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Sample records for electronic gap-driven metal-semiconductor

  1. Evidence for Electronic Gap-Driven Metal-Semiconductor Transition in Phase-Change Materials

    SciTech Connect

    Shakhvorostov, D.; Nistor, R; Krusin-Elbaum, L; Martyna, G; Newns, D; Elmegreen, B; Liu, X; Hughes, Z; Paul, S; et. al.

    2009-01-01

    Phase-change materials are functionally important materials that can be thermally interconverted between metallic (crystalline) and semiconducting (amorphous) phases on a very short time scale. Although the interconversion appears to involve a change in local atomic coordination numbers, the electronic basis for this process is still unclear. Here, we demonstrate that in a nearly vacancy-free binary GeSb system where we can drive the phase change both thermally and, as we discover, by pressure, the transformation into the amorphous phase is electronic in origin. Correlations between conductivity, total system energy, and local atomic coordination revealed by experiments and long time ab initio simulations show that the structural reorganization into the amorphous state is driven by opening of an energy gap in the electronic density of states. The electronic driving force behind the phase change has the potential to change the interconversion paradigm in this material class.

  2. Hybrid Metal-Semiconductor Electron Pump for Quantum Metrology

    NASA Astrophysics Data System (ADS)

    Jehl, X.; Voisin, B.; Charron, T.; Clapera, P.; Ray, S.; Roche, B.; Sanquer, M.; Djordjevic, S.; Devoille, L.; Wacquez, R.; Vinet, M.

    2013-04-01

    Electron pumps capable of delivering a current higher than 100 pA with sufficient accuracy are likely to become the direct mise en pratique of the possible new quantum definition of the ampere. We present here single-island hybrid metal-semiconductor transistor pumps that combine the simplicity and efficiency of Coulomb blockade in metals with the unsurpassed performances of silicon switches. Robust and simple pumping at 650 MHz and 0.5 K is demonstrated. The pumped current obtained over a voltage-bias range of 1.4 mV corresponds to a relative deviation of 5×10-4 from the calculated value, well within the 1.5×10-3 uncertainty of the measurement setup. Multicharge pumping can be performed. The simple design that is fully integrated into an industrial microelectronics process makes it an ideal candidate for national measurement institutes to realize and share a future quantum ampere.

  3. Electronic states of semiconductor-metal-semiconductor quantum-well structures

    NASA Astrophysics Data System (ADS)

    Huberman, M. L.; Maserjian, J.

    1988-05-01

    Quantum-size effects are calculated in thin layered semiconductor-metal-semiconductor structures using an ideal free-electron model for the metal layer. The results suggest new quantum-well structures having device applications. Structures with sufficiently high-quality interfaces should exhibit effects such as negative differential resistance due to tunneling between allowed states. Similarly, optical detection by intersubband absorption may be possible. Ultrathin metal layers are predicted to behave as high-density dopant sheets.

  4. Localized Electron States Near a Metal-SemiconductorNanocontact

    SciTech Connect

    Demchenko, Denis O.; Wang, Lin-Wang

    2007-04-25

    The electronic structure of nanowires in contact withmetallic electrodes of experimentally relevant sizes is calculated byincorporating the electrostatic polarization potential into the atomisticsingle particle Schrodinger equation. We show that the presence of anelectrode produces localized electron/hole states near the electrode, aphenomenon only exhibited in nanostructures and overlooked in the past.This phenomenon will have profound implications on electron transport insuch nanosystems. We calculate several electrode/nanowire geometries,with varying contact depths and nanowire radii. We demonstrate the changein the band gap of up to 0.5 eV in 3 nm diameter CdSe nanowires andcalculate the magnitude of the applied electric field necessary toovercome the localization.

  5. Electronic states of semiconductor/metal/semiconductor quantum well structures

    NASA Astrophysics Data System (ADS)

    Huberman, M. L.; Maserjian, J.

    Quantum size effects are calculated in thin layered semiconductor-metal-semi-conductor structures using an ideal free-electron model for the metal layer. The physical insight thereby gained is used to make projections for the behavior of real material systems. The results suggest new quantum well structures having device applications. Structures with sufficiently high quality interfaces should exhibit effects such as negative differential resistance due to tunneling between allowed states. Similarly, optical detection by intersubband absorption may be possible. We also predict that ultrathin metal layers can behave as high density dopant sheets.

  6. Role of direct electron-phonon coupling across metal-semiconductor interfaces in thermal transport via molecular dynamics

    NASA Astrophysics Data System (ADS)

    Lin, Keng-Hua; Strachan, Alejandro

    2015-07-01

    Motivated by significant interest in metal-semiconductor and metal-insulator interfaces and superlattices for energy conversion applications, we developed a molecular dynamics-based model that captures the thermal transport role of conduction electrons in metals and heat transport across these types of interface. Key features of our model, denoted eleDID (electronic version of dynamics with implicit degrees of freedom), are the natural description of interfaces and free surfaces and the ability to control the spatial extent of electron-phonon (e-ph) coupling. Non-local e-ph coupling enables the energy of conduction electrons to be transferred directly to the semiconductor/insulator phonons (as opposed to having to first couple to the phonons in the metal). We characterize the effect of the spatial e-ph coupling range on interface resistance by simulating heat transport through a metal-semiconductor interface to mimic the conditions of ultrafast laser heating experiments. Direct energy transfer from the conduction electrons to the semiconductor phonons not only decreases interfacial resistance but also increases the ballistic transport behavior in the semiconductor layer. These results provide new insight for experiments designed to characterize e-ph coupling and thermal transport at the metal-semiconductor/insulator interfaces.

  7. Role of direct electron-phonon coupling across metal-semiconductor interfaces in thermal transport via molecular dynamics

    SciTech Connect

    Lin, Keng-Hua; Strachan, Alejandro

    2015-07-21

    Motivated by significant interest in metal-semiconductor and metal-insulator interfaces and superlattices for energy conversion applications, we developed a molecular dynamics-based model that captures the thermal transport role of conduction electrons in metals and heat transport across these types of interface. Key features of our model, denoted eleDID (electronic version of dynamics with implicit degrees of freedom), are the natural description of interfaces and free surfaces and the ability to control the spatial extent of electron-phonon (e-ph) coupling. Non-local e-ph coupling enables the energy of conduction electrons to be transferred directly to the semiconductor/insulator phonons (as opposed to having to first couple to the phonons in the metal). We characterize the effect of the spatial e-ph coupling range on interface resistance by simulating heat transport through a metal-semiconductor interface to mimic the conditions of ultrafast laser heating experiments. Direct energy transfer from the conduction electrons to the semiconductor phonons not only decreases interfacial resistance but also increases the ballistic transport behavior in the semiconductor layer. These results provide new insight for experiments designed to characterize e-ph coupling and thermal transport at the metal-semiconductor/insulator interfaces.

  8. Super-resolution mapping of photogenerated electron and hole separation in single metal-semiconductor nanocatalysts.

    PubMed

    Ha, Ji Won; Ruberu, T Purnima A; Han, Rui; Dong, Bin; Vela, Javier; Fang, Ning

    2014-01-29

    Metal-semiconductor heterostructures are promising visible light photocatalysts for many chemical reactions. Here, we use high-resolution superlocalization imaging to reveal the nature and photocatalytic properties of the surface reactive sites on single Au-CdS hybrid nanocatalysts. We experimentally reveal two distinct, incident energy-dependent charge separation mechanisms that result in completely opposite photogenerated reactive sites (e(-) and h(+)) and divergent energy flows on the hybrid nanocatalysts. We find that plasmon-induced hot electrons in Au are injected into the conduction band of the CdS semiconductor nanorod. The specifically designed Au-tipped CdS heterostructures with a unique geometry (two Au nanoparticles at both ends of each CdS nanorod) provide more convincing high-resolution single-turnover mapping results and clearly prove the two charge separation mechanisms. Engineering the direction of energy flow at the nanoscale can provide an efficient way to overcome important challenges in photocatalysis, such as controlling catalytic activity and selectivity. These results bear enormous potential impact on the development of better visible light photocatalysts for solar-to-chemical energy conversion.

  9. Thickness dependent electronic structure and morphology of rubrene thin films on metal, semiconductor, and dielectric substrates

    NASA Astrophysics Data System (ADS)

    Sinha, Sumona; Mukherjee, M.

    2013-08-01

    The evolution of the electronic structure and morphology of rubrene thin films on noble-metal, semiconductor and dielectric substrates have been investigated as a function of thickness of deposited films by using photoelectron spectroscopy and atomic force microscopy. The clean polycrystalline Au and Ag were used as noble-metals, whereas, H passivated and SiO2 coated Si (100) were used as semiconductors and dielectric substrates. Discussion and comparison on interface dipole, energy level alignment, and surface morphology for the four cases are presented. The formation of dipole at metallic interfaces is found to occur due to push back effect. S parameter obtained from the variation of barrier height with the change of work function of the contacting metal indicates moderately weak interaction between rubrene and the metal substrates. The thickness dependent energy level alignment of the physisorbed rubrene films on different substrates is explained by a dielectric model in terms of electrostatic screening of photo-holes or photoemission final state relaxation energy. Films on all the substrates are found to grow following Stranski-Krastnov type growth mode and are more ordered at higher coverage.

  10. Effect of realistic metal electronic structure on the lower limit of contact resistivity of epitaxial metal-semiconductor contacts

    SciTech Connect

    Hegde, Ganesh Chris Bowen, R.

    2014-08-04

    The effect of realistic metal electronic structure on the lower limit of resistivity in [100] oriented n-Si is investigated using full band Density Functional Theory and Semi-Empirical Tight Binding calculations. It is shown that the “ideal metal” assumption may fail in some situations and, consequently, underestimate the lower limit of contact resistivity in n-Si by at least an order of magnitude at high doping concentrations. The mismatch in transverse momentum space in the metal and the semiconductor, the so-called “valley filtering effect,” is shown to be sensitive to the details of the transverse boundary conditions for the unit cells used. The results emphasize the need for explicit inclusion of the metal atomic and electronic structure in the atomistic modeling of transport across metal-semiconductor contacts.

  11. Electron-phonon coupling and thermal conductance at a metal-semiconductor interface: First-principles analysis

    SciTech Connect

    Sadasivam, Sridhar; Fisher, Timothy S.; Waghmare, Umesh V.

    2015-04-07

    The mechanism of heat transfer and the contribution of electron-phonon coupling to thermal conductance of a metal-semiconductor interface remains unclear in the present literature. We report ab initio simulations of a technologically important titanium silicide (metal)–silicon (semiconductor) interface to estimate the Schottky barrier height, and the strength of electron-phonon and phonon-phonon heat transfer across the interface. The electron and phonon dispersion relations of TiSi{sub 2} with C49 structure and the TiSi{sub 2}-Si interface are obtained using first-principles calculations within the density functional theory framework. These are used to estimate electron-phonon linewidths and the associated Eliashberg function that quantifies coupling. We show that the coupling strength of electrons with interfacial phonon modes is of the same order of magnitude as coupling of electrons to phonon modes in the bulk metal, and its contribution to electron-phonon interfacial conductance is comparable to the harmonic phonon-phonon conductance across the interface.

  12. Prolonged hot electron dynamics in plasmonic-metal/semiconductor heterostructures with implications for solar photocatalysis.

    PubMed

    DuChene, Joseph S; Sweeny, Brendan C; Johnston-Peck, Aaron C; Su, Dong; Stach, Eric A; Wei, Wei David

    2014-07-21

    Ideal solar-to-fuel photocatalysts must effectively harvest sunlight to generate significant quantities of long-lived charge carriers necessary for chemical reactions. Here we demonstrate the merits of augmenting traditional photoelectrochemical cells with plasmonic nanoparticles to satisfy these daunting photocatalytic requirements. Electrochemical techniques were employed to elucidate the mechanics of plasmon-mediated electron transfer within Au/TiO2 heterostructures under visible-light (λ>515 nm) irradiation in solution. Significantly, we discovered that these transferred electrons displayed excited-state lifetimes two orders of magnitude longer than those of electrons photogenerated directly within TiO2 via UV excitation. These long-lived electrons further enable visible-light-driven H2 evolution from water, heralding a new photocatalytic paradigm for solar energy conversion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Evidence of Momentum Conservation at a Nonepitaxial Metal/Semiconductor Interface Using Ballistic Electron Emission Microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.

    1996-01-01

    Ballistic-Electron-Emission Microscopy (BEEM) spectroscopy has been performed on Au/Si(111) structures as a function of Au thickness and temperature. At 77 K a direct signature of parallel momentum conservation at the Au/Si interface is observed in the BEEM spectra. The variation in spectral shape with both Au thickness and temperature places restrictions on allowable values of inelastic and elastic mean-free paths in the metal, and also requires the presence of multiple electron passes within the Au layer. An independent indication of multiple reflections is directly observed in the attenuation of BEEM current with Au thickness.

  14. Detection of Infrared Photons Using the Electronic Stress in Metal-Semiconductor Interfaces

    SciTech Connect

    Datskos, P.G.; Datskou, I.; Egert, C.M.; Rjic, S.

    1999-04-05

    It is well known that the work function of metals decreases when they are placed in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photons using the stress caused by photo-electrons emitted from a metal film surface in contact with a semiconductor microstructure. The photoelectrons diffuse into the microstructure and produce an electronic stress. The photon detection results from the measurement of the photo-induced bending of the microstructure. Internal photoemission has been used in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due to electronic stress. Small changes in position (displacement) of microstructures are routinely measured in atomic force microscopy (AFM) where atomic imaging of surfaces relies on the measurement of small changes (< l0{sup -9} m) in the bending of microcantilevers. In the present work we studied the photon response of Si microcantilevers coated with a thin film of Pt. The Si microcantilevers were 500 nm thick and had a 30 nm layer of Pt. Photons with sufficient energies produce electrons from the platinum-silicon interface which diffuse into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to contract in length but not the Pt layer, the bimaterial microcantilever bends. In our present studies we used the optical detection technique to measure the photometric response of Pt-Si microcantilevers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photoemission using a diode laser with wavelength {lambda} = 1550 nm.

  15. Detection of infrared photons using the electronic stress in metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Datskos, Panos G.; Rajic, Slobodan; Egert, Charles M.; Datskou, Irene

    1999-07-01

    It is well known that the work function of metals decrease when they are placed in a nonpolar liquid. A similar decrease occurs when the metal is placed into contact with a semiconductor forming a Schottky barrier. We report on a new method for detecting photon is using the stress caused by photon-electronics emitted forma metal film surface in contact with a semiconductor microstructure. The photoelectrons diffuse into the microstructure and produced an electronic stress. The photon detection results from the measurement of the photo-induced bending of the microstructure. Internal photo-emission has been sued in the past to detect photons, however, in those cases the detection was accomplished by measuring the current due to photoelectrons and not due to electronic stress. Small changes in position of microstructures are routinely measured in atomic force microscopy where atomic imaging of surface relies on the measurement of small changes in the bending of microcantilevers. In the present work we studied the photon response of Si microcantilevers with a thin film of Pt. The Si microcantilevers. In the present work we studied the photon response of Si microcantilevers with a thin film of Pt. The Si microcantilevers were 500 nm thick and had a 30 nm layer of Pt. Photons with high enough energies produce electrons from the platinum-silicon interface which diffuse into the Si and produce an electronic stress. Since the excess charge carriers cause the Si microcantilever to contact in length but not the Pt layer, the bimaterial microcantilever bends. In our present studies we used the optical detection technique to measure the photometric response of Pt-Si microcantilevers as a function of photon energy. The charge carriers responsible for the photo-induced stress in Si, were produced via internal photo-emission using a diode laser with wavelength (lambda) equals 1550 nm.

  16. Super-Resolution Mapping of Photogenerated Electron and Hole Separation in Single Metal-Semiconductor Nanocatalysts

    SciTech Connect

    Ha, Ji Won; Ruberu, T. Purnima A.; Han, Rui; Dong, Bin; Vela, Javier; Fang, Ning

    2014-01-12

    Metal–semiconductor heterostructures are promising visible light photocatalysts for many chemical reactions. Here, we use high-resolution superlocalization imaging to reveal the nature and photocatalytic properties of the surface reactive sites on single Au–CdS hybrid nanocatalysts. We experimentally reveal two distinct, incident energy-dependent charge separation mechanisms that result in completely opposite photogenerated reactive sites (e– and h+) and divergent energy flows on the hybrid nanocatalysts. We find that plasmon-induced hot electrons in Au are injected into the conduction band of the CdS semiconductor nanorod. The specifically designed Au-tipped CdS heterostructures with a unique geometry (two Au nanoparticles at both ends of each CdS nanorod) provide more convincing high-resolution single-turnover mapping results and clearly prove the two charge separation mechanisms. Engineering the direction of energy flow at the nanoscale can provide an efficient way to overcome important challenges in photocatalysis, such as controlling catalytic activity and selectivity. These results bear enormous potential impact on the development of better visible light photocatalysts for solar-to-chemical energy conversion.

  17. Improvement of Surge Protection by Using an AlGaN/GaN-Based Metal-Semiconductor-Metal Two-Dimensional Electron Gas Varactor

    NASA Astrophysics Data System (ADS)

    Ferng, Yi-Cherng; Chang, Liann-Be; Das, Atanu; Lin, Ching-Chi; Cheng, Chun-Yu; Kuei, Ping-Yu; Chow, Lee

    2012-12-01

    In this paper, a varactor with metal-semiconductor-metal diodes on top of the (NH4)2S/P2S5-treated AlGaN/GaN two-dimensional electron gas epitaxial structure (MSM-2DEG) is proposed to the surge protection for the first time. The sulfur-treated MSM-2DEG varactor properties, including current-voltage (I-V), capacitance-voltage (C-V), and frequency response of the proposed surge protection circuit, are presented. To verify its capability of surge protection, we replace the metal oxide varistor (MOV) and resistor (R) in a state-of-the-art surge protection circuit with the sulfur-treated MSM-2DEG varactor under the application conditions of system-level surge tests. The measured results show that the proposed surge protection circuit, consisted of a gas discharge arrester (GDA) and a sulfur-treated MSM-2DEG varactor, can suppress an electromagnetic pulse (EMP) voltage of 4000 to 360 V, a reduction of 91%, whereas suppression is to 1780 V, a reduction of 55%, when using only a GDA.

  18. Tailoring the Electronic Properties of Colloidal Quantum Dots in Metal-Semiconductor Nanocomposites for High Performance Photodetectors.

    PubMed

    García de Arquer, F Pelayo; Lasanta, Tania; Bernechea, María; Konstantatos, Gerasimos

    2015-06-10

    Metallic nanoparticles tailor the electronic properties of PbS colloidal quantum dots in a post-synthetic, all solution-processable approach. The Fermi level of the resulting nanocomposites can be tuned from p- to n-type due to remote charge transfer and electron trap state passivation. This concurrently reduces dark current, improves time response, and increases sensitivity in PbS photoconductors, yielding an over-two-fold increase in detectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Metal-semiconductor-metal transition in zigzag carbon nanoscrolls

    NASA Astrophysics Data System (ADS)

    Dong, Haixia; Zhang, Yang; Fang, Dangqi; Gong, Baihua; Zhang, Erhu; Zhang, Shengli

    2016-01-01

    Similar to rolling up paper, carbon nanoscrolls (CNSs) can be rolled from graphene nanoribbons (GNRs) using physical approaches. Owing to their peculiar one-dimensional nanostructures, CNSs have attracted great attention over the past few years. In this study, we have investigated the effects of bending deformation on the electronic properties of zigzag CNSs (ZCNSs) during the rolling process from zigzag GNRs (ZGNRs) by means of first-principles calculations. It is found that a metal-semiconductor-metal transition is observed. By analyzing charge density and density of states, the origin of this electronic property transition is discussed. Furthermore, we find that the metal-semiconductor-metal transition in ZCNSs is independent of ribbon width as well as spin-orbit interaction. Our results of the metal-semiconductor-metal transition in the ZCNSs are robust and may open potential applications in nano-electromechanical devices based on the ZCNSs.Similar to rolling up paper, carbon nanoscrolls (CNSs) can be rolled from graphene nanoribbons (GNRs) using physical approaches. Owing to their peculiar one-dimensional nanostructures, CNSs have attracted great attention over the past few years. In this study, we have investigated the effects of bending deformation on the electronic properties of zigzag CNSs (ZCNSs) during the rolling process from zigzag GNRs (ZGNRs) by means of first-principles calculations. It is found that a metal-semiconductor-metal transition is observed. By analyzing charge density and density of states, the origin of this electronic property transition is discussed. Furthermore, we find that the metal-semiconductor-metal transition in ZCNSs is independent of ribbon width as well as spin-orbit interaction. Our results of the metal-semiconductor-metal transition in the ZCNSs are robust and may open potential applications in nano-electromechanical devices based on the ZCNSs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07628

  20. a Study of Some Metal-Semiconductor Interfaces.

    NASA Astrophysics Data System (ADS)

    Maani, Colette

    Available from UMI in association with The British Library. The aim of this study was to investigate a number of specific metal-semiconductor interfaces with the goal of understanding the mechanism responsible for Schottky barrier formation at these interfaces. Metal contacts of group III, gallium, and group V, antimony were evaporated onto the clean cleaved indium phosphide(110) surface. Techniques of low energy electron defraction, Auger electron spectroscopy, ultra violet and X-ray photoelectric spectroscopy, current-voltage and capacitance -voltage measurements were used to probe the structural, chemical and electronic nature of the metal-semiconductor interfaces formed. In addition metal contacts of Al, Ag, Au and Sn were evaporated onto the clean cleaved gallium phosphide(110) surface. Techniques of current-voltage, capacitance-voltage and photoresponse measurements were used in order to determine barrier height. The study of Ga and Sb on InP(110) was used to investigate the importance of chemical reactivity, growth mode, defect formation and interdiffusion at the interface. The investigation of a range of metals on GaP(110) was an attempt to understand metal-semiconductor Schottky barrier formation in terms of this wide band gap material. Both studies were used to test the relevance of various proposed models of Schottky barrier formation at metal-semiconductor interfaces. (Abstract shortened by UMI.).

  1. Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Jha, Pankaj; Sands, Timothy D.; Cassels, Laura; Jackson, Philip; Favaloro, Tela; Kirk, Benjamin; Zide, Joshua; Xu, Xianfan; Shakouri, Ali

    2012-09-01

    applications by a factor of approximately 10-4—in part because the growth conditions chosen for this study yielded relatively high resistivity films—the temperature dependence of the resistivity and the potential for tuning the power factor by engineering strain, oxygen stoichiometry, and electronic band structure suggest that these epitaxial metal/semiconductor superlattices are deserving of further investigation.

  2. High Speed Heterostructure Metal-Semiconductor-Metal Photodetectors

    NASA Astrophysics Data System (ADS)

    Cola, A.; Nabet, B.; Chen, X.; Quaranta, F.

    2005-01-01

    In this work we review the properties of a class of metal-semiconductor-metal photodetectors based on heterojunction structures. Particularly, an AlGaAs/GaAs device is detailed in which the absorption region is in the GaAs layer, and a two-dimensional electron gas is formed at the heterointerface due toδ-doping of the widegap material. This heterostructure metal-semiconductor-metal photodetector also contains an AlGaAs distributed Bragg reflector that forms a resonant cavity for detection at 850 nm. The beneficial effect of the two-dimensional electron gas in the GaAs absorption layer in terms of speed and sensitivity is demonstrated by comparing samples with and without doping in the AlGaAs layer. The design and the physical properties of the grown epitaxial structure are presented, together with the static and dynamic characteristics of the device in time domain. In particular, photocurrent spectra exhibit a 30 nm wide peak at 850 nm, and time response measurements give a bandwidth over 30 GHz. A combination of very low dark current and capacitance, fast response, wavelength selectivity, and compatibility with high electron mobility transistors makes this device suitable for a number of application areas, such as Gigabit and 10 Gigabit Ethernet, wavelength division multiplexing, remote sensing, and medical applications.

  3. Circular Metal/Semiconductor/Metal Photodetectors

    NASA Technical Reports Server (NTRS)

    Mcadoo, James A.; Towe, Elias; Bishop, William L.; Wang, Liang-Guo

    1995-01-01

    Metal/semiconductor/metal (MSM) photodetectors with multiple concentric circular electrodes developed. Some electrical characteristics expected superior to those of older MSM photodetectors containing interdigitated straight electrodes. Response times smaller and shorter, and breakdown voltages larger. Decrease in capacitance allows greater signal-detection bandwidth. Important advantage in fiber-optic telecommunication systems, in which photodectors central components in receiver circuits. Increasing bandwidth of such photodetector enables receiver to handle larger number of channels or increased information rate in each channel.

  4. Analysis of Carbon Nanotube Metal-Semiconductor Diode Device

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2002-01-01

    We study recently reported drain current Id-drain voltage Vd characteristics of a carbon nanotube metal semiconductor diode device with the gate voltage Vg applied to modulate the carrier density in the nanotube. The diode was kink-shaped at the metal-semiconductor interface. It was shown that (1) larger negative Vg blocked Id more effectively in the negative Vd region, resulting in the rectifying Id-Vd characteristics, and that (2) positive Vg allowed Id in the both Vd polarities, resulting in the non-rectifying characteristics. The negative Vd was the Schottky reverse direction, judging from the negligible Id behavior for a wide region of -4 V less than Vd less than 0 V, with Vg = -4 V. Such negative Vg would attract positive charges from the metallic electrodes (charge reservoir) to the nanotube and lower the nanotube Fermi energy (EF). With larger negative Vg, the experiment showed that the Schottky forward direction (Vd greater than 0) had a smaller turn-on voltage and the Schottky reverse direction (Vd less than 0) was more resistant to the tunneling breakdown. Therefore, the majority carriers in the transport would be electrons since they can see a lower tunneling barrier (shallower built-in potential) in the forward direction when EF is lowered, and a thicker tunneling barrier (Schottky barrier) in the reverse direction due to the reduction in the electron density when EF is lowered.

  5. Extraordinary electroconductance in metal-semiconductor hybrid structures.

    PubMed

    Wang, Yun; Newaz, A K M; Wu, Jian; Solin, S A; Kavasseri, V R; Jin, N; Ahmed, I S; Adesida, I

    2008-06-30

    We report the phenomenon of extraordinary electroconductance in microscopic metal-semiconductor hybrid structures fabricated from GaAs epitaxial layer and a Ti thin film shunt. Four-lead Van der Pauw structures show a gain of 5.2% in electroconductance under +2.5 kVcm with zero shunt bias. The increase in the sample conductance results from the thermionic field emission of electrons and the geometrical amplification. A model provides good agreement with the experimental data and clearly demonstrates the geometry dependence of the field effect in extraordinary electroconductance (EEC). The differences between EEC devices and field effect transistors, such as junction field effect transistor (FET) and Schottky barrier gate FET, are discussed.

  6. Analysis of Carbon Nanotube Metal-Semiconductor Diode Device

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2001-01-01

    We study recently reported drain current I(sub d)-drain voltage V(sub d) characteristics of a carbon nanotube metal-semiconductor diode device with the gate voltage V(sub g) applied to modulate the carrier density in the nanotube. The diode was kink-shaped at the metal-semiconductor interface. It was shown that (1) larger negative V(sub g) blocked I(sub d) more effectively in the negative V(sub d) region, resulting in the rectifying I(sub d)-V(sub d) characteristics, and that (2) positive V(sub g) allowed I(sub d) in the both V(sub d) polarities, resulting in the non-rectifying characteristics. The negative V(sub d) was the Schottky reverse direction, judging from the negligible I(sub d) behavior for a wide region of -4 V (is less than) V(sub d) (is less than) 0 V, with V(sub g) = -4 V. Such negative V(sub g) would attract positive charges from the metallic electrodes (charge reservoir) to the nanotube and lower the nanotube Fermi energy (E(sub F)). With larger negative V(sub g), the experiment showed that the Schottky forward direction (V(sub d) (is greater than) 0) had a smaller turn-on voltage and the Schottky reverse direction (V(sub d) (is less than) 0) was more resistant to the tunneling breakdown. Therefore, the majority carriers in the transport would be electrons since they can see a lower tunneling barrier (shallower built-in potential) in the forward direction when E(sub F) is lowered, and a thicker tunneling barrier (Schottky barrier) in the reverse direction due to the reduction in the electron density when E(sub F) is lowered.

  7. Ion Implantation Effects on the Metal-Semiconductor Interfaces.

    NASA Astrophysics Data System (ADS)

    Yapsir, Andrie Setiawan

    1988-12-01

    In this thesis, the effects of ion implantation on metal-semiconductor interfaces are studied. Hydrogen ions have been used as the implanted species. The implantation is carried out on Al/n-Si Schottky contacts. Electrical characterizations, deep level transient spectroscopy measurements, and the ^{15}N hydrogen profiling technique have been used to study the effects of ion implantation. It is demonstrated that the defect centers in the depletion region created by hydrogen implantation have more likely negative or possibly neutral signatures, rather than a positive signature as has been previously speculated. These negatively charged centers compensate for the positive donor resulting in a widening of the depletion region and reduction in the capacitance of the metal-semiconductor contacts. The tendency of hydrogen to passivate its own damage which results in the recovery of electronic transport across the metal-semiconductor junction upon low temperature heat treatment is also demonstrated. In connection with the behavior of hydrogen in silicon, in the second part of this thesis, detailed theoretical calculations on the hydrogen passivation of defects in silicon are carried out. A particular type of defect, namely, a substitutional sulfur in silicon, is chosen and is studied using the modified intermediate neglect of differential overlap (MINDO/3) molecular orbital method. It is found that the sulfur center can be passivated using one or two hydrogen atoms. The calculations indicate that the most stable positions of the hydrogen atoms are between the sulfur and its silicon neighbors. The hydrogens bond to the nearest silicon atoms and only weakly interact with the sulfur. Thermochemistry considerations predict that a single hydrogen passivates the sulfur center, provided these centers are in abundance in the silicon. Hydrogen ion implantation has also been carried out on Schottky contacts having a large difference in metal work function, Ti/p-Si and Pt

  8. Light confinement and absorption in metal-semiconductor-metal nanostructures

    NASA Astrophysics Data System (ADS)

    Collin, Stephane; Pardo, Fabrice; Teissier, Roland; Bardou, Nathalie; Dupuis, Christophe; Mahe, Ronan; Ferlazzo, Laurence; Cambril, Edmond; Thierry-Mieg, Veronique; Lemaitre, Aristide; Pelouard, Jean-Luc

    2005-04-01

    New concepts for efficient light absorption in nanoscale metal-semiconductor-metal photodetectors are analyzed from both theoretical and experimental point of view. They are based on sub-wavelength metallic gratings which allows light confinement in tiny volumes (< 100 nm) close to electrodes (< 100 nm). Two photodetector structures are proposed: (i) a resonant-cavity-enhanced subwavelength metal-semiconductor-metal photodetector, and (ii) a nanoscale metal-semiconductor grating photodetector. External quantum efficiency as high as 9 % has been obtained in 40 x 100 nm2 cross-section GaAs wires, limited by fabrication technology. These results show promising features for highly efficient and ultrafast photodetectors.

  9. Photoemission, vibrational and stimulated desorption studies of metal-semiconductor interfaces and of chemisorbed atoms and molecules

    NASA Astrophysics Data System (ADS)

    Margaritondo, G.

    1984-10-01

    This program has produced in recent years a number of fundamental results on the microscopic properties of metal-semiconductor interfaces and on the mechanism of photon stimulated desorption. Both areas of research are of fundamental interest in condensed matter physics. Furthermore they have important applications in technology. The microscopic metal-semiconductor interface properties are directly related to the behavior and performance of the Schottky barrier, one of the building blocks of modern solid-state devices. This program investigates the formation of metal-semiconductor interfaces with some of the most powerful surface-science experimental probes: photoemission spectroscopy with synchrotron radiation, Auger spectroscopy, low-energy electron defraction in high-resolution electron energy loss surface vibrational spectroscopy. The stimulated desorption process is potentially a good probe of the chemical properties of absorbed species, e.g., in catalytic systems.

  10. Metal-semiconductor hybrid thin films in field-effect transistors

    SciTech Connect

    Okamura, Koshi Dehm, Simone; Hahn, Horst

    2013-12-16

    Metal-semiconductor hybrid thin films consisting of an amorphous oxide semiconductor and a number of aluminum dots in different diameters and arrangements are formed by electron beam lithography and employed for thin-film transistors (TFTs). Experimental and computational demonstrations systematically reveal that the field-effect mobility of the TFTs enhances but levels off as the dot density increases, which originates from variations of the effective channel length that strongly depends on the electric field distribution in a transistor channel.

  11. Ultrafast photoinduced charge separation in metal-semiconductor nanohybrids.

    PubMed

    Mongin, Denis; Shaviv, Ehud; Maioli, Paolo; Crut, Aurélien; Banin, Uri; Del Fatti, Natalia; Vallée, Fabrice

    2012-08-28

    Hybrid nano-objects formed by two or more disparate materials are among the most promising and versatile nanosystems. A key parameter in their properties is interaction between their components. In this context we have investigated ultrafast charge separation in semiconductor-metal nanohybrids using a model system of gold-tipped CdS nanorods in a matchstick architecture. Experiments are performed using an optical time-resolved pump-probe technique, exciting either the semiconductor or the metal component of the particles, and probing the light-induced change of their optical response. Electron-hole pairs photoexcited in the semiconductor part of the nanohybrids are shown to undergo rapid charge separation with the electron transferred to the metal part on a sub-20 fs time scale. This ultrafast gold charging leads to a transient red-shift and broadening of the metal surface plasmon resonance, in agreement with results for free clusters but in contrast to observation for static charging of gold nanoparticles in liquid environments. Quantitative comparison with a theoretical model is in excellent agreement with the experimental results, confirming photoexcitation of one electron-hole pair per nanohybrid followed by ultrafast charge separation. The results also point to the utilization of such metal-semiconductor nanohybrids in light-harvesting applications and in photocatalysis.

  12. Simple way to engineer metal-semiconductor interface for enhanced performance of perovskite organic lead iodide solar cells.

    PubMed

    Xu, Yuzhuan; Shi, Jiangjian; Lv, Songtao; Zhu, Lifeng; Dong, Juan; Wu, Huijue; Xiao, Yin; Luo, Yanhong; Wang, Shirong; Li, Dongmei; Li, Xianggao; Meng, Qingbo

    2014-04-23

    A thin wide band gap organic semiconductor N,N,N',N'-tetraphenyl-benzidine layer has been introduced by spin-coating to engineer the metal-semiconductor interface in the hole-conductor-free perovskite solar cells. The average cell power conversion efficiency (PCE) has been enhanced from 5.26% to 6.26% after the modification and a highest PCE of 6.71% has been achieved. By the aid of electrochemical impedance spectroscopy and dark current analysis, it is revealed that this modification can increase interfacial resistance of CH3NH3PbI3/Au interface and retard electron recombination process in the metal-semiconductor interface.

  13. Fabrication and characterization of metal-semiconductor-metal nanorod using template synthesis

    SciTech Connect

    Kim, Kyohyeok; Kwon, Namyong; Hong, Junki; Chung, Ilsub

    2009-07-15

    The authors attempted to fabricate and characterize one dimensional metal-semiconductor-metal (MSM) nanorod using a template. Cadmium selenide (CdSe) and polypyrrole (Ppy) were chosen as n-type and p-type semiconductor materials, respectively, whereas Au was chosen as a metal electrode. The fabrication of the nanorod was achieved by ''template synthesis'' method using polycarbonate membrane. The structure of the fabricated nanorod was analyzed using scanning electron microscopy and energy dispersive spectroscopy. In addition, the electrical properties of MSM nanorods were characterized using scanning probe microscopy (Seiko Instruments, SPA 300 HV) by probing with a conductive cantilever. I-V characteristics as a function of the temperature give the activation energy, as well as the barrier height of a metal-semiconductor contact, which is useful to understand the conduction mechanism of MSM nanorods.

  14. Photoluminescence mechanisms of metallic Zn nanospheres, semiconducting ZnO nanoballoons, and metal-semiconductor Zn/ZnO nanospheres

    PubMed Central

    Lin, Jin-Han; Patil, Ranjit A.; Devan, Rupesh S.; Liu, Zhe-An; Wang, Yi-Ping; Ho, Ching-Hwa; Liou, Yung; Ma, Yuan-Ron

    2014-01-01

    We utilized a thermal radiation method to synthesize semiconducting hollow ZnO nanoballoons and metal-semiconductor concentric solid Zn/ZnO nanospheres from metallic solid Zn nanospheres. The chemical properties, crystalline structures, and photoluminescence mechanisms for the metallic solid Zn nanospheres, semiconducting hollow ZnO nanoballoons, and metal-semiconductor concentric solid Zn/ZnO nanospheres are presented. The PL emissions of the metallic Zn solid nanospheres are mainly dependent on the electron transitions between the Fermi level (EF) and the 3d band, while those of the semiconducting hollow ZnO nanoballoons are ascribed to the near band edge (NBE) and deep level electron transitions. The PL emissions of the metal-semiconductor concentric solid Zn/ZnO nanospheres are attributed to the electron transitions across the metal-semiconductor junction, from the EF to the valence and 3d bands, and from the interface states to the valence band. All three nanostructures are excellent room-temperature light emitters. PMID:25382186

  15. Metal-Semiconductor Nanocomposites for High Efficiency Thermoelectric Power Generation

    DTIC Science & Technology

    2013-12-07

    the modified phonon and alloy scattering parameters in the modeling to explain the thermoelectric properties of this material. For example, we...near future. 2. Cross-plane thermoelectric properties of perovskite oxide metal/semiconductor superlattices ( Purdue /UCSC) The cross-plane...It therefore became critical that Purdue optimize this characterization technique to extract material properties which show the potential of metal

  16. Fabrication of Metal-Semiconductor Heterostructures in Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Yang, Luyun

    The increasing demand for fossil fuels and the need to reduce greenhouse gases require clean energy sources and more efficient utilization of energy. Thermoelectric materials provide a means toward achieving these goals since they convert heat, including waste heat, directly into an electric potential difference. Metal-semiconductor heterostructures can work as Schottky barriers in thermoelectric materials to increase thermoelectric efficiency. In this project, nickel silicide phases were introduced into silicon nanowires (SiNWs) to build up the Schottky barrier. SiNW arrays were fabricated using a metal-assisted chemical process, creating SiNWs about 200 nm in diameter and 30im in length. Different methods were adopted for nickel deposition: electroless nickel deposition, electro nickel deposition, E-beam deposition, and thermal evaporation. The samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that depositing nickel on SiNWs in an aqueous solution without electricity is a simple way to deposit nickel particles, and the morphology of nickel particles depends on the concentration of the deposition bath. However, an aqueous solution will cause oxidation of the SiNWs and hinder the formation of nickel silicide. To solve this problem, depositing nickel on SiNWs in organic solutions inside an oxygen-free glove box is a way to prevent oxidation, and nickel can diffuse into silicon substrates easily via annealing when there no oxidation layer on the surface of SiNWs. The dominant phase formed in these samples is NiSi2 after being annealed at 650°C for one hour in a tube furnace.

  17. Circular electrode geometry metal-semiconductor-metal photodetectors

    NASA Technical Reports Server (NTRS)

    Mcaddo, James A. (Inventor); Towe, Elias (Inventor); Bishop, William L. (Inventor); Wang, Liang-Guo (Inventor)

    1994-01-01

    The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

  18. Circular electrode geometry metal-semiconductor-metal photodetectors

    NASA Technical Reports Server (NTRS)

    Mcadoo, James A. (Inventor); Towe, Elias (Inventor); Bishop, William L. (Inventor); Wang, Liang-Guo (Inventor)

    1995-01-01

    The invention comprises a high speed, metal-semiconductor-metal photodetector which comprises a pair of generally circular, electrically conductive electrodes formed on an optically active semiconductor layer. Various embodiments of the invention include a spiral, intercoiled electrode geometry and an electrode geometry comprised of substantially circular, concentric electrodes which are interposed. These electrode geometries result in photodetectors with lower capacitances, dark currents and lower inductance which reduces the ringing seen in the optical pulse response.

  19. Mechanisms of current flow in metal-semiconductor ohmic contacts

    SciTech Connect

    Blank, T. V. Gol'dberg, Yu. A.

    2007-11-15

    Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II-VI semiconductors (ZnSe, ZnO), III-V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1-0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3-0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed.

  20. Numerical investigation of metal-semiconductor-insulator-semiconductor passivated hole contacts based on atomic layer deposited AlO x

    NASA Astrophysics Data System (ADS)

    Ke, Cangming; Xin, Zheng; Ling, Zhi Peng; Aberle, Armin G.; Stangl, Rolf

    2017-08-01

    Excellent c-Si tunnel layer surface passivation has been obtained recently in our lab, using atomic layer deposited aluminium oxide (ALD AlO x ) in the tunnel layer regime of 0.9 to 1.5 nm, investigated to be applied for contact passivation. Using the correspondingly measured interface properties, this paper compares the theoretical collection efficiency of a conventional metal-semiconductor (MS) contact on diffused p+ Si to a metal-semiconductor-insulator-semiconductor (MSIS) contact on diffused p+ Si or on undoped n-type c-Si. The influences of (1) the tunnel layer passivation quality at the tunnel oxide interface (Q f and D it), (2) the tunnel layer thickness and the electron and hole tunnelling mass, (3) the tunnel oxide material, and (4) the semiconductor capping layer material properties are investigated numerically by evaluation of solar cell efficiency, open-circuit voltage, and fill factor.

  1. One-dimensional transport in hybrid metal-semiconductor nanotube systems

    NASA Astrophysics Data System (ADS)

    Gelin, M. F.; Bondarev, I. V.

    2016-03-01

    We develop an electron transport theory for the hybrid system of a semiconducting carbon nanotube that encapsulates a one-atom-thick metallic wire. The theory predicts Fano resonances in electron transport through the system, whereby the interaction of electrons on the wire with nanotube plasmon generated near fields blocks some of the wire transmission channels to open up the new coherent plasmon-mediated channel in the nanotube forbidden gap outside the wire transmission band. Such a channel makes the entire hybrid system transparent in the energy domain where neither wire nor nanotube is individually transparent. This effect can be used to control and optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems.

  2. GaN membrane metal-semiconductor-metal ultraviolet photodetector.

    PubMed

    Müller, A; Konstantinidis, G; Dragoman, M; Neculoiu, D; Kostopoulos, A; Androulidaki, M; Kayambaki, M; Vasilache, D

    2008-04-01

    GaN is a wide-bandgap semiconductor with still unexplored capabilities for ultraviolet detection. To exploit GaN properties better for ultraviolet detection, a metal-semiconductor-metal-type photodetector structure was designed and manufactured on a 2.2 microm thin GaN membrane fabricated by micromachining techniques. As a result, a very low dark current (30 pA at 3 V) and a maximum responsivity of 14 mA/W at a wavelength of 370 nm were obtained.

  3. New Concentric Electrode Metal-Semiconductor-Metal Photodetectors

    NASA Technical Reports Server (NTRS)

    Towe, Elias

    1996-01-01

    A new metal-semiconductor-metal (MSM) photodetector geometry is proposed. The new device has concentric metal electrodes which exhibit a high degree of symmetry and a design flexibility absent in the conventional MSM device. The concentric electrodes are biased to alternating potentials as in the conventional interdigitated device. Because of the high symmetry configuration, however, the new device also has a lower effective capacitance. This device and the conventional MSM structure are analyzed within a common theoretical framework which allows for the comparison of the important performance characteristics.

  4. Giant geometrically amplified piezoresistance in metal-semiconductor hybrid resistors

    NASA Astrophysics Data System (ADS)

    Hansen, Ole; Reck, Kasper; Thomsen, Erik V.

    2008-12-01

    We show that very high geometrically amplified piezoresistance can indeed be obtained in microstructured metal-semiconductor hybrid devices, even significantly higher amplification factors than the factor of approximately 8 demonstrated recently by Rowe and co-workers may be achieved. However, we also show that this amplification cannot be used to realize high sensitivity sensor devices due to limitation of the applied voltage across the device when the transfer resistance is smaller than the total resistance of the device. In that case, the sensitivity in units of V V-1 Pa-1 is always less than the sensitivity of conventional piezoresistors fabricated in the same piezoresistive material.

  5. General atomistic approach for modeling metal-semiconductor interfaces using density functional theory and nonequilibrium Green's function

    NASA Astrophysics Data System (ADS)

    Stradi, Daniele; Martinez, Umberto; Blom, Anders; Brandbyge, Mads; Stokbro, Kurt

    2016-04-01

    Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce an atomistic approach based on density functional theory and nonequilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I -Vbias curve simulations. We apply this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as a function of the semiconductor doping. We also demonstrate that the standard "activation energy" method for the analysis of I -Vbias data might be inaccurate for nonideal interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid alternative to conventional procedures for the accurate characterization of metal-semiconductor interfaces.

  6. Ultraviolet random lasing from asymmetrically contacted MgZnO metal-semiconductor-metal device

    SciTech Connect

    Morshed, Muhammad M.; Suja, Mohammad; Zuo, Zheng; Liu, Jianlin

    2014-11-24

    Nitrogen-doped Mg{sub 0.12}Zn{sub 0.88}O nanocrystalline thin film was grown on c-plane sapphire substrate. Asymmetric Ni/Au and Ti/Au Schottky contacts and symmetric Ni/Au contacts were deposited on the thin film to form metal-semiconductor-metal (MSM) laser devices. Current-voltage, photocurrent, and electroluminescence characterizations were performed. Evident random lasing with a threshold current of ∼36 mA is demonstrated only from the asymmetric MSM device. Random lasing peaks are mostly distributed between 340 and 360 nm and an output power of 15 nW is measured at 43 mA injection current. The electron affinity difference between the contact metal and Mg{sub 0.12}Zn{sub 0.88}O:N layer plays an important role for electron and hole injection and subsequent stimulated random lasing.

  7. Tuning the p-type Schottky barrier in 2D metal/semiconductor interface:boron-sheet on MoSe2, and WSe2

    NASA Astrophysics Data System (ADS)

    Couto, W. R. M.; Miwa, R. H.; Fazzio, A.

    2017-10-01

    Van der Waals (vdW) metal/semiconductor heterostructures have been investigated through first-principles calculations. We have considered the recently synthesized borophene (Mannix et al 2015 Science 350 1513), and the planar boron sheets (S1 and S2) (Feng et al 2016 Nat. Chem. 8 563) as the 2D metal layer, and the transition metal dichalcogenides (TMDCs) MoSe2, and WSe2 as the semiconductor monolayer. We find that the energetic stability of those 2D metal/semiconductor heterojunctions is mostly ruled by the vdW interactions; however, chemical interactions also take place in borophene/TMDC. The electronic charge transfer at the metal/semiconductor interface has been mapped, where we find a a net charge transfer from the TMDCs to the boron sheets. Further electronic structure calculations reveal that the metal/semiconductor interfaces, composed by planar boron sheets S1 and S2, present a p-type Schottky barrier which can be tuned to a p-type ohmic contact by an external electric field.

  8. Tuning the p-type Schottky barrier in 2D metal/semiconductor interface:boron-sheet on MoSe2, and WSe2.

    PubMed

    Couto, W R M; Miwa, R H; Fazzio, A

    2017-10-11

    Van der Waals (vdW) metal/semiconductor heterostructures have been investigated through first-principles calculations. We have considered the recently synthesized borophene (Mannix et al 2015 Science 350 1513), and the planar boron sheets (S1 and S2) (Feng et al 2016 Nat. Chem. 8 563) as the 2D metal layer, and the transition metal dichalcogenides (TMDCs) MoSe2, and WSe2 as the semiconductor monolayer. We find that the energetic stability of those 2D metal/semiconductor heterojunctions is mostly ruled by the vdW interactions; however, chemical interactions also take place in borophene/TMDC. The electronic charge transfer at the metal/semiconductor interface has been mapped, where we find a a net charge transfer from the TMDCs to the boron sheets. Further electronic structure calculations reveal that the metal/semiconductor interfaces, composed by planar boron sheets S1 and S2, present a p-type Schottky barrier which can be tuned to a p-type ohmic contact by an external electric field.

  9. Observation of quantum oscillation of work function in ultrathin-metal/semiconductor junctions

    SciTech Connect

    Takhar, Kuldeep; Meer, Mudassar; Khachariya, Dolar; Ganguly, Swaroop; Saha, Dipankar

    2015-09-15

    Quantization in energy level due to confinement is generally observed for semiconductors. This property is used for various quantum devices, and it helps to improve the characteristics of conventional devices. Here, the authors have demonstrated the quantum size effects in ultrathin metal (Ni) layers sandwiched between two large band-gap materials. The metal work function is found to oscillate as a function of its thickness. The thermionic emission current bears the signature of the oscillating work function, which has a linear relationship with barrier heights. This methodology allows direct observation of quantum oscillations in metals at room temperature using a Schottky diode and electrical measurements using source-measure-units. The observed phenomena can provide additional mechanism to tune the barrier height of metal/semiconductor junctions, which are used for various electronic devices.

  10. Equivalent circuit modeling of metal-semiconductor-metal photodiodes with transparent conductor electrodes

    NASA Astrophysics Data System (ADS)

    Rommel, Sean L.; Erby, David N.; Gao, Wei; Berger, Paul R.; Zydzik, George J.; Rhodes, W. W.; O'Bryan, H. M.; Sivco, Deborah L.; Cho, Alfred Y.

    1997-04-01

    Metal-semiconductor-metal (MSM) photodiodes with electrodes fabricated from the transparent conductor cadmium tin oxide (CTO) have been shown to double photoresponsivity. Their bandwidths, however, are significantly lower than those of MSMs fabricated with standard Ti/Au contacts. Though MSMs are generally believed to be limited by the transit time of electrons, it is possible the larger resistivity of CTO has become a significant factor, making the MSMs RC time constant limited instead. Previous models of MSMs only account for one of the two back-to-back Schottky diodes. A new model which takes into account both the forward and reverse biased junctions has been developed from the small signal model of a Schottky diode. This new model was fit to data obtained from S-parameter measurements, and incorporates both the transit time response and RC time constant response.

  11. Interface Schottky barrier engineering via strain in metal-semiconductor composites

    NASA Astrophysics Data System (ADS)

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2016-01-01

    The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures.The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation

  12. Metal-semiconductor interfacial reactions - Ni/Si system

    NASA Technical Reports Server (NTRS)

    Cheung, N. W.; Grunthaner, P. J.; Grunthaner, F. J.; Mayer, J. W.; Ullrich, B. M.

    1981-01-01

    X-ray photoelectron spectroscopy and channeling measurements with MeV He-4(+) ions have been used to probe the structure of the interface in the Ni/Si system. It is found that reactions occur where Ni is deposited on Si at 10 to the -10th torr: Si atoms are displaced from lattice sites, the Ni atoms are in an Si-rich environment, and the Ni/Si interface is graded in composition. Composition gradients are present at both interfaces in the Si/Ni2/Si/Ni system. For the Ni-Si system, cooling the substrate to 100 K slows down the reaction rate. The temperature dependence of the interfacial reactivity indicates the kinetic nature of metal-semiconductor interfaces.

  13. Flexible germanium nanomembrane metal-semiconductor-metal photodiodes

    SciTech Connect

    Kim, Munho; Seo, Jung-Hun; Yu, Zongfu; Ma, Zhenqiang; Zhou, Weidong

    2016-08-01

    We demonstrate flexible Ge nanomembrane (Ge NM) based metal-semiconductor-metal photodiodes. The effect of uniaxial tensile strain on Ge NM based photodiodes was investigated using bending fixtures. Dark current density is decreased from 21.5 to 4.8 mA/cm{sup 2} at 3 V by a tensile strain of 0.42% while photon responsivity is increased from 0.2 to 0.45 A/W at the wavelength of 1.5 μm. Enhanced responsivity is also observed at longer wavelengths up to 1.64 μm. The uniaxial tensile strain effectively reduces the direct bandgap energy of the Ge NM, leading to a shift of the absorption edge toward a longer wavelength.

  14. Metal-semiconductor interfacial reactions - Ni/Si system

    NASA Technical Reports Server (NTRS)

    Cheung, N. W.; Grunthaner, P. J.; Grunthaner, F. J.; Mayer, J. W.; Ullrich, B. M.

    1981-01-01

    X-ray photoelectron spectroscopy and channeling measurements with MeV He-4(+) ions have been used to probe the structure of the interface in the Ni/Si system. It is found that reactions occur where Ni is deposited on Si at 10 to the -10th torr: Si atoms are displaced from lattice sites, the Ni atoms are in an Si-rich environment, and the Ni/Si interface is graded in composition. Composition gradients are present at both interfaces in the Si/Ni2/Si/Ni system. For the Ni-Si system, cooling the substrate to 100 K slows down the reaction rate. The temperature dependence of the interfacial reactivity indicates the kinetic nature of metal-semiconductor interfaces.

  15. Metal/Semiconductor hybrid nanostructures for plasmon-enhanced applications.

    PubMed

    Jiang, Ruibin; Li, Benxia; Fang, Caihong; Wang, Jianfang

    2014-08-20

    Hybrid nanostructures composed of semiconductor and plasmonic metal components are receiving extensive attention. They display extraordinary optical characteristics that are derived from the simultaneous existence and close conjunction of localized surface plasmon resonance and semiconduction, as well as the synergistic interactions between the two components. They have been widely studied for photocatalysis, plasmon-enhanced spectroscopy, biotechnology, and solar cells. In this review, the developments in the field of (plasmonic metal)/semiconductor hybrid nanostructures are comprehensively described. The preparation of the hybrid nanostructures is first presented according to the semiconductor type, as well as the nanostructure morphology. The plasmonic properties and the enabled applications of the hybrid nanostructures are then elucidated. Lastly, possible future research in this burgeoning field is discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Absorption properties of metal-semiconductor hybrid nanoparticles.

    PubMed

    Shaviv, Ehud; Schubert, Olaf; Alves-Santos, Marcelo; Goldoni, Guido; Di Felice, Rosa; Vallée, Fabrice; Del Fatti, Natalia; Banin, Uri; Sönnichsen, Carsten

    2011-06-28

    The optical response of hybrid metal-semiconductor nanoparticles exhibits different behaviors due to the proximity between the disparate materials. For some hybrid systems, such as CdS-Au matchstick-shaped hybrids, the particles essentially retain the optical properties of their original components, with minor changes. Other systems, such as CdSe-Au dumbbell-shaped nanoparticles, exhibit significant change in the optical properties due to strong coupling between the two materials. Here, we study the absorption of these hybrids by comparing experimental results with simulations using the discrete dipole approximation method (DDA) employing dielectric functions of the bare components as inputs. For CdS-Au nanoparticles, the DDA simulation provides insights on the gold tip shape and its interface with the semiconductor, information that is difficult to acquire by experimental means alone. Furthermore, the qualitative agreement between DDA simulations and experimental data for CdS-Au implies that most effects influencing the absorption of this hybrid system are well described by local dielectric functions obtained separately for bare gold and CdS nanoparticles. For dumbbell shaped CdSe-Au, we find a shortcoming of the electrodynamic model, as it does not predict the "washing out" of the optical features of the semiconductor and the metal observed experimentally. The difference between experiment and theory is ascribed to strong interaction of the metal and semiconductor excitations, which spectrally overlap in the CdSe case. The present study exemplifies the employment of theoretical approaches used to describe the optical properties of semiconductors and metal nanoparticles, to achieve better understanding of the behavior of metal-semiconductor hybrid nanoparticles.

  17. Spintronic effects in metallic, semiconductor, metal oxide and metal semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Bratkovsky, A. M.

    2008-02-01

    Spintronics is a rapidly growing field focusing on phenomena and related devices essentially dependent on spin transport. Some of them are already an established part of microelectronics. We review recent theoretical and experimental advances in achieving large spin injection efficiency (polarization of current) and accumulated spin polarization. These include tunnel and giant magnetoresistance, spin-torque and spin-orbit effects on electron transport in various heterostructures. We give a microscopic description of spin tunneling through oxide and modified Schottky barriers between a ferromagnet (FM) and a semiconductor (S). It is shown that in such FM-S junctions electrons with a certain spin projection can be efficiently injected into (or extracted from) S, while electrons with the opposite spin can accumulate in S near the interface. The criterion for efficient injection is opposite to a known Rashba criterion, since the barrier should be rather transparent. In degenerate semiconductors, extraction of spin can proceed at low temperatures. We mention a few novel spin-valve ultrafast devices with small dissipated power: a magnetic sensor, a spin transistor, an amplifier, a frequency multiplier, a square-law detector and a source of polarized radiation. We also discuss effects related to spin-orbital interactions, such as the spin Hall effect (SHE) and a recently predicted positive magnetoresistance accompanying SHE. Some esoteric devices such as 'spinFET', interacting spin logic and spin-based quantum computing are discussed and problems with their realization are highlighted. We demonstrate that the so-called 'ferroelectric tunnel junctions' are unlikely to provide additional functionality because in all realistic situations the ferroelectric barrier would be split into domains by the depolarizing field.

  18. Analysis of the metal-semiconductor structural phase transition in FeSi2 by tight-binding molecular dynamics

    NASA Astrophysics Data System (ADS)

    Miglio, L.; Meregalli, V.; Tavazza, F.; Celino, M.

    1997-02-01

    We show that tight-binding molecular dynamics provides a detailed description of the relations between structural deformations and changes in the electronic features during a Jahn-Teller process. In this case the metal-semiconductor displacitive phase transition occurring in epitaxial FeSi2 with film thickness can be correctly reproduced and interpreted by variable cell molecular dynamics for the bulk configuration. We show that it actually corresponds to a pattern of local Jahn-Teller distortions occurring at selected sites in different times, so that the configurational evolution cannot be described by a global coordinate.

  19. Adjustable metal-semiconductor transition of FeS thin films by thermal annealing

    SciTech Connect

    Fu Ganhua; Polity, Angelika; Volbers, Niklas; Meyer, Bruno K.; Mogwitz, Boris; Janek, Juergen

    2006-12-25

    FeS polycrystalline thin films were prepared on float glass at 500 deg. C by radio-frequency reactive sputtering. The influence of vacuum annealing on the metal-semiconductor transition of FeS films was investigated. It has been found that with the increase of the annealing temperature from 360 to 600 deg. C, the metal-semiconductor transition temperature of FeS films first decreases and then increases, associated with first a reduction and then an enhancement of hysteresis width. The thermal stress is considered to give rise to the abnormal change of the metal-semiconductor transition of the FeS film during annealing.

  20. Multiple percolation tunneling staircase in metal-semiconductor nanoparticle composites

    SciTech Connect

    Mukherjee, Rupam; Huang, Zhi-Feng; Nadgorny, Boris

    2014-10-27

    Multiple percolation transitions are observed in a binary system of RuO{sub 2}-CaCu{sub 3}Ti{sub 4}O{sub 12} metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO{sub 2} metal oxide nanoparticles, at least two additional tunneling percolation transitions are detected in this composite system. Such behavior is consistent with the recently emerged picture of a quantum conductivity staircase, which predicts several percolation tunneling thresholds in a system with a hierarchy of local tunneling conductance, due to various degrees of proximity of adjacent conducting particles distributed in an insulating matrix. Here, we investigate a different type of percolation tunneling staircase, associated with a more complex conductive and insulating particle microstructure of two types of non-spherical constituents. As tunneling is strongly temperature dependent, we use variable temperature measurements to emphasize the hierarchical nature of consecutive tunneling transitions. The critical exponents corresponding to specific tunneling percolation thresholds are found to be nonuniversal and temperature dependent.

  1. One-dimensional quantum transport in hybrid metal-semiconductor nanotube systems

    NASA Astrophysics Data System (ADS)

    Gelin, Maxim; Bondarev, Igor

    We study the inter-play between the intrinsic 1D conductance of metallic atomic wires (AWs) and plasmon mediated near-field effects for semiconducting single wall carbon nanotubes (CNs) that encapsulate AWs of finite length. We use the matrix Green's functions formalism to develop an electron transfer theory for such a hybrid quasi-1D metal-semiconductor nanotube system. The theory predicts Fano resonances in electron transmission through the system. That is the AW-CN near-field interaction blocks some of the pristine AW transmission band channels to open up new coherent channels in the CN forbidden gap outside the pristine AW transmission band. This makes the entire hybrid system transparent in the energy domain where neither of the individual pristine constituents, neither AW nor CN, are transparent. The effect can be used to control electron charge transfer in semiconducting CN based devices for nanoscale energy conversion, separation and storage. Nsf-ECCS-1306871 (M.G.), DOE-DE-SC0007117 (I.B.).

  2. Charge transfer during low energy metal/semiconductor ion-surface interactions

    NASA Astrophysics Data System (ADS)

    Chen, Xiaojian

    Ion-surface charge exchange is a central process in many surface analysis techniques and technical processes. Previous ion scattering studies have extensively investigated the interactions between alkali/noble gas ions and surfaces. Investigations of the interactions between metal/semiconductor ions and metal surfaces have seldom been reported, although they are of central importance in understanding processes involving the removal material from metal/semiconductor surfaces. This dissertation uses low energy ion scattering and direct recoil to reveal charge transfer mechanisms between metal/semiconductor atomic particles and clean and adsorb ate-covered Al and Si surfaces. All involved experiments were performed in ultra-high vacuum. Charge transfer between an Al atom and an Al surface is studied by producing energetic recoiled Al from a Al(100) surface via Xe+ bombardment. The measured neutral fractions of the recoils show that resonant charge transfer (RCT) is a key mechanism. The ion formation of recoiled and sputtered atoms can be both described by RCT. The characteristic difference between recoiled and sputtered atoms is interpreted as due to different surface conditions at the time of ion emission. 1˜5 keV Si+ ions were incident on atomically clean Al(100) surface. All scattered Si was neutralized, while Al ions were found in multi-charged states. In contrast to the traditional sputtering studies, there is an abnormally high yield of Al2+ and Al3+. The multiply charged ions are attributed to the charge promotion of Al 2p level during the electronically nearly-symmetric Si-Al collision, and subsequent shake-off processes. This mechanism is supported by the energy dependence of Al ions as well as ion induced Auger electrons. Si+ ions were scattered from submonolayers of Cs deposited onto Al(100). Because of the high ionization energy of Si, resonant charge transfer would be expected to completely neutralize the scattered projectiles. In contrast, a

  3. Non-radiative relaxation and rectification behavior of metal/semiconductor tetrapod heterostructures

    SciTech Connect

    Kanta Haldar, Krishna; Kundu, Simanta; Patra, Amitava

    2014-02-10

    The metal-semiconductor hetero-structures have recently emerged as functional materials for their potential applications in the areas of photonic, optoelectronic, and other fields. Here, we discuss the structural characterization of Au/CdSe tetrapod hetero-structures by using high-resolution transmission electron microscope, high angle annular dark field-scanning transmission electron microscopic, and X-ray diffraction. The blue shifting of the plasmonic band and red shifting of the excitonic band suggest a strong surface plasmon-exciton interaction between Au and CdSe in Au/CdSe tetrapod heterostructure. A significant photoluminescence quenching (83.4%) of CdSe nanorod (NR) is observed in the presence of Au nanoparticle in Au/CdSe tetrapod heterostructure. The radiative and nonradiative decay rates of CdSe nanorods are found to be modified in Au/CdSe tetrapod structures and the nonradiative rate changes from 1.91 × 10{sup 7} s{sup −1} to 9.33 × 10{sup 9} s{sup −1} for CdSe NR to Au/CdSe tetrapod structure, respectively. Current-voltage characteristics of Au/CdSe heterostructure exhibit the rectification property with a threshold voltage of about 0.85 V and the rectifying ratio is 140 which can open up avenues for developing challenging devices.

  4. Biomolecular detection using a metal semiconductor field effect transistor

    NASA Astrophysics Data System (ADS)

    Estephan, Elias; Saab, Marie-Belle; Buzatu, Petre; Aulombard, Roger; Cuisinier, Frédéric J. G.; Gergely, Csilla; Cloitre, Thierry

    2010-04-01

    In this work, our attention was drawn towards developing affinity-based electrical biosensors, using a MESFET (Metal Semiconductor Field Effect Transistor). Semiconductor (SC) surfaces must be prepared before the incubations with biomolecules. The peptides route was adapted to exceed and bypass the limits revealed by other types of surface modification due to the unwanted unspecific interactions. As these peptides reveal specific recognition of materials, then controlled functionalization can be achieved. Peptides were produced by phage display technology using a library of M13 bacteriophage. After several rounds of bio-panning, the phages presenting affinities for GaAs SC were isolated; the DNA of these specific phages were sequenced, and the peptide with the highest affinity was synthesized and biotinylated. To explore the possibility of electrical detection, the MESFET fabricated with the GaAs SC were used to detect the streptavidin via the biotinylated peptide in the presence of the bovine Serum Albumin. After each surface modification step, the IDS (current between the drain and the source) of the transistor was measured and a decrease in the intensity was detected. Furthermore, fluorescent microscopy was used in order to prove the specificity of this peptide and the specific localisation of biomolecules. In conclusion, the feasibility of producing an electrical biosensor using a MESFET has been demonstrated. Controlled placement, specific localization and detection of biomolecules on a MESFET transistor were achieved without covering the drain and the source. This method of functionalization and detection can be of great utility for biosensing application opening a new way for developing bioFETs (Biomolecular Field-Effect Transistor).

  5. Hybrid metal-semiconductor cavities for multi-band perfect light absorbers and excellent electric conducting interfaces

    NASA Astrophysics Data System (ADS)

    Huang, Zhenping; Chen, Jian; Liu, Yi; Tang, Li; Liu, Guiqiang; Liu, Xiaoshan; Liu, Zhengqi

    2017-08-01

    It is desirable for optoelectronic devices to have the capability to simultaneously achieve excellent optical and electric features. Nevertheless, most investigations were performed separately for photon and electron management. In this work, we numerically propose and demonstrate a hybrid metal-semiconductor interface, which offers multi-band perfect light absorption and simultaneously retains the naturally perfect electrical conductivity of a flat metal film. Multi-band anti-reflection and near-unity light absorption is observed in this hybrid metal-semiconductor cavity based absorber (HMSA). Our results show that, the maximal absorption above 97% and the naturally perfect electric conductivity are realizable, suggesting the capability of providing both excellent optical and electric properties. Optical Mie-like resonances in the semiconductor cavities and the hybrid coupling with plasmonic resonances by the metal resonators cooperatively support strong optical field confinement effects, which eventually create the light trapped in the HMSA. These features indicate a platform wherein excellent electrical conducting and multispectral light absorption are designed for potential optoelectronic applications.

  6. Development of epitaxial AlxSc1-xN for artificially structured metal/semiconductor superlattice metamaterials

    DOE PAGES

    Sands, Timothy D.; Stach, Eric A.; Saha, Bivas; ...

    2015-02-01

    Epitaxial nitride rocksalt metal/semiconductor superlattices are emerging as a novel class of artificially structured materials that have generated significant interest in recent years for their potential application in plasmonic and thermoelectric devices. Though most nitride metals are rocksalt, nitride semiconductors in general have hexagonal crystal structure. We report rocksalt aluminum scandium nitride (Al,Sc)N alloys as the semiconducting component in epitaxial rocksalt metal/semiconductor superlattices. The AlxSc1-xN alloys when deposited directly on MgO substrates are stabilized in a homogeneous rocksalt (single) phase when x < 0.51. Employing 20 nm TiN as a seed layer on MgO substrates, the homogeneity range for stabilizingmore » the rocksalt phase has been extended to x < 0.82 for a 120 nm film. The rocksalt AlxSc1-xN alloys show moderate direct bandgap bowing with a bowing parameter, B = 1.41 ± 0.19 eV. The direct bandgap of metastable rocksalt AlN is extrapolated to be 4.70 ± 0.20 eV. The tunable lattice parameter, bandgap, dielectric permittivity, and electronic properties of rocksalt AlxSc1-xN alloys enable high quality epitaxial rocksalt metal/AlxSc1-xN superlattices with a wide range of accessible metamaterials properties.« less

  7. Size-controllable synthesis of Bi/Bi2O3 heterojunction nanoparticles using pulsed Nd:YAG laser deposition and metal-semiconductor-heterojunction-assisted photoluminescence

    NASA Astrophysics Data System (ADS)

    Patil, Ranjit A.; Wei, Mao-Kuo; Yeh, P.-H.; Liang, Jyun-Bo; Gao, Wan-Ting; Lin, Jin-Han; Liou, Yung; Ma, Yuan-Ron

    2016-02-01

    We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes (LEDs) and laser diodes (LDs).We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes

  8. Plasmon‐Mediated Solar Energy Conversion via Photocatalysis in Noble Metal/Semiconductor Composites

    PubMed Central

    Wang, Mengye; Ye, Meidan; Iocozzia, James

    2016-01-01

    Plasmonics has remained a prominent and growing field over the past several decades. The coupling of various chemical and photo phenomenon has sparked considerable interest in plasmon‐mediated photocatalysis. Given plasmonic photocatalysis has only been developed for a relatively short period, considerable progress has been made in improving the absorption across the full solar spectrum and the efficiency of photo‐generated charge carrier separation. With recent advances in fundamental (i.e., mechanisms) and experimental studies (i.e., the influence of size, geometry, surrounding dielectric field, etc.) on plasmon‐mediated photocatalysis, the rational design and synthesis of metal/semiconductor hybrid nanostructure photocatalysts has been realized. This review seeks to highlight the recent impressive developments in plasmon‐mediated photocatalytic mechanisms (i.e., Schottky junction, direct electron transfer, enhanced local electric field, plasmon resonant energy transfer, and scattering and heating effects), summarize a set of factors (i.e., size, geometry, dielectric environment, loading amount and composition of plasmonic metal, and nanostructure and properties of semiconductors) that largely affect plasmonic photocatalysis, and finally conclude with a perspective on future directions within this rich field of research. PMID:27818901

  9. Plasmonic effect-enhanced Ag nanodisk incorporated ZnO/Si metal-semiconductor-metal photodetectors

    NASA Astrophysics Data System (ADS)

    Kumar, Manjeet; Kojori, Hossein Shokri; Kim, Sung Jin; Park, Hyeong-Ho; Kim, Joondong; Yun, Ju-Hyung

    2016-10-01

    In this work, we present the enhancement of ultraviolet (UV) photodetection of Ag-ZnO thin film deposited by radio frequency magnetron sputtering. The surface morphological, optical, structural, and electrical properties of the deposited thin films were investigated by various characterization techniques. With this Ag-ZnO thin film structure and proper geometry of metal-semiconductor-metal (MSM) interdigitated structure design, photocurrent enhancement has been accomplished. MSM-photodetectors (PDs) using structures of Ag-ZnO gave a 30 times higher magnitude photocurrent at 340 nm of the wavelength. Plasmon-induced hot electrons contributed to improved spectral response to the UV region, while absorption and scattering effect enhanced broadband improvement to a response in the VIS-IR spectrum range. The improvement of Ag-ZnO PD in comparison with ZnO is attributed to the surface plasmon effect using Ag nanodisks. These results indicate that Ag-ZnO thin films can serve as excellent ultraviolet-PD and a very promising candidate for practical applications.

  10. Fabrication of Smooth Patterned Structures of Refractory Metals, Semiconductors, and Oxides via Template Stripping

    PubMed Central

    2013-01-01

    The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics. PMID:24001174

  11. Plasmon-Mediated Solar Energy Conversion via Photocatalysis in Noble Metal/Semiconductor Composites.

    PubMed

    Wang, Mengye; Ye, Meidan; Iocozzia, James; Lin, Changjian; Lin, Zhiqun

    2016-06-01

    Plasmonics has remained a prominent and growing field over the past several decades. The coupling of various chemical and photo phenomenon has sparked considerable interest in plasmon-mediated photocatalysis. Given plasmonic photocatalysis has only been developed for a relatively short period, considerable progress has been made in improving the absorption across the full solar spectrum and the efficiency of photo-generated charge carrier separation. With recent advances in fundamental (i.e., mechanisms) and experimental studies (i.e., the influence of size, geometry, surrounding dielectric field, etc.) on plasmon-mediated photocatalysis, the rational design and synthesis of metal/semiconductor hybrid nanostructure photocatalysts has been realized. This review seeks to highlight the recent impressive developments in plasmon-mediated photocatalytic mechanisms (i.e., Schottky junction, direct electron transfer, enhanced local electric field, plasmon resonant energy transfer, and scattering and heating effects), summarize a set of factors (i.e., size, geometry, dielectric environment, loading amount and composition of plasmonic metal, and nanostructure and properties of semiconductors) that largely affect plasmonic photocatalysis, and finally conclude with a perspective on future directions within this rich field of research.

  12. Fabrication of smooth patterned structures of refractory metals, semiconductors, and oxides via template stripping.

    PubMed

    Park, Jong Hyuk; Nagpal, Prashant; McPeak, Kevin M; Lindquist, Nathan C; Oh, Sang-Hyun; Norris, David J

    2013-10-09

    The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics.

  13. Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Jha, Pankaj

    Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

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

    SciTech Connect

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

    2016-04-22

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

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

    PubMed Central

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

    2016-01-01

    Two-dimensional (2D) semiconductors have shown great potential for electronic and optoelectronic applications. However, their development is limited by a large Schottky barrier (SB) at the metal-semiconductor junction (MSJ), which is difficult to tune by using conventional metals because of the effect of strong Fermi level pinning (FLP). We show that this problem can be overcome by using 2D metals, which are bounded with 2D semiconductors through van der Waals (vdW) interactions. This success relies on a weak FLP at the vdW MSJ, which is attributed to the suppression of metal-induced gap states. Consequently, the SB becomes tunable and can vanish with proper 2D metals (for example, H-NbS2). This work not only offers new insights into the fundamental properties of heterojunctions but also uncovers the great potential of 2D metals for device applications. PMID:27152360

  16. Effects of Photowashing Treatment on Gate Leakage Current of GaAs Metal-Semiconductor Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Choi, Kyoung Jin; Moon, Jae Kyoung; Park, Min; Kim, Haechon; Lee, Jong-Lam

    2002-05-01

    Effects of photowashing treatment on gate leakage current (IGD) of a GaAs metal-semiconductor field-effect transistor were studied by observing changes in atomic composition and band bending at the surface of GaAs through X-ray photoemission spectroscopy. The photowashing treatment produces Ga2O3 on the surface of GaAs, leaving acceptor-type Ga antisites behind under the oxide. The Ga antisites played a role in reducing the maximum electric field at the drain edge of the gate, leading to the decrease of IGD. The longer photowashing time produced thicker oxide on the surface of GaAs, acting as a conducting pass for electrons, leading to the increase of IGD.

  17. Effects of interdigitated platinum finger geometry on spectral response characteristics of germanium metal-semiconductor-metal photodetectors.

    PubMed

    Yang, Hyun-Duk; Janardhanam, V; Shim, Kyu-Hwan; Choi, Chel-Jong

    2014-10-01

    We fabricated interdigitated germanium (Ge) metal-semiconductor-metal photodetectors (MSM PDs) with interdigitated platinum (Pt) finger electrodes and investigated the effects of Pt finger width and spacing on their spectral response. An increase in the incident optical power enhances the creation of electron-hole pairs, resulting in a significant increase in photo current. Lowering of the Schottky barrier could be a main cause of the increase in both photo and dark current with increasing applied bias. The manufactured Ge MSM PDs exhibited a considerable spectral response for wavelengths in the range of 1.53-1.56 μm, corresponding to the entire C-band spectrum range. A reduction in the area fraction of the Pt finger electrode in the active region by decreasing and increasing finger width and spacing, respectively, led to an increase in illuminated active area and suppression of dark current, which was responsible for the improvement in responsivity and quantum efficiency of Ge MSM PDs.

  18. Optical absorption enhancement of hybrid-plasmonic-based metal-semiconductor-metal photodetector incorporating metal nanogratings and embedded metal nanoparticles.

    PubMed

    Tan, Chee Leong; Karar, Ayman; Alameh, Kamal; Lee, Yong Tak

    2013-01-28

    We propose and numerically demonstrate a high absorption hybrid-plasmonic-based metal semiconductor metal photodetector (MSM-PD) comprising metal nanogratings, a subwavelength slit and amorphous silicon or germanium embedded metal nanoparticles (NPs). Simulation results show that by optimizing the metal nanograting parameters, the subwavelength slit and the embedded metal NPs, a 1.3 order of magnitude increase in electric field is attained, leading to 28-fold absorption enhancement, in comparison with conventional MSM-PD structures. This is 3.5 times better than the absorption of surface plasmon polariton (SPP) based MSM-PD structures employing metal nanogratings and a subwavelength slit. This absorption enhancement is due to the ability of the embedded metal NPs to enhance their optical absorption and scattering properties through light-stimulated resonance aided by the conduction electrons of the NPs.

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

    DOE PAGES

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

    2016-04-22

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

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

    PubMed

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

    2016-04-01

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

  1. Metal-semiconductor phase transition of order arrays of VO2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Lopez, Rene; Suh, Jae; Feldman, Leonard; Haglund, Richard

    2004-03-01

    The study of solid-state phase transitions at nanometer length scales provides new insights into the effects of material size on the mechanisms of structural transformations. Such research also opens the door to new applications, either because materials properties are modified as a function of particle size, or because the nanoparticles interact with a surrounding matrix material, or with each other. In this paper, we describe the formation of vanadium dioxide nanoparticles in silicon substrates by pulsed laser deposition of ion beam lithographically selected sites and thermal processing. We observe the collective behavior of 50 nm diameter VO2 oblate nanoparticles, 10 nm high, and ordered in square arrays with arbitrary lattice constant. The metal-semiconductor-transition of the VO2 precipitates shows different features in each lattice spacing substrate. The materials are characterized by electron microscopy, x-ray diffraction, Rutherford backscattering. The features of the phase transition are studied via infrared optical spectroscopy. Of particular interest are the enhanced scattering and the surface plasmon resonance when the particles reach the metallic state. This resonance amplifies the optical contrast in the range of near-infrared optical communication wavelengths and it is altered by the particle-particle coupling as in the case of noble metals. In addition the VO2 nanoparticles exhibit sharp transitions with up to 50 K of hysteresis, one of the largest values ever reported for this transition. The optical properties of the VO2 nanoarrays are correlated with the size of the precipitates and their inter-particle distance. Nonlinear and ultra fast optical measurements have shown that the transition is the fastest known solid-solid transformation. The VO2 nanoparticles show the same bulk property, transforming in times shorter than 150 fs. This makes them remarkable candidates for ultrafast optical and electronic switching applications.

  2. Modeling of wide-area thin-film metal-semiconductor-metal photodetectors for LIDAR applications

    NASA Astrophysics Data System (ADS)

    Glinz, Andreas P.; Morrison, Charles B.; Zhu, Zheng

    1998-07-01

    We report calculations of the collection current of interdigitated InGaAs metal-semiconductor-metal photodetectors. We show how interdigital spacing and thickness of the semiconductor layer influence the collection current. Both front and back illumination of devices carried on thin film membranes by means of epitaxial liftoff are examined.

  3. Crystal Phases in Hybrid Metal-Semiconductor Nanowire Devices.

    PubMed

    David, J; Rossella, F; Rocci, M; Ercolani, D; Sorba, L; Beltram, F; Gemmi, M; Roddaro, S

    2017-04-12

    We investigate the metallic phases observed in hybrid metal-GaAs nanowire devices obtained by controlled thermal annealing of Ni/Au electrodes. Devices are fabricated onto a SiN membrane compatible with transmission electron microscopy studies. Energy dispersive X-ray spectroscopy allows us to show that the nanowire body includes two Ni-rich phases that thanks to an innovative use of electron diffraction tomography can be unambiguously identified as Ni3GaAs and Ni5As2 crystals. The mechanisms of Ni incorporation leading to the observed phenomenology are discussed.

  4. Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction

    NASA Astrophysics Data System (ADS)

    Talukdar, Keka; Shantappa, Anil

    2016-10-01

    Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone-Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

  5. Metal-Semiconductor Interfaces and Patterns in Functionalized Graphene

    NASA Astrophysics Data System (ADS)

    Singh, Abhishek; Penev, Evgeni; Yakobson, Boris

    2010-03-01

    Functionalization offers a novel way to modify the electronic and magnetic properties of graphene. Specific topology is essential to achieve devices with the desired features. Using density functional theory, we demonstrate stability of several such configurations, (in single and double sided functionalized graphene) and analyze their electronic and magnetic properties. We show that ``nanoroads'' [1] and ``nanodots'' [2] of pristine graphene can be carved in the electrically insulating matrix of fully hydrogenated carbon sheet (graphane) [1]. Such one-dimensional roads display individual characteristics and, depending upon zigzag or armchair orientation, can be metallic or semiconducting. Furthermore, the wide enough zigzag roads become magnetic with energetically similar ferro- and antiferromagnetic states. Engineering magnetic, metallic, and semiconducting elements within the same mechanically intact sheet of graphene presents a new opportunity for applications. [1] A. K. Singh and B. I. Yakobson, Nano Lett., 9, 1540 (2009). [2] A. K. Singh, E. S. Penev, and B. I. Yakobson submitted.

  6. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-09

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  7. Is DNA a metal, semiconductor or insulator? A theoretical approach

    NASA Astrophysics Data System (ADS)

    Rey-Gonzalez, Rafael; Fonseca-Romero, Karen; Plazas, Carlos; Grupo de Óptica e Información Cuántica Team

    Over the last years, scientific interest for designing and making low dimensional electronic devices with traditional or novel materials has been increased. These experimental and theoretical researches in electronic properties at molecular scale are looking for developing efficient devices able to carry out tasks which are currently done by silicon transistors and devices. Among the new materials DNA strands are highlighted, but the experimental results have been contradictories pointing to behaviors as conductor, semiconductor or insulator. To contribute to the understanding of the origin of the disparity of the measurements, we perform a numerical calculation of the electrical conductance of DNA segments, modeled as 1D disordered finite chains. The system is described into a Tight binding model with nearest neighbor interactions and a s orbital per site. Hydration effects are included as random variations of self-energies. The electronic current as a function of applied bias is calculated using Launder formalism, where the transmission probability is determined into the transfer matrix formalism. We find a conductor-to-semiconductor-to-insulator transition as a function of the three effects taken into account: chain size, intrinsic disorder, and hydration We thank Fundación para la Promoción de la Investigación y la Tecnología, Colombia, and Dirección de Investigación de Bogotá, Universidad Nacional de Colombia, for partial financial support.

  8. Preparation methodologies and nano/microstructural evaluation of metal/semiconductor thin films.

    PubMed

    Chen, Zhiwen; Jiao, Zheng; Wu, Minghong; Shek, Chan-Hung; Wu, C M Lawrence; Lai, Joseph K L

    2012-01-01

    Metal/semiconductor thin films are a class of unique materials that are widespread technological applications, particularly in the field of microelectronic devices. Assessment strategies of fractal and tures are of fundamental importance in the development of nano/microdevices. This review presents the preparation methodologies and nano/microstructural evaluation of metal/semiconductor thin films including Au/Ge bilayer films and Pd-Ge alloy thin films, which show in the form of fractals and nanocrystals. Firstly, the extended version of Au/Ge thin films for the fractal crystallization of amorphous Ge and the formation of nanocrystals developed with improved micro- and nanostructured features are described in Section 2. Secondly, the nano/microstructural characteristics of Pd/Ge alloy thin films during annealing have been investigated in detail and described in Section 3. Finally, we will draw the conclusions from the present work as shown in Section 4. It is expected that the preparation methodologies developed and the knowledge of nano/microstructural evolution gained in metal/semiconductor thin films, including Au/Ge bilayer films and Pd-Ge alloy thin films, will provide an important fundamental basis underpinning further interdisciplinary research in these fields such as physics, chemistry, materials science, and nanoscience and nanotechnology, leading to promising exciting opportunities for future technological applications involving these thin films.

  9. Genetically Modified Collagen-like Triple helix Protein as Biomimetic Template to Fabricate Metal/Semiconductor Nanowires

    NASA Astrophysics Data System (ADS)

    Bai, Hanying

    collagen-like triple helix that is monodisperse, easily mineralized with metal/ semiconductor precursors, and therefore can be applied as a rigid biomolecular template for metal/semiconductor nanowire fabrications. Moreover the production of triple helix can be large scaled up by means of the cell multiplication. As continued work based on previous study of the application of C7 glycylglycine bolaamphiphilic peptide, the self-assembly of doughnut-shaped nanoreactors from monomer peptides with silica precursors was studied, and uniform size silica (SiO2) nanoparticles were obtained. Possible mechanism in terms of chelating and catalysis functions of the peptide was formulated. Keyword: Collagen-like Triple Helix, Nanowire, Fabrication, Recombinant, Biotemplate.

  10. Reaction Current Phenomenon in Bifunctional Catalytic Metal-Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Hashemian, Mohammad Amin

    Energy transfer processes accompany every elementary step of catalytic chemical processes on material surface including molecular adsorption and dissociation on atoms, interactions between intermediates, and desorption of reaction products from the catalyst surface. Therefore, detailed understanding of these processes on the molecular level is of great fundamental and practical interest in energy-related applications of nanomaterials. Two main mechanisms of energy transfer from adsorbed particles to a surface are known: (i) adiabatic via excitation of quantized lattice vibrations (phonons) and (ii) non-adiabatic via electronic excitations (electron/hole pairs). Electronic excitations play a key role in nanocatalysis, and it was recently shown that they can be efficiently detected and studied using Schottky-type catalytic nanostructures in the form of measureable electrical currents (chemicurrents) in an external electrical circuit. These nanostructures typically contain an electrically continuous nanocathode layers made of a catalytic metal deposited on a semiconductor substrate. The goal of this research is to study the direct observations of hot electron currents (chemicurrents) in catalytic Schottky structures, using a continuous mesh-like Pt nanofilm grown onto a mesoporous TiO2 substrate. Such devices showed qualitatively different and more diverse signal properties, compared to the earlier devices using smooth substrates, which could only be explained on the basis of bifunctionality. In particular, it was necessary to suggest that different stages of the reaction are occurring on both phases of the catalytic structure. Analysis of the signal behavior also led to discovery of a formerly unknown (very slow) mode of the oxyhydrogen reaction on the Pt/TiO2(por) system occurring at room temperature. This slow mode was producing surprisingly large stationary chemicurrents in the range 10--50 microA/cm2. Results of the chemicurrent measurements for the bifunctional

  11. Size-controllable synthesis of Bi/Bi2O3 heterojunction nanoparticles using pulsed Nd:YAG laser deposition and metal-semiconductor-heterojunction-assisted photoluminescence.

    PubMed

    Patil, Ranjit A; Wei, Mao-Kuo; Yeh, P-H; Liang, Jyun-Bo; Gao, Wan-Ting; Lin, Jin-Han; Liou, Yung; Ma, Yuan-Ron

    2016-02-14

    We synthesized Bi/Bi2O3 heterojunction nanoparticles at various substrate temperatures using the pulsed laser deposition (PLD) technique with a pulsed Nd:YAG laser. The Bi/Bi2O3 heterojunction nanoparticles consisted of Bi nanoparticles and Bi2O3 surface layers. The average diameter of the Bi nanoparticles and the thickness of the Bi2O3 surface layer are linearly proportional to the substrate temperature. The heterojunctions between the Bi nanoparticles and Bi2O3 surface layers, which are the metal-semiconductor heterojunctions, can strongly enhance the photoluminescence (PL) of the Bi/Bi2O3 nanoparticles, because the metallic Bi nanoparticles can provide massive free Fermi-level electrons for the electron transitions in the Bi2O3 surface layers. The enhancement of PL emission at room temperature by metal-semiconductor-heterojunctions make the Bi/Bi2O3 heterojunction nanoparticles potential candidates for use in optoelectronic nanodevices, such as light-emitting diodes (LEDs) and laser diodes (LDs).

  12. Dynamically reconfigurable metal-semiconductor Yagi-Uda nanoantenna

    NASA Astrophysics Data System (ADS)

    Savelev, Roman S.; Sergaeva, Olga N.; Baranov, Denis G.; Krasnok, Alexander E.; Alù, Andrea

    2017-06-01

    We theoretically investigate the properties of a tunable Yagi-Uda nanoantenna composed of metal-dielectric (Ag-Ge) core-shell nanoparticles. We show that, due to the combination of two types of resonances in each nanoparticle, such hybrid Yagi-Uda nanoantenna can operate in two different regimes. Besides the conventional nonresonant operation regime at low frequencies, characterized by highly directive emission in the forward direction, there is another one at higher frequencies caused by a hybrid magneto-electric response of the core-shell nanoparticles. This regime is based on the excitation of the van Hove singularity, and emission in this regime is accompanied by high values of directivity and Purcell factor within the same narrow frequency range. Our analysis reveals the possibility of flexible dynamical tuning of the hybrid nanoantenna emission pattern via electron-hole plasma excitation by 100 fs pump pulse with relatively low peak intensities ˜200 MW cm-2 .

  13. Effects of Ge and Sn substitution on the metal-semiconductor transition and thermoelectric properties of Cu12Sb4S13 tetrahedrite.

    PubMed

    Kosaka, Yasufumi; Suekuni, Koichiro; Hashikuni, Katsuaki; Bouyrie, Yohan; Ohta, Michihiro; Takabatake, Toshiro

    2017-03-15

    The synthetic tetrahedrites Cu12-yTrySb4S13 (Tr: Mn, Fe, Co, Ni, Zn) have been extensively studied due to interest in metal-semiconductor transition as well as in superior thermoelectric performance. We have prepared Ge- and Sn-bearing tetrahedrites, Cu12-xMxSb4S13 (M = Ge, Sn; x ≤ 0.6), and investigated the effects of the substitutions on the phase transition and the thermoelectric properties. The substitutions of Ge and Sn for Cu suppress the metal-semiconductor transition and increase the electrical resistivity ρ and the positive thermopower S. This finding suggests that the phase transition is prevented by electron doping into the unoccupied states of the valence band. The variations of ρ, S, and magnetic susceptibility for the present systems correspond well with those for the system with Tr = Zn(2+), confirming the tetravalent states for Ge and Sn. The substitution of M(4+) for Cu(1+) decreases the power factor S(2)/ρ but enhances the dimensionless thermoelectric figure of merit ZT, due to reductions in both the charge carrier contribution and lattice contribution to the thermal conductivity. As a result, ZT has a maximum value of ∼0.65 at 665 K for x = 0.3-0.5 in Cu12-xMxSb4S13 with M = Ge and Sn.

  14. Development of epitaxial AlxSc1-xN for artificially structured metal/semiconductor superlattice metamaterials

    SciTech Connect

    Sands, Timothy D.; Stach, Eric A.; Saha, Bivas; Saber, Sammy; Naik, Gururaj V.; Boltasseva, Alexandra; Kvam, Eric P.

    2015-02-01

    Epitaxial nitride rocksalt metal/semiconductor superlattices are emerging as a novel class of artificially structured materials that have generated significant interest in recent years for their potential application in plasmonic and thermoelectric devices. Though most nitride metals are rocksalt, nitride semiconductors in general have hexagonal crystal structure. We report rocksalt aluminum scandium nitride (Al,Sc)N alloys as the semiconducting component in epitaxial rocksalt metal/semiconductor superlattices. The AlxSc1-xN alloys when deposited directly on MgO substrates are stabilized in a homogeneous rocksalt (single) phase when x < 0.51. Employing 20 nm TiN as a seed layer on MgO substrates, the homogeneity range for stabilizing the rocksalt phase has been extended to x < 0.82 for a 120 nm film. The rocksalt AlxSc1-xN alloys show moderate direct bandgap bowing with a bowing parameter, B = 1.41 ± 0.19 eV. The direct bandgap of metastable rocksalt AlN is extrapolated to be 4.70 ± 0.20 eV. The tunable lattice parameter, bandgap, dielectric permittivity, and electronic properties of rocksalt AlxSc1-xN alloys enable high quality epitaxial rocksalt metal/AlxSc1-xN superlattices with a wide range of accessible metamaterials properties.

  15. Recent progress on ZnO-based metal-semiconductor field-effect transistors and their application in transparent integrated circuits.

    PubMed

    Frenzel, Heiko; Lajn, Alexander; von Wenckstern, Holger; Lorenz, Michael; Schein, Friedrich; Zhang, Zhipeng; Grundmann, Marius

    2010-12-14

    Metal-semiconductor field-effect transistors (MESFETs) are widely known from opaque high-speed GaAs or high-power SiC and GaN technology. For the emerging field of transparent electronics, only metal-insulator-semiconductor field-effect transistors (MISFETs) were considered so far. This article reviews the progress of high-performance MESFETs in oxide electronics and reflects the recent advances of this technique towards transparent MESFET circuitry. We discuss design prospects as well as limitations regarding device performance, reliability and stability. The presented ZnO-based MESFETs and inverters have superior properties compared to MISFETs, i.e., high channel mobilities and on/off-ratios, high gain, and low uncertainty level at comparatively low operating voltages. This makes them a promising approach for future low-cost transparent electronics.

  16. Influence of Deuterium Treatments on the Polysilicon-Based Metal-Semiconductor-Metal Photodetector.

    PubMed

    Lee, Jae-Sung

    2016-06-01

    The electrical behavior of metal-semiconductor-metal (MSM) Schottky barrier photodetector structure, depending on deuterium treatment, is analyzed by means of the dark current and the photocurrent measurements. Al/Ti bilayer was used as Schottky metal. The deuterium incorporation into the absorption layer, undoped polysilicon, was achieved with annealing process and with ion implantation process, respectively. In the photocurrent-to-dark current ratio measurement, deuterium-ion-implanted photodetector shows over hundred higher than the control device. It means that the heightening of the Schottky barrier and the passivation of grain boundary trap were achieved effectively through the deuterium ion implantation process.

  17. Performance optimization of a free space optical interconnect system with a metal-semiconductor-metal detector

    NASA Astrophysics Data System (ADS)

    Al-Ababneh, Nedal; Khader, Ateka

    2011-08-01

    In this paper we study the possibility and the potentiality of using metal semiconductor-metal photodetector (MSM-PD) in three-dimensional parallel free space optical interconnect (FSOI) systems. The signal-to-noise ratio (SNR) and time response are used as performance measures to optimize the geometry of MSM-PD used in FSOI systems. Both SNR and time response are evaluated, analyzed, and their dependence on feature parameters of the MSM-PD, including finger size, spacing, and number of fingers, are considered. Based on the results obtained, we show that the use of MSM-PD in FSOI improves the interconnect speed at a given acceptable SNR.

  18. A silicon metal-semiconductor-metal photodetector macromodel for circuit simulations

    NASA Astrophysics Data System (ADS)

    Pancheri, Lucio; Scandiuzzo, Mauro; Betta, Gian-Franco Dalla; Stoppa, David; Nisi, Fabrizio De; Gonzo, Lorenzo; Simoni, Andrea

    2005-02-01

    In this paper, numerical device simulations are used to get insight into the DC and dynamic behavior of a CMOS metal-semiconductor-metal photodetector, to be used as a mixing device for active pixels based on a differential read-out concept. On the basis of simulation results, a simple electrical macromodel of the photosensor has been defined and implemented in the Cadence package using Spectre AHDL. The proposed macromodel is shown to accurately reproduce the numerical device simulation predictions in all the considered operation modes.

  19. Nanophotonics Based on Semiconductor-Photonic Crystal/Quantum Dot and Metal-/Semiconductor-Plasmonics

    NASA Astrophysics Data System (ADS)

    Asakawa, Kiyoshi; Sugimoto, Yoshimasa; Ikeda, Naoki; Tsuya, Daiju; Koide, Yasuo; Watanabe, Yoshinori; Ozaki, Nobuhiko; Ohkouchi, Shunsuke; Nomura, Tsuyoshi; Inoue, Daisuke; Matsui, Takayuki; Miura, Atsushi; Fujikawa, Hisayoshi; Sato, Kazuo

    This paper reviews our recent activities on nanophotonics based on a photonic crystal (PC)/quantum dot (QD)-combined structure for an all-optical device and a metal/semiconductor composite structure using surface plasmon (SP) and negative refractive index material (NIM). The former structure contributes to an ultrafast signal processing component by virtue of new PC design and QD selective-area-growth technologies, while the latter provides a new RGB color filter with a high precision and optical beam-steering device with a wide steering angle.

  20. Assembling non-ferromagnetic materials to ferromagnetic architectures using metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Liu, Chunting; Chen, Kezheng

    2016-09-01

    In this work, a facile and versatile solution route was used to fabricate room-temperature ferromagnetic fish bone-like, pteridophyte-like, poplar flower-like, cotton-like Cu@Cu2O architectures and golfball-like Cu@ZnO architecture. The ferromagnetic origins in these architectures were found to be around metal-semiconductor interfaces and defects, and the root cause for their ferromagnetism lay in charge transfer processes from metal Cu to semiconductors Cu2O and ZnO. Owing to different metallization at their interfaces, these architectures exhibited different ferromagnetic behaviors, including coercivity, saturation magnetization as well as magnetic interactions.

  1. Assembling non-ferromagnetic materials to ferromagnetic architectures using metal-semiconductor interfaces

    PubMed Central

    Ma, Ji; Liu, Chunting; Chen, Kezheng

    2016-01-01

    In this work, a facile and versatile solution route was used to fabricate room-temperature ferromagnetic fish bone-like, pteridophyte-like, poplar flower-like, cotton-like Cu@Cu2O architectures and golfball-like Cu@ZnO architecture. The ferromagnetic origins in these architectures were found to be around metal-semiconductor interfaces and defects, and the root cause for their ferromagnetism lay in charge transfer processes from metal Cu to semiconductors Cu2O and ZnO. Owing to different metallization at their interfaces, these architectures exhibited different ferromagnetic behaviors, including coercivity, saturation magnetization as well as magnetic interactions. PMID:27680286

  2. High-efficiency metal-semiconductor-metal photodetectors on heteroepitaxially grown Ge on Si.

    PubMed

    Okyay, Ali K; Nayfeh, Ammar M; Saraswat, Krishna C; Yonehara, Takao; Marshall, Ann; McIntyre, Paul C

    2006-09-01

    We demonstrate extremely efficient germanium-on-silicon metal-semiconductor-metal photodetectors with responsivities (R) as high as 0.85 A/W at 1.55 microm and 2V reverse bias. Ge was directly grown on Si by using a novel heteroepitaxial growth technique, which uses multisteps of growth and hydrogen annealing to reduce surface roughness and threading dislocations that form due to the 4.2% lattice mismatch. Photodiodes on such layers exhibit reverse dark currents of 100 mA/cm2 and external quantum efficiency up to 68%. This technology is promising to realize monolithically integrated optoelectronics.

  3. Simulation of Submicronmeter Metal-Semiconductor-Metal Ultraviolet Photodiodes no Gallium Nitride

    SciTech Connect

    Li, J.; Donaldson, W.R.; Hsiang, T.Y.

    2004-09-15

    Ultrafast metal Semiconductor metal ultraviolet photodetectors on GaN with 0.3-mm finger width and spacing were fabricated and packaged with a specially designed fast circuit. The assembly was simulated using a distributed circuit approach with optical illumination at l = 270 nm. This is the first theoretical simulation report of this effect in ultrafast ultraviolet photodetectors on GaN. Comparison of simulations and measurements was made in a wide range of optical energies, and a close agreement was achieved with a single energy-scaling factor.

  4. Boosting photoresponse in silicon metal-semiconductor-metal photodetector using semiconducting quantum dots

    NASA Astrophysics Data System (ADS)

    Biswas, Chandan; Kim, Yonghwan; Lee, Young Hee

    2016-11-01

    Silicon based metal-semiconductor-metal (MSM) photodetectors have faster photogeneration and carrier collection across the metal-semiconductor Schottky contacts, and CMOS integratibility compared to conventional p-n junction photodetectors. However, its operations are limited by low photogeneration, inefficient carrier-separation, and low mobility. Here, we show a simple and highly effective approach for boosting Si MSM photodetector efficiency by uniformly decorating semiconducting CdSe quantum dots on Si channel (Si-QD). Significantly higher photocurrent on/off ratio was achieved up to over 500 compared to conventional Si MSM photodetector (on/off ratio ~5) by increasing photogeneration and improving carrier separation. Furthermore, a substrate-biasing technique invoked wide range of tunable photocurrent on/off ratio in Si-QD photodetector (ranging from 2.7 to 562) by applying suitable combinations of source-drain and substrate biasing conditions. Strong photogeneration and carrier separation were achieved by employing Stark effect into the Si-QD hybrid system. These results highlight a promising method for enhancing Si MSM photodetector efficiency more than 100 times and simultaneously compatible with current silicon technologies.

  5. Hydrogen Sensors Using Nitride-Based Semiconductor Diodes: The Role of Metal/Semiconductor Interfaces

    PubMed Central

    Irokawa, Yoshihiro

    2011-01-01

    In this paper, I review my recent results in investigating hydrogen sensors using nitride-based semiconductor diodes, focusing on the interaction mechanism of hydrogen with the devices. Firstly, effects of interfacial modification in the devices on hydrogen detection sensitivity are discussed. Surface defects of GaN under Schottky electrodes do not play a critical role in hydrogen sensing characteristics. However, dielectric layers inserted in metal/semiconductor interfaces are found to cause dramatic changes in hydrogen sensing performance, implying that chemical selectivity to hydrogen could be realized. The capacitance-voltage (C–V) characteristics reveal that the work function change in the Schottky metal is not responsible mechanism for hydrogen sensitivity. The interface between the metal and the semiconductor plays a critical role in the interaction of hydrogen with semiconductor devises. Secondly, low-frequency C–V characterization is employed to investigate the interaction mechanism of hydrogen with diodes. As a result, it is suggested that the formation of a metal/semiconductor interfacial polarization could be attributed to hydrogen-related dipoles. In addition, using low-frequency C–V characterization leads to clear detection of 100 ppm hydrogen even at room temperature where it is hard to detect hydrogen by using conventional current-voltage (I–V) characterization, suggesting that low-frequency C–V method would be effective in detecting very low hydrogen concentrations. PMID:22346597

  6. Exciton polaritons in one-dimensional metal-semiconductor photonic crystals.

    PubMed

    Márquez-Islas, R; Flores-Desirena, B; Pérez-Rodríguez, F

    2008-12-01

    We investigate theoretically the coupling of exciton with light in a one-dimensional photonic crystal. The unit cell of the crystal consists of two alternating layers, namely a metallic layer and a semiconductor one. The frequency-dependent dielectric function of the metal is described by the Drude model, whereas for the semiconductor we use a nonlocal excitonic dielectric function. The polariton dispersion for s-polarized modes in the metal-semiconductor photonic crystal is compared with that for a dielectric-semiconductor photonic crystal. Because of the metal layers, a low-frequency gap appears in the photonic band structure. The presence of the semiconductor gives rise to photonic bands associated with the coupling of light with size-quantized excitón states. At frequencies above the longitudinal exciton frequency, the photonic band structure exhibits anticrossing phenomena produced by the upper exciton-polariton mode and size-quantized excitons. It is found that the anticrossing phenomena in the metal-semiconductor photonic crystal occur at higher frequencies in comparison with the dielectric-semiconductor case.

  7. Wide-area thin film metal-semiconductor-metal photodetectors for lidar applications

    NASA Astrophysics Data System (ADS)

    Morrison, Charles B.; Glinz, Andreas P.; Zhu, Zheng; Bechtel, James H.; Frimel, Steven M.; Roenker, Kenneth P.

    1998-04-01

    Novel interdigitated metal-semiconductor-metal structures offer new approaches for the development of broad-area, high-speed photodetectors to be used in optical free space communications and light detection and ranging applications. Inherent advantages include: lower capacitance than typical p-i-n structures, a wide dynamic range, and ease of fabrication. We have constructed broad area metal- semiconductor-metal photodetectors (MSM-PDs) by means of epitaxial liftoff and grafting technologies. Two computer models have been used to examine the effects of design parameters on the performance of broad-area, high-speed MSM- PD devices. The first model indicates that inverting the membrane so that the electrodes are placed between the non- conducting host substrate and the semiconductor material improves the signal-to-noise ration of the device, expanding its dynamic range. This model suggests that processing of the backside of the semiconductor material with antireflection coatings further improves device performance. Carrier collection behavior described by the second model suggests new electrode configurations for improved high speed operation which can only be applied to an inverted MSM-PD carried on a thin film membrane. A number of different fully passivated large area MSM-PD configurations have been fabricated and tested. Initial dark current data are compared favorably to published results.

  8. Boosting photoresponse in silicon metal-semiconductor-metal photodetector using semiconducting quantum dots

    PubMed Central

    Biswas, Chandan; Kim, Yonghwan; Lee, Young Hee

    2016-01-01

    Silicon based metal-semiconductor-metal (MSM) photodetectors have faster photogeneration and carrier collection across the metal-semiconductor Schottky contacts, and CMOS integratibility compared to conventional p-n junction photodetectors. However, its operations are limited by low photogeneration, inefficient carrier-separation, and low mobility. Here, we show a simple and highly effective approach for boosting Si MSM photodetector efficiency by uniformly decorating semiconducting CdSe quantum dots on Si channel (Si-QD). Significantly higher photocurrent on/off ratio was achieved up to over 500 compared to conventional Si MSM photodetector (on/off ratio ~5) by increasing photogeneration and improving carrier separation. Furthermore, a substrate-biasing technique invoked wide range of tunable photocurrent on/off ratio in Si-QD photodetector (ranging from 2.7 to 562) by applying suitable combinations of source-drain and substrate biasing conditions. Strong photogeneration and carrier separation were achieved by employing Stark effect into the Si-QD hybrid system. These results highlight a promising method for enhancing Si MSM photodetector efficiency more than 100 times and simultaneously compatible with current silicon technologies. PMID:27886274

  9. Electrostatic effect of Au nanoparticles on near-infrared photoluminescence from Si/SiGe due to nanoscale metal/semiconductor contact.

    PubMed

    Yin, Yefei; Wang, Ze; Wang, Shuguang; Bai, Yujie; Jiang, Zuimin; Zhong, Zhenyang

    2017-04-18

    Photoluminescence (PL) from Si and SiGe is comprehensively modified by Au NPs under excitation without surface plasmon resonance. Moreover, the PL sensitively depends on the size of the Au NPs, the excitation power and the thickness of the Si layer between the Au NPs and SiGe. A model is proposed in terms of the electrostatic effects of Au NPs naturally charged by electron transfer through the nanoscale metal/semiconductor Schottky junction without an external bias or external injection of carriers. The model accounts well for all the unique PL features. It also reveals that Au NPs can substantially modify the energy band structures, distribution and transition of carriers in the nanoscale region below the Au NPs. Our results demonstrate that Au NPs on semiconductors can efficiently modulate light-matter interaction.

  10. High temperature operation of n-AlGaN channel metal semiconductor field effect transistors on low-defect AlN templates

    NASA Astrophysics Data System (ADS)

    Muhtadi, S.; Hwang, S.; Coleman, A.; Asif, F.; Lunev, A.; Chandrashekhar, M. V. S.; Khan, A.

    2017-05-01

    We report room-temperature to 200 °C operation of n-Al0.65Ga0.35N channel metal semiconductor field effect transistors (MESFET) grown over high-quality AlN/sapphire templates. For this temperature range, the source-drain currents, threshold voltages, and dc-transconductance values remain nearly unchanged with an estimated field-effect mobility of ˜90 cm2/V-s at 200 °C and currents of >100 mA/mm. The analysis of the temperature dependent current-voltage characteristics of the gate-source Schottky barrier diode reveals that the leakage currents arise from Frenkel-Poole emission. The capacitance-voltage data show no hysteresis, indicating a high quality Schottky barrier interface. These MESFET's have excellent potential for use as a high temperature power electronic or a solar-blind ultraviolet sensing device.

  11. Electrostatic effect of Au nanoparticles on near-infrared photoluminescence from Si/SiGe due to nanoscale metal/semiconductor contact

    NASA Astrophysics Data System (ADS)

    Yin, Yefei; Wang, Ze; Wang, Shuguang; Bai, Yujie; Jiang, Zuimin; Zhong, Zhenyang

    2017-04-01

    Photoluminescence (PL) from Si and SiGe is comprehensively modified by Au NPs under excitation without surface plasmon resonance. Moreover, the PL sensitively depends on the size of the Au NPs, the excitation power and the thickness of the Si layer between the Au NPs and SiGe. A model is proposed in terms of the electrostatic effects of Au NPs naturally charged by electron transfer through the nanoscale metal/semiconductor Schottky junction without an external bias or external injection of carriers. The model accounts well for all the unique PL features. It also reveals that Au NPs can substantially modify the energy band structures, distribution and transition of carriers in the nanoscale region below the Au NPs. Our results demonstrate that Au NPs on semiconductors can efficiently modulate light–matter interaction.

  12. Characterization of GaN-based metal-semiconductor field-effect transistors by comparing electroluminescence, photoionization, and cathodoluminescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Armani, N.; Grillo, V.; Salviati, G.; Manfredi, M.; Pavesi, M.; Chini, A.; Meneghesso, G.; Zanoni, E.

    2002-09-01

    We report on a methodological comparison between photocurrent (PC), electroluminescence (EL), and cathodoluminescence (CL) investigations on GaN metal-semiconductor field-effect transistors. The purpose of this work is to show the effectiveness and the complementarity of these experimental techniques and to investigate the presence and nature of electron traps which limit the performances of the devices. PC measurements reveal four distinct energy levels, located at 1.75, 2.32, 2.67, and 3.15 eV, responsible for current collapse. The 1.75 eV level has also been observed in low temperature EL curves. The 2.32 and 2.67 eV levels, on the basis of the comparison with CL and EL results, can be correlated with the so-called "yellow band," located at 2.2 eV. The origin of 1.75 and 3.15 eV levels is at present unknown, however a nonradiative nature has been attributed to the 3.15 eV level, due to the absence of this signature in both CL and EL spectra. The luminescence measurements also reveal the presence of the donor-acceptor pair emission at 3.27 eV and the near-band-edge transition at 3.45 eV. EL measurements show a series of emission peaks in the energy range between 1 and 1.4 eV, while the CL spectra reveal a broadband at 2.8 eV, which arises mainly from the semi-insulating layer. This result has been obtained by increasing the energy of the CL electron beam, allowing us to investigate both the conduction channel and the layers underneath it.

  13. Metal-semiconductor-metal neutron detectors based on hexagonal boron nitride epitaxial layers

    NASA Astrophysics Data System (ADS)

    Majety, S.; Li, J.; Cao, X. K.; Dahal, R.; Lin, J. Y.; Jiang, H. X.

    2012-10-01

    Hexagonal boron nitride (hBN) possesses extraordinary potential for solid-state neutron detector applications. This stems from the fact that the boron-10 (10B) isotope has a capture cross-section of 3840 barns for thermal neutrons that is orders of magnitude larger than other isotopes. Epitaxial layers of hBN have been synthesized by metal organic chemical vapor deposition (MOCVD). Experimental measurements indicated that the thermal neutron absorption coefficient and length of natural hBN epilayers are about 0.0036 μm-1 and 277 μm, respectively. To partially address the key requirement of long carrier lifetime and diffusion length for a solid-state neutron detector, micro-strip metal-semiconductor-metal detectors were fabricated and tested. A good current response was generated in these detectors using continuous irradiation with a thermal neutron beam, corresponding to an effective conversion efficiency approaching ~80% for absorbed neutrons.

  14. Lossless propagation in metal-semiconductor-metal plasmonic waveguides using quantum dot active medium.

    PubMed

    Sheikhi, K; Granpayeh, N; Ahmadi, V; Pahlavan, S

    2015-04-01

    In this paper, we analyze and simulate the lossless propagation of lightwaves in the active metal-semiconductor-metal plasmonic waveguides (MSMPWs) at the wavelength range of 1540-1560 nm using a quantum dot (QD) active medium. The Maxwell's equations are solved in the waveguide, and the required gains for achieving lossless propagation are derived. On the other hand, the rate equations in quantum dot active regions are solved by using the Runge-Kutta method, and the achievable optical gain is derived. The analyses results show that the required optical gain for lossless propagation in MSMPWs is achievable using the QD active medium. Also, by adjusting the active medium parameters, the MSMPWs loss can be eliminated in a specific bandwidth, and the propagation length increases obviously.

  15. Metal-semiconductor-metal TiO2 ultraviolet detectors with Ni electrodes

    NASA Astrophysics Data System (ADS)

    Kong, Xiangzi; Liu, Caixia; Dong, Wei; Zhang, Xindong; Tao, Chen; Shen, Liang; Zhou, Jingran; Fei, Yongfeng; Ruan, Shengping

    2009-03-01

    In this letter, metal-semiconductor-metal (MSM) TiO2 ultraviolet (UV) detectors with Ni electrodes have been fabricated. TiO2 thin films were prepared by sol-gel method. At 5 V bias, the dark current of the detector with Ni electrode was 1.83 nA. High photoresponse of 889.6 A/W was found under irradiation of 260 nm UV light, which was much higher than those of other wide bandgap UV detectors with MSM structure. The high photoresponse was due to the great internal gain caused by the hole trapping at interface. The rise time of the device was 13.34 ms and the fall time was 11.43 s.

  16. Theoretical and STM Studies of the Electronic Structure of Metal/Semiconductor/Hydrogen Systems

    DTIC Science & Technology

    1992-11-19

    P. Blaha and K. Schwartz, 1. Phys. F 17, 899 (1987). [9] M.Y. Chou. P. K. Lam, and M. L. Cohen, Phys. Rev. B 28, 4179 (1983). (10] T. L. Loucks and...and H. Partridge, private communication. 22. G. Pichler, A.M. Lyyra, P.D. Kleiber, W.C. Stwalley, R. Hammer, K.M. Sando and H.H. Michels , Chem. Phys

  17. Theoretical Studies of the Electronic Structure of Metal/Semiconductor/ Hydrogen Systems

    DTIC Science & Technology

    1991-04-01

    U"miM .50 w ~Cesium, hydrogen and oxygen adsorption on beryllium clusters are-studied usinq restricted Hartree-Fock (RHF) calculations and ab initio...hydrogen, and oxygen adsorption on the work function of beryllium Publication 10 ....... ..................... .... 52 Imaging of colloidal gold on...involved a series of ab initio self-consistent field (SCF) calculations on clusters of beryllium atoms together with associated cesium and hydrogen atoms

  18. Reflective metal/semiconductor tunnel junctions for hole injection in AlGaN UV LEDs

    NASA Astrophysics Data System (ADS)

    Zhang, Yuewei; Krishnamoorthy, Sriram; Akyol, Fatih; Johnson, Jared M.; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Hwang, Jinwoo; Rajan, Siddharth

    2017-07-01

    In this work, we investigate the use of nanoscale polarization engineering to achieve efficient hole injection from metals to ultra-wide bandgap AlGaN, and we show that UV-reflective aluminum (Al) layers can be used for hole injection into p-AlGaN. The dependence of tunneling on the work function of the metal was investigated, and it was found that highly reflective Al metal layers can enable efficient hole injection into p-AlGaN, despite the relatively low work function of Al. Efficient tunneling hole injection was confirmed by light emission at 326 nm with an on-wafer peak external quantum efficiency and a wall-plug efficiency of 2.43% and 1.33%, respectively. A high power density of 79.0 W/cm2 was measured at 1200 A/cm2. The metal/semiconductor tunnel junction structure demonstrated here could provide significant advantages for efficient and manufacturable device topologies for high power UV emitters.

  19. Study of gain phenomenon in lateral metal-semiconductor-metal detectors for indirect conversion medical imaging

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, Shiva; Allec, Nicholas; Wang, Kai; Chen, Feng; Karim, Karim S.

    2011-03-01

    Previously, metal-semiconductor-metal (MSM) lateral amorphous selenium (a-Se) detectors have been proposed for indirect detector medical imaging applications. These detectors have raised interest due to their high-speed and photogain. The gain measured from these devices was assumed to have been photoconductive gain; however the origin of this gain was not fully understood. In addition, whether or not there was any presence of photocurrent multiplication gain was not investigated. For integration-type applications photocurrent multiplication gain is desirable since the total collected charge can be greater than the total number of absorbed photons. In order to fully appreciate the value of MSM devices and their benefit for different applications, whether it is counting or integration applications, we need to investigate the responsible mechanisms of the observed response. In this paper, we systematically study, through experimental and theoretical means, the nature of the photoresponse and its responsible mechanisms. This study also exposes the possible means to increase the performance of the device and under what conditions it will be most beneficial.

  20. Modeling electrochemical deposition inside nanotubes to obtain metal-semiconductor multiscale nanocables or conical nanopores.

    PubMed

    Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

    2005-08-04

    Nanocables with a radial metal-semiconductor heterostructure have recently been prepared by electrochemical deposition inside metal nanotubes. First, a bare nanoporous polycarbonate track-etched membrane is coated uniformly with a metal film by electroless deposition. The film forms a working electrode for further deposition of a semiconductor layer that grows radially inside the nanopore when the deposition rate is slow. We propose a new physical model for the nanocable synthesis and study the effects of the deposited species concentration, potential-dependent reaction rate, and nanopore dimensions on the electrochemical deposition. The problem involves both axial diffusion through the nanopore and radial transport to the nanopore surface, with a surface reaction rate that depends on the axial position and the time. This is so because the radial potential drop across the deposited semiconductor layer changes with the layer thickness through the nanopore. Since axially uniform nanocables are needed for most applications, we consider the relative role of reaction and axial diffusion rates on the deposition process. However, in those cases where partial, empty-core deposition should be desirable (e.g., for producing conical nanopores to be used in single nanoparticle detection), we give conditions where asymmetric geometries can be experimentally realized.

  1. Formation of heteroepitaxy in different shapes of Au-CdSe metal-semiconductor hybrid nanostructures.

    PubMed

    Haldar, Krishna Kanta; Pradhan, Narayan; Patra, Amitava

    2013-10-25

    Formation of heteroepitaxy and designing different-shaped heterostructured nanomaterials of metal and semiconductor in solution remains a frontier area of research. However, it is evident that the synthesis of such materials is not straightforward and needs a selective approach to retain both metal and semiconductor identities in the reaction system during heterostructure formation. Herein, the epitaxial growth of semiconductor CdSe on selected facets of metal Au seeds is reported and different shapes (flower, tetrapod, and core/shell) hetero-nanostructures are designed. These results are achieved by controlling the reaction parameters, and by changing the sequence and timing for introduction of different reactant precursors. Direct evidence of the formation of heteroepitaxy between {111} facets of Au and (0001) of wurtzite CdSe is observed during the formation of these three heterostructures. The mechanism of the evolution of these hetero-nanostructures and formation of their heteroepitaxy with the planes having minimum lattice mismatch are also discussed. This shape-control growth mechanism in hetero-nanostructures should be helpful to provide more information for establishing the fundamental study of heteroepitaxial growth for designing new nanomaterials. Such metal-semiconductor nanostructures may have great potential for nonlinear optical properties, in photovoltaic devices, and as chemical sensors.

  2. Fermi level dependent native defect formation: Consequences for metal-semiconductor and semiconductor-semiconductor interfaces

    SciTech Connect

    Walukiewicz, W.

    1988-02-01

    The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back-relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p- and n-type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration. 33 refs., 6 figs.

  3. Barrier height enhancement of metal/semiconductor contact by an enzyme biofilm interlayer

    NASA Astrophysics Data System (ADS)

    Ocak, Yusuf Selim; Gul Guven, Reyhan; Tombak, Ahmet; Kilicoglu, Tahsin; Guven, Kemal; Dogru, Mehmet

    2013-06-01

    A metal/interlayer/semiconductor (Al/enzyme/p-Si) MIS device was fabricated using α-amylase enzyme as a thin biofilm interlayer. It was observed that the device showed an excellent rectifying behavior and the barrier height value of 0.78 eV for Al/α-amylase/p-Si was meaningfully larger than the one of 0.58 eV for conventional Al/p-Si metal/semiconductor (MS) contact. Enhancement of the interfacial potential barrier of Al/p-Si MS diode was realized using enzyme interlayer by influencing the space charge region of Si semiconductor. The electrical properties of the structure were executed by the help of current-voltage and capacitance-voltage measurements. The photovoltaic properties of the structure were executed under a solar simulator with AM1.5 global filter between 40 and 100 mW/cm2 illumination conditions. It was also reported that the α-amylase enzyme produced from Bacillus licheniformis had a 3.65 eV band gap value obtained from optical method.

  4. Rectification and Photoconduction Mapping of Axial Metal-Semiconductor Interfaces Embedded in GaAs Nanowires

    NASA Astrophysics Data System (ADS)

    Orrù, Marta; Piazza, Vincenzo; Rubini, Silvia; Roddaro, Stefano

    2015-10-01

    Semiconductor nanowires have emerged as an important enabling technology and are today used in many advanced device architectures, with an impact both for what concerns fundamental science and in view of future applications. One of the key challenges in the development of nanowire-based devices is the fabrication of reliable nanoscale contacts. Recent developments in the creation of metal-semiconductor junctions by thermal annealing of metallic electrodes offer promising perspectives. Here, we analyze the optoelectronic properties of nano-Schottky barriers obtained thanks to the controlled formation of metallic AuGa regions in GaAs nanowire. The junctions display a rectifying behavior and their transport characteristics are analyzed to extract the average ideality factor and barrier height in the current architecture. The presence, location, and properties of the Schottky junctions are cross-correlated with spatially resolved photocurrent measurements. Broadband light emission is reported in the reverse breakdown regime; this observation, combined with the absence of electroluminescence at forward bias, is consistent with the device unipolar nature.

  5. Terahertz Modulator based on Metamaterials integrated with Metal-Semiconductor-Metal Varactors

    PubMed Central

    Nouman, Muhammad Tayyab; Kim, Hyun-Woong; Woo, Jeong Min; Hwang, Ji Hyun; Kim, Dongju; Jang, Jae-Hyung

    2016-01-01

    The terahertz (THz) band of the electromagnetic spectrum, with frequencies ranging from 300 GHz to 3 THz, has attracted wide interest in recent years owing to its potential applications in numerous areas. Significant progress has been made toward the development of devices capable of actively controlling terahertz waves; nonetheless, further advances in device functionality are necessary for employment of these devices in practical terahertz systems. Here, we demonstrate a low voltage, sharp switching terahertz modulator device based on metamaterials integrated with metal semiconductor metal (MSM) varactors, fabricated on an AlGaAs/InGaAs based heterostructure. By varying the applied voltage to the MSM-varactor located at the center of split ring resonator (SRR), the resonance frequency of the SRR-based metamaterial is altered. Upon varying the bias voltage from 0 V to 3 V, the resonance frequency exhibits a transition from 0.52 THz to 0.56 THz, resulting in a modulation depth of 45 percent with an insertion loss of 4.3 dB at 0.58 THz. This work demonstrates a new approach for realizing active terahertz devices with improved functionalities. PMID:27194128

  6. Terahertz Modulator based on Metamaterials integrated with Metal-Semiconductor-Metal Varactors

    NASA Astrophysics Data System (ADS)

    Nouman, Muhammad Tayyab; Kim, Hyun-Woong; Woo, Jeong Min; Hwang, Ji Hyun; Kim, Dongju; Jang, Jae-Hyung

    2016-05-01

    The terahertz (THz) band of the electromagnetic spectrum, with frequencies ranging from 300 GHz to 3 THz, has attracted wide interest in recent years owing to its potential applications in numerous areas. Significant progress has been made toward the development of devices capable of actively controlling terahertz waves; nonetheless, further advances in device functionality are necessary for employment of these devices in practical terahertz systems. Here, we demonstrate a low voltage, sharp switching terahertz modulator device based on metamaterials integrated with metal semiconductor metal (MSM) varactors, fabricated on an AlGaAs/InGaAs based heterostructure. By varying the applied voltage to the MSM-varactor located at the center of split ring resonator (SRR), the resonance frequency of the SRR-based metamaterial is altered. Upon varying the bias voltage from 0 V to 3 V, the resonance frequency exhibits a transition from 0.52 THz to 0.56 THz, resulting in a modulation depth of 45 percent with an insertion loss of 4.3 dB at 0.58 THz. This work demonstrates a new approach for realizing active terahertz devices with improved functionalities.

  7. Ion implantation and low temperature properties of metal-semiconductor alloys

    NASA Astrophysics Data System (ADS)

    Xiao-Xing, Xi; Da-Wei, Zhou; Guang-Lin, Zhao; Qi-Ze, Ran; Jia-Rui, Liu; Wei-Yan, Guan

    1987-09-01

    We review the experimental work on ion implantation with respect to superconductivity and electrical resistivity of metal-semiconductor alloys carried out at the Institute of Physics of Academia Sinica. Samples studied included liquid-quenched AlSiGe ribbons and Al thin films. The liquid-quenched ribbons with a superconducting transition temperature Tc of 3.2 K were implanted with H or H 2 ions at room temperature and a decrease of Tc was observed. The ribbons were also implanted with Si ions at liquid nitrogen temperature, resulting in a higher onset of transition at about 4 K. We also implanted Si ions into Al thin films at room temperature up to 5 at.% Si. The Tc of the films increased from 1.5 to 1.9 K and the temperature-dependence of resistivity was changed from T5 to a T3-dependence within 30-50 K. The superconductivity of Al-semiconductor alloys was proved to be strongly influenced by the disorder, which depends crucially on the implantation temperature.

  8. Optical Design of Plant Canopy Measurement System and Fabrication of Two-Dimensional High-Speed Metal-Semiconductor-Metal Photodetector Arrays

    NASA Technical Reports Server (NTRS)

    Sarto, Anthony; VanZeghbroeck, Bart; Vanderbilt, Vern C.

    1996-01-01

    Electrical and optical designs for the prototype plant canopy architecture measurement system, including specified component and parts lists, are presented. Six single Metal-Semiconductor-Metal (MSM) detectors are mounted in high-speed packages.

  9. Characterization and modeling analysis for metal-semiconductor-metal GaAs diodes with Pd/SiO₂ mixture electrode.

    PubMed

    Tan, Shih-Wei; Lai, Shih-Wen

    2012-01-01

    Characterization and modeling of metal-semiconductor-metal (MSM) GaAs diodes using to evaporate SiO₂ and Pd simultaneously as a mixture electrode (called M-MSM diodes) compared with similar to evaporate Pd as the electrode (called Pd-MSM diodes) were reported. The barrier height (φ(b)) and the Richardson constant (A*) were carried out for the thermionic-emission process to describe well the current transport for Pd-MSM diodes in the consideration of the carrier over the metal-semiconductor barrier. In addition, in the consideration of the carrier over both the metal-semiconductor barrier and the insulator-semiconductor barrier simultaneously, thus the thermionic-emission process can be used to describe well the current transport for M-MSM diodes. Furthermore, in the higher applied voltage, the carrier recombination will be taken into discussion. Besides, a composite-current (CC) model is developed to evidence the concepts. Our calculated results are in good agreement with the experimental ones.

  10. Development of Room Temperature Excitonic Lasing From ZnO and MgZnO Thin Film Based Metal-Semiconductor-Metal Devices

    NASA Astrophysics Data System (ADS)

    Suja, Mohammad Zahir Uddin

    efficiency up to 6 times is demonstrated. Threshold current for lasing is decreased by as much as 30% while the output power is increased up to 350% at an injection current of 40 mA. A numerical simulation study reveals that hole carriers are generated in the ZnO MSM devices from impact ionization processes for subsequent plasmon-exciton coupled lasing. Our results suggest that plasmon-enhanced ZnO MSM random lasers can become a competitive candidate of efficient ultraviolet light sources. Semiconductor lasers in the deep ultraviolet (UV) range have numerous potential applications ranging from water purification and medical diagnosis to high-density data storage and flexible displays. Nevertheless, very little success was achieved in the realization of electrically driven deep UV semiconductor lasers to date. In this thesis, we report the fabrication and characterization of deep UV MgZnO semiconductor lasers. These lasers are operated with continuous current mode at room temperature and the shortest wavelength reaches 284 nm. The wide bandgap MgZnO thin films with various Mg mole fractions were grown on c-sapphire substrate using radio-frequency plasma assisted molecular beam epitaxy. Metal-semiconductor-metal (MSM) random laser devices were fabricated using lithography and metallization processes. Besides the demonstration of scalable emission wavelength, very low threshold current densities of 29 33 A/cm2 are achieved. Numerical modeling reveals that impact ionization process is responsible for the generation of hole carriers in the MgZnO MSM devices. The interaction of electrons and holes leads to radiative excitonic recombination and subsequent coherent random lasing.

  11. Growth and characterization of rutile TiO2 nanorods on various substrates with fabricated fast-response metal-semiconductor-metal UV detector based on Si substrate

    NASA Astrophysics Data System (ADS)

    Selman, Abbas M.; Hassan, Z.

    2015-07-01

    Rutile-phase titanium dioxide nanorods (NRs) were synthesized successfully on p-type silicon (Si) (1 1 1), c-plane sapphire (Al2O3), glass coated with fluorine-doped tin oxide (FTO), glass, and quartz substrates via chemical bath deposition method. All substrates were seeded with a TiO2 seed layer synthesized with a radio frequency reactive magnetron sputtering system prior to NRs growth. The effect of substrate type on structural, morphological, and optical properties of rutile TiO2 NRs was studied. X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy analyses showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were examined with photoluminescence (PL) spectroscopy of the grown rutile NRs on all substrates, with the spectra exhibiting one strong ultraviolet emission peak intensity compared with broad visible peak. The optimal sample of rutile NRs was grown on Si substrate. Thus, a fast-response metal-semiconductor-metal ultraviolet (UV) detector was fabricated. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias, the device displays 2.62 × 10-5 A photocurrent, and the response and recovery times are calculated as 18.5 and 19.1 ms, respectively. These results demonstrate that the fabricated high-quality photodiode is a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

  12. Progressive Design of Plasmonic Metal-Semiconductor Ensemble toward Regulated Charge Flow and Improved Vis-NIR-Driven Solar-to-Chemical Conversion.

    PubMed

    Han, Chuang; Quan, Quan; Chen, Hao Ming; Sun, Yugang; Xu, Yi-Jun

    2017-04-01

    Surface plasmon resonance (SPR)-mediated photocatalysis without the bandgap limitations of traditional semiconductor has aroused significant attention in solar-to-chemical energy conversion. However, the photocatalytic efficiency barely initiated by the SPR effects is still challenged by the low concentration and ineffective extraction of energetic hot electrons, slow charge migration rates, random charge diffusion directions, and the lack of highly active sites for redox reactions. Here, the tunable, progressive harvesting of visible-to-near infrared light (vis-NIR, λ > 570 nm) by designing plasmonic Au nanorods and metal (Au, Ag, or Pt) nanoparticle codecorated 1D CdS nanowire (1D CdS NW) ensemble is reported. The intimate integration of these metal nanostructures with 1D CdS NWs promotes the extraction and manipulated directional separation and migration of hot charge carriers in a more effective manner. Such cooperative synergy with tunable control of interfacial interaction, morphology optimization, and cocatalyst strategy results in the distinctly boosted performance for vis-NIR-driven plasmonic photocatalysis. This work highlights the significance of rationally progressive design of plasmonic metal-semiconductor-based composite system for boosting the regulated directional flow of hot charge carrier and thus the more efficient use of broad-spectrum solar energy conversion.

  13. Cross-plane thermal conductivity of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Saha, Bivas; Koh, Yee Rui; Comparan, Jonathan; Sadasivam, Sridhar; Schroeder, Jeremy L.; Garbrecht, Magnus; Mohammed, Amr; Birch, Jens; Fisher, Timothy; Shakouri, Ali; Sands, Timothy D.

    2016-01-01

    Reduction of cross-plane thermal conductivity and understanding of the mechanisms of heat transport in nanostructured metal/semiconductor superlattices are crucial for their potential applications in thermoelectric and thermionic energy conversion devices, thermal management systems, and thermal barrier coatings. We have developed epitaxial (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices with periodicity ranging from 1 nm to 240 nm that show significantly lower thermal conductivity compared to the parent TiN/(Al,Sc)N superlattice system. The (Ti,W)N/(Al,Sc)N superlattices grow with [001] orientation on the MgO(001) substrates with well-defined coherent layers and are nominally single crystalline with low densities of extended defects. Cross-plane thermal conductivity (measured by time-domain thermoreflectance) decreases with an increase in the superlattice interface density in a manner that is consistent with incoherent phonon boundary scattering. Thermal conductivity values saturate at 1.7 W m-1K-1 for short superlattice periods possibly due to a delicate balance between long-wavelength coherent phonon modes and incoherent phonon scattering from heavy tungsten atomic sites and superlattice interfaces. First-principles density functional perturbation theory based calculations are performed to model the vibrational spectrum of the individual component materials, and transport models are used to explain the interface thermal conductance across the (Ti,W)N/(Al,Sc)N interfaces as a function of periodicity. The long-wavelength coherent phonon modes are expected to play a dominant role in the thermal transport properties of the short-period superlattices. Our analysis of the thermal transport properties of (Ti,W)N/(Al,Sc)N metal/semiconductor superlattices addresses fundamental questions about heat transport in multilayer materials.

  14. Long-wavelength metal-semiconductor-metal photodetectors with transparent and opaque electrodes

    NASA Astrophysics Data System (ADS)

    Wohlmuth, Walter A.; Adesida, Ilesanmi; Caneau, Catherine

    1995-09-01

    In this paper, we present a comparative study of transparent and opaque electrode InAlAs/InGaAs metal-semiconductor-metal photodiodes (MSMPDs) for operation at 1.31 and 1.55 micrometers . The transparent materials are indium-tin-oxide (ITO) and cadmium-tin-oxide (CTO) and the opaque material is Ti-Au. The rf magnetron sputtered films of ITO and CTO, deposited at a substrate temperature of 300 degrees C, exhibited as-deposited resistivities of 5.6(DOT)10-3 (Omega) (DOT)cm and 1.0(DOT)10-3 (Omega) (DOT)cm, respectively. The resistivity of the ITO and CTO films dropped to 1.1(DOT)10-3 (Omega) (DOT)cm and 5.2(DOT)10-4 (Omega) (DOT)cm, respectively, after a 4 minute 400 degree C anneal in an N2 ambient. The interdigitated ITO and CTO electrodes were made by etching in a methane:hydrogen (1 to 3) plasma. The responsivity of 1 micrometers finger by 1 micrometers spacing (1 by 1 micrometers ), 50 X 50 micrometers 2 active area, MSMPDs was 0.40 A/W for the Ti-Au, 0.66 A/W for the CTO, and 0.69 A/W for the ITO MSMPDs. The Ti-Au, CTO and ITO MSMPDs had 3- dB cut-off frequencies of 14.0 GHz, 7.5 GHz, and 5.0 GHz, respectively, from time-domain measurements performed at 1.3 micrometers and 11.26 GHz, 4.00 GHz, and 2.61 GHz, respectively, from frequency-domain measurements performed at 1.55 micrometers . Discrepencies between the 3-dB cut-off frequency obtained from the time-domain and the frequency-domain measurements are attributed to the time-domain measurement system's inability to accurately resolve low frequency behavior (below 2 GHz) and space charge effects.

  15. Studies of High Performance Indium Gallium Arsenide Metal-Semiconductor Photodiodes.

    NASA Astrophysics Data System (ADS)

    Gao, Wei

    1995-01-01

    The purpose of this study is to achieve high speed and high responsivity metal-semiconductor-metal (MSM) photodiodes, which includes material growth, device design, fabrication, and testing. Liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) growth were used to grow high purity InGaAs layers. To obtain high purity InGaAs layers, rare-earth elements (Yb, Ga, and Er) were used during LPE growth. The rare-earth elements react strongly with donor impurities to purify the epitaxial layers, resulting in higher mobility, lower carrier concentration, and higher photoluminescence efficiency in the rare-earth doped melt grown InGaAs layer. Unfortunately, rare-earth elements have high impurity levels and hardly interact with acceptor impurities; thus, causing undesired deep levels. Both abrupt and digital superlattice InAlAs barrier enhancement InGaAs MSM photodiodes were grown by MBE. To improve the photoresponsivity, a transparent conductive material, cadmium tin oxide (CTO) was used as the MSM contacts. The CTO functions as a Schottky contact, an optical window and an anti-reflection coating. The Schottky barrier height, which is vitally important for MSM photodiodes, was studied with CTO, ITO, Au, Ti, and Pt on InAlAs using the Norde method. The CTO MSM photodiodes showed a factor of almost two improvement in responsivity over conventional Ti/Au MSM photodiodes. Abrupt barrier enhancement MSM photodiodes using CTO and Ti/Au electrodes demonstrated 3-dB bandwidths of 0.3 and 0.8 GHz, respectively. However, digital grading of the heterojunction facilitated better carrier extraction resulting in increased bandwidths of 1.3 and 7.1 GHz, respectively, for CTO and Ti/Au. It was demonstrated that CTO possesses a low resistivity, high transparency, and good Schottky barrier height, which makes CTO a very attractive transparent conductor suitable for optoelectronic applications. Lastly, four novel structures were proposed to improve the responsivity and the bandwidth of

  16. The Photoresponse of the Gallium Arsenide Metal Semiconductor Field Effect Transistor

    NASA Astrophysics Data System (ADS)

    Paolella, Arthur

    The combining of optical and microwave technology is imminent, especially the integration of optical and microwave circuit functions on the same circuit or chip. Exploring the properties of the metal semiconductor field effect transistor (MESFET) as an optical detector for the detection of microwave and control signals in fiber optic links make sense because the MESFET is the main active component of GaAs MMICs. In this thesis, photocurrents and photovoltages of three MESFETs were measured as a function of the optical input (wavelength, intensity and modulation frequency), electrical input (gate voltage and gate resistance), and device characteristics. A model of the photoresponse, based on the drift and diffusion equations for the current density was developed, which established the internal photovoltaic effect at the channel-substrate interface as the dominant mechanism for the generation of photocurrent in the MESFET. The gain, bandwidth and gain-bandwidth products for each of the major photoeffects were determined mathematically. A maximum photocurrent of 16 mA, and an internal photovoltage of -0.5 volts was measured at 3.5 mW of optical power. The addition of a resistance in the gate circuit enhanced the photoresponse. With a resistor of 1 MOmega, the maximum photocurrent produced was 84.0 mA, resulting from an external photovoltage of 3.07 volts. The dynamic photoresponse of the MESFET as measured, showed a strong dependence with the intensity of the optical signal as well as with bias. The low frequency response varied from -15 dB to -41 dB, and the bandwidth changed from 50 MHz to 5 MHz as the optical signal decreased 18 dB. The low frequency response and bandwidth also showed strong dependence of bias. The low frequency response varied over a 7 dB range and the bandwidth changed from 45 MHz to 100 MHz as the gate was reversed biased (0 to -3.0 volts). Used as an optical detector, the MESFET function successfully in controlling the gain (15 dB) and phase

  17. Solar blind metal-semiconductor-metal ultraviolet photodetectors using quasi-alloy of BGaN/GaN superlattices

    NASA Astrophysics Data System (ADS)

    Srour, H.; Salvestrini, J. P.; Ahaitouf, A.; Gautier, S.; Moudakir, T.; Assouar, B.; Abarkan, M.; Hamady, S.; Ougazzaden, A.

    2011-11-01

    Large internal gains that can be obtained in wide band gap semiconductors-based (GaN and ZnO types) Schottky and/or metal-semiconductor-metal photodetectors are generally accompanied by large dark current and time response. We show that, using quasi-alloy of BGaN/GaN superlattices as the active layer, the dark current can be lowered while maintaining high internal gain (up to 3 × 104) for optical power in the nW range and low time response (few tens of ns) for optical power in the W range. Furthermore, the boron incorporation allows the tuning of the cutoff wavelength.

  18. Nanoimprinted Hybrid Metal-Semiconductor Plasmonic Multilayers with Controlled Surface Nano Architecture for Applications in NIR Detectors

    PubMed Central

    Khosroabadi, Akram A.; Gangopadhyay, Palash; Hernandez, Steven; Kim, Kyungjo; Peyghambarian, Nasser; Norwood, Robert A.

    2015-01-01

    We present a proof of concept for tunable plasmon resonance frequencies in a core shell nano-architectured hybrid metal-semiconductor multilayer structure, with Ag as the active shell and ITO as the dielectric modulation media. Our method relies on the collective change in the dielectric function within the metal semiconductor interface to control the surface. Here we report fabrication and optical spectroscopy studies of large-area, nanostructured, hybrid silver and indium tin oxide (ITO) structures, with feature sizes below 100 nm and a controlled surface architecture. The optical and electrical properties of these core shell electrodes, including the surface plasmon frequency, can be tuned by suitably changing the order and thickness of the dielectric layers. By varying the dimensions of the nanopillars, the surface plasmon wavelength of the nanopillar Ag can be tuned from 650 to 690 nm. Adding layers of ITO to the structure further shifts the resonance wavelength toward the IR region and, depending on the sequence and thickness of the layers within the structure, we show that such structures can be applied in sensing devices including enhancing silicon as a photodetection material. PMID:28793489

  19. Schottky or Ohmic metal-semiconductor contact: influence on photocatalytic efficiency of Ag/ZnO and Pt/ZnO model systems.

    PubMed

    Yan, Fengpo; Wang, Yonghao; Zhang, Jiye; Lin, Zhang; Zheng, Jinsheng; Huang, Feng

    2014-01-01

    The relationship between the contact type in metal-semiconductor junctions and their photocatalytic efficiencies is investigated. Two metal-semiconductor junctions, silver on zinc oxide (Ag/ZnO) and platinum on zinc oxide (Pt/ZnO) serve as model system for Ohmic and Schottky metal-semiconductor contact, respectively. Ag/ZnO, with Ohmic contact, exhibits a higher photocatalytic efficiency than Pt/ZnO, with Schottky contact. The direction of electric fields within the semiconductor is found to play a crucial role in the separation of photogenerated charges, and thus strongly influences the photocatalytic efficiency. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer

    NASA Astrophysics Data System (ADS)

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-01

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  1. A metal-semiconductor-metal detector based on ZnO nanowires grown on a graphene layer.

    PubMed

    Xu, Qiang; Cheng, Qijin; Zhong, Jinxiang; Cai, Weiwei; Zhang, Zifeng; Wu, Zhengyun; Zhang, Fengyan

    2014-02-07

    High quality ZnO nanowires (NWs) were grown on a graphene layer by a hydrothermal method. The ZnO NWs revealed higher uniform surface morphology and better structural properties than ZnO NWs grown on SiO2/Si substrate. A low dark current metal-semiconductor-metal photodetector based on ZnO NWs with Au Schottky contact has also been fabricated. The photodetector displays a low dark current of 1.53 nA at 1 V bias and a large UV-to-visible rejection ratio (up to four orders), which are significantly improved compared to conventional ZnO NW photodetectors. The improvement in UV detection performance is attributed to the existence of a surface plasmon at the interface of the ZnO and the graphene.

  2. High responsivity A-plane GaN-based metal-semiconductor-metal photodetectors for polarization-sensitive applications

    SciTech Connect

    Navarro, A.; Rivera, C.; Pereiro, J.; Munoz, E.; Imer, B.; DenBaars, S. P.; Speck, J. S.

    2009-05-25

    The fabrication and characterization of metal-semiconductor-metal polarization-sensitive photodetectors based on A-plane GaN grown on R-plane sapphire substrates is reported. These photodetectors take advantage of the in-plane crystal anisotropy, which results in linear dichroism near the band gap energy. The high resistivity of the A-plane GaN material leads to extremely low dark currents. For an optimized finger spacing of 1 {mu}m, dark current density and responsivity at 30 V are 0.3 nA/mm{sup 2} and 2 A/W, respectively. A maximum polarization sensitivity ratio of 1.8 was determined. In a differential configuration, the full width at half maximum of the polarization-sensitive region is 8.5 nm.

  3. Zinc tin oxide metal semiconductor field effect transistors and their improvement under negative bias (illumination) temperature stress

    NASA Astrophysics Data System (ADS)

    Dang, G. T.; Kawaharamura, T.; Furuta, M.; Allen, M. W.

    2017-02-01

    Metal-semiconductor-field-effect-transistors (MESFETs) with silver oxide Schottky gates on zinc tin oxide (ZTO) channels showed fundamental differences in stability compared to conventional amorphous-oxide semiconductor thin-film-transistors (AOS-TFTs). The most severe negative-bias-temperature and negative-bias-illumination-temperature stress conditions, which usually degrade the performance of AOS-TFTs, significantly improved the switching characteristic of these ZTO MESFETs, producing devices with on:off current ratios, mobilities, and subthreshold swings of 8 × 106, 12 cm2 V-1 s-1, and 180 mV/dec, respectively. Further analysis confirmed that both negative bias and temperature (65 °C) were simultaneously required to produce this permanent effect that was linked to the electromigration of ionized donors from the MESFET depletion-region.

  4. GaN metal-semiconductor-metal UV sensor with multi-layer graphene as Schottky electrodes

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Ju; Kang, Sang-Bum; Cha, Hyeon-Gu; Won, Chul-Ho; Hong, Seul-Ki; Cho, Byung-Jin; Park, Hongsik; Lee, Jung-Hee; Hahm, Sung-Ho

    2015-06-01

    We fabricated a GaN-based metal-semiconductor-metal (MSM)-type UV sensor using a multilayer graphene as transparent Schottky electrodes. The fabricated GaN MSM UV sensor showed a high photo-to-dark current contrast ratio of 3.9 × 105 and a UV-to-visible rejection ratio of 1.8 × 103 at 7 V. The as-fabricated GaN MSM UV sensor with graphene electrodes has a low bias dependence of maximum photoresponsivity and a noise-like response at a visible wavelength in the 500 nm region. These problems were successfully solved by treatment with a buffered oxide etcher (BOE), and the photoresponse characteristics of the fabricated GaN MSM UV sensor after the treatment were better than those before the treatment.

  5. Ultra low-loss, isotropic optical negative-index metamaterial based on hybrid metal-semiconductor nanowires

    PubMed Central

    Paniagua-Domínguez, R.; Abujetas, D. R.; Sánchez-Gil, J. A.

    2013-01-01

    Recently, many fascinating properties predicted for metamaterials (negative refraction, superlensing, electromagnetic cloaking,…) were experimentally demonstrated. Unfortunately, the best achievements have no direct translation to the optical domain, without being burdened by technological and conceptual difficulties. Of particular importance within the realm of optical negative-index metamaterials (NIM), is the issue of simultaneously achieving strong electric and magnetic responses and low associated losses. Here, hybrid metal-semiconductor nanowires are proposed as building blocks of optical NIMs. The metamaterial thus obtained, highly isotropic in the plane normal to the nanowires, presents a negative index of refraction in the near-infrared, with values of the real part well below −1, and extremely low losses (an order of magnitude better than present optical NIMs). Tunability of the system allows to select the operating range in the whole telecom spectrum. The design is proven in configurations such as prisms and slabs, directly observing negative refraction. PMID:23514968

  6. The effect of metal-semiconductor contact on the transient photovoltaic characteristic of HgCdTe PV detector.

    PubMed

    Cui, Haoyang; Xu, Yongpeng; Yang, Junjie; Tang, Naiyun; Tang, Zhong

    2013-01-01

    The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S) interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

  7. Theoretical Study of the Effect of an AlGaAs Double Heterostructure on Metal-Semiconductor-Metal Photodetector Performance

    NASA Technical Reports Server (NTRS)

    Salem, Ali F.; Smith, Arlynn W.; Brennan, Kevin F.

    1994-01-01

    The impulse and square-wave input response of different GaAs metal-semiconductor-metal photodetector (MSM) designs are theoretically examined using a two dimensional drift- diffusion numerical calculation with a thermionic-field emission boundary condition model for the heterojunctions. The rise time and the fall time of the output signal current are calculated for a simple GaAs, epitaxially grown, MSM device as well as for various double-heterostructure barrier devices. The double heterostructure devices consist of an AlGaAs layer sandwiched between the top GaAs active, absorption layer and the bottom GaAs substrate. The effect of the depth of the AlGaAs layer on the speed and responsivity of the MSM devices is examined. It is found that there is an optimal depth, at fixed applied bias, of the AlGaAs layer within the structure that provides maximum responsivity at minimal compromise in speed.

  8. Responsivity drop due to conductance modulation in GaN metal-semiconductor-metal Schottky based UV photodetectors on Si(111)

    NASA Astrophysics Data System (ADS)

    Ravikiran, L.; Radhakrishnan, K.; Dharmarasu, N.; Agrawal, M.; Wang, Zilong; Bruno, Annalisa; Soci, Cesare; Lihuang, Tng; Kian Siong, Ang

    2016-09-01

    GaN Schottky metal-semiconductor-metal (MSM) UV photodetectors were fabricated on a 600 nm thick GaN layer, grown on 100 mm Si (111) substrate using an ammonia-MBE growth technique. In this report, the effect of device dimensions, applied bias and input power on the linearity of the GaN Schottky-based MSM photodetectors on Si substrate were investigated. Devices with larger interdigitated spacing, ‘S’ of 9.0 μm between the fingers resulted in good linearity and flat responsivity characteristics as a function of input power with an external quantum efficiency (EQE) of ˜33% at an applied bias of 15 V and an input power of 0.8 W m-2. With the decrease of ‘S’ to 3.0 μm, the EQE was found to increase to ˜97%. However, devices showed non linearity and drop in responsivity from flatness at higher input power. Moreover, the position of dropping from flatter responsivity was found to shift to lower powers with increased bias. The drop in the responsivity was attributed to the modulation of conductance in the MSM due to the trapping of electrons at the dislocations, resulting in the formation of depletion regions around them. In devices with lower ‘S’, both the image force reduction and the enhanced collection efficiency increased the photocurrent as well as the charging of the dislocations. This resulted in the increased depletion regions around the dislocations leading to the modulation of conductance and non-linearity.

  9. Gain mechanism and carrier transport in high responsivity AlGaN-based solar blind metal semiconductor metal photodetectors

    NASA Astrophysics Data System (ADS)

    Rathkanthiwar, Shashwat; Kalra, Anisha; Solanke, Swanand V.; Mohta, Neha; Muralidharan, Rangarajan; Raghavan, Srinivasan; Nath, Digbijoy N.

    2017-04-01

    We report on the highest responsivity for III-nitride Metal Semiconductor Metal solar-blind photodetectors on sapphire. Devices on unintentionally doped AlGaN epilayers grown by Metal Organic Chemical Vapor Deposition exhibited sharp absorption cut-off in the range of 245-290 nm. Very high responsivity >5 A/W at 10 V bias was achieved with visible rejection exceeding three orders of magnitude for front illumination. Compared to the responsivity values reported in the literature for state-of-the-art solar-blind photodetectors, this work presents the highest values of responsivity at a given bias and up to sub-250 nm detection threshold. The high responsivity is attributed to an internal gain mechanism operating on these devices. The reverse-bias leakage current across these samples was found to be dominated by thermionic field emission at low biases and Poole-Frenkel emission from a deep trap level (0.7 eV from the conduction band-edge for Al0.50Ga0.50 N) at high biases.

  10. CdSe Nanowire-Based Flexible Devices: Schottky Diodes, Metal-Semiconductor Field-Effect Transistors, and Inverters.

    PubMed

    Jin, Weifeng; Zhang, Kun; Gao, Zhiwei; Li, Yanping; Yao, Li; Wang, Yilun; Dai, Lun

    2015-06-24

    Novel CdSe nanowire (NW)-based flexible devices, including Schottky diodes, metal-semiconductor field-effect transistors (MESFETs), and inverters, have been fabricated and investigated. The turn-on voltage of a typical Schottky diode is about 0.7 V, and the rectification ratio is larger than 1 × 10(7). The threshold voltage, on/off current ratio, subthreshold swing, and peak transconductance of a typical MESFET are about -0.3 V, 4 × 10(5), 78 mV/dec, and 2.7 μS, respectively. The inverter, constructed with two MESFETs, exhibits clear inverting behavior with the gain to be about 28, 34, and 38, at the supply voltages (V(DD)) of 3, 5, and 7 V, respectively. The inverter also shows good dynamic behavior. The rising and falling times of the output signals are about 0.18 and 0.09 ms, respectively, under 1000 Hz square wave signals input. The performances of the flexible devices are stable and reliable under different bending conditions. Our work demonstrates these flexible NW-based Schottky diodes, MESFETs, and inverters are promising candidate components for future portable transparent nanoelectronic devices.

  11. Plasmonics-enabled metal-semiconductor-metal photodiodes for high-speed interconnects and polarization sensitive detectors

    NASA Astrophysics Data System (ADS)

    Panchenko, Evgeniy; Cadusch, Jasper J.; James, Timothy D.; Roberts, Ann

    2017-02-01

    Metal-semiconductor-metal (MSM) photodiodes are commonly used in ultrafast photoelectronic devices. Recently it was shown that localized surface plasmons can sufficiently enhance photodetector capabilities at both infrared and visible wavelengths. Such structures are of great interest since they can be used for fast, broadband detection. By utilizing the properties of plasmonic structures it is possible to design photodetectors that are sensitive to the polarization state of the incident wave. The direct electrical readout of the polarization state of an incident optical beam has many important applications, especially in telecommunications, bio-imaging and photonic computing. Furthermore, the fact that surface plasmon polaritons can circumvent the diffraction limit, opens up significant opportunities to use them to guide signals between logic gates in modern integrated circuits where small dimensions are highly desirable. Here we demonstrate two MSM photodetectors integrated with aluminum nanoantennas capable of distinguishing orthogonal states of either linearly or circularly polarized light with no additional filters. The localized plasmon resonances of the antennas lead to selective screening of the underlying silicon from light with a particular polarization state. The non-null response of the devices to each of the basis states expands the potential utility of the photodetectors while improving precision. We also demonstrate a design of waveguide-coupled MSM photodetector suitable for planar detection of surface plasmons.

  12. Low dark current metal-semiconductor-metal ultraviolet photodetectors based on sol-gel-derived TiO2 films

    NASA Astrophysics Data System (ADS)

    Xie, Yannan; Huang, Huolin; Yang, Weifeng; Wu, Zhengyun

    2011-01-01

    The titanium dioxide (TiO2) films prepared by sol-gel processing were used to fabricate metal-semiconductor-metal ultraviolet photodetectors. A very low dark current of 5.38 pA (current density of 3.84 nA/cm2) at 5 V bias is obtained, which is ascribed to the high effective Schottky barrier between Au and TiO2 films. The x-ray photoelectron spectroscopy analysis demonstrates that the concentration of oxygen vacancies is very low in the surface of the TiO2 films, which is responsible for the high effective Schottky barrier. The devices exhibit a cutoff wavelength at about 380 nm and a large UV-to-visible rejection ratio (340 versus 400 nm) of three orders of magnitude. The peak responsivity of the devices is 17.5 A/W at 5 V bias, indicating the presence of internal photoconductive gain induced by desorption of oxygen on the TiO2 surface.

  13. A Comprehensive Study on Mo/CdTe Metal-Semiconductor Interface Deposited by Radio Frequency Magnetron Sputtering.

    PubMed

    Dhar, N; Khan, N A; Chelvanathan, P; Akhtaruzzaman, M; Alam, M M; Alothman, Z A; Sopian, K; Amin, N

    2015-11-01

    Metal-semiconductor (MS) junction between Mo and CdTe, which is one of the fundamental issues for CdTe based solar cell, has been investigated for films deposited on different substrates. XRD pattern of Mo/CdTe films on the polyimide (PI) substrate shows a strong preferential orientation of MoTe2 in (100) at 2θ = 29.44 degrees, which becomes less apparent as deposition time of CdTe increases. However, on soda lime glass (SLG) no such XRD reflection pattern is observed. Moreover, from EDX measurement, Mo-Te compound also identifies MoTe2 at Mo/CdTe interface on PI substrate, which is not present on SLG. Bulk carrier concentration of Mo/CdTe films on PI substrate for lower deposition time of CdTe is found 1.42 x 10(18) cm(-3), which is almost equal to MoTe2. Thereafter, it decreases as CdTe growth time increases. The type of unintentionally formed MoTe2 on PI substrate is found to be n-type in nature. Lattice constants of a = 6.5 Å for CdTe and a = 3.52 Å for MoTe2 are found from nanostructure study by TEM.

  14. the effect of the periphery of metal-semiconductor Schottky-barrier contacts on their electrical characteristics

    SciTech Connect

    Torkhov, N. A.; Novikov, V. A.

    2011-01-15

    During the formation of the metal-semiconductor contact with a Schottky barrier (as a gold film on the p- or n-type gallium arsenide surface), an electric field E{sub l} built into the electric contact is induced, which propagates around the contact to the distance l (halo) tens of times larger than space-charge region sizes. This field reduces the electrostatic potential of the {phi}{sub Au} contact by a significant value {phi}*. In the general case, the halo size l and the decrease {phi}* in the electrostatic potential are controlled by the charge value and sign in the space-charge region, which depend on the contact diameter D, semiconductor concentration and conductivity type. For Au/n-GaAs Schottky-barrier contacts, a decrease in D results in the increasing role of periphery, which manifests itself in increasing {phi}* and decreasing {phi}{sub Au} and l. For Au/p-GaAs contacts, a decrease in D results in the decreasing effect of periphery, which appears in decreasing {phi}* and increasing {phi}{sub Au} and l. The absence of the space-charge region in metal-insulator-semiconductor contacts results in the fact that the halo size l and {phi}* are independent of their diameters.

  15. Metal-Semiconductor Transition Concomitant with a Structural Transformation in Tetrahedrite Cu12Sb4S13

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiromi I.; Suekuni, Koichiro; Umeo, Kazunori; Nagasaki, Toshiki; Sato, Hitoshi; Kutluk, Galif; Nishibori, Eiji; Kasai, Hidetaka; Takabatake, Toshiro

    2016-01-01

    The tetrahedrite Cu12Sb4S13 undergoes a metal-semiconductor transition (MST) at TMST = 85 K, whose mechanism remains elusive. Our Cu 2p X-ray photoemission spectroscopy study revealed the monovalent state of Cu ions occupying the two sites in this compound. This fact excludes the possibilities of previously proposed antiferromagnetic order and Jahn-Teller instability inherent in a divalent Cu system. A synchrotron X-ray diffraction study has revealed that the body-centered cubic cell of Cu12Sb4S13 transforms into a body-centered 2a × 2a × 2c tetragonal supercell below TMST, where the cell volume per formula unit expands by 0.25%. We have further studied pressure effects on the MST as well as the effects of the substitution of As for Sb. The application of pressure above 1 GPa completely inhibits the MST and leads to a metallic state, suggesting that the low-temperature structure with a larger volume becomes unstable under pressure. The As substitution also reduces the volume and suppresses the MST but the full substitution induces another transition at 124 K.

  16. Theoretical maximum efficiency of solar energy conversion in plasmonic metal-semiconductor heterojunctions.

    PubMed

    Cushing, Scott K; Bristow, Alan D; Wu, Nianqiang

    2015-11-28

    Plasmonics can enhance solar energy conversion in semiconductors by light trapping, hot electron transfer, and plasmon-induced resonance energy transfer (PIRET). The multifaceted response of the plasmon and multiple interaction pathways with the semiconductor makes optimization challenging, hindering design of efficient plasmonic architectures. Therefore, in this paper we use a density matrix model to capture the interplay between scattering, hot electrons, and dipole-dipole coupling through the plasmon's dephasing, including both the coherent and incoherent dynamics necessary for interactions on the plasmon's timescale. The model is extended to Shockley-Queisser limit calculations for both photovoltaics and solar-to-chemical conversion, revealing the optimal application of each enhancement mechanism based on plasmon energy, semiconductor energy, and plasmon dephasing. The results guide application of plasmonic solar-energy harvesting, showing which enhancement mechanism is most appropriate for a given semiconductor's weakness, and what nanostructures can achieve the maximum enhancement.

  17. Metal-Semiconductor Reaction Phenomena and Microstructural Investigations of Laser Induced Regrowth of Silicon on Insulators.

    DTIC Science & Technology

    1982-01-01

    VAN DER PAUW TECHNIQUE ... ........... . 39 11. BRIGHT-FIELD TRANSMISSION ELECTRON MICROGRAPH SHOWING FORMATION OF As2 Sn 3 PLOTS ... ........... .. 40...Electrical Characterisitcs To further investigate the quality of the Si film, we prepared samples for Hall effect measurements in a Van der Pauw configuration...C, was obtained. A series of 1, 3 and 5 scan frames were performed with the double layer "source-cap" remaining on the substrate. A Van der Pauw luchnique

  18. Characterization and Modeling Analysis for Metal-Semiconductor-Metal GaAs Diodes with Pd/SiO2 Mixture Electrode

    PubMed Central

    Tan, Shih-Wei; Lai, Shih-Wen

    2012-01-01

    Characterization and modeling of metal-semiconductor-metal (MSM) GaAs diodes using to evaporate SiO2 and Pd simultaneously as a mixture electrode (called M-MSM diodes) compared with similar to evaporate Pd as the electrode (called Pd-MSM diodes) were reported. The barrier height (φb) and the Richardson constant (A*) were carried out for the thermionic-emission process to describe well the current transport for Pd-MSM diodes in the consideration of the carrier over the metal-semiconductor barrier. In addition, in the consideration of the carrier over both the metal-semiconductor barrier and the insulator-semiconductor barrier simultaneously, thus the thermionic-emission process can be used to describe well the current transport for M-MSM diodes. Furthermore, in the higher applied voltage, the carrier recombination will be taken into discussion. Besides, a composite-current (CC) model is developed to evidence the concepts. Our calculated results are in good agreement with the experimental ones. PMID:23226352

  19. Synergizing the multiple plasmon resonance coupling and quantum effects to obtain enhanced SERS and PEC performance simultaneously on a noble metal-semiconductor substrate.

    PubMed

    Yang, Tao; Liu, Wenna; Li, Lidong; Chen, Junhong; Hou, Xinmei; Chou, Kuo-Chih

    2017-02-09

    Aiming to achieve the synergistic enhancement of the surface-enhanced Raman scattering (SERS) and photoelectrocatalytic (PEC) performance on a noble metal-semiconductor, such as Au nanoparticles (NPs)-TiO2 nanotube arrays (TiO2 NTAs@hybrid Au NPs), theoretical calculation and experiments are performed. Theoretical calculation indicates that both the SERS and PEC performance can be enhanced by coupling different sized Au NPs on TiO2 NTAs based on synergizing the multiple plasmon resonance coupling and quantum effects. To further verify this mechanism, TiO2 NTAs@hybrid Au NPs are assembled via synthesis of TiO2 NTAs through the anodic oxidation process, followed by the deposition of different sized Au NPs onto the TiO2 surface simultaneously using physical vapor deposition (PVD) in this work. Such substrates exhibit excellent detection sensitivity towards organic dyes including Rhodamine B (RhB), the organic herbicide dichlorophenoxyacetic acid (2,4-D) and the organophosphate pesticide methyl-parathion (MP) with high reproducibility, stability and reusability. Meanwhile the PEC performance based on this substrate remains efficient compared with the reported results in the literature. The efficient PEC performance mainly originates from both the quantum effect of Au nanoparticles and the formation of a metal-semiconductor heterojunction. It is proposed that other noble metal-semiconductor complex nanomaterials can also obtain both enhanced SERS and PEC performance based on the above mechanism.

  20. Plasmonic-exciton coupling in synthesized metal/semiconductor hybrid nanocomposites

    SciTech Connect

    Gadalla, A.; Hamad, D. A.; Mohamed, M. B.

    2015-12-31

    A new method has been developed to grow plasmonic semiconductor nanocomposites of Au/CdSe and Ag/CdSe. Their chemical composition and crystal structure are determined by X-ray diffraction. The collective optical properties of the prepared semiconductor nanohybrid have been measured using spectrophotometer techniques and compared to those of the individual components. The electron transfer processes from CdSe to the gold are faster than that of the silver. Au/CdSe has a strong plasmonic-excitonic coupling, but Ag/CdSe has a weak plasmonic-excitonic coupling.

  1. Chemical reactions at metallic and metal/semiconductor interfaces stimulated by pulsed laser annealing

    NASA Astrophysics Data System (ADS)

    Petit, E. J.; Caudano, R.

    1992-01-01

    Multilayer Al/Sb thin films have been evaporated on GaSb single crystals in ultra-high vacuum and pulsed-laser irradiated in-situ above the energy density threshold for surface melting. Superficial and interfacial chemical reactions have been characterized in-situ by Auger electron spectroscopy; and later, by X-ray photoelectron spectroscopy profiling, Rutherford backscattering spectrometry and scanning electron microscopy. The chemical reaction between the Al and Sb films is considered as a model reaction for laser-assisted synthesis of high-purity intermetallic compounds. The observation of a strong interfacial reaction between the melted film and the substrate is also a subject of great concern for optical data recording and laser alloying of ohmic contacts on semiconductors. We show that a suitable choice of the substrate and adding a low surface tension element into the metallic film can improve its stability during melting, and prevent inhomogeneous reaction and formation of holes, cracks and particles. Finally, other solutions are suggested to improve the control of these reactions.

  2. Strain-induced metal-semiconductor transition observed in atomic carbon chains

    NASA Astrophysics Data System (ADS)

    La Torre, A.; Botello-Mendez, A.; Baaziz, W.; Charlier, J.-C.; Banhart, F.

    2015-03-01

    Carbyne, the sp1-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. While the bulk phases of carbyne remain elusive, the elementary constituents, that is, linear chains of carbon atoms, have already been observed using the electron microscope. Isolated atomic chains are highly interesting one-dimensional conductors that have stimulated considerable theoretical work. Experimental information, however, is still very limited. Here we show electrical measurements and first-principles transport calculations on monoatomic carbon chains. When the 1D system is under strain, the chains are semiconducting corresponding to the polyyne structure with alternating bond lengths. Conversely, when the chain is unstrained, the ohmic behaviour of metallic cumulene with uniform bond lengths is observed. This confirms the recent prediction of a metal-insulator transition that is induced by strain. The key role of the contacting leads explains the rectifying behaviour measured in monoatomic carbon chains in a nonsymmetric contact configuration.

  3. Ion-sculpting of nanopores in amorphous metals, semiconductors, and insulators

    SciTech Connect

    George, H. Bola; Madi, Charbel S.; Aziz, Michael J.; Hoogerheide, David P.; Bell, David C.; Golovchenko, Jene A.

    2010-06-28

    We report the closure of nanopores to single-digit nanometer dimensions by ion sculpting in a range of amorphous materials including insulators (SiO{sub 2} and SiN), semiconductors (a-Si), and metallic glasses (Pd{sub 80}Si{sub 20})--the building blocks of a single-digit nanometer electronic device. Ion irradiation of nanopores in crystalline materials (Pt and Ag) does not cause nanopore closure. Ion irradiation of c-Si pores below 100 deg. C and above 600 deg. C, straddling the amorphous-crystalline dynamic transition temperature, yields closure at the lower temperature but no mass transport at the higher temperature. Ion beam nanosculpting appears to be restricted to materials that either are or become amorphous during ion irradiation.

  4. Metal, Semiconductor, and Carbon Cluster Studies Including the Discovery and Characterization of Carbon -60: Buckminsterfullerene.

    NASA Astrophysics Data System (ADS)

    Heath, James Richard

    Experiments using the laser vaporization technique for production of metal clusters have been performed. The reactions of neutral metal clusters with various gases have been studied using a fast flow reactor. Dramatic reactivity variations were observed which depended on cluster size, metal, and reactant. A laser vaporization disc source has been developed for the study of semiconductor clusters. Some preliminary studies on neutral germanium and silicon clusters were performed. Their ionization potentials have been bracketed and the clusters were found to fragment by a fissioning process and to have long lived (100 nanoseconds) excited electronic states. A detailed study has been undertaken into carbon clusters. Laser synthesis of astrophysically important polyyne molecules such as H-C-(C-C)_{ rm 2n}-N has been done. Chains containing up to 22 carbon atoms are formed in a vaporized carbon and reactant gas plasma. A photophysically stable and chemically inert cluster, C_{60}, has been discovered and hypothesized to have the structure of a truncated icosahedron. All even clusters in the 60 atom size range were found to be inert to highly reactive gases, while odd clusters readily reacted. The results are consistent with a whole series (30-90 atoms) of closed cage-like structures. Closure of even clusters only is possible via the inclusion of twelve pentagons into a hexagonal network. Odd clusters show neither the photophysical nor chemical stability of the even clusters. A mechanism for the formation of spherical soot particles has been developed. Stable organometallic complexes of the formula C_{rm 2n}M (20 < n < 40 and M = La, Ba, Sr, Ca) have been laser synthesized. The dominant complex observed was C_{60}M ^+. These species are photophysically stable, chemically inert, and no C_{rm 2n}M_2^ecies were detected. The ultraviolet and visible absorption spectrum of C_{60} has been measured. Because excited electronic states are not expected to live long in a molecule

  5. Photoluminescence and photocatalytic activities of Ag/ZnO metal-semiconductor heterostructure

    NASA Astrophysics Data System (ADS)

    Sarma, Bikash; Deb, Sujit Kumar; Sarma, Bimal K.

    2016-10-01

    Present article focuses on the photocatalytic activities of ZnO nanorods and Ag/ZnO heterostructure deposited on polyethylene terephthalate (PET) substrate. ZnO nanorods are synthesized by thermal decomposition technique and Ag nanoparticles deposition is done by photo-deposition technique using UV light. X-ray diffraction studies reveal that the ZnO nanorods are of hexagonal wurtzite structure. Further, as-prepared samples are characterized by Scanning Electron Microscopy (SEM), Photoluminescence (PL) spectroscopy and UV-Vis spectroscopy. The surface plasmon resonance response of Ag/ZnO is found at 420 nm. The photocatalytic activities of the samples are evaluated by photocatalytic decolorization of methyl orange (MO) dye with UV irradiation. The degradation rate of MO increases with increase in irradiation time. The degradation of MO follows the first order kinetics. The photocatalytic activity of Ag/ZnO heterostructure is found to be more than that of ZnO nanorods. The PL intensity of ZnO nanorods is stronger than that of the Ag/ZnO heterostructure. The strong PL intensity indicates high recombination rate of photoinduced charge carriers which lowers the photocatalytic activity of ZnO nanorods. The charge carrier recombination is effectively suppressed by introducing Ag nanoparticles on the surface of the ZnO nanorods. This study demonstrates a strong relationship between PL intensity and photocatalytic activity.

  6. Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes.

    PubMed

    Sadaf, S M; Ra, Y H; Szkopek, T; Mi, Z

    2016-02-10

    We have demonstrated for the first time an n(++)-GaN/Al/p(++)-GaN backward diode, wherein an epitaxial Al layer serves as the tunnel junction. The resulting p-contact free InGaN/GaN nanowire light-emitting diodes (LEDs) exhibited a low turn-on voltage (∼2.9 V), reduced resistance, and enhanced power, compared to nanowire LEDs without the use of Al tunnel junction or with the incorporation of an n(++)-GaN/p(++)-GaN tunnel junction. This unique Al tunnel junction overcomes some of the critical issues related to conventional GaN-based tunnel junction designs, including stress relaxation, wide depletion region, and light absorption, and holds tremendous promise for realizing low-resistivity, high-brightness III-nitride nanowire LEDs in the visible and deep ultraviolet spectral range. Moreover, the demonstration of monolithic integration of metal and semiconductor nanowire heterojunctions provides a seamless platform for realizing a broad range of multifunctional nanoscale electronic and photonic devices.

  7. Switching Plasmons: Gold Nanorod-Copper Chalcogenide Core-Shell Nanoparticle Clusters with Selectable Metal/Semiconductor NIR Plasmon Resonances.

    PubMed

    Muhammed, Madathumpady Abubaker Habeeb; Döblinger, Markus; Rodríguez-Fernández, Jessica

    2015-09-16

    Exerting control over the near-infrared (NIR) plasmonic response of nanosized metals and semiconductors can facilitate access to unexplored phenomena and applications. Here we combine electrostatic self-assembly and Cd(2+)/Cu(+) cation exchange to obtain an anisotropic core-shell nanoparticle cluster (NPC) whose optical properties stem from two dissimilar plasmonic materials: a gold nanorod (AuNR) core and a copper selenide (Cu(2-x)Se, x ≥ 0) supraparticle shell. The spectral response of the AuNR@Cu2Se NPCs is governed by the transverse and longitudinal plasmon bands (LPB) of the anisotropic metallic core, since the Cu2Se shell is nonplasmonic. Under aerobic conditions the shell undergoes vacancy doping (x > 0), leading to the plasmon-rich NIR spectrum of the AuNR@Cu(2-x)Se NPCs. For low vacancy doping levels the NIR optical properties of the dually plasmonic NPCs are determined by the LPBs of the semiconductor shell (along its major longitudinal axis) and of the metal core. Conversely, for high vacancy doping levels their NIR optical response is dominated by the two most intense plasmon modes from the shell: the transverse (along the shortest transversal axis) and longitudinal (along the major longitudinal axis) modes. The optical properties of the NPCs can be reversibly switched back to a purely metallic plasmonic character upon reversible conversion of AuNR@Cu(2-x)Se into AuNR@Cu2Se. Such well-defined nanosized colloidal assemblies feature the unique ability of holding an all-metallic, a metallic/semiconductor, or an all-semiconductor plasmonic response in the NIR. Therefore, they can serve as an ideal platform to evaluate the crosstalk between plasmonic metals and plasmonic semiconductors at the nanoscale. Furthermore, their versatility to display plasmon modes in the first, second, or both NIR windows is particularly advantageous for bioapplications, especially considering their strong absorbing and near-field enhancing properties.

  8. Irradiation effects of graphene-enhanced gallium nitride (GaN) metal-semiconductor-metal (MSM) ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Chiamori, Heather C.; Miller, Ruth; Suria, Ateeq; Broad, Nicholas; Senesky, Debbie G.

    2015-05-01

    Ultraviolet (UV) photodetectors are used for applications such as flame detection, space navigation, biomedical and environmental monitoring. Robust operation within large ranges of temperatures, radiation, salinity and/or corrosive chemicals require sensor materials with the ability to withstand and function reliably within these extreme harsh environments. For example, spacecraft can utilize a sun sensor (light-based sensor) to assist with determination of orientation and may be exposed to both ionizing radiation and extreme temperature swings during operation. Gallium nitride (GaN), a wide bandgap semiconductor material, has material properties enabling visible-blindness, tunable cutoff wavelength selection based on ternary alloy mole fraction, high current density, thermal/chemical stability and high radiation tolerance due to the strength of the chemical bond. Graphene, with outstanding electrical, optical and mechanical properties and a flat absorption spectrum from 300 to 2,500 nm, has potential use as a transparent conductor for GaN-based metal-semiconductor-metal (MSM) photodetectors. Here, graphene-enhanced MSM UV photodetectors are fabricated with transparent and conductive graphene interdigitated electrodes on thin film GaN-on-sapphire substrates serving as back-to-back Schottky contacts. We report on the irradiation response of graphene/GaN-based MSM UV photodetectors up to 750 krad total ionizing dose (TID) then tested under dark and UV light (365 nm) conditions. In addition, based on current-voltage measurements from 75 krad to 750 krad TID, calculated photodetector responsivity values change slightly by 25% and 11% at -5 V and -2 V, respectively. These initial findings suggest that graphene/GaN MSM UV photodetectors could potentially be engineered to reliably operate within radiation environments.

  9. Growth of metal-semiconductor core-multishell nanorods with optimized field confinement and nonlinear enhancement

    NASA Astrophysics Data System (ADS)

    Nan, Fan; Xie, Fang-Ming; Liang, Shan; Ma, Liang; Yang, Da-Jie; Liu, Xiao-Li; Wang, Jia-Hong; Cheng, Zi-Qiang; Yu, Xue-Feng; Zhou, Li; Wang, Qu-Quan; Zeng, Jie

    2016-06-01

    This paper describes a facile method for the synthesis of Au/AuAg/Ag2S/PbS core-multishell nanorods with double trapping layers. The synthesis, in sequence, involved deposition of Ag shells onto the surfaces of Au nanorod seeds, formation of AuAg shells by a galvanic replacement reaction, and overgrowth of the Ag2S shells and PbS shells. The resulting core-multishell nanorod possesses an air gap between the Au core and the AuAg shell. Together with the Ag2S shell, the air gap can efficiently trap light, causing strong field confinement and nonlinear enhancement. The as-prepared Au/AuAg/Ag2S/PbS core-multishell nanorods display distinct localized surface plasmon resonance and nonlinear optical properties, demonstrating an effective pathway for maneuvering the optical properties of nanocavities.This paper describes a facile method for the synthesis of Au/AuAg/Ag2S/PbS core-multishell nanorods with double trapping layers. The synthesis, in sequence, involved deposition of Ag shells onto the surfaces of Au nanorod seeds, formation of AuAg shells by a galvanic replacement reaction, and overgrowth of the Ag2S shells and PbS shells. The resulting core-multishell nanorod possesses an air gap between the Au core and the AuAg shell. Together with the Ag2S shell, the air gap can efficiently trap light, causing strong field confinement and nonlinear enhancement. The as-prepared Au/AuAg/Ag2S/PbS core-multishell nanorods display distinct localized surface plasmon resonance and nonlinear optical properties, demonstrating an effective pathway for maneuvering the optical properties of nanocavities. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09151a

  10. Electronic structures of porous nanocarbons

    PubMed Central

    Baskin, Artem; Král, Petr

    2011-01-01

    We use large scale ab-initio calculations to describe electronic structures of graphene, graphene nanoribbons, and carbon nanotubes periodically perforated with nanopores. We disclose common features of these systems and develop a unified picture that permits us to analytically predict and systematically characterize metal-semiconductor transitions in nanocarbons with superlattices of nanopores of different sizes and types. These novel materials with highly tunable band structures have numerous potential applications in electronics, light detection, and molecular sensing. PMID:22355555

  11. Electronic structures of porous nanocarbons.

    PubMed

    Baskin, Artem; Král, Petr

    2011-01-01

    We use large scale ab-initio calculations to describe electronic structures of graphene, graphene nanoribbons, and carbon nanotubes periodically perforated with nanopores. We disclose common features of these systems and develop a unified picture that permits us to analytically predict and systematically characterize metal-semiconductor transitions in nanocarbons with superlattices of nanopores of different sizes and types. These novel materials with highly tunable band structures have numerous potential applications in electronics, light detection, and molecular sensing.

  12. Electronic structures of porous nanocarbons

    NASA Astrophysics Data System (ADS)

    Baskin, Artem; Král, Petr

    2011-07-01

    We use large scale ab-initio calculations to describe electronic structures of graphene, graphene nanoribbons, and carbon nanotubes periodically perforated with nanopores. We disclose common features of these systems and develop a unified picture that permits us to analytically predict and systematically characterize metal-semiconductor transitions in nanocarbons with superlattices of nanopores of different sizes and types. These novel materials with highly tunable band structures have numerous potential applications in electronics, light detection, and molecular sensing.

  13. Electrical characterization and hydrogen gas sensing properties of a n-ZnO /p-SiC Pt-gate metal semiconductor field effect transistor

    NASA Astrophysics Data System (ADS)

    Kandasamy, S.; Wlodarski, W.; Holland, A.; Nakagomi, S.; Kokubun, Y.

    2007-02-01

    A new hydrogen gas sensitive n-ZnO /p-SiC Pt-gate metal semiconductor field effect transistor (MESFET) is reported. The observed current-voltage curves for the source to drain region indicate that this MESFET operates in enhancement mode. A change in gate potential, due to different ambient atmospheres caused a change in the width of the depletion region, hence modulating the current in the n channel (ZnO layer). The H2 gas sensing mechanism of the presented MESFET structure is discussed using energy band diagrams.

  14. Enhanced electrical transparency by ultra-thin LaAlO3 insertion at oxide metal/semiconductor heterointerfaces

    SciTech Connect

    Yajima, Takeaki; Minohara, Makoto; Bell, Christopher; Kumigashira, Hiroshi; Oshima, Masaharu; Hwang, Harold Y.; Hikita, Yasuyuki

    2015-02-05

    We demonstrate that the electrical conductivity of metal/semiconductor oxide heterojunctions can be increased over 7 orders of magnitude by inserting an ultrathin layer of LaAlO3. This counterintuitive result, that an interfacial barrier can be driven transparent by inserting a wide-gap insulator, arises from the large internal electric field between the two polar LaAlO3 surfaces. In conclusion, this field modifies the effective band offset in the device, highlighting the ability to design the electrostatic boundary conditions with atomic precision.

  15. Realization of Mg(x=0.15)Zn(1-x=0.85)O-based metal-semiconductor-metal UV detector on quartz and sapphire

    NASA Astrophysics Data System (ADS)

    Hullavarad, S. S.; Dhar, S.; Varughese, B.; Takeuchi, I.; Venkatesan, T.; Vispute, R. D.

    2005-07-01

    In this article we present the growth of hexagonal phase MgZnO on nonconventional substrates such as quartz and on sapphire for comparison of the device property. We are reporting the realization of MgZnO-based UV detector on quartz by the pulsed laser deposition technique. MgZnO films are characterized by x-ray diffraction, UV-visible spectroscopy, and Rutherford backscattering-channeling techniques. The morphology of the films is studied by atomic force microscopy. The metal-semiconductor-metal device was fabricated on the MgZnO film to study the device photoresponse under proper UV irradiation.

  16. A Web Service and Interface for Remote Electronic Device Characterization (PREPRINT)

    DTIC Science & Technology

    2011-01-01

    focuses on semiconductor physics in electronic devic- es including p-n junctions, metal-semiconductor devices, bipolar transistors , optoelec- tronic devices...terface to make real-time transistor measurements. Recommendations are made on how best to integrate the interface into electronics classes, based on the...Educational technology, engineering education, MOSFETs, online services, transistors The authors are

  17. Probing the nanoscale Schottky barrier of metal/semiconductor interfaces of Pt/CdSe/Pt nanodumbbells by conductive-probe atomic force microscopy.

    PubMed

    Kwon, Sangku; Lee, Seon Joo; Kim, Sun Mi; Lee, Youngkeun; Song, Hyunjoon; Park, Jeong Young

    2015-08-07

    The electrical nature of the nanoscale contact between metal nanodots and semiconductor rods has drawn significant interest because of potential applications for metal-semiconductor hybrid nanostructures in energy conversion or heterogeneous catalysis. Here, we studied the nanoscale electrical character of the Pt/CdSe junction in Pt/CdSe/Pt nanodumbbells on connected Au islands by conductive-probe atomic force microscopy under ultra-high vacuum. Current-voltage plots measured in contact mode revealed Schottky barrier heights of individual nanojunctions of 0.41 ± 0.02 eV. The measured value of the Schottky barrier is significantly lower than that of planar thin-film diodes because of a reduction in the barrier width and enhanced tunneling probability at the interface.

  18. High responsivity in molecular beam epitaxy grown β-Ga2O3 metal semiconductor metal solar blind deep-UV photodetector

    NASA Astrophysics Data System (ADS)

    Singh Pratiyush, Anamika; Krishnamoorthy, Sriram; Vishnu Solanke, Swanand; Xia, Zhanbo; Muralidharan, Rangarajan; Rajan, Siddharth; Nath, Digbijoy N.

    2017-05-01

    In this report, we demonstrate high spectral responsivity (SR) in MBE grown epitaxial β-Ga2O3-based solar blind metal-semiconductor-metal (MSM) photodetectors (PD). The (-201)-oriented β-Ga2O3 thin film was grown using plasma-assisted MBE on c-plane sapphire substrates. MSM devices fabricated with Ni/Au contacts in an interdigitated geometry were found to exhibit peak SR > 1.5 A/W at 236-240 nm at a bias of 4 V with a UV to visible rejection ratio > 105. The devices exhibited very low dark current < 10 nA at 20 V and showed no persistent photoconductivity (PPC) as evident from the sharp transients with a photo-to-dark current ratio > 103. These results represent the state-of-art performance for the MBE-grown β-Ga2O3 MSM solar blind detector.

  19. Dependences of the electrical properties on the diameter and the doping concentration of the Si nanowire field effect transistors with a Schottky metal-semiconductor contact.

    PubMed

    You, Joo Hyung; Lee, Se Han; You, Chan Ho; Yu, Yun Seop; Kim, Tae Whan

    2010-05-01

    A compact model of the current-voltage (I-V) characteristics for the Si nanowire field effect transistor (FET) taking into account dependence of the analytical electrical properties on the diameter and the concentration of the Si nanowire of the FETs with a Schottky metal-semiconductor contact has been proposed. I-V characteristics of the nanowire FETs were analytically calculated by using a quantum drift-diffusion current transport model taking into account an equivalent circuit together with the quantum effect of the Si nanowires and a Schottky model at Schottky barriers. The material parameters dependent on different diameters and concentrations of the Si nanowire were numerically estimated from the physical properties of the Si nanowire. The threshold voltage, the mobility, and the doping density of the Si nanowire and the Schottky barrier height at a metal-Si nanowire heterointerface in the nanowire FET were estimated by using the theoretical model.

  20. Performance improvement of GaN-based metal-semiconductor-metal photodiodes grown on Si(111) substrate by thermal cycle annealing process

    NASA Astrophysics Data System (ADS)

    Lin, Jyun-Hao; Huang, Shyh-Jer; Su, Yan-Kuin

    2014-01-01

    A simple thermal cycle annealing (TCA) process was used to improve the quality of GaN grown on a Si substrate. The X-ray diffraction (XRD) and etch pit density (EPD) results revealed that using more process cycles, the defect density cannot be further reduced. However, the performance of GaN-based metal-semiconductor-metal (MSM) photodiodes (PDs) prepared on Si substrates showed significant improvement. With a two-cycle TCA process, it is found that the dark current of the device was only 1.46 × 10-11 A, and the photo-to-dark-current contrast ratio was about 1.33 × 105 at 5 V. Also, the UV/visible rejection ratios can reach as high as 1077.

  1. AlGaN Metal-Semiconductor-Metal Photodetectors on Planar and Epitaxial Laterally Overgrown AlN/Sapphire Templates for the Ultraviolet C Spectral Region

    NASA Astrophysics Data System (ADS)

    Knigge, Andrea; Brendel, Moritz; Brunner, Frank; Einfeldt, Sven; Knauer, Arne; Kueller, Viola; Zeimer, Ute; Weyers, Markus

    2013-08-01

    Schottky type metal-semiconductor-metal (MSM) Al0.4Ga0.6N photodetectors (PDs) for the ultraviolet C spectral region on conventional planar AlN templates are compared with epitaxial laterally overgrown (ELO) AlN templates. On planar templates solar blind MSM PDs with state-of-the-art dark current in the pA range and a power independent responsivity are obtained. PDs on ELO templates with fingers parallel to the etched stripes have properties similar to those on planar templates. PDs on ELO templates with contact fingers oriented perpendicular to the etched stripe pattern exhibit photoconductive gain leading to external quantum efficiencies of up to 77 at 30 V applied bias surpassing that of the planar grown PDs by a factor of 100. In spite of the high gain these PDs also show low dark currents, short switching times and two operating regimes with power independent responsivity.

  2. Contact resistivity decrease at a metal/semiconductor interface by a solid-to-liquid phase transitional metallo-organic silver.

    PubMed

    Shin, Dong-Youn; Seo, Jun-Young; Kang, Min Gu; Song, Hee-eun

    2014-09-24

    We present a new approach to ensure the low contact resistivity of a silver paste at a metal/semiconductor interface over a broad range of peak firing temperatures by using a solid-to-liquid phase transitional metallo-organic silver, that is, silver neodecanoate. Silver nanoclusters, thermally derived from silver neodecanoate, are readily dissolved into the melt of metal oxide glass frit even at low temperatures, at which point the molten metal oxide glass frit lacks the dissociation capability of bulk silver into Ag(+) ions. In the presence of O(2-) ions in the melt of metal oxide glass frit, the redox reaction from Ag(+) to Ag(0) augments the noble-metal-assisted etching capability to remove the passivation layer of silicon nitride. Moreover, during the cooling stage, the nucleated silver atoms enrich the content of silver nanocolloids in the solidified metal oxide glass layer. The resulting contact resistivity of silver paste with silver neodecanoate at the metal/semiconductor interface thus remains low-between 4.12 and 16.08 mΩ cm(2)-whereas without silver neodecanoate, the paste exhibits a contact resistivity between 2.61 and 72.38 mΩ cm(2) in the range of peak firing temperatures from 750 to 810 °C. The advantage of using silver neodecanoate in silver paste becomes evident in that contact resistivity remains low over the broad range of peak firing temperatures, thus providing greater flexibility with respect to the firing temperature required in silicon solar cell applications.

  3. Ultrasensitive NO2 Sensor Based on Ohmic Metal-Semiconductor Interfaces of Electrolytically Exfoliated Graphene/Flame-Spray-Made SnO2 Nanoparticles Composite Operating at Low Temperatures.

    PubMed

    Tammanoon, Nantikan; Wisitsoraat, Anurat; Sriprachuabwong, Chakrit; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Phanichphant, Sukon; Liewhiran, Chaikarn

    2015-11-04

    In this work, flame-spray-made undoped SnO2 nanoparticles were loaded with 0.1-5 wt % electrolytically exfoliated graphene and systematically studied for NO2 sensing at low working temperatures. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy indicated that high-quality multilayer graphene sheets with low oxygen content were widely distributed within spheriodal nanoparticles having polycrystalline tetragonal SnO2 phase. The 10-20 μm thick sensing films fabricated by spin coating on Au/Al2O3 substrates were tested toward NO2 at operating temperatures ranging from 25 to 350 °C in dry air. Gas-sensing results showed that the optimal graphene loading level of 0.5 wt % provided an ultrahigh response of 26,342 toward 5 ppm of NO2 with a short response time of 13 s and good recovery stabilization at a low optimal operating temperature of 150 °C. In addition, the optimal sensor also displayed high sensor response and relatively short response time of 171 and 7 min toward 5 ppm of NO2 at room temperature (25 °C). Furthermore, the sensors displayed very high NO2 selectivity against H2S, NH3, C2H5OH, H2, and H2O. Detailed mechanisms for the drastic NO2 response enhancement by graphene were proposed on the basis of the formation of graphene-undoped SnO2 ohmic metal-semiconductor junctions and accessible interfaces of graphene-SnO2 nanoparticles. Therefore, the electrolytically exfoliated graphene-loaded FSP-made SnO2 sensor is a highly promising candidate for fast, sensitive, and selective detection of NO2 at low operating temperatures.

  4. Characteristic Improvements of ZnO-Based Metal-Semiconductor-Metal Photodetector on Flexible Substrate with ZnO Cap Layer

    NASA Astrophysics Data System (ADS)

    Ji, Liang-Wen; Wu, Cheng-Zhi; Lin, Chih-Ming; Meen, Teen-Hang; Lam, Kin-Tak; Peng, Shi-Ming; Young, Sheng-Joue; Liu, Chien-Hung

    2010-05-01

    In this work, ZnO-based metal-semiconductor-metal photodetectors with and without a ZnO cap layer were fabricated on flexible substrates of poly(ethylene terephthalate) (PET) for comparative analysis. The ZnO films were prepared by a low-temperature sputtering process. The photodetector with a ZnO cap layer (stack structure: ZnO/Ag/ZnO/PET) shows a much higher UV-to-visible rejection ratio of 1.56 ×103 than that without. This can be attributed to the photocurrents that are not only significantly increased in the UV region but also slightly suppressed in the visible region for such a novel structure. With an incident wavelength of 370 nm and an applied bias of 3 V, the responsivities of both photodetectors with and without a ZnO cap layer are 3.80 ×10-2 and 2.36 ×10-3 A/W, which correspond to quantum efficiencies of 1.13 and 0.07%, respectively. The Schottky barrier height at the Ag/ZnO interface is also determined to be 0.782 eV.

  5. Characteristic Improvements of ZnO-Based Metal-Semiconductor-Metal Photodetector on Flexible Substrate with ZnO Cap Layer

    NASA Astrophysics Data System (ADS)

    Liang-Wen Ji,; Cheng-Zhi Wu,; Chih-Ming Lin,; Teen-Hang Meen,; Kin-Tak Lam,; Shi-Ming Peng,; Sheng-Joue Young,; Chien-Hung Liu,

    2010-05-01

    In this work, ZnO-based metal-semiconductor-metal photodetectors with and without a ZnO cap layer were fabricated on flexible substrates of poly(ethylene terephthalate) (PET) for comparative analysis. The ZnO films were prepared by a low-temperature sputtering process. The photodetector with a ZnO cap layer (stack structure: ZnO/Ag/ZnO/PET) shows a much higher UV-to-visible rejection ratio of 1.56 × 103 than that without. This can be attributed to the photocurrents that are not only significantly increased in the UV region but also slightly suppressed in the visible region for such a novel structure. With an incident wavelength of 370 nm and an applied bias of 3 V, the responsivities of both photodetectors with and without a ZnO cap layer are 3.80 × 10-2 and 2.36 × 10-3 A/W, which correspond to quantum efficiencies of 1.13 and 0.07%, respectively. The Schottky barrier height at the Ag/ZnO interface is also determined to be 0.782 eV.

  6. Influence of Source/Drain Residual Implant Lattice Damage Traps on Silicon Carbide Metal Semiconductor Field-Effect Transistor Drain I-V Characteristics

    NASA Astrophysics Data System (ADS)

    Adjaye, J.; Mazzola, M. S.

    4H-SiC n-channel power metal semiconductor field-effect transistors (MESFETs) with nitrogen n+-implanted source/drain ohmic contact regions, with and without p-buffer layer fabricated on semi-insulating substrates exhibited hysteresis in the drain I-V characteristics of both types of devices at 300 K and 480 K due to traps. However, thermal spectroscopic measurements could detect the traps only in the devices without p-buffer. Device simulation and optical admittance spectroscopy (OAS) are used to resolve the discrepancy in the initial experimental characterization results. Device simulations and OAS suggest that, in addition to the semi-insulating (SI) substrate traps, acceptor traps due to source/drain residual implant lattice damage contribute to the hysteresis observed in the drain I-V characteristics of the devices. Simulations suggest these traps are contained in the lateral straggle of the implanted source and drain regions since the drain current largely flows between the un-gated edges of the source and drain through the volume of lateral straggle traps. Since hysteresis in I-V curves is a manifestation of the presence of defects in devices and since defects degrade carrier mobility and hence device performance, efforts should be made to minimize the source/drain lateral straggle implant damage.

  7. Incorporation of sol-gel-derived Mg into InZnO semiconductor thin films for metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Tsay, Chien-Yie; Wu, Po-Hsien

    2017-03-01

    We incorporated Mg into InZnO (MIZO) semiconductor thin films and fabricated metal-semiconductor-metal (MSM) UV photodetectors by the sol-gel method. The effects of incorporating Mg into IZO films on the electrical and UV photoresponse properties were investigated and photoconductive UV detectors were realized using IZO-based films. The Mg content ([Mg]/[In + Zn]) was varied from 0 to 20% in the resultant solutions. Each as-coated sol-gel film was preheated at 300 °C for 10 min and annealed at 450 °C for 2 h to form dense oxide films. Results showed that all as-prepared IZO-based films had an amorphous phase structure, displayed a flat surface, and exhibited a high visible transmittance (≥90.0%). We found that UV light illumination increased the photocurrents in all IZO-based films, and that MIZO photodetectors exhibited better photocurrent generation than pure IZO photodetectors. The 20% Mg-doped IZO photodetectors exhibited the highest I light-to-I dark ratio (8.57) and the highest percentage of sensitivity (756.9).

  8. Cupric and cuprous oxide by reactive ion beam sputter deposition and the photosensing properties of cupric oxide metal-semiconductor-metal Schottky photodiodes

    NASA Astrophysics Data System (ADS)

    Hong, Min-Jyun; Lin, Yong-Chen; Chao, Liang-Chiun; Lin, Pao-Hung; Huang, Bohr-Ran

    2015-08-01

    Cupric (CuO) and cuprous (Cu2O) oxide thin films have been deposited by reactive ion beam sputter deposition at 400 °C with an Ar:O2 ratio from 2:1 to 12:1. With an Ar:O2 ratio of 2:1, single phase polycrystalline CuO thin films were obtained. Decreasing oxygen flow rate results in CuO + Cu2O and Cu2O + Cu mixed thin films. As Ar:O2 ratio reaches 12:1, Cu2O nanorods with diameter of 250 nm and length longer than 1 μm were found across the sample. Single phase CuO thin film exhibits an indirect band gap of 1.3 eV with a smooth surface morphology. CuO metal-semiconductor-metal (MSM) Schottky photodiodes (PD) were fabricated by depositing Cu interdigitated electrodes on CuO thin films. Photosensing properties of the CuO PD were characterized from 350 to 1300 nm and a maximum responsivity of 43 mA/W was found at λ = 700 nm. The MSM PD is RC limited with a decay time constant less than 1 μs.

  9. Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications.

    PubMed

    Chen, Yuanzhi; Zeng, Deqian; Cortie, Michael B; Dowd, Annette; Guo, Huizhang; Wang, Junbao; Peng, Dong-Liang

    2015-03-25

    The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au-Ni-ZnO metal-semiconductor hybrid nanocrystals with a flower-like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room-temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as-prepared Au-Ni-ZnO nanocrystals are strongly photocatalytic and can be separated and re-cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications.

  10. Steady-state characteristics and transient response of MgZnO-based metal-semiconductor-metal solar-blind ultraviolet photodetector with three types of electrode structures.

    PubMed

    Wang, Ping; Zhen, Qinghong; Tang, Qing; Yang, Yintang; Guo, Lixin; Ding, Kai; Huang, Feng

    2013-07-29

    Detailed studies of MgZnO-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetector with different electrode structures are performed. A two-dimensional physical model is established based on the Poisson's equation and time-dependent continuity equations, which is verified by our experimental data of conventional electrode MSM detector. The steady-state characteristics and transient response of semicircular and triangular electrode MSM detectors are also investigated by this model. Compared with the conventional electrode, semicircular and triangular electrode devices exhibit a substantial improvement on the photocurrent. At a bias of 10 V, the steady-state saturated photocurrents for semicircular and triangular electrode devices are 14.69 nA and 24.37 nA respectively, corresponding to a 20.5% and 100% increase over the conventional electrode detector. Meanwhile, the transient peak photocurrents reach 31.38 nA and 52.09 nA respectively, both of which are notably larger than that of conventional device.

  11. The effect of dielectric constants on noble metal/semiconductor SERS enhancement: FDTD simulation and experiment validation of Ag/Ge and Ag/Si substrates.

    PubMed

    Wang, Tao; Zhang, Zhaoshun; Liao, Fan; Cai, Qian; Li, Yanqing; Lee, Shuit-Tong; Shao, Mingwang

    2014-02-11

    The finite-difference time-domain (FDTD) method was employed to simulate the electric field distribution for noble metal (Au or Ag)/semiconductor (Ge or Si) substrates. The simulation showed that noble metal/Ge had stronger SERS enhancement than noble metal/Si, which was mainly attributed to the different dielectric constants of semiconductors. In order to verify the simulation, Ag nanoparticles with the diameter of ca. 40 nm were grown on Ge or Si wafer (Ag/Ge or Ag/Si) and employed as surface-enhanced Raman scattering substrates to detect analytes in solution. The experiment demonstrated that both the two substrates exhibited excellent performance in the low concentration detection of Rhodamine 6G. Besides, the enhancement factor (1.3 × 10(9)) and relative standard deviation values (less than 11%) of Ag/Ge substrate were both better than those of Ag/Si (2.9 × 10(7) and less than 15%, respectively), which was consistent with the FDTD simulation. Moreover, Ag nanoparticles were grown in-situ on Ge substrate, which kept the nanoparticles from aggregation in the detection. To data, Ag/Ge substrates showed the best performance for their sensitivity and uniformity among the noble metal/semiconductor ones.

  12. In0.53Ga0.47As metal-semiconductor-metal photodiodes with transparent cadmium tin oxide Schottky contacts

    NASA Astrophysics Data System (ADS)

    Gao, Wei; Khan, Al-Sameen; Berger, Paul R.; Hunsperger, R. G.; Zydzik, George; O'Bryan, H. M.; Sivco, D.; Cho, A. Y.

    1994-10-01

    A metal-semiconductor-metal (MSM) In0.53Ga0.47As photodiode using a transparent cadmium tin oxide (CTO) layer for the interdigitated electrodes was investigated. The transparent contact prevents shadowing of the active layer by the electrodes, thus allowing greater collection of incident light. The barrier height (φBn) of CTO on i-In0.52Al0.48As was determined to be 0.47 eV, while the Ti/Au barrier height was 0.595 eV. The reduced barrier height for CTO is caused by tunneling through the sputter-damaged cap layer. Responsivity for 1.3 μm incident light was 0.49 and 0.28 A/W, respectively, for the CTO and Ti/Au MSM photodiodes. No antireflection (AR) coating was utilized over the bare semiconductor surface. The CTO MSM photodiode shows a factor of almost two improvement in responsivity over conventional Ti/Au MSM photodiodes.

  13. Measurement and simulation of top- and bottom-illuminated solar-blind AlGaN metal-semiconductor-metal photodetectors with high external quantum efficiencies

    SciTech Connect

    Brendel, Moritz Helbling, Markus; Knigge, Andrea; Brunner, Frank; Weyers, Markus

    2015-12-28

    A comprehensive study on top- and bottom-illuminated Al{sub 0.5}Ga{sub 0.5}N/AlN metal-semiconductor-metal (MSM) photodetectors having different AlGaN absorber layer thickness is presented. The measured external quantum efficiency (EQE) shows pronounced threshold and saturation behavior as a function of applied bias voltage up to 50 V reaching about 50% for 0.1 μm and 67% for 0.5 μm thick absorber layers under bottom illumination. All experimental findings are in very good accordance with two-dimensional drift-diffusion modeling results. By taking into account macroscopic polarization effects in the hexagonal metal-polar +c-plane AlGaN/AlN heterostructures, new insights into the general device functionality of AlGaN-based MSM photodetectors are obtained. The observed threshold/saturation behavior is caused by a bias-dependent extraction of photoexcited holes from the Al{sub 0.5}Ga{sub 0.5}N/AlN interface. While present under bottom illumination for any AlGaN layer thickness, under top illumination this mechanism influences the EQE-bias characteristics only for thin layers.

  14. Metal-semiconductor-transition observed in Bi2Ca(Sr, Ba)2Co2O8+δ single crystals

    NASA Astrophysics Data System (ADS)

    Dong, Song-Tao; Zhang, Bin-Bin; Zhang, Lun-Yong; Chen, Y. B.; Yao, Shu-Hua; Zhou, Jian; Zhang, Shan-Tao; Gu, Zheng-Bin; Chen, Yan-Feng

    2014-07-01

    Electrical property evolution of Bi2AE2Co2O8+δ single crystals (AE = Ca, Sr and Ba) is systematically explored. When AE changes from Ca to Ba, the electrical property of Bi2Ca2Co2O8+δ and Bi2Sr2Co2O8+δ demonstrates semiconductor-like properties. But Bi2Ba2Co2O8+δ shows the metallic behavior. Analysis of temperature-dependent resistance substantiates that from metallic Bi2Ba2Co2O8+δ to semiconductor-like Bi2Sr2Co2O8+δ can be attributed to Anderson localization. However the semiconductor behaviour of Bi2Sr2Co2O8+δ and Bi2Ca2Co2O8+δ is related to electronic correlations effect that is inferred by large negative magnetoresistance (˜70%). The theoretical electronic structures and valence X-ray photoemission spectroscopy substantiate that there is a relative large density of state around Fermi level in Bi2Ba2Co2O8+δ compared with other two compounds. It suggests that Bi2Ba2Co2O8+δ is more apt to be metal in this material system.

  15. Metal-semiconductor reaction phenomena and microstructural investigations of laser-induced regrowth of silicon on insulators

    NASA Astrophysics Data System (ADS)

    Magee, T. J.; Leung, C.; Ormond, R.; Armistead, R. A.

    1981-01-01

    The defect structure in CVD Si layers on sapphire were investigated before and after scanning laser annealing. Prior to laser annealing, the films were characterized by the presence of stacking faults, twinning zones dislocation lines producing large regions of high disorder. Subsequent to laser annealing under conditions to produce total melting of the Si layers it was shown that liquid phase epitaxial regrowth occurred resulting in regions of defect-free Si and a total absence of twinning regions. Correlated Rutherford backscattering, channeling and transmission electron microscopic analyses showed a dramatic improvement in crystalline perfection relative to the results obtained from films grown by any other technique on sapphire substrates. In separate collaborative experiments with Stanford University, it was also shown that scanning cw laser irradiation could be used to produce diffusion and activation of Sn from a spin-on SnO2/SiO2 source. The formation of a Sn3As2 alloy has been shown to be related to the observed n+ activity.

  16. Photocatalysis-Based Nanoprobes Using Noble Metal-Semiconductor Heterostructure for Visible Light-Driven in Vivo Detection of Mercury.

    PubMed

    Zhi, Lihua; Zeng, Xiaofan; Wang, Hao; Hai, Jun; Yang, Xiangliang; Wang, Baodui; Zhu, Yanhong

    2017-07-18

    The development of sensitive and reliable methods to monitor the presence of mercuric ions in cells and organisms is of great importance to biological research and biomedical applications. In this work, we propose a strategy to construct a solar-driven nanoprobe using a 3D Au@MoS2 heterostructure as a photocatalyst and rhodamine B (RB) as a fluorescent and color change reporter molecule for monitoring Hg(2+) in living cells and animals. The sensing mechanism is based on the photoinduced electron formation of gold amalgam in the 3D Au@MoS2 heterostructure under visible light illumination. This formation is able to remarkably inhibit the photocatalytic activity of the heterostructure toward RB decomposition. As a result, "OFF-ON" fluorescence and color change are produced. Such characteristics enable this new sensing platform to sensitively and selectively detect Hg(2+) in water by fluorescence and colorimetric methods. The detection limits of the fluorescence assay and colorimetric assay are 0.22 and 0.038 nM for Hg(2+), respectively; these values are well below the acceptable limits in drinking water standards (10 nM). For the first time, such photocatalysis-based sensing platform is successfully used to monitor Hg(2+) in live cells and mice. Our work therefore opens a promising photocatalysis-based analysis methodology for highly sensitive and selective in vivo Hg(2+) bioimaging studies.

  17. Metal Semiconductor Field-Effect Transistor with MoS2/Conducting NiO(x) van der Waals Schottky Interface for Intrinsic High Mobility and Photoswitching Speed.

    PubMed

    Lee, Hee Sung; Baik, Seung Su; Lee, Kimoon; Min, Sung-Wook; Jeon, Pyo Jin; Kim, Jin Sung; Choi, Kyujin; Choi, Hyoung Joon; Kim, Jae Hoon; Im, Seongil

    2015-08-25

    Molybdenum disulfide (MoS2) nanosheet, one of two-dimensional (2D) semiconductors, has recently been regarded as a promising material to break through the limit of present semiconductors. With an apparent energy band gap, it certainly provides a high carrier mobility, superior subthreshold swing, and ON/OFF ratio in field-effect transistors (FETs). However, its potential in carrier mobility has still been depreciated since the field-effect mobilities have only been measured from metal-insulator-semiconductor (MIS) FETs, where the transport behavior of conducting carriers located at the insulator/MoS2 interface is unavoidably interfered by the interface traps and gate voltage. Moreover, thin MoS2 MISFETs have always shown large hysteresis with unpredictable negative threshold voltages. Here, we for the first time report MoS2-based metal semiconductor field-effect transistors (MESFETs) using NiOx Schottky electrode which makes van der Waals interface with MoS2. We thus expect that the maximum mobilities or carrier transport behavior of the Schottky devices may hardly be interfered by interface traps or an on-state gate field. Our MESFETs with a few and ∼10 layer MoS2 demonstrate intrinsic-like high mobilities of 500-1200 cm(2)/(V s) at a certain low threshold voltage between -1 and -2 V without much hysteresis. Moreover, they work as a high speed and highly sensitive phototransistor with 2 ms switching and ∼5000 A/W, respectively, supporting their high intrinsic mobility results.

  18. Characterization of the metal-semiconductor interface of gold contacts on CdZnTe formed by electroless deposition

    NASA Astrophysics Data System (ADS)

    Bell, Steven J.; Baker, Mark A.; Duarte, Diana D.; Schneider, Andreas; Seller, Paul; Sellin, Paul J.; Veale, Matthew C.; Wilson, Matthew D.

    2015-06-01

    Fully spectroscopic x/γ-ray imaging is now possible thanks to advances in the growth of wide-bandgap semiconductors. One of the most promising materials is cadmium zinc telluride (CdZnTe or CZT), which has been demonstrated in homeland security, medical imaging, astrophysics and industrial analysis applications. These applications have demanding energy and spatial resolution requirements that are not always met by the metal contacts deposited on the CdZnTe. To improve the contacts, the interface formed between metal and semiconductor during contact deposition must be better understood. Gold has a work function closely matching that of high resistivity CdZnTe and is a popular choice of contact metal. Gold contacts are often formed by electroless deposition however this forms a complex interface. The prior CdZnTe surface preparation, such as mechanical or chemo-mechanical polishing, and electroless deposition parameters, such as gold chloride solution temperature, play important roles in the formation of the interface and are the subject of the presented work. Techniques such as focused ion beam (FIB) cross section imaging, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and current  -  voltage (I-V) analysis have been used to characterize the interface. It has been found that the electroless reaction depends on the surface preparation and for chemo-mechanically polished (1 1 1) CdZnTe, it also depends on the A/B face identity. Where the deposition occurred at elevated temperature, the deposited contacts were found to produce a greater leakage current and suffered from increased subsurface voiding due to the formation of cadmium chloride.

  19. Research on an FM/cw ladar system using a 64 × 64 InGaAs metal-semiconductor-metal self-mixing focal plane array of detectors.

    PubMed

    Gao, Jian; Sun, Jianfeng; Cong, Mingyu

    2017-04-01

    Frequency-modulated/continuous-wave imaging systems are a focal plane array (FPA) ladar architecture that is applicable to smart munitions, reconnaissance, face recognition, robotic navigation, etc. In this paper, we report a 64×64 pixel FPA ladar system we built using a 1550 nm amplified laser diode transmitter and an InAlAs/InGaAs metal-semiconductor-metal self-mixing detector array and the test results attained over the years it was constructed. Finally, we gained 4D imaging (3D range + 1D intensity) of the target with the range of 220 m.

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

    PubMed

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

    2014-04-03

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

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

    PubMed Central

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

    2014-01-01

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%. PMID:24694838

  2. Low-energy electron potentiometry.

    PubMed

    Jobst, Johannes; Kautz, Jaap; Mytiliniou, Maria; Tromp, Rudolf M; van der Molen, Sense Jan

    2017-10-01

    In a lot of systems, charge transport is governed by local features rather than being a global property as suggested by extracting a single resistance value. Consequently, techniques that resolve local structure in the electronic potential are crucial for a detailed understanding of electronic transport in realistic devices. Recently, we have introduced a new potentiometry method based on low-energy electron microscopy (LEEM) that utilizes characteristic features in the reflectivity spectra of layered materials [1]. Performing potentiometry experiments in LEEM has the advantage of being fast, offering a large field of view and the option to zoom in and out easily, and of being non-invasive compared to scanning-probe methods. However, not all materials show clear features in their reflectivity spectra. Here we, therefore, focus on a different version of low-energy electron potentiometry (LEEP) that uses the mirror mode transition, i.e. the drop in electron reflectivity around zero electron landing energy when they start to interact with the sample rather than being reflected in front of it. This transition is universal and sensitive to the local electrostatic surface potential (either workfunction or applied potential). It can consequently be used to perform LEEP experiments on a broader range of material compared to the method described in Ref[1]. We provide a detailed description of the experimental setup and demonstrate LEEP on workfunction-related intrinsic potential variations on the Si(111) surface and for a metal-semiconductor-metal junction with external bias applied. In the latter, we visualize the Schottky effect at the metal-semiconductor interface. Finally, we compare how robust the two LEEP techniques discussed above are against image distortions due to sample inhomogeneities or contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Probing hot-carrier transport and elastic scattering using ballistic-electron-emission microscopy

    NASA Technical Reports Server (NTRS)

    Milliken, A. M.; Manion, S. J.; Kaiser, W. J.; Bell, L. D.; Hecht, M. H.

    1992-01-01

    Ballistic-electron-emission microscopy (BEEM) has been used to characterize electron transport and scattering in metal/semiconductor structures. A SiO2 layer at the Au/Si interface was patterned to form transmitting and nontransmitting regions. By analyzing the BEEM current profiles at the boundaries of these regions, information on the spatial distribution of electrons after transport through the Au layer can be derived. A detailed comparison is made between the results presented here and models which involve modification of the electron distribution by scattering.

  4. Electronic polymers in lipid membranes

    PubMed Central

    Johansson, Patrik K.; Jullesson, David; Elfwing, Anders; Liin, Sara I.; Musumeci, Chiara; Zeglio, Erica; Elinder, Fredrik; Solin, Niclas; Inganäs, Olle

    2015-01-01

    Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into lipid membranes. By preparing complexes between alkyl-ammonium salts and PEDOT-S we were able to integrate PEDOT-S into both liposomes and in lipid bilayers on solid surfaces. This is a step towards efficient electronic conduction within lipid membranes. We also demonstrate that the PEDOT-S@alkyl-ammonium:lipid hybrid structures created in this work affect ion channels in the membrane of Xenopus oocytes, which shows the possibility to access and control cell membrane structures with conductive polyelectrolytes. PMID:26059023

  5. Electronic polymers in lipid membranes.

    PubMed

    Johansson, Patrik K; Jullesson, David; Elfwing, Anders; Liin, Sara I; Musumeci, Chiara; Zeglio, Erica; Elinder, Fredrik; Solin, Niclas; Inganäs, Olle

    2015-06-10

    Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into lipid membranes. By preparing complexes between alkyl-ammonium salts and PEDOT-S we were able to integrate PEDOT-S into both liposomes and in lipid bilayers on solid surfaces. This is a step towards efficient electronic conduction within lipid membranes. We also demonstrate that the PEDOT-S@alkyl-ammonium:lipid hybrid structures created in this work affect ion channels in the membrane of Xenopus oocytes, which shows the possibility to access and control cell membrane structures with conductive polyelectrolytes.

  6. Ballistic-Electron-Emission Microscopy Techniques for Nanometer-scale Characterization of Interfaces

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Grunthaner, F. J.; Hecht, M. H.; Manion, S. J.; Milliken, A. M.; Kaiser, W. J.

    1993-01-01

    Semiconductor interface properties are among the most important phenomena in materials science and technology. The study of metal/semiconductor Schottky barrier interfaces has been the primary focus of a large research and development community for decades. Throughout the long history of interface investigation, the study of interface defect electronic properties have been seriously hindered by the fundamental experimental difficulty of probing subsurface structures. A new method, Ballistic-Electron-Emission Microscopy (BEEM), has been developed which not only enables spectroscopic probing of subsurface interface properties, but also, provides nanometer-resolution imaging capabilities. BEEM employs Scanning Tunneling Microscopy (STM) and a unique spatially localized ballistic electron spectroscopy method...

  7. Ballistic-Electron-Emission Microscopy Techniques for Nanometer-scale Characterization of Interfaces

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Grunthaner, F. J.; Hecht, M. H.; Manion, S. J.; Milliken, A. M.; Kaiser, W. J.

    1993-01-01

    Semiconductor interface properties are among the most important phenomena in materials science and technology. The study of metal/semiconductor Schottky barrier interfaces has been the primary focus of a large research and development community for decades. Throughout the long history of interface investigation, the study of interface defect electronic properties have been seriously hindered by the fundamental experimental difficulty of probing subsurface structures. A new method, Ballistic-Electron-Emission Microscopy (BEEM), has been developed which not only enables spectroscopic probing of subsurface interface properties, but also, provides nanometer-resolution imaging capabilities. BEEM employs Scanning Tunneling Microscopy (STM) and a unique spatially localized ballistic electron spectroscopy method...

  8. Novel WSi/Au T-shaped gate GaAs metal-semiconductor field-effect-transistor fabrication process for super low-noise microwave monolithic integrated circuit amplifiers

    SciTech Connect

    Takano, H.; Hosogi, K.; Kato, T.

    1995-05-01

    A fully ion-implanted self-aligned T-shaped gate Ga As metal-semiconductor field-effect transistor (MESFET) with high frequency and extremely low-noise performance has been successfully fabricated for super low-noise microwave monolithic integrated circuit (MMIC) amplifiers. A subhalf-micrometer gate structure composed of WSi/Ti/Mo/Au is employed to reduce gate resistance effectively. This multilayer gate structure is formed by newly developed dummy SiON self-alignment technology and a photoresist planarization process. At an operating frequency of 12 GHz, a minimum noise figure of 0.87 dB with an associated gain of 10.62 dB has been obtained. Based on the novel FET process, a low-noise single-stage MMIC amplifier with an excellent low-noise figure of 1.2 dB with an associated gain of 8 dB in the 14 GHz band has been realized. This is the lowest noise figure ever reported at this frequency for low-noise MMICs based on ion-implanted self-aligned gate MESFET technology. 14 refs., 9 figs.

  9. A Novel, Free-Space Optical Interconnect Employing Vertical-Cavity Surface Emitting Laser Diodes and InGaAs Metal-Semiconductor-Metal Photodetectors for Gbit/s RF/Microwave Systems

    NASA Technical Reports Server (NTRS)

    Savich, Gregory R.; Simons, Rainee N.

    2006-01-01

    Emerging technologies and continuing progress in vertical-cavity surface emitting laser (VCSEL) diode and metal-semiconductor-metal (MSM) photodetector research are making way for novel, high-speed forms of optical data transfer in communication systems. VCSEL diodes operating at 1550 nm have only recently become commercially available, while MSM photodetectors are pushing the limits of contact lithography with interdigitated electrode widths reaching sub micron levels. We propose a novel, free-space optical interconnect operating at about 1Gbit/s utilizing VCSEL diodes and MSM photodetectors. We report on development, progress, and current work, which are as follows: first, analysis of the divergent behavior of VCSEL diodes for coupling to MSM photodetectors with a 50 by 50 m active area and second, the normalized frequency response of the VCSEL diode as a function of the modulating frequency. Third, the calculated response of MSM photodetectors with varying electrode width and spacing on the order of 1 to 3 m as well as the fabrication and characterization of these devices. The work presented here will lead to the formation and characterization of a fully integrated 1Gbit/s free-space optical interconnect at 1550 nm and demonstrates both chip level and board level functionality for RF/microwave digital systems.

  10. Electronic properties of nanoentities revealed by electrically driven rotation

    PubMed Central

    Fan, D. L.; Zhu, Frank Q.; Xu, Xiaobin; Cammarata, Robert C.; Chien, C. L.

    2012-01-01

    Direct electric measurement via small contacting pads on individual quasi-one-dimensional nanoentities, such as nanowires and carbon nanotubes, are usually required to access its electronic properties. We show in this work that 1D nanoentities in suspension can be driven to rotation by AC electric fields. The chirality of the resultantrotation unambiguously reveals whether the nanoentities are metal, semiconductor, or insulator due to the dependence of the Clausius–Mossotti factor on the material conductivity and frequency. This contactless method provides rapid and parallel identification of the electrical characteristics of 1D nanoentities. PMID:22645373

  11. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

    NASA Astrophysics Data System (ADS)

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

    2016-11-01

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors.

  12. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111).

    PubMed

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E; Sanchez, Ana M; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M; Hasnip, Philip J; Hase, Thomas; Bell, Gavin R; Hirohata, Atsufumi; Lazarov, Vlado K

    2016-11-21

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors.

  13. Realisation of magnetically and atomically abrupt half-metal/semiconductor interface: Co2FeSi0.5Al0.5/Ge(111)

    PubMed Central

    Nedelkoski, Zlatko; Kuerbanjiang, Balati; Glover, Stephanie E.; Sanchez, Ana M.; Kepaptsoglou, Demie; Ghasemi, Arsham; Burrows, Christopher W.; Yamada, Shinya; Hamaya, Kohei; Ramasse, Quentin M.; Hasnip, Philip J.; Hase, Thomas; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

    2016-01-01

    Halfmetal-semiconductor interfaces are crucial for hybrid spintronic devices. Atomically sharp interfaces with high spin polarisation are required for efficient spin injection. In this work we show that thin film of half-metallic full Heusler alloy Co2FeSi0.5Al0.5 with uniform thickness and B2 ordering can form structurally abrupt interface with Ge(111). Atomic resolution energy dispersive X-ray spectroscopy reveals that there is a small outdiffusion of Ge into specific atomic planes of the Co2FeSi0.5Al0.5 film, limited to a very narrow 1 nm interface region. First-principles calculations show that this selective outdiffusion along the Fe-Si/Al atomic planes does not change the magnetic moment of the film up to the very interface. Polarized neutron reflectivity, x-ray reflectivity and aberration-corrected electron microscopy confirm that this interface is both magnetically and structurally abrupt. Finally, using first-principles calculations we show that this experimentally realised interface structure, terminated by Co-Ge bonds, preserves the high spin polarization at the Co2FeSi0.5Al0.5/Ge interface, hence can be used as a model to study spin injection from half-metals into semiconductors. PMID:27869132

  14. Toward understanding the electrical properties of metal/semiconductor Schottky contacts: The effects of barrier inhomogeneities and geometry in bulk and nanoscale structures

    NASA Astrophysics Data System (ADS)

    Sarpatwari, Karthik

    The work presented in this thesis comprises of two parts. Part I deals with Schottky contacts to the wide bandgap (WBG) semiconductors SiC, GaN and ZnO. These semiconductors offer great promise for a wide variety of electronic and optoelectronic applications. Schottky barriers to WBG semiconductors are attractive in particular for high temperature/high power diodes, photodetectors, and gas sensors. However, the Schottky barriers exhibit non-ideal behavior, due in part to inhomogeneities originating from immature crystal growth and device processing technologies. Apart from being a versatile electronic component, the Schottky diode is a valuable test structure. The Schottky contact is routinely used to probe substrate and epilayer quality by different electrical characterization techniques. It is well established that the current-voltage-temperature ( I-V-T) characteristics of Schottky contacts are routinely affected by the presence of barrier height inhomogeneities (BHI). Consequently, Schottky diode parameters such as the Schottky barrier height and the Richardson constant extracted using the I-V-T measurements can deviate from their actual values. The effects of BHI on the extracted Schottky barrier height have been studied in the literature. However, the effects of BHI on the Richardson constant have not been thoroughly explored and are the focus of the first part of this thesis. Based on the inhomogeneous Schottky barrier model provided by Tung, a new method for the extraction of the Richardson constant is developed. The new method is applied to the Richardson constant determination of n-type ZnO and GaN. Excellent agreement with the theoretical value is obtained in both cases. The advent of the nanoelectronics era has resulted in the Schottky contact evolving from the relatively simple, planar structure into a more complex structure. Compared to bulk Schottky contacts, the Schottky barrier properties are expected to be widely different at the nanoscale. For

  15. Nanoscale heat transport via electrons and phonons by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Lin, Keng-Hua

    Nanoscale heat transport has become a crucial research topic due to the growing importance of nanotechnology for manufacturing, energy conversion, medicine and electronics. Thermal transport properties at the nanoscale are distinct from the macroscopic ones since the sizes of nanoscale features, such as free surfaces and interfaces, are comparable to the wavelengths and mean free paths of the heat carriers (electrons and phonons), and lead to changes in thermal transport properties. Therefore, understanding how the nanoscale features and energy exchange between the heat carriers affect thermal transport characteristics are the goals of this research. Molecular dynamics (MD) is applied in this research to understand the details of nanoscale heat transport. The advantage of MD is that the size effect, anharmonicity, atomistic structure, and non-equilibrium behavior of the system can all be captured since the dynamics of atoms are described explicitly in MD. However, MD neglects the thermal role of electrons and therefore it is unable to describe heat transport in metal or metal-semiconductor systems accurately. To address this limitation of MD, we develop a method to simulate electronic heat transport by implementing electronic degrees of freedom to MD. In this research, nanoscale heat transport in semiconductor, metal, and metal-semiconductor systems is studied. Size effects on phonon thermal transport in SiGe superlattice thin films and nanowires are studied by MD. We find that, opposite to the macroscopic trend, superlattice thin films can achieve lower thermal conductivity than nanowires at small scales due to the change of phonon nature caused by adjusting the superlattice periodic length and specimen length. Effects of size and electron-phonon coupling rate on thermal conductivity and thermal interface resistivity in Al and model metal-semiconductor systems are studied by MD with electronic degrees of freedom. The results show that increasing the specimen

  16. Room temperature observation of single electron tunneling effect in self-assembled metal quantum dots on a semiconductor substrate

    NASA Astrophysics Data System (ADS)

    Park, Kang-Ho; Ha, Jeong Sook; Yun, Wan Soo; Shin, Mincheol; Park, Kyoung-Wan; Lee, El-Hang

    1997-09-01

    We report on the observation of room-temperature single electron tunneling phenomena in a metal-insulator-metal-semiconductor double-junction structure. The nanosized Ag dots were self-assembled on a Sb-terminated Si(100) surface, and the Coulomb gap and staircases were observed in the local current-voltage (I-V) measurements using scanning tunneling microscopy. The I-V characteristics exhibiting the single electron tunneling behavior vary significantly with the variation of the measurement position within the same Ag droplet. These phenomena are well described by the tip-dot(Ag)-Si double-junction picture.

  17. Cross-plane thermoelectric transport in p-type La{sub 0.67}Sr{sub 0.33}MnO{sub 3}/LaMnO{sub 3} oxide metal/semiconductor superlattices

    SciTech Connect

    Jha, Pankaj; Shakouri, Ali; Sands, Timothy D.; Jackson, Philip; Favaloro, Tela; Bomberger, Cory; Zide, Joshua; Hodson, Stephen; Xu, Xianfan

    2013-05-21

    The cross-plane thermoelectric transport properties of La{sub 0.67}Sr{sub 0.33}MnO{sub 3} (LSMO)/LaMnO{sub 3} (LMO) oxide metal/semiconductor superlattices were investigated. The LSMO and LMO thin-film depositions were performed using pulsed laser deposition to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate substrates. X-ray diffraction and high-resolution reciprocal space mapping indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively, this coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal a lowering of the effective barrier height to 223 meV as well as an increase in cross-plane conductivity by an order of magnitude compared to high resistivity superlattices. These results suggest that controlling the oxygen deficiency in the constituent materials enables modification of the effective barrier height and increases the cross-plane conductivity in oxide superlattices. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 {mu}V/K at 300 K that increases to 16 640 {mu}V/K at 360 K. The giant increase in the Seebeck coefficient with temperature may include a collective contribution from the interplay of charge, spin current, and phonon drag. The low resistance oxide superlattices exhibited a room temperature cross-plane thermal conductivity of 0.92 W/m K, this indicating that the suppression of thermal conductivities due to the interfaces is preserved in both low and high resistivity superlattices. The high Seebeck coefficient, the order of magnitude improvement in cross-plane conductivity, and the low thermal conductivity in LSMO/LMO superlattices resulted in a two order of magnitude increase in cross-plane power factor and thermoelectric figure of merit (ZT), compared to the properties

  18. Spectroscopic Evidence for Exceptional Thermal Contribution to Electron-Beam Induced Fragmentation

    SciTech Connect

    Caldwell, Marissa A.; Haynor, Ben; Aloni, Shaul; Ogletree, D. Frank; Wong, H.-S. Philip; Urban, Jeffrey J.; Milliron, Delia J.

    2010-11-16

    While electron beam induced fragmentation (EBIF) has been reported to result in the formation of nanocrystals of various compositions, the physical forces driving this phenomenon are still poorly understood. We report EBIF to be a much more general phenomenon than previously appreciated, operative across a wide variety of metals, semiconductors and insulators. In addition, we leverage the temperature dependent bandgap of several semiconductors to quantify -- using in situ cathodoluminescence spectroscopy -- the thermal contribution to EBIF, and find extreme temperature rises upwards of 1000K.

  19. Nanocoaxes for Optical and Electronic Devices

    PubMed Central

    Rizal, Binod; Merlo, Juan M.; Burns, Michael J.; Chiles, Thomas C.; Naughton, Michael J.

    2014-01-01

    The evolution of micro/nanoelectronics technology, including the shrinking of devices and integrated circuit components, has included the miniaturization of linear and coaxial structures to micro/nanoscale dimensions. This reduction in the size of coaxial structures may offer advantages to existing technologies and benefit the exploration and development of new technologies. The reduction in the size of coaxial structures has been realized with various permutations between metals, semiconductors and dielectrics for the core, shield, and annulus. This review will focus on fabrication schemes of arrays of metal – nonmetal – metal nanocoax structures using non-template and template methods, followed by possible applications. The performance and scientific advantages associated with nanocoax-based optical devices including waveguides, negative refractive index materials, light emitting diodes, and photovoltaics are presented. In addition, benefits and challenges that accrue from the application of novel nanocoax structures in energy storage, electronic and sensing devices are summarized. PMID:25279400

  20. Optical detection of spin-filter effect for electron spin polarimetry

    SciTech Connect

    Li, X.; Majee, S.; Lampel, G.; Lassailly, Y.; Paget, D.; Peretti, J.; Tereshchenko, O. E.

    2014-08-04

    We have monitored the cathodoluminescence (CL) emitted upon injection of free electrons into a hybrid structure consisting of a thin magnetic Fe layer deposited on a p-GaAs substrate, in which InGaAs quantum wells are embedded. Electrons transmitted through the unbiased metal/semiconductor junction recombine radiatively in the quantum wells. Because of the electron spin-filtering across the Fe/GaAs structure, the CL intensity, collected from the backside, is found to depend on the relative orientation between the injected electronic spin polarization and the Fe layer magnetization. The spin asymmetry of the CL intensity in such junction provides a compact optical method for measuring spin polarization of free electrons beams or of hot electrons in solid-state devices.

  1. Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography

    PubMed Central

    Velazquez-Salazar, J.; José Yacaman, M.; González, F. J.; Diaz de Leon, R.

    2015-01-01

    In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level. PMID:25641981

  2. Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography.

    PubMed

    Sanchez, J E; Mendoza-Santoyo, F; Cantu-Valle, J; Velazquez-Salazar, J; José Yacaman, M; González, F J; Diaz de Leon, R; Ponce, A

    2015-01-21

    In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.

  3. Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography

    SciTech Connect

    Sanchez, J. E.; Mendoza-Santoyo, F.; Cantu-Valle, J.; Velazquez-Salazar, J.; José Yacaman, M.; Ponce, A.; González, F. J.; Diaz de Leon, R.

    2015-01-21

    In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.

  4. Nanometer-scale modification and welding of silicon and metallic nanowires with a high-intensity electron beam.

    PubMed

    Xu, Shengyong; Tian, Mingliang; Wang, Jinguo; Xu, Jian; Redwing, Joan M; Chan, Moses H W

    2005-12-01

    We demonstrate that a high-intensity electron beam can be applied to create holes, gaps, and other patterns of atomic and nanometer dimensions on a single nanowire, to weld individual nanowires to form metal-metal or metal-semiconductor junctions, and to remove the oxide shell from a crystalline nanowire. In single-crystalline Si nanowires, the beam induces instant local vaporization and local amorphization. In metallic Au, Ag, Cu, and Sn nanowires, the beam induces rapid local surface melting and enhanced surface diffusion, in addition to local vaporization. These studies open up a novel approach for patterning and connecting nanomaterials in devices and circuits at the nanometer scale.

  5. The effect of hot electrons and surface plasmons on heterogeneous catalysis.

    PubMed

    Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

    2016-06-29

    Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal-semiconductor, and metal-insulator-metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles.

  6. The effect of hot electrons and surface plasmons on heterogeneous catalysis

    NASA Astrophysics Data System (ADS)

    Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

    2016-06-01

    Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal-semiconductor, and metal-insulator-metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles.

  7. Stacking-dependent electronic structure of bilayer silicene

    SciTech Connect

    Fu, Huixia; Zhang, Jin; Ding, Zijing; Li, Hui E-mail: smeng@iphy.ac.cn; Meng, Sheng E-mail: smeng@iphy.ac.cn

    2014-03-31

    Bilayer silicene (BLS) is a class of material that possibly holds both topological and superconducting properties; however, its structure is not fully understood. By scanning stacking modes and lattice constants using first principles calculations, several meta-stable configurations are identified, including a slightly faulted-AA packing structure, named slide-2AA. Different from the metallic properties of conventional AA and AB stacking forms, band structure of slide-2AA bilayer presents a sizeable indirect energy gap of ∼1.16 eV. A metal-semiconductor phase transition along the sliding pathway with a small energy barrier is also observed, indicating its electronic properties can be easily tuned by applying small shear force along the BLS surface plane. Such unique quantitative relationship of structure and electronic properties has profound implications in nanoelectronics and electromechanical devices.

  8. Stacking-dependent electronic structure of bilayer silicene

    NASA Astrophysics Data System (ADS)

    Fu, Huixia; Zhang, Jin; Ding, Zijing; Li, Hui; Meng, Sheng

    2014-03-01

    Bilayer silicene (BLS) is a class of material that possibly holds both topological and superconducting properties; however, its structure is not fully understood. By scanning stacking modes and lattice constants using first principles calculations, several meta-stable configurations are identified, including a slightly faulted-AA packing structure, named slide-2AA. Different from the metallic properties of conventional AA and AB stacking forms, band structure of slide-2AA bilayer presents a sizeable indirect energy gap of ˜1.16 eV. A metal-semiconductor phase transition along the sliding pathway with a small energy barrier is also observed, indicating its electronic properties can be easily tuned by applying small shear force along the BLS surface plane. Such unique quantitative relationship of structure and electronic properties has profound implications in nanoelectronics and electromechanical devices.

  9. Electronic structures of geometrically restricted nanocarbons

    NASA Astrophysics Data System (ADS)

    Baskin, Artem; Kral, Petr

    2012-02-01

    We use large scale ab-initio calculations to explore the electronic structures of graphene, graphene nanoribbons, and carbon nanotubes periodically perforated with nanopores. We disclose common features in electronic structures of these porous nanocarbons (PNCs) with nanopores of different size, shapes, and localization. We develop a unified picture that permits to analytically predict and systematically characterize metal-semiconductor transitions in PNCs, allowing mapping of their electronic structures on those in pristine nanocarbons [1]. In contrast to other studies, we show that porous graphene can be metallic for certain arrangements of the pores. When we replace pores by defects (such as SW 55-77), we observe similar features in the electronic structures of the formed nanocarbons. We also study magnetic ordering in these nanocarbons and show that the position of pores/defects can influence the ordering of localized electronic spin states. These periodically modified nanocarbons with highly tunable band structures have great potential applications in electronics and optics. [1] A.I. Baskin and P. Kral, Sci. Rep.1, 36 (2011).

  10. Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence

    NASA Astrophysics Data System (ADS)

    Nedrygailov, Ievgen I.; Lee, Changhwan; Moon, Song Yi; Lee, Hyosun; Park, Jeong Young

    2016-11-01

    Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction.

  11. Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence.

    PubMed

    Nedrygailov, Ievgen I; Lee, Changhwan; Moon, Song Yi; Lee, Hyosun; Park, Jeong Young

    2016-11-01

    Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction.

  12. Formulae for low-energy secondary electron yield from different kinds of emitters as a function of measurable variables

    NASA Astrophysics Data System (ADS)

    Xie, Ai-Gen; Zhon, Kun; Zhao, De-Lin; Xia, Yu-Qing

    2017-04-01

    Based on the characteristics of secondary electron emission and the relationships among parameters of secondary electron yield δ in the low-energy range of Ep0 ≦ Ep0m ≦ 800 eV (low-energy δ), the universal formula for low-energy δ as a function of Ep0, Ep0m and maximum δ(δm) was deduced, where Ep0 and Ep0m are the incident energies of primary electron and of δm, respectively. From the deduced universal formula and experimental low-energy δ from metals, semiconductors and insulators, special formula for low-energy δ from metals as a function of Ep0, Ep0m and δm and that for low-energy δ from semiconductors and insulators as a function of Ep0, Ep0m and δm were deduced, respectively. The results were analyzed, it can be concluded that the two deduced special formulae can be used to calculate low-energy δ from metals, semiconductors and insulators, respectively.

  13. Structural and electronic properties of few-layer graphenes from frist-principles

    NASA Astrophysics Data System (ADS)

    Tsai, M.-H.; Huang, J.-R.; Lin, J.-Y.; Chen, B.-H.

    2008-03-01

    Using first-principles calculation method, it is found that the calculated layer spacing for the two-layer AB stacked FLG is only 2.725å, which is substantially reduced from the calculated value of 3.257å for bulk graphite. The average interlayer spacing for 2-, 3-, 4-, 5-, 6-, 7- and 8-layer FLG's are found to oscillate and approach that of the bulk graphite. The two-layer AA stacked FLG is found to remain metallic for the external electric potential up to 4.5Volts considered in this study. In contrast, the two-layer AB stacked FLG is found to exhibit a semi-metal-semiconductor transition under an external electric potential qualitatively in agreement with previous theoretical studies. However, the energy gap is not limited at 0.3eV as obtained in previous first-principles calculation due to the substantially reduced interlayer spacing. The threshold of the semi-metal-semiconductor transition is 0.04 Volts. The external electric potential also induced energy gaps in 3- and 4-layer AB stacked FLG's. However, in these two thicker FLG's, the induced energy gaps are small within 0.1eV. Based on this study, only the two-layer FLG is useful as a nanoscale electronic switch.

  14. Coaxial Ag/ZnO/Ag nanowire for highly sensitive hot-electron photodetection

    SciTech Connect

    Zhan, Yaohui; Li, Xiaofeng Wu, Kai; Wu, Shaolong; Deng, Jiajia

    2015-02-23

    Single-nanowire photodetectors (SNPDs) are mostly propelled by p-n junctions, where the detection wavelength is constrained by the band-gap width. Here, we present a simple doping-free metal/semiconductor/metal SNPD, which shows strong detection tunability without such a material constraint. The proposed hot-electron SNPD exhibits superior optical and electrical advantages, i.e., optically the coaxial design leads to a strong asymmetrical photoabsorption and results in a high unidirectional photocurrent, as desired by the hot-electron collection; electrically the hot-electrons are generated in the region very close to the barrier, facilitating the electrical transport. Rigorous calculations predict an unbiased photoresponsivity of ∼200 nA/mW.

  15. Coaxial Ag/ZnO/Ag nanowire for highly sensitive hot-electron photodetection

    NASA Astrophysics Data System (ADS)

    Zhan, Yaohui; Li, Xiaofeng; Wu, Kai; Wu, Shaolong; Deng, Jiajia

    2015-02-01

    Single-nanowire photodetectors (SNPDs) are mostly propelled by p-n junctions, where the detection wavelength is constrained by the band-gap width. Here, we present a simple doping-free metal/semiconductor/metal SNPD, which shows strong detection tunability without such a material constraint. The proposed hot-electron SNPD exhibits superior optical and electrical advantages, i.e., optically the coaxial design leads to a strong asymmetrical photoabsorption and results in a high unidirectional photocurrent, as desired by the hot-electron collection; electrically the hot-electrons are generated in the region very close to the barrier, facilitating the electrical transport. Rigorous calculations predict an unbiased photoresponsivity of ˜200 nA/mW.

  16. The electronic structure of graphene tuned by hexagonal boron nitrogen layers: Semimetal-semiconductor transition

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Yang; Chen, Qing-Yuan; Ma, Tai; He, Yao; Cao, Chao

    2016-05-01

    The electronic structure of graphene and hexagonal boron nitrogen (G/h-BN) systems have been carefully investigated using the pseudo-potential plane-wave within density functional theory (DFT) framework. We find that the stacking geometries and interlayer distances significantly affect the electronic structure of G/h-BN systems. By studying four stacking geometries, we conclude that the monolayer G/h-BN systems should possess metallic electronic properties. The monolayer G/h-BN systems can be transited from metallicity to semiconductor by increasing h-BN layers. It reveals that the alteration of interlayer distances 2.50-3.50 Å can obtain the metal-semiconductor-semimetal variation and a tunable band gap for G/h-BN composite systems. The band dispersion along K-H direction is analogous to the band of rhombohedral graphite when the G/h-BN systems are semiconducting.

  17. Interplay of hot electrons from localized and propagating plasmons.

    PubMed

    Hoang, Chung V; Hayashi, Koki; Ito, Yasuo; Gorai, Naoki; Allison, Giles; Shi, Xu; Sun, Quan; Cheng, Zhenzhou; Ueno, Kosei; Goda, Keisuke; Misawa, Hiroaki

    2017-10-03

    Plasmon-induced hot-electron generation has recently received considerable interest and has been studied to develop novel applications in optoelectronics, photovoltaics and green chemistry. Such hot electrons are typically generated from either localized plasmons in metal nanoparticles or propagating plasmons in patterned metal nanostructures. Here we simultaneously generate these heterogeneous plasmon-induced hot electrons and exploit their cooperative interplay in a single metal-semiconductor device to demonstrate, as an example, wavelength-controlled polarity-switchable photoconductivity. Specifically, the dual-plasmon device produces a net photocurrent whose polarity is determined by the balance in population and directionality between the hot electrons from localized and propagating plasmons. The current responsivity and polarity-switching wavelength of the device can be varied over the entire visible spectrum by tailoring the hot-electron interplay in various ways. This phenomenon may provide flexibility to manipulate the electrical output from light-matter interaction and offer opportunities for biosensors, long-distance communications, and photoconversion applications.Plasmon-induced hot electrons have potential applications spanning photodetection and photocatalysis. Here, Hoang et al. study the interplay between hot electrons generated by localized and propagating plasmons, and demonstrate wavelength-controlled polarity-switchable photoconductivity.

  18. Selective control of electron and hole tunneling in 2D assembly

    PubMed Central

    Chu, Dongil; Lee, Young Hee; Kim, Eun Kyu

    2017-01-01

    Recent discoveries in the field of two-dimensional (2D) materials have led to the demonstration of exotic devices. Although they have new potential applications in electronics, thermally activated transport over a metal/semiconductor barrier sets physical subthermionic limitations. The challenge of realizing an innovative transistor geometry that exploits this concern remains. A new class of 2D assembly (namely, “carristor”) with a configuration similar to the metal-insulator-semiconductor structure is introduced in this work. Superior functionalities, such as a current rectification ratio of up to 400,000 and a switching ratio of higher than 106 at room temperature, are realized by quantum-mechanical tunneling of majority and minority carriers across the barrier. These carristors have a potential application as the fundamental building block of low–power consumption electronics. PMID:28439554

  19. Deep level transient spectroscopy study of electron traps in n-type GaAs after pulsed electron beam irradiation

    SciTech Connect

    Marrakchi, G.; Barbier, D.; Guillot, G.; Nouailhat, A.

    1987-10-01

    Electrical and deep level transient spectroscopy measurements on Schottky barriers were performed in order to characterize electrically active defects in n-type GaAs (Bridgman substrates or liquid-phase epitaxial layers) after pulsed electron beam annealing. Both surface damage and bulk defects were observed in the Bridgman substrates depending on the pulse energy density. No electron traps were detected in the liquid-phase epitaxial layers before and after annealing for an energy density of 0.4 J/cm/sup 2/. The existence of an interfacial insulating layer at the metal-semiconductor interface, associated with As out-diffusion during the pulsed electron irradiation, was revealed by the abnormally high values of the Schottky barrier diffusion potential. Moreover, two new electron traps with activation energy of 0.35 and 0.43 eV, called EP1 and EP2, were introduced in the Bridgman substrates after pulsed electron beam annealing. The presence of these traps, related to the As evaporation, was tentatively attributed to the decrease of the EL2 electron trap signal after 0.4-J/cm/sup 2/ annealing. It is proposed that these new defects states are due to the decomposition of the As/sub Ga/-As/sub i/ complex recently considered as the most probable defect configuration for the dominant EL2 electron trap usually detected in as-grown GaAs substrates.

  20. Electronic devices from diamond-like carbon

    NASA Astrophysics Data System (ADS)

    Milne, W. I.

    2003-03-01

    This paper reviews the work carried out over the past few years on the application of diamond-like carbon (DLC) materials to electronic devices. The use of such materials is still in its infancy due to their high defect state density and associated low mobilities. To date, the major effort in the electronic field has been in their attempted use as cold cathode field emitters where their low threshold field has attracted much attention. However, attempts have also been made to produce metal semiconductor metal structures, diodes, a-C/c-Si heterostructures and thin film transistors with varying degrees of success. A brief review of work carried out on the use of DLCs in solar cell manufacture will also be presented but it seems at this early stage in their development that the most promising area for future development will be in the field of microelectromechanical structures where their friction, stiction and wear properties make them prime candidates for use in moving mechanical assemblies.

  1. Cross-plane Thermoelectric Transport in p-type La0.67Sr0.33MnO3/LaMnO3 Oxide Metal/Semiconductor Superlattices

    DTIC Science & Technology

    2013-12-07

    1.4804937] I . INTRODUCTION Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multifer- roics, and...superlattice structure extracted from I -V-T measurements of etched pillars suggests a contribution from thermionic behavior, and the extracted effective...and LMO thin films after two-stage annealing process: Stage- I (750 C, 300 mTorr, 15 h PLD), and Stage-II (900 C, atmospheric O2 pressure, tube

  2. FAST TRACK COMMUNICATION: Synthesis and electron transfer property of sulfhydryl-containing multi-walled carbon nanotube/gold nanoparticle heterojunctions

    NASA Astrophysics Data System (ADS)

    Feng, Xiumei; Hu, Jianqiang; Chen, Xiaohua; Xie, Jingsi; Liu, Yuying

    2009-02-01

    One-dimensional metal/semiconductor heterojunction nanomaterials have opened many new opportunities for future nanodevices because of their novel structures and unique electrical and optical properties. In this work, sulfhydryl-containing multi-walled carbon nanotube/gold nanoparticle (MWCNT/Au) heterojunctions were synthesized in high yield by a sulfhydryl- functionalized self-assembly strategy. The component, size, structure, morphology and bond mode of the MWCNT/Au heterojunctions thus prepared were investigated and demonstrated by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier-transform infrared and UV-visible measurements. Cyclic voltammogram and electrochemical impedance spectroscopy studies indicate that the MWCNT/Au heterojunctions have a novel electron transfer property, which retards electron transfer of the horseradish peroxidase or the ferricyanide in the underlying electrodes. We believe that MWCNT/Au heterojunctions with high stability and a unique electrical property are expected to find potential applications for nanodevices.

  3. Planar Hot-Electron Photodetection with Tamm Plasmons.

    PubMed

    Zhang, Cheng; Wu, Kai; Giannini, Vincenzo; Li, Xiaofeng

    2017-02-28

    There is an increasing interest in harvesting photoejected hot-electrons for sensitive photodetectors, which have highly tunable detection wavelengths controlled by structural engineering rather than the classic doped semiconductors. However, the widely employed metallic nanostructures that excite surface plasmons (SPs) to enhance the photoemission of hot-electrons are usually complex with a high fabrication challenge. Here, we present a purely planar hot-electron photodetector based on Tamm plasmons (TPs) by introducing a distributed Bragg reflector integrated with hot-electron collection layers in metal/semiconductor/metal configuration. Results show that the light incidence can be strongly confined in the localized region between the top metal and the adjacent dielectric layer due to the excitation of TP resonance so that more than 87% of the light incidence can be absorbed by the top metal layer. This enables a strong and unidirectional photocurrent and a photoresponsivity that can even be higher than that of the conventional nanostructured system. Moreover, the planar TP system shows a narrow-band resonance with high tunability, good resistance against the change of the incident angle, and the possibility for extended functionalities. The proposed TP-based planar configuration significantly simplifies the conventional SP-based systems and opens the pathway for high-performance, low-cost, hot-electron photodetection.

  4. Electronically transparent graphene barriers against unwanted doping of silicon.

    PubMed

    Wong, Calvin Pei Yu; Koek, Terence Jun Hui; Liu, Yanpeng; Loh, Kian Ping; Goh, Kuan Eng Johnson; Troadec, Cedric; Nijhuis, Christian A

    2014-11-26

    Diffusion barriers prevent materials from intermixing (e.g., undesired doping) in electronic devices. Most diffusion barrier materials are often very specific for a certain combination of materials and/or change the energetics of the interface because they are insulating or add to the contact resistances. This paper presents graphene (Gr) as an electronically transparent, without adding significant resistance to the interface, diffusion barrier in metal/semiconductor devices, where Gr prevents Au and Cu from diffusion into the Si, and unintentionally dope the Si. We studied the electronic properties of the n-Si(111)/Gr/M Schottky barriers (with and without Gr and M=Au or Cu) by I(V) measurements and at the nanoscale by ballistic electron emission spectroscopy (BEEM). The layer of Gr does not change the Schottky barrier of these junctions. The Gr barrier was stable at 300 °C for 1 h and prevented the diffusion of Cu into n-Si(111) and the formation of Cu3Si. Thus, we conclude that the Gr is mechanically and chemically stable enough to withstand the harsh fabrication methods typically encountered in clean room processes (e.g., deposition of metals in high vacuum conditions at high temperatures), it is electronically transparent (it does not change the energetics of the Si/Au or Si/Cu Schottky barriers), and effectively prevented diffusion of the Cu or Au into the Si at elevated temperatures and vice versa.

  5. Fabrication of Ag/ZnO heterostructure and the role of surface coverage of ZnO microrods by Ag nanoparticles on the photophysical and photocatalytic properties of the metal-semiconductor system

    NASA Astrophysics Data System (ADS)

    Sarma, Bikash; Sarma, Bimal K.

    2017-07-01

    This report presents findings on microstructural, photophysical, and photocatalytic properties of Ag/ZnO heterostructure grown on flexible and silicon substrates. ZnO microrods are prepared by thermal decomposition method for different solute concentrations and Ag/ZnO heterostructure are fabricated by photo-deposition of Ag nanoparticles on ZnO microrods. X-ray diffraction and electron microscopy studies confirm that ZnO microrods belong to the hexagonal wurtzite structure and grown along [001] direction with random alignment showing that majority microrods are aligned with (100) face parallel to the sample surface. Plasmonic Ag nanoparticles are attached to different faces of ZnO. In the optical reflection spectra of Ag/ZnO heterostructure, the surface plasmon resonance peak due to Ag nanoparticles appears at 445 nm. Due to the oxygen vacancies the band gaps of ZnO microrods turn out to be narrower compared to that of bulk ZnO. The presence of Ag nanoparticles decreases the photoluminescence intensity which might be attributed to the non-radiative energy and direct electron transfer in the plasmon-exciton system. The quenching of photoluminescence in Ag/ZnO heterostructure at different growth conditions depend on the extent of surface coverage of ZnO by plasmonic Ag nanoparticles. Photocatalytic degradation efficiency of Ag/ZnO heterostructure is higher than that of ZnO microrods. The extent of surface coverage of ZnO microrods by Ag nanoparticles is crucial for the observed changes in photophysical and photochemical properties.

  6. Substrate induced modulation of electronic, magnetic and chemical properties of MoSe{sub 2} monolayer

    SciTech Connect

    Wasey, A. H. M. Abdul; Chakrabarty, Soubhik; Das, G. P.

    2014-04-15

    Monolayer of MoSe{sub 2}, having a typical direct band gap of ∼1.5 eV, is a promising material for optoelectronic and solar cell applications. When this 2D semiconductor is supported on transition metal substrates, such as Ni(111) and Cu(111), its electronic structure gets modulated. First principles density functional investigation shows the appearance of de-localized mid-gap states in the density of states. The work function of the semiconductor overlayer gets modified considerably, indicating n-type doping caused by the metal contacts. The charge transfer across the metal-semiconductor junction also significantly enhances the chemical reactivity of the MoSe{sub 2} overlayer, as observed by Hydrogen absorption. Furthermore, for Ni contact, there is a signature of induced magnetism in MoSe{sub 2} monolayer.

  7. Theory of hot electron photoemission from graphene

    NASA Astrophysics Data System (ADS)

    Ang, Lay Kee; Liang, Shijun

    Motivated by the development of Schottky-type photodetectors, some theories have been proposed to describe how the hot carriers generated by the incident photon are transported over the Schottky barrier through the internal photoelectric effect. One of them is Fowler's law proposed as early as 1931, which studied the temperature dependence of photoelectric curves of clean metals. This law is very successful in accounting for mechanism of detecting photons of energy lower than the band gap of semiconductor based on conventional metal/semiconductor Schottky diode. With the goal of achieving better performance, graphene/silicon contact-based- graphene/WSe2 heterostructure-based photodetectors have been fabricated to demonstrate superior photodetection efficiency. However, the theory of how hot electrons is photo-excited from graphene into semiconductor remains unknown. In the current work, we first examine the photoemission process from suspended graphene and it is found that traditional Einstein photoelectric effect may break down for suspended graphene due to the unique linear band structure. Furthermore, we find that the same conclusion applies for 3D graphene analog (e.g. 3D topological Dirac semi-metal). These findings are very useful to further improve the performance of graphene-based photodetector, hot-carrier solar cell and other kinds of sensor.

  8. Electronic and magnetic properties of pristine and hydrogenated borophene nanoribbons

    NASA Astrophysics Data System (ADS)

    Meng, Fanchen; Chen, Xiangnan; Sun, Songsong; He, Jian

    2017-07-01

    The groundbreaking works in graphene and graphene nanoribbons (GNRs) over the past decade, and the very recent discovery of borophene naturally draw attention to the yet-to-be-explored borophene nanoribbons (BNRs). We herein report a density functional theory (DFT) study of the electronic and magnetic properties of BNRs. The foci are the impact of orientation (denoted as BxNRs and ByNRs with their respective periodic orientations along x- and y-axis), ribbon width (Nx, Ny=4-15), and hydrogenation effects on the geometric, electronic and magnetic properties of BNRs. We found that the anisotropic quasi-planar geometric structure of BNR and the edge states largely govern its electronic and magnetic properties. In particular, pristine ByNRs adopt a magnetic ground state, either anti-ferromagnetic (AFM) or ferromagnetic (FM) depending on the ribbon width, while pristine BxNRs are non-magnetic (NM). Upon hydrogenation, all BNRs exhibit NM. Interestingly, both pristine and hydrogenated ByNRs undergo a metal-semiconductor-metal transition at Ny=7, while all BxNRs remain metallic.

  9. Ballistic-Electron-Emission-Microscopy of Strained Si(sub 1-x)Ge(sub x) Layers

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Milliken, A. M.; Manion, S. J.; Kaiser, W. J.; Fathauer, R. W.; Pike, W. T.

    1994-01-01

    Ballistic-electron-emission microscopy (BEEM) has been used to investigate the effects of strain on Si(sub 1-x)Ge(sub x) alloys. Lifting of the degeneracy of the conduction-band minimum of Si(sub 1-x)Ge(sub x), due to lattice deformation has been directly measured by application of BEEM spectroscopy to Ag/Si structures. Experimental values for this conduction-band splitting agree well with calculations. In addition, an unexpected heterogeneity in the strain of the Si(sub 1-x)Ge(sub x) layer is introduced by deposition of Au. This effect, not observed with Ag, is attributed to species interdiffusion and has important implications for metal-semiconductor devices based oil pseudomorphic Si(sub 1-x)Ge(sub x)/Si material systems.

  10. Equivalent ambipolar carrier injection of electrons and holes with Au electrodes in air-stable field effect transistors

    SciTech Connect

    Kanagasekaran, Thangavel E-mail: Shimotani@m.tohoku.ac.jp Ikeda, Susumu; Kumashiro, Ryotaro; Shimotani, Hidekazu E-mail: Shimotani@m.tohoku.ac.jp Shang, Hui; Tanigaki, Katsumi E-mail: Shimotani@m.tohoku.ac.jp

    2015-07-27

    Carrier injection from Au electrodes to organic thin-film active layers can be greatly improved for both electrons and holes by nano-structural surface control of organic semiconducting thin films using long-chain aliphatic molecules on a SiO{sub 2} gate insulator. In this paper, we demonstrate a stark contrast for a 2,5-bis(4-biphenylyl)bithiophene (BP2T) active semiconducting layer grown on a modified SiO{sub 2} dielectric gate insulator between two different modifications of tetratetracontane and poly(methyl methacrylate) thin films. Important evidence that the field effect transistor (FET) characteristics are independent of electrode metals with different work functions is given by the observation of a conversion of the metal-semiconductor contact from the Schottky limit to the Bardeen limit. An air-stable light emitting FET with an Au electrode is demonstrated.

  11. Veritable electronic characteristics in ZnO nanowire circuits uncovered by the four-terminal method at a low temperature

    NASA Astrophysics Data System (ADS)

    Li, Xin; Zhang, Qi

    2017-04-01

    Understanding the natural electrical properties in semiconductor channels and the carrier transport across the metal-semiconductor contact is essential to improve the performance of nanowire devices. This work presents the true electronic characteristics of ZnO nanowire devices measured by a four-electrode method at a low-temperature environment. The temperature rise leads to the decrease in near-band-gap emission, which is attributed to two non-radiative recombination processes. For ZnO circuits, thermionic emission carrier transport mechanism plays a dominant role at Ti-Au/ZnO interface and the transport mechanism in ZnO nanowires is governed by two competitive thermal activation conduction processes: optical or acoustic phonons assisting hopping.

  12. Ballistic-Electron-Emission-Microscopy of Strained Si(sub 1-x)Ge(sub x) Layers

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Milliken, A. M.; Manion, S. J.; Kaiser, W. J.; Fathauer, R. W.; Pike, W. T.

    1994-01-01

    Ballistic-electron-emission microscopy (BEEM) has been used to investigate the effects of strain on Si(sub 1-x)Ge(sub x) alloys. Lifting of the degeneracy of the conduction-band minimum of Si(sub 1-x)Ge(sub x), due to lattice deformation has been directly measured by application of BEEM spectroscopy to Ag/Si structures. Experimental values for this conduction-band splitting agree well with calculations. In addition, an unexpected heterogeneity in the strain of the Si(sub 1-x)Ge(sub x) layer is introduced by deposition of Au. This effect, not observed with Ag, is attributed to species interdiffusion and has important implications for metal-semiconductor devices based oil pseudomorphic Si(sub 1-x)Ge(sub x)/Si material systems.

  13. Dynamics of surface catalyzed reactions; the roles of surface defects, surface diffusion, and hot electrons.

    PubMed

    Somorjai, Gabor A; Bratlie, Kaitlin M; Montano, Max O; Park, Jeong Y

    2006-10-12

    The mechanism that controls bond breaking at transition metal surfaces has been studied with sum frequency generation (SFG), scanning tunneling microscopy (STM), and catalytic nanodiodes operating under the high-pressure conditions. The combination of these techniques permits us to understand the role of surface defects, surface diffusion, and hot electrons in dynamics of surface catalyzed reactions. Sum frequency generation vibrational spectroscopy and kinetic measurements were performed under 1.5 Torr of cyclohexene hydrogenation/dehydrogenation in the presence and absence of H(2) and over the temperature range 300-500 K on the Pt(100) and Pt(111) surfaces. The structure specificity of the Pt(100) and Pt(111) surfaces is exhibited by the surface species present during reaction. On Pt(100), pi-allyl c-C6H9, cyclohexyl (C6H11), and 1,4-cyclohexadiene are identified adsorbates, while on the Pt(111) surface, pi-allyl c-C6H9, 1,4-cyclohexadiene, and 1,3-cyclohexadiene are present. A scanning tunneling microscope that can be operated at high pressures and temperatures was used to study the Pt(111) surface during the catalytic hydrogenation/dehydrogenation of cyclohexene and its poisoning with CO. It was found that catalytically active surfaces were always disordered, while ordered surface were always catalytically deactivated. Only in the case of the CO poisoning at 350 K was a surface with a mobile adsorbed monolayer not catalytically active. From these results, a CO-dominated mobile overlayer that prevents reactant adsorption was proposed. By using the catalytic nanodiode, we detected the continuous flow of hot electron currents that is induced by the exothermic catalytic reaction. During the platinum-catalyzed oxidation of carbon monoxide, we monitored the flow of hot electrons over several hours using a metal-semiconductor Schottky diode composed of Pt and TiO2. The thickness of the Pt film used as the catalyst was 5 nm, less than the electron mean free path

  14. Superatoms and Metal-Semiconductor Motifs for Cluster Materials

    SciTech Connect

    Castleman, A. W.

    2013-10-11

    A molecular understanding of catalysis and catalytically active materials is of fundamental importance in designing new substances for applications in energy and fuels. We have performed reactivity studies and ultrafast ionization and coulomb explosion studies on a variety of catalytically-relevant materials, including transition metal oxides of Fe, Co, Ni, Cu, Ti, V, Nb, and Ta. We demonstrate that differences in charge state, geometry, and elemental composition of clusters of such materials determine chemical reactivity and ionization behavior, crucial steps in improving performance of catalysts.

  15. Towards a metal-semiconductor transition in two dimensions

    NASA Astrophysics Data System (ADS)

    Hansson, Anders; de Brito Mota, F.; Rivelino, R.

    2017-07-01

    Two-dimensional (2D) heterosheets built from silicon and boron may exhibit an intrinsic metallic behavior. From density-functional-theory computer simulations, we have demonstrated that a 2D honeycomb binary compound (h-SiB), which exhibits robust structural and thermal stabilities, maintains its metallicity by increasing hydrogen coverages at 25%, 50%, and 75% on boron or silicon sublattices. However, under a total hydrogenation condition (100%) on B or Si sites, h-SiB opens a well-defined bandgap, meaning that it is possible to obtain a metal-insulator transition at zero temperature in 2D. Additional calculations show that the hydrogenation on B sublattices is energetically more favorable than on silicon.

  16. Sulfur Implanted Black Silicon for Metal Semiconductor Metal (MSM) Photodetectors

    DTIC Science & Technology

    2012-12-01

    MD, 2012. 5. Prasad, A.; Balakrishnan, S.; Jain, S. K.; Jain, C. G. J. Electrochem.Soc. 1995, 129, 596. 6. Green, M. A. Silicon Solar Cells ...reflectivity in a broad spectral range, leading to a black surface Si. Si with various structural morphologies is widely used for solar cells and other...of crucial importance, in particular, for high efficiency solar cells , and hence, a variety of approaches has been developed to this end, in many

  17. Iron silicide-based ferromagnetic metal/semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Ovchinnikov, S. G.; Varnakov, S. N.; Lyashchenko, S. A.; Tarasov, I. A.; Yakovlev, I. A.; Popov, E. A.; Zharkov, S. M.; Velikanov, D. A.; Tarasov, A. S.; Zhandun, V. S.; Zamkova, N. G.

    2016-11-01

    Ferromagnetic single-crystal epitaxial Fe3Si films and polycrystalline Fe5Si3 films are obtained on Si substrates by molecular-beam epitaxy with in situ control of the structure, optical, and magnetic properties. The results of the structural, magnetic, and optical measurements are discussed. The experimental data are compared to the results of the microscopic calculation of the spin-polarized structure, the permittivity, and the optical conductivity spectra.

  18. Formation of Defect-Free Metal/Semiconductor Contacts

    DTIC Science & Technology

    1992-12-15

    Benning, Yongjun Hu, TJ. Wagener, M.B. Jost, and J.H. Weaver, "Thermally-Reversible Band Bending for BiIGaAs(1 10): Photoemission and Inverse...34Schottky Barrier Formation at Au/ZnSe(100) Interfaces," 35th National Symposium of the American Vacuum Society, Atlanta, October 1988. 14. Yongjun Hu

  19. Universal metal-semiconductor hybrid nanostructured SERS substrate for biosensing.

    PubMed

    Siddhanta, Soumik; Thakur, Varun; Narayana, Chandrabhas; Shivaprasad, S M

    2012-11-01

    We demonstrate here a novel high surface area GaN nanowall network substrate with plasmonic Ag nanodroplets, that can be employed as a highly sensitive, reproducible, and charge independent SERS substrate. The uniformity of the size and distribution of the Ag droplets and the absence of linker ligands result in large near-field intensity, while the GaN nanowall network morphology provides multiple reflections for signal enhancement. FDTD calculations simulate the observed hot-spot distribution and reiterate the higher performance of this hybrid substrate over conventional ones. Our studies on oppositely charged proteins provide a proof of concept for employing this as a versatile charge independent label free SERS substrate for trace biomolecule detection.

  20. Exciton/plasmon mixing in metal-semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Symonds, Clémentine; Bellessa, Joel; Plenet, Jean-Claude; Cambril, Edmond; Miard, Audrey; Ferlazzo, Laurence; Lemaître, Aristide

    2010-01-01

    We report on the strong coupling between surface plasmons and inorganic quantum well excitons. The sample is formed by a corrugated silver film deposited on the top of a heterostructure consisting of five GaAs/GaAlAs quantum wells grown by molecular beam epitaxy. Reflectometry experiments at low temperature (77 K) evidence the formation of plasmon/heavy-hole exciton/light-hole exciton mixed states. The interaction energies, deduced by fitting the experimental data with a coupled oscillator model, amount to 22 meV for the plasmon/light-hole exciton and 21 meV for the plasmon/heavy-hole exciton. Some particularities of the plasmon-exciton coupling are also discussed and qualitatively related to the plasmon polarization.

  1. Surface plasmon polariton amplification in metal-semiconductor structures.

    PubMed

    Fedyanin, Dmitry Yu; Arsenin, Aleksey V

    2011-06-20

    We propose a novel scheme of surface plasmon polariton (SPP) amplification that is based on a minority carrier injection in a Schottky diode. This scheme uses compact electrical pumping instead of bulky optical pumping. Compact size and a planar structure of the proposed amplifier allow one to utilize it in integrated plasmonic circuits and couple it easily to passive plasmonic devices. Moreover, this technique can be used to obtain surface plasmon lasing.

  2. A Technique for In Situ Ballistic Electron Emission Microscopy

    NASA Astrophysics Data System (ADS)

    Balsano, Robert; Garramone, John; Labella, Vincent

    2012-02-01

    Ballistic electron emission microscopy (BEEM) is a scanning tunneling microscopy (STM) technique that can measure transport of hot electrons through materials and interfaces with high spatial and energetic resolution. BEEM requires an additional contact to ground the metal base layer of a metal semiconductor junction. Performing BEEM in situ with the sample fabrication requires a custom built STM or modifying a commercial one to facilitate the extra contact, which leaves the technique to highly trained experts. This poster will describe our work to develop a special silicon substrate that has the extra contact built in to enable in situ BEEM without modifications to the STM. Electrically isolated contact traces are lithographically patterned ex situ onto the silicon substrate and connected to the BEEM sample plate which is then inserted into the ultra-high vacuum chamber. The metal is then deposited through a shadow mask and then mounted in situ onto the STM for BEEM measurements. BEEM measurements comparing both in situ and ex situ deposited films will be presented.

  3. Multi-level multi-thermal-electron FDTD simulation of plasmonic interaction with semiconducting gain media: applications to plasmonic amplifiers and nano-lasers.

    PubMed

    Chen, X; Bhola, B; Huang, Y; Ho, S T

    2010-08-02

    Interactions between a semiconducting gain medium and confined plasmon-polaritons are studied using a multilevel multi-thermal-electron finite-difference time-domain (MLMTE-FDTD) simulator. We investigated the amplification of wave propagating in a plasmonic metal-semiconductor-metal (MSM) waveguide filled with semiconductor gain medium and obtained the conditions required to achieve net optical gain. The MSM gain waveguide is used to form a plasmonic semiconductor nano-ring laser(PSNRL) with an effective mode volume of 0.0071 microm3, which is about an order of magnitude smaller than the smallest demonstrated integrated photonic crystal based laser cavities. The simulation shows a lasing threshold current density of 1kA/cm2 for a 300 nm outer diameter ring cavity with 80 nm-wide ring. This current density can be realistically achieved in typical III-V semiconductor, which shows the experimental feasibility of the proposed PSNRL structure.

  4. Effect of the finishing treatment of a gallium arsenide surface on the spectrum of electron states in n-GaAs (100)

    SciTech Connect

    Bezryadin, N. N. Kotov, G. I.; Arsentyev, I. N.; Vlasov, Yu. N.; Starodubtsev, A. A.

    2012-06-15

    Deep level transient spectroscopy has been used to study the effect of substrate pretreatment on the spectrum of electron states in Au/n-GaAs(100) Schottky diodes. Two bands of energy-distributed states have been found near the metal/semiconductor interface. The first band appears in the spectra at temperatures of 200-300 K because elemental arsenic accumulates on the surface in clusters in the course of oxide formation in samples exposed to air. Surface disorder in the course of selective etching gives rise to the second band at 100-250 K. Annealing in selenium vapor heals defects in the surface region and removes both bands from the spectra. Samples annealed in Se{sub 2} contain only the set of levels characteristic of bulk GaAs.

  5. Electron transport characteristics of silicon nanowires by metal-assisted chemical etching

    SciTech Connect

    Qi, Yangyang; Wang, Zhen; Zhang, Mingliang; Wang, Xiaodong Ji, An; Yang, Fuhua

    2014-03-15

    The electron transport characteristics of silicon nanowires (SiNWs) fabricated by metal-assisted chemical etching with different doping concentrations were studied. By increasing the doping concentration of the starting Si wafer, the resulting SiNWs were prone to have a rough surface, which had important effects on the contact and the electron transport. A metal-semiconductor-metal model and a thermionic field emission theory were used to analyse the current-voltage (I-V) characteristics. Asymmetric, rectifying and symmetric I-V curves were obtained. The diversity of the I-V curves originated from the different barrier heights at the two sides of the SiNWs. For heavily doped SiNWs, the critical voltage was one order of magnitude larger than that of the lightly doped, and the resistance obtained by differentiating the I-V curves at large bias was also higher. These were attributed to the lower electron tunnelling possibility and higher contact barrier, due to the rough surface and the reduced doping concentration during the etching process.

  6. Electronic Inhomogeneity in PbTe-based High Performance Thermoelectric Materials Observed by NMR

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Schmidt-Rohr, K.; Cook, B. A.; Kanatzidis, M. G.

    2009-03-01

    Effects of composition and synthesis conditions on the local structure and charge carrier concentration in AgxSbyPb18Te20 (LAST-18) thermoelectric (TE) materials have been studied by ^125Te and ^207Pb nuclear magnetic resonance (NMR) with magic-angle spinning. The high-resolution ^125Te NMR spectra show that most Sb and Ag is not part of Sb2Te3, AgSbTe2, or Ag2Te inclusions. Biexponential NMR spin-lattice (T1) relaxation as well as Knight shifts of ^125Te and ^207Pb NMR signals show that many LAST-18 materials contain two phases of similar composition but with free electron concentrations that differ by more than an order of magnitude, i.e. these materials are electronically inhomogeneous. The NMR data were calibrated against Hall- and Seebeck-effect measurements to give the charge carrier concentrations in the two phases. This electronic inhomogeneity may result in the appearance of potential barriers inside TE materials, similar to those observed for semiconductor-semiconductor or metal-semiconductor junctions. Such barriers may affect thermopower, electrical, and thermal conductivity of TE materials.

  7. Solar energy conversion via hot electron internal photoemission in metallic nanostructures: Efficiency estimates

    SciTech Connect

    Leenheer, Andrew J.; Narang, Prineha; Atwater, Harry A.; Lewis, Nathan S.

    2014-04-07

    Collection of hot electrons generated by the efficient absorption of light in metallic nanostructures, in contact with semiconductor substrates can provide a basis for the construction of solar energy-conversion devices. Herein, we evaluate theoretically the energy-conversion efficiency of systems that rely on internal photoemission processes at metal-semiconductor Schottky-barrier diodes. In this theory, the current-voltage characteristics are given by the internal photoemission yield as well as by the thermionic dark current over a varied-energy barrier height. The Fowler model, in all cases, predicts solar energy-conversion efficiencies of <1% for such systems. However, relaxation of the assumptions regarding constraints on the escape cone and momentum conservation at the interface yields solar energy-conversion efficiencies as high as 1%–10%, under some assumed (albeit optimistic) operating conditions. Under these conditions, the energy-conversion efficiency is mainly limited by the thermionic dark current, the distribution of hot electron energies, and hot-electron momentum considerations.

  8. Electronic and magnetic properties of NbSe2 monolayer doped vacancy and transition metal atoms

    NASA Astrophysics Data System (ADS)

    Manchanda, Priyanka; Sellmyer, David; Skomski, Ralph

    2015-03-01

    Two-dimensional transition-metal dichalcogenides (2D TMDs) have attracted much attention recently due to potential applications including optoelectronic devices. Atomically thin layers of materials such as MoS2, WS2, NbS2, NbSe2, TaTe2 can easily be synthesized by exfoliation techniques and exhibit variety electronic phases such as metal, semiconductor, superconductor depending on the choice of metal. Most of the TMDs are nonmagnetic and various techniques have been proposed to induce or modulate magnetic properties that are essential for nanoelectronic device applications. We use DFT calculations to analyze the effect of strain, hydrogen adsorption, and doping. Emphasis is on the magnetic properties of NbSe2 monolayers containing vacancies and 3 d transition metal atoms. We find that magnetism can be induced by vacancy creation and transition metal-substitution in NbSe2, with effects similar to strain and hydrogen adsorption. The moment mainly arises from the localized nonbonding 3d electrons of the transition-metal atoms. Our findings contribute to the ongoing search ``for-better-than-graphene'' thin-film materials for novel electronic devices. This research is partially supported by DOE BES (DE-FG02-04ER46152).

  9. InAlN high electron mobility transistor Ti/Al/Ni/Au Ohmic contact optimisation assisted by in-situ high temperature transmission electron microscopy

    SciTech Connect

    Smith, M. D.; Parbrook, P. J.; O'Mahony, D.; Conroy, M.; Schmidt, M.

    2015-09-14

    This paper correlates the micro-structural and electrical characteristics associated with annealing of metallic multi-layers typically used in the formation of Ohmic contacts to InAlN high electron mobility transistors. The multi-layers comprised Ti/Al/Ni/Au and were annealed via rapid thermal processing at temperatures up to 925 °C with electrical current-voltage analysis establishing the onset of Ohmic (linear IV) behaviour at 750–800 °C. In-situ temperature dependent transmission electron microscopy established that metallic diffusion and inter-mixing were initiated near a temperature of 500 °C. Around 800 °C, inter-diffusion of the metal and semiconductor (nitride) was observed, correlating with the onset of Ohmic electrical behaviour. The sheet resistance associated with the InAlN/AlN/GaN interface is highly sensitive to the anneal temperature, with the range depending on the Ti layer thickness. The relationship between contact resistivity and measurement temperature follow that predicted by thermionic field emission for contacts annealed below 850 °C, but deviated above this due to excessive metal-semiconductor inter-diffusion.

  10. Magnet-in-the-Semiconductor Nanomaterials: High Electron Mobility in All-Inorganic Arrays of FePt/CdSe and FePt/CdS Core-Shell Heterostructures.

    PubMed

    Son, Jae Sung; Lee, Jong-Soo; Shevchenko, Elena V; Talapin, Dmitri V

    2013-06-06

    We report a colloidal synthesis and electrical and magnetotransport properties of multifunctional "magnet-in-the-semiconductor" nanostructures composed of FePt core and CdSe or CdS shell. Thin films of all-inorganic FePt/CdSe and FePt/CdS core-shell nanostructures capped with In2Se4(2-) molecular chalcogenide (MCC) ligands exhibited n-type charge transport with high field-effect electron mobility of 3.4 and 0.02 cm(2)/V·s, respectively. These nanostructures also showed a negative magnetoresistance characteristic for spin-dependent tunneling. We discuss the mechanism of charge transport and gating in the arrays of metal/semiconductor core-shell nanostructures.

  11. Modeling the Charge Transport in Graphene Nano Ribbon Interfaces for Nano Scale Electronic Devices

    NASA Astrophysics Data System (ADS)

    Kumar, Ravinder; Engles, Derick

    2015-05-01

    In this research work we have modeled, simulated and compared the electronic charge transport for Metal-Semiconductor-Metal interfaces of Graphene Nano Ribbons (GNR) with different geometries using First-Principle calculations and Non-Equilibrium Green's Function (NEGF) method. We modeled junctions of Armchair GNR strip sandwiched between two Zigzag strips with (Z-A-Z) and Zigzag GNR strip sandwiched between two Armchair strips with (A-Z-A) using semi-empirical Extended Huckle Theory (EHT) within the framework of Non-Equilibrium Green Function (NEGF). I-V characteristics of the interfaces were visualized for various transport parameters. The distinct changes in conductance and I-V curves reported as the Width across layers, Channel length (Central part) was varied at different bias voltages from -1V to 1 V with steps of 0.25 V. From the simulated results we observed that the conductance through A-Z-A graphene junction is in the range of 10-13 Siemens whereas the conductance through Z-A-Z graphene junction is in the range of 10-5 Siemens. These suggested conductance controlled mechanisms for the charge transport in the graphene interfaces with different geometries is important for the design of graphene based nano scale electronic devices like Graphene FETs, Sensors.

  12. Line defects in graphene: How doping affects the electronic and mechanical properties

    NASA Astrophysics Data System (ADS)

    Berger, Daniel; Ratsch, Christian

    2016-06-01

    Graphene and carbon nanotubes have extraordinary mechanical and electronic properties. Intrinsic line defects such as local nonhexagonal reconstructions or grain boundaries, however, significantly reduce the tensile strength, but feature exciting electronic properties. Here, we address the properties of line defects in graphene from first principles on the level of full-potential density-functional theory, and assess doping as one strategy to strengthen such materials. We carefully disentangle the global and local effect of doping by comparing results from the virtual crystal approximation with those from local substitution of chemical species, in order to gain a detailed understanding of the breaking and stabilization mechanisms. We find that doping primarily affects the occupation of the frontier orbitals. Occupation through n -type doping or local substitution with nitrogen increases the ultimate tensile strength significantly. In particular, it can stabilize the defects beyond the ultimate tensile strength of the pristine material. We therefore propose this as a key strategy to strengthen graphenic materials. Furthermore, we find that doping and/or applying external stress lead to tunable and technologically interesting metal/semiconductor transitions.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

    The effect of electron beam irradiation (EBI) on Al/n-Si Schottky diode has been studied by I-V characterization at room temperature. The behavior of the metal-semiconductor (MS) interface is analyzed by means of variations in the MS contact parameters such as, Schottky barrier height (ΦB), ideality factor (n) and series resistance (Rs). These parameters were found to depend on the EBI dose having a fixed incident beam of energy 7.5 MeV. At different doses (500, 1000, 1500 kGy) of EBI, the Schottky contacts were prepared and extracted their contact parameters by applying thermionic emission and Cheung models. Remarkably, the tuning of ΦB was observed as a function of EBI dose. The improved n with increased ΦB is seen for all the EBI doses. As a consequence of which the thermionic emission is more favored. However, the competing transport mechanisms such as space charge limited emission, tunneling and tunneling through the trap states were ascribed due to n > 1. The analysis of XPS spectra have shown the presence of native oxide and increased radiation induced defect states. The thickness variation in the MS interface contributing to Schottky contact behavior is discussed. This study explains a new technique to tune Schottky contact parameters by metal deposition on the electron beam irradiated n-Si wafers.

  14. The catalytic nanodiode: detecting continuous electron flow at oxide-metal interfaces generated by a gas-phase exothermic reaction.

    PubMed

    Park, Jeong Young; Somorjai, Gabor A

    2006-07-17

    Continuous flow of ballistic charge carriers is generated by an exothermic chemical reaction and detected using the catalytic metal-semiconductor Schottky diode. We obtained a hot electron current for several hours using two types of catalytic nanodiodes, Pt/TiO2 or Pt/GaN, during carbon monoxide oxidation at pressures of 100 Torr of O2 and 40 Torr of CO at 413-573 K. This result reveals that the chemical energy of an exothermic catalytic reaction is directly converted into hot electrons flux in the catalytic nanodiode. By heating the nanodiodes in He, we could measure the thermoelectric current which is in the opposite direction to the flow of the hot electron current. The chemicurrent is well correlated with the turnover rate of CO oxidation, which is separately measured with gas chromatography. The influence of the flow of hot charge carriers on the chemistry at the oxide-metal interface, and the turnover rate in the chemical reaction are discussed.

  15. The Catalytic Nanodiode: Detecting Continous Electron Flow atOxide-Metal Interfaces Generated by a Gas-Phase Exothermic Reaction

    SciTech Connect

    Park, Jeong Young; Somorjai, Gabor A.

    2006-10-31

    Continuous flow of ballistic charge carriers is generated by an exothermic chemical reaction and detected using the catalytic metal-semiconductor Schottky diode. We obtained a hot electron current for several hours using two types of catalytic nanodiodes, Pt/TiO2 or Pt/GaN, during carbon monoxide oxidation at pressures of 100 Torr of O2 and 40 Torr of CO at 413-573 K. This result reveals that the chemical energy of an exothermic catalytic reaction is directly converted into hot electrons flux in the catalytic nanodiode. By heating the nanodiodes in He, we could measure the thermoelectric current which is in the opposite direction to the flow of the hot electron current. The chemicurrent is well correlated with the turnover rate of CO oxidation, which is separately measured with gas chromatography. The influence of the flow of hot charge carriers on the chemistry at the oxide-metal interface, and the turnover rate in the chemical reaction are discussed.

  16. Reliable determination of the Cu/n-Si Schottky barrier height by using in-device hot-electron spectroscopy

    SciTech Connect

    Parui, Subir E-mail: l.hueso@nanogune.eu; Atxabal, Ainhoa; Ribeiro, Mário; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E. E-mail: l.hueso@nanogune.eu

    2015-11-02

    We show the operation of a Cu/Al{sub 2}O{sub 3}/Cu/n-Si hot-electron transistor for the straightforward determination of a metal/semiconductor energy barrier height even at temperatures below carrier-freeze out in the semiconductor. The hot-electron spectroscopy measurements return a fairly temperature independent value for the Cu/n-Si barrier of 0.66 ± 0.04 eV at temperatures below 180 K, in substantial accordance with mainstream methods based on complex fittings of either current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Cu/n-Si hot-electron transistors exhibit an OFF current of ∼2 × 10{sup −13} A, an ON/OFF ratio of ∼10{sup 5}, and an equivalent subthreshold swing of ∼96 mV/dec at low temperatures, which are suitable values for potential high frequency devices.

  17. p-Type Transparent Electronics

    DTIC Science & Technology

    2003-09-25

    23] 2.1.4 CuScO2 CuScO2 is a p-TCO of the delafossite crystal structure with a bandgap of 3.3 eV. [13] Stoichiometric CuScO2 is an insulator. It is...16 2.3.2 Non -Ideal Metal-Semiconductor Contacts . . . . . . . . . . . . . . . . . . . . . . . 17 2.3.3 Injecting Contacts...of 50 mS/cm. This decrease in optical transparency with increasing conductivity is seen in other de- lafossites. The band structure of delafossites is

  18. Comparison of Ti/Pd/Ag, Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-type GaAs for electronic devices handling high current densities

    NASA Astrophysics Data System (ADS)

    Huo, Pengyun; Galiana, Beatriz; Rey-Stolle, Ignacio

    2017-04-01

    In the quest for metal contacts for electronic devices handling high current densities, we report the results of Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-GaAs and compare them to Ti/Pd/Ag and AuGe/Ni/Au. These metal systems have been designed with the goal of producing an electrical contact with (a) low metal-semiconductor specific contact resistance, (b) very high sheet conductance, (c) good bondability, (d) long-term durability and (e) cost-effectiveness. The structure of the contacts consists of an interfacial layer (either Pd or Pd/Ge) intended to produce a low metal-semiconductor specific contact resistance; a diffusion barrier (Ti/Pd) and a thick top layer of Ag to provide the desired high sheet conductance, limited cost and good bondability. The results show that both systems can achieve very low metal resistivity (ρ M ˜ 2 × 10-6 Ω cm), reaching values close to that of pure bulk silver. This fact is attributed to the Ti/Pd bilayer acting as an efficient diffusion barrier, and thus the metal sheet resistance can be controlled by the thickness of the deposited silver layer. Moreover, the use of Pd as interfacial layer produces contacts with moderate specific contact resistance (ρ C ˜ 10-4 Ω cm2) whilst the use of Pd/Ge decreases the specific contact resistance to ρ C ˜ 1.5 × 10-7 Ω cm2, as a result of the formation of a Pd4(GaAs, Ge2) compound at the GaAs interface.

  19. Electronic Cigarettes

    MedlinePlus

    ... New FDA Regulations Text Size: A A A Electronic Cigarettes Electronic cigarettes (e-cigarettes) are battery operated products designed to ... more about: The latest news and events about electronic cigarettes on this FDA page Electronic cigarette basics on ...

  20. Electron photoemission in plasmonic nanoparticle arrays: analysis of collective resonances and embedding effects

    NASA Astrophysics Data System (ADS)

    Zhukovsky, Sergei V.; Babicheva, Viktoriia E.; Uskov, Alexander V.; Protsenko, Igor E.; Lavrinenko, Andrei V.

    2014-09-01

    We theoretically study the characteristics of photoelectron emission in plasmonic nanoparticle arrays. Nanoparticles are partially embedded in a semiconductor, forming Schottky barriers at metal/semiconductor interfaces through which photoelectrons can tunnel from the nanoparticle into the semiconductor; photodetection in the infrared range, where photon energies are below the semiconductor band gap (insufficient for band-to-band absorption in semiconductor), is therefore possible. The nanoparticles are arranged in a sparse rectangular lattice so that the wavelength of the lattice-induced Rayleigh anomalies can overlap the wavelength of the localized surface plasmon resonance of the individual particles, bringing about collective effects from the nanoparticle array. Using full-wave numerical simulations, we analyze the effects of lattice constant, embedding depth, and refractive index step between the semiconductor layer and an adjacent transparent conductive oxide layer. We show that the presence of refractive index mismatch between media surrounding the nanoparticles disrupts the formation of a narrow absorption peak associated with the Rayleigh anomaly, so the role of collective lattice effects in the formation of plasmonic resonance is diminished. We also show that 5-20 times increase of photoemission can be achieved on embedding of nanoparticles without taking into account dynamics of ballistic electrons. The results obtained can be used to increase efficiency of plasmon-based photodetectors and photovoltaic devices. The results may provide clues to designing an experiment where the contributions of surface and volume photoelectric effects to the overall photocurrent would be defined.

  1. Computational design of p-type contacts for MoS2-based electronic devices

    NASA Astrophysics Data System (ADS)

    Kumar, Priyank; Musso, Tiziana; Foster, Adam; Grossman, Jeffrey

    2015-03-01

    The excellent physical and semiconducting properties of transition metal dichalcogenide (TMDC) monolayers make them promising materials for many applications. A well-known example is MoS2, which has gained significant attention as a channel material for next-generation transistors. While n-type MoS2 field-effect transistors (n-FETs) can be fabricated with relative ease, fabrication of p-FETs remains a challenge as the Fermi-level of elemental metals used as contacts are pinned close to the conduction band, leading to large p-type Schottky barrier heights (SBHs). Using ab initio computations, we design and propose efficient hole contacts utilizing high work function oxide-based hole injection materials, with the aim of advancing p-type MoS2 device technology. Our calculations will highlight the possibility to tune and lower the p-type SBH at the metal/semiconductor interface by controlling the structural properties of oxide materials. Taken together, our results provide an interesting platform for experimental design of next-generation MoS2-based electronic and optoelectronic devices.

  2. Analysis of quantum semiconductor heterostructures by ballistic electron emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Guthrie, Daniel K.

    1998-09-01

    The microelectronics industry is diligently working to achieve the goal of gigascale integration (GSI) by early in the 21st century. For the past twenty-five years, progress toward this goal has been made by continually scaling down device technology. Unfortunately, this trend cannot continue to the point of producing arbitrarily small device sizes. One possible solution to this problem that is currently under intensive study is the relatively new area of quantum devices. Quantum devices represent a new class of microelectronic devices that operate by utilizing the wave-like nature (reflection, refraction, and confinement) of electrons together with the laws of quantum mechanics to construct useful devices. One difficulty associated with these structures is the absence of measurement techniques that can fully characterize carrier transport in such devices. This thesis addresses this need by focusing on the study of carrier transport in quantum semiconductor heterostructures using a relatively new and versatile measurement technique known as ballistic electron emission spectroscopy (BEES). To achieve this goal, a systematic approach that encompasses a set of progressively more complex structures is utilized. First, the simplest BEES structure possible, the metal/semiconductor interface, is thoroughly investigated in order to provide a foundation for measurements on more the complex structures. By modifying the semiclassical model commonly used to describe the experimental BEES spectrum, a very complete and accurate description of the basic structure has been achieved. Next, a very simple semiconductor heterostructure, a Ga1-xAlxAs single-barrier structure, was measured and analyzed. Low-temperature measurements on this structure were used to investigate the band structure and electron-wave interference effects in the Ga1-xAlxAs single barrier structure. These measurements are extended to a simple quantum device by designing, measuring, and analyzing a set of

  3. Electronic and magnetic properties of 1T-HfS2 by doping transition-metal atoms

    NASA Astrophysics Data System (ADS)

    Zhao, Xu; Wang, Tianxing; Wang, Guangtao; Dai, Xianqi; Xia, Congxin; Yang, Lin

    2016-10-01

    We explored the electronic and magnetic properties of 1T-HfS2 doped by transition metal (TM) atom using the first-principles calculation. We doped the transition metal atoms from the IIIB to VIB groups in nonmagnetic 1T-HfS2. Numerical results show that the pristine 1T-HfS2 is a semiconductor with indirect gaps of 1.250 eV. Magnetism can be observed for V, Cr, Mn, Fe, Co, and Cu doping. The polarized charges mainly arise from the localized 3d electrons of the TM atom. The strong p-d hybridization was found between the 3d orbitals of TM and 3p orbitals of S. The substituted 1T-HfS2 can be a metal, semiconductor or half-metal. Analysis of the band structure and magnetic properties indicates that TM-doped HfS2 (TM = V, Fe, Cu) are promising systems to explore two-dimensional diluted magnetic semiconductors. The formation energy calculations also indicate that it is energetically favorable and relatively easier to incorporate transition metal atom into the HfS2 under S-rich experimental conditions. In contrast, V-doped HfS2 has relatively wide half-metallic gap and low formation energy. So V-doped 1T-HfS2 is ideal for spin injection, which is important for application in semiconductor spintronics.

  4. Two-dimensional MoS2 under ion irradiation: from controlled defect production to electronic structure engineering

    NASA Astrophysics Data System (ADS)

    Ghorbani-Asl, Mahdi; Kretschmer, Silvan; Spearot, Douglas E.; Krasheninnikov, Arkady V.

    2017-06-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs), like MoS2, have unique electronic and optical properties, which can further be tuned using ion bombardment and post-synthesis ion-beam mediated methods combined with exposure of the irradiated sample to precursor gases. The optimization of these techniques requires a complete understanding of the response of 2D TMDs to ion irradiation, which is affected by the reduced dimensionality of the system. By combining analytical potential molecular dynamics with first-principles calculations, we study the production of defects in free-standing MoS2 sheets under noble gas ion irradiation for a wide range of ion energies when nuclear stopping dominates, and assess the probabilities for different defects to appear. We show that depending on the incident angle, ion type and energy, sulfur atoms can be sputtered away predominantly from the top or bottom layers, creating unique opportunities for engineering mixed MoSX compounds where X are chemical elements from group V or VII. We study the electronic structure of such systems, demonstrate that they can be metals, and finally discuss how metal/semiconductor/metal junctions, which exhibit negative differential resistance, can be designed using focused ion beams combined with the exposure of the system to fluorine.

  5. Low-energy electron diffraction study of Si(111)-(√3x √3)R30∘ -B

    NASA Astrophysics Data System (ADS)

    Marino, K. E.; Huang, Y. T.; Diehl, R. D.; Tu, Weison; Mulugeta, Daniel; Snijders, P. C.; Weitering, H. H.

    2014-03-01

    Metal-semiconductor interfaces are important for the function and manufacture of advanced electronics, such as those used in computers, tablets and phones. They also exhibit many interesting physical phenomena that are interesting from a fundamental point of view, including exotic phases and phase transitions. This study involves the analysis and modeling of the surface structure of a thin film of boron on the Si(111) surface. The addition of metal atoms to the surface of Si(111) simplifies its structure by removing a ``rippling'' that is present on the clean surface. The low-energy electron diffraction (LEED) data were measured at a surface temperature of 80 K at ORNL. The LEED analysis utilized the SATLEED analysis programs. The results are similar to those obtained in an earlier LEED study for this interface, but the precision is higher due to the larger dataset employed., The results of this study will be compared to other studies of this and similar systems. We acknowledge the Eberly College of Science for funding this project. González, Guo, Ortega, Flores, Weitering. Phys. Rev. Lett. 102, 115501 (2009)

  6. Ambient Electronics

    NASA Astrophysics Data System (ADS)

    Sekitani, Tsuyoshi; Someya, Takao

    2012-10-01

    We report the recent research progress and future prospects of flexible and printed electronics, focusing on molecular electronic material-based thin-film transistors, which are expected to usher in a new era of electronics.

  7. The possibility of chemically inert, graphene-based all-carbon electronic devices with 0.8 eV gap.

    PubMed

    Qi, Jing Shan; Huang, Jian Yu; Feng, Ji; Shi, Da Ning; Li, Ju

    2011-05-24

    Graphene is an interesting electronic material. However, flat monolayer graphene does not have significant gap in the electronic density of states, required for a large on-off ratio in logic applications. We propose here a novel device architecture, composed of self-folded carbon nanotube-graphene hybrids, which have been recently observed experimentally in Joule-heated graphene. These experiments demonstrated the feasibility of cutting, folding, and welding few-layer graphene in situ to form all-carbon nanostructures with complex topologies. The electronic gap of self-folded nanotubes can be combined with the semimetallicity of graphene electrodes to form a "metal-semiconductor-metal" junction. By ab initio calculations we demonstrate large energy gaps in the transmission spectra of such junctions, which preserve the intrinsic transport characteristics of the semiconducting nanotubes despite topologically necessary disinclinations at the flat graphene-curved nanotube interface. These all-carbon devices are proposed to be constructed by contact probe cutting and high-temperature annealing and, if produced, would be chemically stable at room temperature under normal gas environments.

  8. Structural, mechanical and electronic properties of in-plane 1T/2H phase interface of MoS{sub 2} heterostructures

    SciTech Connect

    Guo, Xiaoyan; Yang, Guohui; Zhang, Junfeng; Xu, Xiaohong

    2015-09-15

    Two-dimensional (2D) molybdenum disulfide (MoS{sub 2}) phase hybrid system composed by 2H and 1T phase is a natural metal/semiconductor heterostructures and promised a wide range of potential applications. Here, we report the first principle investigations on the structural, mechanical and electronic properties of hybrid system with armchair (AC) and zigzag (ZZ) interfaces. The ZZ type 1T/2H interface are more energy favorable than AC type interface with 3.39 eV/nm. Similar with that of bulked 1T MoS{sub 2}, the intrinsic strengths of the heterostructures are lower than that of the bulk 2H, especially for that with ZZ interface. Analysis of density of states shows that the electronic properties gradually transmitted from the metallic 1T phase to the semiconducting 2H phase for the structural abrupt interface. The present theoretical results constitute a useful picture for the 2D electronic devices using current MoS{sub 2} 1T/2H heterostructures and provide vital insights into the other 2D hybrid materials.

  9. Electrons, Electronic Publishing, and Electronic Display.

    ERIC Educational Resources Information Center

    Brownrigg, Edwin B.; Lynch, Clifford A.

    1985-01-01

    Provides a perspective on electronic publishing by distinguishing between "Newtonian" publishing and "quantum-mechanical" publishing. Highlights include media and publishing, works delivered through electronic media, electronic publishing and the printed word, management of intellectual property, and recent copyright-law issues…

  10. Optical Dark-Field and Electron Energy Loss Imaging and Spectroscopy of Symmetry-Forbidden Modes in Loaded Nanogap Antennas.

    PubMed

    Brintlinger, Todd; Herzing, Andrew A; Long, James P; Vurgaftman, Igor; Stroud, Rhonda; Simpkins, B S

    2015-06-23

    We have produced large numbers of hybrid metal-semiconductor nanogap antennas using a scalable electrochemical approach and systematically characterized the spectral and spatial character of their plasmonic modes with optical dark-field scattering, electron energy loss spectroscopy with principal component analysis, and full wave simulations. The coordination of these techniques reveal that these nanostructures support degenerate transverse modes which split due to substrate interactions, a longitudinal mode which scales with antenna length, and a symmetry-forbidden gap-localized transverse mode. This gap-localized transverse mode arises from mode splitting of transverse resonances supported on both antenna arms and is confined to the gap load enabling (i) delivery of substantial energy to the gap material and (ii) the possibility of tuning the antenna resonance via active modulation of the gap material's optical properties. The resonant position of this symmetry-forbidden mode is sensitive to gap size, dielectric strength of the gap material, and is highly suppressed in air-gapped structures which may explain its absence from the literature to date. Understanding the complex modal structure supported on hybrid nanosystems is necessary to enable the multifunctional components many seek.

  11. Electronic structure, phonons, and thermal properties of ScN, ZrN, and HfN: A first-principles study

    NASA Astrophysics Data System (ADS)

    Saha, Bivas; Acharya, Jagaran; Sands, Timothy D.; Waghmare, Umesh V.

    2010-02-01

    With a motivation to understand microscopic aspects of ScN, ZrN, and HfN relevant to the thermoelectric properties of nitride metal/semiconductor superlattices, we determine their electronic structure, vibrational spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find a large energy gap in the phonon dispersions of metallic ZrN and HfN, but a gapless phonon spectrum for ScN spanning the same energy range, this suggests that a reduced thermal conductivity, suitable for thermoelectric applications, should arise in superlattices made with ScN and ZrN or ScN and HfN. To obtain an electronic energy band gap of ScN comparable to experiment, we use a Hubbard correction with a parameter U (=3.5 eV). Anomalies in the acoustic branches of the phonon dispersion of ZrN and HfN, manifested as dips in the bands, can be understood through the nesting of Fermi surface determined from our calculations. To connect with transport properties, we have determined effective masses of ScN and determined their dependence on the U parameter. Using the relaxation time approximation in the Boltzmann transport theory, we estimate the temperature dependence of the lattice thermal conductivity and discuss the chemical trends among these nitrides.

  12. Electronic properties of GaSe, InSe, GaS and GaTe layered semiconductors: charge neutrality level and interface barrier heights

    NASA Astrophysics Data System (ADS)

    Brudnyi, V. N.; Sarkisov, S. Yu; Kosobutsky, A. V.

    2015-11-01

    Density functional theory calculations have been applied to study the structural and electronic properties of layered ɛ-GaSe, γ-InSe, β-GaS and GaTe compounds. The optimized lattice parameters have been obtained using vdW-DF2-C09 exchange-correlation functional, which is able to describe dispersion forces and produces interlayer distances in close agreement with experiments. Based on the calculated electronic band structures, the energy position of the charge neutrality level (CNL) in the III-VI semiconductors has been estimated for the first time. The room-temperature values of CNL are found to be 0.80 eV, 1.02 eV, 0.72 eV and 0.77 eV for ɛ-GaSe, β-GaS, GaTe and γ-InSe, respectively. The persistent p-type conductivity of the intentionally undoped ɛ-GaSe, β-GaS and GaTe and n-type conductivity of γ-InSe crystals are discussed and explained using the concept of CNL. We also estimated the barrier heights for a number of metal/semiconductor and semiconductor/semiconductor interfaces assuming partial Fermi level pinning at the CNL. A reasonable agreement between our calculations and the available experimental data has been obtained.

  13. Electron Microscopy.

    ERIC Educational Resources Information Center

    Beer, Michael

    1980-01-01

    Reviews technical aspects of structure determination in biological electron microscopy (EM). Discusses low dose EM, low temperature microscopy, electron energy loss spectra, determination of mass or molecular weight, and EM of labeled systems. Cites 34 references. (CS)

  14. Spin Electronics

    DTIC Science & Technology

    2003-08-01

    is now well established in scientific and engineering communities that Moore’s Law, having been an excellent predictor of integrated circuit density...for semiconductor electronics, spin-electronic devices have the potential to achieve much higher integration densities. Conventional electronics is...devices would include non-volatility permitting data retention in non-powered conditions, increased integration densities, higher data processing

  15. Electronics Curriculum.

    ERIC Educational Resources Information Center

    Prickett, Charlotte

    This document presents results of research conducted by industry representatives regarding tasks performed by electronic technicians and line manufacturing electro-mechanical technicians in Arizona electronics industries. Based on this research, a competency-based curriculum was developed for training entry-level electronics technicians. Twelve…

  16. Electronics Curriculum.

    ERIC Educational Resources Information Center

    Prickett, Charlotte

    This document presents results of research conducted by industry representatives regarding tasks performed by electronic technicians and line manufacturing electro-mechanical technicians in Arizona electronics industries. Based on this research, a competency-based curriculum was developed for training entry-level electronics technicians. Twelve…

  17. Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

    SciTech Connect

    Zeng, Chang; Liao, XueYang; Li, RuGuan; Wang, YuanSheng; Chen, Yiqiang Su, Wei; Liu, Yuan; Wang, Li Wei; Lai, Ping; Huang, Yun; En, YunFei

    2015-09-28

    In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Based on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.

  18. Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

    NASA Astrophysics Data System (ADS)

    Zeng, Chang; Liao, XueYang; Li, RuGuan; Wang, YuanSheng; Chen, Yiqiang; Su, Wei; Liu, Yuan; Wang, Li Wei; Lai, Ping; Huang, Yun; En, YunFei

    2015-09-01

    In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Based on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.

  19. Conjugated Polymer Zwitterions: Efficient Interlayer Materials in Organic Electronics.

    PubMed

    Liu, Yao; Duzhko, Volodimyr V; Page, Zachariah A; Emrick, Todd; Russell, Thomas P

    2016-11-15

    Conjugated polymer zwitterions (CPZs) are neutral, hydrophilic, polymer semiconductors. The pendent zwitterions, viewed as side chain dipoles, impart solubility in polar solvents for solution processing, and open opportunities as interfacial components of optoelectronic devices, for example, between metal electrodes and organic semiconductor active layers. Such interlayers are crucial for defining the performance of organic electronic devices, e.g., field-effect transistors (OFETs), light-emitting diodes (OLEDs), and photovoltaics (OPVs), all of which consist of multilayer structures. The interlayers reduce the Schottky barrier height and thus improve charge injection in OFETs and OLEDs. In OPVs, the interlayers serve to increase the built-in electric potential difference (Vbi) across the active layer, ensuring efficient extraction of photogenerated charge carriers. In general, polar and even charged electronically active polymers have gained recognition for their ability to modify metal/semiconductor interfaces to the benefit of organic electronics. While conjugated polyelectrolytes (CPEs) as interlayer materials are well-documented, open questions remain about the role of mobile counterions in CPE-containing devices. CPZs possess the processing advantages of CPEs, but as neutral molecules lack any potential complications associated with counterions. The electronic implications of CPZs on metal electrodes stem from the orientation of the zwitterion dipole moment in close proximity to the metal surface, and the resultant surface-induced polarization. This generates an interfacial dipole (Δ) at the CPZ/metal interface, altering the work function of the electrode, as confirmed by ultraviolet photoelectron spectroscopy (UPS), and improving device performance. An ideal cathode interlayer would reduce electrode work function, have orthogonal processability to the active layer, exhibit good film forming properties (i.e., wettability/uniformity), prevent exciton

  20. Magnetospheric electrons

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.; Thorne, R. M.

    1972-01-01

    Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of magnetospheric electrons. Auroral electrons are controlled by convective transport from a plasma sheet source coupled with a precipitation loss due to whistler and electrostatic plasma turbulence. Outer and inner zone electrons are governed by radial diffusion transport from convection and acceleration sources external to the plasmapause and by parasitic precipitation losses arising from cyclotron and Landau interactions with whistler and ion cyclotron turbulence.

  1. Electronic Photography

    NASA Technical Reports Server (NTRS)

    Payne, Meredith Lindsay

    1995-01-01

    The main objective was to assist in the production of electronic images in the Electronic Photography Lab (EPL). The EPL is a new facility serving the electronic photographic needs of the Langley community. The purpose of the Electronic Photography lab is to provide Langley with access to digital imaging technology. Although the EPL has been in operation for less than one year, almost 1,000 images have been produced. The decision to establish the lab was made after careful determination of the centers needs for electronic photography. The LaRC community requires electronic photography for the production of electronic printing, Web sites, desktop publications, and its increased enhancement capabilities. In addition to general use, other considerations went into the planning of the EPL. For example, electronic photography is much less of a burden on the environment compared to conventional photography. Also, the possibilities of an on-line database and retrieval system could make locating past work more efficient. Finally, information in an electronic image is quantified, making measurements and calculations easier for the researcher.

  2. Electron Bifurcation

    SciTech Connect

    Peters, John W.; Miller, Anne-Frances; Jones, Anne K.; King, Paul W.; Adams, Michael W. W.

    2016-04-01

    Electron bifurcation is the recently recognized third mechanism of biological energy conservation. It simultaneously couples exergonic and endergonic oxidation-reduction reactions to circumvent thermodynamic barriers and minimize free energy loss. Little is known about the details of how electron bifurcating enzymes function, but specifics are beginning to emerge for several bifurcating enzymes. To date, those characterized contain a collection of redox cofactors including flavins and iron-sulfur clusters. Here we discuss the current understanding of bifurcating enzymes and the mechanistic features required to reversibly partition multiple electrons from a single redox site into exergonic and endergonic electron transfer paths.

  3. Microfluidic electronics.

    PubMed

    Cheng, Shi; Wu, Zhigang

    2012-08-21

    Microfluidics, a field that has been well-established for several decades, has seen extensive applications in the areas of biology, chemistry, and medicine. However, it might be very hard to imagine how such soft microfluidic devices would be used in other areas, such as electronics, in which stiff, solid metals, insulators, and semiconductors have previously dominated. Very recently, things have radically changed. Taking advantage of native properties of microfluidics, advances in microfluidics-based electronics have shown great potential in numerous new appealing applications, e.g. bio-inspired devices, body-worn healthcare and medical sensing systems, and ergonomic units, in which conventional rigid, bulky electronics are facing insurmountable obstacles to fulfil the demand on comfortable user experience. Not only would the birth of microfluidic electronics contribute to both the microfluidics and electronics fields, but it may also shape the future of our daily life. Nevertheless, microfluidic electronics are still at a very early stage, and significant efforts in research and development are needed to advance this emerging field. The intention of this article is to review recent research outcomes in the field of microfluidic electronics, and address current technical challenges and issues. The outlook of future development in microfluidic electronic devices and systems, as well as new fabrication techniques, is also discussed. Moreover, the authors would like to inspire both the microfluidics and electronics communities to further exploit this newly-established field.

  4. Paper electronics.

    PubMed

    Tobjörk, Daniel; Österbacka, Ronald

    2011-05-03

    Paper is ubiquitous in everyday life and a truly low-cost substrate. The use of paper substrates could be extended even further, if electronic applications would be applied next to or below the printed graphics. However, applying electronics on paper is challenging. The paper surface is not only very rough compared to plastics, but is also porous. While this is detrimental for most electronic devices manufactured directly onto paper substrates, there are also approaches that are compatible with the rough and absorptive paper surface. In this review, recent advances and possibilities of these approaches are evaluated and the limitations of paper electronics are discussed.

  5. Communications Electronics.

    ERIC Educational Resources Information Center

    Vorderstrasse, Ron; Siebert, Leo

    This module is the third in a series of electronics publications and serves as a supplement to "General Electronics Technician." It is designed to provide students with an overview of the broad field of communications. Included are those tasks above the basic skills level that allow students to progress to a higher level of competency in the…

  6. Printed electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel A. (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2012-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  7. Printed Electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2015-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  8. Printed Electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel A. (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2014-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  9. Printed Electronics

    NASA Technical Reports Server (NTRS)

    Crain, John M. (Inventor); Lettow, John S. (Inventor); Aksay, Ilhan A. (Inventor); Korkut, Sibel (Inventor); Chiang, Katherine S. (Inventor); Chen, Chuan-Hua (Inventor); Prud'Homme, Robert K. (Inventor)

    2016-01-01

    Printed electronic device comprising a substrate onto at least one surface of which has been applied a layer of an electrically conductive ink comprising functionalized graphene sheets and at least one binder. A method of preparing printed electronic devices is further disclosed.

  10. Electronic Cereal.

    ERIC Educational Resources Information Center

    Frentrup, Julie R.; Phillips, Donald B.

    1996-01-01

    Describes activities that use Froot Loops breakfast cereal to help students master the concepts of valence electrons and chemical bonding and the implications of the duet and octet rules. Involves students working in groups to create electron dot structures for various compounds. (JRH)

  11. Communications Electronics.

    ERIC Educational Resources Information Center

    Vorderstrasse, Ron; Siebert, Leo

    This module is the third in a series of electronics publications and serves as a supplement to "General Electronics Technician." It is designed to provide students with an overview of the broad field of communications. Included are those tasks above the basic skills level that allow students to progress to a higher level of competency in the…

  12. Electronic prototyping

    NASA Technical Reports Server (NTRS)

    Hopcroft, J.

    1987-01-01

    The potential benefits of automation in space are significant. The science base needed to support this automation not only will help control costs and reduce lead-time in the earth-based design and construction of space stations, but also will advance the nation's capability for computer design, simulation, testing, and debugging of sophisticated objects electronically. Progress in automation will require the ability to electronically represent, reason about, and manipulate objects. Discussed here is the development of representations, languages, editors, and model-driven simulation systems to support electronic prototyping. In particular, it identifies areas where basic research is needed before further progress can be made.

  13. Electronic neuroprocessors

    NASA Technical Reports Server (NTRS)

    Thakoor, Anil

    1991-01-01

    The JPL Center for Space Microelectronics Technology (CSMT) is actively pursuing research in the neural network theory, algorithms, and electronics as well as optoelectronic neural net hardware implementations, to explore the strengths and application potential for a variety of NASA, DoD, as well as commercial application problems, where conventional computing techniques are extremely time-consuming, cumbersome, or simply non-existent. An overview of the JPL electronic neural network hardware development activities and some of the striking applications of the JPL electronic neuroprocessors are presented.

  14. Superconducting electronics

    NASA Astrophysics Data System (ADS)

    Gubankov, V. N.

    The current status and principal trends, recent achievements, and future prospects of superconducting electronics are reviewed. In particular, attention is given to developments in high-temperature superconductivity; contribution of high-temperature superconductors to superconducting electronics; problems associated with high-temperature superconductor devices and recent achievements in this area; and goals in the field of electronics employing high-temperature superconductor components in comparison with the use of traditional superconductors. Applications discussed include ultrasensitive detection of weak electromagnetic radiation, SQUID-based magnetometry; cryogenic logic and memory systems, and measuring instruments.

  15. Electronic plants

    PubMed Central

    Stavrinidou, Eleni; Gabrielsson, Roger; Gomez, Eliot; Crispin, Xavier; Nilsson, Ove; Simon, Daniel T.; Berggren, Magnus

    2015-01-01

    The roots, stems, leaves, and vascular circuitry of higher plants are responsible for conveying the chemical signals that regulate growth and functions. From a certain perspective, these features are analogous to the contacts, interconnections, devices, and wires of discrete and integrated electronic circuits. Although many attempts have been made to augment plant function with electroactive materials, plants’ “circuitry” has never been directly merged with electronics. We report analog and digital organic electronic circuits and devices manufactured in living plants. The four key components of a circuit have been achieved using the xylem, leaves, veins, and signals of the plant as the template and integral part of the circuit elements and functions. With integrated and distributed electronics in plants, one can envisage a range of applications including precision recording and regulation of physiology, energy harvesting from photosynthesis, and alternatives to genetic modification for plant optimization. PMID:26702448

  16. Electronic Prescribing

    MedlinePlus

    ... 2048 . Electronic eRx Prescribing I went to the pharmacy, and my prescription was ready. You have the ... write and send your prescriptions directly to your pharmacy. This means no more prescriptions on paper and ...

  17. Spectral and Spatial Coherent Emission of Thermal Radiation from Metal-Semiconductor Nanostructures

    DTIC Science & Technology

    2012-03-01

    silver (Ag), gold (Au), sodium (Na), copper (Cu), potassium (K), and aluminum (Al). From [56...CO2 Carbon Dioxide Cu Copper Ge Germanium K Kelvin K Potassium Na Sodium O3 Tri-Oxide Si Silicon SiO2 Silicon...reduction in 31 reflectivity with rising temperature at 0.69 and 10.6 μm for Ag, Au, sodium (Na), copper (Cu), potassium (K), and aluminum (Al

  18. Improvement of metal-semiconductor contact on silicon microstructured surface by electroless nickel technique

    NASA Astrophysics Data System (ADS)

    Long, Fei; Guo, Anran; Huang, Lieyun; Yu, Feng; Li, Wei

    2016-11-01

    Si micro-structures served as anti-reflection layer are widely employed in Si-based solar cells and detectors to enhance light harvesting. However, performance of these devices is suffered from the poor contact between the metal electrode and micro-structured surface. Conventional vacuum deposited metal electrode makes only superficial contact with the top of micro-structured surface and unable to fill the holes in the micro-structures. In this paper, instead, electroless nickel technique is applied to form low resistance ohmic contact. The surface micro-structures were fabricated by electrochemistry etching while the metal electrodes were deposited by sputtering and electroless pasting. Results show that only electroless nickel layer could fully fill the holes and achieve better ohmic contact than the sputtering ones before rapid annealing. Furthermore, a higher temperature rapid annealing process could improve the contact of all samples prepared by different ways. The specific contact resistance achieved by high alkalinity (pH=12) electroless nickel is 1.34×10-1Ω·cm2.

  19. Metal-semiconductor pair nanoparticles by a physical route based on bipolar mixing

    NASA Astrophysics Data System (ADS)

    Kala, Shubhra; Theissmann, Ralf; Rouenhoff, Marcel; Kruis, Frank Einar

    2016-03-01

    In this report a methodology is described and demonstrated for preparing Au-Ge pair nanoparticles with known compositions by extending and modifying the basic steps normally used to synthesize nanoparticles in carrier gas. For the formation of pair nanoparticles by bipolar mixing, two oppositely charged aerosols of nanoparticles having the desired size are produced with the help of two differential mobility analyzers. Then both are allowed to pass through a tube, which provides sufficient residence time to result in nanoparticle pair formation due to Brownian collisions influenced by Coulomb forces. The effect of residence time on the formation of nanoparticle pairs as well as the influence of diffusion and discharging is described. Subsequently, necessary modifications to the experimental setup are demonstrated systematically. The kinetics of nanoparticles pair formation in a carrier gas is also calculated and compared with measurements made with the help of an online aerosol size analysis technique. This synthesis of nanoparticle pairs can be seen as a possible route towards Janus-type nanoparticles.

  20. Optical bistability and hysteresis of a hybrid metal-semiconductor nanodimer

    NASA Astrophysics Data System (ADS)

    Malyshev, A. V.; Malyshev, V. A.

    2011-07-01

    Optical response of an artificial composite nanodimer comprising a semiconductor quantum dot and a metal nanosphere is analyzed theoretically. We show that internal degrees of freedom of the system can manifest bistability and optical hysteresis as functions of the incident field intensity. We argue that these effects can be observed for real-world systems, such as a CdSe quantum dot and an Au nanoparticle hybrid. These properties can be revealed by measuring the optical hysteresis of Rayleigh scattering. We also show that the total dipole moment of the system can be switched abruptly between its two stable states by small changes in the excitation intensity. The latter promises various applications in the field of all-optical processing at the nanoscale, the most basic of them being the volatile optical memory.

  1. Metal-semiconductor pair nanoparticles by a physical route based on bipolar mixing.

    PubMed

    Kala, Shubhra; Theissmann, Ralf; Rouenhoff, Marcel; Kruis, Frank Einar

    2016-03-29

    In this report a methodology is described and demonstrated for preparing Au-Ge pair nanoparticles with known compositions by extending and modifying the basic steps normally used to synthesize nanoparticles in carrier gas. For the formation of pair nanoparticles by bipolar mixing, two oppositely charged aerosols of nanoparticles having the desired size are produced with the help of two differential mobility analyzers. Then both are allowed to pass through a tube, which provides sufficient residence time to result in nanoparticle pair formation due to Brownian collisions influenced by Coulomb forces. The effect of residence time on the formation of nanoparticle pairs as well as the influence of diffusion and discharging is described. Subsequently, necessary modifications to the experimental setup are demonstrated systematically. The kinetics of nanoparticles pair formation in a carrier gas is also calculated and compared with measurements made with the help of an online aerosol size analysis technique. This synthesis of nanoparticle pairs can be seen as a possible route towards Janus-type nanoparticles.

  2. Photoemission, Vibrational and Stimulated Desorption Studies of Metal- Semiconductor Interfaces and of Chemisorbed Atoms and Molecules

    DTIC Science & Technology

    1987-09-30

    Barrier Formation on Compound Semiconductor Surfaces", in The Chemical Physics of Solid Surfaces and Heterogeneous Catalysis , Vol. 5, D. P. Woodruf Ed...Surfaces and Heterogeneous Catalysis . Vol. 5, D. P. Woodruf Ed. (Elsevier, Amsterdam, in press). Patents Filed or Granted: N/A Invited Presentations at

  3. Metal-semiconductor-oxide extreme hyperbolic metamaterials for selectable canalization wavelength

    NASA Astrophysics Data System (ADS)

    Caligiuri, Vincenzo; De Luca, Antonio

    2016-03-01

    Hyperbolic metamaterials (HMMs) are artificial structures whose extreme optical anisotropy opens the way for a broad range of applications in the visible range, from perfect lensing to attomolar biosensing. In this work we investigate the possibility of realizing an HMM structure presenting a dielectric singularity in the anisotropic permittivity response. A transition point of inverted but coexisting anisotropies is obtained at a specified wavelength due to the particular design of the multilayer meta-structure, possessing different optical properties depending on the investigation frequency. Once properly designed for only a few metal-dielectric pairs in the visible range, there is no way to shift the transition wavelength between these coexisting anisotropies and keep the same constituents. We present a simple way of overcoming this problem and set up a method to tune this transition point within almost the entire visible range without changing the constituent fundamental materials.

  4. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting.

    PubMed

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-07-12

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis.

  5. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-07-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis.

  6. Electrical Control of Magnetic Dynamics in Hybrid Metal-Semiconductor Systems

    DTIC Science & Technology

    2014-07-25

    1.4737017 L. Liu, C.-F. Pai, Y. Li, H. W. Tseng, D. C. Ralph, R. A. Buhrman. Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum , Science...with the giant spin Hall effect of tantalum ,” Science 336, 555-558 (2012). 2 Luqiao Liu, Takahiro Moriyama, D. C. Ralph, and R. A. Buhrman, “Spin

  7. Controlled metal-semiconductor sintering/alloying by one-directional reverse illumination

    DOEpatents

    Sopori, Bhushan L.

    1993-01-01

    Metal strips deposited on a top surface of a semiconductor substrate are sintered at one temperature simultaneously with alloying a metal layer on the bottom surface at a second, higher temperature. This simultaneous sintering of metal strips and alloying a metal layer on opposite surfaces of the substrate at different temperatures is accomplished by directing infrared radiation through the top surface to the interface of the bottom surface with the metal layer where the radiation is absorbed to create a primary hot zone with a temperature high enough to melt and alloy the metal layer with the bottom surface of the substrate. Secondary heat effects, including heat conducted through the substrate from the primary hot zone and heat created by infrared radiation reflected from the metal layer to the metal strips, as well as heat created from some primary absorption by the metal strips, combine to create secondary hot zones at the interfaces of the metal strips with the top surface of the substrate. These secondary hot zones are not as hot as the primary hot zone, but they are hot enough to sinter the metal strips to the substrate.

  8. Growth of metal-semiconductor core-multishell nanorods with optimized field confinement and nonlinear enhancement.

    PubMed

    Nan, Fan; Xie, Fang-Ming; Liang, Shan; Ma, Liang; Yang, Da-Jie; Liu, Xiao-Li; Wang, Jia-Hong; Cheng, Zi-Qiang; Yu, Xue-Feng; Zhou, Li; Wang, Qu-Quan; Zeng, Jie

    2016-06-09

    This paper describes a facile method for the synthesis of Au/AuAg/Ag2S/PbS core-multishell nanorods with double trapping layers. The synthesis, in sequence, involved deposition of Ag shells onto the surfaces of Au nanorod seeds, formation of AuAg shells by a galvanic replacement reaction, and overgrowth of the Ag2S shells and PbS shells. The resulting core-multishell nanorod possesses an air gap between the Au core and the AuAg shell. Together with the Ag2S shell, the air gap can efficiently trap light, causing strong field confinement and nonlinear enhancement. The as-prepared Au/AuAg/Ag2S/PbS core-multishell nanorods display distinct localized surface plasmon resonance and nonlinear optical properties, demonstrating an effective pathway for maneuvering the optical properties of nanocavities.

  9. Molecular dynamics simulation of structural change at metal/semiconductor interface induced by nanoindenter

    NASA Astrophysics Data System (ADS)

    Zhao, Bing-Bing; Wang, Ying; Liu, Chang; Wang, Xiao-Chun

    2016-11-01

    The structures of the Si/Cu heterogenous interface impacted by a nanoindenter with different incident angles and depths are investigated in detail using molecular dynamics simulation. The simulation results suggest that for certain incident angles, the nanoindenter with increasing depth can firstly increase the stress of each atom at the interface and it then introduces more serious structural deformation of the Si/Cu heterogenous interface. A nanoindenter with increasing incident angle (absolute value) can increase the length of the Si or Cu extended atom layer. It is worth mentioning that when the incident angle of the nanoindenter is between -45° and 45°, these Si or Cu atoms near the nanoindenter reach a stable state, which has a lower stress and a shorter length of the Si or Cu extended atom layer than those of the other incident angles. This may give a direction to the planarizing process of very large scale integration circuits manufacture. Project supported by the Tribology Science Fund of State Key Laboratory of Tribology, China (Grant No. SKLTKF12A01), the National Natural Science Foundation of China (Grant No. 11474123), the Natural Science Foundation of Jilin Province of China (Grant No. 20130101011JC), and the Fundamental Research Funds for Central Universities at Jilin University, China.

  10. Synthesis, Morphological, and Electro-optical Characterizations of Metal/Semiconductor Nanowire Heterostructures

    PubMed Central

    2016-01-01

    In this letter, we demonstrate the formation of unique Ga/GaAs/Si nanowire heterostructures, which were successfully implemented in nanoscale light-emitting devices with visible room temperature electroluminescence. Based on our recent approach for the integration of InAs/Si heterostructures into Si nanowires by ion implantation and flash lamp annealing, we developed a routine that has proven to be suitable for the monolithic integration of GaAs nanocrystallite segments into the core of silicon nanowires. The formation of a Ga segment adjacent to longer GaAs nanocrystallites resulted in Schottky-diode-like I/V characteristics with distinct electroluminescence originating from the GaAs nanocrystallite for the nanowire device operated in the reverse breakdown regime. The observed electroluminescence was ascribed to radiative band-to-band recombinations resulting in distinct emission peaks and a low contribution due to intraband transition, which were also observed under forward bias. Simulations of the obtained nanowire heterostructure confirmed the proposed impact ionization process responsible for hot carrier luminescence. This approach may enable a new route for on-chip photonic devices used for light emission or detection purposes. PMID:27168031

  11. Electron tube

    DOEpatents

    Suyama, Motohiro [Hamamatsu, JP; Fukasawa, Atsuhito [Hamamatsu, JP; Arisaka, Katsushi [Los Angeles, CA; Wang, Hanguo [North Hills, CA

    2011-12-20

    An electron tube of the present invention includes: a vacuum vessel including a face plate portion made of synthetic silica and having a surface on which a photoelectric surface is provided, a stem portion arranged facing the photoelectric surface and made of synthetic silica, and a side tube portion having one end connected to the face plate portion and the other end connected to the stem portion and made of synthetic silica; a projection portion arranged in the vacuum vessel, extending from the stem portion toward the photoelectric surface, and made of synthetic silica; and an electron detector arranged on the projection portion, for detecting electrons from the photoelectric surface, and made of silicon.

  12. ELECTRONIC SYSTEM

    DOEpatents

    Robison, G.H. et al.

    1960-11-15

    An electronic system is described for indicating the occurrence of a plurality of electrically detectable events within predetermined time intervals. It is comprised of separate input means electrically associated with the events under observation: an electronic channel associated with each input means including control means and indicating means; timing means associated with each of the input means and the control means and adapted to derive a signal from the input means and apply it after a predetermined time to the control means to effect deactivation of each of the channels; and means for resetting the system to its initial condition after observation of each group of events.

  13. Electronic system

    DOEpatents

    Robison, G H; Dickson, J F

    1960-11-15

    An electronic system is designed for indicating the occurrence of a plurality of electrically detectable events within predetermined time intervals. The system comprises separate input means electrically associated with the events under observation an electronic channel associated with each input means, including control means and indicating means; timing means adapted to apply a signal from the input means after a predetermined time to the control means to deactivate each of the channels; and means for resetting the system to its initial condition after the observation of each group of events. (D.L.C.)

  14. Electron Impedances

    SciTech Connect

    P Cameron

    2011-12-31

    It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

  15. Electronic mail.

    PubMed Central

    Pallen, M.

    1995-01-01

    Electronic mail (email) has many advantages over other forms of communication: it is easy to use, free of charge, fast, and delivers information in a digital format. As a text only medium, email is usually less formal in style than conventional correspondence and may contain acronyms and other features, such as smileys, that are peculiar to the Internet. Email client programs that run on your own microcomputer render email powerful and easy to use. With suitable encoding methods, email can be used to send any kind of computer file, including pictures, sounds, programs, and movies. Numerous biomedical electronic mailing lists and other Internet services are accessible by email. PMID:8520343

  16. Electronic Money.

    ERIC Educational Resources Information Center

    Schilling, Tim

    Thirty years ago a cashless society was predicted for the near future; paper currency and checks would be an antiquated symbol of the past. Consumers would embrace a new alternative for making payments: electronic money. But currency is still used for 87% of payments, mainly for "nickel and dime" purchases. And checks are the payment…

  17. Electronic tongue

    NASA Technical Reports Server (NTRS)

    Kuhlman, Kimberly (Inventor); Buehler, Martin G. (Inventor)

    2004-01-01

    An ion selective electrode (ISE) array is described, as well as methods for producing the same. The array can contain multiple ISE which are individually electronically addressed. The addressing allows simplified preparation of the array. The array can be used for water quality monitoring, for example.

  18. Electronic Exams.

    ERIC Educational Resources Information Center

    Bushweller, Kevin

    2000-01-01

    Computerized testing pioneers are forcing educators to consider scrapping paper-and-pencil tests in favor of electronic testing. Critics say standardized testing and curricula will produce standardized children for point-and-click work places. Benefits include immediate and sophisticated analyses to aid teaching adjustments. Equity questions…

  19. Electronic School.

    ERIC Educational Resources Information Center

    Executive Educator, 1994

    1994-01-01

    This issue of "The Electronic School" features a special forum on computer networking. Articles specifically focus on network operating systems, cabling requirements, and network architecture. Tom Wall argues that virtual reality is not yet ready for classroom use. B.J. Novitsky profiles two high schools experimenting with CD-ROM…

  20. Electronics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 27 units to consider for use in a tech prep competency profile for the occupation of electronics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  1. Optical electronics

    NASA Technical Reports Server (NTRS)

    Javan, A.

    1976-01-01

    The development of an optical diode consisting of a metal-dielectric-metal junction in which the high-speed electric conduction process occurs due to quantum mechanical electron tunneling across the dielectric barrier is briefly reviewed. Potential applications of the diode are discussed.

  2. Electron Cooling

    NASA Astrophysics Data System (ADS)

    Ellison, Timothy J. P.

    1991-08-01

    Electron cooling is a method of reducing the 6 -dimensional phase space volume of a stored ion beam. The technique was invented by Budker and first developed by him and his colleagues at the Institute for Nuclear Physics in Novosibirsk. Further studies of electron cooling were subsequently performed at CERN and Fermilab. At the Indiana University Cyclotron Facility (IUCF) an electron cooling system was designed, built, and commissioned in 1988. This was the highest energy system built to date (270 keV for cooling 500 MeV protons) and the first such system to be used as an instrument for performing nuclear and atomic physics experiments. This dissertation summarizes the design principles; measurements of the longitudinal drag rate (cooling force), equilibrium cooled beam properties and effective longitudinal electron beam temperature. These measurements are compared with theory and with the measured performance of other cooling systems. In addition the feasibility of extending this technology to energies an order of magnitude higher are discussed.

  3. Basic Electronics.

    ERIC Educational Resources Information Center

    Hartman, Lonnie; Huston, Jane, Ed.

    The skills taught in these materials for a seven-unit course were those identified as necessary not only for entry-level electronic technicians but for those in other occupations as well, including appliance repair, heating and air conditioning, and auto mechanics. The seven units are on shop orientation and safety principles, introduction to…

  4. Electronic Portfolios.

    ERIC Educational Resources Information Center

    Purves, Alan C.

    1996-01-01

    Outlines three forms of electronic portfolio based on a student's work, a class project about a specific topic, and a class seminar on a broad topic. Discusses logistical problems of management, access, and cross-referencing; technical problems of input, access, and copying; and theoretical issues of the lack of realia, of ownership and copyright,…

  5. Electronics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 27 units to consider for use in a tech prep competency profile for the occupation of electronics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  6. Electronic detectors for electron microscopy.

    PubMed

    Faruqi, A R; McMullan, G

    2011-08-01

    Electron microscopy (EM) is an important tool for high-resolution structure determination in applications ranging from condensed matter to biology. Electronic detectors are now used in most applications in EM as they offer convenience and immediate feedback that is not possible with film or image plates. The earliest forms of electronic detector used routinely in transmission electron microscopy (TEM) were charge coupled devices (CCDs) and for many applications these remain perfectly adequate. There are however applications, such as the study of radiation-sensitive biological samples, where film is still used and improved detectors would be of great value. The emphasis in this review is therefore on detectors for use in such applications. Two of the most promising candidates for improved detection are: monolithic active pixel sensors (MAPS) and hybrid pixel detectors (of which Medipix2 was chosen for this study). From the studies described in this review, a back-thinned MAPS detector appears well suited to replace film in for the study of radiation-sensitive samples at 300 keV, while Medipix2 is suited to use at lower energies and especially in situations with very low count rates. The performance of a detector depends on the energy of electrons to be recorded, which in turn is dependent on the application it is being used for; results are described for a wide range of electron energies ranging from 40 to 300 keV. The basic properties of detectors are discussed in terms of their modulation transfer function (MTF) and detective quantum efficiency (DQE) as a function of spatial frequency.

  7. How Spirals and Gaps Driven by Companions in Protoplanetary Disks Appear in Scattered Light at Arbitrary Viewing Angles

    NASA Astrophysics Data System (ADS)

    Dong, Ruobing; Fung, Jeffrey; Chiang, Eugene

    2016-07-01

    Direct imaging observations of protoplanetary disks at near-infrared (NIR) wavelengths have revealed structures of potentially planetary origin. Investigations of observational signatures from planet-induced features have so far focused on disks viewed face-on. Combining 3D hydrodynamics and radiative transfer simulations, we study how the appearance of the spiral arms and the gap produced in a disk by a companion varies with inclination and position angle in NIR scattered light. We compare the cases of a 3M J and a 0.1M ⊙ companion, and make predictions suitable for testing with Gemini/GPI, Very Large Telescope/NACO/SPHERE, and Subaru/HiCIAO/SCExAO. We find that the two trailing arms produced by an external perturber can have a variety of morphologies in inclined systems—they may appear as one trailing arm; two trailing arms on the same side of the disk; or two arms winding in opposite directions. The disk ring outside a planetary gap may also mimic spiral arms when viewed at high inclinations. We suggest potential explanations for the features observed in HH 30, HD 141569 A, AK Sco, HD 100546, and AB Aur. We emphasize that inclined views of companion-induced features cannot be converted into face-on views using simple and commonly practiced image deprojections.

  8. General Electronics Technician: Basic Electronics.

    ERIC Educational Resources Information Center

    Hilley, Robert

    These instructional materials include a teacher's guide designed to assist instructors in organizing and presenting an introductory course in general electronics and a student guide. The materials are based on the curriculum-alignment concept of first stating the objectives, developing instructional strategies for teaching those objectives, and…

  9. Electronic Nose

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Grace Industries, Inc.'s Electronic Nose is a vapor and gas detector, deriving from NASA's electronic circuitry, capable for sensing the presence of accelerants several days after a fire. The device is powered by rechargeable battery and no special training needed to operate. If an accelerant is present, device will emit a beeping sound and trigger a flashing light; the faster the beep rate, the more volatile the accelerant. Its sensitivity can also detect minute traces of accelerants. Unit saves investigators of fire causes time and expense by providing speedy detection of physical evidence for use in court. Device is also useful for detecting hazardous fumes, locating and detecting gas leaks in refineries and on oil drilling rigs.

  10. Electronic Nose and Electronic Tongue

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Nabarun; Bandhopadhyay, Rajib

    Human beings have five senses, namely, vision, hearing, touch, smell and taste. The sensors for vision, hearing and touch have been developed for several years. The need for sensors capable of mimicking the senses of smell and taste have been felt only recently in food industry, environmental monitoring and several industrial applications. In the ever-widening horizon of frontier research in the field of electronics and advanced computing, emergence of electronic nose (E-Nose) and electronic tongue (E-Tongue) have been drawing attention of scientists and technologists for more than a decade. By intelligent integration of multitudes of technologies like chemometrics, microelectronics and advanced soft computing, human olfaction has been successfully mimicked by such new techniques called machine olfaction (Pearce et al. 2002). But the very essence of such research and development efforts has centered on development of customized electronic nose and electronic tongue solutions specific to individual applications. In fact, research trends as of date clearly points to the fact that a machine olfaction system as versatile, universal and broadband as human nose and human tongue may not be feasible in the decades to come. But application specific solutions may definitely be demonstrated and commercialized by modulation in sensor design and fine-tuning the soft computing solutions. This chapter deals with theory, developments of E-Nose and E-Tongue technology and their applications. Also a succinct account of future trends of R&D efforts in this field with an objective of establishing co-relation between machine olfaction and human perception has been included.

  11. ELECTRONIC MULTIPLIER

    DOEpatents

    Collier, D.M.; Meeks, L.A.; Palmer, J.P.

    1961-01-31

    S>An electronic multiplier is described for use in analog computers. Two electrical input signals are received; one controls the slope of a saw-tooth voltage wave while the other controls the time duration of the wave. A condenser and diode clamps are provided to sustain the crest voltage reached by the wave, and for storing that voltage to provide an output signal which is a steady d-c voltage.

  12. High temperature electron transport properties in AlGaN/GaN heterostructures

    NASA Astrophysics Data System (ADS)

    Tokuda, H.; Yamazaki, J.; Kuzuhara, M.

    2010-11-01

    Hall electron mobility (μH) and sheet concentration (ns) in AlGaN/GaN heterostructures have been measured from 77 to 1020 K. The effect of the deposited Al2O3 layer is also investigated with varying its thickness. It is found that μH decreases monotonously with the temperature (T) and its dependence is well approximated with the function of μH=4.5×103 exp(-0.004T) in the temperatures over 350 K. The function is different from the commonly used one of μH=AT-α (α ˜1.5), which indicates that the mobility is not only governed by the polar optical phonon scattering but also the deformation potential scattering plays a role. The sheet electron concentration (ns) has a weak dependence on the temperature, that is, slightly decreases with temperature in 300-570 K and increases gradually up to 1020 K. The decrease is explained by considering the reduction in the polarization (probably both spontaneous and piezoelectric) charge and the increase seems to be due to the parallel conduction through the interface between GaN buffer layer and sapphire substrate. The dependence of sheet resistance (Rsh) in AlGaN/GaN is compared with that of n-GaN. In the low temperatures, AlGaN/GaN shows a lower Rsh due to its high mobility, however, at the temperatures higher than 350 K, Rsh of AlGaN/GaN becomes higher than that of n-GaN. This result implies that AlGaN/GaN high-electron-mobility-transistors are inferior to GaN metal-semiconductor field-effect transistors in terms of higher source, drain, and channel resistances at high temperature operations, although further investigations on other performances such as output power and reliability are needed. The Al2O3 deposited AlGaN/GaN shows about 15% higher ns than without Al2O3 layer for the whole temperatures. On the contrary, μH at 77 K shows a slight decrease with Al2O3 deposition, which degree is not affected by the layer thickness. In the temperatures higher than 400 K, μH is almost the same for with and without Al2O3 layer.

  13. ELECTRON GUN

    DOEpatents

    Christofilos, N.C.; Ehlers, K.W.

    1960-04-01

    A pulsed electron gun capable of delivering pulses at voltages of the order of 1 mv and currents of the order of 100 amperes is described. The principal novelty resides in a transformer construction which is disposed in the same vacuum housing as the electron source and accelerating electrode structure of the gun to supply the accelerating potential thereto. The transformer is provided by a plurality of magnetic cores disposed in circumferentially spaced relation and having a plurality of primary windings each inductively coupled to a different one of the cores, and a helical secondary winding which is disposed coaxially of the cores and passes therethrough in circumferential succession. Additional novelty resides in the disposition of the electron source cathode filament input leads interiorly of the transformer secondary winding which is hollow, as well as in the employment of a half-wave filament supply which is synchronously operated with the transformer supply such that the transformer is pulsed during the zero current portions of the half-wave cycle.

  14. Rebalance electronics

    NASA Technical Reports Server (NTRS)

    Blalock, T. V.; Kennedy, E. J.

    1972-01-01

    Two basic types of strapdown gyroscope rebalance-electronics were analyzed and compared. These two types were a discrete-pulse ternary system and a width-modulated binary system. In the analyses, major emphasis was placed on the logic sections, the H-switches, the precision voltage reference loops, the noise performance, common-mode rejection, and loop compensation. Results of the analyses were used in identifying specific advantages and disadvantages of system details and in making accuracy and resolution comparisons. Sound engineering principles were applied in the development of both systems; however, it was concluded that each system has some disadvantages that are amenable to improvement.

  15. Rebalance electronics

    NASA Technical Reports Server (NTRS)

    Blalock, T. V.; Kennedy, E. J.

    1972-01-01

    Two basic types of strapdown gyroscope rebalance-electronics were analyzed and compared. These two types were a discrete-pulse ternary system and a width-modulated binary system. In the analyses, major emphasis was placed on the logic sections, the H-switches, the precision voltage reference loops, the noise performance, common-mode rejection, and loop compensation. Results of the analyses were used in identifying specific advantages and disadvantages of system details and in making accuracy and resolution comparisons. Sound engineering principles were applied in the development of both systems; however, it was concluded that each system has some disadvantages that are amenable to improvement.

  16. Electronic Router

    NASA Technical Reports Server (NTRS)

    Crusan, Jason

    2005-01-01

    Electronic Router (E-Router) is an application program for routing documents among the cognizant individuals in a government agency or other organization. E-Router supplants a prior 14 NASA Tech Briefs, May 2005 system in which paper documents were routed physically in packages by use of paper slips, packages could be lost, routing times were unacceptably long, tracking of packages was difficult, and there was a need for much photocopying. E-Router enables a user to create a digital package to be routed. Input accepted by E-Router includes the title of the package, the person(s) to whom the package is to be routed, attached files, and comments to reviewers. Electronic mail is used to notify reviewers of needed actions. The creator of the package can, at any time, see the status of the package in the routing structure. At the end of the routing process, E-Router keeps a record of the package and of approvals and/or concurrences of the reviewers. There are commercial programs that perform the general functions of E-Router, but they are more complicated. E-Router is Web-based, easy to use, and does not require the installation or use of client software.

  17. Epidermal Electronics

    NASA Astrophysics Data System (ADS)

    Kim, Dae-Hyeong; Lu, Nanshu; Ma, Rui; Kim, Yun-Soung; Kim, Rak-Hwan; Wang, Shuodao; Wu, Jian; Won, Sang Min; Tao, Hu; Islam, Ahmad; Yu, Ki Jun; Kim, Tae-il; Chowdhury, Raeed; Ying, Ming; Xu, Lizhi; Li, Ming; Chung, Hyun-Joong; Keum, Hohyun; McCormick, Martin; Liu, Ping; Zhang, Yong-Wei; Omenetto, Fiorenzo G.; Huang, Yonggang; Coleman, Todd; Rogers, John A.

    2011-08-01

    We report classes of electronic systems that achieve thicknesses, effective elastic moduli, bending stiffnesses, and areal mass densities matched to the epidermis. Unlike traditional wafer-based technologies, laminating such devices onto the skin leads to conformal contact and adequate adhesion based on van der Waals interactions alone, in a manner that is mechanically invisible to the user. We describe systems incorporating electrophysiological, temperature, and strain sensors, as well as transistors, light-emitting diodes, photodetectors, radio frequency inductors, capacitors, oscillators, and rectifying diodes. Solar cells and wireless coils provide options for power supply. We used this type of technology to measure electrical activity produced by the heart, brain, and skeletal muscles and show that the resulting data contain sufficient information for an unusual type of computer game controller.

  18. ELECTRON STAINS

    PubMed Central

    Zobel, C. Richard; Beer, Michael

    1961-01-01

    Chemical studies have been carried out on the interaction of DNA with uranyl salts. The effect of variations in pH, salt concentration, and structural integrity of the DNA on the stoichiometry of the salt-substrate complex have been investigated. At pH 3.5 DNA interacts with uranyl ions in low concentration yielding a substrate metal ion complex with a UO2++/P mole ratio of about ½ and having a large association constant. At low pH's (about 2.3) the mole ratio decreases to about ⅓. Destruction of the structural integrity of the DNA by heating in HCHO solutions leads to a similar drop in the amount of metal ion bound. Raising the pH above 3.5 leads to an apparent increase in binding as does increasing the concentration of the salt solution. This additional binding has a lower association constant. Under similar conditions DNA binds about seven times more uranyl ion than bovine serum albumin, indicating useful selectivity in staining for electron microscopy. PMID:13788706

  19. Electronic Preprints

    NASA Astrophysics Data System (ADS)

    Hanisch, R.

    1999-12-01

    Despite the tremendous advances in electronic publications and the increasing rapidity with which papers are now moving from acceptance into ``print,'' preprints continue to be an important mode of communication within the astronomy community. The Los Alamos e-preprint service, astro-ph, provides for rapid and cost-free (to authors and readers) dissemination of manuscripts. As the use of astro-ph has increased the number of paper preprints in circulation to libraries has decreased, and institutional preprint series appear to be waning. It is unfortunate, however, that astro-ph does not function in collaboration with the refereed publications. For example, there is no systematic tracking of manuscripts from preprint to their final, published form, and as a centralized archive it is difficult to distribute the tracking and maintenance functions. It retains documents that have been superseded or have become obsolete. We are currently developing a distributed preprint and document management system which can support both distributed collections of preprints (e.g., traditional institutional preprint series), can link to the LANL collections, can index other documents in the ``grey'' literature (observatory reports, telescope and instrument user's manuals, calls for proposals, etc.), and can function as a manuscript submission tool for the refereed journals. This system is being developed to work cooperatively with the refereed literature so that, for example, links to preprints are updated to links to the final published papers.

  20. Sustainable Management of Electronics

    EPA Pesticide Factsheets

    To provide information on EPAs strategy for electronics stewardship, certified electronics recyclers and the Challenge; as well as where to donate unwanted electronics, how to calculate benefits, and what's going on with electronics mgmt in their states.

  1. EDITORIAL: Synaptic electronics Synaptic electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Gimzewski, James K.; Vuillaume, Dominique

    2013-09-01

    Conventional computers excel in logic and accurate scientific calculations but make hard work of open ended problems that human brains handle easily. Even von Neumann—the mathematician and polymath who first developed the programming architecture that forms the basis of today's computers—was already looking to the brain for future developments before his death in 1957 [1]. Neuromorphic computing uses approaches that better mimic the working of the human brain. Recent developments in nanotechnology are now providing structures with very accommodating properties for neuromorphic approaches. This special issue, with guest editors James K Gimzewski and Dominique Vuillaume, is devoted to research at the serendipitous interface between the two disciplines. 'Synaptic electronics', looks at artificial devices with connections that demonstrate behaviour similar to synapses in the nervous system allowing a new and more powerful approach to computing. Synapses and connecting neurons respond differently to incident signals depending on the history of signals previously experienced, ultimately leading to short term and long term memory behaviour. The basic characteristics of a synapse can be replicated with around ten simple transistors. However with the human brain having around 1011 neurons and 1015 synapses, artificial neurons and synapses from basic transistors are unlikely to accommodate the scalability required. The discovery of nanoscale elements that function as 'memristors' has provided a key tool for the implementation of synaptic connections [2]. Leon Chua first developed the concept of the 'The memristor—the missing circuit element' in 1971 [3]. In this special issue he presents a tutorial describing how memristor research has fed into our understanding of synaptic behaviour and how they can be applied in information processing [4]. He also describes, 'The new principle of local activity, which uncovers a minuscule life-enabling "Goldilocks zone", dubbed the

  2. Joint Services Electronics Program.

    DTIC Science & Technology

    1987-12-31

    neceeemar and Identify by black number) INFORMATION ELECTRONICS QUANTUM ELECTRONICS SOLID STATE ELECTRONICS ELECTROMAGNETICS 20. ABSTRACT (Continue an...Electromagnetics, two in Quantum Electronics, and two in Information Electrn, i DD N 1473 EDITION OF I NOV OS IS OBSOLETED J, A"" UNCLASSIFIED...units in Solid State Electronics, two in Electromagnetics, two in Quantum Electronics, and two in Information Electronics. The Solid State Electronics

  3. Electron-electron interaction in ballistic electron beams

    NASA Astrophysics Data System (ADS)

    Müller, F.; Lengeler, B.; Schäpers, Th.; Appenzeller, J.; Förster, A.; Klocke, Th.; Lüth, H.

    1995-02-01

    The transport of ballistic electrons emitted and detected by adjacent point contacts in a two-dimensional electron gas (2DEG) in the system GaAs/AlxGa1-xAs was measured at 1.2 K as a function of the emitter current. Hot carriers with a surplus energy up to 15 meV above the Fermi level were generated by the current flow. It is shown that electron-electron scattering is the main limitation for the quasiparticle lifetime. The experimental data for the ballistic electron propagation from emitter to detector are explained without free parameters by a theory developed by Chaplik and by Giuliani and Quinn. In addition, it is shown that crossing ballistic electron beams in a 2DEG interact with one another, if one of the beams contains hot electrons in the zone of interaction. Experiments on the influence of impurities on the mean free path of ballistic electrons should be done with currents as low as 10 nA. Otherwise, the mean free path contains a contribution from electron-electron scattering. Electron-electron interaction of hot carriers is a serious basic limitation for future devices based on the transport of electrons in the mesoscopic transport regime.

  4. Electronic Mimosa

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjay; Datta, Meera S.; Rana, Vivek; Grover, Shailesh

    1996-04-01

    This paper describes the design of a low-cost, 2D, electromagnetic tracking device for personal computers. This interface makes use of the well-known principle of electromagnetic induction to locate the position of a transmitter in an x-y plane. This device has a ring which is worn by the user on the index finger. The computer monitor is overlaid with a transparent screen equipped with tuned electromagnetic sensors. These sensors pick up the signals transmitted by the transmitter coil on the finger. The receiver circuit extracts the envelope of the received signal and digitizes it. These digitized values of x and y axis signals are read by the computer through the standard parallel port. The system software running on the computer calculates the x and y co-ordinates of the transmitter coil and displays a cursor at that location. The transmitter also has a button which can be used like a mouse button. This keypress information is also transmitted by the electromagnetic means. The device driver for this tracker replaces the standard mouse driver. Hence most applications which use a mouse can also use this tracker. Its name `Mimosa' indicates that the user need not touch the screen (Mimosa Pudica is the Latin name of a plant whose leaves wilt when touched). Presently work is on to achieve uniform sensitivity over the entire screen and reducing transmitter power consumption. In order to demonstrate its working, a small, 3D game was written. The player has to reach a pre-defined location after traversing through a maze. The paper describes the interface electronics, system software, mechanical design and the sample application.

  5. Carbon nanotube electron gun

    NASA Technical Reports Server (NTRS)

    Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

    2010-01-01

    An electron gun, an electron source for an electron gun, an extractor for an electron gun, and a respective method for producing the electron gun, the electron source and the extractor are disclosed. Embodiments provide an electron source utilizing a carbon nanotube (CNT) bonded to a substrate for increased stability, reliability, and durability. An extractor with an aperture in a conductive material is used to extract electrons from the electron source, where the aperture may substantially align with the CNT of the electron source when the extractor and electron source are mated to form the electron gun. The electron source and extractor may have alignment features for aligning the electron source and the extractor, thereby bringing the aperture and CNT into substantial alignment when assembled. The alignment features may provide and maintain this alignment during operation to improve the field emission characteristics and overall system stability of the electron gun.

  6. Carbon Nanotube Electron Gun

    NASA Technical Reports Server (NTRS)

    Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

    2013-01-01

    An electron gun, an electron source for an electron gun, an extractor for an electron gun, and a respective method for producing the electron gun, the electron source and the extractor are disclosed. Embodiments provide an electron source utilizing a carbon nanotube (CNT) bonded to a substrate for increased stability, reliability, and durability. An extractor with an aperture in a conductive material is used to extract electrons from the electron source, where the aperture may substantially align with the CNT of the electron source when the extractor and electron source are mated to form the electron gun. The electron source and extractor may have alignment features for aligning the electron source and the extractor, thereby bringing the aperture and CNT into substantial alignment when assembled. The alignment features may provide and maintain this alignment during operation to improve the field emission characteristics and overall system stability of the electron gun.

  7. Electron beam generation in Tevatron electron lenses

    SciTech Connect

    Kamerdzhiev, V.; Kuznetsov, G.; Shiltsev, V.; Solyak, N.; Tiunov, M.; /Novosibirsk, IYF

    2006-08-01

    New type of high perveance electron guns with convex cathode has been developed. Three guns described in this article are built to provide transverse electron current density distributions needed for Electron Lenses for beam-beam compensation in the Tevatron collider. The current distribution can be controlled either by the gun geometry or by voltage on a special control electrode located near cathode. We present the designs of the guns and report results of beam measurements on the test bench. Because of their high current density and low transverse temperature of electrons, electron guns of this type can be used in electron cooling and beam-beam compensation devices.

  8. Optically pulsed electron accelerator

    DOEpatents

    Fraser, J.S.; Sheffield, R.L.

    1985-05-20

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  9. Optically pulsed electron accelerator

    DOEpatents

    Fraser, John S.; Sheffield, Richard L.

    1987-01-01

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  10. Backstreaming Electrons Associated With Solar Electron Bursts

    NASA Astrophysics Data System (ADS)

    Skoug, R. M.; Steinberg, J. T.; de Koning, C. A.; Gosling, J. T.; McComas, D. J.

    2007-12-01

    Solar electron bursts are frequently observed in the ACE/SWEPAM suprathermal electron measurements at energies below 1.4 keV. A significant fraction of such events show backscattered electrons, beginning after the burst onset and traveling back towards the Sun along the magnetic field direction. Such backscattered particles imply a scattering mechanism beyond the spacecraft location. Some bursts also show backstreaming conic distributions, implying mirroring at magnetic field enhancements beyond the spacecraft. Here we present a study of these backstreaming particles during solar electron events. We examine the occurrence of backstreaming electrons and their relationship to other burst characteristics such as pitch angle width, duration, and energy range. We also investigate the time delay between burst onset and the appearance of backscattered electrons, including energy and pitch-angle dispersion. We examine the pitch angle distribution and energy dependence of backstreaming electrons, and consider possible origins of these electron distributions and their relationship to solar wind structure beyond the spacecraft.

  11. Nano-Electronics and Bio-Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Kwak, Dochan (Technical Monitor)

    2001-01-01

    Viewgraph presentation on Nano-Electronics and Bio-Electronics is discussed. Topics discussed include: NASA Ames nanotechnology program, Potential Carbon Nanotube (CNT) application, CNT synthesis,Computational Nanotechnology, and protein nanotubes.

  12. Ballistic-electron-emission spectroscopy of Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures: Conduction-band offsets, transport mechanisms, and band-structure effects

    SciTech Connect

    OShea, J.J.; Brazel, E.G.; Rubin, M.E.; Bhargava, S.; Chin, M.A.; Narayanamurti, V.

    1997-07-01

    We report an extensive investigation of semiconductor band-structure effects in single-barrier Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0{le}x{le}1). The initial ({Gamma}) BEES thresholds for Al{sub x}Ga{sub 1{minus}x}As single barriers with 0{le}x{le}0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements at 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime ({ital x}{gt}0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al{sub x}Ga{sub 1{minus}x}As {ital X} valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al{sub x}Ga{sub 1{minus}x}As interface produces a significant fraction of this{ital X} valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al{sub x}Ga{sub 1{minus}x}As {Gamma}, {ital L}, and {ital X} points yields good agreement over the entire composition range. {copyright} {ital 1997} {ital The American Physical Society}

  13. Interface Electronic Circuitry for an Electronic Tongue

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Buehler, Martin

    2007-01-01

    Electronic circuitry has been developed to serve as an interface between an electronic tongue and digital input/output boards in a laptop computer that is used to control the tongue and process its readings. Electronic tongues can be used for a variety of purposes, including evaluating water quality, analyzing biochemicals, analyzing biofilms, and measuring electrical conductivities of soils.

  14. Advances in electronics and electron physics

    SciTech Connect

    Hawkes, P.W. )

    1990-01-01

    This book contains information on electronics and electron physics. Topics covered include: Theory of the Gaseous Detector Device in the ESEM; Carrier Transport in Bulk Silicon and in Weak Silicon Inversion Layers; and Emission-Imaging Electron-Optical System Design.

  15. Electron microscope aperture system

    NASA Technical Reports Server (NTRS)

    Heinemann, K. (Inventor)

    1976-01-01

    An electron microscope including an electron source, a condenser lens having either a circular aperture for focusing a solid cone of electrons onto a specimen or an annular aperture for focusing a hollow cone of electrons onto the specimen, and an objective lens having an annular objective aperture, for focusing electrons passing through the specimen onto an image plane are described. The invention also entails a method of making the annular objective aperture using electron imaging, electrolytic deposition and ion etching techniques.

  16. Electron beam focusing system

    SciTech Connect

    Dikansky, N.; Nagaitsev, S.; Parkhomchuk, V.

    1997-09-01

    The high energy electron cooling requires a very cold electron beam. Thus, the electron beam focusing system is very important for the performance of electron cooling. A system with and without longitudinal magnetic field is presented for discussion. Interaction of electron beam with the vacuum chamber as well as with the background ions and stored antiprotons can cause the coherent electron beam instabilities. Focusing system requirements needed to suppress these instabilities are presented.

  17. Electronic Correlations in Electron Transfer Systems

    NASA Astrophysics Data System (ADS)

    Bulla, Ralf; Tornow, Sabine; Anders, Frithjof

    Electron transfer processes play a central role in many chemical and biological systems. Already the transfer of a single electron from the donor to the acceptor can be viewed as a complicated many-body problem, due to the coupling of the electron to the infinitely many environmental degrees of freedom, realized by density fluctuations of the solvent or molecular vibrations of the protein matrix. We focus on the quantum mechanical modelling of two-electron transfer processes whose dynamics is governed by the Coulomb interaction between the electrons as well as the environmental degrees of freedoms represented by a bosonic bath. We identify the regime of parameters in which concerted transfer of the two electrons occurs and discuss the influence of the Coulomb repulsion and the coupling strength to the environment on the electron transfer rate. Calculations are performed using the non-perturbative numerical renormalization group approach for both equilibrium and non-equilibrium properties.

  18. OPTOELECTRONIC FUNCTIONAL ELECTRONIC BLOCKS.

    DTIC Science & Technology

    INTEGRATED CIRCUITS, SEMICONDUCTOR DEVICES, ELECTRON OPTICS, COUPLING CIRCUITS, PULSE AMPLIFIERS, OPTICAL GLASS, GALLIUM ALLOYS, ARSENIDES, SPECTRUM ANALYZERS, LIGHT TRANSMISSION, MODULES( ELECTRONICS ).

  19. BEEM 94. Annual Workshop on Ballistic Electron Emission Microscopy (5th) Held in New York on January 24, 1994

    DTIC Science & Technology

    1994-01-24

    Bell, W. J. Kaiser, A. M. Milliken, R. W. Fathauer, and M. H. Hecht: "BEEM studies of strain-tuned 5 semiconductor interfaces." I T. SajotoJj...O’Shea, S. Bhargava, D. Leonard, MA. Chin, and V. Narayanamurti: "Transport studies in semiconductor 6 heterostructures using BEEM." I L. Samuelson, J...Kavanagh,AA TaM, T. Ngo, and &S. Williams: "Nanoscopic barrier 2 height distributions at metal/ semiconductor interfaces and observation of critical

  20. Electron-attachment processes

    NASA Astrophysics Data System (ADS)

    Christophorou, L. G.; McCorkle, D. L.; Christodoulides, A. A.

    Topics covered include: modes of production of negative ions, techniques for the study of electron attachment processes, dissociative electron attachment to ground state molecules, dissociative electron attachment to hot molecules (effects of temperature on dissociative electron attachment), molecular parent negative ions, and negative ions formed by ion pair processes and by collisions of molecules with ground state and Rydberg atoms.

  1. Electronic Networking. ERIC Digest.

    ERIC Educational Resources Information Center

    Tucker, Susan

    This digest discusses several aspects of electronic networking, including network functions, implementation, and applications in education. Electronic networking is defined as including the four basic services of electronic mail (E-mail), electronic "bulletin boards," teleconferencing, and online databases, and an overview of these four…

  2. Introduction to Electronic Marketing.

    ERIC Educational Resources Information Center

    Dilbeck, Lettie

    These materials for a five-unit course were developed to introduce secondary and postsecondary students to the use of electronic equipment in marketing. The units cover the following topics: electronic marketing as a valid marketing approach; telemarketing; radio electronic media marketing; television electronic media marketing; and cable TV…

  3. Ballistic Electron Emission Microscopy (BEEM) of Au/Al/GaAs Schottky barriers under Ultra High Vacuum conditions

    NASA Astrophysics Data System (ADS)

    Mani, R. G.; Narayanamurti, V.

    2000-03-01

    BEEM investigations of the Au/GaAs system have reported substantial redirection of the ballistic current into the L-valley of GaAs, based on a study of the I-V spectroscopic measurement. The result has been attributed to the absence of conservation of interface parallel wave-vector in the non-epitaxial Au/GaAs system. Theory has modeled the effect and it suggests an interesting scenario based on a progressive redistribution of the ballistic current between the relevant bands as a function of scattering strength at the interface. Experiments reported here attempt to investigate this regime by examining BEEM in Au/Al/GaAs Schottky barrier devices that preserve the topographic image of Au at the metal surface, while changing the metal semiconductor interface by placing Al between the surface Au surface layer and the GaAs substrate. As aluminum has been reported to grow epitaxially on GaAs, this approach has been pursued here in the hopes of realizing a metal-semiconductor device with varying degree of interfacial order depending upon growth conditions. Thus, we have fabricated Au/Al/GaAs Schottky barrier devices in a three chamber UHV system and subsequently carried out BEEM measurements between 90 K and 300 K. Collector current images and spectroscopic results obtained in such specimens will be compared with expectations based on relevant theory in order to obtain possible new insight into interface scattering in metal semiconductor structures.

  4. Imaging Electronic Motion with Attosecond Electron Pulses

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2010-03-01

    Ultrashort electron pulses have been proposed to observe time-dependent phenomena in atoms and molecules [1]. Owing to the temporal and spatial resolutions of short keV electron pulses, studying electronic motion in attosecond and sub-Angstrom regimes is feasible. We report benchmark calculations for oscillating electronic charge distributions in the H atom and in the H2^+ molecule to determine the effect of such charge oscillations on the elastic scattering cross section for a sub-fs electron pulse. In the pump/probe calculations, a femtosecond laser pulse is used to excite a coherent superposition of states, whose charge distribution oscillates with the beat frequency. The electron pulse scattering cross sections are calculated in the Born approximation. For the H atom, the cross section exhibits an oscillating effective radius. For the H2^+ molecules, the superposed state is chosen such that the electronic charge distribution oscillates from one nucleus to the other; hence, the differential cross section shows the localization of the electron.[4pt] [1] P. Baum and A.H. Zewail, PNAS 104, 18409 (2007).

  5. Electron transporting semiconducting polymers in organic electronics.

    PubMed

    Zhao, Xingang; Zhan, Xiaowei

    2011-07-01

    Significant progress has been achieved in the preparation of semiconducting polymers over the past two decades, and successful commercial devices based on them are slowly beginning to enter the market. However, most of the conjugated polymers are hole transporting, or p-type, semiconductors that have seen a dramatic rise in performance over the last decade. Much less attention has been devoted to electron transporting, or n-type, materials that have lagged behind their p-type counterparts. Organic electron transporting materials are essential for the fabrication of organic p-n junctions, organic photovoltaic cells (OPVs), n-channel organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and complementary logic circuits. In this critical review we focus upon recent developments in several classes of electron transporting semiconducting polymers used in OLEDs, OFETs and OPVs, and survey and analyze what is currently known concerning electron transporting semiconductor architecture, electronic structure, and device performance relationships (87 references).

  6. A combined electron beam/optical lithography process step for the fabrication of sub-half-micron-gate-length MMIC chips

    NASA Technical Reports Server (NTRS)

    Sewell, James S.; Bozada, Christopher A.

    1994-01-01

    eliminating an entire lithography/metallization/lift-off process sequence. This technique has been proven to be reliable for both trapezoidal and mushroom gates and has been successfully applied to metal-semiconductor and high-electron-mobility field-effect transistor (MESFET and HEMT) wafers containing devices with gate lengths down to 0.10 micron and 75 x 75 micron gate pads. The yields and throughput of these wafers have been very high with no loss in device performance. We will discuss the entire EBOL process technology including the multilayer resist structure, exposure conditions, process sensitivities, metal edge definition, device results, comparison to the standard gate-layer process, and its suitability for manufacturing.

  7. A combined electron beam/optical lithography process step for the fabrication of sub-half-micron-gate-length MMIC chips

    NASA Astrophysics Data System (ADS)

    Sewell, James S.; Bozada, Christopher A.

    1994-02-01

    eliminating an entire lithography/metallization/lift-off process sequence. This technique has been proven to be reliable for both trapezoidal and mushroom gates and has been successfully applied to metal-semiconductor and high-electron-mobility field-effect transistor (MESFET and HEMT) wafers containing devices with gate lengths down to 0.10 micron and 75 x 75 micron gate pads. The yields and throughput of these wafers have been very high with no loss in device performance. We will discuss the entire EBOL process technology including the multilayer resist structure, exposure conditions, process sensitivities, metal edge definition, device results, comparison to the standard gate-layer process, and its suitability for manufacturing.

  8. Cosmic electrons. [literature review

    NASA Technical Reports Server (NTRS)

    Ramaty, R.

    1974-01-01

    The published literature on cosmic electrons is summarized. The primary and secondary sources of cosmic electrons are discussed, and the propagation of the electrons in the interstellar medium is studied with respect to energy loss mechanisms, age distributions, and spectral modifications during flight. Various portions of the electron and positron spectra are then considered in relation to problems of astrophysics. New information is presented on such topics as the origin of low-energy positrons, the decay kinematics of the pi-mu-e process, the application of age distributions for nuclear cosmic rays to cosmic electrons, and the possibility of nonidentical sources for cosmic electrons and protons.

  9. RHIC electron lenses upgrades

    SciTech Connect

    Gu, X.; Altinbas, Z.; Bruno, D.; Binello, S.; Costanzo, M.; Drees, A.; Fischer, W.; Gassner, D. M.; Hock, J.; Hock, K.; Harvey, M.; Luo, Y.; Marusic, A.; Mi, C.; Mernick, K.; Minty, M.; Michnoff, R.; Miller, T. A.; Pikin, A. I.; Robert-Demolaize, G.; Samms, T.; Shrey, T. C.; Schoefer, V.; Tan, Y.; Than, R.; Thieberger, P.; White, S. M.

    2015-05-03

    In the Relativistic Heavy Ion Collider (RHIC) 100 GeV polarized proton run in 2015, two electron lenses were used to partially compensate for the head-on beam-beam effect for the first time. Here, we describe the design of the current electron lens, detailing the hardware modifications made after the 2014 commissioning run with heavy ions. A new electron gun with 15-mm diameter cathode is characterized. The electron beam transverse profile was measured using a YAG screen and fitted with a Gaussian distribution. During operation, the overlap of the electron and proton beams was achieved using the electron backscattering detector in conjunction with an automated orbit control program.

  10. High energy electron cooling

    SciTech Connect

    Parkhomchuk, V.

    1997-09-01

    High energy electron cooling requires a very cold electron beam. The questions of using electron cooling with and without a magnetic field are presented for discussion at this workshop. The electron cooling method was suggested by G. Budker in the middle sixties. The original idea of the electron cooling was published in 1966. The design activities for the NAP-M project was started in November 1971 and the first run using a proton beam occurred in September 1973. The first experiment with both electron and proton beams was started in May 1974. In this experiment good result was achieved very close to theoretical prediction for a usual two component plasma heat exchange.

  11. Electronic Commerce and Competitive Procurement

    DTIC Science & Technology

    1991-06-01

    Explains the application of electronic commerce techniques (electronic data interchange (EDI), electronic mail (E-mail), electronic bulletin boards...purchase procedures of the Federal Acquisition Regulation (FAR). Changes to the FAR to recognize electronic commerce are recommended. Also discussed...are opportunities to use electronic commerce and small business and legal considerations of electronic commerce . This report describes how electronic

  12. Narrow electron injector for ballistic electron spectroscopy

    SciTech Connect

    Kast, M.; Pacher, C.; Strasser, G.; Gornik, E.

    2001-06-04

    A three-terminal hot electron transistor is used to measure the normal energy distribution of ballistic electrons generated by an electron injector utilizing an improved injector design. A triple barrier resonant tunneling diode with a rectangular transmission function acts as a narrow (1 meV) energy filter. An asymmetric energy distribution with its maximum on the high-energy side with a full width at half maximum of {Delta}E{sub inj}=10 meV is derived. {copyright} 2001 American Institute of Physics.

  13. Nondestructive Superresolution Imaging of Defects and Nonuniformities in Metals, Semiconductors, Dielectrics, Composites, and Plants Using Evanescent Microwaves

    NASA Technical Reports Server (NTRS)

    Tabib-Azar, M.; Pathak, P. S.; Ponchak, G.; LeClair, S.

    1999-01-01

    We have imaged and mapped material nonuniformities and defects using microwaves generated at the end of a microstripline resonator with 0.4 micrometer lateral spatial resolution at 1 GHz. Here we experimentally examine the effect of microstripline substrate permittivity, the feedline-to-resonator coupling strength, and probe tip geometry on the spatial resolution of the probe. Carbon composites, dielectrics, semiconductors, metals, and botanical samples were scanned for defects, residual stresses, subsurface features, areas of different film thickness, and moisture content. The resulting evanescent microwave probe (EMP) images are discussed. The main objective of this work is to demonstrate the overall capabilities of the EMP imaging technique as well as to discuss various probe parameters that can be used to design EMPs for different applications.

  14. Metal-Semiconductor Nanoparticle Hybrids Formed by Self-Organization: A Platform to Address Exciton-Plasmon Coupling.

    PubMed

    Strelow, Christian; Theuerholz, T Sverre; Schmidtke, Christian; Richter, Marten; Merkl, Jan-Philip; Kloust, Hauke; Ye, Ziliang; Weller, Horst; Heinz, Tony F; Knorr, Andreas; Lange, Holger

    2016-08-10

    Hybrid nanosystems composed of excitonic and plasmonic constituents can have different properties than the sum of of the two constituents, due to the exciton-plasmon interaction. Here, we report on a flexible model system based on colloidal nanoparticles that can form hybrid combinations by self-organization. The system allows us to tune the interparticle distance and to combine nanoparticles of different sizes and thus enables a systematic investigation of the exciton-plasmon coupling by a combination of optical spectroscopy and quantum-optical theory. We experimentally observe a strong influence of the energy difference between exciton and plasmon, as well as an interplay of nanoparticle size and distance on the coupling. We develop a full quantum theory for the luminescence dynamics and discuss the experimental results in terms of the Purcell effect. As the theory describes excitation as well as coherent and incoherent emission, we also consider possible quantum optical effects. We find a good agreement of the observed and the calculated luminescence dynamics induced by the Purcell effect. This also suggests that the self-organized hybrid system can be used as platform to address quantum optical effects.

  15. Nondestructive Superresolution Imaging of Defects and Nonuniformities in Metals, Semiconductors, Dielectrics, Composites, and Plants Using Evanescent Microwaves

    NASA Technical Reports Server (NTRS)

    Tabib-Azar, M.; Pathak, P. S.; Ponchak, G.; LeClair, S.

    1999-01-01

    We have imaged and mapped material nonuniformities and defects using microwaves generated at the end of a microstripline resonator with 0.4 micrometer lateral spatial resolution at 1 GHz. Here we experimentally examine the effect of microstripline substrate permittivity, the feedline-to-resonator coupling strength, and probe tip geometry on the spatial resolution of the probe. Carbon composites, dielectrics, semiconductors, metals, and botanical samples were scanned for defects, residual stresses, subsurface features, areas of different film thickness, and moisture content. The resulting evanescent microwave probe (EMP) images are discussed. The main objective of this work is to demonstrate the overall capabilities of the EMP imaging technique as well as to discuss various probe parameters that can be used to design EMPs for different applications.

  16. Metal-Semiconductor Reaction Phenomena and Microstructural Investigations of Laser-Induced Regrowth of Silicon on Insulators.

    DTIC Science & Technology

    1981-01-01

    RflOl’, was obtained. A series of 1, 3 and 5 scan frames were performed with the douhle layer "source-cap" remaining on the substrate. A Van der Pauw Technique...minutes lo,,qer at 9004C. A series of 5 scans inducinq a maximum temperature of about RO0C was then performed. A differential van der Pauw technique...A) FIGURE 6. ELECTRICAL PROFILES FOR Sn OBTAINED USING A DIFFERENTIAL VAN DER PAUW TECHNIQUE. 20 A uub~tJ oA’A 2000 A FIGURE 7. BRIGHT-FIELD

  17. The Effect of Dynamical Image Forces on The Transport Properties of Charge Carriers and Excitons in Metal-Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Cherqui, Charles

    We examine coupled metal nanoparticle/semiconductor hybrid nano-stuctures and analyze the effect that the surface response metal nanoparticles (MNP) has on the transport properties of the system. This analysis is accomplished by treating surface plasmons as quantum oscillators. We find that charge carriers traveling in the nearby semiconductors experience a repulsion due to the ground state energy of the quantum SP (QSP). This effect is shown to be the quantum analogue of the ponderomotive effect found in plasma physics. We then extend the theory to examine the transport properties of carbon nano-tube excitons in the presence of localized SPs and show that this system maps onto a Fano-Anderson Hamiltonian. Through numerical simulation, we show that the emission patterns of the system are severely modified by the presence of localized surface plasmons.

  18. Development of new generation of perovskite based noble metal/semiconductor photocatalysts for visible-light-driven hydrogen production

    NASA Astrophysics Data System (ADS)

    Shen, Peichuan

    In recent decades, semiconductor photocatalysis has attracted a growing attention as a possible alternative to existing methods of hydrogen production, hydrocarbon conversion and organic compound oxidation. Many types of photocatalysts have been developed and tested for photocatalytic applications. However, most of them do not have notable activity in visible light region, which limits their practical applications. Development of photocatalysts, which can be activated by visible light provides a promising way forward to utilize both UV and visible portions of solar spectrum. In this thesis, two main methods to advance visible light driven photocatalysis, such as bandgap modification through doping and co-catalyst development, are investigated. The photocatalysts studied in this thesis included CdS and SrTiO3, which were extensively investigated and characterized. Rhodium doped strontium titanate was synthesized through different preparation methods. The synthesized samples have been investigated by various characterization techniques including XRD, TEM, STEM, XPS and UV-Vis spectroscopy. The effect of preparation conditions, such as doping concentration, calcination temperature and pH have been investigated and optimized. In addition, the photocatalytic activities for hydrogen production of the samples synthesized by different preparation methods were also studied. Among the preparation methods, polymerizable complex (PC) method was found to be the most effective synthesis method for SrTiO3: Rh. The samples prepared by PC method had higher photocatalytic activity as compared to that of samples synthesized by solid state reaction method and hydrothermal method. The reasons might be attributed to more effective doping and higher surface area. The results of this work suggest that PC method can also be applied to develop other perovskite materials for photocatalytic applications. Co-catalyst development for enhancement of photocatalytic hydrogen production is also described in this dissertation. Noble metal nanoparticles have been proved to be effective co-catalysts due to their unique physical and chemical properties. Au and Pt nanoparticles with different sizes were synthesized and deposited on CdS. Sub-nanometer Au and Pt were found to be promising co-catalysts for photocatalytic hydrogen production reaction. Specifically, sub-nm Au and sub-nm Pt nanoparticles were found to enhance the photocatalytic activity in hydrogen production of CdS by 35 and 15 times respectively. Other noble metal co-catalysts, such as Ru, Pd and Rh were also deposited on CdS and their photocatalytic activities were investigated. Additionally, a novel chamber for photocatalytic reactions was developed as a part of this dissertation. The reaction chamber has several unique features allowing different reactions and measurements. The reactor was proved to be suitable for future projects in photocatalysis such as photocatalytic CO2 conversion into hydrocarbons.

  19. Influence of annealing on the metal/semiconductor contacts deposited on sulfur-treated n-GaAs surface

    SciTech Connect

    Erofeev, E. V.; Kagadei, V. A.

    2011-09-15

    Comparative analysis of the influence of thermal annealing on Ge/Au/Ni-, Ge/Au/Ti/Au-, and Ge/Au/Ni/Ti/Au-based ohmic contacts and Ti/Au-based Schottky contacts deposited on an n-GaAs (100) surface treated and nontreated in (NH{sub 4}){sub 2}S aqueous solution have been performed. Annealing conditions for ohmic contacts are found that lead to a decrease in the specific contact resistance of sulfur-treated samples by a factor of 2.5-15 in comparison with the nontreated samples. Optimal annealing conditions are also determined for sulfur-treated GaAs samples with Schottky contacts, which make it possible to reduce the ideality factor and increase the barrier height and the breakdown voltage with respect to the nontreated samples.

  20. Nondestructive superresolution imaging of defects and nonuniformities in metals, semiconductors, dielectrics, composites, and plants using evanescent microwaves

    NASA Astrophysics Data System (ADS)

    Tabib-Azar, M.; Pathak, P. S.; Ponchak, G.; LeClair, S.

    1999-06-01

    We have imaged and mapped material nonuniformities and defects using microwaves generated at the end of a microstripline resonator with 0.4 μm lateral spatial resolution at 1 GHz. Here we experimentally examine the effect of microstripline substrate permittivity, the feedline-to-resonator coupling strength, and probe tip geometry on the spatial resolution of the probe. Carbon composites, dielectrics, semiconductors, metals, and botanical samples were scanned for defects, residual stresses, subsurface features, areas of different film thickness, and moisture content. The resulting evanescent microwave probe (EMP) images are discussed. The main objective of this work is to demonstrate the overall capabilities of the EMP imaging technique as well as to discuss various probe parameters that can be used to design EMPs for different applications.

  1. Theoretical study of the effect of an AlGaAs double heterostructure on metal-semiconductor-metal photodetector performance

    NASA Technical Reports Server (NTRS)

    Salem, Ali F.; Smith, Arlynn W.; Brennan, Kevin F.

    1994-01-01

    The sizing and efficiency of an aircraft is largely determined by the performance of its high-lift system. Subsonic civil transports most often use deployable multi-element airfoils to achieve the maximum-lift requirements for landing, as well as the high lift-to-drag ratios for take-off. However, these systems produce very complex flow fields which are not fully understood by the scientific community. In order to compete in today's market place, aircraft manufacturers will have to design better high-lift systems. Therefore, a more thorough understanding of the flows associated with these systems is desired. Flight and wind-tunnel experiments have been conducted on NASA Langley's B737-100 research aircraft to obtain detailed full-scale flow measurements on a multi-element high-lift system at various flight conditions. As part of this effort, computational aerodynamic tools are being used to provide preliminary flow-field information for instrumentation development, and to provide additional insight during the data analysis and interpretation process. The purpose of this paper is to demonstrate the ability and usefulness of a three-dimensional low-order potentialflow solver, PMARC, by comparing computational results with data obtained from 1/8 scale wind-tunnel tests. Overall, correlation of experimental and computational data reveals that the panel method is able to predict reasonably well the pressures of the aircraft's multi-element wing at several spanwise stations. PMARC's versatility and usefulness is also demonstrated by accurately predicting inviscid threedimensional flow features for several intricate geometrical regions.

  2. Thermal ionization induced metal-semiconductor transition and room temperature ferromagnetism in trivalent doped ZnO codoped with lithium

    SciTech Connect

    Sivagamasundari, A.; Chandrasekar, S.; Pugaze, R.; Kannan, R.; Rajagopan, S.

    2014-03-07

    Thermal ionization induced metallic to semiconductor (MST) transition occurring at 460 K for Zn{sub 0.97}Al{sub 0.03}O, 463 K for Zn{sub 0.94}Al{sub 0.03}Li{sub 0.03}O, and 503 K for Zn{sub 0.91}Al{sub 0.03}Li{sub 0.03}Mn{sub 0.03}O has been found in the sol-gel synthesized (using hexamethylenetetramine), trivalent doped (Al, Mn) ZnO codoped with lithium. Increase in the thermally ionized carrier concentration due to Al doping is responsible for near band edge (NBE) peak shift causing Fermi level to move into conduction band making it metallic consistent with resistivity results. Free carrier (thermally activated) neutralization with ionized donor is responsible for semiconducting nature, which is supported from the free carrier screening produced energy shift in the NBE of photoluminescence peak. Furthermore, independently band gap shrinkage is also obtained from UV-Visible studies confirming localization induced MST. An anti-correlation is found between defect density (DLE) and room temperature ferromagnetism (RTFM) indicating intrinsic defects are not directly responsible for RTFM.

  3. An Evanescent Microwave Probe for Super-Resolution Nondestructive Imaging of Metals, Semiconductors, Dielectrics, Composites and Biological Specimens

    NASA Technical Reports Server (NTRS)

    Pathak, P. S.; Tabib-Azar, M.; Ponchak, G.

    1998-01-01

    Using evanescent microwaves with decay lengths determined by a combination of microwave wavelength (lambda) and waveguide termination geometry, we have imaged and mapped material non-uniformities and defects with a resolving capability of lambda/3800=79 microns at 1 GHz. In our method a microstrip quarter wavelength resonator was used to generate evanescent microwaves. We imaged materials with a wide range of conductivities. Carbon composites, dielectrics (Duroid, polymers), semiconductors (3C-SiC, polysilicon, natural diamond), metals (tungsten alloys, copper, zinc, steel), high-temperature superconductors, and botanical samples were scanned for defects, residual stresses, integrity of brazed junctions, subsurface features, areas of different film thickness and moisture content. The evanescent microwave probe is a versatile tool and it can be used to perform very fast, large scale mapping of a wide range of materials. This method of characterization compares favorably with ultrasound testing, which has a resolution of about 0.1 mm and suffers from high absorption in composite materials and poor transmission across boundaries. Eddy current methods which can have a resolution on the order of 50 microns are restricted to evaluating conducting materials. Evanescent microwave imaging, with careful choice of operating frequency and probe geometry, can have a resolution of up to 1 micron. In this method we can scan hot and moving objects, sample preparation is not required, testing is non-destructive, non-invasive and non-contact, and can be done in air, in liquid or in vacuum.

  4. Fabrication and characterization of magnetically tunable metal-semiconductor schottky diode using barium hexaferrite thin film on gold

    NASA Astrophysics Data System (ADS)

    Kaur, Jotinder; Sharma, Vinay; Sharma, Vipul; Veerakumar, V.; Kuanr, Bijoy K.

    2016-05-01

    Barium Hexaferrite (BaM) is an extensively studied magnetic material due to its potential device application. In this paper, we study Schottky junction diodes fabricated using gold and BaM and demonstrate the function of a spintronic device. Gold (50 nm)/silicon substrate was used to grow the BaM thin films (100-150 nm) using pulsed laser deposition. I-V characteristics were measured on the Au/BaM structure sweeping the voltage from ±5 volts. The forward and reverse bias current-voltage curves show diode like rectifying characteristics. The threshold voltage decreases while the output current increases with increase in the applied external magnetic field showing that the I-V characteristics of the BaM based Schottky junction diodes can be tuned by external magnetic field. It is also demonstrated that, the fabricated Schottky diode can be used as a half-wave rectifier, which could operate at high frequencies in the range of 1 MHz compared to the regular p-n junction diodes, which rectify below 10 kHz. In addition, it is found that above 1 MHz, Au/BaM diode can work as a rectifier as well as a capacitor filter, making the average (dc) voltage much larger.

  5. Thermal ionization induced metal-semiconductor transition and room temperature ferromagnetism in trivalent doped ZnO codoped with lithium

    NASA Astrophysics Data System (ADS)

    Sivagamasundari, A.; Chandrasekar, S.; Pugaze, R.; Rajagopan, S.; Kannan, R.

    2014-03-01

    Thermal ionization induced metallic to semiconductor (MST) transition occurring at 460 K for Zn0.97Al0.03O, 463 K for Zn0.94Al0.03Li0.03O, and 503 K for Zn0.91Al0.03Li0.03Mn0.03O has been found in the sol-gel synthesized (using hexamethylenetetramine), trivalent doped (Al, Mn) ZnO codoped with lithium. Increase in the thermally ionized carrier concentration due to Al doping is responsible for near band edge (NBE) peak shift causing Fermi level to move into conduction band making it metallic consistent with resistivity results. Free carrier (thermally activated) neutralization with ionized donor is responsible for semiconducting nature, which is supported from the free carrier screening produced energy shift in the NBE of photoluminescence peak. Furthermore, independently band gap shrinkage is also obtained from UV-Visible studies confirming localization induced MST. An anti-correlation is found between defect density (DLE) and room temperature ferromagnetism (RTFM) indicating intrinsic defects are not directly responsible for RTFM.

  6. Ag-CuO-ZnO metal-semiconductor multiconcentric nanotubes for achieving superior and perdurable photodegradation.

    PubMed

    Xu, Kaichen; Wu, Jiagen; Tan, Chuan Fu; Ho, Ghim Wei; Wei, Ang; Hong, Minghui

    2017-08-17

    Solar energy represents a robust and natural form of resource for environment remediation via photocatalytic pollutant degradation with minimum associated costs. However, due to the complexity of the photodegradation process, it has been a long-standing challenge to develop reliable photocatalytic systems with low recombination rates, excellent recyclability, and high utilization rates of solar energy, especially in the visible light range. In this work, a ternary hetero-nanostructured Ag-CuO-ZnO nanotube (NT) composite is fabricated via facile and low-temperature chemical and photochemical deposition methods. Under visible light irradiation, the as-synthesized ZnO NT based ternary composite exhibits a greater enhancement (∼300%) of photocatalytic activity than its counterpart, Ag-CuO-ZnO nanorods (NRs), in pollutant degradation. The enhanced photocatalytic capability is primarily attributed to the intensified visible light harvesting, efficient charge carrier separation and much larger surface area. Furthermore, our as-synthesised hybrid ternary Ag-CuO-ZnO NT composite demonstrates much higher photostability and retains ∼98% of degradation efficiency even after 20 usage cycles, which can be mainly ascribed to the more stable polar planes of ZnO NTs than those of ZnO NRs. These results afford a new route to construct ternary heterostructured composites with perdurable performance in sewage treatment and photocorrosion suppression.

  7. Electron Beam Freeform Fabrication

    NASA Image and Video Library

    Electron Beam Freeform Fabrication (EBF3) is a process by which NASA hopes to build metal parts in zero gravity environments. It's a layer-additive process that uses an electron beam and a solid wi...

  8. Catalac free electron laser

    DOEpatents

    Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

    1979-12-12

    A catalac free electron laser using a rf linac (catalac) which acts as a catalyst to accelerate an electron beam in an initial pass through the catalac and decelerate the electron beam during a second pass through the catalac is described. During the second pass through the catalac, energy is extracted from the electron beam and transformed to energy of the accelerating fields of the catalac to increase efficiency of the device. Various embodiments disclose the use of post linacs to add electron beam energy extracted by the wiggler and the use of supplementary catalacs to extract energy at various energy peaks produced by the free electron laser wiggler to further enhance efficiency of the catalac free electron laser. The catalac free electron laser can be used in conjunction with a simple resonator, a ring resonator, or as an amplifier in conjunction with a master oscillator laser.

  9. Catalac free electron laser

    DOEpatents

    Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

    1982-01-01

    A catalac free electron laser using a rf linac (catalac) which acts as a catalyst to accelerate an electron beam in an initial pass through the catalac and decelerate the electron beam during a second pass through the catalac. During the second pass through the catalac, energy is extracted from the electron beam and transformed to energy of the accelerating fields of the catalac to increase efficiency of the device. Various embodiments disclose the use of post linacs to add electron beam energy extracted by the wiggler and the use of supplementary catalacs to extract energy at various energy peaks produced by the free electron laser wiggler to further enhance efficiency of the catalac free electron laser. The catalac free electron laser can be used in conjunction with a simple resonator, a ring resonator or as an amplifier in conjunction with a master oscillator laser.

  10. Relativistic electron beam generator

    DOEpatents

    Mooney, L.J.; Hyatt, H.M.

    1975-11-11

    A relativistic electron beam generator for laser media excitation is described. The device employs a diode type relativistic electron beam source having a cathode shape which provides a rectangular output beam with uniform current density.

  11. Certified Electronics Recyclers

    EPA Pesticide Factsheets

    Learn how EPA encourages all electronics recyclers become certified by demonstrating to an accredited, independent third-party auditor and that they meet specific standards to safely recycle and manage electronics.

  12. Chapter 9: Electronics

    SciTech Connect

    Grupen, Claus; Shwartz, Boris A.

    2006-12-19

    Sophisticated front-end electronics are a key part of practically all modern radiation detector systems. This chapter introduces the basic principles and their implementation. Topics include signal acquisition, electronic noise, pulse shaping (analog and digital), and data readout techniques.

  13. Electronic Submission of Labels

    EPA Pesticide Factsheets

    Pesticide registrants can provide draft and final labels to EPA electronically for our review as part of the pesticide registration process. The electronic submission of labels by registrants is voluntary but strongly encouraged.

  14. Production of solvated electrons

    NASA Technical Reports Server (NTRS)

    Thomas, J. K.

    1969-01-01

    Current research, both theoretical and experimental, relating to the production and kinetics of interactions of solvated electrons is reviewed. Particular attention is focused on solvated electrons generated by ionizing radiation in water, alcohols, and organic systems.

  15. Electron shuttles in biotechnology.

    PubMed

    Watanabe, Kazuya; Manefield, Mike; Lee, Matthew; Kouzuma, Atsushi

    2009-12-01

    Electron-shuttling compounds (electron shuttles [ESs], or redox mediators) are essential components in intracellular electron transfer, while microbes also utilize self-produced and naturally present ESs for extracellular electron transfer. These compounds assist in microbial energy metabolism by facilitating electron transfer between microbes, from electron-donating substances to microbes, and/or from microbes to electron-accepting substances. Artificially supplemented ESs can create new routes of electron flow in the microbial energy metabolism, thereby opening up new possibilities for the application of microbes to biotechnology processes. Typical examples of such processes include halogenated-organics bioremediation, azo-dye decolorization, and microbial fuel cells. Herein we suggest that ESs can be applied widely to create new microbial biotechnology processes.

  16. Atomicity in Electronic Commerce,

    DTIC Science & Technology

    1996-01-01

    tremendous demand for the ability to electronically buy and sell goods over networks. Electronic commerce has inspired a large variety of work... commerce . It then briefly surveys some major types of electronic commerce pointing out flaws in atomicity. We pay special attention to the atomicity...problems of proposals for digital cash. The paper presents two examples of highly atomic electronic commerce systems: NetBill and Cryptographic Postage Indicia.

  17. ADVANCED ELECTRONIC PACKAGING TECHNIQUES

    DTIC Science & Technology

    MICROMINIATURIZATION (ELECTRONICS), *PACKAGED CIRCUITS, CIRCUITS, EXPERIMENTAL DATA, MANUFACTURING, NONDESTRUCTIVE TESTING, RESISTANCE (ELECTRICAL), SEMICONDUCTORS, TESTS, THIN FILMS (STORAGE DEVICES), WELDING.

  18. Electronics materials research

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The electronic materials and is aimed at the establishment of quantitative relationships underlying crystal growth parameters, materials properties, electronic characteristics and device applications. The overall program evolves about the following main thrust areas: (1) crystal growth novel approaches to engineering of semiconductor materials; (2) investigation of materials properties and electronic characteristics on a macro and microscale; (3) surface properties and surface interactions with the bulk and ambients; (4) electronic properties controlling device applications and device performance.

  19. Electronics materials research

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The electronic materials and is aimed at the establishment of quantitative relationships underlying crystal growth parameters, materials properties, electronic characteristics and device applications. The overall program evolves about the following main thrust areas: (1) crystal growth novel approaches to engineering of semiconductor materials; (2) investigation of materials properties and electronic characteristics on a macro and microscale; (3) surface properties and surface interactions with the bulk and ambients; (4) electronic properties controlling device applications and device performance.

  20. Electron Cyclotron Resonances in Electron Cloud Dynamics

    SciTech Connect

    Celata, Christine; Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Yu, Jennifer W.

    2008-06-25

    We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"POSINST" was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. An electron equilibrium density enhancement of up to a factor of 3 was found at magnetic field values for which the bunch frequency is an integral multiple of the electron cyclotron frequency. At low magnetic fields the effects of the resonance are prominent, but when B exceeds ~;;(2 pi mec/(elb)), with lb = bunch length, effects of the resonance disappear. Thus short bunches and low B fields are required for observing the effect. The reason for the B field dependence, an explanation of the dynamics, and the results of the 2D simulations and of a single-particle tracking code used to elucidate details of the dynamics are discussed.

  1. Electron beam device

    DOEpatents

    Beckner, E.H.; Clauser, M.J.

    1975-08-12

    This patent pertains to an electron beam device in which a hollow target is symmetrically irradiated by a high energy, pulsed electron beam about its periphery and wherein the outer portion of the target has a thickness slightly greater than required to absorb the electron beam pulse energy. (auth)

  2. General Electronics Technician.

    ERIC Educational Resources Information Center

    Vorderstrasse, Ron; Huston, Jane, Ed.

    This module follows the "Basic Electronics" module as a guide for a course preparing students for job entry or further education. It includes those additional tasks required above Basic Electronics for job entry in the electronics field. The module contains eight instructional units that cover the following topics: (1) test equipment; (2)…

  3. ELECTRONS IN NONPOLAR LIQUIDS.

    SciTech Connect

    HOLROYD,R.A.

    2002-10-22

    Excess electrons can be introduced into liquids by absorption of high energy radiation, by photoionization, or by photoinjection from metal surfaces. The electron's chemical and physical properties can then be measured, but this requires that the electrons remain free. That is, the liquid must be sufficiently free of electron attaching impurities for these studies. The drift mobility as well as other transport properties of the electron are discussed here as well as electron reactions, free-ion yields and energy levels, Ionization processes typically produce electrons with excess kinetic energy. In liquids during thermalization, where this excess energy is lost to bath molecules, the electrons travel some distance from their geminate positive ions. In general the electrons at this point are still within the coulombic field of their geminate ions and a large fraction of the electrons recombine. However, some electrons escape recombination and the yield that escapes to become free electrons and ions is termed G{sub fi}. Reported values of G{sub fi} for molecular liquids range from 0.05 to 1.1 per 100 eV of energy absorbed. The reasons for this 20-fold range of yields are discussed here.

  4. Geometric Electron Models.

    ERIC Educational Resources Information Center

    Nika, G. Gerald; Parameswaran, R.

    1997-01-01

    Describes a visual approach for explaining the filling of electrons in the shells, subshells, and orbitals of the chemical elements. Enables students to apply the principles of atomic electron configuration while using manipulatives to model the building up of electron configurations as the atomic numbers of elements increase on the periodic…

  5. Electron interaction in matter

    NASA Technical Reports Server (NTRS)

    Dance, W. E.; Rainwater, W. J.; Rester, D. H.

    1969-01-01

    Data on the scattering of 1-MeV electrons in aluminum for the case of non-normal incidence, electron-bremsstrahlung cross-sections in thin targets, and the production of bremstrahlung by electron interaction in thick targets, are presented both in tabular and graphic form. These results may interest physicists and radiologists.

  6. Syringe injectable electronics

    PubMed Central

    Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

    2015-01-01

    Seamless and minimally-invasive three-dimensional (3D) interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating syringe injection and subsequent unfolding of submicrometer-thick, centimeter-scale macroporous mesh electronics through needles with a diameter as small as 100 micrometers. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with > 90% device yield. We demonstrate several applications of syringe injectable electronics as a general approach for interpenetrating flexible electronics with 3D structures, including (i) monitoring of internal mechanical strains in polymer cavities, (ii) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (iii) in vivo multiplexed neural recording. Moreover, syringe injection enables delivery of flexible electronics through a rigid shell, delivery of large volume flexible electronics that can fill internal cavities and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics. PMID:26053995

  7. Embracing Electronic Publishing.

    ERIC Educational Resources Information Center

    Wills, Gordon

    1996-01-01

    Electronic publishing is the grandest revolution in the capture and dissemination of academic and professional knowledge since Caxton developed the printing press. This article examines electronic publishing, describes different electronic publishing scenarios (authors' cooperative, consolidator/retailer/agent oligopsony, publisher oligopoly), and…

  8. TEAM Electron Microscope Animation

    SciTech Connect

    2012-01-01

    The TEAM Electron Microscope, a device that enables atomic-scale imaging in 3-D, has a rotating stage that can hold and position samples inside electron microscopes with unprecedented stability, position-control accuracy, and range of motion.The TEAM Stage makes one of the world's most powerful electron microscopes even better, and enables previously impossible experiments.

  9. Electron measurement in PHENIX

    SciTech Connect

    Akiba, Y.

    1995-07-15

    Electron Measurement in PHENIX detector at RHIC is discussed. The yield and S/N ratio at vector meson peaks ({phi}, {omega}, {rho}{sup o}, and J/{psi}) are evaluated. The electrons from open charm decay, and its consequence to the di-electron measurements is discussed.

  10. Syringe-injectable electronics

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M.

    2015-07-01

    Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

  11. Developing Basic Electronics Aptitudes.

    ERIC Educational Resources Information Center

    Lakeshore Technical Coll., Cleveland, WI.

    This curriculum guide provides materials for basic training in electrical and electronic theory to enable participants to analyze circuits and use test equipment to verify electrical operations and to succeed in the beginning electrical and electronic courses in the Lakeshore Technical College (Wisconsin) electronics programs. The course includes…

  12. Management of Electronic Information.

    ERIC Educational Resources Information Center

    Breaks, Michael

    This paper discusses the management of library collections of electronic information resources within the classical theoretical framework of collection development and management. The first section provides an overview of electronic information resources, including bibliographic databases, electronic journals, journal aggregation services, and…

  13. Mathematics for Electronics.

    ERIC Educational Resources Information Center

    Clary, Joseph R.; Nery, Karen P.

    This set of 20 modules was designed for use primarily to help teach and reinforce the basic mathematics skills in electronics classes. The modules are based on electronics competencies that require mathematics skills, as determined by a panel of high school electronics and mathematics teachers. Each module consists of one or two pages of basic…

  14. Aspects of Electronic Archives.

    ERIC Educational Resources Information Center

    Blake, Monica

    1986-01-01

    Reviews the current status of electronic archiving, especially in Great Britain and the United States, including current use of various electronic storage media; advantages and utilizations of optical disk technology; trends toward full-text databases and increased videotex use; growing quantity of electronic information; and problems in archiving…

  15. Electronic recordkeeping: An introduction

    SciTech Connect

    Deken, J.M.

    2000-01-19

    This paper begins with a brief overview of records and archival management before the advent of the electronic era; then describe the ways in which the definitions and constructs of archives and records management have been altered in the electronic environment; and outlines the various approaches to the challenges of electronic recordkeeping that are currently being investigated and applied.

  16. Geometric Electron Models.

    ERIC Educational Resources Information Center

    Nika, G. Gerald; Parameswaran, R.

    1997-01-01

    Describes a visual approach for explaining the filling of electrons in the shells, subshells, and orbitals of the chemical elements. Enables students to apply the principles of atomic electron configuration while using manipulatives to model the building up of electron configurations as the atomic numbers of elements increase on the periodic…

  17. Syringe-injectable electronics.

    PubMed

    Liu, Jia; Fu, Tian-Ming; Cheng, Zengguang; Hong, Guosong; Zhou, Tao; Jin, Lihua; Duvvuri, Madhavi; Jiang, Zhe; Kruskal, Peter; Xie, Chong; Suo, Zhigang; Fang, Ying; Lieber, Charles M

    2015-07-01

    Seamless and minimally invasive three-dimensional interpenetration of electronics within artificial or natural structures could allow for continuous monitoring and manipulation of their properties. Flexible electronics provide a means for conforming electronics to non-planar surfaces, yet targeted delivery of flexible electronics to internal regions remains difficult. Here, we overcome this challenge by demonstrating the syringe injection (and subsequent unfolding) of sub-micrometre-thick, centimetre-scale macroporous mesh electronics through needles with a diameter as small as 100 μm. Our results show that electronic components can be injected into man-made and biological cavities, as well as dense gels and tissue, with >90% device yield. We demonstrate several applications of syringe-injectable electronics as a general approach for interpenetrating flexible electronics with three-dimensional structures, including (1) monitoring internal mechanical strains in polymer cavities, (2) tight integration and low chronic immunoreactivity with several distinct regions of the brain, and (3) in vivo multiplexed neural recording. Moreover, syringe injection enables the delivery of flexible electronics through a rigid shell, the delivery of large-volume flexible electronics that can fill internal cavities, and co-injection of electronics with other materials into host structures, opening up unique applications for flexible electronics.

  18. Embracing Electronic Publishing.

    ERIC Educational Resources Information Center

    Wills, Gordon

    1996-01-01

    Electronic publishing is the grandest revolution in the capture and dissemination of academic and professional knowledge since Caxton developed the printing press. This article examines electronic publishing, describes different electronic publishing scenarios (authors' cooperative, consolidator/retailer/agent oligopsony, publisher oligopoly), and…

  19. Electronics Is Our Future.

    ERIC Educational Resources Information Center

    Coffee, Mary Jo

    This document contains the materials for an electronics course that was developed by an ad hoc committee of women employed in electronics and employers and educators in the electronics field and that is targeted toward single parents, displaced homemakers, single pregnant women, and other women interested in pursuing nontraditional careers. The…

  20. Electronics Engineering Technology Curriculum.

    ERIC Educational Resources Information Center

    Georgia State Univ., Atlanta. Dept. of Vocational and Career Development.

    This guide offers information and procedures necessary to train electronics engineering technicians. Discussed first are the rationale and objectives of the curriculum. The occupational field of electronics engineering technology is described. Next, a curriculum model is set forth that contains information on the standard electronics engineering…

  1. Mathematics for Electronics.

    ERIC Educational Resources Information Center

    Clary, Joseph R.; Nery, Karen P.

    This set of 20 modules was designed for use primarily to help teach and reinforce the basic mathematics skills in electronics classes. The modules are based on electronics competencies that require mathematics skills, as determined by a panel of high school electronics and mathematics teachers. Each module consists of one or two pages of basic…

  2. Radially uniform electron source

    NASA Technical Reports Server (NTRS)

    Mccomas, D.; Bame, S. J.

    1982-01-01

    A thermionic electron source capable of producing uniform count rates in a number of channel electron multipliers simultaneously was required for conditioning multipliers for an extended space mission. It was found that a straight tungsten filament in the center of a cylindrically symmetric geometry surrounded by an array of multipliers emits a radially asymmetric distribution of electrons that changes with time. A source was developed which successfully produces a time-independent radially uniform distribution of electrons by moving the filament out of the direct line of sight and replacing it with a centrally located electron 'cloud.'

  3. Electronic energy states

    NASA Technical Reports Server (NTRS)

    1976-01-01

    One-electron wave functions are reviewed and approximate solutions of two-electron systems are given in terms of these one-electron functions. The symmetry effects associated with electron spin are reviewed and the effects of electron exchange on energy levels of the two-electron system are given. The coupling of electronic orbital and spin angular momentum is considered next and the Lande interval rule for Russell-Saunders or LS coupling is derived. The configurations possible for various multi-electron LS couplings are enumerated (examples from the first two rows of the periodic table are given), and the meaning of the spectroscopic nomenclature is discussed, particularly with respect to the degeneracies of the electron states involved. Next the nomenclature, symmetries, and degeneracies for electron states of diatomic molecules are discussed, and some examples for N2, O2, and NO are presented. The electronic partition functions and derivative thermodynamic properties are expressed in terms of these energies and degeneracies, and examples are given for some of the simple gas species encountered in the earth's atmosphere.

  4. Relativistic electrons in space.

    NASA Technical Reports Server (NTRS)

    Simnett, G. M.

    1972-01-01

    This paper reviews the current state of knowledge concerning relativistic electrons, above 0.3 MeV, in interplanetary space, as measured by detectors on board satellites operating beyond the influence of the magnetosphere. The electrons have a galactic component, which at the lower energies is subject both to solar modulation and to spasmodic 'quiet time' increases and a direct solar component correlated with flare activity. The recent measurements have established the form of the differential energy spectrum of solar flare electrons. Electrons have been detected from flares behind the visible solar disk. Relativistic electrons do not appear to leave the sun at the time of the flash phase of the flare, although there are several signatures of electron acceleration at this time. The delay is interpreted as taking place during the transport of the electrons through the lower corona.

  5. High brightness electron accelerator

    SciTech Connect

    Sheffield, R.L.; Carlsten, B.E.; Young, L.M.

    1992-12-31

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electrons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electrons as the electrons enter the first cavity.

  6. Electron Bernstein wave electron temperature profile diagnostic

    SciTech Connect

    G. Taylor; P. Efthimion; B. Jones; T. Munsat; J. Spaleta; J. Hosea; R. Kaita; R. Majeski; J. Menard

    2000-07-20

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. where the plasma frequency is much greater than the electron cyclotron frequency, as in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition. Electron Bernstein waves (EBWs) are electrostatic waves that can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as a result of their large perpendicular wavenumber. This paper reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub o} {approximately} 2 kG, {approximately}10{sup 13} cm{sup {minus}3} and T{sub e} {approx} to 10 -- 200 eV. Results are presented for electromagnetic measurements of EBW emission, mode-converted near the plasma edge. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode converted EBW radiation temperature was found to be less than or equal to T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe and a 140 GHz interferometer were employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance, where the mode conversion of the EBWs is expected to occur. Initial results suggest EBW emission and EBW heating are viable concepts for overdense plasmas.

  7. Femtosecond mega-electron-volt electron microdiffraction.

    PubMed

    Shen, X; Li, R K; Lundström, U; Lane, T J; Reid, A H; Weathersby, S P; Wang, X J

    2017-09-01

    To understand and control the basic functions of physical, chemical and biological processes from micron to nano-meter scale, an instrument capable of visualizing transient structural changes of inhomogeneous materials with atomic spatial and temporal resolutions, is required. One such technique is femtosecond electron microdiffraction, in which a short electron pulse with femtosecond-scale duration is focused into a micron-scale spot and used to obtain diffraction images to resolve ultrafast structural dynamics over a localized crystalline domain. In this letter, we report the experimental demonstration of time-resolved mega-electron-volt electron microdiffraction which achieves a 5 μm root-mean-square (rms) beam size on the sample and a 110 fs rms temporal resolution. Using pulses of 10k electrons at 4.2 MeV energy with a normalized emittance 3 nm-rad, we obtained high quality diffraction from a single 10 μm paraffin (C44H90) crystal. The phonon softening mode in optical-pumped polycrystalline Bi was also time-resolved, demonstrating the temporal resolution limits of the instrument. This new characterization capability will open many research opportunities in material and biological sciences. Published by Elsevier B.V.

  8. Scanning ultrafast electron microscopy.

    PubMed

    Yang, Ding-Shyue; Mohammed, Omar F; Zewail, Ahmed H

    2010-08-24

    Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability.

  9. Scanning ultrafast electron microscopy

    PubMed Central

    Yang, Ding-Shyue; Mohammed, Omar F.; Zewail, Ahmed H.

    2010-01-01

    Progress has been made in the development of four-dimensional ultrafast electron microscopy, which enables space-time imaging of structural dynamics in the condensed phase. In ultrafast electron microscopy, the electrons are accelerated, typically to 200 keV, and the microscope operates in the transmission mode. Here, we report the development of scanning ultrafast electron microscopy using a field-emission-source configuration. Scanning of pulses is made in the single-electron mode, for which the pulse contains at most one or a few electrons, thus achieving imaging without the space-charge effect between electrons, and still in ten(s) of seconds. For imaging, the secondary electrons from surface structures are detected, as demonstrated here for material surfaces and biological specimens. By recording backscattered electrons, diffraction patterns from single crystals were also obtained. Scanning pulsed-electron microscopy with the acquired spatiotemporal resolutions, and its efficient heat-dissipation feature, is now poised to provide in situ 4D imaging and with environmental capability. PMID:20696933

  10. Engineered phages for electronics.

    PubMed

    Cui, Yue

    2016-11-15

    Phages are traditionally widely studied in biology and chemistry. In recent years, engineered phages have attracted significant attentions for functionalization or construction of electronic devices, due to their specific binding, catalytic, nucleating or electronic properties. To apply the engineered phages in electronics, these are a number of interesting questions: how to engineer phages for electronics? How are the engineered phages characterized? How to assemble materials with engineered phages? How are the engineered phages micro or nanopatterned? What are the strategies to construct electronics devices with engineered phages? This review will highlight the early attempts to address these questions and explore the fundamental and practical aspects of engineered phages in electronics, including the approaches for selection or expression of specific peptides on phage coat proteins, characterization of engineered phages in electronics, assembly of electronic materials, patterning of engineered phages, and construction of electronic devices. It provides the methodologies and opens up ex-cit-ing op-por-tu-ni-ties for the development of a variety of new electronic materials and devices based on engineered phages for future applications.

  11. Electron emitting filaments for electron discharge devices

    DOEpatents

    Leung, Ka-Ngo; Pincosy, Philip A.; Ehlers, Kenneth W.

    1988-01-01

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600.degree. C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for non-uniform current distribution along the filament due to the emission of electrons from the filament.

  12. Electron emitting filaments for electron discharge devices

    DOEpatents

    Leung, K.N.; Pincosy, P.A.; Ehlers, K.W.

    1983-06-10

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600/sup 0/C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for nonuniform current distribution along the filament due to the emission of electrons from the filament.

  13. Electronic Publishing or Electronic Information Handling?

    NASA Astrophysics Data System (ADS)

    Heck, A.

    The current dramatic evolution in information technology is bringing major modifications in the way scientists communicate. The concept of 'electronic publishing' is too restrictive and has often different, sometimes conflicting, interpretations. It is thus giving way to the broader notion of 'electronic information handling' encompassing the diverse types of information, the different media, as well as the various communication methodologies and technologies. New problems and challenges result also from this new information culture, especially on legal, ethical, and educational grounds. The procedures for validating 'published material' and for evaluating scientific activities will have to be adjusted too. 'Fluid' information is becoming a common concept. Electronic publishing cannot be conceived without link to knowledge bases nor without intelligent information retrieval tools.

  14. Electron Waveguide Devices

    NASA Astrophysics Data System (ADS)

    Eugster, Cristopher Conrad

    This thesis explores a new frontier for electronic devices: the electron waveguide regime where the confining dimensions are made comparable to the electron wavelength and scattering is removed from the channel. Motivated by the possibility of implementing an "electron directional coupler", we study this new regime of electron transport with a novel device called a dual electron waveguide device. Such a device consists of three split-gates patterned on top of an AlGaAs/GaAs modulation-doped heterostructure. Under proper bias, two one-dimensional electron waveguides can be formed in close proximity of one another. The middle -gate which is used to control the interaction between the two waveguides is only 30 nm wide. The side-gates are used to control the number of occupied subbands in the two respective waveguides. Since these gates can be independently accessed, many different electron waveguide configurations can be implemented using this novel structure. In this thesis, we study the transport and tunneling characteristics of isolated electron waveguides, leaky electron waveguides and closely spaced electron waveguides using our novel device concept. In the tunneling spectroscopy experiments of leaky electron waveguides, we have dramatically uncovered the 1D subband structure of our electron waveguides. We have also observed for the first time 1D to 1D tunneling between two closely spaced electron waveguides. The resulting pattern in the 1D to 1D tunneling regime is consistent with the energy and momentum conservation laws in the tunneling process. In this thesis, we also investigate some of the more practical issues behind electron waveguide devices. We show how only a few local scatterers in the device can degrade the ideal electron waveguide features. We also show how the increased functionality of our dual electron waveguide devices can be used to implement an efficient analog-to-digital conversion architecture. (Copies available exclusively from MIT

  15. Single electron spintronics.

    PubMed

    Dempsey, Kari J; Ciudad, David; Marrows, Christopher H

    2011-08-13

    Single electron electronics is now well developed, and allows the manipulation of electrons one-by-one as they tunnel on and off a nanoscale conducting island. In the past decade or so, there have been concerted efforts in several laboratories to construct single electron devices incorporating ferromagnetic components in order to introduce spin functionality. The use of ferromagnetic electrodes with a non-magnetic island can lead to spin accumulation on the island. On the other hand, making the dot also ferromagnetic introduces new physics such as tunnelling magnetoresistance enhancement in the cotunnelling regime and manifestations of the Kondo effect. Such nanoscale islands are also found to have long spin lifetimes. Conventional spintronics makes use of the average spin-polarization of a large ensemble of electrons: this new approach offers the prospect of accessing the quantum properties of the electron, and is a candidate approach to the construction of solid-state spin-based qubits.

  16. Gridded electron reversal ionizer

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor)

    1993-01-01

    A gridded electron reversal ionizer forms a three dimensional cloud of zero or near-zero energy electrons in a cavity within a filament structure surrounding a central electrode having holes through which the sample gas, at reduced pressure, enters an elongated reversal volume. The resultant negative ion stream is applied to a mass analyzer. The reduced electron and ion space-charge limitations of this configuration enhances detection sensitivity for material to be detected by electron attachment, such as narcotic and explosive vapors. Positive ions may be generated by generating electrons having a higher energy, sufficient to ionize the target gas and pulsing the grid negative to stop the electron flow and pulsing the extraction aperture positive to draw out the positive ions.

  17. Electron-proton spectrometer

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.

    1973-01-01

    An electron-proton spectrometer was designed to measure the geomagnetically trapped radiation in a geostationary orbit at 6.6 earth radii in the outer radiation belt. This instrument is to be flown on the Applications Technology Satellite-F (ATS-F). The electron-proton spectrometer consists of two permanent magnet surface barrier detector arrays and associated electronics capable of selecting and detecting electrons in three energy ranges: (1) 30-50 keV, (2) 150-200 keV, and (3) 500 keV and protons in three energy ranges. The electron-proton spectrometer has the capability of measuring the fluxes of electrons and protons in various directions with respect to the magnetic field lines running through the satellite. One magnet detector array system is implemented to scan between EME north and south through west, sampling the directional flux in 15 steps. The other magnet-detector array system is fixed looking toward EME east.

  18. Natural vacuum electronics

    NASA Technical Reports Server (NTRS)

    Leggett, Nickolaus

    1990-01-01

    The ambient natural vacuum of space is proposed as a basis for electron valves. Each valve is an electron controlling structure similiar to a vacuum tube that is operated without a vacuum sustaining envelope. The natural vacuum electron valves discussed offer a viable substitute for solid state devices. The natural vacuum valve is highly resistant to ionizing radiation, system generated electromagnetic pulse, current transients, and direct exposure to space conditions.

  19. Field emission electron source

    DOEpatents

    Zettl, Alexander Karlwalter; Cohen, Marvin Lou

    2000-01-01

    A novel field emitter material, field emission electron source, and commercially feasible fabrication method is described. The inventive field emission electron source produces reliable electron currents of up to 400 mA/cm.sup.2 at 200 volts. The emitter is robust and the current it produces is not sensitive to variability of vacuum or the distance between the emitter tip and the cathode. The novel emitter has a sharp turn-on near 100 volts.

  20. Electronic Neural Networks

    NASA Technical Reports Server (NTRS)

    Thakoor, Anil

    1990-01-01

    Viewgraphs on electronic neural networks for space station are presented. Topics covered include: electronic neural networks; electronic implementations; VLSI/thin film hybrid hardware for neurocomputing; computations with analog parallel processing; features of neuroprocessors; applications of neuroprocessors; neural network hardware for terrain trafficability determination; a dedicated processor for path planning; neural network system interface; neural network for robotic control; error backpropagation algorithm for learning; resource allocation matrix; global optimization neuroprocessor; and electrically programmable read only thin-film synaptic array.

  1. Electronic Technology (Selected Articles).

    DTIC Science & Technology

    1983-03-07

    4D-A127 369 ELECTRONIC TECHNOLOGY (SELECTED ARTICLESM() FOREIGN 1/1 N TECHNOLOGY DIV WRIGHT-PATTERSON RFB OH 87 MAR 83 FTD-IDCRS) T-8082-3...RS )T-0082-83 - .FOREIGN TECHNOLOGY DIVISION %’, ELECTRONIC TECHNOLOGY (Selected Articles) DTIC ELECTE MAY 1 01983 cw E C.") Approved for public...ELECTRONIC TECHNOLOGY (Selected Articles) K English pages: 14 Source: Dianzijishu, Nr. 8, 1982, pp. 2-5 Country of origin: China Translated by: LEO

  2. Nanocrystals for electronics.

    PubMed

    Panthani, Matthew G; Korgel, Brian A

    2012-01-01

    Semiconductor nanocrystals are promising materials for low-cost large-area electronic device fabrication. They can be synthesized with a wide variety of chemical compositions and size-tunable optical and electronic properties as well as dispersed in solvents for room-temperature deposition using various types of printing processes. This review addresses research progress in large-area electronic device applications using nanocrystal-based electrically active thin films, including thin-film transistors, light-emitting diodes, photovoltaics, and thermoelectrics.

  3. Joint Services Electronics Program.

    DTIC Science & Technology

    1981-04-01

    the barrier is able to change repeatedly, via Andreev reflections, from electron-like to hole-like states . For a clean interface and in the presence...v I. SOLID STATE ELECTRONICS, 1. Electronic Transport in Polycrystalline Semiconductors. D. Montgomery, and H...Optimum Configuration of Pseudogap States in Amorphous Sil-xHx Alloys. D.A. Anderson, G. Moddel, S. Oguz, M.A. Paesler, P. Viktorovich, and W. Paul

  4. Nanosecond electron microscopes

    PubMed

    Bostanjoglo; Elschner; Mao; Nink; Weingartner

    2000-04-01

    Combining electron optics, fast electronics and pulsed lasers, a transmission and a photoelectron emission microscope were built, which visualize events in thin films and on surfaces with a time resolution of several nanoseconds. The high-speed electron microscopy is capable to track fast laser-induced processes in metals below the ablation threshold, which are difficult to detect by other imaging techniques. The material response to nano- and femtosecond laser pulses was found to be very different. It was dominated by thermo/chemocapillary flow and chemical reactions in the case of nanosecond pulses, and by mechanical deformations and non-thermal electron emission after a femtosecond pulse.

  5. Smart Electronic Textiles.

    PubMed

    Weng, Wei; Chen, Peining; He, Sisi; Sun, Xuemei; Peng, Huisheng

    2016-05-17

    This Review describes the state-of-the-art of wearable electronics (smart textiles). The unique and promising advantages of smart electronic textiles are highlighted by comparing them with the conventional planar counterparts. The main kinds of smart electronic textiles based on different functionalities, namely the generation, storage, and utilization of electricity, are then discussed with an emphasis on the use of functional materials. The remaining challenges are summarized together with important new directions to provide some useful clues for the future development of smart electronic textiles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Stationary Electron Atomic Model

    NASA Astrophysics Data System (ADS)

    Pressler, David E.

    1998-04-01

    I will present a novel theory concerning the position and nature of the electron inside the atom. This new concept is consistant with present experimental evidence and adheres strictly to the valence-shell electron-pair repulsion (VSEPR) model presently used in chemistry for predicting the shapes of molecules and ions. In addition, I will discuss the atomic model concept as being a true harmonic oscillator, periodic motion at resonant frequency which produces radiation at discrete frequencies or line spectra is possible because the electron is under the action of two restoring forces, electrostatic attraction and superconducting respulsion of the electron's magnetic field by the nucleus.

  7. Einstein and the Electron

    NASA Astrophysics Data System (ADS)

    Wolff, Milo; Haselhurst, Geoff

    2005-03-01

    Querying Einstein. In his later years, physicists queried Einstein about the plethora of particles found with high-energy accelerators. They wanted Einstein's thought on basic matter. Einstein, a careful thinker, seriously replied, ``I would just like to know what an electron is.'' He implied that the prosaic electron, was more important to science than billions spent on accelerators. Little attention was paid to his remark. But Einstein saw the electron as the leading player of the Universe, because most activity is energy transfers between electrons. At the time, no one understood the energy mechanism of the electron; Although electron forces can be calculated with rules of Physics 101, the rules did not always match Nature. The electron did not appear to be a discrete particle. Something was wrong and Einstein knew it. We follow a suggestion by Clifford and Schroedinger to reject the discrete electron and replace it with a Wave Structure of Matter. This has all the electron's experimental properties, including the origins of the natural laws, fulfilling Einstein's intuition. (www.SpaceAndMotion.com)

  8. Electronics Environmental Benefits Calculator

    EPA Pesticide Factsheets

    The Electronics Environmental Benefits Calculator (EEBC) was developed to assist organizations in estimating the environmental benefits of greening their purchase, use and disposal of electronics.The EEBC estimates the environmental and economic benefits of: Purchasing Electronic Product Environmental Assessment Tool (EPEAT)-registered products; Enabling power management features on computers and monitors above default percentages; Extending the life of equipment beyond baseline values; Reusing computers, monitors and cell phones; and Recycling computers, monitors, cell phones and loads of mixed electronic products.The EEBC may be downloaded as a Microsoft Excel spreadsheet.See https://www.federalelectronicschallenge.net/resources/bencalc.htm for more details.

  9. (Pulsed electron beam precharger)

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    This report discusses the following topics on electron beam guns: Precharger Modification; Installation of Charge vs. Radius Apparatus; High Concentration Aerosol Generation; and Data Acquisition and Analysis System.

  10. NanoElectronics and BioElectronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak

    2001-01-01

    This viewgraph presentation reviews the use of Carbon Nanotube electronics in the bioelectronics. Included is a brief review of the carbon nanotube manufacturing, the use of carbon nanotubes in Atomic Force Microscopy (AFM), and Computational Nanotechnology, that allows designers to understand nanotube characteristics and serves as a design tool.

  11. Optical Electronics. Electronics Module 9. Instructor's Guide.

    ERIC Educational Resources Information Center

    Franken, Bill

    This module is the ninth of 10 modules in the competency-based electronics series. Introductory materials include a listing of competencies addressed in the module, a parts/equipment list, and a cross reference table of instructional materials. Five instructional units cover: fiber optic cable; optical coupler; lasers and masers; optical displays;…

  12. Optical Electronics. Electronics Module 9. Instructor's Guide.

    ERIC Educational Resources Information Center

    Franken, Bill

    This module is the ninth of 10 modules in the competency-based electronics series. Introductory materials include a listing of competencies addressed in the module, a parts/equipment list, and a cross reference table of instructional materials. Five instructional units cover: fiber optic cable; optical coupler; lasers and masers; optical displays;…

  13. Femtosecond Electron Sources and Attosecond Electron Foci

    NASA Astrophysics Data System (ADS)

    Hilbert, Shawn; Fricke, Amanda; Uiterwaal, Cornelis; Batelaan, Herman

    2008-05-01

    We report progress on a nanometer-sized femtosecond electron source. The source consists of an 80-MHz repetition rate femtosecond laser with a tungsten field emission tip. Our autocorrelation spectra support the claim^1 that the emission process is dependent on the electric field of the laser pulse. This field dependence suggests sub-cycle (Tcycle =2π/φ=2.7 fs) electron emission.^1,2 Consistently, we found that the duration of the emission process has an upper bound of 100 fs.^3 However, we now deduce a lower bound for the emission process duration of about 10 fs. Nevertheless, this electron source may be combined with a temporal lens to focus the electron pulses to subcycle temporal widths.^4 ^1P. Hommelhoff, et al, Phys. Rev. Lett. 96, 077401 (2006) ^2P. Hommelhoff, et al, Phys. Rev. Lett. 97, 247402 (2006) ^3B. Barwick, et al, New J. Phys. 9, 142 (2007) ^4P. Baum, A. H. Zewail, Proc. Natl. Acad. Sci. USA. 104, 18409 (2007) * This material is based upon the work supported by the National Science Foundation under Grant Nos. PHY-0355235 and PHY-0653182.

  14. Two Kinds of Electron?

    ERIC Educational Resources Information Center

    Miller, Franklin, Jr.

    2007-01-01

    In the 1930s physicists were confronted by two conflicting values for the charge of the electron as measured with great precision by two different methods. Could it be that there are two kinds of (negative) electrons, differing in charge by a fraction of a percent? The experiments were reconciled when a small systematic error in one of the…

  15. Electron-Tunneling Magnetometer

    NASA Technical Reports Server (NTRS)

    Kaiser, William J.; Kenny, Thomas W.; Waltman, Steven B.

    1993-01-01

    Electron-tunneling magnetometer is conceptual solid-state device operating at room temperature, yet offers sensitivity comparable to state-of-art magnetometers such as flux gates, search coils, and optically pumped magnetometers, with greatly reduced volume, power consumption, electronics requirements, and manufacturing cost. Micromachined from silicon wafer, and uses tunneling displacement transducer to detect magnetic forces on cantilever-supported current loop.

  16. ELECTRONIC DATA PROCESSING EDUCATION.

    ERIC Educational Resources Information Center

    TONDOW, MURRAY

    EDUCATION HAS BEEN SLOW IN FULLY UTILIZING ELECTRONIC DATA PROCESSING EQUIPMENT (EDP). EDUCATOR CONFIDENCE IN THE EDP HAS GROWN, HOWEVER, AS A RESULT OF THE SUCCESS OF ELECTRONIC DATA PROCESSING IN SCIENCE, INDUSTRY, AND OTHER PROFESSIONS. THE DEVELOPMENT OF SOLID STATE TRANSISTORIZED COMPUTERS HAS MADE POWERFUL DESK-SIZE COMPUTERS A REALITY AND…

  17. Electron transfer in peptides.

    PubMed

    Shah, Afzal; Adhikari, Bimalendu; Martic, Sanela; Munir, Azeema; Shahzad, Suniya; Ahmad, Khurshid; Kraatz, Heinz-Bernhard

    2015-02-21

    In this review, we discuss the factors that influence electron transfer in peptides. We summarize experimental results from solution and surface studies and highlight the ongoing debate on the mechanistic aspects of this fundamental reaction. Here, we provide a balanced approach that remains unbiased and does not favor one mechanistic view over another. Support for a putative hopping mechanism in which an electron transfers in a stepwise manner is contrasted with experimental results that support electron tunneling or even some form of ballistic transfer or a pathway transfer for an electron between donor and acceptor sites. In some cases, experimental evidence suggests that a change in the electron transfer mechanism occurs as a result of donor-acceptor separation. However, this common understanding of the switch between tunneling and hopping as a function of chain length is not sufficient for explaining electron transfer in peptides. Apart from chain length, several other factors such as the extent of the secondary structure, backbone conformation, dipole orientation, the presence of special amino acids, hydrogen bonding, and the dynamic properties of a peptide also influence the rate and mode of electron transfer in peptides. Electron transfer plays a key role in physical, chemical and biological systems, so its control is a fundamental task in bioelectrochemical systems, the design of peptide based sensors and molecular junctions. Therefore, this topic is at the heart of a number of biological and technological processes and thus remains of vital interest.

  18. Two Kinds of Electron?

    ERIC Educational Resources Information Center

    Miller, Franklin, Jr.

    2007-01-01

    In the 1930s physicists were confronted by two conflicting values for the charge of the electron as measured with great precision by two different methods. Could it be that there are two kinds of (negative) electrons, differing in charge by a fraction of a percent? The experiments were reconciled when a small systematic error in one of the…

  19. Whither Electronic Journals?

    ERIC Educational Resources Information Center

    Luther, Judy

    2000-01-01

    Discusses Web-based electronic journals for the academic market and presents a chart that includes sources of electronic journals and value added. Considers trends in collections, including remote access, outsourcing, hosting content versus linking, and subject portals; trends in access, including indexing, backfiles, and database usage; and…

  20. Electron pairing without superconductivity.

    PubMed

    Cheng, Guanglei; Tomczyk, Michelle; Lu, Shicheng; Veazey, Joshua P; Huang, Mengchen; Irvin, Patrick; Ryu, Sangwoo; Lee, Hyungwoo; Eom, Chang-Beom; Hellberg, C Stephen; Levy, Jeremy

    2015-05-14

    Strontium titanate (SrTiO3) is the first and best known superconducting semiconductor. It exhibits an extremely low carrier density threshold for superconductivity, and possesses a phase diagram similar to that of high-temperature superconductors--two factors that suggest an unconventional pairing mechanism. Despite sustained interest for 50 years, direct experimental insight into the nature of electron pairing in SrTiO3 has remained elusive. Here we perform transport experiments with nanowire-based single-electron transistors at the interface between SrTiO3 and a thin layer of lanthanum aluminate, LaAlO3. Electrostatic gating reveals a series of two-electron conductance resonances-paired electron states--that bifurcate above a critical pairing field Bp of about 1-4 tesla, an order of magnitude larger than the superconducting critical magnetic field. For magnetic fields below Bp, these resonances are insensitive to the applied magnetic field; for fields in excess of Bp, the resonances exhibit a linear Zeeman-like energy splitting. Electron pairing is stable at temperatures as high as 900 millikelvin, well above the superconducting transition temperature (about 300 millikelvin). These experiments demonstrate the existence of a robust electronic phase in which electrons pair without forming a superconducting state. Key experimental signatures are captured by a model involving an attractive Hubbard interaction that describes real-space electron pairing as a precursor to superconductivity.

  1. Space electronics technology summary

    NASA Technical Reports Server (NTRS)

    1976-01-01

    An overview is given of current electronics R and D activities, potential future thrusts, and related NASA payoffs. Major increases in NASA mission return and significant concurrent reductions in mission cost appear possible through a focused, long range electronics technology program. The overview covers: guidance assessments, navigation and control, and sensing and data acquisition processing, storage, and transfer.

  2. Electronic calorimetric computer

    NASA Technical Reports Server (NTRS)

    Heckelman, J. D.

    1968-01-01

    Electronic calorimetric computer calculates nuclear reactor thermal power output to a nominal accuracy of 1 percent. Heat balance is determined by an electronic approach. The thermal power is calculated using the inlet and outlet temperatures and the volume of cooling water and is displayed by a digital readout system.

  3. Electronic Music Appreciation.

    ERIC Educational Resources Information Center

    Peacock, Kenneth J.

    1984-01-01

    Electronic music can be used to give nonmusic majors an appreciation of musical culture. As final projects, students complete compositions and make the same musical decisions that composers make. Emphasis is on understanding of the electronic medium and on aural analysis. (CS)

  4. GHz-THz Electronics

    DTIC Science & Technology

    2013-03-07

    Schlom & Kyle Shen (Cornell) Tight coupling of molecular-beam epitaxy (MBE) and angle-resolved photoelectron spectroscopy (ARPES) reveals metal...electronics • Paul Maki – nitride electronics • Chagaan Baatar – 2D materials • Marc Ulrich – topological insulators • Pani Varanasi – 2D materials • Mike

  5. The Michigan Electronic Library.

    ERIC Educational Resources Information Center

    Davidsen, Susanna L.

    1997-01-01

    Describes the Michigan Electronic Library (MEL), the largest evaluated and organized Web-based library of Internet resources, that was designed to provide a library of electronic information resources selected by librarians. MEL's partnership is explained, the collection is described, and future developments are considered. (LRW)

  6. Silicones in medical electronics.

    PubMed

    Bruner, Stephen

    2008-01-01

    The use of silicones, although already extensive, is set to grow in medical electronics. Silicones used in medical device applications as tubing or moulded parts should also be considered for electronic applications in the same device. This article outlines the potential reduction in complexity that this solution offers. Benefits include eliminating negative materials interactions and avoiding bonding problems.

  7. Direct Electron Detectors.

    PubMed

    McMullan, G; Faruqi, A R; Henderson, R

    2016-01-01

    Direct electron detectors have played a key role in the recent increase in the power of single-particle electron cryomicroscopy (cryoEM). In this chapter, we summarize the background to these recent developments, give a practical guide to their optimal use, and discuss future directions. © 2016 Elsevier Inc. All rights reserved.

  8. Are electron tweezers possible?

    PubMed

    Oleshko, Vladimir P; Howe, James M

    2011-11-01

    Positively answering the question in the title, we demonstrate in this work single electron beam trapping and steering of 20-300nm solid Al nanoparticles generated inside opaque submicron-sized molten Al-Si eutectic alloy spheres. Imaging of solid nanoparticles and liquid alloy in real time was performed using energy filtering in an analytical transmission electron microscope (TEM). Energy-filtering TEM combined with valence electron energy-loss spectroscopy enabled us to investigate in situ nanoscale transformations of the internal structure, temperature dependence of plasmon losses, and local electronic and optical properties under melting and crystallization of individual binary alloy particles. For particles below 20nm in size, enhanced vibrations of the dynamic solid-liquid interface due to instabilities near the critical threshold were observed just before melting. The obtained results indicate that focused electron beams can act as a tool for manipulation of metal nanoparticles by transferring linear and angular mechanical momenta. Such thermally assisted electron tweezers can be utilized for touchless manipulation and processing of individual nano-objects and potentially for fabrication of assembled nanodevices with atomic level sensitivity and lateral resolution provided by modern electron optical systems. This is by three orders of magnitude better than for light microscopy utilized in conventional optical tweezers. New research directions and potential applications of trapping and tracking of nano-objects by focused electron beams are outlined.

  9. Electron beam polarimetry

    SciTech Connect

    Sinclair, C.K.

    1998-12-01

    Along with its well known charge and mass, the electron also carries an intrinsic angular momentum, or {ital spin}. The rules of quantum mechanics allow us to measure only the probability that the electron spin is in one of two allowed spin states. When a beam carries a net excess of electrons in one of these two allowed spin states, the beam is said to be {ital polarized}. The beam polarization may be measured by observing a sufficient number of electrons scattered by a spin-dependent interaction. For electrons, the useful scattering processes involve Coulomb scattering by heavy nuclei, or scattering from either polarized photons or other polarized electrons (known as Mott, Compton, and Mo/ller scattering, respectively). In this tutorial, we will briefly review how beam polarization is measured through a general scattering process, followed by a discussion of how the three scattering processes above are used to measure electron beam polarization. Descriptions of electron polarimeters based on the three scattering processes will be given. {copyright} {ital 1998 American Institute of Physics.}

  10. Electron beam polarimetry

    NASA Astrophysics Data System (ADS)

    Sinclair, Charles K.

    1998-12-01

    Along with its well known charge and mass, the electron also carries an intrinsic angular momentum, or spin. The rules of quantum mechanics allow us to measure only the probability that the electron spin is in one of two allowed spin states. When a beam carries a net excess of electrons in one of these two allowed spin states, the beam is said to be polarized. The beam polarization may be measured by observing a sufficient number of electrons scattered by a spin-dependent interaction. For electrons, the useful scattering processes involve Coulomb scattering by heavy nuclei, or scattering from either polarized photons or other polarized electrons (known as Mott, Compton, and Mo/ller scattering, respectively). In this tutorial, we will briefly review how beam polarization is measured through a general scattering process, followed by a discussion of how the three scattering processes above are used to measure electron beam polarization. Descriptions of electron polarimeters based on the three scattering processes will be given.

  11. The neutrino electron accelerator

    SciTech Connect

    Shukla, P.K.; Stenflo, L.; Bingham, R.; Bethe, H.A.; Dawson, J.M.; Mendonca, J.T.

    1998-01-01

    It is shown that a wake of electron plasma oscillations can be created by the nonlinear ponderomotive force of an intense neutrino flux. The electrons trapped in the plasma wakefield will be accelerated to high energies. Such processes may be important in supernovas and pulsars. {copyright} {ital 1998 American Institute of Physics.}

  12. Basic Electronics I.

    ERIC Educational Resources Information Center

    Robertson, L. Paul

    Designed for use in basic electronics programs, this curriculum guide is comprised of twenty-nine units of instruction in five major content areas: Orientation, Basic Principles of Electricity/Electronics, Fundamentals of Direct Current, Fundamentals of Alternating Current, and Applying for a Job. Each instructional unit includes some or all of…

  13. Electronically Induced Phase Transformations

    DTIC Science & Technology

    1980-12-01

    ries (w hen the Slater free-electron exchange is used). A systematic the active researcher. study of relativistic electron densities and isomer...comp:wrees aux mesures actuelles d’effet dHvA d’Arko et Schirber. Le calu; du facteur de forme neutronique en presence d’un champ magnetique est en bon

  14. Electronic Networks. ERIC Digest.

    ERIC Educational Resources Information Center

    Garnette, Cheryl Petty

    Electronic network systems, their components--terminal, microcomputer, or communications word processor; telephone, and modem (modulator-demodulator)--and their applications are explained for educators in this digest. Emphasis is on the characteristics and capabilities of: (1) electronic mail, which allows the transmission and reception of…

  15. Whither Electronic Journals?

    ERIC Educational Resources Information Center

    Luther, Judy

    2000-01-01

    Discusses Web-based electronic journals for the academic market and presents a chart that includes sources of electronic journals and value added. Considers trends in collections, including remote access, outsourcing, hosting content versus linking, and subject portals; trends in access, including indexing, backfiles, and database usage; and…

  16. Electronic Portfolios for Whom?

    ERIC Educational Resources Information Center

    Ayala, Javier I.

    2006-01-01

    Electronic portfolios are a recent technology wave hitting the coast of higher education. Since 2000, more than 300 articles have appeared on the topic. Electronic portfolios are described as the panacea for potentially problematic issues ranging from student learning to standards, advising, job hunting, and assessment. The surge of attention…

  17. Electron tunnel sensor technology

    NASA Technical Reports Server (NTRS)

    Waltman, S. B.; Kaiser, W. J.

    1989-01-01

    The recent development of Scanning Tunneling Microscopy technology allows the application of electron tunneling to position detectors for the first time. The vacuum tunnel junction is one of the most sensitive position detection mechanisms available. It is also compact, simple, and requires little power. A prototype accelerometer based on electron tunneling, and other sensor applications of this promising new technology are described.

  18. Electronic Music Appreciation.

    ERIC Educational Resources Information Center

    Peacock, Kenneth J.

    1984-01-01

    Electronic music can be used to give nonmusic majors an appreciation of musical culture. As final projects, students complete compositions and make the same musical decisions that composers make. Emphasis is on understanding of the electronic medium and on aural analysis. (CS)

  19. Nanowire electron scattering spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D. (Inventor); Bronikowski, Michael (Inventor); Wong, Eric W. (Inventor); von Allmen, Paul (Inventor); Oyafuso, Fabiano A. (Inventor)

    2009-01-01

    Methods and devices for spectroscopic identification of molecules using nanoscale wires are disclosed. According to one of the methods, nanoscale wires are provided, electrons are injected into the nanoscale wire; and inelastic electron scattering is measured via excitation of low-lying vibrational energy levels of molecules bound to the nanoscale wire.

  20. Electrons and Mirror Symmetry

    SciTech Connect

    Kumar, Krishna

    2007-04-04

    The neutral weak force between an electron and a target particle, mediated by the Z boson, can be isolated by measuring the fractional change under a mirror reflection of the scattering probability of relativistic longitudinally polarized electrons off unpolarized targets. This technique yields neutral weak force measurements at a length scale of 1 femtometer, in contrast to high energy collider measurements that probe much smaller length scales. Study of the variation of the weak force over a range of length scales provides a stringent test of theory, complementing collider measurements. We describe a recent measurement of the neutral weak force between two electrons by the E158 experiment at the Stanford Linear Accelerator Center. While the weak force between an electron and positron has been extensively studied, that between two electrons had never directly been measured. We conclude by discussing prospects for even more precise measurements at future facilities.