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Sample records for epitaxial channel profile

  1. A channel profile analyser

    International Nuclear Information System (INIS)

    Gobbur, S.G.

    1983-01-01

    It is well understood that due to the wide band noise present in a nuclear analog-to-digital converter, events at the boundaries of adjacent channels are shared. It is a difficult and laborious process to exactly find out the shape of the channels at the boundaries. A simple scheme has been developed for the direct display of channel shape of any type of ADC on a cathode ray oscilliscope display. This has been accomplished by sequentially incrementing the reference voltage of a precision pulse generator by a fraction of a channel and storing ADC data in alternative memory locations of a multichannel pulse height analyser. Alternative channels are needed due to the sharing at the boundaries of channels. In the flat region of the profile alternate memory locations are channels with zero counts and channels with the full scale counts. At the boundaries all memory locations will have counts. The shape of this is a direct display of the channel boundaries. (orig.)

  2. Study of performance scaling of 22-nm epitaxial delta-doped channel MOS transistor

    Science.gov (United States)

    Sengupta, Sarmista; Pandit, Soumya

    2015-06-01

    Epitaxial delta-doped channel (EδDC) profile is a promising approach for extending the scalability of bulk metal oxide semiconductor (MOS) technology for low-power system-on-chip applications. A comparative study between EδDC bulk MOS transistor with gate length Lg = 22 nm and a conventional uniformly doped channel (UDC) bulk MOS transistor, with respect to various digital and analogue performances, is presented. The study has been performed using Silvaco technology computer-aided design device simulator, calibrated with experimental results. This study reveals that at smaller gate length, EδDC transistor outperforms the UDC transistor with respect to various studied performances. The reduced contribution of the lateral electric field in the channel plays the key role in this regard. Further, the carrier mobility in EδDC transistor is higher compared to UDC transistor. For moderate gate and drain bias, the impact ionisation rate of the carriers for EδDC MOS transistor is lower than that of the UDC transistor. In addition, at 22 nm, the performances of a EδDC transistor are competitive to that of an ultra-thin body silicon-on-insulator transistor.

  3. Improved vertical MOSFET performance using an epitaxial channel and a stacked silicon-insulator structure

    International Nuclear Information System (INIS)

    Uchino, T; Gili, E; Ashburn, P; Tan, L; Buiu, O; Hall, S

    2012-01-01

    A vertical MOSFET (VMOST) incorporating an epitaxial channel and a drain junction in a stacked silicon-insulator structure is presented. In this device structure, an oxide layer near the drain junction edge (referred to as a junction stop) acts as a dopant diffusion barrier and consequently a shallow drain junction is formed to suppress short channel effects. To investigate the scalability of this device, a simulation study in the sub-100 nm regime calibrated to measured results on the fabricated devices is carried out. The use of an epitaxial channel delivers 50% higher drive current due to the higher mobility of the retrograde channel and the junction stop structure delivers improvements of threshold voltage roll-off and drain-induced barrier lowering compared with a conventional VMOST. (fast track communication)

  4. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L S; Kenny, M J [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1994-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  5. Multidirectional channeling analysis of epitaxial CdTe layers using an automatic RBS/channeling system

    Energy Technology Data Exchange (ETDEWEB)

    Wielunski, L.S.; Kenny, M.J. [CSIRO, Lindfield, NSW (Australia). Applied Physics Div.

    1993-12-31

    Rutherford Backscattering Spectrometry (RBS) is an ion beam analysis technique used in many fields. The high depth and mass resolution of RBS make this technique very useful in semiconductor material analysis [1]. The use of ion channeling in combination with RBS creates a powerful technique which can provide information about crystal quality and structure in addition to mass and depth resolution [2]. The presence of crystal defects such as interstitial atoms, dislocations or dislocation loops can be detected and profiled [3,4]. Semiconductor materials such as CdTe, HgTe and Hg+xCd{sub 1-x}Te generate considerable interest due to applications as infrared detectors in many technological areas. The present paper demonstrates how automatic RBS and multidirectional channeling analysis can be used to evaluate crystal quality and near surface defects. 6 refs., 1 fig.

  6. High-quality GaN epitaxially grown on Si substrate with serpentine channels

    Science.gov (United States)

    Wei, Tiantian; Zong, Hua; Jiang, Shengxiang; Yang, Yue; Liao, Hui; Xie, Yahong; Wang, Wenjie; Li, Junze; Tang, Jun; Hu, Xiaodong

    2018-06-01

    A novel serpentine-channeled mask was introduced to Si substrate for low-dislocation GaN epitaxial growth and the fully coalesced GaN film on the masked Si substrate was achieved for the first time. Compared with the epitaxial lateral overgrowth (ELOG) growth method, this innovative mask only requires one-step epitaxial growth of GaN which has only one high-dislocation region per mask opening. This new growth method can effectively reduce dislocation density, thus improving the quality of GaN significantly. High-quality GaN with low dislocation density ∼2.4 × 107 cm-2 was obtained, which accounted for about eighty percent of the GaN film in area. This innovative technique is promising for the growth of high-quality GaN templates and the subsequent fabrication of high-performance GaN-based devices like transistors, laser diodes (LDs), and light-emitting diodes (LEDs) on Si substrate.

  7. Epitaxial growth of thin single-crystals and their quality study by Rutherford scattering in channeling conditions

    International Nuclear Information System (INIS)

    Kirsch, Robert.

    1975-01-01

    Some aspects of thin crystalline layers are reminded: vacuum deposition, epitaxial growth, annealing and interdiffusion ion channeling and scattering of 1-2MeV helium ions are used to study the crystalline quality, the annealing effects and in some cases the interdiffusion in epitaxial multilayers of silver, copper gold and nickel. Thin single-crystals of gold and nickel oriented (III) plan parallel to the surface were obtained by successive epitaxial growth from muscovite mica clivages. The mounting techniques of single crystalline, self-supporting, 300 to 1200 Angstroems thick, gold and nickel targets of 3mm diameter are described. The gold single-crystals have dislocation densities of 10 8 cm -2 and the various epitaxial layers are obtained without twinning [fr

  8. Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodak, L.E.; Kuchibhatla, S.; Famouri, P.; Ting, L.; Korakakis, D.

    2008-01-01

    Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nanoelectromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro-channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.

  9. Longitudinal profile of channels cut by springs

    OpenAIRE

    Devauchelle , O.; PETROFF , A. P.; LOBKOVSKY , A. E.; Rothman , D. H.

    2011-01-01

    International audience; We propose a simple theory for the longitudinal profile of channels incised by groundwater flow. The aquifer surrounding the stream is represented in two dimensions through Darcy's law and the Dupuit approximation. The model is based on the assumption that, everywhere in the stream, the shear stress exerted on the sediment by the flow is close to the minimal intensity required to displace a sand grain. Because of the coupling of the stream discharge with the water tabl...

  10. Hydraulic Profiling of a Parallel Channel Type Reactor Core

    International Nuclear Information System (INIS)

    Seo, Kyong-Won; Hwang, Dae-Hyun; Lee, Chung-Chan

    2006-01-01

    An advanced reactor core which consisted of closed multiple parallel channels was optimized to maximize the thermal margin of the core. The closed multiple parallel channel configurations have different characteristics to the open channels of conventional PWRs. The channels, usually assemblies, are isolated hydraulically from each other and there is no cross flow between channels. The distribution of inlet flow rate between channels is a very important design parameter in the core because distribution of inlet flow is directly proportional to a margin for a certain hydraulic parameter. The thermal hydraulic parameter may be the boiling margin, maximum fuel temperature, and critical heat flux. The inlet flow distribution of the core was optimized for the boiling margins by grouping the inlet orifices by several hydraulic regions. The procedure is called a hydraulic profiling

  11. Analysis of temperature profiles and the mechanism of silicon substrate plastic deformation under epitaxial growth

    International Nuclear Information System (INIS)

    Mirkurbanov, H.A.; Sazhnev, S.V.; Timofeev, V.N.

    2004-01-01

    Full text: Thermal treatment of silicon wafers holds one of the major place in the manufacturing of semi-conductor devices. Thermal treatment includes wafer annealing, thermal oxidation, epitaxial growing etc. Quality of wafers in the high-temperature processes (900-1200 deg C) is estimated by the density of structural defects, including areas of plastic deformation, which are shown as the slip lines appearance. Such areas amount to 50-60 % of total wafer surface. The plastic deformation is caused by the thermal stresses. Experimental and theoretical researches allowed to determine thermal balance and to construct a temperature profiles throughout the plate surface. Thermal stresses are caused by temperature drop along the radius of a wafer and at the basic peripheral ring. The threshold temperature drop between center f a wafer and its peripherals (ΔT) for slip lines appearance, amounts to 15-17 deg. C. At the operating temperature of 900-1200 deg. C and ΔT>20 deg. C, the stresses reach the silicon yield point. According to the results of the researches of structure and stress profiles in a wafer, the mechanism of slip lines formation has been constructed. A source of dislocations is the rear broken layer of thickness 8-10 microns, formed after polishing. The micro-fissures with a density 10 5 -10 6 cm -2 are the sources of dislocations. Dislocations move on a surface of a wafer into a slip plane (111). On a wafer surface with orientation (111) it is possible to allocate zones where the tangential stress vector is most favorably directed with respect to a slip plane leaving on a surface, i.e. the shift stresses are maximal in the slip plane. The way to eliminate plastic deformation is to lower the temperature drop to a level of <15 deg. C and elimination of the broken layer in wafer

  12. High-resolution hydrogen profiling in AlGaN/GaN heterostructures grown by different epitaxial methods

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Posada Flores, F; Redondo-Cubero, A; Bengoechea, A; Brana, A F; Munoz, E [Instituto de Sistemas Optoelectronicos y Microtecnologia (ISOM) and Dpto. IngenierIa Electronica (DIE), ETSI de Telecomunicacion, Universidad Politecnica de Madrid, E-28040 Madrid (Spain); Gago, R [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Jimenez, A [Dpto. Electronica, Escuela Politecnica Superior, Universidad de Alcala, E-28805 Alcala de Henares, Madrid (Spain); Grambole, D, E-mail: fposada@die.upm.e [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, PF 51019, D-01314 Dresden (Germany)

    2009-03-07

    Hydrogen (H) incorporation into AlGaN/GaN heterostructures used in high electron mobility transistors, grown by different methods, is studied by high-resolution depth profiling. Samples grown on sapphire and Si(1 1 1) substrates by molecular-beam epitaxy and metal-organic vapour phase epitaxy; involving H-free and H-containing precursors, were analysed to evaluate the eventual incorporation of H into the wafer. The amount of H was measured by means of nuclear reaction analysis (NRA) using the {sup 1}H({sup 15}N,{alpha}{gamma}){sup 12}C reaction up to a depth of {approx}110 nm into the heterostructures. Interestingly, the H profiles are similar in all the samples analysed, with an increasing H content towards the surface and a negligible H incorporation into the GaN layer (0.24 {+-} 0.08 at%) or at the AlGaN/GaN interface. Therefore, NRA shows that H uptake is not related to the growth process or technique employed and that H contamination may be due to external sources after growth. The eventual correlation between topographical defects on the AlGaN surface and the H concentration are also discussed.

  13. Measurement of damage profile in crystals by channeling technique

    International Nuclear Information System (INIS)

    Borovik, A.S.; Shipatov, E.T.

    1984-01-01

    A method of calculation of the random fraction Xsub(R)(l) in a disordered channel containing host and foreign atoms is described. According to this method dechaneling caused by single scattering as well as multiple scattering at defects is calculated taking into account positions of the self-interstitials and foreign atoms with respect to the lattice rows. The results demonstrate that the transverse energy distribution, flux peaking and, hence, Xsub(R)(l) and depth profiles of defects c(l) depend drastically on the defect position, concentration of implanted atoms, their position and the rechanneling process. The method is applied to experimental data for GaAs irradiated by He + and N-implanted Si. The obtained Xsub(R)(l) and c(l) are compared with those obtained using other methods. (author)

  14. Penetration profiles of particles injected into the crystal under channeling conditions

    International Nuclear Information System (INIS)

    Rozhkov, V.V.

    1980-01-01

    A new method of calculating profiles of channeled parricle implantation is proposed. The profile calculation by the method proposed requires only standard computer programs and, consequently, little of the computer time. An analytical expression has been obtained for profiles of the channelled particle implantation under some simplifying allowances, the value of the error due to the allowances being estimated. An analytical formula is also obtained for the distribution function of dechanneling depths with taking account of deceleration of particles in a channel

  15. Investigation of the compositional depth profile in epitaxial submicrometer layers of AIIIBV heterostructures

    International Nuclear Information System (INIS)

    Baumbach, T.; Bruehl, H.G.; Rhan, H.; Pietsch, U.

    1988-01-01

    The compositional depth profile in semiconductor heterostructures can be determined from X-ray diffraction patterns. Different grading profiles were studied through theoretical simulations with regard to their features in the rocking curve. It was found that the thickness and the grading of a particular layer cannot be determined independently of each other. A linear grading gives rise to an increased peak width of the layer diffraction peak whereas an exponential grading can be detected from the damping of high-order interference fringes. The exponential model can be applied to determine the abruptness of the heterointerfaces. The proposed evaluation method of experimental rocking curves includes the case of overlapping peaks of the layer and the substrate diffraction. The simulation results are discussed for a GaAs/Ga 1-x Al x As/GaAs[100] double heterostructure. When the experimental resolution is taken into account, the sensitivity of the interface width determination was 100-200 A. (orig.)

  16. Interdiffusion in epitaxial, single-crystalline Au/Ag thin films studied by Auger electron spectroscopy sputter-depth profiling and positron annihilation

    International Nuclear Information System (INIS)

    Noah, Martin A.; Flötotto, David; Wang, Zumin; Reiner, Markus; Hugenschmidt, Christoph; Mittemeijer, Eric J.

    2016-01-01

    Interdiffusion in epitaxial, single-crystalline Au/Ag bilayered thin films on Si (001) substrates was investigated by Auger electron spectroscopy (AES) sputter-depth profiling and by in-situ positron annihilation Doppler broadening spectroscopy (DBS). By the combination of these techniques identification of the role of vacancy sources and sinks on interdiffusion in the Au/Ag films was possible. It was found that with precise knowledge of the concentration-dependent self-diffusion and impurity diffusion coefficients a distinction between the Darken-Manning treatment and Nernst-Planck treatment can be made, which is not possible on the basis of the determined concentration-depth profiles alone.

  17. In situ ion channeling study of gallium disorder and gold profiles in Au-implanted GaN

    International Nuclear Information System (INIS)

    Jiang, W.; Weber, W. J.; Thevuthasan, S.

    2000-01-01

    Disorder accumulation and annealing behavior on the Ga sublattice in gallium nitride (GaN) implanted with 1.0 MeV Au 2+ (60 degree sign off surface normal) at 180 or 300 K have been studied using in situ Rutherford backscattering spectrometry in a -channeling geometry. Complete amorphization in GaN is attained at 6.0 and 20 Au 2+ /nm 2 for irradiation at 180 and 300 K, respectively. A saturation in the Ga disorder at and behind the damage peak was observed at intermediate ion fluences at both 180 and 300 K. No measurable thermal recovery was found at 300 K for the full range of damage produced at 180 K. However, distinct epitaxial regrowth in the bulk and Ga reordering at surface occurred after annealing at 870 K. The implanted Au readily diffuses into the highly damaged regions at elevated temperatures, and the redistribution of the Au atoms in the implanted GaN varies with the damage profiles. A double-peak Au profile developed with the maxima located in the amorphous surface region and near the Au mean projected range. The result is interpreted as Au atom diffusion into the amorphous regime near the surface and Au trapping at irradiation-induced defects in the crystal structure. This trapping effect is also evidenced in this study by the suppressed recovery of the Au-decorated disorder in GaN. (c) 2000 American Institute of Physics

  18. Liquid-phase epitaxy of InGaAsP solid solutions on profiled substrates of InP(100)

    International Nuclear Information System (INIS)

    Dvoryankin, V.F.; Kaevitser, L.R.; Komarov, A.A.; Telegin, A.A.; Khusid, L.B.; Chernushin, M.D.

    1990-01-01

    Peculiarities of selective growth of InGaAsP solid solutions under liquid-phase epitaxy in shallow grooves are considered. InGaAsP crystals grown in grooves oriented along crystallografic [110] and [011] directions are determined to trend to equilibrium form under two-phase epitaxy, while wedge-shaped form of In 0.77 Ga 0.23 As 0.53 P 0.45 and In 0.53 P o.45 and IN 0.59 Ga 0.41 As 0.83 P 0.12 epitaxial layers obtained in grooves is determined by their composition only and does not depend on groove configuration

  19. Defect distribution in low-temperature molecular beam epitaxy grown Si/Si(100), improved depth profiling with monoenergetic positrons

    International Nuclear Information System (INIS)

    Szeles, C.; Asoka-Kumar, P.; Lynn, K.G.; Gossmann, H.; Unterwald, F.C.; Boone, T.

    1995-01-01

    The depth distribution of open-volume defects has been studied in Si(100) crystals grown by molecular beam epitaxy at 300 degree C by the variable-energy monoenergetic positron beam technique combined with well-controlled chemical etching. This procedure gave a 10 nm depth resolution which is a significant improvement over the inherent depth resolving power of the positron beam technique. The epitaxial layer was found to grow defect-free up to 80 nm, from the interface, where small vacancy clusters, larger than divacancies, appear. The defect density then sharply increases toward the film surface. The result clearly shows that the nucleation of small open-volume defects is a precursor state to the breakdown of epitaxy and to the evolution of an amorphous film

  20. The polarized neutron reflectivity and X-ray reflectivity studies of the magnetic profiles of epitaxial Ni80Fe20/Ru multilayers

    International Nuclear Information System (INIS)

    Su, H.-C.; Peir, J.-J.; Lee, C.-H.; Lin, M.-Z.; Wu, P.-T.; Huang, J.C.A.; Tun Zin

    2005-01-01

    The depth profiles of the epitaxial Ni 80 Fe 20 (1 1 1)/Ru(0 0 0 1) multilayers were studied by polarized neutron reflectivity and X-ray reflectivity. At the Ru thickness that the anti-ferromagnetic coupling was found, the magnetic moments between two Ni 80 Fe 20 interlayers show a biquadratic coupling effect with a double unit cell at low applied fields. A magnetic dead layer of about 0.3 nm was also found at the interface boundaries. The maximal polarization effect applied to the Ru layer is less than 0.03μ B

  1. Theoretical ion implantation profiles for low energy protons under channeling conditions

    International Nuclear Information System (INIS)

    Nobel, J.A.; Sabin, J.R.; Trickey, S.B.

    1994-01-01

    The authors present early results from the CHANNEL code, which simulates the passage of ionized projectiles through bulk solids. CHANNEL solves the classical equations of motion for the projectile using a force obtained from the gradient of the quantum mechanically derived coulombic potential of the solid (determined via a full potential augmented plane wave (FLAPW) calculation on the bulk) and a quantum mechanical energy dissipation term, the stopping power, as determined from the method of Echenique, Neiminen, and Ritchie. The code then generates the trajectory of the ionic projectile for a given incident position on the unit cell face and an initial velocity. The authors use CHANNEL to generate an ion (proton) implantation profile for the test case of simple cubic hydrogen with the projectile's initial velocity parallel to the (100) channel. Further preliminary results for ion implantation profiles of protons in diamond structure Si, with initial velocity along the (100) and (110) channels, are given

  2. Ion channeling study of epitaxially grown HoBa2Cu3Ox thin films on MgO(001)

    International Nuclear Information System (INIS)

    Watamori, Michio; Shoji, Fumiya; Hanawa, Teruo; Oura, Kenjiro; Itozaki, Hideo.

    1990-01-01

    The crystalline quality of high-T c superconducting HoBa 2 Cu 3 O x thin films formed on MgO(001) has been investigated by a high-energy ion channeling technique. Analysis was performed at 3 depth regions (surface, inside, and interface), and the degree of crystalline quality at each depth was estimated. Based on ion channeling measurements carried out with the normal and off-normal and directions, it has been found that (1) the crystalline quality at the film surface is much better than that at the interface, (2) the crystalline disorder can be seen mainly along the c-axis, and (3) the film consists of two domains, 90deg rotated from each other about the c-axis of the film. The crystalline quality of the MgO substrates has also been investigated. (author)

  3. Selfsupported epitaxial silicon films

    International Nuclear Information System (INIS)

    Lazarovici, D.; Popescu, A.

    1975-01-01

    The methods of removing the p or p + support of an n-type epitaxial silicon layer using electrochemical etching are described. So far, only n + -n junctions have been processed. The condition of anodic dissolution for some values of the support and layer resistivity are given. By this method very thin single crystal selfsupported targets of convenient areas can be obtained for channeling - blocking experiments

  4. Ion channel profile of TRPM8 cold receptors reveals a novel role of TASK-3 potassium channels in thermosensation

    Science.gov (United States)

    Morenilla-Palao, Cruz; Luis, Enoch; Fernández-Peña, Carlos; Quintero, Eva; Weaver, Janelle L.; Bayliss, Douglas A.; Viana, Félix

    2017-01-01

    Summary Animals sense cold ambient temperatures through the activation of peripheral thermoreceptors that express TRPM8, a cold- and menthol-activated ion channel. These receptors can discriminate a very wide range of temperatures from innocuous to noxious. The molecular mechanism responsible for the variable sensitivity of individual cold receptors to temperature is unclear. To address this question, we performed a detailed ion channel expression analysis of cold sensitive neurons, combining BAC transgenesis with a molecular profiling approach in FACS purified TRPM8 neurons. We found that TASK-3 leak potassium channels are highly enriched in a subpopulation of these sensory neurons. The thermal threshold of TRPM8 cold neurons is decreased during TASK-3 blockade and in mice lacking TASK-3 and, most importantly, these mice display hypersensitivity to cold. Our results demonstrate a novel role of TASK-3 channels in thermosensation, showing that a channel-based combinatorial strategy in TRPM8 cold thermoreceptors leads to molecular specialization and functional diversity. PMID:25199828

  5. High resolution measurement of the velocity profiles of channel flows using the particle image velocimetry technique

    International Nuclear Information System (INIS)

    Nor Azizi Mohamed

    2000-01-01

    The high resolution velocity profiles of a uniform steady channel flow and a flow beneath waves were obtained using the particle image velocimetry (PIV) technique. The velocity profiles for each flow were calculated for both components. It is shown that the profiles obtained are very precise, displaying the point velocities from a few millimeters from the bottom of the channel up to the water surface across the water depth. In the case of the wave-induced flow, the profiles are shown under the respective wave phases and given in a plane representation. High resolution measurement of point velocities in a flow is achievable using PIV and invaluable when applied to a complex flow. (Author)

  6. Influence of an axial magnetic field on the density profile of capillary plasma channels

    CERN Document Server

    Ivanov, V V; Toma, E S; Bijkerk, F

    2003-01-01

    A narrow capillary plasma channel, with a sizeable depletion of the electron density on the channel axis, has been proposed to guide a laser pulse over a length of several to several tens of centimetres. We discuss the possibility to significantly improve the wave-guiding properties of such a channel by applying an axial magnetic field. Our analytical and numerical studies show that a pulsed axial magnetic field of 10 T in a hydrogen capillary plasma at a pressure of 50 Torr will reduce the on-axis plasma density by a factor of three, and the full width at half maximum of the density profile by a factor of two. The resulting parabolic plasma density profile is expected to be more efficient in guiding laser pulses.

  7. Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire; Wu, Xiaosong; First, Phillip N.; Conrad, Edward H.; Li, Xuebin; Li, Tianbo; Sprinkle, Michael; Hass, Joanna; Sadowski, Marcin L.; Potemski, Marek; Martinez, Gérard

    2007-07-01

    Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties that may persist above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high-mobility epitaxial graphene. It appears that the effect is suppressed due to the absence of localized states in the bulk of the material. Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temperature ballistic devices may be feasible for low-dissipation high-speed nanoelectronics.

  8. Comparing LiDAR-Generated to ground- surveyed channel cross-sectional profiles in a forested mountain stream

    Science.gov (United States)

    Brian C. Dietterick; Russell White; Ryan Hilburn

    2012-01-01

    Airborne Light Detection and Ranging (LiDAR) holds promise to provide an alternative to traditional ground-based survey methods for stream channel characterization and some change detection purposes, even under challenging landscape conditions. This study compared channel characteristics measured at 53 ground-surveyed and LiDAR-derived crosssectional profiles located...

  9. Variation of velocity profile according to blood viscosity in a microfluidic channel

    Science.gov (United States)

    Yeom, Eunseop; Kang, Yang Jun; Lee, Sang-Joon

    2014-11-01

    The shear-thinning effect of blood flows is known to change blood viscosity. Since blood viscosity and motion of red blood cells (RBCs) are closely related, hemorheological variations have a strong influence on hemodynamic characteristics. Therefore, understanding on the relationship between the hemorheological and hemodynamic properties is importance for getting more detailed information on blood circulation in microvessels. In this study, the blood viscosity and velocity profiles in a microfluidic channel were systematically investigated. Rat blood was delivered in the microfluidic device which can measure blood viscosity by monitoring the flow-switching phenomenon. Velocity profiles of blood flows in the microchannel were measured by using a micro-particle image velocimetry (PIV) technique. Shape of velocity profiles measured at different flow rates was quantified by using a curve-fitting equation. It was observed that the shape of velocity profiles is highly correlated with blood viscosity. The study on the relation between blood viscosity and velocity profile would be helpful to understand the roles of hemorheological and hemodynamic properties in cardiovascular diseases. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (No. 2008-0061991).

  10. Theoretical examination of the slot channel waveguide configured in a cylindrically symmetric dielectric ring profile

    Science.gov (United States)

    Gauthier, Robert C.; Alzahrani, Mohammed A.; Jafari, Seyed Hamed

    2014-10-01

    It has recently been experimentally demonstrated that slot channel waveguides, configured in cylindrical space, can support high azimuthal order modes similar to whispering-gallery modes. This paper presents a mode solver based on Maxwell's vector wave equation for the electric field cast into an eigenvalue problem using a Fourier-Bessel basis function space. The modal frequencies and field profiles of the high azimuthal order slot-channel-whispering-gallery (SCWG) modes are computed for a set of nanometer spaced silicon rings supported by oxide. The computations show, that in addition to the traditionally observed, lowest order mode, the structure may support higher order SCWG modes. We complete the analysis by computing structures response as an ambient medium index of refraction sensor which achieves over 400 nm per RIU sensitivity.

  11. EDITORIAL: Epitaxial graphene Epitaxial graphene

    Science.gov (United States)

    de Heer, Walt A.; Berger, Claire

    2012-04-01

    Graphene is widely regarded as an important new electronic material with interesting two-dimensional electron gas properties. Not only that, but graphene is widely considered to be an important new material for large-scale integrated electronic devices that may eventually even succeed silicon. In fact, there are countless publications that demonstrate the amazing applications potential of graphene. In order to realize graphene electronics, a platform is required that is compatible with large-scale electronics processing methods. It was clear from the outset that graphene grown epitaxially on silicon carbide substrates was exceptionally well suited as a platform for graphene-based electronics, not only because the graphene sheets are grown directly on electronics-grade silicon carbide (an important semiconductor in its own right), but also because these sheets are oriented with respect to the semiconductor. Moreover, the extremely high temperatures involved in production assure essentially defect-free and contamination-free materials with well-defined interfaces. Epitaxial graphene on silicon carbide is not a unique material, but actually a class of materials. It is a complex structure consisting of a reconstructed silicon carbide surface, which, for planar hexagonal silicon carbide, is either the silicon- or the carbon-terminated face, an interfacial carbon rich layer, followed by one or more graphene layers. Consequently, the structure of graphene films on silicon carbide turns out to be a rich surface-science puzzle that has been intensively studied and systematically unravelled with a wide variety of surface science probes. Moreover, the graphene films produced on the carbon-terminated face turn out to be rotationally stacked, resulting in unique and important structural and electronic properties. Finally, in contrast to essentially all other graphene production methods, epitaxial graphene can be grown on structured silicon carbide surfaces to produce graphene

  12. Ge p-channel tunneling FETs with steep phosphorus profile source junctions

    Science.gov (United States)

    Takaguchi, Ryotaro; Matsumura, Ryo; Katoh, Takumi; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    The solid-phase diffusion processes of three n-type dopants, i.e., phosphorus (P), arsenic (As), and antimony (Sb), from spin-on-glass (SOG) into Ge are compared. We show that P diffusion can realize both the highest impurity concentration (˜7 × 1019 cm-3) and the steepest impurity profile (˜10 nm/dec) among the cases of the three n-type dopants because the diffusion coefficient is strongly dependent on the dopant concentration. As a result, we can conclude that P is the most suitable dopant for the source formation of Ge p-channel TFETs. Using this P diffusion, we fabricate Ge p-channel TFETs with high-P-concentration and steep-P-profile source junctions and demonstrate their operation. A high ON current of ˜1.7 µA/µm is obtained at room temperature. However, the subthreshold swing and ON current/OFF current ratio are degraded by any generation-recombination-related current component. At 150 K, SSmin of ˜108 mV/dec and ON/OFF ratio of ˜3.5 × 105 are obtained.

  13. Determining the effects of thermal conductivity on epoxy molds using profiled cooling channels with metal inserts

    International Nuclear Information System (INIS)

    Altaf, Khurram; Rani, Abdul Ahmad Majdi; Ahmad, Faiz; Baharom, Masri; Raghavan, Vijay R.

    2016-01-01

    Polymer injection molds are generally manufactured with metallic materials, such as tool steel, which provide reliable working of molds and extended service life. The manufacture of injection molds with steel is a prolonged process because of the strength of steel. For a short prototype production run, one of the suitable choices could be the use of aluminum-filled epoxy material, which can produce a functional mold in a short time as compared with a conventionally machined tool. Aluminum-filled epoxy tooling is a good choice for short production runs for engineering applications, yet works best for relatively simple shapes. The advantages in relation to the fabrication of injection molds with epoxy-based materials include time saving in producing the mold, epoxy curing at ambient temperature, and ease of machining and post processing. Nevertheless, one major drawback of epoxy material is its poor thermal conductivity, which results in a relatively longer cooling time for epoxy injection molds. This study investigates some of the innovative ideas for enhancing the thermal conductivity for epoxy molds. The basic concept behind these ideas was to embed a highly thermally conductive metal insert within the mold between cavities with an innovative design of cooling channels called profiled cooling channels. This technique will increase the effective thermal conductivity of the epoxy mold, leading to the reduction in cooling time for the injection molded polymer part. Experimental analysis conducted in the current study also verified that the mold with profiled cooling channels and embedded metal insert has significantly reduced the cooling time

  14. Determining the effects of thermal conductivity on epoxy molds using profiled cooling channels with metal inserts

    Energy Technology Data Exchange (ETDEWEB)

    Altaf, Khurram; Rani, Abdul Ahmad Majdi; Ahmad, Faiz; Baharom, Masri [Mechanical Engineering Dept., Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia); Raghavan, Vijay R. [OYL Manufacturing, Sungai Buloh (Malaysia)

    2016-11-15

    Polymer injection molds are generally manufactured with metallic materials, such as tool steel, which provide reliable working of molds and extended service life. The manufacture of injection molds with steel is a prolonged process because of the strength of steel. For a short prototype production run, one of the suitable choices could be the use of aluminum-filled epoxy material, which can produce a functional mold in a short time as compared with a conventionally machined tool. Aluminum-filled epoxy tooling is a good choice for short production runs for engineering applications, yet works best for relatively simple shapes. The advantages in relation to the fabrication of injection molds with epoxy-based materials include time saving in producing the mold, epoxy curing at ambient temperature, and ease of machining and post processing. Nevertheless, one major drawback of epoxy material is its poor thermal conductivity, which results in a relatively longer cooling time for epoxy injection molds. This study investigates some of the innovative ideas for enhancing the thermal conductivity for epoxy molds. The basic concept behind these ideas was to embed a highly thermally conductive metal insert within the mold between cavities with an innovative design of cooling channels called profiled cooling channels. This technique will increase the effective thermal conductivity of the epoxy mold, leading to the reduction in cooling time for the injection molded polymer part. Experimental analysis conducted in the current study also verified that the mold with profiled cooling channels and embedded metal insert has significantly reduced the cooling time.

  15. Multiple flow profiles for two-phase flow in single microfluidic channels through site-selective channel coating.

    Science.gov (United States)

    Logtenberg, Hella; Lopez-Martinez, Maria J; Feringa, Ben L; Browne, Wesley R; Verpoorte, Elisabeth

    2011-06-21

    An approach to control two-phase flow systems in a poly(dimethylsiloxane) (PDMS) microfluidic device using spatially selective surface modification is demonstrated. Side-by-side flows of ethanol : water solutions containing different polymers are used to selectively modify both sides of a channel by laminar flow patterning. Introduction of air pockets during modification allows for control over the length of the channel section that is modified. This approach makes it possible to achieve slug flow and side-by-side flow of water : 1-octanol simultaneously within the same PDMS channel, without the need of additional structural elements. A key finding is that conditioning of the PDMS channels with 1-octanol before polymer deposition is crucial to achieving stable side-by-side flows.

  16. Predicting the impact of vegetations in open channels with different distributaries' operations on water surface profile using artificial neural networks

    International Nuclear Information System (INIS)

    Abdeen, Mostafa A. M.

    2008-01-01

    Most of the open water irrigation channels in Egypt suffer from the infestation of aquatic weeds, especially the submerged ones that cause numerous hydraulic problems for the open channels themselves and their water distributaries such as increasing water losses, obstructing water flow, and reducing channels' water distribution efficiencies. Accurate simulation and prediction of flow behavior in such channels is very essential for water distribution decision makers. Artificial neural networks (ANN) have proven to be very successful in the simulation of several physical phenomena, in general, and in the water research field in particular. Therefore, the current study aims towards introducing the utilization of ANN in simulating the impact of vegetation in main open channel, which supplies water to different distributaries, on the water surface profile in this main channel. Specifically, the study, presented in the current paper utilizes ANN technique for the development of various models to simulate the impact of different submerged weeds' densities, different flow discharges, and different distributaries operation scheduling on the water surface profile in an experimental main open channel that supplies water to different distributaries. In the investigated experiment, the submerged weeds were simulated as branched flexible elements. The investigated experiment was considered as an example for implementing the same methodology and technique in a real open channel system. The results showed that the ANN technique is very successful in simulating the flow behavior of the pre-mentioned open channel experiment with the existence of the submerged weeds. In addition, the developed ANN models were capable of predicting the open channel flow behavior in all the submerged weeds' cases that were considered in the ANN development process

  17. Fluorescence-based high-throughput functional profiling of ligand-gated ion channels at the level of single cells.

    Directory of Open Access Journals (Sweden)

    Sahil Talwar

    Full Text Available Ion channels are involved in many physiological processes and are attractive targets for therapeutic intervention. Their functional properties vary according to their subunit composition, which in turn varies in a developmental and tissue-specific manner and as a consequence of pathophysiological events. Understanding this diversity requires functional analysis of ion channel properties in large numbers of individual cells. Functional characterisation of ligand-gated channels involves quantitating agonist and drug dose-response relationships using electrophysiological or fluorescence-based techniques. Electrophysiology is limited by low throughput and high-throughput fluorescence-based functional evaluation generally does not enable the characterization of the functional properties of each individual cell. Here we describe a fluorescence-based assay that characterizes functional channel properties at single cell resolution in high throughput mode. It is based on progressive receptor activation and iterative fluorescence imaging and delivers >100 dose-responses in a single well of a 384-well plate, using α1-3 homomeric and αβ heteromeric glycine receptor (GlyR chloride channels as a model system. We applied this assay with transiently transfected HEK293 cells co-expressing halide-sensitive yellow fluorescent protein and different GlyR subunit combinations. Glycine EC50 values of different GlyR isoforms were highly correlated with published electrophysiological data and confirm previously reported pharmacological profiles for the GlyR inhibitors, picrotoxin, strychnine and lindane. We show that inter and intra well variability is low and that clustering of functional phenotypes permits identification of drugs with subunit-specific pharmacological profiles. As this method dramatically improves the efficiency with which ion channel populations can be characterized in the context of cellular heterogeneity, it should facilitate systems

  18. Seismarmara experiment: results from reprocessing of selected multi-channel seismic reflection profiles

    Science.gov (United States)

    Cetin, S.; Voogd, B.; Carton, H.; Laigle, M.; Becel, A.; Saatcilar, R.; Singh, S.; Hirn, A.

    2003-04-01

    The North Anatolian Fault (NAF) has been responsible for the earthquakes of Izmit and Duzce in 1999. The occurrence of these earthquakes has drawn scientific attention into the Sea of Marmara since the NAF enters into the Sea of Marmara where the latest Izmit earthquake rupture stopped. The SEISMARMARA-2001 survey is a combined seismic reflection, refraction and earthquake experiment carried out in 2001 in the Marmara Region in Turkey by French-Turkish scientific cooperation. The objectives of this survey were to image the various branches of the NAF and related other fault systems. R/V Le Nadir was equipped with a 4.5 km long streamer with 360 channels and a large airgun source. During Leg 1, a grid of large regional lines encompassing the whole Marmara trough was shot. For part of them a strong 8100 cu.in. source for deepest penetration was used, with a 150 m shot interval giving a 15-fold coverage. Another part was shot for a higher resolution with a 2900 cu. in. array at a 50m or 38 m interval to give a 45 or 60-fold coverage. The latter acquisition parameters were used for Leg 2 that was devoted to a very dense grid of lines in the Cinarcik Basin Reprocessing of the multi-channel seismic data is currently being undertaken in several Institutions using different seismic processing softwares (GeoVecteur, ProMAX, Focus), to take advantage of the diverse acquisitions and cope with their limitations, for instance high fold-order for Leg 2 and strength of signal but loose spatial sampling for the bigger source. The main objectives of the reprocessing of the selected profiles are to do a detailed velocity analysis and stacking after deconvolution, filtering to remove or suppress deep sea bottom multiples and out of plane reflections, and time-migration and depth conversion and thus reveal both the shallow and deeper reflection image of the crust in the Sea of Marmara. We show that choosing an appropriate processing sequence for different sources and acquisition

  19. The application of low angle Rutherford backscattering and channelling techniques to determine implantation induced disorder profile distributions in semiconductors

    International Nuclear Information System (INIS)

    Ahmed, N.A.G.; Christodoulides, C.E.; Carter, G.; Nobes, M.J.; Titov, A.I.

    1980-01-01

    Low angle exit (9 0 ) Rutherford backscattering geometry and channelling of 2 MeV 4 He + are employed to investigate the disorder depth profiles created by 40 keV N + implantation in (111) silicon and (100) GaAs targets. Parameters which can influence the disordering rate and its spatial distribution, such as ion fluence flux, substrate type and substrate temperature are examined. Under certain implantation conditions, the damage profile distributions are asymmetric - exhibiting a bimodal form in silicon targets or confined much closer to the GaAs surface than the normally expected mean range of 40 keV N + ions. (orig.)

  20. Dechanneling measurements of defect depth profiles and effective cross-channel distribution of misaligned atoms in ion irradiated gold

    International Nuclear Information System (INIS)

    Pronko, P.P.

    1975-01-01

    Defect depth profiles for self ion and He + irradiated gold are obtained from single and multiple scatter dechanneling analysis in single crystal gold films. Quantitative defect densities are obtained through use of atomic scattering cross sections. Integral damage profiles are extracted from the dechanneling spectra and subsequently differentiated to yield the volume concentration of defects as a function of depth. Results from the self ion irradiations suggest that incident ions produce defect distributions across depths much greater than predicted by random stopping theory. This is in agreement with TEM observations of others. Comparison of the experimental profiles is made with theoretical vacancy distributions predicted by defect diffusion in a radiation environment. Similarities are observed for the low fluence irradiations suggesting that profile characteristics may be controlled by rapid migration and loss of interstitials to the film surfaces during irradiation. Information on the across-channel distribution of misaligned atoms in the damaged films is obtained with the steady increase of transverse energy model applied to the dechanneling spectra. A predominance of slight misalignment is observed with no contribution to dechanneling coming from atoms displaced significantly close to the center of the channels. This is in keeping with what is expected for crystal distortions caused by the strain fields associated with vacancy cluster defects

  1. Dechanneling measurements of defect depth profiles and effective cross-channel distribution of misaligned atoms in ion-irradiated gold

    International Nuclear Information System (INIS)

    Pronko, P.P.

    1976-01-01

    Defect depth profiles for self-ion and He + irradiated gold are obtained from single and multiple scatter dechanneling analysis in single-crystal gold films. Quantitative defect densities are obtained through use of atomic-scattering cross sections. Integral damage profiles are extracted from the dechanneling spectra and subsequently differentiated to yield the volume concentration of defects as a function of depth. Results from the self-ion irradiations suggest that incident ions produce defect distributions across depths much greater than predicted by random stopping theory. This is in agreement with TEM observations of others. Comparison of the experimental profiles is made with theoretical vacancy distributions predicted by defect diffusion in a radiation environment. Similarities are observed for the low-fluence irradiations, suggesting that profile characteristics may be controlled by rapid migration and loss of interstitials to the film surfaces during irradiation. Information on the across-channel distribution of misaligned atoms in the damaged films is obtained with the steady increase of transverse energy model. A predominance of slight misalignment is observed with no contribution to dechanneling coming from atoms displaced significantly close to the center of the channels. This is in keeping with what is expected for crystal distortions caused by the strain fields associated with vacancy cluster defects. (Auth.)

  2. Strain-Modulated Epitaxy

    National Research Council Canada - National Science Library

    Brown, April

    1999-01-01

    Strain-Modulated Epitaxy (SME) is a novel approach, invented at Georgia Tech, to utilize subsurface stressors to control strain and therefore material properties and growth kinetics in the material above the stressors...

  3. Thin epitaxial silicon detectors

    International Nuclear Information System (INIS)

    Stab, L.

    1989-01-01

    Manufacturing procedures of thin epitaxial surface barriers will be given. Some improvements have been obtained: larger areas, lower leakage currents and better resolutions. New planar epitaxial dE/dX detectors, made in a collaboration work with ENERTEC-INTERTECHNIQUE, and a new application of these thin planar diodes to EXAFS measurements, made in a collaboration work with LURE (CNRS,CEA,MEN) will also be reported

  4. Deriving principal channel metrics from bank and long-profile geometry with the R package cmgo

    Science.gov (United States)

    Golly, Antonius; Turowski, Jens M.

    2017-09-01

    Landscape patterns result from landscape forming processes. This link can be exploited in geomorphological research by reversely analyzing the geometrical content of landscapes to develop or confirm theories of the underlying processes. Since rivers represent a dominant control on landscape formation, there is a particular interest in examining channel metrics in a quantitative and objective manner. For example, river cross-section geometry is required to model local flow hydraulics, which in turn determine erosion and thus channel dynamics. Similarly, channel geometry is crucial for engineering purposes, water resource management, and ecological restoration efforts. These applications require a framework to capture and derive the data. In this paper we present an open-source software tool that performs the calculation of several channel metrics (length, slope, width, bank retreat, knickpoints, etc.) in an objective and reproducible way based on principal bank geometry that can be measured in the field or in a GIS. Furthermore, the software provides a framework to integrate spatial features, for example the abundance of species or the occurrence of knickpoints. The program is available at https://github.com/AntoniusGolly/cmgo and is free to use, modify, and redistribute under the terms of the GNU General Public License version 3 as published by the Free Software Foundation.

  5. Recent adjustments to the long profile of Cooksville Creek, an urbanized bedrock channel in Mississauga, Ontario

    Science.gov (United States)

    Tinkler, Keith J.; Parish, John

    Cooksville Creek (33 km2) is based in weak Georgian Bay Formation shale and thin limestone and has been gradually urbanized by the City of Mississauga within the last thirty years. These conditions, together with a mean thalweg gradient of about 0.77%, have produced enhanced rates of channel bed erosion along much of the channel (the order of 2 centimetres per year), as revealed by installed engineering works, such as armour stone blocks and gabion baskets. Erosion rates below drop structures are up to an order of magnitude faster. A year-long monitoring program revealed that weathering of the shale bed by wetting and drying cycles was primarily responsible for fragmenting the shale to a size (a few centimetres on the long axis) which could be removed by frequent and moderate high flows with a magnitude much less than the Mean Annual Flood. Channel bed quarrying of shale and limestone slabs, and the transport of larger clasts and meter dimension armour stones toppled from channel structures, require flood flows with a recurrence interval of about the Mean Annual Flood. Such flows are characterized by critical or supercritical flow conditions along the thalweg, and with velocities typically in the range 4 to 6 meters per second, they are well able to quarry the bed, and transport clasts up to metre dimension in size.

  6. New geological interpretation of multi-channel seismic profiles from the Pacific Margin of the Antarctic Peninsula

    Directory of Open Access Journals (Sweden)

    Okoń Jan

    2016-06-01

    Full Text Available The Polish Geophysical Expedition to West Antarctica in 1979–1980 was carried out by the Institute of Geophysics, Polish Academy of Sciences. Beside deep seismic soundings, 12 multi-channel seismic profiles, with a total length of ca 1000 km have been recorded north and east of the South Shetland Islands and in the Bransfield Strait, but they have never before been completely interpreted and published. All profiles have been processed with modern processing flow including time migration. Profiles crossing the South Shetland Trench revealed distinct reflector inside continental slope, which has been interpreted as border between buried accretionary prism and overlying slope sediments of glacial-marine origin. Profiles in the Bransfield Strait show traces of the Last Glacial Maximum (LGM in the form of glacial foreground valleys, with some of them used as weak spots for young age volcanic intrusions. This paper is the first comprehensive geological interpretation of collected dataset and differences between results from other expeditions are discussed.

  7. Radial dependence of surface streamer-channel luminosity: experimental evidence of Gaussian radiative profiles in Ar and N2

    International Nuclear Information System (INIS)

    Šimek, M; Ambrico, P F

    2012-01-01

    Radial distributions of electronically excited species produced during surface streamer propagation were obtained by applying the Abel inverse transform to projected luminosities of single streamers. The streamers were generated in an argon and nitrogen surface coplanar dielectric barrier discharge at atmospheric pressure and their magnified microscopic images were registered with high time resolution. Selected regions of the projected luminosities were processed by the Abel inverse transform procedure based on the Hankel–Fourier method assuming cylindrical symmetry of the streamer channel. Projected as well as Abel-inverted profiles were fitted by Gaussian functions. It is shown that the projected profiles, in addition to the Abel-inverted ones, can be well approximated by the sum of two coaxial Gaussians with two different half-widths and weights. The sharper Gaussian component with higher weight characterizes the radial dependence of the primary cathode-directed streamer-channel luminosity. The second (broader) Gaussian component probably originates either from the pre-breakdown Townsend phase or from the second wave propagating towards the anode. (paper)

  8. Regional two-dimensional magnetotelluric profile in West Bohemia/Vogtland reveals deep conductive channel into the earthquake swarm region

    Science.gov (United States)

    Muñoz, Gerard; Weckmann, Ute; Pek, Josef; Kováčiková, Světlana; Klanica, Radek

    2018-03-01

    The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohře) Rift and the Mariánské Lázně fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublák and Hartoušov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Nový Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mýtina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Teplá-Barrandian zones, whose surface expression is located only a few kilometres away.

  9. Specific profiles of ion channels and ionotropic receptors define adipose- and bone marrow derived stromal cells.

    Czech Academy of Sciences Publication Activity Database

    Forostyak, Oksana; Butenko, Olena; Anděrová, Miroslava; Forostyak, Serhiy; Syková, Eva; Verkhratsky, A.; Dayanithi, Govindan

    2016-01-01

    Roč. 16, č. 3 (2016), s. 622-634 ISSN 1873-5061 R&D Projects: GA ČR(CZ) GA14-34077S; GA ČR(CZ) GAP304/11/2373; GA ČR(CZ) GBP304/12/G069 Institutional support: RVO:68378041 Keywords : adipose derived stromal cells * bone marrow stromal cell * Ca(2+) signaling * Ion channels Subject RIV: FH - Neurology Impact factor: 3.494, year: 2016

  10. The generation of calandria tube (CT) inner diameter profiles from fuel channel (FC) inspection data

    Energy Technology Data Exchange (ETDEWEB)

    Sedran, P.J., E-mail: paul.sedran@amec.com [AMEC NSS, Toronto, ON (Canada); Rankin, B., E-mail: brankin@nbpower.com [NB Power, Fredericton, NB (Canada); Lemire, C., E-mail: Lemire.Christian@hydro.qc.ca [Hydro-Quebec, Montreal, QC (Canada)

    2015-07-01

    Studies of CT deformation at spacer locations, key to the development of FC deformation modelling, have been limited by the availability of gauging measurements from removed CTs. In [1], it was proposed that CT dimensional profiles could be generated using FC inspection data. Since then, the concept was investigated further by assessing: (1) the normalisation of gap measurements to the diameter of the spacer coil, (2) the validity of gap measurements from inspections of Point Lepreau and Gentilly-2, and the CT dimensional profiles generated from the inspection data.It was concluded, from the work presented in this paper, that the CT-PT gap data and the CT dimensional profiles generated using the data from the two subject inspections are reasonable. (author)

  11. Multi-channel electronics for secondary emission grid profile monitor of TTF linac

    International Nuclear Information System (INIS)

    Reingardt-Nikoulin, P.; Gaidash, V.; Mirzojan, A.; Kocharyan, V.; Noelle, D.

    2004-01-01

    According to the TTF beam experimental program, a measurement f the time dependence of the energy spread within the bunch train should be done by means of a standard device for profile measurements, that is Secondary Emission Grid (SEMG). SEMG on the high-energy TTF beam is placed in the focal plane of the magnet spectrometer. It should measure the total energy spread in the range from 0.1% up to a few percents for any single or any group of electron bunches in the bunch train of TTF Linac. SEMG profile measurements with new high sensitive electronics are described. Beam results of SEMG Monitor test are given for two modifications of an electronic preamplifier

  12. On-current modeling of short-channel double-gate (DG) MOSFETs with a vertical Gaussian-like doping profile

    International Nuclear Information System (INIS)

    Dubey, Sarvesh; Jit, S.; Tiwari Pramod Kumar

    2013-01-01

    An analytic drain current model is presented for doped short-channel double-gate MOSFETs with a Gaussian-like doping profile in the vertical direction of the channel. The present model is valid in linear and saturation regions of device operation. The drain current variation with various device parameters has been demonstrated. The model is made more physical by incorporating the channel length modulation effect. Parameters like transconductance and drain conductance that are important in assessing the analog performance of the device have also been formulated. The model results are validated by numerical simulation results obtained by using the commercially available ATLAS™, a two dimensional device simulator from SILVACO. (semiconductor devices)

  13. Synchrotron radiation excited silicon epitaxy using disilane

    International Nuclear Information System (INIS)

    Akazawa, Housei; Utsumi, Yuichi

    1995-01-01

    Synchrotron radiation (SR) excited chemical reactions provide new crystal growth methods suitable for low-temperature Si epitaxy. The growth kinetics and film properties were investigated by atomic layer epitaxy (ALE) and photochemical vapor deposition (CVD) modes using Si 2 H 6 . SR-ALE, isolating the surface growth channel mediated by photon stimulated hydrogen desorption, achieves digital growth independent of gas exposure time, SR irradiation time, and substrate temperature. On the other hand in SR-CVD, photolysis of Si 2 H 6 is predominant. In the nonirradiated region, Eley-Rideal type reaction between the photofragments and the surface deposit Si adatoms in a layer-by-layer fashion. In the irradiated region, however, multi-layer photolysis and rebounding occurs within the condensed Si 2 H 6 layer. The pertinent elementary processes were identified by using the high-resolution time-of-flight mass spectroscopy. The SR-CVD can grow a uniform and epitaxial Si film down to 200degC. The surface morphology is controlled by the surfactant effect of hydrogen atoms. (author)

  14. Vertical profiles of atmospheric fluorescent aerosols observed by a mutil-channel lidar spectrometer system

    Science.gov (United States)

    Huang, Z.; Huang, J.; Zhou, T.; Sugimoto, N.; Bi, J.

    2015-12-01

    Zhongwei Huang1*, Jianping Huang1, Tian Zhou1, Nobuo Sugimoto2, Jianrong Bi1 and Jinsen Shi11Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou, China. 2Atmospheric Environment Division, National Institutes for Environmental Studies, Tsukuba, Japan Email: huangzhongwei@lzu.edu.cn Abstract Atmospheric aerosols have a significant impact on regional and globe climate. The challenge in quantifying aerosol direct radiative forcing and aerosol-cloud interactions arises from large spatial and temporal heterogeneity of aerosol concentrations, compositions, sizes, shape and optical properties (IPCC, 2007). Lidar offers some remarkable advantages for determining the vertical structure of atmospheric aerosols and their related optical properties. To investigate the characterization of atmospheric aerosols (especially bioaerosols) with high spatial and temporal resolution, we developed a Raman/fluorescence/polarization lidar system employed a multi-channel spectrometer, with capabilities of providing measurements of Raman scattering and laser-induced fluorescence excitation at 355 nm from atmospheric aerosols. Meanwhile, the lidar system operated polarization measurements both at 355nm and 532nm wavelengths, aiming to obtain more information of aerosols. It employs a high power pulsed laser and a received telescope with 350mm diameter. The receiver could simultaneously detect a wide fluorescent spectrum about 178 nm with spectral resolution 5.7 nm, mainly including an F/3.7 Crossed Czerny-Turner spectrograph, a grating (1200 gr/mm) and a PMT array with 32 photocathode elements. Vertical structure of fluorescent aerosols in the atmosphere was observed by the developed lidar system at four sites across northwest China, during 2014 spring field observation that conducted by Lanzhou University. It has been proved that the developed lidar could detect the fluorescent aerosols with high temporal and

  15. Epitaxial growth of hybrid nanostructures

    Science.gov (United States)

    Tan, Chaoliang; Chen, Junze; Wu, Xue-Jun; Zhang, Hua

    2018-02-01

    Hybrid nanostructures are a class of materials that are typically composed of two or more different components, in which each component has at least one dimension on the nanoscale. The rational design and controlled synthesis of hybrid nanostructures are of great importance in enabling the fine tuning of their properties and functions. Epitaxial growth is a promising approach to the controlled synthesis of hybrid nanostructures with desired structures, crystal phases, exposed facets and/or interfaces. This Review provides a critical summary of the state of the art in the field of epitaxial growth of hybrid nanostructures. We discuss the historical development, architectures and compositions, epitaxy methods, characterization techniques and advantages of epitaxial hybrid nanostructures. Finally, we provide insight into future research directions in this area, which include the epitaxial growth of hybrid nanostructures from a wider range of materials, the study of the underlying mechanism and determining the role of epitaxial growth in influencing the properties and application performance of hybrid nanostructures.

  16. EFFECT FOR A SINGLE ROUGHNESS E=5,63mm OF EXPERIMENTAL TO STUDY HYDRAULIC JUMP PROFILE IN A CHANNEL IN U A ROUGH BOTTOM

    Directory of Open Access Journals (Sweden)

    A. Ghomri

    2013-06-01

    Full Text Available This study aims to study the hydraulic jump controlled by threshold, moving in a channel profile 'U' bottomed rough for a single roughness E=5,63mm. Functional relations in dimensionless terms, linking the different characteristics of the projection, showing the effect of roughness of the bottom of the channel are obtained. The hydraulic jump is the primary means used by hydraulic structures to dissipate energy. This hydraulic jump is formed at the sharp transition from a supercritical flow a stream flow.

  17. EFFECT FOR A SINGLE ROUGHNESS E=5,63mm OF EXPERIMENTAL TO STUDY HYDRAULIC JUMP PROFILE IN A CHANNEL IN U A ROUGH BOTTOM

    Directory of Open Access Journals (Sweden)

    A. Ghomri

    2015-07-01

    Full Text Available This study aims to study the hydraulic jump controlled by threshold, moving in a channel profile 'U' bottomed rough for a single roughness E=5,63mm. Functional relations in dimensionless terms, linking the different characteristics of the projection, showing the effect of roughness of the bottom of the channel are obtained. The hydraulic jump is the primary means used by hydraulic structures to dissipate energy. This hydraulic jump is formed at the sharp transition from a supercritical flow a stream flow.

  18. The conserved potassium channel filter can have distinct ion binding profiles: structural analysis of rubidium, cesium, and barium binding in NaK2K.

    Science.gov (United States)

    Lam, Yee Ling; Zeng, Weizhong; Sauer, David Bryant; Jiang, Youxing

    2014-08-01

    Potassium channels are highly selective for K(+) over the smaller Na(+). Intriguingly, they are permeable to larger monovalent cations such as Rb(+) and Cs(+) but are specifically blocked by the similarly sized Ba(2+). In this study, we used structural analysis to determine the binding profiles for these permeant and blocking ions in the selectivity filter of the potassium-selective NaK channel mutant NaK2K and also performed permeation experiments using single-channel recordings. Our data revealed that some ion binding properties of NaK2K are distinct from those of the canonical K(+) channels KcsA and MthK. Rb(+) bound at sites 1, 3, and 4 in NaK2K, as it does in KcsA. Cs(+), however, bound predominantly at sites 1 and 3 in NaK2K, whereas it binds at sites 1, 3, and 4 in KcsA. Moreover, Ba(2+) binding in NaK2K was distinct from that which has been observed in KcsA and MthK, even though all of these channels show similar Ba(2+) block. In the presence of K(+), Ba(2+) bound to the NaK2K channel at site 3 in conjunction with a K(+) at site 1; this led to a prolonged block of the channel (the external K(+)-dependent Ba(2+) lock-in state). In the absence of K(+), however, Ba(2+) acts as a permeating blocker. We found that, under these conditions, Ba(2+) bound at sites 1 or 0 as well as site 3, allowing it to enter the filter from the intracellular side and exit from the extracellular side. The difference in the Ba(2+) binding profile in the presence and absence of K(+) thus provides a structural explanation for the short and prolonged Ba(2+) block observed in NaK2K. © 2014 Lam et al.

  19. Seed layer technique for high quality epitaxial manganite films

    Directory of Open Access Journals (Sweden)

    P. Graziosi

    2016-08-01

    Full Text Available We introduce an innovative approach to the simultaneous control of growth mode and magnetotransport properties of manganite thin films, based on an easy-to-implement film/substrate interface engineering. The deposition of a manganite seed layer and the optimization of the substrate temperature allows a persistent bi-dimensional epitaxy and robust ferromagnetic properties at the same time. Structural measurements confirm that in such interface-engineered films, the optimal properties are related to improved epitaxy. A new growth scenario is envisaged, compatible with a shift from heteroepitaxy towards pseudo-homoepitaxy. Relevant growth parameters such as formation energy, roughening temperature, strain profile and chemical states are derived.

  20. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    International Nuclear Information System (INIS)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes; Hilber, Karlheinz; Sandtner, Walter

    2013-01-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na v 1.5 sodium and Ca v 1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on ion channels are a potential

  1. Anti-addiction drug ibogaine inhibits voltage-gated ionic currents: A study to assess the drug's cardiac ion channel profile

    Energy Technology Data Exchange (ETDEWEB)

    Koenig, Xaver; Kovar, Michael; Rubi, Lena; Mike, Agnes K.; Lukacs, Peter; Gawali, Vaibhavkumar S.; Todt, Hannes [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Hilber, Karlheinz, E-mail: karlheinz.hilber@meduniwien.ac.at [Center for Physiology and Pharmacology, Department of Neurophysiology and -pharmacology, Medical University of Vienna, 1090 Vienna (Austria); Sandtner, Walter [Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, 1090 Vienna (Austria)

    2013-12-01

    The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologously expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na{sub v}1.5 sodium and Ca{sub v}1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on

  2. Epitaxy physical principles and technical implementation

    CERN Document Server

    Herman, Marian A; Sitter, Helmut

    2004-01-01

    Epitaxy provides readers with a comprehensive treatment of the modern models and modifications of epitaxy, together with the relevant experimental and technological framework. This advanced textbook describes all important aspects of the epitaxial growth processes of solid films on crystalline substrates, including a section on heteroepitaxy. It covers and discusses in details the most important epitaxial growth techniques, which are currently widely used in basic research as well as in manufacturing processes of devices, namely solid-phase epitaxy, liquid-phase epitaxy, vapor-phase epitaxy, including metal-organic vapor-phase epitaxy and molecular-beam epitaxy. Epitaxy’s coverage of science and texhnology thin-film is intended to fill the need for a comprehensive reference and text examining the variety of problems related to the physical foundations and technical implementation of epitaxial crystallization. It is intended for undergraduate students, PhD students, research scientists, lecturers and practic...

  3. Expression profile analysis of circulating microRNAs and their effects on ion channels in Chinese atrial fibrillation patients.

    Science.gov (United States)

    Lu, Yingmin; Hou, Shuxin; Huang, Damin; Luo, Xiaohan; Zhang, Jinchun; Chen, Jian; Xu, Weiping

    2015-01-01

    To investigate the changes in expression profile of circulating microRNAs (miRNAs) and the regulatory effect of atrial fibrilation (AF)-related miRNAs on ion channels. 112 patients with AF were assigned into observation group, and another 112 non-AF people were assigned into control group. Total plasma RNAs were extracted from patients' blood samples. Differentially expressed miRNA-1s were transfected into primary-cultured neonatal rat cardiac myocytes. Compared with control group, significant differences were observed in 15 kinds of miRNAs in observation group. Down-regulation of the expression of miRNAs included hsa-miR-328, hsa-miR-145, hsa-miR-222, hsa-miR-1, hsa-miR-162, hsa-miR-432, and hsa-miR-493b; Up-regulation of the expression included hsa-miR634, hsa-miR-664, hsa-miR-9, hsa-miR-152, hsa-miR-19, hsa-miR-454, hsa-miR-146, and hsa-miR-374a. The expression level of CACNB2 protein in miRNA-1 group was significantly lower than that in blank control group, negative control group, MTmiRNA-1 group, AMO-1 group and miRNA-1+AMO-1 cotransfection group (P < 0.05), while in AMO-1 group, the expression level of CACNB2 protein was significantly higher than that in other groups (P < 0.05). These results indicated that transfected miRNA-1 could significantly inhibit the expression of CACNB2 protein. Circulating miRNAs can be used in studies concerning on the regulation mechanism of the occurrence and development of AF. MiRNA-1 can decrease the intracellular Ca(2+) concentration and prevent the AF.

  4. On the ligand binding profile and desensitization of plant ionotropic glutamate receptor (iGluR)-like channels functioning in MAMP-triggered Ca2+ influx

    DEFF Research Database (Denmark)

    Kwaaitaal, Mark Adrianus Cornelis J; Maintz, Jens; Cavdar, Meltem

    2012-01-01

    in the putative agonist binding profile and potential mode of desensitization of MAMP-activated plant iGluRs. Based on results from pharmacological inhibition and desensitization experiments, we propose that plant iGluR complexes responsible for the MAMP-triggered Ca ( 2+) signature have a binding profile...... that combines the specificities of mammalian NMDA-and non-NMDA types of iGluRs, possibly reflecting the evolutionary history of plant and animal iGluRs. We further hypothesize that, analogous to the mammalian NMDA-NR1 receptor, desensitization of plant iGluR-like channels might involve binding of the ubiquitous...

  5. Profiles

    International Nuclear Information System (INIS)

    2004-01-01

    Profiles is a synthetic overview of more than 100 national energy markets in the world, providing insightful facts and key energy statistics. A Profile is structured around 6 main items and completed by key statistics: Ministries, public agencies, energy policy are concerned; main companies in the oil, gas, electricity and coal sectors, status, shareholders; reserve, production, imports and exports, electricity and refining capacities; deregulation of prices, subsidies, taxes; consumption trends by sector, energy market shares; main energy projects, production and consumption prospects. Statistical Profiles are present in about 3 pages the main data and indicators on oil, gas, coal and electricity. (A.L.B.)

  6. Regional two-dimensional magnetotelluric profile in West Bohemia/Vogtland reveals deep conductive channel into the earthquake swarm region

    Czech Academy of Sciences Publication Activity Database

    Muňoz, G.; Weckmann, U.; Pek, Josef; Kováčiková, Světlana; Klanica, Radek

    2018-01-01

    Roč. 727, March (2018), s. 1-11 Institutional support: RVO:67985530 Keywords : magnetotellurics * West Bohemia * Fogtland * earthquake swarm * conductive channel * fluids Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology

  7. Distribution profiles of transient receptor potential melastatin- and vanilloid-related channels in rat spermatogenic cells and sperm.

    Science.gov (United States)

    Li, Shilin; Wang, Xinghuan; Ye, Haixia; Gao, Weicheng; Pu, Xiaoyong; Yang, Zhonghua

    2010-03-01

    In the present study, we aimed to investigate the expression and distribution of transient receptor potential melastatin (TRPM)- and vanilloid (TRPV)- related channels in rat spermatogenic cells and spermatozoa. Spermatogenic cells and spermatozoa were obtained from male Sprague-Dawley rats. Reverse transcription polymerase chain reaction (RT-PCR) were used to detect the expression of all TRPM and TRPV channel members with specific primers. Western blot analysis was applied for detecting the expression of TRPM and TRPV channel proteins. Immunohistochemistry staining for TRPM4, TRPM7 and TRPV5 was also performed in rat testis. The mRNAs of TRPM3, TRPM4, TRPM7 and TRPV5 were detected in the spermatogenic cells and spermatozoa in rat. Western blot analysis verified the expression of TRPM4, TRPM7 and TRPV5 in the rat spermatogenic cells and spermatozoa. Immunocytochemistry staining for TRPM and TRPV channel families indicated that TRPM4 and TRPM7 proteins were highly expressed in different stages of spermatogenic cells and spermatozoa, while TRPV5 protein was lowly expressed in these cells. Our results demonstrate that mRNAs or proteins for TRPM3, TRPM4, TRPM7 and TRPV5 exist in rat spermatogenic cells and spermatozoa. These data presented here may assist in elucidating the possible physiological function of TRPM and TRPV channels in spermatogenic cells and spermatozoa.

  8. Crystallization engineering as a route to epitaxial strain control

    Directory of Open Access Journals (Sweden)

    Andrew R. Akbashev

    2015-10-01

    Full Text Available The controlled synthesis of epitaxial thin films offers opportunities for tuning their functional properties via enabling or suppressing strain relaxation. Examining differences in the epitaxial crystallization of amorphous oxide films, we report on an alternate, low-temperature route for strain engineering. Thin films of amorphous Bi–Fe–O were grown on (001SrTiO3 and (001LaAlO3 substrates via atomic layer deposition. In situ X-ray diffraction and X-ray photoelectron spectroscopy studies of the crystallization of the amorphous films into the epitaxial (001BiFeO3 phase reveal distinct evolution profiles of crystallinity with temperature. While growth on (001SrTiO3 results in a coherently strained film, the same films obtained on (001LaAlO3 showed an unstrained, dislocation-rich interface, with an even lower temperature onset of the perovskite phase crystallization than in the case of (001SrTiO3. Our results demonstrate how the strain control in an epitaxial film can be accomplished via its crystallization from the amorphous state.

  9. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  10. Selenium implantation in epitaxial gallium arsenide layers

    International Nuclear Information System (INIS)

    Inada, T.; Tokunaga, K.; Taka, S.; Yuge, Y.; Kohzu, H.

    1981-01-01

    Selenium implantation at room temperature in S-doped epitaxial GaAs layers as a means of the formation of n + layers has been investigated. Doping profiles for Se-implanted layers have been examined by a C-V technique and/or a differential Hall effect method. It has been shown that n + layers with a maximum carrier concentration of approx. equal to1.5 x 10 18 cm -3 can be formed by implantation followed by a 15 min annealing at 950 0 C. Contact resistance of ohmic electrodes is reduced by use of the Se-implanted n + layers, resulting in the improvement on GaAs FET performance. Measured minimum noise figure of the Se-implanted GaAs FETs is 0.74 dB at 4 GHz. (orig.)

  11. Fluorine incorporation during Si solid phase epitaxy

    International Nuclear Information System (INIS)

    Impellizzeri, G.; Mirabella, S.; Romano, L.; Napolitani, E.; Carnera, A.; Grimaldi, M.G.; Priolo, F.

    2006-01-01

    We have investigated the F incorporation and segregation in preamorphized Si during solid phase epitaxy (SPE) at different temperatures and for several implanted-F energies and fluences. The Si samples were amorphized to a depth of 550 nm by implanting Si at liquid nitrogen temperature and then enriched with F at different energies (65-150 keV) and fluences (0.07-5 x 10 14 F/cm 2 ). Subsequently, the samples were regrown by SPE at different temperatures: 580, 700 and 800 deg. C. We have found that the amount of F incorporated after SPE strongly depends on the SPE temperature and on the energy and fluence of the implanted-F, opening the possibility to tailor the F profile during SPE

  12. Quantum Hall effect in epitaxial graphene with permanent magnets.

    Science.gov (United States)

    Parmentier, F D; Cazimajou, T; Sekine, Y; Hibino, H; Irie, H; Glattli, D C; Kumada, N; Roulleau, P

    2016-12-06

    We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the formation of well-developed quantum Hall states at Landau level filling factors v = ±2, commonly observed with superconducting electro-magnets. Furthermore, the chirality of the QHE edge channels can be changed by a top gate. These results demonstrate that basic QHE physics are experimentally accessible in graphene for a fraction of the price of conventional setups using superconducting magnets, which greatly increases the potential of the QHE in graphene for research and applications.

  13. Quantum Hall effect in epitaxial graphene with permanent magnets

    Science.gov (United States)

    Parmentier, F. D.; Cazimajou, T.; Sekine, Y.; Hibino, H.; Irie, H.; Glattli, D. C.; Kumada, N.; Roulleau, P.

    2016-12-01

    We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the formation of well-developed quantum Hall states at Landau level filling factors v = ±2, commonly observed with superconducting electro-magnets. Furthermore, the chirality of the QHE edge channels can be changed by a top gate. These results demonstrate that basic QHE physics are experimentally accessible in graphene for a fraction of the price of conventional setups using superconducting magnets, which greatly increases the potential of the QHE in graphene for research and applications.

  14. Flow and pressure profiles for the primary heat transport system of Rajasthan Atomic Power Station for the operation with few isolated reactor channels near the end shield cracks

    Energy Technology Data Exchange (ETDEWEB)

    Gaikwad, A J; Chaki, S K; Sehgal, R L; Venkat Raj, V [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai (India)

    1994-06-01

    The RAPS (Rajasthan Atomic Power Station) unit-1 is now operating at reduced power due to the removal of fifteen fuel channels for repair of south end shield cracks. The power level is restricted to 50% of the full power capacity as a precautionary measure. The relative difference that operation at 50% power and higher power would make to the end shield structure is being currently analysed with a view to operate this reactor at higher power levels. As a prerequisite, a detailed thermal hydraulic analysis is essential to assess the effect of reactor operation with isolated channels on the primary heat transport (PHT) system pressure, flow, temperature. The adequacy of the existing trip set points for the plant operation under this mode is also required to be assessed. In the present study, analysis of the PHT system has been carried out to determine the flow and pressure profiles for the RAPS heat transport system for operation of the reactor with isolated channels. (author). 5 refs., 1 fig., 1 tab.

  15. Development and validation of a thallium flux-based functional assay for the sodium channel NaV1.7 and its utility for lead discovery and compound profiling.

    Science.gov (United States)

    Du, Yu; Days, Emily; Romaine, Ian; Abney, Kris K; Kaufmann, Kristian; Sulikowski, Gary; Stauffer, Shaun; Lindsley, Craig W; Weaver, C David

    2015-06-17

    Ion channels are critical for life, and they are targets of numerous drugs. The sequencing of the human genome has revealed the existence of hundreds of different ion channel subunits capable of forming thousands of ion channels. In the face of this diversity, we only have a few selective small-molecule tools to aid in our understanding of the role specific ion channels in physiology which may in turn help illuminate their therapeutic potential. Although the advent of automated electrophysiology has increased the rate at which we can screen for and characterize ion channel modulators, the technique's high per-measurement cost and moderate throughput compared to other high-throughput screening approaches limit its utility for large-scale high-throughput screening. Therefore, lower cost, more rapid techniques are needed. While ion channel types capable of fluxing calcium are well-served by low cost, very high-throughput fluorescence-based assays, other channel types such as sodium channels remain underserved by present functional assay techniques. In order to address this shortcoming, we have developed a thallium flux-based assay for sodium channels using the NaV1.7 channel as a model target. We show that the assay is able to rapidly and cost-effectively identify NaV1.7 inhibitors thus providing a new method useful for the discovery and profiling of sodium channel modulators.

  16. Photovoltaic X-ray detectors based on epitaxial GaAs structures

    Energy Technology Data Exchange (ETDEWEB)

    Achmadullin, R.A. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Artemov, V.V. [Shubnikov Institute of Crystallography, Russian Academy of Sciences, 59 Leninski pr., Moscow B-333, 117333 (Russian Federation); Dvoryankin, V.F. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation)]. E-mail: vfd217@ire216.msk.su; Dvoryankina, G.G. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Dikaev, Yu.M. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Ermakov, M.G. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Ermakova, O.N. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Chmil, V.B. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation); Holodenko, A.G. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation); Kudryashov, A.A.; Krikunov, A.I.; Petrov, A.G.; Telegin, A.A. [Institute of Radio Engineering and Electronics, Russian Academy of Sciences, 1 Ac. Vvedenski square, Fryazino 141190, Moscow region (Russian Federation); Vorobiev, A.P. [Scientific State Center, High Energy Physics Institute, Protvino, Moscow region (Russian Federation)

    2005-12-01

    A new type of the photovoltaic X-ray detector based on epitaxial p{sup +}-n-n'-n{sup +} GaAs structures which provides a high efficiency of charge collection in the non-bias operation mode at room temperature is proposed. The GaAs epitaxial structures were grown by vapor-phase epitaxy on heavily doped n{sup +}-GaAs(1 0 0) substrates. The absorption efficiency of GaAs X-ray detector is discussed. I-V and C-V characteristics of the photovoltaic X-ray detectors are analyzed. The built-in electric field profiles in the depletion region of epitaxial structures are measured by the EBIC method. Charge collection efficiency to {alpha}-particles and {gamma}-radiation are measured. The application of X-ray detectors is discussed.

  17. Defect and dopant depth profiles in boron-implanted silicon studied with channeling and nuclear reaction analysis

    NARCIS (Netherlands)

    Vos, M.; Boerma, D.O.; Smulders, P.J.M.; Oosterhoff, S.

    1986-01-01

    Single crystals of silicon were implanted at RT with 1 MeV boron ions to a dose of 1 × 1015 ions/cm2. The depth profile of the boron was measured using the 2060-keV resonance of the 11B(α, n)14N nuclear reaction. The distribution of the lattice disorder as a function of depth was determined from

  18. Epitaxial Garnets and Hexagonal Ferrites.

    Science.gov (United States)

    1982-04-20

    guide growth of the epitaxial YIG films. Aluminum or gallium substitu- tions for iron were used in combination with lanthanum substitutions for yttrium... gallate spinel sub- strates. There was no difficulty with nucleation in the melt and film quality appeared to be similar to that observed previously...hexagonal ferrites. We succeeded in growing the M-type lead hexaferrite (magnetoplumbite) on gallate spinel substrates. We found that the PbO-based

  19. Quantum Nanostructures by Droplet Epitaxy

    OpenAIRE

    Somsak Panyakeow

    2009-01-01

    Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C). Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic...

  20. Epitaxial rare-earth superlattices and films

    International Nuclear Information System (INIS)

    Salamon, M.B.; Beach, R.S.; Flynn, C.P.; Matheny, A.; Tsui, F.; Rhyne, J.J.

    1992-01-01

    This paper reports on epitaxial growth of rare-earth superlattices which is demonstrated to have opened important new areas of research on magnetic materials. The propagation magnetic order through non-magnetic elements, including its range and anisotropy, has been studied. The importance of magnetostriction in determining the phase diagram is demonstrated by the changes induced by epitaxial clamping. The cyrstallinity of epitaxial superlattices provides the opportunity to study interfacial magnetism by conventional x-ray and neutron scattering methods

  1. High-mobility BaSnO{sub 3} grown by oxide molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Santosh; Schumann, Timo; Kim, Honggyu; Zhang, Jack Y.; Cain, Tyler A.; Stemmer, Susanne, E-mail: stemmer@mrl.ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)

    2016-01-01

    High-mobility perovskite BaSnO{sub 3} films are of significant interest as new wide bandgap semiconductors for power electronics, transparent conductors, and as high mobility channels for epitaxial integration with functional perovskites. Despite promising results for single crystals, high-mobility BaSnO{sub 3} films have been challenging to grow. Here, we demonstrate a modified oxide molecular beam epitaxy (MBE) approach, which supplies pre-oxidized SnO{sub x}. This technique addresses issues in the MBE of ternary stannates related to volatile SnO formation and enables growth of epitaxial, stoichiometric BaSnO{sub 3}. We demonstrate room temperature electron mobilities of 150 cm{sup 2} V{sup −1} s{sup −1} in films grown on PrScO{sub 3}. The results open up a wide range of opportunities for future electronic devices.

  2. Epitaxial growth of CZT(S,Se) on silicon

    Science.gov (United States)

    Bojarczuk, Nestor A.; Gershon, Talia S.; Guha, Supratik; Shin, Byungha; Zhu, Yu

    2016-03-15

    Techniques for epitaxial growth of CZT(S,Se) materials on Si are provided. In one aspect, a method of forming an epitaxial kesterite material is provided which includes the steps of: selecting a Si substrate based on a crystallographic orientation of the Si substrate; forming an epitaxial oxide interlayer on the Si substrate to enhance wettability of the epitaxial kesterite material on the Si substrate, wherein the epitaxial oxide interlayer is formed from a material that is lattice-matched to Si; and forming the epitaxial kesterite material on a side of the epitaxial oxide interlayer opposite the Si substrate, wherein the epitaxial kesterite material includes Cu, Zn, Sn, and at least one of S and Se, and wherein a crystallographic orientation of the epitaxial kesterite material is based on the crystallographic orientation of the Si substrate. A method of forming an epitaxial kesterite-based photovoltaic device and an epitaxial kesterite-based device are also provided.

  3. Epitaxial graphene electronic structure and transport

    International Nuclear Information System (INIS)

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun

    2010-01-01

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.

  4. Epitaxy, thin films and superlattices

    International Nuclear Information System (INIS)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au)

  5. Epitaxy, thin films and superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Jagd Christensen, Morten

    1997-05-01

    This report is the result of structural investigations of 3d transition metal superlattices consisting of Fe/V, Cr/Mn, V/Mn and Fe/Mn, and a structural and magnetic study of a series of Ho/Pr alloys. The work includes preparation and characterization of substrates as well as growth of thin films and Fe/V superlattices by molecular beam epitaxy, including in-situ characterization by reflection high energy electron diffraction and Auger electron spectroscopy. Structural characterization has been done by x-ray diffraction and neutron diffraction. The x-ray diffraction experiments have been performed on the rotating copper anode at Risoe, and at synchrotron facilities in Hamburg and Brookhaven, and the neutron scattering was done at the Danish research reactor DR3 at Risoe. In addition to longitudinal scans, giving information about the structural parameters in the modulation direction, non-specular scans were also performed. This type of scans gives information about in-plane orientation and lattice parameters. From the analysis, structural information is obtained about lattice parameters, epitaxial strain, coherence lengths and crystallographic orientation for the superlattice systems, except Fe/Mn superlattices, which could not be modelled. For the Ho/Pr alloys, x-ray magnetic scattering was performed, and the crystal and magnetic structure was investigated. (au) 14 tabs.; 58 ills., 96 refs.

  6. Frequency Characteristics of Path Loss and Delay-Angular Profile of Propagation Channels in An Indoor Room Environment in SHF Bands

    DEFF Research Database (Denmark)

    HANPINITSAK, Panawit; SAITO, Kentaro; Fan, Wei

    2017-01-01

    Comparison of channel characteristics at many frequency bands is necessary to study the frequency-de-pendency which is important for consistent multi-frequency spatial-temporal channel model. Path loss (PL) and power spectrum characteristics of the channel measured in a typical classroom line...

  7. Pumping requirements and options for molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

    International Nuclear Information System (INIS)

    McCollum, M.J.; Plano, M.A.; Haase, M.A.; Robbins, V.M.; Jackson, S.L.; Cheng, K.Y.; Stillman, G.E.

    1989-01-01

    This paper discusses the use of gas sources in growth by MBE as a result of current interest in growth of InP/InGaAsP/InGaAs lattice matched to InP. For gas flows greater than a few sccm, pumping speed requirements dictate the use of turbomolecular or diffusion pumps. GaAs samples with high p-type mobilities have been grown with diffusion pumped molecular beam epitaxial system. According to the authors, this demonstration of the inherent cleanliness of a properly designed diffusion pumping system indicates that a diffusion pump is an excellent inexpensive and reliable choice for growth by molecular beam epitaxy and gas source molecular beam epitaxy/chemical beam epitaxy

  8. Monte Carlo simulation of channeled and random profiles of heavy ions implanted in silicon at high energy (1.2 MeV)

    International Nuclear Information System (INIS)

    Mazzone, A.M.

    1987-01-01

    In order to study channeling effects and implants of heavy ions with energy of few MeV in silicon, ion distributions are calculated with a Monte Carlo method for axial [(001) axis], planar, and nominally random directions for As + and P + ions implanted into silicon with energies in the range 100 keV to 2 MeV. The calculation indicates an appreciable channeling at the higher energy only for the (001) axis and the (110) planes. For heavy ions with energy in the MeV range the subsidence of channeling into major channels and the disappearance of minor channels are shown

  9. Quantum Nanostructures by Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Somsak Panyakeow

    2009-02-01

    Full Text Available Droplet epitaxy is an alternative growth technique for several quantum nanostructures. Indium droplets are distributed randomly on GaAs substrates at low temperatures (120-350'C. Under background pressure of group V elements, Arsenic and Phosphorous, InAs and InP nanostructures are created. Quantum rings with isotropic shape are obtained at low temperature range. When the growth thickness is increased, quantum rings are transformed to quantum dot rings. At high temperature range, anisotropic strain gives rise to quantum rings with square holes and non-uniform ring stripe. Regrowth of quantum dots on these anisotropic quantum rings, Quadra-Quantum Dots (QQDs could be realized. Potential applications of these quantum nanostructures are also discussed.

  10. Epitaxial growth of silicon for layer transfer

    Science.gov (United States)

    Teplin, Charles; Branz, Howard M

    2015-03-24

    Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

  11. Molecular beam epitaxy a short history

    CERN Document Server

    Orton, J W

    2015-01-01

    This volume describes the development of molecular beam epitaxy from its origins in the 1960s through to the present day. It begins with a short historical account of other methods of crystal growth, both bulk and epitaxial, to set the subject in context, emphasising the wide range of semiconductor materials employed. This is followed by an introduction to molecular beams and their use in the Stern-Gerlach experiment and the development of the microwave MASER.

  12. Resistivity of epitaxial copper nanolines with trapezoidal cross-section

    International Nuclear Information System (INIS)

    Lu, Zonghuan; Frey, David M.; Merkh, Thomas; Lord, Robert; Washington, Morris A.; Lu, Toh-Ming

    2016-01-01

    The resistivity of epitaxial Cu nanolines with line width ranging from 20 to 180 nm and line height from 40 to 50 nm was measured using a four-point probe technique. The Cu nanolines were fabricated using ebeam lithography with a polymethyl methacrylate bilayer resist system for improved line edge smoothness. The cross-section profile of the lines was examined using the focused ion beam milling technique. The results indicate that the cross-section should be more accurately described as trapezoidal rather than as rectangular. Using the trapezoidal profile, the electrical resistivity was calculated from the measured resistance data. Modeling based on the Fuchs–Sondheimer (FS) theory using the trapezoidal profile was also carried out. The results were compared with the experimentally calculated resistivity data. For Cu lines with line width less than 30 nm, the measured resistivity was shown to be up to 20% higher than the value predicted by the FS theory. Further examination of Cu lines using atomic force microscopy and scanning electron microscopy was conducted to extract the surface roughness and line edge roughness information. Their contribution to the resistivity increase was estimated to be only up to 3% for the Cu nanolines fabricated, which did not significantly contribute to the overall resistivity for Cu lines with line width less than 30 nm. Other possible factors affecting the resistivity of the Cu nanolines were also discussed, including the oxide formation on the surface of the Cu lines. - Highlights: • Epitaxial copper nanolines were fabricated using ebeam lithography. • The effect of line cross-section profiles on electrical resistivity was studied. • Trapezoidal cross−section gives better resistivity estimation for lines down to 20 nm. • Impact of surface roughness and line edge roughness to resistivity is small. • Oxidization layer has an effect on the resistivity increase.

  13. Vacancy-related defect distributions in 11B-, 14N-, and 27Al-implanted 4H-SiC: Role of channeling

    International Nuclear Information System (INIS)

    Janson, M.S.; Slotte, J.; Kuznetsov, A.Yu.; Saarinen, K.; Hallen, A.

    2004-01-01

    The defect distributions in 11 B-, 14 N-, and 27 Al-implanted epitaxial 4H-SiC are studied using monoenergetic positron beams. At least three types of defects are needed to account for the Doppler broadening annihilation spectra and two of the defects are tentatively identified as V Si , and V Si V C . By comparing the defect profiles extracted from the annihilation spectra to the chemical profiles determined by secondary ion mass spectrometry, and to the primary defect profiles obtained from binary collision approximation simulations, it is concluded that the defects found at depths considerably deeper than the projected range of the implanted ions mainly originate from deeply channeled ions

  14. Photoenhanced atomic layer epitaxy. Hikari reiki genshiso epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Mashita, M.; Kawakyu, Y. (Toshiba corp., Tokyo (Japan))

    1991-10-01

    The growth temperature range was greatly expanded of atomic layer epitaxy (ALE) expected as the growth process of ultra-thin stacks. Ga layers and As layers were formed one after the other on a GaAs substrate in the atmosphere of trimethylgallium (TMG) or AsH{sub 2} supplied alternately, by KrF excimer laser irradiation normal to the substrate. As a result, the growth temperature range was 460-540{degree}C nearly 10 times that of 500 {plus minus} several degrees centigrade in conventional thermal growth method. Based on the experimental result where light absorption of source molecules adsorbed on a substrate surface was larger than that under gaseous phase condition, new adsorbed layer enhancement model was proposed to explain above irradiation effect verifying it by experiments. As this photoenhancement technique is applied to other materials, possible fabrication of new crystal structures as a super lattice with ultra-thin stacks of single atomic layers is expected because of a larger freedom in material combination for hetero-ALE. 11 refs., 7 figs.

  15. Probing channel temperature profiles in Al{sub x}Ga{sub 1−x}N/GaN high electron mobility transistors on 200 mm diameter Si(111) by optical spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kyaw, L. M., E-mail: a0048661@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Bera, L. K.; Dolmanan, S. B.; Tan, H. R.; Bhat, T. N.; Tripathy, S., E-mail: tripathy-sudhiranjan@imre.a-star.edu.sg [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), Singapore 117602 (Singapore); Liu, Y.; Bera, M. K.; Singh, S. P.; Chor, E. F. [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2014-08-18

    Using micro-Raman and photoluminescence (PL) techniques, the channel temperature profile is probed in Al{sub x}Ga{sub 1-x}N/GaN high electron mobility transistors (HEMTs) fabricated on a 200 mm diameter Si(111) substrate. In particular, RuO{sub x}-based gate is used due to the semitransparent nature to the optical excitation wavelengths, thus allowing much accurate thermal investigations underneath the gate. To determine the channel temperature profile in devices subjected to different electrical bias voltages, the GaN band-edge PL peak shift calibration with respect to temperature is used. PL analyses show a maximum channel temperature up to 435 K underneath the gate edge between gate and drain, where the estimated thermal resistance in such a HEMT structure is about 13.7 KmmW{sup −1} at a power dissipation of ∼10 W/mm. The temperature profiles from micro-Raman measurements are also addressed from the E{sub 2}-high optical phonon peak shift of GaN, and this method also probes the temperature-induced peak shifts of optical phonon from Si thus showing the nature of thermal characteristics at the AlN/Si substrate interface.

  16. Spin transport in epitaxial graphene

    Science.gov (United States)

    Tbd, -

    2014-03-01

    Spintronics is a paradigm focusing on spin as the information vector in fast and ultra-low-power non volatile devices such as the new STT-MRAM. Beyond its widely distributed application in data storage it aims at providing more complex architectures and a powerful beyond CMOS solution for information processing. The recent discovery of graphene has opened novel exciting opportunities in terms of functionalities and performances for spintronics devices. We will present experimental results allowing us to assess the potential of graphene for spintronics. We will show that unprecedented highly efficient spin information transport can occur in epitaxial graphene leading to large spin signals and macroscopic spin diffusion lengths (~ 100 microns), a key enabler for the advent of envisioned beyond-CMOS spin-based logic architectures. We will also show that how the device behavior is well explained within the framework of the Valet-Fert drift-diffusion equations. Furthermore, we will show that a thin graphene passivation layer can prevent the oxidation of a ferromagnet, enabling its use in novel humide/ambient low-cost processes for spintronics devices, while keeping its highly surface sensitive spin current polarizer/analyzer behavior and adding new enhanced spin filtering property. These different experiments unveil promising uses of graphene for spintronics.

  17. Epitaxial growth of rhenium with sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Seongshik [National Institute of Standards and Technology, Boulder, CO 80305 (United States) and Department of Physics, University of Illinois, Urbana, IL 61801 (United States)]. E-mail: soh@boulder.nist.gov; Hite, Dustin A. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Cicak, K. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Osborn, Kevin D. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); Simmonds, Raymond W. [National Institute of Standards and Technology, Boulder, CO 80305 (United States); McDermott, Robert [University of California, Santa Barbara, CA 93106 (United States); Cooper, Ken B. [University of California, Santa Barbara, CA 93106 (United States); Steffen, Matthias [University of California, Santa Barbara, CA 93106 (United States); Martinis, John M. [University of California, Santa Barbara, CA 93106 (United States); Pappas, David P. [National Institute of Standards and Technology, Boulder, CO 80305 (United States)

    2006-02-21

    We have grown epitaxial Rhenium (Re) (0001) films on {alpha}-Al{sub 2}O{sub 3} (0001) substrates using sputter deposition in an ultra high vacuum system. We find that better epitaxy is achieved with DC rather than with RF sputtering. With DC sputtering, epitaxy is obtained with the substrate temperatures above 700 deg. C and deposition rates below 0.1 nm/s. The epitaxial Re films are typically composed of terraced hexagonal islands with screw dislocations, and island size gets larger with high temperature post-deposition annealing. The growth starts in a three dimensional mode but transforms into two dimensional mode as the film gets thicker. With a thin ({approx}2 nm) seed layer deposited at room temperature and annealed at a high temperature, the initial three dimensional growth can be suppressed. This results in larger islands when a thick film is grown at 850 deg. C on the seed layer. We also find that when a room temperature deposited Re film is annealed to higher temperatures, epitaxial features start to show up above {approx}600 deg. C, but the film tends to be disordered.

  18. Precision calibration of the silicon doping level in gallium arsenide epitaxial layers

    Science.gov (United States)

    Mokhov, D. V.; Berezovskaya, T. N.; Kuzmenkov, A. G.; Maleev, N. A.; Timoshnev, S. N.; Ustinov, V. M.

    2017-10-01

    An approach to precision calibration of the silicon doping level in gallium arsenide epitaxial layers is discussed that is based on studying the dependence of the carrier density in the test GaAs layer on the silicon- source temperature using the Hall-effect and CV profiling techniques. The parameters are measured by standard or certified measuring techniques and approved measuring instruments. It is demonstrated that the use of CV profiling for controlling the carrier density in the test GaAs layer at the thorough optimization of the measuring procedure ensures the highest accuracy and reliability of doping level calibration in the epitaxial layers with a relative error of no larger than 2.5%.

  19. Position-controlled epitaxial III-V nanowires on silicon

    NARCIS (Netherlands)

    Roest, A.L.; Verheijen, M.A.; Wunnicke, O.; Serafin, S.N.; Wondergem, H.J.; Bakkers, E.P.A.M.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction

  20. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from MIRAI in the Indian Ocean and Mozambique Channel from 2003-12-09 to 2004-01-24 (NODC Accession 0108101)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0108101 includes discrete sample and profile data collected from MIRAI in the Indian Ocean and Mozambique Channel from 2003-12-09 to 2004-01-24. These...

  1. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from the PRIDE OF BILBAO in the Bay of Biscay, English Channel and North Atlantic Ocean from 2005-09-26 to 2010-09-16 (NODC Accession 0108092)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0108092 includes chemical, discrete sample, physical and profile data collected from PRIDE OF BILBAO in the Bay of Biscay, English Channel and North...

  2. Dissolved inorganic carbon, pH, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from the PELAGIA in the English Channel, North Atlantic Ocean and others from 2001-08-18 to 2002-05-25 (NODC Accession 0112844)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0112844 includes chemical, discrete sample, physical and profile data collected from PELAGIA in the English Channel, North Atlantic Ocean, North Sea,...

  3. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from the PELAGIA in the English Channel, North Atlantic Ocean and others from 2001-08-18 to 2002-05-25 (NODC Accession 0112843)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0112843 includes chemical, discrete sample, physical and profile data collected from PELAGIA in the English Channel, North Atlantic Ocean, North Sea,...

  4. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using Alkalinity titrator, CTD and other instruments from DISCOVERY in the English Channel, Inner Sea - West Coast Scotland and others from 2011-06-06 to 2011-07-09 (NCEI Accession 0157451)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NCEI Accession 0157451 includes chemical, discrete sample, physical and profile data collected from DISCOVERY in the English Channel, Inner Sea - West Coast...

  5. Powder free PECVD epitaxial silicon by plasma pulsing or increasing the growth temperature

    Science.gov (United States)

    Chen, Wanghua; Maurice, Jean-Luc; Vanel, Jean-Charles; Cabarrocas, Pere Roca i.

    2018-06-01

    Crystalline silicon thin films are promising candidates for low cost and flexible photovoltaics. Among various synthesis techniques, epitaxial growth via low temperature plasma-enhanced chemical vapor deposition is an interesting choice because of two low temperature related benefits: low thermal budget and better doping profile control. However, increasing the growth rate is a tricky issue because the agglomeration of clusters required for epitaxy leads to powder formation in the plasma. In this work, we have measured precisely the time evolution of the self-bias voltage in silane/hydrogen plasmas at millisecond time scale, for different values of the direct-current bias voltage applied to the radio frequency (RF) electrode and growth temperatures. We demonstrate that the decisive factor to increase the epitaxial growth rate, i.e. the inhibition of the agglomeration of plasma-born clusters, can be obtained by decreasing the RF OFF time or increasing the growth temperature. The influence of these two parameters on the growth rate and epitaxial film quality is also presented.

  6. A novel series of isoreticular metal organic frameworks: Realizing metastable structures by liquid phase epitaxy

    KAUST Repository

    Liu, Jinxuan

    2012-12-04

    A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

  7. A novel series of isoreticular metal organic frameworks: Realizing metastable structures by liquid phase epitaxy

    KAUST Repository

    Liu, Jinxuan; Lukose, Binit; Shekhah, Osama; Arslan, Hasan Kemal; Weidler, Peter; Gliemann, Hartmut; Brä se, Stefan; Grosjean, Sylvain; Godt, Adelheid; Feng, Xinliang; Mü llen, Klaus; Magdau, Ioan-Bogdan; Heine, Thomas; Wö ll, Christof

    2012-01-01

    A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

  8. Growth and characterization of molecular beam epitaxial GaAs layers on porous silicon

    Science.gov (United States)

    Lin, T. L.; Liu, J. K.; Sadwick, L.; Wang, K. L.; Kao, Y. C.

    1987-01-01

    GaAs layers have been grown on porous silicon (PS) substrates with good crystallinity by molecular beam epitaxy. In spite of the surface irregularity of PS substrates, no surface morphology deterioration was observed on epitaxial GaAs overlayers. A 10-percent Rutherford backscattering spectroscopy minimum channeling yield for GaAs-on-PS layers as compared to 16 percent for GaAs-on-Si layers grown under the same condition indicates a possible improvement of crystallinity when GaAs is grown on PS. Transmission electron microscopy reveals that the dominant defects in the GaAs-on-PS layers are microtwins and stacking faults, which originate from the GaAs/PS interface. GaAs is found to penetrate into the PS layers. n-type GaAs/p-type PS heterojunction diodes were fabricated with good rectifying characteristics.

  9. Epitaxial silicon semiconductor detectors, past developments, future prospects

    International Nuclear Information System (INIS)

    Gruhn, C.R.

    1976-01-01

    A review of the main physical characteristics of epitaxial silicon as it relates to detector development is presented. As examples of applications results are presented on (1) epitaxial silicon avalanche diodes (ESAD); signal-to-noise, non-linear aspects of the avalanche gain mechanism, gain-bandwidth product, (2) ultrathin epitaxial silicon surface barrier (ESSB) detectors, response to heavy ions, (3) an all-epitaxial silicon diode (ESD), response to heavy ions, charge transport and charge defect. Future prospects of epitaxial silicon as it relates to new detector designs are summarized

  10. Momento de inercia a la torsión de barras de perfil canal // Torsional inertia Moment for a profile bar channel

    Directory of Open Access Journals (Sweden)

    R. Rivero Galán

    1998-01-01

    Full Text Available En el presente trabajo se brindan fórmulas y coeficientes para la determinación del momento de inercia a la torsión de una barrade perfil canal. Las fórmulas obtenidas se validan mediante la simulación de diferentes estructuras de uniones entre canales conel uso del método de los elementos finitos._______________________________________________________________________AbstractIn the paper are offered formulations and coefficients for the determination of the moment of inertia to the twist for a profilebar channel. The obtained formulations are validated through the simulation by the finite elements method of differentstructures of unions between channels.

  11. Epitaxial Graphene: A New Material for Electronics

    Science.gov (United States)

    de Heer, Walt A.

    2007-10-01

    Graphene multilayers are grown epitaxially on single crystal silicon carbide. This system is composed of several graphene layers of which the first layer is electron doped due to the built-in electric field and the other layers are essentially undoped. Unlike graphite the charge carriers show Dirac particle properties (i.e. an anomalous Berry's phase, weak anti-localization and square root field dependence of the Landau level energies). Epitaxial graphene shows quasi-ballistic transport and long coherence lengths; properties that may persists above cryogenic temperatures. Paradoxically, in contrast to exfoliated graphene, the quantum Hall effect is not observed in high mobility epitaxial graphene. It appears that the effect is suppressed due to absence of localized states in the bulk of the material. Epitaxial graphene can be patterned using standard lithography methods and characterized using a wide array of techniques. These favorable features indicate that interconnected room temperature ballistic devices may be feasible for low dissipation high-speed nano-electronics.

  12. Investigation of iron film-substrate interfaces using Rutherford backscattering and channeling techniques

    International Nuclear Information System (INIS)

    Maheswaran, S.; Thevuthasan, S.

    1999-01-01

    Thin films of α-Fe 2 O 3 (0001) (hematite) were epitaxially grown on Al 2 O 3 (0001) substrates using the new molecular beam epitaxy (MBE) system at the Environmental Molecular Sciences Laboratory (EMSL). We have investigated the interface between the hematite films and sapphire substrates using Rutherford Backscattering (RBS) and channeling experiments. Theoretical simulations were performed using VEGAS code to investigate the surface and interface structural properties of the films

  13. Liquid phase electro epitaxy growth kinetics of GaAs-A three-dimensional numerical simulation study

    International Nuclear Information System (INIS)

    Mouleeswaran, D.; Dhanasekaran, R.

    2006-01-01

    A three-dimensional numerical simulation study for the liquid phase electro epitaxial growth kinetic of GaAs is presented. The kinetic model is constructed considering (i) the diffusive and convective mass transport, (ii) the heat transfer due to thermoelectric effects such as Peltier effect, Joule effect and Thomson effect, (iii) the electric current distribution with electromigration and (iv) the fluid flow coupled with concentration and temperature fields. The simulations are performed for two configurations namely (i) epitaxial growth from the arsenic saturated gallium rich growth solution, i.e., limited solution model and (ii) epitaxial growth from the arsenic saturated gallium rich growth solution with polycrystalline GaAs feed. The governing equations of liquid phase electro epitaxy are solved numerically with appropriate initial and boundary conditions using the central difference method. Simulations are performed to determine the following, a concentration profiles of solute atoms (As) in the Ga-rich growth solution, shape of the substrate evolution, the growth rate of the GaAs epitaxial film, the contributions of Peltier effect and electromigration of solute atoms to the growth with various experimental growth conditions. The growth rate is found to increase with increasing growth temperature and applied current density. The results are discussed in detail

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

    Science.gov (United States)

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

    2014-09-10

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

  15. Self-Catalyzed Growth of Axial GaAs/GaAsSb Nanowires by Molecular Beam Epitaxy for Photodetectors

    Science.gov (United States)

    2015-06-01

    MOVPE Metal organic vapor phase epitaxy NCA Nano Channel Aluminum NW Nanowire PL Photoluminescence PMMA Poly methyl methacrylate...GaAs (111) B substrate. The NWs were grown using a nanochannel alumina ( NCA ) template. It was later shown by Dubrovskii et al. [16], that the NWs... cathode gun. The type of signals produced are secondary electron (SE), back scattered electron (BSE), characteristic X- rays, specimen current and

  16. Characterization of encapsulated quantum dots via electron channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Deitz, Julia I.; McComb, David W. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Carnevale, Santino D. [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Grassman, Tyler J., E-mail: grassman.5@osu.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2016-08-08

    A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.

  17. Defects in heavily phosphorus-doped Si epitaxial films probed by monoenergetic positron beams

    International Nuclear Information System (INIS)

    Uedono, Akira; Tanigawa, Shoichiro; Suzuki, Ryoichi; Ohgaki, Hideaki; Mikado, Tomohisa.

    1994-01-01

    Vacancy-type defects in heavily phosphorus-doped Si epitaxial films were probed by monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for the epitaxial films grown on the Si substrates by plasma chemical vapor deposition. For the as-deposited film, divacancy-phosphorus complexes were found with high concentration. After 600degC annealing, vacancy clusters were formed near the Si/Si interface, while no drastic change in the depth distribution of the divacancy-phosphorus complexes was observed. By 900degC annealing, the vacancy clusters were annealed out; however, the average number of phosphorus atoms coupled with divacancies increased. The relationship between the vacancy-type defects probed by the positron annihilation technique and the carrier concentration was confirmed. (author)

  18. Defects in heavily phosphorus-doped Si epitaxial films probed by monoenergetic positron beams

    Energy Technology Data Exchange (ETDEWEB)

    Uedono, Akira; Tanigawa, Shoichiro [Tsukuba Univ., Ibaraki (Japan). Inst. of Materials Science; Suzuki, Ryoichi; Ohgaki, Hideaki; Mikado, Tomohisa

    1994-11-01

    Vacancy-type defects in heavily phosphorus-doped Si epitaxial films were probed by monoenergetic positron beams. Doppler broadening profiles of the annihilation radiation and lifetime spectra of positrons were measured for the epitaxial films grown on the Si substrates by plasma chemical vapor deposition. For the as-deposited film, divacancy-phosphorus complexes were found with high concentration. After 600degC annealing, vacancy clusters were formed near the Si/Si interface, while no drastic change in the depth distribution of the divacancy-phosphorus complexes was observed. By 900degC annealing, the vacancy clusters were annealed out; however, the average number of phosphorus atoms coupled with divacancies increased. The relationship between the vacancy-type defects probed by the positron annihilation technique and the carrier concentration was confirmed. (author).

  19. Ion channeling study of defects in multicomponent semiconductor compounds

    International Nuclear Information System (INIS)

    Turos, A.; Nowicki, L.; Stonert, A.

    2002-01-01

    Compound semiconductor crystals are of great technological importance as basic materials for production of modern opto- and microelectronic devices. Ion implantation is one of the principal techniques for heterostructures processing. This paper reports the results of the study of defect formation and transformation in binary and ternary semiconductor compounds subjected to ion implantation with ions of different mass and energy. The principal analytical technique was He-ion channeling. The following materials were studied: GaN and InGaN epitaxial layers. First the semi empirical method of channeling spectra analysis for ion implanted multicomponent single crystal was developed. This method was later complemented by the more sophisticated method based on the Monte Carlo simulation of channeling spectra. Next, the damage buildup in different crystals and epitaxial layers as a function of the implantation dose was studied for N, Mg, Te, and Kr ions. The influence of the substrate temperature on the defect transformations was studied for GaN epitaxial layers implanted with Mg ions. Special attention was devoted to the study of growth conditions of InGaN/GaN/sapphire heterostructures, which are important component of the future blue laser diodes. In-atom segregation and tetragonal distortion of the epitaxial layer were observed and characterized. Next problem studied was the incorporation of hydrogen atoms in GaAs and GaN. Elastic recoil detection (ERDA) and nuclear reaction analysis (NRA) were applied for the purpose. (author)

  20. Gene expression profile of sodium channel subunits in the anterior cingulate cortex during experimental paclitaxel-induced neuropathic pain in mice

    Directory of Open Access Journals (Sweden)

    Willias Masocha

    2016-11-01

    Full Text Available Paclitaxel, a chemotherapeutic agent, causes neuropathic pain whose supraspinal pathophysiology is not fully understood. Dysregulation of sodium channel expression, studied mainly in the periphery and spinal cord level, contributes to the pathogenesis of neuropathic pain. We examined gene expression of sodium channel (Nav subunits by real time polymerase chain reaction (PCR in the anterior cingulate cortex (ACC at day 7 post first administration of paclitaxel, when mice had developed paclitaxel-induced thermal hyperalgesia. The ACC was chosen because increased activity in the ACC has been observed during neuropathic pain. In the ACC of vehicle-treated animals the threshold cycle (Ct values for Nav1.4, Nav1.5, Nav1.7, Nav1.8 and Nav1.9 were above 30 and/or not detectable in some samples. Thus, comparison in mRNA expression between untreated control, vehicle-treated and paclitaxel treated animals was done for Nav1.1, Nav1.2, Nav1.3, Nav1.6, Nax as well as Navβ1–Navβ4. There were no differences in the transcript levels of Nav1.1–Nav1.3, Nav1.6, Nax, Navβ1–Navβ3 between untreated and vehicle-treated mice, however, vehicle treatment increased Navβ4 expression. Paclitaxel treatment significantly increased the mRNA expression of Nav1.1, Nav1.2, Nav1.6 and Nax, but not Nav1.3, sodium channel alpha subunits compared to vehicle-treated animals. Treatment with paclitaxel significantly increased the expression of Navβ1 and Navβ3, but not Navβ2 and Navβ4, sodium channel beta subunits compared to vehicle-treated animals. These findings suggest that during paclitaxel-induced neuropathic pain (PINP there is differential upregulation of sodium channels in the ACC, which might contribute to the increased neuronal activity observed in the area during neuropathic pain.

  1. Geomorphology, denudation rates, and stream channel profiles reveal patterns of mountain building adjacent to the San Andreas fault in northern California, USA

    Science.gov (United States)

    DeLong, Stephen B.; Hilley, George E.; Prentice, Carol S.; Crosby, Christopher J.; Yokelson, Intan N.

    2017-01-01

    Relative horizontal motion along strike-slip faults can build mountains when motion is oblique to the trend of the strike-slip boundary. The resulting contraction and uplift pose off-fault seismic hazards, which are often difficult to detect because of the poor vertical resolution of satellite geodesy and difficulty of locating offset datable landforms in active mountain ranges. Sparse geomorphic markers, topographic analyses, and measurement of denudation allow us to map spatiotemporal patterns of uplift along the northern San Andreas fault. Between Jenner and Mendocino, California, emergent marine terraces found southwest of the San Andreas fault record late Pleistocene uplift rates between 0.20 and 0.45 mm yr–1 along much of the coast. However, on the northeast side of the San Andreas fault, a zone of rapid uplift (0.6–1.0 mm yr–1) exists adjacent to the San Andreas fault, but rates decay northeastward as the coast becomes more distant from the San Andreas fault. A newly dated 4.5 Ma shallow-marine deposit located at ∼500 m above sea level (masl) adjacent to the San Andreas fault is warped down to just 150 masl 15 km northeast of the San Andreas fault, and it is exposed at just 60–110 masl to the west of the fault. Landscape denudation rates calculated from abundance of cosmogenic radionuclides in fluvial sediment northeast of, and adjacent to, the San Andreas fault are 0.16–0.29 mm yr–1, but they are only 0.03–0.07 mm yr–1 west of the fault. Basin-average channel steepness and the denudation rates can be used to infer the erosive properties of the underlying bedrock. Calibrated erosion rates can then be estimated across the entire landscape using the spatial distribution of channel steepness with these erosive properties. The lower-elevation areas of this landscape that show high channel steepness (and hence calibrated erosion rate) are distinct from higher-elevation areas with systematically lower channel steepness and denudation rates

  2. SiGe epitaxial memory for neuromorphic computing with reproducible high performance based on engineered dislocations

    Science.gov (United States)

    Choi, Shinhyun; Tan, Scott H.; Li, Zefan; Kim, Yunjo; Choi, Chanyeol; Chen, Pai-Yu; Yeon, Hanwool; Yu, Shimeng; Kim, Jeehwan

    2018-01-01

    Although several types of architecture combining memory cells and transistors have been used to demonstrate artificial synaptic arrays, they usually present limited scalability and high power consumption. Transistor-free analog switching devices may overcome these limitations, yet the typical switching process they rely on—formation of filaments in an amorphous medium—is not easily controlled and hence hampers the spatial and temporal reproducibility of the performance. Here, we demonstrate analog resistive switching devices that possess desired characteristics for neuromorphic computing networks with minimal performance variations using a single-crystalline SiGe layer epitaxially grown on Si as a switching medium. Such epitaxial random access memories utilize threading dislocations in SiGe to confine metal filaments in a defined, one-dimensional channel. This confinement results in drastically enhanced switching uniformity and long retention/high endurance with a high analog on/off ratio. Simulations using the MNIST handwritten recognition data set prove that epitaxial random access memories can operate with an online learning accuracy of 95.1%.

  3. Temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact

    International Nuclear Information System (INIS)

    Hu, C.Y.; Qin, Z.X.; Feng, Z.X.; Chen, Z.Z.; Ding, Z.B.; Yang, Z.J.; Yu, T.J.; Hu, X.D.; Yao, S.D.; Zhang, G.Y.

    2006-01-01

    The temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact were studied with Rutherford backscattering spectroscopy/channeling (RBS/C) and synchrotron X-ray diffraction (XRD). It is found that the Au diffuses to the surface of p-GaN to form an epitaxial structure on p-GaN after annealing at 450 deg. C. At the same time, the O diffuses to the metal-semiconductor interface and forms NiO. Both of them are suggested to be responsible for the sharp decrease in the specific contact resistance (ρ c ) at 450 deg. C. At 500 deg. C, the epitaxial structure of Au develops further and the O also diffuses deeper into the interface. As a result, the ρ c reaches the lowest value at this temperature. However, when annealing temperature reaches 600 deg. C, part or all of the interfacial NiO is detached from the p-GaN and diffuses out, which cause the ρ c to increase greatly

  4. Structural, electrical and luminescent characteristics of ultraviolet light emitting structures grown by hydride vapor phase epitaxy

    Directory of Open Access Journals (Sweden)

    A.Y. Polyakov

    2017-03-01

    Full Text Available Electrical and luminescent properties of near-UV light emitting diode structures (LEDs prepared by hydride vapor phase epitaxy (HVPE were studied. Variations in photoluminescence and electroluminescence efficiency observed for LEDs grown under nominally similar conditions could be attributed to the difference in the structural quality (dislocation density, density of dislocations agglomerates of the GaN active layers, to the difference in strain relaxation achieved by growth of AlGaN/AlGaN superlattice and to the presence of current leakage channels in current confining AlGaN layers of the double heterostructure.

  5. Irradiation induced improvement in crystallinity of epitaxially grown Ag thin films on Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Takahiro, Katsumi; Nagata, Shinji; Yamaguchi, Sadae [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    1997-03-01

    We report the improvement in crystallinity of epitaxially grown Ag films on Si(100) substrates with ion irradiation. The irradiation of 0.5 MeV Si ions to 2x10{sup 16}/cm{sup 2} at 200degC, for example, reduces the channeling minimum yield from 60% to 6% at Ag surface. The improvement originates from the decrease of mosaic spread in the Ag thin film. In our experiments, ion energy, ion species and irradiation temperature have been varied. The better crystallinity is obtained as the higher concentration of defect is generated. The mechanism involved in the irradiation induced improvement is discussed. (author)

  6. Complex Nanostructures by Pulsed Droplet Epitaxy

    Directory of Open Access Journals (Sweden)

    Noboyuki Koguchi

    2011-06-01

    Full Text Available What makes three dimensional semiconductor quantum nanostructures so attractive is the possibility to tune their electronic properties by careful design of their size and composition. These parameters set the confinement potential of electrons and holes, thus determining the electronic and optical properties of the nanostructure. An often overlooked parameter, which has an even more relevant effect on the electronic properties of the nanostructure, is shape. Gaining a strong control over the electronic properties via shape tuning is the key to access subtle electronic design possibilities. The Pulsed Dropled Epitaxy is an innovative growth method for the fabrication of quantum nanostructures with highly designable shapes and complex morphologies. With Pulsed Dropled Epitaxy it is possible to combine different nanostructures, namely quantum dots, quantum rings and quantum disks, with tunable sizes and densities, into a single multi-function nanostructure, thus allowing an unprecedented control over electronic properties.

  7. Optical Epitaxial Growth of Gold Nanoparticle Arrays.

    Science.gov (United States)

    Huang, Ningfeng; Martínez, Luis Javier; Jaquay, Eric; Nakano, Aiichiro; Povinelli, Michelle L

    2015-09-09

    We use an optical analogue of epitaxial growth to assemble gold nanoparticles into 2D arrays. Particles are attracted to a growth template via optical forces and interact through optical binding. Competition between effects determines the final particle arrangements. We use a Monte Carlo model to design a template that favors growth of hexagonal particle arrays. We experimentally demonstrate growth of a highly stable array of 50 gold particles with 200 nm diameter, spaced by 1.1 μm.

  8. Junction Transport in Epitaxial Film Silicon Heterojunction Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Young, D. L.; Li, J. V.; Teplin, C. W.; Stradins, P.; Branz, H. M.

    2011-07-01

    We report our progress toward low-temperature HWCVD epitaxial film silicon solar cells on inexpensive seed layers, with a focus on the junction transport physics exhibited by our devices. Heterojunctions of i/p hydrogenated amorphous Si (a-Si) on our n-type epitaxial crystal Si on n++ Si wafers show space-charge-region recombination, tunneling or diffusive transport depending on both epitaxial Si quality and the applied forward voltage.

  9. Ion beam deposited epitaxial thin silicon films

    International Nuclear Information System (INIS)

    Orrman-Rossiter, K.G.; Al-Bayati, A.H.; Armour, D.G.; Donnelly, S.E.; Berg, J.A. van den

    1991-01-01

    Deposition of thin films using low energy, mass-separated ion beams is a potentially important low temperature method of producing epitaxial layers. In these experiments silicon films were grown on Si (001) substrates using 10-200 eV 28 Si + and 30 Si + ions at substrate temperatures in the range 273-1073 K, under ultrahigh-vacuum conditions (deposition pressure -7 Pa). The film crystallinity was assessed in situ using medium energy ion scattering (MEIS). Films of crystallinity comparable to bulk samples were grown using 10-40 eV 28 Si + and 30 Si + ions at deposition temperatures in the range 623-823 K. These experiments confirmed the role of key experimental parameters such as ion energy, substrate temperature during deposition, and the surface treatment prior to deposition. It was found that a high temperature in situ anneal (1350-1450 K) gave the best results for epitaxial nucleation, whereas low energy (20-40 eV) Cl + ion bombardment resulted in amorphous film growth. The deposition energy for good epitaxial growth indicates that it is necessary to provide enough energy to induce local mobility but not to cause atomic displacements leading to the buildup of stable defects, e.g. divacancies, below the surface layer of the growing film. (orig.)

  10. Growth of pseudomorphic structures through organic epitaxy

    International Nuclear Information System (INIS)

    Kaviyil, Sreejith Embekkat; Sassella, Adele; Borghesi, Alessandro; Campione, Marcello; Su Genbo; He Youping; Chen Chenjia

    2012-01-01

    The control of molecular orientation in thin solid film phases of organic semiconductors is a basic factor for the exploitation of their physical properties for optoelectronic devices. We compare structural and optical properties of thin films of the organic semiconductor α-quarterthiophene grown by molecular beam epitaxy on different organic substrates. We show how epitactic interactions, characteristic of the surface of organic crystals, can drive the orientation of the crystalline overlayer and the selection of specific polymorphs and new pseudomorphic phases. We identify a key role in this phenomenon played by the marked groove-like corrugations present in some organic crystal surfaces. Since different polymorphs possess rather different performance in terms of, e.g., charge carrier mobility, this strategy is demonstrated to allow for the growth of oriented phases with enhanced physical properties, while keeping the substrate at room temperature. These results provide useful guidelines for the design of technological substrates for organic epitaxy and they substantiate the adoption of an organic epitaxy approach for the fabrication of optoelectronic devices based on thin films of organic semiconductors.

  11. Potassium and ANO1/TMEM16A chloride channel profiles distinguish atypical and typical smooth muscle cells from interstitial cells in the mouse renal pelvis

    Science.gov (United States)

    Iqbal, Javed; Tonta, Mary A; Mitsui, Retsu; Li, Qun; Kett, Michelle; Li, Jinhua; Parkington, Helena C; Hashitani, Hikaru; Lang, Richard J

    2012-01-01

    BACKGROUND AND PURPOSE Although atypical smooth muscle cells (SMCs) in the proximal renal pelvis are thought to generate the pacemaker signals that drive pyeloureteric peristalsis, their location and electrical properties remain obscure. EXPERIMENTAL APPROACH Standard patch clamp, intracellular microelectrode and immunohistochemistry techniques were used. To unequivocally identify SMCs, transgenic mice with enhanced yellow fluorescent protein (eYFP) expressed in cells containing α-smooth muscle actin (α-SMA) were sometimes used. KEY RESULTS Atypical SMCs were distinguished from typical SMCs by the absence of both a transient 4-aminopyridine-sensitive K+ current (IKA) and spontaneous transient outward currents (STOCs) upon the opening of large-conductance Ca2+-activated K+ (BK) channels. Many typical SMCs displayed a slowly activating, slowly decaying Cl- current blocked by niflumic acid (NFA). Immunostaining for KV4.3 and ANO1/ TMEM16A Cl- channel subunits co-localized with α-SMA immunoreactive product predominately in the distal renal pelvis. Atypical SMCs fired spontaneous inward currents that were either selective for Cl- and blocked by NFA, or cation-selective and blocked by La3+. α-SMA- interstitial cells (ICs) were distinguished by the presence of a Xe991-sensitive KV7 current, BK channel STOCs and Cl- selective, NFA-sensitive spontaneous transient inward currents (STICs). Intense ANO1/ TMEM16A and KV7.5 immunostaining was present in Kit-α-SMA- ICs in the suburothelial and adventitial regions of the renal pelvis. CONCLUSIONS AND IMPLICATIONS We conclude that KV4.3+α-SMA+ SMCs are typical SMCs that facilitate muscle wall contraction, that ANO1/ TMEM16A and KV7.5 immunoreactivity may be selective markers of Kit- ICs and that atypical SMCs which discharge spontaneous inward currents are the pelviureteric pacemakers. PMID:22014103

  12. Conduction channels of an InAs-Al nanowire Josephson weak link

    International Nuclear Information System (INIS)

    Goffman, M F; Urbina, C; Pothier, H; Nygård, J; Marcus, C M; Krogstrup, P

    2017-01-01

    We present a quantitative characterization of an electrically tunable Josephson junction defined in an InAs nanowire proximitized by an epitaxially-grown superconducting Al shell. The gate-dependence of the number of conduction channels and of the set of transmission coefficients are extracted from the highly nonlinear current–voltage characteristics. Although the transmissions evolve non-monotonically, the number of independent channels can be tuned, and configurations with a single quasi-ballistic channel achieved. (fast track communication)

  13. Segmentation and profiling consumers in a multi-channel environment using a combination of self-organizing maps (SOM method, and logistic regression

    Directory of Open Access Journals (Sweden)

    Seyed Ali Akbar Afjeh

    2014-05-01

    Full Text Available Market segmentation plays essential role on understanding the behavior of people’s interests in purchasing various products and services through various channels. This paper presents an empirical investigation to shed light on consumer’s purchasing attitude as well as gathering information in multi-channel environment. The proposed study of this paper designed a questionnaire and distributed it among 800 people who were at least 18 years of age and had some experiences on purchasing goods and services on internet, catalog or regular shopping centers. Self-organizing map, SOM, clustering technique was performed based on consumer’s interest in gathering information as well as purchasing products through internet, catalog and shopping centers and determined four segments. There were two types of questions for the proposed study of this paper. The first group considered participants’ personal characteristics such as age, gender, income, etc. The second group of questions was associated with participants’ psychographic characteristics including price consciousness, quality consciousness, time pressure, etc. Using multinominal logistic regression technique, the study determines consumers’ behaviors in each four segments.

  14. Epitaxial-graphene/graphene-oxide junction: an essential step towards epitaxial graphene electronics.

    Science.gov (United States)

    Wu, Xiaosong; Sprinkle, Mike; Li, Xuebin; Ming, Fan; Berger, Claire; de Heer, Walt A

    2008-07-11

    Graphene-oxide (GO) flakes have been deposited to bridge the gap between two epitaxial-graphene electrodes to produce all-graphene devices. Electrical measurements indicate the presence of Schottky barriers at the graphene/graphene-oxide junctions, as a consequence of the band gap in GO. The barrier height is found to be about 0.7 eV, and is reduced after annealing at 180 degrees C, implying that the gap can be tuned by changing the degree of oxidation. A lower limit of the GO mobility was found to be 850 cm2/V s, rivaling silicon. In situ local oxidation of patterned epitaxial graphene has been achieved.

  15. Epitaxial growth and new phase of single crystal Dy by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yang, Kai-Yueh; Homma, Hitoshi; Schuller, I.K.

    1987-09-01

    We have grown two novel epitaxial phases of dysprosium (Dy) on vanadium (V) by molecular beam epitaxy technique. Surface and bulk structures are studied by in-situ reflection high energy electron diffraction (RHEED) and x-ray diffraction techniques. The new hcp phases are ∼4% expanded uniformly in-plane (0001), and ∼9% and ∼4% expanded out of plane along the c-axes for non-interrupted and interrupted deposition case, respectively. We also observed (2 x 2), (3 x 3), and (4 x 4) Dy surface reconstruction patterns and a series of transitions as the Dy film thickness increases. 12 refs., 3 figs

  16. Applications of positron depth profiling

    International Nuclear Information System (INIS)

    Hakvoort, R.A.

    1993-01-01

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM)

  17. Applications of positron depth profiling

    Energy Technology Data Exchange (ETDEWEB)

    Hakvoort, R A

    1993-12-23

    In this thesis some contributions of the positron-depth profiling technique to materials science have been described. Following studies are carried out: Positron-annihilation measurements on neon-implanted steel; Void creation in silicon by helium implantation; Density of vacancy-type defects present in amorphous silicon prepared by ion implantation; Measurements of other types of amorphous silicon; Epitaxial cobalt disilicide prepared by cobalt outdiffusion. Positron-annihilation experiments on low-pressure CVD silicon-nitride films. (orig./MM).

  18. Pharmacological profile of essential oils derived from Lavandula angustifolia and Melissa officinalis with anti-agitation properties: focus on ligand-gated channels.

    Science.gov (United States)

    Huang, Liping; Abuhamdah, Sawsan; Howes, Melanie-Jayne R; Dixon, Christine L; Elliot, Mark S J; Ballard, Clive; Holmes, Clive; Burns, Alistair; Perry, Elaine K; Francis, Paul T; Lees, George; Chazot, Paul L

    2008-11-01

    Both Melissa officinalis (Mo) and Lavandula angustifolia (La) essential oils have putative anti-agitation properties in humans, indicating common components with a depressant action in the central nervous system. A dual radioligand binding and electrophysiological study, focusing on a range of ligand-gated ion channels, was performed with a chemically validated essential oil derived from La, which has shown clinical benefit in treating agitation. La inhibited [35S] TBPS binding to the rat forebrain gamma aminobutyric acid (GABA)(A) receptor channel (apparent IC50 = 0.040 +/- 0.001 mg mL(-1)), but had no effect on N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or nicotinic acetylcholine receptors. A 50:50 mixture of Mo and La essential oils inhibited [3H] flunitrazepam binding, whereas the individual oils had no significant effect. Electrophysiological analyses with rat cortical primary cultures demonstrated that La reversibly inhibited GABA-induced currents in a concentration-dependent manner (0.01-1 mg mL(-1)), whereas no inhibition of NMDA- or AMPA-induced currents was noted. La elicited a significant dose-dependent reduction in both inhibitory and excitatory transmission, with a net depressant effect on neurotransmission (in contrast to the classic GABA(A) antagonist picrotoxin which evoked profound epileptiform burst firing in these cells). These properties are similar to those recently reported for Mo. The anti-agitation effects in patients and the depressant effects of La we report in neural membranes in-vitro are unlikely to reflect a sedative interaction with any of the ionotropic receptors examined here. These data suggest that components common to the two oils are worthy of focus to identify the actives underlying the neuronal depressant and anti-agitation activities reported.

  19. Doping efficiency analysis of highly phosphorous doped epitaxial/amorphous silicon emitters grown by PECVD for high efficiency silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    El-Gohary, H.G.; Sivoththaman, S. [Waterloo Univ., ON (Canada). Dept. of Electrical and Computer Engineering

    2008-08-15

    The efficient doping of hydrogenated amorphous and crystalline silicon thin films is a key factor in the fabrication of silicon solar cells. The most popular method for developing those films is plasma enhanced chemical vapor deposition (PECVD) because it minimizes defect density and improves doping efficiency. This paper discussed the preparation of different structure phosphorous doped silicon emitters ranging from epitaxial to amorphous films at low temperature. Phosphine (PH{sub 3}) was employed as the doping gas source with the same gas concentration for both epitaxial and amorphous silicon emitters. The paper presented an analysis of dopant activation by applying a very short rapid thermal annealing process (RTP). A spreading resistance profile (SRP) and SIMS analysis were used to detect both the active dopant and the dopant concentrations, respectively. The paper also provided the results of a structural analysis for both bulk and cross-section at the interface using high-resolution transmission electron microscopy and Raman spectroscopy, for epitaxial and amorphous films. It was concluded that a unity doping efficiency could be achieved in epitaxial layers by applying an optimized temperature profile using short time processing rapid thermal processing technique. The high quality, one step epitaxial layers, led to both high conductive and high doping efficiency layers.

  20. Thin film evolution equations from (evaporating) dewetting liquid layers to epitaxial growth

    International Nuclear Information System (INIS)

    Thiele, U

    2010-01-01

    In the present contribution we review basic mathematical results for three physical systems involving self-organizing solid or liquid films at solid surfaces. The films may undergo a structuring process by dewetting, evaporation/condensation or epitaxial growth, respectively. We highlight similarities and differences of the three systems based on the observation that in certain limits all of them may be described using models of similar form, i.e. time evolution equations for the film thickness profile. Those equations represent gradient dynamics characterized by mobility functions and an underlying energy functional. Two basic steps of mathematical analysis are used to compare the different systems. First, we discuss the linear stability of homogeneous steady states, i.e. flat films, and second the systematics of non-trivial steady states, i.e. drop/hole states for dewetting films and quantum-dot states in epitaxial growth, respectively. Our aim is to illustrate that the underlying solution structure might be very complex as in the case of epitaxial growth but can be better understood when comparing the much simpler results for the dewetting liquid film. We furthermore show that the numerical continuation techniques employed can shed some light on this structure in a more convenient way than time-stepping methods. Finally we discuss that the usage of the employed general formulation does not only relate seemingly unrelated physical systems mathematically, but does allow as well for discussing model extensions in a more unified way.

  1. Selective epitaxial growth of stepwise SiGe:B at the recessed sources and drains: A growth kinetics and strain distribution study

    Directory of Open Access Journals (Sweden)

    Sangmo Koo

    2016-09-01

    Full Text Available The selective epitaxial growth of Si1-xGex and the related strain properties were studied. Epitaxial Si1-xGex films were deposited on (100 and (110 orientation wafers and on patterned Si wafers with recessed source and drain structures via ultrahigh vacuum chemical vapor deposition using different growing steps and Ge concentrations. The stepwise process was split into more than 6 growing steps that ranged in thicknesses from a few to 120 nm in order to cover the wide stages of epitaxial growth. The growth rates of SiGe on the plane and patterned wafers were examined and a dependence on the surface orientation was identified. As the germanium concentration increased, defects were generated with thinner Si1-xGex growth. The defect generation was the result of the strain evolution which was examined for channel regions with a Si1-xGex source/drain (S/D structure.

  2. The expression profile of acid-sensing ion channel (ASIC) subunits ASIC1a, ASIC1b, ASIC2a, ASIC2b, and ASIC3 in the esophageal vagal afferent nerve subtypes.

    Science.gov (United States)

    Dusenkova, Svetlana; Ru, Fei; Surdenikova, Lenka; Nassenstein, Christina; Hatok, Jozef; Dusenka, Robert; Banovcin, Peter; Kliment, Jan; Tatar, Milos; Kollarik, Marian

    2014-11-01

    Acid-sensing ion channels (ASICs) have been implicated in esophageal acid sensing and mechanotransduction. However, insufficient knowledge of ASIC subunit expression profile in esophageal afferent nerves hampers the understanding of their role. This knowledge is essential because ASIC subunits form heteromultimeric channels with distinct functional properties. We hypothesized that the esophageal putative nociceptive C-fiber nerves (transient receptor potential vanilloid 1, TRPV1-positive) express multiple ASIC subunits and that the ASIC expression profile differs between the nodose TRPV1-positive subtype developmentally derived from placodes and the jugular TRPV1-positive subtype derived from neural crest. We performed single cell RT-PCR on the vagal afferent neurons retrogradely labeled from the esophagus. In the guinea pig, nearly all (90%-95%) nodose and jugular esophageal TRPV1-positive neurons expressed ASICs, most often in a combination (65-75%). ASIC1, ASIC2, and ASIC3 were expressed in 65-75%, 55-70%, and 70%, respectively, of both nodose and jugular TRPV1-positive neurons. The ASIC1 splice variants ASIC1a and ASIC1b and the ASIC2 splice variant ASIC2b were similarly expressed in both nodose and jugular TRPV1-positive neurons. However, ASIC2a was found exclusively in the nodose neurons. In contrast to guinea pig, ASIC3 was almost absent from the mouse vagal esophageal TRPV1-positive neurons. However, ASIC3 was similarly expressed in the nonnociceptive TRPV1-negative (tension mechanoreceptors) neurons in both species. We conclude that the majority of esophageal vagal nociceptive neurons express multiple ASIC subunits. The placode-derived nodose neurons selectively express ASIC2a, known to substantially reduce acid sensitivity of ASIC heteromultimers. ASIC3 is expressed in the guinea pig but not in the mouse vagal esophageal TRPV1-positive neurons, indicating species differences in ASIC expression. Copyright © 2014 the American Physiological Society.

  3. Ion channeling

    International Nuclear Information System (INIS)

    Erramli, H.; Blondiaux, G.

    1994-01-01

    Channeling phenomenon was predicted, many years ago, by stark. The first channeling experiments were performed in 1963 by Davies and his coworkers. Parallely Robinson and Oen have investigated this process by simulating trajectories of ions in monocrystals. This technique has been combined with many methods like Rutherford Backscattering Spectrometry (R.B.S.), Particles Induced X-rays Emission (P.I.X.E) and online Nuclear Reaction (N.R.A.) to localize trace elements in the crystal or to determine crystalline quality. To use channeling for material characterization we need data about the stopping power of the incident particle in the channeled direction. The ratios of channeled to random stopping powers of silicon for irradiation in the direction have been investigated and compared to the available theoretical results. We describe few applications of ion channeling in the field of materials characterization. Special attention is given to ion channeling combined with Charged Particle Activation Analysis (C.P.A.A.) for studying the behaviour of oxygen atoms in Czochralski silicon lattices under the influence of internal gettering and in different gaseous atmospheres. Association between ion channeling and C.P.A.A was also utilised for studying the influence of the growing conditions on concentration and position of carbon atoms at trace levels in the MOVPE Ga sub (1-x) Al sub x lattice. 6 figs., 1 tab., 32 refs. (author)

  4. Epitaxial III-V nanowires on silicon for vertical devices

    NARCIS (Netherlands)

    Bakkers, E.P.A.M.; Borgström, M.T.; Einden, Van Den W.; Weert, van M.H.M.; Helman, A.; Verheijen, M.A.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the Vapor-Liquid-Solid (VLS) mechanism with laser ablation as well as metal organic vapor phase epitaxy. The VLS growth enables the fabrication of complex axial and radial

  5. Interface relaxation and band gap shift in epitaxial layers

    Directory of Open Access Journals (Sweden)

    Ziming Zhu

    2012-12-01

    Full Text Available Although it is well known that the interface relaxation plays the crucial role for the electronic properties in semiconductor epitaxial layers, there is lack of a clear definition of relationship between interfacial bond-energy variation and interface bond-nature-factor (IBNF in epitaxial layers before and after relaxation. Here we establish an analytical method to shed light on the relationship between the IBNF and the bond-energy change, as well as the relation with band offset in epitaxial layers from the perspective of atomic-bond-relaxation consideration and continuum mechanics. The theoretical predictions are consistent with the available evidences, which provide an atomistic understanding on underlying mechanism of interface effect in epitaxial nanostructures. Thus, it will be helpful for opening up to tailor physical-chemical properties of the epitaxial nanostructures to the desired specifications.

  6. Molecular beam epitaxy for the future

    International Nuclear Information System (INIS)

    Takahashi, K.

    1984-01-01

    Molecular beam epitaxy (MBE) is most commonly used to fabricate super-lattices, high electron mobility transistors, multi-quantum well lasers and other new semiconductor devices by utilizing its excellent controlability. MBE for the future is presumed to include techniques such as metalorganic chemical vapor deposition, photochemical reaction process using gas sources and ion implantation. A report on the crystal growth of GaAs using metalorganics, trimethylgallium and triethylgallium, which are usually used in chemical vapor deposition, as gaseous sources of gallium in an MBE system is made. (Author) [pt

  7. Channel box

    International Nuclear Information System (INIS)

    Tanabe, Akira.

    1993-01-01

    In a channel box of a BWR type reactor, protruding pads are disposed in axial position on the lateral side of a channel box opposing to a control rod and facing the outer side portion of the control rod in a reactor core loaded state. In the initial loading stage of fuel assemblies, channel fasteners and spacer pads are abutted against each other in the upper portion between the channel boxes sandwiching the control rod therebetween. Further, in the lower portion, a gap as a channel for the movement of the control rod is ensured by the support of fuel support metals. If the channel box is bent toward the control rod along with reactor operation, the pads are abutted against each other to always ensure the gap through which the control rod can move easily. Further, when the pads are brought into contact with each other, the bending deformation of the channel box is corrected by urging to each other. Thus, the control rod can always be moved smoothly to attain reactor safety operation. (N.H.)

  8. SIMS studies of CI- doped Zn Se epilayers grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Gard, F.S.; Riley, J.D.; Lekey, R.; Usher, B.F.; Prine, K.

    2004-01-01

    Chlorine is one of the most used species to produce n-type zinc selenium epilayers. In this paper, we present secondary ion mass spectrometry profiles of a series of chlorine-doped zinc selenium samples, which were grown in a molecular beam epitaxy chamber. These profiles have been used to examine the limitation of secondary ion mass spectrometry analysis of narrow chlorine-delta layers. In order to covert secondary ion mass spectrometry raw data to quantified data, the depth profile from a chlorine-implanted standard sample has been used to estimate the u seful ion yield o f chlorine and thus the instrument sensitivity for chlorine in a zinc selenium matrix. The u seful ion yield a nd detection limit of chlorine in the zinc selenium host matrix were calculated to be 4.7 X 10 -17 atoms/ cm 3 , respectively

  9. Epitaxy of advanced nanowire quantum devices

    Science.gov (United States)

    Gazibegovic, Sasa; Car, Diana; Zhang, Hao; Balk, Stijn C.; Logan, John A.; de Moor, Michiel W. A.; Cassidy, Maja C.; Schmits, Rudi; Xu, Di; Wang, Guanzhong; Krogstrup, Peter; Op Het Veld, Roy L. M.; Zuo, Kun; Vos, Yoram; Shen, Jie; Bouman, Daniël; Shojaei, Borzoyeh; Pennachio, Daniel; Lee, Joon Sue; van Veldhoven, Petrus J.; Koelling, Sebastian; Verheijen, Marcel A.; Kouwenhoven, Leo P.; Palmstrøm, Chris J.; Bakkers, Erik P. A. M.

    2017-08-01

    Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a superconductor. To exploit the potential of non-Abelian anyons—which are key elements of topological quantum computing—fully, they need to be exchanged in a well-controlled braiding operation. Essential hardware for braiding is a network of crystalline nanowires coupled to superconducting islands. Here we demonstrate a technique for generic bottom-up synthesis of complex quantum devices with a special focus on nanowire networks with a predefined number of superconducting islands. Structural analysis confirms the high crystalline quality of the nanowire junctions, as well as an epitaxial superconductor-semiconductor interface. Quantum transport measurements of nanowire ‘hashtags’ reveal Aharonov-Bohm and weak-antilocalization effects, indicating a phase-coherent system with strong spin-orbit coupling. In addition, a proximity-induced hard superconducting gap (with vanishing sub-gap conductance) is demonstrated in these hybrid superconductor-semiconductor nanowires, highlighting the successful materials development necessary for a first braiding experiment. Our approach opens up new avenues for the realization of epitaxial three-dimensional quantum architectures which have the potential to become key components of various quantum devices.

  10. Graphene nanoribbons epitaxy on boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Xiaobo; Wang, Shuopei; Wu, Shuang; Chen, Peng; Zhang, Jing; Zhao, Jing; Meng, Jianling; Xie, Guibai; Wang, Duoming; Wang, Guole; Zhang, Ting Ting; Yang, Rong; Shi, Dongxia [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Wei [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Laboratoire Pierre Aigrain, ENS-CNRS UMR 8551, Universités Pierre et Marie Curie and Paris-Diderot, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Watanabe, Kenji; Taniguchi, Takashi [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Zhang, Guangyu, E-mail: gyzhang@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China)

    2016-03-14

    In this letter, we report a pilot study on epitaxy of monolayer graphene nanoribbons (GNRs) on hexagonal boron nitride (h-BN). We found that GNRs grow preferentially from the atomic steps of h-BN, forming in-plane heterostructures. GNRs with well-defined widths ranging from ∼15 nm to ∼150 nm can be obtained reliably. As-grown GNRs on h-BN have high quality with a carrier mobility of ∼20 000 cm{sup 2} V{sup −1} s{sup −1} for ∼100-nm-wide GNRs at a temperature of 1.7 K. Besides, a moiré pattern induced quasi-one-dimensional superlattice with a periodicity of ∼15 nm for GNR/h-BN was also observed, indicating zero crystallographic twisting angle between GNRs and h-BN substrate. The superlattice induced band structure modification is confirmed by our transport results. These epitaxial GNRs/h-BN with clean surfaces/interfaces and tailored widths provide an ideal platform for high-performance GNR devices.

  11. High sensitive quasi freestanding epitaxial graphene gas sensor on 6H-SiC

    NARCIS (Netherlands)

    Iezhokin, I.; Offermans, P.; Brongersma, S.H.; Giesbers, A.J.M.; Flipse, C.F.J.

    2013-01-01

    We have measured the electrical response to NO2, N2, NH3, and CO for epitaxial graphene and quasi freestanding epitaxial graphene on 6H-SiC substrates. Quasi freestanding epitaxial graphene shows a 6 fold increase in NO2 sensitivity compared to epitaxial graphene. Both samples show a sensitivity

  12. Surface channeling

    International Nuclear Information System (INIS)

    Sizmann, R.; Varelas, C.

    1976-01-01

    There is experimental evidence that swift light ions incident at small angles towards single crystalline surfaces can lose an appreciable fraction of their kinetic energy during reflection. It is shown that these projectiles penetrate into the bulk surface region of the crystal. They can travel as channeled particles along long paths through the solid (surface channeling). The angular distribution and the depth history of the re-emerged projectiles are investigated by computer simulations. A considerable fraction of the penetrating projectiles re-emerges from the crystal with constant transverse energy if the angle of incidence is smaller than the critical angle for axial channeling. Analytical formulae are derived based on a diffusion model for surface channeling. A comparison with experimental data exhibits the relevance of the analytical solutions. (Auth.)

  13. Hydraulic jumps in a channel

    DEFF Research Database (Denmark)

    Bonn, D.; Andersen, Anders Peter; Bohr, Tomas

    2009-01-01

    We present a study of hydraulic jumps with flow predominantly in one direction, created either by confining the flow to a narrow channel with parallel walls or by providing an inflow in the form of a narrow sheet. In the channel flow, we find a linear height profile upstream of the jump as expected......'s mixing-length theory with a mixing length that is proportional to the height of the fluid layer. Using averaged boundary-layer equations, taking into account the friction with the channel walls and the eddy viscosity, the flow both upstream and downstream of the jump can be understood. For the downstream...... subcritical flow, we assume that the critical height is attained close to the channel outlet. We use mass and momentum conservation to determine the position of the jump and obtain an estimate which is in rough agreement with our experiment. We show that the averaging method with a varying velocity profile...

  14. Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

    Directory of Open Access Journals (Sweden)

    Yuanzhou Gu

    2014-04-01

    Full Text Available We study the magnetic properties of Ho thin films with different crystallinity (either epitaxial or non-epitaxial and investigate their proximity effects with Nb thin films. Magnetic measurements show that epitaxial Ho has large anisotropy in two different crystal directions in contrast to non-epitaxial Ho. Transport measurements show that the superconducting transition temperature (Tc of Nb thin films can be significantly suppressed at zero field by epitaxial Ho compared with non-epitaxial Ho. We also demonstrate a direct control over Tc by changing the magnetic states of the epitaxial Ho layer, and attribute the strong proximity effects to exchange interaction.

  15. Spark Channels

    Energy Technology Data Exchange (ETDEWEB)

    Haydon, S. C. [Department of Physics, University of New England, Armidale, NSW (Australia)

    1968-04-15

    A brief summary is given of the principal methods used for initiating spark channels and the various highly time-resolved techniques developed recently for studies with nanosecond resolution. The importance of the percentage overvoltage in determining the early history and subsequent development of the various phases of the growth of the spark channel is discussed. An account is then given of the recent photographic, oscillographic and spectroscopic investigations of spark channels initiated by co-axial cable discharges of spark gaps at low [{approx} 1%] overvoltages. The phenomena observed in the development of the immediate post-breakdown phase, the diffuse glow structure, the growth of the luminous filament and the final formation of the spark channel in hydrogen are described. A brief account is also given of the salient features emerging from corresponding studies of highly overvolted spark gaps in which the spark channel develops from single avalanche conditions. The essential differences between the two types of channel formation are summarized and possible explanations of the general features are indicated. (author)

  16. Structural properties of relaxed thin film germanium layers grown by low temperature RF-PECVD epitaxy on Si and Ge (100) substrates

    Energy Technology Data Exchange (ETDEWEB)

    Cariou, R., E-mail: romain.cariou@polytechnique.edu [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); III-V lab a joint laboratory between Alcatel-Lucent Bell Labs France, Thales Research and Technology and CEA-LETI, route de Nozay, 91460, Marcoussis, France. (France); Ruggeri, R. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy); Tan, X.; Nassar, J.; Roca i Cabarrocas, P. [LPICM-CNRS, Ecole Polytechnique, 91128, Palaiseau (France); Mannino, Giovanni [CNR-IMM, strada VIII n°5, zona industriale, 95121, Catania (Italy)

    2014-07-15

    We report on unusual low temperature (175 °C) heteroepitaxial growth of germanium thin films using a standard radio-frequency plasma process. Spectroscopic ellipsometry and transmission electron microscopy (TEM) reveal a perfect crystalline quality of epitaxial germanium layers on (100) c-Ge wafers. In addition direct germanium crystal growth is achieved on (100) c-Si, despite 4.2% lattice mismatch. Defects rising from Ge/Si interface are mostly located within the first tens of nanometers, and threading dislocation density (TDD) values as low as 10{sup 6} cm{sup −2} are obtained. Misfit stress is released fast: residual strain of −0.4% is calculated from Moiré pattern analysis. Moreover we demonstrate a striking feature of low temperature plasma epitaxy, namely the fact that crystalline quality improves with thickness without epitaxy breakdown, as shown by TEM and depth profiling of surface TDD.

  17. Ion channeling study of defects in compound crystals using Monte Carlo simulations

    Science.gov (United States)

    Turos, A.; Jozwik, P.; Nowicki, L.; Sathish, N.

    2014-08-01

    Ion channeling is a well-established technique for determination of structural properties of crystalline materials. Defect depth profiles have been usually determined basing on the two-beam model developed by Bøgh (1968) [1]. As long as the main research interest was focused on single element crystals it was considered as sufficiently accurate. New challenge emerged with growing technological importance of compound single crystals and epitaxial heterostructures. Overlap of partial spectra due to different sublattices and formation of complicated defect structures makes the two beam method hardly applicable. The solution is provided by Monte Carlo computer simulations. Our paper reviews principal aspects of this approach and the recent developments in the McChasy simulation code. The latter made it possible to distinguish between randomly displaced atoms (RDA) and extended defects (dislocations, loops, etc.). Hence, complex defect structures can be characterized by the relative content of these two components. The next refinement of the code consists of detailed parameterization of dislocations and dislocation loops. Defect profiles for variety of compound crystals (GaN, ZnO, SrTiO3) have been measured and evaluated using the McChasy code. Damage accumulation curves for RDA and extended defects revealed non monotonous defect buildup with some characteristic steps. Transition to each stage is governed by the different driving force. As shown by the complementary high resolution XRD measurements lattice strain plays here the crucial role and can be correlated with the concentration of extended defects.

  18. Reclamation of a molecular beam epitaxy system and conversion for oxide epitaxy

    International Nuclear Information System (INIS)

    Carver, Alexander G.; Henderson, Walter; Doolittle, W. Alan

    2008-01-01

    An early 1980s vintage molecular beam epitaxy system, a Varian Gen II system, originally used for HgCdTe epitaxy, was converted into a system capable of growing thin-film complex metal oxides. The nature of some of the alternative oxides requires a thorough cleaning and, in some cases, complete replacement of system components. Details are provided regarding the chemistry of the etchants used, safety requirements for properly handling, and disposal of large quantities of etchants and etch by-products, and components that can be reused versus components that require replacement are given. Following the given procedures, an ultimate base pressure of 2x10 -10 Torr was obtained. Films grown in the system after reclamation contained no evidence of previously present materials down to the detection limit of secondary ion mass spectrometry

  19. Self-assembled epitaxial NiSi2 nanowires on Si(001) by reactive deposition epitaxy

    International Nuclear Information System (INIS)

    Chen, S.Y.; Chen, L.J.

    2006-01-01

    Self-assembled epitaxial NiSi 2 nanowires have been fabricated on Si(001) by reactive deposition epitaxy (RDE). The RDE method promoted nanowire growth since it provides deposited atoms sufficient kinetic energy for movement on the Si surface during the growth of silicide islands. The twin-related interface between NiSi 2 and Si is directly related to the nanowire formation since it breaks the symmetry of the surface and leads to the asymmetric growth. The temperature of RDE was found to greatly influence the formation of nanowires. By RDE at 750 deg. C, a high density of NiSi 2 nanowires was formed with an average aspect ratio of 30

  20. Electronic structure of epitaxial chalcopyrite surfaces and interfaces for photovoltaics

    International Nuclear Information System (INIS)

    Hofmann, Andreas

    2012-01-01

    This thesis constitutes a comprehensive study of the surface physics of epitaxial CuInSe 2 films. It comprises analyses of the surface morphology and reconstruction, electronic band structure as well as hetero-junctions relevant to photovoltaic applications. Therefore, especially the aspect of stoichiometry variation from the CuInSe 2 to the copper-deficient defect phases was considered. Preparation and analysis was completely performed under ultra-high vacuum conditions in order to ensure the investigation of well-defined samples free of contaminants. For some of the analysis techniques, single-crystalline samples are indispensable: They allow for the determination of surface periodicity by low-energy electron diffraction (LEED). In combination with concentration depth profiling by angle-resolved x-ray photoemission, to types of surface reconstructions could be distinguished for the near-stoichiometric CuInSe 2 (112) surface. In the copper-rich case, it is stabilized by Cu In anti-site defects and on the indium-rich side by 2 V Cu defects, as predicted by surface total energy calculations by Jaffe and Zunger. Both configurations correspond to a c(4 x 2) reconstruction of the zinc blende type (111) surface. For the defect compound CuIn 3 Se 5 , a sphalerite order of the surface was found, which points at a weakening or absence of the chalcopyrite order in the bulk of the material. The unusual stability of the (112) surface could also be proven by comparison with the reconstruction and surface order of (001) and (220) surfaces. The results from surface analysis were used to measure the valence band structure of the epitaxial samples by synchrotron-based angle-resolved photoelectron spectroscopy. The CuInSe 2 (001) surface gives access to the high symmetry directions Γ-T and Γ-N of momentum space. By contrasting the data obtained for the stoichiometric surface with the copper-poor defect compound, a reduction of the valence band dispersion and a broadening of

  1. Point defect balance in epitaxial GaSb

    International Nuclear Information System (INIS)

    Segercrantz, N.; Slotte, J.; Makkonen, I.; Kujala, J.; Tuomisto, F.; Song, Y.; Wang, S.

    2014-01-01

    Positron annihilation spectroscopy in both conventional and coincidence Doppler broadening mode is used for studying the effect of growth conditions on the point defect balance in GaSb:Bi epitaxial layers grown by molecular beam epitaxy. Positron annihilation characteristics in GaSb are also calculated using density functional theory and compared to experimental results. We conclude that while the main positron trapping defect in bulk samples is the Ga antisite, the Ga vacancy is the most prominent trap in the samples grown by molecular beam epitaxy. The results suggest that the p–type conductivity is caused by different defects in GaSb grown with different methods.

  2. Position-controlled epitaxial III-V nanowires on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Roest, Aarnoud L; Verheijen, Marcel A; Wunnicke, Olaf; Serafin, Stacey; Wondergem, Harry; Bakkers, Erik P A M [Philips Research Laboratories, Professor Holstlaan 4, 5656 AA Eindhoven (Netherlands); Kavli Institute of NanoScience, Delft University of Technology, PO Box 5046, 2600 GA Delft (Netherlands)

    2006-06-14

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction pole figures and cross-sectional transmission electron microscopy. We show preliminary results of two-terminal electrical measurements of III-V nanowires grown on silicon. E-beam lithography was used to predefine the position of the nanowires.

  3. Position-controlled epitaxial III-V nanowires on silicon

    International Nuclear Information System (INIS)

    Roest, Aarnoud L; Verheijen, Marcel A; Wunnicke, Olaf; Serafin, Stacey; Wondergem, Harry; Bakkers, Erik P A M

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction pole figures and cross-sectional transmission electron microscopy. We show preliminary results of two-terminal electrical measurements of III-V nanowires grown on silicon. E-beam lithography was used to predefine the position of the nanowires

  4. One-step Ge/Si epitaxial growth.

    Science.gov (United States)

    Wu, Hung-Chi; Lin, Bi-Hsuan; Chen, Huang-Chin; Chen, Po-Chin; Sheu, Hwo-Shuenn; Lin, I-Nan; Chiu, Hsin-Tien; Lee, Chi-Young

    2011-07-01

    Fabricating a low-cost virtual germanium (Ge) template by epitaxial growth of Ge films on silicon wafer with a Ge(x)Si(1-x) (0 deposition method in one step by decomposing a hazardousless GeO(2) powder under hydrogen atmosphere without ultra-high vacuum condition and then depositing in a low-temperature region. X-ray diffraction analysis shows that the Ge film with an epitaxial relationship is along the in-plane direction of Si. The successful growth of epitaxial Ge films on Si substrate demonstrates the feasibility of integrating various functional devices on the Ge/Si substrates.

  5. Droplet Epitaxy Image Contrast in Mirror Electron Microscopy

    Science.gov (United States)

    Kennedy, S. M.; Zheng, C. X.; Jesson, D. E.

    2017-01-01

    Image simulation methods are applied to interpret mirror electron microscopy (MEM) images obtained from a movie of GaAs droplet epitaxy. Cylindrical symmetry of structures grown by droplet epitaxy is assumed in the simulations which reproduce the main features of the experimental MEM image contrast, demonstrating that droplet epitaxy can be studied in real-time. It is therefore confirmed that an inner ring forms at the droplet contact line and an outer ring (or skirt) occurs outside the droplet periphery. We believe that MEM combined with image simulations will be increasingly used to study the formation and growth of quantum structures.

  6. Organometallic vapor-phase epitaxy theory and practice

    CERN Document Server

    Stringfellow, Gerald B

    1989-01-01

    Here is one of the first single-author treatments of organometallic vapor-phase epitaxy (OMVPE)--a leading technique for the fabrication of semiconductor materials and devices. Also included are metal-organic molecular-beam epitaxy (MOMBE) and chemical-beam epitaxy (CBE) ultra-high-vacuum deposition techniques using organometallic source molecules. Of interest to researchers, students, and people in the semiconductor industry, this book provides a basic foundation for understanding the technique and the application of OMVPE for the growth of both III-V and II-VI semiconductor materials and the

  7. The epitaxial growth and interfacial strain study of VO{sub 2}/MgF{sub 2} (001) films by synchrotron based grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Fan, L.L. [Key Laboratory for Advanced Technology in Environmental Protection of Jiangsu Province, Yancheng Institute of Technology, Yancheng 224051 (China); National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Chen, S. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Liu, Q.H. [Science and Technology on Electro-optical Information Security Control Laboratory, Tianjin 300300 (China); Liao, G.M.; Chen, Y.L.; Ren, H. [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China); Zou, C.W., E-mail: czou@ustc.edu.cn [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

    2016-09-05

    High quality VO{sub 2} films with different thickness were epitaxially grown on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. The evolution of interfacial strain was investigated by synchrotron based grazing incidence X-ray diffraction. By adjusting the incidence angles, the penetration depth of X-ray in VO{sub 2} film could be controlled and the thickness-depend lattice distortion in the epitaxial VO{sub 2} film was investigated. Due to the lattice mismatching, the pronounced tensile strain was observed in ultra-thin VO{sub 2} film. As the film thickness increasing, the interfacial strain relaxed gradually and became fully relaxed for thick VO{sub 2} films. Combined with the electric transport measurement, it was revealed that the phase transition temperature of ultra-thin VO{sub 2} film decreased greatly. The effect of interfacial strain induced phase transition modulation and the intrinsic mechanism was systematically discussed. - Highlights: • We prepared high quality VO{sub 2} epitaxial films on MgF{sub 2} (001) substrates by oxide molecular beam epitaxy method. • Synchrotron radiation grazing incidence X-ray diffraction was employed to detect evolution of strain along depth profile. • Based on a classic band structure model, the mechanism of strain controlled phase transition of VO{sub 2} was discussed.

  8. Multifunctional epitaxial systems on silicon substrates

    Energy Technology Data Exchange (ETDEWEB)

    Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Department of Physics, The University of Texas at El Paso, El Paso, Texas 79968 (United States); Prater, John Thomas [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Materials Science Division, Army Research Office, Research Triangle Park, North Carolina 27709 (United States); Narayan, Jagdish [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2016-09-15

    Multifunctional heterostructures can exhibit a wide range of functional properties, including colossal magneto-resistance, magnetocaloric, and multiferroic behavior, and can display interesting physical phenomena including spin and charge ordering and strong spin-orbit coupling. However, putting this functionality to work remains a challenge. To date, most of the work reported in the literature has dealt with heterostructures deposited onto closely lattice matched insulating substrates such as DyScO{sub 3}, SrTiO{sub 3} (STO), or STO buffered Si(100) using concepts of lattice matching epitaxy (LME). However, strain in heterostructures grown by LME is typically not fully relaxed and the layers contain detrimental defects such as threading dislocations that can significantly degrade the physical properties of the films and adversely affect the device characteristics. In addition, most of the substrates are incompatible with existing CMOS-based technology, where Si (100) substrates dominate. This review discusses recent advances in the integration of multifunctional oxide and non-oxide materials onto silicon substrates. An alternative thin film growth approach, called “domain matching epitaxy,” is presented which identifies approaches for minimizing lattice strain and unwanted defects in large misfit systems (7%–25% and higher). This approach broadly allows for the integration of multifunctional materials onto silicon substrates, such that sensing, computation, and response functions can be combined to produce next generation “smart” devices. In general, pulsed laser deposition has been used to epitaxially grow these materials, although the concepts developed here can be extended to other deposition techniques, as well. It will be shown that TiN and yttria-stabilized zirconia template layers provide promising platforms for the integration of new functionality into silicon-based computer chips. This review paper reports on a number of thin

  9. Magnetic properties of novel epitaxial films

    International Nuclear Information System (INIS)

    Bader, S.D.; Moog, E.R.

    1986-09-01

    The surface magneto-optic Kerr effect (SMOKE) is used to explore the magnetism of ultra-thin Fe Films extending into the monolayer regime. Both bcc α-Fe and fcc γ-Fe single-crystalline, multilayer films are prepared on the bulk-terminated (1 x 1) structures of Au(100) and Cu(100), respectively. The characterizations of epitaxy and growth mode are performed using low energy electron diffraction and Auger electron spectroscopy. Monolayer-range Fe/Au(100) is ferromagnetic with a lower Curie temperature than bulk α-Fe. The controversial γ-Fe/Cu(100) system exhibits a striking, metastable, surface magnetic phase at temperatures above room temperature, but does not exhibit bulk ferromagnetism

  10. Shaping metal nanocrystals through epitaxial seeded growth

    Energy Technology Data Exchange (ETDEWEB)

    Habas, Susan E.; Lee, Hyunjoo; Radmilovic, Velimir; Somorjai,Gabor A.; Yang, Peidong

    2008-02-17

    Morphological control of nanocrystals has becomeincreasingly important, as many of their physical and chemical propertiesare highly shape-dependent. Nanocrystal shape control for both single andmultiple material systems, however, remains fairly empirical andchallenging. New methods need to be explored for the rational syntheticdesign of heterostructures with controlled morphology. Overgrowth of adifferent material on well-faceted seeds, for example, allows for the useof the defined seed morphology to control nucleation and growth of thesecondary structure. Here, we have used highly faceted cubic Pt seeds todirect the epitaxial overgrowth of a secondary metal. We demonstrate thisconcept with lattice matched Pd to produce conformal shape-controlledcore-shell particles, and then extend it to lattice mismatched Au to giveanisotropic growth. Seeding with faceted nanocrystals may havesignificant potential towards the development of shape-controlledheterostructures with defined interfaces.

  11. Epitaxial growth by monolayer restricted galvanic displacement

    Directory of Open Access Journals (Sweden)

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  12. Strain quantification in epitaxial thin films

    International Nuclear Information System (INIS)

    Cushley, M

    2008-01-01

    Strain arising in epitaxial thin films can be beneficial in some cases but devastating in others. By altering the lattice parameters, strain may give a thin film properties hitherto unseen in the bulk material. On the other hand, heavily strained systems are prone to develop lattice defects in order to relieve the strain, which can cause device failure or, at least, a decrease in functionality. Using convergent beam electron diffraction (CBED) and high-resolution transmission electron microscopy (HRTEM), it is possible to determine local strains within a material. By comparing the results from CBED and HRTEM experiments, it is possible to gain a complete view of a material, including the strain and any lattice defects present. As well as looking at how the two experimental techniques differ from each other, I will also look at how results from different image analysis algorithms compare. Strain in Si/SiGe samples and BST/SRO/MgO capacitor structures will be discussed.

  13. Optical characterization of epitaxial semiconductor layers

    CERN Document Server

    Richter, Wolfgang

    1996-01-01

    The last decade has witnessed an explosive development in the growth of expitaxial layers and structures with atomic-scale dimensions. This progress has created new demands for the characterization of those stuctures. Various methods have been refined and new ones developed with the main emphasis on non-destructive in-situ characterization. Among those, methods which rely on the interaction of electromagnetic radiation with matter are particularly valuable. In this book standard methods such as far-infrared spectroscopy, ellipsometry, Raman scattering, and high-resolution X-ray diffraction are presented, as well as new advanced techniques which provide the potential for better in-situ characterization of epitaxial structures (such as reflection anistropy spectroscopy, infrared reflection-absorption spectroscopy, second-harmonic generation, and others). This volume is intended for researchers working at universities or in industry, as well as for graduate students who are interested in the characterization of ...

  14. Reversible Polarization Rotation in Epitaxial Ferroelectric Bilayers

    DEFF Research Database (Denmark)

    Liu, Guangqing; Zhang, Qi; Huang, Hsin-Hui

    2016-01-01

    Polarization rotation engineering is a promising path to giant dielectric and electromechanical responses in ferroelectric materials and devices. This work demonstrates robust and reversible in- to out-of-plane polarization rotation in ultrathin (nanoscale) epitaxial (001) tetragonal PbZr0.3Ti0.7O3...... large-scale polarization rotation switching (≈60 μC cm−2) and an effective d 33 response 500% (≈250 pm V−1) larger than the PZT-R layer alone. Furthermore, this enhancement is stable for more than 107 electrical switching cycles. These bilayers present a simple and highly controllable means to design...... and optimize rotational polar systems as an alternate to traditional composition-based approaches. The precise control of the subtle interface-driven interactions between the lattice and the external factors that control polarization opens a new door to enhanced—or completely new—functional properties....

  15. Molecular beam epitaxy applications to key materials

    CERN Document Server

    Farrow, Robin F C

    1995-01-01

    In this volume, the editor and contributors describe the use of molecular beam epitaxy (MBE) for a range of key materials systems that are of interest for both technological and fundamental reasons. Prior books on MBE have provided an introduction to the basic concepts and techniques of MBE and emphasize growth and characterization of GaAs-based structures. The aim in this book is somewhat different; it is to demonstrate the versatility of the technique by showing how it can be utilized to prepare and explore a range of distinct and diverse materials. For each of these materials systems MBE has played a key role both in their development and application to devices.

  16. Twenty years of molecular beam epitaxy

    Science.gov (United States)

    Cho, A. Y.

    1995-05-01

    The term "molecular beam epitaxy" (MBE) was first used in one of our crystal growth papers in 1970, after having conducted extensive surface physics studies in the late 1960's of the interaction of atomic and molecular beams with solid surfaces. The unique feature of MBE is the ability to prepare single crystal layers with atomic dimensional precision. MBE sets the standard for epitaxial growth and has made possible semiconductor structures that could not be fabricated with either naturally existing materials or by other crystal growth techniques. MBE led the crystal growth technologies when it prepared the first semiconductor quantum well and superlattice structures that gave unexpected and exciting electrical and optical properties. For example, the discovery of the fractional quantized Hall effect. It brought experimental quantum physics to the classroom, and practically all major universities throughout the world are now equipped with MBE systems. The fundamental principles demonstrated by the MBE growth of III-V compound semiconductors have also been applied to the growth of group IV, II-VI, metal, and insulating materials. For manufacturing, the most important criteria are uniformity, precise control of the device structure, and reproducibility. MBE has produced more lasers (3 to 5 million per month for compact disc application) than any other crystal growth technique in the world. New directions for MBE are to incorporate in-situ, real-time monitoring capabilities so that complex structures can be precisely "engineered". In the future, as environmental concerns increase, the use of toxic arsine and phosphine may be limited. Successful use of valved cracker cells for solid arsenic and phosphorus has already produced InP based injection lasers.

  17. Synthesis of Si epitaxial layers from technical silicon by liquid-phase epitaxy method

    International Nuclear Information System (INIS)

    Ibragimov, Sh.I.; Saidov, A.S.; Sapaev, B.; Horvat, M.A.

    2004-01-01

    Full text: For today silicon is one of the most suitable materials because it is investigated, cheap and several its parameters are even just as good as those of connections A III B V . Disintegration of the USSR has led to the must difficult position of the industry of silicon instrument manufacture because of all industry of semiconductor silicon manufacture had generally concentrated in Ukraine. The importance of semiconductor silicon is rather great, because of, in opinion of expects, the nearest decade this material will dominate over not only on microelectronics but also in the majority of basic researches. Research of obtain of semiconductor silicon, power electronics and solar conversion, is topical interest of the science. In the work research of technological conditions of obtain and measurement of parameters of epitaxial layers obtained from technical silicon + stannum is resulted. Growth of silicon epitaxial layer with suitable parameters on thickness, cleanliness uniformity and structural perfection depends on the correct choice of condition of the growth and temperature. It is shown that in this case the growth occurring without preliminary clearing of materials (mix materials and substrates) at crystallization of epitaxial layer from technical silicon is accompanied by clearing of silicon film from majority of impurities order-of-magnitude. As starting raw material technical silicon of mark Kr.3 has been taken. By means of X-ray microanalyzer 'Jeol' JSM 5910 LV - Japan the quantitative analysis from the different points has been and from the different sides and from different points has been carried out. After corresponding chemical and mechanical processing the quantitative analysis of layer on chip has been carried out. Results of the quantitative analysis are shown. More effective clearing occurs that of the impurity atoms such as Al, P, Ca, Ti and Fe. The obtained material (epitaxial layer) has the parameters: specific resistance ρ∼0.1-4.0

  18. MARKETING CHANNELS

    Directory of Open Access Journals (Sweden)

    Ljiljana Stošić Mihajlović

    2014-07-01

    Full Text Available Marketing channel is a set of entities and institutions, completion of distribution and marketing activities, attend the efficient and effective networking of producers and consumers. Marketing channels include the total flows of goods, money and information taking place between the institutions in the system of marketing, establishing a connection between them. The functions of the exchange, the physical supply and service activities, inherent in the system of marketing and trade. They represent paths which products and services are moving after the production, which will ultimately end up buying and eating by the user.

  19. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José ; Burriel, Mó nica

    2010-01-01

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation

  20. Epitaxial Growth and Cracking Mechanisms of Thermally Sprayed Ceramic Splats

    Science.gov (United States)

    Chen, Lin; Yang, Guan-jun

    2018-02-01

    In the present study, the epitaxial growth and cracking mechanisms of thermally sprayed ceramic splats were explored. We report, for the first time, the epitaxial growth of various splat/substrate combinations at low substrate temperatures (100 °C) and large lattice mismatch (- 11.26%). Our results suggest that thermal spray deposition was essentially a liquid-phase epitaxy, readily forming chemical bonding. The interface temperature was also estimated. The results convincingly demonstrated that atoms only need to diffuse and rearrange over a sufficiently short range during extremely rapid solidification. Concurrently, severe cracking occurred in the epitaxial splat/substrate systems, which indicated high tensile stress was produced during splat deposition. The origin of the tensile stress was attributed to the strong constraint of the locally heated substrate by its cold surroundings.

  1. Scheme for the fabrication of ultrashort channel metal-oxide-semiconductor field-effect transistors

    International Nuclear Information System (INIS)

    Appenzeller, J.; Martel, R.; Solomon, P.; Chan, K.; Avouris, Ph.; Knoch, J.; Benedict, J.; Tanner, M.; Thomas, S.; Wang, K. L.

    2000-01-01

    We present a scheme for the fabrication of ultrashort channel length metal-oxide-semiconductor field-effect transistors (MOSFETs) involving nanolithography and molecular-beam epitaxy. The active channel is undoped and is defined by a combination of nanometer-scale patterning and anisotropic etching of an n ++ layer grown on a silicon on insulator wafer. The method is self-limiting and can produce MOSFET devices with channel lengths of less than 10 nm. Measurements on the first batch of n-MOSFET devices fabricated with this approach show very good output characteristics and good control of short-channel effects. (c) 2000 American Institute of Physics

  2. CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.

    Science.gov (United States)

    Simon, Andrew; Hupp, Cliff R.

    1987-01-01

    This study (a) assesses the channel changes and network trends of bed level response after modifications between 1959 and 1972 of alluvial channels in western Tennessee and (b) develops a conceptual model of bank slope development to qualitatively assess bank stability and potential channel widening. A six-step, semiquantitative model of channel evolution in disturbed channels was developed by quantifying bed level trends and recognizing qualitative stages of bank slope development. Development of the bank profile is defined in terms of three dynamic and observable surfaces: (a) vertical face (70 to 90 degrees), (b) upper bank (25 to 50 degrees), and (c) slough line (20 to 25 degrees).

  3. Growth of epitaxial thin films by pulsed laser ablation

    International Nuclear Information System (INIS)

    Lowndes, D.H.

    1992-01-01

    High-quality, high-temperature superconductor (HTSc) films can be grown by the pulsed laser ablation (PLA) process. This article provides a detailed introduction to the advantages and curent limitations of PLA for epitaxial film growth. Emphasis is placed on experimental methods and on exploitation of PLA to control epitaxial growth at either the unit cell or the atomic-layer level. Examples are taken from recent HTSc film growth. 33 figs, 127 refs

  4. Microwave dynamics of YBCO bi-epitaxial Josephson structures

    DEFF Research Database (Denmark)

    Constantinian, K. Y.; Ovsyannikov, G. A.; Mashtakov, A. D.

    1996-01-01

    The processes of interaction of microwaves (frequency View the MathML source) with a single high-Tc superconducting YBa2Cu3Ox (YBCO) bi-epitaxial grain-boundary junction and with an array of two junctions connected in series, have been investigated experimentally at temperatures T = 4.2− 77 K......, as well as the subharmonic detector response at weak magnetic fields φ microwave field induced frequency synchronization of two series connected bi-epitaxial YBCO junctions....

  5. Electrodeposition of epitaxial CdSe on (111) gallium arsenide

    Energy Technology Data Exchange (ETDEWEB)

    Cachet, H.; Cortes, R.; Froment, M. [Universite Pierre et Marie Curie, Paris (France). Phys. des Liquides et Electrochimie; Etcheberry, A. [Institut Lavoisier (IREM) UMR CNRS C0173, Universite de Versailles- St Quentin en Yvelynes, 45 Avenue des Etats Unis, 78035, Versailles (France)

    2000-02-21

    Epitaxial growth of CdSe has been achieved on GaAs(111) by electrodeposition from an aqueous electrolyte. The structure of the film corresponds to the cubic modification of CdSe. The quality of epitaxy has been investigated by reflection high energy electron diffraction, transmission electron microscopy and X-ray diffraction techniques. By XPS measurements the chemistry of the CdSe/GaAs interface and the composition of CdSe are determined. (orig.)

  6. P-N junction solar cell grown by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Hazrati Fard, M.

    2001-01-01

    Growth of GaAs epilayers by Molecular Beam Epitaxy was accomplished for the first time in Iran. The layers were grown on GaAs (001) substrates (p+ wafer) with Si impurity for p n junction solar cell fabrication at a rate of nearly one micron per hour and 0.25 micron per quarter. Crystalline quality of grown layers had been monitored during growth by Reflection High Energy Electron Diffraction system. Doping profile and layer thickness was assessed by electrochemical C-V profiling method. Then Hall measurements were conducted on small samples both in room temperature and liquid nitrogen temperature so giving average carrier concentration and compensation ratio. The results as like: V oc , I sc , F F, η were comparable with other laboratory reports. information for obtaining good and repeatable growths was collected. Therefore, the conditions of repeatable quality growth p n junction solar cells onto GaAs (001) substrates were determined

  7. Epitaxial patterning of thin-films: conventional lithographies and beyond

    International Nuclear Information System (INIS)

    Zhang, Wei; Krishnan, Kannan M

    2014-01-01

    Thin-film based novel magnetic and electronic devices have entered a new era in which the film crystallography, structural coherence, and epitaxy play important roles in determining their functional properties. The capabilities of controlling such structural and functional properties are being continuously developed by various physical deposition technologies. Epitaxial patterning strategies further allow the miniaturization of such novel devices, which incorporates thin-film components into nanoscale architectures while keeping their functional properties unmodified from their ideal single-crystal values. In the past decade, epitaxial patterning methods on the laboratory scale have been reported to meet distinct scientific inquires, in which the techniques and processes used differ from one to the other. In this review we summarize many of these pioneering endeavors in epitaxial patterning of thin-film devices that use both conventional and novel lithography techniques. These methods demonstrate epitaxial patterning for a broad range of materials (metals, oxides, and semiconductors) and cover common device length scales from micrometer to sub-hundred nanometer. Whilst we have been motivated by magnetic materials and devices, we present our outlook on developing systematic-strategies for epitaxial patterning of functional materials which will pave the road for the design, discovery and industrialization of next-generation advanced magnetic and electronic nano-devices. (topical review)

  8. GaN/NbN epitaxial semiconductor/superconductor heterostructures

    Science.gov (United States)

    Yan, Rusen; Khalsa, Guru; Vishwanath, Suresh; Han, Yimo; Wright, John; Rouvimov, Sergei; Katzer, D. Scott; Nepal, Neeraj; Downey, Brian P.; Muller, David A.; Xing, Huili G.; Meyer, David J.; Jena, Debdeep

    2018-03-01

    Epitaxy is a process by which a thin layer of one crystal is deposited in an ordered fashion onto a substrate crystal. The direct epitaxial growth of semiconductor heterostructures on top of crystalline superconductors has proved challenging. Here, however, we report the successful use of molecular beam epitaxy to grow and integrate niobium nitride (NbN)-based superconductors with the wide-bandgap family of semiconductors—silicon carbide, gallium nitride (GaN) and aluminium gallium nitride (AlGaN). We apply molecular beam epitaxy to grow an AlGaN/GaN quantum-well heterostructure directly on top of an ultrathin crystalline NbN superconductor. The resulting high-mobility, two-dimensional electron gas in the semiconductor exhibits quantum oscillations, and thus enables a semiconductor transistor—an electronic gain element—to be grown and fabricated directly on a crystalline superconductor. Using the epitaxial superconductor as the source load of the transistor, we observe in the transistor output characteristics a negative differential resistance—a feature often used in amplifiers and oscillators. Our demonstration of the direct epitaxial growth of high-quality semiconductor heterostructures and devices on crystalline nitride superconductors opens up the possibility of combining the macroscopic quantum effects of superconductors with the electronic, photonic and piezoelectric properties of the group III/nitride semiconductor family.

  9. Surface chemistry and growth mechanisms studies of homo epitaxial (1 0 0) GaAs by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Yan Dawei; Wu Weidong; Zhang Hong; Wang Xuemin; Zhang Hongliang; Zhang Weibin; Xiong Zhengwei; Wang Yuying; Shen Changle; Peng Liping; Han Shangjun; Zhou Minjie

    2011-01-01

    In this paper, GaAs thin film has been deposited on thermally desorbed (1 0 0) GaAs substrate using laser molecular beam epitaxy. Scanning electron microscopy, in situ reflection high energy electron diffraction and in situ X-ray photoelectron spectroscopy are applied for evaluation of the surface morphology and chemistry during growth process. The results show that a high density of pits is formed on the surface of GaAs substrate after thermal treatment and the epitaxial thin film heals itself by a step flow growth, resulting in a smoother surface morphology. Moreover, it is found that the incorporation of As species into GaAs epilayer is more efficient in laser molecular beam epitaxy than conventional molecular beam epitaxy. We suggest the growth process is impacted by surface chemistry and morphology of GaAs substrate after thermal treatment and the growth mechanisms are discussed in details.

  10. REVIEW OF WIRELESS MIMO CHANNEL MODELS

    African Journals Online (AJOL)

    user

    MIMO wireless system, the transmitted signal interacts ... delay spread information, power delay profile, angle of arrival and ... With the advent of the MIMO wireless systems, there arose a ..... associated with channel transmission and reception.

  11. Epitaxial lateral overgrowth - a tool for dislocation blockade in multilayer system

    International Nuclear Information System (INIS)

    Zytkiewicz, Z.R.

    1998-01-01

    Results on epitaxial lateral overgrowth of GaAs layers are reported. The methods of controlling the growth anisotropy, the effect of substrate defects filtration in epitaxial lateral overgrowth procedure and influence of the mask on properties of epitaxial lateral overgrowth layers will be discussed. The case od GaAs epitaxial lateral overgrowth layers grown by liquid phase epitaxy on heavily dislocated GaAs substrates was chosen as an example to illustrate the processes discussed. The similarities between our results and those reported recently for GaN layers grown laterally by metalorganic vapour phase epitaxy will be underlined. (author)

  12. Channel Power in Multi-Channel Environments

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); B. Skiera (Bernd)

    2004-01-01

    textabstractIn the literature, little attention has been paid to instances where companies add an Internet channel to their direct channel portfolio. However, actively managing multiple sales channels requires knowing the customers’ channel preferences and the resulting channel power. Two key

  13. Pulsed laser deposition of epitaxial Sr(RuxSn1-x)O3 thin film electrodes and KNbO3/Sr(RuxSn1-x)O3 bilayers

    International Nuclear Information System (INIS)

    Christen, H.M.; Boatner, L.A.; English, L.Q.; Geea, L.A.; Marrero, P.J.; Norton, D.P.

    1995-01-01

    Sr(Ru x Sn 1-x ) 3 is proposed as a new conducting oxide for use in epitaxial multilayer structures. The Sr(Ru o 48 Sn 0.52 )0 3 composition exhibits an excellent lattice match with (100)-oriented KTaO 3 , and films of this composition grown by pulsed laser deposition on KTaO 3 , SrTiO 3 , and LaAlO 3 substrates have been analyzed by X-ray diffraction, Rutherford backscattering/ion channeling, and resistivity measurements. Epitaxial KNbO 3 /Sr(Ru 0.48 Sn 0.52 )O 3 bilayers have been successfully grown

  14. Control system design for concrete irrigation channels

    OpenAIRE

    Strecker, Timm; Aamo, Ole Morten; Cantoni, Michael

    2017-01-01

    Concrete channels find use at the periphery of irrigation networks, for expansion and to replace small earthen channels given the relative ease of maintenance and elimination of seepage losses. In design, it is important to account for control system performance when dimensioning the channel infrastructure. In this paper, the design of a distributed controller is investigated in terms managing water-levels, and thereby the depth profile (i.e., amount of concrete) needed to support peak flow l...

  15. Epitaxial Integration of Nanowires in Microsystems by Local Micrometer Scale Vapor Phase Epitaxy

    DEFF Research Database (Denmark)

    Mølhave, Kristian; Wacaser, Brent A.; Petersen, Dirch Hjorth

    2008-01-01

    deposition (CVD) or metal organic VPE (MOVPE). However, VPE of semiconducting nanowires is not compatible with several microfabrication processes due to the high synthesis temperatures and issues such as cross-contamination interfering with the intended microsystem or the VPE process. By selectively heating...... a small microfabricated heater, growth of nanowires can be achieved locally without heating the entire microsystem, thereby reducing the compatibility problems. The first demonstration of epitaxial growth of silicon nanowires by this method is presented and shows that the microsystem can be used for rapid...

  16. Molecular beam epitaxy of graphene on mica

    International Nuclear Information System (INIS)

    Lippert, G.; Dabrowski, J.; Yamamoto, Y.; Mehr, W.; Lupina, G.; Herziger, F.; Maultzsch, J.; Baringhaus, J.; Tegenkamp, C.; Lemme, M.C.

    2012-01-01

    Realization of graphene devices is often hindered by the fact that the known layer growth methods do not meet the requirements of the device fabrication in silicon mainstream technology. For example, the relatively straightforward method of decomposition of hexagonal SiC is not CMOS-compatible due to the high-thermal budget it requires [Moon et al., IEEE Electron Device Lett. 31, 260 (2010)]. Techniques based on layer transfer are restricted because of the uncertainty of residual metal contaminants, particles, and structural defects. Of interest is thus a method that would allow one to grow a graphene film directly in the device area where graphene is needed. Production of large area graphene is not necessarily required in this case, but high quality of the film and metal-free growth on an insulating substrate at temperatures below 1000 C are important requirements. We demonstrate direct growth of defect-free graphene on insulators at moderate temperatures by molecular beam epitaxy. The quality of the graphene was probed by high-resolution Raman spectroscopy, indicating a negligible density of defects. The spectra are compared with those from graphene flakes mechanically exfoliated from native graphite onto mica. These results are combined with insights from density functional theory calculations. A model of graphene growth on mica and similar substrates is proposed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. State memory in solution gated epitaxial graphene

    Science.gov (United States)

    Butko, A. V.; Butko, V. Y.; Lebedev, S. P.; Lebedev, A. A.; Davydov, V. Y.; Smirnov, A. N.; Eliseyev, I. A.; Dunaevskiy, M. S.; Kumzerov, Y. A.

    2018-06-01

    We studied electrical transport in transistors fabricated on a surface of high quality epitaxial graphene with density of defects as low as 5·1010 cm-2 and observed quasistatic hysteresis with a time constant in a scale of hours. This constant is in a few orders of magnitude greater than the constant previously reported in CVD graphene. The hysteresis observed here can be described as a shift of ∼+2V of the Dirac point measured during a gate voltage increase from the position of the Dirac point measured during a gate voltage decrease. This hysteresis can be characterized as a nonvolatile quasistatic state memory effect in which the state of the gated graphene is determined by its initial state prior to entering the hysteretic region. Due to this effect the difference in resistance of the gated graphene measured in the hysteretic region at the same applied voltages can be as high as 70%. The observed effect can be explained by assuming that charge carriers in graphene and oppositely charged molecular ions from the solution form quasistable interfacial complexes at the graphene interface. These complexes likely preserve the initial state by preventing charge carriers in graphene from discharging in the hysteretic region.

  18. Thickness periodicity in the auger line shape from epitaxial (111)Cu films

    Energy Technology Data Exchange (ETDEWEB)

    Namba, Y; Vook, R W; Chao, S S

    1981-01-01

    The 61 eV MMM Cu Auger line doublet was recorded in the derivative mode as a function of thickness for epitaxial (111)Cu films approximately 1500 angstrom thick. The overlap of the doublet lines makes it possible to define a measure of the doublet profile called the ''R-factor'' as a ratio of the peak-to-peak heights of the small overlap oscillation to that of the major oscillation. To within the experimental error, it was found that the R-factor varies with a periodicity of approximately one monoatomic layer as the film thickens. Since these films grow by a layer growth mechaniism, the surface topography varies periodically with the number of monolayers deposited, going from a smooth to a rough to a smooth, etc. surface. It is believed that the occurrence of such a periodicity implies that there is a difference in the electronic structure at the surface of the flat areas of the film from that at the edges of monolayer high, flat islands. The amplitude of the oscillation in R is interpreted to be a measure of the relative amounts of edge area compared to flat area. These results show that it is possible to use Auger electron spectroscopy to monitor surface topography and the electronic structure changes that accompany the topographical changes occurring when epitaxial films grow by a layer growth mechanism.

  19. Direct Measurements of Island Growth and Step-Edge Barriers in Colloidal Epitaxy

    KAUST Repository

    Ganapathy, R.; Buckley, M. R.; Gerbode, S. J.; Cohen, I.

    2010-01-01

    -scale particles into microstructures that have numerous technological applications. To determine whether atomic epitaxial growth laws are applicable to the epitaxy of larger particles with attractive interactions, we investigated the nucleation and growth dynamics

  20. Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors.

    Science.gov (United States)

    Hardy, Matthew T; Storm, David F; Katzer, D Scott; Downey, Brian P; Nepal, Neeraj; Meyer, David J

    2016-11-24

    Plasma-assisted molecular beam epitaxy is well suited for the epitaxial growth of III-nitride thin films and heterostructures with smooth, abrupt interfaces required for high-quality high-electron-mobility transistors (HEMTs). A procedure is presented for the growth of N-polar InAlN HEMTs, including wafer preparation and growth of buffer layers, the InAlN barrier layer, AlN and GaN interlayers and the GaN channel. Critical issues at each step of the process are identified, such as avoiding Ga accumulation in the GaN buffer, the role of temperature on InAlN compositional homogeneity, and the use of Ga flux during the AlN interlayer and the interrupt prior to GaN channel growth. Compositionally homogeneous N-polar InAlN thin films are demonstrated with surface root-mean-squared roughness as low as 0.19 nm and InAlN-based HEMT structures are reported having mobility as high as 1,750 cm 2 /V∙sec for devices with a sheet charge density of 1.7 x 10 13 cm -2 .

  1. Lateral epitaxial overgrowth of GaN on a patterned GaN-on-silicon substrate by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wang, Yongjin; Hu, Fangren; Hane, Kazuhiro

    2011-01-01

    We report here the lateral epitaxial overgrowth (LEO) of GaN on a patterned GaN-on-silicon substrate by molecular beam epitaxy (MBE) growth with radio frequency nitrogen plasma as a gas source. Two kinds of GaN nanostructures are defined by electron beam lithography and realized on a GaN substrate by fast atom beam etching. The epitaxial growth of GaN by MBE is performed on the prepared GaN template, and the selective growth of GaN takes place with the assistance of GaN nanostructures. The LEO of GaN produces novel GaN epitaxial structures which are dependent on the shape and the size of the processed GaN nanostructures. Periodic GaN hexagonal pyramids are generated inside the air holes, and GaN epitaxial strips with triangular section are formed in the grating region. This work provides a promising way for producing novel GaN-based devices by the LEO of GaN using the MBE technique

  2. Growth and characterization of Hg 1– Cd Te epitaxial films by ...

    Indian Academy of Sciences (India)

    Growth of Hg1–CdTe epitaxial films by a new technique called asymmetric vapour phase epitaxy (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication have ...

  3. Growth and characterization of Hg1–xCdxTe epitaxial films by ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Growth of Hg1–xCdxTe epitaxial films by a new technique called asymmetric vapour phase epitaxy. (ASVPE) has been carried out on CdTe and CZT substrates. The critical problems faced in normal vapour phase epitaxy technique like poor surface morphology, composition gradient and dislocation multiplication.

  4. Direct formation of thin films and epitaxial overlayers at low temperatures using a low-energy (10-500 eV) ion beam deposition system

    International Nuclear Information System (INIS)

    Zuhr, R.A.; Alton, G.D.; Appleton, B.R.; Herbots, N.; Noggle, T.S.; Pennycook, S.J.

    1987-01-01

    A low-energy ion beam deposition system has been developed at Oak Ridge National Laboratory and has been applied successfully to the growth of epitaxial films at low temperatures for a number of different elements. The deposition system utilizes the ion source and optics of a commercial ion implantation accelerator. The 35 keV mass- and energy-analyzed ion beam from the accelerator is decelerated in a four-element electrostatic lens assembly to energies between 10 and 500 eV for direct deposition onto a target under UHV conditions. Current densities on the order of 10 μA/cm 2 are achieved with good uniformity over a 1.4 cm diameter spot. The completed films are characterized by Rutherford backscattering, ion channeling, cross-section transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning have been studied. Epitaxial overlayers which show good minimum yields by ion channeling (3 to 4%) have been produced at temperatures as low as 375 0 C for Si on Si(100) and 250 0 C for Ge on Ge(100) at growth rates that exceed the solid-phase epitaxy rates at these temperatures by more than an order of magnitude

  5. Ion beam induced epitaxy in Ge- and B- coimplanted silicon

    International Nuclear Information System (INIS)

    Hayashi, N.; Hasegawa, M.; Tanoue, H.; Takahashi, H.; Shimoyama, K.; Kuriyama, K.

    1992-01-01

    The epitaxial regrowth of amorphous surface layers in and Si substrate has been studied under irradiation with 400 keV Ar + ions at the temperature range from 300 to 435degC. The amorphous layers were obtained by Ge + implantation, followed by B + implantation. The ion beam assisted epitaxy was found to be sensitive to both the substrate orientation and the implanted Ge concentration, and the layer-by-layer epitaxial regrowth seemed to be precluded in Si layers with high doses of Ge implants, e.g., 2.5 x 10 15 ions/cm 2 . Electrical activation of implanted dopant B was also measured in the recrystallized Si layer. (author)

  6. Channelling and electromagnetic radiation of channelling particles

    International Nuclear Information System (INIS)

    Kalashnikov, N.

    1983-01-01

    A brief description is presented of the channelling of charged particles between atoms in the crystal lattice. The specificities are discussed of the transverse motion of channelling particles as are the origin and properties of quasi-characteristic radiation of channelling particles which accompany transfers from one band of permissible energies of the transverse motion of channelling particles to the other. (B.S.)

  7. Channel Modeling

    Science.gov (United States)

    Schmitz, Arne; Schinnenburg, Marc; Gross, James; Aguiar, Ana

    For any communication system the Signal-to-Interference-plus-Noise-Ratio of the link is a fundamental metric. Recall (cf. Chapter 9) that the SINR is defined as the ratio between the received power of the signal of interest and the sum of all "disturbing" power sources (i.e. interference and noise). From information theory it is known that a higher SINR increases the maximum possible error-free transmission rate (referred to as Shannon capacity [417] of any communication system and vice versa). Conversely, the higher the SINR, the lower will be the bit error rate in practical systems. While one aspect of the SINR is the sum of all distracting power sources, another issue is the received power. This depends on the transmitted power, the used antennas, possibly on signal processing techniques and ultimately on the channel gain between transmitter and receiver.

  8. Epitaxial graphene-encapsulated surface reconstruction of Ge(110)

    Science.gov (United States)

    Campbell, Gavin P.; Kiraly, Brian; Jacobberger, Robert M.; Mannix, Andrew J.; Arnold, Michael S.; Hersam, Mark C.; Guisinger, Nathan P.; Bedzyk, Michael J.

    2018-04-01

    Understanding and engineering the properties of crystalline surfaces has been critical in achieving functional electronics at the nanoscale. Employing scanning tunneling microscopy, surface x-ray diffraction, and high-resolution x-ray reflectivity experiments, we present a thorough study of epitaxial graphene (EG)/Ge(110) and report a Ge(110) "6 × 2" reconstruction stabilized by the presence of epitaxial graphene unseen in group-IV semiconductor surfaces. X-ray studies reveal that graphene resides atop the surface reconstruction with a 0.34 nm van der Waals (vdW) gap and provides protection from ambient degradation.

  9. Channeling experiment

    International Nuclear Information System (INIS)

    Abelin, H.; Birgersson, L.; Widen, H.; Aagren, T.; Moreno, L.; Neretnieks, I.

    1990-07-01

    Channeling of water flow and tracer transport in real fractures in a granite body at Stripa have been investigated experimentally. The experimental site was located 360 m below the ground level. Two kinds of experiments were performed. In the single hole experiments, 20 cm diameter holes were drilled about 2.5 m into the rock in the plane of the fracture. Specially designed packers were used to inject water into the fracture in 5 cm intervals all along the fracture trace in the hole. The variation of the injection flowrates along the fracture were used to determine the transmissivity variations in the fracture plane. Detailed photographs were taken from inside the hole and the visual fracture aperture was compared with the injection flowrates in the same locations. Geostatistical methods were used to evaluate the results. Five holes were measured in great detail. In addition 7 holes were drilled and scanned by simpler packer systems. A double hole experiment was performed where two parallel holes were drilled in the same fracture plane at nearly 2 m distance. Pressure pulse tests were made between the holes in both directions. Tracers were injected in 5 locations in one hole and monitored for in many locations in the other hole. The single hole experiment and the double hole experiment show that most of the fracture planes are tight but that there are open sections which form connected channels over distances of at least 2 meters. It was also found in the double hole experiment that the investigated fracture was intersected by at least one fracture between the two holes which diverted a large amount of the injected tracers to several distant locations at the tunnel wall. (authours)

  10. Beam profile monitor

    International Nuclear Information System (INIS)

    Krausse, G.J.; Gram, P.A.M.

    1978-05-01

    A system used to monitor secondary beam profiles at the LAMPF Linac for channel tune-up and diagnostics is described. The multiwire proportional chamber design is discussed, and descriptions and drawings of the gate card, the amplifier/multiplexer card, the output amplifier card, and the overall system are given

  11. Epitaxial nanowire formation in metamorphic GaAs/GaPAs short-period superlattices

    Science.gov (United States)

    Zheng, Nan; Ahrenkiel, S. Phillip

    2017-07-01

    Metamorphic growth presents routes to novel nanomaterials with unique properties that may be suitable for a range of applications. We discuss self-assembled, epitaxial nanowires formed during metalorganic chemical vapor deposition of metamorphic GaAs/GaPAs short-period superlattices. The heterostructures incorporate strain-engineered GaPAs compositional grades on 6°-B miscut GaAs substrates. Lateral diffusion within the SPS into vertically aligned, three-dimensional columns results in nanowires extending along A directions with a lateral period of 70-90 nm. The microstructure is probed by transmission electron microscopy to confirm the presence of coherent GaAs nanowires within GaPAs barriers. The compositional profile is inferred from analysis of {200} dark-field image contrast and lattice images.

  12. Abstracts of 4. International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology

    International Nuclear Information System (INIS)

    2001-01-01

    4. International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology is the periodically held forum for discussion the problems connected with manufacturing of different nanostructures (thin films, quantum wells, quantum dots) needed in microelectronics. Preparation of such materials with desirable optical, electrical and magnetic properties being determined by their chemical composition and crystal structure has been discussed in detail during the workshop sessions. Optimization of crystal growth methods such as VPE and MBE from the view point of obtained material properties has also been extensively discussed

  13. Epitaxial growth and characterization of CuGa2O4 films by laser molecular beam epitaxy

    OpenAIRE

    Hongling Wei; Zhengwei Chen; Zhenping Wu; Wei Cui; Yuanqi Huang; Weihua Tang

    2017-01-01

    Ga2O3 with a wide bandgap of ∼ 4.9 eV can crystalize in five crystalline phases. Among those phases, the most stable monoclinic β-Ga2O3 has been studied most, however, it is hard to find materials lattice matching with β-Ga2O3 to grown epitaxial thin films for optoelectronic applications. In this work, CuGa2O4 bulk were prepared by solid state reaction as target, and the films were deposited on sapphire substrates by laser molecular beam epitaxy (L-MBE) at different substrate temperatures. Th...

  14. Epitaxial growth of SrTiO3 thin film on Si by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Zhou, X. Y.; Miao, J.; Dai, J. Y.; Chan, H. L. W.; Choy, C. L.; Wang, Y.; Li, Q.

    2007-01-01

    SrTiO 3 thin films have been deposited on Si (001) wafers by laser molecular beam epitaxy using an ultrathin Sr layer as the template. X-ray diffraction measurements indicated that SrTiO 3 was well crystallized and epitaxially aligned with Si. Cross-sectional observations in a transmission electron microscope revealed that the SrTiO 3 /Si interface was sharp, smooth, and fully crystallized. The thickness of the Sr template was found to be a critical factor that influenced the quality of SrTiO 3 and the interfacial structure. Electrical measurements revealed that the SrTiO 3 film was highly resistive

  15. Direct Measurements of Island Growth and Step-Edge Barriers in Colloidal Epitaxy

    KAUST Repository

    Ganapathy, R.

    2010-01-21

    Epitaxial growth, a bottom-up self-assembly process for creating surface nano- and microstructures, has been extensively studied in the context of atoms. This process, however, is also a promising route to self-assembly of nanometer- and micrometer-scale particles into microstructures that have numerous technological applications. To determine whether atomic epitaxial growth laws are applicable to the epitaxy of larger particles with attractive interactions, we investigated the nucleation and growth dynamics of colloidal crystal films with single-particle resolution. We show quantitatively that colloidal epitaxy obeys the same two-dimensional island nucleation and growth laws that govern atomic epitaxy. However, we found that in colloidal epitaxy, step-edge and corner barriers that are responsible for film morphology have a diffusive origin. This diffusive mechanism suggests new routes toward controlling film morphology during epitaxy.

  16. Growth of high purity semiconductor epitaxial layers by liquid phase ...

    Indian Academy of Sciences (India)

    Unknown

    semiconductor materials in high purity form by liquid phase epitaxy (LPE) technique. Various possible sources of impurities in such ... reference to the growth of GaAs layers. The technique of growing very high purity layers ... the inner walls of the gas lines and (e) the containers for storing, handling and cleaning of the mate-.

  17. Hard gap in epitaxial semiconductor-superconductor nanowires

    DEFF Research Database (Denmark)

    Chang, W.; Albrecht, S. M.; Jespersen, T. S.

    2015-01-01

    a continuum of subgap states---a situation that nullifies topological protection. Here, we report a hard superconducting gap induced by proximity effect in a semiconductor, using epitaxial Al-InAs superconductor-semiconductor nanowires. The hard gap, along with favorable material properties and gate...

  18. Selenidation of epitaxial silicene on ZrB2

    NARCIS (Netherlands)

    Wiggers, F. B.; Yamada-Takamura, Y.; Kovalgin, A. Y.; de Jong, M. P.

    2018-01-01

    The deposition of elemental Se on epitaxial silicene on ZrB2 thin films was investigated with synchrotron-based core-level photoelectron spectroscopy and low-energy electron diffraction. The deposition of Se at room temperature caused the appearance of Si 2p peaks with chemical shifts of n × 0.51 ±

  19. Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

    Science.gov (United States)

    Xia, Wei; Chen, Qiusong; Zhang, Jian; Wang, Hui; Cheng, Qian; Jiang, Yulong; Zhu, Guodong

    2018-04-01

    In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

  20. Electrical properties of epitaxially grown VOx thin films

    NARCIS (Netherlands)

    Rata, A.D.; Chezan, A.R; Presura, C.N.; Hibma, T

    2003-01-01

    High quality VOx thin films on MgO(100) substrates were prepared and studied from the structural and electronic point of view. Epitaxial growth was confirmed by RHEED and XRD techniques. The oxygen content of VOx thin films as a function of oxygen flux was determined using RBS. The upper and lower

  1. Manipulation of Dirac cones in metal-intercalated epitaxial graphene

    Science.gov (United States)

    Wang, Cai-Zhuang; Kim, Minsung; Tringides, Michael; Ho, Kai-Ming

    Graphene is one of the most attractive materials from both fundamental and practical points of view due to its characteristic Dirac cones. The electronic property of graphene can be modified through the interaction with substrate or another graphene layer as illustrated in few-layer epitaxial graphene. Recently, metal intercalation became an effective method to manipulate the electronic structure of graphene by modifying the coupling between the constituent layers. In this work, we show that the Dirac cones of epitaxial graphene can be manipulated by intercalating rare-earth metals. We demonstrate that rare-earth metal intercalated epitaxial graphene has tunable band structures and the energy levels of Dirac cones as well as the linear or quadratic band dispersion can be controlled depending on the location of the intercalation layer and density. Our results could be important for applications and characterizations of the intercalated epitaxial graphene. Supported by the U.S. DOE-BES under Contract No. DE-AC02-07CH11358.

  2. High purity liquid phase epitaxial gallium arsenide nuclear radiation detector

    International Nuclear Information System (INIS)

    Alexiev, D.; Butcher, K.S.A.

    1991-11-01

    Surface barrier radiation detector made from high purity liquid phase epitaxial gallium arsenide wafers have been operated as X- and γ-ray detectors at various operating temperatures. Low energy isotopes are resolved including 241 Am at 40 deg C. and the higher gamma energies of 235 U at -80 deg C. 15 refs., 1 tab., 6 figs

  3. GaN:Co epitaxial layers grown by MOVPE

    Czech Academy of Sciences Publication Activity Database

    Šimek, P.; Sedmidubský, D.; Klímová, K.; Mikulics, M.; Maryško, Miroslav; Veselý, M.; Jurek, Karel; Sofer, Z.

    2015-01-01

    Roč. 44, Mar (2015), 62-68 ISSN 0022-0248 R&D Projects: GA ČR GA13-20507S Institutional support: RVO:68378271 Keywords : doping * metalorganic vapor phase epitaxy * cobalt * gallium compounds * nitrides * magnetic materials spintronics Subject RIV: CA - Inorganic Chemistry Impact factor: 1.462, year: 2015

  4. Single-event burnout of epitaxial bipolar transistors

    Energy Technology Data Exchange (ETDEWEB)

    Kuboyama, S.; Sugimoto, K.; Shugyo, S.; Matsuda, S. [National Space Development Agency of Japan, Tsukuba, Ibaraki (Japan); Hirao, T. [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan)

    1998-12-01

    Single-Event Burnout (SEB) of bipolar junction transistors (BJTs) has been observed nondestructively. It was revealed that all the NPN BJTs, including small signal transistors, with thinner epitaxial layers were inherently susceptible to the SEB phenomenon. It was demonstrated that several design parameters of BJTs were responsible for SEB susceptibility. Additionally, destructive and nondestructive modes of SEB were identified.

  5. Single-event burnout of epitaxial bipolar transistors

    Energy Technology Data Exchange (ETDEWEB)

    Kuboyama, Satoshi; Sugimoto, Kenji; Matsuda, Sumio [National Space Development Agency of Japan, Ysukuba, Ibaraki (Japan); Hirao, Toshio

    1998-10-01

    Single-event burnout (SEB) of bipolar junction transistors (BJTs) has been observed nondestructively. It was revealed that all the NPN BJTs including small signal transistors with thinner epitaxial layer were inherently susceptible to the SEB phenomenon. It was demonstrated that several design parameters of BJTs were responsible for SEB susceptibility. Additionally, destructive and nondestructive modes of SEB were identified. (author)

  6. Concurrent bandgap narrowing and polarization enhancement in epitaxial ferroelectric nanofilms

    Czech Academy of Sciences Publication Activity Database

    Tyunina, Marina; Yao, L.; Chvostová, Dagmar; Dejneka, Alexandr; Kocourek, Tomáš; Jelínek, Miroslav; Trepakov, Vladimír; van Dijken, S.

    2015-01-01

    Roč. 16, č. 2 (2015), 026002 ISSN 1468-6996 R&D Projects: GA ČR GAP108/12/1941 Institutional support: RVO:68378271 Keywords : epitaxial growth * ferroelectric nanofilms Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.433, year: 2015

  7. Giant inelastic tunneling in epitaxial graphene mediated by localized states

    NARCIS (Netherlands)

    Cervenka, J.; Ruit, van de K.; Flipse, C.F.J.

    2010-01-01

    Local electronic structures of nanometer-sized patches of epitaxial graphene and its interface layer with SiC(0001) have been studied by atomically resolved scanning tunneling microscopy and spectroscopy. Localized states belonging to the interface layer of a graphene/SiC system show to have

  8. Strain-induced properties of epitaxial VOx thin films

    NARCIS (Netherlands)

    Rata, AD; Hibma, T

    We have grown VOx thin films on different substrates in order to investigate the influence of epitaxial strain on the transport properties. We found that the electric conductivity is much larger for films grown under compressive strain on SrTiO3 substrates, as compared to bulk material and VOx films

  9. Growth and properties of epitaxial iron oxide layers

    NARCIS (Netherlands)

    Voogt, F.C; Fujii, T; Hibma, T; Zhang, G.L.; Smulders, P.J M

    1996-01-01

    Epitaxial layers of iron oxides have been grown on a MgO(001) substrate by evaporating natural Fe or Fe-57 from Knudsen cells in the presence of a NO2 flow directed to the substrate. The resulting layers have been investigated in situ with LEED, RHEED, AES and XPS and ex situ with GEMS and ion beam

  10. Conductivity of epitaxial and CVD graphene with correlated line defects

    DEFF Research Database (Denmark)

    Radchenko, T. M.; Shylau, Artsem; Zozoulenko, I. V.

    2014-01-01

    Transport properties of single-layer graphene with correlated one-dimensional defects are studied theoretically using the computational model within the time-dependent real-space Kubo-Greenwood formalism. Such defects are present in epitaxial graphene, comprising atomic terraces and steps due...

  11. Epitaxial growth with pulsed deposition: Submonolayer scaling and Villain instability

    DEFF Research Database (Denmark)

    Hinnemann, Berit; Hinrichsen, H.; Wolf, D.E.

    2003-01-01

    It has been observed experimentally that under certain conditions, pulsed laser deposition (PLD) produces smoother surfaces than ordinary molecular beam epitaxy (MBE). So far, the mechanism leading to the improved quality of surfaces in PLD is not yet fully understood. In the present work, we...

  12. On the density of states of disordered epitaxial graphene

    International Nuclear Information System (INIS)

    Davydov, S. Yu.

    2015-01-01

    The study is concerned with two types of disordered epitaxial graphene: (i) graphene with randomly located carbon vacancies and (ii) structurally amorphous graphene. The former type is considered in the coherent potential approximation, and for the latter type, a model of the density of states is proposed. The effects of two types of substrates, specifically, metal and semiconductor substrates are taken into account. The specific features of the density of states of epitaxial graphene at the Dirac point and the edges of the continuous spectrum are analyzed. It is shown that vacancies in epitaxial graphene formed on the metal substrate bring about logarithmic nulling of the density of states of graphene at the Dirac point and the edges of the continuous spectrum. If the Dirac point corresponds to the middle of the band gap of the semiconductor substrate, the linear trend of the density of states to zero in the vicinity of the Dirac point in defect-free graphene transforms into a logarithmic decrease in the presence of vacancies. In both cases, the graphene-substrate interaction is assumed to be weak (quasi-free graphene). In the study of amorphous epitaxial graphene, a simple model of free amorphous graphene is proposed as the initial model, in which account is taken of the nonzero density of states at the Dirac point, and then the interaction of the graphene sheet with the substrate is taken into consideration. It is shown that, near the Dirac point, the quadratic behavior of the density of states of free amorphous graphene transforms into a linear dependence for amorphous epitaxial graphene. In the study, the density of states of free graphene corresponds to the low-energy approximation of the electron spectrum

  13. Redundant Sb condensation on GaSb epilayers grown by molecular beam epitaxy during cooling procedure

    International Nuclear Information System (INIS)

    Arpapay, B.; Şahin, S.; Arıkan, B.; Serincan, U.

    2014-01-01

    The effect of four different cooling receipts on the surface morphologies of unintentionally-doped GaSb epilayers on GaSb (100) substrates grown by molecular beam epitaxy is reported. Those receipts include three different Sb beam equivalent pressure (BEP) levels and two different termination temperatures. Surface morphologies of epilayers were examined by wet etching, surface profiler, atomic force microscopy, scanning electron microscopy and Raman spectroscopy. The results demonstrate that during the cooling period, a Sb BEP of 4.00 × 10 −4 Pa at a termination temperature of 400 °C induces a smooth surface without Sb condensation whereas same Sb BEP at a termination temperature of 350 °C forms a 300 nm thick Sb layer on the surface. In addition, it is revealed that by applying a wet etching procedure and using a surface profiler it is possible to identify this condensed layer from the two-sloped feature of mesa profile. - Highlights: • Sb beam flux termination temperature is crucial for redundant Sb condensation. • Sb beam flux level has a role on the thickness of redundant condensed Sb layer. • Redundant Sb layer thickness can be measured by two-sloped mesa structure

  14. DFT-based channel estimation and noise variance estimation techniques for single-carrier FDMA

    OpenAIRE

    Huang, G; Nix, AR; Armour, SMD

    2010-01-01

    Practical frequency domain equalization (FDE) systems generally require knowledge of the channel and the noise variance to equalize the received signal in a frequency-selective fading channel. Accurate channel estimate and noise variance estimate are thus desirable to improve receiver performance. In this paper we investigate the performance of the denoise channel estimator and the approximate linear minimum mean square error (A-LMMSE) channel estimator with channel power delay profile (PDP) ...

  15. GaAs structures with InAs and As quantum dots produced in a single molecular beam epitaxy process

    International Nuclear Information System (INIS)

    Nevedomskii, V. N.; Bert, N. A.; Chaldyshev, V. V.; Preobrazhenskii, V. V.; Putyato, M. A.; Semyagin, B. R.

    2009-01-01

    Epitaxial GaAs layers containing InAs semiconductor quantum dots and As metal quantum dots are grown by molecular beam epitaxy. The InAs quantum dots are formed by the Stranskii-Krastanow mechanism, whereas the As quantum dots are self-assembled in the GaAs layer grown at low temperature with a large As excess. The microstructure of the samples is studied by transmission electron microscopy. It is established that the As metal quantum dots formed in the immediate vicinity of the InAs semiconductor quantum dots are larger in size than the As quantum dots formed far from the InAs quantum dots. This is apparently due to the effect of strain fields of the InAs quantum dots upon the self-assembling of As quantum dots. Another phenomenon apparently associated with local strains around the InAs quantum dots is the formation of V-like defects (stacking faults) during the overgrowth of the InAs quantum dots with the GaAs layer by low-temperature molecular beam epitaxy. Such defects have a profound effect on the self-assembling of As quantum dots. Specifically, on high-temperature annealing needed for the formation of large-sized As quantum dots by Ostwald ripening, the V-like defects bring about the dissolution of the As quantum dots in the vicinity of the defects. In this case, excess arsenic most probably diffuses towards the open surface of the sample via the channels of accelerated diffusion in the planes of stacking faults.

  16. The physics of epitaxial graphene on SiC(0001)

    International Nuclear Information System (INIS)

    Kageshima, H; Hibino, H; Tanabe, S

    2012-01-01

    Various physical properties of epitaxial graphene grown on SiC(0001) are studied. First, the electronic transport in epitaxial bilayer graphene on SiC(0001) and quasi-free-standing bilayer graphene on SiC(0001) is investigated. The dependences of the resistance and the polarity of the Hall resistance at zero gate voltage on the top-gate voltage show that the carrier types are electron and hole, respectively. The mobility evaluated at various carrier densities indicates that the quasi-free-standing bilayer graphene shows higher mobility than the epitaxial bilayer graphene when they are compared at the same carrier density. The difference in mobility is thought to come from the domain size of the graphene sheet formed. To clarify a guiding principle for controlling graphene quality, the mechanism of epitaxial graphene growth is also studied theoretically. It is found that a new graphene sheet grows from the interface between the old graphene sheets and the SiC substrate. Further studies on the energetics reveal the importance of the role of the step on the SiC surface. A first-principles calculation unequivocally shows that the C prefers to release from the step edge and to aggregate as graphene nuclei along the step edge rather than be left on the terrace. It is also shown that the edges of the existing graphene more preferentially absorb the isolated C atoms. For some annealing conditions, experiments can also provide graphene islands on SiC(0001) surfaces. The atomic structures are studied theoretically together with their growth mechanism. The proposed embedded island structures actually act as a graphene island electronically, and those with zigzag edges have a magnetoelectric effect. Finally, the thermoelectric properties of graphene are theoretically examined. The results indicate that reducing the carrier scattering suppresses the thermoelectric power and enhances the thermoelectric figure of merit. The fine control of the Fermi energy position is thought to

  17. Design of Strain-Compensated Epitaxial Layers Using an Electrical Circuit Model

    Science.gov (United States)

    Kujofsa, Tedi; Ayers, John E.

    2017-12-01

    The design of heterostructures that exhibit desired strain characteristics is critical for the realization of semiconductor devices with improved performance and reliability. The control of strain and dislocation dynamics requires an understanding of the relaxation processes associated with mismatched epitaxy, and the starting point for this analysis is the equilibrium strain profile, because the difference between the actual strain and the equilibrium value determines the driving force for dislocation glide and relaxation. Previously, we developed an electrical circuit model approach for the equilibrium analysis of semiconductor heterostructures, in which an epitaxial layer may be represented by a stack of subcircuits, each of which involves an independent current source, a resistor, an independent voltage source, and an ideal diode. In this work, we have applied the electrical circuit model to study the strain compensation mechanism and show that, for a given compositionally uniform device layer with fixed mismatch and layer thickness, a buffer layer may be designed (in terms of thickness and mismatch) to tailor the strain in the device layer. A special case is that in which the device layer will exhibit zero residual strain in equilibrium (complete strain compensation). In addition, the application of the electrical circuit analogy enables the determination of exact expressions for the residual strain characteristics of both the buffer and device layers in the general case where the device layer may exhibit partial strain compensation. On the basis of this framework, it is possible to develop design equations for the tailoring of the strain in a device layer grown on a uniform composition buffer.

  18. Dimension measuring method for channel box

    International Nuclear Information System (INIS)

    Jo, Hiroto.

    1995-01-01

    The device of the present invention concerns detection of a channel box for spent fuel assemblies of a BWR type reactor, which measures a cross sectional shape and dimension of the channel box to check deformation amount such as expansion. That is, a customary fuel exchanger and a dimension measuring device are used. The lower end of the channel box is measured by a distance sensor of the dimension measuring device when it is aligned with a position of the distance sensor. The channel box is lowered at the same time while detecting axial position data of the fuel exchanger. The position of the channel box in an axial direction is detected based on axial position data of the fuel exchanger. The lower end of the channel box can accurately be recognized by the detection of both of them. Subsequent deformation measurement for the channel box at accurate axial positions is enabled. In addition, since the axial position data of the fuel exchanger per se are detected, an axial profile of the channel box can be measured even if a lifting speed of the channel box is varied on every region. (I.S.)

  19. Epitaxy of Polar Oxides and Semiconductors

    Science.gov (United States)

    Shelton, Christopher Tyrel

    Integrating polar oxide materials with wide-bandgap nitride semiconductors offers the possibility of a tunable 2D carrier gas (2DCG) - provided defect densities are low and interfaces are abrupt. This dissertation investigates a portion of the synthesis science necessary to produce a "semiconductor-grade" interface between these highly dissimilar materials. A significant portion of this work is aligned with efforts to engineer a step-free GaN substrate to produce single in-plane oriented rocksalt oxide films. Initially, we explore the homoepitaxial MOCVD growth conditions necessary to produce highquality GaN films on ammonothermally grown substrates. Ammono substrates are only recently available for purchase and are the market leader in low-dislocation density material. Their novelty requires development of an understanding of morphology trade-offs in processing space. This includes preservation of the epi-polished surface in aggressive MOCVD environments and an understanding of the kinetic barriers affecting growth morphologies. Based on several factors, it was determined that GaN exhibits an 'uphill' diffusion bias that may likely be ascribed to a positive Ehrlich-Schwoebel (ES) barrier. This barrier should have a stabilizing effect against step-bunching but, for many growth conditions, regular step bunching was observed. One possible explanation for the step-bunching instability is the presence of impurities. Experimentally, conditions which incorporate more carbon into GaN homoepitaxial layers are correlated with step-bunching while conditions that suppress carbon produce bilayer stepped morphologies. These observations lead us to the conclusion that GaN homoepitaxial morphology is a competition between impurity induced step-bunching and a stabilizing diffusion bias due to a positive ES barrier. Application of the aforementioned homoepitaxial growth techniques to discrete substrate regions using selected- and confined area epitaxy (SAE,CAE) produces some

  20. Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

    Science.gov (United States)

    Prieto, Pilar; Marco, José F.; Prieto, José E.; Ruiz-Gomez, Sandra; Perez, Lucas; del Real, Rafael P.; Vázquez, Manuel; de la Figuera, Juan

    2018-04-01

    Epitaxial cobalt ferrite thin films with strong in-plane magnetic anisotropy have been grown on Si (001) substrates using a TiN buffer layer. The epitaxial films have been grown by ion beam sputtering using either metallic, CoFe2, or ceramic, CoFe2O4, targets. X-ray diffraction (XRD) and Rutherford spectrometry (RBS) in random and channeling configuration have been used to determine the epitaxial relationship CoFe2O4 [100]/TiN [100]/Si [100]. Mössbauer spectroscopy, in combination with XRD and RBS, has been used to determine the composition and structure of the cobalt ferrite thin films. The TiN buffer layer induces a compressive strain in the cobalt ferrite thin films giving rise to an in-plane magnetic anisotropy. The degree of in-plane anisotropy depends on the lattice mismatch between CoFe2O4 and TiN, which is larger for CoFe2O4 thin films grown on the reactive sputtering process with ceramic targets.

  1. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    International Nuclear Information System (INIS)

    Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J.

    1996-01-01

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs

  2. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Belay, K.B.; Ridgway, M.C.; Llewellyn, D.J. [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

    1996-12-31

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

  3. The influence of microscopic and macroscopic non-stoichiometry on interfacial planarity during the solid-phase epitaxial growth of amorphized GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Belay, K B; Ridgway, M C; Llewellyn, D J [Australian National Univ., Canberra, ACT (Australia). Dept. of Physics

    1997-12-31

    The influence of microscopic and macroscopic non-stoichiometry on the Solid-Phase Epitaxial Growth of GaAs has been studied. Ion implantation has been employed to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. In-situ Time Resolved Reflectivity and Transmission Electron Microscopy and ex-situ Rutherford Backscattering Spectroscopy and Channeling have been used to investigate the regrowth of amorphized GaAs layers. As non-stoichiometry shifts from microscopic to macroscopic the interface loses its planar nature and subsequently gets rougher. 7 refs., 3 figs.

  4. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R G; Kringhoj, P [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1994-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  5. Strain relaxation during solid-phase epitaxial crystallisation of Ge{sub x}Si{sub 1-x} alloy layers with depth dependent G{sub e} compositions

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Wahchung; Elliman, R.G.; Kringhoj, P. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1993-12-31

    The solid-phase epitaxial crystallisation of depth dependent Ge{sub x}Si{sub lx} alloy layers produced by implanting Ge into Si substrates was studied. In-situ monitoring was done using time-resolved reflectivity (TRR) whilst post-anneal defect structures were characterised by Rutherford backscattering and channeling spectrometry (RBS-C) and transmission electron microscopy (TEM). Particular attention was directed at Ge concentrations above the critical concentration for the growth of fully strained layers. Strain relief is shown to be correlated with a sudden reduction in crystallisation velocity caused by roughening of the crystalline/amorphous interface. 11 refs., 1 tab., 2 figs.

  6. Citizens and service channels: channel choice and channel management implications

    NARCIS (Netherlands)

    Pieterson, Willem Jan

    2010-01-01

    The arrival of electronic channels in the 1990s has had a huge impact on governmental service delivery. The new channels have led to many new opportunities to improve public service delivery, not only in terms of citizen satisfaction, but also in cost reduction for governmental agencies. However,

  7. Deposition and characterisation of epitaxial oxide thin films for SOFCs

    KAUST Repository

    Santiso, José

    2010-10-24

    This paper reviews the recent advances in the use of thin films, mostly epitaxial, for fundamental studies of materials for solid oxide fuel cell (SOFC) applications. These studies include the influence of film microstructure, crystal orientation and strain in oxide ionic conducting materials used as electrolytes, such as fluorites, and in mixed ionic and electronic conducting materials used as electrodes, typically oxides with perovskite or perovskite-related layered structures. The recent effort towards the enhancement of the electrochemical performance of SOFC materials through the deposition of artificial film heterostructures is also presented. These thin films have been engineered at a nanoscale level, such as the case of epitaxial multilayers or nanocomposite cermet materials. The recent progress in the implementation of thin films in SOFC devices is also reported. © 2010 Springer-Verlag.

  8. Charge collection properties of heavily irradiated epitaxial silicon detectors

    International Nuclear Information System (INIS)

    Kramberger, G.; Cindro, V.; Dolenc, I.; Fretwurst, E.; Lindstroem, G.; Mandic, I.; Mikuz, M.; Zavrtanik, M.

    2005-01-01

    Detectors processed on epitaxial silicon seem to be a viable solution for the extreme radiation levels in the innermost layers of tracking detectors at upgraded LHC (SLHC). A set of epitaxial pad detectors of 50 and 75μm thicknesses (ρ=50Ωcm) was irradiated with 24GeV/c protons and reactor neutrons up to equivalent fluences of 10 16 cm -2 . Charge collection for minimum ionizing electrons from a 90 Sr source was measured using a charge sensitive preamplifier and a 25ns shaping circuit. The dependence of collected charge on annealing time and operation temperature was studied. Results were used to predict the performance of fine pitch pixel detectors proposed for SLHC

  9. Charge collection properties of heavily irradiated epitaxial silicon detectors

    Energy Technology Data Exchange (ETDEWEB)

    Kramberger, G. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia)]. E-mail: Gregor.Kramberger@ijs.si; Cindro, V. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia); Dolenc, I. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia); Fretwurst, E. [University of Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg (Germany); Lindstroem, G. [University of Hamburg, Institut fuer Experimentalphysik, Luruper Chaussee 149, D-22761 Hamburg (Germany); Mandic, I. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia); Mikuz, M. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia); Zavrtanik, M. [Institute Jozef Stefan, Jamova 39, SI-1111 Ljubljana (Slovenia)

    2005-12-01

    Detectors processed on epitaxial silicon seem to be a viable solution for the extreme radiation levels in the innermost layers of tracking detectors at upgraded LHC (SLHC). A set of epitaxial pad detectors of 50 and 75{mu}m thicknesses ({rho}=50{omega}cm) was irradiated with 24GeV/c protons and reactor neutrons up to equivalent fluences of 10{sup 16}cm{sup -2}. Charge collection for minimum ionizing electrons from a {sup 90}Sr source was measured using a charge sensitive preamplifier and a 25ns shaping circuit. The dependence of collected charge on annealing time and operation temperature was studied. Results were used to predict the performance of fine pitch pixel detectors proposed for SLHC.

  10. MgO monolayer epitaxy on Ni (100)

    Science.gov (United States)

    Sarpi, B.; Putero, M.; Hemeryck, A.; Vizzini, S.

    2017-11-01

    The growth of two-dimensional oxide films with accurate control of their structural and electronic properties is considered challenging for engineering nanotechnological applications. We address here the particular case of MgO ultrathin films grown on Ni (100), a system for which neither crystallization nor extended surface ordering has been established previously in the monolayer range. Using Scanning Tunneling Microscopy and Auger Electron Spectroscopy, we report on experiments showing MgO monolayer (ML) epitaxy on a ferromagnetic nickel surface, down to the limit of atomic thickness. Alternate steps of Mg ML deposition, O2 gas exposure, and ultrahigh vacuum thermal treatment enable the production of a textured film of ordered MgO nano-domains. This study could open interesting prospects for controlled epitaxy of ultrathin oxide films with a high magneto-resistance ratio on ferromagnetic substrates, enabling improvement in high-efficiency spintronics and magnetic tunnel junction devices.

  11. Microwave impedance of epitaxial high-temperature superconductor films

    International Nuclear Information System (INIS)

    Melkov, G.A.; Malyshev, V.Yu.; Bagada, A.V.

    1995-01-01

    In the 3 cm band dependences of the epitaxial HTS film surface resistance on the magnitude of ac and dc magnetic fields have been measured. YBa 2 Cu 3 O 7-σ films on sapphire were investigated. It was established that alternating magnetic field produces a stronger impact on the surface resistance than dc field. To explain experimental results the assumption is made that a HTS film is not an ideal superconductor and consists of series-connected sections of various types: sections of an ideal superconductor, sections of low and large resistance intragranular Josephson junctions, shunted by the ideal superconductor, and finally, sections of intergranular Josephson junctions few for epitaxial films. In these conditions the dependences of the surface resistance on dc magnetic field are caused by Abrikosov's vortices moving in ideal superconductive sections, and dependences on the amplitude of ac magnetic field are caused by switching of large resistance junctions to a low resistance state

  12. On the kinetic barriers of graphene homo-epitaxy

    International Nuclear Information System (INIS)

    Zhang, Wei; Yu, Xinke; Xie, Ya-Hong; Cahyadi, Erica; Ratsch, Christian

    2014-01-01

    The diffusion processes and kinetic barriers of individual carbon adatoms and clusters on graphene surfaces are investigated to provide fundamental understanding of the physics governing epitaxial growth of multilayer graphene. It is found that individual carbon adatoms form bonds with the underlying graphene whereas the interaction between graphene and carbon clusters, consisting of 6 atoms or more, is very weak being van der Waals in nature. Therefore, small carbon clusters are quite mobile on the graphene surfaces and the diffusion barrier is negligibly small (∼6 meV). This suggests the feasibility of high-quality graphene epitaxial growth at very low growth temperatures with small carbon clusters (e.g., hexagons) as carbon source. We propose that the growth mode is totally different from 3-dimensional bulk materials with the surface mobility of carbon hexagons being the highest over graphene surfaces that gradually decreases with further increase in cluster size

  13. Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.

    Science.gov (United States)

    Asaba, Tomoya; Wang, Yongjie; Li, Gang; Xiang, Ziji; Tinsman, Colin; Chen, Lu; Zhou, Shangnan; Zhao, Songrui; Laleyan, David; Li, Yi; Mi, Zetian; Li, Lu

    2018-04-25

    In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe 2 ). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe 2 thin films with a high precision rotation stage, we map the upper critical field H c2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field H c2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of H c2 in Ising superconductors.

  14. Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

    Directory of Open Access Journals (Sweden)

    Lijuan Wang

    2017-02-01

    Full Text Available Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial growth of bismide thin films and nanostructures, surface, structural, electric, transport and optic properties of various binaries and bismide alloys, and device applications.

  15. Misfit dislocations in (001) Cu/(111) Ag epitaxial bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Vook, R W; Chao, S S

    1979-01-01

    Two sets of elongated epitaxial (111) Ag islands rotated by 90/sup 0/ with respect to each other were observed to grow on (001) Cu substrates. In addition, two sets of edge misfit dislocations lay parallel to (110) Cu and (110) Cu or equivalently along (110) Ag and (112) Ag. Their Burgers vectors were determined, together with the elastic strains in these two directions. The island elongation was interpreted as arising from a lower strain energy in the preferred direction of growth.

  16. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya; Shekhah, Osama; Spanopoulos, Ioannis; Trikalitis, Pantelis N.; Eddaoudi, Mohamed

    2017-01-01

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  17. Optical effects induced by epitaxial tension in lead titanate

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Chvostová, Dagmar; Pacherová, Oliva; Kocourek, Tomáš; Jelínek, Miroslav; Tyunina, Marina

    2018-01-01

    Roč. 112, č. 3 (2018), s. 1-5, č. článku 031111. ISSN 0003-6951 R&D Projects: GA ČR GA15-13778S; GA ČR GA15-15123S Institutional support: RVO:68378271 Keywords : epitaxy * inorganic compounds * optical properties * ferroelectric materials * optical metrology Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics , supercond.) Impact factor: 3.411, year: 2016

  18. Liquid phase epitaxial growth of heterostructured hierarchical MOF thin films

    KAUST Repository

    Chernikova, Valeriya

    2017-05-10

    Precise control of epitaxial growth of MOF-on-MOF thin films, for ordered hierarchical tbo-type structures is demonstrated. The heterostructured MOF thin film was fabricated by successful sequential deposition of layers from two different MOFs. The 2-periodic layers, edge-transitive 4,4-square lattices regarded as supermolecular building layers, were commendably cross-linked using a combination of inorganic/organic and organic pillars.

  19. Coupled quantum dot-ring structures by droplet epitaxy

    International Nuclear Information System (INIS)

    Somaschini, C; Bietti, S; Koguchi, N; Sanguinetti, S

    2011-01-01

    The fabrication, by pure self-assembly, of GaAs/AlGaAs dot-ring quantum nanostructures is presented. The growth is performed via droplet epitaxy, which allows for the fine control, through As flux and substrate temperature, of the crystallization kinetics of nanometer scale metallic Ga reservoirs deposited on the surface. Such a procedure permits the combination of quantum dots and quantum rings into a single, multi-functional, complex quantum nanostructure.

  20. Epitaxial growth mechanisms of graphene and effects of substrates

    OpenAIRE

    Özçelik, V. Ongun; Cahangirov, S.; Ciraci, S.

    2012-01-01

    The growth process of single layer graphene with and without substrate is investigated using ab initio, finite temperature molecular dynamic calculations within density functional theory. An understanding of the epitaxial graphene growth mechanisms in the atomic level is provided by exploring the transient stages which occur at the growing edges of graphene. These stages are formation and collapse of large carbon rings together with the formation and healing of Stone-Wales like pentagon-hepta...

  1. Epitaxial growth on porous GaAs substrates

    Czech Academy of Sciences Publication Activity Database

    Grym, Jan; Nohavica, Dušan; Gladkov, Petar; Hulicius, Eduard; Pangrác, Jiří; Piksová, K.

    2013-01-01

    Roč. 16, č. 1 (2013), s. 59-64 ISSN 1631-0748 R&D Projects: GA ČR GAP102/10/1201; GA ČR GAP108/10/0253 Institutional support: RVO:67985882 ; RVO:68378271 Keywords : Electrochemical etching * Porous semiconductors * Epitaxial growth * GaAs Subject RIV: BH - Optics, Masers, Lasers; JA - Electronics ; Optoelectronics, Electrical Engineering (FZU-D) Impact factor: 1.483, year: 2013

  2. Fabrication of high quality GaAs-on-insulator via ion-cut of epitaxial GaAs/Ge heterostructure

    International Nuclear Information System (INIS)

    Chang, Yongwei; Zhang, Miao; Deng, Chuang; Men, Chuanling; Chen, Da; Zhu, Lei; Yu, Wenjie; Wei, Xing; Di, Zengfeng; Wang, Xi

    2015-01-01

    Highlights: • GaAs-on-insulator has been achieved by integrating of epitaxy, ion-cut and selective chemical etching. • Superior to the direct ion-cut of bulk GaAs layer with the H implantation fluence 2.0 × 10 17 cm −2 , the fabrication of GaAs-on-insulator by the transfer of GaAs/Ge heterostructure only needs H implantation fluence as low as 0.8 × 10 17 cm −2 . • The crystalline quality of the top GaAs layer of the final GaAs-on-insulator wafer is not affected by the implantation process and comparable to the as-grown status. - Abstract: Due to the extraordinary electron mobility, III–V compounds are considered as the ideal candidate channel materials for future electronic devices. In this study, a novel approach for the fabrication of high-crystalline quality GaAs-on-insulator has been proposed by integrating of ion-cut and selective chemical etching. GaAs layer with good crystalline quality has been epitaxially grown on Ge by molecular beam epitaxy (MBE). With H implantation and wafer bonding process, the GaAs/Ge heterostructure is transferred onto silicon dioxide wafer after the proper thermal treatment. Superior to the direct ion-cut of GaAs layer, which requires the H implantation fluence as high as 2.0 × 10 17 cm −2 , the transfer of GaAs/Ge heterostructure in the present study only needs the implantation of 0.8 × 10 17 cm −2 H ions. GaAs-on-insulator structure was successfully achieved by the selective chemical etching of defective Ge layer using SF 6 plasma. As the GaAs/Ge heterostructure can be easily epitaxy grown on silicon platform, the proposed approach for GaAs-on-insulator manufacturing is rather compatible with mature Si integrated circuits (ICs) technology and thus can be integrated to push the microelectronic technology to post-Si era

  3. Fabrication of high quality GaAs-on-insulator via ion-cut of epitaxial GaAs/Ge heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Yongwei; Zhang, Miao [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Deng, Chuang; Men, Chuanling [School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China); Chen, Da [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Zhu, Lei; Yu, Wenjie; Wei, Xing [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Di, Zengfeng, E-mail: zfdi@mail.sim.ac.cn [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Xi [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China)

    2015-08-15

    Highlights: • GaAs-on-insulator has been achieved by integrating of epitaxy, ion-cut and selective chemical etching. • Superior to the direct ion-cut of bulk GaAs layer with the H implantation fluence 2.0 × 10{sup 17} cm{sup −2}, the fabrication of GaAs-on-insulator by the transfer of GaAs/Ge heterostructure only needs H implantation fluence as low as 0.8 × 10{sup 17} cm{sup −2}. • The crystalline quality of the top GaAs layer of the final GaAs-on-insulator wafer is not affected by the implantation process and comparable to the as-grown status. - Abstract: Due to the extraordinary electron mobility, III–V compounds are considered as the ideal candidate channel materials for future electronic devices. In this study, a novel approach for the fabrication of high-crystalline quality GaAs-on-insulator has been proposed by integrating of ion-cut and selective chemical etching. GaAs layer with good crystalline quality has been epitaxially grown on Ge by molecular beam epitaxy (MBE). With H implantation and wafer bonding process, the GaAs/Ge heterostructure is transferred onto silicon dioxide wafer after the proper thermal treatment. Superior to the direct ion-cut of GaAs layer, which requires the H implantation fluence as high as 2.0 × 10{sup 17} cm{sup −2}, the transfer of GaAs/Ge heterostructure in the present study only needs the implantation of 0.8 × 10{sup 17} cm{sup −2} H ions. GaAs-on-insulator structure was successfully achieved by the selective chemical etching of defective Ge layer using SF{sub 6} plasma. As the GaAs/Ge heterostructure can be easily epitaxy grown on silicon platform, the proposed approach for GaAs-on-insulator manufacturing is rather compatible with mature Si integrated circuits (ICs) technology and thus can be integrated to push the microelectronic technology to post-Si era.

  4. Hollow core plasma channel generation

    International Nuclear Information System (INIS)

    Quast, Heinrich Martin

    2018-03-01

    The use of a hollow plasma channel in plasma-based acceleration has beneficial properties for the acceleration of electron and positron bunches. In the scope of the FLASHForward facility at DESY, the generation of such a plasma structure is examined. Therefore, the generation of a ring-shaped laser intensity profile with different techniques is analyzed. From the obtained intensity profiles the electron density of a hollow plasma channel is simulated in the focal region. Different parameters are scanned to understand their influence on the electron density distribution - an important parameter being, for example, the radius of the central region of the channel. In addition to the simulations, experiments are presented, during which a laser pulse is transformed into a hollow beam with a spiral phase plate. Subsequently, it forms a plasma during the interaction with hydrogen, where the plasma is imaged with interferometry. For energies above 0.9 mJ a hollow plasma structure can be observed at the location of first plasma formation.

  5. Interaction of GaN epitaxial layers with atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S

    2004-08-15

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H{sub 2} plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states.

  6. Interaction of GaN epitaxial layers with atomic hydrogen

    International Nuclear Information System (INIS)

    Losurdo, M.; Giangregorio, M.M.; Capezzuto, P.; Bruno, G.; Namkoong, G.; Doolittle, W.A.; Brown, A.S.

    2004-01-01

    GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0 0 0 1) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56 MHz) H 2 plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states

  7. Electronic properties of epitaxial 6H silicon carbide

    International Nuclear Information System (INIS)

    Wessels, B.W.; Gatos, H.C.

    1977-01-01

    The electrical conductivity and Hall coefficient were measured in the temperature range from 78 to 900 K for n-type epitaxially grown 6H silicon carbide. A many-valley model of the conduction band was used in the analysis of electron concentration as a function of temperature. From this analysis, the density of states mass to the free electron mass ratio per ellipsoid was calculated to be 0.45. It was estimated that the constant energy surface of the conduction band consists of three ellipsoids. The ionization energy of the shallowest nitrogen donor was found to be 105 meV, when the valley-orbit interaction was taken into account. The electron scattering mechanisms in the epitaxial layers were analyzed and it was shown that the dominant mechanism limiting electron mobility at high temperatures is inter-valley scattering and at low temperatures (200K), impurity and space charge scattering. A value of 360 cm 2 /V sec was calculated for the maximum room temperature Hall mobility expected for electrons in pure 6H SiC. The effect of epitaxial growth temperature on room temperature Hall mobility was also investigated. (author)

  8. Silicon epitaxy on textured double layer porous silicon by LPCVD

    International Nuclear Information System (INIS)

    Cai Hong; Shen Honglie; Zhang Lei; Huang Haibin; Lu Linfeng; Tang Zhengxia; Shen Jiancang

    2010-01-01

    Epitaxial silicon thin film on textured double layer porous silicon (DLPS) was demonstrated. The textured DLPS was formed by electrochemical etching using two different current densities on the silicon wafer that are randomly textured with upright pyramids. Silicon thin films were then grown on the annealed DLPS, using low-pressure chemical vapor deposition (LPCVD). The reflectance of the DLPS and the grown silicon thin films were studied by a spectrophotometer. The crystallinity and topography of the grown silicon thin films were studied by Raman spectroscopy and SEM. The reflectance results show that the reflectance of the silicon wafer decreases from 24.7% to 11.7% after texturing, and after the deposition of silicon thin film the surface reflectance is about 13.8%. SEM images show that the epitaxial silicon film on textured DLPS exhibits random pyramids. The Raman spectrum peaks near 521 cm -1 have a width of 7.8 cm -1 , which reveals the high crystalline quality of the silicon epitaxy.

  9. Auger line shape changes in epitaxial (111)Pd/(111)Cu films

    Energy Technology Data Exchange (ETDEWEB)

    Chao, S S; Knabbe, E A; Vook, R W

    1980-01-01

    Epitaxial Pd films ranging in thickness from a few tenths of a monolayer up to many monolayers were formed on (111)Cu substrate films at room temperature under uhv conditions. The growth of these Pd films was monitored in situ by Auger electron spectroscopy. The line profiles of the Cu MMM (61 eV) and Pd MVV (329 eV) AES doublets varied significantly with the amount of Pd deposited. A new measure of the AES doublet line profile, called the R-factor, was defined. A graph of R/sub Pd/ versus Pd film thickness shows a sharp decline with increasing thickness. Superimposed on the major trends is a cyclical variation. A corresponding periodicity in R/sub Cu/ was observed for the Cu MMM (61 eV) AES doublet. The results suggest that the R-factor provides a direct measure of changes in the electronic structures of the overgrowth and substrate films as the former thickens by a layer-growth mechanism.

  10. Process for depositing an oxide epitaxially onto a silicon substrate and structures prepared with the process

    Science.gov (United States)

    McKee, Rodney A.; Walker, Frederick J.

    1993-01-01

    A process and structure involving a silicon substrate utilizes an ultra high vacuum and molecular beam epitaxy (MBE) methods to grow an epitaxial oxide film upon a surface of the substrate. As the film is grown, the lattice of the compound formed at the silicon interface becomes stabilized, and a base layer comprised of an oxide having a sodium chloride-type lattice structure grows epitaxially upon the compound so as to cover the substrate surface. A perovskite may then be grown epitaxially upon the base layer to render a product which incorporates silicon, with its electronic capabilities, with a perovskite having technologically-significant properties of its own.

  11. Epitaxial growth of ZnO layers on (111) GaAs substrates by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Ding Jian; Zhang Di; Konomi, Takaharu; Saito, Katsuhiko; Guo Qixin

    2012-01-01

    ZnO layers were grown on (111) GaAs substrates by laser molecular epitaxy at substrate temperatures between 200 and 550 °C. X-ray diffraction analysis revealed that c-axis of ZnO epilayer with a wurtzite structure is perpendicular to the substrate surface. X-ray rocking curves and Raman spectroscopy showed that the crystal quality of ZnO epilayers depends on the substrate temperature during the growth. Strong near-band-edge emission in the UV region without any deep-level emissions was observed from the ZnO epilayers at room temperature. The results indicate that laser molecular beam epitaxy is a promising growth method for obtaining high-quality ZnO layers on (111) GaAs substrates.

  12. Real time spectroscopic ellipsometry investigation of homoepitaxial GaN grown by plasma assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tong-Ho; Choi, Soojeong; Wu, Pae; Brown, April [Department of Electrical and Computer Engineering, Duke University, 128 Hudson Hall, Durham, NC (United States); Losurdo, Maria; Giangregorio, Maria M.; Bruno, Giovanni [Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR and INSTM UdR Bari, via Orabona, 4, 70126 Bari (Italy); Moto, Akihiro [Innovation Core SEI, Inc., 3235 Kifer Road, Santa Clara, CA 95051 (United States)

    2006-06-15

    The growth of GaN by plasma assisted molecular beam epitaxy on GaN template substrates (GaN on sapphire) is investigated with in-situ multi-channel spectroscopic ellipsometry. Growth is performed under various Ga/N flux ratios at growth temperatures in the range 710-780 C. The thermal roughening of the GaN template caused by decomposition of the surface is investigated through the temporal variation of the GaN pseudodielectric function over the temperature range of 650 C to 850 C. The structural, morphological, and optical properties are also discussed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Effect of growth temperature on defects in epitaxial GaN film grown by plasma assisted molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    S. S. Kushvaha

    2014-02-01

    Full Text Available We report the effect of growth temperature on defect states of GaN epitaxial layers grown on 3.5 μm thick GaN epi-layer on sapphire (0001 substrates using plasma assisted molecular beam epitaxy. The GaN samples grown at three different substrate temperatures at 730, 740 and 750 °C were characterized using atomic force microscopy and photoluminescence spectroscopy. The atomic force microscopy images of these samples show the presence of small surface and large hexagonal pits on the GaN film surfaces. The surface defect density of high temperature grown sample is smaller (4.0 × 108 cm−2 at 750 °C than that of the low temperature grown sample (1.1 × 109 cm−2 at 730 °C. A correlation between growth temperature and concentration of deep centre defect states from photoluminescence spectra is also presented. The GaN film grown at 750 °C exhibits the lowest defect concentration which confirms that the growth temperature strongly influences the surface morphology and affects the optical properties of the GaN epitaxial films.

  14. Subchannel analysis code development for CANDU fuel channel

    International Nuclear Information System (INIS)

    Park, J. H.; Suk, H. C.; Jun, J. S.; Oh, D. J.; Hwang, D. H.; Yoo, Y. J.

    1998-07-01

    Since there are several subchannel codes such as COBRA and TORC codes for a PWR fuel channel but not for a CANDU fuel channel in our country, the subchannel analysis code for a CANDU fuel channel was developed for the prediction of flow conditions on the subchannels, for the accurate assessment of the thermal margin, the effect of appendages, and radial/axial power profile of fuel bundles on flow conditions and CHF and so on. In order to develop the subchannel analysis code for a CANDU fuel channel, subchannel analysis methodology and its applicability/pertinence for a fuel channel were reviewed from the CANDU fuel channel point of view. Several thermalhydraulic and numerical models for the subchannel analysis on a CANDU fuel channel were developed. The experimental data of the CANDU fuel channel were collected, analyzed and used for validation of a subchannel analysis code developed in this work. (author). 11 refs., 3 tabs., 50 figs

  15. Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

    International Nuclear Information System (INIS)

    Deen, David A.; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J.

    2016-01-01

    A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics f_t/f_m_a_x of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f_t/f_m_a_x of 48/60 GHz.

  16. Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

    Science.gov (United States)

    Deen, David A.; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J.

    2016-08-01

    A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics ft/fmax of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with ft/fmax of 48/60 GHz.

  17. Suppression of surface-originated gate lag by a dual-channel AlN/GaN high electron mobility transistor architecture

    Energy Technology Data Exchange (ETDEWEB)

    Deen, David A., E-mail: david.deen@alumni.nd.edu; Storm, David F.; Scott Katzer, D.; Bass, R.; Meyer, David J. [Naval Research Laboratory, Electronics Science and Technology Division, Washington, DC 20375 (United States)

    2016-08-08

    A dual-channel AlN/GaN high electron mobility transistor (HEMT) architecture is demonstrated that leverages ultra-thin epitaxial layers to suppress surface-related gate lag. Two high-density two-dimensional electron gas (2DEG) channels are utilized in an AlN/GaN/AlN/GaN heterostructure wherein the top 2DEG serves as a quasi-equipotential that screens potential fluctuations resulting from distributed surface and interface states. The bottom channel serves as the transistor's modulated channel. Dual-channel AlN/GaN heterostructures were grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. HEMTs fabricated with 300 nm long recessed gates demonstrated a gate lag ratio (GLR) of 0.88 with no degradation in drain current after bias stressed in subthreshold. These structures additionally achieved small signal metrics f{sub t}/f{sub max} of 27/46 GHz. These performance results are contrasted with the non-recessed gate dual-channel HEMT with a GLR of 0.74 and 82 mA/mm current collapse with f{sub t}/f{sub max} of 48/60 GHz.

  18. Epitaxial growth and properties of YBaCuO thin films

    International Nuclear Information System (INIS)

    Geerk, J.; Linker, G.; Meyer, O.

    1989-08-01

    The growth quality of YBaCuO thin films deposited by sputtering on different substrates (Al 2 O 3 , MgO, SrTiO 3 , Zr(Y)O 2 ) has been studied by X-ray diffraction and channeling experiments as a function of the deposition temperature. Besides the substrate orientation, the substrate temperature is the parameter determining whether films grow in c-, a-, (110) or mixed directions. Epitaxial growth correlates with high critical current values in the films of up to 5.5x10 6 A/cm 2 at 77 K. Ultrathin films with thicknesses down to 2 nm were grown revealing three-dimensional superconducting behaviour. Films on (100) SrTiO 3 of 9 nm thickness and below are partially strained indicating commensurate growth. From the analysis of the surface disorder 1 displaced Ba atom per Ba 2 Y row was obtained indicating that the disordered layer thickness is about 0.6 nm. Tunnel junctions fabricated on these films reveal gap-like structures near ±16 mV and ±30 mV. (orig.) [de

  19. Van der Waals epitaxy and photoresponse of hexagonal tellurium nanoplates on flexible mica sheets.

    Science.gov (United States)

    Wang, Qisheng; Safdar, Muhammad; Xu, Kai; Mirza, Misbah; Wang, Zhenxing; He, Jun

    2014-07-22

    Van der Waals epitaxy (vdWE) is of great interest due to its extensive applications in the synthesis of ultrathin two-dimensional (2D) layered materials. However, vdWE of nonlayered functional materials is still not very well documented. Here, although tellurium has a strong tendency to grow into one-dimensional nanoarchitecture due to its chain-like structure, we successfully realize 2D hexagonal tellurium nanoplates on flexible mica sheets via vdWE. Chemically inert mica surface is found to be crucial for the lateral growth of hexagonal tellurium nanoplates since it (1) facilitates the migration of tellurium adatoms along mica surface and (2) allows a large lattice mismatch. Furthermore, 2D tellurium hexagonal nanoplates-based photodetectors are in situ fabricated on flexible mica sheets. Efficient photoresponse is obtained even after bending the device for 100 times, indicating 2D tellurium hexagonal nanoplates-based photodetectors on mica sheets have a great application potential in flexible and wearable optoelectronic devices. We believe the fundamental understanding of vdWE effect on the growth of 2D tellurium hexagonal nanoplate can pave the way toward leveraging vdWE as a useful channel to realize the 2D geometry of other nonlayered materials.

  20. Dislocations limited electronic transport in hydride vapour phase epitaxy grown GaN templates: A word of caution for the epitaxial growers

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Abhishek, E-mail: cabhishek@rrcat.gov.in; Khamari, Shailesh K.; Kumar, R.; Dixit, V. K.; Oak, S. M.; Sharma, T. K., E-mail: tarun@rrcat.gov.in [Semiconductor Physics and Devices Laboratory, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

    2015-01-12

    GaN templates grown by hydride vapour phase epitaxy (HVPE) and metal organic vapour phase epitaxy (MOVPE) techniques are compared through electronic transport measurements. Carrier concentration measured by Hall technique is about two orders larger than the values estimated by capacitance voltage method for HVPE templates. It is learnt that there exists a critical thickness of HVPE templates below which the transport properties of epitaxial layers grown on top of them are going to be severely limited by the density of charged dislocations lying at layer-substrate interface. On the contrary MOVPE grown templates are found to be free from such limitations.

  1. Singularities of 28Si electrical activation in a single crystal and epitaxial GaAs under radiation annealing

    International Nuclear Information System (INIS)

    Ardyshev, V.M.; Ardyshev, M.V.; Khludkov, S.S.

    2000-01-01

    Using the voltage-capacitance characteristics method, the concentration profiles of 28 Si that is implanted in monocrystal and epitaxial GaAs after fast thermal annealing (FTA) (825, 870, 950 deg C, 12 s) have been studied; using Van-der-Paw method, the electron Hall mobility temperature dependence in the range of 70-400 K has been measured. Unlike thermal annealing (800 deg C, 30 min), the silicon diffusion depth redistribution into GaAs is shown to occur for both types of material. The coefficient of diffusion of Si in the single crystal is 2 times greater, but the electrical activation efficiency is somewhat less than in the epitaxial GaAs for each of the temperatures of FTA. The analysis of the temperature dependence of the electron mobility in ion-implanted layers after FTA gives the evidence about the significantly lower concentration of defects restricting the mobility in comparison with results obtained at thermal annealing during 30 min [ru

  2. Amorphous-crystalline interface evolution during Solid Phase Epitaxy Regrowth of SiGe films amorphized by ion implantation

    International Nuclear Information System (INIS)

    D'Angelo, D.; Piro, A.M.; Mirabella, S.; Bongiorno, C.; Romano, L.; Terrasi, A.; Grimaldi, M.G.

    2007-01-01

    Transmission Electron Microscopy was combined with Time Resolved Reflectivity to study the amorphous-crystalline (a-c) interface evolution during Solid Phase Epitaxy Regrowth (SPER) of Si 0.83 Ge 0.17 films deposited on Si by Molecular Beam Epitaxy and amorphized with Ge + ion implantation. Starting from the Si/SiGe interface, a 20 nm thick layer regrows free of defects with the same SPER rate of pure Si. The remaining SiGe regrows with planar defects and dislocations, accompanied by a decrease of the SPER velocity. The sample was also studied after implantation with B or P. In these cases, the SPER rate raises following the doping concentration profile, but no difference in the defect-free layer thickness was observed compared to the un-implanted sample. On the other hand, B or P introduction reduces the a-c interface roughness, while B-P co-implantation produces roughness comparable to the un-implanted sample

  3. Microstructure of epitaxial YBa2Cu3O7-x thin films grown on LaAlO3 (001)

    International Nuclear Information System (INIS)

    Hsieh, Y.; Siegal, M.P.; Hull, R.; Phillips, J.M.

    1990-01-01

    We report a microstructural investigation of the epitaxial growth of YBa 2 Cu 3 O 7-x (YBCO) thin films on LaAlO 3 (001) substrates using transmission electron microscopy (TEM). Epitaxial films grow with two distinct modes: c epitaxy (YBCO) single crystal with the c (axis normal to the surface and a epitaxy (YBCO) single crystal with the c axis in the interfacial plane), where c epitaxy is the dominant mode grown in all samples 35--200 nm thick. In 35 nm YBCO films annealed at 850 degree C, 97±1% of the surface area is covered by c epitaxy with embedded anisotropic a-epitaxial grains. Quantitative analysis reveals the effect of film thickness and annealing temperature on the density, grain sizes, areal coverages, and anisotropic growth of a epitaxy

  4. Strain induced ionic conductivity enhancement in epitaxial Ce0.9Gd0.1O22d

    DEFF Research Database (Denmark)

    Kant, K. Mohan; Esposito, Vincenzo; Pryds, Nini

    2012-01-01

    -plane ionic conductivity in CGO epitaxial thin films. The ionic conductivity is found to increase with decrease in buffer layer thickness. The tailored ionic conductivity enhancement is explained in terms of close relationships among epitaxy, strain, and ionic conductivity....

  5. InGaN/GaN nanowires epitaxy on large-area MoS2 for high-performance light-emitters

    KAUST Repository

    Zhao, Chao; Ng, Tien Khee; Tseng, Chien-Chih; Li, Jun; Shi, Yumeng; Wei, Nini; Zhang, Daliang; Consiglio, Giuseppe Bernardo; Prabaswara, Aditya; Alhamoud, Abdullah Ali; Albadri, Abdulrahman  M.; Alyamani, Ahmed Y.; Zhang, Xixiang; Li, Lain-Jong; Ooi, Boon S.

    2017-01-01

    The recent study of a wide range of layered transition metal dichalcogenides (TMDCs) has created a new era for device design and applications. In particular, the concept of van der Waals epitaxy (vdWE) utilizing layered TMDCs has the potential to broaden the family of epitaxial growth techniques beyond the conventional methods. We report herein, for the first time, the monolithic high-power, droop-free, and wavelength tunable InGaN/GaN nanowire light-emitting diodes (NW-LEDs) on large-area MoS2 layers formed by sulfurizing entire Mo substrates. MoS2 serves as both a buffer layer for high-quality GaN nanowires growth and a sacrificial layer for epitaxy lift-off. The LEDs obtained on nitridated MoS2 via quasi vdWE show a low turn-on voltage of ∼2 V and light output power up to 1.5 mW emitting beyond the “green gap”, without an efficiency droop up to the current injection of 1 A (400 A cm−2), by virtue of high thermal and electrical conductivities of the metal substrates. The discovery of the nitride/layered TMDCs/metal heterostructure platform also ushers in the unparalleled opportunities of simultaneous high-quality nitrides growth for high-performance devices, ultralow-profile optoelectronics, energy harvesting, as well as substrate reusability for practical applications.

  6. High growth rate GaN on 200 mm silicon by metal-organic vapor phase epitaxy for high electron mobility transistors

    Science.gov (United States)

    Charles, M.; Baines, Y.; Bavard, A.; Bouveyron, R.

    2018-02-01

    It is increasingly important to reduce the cycle time of epitaxial growth, in order to reduce the costs of device fabrication, especially for GaN based structures which typically have growth cycles of several hours. We have performed a comprehensive study using metal-organic vapor phase epitaxy (MOVPE) investigating the effects of changing GaN growth rates from 0.9 to 14.5 μm/h. Although there is no significant effect on the strain incorporated in the layers, we have seen changes in the surface morphology which can be related to the change in dislocation behaviour and surface diffusion effects. At the small scale, as seen by AFM, increased dislocation density for higher growth rates leads to increased pinning of growth terraces, resulting in more closely spaced terraces. At a larger scale of hundreds of μm observed by optical profiling, we have related the formation of grains to the rate of surface diffusion of adatoms using a random walk model, implying diffusion distances from 30 μm for the highest growth rates up to 100 μm for the lowest. The increased growth rate also increases the intrinsic carbon incorporation which can increase the breakdown voltage of GaN films. Despite an increased threading dislocation density, these very high growth rates of 14.5 μm/hr by MOVPE have been shown to be appealing for reducing epitaxial growth cycle times and therefore costs in High Electron Mobility Transistor (HEMT) structures.

  7. InGaN/GaN nanowires epitaxy on large-area MoS2 for high-performance light-emitters

    KAUST Repository

    Zhao, Chao

    2017-05-18

    The recent study of a wide range of layered transition metal dichalcogenides (TMDCs) has created a new era for device design and applications. In particular, the concept of van der Waals epitaxy (vdWE) utilizing layered TMDCs has the potential to broaden the family of epitaxial growth techniques beyond the conventional methods. We report herein, for the first time, the monolithic high-power, droop-free, and wavelength tunable InGaN/GaN nanowire light-emitting diodes (NW-LEDs) on large-area MoS2 layers formed by sulfurizing entire Mo substrates. MoS2 serves as both a buffer layer for high-quality GaN nanowires growth and a sacrificial layer for epitaxy lift-off. The LEDs obtained on nitridated MoS2 via quasi vdWE show a low turn-on voltage of ∼2 V and light output power up to 1.5 mW emitting beyond the “green gap”, without an efficiency droop up to the current injection of 1 A (400 A cm−2), by virtue of high thermal and electrical conductivities of the metal substrates. The discovery of the nitride/layered TMDCs/metal heterostructure platform also ushers in the unparalleled opportunities of simultaneous high-quality nitrides growth for high-performance devices, ultralow-profile optoelectronics, energy harvesting, as well as substrate reusability for practical applications.

  8. USACE Navigation Channels 2012

    Data.gov (United States)

    California Natural Resource Agency — This dataset represents both San Francisco and Los Angeles District navigation channel lines. All San Francisco District channel lines were digitized from CAD files...

  9. Calcium channel blocker overdose

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used ...

  10. Epitaxial ternary nitride thin films prepared by a chemical solution method

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Hongmei [Los Alamos National Laboratory; Feldmann, David M [Los Alamos National Laboratory; Wang, Haiyan [TEXAS A& M; Bi, Zhenxing [TEXAS A& M

    2008-01-01

    It is indispensable to use thin films for many technological applications. This is the first report of epitaxial growth of ternary nitride AMN2 films. Epitaxial tetragonal SrTiN2 films have been successfully prepared by a chemical solution approach, polymer-assisted deposition. The structural, electrical, and optical properties of the films are also investigated.

  11. Ge-on-Si : Single-Crystal Selective Epitaxial Growth in a CVD Reactor

    NARCIS (Netherlands)

    Sammak, A.; De Boer, W.B.; Nanver, L.K.

    2012-01-01

    A standard Si/SiGe ASM CVD reactor that was recently modified for merging GaAs and Si epitaxial growth in one system is utilized to achieve intrinsic and doped epitaxial Ge-on-Si with low threading dislocation and defect densities. For this purpose, the system is equipped with 2% diluted GeH4 as the

  12. Deposition of HgTe by electrochemical atomic layer epitaxy (EC-ALE)

    CSIR Research Space (South Africa)

    Venkatasamy, V

    2006-04-01

    Full Text Available This paper describes the first instance of HgTe growth by electrochemical atomic layer epitaxy (EC-ALE). EC-ALE is the electrochemical analog of atomic layer epitaxy (ALE) and atomic layer deposition (ALD), all of which are based on the growth...

  13. Characterization of GaN/AlGaN epitaxial layers grown

    Indian Academy of Sciences (India)

    GaN and AlGaN epitaxial layers are grown by a metalorganic chemical vapour deposition (MOCVD) system. The crystalline quality of these epitaxially grown layers is studied by different characterization techniques. PL measurements indicate band edge emission peak at 363.8 nm and 312 nm for GaN and AlGaN layers ...

  14. A critical discussion of the vacancy diffusion model of ion beam induced epitaxial crystallization

    International Nuclear Information System (INIS)

    Heera, V.

    1989-01-01

    A simple vacancy diffusion model of ion beam induced epitaxial crystallization of silicon including divacancy formation is developed. The model reproduces some of the experimental findings, as e.g. the dose rate dependence of the crystallization rate. However, the measured activation energy of the ion beam induced epitaxial crystallization cannot be accounted for by vacancy diffusion alone. (author)

  15. Controllable factors affecting the epitaxial quality of LaCoO3 films ...

    Indian Academy of Sciences (India)

    2018-03-23

    Mar 23, 2018 ... ... larger molecular weight contribute to the improvement of epitaxial quality of LaCoO3 epitaxial film. ..... Research Fund of Education Department of Sichuan Province. (grant nos. 16ZA0133 and 15ZB0108); and the Doctoral.

  16. Quantum Channels With Memory

    International Nuclear Information System (INIS)

    Rybar, T.

    2012-01-01

    Quantum memory channels represent a very general, yet simple and comprehensible model for causal processes. As such they have attracted considerable research interest, mostly aimed on their transfer capabilities and structure properties. Most notably it was shown that memory channels can be implemented via physically naturally motivated collision models. We also define the concept of repeatable channels and show that only unital channels can be implemented repeat ably with pure memory channels. In the special case of qubit channels we also show that every unital qubit channel has a repeatable implementation. We also briefly explore the possibilities of stroboscopical simulation of channels and show that all random unitary channels can be stroboscopically simulated. Particularly in qubit case, all indivisible qubit channels are also random unitary, hence for qubit all indivisible channels can be stroboscopically simulated. Memory channels also naturally capture the framework of correlated experiments. We develop methods to gather and interpret data obtained in such setting and in detail examine the two qubit case. We also show that for control unitary interactions the measured data will never contradict a simple unitary evolution. Thus no memory effects can be spotted then. (author)

  17. Eight channel fast scalar

    Energy Technology Data Exchange (ETDEWEB)

    Waddoup, W D; Stubbs, R J [Durham Univ. (UK)

    1977-11-01

    An eight channel 64-bit scaler has been constructed with a static CMOS memory. Scaling frequencies are independently variable, at each channel, as are the number of bits/channel. The scaler, when used in conjunction with a multichannel charge to time converter results in a very flexible, gated multichannel ADC.

  18. KV7 potassium channels

    DEFF Research Database (Denmark)

    Stott, Jennifer B; Jepps, Thomas Andrew; Greenwood, Iain A

    2014-01-01

    Potassium channels are key regulators of smooth muscle tone, with increases in activity resulting in hyperpolarisation of the cell membrane, which acts to oppose vasoconstriction. Several potassium channels exist within smooth muscle, but the KV7 family of voltage-gated potassium channels have been...

  19. All-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayers fabricated by Sn-induced low-temperature epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kawano, M.; Ikawa, M.; Arima, K.; Yamada, S.; Kanashima, T.; Hamaya, K., E-mail: hamaya@ee.es.osaka-u.ac.jp [Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka 560-8531 (Japan)

    2016-01-28

    We demonstrate low-temperature growth of all-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayer structures by developing Sn-induced surfactant-mediated molecular beam epitaxy (SMBE) of Ge on Co{sub 2}FeSi. Despite the growth of a semiconductor on a metal, we verify that the inserted Sn monolayers between Ge and Co{sub 2}FeSi enable to promote the 2D epitaxial growth of Ge up to 5 nm at a T{sub G} of 250 °C. An understanding of the mechanism of the Sn-induced SMBE leads to the achievement of all-epitaxial Co{sub 2}FeSi/Ge/Co{sub 2}FeSi trilayer structures with spin-valve-like magnetization reversals. This study will open a way for vertical-type and high-performance Ge-based spintronics devices.

  20. Improved radiation tolerance of MAPS using a depleted epitaxial layer

    Energy Technology Data Exchange (ETDEWEB)

    Dorokhov, A., E-mail: Andrei.Dorokhov@IReS.in2p3.f [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Bertolone, G.; Baudot, J.; Brogna, A.S.; Colledani, C.; Claus, G.; De Masi, R. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Deveaux, M. [Goethe-Universitaet Frankfurt am Main, Senckenberganlage 31, 60325 Frankfurt am Main (Germany); Doziere, G.; Dulinski, W. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France); Fontaine, J.-C. [Groupe de Recherche en Physique des Hautes Energies (GRPHE), Universite de Haute Alsace, 61, rue Albert Camus, 68093 Mulhouse (France); Goffe, M.; Himmi, A.; Hu-Guo, Ch.; Jaaskelainen, K.; Koziel, M.; Morel, F.; Santos, C.; Specht, M.; Valin, I. [Institut Pluridisciplinaire Hubert Curien (IPHC), 23 rue du loess, BP 28, 67037 Strasbourg (France)

    2010-12-11

    Tracking performance of Monolithic Active Pixel Sensors (MAPS) developed at IPHC (Turchetta, et al., 2001) have been extensively studied (Winter, et al., 2001; Gornushkin, et al., 2002) . Numerous sensor prototypes, called MIMOSA, were fabricated and tested since 1999 in order to optimise the charge collection efficiency and power dissipation, to minimise the noise and to increase the readout speed. The radiation tolerance was also investigated. The highest fluence tolerable for a 10{mu}m pitch device was found to be {approx}10{sup 13}n{sub eq}/cm{sup 2}, while it was only 2x10{sup 12}n{sub eq}/cm{sup 2} for a 20{mu}m pitch device. The purpose of this paper is to show that the tolerance to non-ionising radiation may be extended up to O(10{sup 14}) n{sub eq}/cm{sup 2}. This goal relies on a fabrication process featuring a 15{mu}m thin, high resistivity ({approx}1k{Omega}cm) epitaxial layer. A sensor prototype (MIMOSA-25) was fabricated in this process to explore its detection performance. The depletion depth of the epitaxial layer at standard CMOS voltages (<5V) is similar to the layer thickness. Measurements with m.i.p.s show that the charge collected in the seed pixel is at least twice larger for the depleted epitaxial layer than for the undepleted one, translating into a signal-to-noise ratio (SNR) of {approx}50. Tests after irradiation have shown that this excellent performance is maintained up to the highest fluence considered (3x10{sup 13}n{sub eq}/cm{sup 2}), making evidence of a significant extension of the radiation tolerance limits of MAPS.

  1. Distribution Profile of Inositol 1,4,5-Trisphosphate Receptor/Ca2+ Channels in α and β Cells of Pancreas: Dominant Localization in Secretory Granules and Common Error in Identification of Secretory Granule Membranes.

    Science.gov (United States)

    Hur, Yong Suk; Yoo, Seung Hyun

    2015-01-01

    The α and β cells of pancreatic islet release important hormones in response to intracellular Ca increases that result from Ca releases through the inositol 1,4,5-trisphoshate receptor (IP3R)/Ca channels. Yet no systematic studies on distribution of IP3R/Ca channels have been done, prompting us to investigate the distribution of all 3 IP3R isoforms. Immunogold electron microscopy was performed to determine the presence and the relative concentrations of all 3 IP3R isoforms in 2 major organelles secretory granules (SGs) and the endoplasmic reticulum of α and β cells of rat pancreas. All 3 IP3R isoforms were present in SG membranes of both cells, and the IP3R concentrations in SGs were ∼2-fold higher than those in the endoplasmic reticulum. Moreover, large halos shown in the electron microscope images of insulin-containing SGs of β cells were gap spaces that resulted from separation of granule membranes from the surrounding cytoplasm. These results strongly suggest the important roles of SGs in IP3-induced, Ca-dependent regulatory secretory pathway in pancreas. Moreover, the accurate location of SG membranes of β cells was further confirmed by the location of another integral membrane protein synaptotagmin V and of membrane phospholipid PI(4,5)P2.

  2. Genotypic to expression profiling of bovine calcium channel, voltage-dependent, alpha-2/delta subunit 1 gene, and their association with bovine mastitis among Frieswal (HFX Sahiwal) crossbred cattle of Indian origin.

    Science.gov (United States)

    Deb, Rajib; Singh, Umesh; Kumar, Sushil; Kumar, Arun; Singh, Rani; Sengar, Gyanendra; Mann, Sandeep; Sharma, Arjava

    2014-04-03

    Calcium channel, voltage-dependent, alpha-2/delta subunit 1 (CACNA2D1) gene is considered to be an important noncytokine candidate gene influencing mastitis. Scanty of reports are available until today regarding the role play of CACNA2D1 gene on the susceptibility of bovine mastitis. We interrogated the CACNA2D1 G519663A [A>G] SNP by PCR-RFLP among two hundreds Frieswal (HF X Sahiwal) crossbred cattle of Indian origin. Genotypic frequency of AA (51.5, n=101) was comparatively higher than AG (35, n=70) and GG (14.5, n=29). Association of Somatic cell score (SCS) with genotypes revealed that, GG genotypes showing lesser count (less susceptible to mastitis) compare to AA and AG. Relative expression of CACNA2D1 transcript (in milk samples) was significantly higher among GG than AG and AA. Further we have also isolated blood sample from the all groups and PBMCs were cultured from each blood sample as per the standard protocol. They were treated with Calcium channel blocker and the expression level of the CACNA2D1 gene was evaluated by Real Time PCR. Results show that expression level decline in each genotypic group after treatment and expression level of GG are again significantly higher than AA and AG. Thus, it may be concluded that GG genotypic animals are favorable for selecting disease resistant breeds.

  3. Self-Organized Ni Nanocrystal Embedded in BaTiO3 Epitaxial Film

    Directory of Open Access Journals (Sweden)

    Ge FF

    2010-01-01

    Full Text Available Abstract Ni nanocrystals (NCs were embedded in BaTiO3 epitaxial films using the laser molecular beam epitaxy. The processes involving the self-organization of Ni NCs and the epitaxial growth of BaTiO3 were discussed. With the in situ monitoring of reflection high-energy electron diffraction, the nanocomposite films were engineered controllably by the fine alternation of the self-organization of Ni NCs and the epitaxial growth of BaTiO3. The transmission electron microscopy and the X-ray diffraction characterization confirmed that the composite film consists of the Ni NCs layers alternating with the (001/(100-oriented epitaxial BaTiO3 separation layers.

  4. Single-domain epitaxial silicene on diboride thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fleurence, A., E-mail: antoine@jaist.ac.jp; Friedlein, R.; Aoyagi, K.; Yamada-Takamura, Y. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); Gill, T. G. [School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan); London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Sadowski, J. T. [Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973 (United States); Copel, M.; Tromp, R. M. [IBM Research Division, Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Hirjibehedin, C. F. [London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH (United Kingdom); Department of Chemistry, UCL, London WC1H 0AJ (United Kingdom); Department of Physics and Astronomy, UCL, London WC1E 6BT (United Kingdom)

    2016-04-11

    Epitaxial silicene, which forms spontaneously on ZrB{sub 2}(0001) thin films grown on Si(111) wafers, has a periodic stripe domain structure. By adsorbing additional Si atoms on this surface, we find that the domain boundaries vanish, and a single-domain silicene sheet can be prepared without altering its buckled honeycomb structure. The amount of Si required to induce this change suggests that the domain boundaries are made of a local distortion of the silicene honeycomb lattice. The realization of a single domain sheet with structural and electronic properties close to those of the original striped state demonstrates the high structural flexibility of silicene.

  5. Large-area, laterally-grown epitaxial semiconductor layers

    Science.gov (United States)

    Han, Jung; Song, Jie; Chen, Danti

    2017-07-18

    Structures and methods for confined lateral-guided growth of a large-area semiconductor layer on an insulating layer are described. The semiconductor layer may be formed by heteroepitaxial growth from a selective growth area in a vertically-confined, lateral-growth guiding structure. Lateral-growth guiding structures may be formed in arrays over a region of a substrate, so as to cover a majority of the substrate region with laterally-grown epitaxial semiconductor tiles. Quality regions of low-defect, stress-free GaN may be grown on silicon.

  6. Magnetic-property changes in epitaxial metal-film sandwiches

    International Nuclear Information System (INIS)

    Brodsky, M.B.

    1982-08-01

    Epitaxial metal-film sandwiches (EMFS) containing Pd or Cr, have been prepared between single-crystal Ag or Au. The modified Pd/Cr show major changes in physical properties. Pd has a stretched lattice parameter in Au-Pd-Au, which combines with a tetragonal distortion to cause exchange enhancements up to 28,000 and spin-fluctuation temperatures of 1 to 10 K. In Au-Cr-Au, Cr takes up the fcc structure, leading to superconductivity due to a high N(E/sub F/). These results are contrasted to data for Ag-Pd-Ag and Ag-Cr-Ag EMFS

  7. Epitaxial Growth of Germanium on Silicon for Light Emitters

    Directory of Open Access Journals (Sweden)

    Chengzhao Chen

    2012-01-01

    Full Text Available This paper describes the role of Ge as an enabler for light emitters on a Si platform. In spite of the large lattice mismatch of ~4.2% between Ge and Si, high-quality Ge layers can be epitaxially grown on Si by ultrahigh-vacuum chemical vapor deposition. Applications of the Ge layers to near-infrared light emitters with various structures are reviewed, including the tensile-strained Ge epilayer, the Ge epilayer with a delta-doping SiGe layer, and the Ge/SiGe multiple quantum wells on Si. The fundamentals of photoluminescence physics in the different Ge structures are discussed briefly.

  8. Surface passivation of liquid phase epitaxial GaAs

    International Nuclear Information System (INIS)

    Alexiev, D.; Butcher, K.S.A.; Mo, L.; Edmondson, M.

    1995-10-01

    Passivation of the liquid phase epitaxial GaAs surface was attempted using aqueous P 2 S 5 -NH 4 OH, (NH 4 ) 2 S x and plasma nitrogenation and hydrogenation. Results indicate that plasma nitrogenation with pretreatment of plasma hydrogenation produced consistent reduction in reverse leakage current at room temperature for all p and n type Schottky diodes. Some diodes showed an order of magnitude improvement in current density. (NH 4 ) 2 S x passivation also results in improved I-V characteristics, though the long term stability of this passivation is questionable. 26 refs., 6 figs

  9. Liquid phase epitaxy of gallium arsenide - a review

    International Nuclear Information System (INIS)

    Alexiev, D.; Edmondson, M.; Butcher, K.S.A.; Tansley, T.

    1992-07-01

    Liquid phase epitaxy of gallium arsenide has been investigated intensively from the late 1960's to the present and has now a special place in the manufacture of wide band, compound semiconductor radiation detectors. Although this particular process appears to have gained prominence in the last three decades, the authors point out that its origins reach back to 1836 when Frankenheim made his first observations. A brief review is presented from a semiconductor applications point of view on how this subject developed. 70 refs., 5 figs

  10. SiC epitaxy growth using chloride-based CVD

    International Nuclear Information System (INIS)

    Henry, Anne; Leone, Stefano; Beyer, Franziska C.; Pedersen, Henrik; Kordina, Olof; Andersson, Sven; Janzén, Erik

    2012-01-01

    The growth of thick epitaxial SiC layers needed for high-voltage, high-power devices is investigated with the chloride-based chemical vapor deposition. High growth rates exceeding 100 μm/h can be obtained, however to obtain device quality epilayers adjustments of the process parameters should be carried out appropriately for the chemistry used. Two different chemistry approaches are compared: addition of hydrogen chloride to the standard precursors or using methyltrichlorosilane, a molecule that contains silicon, carbon and chlorine. Optical and electrical techniques are used to characterize the layers.

  11. Subsurface contributions in epitaxial rare-earth silicides

    Energy Technology Data Exchange (ETDEWEB)

    Luebben, Olaf; Shvets, Igor V. [Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), School of Physics, Trinity College, Dublin (Ireland); Cerda, Jorge I. [Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, Madrid (Spain); Chaika, Alexander N. [Institute of Solid State Physics, RAS, Chernogolovka (Russian Federation)

    2015-07-01

    Metallic thin films of heavy rare-earth silicides epitaxially grown on Si(111) substrates have been widely studied in recent years because of their appealing properties: unusually low values of the Schottky barrier height, an abrupt interface, and a small lattice mismatch. Previous studies also showed that these silicides present very similar atomic and electronic structures. Here, we examine one of these silicides (Gd{sub 3}Si{sub 5}) using scanning tunneling microscopy (STM) image simulations that go beyond the Tersoff-Hamann approach. These simulations strongly indicate an unusual STM depth sensitivity for this system.

  12. Atomic layer epitaxy of ZnO for applications in molecular beam epitaxy growth of GaN and InGaN

    International Nuclear Information System (INIS)

    Godlewski, M.; Szczerbakow, A.; Ivanov, V. Yu.; Barski, A.; Goldys, E.M.

    2000-01-01

    We report the successful atomic layer epitaxy growth of thin ZnO films and their use for GaN and InGaN epitaxy. The properties of ZnO epilayers, obtained by four different procedures, are analysed, as well as of GaN and InGaN films grown on ZnO-coated Si and GaAs by MBE. (author)

  13. Coupling of laser energy into plasma channels

    International Nuclear Information System (INIS)

    Dimitrov, D. A.; Giacone, R. E.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

    2007-01-01

    Diffractive spreading of a laser pulse imposes severe limitations on the acceleration length and maximum electron energy in the laser wake field accelerator (LWFA). Optical guiding of a laser pulse via plasma channels can extend the laser-plasma interaction distance over many Rayleigh lengths. Energy efficient coupling of laser pulses into and through plasma channels is very important for optimal LWFA performance. Results from simulation parameter studies on channel guiding using the particle-in-cell (PIC) code VORPAL [C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004)] are presented and discussed. The effects that density ramp length and the position of the laser pulse focus have on coupling into channels are considered. Moreover, the effect of laser energy leakage out of the channel domain and the effects of tunneling ionization of a neutral gas on the guided laser pulse are also investigated. Power spectral diagnostics were developed and used to separate pump depletion from energy leakage. The results of these simulations show that increasing the density ramp length decreases the efficiency of coupling a laser pulse to a channel and increases the energy loss when the pulse is vacuum focused at the channel entrance. Then, large spot size oscillations result in increased energy leakage. To further analyze the coupling, a differential equation is derived for the laser spot size evolution in the plasma density ramp and channel profiles are simulated. From the numerical solution of this equation, the optimal spot size and location for coupling into a plasma channel with a density ramp are determined. This result is confirmed by the PIC simulations. They show that specifying a vacuum focus location of the pulse in front of the top of the density ramp leads to an actual focus at the top of the ramp due to plasma focusing, resulting in reduced spot size oscillations. In this case, the leakage is significantly reduced and is negligibly affected by ramp length

  14. Epitaxial growth of YBa2Cu307−δ films on SrTiO3 (100) by direct solution precursor deposition

    International Nuclear Information System (INIS)

    Bustamante, A; Garcia, Jorge; Osorio, Ana M; Valladares, Luis De Los Santos; Barnes, C H W; González, J C; Azuma, Y; Majima, Y; Aguiar, J Albino

    2014-01-01

    We study the optimal temperature to obtain YBa 2 Cu 3 O 7-δ epitaxial films grown onto SrTiO 3 substrates by direct solution deposition. The samples received heat treatment at 820, 840 and 860 °C, then characterized by XRD, observing the (00l) profiles; and magnetic susceptibility measurements. The T C-onset for all the samples was 90 K. In addition, the current – voltage (I-V) measurements shows typical tunneling signals corresponding to normal metal-superconducting junctions indicating the films are promising for potential electrical applications.

  15. Mobility-limiting mechanisms in single and dual channel strained Si/SiGe MOSFETs

    International Nuclear Information System (INIS)

    Olsen, S.H.; Dobrosz, P.; Escobedo-Cousin, E.; Bull, S.J.; O'Neill, A.G.

    2005-01-01

    Dual channel strained Si/SiGe CMOS architectures currently receive great attention due to maximum performance benefits being predicted for both n- and p-channel MOSFETs. Epitaxial growth of a compressively strained SiGe layer followed by tensile strained Si can create a high mobility buried hole channel and a high mobility surface electron channel on a single relaxed SiGe virtual substrate. However, dual channel n-MOSFETs fabricated using a high thermal budget exhibit compromised mobility enhancements compared with single channel devices, in which both electron and hole channels form in strained Si. This paper investigates the mobility-limiting mechanisms of dual channel structures. The first evidence of increased interface roughness due to the introduction of compressively strained SiGe below the tensile strained Si channel is presented. Interface corrugations degrade electron mobility in the strained Si. Roughness measurements have been carried out using AFM and TEM. Filtering AFM images allowed roughness at wavelengths pertinent to carrier transport to be studied and the results are in agreement with electrical data. Furthermore, the first comparison of strain measurements in the surface channels of single and dual channel architectures is presented. Raman spectroscopy has been used to study channel strain both before and after processing and indicates that there is no impact of the buried SiGe layer on surface macrostrain. The results provide further evidence that the improved performance of the single channel devices fabricated using a high thermal budget arises from improved surface roughness and reduced Ge diffusion into the Si channel

  16. Fine Channel Networks

    Science.gov (United States)

    1997-01-01

    A color image of fine channel networks on Mars; north toward top. The scene shows heavily cratered highlands dissected by dendritic open channel networks that dissect steep slopes of impact crater walls. This image is a composite of Viking high-resolution images in black and white and low-resolution images in color. The image extends from latitude 9 degrees S. to 5 degrees S. and from longitude 312 degrees to 320 degrees; Mercator projection. The dendritic pattern of the fine channels and their location on steep slopes leads to the interpretation that these are runoff channels. The restriction of these types of channels to ancient highland rocks suggests that these channels are old and date from a time on Mars when conditions existed for precipitation to actively erode rocks. After the channels reach a low plain, they appear to end. Termination may have resulted from burial by younger deposits or perhaps the flows percolated into the surface materials and continued underground.

  17. Experiments and Modeling of Si-Ge Interdiffusion with Partial Strain Relaxation in Epitaxial SiGe Heterostructures

    KAUST Repository

    Dong, Y.

    2014-07-26

    Si-Ge interdiffusion and strain relaxation were studied in a metastable SiGe epitaxial structure. With Ge concentration profiling and ex-situ strain analysis, it was shown that during thermal anneals, both Si-Ge interdiffusion and strain relaxation occurred. Furthermore, the time evolutions of both strain relaxation and interdiffusion were characterized. It showed that during the ramp-up stage of thermal anneals at higher temperatures (800°C and 840°C), the degree of relaxation, R, reached a “plateau”, while interdiffusion was negligible. With the approximation that the R value is constant after the ramp-up stage, a quantitative interdiffusivity model was built to account for both the effect of strain relaxation and the impact of the relaxation induced dislocations, which gave good agreement with the experiment data.

  18. Ion channels in plants.

    Science.gov (United States)

    Hedrich, Rainer

    2012-10-01

    Since the first recordings of single potassium channel activities in the plasma membrane of guard cells more than 25 years ago, patch-clamp studies discovered a variety of ion channels in all cell types and plant species under inspection. Their properties differed in a cell type- and cell membrane-dependent manner. Guard cells, for which the existence of plant potassium channels was initially documented, advanced to a versatile model system for studying plant ion channel structure, function, and physiology. Interestingly, one of the first identified potassium-channel genes encoding the Shaker-type channel KAT1 was shown to be highly expressed in guard cells. KAT1-type channels from Arabidopsis thaliana and its homologs from other species were found to encode the K(+)-selective inward rectifiers that had already been recorded in early patch-clamp studies with guard cells. Within the genome era, additional Arabidopsis Shaker-type channels appeared. All nine members of the Arabidopsis Shaker family are localized at the plasma membrane, where they either operate as inward rectifiers, outward rectifiers, weak voltage-dependent channels, or electrically silent, but modulatory subunits. The vacuole membrane, in contrast, harbors a set of two-pore K(+) channels. Just very recently, two plant anion channel families of the SLAC/SLAH and ALMT/QUAC type were identified. SLAC1/SLAH3 and QUAC1 are expressed in guard cells and mediate Slow- and Rapid-type anion currents, respectively, that are involved in volume and turgor regulation. Anion channels in guard cells and other plant cells are key targets within often complex signaling networks. Here, the present knowledge is reviewed for the plant ion channel biology. Special emphasis is drawn to the molecular mechanisms of channel regulation, in the context of model systems and in the light of evolution.

  19. Highly efficient channel waveguide lasers at 1 µm and 2 µm in refractive-index-engineered potassium double tungstates

    NARCIS (Netherlands)

    van Dalfsen, Koop; Geskus, D.; García Blanco, Sonia Maria; Pollnau, Markus

    Epitaxial growth of rare-earth-ion-activated KY(1-x-y)Gd(x)Lu(y)(WO4)2 co-doped thin layers onto KY(WO4)2 substrates has enabled lattice-matched waveguides with high refractive-index contract and large variation of the active rare-earth-ion concentration. In Yb3+-activated micro-structured channel

  20. Data Profiling

    OpenAIRE

    Hladíková, Radka

    2010-01-01

    Title: Data Profiling Author: Radka Hladíková Department: Department of Software Engineering Supervisor: Ing. Vladimír Kyjonka Supervisor's e-mail address: Abstract: This thesis puts mind on problems with data quality and data profiling. This Work analyses and summarizes problems of data quality, data defects, process of data quality, data quality assessment and data profiling. The main topic is data profiling as a process of researching data available in existing...

  1. Advanced in-situ control for III-nitride RF power device epitaxy

    Science.gov (United States)

    Brunner, F.; Zettler, J.-T.; Weyers, M.

    2018-04-01

    In this contribution, the latest improvements regarding wafer temperature measurement on 4H-SiC substrates and, based on this, of film thickness and composition control of GaN and AlGaN layers in power electronic device structures are presented. Simultaneous pyrometry at different wavelengths (950 nm and 405 nm) reveal the advantages and limits of the different temperature measurement approaches. Near-UV pyrometry gives a very stable wafer temperature signal without oscillations during GaN growth since the semi-insulating 4H-SiC substrate material becomes opaque at temperatures above 550 °C at the wavelength of 405 nm. A flat wafer temperature profile across the 100 mm substrate diameter is demonstrated despite a convex wafer shape at AlGaN growth conditions. Based on the precise assignment of wafer temperature during MOVPE we were able to improve the accuracy of the high-temperature n-k database for the materials involved. Consequently, the measurement accuracy of all film thicknesses grown under fixed temperature conditions improved. Comparison of in situ and ex situ determined layer thicknessess indicate an unintended etching of the topmost layer during cool-down. The details and limitations of real-time composition analysis for lower Al-content AlGaN barrier layers during transistor device epitaxy are shown.

  2. Multiple growths of epitaxial lift-off solar cells from a single InP substrate

    International Nuclear Information System (INIS)

    Lee, Kyusang; Shiu, Kuen-Ting; Zimmerman, Jeramy D.; Forrest, Stephen R.; Renshaw, Christopher K.

    2010-01-01

    We demonstrate multiple growths of flexible, thin-film indium tin oxide-InP Schottky-barrier solar cells on a single InP wafer via epitaxial lift-off (ELO). Layers that protect the InP parent wafer surface during the ELO process are subsequently removed by selective wet-chemical etching, with the active solar cell layers transferred to a thin, flexible plastic host substrate by cold welding at room temperature. The first- and second-growth solar cells exhibit no performance degradation under simulated Atmospheric Mass 1.5 Global (AM 1.5G) illumination, and have a power conversion efficiency of η p =14.4±0.4% and η p =14.8±0.2%, respectively. The current-voltage characteristics for the solar cells and atomic force microscope images of the substrate indicate that the parent wafer is undamaged, and is suitable for reuse after ELO and the protection-layer removal processes. X-ray photoelectron spectroscopy, reflection high-energy electron diffraction observation, and three-dimensional surface profiling show a surface that is comparable or improved to the original epiready wafer following ELO. Wafer reuse over multiple cycles suggests that high-efficiency; single-crystal thin-film solar cells may provide a practical path to low-cost solar-to-electrical energy conversion.

  3. Epitaxial growth mechanisms of graphene and effects of substrates

    Science.gov (United States)

    Özçelik, V. Ongun; Cahangirov, S.; Ciraci, S.

    2012-06-01

    The growth process of single layer graphene with and without substrate is investigated using ab initio, finite temperature molecular dynamic calculations within density functional theory. An understanding of the epitaxial graphene growth mechanisms in the atomic level is provided by exploring the transient stages which occur at the growing edges of graphene. These stages are formation and collapse of large carbon rings together with the formation and healing of Stone-Wales like pentagon-heptagon defects. The activation barriers for the healing of these growth induced defects on various substrates are calculated using the climbing image nudge elastic band method and compared with that of the Stone-Wales defect. It is found that the healing of pentagon-heptagon defects occurring near the edge in the course of growth is much easier than that of Stone-Wales defect. The role of the substrate in the epitaxial growth and in the healing of defects are also investigated in detail, along with the effects of using carbon dimers as the building blocks of graphene growth.

  4. Improved radiation tolerance of MAPS using a depleted epitaxial layer

    International Nuclear Information System (INIS)

    Dorokhov, A.; Bertolone, G.; Baudot, J.; Brogna, A.S.; Colledani, C.; Claus, G.; De Masi, R.; Deveaux, M.; Doziere, G.; Dulinski, W.; Fontaine, J.-C.; Goffe, M.; Himmi, A.; Hu-Guo, Ch.; Jaaskelainen, K.; Koziel, M.; Morel, F.; Santos, C.; Specht, M.; Valin, I.

    2010-01-01

    Tracking performance of Monolithic Active Pixel Sensors (MAPS) developed at IPHC (Turchetta, et al., 2001) have been extensively studied (Winter, et al., 2001; Gornushkin, et al., 2002) . Numerous sensor prototypes, called MIMOSA, were fabricated and tested since 1999 in order to optimise the charge collection efficiency and power dissipation, to minimise the noise and to increase the readout speed. The radiation tolerance was also investigated. The highest fluence tolerable for a 10μm pitch device was found to be ∼10 13 n eq /cm 2 , while it was only 2x10 12 n eq /cm 2 for a 20μm pitch device. The purpose of this paper is to show that the tolerance to non-ionising radiation may be extended up to O(10 14 ) n eq /cm 2 . This goal relies on a fabrication process featuring a 15μm thin, high resistivity (∼1kΩcm) epitaxial layer. A sensor prototype (MIMOSA-25) was fabricated in this process to explore its detection performance. The depletion depth of the epitaxial layer at standard CMOS voltages ( 13 n eq /cm 2 ), making evidence of a significant extension of the radiation tolerance limits of MAPS.

  5. The Interfacial Thermal Conductance of Epitaxial Metal-Semiconductor Interfaces

    Science.gov (United States)

    Ye, Ning

    Understanding heat transport at nanometer and sub-nanometer lengthscales is critical to solving a wide range of technological challenges related to thermal management and energy conversion. In particular, finite Interfacial Thermal Conductance (ITC) often dominates transport whenever multiple interfaces are closely spaced together or when heat originates from sources that are highly confined by interfaces. Examples of the former include superlattices, thin films, quantum cascade lasers, and high density nanocomposites. Examples of the latter include FinFET transistors, phase-change memory, and the plasmonic transducer of a heat-assisted magnetic recording head. An understanding of the physics of such interfaces is still lacking, in part because experimental investigations to-date have not bothered to carefully control the structure of interfaces studied, and also because the most advanced theories have not been compared to the most robust experimental data. This thesis aims to resolve this by investigating ITC between a range of clean and structurally well-characterized metal-semiconductor interfaces using the Time-Domain Thermoreflectance (TDTR) experimental technique, and by providing theoretical/computational comparisons to the experimental data where possible. By studying the interfaces between a variety of materials systems, each with unique aspects to their tunability, I have been able to answer a number of outstanding questions regarding the importance of interfacial quality (epitaxial/non-epitaxial interfaces), semiconductor doping, matching of acoustic and optical phonon band structure, and the role of phonon transport mechanisms apart from direct elastic transmission on ITC. In particular, we are able to comment on the suitability of the diffuse mismatch model (DMM) to describe the transport across epitaxial interfaces. To accomplish this goal, I studied interfacial thermal transport across CoSi2, TiSi2, NiSi and PtSi - Si(100) and Si(111), (silicides

  6. Epitaxial hexagonal materials on IBAD-textured substrates

    Science.gov (United States)

    Matias, Vladimir; Yung, Christopher

    2017-08-15

    A multilayer structure including a hexagonal epitaxial layer, such as GaN or other group III-nitride (III-N) semiconductors, a oriented textured layer, and a non-single crystal substrate, and methods for making the same. The textured layer has a crystalline alignment preferably formed by the ion-beam assisted deposition (IBAD) texturing process and can be biaxially aligned. The in-plane crystalline texture of the textured layer is sufficiently low to allow growth of high quality hexagonal material, but can still be significantly greater than the required in-plane crystalline texture of the hexagonal material. The IBAD process enables low-cost, large-area, flexible metal foil substrates to be used as potential alternatives to single-crystal sapphire and silicon for manufacture of electronic devices, enabling scaled-up roll-to-roll, sheet-to-sheet, or similar fabrication processes to be used. The user is able to choose a substrate for its mechanical and thermal properties, such as how well its coefficient of thermal expansion matches that of the hexagonal epitaxial layer, while choosing a textured layer that more closely lattice matches that layer.

  7. Epitaxial GaN around ZnO nanopillars

    Energy Technology Data Exchange (ETDEWEB)

    Fikry, Mohamed; Scholz, Ferdinand [Institut fuer Optoelektronik, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany); Madel, Manfred; Tischer, Ingo; Thonke, Klaus [Institut fuer Quantenmaterie, Universitaet Ulm, Albert-Einstein-Allee 45, 89081 Ulm (Germany)

    2011-07-01

    We report on an investigation of the epitaxial quality of GaN layers overgrown coaxially around ZnO nanopillars. In a first step, regularly arranged ZnO nanopillars were grown using pre-patterning by e-beam lithography or self-organized hexagonal polystyrene sphere masks. Alternatively, ZnO pillars were also successfully grown on top of GaN pyramids. In a second step, GaN layers were grown around the ZnO pillars by Metal Organic Vapor Phase Epitaxy. At growth temperatures above 800 C, the ZnO pillars are dissolved by the hydrogen carrier gas leaving hollow GaN nanotubes. Characterization involved photoluminescence (PL), scanning electron microscopy and cathodoluminescence. The fair quality of the deposited GaN layers is confirmed by a sharp low temperature PL peak at 3.48 eV attributed to the donor bound exciton emission. Further peaks at 3.42 eV and 3.29 eV show the possible existence of basal plane and prismatic stacking faults.

  8. Disorder in silicon films grown epitaxially at low temperature

    International Nuclear Information System (INIS)

    Schwarzkopf, J.; Selle, B.; Bohne, W.; Roehrich, J.; Sieber, I.; Fuhs, W.

    2003-01-01

    Homoepitaxial Si films were prepared by electron cyclotron resonance plasma enhanced chemical vapor deposition on Si(100) substrates at temperatures of 325-500 deg. C using H 2 , Ar, and SiH 4 as process gases. The gas composition, substrate temperature, and substrate bias voltage were systematically varied to study the breakdown of epitaxial growth. Information from ion beam techniques, like Rutherford backscattering and heavy-ion elastic recoil detection analysis, was combined with transmission and scanning electron micrographs to examine the transition from ordered to amorphous growth. The results suggest that the breakdown proceeds in two stages: (i) highly defective but still ordered growth with a defect density increasing with increasing film thickness and (ii) formation of conically shaped amorphous precipitates. The hydrogen content is found to be directly related to the degree of disorder which acts as sink for excessive hydrogen. Only in almost perfect epitaxially grown films is the hydrogen level low, and an exponential tail of the H concentration into the crystalline substrate is observed as a result of the diffusive transport of hydrogen

  9. Epitaxial Ge-crystal arrays for X-ray detection

    International Nuclear Information System (INIS)

    Kreiliger, T; Falub, C V; Müller, E; Känel, H von; Isa, F; Isella, G; Chrastina, D; Bergamaschini, R; Marzegalli, A; Miglio, L; Kaufmann, R; Niedermann, P; Neels, A; Dommann, A; Meduňa, M

    2014-01-01

    Monolithic integration of an X-ray absorber layer on a Si CMOS chip might be a potentially attractive way to improve detector performance at acceptable costs. In practice this requires, however, the epitaxial growth of highly mismatched layers on a Si-substrate, both in terms of lattice parameters and thermal expansion coefficients. The generation of extended crystal defects, wafer bowing and layer cracking have so far made it impossible to put the simple concept into practice. Here we present a way in which the difficulties of fabricating very thick, defect-free epitaxial layers may be overcome. It consists of an array of densely packed, three-dimensional Ge-crystals on a patterned Si(001) substrate. The finite gap between neighboring micron-sized crystals prevents layer cracking and substrate bowing, while extended defects are driven to the crystal sidewalls. We show that the Ge-crystals are indeed defect-free, despite the lattice misfit of 4.2%. The electrical characteristics of individual Ge/Si heterojunction diodes are obtained from in-situ measurements inside a scanning electron microscope. The fabrication of monolithically integrated detectors is shown to be compatible with Si-CMOS processing

  10. Dewetting of Epitaxial Silver Film on Silicon by Thermal Annealing

    Science.gov (United States)

    Sanders, Charlotte E.; Kellogg, Gary L.; Shih, C.-K.

    2013-03-01

    It has been shown that noble metals can grow epitaxially on semiconducting and insulating substrates, despite being a non-wetting system: low temperature deposition followed by room temperature annealing leads to atomically flat film morphology. However, the resulting metastable films are vulnerable to dewetting, which has limited their utility for applications under ambient conditions. The physics of this dewetting is of great interest but little explored. We report on an investigation of the dewetting of epitaxial Ag(111) films on Si(111) and (100). Low energy electron microscopy (LEEM) shows intriguing evolution in film morphology and crystallinity, even at temperatures below 100oC. On the basis of these findings, we can begin to draw compelling inferences about film-substrate interaction and the kinetics of dewetting. Financial support is from NSF, DGE-0549417 and DMR-0906025. This work was performed, in part, at the Center for Integrated Nanotechnologies, User Facility operated for the U.S. DOE Office of Science. Sandia National Lab is managed and operated by Sandia Corp., a subsidiary of Lockheed Martin Corp., for the U.S. DOE's National Nuclear Security Administration under DE-AC04-94AL85000.

  11. New synthesis method for the growth of epitaxial graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yu, X.Z. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Laboratory of Condensed Matter Spectroscopy and Opto-Electronic Physics, Department of Physics, Shanghai Jiao Tong University, 1954 Hua Shan Road, Shanghai 200030 (China); Hwang, C.G.; Jozwiak, C.M.; Koehl, A. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Schmid, A.K. [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94709 (United States); Lanzara, A., E-mail: ALanzara@lbl.gov [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Department of Physics, University of California, Berkeley, CA 94720 (United States)

    2011-04-15

    Highlights: {yields} We report a new straightforward method for the synthesis of micrometer scale graphene sheets. {yields} The process is based on a face to face mehtod in which two SiC substrates are placed one on top of the other and are heated simultaneously, leading to highly homogeneous samples. {yields} The number of graphene layers is determined by the annealing temperature. - Abstract: As a viable candidate for an all-carbon post-CMOS electronics revolution, epitaxial graphene has attracted significant attention. To realize its application potential, reliable methods for fabricating large-area single-crystalline graphene domains are required. A new way to synthesize high quality epitaxial graphene, namely 'face-to-face' method, has been reported in this paper. The structure and morphologies of the samples are characterized by low-energy electron diffraction, atomic force microscopy, angle-resolved photoemission spectroscopy and Raman spectroscopy. The grown samples show better quality and larger length scales than samples grown through conventional thermal desorption. Moreover, the graphene thickness can be easily controlled by changing annealing temperature.

  12. Epitaxial hexagonal materials on IBAD-textured substrates

    Energy Technology Data Exchange (ETDEWEB)

    Matias, Vladimir; Yung, Christopher

    2017-08-15

    A multilayer structure including a hexagonal epitaxial layer, such as GaN or other group III-nitride (III-N) semiconductors, a <111> oriented textured layer, and a non-single crystal substrate, and methods for making the same. The textured layer has a crystalline alignment preferably formed by the ion-beam assisted deposition (IBAD) texturing process and can be biaxially aligned. The in-plane crystalline texture of the textured layer is sufficiently low to allow growth of high quality hexagonal material, but can still be significantly greater than the required in-plane crystalline texture of the hexagonal material. The IBAD process enables low-cost, large-area, flexible metal foil substrates to be used as potential alternatives to single-crystal sapphire and silicon for manufacture of electronic devices, enabling scaled-up roll-to-roll, sheet-to-sheet, or similar fabrication processes to be used. The user is able to choose a substrate for its mechanical and thermal properties, such as how well its coefficient of thermal expansion matches that of the hexagonal epitaxial layer, while choosing a textured layer that more closely lattice matches that layer.

  13. Extraordinary epitaxial alignment of graphene islands on Au(111)

    International Nuclear Information System (INIS)

    Wofford, Joseph M; Dubon, Oscar D; Starodub, Elena; Nie Shu; Bartelt, Norman C; Thürmer, Konrad; McCarty, Kevin F; Walter, Andrew L; Bostwick, Aaron; Rotenberg, Eli

    2012-01-01

    Pristine, single-crystalline graphene displays a unique collection of remarkable electronic properties that arise from its two-dimensional, honeycomb structure. Using in situ low-energy electron microscopy, we show that when deposited on the (111) surface of Au carbon forms such a structure. The resulting monolayer, epitaxial film is formed by the coalescence of dendritic graphene islands that nucleate at a high density. Over 95% of these islands can be identically aligned with respect to each other and to the Au substrate. Remarkably, the dominant island orientation is not the better lattice-matched 30° rotated orientation but instead one in which the graphene [01] and Au [011] in-plane directions are parallel. The epitaxial graphene film is only weakly coupled to the Au surface, which maintains its reconstruction under the slightly p-type doped graphene. The linear electronic dispersion characteristic of free-standing graphene is retained regardless of orientation. That a weakly interacting, non-lattice matched substrate is able to lock graphene into a particular orientation is surprising. This ability, however, makes Au(111) a promising substrate for the growth of single crystalline graphene films. (paper)

  14. Solid phase epitaxy of amorphous silicon carbide: Ion fluence dependence

    International Nuclear Information System (INIS)

    Bae, I.-T.; Ishimaru, Manabu; Hirotsu, Yoshihiko; Sickafus, Kurt E.

    2004-01-01

    We have investigated the effect of radiation damage and impurity concentration on solid phase epitaxial growth of amorphous silicon carbide (SiC) as well as microstructures of recrystallized layer using transmission electron microscopy. Single crystals of 6H-SiC with (0001) orientation were irradiated with 150 keV Xe ions to fluences of 10 15 and 10 16 /cm 2 , followed by annealing at 890 deg. C. Full epitaxial recrystallization took place in a specimen implanted with 10 15 Xe ions, while retardation of recrystallization was observed in a specimen implanted with 10 16 /cm 2 Xe ions. Atomic pair-distribution function analyses and energy dispersive x-ray spectroscopy results suggested that the retardation of recrystallization of the 10 16 Xe/cm 2 implanted sample is attributed to the difference in amorphous structures between the 10 15 and 10 16 Xe/cm 2 implanted samples, i.e., more chemically disordered atomistic structure and higher Xe impurity concentration in the 10 16 Xe/cm 2 implanted sample

  15. Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren; Ndione, Paul; Ginley, David; Persson, Kristin A.

    2016-05-25

    With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO2 compounds which provides a rich chemical and structural polymorph space. We find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO2 substrates, where the VO2 brookite phase would be preferentially grown on the a-c TiO2 brookite plane while the columbite and anatase structures favor the a-b plane on the respective TiO2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. These criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.

  16. Rutherford Backscattering and Channeling Studies of Al and Mg Diffusion in Iron Oxide Thin Films

    International Nuclear Information System (INIS)

    Thevuthasan, Theva; McCready, David E.; Jiang, Weilin; Mcdaniel, Emily P.; Yi, Sang I.; Chambers, Scott A.; J.L. Duggan and I.L. Morgan

    1999-01-01

    Thin films of alpha-Fe2O3(0001) (hermatite) and gamma-Fe2O3 (001) (maghemite) were epitaxially grown on Al2O3(0001) substrates, respectively, using the new molecular beam epitaxy (MBE) system at the Environmental Molecular Sciences Laboratory (EMSL). We have investigated the crystalline quality of these films using Rutherford Backscattering (RBS) and channeling experiments. Minimum yields obtained from aligned and random spectra are 2.7+-0.3% for the alpha-Fe2o3(0001) film and 14.5+-0.6% for the gamma-Fe2O3 (001) film. Al and Mg outdiffusion into the hematite and maghemite films were observed at higher temperatures. Indiffusion of Fe atoms from the film into the substrate was observed for the gamma-Fe2o3(001)/MgO(001) system. In contrast, no Fe indiffusion was observed for the sapphire substrate

  17. Anatase thin film with diverse epitaxial relationship grown on yttrium stabilized zirconia substrate by chemical vapor deposition

    International Nuclear Information System (INIS)

    Miyagi, Takahira; Ogawa, Tomoyuki; Kamei, Masayuki; Wada, Yoshiki; Mitsuhashi, Takefumi; Yamazaki, Atsushi

    2003-01-01

    An anatase epitaxial thin film with diverse epitaxial relationship, YSZ (001) // anatase (001), YSZ (010) // anatase (110), was grown on a single crystalline yttrium stabilized zirconia (YSZ) (001) substrate by metal organic chemical vapor deposition (MOCVD). The full width at half maximum (FWHM) of the (004) reflection of this anatase epitaxial film was 0.4deg, and the photoluminescence of this anatase epitaxial film showed visible emission with broad spectral width and large Stokes shift at room temperature. These results indicate that this anatase epitaxial film possessed almost equal crystalline quality compared with that grown under identical growth conditions on single crystalline SrTiO 3 substrate. (author)

  18. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Shlomo Shamai (Shitz

    2009-01-01

    Full Text Available This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom (s.d.o.f. are derived for the degraded case with one receiver. Schemes to achieve the s.d.o.f. for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable s.d.o.f. is given for the general case.

  19. Compound Wiretap Channels

    Directory of Open Access Journals (Sweden)

    Kramer Gerhard

    2009-01-01

    Full Text Available Abstract This paper considers the compound wiretap channel, which generalizes Wyner's wiretap model to allow the channels to the (legitimate receiver and to the eavesdropper to take a number of possible states. No matter which states occur, the transmitter guarantees that the receiver decodes its message and that the eavesdropper is kept in full ignorance about the message. The compound wiretap channel can also be viewed as a multicast channel with multiple eavesdroppers, in which the transmitter sends information to all receivers and keeps the information secret from all eavesdroppers. For the discrete memoryless channel, lower and upper bounds on the secrecy capacity are derived. The secrecy capacity is established for the degraded channel and the semideterministic channel with one receiver. The parallel Gaussian channel is further studied. The secrecy capacity and the secrecy degree of freedom ( are derived for the degraded case with one receiver. Schemes to achieve the for the case with two receivers and two eavesdroppers are constructed to demonstrate the necessity of a prefix channel in encoder design. Finally, the multi-antenna (i.e., MIMO compound wiretap channel is studied. The secrecy capacity is established for the degraded case and an achievable is given for the general case.

  20. ATP Release Channels

    Directory of Open Access Journals (Sweden)

    Akiyuki Taruno

    2018-03-01

    Full Text Available Adenosine triphosphate (ATP has been well established as an important extracellular ligand of autocrine signaling, intercellular communication, and neurotransmission with numerous physiological and pathophysiological roles. In addition to the classical exocytosis, non-vesicular mechanisms of cellular ATP release have been demonstrated in many cell types. Although large and negatively charged ATP molecules cannot diffuse across the lipid bilayer of the plasma membrane, conductive ATP release from the cytosol into the extracellular space is possible through ATP-permeable channels. Such channels must possess two minimum qualifications for ATP permeation: anion permeability and a large ion-conducting pore. Currently, five groups of channels are acknowledged as ATP-release channels: connexin hemichannels, pannexin 1, calcium homeostasis modulator 1 (CALHM1, volume-regulated anion channels (VRACs, also known as volume-sensitive outwardly rectifying (VSOR anion channels, and maxi-anion channels (MACs. Recently, major breakthroughs have been made in the field by molecular identification of CALHM1 as the action potential-dependent ATP-release channel in taste bud cells, LRRC8s as components of VRACs, and SLCO2A1 as a core subunit of MACs. Here, the function and physiological roles of these five groups of ATP-release channels are summarized, along with a discussion on the future implications of understanding these channels.

  1. Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz

    Directory of Open Access Journals (Sweden)

    Haibing Yang

    2007-05-01

    Full Text Available Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a K-factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS and non-LOS (NLOS channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas.

  2. Channel Characteristics and Transmission Performance for Various Channel Configurations at 60 GHz

    Directory of Open Access Journals (Sweden)

    Yang Haibing

    2007-01-01

    Full Text Available Extensive measurements are conducted in room environments at 60 GHz to analyze the channel characteristics for various channel configurations. Channel parameters retrieved from measurements are presented and analyzed based on generic channel models. Particularly, a simple single-cluster model is applied for the parameter retrieval and performance evaluation. By this model, power delay profiles are simply described by a -factor, a root-mean-squared delay spread, and a shape parameter. The considered channels are configured with the combination of omnidirectional, fan-beam, and pencil-beam antennas at transmitter and receiver sides. Both line-of-sight (LOS and non-LOS (NLOS channels are considered. Further, to evaluate the transmission performance, we analyze the link budget in the considered environments, then design and simulate an OFDM system with a data rate of 2 Gbps to compare the bit-error-rate (BER performance by using the measured and modeled channels. Both coded and uncoded OFDM systems are simulated. It is observed that the BER performance agrees well for the measured and modeled channels. In addition, directive configurations can provide sufficient link margins and BER performance for high data rate communications. To increase the coverage and performance in the NLOS area, it is preferable to apply directive antennas.

  3. Electrical, optical, and structural properties of GaN films prepared by hydride vapor phase epitaxy

    International Nuclear Information System (INIS)

    Polyakov, A.Y.; Smirnov, N.B.; Yakimov, E.B.; Usikov, A.S.; Helava, H.; Shcherbachev, K.D.; Govorkov, A.V.; Makarov, Yu N.; Lee, In-Hwan

    2014-01-01

    Highlights: • GaN films are prepared by hydride vapor phase epitaxy (HVPE). • Residual donors and deep traps show a minimum density versus growth temperature. • This minimum is located close to the HVPE growth temperature of 950 °C. • Good crystalline GaN with residual donor density < 10 16 cm −3 can be grown at 950 °C. - Abstract: Two sets of undoped GaN films with the thickness of 10–20 μm were prepared by hydride vapor phase epitaxy (HVPE) and characterized by capacitance–voltage (C–V) profiling, microcathodoluminescence (MCL) spectra measurements, MCL imaging, electron beam induced current (EBIC) imaging, EBIC dependence on accelerating voltage, deep levels transient spectroscopy, high resolution X-ray diffraction measurements. The difference in growth conditions was mainly related to the lower (850 °C, group 1) or higher (950 °C, group 2) growth temperature. Both groups of samples showed similar crystalline quality with the dislocation density close to 10 8 cm −2 , but very different electrical and optical properties. In group 1 samples the residual donors concentration was ∼10 17 cm −3 or higher, the MCL spectra were dominated by the band-edge luminescence, and the diffusion length of charge carriers was close to 0.1 μm. Group 2 samples had a 2–4.5 μm thick highly resistive layer on top, for which MCL spectra were determined by green, yellow and red defect bands, and the diffusion length was 1.5 times higher than in group 1. We also present brief results of growth at the “standard” HVPE growth temperature of 1050 °C that show the presence of a minimum in the net donor concentration and deep traps density as a function of the growth temperature. Possible reasons for the observed results are discussed in terms of the electrical compensation of residual donors by deep traps

  4. Bromine doping of CdTe and CdMnTe epitaxial layers grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Waag, A. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Scholl, S. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Schierstedt, K. von (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Hommel, D. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Landwehr, G. (Physikalisches Inst. der Univ. Wuerzburg (Germany)); Bilger, G. (Zentrum fuer Sonnenenergie und Wasserstoff-Forschung, Stuttgart (Germany))

    1993-03-01

    We report on the n-type doping of CdTe and CdMnTe with bormine as a novel dopant material. /the thin films were grown by molecular beam epitaxy. ZnBr[sub 2] was used as a source material for the n-type doping. Free carrier concentrations at room temperature of up to 2.8x10[sup 18] cm[sup -3] could be readily obtained for both CdTe as well as CdMnTe thin films with Mn concentrations below 10%. This is to our knowledge the highest value ever obtained for the dilute magnetic semiconductor CdMnTe. For ZnBr[sub 2] source temperatures up to 60 C - corresponding to a free carrier concentration of (2-3)x10[sup 18] cm[sup -3] - the free carrier concentration of the epitaxial film increases with ZnBr[sub 2] source temperature. For higher ZnBr[sub 2] source temperatures compensation becomes dominant, which is indicated by a steep decrease of the free carrier concentration with increasing ZnBr[sub 2] source temperature. In addition the carrier mobility decreases drastically for such high dopant fluxes. A model of bromine incorporation is proposed. (orig.)

  5. Epitaxial growth and characterization of CuGa2O4 films by laser molecular beam epitaxy

    Directory of Open Access Journals (Sweden)

    Hongling Wei

    2017-11-01

    Full Text Available Ga2O3 with a wide bandgap of ∼ 4.9 eV can crystalize in five crystalline phases. Among those phases, the most stable monoclinic β-Ga2O3 has been studied most, however, it is hard to find materials lattice matching with β-Ga2O3 to grown epitaxial thin films for optoelectronic applications. In this work, CuGa2O4 bulk were prepared by solid state reaction as target, and the films were deposited on sapphire substrates by laser molecular beam epitaxy (L-MBE at different substrate temperatures. The influences of substrate temperature on structural and optical properties have been systematically investigated by means of X-ray diffraction, Transmission electron microscope and UV-vis absorption spectra. High quality cubic structure and [111] oriented CuGa2O4 film can be obtained at substrate temperature of 750 °C. It’s also demonstrated that the CuGa2O4 film has a bandgap of ∼ 4.4 eV and a best crystal quality at 750 °C, suggesting that CuGa2O4 film is a promising candidate for applications in ultraviolet optoelectronic devices.

  6. Volume Regulated Channels

    DEFF Research Database (Denmark)

    Klausen, Thomas Kjær

    of volume perturbations evolution have developed system of channels and transporters to tightly control volume homeostasis. In the past decades evidence has been mounting, that the importance of these volume regulated channels and transporters are not restricted to the defense of cellular volume...... but are also essential for a number of physiological processes such as proliferation, controlled cell death, migration and endocrinology. The thesis have been focusing on two Channels, namely the swelling activated Cl- channel (ICl, swell) and the transient receptor potential Vanilloid (TRPV4) channel. I: Cl......- serves a multitude of functions in the mammalian cell, regulating the membrane potential (Em), cell volume, protein activity and the driving force for facilitated transporters giving Cl- and Cl- channels a major potential of regulating cellular function. These functions include control of the cell cycle...

  7. Karolinske psychodynamic profile (KAPP)

    DEFF Research Database (Denmark)

    Mathiesen, Birgit Bork; Søgaard, Ulf

    2006-01-01

    psykologiske testmetoder, assesment, Karolinska psychodynamic profile (KAPP), psykodynamisk profil......psykologiske testmetoder, assesment, Karolinska psychodynamic profile (KAPP), psykodynamisk profil...

  8. Preparation and Characterization of Epitaxial VO2 Films on Sapphire Using Postepitaxial Topotaxy Route via Epitaxial V2O3 Films

    Science.gov (United States)

    Yamaguchi, Iwao; Manabe, Takaaki; Tsuchiya, Tetsuo; Nakajima, Tomohiko; Sohma, Mitsugu; Kumagai, Toshiya

    2008-02-01

    Epitaxial VO2 films were prepared on the C-planes of α-Al2O3 substrates by a metal organic deposition (MOD) process. It was difficult to obtain the single phase of (010)M-oriented VO2 films, in which the subscript M refers to the monoclinic indices, by the heat treatment of amorphous precursor films in the VO2-stable region after the pyrolysis of the coating solution. The product films consisted of discontinuous circular grains of 1-2 µm size on the substrate surface. Therefore, we prepared the (010)M-oriented epitaxial VO2 films using postepitaxial topotaxy (PET), that is, topotactic oxidation of (0001)-oriented epitaxial V2O3 films. First, epitaxial V2O3(0001) films were obtained by MOD starting with a vanadium naphthenate solution. Second, the epitaxial V2O3(0001) films were topotactically oxidized at 500 °C in an Ar-O2 gas mixture with pO2 = 10-4 atm to obtain (010)M-oriented epitaxial VO2 films. The epitaxial relationships were VO2(010)M ∥ α-Al2O3(0001) and VO2[100]M ∥ α-Al2O3[0110], [1010], [1100]. The VO2(010)M films exhibited metal-semiconductor transitions with hysteresis loops at 60-80 °C. The resistivity change before and after the transition of the VO2(010)M film oxidized for 6 h was three orders of magnitude.

  9. In Situ Observation of Oxygen Vacancy Dynamics and Ordering in the Epitaxial LaCoO3 System.

    Science.gov (United States)

    Jang, Jae Hyuck; Kim, Young-Min; He, Qian; Mishra, Rohan; Qiao, Liang; Biegalski, Michael D; Lupini, Andrew R; Pantelides, Sokrates T; Pennycook, Stephen J; Kalinin, Sergei V; Borisevich, Albina Y

    2017-07-25

    Vacancy dynamics and ordering underpin the electrochemical functionality of complex oxides and strongly couple to their physical properties. In the field of the epitaxial thin films, where connection between chemistry and film properties can be most clearly revealed, the effects related to oxygen vacancies are attracting increasing attention. In this article, we report a direct, real-time, atomic level observation of the formation of oxygen vacancies in the epitaxial LaCoO 3 thin films and heterostructures under the influence of the electron beam utilizing scanning transmission electron microscopy (STEM). In the case of LaCoO 3 /SrTiO 3 superlattice, the formation of the oxygen vacancies is shown to produce quantifiable changes in the interatomic distances, as well as qualitative changes in the symmetry of the Co sites manifested as off-center displacements. The onset of these changes was observed in both the [100] pc and [110] pc orientations in real time. Additionally, annular bright field images directly show the formation of oxygen vacancy channels along [110]pc direction. In the case of 15 u.c. LaCoO 3 thin film, we observe the sequence of events during beam-induced formation of oxygen vacancy ordered phases and find them consistent with similar processes in the bulk. Moreover, we record the dynamics of the nucleation, growth, and defect interaction at the atomic scale as these transformations happen. These results demonstrate that we can track dynamic oxygen vacancy behavior with STEM, generating atomic-level quantitative information on phase transformation and oxygen diffusion.

  10. HIPPI and Fibre Channel

    International Nuclear Information System (INIS)

    Tolmie, D.E.

    1992-01-01

    The High-Performance Parallel Interface (HIPPI) and Fibre Channel are near-gigabit per second data communications interfaces being developed in ANSI standards Task Group X3T9.3. HIPPI is the current interface of choice in the high-end and supercomputer arena, and Fibre Channel is a follow-on effort. HIPPI came from a local area network background, and Fibre Channel came from a mainframe to peripheral interface background

  11. Nuclear reactor coolant channels

    International Nuclear Information System (INIS)

    Macbeth, R.V.

    1978-01-01

    Reference is made to coolant channels for pressurised water and boiling water reactors and the arrangement described aims to improve heat transfer between the fuel rods and the coolant. Baffle means extending axially within the channel are provided and disposed relative to the fuel rods so as to restrict flow oscillations occurring within the coolant from being propagated transversely to the axis of the channel. (UK)

  12. Conductance of Ion Channels - Theory vs. Experiment

    Science.gov (United States)

    Pohorille, Andrew; Wilson, Michael; Mijajlovic, Milan

    2013-01-01

    Transmembrane ion channels mediate a number of essential physiological processes in a cell ranging from regulating osmotic pressure to transmission of neural signals. Kinetics and selectivity of ion transport is of critical importance to a cell and, not surprisingly, it is a subject of numerous experimental and theoretical studies. In this presentation we will analyze in detail computer simulations of two simple channels from fungi - antiamoebin and trichotoxin. Each of these channels is made of an alpha-helical bundle of small, nongenomically synthesized peptides containing a number of rare amino acids and exhibits strong antimicrobial activity. We will focus on calculating ionic conductance defined as the ratio of ionic current through the channel to applied voltage. From molecular dynamics simulations, conductance can be calculated in at least two ways, each involving different approximations. Specifically, the current, given as the number of charges transferred through the channel per unit of time, can be obtained from the number of events in which ions cross the channel during the simulation. This method works well for large currents (high conductance values and/or applied voltages). If the number of crossing events is small, reliable estimates of current are difficult to achieve. Alternatively, conductance can be estimated assuming that ion transport can be well approximated as diffusion in the external potential given by the free energy profile. Then, the current can be calculated by solving the one-dimensional diffusion equation in this external potential and applied voltage (the generalized Nernst-Planck equation). To do so three ingredients are needed: the free energy profile, the position-dependent diffusion coefficient and the diffusive flux of ions into the channel. All these quantities can be obtained from molecular dynamics simulations. An important advantage of this method is that it can be used equally well to estimating large and small currents

  13. New Channels, New Possibilities

    DEFF Research Database (Denmark)

    Pieterson, Willem; Ebbers, Wolfgang; Østergaard Madsen, Christian

    2017-01-01

    In this contribution we discuss the characteristics of what we call the fourth generation of public sector service channels: social robots. Based on a review of relevant literature we discuss their characteristics and place into multi-channel models of service delivery. We argue that social robots......-channel models of service delivery. This is especially relevant given the current lack of evaluations of such models, the broad range of channels available, and their different stages of deployment at governments around the world. Nevertheless, social robots offer an potentially very relevant addition...

  14. Calcium Channel Blockers

    Science.gov (United States)

    ... Certain calcium channel blockers interact with grapefruit products. Kaplan NM, et al. Treatment of hypertension: Drug therapy. In: Kaplan's Clinical Hypertension. 11th ed. Philadelphia, Pa.: Wolters Kluwer ...

  15. Top-gate dielectric induced doping and scattering of charge carriers in epitaxial graphene

    Science.gov (United States)

    Puls, Conor P.; Staley, Neal E.; Moon, Jeong-Sun; Robinson, Joshua A.; Campbell, Paul M.; Tedesco, Joseph L.; Myers-Ward, Rachael L.; Eddy, Charles R.; Gaskill, D. Kurt; Liu, Ying

    2011-07-01

    We show that an e-gun deposited dielectric impose severe limits on epitaxial graphene-based device performance based on Raman spectroscopy and low-temperature transport measurements. Specifically, we show from studies of epitaxial graphene Hall bars covered by SiO2 that the measured carrier density is strongly inhomogenous and predominantly induced by charged impurities at the grapheme/dielectric interface that limit mobility via Coulomb interactions. Our work emphasizes that material integration of epitaxial graphene and a gate dielectric is the next major road block towards the realization of graphene-based electronics.

  16. Epitaxial YBa2Cu3O7-δ/Sr2RuO4 heterostructures

    International Nuclear Information System (INIS)

    Schlom, D.G.; Merritt, B.A.; Madhavan, S.

    1997-01-01

    The anisotropic oxide superconductors YBa 2 Cu 3 O 7-δ and Sr 2 RuO 4 have been epitaxially combined in various ways (c-axis on c-axis, c-axis on a-axis, and a-axis on a-axis) though the use of appropriate substrates. Phase-pure a-axis oriented or c-axis oriented epitaxial Sr 2 RuO 4 films were grown by pulsed laser deposition. YBa 2 Cu 3 O 7-δ films were then grown on both orientations of Sr 2 RuO 4 films and the resulting epitaxy was characterized

  17. Use of epitaxial silicon diodes in photon dosimetry

    International Nuclear Information System (INIS)

    Pereira, Lilian Nunes

    2013-01-01

    In this work we report on results obtained with two rad-hard epitaxial (EPI) silicon diodes as on-line dosimeter for diagnostic radiology, mammography and computed tomography, in the 28 kV to 150 kV range. The epitaxial diodes used were processed at University of Hamburg on 50 μm thick epitaxial silicon layer. One sample was not irradiated before using as a dosimeter, while the other received a gamma pre-dose of 200kGy from 60 Co. For comparison, a standard float zone silicon diode was also studied. The samples irradiation was performed using X-ray beams from a Pantak/Seifert generator, model Isovolt 160 HS, previously calibrated with standardized ionization chambers, located at Laboratorio de Calibracao de Instrumentos of IPEN-CNEN/SP. The diode was connected to an electrometer Keithley 6517B in the photovoltaic mode. Irradiations were carried out with the diodes positioned at lm from the X-ray tube (focal spot). The main dosimetric parameters of the EPI samples were evaluated in according to IEC 61674 norm. The calibration coefficients of the diode, in terms of air kerma, were also determined. The repeatability was measured with photon beams of all qualities. The current signals induced showed the diodes are stable, characterized by coefficients of variation less than 0.3%. The current response of the unirradiated EPI diode has been shown to be very linear with dose-rate in the range of 0.8 up to 77.2 mGy/min. A linear relation between charge and dose in the whole energy range was observed for the three samples. It is important to notice that for EPI diodes non energy dependence was observed for mammography beams and until 70kV for radiodiagnostic qualities. The unirradiated diode presented sensitivity higher than the others, showing a decrease of 8% in this parameter after accumulated dose of 49.15 Gy. The dark currents were stable about 0.4 pA during the irradiations, value 10 4 higher than the lowest photocurrents measured. The directional response of both

  18. Evaporative Lithography in Open Microfluidic Channel Networks

    KAUST Repository

    Lone, Saifullah

    2017-02-24

    We demonstrate a direct capillary-driven method based on wetting and evaporation of various suspensions to fabricate regular two-dimensional wires in an open microfluidic channel through continuous deposition of micro- or nanoparticles under evaporative lithography, akin to the coffee-ring effect. The suspension is gently placed in a loading reservoir connected to the main open microchannel groove on a PDMS substrate. Hydrophilic conditions ensure rapid spreading of the suspension from the loading reservoir to fill the entire channel length. Evaporation during the spreading and after the channel is full increases the particle concentration toward the end of the channel. This evaporation-induced convective transport brings particles from the loading reservoir toward the channel end where this flow deposits a continuous multilayered particle structure. The particle deposition front propagates backward over the entire channel length. The final dry deposit of the particles is thereby much thicker than the initial volume fraction of the suspension. The deposition depth is characterized using a 3D imaging profiler, whereas the deposition topography is revealed using a scanning electron microscope. The patterning technology described here is robust and passive and hence operates without an external field. This work may well become a launching pad to construct low-cost and large-scale thin optoelectronic films with variable thicknesses and interspacing distances.

  19. CFD analyses of coolant channel flowfields

    Science.gov (United States)

    Yagley, Jennifer A.; Feng, Jinzhang; Merkle, Charles L.

    1993-01-01

    The flowfield characteristics in rocket engine coolant channels are analyzed by means of a numerical model. The channels are characterized by large length to diameter ratios, high Reynolds numbers, and asymmetrical heating. At representative flow conditions, the channel length is approximately twice the hydraulic entrance length so that fully developed conditions would be reached for a constant property fluid. For the supercritical hydrogen that is used as the coolant, the strong property variations create significant secondary flows in the cross-plane which have a major influence on the flow and the resulting heat transfer. Comparison of constant and variable property solutions show substantial differences. In addition, the property variations prevent fully developed flow. The density variation accelerates the fluid in the channels increasing the pressure drop without an accompanying increase in heat flux. Analyses of the inlet configuration suggest that side entry from a manifold can affect the development of the velocity profile because of vortices generated as the flow enters the channel. Current work is focused on studying the effects of channel bifurcation on the flow field and the heat transfer characteristics.

  20. A linearization of quantum channels

    Science.gov (United States)

    Crowder, Tanner

    2015-06-01

    Because the quantum channels form a compact, convex set, we can express any quantum channel as a convex combination of extremal channels. We give a Euclidean representation for the channels whose inverses are also valid channels; these are a subset of the extreme points. They form a compact, connected Lie group, and we calculate its Lie algebra. Lastly, we calculate a maximal torus for the group and provide a constructive approach to decomposing any invertible channel into a product of elementary channels.

  1. A high resolution cross section transmission electron microscopy study of epitaxial rare earth fluoride/GaAs(111) interfaces prepared by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Chien, C.J.; Bravman, J.C.

    1990-01-01

    The authors report the HRXTEM study of epitaxial rare earth fluoride/GaAs(111) interfaces. Such interfaces are of interest because they are the starting point for growth of buried epitaxial rare earth/rare earth fluoride sandwich structures which exhibit interesting and non bulk-like magnetic properties. Also, the optical transitions in ultrathin epitaxial NdF 3 films may be influenced by strain and defects in the NdF 3 film and the nature of the interface to GaAs. The authors find that the rare earth fluoride/GaAs interfaces are semi-coherent but chemically abrupt with the transition taking place within 3 Angstrom. However, the interface is physically rough and multiple monolayer steps in the GaAs surface tend to tilt boundaries in the fluoride. The origin of these steps is believed to be thermal etching of the GaAs during the heat- cleaning stage prior to epitaxy. The surface of the fluoride film is much smoother than the initial GaAs surface indicating planarization during epitaxy

  2. Electronic cooling via interlayer Coulomb coupling in multilayer epitaxial graphene

    Science.gov (United States)

    Mihnev, Momchil T.; Tolsma, John R.; Divin, Charles J.; Sun, Dong; Asgari, Reza; Polini, Marco; Berger, Claire; de Heer, Walt A.; MacDonald, Allan H.; Norris, Theodore B.

    2015-01-01

    In van der Waals bonded or rotationally disordered multilayer stacks of two-dimensional (2D) materials, the electronic states remain tightly confined within individual 2D layers. As a result, electron–phonon interactions occur primarily within layers and interlayer electrical conductivities are low. In addition, strong covalent in-plane intralayer bonding combined with weak van der Waals interlayer bonding results in weak phonon-mediated thermal coupling between the layers. We demonstrate here, however, that Coulomb interactions between electrons in different layers of multilayer epitaxial graphene provide an important mechanism for interlayer thermal transport, even though all electronic states are strongly confined within individual 2D layers. This effect is manifested in the relaxation dynamics of hot carriers in ultrafast time-resolved terahertz spectroscopy. We develop a theory of interlayer Coulomb coupling containing no free parameters that accounts for the experimentally observed trends in hot-carrier dynamics as temperature and the number of layers is varied. PMID:26399955

  3. Molecular beam epitaxy of LiMnAs

    Czech Academy of Sciences Publication Activity Database

    Novák, Vít; Cukr, Miroslav; Šobáň, Zbyněk; Jungwirth, Tomáš; Martí, X.; Holý, V.; Horodyská, P.; Němec, P.

    2011-01-01

    Roč. 323, č. 1 (2011), s. 348-350 ISSN 0022-0248 R&D Projects: GA MŠk LC510; GA AV ČR KAN400100652; GA MŠk(CZ) 7E08087 EU Projects: European Commission(XE) 215368 - SemiSpinNet; European Commission(XE) 214499 - NAMASTE Grant - others:AV ČR(CZ) AP0801 Program:Akademická prémie - Praemium Academiae Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : crystal structure * molecular beam epitaxy * lithium compounds * magnetic semiconductors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.726, year: 2011

  4. Epitaxial growth of Cu on Cu(001): Experiments and simulations

    International Nuclear Information System (INIS)

    Furman, Itay; Biham, Ofer; Zuo, Jiang-Kai; Swan, Anna K.; Wendelken, John

    2000-01-01

    A quantitative comparison between experimental and Monte Carlo simulation results for the epitaxial growth of Cu/Cu(001) in the submonolayer regime is presented. The simulations take into account a complete set of hopping processes whose activation energies are derived from semiempirical calculations using the embedded-atom method. The island separation is measured as a function of the incoming flux and the temperature. A good quantitative agreement between the experiment and simulation is found for the island separation, the activation energies for the dominant processes, and the exponents that characterize the growth. The simulation results are then analyzed at lower coverages, which are not accessible experimentally, providing good agreement with theoretical predictions as well

  5. Magnetic x-ray dichroism in ultrathin epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Cummins, T.R. [Univ. of Missouri, Rolla, MO (United States)] [and others

    1997-04-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.

  6. Spin Filtering in Epitaxial Spinel Films with Nanoscale Phase Separation

    KAUST Repository

    Li, Peng

    2017-05-08

    The coexistence of ferromagnetic metallic phase and antiferromagnetic insulating phase in nanoscaled inhomogeneous perovskite oxides accounts for the colossal magnetoresistance. Although the model of spin-polarized electron transport across antiphase boundaries has been commonly employed to account for large magnetoresistance (MR) in ferrites, the magnetic anomalies, the two magnetic phases and enhanced molecular moment, are still unresolved. We observed a sizable MR in epitaxial spinel films (NiCo2O4-δ) that is much larger than that commonly observed in spinel ferrites. Detailed analysis reveals that this MR can be attributed to phase separation, in which the perfect ferrimagnetic metallic phase and ferrimagnetic insulating phase coexist. The magnetic insulating phase plays an important role in spin filtering in these phase separated spinel oxides, leading to a sizable MR effect. A spin filtering model based on Zeeman effect and direct tunneling is developed to account for MR of the phase separated films.

  7. Self-consistent expansion for the molecular beam epitaxy equation.

    Science.gov (United States)

    Katzav, Eytan

    2002-03-01

    Motivated by a controversy over the correct results derived from the dynamic renormalization group (DRG) analysis of the nonlinear molecular beam epitaxy (MBE) equation, a self-consistent expansion for the nonlinear MBE theory is considered. The scaling exponents are obtained for spatially correlated noise of the general form D(r-r('),t-t('))=2D(0)[r-->-r(')](2rho-d)delta(t-t(')). I find a lower critical dimension d(c)(rho)=4+2rho, above which the linear MBE solution appears. Below the lower critical dimension a rho-dependent strong-coupling solution is found. These results help to resolve the controversy over the correct exponents that describe nonlinear MBE, using a reliable method that proved itself in the past by giving reasonable results for the strong-coupling regime of the Kardar-Parisi-Zhang system (for d>1), where DRG failed to do so.

  8. In situ observation of stress relaxation in epitaxial graphene

    International Nuclear Information System (INIS)

    N'Diaye, Alpha T; Coraux, Johann; Busse, Carsten; Michely, Thomas; Gastel, Raoul van; Poelsema, Bene; MartInez-Galera, Antonio J; Gomez-RodrIguez, Jose M; Hattab, Hichem; Wall, Dirk; Heringdorf, Frank-J Meyer zu; Hoegen, Michael Horn-von

    2009-01-01

    Upon cooling, branched line defects develop in epitaxial graphene grown at high temperature on Pt(111) and Ir(111). Using atomically resolved scanning tunneling microscopy, we demonstrate that these defects are wrinkles in the graphene layer, i.e. stripes of partially delaminated graphene. With low energy electron microscopy (LEEM), we investigate the wrinkling phenomenon in situ. Upon temperature cycling, we observe hysteresis in the appearance and disappearance of the wrinkles. Simultaneously with wrinkle formation a change in bright field imaging intensity of adjacent areas and a shift in the moire spot positions for micro diffraction of such areas takes place. The stress relieved by wrinkle formation results from the mismatch in thermal expansion coefficients of graphene and the substrate. A simple one-dimensional model taking into account the energies related to strain, delamination and bending of graphene is in qualitative agreement with our observations.

  9. Chemically stabilized epitaxial wurtzite-BN thin film

    Science.gov (United States)

    Vishal, Badri; Singh, Rajendra; Chaturvedi, Abhishek; Sharma, Ankit; Sreedhara, M. B.; Sahu, Rajib; Bhat, Usha; Ramamurty, Upadrasta; Datta, Ranjan

    2018-03-01

    We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

  10. Study of epitaxial YBa2Cu3Ox films

    International Nuclear Information System (INIS)

    Lee, S.G.; Chi, C.C.; Koren, G.; Gupta, A.; Segmuller, A.

    1990-01-01

    In this paper, the authors present a systematic study of epitaxial YBa 2 Cu 3 O x films laser ablated on Y-cut LiNbO 3 substrates. X-ray diffraction pattern indicates that the c-axis is perpendicular to the substrate plane and the (110) direction of the film is parallel to the (110) of the substrate with two domains with the (110) as a mirror plane. Resistivity of the film shows a typical metallic behavior in the normal state with a sharp transition at 92K. The effects of oxygen deficiency on the resistivity are also studied. Oxygen content is controlled by annealing the sample either in low oxygen pressure or in vacuum and estimated from the c-axis lattice parameter determined by X-ray diffraction. As oxygen is depleted gradually, the film resistivity shows metallic, semiconducting, and eventually insulating behaviors. Superconducting percolation phenomenon is observed for the semiconducting sample at low temperatures

  11. Resistance switching in epitaxial SrCoOx thin films

    Science.gov (United States)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-08-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO2.5) and conducting perovskite (SrCoO3-δ) depending on the oxygen content. The current-voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoOx thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO2.5.

  12. Resistance switching in epitaxial SrCoOx thin films

    International Nuclear Information System (INIS)

    Tambunan, Octolia T.; Parwanta, Kadek J.; Acharya, Susant K.; Lee, Bo Wha; Jung, Chang Uk; Kim, Yeon Soo; Park, Bae Ho; Jeong, Huiseong; Park, Ji-Yong; Cho, Myung Rae; Park, Yun Daniel; Choi, Woo Seok; Kim, Dong-Wook; Jin, Hyunwoo; Lee, Suyoun; Song, Seul Ji; Kang, Sung-Jin; Kim, Miyoung; Hwang, Cheol Seong

    2014-01-01

    We observed bipolar switching behavior from an epitaxial strontium cobaltite film grown on a SrTiO 3 (001) substrate. The crystal structure of strontium cobaltite has been known to undergo topotactic phase transformation between two distinct phases: insulating brownmillerite (SrCoO 2.5 ) and conducting perovskite (SrCoO 3−δ ) depending on the oxygen content. The current–voltage characteristics of the strontium cobaltite film showed that it could have a reversible insulator-to-metal transition triggered by electrical bias voltage. We propose that the resistance switching in the SrCoO x thin film could be related to the topotactic phase transformation and the peculiar structure of SrCoO 2.5

  13. Coherence in a transmon qubit with epitaxial tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Weides, Martin [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Karlsruhe Institute of Technology (Germany); Kline, Jeffrey; Vissers, Michael; Sandberg, Martin; Pappas, David [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Wisbey, David [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Saint Louis University, St. Louis, Missouri 63103 (United States); Johnson, Blake; Ohki, Thomas [Raytheon BBN Technologies, Cambridge, Massachusetts 02138 (United States)

    2012-07-01

    Transmon qubits based on epitaxial tunnel junctions and interdigitated capacitors were developed. This multileveled qubit, patterned by use of all-optical lithography, is a step towards scalable qubits with a high integration density. The relaxation time T{sub 1} is.72-.86 {mu} sec and the ensemble dephasing time T{sub 2}{sup *} is slightly larger than T{sub 1}. The dephasing time T{sub 2} (1.36 {mu} sec) is nearly energy-relaxation-limited. Qubit spectroscopy yields weaker level splitting than observed in qubits with amorphous barriers in equivalent-size junctions. The qubit's inferred microwave loss closely matches the weighted losses of the individual elements (junction, wiring dielectric, and interdigitated capacitor), determined by independent resonator measurements.

  14. New phenomena in epitaxial growth: solid films on quasicrystalline substrates

    International Nuclear Information System (INIS)

    Fournee, V; Thiel, P A

    2005-01-01

    An overview is given of the research conducted in the field of solid film growth on quasiperiodic surfaces. An atomistic description of quasicrystalline surfaces is presented and discussed in relation to bulk structural models. The various systems for which thin film growth has been attempted so far are reviewed. Emphasis is placed on the nucleation mechanisms of the solid films, on their growth modes in relation to the nature of the deposited metals, on the possibility of intermixing or alloying at the interface and on the epitaxial relationships at the crystal-quasicrystal interfaces. We also describe situations where the deposited elements adopt a quasiperiodic structure, which opens up the possibility of extending our understanding of the relation between quasiperiodicity and the physical properties of such structurally and chemically complex solids. (topical review)

  15. Spin-injection into epitaxial graphene on silicon carbide

    Science.gov (United States)

    Konishi, Keita; Cui, Zhixin; Hiraki, Takahiro; Yoh, Kanji

    2013-09-01

    We have studied the spin-injection properties in epitaxial graphene on SiC. The ferromagnetic metal (FM) electrodes were composed of a tunnel barrier layer AlOx (14 Å) and a ferromagnetic Co (600 Å) layer. We have successfully observed the clear resistance peaks indicating spin-injection both in the "local" and "non-local" spin measurement set-ups at low temperatures. We estimate spin-injection rate of 1% based on "non-local" measurement and 1.6% based on local measurements. Spin-injection rate of multilayer graphene by mechanical exfoliation method was twice as high as single layer graphene on SiC based on "local" measurement.

  16. Magnetic x-ray dichroism in ultrathin epitaxial films

    International Nuclear Information System (INIS)

    Tobin, J.G.; Goodman, K.W.; Cummins, T.R.

    1997-01-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction

  17. Molecular beam epitaxy of single crystal colossal magnetoresistive material

    International Nuclear Information System (INIS)

    Eckstein, J.N.; Bozovic, I.; Rzchowski, M.; O'Donnell, J.; Hinaus, B.; Onellion, M.

    1996-01-01

    The authors have grown films of (LaSr)MnO 3 (LSMO) and (LaCa)MnO 3 (LCMO) using atomic layer-by-layer molecular beam epitaxy (ALL-MBE). Depending on growth conditions, substrate lattice constant and the exact cation stoichiometry, the films are either pseudomorphic or strain relaxed. The pseudomorphic films show atomically flat surfaces, with a unit cell terrace structure that is a replica of that observed on the slightly vicinal substrates, while the strain relaxed films show bumpy surfaces correlated with a dislocation network. All films show tetragonal structure and exhibit anisotropic magnetoresistance, with a low field response, (1/R)(dR/dH) as large as 5 T -1

  18. Equilibrium stability of strained epitaxial layers on a rigid substrate

    International Nuclear Information System (INIS)

    Granato, E.; Kosterlitz, J.M.; Ying, S.C.

    1987-07-01

    A simple theory of the equilibrium stability of an strained epitaxial layer on a rigid substrate is presented. We generalise the Frankvan der Merwe model of a single layer and consider N layers of adsorbate on a substrate. Continuum elasticity theory is used to describe each layer, but the coupling between layers is treated ina discrete fashion. Our method interpolates between a few layers and the thick film limit of standard dislocation theory, and in this limit the standard results are obtained. In addition, we developed a variational approach which agrees well with our exact calculations. The advantage of our method over previous ores is that it allows to perform stability analyses of arbitrary superlattice configurations. (author) [pt

  19. Photoemission electronic states of epitaxially grown magnetite films

    International Nuclear Information System (INIS)

    Zalecki, R.; Kolodziejczyk, A.; Korecki, J.; Spiridis, N.; Zajac, M.; Kozlowski, A.; Kakol, Z.; Antolak, D.

    2007-01-01

    The valence band photoemission spectra of epitaxially grown 300 A single crystalline magnetite films were measured by the angle-resolved ultraviolet photoemission spectroscopy (ARUPS) at 300 K. The samples were grown either on MgO(0 0 1) (B termination) or on (0 0 1) Fe (iron-rich A termination), thus intentionally presenting different surface stoichiometry, i.e. also different surface electronic states. Four main features of the electron photoemission at about -1.0, -3.0, -5.5 and -10.0 eV below a chemical potential show systematic differences for two terminations; this difference depends on the electron outgoing angle. Our studies confirm sensitivity of angle resolved PES technique on subtleties of surface states

  20. Coercive force features in stressed epitaxial ferrite-garnet films

    International Nuclear Information System (INIS)

    Dubinko, S.V.; Nedviga, A.S.; Vishnevskij, V.G.; Shaposhnikov, A.N.; Yagupov, V.S.; Nesteruk, A.G.; Prokopov, A.R.

    2005-01-01

    One has investigated into effect of a relative mismatching of periods of lattices of a film and of a substrate within 0.5-0.85% range on behavior of the coercive force of (Bi, Sm, Lu, Ca) 3 (Fe, Sc, Ga, Al) 5 O 12 composition ferrite garnet epitaxial films (FGEF) synthesized at (111) orientation gadolinium-gallium garnet substrates. One has revealed that the FGEF coercive force at increase of the relative mismatching of periods of lattices of a film and of a substrate increases at first, while when reaching the maximum value it begins to decrease. The coercive force maximum value is shown to result from the periodical localized stresses. The period of the localized stresses is determined by the value of mismatching of periods of lattices of a film and of a substrate [ru

  1. Omni channel fashion shopping

    NARCIS (Netherlands)

    Kemperman, A.D.A.M.; van Delft, L.; Borgers, A.W.J.; Pantano, E.

    2015-01-01

    This chapter gives insight into consumers' online and offline fashion shopping behavior, consumers' omni-channel usage during the shopping process, and consumer fashion shopper segments. Based on a literature review, omni-channel shopping behavior during the shopping process was operationalized.

  2. Transformation behaviour of freestanding epitaxial Ni–Mn–Ga films

    International Nuclear Information System (INIS)

    Yeduru, S.R.; Backen, A.; Fähler, S.; Schultz, L.; Kohl, M.

    2013-01-01

    Highlights: ► The complex martensite microstructure of free-standing epitaxial Ni–Mn–Ga films. ► A two-stage transformation in the temperature range between 40 °C and 160 °C. ► Temperature dependent mechanical properties of free-standing Ni–Mn–Ga films. ► With increasing temperature, the twinning stress decreases due to thermal activation of twin boundaries. ► Large superplastic strain increases from about 10% at 110 °C to 14% at RT. -- Abstract: We analyze the transformation behaviour of a 2 μm thick epitaxial Ni–Mn–Ga film by combining temperature dependent measurements of magnetization, electrical resistance, X-ray diffraction (XRD) and tensile stress–strain characteristics. While the magnetization measurements hint for a simple austenite–martensite transformation below the Curie temperature at about 90 °C, resistivity measurements reveal a two-stage transformation in the temperature regimes (I) of 40–80 °C and (II) of 140–160 °C. XRD and pseudoplastic behaviour prove the presence of martensite well above the Curie point. The combination of four independent methods suggests that the transformation at (II) may originate from a weakly first order transformation followed by an intermartensitic transformation at (I). This interpretation is in line with the large superplastic strain observed for the tensile direction parallel to the [1 0 0] direction of the Ni–Mn–Ga unit cell. The strain increases from about 10% at 110 °C to 14% at room temperature suggesting an increase in tetragonal distortion

  3. Epitaxially Grown Layered MFI–Bulk MFI Hybrid Zeolitic Materials

    KAUST Repository

    Kim, Wun-gwi

    2012-11-27

    The synthesis of hybrid zeolitic materials with complex micropore-mesopore structures and morphologies is an expanding area of recent interest for a number of applications. Here we report a new type of hybrid zeolite material, composed of a layered zeolite material grown epitaxially on the surface of a bulk zeolite material. Specifically, layered (2-D) MFI sheets were grown on the surface of bulk MFI crystals of different sizes (300 nm and 10 μm), thereby resulting in a hybrid material containing a unique morphology of interconnected micropores (∼0.55 nm) and mesopores (∼3 nm). The structure and morphology of this material, referred to as a "bulk MFI-layered MFI" (BMLM) material, was elucidated by a combination of XRD, TEM, HRTEM, SEM, TGA, and N2 physisorption techniques. It is conclusively shown that epitaxial growth of the 2-D layered MFI sheets occurs in at least two principal crystallographic directions of the bulk MFI crystal and possibly in the third direction as well. The BMLM material combines the properties of bulk MFI (micropore network and mechanical support) and 2-D layered MFI (large surface roughness, external surface area, and mesoporosity). As an example of the uses of the BMLM material, it was incorporated into a polyimide and fabricated into a composite membrane with enhanced permeability for CO2 and good CO2/CH4 selectivity for gas separations. SEM-EDX imaging and composition analysis showed that the polyimide and the BMLM interpenetrate into each other, thereby forming a well-adhered polymer/particle microstructure, in contrast with the defective interfacial microstructure obtained using bare MFI particles. Analysis of the gas permeation data with the modified Maxwell model also allows the estimation of the effective volume of the BMLM particles, as well as the CO2 and CH4 gas permeabilities of the interpenetrated layer at the BMLM/polyimide interface. © 2012 American Chemical Society.

  4. Nanoscale abnormal grain growth in (001) epitaxial ceria

    International Nuclear Information System (INIS)

    Solovyov, Vyacheslav F.; Develos-Bagarinao, Katherine; Nykypanchuk, Dmytro

    2009-01-01

    X-ray reciprocal-space mapping and atomic force microscopy (AFM) are used to study kinetics and mechanisms of lateral grain growth in epitaxial (001) ceria (CeO 2 ) deposited by pulsed laser deposition on (001) yttria-stabilized zirconia (YSZ) and (12 lowbar 10) (r-cut) sapphire. Rate and character of the grain growth during postannealing at 1050 deg. C are found to be strongly dependent on the type of the epitaxial substrate. Films deposited on YSZ exhibit signatures of normal grain growth, which stagnated after the lateral grain size reaches 40 nm, consistent with the grain-boundary pinning by the thermal grooving. In contrast, when r-cut sapphire substrate was used, abnormal (secondary) grain growth is observed. A small population of grains grow to well over 100 nm consuming smaller, 100 nm large (001) terminations and rendering the sample single-crystalline quality. The grain growth is accompanied by reduction in lateral rms strain, resulting in a universal grain size--rms strain dependence. Analysis of the AFM and x-ray diffraction data leads to the conclusion that bimodal initial grain population consisting of grains with very different sizes is responsible for initiation of the abnormal growth in (001) CeO 2 films on r-cut sapphire. Due to different surface chemistry, when a YSZ substrate is used, the initial grain distribution is monomodal, therefore only normal growth is active. We demonstrate that a 2.2 deg. miscut of the sapphire substrate eliminates the large-grain population, thus suppressing abnormal grain growth. It is concluded that utilization of abnormal grain growth is a promising way for synthesis of large (001) ceria terminations.

  5. Computer graphic investigation on the epitaxial growth of superconductor films

    International Nuclear Information System (INIS)

    Miyamoto, A.; Iwamoto, S.; Inui, T.; Agusa, K.

    1989-01-01

    A mechanism of the epitaxial growth the oxide superconductor films has been investigated by using the computer graphics for the combination of orthorhombic Ba 2 YCu 3 O 7-x with substrate crystals such as SrTiO 3 MgO, and ZrO 2 . The (001) plane Ba 2 YCu 3 O 7-x with substrate crystals such as SrTiO 3 , MgO, and ZrO 2 . The (001) plane of Ba 2 YCu 3 O 7-x has been shown to fit the (100) plane of SrTiO 3 , MgO, and ZrO 2 . A crystallographic fit has also been proved between the (110) plane of Ba 2 YCu 3 O 7-x and the (110) plane of SrTiO 3 . These results are consistent with the experimental data about the epitaxial growth of the Ba 2 YCu 3 O 7-x films. Furthermore, detailed investigation of atomic arrangements has indicated some differences in the ionic interaction at the superconductor-substrate interface among SrTiO 3 , MgO, and ZrO 2 substrates. As for ZrO 2 (100) plane, for examples, ionic arrangements at the oxide layer is favorable only for the interaction with Y 3+ layer of Ba 2 YCu 3 O 7-x , while the Zr-O layer of ZrO 2 can interact with both Ba-O layer and Cu-O layer of Ba 2 YCu 3 O 7-x

  6. Channel electron multipliers

    International Nuclear Information System (INIS)

    Seidman, A.; Avrahami, Z.; Sheinfux, B.; Grinberg, J.

    1976-01-01

    A channel electron multiplier is described having a tubular wall coated with a secondary-electron emitting material and including an electric field for accelerating the electrons, the electric field comprising a plurality of low-resistive conductive rings each alternating with a high-resistive insulating ring. The thickness of the low-resistive rings is many times larger than that of the high-resistive rings, being in the order of tens of microns for the low-resistive rings and at least one order of magnitude lower for the high-resistive rings; and the diameter of the channel tubular walls is also many times larger than the thickness of the high-resistive rings. Both single-channel and multiple-channel electron multipliers are described. A very important advantage, particularly in making multiple-channel multipliers, is the simplicity of the procedure that may be used in constructing such multipliers. Other operational advantages are described

  7. Cardiac potassium channel subtypes

    DEFF Research Database (Denmark)

    Schmitt, Nicole; Grunnet, Morten; Olesen, Søren-Peter

    2014-01-01

    About 10 distinct potassium channels in the heart are involved in shaping the action potential. Some of the K(+) channels are primarily responsible for early repolarization, whereas others drive late repolarization and still others are open throughout the cardiac cycle. Three main K(+) channels...... drive the late repolarization of the ventricle with some redundancy, and in atria this repolarization reserve is supplemented by the fairly atrial-specific KV1.5, Kir3, KCa, and K2P channels. The role of the latter two subtypes in atria is currently being clarified, and several findings indicate...... that they could constitute targets for new pharmacological treatment of atrial fibrillation. The interplay between the different K(+) channel subtypes in both atria and ventricle is dynamic, and a significant up- and downregulation occurs in disease states such as atrial fibrillation or heart failure...

  8. Cl- channels in apoptosis

    DEFF Research Database (Denmark)

    Wanitchakool, Podchanart; Ousingsawat, Jiraporn; Sirianant, Lalida

    2016-01-01

    A remarkable feature of apoptosis is the initial massive cell shrinkage, which requires opening of ion channels to allow release of K(+), Cl(-), and organic osmolytes to drive osmotic water movement and cell shrinkage. This article focuses on the role of the Cl(-) channels LRRC8, TMEM16/anoctamin......, and cystic fibrosis transmembrane conductance regulator (CFTR) in cellular apoptosis. LRRC8A-E has been identified as a volume-regulated anion channel expressed in many cell types. It was shown to be required for regulatory and apoptotic volume decrease (RVD, AVD) in cultured cell lines. Its presence also......(-) channels or as regulators of other apoptotic Cl(-) channels, such as LRRC8. CFTR has been known for its proapoptotic effects for some time, and this effect may be based on glutathione release from the cell and increase in cytosolic reactive oxygen species (ROS). Although we find that CFTR is activated...

  9. CHANNEL ESTIMATION TECHNIQUE

    DEFF Research Database (Denmark)

    2015-01-01

    A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over the communicat......A method includes determining a sequence of first coefficient estimates of a communication channel based on a sequence of pilots arranged according to a known pilot pattern and based on a receive signal, wherein the receive signal is based on the sequence of pilots transmitted over...... the communication channel. The method further includes determining a sequence of second coefficient estimates of the communication channel based on a decomposition of the first coefficient estimates in a dictionary matrix and a sparse vector of the second coefficient estimates, the dictionary matrix including...... filter characteristics of at least one known transceiver filter arranged in the communication channel....

  10. Critical voltage effects in electron channeling patterns

    International Nuclear Information System (INIS)

    Farrow, R.C.

    1984-01-01

    Electron channeling patterns were used to study critical voltage effects in the metals molybdenum and tungsten. The purpose was to characterize both theoretically and experimentally how a critical voltage will affect the channeling pattern line shapes. The study focused on the second order critical voltage that results from the degeneracy between the Bloch wave states of the (110) and (220) reflections. Theoretical (110) series electron channeling pattern line profiles were calculated using the dynamical theory of Hirsch and Humphreys (1970). A 10 beam dynamical electron diffraction calculation was performed (using complex Fourier lattice potentials) to generate Bloch wave coefficients, excitation amplitudes, and absorption coefficients needed for determining backscattering coefficients and subsequent backscattered electron intensities. The theoretical model is applicable to electron diffraction at all energies since no high energy approximation or perturbation method was used

  11. Solution-phase epitaxial growth of quasi-monocrystalline cuprous oxide on metal nanowires

    NARCIS (Netherlands)

    Sciacca, Beniamino; Mann, Sander A.; Tichelaar, Frans D.; Zandbergen, Henny W.; Van Huis, Marijn A.; Garnett, Erik C.

    2014-01-01

    The epitaxial growth of monocrystalline semiconductors on metal nanostructures is interesting from both fundamental and applied perspectives. The realization of nanostructures with excellent interfaces and material properties that also have controlled optical resonances can be very challenging. Here

  12. The influence of Fe doping on the surface topography of GaN epitaxial material

    International Nuclear Information System (INIS)

    Cui Lei; Yin Haibo; Jiang Lijuan; Wang Quan; Feng Chun; Xiao Hongling; Wang Cuimei; Wang Xiaoliang; Gong Jiamin; Zhang Bo; Li Baiquan; Wang Zhanguo

    2015-01-01

    Fe doping is an effective method to obtain high resistivity GaN epitaxial material. But in some cases, Fe doping could result in serious deterioration of the GaN material surface topography, which will affect the electrical properties of two dimensional electron gas (2DEG) in HEMT device. In this paper, the influence of Fe doping on the surface topography of GaN epitaxial material is studied. The results of experiments indicate that the surface topography of Fe-doped GaN epitaxial material can be effectively improved and the resistivity could be increased after increasing the growth rate of GaN materials. The GaN material with good surface topography can be manufactured when the Fe doping concentration is 9 × 10 19 cm −3 . High resistivity GaN epitaxial material which is 1 × 10 9 Ω·cm is achieved. (paper)

  13. Lattice-Symmetry-Driven Epitaxy of Hierarchical GaN Nanotripods

    KAUST Repository

    Wang, Ping

    2017-01-18

    Lattice-symmetry-driven epitaxy of hierarchical GaN nanotripods is demonstrated. The nanotripods emerge on the top of hexagonal GaN nanowires, which are selectively grown on pillar-patterned GaN templates using molecular beam epitaxy. High-resolution transmission electron microscopy confirms that two kinds of lattice-symmetry, wurtzite (wz) and zinc-blende (zb), coexist in the GaN nanotripods. Periodical transformation between wz and zb drives the epitaxy of the hierarchical nanotripods with N-polarity. The zb-GaN is formed by the poor diffusion of adatoms, and it can be suppressed by improving the ability of the Ga adatoms to migrate as the growth temperature increased. This controllable epitaxy of hierarchical GaN nanotripods allows quantum dots to be located at the phase junctions of the nanotripods and nanowires, suggesting a new recipe for multichannel quantum devices.

  14. GaN Bulk Growth and Epitaxy from Ca-Ga-N Solutions, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR proposal addresses the liquid phase epitaxy (LPE) of gallium nitride (GaN) films using nitrogen-enriched metal solutions. Growth of GaN from solutions...

  15. AASERT: Rare Earth Arsenides, Magnetic Semi-Metal Epitaxy for Opto-Electronics

    National Research Council Canada - National Science Library

    Palmstrom, Chris

    2000-01-01

    ...). An ultra-high vacuum sample transfer system and a variable temperature scanning tunneling microscope were attached to two already existing molecular beam epitaxy systems and surface science equipment...

  16. The role of Energy Deposition in the Epitaxial Layer in Triggering SEGR in Power MOSFETs

    Science.gov (United States)

    Selva, L.; Swift, G.; Taylor, W.; Edmonds, L.

    1999-01-01

    In these SEGR experiments, three identical-oxide MOSFET types were irradiated with six ions of significantly different ranges. Results show the prime importance of the total energy deposited in the epitaxial layer.

  17. Fabrication of GaAs concentric multiple quantum rings by droplet epitaxy

    International Nuclear Information System (INIS)

    Somaschini, C; Bietti, S; Sanguinetti, S; Koguchi, N; Fedorov, A; Abbarchi, M; Gurioli, M

    2009-01-01

    We present the fabrication of a novel quantum nanostructure, constituted by three concentric quantum rings by droplet epitaxy. Atomic Force Microscopy and photoluminescence characterization of these nanostructures is reported.

  18. Crystalline and electronic structure of epitaxial γ-Al2O3 films

    International Nuclear Information System (INIS)

    Wu, Huiyan; Lu, Dawei; Zhu, Kerong; Xu, Guoyong; Wang, Hu

    2013-01-01

    Epitaxial γ-Al 2 O 3 films were fabricated on SrTiO 3 (1 0 0) substrates using pulsed laser deposition (PLD) technique. The high quality of epitaxial growth γ-Al 2 O 3 films was confirmed by X-ray diffraction (XRD). Atomic force microscopy (AFM) images indicated the smooth surfaces and the step-flow growth of the films. In order to illuminate the electronic properties and the local structure of the epitaxial γ-Al 2 O 3 , we experimentally measured the X-ray absorption near-edge structure (XANES) spectrum at the O K-edge and compared the spectrum with the theoretical simulations by using various structure models. Our results based on XANES spectrum analysis indicated that the structure of the epitaxial γ-Al 2 O 3 film was a defective spinel with Al vacancies, which prefer to be located at the octahedral sites

  19. Molecular-beam epitaxial growth and ion-beam analysis systems for functional materials research

    International Nuclear Information System (INIS)

    Takeshita, H.; Aoki, Y.; Yamamoto, S.; Naramoto, H.

    1992-01-01

    Experimental systems for molecular beam epitaxial growth and ion beam analysis have been designed and constructed for the research of inorganic functional materials such as thin films and superlattices. (author)

  20. Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111/Si(111

    Directory of Open Access Journals (Sweden)

    Abe Shunsuke

    2010-01-01

    Full Text Available Abstract Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111 thin films on Si(111 has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D2-TPD and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111/Si(111 is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001 proceeds.

  1. Development of Epitaxial GaN Films for RF Communications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The primary objective of this SBIR is to develop epitaxial GaN films with threading dislocation density less than 10^6 cm^-2. We propose an innovative approach...

  2. GaN Bulk Growth and Epitaxy from Ca-Ga-N Solutions, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The innovations proposed here are Ka-band (38 GHz) group III-nitride power FETs and the dislocation density reducing epitaxial growth methods (LPE) needed for their...

  3. Controllable factors affecting the epitaxial quality of LaCoO 3 films ...

    Indian Academy of Sciences (India)

    treatment temperature and a relatively rapid rate of heating can effectively preventnucleus from growing in other orientations, thereby improving the epitaxial quality of film. Besides, the choice of spin speed will directly affect the thickness and ...

  4. Probing the bulk ionic conductivity by thin film hetero-epitaxial engineering

    KAUST Repository

    Pergolesi, Daniele; Roddatis, Vladimir; Fabbri, Emiliana; Schneider, Christof W; Lippert, Thomas; Traversa, Enrico; Kilner, John A

    2015-01-01

    Highly textured thin films with small grain boundary regions can be used as model systems to directly measure the bulk conductivity of oxygen ion conducting oxides. Ionic conducting thin films and epitaxial heterostructures are also widely used

  5. High-rate deposition of epitaxial layers for efficient low-temperature thin film epitaxial silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Oberbeck, L.; Schmidt, J.; Wagner, T.A.; Bergmann, R.B. [Stuttgart Univ. (Germany). Inst. of Physical Electronics

    2001-07-01

    Low-temperature deposition of Si for thin-film solar cells has previously been hampered by low deposition rates and low material quality, usually reflected by a low open-circuit voltage of these solar cells. In contrast, ion-assisted deposition produces Si films with a minority-carrier diffusion length of 40 {mu}m, obtained at a record deposition rate of 0.8 {mu}m/min and a deposition temperature of 650{sup o}C with a prebake at 810{sup o}C. A thin-film Si solar cell with a 20-{mu}m-thick epitaxial layer achieves an open-circuit voltage of 622 mV and a conversion efficiency of 12.7% without any light trapping structures and without high-temperature solar cell process steps. (author)

  6. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    OpenAIRE

    Hyoungjeen Jeen; Ho Nyung Lee

    2015-01-01

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model syste...

  7. Pseudomorphic growth of organic semiconductor thin films driven by incommensurate epitaxy

    International Nuclear Information System (INIS)

    Sassella, A.; Campione, M.; Raimondo, L.; Borghesi, A.; Bussetti, G.; Cirilli, S.; Violante, A.; Goletti, C.; Chiaradia, P.

    2009-01-01

    A stable pseudomorphic phase of α-quaterthiophene, a well known organic semiconductor, is obtained by growing films with organic molecular beam epitaxy (OMBE) on a single crystal of another organic semiconductor, namely, tetracene. The structural characteristics of the new phase are investigated by monitoring in situ the OMBE process by reflectance anisotropy spectroscopy; thus assessing that incommensurate epitaxy is in this case, the driving force for tuning the molecular packing in organic molecular films and in turn, their solid state properties

  8. Increased carrier lifetimes in epitaxial silicon layers on buried silicon nitride produced by ion implantation

    International Nuclear Information System (INIS)

    Skorupa, W.; Kreissig, U.; Hensel, E.; Bartsch, H.

    1984-01-01

    Carrier lifetimes were measured in epitaxial silicon layers deposited on buried silicon nitride produced by high-dose nitrogen implantation at 330 keV. The values were in the range 20-200 μs. The results are remarkable taking into account the high density of crystal defects in the epitaxial layers. Comparing with other SOI technologies the measured lifetimes are higher by 1-2 orders of magnitude. (author)

  9. Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Satapathy, D.K.

    2005-12-19

    The present work is devoted to the growth of the ferromagnetic metal MnAs on the semiconductor GaAs by molecular-beam epitaxy (MBE). The MnAs thin films are deposited on GaAs by molecular-beam epitaxy (MBE). Grazing incidence diffraction (GID) and reflection high-energy electron diffraction (RHEED) are used in situ to investigate the nucleation, evolution of strain, morphology and interfacial structure during the MBE growth. Four stages of the nucleation process during growth of MnAs on GaAs(001) are revealed by RHEED azimuthal scans. GID shows that further growth of MnAs films proceed via the formation of relaxed islands at a nominal thickness of 2.5 ML which increase in size and finally coalesce to form a continuous film. Early on, an ordered array of misfit dislocations forms at the interface releasing the misfit strain even before complete coalescence occurs. The fascinating complex nucleation process of MnAs on GaAs(0 0 1) contains elements of both Volmer-Weber and Stranski-Krastanov growth. A nonuniform strain amounting to 0.66%, along the [1 -1 0] direction and 0.54%, along the [1 1 0] direction is demonstrated from x-ray line profile analysis. A high correlation between the defects is found along the GaAs[1 1 0] direction. An extremely periodic array of misfit dislocations with a period of 4.95{+-}0.05 nm is formed at the interface along the [1 1 0] direction which releases the 7.5% of misfit. The inhomogeneous strain due to the periodic dislocations is confined at the interface within a layer of 1.6 nm thickness. The misfit along the [1 -1 0] direction is released by the formation of a coincidence site lattice. (orig.)

  10. Coherifying quantum channels

    Science.gov (United States)

    Korzekwa, Kamil; Czachórski, Stanisław; Puchała, Zbigniew; Życzkowski, Karol

    2018-04-01

    Is it always possible to explain random stochastic transitions between states of a finite-dimensional system as arising from the deterministic quantum evolution of the system? If not, then what is the minimal amount of randomness required by quantum theory to explain a given stochastic process? Here, we address this problem by studying possible coherifications of a quantum channel Φ, i.e., we look for channels {{{Φ }}}{ \\mathcal C } that induce the same classical transitions T, but are ‘more coherent’. To quantify the coherence of a channel Φ we measure the coherence of the corresponding Jamiołkowski state J Φ. We show that the classical transition matrix T can be coherified to reversible unitary dynamics if and only if T is unistochastic. Otherwise the Jamiołkowski state {J}{{Φ }}{ \\mathcal C } of the optimally coherified channel is mixed, and the dynamics must necessarily be irreversible. To assess the extent to which an optimal process {{{Φ }}}{ \\mathcal C } is indeterministic we find explicit bounds on the entropy and purity of {J}{{Φ }}{ \\mathcal C }, and relate the latter to the unitarity of {{{Φ }}}{ \\mathcal C }. We also find optimal coherifications for several classes of channels, including all one-qubit channels. Finally, we provide a non-optimal coherification procedure that works for an arbitrary channel Φ and reduces its rank (the minimal number of required Kraus operators) from {d}2 to d.

  11. CANDU channel flow verification

    International Nuclear Information System (INIS)

    Mazalu, N.; Negut, Gh.

    1997-01-01

    The purpose of this evaluation was to obtain accurate information on each channel flow that enables us to assess precisely the level of reactor thermal power and, for reasons of safety, to establish which channel is boiling. In order to assess the channel flow parameters, computer simulations were done with the NUCIRC code and the results were checked by measurements. The complete channel flow measurements were made in the zero power cold condition. In hot conditions there were made flow measurements using the Shut Down System 1 (SDS 1) flow devices from 0.1 % F.P. up to 100 % F.P. The NUCIRC prediction for CANDU channel flows and the measurements by Ultrasonic Flow Meter at zero power cold conditions and SDS 1 flow channel measurements at different reactor power levels showed an acceptable agreement. The 100 % F.P. average errors for channel flow of R, shows that suitable NUCIRC flow assessment can be made. So, it can be done a fair prediction of the reactor power distribution. NUCIRC can predict accurately the onset of boiling and helps to warn at the possible power instabilities at high powers or it can detect the flow blockages. The thermal hydraulic analyst has in NUCIRC a suitable tool to do accurate predictions for the thermal hydraulic parameters for different steady state power levels which subsequently leads to an optimal CANDU reactor operation. (authors)

  12. STM investigation of epitaxial Si growth for the fabrication of a Si-based quantum computer

    Energy Technology Data Exchange (ETDEWEB)

    Oberbeck, Lars; Hallam, Toby; Curson, Neil J.; Simmons, Michelle Y.; Clark, Robert G

    2003-05-15

    We investigate the morphology of epitaxial Si layers grown on clean and on hydrogen terminated Si(0 0 1) to explore the growth strategy for the fabrication of a Si-based quantum computer. We use molecular beam epitaxy to deposit 5 monolayers of silicon at a temperature of 250 deg. C and scanning tunnelling microscopy to image the surface at room temperature after growth and after various rapid annealing steps in the temperature range of 350-600 deg. C. The epitaxial layer grown on the hydrogenated surface shows a significantly higher surface roughness due to a lower mobility of silicon surface atoms in the presence of hydrogen. Annealing at temperatures {>=}550 deg. C reduces the roughness of both epitaxial layers to the value of a clean silicon surface. However, the missing dimer defect density of the epitaxial layer grown on the hydrogenated surface remains higher by a factor of two compared to the layer grown on clean Si(0 0 1). Our results suggest a quantum computer growth strategy in which the hydrogen resist layer is desorbed before the epitaxial silicon layer is grown at low temperature to encapsulate phosphorus quantum bits.

  13. All-perovskite transparent high mobility field effect using epitaxial BaSnO3 and LaInO3

    Directory of Open Access Journals (Sweden)

    Useong Kim

    2015-03-01

    Full Text Available We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO3 and LaInO3. We have developed epitaxial LaInO3 as the gate oxide on top of BaSnO3, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO3 films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO3 as a gate dielectric and the La-doped BaSnO3 as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm2 V−1 s−1, the on/off ratio was larger than 107, and the subthreshold swing was 0.65 V dec−1. We discuss the possible origins for such device performance and the future directions for further improvement.

  14. All-perovskite transparent high mobility field effect using epitaxial BaSnO{sub 3} and LaInO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Useong; Park, Chulkwon; Kim, Young Mo; Ju, Chanjong; Park, Jisung; Char, Kookrin, E-mail: kchar@phya.snu.ac.kr [Institute of Applied Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Ha, Taewoo; Kim, Jae Hoon [Department of Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Namwook; Yu, Jaejun [Center for Theoretical Physics, Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

    2015-03-01

    We demonstrate an all-perovskite transparent heterojunction field effect transistor made of two lattice-matched perovskite oxides: BaSnO{sub 3} and LaInO{sub 3}. We have developed epitaxial LaInO{sub 3} as the gate oxide on top of BaSnO{sub 3}, which were recently reported to possess high thermal stability and electron mobility when doped with La. We measured the dielectric properties of the epitaxial LaInO{sub 3} films, such as the band gap, dielectric constant, and the dielectric breakdown field. Using the LaInO{sub 3} as a gate dielectric and the La-doped BaSnO{sub 3} as a channel layer, we fabricated field effect device structure. The field effect mobility of such device was higher than 90 cm{sup 2} V{sup −1} s{sup −1}, the on/off ratio was larger than 10{sup 7}, and the subthreshold swing was 0.65 V dec{sup −1}. We discuss the possible origins for such device performance and the future directions for further improvement.

  15. Blue-violet InGaN laser diodes grown on bulk GaN substrates by plasma-assisted molecular-beam epitaxy

    International Nuclear Information System (INIS)

    Skierbiszewski, C.; Wasilewski, Z.R.; Siekacz, M.; Feduniewicz, A.; Perlin, P.; Wisniewski, P.; Borysiuk, J.; Grzegory, I.; Leszczynski, M.; Suski, T.; Porowski, S.

    2005-01-01

    We report on the InGaN multiquantum laser diodes (LDs) made by rf plasma-assisted molecular beam epitaxy (PAMBE). The laser operation at 408 nm is demonstrated at room temperature with pulsed current injections using 50 ns pulses at 0.25% duty cycle. The threshold current density and voltage for the LDs with cleaved uncoated mirrors are 12 kA/cm 2 (900 mA) and 9 V, respectively. High output power of 0.83 W is obtained during pulse operation at 3.6 A and 9.6 V bias with the slope efficiency of 0.35 W/A. The laser structures are deposited on the high-pressure-grown low dislocation bulk GaN substrates taking full advantage of the adlayer enhanced lateral diffusion channel for adatoms below the dynamic metallic cover. Our devices compare very favorably to the early laser diodes fabricated using the metalorganic vapor phase epitaxy technique, providing evidence that the relatively low growth temperatures used in this process pose no intrinsic limitations on the quality of the blue optoelectronic components that can be fabricated using PAMBE

  16. Reconfigurable virtual electrowetting channels.

    Science.gov (United States)

    Banerjee, Ananda; Kreit, Eric; Liu, Yuguang; Heikenfeld, Jason; Papautsky, Ian

    2012-02-21

    Lab-on-a-chip systems rely on several microfluidic paradigms. The first uses a fixed layout of continuous microfluidic channels. Such lab-on-a-chip systems are almost always application specific and far from a true "laboratory." The second involves electrowetting droplet movement (digital microfluidics), and allows two-dimensional computer control of fluidic transport and mixing. The merging of the two paradigms in the form of programmable electrowetting channels takes advantage of both the "continuous" functionality of rigid channels based on which a large number of applications have been developed to date and the "programmable" functionality of digital microfluidics that permits electrical control of on-chip functions. In this work, we demonstrate for the first time programmable formation of virtual microfluidic channels and their continuous operation with pressure driven flows using an electrowetting platform. Experimental, theoretical, and numerical analyses of virtual channel formation with biologically relevant electrolyte solutions and electrically-programmable reconfiguration are presented. We demonstrate that the "wall-less" virtual channels can be formed reliably and rapidly, with propagation rates of 3.5-3.8 mm s(-1). Pressure driven transport in these virtual channels at flow rates up to 100 μL min(-1) is achievable without distortion of the channel shape. We further demonstrate that these virtual channels can be switched on-demand between multiple inputs and outputs. Ultimately, we envision a platform that would provide rapid prototyping of microfluidic concepts and would be capable of a vast library of functions and benefitting applications from clinical diagnostics in resource-limited environments to rapid system prototyping to high throughput pharmaceutical applications.

  17. Evaluation channel performance in multichannel environments

    NARCIS (Netherlands)

    Gensler, S.; Dekimpe, M.; Skiera, B.

    2007-01-01

    Evaluating channel performance is crucial for actively managing multiple sales channels, and requires understanding the customers' channel preferences. Two key components of channel performance are (i) the existing customers' intrinsic loyalty to a particular channel and (ii) the channel's ability

  18. Channel follower leakage restrictor

    International Nuclear Information System (INIS)

    Williamson, H.E.; Smith, B.A.

    1977-01-01

    An improved means is provided to control coolant leakage between the flow channel and the lower tie plate of a nuclear fuel assembly. The means includes an opening in the lower tie plate and a movable element adjacent thereto. The coolant pressure within the tie plate biases the movable means toward the inner surface of the surrounding flow channel to compensate for any movement of the flow channel away from the lower tie plate to thereby control the leakage of coolant flow from the fuel assemblies to the spaces among the fuel assemblies of the core. 9 figures

  19. Transient bedrock channel evolution across a precipitation gradient: A case study from Kohala, Hawaii.

    Science.gov (United States)

    Gasparini, N. M.; Han, J.; Johnson, J. P.; Menking, J. A.

    2011-12-01

    This study uses observations from the Kohala Peninsula, on the Big Island of Hawaii, and numerical modeling, to explore how precipitation gradients may affect fluvial bedrock incision and channel morphology. Orographic precipitation patterns result in over 4 m/yr of rainfall on the wet side of the peninsula and less than 0.5 m/yr on the dry side. These precipitation patterns likely strongly contribute to the observed channel morphology. Further, the region is subsiding, leading to prolonged transient channel evolution. We explore changes in a number of channel morphologic parameters with watershed averaged precipitation rate. We use PRISM precipitation data and data from isohyets developed from historic rain gauge data. Not surprisingly, valley depth, measured from a 10 meter DEM, increases with spatially averaged precipitation rate. We also find that channel profile form varies with precipitation rate, with drier channels exhibiting a straight to slightly concave channel form and wetter channels exhibiting a convex to concave channel form. The precipitation value at which this transition in channel profile form occurs depends on the precipitation data-set used, highlighting the need for more accurate measurements of precipitation in settings with extreme precipitation patterns similar to our study area. The downstream pattern in precipitation is likely significant in the development of the convex-concave profile form. Numerical modeling results support that precipitation patterns such as those observed on the wet-side of the Kohala Peninsula may contribute to the convex-concave profile form. However, we emphasize that while precipitation patterns may contribute to the channel form, these channel features are transient and not expected to be sustained in steady-state landscapes. We also emphasize that it is fluvial discharge, as driven by precipitation, rather than precipitation alone, that drives the processes shaping the channel form. Because fluvial discharge is

  20. Direct channel problems and phenomena

    International Nuclear Information System (INIS)

    Cutkosky, R.E.

    1975-01-01

    Direct channel problems and phenomena are considered covering the need for precision hadron spectroscopy, the data base for precision hadron spectroscopy, some relations between direct-channel and cross-channel effects, and spin rotation phenomena

  1. AlGaN Channel Transistors for Power Management and Distribution

    Science.gov (United States)

    VanHove, James M.

    1996-01-01

    Contained within is the Final report of a Phase 1 SBIR program to develop AlGaN channel junction field effect transistors (JFET). The report summarizes our work to design, deposit, and fabricate JFETS using molecular beam epitaxy growth AlGaN. Nitride growth is described using a RF atomic nitrogen plasma source. Processing steps needed to fabricate the device such as ohmic source-drain contacts, reactive ion etching, gate formation, and air bride fabrication are documented. SEM photographs of fabricated power FETS are shown. Recommendations are made to continue the effort in a Phase 2 Program.

  2. Ion blocking and channeling studies of heteroepitaxial GaN layers

    International Nuclear Information System (INIS)

    Flagmeyer, R.; Ehrlich, C.; Geist, V.; Otto, G.

    1978-01-01

    Ion channeling and blocking in backscattering measurements were used for the characterization of thin epitaxial GaN layers, which have varied lattice imperfections involved by different growth conditions. In particular, the following characteristics were examined: (1) the thickness and the uniformity of the layers, (2) the depth dependence of the crystalline imperfection, (3) the dislocation density, (4) the spread in the orientation distribution of tilted crystallites, and (5) some other types of imperfections, such as stacking faults, double positioning, twins and bending of the layer

  3. Advanced applications of ion channeling for the study of imperfections in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Swanson, M L [North Carolina Univ., Chapel Hill, NC (United States)

    1997-03-01

    A review will be given of the applications of medium energy ion channeling for the studies of imperfections in the near-surface regions of crystals. The following topics will be discussed: (1.) epitaxial layers, including elemental depositions of a few monolayers, strained-layer superlattices, and compound layers; (2.) lattice defects, including ion damage in diamond, dislocation networks in Si, and anomalous lattice vibrations in high temperature superconductors; (3.) lattice sites of solute atoms, including substitutional sites in compounds (LiNbO{sub 3} and GaP), and interstitial sites produced by association with point defects. (author)

  4. Many channel spectrum unfolding

    International Nuclear Information System (INIS)

    Najzer, M.; Glumac, B.; Pauko, M.

    1980-01-01

    The principle of the ITER unfolding code as used for the many channel spectrum unfolding is described. Its unfolding ability is tested on seven typical neutron spectra. The effect of the initial spectrum approximation upon the solution is discussed

  5. Channelized Streams in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This draft dataset consists of all ditches or channelized pieces of stream that could be identified using three input datasets; namely the1:24,000 National...

  6. Coding for optical channels

    CERN Document Server

    Djordjevic, Ivan; Vasic, Bane

    2010-01-01

    This unique book provides a coherent and comprehensive introduction to the fundamentals of optical communications, signal processing and coding for optical channels. It is the first to integrate the fundamentals of coding theory and optical communication.

  7. Sensing with Ion Channels

    CERN Document Server

    Martinac, Boris

    2008-01-01

    All living cells are able to detect and translate environmental stimuli into biologically meaningful signals. Sensations of touch, hearing, sight, taste, smell or pain are essential to the survival of all living organisms. The importance of sensory input for the existence of life thus justifies the effort made to understand its molecular origins. Sensing with Ion Channels focuses on ion channels as key molecules enabling biological systems to sense and process the physical and chemical stimuli that act upon cells in their living environment. Its aim is to serve as a reference to ion channel specialists and as a source of new information to non specialists who want to learn about the structural and functional diversity of ion channels and their role in sensory physiology.

  8. Calcium channel blocker poisoning

    Directory of Open Access Journals (Sweden)

    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  9. TRP channels: an overview

    DEFF Research Database (Denmark)

    Pedersen, Stine Falsig; Owsianik, Grzegorz; Nilius, Bernd

    2005-01-01

    The TRP ("transient receptor potential") family of ion channels now comprises more than 30 cation channels, most of which are permeable for Ca2+, and some also for Mg2+. On the basis of sequence homology, the TRP family can be divided in seven main subfamilies: the TRPC ('Canonical') family......, the TRPV ('Vanilloid') family, the TRPM ('Melastatin') family, the TRPP ('Polycystin') family, the TRPML ('Mucolipin') family, the TRPA ('Ankyrin') family, and the TRPN ('NOMPC') family. The cloning and characterization of members of this cation channel family has exploded during recent years, leading...... to a plethora of data on the roles of TRPs in a variety of tissues and species, including mammals, insects, and yeast. The present review summarizes the most pertinent recent evidence regarding the structural and functional properties of TRP channels, focusing on the regulation and physiology of mammalian TRPs....

  10. A simulation of low energy channeling of protons in silicon

    International Nuclear Information System (INIS)

    Sabin, J.R.

    1994-01-01

    The authors present early results from the CHANNEL code, which simulates the passage of ionized projectiles through bulk solids. CHANNEL solves the classical equations of motion for the projectile using the force obtained from the gradient of the quantum mechanically derived coulombic potential of the solid (determined via a full potential augmented plane wave FLAPW calculation on the bulk) and a quantum mechanical energy dissipation term, the stopping power, as determined from the local electron density, using the method of Echenique, Nieminen, and Ritchie. The code then generates the trajectory of the ionic projectile for a given initial velocity and a given incident position on the unit cell face. For each incident projectile velocity, the authors generate trajectories for incidence distributed over the channel face. The distribution of ranges generates an implantation profile. In this paper, they report ion (proton) implantation profiles for low energy protons with initial velocity along the (100) and (110) channel directions of diamond structured Silicon

  11. Magnetic and electrical properties of epitaxial GeMn

    Energy Technology Data Exchange (ETDEWEB)

    Ahlers, Stefan

    2009-01-15

    In this work, GeMn magnetic semiconductors will be investigated. The fabrication of GeMn thin films with Mn contents up to 11.7% was realised with molecular beam epitaxy. At a fabrication temperature of 60 C, the suppression of Mn{sub x}Ge{sub y} phases could reproducibly be obtained. Dislocation free epitaxy of diamond-lattice type GeMn thin films was observed. In all fabrication conditions where Mn{sub x}Ge{sub y} suppression was feasible, an inhomogeneous dispersion of Mn was observed in form of a self-assembly of nanometre sized, Mn rich regions in a Ge rich matrix. Each Mn rich region exhibits ferromagnetic coupling with high Curie temperatures exceeding, in part, room temperature. The local ferromagnetic ordering leads to the formation of large, spatially separated magnetic moments, which induce a superparamagnetic behaviour of the GeMn thin films. At low temperatures {<=} 20 K, remanent behaviour was found to emerge. X-ray absorption experiments revealed a similarity of the Mn incorporation in diamond-lattice type GeMn thin films and in the hexagonal lattice of the intermetallic Mn{sub 5}Ge{sub 3} phase, respectively. These tetrahedra represent building blocks of the Mn{sub 5}Ge{sub 3} unit cell. The incorporation of Mn{sub 5}Ge{sub 3} building blocks was found to be accompanied by local structural disorder. The electrical properties of GeMn thin films were addressed by transport measurements. It was shown that by using a n-type Ge substrate, a pn energy barrier between epilayers and substrate to suppress parallel substrate conduction paths can be introduced. With the pn barrier concept, first results on the magnetotransport behaviour of GeMn thin films were obtained. GeMn was found to be p-type, but of high resistivity. a series of GeMn thin films was fabricated, where intermetallic Mn{sub x}Ge{sub y} phase separation was supported in a controlled manner. Phase separation was found to result in the formation of partially coherent, nanometre sized Mn{sub 5

  12. Comprehensive modeling of solid phase epitaxial growth using Lattice Kinetic Monte Carlo

    International Nuclear Information System (INIS)

    Martin-Bragado, Ignacio

    2013-01-01

    Damage evolution of irradiated silicon is, and has been, a topic of interest for the last decades for its applications to the semiconductor industry. In particular, sometimes, the damage is heavy enough to collapse the lattice and to locally amorphize the silicon, while in other cases amorphization is introduced explicitly to improve other implanted profiles. Subsequent annealing of the implanted samples heals the amorphized regions through Solid Phase Epitaxial Regrowth (SPER). SPER is a complicated process. It is anisotropic, it generates defects in the recrystallized silicon, it has a different amorphous/crystalline (A/C) roughness for each orientation, leaving pits in Si(1 1 0), and in Si(1 1 1) it produces two modes of recrystallization with different rates. The recently developed code MMonCa has been used to introduce a physically-based comprehensive model using Lattice Kinetic Monte Carlo that explains all the above singularities of silicon SPER. The model operates by having, as building blocks, the silicon lattice microconfigurations and their four twins. It detects the local configurations, assigns microscopical growth rates, and reconstructs the positions of the lattice locally with one of those building blocks. The overall results reproduce the (a) anisotropy as a result of the different growth rates, (b) localization of SPER induced defects, (c) roughness trends of the A/C interface, (d) pits on Si(1 1 0) regrown surfaces, and (e) bimodal Si(1 1 1) growth. It also provides physical insights of the nature and shape of deposited defects and how they assist in the occurrence of all the above effects

  13. Authentication over Noisy Channels

    OpenAIRE

    Lai, Lifeng; Gamal, Hesham El; Poor, H. Vincent

    2008-01-01

    In this work, message authentication over noisy channels is studied. The model developed in this paper is the authentication theory counterpart of Wyner's wiretap channel model. Two types of opponent attacks, namely impersonation attacks and substitution attacks, are investigated for both single message and multiple message authentication scenarios. For each scenario, information theoretic lower and upper bounds on the opponent's success probability are derived. Remarkably, in both scenarios,...

  14. Channelling versus inversion

    DEFF Research Database (Denmark)

    Gale, A.S.; Surlyk, Finn; Anderskouv, Kresten

    2013-01-01

    Evidence from regional stratigraphical patterns in Santonian−Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW−SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. W......−Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected....

  15. Stream Channel Stability.

    Science.gov (United States)

    1981-04-01

    Cycles of wetting and drying are also t ,v itiue swelling and shrinkage of the soil. S 11ied blocks or peds of soil fabric ,,ks. id downslope soil creep ...hydrographs of water and sediment at the point in question. By feeding the output from the hydrology-transport model into the finite element model...the banks as undercut banks fail. Channel irregularities such as seepage zones, cattle crossings, overbank drainage, buried channels, organic deposits

  16. Channeling and dynamic chaos

    Energy Technology Data Exchange (ETDEWEB)

    Bolotin, IU L; Gonchar, V IU; Truten, V I; Shulga, N F

    1986-01-01

    It is shown that axial channeling of relativistic electrons can give rise to the effect of dynamic chaos which involves essentially chaotic motion of a particle in the channel. The conditions leading to the effect of dynamic chaos and the manifestations of this effect in physical processes associated with the passage of particles through a crystal are examined using a silicon crystal as an example. 7 references.

  17. Solid phase epitaxial growth of high mobility La:BaSnO_3 thin films co-doped with interstitial hydrogen

    International Nuclear Information System (INIS)

    Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Moram, Michelle A.; Ide, Keisuke; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-01

    This work presents the solid phase epitaxial growth of high mobility La:BaSnO_3 thin films on SrTiO_3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO_3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm"2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO_3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO_3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO_3 thin films were increased to 3 × 10"1"9" cm"−"3 and in La:BaSnO_3 thin films from 6 × 10"1"9" cm"−"3 to 1.5 × 10"2"0" cm"−"3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO_3 electron effective mass of 0.27 ± 0.05 m_0 and an optical mobility of 26 ± 7 cm"2/Vs. As compared to La:BaSnO_3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO_3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

  18. Course on Ionic Channels

    CERN Document Server

    1986-01-01

    This book is based on a series of lectures for a course on ionic channels held in Santiago, Chile, on November 17-20, 1984. It is intended as a tutorial guide on the properties, function, modulation, and reconstitution of ionic channels, and it should be accessible to graduate students taking their first steps in this field. In the presentation there has been a deliberate emphasis on the spe­ cific methodologies used toward the understanding of the workings and function of channels. Thus, in the first section, we learn to "read" single­ channel records: how to interpret them in the theoretical frame of kinetic models, which information can be extracted from gating currents in re­ lation to the closing and opening processes, and how ion transport through an open channel can be explained in terms of fluctuating energy barriers. The importance of assessing unequivocally the origin and purity of mem­ brane preparations and the use of membrane vesicles and optical tech­ niques in the stUGY of ionic channels a...

  19. Profiling cancer

    DEFF Research Database (Denmark)

    Ciro, Marco; Bracken, Adrian P; Helin, Kristian

    2003-01-01

    In the past couple of years, several very exciting studies have demonstrated the enormous power of gene-expression profiling for cancer classification and prediction of patient survival. In addition to promising a more accurate classification of cancer and therefore better treatment of patients......, gene-expression profiling can result in the identification of novel potential targets for cancer therapy and a better understanding of the molecular mechanisms leading to cancer....

  20. Ion channelling in diamond

    International Nuclear Information System (INIS)

    Derry, T.E.

    1978-06-01

    Diamond is one of the most extreme cases from a channelling point of view, having the smallest thermal vibration amplitude and the lowest atomic number of commonly-encountered crystals. These are the two parameters most important for determining channelling behaviour. It is of consiberable interest therefore to see how well the theories explaining and predicting the channeling properties of other substance, succeed with diamond. Natural diamond, although the best available form for these experiments, is rather variable in its physical properties. Part of the project was devoted to considering and solving the problem of obtaining reproducible results representative of the ideal crystal. Channelling studies were performed on several good crystals, using the Rutherford backscattering method. Critical angles for proton channelling were measured for incident energies from 0.6 to 4.5 MeV, in the three most open axes and three most open planes of the diamond structure, and for α-particle channelling at 0.7 and 1.0 MeV (He + ) in the same axes and planes. For 1.0 MeV protons, the crystal temperature was varied from 20 degrees Celsius to 700 degrees Celsius. The results are presented as curves of backscattered yield versus angle in the region of each axis or plane, and summarised in the form of tables and graphs. Generally the critical angles, axial minimum yields, and temperature dependence are well predicted by the accepted theories. The most valuable overall conclusion is that the mean thermal vibration amplitude of the atoms in a crytical determines the critical approach distance to the channel walls at which an ion can remain channelled, even when this distance is much smaller than the Thomas-Fermi screening distance of the atomic potential, as is the case in diamond. A brief study was made of the radiation damage caused by α-particle bombardment, via its effect on the channelling phenomenon. It was possible to hold damage down to negligible levels during the

  1. Nanoselective area growth of GaN by metalorganic vapor phase epitaxy on 4H-SiC using epitaxial graphene as a mask

    International Nuclear Information System (INIS)

    Puybaret, Renaud; Jordan, Matthew B.; Voss, Paul L.; Ougazzaden, Abdallah; Patriarche, Gilles; Sundaram, Suresh; El Gmili, Youssef; Salvestrini, Jean-Paul; Heer, Walt A. de; Berger, Claire

    2016-01-01

    We report the growth of high-quality triangular GaN nanomesas, 30-nm thick, on the C-face of 4H-SiC using nanoselective area growth (NSAG) with patterned epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the problems of defects in heteroepitaxy, and the high mobility graphene film could readily provide the back low-dissipative electrode in GaN-based optoelectronic devices. A 5–8 graphene-layer film is first grown on the C-face of 4H-SiC by confinement-controlled sublimation of silicon carbide. Graphene is then patterned and arrays of 75-nm-wide openings are etched in graphene revealing the SiC substrate. A 30-nm-thick GaN is subsequently grown by metal organic vapor phase epitaxy. GaN nanomesas grow epitaxially with perfect selectivity on SiC, in the openings patterned through graphene. The up-or-down orientation of the mesas on SiC, their triangular faceting, and cross-sectional scanning transmission electron microscopy show that they are biphasic. The core is a zinc blende monocrystal surrounded with single-crystal wurtzite. The GaN crystalline nanomesas have no threading dislocations or V-pits. This NSAG process potentially leads to integration of high-quality III-nitrides on the wafer scalable epitaxial graphene/silicon carbide platform.

  2. Nanoselective area growth of GaN by metalorganic vapor phase epitaxy on 4H-SiC using epitaxial graphene as a mask

    Energy Technology Data Exchange (ETDEWEB)

    Puybaret, Renaud; Jordan, Matthew B.; Voss, Paul L.; Ougazzaden, Abdallah, E-mail: aougazza@georgiatech-metz.fr [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); CNRS UMI 2958, Georgia Institute of Technology, 2 Rue Marconi, 57070 Metz (France); Patriarche, Gilles [CNRS, Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis (France); Sundaram, Suresh; El Gmili, Youssef [CNRS UMI 2958, Georgia Institute of Technology, 2 Rue Marconi, 57070 Metz (France); Salvestrini, Jean-Paul [Université de Lorraine, CentraleSupélec, LMOPS, EA4423, 57070 Metz (France); Heer, Walt A. de [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Berger, Claire [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); CNRS, Institut Néel, BP166, 38042 Grenoble Cedex 9 (France)

    2016-03-07

    We report the growth of high-quality triangular GaN nanomesas, 30-nm thick, on the C-face of 4H-SiC using nanoselective area growth (NSAG) with patterned epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the problems of defects in heteroepitaxy, and the high mobility graphene film could readily provide the back low-dissipative electrode in GaN-based optoelectronic devices. A 5–8 graphene-layer film is first grown on the C-face of 4H-SiC by confinement-controlled sublimation of silicon carbide. Graphene is then patterned and arrays of 75-nm-wide openings are etched in graphene revealing the SiC substrate. A 30-nm-thick GaN is subsequently grown by metal organic vapor phase epitaxy. GaN nanomesas grow epitaxially with perfect selectivity on SiC, in the openings patterned through graphene. The up-or-down orientation of the mesas on SiC, their triangular faceting, and cross-sectional scanning transmission electron microscopy show that they are biphasic. The core is a zinc blende monocrystal surrounded with single-crystal wurtzite. The GaN crystalline nanomesas have no threading dislocations or V-pits. This NSAG process potentially leads to integration of high-quality III-nitrides on the wafer scalable epitaxial graphene/silicon carbide platform.

  3. Epitaxial properties of ZnO thin films on SrTiO3 substrates grown by laser molecular beam epitaxy

    International Nuclear Information System (INIS)

    Wei, X. H.; Li, Y. R.; Zhu, J.; Huang, W.; Zhang, Y.; Luo, W. B.; Ji, H.

    2007-01-01

    Epitaxial ZnO thin films with different orientations have been grown by laser molecular beam epitaxy on (001)- (011)-, and (111)-orientated SrTiO 3 single-crystal substrates. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial orientation relations were reconfirmed by ex situ x-ray diffraction measurements. In the case of ZnO on SrTiO 3 (001), four orthogonal domains coexisted in the ZnO epilayer, i.e., ZnO(110) parallel SrTiO 3 (001) and ZnO[-111] parallel SrTiO 3 . For (011)- and (111)-orientated substrates, single-domain epitaxy with c axial orientation was observed, in which the in-plane relationship was ZnO[110] parallel SrTiO 3 [110] irrespective of the substrate orientations. Additionally, the crystalline quality of ZnO on SrTiO 3 (111) was better than that of ZnO on SrTiO 3 (011) because of the same symmetry between the (111) substrates and (001) films. The obtained results can be attributed to the difference of the in-plane crystallographic symmetry. Furthermore, those alignments can be explained by the interface stress between the substrates and the films

  4. Sedimentary processes of the lower Monterey Fan channel and channel-mouth lobe

    Science.gov (United States)

    Klaucke, I.; Masson, D.G.; Kenyon, Neil H.; Gardner, J.V.

    2004-01-01

    The distribution of deposits, sediment transport pathways and processes on the lower Monterey Fan channel and channel-mouth lobe (CML) are studied through the integration of GLORIA and TOBI sidescan sonar data with 7-kHz subbottom profiler records and sediment cores for ground-truthing. The lower Monterey channel is characterised by an up to 30-m-deep channel with poorly developed levees and alternating muddy and silty muddy overbank deposits. The channel is discontinuous, disappearing where gradients are less than about 1:350. Ground-truthing of the large CML shows that the entire CML is characterised by widespread deposits of generally fine sand, with coarser sand at the base of turbidites. Sand is particularly concentrated in finger-like areas of low-backscatter intensity and is interpreted as the result of non-turbulent sediment-gravity flows depositing metres thick massive, fine sand. TOBI sidescan sonar data reveal recent erosional features in the form of scours, secondary channels, large flow slides, and trains of blocks at the distal end of the CML. Erosion is probably related to increasing gradient as the CML approaches Murray Fracture zone and to differential loading of sandy submarine fan deposits onto pelagic clays. Reworking of older flow slides by sediment transport processes on the lobe produces trains of blocks that are several metres in diameter and aligned parallel to the flow direction. ?? 2004 Elsevier B.V. All rights reserved.

  5. Helium-air counter flow in rectangular channels

    International Nuclear Information System (INIS)

    Fumizawa, Motoo; Tanaka, Gaku; Zhao, Hong; Hishida, Makoto; Shiina, Yasuaki

    2004-01-01

    This paper deals with numerical analysis of helium-air counter flow in a rectangular channel with an aspect ratio of 10. The channel has a cross sectional area of 5-50 mm and a length of 200 mm. The inclination angle was varied from 0 to 90 degree. The velocity profiles and concentration profiles were analyzed with a computer program [FLUENT]. Following main features of the counter flow are discussed based on the calculated results. (1) Time required for establishing a quasi-steady state counter flow. (2) The relationship between the inclination angle and the flow patterns of the counter flow. (3) The developing process of velocity profiles and concentration profiles. (4) The relationship between the inclination angle of the channel and the velocity profiles of upward flow and the downward flow. (5) The relationship between the concentration profile and the inclination angle. (6) The relationship between the net in-flow rate and the inclination angle. We compared the computed velocity profile and the net in-flow rate with experimental data. A good agreement was obtained between the calculation results and the experimental results. (author)

  6. Optical Communications Channel Combiner

    Science.gov (United States)

    Quirk, Kevin J.; Quirk, Kevin J.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    NASA has identified deep-space optical communications links as an integral part of a unified space communication network in order to provide data rates in excess of 100 Mb/s. The distances and limited power inherent in a deep-space optical downlink necessitate the use of photon-counting detectors and a power-efficient modulation such as pulse position modulation (PPM). For the output of each photodetector, whether from a separate telescope or a portion of the detection area, a communication receiver estimates a log-likelihood ratio for each PPM slot. To realize the full effective aperture of these receivers, their outputs must be combined prior to information decoding. A channel combiner was developed to synchronize the log-likelihood ratio (LLR) sequences of multiple receivers, and then combines these into a single LLR sequence for information decoding. The channel combiner synchronizes the LLR sequences of up to three receivers and then combines these into a single LLR sequence for output. The channel combiner has three channel inputs, each of which takes as input a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The cross-correlation between the channels LLR time series are calculated and used to synchronize the sequences prior to combining. The output of the channel combiner is a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The unit is controlled through a 1 Gb/s Ethernet UDP/IP interface. A deep-space optical communication link has not yet been demonstrated. This ground-station channel combiner was developed to demonstrate this capability and is unique in its ability to process such a signal.

  7. Nanoporous Silica Templated HeteroEpitaxy: Final LDRD Report.

    Energy Technology Data Exchange (ETDEWEB)

    Burckel, David Bruce; Koleske, Daniel; Rowen, Adam M.; Williams, John Dalton; Fan, Hongyou; Arrington, Christian Lew

    2006-11-01

    This one-year out-of-the-box LDRD was focused on exploring the use of porous growth masks as a method for defect reduction during heteroepitaxial crystal growth. Initially our goal was to investigate porous silica as a growth mask, however, we expanded the scope of the research to include several other porous growth masks on various size scales, including mesoporous carbon, and the UV curable epoxy, SU-8. Use of SU-8 as a growth mask represents a new direction, unique in the extensive literature of patterned epitaxial growth, and presents the possibility of providing a single step growth mask. Additional research included investigation of pore viability via electrochemical deposition into high aspect ratio photoresist patterns and pilot work on using SU-8 as a DUV negative resist, another significant potential result. While the late start nature of this project pushed some of the initial research goals out of the time table, significant progress was made. 3 Acknowledgements This work was performed in part at the Nanoscience @ UNM facility, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation (Grant ECS 03-35765). Sandia is multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United Stated Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. This work was supported under the Sandia LDRD program (Project 99405). 4

  8. Lattice-polarity-driven epitaxy of hexagonal semiconductor nanowires

    KAUST Repository

    Wang, Ping

    2015-12-22

    Lattice-polarity-driven epitaxy of hexagonal semiconductor nanowires (NWs) is demonstrated on InN NWs. In-polarity InN NWs form typical hexagonal structure with pyramidal growth front, whereas N-polarity InN NWs slowly turn to the shape of hexagonal pyramid and then convert to an inverted pyramid growth, forming diagonal pyramids with flat surfaces and finally coalescence with each other. This contrary growth behavior driven by lattice-polarity is most likely due to the relatively lower growth rate of the (0001 ̅) plane, which results from the fact that the diffusion barriers of In and N adatoms on the (0001) plane (0.18 and 1.0 eV, respectively) are about two-fold larger in magnitude than those on the (0001 ̅) plane (0.07 and 0.52 eV), as calculated by first-principles density functional theory (DFT). The formation of diagonal pyramids for the N-polarity hexagonal NWs affords a novel way to locate quantum dot in the kink position, suggesting a new recipe for the fabrication of dot-based devices.

  9. Creating Ruddlesden-Popper phases by hybrid molecular beam epitaxy

    International Nuclear Information System (INIS)

    Haislmaier, Ryan C.; Stone, Greg; Alem, Nasim; Engel-Herbert, Roman

    2016-01-01

    The synthesis of a 50 unit cell thick n = 4 Sr_n_+_1Ti_nO_3_n_+_1 (Sr_5Ti_4O_1_3) Ruddlesden-Popper (RP) phase film is demonstrated by sequentially depositing SrO and TiO_2 layers in an alternating fashion using hybrid molecular beam epitaxy (MBE), where Ti was supplied using titanium tetraisopropoxide (TTIP). A detailed calibration procedure is outlined for determining the shuttering times to deposit SrO and TiO_2 layers with precise monolayer doses using in-situ reflection high energy electron diffraction (RHEED) as feedback. Using optimized Sr and TTIP shuttering times, a fully automated growth of the n = 4 RP phase was carried out over a period of >4.5 h. Very stable RHEED intensity oscillations were observed over the entire growth period. The structural characterization by X-ray diffraction and high resolution transmission electron microscopy revealed that a constant periodicity of four SrTiO_3 perovskite unit cell blocks separating the double SrO rocksalt layer was maintained throughout the entire film thickness with a very little amount of planar faults oriented perpendicular to the growth front direction. These results illustrate that hybrid MBE is capable of layer-by-layer growth with atomic level precision and excellent flux stability.

  10. Oriented epitaxial TiO2 nanowires for water splitting

    Science.gov (United States)

    Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

    2017-06-01

    Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

  11. Low-temperature epitaxy of silicon by electron beam evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Gorka, B. [Hahn-Meitner-Institut Berlin, Kekulestr. 5, 12489 Berlin (Germany); Dogan, P. [Hahn-Meitner-Institut Berlin, Kekulestr. 5, 12489 Berlin (Germany)], E-mail: pinar.dogan@hmi.de; Sieber, I.; Fenske, F.; Gall, S. [Hahn-Meitner-Institut Berlin, Kekulestr. 5, 12489 Berlin (Germany)

    2007-07-16

    In this paper we report on homoepitaxial growth of thin Si films at substrate temperatures T{sub s} = 500-650 deg. C under non-ultra-high vacuum conditions by using electron beam evaporation. Si films were grown at high deposition rates on monocrystalline Si wafers with (100), (110) and (111) orientations. The ultra-violet visible reflectance spectra of the films show a dependence on T{sub s} and on the substrate orientation. To determine the structural quality of the films in more detail Secco etch experiments were carried out. No etch pits were found on the films grown on (100) oriented wafers. However, on films grown on (110) and (111) oriented wafers different types of etch pits could be detected. Films were also grown on polycrystalline silicon (poly-Si) seed layers prepared by an Aluminum-Induced Crystallisation (AIC) process on glass substrates. Electron Backscattering Diffraction (EBSD) shows that the film growth proceeds epitaxially on the grains of the seed layer. But a considerably higher density of extended defects is revealed by Secco etch experiments.

  12. Chemical gating of epitaxial graphene through ultrathin oxide layers.

    Science.gov (United States)

    Larciprete, Rosanna; Lacovig, Paolo; Orlando, Fabrizio; Dalmiglio, Matteo; Omiciuolo, Luca; Baraldi, Alessandro; Lizzit, Silvano

    2015-08-07

    We achieved a controllable chemical gating of epitaxial graphene grown on metal substrates by exploiting the electrostatic polarization of ultrathin SiO2 layers synthesized below it. Intercalated oxygen diffusing through the SiO2 layer modifies the metal-oxide work function and hole dopes graphene. The graphene/oxide/metal heterostructure behaves as a gated plane capacitor with the in situ grown SiO2 layer acting as a homogeneous dielectric spacer, whose high capacity allows the Fermi level of graphene to be shifted by a few hundreds of meV when the oxygen coverage at the metal substrate is of the order of 0.5 monolayers. The hole doping can be finely tuned by controlling the amount of interfacial oxygen, as well as by adjusting the thickness of the oxide layer. After complete thermal desorption of oxygen the intrinsic doping of SiO2 supported graphene is evaluated in the absence of contaminants and adventitious adsorbates. The demonstration that the charge state of graphene can be changed by chemically modifying the buried oxide/metal interface hints at the possibility of tuning the level and sign of doping by the use of other intercalants capable of diffusing through the ultrathin porous dielectric and reach the interface with the metal.

  13. Structure and Properties of Epitaxial Dielectrics on gallium nitride

    Science.gov (United States)

    Wheeler, Virginia Danielle

    GaN is recognized as a possible material for metal oxide semiconductor field effect transistors (MOSFETs) used in high temperature, high power and high speed electronic applications. However, high gate leakage and low device breakdown voltages limit their use in these applications. The use of high-kappa dielectrics, which have both a high permittivity (ε) and high band gap energy (Eg), can reduce the leakage current density that adversely affects MOS devices. La2O3 and Sc2O 3 are rare earth oxides with a large Eg (6.18 eV and 6.3 eV respectively) and a relatively high ε (27 and 14.1 respectively), which make them good candidates for enhancing MOSFET performance. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. In this work, La2O3 and Sc2O 3 were characterized structurally and electronically as potential epitaxial gate dielectrics for use in GaN based MOSFETs. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation. Potassium persulfate (K2(SO4)2) and potassium hydroxide (KOH) were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition (MOCVD). X-ray photoelectron spectroscopy (XPS) showed that KOH left a nitrogen-rich interface, while K2(SO 4)2 left a gallium-rich interface, which provides a way to control surface oxide formation. K2(SO4)2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2(SO4)2 resulted in an additional 0.4 eV of

  14. Deposition of yttrium oxysulfide thin films by atomic layer epitaxy

    International Nuclear Information System (INIS)

    Kukli, K.; University of Tartu, Tartu,; Johansson, L-S.; Nykaenen, E.; Peussa, M.; Ninistoe, L.

    1998-01-01

    Full text: Yttrium oxysulfide is a highly interesting material for optoelectronic applications. It is industrially exploited in the form of doped powder in catholuminescent phosphors, e.g. Y 2 O 2 S: Eu 3+ for colour TV. Attempts to grow thin films of Y 2 O 2 S have not been frequent and only partially successful due to the difficulties in obtaining crystalline films at a reasonable temperature. Furthermore, sputtering easily leads to a sulphur deficiency. Evaporation of the elements from a multi-source offers a better control of the stoichiometry resulting in hexagonal (0002) oriented films at 580 deg C. In this paper we present the first successful thin film growth experiments using a chemical process with molecular precursors. Atomic layer epitaxy (ALE) allows the use of a relatively low deposition temperature and thus compatibility with other technologies. Already at 425 deg C the reaction between H 2 S and Y(thd) 3 (thd = 2,2,6,6 - tetramethyl-heptane-3,5- dione) yields a crystalline Y 2 O 2 S thin film which was characterized by XRD, XRF and XPS

  15. Epitaxial growth of fcc Ti films on Al(001) surfaces

    International Nuclear Information System (INIS)

    Saleh, A.A.; Shutthanandan, V.; Shivaparan, N.R.; Smith, R.J.; Tran, T.T.; Chambers, S.A.

    1997-01-01

    High-energy ion scattering (HEIS), x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction (XPD) were used to study the growth of thin Ti films on Al(001) surfaces. The Al surface peak area in the backscattered ion spectrum of MeV He + ions, incident along the [00 bar 1] direction, was used to monitor the atomic structure of the Ti films during growth. An initial decrease in the area was observed indicating epitaxial film growth. This decrease continued up to a critical film thickness of about 5.5 ML, after which point the structure of the film changed. Titanium films 3, 5, and 9 ML thick were characterized using XPD in the same chamber. Both the HEIS and XPD results show that the Ti films grow with an fcc structure on Al(001). A tetragonal distortion of 2.4% in the fcc Ti film was measured using ions incident along the [10 bar 1] direction. Although there is a general similarity of fcc Ti growth on both Al(001) and Al(110), the submonolayer growth regime does show differences for the two surfaces. copyright 1997 The American Physical Society

  16. Creating Ruddlesden-Popper phases by hybrid molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Haislmaier, Ryan C.; Stone, Greg; Alem, Nasim; Engel-Herbert, Roman, E-mail: rue2@psu.edu [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2016-07-25

    The synthesis of a 50 unit cell thick n = 4 Sr{sub n+1}Ti{sub n}O{sub 3n+1} (Sr{sub 5}Ti{sub 4}O{sub 13}) Ruddlesden-Popper (RP) phase film is demonstrated by sequentially depositing SrO and TiO{sub 2} layers in an alternating fashion using hybrid molecular beam epitaxy (MBE), where Ti was supplied using titanium tetraisopropoxide (TTIP). A detailed calibration procedure is outlined for determining the shuttering times to deposit SrO and TiO{sub 2} layers with precise monolayer doses using in-situ reflection high energy electron diffraction (RHEED) as feedback. Using optimized Sr and TTIP shuttering times, a fully automated growth of the n = 4 RP phase was carried out over a period of >4.5 h. Very stable RHEED intensity oscillations were observed over the entire growth period. The structural characterization by X-ray diffraction and high resolution transmission electron microscopy revealed that a constant periodicity of four SrTiO{sub 3} perovskite unit cell blocks separating the double SrO rocksalt layer was maintained throughout the entire film thickness with a very little amount of planar faults oriented perpendicular to the growth front direction. These results illustrate that hybrid MBE is capable of layer-by-layer growth with atomic level precision and excellent flux stability.

  17. Molecular beam epitaxy of InN nanowires on Si

    Science.gov (United States)

    Golam Sarwar, A. T. M.; Carnevale, Santino D.; Kent, Thomas F.; Laskar, Masihhur R.; May, Brelon J.; Myers, Roberto C.

    2015-10-01

    We report on a systematic growth study of the nucleation process of InN nanowires on Si(1 1 1) substrates using plasma assisted molecular beam epitaxy (PAMBE). Samples are grown with various substrate temperatures and III/V ratios. Scanning electron microscopy, X-ray diffraction spectroscopy, energy dispersive X-ray spectroscopy, and photoluminescence are carried out to map out the variation in structural and optical properties versus growth conditions. Statistical averages of areal density, height, and radius are mapped as a function of substrate temperature and III/V ratio. Three different morphological phases are identified on the growth surface: InN, α-In and β-In. Based on SEM image analysis of samples grown at different conditions, the formation mechanism of these phases is proposed. Finally, the growth phase diagram of PAMBE grown InN on Si under N-rich condition is presented, and tapered versus non-tapered growth conditions are identified. It is found that high growth temperature and low III/V ratio plays a critical role in the growth of non-tapered InN nanowires.

  18. Magnetoresistance at artificial interfaces in epitaxial ferromagnetic thin films

    International Nuclear Information System (INIS)

    Fontcuberta, J.; Bibes, M.; Martinez, B.; Trtik, V.; Ferrater, C.; Sanchez, F.; Varela, M.

    2000-01-01

    Epitaxial La 2/3 Sr 1/3 MnO 3 and SrRuO 3 thin films have been grown by laser ablation on single-crystalline SrTiO 3 substrates. Prior to manganite or ruthenate deposition tracks have been patterned on the SrTiO 3 substrate by using an appropriately focused laser beam. In the experiments here reported linear tracks have been formed. The magnetotransport properties of the films, particularly the magnetoresistance, along paths parallel and perpendicular to the track have been extensively investigated and compared to similar data recorded on films grown on bicrystalline STO substrates. Whereas in LSMO a significant low-field tunnel magnetoresistance develops across the artificial interface, in SRO this tunnel contribution is absent. However, a significant high-field magnetoresistance is observed for both metallic and ferromagnetic systems. The results are analysed and discussed within the framework of the current understanding of double exchange and itinerant ferromagnets. Magnetoresistance data for various configurations of the track array are presented

  19. Epitaxially grown strained pentacene thin film on graphene membrane.

    Science.gov (United States)

    Kim, Kwanpyo; Santos, Elton J G; Lee, Tae Hoon; Nishi, Yoshio; Bao, Zhenan

    2015-05-06

    Organic-graphene system has emerged as a new platform for various applications such as flexible organic photovoltaics and organic light emitting diodes. Due to its important implication in charge transport, the study and reliable control of molecular packing structures at the graphene-molecule interface are of great importance for successful incorporation of graphene in related organic devices. Here, an ideal membrane of suspended graphene as a molecular assembly template is utilized to investigate thin-film epitaxial behaviors. Using transmission electron microscopy, two distinct molecular packing structures of pentacene on graphene are found. One observed packing structure is similar to the well-known bulk-phase, which adapts a face-on molecular orientation on graphene substrate. On the other hand, a rare polymorph of pentacene crystal, which shows significant strain along the c-axis, is identified. In particular, the strained film exhibits a specific molecular orientation and a strong azimuthal correlation with underlying graphene. Through ab initio electronic structure calculations, including van der Waals interactions, the unusual polymorph is attributed to the strong graphene-pentacene interaction. The observed strained organic film growth on graphene demonstrates the possibility to tune molecular packing via graphene-molecule interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Substrate-induced magnetism in epitaxial graphene buffer layers.

    Science.gov (United States)

    Ramasubramaniam, A; Medhekar, N V; Shenoy, V B

    2009-07-08

    Magnetism in graphene is of fundamental as well as technological interest, with potential applications in molecular magnets and spintronic devices. While defects and/or adsorbates in freestanding graphene nanoribbons and graphene sheets have been shown to cause itinerant magnetism, controlling the density and distribution of defects and adsorbates is in general difficult. We show from first principles calculations that graphene buffer layers on SiC(0001) can also show intrinsic magnetism. The formation of graphene-substrate chemical bonds disrupts the graphene pi-bonds and causes localization of graphene states near the Fermi level. Exchange interactions between these states lead to itinerant magnetism in the graphene buffer layer. We demonstrate the occurrence of magnetism in graphene buffer layers on both bulk-terminated as well as more realistic adatom-terminated SiC(0001) surfaces. Our calculations show that adatom density has a profound effect on the spin distribution in the graphene buffer layer, thereby providing a means of engineering magnetism in epitaxial graphene.

  1. Mini array of quantum Hall devices based on epitaxial graphene

    International Nuclear Information System (INIS)

    Novikov, S.; Lebedeva, N.; Hämäläinen, J.; Iisakka, I.; Immonen, P.; Manninen, A. J.; Satrapinski, A.

    2016-01-01

    Series connection of four quantum Hall effect (QHE) devices based on epitaxial graphene films was studied for realization of a quantum resistance standard with an up-scaled value. The tested devices showed quantum Hall plateaux R H,2 at a filling factor v = 2 starting from a relatively low magnetic field (between 4 T and 5 T) when the temperature was 1.5 K. The precision measurements of quantized Hall resistance of four QHE devices connected by triple series connections and external bonding wires were done at B = 7 T and T = 1.5 K using a commercial precision resistance bridge with 50 μA current through the QHE device. The results showed that the deviation of the quantized Hall resistance of the series connection of four graphene-based QHE devices from the expected value of 4×R H,2  = 2 h/e 2 was smaller than the relative standard uncertainty of the measurement (<1 × 10 −7 ) limited by the used resistance bridge.

  2. Modeling two-phase flow in PEM fuel cell channels

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yun; Basu, Suman; Wang, Chao-Yang [Electrochemical Engine Center (ECEC), and Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2008-05-01

    This paper is concerned with the simultaneous flow of liquid water and gaseous reactants in mini-channels of a proton exchange membrane (PEM) fuel cell. Envisaging the mini-channels as structured and ordered porous media, we develop a continuum model of two-phase channel flow based on two-phase Darcy's law and the M{sup 2} formalism, which allow estimate of the parameters key to fuel cell operation such as overall pressure drop and liquid saturation profiles along the axial flow direction. Analytical solutions of liquid water saturation and species concentrations along the channel are derived to explore the dependences of these physical variables vital to cell performance on operating parameters such as flow stoichiometric ratio and relative humility. The two-phase channel model is further implemented for three-dimensional numerical simulations of two-phase, multi-component transport in a single fuel-cell channel. Three issues critical to optimizing channel design and mitigating channel flooding in PEM fuel cells are fully discussed: liquid water buildup towards the fuel cell outlet, saturation spike in the vicinity of flow cross-sectional heterogeneity, and two-phase pressure drop. Both the two-phase model and analytical solutions presented in this paper may be applicable to more general two-phase flow phenomena through mini- and micro-channels. (author)

  3. Low-Complexity Bayesian Estimation of Cluster-Sparse Channels

    KAUST Repository

    Ballal, Tarig; Al-Naffouri, Tareq Y.; Ahmed, Syed

    2015-01-01

    This paper addresses the problem of channel impulse response estimation for cluster-sparse channels under the Bayesian estimation framework. We develop a novel low-complexity minimum mean squared error (MMSE) estimator by exploiting the sparsity of the received signal profile and the structure of the measurement matrix. It is shown that due to the banded Toeplitz/circulant structure of the measurement matrix, a channel impulse response, such as underwater acoustic channel impulse responses, can be partitioned into a number of orthogonal or approximately orthogonal clusters. The orthogonal clusters, the sparsity of the channel impulse response and the structure of the measurement matrix, all combined, result in a computationally superior realization of the MMSE channel estimator. The MMSE estimator calculations boil down to simpler in-cluster calculations that can be reused in different clusters. The reduction in computational complexity allows for a more accurate implementation of the MMSE estimator. The proposed approach is tested using synthetic Gaussian channels, as well as simulated underwater acoustic channels. Symbol-error-rate performance and computation time confirm the superiority of the proposed method compared to selected benchmark methods in systems with preamble-based training signals transmitted over clustersparse channels.

  4. Low-Complexity Bayesian Estimation of Cluster-Sparse Channels

    KAUST Repository

    Ballal, Tarig

    2015-09-18

    This paper addresses the problem of channel impulse response estimation for cluster-sparse channels under the Bayesian estimation framework. We develop a novel low-complexity minimum mean squared error (MMSE) estimator by exploiting the sparsity of the received signal profile and the structure of the measurement matrix. It is shown that due to the banded Toeplitz/circulant structure of the measurement matrix, a channel impulse response, such as underwater acoustic channel impulse responses, can be partitioned into a number of orthogonal or approximately orthogonal clusters. The orthogonal clusters, the sparsity of the channel impulse response and the structure of the measurement matrix, all combined, result in a computationally superior realization of the MMSE channel estimator. The MMSE estimator calculations boil down to simpler in-cluster calculations that can be reused in different clusters. The reduction in computational complexity allows for a more accurate implementation of the MMSE estimator. The proposed approach is tested using synthetic Gaussian channels, as well as simulated underwater acoustic channels. Symbol-error-rate performance and computation time confirm the superiority of the proposed method compared to selected benchmark methods in systems with preamble-based training signals transmitted over clustersparse channels.

  5. Two-channel totally asymmetric simple exclusion processes

    International Nuclear Information System (INIS)

    Pronina, Ekaterina; Kolomeisky, Anatoly B

    2004-01-01

    Totally asymmetric simple exclusion processes, consisting of two coupled parallel lattice chains with particles interacting with hard-core exclusion and moving along the channels and between them, are considered. In the limit of strong coupling between the channels, the particle currents, density profiles and a phase diagram are calculated exactly by mapping the system into an effective one-channel totally asymmetric exclusion model. For intermediate couplings, a simple approximate theory, that describes the particle dynamics in vertical clusters of two corresponding parallel sites exactly and neglects the correlations between different vertical clusters, is developed. It is found that, similarly to the case of one-channel totally asymmetric simple exclusion processes, there are three stationary state phases, although the phase boundaries and stationary properties strongly depend on inter-channel coupling. Extensive computer Monte Carlo simulations fully support the theoretical predictions

  6. Damage evolution of ion irradiated defected-fluorite La 2 Zr 2 O 7 epitaxial thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kaspar, Tiffany C.; Gigax, Jonathan G.; Shao, Lin; Bowden, Mark E.; Varga, Tamas; Shutthanandan, Vaithiyalingam; Spurgeon, Steven R.; Yan, Pengfei; Wang, Chongmin; Ramuhalli, Pradeep; Henager, Charles H.

    2017-05-01

    Pyrochlore-structure oxides, A2B2O7, may exhibit remarkable radiation tolerance due to the ease with which they can accommodate disorder by transitioning to a defected fluorite structure. The mechanism of defect formation was explored by evaluating the radiation damage behavior of high quality epitaxial La2Zr2O7 thin films with the defected fluorite structure, irradiated with 1 MeV Zr+ at doses up to 10 displacements per atom (dpa). The level of film damage was evaluated as a function of dose by Rutherford backscattering spectrometry in the channeling geometry (RBS/c) and scanning transmission electron microscopy (STEM). At lower doses, the surface of the La2Zr2O7 film amorphized, and the amorphous fraction as a function of dose fit well to a stimulated amorphization model. As the dose increased, the surface amorphization slowed, and amorphization appeared at the interface. Even at a dose of 10 dpa, the core of the film remained crystalline, despite the prediction of amorphization from the model. To inform future ab initio simulations of La2Zr2O7, the bandgap of a thick La2Zr2O7 film was measured to be indirect at 4.96 eV, with a direct transition at 5.60 eV.

  7. Enhanced Electron Mobility in Nonplanar Tensile Strained Si Epitaxially Grown on SixGe1-x Nanowires.

    Science.gov (United States)

    Wen, Feng; Tutuc, Emanuel

    2018-01-10

    We report the growth and characterization of epitaxial, coherently strained Si x Ge 1-x -Si core-shell nanowire heterostructure through vapor-liquid-solid growth mechanism for the Si x Ge 1-x core, followed by an in situ ultrahigh-vacuum chemical vapor deposition for the Si shell. Raman spectra acquired from individual nanowire reveal the Si-Si, Si-Ge, and Ge-Ge modes of the Si x Ge 1-x core and the Si-Si mode of the shell. Because of the compressive (tensile) strain induced by lattice mismatch, the core (shell) Raman modes are blue (red) shifted compared to those of unstrained bare Si x Ge 1-x (Si) nanowires, in good agreement with values calculated using continuum elasticity model coupled with lattice dynamic theory. A large tensile strain of up to 2.3% is achieved in the Si shell, which is expected to provide quantum confinement for electrons due to a positive core-to-shell conduction band offset. We demonstrate n-type metal-oxide-semiconductor field-effect transistors using Si x Ge 1-x -Si core-shell nanowires as channel and observe a 40% enhancement of the average electron mobility compared to control devices using Si nanowires due to an increased electron mobility in the tensile-strained Si shell.

  8. The crystal orientation relation and macroscopic surface roughness in hetero-epitaxial graphene grown on Cu/mica

    International Nuclear Information System (INIS)

    Qi, J L; Nagashio, K; Nishimura, T; Toriumi, A

    2014-01-01

    Clean, flat and orientation-identified graphene on a substrate is in high demand for graphene electronics. In this study, the hetero-epitaxial graphene growth on Cu(111)/mica(001) by chemical vapor deposition is investigated to check the applicability for top-gate insulator research on graphene, as well as graphene channel research, by transferring graphene on to SiO 2 /Si substrates. After adjusting the graphene growth conditions, the surface roughness of the graphene/Cu/mica substrate and the average smoothed areas are ∼0.34 nm and ∼100 μm 2 , respectively. The orientation of graphene in the graphene/Cu/mica substrate can be identified by the hexagonal void morphology of Cu. Moreover, we demonstrate a relatively high mobility of ∼4500 cm 2 V −1 s −1 in graphene transferred on the SiO 2 /Si substrate. These results suggest that the present graphene/Cu/mica substrate can be used for top-gate insulator research on graphene. (papers)

  9. Frequency response improvement of a two-port surface acoustic wave device based on epitaxial AlN thin film

    Science.gov (United States)

    Gao, Junning; Hao, Zhibiao; Luo, Yi; Li, Guoqiang

    2018-01-01

    This paper presents an exploration on improving the frequency response of the symmetrical two-port AlN surface acoustic wave (SAW) device, using epitaxial AlN thin film on (0001) sapphire as the piezoelectric substrate. The devices were fabricated by lift-off processes with Ti/Al composite electrodes as interleaved digital transducers (IDT). The impact of DL and the number of the IDT finger pairs on the frequency response was carefully investigated. The overall properties of the device are found to be greatly improved with DL elongation, indicated by the reduced pass band ripple and increased stop band rejection ratio. The rejection increases by 8.3 dB when DL elongates from 15.5λ to 55.5λ and 4.4 dB further accompanying another 50λ elongation. This is because larger DL repels the stray acoustic energy out of the propagation path and provides a cleaner traveling channel for functional SAW, and at the same time restrains electromagnetic feedthrough. It is also found that proper addition of the IDT finger pairs is beneficial for the device response, indicated by the ripple reduction and the insertion loss drop.

  10. Channel Choice: A Literature Review

    DEFF Research Database (Denmark)

    Østergaard Madsen, Christian; Kræmmergaard, Pernille

    2015-01-01

    The channel choice branch of e-government studies citizens’ and businesses’ choice of channels for interacting with government, and how government organizations can integrate channels and migrate users towards the most cost-efficient channels. In spite of the valuable contributions offered...

  11. Defect analysis of NiMnSb epitaxial layers

    Energy Technology Data Exchange (ETDEWEB)

    Nowicki, L. [Andrzej SoItan Institute for Nuclear Studies, ul. Hoza 69, 00-681 Warsaw (Poland)]. E-mail: lech.nowicki@fuw.edu.pl; Turos, A. [Andrzej SoItan Institute for Nuclear Studies, ul. Hoza 69, 00-681 Warsaw (Poland); Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); Stonert, A. [Andrzej SoItan Institute for Nuclear Studies, ul. Hoza 69, 00-681 Warsaw (Poland); Garrido, F. [Centre de Spectrometrie Nucleaire et Spectrometrie de Masse, CNRS-IN2P3-Universite Paris-Sud, 91405 Orsay (France); Molenkamp, L.W. [Department of Physics, University Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany); Bach, P. [Department of Physics, University Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany); Schmidt, G. [Department of Physics, University Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany); Karczewski, G. [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Muecklich, A. [Forschungszentrum Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, POB 510119, 01314 Dresden (Germany)

    2005-10-15

    NiMnSb layers grown on InP substrates with InGaAs buffer were studied by the backscattering/channeling spectrometry (RBS/C) with He beams. The nature of predominant defects observed in the layers was studied by determination of incident-energy dependence of the relative channeling yield. The defects are described as a combination of large amount of interstitial atoms and of stacking faults or grain boundaries. The presence of grains was confirmed by transmission electron microscopy.

  12. Channel Identification Machines

    Directory of Open Access Journals (Sweden)

    Aurel A. Lazar

    2012-01-01

    Full Text Available We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.

  13. Channel identification machines.

    Science.gov (United States)

    Lazar, Aurel A; Slutskiy, Yevgeniy B

    2012-01-01

    We present a formal methodology for identifying a channel in a system consisting of a communication channel in cascade with an asynchronous sampler. The channel is modeled as a multidimensional filter, while models of asynchronous samplers are taken from neuroscience and communications and include integrate-and-fire neurons, asynchronous sigma/delta modulators and general oscillators in cascade with zero-crossing detectors. We devise channel identification algorithms that recover a projection of the filter(s) onto a space of input signals loss-free for both scalar and vector-valued test signals. The test signals are modeled as elements of a reproducing kernel Hilbert space (RKHS) with a Dirichlet kernel. Under appropriate limiting conditions on the bandwidth and the order of the test signal space, the filter projection converges to the impulse response of the filter. We show that our results hold for a wide class of RKHSs, including the space of finite-energy bandlimited signals. We also extend our channel identification results to noisy circuits.

  14. Resistivity analysis of epitaxially grown, doped semiconductors using energy dependent secondary ion mass spectroscopy

    International Nuclear Information System (INIS)

    Burnham, Shawn D.; Thomas, Edward W.; Doolittle, W. Alan

    2006-01-01

    A characterization technique is discussed that allows quantitative optimization of doping in epitaxially grown semiconductors. This technique uses relative changes in the host atom secondary ion (HASI) energy distribution from secondary ion mass spectroscopy (SIMS) to indicate relative changes in conductivity of the material. Since SIMS is a destructive process due to sputtering through a film, a depth profile of the energy distribution of sputtered HASIs in a matrix will contain information on the conductivity of the layers of the film as a function of depth. This process is demonstrated with Mg-doped GaN, with the Mg flux slowly increased through the film. Three distinct regions of conductivity were observed: one with Mg concentration high enough to cause compensation and thus high resistivity, a second with moderate Mg concentration and low resistivity, and a third with little to no Mg doping, causing high resistivity due to the lack of free carriers. During SIMS analysis of the first region, the energy distributions of sputtered Ga HASIs were fairly uniform and unchanging for a Mg flux above the saturation, or compensation, limit. For the second region, the Ga HASI energy distributions shifted and went through a region of inconsistent energy distributions for Mg flux slightly below the critical flux for saturation, or compensation. Finally, for the third region, the Ga HASI energy distributions then settled back into another fairly unchanging, uniform pattern. These three distinct regions were analyzed further through growth of Mg-doped step profiles and bulk growth of material at representative Mg fluxes. The materials grown at the two unchanging, uniform regions of the energy distributions yielded highly resistive material due to too high of Mg concentration and low to no Mg concentration, respectively. However, material grown in the transient energy distribution region with Mg concentration between that of the two highly resistive regions yielded low

  15. Resistivity analysis of epitaxially grown, doped semiconductors using energy dependent secondary ion mass spectroscopy

    Science.gov (United States)

    Burnham, Shawn D.; Thomas, Edward W.; Doolittle, W. Alan

    2006-12-01

    A characterization technique is discussed that allows quantitative optimization of doping in epitaxially grown semiconductors. This technique uses relative changes in the host atom secondary ion (HASI) energy distribution from secondary ion mass spectroscopy (SIMS) to indicate relative changes in conductivity of the material. Since SIMS is a destructive process due to sputtering through a film, a depth profile of the energy distribution of sputtered HASIs in a matrix will contain information on the conductivity of the layers of the film as a function of depth. This process is demonstrated with Mg-doped GaN, with the Mg flux slowly increased through the film. Three distinct regions of conductivity were observed: one with Mg concentration high enough to cause compensation and thus high resistivity, a second with moderate Mg concentration and low resistivity, and a third with little to no Mg doping, causing high resistivity due to the lack of free carriers. During SIMS analysis of the first region, the energy distributions of sputtered Ga HASIs were fairly uniform and unchanging for a Mg flux above the saturation, or compensation, limit. For the second region, the Ga HASI energy distributions shifted and went through a region of inconsistent energy distributions for Mg flux slightly below the critical flux for saturation, or compensation. Finally, for the third region, the Ga HASI energy distributions then settled back into another fairly unchanging, uniform pattern. These three distinct regions were analyzed further through growth of Mg-doped step profiles and bulk growth of material at representative Mg fluxes. The materials grown at the two unchanging, uniform regions of the energy distributions yielded highly resistive material due to too high of Mg concentration and low to no Mg concentration, respectively. However, material grown in the transient energy distribution region with Mg concentration between that of the two highly resistive regions yielded low

  16. Growth mechanisms for Si epitaxy on O atomic layers: Impact of O-content and surface structure

    Energy Technology Data Exchange (ETDEWEB)

    Jayachandran, Suseendran, E-mail: suseendran.jayachandran@imec.be [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Billen, Arne [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium); Douhard, Bastien; Conard, Thierry; Meersschaut, Johan; Moussa, Alain; Caymax, Matty; Bender, Hugo [Imec, Kapeldreef 75, 3001 Leuven (Belgium); Vandervorst, Wilfried [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Physics and Astronomy, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Heyns, Marc [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Metallurgy and Materials, Castle Arenberg 44, B-3001 Leuven (Belgium); Delabie, Annelies [Imec, Kapeldreef 75, 3001 Leuven (Belgium); KU Leuven (University of Leuven), Department of Chemistry, Celestijnenlaan 200F, B-3001 Leuven (Belgium)

    2016-10-30

    Highlights: • O{sub 3} or O{sub 2} exposures on H-Si(100) result in O ALs with different surface structures. • Si-EPI on O AL using O{sub 3} process is by direct epitaxial growth mechanism. • Si-EPI on O AL using O{sub 2} process is by epitaxial lateral overgrowth mechanism. • Distortions by O AL, SiH{sub 4} flux rate and Si thickness has an impact on Si-EPI quality. - Abstract: The epitaxial growth of Si layers on Si substrates in the presence of O atoms is generally considered a challenge, as O atoms degrade the epitaxial quality by generating defects. Here, we investigate the growth mechanisms for Si epitaxy on O atomic layers (ALs) with different O-contents and structures. O ALs are deposited by ozone (O{sub 3}) or oxygen (O{sub 2}) exposure on H-terminated Si at 50 °C and 300 °C respectively. Epitaxial Si is deposited by chemical vapor deposition using silane (SiH{sub 4}) at 500 °C. After O{sub 3} exposure, the O atoms are uniformly distributed in Si-Si dimer/back bonds. This O layer still allows epitaxial seeding of Si. The epitaxial quality is enhanced by lowering the surface distortions due to O atoms and by decreasing the arrival rate of SiH{sub 4} reactants, allowing more time for surface diffusion. After O{sub 2} exposure, the O atoms are present in the form of SiO{sub x} clusters. Regions of hydrogen-terminated Si remain present between the SiO{sub x} clusters. The epitaxial seeding of Si in these structures is realized on H-Si regions, and an epitaxial layer grows by a lateral overgrowth mechanism. A breakdown in the epitaxial ordering occurs at a critical Si thickness, presumably by accumulation of surface roughness.

  17. Performance enhancement in p-channel charge-trapping flash memory devices with Si/Ge super-lattice channel and band-to-band tunneling induced hot-electron injection

    International Nuclear Information System (INIS)

    Liu, Li-Jung; Chang-Liao, Kuei-Shu; Jian, Yi-Chuen; Wang, Tien-Ko; Tsai, Ming-Jinn

    2013-01-01

    P-channel charge-trapping flash memory devices with Si, SiGe, and Si/Ge super-lattice channel are investigated in this work. A Si/Ge super-lattice structure with extremely low roughness and good crystal structure is obtained by precisely controlling the epitaxy thickness of Ge layer. Both programming and erasing (P/E) speeds are significantly improved by employing this Si/Ge super-lattice channel. Moreover, satisfactory retention and excellent endurance characteristics up to 10 6 P/E cycles with 3.8 V memory window show that the degradation on reliability properties is negligible when super-lattice channel is introduced. - Highlights: ► A super-lattice structure is proposed to introduce more Ge content into channel. ► Super-lattice structure possesses low roughness and good crystal structure. ► P-channel flash devices with Si, SiGe, and super-lattice channel are investigated. ► Programming/erasing speeds are significantly improved. ► Reliability properties can be kept for device with super-lattice channel

  18. Molecular beam epitaxy of Cd3As2 on a III-V substrate

    Directory of Open Access Journals (Sweden)

    Timo Schumann

    2016-12-01

    Full Text Available Epitaxial, strain-engineered Dirac semimetal heterostructures promise tuning of the unique properties of these materials. In this study, we investigate the growth of thin films of the recently discovered Dirac semimetal Cd3As2 by molecular beam epitaxy. We show that epitaxial Cd3As2 layers can be grown at low temperatures (110 °C–220 °C, in situ, on (111 GaSb buffer layers deposited on (111 GaAs substrates. The orientation relationship is described by ( 112 Cd 3 As 2 || (111 GaSb and [ 1 1 ¯ 0 ] Cd 3 As 2 || [ 1 ¯ 01 ] GaSb . The films are shown to grow in the low-temperature, vacancy ordered, tetragonal Dirac semimetal phase. They exhibit high room temperature mobilities of up to 19300 cm2/Vs, despite a three-dimensional surface morphology indicative of island growth and the presence of twin variants. The results indicate that epitaxial growth on more closely lattice matched buffer layers, such as InGaSb or InAlSb, which allow for imposing different degrees of epitaxial coherency strains, should be possible.

  19. Optical properties of pure and Ce3+ doped gadolinium gallium garnet crystals and epitaxial layers

    International Nuclear Information System (INIS)

    Syvorotka, I.I.; Sugak, D.; Wierzbicka, A.; Wittlin, A.; Przybylińska, H.; Barzowska, J.; Barcz, A.; Berkowski, M.; Domagała, J.; Mahlik, S.; Grinberg, M.; Ma, Chong-Geng

    2015-01-01

    Results of X-ray diffraction and low temperature optical absorption measurements of cerium doped gadolinium gallium garnet single crystals and epitaxial layers are reported. In the region of intra-configurational 4f–4f transitions the spectra of the bulk crystals exhibit the signatures of several different Ce 3+ related centers. Apart from the dominant center, associated with Ce substituting gadolinium, at least three other centers are found, some of them attributed to the so-called antisite locations of rare-earth ions in the garnet host, i.e., in the Ga positions. X-ray diffraction data prove lattice expansion of bulk GGG crystals due to the presence of rare-earth antisites. The concentration of the additional Ce-related centers in epitaxial layers is much lower than in the bulk crystals. However, the Ce-doped layers incorporate a large amount of Pb from flux, which is the most probable source of nonradiative quenching of Ce luminescence, not observed in crystals grown by the Czochralski method. - Highlights: • Ce 3+ multicenters found in Gadolinium Gallium Garnet crystals and epitaxial layers. • High quality epitaxial layers of pure and Ce-doped GGG were grown. • Luminescence quenching of Ce 3+ by Pb ions from flux detected in GGG epitaxial layers. • X-ray diffraction allows measuring the amount of the rare-earth antisites in GGG

  20. Defect mediated van der Waals epitaxy of hexagonal boron nitride on graphene

    Science.gov (United States)

    Heilmann, M.; Bashouti, M.; Riechert, H.; Lopes, J. M. J.

    2018-04-01

    Van der Waals heterostructures comprising of hexagonal boron nitride and graphene are promising building blocks for novel two-dimensional devices such as atomically thin transistors or capacitors. However, demonstrators of those devices have been so far mostly fabricated by mechanical assembly, a non-scalable and time-consuming method, where transfer processes can contaminate the surfaces. Here, we investigate a direct growth process for the fabrication of insulating hexagonal boron nitride on high quality epitaxial graphene using plasma assisted molecular beam epitaxy. Samples were grown at varying temperatures and times and studied using atomic force microscopy, revealing a growth process limited by desorption at high temperatures. Nucleation was mostly commencing from morphological defects in epitaxial graphene, such as step edges or wrinkles. Raman spectroscopy combined with x-ray photoelectron measurements confirm the formation of hexagonal boron nitride and prove the resilience of graphene against the nitrogen plasma used during the growth process. The electrical properties and defects in the heterostructures were studied with high lateral resolution by tunneling current and Kelvin probe force measurements. This correlated approach revealed a nucleation apart from morphological defects in epitaxial graphene, which is mediated by point defects. The presented results help understanding the nucleation and growth behavior during van der Waals epitaxy of 2D materials, and point out a route for a scalable production of van der Waals heterostructures.

  1. Kinetic-energy induced smoothening and delay of epitaxial breakdown in pulsed-laser deposition

    International Nuclear Information System (INIS)

    Shin, Byungha; Aziz, Michael J.

    2007-01-01

    We have isolated the effect of kinetic energy of depositing species from the effect of flux pulsing during pulsed-laser deposition (PLD) on surface morphology evolution of Ge(001) homoepitaxy at low temperature (100 deg. C). Using a dual molecular beam epitaxy (MBE) PLD chamber, we compare morphology evolution from three different growth methods under identical experimental conditions except for the differing nature of the depositing flux: (a) PLD with average kinetic energy 300 eV (PLD-KE); (b) PLD with suppressed kinetic energy comparable to thermal evaporation energy (PLD-TH); and (c) MBE. The thicknesses at which epitaxial breakdown occurs are ranked in the order PLD-KE>MBE>PLD-TH; additionally, the surface is smoother in PLD-KE than in MBE. The surface roughness of the films grown by PLD-TH cannot be compared due to the early epitaxial breakdown. These results demonstrate convincingly that kinetic energy is more important than flux pulsing in the enhancement of epitaxial growth, i.e., the reduction in roughness and the delay of epitaxial breakdown

  2. On the capacity of cognitive radio under limited channel state information over fading channels

    KAUST Repository

    Rezki, Zouheir

    2011-06-01

    A spectrum-sharing communication system where the secondary user is aware of the instantaneous channel state information (CSI) of the secondary link, but knows only the statistics and an estimated version of the secondary transmitter-primary receiver (ST-PR) link, is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels (with continuous probability density function) under average and peak transmit-power constraints and with respect to two different interference constraints: an interference outage constraint and a signal-to-interference (SI) outage constraint. When applied to Rayleigh fading channels, our results show, for instance, that the interference constraint is harmful at high-power regime, whereas at low-power regime, it has a marginal impact and no-interference performance may be achieved. © 2011 IEEE.

  3. Cryogenic microwave channelized receiver

    International Nuclear Information System (INIS)

    Rauscher, C.; Pond, J.M.; Tait, G.B.

    1996-01-01

    The channelized receiver being presented demonstrates the use of high temperature superconductor technology in a microwave system setting where superconductor, microwave-monolithic-integrated-circuit, and hybrid-integrated-circuit components are united in one package and cooled to liquid-nitrogen temperatures. The receiver consists of a superconducting X-band four-channel demultiplexer with 100-MHz-wide channels, four commercial monolithically integrated mixers, and four custom-designed hybrid-circuit detectors containing heterostructure ramp diodes. The composite receiver unit has been integrated into the payload of the second-phase NRL high temperature superconductor space experiment (HTSSE-II). Prior to payload assembly, the response characteristics of the receiver were measured as functions of frequency, temperature, and drive levels. The article describes the circuitry, discusses the key issues related to design and implementation, and summarizes the experimental results

  4. Chaos in quantum channels

    Energy Technology Data Exchange (ETDEWEB)

    Hosur, Pavan; Qi, Xiao-Liang [Department of Physics, Stanford University,476 Lomita Mall, Stanford, California 94305 (United States); Roberts, Daniel A. [Center for Theoretical Physics and Department of Physics, Massachusetts Institute of Technology,77 Massachusetts Ave, Cambridge, Massachusetts 02139 (United States); Yoshida, Beni [Perimeter Institute for Theoretical Physics,31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Walter Burke Institute for Theoretical Physics, California Institute of Technology,1200 E California Blvd, Pasadena CA 91125 (United States)

    2016-02-01

    We study chaos and scrambling in unitary channels by considering their entanglement properties as states. Using out-of-time-order correlation functions to diagnose chaos, we characterize the ability of a channel to process quantum information. We show that the generic decay of such correlators implies that any input subsystem must have near vanishing mutual information with almost all partitions of the output. Additionally, we propose the negativity of the tripartite information of the channel as a general diagnostic of scrambling. This measures the delocalization of information and is closely related to the decay of out-of-time-order correlators. We back up our results with numerics in two non-integrable models and analytic results in a perfect tensor network model of chaotic time evolution. These results show that the butterfly effect in quantum systems implies the information-theoretic definition of scrambling.

  5. Distribution Channels Conflict and Management

    OpenAIRE

    Kiran, Dr Vasanth; Majumdar, Dr Mousumi; Kishore, Dr Krishna

    2012-01-01

    Relationships in distribution channels tend to be long-term oriented and members of the channel rely on each other to jointly realize their goals by serving buyers. Despite the channels focus on serving buyers, conflicts often arise between channel members because of each members self-interest. When conflicts arise, the perceptions of a channel member based on normative, rational/instrumental, or emotional reasoning will influence relational norms like trust and commitment that characterize t...

  6. Canonical sound speed profile for the central Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, T.V.R.; PrasannaKumar, S.; Somayajulu, Y.K.; Sastry, J.S.; De Figueiredo, R.J.P.

    Following Munk's canonical theory, an algorithm has been presented for computing sound channel parameters in the western and southern Bay of Bengal. The estimated canonical sound speed profile using these parameters has been compared with computed...

  7. Fuel channel refilling

    International Nuclear Information System (INIS)

    Shoukri, M.; Abdul-Razzak, A.

    1992-11-01

    This report extends the work reported in document INFO-0370 on fuel channel refilling by providing analysis of the refilling tests conducted using the RD-14 and RD-14M test facilities. The analysis focuses on the general thermal-hydraulic characteristics of the facilities following various small and large inlet and outlet header breaks with emergency coolant injection. The two-fluid model thermal-hydraulic computer code CATHENA was tested against results obtained from selected experiments carried out in the two facilities. Conclusions related to the effect of break size, mode of emergency core injection, primary pump operation and parallel channels are presented. (Author) (116 figs., 17 tabs., 53 refs.)

  8. Ion channels in glioblastoma.

    Science.gov (United States)

    Molenaar, Remco J

    2011-01-01

    Glioblastoma is the most common primary brain tumor with the most dismal prognosis. It is characterized by extensive invasion, migration, and angiogenesis. Median survival is only 15 months due to this behavior, rendering focal surgical resection ineffective and adequate radiotherapy impossible. At this moment, several ion channels have been implicated in glioblastoma proliferation, migration, and invasion. This paper summarizes studies on potassium, sodium, chloride, and calcium channels of glioblastoma. It provides an up-to-date overview of the literature that could ultimately lead to new therapeutic targets.

  9. Fuel channel refilling

    International Nuclear Information System (INIS)

    Shoukri, M.; Abdul-Razzak, A.

    1990-04-01

    Analysis of existing data on fuel channel refilling is presented. The analysis focuses on the data obtained using the Stern Laboratories Cold Water Injection Test (CWIT) Facility. The two-fluid model thermal-hydraulics computer code CATHENA is also used to simulate experimental results on fuel channel refilling from both the CWIT and RD-14 facilities. Conclusions related to single and double break tests, including the effect of non-condensible gases, are presented. A set of recommendations is given for further analysis and separate effect experiments. (67 figs., 5 tabs., 24 refs.)

  10. General Top-Down Ion Exchange Process for the Growth of Epitaxial Chalcogenide Thin Films and Devices

    KAUST Repository

    Xia, Chuan; Li, Peng; Li, Jun; Jiang, Qiu; Zhang, Xixiang; Alshareef, Husam N.

    2016-01-01

    ) epitaxial chalcogenide metallic and semiconducting films and (2) free-standing chalcogenide films and (3) completed in situ formation of atomically sharp heterojunctions by selective ion exchange. Epitaxial NiCo2S4 thin films prepared by our process show 115

  11. Photoacoustic study of the effect of doping concentration on the transport properties of GaAs epitaxial layers

    NARCIS (Netherlands)

    George, S.D.; Dilna, S.; Prasanth, R.; Radhakrishnan, P.; Vallabhan, C.P.G.; Nampoori, V.P.N.

    2003-01-01

    We report a photoacoustic (PA) study of the thermal and transport properties of a GaAs epitaxial layer doped with Si at varying doping concentration, grown on GaAs substrate by molecular beam epitaxy. The data are analyzed on the basis of Rosencwaig and Gersho's theory of the PA effect. The

  12. Potassium channels in brain mitochondria.

    Science.gov (United States)

    Bednarczyk, Piotr

    2009-01-01

    Potassium channels are the most widely distributed class of ion channels. These channels are transmembrane proteins known to play important roles in both normal and pathophysiological functions in all cell types. Various potassium channels are recognised as potential therapeutic targets in the treatment of Parkinson's disease, Alzheimer's disease, brain/spinal cord ischaemia and sepsis. In addition to their importance as therapeutic targets, certain potassium channels are known for their beneficial roles in anaesthesia, cardioprotection and neuroprotection. Some types of potassium channels present in the plasma membrane of various cells have been found in the inner mitochondrial membrane as well. Potassium channels have been proposed to regulate mitochondrial membrane potential, respiration, matrix volume and Ca(+) ion homeostasis. It has been proposed that mitochondrial potassium channels mediate ischaemic preconditioning in various tissues. However, the specificity of a pharmacological agents and the mechanisms underlying their effects on ischaemic preconditioning remain controversial. The following potassium channels from various tissues have been identified in the inner mitochondrial membrane: ATP-regulated (mitoK(ATP)) channel, large conductance Ca(2+)-regulated (mitoBK(Ca)) channel, intermediate conductance Ca(2+)-regulated (mitoIK(Ca)) channel, voltage-gated (mitoKv1.3 type) channel, and twin-pore domain (mitoTASK-3) channel. It has been shown that increased potassium flux into brain mitochondria induced by either the mitoK(ATP) channel or mitoBK(Ca) channel affects the beneficial effects on neuronal cell survival under pathological conditions. Recently, differential distribution of mitoBK(Ca) channels has been observed in neuronal mitochondria. These findings may suggest a neuroprotective role for the mitoBK(Ca) channel in specific brain structures. This minireview summarises current data on brain mitochondrial potassium channels and the efforts to identify

  13. Classification Order of Surface-Confined Intermixing at Epitaxial Interface

    Science.gov (United States)

    Michailov, M.

    The self-organization phenomena at epitaxial interface hold special attention in contemporary material science. Being relevant to the fundamental physical problem of competing, long-range and short-range atomic interactions in systems with reduced dimensionality, these phenomena have found exacting academic interest. They are also of great technological importance for their ability to bring spontaneous formation of regular nanoscale surface patterns and superlattices with exotic properties. The basic phenomenon involved in this process is surface diffusion. That is the motivation behind the present study which deals with important details of diffusion scenarios that control the fine atomic structure of epitaxial interface. Consisting surface imperfections (terraces, steps, kinks, and vacancies), the interface offers variety of barriers for surface diffusion. Therefore, the adatoms and clusters need a certain critical energy to overcome the corresponding diffusion barriers. In the most general case the critical energies can be attained by variation of the system temperature. Hence, their values define temperature limits of system energy gaps associated with different diffusion scenarios. This systematization imply classification order of surface alloying: blocked, incomplete, and complete. On that background, two diffusion problems, related to the atomic-scale surface morphology, will be discussed. The first problem deals with diffusion of atomic clusters on atomically smooth interface. On flat domains, far from terraces and steps, we analyzed the impact of size, shape, and cluster/substrate lattice misfit on the diffusion behavior of atomic clusters (islands). We found that the lattice constant of small clusters depends on the number N of building atoms at 1 < N ≤ 10. In heteroepitaxy, this effect of variable lattice constant originates from the enhanced charge transfer and the strong influence of the surface potential on cluster atomic arrangement. At constant

  14. TRESK potassium channel in human T lymphoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Miguel, Dénison Selene, E-mail: amurusk@hotmail.com [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); García-Dolores, Fernando, E-mail: garciaddf@yahoo.com [Department of Pathology, Institute of Forensic Sciences, Av. Niños Héroes 130, Col. Doctores, C.P. 06720 Mexico, DF (Mexico); Rosa Flores-Márquez, María, E-mail: mariafo31@yahoo.com.mx [National Medical Center of Occident (CMNO) IMSS, Belisario Dominguez 735, Col. Independencia Oriente, C.P. 44340 Guadalajara, Jalisco (Mexico); Delgado-Enciso, Iván [University of Colima, School of Medicine, Av. Universidad 333, Col. Las Viboras, C.P. 28040 Colima (Mexico); Pottosin, Igor, E-mail: pottosin@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico); Dobrovinskaya, Oxana, E-mail: oxana@ucol.mx [Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima (Mexico)

    2013-05-03

    Highlights: • TRESK (KCNK18) mRNA is present in different T lymphoblastic cell lines. • KCNK18 mRNA was not found in resting peripheral blood lymphocytes. • Clinical samples of T lymphoblastic leukemias and lymphomas were positive for TRESK. • TRESK in T lymphoblasts has dual localization, in plasma membrane and intracellular. -- Abstract: TRESK (TWIK-related spinal cord K{sup +}) channel, encoded by KCNK18 gene, belongs to the double-pore domain K{sup +} channel family and in normal conditions is expressed predominantly in the central nervous system. In our previous patch-clamp study on Jurkat T lymphoblasts we have characterized highly selective K{sup +} channel with pharmacological profile identical to TRESK. In the present work, the presence of KCNK18 mRNA was confirmed in T lymphoblastic cell lines (Jurkat, JCaM, H9) but not in resting peripheral blood lymphocytes of healthy donors. Positive immunostaining for TRESK was demonstrated in lymphoblastic cell lines, in germinal centers of non-tumoral lymph nodes, and in clinical samples of T acute lymphoblastic leukemias/lymphomas. Besides detection in the plasma membrane, intracellular TRESK localization was also revealed. Possible involvement of TRESK channel in lymphocyte proliferation and tumorigenesis is discussed.

  15. TRESK potassium channel in human T lymphoblasts

    International Nuclear Information System (INIS)

    Sánchez-Miguel, Dénison Selene; García-Dolores, Fernando; Rosa Flores-Márquez, María; Delgado-Enciso, Iván; Pottosin, Igor; Dobrovinskaya, Oxana

    2013-01-01

    Highlights: • TRESK (KCNK18) mRNA is present in different T lymphoblastic cell lines. • KCNK18 mRNA was not found in resting peripheral blood lymphocytes. • Clinical samples of T lymphoblastic leukemias and lymphomas were positive for TRESK. • TRESK in T lymphoblasts has dual localization, in plasma membrane and intracellular. -- Abstract: TRESK (TWIK-related spinal cord K + ) channel, encoded by KCNK18 gene, belongs to the double-pore domain K + channel family and in normal conditions is expressed predominantly in the central nervous system. In our previous patch-clamp study on Jurkat T lymphoblasts we have characterized highly selective K + channel with pharmacological profile identical to TRESK. In the present work, the presence of KCNK18 mRNA was confirmed in T lymphoblastic cell lines (Jurkat, JCaM, H9) but not in resting peripheral blood lymphocytes of healthy donors. Positive immunostaining for TRESK was demonstrated in lymphoblastic cell lines, in germinal centers of non-tumoral lymph nodes, and in clinical samples of T acute lymphoblastic leukemias/lymphomas. Besides detection in the plasma membrane, intracellular TRESK localization was also revealed. Possible involvement of TRESK channel in lymphocyte proliferation and tumorigenesis is discussed

  16. Radiation damage in proton-irradiated epitaxial silicon detectors

    International Nuclear Information System (INIS)

    Lange, Joern

    2009-07-01

    In this work radiation hardness of 75 μm, 100 μm and 150 μm thick epitaxial silicon pad diodes of both standard and oxygenated material was investigated. Damage after 24 GeV/c proton irradiation in a 1MeV neutron equivalent fluence range between 10 14 cm -2 and 10 16 cm -2 was studied and isothermal annealing experiments at 80 C were carried out. Standard CV/IV measurements could be performed up to 4 x 10 15 cm -2 . The volume-normalised reverse current was found to increase linearly with fluence with a slope independent of the thickness and impurity concentration. However, due to large fluctuations the fluences had to be renormalised using the current-related damage parameter. Concerning the depletion voltage, nearly all materials remained at a moderate level up to 4 x 10 15 cm -2 . During short-term annealing acceptors annealed out, whereas others were introduced during the long-term annealing. The stable damage was characterised by donor removal at low fluences and fluence-proportional predominant donor introduction for highly irradiated diodes, depending on the oxygen level. No type inversion was observed. Time-resolved measurements with a new 670 nm laser-TCT setup made the determination of the trapping time constant with the charge correction method possible. The results agreed with expectations and showed a linear increase of trapping probability with fluence. The electric field exhibited a double peak structure in highly irradiated diodes. Charge collection efficiency measurements with α-particles were independent of oxygen concentration, but showed an improved efficiency for thinner diodes. A comparison to simulation revealed systematic discrepancies. A non-constant trapping time parameter was proposed as possible solution. (orig.)

  17. Molecular Beam Epitaxy Growth of Transition Metal Dichalcogenides

    Science.gov (United States)

    Yue, Ruoyu

    The exponential growth of Si-based technology has finally reached its limit, and a new generation of devices must be developed to continue scaling. A unique class of materials, transition metal dichalcogenides (TMD), have attracted great attention due to their remarkable optical and electronic properties at the atomic thickness scale. Over the past decade, enormous efforts have been put into TMD research for application in low-power devices. Among these studies, a high-quality TMD synthesis method is essential. Molecular beam epitaxy (MBE) can enable high-quality TMD growth by combining high purity elemental sources and an ultra-high vacuum growth environment, together with the back-end-of-line compatible growth temperatures. Although many TMD candidates have been grown by MBE with promising microstructure, the limited grain size (improvement in grain size was achieved through this study. Results from both experiment and simulation showed that reducing the growth rate, enabled by high growth temperature and low metal flux, is vital to nucleation density control. Meanwhile, providing a chalcogen-rich growth environment will promote larger grain lateral growth by suppressing vertical growth. Applying the knowledge learned from the nucleation study, we sucessfully integrated the MBE-grown WSe2 into Si complementary metal-oxide-semiconductor (CMOS) compatible field-effect transistors (FETs). Excellent transport properties, such as field effect hole mobilities (40 cm 2/V·s) with orders of magnitude improvement over the reported values of MBE-grown TMDs, are shown. These studies provide a comprehensive understanding of the MBE synthesis of TMDs and devices, indicating the great potential of integrating TMDs into CMOS process flows for the future electronics.

  18. Mg doping of GaN by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Lieten, R R; Buchowicz, G; Dubon, O; Motsnyi, V; Zhang, L; Cheng, K; Leys, M; Degroote, S; Borghs, G

    2011-01-01

    We present a systematic study on the influence of growth conditions on the incorporation and activation of Mg in GaN layers grown by plasma-assisted molecular beam epitaxy. We show that high quality p-type GaN layers can be obtained on GaN-on-silicon templates. The Mg incorporation and the electrical properties have been investigated as a function of growth temperature, Ga : N flux ratio and Mg : Ga flux ratio. It was found that the incorporation of Mg and the electrical properties are highly sensitive to the Ga : N flux ratio. The highest hole mobility and lowest resistivity were achieved for slightly Ga-rich conditions. In addition to an optimal Ga : N ratio, an optimum Mg : Ga flux ratio was also observed at around 1%. We observed a clear Mg flux window for p-type doping of GaN : 0.31% 17 cm -3 and a mobility of 15 cm 2 V -1 s -1 . Temperature-dependent Hall effect measurements indicate an acceptor depth in these samples of 100 meV for a hole concentration of 5.5 x 10 17 cm -3 . The corresponding Mg concentration is 5 x 10 19 cm -3 , indicating approximately 1% activation at room temperature. In addition to continuous growth of Mg-doped GaN layers we also investigated different modulated growth procedures. We show that a modulated growth procedure has only limited influence on Mg doping at a growth temperature of 800 deg. or higher. This result is thus in contrast to previously reported GaN : Mg doping at much lower growth temperatures of 500 deg. C.

  19. Radiation damage in proton-irradiated epitaxial silicon detectors

    Energy Technology Data Exchange (ETDEWEB)

    Lange, Joern

    2009-07-15

    In this work radiation hardness of 75 {mu}m, 100 {mu}m and 150 {mu}m thick epitaxial silicon pad diodes of both standard and oxygenated material was investigated. Damage after 24 GeV/c proton irradiation in a 1MeV neutron equivalent fluence range between 10{sup 14} cm{sup -2} and 10{sup 16} cm{sup -2} was studied and isothermal annealing experiments at 80 C were carried out. Standard CV/IV measurements could be performed up to 4 x 10{sup 15} cm{sup -2}. The volume-normalised reverse current was found to increase linearly with fluence with a slope independent of the thickness and impurity concentration. However, due to large fluctuations the fluences had to be renormalised using the current-related damage parameter. Concerning the depletion voltage, nearly all materials remained at a moderate level up to 4 x 10{sup 15} cm{sup -2}. During short-term annealing acceptors annealed out, whereas others were introduced during the long-term annealing. The stable damage was characterised by donor removal at low fluences and fluence-proportional predominant donor introduction for highly irradiated diodes, depending on the oxygen level. No type inversion was observed. Time-resolved measurements with a new 670 nm laser-TCT setup made the determination of the trapping time constant with the charge correction method possible. The results agreed with expectations and showed a linear increase of trapping probability with fluence. The electric field exhibited a double peak structure in highly irradiated diodes. Charge collection efficiency measurements with {alpha}-particles were independent of oxygen concentration, but showed an improved efficiency for thinner diodes. A comparison to simulation revealed systematic discrepancies. A non-constant trapping time parameter was proposed as possible solution. (orig.)

  20. Control growth of silicon nanocolumns' epitaxy on silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chong, Su Kong, E-mail: sukong1985@yahoo.com.my [University of Malaya, Low Dimensional Materials Research Centre, Department of Physics (Malaysia); Dee, Chang Fu [Universiti Kebangsaan Malaysia (UKM), Institute of Microengineering and Nanoelectronics (IMEN) (Malaysia); Yahya, Noorhana [Universiti Teknologi PETRONAS, Faculty of Science and Information Technology (Malaysia); Rahman, Saadah Abdul [University of Malaya, Low Dimensional Materials Research Centre, Department of Physics (Malaysia)

    2013-04-15

    The epitaxial growth of Si nanocolumns on Si nanowires was studied using hot-wire chemical vapor deposition. A single-crystalline and surface oxide-free Si nanowire core (core radius {approx}21 {+-} 5 nm) induced by indium crystal seed was used as a substance for the vapor phase epitaxial growth. The growth process is initiated by sidewall facets, which then nucleate upon certain thickness to form Si islands and further grow to form nanocolumns. The Si nanocolumns with diameter of 10-20 nm and aspect ratio up to 10 can be epitaxially grown on the surface of nanowires. The results showed that the radial growth rate of the Si nanocolumns remains constant with the increase of deposition time. Meanwhile, the radial growth rates are controllable by manipulating the hydrogen to silane gas flow rate ratio. The optical antireflection properties of the Si nanocolumns' decorated SiNW arrays are discussed in the text.