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Sample records for junction barrier schottky

  1. Measuring Schottky barrier height at graphene/SiC junction

    Science.gov (United States)

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

    2014-03-01

    When graphene is interfaced with a semiconductor, a Schottky junction forms with rectifying properties. In this work, we measured the Schottky barrier heights of graphene/SiC Schottky diodes using current-voltage (I-V) measurement. Chemical vapor deposited graphene was transferred onto semiconductor surfaces of opposite polarization: the hydrogen-terminated Si- and C-faces of α-SiC, which was confirmed by Raman spectroscopy and scanning tunneling microscopy. The Schottky barrier height is found to be sensitive to the polarization of the substrate and surface preparation. On the Si-face, a barrier of 0.47 eV is found. These results will be compared with earlier work as well as our in situ scanning tunneling spectroscopy results. Supported by DOE (DE-FG02-07ER46228).

  2. 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...

  3. Characteristics of Schottky Barrier Junction Based on Hexagonal Microtube ZnO

    Institute of Scientific and Technical Information of China (English)

    GAO Hui; LI Yan; YANG Li-ping; DENG Hong

    2005-01-01

    Hexagonal microtube ZnO was firstly grown on single crystal p-Si (111) substrates by hydrothermal method, and fabricated Ag/n-ZnO and Au/n-ZnO Schottky junction. Schottky effective barrier heights were calculated by I-V measurement. It is confirmed that the presence of a large amount of surface states related possibly to lattice imperfections existed near the surface leads to the pinning of the surface Fermi level at 0.35 eV below the conduction-band edge. Then the fabricated Schottky barrier junctions are evaluated for their use as UV photodetectors.

  4. Intrinsic inhomogeneity in barrier height at monolayer graphene/SiC Schottky junction

    Science.gov (United States)

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2014-07-01

    Graphene interfaced with a semiconductor forms a Schottky junction with rectifying properties. The inherent spatial inhomogeneity due to the formation of ripples and ridges in graphene can lead to fluctuations in the Schottky barrier height (SBH). The non-ideal behavior of the temperature dependent barrier height and ideality factor greater than 4 can be attributed to these spatial inhomogeneities. Assuming a Gaussian distribution of the barrier, mean SBHs of 1.30 ± 0.18 eV and 1.16 ± 0.16 eV are found for graphene/SiC junctions on the C- and Si-face, respectively. These findings reveal intrinsic spatial inhomogeneities in the SBHs in graphene based Schottky junctions.

  5. Optimized design of 4H-SiC floating junction power Schottky barrier diodes

    Institute of Scientific and Technical Information of China (English)

    Pu Hongbin; Cao Lin; Chen Zhiming; Ren Jie

    2009-01-01

    SiC floating junction Schottky barrier diodes were simulated with software MEDICI 4.0 and their device structures were optimized based on forward and reverse electrical characteristics.Compared with the conventional power Schottky barrier diode,the device structure is featured by a highly doped drift region and embedded floating junction region,which can ensure high breakdown voltage while keeping lower specific on-state resistance,solved the contradiction between forward voltage drop and breakdown voltage.The simulation results show that with optimized structure parameter,the breakdown voltage Can reach 4 kV and the specific on-resistance is 8.3 mΩ·cm2.

  6. Silicon Carbide Schottky Barrier Diode

    Science.gov (United States)

    Zhao, Jian H.; Sheng, Kuang; Lebron-Velilla, Ramon C.

    2004-01-01

    This chapter reviews the status of SiC Schottky barrier diode development. The fundamental of Schottky barrier diodes is first provided, followed by the review of high-voltage SiC Schottky barrier diodes, junction-barrier Schottky diodes, and merged-pin-Schottky diodes. The development history is reviewed ad the key performance parameters are discussed. Applications of SiC SBDs in power electronic circuits as well as other areas such as gas sensors, microwave and UV detections are also presented, followed by discussion of remaining challenges.

  7. Characterization of deep electron traps in 4H-SiC Junction Barrier Schottky rectifiers

    Science.gov (United States)

    Gelczuk, Ł.; Dąbrowska-Szata, M.; Sochacki, M.; Szmidt, J.

    2014-04-01

    Conventional deep level transient spectroscopy (DLTS) technique was used to study deep electron traps in 4H-SiC Junction Barrier Schottky (JBS) rectifiers. 4H-SiC epitaxial layers, doped with nitrogen and grown on standard n+-4H-SiC substrates were exposed to low-dose aluminum ion implantation process under the Schottky contact in order to form both JBS grid and junction termination extension (JTE), and assure good rectifying properties of the diodes. Several deep electron traps were revealed and attributed to impurities or intrinsic defects in 4H-SiC epitaxial layers, on the basis of comparison of their electrical parameters (i.e. activation energies, apparent capture cross sections and concentrations) with previously published results.

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

    Institute of Scientific and Technical Information of China (English)

    Chen Fengping; Zhang Yuming; Lü 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 Ptype 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen Fengping; Zhang Yuming; Lue Hongliang; Zhang Yimen; Guo Hui; Guo Xin, E-mail: fpchen@yeah.net [School of Microelectronics, Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, Xidian University, Xi' an 710071 (China)

    2011-06-15

    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)

  10. Study of Au, Ni-(n)ZnSe Thin Film Schottky Barrier Junctions

    Science.gov (United States)

    Chaliha, Sumbit; Borah, Mothura Nath; Sarmah, P. C.; Rahman, A.

    2010-10-01

    Schottky barrier junctions of Al-doped n-type Zinc selenide (ZnSe) thin films of doping concentrations up to 9.7 × 1014 cm -3 have been fabricated with Au and Ni electrodes on glass substrates by sequential thermal evaporation. All of the junctions of different doping concentrations exhibited rectifying current-voltage characteristics with a non-saturating reverse current. From the current-voltage characteristics, the different junction parameters such as ideality factor, saturation current density, series resistance, etc., were measured. Both types of junctions were found to possess a high ideality factor and a high series resistance. The barrier heights of the junctions were measured from Richardson plots and found to be around 0.8 eV. The structures were found to exhibit a poor photovoltaic effect with a fill factor not greater than 0.4. The diode quality as well as the photovoltaic performance of the diodes were improved following a short heat treatment in vacuum.

  11. Schottky barrier modulation of metal/4H-SiC junction with thin interface spacer driven by surface polarization charge on 4H-SiC substrate

    Science.gov (United States)

    Choi, Gahyun; Yoon, Hoon Hahn; Jung, Sungchul; Jeon, Youngeun; Lee, Jung Yong; Bahng, Wook; Park, Kibog

    2015-12-01

    The Au/Ni/Al2O3/4H-SiC junction with the Al2O3 film as a thin spacer layer was found to show the electrical characteristics of a typical rectifying Schottky contact, which is considered to be due to the leakiness of the spacer layer. The Schottky barrier of the junction was measured to be higher than an Au/Ni/4H-SiC junction with no spacer layer. It is believed that the negative surface bound charge originating from the spontaneous polarization of 4H-SiC causes the Schottky barrier increase. The use of a thin spacer layer can be an efficient experimental method to modulate Schottky barriers of metal/4H-SiC junctions.

  12. Plastic Schottky barrier solar cells

    Science.gov (United States)

    Waldrop, James R.; Cohen, Marshall J.

    1984-01-24

    A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.

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

    Science.gov (United States)

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

    2013-09-01

    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·cm2 with a total active area of 2.46 × 10-3 cm2. 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.

  14. Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier.

    Science.gov (United States)

    Liu, Yuanyue; Stradins, Paul; Wei, Su-Huai

    2016-04-01

    Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications.

  15. Effect of gating and pressure on the electronic transport properties of crossed nanotube junctions: formation of a Schottky barrier

    Energy Technology Data Exchange (ETDEWEB)

    Havu, P; Hashemi, M J; Kaukonen, M; Nieminen, R M [Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto (Finland); Seppaelae, E T [Nokia Research Center, Itaemerenkatu 11-13, FI-00180 Helsinki (Finland)

    2011-03-23

    The electronic transport properties of crossed carbon nanotube junctions are investigated using ab initio methods. The optimal atomic structures and the intertube distances of the junctions are obtained using van der Waals corrected density functional theory. The effect of gating on the intertube conductance of the junctions is explored, showing the charge accumulation to the nanotube contact and the charge depletion region at the metal-semiconductor Schottky contact. Finally, it is shown how the conductance of the junctions under the gate voltage is affected by pressure applied to the nanotube film. (fast track communication)

  16. Optimum Barrier Height for SiC Schottky Barrier Diode

    OpenAIRE

    Mohamed Abd El-Latif; Alaa El-Din Sayed Hafez

    2013-01-01

    The study of barrier height control and optimization for Schottky barrier diode (SBD) from its physical parameters have been introduced using particle swarm optimization (PSO) algorithm. SBD is the rectifying barrier for electrical conduction across the metal semiconductor (MS) junction and, therefore, is of vital importance to the successful operation of any semiconductor device. 4H-SiC is used as a semiconductor material for its good electrical characteristics with high-power semiconductor ...

  17. Plastic Schottky-barrier solar cells

    Science.gov (United States)

    Waldrop, J.R.; Cohen, M.J.

    1981-12-30

    A photovoltaic cell structure is fabricated from an active medium including an undoped polyacetylene, organic semiconductor. When a film of such material is in rectifying contact with a metallic area electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates a magnesium layer on the undoped polyacetylene film. With the proper selection and location of elements a photovoltaic cell structure and solar cell are obtained.

  18. Radioisotope battery using Schottky barrier devices

    Energy Technology Data Exchange (ETDEWEB)

    Manasse, F.K. (Drexel Univ., Philadelphia); Tse, A.N.

    1976-05-01

    Based on the well-known betavoltaic effect, a new nuclear battery, which uses a Schottky barrier, has been used in place of the more standard p-n junction diode, along with /sup 147/Pm metal film rather than Pm/sub 2/O/sub 3/ oxide, as in the commercially available Betacel. Measurement of absorption, conversion efficiency, thickness, etc., as functions of resistivity and other cell parameters, and assessment of performance are being researched to design a prototype battery.

  19. Effect of graphene tunnel barrier on Schottky barrier height of Heusler alloy Co2MnSi/graphene/n-Ge junction

    Science.gov (United States)

    Gui-fang, Li; Jing, Hu; Hui, Lv; Zhijun, Cui; Xiaowei, Hou; Shibin, Liu; Yongqian, Du

    2016-02-01

    We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co2MnSi and the germanium (Ge) channel modulates the Schottky barrier height and the resistance-area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height (SBH) occurs following the insertion of the graphene layer between Co2MnSi and Ge. The electron SBH is modulated in the 0.34 eV-0.61 eV range. Furthermore, the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility. Project supported by the National Natural Science Foundation of China (Grant No. 61504107) and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 3102014JCQ01059 and 3102015ZY043).

  20. Experimental and numerical analyses of high voltage 4H-SiC junction barrier Schottky rectifiers with linearly graded field limiting ring

    Science.gov (United States)

    Wang, Xiang-Dong; Deng, Xiao-Chuan; Wang, Yong-Wei; Wang, Yong; Wen, Yi; Zhang, Bo

    2014-05-01

    This paper describes the successful fabrication of 4H-SiC junction barrier Schottky (JBS) rectifiers with a linearly graded field limiting ring (LG-FLR). Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2 (about 80% of the theoretical value). Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termination, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length.

  1. Surge current capabilities and isothermal current-voltage characteristics of high-voltage 4H-SiC junction barrier Schottky rectifiers

    Science.gov (United States)

    Palmour, J. W.; Levinshtein, M. E.; Ivanov, P. A.; Zhang, Q. J.

    2015-06-01

    Isothermal forward current-voltage characteristics of high-voltage 4H-SiC junction barrier Schottky rectifiers (JBS) have been studied for the first time. Isothermal characteristics were measured with JBS having a blocking voltage of 1700 V up to a current density j  ≈  4200 A cm-2 in the temperature range 297-460 K. Quasi-isothermal current-voltage characteristics of these devices were studied with injection of minority carriers (holes) up to j  ≈  7200 A cm-2 and ambient temperatures of 297 and 460 K. The isothermal forward current-voltage characteristics make it possible to numerically calculate (for example, by an iteration procedure) the overheating in an arbitrary operation mode.

  2. Influence of three-dimensional p-buried layer pattern on the performance of 4H-SiC floating junction Schottky barrier diode

    Science.gov (United States)

    Yang, Shuai; Zhang, Yuming; Song, Qingwen; Tang, Xiaoyan; Zhang, Yimen; Huo, Tianjia; Liu, Sicheng; Yuan, Hao

    2015-10-01

    4H-SiC floating junction Schottky barrier diodes (FJ-SBDs) are excellent SiC devices with high Baliga’s figure of merit (BFOM). However, the p-type buried layers in epilayers partially obstruct the current paths, and increase the on-resistance, while the buried layers of dot patterns can reduce the obstruction. In this paper, a three-dimensional (3D) simulation of 4H-SiC FJ-SBDs with dot patterns is reported for the first time. By comparing the results obtained from stripe, square, octagon, and circle patterns, dot patterns are proved to be good choices for buried layers in 4H-SiC FJ-SBDs, and the FJ-SBD with the circle pattern has the highest BFOM of 12.09 GW/cm2, which is 22.62% greater than that of the FJ-SBD with the stripe pattern.

  3. Graphene applications in Schottky barrier solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lancellotti, L., E-mail: laura.lancellotti@enea.it [ENEA Research Centre Portici, Piazzale E. Fermi 1, 80055 Portici (Napoli) (Italy); Polichetti, T.; Ricciardella, F. [ENEA Research Centre Portici, Piazzale E. Fermi 1, 80055 Portici (Napoli) (Italy); Tari, O., E-mail: orlando.tari@unina.it [University of Naples ' Federico II' , Dept. of Electronic Engineering, Via Claudio 21, 80125 Napoli (Italy); Gnanapragasam, S. [ENEA Research Centre Portici, Piazzale E. Fermi 1, 80055 Portici (Napoli) (Italy); Daliento, S. [University of Naples ' Federico II' , Dept. of Electronic Engineering, Via Claudio 21, 80125 Napoli (Italy); Di Francia, G. [ENEA Research Centre Portici, Piazzale E. Fermi 1, 80055 Portici (Napoli) (Italy)

    2012-11-01

    We report a theoretical study about the performances of graphene on semiconductor Schottky barrier solar cells with the aim to show the potentiality of this kind of device. The simulations are carried by a generalized equivalent circuit model, where the circuital parameters are strictly dependent on the physical properties of the graphene and semiconductor which form the Schottky junction. We have realized graphene samples and characterized them by optical and atomic force microscopy, and Raman spectroscopy. Capacitance-voltage measurements have been made on some 'ad hoc' graphene based devices in order to obtain graphene workfunction, a very essential physical parameter. The estimated value is compatible with four layer graphene. This result is in agreement with the morphological characterizations of our material. - Highlights: Black-Right-Pointing-Pointer An equivalent circuit model simulates graphene based Schottky barrier solar cells. Black-Right-Pointing-Pointer Graphene flakes are identified through Raman spectroscopy and Atomic Force Microscopy. Black-Right-Pointing-Pointer Workfunction estimation by Capacitance-Voltage (C-V) on graphene based devices Black-Right-Pointing-Pointer A multilayered structure is evidenced by morphological and C-V characterization.

  4. Simulation of low Schottky barrier MOSFETs using an improved Multi-subband Monte Carlo model

    Science.gov (United States)

    Gudmundsson, Valur; Palestri, Pierpaolo; Hellström, Per-Erik; Selmi, Luca; Östling, Mikael

    2013-01-01

    We present a simple and efficient approach to implement Schottky barrier contacts in a Multi-subband Monte Carlo simulator by using the subband smoothening technique to mimic tunneling at the Schottky junction. In the absence of scattering, simulation results for Schottky barrier MOSFETs are in agreement with ballistic Non-Equilibrium Green's Functions calculations. We then include the most relevant scattering mechanisms, and apply the model to the study of double gate Schottky barrier MOSFETs representative of the ITRS 2015 high performance device. Results show that a Schottky barrier height of less than approximately 0.15 eV is required to outperform the doped source/drain structure.

  5. Current voltage analysis and band diagram of Ti/TiO{sub 2} nanotubes Schottky junction

    Energy Technology Data Exchange (ETDEWEB)

    Mini, P.A.; Sherine, Alex; Shalumon, K.T.; Balakrishnan, Avinash; Nair, S.V.; Subramanian, K.R.V. [Amrita Vishwa Vidyapeetham (University), Amrita Centre for Nanosciences and Molecular Medicine, Kochi (India)

    2012-08-15

    Here, we report on how the energy band diagram of a nanostructured semiconductor- metal interface aligns in accordance with semiconductor morphology. Electrochemically, titanium metal is anodized to form titanium dioxide nanotubes, which forms a junction with the free Ti substrate and this junction forms a natural Schottky barrier. With reduced dimensionality of the nanotube structures (lower wall thickness), we have observed band edge movements and band gap quantum confinement effects and lowering of the Schottky barrier. These results were corroborated with the help of cyclic voltammetry, ultraviolet-visible spectrometry, and impedance analysis. Current voltage analysis of the Schottky barrier showed a lowering of the barrier (by 25 %) with reducing dimensionality of the nanotube structures. At externally applied voltages higher than the Schottky barrier, charges can travel along the nanotubes and reside at an interface between the nanotubes and a high-{kappa} dielectric. This property was utilized to develop high surface area solid-state capacitors. (orig.)

  6. Current voltage analysis and band diagram of Ti/TiO2 nanotubes Schottky junction

    Science.gov (United States)

    Mini, P. A.; Sherine, Alex; Shalumon, K. T.; Balakrishnan, Avinash; Nair, S. V.; Subramanian, K. R. V.

    2012-08-01

    Here, we report on how the energy band diagram of a nanostructured semiconductor- metal interface aligns in accordance with semiconductor morphology. Electrochemically, titanium metal is anodized to form titanium dioxide nanotubes, which forms a junction with the free Ti substrate and this junction forms a natural Schottky barrier. With reduced dimensionality of the nanotube structures (lower wall thickness), we have observed band edge movements and band gap quantum confinement effects and lowering of the Schottky barrier. These results were corroborated with the help of cyclic voltammetry, ultraviolet-visible spectrometry, and impedance analysis. Current voltage analysis of the Schottky barrier showed a lowering of the barrier (by 25 %) with reducing dimensionality of the nanotube structures. At externally applied voltages higher than the Schottky barrier, charges can travel along the nanotubes and reside at an interface between the nanotubes and a high- κ dielectric. This property was utilized to develop high surface area solid-state capacitors.

  7. Analytical models of on-resistance and breakdown voltage for 4H-SiC floating junction Schottky barrier diodes

    Science.gov (United States)

    Yuan, Hao; Tang, Xiaoyan; Song, Qingwen; Zhang, Yimen; Zhang, Yuming; Yang, Fei; Niu, Yingxi

    2015-01-01

    The analytical models of on-resistance and reverse breakdown voltage for 4H-SiC floating junction SBD are presented with the analysis of the transport path of the carriers and electric field distribution in the drift region. The calculation results from the analytical models well agree with the simulation results. The effects of the key structure parameters on specific on-resistance and breakdown voltage are described respectively by analytical models. Moreover, the relationship between BFOM and parameters of floating junction are investigated. It is proved that the analytical models are more convenient for the design of the floating junction SBDs.

  8. Carrier transport in reverse-biased graphene/semiconductor Schottky junctions

    Science.gov (United States)

    Tomer, D.; Rajput, S.; Hudy, L. J.; Li, C. H.; Li, L.

    2015-04-01

    Reverse-biased graphene (Gr)/semiconductor Schottky diodes exhibit much enhanced sensitivity for gas sensing. However, carrier transport across these junctions is not fully understood yet. Here, Gr/SiC, Gr/GaAs, and Gr/Si Schottky junctions under reverse bias are investigated by temperature-dependent current-voltage measurements. A reduction in barrier height with increasing bias is observed for all junctions, suggesting electric-field enhanced thermionic emission. Further analysis of the field dependence of the reverse current reveals that while carrier transport in Gr/SiC Schottky junctions follows the Poole-Frenkel mechanism, it deviates from both the Poole-Frankel and Schottky mechanisms in Gr/Si and Gr/GaAs junctions, particularly for low temperatures and fields.

  9. Comparison Study of Super junction and Floating Junction Schottky Barrier Diodes%超结与浮结型肖特基势垒二极管的比较研究

    Institute of Scientific and Technical Information of China (English)

    曹琳; 蒲红斌; 陈治明

    2011-01-01

    对浮结型及超结型肖特基势垒二极管静态及动态特性进行了解析及模拟.静态特性通过解析击穿电压与导通电阻之间的关系得到.反向恢复特性通过二极管电容随反向电压变化关系解释,商用混合模拟器MEDICI模拟结果表明浮结结构具有软恢复特性,软度因子为0.949.超结结构恢复特性较硬,软度因子为0.7807.当考虑这两种耐压结构时,必须权衡静态及动态之间的关系.%In this paper,the static and dynamic characteristics of superjunction and floating junction Schottky barrier diodes were analyzed and simulated.Work principles of the device were reported,tradeoff between breakdown voltage and specific resistance was theoretically calculated and compared.The reverse recovery characteristics were analyzed by diode capacitance as function of diode reverse voltage,the mixed circuit-device simulator MEDICI shown that floating junction had softness factor 0.949,while hard recovery characteristics were obtain for superjunction structure with softness factor 0.780 7.Trade-off must be made when static and dynamic performance is considered.

  10. Electromechanical resistive switching via back-to-back Schottky junctions

    Science.gov (United States)

    Li, Lijie

    2015-09-01

    The physics of the electromechanical resistive switching is uncovered using the theory of back-to-back Schottky junctions combined with the quantum domain space charge transport. A theoretical model of the basic element of resistive switching devices realized by the metal-ZnO nanowires-metal structure has been created and analyzed. Simulation results show that the reverse biased Schottky junction and the air gap impedance dominate the current-voltage relation at higher external voltages; thereby electromechanically varying the air gap thickness causes the device exhibit resistive tuning characteristics. As the device dimension is in nanometre scale, investigation of the model based on quantum mechanics has also been conducted.

  11. Guard-ring termination for high-voltage SiC Schottky barrier diodes; Guard ring shutan kozo wo sonaeta kotaiatsu SiC Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, K.; Urushidani, T.; Seki, Y. [Fuji Electric Corporate Research and Development, Ltd., Kanagawa (Japan)

    1996-03-10

    Silicon carbide (SiC) has been attracting attention as a material for power devices, and has already demonstrated its favorable characteristics in Schottky barrier diodes (SBD) with gold or platinum. However, few researchers have discussed the device terminal structures, and the authors propose a simple, efficient guard-ring terminal structure. The SBD of SiC is prepared, with Al/Ti as the Schottky metals. The Al/Ti electrode forms a Schottky barrier with the n-type drift region, and an ohmic contact with the p-type region, i.e., guard-ring region. Resistance of this structure to voltage is determined by that of the mesa section of the p-n junction, and the mesa structure is formed by selective oxidation. The SBD shows a break-down voltage of 550V, which is roughly twice as high as that of an SBD having no guard-ring structure. 7 refs., 3 figs.

  12. Investigation on a radiation tolerant betavoltaic battery based on Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yebing [Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Hu Rui; Yang Yuqing; Wang Guanquan [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Luo Shunzhong, E-mail: Luoshzh@caep.ca.cn [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Liu Ning [Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China)

    2012-03-15

    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{sub sc} and harder radiation tolerance but lower V{sub 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: Black-Right-Pointing-Pointer The Schottky diode was used as the converter of the betavoltaic battery. Black-Right-Pointing-Pointer The radiation damage of converter was accelerated by using alpha particles. Black-Right-Pointing-Pointer The Schottky diode has higher radiation resistance than that of the p-n junction. Black-Right-Pointing-Pointer The Schottky diode could still be a promising converter of the betavoltaic battery.

  13. Planar Schottky barrier mixer diodes for space applications at submillimeter wavelengths

    Science.gov (United States)

    Bishop, W. L.; Crowe, T. W.; Mattauch, R. J.; Ostdiek, P. H.

    1991-01-01

    Available planar diodes for space-based applications at submillimeter wavelengths have not achieved either the required low junction capacitance or the low series resistance-junction capacitance product. Here, the development of a novel planar diode structure that overcomes both of these difficulties is outlined. The characteristics of these Schottky barrier mixer diodes are presented and electron micrographs are shown. The diode structure will allow planar technology to be extended throughout the submillimeter wavelength range.

  14. 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.

  15. Electromechanical resistive switching via back-to-back Schottky junctions

    Directory of Open Access Journals (Sweden)

    Lijie Li

    2015-09-01

    Full Text Available The physics of the electromechanical resistive switching is uncovered using the theory of back-to-back Schottky junctions combined with the quantum domain space charge transport. A theoretical model of the basic element of resistive switching devices realized by the metal-ZnO nanowires-metal structure has been created and analyzed. Simulation results show that the reverse biased Schottky junction and the air gap impedance dominate the current-voltage relation at higher external voltages; thereby electromechanically varying the air gap thickness causes the device exhibit resistive tuning characteristics. As the device dimension is in nanometre scale, investigation of the model based on quantum mechanics has also been conducted.

  16. Weak Fermi Level Pinning Effect in Schottky Junction of α-MoTe2

    Science.gov (United States)

    Nakaharai, Shu; Yamamoto, Mahito; Ueno, Keiji; Tsukagoshi, Kazuhito

    Difficulty in hole injection from metal contacts to transition metal dichalcogenide (TMDC) semiconductors has been one of the most serious issues in the application of these 2D materials to future nanoelectronics, which is caused by the strong Fermi level pinning effect in the metal/TMDC Schottky junction. In this work, we found that the holes can be injected efficiently from a large work function metal of Pt to α-molybdenum ditelluride (α-MoTe2; 2H-type), a TMDC semiconductor. The Schottky barrier height for holes at the Pt/ α-MoTe2 interface was extracted to be 40 meV by the temperature dependence of back-gate modulated currents under the flat band condition at the junction, while the Schottky barrier for electrons in the junction with a small work function metal of Ti was found to be 50 meV. Considering the difference in the work functions of Pt and Ti, the Fermi level pinning effect in α-MoTe2 was found to be much weaker than that in other TMDC semiconductors such as MoS2. These results open a way to the realization of complementary type circuits in the 2D materials for future low-power consumption electronics. This work was supported by JSPS KAKENHI Grant Numbers 15K06006, 25107004.

  17. Enhanced Plasmonic Light Absorption for Silicon Schottky-Barrier Photodetectors

    DEFF Research Database (Denmark)

    Hashemi, Mahdieh; Farzad, Mahmood Hosseini; Mortensen, N. Asger;

    2013-01-01

    Quantum efficiency of the silicon Schottky-barrier photodetector is limited by the weak interaction between the photons and electrons in the metal. By engineering the metal surfaces, metallic groove structures are proposed to achieve strong light absorption in the metal, where most of the energy...... is transferred into hot carriers near the Schottky barrier. The proposed broadband photodetector with a bi-grating metallic structure on the silicon substrate enables to absorb 76 % of the infrared light in the metal with a 200-nm bandwidth, while staying insensitive to the incident angle. These results pave...... a new promising way to attain high quantum efficiency silicon Schottky-barrier photodetectors....

  18. Multiple Schottky Barrier-Limited Field-Effect Transistors on a Single Si Nanowire with an Intrinsic Doping Gradient.

    Science.gov (United States)

    Barreda, Jorge L; Keiper, Timothy D; Zhang, Mei; Xiong, Peng

    2017-03-09

    In comparison to conventional (channel-limited) field-effect transistors (FETs), Schottky barrier-limited FETs possess some unique characteristics which make them attractive candidates for some electronic and sensing applications. Consequently, modulation of the nano Schottky barrier at a metal-semiconductor interface promises higher performance for chemical and biomolecular sensor applications when compared to conventional FETs with Ohmic contacts. However, the fabrication and optimization of devices with a combination of ideal Ohmic and Schottky contacts as the source and drain respectively present many challenges. We address this issue by utilizing Si nanowires (NWs) synthesized by a chemical vapor deposition process which yields a pronounced doping gradient along the length of the NWs. Devices with a series of metal contacts on a single Si NW are fabricated in a single lithography and metallization process. The graded doping profile of the NW is manifested in monotonic increases in the channel and junction resistances and variation of the nature of the contacts from Ohmic to Schottky of increasing effective barrier height along the NW. Hence multiple single Schottky junction-limited FETs with extreme asymmetry and high reproducibility are obtained on an individual NW. A definitive correlation between increasing Schottky-barrier height and enhanced gate modulation is revealed. Having access to systematically varying Schottky barrier contacts on the same NW device provides an ideal platform for identifying optimal device characteristics for sensing and electronic applications.

  19. 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.

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

    Directory of Open Access Journals (Sweden)

    Chaochao Fu

    2016-04-01

    Full Text Available 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.

  1. Physical based Schottky barrier diode modeling for THz applications

    DEFF Research Database (Denmark)

    Yan, Lei; Krozer, Viktor; Michaelsen, Rasmus Schandorph;

    2013-01-01

    In this work, a physical Schottky barrier diode model is presented. The model is based on physical parameters such as anode area, Ohmic contact area, doping profile from epitaxial (EPI) and substrate (SUB) layers, layer thicknesses, barrier height, specific contact resistance, and device...... temperature. The effects of barrier height lowering, nonlinear resistance from the EPI layer, and hot electron noise are all included for accurate characterization of the Schottky diode. To verify the diode model, measured I-V and C-V characteristics are compared with the simulation results. Due to the lack...

  2. Ambient organic molecular passivation of Si yields near-ideal, Schottky-Mott limited, junctions

    Directory of Open Access Journals (Sweden)

    Rotem Har-Lavan

    2012-03-01

    Full Text Available We report near-perfect transfer of the electrical properties of oxide-free Si surface, modified by a molecular monolayer, to the interface of a junction made with that modified Si surface. Such behavior is highly unusual for a covalent, narrow bandgap semiconductor, such as Si. Short, ambient atmosphere, room temperature treatment of oxide-free Si(100 in hydroquinone (HQ/alkyl alcohol solutions, fully passivates the Si surface, while allowing controlled change of the resulting surface potential. The junctions formed, upon contacting such surfaces with Hg, a metal that does not chemically interact with Si, follow the Schottky-Mott model for metal-semiconductor junctions closer than ever for Si-based junctions. Two examples of such ideal behavior are demonstrated: a Tuning the molecular surface dipole over 400 mV, with only negligible band bending, by changing the alkyl chain length. Because of the excellent passivation this yields junctions with Hg with barrier heights that follow the change in the Si effective electron affinity nearly ideally. b HQ/ methanol passivation of Si is accompanied by a large surface dipole, which suffices, as interface dipole, to drive the Si into strong inversion as shown experimentally via its photovoltaic effect. With only ∼0.3 nm molecular interlayer between the metal and the Si, our results proves that it is passivation and prevention of metal-semiconductor interactions that allow ideal metal-semiconductor junction behavior, rather than an insulating transport barrier.

  3. 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.

  4. Control of pn-junction turn-on voltage in 4H-SiC merged PiN Schottky diode

    Science.gov (United States)

    Park, Junbo; Park, Kun-Sik; Won, Jong-il; Kim, Ki-hwan; Koo, Sangmo; Kim, Sang-gi; Mun, Jae-Kyoung

    2017-04-01

    We present numerical simulation results and experimental measurements that explain the physical mechanism behind the high critical voltage, Vcrit, required to turn on a pn junction in a merged PiN Schottky (MPS) diode. The 2D simulation of potential distribution within a unit MPS cell demonstrated that the potential gradient set by the Schottky junction raises the potential barrier formed at the pn junction, thereby increasing Vcrit. Based on this knowledge, we propose that changing the ratio of the Schottky contact and the p+ region area, as well as shallow p-doping of the Schottky interface, can be used to control the magnitude of Vcrit. We present simulation and measurement results that demonstrate the feasibility of our approach.

  5. Barrier height enhancement of InP-based n-Ga(0.47)In(0.53)As Schottky-barrier diodes grown by molecular beam epitaxy

    Science.gov (United States)

    Kim, J. H.; Li, S. S.; Figueroa, L.

    1988-01-01

    Barrier height enhancement of an InP-based p(+)n-Ga(0.47)In(0.53)As Schottky diode grown by MBE has been demonstrated for infra-red photodetector applications. A barrier height of 0.35 eV for n-Ga(0.47)In(0.53)As Schottky barrier diodes, was increased to the effective barrier height of 0.55 eV, with a p(+)-Ga(0.47)In(0.53)As surface layer of 30 nm thick. The results show a reverse leakage current density of 0.0015 A/sq cm and a junction capacitance of 0.3 pF, which are comparable to those of p-Ga(0.47)In(0.53)As Schottky-barrier diodes at a reverse bias voltage of 5 V.

  6. Boron implantation effects on Au:GaAs Schottky barrier

    Energy Technology Data Exchange (ETDEWEB)

    Perez, A.; Roura, P.; Esteve, J.; Altelarrea, H.; Anton, J.A.; Cornet, A.; Morante, J.R.

    1987-01-01

    In this work, we analyse the use of boron implantation in order to change the barrier height of GaAs Schottky contacts. The dependence on the annealing temperature and implantation dose of the barrier height variation, as well as of the diode quality factor are also reported. In both cases, the observed behaviour is related to the presence of defects created by implantation in the surface layer, and their annealing kinetics.

  7. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    Directory of Open Access Journals (Sweden)

    Meisam Rahmani

    2013-01-01

    Full Text Available Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking and metal (AA stacking layers. To this end, an analytical model joint with numerical solution of carrier concentration for bilayer graphene nanoribbon in the degenerate and nondegenerate regimes is presented. Moreover, to determine the proposed diode performance, the carrier concentration model is adopted to derive the current-voltage characteristic of the device. The simulated results indicate a strong bilayer graphene nanoribbon geometry and temperature dependence of current-voltage characteristic showing that the forward current of the diode rises by increasing of width. In addition, the lower value of turn-on voltage appears as the more temperature increases. Finally, comparative study indicates that the proposed diode has a better performance compared to the silicon schottky diode, graphene nanoribbon homo-junction contact, and graphene-silicon schottky diode in terms of electrical parameters such as turn-on voltage and forward current.

  8. 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.

  9. Revised diode equation for Ideal Graphene-Semiconductor Schottky Junction

    OpenAIRE

    Liang, Shi-Jun; Ang, Lay Kee

    2015-01-01

    In this paper we carry out a theoretical and experimental study of the nature of graphene/semiconductor Schottky contact. We present a simple and parameter-free carrier transport model of graphene/semiconductor Schottky contact derived from quantum statistical theory, which is validated by the quantum Landauer theory and first-principle calculations. The proposed model can well explain experimental results for samples of different types of graphene/semiconductor Schottky contact.

  10. Schottky barrier enhancement on n-InP solar cell applications

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1994-01-01

    It is demonstrated that the Schottky barrier height on n-type InP can be enhanced to values close to the energy bandgap (1.35 eV) by employing a AuZnCr metallization. The process is simple and requires only mild and fast annealing sequences with temperatures not exceeding 500°C. Also, no critical...... epitaxial growth step of junctions is needed, making the process fairly cheap. Thus, prospects for an efficient and simple solar cell device structure for space application purposes based on highly radiant-resistant InP are greatly improved...

  11. 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.

  12. A novel nanoscaled Schottky barrier based transmission gate and its digital circuit applications

    Science.gov (United States)

    Kumar, Sunil; Loan, Sajad A.; Alamoud, Abdulrahman M.

    2017-04-01

    In this work we propose and simulate a compact nanoscaled transmission gate (TG) employing a single Schottky barrier based transistor in the transmission path and a single transistor based Sajad-Sunil-Schottky (SSS) device as an inverter. Therefore, just two transistors are employed to realize a complete transmission gate which normally consumes four transistors in the conventional technology. The transistors used to realize the transmission path and the SSS inverter in the proposed TG are the double gate Schottky barrier devices, employing stacks of two metal silicides, platinum silicide (PtSi) and erbium silicide (ErSi). It has been observed that the realization of the TG gate by the proposed technology has resulted into a compact structure, with reduced component count, junctions, interconnections and regions in comparison to the conventional technology. The further focus of this work is on the application part of the proposed technology. So for the first time, the proposed technology has been used to realize various combinational circuits, like a two input AND gate, a 2:1 multiplexer and a two input XOR circuits. It has been observed that the transistor count has got reduced by half in a TG, two input AND gate, 2:1 multiplexer and in a two input XOR gate. Therefore, a significant reduction in transistor count and area requirement can be achieved by using the proposed technology. The proposed technology can be also used to perform the compact realization of other combinational and sequential circuitry in future.

  13. A sensitive ultraviolet light photodiode based on graphene-on-zinc oxide Schottky junction

    Directory of Open Access Journals (Sweden)

    Zhang Teng-Fei

    2016-11-01

    Full Text Available In this study, we present a simple ultraviolet (UV light photodiode by transferring a layer of graphene film on single-crystal ZnO substrate. The as-fabricated heterojunction exhibited typical rectifying behavior, with a Schottky barrier height of 0.623 eV. Further optoelectronic characterization revealed that the graphene-ZnO Schottky junction photodiode displayed obvious sensitivity to 365-nm light illumination with good reproducibility. The responsivity and photoconductive gain were estimated to be 3×104 A/W and 105, respectively, which were much higher than other ZnO nanostructure-based devices. In addition, it was found that the on/off ratio of the present device can be considerably improved from 2.09 to 12.1, when the device was passivated by a layer of AlOx film. These results suggest that the present simply structured graphene-ZnO UV photodiode may find potential application in future optoelectronic devices.

  14. Monolayer graphene film on ZnO nanorod array for high-performance Schottky junction ultraviolet photodetectors.

    Science.gov (United States)

    Nie, Biao; Hu, Ji-Gang; Luo, Lin-Bao; Xie, Chao; Zeng, Long-Hui; Lv, Peng; Li, Fang-Ze; Jie, Jian-Sheng; Feng, Mei; Wu, Chun-Yan; Yu, Yong-Qiang; Yu, Shu-Hong

    2013-09-09

    A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 μm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices.

  15. Application of well characterized e - beam evaporated WSe2 thin films in Schottky Barrier diodes

    Science.gov (United States)

    Patel, Mayurkumar M.

    The studies of semiconductor thin films and their junctions such as metal semiconductor junctions (Schottky Barriers) have received much attention due to their applications in various electronic and optoelectronic devices including high frequency switching device, Schottky barrier devices, solar cells etc. But, realization of any electronic device using a combination of bulk and thin film or all bulk or all thin film components essentially requires metallization of metal contacts for electrical signals to flow into and out of the device. Thus junction between two metals and metal-semiconductor is an integral part of the device without which communication to the external circuit components would not be possible. In this reference stable metalsemiconductor contacts of ohmic as well as rectifying nature are very much important from technological point of view. In both cases preparation of reliable and efficient metal contacts with high yield and stability is challenging task for devices operating at high frequencies when packing density is increased by many fold. Thus, the behavior of metal-semiconductor contacts at microscopic scale may be explored for the development of future technology. The subject matter of such contacts is well documented in many books with review of developments in the recent past. Earlier devices were prepared on the bulk elemental semiconductors as an active region which was then followed by crystalline/amorphous compound semiconductors in bulk as well as thin film forms like Solar cells, p-n junction diodes, Schottky barrier devices etc. in recent past. Normally bulk crystalline'or amorphous substrate is used to support device structure made from crystalline/amorphous bulk and thin film. However, to the best of author's knowledge no attempts have been made to study the devices prepared by depositing semiconductor thin film with thin metal film supported by a by a non-conducting glass substrate. For this purpose, studies were carried out on

  16. Temperature-dependent Schottky barrier in high-performance organic solar cells

    Science.gov (United States)

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions.

  17. Evidence of minority carrier injection efficiency >90% in an epitaxial graphene/SiC Schottky emitter bipolar junction phototransistor for ultraviolet detection

    Energy Technology Data Exchange (ETDEWEB)

    Chava, Venkata S. N., E-mail: vchava@email.sc.edu; Omar, Sabih U.; Brown, Gabriel; Shetu, Shamaita S.; Andrews, J.; Sudarshan, T. S.; Chandrashekhar, M. V. S. [Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 (United States)

    2016-01-25

    In this letter, we report the UV detection characteristics of an epitaxial graphene (EG)/SiC based Schottky emitter bipolar phototransistor (SEPT) with EG on top as the transparent Schottky emitter layer. Under 0.43 μW UV illumination, the device showed a maximum common emitter current gain of 113, when operated in the Schottky emitter mode. We argue that avalanche gain and photoconductive gain can be excluded, indicating minority carrier injection efficiency, γ, as high as 99% at the EG/p-SiC Schottky junction. This high γ is attributed to the large, highly asymmetric barrier, which EG forms with the p-SiC. The maximum responsivity of the UV phototransistor is estimated to be 7.1 A/W. The observed decrease in gain with increase in UV power is attributed to recombination in the base region, which reduces the minority carrier lifetime.

  18. Evidence of minority carrier injection efficiency >90% in an epitaxial graphene/SiC Schottky emitter bipolar junction phototransistor for ultraviolet detection

    Science.gov (United States)

    Chava, Venkata S. N.; Omar, Sabih U.; Brown, Gabriel; Shetu, Shamaita S.; Andrews, J.; Sudarshan, T. S.; Chandrashekhar, M. V. S.

    2016-01-01

    In this letter, we report the UV detection characteristics of an epitaxial graphene (EG)/SiC based Schottky emitter bipolar phototransistor (SEPT) with EG on top as the transparent Schottky emitter layer. Under 0.43 μW UV illumination, the device showed a maximum common emitter current gain of 113, when operated in the Schottky emitter mode. We argue that avalanche gain and photoconductive gain can be excluded, indicating minority carrier injection efficiency, γ, as high as 99% at the EG/p-SiC Schottky junction. This high γ is attributed to the large, highly asymmetric barrier, which EG forms with the p-SiC. The maximum responsivity of the UV phototransistor is estimated to be 7.1 A/W. The observed decrease in gain with increase in UV power is attributed to recombination in the base region, which reduces the minority carrier lifetime.

  19. 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.

  20. Barrier height determination in homogeneous nonideal Schottky contacts

    Science.gov (United States)

    Hernández, M. P.; Alonso, C. F.; Peña, J. L.

    2001-04-01

    A novel method is proposed to determine effective barrier heights in homogeneous nonideal Schottky contact from I-V measurements. This method takes into account the different mechanisms of current flow through the metal-semiconductor interface. The total current has been expressed as the sum of two independent terms which are: (1) the thermionic current where the ideality factor value is equal to one and (2) the contribution of different transport mechanisms. The second term responds to a general expression of the thermionic emission theory where the barrier height and the ideality factor are voltage dependent. The effective barrier height is found by means of subtraction of the transport mechanism terms from the total current. The method was applied to a group of I-V experimental curves which were reported by M Barus and D Donoval 1993 Solid State Electron. 36 969.

  1. Tuning the tunneling probability by mechanical stress in Schottky barrier based reconfigurable nanowire transistors

    Science.gov (United States)

    Baldauf, Tim; Heinzig, André; Trommer, Jens; Mikolajick, Thomas; Weber, Walter Michael

    2017-02-01

    Mechanical stress is an established and important tool of the semiconductor industry to improve the performance of modern transistors. It is well understood for the enhancement of carrier mobility but rather unexplored for the control of the tunneling probability for injection dominated research devices based on tunneling phenomena, such as tunnel FETs, resonant tunnel FETs and reconfigurable Schottky FETs. In this work, the effect of stress on the tunneling probability and overall transistor characteristics is studied by three-dimensional device simulations in the example of reconfigurable silicon nanowire Schottky barrier transistors using two independently gated Schottky junctions. To this end, four different stress sources are investigated. The effects of mechanical stress on the average effective tunneling mass and on the multi-valley band structure applying the deformation potential theory are being considered. The transfer characteristics of strained transistors in n- and p-configuration and corresponding charge carrier tunneling are analyzed with respect to the current ratio between electron and hole conduction. For the implementation of these devices into complementary circuits, the mandatory current ratio of unity can be achieved by appropriate mechanical stress either by nanowire oxidation or the application of a stressed top layer.

  2. Detection of alpha particles using DNA/Al Schottky junctions

    Energy Technology Data Exchange (ETDEWEB)

    Al-Ta' ii, Hassan Maktuff Jaber, E-mail: hassankirkukly@gmail.com, E-mail: vengadeshp@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), 50603 Kuala Lumpur (Malaysia); Department of Physics, Faculty of Science, University of Al-Muthana, Al-Muthana 66001 (Iraq); Periasamy, Vengadesh, E-mail: hassankirkukly@gmail.com, E-mail: vengadeshp@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), 50603 Kuala Lumpur (Malaysia); Amin, Yusoff Mohd [Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2015-09-21

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current–voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors.

  3. Modeling of Schottky Barrier Diode Millimeter-Wave Multipliers at Cryogenic Temperatures

    DEFF Research Database (Denmark)

    Johansen, Tom K.; Rybalko, Oleksandr; Zhurbenko, Vitaliy

    2015-01-01

    We report on the evaluation of Schottky barrier diode GaAs multipliers at cryogenic temperatures. A GaAs Schottky barrier diode model is developed for theoretical estimation of doubler performance. The model is used to predict efficiency of doublers from room to cryogenic temperatures...

  4. Schottky barriers at metal-finite semiconducting carbon nanotube interfaces

    OpenAIRE

    Xue, Yongqiang; Ratner, Mark A.

    2003-01-01

    Electronic properties of metal-finite semiconducting carbon nanotube interfaces are studied as a function of the nanotube length using a self-consistent tight-binding theory. We find that the shape of the potential barrier depends on the long-range tail of the charge transfer, leading to an injection barrier thickness comparable to half of the nanotube length until the nanotube reaches the bulk limit. The conductance of the nanotube junction shows a transition from tunneling to thermally-acti...

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

    Energy Technology Data Exchange (ETDEWEB)

    Park, No-Won; Lee, Won-Yong; Lee, Sang-Kwon; Koh, Jung-Hyuk [Chung-Ang University, Seoul (Korea, Republic of); Kim, Dong-Joo; Kim, Gil-Sung; Hyung, Jung-Hwan; Hong, Chang-Hee [Chonbuk National University, Jeonju (Korea, Republic of); Kim, Keun-Soo [Sejong University, Seoul (Korea, Republic of)

    2015-01-15

    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{sup 15} cm{sup -3}, respectively. From the J - V characteristics, we obtained a relatively low reverse leakage current of ∼2.56 x 10{sup -6} mA/cm{sup -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.

  6. Schottky Barrier CdTe(Cl) Detectors for Planetary Missions

    Science.gov (United States)

    Eisen, Yosef; Floyd, Samuel

    2002-10-01

    Schottky barrier cadmium telluride (CdTe) radiation detectors of dimensions 2mm × 2mm × 1mm and segmented monolithic 3cm × 3 cm × 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 × 2mm × 1mm CdTe operating at -30°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 × 3cm × 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. 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

  8. 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.

  9. Tuning a Schottky barrier of epitaxial graphene/4H-SiC (0001) by hydrogen intercalation

    Science.gov (United States)

    Dharmaraj, P.; Justin Jesuraj, P.; Jeganathan, K.

    2016-02-01

    We report the electron transport properties of epitaxial graphene (EG) grown on 4H-SiC (0001) by low energy electron-beam irradiation. As-grown EG (AEG) on SiC interface exhibits rectifying current-voltage characteristics with a low Schottky barrier (SB) of 0.55 ± 0.05 eV and high reverse current leakage. The SB of AEG/SiC junction is extremely impeded by the Fermi level pinning (FLP) above the Dirac point due to charged states at the interface. Nevertheless, a gentle hydrogen intercalation at 900 °C enables the alleviation of both FLP and carrier scattering owing to the saturation of dangling bonds as evidenced by the enhancement of SB (0.75 ± 0.05 eV) and high electron mobility well excess of 6000 cm2 V-1 s-1.

  10. Additional electric field in real trench MOS barrier Schottky diode

    Science.gov (United States)

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

    2016-04-01

    In real trench MOS barrier Schottky diode (TMBS diode) additional electric field (AEF) the whole is formed in the near contact region of the semiconductor and its propagation space is limited with the barrier metal and the metallic electrodes of MOS structures. Effective potential barrier height TMBS diode is formed via resulting electric field of superposition AEF and electric field of space charge region (SCR) semiconductor. The dependence of the resulting electric field intensity of the distance towards the inside the semiconductor is nonlinear and characterized by a peak at a certain distance from the interface. The thickness of the SCR in TMBS diode becomes equal to the trench depth. Force and energy parameters of the AEF, and thus resulting electric field in the SCR region, become dependent on the geometric design parameters TMBS diode. The forward I-V characteristic TMBS diode is described by the thermionic emission theory as in conventional flat Scottky diode, and in the reverse bias, current is virtually absent at initial voltage, appears abruptly at a certain critical voltage.

  11. 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.

  12. Novel palladium germanide schottky contact for high performance schottky barrier ge MOSFETs and characterization of its leakage current mechanism.

    Science.gov (United States)

    Oh, Se-Kyung; Shin, Hong-Sik; Kang, Min-Ho; Lee, Ga-Won; Lee, Hi-Deok

    2012-07-01

    The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

  13. Alloyed 2D Metal-Semiconductor Heterojunctions: Origin of Interface States Reduction and Schottky Barrier Lowering.

    Science.gov (United States)

    Kim, Yonghun; Kim, Ah Ra; Yang, Jin Ho; Chang, Kyoung Eun; Kwon, Jung-Dae; Choi, Sun Young; Park, Jucheol; Lee, Kang Eun; Kim, Dong-Ho; Choi, Sung Mook; Lee, Kyu Hwan; Lee, Byoung Hun; Hahm, Myung Gwan; Cho, Byungjin

    2016-09-14

    The long-term stability and superior device reliability through the use of delicately designed metal contacts with two-dimensional (2D) atomic-scale semiconductors are considered one of the critical issues related to practical 2D-based electronic components. Here, we investigate the origin of the improved contact properties of alloyed 2D metal-semiconductor heterojunctions. 2D WSe2-based transistors with mixed transition layers containing van der Waals (M-vdW, NbSe2/WxNb1-xSe2/WSe2) junctions realize atomically sharp interfaces, exhibiting long hot-carrier lifetimes of approximately 75,296 s (78 times longer than that of metal-semiconductor, Pd/WSe2 junctions). Such dramatic lifetime enhancement in M-vdW-junctioned devices is attributed to the synergistic effects arising from the significant reduction in the number of defects and the Schottky barrier lowering at the interface. Formation of a controllable mixed-composition alloyed layer on the 2D active channel would be a breakthrough approach to maximize the electrical reliability of 2D nanomaterial-based electronic applications.

  14. Thermally Stable Silver Nanowires-Embedding Metal Oxide for Schottky Junction Solar Cells.

    Science.gov (United States)

    Kim, Hong-Sik; Patel, Malkeshkumar; Park, Hyeong-Ho; Ray, Abhijit; Jeong, Chaehwan; Kim, Joondong

    2016-04-06

    Thermally stable silver nanowires (AgNWs)-embedding metal oxide was applied for Schottky junction solar cells without an intentional doping process in Si. A large scale (100 mm(2)) Schottky solar cell showed a power conversion efficiency of 6.1% under standard illumination, and 8.3% under diffused illumination conditions which is the highest efficiency for AgNWs-involved Schottky junction Si solar cells. Indium-tin-oxide (ITO)-capped AgNWs showed excellent thermal stability with no deformation at 500 °C. The top ITO layer grew in a cylindrical shape along the AgNWs, forming a teardrop shape. The design of ITO/AgNWs/ITO layers is optically beneficial because the AgNWs generate plasmonic photons, due to the AgNWs. Electrical investigations were performed by Mott-Schottky and impedance spectroscopy to reveal the formation of a single space charge region at the interface between Si and AgNWs-embedding ITO layer. We propose a route to design the thermally stable AgNWs for photoelectric device applications with investigation of the optical and electrical aspects.

  15. Fabrication of Schottky Junction Between Au and SrTiO3

    Science.gov (United States)

    Inoue, Akira; Izumisawa, Kei; Uwe, Hiromoto

    2001-05-01

    A Schottky junction with a high rectification ratio between Au and La-doped SrTiO3 has been fabricated using a simple surface treatment. Highly La-doped (5%) SrTiO3 single crystals are annealed in O2 atmosphere at about 1000°C for 1 h and etched in HNO3 for more than five min. The HNO3 etching is performed in a globe box containing N2 to prevent pollution from the air. After the treatment, Au is deposited on the SrTiO3 surface in a vacuum (˜ 10-7 Torr) with an e-gun evaporator. The current voltage characteristics of the junction have shown excellent rectification properties, although junctions using neither annealed nor etched SrTiO3 exhibit high leak current in reverse voltage. The rectification ratio of the junction at 1 V is more than six orders of magnitude and there is no hysteresis in the current voltage spectra. The logarithm of the current is linear with the forward bias voltage. The ideal factor of the junction is estimated to be about 1.68. These results suggest that, if prevented from being pollution by the air, a good Schottky junction can be obtained by easy processes such as annealing in oxygen atmosphere and surface etching with acid.

  16. Bias stress instability involving subgap state transitions in a-IGZO Schottky barrier diodes

    Science.gov (United States)

    Qian, Huimin; Wu, Chenfei; Lu, Hai; Xu, Weizong; Zhou, Dong; Ren, Fangfang; Chen, Dunjun; Zhang, Rong; Zheng, Youdou

    2016-10-01

    Vertical Schottky barrier diodes (SBDs) based on amorphous indium-gallium-zinc-oxide (a-IGZO) with either a top or bottom Schottky contact are fabricated by controlling the oxygen partial pressure during a-IGZO deposition. Although Au electrodes are employed for both Schottky and Ohmic contacts, it is found that Schottky contacts are preferentially formed on a-IGZO film in lower oxygen vacancy concentrations. The effect of negative bias stress on device performance is studied. The Schottky barrier height and series resistance of the a-IGZO SBD are found to increase upon negative bias stress, which is correlated with a reduction of the trap state and background carrier concentration within the a-IGZO film. A physical model based on subgap state transitions from ionized V\\text{O}2+ states to neutralized V O states is proposed to explain the observed electrical instability behavior.

  17. The Effect of Bilayer Graphene Nanoribbon Geometry on Schottky-Barrier Diode Performance

    OpenAIRE

    Meisam Rahmani; Razali Ismail; Mohammad Taghi Ahmadi; Mohammad Javad Kiani; Mehdi Saeidmanesh; F. A. Hediyeh Karimi; Elnaz Akbari; Komeil Rahmani

    2013-01-01

    Bilayer graphene nanoribbon is a promising material with outstanding physical and electrical properties that offers a wide range of opportunities for advanced applications in future nanoelectronics. In this study, the application of bilayer graphene nanoribbon in schottky-barrier diode is explored due to its different stacking arrangements. In other words, bilayer graphene nanoribbon schottky-barrier diode is proposed as a result of contact between a semiconductor (AB stacking) and metal (AA ...

  18. 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.

  19. 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.

  20. Lateral resistance reduction induced by light-controlled leak current in silicon-based Schottky junction

    Institute of Scientific and Technical Information of China (English)

    王拴虎; 张勖; 邹吕宽; 赵靓; 王文鑫; 孙继荣

    2015-01-01

    Lateral resistance of silicon-based p-type and n-type Schottky junctions is investigated. After one electrode on a metallic film is irradiated, the differential lateral resistance of the system is dependent on the direction of the bias current:it keeps constant in one direction and decreases in the opposite direction. By systematically investigating the electrical potential changes in silicon and the junction, we propose a new mechanism based on light-controlled leak current. Our work provides an insight into the nature of this phenomenon and will facilitate the advanced design of switchable devices.

  1. Improved surface plasmon enhanced photodetection at an Au-GaAs Schottky junction using a novel molecular beam epitaxy grown Otto coupling structure

    Energy Technology Data Exchange (ETDEWEB)

    Daboo, C.; Baird, M.J.; Hughes, H.P. (PCS Group, Cavendish Lab., Cambridge (UK)); Apsley, N.; Emeny, M.T. (Royal Signals and Radar Establishment, Great Malvern (UK))

    1991-06-05

    Measurements of reflectivity and photocurrent as a function of angle of incidence and wavelength have been made for a GaAs-AlAs-GaAs-Au Schottky structure based on an Otto coupling geometry which allows incident p-polarized radiation to couple to the surface plasmon (SP) mode at the Au-GaAs interface. At resonance, E fields associated with the SP excitation are concentrated at the GaAs-Au Schottky interface itself, enabling strong enhancement of the internal photoemission photocurrent across the Schottky barrier. Enhancement factors of the order of 20 have been achieved. A direct comparison between the resonant effects of exciting the SP at the GaAs-Au Schottky junction itself and at the outer Au-air interface has been made. A simple model for the photocurrent in the device indicates that the excited photocarriers created in the gold film have a very short scattering length {delta}{approx equal}10 nm, which emphasizes the importance of exciting the SP at the Schottky interface. (orig.).

  2. Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier

    Science.gov (United States)

    Ling, Zhi-Peng; Sakar, Soumya; Mathew, Sinu; Zhu, Jun-Tao; Gopinadhan, K.; Venkatesan, T.; Ang, Kah-Wee

    2015-12-01

    Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec).

  3. Oxygen modulation of flexible PbS/Pb Schottky junction PEC cells with improved photoelectric performance

    Science.gov (United States)

    Wang, Peng; Fan, Libo; Guo, Qiuquan; Shi, Hongcai; Wang, Liwen; Liu, Yujian; Li, Ming; Zhang, Chunli; Yang, Jun; Zheng, Zhi

    2016-09-01

    Flexible photoelectric devices are emerging as a new class of photovoltaic cells. In this study, lead (Pb) foil was used as a flexible substrate to grow in situ lead sulfide (PbS) film with good uniformity and adhesion by a solvothermal elemental direct reaction, resulting in a PbS/Pb Schottky junction formed naturally between the PbS film and underlying Pb foil. We found that the photocurrent response of the photoelectrochemical (PEC) cell was greatly improved through a facile oxygen (O2)-modulation-based post-processing technique. O2 could decompose the organic residue and oxidize the Pb at the interface between the PbS film and Pb foils. Different characterization techniques, including thermogravimetric analysis, differential scanning calorimetry, x-ray diffraction, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, the change in transient photocurrent density (J p) with time (t), dark current-voltage (I-V) and absorption spectra were applied to get a full understanding of the O2 modulation effect. The oxidization treatment of the PbS film could regulate the flow of charge carriers to reduce their recombination, leading to photoresponse enhancement for the PEC cells. In particular, the process could modulate the tunneling current and interface states to optimize dark I-V characteristics. In addition, the magnitude of the barrier height can be tuned by O2 modulation, which was explained by theoretical analysis and calculation. We also demonstrated that the in situ formed PbS film has outstanding adhesion on the flexible Pb substrate. Our film synthesis method and post O2-modulation design as well as the corresponding device assembly may provide a novel perspective to the flexible PCE-cell-related research.

  4. Investigation of nanostructured Pd-Ag/n-ZnO thin film based Schottky junction for methane sensing

    Science.gov (United States)

    Roy, S.; Das, S.; Sarkar, C. K.

    2016-07-01

    Undoped nanocrystalline n-type ZnO thin film was deposited by chemical deposition technique on a thermally oxidized p-Si (~5 Ω cm resistivity and orientation) substrate. Formation of stable zinc oxide thin film was confirmed by two-dimensional X-Ray Diffraction (XRD) and EDX analysis. The average crystallite size of the ZnO sample was evaluated as ~50 nm. The surface was characterized by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) that confirm the formation of nanocrystalline (grain size ~50 nm) ZnO thin film with surface roughness of ~100 nm. Good conversion of precursor into ZnO thin film in the chemical deposition method was evident by Fourier Transform Infrared Spectroscopy (FTIR). A small peak at 479 cm-1was observed in the FTIR spectrum confirming the formation of quartzite structure of the ZnO. The band gap (~3.44 eV) of the material was calculated from the optical absorption spectroscopy. To prepare Pd-Ag/n-ZnO Schottky junction, Pd-Ag contacts were taken by electron beam evaporation method. I-V characteristics of the junction were studied at different temperatures in inert and reducing ambient (N2 and N2 + CH4) with turn on voltage of around 0.2 V. The parameters like ideality factor ( η), saturation current ( I 0), series resistance ( Rs), and barrier height ( Φ BO) of the junction were calculated in the temperature range 50-200 °C in N2 as well as in 1 % CH4 + N2 ambient. It was observed that the ideality factor decreases in the temperature range 50-200 °C ( η = 12.34 at 50 °C and η = 1.52 at 200 °C) in N2 ambient and η = 1.18 in N2 +CH4 ambient at 200 °C. Schottky Barrier Height ( Φ BO) of the Pd-Ag/n-ZnO junction was found to increase with temperature. A close observation of Pd-Ag/n-ZnO junction in the presence of methane was performed to appreciate its application as methane sensor. The sensing mechanism was illustrated by a simplified energy band diagram.

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

    KAUST Repository

    Shaikh, Parvez A.

    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.

  6. 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.

  7. A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Liu Chin-Yi

    2010-01-01

    Full Text Available Abstract Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture. We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals (Si NCs from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange, or removal reactions. The Schottky junction device showed a photovoltaic response with a power conversion efficiency of 0.02%, a fill factor of 0.26, short circuit-current density of 0.148 mA/cm2, and open-circuit voltage of 0.51 V.

  8. Carbon nanotube and CdSe nanobelt Schottky junction solar cells.

    Science.gov (United States)

    Zhang, Luhui; Jia, Yi; Wang, Shanshan; Li, Zhen; Ji, Chunyan; Wei, Jinquan; Zhu, Hongwei; Wang, Kunlin; Wu, Dehai; Shi, Enzheng; Fang, Ying; Cao, Anyuan

    2010-09-08

    Developing nanostructure junctions is a general and effective way for making photovoltaics. We report Schottky junction solar cells by coating carbon nanotube films on individual CdSe nanobelts with open-circuit voltages of 0.5 to 0.6 V and modest power-conversion efficiencies (0.45-0.72%) under AM 1.5G, 100 mW/cm(2) light condition. In our planar device structure, the CdSe nanobelt serves as a flat substrate to sustain a network of nanotubes, while the nanotube film forms Shottky junction with the underlying nanobelt at their interface and also makes a transparent electrode for the device. The nanotube-on-nanobelt solar cells can work either in front (nanotube side) or back (nanobelt side) illumination with stable performance in air. Our results demonstrate a promising way to develop large-area solar cells based on thin films of carbon nanotubes and semiconducting nanostructures.

  9. Annealing temperature influence on the degree of inhomogeneity of the Schottky barrier in Ti/4H—SiC contacts

    Science.gov (United States)

    Han, Lin-Chao; Shen, Hua-Jun; Liu, Ke-An; Wang, Yi-Yu; Tang, Yi-Dan; Bai, Yun; Xu, Heng-Yu; Wu, Yu-Dong; Liu, Xin-Yu

    2014-12-01

    Tung's model was used to analyze anomalies observed in Ti/SiC Schottky contacts. The degree of the inhomogeneous Schottky barrier after annealing at different temperatures is characterized by the ‘T0 anomaly’ and the difference (△Φ) between the uniformly high barrier height (ΦB0) and the effective barrier height (ΦBeff). Those two parameters of Ti Schottky contacts on 4H—SiC were deduced from I-V measurements in the temperature range of 298 K-503 K. The increase in Schottky barrier (SB) height (ΦB) and decrease in the ideality factor (n) with an increase measurement temperature indicate the presence of an inhomogeneous SB. The degree of inhomogeneity of the Schottky barrier depends on the annealing temperature, and it is at its lowest for 500-°C thermal treatment. The degree of inhomogeneity of the SB could reveal effects of thermal treatments on Schottky contacts in other aspects.

  10. Evaluation of Schottky barrier height on 4H-SiC m-face \\{ 1\\bar{1}00\\} for Schottky barrier diode wall integrated trench MOSFET

    Science.gov (United States)

    Kobayashi, Yusuke; Ishimori, Hiroshi; Kinoshita, Akimasa; Kojima, Takahito; Takei, Manabu; Kimura, Hiroshi; Harada, Shinsuke

    2017-04-01

    We proposed an Schottky barrier diode wall integrated trench MOSFET (SWITCH-MOS) for the purposes of shrinking the cell pitch and suppressing the forward degradation of the body diode. A trench Schottky barrier diode (SBD) was integrated into a trench gate MOSFET with a wide shielding p+ region that protected the trench bottoms of both the SBD and the MOS gate from high electrical fields in the off state. The SBD was placed on the trench sidewall of the \\{ 1\\bar{1}00\\} plane (m-face). Static and transient simulations revealed that SWITCH-MOS sufficiently suppressed the bipolar current that induced forward degradation, and we determined that the optimum Schottky barrier height (SBH) was from 0.8 to 2.0 eV. The SBH depends on the crystal planes in 4H-SiC, but the SBH of the m-face was unclear. We fabricated a planar m-face SBD for the first time, and we obtained SBHs from 1.4 to 1.8 eV experimentally with titanium or nickel as a Schottky metal.

  11. Transport and performance of a zero-Schottky barrier and doped contacts graphene nanoribbon transistors

    Science.gov (United States)

    Alam, Khairul

    2009-01-01

    The transport physics and performance of a top gate graphene nanoribbon (GNR) on an insulator transistor are studied for both the MOSFET like doped source-drain and the zero-Schottky barrier source-drain contacts. A voltage controlled tunnel barrier is the device transport physics. The doped source-drain contact device has a higher gate capacitance, higher transconductance, higher on/off current ratio and higher on-state current. The higher on-state current results in a lower switching delay of 17 fs, and the higher transconductance results in a higher intrinsic cut-off frequency of 27 THz in the doped source-drain contact device. The gate voltage, beyond the source-channel flat band condition, modulates both the tunnel and the thermal barrier in the doped source-drain contact devices and the tunnel barrier only in the Schottky contact devices. This limits the on-state current of Schottky contact devices.

  12. Quantum compact model for thin-body double-gate Schottky barrier MOSFETs

    Institute of Scientific and Technical Information of China (English)

    Luan Su-Zhen; Liu Hong-Xia

    2008-01-01

    Nanoscale Schottky barrier metal oxide semiconductor field-effect transistors (MOSFETs) are explored by using quantum mechanism effects for thin-body devices. The results suggest that for small nonnegative Schottky barrier heights, even for zero barrier height, the tunnelling current also plays a role in the total on-state current. Owing to the thin body of device, quantum confinement raises the electron energy levels in the silicon, and the tradeoff takes place between the quantum confinement energy and Schottky barrier lowering (SBL). It is concluded that the inclusion of the quantum mechanism effect in this model, which considers an infinite rectangular well with a first-order perturbation in the channel, can lead to the good agreement with numerical result for thin silicon film. The error increases with silicon thickness increasing.

  13. 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.

  14. Investigation of significantly high barrier height in Cu/GaN Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Manjari, E-mail: meghagarg142@gmail.com; Kumar, Ashutosh; Singh, R. [Department of Physics, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi-110016 (India); Nagarajan, S.; Sopanen, M. [Department of Micro and Nanosciences, Aalto University, P.O. Box 13500, FI-00076, Aalto (Finland)

    2016-01-15

    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 (Cu{sub 2}O) layer at the interface between Cu and GaN. With Cu{sub 2}O 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/Cu{sub 2}O/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.

  15. Measurements of femtosecond pulse temporal profile by means of a Michelson interferometer with a Schottky junction.

    Science.gov (United States)

    Ling, Yan; Lu, Fang

    2006-12-20

    We introduce a new method for femtosecond pulse shape measurement. The interference of two pulses is employed rather than the second-harmonic generation (SHG). Usually, the measurements of the femtosecond pulse is realized by an interferometer in combination with a nonlinear optical material, while the measurement that we describe is realized by means of a Michelson interferometer with a Schottky junction. Only a metal-semiconductor junction (Schottky junction) is needed, and neither the nonlinear optical material nor a photodetector is included. The two-photon absorption arises when the light is strong enough, while there is only a one-photon absorption when the light is weak. And the calculations are in good agreement with the experimental results. In principle, the new technique could be used for the measuring of pulses with any duration and with very low power. Unlike the SHG scheme, in the new method the quality of optics, mechanics, and other elements of the scheme are not essential, and the measurement is easily realized, but the results are quite precise and very sensitive to the light.

  16. 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......-voltage characteristics were studied in order to investigate which of the tested compounds could possibly reach the requirements for non-volatile memory applications. All the investigated devices displayed good rectifying properties, ranging from 10(2) to 10(4). On the other hand, one of the compounds reveals higher...

  17. 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 Mo1-xWxSe2 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. Mo0.5W0.5Se2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe2 and WSe2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo0.5W0.5Se2 devices. Furthermore, we showed that Mo0.5W0.5Se2-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.

  18. 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.

  19. Phase Transition Sensitive Schottky Barriers In Ga-Si(P Contacts

    Directory of Open Access Journals (Sweden)

    B.P. Modi

    2013-05-01

    Full Text Available Investigation and understanding of Schottky diodes continue to be interesting both for basic as well as technological points of view. Even now the evolutionary aspects of such contacts are not very clearly understood. In this paper it is shown that in respect of interfacial strain contribution to the barrier heights of such contacts semiconductor – liquid metal contacts are relatively better placed than solid semiconductor-solid metal contacts. Results on Ga-Si(p contact are discussed in this paper to show phase sensitive contribution to the barrier height of such Schottky contacts.

  20. An Anomalous Gain Mechanism in GaN Schottky Barrier Ultraviolet Photodetectors

    Institute of Scientific and Technical Information of China (English)

    ZHAO De-Gang; JIANG De-Sheng; LIU Zong-Shun; ZHU Jian-Jun; WANG Hui; ZHANG Shu-Ming; YANG Hui

    2009-01-01

    The gain mechanism in GaN Sehottky barrier ultraviolet photodetectors is investigated by focused light beam.When the incident light illuminates the central region of the Schottky contact electrode, the responsivity changes very little with the increase of reverse bias voltage. However, when the incident light illuminates the edge region of the electrode, the responsivity increases remarkably with the increase of reverse bias voltage, and the corresponding quantum efficiency could be even higher than 100%. It is proposed that the surface states near the edge of the electrode may lead to a reduction of effective Schottky barrier height and an enhancement of electron injection, resulting in the anomalous gain.

  1. Tuning a Schottky barrier of epitaxial graphene/4H-SiC (0001) by hydrogen intercalation

    Energy Technology Data Exchange (ETDEWEB)

    Dharmaraj, P.; Justin Jesuraj, P.; Jeganathan, K., E-mail: kjeganathan@yahoo.com [Centre for Nanoscience and Nanotechnology, School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2016-02-01

    We report the electron transport properties of epitaxial graphene (EG) grown on 4H-SiC (0001) by low energy electron-beam irradiation. As-grown EG (AEG) on SiC interface exhibits rectifying current-voltage characteristics with a low Schottky barrier (SB) of 0.55 ± 0.05 eV and high reverse current leakage. The SB of AEG/SiC junction is extremely impeded by the Fermi level pinning (FLP) above the Dirac point due to charged states at the interface. Nevertheless, a gentle hydrogen intercalation at 900 °C enables the alleviation of both FLP and carrier scattering owing to the saturation of dangling bonds as evidenced by the enhancement of SB (0.75 ± 0.05 eV) and high electron mobility well excess of 6000 cm{sup 2} V{sup −1} s{sup −1}.

  2. Enhanced efficiency of Schottky-barrier solar cell with periodically nonhomogeneous indium gallium nitride layer

    Science.gov (United States)

    Anderson, Tom H.; Mackay, Tom G.; Lakhtakia, Akhlesh

    2017-01-01

    A two-dimensional finite-element model was developed to simulate the optoelectronic performance of a Schottky-barrier solar cell. The heart of this solar cell is a junction between a metal and a layer of n-doped indium gallium nitride (InξGaN) alloy sandwiched between a reflection-reducing front window and a periodically corrugated metallic back reflector. The bandgap of the InξGaN layer was varied periodically in the thickness direction by varying the parameter ξ∈(0,1). First, the frequency-domain Maxwell postulates were solved to determine the spatial profile of photon absorption and, thus, the generation of electron-hole pairs. The AM1.5G solar spectrum was taken to represent the incident solar flux. Next, the drift-diffusion equations were solved for the steady-state electron and hole densities. Numerical results indicate that a corrugated back reflector of a period of 600 nm is optimal for photon absorption when the InξGaN layer is homogeneous. The efficiency of a solar cell with a periodically nonhomogeneous InξGaN layer may be higher by as much as 26.8% compared to the analogous solar cell with a homogeneous InξGaN layer.

  3. Effect of temperature and post-deposition annealing on Schottky barrier characterization of Bromoindium phthalocyanine/aluminum interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Azim-Araghi, M.E.; Sahebi, R., E-mail: ramezan.sahebi@yahoo.com

    2014-01-15

    To investigate DC electrical properties and Schottky barrier characterization between BrInPc/Al interfaces, some thin films of BrInPc in sandwich form were prepared with Al electrodes. J–V characterization showed ohmic behavior at lower voltages upto 0.3 V followed by Schottky emission conduction mechanism at higher voltages. In the Schottky region two different slopes in the plot of ln (J) against V{sup 1/2} were observed and two different values of Schottky barrier height was determined for these regions. To investigate the effect of temperature on Schottky barrier behavior between BrInPc and aluminum interface, we studied the J–V characteristics of devices at the temperature range of 298–373 K. By increasing the temperature, the width of Schottky depletion region decreased and the Schottky barrier height increased, and at temperatures higher than 333 K the dominant conduction mechanism changed to Poole–Frenkel type. For annealed samples at 373 K and 423 K, the Schottky barrier height increased as the result of thermal annealing and increasing annealing temperature. The width of the Schottky depletion region decreased by annealing and increasing the annealing temperature.

  4. Highly sensitive wide bandwidth photodetector based on internal photoemission in CVD grown p-type MoS2/graphene Schottky junction.

    Science.gov (United States)

    Vabbina, PhaniKiran; Choudhary, Nitin; Chowdhury, Al-Amin; Sinha, Raju; Karabiyik, Mustafa; Das, Santanu; Choi, Wonbong; Pala, Nezih

    2015-07-22

    Two dimensional (2D) Molybdenum disulfide (MoS2) has evolved as a promising material for next generation optoelectronic devices owing to its unique electrical and optical properties, such as band gap modulation, high optical absorption, and increased luminescence quantum yield. The 2D MoS2 photodetectors reported in the literature have presented low responsivity compared to silicon based photodetectors. In this study, we assembled atomically thin p-type MoS2 with graphene to form a MoS2/graphene Schottky photodetector where photo generated holes travel from graphene to MoS2 over the Schottky barrier under illumination. We found that the p-type MoS2 forms a Schottky junction with graphene with a barrier height of 139 meV, which results in high photocurrent and wide spectral range of detection with wavelength selectivity. The fabricated photodetector showed excellent photosensitivity with a maximum photo responsivity of 1.26 AW(-1) and a noise equivalent power of 7.8 × 10(-12) W/√Hz at 1440 nm.

  5. Investigation of Thickness Dependence of Metal Layer in Al/Mo/4H-SiC Schottky Barrier Diodes.

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; Kang, Tai-Young; Kyoung, Sinsu; Jung, Eun Sik; Kim, Kyung Hwan

    2015-11-01

    In this paper, we present the preparation and characterization of Schottky barrier diodes based on silicon carbide with various Schottky metal layer thickness values. In this structure, molybdenum and aluminum were employed as the Schottky barrier metal and top electrode, respectively. Schottky metal layers were deposited with thicknesses ranging from 1000 to 3000 Å, and top electrodes were deposited with thickness as much as 3000 Å. The deposition of both metal layers was performed using the facing target sputtering (FTS) method, and the fabricated samples were annealed with the tubular furnace at 300 degrees C under argon ambient for 10 min. The Schottky barrier height, series resistance, and ideality factor was calculated from the forward I-V characteristic curve using the methods proposed by Cheung and Cheung, and by Norde. For as-deposited Schottky diodes, we observed an increase of the threshold voltage (V(T)) as the thickness of the Schottky metal layer increased. After the annealing, the Schottky barrier heights (SBHs) of the diodes, including Schottky metal layers of over 2000 Å, increased. In the case of the Schottky metal layer deposited to 1000 Å, the barrier heights decreased due to the annealing process. This may have been caused by the interfacial penetration phenomenon through the Schottky metal layer. For variations of V(T), the SBH changed with a similar tendency. The ideality factor and series resistance showed no significant changes before or after annealing. This indicates that this annealing condition is appropriate for Mo SiC structures. Our results confirm that it is possible to control V(T) by adjusting the thickness of the Schottky metal layer.

  6. INTERFACE STRUCTURE AND SCHOTTKY BARRIERS AT EPITAXIAL SI(111)/PB INTERFACES

    NARCIS (Netherlands)

    WEITERING, HH; HIBMA, T; HESLINGA, DR; KLAPWIJK, TM

    1991-01-01

    Two different epitaxial Si(111)/Pb interfaces can be prepared, i.e. a metastable interface with a (7 x 7) and a stable interface with an incommensurate but close to (square-root 3 x square-root 3)R30-degrees surface unit cell. Schottky barrier heights of diodes made by depositing thick Pb layers on

  7. Summary of Schottky barrier height data on epitaxially grown n-and p-GaAs

    CSIR Research Space (South Africa)

    Myburg, G

    1998-07-18

    Full Text Available epitaxially (OMVPE) grown (100) n-type GaAs material and 13 metals on molecular beam epitaxially grown (MBE) p-GaAs, are presented. Of all the metals involved in this study, Ga had the lowest mean Schottky barrier height of about 0.60 eV on n-GaAs...

  8. Tantalum oxide barrier in magnetic tunnel junctions

    Institute of Scientific and Technical Information of China (English)

    Guanghua Yu; Tingting Ren; Wei Ji; Jiao Teng; Fengwu Zhu

    2004-01-01

    Tantalum as an insulating barrier can take the place of Al in magnetic tunnel junctions (MTJs). Ta barriers in MTJs were fabricated by natural oxidation. X-ray photoelectron spectroscopy (XPS) was used to characterize the oxidation states of Ta barrier.The experimental results show that the chemical state of tantalum is pure Ta5+ and the thickness of the oxide is 1.3 nm. The unoxidized Ta in the barrier may chemically reacted with NiFe layer which is usually used in MTJs to form an intermetallic compound,NiTa2. A magnetic "dead layer" could be produced in the NiFe/Ta interface. The "dead layer" is likely to influence the spinning electron transport and the magnetoresistance effect.

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

    Science.gov (United States)

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

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Xu, Ke, E-mail: kxu2006@sinano.ac.cn; Wang, Jianfeng; Ren, Guoqiang [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-01-07

    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.

  11. Modeling and Design of a New Flexible Graphene-on-Silicon Schottky Junction Solar Cell

    Directory of Open Access Journals (Sweden)

    Francesco Dell’Olio

    2016-10-01

    Full Text Available A new graphene-based flexible solar cell with a power conversion efficiency >10% has been designed. The environmental stability and the low complexity of the fabrication process are the two main advantages of the proposed device with respect to other flexible solar cells. The designed solar cell is a graphene/silicon Schottky junction whose performance has been enhanced by a graphene oxide layer deposited on the graphene sheet. The effect of the graphene oxide is to dope the graphene and to act as anti-reflection coating. A silicon dioxide ultrathin layer interposed between the n-Si and the graphene increases the open-circuit voltage of the cell. The solar cell optimization has been achieved through a mathematical model, which has been validated by using experimental data reported in literature. The new flexible photovoltaic device can be integrated in a wide range of microsystems powered by solar energy.

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

    Science.gov (United States)

    Vali, Indudhar Panduranga; Shetty, Pramoda Kumara; Mahesha, M. G.; Petwal, V. C.; Dwivedi, Jishnu; Choudhary, R. J.

    2017-06-01

    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 (ΦB), ideality factor (n) and series resistance (Rs). 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 ΦB was observed as a function of EBI dose. The improved n with increased ΦB 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 Schottky contact parameters by metal deposition on the electron beam irradiated n-Si wafers.

  13. Near-ultraviolet lateral photovoltaic effect in Fe3O4/3C-SiC Schottky junctions.

    Science.gov (United States)

    Song, Bingqian; Wang, Xianjie; Li, Bo; Zhang, Lingli; Lv, Zhe; Zhang, Yu; Wang, Yang; Tang, Jinke; Xu, Ping; Li, Bingsheng; Yang, Yanqiang; Sui, Yu; Song, Bo

    2016-10-17

    In this paper, we report a sensitive lateral photovoltaic effect (LPE) in Fe3O4/3C-SiC Schottky junctions with a fast relaxation time at near-ultraviolet wavelengths. The rectifying behavior suggests that the large build-in electric field was formed in the Schottky junctions. This device has excellent position sensitivity as high as 67.8 mV mm-1 illuminated by a 405 nm laser. The optical relaxation time of the LPE is about 30 μs. The fast relaxation and high positional sensitivity of the LPE make the Fe3O4/3C-SiC junction a promising candidate for a wide range of ultraviolet/near-ultraviolet optoelectronic applications.

  14. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers.

    Science.gov (United States)

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-04-03

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%.

  15. 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.

  16. The energy barrier at noble metal/TiO{sub 2} junctions

    Energy Technology Data Exchange (ETDEWEB)

    Hossein-Babaei, F., E-mail: fhbabaei@kntu.ac.ir, E-mail: fhbabaei@yahoo.com; Lajvardi, Mehdi M., E-mail: mm.lajvardi@gmail.com; Alaei-Sheini, Navid, E-mail: navid-alaei@yahoo.com [Electronic Materials Laboratory, Industrial Control Center of Excellence, Electrical Engineering Department, K. N. Toosi University of Technology, Tehran 16317-14191 (Iran, Islamic Republic of)

    2015-02-23

    Nobel metal/TiO{sub 2} structures are used as catalysts in chemical reactors, active components in TiO{sub 2}-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO{sub 2} layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO{sub 2} behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 10{sup 6} times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO{sub 2} contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

  17. 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.

  18. Single Schottky junction FETs based on Si:P nanowires with axially graded doping

    Science.gov (United States)

    Barreda, Jorge; Keiper, Timothy; Zhang, Mei; Xiong, Peng

    2015-03-01

    Si nanowires (NWs) with a systematic axial increase in phosphorus doping have been synthesized via a vapor-liquid-solid method. Silane and phosphine precursor gases are utilized for the growth and doping, respectively. The phosphorous doping profile is controlled by the flow ratio of the precursor gases. After the as-grown product is ultrasonically agitated into a solution, the Si NWs are dispersed on a SiO2 substrate with a highly doped Si back gate. Individual NWs are identified for the fabrication of field-effect transistors (FETs) with multiple Cr/Ag contacts along the NW. Two-probe and four-probe measurements are taken systematically under vacuum conditions at room temperature and the contribution from each contact and each NW section between adjacent contacts is determined. The graded doping level, produced by a systematic reduction in dopant density along the length of the NWs, is manifested in the regular increases in the channel and contact resistances. Our Si NWs facilitate the fabrication of asymmetric FETs with one ohmic and one Schottky contact. A significant increase in gate modulation is obtained due to the single Schottky-barrier contact. Characterization details and the applicability for sensing purposes will be discussed.

  19. Surface-plasmon-enhanced photodetection in planar Au-GaAs Schottky junctions

    Energy Technology Data Exchange (ETDEWEB)

    Daboo, C.; Baird, M.J.; Hughes, H.P. (PCS Group, Cavendish Lab., Cambridge (UK)); Apsley, N. (Royal Signals and Radar Establishment, Great Malvern (UK)); Jones, G.A.C.; Frost, J.E.F.; Peacock, D.C.; Ritchie, D.A. (Semiconductor Physics Group, Cavendish Lab., Cambridge (UK))

    1990-08-01

    Surface plasmon resonances have been used to enhance the quantum efficiency in a gold on n-type GaAs Schottky barrier on a suitable prism coupler in the Kretschmann-Raether attenuated total reflection geometry. We have investigated the gold thickness dependence of reflectivity and quantum efficiency for p-polarized and s-polarized light of a wavelength 1152 nm, below the GaAs band gap. Theoretical modelling of the reflectivity and quantum efficiency has been carried out. Both the experimental data and modelling indicate that optimum coupling to the surface plasmon, evidenced by a minimum in reflectivity with a corresponding peak in quantum efficiency for p-polarized light only, occurs for a gold thickness of about 40 nm. (orig.).

  20. 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.

  1. High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.; Li, X.; Xu, P.; Wang, Y.; Shen, X.; Liu, X.; Yang, Q., E-mail: qingyang@zju.edu.cn [State Key Laboratory of Modern Optical Instrumentation, Department of Optical Engineering, Zhejiang University, Hangzhou 310027 (China); Hasan, T. [Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA (United Kingdom)

    2015-02-02

    We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 μA) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 μA current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecture offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.

  2. Observation of strain relaxation in Si{sub 1-x}Ge{sub x} layers by optical and electrical characterisation of a Schottky junction

    Energy Technology Data Exchange (ETDEWEB)

    Turan, R.; Aslan, B. [Middle East Technical Univ., Ankara (Turkey). Dept. of Physics; Nur, O.; Yousif, M.Y.A.; Willander, M. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Physics

    2001-05-01

    We have studied the effect of the strain relaxation on the band-edge alignments in a Pt/p-Si{sub 1-x}Ge{sub x} Schottky junction with x=0.14 by internal photoemission spectroscopy and current-voltage measurements. We have shown that the variations in the band-edge alignments can be observed directly by measuring the optical and electrical properties of a simple Schottky junction. The strain in the Si{sub 1-x}Ge{sub x} layer has been partially relaxed by thermal treatments at two different temperatures. The degree of relaxation and other structural changes have been determined by a high-resolution X-ray diffractometer. Both optical and electrical techniques have shown that the barrier height of the Pt/Si{sub 0.86}Ge{sub 0.14} junction increases with the amount of relaxation in the Si{sub 1-x}Ge{sub x} layer. This shows that the valence-band edge of the Si{sub 1-x}Ge{sub x} layer moves away from the Fermi level of the Pt/Si{sub 1-x}Ge{sub x} junction. The band-edge movement results from the increase in the band gap of the Si{sub 1-x}Ge{sub x} layer after the strain relaxation. This result agrees with the theoretical predictions for the strain-induced effects on the Si{sub 1-x}Ge{sub x} band structure. (orig.)

  3. 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.

  4. Electronic parameters of high barrier Au/Rhodamine-101/n-Inp Schottky diode with organic Latin-Small-Letter-Dotless-I nterlayer

    Energy Technology Data Exchange (ETDEWEB)

    Guellue, Oe. [Batman University, Faculty of Sciences and Arts, Department of Physics, Batman (Turkey); Aydogan, S., E-mail: saydogan@atauni.edu.tr [Atatuerk University, Faculty of Sciences, Department of Physics, 25240-Erzurum (Turkey); Tueruet, A. [Atatuerk University, Faculty of Sciences, Department of Physics, 25240-Erzurum (Turkey)

    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 {mu}A and 240 mV, respectively.

  5. 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.

  6. Demonstration of a 4H SiC Betavoltaic Nuclear Battery Based on Schottky Barrier Diode

    Institute of Scientific and Technical Information of China (English)

    QIAO Da-Yong; YUAN Wei-Zheng; GAO Peng; YAO Xian-Wang; ZANG Bo; ZHANG Lin; GUO Hui; ZHANG Hong-Jian

    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 4mCi/cm2, an open circuit voltage of 0.49 V and a short circuit current density of 29.44 nA/cm2 are measured. A power conversion effciency 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.

  7. High ethanol sensitivity of palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions.

    Science.gov (United States)

    Wang, Dongzhou; Zhou, Weijia; Hu, Peiguang; Guan, Yu; Chen, Limei; Li, Jianhua; Wang, Guancong; Liu, Hong; Wang, Jiyang; Cao, Guozhong; Jiang, Huaidong

    2012-12-15

    TiO(2) nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO(2) nanobelts, surface-coarsened TiO(2) nanobelts and Pd nanoparticle/TiO(2) nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO(2) nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO(2) nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO(2) nanobelts.

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

    Science.gov (United States)

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

    2015-12-01

    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.

  9. Subthreshold Schottky-barrier thin-film transistors with ultralow power and high intrinsic gain

    Science.gov (United States)

    Lee, Sungsik; Nathan, Arokia

    2016-10-01

    The quest for low power becomes highly compelling in newly emerging application areas related to wearable devices in the Internet of Things. Here, we report on a Schottky-barrier indium-gallium-zinc-oxide thin-film transistor operating in the deep subthreshold regime (i.e., near the OFF state) at low supply voltages (400) that was both bias and geometry independent. The transistor reported here is useful for sensor interface circuits in wearable devices where high current sensitivity and ultralow power are vital for battery-less operation.

  10. Double ferromagnetic metal/semiconductor schottky barrier confined quasi-ballistic transport channel as spin polarizer

    Institute of Scientific and Technical Information of China (English)

    Wen Wu

    2007-01-01

    Spin polarizer is one of the most important devices for the newly developing field of spintronics, which may revolute the popular information techniques. Here we present a phenomenal model for a novel spin polarizer, which utilizes two back to back ferromagnetic metal/semiconductor Schottky barriers to define a semiconductor transport channel whose length is less than the spin decoherence length of the host semiconductor. Along this channel, conducting electrons move diffusively in momentum space while they keep ballistic motion in spin space. Across the channel, electrons suffer a spin dependent tunneling, which establishes spin polarization along the channel.

  11. 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

    Using ab initio calculations we investigate the energy level alignment at the graphene/MoS2 heterostructure and the use of electron doping as a strategy to lower the Schottky barrier and achieve a low-resistance Ohmic contact. For the neutral heterostructure, density functional theory (DFT...... 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...... concentration is shown to be mainly governed by the electrostatic potential resulting from the doping charge....

  12. Schottky barrier height in metal-SiC contact - new approach to modelling

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, P.A.; Ignat`ev, K.I. [Ioffe Physico-Technical Inst., St. Petersburg (Russian Federation)

    1998-08-01

    A new approach to calculate Schottky barrier height in a metal-SiC contact is proposed proceeding from uniform spatial distribution of electron traps within metal-to-SiC gap represented by native oxide. The model explains well experimental data on metal-6H-SiC contacts, with comparatively low mid-gap surface state density. This is in contrast with widely used analytical model by Cowley and Sze providing high interface state density at the 6H-SiC mid-gap. (orig.) 5 refs.

  13. Anomalous forward I-V characteristics of Ti/Au SiC Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, D.J.; Wright, N.G.; Johnson, C.M.; O' Neill, A.G. [Newcastle upon Tyne Univ. (UK). Dept. of Electr. and Electron. Eng.; Hilton, K.P.; Uren, M.J. [Defence Evaluation Research Agency, Malvern, Worcestershire (United Kingdom)

    1999-07-30

    The aim of this study was to improve the adhesion of Au Schottky contacts to SiC. In order to do this, before the deposition of the Au layer, a thin layer of Ti was deposited. However, this resulted in an anomalous step in the forward bias electrical characteristic for some diodes. An equivalent circuit model is introduced to explain this irregularity in terms of two barrier heights. PSPICE is used to simulate this model. Simulated and experimental data are in good agreement over the temperature range 25 to 250 C. (orig.)

  14. Formation of Schottky-type metal/SrTiO{sub 3} junctions and their resistive properties

    Energy Technology Data Exchange (ETDEWEB)

    Stoecker, Hartmut; Zschornak, Matthias [Technische Universitaet Dresden, Institut fuer Strukturphysik, Dresden (Germany); TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Seibt, Juliane; Hanzig, Florian; Wintz, Susi; Abendroth, Barbara; Meyer, Dirk C. [TU Bergakademie Freiberg, Institut fuer Experimentelle Physik, Freiberg (Germany); Kortus, Jens [TU Bergakademie Freiberg, Institut fuer Theoretische Physik, Freiberg (Germany)

    2010-08-15

    Motivated by the successful use of strontium titanate with different doping metals for memory cells on the basis of resistive switching and the recent findings on the major importance of oxygen vacancy redistribution in this compound, the present work shows the possibility of a non-volatile resistance change memory based on vacancy-doped SrTiO{sub 3}. The formation of corresponding metal/SrTiO{sub 3-{delta}} junctions ({delta}>0) in an electric field will be discussed as well as the switching between ohmic and Schottky-type contact behavior. A notable hysteresis in the current-voltage characteristics is used to carry out Write, Read, and Erase operations exemplifying the memory cell properties of such junctions. But whereas the electric field-induced formation of Schottky-type junctions is explainable by oxygen vacancy redistribution, the resistive switching needs to be discussed in terms of vacancies serving as electron trap states at the metal/oxide interface. (orig.)

  15. Annealing dependence of diamond-metal Schottky barrier heights probed by hard x-ray photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gaowei, M.; Muller, E. M. [Department of Materials Science and Engineering, SUNY Stony Brook, Stony Brook, New York 11794 (United States); Rumaiz, A. K. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States); Weiland, C.; Cockayne, E.; Woicik, J. C. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Jordan-Sweet, J. [IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Smedley, J. [Instrumentation Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

    2012-05-14

    Hard x-ray photoelectron spectroscopy was applied to investigate the diamond-metal Schottky barrier heights for several metals and diamond surface terminations. The position of the diamond valence-band maximum was determined by theoretically calculating the diamond density of states and applying cross section corrections. The diamond-platinum Schottky barrier height was lowered by 0.2 eV after thermal annealing, indicating annealing may increase carrier injection in diamond devices leading to photoconductive gain. The platinum contacts on oxygen-terminated diamond was found to provide a higher Schottky barrier and therefore a better blocking contact than that of the silver contact in diamond-based electronic devices.

  16. 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.)

  17. A novel ultra steep dynamically reconfigurable electrostatically doped silicon nanowire Schottky Barrier FET

    Science.gov (United States)

    Singh, Sangeeta; Sinha, Ruchir; Kondekar, P. N.

    2016-05-01

    In this paper, an ultra steep, symmetric and dynamically configurable, electrostatically doped silicon nanowire Schottky FET (E-SiNW-SB-FET) based on dopant-free technology is investigated. It achieves the ultra steep sub-threshold slope (SS) due to the cumulative effect of weak impact-ionization induced positive feedback and electrostatic modulation of Schottky barrier heights at both source and drain terminals. It consists of axial nanowire heterostructure (silicide-intrinsic silicon-silicide) with three independent all-around gates, two gates are polarity control gates for dynamically reconfiguring the device polarity by modulating the effective Schottky barrier heights and a control gate switches the device ON and OFF. The most interesting features of the proposed structure are simplified fabrication process as the state-of-the-art for ion implantation and high thermal budget no more required for annealing. It is highly immune to process variations, doping control issues and random dopant fluctuations (RDF) and there are no mobility degradation issues related to high doping. A calibrated 3-D TCAD simulation results exhibit the SS of 2 mV/dec for n-type E-SiNW-SB-FET and 9 mV/dec for p-type E-SiNW-SB-FET for about five decades of current. Further, it resolves all the reliability related issues of IMOS as hot electron effects are no more limiting our device performance. It offers significant drive current of the order of 10-5-10-4 A and magnificently high ION/IOFF ratio of ∼108 along with the inherent advantages of symmetric device structure for its circuit realization.

  18. Enhanced Thermionic Emission and Low 1/f Noise in Exfoliated Graphene/GaN Schottky Barrier Diode.

    Science.gov (United States)

    Kumar, Ashutosh; Kashid, Ranjit; Ghosh, Arindam; Kumar, Vikram; Singh, Rajendra

    2016-03-01

    Temperature-dependent electrical transport characteristics of exfoliated graphene/GaN Schottky diodes are investigated and compared with conventional Ni/GaN Schottky diodes. The ideality factor of graphene/GaN and Ni/GaN diodes are measured to be 1.33 and 1.51, respectively, which is suggestive of comparatively higher thermionic emission current in graphene/GaN diode. The barrier height values for graphene/GaN diode obtained using thermionic emission model and Richardson plots are found to be 0.60 and 0.72 eV, respectively, which are higher than predicted barrier height ∼0.40 eV as per the Schottky-Mott model. The higher barrier height is attributed to hole doping of graphene due to graphene-Au interaction which shifts the Fermi level in graphene by ∼0.3 eV. The magnitude of flicker noise of graphene/GaN Schottky diode increases up to 175 K followed by its decrease at higher temperatures. This indicates that diffusion currents and barrier inhomogeneities dominate the electronic transport at lower and higher temperatures, respectively. The exfoliated graphene/GaN diode is found to have lower level of barrier inhomogeneities than conventional Ni/GaN diode, as well as earlier reported graphene/GaN diode fabricated using chemical vapor deposited graphene. The lesser barrier inhomogeneities in graphene/GaN diode results in lower flicker noise by 2 orders of magnitude as compared to Ni/GaN diode. Enhanced thermionic emission current, lower level of inhomogeneities, and reduced flicker noise suggests that graphene-GaN Schottky diodes may have the underlying trend for replacing metal-GaN Schottky diodes.

  19. Carrier dynamics and design optimization of electrolyte-induced inversion layer carbon nanotube-silicon Schottky junction solar cell

    Science.gov (United States)

    Chen, Wenchao; Seol, Gyungseon; Rinzler, Andrew G.; Guo, Jing

    2012-03-01

    Carrier dynamics of the electrolyte-induced inversion layer carbon nanotube-silicon Schottky junction solar cells is explored by numerical simulations. Operation mechanisms of the solar cells with and without the electrolyte-induced inversion layer are presented and compared, which clarifies the current flow mechanisms in a solar cell with an induced inversion layer. A heavily doped back contact layer can behave as a hole block layer. In addition to lowering contact resistance and surface recombination, it is particularly useful for improving carrier separation in an electrolyte-induced inversion layer solar cell or a metal-insulator-semiconductor grating solar cell.

  20. A planar Al-Si Schottky barrier metal–oxide–semiconductor field effect transistor operated at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Purches, W. E. [School of Physics, UNSW, Sydney 2052 (Australia); Rossi, A.; Zhao, R. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Kafanov, S.; Duty, T. L. [School of Physics, UNSW, Sydney 2052 (Australia); Centre for Engineered Quantum Systems (EQuS), School of Physics, UNSW, Sydney 2052 (Australia); Dzurak, A. S. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia); Rogge, S.; Tettamanzi, G. C., E-mail: g.tettamanzi@unsw.edu.au [School of Physics, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia)

    2015-08-10

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  1. High-voltage (> 1 kV) SiC Schottky barrier diodes with low on-resistance

    Energy Technology Data Exchange (ETDEWEB)

    Kimoto, Tsunenobu; Urushidani, Tatsuo; Kobayashi, Sota; Matsunami, Hiroyuki (Kyoto Univ. (Japan). Dept. of Electrical Engineering)

    1993-12-01

    Au/6H-SiC Schottky barrier diodes with high blocking voltages were successfully fabricated using layers grown by step-controlled epitaxy. A breakdown voltage over 1,100 V could be achieved, which is the highest ever reported for silicon carbide (SiC) Schottky barrier diodes. These high-voltage SiC rectifiers had specific on-resistances lower than the theoretical limits of Si rectifiers by more than one order of magnitude. The specific on-resistance increased with temperature according to T[sup 2.0] dependence. The diodes showed good characteristics at temperature as high as 400 C.

  2. Controllable Schottky barrier in GaSe/graphene heterostructure: the role of interface dipole

    Science.gov (United States)

    Si, Chen; Lin, Zuzhang; Zhou, Jian; Sun, Zhimei

    2017-03-01

    The discoveries of graphene and other related two-dimensional crystals have recently led to a new technology: van der Waals (vdW) heterostructures based on these atomically thin materials. Such a paradigm has been proved promising for a wide range of applications from nanoelectronics to optoelectronics and spintronics. Here, using first-principles calculations, we investigate the electronic structure and interface characteristics of a newly synthesized GaSe/graphene (GaSe/g) vdW heterostructure. We show that the intrinsic electronic properties of GaSe and graphene are both well preserved in the heterostructure, with a Schottky barrier formed at the GaSe/g interface. More interestingly, the band alignment between graphene and GaSe can be effectively modulated by tuning the interfacial distance or applying an external electric filed. This makes the Schottky barrier height (SBH) controllable, which is highly desirable in the electronic and optoelectronic devices based on vdW heterostructures. In particular, the tunability of the interface dipole and potential step is further uncovered to be the underlying mechanism that ensures this controllable tuning of SBH.

  3. Performance comparison of zero-Schottky-barrier and doped contacts carbon nanotube transistors with strain applied

    Institute of Scientific and Technical Information of China (English)

    Md Abdul Wahab; Khairul Alam

    2010-01-01

    Atomistic quantum simulation is performed to compare the performance of zero-Schottky-barrier and doped source-drain contacts carbon nanotube field effect transistors (CNTFETs) with strain applied. The doped source-drain contact CNTFETs outperform the Schottky contact devices with and without strain applied. The off-state current in both types of contact is similar with and without strain applied. This is because both types of contact offer very similar potential barrier in off-state. However, the on-state current in doped contact devices is much higher due to better modulation of on-state potential profile, and its variation with strain is sensitive to the device contact type. The on/off current ratio and the inverse subthreshold slope are better with doped source-drain contact, and their variations with strain are relatively less sensitive to the device contact type. The channel transconductance and device switching performance are much better with doped source-drain contact, and their variations with strain are sensitive to device contact type.

  4. Novel field-effect schottky barrier transistors based on graphene-MoS 2 heterojunctions

    KAUST Repository

    Tian, He

    2014-08-11

    Recently, two-dimensional materials such as molybdenum disulphide (MoS 2) have been demonstrated to realize field effect transistors (FET) with a large current on-off ratio. However, the carrier mobility in backgate MoS2 FET is rather low (typically 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 in the novel transistors. Large modulation on the device current (on/off ratio of 105) is achieved by adjusting the backgate (through 300 nm SiO2) voltage to modulate the graphene-MoS2 Schottky barrier. Moreover, the field effective mobility of the FESBT is up to 58.7 cm2/V.s. Our theoretical analysis shows that if the thickness of oxide is further reduced, a subthreshold swing (SS) of 40 mV/decade can be maintained within three orders of drain current at room temperature. This provides an opportunity to overcome the limitation of 60 mV/decade for conventional CMOS devices. The FESBT implemented with a high on-off ratio, a relatively high mobility and a low subthreshold promises low-voltage and low-power applications for future electronics.

  5. Schottky barrier and contact resistance of InSb nanowire field-effect transistors

    Science.gov (United States)

    Fan, Dingxun; Kang, N.; Gorji Ghalamestani, Sepideh; Dick, Kimberly A.; Xu, H. Q.

    2016-07-01

    Understanding of the electrical contact properties of semiconductor nanowire (NW) field-effect transistors (FETs) plays a crucial role in the use of semiconducting NWs as building blocks for future nanoelectronic devices and in the study of fundamental physics problems. Here, we report on a study of the contact properties of Ti/Au, a widely used contact metal combination, when contacting individual InSb NWs via both two-probe and four-probe transport measurements. We show that a Schottky barrier of height {{{Φ }}}{{SB}}˜ 20 {{meV}} is present at the metal-InSb NW interfaces and its effective height is gate-tunable. The contact resistance ({R}{{c}}) in the InSb NWFETs is also analyzed by magnetotransport measurements at low temperatures. It is found that {R}{{c}} in the on-state exhibits a pronounced magnetic field-dependent feature, namely it is increased strongly with increasing magnetic field after an onset field {B}{{c}}. A qualitative picture that takes into account magnetic depopulation of subbands in the NWs is provided to explain the observation. Our results provide solid experimental evidence for the presence of a Schottky barrier at Ti/Au-InSb NW interfaces and can be used as a basis for design and fabrication of novel InSb NW-based nanoelectronic devices and quantum devices.

  6. Electrical Characterization of High Energy Electron Irradiated Ni/4 H-SiC Schottky Barrier Diodes

    Science.gov (United States)

    Paradzah, A. T.; Omotoso, E.; Legodi, M. J.; Auret, F. D.; Meyer, W. E.; Diale, M.

    2016-08-01

    The effect of high energy electron irradiation on Ni/4 H-SiC Schottky barrier diodes was evaluated by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements at room temperature. Electron irradiation was achieved by using a radioactive strontium source with peak emission energy of 2.3 MeV. Irradiation was performed in fluence steps of 4.9 × 1013 cm-2 until a total fluence of 5.4 × 1014 cm-2 was reached. The Schottky barrier height determined from I- V measurements was not significantly changed by irradiation while that obtained from C- V measurements increased with irradiation. The ideality factor was obtained before irradiation as 1.05 and this value did not significantly change as a result of irradiation. The series resistance increased from 47 Ω before irradiation to 74 Ω after a total electron fluence of 5.4 × 1014 cm-2. The net donor concentration decreased with increasing irradiation fluence from 4.6 × 1014 cm-3 to 3.0 × 1014 cm-3 from which the carrier removal rate was calculated to be 0.37 cm-1.

  7. The dependence of the Schottky barrier height on carbon nanotube diameter for Pd-carbon nanotube contacts

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Johannes; Sourab, Abdelrahim A; Campbell, Eleanor E B [Department of Physics, Goeteborg University, SE-41296 Goeteborg (Sweden); Tarakanov, Yury [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Lee, Dong Su [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany); Park, Seung Joo; Baek, Seung Jae; Park, Yung Woo [School of Physics, Seoul National University, Seoul 151-747 (Korea, Republic of)], E-mail: ywpark@phya.snu.ac.kr, E-mail: eleanor.campbell@ed.ac.uk

    2009-04-29

    Direct measurements are presented of the Schottky barrier (SB) heights of carbon nanotube devices contacted with Pd electrodes. The SB barrier heights were determined from the activation energy of the temperature-dependent thermionic emission current in the off-state of the devices. The barrier heights generally decrease with increasing diameter of the nanotubes and they are in agreement with the values expected when assuming little or no influence of Fermi level pinning.

  8. The dependence of the Schottky barrier height on carbon nanotube diameter for Pd-carbon nanotube contacts

    OpenAIRE

    Svensson, Johannes; Sourab, Abdelrahim A.; Tarakanov, Yury; Lee, Dong Su; Park, Seung Joo; Baek, Seung Jae; Park, Yung Woo; Campbell, Eleanor E. B.

    2009-01-01

    Direct measurements are presented of the Schottky barrier (SB) heights of carbon nanotube devices contacted with Pd electrodes. The SB barrier heights were determined from the activation energy of the temperature-dependent thermionic emission current in the off-state of the devices. The barrier heights generally decrease with increasing diameter of the nanotubes and they are in agreement with the values expected when assuming little or no influence of Fermi level pinning.

  9. Schottky barrier contrasts in single and bi-layer graphene contacts for MoS2 field-effect transistors

    Science.gov (United States)

    Du, Hyewon; Kim, Taekwang; Shin, Somyeong; Kim, Dahye; Kim, Hakseong; Sung, Ji Ho; Lee, Myoung Jae; Seo, David H.; Lee, Sang Wook; Jo, Moon-Ho; Seo, Sunae

    2015-12-01

    We have investigated single- and bi-layer graphene as source-drain electrodes for n-type MoS2 transistors. Ti-MoS2-graphene heterojunction transistors using both single-layer MoS2 (1M) and 4-layer MoS2 (4M) were fabricated in order to compare graphene electrodes with commonly used Ti electrodes. MoS2-graphene Schottky barrier provided electron injection efficiency up to 130 times higher in the subthreshold regime when compared with MoS2-Ti, which resulted in VDS polarity dependence of device parameters such as threshold voltage (VTH) and subthreshold swing (SS). Comparing single-layer graphene (SG) with bi-layer graphene (BG) in 4M devices, SG electrodes exhibited enhanced device performance with higher on/off ratio and increased field-effect mobility (μFE) due to more sensitive Fermi level shift by gate voltage. Meanwhile, in the strongly accumulated regime, we observed opposing behavior depending on MoS2 thickness for both SG and BG contacts. Differential conductance (σd) of 1M increases with VDS irrespective of VDS polarity, while σd of 4M ceases monotonic growth at positive VDS values transitioning to ohmic-like contact formation. Nevertheless, the low absolute value of σd saturation of the 4M-graphene junction demonstrates that graphene electrode could be unfavorable for high current carrying transistors.

  10. Mechanisms of the degradation of Schottky-barrier photodiodes based on ZnS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Korsunska, N. E.; Shulga, E. P.; Stara, T. R., E-mail: stara-t@ukr.net; Litvin, P. M.; Bondarenko, V. A. [National Academy of Sciences of Ukraine, Lashkarev Institute of Semiconductor Physics (Ukraine)

    2016-01-15

    The effect of ultraviolet (UV) illumination on the electrical and spectral characteristics of Schottky-barrier photodiodes based on ZnS single crystals is studied. It is found that irradiation deteriorates their photosensitivity and changes the current–voltage and capacitance–voltage characteristics and the surface profile of the blocking electrode. It is shown that the main reason for a decrease in the photosensitivity of the diodes is the photoinduced drift of mobile donors in the electric field of the barrier. This drift depends on the crystallographic orientation of the surface being irradiated. Another photoinduced process observed in the diodes is photolysis of the ZnS crystal. This process mainly determines the change in the electrical characteristics of the diodes and in the surface profile of the electrode at an insignificant change in the photosensitivity.

  11. Intermediate type excitons in Schottky barriers of A3B6 layer semiconductors and UV photodetectors

    Science.gov (United States)

    Alekperov, O. Z.; Guseinov, N. M.; Nadjafov, A. I.

    2006-09-01

    Photoelectric and photovoltaic spectra of Schottky barrier (SB) structures of InSe, GaSe and GaS layered semiconductors (LS) are investigated at quantum energies from the band edge excitons of corresponding materials up to 6.5eV. Spectral dependences of photoconductivity (PC) of photo resistors and barrier structures are strongly different at the quantum energies corresponding to the intermediate type excitons (ITE) observed in these semiconductors. It was suggested that high UV photoconductivity of A3B6 LS is due to existence of high mobility light carriers in the depth of the band structure. It is shown that SB of semitransparent Au-InSe is high sensitive photo detector in UV region of spectra.

  12. Direct control and characterization of a Schottky barrier by scanning tunneling microscopy

    Science.gov (United States)

    Bell, L. D.; Kaiser, W. J.; Hecht, M. H.; Grunthaner, F. J.

    1988-01-01

    Scanning tunneling microscopy (STM) methods are used to directly control the barrier height of a metal tunnel tip-semiconductor tunnel junction. Barrier behavior is measured by tunnel current-voltage spectroscopy and compared to theory. A unique surface preparation method is used to prepare a low surface state density Si surface. Control of band bending with this method enables STM investigation of semiconductor subsurface properties.

  13. Composite Transparent Electrode of Graphene Nanowalls and Silver Nanowires on Micropyramidal Si for High-Efficiency Schottky Junction Solar Cells.

    Science.gov (United States)

    Jiao, Tianpeng; Liu, Jian; Wei, Dapeng; Feng, Yanhui; Song, Xuefen; Shi, Haofei; Jia, Shuming; Sun, Wentao; Du, Chunlei

    2015-09-16

    The conventional graphene-silicon Schottky junction solar cell inevitably involves the graphene growth and transfer process, which results in complicated technology, loss of quality of the graphene, extra cost, and environmental unfriendliness. Moreover, the conventional transfer method is not well suited to conformationally coat graphene on a three-dimensional (3D) silicon surface. Thus, worse interfacial conditions are inevitable. In this work, we directly grow graphene nanowalls (GNWs) onto the micropyramidal silicon (MP) by the plasma-enhanced chemical vapor deposition method. By controlling growth time, the cell exhibits optimal pristine photovoltaic performance of 3.8%. Furthermore, we improve the conductivity of the GNW electrode by introducing the silver nanowire (AgNW) network, which could achieve lower sheet resistance. An efficiency of 6.6% has been obtained for the AgNWs-GNWs-MP solar cell without any chemical doping. Meanwhile, the cell exhibits excellent stability exposed to air. Our studies show a promising way to develop simple-technology, low-cost, high-efficiency, and stable Schottky junction solar cells.

  14. Titanium Oxide Crystallization and Interface Defect Passivation for High Performance Insulator-Protected Schottky Junction MIS Photoanodes.

    Science.gov (United States)

    Scheuermann, Andrew G; Lawrence, John P; Meng, Andrew C; Tang, Kechao; Hendricks, Olivia L; Chidsey, Christopher E D; McIntyre, Paul C

    2016-06-15

    Atomic layer deposited (ALD) TiO2 protection layers may allow for the development of both highly efficient and stable photoanodes for solar fuel synthesis; however, the very different conductivities and photovoltages reported for TiO2-protected silicon anodes prepared using similar ALD conditions indicate that mechanisms that set these key properties are, as yet, poorly understood. In this report, we study hydrogen-containing annealing treatments and find that postcatalyst-deposition anneals at intermediate temperatures reproducibly yield decreased oxide/silicon interface trap densities and high photovoltage. A previously reported insulator thickness-dependent photovoltage loss in metal-insulator-semiconductor Schottky junction photoanodes is suppressed. This occurs simultaneously with TiO2 crystallization and an increase in its dielectric constant. At small insulator thickness, a record for a Schottky junction photoanode of 623 mV photovoltage is achieved, yielding a photocurrent turn-on at 0.92 V vs NHE or -0.303 V with respect to the thermodynamic potential for water oxidation.

  15. Ni/SiC–6H Schottky Barrier Diode interfacial states characterization related to temperature

    Energy Technology Data Exchange (ETDEWEB)

    Benamara, Mekki [Applied Microelectronics Laboratory (AMEL), Electronics Department, Faculty of Technology, Djillali Liabes University of Sidi Bel Abbes, BP 89, 22000 Sidi Bel Abbes (Algeria); Anani, Macho, E-mail: anani66@yahoo.fr [Laboratoire des Réseaux de Communications, d’Architecture et de Multimédia, Electronics Department, Faculty of Technology, Djillali Liabes University of Sidi Bel Abbes, BP 89, 22000 Sidi Bel Abbes (Algeria); Akkal, Boudali; Benamara, Zineb [Applied Microelectronics Laboratory (AMEL), Electronics Department, Faculty of Technology, Djillali Liabes University of Sidi Bel Abbes, BP 89, 22000 Sidi Bel Abbes (Algeria)

    2014-08-01

    Highlights: • This article is dealing with the evaluation of the mean interfacial states density of a Ni/SiC–6H Schottky Barrier Diode related to temperature. It appears a phenomenon of two barriers materializing one high diode and one low one. The other conclusion is that the interfacial states are diminishing when temperature is increasing. • This article has not, also, been published previously, is not under consideration for publication elsewhere, and its publication is approved by all authors. • The article has been correctly and thoroughly inspected and revised according to the reviewers’ recommendations. - Abstract: This study presents a Ni/SiC–6H Schottky Barrier Diode (SBD) characterization at different temperatures going from 77 K to 450 K. The electronic properties of this diode were reported by the analysis of its C(V{sub G}) and I(V{sub G}) characteristics as a function of temperature. At low temperature when T < 100 K the high part ideality factors n{sup H} were close to 2 showing that the conduction is dominated by the generation–recombination at deep centers. Also, the values of low part ideality factor n{sup L} varied from 2.69 down to 1.89. These values were also much closer to 2, showing that the conduction mechanism was then dominated by a tunneling current assisted by default. The mean interfacial states density D{sub s(mean)} decreased with increasing temperature from 1.2×10{sup 13} eV{sup −1} cm{sup −2} to 6.3 × 10{sup 12} eV{sup −1} cm{sup −2}. This reducing appeared to be due to the restructuring and rearrangement which occurs under molecules thermal activation within the Ni/SiC–6H metal/semiconductor interface.

  16. Inhomogeneous barrier height effect on the current-voltage characteristics of an Au/n-InP Schottky diode

    Science.gov (United States)

    Zeghdar, Kamal; Dehimi, Lakhdar; Saadoune, Achour; Sengouga, Nouredine

    2015-12-01

    We report the current-voltage (I-V) characteristics of the Schottky diode (Au/n-InP) as a function of temperature. The SILVACO-TCAD numerical simulator is used to calculate the I-V characteristic in the temperature range of 280-400 K. This is to study the effect of temperature on the I-V curves and assess the main parameters that characterize the Schottky diode such as the ideality factor, the height of the barrier and the series resistance. The I-V characteristics are analyzed on the basis of standard thermionic emission (TE) theory and the inhomogeneous barrier heights (BHs) assuming a Gaussian distribution. It is shown that the ideality factor decreases while the barrier height increases with increasing temperature, on the basis of TE theory. Furthermore, the homogeneous BH value of approximately 0.524 eV for the device has been obtained from the linear relationship between the temperature-dependent experimentally effective BHs and ideality factors. The modified Richardson plot, according to the inhomogeneity of the BHs, has a good linearity over the temperature range. The evaluated Richardson constant A* was 10.32 A·cm-2·K-2, which is close to the theoretical value of 9.4 A·cm-2·K-2 for n-InP. The temperature dependence of the I-V characteristics of the Au/n-InP Schottky diode have been successfully explained on the basis of the thermionic emission (TE) mechanism with a Gaussian distribution of the Schottky barrier heights (SBHs). Simulated I-V characteristics are in good agreement with the measurements [Korucu D, Mammadov T S. J Optoelectronics Advanced Materials, 2012, 14: 41]. The barrier height obtained using Gaussian Schottky barrier distribution is 0.52 eV, which is about half the band gap of InP.

  17. Barrier Enhancement Effect of Postannealing in Oxygen Ambient on Ni/AlGaN Schottky Contacts

    Institute of Scientific and Technical Information of China (English)

    SANG Li-Wen; QIN Zhi-Xin; CEN Long-Bin; CHEN Zhi-Zhong; YANG Zhi-Jian; SHEN Bo; ZHANG Guo-Yi

    2007-01-01

    Al0.2Ga0.sN/GaN samples are grown by metalorganic chemical vapour deposition (MOCVD) method on (0001) sapphire substrates. A 10nm-thick Ni layer is deposited on AlGaN as the transparent Schottky contact. The effect of postannealing in oxygen ambient on the electrical properties of Ni/AlGaN is studied by current voltagetemperature (I-V-T) measurement. The annealing at a relatively low temperature of 300℃ for 90 s results in a decrease of the ideality factor from 2.03 to 1.30 and an increase of the Schottky barrier height from 0.77eV to 0.954 eV. The I-V-T analysis confirms the improvement originated from the formation of NiO, a layer with higher resistatce, which could passivate the surface states of AlGaN and suppress the tunnelling current. Furthermore,the annealing also leads to an increase of the transmittance of the contacts from 57.5% to 78.2%, which would be favourable for AlGaN-based photodetectors.

  18. Zinc Selenide-Based Schottky Barrier Detectors for Ultraviolet-A and Ultraviolet-B Detection

    Directory of Open Access Journals (Sweden)

    V. Naval

    2010-01-01

    Full Text Available Wide-bandgap semiconductors such as zinc selenide (ZnSe have become popular for ultraviolet (UV photodetectors due to their broad UV spectral response. Schottky barrier detectors made of ZnSe in particular have been shown to have both low dark current and high responsivity. This paper presents the results of electrical and optical characterization of UV sensors based on ZnSe/Ni Schottky diodes fabricated using single-crystal ZnSe substrate with integrated UV-A (320–400 nm and UV-B (280–320 nm filters. For comparison, characteristics characterization of an unfiltered detector is also included. The measured photoresponse showed good discrimination between the two spectral bands. The measured responsivities of the UV-A and UV-B detectors were 50 mA/W and 10 mA/W, respectively. A detector without a UV filter showed a maximum responsivity of about 110 mA/W at 375 nm wavelength. The speed of the unfiltered detector was found to be about 300 kHz primarily limited by the RC time constant determined largely by the detector area.

  19. Fabrication of a 600-V/20-A 4H-SiC schottky barrier diode

    Science.gov (United States)

    Kang, In-Ho; Kim, Sang-Cheol; Moon, Jung-Hyeon; Bahng, Wook; Kim, Nam-Kyun

    2014-06-01

    In this study, 600-V/20-A 4H-SiC Schottky barrier diodes (SBDs) were fabricated to investigate the effect of key processing steps, especially before and after the formation of a Schottky contact, on the electrical performances of SBDs and on their long-term reliabilities. The results show that 4H-SiC SBDs that had been subjected to a hydrogen-ambient annealing at 470 °C for 10 min and sacrificial treatment right after ion activation exhibited a lower forward voltage drop (V F ) at a rated current of 20 A, a higher blocking voltage of 800 V, and a very short reverse recovery time of 17.5 ns. Despite the harsh reverse bias condition and temperature, a long-term reliability test showed that changes in the forward voltage drop and the reverse leakage current (I R ) were 0.7% and 8.9% and that the blocking voltage was enhanced. This is attributed to the presence of a stabilized interface between the passivation layer and the SiC due to aging.

  20. Schottky barrier heights at the interfaces between pure-phase InAs nanowires and metal contacts

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Boyong; Huang, Shaoyun, E-mail: syhuang@pku.edu.cn, E-mail: hqxu@pku.edu.cn; Wang, Jiyin [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Pan, Dong; Zhao, Jianghua [State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Xu, H. Q., E-mail: syhuang@pku.edu.cn, E-mail: hqxu@pku.edu.cn [Key Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China); Division of Solid-State Physics, Lund University, Box 118, S-221 00 Lund (Sweden)

    2016-02-07

    Understanding of the Schottky barriers formed at metal contact-InAs nanowire interfaces is of great importance for the development of high-performance InAs nanowire nanoelectronic and quantum devices. Here, we report a systematical study of InAs nanowire field-effect transistors (FETs) and the Schottky barrier heights formed at the contact-nanowire interfaces. The InAs nanowires employed are grown by molecular beam epitaxy and are high material quality single crystals, and the devices are made by directly contacting the nanowires with a series of metals of different work functions. The fabricated InAs nanowire FET devices are characterized by electrical measurements at different temperatures and the Schottky barrier heights are extracted from the measured temperature and gate-voltage dependences of the channel current. We show that although the work functions of the contact metals are widely spread, the Schottky barrier heights are determined to be distributed over 35–55 meV, showing a weak but not negligible dependence on the metals. The deduced Fermi level in the InAs nanowire channels is found to be in the band gap and very close to the conduction band. The physical origin of the results is discussed in terms of Fermi level pinning by the surface states of the InAs nanowires and a shift in pinned Fermi level induced by the metal-related interface states.

  1. Field plate engineering for GaN-based Schottky barrier diodes

    Institute of Scientific and Technical Information of China (English)

    Lei Yong; Shi Hongbiao; Lu Hai; Chen Dunjun; Zhang Rong; Zheng Youdou

    2013-01-01

    The practical design of GaN-based Schottky barrier diodes (SBDs) incorporating a field plate (FP)structure necessitates an understanding of their working mechanism and optimization criteria.In this work,the influences of the parameters of FPs upon breakdown of the diode are investigated in detail and the design rules of FP structures for GaN-based SBDs are presented for a wide scale of material and device parameters.By comparing three representative dielectric materials (SiO2,Si3N4 and A12O3) selected for fabricating FPs,it is found that the product of dielectric permittivity and critical field strength of a dielectric material could be used as an index to predict its potential performance for FP applications.

  2. Formation and Schottky barrier height of Au contacts to CuInSe sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A.J.; Gebhard, S.; Kazmerski, L.L. (Solar Energy Research Institute, Golden, Colorado 80401 (USA)); Colavita, E. (Physics Department, University of Calabria, 87036 Arcavacata di Rende, Cosenza, Italy (IT)); Engelhardt, M.; Hoechst, H. (Synchrotron Radiation Center, University of Wisconsin-Madison, Stoughton, Wisconsin 53589 (USA))

    1991-05-01

    Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the Au/CuInSe{sub 2} interface. Au overlayers were deposited in steps on single-crystal {ital p} and {ital n}-type CuInSe{sub 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 4{ital d} and Se 3{ital d} 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{sub 2} Schottky barrier height.

  3. 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.

  4. A performance optimization and analysis of graphene based schottky barrier GaAs solar cell

    Science.gov (United States)

    Jolson Singh, Khomdram; Chettri, Dhanu; Jayenta Singh, Thokchom; Thingujam, Terirama; Sarkar, Subir kumar

    2017-06-01

    Performance optimization of Graphene-GaAs schottky barrier solar cell have been performed by considering variables such as substrate thickness, Graphene thickness, dependence between graphene work function and transmittance. The optimized parameter was extensively used to numerically model the design using TCAD Atlas. The results show the enhanced performance of the design with the optimized thickness of Graphene (0.3μm) and GaAs (10μm), resulting in significant increase in power conversion efficiency from 0.732% to 2.581% and reasonable fill factor up to 70%. It was further analysed that maximum potential was developed in the vicinity of the anode, which results in better charge collection hence improving the overall performance of the solar cell. The results are validated with the reported experimental work.

  5. Characterization of breakdown behavior of diamond Schottky barrier diodes using impact ionization coefficients

    Science.gov (United States)

    Driche, Khaled; Umezawa, Hitoshi; Rouger, Nicolas; Chicot, Gauthier; Gheeraert, Etienne

    2017-04-01

    Diamond has the advantage of having an exceptionally high critical electric field owing to its large band gap, which implies its high ability to withstand high voltages. At this maximum electric field, the operation of Schottky barrier diodes (SBDs), as well as FETs, may be limited by impact ionization, leading to avalanche multiplication, and hence the devices may breakdown. In this study, three of the reported impact ionization coefficients for electrons, αn, and holes, αp, in diamond at room temperature (300 K) are analyzed. Experimental data on reverse operation characteristics obtained from two different diamond SBDs are compared with those obtained from their corresponding simulated structures. Owing to the crucial role played by the impact ionization rate in determining the carrier transport, the three reported avalanche parameters implemented affect the behavior not only of the breakdown voltage but also of the leakage current for the same structure.

  6. 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

    2017-01-01

    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. PMID:28165485

  7. Evaluation of Schottky barrier diodes fabricated directly on processed 4H-SiC(0001) surfaces.

    Science.gov (United States)

    Sano, Yasuhisa; Shirasawa, Yuki; Okamoto, Takeshi; Yamauchi, Kazuto

    2011-04-01

    Silicon carbide (SiC) is a suitable substrate for low-power-consumption power devices and high-temperature applications. However, this material is difficult to machine because of its hardness and chemical inertness, and many machining methods have been studied intensively in recent years. In this paper, we present a simple method to evaluate the electrical properties of the processed surface using the ideal factor n of a Schottky barrier diode (SBD) fabricated directly on the processed surface. Upon comparing the values of n for SBDs fabricated on a damaged SiC surface and a non-damaged SiC surface, we found that there is a significant difference in the dispersion and magnitude of n. Furthermore, by combining this technique with slope etching, we were able to estimate the thickness of the damaged sub-surface layer.

  8. Heavy ion-induced damage in SiC Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Kamezawa, C. [Japan Aerospace Exploration Agency, Tsukuba Space Center, 2-1-1 Sengen, Ibaraki 305-8505 (Japan)]. E-mail: kamezawa.chihiro@jaxa.jp; Sindou, H. [Japan Aerospace Exploration Agency, Tsukuba Space Center, 2-1-1 Sengen, Ibaraki 305-8505 (Japan); Hirao, T. [Japan Atomic Energy Research Institute, Gunma 370-1292 (Japan); Ohyama, H. [Kumamoto National College of Technology, Kumamoto 861-1102 (Japan); Kuboyama, S. [Japan Aerospace Exploration Agency, Tsukuba Space Center, 2-1-1 Sengen, Ibaraki 305-8505 (Japan)

    2006-04-01

    Silicon carbide (SiC) is a very promising material for future electronic devices. Also it is an attractive material for space applications, that require long-term endurance and higher efficiency, where tolerance to space radiations is a major problem. In this study, we have performed some irradiation examinations and evaluations on a commercial SiC Schottky barrier diode by looking at the damage caused by ion incidence using heavy ions. Ions of Xe, Kr, Ar, Ne, and N, with specific energies, were used in the irradiation process. Sudden breakdown condition at higher bias voltage and gradual damage created by heavy ion incidence were confirmed. The collected charge spectra were also obtained and revealed mechanisms that resulted to permanent damage. The observed anomalous charge collection was an essential factor for the susceptibility. This indicates a problem that need to be solved in the future for SiC space application.

  9. Defect-induced performance degradation of 4H-SiC Schottky barrier diode particle detectors

    Science.gov (United States)

    Iwamoto, N.; Johnson, B. C.; Hoshino, N.; Ito, M.; Tsuchida, H.; Kojima, K.; Ohshima, T.

    2013-04-01

    The formation and evolution of defects in 4H-SiC Schottky barrier diode high-energy particle detectors have been investigated and correlated with the detectors' properties. Low temperature annealing at 300 °C is found to significantly recover the charge collection efficiency as degraded by 1 MeV electron irradiation. At higher temperatures, an anneal-induced degradation in the detector's performance is observed. Current-voltage, capacitance-voltage, and deep level transient spectroscopy (DLTS) measurements are used to ascertain the effect of defects on the detector performance. The latter reveals that the DLTS defect levels, EH1 and EH3, are related to the initial recovery of the charge collection efficiency.

  10. Analysis on partial thermal resistances of packaged SiC schottky barrier diodes at elevated temperatures

    Science.gov (United States)

    Kim, Taehwa; Funaki, Tsuyoshi

    2016-04-01

    This paper investigates the temperature dependence of partial thermal resistances of a packaged SiC schottky barrier diode (SBD) for high temperature applications. Transient thermal resistances of the packaged SiC SBD were measured and characterized in temperature range from 27 to 275 °C. The partial thermal resistances were extracted and analyzed using the cumulative and differential thermal structure functions. The extracted partial thermal resistances were compared to the results from the finite difference thermal model, and both results were in good agreement. The temperature dependence of the partial thermal resistance of the SiC device and the Si3N4 substrate contributes to the overall thermal characteristics variation of the packaged SiC SBD.

  11. A comparative study of IR Ge photodiodes with a Schottky barrier contact and metal-semiconductor-metal structure

    Energy Technology Data Exchange (ETDEWEB)

    Khurelbaatar, Zagarzusem; Kil, Yeonho; Lee, Hunki; Yang, Jonghan; Kang, Sukill; Kim, Taeksung; Shim, Kyuhwan [Chonbuk National University, Jeonju (Korea, Republic of)

    2014-12-15

    We report the characterization of germanium (Ge) infrared photodiodes fabricated with a Schottky barrier contact and a interdigitated metal-semiconductor-metal (MSM) structure with gold electrodes on n-Ge substrates. The current-volage (I-V) characteristics were studied, and parameters such as the ideality factor and the barrier height of the Schottky contacts were extracted. Furthemore, we estimated the dark current and the photocurrent under illumination with λ = 1550 nm light, and we measured the capacitance-voltage (C-V) characteristics and the dependence of the responsivity on the bias voltage of both photodiodes at room temperature. The dark currents of the Schottky and the MSM photodiodes were ∼ 20.2 μA and ∼ 26.0 μA under .1 V bias and .2 V bias, respectively. In addition, the reverse breakdown voltage was high, in excess of ∼ -30 V. The Schottky barrier height was deduced to be 0.546 eV. A maximum responsivity of 0.27 A/W was achieved under illumination with λ = 1550 nm light at a 2-V bias. A typical peak was observed at a wavelength of 1600 nm, and a high responsivity was observed in the wavelength range from 1200 to 1800 nm.

  12. 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.

  13. InGaAs Schottky barrier diode array detectors integrated with broadband antenna (Conference Presentation)

    Science.gov (United States)

    Park, Dong Woo; Lee, Eui Su; Park, Jeong-Woo; Kim, Hyun-Soo; Lee, Il-Min; Park, Kyung Hyun

    2017-02-01

    Terahertz (THz) waves have been actively studied for the applications of astronomy, communications, analytical science and bio-technologies due to their low energy and high frequency. For example, THz systems can carry more information with faster rates than GHz systems. Besides, THz waves can be applied to imaging, sensing, and spectroscopy. Furthermore, THz waves can be used for non-destructive and non-harmful tomography of living objects. In this reasons, Schottky barrier diodes (SBD) have been widely used as a THz detector for their ultrafast carrier transport, high responsivity, high sensitivity, and excellent noise equivalent power. Furthermore, SBD detectors envisage developing THz applications at low cost, excellent capability, and high yield. Since the major concerns in the THz detectors for THz imaging systems are the realizations of the real-time image acquisitions via a reduced acquisition time, rather than the conventional raster scans that obtains an image by pixel-by-pixel acquisitions, a line-scan based systems utilizes an array detector with an 1 × n SBD array is preferable. In this study, we fabricated the InGaAs based SBD array detectors with broadband antennas of log-spiral and square-spiral patterns. To optimize leakage current and ideality factor, the dependence to the doping levels of ohmic and Schottky layers have been investigated. In addition, the dependence to the capacitance and resistance to anode size are also examined as well. As a consequence, the real-time THz imaging with our InGaAs SBD array detector have been successfully obtained.

  14. 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.

  15. Elucidation of barrier homogeneity in ZnO/P3HT:PCBM junctions through temperature dependent I-V characteristics

    Science.gov (United States)

    Khare, Neeraj; Zubair Ansari, Mohd; Hoye, Robert L. Z.; Iza, Diana C.; MacManus-Driscoll, Judith L.

    2016-07-01

    The current-voltage (I-V) characteristics of ZnO/P3HT:PCBM junctions using as-deposited ZnO and 300 °C-annealed ZnO (prior to device fabrication) were probed as a function of temperature. The ZnO films were synthesized using two scalable, low temperature methods: Atmospheric pressure spatial atomic layer deposition (AP-SALD) and electrodeposition (ED). In both cases the zero bias Schottky barrier height ({Φ\\text{B}} ) decreases and ideality factor (n) increases with a reduction in the operating temperature of the junctions. This was attributed to the presence of barrier inhomogeneities at the interface from surface states/defects in the ZnO causing a localized variation of work function. For the as-deposited ZnO junctions, two mean barrier heights, arising from a large density of surface states was observed. For the annealed ZnO junction one mean barrier height was observed, indicating reduction in the inhomogeneities of barrier height at the interface for the annealed ZnO. The photoresponce of ZnO/P3HT:PCBM junction was higher for the annealed ZnO which is due to the higher mean barrier height and lower value of ideality factor. This demonstrates that moderate annealing of chemically grown ZnO is crucial for reducing surface defects and barrier inhomogeneities.

  16. Electric field modulation of Schottky barrier height in graphene/MoSe{sub 2} van der Waals heterointerface

    Energy Technology Data Exchange (ETDEWEB)

    Sata, Yohta; Moriya, Rai, E-mail: moriyar@iis.u-tokyo.ac.jp, E-mail: tmachida@iis.u-tokyo.ac.jp; Morikawa, Sei; Yabuki, Naoto [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Masubuchi, Satoru; Machida, Tomoki, E-mail: moriyar@iis.u-tokyo.ac.jp, E-mail: tmachida@iis.u-tokyo.ac.jp [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan); Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro, Tokyo 153-8505 (Japan)

    2015-07-13

    We demonstrate a vertical field-effect transistor based on a graphene/MoSe{sub 2} van der Waals (vdW) heterostructure. The vdW interface between the graphene and MoSe{sub 2} exhibits a Schottky barrier with an ideality factor of around 1.3, suggesting a high-quality interface. Owing to the low density of states in graphene, the position of the Fermi level in the graphene can be strongly modulated by an external electric field. Therefore, the Schottky barrier height at the graphene/MoSe{sub 2} vdW interface is also modulated. We demonstrate a large current ON-OFF ratio of 10{sup 5}. These results point to the potential high performance of the graphene/MoSe{sub 2} vdW heterostructure for electronics applications.

  17. Effect of temperature on the carrier transport property of 4H-SiC based Schottky barrier diode

    Directory of Open Access Journals (Sweden)

    TONG Wulin

    2015-08-01

    Full Text Available In this paper,the current-voltage (I-V measurement under different temperatures was carried out on the 4H-SiC Schottky barrier diode (SBD purchased from Cree Inc.The carrier transport mechanism and the temperature effect of SBD were investigated through the theoretical simulation based on the experimental data.The Schottky barrier height is decreased and leakage current is increased sharply for SBD when the temperatures are increased.The SBD forward bias obeys the hot electron emission mechanism.Taking the image force correction and tunneling effect into consideration,the high leakage current under reverse bias can be reasonably explained and is good agreement with the experiment results.

  18. Temperature dependence of the inhomogeneous parameters of the Mo/4H-SiC Schottky barrier diodes

    Science.gov (United States)

    Latreche, A.; Ouennoughi, Z.; Weiss, R.

    2016-08-01

    The inhomogeneous parameters of Mo/4H-SiC Schottky barrier diodes were determined from current-voltage (I-V) characteristics in the temperature range of 303-498 K by using a general approach for the real Schottky diode. In this approach the total series resistances is divided into two resistances; the first one (R P) is the sum of the series resistances (r) of the particular diodes connected in parallel and the second is the common resistance (R C) to all particular diodes. The mean barrier height (\\bar{φ }) and the standard deviation (σ) decrease linearly with decreasing temperature and they are between the values for the diodes with the two limiting cases; no current spreading and full current spreading. The series resistance R C increases, while the series resistance R P slightly decreases with decreasing temperature.

  19. The electronic and chemical structure of the a-B3CO0.5:Hy-to-metal interface from photoemission spectroscopy: implications for Schottky barrier heights.

    Science.gov (United States)

    Driver, M Sky; Paquette, Michelle M; Karki, S; Nordell, B J; Caruso, A N

    2012-11-01

    The electronic and chemical structure of the metal-to-semiconductor interface was studied by photoemission spectroscopy for evaporated Cr, Ti, Al and Cu overlayers on sputter-cleaned as-deposited and thermally treated thin films of amorphous hydrogenated boron carbide (a-B(x)C:H(y)) grown by plasma-enhanced chemical vapor deposition. The films were found to contain ~10% oxygen in the bulk and to have approximate bulk stoichiometries of a-B(3)CO(0.5):H(y). Measured work functions of 4.7/4.5 eV and valence band maxima to Fermi level energy gaps of 0.80/0.66 eV for the films (as-deposited/thermally treated) led to predicted Schottky barrier heights of 1.0/0.7 eV for Cr, 1.2/0.9 eV for Ti, 1.2/0.9 eV for Al, and 0.9/0.6 eV for Cu. The Cr interface was found to contain a thick partial metal oxide layer, dominated by the wide-bandgap semiconductor Cr(2)O(3), expected to lead to an increased Schottky barrier at the junction and the formation of a space-charge region in the a-B(3)CO(0.5):H (y) layer. Analysis of the Ti interface revealed a thick layer of metal oxide, comprising metallic TiO and Ti (2)O (3), expected to decrease the barrier height. A thinner, insulating Al(2)O(3) layer was observed at the Al-to-a-B(3)CO(0.5):H(y) interface, expected to lead to tunnel junction behavior. Finally, no metal oxides or other new chemical species were evident at the Cu-to-a-B(3)CO(0.5):H(y) interface in either the core level or valence band photoemission spectra, wherein characteristic metallic Cu features were observed at very thin overlayer coverages. These results highlight the importance of thin-film bulk oxygen content on the metal-to-semiconductor junction character as well as the use of Cu as a potential Ohmic contact material for amorphous hydrogenated boron carbide semiconductor devices such as high-efficiency direct-conversion solid-state neutron detectors.

  20. Schottky barrier engineering via adsorbing gases at the sulfur vacancies in the metal-MoS2 interface.

    Science.gov (United States)

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

    2017-03-10

    Sulfur vacancies (S-vacancies) are common in monolayer MoS2 (mMoS2). Finding an effective way to control rather than abolish the effect of S-vacancies on contact properties is vital for the application of mMoS2. Here, we propose the adsorption of gases to passivate the S-vacancies in Pt-mMoS2 interfaces. Results demonstrate that gases are stably and preferentially adsorbed at S-vacancies. The n-type Schottky barriers of Pt-mMoS2 interfaces are reduced significantly upon the adsorption electron-donor gases, especially Cl2. The n-type transport character of the Pt-mMoS2 interface can be changed to p-type by the adsorption of electron-acceptor gases. As the adsorption concentration increases, both n- and p-type Schottky barriers are further reduced, and the lowest n- and p-type Schottky barriers are 0.36 and 0 eV, respectively. Note that the variations in Schottky barriers are independent of the oxidizing ability of gases but relative to the average number of valence electrons per gas atom. Analysis demonstrates that although gases at S-vacancies cannot cause gap states to vanish, and can even enhance Fermi level pinning, they modulate charge redistribution and the potential step at the interface region. Moreover, with increasing adsorption concentration, the valence band maximum of mMoS2 shows the opposite variation tendency to that of the potential step. Our results suggest that adsorption of gases is an effective way to passivate S-vacancies to modulate the transport properties of Pt-mMoS2 interfaces.

  1. Schottky barrier engineering via adsorbing gases at the sulfur vacancies in the metal–MoS2 interface

    Science.gov (United States)

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

    2017-03-01

    Sulfur vacancies (S-vacancies) are common in monolayer MoS2 (mMoS2). Finding an effective way to control rather than abolish the effect of S-vacancies on contact properties is vital for the application of mMoS2. Here, we propose the adsorption of gases to passivate the S-vacancies in Pt–mMoS2 interfaces. Results demonstrate that gases are stably and preferentially adsorbed at S-vacancies. The n-type Schottky barriers of Pt–mMoS2 interfaces are reduced significantly upon the adsorption electron-donor gases, especially Cl2. The n-type transport character of the Pt–mMoS2 interface can be changed to p-type by the adsorption of electron-acceptor gases. As the adsorption concentration increases, both n- and p-type Schottky barriers are further reduced, and the lowest n- and p-type Schottky barriers are 0.36 and 0 eV, respectively. Note that the variations in Schottky barriers are independent of the oxidizing ability of gases but relative to the average number of valence electrons per gas atom. Analysis demonstrates that although gases at S-vacancies cannot cause gap states to vanish, and can even enhance Fermi level pinning, they modulate charge redistribution and the potential step at the interface region. Moreover, with increasing adsorption concentration, the valence band maximum of mMoS2 shows the opposite variation tendency to that of the potential step. Our results suggest that adsorption of gases is an effective way to passivate S-vacancies to modulate the transport properties of Pt–mMoS2 interfaces.

  2. A new model of noise characteristics of SiC Schottky barrier MESFET with deep impurity levels and traps

    Energy Technology Data Exchange (ETDEWEB)

    Aroutiounian, V.M. [Yerevan State University, Al. Manoukian Str. 1, 375025 Yerevan (Armenia)]. E-mail: kisahar@ysu.am; Avetisyan, G.A. [Yerevan State University, Al. Manoukian Str. 1, 375025 Yerevan (Armenia); Buniatyan, V.V. [State Engineering University of Armenia, 105 Teryan Str., 375009 Yerevan (Armenia); Soukiassian, P.G. [Commissariat a l' Energie Atomique, Laboratoire Surfaces et Interfaces de Materiaux, Avances associe a l' Universite de Paris-Sud/Orsay, DSM-DRECAM-SPCSI, Batiment 462, Saclay, 91191 Gif sur Yvette Cedex (France); Buniatyan, Vaz.V. [State Engineering University of Armenia, 105 Teryan Str., 375009 Yerevan (Armenia)

    2006-05-30

    Noise characteristics of silicon carbide Schottky barrier field effect transistors (MESFET) are examined for the case of the operation in small-signal regime and the presence of deep impurity levels and electron traps in the band gap of the channel. A new model of calculations of noise is suggested. It is shown that the noise measure of the short channel MESFET can be decreased within certain high frequency range.

  3. Schottky junction/ohmic contact behavior of a nanoporous TiO(2) thin film photoanode in contact with redox electrolyte solutions.

    Science.gov (United States)

    Kaneko, Masao; Ueno, Hirohito; Nemoto, Junichi

    2011-01-01

    The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO(2) thin film photoanode was soaked in an aqueous methanol solution using an O(2)-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV) that the nanosurface of the mesoporous n-TiO(2) film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction) was also proved by Mott-Schottky plots at the mesoporous TiO(2) thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at -0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN)(6)](4-) and the absence of methanol brought about ohmic contact behavior on the TiO(2) film and exhibited reversible redox waves in the dark due to the [Fe(CN)(6)](4-/3-) couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO(2) photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN)(6)](4-). That is, the TiO(2) nanosurface responds to [Fe(CN)(6)](4-) to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN)(6)](4-) around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (E(fb)) lies near the redox potential of the iron complex.

  4. Schottky junction/ohmic contact behavior of a nanoporous TiO2 thin film photoanode in contact with redox electrolyte solutions

    Directory of Open Access Journals (Sweden)

    Masao Kaneko

    2011-02-01

    Full Text Available The nature and photoelectrochemical reactivity of nanoporous semiconductor electrodes have attracted a great deal of attention. Nanostructured materials have promising capabilities applicable for the construction of various photonic and electronic devices. In this paper, a mesoporous TiO2 thin film photoanode was soaked in an aqueous methanol solution using an O2-reducing Pt-based cathode in contact with atmospheric air on the back side. It was shown from distinct photocurrents in the cyclic voltammogram (CV that the nanosurface of the mesoporous n-TiO2 film forms a Schottky junction with water containing a strong electron donor such as methanol. Formation of a Schottky junction (liquid junction was also proved by Mott–Schottky plots at the mesoporous TiO2 thin film photoanode, and the thickness of the space charge layer was estimated to be very thin, i.e., only 3.1 nm at −0.1 V vs Ag/AgCl. On the other hand, the presence of [Fe(CN6]4− and the absence of methanol brought about ohmic contact behavior on the TiO2 film and exhibited reversible redox waves in the dark due to the [Fe(CN6]4−/3− couple. Further studies showed that multiple Schottky junctions/ohmic contact behavior inducing simultaneously both photocurrent and overlapped reversible redox waves was found in the CV of a nanoporous TiO2 photoanode soaked in an aqueous redox electrolyte solution containing methanol and [Fe(CN6]4−. That is, the TiO2 nanosurface responds to [Fe(CN6]4− to give ohmic redox waves overlapped simultaneously with photocurrents due to the Schottky junction. Additionally, a second step photocurrent generation was observed in the presence of both MeOH and [Fe(CN6]4− around the redox potential of the iron complex. It was suggested that the iron complex forms a second Schottky junction for which the flat band potential (Efb lies near the redox potential of the iron complex.

  5. Interface Engineering of Organic Schottky Barrier Solar Cells and Its Application in Enhancing Performances of Planar Heterojunction Solar Cells.

    Science.gov (United States)

    Jin, Fangming; Su, Zisheng; Chu, Bei; Cheng, Pengfei; Wang, Junbo; Zhao, Haifeng; Gao, Yuan; Yan, Xingwu; Li, Wenlian

    2016-05-17

    In this work, we describe the performance of organic Schottky barrier solar cells with the structure of ITO/molybdenum oxide (MoOx)/boron subphthalocyanine chloride (SubPc)/bathophenanthroline (BPhen)/Al. The SubPc-based Schottky barrier solar cells exhibited a short-circuit current density (Jsc) of 2.59 mA/cm(2), an open-circuit voltage (Voc) of 1.06 V, and a power conversion efficiency (PCE) of 0.82% under simulated AM1.5 G solar illumination at 100 mW/cm(2). Device performance was substantially enhanced by simply inserting thin organic hole transport material into the interface of MoOx and SubPc. The optimized devices realized a 180% increase in PCE of 2.30% and a peak Voc as high as 1.45 V was observed. We found that the improvement is due to the exciton and electron blocking effect of the interlayer and its thickness plays a vital role in balancing charge separation and suppressing quenching effect. Moreover, applying such interface engineering into MoOx/SubPc/C60 based planar heterojunction cells substantially enhanced the PCE of the device by 44%, from 3.48% to 5.03%. Finally, we also investigated the requirements of the interface material for Schottky barrier modification.

  6. Time dependent changes in Schottky barrier mapping of the W/Si(001) interface utilizing ballistic electron emission microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Durcan, Chris A.; Balsano, Robert [College of Nanoscale Science and Engineering, State University of New York, Albany, New York 12203 (United States); LaBella, Vincent P., E-mail: vlabella@albany.edu [Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12203 (United States)

    2015-06-28

    The W/Si(001) Schottky barrier height is mapped to nanoscale dimensions using ballistic electron emission microscopy (BEEM) over a period of 21 days to observe changes in the interface electrostatics. Initially, the average spectrum is fit to a Schottky barrier height of 0.71 eV, and the map is uniform with 98% of the spectra able to be fit. After 21 days, the average spectrum is fit to a Schottky barrier height of 0.62 eV, and the spatial map changes dramatically with only 27% of the spectra able to be fit. Transmission electron microscopy shows the formation of an ultra-thin tungsten silicide at the interface, which increases in thickness over the 21 days. This increase is attributed to an increase in electron scattering and the changes are observed in the BEEM measurements. Interestingly, little to no change is observed in the I-V measurements throughout the 21 day period.

  7. Room Temperature Magnetic Barrier Layers in Magnetic Tunnel Junctions

    Energy Technology Data Exchange (ETDEWEB)

    Nelson-Cheeseman, B. B.; Wong, F. J.; Chopdekar, R. V.; Arenholz, E.; Suzuki, Y.

    2010-03-09

    We investigate the spin transport and interfacial magnetism of magnetic tunnel junctions with highly spin polarized LSMO and Fe3O4 electrodes and a ferrimagnetic NiFe2O4 (NFO) barrier layer. The spin dependent transport can be understood in terms of magnon-assisted spin dependent tunneling where the magnons are excited in the barrier layer itself. The NFO/Fe3O4 interface displays strong magnetic coupling, while the LSMO/NFO interface exhibits clear decoupling as determined by a combination of X-ray absorption spectroscopy and X-ray magnetic circular dichroism. This decoupling allows for distinct parallel and antiparallel electrode states in this all-magnetic trilayer. The spin transport of these devices, dominated by the NFO barrier layer magnetism, leads to a symmetric bias dependence of the junction magnetoresistance at all temperatures.

  8. Nanoscale inhomogeneity of the Schottky barrier and resistivity in MoS2 multilayers

    Science.gov (United States)

    Giannazzo, F.; Fisichella, G.; Piazza, A.; Agnello, S.; Roccaforte, F.

    2015-08-01

    Conductive atomic force microscopy (CAFM) is employed to investigate the current injection from a nanometric contact (a Pt coated tip) to the surface of MoS2 thin films. The analysis of local current-voltage characteristics on a large array of tip positions provides high spatial resolution information on the lateral homogeneity of the tip /MoS2 Schottky barrier ΦB and ideality factor n , and on the local resistivity ρloc of the MoS2 region under the tip. Here, ΦB=300 ±24 meV , n =1.60 ±0.23 , and ρloc=2.99 ±0.68 Ω cm are calculated from the distributions of locally measured values. A linear correlation is found between the ρloc and ΦB values at each tip position, indicating a similar origin of the ρloc and ΦB inhomogeneities. These findings are compared with recent literature results on the role of sulfur vacancy clusters on the MoS2 surface as preferential paths for current injection from metal contacts. Furthermore, their implications on the behavior of MoS2 based transistors are discussed.

  9. Surface Passivation of Ti/4H-SiC Schottky Barrier Diode

    Institute of Scientific and Technical Information of China (English)

    Muhammad Khalid; Saira Riaz; Shahzad Naseem

    2012-01-01

    Surface properties of SiC power devices mostly depend on the passivation layer (PL).This layer has direct influence on electrical characteristics of devices.2D numerical simulation of forward and reverse characteristics with and without different (PLs) (SiO2,HfO2 and Si3N4) has been performed.Simulation results show that the breakdown voltage increases with increasing PL thickness,and there is a lesser significant effect on forward characteristics.The maximum breakdown voltage with and without SiO2 PL is 1240 V and 276 V,respectively.SiO2 PL has compatibility with SiC surface providing high breakdown voltage,6 and 8% higher than that of HfO2 and Si3N4 respectively.Low leakage current is observed which then further decreases on reducing the thickness of PL.Furthermore,variation of forward current with dielectric constant and thickness of PLs was observed.Finally,it is suggested that matches of our results with published experimental results indicate that the Sentaurus TCAD simulator is a predictive tool for the SiC Schottky barrier diode simulation.

  10. Microscopic analysis of electron noise in GaAs Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, T.; Pardo, D. [Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain); Reggiani, L. [Istituto Nazionale di Fisica della Materia, Dipartimento di Scienza dei Materiali, Universita di Lecce, Via Arnesano, 73100 Lecce (Italy); Varani, L. [Centre dElectronique et de Micro-Optoelectronique de Montpellier (CNRS UMR 5507), Universite Montpellier II, F-34095 Montpellier Cedex 5 (France)

    1997-09-01

    A microscopic analysis of current and voltage fluctuations in GaAs Schottky barrier diodes under forward-bias conditions in the absence of 1/f contributions is presented. Calculations are performed by coupling self-consistently an ensemble Monte Carlo simulator with a one-dimensional Poisson solver. By using current- and voltage-operation modes the microscopic origin and the spatial location of the noise sources, respectively, is provided. At different voltages the device exhibits different types of noise (shot, thermal, and excess), which are explained as a result of the coupling between fluctuations in carrier velocity and self-consistent field. The essential role of the field fluctuations to correctly determine the noise properties in these diodes is demonstrated. The results obtained for the equivalent noise temperature are found to reproduce the typical behavior of experimental measurements. An equivalent circuit is proposed to predict and explain the noise spectra of the device under thermionic emission-based operation. {copyright} {ital 1997 American Institute of Physics.}

  11. Electrical Characteristics of Co/n-Si Schottky Barrier Diodes Using I-V and C-V Measurements

    Institute of Scientific and Technical Information of China (English)

    G.Gfüler; (O).Güllü; (S).Karata(s); (O).F.Bakkalo(g)lu

    2009-01-01

    Electrical characteristics of Co/n-Si Schottky barrier diodes are analysed by current-voltage (I- V) and capacitancevoltage (C-V) techniques at room temperature.The electronic parameters such as ideality factor,barrier height and average series resistance are determined.The barrier height 0.76 eV obtained from the C-V measurements is higher than that of the value 0.70 eV obtained from the I-V measurements.The series resistance Rs and the ideality factor n are determined from the d ln( I ) / dV plot and are found to be 193.62Ω and 1.34,respectively.The barrier height and the Rs value are calculated from the H(I) - I plot and are found to be 0.71 eV and 205.95Ω.Furthermore,the energy distribution of the interface state density is determined from the forward bias I-V characteristics by taking into account the bias dependence of the effective barrier height.The interface state density Nss ranges from 6.484×1011 cm-2eV-1 in (Ec-0.446) eV to 2.801×1010 cm-2eV-1 in (Ec-0.631) eV,of the Co/n-Si Schottky barrier diode.The results show the presence of a thin interracial layer between the metal and the semiconductor.

  12. Spin-filtering junctions with double ferroelectric barriers

    Institute of Scientific and Technical Information of China (English)

    Ju Yan; Xing Ding-Yu

    2009-01-01

    An FS/FE/NS/FE/FS double tunnel junction is suggested to have the ability to inject, modulate and detect the spin-polarized current electrically in a single device, where FS is the ferromagnetic semiconductor electrode, NS is the nonmagnetic semiconductor, and FE the ferroelectric barrier. The spin polarization of the current injected into the NS region can be switched between a highly spin-polarized state and a spin unpolarized state. The high spin polarization may be detected by measuring the tunneling magnetoresistance ratio of the double tunnel junction.

  13. Large area, low capacitance, GaAs nanowire photodetector with a transparent Schottky collecting junction

    Energy Technology Data Exchange (ETDEWEB)

    Seyedi, M. A., E-mail: seyedi@usc.edu; Yao, M.; O' Brien, J.; Dapkus, P. D. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Wang, S. Y. [Center for Energy Nanoscience, University of Southern California, Los Angeles, California 90089 (United States); Nanostructured Energy Conversion Technology and Research (NECTAR), Advanced Studies Laboratories, University of California, Santa Cruz, California 95064, USA and NASA Ames Research Center, Moffett Field, California 94035 (United States)

    2013-12-16

    We present experimental results on a GaAs/Indium-Tin-Oxide Schottky-like heterojunction photodetector based on a nanowire device geometry. By distributing the active detecting area over an array of nanowires, it is possible to achieve large area detection with low capacitance. Devices with bare GaAs and passivated AlGaAs/GaAs nanowires are fabricated to compare the responsivity with and without surface passivation. We are able to achieve responsivity of >0.5A/W and Signal-Noise-Ratio in excess of 7 dB for 2 V applied reverse bias with passivated nanowire devices. Capacitance-voltage measurement yields <5 nF/cm{sup 2}, which shows a strong possibility for high-speed applications with a broad area device.

  14. Study of barrier inhomogeneities using I–V–T characteristics of Mo/4H–SiC Schottky diode

    Energy Technology Data Exchange (ETDEWEB)

    Ouennoughi, Z. [Laboratoire optoélectronique et composants, Department of Physics, Sétif (Algeria); Toumi, S., E-mail: sihem.toumi@gmail.com [Laboratoire optoélectronique et composants, Department of Physics, Sétif (Algeria); Weiss, R. [FIIS, Schottkystrasse 10, 91058 Erlangen (Germany)

    2015-01-01

    In the present work we investigate the forward current–voltage (I–V) characteristics, over a wide temperature range 298–498 K, of Mo/4H–SiC Schottky diode for which aluminum ion implantation was used to create the high resistivity layer forming the guard ring. The (I–V) analysis based on Thermionic Emission (TE) theory shows a decrease of the barrier height ϕ{sub B} and an increase of the ideality factor n when the temperature decreases. These anomalies are mainly due to the barrier height inhomogeneities at the metal/semiconductor interface as we get a Gaussian distribution of the barrier heights when we plot the apparent barrier height ϕ{sub ap} versus q/2kT. The mean barrier height and the standard deviation obtained values are ϕ{sup ¯}{sub B0}=1.160 eV and σ{sub 0}=88.049 mV, respectively. However, by means of the modified Richardson plot Ln(I{sub s}/T{sup 2})−(q{sup 2}σ{sub 0}{sup 2}/2k{sup 2}T{sup 2}) versus q/kT, the mean barrier height and the Richardson constant values obtained are ϕ{sup ¯}{sub B0}=1.139 eV and A{sup *}=129.425 A/cm{sup 2} K{sup 2}, respectively. The latter value of ϕ{sup ¯}{sub B0} matches very well with the mean barrier height obtained from the plot of ϕ{sub ap} versus q/2kT. The Richardson constant is much closer to the theoretical value of 146 A/cm{sup 2} K{sup 2}. The series resistance R{sub s} is also estimated from the forward current–voltage characteristics of Mo/4H–SiC Schottky contact. This parameter shows strong temperature dependence. The T{sub 0} effect is validated for the 298–498 K temperature range for the used Schottky diode and provides a clear evidence for the barrier inhomogeneity at the Mo/4H–SiC interface. Finally, we note the impact of the implantation process as well as the choice of the used ion on the characterized parameters of the Schottky contact.

  15. Study of barrier inhomogeneities using I-V-T characteristics of Mo/4H-SiC Schottky diode

    Science.gov (United States)

    Ouennoughi, Z.; Toumi, S.; Weiss, R.

    2015-01-01

    In the present work we investigate the forward current-voltage (I-V) characteristics, over a wide temperature range 298-498 K, of Mo/4H-SiC Schottky diode for which aluminum ion implantation was used to create the high resistivity layer forming the guard ring. The (I-V) analysis based on Thermionic Emission (TE) theory shows a decrease of the barrier height ϕB and an increase of the ideality factor n when the temperature decreases. These anomalies are mainly due to the barrier height inhomogeneities at the metal/semiconductor interface as we get a Gaussian distribution of the barrier heights when we plot the apparent barrier height ϕap versus q/2kT. The mean barrier height and the standard deviation obtained values are ϕbarB0=1.160 eV and σ0=88.049 mV, respectively. However, by means of the modified Richardson plot Ln (Is /T2) - (q2 σ 0 2 / 2k2T2) versus q/kT, the mean barrier height and the Richardson constant values obtained are ϕbarB0=1.139 eV and A*=129.425 A/cm2 K2, respectively. The latter value of ϕbarB0 matches very well with the mean barrier height obtained from the plot of ϕap versus q/2kT. The Richardson constant is much closer to the theoretical value of 146 A/cm2 K2. The series resistance Rs is also estimated from the forward current-voltage characteristics of Mo/4H-SiC Schottky contact. This parameter shows strong temperature dependence. The T0 effect is validated for the 298-498 K temperature range for the used Schottky diode and provides a clear evidence for the barrier inhomogeneity at the Mo/4H-SiC interface. Finally, we note the impact of the implantation process as well as the choice of the used ion on the characterized parameters of the Schottky contact.

  16. 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.

  17. High-barrier Schottky contact on n-type 4H-SiC epitaxial layer and studies of defect levels by deep level transient spectroscopy (DLTS)

    Science.gov (United States)

    Nguyen, Khai V.; Pak, Rahmi O.; Oner, Cihan; Mannan, Mohammad A.; Mandal, Krishna C.

    2015-08-01

    High barrier Schottky contact has been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 350 μm thick substrate 8° off-cut towards the [11̅20] direction. The 4H-SiC epitaxial wafer was diced into 10 x 10 mm2 samples. The metal-semiconductor junctions were fabricated by photolithography and dc sputtering with ruthenium (Ru). The junction properties were characterized through current-voltage (I-V) and capacitance-voltage (C-V) measurements. Detectors were characterized by alpha spectroscopy measurements in terms of energy resolution and charge collection efficiency using a 0.1 μCi 241Am radiation source. It was found that detectors fabricated from high work function rare transition metal Ru demonstrated very low leakage current and significant improvement of detector performance. Defect characterization of the epitaxial layers was conducted by deep level transient spectroscopy (DLTS) to thoroughly investigate the defect levels in the active region. The presence of a new defect level induced by this rare transition metal-semiconductor interface has been identified and characterized.

  18. Theoretical investigation of silicide Schottky barrier detector integrated in horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguide.

    Science.gov (United States)

    Zhu, Shiyang; Lo, G Q; Kwong, D L

    2011-08-15

    An ultracompact integrated silicide Schottky barrier detector (SBD) is designed and theoretically investigated to electrically detect the surface plasmon polariton (SPP) propagating along horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguides at the telecommunication wavelength of 1550 nm. An ultrathin silicide layer inserted between the silicon core and the insulator, which can be fabricated precisely using the well-developed self-aligned silicide process, absorbs the SPP power effectively if a suitable silicide is chosen. Moreover, the Schottky barrier height in the silicide-silicon-silicide configuration can be tuned substantially by the external voltage through the Schottky effect owing to the very narrow silicon core. For a TaSi(2) detector with optimized dimensions, numerical simulation predicts responsivity of ~0.07 A/W, speed of ~60 GHz, dark current of ~66 nA at room temperature, and minimum detectable power of ~-29 dBm. The design also suggests that the device's size can be reduced and the overall performances will be further improved if a silicide with smaller permittivity is used.

  19. High energy electron radiation effect on Ni and Ti/4H-SiC Schottky barrier diodes at room temperature

    Institute of Scientific and Technical Information of China (English)

    Zhang Lin; Zhang Yi-Men; Zhang Yu-Ming; Han Chao; Ma Yong-Ji

    2009-01-01

    This paper reports that Ni and Ti/4H-SiC Schottky barrier diodes (SBDs) were fabricated and irradiated with 1 MeV electrons up to a dose of 3.43×1014 e/cm2. After radiation, the Schottky barrier height φB of the Ni/4H-SiC SBD increased from 1.20 eV to 1.21 eV, but decreased from 0.95 eV to 0.94 eV for the Ti/4H-SiC SBD. The degradation of φB could be explained by interface states of changed Schottky contacts. The on-state resistance RS of both diodes increased with the dose, which can be ascribed to the radiation defects. The reverse current of the Ni/4H-SiC SBD slightly increased, but for the Ti/4H-SiC SBD it basically remained the same. At room temperature, φB of the diodes recovered completely after one week, and the RS partly recovered.

  20. High-performance room-temperature hydrogen sensors based on combined effects of Pd decoration and Schottky barriers

    Science.gov (United States)

    Liu, Bin; Cai, Daoping; Liu, Yuan; Li, Han; Weng, Chao; Zeng, Guoshi; Li, Qiuhong; Wang, Taihong

    2013-02-01

    A new hydrogen sensor was fabricated by coating a Pd-decorated In2O3 film on Au electrodes. In response to 1 vol% H2 at room temperature, an ultra high sensitivity of 4.6 × 107 was achieved. But after an annealing treatment in vacuum, its sensitivity degenerated by 4 orders of magnitude. In addition, the response time and recovery time were also extended from 28 s and 32 s to 242 s and 108 s, respectively. It was found from contrast experiments that Pd decoration was essential to make the sensor work at room temperature and Schottky barriers played a vital role in enhancing the sensor's performance. The methodology demonstrated in this paper shows that a combination of novel sensing materials and Schottky contact is an effective approach to design high-performance gas sensors.A new hydrogen sensor was fabricated by coating a Pd-decorated In2O3 film on Au electrodes. In response to 1 vol% H2 at room temperature, an ultra high sensitivity of 4.6 × 107 was achieved. But after an annealing treatment in vacuum, its sensitivity degenerated by 4 orders of magnitude. In addition, the response time and recovery time were also extended from 28 s and 32 s to 242 s and 108 s, respectively. It was found from contrast experiments that Pd decoration was essential to make the sensor work at room temperature and Schottky barriers played a vital role in enhancing the sensor's performance. The methodology demonstrated in this paper shows that a combination of novel sensing materials and Schottky contact is an effective approach to design high-performance gas sensors. Electronic supplementary information (ESI) available: Hydrogen sensing test details and detailed material characterizations before and after the annealing treatment at 120 °C. See DOI: 10.1039/c3nr33872j

  1. Flexible MgO Barrier Magnetic Tunnel Junctions.

    Science.gov (United States)

    Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

    2016-07-01

    Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. A Study of the Parasitic Properties of the Schottky Barrier Diode

    Science.gov (United States)

    Ren, Tianhao; Zhang, Yong; Liu, Shuang; Guo, Fangzhou; Jin, Zhi; Zhou, Jingtao; Yang, Chengyue

    2016-09-01

    In this paper, we present a newly designed parameter extraction method of the Schottky barrier diode (SBD) with the purpose of measuring and studying its parasitic properties. This method includes three kinds of auxiliary configurations and is named as three-configuration parameter extraction method (TPEM). TPEM has such features as simplicity of operation, self-consistence, and accuracy. With TPEM, the accurate parasitic parameters of the diode can be easily obtained. Taking a GaAs SBD as an example, the pad-to-pad capacitance is 7 fF, the air-bridge finger self-inductance 11 pH, the air-bridge finger self-resistance 0.6 Ω, and the finger-to-pad capacitance 2.1 fF. A more accurate approach to finding the value of the series resistant of the SBD is also proposed, and then a complete SBD model is built. The evaluation of the modeling technology, as well as TPEM, is implemented by comparing the simulated and measured I-V curves and the S-parameters. And good agreements are observed. By using TPEM, the influence of the variation of the geometric parameters is studied, and several ways to reduce the parasitic effect are presented. The results show that the width of the air-bridge finger and the length of the channel are the two largest influencing parameters, with the normalized impact factors 0.56 and 0.29, respectively. By using TPEM and the modeling technology presented in this paper, a design process of the SBD is proposed. As an example, a type of SBD suitable for 500-600 GHz zero-biased detection is designed, and the agreement between the simulated and measured results has been improved. SBDs for other applications could be designed in a similar way.

  3. A Study of the Parasitic Properties of the Schottky Barrier Diode

    Science.gov (United States)

    Ren, Tianhao; Zhang, Yong; Liu, Shuang; Guo, Fangzhou; Jin, Zhi; Zhou, Jingtao; Yang, Chengyue

    2017-02-01

    In this paper, we present a newly designed parameter extraction method of the Schottky barrier diode (SBD) with the purpose of measuring and studying its parasitic properties. This method includes three kinds of auxiliary configurations and is named as three-configuration parameter extraction method (TPEM). TPEM has such features as simplicity of operation, self-consistence, and accuracy. With TPEM, the accurate parasitic parameters of the diode can be easily obtained. Taking a GaAs SBD as an example, the pad-to-pad capacitance is 7 fF, the air-bridge finger self-inductance 11 pH, the air-bridge finger self-resistance 0.6 Ω, and the finger-to-pad capacitance 2.1 fF. A more accurate approach to finding the value of the series resistant of the SBD is also proposed, and then a complete SBD model is built. The evaluation of the modeling technology, as well as TPEM, is implemented by comparing the simulated and measured I-V curves and the S-parameters. And good agreements are observed. By using TPEM, the influence of the variation of the geometric parameters is studied, and several ways to reduce the parasitic effect are presented. The results show that the width of the air-bridge finger and the length of the channel are the two largest influencing parameters, with the normalized impact factors 0.56 and 0.29, respectively. By using TPEM and the modeling technology presented in this paper, a design process of the SBD is proposed. As an example, a type of SBD suitable for 500-600 GHz zero-biased detection is designed, and the agreement between the simulated and measured results has been improved. SBDs for other applications could be designed in a similar way.

  4. The barrier-height inhomogeneity in identically prepared Ni/n-type 6H-SiC Schottky diodes

    Science.gov (United States)

    Duman, S.; Dogan, S.; Gürbulak, B.; Türüt, A.

    2008-05-01

    The effective barrier heights and ideality factors of identically fabricated Ni/n-type 6 H-SiC Schottky diodes (23 dots) have been calculated from their experimental forward bias current voltage (I V) and reverse bias capacitance voltage (C V) characteristics. A statistical study related to the experimental barrier heights (BHs) and ideality factors of the diodes has been made. The effective Schottky barrier heights (SBHs) and ideality factors obtained from the I V and C V characteristics have differed from diode to diode. The BHs obtained from the I V characteristics varied from 0.85 to 1.03 eV, the ideality factors varied from 1.13 to 1.40 and the BHs from C-2 V characteristics varied from 1.10 to 1.70 eV. The experimental BH and ideality factor distributions obtained from the I V characteristics are fitted by a Gaussian function, and their mean values are found to be 0.92±0.04 eV and 1.29±0.08 eV, respectively. The lateral homogeneous SBH value of 1.16 eV for the Ni/n-type 6H-SiC diodes has been calculated from a linear extrapolation of the effective barrier heights to nif=1.03.

  5. Spin accumulation at in-situ grown Fe/GaAs(100) Schottky barriers measured using the three- and four-terminal methods

    Science.gov (United States)

    Nam, Song Hyeon; Park, Tae-Eon; Park, Youn Ho; Ihm, Hae-In; Koo, Hyun Cheol; Kim, Hyung-jun; Han, Suk Hee; Chang, Joonyeon

    2016-09-01

    We examined the spin accumulation in Fe/n-GaAs Schottky barriers to evaluate the accuracy of the three-terminal (3T) and four-terminal (4T) measurement geometries. A fully epitaxial Fe/n-GaAs junction was grown in situ using cluster molecular beam epitaxy without breaking the vacuum to exclude the formation of an oxide layer or surface roughness at the interface during intermixing. The spin resistance of the 4T nonlocal spin valve (ΔRNLSV = 0.71 Ω) was twice the value obtained using the 4T Hanle effect method (ΔR4TH = 0.35 Ω) at 10 K, as predicted theoretically, and this value remained constant over the temperature range examined, from 10 K to 77 K. The temperature-dependent spin lifetimes measured using the 3T and 4T Hanle effects exhibited similar behaviors. Although the spin resistance obtained using the 3T Hanle effect was enhanced compared with that obtained using the 4T effect, it was reasonable to conclude that the spin signals obtained from the 3T and 4T measurements originated from spin accumulation in n-GaAs due to the absence of an oxide tunnel barrier or a well-defined interface in our samples. These results completely ruled out any other sources of artifacts.

  6. Investigation of Current-Voltage Characteristics of Ni/GaN Schottky Barrier Diodes for Potential HEMT Applications

    Directory of Open Access Journals (Sweden)

    Ashish Kumar

    2011-01-01

    Full Text Available In the present work, the I-V characteristics of Ni/GaN Schottky diodes have been studied. The Schottky diodes, having different sizes using Ni/Au and ohmic contacts using Ti/Al/Ni/Au were made on n-GaN. The GaN was epitaxially grown on c-plane sapphire by metal organic chemical vapor deposition (MOCVD technique and had a thickness of about 3.7 µm. The calculated ideality factor and barrier height from current-voltage (I-V characteristics (at 300 K for two GaN Schottky diodes were close to ~1.3 and ~ 0.8 eV respectively. A high reverse leakage current in the order of 10 – 4A/cm2 (at – 1 V was observed in both diodes. A careful analysis of forward bias I-V characteristics showed very high series resistance and calculation for ideality factor indicated presence of other current transport mechanism apart from thermionic model at room temperature.

  7. Charge transport in molecular electronic junctions: compression of the molecular tunnel barrier in the strong coupling regime.

    Science.gov (United States)

    Sayed, Sayed Y; Fereiro, Jerry A; Yan, Haijun; McCreery, Richard L; Bergren, Adam Johan

    2012-07-17

    Molecular junctions are essentially modified electrodes familiar to electrochemists where the electrolyte is replaced by a conducting "contact." It is generally hypothesized that changing molecular structure will alter system energy levels leading to a change in the transport barrier. Here, we show the conductance of seven different aromatic molecules covalently bonded to carbon implies a modest range ( 2 eV range). These results are explained by considering the effect of bonding the molecule to the substrate. Upon bonding, electronic inductive effects modulate the energy levels of the system resulting in compression of the tunneling barrier. Modification of the molecule with donating or withdrawing groups modulate the molecular orbital energies and the contact energy level resulting in a leveling effect that compresses the tunneling barrier into a range much smaller than expected. Whereas the value of the tunneling barrier can be varied by using a different class of molecules (alkanes), using only aromatic structures results in a similar equilibrium value for the tunnel barrier for different structures resulting from partial charge transfer between the molecular layer and the substrate. Thus, the system does not obey the Schottky-Mott limit, and the interaction between the molecular layer and the substrate acts to influence the energy level alignment. These results indicate that the entire system must be considered to determine the impact of a variety of electronic factors that act to determine the tunnel barrier.

  8. Electron Excess Doping and Effective Schottky Barrier Reduction on the MoS2/h-BN Heterostructure.

    Science.gov (United States)

    Joo, Min-Kyu; Moon, Byoung Hee; Ji, Hyunjin; Han, Gang Hee; Kim, Hyun; Lee, Gwanmu; Lim, Seong Chu; Suh, Dongseok; Lee, Young Hee

    2016-10-12

    Layered hexagonal boron nitride (h-BN) thin film is a dielectric that surpasses carrier mobility by reducing charge scattering with silicon oxide in diverse electronics formed with graphene and transition metal dichalcogenides. However, the h-BN effect on electron doping concentration and Schottky barrier is little known. Here, we report that use of h-BN thin film as a substrate for monolayer MoS2 can induce ∼6.5 × 10(11) cm(-2) electron doping at room temperature which was determined using theoretical flat band model and interface trap density. The saturated excess electron concentration of MoS2 on h-BN was found to be ∼5 × 10(13) cm(-2) at high temperature and was significantly reduced at low temperature. Further, the inserted h-BN enables us to reduce the Coulombic charge scattering in MoS2/h-BN and lower the effective Schottky barrier height by a factor of 3, which gives rise to four times enhanced the field-effect carrier mobility and an emergence of metal-insulator transition at a much lower charge density of ∼1.0 × 10(12) cm(-2) (T = 25 K). The reduced effective Schottky barrier height in MoS2/h-BN is attributed to the decreased effective work function of MoS2 arisen from h-BN induced n-doping and the reduced effective metal work function due to dipole moments originated from fixed charges in SiO2.

  9. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y.; Hsu, C.-H.

    2016-08-01

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  10. Relationship between crystal defects and leakage current in β-Ga2O3 Schottky barrier diodes

    Science.gov (United States)

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

    2016-12-01

    We fabricated Schottky barrier diodes (SBDs) on the entire surface of a (0\\bar{1}0) β-Ga2O3 single crystal, and investigated the leakage current in both forward and reverse directions. Subsequently, we investigated the distribution of dislocation and void etch pits on the entire surface. The dislocation etch pit density on the surface ranged from void etch pit density on the surface ranged from void etch pit densities, we found that dislocations are closely related to the SBD reverse leakage current, and that not all voids produce the leakage current.

  11. Performance Improvement of GaN Based Schottky Barrier Ultraviolet Photodetector by Adding a Thin AlGaN Window Layer

    Institute of Scientific and Technical Information of China (English)

    ZHOU Mei; ZHAO De-Gang

    2007-01-01

    We propose a new structure of GaN based Schottky barrier ultraviolet photodetector, in which a thin n-type AlGaN window layer is added on the conventional n--GaN/n+-GaN device structure. The performance of the Schottky barrier ultraviolet photodetector is found to be improved by the new structure. The simulation result shows that the new structure can reduce the negative effect of surface states on the performance of Schottky barrier GaN photodetectors, improving the quantum efficiency and decreasing the dark current. The investigations suggest that the new photodetector can exhibit a better responsivity by choosing a suitably high carrier concentration and thin thickness for the AlGaN window layer.

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

    KAUST Repository

    Guo, Wei

    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.

  13. Theory of potential distributions in abrupt heterojunction crystalline semiconductor devices: Treatment of Schottky barriers and rectifiers

    Science.gov (United States)

    Mohammad, S. Noor

    1988-03-01

    present formulas a general form for potential distribution in Schottky barriers has been derived. The relation reduces to that of Gummel and Scarfetter [J. Appl. Phys. 38, 2148 (1967)] under special conditions. Theoretical reasons underlying the lack of rectification in various n-N HJs have been analyzed. In light of this analysis, a theoretical model in terms of many-body electron-electron and electron-donor interactions, and in terms of lowering of band edge in the vicinity of transition region, has been proposed. Numerical results obtained from this model for n-GaAs agree remarkably with observations from experimental measurements.

  14. Band structure, band offsets, substitutional doping, and Schottky barriers of bulk and monolayer InSe

    Science.gov (United States)

    Guo, Yuzheng; Robertson, John

    2017-09-01

    We present a detailed study of the electronic structure of the layered semiconductor InSe. We calculate the band structure of the monolayer and bulk material using density functional theory, hybrid functionals, and G W . The band gap of the monolayer InSe is calculated to be 2.4 eV in screened exchange hybrid functional, close to the experimental photoluminescence gap. The electron affinities and band offsets are calculated for vertical stacked-layer heterostructures, and are found to be suitable for tunnel field effect transistors (TFETs) in combination with WS e2 or similar. The valence-band edge of InSe is calculated to lie 5.2 eV below the vacuum level, similar to that for the closed shell systems HfS e2 or SnS e2 . Hence InSe would be suitable to act as a p -type drain in the TFET. The intrinsic defects are calculated. For Se-rich layers, the Se adatom (interstitial) is found to be the most stable defect, whereas for In-rich layers, the Se vacancy is the most stable for the neutral state. Antisites tend to have energies just above those of vacancies. The Se antisite distorts towards a bond-breaking distortion as in the EL2 center of GaAs. Both substitutional donors and acceptors are calculated to be shallow, and effective dopants. They do not reconstruct to form nondoping configurations as occurs in black phosphorus. Finally, the Schottky barriers of metals on InSe are found to be strongly pinned by metal induced gap states (MIGS) at ˜0.5 eV above the valence-band edge. Any interfacial defects would lead to a stronger pinning at a similar energy. Overall, InSe is an effective semiconductor combining the good features of 2D (lack of dangling bonds, etc.) with the good features of 3D (effective doping), which few others achieve.

  15. Schottky barrier detectors on 4H-SiC n-type epitaxial layer for alpha particles

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhuri, S.K.; Krishna, R.M.; Zavalla, K.J. [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Mandal, K.C., E-mail: mandalk@cec.sc.edu [Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2013-02-11

    Schottky barrier detectors have been fabricated on 50 μm n-type 4H-SiC epitaxial layers grown on 360 μm SiC substrates by depositing ∼10 nm nickel contact. Current–voltage (I–V) and capacitance–voltage (C–V) measurements were carried out to investigate the Schottky barrier properties. The detectors were evaluated for alpha particle detection using a {sup 241}Am alpha source. An energy resolution of ∼2.7% was obtained with a reverse bias of 100 V for 5.48 MeV alpha particles. The measured charge collection efficiency (CCE) was seen to vary as a function of bias voltage following a minority carrier diffusion model. Using this model, a diffusion length of∼3.5 μm for holes was numerically calculated from the CCE vs. bias voltage plot. Rise-time measurements of digitally recorded charge pulses for the 5.48 MeV alpha particles showed a presence of two sets of events having different rise-times at a higher bias of 200 V. A biparametric correlation scheme was successfully implemented for the first time to visualize the correlated pulse-height distribution of the events with different rise-times. Using the rise-time measurements and the biparametric plots, the observed variation of energy resolution with applied bias was explained.

  16. Schottky barrier height modification of metal/4H-SiC contact using ultrathin TiO2 insertion method

    Science.gov (United States)

    Tsui, Bing-Yue; Cheng, Jung-Chien; Lee, Lurng-Shehng; Lee, Chwan-Ying; Tsai, Ming-Jinn

    2014-01-01

    The fabrication processes, electrical characteristics, and reliability of the Schottky barrier diodes (SBDs) on an n-type 4H-silicon carbide (SiC) substrate are investigated. To modulate the Schottky barrier height (SBH), titanium dioxide (TiO2) is inserted at the interface between the metal and the SiC substrate. Ni, Mo, Ti, and Al are chosen to form SBDs. The maximum SBH modulation of 0.3 eV is obtained with a 5-nm-thick TiO2 layer. The SBH pinning factors of the SBDs without TiO2 insertion and with 2-nm-thick TiO2 insertion are similar. Therefore, the mechanism of the SBH modulation is attributed to the interface dipole-induced potential drop. Finally, the reliability of the SBD with TiO2 insertion is evaluated. The SBH, ideality factor, and reverse leakage current are stable after high forward current stress at 300 A/cm2 for 15000 s. This work provides a simple method to modulate the SBH on SiC and is feasible for SBD application.

  17. Enhancement of programming speed on gate-all-around poly-silicon nanowire nonvolatile memory using self-aligned NiSi Schottky barrier source/drain

    Science.gov (United States)

    Ho, Ching-Yuan; Chang, Yaw-Jen; Chiou, Y. L.

    2013-08-01

    The programming characteristics of gate-all-around silicon-oxide-nitride-oxide silicon (SONOS) nonvolatile memories are presented using NiSi/poly-Si nanowires (SiNW) Schottky barrier (SB) heterojunctions. The non-uniform thermal stress distribution on SiNW channels due to joule heating affected the carrier transport behavior. Under a high drain voltage, impact ionization was found as a large lateral field enhances carrier velocity. As gate voltage (Vg) increased, the difference in the drain current within a range of various temperature conditions can be mitigated because a high gate field lowers the SB height of a NiSi source/SiNW/NiSi drain junction to ensure efficient hot-carrier generation. By applying the Fowler-Nordheim programming voltage to the SONOS nanowire memory, the SB height (Φn = 0.34 eV) could be reduced by image force; thus, hot electrons could be injected from SB source/drain electrodes into the SiN storage node. To compare both SiNW and Si nanocrystal SONOS devices, the SB SiNW SONOS device was characterized experimentally to propose a wider threshold-voltage window, exhibiting efficient programming characteristics.

  18. Observation and Measurement of Negative Differential Resistance on PtSi Schottky Junctions on Porous Silicon

    Directory of Open Access Journals (Sweden)

    Mansor Mohtashamifar

    2010-01-01

    Full Text Available Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM. Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6.

  19. Barrier characteristics of Pt/Ru Schottky contacts on -type GaN based on –– and –– measurements

    Indian Academy of Sciences (India)

    N Nanda Kumar Reddy; V Rajagopal Reddy

    2012-02-01

    We have investigated the current–voltage (–) and capacitance–voltage (–) characteristics of Ru/Pt/-GaN Schottky diodes in the temperature range 100–420 K. The calculated values of barrier height and ideality factor for the Ru/Pt/-GaN Schottky diode are 0.73 eV and 1.4 at 420 K, 0.18 eV and 4.2 at 100 K, respectively. The zero-bias barrier height ($\\Phi_{\\text{b}0}$) calculated from – characteristics is found to be increased and the ideality factor () decreased with increasing temperature. Such a behaviour of $\\Phi_{\\text{b}0}$ and n is attributed to Schottky barrier (SB) inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at themetal/semiconductor interface. The current–voltage–temperature (––) characteristics of the Ru/Pt/-GaN Schottky diode have shown a double Gaussian distribution having mean barrier heights ($\\bar{\\Phi}_{\\text{b}0}$) of 1.001 eV and 0.4701 eV and standard deviations ($\\sigma_{0}$) of 0.1491 V and 0.0708 V, respectively. The modified ln($J_{0}/T^{2}$) − ($q^{2}\\sigma^{2}_{0}/2k^{2}T^{2}$) vs 10$^{3}/T$ plot gives $\\bar{\\Phi}_{\\text{b}0}$ and Richardson constant values as 0.99 eV and 0.47 eV, and 27.83 and 10.29 A/cm2K2, respectively without using the temperature coefficient of the barrier height. The difference between the apparent barrier heights (BHs) evaluated from the – and – methods has been attributed to the existence of Schottky barrier height inhomogeneities.

  20. Internal photoemission in molecular junctions: parameters for interfacial barrier determinations.

    Science.gov (United States)

    Fereiro, Jerry A; Kondratenko, Mykola; Bergren, Adam Johan; McCreery, Richard L

    2015-01-28

    The photocurrent spectra for large-area molecular junctions are reported, where partially transparent copper top contacts permit illumination by UV-vis light. The effect of variation of the molecular structure and thickness are discussed. Internal photoemission (IPE), a process involving optical excitation of hot carriers in the contacts followed by transport across internal system barriers, is dominant when the molecular component does not absorb light. The IPE spectrum contains information regarding energy level alignment within a complete, working molecular junction, with the photocurrent sign indicating transport through either the occupied or unoccupied molecular orbitals. At photon energies where the molecular layer absorbs, a secondary phenomenon is operative in addition to IPE. In order to distinguish IPE from this secondary mechanism, we show the effect of the source intensity as well as the thickness of the molecular layer on the observed photocurrent. Our results clearly show that the IPE mechanism can be differentiated from the secondary mechanism by the effects of variation of experimental parameters. We conclude that IPE can provide valuable information regarding interfacial energetics in intact, working molecular junctions, including clear discrimination of charge transport mediated by electrons through unoccupied system orbitals from that mediated by hole transport through occupied system orbitals.

  1. Intermediate type excitons in Schottky barriers of A{sup 3}B{sup 6} layer semiconductors and UV photodetectors

    Energy Technology Data Exchange (ETDEWEB)

    Alekperov, O.Z.; Guseinov, N.M.; Nadjafov, A.I. [Insitute of Physics of National Academy of Sinces of Azerbaijan, H. Javid av. 33, 1133 Baku (Azerbaijan)

    2006-09-15

    Photoelectric and photovoltaic spectra of Schottky barrier (SB) structures of InSe, GaSe and GaS layered semiconductors (LS) are investigated at quantum energies from the band edge excitons of corresponding materials up to 6.5eV. Spectral dependences of photoconductivity (PC) of photo resistors and barrier structures are strongly different at the quantum energies corresponding to the intermediate type excitons (ITE) observed in these semiconductors. It was suggested that high UV photoconductivity of A{sup 3}B{sup 6} LS is due to existence of high mobility light carriers in the depth of the band structure. It is shown that SB of semitransparent Au-InSe is high sensitive photo detector in UV region of spectra. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. DLTS analysis of electron and hole traps in proton implanted VPE grown n-GaAs using Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Auret, F.D.; Nel, M.; Snyman, H.C.

    1988-02-01

    Schottky barrier diodes (SBDs) were used for Deep Level Transient Spectroscopy (DLTS) characterization of electrically active defects in proton implanted n-GaAs. Although SBDs are usually only used for the detection of majority carrier defects (electron traps in n-GaAs), the fabrication of high barrier height SBDs on lowly doped ( less than or equal to 1 x 10/sup 15/cm/sup 3/) n-GaAs in conjunction with a forward bias DLTS filling pulse enabled the detection of minority carrier defects (hole traps in n-GaAs) as well, without using optical excitation. The most prominent electron and hole traps detected had properties that corresponded with those of the well known irradiation-induced electron traps E1-E4 and hole traps H0-H4, associated with the damage produced during high energy particle irradiation.

  3. Schottky barrier height of Ni to β-(AlxGa1‑x)2O3 with different compositions grown by plasma-assisted molecular beam epitaxy

    Science.gov (United States)

    Ahmadi, Elaheh; Oshima, Yuichi; Wu, Feng; Speck, James S.

    2017-03-01

    Coherent β-(AlxGa1‑x)2O3 films (x = 0, 0.038, 0.084, 0.164) were grown successfully on a Sn-doped β-Ga2O3 (010) substrate using plasma-assisted molecular beam epitaxy. Atom probe tomography, transmission electron microscopy, and high resolution x-ray diffraction were used to verify the alloy composition and high quality of the films. Schottky diodes were then fabricated using Ni as the Schottky metal. Capacitance–voltage measurements revealed a very low (current–voltage (I–V) measurements performed at temperatures varying from 300 K to 500 K on the Schottky diodes. These measurements revealed that the apparent Schottky barrier height could have similar values for different compositions of β-(AlxGa1‑x)2O3. We believe this is attributed to the lateral fluctuation in the alloy’s composition. This results in a lateral variation in the barrier height. Therefore, the average Schottky barrier height extracted from I–V measurements could be similar for β-(AlxGa1‑x)2O3 films with different compositions.

  4. High-voltage (900 V) 4 H-SiC Schottky diodes with a boron-implanted guard p-n junction

    Energy Technology Data Exchange (ETDEWEB)

    Grekhov, I. V.; Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Il' inskaya, N. D.; Kon' kov, O. I.; Potapov, A. S.; Samsonova, T. P. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2008-02-15

    High-voltage (900 V) 4H-SiC Schottky diodes terminated with a guard p-n junction were fabricated and studied. The guard p-n junction was formed by room-temperature boron implantation with subsequent high-temperature annealing. Due to transient enhanced boron diffusion during annealing, the depth of the guard p-n junction was equal to about 1.7 {mu}m, which is larger by approximately 1 {mu}m than the projected range of 11 B ions in 4H-SiC. The maximum reverse voltage of fabricated 4H-SiC Schottky diodes is found to be limited by avalanche breakdown of the planar p-n junction; the value of the breakdown voltage (910 V) is close to theoretical estimate in the case of the impurity concentration N = 2.5 Multiplication-Sign 10{sup 15} cm{sup -3} in the n-type layer, thickness of the n-type layer d = 12.5 {mu}m, and depth of the p-n junction r{sub j} = 1.7 {mu}m. The on-state diode resistance (3.7 m{Omega} cm{sup 2}) is controlled by the resistance of the epitaxial n-type layer. The recovery charge of about 1.3 nC is equal to the charge of majority charge carriers that are swept out of an epitaxial n-type layer under the effect of a reverse voltage.

  5. Large barrier, highly uniform and reproducible Ni-Si/4H-SiC forward Schottky diode characteristics: testing the limits of Tung's model

    Science.gov (United States)

    Omar, Sabih U.; Sudarshan, Tangali S.; Rana, Tawhid A.; Song, Haizheng; Chandrashekhar, M. V. S.

    2014-07-01

    We report highly ideal (n < 1.1), uniform nickel silicide (Ni-Si)/SiC Schottky barrier (1.60-1.67 eV with a standard deviation <2.8%) diodes, fabricated on 4H-SiC epitaxial layers grown by chemical vapour deposition. The barrier height was constant over a wide epilayer doping range of 1014-1016 cm-3, apart from a slight decrease consistent with image force lowering. This remarkable uniformity was achieved by careful optimization of the annealing of the Schottky interface to minimize non-idealities that could lead to inhomogeneity. Tung's barrier inhomogeneity model was used to quantify the level of inhomogeneity in the optimized annealed diodes. The estimated ‘bulk’ barrier height (1.75 eV) was consistent with the Shockley-Mott limit for the Ni-Si/4H-SiC interface, implying an unpinned Fermi level. But the model was not useful to explain the poor ideality in unoptimized, as-deposited Schottky contacts (n = 1.6 - 2.5). We show analytically and numerically that only idealities n < 1.21 can be explained using Tung's model, irrespective of material system, indicating that the barrier height inhomogeneity is not the only cause of poor ideality in Schottky diodes. For explaining this highly non-ideal behaviour, other factors (e.g. interface traps, morphological defects, extrinsic impurities, etc) need to be considered.

  6. 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.

  7. 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.

  8. Isolating the Photovoltaic Junction: Atomic Layer Deposited TiO2-RuO2 Alloy Schottky Contacts for Silicon Photoanodes.

    Science.gov (United States)

    Hendricks, Olivia L; Scheuermann, Andrew G; Schmidt, Michael; Hurley, Paul K; McIntyre, Paul C; Chidsey, Christopher E D

    2016-09-14

    We synthesized nanoscale TiO2-RuO2 alloys by atomic layer deposition (ALD) that possess a high work function and are highly conductive. As such, they function as good Schottky contacts to extract photogenerated holes from n-type silicon while simultaneously interfacing with water oxidation catalysts. The ratio of TiO2 to RuO2 can be precisely controlled by the number of ALD cycles for each precursor. Increasing the composition above 16% Ru sets the electronic conductivity and the metal work function. No significant Ohmic loss for hole transport is measured as film thickness increases from 3 to 45 nm for alloy compositions ≥ 16% Ru. Silicon photoanodes with a 2 nm SiO2 layer that are coated by these alloy Schottky contacts having compositions in the range of 13-46% Ru exhibit average photovoltages of 525 mV, with a maximum photovoltage of 570 mV achieved. Depositing TiO2-RuO2 alloys on nSi sets a high effective work function for the Schottky junction with the semiconductor substrate, thus generating a large photovoltage that is isolated from the properties of an overlying oxygen evolution catalyst or protection layer.

  9. Schottky barrier height of Ni/TiO2/4H-SiC metal-insulator-semiconductor diodes

    Science.gov (United States)

    Kaufmann, Ivan R.; Pereira, Marcelo B.; Boudinov, Henri I.

    2015-12-01

    Ni/TiO2/4H-SiC diodes were analysed through measurements of current-voltage curves varying the temperature. The Schottky Barrier Height (SBH) which increased with temperature was studied by simulation of the Thermionic Emission Model, considering Ni/SiC Schottky structures with an insulator layer between the metal and semiconductor. This model shows that a new method of calculation should be applied to diodes that have a metal-insulator-semiconductor structure. Misleading results for SBH are obtained if the thin insulator layer is not considered. When applying the suggested method to the Ni/TiO2/4H-SiC diodes it was necessary to consider not only the deposited TiO2 layer, but also a second dielectric layer of native SiCxOy at the surface of SiC. By measuring I-V-T curves for two samples with different thicknesses of TiO2, the suggested method allows one to estimate the thicknesses of both dielectric layers: TiO2 and SiOxCy.

  10. Mg doping of InGaN layers grown by PA-MBE for the fabrication of Schottky barrier photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Pereiro, J; Redondo-Cubero, A; Fernandez-Garrido, S; Rivera, C; Navarro, A; Munoz, E; Calleja, E [Instituto de Sistemas Optoelectronicos y MicrotecnologIa, Universidad Politecnica de Madrid, E-28040 Madrid (Spain); Gago, R, E-mail: jpereiro@die.upm.e [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain)

    2010-08-25

    This work reports on the fabrication of Schottky barrier based Mg-doped (In,Ga)N layers for fluorescence applications. Mg acceptors are used in order to compensate surface and bulk donors that prevent the fabrication of Schottky contacts on unintentionally doped (In,Ga)N layers grown by plasma-assisted molecular beam epitaxy (PA-MBE). Rectifying properties of the contacts exhibited a major improvement when (In,Ga)N : Mg was used. The electrical and optical measurements of the layers showed a hole concentration of up to 3 x 10{sup 19} holes cm{sup -3} with a Mg acceptor activation energy of {approx}60 meV. Back-illuminated photodiodes fabricated on 800 nm thick Mg-doped In{sub 0.18}Ga{sub 0.82}N layers exhibited a band pass photo-response with a rejection ratio >10{sup 2} between 420 and 470 nm and peak responsivities of 87 mA W{sup -1} at {approx}470 nm. The suitability of these photodiodes for fluorescence measurements was demonstrated.

  11. Modeling of Schottky Barrier Height and Volt-Amper Characteristics for Transition Metal-solid Solution (SіC1 – x(AlNx

    Directory of Open Access Journals (Sweden)

    V.I. Altukhov

    2016-11-01

    Full Text Available Proposed nonlinear defect concentration model of metal-semiconductor contact. It is shown that taking into account nonlinear dependence of the Fermi energy EF defect concentration leads to higher barrier Schottky in 15-25 %. Calculated Volt-Amper characteristics of the diodes are consistent with experiment.

  12. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.; Anane, A.; Petroff, F.; Fert, A.; Dlubak, B.; Seneor, P. [Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau 91767 (France); Caneva, S.; Martin, M.-B.; Weatherup, R. S.; Kidambi, P. R.; Robertson, J.; Hofmann, S. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Xavier, S. [Thales Research and Technology, 1 avenue Augustin Fresnel, Palaiseau 91767 (France)

    2016-03-07

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  13. InGaAs Schottky barrier diode array detector for a real-time compact terahertz line scanner.

    Science.gov (United States)

    Han, Sang-Pil; Ko, Hyunsung; Park, Jeong-Woo; Kim, Namje; Yoon, Young-Jong; Shin, Jun-Hwan; Kim, Dae Yong; Lee, Dong Hun; Park, Kyung Hyun

    2013-11-04

    We present a terahertz (THz) broadband antenna-integrated 1 × 20 InGaAs Schottky barrier diode (SBD) array detector with an average responsivity of 98.5 V/W at a frequency of 250 GHz, which is measured without attaching external amplifiers and Si lenses, and an average noise equivalent power (NEP) of 106.6 pW/√Hz. The 3-dB bandwidth of the SBD detector is also investigated at approximately 180 GHz. For implementing an array-type SBD detector by a simple fabrication process to achieve a high yield, a structure comprising an SiN(x) layer instead of an air bridge between the anode and the cathode is designed. THz line beam imaging using a Gunn diode emitter with a center frequency of 250 GHz and a 1 × 20 SBD array detector is successfully demonstrated.

  14. Effect of side-chain length on rectification and photovoltaic characteristics of poly(3-alkylthiophene) Schottky barriers

    Energy Technology Data Exchange (ETDEWEB)

    Fang Yih; Chen Showan (Dept. of Chemical Engineering, National Tsing-Hua Univ., Hsinchu (Taiwan)); Chu, M.L. (Inst. of Electro-Optical Engineering, National Chiao-Tung Univ., Hsinchu (Taiwan))

    1992-10-15

    Schottky diodes of aluminium/poly(3-alkylthiophene) (P3AT)/indium-tin oxide (ITO) with large area (0.15-0.5 cm[sup 2]) are prepared using the proposed new casting technique. The P3ATs investigated involve poly(3-butylthiophene) (P3BT), poly(3-octylthiophene) (P3OT) and poly(3-dodecylthiophene) (P3DDT), which are prepared using the chemical method. The diodes, in which P3AT behaves as a p-type semiconductor, exhibit a moderate rectifying behaviour and low leakage current. Photovoltaic measurements show a power conversion efficiency of about 10[sup -2]-10[sup -3]% at a light intensity of 0.5-5 mW/cm[sup 2], which decreases with increasing light intensity. The longer alkyl side-chain length of P3ATs can cause a lower rectifying effect, barrier height, depletion region width and photovoltaic conversion efficiency. (orig.).

  15. 4H-SiC Schottky barrier diodes with semi-insulating polycrystalline silicon field plate termination

    Science.gov (United States)

    Yuan, Hao; Tang, Xiao-Yan; Zhang, Yi-Men; Zhang, Yu-Ming; Song, Qing-Wen; Yang, Fei; Wu, Hao

    2014-05-01

    Based on the theoretical analysis of the 4H-SiC Schottky-barrier diodes (SBDs) with field plate termination, 4H-SiC SBD with semi-insulating polycrystalline silicon (SIPOS) FP termination has been fabricated. The relative dielectric constant of the SIPOS dielectric first used in 4H-SiC devices is 10.4, which is much higher than that of the SiO2 dielectric, leading to benefitting the performance of devices. The breakdown voltage of the fabricated SBD could reach 1200 V at leakage current 20 μA, about 70% of the theoretical breakdown voltage. Meanwhile, both of the simulation and experimental results show that the length of the SIPOS FP termination is an important factor for structure design.

  16. Intestinal epithelial barrier function and tight junction proteins with heat and exercise

    DEFF Research Database (Denmark)

    Dokladny, Karol; Zuhl, Micah N; Moseley, Pope L

    2016-01-01

    (passive hyperthermia) heat stress on tight junction barrier function in in vitro and in vivo (animals and humans) models. Our secondary focus is to review changes in tight junction proteins in response to exercise or hyperthermic conditions. Finally, we discuss some pharmacological or nutritional...... interventions that may affect the cellular mechanisms involved in maintaining homeostasis of the intestinal epithelial tight junction barrier during heat stress or exercise....

  17. Experimental realization of single electron tunneling diode based on vertical graphene two-barrier junction

    OpenAIRE

    Xu, Rui; Bai, Ke-Ke; Nie, Jia-Cai; He, Lin

    2012-01-01

    Usually, graphene is used in its horizontal directions to design novel concept devices. Here, we report a single electron tunneling diode based on quantum tunneling through a vertical graphene two-barrier junction. The junction is formed by positioning a scanning tunnelling microscopy (STM) tip above a graphene nanoribbon that was deposited on a graphite surface. Because of the asymmetry of the two-barrier junction, the electrons can unidirectional transfer from the tip to the graphene nanori...

  18. Rapid thermal annealing effects on the electrical and structural properties of Ru/V/n-InP Schottky barrier diode

    Science.gov (United States)

    Padma, R.; Shanthi Latha, K.; Rajagopal Reddy, V.; Choi, Chel-Jong

    2015-07-01

    A Ru/V/n-InP Schottky barrier diode (SBD) is fabricated and investigated its electrical and structural properties as a function of annealing temperature. Measurements showed that the barrier height (BH) of the as-deposited Ru/V/n-InP SBD is found to be 0.83 eV (I-V) and 1.03 eV (C-V). Experimental results indicate that the SBD with high BH and low ideality factors (0.87 eV (I-V), 1.20 eV (C-V), and 1.12) can be achieved after annealing at 400 °C for 1 min in N2 atmosphere. Further, it is observed that the BH slightly decreases to 0.85 eV (I-V) and 1.09 eV (C-V) upon annealing at 500 °C. The BH, ideality factor and series resistance are also determined by Cheung's functions and Norde method. Further, the energy distribution of interface state density of Ru/V/n-InP SBD is calculated from the forward bias I-V characteristics as a function of annealing temperature. It is found that the interface state density decreases upon annealing at 400 °C and then slightly increases after annealing at 500 °C. The AES and XRD results revealed that the formation of indium phases at the Ru/V/n-InP interface could be the reason for the increase of BH upon annealing at 400 °C. The formation of phosphide phases at the interface may be the cause for the decrease of BH after annealing at 500 °C. The overall surface morphology of Ru/V Schottky contacts is considerably smooth at elevated temperatures.

  19. Analysis of Schottky barrier heights of metal/SiC contacts and its possible application to high-voltage rectifying devices

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, A. [Tokyo Inst. of Technol. (Japan). Dept. of Phys. Electron.; Matsunami, H. [Dept. of Electronic Science and Engineering, Kyoto Univ. (Japan)

    1997-07-16

    Schottky contacts of metal/3C-, 6H-, and 4H-SiC systems are investigated in this review. Most Schottky contacts having large barrier heights show good characteristics with low ideality factors. The barrier height depends on the metal work function without strong Fermi-level pinning for all polytypes, and linear relationships with slopes of about 0.2 to 0.7 are observed between the barrier height and the metal work function. Based on the analysis of metal/SiC systems, the fabrication of high-voltage rectifiers has been reported, and high voltages from 400 to 1100 V have been achieved using Pt/, Ti/, and Au/6H-SiC structures. In addition, high-temperature operation at 400 C is performed for an Au/6H-SiC structure while supporting a high reverse bias (460 V). Using Ti/4H-SiC structures, high-voltage ({approx}1000 V) and low-power loss characteristics are realized, which is superior to Ti/6H-SiC Schottky rectifiers. To improve the reverse bias characteristics, an edge termination technique is employed for Ti/4H-SiC Schottky rectifiers, and the devices show excellent characteristics with a higher blocking voltage up to 1750 V compared with unterminated devices. (orig.) 78 refs.

  20. Electrical parameters and series resistance analysis of Au/Y/p-InP/Pt Schottky barrier diode at room temperature

    Science.gov (United States)

    Rao, L. Dasaradha; Reddy, V. Rajagopal

    2016-05-01

    The current-voltage (I-V) characteristics of Au/Y/p-InP/Pt Schottky barrier diode (SBD) are analyzed at room temperature. The Au/Y/p-InP/Pt SBD shows a good rectification behavior. The ideality factor (n), barrier height (Φb), series resistance (Rs) and shunt resistance (Rsh) are determined from the I-V measurements. The n and Φb values of Au/Y/p-InP/Pt SBD are found to be 1.32 and 0.62 eV respectively. The value of barrier height (BH) obtained from Norde function is compared with those calculated from Cheung's functions. The series resistance (Rs) is calculated from Cheung's and modified Norde functions. Additionally, it is found that n, Φb, Rs, and Rsh have strong correlation with the applied bias. Furthermore, at low and high voltage regions, ohmic and space-charge-limited conduction mechanisms are found to govern the current flow in the diode.

  1. Theoretical Analysis of Current Crowding Effect in Metal/AlGaN/GaN Schottky Diodes and Its Reduction by Using Polysilicon in Anode

    Institute of Scientific and Technical Information of China (English)

    CHEN Jia-Rong; HAN Qi-Feng; DUAN Cheng-Hong; ZHOU Xiu-Ju; CHEN Wen-Jin; WANG Yu-Qi; QIU Kai; LI Xin-Hua; ZHONG Fei; YIN Zhi-Jun; JI Chang-Jian; CAO Xian-Cun

    2007-01-01

    There exists a current crowding effect in the anode of A1GaN/GaN heteto junction Schottky diodes, causing local overheating when working at high power density, and undermining their performance. The seriousness of this effect is illustrated by theoretical analysis. A method of reducing this effect is proposed by depositing a polysilicon layer on the Schottky barrier metal. The effectiveness of this method is provided through computer simulation.Power consumption of the polysilicon layer is also calculated and compared to that of the Schottky junction to ensure the applicability of this method.

  2. Barrier inhomogeneities and interface states of metal/4H-SiC Schottky contacts

    Science.gov (United States)

    Huang, Lingqin; Geiod, Rechard; Wang, Dejun

    2016-12-01

    The barrier and interface states of Ti, Mo, Ni, and Pt contacts to 4H-SiC were investigated. It is found that the barrier heights for all the contacts are Gaussianly distributed and the barrier inhomogeneity varies with the contact metal type. However, the energy-averaged interface states density in the band gap is metal-insensitive. When considering Gaussian distribution, the interface states density extracted from the electrical properties is consistent with the average density of Gaussianly distributed 4H-SiC surface states, indicating that the barrier inhomogeneities at metal/SiC contacts mainly originate from the spatial variation of surface states on SiC surface. The barrier height and barrier inhomogeneity could be modulated by the contact metal, obeying the barrier height theory of Cowley and Sze.

  3. DLTS detection of hole traps in MBE grown p-GaAs using Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Auret, F.D.; Goodman, S.A.; Myburg, G. (Univ. of Pretoria (South Africa))

    1992-12-01

    The presence of hole traps has been studied by deep level transient spectroscopy (DLTS) characterization of low carrier density p-type GaAs grown by MBE on p[sup +]-GaAs substrates using Al and Co Schottky contacts. The results obtained indicate the presence of several hole traps with energy levels of between 0.06 and 0.65 eV above the valence band in concentrations up to 2 [times] 10[sup 12]/cm[sup 3]. Some of these defects, e.g. Cu, are ascribed to system-, source- or substrate-related impurities, but the origin of several other defects is unknown. 18 refs., 2 figs., 1 tab.

  4. Schottky barrier contrasts in single and bi-layer graphene contacts for MoS{sub 2} field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Du, Hyewon; Kim, Taekwang; Shin, Somyeong; Kim, Dahye; Seo, Sunae, E-mail: sunaeseo@sejong.ac.kr [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Kim, Hakseong; Lee, Sang Wook [Divison of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701 (Korea, Republic of); Sung, Ji Ho; Jo, Moon-Ho [Center for Artificial Low-Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784 (Korea, Republic of); Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784 (Korea, Republic of); Lee, Myoung Jae [Center for Artificial Low-Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784 (Korea, Republic of); Seo, David H. [Samsung Electronics Company, Limited, System LSI Division, TD Team, Gyunggi 446-711 (Korea, Republic of)

    2015-12-07

    We have investigated single- and bi-layer graphene as source-drain electrodes for n-type MoS{sub 2} transistors. Ti-MoS{sub 2}-graphene heterojunction transistors using both single-layer MoS{sub 2} (1M) and 4-layer MoS{sub 2} (4M) were fabricated in order to compare graphene electrodes with commonly used Ti electrodes. MoS{sub 2}-graphene Schottky barrier provided electron injection efficiency up to 130 times higher in the subthreshold regime when compared with MoS{sub 2}-Ti, which resulted in V{sub DS} polarity dependence of device parameters such as threshold voltage (V{sub TH}) and subthreshold swing (SS). Comparing single-layer graphene (SG) with bi-layer graphene (BG) in 4M devices, SG electrodes exhibited enhanced device performance with higher on/off ratio and increased field-effect mobility (μ{sub FE}) due to more sensitive Fermi level shift by gate voltage. Meanwhile, in the strongly accumulated regime, we observed opposing behavior depending on MoS{sub 2} thickness for both SG and BG contacts. Differential conductance (σ{sub d}) of 1M increases with V{sub DS} irrespective of V{sub DS} polarity, while σ{sub d} of 4M ceases monotonic growth at positive V{sub DS} values transitioning to ohmic-like contact formation. Nevertheless, the low absolute value of σ{sub d} saturation of the 4M-graphene junction demonstrates that graphene electrode could be unfavorable for high current carrying transistors.

  5. Schottky barrier diode based on β-Ga2O3 (100) single crystal substrate and its temperature-dependent electrical characteristics

    Science.gov (United States)

    He, Qiming; Mu, Wenxiang; Dong, Hang; Long, Shibing; Jia, Zhitai; Lv, Hangbing; Liu, Qi; Tang, Minghua; Tao, Xutang; Liu, Ming

    2017-02-01

    The Pt/β-Ga2O3 Schottky barrier diode and its temperature-dependent current-voltage characteristics were investigated for power device application. The edge-defined film-fed growth (EFG) technique was utilized to grow the (100)-oriented β-Ga2O3 single crystal substrate that shows good crystal quality characterized by X-ray diffraction and high resolution transmission electron microscope. Ohmic and Schottky electrodes were fabricated by depositing Ti and Pt metals on the two surfaces, respectively. Through the current-voltage (I-V) measurement under different temperature and the thermionic emission modeling, the fabricated Pt/β-Ga2O3 Schottky diode was found to show good performances at room temperature, including rectification ratio of 1010, ideality factor (n) of 1.1, Schottky barrier height (ΦB) of 1.39 eV, threshold voltage (Vbi) of 1.07 V, ON-resistance (RON) of 12.5 mΩ.cm2, forward current density at 2 V (J@2V) of 56 A/cm2, and saturation current density (J0) of 2 × 10-16 A/cm2. The effective donor concentration Nd - Na was calculated to be about 2.3 × 1014 cm3. Good temperature dependent performance was also found in the device. The Schottky barrier height was estimated to be about 1.3 eV-1.39 eV at temperatures ranging from room temperature to 150 °C. With increasing temperature, parameters such as RON and J@2V become better, proving that the diode can work well at high temperature. The EFG grown β-Ga2O3 single crystal is a promising material to be used in the power devices.

  6. Analytical model of threshold voltage degradation due to localized charges in gate material engineered Schottky barrier cylindrical GAA MOSFETs

    Science.gov (United States)

    Kumar, Manoj; Haldar, Subhasis; Gupta, Mridula; Gupta, R. S.

    2016-10-01

    The threshold voltage degradation due to the hot carrier induced localized charges (LC) is a major reliability concern for nanoscale Schottky barrier (SB) cylindrical gate all around (GAA) metal-oxide-semiconductor field-effect transistors (MOSFETs). The degradation physics of gate material engineered (GME)-SB-GAA MOSFETs due to LC is still unexplored. An explicit threshold voltage degradation model for GME-SB-GAA-MOSFETs with the incorporation of localized charges (N it) is developed. To accurately model the threshold voltage the minimum channel carrier density has been taken into account. The model renders how +/- LC affects the device subthreshold performance. One-dimensional (1D) Poisson’s and 2D Laplace equations have been solved for two different regions (fresh and damaged) with two different gate metal work-functions. LCs are considered at the drain side with low gate metal work-function as N it is more vulnerable towards the drain. For the reduction of carrier mobility degradation, a lightly doped channel has been considered. The proposed model also includes the effect of barrier height lowering at the metal-semiconductor interface. The developed model results have been verified using numerical simulation data obtained by the ATLAS-3D device simulator and excellent agreement is observed between analytical and simulation results.

  7. Valence-band offsets and Schottky barrier heights of layered semiconductors explained by interface-induced gap states

    Science.gov (United States)

    Mönch, Winfried

    1998-04-01

    Many metal chalcogenides are layered semiconductors. They consist of chalcogen-metal-chalcogen layers that are themselves bound by van der Waals forces. Hence, heterostructures involving layered compounds are abrupt and strain-free. Experimental valence-band offsets of heterostructures between GaSe, InSe, SnS2, SnSe2, MoS2, MoTe2, WSe2, and CuInSe2 and between some of these compounds and ZnSe, CdS, and CdTe as well as barrier heights of Au contacts on GaSe, InSe, MoS2, MoTe2, WSe2, ZnSe, CdS, and CdTe are analyzed. The valence-band discontinuities of the heterostructures and the barrier heights of the Schottky contact compounds are consistently described by the continuum of interface-induced gap states as the primary mechanism that governs the band lineup at semiconductor interfaces.

  8. Magnetic tunneling junctions with permalloy electrodes: a study of barrier, thermal annealing, and interlayer coupling

    Energy Technology Data Exchange (ETDEWEB)

    Liu Xiaoyong E-mail: xiaoyong_liu@brown.edu; Ren Cong; Ritchie, Lance; Schrag, B.D.; Xiao Gang; Li Laifeng

    2003-11-01

    Magnetic properties of Ni{sub 81}Fe{sub 19}/Al{sub 2}O{sub 3}/Ni{sub 81}Fe{sub 19} tunneling junctions are studied for different Al thicknesses and plasma oxidation times. A maximal magnetoresistance of 34% is obtained with Al thickness of 20 A. Magnetometry reveals large exchange bias fields ({approx}400 Oe) over a wide range of barrier thicknesses, indicating junctions of high quality. Transport measurements conducted on junctions before and after thermal annealing show a dramatic improvement in barrier quality after annealing. Interlayer coupling fields have been measured as a function of barrier thickness for different oxidation times.

  9. Effect of Barrier Width on Bias-Dependent Tunnelling in Ferromagnetic Junctions

    Institute of Scientific and Technical Information of China (English)

    LI Fei-Fei; XIAO Ming-Wen; LI Zheng-Zhong; HU An; XU Wang

    2004-01-01

    @@ We present a finite temperature theory for bias-dependent tunnelling in ferromagnetic tunnelling junctions. The effects of the barrier width d on the tunnelling magnetoresistance (TMR) and its sign change behaviour are discussed with this theory. Numerical results show that both the zero-bias TMR and the critical voltage Vc at which the TMR changes its sign decrease with the increasing barrier width for a considerably thick barrier junction. Furthermore, it is found that a minimum exists in the curve of Vc versus d if a composite junction is under oxidized.

  10. Highly reproducible ideal SiC Schottky rectifiers: effects of surface preparation and thermal annealing on the Ni/6H-SiC barrier height

    Energy Technology Data Exchange (ETDEWEB)

    Roccaforte, F.; La Via, F.; Raineri, V. [Sezione di Catania, CNR-IMM, Stradale Primosole 50, 95121, Catania (Italy); Musumeci, P.; Calcagno, L. [INFM and Dipartimento di Fisica e Astronomia, via Santa Sofia 64, 95125, Catania (Italy); Condorelli, G.G. [Dipartimento di Chimica, viale A. Doria 6, 95125, Catania (Italy)

    2003-11-01

    In this work, the effects of surface preparation and thermal annealing on the Ni/6H-SiC Schottky barrier height were studied by monitoring the forward I-V characteristics of Schottky diodes. The ideality factor n and the barrier height {phi}{sub B} were found to be strongly dependent on the impurity species present at the metal/SiC interface. The physical mechanism which rules the Schottky barrier formation is discussed by considering the nature of the impurities left from the different surface preparation methods prior to metal deposition. In contrast, nickel silicide/SiC rectifiers (Ni{sub 2}Si/6H-SiC), formed by thermal reaction of Ni/6H-SiC above 600 C, have an almost ideal I-V curve, independent of the surface preparation. Further improvement in the barrier height distribution can be obtained by increasing the annealing temperature to 950 C. This behaviour is discussed in terms of the silicide phases and the consumption of a SiC layer during the thermal reaction. (orig.)

  11. Calculation of the Electronic Parameters of an Al/DNA/p-Si Schottky Barrier Diode Influenced by Alpha Radiation

    Directory of Open Access Journals (Sweden)

    Hassan Maktuff Jaber Al-Ta'ii

    2015-02-01

    Full Text Available Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al/DNA/silicon (Si rectifying junctions using their current-voltage (I-V characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0 was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min. These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors.

  12. Electroluminescence from a forward-biased Schottky barrier diode on modulation Si {delta}-doped GaAs/InGaAs/AlGaAs heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Babinski, Adam; Witczak, P.; Twardowski, A.; Baranowski, J. M.

    2001-06-18

    Electroluminescence (EL) from a forward-biased Schottky barrier diode on modulation Si {delta}-doped pseudomorphic GaAs/InGaAs/AlGaAs heterostructure with high mobility electron gas is investigated in this work. It has been found that the EL from the InGaAs quantum well can be observed at temperatures up to 90 K. The EL line shape depends on the current density, which reflects the filling of the InGaAs channel with electrons. The total integrated EL intensity depends linearly on the current density. We propose that hole diffusion from an inversion layer at the Schottky barrier is responsible for the observed optical recombination with electrons in the InGaAs quantum well. {copyright} 2001 American Institute of Physics.

  13. Nonlinear absorption coefficient and relative refraction index change for an asymmetrical double δ-doped quantum well in GaAs with a Schottky barrier potential

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)

    2013-09-01

    In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.

  14. 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)

  15. Analysis of temperature-dependant current–voltage characteristics and extraction of series resistance in Pd/ZnO Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Mayimele, M A, E-mail: meehleketo@gmail.com; Rensburg, J P van. Janse; Auret, F D; Diale, M

    2016-01-01

    We report on the analysis of current voltage (I–V) measurements performed on Pd/ZnO Schottky barrier diodes (SBDs) in the 80–320 K temperature range. Assuming thermionic emission (TE) theory, the forward bias I–V characteristics were analysed to extract Pd/ZnO Schottky diode parameters. Comparing Cheung’s method in the extraction of the series resistance with Ohm’s law, it was observed that at lower temperatures (T<180 K) the series resistance decreased with increasing temperature, the absolute minimum was reached near 180 K and increases linearly with temperature at high temperatures (T>200 K). The barrier height and the ideality factor decreased and increased, respectively, with decrease in temperature, attributed to the existence of barrier height inhomogeneity. Such inhomogeneity was explained based on TE with the assumption of Gaussian distribution of barrier heights with a mean barrier height of 0.99 eV and a standard deviation of 0.02 eV. A mean barrier height of 0.11 eV and Richardson constant value of 37 A cm{sup −2} K{sup −2} were determined from the modified Richardson plot that considers the Gaussian distribution of barrier heights.

  16. The modulation of Schott ky barrier height of NiSi/n-Si Schottky diodes by silicide as diffusion source technique

    Institute of Scientific and Technical Information of China (English)

    An Xia; Fan Chun-Hui; Huang Ru; Guo Yue; Xu Cong; Zhang Xing; Wang Yang-Yuan

    2009-01-01

    This paper reports that the Schottky barrier height modulation of NiSi/n-si is experimentally investigated by adopting a novel silicide-as-diffusion-source technique. which avoids the damage to the NiSi/Si interface induced from the conventional dopant segregation method. In addition, the impact of post-BF_2 implantation after silicidation on the surface morphology of Ni silicides is also illustrated. The thermal stability of Ni silicides can be improved by sihcideas-diffusion-source technique. Besides, the electron Schottky barrier height is successfully modulated by 0.11 eV at a boron dose of 10~(15) cm~(-2) in comparison with the non. implanted samples. The change of barrier height is not attributed to the phase change of silicide films but due to the boron pile-up at the interface of NiSi and Si substrate which causes the upward bending of conducting band. The results demonstrate the feasibility of novel silicide-as-diffusion-source technique for the fabrication of Schottky source/drain Si MOS devices.

  17. Influence of neighboring coupling on metal-insulator-semiconductor (MIS) deep-depletion tunneling current via Schottky barrier height modulation mechanism

    Science.gov (United States)

    Yang, Ming-Han; Hwu, Jenn-Gwo

    2017-04-01

    A metal-insulator-semiconductor (MIS) tunneling diode is a very promising sensor due to its deep depletion phenomenon. The coupling effect between two adjacent devices is therefore of importance. To study the MIS deep-depletion tunneling current coupling phenomenon, a device pattern of one centric circle coupled with one or two surrounding rings was devised. It was found that MIS(p) tunneling current with the Schottky barrier height modulation mechanism is enhanced just by locating more MIS(p) structures nearby or by shortening their relative distance, which can again be verified under light exposure. The MIS(n) structure was also fabricated for comparison. It was observed in MIS(n) that, with the lack of the Schottky barrier height modulation mechanism, tunneling current is greater and almost immune to light irradiance compared to MIS(p). Besides, the edge oxide of MIS(p) is removed to change its Schottky barrier height modulation capability. Significantly lower deep-depletion tunneling current and invulnerability to the adjacent minority condition were observed. Surprisingly, it offers smaller saturation voltage and better photosensitivity.

  18. Atomic and electronic structure of CdTe/metal (Cu, Al, Pt) interfaces and their influence to the Schottky barrier

    Science.gov (United States)

    Odkhuu, Dorj; Miao, Mao-sheng; Aqariden, F.; Grein, Christoph; Kioussis, Nicholas

    2016-11-01

    Schottky barrier heights (SBHs) and other features of the interfaces are determining factors for the performance of the CdTe based high-energy photon detectors. Although known for long time that SBH is sensitive to surface treatment and metal contact growth method, there is a lack of understanding of the effect of the atomic and electronic structures of CdTe/metal interface on the SBH. Employing first-principles electronic structure calculations, we have systematically studied the structural stability and electronic properties of a number of representing structures of Cd Terminated CdTe/metal (Cu, Pt, and Al) interfaces. Comparison of the total energies of the various optimized structural configurations allows to identify the existence of Te-metal alloy formation at the interface. The SBHs of Cu, Pt, and Al metal contacts with a number of stable interface structures are determined by aligning the band edges of bulk CdTe with the Fermi level of the metal/CdTe system. We find that the metal-induced states in the gap play an essential role in determining the SBH.

  19. Radiation hardness of n-type SiC Schottky barrier diodes irradiated with MeV He ion microbeam

    Science.gov (United States)

    Pastuović, Željko; Capan, Ivana; Cohen, David D.; Forneris, Jacopo; Iwamoto, Naoya; Ohshima, Takeshi; Siegele, Rainer; Hoshino, Norihiro; Tsuchida, Hidekazu

    2015-04-01

    We studied the radiation hardness of 4H-SiC Schottky barrier diodes (SBD) for the light ion detection and spectroscopy in harsh radiation environments. n-Type SBD prepared on nitrogen-doped (∼4 × 1014 cm-3) epitaxial grown 4H-SiC thin wafers have been irradiated by a raster scanning alpha particle microbeam (2 and 4 MeV He2+ ions separately) in order to create patterned damage structures at different depths within a sensitive volume of tested diodes. Deep Level Transient Spectroscopy (DLTS) analysis revealed the formation of two deep electron traps in the irradiated and not thermally treated 4H-SiC within the ion implantation range (E1 and E2). The E2 state resembles the well-known Z1/2 center, while the E1 state could not be assigned to any particular defect reported in the literature. Ion Beam Induced Charge (IBIC) microscopy with multiple He ion probe microbeams (1-6 MeV) having different penetration depths in tested partly damaged 4H-SiC SBD has been used to determine the degradation of the charge collection efficiency (CCE) over a wide fluence range of damaging alpha particle. A non-linear behavior of the CCE decrease and a significant degradation of the spectroscopic performance with increasing He ion fluence were observed above the value of 1011 cm-2.

  20. Radiation hardness of n-type SiC Schottky barrier diodes irradiated with MeV He ion microbeam

    Energy Technology Data Exchange (ETDEWEB)

    Pastuović, Željko, E-mail: zkp@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Capan, Ivana [Material Physics Division, Institute Rudjer Boskovic, PO Box 180, 10000 Zagreb (Croatia); Cohen, David D. [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Forneris, Jacopo [Physics Department and NIS Excellence Centre, University of Torino, via P. Giuria 1, 10125 Torino (Italy); Iwamoto, Naoya; Ohshima, Takeshi [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Siegele, Rainer [Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); Hoshino, Norihiro; Tsuchida, Hidekazu [Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan)

    2015-04-01

    We studied the radiation hardness of 4H-SiC Schottky barrier diodes (SBD) for the light ion detection and spectroscopy in harsh radiation environments. n-Type SBD prepared on nitrogen-doped (∼4 × 10{sup 14} cm{sup −3}) epitaxial grown 4H-SiC thin wafers have been irradiated by a raster scanning alpha particle microbeam (2 and 4 MeV He{sup 2+} ions separately) in order to create patterned damage structures at different depths within a sensitive volume of tested diodes. Deep Level Transient Spectroscopy (DLTS) analysis revealed the formation of two deep electron traps in the irradiated and not thermally treated 4H-SiC within the ion implantation range (E1 and E2). The E2 state resembles the well-known Z{sub 1/2} center, while the E1 state could not be assigned to any particular defect reported in the literature. Ion Beam Induced Charge (IBIC) microscopy with multiple He ion probe microbeams (1–6 MeV) having different penetration depths in tested partly damaged 4H-SiC SBD has been used to determine the degradation of the charge collection efficiency (CCE) over a wide fluence range of damaging alpha particle. A non-linear behavior of the CCE decrease and a significant degradation of the spectroscopic performance with increasing He ion fluence were observed above the value of 10{sup 11} cm{sup −2}.

  1. Au and Al Schottky barrier formation on GaAs (100) surfaces prepared by thermal desorption of a protective arsenic coating

    Energy Technology Data Exchange (ETDEWEB)

    Spindt, C.J.; Yamada, M.; Meissner, P.L.; Miyano, K.E.; Herrera, A.; Spicer, W.E. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305-4055 (US)); Arko, A.J. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (US))

    1991-07-01

    Soft x-ray photoemission spectroscopy has been used to investigate the initial stages of Schottky barrier formation on GaAs (100) surfaces prepared by the thermal desorption of an As cap. This work was motivated by a previous study (Brillson {ital et} {ital al}., J. Vac. Sci. Technol. B {bold 6}, 1263 (1988)) of identically grown and capped samples which reported unpinned'' Schottky barrier formation, with barrier heights falling over a wide range (0.75 eV) of energies. This large energy range is a striking result, as a considerable number of prior studies on both (110) and (100) surfaces have found that all metals will pin in a narrow (0.25 eV) range near midgap. Since Au and Al are the extremes of the larger 0.75 eV span of Schottky barriers, we have studied the deposition of these two metals. We found that the barrier height measurements on the low doped {ital n}-type samples used in this work and in the paper referenced above are affected by photovoltaic effects, even at room temperature. These photovoltaic effects cause shifts in the band bending, which are an artifact of the measurement. We also performed measurements on more heavily doped samples, and the photovoltaic effects were removed. In addition, we point out that Au--Ga alloying makes the case of Au potentially misleading. With the photovoltaic effects removed, and the Au--Ga alloying carefully accounted for, we found that the barriers heights for Au and Al differ by only 0.25 eV.

  2. Temperature dependent electrical characteristics of Pt Schottky barriers fabricated on lightly and highly doped n-type 4H-SiC

    Science.gov (United States)

    Huang, Lingqin; Wang, Dejun

    2015-11-01

    The temperature dependent electronic characteristics of Pt Schottky barriers fabricated on lightly and relatively highly doped n-type 4H-SiC (1 × 1016 and 1 × 1018 cm-3) are comparatively investigated. It is found that the abnormal temperature dependence of barrier height and ideality factor estimated from the thermionic emission (TE) model for both lightly and highly doped samples could be successfully explained in terms of Gaussian distribution of inhomogeneous barrier heights. However, the estimated mean barrier height according to Gaussian distribution for the highly doped sample is much lower than the actual mean value from the capacitance-voltage (C-V) measurements. Interestingly, the values of barrier height from the thermionic field emission (TFE) model are found to be close to those from the C-V measurements, indicating that the TFE model is more appropriate to explain the electrical transport for the highly doped sample.

  3. Determination of the laterally homogeneous barrier height of palladium Schottky barrier diodes on n-Ge (111)

    CSIR Research Space (South Africa)

    Chawanda, A

    2011-05-01

    Full Text Available The authors have studied the experimental linear relationship between barrier heights and ideality factors for palladium (Pd) on bulk-grown (1 1 1) Sb-doped n-type germanium (Ge) metal-semiconductor structures with a doping density of about 2...

  4. Investigation of the tunnel magnetoresistance in junctions with a strontium stannate barrier

    Science.gov (United States)

    Althammer, Matthias; Vikam Singh, Amit; Keshavarz, Sahar; Kenan Yurtisigi, Mehmet; Mishra, Rohan; Borisevich, Albina Y.; LeClair, Patrick; Gupta, Arunava

    2016-12-01

    We experimentally investigate the structural, magnetic, and electrical transport properties of La0.67 Sr0.33 MnO3 based magnetic tunnel junctions with a SrSnO3 barrier. Our results show that despite the high density of defects in the strontium stannate barrier, due to the large lattice mismatch, the observed tunnel magnetoresistance (TMR) is comparable to tunnel junctions with a better lattice matched SrTiO3 barrier, reaching values of up to 350 % at T =5 K . Further analysis of the current-voltage characteristics of the junction and the bias voltage dependence of the observed tunnel magnetoresistance show a decrease of the TMR with increasing bias voltage. In addition, the observed TMR vanishes for T >200 K . Our results suggest that by employing a better lattice matched ferromagnetic electrode, and thus reducing the structural defects in the strontium stannate barrier, even larger TMR ratios might be possible in the future.

  5. The ultraviolet radiation detectors based on wide-bandgap Schottky barrier structures

    CERN Document Server

    Blank, T V; Konstantinov, O V

    2002-01-01

    Recently, much attention has been given to measure and control ultraviolet radiation (UVR) from the Sun and artificial sources. We present photodetectors based on different wide-bandgap surface-barrier structures, which exhibit linear photocurrent-radiant flux characteristics in the range 10 sup - sup 2 -10 sup 3 W/m sup 2 and can register different types of UVR. The use of light filter UFS-6 with GaP photodetector results in a spectral photosensitivity range corresponding to the Sun UV radiation if observed on Earth. The spectral sensitivity range of the photodetectors based on 4H-SiC is near the spectrum of relative effectiveness of various wavelengths in bactericidal UVR. The photosensitivity of the surface-barrier photodetectors based on wide-bandgap semiconductors exhibits the essential decline in the short-wavelength UVR region (5-6 eV), which is the region of intrinsic absorption of the semiconductor. We propose a hot exciton model, according to which the hot excitons can form in the process of the pho...

  6. Au and Al Schottky barrier formation on GaAs (100) surfaces prepared by thermal desorption of a protective arsenic coating

    Energy Technology Data Exchange (ETDEWEB)

    Spindt, C.J.; Yamada, M.; Meissner, P.L.; Miyano, K.E.; Herrera, A.; Spicer, W.E. (Stanford Univ., CA (United States). Stanford Electronics Labs.); Arko, A.J. (Los Alamos National Lab., NM (United States)); Woodall, J.M.; Pettit, G.D. (International Business Machines Corp., Yorktown Heights, NY (United States). Thomas J. Watson Research Center)

    1991-01-01

    Photoelectron spectroscopy has been used as a tool to investigate the initial stages of Schottky barrier formation on GaAs (100) surfaces. This is a popular technique that has been used by many researchers in the past to measure the band bending (or shift) of the valence band and conduction band (a measure of the Schottky barrier shift), while the Fermi level remains fixed at the system ground (i.e., the ground of the spectrometer). Metal deposition on a semiconductor surface can alter the Schottky barrier at the surface and pin the Fermi level near the middle of the energy gap. Extremely clean and crystallographically perfect surfaces are required in this study. Toward this end, a method of protecting the GaAs surface was employed which consists of capping the GaAs surface with a layer of As. Upon introduction into the high vacuum system the As is thermally desorbed, revealing a pure GaAs surface. Our work was motivated by a previous study (Brillson et al) on similarly capped specimens, which suggested that metal overlayers do not pin the Schottky barrier in GaAs. Barrier heights varied by as much as 0.75 eV between Al and Au overlayers. This large energy range is a striking result in view of the fact that a considerable number of prior studies on both (110) and (100) surfaces have found that all metals will pin within a narrow (0.25 eV) range at midgap. We repeated the measurements of Brillson on the identically doped samples used in their study using two extreme range metals of Au and Al as overlayers. We found that the barrier height measurements on low doped n-type samples used in this work and in the previous work are affected by photovoltaic effects, even at room temperature. This was determined from taking spectra at a number of temperatures between 20 K and room temperature and looking for shifts. 16 refs., 7 figs.

  7. Gate-controlled energy barrier at a graphene/molecular semiconductor junction

    Science.gov (United States)

    Parui, S.; Pietrobon, L.; Ciudad, D.; Velez, S.; Sun, X.; Stoliar, P.; Casanova, F.; Hueso, L. E.

    The formation of an energy barrier at a metal/molecular semiconductor junction is both a ubiquitous phenomenon as well as the subject of intense research in order to improve the performance of molecular semiconductor-based electronic and optoelectronic devices. For these devices, a junction with a large energy barrier provides rectification, leading to a diode behavior, whereas a relatively small energy barrier provides nearly-ohmic behavior, resulting in efficient carrier injection (extraction) into the molecular semiconductor. Typically, a specific metal/molecular semiconductor combination leads to a fixed energy barrier; therefore, the possibility of a gate-controlled energy barrier is very appealing for advanced applications. Here, we present a graphene/C60 junction-based vertical field-effect transistor in which we demonstrate control of the interfacial energy-barrier such that the junction switches from a highly rectifying diode at negative gate voltages to a nearly-ohmic behavior at positive gate voltages and at room temperature. We extract an energy-barrier modulation of up to 660 meV, a transconductance of up to five orders of magnitude and a gate-modulated photocurrent.

  8. Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

    Energy Technology Data Exchange (ETDEWEB)

    Omotoso, E., E-mail: ezekiel.omotoso@up.ac.za [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa); Departments of Physics, Obafemi Awolowo University, Ile-Ife 220005 (Nigeria); Meyer, W.E.; Auret, F.D.; Diale, M.; Ngoepe, P.N.M. [Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028 (South Africa)

    2016-01-01

    Irradiation experiments have been carried out on 1.9×10{sup 16} cm{sup −3} nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6×10{sup 10} to 9.2×10{sup 11} cm{sup −2}. Current–voltage (I–V), capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation, respectively. As radiation fluence increases, the ideality factors increased from 1.20 to 1.85 but the Schottky barrier height (SBH{sub I–V}) decreased from 1.47 to 1.34 eV. Free carrier concentration, N{sub d} decreased with increasing fluence from 1.7×10{sup 16} to 1.1×10{sup 16} cm{sup −2} at approximately 0.70 μm depth. The reduction in N{sub d} shows that defects were induced during the irradiation and have effect on compensating the free carrier. The free carrier removal rate was estimated to be 6480±70 cm{sup −1}. Alpha-particle irradiation introduced two electron traps (E{sub 0.39} and E{sub 0.62}), with activation energies of 0.39±0.03 eV and 0.62±0.08 eV, respectively. The E{sub 0.39} as attribute related to silicon or carbon vacancy, while the E{sub 0.62} has the attribute of Z{sub 1}/Z{sub 2}.

  9. Prospects of zero Schottky barrier height in a graphene-inserted MoS{sub 2}-metal interface

    Energy Technology Data Exchange (ETDEWEB)

    Chanana, Anuja; Mahapatra, Santanu [Nano-Scale Device Research Laboratory, Department of Electronic Systems Engineering, Indian Institute of Science (IISc) Bangalore, Bangalore 560012 (India)

    2016-01-07

    A low Schottky barrier height (SBH) at source/drain contact is essential for achieving high drive current in atomic layer MoS{sub 2}-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 MoS{sub 2} and metal. Recent experiments demonstrate significant SBH reduction when graphene layer is inserted between metal slab (Ti and Ni) and MoS{sub 2}. 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 MoS{sub 2} 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 MoS{sub 2}-metal interface, the projected dispersion of MoS{sub 2} remains preserved in any MoS{sub 2}-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 MoS{sub 2}-metal contact. These understandings would provide a direction in developing high-performance transistors involving heteroatomic layers as contact electrodes.

  10. Response of Ni/4H-SiC Schottky barrier diodes to alpha-particle irradiation at different fluences

    Science.gov (United States)

    Omotoso, E.; Meyer, W. E.; Auret, F. D.; Diale, M.; Ngoepe, P. N. M.

    2016-01-01

    Irradiation experiments have been carried out on 1.9×1016 cm-3 nitrogen-doped 4H-SiC at room temperature using 5.4 MeV alpha-particle irradiation over a fluence ranges from 2.6×1010 to 9.2×1011 cm-2. Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements have been carried out to study the change in characteristics of the devices and free carrier removal rate due to alpha-particle irradiation, respectively. As radiation fluence increases, the ideality factors increased from 1.20 to 1.85 but the Schottky barrier height (SBHI-V) decreased from 1.47 to 1.34 eV. Free carrier concentration, Nd decreased with increasing fluence from 1.7×1016 to 1.1×1016 cm-2 at approximately 0.70 μm depth. The reduction in Nd shows that defects were induced during the irradiation and have effect on compensating the free carrier. The free carrier removal rate was estimated to be 6480±70 cm-1. Alpha-particle irradiation introduced two electron traps (E0.39 and E0.62), with activation energies of 0.39±0.03 eV and 0.62±0.08 eV, respectively. The E0.39 as attribute related to silicon or carbon vacancy, while the E0.62 has the attribute of Z1/Z2.

  11. Superconductor-semiconductor-superconductor planar junctions of aluminium on DELTA-doped gallium arsenide

    DEFF Research Database (Denmark)

    Taboryski, Rafael Jozef; Clausen, Thomas; Kutchinsky, jonatan

    1997-01-01

    We have fabricated and characterized planar superconductor-semiconductor-superconductor (S-Sm-S) junctions with a high quality (i.e. low barrier) interface between an n++ modulation doped conduction layer in MBE grown GaAs and in situ deposited Al electrodes. The Schottky barrier at the S...

  12. Irsogladine maleate regulates gap junctional intercellular communication-dependent epithelial barrier in human nasal epithelial cells.

    Science.gov (United States)

    Miyata, Ryo; Nomura, Kazuaki; Kakuki, Takuya; Takano, Ken-Ichi; Kohno, Takayuki; Konno, Takumi; Sawada, Norimasa; Himi, Tetsuo; Kojima, Takashi

    2015-04-01

    The airway epithelium of the human nasal mucosa acts as the first physical barrier that protects against inhaled substances and pathogens. Irsogladine maleate (IM) is an enhancer of gastric mucosal protective factors via upregulation of gap junctional intercellular communication (GJIC). GJIC is thought to participate in the formation of functional tight junctions. However, the effects of IM on GJIC and the epithelial barrier in human nasal epithelial cells (HNECs) remain unknown. To investigate the effects of IM on GJIC and the tight junctional barrier in HNECs, primary cultures of HNECs transfected with human telomerase reverse transcriptase (hTERT-HNECs) were treated with IM and the GJIC inhibitors oleamide and 18β-GA. Some cells were pretreated with IM before treatment with TLR3 ligand poly(I:C) to examine whether IM prevented the changes via TLR3-mediated signal pathways. In hTERT-HNECs, GJIC blockers reduced the expression of tight junction molecules claudin-1, -4, -7, occludin, tricellulin, and JAM-A. IM induced GJIC activity and enhanced the expression of claudin-1, -4, and JAM-A at the protein and mRNA levels with an increase of barrier function. GJIC blockers prevented the increase of the tight junction proteins induced by IM. Furthermore, IM prevented the reduction of JAM-A but not induction of IL-8 and TNF-α induced by poly(I:C). In conclusion, IM can maintain the GJIC-dependent tight junctional barrier via regulation of GJIC in upper airway nasal epithelium. Therefore, it is possible that IM may be useful as a nasal spray to prevent the disruption of the epithelial barrier by viral infections and exposure to allergens in human nasal mucosa.

  13. Estimation of power dissipation of a 4H-SiC Schottky barrier diode with a linearly graded doping profile in the drift region

    Directory of Open Access Journals (Sweden)

    Rajneesh Talwar

    2009-09-01

    Full Text Available The aim of this paper is to establish the importance of a linearly graded profile in the drift region of a 4H-SiC Schottky barrier diode (SBD. The power dissipation of the device is found to be considerably lower at any given current density as compared to its value obtained for a uniformly doped drift region. The corresponding values of breakdown voltages obtained are similar to those obtained with uniformly doped wafers of 4H-SiC.

  14. MgGa2O4 spinel barrier for magnetic tunnel junctions: Coherent tunneling and low barrier height

    Science.gov (United States)

    Sukegawa, Hiroaki; Kato, Yushi; Belmoubarik, Mohamed; Cheng, P.-H.; Daibou, Tadaomi; Shimomura, Naoharu; Kamiguchi, Yuuzo; Ito, Junichi; Yoda, Hiroaki; Ohkubo, Tadakatsu; Mitani, Seiji; Hono, Kazuhiro

    2017-03-01

    Epitaxial Fe/magnesium gallium spinel oxide (MgGa2O4)/Fe(001) magnetic tunnel junctions (MTJs) were fabricated by magnetron sputtering. A tunnel magnetoresistance (TMR) ratio up to 121% at room temperature (196% at 4 K) was observed, suggesting a TMR enhancement by the coherent tunneling effect in the MgGa2O4 barrier. The MgGa2O4 layer had a spinel structure and it showed good lattice matching with the Fe layers owing to slight tetragonal lattice distortion of MgGa2O4. Barrier thickness dependence of the tunneling resistance and current-voltage characteristics revealed that the height of the MgGa2O4 barrier is much lower than that of an MgAl2O4 barrier. This study demonstrates the potential of Ga-based spinel oxides for MTJ barriers having a large TMR ratio at a low resistance area product.

  15. Electric Field Control of the Resistance of Multiferroic Tunnel Junctions with Magnetoelectric Antiferromagnetic Barriers

    Science.gov (United States)

    Merodio, P.; Kalitsov, A.; Chshiev, M.; Velev, J.

    2016-06-01

    Based on model calculations, we predict a magnetoelectric tunneling electroresistance effect in multiferroic tunnel junctions consisting of ferromagnetic electrodes and magnetoelectric antiferromagnetic barriers. Switching of the antiferromagnetic order parameter in the barrier in applied electric field by means of the magnetoelectric coupling leads to a substantial change of the resistance of the junction. The effect is explained in terms of the switching of the orientations of local magnetizations at the barrier interfaces affecting the spin-dependent interface transmission probabilities. Magnetoelectric multiferroic materials with finite ferroelectric polarization exhibit an enhanced resistive change due to polarization-induced spin-dependent screening. These results suggest that devices with active barriers based on single-phase magnetoelectric antiferromagnets represent an alternative nonvolatile memory concept.

  16. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2012-06-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  17. 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.

  18. Investigation of Schottky Barriers

    Science.gov (United States)

    1989-12-01

    gallium site was favored; this is consistent with the earlier tight-binding treatment[13]. In addition, the total energy difference per primitive cell (each... primitive cell contained one aluminum adatom) was 0.36 eV. The tight-binding energy differ- ence was 0.30 eV[15]. The agreement between the two...the gallium and arsenic sites) and two interstitial sites in every primitive cell . We have performed the calculations for several different coverages

  19. Kiwifruit cysteine protease actinidin compromises the intestinal barrier by disrupting tight junctions

    NARCIS (Netherlands)

    Grozdanovic, Milica M; Čavić, Milena; Nešić, Andrijana; Andjelković, Uroš; Akbari, Peyman; Smit, Joost J; Gavrović-Jankulović, Marija

    2016-01-01

    BACKGROUND: The intestinal epithelium forms a barrier that food allergens must cross in order to induce sensitization. The aim of this study was to evaluate the impact of the plant-derived food cysteine protease--actinidin (Act d1) on the integrity of intestinal epithelium tight junctions (TJs). MET

  20. High-voltage 4H-SiC trench MOS barrier Schottky rectifier with low forward voltage drop using enhanced sidewall layer

    Science.gov (United States)

    Cho, Doohyung; Sim, Seulgi; Park, Kunsik; Won, Jongil; Kim, Sanggi; Kim, Kwangsoo

    2015-12-01

    In this paper, a 4H-SiC trench MOS barrier Schottky (TMBS) rectifier with an enhanced sidewall layer (ESL) is proposed. The proposed structure has a high doping concentration at the trench sidewall. This high doping concentration improves both the reverse blocking and forward characteristics of the structure. The ESL-TMBS rectifier has a 7.4% lower forward voltage drop and a 24% higher breakdown voltage. However, this structure has a reverse leakage current that is approximately three times higher than that of a conventional TMBS rectifier owing to the reduction in energy barrier height. This problem is solved when ESL is used partially, since its use provides a reverse leakage current that is comparable to that of a conventional TMBS rectifier. Thus, the forward voltage drop and breakdown voltage improve without any loss in static and dynamic characteristics in the ESL-TMBS rectifier compared with the performance of a conventional TMBS rectifier.

  1. Enhancement of thermal spin transfer torque by double-barrier magnetic tunnel junctions with a nonmagnetic metal spacer

    Science.gov (United States)

    Chen, C. H.; Tseng, P.; Yang, Y. Y.; Hsueh, W. J.

    2017-01-01

    Enhancement of thermal spin transfer torque in a double-barrier magnetic tunnel junction with a nonmagnetic-metal spacer is proposed in this study. The results indicate that, given the same temperature difference, thermal spin transfer torque and charge current density for the proposed double barrier magnetic tunnel junction configuration can be approximately twice as much as that of the traditional single-barrier magnetic tunnel junctions. This enhancement can be attributed to the resonant tunneling mechanism in the double-barrier structure.

  2. Investigation of helicity-dependent photocurrent at room temperature from a Fe/x-AlO x /p-GaAs Schottky junction with oblique surface illumination

    Science.gov (United States)

    Roca, Ronel Christian; Nishizawa, Nozomi; Nishibayashi, Kazuhiro; Munekata, Hiro

    2017-04-01

    In view of a study on spin-polarized photodiodes, the helicity-dependent photocurrent (ΔI) in a Fe/γ-AlO x /p-GaAs Schottky diode is measured at room temperature by illuminating a circularly polarized light beam (λ = 785 nm) either horizontally on the cleaved sidewall or at an oblique angle on the top metal surface. The plane of incidence is fixed to be parallel to the magnetization vector of the in-plane magnetized Fe electrode. The conversion efficiency F, which is a relative value of ΔI with respect to the total photocurrent I ph, is determined to be 1.0 × 10-3 and 1.2 × 10-2 for sidewall illumination and oblique-angle illumination, respectively. Experimental data are compared with the results of a model calculation consisting of drift-diffusion and Julliere spin-dependent tunneling transports, from which two conclusions are obtained: the model accounts fairly well for the experimental data without introducing the annihilation of spin-polarized carriers at the γ-AlO x /p-GaAs interface for the oblique-angle illumination, but the model does not fully explain the relatively low F in terms of the surface recombination at the cleaved sidewall in the case of sidewall illumination. Microscopic damage to the tunneling barrier at the cleaved edge would be one possible cause of the reduced F.

  3. Output voltage calculations in double barrier magnetic tunnel junctions with asymmetric voltage behavior

    KAUST Repository

    Useinov, Arthur

    2011-10-22

    In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR-V curves, output voltages and I-V characteristics for negative and positive values of applied voltages were carried out using MTJs with CoFeB/MgO interfaces as an example. Asymmetry of the experimental TMR-V curves is explained by different values of the minority and majority Fermi wave vectors for the left and right sides of the tunnel barrier, which arises due to different annealing regimes. Electron tunneling in DMTJs was simulated in two ways: (i) Coherent tunneling, where the DMTJ is modeled as one tunnel system and (ii) consecutive tunneling, where the DMTJ is modeled by two single barrier junctions connected in series. © 2012 Elsevier B.V. All rights reserved.

  4. Electrical properties of graphene tunnel junctions with high-κ metal-oxide barriers

    Science.gov (United States)

    Feng, Ying; Trainer, Daniel J.; Chen, Ke

    2017-04-01

    An insulating barrier is one of the key components in electronic devices that makes use of quantum tunneling principles. Many metal-oxides have been used as a good barrier material in a tunnel junction for their large band gap, stable chemical properties and superb properties for forming a thin and pin-hole-free insulating layer. The reduced dimensions of transistors have led to the need for alternative, high dielectric constant (high-κ) oxides to replace conventional silicon-based dielectrics to reduce the leaking current induced by electron tunneling. On the other hand, a tunnel junction with one or both electrodes made of graphene may lead to novel applications due to the massless Dirac fermions from the graphene. Here we have fabricated sandwich-type graphene tunnel junctions with high-κ metal-oxides as barriers, including Al2O3, HfO2, ZrO2, and TiO2. Tunneling properties are investigated by observing the temperature and time dependences of the tunneling spectra. Our results show the potential for applications of high-κ oxides in graphene tunnel junctions and bringing new opportunities for memory and logic electronic devices.

  5. Huge spin-transfer torque in a magnetic tunnel junction by a superlattice barrier

    Science.gov (United States)

    Chen, C. H.; Tseng, P.; Ko, C. W.; Hsueh, W. J.

    2017-09-01

    Huge spin-transfer torque (STT) in a magnetic tunnel junction (MTJ) achieved by superlattice barrier composed of alternate layers of a nonmagnetic metal and an insulator is proposed. The magnitude of the STT depends on the number of cells in the superlattice barrier and the nonmagnetic metal layer's thickness. The result shows that the STT of the novel superlattice-barrier MTJ can reach values up to four orders of magnitude greater than those of traditional single-barrier stacks based on three cells superlattice by designing the nonmagnetic metal layer's thickness. In addition, the spin-transfer torque of the proposed MTJ can also be thousands of magnitude greater than those of traditional double-barrier MTJs.

  6. Direct optical determination of interfacial transport barriers in molecular tunnel junctions.

    Science.gov (United States)

    Fereiro, Jerry A; McCreery, Richard L; Bergren, Adam Johan

    2013-07-03

    Molecular electronics seeks to build circuitry using organic components with at least one dimension in the nanoscale domain. Progress in the field has been inhibited by the difficulty in determining the energy levels of molecules after being perturbed by interactions with the conducting contacts. We measured the photocurrent spectra for large-area aliphatic and aromatic molecular tunnel junctions with partially transparent copper top contacts. Where no molecular absorption takes place, the photocurrent is dominated by internal photoemission, which exhibits energy thresholds corresponding to interfacial transport barriers, enabling their direct measurement in a functioning junction.

  7. 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.

  8. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    Science.gov (United States)

    Zdansky, Karel

    2011-08-01

    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.

  9. Correlation between barrier inhomogeneities of 4H-SiC 1 A/600 V Schottky rectifiers and deep-level defects revealed by DLTS and Laplace DLTS

    Science.gov (United States)

    Gelczuk, Ł.; Kamyczek, P.; Płaczek-Popko, E.; Dąbrowska-Szata, M.

    2014-09-01

    Electrical properties of commercial silicon carbide (SiC) Schottky rectifiers are investigated through the measurement and analysis of the forward current-voltage (I-V) and reverse capacitance-voltage (C-V) characteristics in a large temperature range. Some of devices show distinct discrepancies in specific ranges of their electrical characteristics, especially the excess current dominates at voltage <1 V and temperature <300 K. Standard deep level transient spectroscopy (DLTS) revealed the presence of a single deep-level defect with activation energy of about 0.3 eV, exhibiting the features characteristic for extended defects (e.g. dislocations), such as logarithmic capture kinetics. Furthermore, high-resolution Laplace DLTS showed that this deep level consists actually of three closely spaced levels with activation energies ranging from about 0.26 eV to 0.29 eV. A strong correlation between these two techniques implies that the revealed trap level is due to extended defects surrounded by point traps or clusters of defects. On the basis of obtained specific features of the deep-level defect, it was proposed that this defect is arguably responsible for the observed Schottky barrier inhomogeneities.

  10. Enteropathogenic E. coli: breaking the intestinal tight junction barrier [version 2; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Anand Prakash Singh

    2016-05-01

    Full Text Available Enteropathogenic E. coli (EPEC causes acute intestinal infections in infants in the developing world. Infection typically spreads through contaminated food and water and leads to severe, watery diarrhea. EPEC attaches to the intestinal epithelial cells and directly injects virulence factors which modulate multiple signaling pathways leading to host cell dysfunction. However, the molecular mechanisms that regulate the onset of diarrhea are poorly defined. A major target of EPEC is the host cell tight junction complex which acts as a barrier and regulates the passage of water and solutes through the paracellular space. In this review, we focus on the EPEC effectors that target the epithelial barrier, alter its functions and contribute to leakage through the tight junctions.

  11. Analysis of the effect of sidewall on the performance of 6H-SiC Schottky barrier source/drain NMOSFETs

    Institute of Scientific and Technical Information of China (English)

    Tang Xiao-Yan; Zhang Yi-Men; Zhang Yu-Ming; Gao Jin-Xia

    2004-01-01

    Between source/drain and gate of SiC Schottky barrier source/drain MOSFET (SiC SBSD-MOSFET), there must be a sidewall as isolation. The width of sidewall strongly affects on the device performance. In this paper the effect of sidewall on the performance of 6H-SiC SBSD-NMOSFET is simulated with the 2D simulator MEDICI. The simulated results show that a sidewall with width less than 0.1μm slightly affects the device performance. However, when the width of sidewall exceeds 0.1μm, the conduction does not occur until the drain voltage is high enough and saturation current sharply decreases. The effect of the sidewall on device performance can be reduced by decreasing the doping concentration in the epitaxial layer.

  12. External quantum efficiency-enhanced PtSi Schottky-barrier detector utilizing plasmonic ZnO:Al nanoparticles and subwavelength gratings

    Institute of Scientific and Technical Information of China (English)

    Bingxin Kang; Yi Cai; Lingxue Wang

    2016-01-01

    A infrared light trapping structure combining front subwavelength gratings and rear ZnO:Al nanoparticles for a PtSi Schottky-barrier detector over a 3-5 μm waveband is theoretically investigated.By selecting the proper plasmonic material and optimizing the parameters for the proposed structure,the absorption of the PtSi layer is dramatically improved.The theoretical results show that this improvement eventually translates into an equivalent external quantum efficiency (EQE) enhancement of 2.46 times at 3-3.6 μm and 2.38 times at 3.6-5 μm compared to conventional structures.This improvement in the EQE mainly lies in the increase of light path lengths within the PtSi layer by the subwavelength grating diffraction and nanoparticle-scattering effects.

  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

    2015-12-17

    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.

  14. High Performance P-Channel Schottky Barrier MOSFETs with Self-Aligned PtSi Source/Drain on Thin Film SOI Substrate

    Institute of Scientific and Technical Information of China (English)

    ZHU Shi-Yang; LI Ming-Fu

    2005-01-01

    @@ P-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) with PtSi Schottky barrier source/drain, high-k gate dielectric and metal gate electrode were fabricated on a thin p-type silicon-on-insulator (SOI) substrateusing a simplified low temperature process. The device works on a fully-depleted accumulation-mode and hasan excellent electrical performance. It reaches Ion/Ioff ratio of about 107, subthreshold swing of 65mV/decade and saturation drain current of Ids= 8.8μA/μm at |Vg - Vth| = |Vd| = 1 V for devices with the channel length 4.0μm and the equivalent oxide thickness 2.0nm. Compared to the corresponding bulk-Si counterparts, SOI p-SBMOSFETs have smaller off-state current due to reduction of the PtSi/Si contact area.

  15. Capacitance-voltage profile characteristics of Schottky barrier structure with InAs quantum dots grown on InAlAs/InP(001)

    Energy Technology Data Exchange (ETDEWEB)

    Baira, M. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Departement de Physique, Faculte des Sciences, 5019 Monastir (Tunisia); Ajjel, R. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Departement de Physique, Faculte des Sciences, 5019 Monastir (Tunisia)]. E-mail: ridha.ajjel@fsm.rnu.tn; Maaref, H. [Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Departement de Physique, Faculte des Sciences, 5019 Monastir (Tunisia); Salem, B. [Laboratoire de Physique de la Matiere-LPM (UMR-CNRS 5511), INSA de Lyon, Batiment Blaise Pascal, 7 Avenue J. Capelle, 69621 Villeurbanne (France); Bremond, G. [Laboratoire de Physique de la Matiere-LPM (UMR-CNRS 5511), INSA de Lyon, Batiment Blaise Pascal, 7 Avenue J. Capelle, 69621 Villeurbanne (France); Gendry, M. [Laboratoire d' Electronique, Optoelectronique et Microsystemes-LEOM (UMR-CNRS 5512), Ecole Centrale de Lyon, 36 Avenue G. de Collongue, 69134 Ecully (France); Marty, O. [Laboratoire d' Electronique-LENAC, Universite Lyon 1, F-69622 Villeurbanne, Lyon (France)

    2006-03-15

    Capacitance-voltage, C(V) studies have been carried out on Schottky barrier structure containing a sheet of self-organized InAs quantum dots (QDs) grown on InAlAs lattice matched to InP in order to deduce the electrical properties of the QDs. Three electron levels have been detected in n-type material, and were attributed to the s ground, the p excited, and the d excited states. Some parameters of the structure, such as the position of the InAs QD plane, the electron concentration in the QDs and an approximate QD height were deduced from the C(V) profile analysis. These results are in good agreement with the transmission electron microscopy (TEM) study realized on the structure.

  16. Electron Holography of Barrier Structures in Co/ZrAlOx/Co Magnetic Tunnel Junctions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhe; ZHU Tao; SHEN Feng; SHENG Wen-Ting; WANG Wei-Gang; XIAO John Q; ZHANG Ze

    2005-01-01

    @@ We investigate the potential profiles and elemental distribution of barriers in Co/ZrAlOx/Co magnetic tunnel junctions (MTJs) using electron holography (EH) and scanning transmission electron microscopy. The MTJ barriers are introduced by oxidizing a bilayer consisting with a uniform 0.45-nm Al layer and a wedge-shaped Zr layer (0-2 nm). From the scanning transmission electron microscopy, AlOx and ZrOx layers are mixed together,indicating that compact AlOx layer cannot be formed in such a bilayer structure of barriers. The EH results reveal that there are no sharp interfaces between the barrier and magnetic electrodes, which may be responsible for a smaller tunnelling magnetoresistance compared with the MTJs of Co/AlOx/Co.

  17. 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.

  18. Electronic structure and Schottky-barrier formation on GaAs (100) surfaces prepared by thermal desorption of a protective arsenic coating

    Energy Technology Data Exchange (ETDEWEB)

    Spindt, C.J.; Yamada, M.; Meissner, P.L.; Miyano, K.E.; Kendelewicz, T.; Herrera-Gomez, A.; Spicer, W.E. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94305-4055 (United States)); Arko, A.J. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

    1992-05-15

    Soft-x-ray photoemission spectroscopy has been used to characterize GaAs(100) surfaces and interfaces grown by molecular-beam epitaxy and prepared by the thermal desorption of a protective As coating. The samples studied were grown and arsenic capped identically to those used in a previous study (Brillson {ital et} {ital al}., J. Vac. Sci. Technol. B 6, 1263 (1988)). In this previous work, unpinned'' Schottky-barrier formation was reported, with barrier heights over a wide (0.75-eV) range. This is a striking result, as it was previously believed that all metals will pin GaAs surfaces in a narrow energy range near the middle of the band gap. This large range of barrier heights later led to the suggestion that the (100) surface could become an insulating layer that could screen out the effects of metal-induced gap states. Motivated by this work, we have studied Al and Au Schottky barriers since the deposition of these two metals gave the extreme low and high barriers in the 0.75-eV range. We have also characterized the clean surfaces prepared by desorbing the As caps at different temperatures. The As 3{ital d} and Ga 3{ital d} core levels showed that the surface stoichiometry could be varied significantly with the desorption temperature. The As 3{ital d} line shape was found to be the best indication of the surface stoichiometry after the anneal. The valence-band spectra did not show any strong features which could be used to determine when the sample was completely decapped. The electronic structure of the surface layer was investigated experimentally, and no evidence of an insulating reconstruction was found. In our study of band bending, we found that the low-doped samples used here and in the earlier study showed significant photovoltages resulting in incorrect band-bending measurements. We also found that the Au measurements are made difficult by the presence of core-level shifts due to Au-Ga alloying.

  19. Tight junction disruption: Helicobacter pylori and dysregulation of the gastric mucosal barrier.

    Science.gov (United States)

    Caron, Tyler J; Scott, Kathleen E; Fox, James G; Hagen, Susan J

    2015-10-28

    Long-term chronic infection with Helicobacter pylori (H. pylori) is a risk factor for gastric cancer development. In the multi-step process that leads to gastric cancer, tight junction dysfunction is thought to occur and serve as a risk factor by permitting the permeation of luminal contents across an otherwise tight mucosa. Mechanisms that regulate tight junction function and structure in the normal stomach, or dysfunction in the infected stomach, however, are largely unknown. Although conventional tight junction components are expressed in gastric epithelial cells, claudins regulate paracellular permeability and are likely the target of inflammation or H. pylori itself. There are 27 different claudin molecules, each with unique properties that render the mucosa an intact barrier that is permselective in a way that is consistent with cell physiology. Understanding the architecture of tight junctions in the normal stomach and then changes that occur during infection is important but challenging, because most of the reports that catalog claudin expression in gastric cancer pathogenesis are contradictory. Furthermore, the role of H. pylori virulence factors, such as cytotoxin-associated gene A and vacoulating cytotoxin, in regulating tight junction dysfunction during infection is inconsistent in different gastric cell lines and in vivo, likely because non-gastric epithelial cell cultures were initially used to unravel the details of their effects on the stomach. Hampering further study, as well, is the relative lack of cultured cell models that have tight junction claudins that are consistent with native tissues. This summary will review the current state of knowledge about gastric tight junctions, normally and in H. pylori infection, and make predictions about the consequences of claudin reorganization during H. pylori infection.

  20. Correlation between amplitude of spin accumulation signals investigated by Hanle effect measurement and effective junction barrier height in CoFe/MgO/n+-Si junctions

    Science.gov (United States)

    Saito, Y.; Ishikawa, M.; Sugiyama, H.; Inokuchi, T.; Hamaya, K.; Tezuka, N.

    2015-05-01

    Correlation between the amplitude of the spin accumulation signals and the effective barrier height estimated from the slope of the log (RA) - tMgO plot (RA: resistance area product, tMgO: thickness of MgO tunnel barrier) in CoFe/MgO/n+-Si junctions was investigated. The amplitude of spin accumulation signals increases with increasing effective barrier heights. This increase of the amplitude of spin accumulation is originated from the increase of the spin polarization ( P S i ) in Si. The estimated absolute values of P S i using three-terminal Hanle signals are consistent with those estimated by four-terminal nonlocal-magnetoresistance (MR) and two-terminal local-MR. To demonstrate large spin accumulation in Si bulk band and enhance the local-MR through Si channel, these results indicate that the increase of the effective barrier height at ferromagnet/(tunnel barrier)/n+-Si junction electrode is important.

  1. Complementary Barrier Infrared Detector (CBIRD) with Double Tunnel Junction Contact and Quantum Dot Barrier Infrared Detector (QD-BIRD)

    Science.gov (United States)

    Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.; Gunapala, Sarath D.

    2012-01-01

    The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.

  2. Complementary Barrier Infrared Detector (CBIRD) with Double Tunnel Junction Contact and Quantum Dot Barrier Infrared Detector (QD-BIRD)

    Science.gov (United States)

    Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.; hide

    2012-01-01

    The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.

  3. Plasma Separation Process: Betacell (BCELL) code: User's manual. [Bipolar barrier junction

    Energy Technology Data Exchange (ETDEWEB)

    Taherzadeh, M.

    1987-11-13

    The emergence of clearly defined applications for (small or large) amounts of long-life and reliable power sources has given the design and production of betavoltaic systems a new life. Moreover, because of the availability of the plasma separation program, (PSP) at TRW, it is now possible to separate the most desirable radioisotopes for betacell power generating devices. A computer code, named BCELL, has been developed to model the betavoltaic concept by utilizing the available up-to-date source/cell parameters. In this program, attempts have been made to determine the betacell energy device maximum efficiency, degradation due to the emitting source radiation and source/cell lifetime power reduction processes. Additionally, comparison is made between the Schottky and PN junction devices for betacell battery design purposes. Certain computer code runs have been made to determine the JV distribution function and the upper limit of the betacell generated power for specified energy sources. A Ni beta emitting radioisotope was used for the energy source and certain semiconductors were used for the converter subsystem of the betacell system. Some results for a Promethium source are also given here for comparison. 16 refs.

  4. HfO2 and SiO2 as barriers in magnetic tunneling junctions

    Science.gov (United States)

    Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

    2017-05-01

    SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

  5. Inflammation and the Intestinal Barrier: Leukocyte–Epithelial Cell Interactions, Cell Junction Remodeling, and Mucosal Repair

    Science.gov (United States)

    Luissint, Anny-Claude; Parkos, Charles A.; Nusrat, Asma

    2017-01-01

    The intestinal tract is lined by a single layer of columnar epithelial cells that forms a dynamic, permeable barrier allowing for selective absorption of nutrients, while restricting access to pathogens and food-borne antigens. Precise regulation of epithelial barrier function is therefore required for maintaining mucosal homeostasis and depends, in part, on barrier-forming elements within the epithelium and a balance between pro- and anti-inflammatory factors in the mucosa. Pathologic states, such as inflammatory bowel disease, are associated with a leaky epithelial barrier, resulting in excessive exposure to microbial antigens, recruitment of leukocytes, release of soluble mediators, and ultimately mucosal damage. An inflammatory microenvironment affects epithelial barrier properties and mucosal homeostasis by altering the structure and function of epithelial intercellular junctions through direct and indirect mechanisms. We review our current understanding of complex interactions between the intestinal epithelium and immune cells, with a focus on pathologic mucosal inflammation and mechanisms of epithelial repair. We discuss leukocyte–epithelial interactions, as well as inflammatory mediators that affect the epithelial barrier and mucosal repair. Increased knowledge of communication networks between the epithelium and immune system will lead to tissue-specific strategies for treating pathologic intestinal inflammation. PMID:27436072

  6. Sodium caprate transiently opens claudin-5-containing barriers at tight junctions of epithelial and endothelial cells

    DEFF Research Database (Denmark)

    Del Vecchio, Giovanna; Tscheik, Christian; Tenz, Kareen

    2012-01-01

    Claudin-5 is a tight junction (TJ) protein which limits the diffusion of small hydrophilic molecules. Thus, it represents a potential pharmacological target to improve drug delivery to the tissues protected by claudin-5-dependent barriers. Sodium caprate is known as an absorption enhancer which...... opens the paracellular space acting on TJ proteins and actin cytoskeleton. Its action on claudin-5 is not understood so far. Epithelial and endothelial systems were used to evaluate the effect of caprate on claudin-5 in TJ-free cells and on claudin-5 fully integrated in TJ. To this aim, confocal...... of endothelial and epithelial cells. In conclusion, the study further elucidates the cellular effects of caprate at the tight junctions....

  7. Tunnel magnetoresistance in magnetic tunnel junctions with ZnS barrier

    Energy Technology Data Exchange (ETDEWEB)

    Guth, M.; Da Costa, V.; Schmerber, G.; Dinia, A.; van den Berg, H. A. M.

    2001-06-01

    A first experimental evidence of a significant tunneling magnetoresistance signal of about 5% at 300 K for a magnetic tunnel junction consisting of hard and soft magnetic layers separated by a 2 nm ZnS semiconducting barrier is reported. The samples have been grown by sputtering on Si(111) substrate at room temperature and have the following structure: Fe{sub 6nm}Cu{sub 30nm}CoFe{sub 1.8nm}Ru{sub 0.8nm}CoFe{sub 3nm}ZnS{sub x}CoFe{sub 1nm}Fe{sub 4nm}Cu{sub 10nm}Ru{sub 3nm}. The hard magnetic bottom electrode consists of the artificial antiferromagnetic structure in which the rigidity is ensured by the antiferromagnetic exchange coupling between two FeCo layers through a Ru spacer layer. Barrier impedance scanning microscope (BISM) measurements reveal a good homogeneity of the barrier thickness. Electric transport measurements over square tunnel elements with lateral sizes between 3 and 100 {mu}m, exhibit a typical tunnel current{endash}voltage variations and tunnel resistance of 2{endash}3 k{Omega}{mu}m2 with small variations which never exceed a factor of 2, which is in good agreement with the BISM results. This good reproducibility of the junctions is very promising for MRAMs and transistors applications. {copyright} 2001 American Institute of Physics.

  8. Electron Density and Capacitance at the interface of Au-ZnO Based Schottky Diode

    Science.gov (United States)

    Wu, Chin-Sheng

    ZnO with wide direct band gap (3.37 eV) is a well-known and an interesting compound semiconducting material, which have been used for the fabrication of optical, electrical, and piezoelectric devices such as light emitting diodes, solar cells. Schottky diodes are associated with quicker switching and lower turn on voltages compared to p-n junction diodes. J-V characteristics exhibit nonlinear rectifying behavior with threshold voltage of 2.1 V. The barrier heights were found to be 0.61 eV. The measured capacitance for the Schottky junction depends on the reverse bias potential and frequency. At the lower frequencies the capacitance has the higher values due to the trapping occurred at the interface through the surface roughness and lattice mismatch. We perform model potential calculation with quantum well around the interface. Model potentials allow some degree of freedom in the design of the emitted wavelength through adjustment of the energy levels. We apply the various well width w and barrier height V in order to match the device information made by Willander. Solving the Schrödinger equation with exchange- correlation energy and effective mass of electrons will produce values of the energy levels and states. The variational barrier heights result in the change of the electron density This accounts for the excessive capacitance at the interface of Schottky diode.

  9. AlOx barrier growth in magnetic tunnel junctions for sensor applications

    Science.gov (United States)

    Knudde, S.; Farinha, G.; Leitao, D. C.; Ferreira, R.; Cardoso, S.; Freitas, P. P.

    2016-08-01

    Magnetic tunnel junction (MTJ) research has been focused on MgO-based crystalline structures due to high tunnel magnetoresistance (TMR), despite requiring a more severe process control than previous generations of MTJ stacks based on amorphous barriers (e.g. AlOx). In this work, we study the electrical transport properties in AlOx barriers in MTJ sensors fabricated using Ion beam sputtering and remote plasma oxidation. Amorphous barriers were prepared from oxidation of thin Al films, deposited in single step barrier (SSB-Al 1 nm/oxidation) or double step barrier (DSB-Al 0.5 nm/oxidation/Al 0.5 nm/oxidation) structures. We show tunable resistance-area products (RxA) ranging from ≈ 10 Ω μ m2 (suited for nano devices) up to ≈ 100 k Ω μ m2 (suited for large area sensors) with TMR above 30%. For all geometries studied, the structures have a coercivity free linear response and require none or one annealing step. This makes them very competitive for all industrial applications where the TMR level is not the dominant specification to meet.

  10. Claudin-1 induced sealing of blood–brain barrier tight junctions ameliorates chronic experimental autoimmune encephalomyelitis

    OpenAIRE

    Pfeiffer, Friederike; Schäfer, Julia; Lyck, Ruth; Makrides, Victoria; Brunner, Sarah; Schaeren-Wiemers, Nicole; Deutsch, Urban; ENGELHARDT, Britta

    2011-01-01

    In experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis (MS), loss of the blood–brain barrier (BBB) tight junction (TJ) protein claudin-3 correlates with immune cell infiltration into the CNS and BBB leakiness. Here we show that sealing BBB TJs by ectopic tetracycline-regulated expression of the TJ protein claudin-1 in Tie-2 tTA//TRE-claudin-1 double transgenic C57BL/6 mice had no influence on immune cell trafficking across the BBB during EAE and furthermore...

  11. Non-UV Photoelectric Properties of the Ni/n-Si/N+-SiC Isotype Heterostructure Schottky Barrier Photodiode

    Science.gov (United States)

    Li, Lian-Bi; Chen, Zhi-Ming; Ren, Zhan-Qiang; Gao, Zhan-Jun

    2013-09-01

    The energy-band structure and non-ultraviolet photoelectric properties of a Ni/n-Si/N+-SiC isotype heterostructure Schottky photodiode are simulated by using Silvaco-Atlas. There are energy offsets in the conduction and valance band of the heterojunction, which are about 0.09 eV and 1.79 eV, respectively. The non-UV photodiode with this structure is fabricated on a 6H-SiC(0001) substrate. J—V measurements indicate that the device has good rectifying behavior with a rectification ratio up to 200 at 5 V, and the turn-on voltage is about 0.7 V. Under non-ultraviolet illumination of 0.6 W/cm2, the device demonstrates a significant photoelectric response with a photocurrent density of 2.9 mA/cm2 and an open-circuit voltage of 63.0 mV. Non-ultraviolet operation of the SiC-based photoelectric device is initially realized.

  12. Properties of Schottky Barrier Diodes on (In(x)Ga(1-x))₂O₃ for 0.01 ≤ x ≤ 0.85 Determined by a Combinatorial Approach.

    Science.gov (United States)

    von Wenckstern, H; Splith, D; Werner, A; Müller, S; Lorenz, M; Grundmann, M

    2015-12-14

    We investigated properties of an (In(x)Ga(1-x))2O3 thin film with laterally varying cation composition that was realized by a large-area offset pulsed laser deposition approach. Within a two inch diameter thin film, the composition varies between 0.01 ≤ x ≤ 0.85, and three crystallographic phases (cubic, hexagonal, and monoclinic) were identified. We observed a correlation between characteristic parameters of Schottky barrier diodes fabricated on the thin film and its chemical and structural material properties. The highest Schottky barriers and rectification of the diodes were found for low indium contents. The thermal stability of the diodes is also best for Ga-rich parts of the sample. Conversely, the series resistance is lowest for large In content. Overall, the (In(x)Ga(1-x))2O3 alloy is well-suited for potential applications such as solar-blind photodetectors with a tunable absorption edge.

  13. Effect of Stacking Faults in Triangular Defects on 4H-SiC Junction Barrier Schottky Diodes

    Science.gov (United States)

    Konishi, Kazuya; Nakata, Shuhei; Nakaki, Yoshiyuki; Nakao, Yukiyasu; Nagae, Akemi; Tanaka, Takanori; Nakamura, Yu; Toyoda, Yoshihiko; Sumitani, Hiroaki; Oomori, Tatsuo

    2013-04-01

    The relationship between stacking faults and the position of the leakage current inside a triangular defect was analyzed. Triangular defects are categorized into two types on the basis of the current-voltage (I-V) characteristics. It was found that stacking faults (SFs) of the 3C structure inside a triangular defect increase leakage current at a reverse bias voltage as well as forward current at a low bias voltage, while SFs of the SF(4,2) structure inside a triangular defect do not lead to deterioration of device performance in this case.

  14. Interfacial electronic transport phenomena in single crystalline Fe-MgO-Fe thin barrier junctions

    Energy Technology Data Exchange (ETDEWEB)

    Gangineni, R. B., E-mail: rameshg.phy@pondiuni.edu.in [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R. V. Nagar, Kalapet, Pondicherry 605 014 (India); SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Bellouard, C., E-mail: christine.bellouard@ijl.nancy-universite.fr; Duluard, A. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Negulescu, B. [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); UFR de Sciences et Techniques, Matériaux, microélectronique, acoustique, nanotechnologies (GREMAN), University François Rabelais, Parc de Grandmont, 37200 Tours (France); Baraduc, C.; Gaudin, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF-Grenoble 1/Grenoble INP, INAC, 17 rue des Martyrs, F-38054 Grenoble Cedex (France); Tiusan, C., E-mail: coriolan.tiusan@phys.utcluj.ro [Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP 239, 54506 Vandoeuvre (France); Department of Physics and Chemistry, Center of Superconductivity, Spintronics and Surface Science, Technical University of Cluj Napoca, Str. Memorandumului No. 28, RO-400114 Cluj-Napoca (Romania)

    2014-05-05

    Spin filtering effects in nano-pillars of Fe-MgO-Fe single crystalline magnetic tunnel junctions are explored with two different sample architectures and thin MgO barriers (thickness: 3–8 monolayers). The two architectures, with different growth and annealing conditions of the bottom electrode, allow tuning the quality of the bottom Fe/MgO interface. As a result, an interfacial resonance states (IRS) is observed or not depending on this interface quality. The IRS contribution, observed by spin polarized tunnel spectroscopy, is analyzed as a function of the MgO barrier thickness. Our experimental findings agree with theoretical predictions concerning the symmetry of the low energy (0.2 eV) interfacial resonance states: a mixture of Δ{sub 1}-like and Δ{sub 5}-like symmetries.

  15. The Ly6 protein coiled is required for septate junction and blood brain barrier organisation in Drosophila.

    Directory of Open Access Journals (Sweden)

    Assia Hijazi

    Full Text Available BACKGROUND: Genetic analysis of the Drosophila septate junctions has greatly contributed to our understanding of the mechanisms controlling the assembly of these adhesion structures, which bear strong similarities with the vertebrate tight junctions and the paranodal septate junctions. These adhesion complexes share conserved molecular components and have a common function: the formation of paracellular barriers restraining the diffusion of solutes through epithelial and glial envelopes. METHODOLOGY/PRINCIPAL FINDINGS: In this work we characterise the function of the Drosophila cold gene, that codes for a protein belonging to the Ly6 superfamily of extracellular ligands. Analysis of cold mutants shows that this gene is specifically required for the organisation of the septate junctions in epithelial tissues and in the nervous system, where its contribution is essential for the maintenance of the blood-brain barrier. We show that cold acts in a cell autonomous way, and we present evidence indicating that this protein could act as a septate junction component. CONCLUSION/SIGNIFICANCE: We discuss the specific roles of cold and three other Drosophila members of the Ly6 superfamily that have been shown to participate in a non-redundant way in the process of septate junction assembly. We propose that vertebrate Ly6 proteins could fulfill analogous roles in tight junctions and/or paranodal septate junctions.

  16. Study on electrical properties of Al/Cu(In,Ga)Se{sub 2} Schottky junction and ZnO/CdS/Cu(In,Ga)Se{sub 2} heterojunction using admittance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sakurai, T.; Ishida, N.; Paul, G.K.; Akimoto, K. [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Ishizuka, S.; Matsubara, K.; Sakurai, K.; Yamada, A.; Niki, S. [National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2006-09-15

    The electrical properties of Al/Cu(In,Ga)Se{sub 2}(Al/CIGSe) Schottky junction and ZnO/CdS/CIGSe heterojunction were studied by admittance spectroscopy. Three distinct peaks (peaks {alpha}, {zeta}, and {epsilon}) were detected from all the CIGSe samples. The activation energies for the traps corresponding to peaks {alpha} and {zeta} were estimated to be approximately 10 meV and 300 meV, respectively. The peak {alpha} may be due to the shallow acceptor, and peaks {zeta} and {epsilon} may be due to defects in the CIGSe layer. The characteristics of the peak {zeta} have close correlation with the surface potential of the CIGSe layer. Therefore, the peak {zeta} may be caused by traps such as grain boundary defects near the surface of the CIGSe layer. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Study on electrical properties of Al/Cu(In,Ga)Se2 Schottky junction and ZnO/CdS/Cu(In,Ga)Se2 heterojunction using admittance spectroscopy

    Science.gov (United States)

    Sakurai, T.; Ishida, N.; Ishizuka, S.; Matsubara, K.; Sakurai, K.; Yamada, A.; Paul, G. K.; Akimoto, K.; Niki, S.

    2006-09-01

    The electrical properties of Al/Cu(In,Ga)Se2 (Al/CIGSe) Schottky junction and ZnO/CdS/CIGSe heterojunction were studied by admittance spectroscopy. Three distinct peaks (peaks , , and ) were detected from all the CIGSe samples. The activation energies for the traps corresponding to peaks and were estimated to be approximately 10 meV and 300 meV, respectively. The peak may be due to the shallow acceptor, and peaks and may be due to defects in the CIGSe layer. The characteristics of the peak have close correlation with the surface potential of the CIGSe layer. Therefore, the peak may be caused by traps such as grain boundary defects near the surface of the CIGSe layer.

  18. Spin Injection, Transport, and Detection at Room Temperature in a Lateral Spin Transport Device with Co2FeAl0.5Si0.5/n-GaAs Schottky Tunnel Junctions

    Science.gov (United States)

    Saito, Tatsuya; Tezuka, Nobuki; Matsuura, Masashi; Sugimoto, Satoshi

    2013-10-01

    We observed spin-valve signals and Hanle signals in four-terminal nonlocal measurements on a lateral spin transport device with Co2FeAl0.5Si0.5(CFAS)/n-GaAs Schottky tunnel junctions. The estimated spin injection/detection efficiency was 0.06 at 4.2 K, which is larger than those of the devices with Fe and CoFe electrodes [Nature Physics 3 (2007) 197 and Appl. Phys. Lett. 99 (2011) 082108]. The spin diffusion length estimated from Hanle signals was consistent with the gap length dependency of the spin-valve signals. Furthermore, the spin-valve signals were observed at up to 290 K. This is the first demonstration of detecting spin accumulation in semiconductor with full-Heusler alloys electrodes at room temperature.

  19. 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.

  20. 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.

  1. Tight junction modulation of the blood brain barrier: CNS delivery of small molecules.

    Science.gov (United States)

    Greene, Chris; Campbell, Matthew

    2016-01-01

    The blood brain barrier (BBB) represents a major obstacle for targeted drug delivery to the brain for the treatment of central nervous system (CNS) disorders. Significant advances in barrier research over the past decade has led to the discovery of an increasing number of structural and regulatory proteins in tight junctions (TJ) and adherens junctions (AJ). These discoveries are providing the framework for the development of novel TJ modulators which can act specifically and temporarily to alter BBB function and regulate paracellular uptake of molecules. TJ modulators that have shown therapeutic potential in preclinical models include claudin-5 and occludin siRNAs, peptides derived from zonula occludens toxin as well as synthetic peptides targeting the extracellular loops of TJs. Adding to the array of modulating agents are novel mechanisms of BBB regulation such as focused ultrasound (FUS). This review will give a succinct overview of BBB biology and TJ modulation in general. Novel insights into BBB regulation in health and disease will also be summarized.

  2. High Performance MgO-barrier Magnetic Tunnel Junctions for Flexible and Wearable Spintronic Applications.

    Science.gov (United States)

    Chen, Jun-Yang; Lau, Yong-Chang; Coey, J M D; Li, Mo; Wang, Jian-Ping

    2017-02-02

    The magnetic tunnel junction (MTJ) using MgO barrier is one of most important building blocks for spintronic devices and has been widely utilized as miniaturized magentic sensors. It could play an important role in wearable medical devices if they can be fabricated on flexible substrates. The required stringent fabrication processes to obtain high quality MgO-barrier MTJs, however, limit its integration with flexible electronics devices. In this work, we have developed a method to fabricate high-performance MgO-barrier MTJs directly onto ultrathin flexible silicon membrane with a thickness of 14 μm and then transfer-and-bond to plastic substrates. Remarkably, such flexible MTJs are fully functional, exhibiting a TMR ratio as high as 190% under bending radii as small as 5 mm. The devices' robustness is manifested by its retained excellent performance and unaltered TMR ratio after over 1000 bending cycles. The demonstrated flexible MgO-barrier MTJs opens the door to integrating high-performance spintronic devices in flexible and wearable electronics devices for a plethora of biomedical sensing applications.

  3. High Performance MgO-barrier Magnetic Tunnel Junctions for Flexible and Wearable Spintronic Applications

    Science.gov (United States)

    Chen, Jun-Yang; Lau, Yong-Chang; Coey, J. M. D.; Li, Mo; Wang, Jian-Ping

    2017-02-01

    The magnetic tunnel junction (MTJ) using MgO barrier is one of most important building blocks for spintronic devices and has been widely utilized as miniaturized magentic sensors. It could play an important role in wearable medical devices if they can be fabricated on flexible substrates. The required stringent fabrication processes to obtain high quality MgO-barrier MTJs, however, limit its integration with flexible electronics devices. In this work, we have developed a method to fabricate high-performance MgO-barrier MTJs directly onto ultrathin flexible silicon membrane with a thickness of 14 μm and then transfer-and-bond to plastic substrates. Remarkably, such flexible MTJs are fully functional, exhibiting a TMR ratio as high as 190% under bending radii as small as 5 mm. The devices‘ robustness is manifested by its retained excellent performance and unaltered TMR ratio after over 1000 bending cycles. The demonstrated flexible MgO-barrier MTJs opens the door to integrating high-performance spintronic devices in flexible and wearable electronics devices for a plethora of biomedical sensing applications.

  4. High Performance MgO-barrier Magnetic Tunnel Junctions for Flexible and Wearable Spintronic Applications

    Science.gov (United States)

    Chen, Jun-Yang; Lau, Yong-Chang; Coey, J. M. D.; Li, Mo; Wang, Jian-Ping

    2017-01-01

    The magnetic tunnel junction (MTJ) using MgO barrier is one of most important building blocks for spintronic devices and has been widely utilized as miniaturized magentic sensors. It could play an important role in wearable medical devices if they can be fabricated on flexible substrates. The required stringent fabrication processes to obtain high quality MgO-barrier MTJs, however, limit its integration with flexible electronics devices. In this work, we have developed a method to fabricate high-performance MgO-barrier MTJs directly onto ultrathin flexible silicon membrane with a thickness of 14 μm and then transfer-and-bond to plastic substrates. Remarkably, such flexible MTJs are fully functional, exhibiting a TMR ratio as high as 190% under bending radii as small as 5 mm. The devices‘ robustness is manifested by its retained excellent performance and unaltered TMR ratio after over 1000 bending cycles. The demonstrated flexible MgO-barrier MTJs opens the door to integrating high-performance spintronic devices in flexible and wearable electronics devices for a plethora of biomedical sensing applications. PMID:28150807

  5. Study of the interface properties of CuInSe2 single-crystal heterojunctions and Schottky barriers

    Science.gov (United States)

    Abou-Elfotouh, F.; Matson, R. J.; Bakry, A. M.; Kazmerski, L. L.

    High resolution photoluminescence measurements performed at different excitation powers and different temperatures (7.8-90 K) are used to identify the origin and location of the various defect levels in single-crystal CuInSe2. Extrinsic radiative recombination surface states resulting from surface and heat treatments during the device fabrication steps have been determined. The correlation between the type and relative concentration of the intrinsic defect states dominating a particular surface of the material and the junction characteristic of the devices fabricated on that surface are noted.

  6. Study of the interface properties of CuInSe sub 2 single-crystal heterojunctions and Schottky barriers

    Energy Technology Data Exchange (ETDEWEB)

    Abou-Elfotouh, F.; Matson, R.J.; Bakry, A.M.; Kazmerski, L.L. (Solar Energy Research Inst., Golden, CO (USA))

    1990-12-15

    High resolution photoluminescence measurements performed at different excitation powers and different temperatures (7.8-90K) are used to identify the origin and location of the various defect levels in single-crystal CuInSe{sub 2}. Extrinsic radiative recombination surface states resulting from surface and heat treatments during the device fabrication steps have been determined. The correlation between the type and relative concentration of the intrinsic defect states dominating a particular surface of the material and the junction characteristic of the devices fabricated on that surface are noted. (orig.).

  7. 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.

  8. 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...

  9. Atomic structure and oxygen deficiency of the ultrathin aluminium oxide barrier in Al/AlOx/Al Josephson junctions

    Science.gov (United States)

    Zeng, Lunjie; Tran, Dung Trung; Tai, Cheuk-Wai; Svensson, Gunnar; Olsson, Eva

    2016-07-01

    Al/AlOx/Al Josephson junctions are the building blocks of a wide range of superconducting quantum devices that are key elements for quantum computers, extremely sensitive magnetometers and radiation detectors. The properties of the junctions and the superconducting quantum devices are determined by the atomic structure of the tunnel barrier. The nanoscale dimension and disordered nature of the barrier oxide have been challenges for the direct experimental investigation of the atomic structure of the tunnel barrier. Here we show that the miniaturized dimension of the barrier and the interfacial interaction between crystalline Al and amorphous AlOx give rise to oxygen deficiency at the metal/oxide interfaces. In the interior of the barrier, the oxide resembles the atomic structure of bulk aluminium oxide. Atomic defects such as oxygen vacancies at the interfaces can be the origin of the two-level systems and contribute to decoherence and noise in superconducting quantum circuits.

  10. Atomic structure and oxygen deficiency of the ultrathin aluminium oxide barrier in Al/AlOx/Al Josephson junctions.

    Science.gov (United States)

    Zeng, Lunjie; Tran, Dung Trung; Tai, Cheuk-Wai; Svensson, Gunnar; Olsson, Eva

    2016-07-12

    Al/AlOx/Al Josephson junctions are the building blocks of a wide range of superconducting quantum devices that are key elements for quantum computers, extremely sensitive magnetometers and radiation detectors. The properties of the junctions and the superconducting quantum devices are determined by the atomic structure of the tunnel barrier. The nanoscale dimension and disordered nature of the barrier oxide have been challenges for the direct experimental investigation of the atomic structure of the tunnel barrier. Here we show that the miniaturized dimension of the barrier and the interfacial interaction between crystalline Al and amorphous AlOx give rise to oxygen deficiency at the metal/oxide interfaces. In the interior of the barrier, the oxide resembles the atomic structure of bulk aluminium oxide. Atomic defects such as oxygen vacancies at the interfaces can be the origin of the two-level systems and contribute to decoherence and noise in superconducting quantum circuits.

  11. Enhanced photo-response properties of a single ZnO microwire photodetector by coupling effect between localized Schottky barriers and piezoelectric potential.

    Science.gov (United States)

    Li, Haixia; Zhang, Xianghui; Liu, Nishuang; Ding, Longwei; Tao, Jiayou; Wang, Siliang; Su, Jun; Li, Luying; Gao, Yihua

    2015-08-10

    The coupling effect between localized Schottky barriers (SBs) and piezoelectric potential that impact the photo-response properties of a single ZnO microwire (MW) photodetector (PD) is studied. Localized SBs is introduced by Au NPs decoration. The negatively charged Au NPs deplete more carriers near the ZnO surface, which raises the SB height and sharply reduces the recover time of the PD from 142.4 s to 0.7 s. Moreover, after applying the compressive strain, the band structure of ZnO MW changes and piezoelectric potential generates, which further raises the SB height, thickens the depletion region and improves photo-response properties of the detector. The dark current is reduced by about 5 orders and its on/off current ratio increased by about 6 orders, which decreases the power consumption of the detector significantly. Under the above coupling effect between piezoelectric potential and localized SBs, the recover time of the detector is further reduced to 0.1 s ultimately. This work suggests that rational integration of localized SBs and piezoelectric potential is a viable approach to get ZnO MW PDs with high on/off ratio, ultrafast response speed and low power consumption.

  12. The effect of Al segregation on Schottky barrier height and effective work function in TiAl/TiN/HfO2 gate stacks

    Science.gov (United States)

    Kim, Geun-Myeong; Oh, Young Jun; Chang, K. J.

    2016-07-01

    We perform first-principles density functional calculations to investigate the effects of Al incorporation on the p-type Schottky barrier height ≤ft({φ\\text{p}}\\right) and the effective work function for various high-k/metal gate stacks, such as TiN/HfO2 with interface Al impurities, Ti1-x Al x N/HfO2, and TiAl/TiN/HfO2. When Al atoms substitute for the interface Ti atoms at TiN/HfO2 interface, interface dipole fields become stronger, leading to the increase of {φ\\text{p}} and thereby the n-type shift of effective work function. In Ti1-x Al x N/HfO2 interface, {φ\\text{p}} linearly increases with the Al content, attributed to the presence of interface Al atoms. On the other hand, in TiAl/TiN/HfO2 interface, where Al is assumed not to segregate from TiAl to TiN, {φ\\text{p}} is nearly independent of the thickness of TiAl. Our results indicate that Al impurities at the metal/dielectric interface play an important role in controlling the effective work function, and provide a clue to understanding the n-type shift of the effective work function observed in TiAl/TiN/HfO2 gate stacks fabricated by using thegate-last process.

  13. Recrystallization effects of swift heavy {sup 209}Bi ions irradiation on electrical degradation in 4H-SiC Schottky barrier diode

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhimei; Ma, Yao; Gong, Min [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Li, Yun [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Huang, Mingmin [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Gao, Bo [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhao, Xin, E-mail: zhaoxin1234@scu.edu.cn [Key Laboratory for Microelectronics, College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China)

    2017-06-15

    In this paper, the phenomenon that the recrystallization effects of swift heavy {sup 209}Bi ions irradiation can partially recovery damage with more than 1 × 10{sup 10} ions/cm{sup 2} is investigated by the degradation of the electrical characteristics of 4H-SiC Schottky barrier diode (SBD) with swift heavy ion irradiation. Deep level transient spectroscopy (DLTS) and Current-Voltage (I-V) measurements clearly indicated that E{sub 0.62} defect induced by swift heavy ion irradiation, which was a recombination center, could result in the increase of reverse leakage current (I{sub R}) at fluence less than 1 × 10{sup 9} ions/cm{sup 2} and the recovery of I{sub R} at fluence more than 1 × 10{sup 10} ions/cm{sup 2} in 4H-SiC SBD. The variation tendency of I{sub R} is consisted with the change of E{sub 0.62} defect. Furthermore, it is reasonable explanation that the damage or defect formed at low fluence in SiC may be recovered by further swift heavy ion irradiation with high fluence, which is due to the melting with the ion tracks of the amorphous zones through a thermal spike and subsequent epitaxial recrystallization initiated from the neighboring crystalline regions.

  14. Recrystallization effects of swift heavy 209Bi ions irradiation on electrical degradation in 4H-SiC Schottky barrier diode

    Science.gov (United States)

    Yang, Zhimei; Ma, Yao; Gong, Min; Li, Yun; Huang, Mingmin; Gao, Bo; Zhao, Xin

    2017-06-01

    In this paper, the phenomenon that the recrystallization effects of swift heavy 209Bi ions irradiation can partially recovery damage with more than 1 × 1010 ions/cm2 is investigated by the degradation of the electrical characteristics of 4H-SiC Schottky barrier diode (SBD) with swift heavy ion irradiation. Deep level transient spectroscopy (DLTS) and Current-Voltage (I-V) measurements clearly indicated that E0.62 defect induced by swift heavy ion irradiation, which was a recombination center, could result in the increase of reverse leakage current (IR) at fluence less than 1 × 109 ions/cm2 and the recovery of IR at fluence more than 1 × 1010 ions/cm2 in 4H-SiC SBD. The variation tendency of IR is consisted with the change of E0.62 defect. Furthermore, it is reasonable explanation that the damage or defect formed at low fluence in SiC may be recovered by further swift heavy ion irradiation with high fluence, which is due to the melting with the ion tracks of the amorphous zones through a thermal spike and subsequent epitaxial recrystallization initiated from the neighboring crystalline regions.

  15. Schottky-barrier heights of metal/alpha-SiC{l_brace}0001{r_brace} interfaces by first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Shingo; Okazaki, Kazuyuki; Kohyama, Masanori [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology (AIST), Ikeda, Osaka 5638577 (Japan); Tamura, Tomoyuki; Ishibashi, Shoji [Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 3058568 (Japan)

    2007-07-01

    Atomic and electronic structures and Schottky barrier heights (SBH) of multi-layer metal (=Al, Ti, Fe, Co, Ni, Cu, Pt and Au)/6H-SiC{l_brace}0001{r_brace} interfaces have been calculated by the projector augmented wave (PAW) method. The p-type SBHs of the C-terminated interfaces are smaller than those of the Si-terminated ones due to the different interface dipoles. About the dependence on the metal species, the SBHs of the Si-terminated interfaces range within a relatively narrow energy region because of more metallic characters, although those of the C-terminated ones show clearer dependence, where the SBHs decrease for the increment of metal electronegativity or work function. This inverse proportion is different from the results of monolayer metal/SiC interfaces, while consistent with experiments. All the results can be explained by the viewpoint of the interface dipole and the intrinsic relation of the band structures. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

    Science.gov (United States)

    Taşçıoğlu, İ.; Tüzün Özmen, Ö.; Şağban, H. M.; Yağlıoğlu, E.; Altındal, Ş.

    2017-04-01

    In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements in the frequency range of 10 kHz-2 MHz. The C- V- f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states ( N ss). The values of N ss located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant ( ɛ') and dielectric loss ( ɛ″) decrease with increasing frequency, whereas loss tangent (tan δ) remains nearly the same. The decrease in ɛ' and ɛ″ was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity ( σ ac) and electric modulus ( M' and M″) increase with increasing frequency.

  17. Schottky Contact of Gallium on p-Type Silicon

    Directory of Open Access Journals (Sweden)

    B.P. Modi

    2011-01-01

    Full Text Available The evolution of barrier at Schottky contact and its stabilization to value characterized by the barrier height and unambiguous measurement is still being curiously perused as they hold the key control and manufacture of tailor made Schottky devices for a host of existing and potential for future applications in electronics, optoelectronics and microwave devices. In this context, gallium – silicon Schottky diode has been fabricated and analyzed.

  18. Fabrication of Schottky barrier diodes using H{sub 2}O{sub 2}-treated non-polar ZnO (101{sup ¯}0) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kashiwaba, Yasuhiro, E-mail: kashi@sendai-nct.ac.jp [Sendai National College of Technology, Advanced Course of Information and Electronic System Engineering, 4-16-1 Ayashi-chuo, Sendai 989-3128 (Japan); Sakuma, Mio [Sendai National College of Technology, Advanced Course of Information and Electronic System Engineering, 4-16-1 Ayashi-chuo, Sendai 989-3128 (Japan); Abe, Takami; Nakagawa, Akira; Niikura, Ikuo; Kashiwaba, Yasube; Daibo, Masahiro; Osada, Hiroshi [Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan)

    2013-12-01

    Non-polar single crystal ZnO (101{sup ¯}0) substrates with hydrogen peroxide (H{sub 2}O{sub 2}) treatment were characterized and applied to Schottky barrier diodes. Formation of a ZnO{sub 2} layer with a polycrystalline structure was confirmed by 2θ scans of X-ray diffraction (XRD) measurements. Tails of the X-ray rocking curve of ZnO (101{sup ¯}0) planes were broadened with increase in H{sub 2}O{sub 2} treatment time. Grain structures were clearly observed on the surfaces of ZnO (101{sup ¯}0) substrates with H{sub 2}O{sub 2} treatment by an atomic force microscope, and the root mean square roughness of the ZnO{sub 2} surface was about 5 nm. The current density–voltage (J–V) characteristics of Pd/ZnO/Al structures using ZnO (101{sup ¯}0) substrates without H{sub 2}O{sub 2} treatment were ohmic. The J–V characteristics of Pd/ZnO{sub 2}/ZnO/Al structures using ZnO (101{sup ¯}0) substrates with H{sub 2}O{sub 2} treatment time of 5 min showed good rectifying characteristics. The ideality factor n of this diode was 1.7 and the barrier height between Pd films and the ZnO{sub 2} layer on the ZnO (101{sup ¯}0) plane was estimated to be 0.92 eV.

  19. Radio-frequency shot-noise measurement in a magnetic tunnel junction with a MgO barrier

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, Mushtaq; Park, Junghwan; Song, Woon; Chong, Yonuk [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Lee, Yeonsub; Min, Byoungchul; Shin, Kyungho [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Ryu, Sangwan [Chonnam National University, Gwangju (Korea, Republic of); Khim, Zheong [Seoul National University, Seoul (Korea, Republic of)

    2010-10-15

    We measured the noise power of a magnetic tunnel junction in the frequency range of 710 {approx} 1200 MHz. A low-noise cryogenic HEMT amplifier was used to measure the small noise signal at a high frequency with wide bandwidth. The MgO-barrier tunnel junction showed large tunnel magnetoresistance ratio of 215% at low temperature, which indicates electronic transport through the tunnel barrier without any significant spin-flip scattering. In the bias-dependent noise measurement, however, the zero-bias shot noise was enhanced compared to the value expected from a perfect tunnel barrier or the value observed from a good Al-AlO{sub x}-Al tunnel junction. We assume that this enhanced noise comes from inelastic tunneling processes through the barrier, which may be related to the observed zero-bias anomaly in the differential resistance of the tunnel junctions. We present a simple phenomenological model for how the inelastic scattering process can enhance the zero-bias noise in a tunnel junction.

  20. Evidence of a Symmetry-Dependent Metallic Barrier in Fully Epitaxial MgO Based Magnetic Tunnel Junctions

    Science.gov (United States)

    Greullet, F.; Tiusan, C.; Montaigne, F.; Hehn, M.; Halley, D.; Bengone, O.; Bowen, M.; Weber, W.

    2007-11-01

    We report on the experimental observation of tunneling across an ultrathin metallic Cr spacer layer that is inserted at the interface of a Fe/MgO/Fe(001) junction. We show how this remarkable behavior in a solid-state device reflects a quenching in the transmission of particular electronic states, as expected from the symmetry-filtering properties of the MgO barrier and the band structure of the bcc Cr(001) spacer in the epitaxial junction stack. This ultrathin Cr metallic barrier can promote quantum well states in an adjacent Fe layer.

  1. Current Transport Behaviour of Au/n-GaAs Schottky Diodes Grown on Ge Substrate With Different Epitaxial Layer Thickness Over a Wide Temperature Range

    Directory of Open Access Journals (Sweden)

    N. Padha

    2011-01-01

    Full Text Available The work presents temperature dependent forward and reverse current-voltage (I-V analyses of n-GaAs/Au Schottky Diodes grown on n+ Ge substrate with different epitaxial layer thicknesses. While some of the Schottky diodes follow TED mechanism, others exceed significantly from this theory due to existence of patches of reduced barrier height embedded in the Schottky interface. The zero bias barrier heights (φbo increase (0.649 to 0.809 eV while the ideality factors (η decrease (1.514 to 1.052 with increase in epitaxial layer thickness (1-4 μm, thus, indicating similar behaviour to that observed for the I-V characteristics of the undertaken Schottky diodes with decreasing temperature. It all indicated the existence of barrier inhomogenities over the M-S interface. The breakdown behaviour analysis of these diodes showed some interesting results; the breakdown voltage (VBR decreases with temperature and shows ‘Defect Assisted Tunneling’ phenomenon through surface or defect states in the 1 μm thick epitaxial layer Schottky diode while VBR increases with temperature in 3 μm and 4 μm thick epitaxial layer Schottky diodes which demonstrate ‘Avalanche Multiplication’ mechanism responsible for junction breakdown. The reverse breakdown voltage is also seen to increase (2.7-5.9 Volts with the increase in epitaxial layer thickness of the diodes. The undertaken diodes have been observed to follow TFE mechanism at low temperatures (below 200 K in which the tunneling current component increases with epitaxial layer thickness which has been ascribed as an impact of GaAs/Ge hetero-interface over the Au/n-GaAs Schottky barrier.

  2. Autophagy enhances intestinal epithelial tight junction barrier function by targeting claudin-2 protein degradation.

    Science.gov (United States)

    Nighot, Prashant K; Hu, Chien-An Andy; Ma, Thomas Y

    2015-03-13

    Autophagy is an intracellular degradation pathway and is considered to be an essential cell survival mechanism. Defects in autophagy are implicated in many pathological processes, including inflammatory bowel disease. Among the innate defense mechanisms of intestinal mucosa, a defective tight junction (TJ) barrier has been postulated as a key pathogenic factor in the causation and progression of inflammatory bowel disease by allowing increased antigenic permeation. The cross-talk between autophagy and the TJ barrier has not yet been described. In this study, we present the novel finding that autophagy enhances TJ barrier function in Caco-2 intestinal epithelial cells. Nutrient starvation-induced autophagy significantly increased transepithelial electrical resistance and reduced the ratio of sodium/chloride paracellular permeability. Nutrient starvation reduced the paracellular permeability of small-sized urea but not larger molecules. The role of autophagy in the modulation of paracellular permeability was confirmed by pharmacological induction as well as pharmacological and genetic inhibition of autophagy. Consistent with the autophagy-induced reduction in paracellular permeability, a marked decrease in the level of the cation-selective, pore-forming TJ protein claudin-2 was observed after cell starvation. Starvation reduced the membrane presence of claudin-2 and increased its cytoplasmic, lysosomal localization. Therefore, our data show that autophagy selectively reduces epithelial TJ permeability of ions and small molecules by lysosomal degradation of the TJ protein claudin-2.

  3. Gate tunable graphene-silicon Ohmic/Schottky contacts

    Science.gov (United States)

    Chen, Chun-Chung; Chang, Chia-Chi; Li, Zhen; Levi, A. F. J.; Cronin, Stephen B.

    2012-11-01

    We show that the I-V characteristics of graphene-silicon junctions can be actively tuned from rectifying to Ohmic behavior by electrostatically doping the graphene with a polymer electrolyte gate. Under zero applied gate voltage, we observe rectifying I-V characteristics, demonstrating the formation of a Schottky junction at the graphene-silicon interface. Through appropriate gating, the Fermi energy of the graphene can be varied to match the conduction or valence band of silicon, thus forming Ohmic contacts with both n- and p-type silicon. Over the applied gate voltage range, the low bias conductance can be varied by more than three orders of magnitude. By varying the top gate voltage from -4 to +4 V, the Fermi energy of the graphene is shifted between -3.78 and -5.47 eV; a shift of ±0.85 eV from the charge neutrality point. Since the conduction and valence bands of the underlying silicon substrate lie within this range, at -4.01 and -5.13 eV, the Schottky barrier height and depletion width can be decreased to zero for both n- and p-type silicon under the appropriate top gating conditions. I-V characteristics taken under illumination show that the photo-induced current can be increased or decreased based on the graphene-silicon work function difference.

  4. Correlation between amplitude of spin accumulation signals investigated by Hanle effect measurement and effective junction barrier height in CoFe/MgO/n{sup +}-Si junctions

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Y., E-mail: yoshiaki.saito@toshiba.co.jp; Ishikawa, M.; Sugiyama, H.; Inokuchi, T. [Corporate Research and Development Center, Toshiba Corporation, 1, Komukai-Toshiba-cho, 212-8582 Kawasaki (Japan); Hamaya, K. [Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama-cho, Toyonaka city, Osaka 560-8531 (Japan); Tezuka, N. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2015-05-07

    Correlation between the amplitude of the spin accumulation signals and the effective barrier height estimated from the slope of the log (RA) - t{sub MgO} plot (RA: resistance area product, t{sub MgO}: thickness of MgO tunnel barrier) in CoFe/MgO/n{sup +}-Si junctions was investigated. The amplitude of spin accumulation signals increases with increasing effective barrier heights. This increase of the amplitude of spin accumulation is originated from the increase of the spin polarization (P{sub Si}) in Si. The estimated absolute values of P{sub Si} using three-terminal Hanle signals are consistent with those estimated by four-terminal nonlocal-magnetoresistance (MR) and two-terminal local-MR. To demonstrate large spin accumulation in Si bulk band and enhance the local-MR through Si channel, these results indicate that the increase of the effective barrier height at ferromagnet/(tunnel barrier)/n{sup +}-Si junction electrode is important.

  5. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Clément, P.-Y.; Baraduc, C., E-mail: claire.baraduc@cea.fr; Chshiev, M.; Diény, B. [Univ. Grenoble Alpes, INAC-SPINTEC, F-38000 Grenoble (France); CNRS, INAC-SPINTEC, F-38000 Grenoble (France); CEA, INAC-SPINTEC, F-38000 Grenoble (France); Ducruet, C. [Crocus-Technology, 5, Place Robert Schuman, F-38054 Grenoble (France); Vila, L. [Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France and CEA, INAC-SP2M, F-38000 Grenoble (France)

    2015-09-07

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  6. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    Science.gov (United States)

    Clément, P.-Y.; Baraduc, C.; Ducruet, C.; Vila, L.; Chshiev, M.; Diény, B.

    2015-09-01

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  7. Degradation of magnetic tunnel junctions with thin AlOx barrier

    Directory of Open Access Journals (Sweden)

    Tadashi Mihara, Yoshinari Kamakura, Masato Morifuji and Kenji Taniguchi

    2007-01-01

    Full Text Available The degradation of magnetic tunnel junctions (MTJs with AlOx barrier was experimentally investigated. Constant voltage stress (CVS measurement was carried out to monitor the time evolution of the conductance and tunneling magnetoresistance (TMR of MTJs. The gradual increase of the stress-induced leakage current (SILC was observed prior to the breakdown, following a power law function of stress time with an exponent of about 0.2–0.4, which is similar to the case of the ultrathin gate oxide films in MOSFETs. The measured TMR for SILC suggests that the spin-dependent current component would be involved in the early stage of degradation, while spin-independent conduction becomes dominant before the breakdown resulting in a decrease of TMR.

  8. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.

    2011-08-24

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  9. Peanut Allergens Alter Intestinal Barrier Permeability and Tight Junction Localisation in Caco-2 Cell Cultures1

    Directory of Open Access Journals (Sweden)

    Dwan B. Price

    2014-05-01

    Full Text Available Background/Aims: Allergen absorption by epithelia may play an important role in downstream immune responses. Transport mechanisms that can bypass Peyer's patches include transcellular and paracellular transport. The capacity of an allergen to cross via these means can modulate downstream processing of the allergen by the immune system. The aim of this study was to investigate allergen-epithelial interactions of peanut allergens with the human intestinal epithelium. Methods: We achieved this using the human Caco-2 cell culture model, exposed to crude peanut extract. Western and immunofluorescence analysis were used to identify the cellular and molecular changes of peanut extract on the intestinal epithelium. Results: Following exposure of Caco-2 cells to peanut extract, binding of the peanut allergens Ara h 1 and Ara h 2 to the apical cellular membrane and transcytosis across the monolayers were observed. Additionally, the co-localisation of the transmembrane tight junction proteins occludin, JAM-A and claudin-1, with the intracellular adhesion protein ZO-1 was modified. Conclusion: Disruption of Caco-2 barrier integrity through tight junction disruption may enable movement of peanut proteins across the intestinal epithelium. This accounts for peanut's increased allergenicity, compared to other food allergens, and provides an explanation for the potency of peanut allergens in immune response elicitation.

  10. Lipopolysaccharide disrupts the milk-blood barrier by modulating claudins in mammary alveolar tight junctions.

    Directory of Open Access Journals (Sweden)

    Ken Kobayashi

    Full Text Available Mastitis, inflammation of the mammary gland, is the most costly common disease in the dairy industry, and is caused by mammary pathogenic bacteria, including Escherichia coli. The bacteria invade the mammary alveolar lumen and disrupt the blood-milk barrier. In normal mammary gland, alveolar epithelial tight junctions (TJs contribute the blood-milk barrier of alveolar epithelium by blocking the leakage of milk components from the luminal side into the blood serum. In this study, we focused on claudin subtypes that participate in the alveolar epithelial TJs, because the composition of claudins is an important factor that affects TJ permeability. In normal mouse lactating mammary glands, alveolar TJs consist of claudin-3 without claudin-1, -4, and -7. In lipopolysaccharide (LPS-induced mastitis, alveolar TJs showed 2-staged compositional changes in claudins. First, a qualitative change in claudin-3, presumably caused by phosphorylation and participation of claudin-7 in alveolar TJs, was recognized in parallel with the leakage of fluorescein isothiocyanate-conjugated albumin (FITC-albumin via the alveolar epithelium. Second, claudin-4 participated in alveolar TJs with claudin-3 and claudin-7 12 h after LPS injection. The partial localization of claudin-1 was also observed by immunostaining. Coinciding with the second change of alveolar TJs, the severe disruption of the blood-milk barrier was recognized by ectopic localization of β-casein and much leakage of FITC-albumin. Furthermore, the localization of toll-like receptor 4 (TLR4 on the luminal side and NFκB activation by LPS was observed in the alveolar epithelial cells. We suggest that the weakening and disruption of the blood-milk barrier are caused by compositional changes of claudins in alveolar epithelial TJs through LPS/TLR4 signaling.

  11. Acidic bile salts modulate the squamous epithelial barrier function by modulating tight junction proteins.

    Science.gov (United States)

    Chen, Xin; Oshima, Tadayuki; Tomita, Toshihiko; Fukui, Hirokazu; Watari, Jiro; Matsumoto, Takayuki; Miwa, Hiroto

    2011-08-01

    Experimental models for esophageal epithelium in vitro either suffer from poor differentiation or complicated culture systems. An air-liquid interface system with normal human bronchial epithelial cells can serve as a model of esophageal-like squamous epithelial cell layers. Here, we explore the influence of bile acids on barrier function and tight junction (TJ) proteins. The cells were treated with taurocholic acid (TCA), glycocholic acid (GCA), or deoxycholic acid (DCA) at different pH values, or with pepsin. Barrier function was measured by transepithelial electrical resistance (TEER) and the diffusion of paracellular tracers (permeability). The expression of TJ proteins, including claudin-1 and claudin-4, was examined by Western blotting of 1% Nonidet P-40-soluble and -insoluble fractions. TCA and GCA dose-dependently decreased TEER and increased paracellular permeability at pH 3 after 1 h. TCA (4 mM) or GCA (4 mM) did not change TEER and permeability at pH 7.4 or pH 4. The combination of TCA and GCA at pH 3 significantly decreased TEER and increased permeability at lower concentrations (2 mM). Pepsin (4 mg/ml, pH 3) did not have any effect on barrier function. DCA significantly decreased the TEER and increased permeability at pH 6, a weakly acidic condition. TCA (4 mM) and GCA (4 mM) significantly decreased the insoluble fractions of claudin-1 and claudin-4 at pH 3. In conclusion, acidic bile salts disrupted the squamous epithelial barrier function partly by modulating the amounts of claudin-1 and claudin-4. These results provide new insights for understanding the role of TJ proteins in esophagitis.

  12. Reliability enhancement due to in-situ post-oxidation of sputtered MgO barrier in double MgO barrier magnetic tunnel junction

    Science.gov (United States)

    Yoshida, Chikako; Noshiro, Hideyuki; Yamazaki, Yuichi; Sugii, Toshihiro

    2017-06-01

    We have investigated the effects of in-situ post-oxidation (PO) of a sputtered MgO barrier in a double-MgO-barrier magnetic tunnel junction (MTJ) and found that the short error rate was significantly reduced, the magnetoresistance (MR) ratio was increased approximately 18%, and the endurance lifetime was extend. In addition, we found that the distribution of breakdown number (a measure of endurance) exhibits trimodal characteristics, which indicates competition between extrinsic and intrinsic failures. This improvement in reliability might be related to the suppression of Fe and Co diffusion to the MgO barrier, as revealed by electron energy-loss spectroscopy (EELS) analysis.

  13. Enteric Pathogens and Their Toxin-Induced Disruption of the Intestinal Barrier through Alteration of Tight Junctions in Chickens

    Science.gov (United States)

    Awad, Wageha A.; Hess, Claudia; Hess, Michael

    2017-01-01

    Maintaining a healthy gut environment is a prerequisite for sustainable animal production. The gut plays a key role in the digestion and absorption of nutrients and constitutes an initial organ exposed to external factors influencing bird’s health. The intestinal epithelial barrier serves as the first line of defense between the host and the luminal environment. It consists of a continuous monolayer of intestinal epithelial cells connected by intercellular junctional complexes which shrink the space between adjacent cells. Consequently, free passing of solutes and water via the paracellular pathway is prevented. Tight junctions (TJs) are multi-protein complexes which are crucial for the integrity and function of the epithelial barrier as they not only link cells but also form channels allowing permeation between cells, resulting in epithelial surfaces of different tightness. Tight junction’s molecular composition, ultrastructure, and function are regulated differently with regard to physiological and pathological stimuli. Both in vivo and in vitro studies suggest that reduced tight junction integrity greatly results in a condition commonly known as “leaky gut”. A loss of barrier integrity allows the translocation of luminal antigens (microbes, toxins) via the mucosa to access the whole body which are normally excluded and subsequently destroys the gut mucosal homeostasis, coinciding with an increased susceptibility to systemic infection, chronic inflammation and malabsorption. There is considerable evidence that the intestinal barrier dysfunction is an important factor contributing to the pathogenicity of some enteric bacteria. It has been shown that some enteric pathogens can induce permeability defects in gut epithelia by altering tight junction proteins, mediated by their toxins. Resolving the strategies that microorganisms use to hijack the functions of tight junctions is important for our understanding of microbial pathogenesis, because some pathogens

  14. Enteric Pathogens and Their Toxin-Induced Disruption of the Intestinal Barrier through Alteration of Tight Junctions in Chickens

    Directory of Open Access Journals (Sweden)

    Wageha A. Awad

    2017-02-01

    Full Text Available Maintaining a healthy gut environment is a prerequisite for sustainable animal production. The gut plays a key role in the digestion and absorption of nutrients and constitutes an initial organ exposed to external factors influencing bird’s health. The intestinal epithelial barrier serves as the first line of defense between the host and the luminal environment. It consists of a continuous monolayer of intestinal epithelial cells connected by intercellular junctional complexes which shrink the space between adjacent cells. Consequently, free passing of solutes and water via the paracellular pathway is prevented. Tight junctions (TJs are multi-protein complexes which are crucial for the integrity and function of the epithelial barrier as they not only link cells but also form channels allowing permeation between cells, resulting in epithelial surfaces of different tightness. Tight junction’s molecular composition, ultrastructure, and function are regulated differently with regard to physiological and pathological stimuli. Both in vivo and in vitro studies suggest that reduced tight junction integrity greatly results in a condition commonly known as “leaky gut”. A loss of barrier integrity allows the translocation of luminal antigens (microbes, toxins via the mucosa to access the whole body which are normally excluded and subsequently destroys the gut mucosal homeostasis, coinciding with an increased susceptibility to systemic infection, chronic inflammation and malabsorption. There is considerable evidence that the intestinal barrier dysfunction is an important factor contributing to the pathogenicity of some enteric bacteria. It has been shown that some enteric pathogens can induce permeability defects in gut epithelia by altering tight junction proteins, mediated by their toxins. Resolving the strategies that microorganisms use to hijack the functions of tight junctions is important for our understanding of microbial pathogenesis

  15. Design of 340 GHz 2× and 4× Sub-Harmonic Mixers Using Schottky Barrier Diodes in Silicon-Based Technology

    Directory of Open Access Journals (Sweden)

    Chao Liu

    2015-05-01

    Full Text Available This paper presents the design of terahertz 2× and 4× sub-harmonic down-mixers using Schottky Barrier Diodes fabricated in standard 0.13 μm SiGe BiCMOS technology. The 340 GHz sub-harmonic mixers (SHMs are designed based on anti-parallel-diode-pairs (APDPs. With the 2nd and 4th harmonic, local oscillator (LO frequencies of 170 GHz and 85 GHz are used to pump the two 340 GHz SHMs. With LO power of 7 dBm, the 2× SHM exhibits a conversion loss of 34.5–37 dB in the lower band (320–340 GHz and 35.5–41 dB in the upper band (340–360 GHz; with LO power of 9 dBm, the 4× SHM exhibits a conversion loss of 39–43 dB in the lower band (320–340 GHz and 40–48 dB in the upper band (340–360 GHz. The measured input 1-dB conversion gain compression point for the 2× and 4× SHMs are −8 dBm and −10 dBm at 325 GHz, respectively. The simulated LO-IF (intermediate frequency isolation of the 2× SHM is 21.5 dB, and the measured LO-IF isolation of the 4× SHM is 32 dB. The chip areas of the 2× and 4× SHMs are 330 μm × 580 μm and 550 μm × 610 μm, respectively, including the testing pads.

  16. Tight junctions at the blood brain barrier: physiological architecture and disease-associated dysregulation

    Directory of Open Access Journals (Sweden)

    Luissint Anny-Claude

    2012-11-01

    Full Text Available Abstract The Blood–brain barrier (BBB, present at the level of the endothelium of cerebral blood vessels, selectively restricts the blood-to-brain paracellular diffusion of compounds; it is mandatory for cerebral homeostasis and proper neuronal function. The barrier properties of these specialized endothelial cells notably depend on tight junctions (TJs between adjacent cells: TJs are dynamic structures consisting of a number of transmembrane and membrane-associated cytoplasmic proteins, which are assembled in a multimolecular complex and acting as a platform for intracellular signaling. Although the structural composition of these complexes has been well described in the recent years, our knowledge about their functional regulation still remains fragmentary. Importantly, pericytes, embedded in the vascular basement membrane, and perivascular microglial cells, astrocytes and neurons contribute to the regulation of endothelial TJs and BBB function, altogether constituting the so-called neurovascular unit. The present review summarizes our current understanding of the structure and functional regulation of endothelial TJs at the BBB. Accumulating evidence points to a correlation between BBB dysfunction, alteration of TJ complexes and progression of a variety of CNS diseases, such as stroke, multiple sclerosis and brain tumors, as well as neurodegenerative diseases like Parkinson’s and Alzheimer’s diseases. Understanding how TJ integrity is controlled may thus help improve drug delivery across the BBB and the design of therapeutic strategies for neurological disorders.

  17. Improved broadband antireflection in Schottky-like junction of conformal Al-doped ZnO layer on chemically textured Si surfaces

    Science.gov (United States)

    Saini, C. P.; Barman, A.; Kumar, M.; Sahoo, P. K.; Som, T.; Kanjilal, A.

    2014-09-01

    Chemically textured Si with improved absorption in the complete range of solar spectrum is investigated by ultraviolet/visible/near-infrared (UV/Vis/NIR) spectroscopy, showing an average specular reflectance of ˜0.4% in the wavelength of 500-3000 nm. The pyramidal structures on such solar-blind Si can reduce the reflectance further below 0.1% in the UV region by conformal growth of granular Al-doped ZnO (AZO) films. X-ray diffraction analyses suggest the growth of polycrystalline AZO on faceted-Si. Moreover, marginal increase in electrical conductivity of AZO is found on textured surfaces, whereas rise in leakage current in Schottky-like Ag/AZO/Si/Ag heterostructure devices is noticed with increasing Si surface area.

  18. Analysis of temperature dependent current-conduction mechanisms in Au/TiO2/n-4H-SiC (metal/insulator/semiconductor) type Schottky barrier diodes

    Science.gov (United States)

    Alialy, S.; Altındal, Ş.; Tanrıkulu, E. E.; Yıldız, D. E.

    2014-08-01

    In order to determine the effective current-conduction mechanisms in Au/TiO2/n-4H-SiC (metal-insulator semiconductor) type Schottky barrier diodes (SBDs), their current-voltage (I-V) measurements were carried out in the temperature range of 200-380 K. Some electrical parameters, such as ideality factor (n), zero-bias barrier height (BH) (ΦBo), series and shunt resistances (Rs, Rsh), were obtained as 5.09, 0.81 eV, 37.43 Ω, and 435 kΩ at 200 K and 2.68, 0.95 eV, 5.99 Ω, and 73 kΩ at 380 K, respectively. The energy density distribution profile of surface states (Nss) was extracted from the forward-bias I-V data by taking into account voltage dependent of the ideality factor (nV), effective BH (Φe), and Rs for 200, 300, and 380 K. The Ln(I) vs V plots are completely parallel in the intermediate bias voltages, which may be well explained by field emission (FE) mechanism for each temperature. On the other hand, the high value of n cannot be explained with this mechanism. Therefore, to explain the change in BH and n with temperature, ΦBo vs q/2kT plot was drawn to obtain an evidence of a Gaussian distribution (GD) of the BHs and thus the mean value of BH (Φ¯Bo) and standard deviation (σso) values were found from this plot as 1.396 eV and 0.176 V, respectively. The Φ¯Bo and Richardson constant (A*) values were found as 1.393 eV and 145.5 A.cm-2 K-2 using modified Ln(Io/T2)-(q2σs2/2k2T2) vs q/kT plot, respectively. It is clear that all of the obtained main electrical parameters were found as a strong function of temperature. These results indicated that the current conduction mechanism in Au/TiO2/n-4 H-SiC (SBD) well obey the FE and GD mechanism rather than other mechanisms.

  19. Gap junction proteins in the blood-brain barrier control nutrient-dependent reactivation of Drosophila neural stem cells.

    Science.gov (United States)

    Spéder, Pauline; Brand, Andrea H

    2014-08-11

    Neural stem cells in the adult brain exist primarily in a quiescent state but are reactivated in response to changing physiological conditions. How do stem cells sense and respond to metabolic changes? In the Drosophila CNS, quiescent neural stem cells are reactivated synchronously in response to a nutritional stimulus. Feeding triggers insulin production by blood-brain barrier glial cells, activating the insulin/insulin-like growth factor pathway in underlying neural stem cells and stimulating their growth and proliferation. Here we show that gap junctions in the blood-brain barrier glia mediate the influence of metabolic changes on stem cell behavior, enabling glia to respond to nutritional signals and reactivate quiescent stem cells. We propose that gap junctions in the blood-brain barrier are required to translate metabolic signals into synchronized calcium pulses and insulin secretion.

  20. Influence of the MgO barrier thickness on the lifetime characteristics of magnetic tunnelling junctions for sensors

    Science.gov (United States)

    Conca, A.; Casper, F.; Paul, J.; Lehndorff, R.; Jakob, G.; Kläui, M.; Hillebrands, B.; Leven, B.

    2016-06-01

    Magnetic tunnelling junctions increasingly enter the market for magnetic sensor applications. Thus, technological parameters such as the lifetime characteristics become more and more important. Here, an analysis of the lifetime characteristics of magnetic tunnelling junctions using the Weibull statistical distribution for CoFeB/MgO/CoFeB junctions is presented. The Weibull distribution is governed by two parameters, the characteristic lifetime η of the population and the shape parameter β, which gives information about the presence of an infant mortality. The suitability of the Weibull distribution is demonstrated for the description of dielectric breakdown processes in MgO-based tunnelling junctions at different voltages. A study of the dependence of the characteristic lifetime extrapolated to the low voltage regime, and the β parameter on the nominal barrier thickness and the resistance  ×  area product of the MgO barrier is shown. The influence of the RF deposition power for the MgO barrier and an annealing step on the Weibull parameters is also discussed.

  1. Effects of sputtering power Schottky metal layers on rectifying performance of Mo-SiC Schottky contacts

    Science.gov (United States)

    Lee, Seula; Lee, Jinseon; You, Sslimsearom; Kyoung, Sinsu; Kim, Kyung Hwan

    2016-01-01

    In this study, Schottky barrier diodes based on silicon carbide with various levels of Schottky metal layer input power were prepared and characterized. In this structure, molybdenum and aluminum were employed as the Schottky metal and top electrode, respectively. Schottky metal layers were deposited with input power ranging from 30 to 210 W. Schottky metal layers and top electrodes were deposited with a thickness of 3000 Å. The Schottky barrier heights, series resistances, and ideality factor were calculated from current-voltage (I-V) curves obtained using the Cheung-Cheung and Norde methods. All deposition processes were conducted using a facing targets sputtering system. Turn on voltage was minimized when the input power was 90 W, at which point electrical characteristics were observed to have properties superior to those at other levels of input power.

  2. Barrier characteristics of biopolymer-based organic/inorganic Au/CTS/n-InP hybrid junctions

    Science.gov (United States)

    Abay, Bahattin

    2015-11-01

    Thin film of biopolymeric compound chitosan (CTS) has been surfaced on moderately doped n-InP substrate as an interfacial layer by means of spin coating for the electronic modification of Au/n-InP structure. Electrical characterization of Au/CTS/n-InP hybrid junction has been performed by I-V and C-V measurements at room temperature. An effective barrier height (BH) value of 0.678 eV and an ideality factor of n = 1.665 have been obtained for the hybrid junction. The CTS interfacial layer has been found to reduce the reverse bias leakage current of the junction by about three orders of magnitude and enhance the BH by about 0.213 eV. Furthermore, the BH value of the hybrid junction has been obtained as 0.693 eV by C-V measurement. Good performance of the device could be ascribed to the passivation effect of the CTS interfacial layer between Au and n-InP. The BH values of 0.678 and 0.693 eV for the hybrid junction have been significantly higher than that of the conventional Au/n-InP junction (~0.465 eV). The results indicated that biopolymeric thin interfacial CTS layer might lead to the modification of the potential barrier for metal/n-InP junctions. Moreover, band gap of the CTS layer has been determined as 4.60 eV via UV-vis spectroscopy.

  3. Current–voltage characteristics of Ag, Al, Ni–()CdTe junctions

    Indian Academy of Sciences (India)

    P C Sarmah; A Rahman

    2001-08-01

    Schottky barriers of Ag, Al, Ni–()CdTe structures have been prepared and studied. The films were prepared by rf sputtering and doped with Cd metal. Diode ideality factor of these junctions are greater than unity and barrier height varies from 0.6–0.7 eV and are affected by room illumination. Photovoltaic effect of these junctions was very poor and fill factor below 0.4. Low doping concentration, high defect density, presence of an interfacial layer and presence of high series resistance are perceived to affect the – characteristic.

  4. Self-Powered Solar-Blind Photodetector with Fast Response Based on Au/β-Ga2O3 Nanowires Array Film Schottky Junction.

    Science.gov (United States)

    Chen, Xing; Liu, Kewei; Zhang, Zhenzhong; Wang, Chunrui; Li, Binghui; Zhao, Haifeng; Zhao, Dongxu; Shen, Dezhen

    2016-02-17

    Because of the direct band gap of 4.9 eV, β-Ga2O3 has been considered as an ideal material for solar-blind photodetection without any bandgap tuning. Practical applications of the photodetectors require fast response speed, high signal-to-noise ratio, low energy consumption and low fabrication cost. Unfortunately, most reported β-Ga2O3-based photodetectors usually possess a relatively long response time. In addition, the β-Ga2O3 photodetectors based on bulk, the individual 1D nanostructure, and the film often suffer from the high cost, the low repeatability, and the relatively large dark current, respectively. In this paper, a Au/β-Ga2O3 nanowires array film vertical Schottky photodiode is successfully fabricated by a simple thermal partial oxidation process. The device exhibits a very low dark current of 10 pA at -30 V with a sharp cutoff at 270 nm. More interestingly, the 90-10% decay time of our device is only around 64 μs, which is much quicker than any other previously reported β-Ga2O3-based photodetectors. Besides, the self-powering, the excellent stability and the good reproducibility of Au/β-Ga2O3 nanowires array film photodetector are helpful to its commercialization and practical applications.

  5. Flexible thin-film solar cells based on graphene/CdTe Schottky junction%石墨烯/CdTe肖特基结柔性薄膜太阳能电池研究

    Institute of Scientific and Technical Information of China (English)

    贾树明; 魏大鹏; 焦天鹏; 汪岳峰; 周全

    2015-01-01

    利用Matlab仿真模拟了石墨烯/P-CdTe肖特基结太阳能电池的光电特性。结果表明,电池的短路电流密度Jsc为23.9×10–3A/cm2、开路电压Voc为0.64 V、填充因子FF为79.0,转换效率η高达12%。与传统的氧化铟锡(ITO)电极比较,石墨烯柔韧性好,同时具备高透光和高导电的特性,可替代ITO作为新型电极材料来制备柔性薄膜太阳能电池。%By using Matlab, photoelectric properties of the graphene/CdTe Schottky junction solar cells was simulated. Results show that the short-circuit currentJsc of solar cells is 23.9×10–3A /cm2, the open circuit voltageVoc is 0.64 V, the fill factor FF is 79.0 and conversion efficiencyη is 12%. Compared with traditional indium tin oxide (ITO) electrode, graphene is flexible, and also has higher transmittance and conductivity. Therefore, graphene could replace ITO as a new electrode material for the preparation of flexible thin-film solar cells.

  6. 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.

  7. Resonant spin-transfer torque in asymmetric double barrier magnetic tunnel junctions (MTJs)

    Science.gov (United States)

    Daqiq, Reza; Ghobadi, Nader

    2017-02-01

    The substitution effect of a Ferro-magnet (FM) electrode by a half-metallic FM material La0.7Sr0.3MnO3 (LSMO) on charge current and spin-transfer torque (STT) components is studied in MgO-based double barrier magnetic tunnel junctions (DBMTJs) with a middle non-magnetic metal (NM) layer. Using non-equilibrium Green's function (NEGF) formalism, it is observed that the current and STT components show oscillatory behavior due to quantum well states in the middle NM layer and resonant tunneling effect. We also study effect of difference in the thickness of the MgO insulators. Bias dependence demonstrate the magnitude enhancement of the current and in-plane STT in new asymmetric DBMTJs (A-DBMTJs) compared with symmetric DBMTJs (S-DBMTJs), however, perpendicular STT decreases in the A-DBMTJs. Results also show different behavior compared with conventional asymmetric MTJs and spin valves (SVs). Therefore, one can design new memory devices by means of suitable insulator and FM electrodes with proper thicknesses.

  8. TLR2 mediates gap junctional intercellular communication through connexin-43 in intestinal epithelial barrier injury.

    Science.gov (United States)

    Ey, Birgit; Eyking, Annette; Gerken, Guido; Podolsky, Daniel K; Cario, Elke

    2009-08-14

    Gap junctional intercellular communication (GJIC) coordinates cellular functions essential for sustaining tissue homeostasis; yet its regulation in the intestine is not well understood. Here, we identify a novel physiological link between Toll-like receptor (TLR) 2 and GJIC through modulation of Connexin-43 (Cx43) during acute and chronic inflammatory injury of the intestinal epithelial cell (IEC) barrier. Data from in vitro studies reveal that TLR2 activation modulates Cx43 synthesis and increases GJIC via Cx43 during IEC injury. The ulcerative colitis-associated TLR2-R753Q mutant targets Cx43 for increased proteasomal degradation, impairing TLR2-mediated GJIC during intestinal epithelial wounding. In vivo studies using mucosal RNA interference show that TLR2-mediated mucosal healing depends functionally on intestinal epithelial Cx43 during acute inflammatory stress-induced damage. Mice deficient in TLR2 exhibit IEC-specific alterations in Cx43, whereas administration of a TLR2 agonist protects GJIC by blocking accumulation of Cx43 and its hyperphosphorylation at Ser368 to prevent spontaneous chronic colitis in MDR1alpha-deficient mice. Finally, adding the TLR2 agonist to three-dimensional intestinal mucosa-like cultures of human biopsies preserves intestinal epithelial Cx43 integrity and polarization ex vivo. In conclusion, Cx43 plays an important role in innate immune control of commensal-mediated intestinal epithelial wound repair.

  9. Butyrate Enhances the Intestinal Barrier by Facilitating Tight Junction Assembly via Activation of AMP-Activated Protein Kinase in Caco-2 Cell Monolayers12

    Science.gov (United States)

    Peng, Luying; Li, Zhong-Rong; Green, Robert S.; Holzman, Ian R.; Lin, Jing

    2009-01-01

    Butyrate, one of the SCFA, promotes the development of the intestinal barrier. However, the molecular mechanisms underlying the butyrate regulation of the intestinal barrier are unknown. To test the hypothesis that the effect of butyrate on the intestinal barrier is mediated by the regulation of the assembly of tight junctions involving the activation of the AMP-activated protein kinase (AMPK), we determined the effect of butyrate on the intestinal barrier by measuring the transepithelial electrical resistance (TER) and inulin permeability in a Caco-2 cell monolayer model. We further used a calcium switch assay to study the assembly of epithelial tight junctions and determined the effect of butyrate on the assembly of epithelial tight junctions and AMPK activity. We demonstrated that the butyrate treatment increased AMPK activity and accelerated the assembly of tight junctions as shown by the reorganization of tight junction proteins, as well as the development of TER. AMPK activity was also upregulated by butyrate during calcium switch-induced tight junction assembly. Compound C, a specific AMPK inhibitor, inhibited the butyrate-induced activation of AMPK. The facilitating effect of butyrate on the increases in TER in standard culture media, as well as after calcium switch, was abolished by compound C. We conclude that butyrate enhances the intestinal barrier by regulating the assembly of tight junctions. This dynamic process is mediated by the activation of AMPK. These results suggest an intriguing link between SCFA and the intracellular energy sensor for the development of the intestinal barrier. PMID:19625695

  10. Butyrate enhances the intestinal barrier by facilitating tight junction assembly via activation of AMP-activated protein kinase in Caco-2 cell monolayers.

    Science.gov (United States)

    Peng, Luying; Li, Zhong-Rong; Green, Robert S; Holzman, Ian R; Lin, Jing

    2009-09-01

    Butyrate, one of the SCFA, promotes the development of the intestinal barrier. However, the molecular mechanisms underlying the butyrate regulation of the intestinal barrier are unknown. To test the hypothesis that the effect of butyrate on the intestinal barrier is mediated by the regulation of the assembly of tight junctions involving the activation of the AMP-activated protein kinase (AMPK), we determined the effect of butyrate on the intestinal barrier by measuring the transepithelial electrical resistance (TER) and inulin permeability in a Caco-2 cell monolayer model. We further used a calcium switch assay to study the assembly of epithelial tight junctions and determined the effect of butyrate on the assembly of epithelial tight junctions and AMPK activity. We demonstrated that the butyrate treatment increased AMPK activity and accelerated the assembly of tight junctions as shown by the reorganization of tight junction proteins, as well as the development of TER. AMPK activity was also upregulated by butyrate during calcium switch-induced tight junction assembly. Compound C, a specific AMPK inhibitor, inhibited the butyrate-induced activation of AMPK. The facilitating effect of butyrate on the increases in TER in standard culture media, as well as after calcium switch, was abolished by compound C. We conclude that butyrate enhances the intestinal barrier by regulating the assembly of tight junctions. This dynamic process is mediated by the activation of AMPK. These results suggest an intriguing link between SCFA and the intracellular energy sensor for the development of the intestinal barrier.

  11. Spin asymmetry calculations of the TMR-V curves in single and double-barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2011-10-01

    Spin-polarization asymmetry is the key parameter in asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) in magnetic tunnel junctions. In this paper, we study the value of the TMR as a function of the applied voltage Va in the single as well as double barrier magnetic tunnel junctions (SMTJ & DMTJ, which are constructed from CoFeB/MgO interfaces) and numerically estimate the possible difference of the TMR-V a curves for negative and positive voltages in the homojunctions. As a result, we found that AVB may help to determine the exact values of Fermi wave vectors for minority and majority conducting spin sub-bands. Moreover, significant asymmetry of the experimental TMR-Va curves, which arises due to different annealing regimes, is explained by different heights of the tunnel barriers and values of the spin asymmetry. The numerical TMR-V a data are in good agreement with experimental ones. © 2011 IEEE.

  12. Frequency and voltage dependence of electric and dielectric properties of Au/TiO2/n-4H-SiC (metal-insulator-semiconductor) type Schottky barrier diodes

    Science.gov (United States)

    Tanrıkulu, E. E.; Yıldız, D. E.; Günen, A.; Altındal, Ş.

    2015-09-01

    The main electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) have been investigated as functions of frequency and applied bias voltage. We believe that the use of high dielectric interfacial layer between metal and semiconductor can improve the performance of Schottky diodes. From the experimental data, both electrical and dielectric parameters were found as strong function of frequency and applied bias voltage. The Fermi energy level (EF), the concentration of doping donor atoms (P), barrier height (ΦB) and series resistance (Rs) values were obtained from reverse and forward bias C-V characteristics. The changes in EF and ND with frequency are considerably low. Therefore, their values were taken at about constant. The real and imaginary parts of dielectric constant (\\varepsilon \\prime , \\varepsilon \\prime\\prime ), tangent loss (tanδ), ac electrical conductivity (σac), and real and imaginary parts of electric modulus (M‧ and M″) values were also obtained from reverse and forward bias C-V and G/ω-V characteristics. In addition, the voltage dependent profiles of all these electrical and dielectric parameters were drawn for each frequency. These results confirmed that both electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type SBD are quite sensitive to both the frequency and applied bias voltage due to surface polarization, density distribution of interface traps (Dit), and interfacial layer.

  13. Charge transport in molecular electronic junctions: Compression of the molecular tunnel barrier in the strong coupling regime

    OpenAIRE

    Sayed, Sayed Y.; Fereiro, Jerry A.; Yan, Haijun; Richard L. McCreery; Bergren, Adam Johan

    2012-01-01

    Molecular junctions are essentially modified electrodes familiar to electrochemists where the electrolyte is replaced by a conducting “contact.” It is generally hypothesized that changing molecular structure will alter system energy levels leading to a change in the transport barrier. Here, we show the conductance of seven different aromatic molecules covalently bonded to carbon implies a modest range ( 2 eV range). These results are explained by considering the effect of bonding the molecule...

  14. Volatile Anesthetics Influence Blood-Brain Barrier Integrity by Modulation of Tight Junction Protein Expression in Traumatic Brain Injury

    OpenAIRE

    Thal, Serge C.; Clara Luh; Eva-Verena Schaible; Ralph Timaru-Kast; Jana Hedrich; Luhmann, Heiko J.; Kristin Engelhard; Zehendner, Christoph M.

    2012-01-01

    Disruption of the blood-brain barrier (BBB) results in cerebral edema formation, which is a major cause for high mortalityrnafter traumatic brain injury (TBI). As anesthetic care is mandatory in patients suffering from severe TBI it may be importantrnto elucidate the effect of different anesthetics on cerebral edema formation. Tight junction proteins (TJ) such as zonularnoccludens-1 (ZO-1) and claudin-5 (cl5) play a central role for BBB stability. First, the influence of the volatile anesthet...

  15. Correlation between Barrier Width, Barrier Height, and DC Bias Voltage Dependences on the Magnetoresistance Ratio in Ir-Mn Exchange Biased Single and Double Tunnel Junctions

    Science.gov (United States)

    Saito, Yoshiaki; Amano, Minoru; Nakajima, Kentaro; Takahashi, Shigeki; Sagoi, Masayuki; Inomata, Koichiro

    2000-10-01

    Dual spin-valve-type double tunnel junctions (DTJs) of Ir-Mn/CoFe/AlOx/Co90Fe10/AlOx/CoFe/Ir-Mn and spin-valve-type single tunnel junctions (STJs) of Ir-Mn/CoFe/AlOx/CoFe/Ni-Fe were fabricated using an ultrahigh vacuum sputtering system, conventional photolithography and ion-beam milling. The STJs could be fabricated with various barrier heights by changing the oxidization conditions during deposition and changing the annealing temperature after deposition, while the AlOx layer thickness remained unchanged. There was a correlation between barrier width, height estimated using Simmons’ expressions, and dc bias voltage dependence on the MR ratio. The VB dependence on the tunneling magnetoresistance (TMR) ratio was mainly related to the barrier width, and the decrease in the TMR ratio with increasing bias voltage is well explained, taking into account the spin-independent two-step tunneling via defect states in the barrier, as a main mechanism, at room temperature. Under optimized oxidization and annealing conditions, the maximum TMR ratio at a low bias voltage, and the dc bias voltage value at which the TMR ratio decreases in value by half (V1/2) were 42.4% and 952 mV in DTJs, and 49.0% and 425 mV in STJs, respectively.

  16. The interface states and series resistance effects on the forward and reverse bias I-V, C-V and G/{omega}-V characteristics of Al-TiW-Pd{sub 2}Si/n-Si Schottky barrier diodes

    Energy Technology Data Exchange (ETDEWEB)

    Uslu, H.; Altindal, S.; Aydemir, U. [Department of Physics, Gazi University, 06500 Ankara (Turkey); Doekme, I., E-mail: ilbilgedokme@gazi.edu.t [Science Education Department, Gazi Education Faculty, Gazi University, 06500 Ankara (Turkey); Afandiyeva, I.M. [Baku State University, Baku (Azerbaijan)

    2010-07-30

    Illumination intensity effects on the electrical characteristics of Al-TiW-Pd{sub 2}Si/n-Si Schottky structures have been investigated in this study for the first time. The electrical parameters such as ideality factor (n), zero-bias-barrier height ({Phi}{sub B0}), series resistance (R{sub s}), depletion layer width (W{sub D}) and dopping concentration (N{sub D}) of Al-TiW-Pd{sub 2}Si/n-Si Schottky barrier diodes (SBDs) have been investigated by using the forward and reverse bias current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/{omega}-V) measurements in dark and under illumination conditions at room temperature. The values of C and G/{omega} increase with increasing illumination intensity due to the illumination induced electron-hole pairs in the depletion region. The density of interface states (N{sub ss}) distribution profiles as a function of (E{sub c} - E{sub ss}) was extracted from the forward I-V measurements by taking into account the bias dependence of the effective barrier heights ({Phi}{sub e}) for device in dark and under various illumination intensities. The high values of N{sub ss} were responsible for the nonideal behavior of I-V, C-V and G/{omega} characteristics. The values of R{sub s} obtained from Cheung and Nicollian methods decrease with increasing illumination intensity. The high values of n and R{sub s} have been attributed to the particular distribution of N{sub ss}, surface preparation, inhomogeneity of interfacial layer and barrier height at metal/semiconductor (M/S) interface. As a result, the characteristics of SBD are affected not only in N{sub ss} but also in R{sub s}, and these two parameters strongly influence the electrical parameters.

  17. Reliability enhancement due to in-situ post-oxidation of sputtered MgO barrier in double MgO barrier magnetic tunnel junction

    Directory of Open Access Journals (Sweden)

    Chikako Yoshida

    2017-06-01

    Full Text Available We have investigated the effects of in-situ post-oxidation (PO of a sputtered MgO barrier in a double-MgO-barrier magnetic tunnel junction (MTJ and found that the short error rate was significantly reduced, the magnetoresistance (MR ratio was increased approximately 18%, and the endurance lifetime was extend. In addition, we found that the distribution of breakdown number (a measure of endurance exhibits trimodal characteristics, which indicates competition between extrinsic and intrinsic failures. This improvement in reliability might be related to the suppression of Fe and Co diffusion to the MgO barrier, as revealed by electron energy-loss spectroscopy (EELS analysis.

  18. I-V characteristics simulation of silicon carbide Ti/4H-SiC Schottky diode

    Science.gov (United States)

    Panchenko, P.; Rybalka, S.; Malakhanov, A.; Krayushkina, E.; Radkov, A.

    2016-12-01

    The simulation of current-voltage characteristics for 4H-SiC Schottky diode with Ti Schottky contact has been carried out with used of TCAD program. Obtained current-voltage characteristics has been analyzed and compared with theoretical and experimental results. It is established that the Schottky diode parameters (forward current, ideality coefficient, Schottky barrier height, breakdown voltage) obtained in proposed model are good agreement with data for such type diodes.

  19. Tunable reverse-biased graphene/silicon heterojunction Schottky diode sensor.

    Science.gov (United States)

    Singh, Amol; Uddin, Ahsan; Sudarshan, Tangali; Koley, Goutam

    2014-04-24

    A new chemical sensor based on reverse-biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ∼500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance-voltage measurements.

  20. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    Science.gov (United States)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  1. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    Science.gov (United States)

    Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

    2016-03-01

    Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

  2. Scaling of nano-Schottky-diodes

    NARCIS (Netherlands)

    Smit, G.D.J.; Rogge, S.; Klapwijk, T.M.

    2002-01-01

    A generally applicable model is presented to describe the potential barrier shape in ultrasmall Schottky diodes. It is shown that for diodes smaller than a characteristic length lc (associated with the semiconductor doping level) the conventional description no longer holds. For such small diodes th

  3. EMP-induced alterations of tight junction protein expression and disruption of the blood-brain barrier.

    Science.gov (United States)

    Ding, Gui-Rong; Qiu, Lian-Bo; Wang, Xiao-Wu; Li, Kang-Chu; Zhou, Yong-Chun; Zhou, Yan; Zhang, Jie; Zhou, Jia-Xing; Li, Yu-Rong; Guo, Guo-Zhen

    2010-07-15

    The blood-brain barrier (BBB) is critical to maintain cerebral homeostasis. In this study, we examined the effects of exposure to electromagnetic pulse (EMP) on the functional integrity of BBB and, on the localization and expression of tight junction (TJ) proteins (occludin and ZO-1) in rats. Animals were sham or whole-body exposed to EMP at 200 kV/m for 400 pulses. The permeability of BBB in rat cerebral cortex was examined by using Evans Blue (EB) and lanthanum nitrate as vascular tracers. The localization and expression of TJ proteins were assessed by western blot and immunofluorescence analysis, respectively. The data indicated that EMP exposure caused: (i) increased permeability of BBB, and (ii) altered localization as well as decreased levels of TJ protein ZO-1. These results suggested that the alteration of ZO-1 may play an important role in the disruption of tight junctions, which may lead to dysfunction of BBB after EMP exposure.

  4. Mild hypothermia alleviates brain oedema and blood-brain barrier disruption by attenuating tight junction and adherens junction breakdown in a swine model of cardiopulmonary resuscitation

    Science.gov (United States)

    Li, Jiebin; Li, Chunsheng; Yuan, Wei; Wu, Junyuan; Li, Jie; Li, Zhenhua; Zhao, Yongzhen

    2017-01-01

    Mild hypothermia improves survival and neurological recovery after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). However, the mechanism underlying this phenomenon is not fully elucidated. The aim of this study was to determine whether mild hypothermia alleviates early blood–brain barrier (BBB) disruption. We investigated the effects of mild hypothermia on neurologic outcome, survival rate, brain water content, BBB permeability and changes in tight junctions (TJs) and adherens junctions (AJs) after CA and CPR. Pigs were subjected to 8 min of untreated ventricular fibrillation followed by CPR. Mild hypothermia (33°C) was intravascularly induced and maintained at this temperature for 12 h, followed by active rewarming. Mild hypothermia significantly reduced cortical water content, decreased BBB permeability and attenuated TJ ultrastructural and basement membrane breakdown in brain cortical microvessels. Mild hypothermia also attenuated the CPR-induced decreases in TJ (occludin, claudin-5, ZO-1) and AJ (VE-cadherin) protein and mRNA expression. Furthermore, mild hypothermia decreased the CA- and CPR-induced increases in matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression and increased angiogenin-1 (Ang-1) expression. Our findings suggest that mild hypothermia attenuates the CA- and resuscitation-induced early brain oedema and BBB disruption, and this improvement might be at least partially associated with attenuation of the breakdown of TJ and AJ, suppression of MMP-9 and VEGF expression, and upregulation of Ang-1 expression. PMID:28355299

  5. Increased inspiratory esophagogastric junction pressure in systemic sclerosis: An add-on to antireflux barrier

    Science.gov (United States)

    Nobre e Souza, Miguel Ângelo; Bezerra, Patrícia Carvalho; Nobre, Rivianny Arrais; Holanda, Esther Studart da Fonseca; dos Santos, Armênio Aguiar

    2015-01-01

    AIM: To investigate crural diaphragm (CD) function in systemic sclerosis (SSc) using high-resolution manometry and standardized inspiratory maneuvers. METHODS: Eight SSc volunteers (average age, 40.1 years; one male) and 13 controls (average age, 32.2 years; six males) participated in the study. A high-resolution manometry/impedance system measured the esophagus and esophagogastric junction (EGJ) pressure profile during swallows and two respiratory maneuvers: sinus arrhythmia maneuver (SAM; the average of six EGJ peak pressures during 5-s deep inhalations) and threshold maneuver (TM; the EGJ peak pressures during forced inhalation under 12 and 24 cmH2O loads). Inspiratory diaphragm lowering (IDL) was taken as the displacement of the EGJ high-pressure zone during the SAM. RESULTS: SSc patients had lower mean lower esophageal sphincter pressure than controls during normal breathing (19.7 ± 2.8 mmHg vs 32.2 ± 2.7 mmHg, P = 0.007). Sinus arrhythmia maneuver pressure was higher in SSc patients than in controls (142.6 ± 9.4 mmHg vs 104.6 ± 13.8 mmHg, P = 0.019). Sinus arrhythmia maneuver pressure normalized to IDL was also higher in SSc patients than in controls (83.8 ± 13.4 mmHg vs 37.5 ± 6.9 mmHg, P = 0.005). Threshold maneuver pressures normalized to IDL were also greater in SSc patients than in controls (TM 12 cmH2O: 85.1 ± 16.4 mmHg vs 43.9 ± 6.3 mmHg, P = 0.039; TM 24 cmH2O: 85.2 ± 16.4 mmHg vs 46.2 ± 6.6 mmHg, P = 0.065). Inspiratory diaphragm lowering in SSc patients was less than in controls (2.1 ± 0.3 cm vs 3 ± 0.2 cm, P = 0.011). CONCLUSION: SSc patients had increased inspiratory EGJ pressure. This is an add-on to EGJ pressure and indicates that the antireflux barrier can be trained. PMID:25717239

  6. On the electrical behavior of V2O5/4H-SiC Schottky diodes

    Science.gov (United States)

    Bellone, S.; Di Benedetto, L.; Rubino, A.

    2013-06-01

    A complete analysis of the rectifying behavior of V2O5/4H-SiC (divanadium pentoxide/4H polytype of silicon carbide) junction is reported. The analysis of forward and reverse JD-VD curves of samples fabricated with 5 nm-thick V2O5 films shows that the carrier transport across junction is dominated by the field enhanced thermionic emission mechanism. All the physical and electrical parameters, such as Schottky barrier height, ideality factor, and series resistance, have been evaluated from temperature behavior of JD-VD curves in the range 100-425 K and from CD-VD measurements. It is shown that the barrier height extracted from measurements can be justified in terms of inhomogeneities localized at the interface.

  7. Fabrication and Characterization of Al/p-CuInAlSe2 Thin Film Schottky Diodes

    Directory of Open Access Journals (Sweden)

    Usha Parihar

    2013-05-01

    Full Text Available Al/p-CuInAlSe2 polycrystalline schottky diodes fabricated by flash evaporation method were undertaken for their electrical analysis at room temperature. Diode parameters of the undertaken diodes were then derived from the current-voltage (I-V as well as capacitance-voltage (C-V characteristics. It has been observed that the schottky barrier height deduced from the room temperature I-V is lower to that obtained from the C-V characteristics and is attributed to the fact that I-V analysis includes both the image force and dipole lowering effects and is also reduced by the tunneling and leakage currents. The slope variation of the frequency dependent C – 2-V characteristics for the Al/p-CuInAlSe2 Schottky diode at varying frequency values from 50 kHz to 1 MHz suggests a large density of slow traps or interface states at the M-S junction. As emerging from the parameters values energy band diagram of Al and P-CuInAlSe2 has been reconstructed.

  8. Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    Directory of Open Access Journals (Sweden)

    J. Rogge

    2015-07-01

    Full Text Available We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs. By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR ratio of -10% is found for Co2FeAl (24 nm / BaO (5 nm / Fe (7 nm MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM, it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  9. 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.

  10. Clostridium perfringens enterotoxin fragment removes specific claudins from tight junction strands: Evidence for direct involvement of claudins in tight junction barrier.

    Science.gov (United States)

    Sonoda, N; Furuse, M; Sasaki, H; Yonemura, S; Katahira, J; Horiguchi, Y; Tsukita, S

    1999-10-04

    Claudins, comprising a multigene family, constitute tight junction (TJ) strands. Clostridium perfringens enterotoxin (CPE), a single approximately 35-kD polypeptide, was reported to specifically bind to claudin-3/RVP1 and claudin-4/CPE-R at its COOH-terminal half. We examined the effects of the COOH-terminal half fragment of CPE (C-CPE) on TJs in L transfectants expressing claudin-1 to -4 (C1L to C4L, respectively), and in MDCK I cells expressing claudin-1 and -4. C-CPE bound to claudin-3 and -4 with high affinity, but not to claudin-1 or -2. In the presence of C-CPE, reconstituted TJ strands in C3L cells gradually disintegrated and disappeared from their cell surface. In MDCK I cells incubated with C-CPE, claudin-4 was selectively removed from TJs with its concomitant degradation. At 4 h after incubation with C-CPE, TJ strands were disintegrated, and the number of TJ strands and the complexity of their network were markedly decreased. In good agreement with the time course of these morphological changes, the TJ barrier (TER and paracellular flux) of MDCK I cells was downregulated by C-CPE in a dose-dependent manner. These findings provided evidence for the direct involvement of claudins in the barrier functions of TJs.

  11. The serine protease-mediated increase in intestinal epithelial barrier function is dependent on occludin and requires an intact tight junction.

    Science.gov (United States)

    Ronaghan, Natalie J; Shang, Judie; Iablokov, Vadim; Zaheer, Raza; Colarusso, Pina; Dion, Sébastien; Désilets, Antoine; Leduc, Richard; Turner, Jerrold R; MacNaughton, Wallace K

    2016-09-01

    Barrier dysfunction is a characteristic of the inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis. Understanding how the tight junction is modified to maintain barrier function may provide avenues for treatment of IBD. We have previously shown that the apical addition of serine proteases to intestinal epithelial cell lines causes a rapid and sustained increase in transepithelial electrical resistance (TER), but the mechanisms are unknown. We hypothesized that serine proteases increase barrier function through trafficking and insertion of tight junction proteins into the membrane, and this could enhance recovery of a disrupted monolayer after calcium switch or cytokine treatment. In the canine epithelial cell line, SCBN, we showed that matriptase, an endogenous serine protease, could potently increase TER. Using detergent solubility-based cell fractionation, we found that neither trypsin nor matriptase treatment changed levels of tight junction proteins at the membrane. In a fast calcium switch assay, serine proteases did not enhance the rate of recovery of the junction. In addition, serine proteases could not reverse barrier disruption induced by IFNγ and TNFα. We knocked down occludin in our cells using siRNA and found this prevented the serine protease-induced increase in TER. Using fluorescence recovery after photobleaching (FRAP), we found serine proteases induce a greater mobile fraction of occludin in the membrane. These data suggest that a functional tight junction is needed for serine proteases to have an effect on TER, and that occludin is a crucial tight junction protein in this mechanism.

  12. Porcine lactoferrin-derived peptide LFP-20 protects intestinal barrier by maintaining tight junction complex and modulating inflammatory response.

    Science.gov (United States)

    Zong, Xin; Hu, Wangyang; Song, Deguang; Li, Zhi; Du, Huahua; Lu, Zeqing; Wang, Yizhen

    2016-03-15

    LFP-20, a 20-amino acid antimicrobial peptide in the N terminus of porcine lactoferrin, has antimicrobial and immunomodulatory activities. This study assessed the protective effects of LFP-20 on LPS-induced intestinal damage in a LPS-induced mouse model and in vitro, using intestinal porcine epithelial cell line 1 (IPEC-1) cells. LFP-20 prevented LPS-induced impairment in colon epithelium tissues, infiltration of macrophages or leukocytes, histological evidence of inflammation and increased levels of TNF-a, IL-6 and IFN-γ. LFP-20 increased the expression of zonula occludens-1, occludin and claudin-1 and reduced permeability as well as apoptosis of the colon in LPS-treated mice. In IPEC-1 cells, LFP-20 increased transepithelial electrical resistance and tight junction expression. Moreover, we found LFP-20 decreased the MyD88 and AKT levels to affect the NF-κB signaling pathway, to modulate inflammation response and tight junction networks in the processing of LPS stimulation. In summary, LFP-20 prevents the inflammatory response and disruption of tight junction structure induced by LPS, suggesting the potential use of LFP-20 as a prophylactic agent to protect intestinal barrier function.

  13. Lamellar granule secretion starts before the establishment of tight junction barrier for paracellular tracers in mammalian epidermis.

    Directory of Open Access Journals (Sweden)

    Akemi Ishida-Yamamoto

    Full Text Available Defects in epidermal barrier function and/or vesicular transport underlie severe skin diseases including ichthyosis and atopic dermatitis. Tight junctions (TJs form a single layered network in simple epithelia. TJs are important for both barrier functions and vesicular transport. Epidermis is stratified epithelia and lamellar granules (LGs are secreted from the stratum granulosum (SG in a sequential manner. Previously, continuous TJs and paracellular permeability barriers were found in the second layer (SG2 of SG in mice, but their fate and correlation with LG secretion have been poorly understood. We studied epidermal TJ-related structures in humans and in mice and found occludin/ZO-1 immunoreactive multilayered networks spanning the first layer of SG (SG1 and SG2. Paracellular penetration tracer passed through some TJs in SG2, but not in SG1. LG secretion into the paracellular tracer positive spaces started below the level of TJs of SG1. Our study suggests that LG-secretion starts before the establishment of TJ barrier in the mammalian epidermis.

  14. Epitaxial wurtzite-MgZnO barrier based magnetic tunnel junctions deposited on a metallic ferromagnetic electrode

    Energy Technology Data Exchange (ETDEWEB)

    Belmoubarik, M., E-mail: bmm-dhr@ecei.tohoku.ac.jp; Al-Mahdawi, M.; Sato, H.; Nozaki, T.; Sahashi, M. [Department of Electronic Engineering, Tohoku University, Sendai 890-8579 (Japan)

    2015-06-22

    An epitaxial wurtzite (WZ) Mg{sub 0.23}Zn{sub 0.77}O barrier based magnetic tunnel junction (MTJ), with electrode-barrier structure of Co{sub 0.30}Pt{sub 0.70} (111)/Mg{sub 0.23}Zn{sub 0.77}O (0001)/Co (0001), was fabricated. The good crystallinity and tunneling properties were experimentally confirmed. Electrical and magnetic investigations demonstrated its high resistance-area product of 1.05 MΩ μm{sup 2}, a maximum tunneling magneto-resistance (TMR) of 35.5%, and the existence of localized states within the tunneling barrier producing TMR rapid decrease and oscillation when increasing the applied bias voltage. The TMR value almost vanished at 200 K, which was attributed to the induced moment and strong spin-orbit coupling in Pt atoms at the Co{sub 0.30}Pt{sub 0.70}/Mg{sub 0.23}Zn{sub 0.77}O interface. Owing to the ferroelectric behavior in WZ-MgZnO materials, the fabrication of WZ-MgZnO barrier based MTJs deposited on a metallic ferromagnetic electrode will open routes for electrically controllable non-volatile devices that are compatible with CMOS technology.

  15. Group A Streptococcus exploits human plasminogen for bacterial translocation across epithelial barrier via tricellular tight junctions

    Science.gov (United States)

    Sumitomo, Tomoko; Nakata, Masanobu; Higashino, Miharu; Yamaguchi, Masaya; Kawabata, Shigetada

    2016-01-01

    Group A Streptococcus (GAS) is a human-specific pathogen responsible for local suppurative and life-threatening invasive systemic diseases. Interaction of GAS with human plasminogen (PLG) is a salient characteristic for promoting their systemic dissemination. In the present study, a serotype M28 strain was found predominantly localized in tricellular tight junctions of epithelial cells cultured in the presence of PLG. Several lines of evidence indicated that interaction of PLG with tricellulin, a major component of tricellular tight junctions, is crucial for bacterial localization. A site-directed mutagenesis approach revealed that lysine residues at positions 217 and 252 within the extracellular loop of tricellulin play important roles in PLG-binding activity. Additionally, we demonstrated that PLG functions as a molecular bridge between tricellulin and streptococcal surface enolase (SEN). The wild type strain efficiently translocated across the epithelial monolayer, accompanied by cleavage of transmembrane junctional proteins. In contrast, amino acid substitutions in the PLG-binding motif of SEN markedly compromised those activities. Notably, the interaction of PLG with SEN was dependent on PLG species specificity, which influenced the efficiency of bacterial penetration. Our findings provide insight into the mechanism by which GAS exploits host PLG for acceleration of bacterial invasion into deeper tissues via tricellular tight junctions. PMID:26822058

  16. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    Science.gov (United States)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  17. 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.

  18. Hypoxia/Aglycemia-induced endothelial barrier dysfunction and tight junction protein downregulation can be ameliorated by citicoline.

    Directory of Open Access Journals (Sweden)

    Xiaotang Ma

    Full Text Available This study explores the effect of citicoline on the permeability and expression of tight junction proteins (TJPs in endothelial cells under hypoxia/aglycemia conditions. Hypoxia or oxygen and glucose deprivation (OGD was utilized to induce endothelial barrier breakdown model on human umbilical vein endothelial cells (HUVECs and mouse brain microvascular endothelial cells (bEnd.3s. The effect of citicoline on endothelial barrier breakdown models was determined at either low or high concentrations. FITC-Dextran flux was used to examine the endothelial permeability. The expression of TJPs was measured by immunofluorescence, Real-time PCR and Western Blot methods. Results showed that hypoxia or OGD increased the permeability of HUVECs accompanied with down-regulation of occludens-1 (ZO-1 and occludin at both mRNA and protein levels. Similarly in bEnd.3s, hypoxia increased the permeability and decreased the expression of ZO-1 and claudin-5. Citicoline treatment dose-dependently decreased the permeability in these two models, which paralleled with elevated expression of TJPs. The data demonstrate that citicoline restores the barrier function of endothelial cells compromised by hypoxia/aglycemia probably via up-regulating the expression of TJPs.

  19. Hypoxia/Aglycemia-induced endothelial barrier dysfunction and tight junction protein downregulation can be ameliorated by citicoline.

    Science.gov (United States)

    Ma, Xiaotang; Zhang, Huiting; Pan, Qunwen; Zhao, Yuhui; Chen, Ji; Zhao, Bin; Chen, Yanfang

    2013-01-01

    This study explores the effect of citicoline on the permeability and expression of tight junction proteins (TJPs) in endothelial cells under hypoxia/aglycemia conditions. Hypoxia or oxygen and glucose deprivation (OGD) was utilized to induce endothelial barrier breakdown model on human umbilical vein endothelial cells (HUVECs) and mouse brain microvascular endothelial cells (bEnd.3s). The effect of citicoline on endothelial barrier breakdown models was determined at either low or high concentrations. FITC-Dextran flux was used to examine the endothelial permeability. The expression of TJPs was measured by immunofluorescence, Real-time PCR and Western Blot methods. Results showed that hypoxia or OGD increased the permeability of HUVECs accompanied with down-regulation of occludens-1 (ZO-1) and occludin at both mRNA and protein levels. Similarly in bEnd.3s, hypoxia increased the permeability and decreased the expression of ZO-1 and claudin-5. Citicoline treatment dose-dependently decreased the permeability in these two models, which paralleled with elevated expression of TJPs. The data demonstrate that citicoline restores the barrier function of endothelial cells compromised by hypoxia/aglycemia probably via up-regulating the expression of TJPs.

  20. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Science.gov (United States)

    Ali, Hassan; Khan, Usman; Rafiq, M. A.; Falak, Attia; Narain, Adeela; Jing, Tang; Xu, Xiulai

    2016-05-01

    We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  1. Richardson-Schottky transport mechanism in ZnS nanoparticles

    Directory of Open Access Journals (Sweden)

    Hassan Ali

    2016-05-01

    Full Text Available We report the synthesis and electrical transport mechanism in ZnS semiconductor nanoparticles. Temperature dependent direct current transport measurements on the compacts of ZnS have been performed to investigate the transport mechanism for temperature ranging from 300 K to 400 K. High frequency dielectric constant has been used to obtain the theoretical values of Richardson-Schottky and Poole-Frenkel barrier lowering coefficients. Experimental value of the barrier lowering coefficient has been calculated from conductance-voltage characteristics. The experimental value of barrier lowering coefficient βexp lies close to the theoretical value of Richardson-Schottky barrier lowering coefficient βth,RS showing Richardson-Schottky emission has been responsible for conduction in ZnS nanoparticles for the temperature range studied.

  2. Double threshold behaviour of I-V characteristics of CoSi2/Si Schottky contacts

    Institute of Scientific and Technical Information of China (English)

    Zhu Shi-Yang(竺士炀); Ru Guo-Ping(茹国平); Qu Xin-Ping(屈新萍); Li Bing-Zong(李炳宗); R.L.Van Meirhaeghe; C.Detavernier; F.Cardon

    2002-01-01

    The forward current-voltage (I-V) characteristics of polycrystalline CoSi2/n-Si(100) Schottky contacts have beenmeasured in a wide temperature range. At low temperatures (≤200K), a plateau-like section is observed in the I-Vmodel based on thermionic emission (TE) and a Gaussian distribution of Schottky barrier height (SBH). Such a doublethreshold behaviour can be explained by the barrier height inhomogeneity, i.e. at low temperatures the current throughpatches with low SBH dominates at small bias region With increasing bias voltage, the Ohmic effect becomes someimportant and the current through the whole junction area exc eeds the patch current, thus resulting in a plateau-likesection in the I-V curves at moderate bias. For the polycrystalline CoSi2/Si contacts studied in this paper, the apparentideality factor of the patch current is much larger than that calculated from the TE model taking the pinch-off effectinto account. This suggests that the current flowing through these patches is of the tunnelling type, rather than thethermionic emission type. The experimental I-V characteristics can be fitted reasonably well in the whole temperatureregion using the model based on tunnelling and pinch-off.

  3. Influence of spin-orbit interaction within the insulating barrier on the electron transport in magnetic tunnel junctions

    Science.gov (United States)

    Vedyayev, A.; Ryzhanova, N.; Strelkov, N.; Titova, M.; Chshiev, M.; Rodmacq, B.; Auffret, S.; Cuchet, L.; Nistor, L.; Dieny, B.

    2017-02-01

    We present a theory of the anisotropy of tunneling magnetoresistance (ATMR) phenomenon in magnetic tunnel junctions (MTJs) attributed to Rashba spin-orbit interaction in the insulating barrier. ATMR represents the difference of tunnel magnetoresistance (TMR) amplitude measured with in-plane and out-of-plane magnetic configurations. It is demonstrated that within the spin-polarized free-electron model the change of conductance associated with the ATMR is exactly twice the change of conductance measured at full saturation (i.e., in parallel configuration of magnetizations) between in-plane and out-of-plane configuration, i.e., the tunneling anisotropic magnetoresistance (TAMR). Both ATMR and TAMR are closely related to the TMR amplitude and spin-orbit constant. The predicted ATMR phenomenon is confirmed experimentally, showing a few percent value in the case of the widely studied CoFeB/MgO/CoFeB based MTJ.

  4. Modulation of intercellular junctions by cyclic-ADT peptides as a method to reversibly increase blood-brain barrier permeability.

    Science.gov (United States)

    Laksitorini, Marlyn D; Kiptoo, Paul K; On, Ngoc H; Thliveris, James A; Miller, Donald W; Siahaan, Teruna J

    2015-03-01

    It is challenging to deliver molecules to the brain for diagnosis and treatment of brain diseases. This is primarily because of the presence of the blood-brain barrier (BBB), which restricts the entry of many molecules into the brain. In this study, cyclic-ADT peptides (ADTC1, ADTC5, and ADTC6) have been shown to modify the BBB to enhance the delivery of marker molecules [e.g., (14) C-mannitol, gadolinium-diethylenetriaminepentacetate (Gd-DTPA)] to the brain via the paracellular pathways of the BBB. The hypothesis is that these peptides modulate cadherin interactions in the adherens junctions of the vascular endothelial cells forming the BBB to increase paracellular drug permeation. In vitro studies indicated that ADTC5 had the best profile to inhibit adherens junction resealing in Madin-Darby canine kidney cell monolayers in a concentration-dependent manner (IC50 = 0.3 mM) with a maximal response at 0.4 mM. Under the current experimental conditions, ADTC5 improved the delivery of (14) C-mannitol to the brain about twofold compared with the negative control in the in situ rat brain perfusion model. Furthermore, ADTC5 peptide increased in vivo delivery of Gd-DTPA to the brain of Balb/c mice when administered intravenously. In conclusion, ADTC5 has the potential to improve delivery of diagnostic and therapeutic agents to the brain.

  5. Glutamine supplementation attenuates ethanol-induced disruption of apical junctional complexes in colonic epithelium and ameliorates gut barrier dysfunction and fatty liver in mice.

    Science.gov (United States)

    Chaudhry, Kamaljit K; Shukla, Pradeep K; Mir, Hina; Manda, Bhargavi; Gangwar, Ruchika; Yadav, Nikki; McMullen, Megan; Nagy, Laura E; Rao, RadhaKrishna

    2016-01-01

    Previous in vitro studies showed that glutamine (Gln) prevents acetaldehyde-induced disruption of tight junctions and adherens junctions in Caco-2 cell monolayers and human colonic mucosa. In the present study, we evaluated the effect of Gln supplementation on ethanol-induced gut barrier dysfunction and liver injury in mice in vivo. Ethanol feeding caused a significant increase in inulin permeability in distal colon. Elevated permeability was associated with a redistribution of tight junction and adherens junction proteins and depletion of detergent-insoluble fractions of these proteins, suggesting that ethanol disrupts apical junctional complexes in colonic epithelium and increases paracellular permeability. Ethanol-induced increase in colonic mucosal permeability and disruption of junctional complexes were most severe in mice fed Gln-free diet. Gln supplementation attenuated ethanol-induced mucosal permeability and disruption of tight junctions and adherens junctions in a dose-dependent manner, indicating the potential role of Gln in nutritional intervention to alcoholic tissue injury. Gln supplementation dose-dependently elevated reduced-protein thiols in colon without affecting the level of oxidized-protein thiols. Ethanol feeding depleted reduced protein thiols and elevated oxidized protein thiols. Ethanol-induced protein thiol oxidation was most severe in mice fed with Gln-free diet and absent in mice fed with Gln-supplemented diet, suggesting that antioxidant effect is one of the likely mechanisms involved in Gln-mediated amelioration of ethanol-induced gut barrier dysfunction. Ethanol feeding elevated plasma transaminase and liver triglyceride, which was accompanied by histopathologic lesions in the liver; ethanol-induced liver damage was attenuated by Gln supplementation. These results indicate that Gln supplementation ameliorates alcohol-induced gut and liver injury.

  6. Schottky diode characteristics and 1/f noise of high sensitivity reduced graphene oxide/Si heterojunction photodetector

    Science.gov (United States)

    Zhu, Miao; Li, Xinming; Li, Xiao; Zang, Xiaobei; Zhen, Zhen; Xie, Dan; Fang, Ying; Zhu, Hongwei

    2016-03-01

    Reduced graphene oxide (RGO)/Si Schottky diode has been reported nowadays to show excellent performances in photodetection and other photoelectrical devices. Different from pure graphene, there are large amounts of function groups and structural defects left on the base plane of RGO, which may influence the interfacial properties of RGO/Si Schottky diode. Herein, the barrier inhomogeneity and junction characteristics were systematically investigated to help to describe the interface of RGO/Si diode. From the perspective of its applications, the influences of gas molecule and noise properties are considered to be important. Thus, the photovoltaic performance of RGO/Si devices in air and vacuum is investigated to analyze their effects. Meanwhile, 1/f noise of RGO/Si diodes is investigated under air/vacuum conditions and varied temperatures. It is found that the devices in vacuum and under higher power incident light show much lower 1/f noise. These results are meaningful to the noise control and performance improvement in the development of Schottky diode based devices.

  7. Esophagogastric Junction Contractility Integral Reflect the Anti-reflux Barrier Dysfunction in Patients with Gastroesophageal Reflux Disease

    Science.gov (United States)

    Xie, Chenxi; Wang, Jinhui; Li, Yuwen; Tan, Niandi; Cui, Yi; Chen, Minhu; Xiao, Yinglian

    2017-01-01

    Background/Aims Anti-reflux barrier dysfunction is one of the primary mechanisms in gastroesophageal reflux disease (GERD) pathogenesis. The esophagogastric junction contractile integral (EGJ-CI) is a new metric adopted to evaluate the EGJ contractility, which implies the anti-reflux barrier function. The aim of the current study was to validate this new metric in patients with GERD and its correlation with the esophageal acid exposure, as well as the efficacy of proton pump inhibitor treatment. Methods Ninety-eight patients with GERD and 21 healthy controls were included in the study. Upper endoscopy, high-resolution manometry (HRM) and 24-hour multichannel intraluminal impedance-pH monitoring were performed in all patients. Three respiration cycles were chosen at the initial HRM resting frame and the value computed with distal contractile integral tool was then divided by the duration of the cycles to yield EGJ-CI. All the patients were treated with esomeprazole 20 mg twice-daily for 8 weeks. Results EGJ-CI was lower in the patients with GERD than that of the controls (P < 0.05). For patients with GERD, EGJ-CI was lower in those with hiatal hernia (P < 0.05). The new metric correlated with esophageal acid exposure in the supine position (P < 0.05), and it also negatively correlated to the total reflux episodes (P < 0.05). There was no significant difference on EGJ-CI between patients with and without response to the esomeprazole treatment (P = 0.627). Conclusions EGJ-CI reflected the dysfunction of the anti-reflux barrier in patients with GERD, but it had little impact on the esomeprazole response. PMID:27426485

  8. Oxygen adsorption at noble metal/TiO2 junctions

    Science.gov (United States)

    Hossein-Babaei, F.; Alaei-Sheini, Navid; Lajvardi, Mehdi M.

    2016-03-01

    Electric conduction in titanium dioxide is known to be oxygen sensitive and the conductivity of a TiO2 ceramic body is determined mainly by the concentration of its naturally occurring oxygen vacancy. Recently, fabrications and electronic features of a number of noble metal/TiO2-based electronic devices, such as solar cells, UV detectors, gas sensors and memristive devices have been demonstrated. Here, we investigate the effect of oxygen adsorption at the noble metal/TiO2 junction in such devices, and show the potentials of these junctions in chemical sensor fabrication. The polycrystalline, poly-phase TiO2 layers are grown by the selective and controlled oxidation of titanium thin films vacuum deposited on silica substrates. Noble metal thin films are deposited on the oxide layers by physical vapor deposition. Current-voltage (I-V) diagrams of the fabricated devices are studied for Ag/, Au/, and Pt/TiO2 samples. The raw samples show no junction energy barrier. After a thermal annealing in air at 250° C, I-V diagrams change drastically. The annealed samples demonstrate highly non-linear I-V indicating the formation of high Schottky energy barriers at the noble metal/TiO2 junctions. The phenomenon is described based on the effect of the oxygen atoms adsorbed at the junction.

  9. Anisotropic transport of normal metal-barrier-normal metal junctions in monolayer phosphorene

    Science.gov (United States)

    De Sarkar, Sangita; Agarwal, Amit; Sengupta, K.

    2017-07-01

    We study transport properties of a phosphorene monolayer in the presence of single and multiple potential barriers of height U 0 and width d, using both continuum and microscopic lattice models, and show that the nature of electron transport along its armchair edge (x direction) is qualitatively different from its counterpart in both conventional two-dimensional electron gas with Schrödinger-like quasiparticles and graphene or surfaces of topological insulators hosting massless Dirac quasiparticles. We show that the transport, mediated by massive Dirac electrons, allows one to achieve collimated quasiparticle motion along x and thus makes monolayer phosphorene an ideal experimental platform for studying Klein paradox in the context of gapped Dirac materials. We study the dependence of the tunneling conductance G\\equiv {{G}xx} as a function of d and U 0, and demonstrate that for a given applied voltage V its behavior changes from oscillatory to decaying function of d for a range of U 0 with finite non-zero upper and lower bounds, and provide analytical expression for these bounds within which G decays with d. We contrast such behavior of G with that of massless Dirac electrons in graphene and also with that along the zigzag edge (y direction) in phosphorene where the quasiparticles obey an effective Schrödinger equation at low energy. We also study transport through multiple barriers along x and demonstrate that these properties hold for transport through multiple barriers as well. Finally, we suggest concrete experiments which may verify our theoretical predictions.

  10. Evaluation of soluble junctional adhesion molecule-A as a biomarker of human brain endothelial barrier breakdown.

    Directory of Open Access Journals (Sweden)

    Axel Haarmann

    Full Text Available BACKGROUND: An inducible release of soluble junctional adhesion molecule-A (sJAM-A under pro-inflammatory conditions was described in cultured non-CNS endothelial cells (EC and increased sJAM-A serum levels were found to indicate inflammation in non-CNS vascular beds. Here we studied the regulation of JAM-A expression in cultured brain EC and evaluated sJAM-A as a serum biomarker of blood-brain barrier (BBB function. METHODOLOGY/PRINCIPAL FINDINGS: As previously reported in non-CNS EC types, pro-inflammatory stimulation of primary or immortalized (hCMEC/D3 human brain microvascular EC (HBMEC induced a redistribution of cell-bound JAM-A on the cell surface away from tight junctions, along with a dissociation from the cytoskeleton. This was paralleled by reduced immunocytochemical staining of occludin and zonula occludens-1 as well as by increased paracellular permeability for dextran 3000. Both a self-developed ELISA test and Western blot analysis detected a constitutive sJAM-A release by HBMEC into culture supernatants, which importantly was unaffected by pro-inflammatory or hypoxia/reoxygenation challenge. Accordingly, serum levels of sJAM-A were unaltered in 14 patients with clinically active multiple sclerosis compared to 45 stable patients and remained unchanged in 13 patients with acute ischemic non-small vessel stroke over time. CONCLUSION: Soluble JAM-A was not suited as a biomarker of BBB breakdown in our hands. The unexpected non-inducibility of sJAM-A release at the human BBB might contribute to a particular resistance of brain EC to inflammatory stimuli, protecting the CNS compartment.

  11. Tight junctions: a barrier to the initiation and progression of breast cancer?

    LENUS (Irish Health Repository)

    Brennan, Kieran

    2010-01-01

    Breast cancer is a complex and heterogeneous disease that arises from epithelial cells lining the breast ducts and lobules. Correct adhesion between adjacent epithelial cells is important in determining the normal structure and function of epithelial tissues, and there is accumulating evidence that dysregulated cell-cell adhesion is associated with many cancers. This review will focus on one cell-cell adhesion complex, the tight junction (TJ), and summarize recent evidence that TJs may participate in breast cancer development or progression. We will first outline the protein composition of TJs and discuss the functions of the TJ complex. Secondly we will examine how alterations in these functions might facilitate breast cancer initiation or progression; by focussing on the regulatory influence of TJs on cell polarity, cell fate and cell migration. Finally we will outline how pharmacological targeting of TJ proteins may be useful in limiting breast cancer progression. Overall we hope to illustrate that the relationship between TJ alterations and breast cancer is a complex one; but that this area offers promise in uncovering fundamental mechanisms linked to breast cancer progression.

  12. Identification of neuronal and angiogenic growth factors in an in vitro blood-brain barrier model system: Relevance in barrier integrity and tight junction formation and complexity.

    Science.gov (United States)

    Freese, Christian; Hanada, Sanshiro; Fallier-Becker, Petra; Kirkpatrick, C James; Unger, Ronald E

    2017-05-01

    We previously demonstrated that the co-cultivation of endothelial cells with neural cells resulted in an improved integrity of the in vitro blood-brain barrier (BBB), and that this model could be useful to evaluate the transport properties of potential central nervous system disease drugs through the microvascular brain endothelial. In this study we have used real-time PCR, fluorescent microscopy, protein arrays and enzyme-linked immunosorbent assays to determine which neural- and endothelial cell-derived factors are produced in the co-culture and improve the integrity of the BBB. In addition, a further improvement of the BBB integrity was achieved by adjusting serum concentrations and growth factors or by the addition of brain pericytes. Under specific conditions expression of angiogenic, angiostatic and neurotrophic factors such as endostatin, pigment epithelium derived factor (PEDF/serpins-F1), tissue inhibitor of metalloproteinases (TIMP-1), and vascular endothelial cell growth factor (VEGF) closely mimicked the in vivo situation. Freeze-fracture analysis of these cultures demonstrated the quality and organization of the endothelial tight junction structures and their association to the two different lipidic leaflets of the membrane. Finally, a multi-cell culture model of the BBB with a transendothelial electrical resistance up to 371 (±15) Ω×cm(2) was developed, which may be useful for preliminary screening of drug transport across the BBB and to evaluate cellular crosstalk of cells involved in the neurovascular unit.

  13. 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

  14. 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.

  15. Volatile anesthetics influence blood-brain barrier integrity by modulation of tight junction protein expression in traumatic brain injury.

    Directory of Open Access Journals (Sweden)

    Serge C Thal

    Full Text Available Disruption of the blood-brain barrier (BBB results in cerebral edema formation, which is a major cause for high mortality after traumatic brain injury (TBI. As anesthetic care is mandatory in patients suffering from severe TBI it may be important to elucidate the effect of different anesthetics on cerebral edema formation. Tight junction proteins (TJ such as zonula occludens-1 (ZO-1 and claudin-5 (cl5 play a central role for BBB stability. First, the influence of the volatile anesthetics sevoflurane and isoflurane on in-vitro BBB integrity was investigated by quantification of the electrical resistance (TEER in murine brain endothelial monolayers and neurovascular co-cultures of the BBB. Secondly brain edema and TJ expression of ZO-1 and cl5 were measured in-vivo after exposure towards volatile anesthetics in native mice and after controlled cortical impact (CCI. In in-vitro endothelial monocultures, both anesthetics significantly reduced TEER within 24 hours after exposure. In BBB co-cultures mimicking the neurovascular unit (NVU volatile anesthetics had no impact on TEER. In healthy mice, anesthesia did not influence brain water content and TJ expression, while 24 hours after CCI brain water content increased significantly stronger with isoflurane compared to sevoflurane. In line with the brain edema data, ZO-1 expression was significantly higher in sevoflurane compared to isoflurane exposed CCI animals. Immunohistochemical analyses revealed disruption of ZO-1 at the cerebrovascular level, while cl5 was less affected in the pericontusional area. The study demonstrates that anesthetics influence brain edema formation after experimental TBI. This effect may be attributed to modulation of BBB permeability by differential TJ protein expression. Therefore, selection of anesthetics may influence the barrier function and introduce a strong bias in experimental research on pathophysiology of BBB dysfunction. Future research is required to investigate

  16. The epithelial membrane protein 1 is a novel tight junction protein of the blood-brain barrier.

    Science.gov (United States)

    Bangsow, Thorsten; Baumann, Ewa; Bangsow, Carmen; Jaeger, Martina H; Pelzer, Bernhard; Gruhn, Petra; Wolf, Sabine; von Melchner, Harald; Stanimirovic, Danica B

    2008-06-01

    In the central nervous system, a constant microenvironment required for neuronal cell activity is maintained by the blood-brain barrier (BBB). The BBB is formed by the brain microvascular endothelial cells (BMEC), which are sealed by tight junctions (TJ). To identify genes that are differentially expressed in BMEC compared with peripheral endothelial cells, we constructed a subtractive cDNA library from porcine BMEC (pBMEC) and aortic endothelial cells (AOEC). Screening the library for differentially expressed genes yielded 26 BMEC-specific transcripts, such as solute carrier family 35 member F2 (SLC35F2), ADP-ribosylation factor-like 5B (ARL5B), TSC22 domain family member 1 (TSC22D1), integral membrane protein 2A (ITM2A), and epithelial membrane protein 1 (EMP1). In this study, we show that EMP1 transcript is enriched in pBMEC compared with brain tissue and that EMP1 protein colocalizes with the TJ protein occludin in mouse BMEC by coimmunoprecipitation and in rat brain vessels by immunohistochemistry. Epithelial membrane protein 1 expression was transiently induced in laser-capture microdissected rat brain vessels after a 20-min global cerebral ischemia, in parallel with the loss of occludin immunoreactivity. The study identifies EMP1 as a novel TJ-associated protein of the BBB and suggests its potential role in the regulation of the BBB function in cerebral ischemia.

  17. Esophagogastric junction contractile integral and morphology: Two high-resolution manometry metrics of the anti-reflux barrier.

    Science.gov (United States)

    Ham, Hyoju; Cho, Yu Kyung; Lee, Han Hee; Yoon, Seung Bae; Lim, Chul-Hyun; Kim, Jin Su; Park, Jae Myung; Choi, Myung-Gyu

    2017-08-01

    We evaluated associations of esophagogastric junction (EGJ) metrics as an anti-reflux barrier with impedance-pH, endoscopic esophagitis, and lower esophageal sphincter (LES) metrics. We reviewed high-resolution manometry data from consecutive patients with gastroesophageal reflux disease (GERD) symptoms who underwent impedance-pH and endoscopy, and asymptomatic volunteers. The EGJ contractile integral (CI) was calculated as the mean contractile integral/second during three respiratory cycles. EGJ morphology was classified according to LES-crural diaphragm (CD) separation. In total, 137 patients (65 male, age 55 years) and 23 (9 male, age 33 years) controls were enrolled. Twenty-five patients had erosive reflux disease (ERD), 16 had non-erosive reflux disease (NERD), 5 had reflux hypersensitivity, and 91 were not GERD. EGJ-CI were lower in patients with GERD (22.6 [13.8-29.2] mmHg cm) than non-GERD (50.3 [31-69.9] mmHg cm, P integral showed good diagnostic accuracy with high specificity in predicting GERD. LES-CD separation is associated with an increase in acid reflux, but EGJ-CI was associated more strongly with GERD than was EGJ morphology. © 2017 Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.

  18. Fluorine plasma treatment induced deep level traps and their effect on current transportation in Al0.83In0.17N/AlN/GaN Schottky barrier diodes

    Science.gov (United States)

    Xiang, Yong; Yu, Tongjun; Ji, Cheng; Cheng, Yutian; Yang, Xuelin; Kang, Xiangning; Shen, Bo; Zhang, Guoyi

    2016-08-01

    The deep level traps and the electrical properties of fluorine plasma treated (F-treated) and non-treated Al0.83In0.17N/AlN/GaN Schottky barrier diodes (SBDs) were investigated by the temperature-dependent current-voltage (I-V) and deep level transient spectroscopy (DLTS) measurements. Three deep level traps were detected in the SBD after F-treatment at ~E c  -  0.17 eV, ~E c  -  0.27 eV and ~E c  -  1.14 eV. One of the deep level traps at ~E c  -  1.14 eV is mainly located in the Al0.83In0.17N barrier layer with a captured cross section (σ) of ~6.50  ×  10-18 cm2. This F-related deep level trap has 3-4 orders of magnitude of the larger σ and ~0.46 eV greater active energy than that of the dislocation-related one at ~E c  -  0.68 eV with σ of ~1.92  ×  10-21 cm2. Meanwhile, the leakage current of F-treated SBD at  -5 V is reduced by ~2 orders of magnitude compared with that of the non-treated one. This leakage current reduction is mainly attributed to the increase of the Poole-Frenkel emission barrier height from ~0.09 eV in non-treated SBD to ~0.46 eV in the F-treated one. It is believed that the main reverse current transportation is the Poole-Frenkel emission from the F-related deep level trap states into the continuum states of the dislocations in F-treated Al0.83In0.17N/AlN/GaN SBD.

  19. Current transport mechanism of p-GaN Schottky contacts

    Science.gov (United States)

    Shiojima, Kenji; Sugahara, Tomoya; Sakai, Shiro

    2000-12-01

    Transient measurements of I-V and depletion layer capacitance were conducted to clarify the leaky current flow mechanism in Ni Schottky contacts formed on Mg-doped p-GaN. We found that carrier capture and emission from acceptor-like deep level defects cause depletion layer width (Wdep) to vary significantly. Upon ionization of the defects by white light, which results in small Wdep, current can go through the Schottky barrier and a leaky I-V curve is observed. Upon filling by current injection, Wdep becomes larger and the large original Schottky barrier height is seen. The time constant of carrier emission is as long as 8.3×103 min.

  20. La3+、Cu2+、Fe3+/TiO2对金属-半导体表面肖特基势垒的影响%Study on the influence of La3+,Cu2+,Fe3+/TiO2 on Schottky barrier on the surface of metal-semiconductors

    Institute of Scientific and Technical Information of China (English)

    康华; 李桂春; 单志强

    2009-01-01

    分析了金属-半导体表面的接触机理及肖特基势垒的形成,探讨了离子掺杂行为对势垒的影响机理,研究了光生载流子的迁移对TiO2半导体复合材料光催化活性的影响.结果表明,不同金属基体材料对表面势垒高度的影响程度不同,同掺杂离子的表面态对金属-半导体接触的影响也有差别,离子可以改变半导体功函数,La3+、Cu2+和Fe3+在同一浓度掺杂,对半导体的功函数影响不同,使载体和离子对电子和空穴捕获能力有所差异.%The mechanisms for contact between metal and semiconductor surface and formation of Schott-ky barriers were discussed. The influence of ions-doping on the barriers and effects of e-h+ transfer on photocatalytic activity of TiO2 films were studied. The results indicated that different metal substrates had different influence on Schottky barriers;doping ions changed work function of the semiconductor; different doping ions metal with the same concentration changed work function of the semiconductor to different extent, thus changed Schottky barriers, resulting in different photocatalytic activity of TiO2 films.

  1. Ni based planar Schottky diodes on gallium nitride (GaN) grown on sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Menard, Olivier [Universite de Francois Rabelais, Laboratoire de Microelectronique de Puissance, 16 Rue Pierre et Marie Curie, BP7155, 37071 Tours (France); STMicroelectronics, 16 Rue Pierre et Marie Curie, BP7155, 37071 Tours (France); Cayrel, Frederic; Alquier, Daniel [Universite de Francois Rabelais, Laboratoire de Microelectronique de Puissance, 16 Rue Pierre et Marie Curie, BP7155, 37071 Tours (France); Collard, Emmanuel [STMicroelectronics, 16 Rue Pierre et Marie Curie, BP7155, 37071 Tours (France)

    2010-01-15

    In this work, Schottky barrier diodes (SBD), made using lift-off process, were realized on low doped n-type GaN grown by MOCVD. Schottky to Schottky structures were first realized, allowing to select convenient process parameters that reduce the leakage current, such as surface cleaning, thickness of the metallic contact and annealing time or temperature. Then, planar Schottky diodes were patterned and characterized to extract barrier height and ideality factor. Results show that good rectifying behaviour can be obtained with a 300nm thick Ni Schottky contact annealed in RTA at 450 C during 3 min under Argon. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Effect of asymmetric molecule-electrode coupling and molecular bias on rectification in molecular junctions

    Science.gov (United States)

    Kaur, Rupan Preet; Sawhney, Ravinder Singh; Engles, Derick

    2016-12-01

    In this research work, we compare the rectification trends of two symmetrical and one asymmetrical molecular junction formed with gold and silver electrodes bridging benzenedithiol molecule. The origin of rectification is attributed to both molecular bias drop and asymmetric molecule-electrode coupling. The electronic transport properties are computed by using semi-empirical extended Huckel method combined with non-equilibrium Green's function framework. The results are fully rationalized by analysing the distribution of molecular orbitals with changing bias voltage, available density of states and area of transmission spectra spanned within bias window, transmission eigenstates and transmission pathways. We deduce through this work that the molecular rectification is not only the property of asymmetric molecule-metal coupling, but molecular bias also plays vital role in stemming asymmetric I- V characteristics. Our results suggest how to realize molecular rectification by using different electrode materials which act as Schottky barriers in molecular junctions that emulate p-n junction diode in semiconductor electronics.

  3. Doping-Spike PtSi Schottky Infrared Detectors with Extended Cutoff Wavelengths

    Science.gov (United States)

    Lin, T. L.; Park, J. S.; Gunapala, S. D.; Jones, E. W.; Castillo, H. M. Del

    1994-01-01

    A technique incorporating a p+ doping spike at the silicide/Si interface to reduce the effective Schottky barrier of the silicide infrared detectors and thus extend the cutoff wavelength has been developed.

  4. A 200 GHz tripler using a single barrier varactor

    Science.gov (United States)

    Choudhury, Debabani; Frerking, Margaret A.; Batelaan, Paul D.

    1993-01-01

    The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.

  5. A 200 GHz tripler using single barrier varactor

    Science.gov (United States)

    Choudhury, Debabani; Frerking, Margaret A.; Batelaan, Paul D.

    1992-01-01

    The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has a potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.

  6. 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.

  7. 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.

  8. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Pristavu, G.; Brezeanu, G.; Badila, M. [Electronics, Telecommunications and Information Technology, University Politehnica Bucharest, Bucharest 061071 (Romania); Pascu, R. [Electronics, Telecommunications and Information Technology, University Politehnica Bucharest, Bucharest 061071 (Romania); National Institute for Research and Development in Microtechnologies, Erou Iancu Nicolae Street 126A, 077190 Bucharest (Romania); Danila, M. [National Institute for Research and Development in Microtechnologies, Erou Iancu Nicolae Street 126A, 077190 Bucharest (Romania); Godignon, P. [Centro Nacional de Microelectronica, C/del Tillers, Campus Universitat Autònoma de Barcelona, 08193 Barcelona (Spain)

    2015-06-29

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (Φ{sub Bn,l}) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured I{sub F}–V{sub F}–T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni{sub 2}Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni{sub 2}Si/4H-SiC Schottky contacts.

  9. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    Science.gov (United States)

    Pristavu, G.; Brezeanu, G.; Badila, M.; Pascu, R.; Danila, M.; Godignon, P.

    2015-06-01

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (ΦBn,l) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured IF-VF-T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni2Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni2Si/4H-SiC Schottky contacts.

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

    Institute of Scientific and Technical Information of China (English)

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

    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 tunnelhng and so on. The most remarkable finding in the present paper is that these three kinds of Sehottky diodes are revealed to have different behaviours of high-temperature reverse currents. For the n-Si Sehottky 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 AIGaN/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.

  11. SCHOTTKY MEASUREMENTS DURING RHIC 2000.

    Energy Technology Data Exchange (ETDEWEB)

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

    2001-06-18

    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.

  12. Temperature dependence of current–voltage characteristics of Au/-GaAs epitaxial Schottky diode

    Indian Academy of Sciences (India)

    R Singh; S K Arora; Renu Tyagi; S K Agarwal; D Kanjilal

    2000-12-01

    The influence of temperature on current–voltage (–) characteristics of Au/-GaAs Schottky diode formed on -GaAs epitaxial layer grown by metal organic chemical vapour deposition technique has been investigated. The dopant concentration in the epitaxial layer is 1 × 1016 cm−3 . The change in various parameters of the diode like Schottky barrier height (SBH), ideality factor and reverse breakdown voltage as a function of temperature in the range 80−300 K is presented. The variation of apparent Schottky barrier height and ideality factor with temperature has been explained considering lateral inhomogeneities in the Schottky barrier height in nanometer scale lengths at the metal–semiconductor interface.

  13. Silver nanoparticles induce tight junction disruption and astrocyte neurotoxicity in a rat blood–brain barrier primary triple coculture model

    Directory of Open Access Journals (Sweden)

    Xu L

    2015-09-01

    Full Text Available Liming Xu,1,2,* Mo Dan,1,* Anliang Shao,1 Xiang Cheng,1,3 Cuiping Zhang,4 Robert A Yokel,5 Taro Takemura,6 Nobutaka Hanagata,6 Masami Niwa,7,8 Daisuke Watanabe7,81National Institutes for Food and Drug Control, No 2, Temple of Heaven, Beijing, 2School of Information and Engineering, Wenzhou Medical University, Wenzhou, 3School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, 4Beijing Neurosurgical Institute, Capital Medical University, Beijing, People’s Republic of China; 5College of Pharmacy, University of Kentucky, Lexington, KY, USA; 6Nanotechnology Innovation Station for Nanoscale Science and Technology, National Institute for Materials Science, Tsukuba, Ibaraki, 7Department of Pharmacology, Nagasaki University, 8BBB Laboratory, PharmaCo-Cell Company, Ltd., Nagasaki, Japan*These authors contributed equally to this workBackground: Silver nanoparticles (Ag-NPs can enter the brain and induce neurotoxicity. However, the toxicity of Ag-NPs on the blood–brain barrier (BBB and the underlying mechanism(s of action on the BBB and the brain are not well understood.Method: To investigate Ag-NP suspension (Ag-NPS-induced toxicity, a triple coculture BBB model of rat brain microvascular endothelial cells, pericytes, and astrocytes was established. The BBB permeability and tight junction protein expression in response to Ag-NPS, NP-released Ag ions, and polystyrene-NP exposure were investigated. Ultrastructural changes of the microvascular endothelial cells, pericytes, and astrocytes were observed using transmission electron microscopy (TEM. Global gene expression of astrocytes was measured using a DNA microarray.Results: A triple coculture BBB model of primary rat brain microvascular endothelial cells, pericytes, and astrocytes was established, with the transendothelial electrical resistance values >200 Ω·cm2. After Ag-NPS exposure for 24 hours, the BBB permeability was significantly increased and expression of the

  14. Terahertz pulse detection by the GaAs Schottky diodes

    Science.gov (United States)

    Laperashvili, Tina; Kvitsiani, Orest; Imerlishvili, Ilia; Laperashvili, David

    2010-06-01

    We present the results of experimental studies of physical properties of the detection process of GaAs Schottky diodes for terahertz frequency radiation. The development of technology in the THz frequency band has a rapid progress recently. Considered as an extension of the microwave and millimeter wave bands, the THz frequency offers greater communication bandwidth than is available at microwave frequencies. The Schottky barrier contact has an important role in the operation of many GaAs devices. GaAs Schottky diodes have been the primary nonlinear device used in millimeter and sub millimeter wave detectors and receivers. GaAs Schottky diodes are especially interesting due to their high mobility transport characteristics, which allows for a large reduction of the resistance-capacitance (RC) time constant and thermal noise. In This work are investigated the electrical and photoelectric properties of GaAs Schottky diodes. Samples were obtained by deposition of different metals (Au, Ni, Pt, Pd, Fe, In, Ga, Al) on semiconductor. For fabrication metal-semiconductor (MS) structures is used original method of metal electrodepositing. In this method electrochemical etching of semiconductor surface occurs just before deposition of metal from the solution, which contains etching material and metal ions together. For that, semiconductor surface cleaning processes and metal deposition carries out in the same technological process. In the experiments as the electrolyte was used aqueous solution of chlorides. Metal deposition was carried out at room temperature.

  15. Rictor/mTORC2 regulates blood-testis barrier dynamics via its effects on gap junction communications and actin filament network.

    Science.gov (United States)

    Mok, Ka-Wai; Mruk, Dolores D; Lee, Will M; Cheng, C Yan

    2013-03-01

    In the mammalian testis, coexisting tight junctions (TJs), basal ectoplasmic specializations, and gap junctions (GJs), together with desmosomes near the basement membrane, constitute the blood-testis barrier (BTB). The most notable feature of the BTB, however, is the extensive network of actin filament bundles, which makes it one of the tightest blood-tissue barriers. The BTB undergoes restructuring to facilitate the transit of preleptotene spermatocytes at stage VIII-IX of the epithelial cycle. Thus, the F-actin network at the BTB undergoes cyclic reorganization via a yet-to-be explored mechanism. Rictor, the key component of mTORC2 that is known to regulate actin cytoskeleton, was shown to express stage-specifically at the BTB in the seminiferous epithelium. Its expression was down-regulated at the BTB in stage VIII-IX tubules, coinciding with BTB restructuring at these stages. Using an in vivo model, a down-regulation of rictor at the BTB was also detected during adjudin-induced BTB disruption, illustrating rictor expression is positively correlated with the status of the BTB integrity. Indeed, the knockdown of rictor by RNAi was found to perturb the Sertoli cell TJ-barrier function in vitro and the BTB integrity in vivo. This loss of barrier function was accompanied by changes in F-actin organization at the Sertoli cell BTB in vitro and in vivo, associated with a loss of interaction between actin and α-catenin or ZO-1. Rictor knockdown by RNAi was also found to impede Sertoli cell-cell GJ communication, disrupting protein distribution (e.g., occludin, ZO-1) at the BTB, illustrating that rictor is a crucial BTB regulator.

  16. SiC merged p-n/Schottky rectifiers for high voltage applications

    Energy Technology Data Exchange (ETDEWEB)

    Held, R.; Kaminski, N.; Niemann, E. [Daimler-Benz AG, Frankfurt am Main (Germany). Forschung und Technik

    1998-08-01

    A method of reducing reverse currents and increasing breakdown voltages without inducing negative effects on switching behavior in silicon carbide Schottky diodes is proved successfully. Implantation of p-regions in the surface of the n-drift region below the Schottky metal form face to face p-n junctions which screen the Schottky contact from high electrical fields. This results in a reduction of the reverse current and an increase of the breakdown voltage to the limit of a `pure` SiC p-n diode. It is shown, that in contrast to silicon based devices, SiC merged p-n/Schottky (MPS) rectifier preserve their excellent unipolar switching behavior. (orig.) 5 refs.

  17. On Chip Bioelectric Impedance Spectroscopy Reveals the Effect of P-Glycoprotein Efflux Pumps on the Paracellular Impedance of Tight Junctions at the Blood-Brain Barrier.

    Science.gov (United States)

    Kraya, Ramsey; Komin, Alexander; Searson, Peter

    2016-10-01

    Bioelectric impedance spectroscopy was used to elucidate the influence of P-gp efflux pumps on the kinetics of tight junction down-regulation in confluent monolayers of Madine Darby Canine Kidney Epithelial Cells (MDCK) following administration of phenylarsine oxide (PAO), a molecule that inhibits protein tyrosine phosphatases (PTP) and induces matrix metalloproteinase activity. Matrix metalloproteinases (MMPs) and phosphatase inhibitors induce modification of occludin tight junction proteins critical for the proper function of the blood-brain barrier. The addition of PAO to MDCKII cell lines resulted in a dramatic decrease in monolayer resistance. In contrast, MDCKII-MDR1 cells transfected with the MDR1 gene treated with PAO showed an initial decrease in monolayer resistance followed by a partial recovery and subsequent decrease. This resistance decay reversal was suppressed with the addition of the P-glycoprotein (P-gp) pump inhibitor elacridar, and is attributed to PAO efflux. These results illustrate impedance spectroscopy can be used to characterize the competing kinetics of efflux and down-regulation of tight junctions. In addition, the resistance decay reversal effect can be used to evaluate P-gp pump inhibitor efficacy.

  18. Downregulation of blood-brain barrier phenotype by proinflammatory cytokines involves NADPH oxidase-dependent ROS generation: consequences for interendothelial adherens and tight junctions.

    Directory of Open Access Journals (Sweden)

    Keith D Rochfort

    Full Text Available Blood-brain barrier (BBB dysfunction is an integral feature of neurological disorders and involves the action of multiple proinflammatory cytokines on the microvascular endothelial cells lining cerebral capillaries. There is still however, considerable ambiguity throughout the scientific literature regarding the mechanistic role(s of cytokines in this context, thereby warranting a comprehensive in vitro investigation into how different cytokines may cause dysregulation of adherens and tight junctions leading to BBB permeabilization.The present study employs human brain microvascular endothelial cells (HBMvECs to compare/contrast the effects of TNF-α and IL-6 on BBB characteristics ranging from the expression of interendothelial junction proteins (VE-cadherin, occludin and claudin-5 to endothelial monolayer permeability. The contribution of cytokine-induced NADPH oxidase activation to altered barrier phenotype was also investigated.In response to treatment with either TNF-α or IL-6 (0-100 ng/ml, 0-24 hrs, our studies consistently demonstrated significant dose- and time-dependent decreases in the expression of all interendothelial junction proteins examined, in parallel with dose- and time-dependent increases in ROS generation and HBMvEC permeability. Increased expression and co-association of gp91 and p47, pivotal NADPH oxidase subunits, was also observed in response to either cytokine. Finally, cytokine-dependent effects on junctional protein expression, ROS generation and endothelial permeability could all be attenuated to a comparable extent using a range of antioxidant strategies, which included ROS depleting agents (superoxide dismutase, catalase, N-acetylcysteine, apocynin and targeted NADPH oxidase blockade (gp91 and p47 siRNA, NSC23766.A timely and wide-ranging investigation comparing the permeabilizing actions of TNF-α and IL-6 in HBMvECs is presented, in which we demonstrate how either cytokine can similarly downregulate the

  19. Quantum size effects on spin-transfer torque in a double barrier magnetic tunnel junction with a nonmagnetic-metal (semiconductor) spacer

    Energy Technology Data Exchange (ETDEWEB)

    Daqiq, Reza; Ghobadi, Nader

    2016-07-15

    We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching. - Highlights: • The quantum size effects are studied in double barrier magnetic tunnel junctions. • Spin torque (ST) components oscillate for increasing of middle spacer thicknesses. • Due to the resonant tunneling in the quantum well, oscillations have appeared. • By replacement a metal spacer with a semiconductor (ZnO) ST has increased. • The ST components vs. bias show gradually decreasing unlike spin valves or MTJs.

  20. Capacitance-frequency Spectrum Characterization of Organics/Metal Schottky Diodes

    Institute of Scientific and Technical Information of China (English)

    GUO Wen-ge; ZHANG Yan-cao; ZHANG Shou-gang

    2006-01-01

    An organics/metal Schottky diode is fabricated using 3, 4∶9, 10-perylenetetracarboxylic-dianhydride(PTCDA) thin film sandwiched between ITO and Au by simple thermal evaporation technique. The current-voltage(I-V) characteristics are investigated at room temperature in open air. The results show the rectification ratio is in excess of 100. From the capacitance-frequency(C-f) and capacitance-voltage(C-V) measurements, the Schottky barrier height between 0.2~0.3 eV is obtained according to standard Schottky theory.

  1. Relationship of gelatinases-tight junction proteins and blood-brain barrier permeability in the early stage of cerebral ischemia and reperfusion

    Institute of Scientific and Technical Information of China (English)

    Haolin Xin; Wenzhao Liang; Jing Mang; Lina Lin; Na Guo; Feng Zhang; Zhongxin Xu

    2012-01-01

    Gelatinases matrix metalloproteinase-2 and matrix metalloproteinase-9 have been shown to mediate claudin-5 and occludin degradation, and play an important regulatory role in blood-brain barrier permeability. This study established a rat model of 1.5-hour middle cerebral artery occlusion with reperfusion. Protein expression levels of claudin-5 and occludin gradually decreased in the early stage of reperfusion, which corresponded to the increase of the gelatinolytic activity of matrix metalloproteinase-2 and matrix metalloproteinase-9. In addition, rats that received treatment with matrix metalloproteinase inhibitor N-[(2R)-2-(hydroxamidocarbonylmethyl)-4-methylpenthanoyl]-L- tryptophan methylamide (GM6001) showed a significant reduction in Evans blue leakage and an inhibition of claudin-5 and occludin protein degradation in striatal tissue. These data indicate that matrix metalloproteinase-2 and matrix metalloproteinase-9-mediated claudin-5 and occludin degradation is an important reason for blood-brain barrier leakage in the early stage of reperfusion. The leakage of the blood-brain barrier was present due to gelatinases-mediated degradation of claudin-5 and occludin proteins. We hypothesized that the timely closure of the structural component of the blood-brain barrier (tight junction proteins) is of importance.

  2. Fabrication of Ni/Ti/Al Schottky contact to n-type 4H-SiC under various annealing conditions

    Science.gov (United States)

    Yousuf Zaman, M.; Ferrero, S.; Perrone, D.; Scaltrito, L.; Shahzad, N.; Pugliese, D.

    2013-06-01

    Forward I-V characteristics of a silicon carbide Schottky diode, with triple layer metallization Ni/Ti/Al as Schottky contact, are presented. Effects of different annealing conditions on the Schottky barrier height and ideality factor are discussed. The diodes were annealed in inert Ar atmosphere for 30 minutes at temperatures ranging from 600 °C to 800 °C. The ideality factors of the four diodes, chosen out of 20 diodes, range from 1.02 to 1.13 and the Schottky barrier heights range from 1.47 eV to 3.17 eV.

  3. Differential distribution of tight junction proteins suggests a role for tanycytes in blood-hypothalamus barrier regulation in the adult mouse brain.

    Science.gov (United States)

    Mullier, Amandine; Bouret, Sebastien G; Prevot, Vincent; Dehouck, Bénédicte

    2010-04-01

    The median eminence is one of the seven so-called circumventricular organs. It is located in the basal hypothalamus, ventral to the third ventricle and adjacent to the arcuate nucleus. This structure characteristically contains a rich capillary plexus and features a fenestrated endothelium, making it a direct target of blood-borne molecules. The median eminence also contains highly specialized ependymal cells called tanycytes, which line the floor of the third ventricle. It has been hypothesized that one of the functions of these cells is to create a barrier that prevents substances in the portal capillary spaces from entering the brain. In this paper, we utilize immunohistochemistry to study the expression of tight junction proteins in the cells that compose the median eminence in adult mice. Our results indicate that tanycytes of the median eminence express occludin, ZO-1, and claudin 1 and 5, but not claudin 3. Remarkably, these molecules are organized as a continuous belt around the cell bodies of the tanycytes that line the ventral part of the third ventricle. In contrast, the tanycytes at the periphery of the arcuate nucleus do not express claudin 1 and instead exhibit a disorganized expression pattern of occludin, ZO-1, and claudin 5. Consistent with these observations, permeability studies using peripheral or central injections of Evans blue dye show that only the tanycytes of the median eminence are joined at their apices by functional tight junctions, whereas tanycytes located at the level of the arcuate nucleus form a permeable layer. In conclusion, this study reveals a unique expression pattern of tight junction proteins in hypothalamic tanycytes, which yields new insights into their barrier properties.

  4. Loss of occludin expression and impairment of blood-testis barrier permeability in rats with autoimmune orchitis: effect of interleukin 6 on Sertoli cell tight junctions.

    Science.gov (United States)

    Pérez, Cecilia Valeria; Sobarzo, Cristian Marcelo; Jacobo, Patricia Verónica; Pellizzari, Eliana Herminia; Cigorraga, Selva Beatriz; Denduchis, Berta; Lustig, Livia

    2012-11-01

    Inflammation of the male reproductive tract is accepted as being an important etiological factor of infertility. Experimental autoimmune orchitis (EAO) is characterized by interstitial lymphomononuclear cell infiltration and severe damage of seminiferous tubules with germ cells that undergo apoptosis and sloughing. Because the blood-testis barrier (BTB) is relevant for the protection of haploid germ cells against immune attack, the aim of this study was to analyze BTB permeability and the expression of tight junction proteins (occludin, claudin 11, and tight junction protein 1 [TJP1]) in rats during development of autoimmune orchitis. The role of IL6 as modulator of tight junction dynamics was also evaluated because intratesticular content of this cytokine is increased in EAO rats. Orchitis was induced in Sprague-Dawley adult rats by active immunization with testicular homogenate and adjuvants. Control rats (C) were injected with saline solution and adjuvants. Untreated (N) rats were also studied. Concomitant with early signs of germ cell sloughing, a reduced expression of occludin and delocalization of claudin 11 and TJP1 were detected in the testes of rats with EAO compared to C and N groups. The use of tracers showed increased BTB permeability in EAO rats. Intratesticular injection of IL6 induced focal testicular inflammation, which is associated with damaged seminiferous tubules. Rat Sertoli cells cultured in the presence of IL6 exhibited a redistribution of tight junction proteins and reduced transepithelial electrical resistance. These data indicate the possibility that IL6 might be involved in the downregulation of occludin expression and in the modulation of BTB permeability that occur in rats undergoing autoimmune orchitis.

  5. Double exponential I-V characteristics and double Gaussian distribution of barrier heights in (Au/Ti)/Al2O3/ n-GaAs (MIS)-type Schottky barrier diodes in wide temperature range

    Science.gov (United States)

    Güçlü, Çiğdem Ş.; Özdemir, Ahmet Faruk; Altindal, Şemsettin

    2016-12-01

    In this study, current conduction mechanisms of the sample (Au/Ti)/Al2O3/ n-GaAs were investigated in detail using current-voltage (I-V) measurements in the temperature range of 80-380 K. The semilogarithmic I-V plots reveal two distinct linear regions with different slopes between 0.07-0.30 and 0.30-0.69 V which are called as Region I (RI) and Region II (RII), respectively. The ideality factor ( n) and zero-bias barrier height (Φ_{{bo}}) were found to be strong functions of temperature and voltage. In both regions, as the temperature increases, Φ_{{bo}} increases, whereas the value of n decreases. The high value of n at low temperatures is an evidence of deviation from thermionic emission, and it cannot be explained solely by tunneling mechanism, the existence of surface states and interfacial layer. Therefore, the Φ_{{bo}} versus q/kT plots were drawn for two linear regions of lnI-V plots, and these plots also revealed two distinct linear regions with different slopes between two temperature regions of 80-170 and 200-380 K which are called as low- and high-temperature range (LTR and HTR), respectively. Such behavior of these plots confirmed the existence of double Gaussian distribution (DGD) in the samples which in turn has mean barrier heights bar{Φ}_{{bo}} and standard deviations ( σ s). These values were obtained from the intercept and slope of these plots as 0.38 eV and 0.061 V for LTR and as 0.88 eV and 0.142 V for HTR (in RI), whereas they were obtained as 0.37 eV and 0.061 V for LTR and as 0.92 eV and 0.148 V for HTR (in RII), respectively. Thus, the modified ln( I s/ T 2)- q 2 σ s 2 /2 k 2 T 2 versus q/ kT plots were drawn, and the values of (bar{Φ}_{{bo}}) and effective Richardson constant ( A *) were extracted from the intercept and slope of these plots as 0.39 eV and 7.07 A/cm2 K2 for LTR and as 0.92 eV and 8.158 A/cm2 K2 for HTR (in RI), whereas they were extracted as 0.38 eV and 7.92 A/cm2 K2 for LTR and as 0.94 eV and 4.66 A/cm2 K2 for HTR

  6. 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.

  7. Polymer/metal hybrid multilayers modified Schottky devices

    Energy Technology Data Exchange (ETDEWEB)

    Torrisi, V.; Isgrò, G.; Li Destri, G.; Marletta, G. [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemical Sciences, University of Catania and CSGI, Viale A. Doria 6, 95125 Catania (Italy); Ruffino, F.; Grimaldi, M. G. [Dipartimento di Fisica ed Astronomia-Università di Catania, via S. Sofia 64, 95123 Catania (Italy); MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy); Crupi, I. [MATIS IMM-CNR, via S. Sofia 64, 95123 Catania (Italy)

    2013-11-04

    Insulating, polymethylmethacrylate (PMMA), and semiconducting, poly(3-hexylthiophene) (P3HT), nanometer thick polymers/Au nanoparticles based hybrid multilayers (HyMLs) were fabricated on p-Si single-crystal substrate. An iterative method, which involves, respectively, spin-coating (PMMA and P3HT deposition) and sputtering (Au nanoparticles deposition) techniques to prepare Au/HyMLs/p-Si Schottky device, was used. The barrier height and the ideality factor of the Au/HyMLs/p-Si Schottky devices were investigated by current-voltage measurements in the thickness range of 1–5 bilayers. It was observed that the barrier height of such hybrid layered systems can be tuned as a function of bilayers number and its evolution was quantified and analyzed.

  8. A new route for the synthesis of graphene oxide–Fe{sub 3}O{sub 4} (GO–Fe{sub 3}O{sub 4}) nanocomposites and their Schottky diode applications

    Energy Technology Data Exchange (ETDEWEB)

    Metin, Önder [Department of Chemistry, Faculty of Science, Atatürk University, 25240 Erzurum (Turkey); Aydoğan, Şakir [Department of Physics, Faculty of Science, Atatürk University, 25240 Erzurum (Turkey); Meral, Kadem, E-mail: kademm@atauni.edu.tr [Department of Chemistry, Faculty of Science, Atatürk University, 25240 Erzurum (Turkey)

    2014-02-05

    Highlights: • Graphene Oxide (GO)–Fe{sub 3}O{sub 4} nanocomposites were prepared by a novel and facile method. • The successful assembly of Fe{sub 3}O{sub 4} NPs onto GO sheets was displayed by TEM. • The GO–Fe{sub 3}O{sub 4} nanocomposites/p-Si junction showed good rectifying property. -- Abstract: Addressed herein is a facile method for the preparation of magnetic graphene oxide–Fe{sub 3}O{sub 4} (GO–Fe{sub 3}O{sub 4}) nanocomposites and the rectifying properties of (GO–Fe{sub 3}O{sub 4})/p-Si junction in a Schottky diode. GO–Fe{sub 3}O{sub 4} nanocomposites were prepared by a novel method in which as-prepared GO sheets were decorated with the monodisperse Fe{sub 3}O{sub 4} nanoparticles (NPs) in dimethylformamide/chloroform mixture via a sonication process. The successful assembly of Fe{sub 3}O{sub 4} NPs onto GO sheets was displayed by transmission electron microscopy (TEM). Inductively couple plasma optical emission spectroscopy (ICP-OES) analysis of the GO–Fe{sub 3}O{sub 4} nanocomposite showed that the nanocomposite consists of 20.1 wt% Fe{sub 3}O{sub 4} NPs which provides a specific saturation magnetization (Ms) as 16 emu/g. The current–voltage (I–V) characteristics of the (GO–Fe{sub 3}O{sub 4})/p-Si junction in a Schottky diode were studied in the temperature range of 50–350 K in the steps of 25 K. It was determined that the barrier height and ideality factor of the Au/GO–Fe{sub 3}O{sub 4}/p-Si/Al Schottky diode were depended on temperature as the barrier height increased while the ideality factor decreased with increasing temperature. The experimental values of barrier height and ideality factor were varied from 0.12 eV and 11.24 at 50 K to 0.76 eV and 2.49 at 350 K, respectively. The Richardson plot exhibited non-linearity at low temperatures that was attributed to the barrier inhomogeneities prevailing at the GO–Fe{sub 3}O{sub 4}/p-Si junction.

  9. Air pollution and children: neural and tight junction antibodies and combustion metals, the role of barrier breakdown and brain immunity in neurodegeneration.

    Science.gov (United States)

    Calderón-Garcidueñas, Lilian; Vojdani, Aristo; Blaurock-Busch, Eleonore; Busch, Yvette; Friedle, Albrecht; Franco-Lira, Maricela; Sarathi-Mukherjee, Partha; Martínez-Aguirre, Xavier; Park, Su-Bin; Torres-Jardón, Ricardo; D'Angiulli, Amedeo

    2015-01-01

    Millions of children are exposed to concentrations of air pollutants, including fine particulate matter (PM2.5), above safety standards. In the Mexico City Metropolitan Area (MCMA) megacity, children show an early brain imbalance in oxidative stress, inflammation, innate and adaptive immune response-associated genes, and blood-brain barrier breakdown. We investigated serum and cerebrospinal fluid (CSF) antibodies to neural and tight junction proteins and environmental pollutants in 139 children ages 11.91 ± 4.2 y with high versus low air pollution exposures. We also measured metals in serum and CSF. MCMA children showed significantly higher serum actin IgG, occludin/zonulin 1 IgA, IgG, myelin oligodendrocyte glycoprotein IgG and IgM (p brain barrier. Defining the air pollution linkage of the brain/immune system interactions and damage to physical and immunological barriers with short and long term neural detrimental effects to children's brains ought to be of pressing importance for public health.

  10. Magnetic tunnel junctions (MTJs)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We review the giant tunnel magnetoresistance (TMR) in ferromagnetic-insulator-ferromagnetic junctions discovered in recent years, which is the magnetoresistance (MR) associated with the spin-dependent tunneling between two ferromagnetic metal films separated by an insulating thin tunnel barrier. The theoretical and experimental results including junction conductance, magnetoresistance and their temperature and bias dependences are described.

  11. Longitudinal peak detected Schottky spectrum

    CERN Document Server

    Shaposhnikova, E

    2009-01-01

    The "peak detected Schottky" spectrum is a diagnostic used since the late seventies for beam observation in the SPS and now already applied to the LHC. This tool was always believed, however without proof, to give a good picture of the particle distribution in synchrotron frequencies similar to the longitudinal Schottky spectrum of unbunched beam for revolution frequencies.In this paper an analysis of this measurement technique is presented both in a general form and for the particular realisation in the SPS. In addition the limitations of the present experimental set-up are discussed together with possible improvements. The analysis shows that for an optimised experimental set-up the spectrum of the peak detected signal is very close to the synchrotron frequency distribution inside the bunch - much closer than that given by the traditional longitudinal bunched-beam Schottky spectrum.

  12. Ablation of CD11c(hi) dendritic cells exacerbates Japanese encephalitis by regulating blood-brain barrier permeability and altering tight junction/adhesion molecules.

    Science.gov (United States)

    Kim, Jin Hyoung; Hossain, Ferdaus Mohd Altaf; Patil, Ajit Mahadev; Choi, Jin Young; Kim, Seong Bum; Uyangaa, Erdenebelig; Park, Sang-Youel; Lee, John-Hwa; Kim, Bumseok; Kim, Koanhoi; Eo, Seong Kug

    2016-10-01

    Japanese encephalitis (JE), characterized by extensive neuroinflammation following infection with neurotropic JE virus (JEV), is becoming a leading cause of viral encephalitis due to rapid changes in climate and demography. The blood-brain barrier (BBB) plays an important role in restricting neuroinvasion of peripheral leukocytes and virus, thereby regulating the progression of viral encephalitis. In this study, we explored the role of CD11c(hi) dendritic cells (DCs) in regulating BBB integrity and JE progression using a conditional depletion model of CD11c(hi) DCs. Transient ablation of CD11c(hi) DCs resulted in markedly increased susceptibility to JE progression along with highly increased neuro-invasion of JEV. In addition, exacerbated JE progression in CD11c(hi) DC-ablated hosts was closely associated with increased expression of proinflammatory cytokines (IFN-β, IL-6, and TNF-α) and CC chemokines (CCL2, CCL3, CXCL2) in the brain. Moreover, our results revealed that the exacerbation of JE progression in CD11c(hi) DC-ablated hosts was correlated with enhanced BBB permeability and reduced expression of tight junction and adhesion molecules (claudin-5, ZO-1, occluding, JAMs). Ultimately, our data conclude that the ablation of CD11c(hi) DCs provided a subsidiary impact on BBB integrity and the expression of tight junction/adhesion molecules, thereby leading to exacerbated JE progression. These findings provide insight into the secondary role of CD11c(hi) DCs in JE progression through regulation of BBB integrity and the expression of tight junction/adhesion molecules.

  13. First-principles study on magnetic tunneling junctions with semiconducting CuInSe2 and CuGaSe2 barriers

    Science.gov (United States)

    Masuda, Keisuke; Miura, Yoshio

    2017-02-01

    We theoretically investigate two magnetic tunneling junctions (MTJs) with different semiconductor barriers, CuInSe2 (CIS) and CuGaSe2 (CGS), sandwiched between Fe electrodes. We find that Δ1 wave functions provide dominant contributions to spin-dependent tunneling transport in both CIS- and CGS-based MTJs. We also find that the CGS-based MTJ has a much higher magnetoresistive (MR) ratio than the CIS-based MTJ, which indicates that a higher MR ratio is expected for a higher Ga concentration x in the recently reported CuIn1- x Ga x Se2-based MTJs. Furthermore, we show that the CIS- and CGS-based MTJs have much smaller resistance-area products (RA) than the conventional MgO-based MTJs.

  14. Quantum size effects on spin-transfer torque in a double barrier magnetic tunnel junction with a nonmagnetic-metal (semiconductor) spacer

    Science.gov (United States)

    Daqiq, Reza; Ghobadi, Nader

    2016-07-01

    We study the quantum size effects of an MgO-based double barrier magnetic tunnel junction with a nonmagnetic-metal (DBMTJ-NM) (semiconductor (DBMTJ-SC)) spacer on the charge current and the spin-transfer torque (STT) components using non-equilibrium Green's function (NEGF) formalism. The results show oscillatory behavior due to the resonant tunneling effect depending on the structure parameters. We find that the charge current and the STT components in the DBMTJ-SC demonstrate the magnitude enhancement in comparison with the DBMTJ-NM. The bias dependence of the STT components in a DBMTJ-NM shows different behavior in comparison with spin valves and conventional MTJs. Therefore, by choosing a specific SC spacer with suitable thickness in a DBMTJ the charge current and the STT components significantly increase so that one can design a device with high STT and faster magnetization switching.

  15. Real-time acquisition of transendothelial electrical resistance in an all-human, in vitro, 3-dimensional, blood-brain barrier model exemplifies tight-junction integrity.

    Science.gov (United States)

    Maherally, Zaynah; Fillmore, Helen L; Tan, Sim Ling; Tan, Suk Fei; Jassam, Samah A; Quack, Friederike I; Hatherell, Kathryn E; Pilkington, Geoffrey J

    2017-09-07

    The blood-brain barrier (BBB) consists of endothelial cells, astrocytes, and pericytes embedded in basal lamina (BL). Most in vitro models use nonhuman, monolayer cultures for therapeutic-delivery studies, relying on transendothelial electrical resistance (TEER) measurements without other tight-junction (TJ) formation parameters. We aimed to develop reliable, reproducible, in vitro 3-dimensional (3D) models incorporating relevant human, in vivo cell types and BL proteins. The 3D BBB models were constructed with human brain endothelial cells, human astrocytes, and human brain pericytes in mono-, co-, and tricultures. TEER was measured in 3D models using a volt/ohmmeter and cellZscope. Influence of BL proteins-laminin, fibronectin, collagen type IV, agrin, and perlecan-on adhesion and TEER was assessed using an electric cell-substrate impedance-sensing system. TJ protein expression was assessed by Western blotting (WB) and immunocytochemistry (ICC). Perlecan (10 µg/ml) evoked unreportedly high, in vitro TEER values (1200 Ω) and the strongest adhesion. Coculturing endothelial cells with astrocytes yielded the greatest resistance over time. ICC and WB results correlated with resistance levels, with evidence of prominent occludin expression in cocultures. BL proteins exerted differential effects on TEER, whereas astrocytes in contact yielded higher TEER values and TJ expression.-Maherally, Z., Fillmore, H. L., Tan, S. L., Tan, S. F., Jassam, S. A., Quack, F. I., Hatherell, K. E., Pilkington, G. J. Real-time acquisition of transendothelial electrical resistance in an all-human, in vitro, 3-dimensional, blood-brain barrier model exemplifies tight-junction integrity. © FASEB.

  16. Semiconductor systems utilizing materials that form rectifying junctions in both N and P-type doping regions, whether metallurgically or field induced, and methods of use

    Science.gov (United States)

    Welch, James D.

    2000-01-01

    Disclosed are semiconductor systems, such as integrated circuits utilizing Schotky barrier and/or diffused junction technology, which semiconductor systems incorporate material(s) that form rectifying junctions in both metallurgically and/or field induced N and P-type doping regions, and methods of their use. Disclosed are Schottky barrier based inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems and which can be operated as modulators, N and P-channel MOSFETS and CMOS formed therefrom, and (MOS) gate voltage controlled rectification direction and gate voltage controlled switching devices, and use of such material(s) to block parasitic current flow pathways. Simple demonstrative five mask fabrication procedures for inverting and non-inverting gate voltage channel induced semiconductor single devices with operating characteristics similar to multiple device CMOS systems are also presented.

  17. Engineering of contact resistance between transparent single-walled carbon nanotube films and a-Si:H single junction solar cells by gold nanodots.

    Science.gov (United States)

    Kim, Jeehwan; Hong, Augustin J; Chandra, Bhupesh; Tulevski, George S; Sadana, Devendra K

    2012-04-10

    The viability of single-walled carbon nanotubes (SWCNTs) as a transparent conducting electrode on a-Si:H based single junction solar cells was explored. A Schottky barrier formed at a SWCNT/a-Si:H interface was removed by introducing high work function gold nanodots at the SWCNT/a-Si:H interface. This allows comparable device performance from SWCNT-electrode-based a-Si:H solar cells to that obtained by using conventional transparent conducting oxides. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Observation of quantum oscillation of work function in ultrathin-metal/semiconductor junctions

    Energy Technology Data Exchange (ETDEWEB)

    Takhar, Kuldeep; Meer, Mudassar; Khachariya, Dolar; Ganguly, Swaroop; Saha, Dipankar, E-mail: dipankarsaha@iitb.ac.in [Applied Quantum Mechanics Laboratory, Centre of Excellence in Nanoelectronics, Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076 (India)

    2015-09-15

    Quantization in energy level due to confinement is generally observed for semiconductors. This property is used for various quantum devices, and it helps to improve the characteristics of conventional devices. Here, the authors have demonstrated the quantum size effects in ultrathin metal (Ni) layers sandwiched between two large band-gap materials. The metal work function is found to oscillate as a function of its thickness. The thermionic emission current bears the signature of the oscillating work function, which has a linear relationship with barrier heights. This methodology allows direct observation of quantum oscillations in metals at room temperature using a Schottky diode and electrical measurements using source-measure-units. The observed phenomena can provide additional mechanism to tune the barrier height of metal/semiconductor junctions, which are used for various electronic devices.

  19. (In,Sn)2O3/TiO2/Pt Schottky-type diode switch for the TiO2 resistive switching memory array

    Science.gov (United States)

    Shin, Yong Cheol; Song, Jaewon; Kim, Kyung Min; Choi, Byung Joon; Choi, Seol; Lee, Hyun Ju; Kim, Gun Hwan; Eom, Taeyong; Hwang, Cheol Seong

    2008-04-01

    A Schottky-type diode switch consisting of a Pt /(In,Sn)2O3/TiO2/Pt stack was fabricated for applications to cross-bar type resistive-switching memory arrays. The high (0.55eV) and low potential barrier at the TiO2/Pt and TiO2/(In,Sn)2O3 junctions, respectively, constitute the rectifying properties of the stacked structure. The forward/reverse current ratio was as high as ˜1.6×104 at an applied voltage of ˜1V. When Pt /TiO2/Pt memory was connected to this diode in series, there was an insignificant interference on the memory function from the diode under the forward bias and virtually no resistive switching under a reverse bias.

  20. Schottky bipolar I-MOS: An I-MOS with Schottky electrodes and an open-base BJT configuration for reduced operating voltage

    Science.gov (United States)

    Kannan, N.; Kumar, M. Jagadesh

    2017-04-01

    In this paper, we have proposed a novel impact ionization MOS (I-MOS) structure, called the Schottky bipolar I-MOS, with Schottky source and drain electrodes and utilizing the open-base bipolar junction transistor (BJT) configuration for achieving reduction in the operating voltage of the I-MOS transistor. We report, using 2-D simulations, a low operating voltage (∼1.1 V) and a low subthreshold swing (∼3.6 mV/Decade). For the corresponding p-i-n I-MOS, the operating voltage is ∼5.5 V. The operating voltage of the Schottky bipolar I-MOS is the lowest reported operating voltage for silicon based I-MOS transistors. The nearly 80% reduction in the operating voltage of the Schottky bipolar I-MOS makes it suitable for applications requiring low operating voltages. The Schottky bipolar I-MOS is also expected to have an improved reliability over the p-i-n I-MOS since high energy carriers, induced by impact ionization near the drain, do not have to pass under the gate region in the channel. The use of Schottky contacts instead of heavily doped source and drain regions and the low channel doping level reduces the required thermal budget for device fabrication. The low operating voltage, low subthreshold swing and possibly improved reliability of the Schottky bipolar I-MOS, makes it a potential solution for applications where steep subthreshold slope transistors are being explored as alternative to the conventional MOS transistor.

  1. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    Science.gov (United States)

    Patel, Malkeshkumar; Kim, Hong-Sik; Park, Hyeong-Ho; Kim, Joondong

    2016-04-01

    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-1) and detectivity (2.75 × 1015 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.

  2. E. coli O124 K72 alters the intestinal barrier and the tight junctions proteins of guinea pig intestine.

    Science.gov (United States)

    Ren, Xiaomeng; Zhu, Yanyan; Gamallat, Yaser; Ma, Shenhao; Chiwala, Gift; Meyiah, Abdo; Xin, Yi

    2017-10-01

    Our research group previously isolated and identified a strain of pathogenic Escherichia coli from clinical samples called E. coli O124 K72. The present study was aimed at determining the potential effects of E. coli O124 K72 on intestinal barrier functions and structural proteins integrity in guinea pig. Guinea pigs were grouped into three groups; control (CG); E. coli O124 K72 (E. coli); and probiotics Lactobacillus rhamnosus (LGG). Initially, we create intestinal dysbiosis by giving all animals Levofloxacin for 10days, but the control group (CG) received the same volume of saline. Then, the animals received either E. coli O124 K72 (E. coli) or Lactobacillus rhamnosus (LGG) according to their assigned group. E. coli O124 K72 treatment significantly affected colon morphology and distorted intestinal barrier function by up-regulating Claudin2 and down-regulating Occludin. In addition, E. coli upregulated the mRNA expression of MUC1, MUC2, MUC13 and MUC15. Furthermore, suspected tumor was found in the E. coli treated animals. Our results suggested that E. coli O124 K72 strain has adverse effects on intestinal barrier functions and is capable of altering integrity of structural proteins in guinea pig model while at same time it may have a role in colon carcinogenesis. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Rajiv K. Pandey

    2013-12-01

    Full Text Available 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.

  4. Nanocrystalline Zn{sub 1−x}Mn{sub x}O thin film based transparent Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Gayen, R.N. [Department of Physics, Presidency University, Kolkata 700073 (India); Paul, R., E-mail: rajiv2008juniv@gmail.com [Birck Nanotechnology Center, Purdue University, IN 47907 (United States)

    2016-04-30

    Highly transparent and nanocrystalline Zn{sub 1−x}Mn{sub x}O (x = 0, 0.008, 0.017, 0.046) thin films have been synthesized by sol–gel spin coating technique on glass and SnO{sub 2} coated glass substrates. The microstructural and compositional analyses confirm the incorporation of Mn in hexagonal ZnO lattice without affecting its structure. Zn{sub 1−x}Mn{sub x}O thin films are highly transparent in the visible region of electromagnetic spectrum. The optical band gap, estimated from the transmittance spectra, decreases from 3.32 to 3.21 eV with the increase in Mn content in ZnO films. Photoluminescence study reveals that Mn introduces more defects in ZnO suppressing the excitonic recombination by the defect center (oxygen vacancy) induced recombination. The non-linear current–voltage characteristics at room temperature reveal Schottky barrier junction formation of Zn{sub 1−x}Mn{sub x}O films with Ag. The diode parameters, extracted from the thermionic emission model, vary with Mn incorporation in ZnO. Both the ideality factor and potential barrier height decrease from 6.5 and 0.63 for pure ZnO to 4.7 and 0.54 respectively, for Zn{sub 0.954}Mn{sub 0.046}O film. The series resistance that arises from the defect distributions at the interface and effects the charge transport through the junction, also decreases for higher percentage of Mn in Zn{sub 1−x}Mn{sub x}O thin films. - Highlights: • Mn doped transparent ZnO thin film synthesis using sol–gel spin coating • Particle size and optical band-gap decreases with increasing Mn doping. • Absence of any secondary phase upto 4.6 at.% of Mn which substitutes Zn sites in ZnO lattice • Interesting Schottky diode characteristics with Ag contact • Ideality factor and barrier height decreases with increasing Mn content.

  5. Electrical parameters and current conduction mechanism in Cr/Au/n-InP Schottky structure at different annealing temperatures

    Science.gov (United States)

    Reddy, M. Bhaskar; Padma, R.; Reddy, V. Rajagopal

    2015-06-01

    Cr/Au/n-InP Schottky structures are fabricated and their electrical characteristics are investigated at different annealing temperatures. As-deposited Cr/Au/n-InP Schottky diode exhibits a barrier height of 0.51 eV (I-V) and 0.64 eV (C-V), which increases to 0.63 eV (I-V) and 0.75 eV (C-V) after annealing at 100 °C. A maximum barrier height of 0.71 eV (I-V) and 0.81 eV (C-V) is achieved for the Cr/Au Schottky contacts after annealing at 200 °C. Further, it is observed that the Schottky barrier height slightly decreases upon annealing at temperature of 300 °C and the obtained values are 0.58 eV (I-V), 0.69 eV (C-V). The reverse-bias leakage current mechanism of Cr/Au/n-InP Schottky barrier diode is investigated. Investigations reveal that the Schottky emission is the dominant mechanism and the Poole-Frenkel emission occurs only in the high voltage region.

  6. Structural analysis of SiC Schottky diodes failure mechanism under current overload

    Science.gov (United States)

    León, J.; Berthou, M.; Perpiñà, X.; Banu, V.; Montserrat, J.; Vellvehi, M.; Godignon, P.; Jordà, X.

    2014-02-01

    1.2 kV-10 A tungsten Schottky diodes (W-SBD) have been aged and tested at limit under current overload (surge current pulses) to determine their structural weakest spots. All devices showed no ageing at 40 A amplitudes and a surge current capability higher than 60 A. Infrared lock-in measurements have located the weakest spots on the surface of failed chips and allowed us to non-invasively infer their origin: Schottky barrier modification by metal contact change. After, a focused ion beam coupled with scanning electron microscope has been used to analyse the physical signature at these locations. These inspections have revealed that the destruction mechanism responsible for their failure was the electromigration and thermomigration of tungsten into aluminum, locally modifying the electrical behaviour of the Schottky barrier (loss of blocking capability).

  7. ALD grown bilayer junction of ZnO:Al and tunnel oxide barrier for SIS solar cell☆

    Science.gov (United States)

    Bethge, O.; Nobile, M.; Abermann, S.; Glaser, M.; Bertagnolli, E.

    2013-01-01

    Various metal oxides are probed as extrinsic thin tunnel barriers in Semiconductor Insulator Semiconductor solar cells. Namely Al2O3, ZrO2, Y2O3, and La2O3 thin films are in between n-type ZnO:Al (AZO) and p-type Si substrates by means of Atomic Layer Deposition. Low reverse dark current–density as low as 3×10−7 A/cm2, a fill factor up to 71.3%, and open-circuit voltage as high as 527 mV are obtained, achieving conversion efficiency of 8% for the rare earth oxide La2O3. ZrO2 and notably Al2O3 show drawbacks in performance suggesting an adverse reactivity with AZO as also indicated by X-ray Photoelectron Spectroscopy. PMID:26877596

  8. Current Transport in Copper Schottky Contacts to a-Plane/c-Plane n-Type MoSe2

    Institute of Scientific and Technical Information of China (English)

    C. K. Sumesh; K. D. Patel; V. M. Pathak; R. Srivastav

    2011-01-01

    @@ We identically prepared Cu-nMoSe2(a-plane) and Cu-nMoSe2(c-plane) Schottky barrier diodes(SBDs) on the same n-type MoSe2 single crystal.The effective Schottky barrier heights(SBHs) and ideality factors were obtained from the current-voltage-temperature(I-V-T) characteristics.The barrier height and ideality factor,estimated from the conventional thermionic emission model by assuming a Gaussian barrier distribution, are highly dependent on temperature.A notable deviation from the theoretical Richardson constant value is also observed in the conventional Richardson plot.The decrease in the experimental barrier height φBO and an increase in the ideality factor n with a decrease in temperature have been explained on the basis of barrier height inhomogeneities at the metal-semiconductor interface.It is proven that the presence of a distribution of barrier heights is responsible for the apparent decrease of the zero bias barrier height.The voltage dependence of the standard deviation causes the increase of the ideality factor at low temperatures.The value of the Richardson constant obtained without considering the inhomogeneous barrier heights is much closer than the theoretical value.The Cu-nMoSe2(a-plane) Schottky diode shows better results in comparison with the nMoSe2(c-plane)Schottky diode.

  9. The comparison of electrical characteristics of Au/n-InP/In and Au/In{sub 2}S{sub 3}/n-InP/In junctions at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Çakıcı, T.; Sağlam, M., E-mail: msaglam@atauni.edu.tr; Güzeldir, B.

    2015-03-15

    Highlights: • InP has a major disadvantage of low Schottky barrier height and it is difficult to achieve a Schottky barrier height greater than 0.5 eV, due to the large current for metal–InP substrate at room temperature. • The barrier height of device can be increased by using thin film layer at InP metal–semiconductor junctions. • There has been no report on preparation of Au/In{sub 2}S{sub 3}/n-InP/In junction by means of spray pyrolysis method in the literature. • This article has been investigated the suitability and possibility of the In{sub 2}S{sub 3} thin film for use in barrier modification of n-InP metal–semiconductor devices. • An effective barrier height as 0.543 eV has been achieved for Au/In{sub 2}S{sub 3}/n-InP/In junction. - Abstract: We fabricated Au/n-InP/In and Au/In{sub 2}S{sub 3}/n-InP/In junctions and investigated their electrical properties at room temperature. The In{sub 2}S{sub 3} thin film has been directly formed on n-type InP substrate with spray pyrolysis method at 200 °C substrate temperature. Detailed structural and optical properties of the film have been investigated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and absorption techniques. The band gap energy of In{sub 2}S{sub 3} by using spectral data of absorption has been determined to be about 2.80 eV. The values of the ideality factor and barrier height of the Au/n-InP/In and Au/In{sub 2}S{sub 3}/n-InP/In junctions have been found as n = 1.01, Φ{sub b} = 0.469 eV and n = 1.07, Φ{sub b} = 0.543 eV, respectively. Likewise, the values of barrier height and series resistance of both samples have been obtained from Norde method and they have been calculated as 0.456 eV, 59.081 Ω for Au/n-InP/In junction and 0.518 eV, 101.302 Ω for Au/In{sub 2}S{sub 3}/n-InP/In junction, respectively.

  10. 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.

  11. Photo-detection characteristics of In-Zn-O/SiO{sub x}/n-Si hetero-junctions

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Hau-Wei [Department of Materials Science and Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30010, Taiwan, ROC (China); Hsieh, Tsung-Eong, E-mail: tehsieh@mail.nctu.edu.tw [Department of Materials Science and Engineering, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30010, Taiwan, ROC (China); Juang, Jenh-Yih [Department of Electrophysics, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, 30010, Taiwan, ROC (China)

    2015-08-01

    Highlights: • Semiconductor-insulator-semiconductor hetero-junction photodetectors was fabricated. • Photodetectors adopted low-resistivity, high-transmittance IZO film as window layer. • Hetero-junction photodetector exhibited response of 35 AW{sup −1} in visible light. • Hetero-junction photodetector exhibited response of 6.15 AW{sup −1} in ultraviolet light. - Abstract: A layer of indium zinc oxide (IZO) was deposited on the n-type Si substrate clad with a thin thermally grown SiO{sub x} layer by pulsed laser deposition to form the semiconductor-insulator-semiconductor (SIS) hetero-junction which exhibits substantial photo-induced responses. Investigation on the IZO layer deposited at various temperatures indicated that IZO film grown at 250 °C possesses a resistivity of 4.9 × 10{sup −4} Ω cm with the transmittance exceeding 80% in the wavelength range between near infrared to ultraviolet light. The photodetection device made of the SIS hetero-junction structure was found to exhibit the photoresponse (R) of 35 AW{sup −1} and 6.15 AW{sup −1} with a quick photo-response time less than 80 ms under the illumination of visible light and ultraviolet light, respectively. The underlying mechanism for such a unique characteristic was attributed to the suppression of majority carrier tunneling resulted from the Schottky barrier established at the SIS interfaces.

  12. Early Activation of MAPK p44/42 Is Partially Involved in DON-Induced Disruption of the Intestinal Barrier Function and Tight Junction Network

    Science.gov (United States)

    Springler, Alexandra; Hessenberger, Sabine; Schatzmayr, Gerd; Mayer, Elisabeth

    2016-01-01

    Deoxynivalenol (DON), produced by the plant pathogens Fusarium graminearum and Fusarium culmorum, is one of the most common mycotoxins, contaminating cereal and cereal-derived products. Although worldwide contamination of food and feed poses health threats to humans and animals, pigs are particularly susceptible to this mycotoxin. DON derivatives, such as deepoxy-deoxynivalenol (DOM-1), are produced by bacterial transformation of certain intestinal bacteria, which are naturally occurring or applied as feed additives. Intestinal epithelial cells are the initial barrier against these food- and feed-borne toxins. The present study confirms DON-induced activation of MAPK p44/42 and inhibition of p44/42 by MAPK-inhibitor U0126 monoethanolate. Influence of DON and DOM-1 on transepithelial electrical resistance (TEER), viability and expression of seven tight junction proteins (TJ), as well as the potential of U0126 to counteract DON-induced effects, was assessed. While DOM-1 showed no effect, DON significantly reduced TEER of differentiated IPEC-J2 and decreased expression of claudin-1 and -3, while leaving claudin-4; ZO-1, -2, and -3 and occludin unaffected. Inhibition of p44/42 counteracted DON-induced TEER decrease and restored claudin-3, but not claudin-1 expression. Therefore, effects of DON on TEER and claudin-3 are at least partially p44/42 mediated, while effects on viability and claudin-1 are likely mediated via alternative pathways. PMID:27618100

  13. ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

    Indian Academy of Sciences (India)

    Sefa B K Aydin; Dilber E Yildiz; Hatice Kanbur Çavuş; Recep Şahingöz

    2014-12-01

    Electrical analysis of Al/p-Si Schottky diode with titanium dioxide (TiO2) thin film was performed at room temperature. The forward and reverse bias current–voltage (–) characteristics of diode were studied. Using thermionic emission (TE) theory, the main electrical parameters of the Al/TiO2/p-Si Schottky diode such as ideality factor (), zero bias barrier height (Bo) and series resistance (s) were estimated from forward bias – plots. At the same time, values of , Bo and s were obtained from Cheung’s method. It was shown that electrical parameters obtained from TE theory and Cheung’s method exhibit close agreement with each other. The reverse-bias leakage current mechanism of Al/TiO2/p-Si Schottky barrier diodes was investigated. The – curves in the reverse direction are taken and interpreted via both Schottky and Poole–Frenkel effects. Schottky effect was found to be dominant in the reverse direction. In addition, the capacitance–voltage (–) and conductance–voltage (/–) characteristics of diode were investigated at different frequencies (50–500 kHz). The frequency dependence of interface states density was obtained from the Hill–Coleman method and the voltage dependence of interface states density was obtained from the high–low frequency capacitance method.

  14. Hexavalent chromium at low concentration alters Sertoli cell barrier and connexin 43 gap junction but not claudin-11 and N-cadherin in the rat seminiferous tubule culture model

    Energy Technology Data Exchange (ETDEWEB)

    Carette, Diane [INSERM U 1065, Team 5 “Physiopathology of Germ Cell Control: Genomic and Non Genomic Mechanisms” C3M, University of Nice Sophia Antipolis, Nice (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Perrard, Marie-Hélène, E-mail: marie-helene.durand@ens-lyon.fr [Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon I, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon (France); Prisant, Nadia [University of Versailles/St Quentin-en-Yvelines (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Gilleron, Jérome; Pointis, Georges [INSERM U 1065, Team 5 “Physiopathology of Germ Cell Control: Genomic and Non Genomic Mechanisms” C3M, University of Nice Sophia Antipolis, Nice (France); Segretain, Dominique [University of Versailles/St Quentin-en-Yvelines (France); UMR S775, University Paris Descartes, 45 rue des Saints Pères, 75006, Paris (France); Durand, Philippe [Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, Université Lyon I, CNRS, INRA, Ecole Normale Supérieure de Lyon, Lyon (France); Kallistem SAS Ecole Normale Supérieure de Lyon, Lyon (France)

    2013-04-01

    Exposure to toxic metals, specifically those belonging to the nonessential group leads to human health defects and among them reprotoxic effects. The mechanisms by which these metals produce their negative effects on spermatogenesis have not been fully elucidated. By using the Durand's validated seminiferous tubule culture model, which mimics the in vivo situation, we recently reported that concentrations of hexavalent chromium, reported in the literature to be closed to that found in the blood circulation of men, increase the number of germ cell cytogenetic abnormalities. Since this metal is also known to affect cellular junctions, we investigated, in the present study, its potential influence on the Sertoli cell barrier and on junctional proteins present at this level such as connexin 43, claudin-11 and N-cadherin. Cultured seminiferous tubules in bicameral chambers expressed the three junctional proteins and ZO-1 for at least 12 days. Exposure to low concentrations of chromium (10 μg/l) increased the trans-epithelial resistance without major changes of claudin-11 and N-cadherin expressions but strongly delocalized the gap junction protein connexin 43 from the membrane to the cytoplasm of Sertoli cells. The possibility that the hexavalent chromium-induced alteration of connexin 43 indirectly mediates the effect of the toxic metal on the blood–testis barrier dynamic is postulated. - Highlights: ► Influence of Cr(VI) on the Sertoli cell barrier and on junctional proteins ► Use of cultured seminiferous tubules in bicameral chambers ► Low concentrations of Cr(VI) (10 μg/l) altered the trans-epithelial resistance. ► Cr(VI) did not alter claudin-11 and N-cadherin. ► Cr(VI) delocalized connexin 43 from the membrane to the cytoplasm of Sertoli cells.

  15. 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.

  16. Schottky contact formation on polar and non-polar AlN

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Pramod; Bryan, Isaac; Bryan, Zachary; Tweedie, James; Kirste, Ronny; Collazo, Ramon; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States)

    2014-11-21

    The interfaces of m- and c-plane AlN with metals of different work functions and electro-negativities were characterized and the Schottky barrier heights were measured. The Schottky barrier height was determined by measuring the valence band maximum (VBM) with respect to the Fermi level at the surface (interface) before (after) metallization. VBM determination included accurate modeling and curve fitting of density of states at the valence band edge with the XPS data. The experimental behavior of the barrier heights could not be explained by the Schottky-Mott model and was modeled using InterFace-Induced Gap States (IFIGS). A slope parameter (S{sub X}) was used to incorporate the density of surface states and is a measure of Fermi level pinning. The experimental barriers followed theoretical predictions with a barrier height at the surface Fermi level (Charge neutrality level (CNL)) of ∼2.1 eV (∼2.7 eV) on m-plane (c-plane) and S{sub X} ∼ 0.36 eV/Miedema unit. Slope parameter much lower than 0.86 implied a surface/interface states dominated behavior with significant Fermi level pinning and the measured barrier heights were close to the CNL. Titanium and zirconium provided the lowest barriers (1.6 eV) with gold providing the highest (2.3 eV) among the metals analyzed on m-plane. It was consistently found that barrier heights decreased from metal polar to non-polar surfaces, in general, due to an increasing CNL. The data indicated that charged IFIGS compensate spontaneous polarization charge. These barrier height and slope parameter measurements provided essential information for designing Schottky diodes and other contact-based devices on AlN.

  17. Structural and electrical characterization of ultra-thin SrTiO3 tunnel barriers grown over YBa2Cu3O7 electrodes for the development of high Tc Josephson junctions.

    Science.gov (United States)

    Félix, L Avilés; Sirena, M; Guzmán, L A Agüero; Sutter, J González; Vargas, S Pons; Steren, L B; Bernard, R; Trastoy, J; Villegas, J E; Briático, J; Bergeal, N; Lesueur, J; Faini, G

    2012-12-14

    The transport properties of ultra-thin SrTiO(3) (STO) layers grown over YBa(2)Cu(3)O(7) electrodes were studied by conductive atomic force microscopy at the nano-scale. A very good control of the barrier thickness was achieved during the deposition process. A phenomenological approach was used to obtain critical parameters regarding the structural and electrical properties of the system. The STO layers present an energy barrier of 0.9 eV and an attenuation length of 0.23 nm, indicating very good insulating properties for the development of high-quality Josephson junctions.

  18. Impedance spectroscopic analysis of nanoparticle functionalized graphene/p-Si Schottky diode sensors

    Science.gov (United States)

    Uddin, Md Ahsan; Singh, Amol; Daniels, Kevin; Vogt, Thomas; Chandrashekhar, M. V. S.; Koley, Goutam

    2016-11-01

    Metallic nanoparticle (NP) functionalized graphene/p-Si Schottky diode (chemidiode) sensors have been investigated through dc amperometric and ac impedance spectroscopic (IS) measurements. Four fold sensitivity enhancement for NH3 is demonstrated after Pt nanoparticle functionalization of graphene/p-Si Schottky diode sensor, and the response is also orders of magnitude higher compared to functionalized graphene chemiresistor. Experimentally obtained impedance spectra were modeled utilizing an equivalent circuit for both sensor types, and the junction resistance and capacitance were extracted for various gaseous analytes exposure. Variations in junction resistance, capacitance and 3-dB cut-off frequency plotted in three-dimensional (3D) enables extraction of unique signatures for various analyte gases.

  19. Radiation hardness of n-GaN schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, A. A., E-mail: shura.lebe@mail.ioffe.ru; Belov, S. V.; Mynbaeva, M. G.; Strel’chuk, A. M.; Bogdanova, E. V. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation); Makarov, Yu. N. [Nitride Crystals Group (Russian Federation); Usikov, A. S. [Nitride Crystals Inc. (United States); Kurin, S. Yu.; Barash, I. S.; Roenkov, A. D. [Nitride Crystals Group (Russian Federation); Kozlovski, V. V. [St. Petersburg State Polytechnic University (Russian Federation)

    2015-10-15

    Schottky-barrier diodes with a diameter of ∼10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm{sup –1}. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

  20. Epitaxial Al/GaN and Au/GaN junctions on as-grown GaN(0001) 1 x 1 surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Orani, D.; Rubini, S.; Pelucchi, E.; Bonanni, B. [Laboratorio Nazionale TASC-INFM, Area di Ricerca, S.S. 14, Km. 163.5, 34012 Trieste (Italy); Piccin, M. [Laboratorio Nazionale TASC-INFM, Area di Ricerca, S.S. 14, Km. 163.5, 34012 Trieste (Italy); Also with Dipartimento di Fisica, Universita' di Trieste, 34127 Trieste (Italy); Franciosi, A. [Laboratorio Nazionale TASC-INFM, Area di Ricerca, S.S. 14, Km. 163.5, 34012 Trieste (Italy); Passaseo, A.; Cingolani, R. [INFM e Dipartimento di Scienza dei Materiali, Universita' di Lecce, Via per Arnesano, 73100 Lecce (Italy); Khan, A. [Department of Electrical and Computer Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2005-04-01

    GaN(0001) epilayers were fabricated by rf-plasma enhanced molecular beam epitaxy on GaN templates. The templates were grown by metalorganic chemical vapor deposition on sapphire. The layers exhibited the 2 x 2 reconstruction of the Ga-face during growth and the 1 x 1 reconstruction upon cooling. On such surfaces, Al/n-GaN and Au/n-GaN junctions were fabricated in-situ by molecular beam epitaxy. X-ray photoemission spectroscopy studies allowed us to determine n-type Schottky barrier heights of 0.61{+-}0.06 and 0.98{+-}0.06 eV, respectively, for the two types of epitaxial junctions. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. 1/f noise in forward biased high voltage 4H-SiC Schottky diodes

    Science.gov (United States)

    Shabunina, Eugenia I.; Levinshtein, Michael E.; Shmidt, Natalia M.; Ivanov, Pavel A.; Palmour, John W.

    2014-06-01

    The 1/f noise has been investigated for the first time at 300 and 77 K in high-quality 4H-SiC Schottky diodes. It is shown that, at 77 K, the dependence of the spectral noise density on current, SI(I), differs fundamentally between the cases of the current flowing through the main part of the diode with a comparatively high barrier and the current flowing through the nano-sized patches with a comparatively low barrier.

  2. Effect of CO on Characteristics of AlGaN/GaN Schottky Diode

    Institute of Scientific and Technical Information of China (English)

    FENG Chun; WANG Zhan-Guo; WANG Xiao-Liang; YANG Cui-Bai; XIAO Hong-Ling; ZHANG Ming-Lan; JIANG Li-Juan; TANG Jian; HU Guo-Xin; WANG Jun-Xi

    2008-01-01

    @@ Pt Schottky diode gas sensors for CO are fabricated using AlGaN/GaN high electron mobility transistor (HEMTs) structure. The diodes show a remarkable sensor signal (3 mA, in N2; 2mA in air ambient) biased 2 V after 1% CO is introduced at 50℃. The Schottky barrier heights decrease for 36 meV and 27 meV in the two cases respectively. The devices exhibit a slow recovery characteristic in air ambient but almost none in the background of pure N2, which reveals that oxygen molecules could accelerate the desorption of CO and offer restrictions to CO detection.

  3. Parameter extraction for a Ti/4H-SiC Schottky diode

    Institute of Scientific and Technical Information of China (English)

    王守国; 张义门; 张玉明

    2003-01-01

    Based on the MIS model, a simple method to extract parameters of SiC Schottky diodes is presented using the I-V characteristics. The interface oxide capacitance Ci is extracted for the first time, as far as we know. Parameters of 4H-SiC Schottky diodes fabricated for testing in this paper are: the ideality factor n, the series resistance Rs, the zero-field barrier height φB0, the interface state density Dit, the interface oxide capacitance Ci and the neutral level of interface states φ0.

  4. 1700 V SiC Schottky diodes scaled to 25 A

    Energy Technology Data Exchange (ETDEWEB)

    Peters, D.; Dohnke, K.O.; Hecht, C.; Stephani, D. [SiCED Electronics Development Ltd., Erlangen (Germany)

    2001-07-01

    This paper reports on a study of SiC Schottky diodes focused on high current rating and high blocking voltage: 25 A / 1200 V and 1700V, resp. With an active area of 10 mm{sup 2} we successfully explored new ground for SiC devices. The device concept, fabrication process, yield aspects and measured results of static and dynamic characteristics as well as the temperature behavior are described. The reverse currents are very low (<500 {mu}A) even at 125 C and their temperature dependence is lower than expected by thermionic emission since tunneling mechanisms through the Schottky barrier rule the current transport at high blocking voltages. (orig.)

  5. Fabrication of novel electrolyte-layer free fuel cell with semi-ionic conductor (Ba0.5Sr0.5Co0.8Fe0.2O3-δ- Sm0.2Ce0.8O1.9) and Schottky barrier

    Science.gov (United States)

    Afzal, Muhammad; Saleemi, Mohsin; Wang, Baoyuan; Xia, Chen; Zhang, Wei; He, Yunjuan; Jayasuriya, Jeevan; Zhu, Bin

    2016-10-01

    Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is synthesized via a chemical co-precipitation technique for a low temperature solid oxide fuel cell (LTSOFC) (300-600 °C) and electrolyte-layer free fuel cell (EFFC) in a comprehensive study. The EFFC with a homogeneous mixture of samarium doped ceria (SDC): BSCF (60%:40% by weight) which is rather similar to the cathode (SDC: BSCF in 50%:50% by weight) used for a three layer SOFC demonstrates peak power densities up to 655 mW/cm2, while a three layer (anode/electrolyte/cathode) SOFC has reached only 425 mW/cm2 at 550 °C. Chemical phase, crystal structure and morphology of the as-prepared sample are characterized by X-ray diffraction and field emission scanning electron microscopy coupled with energy dispersive spectroscopy. The electrochemical performances of 3-layer SOFC and EFFC are studied by electrochemical impedance spectroscopy (EIS). As-prepared BSCF has exhibited a maximum conductivity above 300 S/cm at 550 °C. High performance of the EFFC device corresponds to a balanced combination between ionic and electronic (holes) conduction characteristic. The Schottky barrier prevents the EFFC from the electronic short circuiting problem which also enhances power output. The results provide a new way to produce highly effective cathode materials for LTSOFC and semiconductor designs for EFFC functions using a semiconducting-ionic material.

  6. Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption.

    Directory of Open Access Journals (Sweden)

    Christoph M Zehendner

    Full Text Available Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR on the evolution of reactive oxygen species (ROS and blood-brain barrier (BBB integrity in brain endothelial cells (BEC. BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC or towards occlusion of the arteria cerebri media (MCAO with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF, MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1 and claudin 5 (Cl5, decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role

  7. ATP Induces Disruption of Tight Junction Proteins via IL-1 Beta-Dependent MMP-9 Activation of Human Blood-Brain Barrier In Vitro

    Directory of Open Access Journals (Sweden)

    Fuxing Yang

    2016-01-01

    Full Text Available Disruption of blood-brain barrier (BBB follows brain trauma or central nervous system (CNS stress. However, the mechanisms leading to this process or the underlying neural plasticity are not clearly known. We hypothesized that ATP/P2X7R signaling regulates the integrity of BBB. Activation of P2X7 receptor (P2X7R by ATP induces the release of interleukin-1β (IL-1β, which in turn enhances the activity of matrix metalloproteinase-9 (MMP-9. Degradation of tight junction proteins (TJPs such as ZO-1 and occludin occurs, which finally contributes to disruption of BBB. A contact coculture system using human astrocytes and hCMEC/D3, an immortalized human brain endothelial cell line, was used to mimic BBB in vitro. Permeability was used to evaluate changes in the integrity of TJPs. ELISA, Western blot, and immunofluorescent staining procedures were used. Our data demonstrated that exposure to the photoreactive ATP analog, 3′-O-(4-benzoylbenzoyl adenosine 5′-triphosphate (BzATP, induced a significant decrease in ZO-1 and occludin expression. Meanwhile, the decrease of ZO-1 and occludin was significantly attenuated by P2X7R inhibitors, as well as IL-1R and MMP antagonists. Further, the induction of IL-1β and MMP-9 was closely linked to ATP/P2X7R-associated BBB leakage. In conclusion, our study explored the mechanism of ATP/P2X7R signaling in the disruption of BBB following brain trauma/stress injury, especially focusing on the relationship with IL-1β and MMP-9.

  8. Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption.

    Science.gov (United States)

    Zehendner, Christoph M; Librizzi, Laura; Hedrich, Jana; Bauer, Nina M; Angamo, Eskedar A; de Curtis, Marco; Luhmann, Heiko J

    2013-01-01

    Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this

  9. Schottky or Ohmic metal-semiconductor contact: influence on photocatalytic efficiency of Ag/ZnO and Pt/ZnO model systems.

    Science.gov (United States)

    Yan, Fengpo; Wang, Yonghao; Zhang, Jiye; Lin, Zhang; Zheng, Jinsheng; Huang, Feng

    2014-01-01

    The relationship between the contact type in metal-semiconductor junctions and their photocatalytic efficiencies is investigated. Two metal-semiconductor junctions, silver on zinc oxide (Ag/ZnO) and platinum on zinc oxide (Pt/ZnO) serve as model system for Ohmic and Schottky metal-semiconductor contact, respectively. Ag/ZnO, with Ohmic contact, exhibits a higher photocatalytic efficiency than Pt/ZnO, with Schottky contact. The direction of electric fields within the semiconductor is found to play a crucial role in the separation of photogenerated charges, and thus strongly influences the photocatalytic efficiency.

  10. Electrical characteristics of Pt-ZnO Schottky nano-contact

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The electrical characteristics of Pt-ZnO Schottky nano-contact have been studied. Well aligned ZnO nanorod arrays were synthesized by two-step wet-chemical method. A Pt-coated conducting probe of atomic force microscope was placed on the head face of the ZnO nanorod, thereby forming a Pt-ZnO nano-contact. The I-V characteristic curve shows that the Pt-ZnO nano-contact exhibits rectifying effect, like a Schottky diode with an ideality factor of 3.2 and a reverse-bias breakdown voltage more than -10 V. The study suggests that a high electric field is induced on the ZnO beneath the contact point when a bias voltage is applied, hence, the Schottky barrier thickness is decreased, and results in easier tunneling across the Pt-ZnO interface and a large ideality factor.

  11. Improved Schottky contacts to InGaN alloys by a photoelectrochemical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yin; Cai, Qing; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou [Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing, 210093 (China); Yang, Lianhong [Department of Physics, Changji College, Changji, 831100 (China); Xue, Junjun [School of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing, 210093 (China)

    2016-04-15

    We report on improved electrical properties of Schottky contacts to InGaN alloys by introducing a photoelectrochemical treatment. The Schottky barrier height determined by a thermionic-field emission model, a dominating forward-current-transport mechanism, increased by 0.15 eV from 1.02 eV for conventional contacts to 1.17 eV for those with photoelectrochemical treatment at room temperature, while the ideality factors is closer to 1 after photoelectrochemical treatment. Furthermore, the reverse leakage mechanism varies from an ohmic transport mechanism at relatively low voltage and space charge-limited current mechanism at relatively high voltage for conventional contacts to Frenkel-Poole emission for improved Schottky contacts, which is attributed to partly removing surface states by the photoelectrochemical treatment. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  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. Development of NbN Josephson junctions with Ta{sub x}N semi-metal barrier; application to RSFQ circuits; Etude et realisation de jonction Josephson en NbN a barriere semi-metallique en Ta{sub x}N; application aux circuits logiques RSFQ

    Energy Technology Data Exchange (ETDEWEB)

    Setzu, R

    2007-11-15

    This thesis research, brought to the development and optimization of SNS (Superconductor / Normal Metal / Superconductor) Josephson junctions with NbN electrodes and a high resistivity Ta{sub x}N barrier. We were able to point out Josephson oscillations for frequencies above 1 THz and operation temperatures up to 10 K, which constituted the original goal of the project. This property makes these junctions unique and well adapted for realizing ultra-fast RSFQ (Rapid Single Flux Quantum) logic circuits suitable for spatial telecommunications. We showed a good reproducibility of Ta{sub x}N film properties as a function of the sputtering parameters. The NbN/Ta{sub x}N/NbN tri-layers exhibit high critical temperature (16 K). The junctions showed a clear dependence of the R{sub n}I{sub c} product as a function of the partial nitrogen pressure inside the reactive plasma; the R{sub n}I{sub c} is the product between the junction critical current and its normal resistance, and indicates the upper limit Josephson frequency. We have also obtained some really high R{sub n}I{sub c} products, up to 3.74 mV at 4.2 K for critical current densities of about 15 kA/cm{sup 2}. Junctions show the expected Josephson behaviors, respectively Fraunhofer diffraction and Shapiro steps. up to 14 K. This allows expecting good circuit operations in a relaxed cryogenics environment (with respect to the niobium circuits limited at 4.2 K). The junctions appear to be self-shunted. The SNOP junctions J{sub c}-temperature dependence has been fitted by using the long SNS junction model in the dirty limit, which gives a normal metal coherence length of about 3.8 nm at 4.2 K. We have finally studied a multilayer fabrication process, including a common ground plane and bias resistors, suitable for RSFQ logic basic circuits. To conclude we have been able to show the performance superiority of NbN/Ta{sub x}N/NbN junctions over the actual niobium junctions, as well as their interest for realizing compact

  14. Fabrication and characterization of graphene/AlGaN/GaN ultraviolet Schottky photodetector

    Science.gov (United States)

    Kumar, M.; Jeong, H.; Polat, K.; Okyay, A. K.; Lee, D.

    2016-07-01

    We report on the fabrication and characterization of a Schottky ultraviolet graphene/AlGaN/GaN photodetector (PD). The fabricated device clearly exhibits rectification behaviour, indicating that the Schottky barrier is formed between the AlGaN and the mechanically transferred graphene. The Schottky parameters are evaluated using an equivalent circuit with two diodes connected back-to-back in series. The PD shows a low dark current of 4.77  ×  10-12 A at a bias voltage of  -2.5 V. The room temperature current-voltage (I-V) measurements of the graphene/AlGaN/GaN Schottky PD exhibit a large photo-to-dark contrast ratio of more than four orders of magnitude. Furthermore, the device shows peak responsivity at a wavelength of 350 nm, corresponding to GaN band edge and a small hump at 300 nm associated to the AlGaN band edge. In addition, we examine the behaviour of Schottky PDs with responsivities of 0.56 and 0.079 A W-1 at 300 and 350 nm, respectively, at room temperature.

  15. 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.

  16. Transcriptional mechanisms coordinating tight junction assembly during epithelial differentiation.

    Science.gov (United States)

    Boivin, Felix J; Schmidt-Ott, Kai M

    2017-06-01

    Epithelial tissues form a selective barrier via direct cell-cell interactions to separate and establish concentration gradients between the different compartments of the body. Proper function and formation of this barrier rely on the establishment of distinct intercellular junction complexes. These complexes include tight junctions, adherens junctions, desmosomes, and gap junctions. The tight junction is by far the most diverse junctional complex in the epithelial barrier. Its composition varies greatly across different epithelial tissues to confer various barrier properties. Thus, epithelial cells rely on tightly regulated transcriptional mechanisms to ensure proper formation of the epithelial barrier and to achieve tight junction diversity. Here, we review different transcriptional mechanisms utilized during embryogenesis and disease development to promote tight junction assembly and maintenance of intercellular barrier integrity. We focus particularly on the Grainyhead-like transcription factors and ligand-activated nuclear hormone receptors, two central families of proteins in epithelialization. © 2017 New York Academy of Sciences.

  17. 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.

  18. Outer Membrane Vesicles and Soluble Factors Released by Probiotic Escherichia coli Nissle 1917 and Commensal ECOR63 Enhance Barrier Function by Regulating Expression of Tight Junction Proteins in Intestinal Epithelial Cells

    Science.gov (United States)

    Alvarez, Carina-Shianya; Badia, Josefa; Bosch, Manel; Giménez, Rosa; Baldomà, Laura

    2016-01-01

    The gastrointestinal epithelial layer forms a physical and biochemical barrier that maintains the segregation between host and intestinal microbiota. The integrity of this barrier is critical in maintaining homeostasis in the body and its dysfunction is linked to a variety of illnesses, especially inflammatory bowel disease. Gut microbes, and particularly probiotic bacteria, modulate the barrier integrity by reducing gut permeability and reinforcing tight junctions. Probiotic Escherichia coli Nissle 1917 (EcN) is a good colonizer of the human gut with proven therapeutic efficacy in the remission of ulcerative colitis in humans. EcN positively modulates the intestinal epithelial barrier through upregulation and redistribution of the tight junction proteins ZO-1, ZO-2 and claudin-14. Upregulation of claudin-14 has been attributed to the secreted protein TcpC. Whether regulation of ZO-1 and ZO-2 is mediated by EcN secreted factors remains unknown. The aim of this study was to explore whether outer membrane vesicles (OMVs) released by EcN strengthen the epithelial barrier. This study includes other E. coli strains of human intestinal origin that contain the tcpC gene, such as ECOR63. Cell-free supernatants collected from the wild-type strains and from the derived tcpC mutants were fractionated into isolated OMVs and soluble secreted factors. The impact of these extracellular fractions on the epithelial barrier was evaluated by measuring transepithelial resistance and expression of several tight junction proteins in T-84 and Caco-2 polarized monolayers. Our results show that the strengthening activity of EcN and ECOR63 does not exclusively depend on TcpC. Both OMVs and soluble factors secreted by these strains promote upregulation of ZO-1 and claudin-14, and down-regulation of claudin-2. The OMVs-mediated effects are TcpC-independent. Soluble secreted TcpC contributes to the upregulation of ZO-1 and claudin-14, but this protein has no effect on the transcriptional

  19. Modification of electrical properties of Au/n-type InP Schottky diode with a high-k Ba0.6Sr0.4TiO3 interlayer

    Science.gov (United States)

    Thapaswini, P. Prabhu; Padma, R.; Balaram, N.; Bindu, B.; Rajagopal Reddy, V.

    2016-05-01

    Au/Ba0.6Sr0.4TiO3 (BST)/n-InP metal/insulator/semiconductor (MIS) Schottky diodes have been analyzed by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The surface morphology of the BST films on InP is fairly smooth. The Au/BST/n-InP MIS Schottky diode shows better rectification ratio and low leakage current compared to the conventional Au/n-InP metal-semiconductor (MS) Schottky diode. Higher barrier height is achieved for the MIS Schottky diode compared to the MS Schottky diode. The Norde and Cheung's methods are employed to determine the barrier height, ideality factor and series resistance. The interface state density (NSS) is determined from the forward bias I-V data for both the MS and MIS Schottky diodes. Results reveal that the NSS of the MIS Schottky diode is lower than that of the MS Schottky diode. The Poole-Frenkel emission is found dominating the reverse current in both Au/n-InP MS and Au/BST/n-InP MIS Schottky diodes, indicating the presence of structural defects and trap levels in the dielectric film.

  20. Instrumentation And Diagnostics Using Schottky Signals

    CERN Document Server

    Nolden, F

    2001-01-01

    Schottky signal measurements are a widely used tool for the determination of longitudinal and transverse dynamical properties of hadron beams in circular accelerators and storage rings. When applied to coasting beams, it is possible to deduce properties as the momentum distribution. the Qx,y-values and the average betatron amplitudes. Scientific applications have been developed in the past few years, as well, namely nuclear Schottky mass spectrometry and lifetime measurements. Schottky signals from a coasting beam are random signals which appear at every revolution harmonic and the respective betatron sidebands. Their interpretation is more or less straightforward unless the signal is perturbed by collective effects in the case of high phase space density. Schottky signals from bunched beams reveal the synchrotron oscillation frequency, from which the effective rf voltage seen by the beam can be deduced. The detection devices can be broad-band or narrowband. The frequency range is usually in the range between...