrical

  2. Schottky barrier MOSFET systems and fabrication thereof

    Science.gov (United States)

    Welch, J.D.

    1997-09-02

    (MOS) device systems-utilizing Schottky barrier source and drain to channel region junctions are disclosed. Experimentally derived results which demonstrate operation of fabricated N-channel and P-channel Schottky barrier (MOSFET) devices, and of fabricated single devices with operational characteristics similar to (CMOS) and to a non-latching (SRC) are reported. Use of essentially non-rectifying Schottky barriers in (MOS) structures involving highly doped and the like and intrinsic semiconductor to allow non-rectifying interconnection of, and electrical accessing of device regions is also disclosed. Insulator effected low leakage current device geometries and fabrication procedures therefore are taught. Selective electrical interconnection of drain to drain, source to drain, or source to source, of N-channel and/or P-channel Schottky barrier (MOSFET) devices formed on P-type, N-type and Intrinsic semiconductor allows realization of Schottky Barrier (CMOS), (MOSFET) with (MOSFET) load, balanced differential (MOSFET) device systems and inverting and non-inverting single devices with operating characteristics similar to (CMOS), which devices can be utilized in modulation, as well as in voltage controlled switching and effecting a direction of rectification. 89 figs.

  3. Negative ion beam formation using thermal contact ionization type plasma source

    Energy Technology Data Exchange (ETDEWEB)

    Fukuura, Yoshiyuki; Murakami, Kazutugu; Masuoka, Toshio; Katsumata, Itsuo [Osaka City Univ. (Japan). Faculty of Engineering

    1997-02-01

    The small ion sources utilizing thermal ionization have been already developed, and at present, in order to increase ion yield, that being developed to the cylindrical plasma prototype having the inner surface of a Re foil cylinder as the ionization surface, and stably functioning at 3,000 K has been developed, and by using this plasma source, the research on the formation of various ions has been carried out. At present, the research on the formation of Li negative ion beam is carried out. The separation of negative ions from electrons is performed with the locally limited magnetic field using a small iron core electromagnet placed behind the electrostatic accelerating lens system. So for, the formation of about 2 {mu}A at maximum of negative ions was confirmed. It was decided to identify the kinds of ions by time of flight (TOF) process, and the various improvements for this purpose were carried out. The experimental setup, the structure of the plasma source, the circuits for TOF measurement and so on are explained. The experimental results are reported. The problems are the possibility of the formation of alkali metals, the resolution of the time axis of the TOF system and so on. (K.I.)

  4. The physics and chemistry of the Schottky barrier height

    International Nuclear Information System (INIS)

    Tung, Raymond T.

    2014-01-01

    The formation of the Schottky barrier height (SBH) is a complex problem because of the dependence of the SBH on the atomic structure of the metal-semiconductor (MS) interface. Existing models of the SBH are too simple to realistically treat the chemistry exhibited at MS interfaces. This article points out, through examination of available experimental and theoretical results, that a comprehensive, quantum-mechanics-based picture of SBH formation can already be constructed, although no simple equations can emerge, which are applicable for all MS interfaces. Important concepts and principles in physics and chemistry that govern the formation of the SBH are described in detail, from which the experimental and theoretical results for individual MS interfaces can be understood. Strategies used and results obtained from recent investigations to systematically modify the SBH are also examined from the perspective of the physical and chemical principles of the MS interface

  5. Passivation layer breakdown during laser-fired contact formation for photovoltaic devices

    International Nuclear Information System (INIS)

    Raghavan, A.; DebRoy, T.; Palmer, T. A.

    2014-01-01

    Low resistance laser-fired ohmic contacts (LFCs) can be formed on the backside of Si-based solar cells using microsecond pulses. However, the impact of these longer pulse durations on the dielectric passivation layer is not clear. Retention of the passivation layer during processing is critical to ensure low recombination rates of electron-hole pairs at the rear surface of the device. In this work, advanced characterization tools are used to demonstrate that although the SiO 2 passivation layer melts directly below the laser, it is well preserved outside the immediate LFC region over a wide range of processing parameters. As a result, low recombination rates at the passivation layer/wafer interface can be expected despite higher energy densities associated with these pulse durations.

  6. A fluorescence-based method for direct measurement of submicrosecond intramolecular contact formation in biopolymers: an exploratory study with polypeptides.

    Science.gov (United States)

    Hudgins, Robert R; Huang, Fang; Gramlich, Gabriela; Nau, Werner M

    2002-01-30

    A fluorescent amino acid derivative (Fmoc-DBO) has been synthesized, which contains 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as a small, hydrophilic fluorophore with an extremely long fluorescence lifetime (325 ns in H2O and 505 ns in D2O under air). Polypeptides containing both the DBO residue and an efficient fluorescence quencher allow the measurement of rate constants for intramolecular end-to-end contact formation. Bimolecular quenching experiments indicated that Trp, Cys, Met, and Tyr are efficient quenchers of DBO (k(q) = 20, 5.1, 4.5, and 3.6 x 10(8) M(-1) x s(-1) in D2O), while the other amino acids are inefficient. The quenching by Trp, which was selected as an intrinsic quencher, is presumed to involve exciplex-induced deactivation. Flexible, structureless polypeptides, Trp-(Gly-Ser)n-DBO-NH2, were prepared by standard solid-phase synthesis, and the rates of contact formation were measured through the intramolecular fluorescence quenching of DBO by Trp with time-correlated single-photon counting, laser flash photolysis, and steady-state fluorometry. Rate constants of 4.1, 6.8, 4.9, 3.1, 2.0, and 1.1 x 10(7) s(-1) for n = 0, 1, 2, 4, 6, and 10 were obtained. Noteworthy was the relatively slow quenching for the shortest peptide (n = 0). The kinetic data are in agreement with recent transient absorption studies of triplet probes for related peptides, but the rate constants are significantly larger. In contrast to the flexible structureless Gly-Ser polypeptides, the polyproline Trp-Pro4-DBO-NH2 showed insignificant fluorescence quenching, suggesting that a high polypeptide flexibility and the possibility of probe-quencher contact is essential to induce quenching. Advantages of the new fluorescence-based method for measuring contact formation rates in biopolymers include high accuracy, fast time range (100 ps-1 micros), and the possibility to perform measurements in water under air.

  7. A three-phase in-vitro system for studying Pseudomonas aeruginosa adhesion and biofilm formation upon hydrogel contact lenses

    Directory of Open Access Journals (Sweden)

    Kohlmann Thomas

    2010-11-01

    Full Text Available Abstract Background Pseudomonas aeruginosa is commonly associated with contact lens (CL -related eye infections, for which bacterial adhesion and biofilm formation upon hydrogel CLs is a specific risk factor. Whilst P. aeruginosa has been widely used as a model organism for initial biofilm formation on CLs, in-vitro models that closely reproduce in-vivo conditions have rarely been presented. Results In the current investigation, a novel in-vitro biofilm model for studying the adherence of P. aeruginosa to hydrogel CLs was established. Nutritional and interfacial conditions similar to those in the eye of a CL wearer were created through the involvement of a solid:liquid and a solid:air interface, shear forces and a complex artificial tear fluid. Bioburdens varied depending on the CL material and biofilm maturation occurred after 72 h incubation. Whilst a range of biofilm morphologies were visualised including dispersed and adherent bacterial cells, aggregates and colonies embedded in extracellular polymer substances (EPS, EPS fibres, mushroom-like formations, and crystalline structures, a compact and heterogeneous biofilm morphology predominated on all CL materials. Conclusions In order to better understand the process of biofilm formation on CLs and to test the efficacy of CL care solutions, representative in-vitro biofilm models are required. Here, we present a three-phase biofilm model that simulates the environment in the eye of a CL wearer and thus generates biofilms which resemble those commonly observed in-situ.

  8. Spectrally dependent photovoltages in Schottky photodiode based on (100) B-doped diamond

    International Nuclear Information System (INIS)

    Čermák, Jan; Rezek, Bohuslav; Koide, Yasuo; Takeuchi, Daisuke

    2014-01-01

    Spectrally and spatially resolved photovoltages were measured by Kelvin probe force microscopy (KPFM) on a Schottky photo-diode made of a 4 nm thin tungsten-carbide (WC) layer on a 500 nm oxygen-terminated boron-doped diamond epitaxial layer (O-BDD) that was grown on a Ib (100) diamond substrate. The diode was grounded by the sideways ohmic contact (Ti/WC), and the semitransparent Schottky contact was let unconnected. The electrical potentials across the device were measured in dark (only 650 nm LED of KPFM being on), under broad-band white light (halogen lamp), UV (365 nm diode), and deep ultraviolet (deuterium lamp) illumination. Illumination induced shift of the electrical potential remains within 210 mV. We propose that the photovoltage actually corresponds to a shift of Fermi level inside the BDD channel and thereby explains orders of magnitude changes in photocurrent

  9. Spectrally dependent photovoltages in Schottky photodiode based on (100) B-doped diamond

    Science.gov (United States)

    Čermák, Jan; Koide, Yasuo; Takeuchi, Daisuke; Rezek, Bohuslav

    2014-02-01

    Spectrally and spatially resolved photovoltages were measured by Kelvin probe force microscopy (KPFM) on a Schottky photo-diode made of a 4 nm thin tungsten-carbide (WC) layer on a 500 nm oxygen-terminated boron-doped diamond epitaxial layer (O-BDD) that was grown on a Ib (100) diamond substrate. The diode was grounded by the sideways ohmic contact (Ti/WC), and the semitransparent Schottky contact was let unconnected. The electrical potentials across the device were measured in dark (only 650 nm LED of KPFM being on), under broad-band white light (halogen lamp), UV (365 nm diode), and deep ultraviolet (deuterium lamp) illumination. Illumination induced shift of the electrical potential remains within 210 mV. We propose that the photovoltage actually corresponds to a shift of Fermi level inside the BDD channel and thereby explains orders of magnitude changes in photocurrent.

  10. Fabrication of 4H-SiC Schottky barrier diodes with high breakdown voltages

    CERN Document Server

    Kum, B H; Shin, M W; Park, J D

    1999-01-01

    This paper discusses the fabrication and the breakdown characteristics of 4H-SiC Schottky barrier diodes (SBDs). Optimal processing conditions for the ohmic contacts were extracted using the transmission-line method (TLM) and were applied to the device fabrication. The Ti/4H-SiC SBDs with Si sub x B sub y passivation showed a maximum reverse breakdown voltage of 268 V with a forward current density as high as 70 mA/cm sup 2 at a forward voltage of 2 V. The breakdown of the Pt. 4H-SiC SBDs without any passivation occurred at near 110 V. It is concluded that the breakdown enhancement in the Ti/4H-SiC SBDs can be attributed to the passivation; otherwise, excess surface charge near the edge of the Schottky contact would lead to electric fields of sufficient magnitude to cause field emission.

  11. High performance and transparent multilayer MoS2 transistors: Tuning Schottky barrier characteristics

    Directory of Open Access Journals (Sweden)

    Young Ki Hong

    2016-05-01

    Full Text Available Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2 thin-film transistor (TFT, which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  12. High performance and transparent multilayer MoS{sub 2} transistors: Tuning Schottky barrier characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Young Ki; Kwon, Junyeon; Hong, Seongin; Song, Won Geun; Liu, Na; Omkaram, Inturu; Kim, Sunkook, E-mail: kimskcnt@gmail.com, E-mail: ohms@keti.re.kr [Multi-Functional Bio/Nano Lab., Kyung Hee University, Gyeonggi 446-701 (Korea, Republic of); Yoo, Geonwook; Yoo, Byungwook; Oh, Min Suk, E-mail: kimskcnt@gmail.com, E-mail: ohms@keti.re.kr [Display Convergence Research Center, Korea Electronics Technology Institute, Gyeonggi 463-816 (Korea, Republic of); Ju, Sanghyun [Department of Physics, Kyonggi University, Suwon, Gyeonggi-Do 443-760 (Korea, Republic of)

    2016-05-15

    Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS{sub 2}) thin-film transistor (TFT), which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS{sub 2} TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS{sub 2} and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  13. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    International Nuclear Information System (INIS)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui; Xu, Ke; Wang, Jianfeng; Ren, Guoqiang

    2014-01-01

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure

  14. Spectrally dependent photovoltages in Schottky photodiode based on (100) B-doped diamond

    Energy Technology Data Exchange (ETDEWEB)

    Čermák, Jan, E-mail: cermakj@fzu.cz; Rezek, Bohuslav [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16200 Prague 6 (Czech Republic); Koide, Yasuo [Sensor Materials Center, National Institute for Material Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Takeuchi, Daisuke [Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8568 (Japan)

    2014-02-07

    Spectrally and spatially resolved photovoltages were measured by Kelvin probe force microscopy (KPFM) on a Schottky photo-diode made of a 4 nm thin tungsten-carbide (WC) layer on a 500 nm oxygen-terminated boron-doped diamond epitaxial layer (O-BDD) that was grown on a Ib (100) diamond substrate. The diode was grounded by the sideways ohmic contact (Ti/WC), and the semitransparent Schottky contact was let unconnected. The electrical potentials across the device were measured in dark (only 650 nm LED of KPFM being on), under broad-band white light (halogen lamp), UV (365 nm diode), and deep ultraviolet (deuterium lamp) illumination. Illumination induced shift of the electrical potential remains within 210 mV. We propose that the photovoltage actually corresponds to a shift of Fermi level inside the BDD channel and thereby explains orders of magnitude changes in photocurrent.

  15. Schottky barrier tuning of the graphene/SnS2 van der Waals heterostructures through electric field

    Science.gov (United States)

    Zhang, Fang; Li, Wei; Ma, Yaqiang; Dai, Xianqi

    2018-03-01

    Combining the electronic structures of two-dimensional monolayers in ultrathin hybrid nanocomposites is expected to display new properties beyond their single components. The effects of external electric field (Eext) on the electronic structures of monolayer SnS2 with graphene hybrid heterobilayers are studied by using the first-principle calculations. It is demonstrated that the intrinsic electronic properties of SnS2 and graphene are quite well preserved due to the weak van der Waals (vdW) interactions. We find that the n-type Schottky contacts with the significantly small Schottky barrier are formed at the graphene/SnS2 interface. In the graphene/SnS2 heterostructure, the vertical Eext can control not only the Schottky barriers (n-type and p-type) but also contact types (Schottky contact or Ohmic contact) at the interface. The present study would open a new avenue for application of ultrathin graphene/SnS2 heterostructures in future nano- and optoelectronics.

  16. Schottky barrier parameters and structural properties of rapidly annealed Zr Schottky electrode on p-type GaN

    Science.gov (United States)

    Rajagopal Reddy, V.; Asha, B.; Choi, Chel-Jong

    2017-06-01

    The Schottky barrier junction parameters and structural properties of Zr/p-GaN Schottky diode are explored at various annealing temperatures. Experimental analysis showed that the barrier height (BH) of the Zr/p-GaN Schottky diode increases with annealing at 400 °C (0.92 eV (I-V)/1.09 eV (C-V)) compared to the as-deposited one (0.83 eV (I-V)/0.93 eV (C-V)). However, the BH decreases after annealing at 500 °C. Also, at different annealing temperatures, the series resistance and BH are assessed by Cheung's functions and their values compared. Further, the interface state density (N SS) of the diode decreases after annealing at 400 °C and then somewhat rises upon annealing at 500 °C. Analysis reveals that the maximum BH is obtained at 400 °C, and thus the optimum annealing temperature is 400 °C for the diode. The XPS and XRD analysis revealed that the increase in BH may be attributed to the creation of Zr-N phases with increasing annealing up to 400 °C. The BH reduces for the diode annealed at 500 °C, which may be due to the formation of Ga-Zr phases at the junction. The AFM measurements reveal that the overall surface roughness of the Zr film is quite smooth during rapid annealing process. Project supported by the R&D Program for Industrial Core Technology (No. 10045216) and the Transfer Machine Specialized Lighting Core Technology Development Professional Manpower Training Project (No. N0001363) Funded by the Ministry of Trade, Industry and Energy (MOTIE), Republic of Korea.

  17. Meniscus formation in a capillary and the role of contact line friction.

    Science.gov (United States)

    Andrukh, Taras; Monaenkova, Daria; Rubin, Binyamin; Lee, Wah-Keat; Kornev, Konstantin G

    2014-01-28

    We studied spontaneous formation of an internal meniscus by dipping glass capillaries of 25 μm to 350 μm radii into low volatile hexadecane and tributyl phosphate. X-ray phase contrast and high speed optical microscopy imaging were employed. We showed that the meniscus completes its formation when the liquid column is still shorter than the capillary radius. After that, the meniscus travels about ten capillary radii at a constant velocity. We demonstrated that the experimental observations can be explained by introducing a friction force linearly proportional to the meniscus velocity with a friction coefficient depending on the air/liquid/solid triplet. It was demonstrated that the friction coefficient does not depend on the capillary radius. Numerical solution of the force balance equation revealed four different uptake regimes that can be specified in a phase portrait. This phase portrait was found to be in good agreement with the experimental results and can be used as a guide for the design of thin porous absorbers.

  18. AlGaN/GaN high electron mobility transistors with implanted ohmic contacts

    International Nuclear Information System (INIS)

    Wang, H.T.; Tan, L.S.; Chor, E.F.

    2007-01-01

    Selective area silicon implantation for source/drain regions was integrated into the fabrication of molecular beam epitaxy-grown AlGaN/GaN HEMTs. Dopant activation was achieved by rapid thermal annealing at 1100 deg. C in flowing N 2 ambient for 120 s with an AlN encapsulation. Linear transmission line measurements showed that the resistance of the overlay Ti/Al/Ni/Au ohmic contacts was reduced by 61% compared to the control sample. After the Schottky Ni/Au gate formation, the typical DC characteristics displayed a higher current drive, smaller knee voltage and better gate control properties for HEMTs with implanted source and drain regions

  19. Atomic composition of WC/ and Zr/O-terminated diamond Schottky interfaces close to ideality

    Energy Technology Data Exchange (ETDEWEB)

    Piñero, J.C., E-mail: josecarlos.pinero@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Araújo, D. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Fiori, A. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan); Traoré, A. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Villar, M.P. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, Puerto Real, Cádiz,11510 (Spain); Eon, D.; Muret, P.; Pernot, J. [Institut Néel, CNRS-UJF, av. des Martyrs, Grenoble,38042 France (France); Teraji, T. [National Institute for Materials Science, Tsukuba, Ibaraki (Japan)

    2017-02-15

    Highlights: • Metal/O-terminated diamond interfaces are analyzed by a variety of TEM techniques. • Thermal treatment is shown to modify structural and chemical interface properties. • Electrical behavior vs annealing is shown to be related with interface modification. • Interfaces are characterized with atomic resolution to probe inhomogeneities. • Oxide formation and modification is demonstrated in both Schottky diodes. - Abstract: Electrical and nano-structural properties of Zr and WC-based Schottky power diodes are compared and used for investigating oxide-related effects at the diamond/metal interface. Differences in Schottky barrier heights and ideality factors of both structures are shown to be related with the modification of the oxygen-terminated diamond/metal interface configuration. Oxide formation, oxide thickness variations and interfacial oxygen redistribution, associated with thermal treatment are demonstrated. Ideality factors close to ideality (n{sub WC} = 1.02 and n{sub Zr} = 1.16) are obtained after thermal treatment and are shown to be related with the relative oxygen content at the surface (OCR{sub WC} = 3.03 and OCR{sub Zr} = 1.5). Indeed, thermal treatment at higher temperatures is shown to promote an escape of oxygen for the case of the WC diode, while it generates a sharper accumulation of oxygen at the metal/diamond interface for the case of Zr diode. Therefore, the metal-oxygen affinity is shown to be a key parameter to improve diamond-based Schottky diodes.

  20. Wide- and contact-binary formation in substructured young stellar clusters

    Science.gov (United States)

    Dorval, J.; Boily, C. M.; Moraux, E.; Roos, O.

    2017-02-01

    We explore with collisional gravitational N-body models the evolution of binary stars in initially fragmented and globally subvirial clusters of stars. Binaries are inserted in the (initially) clumpy configurations so as to match the observed distributions of the field-binary-stars' semimajor axes a and binary fraction versus primary mass. The dissolution rate of wide binaries is very high at the start of the simulations, and is much reduced once the clumps are eroded by the global infall. The transition between the two regimes is sharper as the number of stars N is increased, from N = 1.5 k up to 80 k. The fraction of dissolved binary stars increases only mildly with N, from ≈15 per cent to ≈25 per cent for the same range in N. We repeated the calculation for two initial system mean number densities of 6 per pc3 (low) and 400 per pc3 (high). We found that the longer free-fall time of the low-density runs allows for prolonged binary-binary interactions inside clumps and the formation of very tight (a ≈ 0.01 au) binaries by exchange collisions. This is an indication that the statistics of such compact binaries bear a direct link to their environment at birth. We also explore the formation of wide (a ≳ 5 × 104 au) binaries and find a low (≈0.01 per cent) fraction mildly bound to the central star cluster. The high-precision astrometric mission Gaia could identify them as outflowing shells or streams.

  1. Annealing effect on Schottky barrier inhomogeneity of graphene/n-type Si Schottky diodes

    International Nuclear Information System (INIS)

    Lin, Yow-Jon; Lin, Jian-Huang

    2014-01-01

    Highlights: • The current–voltage characteristics of graphene/n-type Si devices were measured. • The ideality factor increases with the decrease measurement temperatures. • Such behavior is attributed to Schottky barrier inhomogeneities. • Both Schottky barrier inhomogeneity and the T 0 effect are affected by annealing. • Stoichiometry of SiO x has a noticeable effect on the inhomogeneous barriers. - Abstract: The current–voltage characteristics of graphene/n-type Si (n-Si) Schottky diodes with and without annealing were measured in the temperature range of −120 to 30 °C and analyzed on the basis of thermionic emission theory. It is found that the barrier height decreases and the ideality factor increases with the decrease measurement temperatures. Such behavior is attributed to Schottky barrier inhomogeneities. It is shown that both the barrier height and the ideality factor can be tuned by changing the annealing temperature. Through the analysis, it can be suspected that a SiO x layer at the graphene/n-Si interfaces influences the electronic conduction through the device and stoichiometry of SiO x is affected by annealing treatment. In addition, both Schottky barrier inhomogeneity and the T 0 effect are affected by annealing treatment, implying that stoichiometry of SiO x has a noticeable effect on the inhomogeneous barriers of graphene/n-Si Schottky diodes

  2. Transparent indium-tin oxide/indium-gallium-zinc oxide Schottky diodes formed by gradient oxygen doping

    Science.gov (United States)

    Ho, Szuheng; Yu, Hyeonggeun; So, Franky

    2017-11-01

    Amorphous InGaZnO (a-IGZO) is promising for transparent electronics due to its high carrier mobility and optical transparency. However, most metal/a-IGZO junctions are ohmic due to the Fermi-level pinning at the interface, restricting their device applications. Here, we report that indium-tin oxide/a-IGZO Schottky diodes can be formed by gradient oxygen doping in the a-IGZO layer that would otherwise form an ohmic contact. Making use of back-to-back a-IGZO Schottky junctions, a transparent IGZO permeable metal-base transistor is also demonstrated with a high common-base gain.

  3. Glia co-culture with neurons in microfluidic platforms promotes the formation and stabilization of synaptic contacts.

    Science.gov (United States)

    Shi, Mingjian; Majumdar, Devi; Gao, Yandong; Brewer, Bryson M; Goodwin, Cody R; McLean, John A; Li, Deyu; Webb, Donna J

    2013-08-07

    Two novel microfluidic cell culture schemes, a vertically-layered set-up and a four chamber set-up, were developed for co-culturing central nervous system (CNS) neurons and glia. The cell chambers in these devices were separated by pressure-enabled valve barriers, which permitted us to control communication between the two cell types. The unique design of these devices facilitated the co-culture of glia with neurons in close proximity (∼50-100 μm), differential transfection of neuronal populations, and dynamic visualization of neuronal interactions, such as the development of synapses. With these co-culture devices, initial synaptic contact between neurons transfected with different fluorescent markers, such as green fluorescent protein (GFP) and mCherry-synaptophysin, was imaged using high-resolution fluorescence microscopy. The presence of glial cells had a profound influence on synapses by increasing the number and stability of synaptic contacts. Interestingly, as determined by liquid chromatography-ion mobility-mass spectrometry, neuron-glia co-cultures produced elevated levels of soluble factors compared to that secreted by individual neuron or glia cultures, suggesting a potential mechanism by which neuron-glia interactions could modulate synaptic function. Collectively, these results show that communication between neurons and glia is critical for the formation and stability of synapses and point to the importance of developing neuron-glia co-culture systems such as the microfluidic platforms described in this study.

  4. Evaluation of susceptibility of polymer and rubber materials intended into contact with drinking water on biofilm formation

    Science.gov (United States)

    Szczotko, Maciej; Stankiewicz, Agnieszka; Jamsheer-Bratkowska, Małgorzata

    Plumbing materials in water distribution networks and indoor installations are constantly evolving. The application of new, more economical solutions with plastic materials eliminates the corrosion problems, however, do not fully protect the consumer against secondary microbial contamination of water intended for human consumption caused by the presence of a biofilm on the inner surface of materials applied. National Institute of Public Health - National Institute of Hygiene conducts research aimed at a comprehensive assessment of this type of materials, resulting their further marketing authorization in Poland. Evaluation and comparison of polymer and rubber materials intended to contact with water for the susceptibility to biofilm formation. Plastic materials (polyethylene, polypropylene, polyvinyl chloride) and rubber compounds (EPDM, NBR), from different manufacturers were evaluated. The study was carried out on 37 samples, which were divided into groups according to the material of which they were made. The testing was conducted according to the method based on conditions of dynamic flow of tap water. The level of bioluminescence in swabs taken from the surface of the tested materials was investigated with a luminometer. Evaluation of plastic materials does not show major objections in terms of hygienic assessment. All materials met the evaluation criteria established for methodology used. In case of rubber compounds, a substantial part clearly exceeded the limit values, which resulted in their negative assessment and elimination of these materials from domestic market. High susceptibility to the formation of biofilm in the group of products made of rubber compounds has been demonstrated. Examined plastic materials, except for several cases, do not revealed susceptibility to biofilm formation, but application of plastics for distribution of water intended for human consumption does not fully protect water from secondary, microbiological contamination. Complete

  5. Myotube formation is affected by adipogenic lineage cells in a cell-to-cell contact-independent manner

    International Nuclear Information System (INIS)

    Takegahara, Yuki; Yamanouchi, Keitaro; Nakamura, Katsuyuki; Nakano, Shin-ichi; Nishihara, Masugi

    2014-01-01

    Intramuscular adipose tissue (IMAT) formation is observed in some pathological conditions such as Duchenne muscular dystrophy (DMD) and sarcopenia. Several studies have suggested that IMAT formation is not only negatively correlated with skeletal muscle mass but also causes decreased muscle contraction in sarcopenia. In the present study, we examined w hether adipocytes affect myogenesis. For this purpose, skeletal muscle progenitor cells were transfected with siRNA of PPARγ (siPPARγ) in an attempt to inhibit adipogenesis. Myosin heavy chain (MHC)-positive myotube formation was promoted in cells transfected with siPPARγ compared to that of cells transfected with control siRNA. To determine whether direct cell-to-cell contact between adipocytes and myoblasts is a prerequisite for adipocytes to affect myogenesis, skeletal muscle progenitor cells were cocultured with pre- or mature adipocytes in a Transwell coculture system. MHC-positive myotube formation was inhibited when skeletal muscle progenitor cells were cocultured with mature adipocytes, but was promoted when they were cocultured with preadipocytes. Similar effects were observed when pre- or mature adipocyte-conditioned medium was used. These results indicate that preadipocytes play an important role in maintaining skeletal muscle mass by promoting myogenesis; once differentiated, the resulting mature adipocytes negatively affect myogenesis, leading to the muscle deterioration observed in skeletal muscle pathologies. - Highlights: • We examined the effects of pre- and mature adipocytes on myogenesis in vitro. • Preadipocytes and mature adipocytes affect myoblast fusion. • Preadipocytes play an important role in maintaining skeletal muscle mass. • Mature adipocytes lead to muscle deterioration observed in skeletal muscle pathologies

  6. Myotube formation is affected by adipogenic lineage cells in a cell-to-cell contact-independent manner

    Energy Technology Data Exchange (ETDEWEB)

    Takegahara, Yuki; Yamanouchi, Keitaro, E-mail: akeita@mail.ecc.u-tokyo.ac.jp; Nakamura, Katsuyuki; Nakano, Shin-ichi; Nishihara, Masugi

    2014-05-15

    Intramuscular adipose tissue (IMAT) formation is observed in some pathological conditions such as Duchenne muscular dystrophy (DMD) and sarcopenia. Several studies have suggested that IMAT formation is not only negatively correlated with skeletal muscle mass but also causes decreased muscle contraction in sarcopenia. In the present study, we examined w hether adipocytes affect myogenesis. For this purpose, skeletal muscle progenitor cells were transfected with siRNA of PPARγ (siPPARγ) in an attempt to inhibit adipogenesis. Myosin heavy chain (MHC)-positive myotube formation was promoted in cells transfected with siPPARγ compared to that of cells transfected with control siRNA. To determine whether direct cell-to-cell contact between adipocytes and myoblasts is a prerequisite for adipocytes to affect myogenesis, skeletal muscle progenitor cells were cocultured with pre- or mature adipocytes in a Transwell coculture system. MHC-positive myotube formation was inhibited when skeletal muscle progenitor cells were cocultured with mature adipocytes, but was promoted when they were cocultured with preadipocytes. Similar effects were observed when pre- or mature adipocyte-conditioned medium was used. These results indicate that preadipocytes play an important role in maintaining skeletal muscle mass by promoting myogenesis; once differentiated, the resulting mature adipocytes negatively affect myogenesis, leading to the muscle deterioration observed in skeletal muscle pathologies. - Highlights: • We examined the effects of pre- and mature adipocytes on myogenesis in vitro. • Preadipocytes and mature adipocytes affect myoblast fusion. • Preadipocytes play an important role in maintaining skeletal muscle mass. • Mature adipocytes lead to muscle deterioration observed in skeletal muscle pathologies.

  7. Impact of nitrogen plasma passivation on the Al/n-Ge contact

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Shumei; Mao, Danfeng [Department of Physics, Xiamen University, Xiamen, Fujian 361005 (China); Ruan, Yujiao [Xiamen Institute of Measurement and Testing, Xiamen, Fujian 361004 (China); Xu, Yihong; Huang, Zhiwei; Huang, Wei [Department of Physics, Xiamen University, Xiamen, Fujian 361005 (China); Chen, Songyan, E-mail: sychen@xmu.edu.cn [Department of Physics, Xiamen University, Xiamen, Fujian 361005 (China); Li, Cheng; Wang, Jianyuan [Department of Physics, Xiamen University, Xiamen, Fujian 361005 (China); Tang, Dingliang [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian 361005 (China)

    2016-09-15

    Highlights: • A thin GeO{sub x}N{sub y} layer was formed by N{sub 2} plasma. • The principal parameters of N{sub 2} plasma treatment and additional post anneal have a great impact on the Al/n-Ge contact. • A model was proposed to explain the variation of Schottky barrier height. • The GeO{sub x}N{sub y} layer was also benefit to achieve a low leakage current density for HfO{sub 2}/Ge MOS capacitors. - Abstract: Severe Fermi level pinning at the interface of metal/n-Ge leads to the formation of a Schottky barrier. Therefore, a high contact resistance is introduced, debasing the performance of Ge devices. In this study, a Ge surface was treated by nitrogen plasma to form an ultra-thin Germanium oxynitride (GeO{sub x}N{sub y}) passivation layer. It was found that the Schottky barrier height (SBH) of metal/n-Ge contact was strongly modulated by the GeO{sub x}N{sub y} interlayer, indicating alleviation of Fermi-level pinning effect. By adjusting the principal parameters of N{sub 2} plasma treatment and additional post anneal, a Quasi-ohmic Al/n-Ge contact was achieved. Furthermore, the introduced GeO{sub x}N{sub y} layer gave extremely lower leakage current density of the gate stack for HfO{sub 2}/Ge devices. These results demonstrate that GeO{sub x}N{sub y} formed by N{sub 2} plasma would be greatly beneficial to the fabrication of the Ge-based devices.

  8. Cumulative dose 60Co gamma irradiation effects on AlGaN/GaN Schottky diodes and its area dependence

    Science.gov (United States)

    Sharma, Chandan; Laishram, Robert; Rawal, Dipendra Singh; Vinayak, Seema; Singh, Rajendra

    2018-04-01

    Cumulative dose gamma radiation effects on current-voltage characteristics of GaN Schottky diodes have been investigated. The different area diodes have been fabricated on AlGaN/GaN high electron mobility transistor (HEMT) epi-layer structure grown over SiC substrate and irradiated with a dose up to the order of 104 Gray (Gy). Post irradiation characterization shows a shift in the turn-on voltage and improvement in reverse leakage current. Other calculated parameters include Schottky barrier height, ideality factor and reverse saturation current. Schottky barrier height has been decreased whereas reverse saturation current shows an increase in the value post irradiation with improvement in the ideality factor. Transfer length measurement (TLM) characterization shows an improvement in the contact resistance. Finally, diodes with larger area have more variation in the calculated parameters due to the induced local heating effect.

  9. Transfer, attachment, and formation of biofilms by Escherichia coli O157:H7 on meat-contact surface materials.

    Science.gov (United States)

    Simpson Beauchamp, Catherine; Dourou, Dimitra; Geornaras, Ifigenia; Yoon, Yohan; Scanga, John A; Belk, Keith E; Smith, Gary C; Nychas, George-John E; Sofos, John N

    2012-06-01

    Studies examined the effects of meat-contact material types, inoculation substrate, presence of air at the liquid-solid surface interface during incubation, and incubation substrate on the attachment/transfer and subsequent biofilm formation by Escherichia coli O157:H7 on beef carcass fabrication surface materials. Materials studied as 2 × 5 cm coupons included stainless steel, acetal, polypropylene, and high-density polyethylene. A 6-strain rifampicin-resistant E. coli O157:H7 composite was used to inoculate (6 log CFU/mL, g, or cm²) tryptic soy broth (TSB), beef fat/lean tissue homogenate (FLH), conveyor belt-runoff fluids, ground beef, or beef fat. Coupons of each material were submerged (4 °C, 30 min) in the inoculated fluids or ground beef, or placed between 2 pieces of inoculated beef fat with pressure (20 kg) applied. Attachment/transfer of the pathogen was surface material and substrate dependent, although beef fat appeared to negate differences among surface materials. Beef fat was the most effective (P transfer and subsequent biofilm formation by E. coli O157:H7. The results highlight the importance of thoroughly cleaning soiled surfaces to remove all remnants of beef fat or other organic material that may harbor or protect microbial contaminants during otherwise lethal antimicrobial interventions. © 2012 Institute of Food Technologists®

  10. Reducing the Schottky barrier between few-layer MoTe2 and gold

    Science.gov (United States)

    Qi, Dianyu; Wang, Qixing; Han, Cheng; Jiang, Jizhou; Zheng, Yujie; Chen, Wei; Zhang, Wenjing; Thye Shen Wee, Andrew

    2017-12-01

    Schottky barriers greatly influence the performance of optoelectronic devices. Schottky barriers can be reduced by harnessing the polymorphism of 2D metal transition dichalcogenides, since both semiconducting and metallic phases exist. However, high energy, high temperature or chemicals are normally required for phase transformation, or the processes are complex. In this work, stable low-resistance contacts between few layer MoTe2 flakes and gold electrodes are achieved by a simple thermal annealing treatment at low temperature (200-400 °C). The resulting Schottky barrier height of the annealed MoTe2/Au interface is low (~23 meV). A new Raman A g mode of the 1T‧ metallic phase of MoTe2 on gold electrode is observed, indicating that the low-resistance contact is due to the phase transition of 2H-MoTe2. The gold substrate plays an important role in the transformation, and a higher gold surface roughness increases the transformation rate. With this method, the mobility and ON-state current of the MoTe2 transistor increase by ~3-4 orders of magnitude, the photocurrent of vertically stacked graphene/MoTe2/Au device increases ~300%, and the response time decreases by ~20%.

  11. Planar edge Schottky barrier-tunneling transistors using epitaxial graphene/SiC junctions.

    Science.gov (United States)

    Kunc, Jan; Hu, Yike; Palmer, James; Guo, Zelei; Hankinson, John; Gamal, Salah H; Berger, Claire; de Heer, Walt A

    2014-09-10

    A purely planar graphene/SiC field effect transistor is presented here. The horizontal current flow over one-dimensional tunneling barrier between planar graphene contact and coplanar two-dimensional SiC channel exhibits superior on/off ratio compared to conventional transistors employing vertical electron transport. Multilayer epitaxial graphene (MEG) grown on SiC(0001̅) was adopted as the transistor source and drain. The channel is formed by the accumulation layer at the interface of semi-insulating SiC and a surface silicate that forms after high vacuum high temperature annealing. Electronic bands between the graphene edge and SiC accumulation layer form a thin Schottky barrier, which is dominated by tunneling at low temperatures. A thermionic emission prevails over tunneling at high temperatures. We show that neglecting tunneling effectively causes the temperature dependence of the Schottky barrier height. The channel can support current densities up to 35 A/m.

  12. Pentacene-based photodiode with Schottky junction

    International Nuclear Information System (INIS)

    Lee, Jiyoul; Hwang, D.K.; Park, C.H.; Kim, S.S.; Im, Seongil

    2004-01-01

    We have fabricated a metal/organic semiconductor Schottky photodiode based on Al/pentacene junction. Since the energy band gap of thin solid pentacene was determined to be 1.82 eV, as characterized by direct absorption spectroscopy, we measured spectral photoresponses on our Schottky photodiode in the monochromatic light illumination range of 325-650 nm applying a reverse bias of -2 V. The main features of photo-response spectra were found to shift from those of direct absorption spectra toward higher photon energies. It is because the direct absorption spectra mainly show exciton level peaks rather than the true highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps while the photo-response spectra clearly represents the true HOMO-LUMO gap. Our photo-response spectra reveal 1.97 eV as the HOMO-LUMO gap

  13. Gallium Nitride Schottky betavoltaic nuclear batteries

    International Nuclear Information System (INIS)

    Lu Min; Zhang Guoguang; Fu Kai; Yu Guohao; Su Dan; Hu Jifeng

    2011-01-01

    Research highlights: → Gallium Nitride nuclear batteries with Ni-63 are demonstrated for the first time. → Open circuit voltage of 0.1 V and conversion efficiency of 0.32% have been obtained. → The limited performance is due to thin effective energy deposition layer. → The output power is expected to greatly increase with growing thick GaN films. -- Abstract: Gallium Nitride (GaN) Schottky betavoltaic nuclear batteries (GNBB) are demonstrated in our work for the first time. GaN films are grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD), and then GaN Schottky diodes are fabricated by normal micro-fabrication process. Nickel with mass number of 63 ( 63 Ni), which emits β particles, is loaded on the GaN Schottky diodes to achieve GNBB. X-ray diffraction (XRD) and photoluminescence (PL) are carried out to investigate the crystal quality for the GaN films as grown. Current-voltage (I-V) characteristics shows that the GaN Schottky diodes are not jet broken down at -200 V due to consummate fabrication processes, and the open circuit voltage of the GNBB is 0.1 V and the short circuit current density is 1.2 nA cm -2 . The limited performance of the GNBB is due to thin effective energy deposition layer, which is only 206 nm to absorb very small partial energy of the β particles because of the relatively high dislocation density and carrier concentration. However, the conversion efficiency of 0.32% and charge collection efficiency (CCE) of 29% for the GNBB have been obtained. Therefore, the output power of the GNBB are expected to greatly increase with growing high quality thick GaN films.

  14. Vertically grown Ge nanowire Schottky diodes on Si and Ge substrates

    Science.gov (United States)

    Chandra, Nishant; Tracy, Clarence J.; Cho, Jeong-Hyun; Picraux, S. T.; Hathwar, Raghuraj; Goodnick, Stephen M.

    2015-07-01

    The processing and performance of Schottky diodes formed from arrays of vertical Ge nanowires (NWs) grown on Ge and Si substrates are reported. The goal of this work is to investigate CMOS compatible processes for integrating NWs as components of vertically scaled integrated circuits, and elucidate transport in vertical Schottky NWs. Vertical phosphorus (P) doped Ge NWs were grown using vapor-liquid-solid epitaxy, and nickel (Ni)-Ge Schottky contacts were made to the tops of the NWs. Current-voltage (I-V) characteristics were measured for variable ranges of NW diameters and numbers of nanowires in the arrays, and the I-V characteristics were fit using modified thermionic emission theory to extract the barrier height and ideality factor. As grown NWs did not show rectifying behavior due to the presence of heavy P side-wall doping during growth, resulting in a tunnel contact. After sidewall etching using a dilute peroxide solution, rectifying behavior was obtained. Schottky barrier heights of 0.3-0.4 V and ideality factors close to 2 were extracted using thermionic emission theory, although the model does not give an accurate fit across the whole bias range. Attempts to account for enhanced side-wall conduction due to non-uniform P doping profile during growth through a simple shunt resistance improve the fit, but are still insufficient to provide a good fit. Full three-dimensional numerical modeling using Silvaco Atlas indicates that at least part of this effect is due to the presence of fixed charge and acceptor like traps on the NW surface, which leads to effectively high ideality factors.

  15. Experimental and computational investigation of graphene/SAMs/n-Si Schottky diodes

    Science.gov (United States)

    Aydin, H.; Bacaksiz, C.; Yagmurcukardes, N.; Karakaya, C.; Mermer, O.; Can, M.; Senger, R. T.; Sahin, H.; Selamet, Y.

    2018-01-01

    We have investigated the effect of two different self-assembled monolayers (SAMs) on electrical characteristics of bilayer graphene (BLG)/n-Si Schottky diodes. Novel 4″bis(diphenylamino)-1, 1‧:3″-terphenyl-5‧ carboxylic acids (TPA) and 4,4-di-9H-carbazol-9-yl-1,1‧:3‧1‧-terphenyl-5‧ carboxylic acid (CAR) aromatic SAMs have been used to modify n-Si surfaces. Cyclic voltammetry (CV) and Kelvin probe force microscopy (KPFM) results have been evaluated to verify the modification of n-Si surface. The current-voltage (I-V) characteristics of bare and SAMs modified devices show rectification behaviour verifying a Schottky junction at the interface. The ideality factors (n) from ln(I)-V dependences were determined as 2.13, 1.96 and 2.07 for BLG/n-Si, BLG/TPA/n-Si and BLG/CAR/n-Si Schottky diodes, respectively. In addition, Schottky barrier height (SBH) and series resistance (Rs) of SAMs modified diodes were decreased compared to bare diode due to the formation of a compatible interface between graphene and Si as well as π-π interaction between aromatic SAMs and graphene. The CAR-based device exhibits better diode characteristic compared to the TPA-based device. Computational simulations show that the BLG/CAR system exhibits smaller energy-level-differences than the BLG/TPA, which supports the experimental findings of a lower Schottky barrier and series resistance in BLG/CAR diode.

  16. Gate Modulation of Graphene-ZnO Nanowire Schottky Diode

    OpenAIRE

    Liu, Ren; You, Xu-Chen; Fu, Xue-Wen; Lin, Fang; Meng, Jie; Yu, Da-Peng; Liao, Zhi-Min

    2015-01-01

    Graphene-semiconductor interface is important for the applications in electronic and optoelectronic devices. Here we report the modulation of the electric transport properties of graphene/ZnO nanowire Schottky diode by gate voltage (Vg). The ideality factor of the graphene/ZnO nanowire Schottky diode is ~1.7, and the Schottky barrier height is ~0.28?eV without external Vg. The Schottky barrier height is sensitive to Vg due to the variation of Fermi level of graphene. The barrier height increa...

  17. Ultraviolet photoelectron spectroscopy investigation of interface formation in an indium-tin oxide/fluorocarbon/organic semiconductor contact

    International Nuclear Information System (INIS)

    Tong, S.W.; Lau, K.M.; Sun, H.Y.; Fung, M.K.; Lee, C.S.; Lifshitz, Y.; Lee, S.T.

    2006-01-01

    It has been demonstrated that hole-injection in organic light-emitting devices (OLEDs) can be enhanced by inserting a UV-illuminated fluorocarbon (CF x ) layer between indium-tin oxide (ITO) and organic hole-transporting layer (HTL). In this work, the process of interface formation and electronic properties of the ITO/CF x /HTL interface were investigated with ultraviolet photoelectron spectroscopy. It was found that UV-illuminated fluorocarbon layer decreases the hole-injection barrier from ITO to α-napthylphenylbiphenyl diamine (NPB). Energy level diagrams deduced from the ultraviolet photoelectron spectroscopy (UPS) spectra show that the hole-injection barrier in ITO/UV-treated CF x /NPB is the smallest (0.46 eV), compared to that in the ITO/untreated CF x /NPB (0.60 eV) and the standard ITO/NPB interface (0.68 eV). The improved current density-voltage (I-V) characteristics in the UV-treated CF x -coated ITO contact are consistent with its smallest barrier height

  18. Contact between the β1 and β2 Segments of α-Synuclein that Inhibits Amyloid Formation.

    Science.gov (United States)

    Shaykhalishahi, Hamed; Gauhar, Aziz; Wördehoff, Michael M; Grüning, Clara S R; Klein, Antonia N; Bannach, Oliver; Stoldt, Matthias; Willbold, Dieter; Härd, Torleif; Hoyer, Wolfgang

    2015-07-20

    Conversion of the intrinsically disordered protein α-synuclein (α-syn) into amyloid aggregates is a key process in Parkinson's disease. The sequence region 35-59 contains β-strand segments β1 and β2 of α-syn amyloid fibril models and most disease-related mutations. β1 and β2 frequently engage in transient interactions in monomeric α-syn. The consequences of β1-β2 contacts are evaluated by disulfide engineering, biophysical techniques, and cell viability assays. The double-cysteine mutant α-synCC, with a disulfide linking β1 and β2, is aggregation-incompetent and inhibits aggregation and toxicity of wild-type α-syn. We show that α-syn delays the aggregation of amyloid-β peptide and islet amyloid polypeptide involved in Alzheimer's disease and type 2 diabetes, an effect enhanced in the α-synCC mutant. Tertiary interactions in the β1-β2 region of α-syn interfere with the nucleation of amyloid formation, suggesting promotion of such interactions as a potential therapeutic approach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Fabrication of a Schottky junction diode with direct growth graphene on silicon by a solid phase reaction

    International Nuclear Information System (INIS)

    Kalita, Golap; Hirano, Ryo; Ayhan, Muhammed E; Tanemura, Masaki

    2013-01-01

    We demonstrate fabrication of a Schottky junction diode with direct growth graphene on n-Si by the solid phase reaction approach. Metal-assisted crystallization of a-C thin film was performed to synthesize transfer-free graphene directly on a SiO 2 patterned n-Si substrate. Graphene formation at the substrate and catalyst layer interface is achieved in presence of a Co catalytic and CoO carbon diffusion barrier layer. The as-synthesized material shows a linear current–voltage characteristic confirming the metallic behaviour of the graphene structure. The direct grown graphene on n-Si substrate creates a Schottky junction with a potential barrier of 0.44 eV and rectification diode characteristic. Our finding shows that the directly synthesized graphene on Si substrate by a solid phase reaction process can be a promising technique to fabricate an efficient Schottky junction device. (paper)

  20. Thermionic field emission in gold nitride Schottky nanodiodes

    Science.gov (United States)

    Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

    2012-11-01

    We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

  1. Oxygen vacancy tuned Ohmic-Schottky conversion for enhanced performance in β-Ga{sub 2}O{sub 3} solar-blind ultraviolet photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Guo, D. Y.; Wu, Z. P.; An, Y. H.; Guo, X. C.; Chu, X. L.; Sun, C. L.; Tang, W. H., E-mail: whtang@bupt.edu.cn [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Li, L. H. [Physics Department, The State University of New York at Potsdam, Potsdam, New York 13676-2294 (United States); Li, P. G., E-mail: pgli@zstu.edu.cn [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Center for Optoelectronics Materials and Devices, Department of Physics, Zhejiang Sci-Tech University, Hangzhou, 310018 Zhejiang (China)

    2014-07-14

    β-Ga{sub 2}O{sub 3} epitaxial thin films were deposited using laser molecular beam epitaxy technique and oxygen atmosphere in situ annealed in order to reduce the oxygen vacancy. Metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately. Au/Ti electrodes were Ohmic contact with the as-grown films and Schottky contact with the annealed films. In compare with the Ohmic-type photodetector, the Schottky-type photodetector takes on lower dark current, higher photoresponse, and shorter switching time, which benefit from Schottky barrier controlling electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.

  2. Paper S12 5 : Self-aligned a-IGZO TFTs : Impact of S/D contacts formation on their Negative-Bias-Illumination-Stress (NBIS) instability

    NARCIS (Netherlands)

    Nag, M.; Steudel, S.; Smout, S.; Bhoolokam, A.; Genoe, J.; Cobb, B.; Kumar, A.; Groeseneken, G.; Heremans, P.

    2015-01-01

    In this work, we present the impact of S/D contact formation, that is, by SiN plasma doping (hydrogen incorporation), metallic reduction (by calcium) and by argon plasma (compositional change) on NBIS instabilities of self-aligned a-IGZO TFTs.

  3. Effects of thin heavily Mg-doped GaN capping layer on ohmic contact formation of p-type GaN

    International Nuclear Information System (INIS)

    Wu, L L; Zhao, D G; Jiang, D S; Chen, P; Le, L C; Li, L; Liu, Z S; Zhang, S M; Zhu, J J; Wang, H; Zhang, B S; Yang, H

    2013-01-01

    The growth condition of thin heavily Mg-doped GaN capping layer and its effect on ohmic contact formation of p-type GaN were investigated. It is confirmed that the excessive Mg doping can effectively enhance the Ni/Au contact to p-GaN after annealing at 550 °C. When the flow rate ratio between Mg and Ga gas sources is 6.4% and the layer width is 25 nm, the capping layer grown at 850 °C exhibits the best ohmic contact properties with respect to the specific contact resistivity (ρ c ). This temperature is much lower than the conventional growth temperature of Mg-doped GaN, suggesting that the deep-level-defect induced band may play an important role in the conduction of capping layer. (paper)

  4. Interface feature characterization and Schottky interfacial layer confirmation of TiO{sub 2} nanotube array film

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongchao [State Key Laboratory of Powder Metallurgy, Central South University, 410083 Changsha (China); Chongyi Zhangyuan Tungsten Industry Corporation Limited, 341300 Ganzhou (China); Tang, Ningxin; Yang, Hongzhi; Leng, Xian [State Key Laboratory of Powder Metallurgy, Central South University, 410083 Changsha (China); Zou, Jianpeng, E-mail: zoujp@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, 410083 Changsha (China)

    2015-11-15

    Highlights: • Interfacial fusion of TiO{sub 2} nanotube film increases with annealing temperature. • Interface bonding force of the film increases with annealing temperature. • We report the forth stage of nanofibers formation in the growing mechanism. • TiO{sub 2} nanotubes grow from Schottky interface layer rather than from Ti substrate. • Schottky interface layer's thickness of 35–45 nm is half the diameter of nanotube. - Abstract: We report here characterization of the interfacial microstructure and properties of titanium dioxide (TiO{sub 2}) nanotube array films fabricated by anodization. Field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the interface of the film. With increasing annealing temperature from 200 °C to 800 °C, the interfacial fusion between the film and the Ti substrate increased. The phase transformation of the TiO{sub 2} nanotube film from amorphous to anatase to rutile took place gradually; as the phase transformation progressed, the force needed to break the film increased. The growth of TiO{sub 2} nanotube arrays occurs in four stages: barrier layer formation, penetrating micropore formation, regular nanotube formation, and nanofiber formation. The TiO{sub 2} nanotubes grow from the Schottky interface layer rather than from the Ti substrate. The Schottky interface layer's thickness of 35–45 nm was identified as half the diameter of the corresponding nanotube, which shows good agreement to the Schottky interface layer growth model. The TiO{sub 2} nanotube film was amorphous and the Ti substrate was highly crystallized with many dislocation walls.

  5. Involvement of YAP, TAZ and HSP90 in contact guidance and intercellular junction formation in corneal epithelial cells.

    Directory of Open Access Journals (Sweden)

    Vijay Krishna Raghunathan

    Full Text Available The extracellular environment possesses a rich milieu of biophysical and biochemical signaling cues that are simultaneously integrated by cells and influence cellular phenotype. Yes-associated protein (YAP and transcriptional co-activator with PDZ-binding motif (WWTR1; TAZ, two important signaling molecules of the Hippo pathway, have been recently implicated as nuclear relays of cytoskeletal changes mediated by substratum rigidity and topography. These proteins intersect with other important intracellular signaling pathways (e.g. Wnt and TGFβ. In the cornea, epithelial cells adhere to the stroma through a 3-dimensional topography-rich basement membrane, with features in the nano-submicron size-scale that are capable of profoundly modulating a wide range of fundamental cell behaviors. The influences of substratum-topography, YAP/TAZ knockdown, and HSP90 inhibition on cell morphology, YAP/TAZ localization, and the expression of TGFβ2 and CTGF, were investigated. The results demonstrate (a that knockdown of TAZ enhances contact guidance in a YAP dependent manner, (b that CTGF is predominantly regulated by YAP and not TAZ, and (c that TGFβ2 is regulated by both YAP and TAZ in these cells. Additionally, inhibition of HSP90 resulted in nuclear localization and subsequent transcriptional-activation of YAP, formation of cell-cell junctions and co-localization of E-cadherin and β-catenin at adherens junctions. Results presented in this study reflect the complexities underlying the molecular relationships between the cytoskeleton, growth factors, heat shock proteins, and co-activators of transcription that impact mechanotransduction. The data reveal the importance of YAP/TAZ on the cell behaviors, and gene and protein expression.

  6. Schottky Barrier Height Tuning via the Dopant Segregation Technique through Low-Temperature Microwave Annealing.

    Science.gov (United States)

    Fu, Chaochao; Zhou, Xiangbiao; Wang, Yan; Xu, Peng; Xu, Ming; Wu, Dongping; Luo, Jun; Zhao, Chao; Zhang, Shi-Li

    2016-04-27

    The Schottky junction source/drain structure has great potential to replace the traditional p/n junction source/drain structure of the future ultra-scaled metal-oxide-semiconductor field effect transistors (MOSFETs), as it can form ultimately shallow junctions. However, the effective Schottky barrier height (SBH) of the Schottky junction needs to be tuned to be lower than 100 meV in order to obtain a high driving current. In this paper, microwave annealing is employed to modify the effective SBH of NiSi on Si via boron or arsenic dopant segregation. The barrier height decreased from 0.4-0.7 eV to 0.2-0.1 eV for both conduction polarities by annealing below 400 °C. Compared with the required temperature in traditional rapid thermal annealing, the temperature demanded in microwave annealing is ~60 °C lower, and the mechanisms of this observation are briefly discussed. Microwave annealing is hence of high interest to future semiconductor processing owing to its unique capability of forming the metal/semiconductor contact at a remarkably lower temperature.

  7. Irradiation effects on electrical properties of DNA solution/Al Schottky diodes

    Science.gov (United States)

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Iwamoto, Mitsumasa

    2018-04-01

    Deoxyribonucleic acid (DNA) has emerged as one of the most exciting organic material and as such extensively studied as a smart electronic material since the last few decades. DNA molecules have been reported to be utilized in the fabrication of small-scaled sensors and devices. In this current work, the effect of alpha radiation on the electrical properties of an Al/DNA/Al device using DNA solution was studied. It was observed that the carrier transport was governed by electrical interface properties at the Al-DNA interface. Current ( I)-voltage ( V) curves were analyzed by employing the interface limited Schottky current equations, i.e., conventional and Cheung and Cheung's models. Schottky parameters such as ideality factor, barrier height and series resistance were also determined. The extracted barrier height of the Schottky contact before and after radiation was calculated as 0.7845, 0.7877, 0.7948 and 0.7874 eV for the non-radiated, 12, 24 and 36 mGy, respectively. Series resistance of the structure was found to decline with the increase in the irradiation, which was due to the increase in the free radical root effects in charge carriers in the DNA solution. Results pertaining to the electronic profiles obtained in this work may provide a better understanding for the development of precise and rapid radiation sensors using DNA solution.

  8. Interdigitated Pt-GaN Schottky interfaces for high-temperature soot-particulate sensing

    Science.gov (United States)

    So, Hongyun; Hou, Minmin; Jain, Sambhav R.; Lim, Jongwoo; Senesky, Debbie G.

    2016-04-01

    A microscale soot-particulate sensor using interdigitated platinum-gallium nitride (Pt-GaN) Schottky interfaces was developed to monitor fine soot particles within high-temperature environments (e.g., combustion exhausts and flues). Upon exposure to soot particles (30 to 50 nm in diameter) from an experimental chimney, an increased current (∼43.6%) is observed through the back-to-back Schottky contact to n-type GaN. This is attributed to a reduction in the effective Schottky barrier height (SBH) of ∼10 meV due to the electric field from the charged soot particles in the depletion region and exposed GaN surface. Furthermore, the microfabricated sensor was shown to recover sensitivity and regenerate the sensing response (∼11 meV SBH reduction) after exposure to temperature as high as 550 °C. This study supports the feasibility of a simple and reliable soot sensor to meet the increasing market demand for particulate matter sensing in harsh environments.

  9. Controlling Schottky energy barriers in organic electronic devices using self-assembled monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, I.H.; Rubin, S.; Zawodzinski, T.A.; Kress, J.D.; Martin, R.L.; Smith, D.L. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Barashkov, N.N.; Ferraris, J.P. [The University of Texas at Dallas, Richardson, Texas 75083 (United States)

    1996-11-01

    We demonstrate tuning of Schottky energy barriers in organic electronic devices by utilizing chemically tailored electrodes. The Schottky energy barrier of Ag on poly[2-methoxy], 5-(2{prime}-ethyl-hexyloxy)- 1,4-phenylene was tuned over a range of more than 1 eV by using self-assembled monolayers (SAM{close_quote}s) to attach oriented dipole layers to the Ag prior to device fabrication. Kelvin probe measurements were used to determine the effect of the SAM{close_quote}s on the Ag surface potential. {ital Ab} {ital initio} Hartree-Fock calculations of the molecular dipole moments successfully describe the surface potential changes. The chemically tailored electrodes were then incorporated in organic diode structures and changes in the metal/organic Schottky energy barriers were measured using an electroabsorption technique. These results demonstrate the use of self-assembled monolayers to control metal/organic interfacial electronic properties. They establish a physical principle for manipulating the relative energy levels between two materials and demonstrate an approach to improve metal/organic contacts in organic electronic devices. {copyright} {ital 1996 The American Physical Society.}

  10. Controlling Schottky energy barriers in organic electronic devices using self-assembled monolayers

    International Nuclear Information System (INIS)

    Campbell, I.H.; Rubin, S.; Zawodzinski, T.A.; Kress, J.D.; Martin, R.L.; Smith, D.L.; Barashkov, N.N.; Ferraris, J.P.

    1996-01-01

    We demonstrate tuning of Schottky energy barriers in organic electronic devices by utilizing chemically tailored electrodes. The Schottky energy barrier of Ag on poly[2-methoxy], 5-(2'-ethyl-hexyloxy)- 1,4-phenylene was tuned over a range of more than 1 eV by using self-assembled monolayers (SAM close-quote s) to attach oriented dipole layers to the Ag prior to device fabrication. Kelvin probe measurements were used to determine the effect of the SAM close-quote s on the Ag surface potential. Ab initio Hartree-Fock calculations of the molecular dipole moments successfully describe the surface potential changes. The chemically tailored electrodes were then incorporated in organic diode structures and changes in the metal/organic Schottky energy barriers were measured using an electroabsorption technique. These results demonstrate the use of self-assembled monolayers to control metal/organic interfacial electronic properties. They establish a physical principle for manipulating the relative energy levels between two materials and demonstrate an approach to improve metal/organic contacts in organic electronic devices. copyright 1996 The American Physical Society

  11. Controlling Schottky energy barriers in organic electronic devices using self-assembled monolayers

    Science.gov (United States)

    Campbell, I. H.; Rubin, S.; Zawodzinski, T. A.; Kress, J. D.; Martin, R. L.; Smith, D. L.; Barashkov, N. N.; Ferraris, J. P.

    1996-11-01

    We demonstrate tuning of Schottky energy barriers in organic electronic devices by utilizing chemically tailored electrodes. The Schottky energy barrier of Ag on poly[2-methoxy, 5-(2'-ethyl-hexyloxy)- 1,4-phenylene was tuned over a range of more than 1 eV by using self-assembled monolayers (SAM's) to attach oriented dipole layers to the Ag prior to device fabrication. Kelvin probe measurements were used to determine the effect of the SAM's on the Ag surface potential. Ab initio Hartree-Fock calculations of the molecular dipole moments successfully describe the surface potential changes. The chemically tailored electrodes were then incorporated in organic diode structures and changes in the metal/organic Schottky energy barriers were measured using an electroabsorption technique. These results demonstrate the use of self-assembled monolayers to control metal/organic interfacial electronic properties. They establish a physical principle for manipulating the relative energy levels between two materials and demonstrate an approach to improve metal/organic contacts in organic electronic devices.

  12. Electrical characterization of CdTe pixel detectors with Al Schottky anode

    International Nuclear Information System (INIS)

    Turturici, A.A.; Abbene, L.; Gerardi, G.; Principato, F.

    2014-01-01

    Pixelated Schottky Al/p-CdTe/Pt detectors are very attractive devices for high-resolution X-ray spectroscopic imaging, even though they suffer from bias-induced time instability (polarization). In this work, we present the results of the electrical characterization of a (4×4) pixelated Schottky Al/p-CdTe/Pt detector. Current–voltage (I–V) characteristics and current transients were investigated at different temperatures. The results show deep levels that play a dominant role in the charge transport mechanism. The conduction mechanism is dominated by the space charge limited current (SCLC) both under forward bias and at high reverse bias. Schottky barrier height of the Al/CdTe contact was estimated by using the thermionic-field emission model at low reverse bias voltages. Activation energy of the deep levels was measured through the analysis of the reverse current transients at different temperatures. Finally, we employed an analytical method to determine the density and the energy distribution of the traps from SCLC current–voltage characteristics

  13. Gate Modulation of Graphene-ZnO Nanowire Schottky Diode.

    Science.gov (United States)

    Liu, Ren; You, Xu-Chen; Fu, Xue-Wen; Lin, Fang; Meng, Jie; Yu, Da-Peng; Liao, Zhi-Min

    2015-05-06

    Graphene-semiconductor interface is important for the applications in electronic and optoelectronic devices. Here we report the modulation of the electric transport properties of graphene/ZnO nanowire Schottky diode by gate voltage (Vg). The ideality factor of the graphene/ZnO nanowire Schottky diode is ~1.7, and the Schottky barrier height is ~0.28 eV without external Vg. The Schottky barrier height is sensitive to Vg due to the variation of Fermi level of graphene. The barrier height increases quickly with sweeping Vg towards the negative value, while decreases slowly towards the positive Vg. Our results are helpful to understand the fundamental mechanism of the electric transport in graphene-semiconductor Schottky diode.

  14. Lateral polarity control of III-nitride thin film and application in GaN Schottky barrier diode

    Science.gov (United States)

    Li, Junmei; Guo, Wei; Sheikhi, Moheb; Li, Hongwei; Bo, Baoxue; Ye, Jichun

    2018-05-01

    N-polar and III-polar GaN and AlN epitaxial thin films grown side by side on single sapphire substrate was reported. Surface morphology, wet etching susceptibility and bi-axial strain conditions were investigated and the polarity control scheme was utilized in the fabrication of Schottky barrier diode where ohmic contact and Schottky contact were deposited on N-polar domains and Ga-polar domains, respectively. The influence of N-polarity on on-state resistivity and I–V characteristic was discussed, demonstrating that lateral polarity structure of GaN and AlN can be widely used in new designs of optoelectronic and electronic devices. Project partially supported by the National Key Research and Development Program of China (No. 2016YFB0400802), the National Natural Science Foundation of China (No. 61704176), and the Open project of Zhejiang Key Laboratory for Advanced Microelectronic Intelligent Systems and Applications (No. ZJUAMIS1704).

  15. Evaluation of Schottky and MgO-based tunnelling diodes with different ferromagnets for spin injection in n-Si

    International Nuclear Information System (INIS)

    Uhrmann, T; Dimopoulos, T; Brueckl, H; Kovacs, A; Kohn, A; Weyers, S; Paschen, U; Smoliner, J

    2009-01-01

    In this work we present the electrical properties of sputter-deposited ferromagnetic (FM) Schottky diodes and MgO-based tunnelling diodes to n-doped (0 0 1) silicon. The effective Schottky barrier height (SBH) has been evaluated as a function of the FM electrode (Co 70 Fe 30 , Co 40 Fe 40 B 20 and Ni 80 Fe 20 ), the silicon doping density (10 15 to 10 18 cm -3 ), the MgO tunnelling barrier thickness (0, 1.5 and 2.5 nm) and post-deposition annealing up to 400 0 C. The ideality factors of the Schottky diodes are close to unity, indicating transport by thermionic emission and the absence of an interfacial oxide layer, which is confirmed by transmission electron microscopy. The effective SBH is found to be approximately 0.65 eV, independent of the FM material and decreasing with increasing doping density. The changes induced by high temperature annealing at the current-voltage characteristic of the Schottky diodes depend strongly on the FM electrode. The effective SBH for the tunnelling diodes is as low as 0.3 eV, which suggests a high density of oxide and interface traps. It is again independent of the FM electrode, decreasing with increasing doping density and annealing temperature. The inclusion of MgO leads to higher thermal stability of the tunnelling diodes. The measured contact resistance values are discussed with respect to the conductivity mismatch for spin injection and detection.

  16. Modulation of electrical properties in Cu/n-type InP Schottky junctions using oxygen plasma treatment

    International Nuclear Information System (INIS)

    Kim, Hogyoung; Jung, Chan Yeong; Hyun Kim, Se; Cho, Yunae; Kim, Dong-Wook

    2015-01-01

    Using current–voltage (I–V) measurements, we investigated the effect of oxygen plasma treatment on the temperature-dependent electrical properties of Cu/n-type indium phosphide (InP) Schottky contacts at temperatures in the range 100–300 K. Changes in the electrical parameters were evident below 180 K for the low-plasma-power sample (100 W), which is indicative of the presence of a wider distribution of regions of low barrier height. Modified Richardson plots were used to obtain Richardson constants, which were similar to the theoretical value of 9.4 A cm −2 K −2 for n-type InP. This suggests that, for all the samples, a thermionic emission model including a spatially inhomogeneous Schottky barrier can be used to describe the charge transport phenomena at the metal/semiconductor interface. The voltage dependence of the reverse-bias current revealed that Schottky emission was dominant for the untreated and high-plasma-power (250 W) samples. For the low-plasma-power sample, Poole–Frenkel emission was dominant at low voltages, whereas Schottky emission dominated at higher voltages. Defect states and nonuniformity of the interfacial layer appear to be significant in the reverse-bias charge transport properties of the low-plasma-power sample. (paper)

  17. Fabrication and characterization of Pd/Cu doped ZnO/Si and Ni/Cu doped ZnO/Si Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Lucky; Singh, Brijesh Kumar; Tripathi, Shweta [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Chakrabarti, P., E-mail: pchakrabarti.ece@iitbhu.ac.in [Department of Electronics & Communication Engineering, Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Department of Electronics Engineering, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2016-08-01

    In this paper, fabrication and characterization of copper doped ZnO (Cu doped ZnO) based Schottky devices have been reported. Cu doped ZnO thin films have been deposited on p-Si (100) samples by the sol-gel spin coating method. X-Ray diffraction (XRD) and atomic force microscopy (AFM) studies have been done in order to evaluate the structural and morphological properties of the film. The optical properties of the film have been determined by using variable angle ellipsometry. Further, Seebeck measurement of the deposited Cu doped ZnO film leads to positive Seebeck coefficient confirming the p-type conductivity of the sample. The resistivity and acceptor concentration of the film has also been evaluated using four probe measurement system. Pd and Ni metals have been deposited on separate Cu doped ZnO thin film samples using low cost thermal evaporation method to form Schottky contacts. The electrical characterization of the Schottky diode has been performed by semiconductor device analyzer (SDA). Electrical parameters such as barrier height, ideality factor, reverse saturation current and rectification ratio have also been determined for the as-prepared Schottky diode using conventional thermionic emission model and Cheung's method. - Highlights: • Fabrication of sol-gel derived Cu doped ZnO (p-type) Schottky contact proposed. • The p-type Conductivity of the sample confirmed by Seebeck Measurement. • Pd and Ni deposited on Cu doped ZnO film to form Schottky contacts. • Cu doped ZnO expected to emerge as a potential material for thin film solar cells.

  18. Fabrication and characterization of Pd/Cu doped ZnO/Si and Ni/Cu doped ZnO/Si Schottky diodes

    International Nuclear Information System (INIS)

    Agarwal, Lucky; Singh, Brijesh Kumar; Tripathi, Shweta; Chakrabarti, P.

    2016-01-01

    In this paper, fabrication and characterization of copper doped ZnO (Cu doped ZnO) based Schottky devices have been reported. Cu doped ZnO thin films have been deposited on p-Si (100) samples by the sol-gel spin coating method. X-Ray diffraction (XRD) and atomic force microscopy (AFM) studies have been done in order to evaluate the structural and morphological properties of the film. The optical properties of the film have been determined by using variable angle ellipsometry. Further, Seebeck measurement of the deposited Cu doped ZnO film leads to positive Seebeck coefficient confirming the p-type conductivity of the sample. The resistivity and acceptor concentration of the film has also been evaluated using four probe measurement system. Pd and Ni metals have been deposited on separate Cu doped ZnO thin film samples using low cost thermal evaporation method to form Schottky contacts. The electrical characterization of the Schottky diode has been performed by semiconductor device analyzer (SDA). Electrical parameters such as barrier height, ideality factor, reverse saturation current and rectification ratio have also been determined for the as-prepared Schottky diode using conventional thermionic emission model and Cheung's method. - Highlights: • Fabrication of sol-gel derived Cu doped ZnO (p-type) Schottky contact proposed. • The p-type Conductivity of the sample confirmed by Seebeck Measurement. • Pd and Ni deposited on Cu doped ZnO film to form Schottky contacts. • Cu doped ZnO expected to emerge as a potential material for thin film solar cells.

  19. Effect of Barrier Metal Based on Titanium or Molybdenum in Characteristics of 4H-SiC Schottky Diodes

    Directory of Open Access Journals (Sweden)

    M. Ben Karoui

    2014-05-01

    Full Text Available The electrical properties were extracted by I-V and C-V analysis, performed from 10 K to 450 K. When the annealing temperature varied to 400 °C, the Schottky barrier height (SBH increased from 0.85 Ev to 1.20 eV in Ti/4H-SiC whereas in the Mo/4H-SiC the SBH varied from 1.04 eV to 1.10 eV. Deformation of J-V-T characteristics was observed in two types of devices when the temperature decreases from 300 K to 10 K. The electrical properties and the stability of the devices have been correlated to the fabrication processes and to the metal/semiconductor interfaces. Mo-based contacts show better behaviour in forward polarization when compared to the Ti-based Schottky contacts, with ideality factors close to the unity even after the annealing process. However, Mo-based contacts show leakage currents higher than that measured on the more optimized Ti-based Schottky.

  20. Formation Process and Properties of Ohmic Contacts Containing Molybdenum to AlGaN/GaN Heterostructures

    Directory of Open Access Journals (Sweden)

    Wojciech Macherzynski

    2016-01-01

    Full Text Available Properties of wide bandgap semiconductors as chemical inertness to harsh conditions and possibility of working at high temperature ensure possible applications in the field as military, aerospace, automotive, engine monitoring, flame detection and solar UV detection. Requirements for ohmic contacts in semiconductor devices are determined by the proposed application. These contacts to AlGaN/GaN heterostructure for application as high temperature, high frequency and high power devices have to exhibit good surface morphology and low contact resistance. The latter is a crucial factor in limiting the development of high performance AlGaN/GaN devices. Lowering of the resistance is assured by rapid thermal annealing process. The paper present studies of Ti/Al/Mo/Au ohmic contacst annealed at temperature range from 825°C to 885°C in N2 atmosphere. The electrical parameters of examined samples as a function of the annealing process condition have been studied. Initially the annealing temperature increase caused lowering of the contacts resistance. The lowest value was noticed for the temperature of annealing equal to 885°C. Further increase of annealing temperature led to deterioration of contact resistance of investigated ohmic contacts.

  1. Asymmetric contacts on a single SnO₂ nanowire device: an investigation using an equivalent circuit model.

    Science.gov (United States)

    Huh, Junghwan; Na, Junhong; Ha, Jeong Sook; Kim, Sangtae; Kim, Gyu Tae

    2011-08-01

    Electrical contacts between the nanomaterial and metal electrodes are of crucial importance both from fundamental and practical points of view. We have systematically compared the influence of contact properties by dc and EIS (Electrochemical impedance spectroscopy) techniques at various temperatures and environmental atmospheres (N(2) and 1% O(2)). Electrical behaviors are sensitive to the variation of Schottky barriers, while the activation energy (E(a)) depends on the donor states in the nanowire rather than on the Schottky contact. Equivalent circuits in terms of dc and EIS analyses could be modeled by Schottky diodes connected with a series resistance and parallel RC circuits, respectively. These results can facilitate the electrical analysis for evaluating the nanowire electronic devices with Schottky contacts.

  2. Ohmic Contacts to 2D Semiconductors through van der Waals Bonding

    NARCIS (Netherlands)

    Farmanbar Gelepordsari, M.; Brocks, G.

    2016-01-01

    High contact resistances have blocked the progress of devices based on MX2 (M = Mo, W; X = S, Se, Te) 2D semiconductors. Interface states formed at MX2/metal contacts pin the Fermi level, leading to sizable Schottky barriers for p-type contacts in particular. It is shown that i) one can remove the

  3. Electrical characteristics of {sup 60}Co {gamma}-ray irradiated MIS Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Tataroglu, A. [Department of Physics, Faculty of Arts and Sciences, Gazi University, 06500 Ankara (Turkey)]. E-mail: ademt@gazi.edu.tr; Altindal, S. [Department of Physics, Faculty of Arts and Sciences, Gazi University, 06500 Ankara (Turkey)

    2006-11-15

    In order to interpret the effect of {sup 60}Co {gamma}-ray irradiation dose on the electrical characteristics of MIS Schottky diodes, they were stressed with a zero bias at 1 MHz in dark and room temperature during {gamma}-ray irradiation and the total dose range was 0-450 kGy. The effect of {gamma}-ray exposure on the electrical characteristics of MIS Schottky diodes has been investigated using C-V and G/{omega}-V measurements at room temperature. Experimental results show that {gamma}-ray irradiation induces a decrease in the barrier height {phi} {sub B} and series resistance R {sub s}, decreasing with increasing dose rate. Also, the acceptor concentration N {sub A} increases with increasing radiation dose. The C-V characteristics prove that there is a reaction for extra recombination centers in case of MIS Schottky diodes exposed to {gamma}-ray radiation. Furthermore, the density of interface states N {sub ss} by Hill-Coleman method increases with increasing radiation dose. Experimental results indicate that the interface-trap formation at high irradiation dose is reduced due to positive charge build-up in the Si/SiO{sub 2} interface (due to the trapping of holes) that reduces the flow rate of subsequent holes and protons from the bulk of the insulator to the Si/SiO{sub 2} interface.

  4. Determination of the characteristics of a Schottky barrier formed by latent finger mark corrosion of brass

    International Nuclear Information System (INIS)

    Bond, J W

    2009-01-01

    The ideality factor (η) and barrier height (φ B ) for a metal-copper(I) oxide rectifying contact formed by the latent finger mark corrosion of α phase brass have been determined from forward bias I/V characteristics in the range 0.4 V ≤ V ≤ 0.55 V. Rectifying contacts formed from the finger mark deposits of different people gave η = 1.5-1.6 ± 0.1 and φ B = 0.49-0.52 ± 0.04 V. A Mott-Schottky plot of capacitance-voltage measurements in reverse bias gave the built in potential ψ bi = 0.4 ± 0.1 V, the gradient of the plot confirming the conductivity of the finger mark corrosion as p type. X-ray photoelectron spectroscopy spectra of the corrosion showed that Cu(I), Cu(II) and Zn(II) can co-exist on the surface, the Cu(I) : Cu(II) and Zn : Cu ratios determining whether a rectifying contact is formed. Initial findings suggest that when the concentration of Cu(I) dominates the Cu(I) : Cu(II) ratio (approximately 6 : 1), or when Cu(II) is absent, a rectifying contact can be formed subject to the Zn : Cu ratio being approximately 1 : 3. As the surface concentration of zinc increases, the rectifying contact is degraded until the concentration of zinc approaches that of copper when no evidence of a Schottky barrier is observed and the contact appears ohmic.

  5. Schottky barrier parameters and low frequency noise characteristics of graphene-germanium Schottky barrier diode

    Science.gov (United States)

    Khurelbaatar, Zagarzusem; Kil, Yeon-Ho; Shim, Kyu-Hwan; Cho, Hyunjin; Kim, Myung-Jong; Lee, Sung-Nam; Jeong, Jae-chan; Hong, Hyobong; Choi, Chel-Jong

    2016-03-01

    We investigated the electrical properties of chemical vapor deposition-grown monolayer graphene/n-type germanium (Ge) Schottky barrier diodes (SBD) using current-voltage (I-V) characteristics and low frequency noise measurements. The Schottky barrier parameters of graphene/n-type Ge SBDs, such as Schottky barrier height (VB), ideality factor (n), and series resistance (Rs), were extracted using the forward I-V and Cheung's methods. The VB and n extracted from the forward ln(I)-V plot were found to be 0.63 eV and 1.78, respectively. In contrast, from Cheung method, the VB and n were calculated to be 0.53 eV and 1.76, respectively. Such a discrepancy between the values of VB calculated from the forward I-V and Cheung's methods indicated a deviation from the ideal thermionic emission of graphene/n-type Ge SBD associated with the voltage drop across graphene. The low frequency noise measurements performed at the frequencies in the range of 10 Hz-1 kHz showed that the graphene/n-type Ge SBD had 1/f γ frequency dependence, with γ ranging from 1.09 to 1.12, regardless of applied forward biases. Similar to forward-biased SBDs operating in the thermionic emission mode, the current noise power spectral density of graphene/n-type Ge SBD was linearly proportional to the forward current.

  6. Barrier height of Pt–In[sub x]Ga[sub 1−x]N (0≤x≤0.5) nanowire Schottky diodes

    KAUST Repository

    Guo, Wei; Banerjee, Animesh; Zhang, Meng; Bhattacharya, Pallab

    2011-01-01

    The barrier height of Schottky diodes made on Inx Ga 1-x N nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are ∼1 μm, 20 nm, and 1× 1011 cm-2. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height B varies from 1.4 eV (GaN) to 0.44 eV (In0.5 Ga0.5 N) and agrees well with the ideal barrier heights in the Schottky limit. © 2011 American Institute of Physics.

  7. A low knee voltage and high breakdown voltage of 4H-SiC TSBS employing poly-Si/Ni Schottky scheme

    Science.gov (United States)

    Kim, Dong Young; Seok, Ogyun; Park, Himchan; Bahng, Wook; Kim, Hyoung Woo; Park, Ki Cheol

    2018-02-01

    We report a low knee voltage and high breakdown voltage 4H-SiC TSBS employing poly-Si/Ni dual Schottky contacts. A knee voltage was significantly improved from 0.75 to 0.48 V by utilizing an alternative low work-function material of poly-Si as an anode electrode. Also, reverse breakdown voltage was successfully improved from 901 to 1154 V due to a shrunk low-work-function Schottky region by a proposed self-align etching process between poly-Si and SiC. SiC TSBS with poly-Si/Ni dual Schottky scheme is a suitable structure for high-efficiency rectification and high-voltage blocking operation.

  8. Improved designs of Si-based quantum wells and Schottky diodes for IR detection

    Energy Technology Data Exchange (ETDEWEB)

    Moeen, M., E-mail: moeen@kth.se [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden); Kolahdouz, M. [School of Electrical and Computer Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Salemi, A.; Abedin, A.; Östling, M. [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden); Radamson, H.H., E-mail: rad@kth.se [School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, 16640, Kista (Sweden)

    2016-08-31

    Novel structures of intrinsic or carbon-doped multi quantum wells (MQWs) and intrinsic or carbon-doped Si Schottky diodes (SD), individually or in combination, have been manufactured to detect the infrared (IR) radiation. The carbon concentration in the structures was 5 × 10{sup 20} cm{sup −3} and the MQWs are located in the active part of the IR detector. A Schottky diode was designed and formed as one of the contacts (based on NiSi(C)/TiW) to MQWs where on the other side the structure had an Ohmic contact. The thermal response of the detectors is expressed in terms of temperature coefficient of resistance (TCR) and the quality of the electrical signal is quantified by the signal-to-noise ratio. The noise measurements provide the K{sub 1/f} parameter which is obtained from the power spectrum density. An excellent value of TCR = − 6%/K and K{sub 1/f} = 4.7 × 10{sup −14} was measured for the detectors which consist of the MQWs in series with the SD. These outstanding electrical results indicate a good opportunity to manufacture low cost Si-based IR detectors in the near future. - Highlights: • SiGe (C)/Si(C) multi quantum wells (MQWs) are evaluated to detect IR radiation. • Schottky diodes (SDs), individually or in series with MQWs are also fabricated. • Detectors consisted of MQWs in series with SD show excellent thermal sensing. • The noise values are also extremely low for MQWs in series with SD.

  9. Improved designs of Si-based quantum wells and Schottky diodes for IR detection

    International Nuclear Information System (INIS)

    Moeen, M.; Kolahdouz, M.; Salemi, A.; Abedin, A.; Östling, M.; Radamson, H.H.

    2016-01-01

    Novel structures of intrinsic or carbon-doped multi quantum wells (MQWs) and intrinsic or carbon-doped Si Schottky diodes (SD), individually or in combination, have been manufactured to detect the infrared (IR) radiation. The carbon concentration in the structures was 5 × 10 20 cm −3 and the MQWs are located in the active part of the IR detector. A Schottky diode was designed and formed as one of the contacts (based on NiSi(C)/TiW) to MQWs where on the other side the structure had an Ohmic contact. The thermal response of the detectors is expressed in terms of temperature coefficient of resistance (TCR) and the quality of the electrical signal is quantified by the signal-to-noise ratio. The noise measurements provide the K 1/f parameter which is obtained from the power spectrum density. An excellent value of TCR = − 6%/K and K 1/f = 4.7 × 10 −14 was measured for the detectors which consist of the MQWs in series with the SD. These outstanding electrical results indicate a good opportunity to manufacture low cost Si-based IR detectors in the near future. - Highlights: • SiGe (C)/Si(C) multi quantum wells (MQWs) are evaluated to detect IR radiation. • Schottky diodes (SDs), individually or in series with MQWs are also fabricated. • Detectors consisted of MQWs in series with SD show excellent thermal sensing. • The noise values are also extremely low for MQWs in series with SD.

  10. Schottky diodes between Bi2S3 nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

    International Nuclear Information System (INIS)

    Saha, Sudip K.; Pal, Amlan J.

    2015-01-01

    We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi 2 S 3 nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi 2 S 3 nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells

  11. Dual-Functional On-Chip AlGaAs/GaAs Schottky Diode for RF Power Detection and Low-Power Rectenna Applications

    Directory of Open Access Journals (Sweden)

    Abdul Manaf Hashim

    2011-08-01

    Full Text Available A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT structure. Current-voltage (I-V measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device’s good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  12. Dual-functional on-chip AlGaAs/GaAs Schottky diode for RF power detection and low-power rectenna applications.

    Science.gov (United States)

    Hashim, Abdul Manaf; Mustafa, Farahiyah; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul

    2011-01-01

    A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV) are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device's good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

  13. Silicon passivation and tunneling contact formation by atomic layer deposited Al2O3/ZnO stacks

    NARCIS (Netherlands)

    Garcia-Alonso Garcia, D.; Smit, S.; Bordihn, S.; Kessels, W.M.M.

    2013-01-01

    The passivation of Si by Al2O3/ZnO stacks, which can serve as passivated tunneling contacts or heterojunctions in silicon photovoltaics, was investigated. It was demonstrated that stacks with Al2O3 thicknesses >3 nm lead to lower surface recombination velocities (Seff,max <4 cm s-1) on n- and p-type

  14. Failure Analysis of Heavy-Ion-Irradiated Schottky Diodes

    Science.gov (United States)

    Casey, Megan C.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Topper, Alyson D.; Campola, Michael J.; Label, Kenneth A.

    2017-01-01

    In this work, we use high- and low-magnitude optical microscope images, infrared camera images, and scanning electron microscope images to identify and describe the failure locations in heavy-ion-irradiated Schottky diodes.

  15. Durability of PEDOT: PSS-pentacene Schottky diode

    International Nuclear Information System (INIS)

    Kang, K S; Lim, H K; Cho, K Y; Han, K J; Kim, Jaehwan

    2008-01-01

    The durability and failure cause of a polymer Schottky diode made with PEDOT : PSS-pentacene were investigated. A polymer Schottky diode was fabricated by dissolving pentacene in N-methylpyrrolidone (NMP) and mixing with PEDOT : PSS. Pentacene solution having a maximum concentration of approximately 9.7 mmoles was prepared by simply stirring the solution at room temperature for 36 h. As the pentacene concentration increased, the absorption of the broad UV regime increased dramatically. However, absorption peaks of pentacene at 301 and 260 nm were not observed for the PEDOT : PSS-pentacene. A three-layered polymer Schottky diode was fabricated and its current-voltage (I-V) characteristic was evaluated. The current was reduced by 7% in the first 50 min and then stabilized during biased electrical field sweeps. After 500 and 800 min, catastrophic failure occurred. FESEM images revealed that the electrode damage caused catastrophic failure of the Schottky diode. (fast track communication)

  16. Fluorinated tin oxide back contact for AZTSSe photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Gershon, Talia S.; Gunawan, Oki; Haight, Richard A.; Lee, Yun Seog

    2017-03-28

    A photovoltaic device includes a substrate, a back contact comprising a stable low-work function material, a photovoltaic absorber material layer comprising Ag.sub.2ZnSn(S,Se).sub.4 (AZTSSe) on a side of the back contact opposite the substrate, wherein the back contact forms an Ohmic contact with the photovoltaic absorber material layer, a buffer layer or Schottky contact layer on a side of the absorber layer opposite the back contact, and a top electrode on a side of the buffer layer opposite the absorber layer.

  17. Piezotronically modified double Schottky barriers in ZnO varistors.

    Science.gov (United States)

    Raidl, Nadine; Supancic, Peter; Danzer, Robert; Hofstätter, Michael

    2015-03-25

    Double Schottky barriers in ZnO are modified piezotronically by the application of mechanical stresses. New effects such as the enhancement of the potential barrier height and the increase or decrease of the natural barrier asymmetry are presented. Also, an extended model for the piezotronic modification of double Schottky barriers is given. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A FIB/TEM study of butterfly crack formation and white etching area (WEA) microstructural changes under rolling contact fatigue in 100Cr6 bearing steel

    International Nuclear Information System (INIS)

    Evans, M.-H.; Walker, J.C.; Ma, C.; Wang, L.; Wood, R.J.K.

    2013-01-01

    Butterflies are microscopic damage features forming at subsurface material imperfections induced during rolling contact fatigue (RCF) in rolling element bearings. Butterflies can lead to degradation of the load bearing capacity of the material by their associated cracks causing premature spalling failures. Recently, butterfly formation has been cited to be related to a premature failure mode in wind turbine gearbox bearings; white structure flaking (WSF). Butterflies consist of cracks with surrounding microstructural change called ‘white etching area’ (WEA) forming wings that revolve around their initiators. The formation mechanisms of butterflies in bearing steels have been studied over the last 50 years, but are still not fully understood. This paper presents a detailed microstructural analysis of a butterfly that has initiated from a void in standard 100Cr6 bearing steel under rolling contact fatigue on a laboratory two-roller test rig under transient operating conditions. Analysis was conducted using focused ion beam (FIB) tomography, 3D reconstruction and transmission electron microscopy (STEM/TEM) methods. FIB tomography revealed an extensive presence of voids/cavities immediately adjacent to the main crack on the non-WEA side and at the crack tip. This provides evidence for a void/cavity coalescence mechanism for the butterfly cracks formation. Spherical M 3 C carbide deformation and dissolution as part of the microstructural change in WEA were observed in both FIB and STEM/TEM analyses, where TEM analyses also revealed the formation of superfine nano-grains (3–15 nm diameter) intersecting a dissolving spherical M 3 C carbide. This is evidence of the early formation of nano-grains associated with the WEA formation mechanism

  19. A FIB/TEM study of butterfly crack formation and white etching area (WEA) microstructural changes under rolling contact fatigue in 100Cr6 bearing steel

    Energy Technology Data Exchange (ETDEWEB)

    Evans, M.-H., E-mail: martin.evans@soton.ac.uk [National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ (United Kingdom); Walker, J.C.; Ma, C.; Wang, L.; Wood, R.J.K. [National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, SO17 1BJ (United Kingdom)

    2013-05-15

    Butterflies are microscopic damage features forming at subsurface material imperfections induced during rolling contact fatigue (RCF) in rolling element bearings. Butterflies can lead to degradation of the load bearing capacity of the material by their associated cracks causing premature spalling failures. Recently, butterfly formation has been cited to be related to a premature failure mode in wind turbine gearbox bearings; white structure flaking (WSF). Butterflies consist of cracks with surrounding microstructural change called ‘white etching area’ (WEA) forming wings that revolve around their initiators. The formation mechanisms of butterflies in bearing steels have been studied over the last 50 years, but are still not fully understood. This paper presents a detailed microstructural analysis of a butterfly that has initiated from a void in standard 100Cr6 bearing steel under rolling contact fatigue on a laboratory two-roller test rig under transient operating conditions. Analysis was conducted using focused ion beam (FIB) tomography, 3D reconstruction and transmission electron microscopy (STEM/TEM) methods. FIB tomography revealed an extensive presence of voids/cavities immediately adjacent to the main crack on the non-WEA side and at the crack tip. This provides evidence for a void/cavity coalescence mechanism for the butterfly cracks formation. Spherical M{sub 3}C carbide deformation and dissolution as part of the microstructural change in WEA were observed in both FIB and STEM/TEM analyses, where TEM analyses also revealed the formation of superfine nano-grains (3–15 nm diameter) intersecting a dissolving spherical M{sub 3}C carbide. This is evidence of the early formation of nano-grains associated with the WEA formation mechanism.

  20. W and WSix Ohmic contacts on p- and n-type GaN

    International Nuclear Information System (INIS)

    Cao, X.A.; Ren, F.; Pearton, S.J.; Zeitouny, A.; Eizenberg, M.; Zolper, J.C.; Abernathy, C.R.; Han, J.; Shul, R.J.; Lothian, J.R.

    1999-01-01

    W and WSi Ohmic contacts on both p- and n-type GaN have been annealed at temperatures from 300 to 1000 degree C. There is minimal reaction (≤100 Angstrom broadening of the metal/GaN interface) even at 1000 degree C. Specific contact resistances in the 10 -5 Ω cm 2 range are obtained for WSi x on Si-implanted GaN with a peak doping concentration of ∼5x10 20 cm -3 , after annealing at 950 degree C. On p-GaN, leaky Schottky diode behavior is observed for W, WSi x and Ni/Au contacts at room temperature, but true Ohmic characteristics are obtained at 250 - 300 degree C, where the specific contact resistances are, typically, in the 10 -2 Ω cm 2 range. The best contacts for W and WSi x are obtained after 700 degree C annealing for periods of 30 - 120 s. The formation of β-W 2 N interfacial phases appear to be important in determining the contact quality. copyright 1999 American Vacuum Society

  1. Electrical properties of Schottky barrier diodes fabricated on (001) β-Ga2O3 substrates with crystal defects

    Science.gov (United States)

    Oshima, Takayoshi; Hashiguchi, Akihiro; Moribayashi, Tomoya; Koshi, Kimiyoshi; Sasaki, Kohei; Kuramata, Akito; Ueda, Osamu; Oishi, Toshiyuki; Kasu, Makoto

    2017-08-01

    The electrical properties of Schottky barrier diodes (SBDs) on a (001) β-Ga2O3 substrate were characterized and correlated with wet etching-revealed crystal defects below the corresponding Schottky contacts. The etching process revealed etched grooves and etched pits, indicating the presence of line-shaped voids and small defects near the surface, respectively. The electrical properties (i.e., leakage currents, ideality factor, and barrier height) exhibited almost no correlation with the density of the line-shaped voids. This very weak correlation was reasonable considering the parallel positional relation between the line-shaped voids extending along the [010] direction and the (001) basal plane in which the voids are rarely exposed on the initial surface in contact with the Schottky metals. The distribution of small defects and SBDs with unusually large leakage currents showed similar patterns on the substrate, suggesting that these defects were responsible for the onset of fatal leak paths. These results will encourage studies on crystal defect management of (001) β-Ga2O3 substrates for the fabrication of devices with enhanced performance using these substrates.

  2. Ohmic contact formation process on low n-type gallium arsenide (GaAs) using indium gallium zinc oxide (IGZO)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Seong-Uk [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Product and Test Engineering Team, System LSI Division, Samsung Electronics Co., Ltd, Yongin 446-711 (Korea, Republic of); Jung, Woo-Shik [Department of Electrical Engineering, Stanford University, Stanford, CA 94305 (United States); Lee, In-Yeal; Jung, Hyun-Wook; Kim, Gil-Ho [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, Jin-Hong, E-mail: jhpark9@skku.edu [Samsung-SKKU Graphene Center and School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-02-01

    Highlights: • We propose a method to fabricate non-gold Ohmic contact on low n-type GaAs with IGZO. • 0.15 A/cm{sup 2} on-current and 1.5 on/off-current ratio are achieved in the junction. • InAs and InGaAs formed by this process decrease an electron barrier height. • Traps generated by diffused O atoms also induce a trap-assisted tunneling phenomenon. - Abstract: Here, an excellent non-gold Ohmic contact on low n-type GaAs is demonstrated by using indium gallium zinc oxide and investigating through time of flight-secondary ion mass spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, J–V measurement, and H [enthalpy], S [entropy], Cp [heat capacity] chemistry simulation. In is diffused through GaAs during annealing and reacts with As, forming InAs and InGaAs phases with lower energy bandgap. As a result, it decreases the electron barrier height, eventually increasing the reverse current. In addition, traps generated by diffused O atoms induce a trap-assisted tunneling phenomenon, increasing generation current and subsequently the reverse current. Therefore, an excellent Ohmic contact with 0.15 A/cm{sup 2} on-current density and 1.5 on/off-current ratio is achieved on n-type GaAs.

  3. Spontaneous imbibition of water and determination of effective contact angles in the Eagle Ford Shale Formation using neutron imaging

    Energy Technology Data Exchange (ETDEWEB)

    DiStefano, Victoria H.; Cheshire, Michael C.; McFarlane, Joanna; Kolbus, Lindsay M.; Hale, Richard E.; Perfect, Edmund; Bilheux, Hassina Z.; Santodonato, Louis J.; Hussey, Daniel S.; Jacobson, David L.; LaManna, Jacob M.; Bingham, Philip R.; Starchenko, Vitaliy; Anovitz, Lawrence M.

    2017-10-01

    Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extraction. Although, the modern analytical and computational models can capture fracture growth, there is a lack of experimental data on spontaneous imbibition and wettability in oil and gas reservoirs for the validation of further model development. In this work, we used neutron imaging to measure the spontaneous imbibition of water into fractures of Eagle Ford Shale with known geometries and fracture orientations. An analytical solution for a set of nonlinear second-order differential equations was applied to the measured imbibition data to determine effective contact angles. The analytical solution fit the measured imbibition data reasonably well and determined effective contact angles were slightly higher than static contact angles due to effects of in-situ changes in velocity, surface roughness, and heterogeneity of mineral surfaces on the fracture surface. Additionally, small fracture widths may have retarded imbibition and affected model fits, which suggests that average fracture widths are not satisfactory for modeling imbibition in natural systems.

  4. Interface gap states and Schottky barrier inhomogeneity at metal/n-type GaN Schottky contacts

    International Nuclear Information System (INIS)

    Mamor, M

    2009-01-01

    The barrier heights (BH) of various metals including Pd, Pt and Ni on n-type GaN (M/n-GaN) have been measured in the temperature range 80-400 K with using a current-voltage (I-V) technique. The temperature dependence of the I-V characteristics of M/n-GaN have shown non-ideal behaviors and indicate the presence of a non-uniform distribution of surface gap states, resulting from the residual defects in the as grown GaN. The surface gap states density N ss , as well as its temperature dependence were obtained from the bias and temperature dependence of the ideality factor n(V,T) and the barrier height Φ Bn (V,T). Further, a dependence of zero-bias BH Φ 0Bn on the metal work function (Φ m ) with an interface parameter coefficient of proportionality of 0.47 is found. This result indicates that the Fermi level at the M/n-GaN interface is unpinned. Additionally, the presence of lateral inhomogeneities of the BH, with two Gaussian distributions of the BH values is seen. However, the non-homogeneous SBH is found to be correlated to the surface gap states density, in that Φ 0Bn becomes smaller with increasing N ss . These findings suggest that the lateral inhomogeneity of the SBH is connected to the non-uniform distribution of the density of surface gap states at metal/GaN which is attributed to the presence of native defects in the as grown GaN. Deep level transient spectroscopy confirms the presence of native defects with discrete energy levels at GaN and provides support to this interpretation.

  5. White-light emission from porous-silicon-aluminium Schottky junctions

    International Nuclear Information System (INIS)

    Masini, G.; La Monica, S.; Maiello, G.

    1996-01-01

    Porous-silicon-based white-light-emitting devices are presented. The fabrication process on different substrates is described. The peculiarities of technological steps for device fabrication (porous-silicon formation and aluminium treatment) are underlined. Doping profile of the porous layer, current-voltage characteristics, time response, lifetime tests and electroluminescence emission spectrum of the device are presented. A model for electrical behaviour of Al/porous silicon Schottky junction is presented. Electroluminescence spectrum of the presented devices showed strong similarities with white emission from crystalline silicon junctions in the breakdown region

  6. An all-carbon vdW heterojunction composed of penta-graphene and graphene: Tuning the Schottky barrier by electrostatic gating or nitrogen doping

    Science.gov (United States)

    Guo, Yaguang; Wang, Fancy Qian; Wang, Qian

    2017-08-01

    The non-zero band gap together with other unique properties endows penta-graphene with potential for device applications. Here, we study the performance of penta-graphene as the channel material contacting with graphene to form a van der Waals heterostructure. Based on first-principles calculations, we show that the intrinsic properties of penta-graphene are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The stacked system forms an n-type Schottky barrier (Φe) at the vertical interface, while a negative band bending occurs at the lateral interface in a current-in-plane model. From the device point of view, we further demonstrate that a low-Φe or an Ohmic contact can be realized by applying an external electric field or doping graphene with nitrogen atoms. This allows the control of the Schottky barrier height, which is essential in fabricating penta-graphene-based nanotransistors.

  7. Silver-Nanowire-Embedded Transparent Metal-Oxide Heterojunction Schottky Photodetector.

    Science.gov (United States)

    Abbas, Sohail; Kumar, Mohit; Kim, Hong-Sik; Kim, Joondong; Lee, Jung-Ho

    2018-05-02

    We report a self-biased and transparent Cu 4 O 3 /TiO 2 heterojunction for ultraviolet photodetection. The dynamic photoresponse improved 8.5 × 10 4 % by adding silver nanowires (AgNWs) Schottky contact and maintaining 39% transparency. The current density-voltage characteristics revealed a strong interfacial electric field, responsible for zero-bias operation. In addition, the dynamic photoresponse measurement endorsed the effective holes collection by embedded-AgNWs network, leading to fast rise and fall time of 0.439 and 0.423 ms, respectively. Similarly, a drastic improvement in responsivity and detectivity of 187.5 mAW -1 and of 5.13 × 10 9 Jones, is observed, respectively. The AgNWs employed as contact electrode can ensure high-performance for transparent and flexible optoelectronic applications.

  8. Ultra-short channel GaN high electron mobility transistor-like Gunn diode with composite contact

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Yang, Lin' an, E-mail: layang@xidian.edu.cn; Wang, Zhizhe; Chen, Qing; Huang, Yonghong; Dai, Yang; Chen, Haoran; Zhao, Hongliang; Hao, Yue [The State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an 710071 (China)

    2014-09-07

    We present a numerical analysis on an ultra-short channel AlGaN/GaN HEMT-like planar Gunn diode based on the velocity-field dependence of two-dimensional electron gas (2-DEG) channel accounting for the ballistic electron acceleration and the inter-valley transfer. In particular, we propose a Schottky-ohmic composite contact instead of traditional ohmic contact for the Gunn diode in order to significantly suppress the impact ionization at the anode side and shorten the “dead zone” at the cathode side, which is beneficial to the formation and propagation of dipole domain in the ultra-short 2-DEG channel and the promotion of conversion efficiency. The influence of the surface donor-like traps on the electron domain in the 2-DEG channel is also included in the simulation.

  9. Technology CAD of silicided Schottky barrier MOSFET for elevated source-drain engineering

    International Nuclear Information System (INIS)

    Saha, A.R.; Chattopadhyay, S.; Bose, C.; Maiti, C.K.

    2005-01-01

    Technology CAD has been used to study the performance of a silicided Schottky barrier (SB) MOSFET with gate, source and drain contacts realized with nickel-silicide. Elevated source-drain structures have been used towards the S/D engineering of CMOS devices. A full process-to-device simulation has been employed to predict the performance of sub-micron SB n-MOSFETs for the first time. A model for the diffusion and alloy growth kinetics has been incorporated in SILVACO-ATLAS and ATHENA to explore the processing and design parameter space for the Ni-silicided MOSFETs. The temperature and concentration dependent diffusion model for NiSi have been developed and necessary material parameters for nickel-silicide and epitaxial-Si have been incorporated through the C-interpreter function. Two-dimensional (2D) process-to-device simulations have also been used to study the dc and ac (RF) performance of silicided Schottky barrier (SB) n-MOSFETs. The extracted sheet resistivity, as a function of annealing temperature of the silicided S/D contacts, is found to be lower than the conventional contacts currently in use. It is also shown that the Technology CAD has the full capability to predict the possible dc and ac performance enhancement of a MOSFET with elevated S/D structures. While the simulated dc performance shows a clear enhancement, the RF analyses show no performance degradation in the cut-off frequency/propagation delay and also improve the ac performance due to the incorporation of silicide contacts in the S/D region

  10. Technology CAD of silicided Schottky barrier MOSFET for elevated source-drain engineering

    Energy Technology Data Exchange (ETDEWEB)

    Saha, A.R. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)]. E-mail: ars.iitkgp@gmail.com; Chattopadhyay, S. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India); School of Electrical, Electronics and Computer Engineering, University of Newcastle, Newcastle upon Tyne (United Kingdom); Bose, C. [Department of Electronics and Telecommunication Engineering, Jadavpur University, Calcutta 700032 (India); Maiti, C.K. [Department of Electronics and ECE, IIT, Kharagpur 721302 (India)

    2005-12-05

    Technology CAD has been used to study the performance of a silicided Schottky barrier (SB) MOSFET with gate, source and drain contacts realized with nickel-silicide. Elevated source-drain structures have been used towards the S/D engineering of CMOS devices. A full process-to-device simulation has been employed to predict the performance of sub-micron SB n-MOSFETs for the first time. A model for the diffusion and alloy growth kinetics has been incorporated in SILVACO-ATLAS and ATHENA to explore the processing and design parameter space for the Ni-silicided MOSFETs. The temperature and concentration dependent diffusion model for NiSi have been developed and necessary material parameters for nickel-silicide and epitaxial-Si have been incorporated through the C-interpreter function. Two-dimensional (2D) process-to-device simulations have also been used to study the dc and ac (RF) performance of silicided Schottky barrier (SB) n-MOSFETs. The extracted sheet resistivity, as a function of annealing temperature of the silicided S/D contacts, is found to be lower than the conventional contacts currently in use. It is also shown that the Technology CAD has the full capability to predict the possible dc and ac performance enhancement of a MOSFET with elevated S/D structures. While the simulated dc performance shows a clear enhancement, the RF analyses show no performance degradation in the cut-off frequency/propagation delay and also improve the ac performance due to the incorporation of silicide contacts in the S/D region.

  11. Determination of Schottky barrier heights and Fermi-level unpinning at the graphene/n-type Si interfaces by X-ray photoelectron spectroscopy and Kelvin probe

    International Nuclear Information System (INIS)

    Lin, Yow-Jon; Zeng, Jian-Jhou

    2014-01-01

    Highlights: • The interface characteristics of graphene/n-type Si devices are measured. • The actual work function of graphene is examined with the Kelvin probe. • An analysis is conducted according to the Schottky–Mott limit. • The Fermi energy level at the graphene/n-type Si interfaces is unpinned. • The Schottky barrier value is dependent on the work function of graphene. - Abstract: The interface characteristics of graphene/n-type Si samples using X-ray photoelectron spectroscopy (XPS) measurements are investigated. XPS makes it possible to extract a reliable Schottky barrier value. For graphene/n-type Si samples with (without) sulfide treatment, the Schottky barrier height is 0.86 (0.78) eV. The Schottky barrier height was increased from 0.78 to 0.86 eV, indicating that sulfide treatment is effective in passivating the surface of Si (owing to the formation of Si–S bonds). To determine the Fermi-level pinning/unpinning at the graphene/n-type Si interfaces with sulfide treatment, an analysis is conducted according to the Schottky–Mott limit and the actual work function of graphene is examined with the Kelvin probe. It is shown that the Fermi energy level is unpinned and the Schottky barrier value is dependent on the work function of graphene. Investigation of graphene/n-type Si interfaces is important, and providing the other technique for surface potential control is possible

  12. Investigation of pentacene growth on SiO2 gate insulator after photolithography for nitrogen-doped LaB6 bottom-contact electrode formation

    Science.gov (United States)

    Maeda, Yasutaka; Hiroki, Mizuha; Ohmi, Shun-ichiro

    2018-04-01

    Nitrogen-doped (N-doped) LaB6 is a candidate material for the bottom-contact electrode of n-type organic field-effect transistors (OFETs). However, the formation of a N-doped LaB6 electrode affects the surface morphology of a pentacene film. In this study, the effects of surface treatments and a N-doped LaB6 interfacial layer (IL) were investigated to improve the pentacene film quality after N-doped LaB6 electrode patterning with diluted HNO3, followed by resist stripping with acetone and methanol. It was found that the sputtering damage during N-doped LaB6 deposition on a SiO2 gate insulator degraded the crystallinity of pentacene. The H2SO4 and H2O2 (SPM) and diluted HF treatments removed the damaged layer on the SiO2 gate insulator surface. Furthermore, the N-doped LaB6 IL improved the crystallinity of pentacene and realized dendritic grain growth. Owing to these surface treatments, the hole mobility improved from 2.8 × 10-3 to 0.11 cm2/(V·s), and a steep subthreshold swing of 78 mV/dec for the OFET with top-contact configuration was realized in air even after bottom-contact electrode patterning.

  13. Synthesis of indium nanoclusters and formation of thin film contacts on plastic substrates for organic and flexible electronics applications

    International Nuclear Information System (INIS)

    Shi, Frank F; Bulkowski, Michal; Hsieh, K C

    2007-01-01

    In this work, we described the processes of synthesizing free-standing indium nanoclusters using inverse micelles and microemulsions as well as synthesizing organic-encapsulated indium nanoclusters using alkanethiols as the organic encapsulants. The synthesized organic-encapsulated indium nanoclusters have demonstrated the feasibilities to be used as plastic compatible soft metal contacts for emerging organic devices. The homogeneously distributed indium nanoclusters with sizes of 10-30 nm have been fabricated on a few different plastic substrates. By changing the alkanethiol carbon chain length and the sizes of the indium nanoclusters, the annealing temperature required to form low-resistance indium thin film conductors has been reduced to 80-100 deg. C, which is acceptable for a variety of organic thin films

  14. Few-Layer WSe2 Schottky Junction-Based Photovoltaic Devices through Site-Selective Dual Doping.

    Science.gov (United States)

    Ko, Seungpil; Na, Junhong; Moon, Young-Sun; Zschieschang, Ute; Acharya, Rachana; Klauk, Hagen; Kim, Gyu-Tae; Burghard, Marko; Kern, Klaus

    2017-12-13

    Ultrathin sheets of two-dimensional (2D) materials like transition metal dichalcogenides have attracted strong attention as components of high-performance light-harvesting devices. Here, we report the implementation of Schottky junction-based photovoltaic devices through site-selective surface doping of few-layer WSe 2 in lateral contact configuration. Specifically, whereas the drain region is covered by a strong molecular p-type dopant (NDP-9) to achieve an Ohmic contact, the source region is coated with an Al 2 O 3 layer, which causes local n-type doping and correspondingly an increase of the Schottky barrier at the contact. By scanning photocurrent microscopy using green laser light, it could be confirmed that photocurent generation is restricted to the region around the source contact. The local photoinduced charge separation is associated with a photoresponsivity of up to 20 mA W -1 and an external quantum efficiency of up to 1.3%. The demonstrated device concept should be easily transferrable to other van der Waals 2D materials.

  15. MD 2408: Study of Schottky Monitors for Q' Measurement at Injection

    CERN Document Server

    Tydecks, Tobias; Levens, Tom; Wendt, Manfred; Wenninger, Jorg; CERN. Geneva. ATS Department

    2018-01-01

    The Schottky monitors installed at the LHC enable the detection of Schottky noise of the two circulating proton / ion beams. From Schottky noise, beam parameters like tune, chromaticity, and relative emittance, can be extracted in a non-destructive and purely parasitic method of measurement. The primary goal of this MD was to study the Schottky monitors capability to reliably and accurately determine the beam chromaticities at injection energy. Furthermore, the possibility to track the beam emittance has been investigated.

  16. Electrical Contacts in Monolayer Arsenene Devices.

    Science.gov (United States)

    Wang, Yangyang; Ye, Meng; Weng, Mouyi; Li, Jingzhen; Zhang, Xiuying; Zhang, Han; Guo, Ying; Pan, Yuanyuan; Xiao, Lin; Liu, Junku; Pan, Feng; Lu, Jing

    2017-08-30

    Arsenene, arsenic analogue of graphene, as an emerging member of two-dimensional semiconductors (2DSCs), is quite promising in next-generation electronic and optoelectronic applications. The metal electrical contacts play a vital role in the charge transport and photoresponse processes of nanoscale 2DSC devices and even can mask the intrinsic properties of 2DSCs. Here, we present a first comprehensive study of the electrical contact properties of monolayer (ML) arsenene with different electrodes by using ab initio electronic calculations and quantum transport simulations. Schottky barrier is always formed with bulk metal contacts owing to the Fermi level pinning (pinning factor S = 0.33), with electron Schottky barrier height (SBH) of 0.12, 0.21, 0.25, 0.35, and 0.50 eV for Sc, Ti, Ag, Cu, and Au contacts and hole SBH of 0.75 and 0.78 eV for Pd and Pt contacts, respectively. However, by contact with 2D graphene, the Fermi level pinning effect can be reduced due to the suppression of metal-induced gap states. Remarkably, a barrier free hole injection is realized in ML arsenene device with graphene-Pt hybrid electrode, suggestive of a high device performance in such a ML arsenene device. Our study provides a theoretical foundation for the selection of favorable electrodes in future ML arsenene devices.

  17. Current-voltage temperature characteristics of Au/n-Ge (1 0 0) Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Chawanda, Albert, E-mail: albert.chawanda@up.ac.za [Midlands State University, Bag 9055 Gweru (Zimbabwe); University of Pretoria, 0002 Pretoria (South Africa); Mtangi, Wilbert; Auret, Francois D; Nel, Jacqueline [University of Pretoria, 0002 Pretoria (South Africa); Nyamhere, Cloud [Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Diale, Mmantsae [University of Pretoria, 0002 Pretoria (South Africa)

    2012-05-15

    The variation in electrical characteristics of Au/n-Ge (1 0 0) Schottky contacts have been systematically investigated as a function of temperature using current-voltage (I-V) measurements in the temperature range 140-300 K. The I-V characteristics of the diodes indicate very strong temperature dependence. While the ideality factor n decreases, the zero-bias Schottky barrier height (SBH) ({Phi}{sub B}) increases with the increasing temperature. The I-V characteristics are analyzed using the thermionic emission (TE) model and the assumption of a Gaussian distribution of the barrier heights due to barrier inhomogeneities at the metal-semiconductor interface. The zero-bias barrier height {Phi}{sub B} vs. 1/2 kT plot has been used to show the evidence of a Gaussian distribution of barrier heights and values of {Phi}{sub B}=0.615 eV and standard deviation {sigma}{sub s0}=0.0858 eV for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively. The Richardson constant and the mean barrier height from the modified Richardson plot were obtained as 1.37 A cm{sup -2} K{sup -2} and 0.639 eV, respectively. This Richardson constant is much smaller than the reported of 50 A cm{sup -2} K{sup -2}. This may be due to greater inhomogeneities at the interface.

  18. Features of current-voltage characteristic of nonequilibrium trench MOS barrier Schottky diode

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2018-06-01

    The trench MOS barrier Schottky diodes (TMBS diode) under the influence of the voltage drop of the additional electric field (AEF) appearing in the near-contact region of the semiconductor are in a nonequilibrium state and their closed external circuit flows currents in the absence of an external voltage. When an external voltage is applied to the TMBS diode, the current transmission is described by the thermionic emission theory with a specific feature. Both forward and reverse I-V characteristics of the TMBS diode consist of two parts. In the initial first part of the forward I-V characteristic there are no forward currents, but reverse saturation currents flow, in its subsequent second part the currents increase exponentially with the voltage. In the initial first part of the reverse I-V characteristic, the currents increase in an abrupt way and in the subsequent second part the saturation currents flow under the action of the image force. The mathematical expressions for forward and reverse I-V characteristic of the TMBS diode and also narrow or nanostructure Schottky diode are proposed, which are in good agreement with the results of experimental and calculated I-V characteristics.

  19. Schottky junctions on perovskite single crystals: light-modulated dielectric constant and self-biased photodetection

    KAUST Repository

    Shaikh, Parvez Abdul Ajij

    2016-08-16

    Schottky junctions formed between semiconductors and metal contacts are ubiquitous in modern electronic and optoelectronic devices. Here we report on the physical properties of Schottky-junctions formed on hybrid perovskite CH3NH3PbBr3 single crystals. It is found that light illumination can significantly increase the dielectric constant of perovskite junctions by 2300%. Furthermore, such Pt/perovskite junctions are used to fabricate self-biased photodetectors. A photodetectivity of 1.4 × 1010 Jones is obtained at zero bias, which increases to 7.1 × 1011 Jones at a bias of +3 V, and the photodetectivity remains almost constant in a wide range of light intensity. These devices also exhibit fast responses with a rising time of 70 μs and a falling time of 150 μs. As a result of the high crystal quality and low defect density, such single-crystal photodetectors show stable performance after storage in air for over 45 days. Our results suggest that hybrid perovskite single crystals provide a new platform to develop promising optoelectronic applications. © 2016 The Royal Society of Chemistry.

  20. Fabrication and electrical properties of organic-on-inorganic Schottky devices

    International Nuclear Information System (INIS)

    Guellue, Oe; Biber, M; Tueruet, A; Cankaya, M

    2008-01-01

    In this paper, we fabricated an Al/new fuchsin/p-Si organic-inorganic (OI) Schottky diode structure by direct evaporation of an organic compound solution on a p-Si semiconductor wafer. A direct optical band gap energy value of the new fuchsin organic film on a glass substrate was obtained as 1.95 eV. Current-voltage (I-V) and capacitance-voltage (C-V) measurements of the OI device were carried out at room temperature. From the I-V characteristics, it was seen that the Al/new fuchsin/p-Si contacts showed good rectifying behavior. An ideality factor value of 1.47 and a barrier height (BH) value of 0.75 eV for the Al/new fuchsin/p-Si contact were determined from the forward bias I-V characteristics. A barrier height value of 0.78 eV was obtained from the capacitance-voltage (C-V) characteristics. It has been seen that the BH value of 0.75 eV obtained for the Al/new fuchsin/p-Si contact is significantly larger than that of conventional Al/p-Si Schottky metal-semiconductor (MS) diodes. Thus, modification of the interfacial potential barrier for Al/p-Si diodes has been achieved using a thin interlayer of the new fuchsin organic semiconductor; this has been ascribed to the fact that the new fuchsin interlayer increases the effective barrier height because of the interface dipole induced by passivation of the organic layer

  1. Room temperature current-voltage (I-V) characteristics of Ag/InGaN/n-Si Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Erdoğan, Erman, E-mail: e.erdogan@alparslan.edu.tr [Department of Physics, Faculty of Art and Science, Muş Alparslan University, Muş 49250 (Turkey); Kundakçı, Mutlu [Department of Physics, Faculty of Science, Atatürk University, Erzurum 25240 (Turkey)

    2017-02-01

    Metal-semiconductors (MSs) or Schottky barrier diodes (SBDs) have a significant potential in the integrated device technology. In the present paper, electrical characterization of Ag/InGaN/n-Si Schottky diode have been systematically carried out by simple Thermionic method (TE) and Norde function based on the I-V characteristics. Ag ohmic and schottky contacts are deposited on InGaN/n-Si film by thermal evaporation technique under a vacuum pressure of 1×10{sup −5} mbar. Ideality factor, barrier height and series resistance values of this diode are determined from I-V curve. These parameters are calculated by TE and Norde methods and findings are given in a comparetive manner. The results show the consistency for both method and also good agreement with other results obtained in the literature. The value of ideality factor and barrier height have been determined to be 2.84 and 0.78 eV at room temperature using simple TE method. The value of barrier height obtained with Norde method is calculated as 0.79 eV.

  2. Room temperature current-voltage (I-V) characteristics of Ag/InGaN/n-Si Schottky barrier diode

    Science.gov (United States)

    Erdoğan, Erman; Kundakçı, Mutlu

    2017-02-01

    Metal-semiconductors (MSs) or Schottky barrier diodes (SBDs) have a significant potential in the integrated device technology. In the present paper, electrical characterization of Ag/InGaN/n-Si Schottky diode have been systematically carried out by simple Thermionic method (TE) and Norde function based on the I-V characteristics. Ag ohmic and schottky contacts are deposited on InGaN/n-Si film by thermal evaporation technique under a vacuum pressure of 1×10-5 mbar. Ideality factor, barrier height and series resistance values of this diode are determined from I-V curve. These parameters are calculated by TE and Norde methods and findings are given in a comparetive manner. The results show the consistency for both method and also good agreement with other results obtained in the literature. The value of ideality factor and barrier height have been determined to be 2.84 and 0.78 eV at room temperature using simple TE method. The value of barrier height obtained with Norde method is calculated as 0.79 eV.

  3. High-performance 4H-SiC junction barrier Schottky diodes with double resistive termination extensions

    International Nuclear Information System (INIS)

    Zheng Liu; Zhang Feng; Liu Sheng-Bei; Dong Lin; Liu Xing-Fang; Liu Bin; Yan Guo-Guo; Wang Lei; Zhao Wan-Shun; Sun Guo-Sheng; He Zhi; Fan Zhong-Chao; Yang Fu-Hua

    2013-01-01

    4H-SiC junction barrier Schottky (JBS) diodes with a high-temperature annealed resistive termination extension (HARTE) are designed, fabricated and characterized in this work. The differential specific on-state resistance of the device is as low as 3.64 mΩ·cm 2 with a total active area of 2.46 × 10 −3 cm 2 . Ti is the Schottky contact metal with a Schottky barrier height of 1.08 V and a low onset voltage of 0.7 V. The ideality factor is calculated to be 1.06. Al implantation annealing is performed at 1250°C in Ar, while good reverse characteristics are achieved. The maximum breakdown voltage is 1000 V with a leakage current of 9 × 10 −5 A on chip level. These experimental results show good consistence with the simulation results and demonstrate that high-performance 4H-SiC JBS diodes can be obtained based on the double HARTE structure. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  4. Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (1 0 0)

    International Nuclear Information System (INIS)

    Chawanda, A.; Coelho, S.M.M.; Auret, F.D.; Mtangi, W.; Nyamhere, C.; Nel, J.M.; Diale, M.

    2012-01-01

    Highlights: ► Ir/n-Ge (1 0 0) Schottky diodes were characterized using I–V, C–V and SEM techniques under various annealing conditions. ► The variation of the electrical and structural properties can be due to effects phase transformation during annealing. ► Thermal stability of these diodes is maintained up to 500 °C anneal. ► SEM results depicts that the onset temperature for agglomeration in 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 °C. - Abstract: Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current–voltage (I–V) and capacitance–voltage (C–V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 °C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 °C.

  5. Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers

    Directory of Open Access Journals (Sweden)

    Evandro Leite de Souza

    2014-01-01

    Full Text Available This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 x 2 cm when cultivated in a meat-based broth at 28 and 7 ºC. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L and peracetic acid (30 mg/L in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers.

  6. Spatial inhomogeneous barrier heights at graphene/semiconductor Schottky junctions

    Science.gov (United States)

    Tomer, Dushyant

    Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors. To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point position, which is directly related to the Schottky barrier height. We find a direct correlation of Dirac point variation with the topographic undulations of graphene ripples at the graphene/SiC junction. However, no such correlation is established at graphene/Si and Graphene/GaAs junctions and Dirac point variations are attributed to surface states and trapped charges at the interface. In addition to graphene ripples and ridges, we also observe atomic scale moire patterns at graphene/MoS2 junction due to van der Waals interaction at the interface. Periodic topographic modulations due to moire pattern do not lead to local variation in graphene Dirac point, indicating that moire pattern does not contribute to fluctuations in electronic properties of the heterojunction. We perform temperature dependent current-voltage measurements to investigate the impact of topographic inhomogeneities on electrical properties of the Schottky junctions. We observe temperature dependence in junction parameters, such as Schottky barrier height and ideality factor, for all types of Schottky junctions in forward bias measurements. Standard thermionic emission theory which assumes a perfect

  7. TCAD analysis of graphene silicon Schottky junction solar cell

    Science.gov (United States)

    Kuang, Yawei; Liu, Yushen; Ma, Yulong; Xu, Jing; Yang, Xifeng; Feng, Jinfu

    2015-08-01

    The performance of graphene based Schottky junction solar cell on silicon substrate is studied theoretically by TCAD Silvaco tools. We calculate the current-voltage curves and internal quantum efficiency of this device at different conditions using tow dimensional model. The results show that the power conversion efficiency of Schottky solar cell dependents on the work function of graphene and the physical properties of silicon such as thickness and doping concentration. At higher concentration of 1e17cm-3 for n-type silicon, the dark current got a sharp rise compared with lower doping concentration which implies a convert of electron emission mechanism. The biggest fill factor got at higher phos doping predicts a new direction for higher performance graphene Schottky solar cell design.

  8. Mott-Schottky analysis of thin ZnO films

    International Nuclear Information System (INIS)

    Windisch, Charles F. Jr.; Exarhos, Gregory J.

    2000-01-01

    Thin ZnO films, both native and doped with secondary metal ions, have been prepared by sputter deposition and also by casting from solutions containing a range of precursor salts. The conductivity and infrared reflectivity of these films are subsequently enhanced chemically following treatment in H 2 gas at 400 degree sign C or by cathodic electrochemical treatment in a neutral (pH=7) phosphate buffer solution. While Hall-type measurements usually are used to evaluate the electrical properties of such films, the present study investigated whether a conventional Mott-Schottky analysis could be used to monitor the change in concentration of free carriers in these films before and after chemical and electrochemical reduction. The Mott-Schottky approach would be particularly appropriate for electrochemically modified films since the measurements could be made in the same electrolyte used for the post-deposition electrochemical processing. Results of studies on sputtered pure ZnO films in ferricyanide solution were promising. Mott-Schottky plots were linear and gave free carrier concentrations typical for undoped semiconductors. Film thicknesses estimated from the Mott-Schottky data were also reasonably close to thicknesses calculated from reflectance measurements. Studies on solution-deposited films were less successful. Mott-Schottky plots were nonlinear, apparently due to film porosity. A combination of dc polarization and atomic force microscopy measurements confirmed this conclusion. The results suggest that Mott-Schottky analysis would be suitable for characterizing solution-deposited ZnO films only after extensive modeling was performed to incorporate the effects of film porosity on the characteristics of the space-charge region of the semiconductor. (c) 2000 American Vacuum Society

  9. Correlation between the electrical properties and the interfacial microstructures of TiAl-based ohmic contacts to p-type 4H-SiC

    Science.gov (United States)

    Tsukimoto, S.; Nitta, K.; Sakai, T.; Moriyama, M.; Murakami, Masanori

    2004-05-01

    In order to understand a mechanism of TiAl-based ohmic contact formation for p-type 4H-SiC, the electrical properties and microstructures of Ti/Al and Ni/Ti/Al contacts, which provided the specific contact resistances of approximately 2×10-5 Ω-cm2 and 7×10-5 Ω-cm2 after annealing at 1000°C and 800°C, respectively, were investigated using x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Ternary Ti3SiC2 carbide layers were observed to grow on the SiC surfaces in both the Ti/Al and the Ni/Ti/Al contacts when the contacts yielded low resistance. The Ti3SiC2 carbide layers with hexagonal structures had an epitaxial orientation relationship with the 4H-SiC substrates. The (0001)-oriented terraces were observed periodically at the interfaces between the carbide layers and the SiC, and the terraces were atomically flat. We believed the Ti3SiC2 carbide layers primarily reduced the high Schottky barrier height at the contact metal/p-SiC interface down to about 0.3 eV, and, thus, low contact resistances were obtained for p-type TiAl-based ohmic contacts.

  10. Au/n-ZnO rectifying contact fabricated with hydrogen peroxide pretreatment

    Science.gov (United States)

    Gu, Q. L.; Cheung, C. K.; Ling, C. C.; Ng, A. M. C.; Djurišić, A. B.; Lu, L. W.; Chen, X. D.; Fung, S.; Beling, C. D.; Ong, H. C.

    2008-05-01

    Au contacts were deposited on n-type ZnO single crystals with and without hydrogen peroxide pretreatment for the ZnO substrate. The Au/ZnO contacts fabricated on substrates without H2O2 pretreatment were Ohmic and those with H2O2 pretreatment were rectifying. With an aim of fabricating a good quality Schottky contact, the rectifying property of the Au/ZnO contact was systemically investigated by varying the treatment temperature and duration. The best performing Schottky contact was found to have an ideality factor of 1.15 and a leakage current of ˜10-7 A cm-2. A multispectroscopic study, including scanning electron microscopy, positron annihilation spectroscopy, deep level transient spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence, showed that the H2O2 treatment removed the OH impurity and created Zn-vacancy related defects hence decreasing the conductivity of the ZnO surface layer, a condition favorable for forming good Schottky contact. However, the H2O2 treatment also resulted in a deterioration of the surface morphology, leading to an increase in the Schottky contact ideality factor and leakage current in the case of nonoptimal treatment time and temperature.

  11. Growth and characterization of GaN nanostructures under various ammoniating time with fabricated Schottky gas sensor based on Si substrate

    Science.gov (United States)

    Abdullah, Q. N.; Ahmed, A. R.; Ali, A. M.; Yam, F. K.; Hassan, Z.; Bououdina, M.; Almessiere, M. A.

    2018-05-01

    This paper presents the investigation of the influence of the ammoniating time of GaN nanowires (NWs) on the crystalline structure, surface morphology, and optical characteristics. Morphological analysis indicates the growth of good quality and high density of NWs with diameters around 50 nm and lengths up to tens of microns after ammoniating for 30 min. Structural analysis shows that GaN NWs have a typical hexagonal wurtzite crystal structure. Raman spectroscopy confirms the formation of GaN compound with the presence of compressive stress. Photoluminescence (PL) measurements revealed two band emissions, an UV and a broad visible emission. Hydrogen sensor was subsequently fabricated by depositing Pt Schottky contact onto GaN NWs film. The sensor response was measured at various H2 concentrations ranged from 200 up to 1200 ppm at room temperature. It was found that the response increases significantly for low H2 concentration (200-300 ppm) to reach about 50% then increases smoothly to reach 60% at 1200 ppm. The as-fabricated sensor possesses higher performances as compared to similar devices reported in the literature.

  12. Characterization and Modeling I(V of the Gate Schottky Structures HEMTs Ni/Au/AlInN/GaN

    Directory of Open Access Journals (Sweden)

    N. Benyahya

    2014-05-01

    Full Text Available In this paper, we have studied the Schottky contact of Ni/Au/AlInN/GaN HEMTs. The current–voltage Igs (Vgs of Ni/Au/AlInN/GaN structures were investigated at room temperature. The electrical parameters such as ideality factor (2.3, barrier height (0.72 eV and series resistance (33 W were evaluated from I(V data, the threshold voltage (-2.42 V, the 2D gas density (1.35 ´ 1013 cm-2 and barrier height (0.94 eV were evaluated from C(V data.

  13. Fundamental studies of graphene/graphite and graphene-based Schottky photovoltaic devices

    Science.gov (United States)

    Miao, Xiaochang

    In the carbon allotropes family, graphene is one of the most versatile members and has been extensively studied since 2004. The goal of this dissertation is not only to investigate the novel fundamental science of graphene and its three-dimensional sibling, graphite, but also to explore graphene's promising potential in modern electronic and optoelectronic devices. The first two chapters provide a concise introduction to the fundamental solid state physics of graphene (as well as graphite) and the physics at the metal/semiconductor interfaces. In the third chapter, we demonstrate the formation of Schottky junctions at the interfaces of graphene (semimetal) and various inorganic semiconductors that play dominating roles in today's semiconductor technology, such as Si, SiC, GaAs and GaN. As shown from their current-voltage (I -V) and capacitance-voltage (C-V) characteristics, the interface physics can be well described within the framework of the Schottky-Mott model. The results are also well consist with that from our previous studies on graphite based Schottky diodes. In the fourth chapter, as an extension of graphene based Schottky work, we investigate the photovoltaic (PV) effect of graphene/Si junctions after chemically doped with an organic polymer (TFSA). The power conversion efficiency of the solar cell improves from 1.9% to 8.6% after TFSA doping, which is the record in all graphene based PVs. The I -V, C-V and external quantum efficiency measurements suggest 12 that such a significant enhancement in the device performance can be attributed to a doping-induced decrease in the series resistance and a simultaneous increase in the built-in potential. In the fifth chapter, we investigate for the first time the effect of uniaxial strains on magneto-transport properties of graphene. We find that low-temperature weak localization effect in monolayer graphene is gradually suppressed under increasing strains, which is due to a strain-induced decreased intervalley

  14. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations

    Science.gov (United States)

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-02-01

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

  15. Schottky barrier at graphene/metal oxide interfaces: insight from first-principles calculations.

    Science.gov (United States)

    Cheng, Kai; Han, Nannan; Su, Yan; Zhang, Junfeng; Zhao, Jijun

    2017-02-06

    Anode materials play an important role in determining the performance of lithium ion batteries. In experiment, graphene (GR)/metal oxide (MO) composites possess excellent electrochemical properties and are promising anode materials. Here we perform density functional theory calculations to explore the interfacial interaction between GR and MO. Our result reveals generally weak physical interactions between GR and several MOs (including Cu2O, NiO). The Schottky barrier height (SBH) in these metal/semiconductor heterostructures are computed using the macroscopically averaged electrostatic potential method, and the role of interfacial dipole is discussed. The calculated SBHs below 1 eV suggest low contact resistance; thus these GR/MO composites are favorable anode materials for better lithium ion batteries.

  16. Measuring size dependent electrical properties from nanoneedle structures: Pt/ZnO Schottky diodes

    International Nuclear Information System (INIS)

    Mao, Shimin; Anderson, Daniel D.; Shang, Tao; Park, Byoungnam; Dillon, Shen J.

    2014-01-01

    This work reports the fabrication and testing of nanoneedle devices with well-defined interfaces that are amenable to a variety of structural and electrical characterization, including transmission electron microscopy. Single Pt/ZnO nanoneedle Schottky diodes were fabricated by a top down method using a combination of electro-polishing, sputtering, and focused ion beam milling. The resulting structures contained nanoscale planar heterojunctions with low ideality factors, the dimensions of which were tuned to study size-dependent electrical properties. The diameter dependence of the Pt/ZnO diode barrier height is explained by a joule heating effect and/or electronic inhomogeneity in the Pt/ZnO contact area

  17. A simulation study of 6H-SiC Schottky barrier source/drain MOSFET

    International Nuclear Information System (INIS)

    Wang Yuan; Zhang Yimen; Zhang Yuming; Tang Xiaoyan

    2003-01-01

    A novel SiC metal-oxide-semiconductor field-effect transistor (SiC SBSD-MOSFET) with Schottky barrier contacts for source and drain is presented in this paper. This kind of device gives a fabrication advantage of avoiding the steps of ion implantation and annealing at high temperatures of the conventional SiC MOSFET. Also it has no problems of crystal damage caused by ion implantation and low activation rate of implanted atoms. The operational mechanism of this device is analyzed and its characteristics are comparable to the conventional SiC MOSFET from the simulation with MEDICI. The effects of different metal workfunctions, oxide thickness, and gate length on the device performance are discussed

  18. Proposal of a broadband, polarization-insensitive and high-efficiency hot-carrier schottky photodetector integrated with a plasmonic silicon ridge waveguide

    International Nuclear Information System (INIS)

    Yang, Liu; Kou, Pengfei; Shen, Jianqi; Lee, El Hang; He, Sailing

    2015-01-01

    We propose a broadband, polarization-insensitive and high-efficiency plasmonic Schottky diode for detection of sub-bandgap photons in the optical communication wavelength range through internal photoemission (IPE). The distinctive features of this design are that it has a gold film covering both the top and the sidewalls of a dielectric silicon ridge waveguide with the Schottky contact formed at the gold–silicon interface and the sidewall coverage of gold can be easily tuned by an insulating layer. An extensive physical model on IPE of hot carriers is presented in detail and is applied to calculate and examine the performance of this detector. In comparison with a diode having only the top gold contact, the polarization sensitivity of the responsivity is greatly minimized in our photodetector with gold film covering both the top and the sidewall. Much higher responsivities for both polarizations are also achieved over a broad wavelength range of 1.2–1.6 μm. Moreover, the Schottky contact is only 4 μm long, leading to a very small dark current. Our design is very promising for practical applications in high-density silicon photonic integration. (paper)

  19. Performance enhancement of polymer Schottky diode by doping pentacene

    International Nuclear Information System (INIS)

    Kang, K.S.; Chen, Y.; Lim, H.K.; Cho, K.Y.; Han, K.J.; Kim, Jaehwan

    2009-01-01

    Schottky diodes have been fabricated using pentacene-doped poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as a semiconducting material. To understand the fundamental properties of the pentacene-doped PEDOT:PSS, ultraviolet visible (UV) absorption spectroscopy was employed. It was found that a significant amount of pentacene can dissolve in n-methylpyrrolidone solvent. No characteristic absorption peak of pentacene was observed in the UV-visible spectra of PEDOT:PSS films doped with pentacene,. However, the absorption intensity of the doped PEDOT:PSS films increased as the pentacene concentration increased in particular in the UV region. The atomic force microscope images show that the surface roughnesses of PEDOT:PSS films increased as the pentacene concentration increased. Three-layer Schottky diodes comprising Al/PEDOT:PSS/Au or Al/PEDOT:PSS-pentacene/Au were fabricated. The maximum forward currents of non-doped and doped Schottky diodes were 4.8 and 440 μA/cm 2 at 3.3 MV/m, respectively. The forward current increased nearly two orders of magnitude for Schottky diode doped with 11.0 wt.% of pentacene.

  20. Silicon Schottky photovoltaic diodes for solar energy conversion

    Science.gov (United States)

    Anderson, W. A.

    1975-01-01

    Various factors in Schottky barrier solar cell fabrication are evaluated in order to improve understanding of the current flow mechanism and to isolate processing variables that improve efficiency. Results of finger design, substrate resistivity, surface finishing and activation energy studies are detailed. An increased fill factor was obtained by baking of the vacuum system to remove moisture.

  1. Particle detectors based on InP Schottky diodes

    Czech Academy of Sciences Publication Activity Database

    Yatskiv, Roman; Grym, Jan

    2012-01-01

    Roč. 10, č. 7 (2012), C100051-C100055 ISSN 1748-0221 R&D Projects: GA MŠk(CZ) OC10021; GA MŠk LD12014 Institutional support: RVO:67985882 Keywords : Particle detector * High purity InP layer * Schottky diode Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.869, year: 2011

  2. Language Contact.

    Science.gov (United States)

    Nelde, Peter Hans

    1995-01-01

    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  3. Application of CTLM method combining interfacial structure characterization to investigate contact formation of silver paste metallization on crystalline silicon solar cells

    Science.gov (United States)

    Xiong, Shenghu; Yuan, Xiao; Tong, Hua; Yang, Yunxia; Liu, Cui; Ye, Xiaojun; Li, Yongsheng; Wang, Xianhao; Luo, Lan

    2018-04-01

    Circular transmission line model (CTLM) measurements were applied to study the contact formation mechanism of the silver paste metallization on n-type emitter of crystalline silicon solar cells. The electrical performance parameters ρc,Rsk , and Lt , which are related to the physical and chemical states of the multiphase materials at the interface, were extracted from the CTLM measurements, and were found to be sensitive to sintering temperature. As the temperature increased from 585 °C to 780 °C, initially the ρc value decreased rapidly, then flattened out and increased slightly. The order of resistivity magnitude was restricted by the SiNx passivation layer in the early sintering stages, and relied on the carrier tunneling probability affected by the precipitated silver crystallites or colloids, emitter doping concentration and molten glass layer. Based on the calculations that the sheet resistance underneath the electrode was reduced form 110 Ω / □ to 0.186 Ω / □ , it could be inferred that there was formation of a highly conductive layer of silver crystallites and colloids contained glass on the emitter. The transfer length Lt exhibited a U-shaped variation along with the temperature, reflecting the variation of the interfacial electrical properties. Overall, this article shows that the CTLM method can become a new powerful tool for researchers to meet the challenges of silver paste metallization innovation for manufacturing high-efficiency silicon solar cells.

  4. Passivity of AISI 321 stainless steel in 0.5 M H2SO4 solution studied by Mott–Schottky analysis in conjunction with the point defect model

    Directory of Open Access Journals (Sweden)

    A. Fattah-alhosseini

    2016-11-01

    Full Text Available The passivity of AISI 321 stainless steel in 0.5 M H2SO4 solution, in the steady-state condition, has been explored using electrochemical impedance spectroscopy (EIS and Mott–Schottky analysis. Based on the Mott–Schottky analysis in conjunction with the point defect model (PDM, it was shown that the calculated donor density decreases exponentially with increasing passive film formation potential. The thickness of the passive film was increased linearly with the formation potential. These observations were consistent with the predictions of the PDM, noting that the point defects within the passive film are metal interstitials, oxygen vacancies, or both.

  5. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals.

    Science.gov (United States)

    Shtepliuk, Ivan; Eriksson, Jens; Khranovskyy, Volodymyr; Iakimov, Tihomir; Lloyd Spetz, Anita; Yakimova, Rositsa

    2016-01-01

    A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current-voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium-graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT) calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I - V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.

  6. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals

    Directory of Open Access Journals (Sweden)

    Ivan Shtepliuk

    2016-11-01

    Full Text Available A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current–voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium–graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I–V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.

  7. Temperature dependent electrical characterisation of Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Shetty, Arjun, E-mail: arjun@ece.iisc.ernet.in; Vinoy, K. J. [Electrical Communication Engineering, Indian Institute of Science, Bangalore, India 560012 (India); Roul, Basanta; Mukundan, Shruti; Mohan, Lokesh; Chandan, Greeshma; Krupanidhi, S. B. [Materials Research Centre, Indian Institute of Science, Bangalore, India 560012 (India)

    2015-09-15

    This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO{sub 2} (5 nm) between the metal and semiconductor interface. The resulting Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V), increase in barrier height (0.52 eV to 0.63eV) and a reduction in ideality factor (2.1 to 1.3) as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE). The crystalline and optical qualities of the films were confirmed using high resolution X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN) and metal-insulator-semiconductor (Pt/HfO{sub 2}/n-GaN) Schottky diodes were fabricated. To gain further understanding of the Pt/HfO{sub 2}/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV) and the ideality factor decreased (3.6 to 1.2) with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights.

  8. Diagraphies de cimentation : vers une analyse de la qualité du contact ciment-formation Cement Logging: Toward an Analysis of the Quality of Cement-Formation Bonding

    Directory of Open Access Journals (Sweden)

    Isambourg P.

    2006-11-01

    example, promote the premature arrival of gas in the oil produced. The cementing defects that can disturb this seal are:(a Cement-casing micro- or macro-annulus. (b Mud channel at the level of the casing. (c Cement-formation micro- or macro-annulus. (d Mud channel at the level of the formation. (e Gas percolation in the cement sheath. (f Gas channel in the cement sheath. The aim of these logs is to determine whether one of these defect is present in the cement sheath. The causes of these defects may be numerous and varied:(a Poor displacement of the drilling mud. (b Improper spacer formulation. (c Cement formulation not conforming to the requirements of the well. (d Cracks in the cemented annulus as the result of thermal and hydraulic shocks and aging. (e Variation of the permeability during aging. With the battery of logs now available, we know how to detect defects quite accurately at the level of the cement-casing contact as well as any gas percolation in the cement. On the contrary, local defects at the level of the cement-formation contact can be assessed only very qualitatively by a log of the VDL type. In addition, a VDL analysis requires serious expertise. The present challenge is thus to obtain a cementing log capable of making the same analysis at the level of the formation as what is now done at the level of the casing. This is all the more important as the percentage of risk in the presence of a defect is greater at the level of the cement-formation interface. We have thus worked on the possibility of making use of ultrasonic echo techniques for analyzing the quality of the cement-formation contact.

  9. Deep-level transient spectroscopy on an amorphous InGaZnO{sub 4} Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Chasin, Adrian, E-mail: adrian.chasin@imec.be; Bhoolokam, Ajay; Nag, Manoj; Genoe, Jan; Heremans, Paul [imec, Kapeldreef 75, 3001 Leuven (Belgium); ESAT, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven (Belgium); Simoen, Eddy [imec, Kapeldreef 75, 3001 Leuven (Belgium); Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Gent (Belgium); Gielen, Georges [ESAT, KU Leuven, Kasteelpark Arenberg 10, 3001 Leuven (Belgium)

    2014-02-24

    The first direct measurement is reported of the bulk density of deep states in amorphous IGZO (indium-gallium-zinc oxide) semiconductor by means of deep-level transient spectroscopy (DLTS). The device under test is a Schottky diode of amorphous IGZO semiconductor on a palladium (Pd) Schottky-barrier electrode and with a molybdenum (Mo) Ohmic contact at the top. The DLTS technique allows to independently measure the energy and spatial distribution of subgap states in the IGZO thin film. The subgap trap concentration has a double exponential distribution as a function energy, with a value of ∼10{sup 19} cm{sup −3} eV{sup −1} at the conduction band edge and a value of ∼10{sup 17} cm{sup −3} eV{sup −1} at an energy of 0.55 eV below the conduction band. Such spectral distribution, however, is not uniform through the semiconductor film. The spatial distribution of subgap states correlates well with the background doping density distribution in the semiconductor, which increases towards the Ohmic Mo contact, suggesting that these two properties share the same physical origin.

  10. First-principles study of the effects of Silicon doping on the Schottky barrier of TiSi2/Si interfaces

    Science.gov (United States)

    Wang, Han; Silva, Eduardo; West, Damien; Sun, Yiyang; Restrepo, Oscar; Zhang, Shengbai; Kota, Murali

    As scaling of semiconductor devices is pursued in order to improve power efficiency, quantum effects due to the reduced dimensions on devices have become dominant factors in power, performance, and area scaling. In particular, source/drain contact resistance has become a limiting factor in the overall device power efficiency and performance. As a consequence, techniques such as heavy doping of source and drain have been explored to reduce the contact resistance, thereby shrinking the width of depletion region and lowering the Schottky barrier height. In this work, we study the relation between doping in Silicon and the Schottky barrier of a TiSi2/Si interface with first-principles calculation. Virtual Crystal Approximation (VCA) is used to calculate the average potential of the interface with varying doping concentration, while the I-V curve for the corresponding interface is calculated with a generalized one-dimensional transfer matrix method. The relation between substitutional and interstitial Boron and Phosphorus dopant near the interface, and their effect on tuning the Schottky barrier is studied. These studies provide insight to the type of doping and the effect of dopant segregation to optimize metal-semiconductor interface resistance.

  11. Active and fast charge-state switching of single NV centres in diamond by in-plane Al-Schottky junctions

    Directory of Open Access Journals (Sweden)

    Christoph Schreyvogel

    2016-11-01

    Full Text Available In this paper, we demonstrate an active and fast control of the charge state and hence of the optical and electronic properties of single and near-surface nitrogen-vacancy centres (NV centres in diamond. This active manipulation is achieved by using a two-dimensional Schottky-diode structure from diamond, i.e., by using aluminium as Schottky contact on a hydrogen terminated diamond surface. By changing the applied potential on the Schottky contact, we are able to actively switch single NV centres between all three charge states NV+, NV0 and NV− on a timescale of 10 to 100 ns, corresponding to a switching frequency of 10–100 MHz. This switching frequency is much higher than the hyperfine interaction frequency between an electron spin (of NV− and a nuclear spin (of 15N or 13C for example of 2.66 kHz. This high-frequency charge state switching with a planar diode structure would open the door for many quantum optical applications such as a quantum computer with single NVs for quantum information processing as well as single 13C atoms for long-lifetime storage of quantum information. Furthermore, a control of spectral emission properties of single NVs as a single photon emitters – embedded in photonic structures for example – can be realized which would be vital for quantum communication and cryptography.

  12. New evidence on the formation of oxidizing species in corona discharge in contact with liquid and their reactions with organic compounds.

    Science.gov (United States)

    Magureanu, M; Dobrin, D; Bradu, C; Gherendi, F; Mandache, N B; Parvulescu, V I

    2016-12-01

    The objective of these investigations is to understand in more detail how organic compounds in water are degraded during plasma treatment. The formation of oxidizing species (ozone (O 3 ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (OH)) in a pulsed corona discharge in contact with liquid is investigated. The degradation of a target organic compound (methylparaben) in aqueous solution was increased when combining plasma treatment with ozonation, using the O 3 generated in the discharge. Enhanced mass transfer of O 3 obtained in this plasma+O 3 configuration leads to a six fold increase of MeP oxidation rate. The evolution of oxidants concentration during treatment of MeP solutions provides information on their consumption in reactions with MeP and its oxidation products. The correlation of MeP degradation results (MeP removal and mineralization) with O 3 consumption and the identified reaction products confirms that although O 3 plays an important role in the degradation, for the mineralization OH radicals have an essential contribution. The concentration of OH radicals is diminished in the solutions containing MeP as compared to plasma-treated water, indicating OH consumption in reactions with the target compound and its degradation products. The concentration of H 2 O 2 in the liquid can be either increased or reduced in the presence of MeP, depending on its initial concentration. On the one hand, decomposition of H 2 O 2 by OH or O 3 is suppressed in the presence of MeP, but on the other hand less OH radicals are available for its formation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Design consideration of high voltage Ga2O3 vertical Schottky barrier diode with field plate

    Science.gov (United States)

    Choi, J.-H.; Cho, C.-H.; Cha, H.-Y.

    2018-06-01

    Gallium oxide (Ga2O3) based vertical Schottky barrier diodes (SBDs) were designed for high voltage switching applications. Since p-type Ga2O3 epitaxy growth or p-type ion implantation technique has not been developed yet, a field plate structure was employed in this study to maximize the breakdown voltage by suppressing the electric field at the anode edge. TCAD simulation was used for the physical analysis of Ga2O3 SBDs from which it was found that careful attention must be paid to the insulator under the field plate. Due to the extremely high breakdown field property of Ga2O3, an insulator with both high permittivity and high breakdown field must be used for the field plate formation.

  14. Characterization of Schottky barrier diodes fabricated from electrochemical oxidation of {alpha} phase brass

    Energy Technology Data Exchange (ETDEWEB)

    Bond, John W., E-mail: jwb13@le.ac.u [Forensic Research Centre, University of Leicester, Leicester LE1 7 EA (United Kingdom)

    2011-04-01

    By careful selection of chloride ion concentration in aqueous sodium chloride, electrochemical oxidation of {alpha} phase brass is shown to permit fabrication of either p-type copper (I) oxide/metal or n-type zinc oxide/metal Schottky barrier diodes. X-ray photoelectron and Auger electron spectroscopies provide evidence that barrier formation and rectifying qualities depend on the relative surface abundance of copper (I) oxide and zinc oxide. X-ray diffraction of the resulting diodes shows polycrystalline oxides embedded in amorphous oxidation products that have a lower relative abundance than the diode forming oxide. Conventional I/V characteristics of these diodes show good rectifying qualities. When neither of the oxides dominate, the semiconductor/metal junction displays an absence of rectification.

  15. Evaluation of 320x240 pixel LEC GaAs Schottky barrier X-ray imaging arrays, hybridized to CMOS readout circuit based on charge integration

    CERN Document Server

    Irsigler, R; Alverbro, J; Borglind, J; Froejdh, C; Helander, P; Manolopoulos, S; O'Shea, V; Smith, K

    1999-01-01

    320x240 pixels GaAs Schottky barrier detector arrays were fabricated, hybridized to silicon readout circuits, and subsequently evaluated. The detector chip was based on semi-insulating LEC GaAs material. The square shaped pixel detector elements were of the Schottky barrier type and had a pitch of 38 mu m. The GaAs wafers were thinned down prior to the fabrication of the ohmic back contact. After dicing, the chips were indium bump, flip-chip bonded to CMOS readout circuits based on charge integration, and finally evaluated. A bias voltage between 50 and 100 V was sufficient to operate the detector. Results on I-V characteristics, noise behaviour and response to X-ray radiation are presented. Images of various objects and slit patterns were acquired by using a standard dental imaging X-ray source. The work done was a part of the XIMAGE project financed by the European Community (Brite-Euram). (author)

  16. A charge-based model of Junction Barrier Schottky rectifiers

    Science.gov (United States)

    Latorre-Rey, Alvaro D.; Mudholkar, Mihir; Quddus, Mohammed T.; Salih, Ali

    2018-06-01

    A new charge-based model of the electric field distribution for Junction Barrier Schottky (JBS) diodes is presented, based on the description of the charge-sharing effect between the vertical Schottky junction and the lateral pn-junctions that constitute the active cell of the device. In our model, the inherently 2-D problem is transformed into a simple but accurate 1-D problem which has a closed analytical solution that captures the reshaping and reduction of the electric field profile responsible for the improved electrical performance of these devices, while preserving physically meaningful expressions that depend on relevant device parameters. The validation of the model is performed by comparing calculated electric field profiles with drift-diffusion simulations of a JBS device showing good agreement. Even though other fully 2-D models already available provide higher accuracy, they lack physical insight making the proposed model an useful tool for device design.

  17. Comparison of stability of WSiX/SiC and Ni/SiC Schottky rectifiers to high dose gamma-ray irradiation

    International Nuclear Information System (INIS)

    Kim, Jihyun; Ren, F.; Chung, G.Y.; MacMillan, M.F.; Baca, A.G.; Briggs, R.D.; Schoenfeld, D.; Pearton, S.J.

    2004-01-01

    SiC Schottky rectifiers with moderate breakdown voltages of ∼450 V and with either WSi X or Ni rectifying contacts were irradiated with Co-60 γ-rays to doses up to ∼315 Mrad. The Ni/SiC rectifiers show severe reaction of the contact after irradiation at the highest dose, badly degrading the forward current characteristics and increasing the on-state resistance by up to a factor of 6 after irradiation. By sharp contrast, the WSi X /SiC devices show little deterioration of the contact with the same conditions and changes in on-state resistance of X contacts appear promising for applications requiring improved contact stability

  18. Investigation on a radiation tolerant betavoltaic battery based on Schottky barrier diode

    International Nuclear Information System (INIS)

    Liu Yebing; Hu Rui; Yang Yuqing; Wang Guanquan; Luo Shunzhong; Liu Ning

    2012-01-01

    An Au–Si Schottky barrier diode was studied as the energy conversion device of betavoltaic batteries. Its electrical performance under radiation of Ni-63 and H-3 sources and radiation degradation under Am-241 were investigated and compared with those of the p–n junction. The results show that the Schottky diode had a higher I sc and harder radiation tolerance but lower V oc than the p–n junction. The results indicated that the Schottky diode can be a promising candidate for energy conversion of betavoltaic batteries. - Highlights: ► The Schottky diode was used as the converter of the betavoltaic battery. ► The radiation damage of converter was accelerated by using alpha particles. ► The Schottky diode has higher radiation resistance than that of the p–n junction. ► The Schottky diode could still be a promising converter of the betavoltaic battery.

  19. High-temperature Schottky diode characteristics of bulk ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Guer, Emre; Tuezemen, S; Kilic, Bayram; Coskun, C [Department of Physics, Faculty of Arts and Sciences, Atatuerk University, 25240 Erzurum (Turkey)

    2007-05-16

    Current-voltage (I-V) measurements of Ag/n-ZnO have been carried out at temperatures of 200-500 K in order to understand the temperature dependence of the diode characteristics. Forward-bias I-V analysis results in a Schottky barrier height of 0.82 eV and an ideality factor of 1.55 at room temperature. The barrier height of 0.74 eV and Richardson constant of 0.248 A K{sup -2} cm{sup -2} were also calculated from the Richardson plot, which shows nearly linear characteristics in the temperature range 240-440 K. From the nk{sub b}T/q versus k{sub b}T/q graph, where n is ideality factor, k{sub b} the Boltzmann constant, T the temperature and q the electronic charge we deduce that thermionic field emission (TFE) is dominant in the charge transport mechanism. At higher sample temperatures (>440 K), a trap-assisted tunnelling mechanism is proposed due to the existence of a deep donor situated at E{sub c}-0.62 eV with 3.3 x 10{sup -15} cm{sup 2} capture cross section observed by both deep-level transient spectroscopy (DLTS) and lnI{sub 0} versus 1/k{sub b}T plots. The ideality factor almost remains constant in the temperature range 240-400 K, which shows the stability of the Schottky contact in this temperature range.

  20. Low-frequency noise properties in Pt-indium gallium zinc oxide Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiawei; Zhang, Linqing; Ma, Xiaochen; Wilson, Joshua [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Jin, Jidong [Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool L69 3GJ (United Kingdom); Du, Lulu; Xin, Qian [School of Physics, Shandong University, Jinan 250100 (China); Song, Aimin, E-mail: A.Song@manchester.ac.uk [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); School of Physics, Shandong University, Jinan 250100 (China)

    2015-08-31

    The low-frequency noise properties of Pt-indium gallium zinc oxide (IGZO) Schottky diodes at different forward biases are investigated. The IGZO layer and Pt contact were deposited by RF sputtering at room temperature. The diode showed an ideality factor of 1.2 and a barrier height of 0.94 eV. The current noise spectral density exhibited 1/f behavior at low frequencies. The analysis of the current dependency of the noise spectral density revealed that for the as-deposited diode, the noise followed Luo's mobility and diffusivity fluctuation model in the thermionic-emission-limited region and Hooge's empirical theory in the series-resistance-limited region. A low Hooge's constant of 1.4 × 10{sup −9} was found in the space-charge region. In the series-resistance-limited region, the Hooge's constant was 2.2 × 10{sup −5}. After annealing, the diode showed degradation in the electrical performance. The interface-trap-induced noise dominated the noise spectrum. By using the random walk model, the interface-trap density was obtained to be 3.6 × 10{sup 15 }eV{sup −1 }cm{sup −2}. This work provides a quantitative approach to analyze the properties of Pt-IGZO interfacial layers. These low noise properties are a prerequisite to the use of IGZO Schottky diodes in switch elements in memory devices, photosensors, and mixer diodes.

  1. Influence of interface inhomogeneities in thin-film Schottky diodes

    Science.gov (United States)

    Wilson, Joshua; Zhang, Jiawei; Li, Yunpeng; Wang, Yiming; Xin, Qian; Song, Aimin

    2017-11-01

    The scalability of thin-film transistors has been well documented, but there have been very few investigations into the effects of device scalability in Schottky diodes. Indium-gallium-zinc-oxide (IGZO) Schottky diodes were fabricated with IGZO thicknesses of 50, 150, and 250 nm. Despite the same IGZO-Pt interface and Schottky barrier being formed in all devices, reducing the IGZO thickness caused a dramatic deterioration of the current-voltage characteristics, most notably increasing the reverse current by nearly five orders of magnitude. Furthermore, the forward characteristics display an increase in the ideality factor and a reduction in the barrier height. The origins of this phenomenon have been elucidated using device simulations. First, when the semiconductor layer is fully depleted, the electric field increases with the reducing thickness, leading to an increased diffusion current. However, the effects of diffusion only offer a small contribution to the huge variations in reverse current seen in the experiments. To fully explain this effect, the role of inhomogeneities in the Schottky barrier height has been considered. Contributions from lower barrier regions (LBRs) are found to dominate the reverse current. The conduction band minimum below these LBRs is strongly dependent upon thickness and bias, leading to reverse current variations as large as several orders of magnitude. Finally, it is demonstrated that the thickness dependence of the reverse current is exacerbated as the magnitude of the inhomogeneities is increased and alleviated in the limit where the LBRs are large enough not to be influenced by the adjacent higher barrier regions.

  2. Tunable spin-tunnel contacts to silicon using low-work-function ferromagnets

    Science.gov (United States)

    Min, Byoung-Chul; Motohashi, Kazunari; Lodder, Cock; Jansen, Ron

    2006-10-01

    Magnetic tunnel junctions have become ubiquitous components appearing in magnetic random-access memory, read heads of magnetic disk drives and semiconductor-based spin devices. Inserting a tunnel barrier has been key to achieving spin injection from ferromagnetic (FM) metals into GaAs, but spin injection into Si has remained elusive. We show that Schottky barrier formation leads to a huge conductivity mismatch of the FM tunnel contact and Si, which cannot be solved by the well-known method of adjusting the tunnel barrier thickness. We present a radically different approach for spin-tunnelling resistance control using low-work-function ferromagnets, inserted at the FM/tunnel barrier interface. We demonstrate that in this way the resistance-area (RA) product of FM/Al2O3/Si contacts can be tuned over eight orders of magnitude, while simultaneously maintaining a reasonable tunnel spin polarization. This raises prospects for Si-based spintronics and presents a new category of ferromagnetic materials for spin-tunnel contacts in low-RA-product applications.

  3. Inhomogeneity in barrier height at graphene/Si (GaAs) Schottky junctions

    OpenAIRE

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2015-01-01

    Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties, however, fluctuations in the Schottky barrier height are often observed. In this work, Schottky junctions are fabricated by transferring chemical vapor deposited monolayer graphene onto n-type Si and GaAs substrates. Temperature dependence of the barrier height and ideality factor are obtained by current-voltage measurements between 215 and 350 K. An increase in the zero bias barrier height and decr...

  4. Examinations of Selected Thermal Properties of Packages of SiC Schottky Diodes

    Directory of Open Access Journals (Sweden)

    Bisewski Damian

    2016-09-01

    Full Text Available This paper describes the study of thermal properties of packages of silicon carbide Schottky diodes. In the paper the packaging process of Schottky diodes, the measuring method of thermal parameters, as well as the results of measurements are presented. The measured waveforms of transient thermal impedance of the examined diodes are compared with the waveforms of this parameter measured for commercially available Schottky diodes.

  5. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong, E-mail: joonkim@inu.ac.kr [Photoelectric and Energy Device Application Lab (PEDAL) and Department of Electrical Engineering, Incheon National University, 119 Academy Rd. Yeonsu, Incheon 406772 (Korea, Republic of); Park, Hyeong-Ho [Applied Device and Material Lab., Device Technology Division, Korea Advanced Nano Fab Center (KANC), Suwon 443270 (Korea, Republic of)

    2016-04-04

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W{sup −1}) and detectivity (2.75 × 10{sup 15} Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  6. Successful observation of Schottky signals at the Tevatron collider

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Lambertson, G.R.

    1989-08-01

    We have constructed a Schottky detector for the Tevatron collider in the form of a high-Q (∼5000) cavity which operates at roughly 2 GHz, well above the frequency at which the Tevatron's single-bunch frequency spectrum begins to roll off. Initial spectra obtained from the detector show clearly observable Schottky betatron lines, free of coherent contaminants; also seen are the ''common-mode'' longitudinal signals due to the offset of the beam from the detector center. The latter signals indicate that at 2 GHz, the coherent single-bunch spectrum from the detector is reduced by >80 dB; therefore, in normal collider operation, the Schottky betatron lines are >40 dB greater than their coherent counterparts. We describe how the data we have obtained give information on transverse and longitudinal emittances, synchrotron frequency, and betatron tunes, as well as reveal what may be previously unobserved phenomena. Space limitations restrict us to presenting only as much data as should be necessary to convince even the skeptical reader of the validity of the claim made in the paper's title. 3 refs., 2 figs

  7. Fabrication and characterization of well-aligned zinc oxide nanowire arrays and their realizations in Schottky-device applications

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Kin Mun; Grote, Fabian; Sun, Hui; Lei, Yong [Institute of Materials Physics, Center for Nanotechnology, University of Muenster (Germany); Wen, Liaoyong; Fang, Yaoguo [Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai 201800 (China)

    2011-07-01

    Highly ordered arrays of vertical zinc oxide (ZnO) nanowires (NWs) or nanopores were fabricated in our group by first thermal evaporating a thin film of gold on the ultrathin alumina membrane (UTAM). The UTAM was then utilized as a substrate for the growth of the ordered arrays using a chemical vapour deposition (CVD) process. Alternatively, a modified CVD process was also used to fabricate ultra-long ZnO NWs with the length of the nanowire exceeding 100 micrometres. Subsequently, densely packed arrays of ZnO NWs Schottky diodes were synthesized by transferring the long NWs on a substrate using a dry contact printing method and the electrical contacts were made on the NWs with a photolithographic process. The interesting electrical properties of the ZnO NWs, diodes or other metal oxide NWs such as the field emission, electron transport and piezoelectric properties were characterized by current-voltage or by other appropriate measurements.

  8. Growth and biofilm formation by Listeria monocytogenes in catfish mucus extract on four food-contact surfaces at 22°C and 10°C and their reduction by commercial disinfectants

    Science.gov (United States)

    The objective of this study was to determine the effect of strain and temperature on growth and biofilm formation by Listeria monocytogenes (Lm) in high and low concentrations of catfish mucus extract on different food-contact surfaces at 10°C and 22°C. The second objective of this study was to eval...

  9. CONTACT RESISTANCE MODELING

    Directory of Open Access Journals (Sweden)

    S. V. LOSKUTOV

    2018-05-01

    Full Text Available Purpose. To determine the contribution of the real contact spots distribution in the total conductivity of the conductors contact. Methodology. The electrical contact resistance research was carried out on models. The experimental part of this work was done on paper with a graphite layer with membranes (the first type and conductive liquids with discrete partitions (the second type. Findings. It is shown that the contact electrical resistance is mainly determined by the real area of metal contact. The experimental dependence of the electrical resistance of the second type model on the distance between the electrodes and the potential distribution along the sample surface for the first type model were obtained. The theoretical model based on the principle of electric field superposition was considered. The dependences obtained experimentally and calculated by using the theoretical model are in good agreement. Originality. The regularity of the electrical contact resistance formation on a large number of membranes was researched for the first time. A new model of discrete electrical contact based on the liquid as the conducting environment with nuclear membrane partitions was developed. The conclusions of the additivity of contact and bulk electrical resistance were done. Practical value. Based on these researches, a new experimental method of kinetic macroidentation that as a parameter of the metal surface layer deformation uses the real contact area was developed. This method allows to determine the value of average contact stresses, yield point, change of the stress on the depth of deformation depending on the surface treatment.

  10. Compact modeling of SiC Schottky barrier diode and its extension to junction barrier Schottky diode

    Science.gov (United States)

    Navarro, Dondee; Herrera, Fernando; Zenitani, Hiroshi; Miura-Mattausch, Mitiko; Yorino, Naoto; Jürgen Mattausch, Hans; Takusagawa, Mamoru; Kobayashi, Jun; Hara, Masafumi

    2018-04-01

    A compact model applicable for both Schottky barrier diode (SBD) and junction barrier Schottky diode (JBS) structures is developed. The SBD model considers the current due to thermionic emission in the metal/semiconductor junction together with the resistance of the lightly doped drift layer. Extension of the SBD model to JBS is accomplished by modeling the distributed resistance induced by the p+ implant developed for minimizing the leakage current at reverse bias. Only the geometrical features of the p+ implant are necessary to model the distributed resistance. Reproduction of 4H-SiC SBD and JBS current-voltage characteristics with the developed compact model are validated against two-dimensional (2D) device-simulation results as well as measurements at different temperatures.

  11. Novel Sn-Based Contact Structure for GeTe Phase Change Materials.

    Science.gov (United States)

    Simchi, Hamed; Cooley, Kayla A; Ding, Zelong; Molina, Alex; Mohney, Suzanne E

    2018-05-16

    Germanium telluride (GeTe) is a phase change material (PCM) that has gained recent attention because of its incorporation as an active material for radio frequency (RF) switches, as well as memory and novel optoelectronic devices. Considering PCM-based RF switches, parasitic resistances from Ohmic contacts can be a limiting factor in device performance. Reduction of the contact resistance ( R c ) is therefore critical for reducing the on-state resistance to meet the requirements of high-frequency RF applications. To engineer the Schottky barrier between the metal contact and GeTe, Sn was tested as an interesting candidate to alter the composition of the semiconductor near its surface, potentially forming a narrow band gap (0.2 eV) SnTe or a graded alloy with SnTe in GeTe. For this purpose, a novel contact stack of Sn/Fe/Au was employed and compared to a conventional Ti/Pt/Au stack. Two different premetallization surface treatments of HCl and deionized (DI) H 2 O were employed to make a Te-rich and Ge-rich interface, respectively. Contact resistance values were extracted using the refined transfer length method. The best results were obtained with DI H 2 O for the Sn-based contacts but HCl treatment for the Ti/Pt/Au contacts. The as-deposited contacts had the R c (ρ c ) of 0.006 Ω·mm (8 × 10 -9 Ω·cm 2 ) for Sn/Fe/Au and 0.010 Ω·mm (3 × 10 -8 Ω·cm 2 ) for Ti/Pt/Au. However, the Sn/Fe/Au contacts were thermally stable, and their resistance decreased further to 0.004 Ω·mm (4 × 10 -9 Ω·cm 2 ) after annealing at 200 °C. In contrast, the contact resistance of the Ti/Pt/Au stack increased to 0.012 Ω·mm (4 × 10 -8 Ω·cm 2 ). Transmission electron microscopy was used to characterize the interfacial reactions between the metals and GeTe. It was found that formation of SnTe at the interface, in addition to Fe diffusion (doping) into GeTe, is likely responsible for the superior performance of Sn/Fe/Au contacts, resulting in one of the lowest reported

  12. Effect of thermal treatment on the characteristics of iridium Schottky barrier diodes on n-Ge (1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Chawanda, A., E-mail: albert.chawanda@up.ac.za [Department of Physics, University of Pretoria, 0002 (South Africa); Department of Physics, Midlands State University, Bag 9055, Gweru (Zimbabwe); Coelho, S.M.M.; Auret, F.D.; Mtangi, W. [Department of Physics, University of Pretoria, 0002 (South Africa); Nyamhere, C. [Department of Physics, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Nel, J.M.; Diale, M. [Department of Physics, University of Pretoria, 0002 (South Africa)

    2012-02-05

    Highlights: Black-Right-Pointing-Pointer Ir/n-Ge (1 0 0) Schottky diodes were characterized using I-V, C-V and SEM techniques under various annealing conditions. Black-Right-Pointing-Pointer The variation of the electrical and structural properties can be due to effects phase transformation during annealing. Black-Right-Pointing-Pointer Thermal stability of these diodes is maintained up to 500 Degree-Sign C anneal. Black-Right-Pointing-Pointer SEM results depicts that the onset temperature for agglomeration in 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 Degree-Sign C. - Abstract: Iridium (Ir) Schottky barrier diodes were deposited on bulk grown (1 0 0) Sb-doped n-type germanium by using the electron beam deposition system. Electrical characterization of these contacts using current-voltage (I-V) and capacitance-voltage (C-V) measurements was performed under various annealing conditions. The variation of the electrical properties of these Schottky diodes can be attributed to combined effects of interfacial reaction and phase transformation during the annealing process. Thermal stability of the Ir/n-Ge (1 0 0) was observed up to annealing temperature of 500 Degree-Sign C. Furthermore, structural characterization of these samples was performed by using a scanning electron microscopy (SEM) at different annealing temperatures. Results have also revealed that the onset temperature for agglomeration in a 20 nm Ir/n-Ge (1 0 0) system occurs between 600 and 700 Degree-Sign C.

  13. Sub-bandgap response of graphene/SiC Schottky emitter bipolar phototransistor examined by scanning photocurrent microscopy

    Science.gov (United States)

    Barker, Bobby G., Jr.; Chava, Venkata Surya N.; Daniels, Kevin M.; Chandrashekhar, M. V. S.; Greytak, Andrew B.

    2018-01-01

    Graphene layers grown epitaxially on SiC substrates are attractive for a variety of sensing and optoelectronic applications because the graphene acts as a transparent, conductive, and chemically responsive layer that is mated to a wide-bandgap semiconductor with large breakdown voltage. Recent advances in control of epitaxial growth and doping of SiC epilayers have increased the range of electronic device architectures that are accessible with this system. In particular, a recently-introduced Schottky-emitter bipolar phototransistor (SEPT) based on an epitaxial graphene (EG) emitter grown on a p-SiC base epilayer has been found to exhibit a maximum common emitter current gain of 113 and a UV responsivity of 7.1 A W-1. The behavior of this device, formed on an n +-SiC substrate that serves as the collector, was attributed to a very large minority carrier injection efficiency at the EG/p-SiC Schottky contact. This large minority carrier injection efficiency is in turn related to the large built-in potential found at a EG/p-SiC Schottky junction. The high performance of this device makes it critically important to analyze the sub bandgap visible response of the device, which provides information on impurity states and polytype inclusions in the crystal. Here, we employ scanning photocurrent microscopy (SPCM) with sub-bandgap light as well as a variety of other techniques to clearly demonstrate a localized response based on the graphene transparent electrode and an approximately 1000-fold difference in responsivity between 365 nm and 444 nm excitation. A stacking fault propagating from the substrate/epilayer interface, assigned as a single layer of the 8H-SiC polytype within the 4H-SiC matrix, is found to locally increase the photocurrent substantially. The discovery of this polytype heterojunction opens the potential for further development of heteropolytype devices based on the SEPT architecture.

  14. Barrier height and interface effect of Pt-n-GaN and Pd-n-GaN Schottky diodes

    International Nuclear Information System (INIS)

    Khan, M.R.H.; Saha, S.L.; Sawaki, N.

    1999-01-01

    Schottky barriers on n-type GaN films by Pt and Pd are fabricated and characterized. A thin Pt or Pd layer is deposited on n-GaN layers to form Schottky contacts in a vacuum below 1x10/sup -6/ Torr. The area of all diodes is 3.46 x 10-4 cm/sup 2/. Several samples of Pt-n GaN and Pd-n GaN were studied. The ideality factor of Pt-n-GaN diode is 1.26 and of Pd-n-GaN is 1.17. The breakdown voltage of Pt-n-GaN and Pd-n-GaN diodes is 21 V and 26 V respectively. In both the cases the leakage current varies between 1x10-9 A and 5x 10-9 A. The Schottky barrier heights (phi/sub B/ ) of Pt-GaN diode is been determined to be 1.02 eV by current voltage (I-V) and 1.07 eV by capacitance (C-V) measurements Also, phi/sub B/ of Pd-GaN diode is determined to be 0.91 eV by I-V and 0.98 eV, by C-V measurements. The departure of the values of the ideality factor is considered to be due to spatial inhomogeneities at the meal semiconductor interface. The difference in the values of phi/sub B/ determined by I-V and C-V measurements is attributed to the deformation of the spatial barrier distribution. (author)

  15. Unexpected current lowering by a low work-funkction metal contact: Mg/SI-GaAs

    Czech Academy of Sciences Publication Activity Database

    Dubecký, F.; Dubecký, M.; Hubík, Pavel; Kindl, Dobroslav; Gombia, E.; Baldini, M.; Nečas, V.

    2013-01-01

    Roč. 82, APR (2013), s. 72-76 ISSN 0038-1101 Institutional support: RVO:68378271 Keywords : Schottky barrier * low-bias transport * semi-insulating GaAs * low work -function * high resistence * low leakage current * blocking contact Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.514, year: 2013

  16. Coherent electron focusing with quantum point contacts in a two-dimensional electron gas

    NARCIS (Netherlands)

    Houten, H. van; Beenakker, C.W.J.; Williamson, J.G.; Broekaart, M.E.I.; Loosdrecht, P.H.M. van; Wees, B.J. van; Mooij, J.E.; Foxon, C.T.; Harris, J.J.

    1989-01-01

    Transverse electron focusing in a two-dimensional electron gas is investigated experimentally and theoretically for the first time. A split Schottky gate on top of a GaAs-AlxGa1–xAs heterostructure defines two point contacts of variable width, which are used as injector and collector of ballistic

  17. Metal Contacts to Gallium Arsenide.

    Science.gov (United States)

    Ren, Fan

    1991-07-01

    While various high performance devices fabricated from the gallium arsenide (GaAs) and related materials have generated considerable interest, metallization are fundamental components to all semiconductor devices and integrated circuits. The essential roles of metallization systems are providing the desired electrical paths between the active region of the semiconductor and the external circuits through the metal interconnections and contacts. In this work, in-situ clean of native oxide, high temperature n-type, low temperature n-type and low temperature p-type ohmic metal systems have been studied. Argon ion mill was used to remove the native oxide prior to metal deposition. For high temperature process n-type GaAs ohmic contacts, Tungsten (W) and Tungsten Silicide (WSi) were used with an epitaxial grown graded Indium Gallium Arsenide (InGaAs) layer (0.2 eV) on GaAs. In addition, refractory metals, Molybdenum (Mo), was incorporated in the Gold-Germanium (AuGe) based on n-type GaAs ohmic contacts to replace conventional silver as barrier to prevent the reaction between ohmic metal and chlorine based plasma as well as the ohmic metallization intermixing which degrades the device performance. Finally, Indium/Gold-Beryllium (In/Au-Be) alloy has been developed as an ohmic contact for p-type GaAs to reduce the contact resistance. The Fermi-level pinning of GaAs has been dominated by the surface states. The Schottky barrier height of metal contacts are about 0.8 V regardless of the metal systems. By using p-n junction approach, barrier height of pulsed C-doped layers was achieved as high as 1.4 V. Arsenic implantation into GaAs method was also used to enhance the barrier height of 1.6 V.

  18. P3HT-graphene bilayer electrode for Schottky junction photodetectors

    Science.gov (United States)

    Aydın, H.; Kalkan, S. B.; Varlikli, C.; Çelebi, C.

    2018-04-01

    We have investigated the effect of a poly (3-hexylthiophene-2.5-diyl)(P3HT)-graphene bilayer electrode on the photoresponsivity characteristics of Si-based Schottky photodetectors. P3HT, which is known to be an electron donor and absorb light in the visible spectrum, was placed on CVD grown graphene by dip-coating method. The results of the UV-vis and Raman spectroscopy measurements have been evaluated to confirm the optical and electronic modification of graphene by the P3HT thin film. Current-voltage measurements of graphene/Si and P3HT-graphene/Si revealed rectification behavior confirming a Schottky junction formation at the graphene/Si interface. Time-resolved photocurrent spectroscopy measurements showed the devices had excellent durability and a fast response speed. We found that the maximum spectral photoresponsivity of the P3HT-graphene/Si photodetector increased more than three orders of magnitude compared to that of the bare graphene/Si photodetector. The observed increment in the photoresponsivity of the P3HT-graphene/Si samples was attributed to the charge transfer doping from P3HT to graphene within the spectral range between near-ultraviolet and near-infrared. Furthermore, the P3HT-graphene electrode was found to improve the specific detectivity and noise equivalent power of graphene/Si photodetectors. The obtained results showed that the P3HT-graphene bilayer electrodes significantly improved the photoresponsivity characteristics of our samples and thus can be used as a functional component in Si-based optoelectronic device applications.

  19. A gas sensor comprising two back-to-back connected Au/TiO2 Schottky diodes

    Science.gov (United States)

    Dehghani, Niloofar; Yousefiazari, Ehsan

    2018-04-01

    A miniature, but sturdy, gas sensor capable of operation at temperatures as high as 600 °C is presented. The device comprises two back-to-back connected gold/rutile Schottky diodes, which are fabricated on the opposite bases of a self-standing 100 μm-thick pellet of polycrystalline rutile. The rutile layer is formed by the direct oxidation of titanium metal in air at 900 °C, and the Au/rutile diodes are formed by the diffusion bonding of the gold wire segments to the pellet bases. The current versus voltage diagrams and gas sensing properties of the Au/rutile/Au structured device are recorded at different voltage sweeping frequencies and operating temperatures. The interesting features of these diagrams are explained based on an equivalent circuit of the device, which considers Schottky-type contacts at both bases and memristive conduction for the rutile in between. The device current is controlled by the leakage current of the reverse biased diode, which depends on the concentration of the oxygen vacancy at the Au/rutile interface and, hence, on the composition of the surrounding atmosphere. The device current increases 15 times in response to the presence of 1000 ppm of ethanol vapor in air. Consisting only of bulk gold and bulk rutile, the device is resilient to harsh environments and elevated temperatures; a suitable gas sensor for in-exhaust installation.

  20. A high speed PE-ALD ZnO Schottky diode rectifier with low interface-state density

    Science.gov (United States)

    Jin, Jidong; Zhang, Jiawei; Shaw, Andrew; Kudina, Valeriya N.; Mitrovic, Ivona Z.; Wrench, Jacqueline S.; Chalker, Paul R.; Balocco, Claudio; Song, Aimin; Hall, Steve

    2018-02-01

    Zinc oxide (ZnO) has recently attracted attention for its potential application to high speed electronics. In this work, a high speed Schottky diode rectifier was fabricated based on a ZnO thin film deposited by plasma-enhanced atomic layer deposition and a PtOx Schottky contact deposited by reactive radio-frequency sputtering. The rectifier shows an ideality factor of 1.31, an effective barrier height of 0.79 eV, a rectification ratio of 1.17  ×  107, and cut-off frequency as high as 550 MHz. Low frequency noise measurements reveal that the rectifier has a low interface-state density of 5.13  ×  1012 cm-2 eV-1, and the noise is dominated by the mechanism of a random walk of electrons at the PtO x /ZnO interface. The work shows that the rectifier can be used for both noise sensitive and high frequency electronics applications.

  1. Development of a Schottky CdTe Medipix3RX hybrid photon counting detector with spatial and energy resolving capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, E.N., E-mail: Eva.Gimenez@diamond.ac.uk [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom); Astromskas, V. [University of Surrey (United Kingdom); Horswell, I.; Omar, D.; Spiers, J.; Tartoni, N. [Diamond Light Source, Harwell Campus, Oxforshire OX11 0DE (United Kingdom)

    2016-07-11

    A multichip CdTe-Medipix3RX detector system was developed in order to bring the advantages of photon-counting detectors to applications in the hard X-ray range of energies. The detector head consisted of 2×2 Medipix3RX ASICs bump-bonded to a 28 mm×28 mm e{sup −} collection Schottky contact CdTe sensor. Schottky CdTe sensors undergo performance degrading polarization which increases with temperature, flux and the longer the HV is applied. Keeping the temperature stable and periodically refreshing the high voltage bias supply was used to minimize the polarization and achieve a stable and reproducible detector response. This leads to good quality images and successful results on the energy resolving capabilities of the system. - Highlights: • A high atomic number (CdTe sensor based) photon-counting detector was developed. • Polarization effects affected the image were minimized by regularly refreshing the bias voltage and stabilizing the temperature. • Good spatial resolution and image quality was achieved following this procedure.

  2. 60Co gamma irradiation effects on the the capacitance and conductance characteristics of Au/PMI/n-Si Schottky diodes

    Science.gov (United States)

    Tuğluoğlu, N.; Karadeniz, S.; Yüksel, Ö. F.; Şafak, H.; Kuş, M.

    2015-08-01

    In this work, the perylene-monoimide/n-Si (100) Schottky structures have been fabricated by spin coating process. We have studied the capacitance-voltage ( C- V) and conductance-voltage ( G- V) characteristics of the Au/perylene-monoimide/n-Si diodes at 500 kHz before and after 60Co γ-ray irradiation. The effects of 60Co γ -ray irradiation on the electrical characteristics of a perylene-monoimide/n-Si Schottky diode have been investigated. A decrease both in the capacitance and conductance has been observed after 60Co γ -ray irradiation. This has been attributed to a decrease in the net ionized dopant concentration that occurred as a result of 60Co γ-ray irradiation. Some contact parameters such as barrier height (Φ B ) interface state density ( N ss ) and series resistance ( R s ) have been calculated from the C- V and G- V characteristics of the diode before and after irradiation. It has been observed that the Φ B and N ss values are decreased after the applied radiation, while the R s value is increased.

  3. Effects of 5.4 MeV alpha-particle irradiation on the electrical properties of nickel Schottky diodes on 4H–SiC

    Energy Technology Data Exchange (ETDEWEB)

    Omotoso, E. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Department of Physics, Obafemi Awolowo University, Ile-Ife 220005 (Nigeria); Meyer, W.E.; Auret, F.D.; Paradzah, A.T.; Diale, M.; Coelho, S.M.M.; Janse van Rensburg, P.J.; Ngoepe, P.N.M. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa)

    2015-12-15

    Current–voltage, capacitance–voltage and conventional deep level transient spectroscopy at temperature ranges from 40 to 300 K have been employed to study the influence of alpha-particle irradiation from an {sup 241}Am source on Ni/4H–SiC Schottky contacts. The nickel Schottky barrier diodes were resistively evaporated on n-type 4H–SiC samples of doping density of 7.1 × 10{sup 15} cm{sup −3}. It was observed that radiation damage caused an increase in ideality factors of the samples from 1.04 to 1.07, an increase in Schottky barrier height from 1.25 to 1.31 eV, an increase in series resistance from 48 to 270 Ω but a decrease in saturation current density from 55 to 9 × 10{sup −12} A m{sup −2} from I–V plots at 300 K. The free carrier concentration of the sample decreased slightly after irradiation. Conventional DLTS showed peaks due to four deep levels for as-grown and five deep levels after irradiation. The Richardson constant, as determined from a modified Richardson plot assuming a Gaussian distribution of barrier heights for the as-grown and irradiated samples were 133 and 151 A cm{sup −2} K{sup −2}, respectively. These values are similar to literature values.

  4. Effects of electron-irradiation on electrical properties of AgCa/Si Schottky diodes

    International Nuclear Information System (INIS)

    Harmatha, L.; Zizka, M.; Sagatova, A.; Nemec, M.; Hybler, P.

    2013-01-01

    This contribution presents the results of the current-voltage I-V and the capacitance-voltage C-V measurement on the Schottky diodes with the AgCa gate on the silicon n-type substrate. The Si substrate was irradiated by 5 MeV electrons with a different dose value before the Schottky diode preparation. (authors)

  5. Deep-level transient spectroscopy on an amorphous InGaZnO4 Schottky diode

    NARCIS (Netherlands)

    Chasin, A.; Simoen, E.; Bhoolokam, A.; Nag, M.; Genoe, J.; Gielen, G.; Heremans, P.

    2014-01-01

    The first direct measurement is reported of the bulk density of deep states in amorphous IGZO (indium-gallium-zinc oxide) semiconductor by means of deep-level transient spectroscopy (DLTS). The device under test is a Schottky diode of amorphous IGZO semiconductor on a palladium (Pd) Schottky-barrier

  6. Schottky barrier CdTe(Cl) detectors for planetary missions

    International Nuclear Information System (INIS)

    Eisen, Yosef; Floyd, Samuel

    2002-01-01

    Schottky barrier cadmium telluride (CdTe) radiation detectors of dimensions 2mm x 2mm x 1mm and segmented monolithic 3cm x 3 cm x 1mm are under study at GSFC for future NASA planetary instruments. These instruments will perform x-ray fluorescence spectrometry of the surface and monitor the solar x-ray flux spectrum, the excitation source for the characteristic x-rays emitted from the planetary body. The Near Earth Asteroid Rendezvous (NEAR) mission is the most recent example of such a remote sensing technique. Its x-ray fluorescence detectors were gas proportional counters with a back up Si PIN solar monitor. Analysis of NEAR data has shown the necessity to develop a solar x-ray detector with efficiency extending to 30keV. Proportional counters and Si diodes have low sensitivity above 9keV. Our 2mm x 2mm x 1mm CdTe operating at -30 degree sign C possesses an energy resolution of 250eV FWHM for 55Fe with unit efficiency to up to 30keV. This is an excellent candidate for a solar monitor. Another ramification of the NEAR data is a need to develop a large area detector system, 20-30 cm2, with cosmic ray charged particle rejection, for measuring the characteristic radiation. A 3cm x 3cm x 1mm Schottky CdTe segmented monolithic detector is under investigation for this purpose. A tiling of 2-3 such detectors will result in the desired area. The favorable characteristics of Schottky CdTe detectors, the system design complexities when using CdTe and its adaptation to future missions will be discussed

  7. Optimization of transition-metal dichalcogenides based field-effecttransistors via contact engineering

    Science.gov (United States)

    Perera, Meeghage Madusanka

    Layered transition Metal Dichalcogenides (TMDs) have demonstrated a wide range of remarkable properties for applications in next generation nano-electronics. These systems have displayed many "graphene-like" properties including a relatively high carrier mobility, mechanical flexibility, chemical and thermal stability, and moreover offer the significant advantage of a substantial band gap. However, the fabrication of high performance field-effect transistors (FETs) of TMDs is challenging mainly due to the formation of a significant Schottky barrier at metal/TMD interface in most cases. The main goal of this study is to develop novel contact engineering strategies to achieve low-resistance Ohmic contacts. Our first approach is to use Ionic Liquid (IL) gating of metal contacted MoS2 FETs to achieve highly transparent tunneling contacts due to the strong band banding at metal/MoS2 interface. The substantially reduced contact resistance in ionic-liquid-gated bilayer and few-layer MoS 2 FETs results in an ambipolar behavior with high ON/OFF ratios, a near-ideal subthreshold swing, and significantly improved field-effect mobility. Remarkably, the mobility of a 3-nm-thick MoS2 FET with an IL gate was found to increase from ˜ 100 cm2V-1s-1 to ˜ 220 cm2V-1s-1 as the temperature decreased from 180 K to 77 K. This finding is in quantitative agreement with the true channel mobility measured by four-terminal measurement, suggesting that the mobility is predominantly limited by phonon-scattering. To further improve the contacts of TMD devices, graphene was used as work function tunable electrodes. In order to achieve low Schottky barrier height, both IL gating and surface charge transfer doping were used to tune the work function of graphene electrodes close to the conduction band edge of MoS 2. As a result, the performance of our graphene contacted MoS2 FETs is limited by the channel rather than contacts, which is further verified by four-terminal measurements. Finally

  8. Investigation of the Electrical Characteristics of Al/p-Si/Al Schottky Diode

    International Nuclear Information System (INIS)

    Şenarslan, Elvan; Güzeldir, Betül; Sağlam, Mustafa

    2016-01-01

    In this study, p-type Si semiconductor wafer with (100) orientation, 400 μm thickness and 1-10 Ω cm resistivity was used. The Si wafer before making contacts were chemically cleaned with the Si cleaning procedure which for remove organic contaminations were ultrasonically cleaned at acetone and methanol for 10 min respectively and then rinsed in deionized water of 18 MΩ and dried with high purity N 2 . Then respectively RCA1(i.e., boiling in NH 3 +H 2 O 2 +6H 2 O for 10 min at 60°C ), RCA2 (i.e., boiling in HCl+H 2 O 2 +6H 2 O for 10 min at 60°C ) cleaning procedures were applied and rinsed in deionized water followed by drying with a stream of N 2 . After the cleaning process, the wafer is immediately inserted in to the coating unit. Ohmic contact was made by evaporating of Al on the non-polished side of the p-Si wafer pieces under ∼ 4,2 10 -6 Torr pressure. After process evaporation, p-Si with omic contac thermally annealed 580°C for 3 min in a quartz tube furnace in N 2 . Then, the rectifier contact is made by evaporation Al metal diameter of about 1.0 mm on the polished surface of p-Si in turbo molecular pump at about ∼ 1 10 -6 Torr. Consequently, Al/p-Si/Al Schottky diode was obtained. The I–V measurements of this diode performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C–V measurements were performed with HP 4192A (50–13 MHz) LF Impedance Analyzer at room temperature and in dark. (paper)

  9. Investigation of the Electrical Characteristics of Al/p-Si/Al Schottky Diode

    Science.gov (United States)

    Şenarslan, Elvan; Güzeldir, Betül; Sağlam, Mustafa

    2016-04-01

    In this study, p-type Si semiconductor wafer with (100) orientation, 400 μm thickness and 1-10 Ω cm resistivity was used. The Si wafer before making contacts were chemically cleaned with the Si cleaning procedure which for remove organic contaminations were ultrasonically cleaned at acetone and methanol for 10 min respectively and then rinsed in deionized water of 18 MΩ and dried with high purity N2. Then respectively RCA1(i.e., boiling in NH3+H2O2+6H2O for 10 min at 60°C ), RCA2 (i.e., boiling in HCl+H2O2+6H2O for 10 min at 60°C ) cleaning procedures were applied and rinsed in deionized water followed by drying with a stream of N2. After the cleaning process, the wafer is immediately inserted in to the coating unit. Ohmic contact was made by evaporating of Al on the non-polished side of the p-Si wafer pieces under ~ 4,2 10-6 Torr pressure. After process evaporation, p-Si with omic contac thermally annealed 580°C for 3 min in a quartz tube furnace in N2. Then, the rectifier contact is made by evaporation Al metal diameter of about 1.0 mm on the polished surface of p-Si in turbo molecular pump at about ~ 1 10-6 Torr. Consequently, Al/p-Si/Al Schottky diode was obtained. The I-V measurements of this diode performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C-V measurements were performed with HP 4192A (50-13 MHz) LF Impedance Analyzer at room temperature and in dark.

  10. Role of Metal Contacts in High-Performance Phototransistors Based on WSe 2 Monolayers

    KAUST Repository

    Zhang, Wenjing; Chiu, Ming-Hui; Chen, Chang-Hsiao; Chen, Wei; Li, Lain-Jong; Wee, Andrew Thye Shen

    2014-01-01

    Phototransistors based on monolayer transition metal dichalcogenides (TMD) have high photosensitivity due to their direct band gap transition. However, there is a lack of understanding of the effect of metal contacts on the performance of atomically thin TMD phototransistors. Here, we fabricate phototransistors based on large-area chemical vapor deposition (CVD) tungsten diselenide (WSe2) monolayers contacted with the metals of different work function values. We found that the low Schottky-contact WSe2 phototransistors exhibit a very high photo gain (105) and specific detectivity (1014Jones), values higher than commercial Si- and InGaAs-based photodetectors; however, the response speed is longer than 5 s in ambient air. In contrast, the high Schottky-contact phototransistors display a fast response time shorter than 23 ms, but the photo gain and specific detectivity decrease by several orders of magnitude. Moreover, the fast response speed of the high Schottky-contact devices is maintained for a few months in ambient air. This study demonstrates that the contact plays an important role in TMD phototransistors, and barrier height tuning is critical for optimizing the photoresponse and photoresponsivity. © 2014 American Chemical Society.

  11. Role of Metal Contacts in High-Performance Phototransistors Based on WSe 2 Monolayers

    KAUST Repository

    Zhang, Wenjing

    2014-08-26

    Phototransistors based on monolayer transition metal dichalcogenides (TMD) have high photosensitivity due to their direct band gap transition. However, there is a lack of understanding of the effect of metal contacts on the performance of atomically thin TMD phototransistors. Here, we fabricate phototransistors based on large-area chemical vapor deposition (CVD) tungsten diselenide (WSe2) monolayers contacted with the metals of different work function values. We found that the low Schottky-contact WSe2 phototransistors exhibit a very high photo gain (105) and specific detectivity (1014Jones), values higher than commercial Si- and InGaAs-based photodetectors; however, the response speed is longer than 5 s in ambient air. In contrast, the high Schottky-contact phototransistors display a fast response time shorter than 23 ms, but the photo gain and specific detectivity decrease by several orders of magnitude. Moreover, the fast response speed of the high Schottky-contact devices is maintained for a few months in ambient air. This study demonstrates that the contact plays an important role in TMD phototransistors, and barrier height tuning is critical for optimizing the photoresponse and photoresponsivity. © 2014 American Chemical Society.

  12. Hybrid graphene/silicon Schottky photodiode with intrinsic gating effect

    Science.gov (United States)

    Di Bartolomeo, Antonio; Luongo, Giuseppe; Giubileo, Filippo; Funicello, Nicola; Niu, Gang; Schroeder, Thomas; Lisker, Marco; Lupina, Grzegorz

    2017-06-01

    We propose a hybrid device consisting of a graphene/silicon (Gr/Si) Schottky diode in parallel with a Gr/SiO2/Si capacitor for high-performance photodetection. The device, fabricated by transfer of commercial graphene on low-doped n-type Si substrate, achieves a photoresponse as high as 3 \\text{A} {{\\text{W}}-1} and a normalized detectivity higher than 3.5× {{10}12} \\text{cm} \\text{H}{{\\text{z}}1/2} {{\\text{W}}-1} in the visible range. It exhibits a photocurrent exceeding the forward current because photo-generated minority carriers, accumulated at Si/SiO2 interface of the Gr/SiO2/Si capacitor, diffuse to the Gr/Si junction. We show that the same mechanism, when due to thermally generated carriers, although usually neglected or disregarded, causes the increased leakage often measured in Gr/Si heterojunctions. We perform extensive I-V and C-V characterization at different temperatures and we measure a zero-bias Schottky barrier height of 0.52 eV at room temperature, as well as an effective Richardson constant A **  =  4× {{10}-5} \\text{A} \\text{c}{{\\text{m}}-2} {{\\text{K}}-2} and an ideality factor n≈ 3.6 , explained by a thin (<1 nm) oxide layer at the Gr/Si interface.

  13. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    International Nuclear Information System (INIS)

    Hathwar, Raghuraj; Dutta, Maitreya; Chowdhury, Srabanti; Goodnick, Stephen M.; Koeck, Franz A. M.; Nemanich, Robert J.

    2016-01-01

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco ® Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures

  14. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Science.gov (United States)

    Hathwar, Raghuraj; Dutta, Maitreya; Koeck, Franz A. M.; Nemanich, Robert J.; Chowdhury, Srabanti; Goodnick, Stephen M.

    2016-06-01

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco® Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures

  15. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    Energy Technology Data Exchange (ETDEWEB)

    Hathwar, Raghuraj; Dutta, Maitreya; Chowdhury, Srabanti; Goodnick, Stephen M. [Department of Electrical Engineering, Arizona State University, Tempe, Arizona 85287-8806 (United States); Koeck, Franz A. M.; Nemanich, Robert J. [Department of Physics, Arizona State University, Tempe, Arizona 85287-8806 (United States)

    2016-06-14

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco{sup ®} Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures.

  16. Measurements of Effective Schottky Barrier in Inverse Extraordinary Optoconductance Structures

    Science.gov (United States)

    Tran, L. C.; Werner, F. M.; Solin, S. A.; Gilbertson, Adam; Cohen, L. F.

    2013-03-01

    Individually addressable optical sensors with dimensions as low as 250nm, fabricated from metal semiconductor hybrid structures (MSH) of AuTi-GaAs Schottky interfaces, display a transition from resistance decreasing with intensity in micron-scale sensors (Extraordinary Optoconductance, EOC) to resistance increasing with intensity in nano-scale sensors (Inverse Extraordinary Optoconductance I-EOC). I-EOC is attributed to a ballistic to diffusive crossover with the introduction of photo-induced carriers and gives rise to resistance changes of up to 9462% in 250nm devices. We characterize the photo-dependence of the effective Schottky barrier in EOC/I-EOC structures by the open circuit voltage and reverse bias resistance. Under illumination by a 5 mW, 632.8 nm HeNe laser, the barrier is negligible and the Ti-GaAs interface becomes Ohmic. Comparing the behavior of two devices, one with leads exposed, another with leads covered by an opaque epoxy, the variation in Voc with the position of the laser can be attributed to a photovoltaic effect of the lead metal and bulk GaAs. The resistance is unaffected by the photovoltaic offset of the leads, as indicated by the radial symmetry of 2-D resistance maps obtained by rastering a laser across EOC/IEOC devices. SAS has a financial interest in PixelEXX, a start-up company whose mission is to market imaging arrays.

  17. Tuning the Schottky Barrier at the Graphene/MoS2 Interface by Electron Doping

    DEFF Research Database (Denmark)

    Jin, Chengjun; Rasmussen, Filip Anselm; Thygesen, Kristian Sommer

    2015-01-01

    ) with a generalized gradient approximation predicts a Schottky barrier height of 0.18 eV, whereas the G0W0 method increases this value to 0.60 eV. While the DFT band gap of MoS2 does not change when the heterostructure is formed, the G0W0 gap is reduced by 0.30 eV as a result of the enhanced screening by the graphene...... layer. In contrast to the case of metal substrates, where the band alignment is governed by Pauli repulsion-induced interface dipoles, the graphene/MoS2 heterostructure shows only a negligible interface dipole. As a consequence, the band alignment at the neutral heterostructure is not changed when...... the two layers are brought into contact. We systematically follow the band alignment as a function of doping concentration and find that the Fermi level of the graphene crosses the MoS2 conduction band at a doping concentration of around 1012 cm–2. The variation of the energy levels with doping...

  18. A high-sensitive ultraviolet photodetector composed of double-layered TiO{sub 2} nanostructure and Au nanoparticles film based on Schottky junction

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huan; Qin, Pei [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Yi, Guobin, E-mail: ygb702@163.com [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Zu, Xihong [School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 (China); Zhang, Li, E-mail: zhangli2368@126.com [School of Materials and Energy, Guangdong University of Technology, Guangzhou, 510006 (China); Hong, Wei; Chen, Xudong [School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275 (China)

    2017-06-15

    In this study, a Schottky-type ultraviolet (UV) photodetector based on double-layered nanostructured TiO{sub 2}/Au films was fabricated. Double-layered titanium dioxide (TiO{sub 2}) nanostructures composed of one layer of TiO{sub 2} nano-flowers on one layer of TiO{sub 2} nanorods on fluorine-doped tin oxide (FTO) pre-coated glass substrates were synthesized via a convenient hydrothermal method using titanium butoxide and hydrochloric acid as the starting precursor, without involving the use of any other surfactants and catalysts. A granular-shaped thin-layer of Au film using vacuum sputter coating technique was subsequently deposited on TiO{sub 2} for the formation of Schottky-type photodetector. The as-fabricated Schottky device showed various photocurrent responses when irradiated with different wavelength of UV light. This suggests that the newly-developed photodetectors have promising potential for identifying different UV light wavelengths. - Highlights: • A novel double-layered TiO{sub 2} nanostructure was synthesized by a simple method. • An UV photodetector composed of TiO{sub 2} and Au was designed and fabricated. • The preparation method of TiO{sub 2}/Au UV photodetector was simple and convenient. • The UV photodetector based on TiO{sub 2}/Au showed excellent sensitivity to UV light.

  19. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Congxin, E-mail: xiacongxin@htu.edu.cn; Xue, Bin; Wang, Tianxing; Peng, Yuting [Department of Physic, Henan Normal University, Xinxiang 453007 (China); Jia, Yu [School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052 (China)

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  20. Graphene-Based Reversible Nano-Switch/Sensor Schottky Diode

    Science.gov (United States)

    Miranda, Felix A.; Meador, Michael A.; Theofylaktos, Onoufrios; Pinto, Nicholas J.; Mueller, Carl H.; Santos-Perez, Javier

    2010-01-01

    This proof-of-concept device consists of a thin film of graphene deposited on an electrodized doped silicon wafer. The graphene film acts as a conductive path between a gold electrode deposited on top of a silicon dioxide layer and the reversible side of the silicon wafer, so as to form a Schottky diode. By virtue of the two-dimensional nature of graphene, this device has extreme sensitivity to different gaseous species, thereby serving as a building block for a volatile species sensor, with the attribute of having reversibility properties. That is, the sensor cycles between active and passive sensing states in response to the presence or absence of the gaseous species.

  1. Electrical characterization of MEH-PPV based Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Nimith, K. M., E-mail: nimithkm@gmail.com; Satyanarayan, M. N., E-mail: satya-mn@nitk.edu.in; Umesh, G., E-mail: umesh52@gmail.com [Optoelectronics Laboratory (OEL), Department of Physics, National Institute of Technology Karnataka (NITK),Surathkal, PO Srinivasnagar, Mangalore, DK-575025 (India)

    2016-05-06

    MEH-PPV Schottky diodes with and without Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been fabricated and characterized. The highlight of this work is that all the fabrication and characterization steps had been carried out in the ambient conditions and the device fabrication was done without any UV-Ozone surface treatment of ITO anodes. Current Density-Voltage characteristics shows that the addition of hole injection layer (HIL) enhances the charge injection into the polymer layer by reducing the energy barrier across the Indium Tin Oxide (ITO)-Organic interface. The rectification ratio increases to 2.21 from 0.76 at 5V for multilayer devices compared to single layer devices. Further we investigated the effect of an alkali metal fluoride (LiF) by inserting a thin layer in between the organic layer and Aluminum (Al) cathode. The results of these investigations will be discussed in detail.

  2. Aluminum break-point contacts

    NARCIS (Netherlands)

    Heinemann, Martina; Groot, R.A. de

    1997-01-01

    Ab initio molecular dynamics is used to study the contribution of a single Al atom to an aluminum breakpoint contact during the final stages of breaking and the initial stages of the formation of such a contact. A hysteresis effect is found in excellent agreement with experiment and the form of the

  3. LANL Contacts

    Science.gov (United States)

    : (505) 665-3664 ethics@lanl.gov Journalist queries Communications Office (505) 667-7000 Media contacts programs and employee resources. General Employee directory Emergency communication Communications Office (505) 667-7000 Ethics & Audits Internal Audit: (505) 665-3104 Ethics Office: (505) 667-7506 Fax

  4. Role of metal/silicon semiconductor contact engineering for enhanced output current in micro-sized microbial fuel cells

    KAUST Repository

    Mink, Justine E.

    2013-11-25

    We show that contact engineering plays an important role to extract the maximum performance from energy harvesters like microbial fuel cells (MFCs). We experimented with Schottky and Ohmic methods of fabricating contact areas on silicon in an MFC contact material study. We utilized the industry standard contact material, aluminum, as well as a metal, whose silicide has recently been recognized for its improved performance in smallest scale integration requirements, cobalt. Our study shows that improvements in contact engineering are not only important for device engineering but also for microsystems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Electrically Tunable and Negative Schottky Barriers in Multi-layered Graphene/MoS2 Heterostructured Transistors

    Science.gov (United States)

    Qiu, Dongri; Kim, Eun Kyu

    2015-09-01

    We fabricated multi-layered graphene/MoS2 heterostructured devices by positioning mechanically exfoliated bulk graphite and single-crystalline 2H-MoS2 onto Au metal pads on a SiO2/Si substrate via a contamination-free dry transfer technique. We also studied the electrical transport properties of Au/MoS2 junction devices for systematic comparison. A previous work has demonstrated the existence of a positive Schottky barrier height (SBH) in the metal/MoS2 system. However, analysis of the SBH indicates that the contacts of the multi-layered graphene/MoS2 have tunable negative barriers in the range of 300 to -46 meV as a function of gate voltage. It is hypothesized that this tunable SBH is responsible for the modulation of the work function of the thick graphene in these devices. Despite the large number of graphene layers, it is possible to form ohmic contacts, which will provide new opportunities for the engineering of highly efficient contacts in flexible electronics and photonics.

  6. Electrically Tunable and Negative Schottky Barriers in Multi-layered Graphene/MoS2 Heterostructured Transistors.

    Science.gov (United States)

    Qiu, Dongri; Kim, Eun Kyu

    2015-09-03

    We fabricated multi-layered graphene/MoS2 heterostructured devices by positioning mechanically exfoliated bulk graphite and single-crystalline 2H-MoS2 onto Au metal pads on a SiO2/Si substrate via a contamination-free dry transfer technique. We also studied the electrical transport properties of Au/MoS2 junction devices for systematic comparison. A previous work has demonstrated the existence of a positive Schottky barrier height (SBH) in the metal/MoS2 system. However, analysis of the SBH indicates that the contacts of the multi-layered graphene/MoS2 have tunable negative barriers in the range of 300 to -46 meV as a function of gate voltage. It is hypothesized that this tunable SBH is responsible for the modulation of the work function of the thick graphene in these devices. Despite the large number of graphene layers, it is possible to form ohmic contacts, which will provide new opportunities for the engineering of highly efficient contacts in flexible electronics and photonics.

  7. Bulk GaN Schottky Diodes for Millimeter Wave Frequency Multipliers, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Within the context of this project, White Light Power Inc. (WLPI) will demonstrate the feasibility of using vertical GaN Schottky diodes for high-power rectification...

  8. High Power Ga2O3-based Schottky Diode, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Program will develop a new generation of radiation hard high-power high-voltage Ga2O3-based Schottky diode, which is suitable for applications in the space...

  9. Fabrication and characterization of 8.87 THz schottky barrier mixer diodes for mixer

    Science.gov (United States)

    Wang, Wenjie; Li, Qian; An, Ning; Tong, Xiaodong; Zeng, Jianping

    2018-04-01

    In this paper we report on the fabrication and characterization of GaAs-based THz schottky barrier mixer diodes. Considering the analyzed results as well as fabrication cost and complexity, a group of trade-off parameters was determined. Electron-beam lithography and air-bridge technique have been used to obtain schottky diodes with a cut off frequency of 8.87 THz. Equivalent values of series resistance, ideal factor and junction capacitance of 10.2 (1) Ω, 1.14 (0.03) and 1.76(0.03) respectively have been measured for 0.7um diameter anode devices by DC and RF measurements. The schottky barrier diodes fabrication process is fully planar and very suitable for integration in THz frequency multiplier and mixer circuits. THz Schottky barrier diodes based on such technology with 2 μm diameter anodes have been tested at 1.6 THz in a sub-harmonic mixer.

  10. Bulk GaN Schottky Diodes for Millimeter Wave Frequency Multipliers, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Within the context of this project, White Light Power Inc. (WLPI) will demonstrate prototype vertical GaN Schottky diodes for high-power rectification at W-band. To...

  11. Integration of organic based Schottky junctions for crossbar non-volatile memory applications

    DEFF Research Database (Denmark)

    Katsia, E.; Tallarida, G.; Ferrari, S.

    2008-01-01

    Small size Schottky junctions using two different synthesized organic semiconductors (oligophenylene-vinylenes) were integrated by standard UV lithography into crossbar arrays. The proposed integration scheme can be applied to a wide class of organics without affecting material properties. Current...

  12. Non-classical logic inverter coupling a ZnO nanowire-based Schottky barrier transistor and adjacent Schottky diode.

    Science.gov (United States)

    Hosseini Shokouh, Seyed Hossein; Raza, Syed Raza Ali; Lee, Hee Sung; Im, Seongil

    2014-08-21

    On a single ZnO nanowire (NW), we fabricated an inverter-type device comprising a Schottky diode (SD) and field-effect transistor (FET), aiming at 1-dimensional (1D) electronic circuits with low power consumption. The SD and adjacent FET worked respectively as the load and driver, so that voltage signals could be easily extracted as the output. In addition, NW FET with a transparent conducting oxide as top gate turned out to be very photosensitive, although ZnO NW SD was blind to visible light. Based on this, we could achieve an array of photo-inverter cells on one NW. Our non-classical inverter is regarded as quite practical for both logic and photo-sensing due to its performance as well as simple device configuration.

  13. Walter Schottky. Atom-theorist and electrotechnician. His life and work until the year 1941; Walter Schottky. Atomtheoretiker und Elektrotechniker. Sein Leben und Werk bis ins Jahr 1941

    Energy Technology Data Exchange (ETDEWEB)

    Serchinger, Reinhard W.

    2008-07-01

    In this first scientific biography of Walter Schottky at the one hand the origin of his scientific and technical works is reproduced and put in the physical-historical connection of his time. At the other hand his special role in the research strategy of the Siemens company becomes clear, which could in the framework of this research project for the first time be identified. Also psychological aspects were essentially included in the study, because else the binding of the particular more corresponding to an ivory-tower than and industrial physicist personality of Schottky to the Siemens trust not would be understandable. The example of Walter Schottky shows the importance of the researching individuum, which until today undoubtly can be an important element of company-internal innovation processes not only contrarily but also in the transition to scientific team work.

  14. Modelling the metal–semiconductor band structure in implanted ohmic contacts to GaN and SiC

    International Nuclear Information System (INIS)

    Pérez-Tomás, A; Fontserè, A; Placidi, M; Jennings, M R; Gammon, P M

    2013-01-01

    Here we present a method to model the metal–semiconductor (M–S) band structure to an implanted ohmic contact to a wide band gap semiconductor (WBG) such as GaN and SiC. The performance and understanding of the M–S contact to a WBG semiconductor is of great importance as it influences the overall performance of a semiconductor device. In this work we explore in a numerical fashion the ohmic contact properties to a WBG semiconductor taking into account the partial ionization of impurities and analysing its dependence on the temperature, the barrier height, the impurity level band energy and carrier concentration. The effect of the M–S Schottky barrier lowering and the Schottky barrier inhomogeneities are discussed. The model is applied to a fabricated ohmic contact to GaN where the M–S band structure can be completely determined. (paper)

  15. Simulation of a perfect CVD diamond Schottky diode steep forward current–voltage characteristic

    Energy Technology Data Exchange (ETDEWEB)

    Kukushkin, V.A., E-mail: vakuk@appl.sci-nnov.ru [Institute of Applied Physics of the Russian Academy of Science, 46 Ulyanov St., 603950 Nizhny Novgorod (Russian Federation); Nizhny Novgorod State University named after N.I. Lobachevsky, 23 Gagarin pr., 603950 Nizhny Novgorod (Russian Federation)

    2016-10-01

    The kinetic equation approach to the simulation of the perfect CVD diamond Schottky diode current–voltage characteristic is considered. In result it is shown that the latter has a significantly steeper forward branch than that of perfect devices of such a type on usual semiconductors. It means that CVD diamond-based Schottky diodes have an important potential advantage over analogous devices on conventional materials.

  16. Physical Mechanisms Responsible for Electrical Conduction in Pt/GaN Schottky Diodes

    OpenAIRE

    H. MAZARI; K. AMEUR; N. BENSEDDIK; Z. BENAMARA; R. KHELIFI; M. MOSTEFAOUI; N. ZOUGAGH; N. BENYAHYA; R. BECHAREF; G. BASSOU; B. GRUZZA; J. M. BLUET; C. BRU-CHEVALLIER

    2014-01-01

    The current-voltage (I-V) characteristics of Pt/(n.u.d)-GaN and Pt/Si-doped-GaN diodes Schottky are investigated. Based on these measurements, physical mechanisms responsible for electrical conduction have been suggested. The contribution of thermionic-emission current and various other current transport mechanisms were assumed when evaluating the Schottky barrier height. Thus the generation-recombination, tunneling and leakage currents caused by inhomogeneities and defects at metal-semicondu...

  17. Heavy Ion Induced Degradation in SiC Schottky Diodes: Bias and Energy Deposition Dependence

    Science.gov (United States)

    Javanainen, Arto; Galloway, Kenneth F.; Nicklaw, Christopher; Bosser, Alexandre L.; Ferlet-Cavrois, Veronique; Lauenstein, Jean-Marie; Pintacuda, Francesco; Reed, Robert A.; Schrimpf, Ronald D.; Weller, Robert A.; hide

    2016-01-01

    Experimental results on ion-induced leakage current increase in 4H-SiC Schottky power diodes are presented. Monte Carlo and TCAD simulations show that degradation is due to the synergy between applied bias and ion energy deposition. This degradation is possibly related to thermal spot annealing at the metal semiconductor interface. This thermal annealing leads to an inhomogeneity of the Schottky barrier that could be responsible for the increase leakage current as a function of fluence.

  18. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    Directory of Open Access Journals (Sweden)

    Zdansky Karel

    2011-01-01

    Full Text Available Abstract Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd nanoparticles (NPs in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures.

  19. Self-assembled H-aggregation induced high performance poly (3-hexylthiophene) Schottky diode

    Science.gov (United States)

    Chaudhary, Vivek; Pandey, Rajiv K.; Prakash, Rajiv; Singh, Arun Kumar

    2017-12-01

    The investigation of size confinement and chain orientation within the microstructure of a polymer thin film is very important for electronic device applications and fundamental research. Here, we present single step methodology for the synthesis of solution-processable poly (3-hexylthiophene) (P3HT) nanofibers via a self-assembly process. The formation of P3HT nanofibers is confirmed by atomic force microscopy. The synthesized nanofibers are characterized by UV-visible absorption, photoluminescence, and Raman spectroscopy. The aggregation type of self-assembled P3HT is studied by both UV-visible absorbance and photoluminescence spectroscopy. The exciton bandwidth in polymer films is calculated by following the Spano's H-aggregate model and found to be 28 meV. Raman spectroscopy is used to identify the various stretching modes present in nanofibers. The structural investigation using grazing angle X-ray diffraction of nanofibers reveals the presence of alkyl chain ordering. We have fabricated organic Schottky diodes with P3HT nanofibers on indium tin oxide (ITO) coated glass with configuration Al/P3HT/ITO, and current density-voltage characteristics are subsequently used for extracting the electronic parameters of the device. We have also discussed the charge transport mechanism at the metal/polymer interface.

  20. N-cadherin in adult rat cardiomyocytes in culture. II. Spatio-temporal appearance of proteins involved in cell-cell contact and communication. Formation of two distinct N-cadherin/catenin complexes.

    Science.gov (United States)

    Hertig, C M; Butz, S; Koch, S; Eppenberger-Eberhardt, M; Kemler, R; Eppenberger, H M

    1996-01-01

    The spatio-temporal appearance and distribution of proteins forming the intercalated disc were investigated in adult rat cardiomyocytes (ARC). The 'redifferentiation model' of ARC involves extensive remodelling of the plasma membrane and of the myofibrillar apparatus. It represents a valuable system to elucidate the formation of cell-cell contact between cardiomyocytes and to assess the mechanisms by which different proteins involved in the cell-cell adhesion process are sorted in a precise manner to the sites of function. Appearance of N-cadherin, the catenins and connexin43 within newly formed adherens and gap junctions was studied. Here first evidence is provided for a formation of two distinct and separable N-cadherin/catenin complexes in cardiomyocytes. Both complexes are composed of N-cadherin and alpha-catenin which bind to either beta-catenin or plakoglobin in a mutually exclusive manner. The two N-cadherin/catenin complexes are assumed to be functionally involved in the formation of cell-cell contacts in ARC; however, the differential appearance and localization of the two types of complexes may also point to a specific role during ARC differentiation. The newly synthesized beta-catenin containing complex is more abundant during the first stages in culture after ARC isolation, while the newly synthesized plakoglobin containing complex progressively accumulates during the morphological changes of ARC. ARC formed a tissue-like pattern in culture whereby the new cell-cell contacts could be dissolved through Ca2+ depletion. Presence of cAMP and replenishment of Ca2+ content in the culture medium not only allowed reformation of cell-cell contacts but also affected the relative protein ratio between the two N-cadherin/catenin complexes, increasing the relative amount of newly synthesized beta-catenin over plakoglobin at a particular stage of ARC differentiation. The clustered N-cadherin/catenin complexes at the plasma membrane appear to be a prerequisite for the

  1. Study of 4H-SiC junction barrier Schottky diode using field guard ring termination

    International Nuclear Information System (INIS)

    Feng-Ping, Chen; Yu-Ming, Zhang; Hong-Liang, Lü; Yi-Men, Zhang; Jian-Hua, Huang

    2010-01-01

    This paper reports that the 4H-SiC Schottky barrier diode, PiN diode and junction barrier Schottky diode terminated by field guard rings are designed, fabricated and characterised. The measurements for forward and reverse characteristics have been done, and by comparison with each other, it shows that junction barrier Schottky diode has a lower reverse current density than that of the Schottky barrier diode and a higher forward drop than that of the PiN diode. High-temperature annealing is presented in this paper as well to figure out an optimised processing. The barrier height of 0.79 eV is formed with Ti in this work, the forward drop for the Schottky diode is 2.1 V, with an ideality factor of 3.2, and junction barrier Schottky diode with blocking voltage higher than 400 V was achieved by using field guard ring termination. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  2. Interagency Contact and Training for a Comprehensive Approach to Operations: Assessment of the Formation Operations Center of Excellence ’Civil-Military Seminar’

    Science.gov (United States)

    2012-03-01

    formation interorganismes rassemblant des acteurs civils et militaires a été présentée comme un instrument de premier plan qui permet d’atténuer...soutient qu’une telle formation intégrée est un outil déterminant qui permet d’établir une connaissance partagée de la situation et une...interorganismes rassemblant des acteurs civils et militaires a été présentée comme un instrument de premier plan qui permet d’atténuer certains des

  3. General predictive model of friction behavior regimes for metal contacts based on the formation stability and evolution of nanocrystalline surface films.

    Energy Technology Data Exchange (ETDEWEB)

    Argibay, Nicolas [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Cheng, Shengfeng [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Sawyer, W. G. [Univ. of Florida, Gainesville, FL (United States); Michael, Joseph R. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Chandross, Michael E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2015-09-01

    The prediction of macro-scale friction and wear behavior based on first principles and material properties has remained an elusive but highly desirable target for tribologists and material scientists alike. Stochastic processes (e.g. wear), statistically described parameters (e.g. surface topography) and their evolution tend to defeat attempts to establish practical general correlations between fundamental nanoscale processes and macro-scale behaviors. We present a model based on microstructural stability and evolution for the prediction of metal friction regimes, founded on recently established microstructural deformation mechanisms of nanocrystalline metals, that relies exclusively on material properties and contact stress models. We show through complementary experimental and simulation results that this model overcomes longstanding practical challenges and successfully makes accurate and consistent predictions of friction transitions for a wide range of contact conditions. This framework not only challenges the assumptions of conventional causal relationships between hardness and friction, and between friction and wear, but also suggests a pathway for the design of higher performance metal alloys.

  4. Electrical Characterization of Graphite/InP Schottky Diodes by I-V-T and C-V Methods

    Science.gov (United States)

    Tiagulskyi, Stanislav; Yatskiv, Roman; Grym, Jan

    2018-02-01

    A rectifying junction was prepared by casting a drop of colloidal graphite on the surface of an InP substrate. The electrophysical properties of graphite/InP junctions were investigated in a wide temperature range. Temperature-dependent I-V characteristics of the graphite/InP junctions are explained by the thermionic emission mechanism. The Schottky barrier height (SBH) and the ideality factor were found to be 0.9 eV and 1.47, respectively. The large value of the SBH and its weak temperature dependence are explained by lateral homogeneity of the junction, which is related to the structure of the graphite layer. The moderate disagreement between the current-voltage and capacitance-voltage measurements is attributed to the formation of interfacial native oxide film on the InP surface.

  5. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jian; Yan, Dawei, E-mail: daweiyan@jiangnan.edu.cn; Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng [Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China)

    2015-04-21

    Lattice-matched Pt/Au-In{sub 0.17}Al{sub 0.83}N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  6. Exploring Communication and Course Format: Conversation Frequency and Duration, Student Motives, and Perceived Teacher Approachability for Out-of-Class Contact

    Science.gov (United States)

    Brooks, Catherine F.; Young, Stacy L.

    2016-01-01

    This study explored how course instructional format (i.e., online, face-to-face, or hybrid) is related to the frequency and duration of out-of-class communication (OCC) between college instructors and students, to student motives for communicating with teachers, and to perceived teacher approachability for conversation outside of class. Though…

  7. Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk GaN Substrates FY2016

    Science.gov (United States)

    2016-12-01

    ARL-TR-7913 ● DEC 2016 US Army Research Laboratory Fabrication and Characterization of Vertical Gallium Nitride Power Schottky...TR-7913 ● DEC 2016 US Army Research Laboratory Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk...Fabrication and Characterization of Vertical Gallium Nitride Power Schottky Diodes on Bulk GaN Substrates FY2016 5a. CONTRACT NUMBER 5b. GRANT NUMBER

  8. Current-voltage characterization of Au contact on sol-gel ZnO films with and without conducting polymer

    International Nuclear Information System (INIS)

    Lin, Yow-Jon; Jheng, Mei-Jyuan; Zeng, Jian-Jhou

    2010-01-01

    This study investigates the current density-voltage (J-V) characteristics of Au/n-type ZnO and Au/polyaniline (PANI)/n-type ZnO devices. ZnO films were prepared by the sol-gel method. For Au/n-type ZnO devices, native defects and impurities resident within the ZnO depletion region contribute to barrier thinning of, carrier hopping across, and tunneling through the Schottky barrier. This leads to the formation of nonalloyed ohmic contacts. However, rectifying junctions were formed on n-type ZnO by employing the simple technique of spin-coating PANI to act as the electron-blocking layer. Our present results suggest that the ZnO depletion region at the PANI/n-type ZnO interface is not the origin of the rectifying behavior of Au/PANI/n-type ZnO contact. In addition, the presence of the built-in potential of Au/PANI/n-type ZnO devices could result in the shift of the J-V curve toward negative voltage. Excellent agreement between simulated and measured data was obtained when the built-in potential was taken into account in the J-V relationship.

  9. In-plane Schottky-barrier field-effect transistors based on 1T/2H heterojunctions of transition-metal dichalcogenides

    Science.gov (United States)

    Fan, Zhi-Qiang; Jiang, Xiang-Wei; Luo, Jun-Wei; Jiao, Li-Ying; Huang, Ru; Li, Shu-Shen; Wang, Lin-Wang

    2017-10-01

    As Moore's law approaches its end, two-dimensional (2D) materials are intensely studied for their potentials as one of the "More than Moore' (MM) devices. However, the ultimate performance limits and the optimal design parameters for such devices are still unknown. One common problem for the 2D-material-based device is the relative weak on-current. In this study, two-dimensional Schottky-barrier field-effect transistors (SBFETs) consisting of in-plane heterojunctions of 1T metallic-phase and 2H semiconducting-phase transition-metal dichalcogenides (TMDs) are studied following the recent experimental synthesis of such devices at a much larger scale. Our ab initio simulation reveals the ultimate performance limits of such devices and offers suggestions for better TMD materials. Our study shows that the Schottky-barrier heights (SBHs) of the in-plane 1T/2H contacts are smaller than the SBHs of out-of-plane contacts, and the contact coupling is also stronger in the in-plane contact. Due to the atomic thickness of the monolayer TMD, the average subthreshold swing of the in-plane TMD-SBFETs is found to be close to the limit of 60 mV/dec, and smaller than that of the out-of-plane TMD-SBFET device. Different TMDs are considered and it is found that the in-plane WT e2-SBFET provides the best performance and can satisfy the performance requirement of the sub-10-nm high-performance transistor outlined by the International Technology Roadmap for Semiconductors, and thus could be developed into a viable sub-10-nm MM device in the future.

  10. Theoretical study of the performance for short channel carbon nanotube transistors with asymmetric contacts

    International Nuclear Information System (INIS)

    Zou Jianping; Zhang Qing; Marzari, Nicola; Li Hong

    2008-01-01

    We have simulated short channel carbon nanotube field-effect transistors with asymmetric source and drain contacts using a coupled mode space approach within the non-equilibrium Green's function framework. The simulated results show that the asymmetric conduction properties under positive and negative drain-to-source voltages are caused by the asymmetric Schottky barriers to carriers at the source and drain contacts. Under negative drain-to-source voltages, hole and electron conduction are dominated by thermionic emission and tunneling through the Schottky barrier, respectively, leading to the different subthreshold behaviors of the hole and electron conduction. With increasing channel length, short channel effects can be suppressed effectively and ON/OFF ratio can be improved

  11. Prioritized Contact Transport Stream

    Science.gov (United States)

    Hunt, Walter Lee, Jr. (Inventor)

    2015-01-01

    A detection process, contact recognition process, classification process, and identification process are applied to raw sensor data to produce an identified contact record set containing one or more identified contact records. A prioritization process is applied to the identified contact record set to assign a contact priority to each contact record in the identified contact record set. Data are removed from the contact records in the identified contact record set based on the contact priorities assigned to those contact records. A first contact stream is produced from the resulting contact records. The first contact stream is streamed in a contact transport stream. The contact transport stream may include and stream additional contact streams. The contact transport stream may be varied dynamically over time based on parameters such as available bandwidth, contact priority, presence/absence of contacts, system state, and configuration parameters.

  12. Temperature dependent I-V characteristics of an Au/n-GaAs Schottky diode analyzed using Tung’s model

    Science.gov (United States)

    Korucu, Demet; Turut, Abdulmecit; Efeoglu, Hasan

    2013-04-01

    The current-voltage (I-V) characteristics of Au/n-GaAs contacts prepared with photolithography technique have been measured in the temperature range of 80-320 K. The ideality factor and barrier height (BH) values have remained almost unchanged between 1.04 and 1.10 and at a value of about 0.79 eV at temperatures above 200 K, respectively. Therefore, the ideality factor values near unity say that the experimental I-V data are almost independent of the sample temperature, that is, contacts have shown excellent Schottky diode behavior above 200 K. An abnormal decrease in the experimental BH Φb and an increase in the ideality factor with a decrease in temperature have been observed below 200 K. This behavior has been attributed to the barrier inhomogeneity by assuming a Gaussian distribution of nanometer-sized patches with low BH at the metal-semiconductor interface. The barrier inhomogeneity assumption is also confirmed by the linear relationship between the BH and the ideality factor. According to Tung’s barrier inhomogeneity model, it has been seen that the value of σT=7.41×10-5 cm2/3 V1/3from ideality factor versus (kT)-1 curve is in close agreement with σT=7.95×10-5 cm2/3 V1/3 value from the Φeff versus (2kT)-1 curve in the range of 80-200 K. The modified Richardson ln(J0/T2)-(qσT)2(Vb/η)2/3/[2(kT)2] versus (kT)-1 plot, from Tung’s Model, has given a Richardson constant value of 8.47 A cm-2 K-2which is in very close agreement with the known value of 8.16 A cm-2 K-2 for n-type GaAs; considering the effective patch area which is significantly lower than the entire geometric area of the Schottky contact, in temperature range of 80-200 K. Thus, it has been concluded that the use of Tung’s lateral inhomogeneity model is more appropriate to interpret the temperature-dependent I-V characteristics in the Schottky contacts.

  13. Cooling of radioactive isotopes for Schottky mass spectrometry

    International Nuclear Information System (INIS)

    Steck, M.; Beckert, K.; Eickhoff, H.; Franzke, B.; Nolden, F.; Reich, H.; Schlitt, B.; Winkler, T.

    1999-01-01

    Nuclear masses of radioactive isotopes can be determined by measurement of their revolution frequency relative to the revolution frequency of reference ions with well-known masses. The resolution of neighboring frequency lines and the accuracy of the mass measurement is dependent on the achievable minimum longitudinal momentum spread of the ion beam. Electron cooling allows an increase of the phase space density by several orders of magnitude. For high intensity beams Coulomb scattering in the dense ion beam limits the beam quality. For low intensity beams a regime exists in which the diffusion due to intrabeam scattering is not dominating any more. The minimum momentum spread δp/p=5x10 -7 which is observed by Schottky noise analysis is considerably higher than the value expected from the longitudinal electron temperature. The measured frequency spread results from fluctuations of the magnetic field in the storage ring magnets. Systematic mass measurements have started and can be presently used for ions with half-lives of some ten seconds. For shorter-lived nuclei a stochastic precooling system is in preparation

  14. Large room-temperature tunneling anisotropic magnetoresistance and electroresistance in single ferromagnet/Nb:SrTiO3 Schottky devices.

    Science.gov (United States)

    Kamerbeek, Alexander M; Ruiter, Roald; Banerjee, Tamalika

    2018-01-22

    There is a large effort in research and development to realize electronic devices capable of storing information in new ways - for instance devices which simultaneously exhibit electro and magnetoresistance. However it remains a challenge to create devices in which both effects coexist. In this work we show that the well-known electroresistance in noble metal-Nb:SrTiO 3 Schottky junctions can be augmented by a magnetoresistance effect in the same junction. This is realized by replacing the noble metal electrode with ferromagnetic Co. This magnetoresistance manifests as a room temperature tunneling anisotropic magnetoresistance (TAMR). The maximum room temperature TAMR (1.6%) is significantly larger and robuster with bias than observed earlier, not using Nb:SrTiO 3 . In a different set of devices, a thin amorphous AlO x interlayer inserted between Co and Nb:SrTiO 3 , reduces the TAMR by more than 2 orders of magnitude. This points to the importance of intimate contact between the Co and Nb:SrTiO 3 for the TAMR effect. This is explained by electric field enhanced spin-orbit coupling of the interfacial Co layer in contact with Nb:SrTiO 3 . We propose that the large TAMR likely has its origin in the 3d orbital derived conduction band and large relative permittivity of Nb:SrTiO 3 and discuss ways to further enhance the TAMR.

  15. Electron Barrier Formation at the Organic-Back Contact Interface is the First Step in Thermal Degradation of Polymer Solar Cells

    KAUST Repository

    Sachs-Quintana, I. T.

    2014-03-24

    Long-term stability of polymer solar cells is determined by many factors, one of which is thermal stability. Although many thermal stability studies occur far beyond the operating temperature of a solar cell which is almost always less than 65 °C, thermal degradation is studied at temperatures that the solar cell would encounter in real-world operating conditions. At these temperatures, movement of the polymer and fullerenes, along with adhesion of the polymer to the back contact, creates a barrier for electron extraction. The polymer barrier can be removed and the performance can be restored by peeling off the electrode and depositing a new one. X-ray photoelectron spectroscopy measurements reveal a larger amount of polymer adhered to electrodes peeled from aged devices than electrodes peeled from fresh devices. The degradation caused by hole-transporting polymer adhering to the electrode can be suppressed by using an inverted device where instead of electrons, holes are extracted at the back metal electrode. The problem can be ultimately eliminated by choosing a polymer with a high glass transition temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Current simulation of symmetric contacts on CdTe

    International Nuclear Information System (INIS)

    Ruzin, A.

    2011-01-01

    This article presents the calculated current-voltage characteristics of symmetric Metal-Semiconductor-Metal configurations for Schottky, Ohmic, and injecting-Ohmic contacts on high resistivity CdTe. The results clearly demonstrate that in the wide band-gap, semi-insulating semiconductors, such as high resistivity CdTe, the linearity of the I-V curves cannot be considered a proof of the ohmicity of the contacts. It is shown that the linear I-V curves are expected for a wide range of contact barriers. Furthermore, the slope of these linear curves is governed by the barrier height, rather than the bulk doping concentration. Therefore the deduction of bulk's resistivity from the I-V curves may be false.

  17. Current simulation of symmetric contacts on CdTe

    Energy Technology Data Exchange (ETDEWEB)

    Ruzin, A., E-mail: aruzin@post.tau.ac.il [School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, 69978 Tel Aviv (Israel)

    2011-12-01

    This article presents the calculated current-voltage characteristics of symmetric Metal-Semiconductor-Metal configurations for Schottky, Ohmic, and injecting-Ohmic contacts on high resistivity CdTe. The results clearly demonstrate that in the wide band-gap, semi-insulating semiconductors, such as high resistivity CdTe, the linearity of the I-V curves cannot be considered a proof of the ohmicity of the contacts. It is shown that the linear I-V curves are expected for a wide range of contact barriers. Furthermore, the slope of these linear curves is governed by the barrier height, rather than the bulk doping concentration. Therefore the deduction of bulk's resistivity from the I-V curves may be false.

  18. Prospects of zero Schottky barrier height in a graphene-inserted MoS2-metal interface

    Science.gov (United States)

    Chanana, Anuja; Mahapatra, Santanu

    2016-01-01

    A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS2-channel-based field effect transistors. Approaches such as choosing metals with appropriate work functions and chemical doping are employed previously to improve the carrier injection from the contact electrodes to the channel and to mitigate the SBH between the MoS2 and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS2. However, the physical or chemical origin of this phenomenon is not yet clearly understood. In this work, density functional theory simulations are performed, employing pseudopotentials with very high basis sets to get insights of the charge transfer between metal and monolayer MoS2 through the inserted graphene layer. Our atomistic simulations on 16 different interfaces involving five different metals (Ti, Ag, Ru, Au, and Pt) reveal that (i) such a decrease in SBH is not consistent among various metals, rather an increase in SBH is observed in case of Au and Pt; (ii) unlike MoS2-metal interface, the projected dispersion of MoS2 remains preserved in any MoS2-graphene-metal system with shift in the bands on the energy axis. (iii) A proper choice of metal (e.g., Ru) may exhibit ohmic nature in a graphene-inserted MoS2-metal contact. These understandings would provide a direction in developing high-performance transistors involving heteroatomic layers as contact electrodes.

  19. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    International Nuclear Information System (INIS)

    Paret, Stefan

    2010-01-01

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  20. Longitudinal schottky spectra of a bunched Ne10+ ion beam at the CSRe

    International Nuclear Information System (INIS)

    Wen Weiqiang; Ma Xinwen; Zhang Dacheng

    2013-01-01

    The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled 22Ne 10+ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of Δp/p=1.6 × 10 -5 has been reached with less than 107 stored ions. The reduction of momentum spread compared with a coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25 th , 50 th and 75 th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe. (authors)

  1. Analysing black phosphorus transistors using an analytic Schottky barrier MOSFET model.

    Science.gov (United States)

    Penumatcha, Ashish V; Salazar, Ramon B; Appenzeller, Joerg

    2015-11-13

    Owing to the difficulties associated with substitutional doping of low-dimensional nanomaterials, most field-effect transistors built from carbon nanotubes, two-dimensional crystals and other low-dimensional channels are Schottky barrier MOSFETs (metal-oxide-semiconductor field-effect transistors). The transmission through a Schottky barrier-MOSFET is dominated by the gate-dependent transmission through the Schottky barriers at the metal-to-channel interfaces. This makes the use of conventional transistor models highly inappropriate and has lead researchers in the past frequently to extract incorrect intrinsic properties, for example, mobility, for many novel nanomaterials. Here we propose a simple modelling approach to quantitatively describe the transfer characteristics of Schottky barrier-MOSFETs from ultra-thin body materials accurately in the device off-state. In particular, after validating the model through the analysis of a set of ultra-thin silicon field-effect transistor data, we have successfully applied our approach to extract Schottky barrier heights for electrons and holes in black phosphorus devices for a large range of body thicknesses.

  2. Design and simulation of GaN based Schottky betavoltaic nuclear micro-battery

    International Nuclear Information System (INIS)

    San, Haisheng; Yao, Shulin; Wang, Xiang; Cheng, Zaijun; Chen, Xuyuan

    2013-01-01

    The current paper presents a theoretical analysis of Ni-63 nuclear micro-battery based on a wide-band gap semiconductor GaN thin-film covered with thin Ni/Au films to form Schottky barrier for carrier separation. The total energy deposition in GaN was calculated using Monte Carlo methods by taking into account the full beta spectral energy, which provided an optimal design on Schottky barrier width. The calculated results show that an 8 μm thick Schottky barrier can collect about 95% of the incident beta particle energy. Considering the actual limitations of current GaN growth technique, a Fe-doped compensation technique by MOCVD method can be used to realize the n-type GaN with a carrier concentration of 1×10 15 cm −3 , by which a GaN based Schottky betavoltaic micro-battery can achieve an energy conversion efficiency of 2.25% based on the theoretical calculations of semiconductor device physics. - Highlights: • Ni-63 is employed as the pure beta radioisotope source. • The Schottky junction betavoltaic battery is based on the wide-band gap semiconductor GaN. • The total energy deposition of incident beta particles in GaN was simulated by the Monte Carlo method. • A Fe-doped compensation technique is suggested to increase the energy conversion efficiency

  3. Investigation of significantly high barrier height in Cu/GaN Schottky diode

    Directory of Open Access Journals (Sweden)

    Manjari Garg

    2016-01-01

    Full Text Available Current-voltage (I-V measurements combined with analytical calculations have been used to explain mechanisms for forward-bias current flow in Copper (Cu Schottky diodes fabricated on Gallium Nitride (GaN epitaxial films. An ideality factor of 1.7 was found at room temperature (RT, which indicated deviation from thermionic emission (TE mechanism for current flow in the Schottky diode. Instead the current transport was better explained using the thermionic field-emission (TFE mechanism. A high barrier height of 1.19 eV was obtained at room temperature. X-ray photoelectron spectroscopy (XPS was used to investigate the plausible reason for observing Schottky barrier height (SBH that is significantly higher than as predicted by the Schottky-Mott model for Cu/GaN diodes. XPS measurements revealed the presence of an ultrathin cuprous oxide (Cu2O layer at the interface between Cu and GaN. With Cu2O acting as a degenerate p-type semiconductor with high work function of 5.36 eV, a high barrier height of 1.19 eV is obtained for the Cu/Cu2O/GaN Schottky diode. Moreover, the ideality factor and barrier height were found to be temperature dependent, implying spatial inhomogeneity of barrier height at the metal semiconductor interface.

  4. Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

    Energy Technology Data Exchange (ETDEWEB)

    Paret, Stefan

    2010-02-22

    A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

  5. The study of the deep levels of In/CdTe Schottky diode

    International Nuclear Information System (INIS)

    Kim, Hey-kyeong; Jeen, Gwangsoo; Nam, S.H.

    2000-01-01

    p-type CdTe is an important component of II-VI compound based solar cells as well as a promising substance for X- and gamma-ray detector. Despite that a lot of researches has been performed on CdTe, the manufacture of large homogeneous ingots with high resistivity (ρ) and a high value of lifetime-mobility product (μτ) still difficult. Both ρ and μτ, which determine detection properties, are strongly dependent on the impurity and defect levels of crystals. As in general, deep defect levels act as recombination centers and influence strongly the efficiency of the detector material, so information about deep levels is an essential need. To estimate deep levels of semiconductor materials, the TSC (thermally stimulated current), TSCD (thermally stimulated capacitor discharges) and admittance spectroscopic method are used. In order to study the deep levels of CdTe, the samples were taken from a CdTe-crystal grown by the vertical Bridgman method. From this boule single crystalline samples of about 0.5 mm thickness were prepared. All samples were initially p-type which was determined by the hot-probe method. In-CdTe Schottky diodes were prepared by the process of evaporation of In in the vacuum of 10 -6 Torr on surface of CdTe. The area of the deposited contact was equal to 1.626 mm 2 . As ohmic contacts, dots of Au soldered for 30 min. in temperature 160 deg C. Measurements were carried out within a 100-250 K temperature and 1-10 kHz frequency range. Related Arrhenius plots, i.e. the experimentally determined emission rates corresponding to the signal maximum divided by the square of temperature as a function of reciprocal temperature are plotted. The experimental data were best fitted by the least-square method. The fitting yielded the defect level energies E T . In this study, by using admittance spectroscopy measurements, we presented the information about the energy and concentration of the defect levels inside the gap, in order to improve the quality of

  6. Influence of zinc dialkyldithiophosphate tribofilm formation on the tribological performance of self-mated diamond-like carbon contacts under boundary lubrication

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah Tasdemir, H., E-mail: habdullah46@gmail.com [Department of Mechanical Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Tokoroyama, Takayuki; Kousaka, Hiroyuki; Umehara, Noritsugu [Department of Mechanical Science and Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Mabuchi, Yutaka [Nissan Motor Co. (Japan)

    2014-07-01

    Diamond-like carbon (DLC) coatings offer excellent mechanical and tribological properties that make them suitable protective coatings for various industrial applications. In recent years, several engine and power train components in passenger cars, which work under boundary lubricated conditions, have been coated with DLC coatings. Since conventional lubricants and lubricant additives are formulated for metal surfaces, there are still controversial questions concerning chemical reactivity between DLC surfaces and common lubricant additives owing to the chemical inertness of DLC coatings. In this work, we present the influence of zinc dialkyldithiophosphate (ZnDTP) anti-wear additives on the tribological performance of various self-mated DLC coatings under boundary lubrication conditions. The effects of hydrogen, doping elements, and surface morphology on the reactivity of DLC coatings to form a ZnDTP-derived tribofilm were investigated by atomic force microscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The results confirmed that ZnDTP-derived pad-like or patchy tribofilm forms on the surfaces depending on the DLC coating. It is seen that hydrogen content and doping elements increase pad-like tribofilm formation. Doped DLC coatings are found to give better wear resistance than non-doped DLC coatings. Furthermore, the addition of ZnDTP additives to the base oil significantly improves the wear resistance of hydrogenated DLC, silicon-doped hydrogenated DLC, and chromium-doped hydrogenated DLC. Hydrogen-free tetrahedral amorphous DLC coatings provide the lowest friction coefficient both in PAO (poly-alpha-olefin) and PAO + ZnDTP oils. - Highlights: • Zinc dialkyldithiophosphate (DTP) tribofilm formation on various DLC surfaces was evidenced. • Pad-like tribofilm was found on a-C:H, a-C, Si-DLC and Cr-DLC. • Pad-like tribofilm on DLC surfaces greatly increased the wear resistance. • Hydrogenated and doped DLC coatings are

  7. Influence of zinc dialkyldithiophosphate tribofilm formation on the tribological performance of self-mated diamond-like carbon contacts under boundary lubrication

    International Nuclear Information System (INIS)

    Abdullah Tasdemir, H.; Tokoroyama, Takayuki; Kousaka, Hiroyuki; Umehara, Noritsugu; Mabuchi, Yutaka

    2014-01-01

    Diamond-like carbon (DLC) coatings offer excellent mechanical and tribological properties that make them suitable protective coatings for various industrial applications. In recent years, several engine and power train components in passenger cars, which work under boundary lubricated conditions, have been coated with DLC coatings. Since conventional lubricants and lubricant additives are formulated for metal surfaces, there are still controversial questions concerning chemical reactivity between DLC surfaces and common lubricant additives owing to the chemical inertness of DLC coatings. In this work, we present the influence of zinc dialkyldithiophosphate (ZnDTP) anti-wear additives on the tribological performance of various self-mated DLC coatings under boundary lubrication conditions. The effects of hydrogen, doping elements, and surface morphology on the reactivity of DLC coatings to form a ZnDTP-derived tribofilm were investigated by atomic force microscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The results confirmed that ZnDTP-derived pad-like or patchy tribofilm forms on the surfaces depending on the DLC coating. It is seen that hydrogen content and doping elements increase pad-like tribofilm formation. Doped DLC coatings are found to give better wear resistance than non-doped DLC coatings. Furthermore, the addition of ZnDTP additives to the base oil significantly improves the wear resistance of hydrogenated DLC, silicon-doped hydrogenated DLC, and chromium-doped hydrogenated DLC. Hydrogen-free tetrahedral amorphous DLC coatings provide the lowest friction coefficient both in PAO (poly-alpha-olefin) and PAO + ZnDTP oils. - Highlights: • Zinc dialkyldithiophosphate (DTP) tribofilm formation on various DLC surfaces was evidenced. • Pad-like tribofilm was found on a-C:H, a-C, Si-DLC and Cr-DLC. • Pad-like tribofilm on DLC surfaces greatly increased the wear resistance. • Hydrogenated and doped DLC coatings are

  8. A Pt/TiO(2)/Ti Schottky-type selection diode for alleviating the sneak current in resistance switching memory arrays.

    Science.gov (United States)

    Park, Woo Young; Kim, Gun Hwan; Seok, Jun Yeong; Kim, Kyung Min; Song, Seul Ji; Lee, Min Hwan; Hwang, Cheol Seong

    2010-05-14

    This study examined the properties of Schottky-type diodes composed of Pt/TiO(2)/Ti, where the Pt/TiO(2) and TiO(2)/Ti junctions correspond to the blocking and ohmic contacts, respectively, as the selection device for a resistive switching cross-bar array. An extremely high forward-to-reverse current ratio of approximately 10(9) was achieved at 1 V when the TiO(2) film thickness was 19 nm. TiO(2) film was grown by atomic layer deposition at a substrate temperature of 250 degrees C. Conductive atomic force microscopy revealed that the forward current flew locally, which limits the maximum forward current density to current measurement showed a local forward current density as high as approximately 10(5) A cm(-2). Therefore, it is expected that this type of Schottky diode effectively suppresses the sneak current without adverse interference effects in a nano-scale resistive switching cross-bar array with high block density.

  9. Modification of metal–InGaAs Schottky barrier behaviour by atomic layer deposition of ultra-thin Al2O3 interlayers

    International Nuclear Information System (INIS)

    Chauhan, Lalit; Gupta, Suman; Jaiswal, Piyush; Bhat, Navakanta; Shivashankar, S.A.; Hughes, G.

    2015-01-01

    The effect of inserting ultra-thin atomic layer deposited Al 2 O 3 dielectric layers (1 nm and 2 nm thick) on the Schottky barrier behaviour for high (Pt) and low (Al) work function metals on n- and p-doped InGaAs substrates has been investigated. Rectifying behaviour was observed for the p-type substrates (both native oxide and sulphur passivated) for both the Al/p-InGaAs and Al/Al 2 O 3 /p-InGaAs contacts. The Pt contacts directly deposited on p-InGaAs displayed evidence of limited rectification which increased with Al 2 O 3 interlayer thickness. Ohmic contacts were formed for both metals on n-InGaAs in the absence of an Al 2 O 3 interlayer, regardless of surface passivation. However, limited rectifying behaviour was observed for both metals on the 2 nm Al 2 O 3 /n-InGaAs samples for the sulphur passivated InGaAs surface, indicating the importance of both surface passivation and the presence of an ultra-thin dielectric interlayer on the current–voltage characteristics displayed by these devices. - Highlights: • Investigation of the modification of metal–InGaAs Schottky barrier (SB) behaviour • Improving metal–InGaAs interface by sulphur passivation and ultrathin interlayer • Examine the effect of low work function and high work function metals on SB • Different SB behaviours observed on both n-type InGaAs and p-type InGaAs • Metal/n-InGaAs interface is more strongly pinned than the metal/p-InGaAs interface

  10. Modification of metal–InGaAs Schottky barrier behaviour by atomic layer deposition of ultra-thin Al{sub 2}O{sub 3} interlayers

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Lalit [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland); Gupta, Suman; Jaiswal, Piyush; Bhat, Navakanta; Shivashankar, S.A. [Centre for Nano Science and Engineering (CeNSE), Indian Institute of Science, Bangalore 560012 (India); Hughes, G. [School of Physical Sciences, Dublin City University, Dublin 9 (Ireland)

    2015-08-31

    The effect of inserting ultra-thin atomic layer deposited Al{sub 2}O{sub 3} dielectric layers (1 nm and 2 nm thick) on the Schottky barrier behaviour for high (Pt) and low (Al) work function metals on n- and p-doped InGaAs substrates has been investigated. Rectifying behaviour was observed for the p-type substrates (both native oxide and sulphur passivated) for both the Al/p-InGaAs and Al/Al{sub 2}O{sub 3}/p-InGaAs contacts. The Pt contacts directly deposited on p-InGaAs displayed evidence of limited rectification which increased with Al{sub 2}O{sub 3} interlayer thickness. Ohmic contacts were formed for both metals on n-InGaAs in the absence of an Al{sub 2}O{sub 3} interlayer, regardless of surface passivation. However, limited rectifying behaviour was observed for both metals on the 2 nm Al{sub 2}O{sub 3}/n-InGaAs samples for the sulphur passivated InGaAs surface, indicating the importance of both surface passivation and the presence of an ultra-thin dielectric interlayer on the current–voltage characteristics displayed by these devices. - Highlights: • Investigation of the modification of metal–InGaAs Schottky barrier (SB) behaviour • Improving metal–InGaAs interface by sulphur passivation and ultrathin interlayer • Examine the effect of low work function and high work function metals on SB • Different SB behaviours observed on both n-type InGaAs and p-type InGaAs • Metal/n-InGaAs interface is more strongly pinned than the metal/p-InGaAs interface.

  11. Vacancy formation energy of Li(H,D) and Na(H,D) systems

    International Nuclear Information System (INIS)

    Islam, A.K.M.A.

    1993-06-01

    Vacancy defect formation energy (Schottky defect) of lighter hydrides and deuterides of alkali metals are discussed with reference to conductivity measurements and the recent computer simulation calculations. An empirical relation with Debye temperature is found to yield values of Schottky defect formation energies of Li(H,D) systems in agreement with experiments. The relationship is also utilized to obtain the formation energies for Na(H,D) systems for which experimental values are available in the literature. (author). 37 refs, 1 fig., 1 tab

  12. Understanding Pt-ZnO:In Schottky nanocontacts by conductive atomic force microscopy

    Science.gov (United States)

    Chirakkara, Saraswathi; Choudhury, Palash Roy; Nanda, K. K.; Krupanidhi, S. B.

    2016-04-01

    Undoped and In doped ZnO (IZO) thin films are grown on Pt coated silicon substrates Pt/Si by pulsed laser deposition to fabricate Pt/ZnO:In Schottky diodes. The Schottky diodes were investigated by conventional two-probe current-voltage (I-V) measurements and by the I-V spectroscopy tool of conductive atomic force microscopy (C-AFM). The large deviation of the ideality factor from unity and the temperature dependent Schottky barrier heights (SBHs) obtained from the conventional method imply the presence of inhomogeneous interfaces. The inhomogeneity of SBHs is confirmed by C-AFM. Interestingly, the I-V curves at different points are found to be different, and the SBHs deduced from the point diodes reveal inhomogeneity at the nanoscale at the metal-semiconductor interface. A reduction in SBH and turn-on voltage along with enhancement in forward current are observed with increasing indium concentration.

  13. ON current enhancement of nanowire Schottky barrier tunnel field effect transistors

    Science.gov (United States)

    Takei, Kohei; Hashimoto, Shuichiro; Sun, Jing; Zhang, Xu; Asada, Shuhei; Xu, Taiyu; Matsukawa, Takashi; Masahara, Meishoku; Watanabe, Takanobu

    2016-04-01

    Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler-Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

  14. The controlled growth of graphene nanowalls on Si for Schottky photodetector

    Directory of Open Access Journals (Sweden)

    Quan Zhou

    2017-12-01

    Full Text Available Schottky diode with directly-grown graphene on silicon substrate has advantage of clean junction interface, promising for photodetectors with high-speed and low noise. In this report, we carefully studied the influence of growth parameters on the junction quality and photoresponse of graphene nanowalls (GNWs-based Schottky photodetectors. We found that shorter growth time is critical for lower dark current, but at the same time higher photocurrent. The influence of growth parameters was attributed to the defect density of various growth time, which results in different degrees of surface absorption for H2O/O2 molecules and P-type doping level. Raman characterization and vacuum annealing treatment were carried out to confirm the regulation mechanism. Meanwhile, the release of thermal stress also makes the ideality factor η of thinner sample better than the thicker. Our results are important for the response improvement of photodetectors with graphene-Si schottky junction.

  15. High performance Schottky diodes based on indium-gallium-zinc-oxide

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jiawei; Song, Aimin, E-mail: A.Song@manchester.ac.uk [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Xin, Qian [School of Physics, Shandong University, Jinan 250100 (China)

    2016-07-15

    Indium-gallium-zinc-oxide (IGZO) Schottky diodes exhibit excellent performance in comparison with conventional devices used in future flexible high frequency electronics. In this work, a high performance Pt IGZO Schottky diode was presented by using a new fabrication process. An argon/oxygen mixture gas was introduced during the deposition of the Pt layer to reduce the oxygen deficiency at the Schottky interface. The diode showed a high barrier height of 0.92 eV and a low ideality factor of 1.36 from the current–voltage characteristics. Even the radius of the active area was 0.1 mm, and the diode showed a cut-off frequency of 6 MHz in the rectifier circuit. Using the diode as a demodulator, a potential application was also demonstrated in this work.

  16. First results from the LHC Schottky Monitor operated with Direct Diode Detection

    CERN Document Server

    Gasior, M

    2012-01-01

    The LHC is equipped with a Schottky diagnostic system based on 4.8 GHz resonant pick-ups. Their signals are processed according to a three-stage down-mixing scheme, working well in most beam conditions. An important exception is the period of energy ramp of proton beams, when the noise floor of the observed beam spectrum increases dramatically and the Schottky sidebands disappear. To study beam spectra in such conditions the signals from the Schottky pick-ups were split and the second half of their power was processed with a copy of the LHC tune measurement electronics, modified for this application. The experimental set-up is based on simple diode detectors followed by signal processing in the kHz range and 24-bit audio ADCs. With such a test system LHC beam spectra were successfully observed. This contribution presents the used hardware and obtained results.

  17. Analysis and modelling of GaN Schottky-based circuits at millimeter wavelengths

    International Nuclear Information System (INIS)

    Pardo, D; Grajal, J

    2015-01-01

    This work presents an analysis of the capabilities of GaN Schottky diodes for frequency multipliers and mixers at millimeter wavelengths. By using a Monte Carlo (MC) model of the diode coupled to a harmonic balance technique, the electrical and noise performances of these circuits are investigated. Despite the lower electron mobility of GaN compared to GaAs, multipliers based on GaN Schottky diodes can be competitive in the first stages of multiplier chains, due to the excellent power handling capabilities of this material. The performance of these circuits can be improved by taking advantage of the lateral Schottky diode structures based on AlGaN/GaN HEMT technology. (paper)

  18. Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite based thin films for Schottky diode application

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Bhavana, E-mail: bgupta1206@gmail.com [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Mehta, Minisha, E-mail: mehta.mini@gmail.com [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India); Melvin, Ambrose [Catalysis Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha, Pune 411008 (India); Kamalakannan, R.; Dash, S.; Kamruddin, M.; Tyagi, A.K. [Surface and Nanoscience Division, Materials Science Group, Indira Gandhi Centre of Atomic Research, Kalpakkam, Tamil Nadu 603102 (India)

    2014-10-15

    Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV–Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq{sup −1} and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes. - Highlights: • Single step synthesis of PEDOT and PEDOT-FWCNT nanocomposites films via in-situ oxidative polymerization. • Thermal, electrical and electrochemical properties of films show positive effect of FWCNT on PEDOT films. • Schottky diodes based on metal Al/PEDOT or PEDOT-FWCNT composites/ITO glass are fabricated. • Improved electrical characteristics with better reliability is achieved for PEDOT-FWCNT based diodes.

  19. Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite based thin films for Schottky diode application

    International Nuclear Information System (INIS)

    Gupta, Bhavana; Mehta, Minisha; Melvin, Ambrose; Kamalakannan, R.; Dash, S.; Kamruddin, M.; Tyagi, A.K.

    2014-01-01

    Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV–Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq −1 and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes. - Highlights: • Single step synthesis of PEDOT and PEDOT-FWCNT nanocomposites films via in-situ oxidative polymerization. • Thermal, electrical and electrochemical properties of films show positive effect of FWCNT on PEDOT films. • Schottky diodes based on metal Al/PEDOT or PEDOT-FWCNT composites/ITO glass are fabricated. • Improved electrical characteristics with better reliability is achieved for PEDOT-FWCNT based diodes

  20. Effect of 60Co γ-irradiation on the nature of electronic transport in heavily doped n-type GaN based Schottky photodetectors

    Science.gov (United States)

    Chatterjee, Abhishek; Khamari, Shailesh K.; Porwal, S.; Kher, S.; Sharma, T. K.

    2018-04-01

    GaN Schottky photodetectors are fabricated on heavily doped n-type GaN epitaxial layers grown by the hydride vapour phase epitaxy technique. The effect of 60Co γ-radiation on the electronic transport in GaN epilayers and Schottky detectors is studied. In contrast to earlier observations, a steady rise in the carrier concentration with increasing irradiation dose is clearly seen. By considering a two layer model, the contribution of interfacial dislocations in carrier transport is isolated from that of the bulk layer for both the pristine and irradiated samples. The bulk carrier concentration is fitted by using the charge balance equation which indicates that no new electrically active defects are generated by γ-radiation even at 500 kGy dose. The irradiation induced rise in the bulk carrier concentration is attributed to the activation of native Si impurities that are already present in an electrically inert form in the pristine sample. Further, the rise in interfacial contribution in the carrier concentration is governed by the enhanced rate of formation of nitrogen vacancies by irradiation, which leads to a larger diffusion of oxygen impurities. A large value of the characteristic tunnelling energy for both the pristine and irradiated Au/Ni/GaN Schottky devices confirms that the dislocation-assisted tunnelling dominates the low temperature current transport even after irradiation. The advantage of higher displacement energy and larger bandgap of GaN as compared to GaAs is evident from the change in leakage current after irradiation. Further, a fast recovery of the photoresponse of GaN photodetectors after irradiation signifies their compatibility to operate in high radiation zones. The results presented here are found to be crucial in understanding the interaction of 60Co γ-irradiation with n+-GaN epilayers.

  1. Physical Mechanisms Responsible for Electrical Conduction in Pt/GaN Schottky Diodes

    Directory of Open Access Journals (Sweden)

    H. MAZARI

    2014-05-01

    Full Text Available The current-voltage (I-V characteristics of Pt/(n.u.d-GaN and Pt/Si-doped-GaN diodes Schottky are investigated. Based on these measurements, physical mechanisms responsible for electrical conduction have been suggested. The contribution of thermionic-emission current and various other current transport mechanisms were assumed when evaluating the Schottky barrier height. Thus the generation-recombination, tunneling and leakage currents caused by inhomogeneities and defects at metal-semiconductor interface were taken into account.

  2. Effect of the ion bombardment on the apparent barrier height in GaAs Schottky junctions

    International Nuclear Information System (INIS)

    Horvath, Zs. J.

    1994-01-01

    The bombardment of the semiconductor with different particles often results in the change of the doping concentration at the semiconductor surface. In this paper the effects of this near-interface concentration change on the apparent and real Schottky barrier heights are discussed. Experimental results obtained in GaAs Schottky junctions prepared on ion-bombarded semiconductor surfaces are analysed, and it is shown that their electrical characteristics are strongly influenced by the near-interface concentration change due to the ion bombardment. (author). 36 refs., 2 figs

  3. Demonstration of a 4H SiC betavoltaic nuclear battery based on Schottky barrier diode

    International Nuclear Information System (INIS)

    Qiao Dayong; Yuan Weizheng; Gao Peng; Yao Xianwang; Zang Bo; Zhang Lin; Guo Hui; Zhang Hongjian

    2008-01-01

    A 4H SiC betavoltaic nuclear battery is demonstrated. A Schottky barrier diode is utilized for carrier separation. Under illumination of Ni-63 source with an apparent activity of 4 mCi/cm 2 an open circuit voltage of 0.49 V and a short circuit current density of 29.44 nA/cm 2 are measured. A power conversion efficiency of 1.2% is obtained. The performance of the device is limited by low shunt resistance, backscattering and attenuation of electron energy in air and Schottky electrode. It is expected to be significantly improved by optimizing the design and processing technology of the device. (authors)

  4. Demonstration of a 4H SiC Betavoltaic Nuclear Battery Based on Schottky Barrier Diode

    International Nuclear Information System (INIS)

    Da-Yong, Qiao; Wei-Zheng, Yuan; Peng, Gao; Xian-Wang, Yao; Bo, Zang; Lin, Zhang; Hui, Guo; Hong-Jian, Zhang

    2008-01-01

    A 4H SiC betavoltaic nuclear battery is demonstrated. A Schottky barrier diode is utilized for carrier separation. Under illumination of Ni-63 source with an apparent activity of 4 mCi/cm 2 an open circuit voltage of 0.49 V and a short circuit current density of 29.44 nA/cm 2 are measured. A power conversion efficiency of 1.2% is obtained. The performance of the device is limited by low shunt resistance, backscattering and attenuation of electron energy in air and Schottky electrode. It is expected to be significantly improved by optimizing the design and processing technology of the device

  5. GaAs Schottky versus p/i/n diodes for pixellated X-ray detectors

    CERN Document Server

    Bourgoin, J C

    2002-01-01

    We discuss the performances of GaAs p/i/n structures and Schottky barriers for application as photodetectors for high-energy photons. We compare the magnitude of the leakage current and the width of the depleted region for a given reverse bias. We mention the effect of states present at the metal-semiconductor interface on the extension of the space charge region in Schottky barriers. We illustrate this effect by a description of the capacitance behaviour of a Au-GaAs barrier under gamma irradiation.

  6. Contact Lens Care

    Science.gov (United States)

    ... Consumers Consumer Information by Audience For Women Contact Lens Care Share Tweet Linkedin Pin it More sharing ... www.fda.gov/medwatch Learn More about Contact Lens Care Other Tips on Contact Lenses Decorative Contact ...

  7. Mechanisms of current flow in metal-semiconductor ohmic contacts

    International Nuclear Information System (INIS)

    Blank, T. V.; Gol'dberg, Yu. A.

    2007-01-01

    Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II-VI semiconductors (ZnSe, ZnO), III-V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1-0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3-0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed

  8. Measurement and Modeling of Blocking Contacts for Cadmium Telluride Gamma Ray Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Beck, Patrick R. [California Polytechnic State Univ. (CalPoly), San Luis Obispo, CA (United States)

    2010-01-07

    Gamma ray detectors are important in national security applications, medicine, and astronomy. Semiconductor materials with high density and atomic number, such as Cadmium Telluride (CdTe), offer a small device footprint, but their performance is limited by noise at room temperature; however, improved device design can decrease detector noise by reducing leakage current. This thesis characterizes and models two unique Schottky devices: one with an argon ion sputter etch before Schottky contact deposition and one without. Analysis of current versus voltage characteristics shows that thermionic emission alone does not describe these devices. This analysis points to reverse bias generation current or leakage through an inhomogeneous barrier. Modeling the devices in reverse bias with thermionic field emission and a leaky Schottky barrier yields good agreement with measurements. Also numerical modeling with a finite-element physics-based simulator suggests that reverse bias current is a combination of thermionic emission and generation. This thesis proposes further experiments to determine the correct model for reverse bias conduction. Understanding conduction mechanisms in these devices will help develop more reproducible contacts, reduce leakage current, and ultimately improve detector performance.

  9. Novel field-effect schottky barrier transistors based on graphene-MoS 2 heterojunctions

    KAUST Repository

    Tian, He; Tan, Zhen; Wu, Can; Wang, Xiaomu; Mohammad, Mohammad Ali; Xie, Dan; Yang, Yi; Wang, Jing; Li, Lain-Jong; Xu, Jun; Ren, Tian-Ling

    2014-01-01

    0.5-20 cm2/V.s). Here, we report a novel field-effect Schottky barrier transistors (FESBT) based on graphene-MoS2 heterojunction (GMH), where the characteristics of high mobility from graphene and high on-off ratio from MoS2 are properly balanced

  10. Spatially inhomogeneous barrier height in graphene/MoS2 Schottky junctions

    Science.gov (United States)

    Tomer, Dushyant; Rajput, Shivani; Li, Lian

    Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. In this study, graphene Schottky junctions are fabricated by transferring CVD monolayer graphene on mechanically exfoliated MoS2 multilayers. The forward bias current-voltage characteristics are measured in the temperature range of 210-300 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature. Such behavior is attributed to Schottky barrier inhomogeneities possibly due to graphene ripples and ridges at the junction interface as suggested by atomic force microscopy. Assuming a Gaussian distribution of the barrier height, mean barrier of 0.97+/-0.10 eV is found for the graphene MoS2 junction. Our findings provide significant insight on the barrier height inhomogeneities in graphene/two dimensional semiconductor Schottky junctions. U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering Award No. DEFG02-07ER46228.

  11. Inhomogeneity in barrier height at graphene/Si (GaAs) Schottky junctions.

    Science.gov (United States)

    Tomer, D; Rajput, S; Hudy, L J; Li, C H; Li, L

    2015-05-29

    Graphene (Gr) interfaced with a semiconductor forms a Schottky junction with rectifying properties, however, fluctuations in the Schottky barrier height are often observed. In this work, Schottky junctions are fabricated by transferring chemical vapor deposited monolayer Gr onto n-type Si and GaAs substrates. Temperature dependence of the barrier height and ideality factor are obtained by current-voltage measurements between 215 and 350 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature for both junctions. Such behavior is attributed to barrier inhomogeneities that arise from interfacial disorders as revealed by scanning tunneling microscopy/spectroscopy. Assuming a Gaussian distribution of the barrier heights, mean values of 1.14 ± 0.14 eV and 0.76 ± 0.10 eV are found for Gr/Si and Gr/GaAs junctions, respectively. These findings resolve the origin of barrier height inhomogeneities in these Schottky junctions.

  12. Inhomogeneity in barrier height at graphene/Si (GaAs) Schottky junctions

    International Nuclear Information System (INIS)

    Tomer, D; Rajput, S; Hudy, L J; Li, L; Li, C H

    2015-01-01

    Graphene (Gr) interfaced with a semiconductor forms a Schottky junction with rectifying properties, however, fluctuations in the Schottky barrier height are often observed. In this work, Schottky junctions are fabricated by transferring chemical vapor deposited monolayer Gr onto n-type Si and GaAs substrates. Temperature dependence of the barrier height and ideality factor are obtained by current–voltage measurements between 215 and 350 K. An increase in the zero bias barrier height and decrease in the ideality factor are observed with increasing temperature for both junctions. Such behavior is attributed to barrier inhomogeneities that arise from interfacial disorders as revealed by scanning tunneling microscopy/spectroscopy. Assuming a Gaussian distribution of the barrier heights, mean values of 1.14 ± 0.14 eV and 0.76 ± 0.10 eV are found for Gr/Si and Gr/GaAs junctions, respectively. These findings resolve the origin of barrier height inhomogeneities in these Schottky junctions. (paper)

  13. Study of Schottky diodes made on Mn doped p-type InP

    Czech Academy of Sciences Publication Activity Database

    Žďánský, Karel; Kozak, Halina; Sopko, B.; Pekárek, Ladislav

    2008-01-01

    Roč. 19, č. 1 (2008), S333-S337 ISSN 0957-4522 R&D Projects: GA AV ČR KAN400670651 Institutional research plan: CEZ:AV0Z20670512; CEZ:AV0Z10100520 Keywords : Schottky effect * semiconductors * deep levels Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.054, year: 2008

  14. A graphene/single GaAs nanowire Schottky junction photovoltaic device.

    Science.gov (United States)

    Luo, Yanbin; Yan, Xin; Zhang, Jinnan; Li, Bang; Wu, Yao; Lu, Qichao; Jin, Chenxiaoshuai; Zhang, Xia; Ren, Xiaomin

    2018-05-04

    A graphene/nanowire Schottky junction is a promising structure for low-cost high-performance optoelectronic devices. Here we demonstrate a graphene/single GaAs nanowire Schottky junction photovoltaic device. The Schottky junction is fabricated by covering a single layer graphene onto an n-doped GaAs nanowire. Under 532 nm laser excitation, the device exhibits a high responsivity of 231 mA W-1 and a short response/recover time of 85/118 μs at zero bias. Under AM 1.5 G solar illumination, the device has an open-circuit voltage of 75.0 mV and a short-circuit current density of 425 mA cm-2, yielding a remarkable conversion efficiency of 8.8%. The excellent photovoltaic performance of the device is attributed to the strong built-in electric field in the Schottky junction as well as the transparent property of graphene. The device is promising for self-powered high-speed photodetectors and low-cost high-efficiency solar cells.

  15. Development of high performance Schottky barrier diode and its application to plasma diagnostics

    International Nuclear Information System (INIS)

    Fujita, Junji; Kawahata, Kazuo; Okajima, Shigeki

    1993-10-01

    At the conclusion of the Supporting Collaboration Research on 'Development of High Performance Detectors in the Far Infrared Range' carried out from FY1990 to FY1992, the results of developing Schottky barrier diode and its application to plasma diagnostics are summarized. Some remarks as well as technical know-how for the correct use of diodes are also described. (author)

  16. Simulation of electrical characteristics of GaN vertical Schottky diodes

    Science.gov (United States)

    Łukasiak, Lidia; Jasiński, Jakub; Jakubowski, Andrzej

    2016-12-01

    Reverse current of GaN vertical Schottky diodes is simulated using Silvaco ATLAS to optimize the geometry for the best performance. Several physical quantities and phenomena, such as carrier mobility and tunneling mechanism are studied to select the most realistic models. Breakdown voltage is qualitatively estimated based on the maximum electric field in the structure.

  17. Plasmonic silicon Schottky photodetectors: the physics behind graphene enhanced internal photoemission

    DEFF Research Database (Denmark)

    Levy, Uriel; Grajower, Meir; Gonçalves, P. A. D.

    2017-01-01

    a physical model where surface plasmon polaritons enhance the absorption in a single-layer graphene by enhancing the field along the interface. The relatively long relaxation time in graphene allows for multiple attempts for the carrier to overcome the Schottky barrier and penetrate into the semiconductor...

  18. ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

    Indian Academy of Sciences (India)

    Abstract. Electrical analysis of Al/p-Si Schottky diode with titanium dioxide (TiO2) thin film was performed at ..... This work was partially supported by The Management Unit of Scientific Research Project of Bozok University and Hitit. University.

  19. Schottky barriers based on metal nanoparticles deposited on InP epitaxial layers

    Czech Academy of Sciences Publication Activity Database

    Grym, Jan; Yatskiv, Roman

    2013-01-01

    Roč. 28, č. 4 (2013) ISSN 0268-1242 R&D Projects: GA MŠk LD12014 Institutional support: RVO:67985882 Keywords : Colloidal graphite * Epitaxial growth * Schottky barrier diodes Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.206, year: 2013

  20. An X-band Schottky diode mixer in SiGe technology with tunable Marchand balun

    DEFF Research Database (Denmark)

    Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.

    2017-01-01

    In this paper, we propose a double balanced mixer with a tunable Marchand balun. The circuit is designed in a SiGe BiCMOS process using Schottky diodes. The tunability of the Marchand balun is used to enhance critical parameters for double balanced mixers. The local oscillator-IF isolation can...

  1. Summer Student Report 2014: Schottky component qualification and RF filter characterization

    CERN Document Server

    Egidos Plaja, Nuria

    2014-01-01

    This Summer Student project has been developed in BE-BI-QP department under the supervision of Manfred Wendt. Main goals of the task to be performed are the following: 1)\tFilter characterization: the student will get familiar with the Vector Network Analizer (VNA), S-parameter measurement and PSPICE modelling of low-pass filters. 2)\tFilter response matching: an algorithm to compare and classify filter responses into best-matching pairs will be developed. 3)\tSchottky monitor filter qualification: S-parameter and time domain measurements will be carried out with filters related to Schottky monitor and results will be benchmarked. 4)\tSchottky monitor amplifier measurement: noise figure and gain at a given frequency will be measured for a set of Low Noise Amplifiers related to Schottky monitor. -1dB compression point and 3rd order interception point will be measured too for education purposes. For the development of this project, the student will get familiar with RF measure devices (VNA, VSA), theoretical concep...

  2. Comparison of magnetic and electrostatic Schottky pick-up in the CERN AD

    CERN Document Server

    Federmann, S

    2013-01-01

    The present note is intended to exploit the possibility of using a dedicated electrostatic beam pick-up for Schottky diagnostics in the future ELENA ring. A test setup is described allowing the evaluation of its performance compared to the extra low-noise beam current transformer used successfully in the AD. The results of this experiment are summarized and discussed.

  3. RF fields due to Schottky noise in a coasting particle beam

    CERN Document Server

    Faltin, L

    1977-01-01

    The RF fields inside a rectangular chamber excited by the Schottky noise current inherently present in a coasting particle beam are calculated, using a simple beam model. Vertical betatron oscillations are assumed. The power flow accompanying the beam is given as well as the resulting characteristic impedance. Numerical results are presented.

  4. 63Ni schottky barrier nuclear battery of 4H-SiC

    International Nuclear Information System (INIS)

    Xiao-Ying Li; Yong Ren; Xue-Jiao Chen; Da-Yong Qiao; Wei-Zheng Yuan

    2011-01-01

    The design, fabrication, and testing of a 4H-SiC Schottky betavoltaic nuclear battery based on MEMS fabrication technology are presented in this paper. It uses a Schottky diode with an active area of 3.14 mm 2 to collect the charge from a 4 mCi/cm 2 63 Ni source. Some of the critical steps in process integration for fabricating silicon carbide-based Schottky diode were addressed. A prototype of this battery was fabricated and tested under the illumination of the 63 Ni source with an activity of 0.12 mCi. An open circuit voltage (V OC ) of 0.27 V and a short circuit current density (J SC ) of 25.57 nA/cm 2 are measured. The maximum output power density (P max ) of 4.08 nW/cm 2 and power conversion efficiency (η) of 1.01% is obtained. The performance of this battery is expected to be significantly improved by using larger activity and optimizing the design and processing technology of the battery. By achieving comparable performance with previously constructed p-n or p-i-n junction energy conversion structures, the Schottky barrier diode proves to be a feasible approach to achieve practical betavoltaics. (author)

  5. Utilizing Schottky barriers to suppress short-channel effects in organic transistors

    Science.gov (United States)

    Fernández, Anton F.; Zojer, Karin

    2017-10-01

    Transistors with short channel lengths exhibit profound deviations from the ideally expected behavior. One of the undesired short-channel effects is an enlarged OFF current that is associated with a premature turn on of the transistor. We present an efficient approach to suppress the OFF current, defined as the current at zero gate source bias, in short-channel organic transistors. We employ two-dimensional device simulations based on the drift-diffusion model to demonstrate that intentionally incorporating a Schottky barrier for injection enhances the ON-OFF ratio in both staggered and coplanar transistor architectures. The Schottky barrier is identified to directly counteract the origin of enlarged OFF currents: Short channels promote a drain-induced barrier lowering. The latter permits unhindered injection of charges even at reverse gate-source bias. An additional Schottky barrier hampers injection for such points of operations. We explain how it is possible to find the Schottky barrier of the smallest height necessary to exactly compensate for the premature turn on. This approach offers a substantial enhancement of the ON-OFF ratio. We show that this roots in the fact that such optimal barrier heights offer an excellent compromise between an OFF current diminished by orders of magnitude and an only slightly reduced ON current.

  6. C-V characterization of Schottky- and MIS-gate SiGe/Si HEMT structures

    International Nuclear Information System (INIS)

    Onojima, Norio; Kasamatsu, Akihumi; Hirose, Nobumitsu; Mimura, Takashi; Matsui, Toshiaki

    2008-01-01

    Electrical properties of Schottky- and metal-insulator-semiconductor (MIS)-gate SiGe/Si high electron mobility transistors (HEMTs) were investigated with capacitance-voltage (C-V) measurements. The MIS-gate HEMT structure was fabricated using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. We previously investigated device characteristics of sub-100-nm-gate-length Schottky- and MIS-gate HEMTs, and reported that the MIS-gate device had larger maximum drain current density and transconductance (g m ) than the Schottky-gate device. The radio frequency (RF) measurement of the MIS-gate device, however, showed a relatively lower current gain cutoff frequency f T compared with that of the Schottky-gate device. In this study, C-V characterization of the MIS-gate HEMT structure demonstrated that two electron transport channels existed, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel

  7. C-V characterization of Schottky- and MIS-gate SiGe/Si HEMT structures

    Energy Technology Data Exchange (ETDEWEB)

    Onojima, Norio [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan)], E-mail: nonojima@nict.go.jp; Kasamatsu, Akihumi; Hirose, Nobumitsu [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan); Mimura, Takashi [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan); Fujitsu Laboratories Ltd., Atsugi, Kanagawa 243-0197 (Japan); Matsui, Toshiaki [National Institute of Information and Communications Technology (NICT), Koganei, Tokyo 184-8795 (Japan)

    2008-07-30

    Electrical properties of Schottky- and metal-insulator-semiconductor (MIS)-gate SiGe/Si high electron mobility transistors (HEMTs) were investigated with capacitance-voltage (C-V) measurements. The MIS-gate HEMT structure was fabricated using a SiN gate insulator formed by catalytic chemical vapor deposition (Cat-CVD). The Cat-CVD SiN thin film (5 nm) was found to be an effective gate insulator with good gate controllability and dielectric properties. We previously investigated device characteristics of sub-100-nm-gate-length Schottky- and MIS-gate HEMTs, and reported that the MIS-gate device had larger maximum drain current density and transconductance (g{sub m}) than the Schottky-gate device. The radio frequency (RF) measurement of the MIS-gate device, however, showed a relatively lower current gain cutoff frequency f{sub T} compared with that of the Schottky-gate device. In this study, C-V characterization of the MIS-gate HEMT structure demonstrated that two electron transport channels existed, one at the SiGe/Si buried channel and the other at the SiN/Si surface channel.

  8. Schottky diode model for non-parabolic dispersion in narrow-gap semiconductor and few-layer graphene

    Science.gov (United States)

    Ang, Yee Sin; Ang, L. K.; Zubair, M.

    Despite the fact that the energy dispersions are highly non-parabolic in many Schottky interfaces made up of 2D material, experimental results are often interpreted using the conventional Schottky diode equation which, contradictorily, assumes a parabolic energy dispersion. In this work, the Schottky diode equation is derived for narrow-gap semiconductor and few-layer graphene where the energy dispersions are highly non-parabolic. Based on Kane's non-parabolic band model, we obtained a more general Kane-Schottky scaling relation of J (T2 + γkBT3) which connects the contrasting J T2 in the conventional Schottky interface and the J T3 scaling in graphene-based Schottky interface via a non-parabolicity parameter, γ. For N-layer graphene of ABC -stacking and of ABA -stacking, the scaling relation follows J T 2 / N + 1 and J T3 respectively. Intriguingly, the Richardson constant extracted from the experimental data using an incorrect scaling can differ with the actual value by more than two orders of magnitude. Our results highlights the importance of using the correct scaling relation in order to accurately extract important physical properties, such as the Richardson constant and the Schottky barrier's height.

  9. Highly efficient ZnO/Au Schottky barrier dye-sensitized solar cells: Role of gold nanoparticles on the charge-transfer process

    Directory of Open Access Journals (Sweden)

    Tanujjal Bora

    2011-10-01

    Full Text Available Zinc oxide (ZnO nanorods decorated with gold (Au nanoparticles have been synthesized and used to fabricate dye-sensitized solar cells (DSSC. The picosecond-resolved, time-correlated single-photon-count (TCSPC spectroscopy technique was used to explore the charge-transfer mechanism in the ZnO/Au-nanocomposite DSSC. Due to the formation of the Schottky barrier at the ZnO/Au interface and the higher optical absorptions of the ZnO/Au photoelectrodes arising from the surface plasmon absorption of the Au nanoparticles, enhanced power-conversion efficiency (PCE of 6.49% for small-area (0.1 cm2 ZnO/Au-nanocomposite DSSC was achieved compared to the 5.34% efficiency of the bare ZnO nanorod DSSC. The TCSPC studies revealed similar dynamics for the charge transfer from dye molecules to ZnO both in the presence and absence of Au nanoparticles. A slower fluorescence decay associated with the electron recombination process, observed in the presence of Au nanoparticles, confirmed the blocking of the electron transfer from ZnO back to the dye or electrolyte by the Schottky barrier formed at the ZnO/Au interface. For large area DSSC (1 cm2, ~130% enhancement in PCE (from 0.50% to 1.16% was achieved after incorporation of the Au nanoparticles into the ZnO nanorods.

  10. Microstructure, electrical, and optical properties of evaporated PtSi/p-Si(100) Schottky barriers as high quantum efficient infrared detectors

    International Nuclear Information System (INIS)

    Wu Jihhuah; Chang Rongsen; Horng Gwoji

    2004-01-01

    The effects of the microstructure and the electrical and optical properties on the formation at highly efficient infrared PtSi Schottky barrier detectors (SBD) have been studied in detail. Two- to twelve-nanometer-thick PtSi films were grown by evaporation at temperature ranging from 350 to 550 deg. C. The electron diffraction patterns indicate the existence of both the (11-bar0) and (12-bar1) orientations when PtSi films formed at 350 deg. C. However, the diffraction patterns show only the (12-bar1) orientation when the PtSi films are formed at 450 deg. C or above. The electrical barrier height of the Schottky barrier detector that formed at 350 deg. C was about 20 meV higher than that formed at 450 deg. C or above. The grain size and the film thickness had a negligible effect on the electrical barrier height. However, the optical performance was strongly dependent on the film thickness and the growth conditions. The 350 deg. C PtSi film showed increased quantum efficiency as the film thickness decreased. The optimal thickness that provided the highest responsivity was 2 nm. On the other hand, the optimal thickness shifted to 8 nm for PtSi film formed at 450 deg. C or above. These results indicate that the quantum efficiency of a detector can be improved if the PtSi film has an orientation at (12-bar1), a larger grain size, and an optimal film thickness

  11. Occupational contact urticaria and protein contact dermatitis.

    Science.gov (United States)

    Doutre, Marie-Sylvie

    2005-01-01

    Irritant dermatitis and eczema are the most prevalent occupational skin diseases. Less common are immediate contact reactions such as contact urticaria and protein contact dermatitis. Occupational contact urticaria can be subdivided into two categories, immunological and non immunological. However, some agents can induce these two types of reactions. Contact urticaria to natural rubber latex is particularly frequent among health care personnel, but contact urticaria to a wide variety of other substances occurs in many other occupations. Among those at risk are cooks, bakers, butchers, restaurant personnel, veterinarians, hairdressers, florists, gardeners, and forestry workers. Protein contact dermatitis in some of these occupations is caused principally by proteins of animal or plant origin, especially among individuals with a history of atopic dermatitis. Diagnosis requires careful interrogation, clinical examination and skin tests (open tests and prick tests with immediate lecture) to identify a particular contact allergen.

  12. Effects of sulfide treatment on electronic transport of graphene/n-type Si Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Jian-Jhou; Lin, Yow-Jon, E-mail: rzr2390@yahoo.com.tw

    2014-05-01

    The present work reports the fabrication and detailed electrical properties of graphene/n-type Si Schottky diodes with and without sulfide treatment. The graphene/n-type Si Schottky diode without sulfide treatment shows a poor rectifying behavior with an ideality factor (η) of 4.2 and high leakage. η > 2 implies that the interfacial defects influence the electronic conduction through the device. However, the graphene/n-type Si Schottky diode with sulfide treatment for 5 min shows a good rectifying behavior with η of 1.8 and low leakage. Such an improvement indicates that a good passivation is formed at the interface as a result of the reduction of the defect density. These experimental demonstrations suggest that it may be possible to minimize the adverse effects of the interface states to obtain functional devices using sulfide treatment. In addition, the graphene/n-type Si Schottky diode with sulfide treatment for 10 min shows a poor rectifying behavior with η of 2.5 and high leakage. Note, a suitable sulfide treatment time is an important issue for improving the device performance. - Highlights: • Graphene/Si diodes with sulfide treatment for 5 min show a good rectifying behavior. • Graphene/Si diodes without sulfide treatment show a poor rectifying behavior. • The interfacial defects of Schottky diodes were controlled by sulfide treatment. • Such an improvement indicates that a good passivation is formed at the interface. • A suitable sulfide treatment time is an important issue for improving performances.

  13. Effects of sulfide treatment on electronic transport of graphene/n-type Si Schottky diodes

    International Nuclear Information System (INIS)

    Zeng, Jian-Jhou; Lin, Yow-Jon

    2014-01-01

    The present work reports the fabrication and detailed electrical properties of graphene/n-type Si Schottky diodes with and without sulfide treatment. The graphene/n-type Si Schottky diode without sulfide treatment shows a poor rectifying behavior with an ideality factor (η) of 4.2 and high leakage. η > 2 implies that the interfacial defects influence the electronic conduction through the device. However, the graphene/n-type Si Schottky diode with sulfide treatment for 5 min shows a good rectifying behavior with η of 1.8 and low leakage. Such an improvement indicates that a good passivation is formed at the interface as a result of the reduction of the defect density. These experimental demonstrations suggest that it may be possible to minimize the adverse effects of the interface states to obtain functional devices using sulfide treatment. In addition, the graphene/n-type Si Schottky diode with sulfide treatment for 10 min shows a poor rectifying behavior with η of 2.5 and high leakage. Note, a suitable sulfide treatment time is an important issue for improving the device performance. - Highlights: • Graphene/Si diodes with sulfide treatment for 5 min show a good rectifying behavior. • Graphene/Si diodes without sulfide treatment show a poor rectifying behavior. • The interfacial defects of Schottky diodes were controlled by sulfide treatment. • Such an improvement indicates that a good passivation is formed at the interface. • A suitable sulfide treatment time is an important issue for improving performances

  14. Physics of Schottky-barrier change by segregation and structural disorder at metal/Si interfaces: First-principles study

    International Nuclear Information System (INIS)

    Nakayama, T.; Kobinata, K.

    2012-01-01

    Schottky-barrier changes by the segregation and structural disorder are studied using the first-principles calculations and adopting Au/Si interface. The Schottky barrier for electrons simply decreases as increasing the valency of segregated atoms from II to VI families, which variation is shown closely related to how the Si atoms are terminated at the interface. On the other hand, the structural disorders (defects) prefer to locate near the interface and the Schottky barrier for hole carriers does not change in cases of Si vacancy and Au substitution, while it increases in cases of Si and Au interstitials reflecting the appearance of Si dangling bonds.

  15. Schottky barrier formation at amorphous-crystalline interfaces of GeSb phase change materials

    NARCIS (Netherlands)

    Kroezen, H. J.; Eising, G.; ten Brink, Gert; Palasantzas, G.; Kooi, B. J.; Pauza, A.

    2012-01-01

    The electrical properties of amorphous-crystalline interfaces in phase change materials, which are important for rewritable optical data storage and for random access memory devices, have been investigated by surface scanning potential microscopy. Analysis of GeSb systems indicates that the surface

  16. Fabrication, characterization and simulation of 4H-SiC Schottky diode alpha particle detectors for pyroprocessing actinide monitoring

    Science.gov (United States)

    Garcia, Timothy Richard

    Pyroprocessing is a method of using high-temperature molten salts and electric fields to separate and collect fuel isotopes of used nuclear fuel. It has been has been tested in the U.S. at Idaho National Laboratory as a key step in closing the nuclear fuel cycle. One technical problem with the pyroprocessing method is a lack of knowledge regarding the actinide concentrations in the salt bath during operation, since on-line techniques for measuring these concentrations are not presently available. 4H-SiC Schottky diode detectors can potentially fulfill this need. Such detectors would operate in contact with the molten salt, and measure concentrations via alpha-particle spectroscopy. This work seeks to fabricate and characterize 4H-SiC Schottky diode detectors at high temperature, model the alpha particle spectrum expected in a molten salt, and model the operation of the detectors to confirm the physics of operation is as expected. In this work, 4H-SiC Schottky diode detectors were fabricated at OSU Nanotech West. After fabrication, these detectors were characterized using both I-V curves and Am-241 alpha-particle energy spectra. All measurements were made as a function of temperature, from room temperature up to 500°C. The average energy required to create an electron-hole pair was observed to decrease with an increase of temperature, due to a decrease of both the 4H-SiC bandgap and non-linear energy loss terms. Furthermore, the FWHM of the spectra was observed to be dependent on the leakage current at a certain temperature, and not dependent on the temperature itself. Secondly, the alpha particle energy spectrum in the pyroprocessing environment was modeled using SRIM. The molten salt was modeled in 3 different geometries, with or without a protective cover material on top of the detector. Due to the loss of alpha-particle energy in the molten salt itself, a high-energy alpha emitter may completely cover the spectrum from a lower-energy alpha emitter. Each of the

  17. Radiation-resistant photostructure for Schottky diode based on Cr/In2Hg3Te6

    Directory of Open Access Journals (Sweden)

    Ashcheulov A. A.

    2016-05-01

    Full Text Available Ge, Si, InGaAs, GaInAsP photodiodes are used as optical radiation receivers and function in a spectral range of transparency of quartz fiberglass. For the optical systems operated in the increased radioactivity the photodetectors' application on In2Hg3Te6 crystal base characterized by a photosensitivity in the spectral range of 0,5-1,6 mm and also by increased radiation resistance to alpha, beta and gamma radiation is most acceptable. Schottky photodiode structure was designed on the base of this semiconductor formed by a modified floating zone recrystallization technique where the sedimentation effect was leveled. It consists of n-In2Hg3Te6 substrate and deposited by cathode sputtering Cr barrier layer of thickness within a range 10-11 nm choice of Cr is determined by its optimal optical, electric and adhesive features in high quality radiation-resistant photodiode structures manufacturing. Indium and nichrome are used as ohmic contacts. The barrier structures have the contact area of 1,13 mm2 with photo response of 0,6-1,6 mm at the maximal sensitivity 0,43 A/W on the wavelength l,55 mm. Reverse dark current of these structures do not exceed 4 mA at the bias of 1 V (T=295 K, and the potential barrier height is equal to 0,41 eV. The tests of radiation resistance of these structures demonstrated their ability to function at doses of 2⋅108 rem without evident parameters changes. This allows using them in practical aims in the conditions of high radiation.

  18. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... Costume Contact Lenses Can Ruin Vision Eye Makeup Safety In fact, it is illegal to sell colored ...

  19. Colored Contact Lens Dangers

    Medline Plus

    Full Text Available ... One Use Facts About Colored Contacts and Halloween Safety Colored Contact Lens Facts Over-the-Counter Costume ... use of colored contact lenses , from the U.S. Food and Drug Administration (FDA). Are the colored lenses ...

  20. Transport characteristics of Pd Schottky barrier diodes on epitaxial n-GaSb as determined from temperature dependent current–voltage measurements

    Energy Technology Data Exchange (ETDEWEB)

    Venter, A., E-mail: andre.venter@nmmu.ac.za [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Murape, D.M.; Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Auret, F.D. [Department of Physics, University of the Pretoria, Lynnwood Road, Pretoria 0002 (South Africa)

    2015-01-01

    The temperature dependent transport characteristics of Pd/n-GaSb:Te Schottky contacts with low and saturating reverse current are investigated by means of current–voltage measurements between 80 K and 320 K. The apparent barrier height and ideality factor increase with a decrease in temperature. Neither thermionic nor thermionic field emission can explain the low temperature characteristics of these diodes. Instead, evidence is presented for barrier inhomogeneity across the metal/semiconductor contact. A plot of the barrier height, ϕ{sub b} vs. 1/2kT revealed a double Gaussian distribution for the barrier height with ϕ{sub b,mean} assuming values of 0.59 eV ± 0.07 (80–140 K) and 0.25 eV ± 0.12 (140–320 K) respectively. - Highlights: • Transport characteristics of Pd/epitaxial n-GaSb:Te SBDs are studied by means of I-V-T measurements. • SBDs have remarkably low and saturating reverse current – of the lowest ever reported for GaSb. • Transport behaviour is explained by considering electronic states present on the GaSb surface. • Evidence is presented for barrier inhomogeneity across the metal-semiconductor contact.

  1. Transport characteristics of Pd Schottky barrier diodes on epitaxial n-GaSb as determined from temperature dependent current–voltage measurements

    International Nuclear Information System (INIS)

    Venter, A.; Murape, D.M.; Botha, J.R.; Auret, F.D.

    2015-01-01

    The temperature dependent transport characteristics of Pd/n-GaSb:Te Schottky contacts with low and saturating reverse current are investigated by means of current–voltage measurements between 80 K and 320 K. The apparent barrier height and ideality factor increase with a decrease in temperature. Neither thermionic nor thermionic field emission can explain the low temperature characteristics of these diodes. Instead, evidence is presented for barrier inhomogeneity across the metal/semiconductor contact. A plot of the barrier height, ϕ b vs. 1/2kT revealed a double Gaussian distribution for the barrier height with ϕ b,mean assuming values of 0.59 eV ± 0.07 (80–140 K) and 0.25 eV ± 0.12 (140–320 K) respectively. - Highlights: • Transport characteristics of Pd/epitaxial n-GaSb:Te SBDs are studied by means of I-V-T measurements. • SBDs have remarkably low and saturating reverse current – of the lowest ever reported for GaSb. • Transport behaviour is explained by considering electronic states present on the GaSb surface. • Evidence is presented for barrier inhomogeneity across the metal-semiconductor contact

  2. Contact fatigue in rolling-element bearings

    CSIR Research Space (South Africa)

    Fernandes, PJL

    1997-06-01

    Full Text Available to the "cyclone pitting effect" also observed in gear teeth \\[1\\]. The initiation of surface cracks under rollin~sliding contact can be significantly accelerated by the presence of stress concentration sites on the contact surf... formed by rolling and rollin~sliding contact fatigue may progress to form a more severe form of damage known as flaking \\[3\\]. This results in the formation of large, irregular pits which cause rapid deterioration...

  3. Lateral current generation in n-AlGaAs/GaAs heterojunction channels by Schottky-barrier gate illumination

    Energy Technology Data Exchange (ETDEWEB)

    Kawazu, Takuya; Noda, Takeshi; Sakuma, Yoshiki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Sakaki, Hiroyuki [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan)

    2015-01-12

    We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate.

  4. Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes

    Science.gov (United States)

    Kumar, Ashutosh; Heilmann, M.; Latzel, Michael; Kapoor, Raman; Sharma, Intu; Göbelt, M.; Christiansen, Silke H.; Kumar, Vikram; Singh, Rajendra

    2016-01-01

    The electrical behaviour of Schottky barrier diodes realized on vertically standing individual GaN nanorods and array of nanorods is investigated. The Schottky diodes on individual nanorod show highest barrier height in comparison with large area diodes on nanorods array and epitaxial film which is in contrast with previously published work. The discrepancy between the electrical behaviour of nanoscale Schottky diodes and large area diodes is explained using cathodoluminescence measurements, surface potential analysis using Kelvin probe force microscopy and 1ow frequency noise measurements. The noise measurements on large area diodes on nanorods array and epitaxial film suggest the presence of barrier inhomogeneities at the metal/semiconductor interface which deviate the noise spectra from Lorentzian to 1/f type. These barrier inhomogeneities in large area diodes resulted in reduced barrier height whereas due to the limited role of barrier inhomogeneities in individual nanorod based Schottky diode, a higher barrier height is obtained. PMID:27282258

  5. Electrical properties of Au/perylene-monoimide/p-Si Schottky diode

    International Nuclear Information System (INIS)

    Yüksel, Ö.F.; Tuğluoğlu, N.; Gülveren, B.; Şafak, H.; Kuş, M.

    2013-01-01

    Graphical abstract: In this work, we have fabricated an Au/perylene-monoimide (PMI)/p-Si Schottky barrier diode. An emphasis is placed on how electrical and interface characteristics like current–voltage (I–V) variation, ideality factor (n), barrier height (Φ B ) and series resistance (R s ) of Au/PMI/p-Si diode structure change with the temperatures between 100 and 300 K. The temperature dependence of barrier height shows that the Schottky barrier height is inhomogeneous in nature at the interface. Such inhomogeneous behavior was explained on the basis of thermionic emission mechanism by assuming the existence of a Gaussian distribution of barrier heights. -- Highlights: •An Au/perylene-monoimide (PMI)/p-Si Schottky diode having an organic interlayer has been fabricated. •I–V characteristics have been investigated over a wide temperature range 100–300 K. •C–V measurements have been analyzed at room temperature. -- Abstract: In this work, we have fabricated an Au/perylene-monoimide (PMI)/p-Si Schottky barrier diode. We have investigated how electrical and interface characteristics like current–voltage characteristics (I–V), ideality factor (n), barrier height (Φ B ) and series resistance (R s ) of diode change with temperature over a wide range of 100–300 K. Detailed analysis on the electrical properties of structure is performed by assuming the standard thermionic emission (TE) model. Possible mechanisms such as image force lowering, generation–recombination processes and interface states which cause deviations of n values from the unity have been discussed. Cheung–Cheung method is also employed to analysis the current–voltage characteristics and a good agreement is observed between the results. It is shown that the electronic properties of Schottky diode are very sensitive to the modification of perylene-monoimide (PMI) interlayer organic material and also to the temperature. The ideality factor was found to decrease and the barrier

  6. 2D halide perovskite-based van der Waals heterostructures: contact evaluation and performance modulation

    Science.gov (United States)

    Guo, Yaguang; Saidi, Wissam A.; Wang, Qian

    2017-09-01

    Halide perovskites and van der Waals (vdW) heterostructures are both of current interest owing to their novel properties and potential applications in nano-devices. Here, we show the great potential of 2D halide perovskite sheets (C4H9NH3)2PbX4 (X  =  Cl, Br and I) that were synthesized recently (Dou et al 2015 Science 349 1518-21) as the channel materials contacting with graphene and other 2D metallic sheets to form van der Waals heterostructures for field effect transistor (FET). Based on state-of-the-art theoretical simulations, we show that the intrinsic properties of the 2D halide perovskites are preserved in the heterojunction, which is different from the conventional contact with metal surfaces. The 2D halide perovskites form a p-type Schottky barrier (Φh) contact with graphene, where tunneling barrier exists, and a negative band bending occurs at the lateral interface. We demonstrate that the Schottky barrier can be turned from p-type to n-type by doping graphene with nitrogen atoms, and a low-Φh or an Ohmic contact can be realized by doping graphene with boron atoms or replacing graphene with other high-work-function 2D metallic sheets such as ZT-MoS2, ZT-MoSe2 and H-NbS2. This study not only predicts a 2D halide perovskite-based FETs, but also enhances the understanding of tuning Schottky barrier height in device applications.

  7. Improved speed of hydrogen detection by Schottky diodes on InP with electrophoretically deposited Pt nanoparticles and graphite contacts

    Czech Academy of Sciences Publication Activity Database

    Žďánský, Karel; Dickerson, J.H.

    -, č. 184 (2013), s. 295-300 ISSN 0925-4005 R&D Projects: GA MŠk(CZ) OC10021 Institutional support: RVO:67985882 Keywords : Metal nanoparticles * Keyed electrophoresis * Hydrogen sensors Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 3.840, year: 2013

  8. Charge plasma based source/drain engineered Schottky Barrier MOSFET: Ambipolar suppression and improvement of the RF performance

    Science.gov (United States)

    Kale, Sumit; Kondekar, Pravin N.

    2018-01-01

    This paper reports a novel device structure for charge plasma based Schottky Barrier (SB) MOSFET on ultrathin SOI to suppress the ambipolar leakage current and improvement of the radio frequency (RF) performance. In the proposed device, we employ dual material for the source and drain formation. Therefore, source/drain is divided into two parts as main source/drain and source/drain extension. Erbium silicide (ErSi1.7) is used as main source/drain material and Hafnium metal is used as source/drain extension material. The source extension induces the electron plasma in the ultrathin SOI body resulting reduction of SB width at the source side. Similarly, drain extension also induces the electron plasma at the drain side. This significantly increases the SB width due to increased depletion at the drain end. As a result, the ambipolar leakage current can be suppressed. In addition, drain extension also reduces the parasitic capacitances of the proposed device to improve the RF performance. The optimization of length and work function of metal used in the drain extension is performed to achieve improvement in device performance. Moreover, the proposed device makes fabrication simpler, requires low thermal budget and free from random dopant fluctuations.

  9. Wetting dynamics at high values of contact line speed

    OpenAIRE

    Пономарев, К. О.; Феоктистов, Дмитрий Владимирович; Орлова, Евгения Георгиевна

    2015-01-01

    Experimental results analyses of dynamic contact angle change under the conditions of substrate wetting by distilled water at high values of the contact line speed was conducted. Three spreading modes for copper substrates with different roughness were selected: drop formation, spreading and equilibrium contact angle formation. Peculiarity of droplet spreading on superhydrophobic surface is found. It consists in a monotonic increase of the advancing dynamic contact angle. The effect of the dr...

  10. Enhanced Schottky signals from electron-cooled, coasting beams in a heavy-ion storage ring

    Energy Technology Data Exchange (ETDEWEB)

    Krantz, C., E-mail: claude.krantz@mpi-hd.mpg.d [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Blaum, K.; Grieser, M. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Litvinov, Yu.A. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt (Germany); Repnow, R.; Wolf, A. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

    2011-02-11

    Measurements at the Test Storage Ring of the Max-Planck-Institut fuer Kernphysik in Heidelberg (Germany) have shown that the signal amplitude induced in a Schottky-noise pickup electrode by a coasting electron-cooled ion beam can be greatly enhanced by exposure of the latter to a perturbing radiofrequency signal which is detuned from the true beam revolution frequency. The centre frequencies obtained from harmonic analysis of the observed pickup signal closely follow those imposed on the ions by the electron cooling force. The phenomenon can be exploited to measure the true revolution frequency of ion beams of very low intensity, whose pure Schottky noise is too weak to be measurable under normal circumstances.

  11. Operation and scalability of dopant-segregated Schottky barrier MOSFETs with recessed channels

    International Nuclear Information System (INIS)

    Shih, Chun-Hsing; Hsia, Jui-Kai

    2013-01-01

    Recessed channels were used in scaled dopant-segregated Schottky barrier MOSFETs (DS-SBMOS) to control the severe short-channel effect. The physical operation and device scalability of the DS-SBMOS resulting from the presence of recessed channels and associated gate-corners are elucidated. The coupling of Schottky and gate-corner barriers has a key function in determining the on–off switching and drain current. The gate-corner barriers divide the channel into three regions for protection from the drain penetration field. To prevent resistive degradations in the drive current, an alternative asymmetric recessed channel (ARC) without a source-side gate-corner is proposed to simultaneously optimize both the short-channel effect and drive current in the scaled DS-SBMOS. By employing the proposed ARC architecture, the DS-SBMOS devices can be successfully scaled down, making them promising candidates for next-generation CMOS devices. (paper)

  12. Model and observations of Schottky-noise suppression in a cold heavy-ion beam.

    Science.gov (United States)

    Danared, H; Källberg, A; Rensfelt, K-G; Simonsson, A

    2002-04-29

    Some years ago it was found at GSI in Darmstadt that the momentum spread of electron-cooled beams of highly charged ions dropped abruptly to very low values when the particle number decreased to 10 000 or less. This has been interpreted as an ordering of the ions, such that they line up after one another in the ring. We report observations of similar transitions at CRYRING, including an accompanying drop in Schottky-noise power. We also introduce a model of the ordered beam from which the Schottky-noise power can be calculated numerically. The good agreement between the model calculation and the experimental data is seen as evidence for a spatial ordering of the ions.

  13. Study of breakdown voltage of indium-gallium-zinc-oxide-based Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Xin, Qian; Yan, Linlong; Luo, Yi [School of Physics, Shandong University, Jinan 250100 (China); Song, Aimin, E-mail: A.Song@manchester.ac.uk [School of Physics, Shandong University, Jinan 250100 (China); School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-03-16

    In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as −2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to −15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate.

  14. Study of breakdown voltage of indium-gallium-zinc-oxide-based Schottky diode

    International Nuclear Information System (INIS)

    Xin, Qian; Yan, Linlong; Luo, Yi; Song, Aimin

    2015-01-01

    In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as −2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to −15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate

  15. Schottky effect model of electrical activity of metallic precipitates in silicon

    International Nuclear Information System (INIS)

    Plekhanov, P. S.; Tan, T. Y.

    2000-01-01

    A quantitative model of the electrical activity of metallic precipitates in Si is formulated with an emphasis on the Schottky junction effects of the precipitate-Si system. Carrier diffusion and carrier drift in the Si space charge region are accounted for. Carrier recombination is attributed to the thermionic emission mechanism of charge transport across the Schottky junction rather than the surface recombination. It is shown that the precipitates can have a very large minority carrier capture cross-section. Under weak carrier generation conditions, the supply of minority carriers is found to be the limiting factor of the recombination process. The plausibility of the model is demonstrated by a comparison of calculated and available experimental results. (c) 2000 American Institute of Physics

  16. A gate enhanced power U-shaped MOSFET integrated with a Schottky rectifier

    International Nuclear Information System (INIS)

    Wang Ying; Jiao Wen-Li; Hu Hai-Fan; Liu Yun-Tao; Cao Fei

    2012-01-01

    An accumulation gate enhanced power U-shaped metal-oxide-semiconductor field-effect-transistor (UMOSFET) integrated with a Schottky rectifier is proposed. In this device, a Schottky rectifier is integrated into each cell of the accumulation gate enhanced power UMOSFET. Specific on-resistances of 7.7 mΩ·mm 2 and 6.5 mΩ·mm 2 for the gate bias voltages of 5 V and 10 V are achieved, respectively, and the breakdown voltage is 61 V. The numerical simulation shows a 25% reduction in the reverse recovery time and about three orders of magnitude reduction in the leakage current as compared with the accumulation gate enhanced power UMOSFET. (condensed matter: structural, mechanical, and thermal properties)

  17. Study of polarization phenomena in Schottky CdTe diodes using infrared light illumination

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Goro, E-mail: gsato@astro.isas.jaxa.jp [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Fukuyama, Taro [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033 (Japan); Watanabe, Shin; Ikeda, Hirokazu; Ohta, Masayuki; Ishikawa, Shin' nosuke [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Takahashi, Tadayuki [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033 (Japan); Shiraki, Hiroyuki; Ohno, Ryoichi [ACRORAD Co., Ltd., 13-23 Suzaki, Uruma, Okinawa 904-2234 (Japan)

    2011-10-01

    Schottky CdTe diode detectors suffer from a polarization phenomenon, which is characterized by degradation of the spectral properties over time following exposure to high bias voltage. This is considered attributable to charge accumulation at deep acceptor levels. A Schottky CdTe diode was illuminated with an infrared light for a certain period during a bias operation, and two opposite behaviors emerged. The detector showed a recovery when illuminated after the bias-induced polarization had completely progressed. Conversely, when the detector was illuminated before the emergence of bias-induced polarization, the degradation of the spectral properties was accelerated. Interpretation of these effects and discussion on the energy level of deep acceptors are presented.

  18. New Type Far IR and THz Schottky Barrier Detectors for Scientific and Civil Application

    Directory of Open Access Journals (Sweden)

    V. G. Ivanov

    2011-01-01

    Full Text Available The results of an experimental investigation into a new type of VLWIR detector based on hot electron gas emission and architecture of the detector are presented and discussed. The detectors (further referred to as HEGED take advantage of the thermionic emission current change effect in a semiconductor diode with a Schottky barrier (SB as a result of the direct transfer of the absorbed radiation energy to the system of electronic gas in the quasimetallic layer of the barrier. The possibility of detecting radiation having the energy of quantums less than the height of the Schottky diode potential barrier and of obtaining a substantial improvement of a cutoff wavelength to VLWIR of the PtSi/Si detector has been demonstrated. The complementary contribution of two physical mechanisms of emanation detection—“quantum” and hot electrons gas emission—has allowed the creation of a superwideband IR detector using standard silicon technology.

  19. Fabrication of polymer Schottky diode with Al-PANI/MWCNT-Au structure

    Directory of Open Access Journals (Sweden)

    A Hajibadali

    2014-11-01

    Full Text Available In this research, Schottky diode with Al-PANI/MWCNT-Au structure was fabricated using spin coating of composite polymer and physical vapor deposition of metals. For this purpose, a thin layer of gold was coated on glass and then composite of polyaniline/multi-walled carbon nanotube was synthesized and spin-coated on gold layer. Finally, a thin layer of aluminum was coated on polymer layer. The current-voltage characteristics of diode were studied and found that I-V curve is nonlinear and nonsymmetrical, showing rectifying behavior. I-V characteristics plotted on a logarithmic scale for Schottky diode showed two distinct power law regions. At lower voltages, the mechanism follows Ohm’s Law and at higher voltages, the mechanism is consistent with space charge limited conduction (SCLC emission. The parameters extracted from I-V characteristics were also calculated.

  20. The effects of temperature on Schottky diode barrier height and evidence of multiple barrier

    International Nuclear Information System (INIS)

    Rabah, K.V.O.

    1994-07-01

    Experimental study of Capacitance-Voltage-Temperature (C-V-T) plots, Current-Voltage-Temperature (I-V-T) characteristics have been undertaken in order to determine the height of the Schottky barrier. The results of the barrier height obtained by the above two methods were found to differ as well as vary with temperature change. In view of this discrepancy in barrier height values, two further experiments were performed: one on activation energy (I-T) plots and the other on pulsed (I-V-T) characteristics, and the results were found to show a similar trend. The Schottky diode studied was a 30CP040. (author). 23 refs, 9 figs, 3 tabs

  1. Contact Dermatitis in Pediatrics.

    Science.gov (United States)

    Pelletier, Janice L; Perez, Caroline; Jacob, Sharon E

    2016-08-01

    Contact dermatitis is an umbrella term that describes the skin's reaction to contacted noxious or allergenic substances. The two main categories of contact dermatitis are irritant type and allergic type. This review discusses the signs, symptoms, causes, and complications of contact dermatitis. It addresses the testing, treatment, and prevention of contact dermatitis. Proper management of contact dermatitis includes avoidance measures for susceptible children. Implementation of a nickel directive (regulating the use of nickel in jewelry and other products that come into contact with the skin) could further reduce exposure to the most common allergens in the pediatric population. [Pediatr Ann. 2016;45(8):e287-e292.]. Copyright 2016, SLACK Incorporated.

  2. Tuning on-off current ratio and field-effect mobility in a MoS(2)-graphene heterostructure via Schottky barrier modulation.

    Science.gov (United States)

    Shih, Chih-Jen; Wang, Qing Hua; Son, Youngwoo; Jin, Zhong; Blankschtein, Daniel; Strano, Michael S

    2014-06-24

    Field-effect transistor (FET) devices composed of a MoS2-graphene heterostructure can combine the advantages of high carrier mobility in graphene with the permanent band gap of MoS2 for digital applications. Herein, we investigate the electron transfer, photoluminescence, and gate-controlled carrier transport in such a heterostructure. We show that the junction is a Schottky barrier, whose height can be artificially controlled by gating or doping graphene. When the applied gate voltage (or the doping level) is zero, the photoexcited electron-hole pairs in monolayer MoS2 can be split by the heterojunction, significantly reducing the photoluminescence. By applying negative gate voltage (or p-doping) in graphene, the interlayer impedance formed between MoS2 and graphene exhibits an 100-fold increase. For the first time, we show that the gate-controlled interlayer Schottky impedance can be utilized to modulate carrier transport in graphene, significantly depleting the hole transport, but preserving the electron transport. Accordingly, we demonstrate a new type of FET device, which enables a controllable transition from NMOS digital to bipolar characteristics. In the NMOS digital regime, we report a very high room temperature on/off current ratio (ION/IOFF ∼ 36) in comparison to graphene-based FET devices without sacrificing the field-effect electron mobilities in graphene. By engineering the source/drain contact area, we further estimate that a higher value of ION/IOFF up to 100 can be obtained in the device architecture considered. The device architecture presented here may enable semiconducting behavior in graphene for digital and analogue electronics.

  3. Superposed orogenic collision and core-complex formation at the present contact between the Dinarides and the Pannonian basin: The Bukulja and Cer Mountains in central and western Serbia

    Science.gov (United States)

    Matenco, Liviu; Toljic, Marinko; Ducea, Mihai; Stojadinovic, Uros

    2010-05-01

    Formation of large extensional detachments during orogenic collapse can follow inherited weakness zones such as major asymmetries given by pre-existing subduction zones active during mountain building processes. This is valid in particular in low-topography foreland coupling orogens of Mediterranean type where large amounts of deformation is concentrated in their lower plates, favoring weakness zones activated during a subsequent phase of extensional collapse. One good place to study the orogenic collapse post-dating major collision is the NE margin of the Dinarides in central and western Serbia, where Cretaceous-Eocene shortening and collision was recorded in the Alpine Tethys Sava zone between the European-derived Dacia and Tisza mega-units and the lower Adriatic plate. This is the same place where the Pannonian basin formed as a Miocene back-arc basin in response to a different subduction and roll-back taking place along the external Carpathians. A lineament of Paleogene and Miocene plutons is observed at the northern and eastern margin of the Dinarides, interpreted to be the product of both syn- to post-orogenic subduction magmatism and of decompressional melting during the Pannonian extension. Two of these plutons, Cer and Bukulja, located in western and respectively central Serbia, are intruded in the Jadar-Kopaonik composite thrust sheet, part of the lower Adriatic plate, near the contact with the main suture formed during the Cretaceous-Eocene subduction of the Sava zone. The Lower Miocene age (19-17Ma) Bukulja intrusion is a S-type granite with rare aplitic veins (Cvetkovic et al., 2007). The Cer intrusive complex is a S type two mica granite of around 16Ma in age with an older I-type quartz monzonite component (Koroneos et al. in press). Both granitoids are intruded into the Jadar-Kopaonik metamorphic series, which are in direct contact along the northern, eastern and southern flank with non-metamorphosed, mainly clastic sediments of Cretaceous-Miocene in

  4. Effect of aromatic SAMs molecules on graphene/silicon schottky diode performance

    OpenAIRE

    Yağmurcukardeş, Nesli; Aydın, Hasan; Can, Mustafa; Yanılmaz, Alper; Mermer, Ömer; Okur, Salih; Selamet, Yusuf

    2016-01-01

    Au/n-Si/Graphene/Au Schottky diodes were fabricated by transferring atmospheric pressure chemical vapor deposited (APCVD) graphene on silicon substrates. Graphene/n-Si interface properties were improved by using 5-[(3-methylphenyl)(phenyl) amino]isophthalic acid (MePIFA) and 5-(diphenyl)amino]isophthalic acid (DPIFA) aromatic self-assembled monolayer (SAM) molecules. The surface morphologies of modified and non-modified films were investigated by atomic force microscopy and scanning electron ...

  5. Electrical degradation of double-Schottky barrier in ZnO varistors

    Energy Technology Data Exchange (ETDEWEB)

    He, Jinliang, E-mail: hejl@tsinghua.edu.cn; Cheng, Chenlu; Hu, Jun [The State Key Lab of Power System, Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

    2016-03-15

    Researches on electrical degradation of double-Schottky barrier in ZnO varistors are reviewed, aimed at the constitution of a full picture of universal degradation mechanism within the perspective of defect. Recent advances in study of ZnO materials by atomic-scale first-principles calculations are partly included and discussed, which brings to our attention distinct cognition on the native point defects and their profound impact on degradation.

  6. Tunable Schottky diodes fabricated from crossed electrospun SnO{sub 2}/PEDOT-PSSA nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Carrasquillo, Katherine V. [Department of Physics and Electronics, University of Puerto Rico-Humacao, Humacao, PR 00792 (Puerto Rico); Pinto, Nicholas J., E-mail: nicholas.pinto@upr.edu [Department of Physics and Electronics, University of Puerto Rico-Humacao, Humacao, PR 00792 (Puerto Rico)

    2012-06-25

    Graphical abstract: Crossed SnO{sub 2}/PEDOT-PSSA nanoribbon Schottky diodes. Highlight: Black-Right-Pointing-Pointer An inexpensive electrospinning technique is used to fabricate crossed nanoribbons of n-doped tin oxide and p-PEDOT. Black-Right-Pointing-Pointer Each intersection is a localized Schottky diode that is completely exposed to the environment after electrodes deposition. Black-Right-Pointing-Pointer This makes it useful as a gas and light sensor. Black-Right-Pointing-Pointer In addition, the ability to tune the diode parameters via a back gate truly makes this device multifunctional. Black-Right-Pointing-Pointer A half wave rectifier has been demonstrated with this device under UV illumination. - Abstract: Schottky diodes have been fabricated on doped Si/SiO{sub 2} substrates in air, by simply crossing individual electrospun tin oxide (SnO{sub 2}) and poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT-PSSA) nanoribbons. The conductivity of PEDOT-PSSA was {approx}6 S/cm with no observable field effect, while SnO{sub 2} exhibited n-doped field effect behavior with a charge mobility of {approx}3.1 cm{sup 2}/V-s. The diodes operate in air or in vacuum, under ambient illumination or in the dark, with low turn-on voltages and device parameters that are tunable via a back gate bias or a UV light source. Their unique design involves a highly localized active region that is completely exposed to the surrounding environment, making them potentially attractive for use as sensors. The standard thermionic emission model of a Schottky junction was applied to analyze the forward bias diode characteristics and was successfully tested as a half wave rectifier.

  7. Far-ir heterodyne radiometric measurements with quasioptical Schottky diode mixers

    International Nuclear Information System (INIS)

    Fetterman, H.R.; Tannenwald, P.E.; Clifton, B.J.; Parker, C.D.; Fitzgerald, W.D.; Erickson, N.R.

    1978-01-01

    We have made heterodyne radiometric measurements with GaAs Schottky diode mixers, mounted in a corner-reflector configuration, over the spectral range 170 μm to 1 mm. At 400 μm, system noise temperatures of 9700 K DSB (NEP=1.4 x 10 - 19 W/Hz) and mixer noise temperatures of 5900 K have been achieved. This same quasioptical mixer has also been used to generate 10 - 7 W of tunable radiation suitable for spectroscopic applications

  8. Si and SiC Schottky diodes in smart power circuits: a comparative study by I-V-T and C-V measurements

    Energy Technology Data Exchange (ETDEWEB)

    Hadzi-Vukovic, J [Infineon Technologies, Siemensstrasse 2, 9500 Villach (Austria); Jevtic, M [Institute for Physics, Pregrevica 118, 11080 Zemun (Serbia and Montenegro); Rothleitner, H [Infineon Technologies, Siemensstrasse 2, 9500 Villach (Austria); Croce, P Del [Infineon Technologies, Siemensstrasse 2, 9500 Villach (Austria)

    2005-01-01

    In this paper we analyze a possibility of manufacturing and implementation of Schottky diodes in the smart power circuits. Three different Schottky diodes, in three different technologies, are realized in Si and SiC processes. The electrical characterizations with I-V-T and C-V measurements are done for all structures. It is shown that Si based Schottky diodes also are suitable to be integrated in the typical smart power circuits.

  9. Si and SiC Schottky diodes in smart power circuits: a comparative study by I-V-T and C-V measurements

    International Nuclear Information System (INIS)

    Hadzi-Vukovic, J; Jevtic, M; Rothleitner, H; Croce, P Del

    2005-01-01

    In this paper we analyze a possibility of manufacturing and implementation of Schottky diodes in the smart power circuits. Three different Schottky diodes, in three different technologies, are realized in Si and SiC processes. The electrical characterizations with I-V-T and C-V measurements are done for all structures. It is shown that Si based Schottky diodes also are suitable to be integrated in the typical smart power circuits

  10. Fabrication and characterization of Au/n-CdTe Schottky barrier under illumination and dark

    Science.gov (United States)

    Bera, Swades Ranjan; Saha, Satyajit

    2018-04-01

    CdTe nanoparticles have been grown by chemical reduction method using EDA as capping agent. These are used to fabricate Schottky barrier in a simple cost-effective way at room temperature. The grown nanoparticles are structurally characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM). The optical properties of nano CdTe is characterized by UV-Vis absorption spectra, PL spectra. The band gap of the CdTe nanoparticles is increased as compared to CdTe bulk form indicating there is blue shift. The increase of band gap is due to quantum confinement. Photoluminescence spectra shows peak which corresponds to emission from surface state. CdTe nanofilm is grown on ITO coated glass substrate by dipping it on toluene containing dispersed CdTe nanoparticles. Schottky barrier of Au/n-CdTe is fabricated on ITO coated glass by vacuum deposition of gold. I- V and C- V characteristics of Au/n-CdTe Schottky barrier junction have been studied under dark and light condition. It is found that these characteristics are influenced by surface or interface traps. The values of barrier height, ideality factor, donor concentration and series resistance are obtained from the reverse bias capacitance-voltage measurements.

  11. Tunable Schottky barrier and high responsivity in graphene/Si-nanotip optoelectronic device

    Science.gov (United States)

    Di Bartolomeo, Antonio; Giubileo, Filippo; Luongo, Giuseppe; Iemmo, Laura; Martucciello, Nadia; Niu, Gang; Fraschke, Mirko; Skibitzki, Oliver; Schroeder, Thomas; Lupina, Grzegorz

    2017-03-01

    We demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity (3 {{A}} {{{W}}}-1 for white LED light at 3 {{mW}} {{{cm}}}-2 intensity) almost an order of magnitude higher than commercial photodiodes. We extensively characterize the voltage and the temperature dependence of the device parameters, and prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. We also introduce a new phenomenological graphene/semiconductor diode equation, which well describes the experimental I-V characteristics both in forward and reverse bias.

  12. Impact of substrate off-angle on the m-plane GaN Schottky diodes

    Science.gov (United States)

    Yamada, Hisashi; Chonan, Hiroshi; Takahashi, Tokio; Shimizu, Mitsuaki

    2018-04-01

    We investigated the effects of the substrate off-angle on the m-plane GaN Schottky diodes. GaN epitaxial layers were grown by metal-organic chemical vapor deposition on m-plane GaN substrates having an off-angle of 0.1, 1.1, 1.7, or 5.1° toward [000\\bar{1}]. The surface of the GaN epitaxial layers on the 0.1°-off substrate consisted of pyramidal hillocks and contained oxygen (>1017 cm-3) and carbon (>1016 cm-3) impurities. The residual carbon and oxygen impurities decreased to current of the 0.1°-off m-plane GaN Schottky diodes originated from the +c facet of the pyramidal hillocks. The leakage current was efficiently suppressed through the use of an off-angle that was observed to be greater than 1.1°. The off-angle of the m-plane GaN substrate is critical in obtaining high-performance Schottky diodes.

  13. InGaAs/InP heteroepitaxial Schottky barrier diodes for terahertz applications

    Science.gov (United States)

    Bhapkar, Udayan V.; Li, Yongjun; Mattauch, Robert J.

    1992-01-01

    This paper explores the feasibility of planar, sub-harmonically pumped, anti-parallel InGaAs/InP heteroepitaxial Schottky diodes for terahertz applications. We present calculations of the (I-V) characteristics of such diodes using a numerical model that considers tunneling. We also present noise and conversion loss predictions of diode mixers operated at 500 GHz, and obtained from a multi-port mixer analysis, using the I-V characteristics predicted by our model. Our calculations indicate that InGaAs/InP heteroepitaxial Schottky barrier diodes are expected to have an I-V characteristic with an ideality factor comparable to that of GaAs Schottky diodes. However, the reverse saturation current of InGaAs/InP diodes is expected to be much greater than that of GaAs diodes. These predictions are confirmed by experiment. The mixer analyses predict that sub-harmonically pumped anti-parallel InGaAs/InP diode mixers are expected to offer a 2 dB greater conversion loss and a somewhat higher single sideband noise temperature than their GaAs counterparts. More importantly, the InGaAs/InP devices are predicted to require only one-tenth of the local oscillator power required by similar GaAs diodes.

  14. 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF

    Science.gov (United States)

    Chattopadhyay, Goutam; Schlecht, Erich T.; Lee, Choonsup; Lin, Robert H.; Gill, John J.; Mehdi, Imran; Sin, Seth; Deal, William; Loi, Kwok K.; Nam, Peta; hide

    2012-01-01

    GaAs-based, sub-harmonically pumped Schottky diode mixers offer a number of advantages for array implementation in a heterodyne receiver system. Since the radio frequency (RF) and local oscillator (LO) signals are far apart, system design becomes much simpler. A proprietary planar GaAs Schottky diode process was developed that results in very low parasitic anodes that have cutoff frequencies in the tens of terahertz. This technology enables robust implementation of monolithic mixer and frequency multiplier circuits well into the terahertz frequency range. Using optical and e-beam lithography, and conventional epitaxial layer design with innovative usage of GaAs membranes and metal beam leads, high-performance terahertz circuits can be designed with high fidelity. All of these mixers use metal waveguide structures for housing. Metal machined structures for RF and LO coupling hamper these mixers to be integrated in multi-pixel heterodyne array receivers for spectroscopic and imaging applications. Moreover, the recent developments of terahertz transistors on InP substrate provide an opportunity, for the first time, to have integrated amplifiers followed by Schottky diode mixers in a heterodyne receiver at these frequencies. Since the amplifiers are developed on a planar architecture to facilitate multi-pixel array implementation, it is quite important to find alternative architecture to waveguide-based mixers.

  15. Effect of inhomogeneous Schottky barrier height of SnO2 nanowires device

    Science.gov (United States)

    Amorim, Cleber A.; Bernardo, Eric P.; Leite, Edson R.; Chiquito, Adenilson J.

    2018-05-01

    The current–voltage (I–V) characteristics of metal–semiconductor junction (Au–Ni/SnO2/Au–Ni) Schottky barrier in SnO2 nanowires were investigated over a wide temperature range. By using the Schottky–Mott model, the zero bias barrier height Φ B was estimated from I–V characteristics, and it was found to increase with increasing temperature; on the other hand the ideality factor (n) was found to decrease with increasing temperature. The variation in the Schottky barrier and n was attributed to the spatial inhomogeneity of the Schottky barrier height. The experimental I–V characteristics exhibited a Gaussian distribution having mean barrier heights {\\overline{{{Φ }}}}B of 0.30 eV and standard deviation σ s of 60 meV. Additionally, the Richardson modified constant was obtained to be 70 A cm‑2 K‑2, leading to an effective mass of 0.58m 0. Consequently, the temperature dependence of I–V characteristics of the SnO2 nanowire devices can be successfully explained on the Schottky–Mott theory framework taking into account a Gaussian distribution of barrier heights.

  16. Thermal activation of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height

    International Nuclear Information System (INIS)

    Guo-Ping, Ru; Rong, Yu; Yu-Long, Jiang; Gang, Ruan

    2010-01-01

    This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I-V-T curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage V j , excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, V j needs to be smaller than the barrier height ø. With proper scheme of series resistance connection where the condition of V j > ø is guaranteed, I-V-T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I-V-T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I-V-T curves only for small barrier height inhomogeneity. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. External electric field effects on Schottky barrier at Gd3N@C80/Au interface

    Science.gov (United States)

    Onishi, Koichi; Nakashima, Fumihiro; Jin, Ge; Eto, Daichi; Hattori, Hayami; Miyoshi, Noriko; Kirimoto, Kenta; Sun, Yong

    2017-08-01

    The effects of the external electric field on the height of the Schottky barrier at the Gd3N@C80/Au interface were studied by measuring current-voltage characteristics at various temperatures from 200 K to 450 K. The Gd3N@C80 sample with the conduction/forbidden/valence energy band structure had a face-centered cubic crystal structure with the average grain size of several nanometers. The height of the Gd3N@C80/Au Schottky barrier was confirmed to be 400 meV at a low electric field at room temperature. Moreover, the height decreases with the increasing external electric field through a change of permittivity in the Gd3N@C80 sample due to a polarization of the [Gd3] 9 +-[N3 -+("separators="|C80 ) 6 -] dipoles in the Gd3N@C80 molecule. The field-dependence of the barrier height can be described using a power math function of the electric field strength. The results of the field-dependent barrier height indicate that the reduction in the Schottky barrier is due to an image force effect of the transport charge carrier at the Gd3N@C80/Au interface.

  18. Mo1-xWxSe2-Based Schottky Junction Photovoltaic Cells.

    Science.gov (United States)

    Yi, Sum-Gyun; Kim, Sung Hyun; Park, Sungjin; Oh, Donggun; Choi, Hwan Young; Lee, Nara; Choi, Young Jai; Yoo, Kyung-Hwa

    2016-12-14

    We developed Schottky junction photovoltaic cells based on multilayer Mo 1-x W x Se 2 with x = 0, 0.5, and 1. To generate built-in potentials, Pd and Al were used as the source and drain electrodes in a lateral structure, and Pd and graphene were used as the bottom and top electrodes in a vertical structure. These devices exhibited gate-tunable diode-like current rectification and photovoltaic responses. Mo 0.5 W 0.5 Se 2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe 2 and WSe 2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo 0.5 W 0.5 Se 2 devices. Furthermore, we showed that Mo 0.5 W 0.5 Se 2 -based vertical Schottky diodes yield a power conversion efficiency of ∼16% under 532 nm light and ∼13% under a standard air mass 1.5 spectrum, demonstrating their remarkable potential for photovoltaic applications.

  19. Capacitance properties and simulation of the AlGaN/GaN Schottky heterostructure

    International Nuclear Information System (INIS)

    Harmatha, Ladislav; Ľubica, Stuchlíková; Juraj, Racko; Juraj, Marek; Juraj, Pecháček; Peter, Benko; Michal, Nemec; Juraj, Breza

    2014-01-01

    Highlights: • Dependences of CV characteristics of the AlGaN/GaN structure on frequency and temperature variations. • Identification of electrical activity of defects by capacitance DLTS. • Simulating the properties of the GaN/Al 0.2 GaN 0.8 /GaN Schottky heterostructure. - Abstract: The paper presents the results of capacitance measurements on GaN/AlGaN/GaN Schottky heterostructures grown on an Al 2 O 3 substrate by Low-Pressure Metal–Organic Vapour-Phase Epitaxy (LP-MOVPE). Dependences of the capacitance–voltage (CV) characteristics on the frequency of the measuring signal allow analysing the properties of the 2D electron gas (2DEG) at the AlGaN/GaN heterojunction. Exact location of the hetero-interface below the surface (20 nm) was determined from the concentration profile. Temperature variations of the CV curves reveal the influence of bulk defects in GaN and of the traps at the AlGaN/GaN interface. Electrical activity of these defects was characterized by capacitance Deep Level Transient Fourier Spectroscopy (DLTFS). Experimental results of CV measurements were supported by simulating the properties of the GaN/Al 0.2 GaN 0.8 /GaN Schottky heterostructure in dependence on the influence of the concentration of donor-like traps in GaN and of the temperature upon the CV curves

  20. Analytical modeling of Schottky tunneling source impact ionization MOSFET with reduced breakdown voltage

    Directory of Open Access Journals (Sweden)

    Sangeeta Singh

    2016-03-01

    Full Text Available In this paper, we have investigated a novel Schottky tunneling source impact ionization MOSFET (STS-IMOS to lower the breakdown voltage of conventional impact ionization MOS (IMOS and developed an analytical model for the same. In STS-IMOS there is an accumulative effect of both impact ionization and source induced barrier tunneling. The silicide source offers very low parasitic resistance, the outcome of which is an increment in voltage drop across the intrinsic region for the same applied bias. This reduces operating voltage and hence, it exhibits a significant reduction in both breakdown and threshold voltage. STS-IMOS shows high immunity against hot electron damage. As a result of this the device reliability increases magnificently. The analytical model for impact ionization current (Iii is developed based on the integration of ionization integral (M. Similarly, to get Schottky tunneling current (ITun expression, Wentzel–Kramers–Brillouin (WKB approximation is employed. Analytical models for threshold voltage and subthreshold slope is optimized against Schottky barrier height (ϕB variation. The expression for the drain current is computed as a function of gate-to-drain bias via integral expression. It is validated by comparing it with the technology computer-aided design (TCAD simulation results as well. In essence, this analytical framework provides the physical background for better understanding of STS-IMOS and its performance estimation.