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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

    PubMed Central

    Shakhvorostov, Dmitry; Nistor, Razvan A.; Krusin-Elbaum, Lia; Martyna, Glenn J.; Newns, Dennis M.; Elmegreen, Bruce G.; Liu, Xiao-hu; Hughes, Zak E.; Paul, Sujata; Cabral, Cyril; Raoux, Simone; Shrekenhamer, David B.; Basov, Dimitri N.; Song, Young; Müser, Martin H.

    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. PMID:19549858

  2. Metal-semiconductor contacts: electronic properties

    NASA Astrophysics Data System (ADS)

    Mönch, Winfried

    1994-01-01

    Rectification in metal-semiconductor contacts was first described by Braun in 1874. We owe the explanation of this observation to Schottky. He demonstrated that depletion layers exist on the semiconductor side of such interfaces. The current transport across such contacts is determined by their barrier heights, i.e., the respective energy difference between the Fermi level and the edge of the majority-carrier band. Since Schottky had published his pioneering work in 1938 the mechanisms, which determine the barrier heights of metal-semiconductor contacts, have remained under discussion. In 1947, Bardeen attributed the failure of the early Schottky-Mott rule to the neglect of electronic interface states. The foundations for a microscopic description of interface states in ideal Schottky contacts was laid by Heine in 1965. He demonstrated that a continuum of metal-induced gap states (MIGS), as they were called later, derives from the virtual gap states of the complex semiconductor band-structure. Neither this MIGS model nor any of the many other monocausal approaches, the most prominent is Spicer's Unified Defect Model, can explain the experimental data. In 1987, Mönch concluded that the continuum of MIG states represents the primary mechanism, which determines the barrier heights in ideal, i.e., intimate, abrupt, and homogeneous metal-semiconductor contacts. He attributed deviations from what is predicted by the MIGS model to other and then secondary mechanisms. In this respect, interface defects, structure-related interface dipoles. interface strain, interface compound formation, and interface intermixing, to name a few examples, were considered.

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

    NASA Technical Reports Server (NTRS)

    Huberman, M. L.; Maserjian, J.

    1988-01-01

    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. Surface plasmon assisted hot electron collection in wafer-scale metallic-semiconductor photonic crystals.

    PubMed

    Chou, Jeffrey B; Li, Xin-Hao; Wang, Yu; Fenning, David P; Elfaer, Asmaa; Viegas, Jaime; Jouiad, Mustapha; Shao-Horn, Yang; Kim, Sang-Gook

    2016-09-01

    Plasmon assisted photoelectric hot electron collection in a metal-semiconductor junction can allow for sub-bandgap optical to electrical energy conversion. Here we report hot electron collection by wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC), with a broadband photoresponse below the bandgap of TiO2. Multiple absorption modes supported by the 2D nano-cavity structure of the MSPhC extend the photon-metal interaction time and fulfill a broadband light absorption. The surface plasmon absorption mode provides access to enhanced electric field oscillation and hot electron generation at the interface between Au and TiO2. A broadband sub-bandgap photoresponse centered at 590 nm was achieved due to surface plasmon absorption. Gold nanorods were deposited on the surface of MSPhC to study localized surface plasmon (LSP) mode absorption and subsequent injection to the TiO2 catalyst at different wavelengths. Applications of these results could lead to low-cost and robust photo-electrochemical applications such as more efficient solar water splitting.

  5. Surface plasmon assisted hot electron collection in wafer-scale metallic-semiconductor photonic crystals.

    PubMed

    Chou, Jeffrey B; Li, Xin-Hao; Wang, Yu; Fenning, David P; Elfaer, Asmaa; Viegas, Jaime; Jouiad, Mustapha; Shao-Horn, Yang; Kim, Sang-Gook

    2016-09-01

    Plasmon assisted photoelectric hot electron collection in a metal-semiconductor junction can allow for sub-bandgap optical to electrical energy conversion. Here we report hot electron collection by wafer-scale Au/TiO2 metallic-semiconductor photonic crystals (MSPhC), with a broadband photoresponse below the bandgap of TiO2. Multiple absorption modes supported by the 2D nano-cavity structure of the MSPhC extend the photon-metal interaction time and fulfill a broadband light absorption. The surface plasmon absorption mode provides access to enhanced electric field oscillation and hot electron generation at the interface between Au and TiO2. A broadband sub-bandgap photoresponse centered at 590 nm was achieved due to surface plasmon absorption. Gold nanorods were deposited on the surface of MSPhC to study localized surface plasmon (LSP) mode absorption and subsequent injection to the TiO2 catalyst at different wavelengths. Applications of these results could lead to low-cost and robust photo-electrochemical applications such as more efficient solar water splitting. PMID:27607726

  6. Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes.

    PubMed

    Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

    2016-06-29

    Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation. PMID:27168177

  7. Hot-electron-based solar energy conversion with metal-semiconductor nanodiodes.

    PubMed

    Lee, Young Keun; Lee, Hyosun; Lee, Changhwan; Hwang, Euyheon; Park, Jeong Young

    2016-06-29

    Energy dissipation at metal surfaces or interfaces between a metal and a dielectric generally results from elementary excitations, including phonons and electronic excitation, once external energy is deposited to the surface/interface during exothermic chemical processes or an electromagnetic wave incident. In this paper, we outline recent research activities to develop energy conversion devices based on hot electrons. We found that photon energy can be directly converted to hot electrons and that hot electrons flow through the interface of metal-semiconductor nanodiodes where a Schottky barrier is formed and the energy barrier is much lower than the work function of the metal. The detection of hot electron flow can be successfully measured using the photocurrent; we measured the photoyield of photoemission with incident photons-to-current conversion efficiency (IPCE). We also show that surface plasmons (i.e. the collective oscillation of conduction band electrons induced by interaction with an electromagnetic field) are excited on a rough metal surface and subsequently decay into secondary electrons, which gives rise to enhancement of the IPCE. Furthermore, the unique optical behavior of surface plasmons can be coupled with dye molecules, suggesting the possibility for producing additional channels for hot electron generation.

  8. 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.

  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. Indirect exchange interaction in fully metal-semiconductor separated single-walled carbon nanotubes revealed by electron spin resonance

    NASA Astrophysics Data System (ADS)

    Havlicek, M.; Jantsch, W.; Wilamowski, Z.; Yanagi, K.; Kataura, H.; Rümmeli, M. H.; Malissa, H.; Tyryshkin, A.; Lyon, S.; Chernov, A.; Kuzmany, H.

    2012-07-01

    The ESR response from highly metal-semiconductor (M-SC) separated single-walled carbon nanotubes (SWCNTs) for temperatures T between 0.39 and 200 K is characteristically different for the two systems. The signal originates from defect spins but interaction with free electrons leads to a larger linewidth for M tubes. The latter decreases with increasing T, whereas it increases with T for SC tubes. The spins undergo a ferromagnetic phase transition below around 10 K. Indirect exchange is suggested to be responsible for the spin-spin interaction, supported by RKKY interaction in the case of M tubes. For SC tubes, the spin-lattice relaxation via an Orbach process is suggested to determine the linewidth.

  12. 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.

  13. Strong and highly asymmetrical optical absorption in conformal metal-semiconductor-metal grating system for plasmonic hot-electron photodetection application

    PubMed Central

    Wu, Kai; Zhan, Yaohui; Zhang, Cheng; Wu, Shaolong; Li, Xiaofeng

    2015-01-01

    We propose an architecture of conformal metal-semiconductor-metal (MSM) device for hot-electron photodetection by asymmetrical alignment of the semiconductor barrier relative to the Fermi level of metals and strong energy localization through plasmonic resonances. Compared with the conventional grating design, the multi-layered grating system under conformal configuration is demonstrated to possess both optical and electrical advantages for high-sensitivity hot-electron photodetection. Finite-element simulation reveals that a strong and highly asymmetrical optical absorption (top metal absorption >99%) can be realized under such a conformal arrangement. An analytical probability-based electrical simulation verifies the strong unidirectional photocurrent, by taking advantage of the extremely high net absorption and a low metal/semiconductor barrier height, and predicts that the corresponding photoresponsivity can be ~3 times of that based on the conventional grating design in metal-insulator-metal (MIM) configuration. PMID:26387836

  14. 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.

  15. 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.

  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. Electronic Characterization of Au/DNA/ITO Metal-Semiconductor-Metal Diode and Its Application as a Radiation Sensor

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2016-01-01

    Deoxyribonucleic acid or DNA molecules expressed as double-stranded (DSS) negatively charged polymer plays a significant role in electronic states of metal/silicon semiconductor structures. Electrical parameters of an Au/DNA/ITO device prepared using self-assembly method was studied by using current–voltage (I-V) characteristic measurements under alpha bombardment at room temperature. The results were analyzed using conventional thermionic emission model, Cheung and Cheung’s method and Norde’s technique to estimate the barrier height, ideality factor, series resistance and Richardson constant of the Au/DNA/ITO structure. Besides demonstrating a strongly rectifying (diode) characteristic, it was also observed that orderly fluctuations occur in various electrical parameters of the Schottky structure. Increasing alpha radiation effectively influences the series resistance, while the barrier height, ideality factor and interface state density parameters respond linearly. Barrier height determined from I–V measurements were calculated at 0.7284 eV for non-radiated, increasing to about 0.7883 eV in 0.036 Gy showing an increase for all doses. We also demonstrate the hypersensitivity phenomena effect by studying the relationship between the series resistance for the three methods, the ideality factor and low-dose radiation. Based on the results, sensitive alpha particle detectors can be realized using Au/DNA/ITO Schottky junction sensor. PMID:26799703

  18. Electronic Characterization of Au/DNA/ITO Metal-Semiconductor-Metal Diode and Its Application as a Radiation Sensor.

    PubMed

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2016-01-01

    Deoxyribonucleic acid or DNA molecules expressed as double-stranded (DSS) negatively charged polymer plays a significant role in electronic states of metal/silicon semiconductor structures. Electrical parameters of an Au/DNA/ITO device prepared using self-assembly method was studied by using current-voltage (I-V) characteristic measurements under alpha bombardment at room temperature. The results were analyzed using conventional thermionic emission model, Cheung and Cheung's method and Norde's technique to estimate the barrier height, ideality factor, series resistance and Richardson constant of the Au/DNA/ITO structure. Besides demonstrating a strongly rectifying (diode) characteristic, it was also observed that orderly fluctuations occur in various electrical parameters of the Schottky structure. Increasing alpha radiation effectively influences the series resistance, while the barrier height, ideality factor and interface state density parameters respond linearly. Barrier height determined from I-V measurements were calculated at 0.7284 eV for non-radiated, increasing to about 0.7883 eV in 0.036 Gy showing an increase for all doses. We also demonstrate the hypersensitivity phenomena effect by studying the relationship between the series resistance for the three methods, the ideality factor and low-dose radiation. Based on the results, sensitive alpha particle detectors can be realized using Au/DNA/ITO Schottky junction sensor.

  19. 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.

  20. Silicon metal-semiconductor-metal photodetector

    DOEpatents

    Brueck, Steven R. J.; Myers, David R.; Sharma, Ashwani K.

    1995-01-01

    Silicon MSM photodiodes sensitive to radiation in the visible to near infrared spectral range are produced by altering the absorption characteristics of crystalline Si by ion implantation. The implantation produces a defected region below the surface of the silicon with the highest concentration of defects at its base which acts to reduce the contribution of charge carriers formed below the defected layer. The charge carriers generated by the radiation in the upper regions of the defected layer are very quickly collected between biased Schottky barrier electrodes which form a metal-semiconductor-metal structure for the photodiode.

  1. Silicon metal-semiconductor-metal photodetector

    DOEpatents

    Brueck, Steven R. J.; Myers, David R.; Sharma, Ashwani K.

    1997-01-01

    Silicon MSM photodiodes sensitive to radiation in the visible to near infrared spectral range are produced by altering the absorption characteristics of crystalline Si by ion implantation. The implantation produces a defected region below the surface of the silicon with the highest concentration of defects at its base which acts to reduce the contribution of charge carriers formed below the defected layer. The charge carriers generated by the radiation in the upper regions of the defected layer are very quickly collected between biased Schottky barrier electrodes which form a metal-semiconductor-metal structure for the photodiode.

  2. 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.

  3. 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. PMID:22792998

  4. 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.

  5. Metal Semiconductor Heterostructures for Photocatalytic Conversion of Light Energy.

    PubMed

    Dutta, Sumit Kumar; Mehetor, Shyamal Kumar; Pradhan, Narayan

    2015-03-19

    For fast separation of the photogenerated charge carriers, metal semiconductor heterostructures have emerged as one of the leading materials in recent years. Among these, metal Au coupled with low bandgap semiconductors remain as ideal materials where both can absorb the solar light in the visible region. It is also established that on excitation, the plasmonic state of gold interacts with excited state of semiconductor and helps for the delocalization of the photogenerated electrons. Focusing these materials where electron transfer preferably occurs from semiconductor to metal Au on excitation, in this Perspective, we report the latest developments in the synthetic chemistry in designing such nano heterostructures and discuss their photocatalytic activities in organic dye degradation/reduction and/or photocatalytic water splitting for generation of hydrogen. Among these, materials such as Au-CZTS, Au-SnS, Au-Bi2S3, Au-ZnSe, and so forth are emphasized, and their formation chemistry as well as their photocatalytic activities are discussed in this Perspective. PMID:26262849

  6. 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.

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

    PubMed

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

    2014-11-10

    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 (E(F)) 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 E(F) to the valence and 3d bands, and from the interface states to the valence band. All three nanostructures are excellent room-temperature light emitters.

  8. First-principles analysis of ZrN/ScN metal/semiconductor superlattices for thermoelectric energy conversion

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    We present a first-principles density functional theory-based analysis of the electronic structure, vibrational spectra, and transport properties of ZrN/ScN metal/semiconductor superlattices aiming to understand its potential and suitability for thermoelectric applications. We demonstrate (a) the presence of Schottky barriers of 0.34 eV at the metal/semiconductor interface and (b) a large asymmetry in the electronic densities of states and flattening of electronic bands along the cross-plane directions near the Fermi energy of these superlattices, desirable for high Seebeck coefficient. The vibrational spectra of these superlattices show softening of transverse acoustic phonon modes along the growth direction and localization of ScN phonons in the vibrational energy gap between metal and semiconductor layers. Boltzmann transport theory-based analysis suggests a reduction of lattice thermal conductivity by an order of magnitude compared to its individual bulk components, which makes these materials suitable for thermoelectric applications.

  9. Valence bond cluster studies of alkali metal/semiconductor bonding

    NASA Astrophysics Data System (ADS)

    Tatar, Robert C.; Messmer, Richard P.

    1986-12-01

    We present results of cluster studies of alkali metal/semiconductor bonding. Using the Generalized Valence Bond (GVB) method, we find a remarkable consistency in the behavoir of bonding orbitals for a variety of systems, including: LiH, CLi4, LiH4 and several hypervalent systems, such as SiH3Li2, SiH4Li2. Our results show that the metal-semiconductor bonding in these systems can be understood in terms of a pairing between McAdon-Goddard type metallic bonding orbitals and a set of equivalent orbitals of the non-metallic species. We propose that the results are relevant to the initial stages of alkali overlayer growth on semiconductor surfaces and lead to a simple picture of the bonding including the transition from a non-conducting to a conducting layer. We have considered numerous proposed hypervalent structures in light of the above results and find that they can be understood.

  10. 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.

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

    PubMed

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

    2016-09-14

    The long-term stability and superior device reliability through the use of delicately designed metal contacts with two-dimensional (2D) atomic-scale semiconductors are considered one of the critical issues related to practical 2D-based electronic components. Here, we investigate the origin of the improved contact properties of alloyed 2D metal-semiconductor heterojunctions. 2D WSe2-based transistors with mixed transition layers containing van der Waals (M-vdW, NbSe2/WxNb1-xSe2/WSe2) junctions realize atomically sharp interfaces, exhibiting long hot-carrier lifetimes of approximately 75,296 s (78 times longer than that of metal-semiconductor, Pd/WSe2 junctions). Such dramatic lifetime enhancement in M-vdW-junctioned devices is attributed to the synergistic effects arising from the significant reduction in the number of defects and the Schottky barrier lowering at the interface. Formation of a controllable mixed-composition alloyed layer on the 2D active channel would be a breakthrough approach to maximize the electrical reliability of 2D nanomaterial-based electronic applications. PMID:27552187

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Effect of photovoltage on current flow in metal-semiconductor schottky-barrier contacts

    SciTech Connect

    Torkhov, N. A.

    2011-07-15

    It is shown that changes in device characteristics and an increase in the light-to-electrical energy conversion efficiency in metal-semiconductor Schottky barrier contacts are associated with a peripheral electric field built into the contact. For contacts with longer perimeters, variations in device characteristics and the light-to-electrical energy conversion efficiency are significantly larger. Since the photovoltage and peripheral electric fields in the contact region are codirected with the intrinsic electric field of the space-charge region, contact illumination results in a larger increase in the 'dead' zone in forward portions of current-voltage characteristics, a larger decrease in the effective Schottky barrier height, and an increase in the field electron emission. An increase in the reverse field emission under photovoltage leads to an increase in the recombination current in the space-charge region, which provides dc photocurrent flow in the circuit.

  18. Quantum dot-doped porous silicon metal-semiconductor metal photodetector.

    PubMed

    Chou, Chia-Man; Cho, Hsing-Tzu; Hsiao, Vincent K S; Yong, Ken-Tye; Law, Wing-Cheung

    2012-06-06

    In this paper, we report on the enhancement of spectral photoresponsivity of porous silicon metal-semiconductor metal (PS-MSM) photodetector embedded with colloidal quantum dots (QDs) inside the pore layer. The detection efficiency of QDs/PS hybrid-MSM photodetector was enhanced by five times larger than that of the undoped PS-MSM photodetector. The bandgap alignment between PS (approximately 1.77 eV) and QDs (approximately 1.91 eV) facilitates the photoinduced electron transfer from QDs to PS whereby enhancing the photoresponsivity. We also showed that the photoresponsitivity of QD/PS hybrid-MSM photodetector depends on the number of layer coatings of QDs and the pore sizes of PS.

  19. 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.

  20. 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.

  1. Flexible germanium nanomembrane metal-semiconductor-metal photodiodes

    NASA Astrophysics Data System (ADS)

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

    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/cm2 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Metal-Semiconductor Photodetectors for Optoelectric Receiver Applications.

    NASA Astrophysics Data System (ADS)

    Seo, Jong-Wook

    It has been found that the barrier height lowering observed in reverse-biased Schottky junction is due mainly to the change in electrical potential across the interfacial layer at the metal-semiconductor contact. The voltage dependence of barrier height is described, and excellent agreement with experimental data is shown. The surface state density and interfacial layer thickness of a (Ti/Au) /n-InAlAs Schottky junction are estimated from its I-V characteristics. The expressions of the barrier heights of junctions in a metal-semiconductor-metal photodiode (MSMPD) are derived, and excellent agreement with experiment is shown. The adjustment of barrier height and dark current by annealing is investigated based on the theory. The merit of transparent electrodes for MSMPD in an optoelectronic -integrated-circuit (OEIC) is described, and it is shown that the signal-to-noise-ratio (SNR) of a receiver can be improved by the employment of transparent electrodes. The design, fabrication, and characterization of MSMPDs for long- (lambda = 1.3 μm) and short-wavelength (lambda = 0.85 μm) applications are presented in detail. The deposition by RF magnetron sputtering and etching by reactive-ion-etching (RIE) of ITO film are described. It has been found that H_2 incorporation in an Ar plasma during ITO deposition improves the optical transmittance of the film at lambda = 1.3 mum. Responsivity was doubled by ITO electrodes and an anti-reflection (AR) coating. Bandwidths (3-dB) of 22 GHz and 16.6 GHz were obtained for long- and short-wavelength MSMPD, respectively. A 3-dB bandwidth of 6 GHz was obtained for both long-and short-wavelength ITO-MSMPDs. It is shown that the wide band-gap barrier enhancement layer reduces optical responsivity by capturing carriers at the heterointerface. The effects of surface and surface passivation on MSMPD performance are studied. The characterization of OEIC receiver with a transimpedance amplifier is described.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Multiple percolation transitions are observed in a binary system of RuO2-CaCu3Ti4O12 metal-semiconductor nanoparticle composites near percolation thresholds. Apart from a classical percolation transition, associated with the appearance of a continuous conductance path through RuO2 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.

  8. 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.

  9. Scale dependence of resistance fluctuations at metal-semiconductor junctions

    SciTech Connect

    Boudville, W.J.; McGill, T.C.

    1988-05-15

    The resistance fluctuations at a metal-semiconductor junction have been simulated as a function of the cross-sectional area of the contact at the interface. The fluctuations are due to the random spatial configurations of the dopants in the depletion region. The semiconductor is taken to be heavily doped n-GaAs. The conductance is computed over a square area. Dopings in the range of 10/sup 18/--2.5 x 10/sup 19/ cm/sup -3/ and square contacts with linear dimensions between 200 and 2000 A are considered. An analysis of this problem yields the result that the standard deviation of the conductance of the contacts scales as 1ln/sup 34/, where n is the doping and l is the device size. From simulations, the relative fluctuations are found to fall significantly as the device sizes are increased beyond 1000 A and as the doping is increased. The results of our simulations are found to agree with our scaling arguments

  10. 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.).

  11. 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).

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

    DOE PAGES

    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 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

  13. 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

  14. 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

  15. 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.

  16. 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

    2013-10-01

    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.

  17. Effects of radiation and temperature on gallium nitride (GaN) metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Chiamori, Heather C.; Angadi, Chetan; Suria, Ateeq; Shankar, Ashwin; Hou, Minmin; Bhattacharya, Sharmila; Senesky, Debbie G.

    2014-06-01

    The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

  18. 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

  19. 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

  20. 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

    2016-03-01

    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.

  1. 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

    2016-03-01

    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. PMID:26839956

  2. 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.

  3. The AMOS cell - An improved metal-semiconductor solar cell. [Antireflection coated Metal Oxide Semiconductor

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y.-C. M.

    1975-01-01

    A new fabrication process is being developed which significantly improves the efficiency of metal-semiconductor solar cells. The resultant effect, a marked increase in the open-circuit voltage, is produced by the addition of an interfacial layer oxide on the semiconductor. Cells using gold on n-type gallium arsenide have been made in small areas (0.17 sq cm) with conversion efficiencies of 15% in terrestrial sunlight.

  4. Interface recombination feature in metal-semiconductor junction at high photo-excitation

    NASA Astrophysics Data System (ADS)

    Konin, A.

    2014-09-01

    A theory of the photo-induced electromotive force in a p-type semiconductor accounting for the energy band bending and interface recombination dependence on excitation level is developed. It is shown that at high photo-excitation the effective interface recombination velocity in the metal-semiconductor junction is negligible compared with the volume one, when the surface potential is less than its critical value. The photo-induced electromotive force value is maximal at this condition.

  5. 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

  6. 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).

  7. Two-dimensional device modeling and analysis of GaInAs metal-semiconductor-metal photodiode structures

    NASA Astrophysics Data System (ADS)

    Averin, S.; Sachot, R.; Hugi, J.; de Fays, M.; Ilegems, M.

    1996-08-01

    A two-dimensional self-consistent time-dependent simulation technique has been developed to investigate electron-hole transport processes in the active region of metal-semiconductor-metal (MSM) interdigitated photodiode structures and to analyze their high-speed response. The distribution of the electric field inside the MSM device is determined by numerically solving the two-dimensional Poisson's equation by the modified fast elliptic solver method. A set of superparticles photogenerated at a particular wavelength is analyzed with a given initial distribution of the potential and given boundary conditions, and the evolution of the particles is traced in time through the active region of the MSM device. Circuit loading, electric field effects in the MSM structure with various finger separations, background doping, carrier trapping, and recombination are included in the simulation program. Owing to miniaturization of devices, the classical scaling laws lose their validity while various performance degrading effects appear. The simulations show that the main problem in MSM devices with a small contact separation is the low electric field penetration depth. This results in different electron and hole collection rates and in a poor response time. The trade-off between the high-speed response and the internal quantum efficiency is examined and ways to improve the high-speed response are indicated. Modeling results are compared with experimental data on Ga0.47In0.53As based MSM photodiodes.

  8. 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.

  9. Chemical trends of barrier heights in metal-semiconductor contacts: on the theory of the slope parameter

    NASA Astrophysics Data System (ADS)

    Mönch, Winfried

    1996-02-01

    The barrier heights in ideal metal-semiconductor contacts are determined by the continuum of the metal-induced gap states (MIGS). In generalizing Pauling's concept, the charge transfer across such interfaces may be modeled by the difference Xm - Xs of the metal and the semiconductor electronegativities. For n-type semiconductors this MIGS-and-electronegativity model describes the chemical trends of the barrier heights as φBn = φcnl + Sx( Xm - Xs). The zero-chargetransfer barrier heights φcnl were calculated for almost all semiconductors. The slope parameters Sx are determined by the density of states of the MIG states, the thickness of the respective interfacial double layer, and the interface dielectric constant ɛi. The densities of states and decay lengths of the metal-induced gap states at their charge neutrality level were computed by others for some of the semiconductors. It is demonstrated that these theoretical data predict the slope parameters Sx to vary proportional to (ɛ ∞ - 1) 2/ɛ i where ɛ∞ is the electronic contribution to the static dielectric constant of the semiconductor. This result confirms a previously found semi-empirical rule.

  10. 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.

  11. High responsivity 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Yang, Weifeng; Zhang, Feng; Liu, Zhuguang; Lü, Ying; Wu, Zhengyun

    2008-11-01

    4H-SiC based metal-semiconductor-metal (MSM) photodetectors with diverse spacing were designed, fabricated, and characterized, in which nickel Schottky contacts were needed. Current-voltage and spectral responsivity measurements were carried out at room temperature. The fabricated 4 μm-spacing device showed a very low dark current (0.25 pA at 5 V bias voltage), a typical responsivity of 0.103 A/W at 20 V, and a peak response wavelength at 290 nm. The fabricated devices held a high DUV to visible rejection ratio of >103.

  12. 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. PMID:27427689

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. Hydrogen sensors using nitride-based semiconductor diodes: the role of metal/semiconductor interfaces.

    PubMed

    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

  18. Metal semiconductor transition in undoped ZnO films deposited by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Kavasoglu, Nese; Sertap Kavasoglu, A.

    2008-08-01

    ZnO films were deposited on glass substrate by using spray pyrolysis method. Films were deposited at different solution molarities 0.02 and 0.1 M. The films are highly transparent in the visible range of the electromagnetic spectrum with a transmission reaching up values to 90%. Band gaps were calculated as 3.24 and 3.28 eV with the help of transmission spectrums. When the solution molarity of the sprayed solution is increased from 0.02 to 0.1 M, carrier concentrations of the films increase from 1.6×10 19 cm -3 to 5.1×10 19 cm -3. Temperature-dependent conductivity measurements of these conducting and transparent films also showed, for the first time, a metal-semiconductor transition (MST). The deposited ZnO films show metallic conductivity above ∼420 K and semiconducting behavior at temperatures below it.

  19. Fisrt-principles calculations on metal-induced gap states at metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Gohda, Y.; Tsuneyuki, S.

    2010-03-01

    Metal-induced gap states (MIGS) are responsible for Fermi-level pinning for narrow-gap semiconductors such as Si and GaAs. First-principles calculations have demonstrated that MIGS are related to the tails of metal states penetrating into the semiconductor corresponding to Bloch states with wave vectors having an imaginary part. Thus, their existence is a consequence of intrinsic properties of the bulk semiconductor. In contrast, a removal of FLP has been reported experimentally at atomically controlled Al-Si(100) interfaces, suggesting that MIGS play a less dominant role in determining the interface properties. This inconsistency between experimental results and the accepted view of MIGS calls for a detailed theoretical investigation. Here, we report our recent progresses on MIGS at a few metal-semiconductor interfaces investigated by means of first-principles calculations.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02285a

  1. 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.

  2. Nanomesh electrode on MgZnO-based metal-semiconductor-metal ultraviolet photodetectors

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lin, Heng-Yu; Tseng, Chun-Yen

    2015-09-01

    In this work, the nano-scaled mesh electrodes are fabricated by obliquely depositing metals through the highly ordered polystyrene nanosphere mask. Furthermore, the intrinsic MgZnO film is deposited as the absorption layer for the metal-semiconductor-metal ultraviolet photodetectors (MSM-UV-PDs) using the vapor cooling condensation system. The 100-nm-linewidth nanomesh electrodes with metal occupying a roughly 10% of the device surface region consequently render PDs with a high transmittance in the ultraviolet (UV) wavelength range. The photoresponsivity of MgZnO-based MSM-UV-PDs evaluated at the wavelength of 330 nm with the operating bias voltage of 5 V is elevated from 0.135 to 0.248 A/W when the thin metal electrode is replaced by the nanomesh electrode, and the corresponding quantum efficiency is improved from 50.75 to 93.23%. Finally, adopting the nanomesh electrode also helps to enhance the UV-visible rejection ratio (R330nm/R450nm) and the detectivity from 1663 and 1.78 × 1010 cmHz0.5W-1 to 2480 and 2.43 × 1010 cmHz0.5W-1, respectively.

  3. Thermal conductivity of (Zr,W)N/ScN metal/semiconductor multilayers and superlattices

    SciTech Connect

    Rawat, Vijay; Sands, Timothy D.; Koh, Yee Kan; Cahill, David G.

    2009-01-15

    The cross-plane thermal conductivities of metal/semiconductor multilayers and epitaxial superlattices have been measured as a function of period by time-domain thermoreflectance at room temperature. (001)-oriented ZrN (metal)/ScN (semiconductor) multilayers and (Zr,W)N/ScN epitaxial superlattices with the rocksalt crystal structure were grown on (001)MgO substrates by reactive magnetron sputtering. A distinct minimum in thermal conductivity at a period of {approx}6 nm is observed for ZrN/ScN multilayers. The minimum thermal conductivity of 5.25 W/m K is a factor of {approx}2.7 smaller than the mean of the thermal conductivities (including only the lattice contributions) of the values measured for films of the constituent materials, and approximately equal to the lattice component of the thermal conductivity of a Zr{sub 0.65}Sc{sub 0.35}N alloy film ({approx}5 W/m K). Alloying the ZrN layers with WN{sub x} reduces the lattice mismatch, yielding epitaxial (Zr,W)N/ScN superlattices. The addition of WN{sub x} also reduces the thermal conductivity to {approx}2 W/m K, a value that is sufficiently low to suggest promise for these materials as solid-state thermionic generators.

  4. 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.

  5. Alkyl monolayer passivated metal-semiconductor diodes: 2: Comparison with native silicon oxide.

    PubMed

    Liu, Yong-Jun; Yu, Hua-Zhong

    2003-04-14

    To understand the electrical properties at passivated metal-semiconductor interfaces, two types of mercury-insulator-silicon (n-type) junctions, Hg\\C10H21-Si and Hg\\SiO2-Si, were fabricated and their current-voltage and capacitance-voltage characteristics compared. Both of them exhibited near-ideal rectifying characteristics with an excellent saturation current at reverse bias, which is in contrast to the previously reported ohmic behavior of an unmodified mercury-silicon junction. The experimental results also indicated that the n-decyl monolayer passivated junction possesses a higher effective barrier height, a lower ideality factor (that is, closer to unity), and better reproducibility than that of native silicon oxide. In addition, the dopant density and build-in potential, extracted from capacitance-voltage measurements of these passivated mercury-silicon junctions, revealed that alkyl monolayer derivatization does not alter the intrinsic properties of the silicon substrate. The calculated surface state density at the alkyl monolayer\\silicon interface is lower than that of the silicon oxide\\silicon interface. The present study increases the possibility of using advanced organic materials as ultrathin insulator layers for miniaturized, silicon-based microelectronic devices.

  6. 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.

  7. 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.

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

    PubMed

    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

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

    PubMed

    Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

    2005-08-01

    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. PMID:16852830

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

    PubMed

    Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

    2005-08-01

    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.

  11. 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

  12. 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.

  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. 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

  15. 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.

  16. 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

  17. Dynamics of the formation of laser-induced periodic surface structures (LIPSS) upon femtosecond two-color double-pulse irradiation of metals, semiconductors, and dielectrics

    NASA Astrophysics Data System (ADS)

    Höhm, S.; Herzlieb, M.; Rosenfeld, A.; Krüger, J.; Bonse, J.

    2016-06-01

    In order to address the dynamics and physical mechanisms of LIPSS formation for three different classes of materials (metals, semiconductors, and dielectrics), two-color double-fs-pulse experiments were performed on Titanium, Silicon and Fused Silica. For that purpose a Mach-Zehnder interferometer generated polarization controlled (parallel or cross-polarized) double-pulse sequences at 400 nm and 800 nm wavelength, with inter-pulse delays up to a few picoseconds. Multiple of these two-color double-pulse sequences were collinearly focused by a spherical mirror to the sample surfaces. The fluence of each individual pulse (400 nm and 800 nm) was always kept below its respective ablation threshold and only the joint action of both pulses lead to the formation of LIPSS. Their resulting characteristics (periods, areas) were analyzed by scanning electron microscopy. The periods along with the LIPSS orientation allow a clear identification of the pulse which dominates the energy coupling to the material. For strong absorbing materials (Silicon, Titanium), a wavelength-dependent plasmonic mechanism can explain the delay-dependence of the LIPSS. In contrast, for dielectrics (Fused Silica) the first pulse always dominates the energy deposition and LIPSS orientation, supporting a non-plasmonic formation scenario. For all materials, these two-color experiments confirm the importance of the ultrafast energy deposition stage for LIPSS formation.

  18. Formation of Metal-Semiconductor Interfaces on Mbe-Grown Gallium ARSENIDE(100): Surface Photovoltage, Chemistry and Band Bending

    NASA Astrophysics Data System (ADS)

    Mao, Duli

    1992-01-01

    found for all three interfaces, supporting the metal induced gap states (MIGS) model for Schottky barrier formation. The synchrotron radiation-induced surface photovoltage (SPV), which could invalidate the apparent band bending measured with PES, is studied as a function of metal coverage and temperature, using a Kelvin probe. A large (0.55eV) and quasi-permanent SPV is observed on lightly doped n -GaAs at LT. A non-negligible (0.2eV) SPV is also observed at room temperature. No SPV is detected on highly doped GaAs. The impact of this synchrotron radiation induced SPV on the photoemission study of metal-semiconductor interfaces is discussed.

  19. Dependence of GaAs-AlxGa1 - xAs heterostructures on Al composition for metal-semiconductor field-effect transistor operation

    NASA Astrophysics Data System (ADS)

    Hiruma, Kenji; Mori, Mitsuhiro; Kakibayashi, Hiroji; Ihara, Ayako; Takahashi, Susumu; Yanokura, Eiji

    1989-08-01

    High-quality GaAs-AlxGa1-xAs heterostructures for metal-semiconductor field-effect transistor (MESFET) applications have been grown by metalorganic vapor-phase epitaxy. High electron Hall mobility of up to 4000 cm2/(V s) for a carrier concentration of 3.5×1017 cm-3 was obtained for Si-doped GaAs grown on AlxGa1-xAs. It was learned that the electron Hall mobility of GaAs is not dependent on the Al composition of the AlxGa1-xAs buffer layer for 0≤x≤0.8. Good drain current-voltage saturation characteristics were observed for GaAs MESFETs with a 0.3-μm gate length and AlxGa1-xAs buffer layers. At drain voltages below 3 V, the drain conductance was at its lowest for Al composition around x=0.6. However, an anomalous peak in the drain conductance was observed at drain voltages of 3-6 V and at Al compositions of x=0.6 and 0.8. Drain conductance also increased as x did for x≥0.45 when measured at a microwave frequency. These phenomena can be understood by considering electron injection into the buffer/substrate region from the GaAs channel. The amount of this injection coincided well with the reduction in the conduction-band energy barrier at the GaAs-AlxGa1-xAs heterointerface for x>0.45 for electron transport.

  20. Single- and dual-wavelength photodetectors with MgZnO/ZnO metal-semiconductor-metal structure by varying the bias voltage

    NASA Astrophysics Data System (ADS)

    Hwang, J. D.; Lin, G. S.

    2016-09-01

    By varying the bias voltage of an Mg x Zn1-x O/ZnO metal-semiconductor-metal photodetector (MSM-PDs), the detection wavelength can be modulated from a single to a dual wavelength. A long-wavelength band response is caused by the ZnO absorption and a short-wavelength band response is caused by Mg x Zn1-x O. At a 0 V bias voltage, the photogenerated electrons in ZnO are confined to the Mg x Zn1-x O/ZnO interface, arising from the piezoelectric polarization. The accumulated electrons hop the Mg x Zn1-x O layer through the assistance of defects; however, the photogenerated electrons in Mg x Zn1-x O cannot cross over the large barrier height at the Au/MgZnO interface, resulting in a single-wavelength photodetector with a long-wavelength band (345-400 nm) having a peak wavelength of 370 nm. By increasing the bias voltage to 1-2 V, the barrier height is lowered, enabling the photogenerated electrons in Mg x Zn1-x O to easily cross over the low barrier height, leading to dual-wavelength photodetectors having peak wavelengths of 370 and 340 nm. On further increasing the bias voltage beyond 2 V, the photogenerated electrons in ZnO sink deeply in the hollow at the Mg x Zn1-x O/ZnO interface owing to the large applied voltage. These electrons are effectively confined at the Mg x Zn1-x O/ZnO interface, which retards the tunneling of the photogenerated electrons in ZnO through the Mg x Zn1-x O layer; hence the MSM-PDs revert back to single wavelength photodetectors; however, the detection wavelength is different from that of the MSM-PDs biased at 0 V. Instead of having a long-wavelength band (345-400 nm), the MSM-PDs demonstrate a short-wavelength band (320-345 nm) at a 3 V bias voltage.

  1. Single- and dual-wavelength photodetectors with MgZnO/ZnO metal-semiconductor-metal structure by varying the bias voltage.

    PubMed

    Hwang, J D; Lin, G S

    2016-09-16

    By varying the bias voltage of an Mg x Zn1-x O/ZnO metal-semiconductor-metal photodetector (MSM-PDs), the detection wavelength can be modulated from a single to a dual wavelength. A long-wavelength band response is caused by the ZnO absorption and a short-wavelength band response is caused by Mg x Zn1-x O. At a 0 V bias voltage, the photogenerated electrons in ZnO are confined to the Mg x Zn1-x O/ZnO interface, arising from the piezoelectric polarization. The accumulated electrons hop the Mg x Zn1-x O layer through the assistance of defects; however, the photogenerated electrons in Mg x Zn1-x O cannot cross over the large barrier height at the Au/MgZnO interface, resulting in a single-wavelength photodetector with a long-wavelength band (345-400 nm) having a peak wavelength of 370 nm. By increasing the bias voltage to 1-2 V, the barrier height is lowered, enabling the photogenerated electrons in Mg x Zn1-x O to easily cross over the low barrier height, leading to dual-wavelength photodetectors having peak wavelengths of 370 and 340 nm. On further increasing the bias voltage beyond 2 V, the photogenerated electrons in ZnO sink deeply in the hollow at the Mg x Zn1-x O/ZnO interface owing to the large applied voltage. These electrons are effectively confined at the Mg x Zn1-x O/ZnO interface, which retards the tunneling of the photogenerated electrons in ZnO through the Mg x Zn1-x O layer; hence the MSM-PDs revert back to single wavelength photodetectors; however, the detection wavelength is different from that of the MSM-PDs biased at 0 V. Instead of having a long-wavelength band (345-400 nm), the MSM-PDs demonstrate a short-wavelength band (320-345 nm) at a 3 V bias voltage. PMID:27501372

  2. 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.

  3. 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.

  4. Stability of In-Ga-Zn-O metal-semiconductor field-effect-transistors under bias, illumination, and temperature stress

    NASA Astrophysics Data System (ADS)

    Dang, Giang T.; Kawaharamura, Toshiyuki; Furuta, Mamoru; Saxena, Saurabh; Allen, Martin W.

    2015-10-01

    The stability of metal-semiconductor field-effect-transistors (MESFETs) with silver oxide Schottky gates on In-Ga-Zn-O (IGZO) channels, grown by mist chemical-vapor-deposition, was examined under different combinations of positive and negative bias, illumination, and temperature stress. These devices were remarkably stable, even under the most severe condition of negative-bias-illumination-temperature-stress (NBITS), where the threshold voltage shift after 10 h NBITS was only +0.12 V and was mainly attributed to a decrease in the carrier density of the channel. The stability of these IGZO MESFETs is associated with the use of a conducting Schottky gate that significantly reduces charge trapping at the gate-channel interface.

  5. 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.

  6. 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

  7. 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.

  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. 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.

  10. 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.

  11. 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. PMID:26726685

  12. 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.

  13. SEMICONDUCTOR DEVICES: Simulation and optimization of a 6H-SiC metal-semiconductor-metal ultraviolet photodetector

    NASA Astrophysics Data System (ADS)

    Bin, Chen; Yintang, Yang; Yuejin, Li; Hongxia, Liu

    2010-06-01

    Based on thermionic emission theory, a model of a 6H-SiC metal-semiconductor-metal (MSM) ultraviolet photodetector is established with the simulation package ISE-TCAD. A device with 3 μm electrode width (W) and 3 μm electrode spacing (L) is simulated. The findings show that the MSM photodetector has quite a low dark current of 15 pA at 10 V bias and the photocurrent is two orders of magnitude higher than the dark current. The influences of different structures on dark and illuminated current-voltage characteristics of the MSM photodetector are investigated to optimize the device parameters. Simulation results indicate that the maximum photocurrent and the highest ratio of photocurrent to dark current at 15 V bias are 5.3 nA and 327 with device parameters of W = 6 μm, L = 3 μm and W = 3 μm, L = 6 μm, respectively.

  14. Surface-emitting quantum cascade laser with 2nd-order metal-semiconductor gratings for single-lobe emission

    NASA Astrophysics Data System (ADS)

    Boyle, C.; Sigler, C.; Kirch, J. D.; Lindberg, D.; Earles, T.; Botez, D.; Mawst, L. J.

    2016-03-01

    Grating-coupled, surface-emitting (GCSE) quantum-cascade lasers (QCLs) are demonstrated with high-power, single-lobe surface emission. A 2nd-order Au-semiconductor distributed-feedback (DFB)/ distributed-Bragg-reflector (DBR) grating is used for feedback and out-coupling. The DFB and DBR grating regions are 2.55 mm- and 1.28 mm-long, respectively, for a total grating length of 5.1 mm. The lasers are designed to operate in a symmetric longitudinal mode by causing resonant coupling of the guided optical mode to the antisymmetric surface-plasmon modes of the 2nd-order metal/semiconductor grating. In turn, the antisymmetric longitudinal modes are strongly absorbed by the metal in the grating, causing the symmetric longitudinal mode to be favored to lase, which produces a single lobe beam over a grating duty-cycle range of 36-41 %. Simulations indicate that the symmetric mode is always favored to lase, independent of the random phase of residual reflections from the device's cleaved ends. Peak pulsed output powers of ~ 0.4 W were measured with single-lobe, single-mode operation near 4.75 μm.

  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. 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

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. Enhancement effect of short-circuit currents of Si solar cells with inclusion of indium tin oxide layers on metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Ji, Hyung Yong; Parida, Bhaskar; Park, Seungil; Kim, Myeong Jun; Chung, Sang Jo; Kim, Keunjoo

    2015-10-01

    We investigated the enhancement effect on short-circuit currents by indium tin oxide contact layers imbedded in metal-semiconductor interfaces in Si solar cells. Both samples that incorporate the thin film layer and the crossed finger lines of indium tin oxide exhibit an enhancement of p-n junction photocurrents and depletion capacitances with enhanced bulk donor concentrations at the emitter contacts. The indium tin oxide layer provides the passivation layer on the Si emitter surface with reduced trap states and the carrier transport layer for charge collection. The Si solar cells with indium tin oxide showed improved performance in shunt resistance and short-circuit current.

  2. 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.

  3. Coplanar metal-semiconductor-metal light-emitting devices with an n++ InGaN layer and their application to display

    NASA Astrophysics Data System (ADS)

    Long, H.; Zeng, Y. P.; Mei, Y.; Ying, L. Y.; Zhang, B. P.

    2016-06-01

    We demonstrated a new kind of InGaN/GaN multi-quantum well (MQW) light-emitting diode (LED) with simplified fabrication processes, where only one round of photolithography and electrode deposition is necessary. The electrical and optical properties of this LED, which is defined as a coplanar metal-semiconductor-metal (CMSM) LED, were characterized. The electroluminescence spectrum only exhibits blue emission at 450 nm, meaning that the light comes exclusively from MQWs. The optical output at 20 mA was comparable to that of conventional LEDs. A shunt circuit model with a surface thin film resistance, an n++ InGaN/p-GaN/n-GaN structure and a p-GaN/n-GaN junction was proposed to explain the working mechanism of the CMSM LED. A proof-of-concept display was demonstrated, exploiting the promising application of CMSM LED to display.

  4. 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.

  5. 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

    2015-08-01

    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.

  6. Improved performance of GaN metal-semiconductor-metal ultraviolet detectors by depositing SiO2 nanoparticles on a GaN surface

    NASA Astrophysics Data System (ADS)

    Sun, Xiaojuan; Li, Dabing; Jiang, Hong; Li, Zhiming; Song, Hang; Chen, Yiren; Miao, Guoqing

    2011-03-01

    GaN metal-semiconductor-metal (MSM) ultraviolet detectors were investigated by depositing different density of SiO2 nanoparticles (SNPs) on the GaN. It was shown that the dark current of the detectors with SNPs was more than one order of magnitude lower than that without SNPs and the peak responsivity was enhanced after deposition of the SNPs. Atomic force microscopy observations indicated that the SNPs usually formed at the termination of screw and mixed dislocations, and further current-voltage measurements showed that the leakage of the Schottky contact for the GaN MSM detector decreased with deposited the SNPs. Moreover, the leakage obeyed the Frenkel-Poole emission model, which meant that the mechanism for improving the performance is the SNPs passivation of the dislocations followed by the reduction in the dark current.

  7. 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. PMID:25182502

  8. 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

    2015-11-01

    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. PMID:26479951

  9. High-performance AlGaN metal-semiconductor-metal solar-blind ultraviolet photodetectors by localized surface plasmon enhancement

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Xu, Jin; Ye, Wei; Li, Yang; Qi, Zhiqiang; Dai, Jiangnan; Wu, Zhihao; Chen, Changqing; Yin, Jun; Li, Jing; Jiang, Hao; Fang, Yanyan

    2015-01-01

    AlGaN-based solar-blind ultraviolet photodetectors have attractive potential applications in the fields of missile plume detection, biochemical sensing, solar astronomy, etc. In this work, significant deep ultraviolet detection enhancement is demonstrated on AlGaN-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetectors by introducing the coupling of localized surface plasmon from Al nanoparticles with the high-Al-content AlGaN epilayer. The size-controlled Al nanoparticle arrays fabricated by nanosphere lithography can not only reduce the detectors' dark current but also bring about greatly enhanced responsivity. The peak responsivity of AlGaN-based MSM solar-blind ultraviolet photodetectors with Al nanoparticles can reach 2.34 A/W at 269 nm under 20 V bias, enhanced more than 25 times than that without Al nanoparticles. Our approach shows an efficient fabrication technique of high-performance and low-cost plasmonic enhanced AlGaN solar-blind MSM ultraviolet photodetectors.

  10. ZnO-based hollow nanoparticles by selective etching: elimination and reconstruction of metal-semiconductor interface, improvement of blue emission and photocatalysis.

    PubMed

    Zeng, Haibo; Cai, Weiping; Liu, Peisheng; Xu, Xiaoxia; Zhou, Huijuan; Klingshirn, Claus; Kalt, Heinz

    2008-08-01

    A weak acid selective etching strategy was put forward to fabricate oxide-based hollow nanoparticles (HNPs) using core/shell nanostructures of active metal/oxide nanoparticles as sacrificial templates. ZnO-based HNPs, including pure ZnO, Au/ZnO, Pt/ZnO, and Au/Pt/ZnO HNPs with diameter below 50 nm and shell thickness below 6 nm has been first achieved at low temperature. The diameter, thickness, and even sizes of ZnO and noble metal ultrafine crystals of HNPs can be well adjusted by the etching process. Synchronous with the formation of HNPs, the internal metal-semiconductor interfaces can be controllably eliminated (Zn-ZnO) and reconstructed (noble metal-ZnO). Excitingly, such microstructure manipulation has endued them with giant improvements in related performances, including the very strong blue luminescence with enhancement over 3 orders of magnitude for the pure ZnO HNPs and the greatly improved photocatalytic activity for the noble metal/ZnO HNPs. These give them strong potentials in relevant applications, such as blue light emitting devices, environment remediation, drug delivery and release, energy storage and conversion, and sensors. The designed fabrication procedure is simple, feasible, and universal for a series of oxide and noble metal/oxide HNPs with controlled microstructure and improved performances.

  11. Metal-Semiconductor-Metal Near-Ultraviolet (~380 nm) Photodetectors by Selective Area Growth of ZnO Nanorods and SiO2 Passivation

    NASA Astrophysics Data System (ADS)

    Lee, Soo Hyun; Kim, Sang Hun; Yu, Jae Su

    2016-07-01

    Metal-semiconductor-metal near-ultraviolet (NUV) photodetectors (PDs) based on zinc oxide (ZnO) nanorods (NRs), operating at λ ~ 380 nm, were fabricated using conventional photolithography and hydrothermal synthesis processes. The vertically aligned ZnO NRs were selectively grown in the channel area of PDs. The performance of ZnO NR-based NUV PDs was optimized by varying the solution concentration and active channel width ( W ch). For the fabricated samples, their electrical and photoresponse properties were investigated under the dark state and the illumination at wavelength of ~380 nm, respectively. For the device ( W ch = 30 μm) with ZnO NRs at 25 mM, the highest photocurrent of 0.63 mA was obtained with the on/off ratio of 1720 at the bias of 5 V. The silicon dioxide passivation was also carried out to improve the photoresponse properties of PDs. The passivated devices exhibited faster rise and reset times rather than those of the unpassivated devices.

  12. Metal-Semiconductor-Metal Near-Ultraviolet (~380 nm) Photodetectors by Selective Area Growth of ZnO Nanorods and SiO2 Passivation.

    PubMed

    Lee, Soo Hyun; Kim, Sang Hun; Yu, Jae Su

    2016-12-01

    Metal-semiconductor-metal near-ultraviolet (NUV) photodetectors (PDs) based on zinc oxide (ZnO) nanorods (NRs), operating at λ ~ 380 nm, were fabricated using conventional photolithography and hydrothermal synthesis processes. The vertically aligned ZnO NRs were selectively grown in the channel area of PDs. The performance of ZnO NR-based NUV PDs was optimized by varying the solution concentration and active channel width (W ch). For the fabricated samples, their electrical and photoresponse properties were investigated under the dark state and the illumination at wavelength of ~380 nm, respectively. For the device (W ch = 30 μm) with ZnO NRs at 25 mM, the highest photocurrent of 0.63 mA was obtained with the on/off ratio of 1720 at the bias of 5 V. The silicon dioxide passivation was also carried out to improve the photoresponse properties of PDs. The passivated devices exhibited faster rise and reset times rather than those of the unpassivated devices. PMID:27422775

  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. 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.

  15. 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.

  16. Collective excitation of plasmonic hot-spots for enhanced hot charge carrier transfer in metal/semiconductor contacts

    NASA Astrophysics Data System (ADS)

    Piot, Adrien; Earl, Stuart K.; Ng, Charlene; Dligatch, Svetlana; Roberts, Ann; Davis, Timothy J.; Gómez, Daniel E.

    2015-04-01

    We show how a combination of near- and far-field coupling of the localised surface plasmon resonances in aluminium nanoparticles deposited on TiO2 films greatly enhances the visible light photocatalytic activity of the semiconductor material. We demonstrate two orders of magnitude enhancement in the rate of decomposition of methylene blue under visible light illumination when the surface of TiO2 films is decorated with gratings of Al nanoparticle dimers.We show how a combination of near- and far-field coupling of the localised surface plasmon resonances in aluminium nanoparticles deposited on TiO2 films greatly enhances the visible light photocatalytic activity of the semiconductor material. We demonstrate two orders of magnitude enhancement in the rate of decomposition of methylene blue under visible light illumination when the surface of TiO2 films is decorated with gratings of Al nanoparticle dimers. Electronic supplementary information (ESI) available: Detailed information on estimates of hot-electron injection efficiencies, electrodynamic simulations, sample preparation, spectroscopic and structural characterization and photocatalytic experiments. See DOI: 10.1039/c5nr01592h

  17. 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.

  18. Effects of variations in precursor concentration on the growth of rutile TiO2 nanorods on Si substrate with fabricated fast-response metal-semiconductor-metal UV detector

    NASA Astrophysics Data System (ADS)

    Selman, Abbas M.; Hassan, Z.

    2015-06-01

    This study aimed to investigate the effects of variations in precursor concentration (TiCl3 solution) on the structural, morphological, and optical properties of rutile titanium dioxide (TiO2) nanorods and fabricated metal-semiconductor-metal UV detector depending on the optimal sample. The nanorods were prepared from an aqueous solution of titanium (III) chloride (TiCl3) on p-type, (1 1 1)-oriented Si substrates at different concentrations of TiCl3 solutions (2, 3, 4, and 5 mM). The experimental results showed that the TiO2 nanorods grown at 4 mM concentration exhibited optimal structural properties. A fast-response metal-semiconductor-metal UV detector was fabricated by depositing Pt contacts on the front of the optimal sample via RF reactive magnetron sputtering. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias voltage, the device showed 44.4 sensitivity. In addition, the internal gain was 1.45, and the photoresponse peak was 70 mA/W. The response and the recovery times were calculated to be 7.8 ms upon illumination to a pulse UV light (365 nm) at 5 V bias voltage.

  19. 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

  20. Electron

    NASA Astrophysics Data System (ADS)

    Springford, Michael

    1997-03-01

    1. J. J. Thomson and the discovery of the electron A. B. P. Pippard; 2. The isolated electron W. N. Cottingham; 3. The relativistic electron D. I. Olive; 4. The electron glue B. L. Gyorffy; 5. The electron fluid P. Coleman; 6. The magnetic electron G. G. Lonzarich; 7. The paired electron A. J. Leggett; 8. The heavy electron M. Springford; 9. The coherent electron Y. Imry and M. Peskin; 10. The composite electron R. Nicholas; 11. The electron in the cosmos M. S. Longair.

  1. Electron

    NASA Astrophysics Data System (ADS)

    Springford, Michael

    2008-12-01

    1. J. J. Thomson and the discovery of the electron A. B. P. Pippard; 2. The isolated electron W. N. Cottingham; 3. The relativistic electron D. I. Olive; 4. The electron glue B. L. Gyorffy; 5. The electron fluid P. Coleman; 6. The magnetic electron G. G. Lonzarich; 7. The paired electron A. J. Leggett; 8. The heavy electron M. Springford; 9. The coherent electron Y. Imry and M. Peskin; 10. The composite electron R. Nicholas; 11. The electron in the cosmos M. S. Longair.

  2. 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

  3. 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.

  4. 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...

  5. Visible-light photodecomposition of acetaldehyde by TiO2-coated gold nanocages: plasmon-mediated hot electron transport via defect states.

    PubMed

    Kodiyath, Rajesh; Manikandan, Maidhily; Liu, Lequan; Ramesh, Gubbala V; Koyasu, Satoshi; Miyauchi, Masahiro; Sakuma, Yoshiki; Tanabe, Toyokazu; Gunji, Takao; Duy Dao, Thang; Ueda, Shigenori; Nagao, Tadaaki; Ye, Jinhua; Abe, Hideki

    2014-12-21

    Skeletal gold nanocages (Au NCs) are synthesized and coated with TiO2 layers (TiO2-Au NCs). The TiO2-Au NCs exhibit enhanced photodecomposition activity toward acetaldehyde under visible light (>400 nm) illumination because hot electrons are generated over the Au NCs by local surface plasmon resonance (LSPR) and efficiently transported across the metal/semiconductor interface via the defect states of TiO2. PMID:25357137

  6. 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

  7. Metal-semiconductor-transition observed in Bi{sub 2}Ca(Sr, Ba){sub 2}Co{sub 2}O{sub 8+δ} single crystals

    SciTech Connect

    Dong, Song-Tao; Zhang, Bin-Bin; Zhang, Lun-Yong; Yao, Shu-Hua E-mail: shyao@nju.edu.cn; Zhou, Jian; Zhang, Shan-Tao; Gu, Zheng-Bin; Chen, Yan-Feng; Chen, Y. B. E-mail: shyao@nju.edu.cn

    2014-07-28

    Electrical property evolution of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} single crystals (AE = Ca, Sr and Ba) is systematically explored. When AE changes from Ca to Ba, the electrical property of Bi{sub 2}Ca{sub 2}Co{sub 2}O{sub 8+δ} and Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} demonstrates semiconductor-like properties. But Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} shows the metallic behavior. Analysis of temperature-dependent resistance substantiates that from metallic Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} to semiconductor-like Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} can be attributed to Anderson localization. However the semiconductor behaviour of Bi{sub 2}Sr{sub 2}Co{sub 2}O{sub 8+δ} and Bi{sub 2}Ca{sub 2}Co{sub 2}O{sub 8+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 Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} compared with other two compounds. It suggests that Bi{sub 2}Ba{sub 2}Co{sub 2}O{sub 8+δ} is more apt to be metal in this material system.

  8. Embedding plasmonic nanostructure diodes enhances hot electron emission.

    PubMed

    Knight, Mark W; Wang, Yumin; Urban, Alexander S; Sobhani, Ali; Zheng, Bob Y; Nordlander, Peter; Halas, Naomi J

    2013-04-10

    When plasmonic nanostructures serve as the metallic counterpart of a metal-semiconductor Schottky interface, hot electrons due to plasmon decay are emitted across the Schottky barrier, generating measurable photocurrents in the semiconductor. When the plasmonic nanostructure is atop the semiconductor, only a small percentage of hot electrons are excited with a wavevector permitting transport across the Schottky barrier. Here we show that embedding plasmonic structures into the semiconductor substantially increases hot electron emission. Responsivities increase by 25× over planar diodes for embedding depths as small as 5 nm. The vertical Schottky barriers created by this geometry make the plasmon-induced hot electron process the dominant contributor to photocurrent in plasmonic nanostructure-diode-based devices. PMID:23452192

  9. 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.

  10. Conductors, semiconductors, and insulators irradiated with short-wavelength free-electron laser

    NASA Astrophysics Data System (ADS)

    Krzywinski, J.; Sobierajski, R.; Jurek, M.; Nietubyc, R.; Pelka, J. B.; Juha, L.; Bittner, M.; Létal, V.; Vorlíček, V.; Andrejczuk, A.; Feldhaus, J.; Keitel, B.; Saldin, E. L.; Schneidmiller, E. A.; Treusch, R.; Yurkov, M. V.

    2007-02-01

    The results of a study of irreversible changes induced at surfaces of metals, semiconductors, and insulators by extreme ultraviolet (λ<100nm) ultrashort pulses provided by TESLA Test Facility Free-Electron Laser, Phase 1 (TTF1 FEL) are reported and discussed. The laser was tuned at 86, 89, and 98nm during the experiments reported here. Energy spectra of ions ejected from the irradiated surfaces are also reported. Special attention is paid to the difference in the ablation behavior of (semi)conductors and insulators that we have observed. The difference is dramatic, while the absorption coefficients are similar for all materials at the TTF1 FEL wavelength.

  11. 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

  12. Electronic, magnetic and transport properties of rare-earth monopnictides.

    PubMed

    Duan, Chun-Gang; Sabirianov, R F; Mei, W N; Dowben, P A; Jaswal, S S; Tsymbal, E Y

    2007-08-01

    The electronic structures and magnetic properties of many rare-earth monopnictides are reviewed in this article. Possible candidate materials for spintronics devices from the rare-earth monopnictide family, i.e. high polarization (nominally half-metallic) ferromagnets and antiferromagnets, are identified. We attempt to provide a unified picture of the electronic properties of these strongly correlated systems. The relative merits of several ab initio theoretical methods, useful in the study of the rare-earth monopnictides, are discussed. We present our current understanding of the possible half-metallicity, semiconductor-metal transitions, and magnetic orderings in the rare-earth monopnictides. Finally, we propose some potential strategies to improve the magnetic and electronic properties of these candidate materials for spintronics devices. PMID:21694120

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. Influence of electromechanical coupling and electron irradiation on the conductivity of individual ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Li, Huifeng; Huang, Yunhua; Zhang, Qi; Liu, Jing; Zhang, Yue

    2011-03-01

    We reported the electrical properties of individual ZnO nanowire (NW) with length 20 μm and diameter 100 nm, which prepared by thermal evaporation process. The individual ZnO NW was connected to the tungsten tips with typical metal-semiconductor-metal model, and the current-voltage curves were measured in a nano-manipulation and measurement system. The results indicated that the conductivity of the individual ZnO NW was decreased for inflicting an additional force on ZnO NW from tungsten tip. Moreover, the rectifier characteristics of ZnO NW were affected with the electron beam turning on or off in the chamber of scanning electron microscope.

  18. 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.

  19. Damage to III-V Devices During Electron Cyclotron Resonance Chemical Vapor Deposition

    SciTech Connect

    Abernathy, C.R.; Hahn, Y.B.; Hays, D.C.; Johnson, D.; Lee, J.W.; MacKenzie, K.; Pearton, S.J.; Ren, F.; Shul, R.J.

    1998-10-14

    GaAs-based metal semiconductor field effect transistors (MESFETS), heterojunction bipolar transistors (HBTs) and high electron mobility transistors (HEMTs) have been exposed to ECR SiJ&/NH3 discharges for deposition of SiNX passivating layers. The effect of source power, rf chuck power, pressure and plasma composition have been investigated. Effects due to both ion damage and hydrogenation of dopants are observed. For both HEMTs and MESFETS there are no conditions where substantial increases in channel sheet resistivity are not observed, due primarily to (Si-H)O complex formation. In HBTs the carbon-doped base layer is the most susceptible layer to hydrogenation. Ion damage in all three devices is minimized at low rf chuck power, moderate ECR source power and high deposition rates.

  20. The effects on the electronic properties of BN nanoribbon with C-chain substitution doping

    NASA Astrophysics Data System (ADS)

    Wang, Zhiyong; Zhao, Yayun; Sun, Mengyao; Xiao, Jianrong; Lu, Maowang; Wang, Liu; Zeng, Yaping; Long, Mengqiu

    2016-08-01

    The electronic properties of Boron-Nitrogen (BN) nanoribbon with Carbon (C)-chain substitution doping are investigated by performing first-principle calculations based on density functional theory. For the zigzag BN nanoribbon, the spin-unpolarized calculated results exhibit the insulator-semiconductor-metal transition with the number of substitution C-chain increasing. But for the armchair BN nanoribbon in the spin-unpolarized calculations, it is found that it appears the insulator-metal-semiconductor transition. The band gap of BN nanoribbon can be tuned according to the C-chain doping ratio. Interestingly, spin-polarized calculations exhibiting half-metallic may be tuned by changing the number of C-chain in the zigzag BN nanoribbon, opening a possibility in spintronics device based on BN nanoribbon.

  1. 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.

  2. Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

    PubMed

    Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

    2015-08-18

    nanoparticles on oxide supports and Pt-CdSe-Pt nanodumbbells. We show that the accumulation or depletion of hot electrons on metal nanoparticles, in turn, can also influence catalytic reactions. Mechanisms suggested for hot-electron-induced chemical reactions on a photoexcited plasmonic metal are discussed. We propose that the manipulation of the flow of hot electrons by changing the electrical characteristics of metal-oxide and metal-semiconductor interfaces can give rise to the intriguing capability of tuning the catalytic activity of hybrid nanocatalysts. PMID:26181684

  3. Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

    PubMed

    Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

    2015-08-18

    nanoparticles on oxide supports and Pt-CdSe-Pt nanodumbbells. We show that the accumulation or depletion of hot electrons on metal nanoparticles, in turn, can also influence catalytic reactions. Mechanisms suggested for hot-electron-induced chemical reactions on a photoexcited plasmonic metal are discussed. We propose that the manipulation of the flow of hot electrons by changing the electrical characteristics of metal-oxide and metal-semiconductor interfaces can give rise to the intriguing capability of tuning the catalytic activity of hybrid nanocatalysts.

  4. 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.

  5. From heterojunction interfaces to metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Niles, D. W.; Tang, M.; McKinley, J.; Zanoni, R.; Margaritondo, G.

    1989-11-01

    Systematic studies of Schottky barrier heights and heterojunction band discontinuities have revealed a clear correlation between these two fundamental semiconductor interface parameters. The correlation is qualitatively predicted by all major semiconductor interface models, i.e., the defect model, theories based on metal-induced gap states (MIGS), and Schottky-like models. However, the experimentally observed correlation substantially deviates from the common prediction of all these theories. We investigated the causes of this discrepancy by measuring band line-ups at semiconductor-semiconductor interfaces with metal intralayers of thickness ranging from zero to back-to-back Schottky barrier configurations. The photoemission experiments discussed here identify the chemical and morphological properties of the CdS/Al/Ge system, and indicate that the cause of the discrepancy is a Schottky-like correction term.

  6. From heterojunction interfaces to metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Niles, D. W.; Tang, M.; McKinley, J.; Zanoni, R.; Margaritondo, G.

    1990-01-01

    Systematic studies of Schottky barrier heights and heterojunction band discontinuities have revealed a clear correlation between these two fundamental semiconductor interface parameters. The correlation is qualitatively predicted by all major semiconductor interface models, i.e., the defect model, theories based on metal-induced gap states (MIGS), and Schottky-like models. However, the experimentally observed correlation substantially deviates from the common prediction of all these theories. We investigated the causes of this discrepancy by measuring band line-ups at semiconductor-semiconductor interfaces with metal intralayers of thickness ranging from zero to back-to-back Schottky barrier configurations. The photoemission experiments discussed here identify the chemical and morphological properties of the CdS/Al/Ge system, and indicate that the cause of the discrepancy is a Schottky-like correction term.

  7. Infrared detection with point contact-metal semiconductor diodes

    NASA Astrophysics Data System (ADS)

    Eisenstein, G.

    1980-03-01

    Point contact Schottky barrier diodes, operating as video detectors and harmonic mixers at infrared frequencies, are studied, and theoretical models are developed and tested. A model extending the frequency response of the nonlinear barrier into the infrared is developed. Conductive and capacitive detection in highly doped semiconductors is considered. A model in which the low frequency spreading resistance is replaced by a complex spreading impedance is developed. The model predicts that optimal operation requires a semiconductor whose plasma frequency is one-third the operation frequency. Physical processes taking place simultaneously in the active region and in general thermal in nature are investigated. A thermo-electric detection model is developed and confirmed experimentally. The manufacturing of bulk point contact diodes is described in detail. Experimental results are compared with theoretical predictions. A method for producing thin crystaline semiconducting films on a metallic substrate is described.

  8. Hybrid metal-semiconductor mirror for high power VECSEL

    NASA Astrophysics Data System (ADS)

    Laurain, Alexandre; Gbele, Kokou; Hader, Jorg; Stolz, Wolfgang; Koch, Stephan; Ruiz Perez, Antje; Moloney, Jerome V.

    2016-03-01

    We demonstrate a low thermal impedance hybrid mirror VECSEL. We used only 14 pairs of AlGaAs/AlAs, transparent at the pump wavelength, and we used a patterned mask to deposit pure gold on areas of the chip to be pumped, and Ti/Au on other area to circumvent the poor adhesion of gold on GaAs. A higher gain is observed on an area metallized with pure gold and an output power of 4W was obtained, showing the effectiveness of the metallic mirror and validating the bonding quality. Chip processing and laser characteristics are studied in detail and compared to simulations.

  9. High-speed, efficient metal - semiconductor - metal photodetectors

    SciTech Connect

    Collin, St; Pardo, F; Bardou, N; Pelouard, J.-L.; Averin, S V

    2010-08-03

    Design principles and the fabrication technique of highly efficient, high-speed photodetectors based on MSM nanostructures are developed. To efficiently confine light in the region of the strong field as well as to decrease light losses due to reflection from the diode contacts, use is made of a nanoscale interdigital diffraction grating and a multilayer Bragg grating. Measurements of the reflection coefficients and the quantum efficiency for a multilayer structure are in good agreement with theoretical estimates. A record-high quantum efficiency (QE = 46 %) is obtained for high speed MSM photodetectors. The detector has a high spectral selectivity ({Delta}{lambda}{sub 1/2} = 17 nm) at a wavelength of 800 nm. Taking into account the diode capacitance and the drift time of photogenerated carriers, the performance of the detectors under study is {approx} 500 GHz. The low level of the dark current density in the structures under study (j={sup 1} pA {mu}m{sup -2}) makes it possible to realise on their basis highly sensitive, high-speed selective detectors of optical radiation.

  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. Laplace deep level transient spectroscopy of electron traps in epitaxial metalorganic chemical vapor deposition grown n-GaSb

    NASA Astrophysics Data System (ADS)

    Venter, A.; Botha, J. R.; Wagener, V.; Murape, D. M.

    2013-01-01

    Three prominent electron traps, 0.167 eV, 0.243 eV, and 0.295 eV below the conduction band minimum were detected in Te doped MOCVD grown n-GaSb using an Au Schottky barrier diode. The free carrier concentration of the ˜3 μm epilayer grown on n+ (>1018 cm-3) substrate, confirmed by Hall and capacitance-voltage measurements, was 5-7 × 1016 cm-3. The low doping concentration of the epitaxial layers was achieved using diethyl tellurium as the dopant source. Defect concentration profiles suggest that Ec-0.167 eV and Ec-0.243 are predominantly confined to the surface of the epilayer and that the concentration, thereof, approximates the free carrier concentration of the material close to the metal-semiconductor interface.

  12. 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

    2010-08-01

    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.

  13. Polyaniline/single-walled carbon nanotube composite electronic devices

    NASA Astrophysics Data System (ADS)

    Ramamurthy, P. C.; Malshe, A. M.; Harrell, W. R.; Gregory, R. V.; McGuire, K.; Rao, A. M.

    2004-11-01

    Composites of high molecular weight polyaniline (PANI) and various weight percentages of single-walled carbon nanotubes (SWNT) were fabricated using solution processing. Electrical characteristics of metal-semiconductor (MS) devices fabricated from the PANI/SWNT composites were studied. Current-voltage ( I- V) characteristics of these devices indicate a significant increase in current with an increase in carbon nanotube concentration in the composite. The dominant transport mechanisms operating in these devices were investigated by plotting the forward I- V data on a log-log scale, which revealed two power-law regions with different exponents. In the lower voltage range, the exponent is approximately 1, implying that the charge transport mechanism is governed by Ohm's law. The charge transport mechanism in the higher voltage range, where the exponent varies between 1.1 and 1.7, is consistent with space-charge-limited (SCL) emission in the presence of shallow traps. The critical voltage ( Vc), which characterizes the onset of SCL conduction, decreases with increasing SWNT concentration. In addition, Vc was observed to increase with temperature. These initial results indicate that with further improvements in material consistency and reduction in defect densities, the polyaniline/single-walled carbon nanotube composite material can be used to fabricate organic electronic devices leading to many useful applications in microelectronics.

  14. Strongly correlated valence electrons and core-level chemical bonding of Lithium at terapascal pressures

    NASA Astrophysics Data System (ADS)

    Hu, Anguang; Zhang, Fan

    2015-03-01

    As the simplest pure metal, lithium exhibits some novel properties on electrical conductivity and crystal structures under high pressure. All-electron density functional theory simulations, recently developed by using the linear combination of localized Slater atomic orbitals, revealed that the bandwidth of its valence bands remains almost unchanged within about 3.5 eV even up to a terapascal pressure range. This indicates that the development from delocalized to strongly correlated electronic systems takes place under compression, resulting in metal-semiconductor and superconductivity transitions together with a sequence of new high-pressure crystal phases, discovered experimentally. In contrast to the valence bands, the core-level bands become broadening up to about 10 eV at terapascal pressures. It means the transformation from chemical non-bonding to bonding for core electrons. Thus, dense lithium under compression can be characterized as core-level chemical bonding and a completely new class of strongly correlated materials with narrow bands filled in s-electron shells only.

  15. Effect of interfaces on electron transport properties of MoS2-Au Contacts

    NASA Astrophysics Data System (ADS)

    Aminpour, Maral; Hapala, Prokop; Le, Duy; Jelinek, Pavel; Rahman, Talat S.; Rahman's Group Collaboration; Nanosurf Lab Collaboration

    2014-03-01

    Single layer MoS2 is a promising material for future electronic devices such as transistors since it has good transport characteristics with mobility greater than 200 cm-1V-1s-1 and on-off current ratios up to 108. However, before MoS2 can become a mainstream electronic material for the semiconductor industry, the design of low resistive metal-semiconductor junctions as contacts of the electronic devices needs to be addressed and studied systematically. We have examined the effect of Au contacts on the electronic transport properties of single layer MoS2 using density functional theory in combination with the non-equilibrium Green's function method. The Schottky barrier between Au contact and MoS2, transmission spectra, and I-V curves will be reported and discussed as a function of MoS2 and Au interfaces of varying geometry. This work is supported in part by the US Department of Energy under grant DE-FG02-07ER15842.

  16. On the application of quantum transport theory to electron sources.

    PubMed

    Jensen, Kevin L

    2003-01-01

    Electron sources (e.g., field emitter arrays, wide band-gap (WBG) semiconductor materials and coatings, carbon nanotubes, etc.) seek to exploit ballistic transport within the vacuum after emission from microfabricated structures. Regardless of kind, all sources strive to minimize the barrier to electron emission by engineering material properties (work function/electron affinity) or physical geometry (field enhancement) of the cathode. The unique capabilities of cold cathodes, such as instant ON/OFF performance, high brightness, high current density, large transconductance to capacitance ratio, cold emission, small size and/or low voltage operation characteristics, commend their use in several advanced devices when physical size, weight, power consumption, beam current, and pulse repletion frequency are important, e.g., RF power amplifier such as traveling wave tubes (TWTs) for radar and communications, electrodynamic tethers for satellite deboost/reboost, and electric propulsion systems such as Hall thrusters for small satellites. The theoretical program described herein is directed towards models to evaluate emission current from electron sources (in particular, emission from WBG and Spindt-type field emitter) in order to assess their utility, capabilities and performance characteristics. Modeling efforts particularly include: band bending, non-linear and resonant (Poole-Frenkel) potentials, the extension of one-dimensional theory to multi-dimensional structures, and emission site statistics due to variations in geometry and the presence of adsorbates. Two particular methodologies, namely, the modified Airy approach and metal-semiconductor statistical hyperbolic/ellipsoidal model, are described in detail in their present stage of development.

  17. 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.

  18. 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.

  19. Spin-Resolved Electronic Structure of Ultrathin Epitaxial Fe Films on Vicinal and Singular GaAs(100) Substrates

    SciTech Connect

    Morton, S A; Waddill, G D; Spangenberg, M; Seddon, E A; Neal, J; Shen, T; Tobin, J G

    2003-03-10

    Recently there has been considerable interest in the study of spin injection at ferromagnetic semiconductor heterojunctions and ferromagnetic metal--semiconductor contacts. Studies of ntype semiconductors have demonstrated spin-coherent transport over large distances5 and the persistence of spin coherence over a sizeable time scale. Clearly such investigations have been stimulated by the potential of the development of ''spintronics'', electronic devices utilizing the information of the electron spin states. To understand and improve the magnetic properties of ultrathin Fe films on GaAs has been the aim of many research groups over recent years. The interest in this system has both technological and fundamental scientific motivations. Technologically, Fe on GaAs may serve to realize spin electronic devices. From a fundamental science point of view, Fe on GaAs serves as a prototype for studies of the interplay between the crystalline structure and morphology of an ultrathin film, its electronic structure and the long range magnetic order it exhibits. Furthermore, it is well known that an oxidized Cs layer on GaAs substantially alters the work-function of the GaAs surface, which plays a very important role in the application of GaAs as a spin polarized electron source.

  20. 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.

  1. Low-Contact-Resistance Non-Gold Ta/Si/Ti/Al/Ni/Ta Ohmic Contacts on Undoped AlGaN/GaN High-Electron-Mobility Transistors Grown on Silicon

    NASA Astrophysics Data System (ADS)

    Li, Yang; Ng, Geok Ing; Arulkumaran, Subramaniam; Mohan Manoj Kumar, Chandra; Ang, Kian Siong; Jesudas Anand, Mulagumoottil; Wang, Hong; Hofstetter, René; Ye, Gang

    2013-11-01

    Low-contact-resistance (Rc) non-gold Ta/Si/Ti/Al/Ni/Ta ohmic contacts were realized on an undoped AlGaN/GaN high-electron-mobility transistor (HEMT) grown on a silicon substrate. Optimization of the rapid thermal process reveals that Rc decreases drastically from the annealing temperature of 700 to 850 °C and slightly increases from 875 to 900 °C. The sample annealed at 850 °C exhibited the lowest Rc of 0.22±0.03 Ω·mm [specific contact resistivity, ρc=(0.78±0.22)×10-6 Ω·cm2] with a smooth surface morphology (RMS roughness ˜5.5 nm). The low Rc is due to the formation of TixSiy and the intermixing of TixSiy with the bottom Ta layer at the metal/semiconductor interface.

  2. Graphene nanoribbon blends with P3HT for organic electronics

    NASA Astrophysics Data System (ADS)

    El Gemayel, Mirella; Narita, Akimitsu; Dössel, Lukas F.; Sundaram, Ravi S.; Kiersnowski, Adam; Pisula, Wojciech; Hansen, Michael Ryan; Ferrari, Andrea C.; Orgiu, Emanuele; Feng, Xinliang; Müllen, Klaus; Samorì, Paolo

    2014-05-01

    In organic field-effect transistors (OFETs) the electrical characteristics of polymeric semiconducting materials suffer from the presence of structural/morphological defects and grain boundaries as well as amorphous domains within the film, hindering an efficient transport of charges. To improve the percolation of charges we blend a regioregular poly(3-hexylthiophene) (P3HT) with newly designed N = 18 armchair graphene nanoribbons (GNRs). The latter, prepared by a bottom-up solution synthesis, are expected to form solid aggregates which cannot be easily interfaced with metallic electrodes, limiting charge injection at metal-semiconductor interfaces, and are characterized by a finite size, thus by grain boundaries, which negatively affect the charge transport within the film. Both P3HT and GNRs are soluble/dispersible in organic solvents, enabling the use of a single step co-deposition process. The resulting OFETs show a three-fold increase in the charge carrier mobilities in blend films, when compared to pure P3HT devices. This behavior can be ascribed to GNRs, and aggregates thereof, facilitating the transport of the charges within the conduction channel by connecting the domains of the semiconductor film. The electronic characteristics of the devices such as the Ion/Ioff ratio are not affected by the addition of GNRs at different loads. Studies of the electrical characteristics under illumination for potential use of our blend films as organic phototransistors (OPTs) reveal a tunable photoresponse. Therefore, our strategy offers a new method towards the enhancement of the performance of OFETs, and holds potential for technological applications in (opto)electronics.In organic field-effect transistors (OFETs) the electrical characteristics of polymeric semiconducting materials suffer from the presence of structural/morphological defects and grain boundaries as well as amorphous domains within the film, hindering an efficient transport of charges. To improve the

  3. Atomic scale structure and chemistry of interfaces by Z-contrast imaging and electron energy loss spectroscopy in the STEM

    SciTech Connect

    McGibbon, M.M.; Browning, N.D.; Chisholm, M.F.; Pennycook, S.J.

    1993-12-01

    The macroscopic properties of many materials are controlled by the structure and chemistry at the grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. The high-resolution Z-contrast imaging technique in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition can be interpreted intuitively. This direct image allows the electron probe to be positioned over individual atomic columns for parallel detection electron energy loss spectroscopy (PEELS) at a spatial resolution approaching 0.22nm. The bonding information which can be obtained from the fine structure within the PEELS edges can then be used in conjunction with the Z-contrast images to determine the structure at the grain boundary. In this paper we present 3 examples of correlations between the structural, chemical and electronic properties at materials interfaces in metal-semiconductor systems, superconducting and ferroelectric materials.

  4. New basic insights into the low hot electron injection efficiency of gold-nanoparticle-photosensitized titanium dioxide.

    PubMed

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

    2014-08-13

    The low hot electrons injection efficiency (HEIE) from plasmonic metal to semiconductor significantly affects the performance of metal-semiconductor composite. However, there are few reports about the origin of this low HEIE. In the present work, the factors affecting the transfer process and generation efficiency of hot electron in Au@TiO2 composite are investigated using first-principles calculations and Maxwell's electrodynamics theory. The occupation of surface oxygen vacancies of TiO2 by gold atoms is found to increase the hot electrons transfer barrier and expand the space charge region, which decrease the HEIE. In addition, the existing Au@TiO2 structure going against the generation of large amount of hot electrons may also lead to low HEIE. Our results reveal that the replacement of divalent host oxygen atoms with monovalent atoms can decrease the HEIE and comparison with experimental results allows us to validate our predictions. Furthermore, proper surface treatment of semiconductor before depositing metal particles and structure optimization of the composite are suggested to improve the HEIE.

  5. Chemical bonding, interdiffusion and electronic structure at InP, GaAs, and Si-metal interfaces

    NASA Astrophysics Data System (ADS)

    Brillson, L. J.

    1985-10-01

    An experimental program investigates the interface electronic states and band structure at Germanium Arsenides, Indium Phosphides and Silicon-metal interfaces formed by chemical reaction and interdiffusion at room temperature, elevated temperatures, as well as following pulsed-laser annealing; uses soft X-ray photoemission spectroscopy (SXPS) and Auger electron spectroscopy (AES)/depth profiling to characterize atomic redistribution and new chemical bonding near the surfaces and interfaces on an atomic scale; refines the technique of cathodoluminescence spectroscopy (CLS) for investigations of new compound and defect formation at buried metal-semiconductor interfaces; and employs temperature-dependent current-voltage and capacitance-voltage measurements to characterize the electronic properties and spatial distribution of interface states of metal-InP interfaces prepared and processed under carefully controlled conditions. The work can be grouped into four areas: (1) chemical and electronic structure of buried III-V and II-VI compound semiconductor-metal interfaces, (2) localized chemical reactions at Aluminum interfaces with III-V compound semiconductors promoted by pulsed-laser annealing as well as laser-induced oxidation of Si, (3) eletrical characterization of the UHV-prepared Al-InP (110) interface, and (4) control of competitive Ti-Si and Ti-SiO2 interfacial reactions by rapid thermal annealing.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Electron radiography

    DOEpatents

    Merrill, Frank E.; Morris, Christopher

    2005-05-17

    A system capable of performing radiography using a beam of electrons. Diffuser means receive a beam of electrons and diffuse the electrons before they enter first matching quadrupoles where the diffused electrons are focused prior to the diffused electrons entering an object. First imaging quadrupoles receive the focused diffused electrons after the focused diffused electrons have been scattered by the object for focusing the scattered electrons. Collimator means receive the scattered electrons and remove scattered electrons that have scattered to large angles. Second imaging quadrupoles receive the collimated scattered electrons and refocus the collimated scattered electrons and map the focused collimated scattered electrons to transverse locations on an image plane representative of the electrons' positions in the object.

  11. 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.

  12. 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)

  13. Electron cooling of electron beams

    SciTech Connect

    Larson, D.J.

    1993-09-01

    Electron cooling of electron (and positron) sources may be important for future linear collider applications. In order to cool electrons with electrons, an intermediary positron beam must be employed, since it is impossible to merge two beams of identical particles into the cooling straight. By adjusting the beta functions of the electron and positron lattices appropriately, the final emittance of the stored electron beam can be made less than the emittance of the cooling electron beam. This paper will discuss accelerator physics issues relating to an electron-cooled electron beam source.

  14. 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 and their…

  15. Electron cooling

    NASA Astrophysics Data System (ADS)

    Meshkov, I.; Sidorin, A.

    2004-10-01

    The brief review of the most significant and interesting achievements in electron cooling method, which took place during last two years, is presented. The description of the electron cooling facilities-storage rings and traps being in operation or under development-is given. The applications of the electron cooling method are considered. The following modern fields of the method development are discussed: crystalline beam formation, expansion into middle and high energy electron cooling (the Fermilab Recycler Electron Cooler, the BNL cooler-recuperator, cooling with circulating electron beam, the GSI project), electron cooling in traps, antihydrogen generation, electron cooling of positrons (the LEPTA project).

  16. 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.

  17. A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: the problem of Coulomb explosion

    NASA Astrophysics Data System (ADS)

    Bulgakova, Nadezhda M.; Stoian, Razvan; Rosenfeld, Arkadi; Marine, Wladimir; Campbell, Eleanor E.

    2004-09-01

    We present a continuum model, based on a drift-diffusion approach, aimed to describe the dynamics of electronic excitation, heating and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, under near-infrared femtosecond irradiation regimes, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, simulations of UV nanosecond pulsed laser interaction with bulk silicon have pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.

  18. A general continuum approach to describe fast electronic transport in pulsed laser irradiated materials: The problem of Coulomb explosion

    NASA Astrophysics Data System (ADS)

    Bulgakova, N. M.; Stoian, R.; Rosenfeld, A.; Hertel, I. V.; Marine, W.; Campbell, E. E. B.

    2005-07-01

    We present a continuum model, based on a drift-diffusion approach, aimed at describing the dynamics of electronic excitation, heating, and charge-carrier transport in different materials (metals, semiconductors, and dielectrics) under femtosecond and nanosecond pulsed laser irradiation. The laser-induced charging of the targets is investigated at laser intensities above the material removal threshold. It is demonstrated that, for near-infrared femtosecond irradiation, charging of dielectric surfaces causes a sub-picosecond electrostatic rupture of the superficial layers, alternatively called Coulomb explosion (CE), while this effect is strongly inhibited for metals and semiconductors as a consequence of superior carrier transport properties. On the other hand, application of the model to UV nanosecond pulsed laser interaction with bulk silicon has pointed out the possibility of Coulomb explosion in semiconductors. For such regimes a simple analytical theory for the threshold laser fluence of CE has been developed, showing results in agreement with the experimental observations. Various related aspects concerning the possibility of CE depending on different irradiation parameters (fluence, wavelength and pulse duration) and material properties are discussed. This includes the temporal and spatial dynamics of charge-carrier generation in non-metallic targets and evolution of the reflection and absorption characteristics.

  19. 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.

  20. 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)

  1. 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.

  2. Electronic Mail.

    ERIC Educational Resources Information Center

    Pollard, Jim; Holznagel, Don

    1984-01-01

    Decision makers must address the issues of (1) just what are electronic communications? (2) how will they help me teach, administer, or survive? and (3) what will it cost in time and money? Electronic mail allows the sending of letters, memos, and messages to anyone who uses the same electronic mail system, and provides most of the options that…

  3. 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…

  4. 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.

  5. 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.

  6. 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.

  7. Paper electronics.

    PubMed

    Tobjörk, Daniel; Österbacka, Ronald

    2011-05-01

    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.

  8. 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.

  9. Electron bifurcation.

    PubMed

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

    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. PMID:27016613

  10. 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…

  11. 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)

  12. 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.

  13. 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.

  14. 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.

  15. Physical vapour deposition growth and transmission electron microscopy characterization of epitaxial thin metal films on single-crystal Si and Ge substrates

    NASA Astrophysics Data System (ADS)

    Westmacott, K. H.; Hinderberger, S.; Dahmen, U.

    2001-06-01

    Epitaxial fcc, bcc and hcp metal and alloy films were grown in high vacuum by physical vapour deposition at high rate ('flash' deposition) on the (111), (110) and (100) surfaces of Si and Ge at different deposition temperatures. The resulting epitaxial relationships and morphological features of these films were characterized by transmission electron microscopy and diffraction. Simple epitaxial relationships were found mainly for the fcc metals that form binary eutectic systems with Si and G e. Of these, Ag exhibited exceptional behaviour by forming in a single crystal cube-cube relationship on all six semiconductor surfaces. Al and Au both formed bicrystal films on (100) substrates but differed in their behaviours on (111) substrates. Silicide formers such as the fcc metals Cu and Ni, as well as all bcc and hcp metals investigated, did not adopt epitaxial relationships on most semiconductor substrates. However, epitaxial single-crystal, bicrystal and tricrystal films of several metals and alloys could be grown by using a Ag buffer layer. The factors controlling the epitaxial growth of metal films are discussed in the light of the observations and compared with the predictions of established models for epitaxial relationships. It is concluded that epitaxial films can be grown easily if the film forms a simple eutectic or monotectic system with the substrate. The epitaxial relationships of those films depend on crystallographic factors for metal-metal epitaxy and on the substrate surface structure for metal-semiconductor epitaxy.

  16. 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.

  17. 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.

  18. Electronic properties of the silver-silver chloride cluster interface.

    PubMed

    Glaus, Stephan; Calzaferri, Gion; Hoffmann, Roald

    2002-04-15

    The objective of this study was to gain insight into the electronic structure of silver-silver chloride cluster composites and especially into the metal-semiconductor interface. For this purpose a theoretical study of (AgCl)(n) (n=4, 32, 108, 192, and 256), of Ag(m) (m=1-9, 30, 115, 276, and 409), and of the cluster composites Ag(115)-(AgCl)(192) and Ag(409)-(AgCl)(192) has been carried out. Density of levels (DOL), local density of levels (l-DOL), and projection of surface states, as well as projection of properties of individual atoms or groups of atoms obtained in molecular orbital calculations, are shown to be powerful tools for gaining deep insight into the properties of these large systems. The Ag(115)-(AgCl)(192) aggregate, consisting of a cubic Ag(115) cluster without corner atoms on top of a cubic (AgCl)(192) cluster, was found to be remarkably stable with a cluster-to-cluster distance of about 280 pm, and a geometry in which the number of bonding interactions between the silver atoms of Ag(115) and the chloride ions of (AgCl)(192) is at its maximum. A sharp jump in charge distribution occurs at the Ag(115)-(AgCl)(192) composite interface. The first AgCl slab picks up negative charge from the two adjacent silver slabs, so that in total the silver cluster is positively charged. In addition, the core of the silver cluster is positively charged with respect to its outermost layer. The main reason for the charge transfer from the silver cluster to the silver chloride is the newly formed MIGS (metal induced gap states) in the energy-gap range of the silver chloride and the MIdS (metal induced d states) in the d-orbital region. Their wave functions mix with orbitals of the silver cluster and with both the orbitals of the silver and the chloride ions of the silver chloride. The MIGS and the MIdS are of a quite localized nature. In them, nearest neighbor interactions dominate, with the exception of close-lying silver chloride surface states-which mix in to a large

  19. Electronic Prescribing

    MedlinePlus

    ... 1-877-486-2048 . I went to the pharmacy, and my prescription was ready. Electronic eRx Prescribing ... write and send your prescriptions directly to your pharmacy. This means no more prescriptions on paper and ...

  20. Electronic Cigarettes

    MedlinePlus

    ... and Figures Tobacco and Nicotine Smoked Tobacco Products Smokeless Tobacco Products Electronic Cigarettes New FDA Regulations HEALTH EFFECTS ... Secondhand Smoke Effects of Smoking on Your Health Smokeless Tobacco and Your Health Tobacco Use and Fertility Tobacco ...

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Evidence of Momentum Conservation at a Non-Eptitaxial Metal/Semiconductor Interface Using BEEM

    NASA Technical Reports Server (NTRS)

    Bell, L. D.

    1996-01-01

    BEEM spectroscopy has been performed on Au/Si(111) structures as a function of Au thickness and temperature. At 77K a direct signature of parallel momentum conservation at the Au/Si interface is observed in the BEEM spectra.

  7. Properties of Metal-Semiconductor Interfaces Formed on n-Type GaN

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hideki; Koyama, Yuji; Hashizume, Tamotsu

    1999-04-01

    Properties of metal/GaN Schottky diodes formed by theconventional vacuum deposition process and a novel in situelectrochemical process are investigated by detailed I V, C V andX-ray photoelectron spectroscopy (XPS) measurements with a specialfocus on the correlation between the contact formation process and thebehavior of Schottky barrier height. Schottky diodes formed by vacuumdeposition pretreated with a warm NH4OH solution showed nearly idealthermionic emission I V characteristics with Schottky barrier height(SBH) values weakly dependent on metal work function with the slopefactor of about 0.1. On the other hand, Schottky diodes formed by thein situ electrochemical process also showed high-quality nearly idealthermionic emission I V characteristics, but they realized stronglymetal-work-function-dependent SBH values. The slope factor, S, was aslarge as 0.49. These results could not be explained by the recentlyproposed formula based on the metal induced gap state (MIGS)model. They are explained here from the viewpoint of the disorderinduced gap state (DIGS) model.

  8. 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

  9. Multilevel memristor effect in metal-semiconductor core-shell nanoparticles tested by scanning tunneling spectroscopy.

    PubMed

    Chakrabarti, Sudipto; Pal, Amlan J

    2015-06-01

    We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility, reversibility, and retentivity of the multilevel memristors. From the normalized density of states (NDOS), we infer that the memristor effect is correlated to a decrease in the transport gap of the nanostructures. We also infer that the memristor effect occurs in the nanostructures due to an increase in the density of available states upon application of a voltage pulse. PMID:25966930

  10. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    PubMed Central

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    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. PMID:27404510

  11. Ultrathin metal-semiconductor-metal resonator for angle invariant visible band transmission filters

    SciTech Connect

    Lee, Kyu-Tae; Seo, Sungyong; Yong Lee, Jae; Jay Guo, L.

    2014-06-09

    We present transmission visible wavelength filters based on strong interference behaviors in an ultrathin semiconductor material between two metal layers. The proposed devices were fabricated on 2 cm × 2 cm glass substrate, and the transmission characteristics show good agreement with the design. Due to a significantly reduced light propagation phase change associated with the ultrathin semiconductor layer and the compensation in phase shift of light reflecting from the metal surface, the filters show an angle insensitive performance up to ±70°, thus, addressing one of the key challenges facing the previously reported photonic and plasmonic color filters. This principle, described in this paper, can have potential for diverse applications ranging from color display devices to the image sensors.

  12. 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

    2016-01-01

    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. PMID:27404510

  13. Multilevel memristor effect in metal-semiconductor core-shell nanoparticles tested by scanning tunneling spectroscopy.

    PubMed

    Chakrabarti, Sudipto; Pal, Amlan J

    2015-06-01

    We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility, reversibility, and retentivity of the multilevel memristors. From the normalized density of states (NDOS), we infer that the memristor effect is correlated to a decrease in the transport gap of the nanostructures. We also infer that the memristor effect occurs in the nanostructures due to an increase in the density of available states upon application of a voltage pulse.

  14. 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.

  15. Enhancement and quenching regimes in metal-semiconductor hybrid optical nanosources.

    PubMed

    Viste, Pierre; Plain, Jérome; Jaffiol, Rodolphe; Vial, Alexandre; Adam, Pierre Michel; Royer, Pascal

    2010-02-23

    We report on the emission of hybrid nanosources composed of gold nanoparticles coupled with quantum dots. The emission relies on energy transfer from the quantum dots to gold nanoparticles which could be de-excited through radiative plasmon relaxation. The dependence of the emission efficiency is studied systematically as a function of the size of gold nanoparticles and interdistance between gold nanoparticles and quantum dots. We demonstrate a size-dependent transition between quenching and enhancement and a nonradiative energy transfer from the quantum dots to the gold nanoparticles.

  16. Molecular Electronics

    NASA Astrophysics Data System (ADS)

    Petty, Michael

    The prospects of using organic materials in electronics and optoelectronics applications have attracted scientists and technologists since the 1970s. This field has become known as molecular electronics. Some successes have already been achieved, for example the liquid-crystal display. Other products such as organic light-emitting displays, chemical sensors and plastic transistors are developing fast. There is also a keen interest in exploiting technologies at the molecular scale that might eventually replace silicon devices. This chapter provides some of the background physics and chemistry to the interdisciplinary subject of molecular electronics. A review of some of the possible application areas for organic materials is presented and some speculation is provided regarding future directions.

  17. Electron tube

    DOEpatents

    Suyama, Motohiro; Fukasawa, Atsuhito; Arisaka, Katsushi; Wang, Hanguo

    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.

  18. 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.

  19. 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.)

  20. 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.

  1. 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 yearbooks. Bill…

  2. 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 choice for…

  3. 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.

  4. 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…

  5. Electronic Homework.

    ERIC Educational Resources Information Center

    Lee, Fong-lok; Heyworth, Rex M.

    The Electronic Homework assistant system is composed of two components: the Computer Tutor and the Homework Administrator. The Computer Tutor is an intelligent tutoring system that can provide personal assistance like supplying hints, checking errors, providing remediation and prioritizing problems. The Homework Administrator is a teacher's…

  6. 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.

  7. 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,…

  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. Electron Cryotomography

    PubMed Central

    Tocheva, Elitza I.; Li, Zhuo; Jensen, Grant J.

    2010-01-01

    Electron cryotomography (ECT) is an emerging technology that allows thin samples such as macromolecular complexes and small bacterial cells to be imaged in 3-D in a nearly native state to “molecular” (∼4 nm) resolution. As such, ECT is beginning to deliver long-awaited insight into the positions and structures of cytoskeletal filaments, cell wall elements, motility machines, chemoreceptor arrays, internal compartments, and other ultrastructures. This article describes the technique and summarizes its contributions to bacterial cell biology. For comparable recent reviews, see (Subramaniam 2005; Jensen and Briegel 2007; Murphy and Jensen 2007; Li and Jensen 2009). For reviews on the history, technical details, and broader application of electron tomography in general, see for example (Subramaniam and Milne 2004; Lucić et al. 2005; Leis et al. 2008; Midgley and Dunin-Borkowski 2009). PMID:20516135

  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. 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.

  13. 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.

  14. 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.

  15. Solar-blind photodetectors for harsh electronics.

    PubMed

    Tsai, Dung-Sheng; Lien, Wei-Cheng; Lien, Der-Hsien; Chen, Kuan-Ming; Tsai, Meng-Lin; Senesky, Debbie G; Yu, Yueh-Chung; Pisano, Albert P; He, Jr-Hau

    2013-01-01

    We demonstrate solar-blind photodetectors (PDs) by employing AlN thin films on Si(100) substrates with excellent temperature tolerance and radiation hardness. Even at a bias higher than 200 V the AlN PDs on Si show a dark current as low as ~ 1 nA. The working temperature is up to 300°C and the radiation tolerance is up to 10(13) cm(-2) of 2-MeV proton fluences for AlN metal-semiconductor-metal (MSM) PDs. Moreover, the AlN PDs show a photoresponse time as fast as ~ 110 ms (the rise time) and ~ 80 ms (the fall time) at 5 V bias. The results demonstrate that AlN MSM PDs hold high potential in next-generation deep ultraviolet PDs for use in harsh environments.

  16. Study of Ballistic Carrier Transport Using Ballistic Electron-Emission Microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Edwin Yoon

    Ballistic-electron-emission microscopy (BEEM) was used to study the ballistic carrier transport of electrons and holes. Several distinct transport processes were studied to model transport processes relevant to BEEM, in which a scanning-tunneling microscope (STM) tip functions as an emitter of electrons, and the electrons tunnel across the vacuum energy barrier into a metal overlayer region on a semiconductor substrate. Some of the injected electrons from the STM tip travel into the semiconductor and are collected as the BEEM current. By doing experiments in BEEM and by doing theoretical modeling, it was found that the quantum mechanical reflection and the phonon scattering at the Schottky barrier result in a nearly energy independent reduction of the ballistic transport across the Schottky barrier of Au/Si and of Au/GaAs. Also, the conservation of parallel wave vector and of energy at the plane of the Schottky barrier energy maximum was found necessary to explain the shape of the BEEM spectrum. For the coherent metal/semiconductor (M/S) interface formed by type-B CoSi _2/Si(111) (n-type), the conservation laws were found to hold even at the metallurgical M/S interface, and this gave rise to a novel phenomenon in which the electron transport across the M/S interface was forbidden at the energy of the top of the Schottky barrier. The transport in the metal overlayer was found to be dominated by elastic scattering of the electrons, and this was modeled by the Monte Carlo method. The Monte Carlo modeling showed that the ratio of the inelastic mean free path length to the elastic mean free path length for electron in Au should be about 10 in order to explain a set of existing BEEM data showing the attenuation of the BEEM current as a function of the metal overlayer thickness. The transport across the M/S interface was found to involve scattering involving M/S interface states and states in the semiconductor band gap near the interface. Among these processes, electron

  17. 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.

  18. 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

  19. 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.

  20. 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.

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Electron Diffraction Experiments using Laser Plasma Electrons

    SciTech Connect

    Fill, E E; Trushin, S; Tommasini, R; Bruch, R

    2005-09-07

    We demonstrate that electrons emitted from a laser plasma can be used to generate diffraction patterns in reflection and transmission. The electrons are emitted in the direction of laser polarization with energies up to 100 keV. The broad electron energy spectrum makes possible the generation of a ''streaked'' diffraction pattern which allows recording fast processes in a single run.

  9. Sub-Half Micrometer Gate Lift-Off By Three Layer Resist Process Via Electron Beam Lithography For Gallium Arsenide Monolithic Microwave Integrated Circuits (MIMICs)

    NASA Astrophysics Data System (ADS)

    Nagarajan, Rao M.; Rask, Steven D.; King, Michael R.; Yard, Thomas K.

    1988-06-01

    fabricate a 0.20μm gate Metal Semiconductor Field Effect Transistors on GaAS. These results are discussed in detail.

  10. Electron Diffraction Using Transmission Electron Microscopy

    PubMed Central

    Bendersky, Leonid A.; Gayle, Frank W.

    2001-01-01

    Electron diffraction via the transmission electron microscope is a powerful method for characterizing the structure of materials, including perfect crystals and defect structures. The advantages of electron diffraction over other methods, e.g., x-ray or neutron, arise from the extremely short wavelength (≈2 pm), the strong atomic scattering, and the ability to examine tiny volumes of matter (≈10 nm3). The NIST Materials Science and Engineering Laboratory has a history of discovery and characterization of new structures through electron diffraction, alone or in combination with other diffraction methods. This paper provides a survey of some of this work enabled through electron microscopy. PMID:27500060

  11. Molecular Electronics - Current Challenges

    SciTech Connect

    Vilan, Ayelet; Cahen, David

    2010-12-01

    Molecular electronics is a flourishing area of nano-science and -technology, with a promise for cheap electronics of novel functionality. Here we outline the major challenges for molecular electronics becoming an established scientific discipline, including models with predictive power.

  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. 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.

  14. Electron-electron interaction in projectile electron loss

    SciTech Connect

    Huelskoetter, H.; Meyerhof, W.E.; Dillard, E.A.; Guardala, N.; Spooner, D.W. ); Feinberg, B. ); Belkacem, A. Sciences Division, Building 71-259, Lawrence Berkeley Laboratory, One Cyclotron Road, Berkeley, CA ); Alonso, J.R.; Krebs, G.F.; McMahan, M.A.; Rude, B.S ); Blumenfeld, L.; Gould, H. ); Rhoades-Brown, M.E. ); Schweppe, J. (Chemical Sciences Division, Building 71-259, Lawrence Berkeley Laboratory, One Cyclotron Road, Berkeley, CA (

    1991-08-01

    In ion-atom collisions where the projectile is ionized, target electrons act not only coherently by screening the target nucleus but they may also act incoherently by directly ejecting a projectile electron. This electron-electron interaction should be relatively most important for targets that have a low nuclear charge, since the cross section for a neutral target is roughly proportional to {ital Z}{sub {ital t}}{sup 2}+{ital Z}{sub {ital t}}, where {ital Z}{sub {ital t}}{sup 2} is the contribution due to the target nucleus and {ital Z}{sub {ital t}} comes from the target electrons. In order to investigate the electron-electron interaction, we have measured and calculated cross sections for Li{sup 2+}, C{sup 5+}, and O{sup 7+} on H{sub 2} and He, Au{sup 52+} on H{sub 2}, He, C, and N{sub 2}, Au{sup 75+} on H{sub 2} and N{sub 2}, U{sup 86+} on H{sub 2} and He, and U{sup 90+} on H{sub 2}. The collision energies range from 0.75 to 405 MeV/nucleon. The calculations have been performed in the plane-wave Born approximation. We demonstrate that for energies where the target electrons have sufficient kinetic energy in the projectile frame to ionize the projectile, the electron-electron interaction can lead to a significant increase in the total electron-loss cross section.

  15. Attraction by Repulsion: Pairing Electrons using Electrons

    NASA Astrophysics Data System (ADS)

    Ilani, Shahal

    One of the fundamental properties of electrons is their mutual Columbic repulsion. If electrons are placed in a solid, however, this basic property may change. A famous example is that of superconductors, where coupling to lattice vibrations makes electrons attractive and leads to the formation of bound pairs. But what if all the degrees of freedom in the solid are electronic? Is it possible to make electrons attract each other only by their repulsion to other electrons? Such an `excitonic' mechanism for attraction was proposed fifty years ago by W. A. Little, with the hope that it could lead to better and more exotic superconductivity. Yet, despite many efforts to synthesize materials that possess this unique property, to date there is still no evidence for electronic-based attraction. In this talk I will present our recent experiments that observe this unusual electronic attraction using a different, bottom-up approach. Our experiments are based on a new generation of quantum devices made from pristine carbon nanotubes, combined with precision cryogenic manipulation. Using this setup we can now assemble the fundamental building block of the excitonic attraction and demonstrate that two electrons that naturally repel each other can be made attractive using an independent electronic system as the binding glue. I will discuss the lessons learned from these experiments on what is achievable with plain electrostatics, and on the possibility to use the observed mechanism for creating exotic states of matter.

  16. 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 functions…

  17. 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…

  18. Electronic properties of nanohorns

    NASA Astrophysics Data System (ADS)

    Garaj, Slaven; Gaál, Richard; Bonard, J.-M.; Thien-Nga, L.; Forró, L.; Takahashi, K.; Kokai, F.; Yudasaka, M.; Iijima, S.

    2001-11-01

    Electronic properties of nanohorns were investigated by electron spin resonance, resistivity and thermo-electric power measurements. Electron transport and spin relaxation is governed by hopping between "dahlia"-like aggregates of conducting nanohorn structures. Upon doping, conduction electron part of paramagnetic susceptibility increases significantly. Field emission properties of nanohorns rank them among the best field-emitters currently available.

  19. Electron-Electron Interactions in Artificial Graphene

    NASA Astrophysics Data System (ADS)

    Räsänen, E.; Rozzi, C. A.; Pittalis, S.; Vignale, G.

    2012-06-01

    Recent advances in the creation and modulation of graphenelike systems are introducing a science of “designer Dirac materials”. In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points.

  20. Electron-electron interactions in artificial graphene

    NASA Astrophysics Data System (ADS)

    Rasanen, Esa

    2013-03-01

    Recent advances in the creation and modulation of graphenelike systems are introducing a science of ``designer Dirac materials.'' In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points, and discuss future investigations and challenges in this field.

  1. Carbon nanotube electron sources for electron microscopes

    SciTech Connect

    De Jonge, Niels

    2009-01-01

    Electron sources were made from individual multi-walled carbon nanotubes with closed caps and thoroughly cleaned surfaces. Nanotubes from both chemical vapor deposition growth and arc discharge growth were investigated. These emitters provide a highly stable emission current up to a threshold current of a few microamperes. At too large currents several processes take place such as splitting, breaking and cap closing. The emission process is field emission for a workfunction of 5 eV. The electron optical per-formance is highly beneficial for their use as high-brightness point sources in electron microscopes and advantageous with respect to state-of-the-art electron sources. The life-time is at least two years. We have tested the source successfully in a scanning electron microscope.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Determination of hydrogen in metals, semiconductors, and other materials by cold neutron prompt gamma-ray activation analysis

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.

    1998-12-31

    Cold neutron prompt gamma-ray activation analysis has proven useful for nondestructive measurement of trace hydrogen. The sample is irradiated in a beam of neutrons; the presence of hydrogen is confirmed by the emission of a 2223 keV gamma-ray. Detection limits for hydrogen are 3 mg/kg in quartz and 8 mg/kg in titanium. The authors have used the technique to measure hydrogen in titanium alloys, germanium, quartz, fullerenes and their derivatives, and other materials.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  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. 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.

  15. Electron Beam Freeform Fabrication

    NASA Video Gallery

    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...

  16. Copyright of Electronic Publishing.

    ERIC Educational Resources Information Center

    Dong, Elaine; Wang, Bob

    2002-01-01

    Analyzes the importance of copyright, considers the main causes of copyright infringement in electronic publishing, discusses fair use of a copyrighted work, and suggests methods to safeguard copyrighted electronic publishing, including legislation, contracts, and technology. (Author/LRW)

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Electronic health record and electronic patient record.

    PubMed

    Dimond, Bridgit

    This article considers the government plans for the development of electronic health and patient records as set out in the NHS Plan and the progress and problems which have been encountered in their realization. PMID:16116372

  3. 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…

  4. 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…

  5. 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…

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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…

  11. 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…

  12. 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)…

  13. Electron Induction Linacs

    NASA Astrophysics Data System (ADS)

    Caporaso, George J.; Chen, Yu-Jiuan

    Electron induction linacs have been used for over four decades for a variety of applications. As discussed in Chap. 8, these include basic studies in magnetically confined fusion, transport of intense electron beams in various gases, the generation of electromagnetic radiation from free electron lasers, radiation processing of materials and food, and flash X-ray radiography sources.

  14. 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.

  15. Electronic Education System Model.

    ERIC Educational Resources Information Center

    Cloete, Elsabe

    2001-01-01

    Discusses electronic learning efforts and problems in implementing computers in schools. Defines and describes an electronic educational system model that was developed to assist the designers of different electronic learning settings to plan and successfully implement a specific learning situation, with the focus on the individual requirements of…

  16. 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.

  17. 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…

  18. 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)

  19. Electron-electron collisions at TESLA

    NASA Astrophysics Data System (ADS)

    Schreiber, Siegfried; Reyzl, Ingrid

    2001-07-01

    Electron-electron collisions at the future TESLA linear collider is a promising complement to e+e- collisions. A critical issue for the physics potential of this option is the achievable luminosity. For e+e- collisions, the pinch effect enhances the luminosity, while due to the repelling forces for e-e- collisions, the luminosity is significantly reduced and is more sensitive to beam separations. This report discusses the e-e- option for TESLA and the expected luminosity.

  20. Polarized Electron Source Developments

    SciTech Connect

    Charles K. Sinclair

    1990-02-23

    Presently, only two methods of producing beams of polarized electrons for injection into linear accelerators are in use. Each of these methods uses optical pumping by circularly polarized light to produce electron polarization. In one case, electron polarization is established in metastable helium atoms, while in the other case, the polarized electrons are produced in the conduction band of appropriate semiconductors. The polarized electrons are liberated from the helium metastable by chemi-ionization, and from the semiconductors by lowering the work function at the surface of the material. Developments with each of these sources since the 1988 Spin Physics Conference are reviewed, and the prospects for further improvements discussed.

  1. Quantifying solvated electrons' delocalization.

    PubMed

    Janesko, Benjamin G; Scalmani, Giovanni; Frisch, Michael J

    2015-07-28

    Delocalized, solvated electrons are a topic of much recent interest. We apply the electron delocalization range EDR(r;u) (J. Chem. Phys., 2014, 141, 144104) to quantify the extent to which a solvated electron at point r in a calculated wavefunction delocalizes over distance u. Calculations on electrons in one-dimensional model cavities illustrate fundamental properties of the EDR. Mean-field calculations on hydrated electrons (H2O)n(-) show that the density-matrix-based EDR reproduces existing molecular-orbital-based measures of delocalization. Correlated calculations on hydrated electrons and electrons in lithium-ammonia clusters illustrates how electron correlation tends to move surface- and cavity-bound electrons onto the cluster or cavity surface. Applications to multiple solvated electrons in lithium-ammonia clusters provide a novel perspective on the interplay of delocalization and strong correlation central to lithium-ammonia solutions' concentration-dependent insulator-to-metal transition. The results motivate continued application of the EDR to simulations of delocalized electrons.

  2. 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.

  3. Electron crystallography and aquaporins.

    PubMed

    Schenk, Andreas D; Hite, Richard K; Engel, Andreas; Fujiyoshi, Yoshinori; Walz, Thomas

    2010-01-01

    Electron crystallography of two-dimensional (2D) crystals can provide information on the structure of membrane proteins at near-atomic resolution. Originally developed and used to determine the structure of bacteriorhodopsin (bR), electron crystallography has recently been applied to elucidate the structure of aquaporins (AQPs), a family of membrane proteins that form pores mostly for water but also other solutes. While electron crystallography has made major contributions to our understanding of the structure and function of AQPs, structural studies on AQPs, in turn, have fostered a number of technical developments in electron crystallography. In this contribution, we summarize the insights electron crystallography has provided into the biology of AQPs, and describe technical advancements in electron crystallography that were driven by structural studies on AQP 2D crystals. In addition, we discuss some of the lessons that were learned from electron crystallographic work on AQPs.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. (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.

  16. Heliospheric Electrons from Jupiter

    NASA Astrophysics Data System (ADS)

    Gomez-Herrero, R.; Rodriguez-Frias, M. D.; del Peral, L.; Sequeiros, J.; Mueller-Mellin, R.; Kunow, H.

    2001-08-01

    The electron spectrum in the energy range 250 keV to 10 MeV measured by EPHIN sensor onboard SOHO observatory during 1996 quiet time periods is presented. The results show that the dominant electron population is of Jovian origin. The spectral indexes obtained range from 1.5 to 1.8 in this work an estimation of the emission intensity of electrons from the Jovian magnetosphere is also obtained. Unexpected recurrence of Jovian electrons at the middle of 1996, during poor EarthJupiter magnetic connection has been observed.

  17. 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.

  18. 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. PMID:27005410

  19. 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;…

  20. 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.

  1. Electron Beam Lithography

    NASA Astrophysics Data System (ADS)

    Harriott, Lloyd R.

    1997-04-01

    Electron beams have played a significant role in semiconductor technology for more than twenty years. Early electron beam machines used a raster scanned beam spot to write patterns in electron-sensitive polymer resist materials. The main application of electron beam lithography has been in mask making. Despite the inherently high spatial resolution and wide process margins of electron beam lithography, the writing rate for semiconductor wafers has been too slow to be economically viable on a large scale. In the late 1970's, variable shape electron beam writing was developed, projecting a rectangular beam whose size can be varied for each "shot" exposure of a particular pattern, allowing some integrated circuits to be made economically where a variety of "customized" patterns are desired. In the cell or block projection electron beam exposure technique, a unit cell of a repetitive pattern is projected repeatedly to increase the level of parallelism. This can work well for highly repetitive patterns such as memory chips but is not well suited to complex varying patterns such as microprocessors. The rapid progress in the performance of integrated circuits has been largely driven by progress in optical lithography, through improvements in lens design and fabrication as well as the use of shorter wavelengths for the exposure radiation. Due to limitations from the opacity of lens and mask materials, it is unlikely that conventional optical printing methods can be used at wavelengths below 193 nm or feature sizes much below 180 nm. One candidate technology for a post-optical era is the Scattering with Angular Limitation Projection Electron-beam Lithography (SCALPEL) approach, which combines the high resolution and wide process latitude inherent in electron beam lithography with the throughput of a parallel projection system. A mask consisting of a low atomic number membrane and a high atomic number pattern layer is uniformly illuminated with high energy (100 ke

  2. 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…

  3. 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.

  4. 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…

  5. 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.}

  6. 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.

  7. 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.

  8. Electronically Controlled Resistor Bank

    NASA Technical Reports Server (NTRS)

    Ross, Walter L.

    1987-01-01

    Resistance quickly varied in small steps over wide range. Device with no moving parts provides variable electrical resistance. Used with analog or digital circuity to provide electronic selection of large number of resistance values for testing, simulation, control, or other purposes. Nearest electromechanical equivalent of all-electronic device is potentiometer driven by servomotor.

  9. 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. PMID:25971511

  10. Electron pairing without superconductivity

    NASA Astrophysics Data System (ADS)

    Levy, Jeremy

    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. Support from AFOSR, ONR, ARO, NSF, DOE and NSSEFF is gratefully acknowledged.

  11. 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.

  12. 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)

  13. Electronic neural networks

    SciTech Connect

    Howard, R.E.; Jackel, L.D.; Graf, H.P.

    1988-02-01

    The use of electronic neural networks to handle some complex computing problems is discussed. A simple neural model is shown and discussed in terms of its computational aspects. The use of electronic neural networks in machine pattern recognition and classification and in machine learning is examined. CMOS programmable networks are discussed. 15 references.

  14. Flexible electronics: Sophisticated skin

    NASA Astrophysics Data System (ADS)

    Bauer, Siegfried

    2013-10-01

    Advances in materials science and layout design have enabled the realization of flexible and multifunctional electronic devices. Two demonstrations of electronic skins, which combine temperature and pressure sensing with integrated thermal actuators and organic displays, unveil the potential of these devices for robotics and clinical applications.

  15. Planning the Electronic Library.

    ERIC Educational Resources Information Center

    Trolley, Jacqueline

    1995-01-01

    Introduces the Institute for Scientific Information's (ISI) electronic library project, and discusses the project's technological, economic, and legal issues. Describes computer system requirements that allow ISI's electronic library prototype to provide users with bibliographic information, abstracts, and full images of journals. (JMV)

  16. Multimedia electronic mail

    NASA Astrophysics Data System (ADS)

    Yamamoto, Brian

    1990-08-01

    Electronic mail is a facility, analogous to postal mail, in which computers are used to compose, deliver, and receive messages. Traditional electronic mail systems rely solely on text as the medium of communication. A multi-media electronic mall application, Mail, combines the media of Rich Text, voice, images, and electronic documents to facilitate interpersonal communication. With Mail, these various media can be integrated into a single message. The variety of available media and the complexity of the messages that result from their combination make it important for Mail to have a simple user interface. It was possible to develop a simple, graphically-based interface that would accommodate Mail's message complexity. The integration of these diverse media is made practical by the rich operating environment in which Mail runs. Modern advances in hardware, operating systems, libraries, and servers make possible this powerful multi-media electronic mail application.

  17. Silicon Carbide Electronic Devices

    NASA Technical Reports Server (NTRS)

    Neudeck, P. G.

    2001-01-01

    The status of emerging silicon carbide (SiC) widebandgap semiconductor electronics technology is briefly surveyed. SiC-based electronic devices and circuits are being developed for use in high-temperature, high-power, and/or high-radiation conditions under which conventional semiconductors cannot function. Projected performance benefits of SiC electronics are briefly illustrated for several applications. However, most of these operational benefits of SiC have yet to be realized in actual systems, primarily owing to the fact that the growth techniques of SiC crystals are relatively immature and device fabrication technologies are not yet sufficiently developed to the degree required for widespread, reliable commercial use. Key crystal growth and device fabrication issues that limit the performance and capability of high-temperature and/or high-power SiC electronics are identified. The electrical and material quality differences between emerging SiC and mature silicon electronics technology are highlighted.

  18. Beyond an Electronic Logbook

    SciTech Connect

    Theodore Larrieu; Theo McGuckin

    2005-03-01

    Beyond an Electronic Logbook Larrieu, Theodore L. and McGuckin, Theodore S. The advantages of an electronic logbook over a paper logbook have been well-established by presenters at various conferences: multiple simultaneous access, readily attached supporting documentation, easy searchability. At Jefferson Lab, we view these benefits as a start rather than an end. Instead of a being a static repository for operational history, the electronic logbook should actively inform machine operations. We take advantage of a decision early in development to make our operational problem reporting system integral to the electronic logbook. Log entries requiring attention of system experts are dispatched directly from within the logbook. And more importantly, the follow-up and resolution of those same problems is also captured in the electronic logbook. The interface for making log entries is being extended to query the logbook database immediately when a new problem report is initiated

  19. Modular electronics packaging system

    NASA Technical Reports Server (NTRS)

    Hunter, Don J. (Inventor)

    2001-01-01

    A modular electronics packaging system includes multiple packaging slices that are mounted horizontally to a base structure. The slices interlock to provide added structural support. Each packaging slice includes a rigid and thermally conductive housing having four side walls that together form a cavity to house an electronic circuit. The chamber is enclosed on one end by an end wall, or web, that isolates the electronic circuit from a circuit in an adjacent packaging slice. The web also provides a thermal path between the electronic circuit and the base structure. Each slice also includes a mounting bracket that connects the packaging slice to the base structure. Four guide pins protrude from the slice into four corresponding receptacles in an adjacent slice. A locking element, such as a set screw, protrudes into each receptacle and interlocks with the corresponding guide pin. A conduit is formed in the slice to allow electrical connection to the electronic circuit.

  20. High brightness electron accelerator

    DOEpatents

    Sheffield, Richard L.; Carlsten, Bruce E.; Young, Lloyd M.

    1994-01-01

    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 electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

  1. Electron resonances in DIET

    NASA Astrophysics Data System (ADS)

    Sanche, Léon

    2000-04-01

    The appearance of peaks or maxima in desorption yield functions, obtained by 5 to 20 eV electrons impinging from vacuum onto atomic or molecular solid films, reveals the formation of transient anions (i.e. electron resonances) at specific energies. Depending on the interaction of the incident electron with a particular atom or molecule and with the surrounding medium, the transient anion can cause desorption of a stable anion and one or more neutral fragments or only neutral particle ejection. The former process occurs when the transitory anionic state dissociates before autoionization, whereas decay by electron emission can, under certain circumstances, result in neutral atom or molecule desorption. Details on these mechanisms are given in this article. They are illustrated from desorption yield functions recorded for 5-20 eV electron impact on thin film targets made of pure Ar, CO 2, D 2O and mixtures of Ar with H 2O, O 2 and n-hexane.

  2. Electrons and Mirror Symmetry

    ScienceCinema

    Kumar, Krishna

    2016-07-12

    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.

  3. Developing electronic textbooks

    SciTech Connect

    Zadoks, R.I.; Ratner, J.A.

    1996-03-01

    This paper discusses a new approach to the development of engineering education materials. The ``Electronic Textbook`` represents the logical progression of the printed textbook in the Electronic Age. The concept behind this approach is simple; to place all of the information contained in a textbook in electronic form. Currently, paper texts exist on the market with electronic supplements, however, this Electronic Textbook would include supplements fully integrated in the whole text. The computer hardware and software needed to make this advance possible have existed for nearly ten years, and they have been readily available to engineering educators and students for over three years. Computer based ``tools`` in engineering textbooks as are prevalent today range from computer styled algorithms and code snippets, to fully developed software applications with graphical user interfaces on floppy disks attached to the back covers of books. The next logical step in publishing is to dispense with the paper book entirely, by distributing textbooks via electronic media such as CD-ROM. Electronic Textbooks use the full range of multi-media technologies in the learning and teaching process including video clips, computer animations and fully functional numerical engines as integral parts of the textbook material. This is very appealing since interactive media provide teaching tools that appeal to divergent learning styles. The advantages of Electronic Textbooks lead to several challenges. Special attention must be paid to the development of user interfaces; navigation is of particular importance when non- linear exploration is encouraged. These issues are being addressed at the Sandia National Laboratories by an electronic documentation development team. This team includes experts in engineering, in human factors, and in computer hardware and software development. Guidelines for the development of electronic textbooks based on the experiences of this team are provided.

  4. Simulations of Gaussian electron guns for RHIC electron lens

    SciTech Connect

    Pikin, A.

    2014-02-28

    Simulations of two versions of the electron gun for RHIC electron lens are presented. The electron guns have to generate an electron beam with Gaussian radial profile of the electron beam density. To achieve the Gaussian electron emission profile on the cathode we used a combination of the gun electrodes and shaping of the cathode surface. Dependence of electron gun performance parameters on the geometry of electrodes and the margins for electrodes positioning are presented.

  5. Electron transfer in biology

    NASA Astrophysics Data System (ADS)

    Williams, R. J. P.

    Electron transfer is one of the key reactions of biology not just in catalysis of oxidation/reduction reactions but in the conversion of sources of energy such as light to usable form for chemical transformations. There are then two intriguing problems. What is the nature of the matrix in which electrons flow in a biological cell after the initial charge separation due for example to the absorption of light. Here we are examining biological structures similar to man's electronic wires and the construction must be of low resistance in what are apparently insulators - organic polymers. It has been found that the electronic conduction system is largely made from metallo-proteins associated with lipid membranes. We understand much about these biological wires today. The second problem concerns the conversion of the energy captured from the light into usable chemical form. The major synthetic step in the production of biological polymers, including proteins, DNA, RNA, polysaccharides and fats, is condensation, i.e. the removal of water in the formation of amides, esters and so on. Now these condensation reactions are driven in biology by using a drying agent in water, namely the anhydride, pyrophosphate, in a special compound ATP, adenosine triphosphate. The central problem is to discover exactly how the flow of electrons can be related to the synthesis of (bound) pyrophosphate. (In a thermodynamic sense pyrophosphate is a water soluble kinetically stable drying agent comparable with solid P2O5.) In the biological systems the connection between these different classes of reaction, electron transfer and condensation, is known to be via the production of an energized gradient of protons across the biological membrane which arises from the flow of electrons across the same membrane in the electron transport wires of biology. However we do not understand thoroughly the steps which lead from electron flow in a membrane to proton gradients in that membrane, i.e. electron

  6. Electron Cooling of RHIC

    SciTech Connect

    I. Ben-Zvi; D.S. Barton; D.B. Beavis; M. Blaskiewicz; J.M. Brennan; A. Burrill; R. Calaga; P. Cameron; X.Y. Chang; R. Connolly; Yu.I. Eidelman; A.V. Fedotov; W. Fischer; D.M. Gassner; H. Hahn; M. Harrison; A. Hershcovitch; H.-C. Hseuh; A.K. Jain; P.D.J. Johnson; D. Kayran; J. Kewisch; R.F. Lambiase; V. Litvinenko; W.W. MacKay; G.J. Mahler; N. Malitsky; G.T. McIntyre; W. Meng; K.A.M. Mirabella; C. Montag; T.C.N. Nehring; T. Nicoletti; B. Oerter; G. Parzen; D. Pate; J. Rank; T. Rao; T. Roser; T. Russo; J. Scaduto; K. Smith; D. Trbojevic; G. Wang; J. Wei; N.W.W. Williams; K.-C. Wu; V. Yakimenko; A. Zaltsman; Y. Zhao; D.T. Abell; D.L. Bruhwiler; H. Bluem; A. Burger; M.D. Cole; A.J. Favale; D. Holmes; J. Rathke; T. Schultheiss; A.M.M. Todd; A.V. Burov; S. Nagaitsev; J.R. Delayen; Y.S. Derbenev; L. W. Funk; P. Kneisel; L. Merminga; H.L. Phillips; J.P. Preble; I. Koop; V.V. Parkhomchuk; Y.M. Shatunov; A.N. Skrinsky; I. Koop; V.V. Parkhomchuk; Y.M. Shatunov; A.N. Skrinsky; J.S. Sekutowicz

    2005-05-16

    We report progress on the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeV/nucleon at storage energy using 54 MeV electrons. The electron source will be a superconducting RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum electron bunch frequency is 9.38 MHz, with bunch charge of 20 nC. The R&D program has the following components: The photoinjector and its photocathode, the superconducting linac cavity, start-to-end beam dynamics with magnetized electrons, electron cooling calculations including benchmarking experiments and development of a large superconducting solenoid. The photoinjector and linac cavity are being incorporated into an energy recovery linac aimed at demonstrating ampere class current at about 20 MeV. A Zeroth Order Design Report is in an advanced draft state, and can be found on the web at http://www.agsrhichome.bnl.gov/eCool/.

  7. Dissociative Electron Attachment

    NASA Astrophysics Data System (ADS)

    Arreola, Esmeralda; Esmeralda Arreola Collaboration; Leigh Hargreaves Collaboration

    Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.

  8. Electronically cloaked nanoparticles

    NASA Astrophysics Data System (ADS)

    Shen, Wenqing

    The concept of electronic cloaking is to design objects invisible to conduction electrons. The approach of electronic cloaking has been recently suggested to design invisible nanoparticle dopants with electronic scattering cross section smaller than 1% of the physical cross section (pi a2), and therefore to enhance the carrier mobility of bulk materials. The proposed nanoparticles have core-shell structures. The dopants are incorporated inside the core, while the shell layer serves both as a spacer to separate the charge carriers from their parent atoms and as a cloaking shell to minimize the scattering cross section of the electrons from the ionized nanoparticles. Thermoelectric materials are usually highly doped to have enough carrier density. Using invisible dopants could achieve larger thermoelectric power factors by enhancing the electronic mobility. Core-shell nanoparticles show an advantage over one-layer nanoparticles, which are proposed in three-dimensional modulation doping. However designing such nanoparticles is not easy as there are too many parameters to be considered. This thesis first shows an approach to design hollow nanoparticles by applying constrains on variables. In the second part, a simple mapping approach is introduced where one can identify possible core-shell particles by comparing the dimensionless parameters of chosen materials with provided maps. In both parts of this work, several designs with realistic materials were made and proven to achieve electronic cloaking. Improvement in the thermoelectric power factor compared to the traditional impurity doping method was demonstrated in several cases.

  9. Aerogels for electronics

    SciTech Connect

    Hrubesh, L.W.

    1994-10-01

    In addition to their other exceptional properties, aerogels also exhibit unusual dielectric and electronic properties due to their nano-sized structures and high porosities. For example, aerogels have the lowest dielectric constants measured for a solid material (having values approaching 1.0); they have exceptionally high dielectric resistivities and strengths (i.e., ability to insulate very high voltages); they exhibit low dielectric loss at microwave frequencies; and some aerogels are electrically conductive and photoconductive. These properties are being exploited to provide the next generation of materials for energy storage, low power consumption, and ultra-fast electronics. We are working toward adapting these unusual materials for microelectronic applications, particularly, making thin aerogel films for dielectric substrates and for energy storage devices such as supercapacitors. Measurements are presented in this paper for the dielectric and electronic properties of aerogels, including the dielectric constant, loss factor, dielectric and electrical conductivity, volume resistivity, and dielectric strength. We also describe methods to form and characterize thin aerogel films which are being developed for numerous electronic applications. Finally, some of the electronic applications proposed for aerogels are presented. Commercialization of aerogels for electronics must await further feasibility, prototype development, and cost studies, but they are one of the key materials and are sure to have a major impact on future electronics.

  10. Processing dental claims electronically.

    PubMed

    Mylan, V

    1996-01-01

    A reduction of healthcare costs is an important part of the reform our society is demanding. We cannot ignore this. Lowering administrative costs is a particularly good way to reduce health care expenditures since this decreases the cost without compromising the quality of services. Implementing an EDI structure for submitting claims and receiving claim remittance advice is one way to significantly reduce the cost of health care by lowering administrative costs. EDI allows the consumer to receive the same level of health care at a lower cost. To accomplish this goal, the industry must accept some standardization. While providers, dental software vendors, and clearinghouses request an electronic claims system that is uniform-payers (insurance companies, State-administered Medicaid programs, etc.) often insist on proprietary formats that fit their own requirements. This impedes the implementation of a successful electronic interchange of data. Under the leadership of the Canadian Dental Association, payers and dentists in Canada were able to create a superior electronic claim processing network, CDAnet. Providers and payers using CDAnet agree that the system works very well. The Canadian dentist does not pay for this service, and insurance companies benefit significantly. Dentists in the USA do not have a universal electronic claim processing network. A USA dentist who wants to send claims electronically has limited selections and often pays additional fees. Organized dentistry has the best opportunity of establishing electronic data interchange between providers and payers in the USA. The first step is creating a universal electronic claim processing system. This system must protect confidentiality by maintaining data that keeps anonymous provider and patient data. It is the dentist who produces the claim. Dentists must become involved in the decisions affecting electronic claim processing. The proper guidance from organized dentistry will enable providers, payers

  11. Electron tomography of cells.

    PubMed

    Gan, Lu; Jensen, Grant J

    2012-02-01

    The electron microscope has contributed deep insights into biological structure since its invention nearly 80 years ago. Advances in instrumentation and methodology in recent decades have now enabled electron tomography to become the highest resolution three-dimensional (3D) imaging technique available for unique objects such as cells. Cells can be imaged either plastic-embedded or frozen-hydrated. Then the series of projection images are aligned and back-projected to generate a 3D reconstruction or 'tomogram'. Here, we review how electron tomography has begun to reveal the molecular organization of cells and how the existing and upcoming technologies promise even greater insights into structural cell biology. PMID:22082691

  12. Biological Electron Transport Systems

    PubMed Central

    Cowan, Dwaine O.; Pasternak, Gavril; Kaufman, Frank

    1970-01-01

    The solid-state electrical conductivities of a number of ferredoxin model compounds are reported. For one of these compounds, (KFeS2)n, an electron transfer rate for a 25 Å unit is shown to be at least 1 × 108 electrons sec-1. The rate becomes proportionally larger for smaller molecular units. This rapid rate is consistant with a short pipe model for electron transport between two reaction sites. Some of the factors leading to this rapid transfer rate are considered. PMID:5269247

  13. Electron screening in metals

    NASA Astrophysics Data System (ADS)

    Gajević, J.; Lipoglavšek, M.; Likar, A.; Petrovič, T.; Pelicon, P.; Sánchez Ortiz, A.; Cvetinović, A.

    2016-01-01

    In order to further investigate electron screening effect we studied proton induced nuclear reactions over an energy range from 0.8 to 2.6 MeV for different environments: Mn and Cd metals and MnO and CdO insulators. Shifts in resonance energy for metallic relative to insulator targets were not observed. No large electron screening could be deduced for (p,γ) and (p,n) reactions in Mn. Moreover, no large electron screening can be deduced with certainty for the (p,n) reaction in Cd.

  14. Coding for Electronic Mail

    NASA Technical Reports Server (NTRS)

    Rice, R. F.; Lee, J. J.

    1986-01-01

    Scheme for coding facsimile messages promises to reduce data transmission requirements to one-tenth current level. Coding scheme paves way for true electronic mail in which handwritten, typed, or printed messages or diagrams sent virtually instantaneously - between buildings or between continents. Scheme, called Universal System for Efficient Electronic Mail (USEEM), uses unsupervised character recognition and adaptive noiseless coding of text. Image quality of resulting delivered messages improved over messages transmitted by conventional coding. Coding scheme compatible with direct-entry electronic mail as well as facsimile reproduction. Text transmitted in this scheme automatically translated to word-processor form.

  15. Electron Beam Materials Irradiators

    NASA Astrophysics Data System (ADS)

    Cleland, Marshall R.

    2012-06-01

    Radiation processing is a well established method for enhancing the properties of materials and commercial products by treating them with ionizing energy in the form of high-energy electrons, X-rays, and gamma rays. Beneficial effects include polymerizing, cross-linking, grafting and degrading plastics, sterilizing single-use medical devices, disinfecting and disinfesting fresh foods, purifying drinking water, treating wastewater and other toxic waste materials that harm the environment, and many other applications that are still being evaluated. Industrial electron accelerators of several types have been developed and are being used for these applications. More than 1800 electron accelerators are presently installed in facilities worldwide for these purposes.

  16. High brightness electron sources

    SciTech Connect

    Sheffield, R.L.

    1995-07-01

    High energy physics accelerators and free electron lasers put increased demands on the electron beam sources. This paper describes the present research on attaining intense bright electron beams using photoinjectors. Recent results from the experimental programs will be given. The performance advantages and difficulties presently faced by researchers will be discussed, and the following topics will be covered. Progress has been made in photocathode materials, both in lifetime and quantum efficiency. Cesium telluride has demonstrated significantly longer lifetimes than cesium antimonide at 10{sup {minus}8} torr. However, the laser system is more difficult because cesium telluride requires quadrupled YLF instead of the doubled YLF required for cesium antimonide. The difficulty in using photoinjectors is primarily the drive laser, in particular the amplitude stability. Finally, emittance measurements of photoinjector systems can be complicated by the non-thermal nature of the electron beam. An example of the difficulty in measuring beam emittance is given.

  17. Telecommunications--Electronic Mail.

    ERIC Educational Resources Information Center

    Kelly, Luke E.; Zuckerman, B. Michael

    1989-01-01

    This article identifies resources needed in order for physical education, recreation, and dance professionals to use computer-based telecommunications; discusses electronic mail; and explains how telecommunications can enhance communication in the field, both within and across professions. (IAH)

  18. Electronic Falling Body Simulator

    ERIC Educational Resources Information Center

    Goodman, John M.

    1975-01-01

    Describes an analog electronic simulator for the motion of an object projected horizontally in a vertical acceleration field. The device features adjustable values for the horizontal speeds and "gravity." Trajectories are displayed on an oscilloscope. (Author/CP)

  19. Fracture in Electronics

    NASA Astrophysics Data System (ADS)

    Plumbridge, William J.

    Although the World’s largest industrial sector, Electronics has received relatively little attention with regard to mechanical failure of its equipment. Design strategies against fracture are advanced for applications, such as aerospace, automotive, pressure vessel and engine applications. So a fundamental question arises as to the extent to which these can be applied to Electronics. The paper describes the special characteristics of electronics equipment in service, and outlines common modes of failure, with emphasis on thermomechanical fatigue. The particular challenge of size is considered when behaviour determined from conventional bulk samples is no longer representative of actual components. Two case studies are presented that illustrate the special nature of electronics. It is suggested that as miniaturisation continues, fracture will become a major cause of failure.

  20. Introduction to electron crystallography.

    PubMed

    Kühlbrandt, Werner

    2013-01-01

    From the earliest work on regular arrays in negative stain, electron crystallography has contributed greatly to our understanding of the structure and function of biological macromolecules. The development of electron cryo-microscopy (cryo-EM) then lead to the first groundbreaking atomic models of the membrane proteins bacteriorhodopsin and light harvesting complex II within lipid bilayers. Key contributions towards cryo-EM and electron crystallography methods included specimen preparation and vitrification, liquid-helium cooling, data collection, and image processing. These methods are now applied almost routinely to both membrane and soluble proteins. Here we outline the advances and the breakthroughs that paved the way towards high-resolution structures by electron crystallography, both in terms of methods development and biological milestones.

  1. Issues in Electronic Publishing.

    ERIC Educational Resources Information Center

    Meadow, Charles T.

    1997-01-01

    Discusses issues related to electronic publishing. Topics include writing; reading; production, distribution, and commerce; copyright and ownership of intellectual property; archival storage; technical obsolescence; control of content; equality of access; and cultural changes. (Author/LRW)

  2. Electron-impact spectroscopy

    NASA Technical Reports Server (NTRS)

    Trajmar, S.

    1990-01-01

    The methods of electron impact spectroscopy and cross section measurements are discussed and compared to optical spectroscopy. A brief summary of the status of this field and the available data is given.

  3. Computation in electron microscopy.

    PubMed

    Kirkland, Earl J

    2016-01-01

    Some uses of the computer and computation in high-resolution transmission electron microscopy are reviewed. The theory of image calculation using Bloch wave and multislice methods with and without aberration correction is reviewed and some applications are discussed. The inverse problem of reconstructing the specimen structure from an experimentally measured electron microscope image is discussed. Some future directions of software development are given. PMID:26697863

  4. Electron spectroscopy analysis

    NASA Technical Reports Server (NTRS)

    Gregory, John C.

    1992-01-01

    The Surface Science Laboratories at the University of Alabama in Huntsville (UAH) are equipped with x-ray photoelectron spectroscopy (XPS or ESCA) and Auger electron spectroscopy (AES) facilities. These techniques provide information from the uppermost atomic layers of a sample, and are thus truly surface sensitive. XPS provides both elemental and chemical state information without restriction on the type of material that can be analyzed. The sample is placed into an ultra high vacuum (UHV) chamber and irradiated with x-rays which cause the ejection of photoelectrons from the sample surface. Since x-rays do not normally cause charging problems or beam damage, XPS is applicable to a wide range of samples including metals, polymers, catalysts, and fibers. AES uses a beam of high energy electrons as a surface probe. Following electronic rearrangements within excited atoms by this probe, Auger electrons characteristic of each element present are emitted from the sample. The main advantage of electron induced AES is that the electron beam can be focused down to a small diameter and localized analysis can be carried out. On the rastering of this beam synchronously with a video display using established scanning electron microscopy techniques, physical images and chemical distribution maps of the surface can be produced. Thus very small features, such as electronic circuit elements or corrosion pits in metals, can be investigated. Facilities are available on both XPS and AES instruments for depth-profiling of materials, using a beam of argon ions to sputter away consecutive layers of material to reveal sub-surface (and even semi-bulk) analyses.

  5. Electronic engine controls

    SciTech Connect

    Hodges, S.

    1991-07-01

    This paper reports that pioneered in the mid-80s to manage and optimize engine performance under continually changing conditions, electronic controls have made a significant impact on truck maintenance. But they also served another important purpose: they curbed emissions enough to meet EPA's new heavy-truck standards set in 1985 (see sidebar). In that same year, Detroit Diesel introduced its Detroit Diesel Electronic Controls (DDEC) system, and a trend was born. Suddenly horsepower rating, torque curve, and maximum engine and road speed could be governed by electronics. Engine-mounted sensors could provide drivers with precise information about fluid and pressure levels, inside and outside temperatures, and a host of other information. The advent of electronic engine controls signaled the dawn of a revolution in trucking. For company owners who wanted greater control of their operations, electronics were wonderful news. But new controls meant new engine designs and radical changes in engine maintenance and repair. So for many members of the waste-hauling industry, electronics were far from wonderful. It's not that haulers didn't want cleaner air or trucks that were increasingly fuel efficient. It's more that they winced at the thought of retraining their mechanics - already hard to find and retain - to work on a new breed of engine. Then there were other considerations. drivers, for example, might not cotton to the fancy electronic dashboard displays. They might also rebel at having their maximum road speed present at a rate they couldn't change. Then there was the cost factor: Electronics and other provisions used to meet Clean Air Act reductions of oxides of nitrogen between 1991, 94 and 98 model years could add as much as $10,000 to $15,000 to the cost of each truck.

  6. Pulsed electron beam precharger

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1991-01-01

    Electron beam precharging of a high resistivity aerosol was successfully performed under a range of experimental conditions during Quarter Six of the contract. The initial E-beam particle precharging experiments completed this term were designed to extend the efficiency of particle charging and collection using a fine, monodisperse aerosol at relatively large loadings in the FSU Electron Beam Precipitator wind tunnel. There are several reasons for doing this: (1) to re-establish a baseline performance criterion for comparison to other runs, (2) to test several recently upgraded or repaired subsystems, and (3) to improve upon the collection efficiency of the electron beam precipitator when testing precharging effectiveness with a very high resistivity, moderate-to-high dust concentration. In addition, these shakedown runs were used to determine a set of suitable operational parameters for the wind tunnel, the electrostatic collecting sections, and the MINACC E-beam accelerator. These parameters will normally be held constant while the precharging parameters are varied to produce an optimum particle charge. The electron beam precharging investigation performed during the period covered by Quarter Six used virtually the same experimental apparatus and procedures as in previous contract work, and these are described for review in this report. This investigation was part of an experimental effort which ran nearly continuously for nine months, encompassing work on the electrostatic collecting section, electron beam precharger, and particle charge-to-radius measuring apparatus. A summary of the work on dc electron beam precipitation is presented here.

  7. BOK-Printed Electronics

    NASA Technical Reports Server (NTRS)

    Ghaffarian, Reza

    2013-01-01

    The use of printed electronics technologies (PETs), 2D or 3D printing approaches either by conventional electronic fabrication or by rapid graphic printing of organic or nonorganic electronic devices on various small or large rigid or flexible substrates, is projected to grow exponentially in commercial industry. This has provided an opportunity to determine whether or not PETs could be applicable for low volume and high-reliability applications. This report presents a summary of literature surveyed and provides a body of knowledge (BOK) gathered on the current status of organic and printed electronics technologies. It reviews three key industry roadmaps- on this subject-OE-A, ITRS, and iNEMI-each with a different name identification for this emerging technology. This followed by a brief review of the status of the industry on standard development for this technology, including IEEE and IPC specifications. The report concludes with key technologies and applications and provides a technology hierarchy similar to those of conventional microelectronics for electronics packaging. Understanding key technology roadmaps, parameters, and applications is important when judicially selecting and narrowing the follow-up of new and emerging applicable technologies for evaluation, as well as the low risk insertion of organic, large area, and printed electronics.

  8. Free electron laser

    DOEpatents

    Villa, Francesco

    1990-01-01

    A high gain, single-pass free electron laser formed of a high brilliance electron injector source, a linear accelerator which imparts high energy to the electron beam, and an undulator capable of extremely high magnetic fields, yet with a very short period. The electron injector source is the first stage (gap) of the linear accelerator or a radial line transformer driven by fast circular switch. The linear accelerator is formed of a plurality of accelerating gaps arranged in series. These gaps are energized in sequence by releasing a single pulse of energy which propagates simultaneously along a plurality of transmission lines, each of which feeds the gaps. The transmission lines are graduated in length so that pulse power is present at each gap as the accelerated electrons pass therethrough. The transmission lines for each gap are open circuited at their ends. The undualtor has a structure similar to the accelerator, except that the transmission lines for each gap are substantially short circuited at their ends, thus converting the electric field into magnetic field. A small amount of resistance is retained in order to generate a small electric field for replenishing the electron bunch with the energy lost as it traverses through the undulator structure.

  9. Electronic Properties of DNA-Based Schottky Barrier Diodes in Response to Alpha Particles.

    PubMed

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2015-01-01

    Detection of nuclear radiation such as alpha particles has become an important field of research in recent history due to nuclear threats and accidents. In this context; deoxyribonucleic acid (DNA) acting as an organic semiconducting material could be utilized in a metal/semiconductor Schottky junction for detecting alpha particles. In this work we demonstrate for the first time the effect of alpha irradiation on an Al/DNA/p-Si/Al Schottky diode by investigating its current-voltage characteristics. The diodes were exposed for different periods (0-20 min) of irradiation. Various diode parameters such as ideality factor, barrier height, series resistance, Richardson constant and saturation current were then determined using conventional, Cheung and Cheung's and Norde methods. Generally, ideality factor or n values were observed to be greater than unity, which indicates the influence of some other current transport mechanism besides thermionic processes. Results indicated ideality factor variation between 9.97 and 9.57 for irradiation times between the ranges 0 to 20 min. Increase in the series resistance with increase in irradiation time was also observed when calculated using conventional and Cheung and Cheung's methods. These responses demonstrate that changes in the electrical characteristics of the metal-semiconductor-metal diode could be further utilized as sensing elements to detect alpha particles. PMID:26007733

  10. Electronic Properties of DNA-Based Schottky Barrier Diodes in Response to Alpha Particles

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2015-01-01

    Detection of nuclear radiation such as alpha particles has become an important field of research in recent history due to nuclear threats and accidents. In this context; deoxyribonucleic acid (DNA) acting as an organic semiconducting material could be utilized in a metal/semiconductor Schottky junction for detecting alpha particles. In this work we demonstrate for the first time the effect of alpha irradiation on an Al/DNA/p-Si/Al Schottky diode by investigating its current-voltage characteristics. The diodes were exposed for different periods (0–20 min) of irradiation. Various diode parameters such as ideality factor, barrier height, series resistance, Richardson constant and saturation current were then determined using conventional, Cheung and Cheung’s and Norde methods. Generally, ideality factor or n values were observed to be greater than unity, which indicates the influence of some other current transport mechanism besides thermionic processes. Results indicated ideality factor variation between 9.97 and 9.57 for irradiation times between the ranges 0 to 20 min. Increase in the series resistance with increase in irradiation time was also observed when calculated using conventional and Cheung and Cheung’s methods. These responses demonstrate that changes in the electrical characteristics of the metal-semiconductor-metal diode could be further utilized as sensing elements to detect alpha particles. PMID:26007733

  11. Electronic Paper Turns the Page.

    ERIC Educational Resources Information Center

    Mann, Charles C.

    2001-01-01

    Documents the development of electronic paper focusing on significant events and inventors. Includes a graphic of the process of making electronic paper. Illustrates the multidisciplinary nature of the development of electronic paper. (DDR)

  12. Imaging Coherent Electronic Motion in Atoms by Ultrafast Electron Diffraction

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2014-05-01

    Ultrafast electron diffraction from time-varying coherent electronic states of the H atom is investigated. Electron diffraction from coherent electronic states exhibiting breathing and wiggling modes of electronic motion are simulated in order to demonstrate the capability of attosecond electron pulses to image electron dynamics. A theoretical analysis identifies the conditions necessary to obtain time-resolved measurements. The scattering patterns and their temporal behaviors are shown to differentiate the two kinds of target electronic motion. Moreover, our simulations show that inelastic processes contribute significantly to the diffraction patterns. Thus although the diffraction patterns clearly distinguish different modes of target electronic motion, they cannot be easily related to the time-dependent target charge density. Finally, we note that detection of the scattered electron energy can provide more information on time-dependent target electronic motion. This work is supported in part by AFOSR Award No. FA9550-12-1-0149.

  13. Low energy electron magnetometer using a monoenergetic electron beam

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Wood, G. M.; Rayborn, G. H.; White, F. A. (Inventor)

    1983-01-01

    A low energy electron beam magnetometer utilizes near-monoenergetic electrons thereby reducing errors due to electron energy spread and electron nonuniform angular distribution. In a first embodiment, atoms in an atomic beam of an inert gas are excited to a Rydberg state and then electrons of near zero energy are detached from the Rydberg atoms. The near zero energy electrons are then accelerated by an electric field V(acc) to form the electron beam. In a second embodiment, a filament emits electrons into an electrostatic analyzer which selects electrons at a predetermined energy level within a very narrow range. These selected electrons make up the electron beam that is subjected to the magnetic field being measured.

  14. Cooling system for electronic components

    DOEpatents

    Anderl, William James; Colgan, Evan George; Gerken, James Dorance; Marroquin, Christopher Michael; Tian, Shurong

    2016-05-17

    Embodiments of the present invention provide for non interruptive fluid cooling of an electronic enclosure. One or more electronic component packages may be removable from a circuit card having a fluid flow system. When installed, the electronic component packages are coincident to and in a thermal relationship with the fluid flow system. If a particular electronic component package becomes non-functional, it may be removed from the electronic enclosure without affecting either the fluid flow system or other neighboring electronic component packages.

  15. Cooling system for electronic components

    SciTech Connect

    Anderl, William James; Colgan, Evan George; Gerken, James Dorance; Marroquin, Christopher Michael; Tian, Shurong

    2015-12-15

    Embodiments of the present invention provide for non interruptive fluid cooling of an electronic enclosure. One or more electronic component packages may be removable from a circuit card having a fluid flow system. When installed, the electronic component packages are coincident to and in a thermal relationship with the fluid flow system. If a particular electronic component package becomes non-functional, it may be removed from the electronic enclosure without affecting either the fluid flow system or other neighboring electronic component packages.

  16. Pulsed electron beam precharger

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1990-01-01

    Electrostatic collection of a high resistivity aerosol using the Electron Beam Precipitator (EBP) collecting section was demonstrated during this reporting period (Quarter Five). Collection efficiency experiments were designed to confirm and extend some of the work performed under the previous contract. The reason for doing this was to attempt to improve upon the collection efficiency of the precipitator alone when testing with a very high resistivity, moderate-to-high concentration dust load. From the collector shakedown runs, a set of suitable operational parameters were determined for the downstream electrostatic collecting sections of the Electron Beam Precipitator wind tunnel. These parameters, along with those for the MINACC electron beam, will generally be held constant while the numerous precharging parameters are varied to produce an optimum particle charge. The electrostatic collector experiments were part of a larger, comprehensive investigation on electron beam precharging of high resistivity aerosol particles performed during the period covered by Quarters Five, Six, and Seven. This body of work used the same experimental apparatus and procedures and the experimental run period lasted nearly continuously for six months. A summary of the Quarter Five work is presented in the following paragraphs. Section II-A of TPR 5 contains a report on the continuing effort which was expended on the modification and upgrade of the pulsed power supply and the monitoring systems prior to the initiation of the electron beam precharging experimental work.

  17. Electronic Spectroscopy & Dynamics

    SciTech Connect

    Mark Maroncelli, Nancy Ryan Gray

    2010-06-08

    The Gordon Research Conference (GRC) on Electronic Spectroscopy and Dynamics was held at Colby College, Waterville, NH from 07/19/2009 thru 07/24/2009. The Conference was well-attended with participants (attendees list attached). The attendees represented the spectrum of endeavor in this field coming from academia, industry, and government laboratories, both U.S. and foreign scientists, senior researchers, young investigators, and students. The GRC on Electronic Spectroscopy & Dynamics showcases some of the most recent experimental and theoretical developments in electronic spectroscopy that probes the structure and dynamics of isolated molecules, molecules embedded in clusters and condensed phases, and bulk materials. Electronic spectroscopy is an important tool in many fields of research, and this GRC brings together experts having diverse backgrounds in physics, chemistry, biophysics, and materials science, making the meeting an excellent opportunity for the interdisciplinary exchange of ideas and techniques. Topics covered in this GRC include high-resolution spectroscopy, biological molecules in the gas phase, electronic structure theory for excited states, multi-chromophore and single-molecule spectroscopies, and excited state dynamics in chemical and biological systems.

  18. Microfluidic stretchable RF electronics.

    PubMed

    Cheng, Shi; Wu, Zhigang

    2010-12-01

    Stretchable electronics is a revolutionary technology that will potentially create a world of radically different electronic devices and systems that open up an entirely new spectrum of possibilities. This article proposes a microfluidic based solution for stretchable radio frequency (RF) electronics, using hybrid integration of active circuits assembled on flex foils and liquid alloy passive structures embedded in elastic substrates, e.g. polydimethylsiloxane (PDMS). This concept was employed to implement a 900 MHz stretchable RF radiation sensor, consisting of a large area elastic antenna and a cluster of conventional rigid components for RF power detection. The integrated radiation sensor except the power supply was fully embedded in a thin elastomeric substrate. Good electrical performance of the standalone stretchable antenna as well as the RF power detection sub-module was verified by experiments. The sensor successfully detected the RF radiation over 5 m distance in the system demonstration. Experiments on two-dimensional (2D) stretching up to 15%, folding and twisting of the demonstrated sensor were also carried out. Despite the integrated device was severely deformed, no failure in RF radiation sensing was observed in the tests. This technique illuminates a promising route of realizing stretchable and foldable large area integrated RF electronics that are of great interest to a variety of applications like wearable computing, health monitoring, medical diagnostics, and curvilinear electronics.

  19. Secondary Electron Emission Yields

    NASA Technical Reports Server (NTRS)

    Krainsky, I.; Lundin, W.; Gordon, W. L.; Hoffman, R. W.

    1981-01-01

    The secondary electron emission (SEE) characteristics for a variety of spacecraft materials were determined under UHV conditions using a commercial double pass CMA which permits sequential Auger electron electron spectroscopic analysis of the surface. The transparent conductive coating indium tin oxide (ITO) was examined on Kapton and borosilicate glass and indium oxide on FED Teflon. The total SEE coefficient ranges from 2.5 to 2.6 on as-received surfaces and from 1.5 to 1.6 on Ar(+) sputtered surfaces with 5 nm removed. A cylindrical sample carousel provides normal incidence of the primary beam as well as a multiple Faraday cup measurement of the approximately nA beam currents. Total and true secondary yields are obtained from target current measurements with biasing of the carousel. A primary beam pulsed mode to reduce electron beam dosage and minimize charging of insulating coatings was applied to Mg/F2 coated solar cell covers. Electron beam effects on ITO were found quite important at the current densities necessary to do Auger studies.

  20. Electron microscope phase enhancement

    DOEpatents

    Jin, Jian; Glaeser, Robert M.

    2010-06-15

    A microfabricated electron phase shift element is used for modifying the phase characteristics of an electron beam passing though its center aperture, while not affecting the more divergent portion of an incident beam to selectively provide a ninety-degree phase shift to the unscattered beam in the back focal plan of the objective lens, in order to realize Zernike-type, in-focus phase contrast in an electron microscope. One application of the element is to increase the contrast of an electron microscope for viewing weakly scattering samples while in focus. Typical weakly scattering samples include biological samples such as macromolecules, or perhaps cells. Preliminary experimental images demonstrate that these devices do apply a ninety degree phase shift as expected. Electrostatic calculations have been used to determine that fringing fields in the region of the scattered electron beams will cause a negligible phase shift as long as the ratio of electrode length to the transverse feature-size aperture is about 5:1. Calculations are underway to determine the feasibility of aspect smaller aspect ratios of about 3:1 and about 2:1.

  1. Circular free-electron laser

    DOEpatents

    Brau, Charles A.; Kurnit, Norman A.; Cooper, Richard K.

    1984-01-01

    A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.

  2. Electron holes in inhomogeneous magnetic field: Electron heating and electron hole evolution

    NASA Astrophysics Data System (ADS)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.; Drake, J. F.

    2016-05-01

    Electron holes are electrostatic non-linear structures widely observed in the space plasma. In the present paper, we analyze the process of energy exchange between electrons trapped within electron hole, untrapped electrons, and an electron hole propagating in a weakly inhomogeneous magnetic field. We show that as the electron hole propagates into the region with stronger magnetic field, trapped electrons are heated due to the conservation of the first adiabatic invariant. At the same time, the electron hole amplitude may increase or decrease in dependence on properties of distribution functions of trapped and untrapped resonant electrons. The energy gain of trapped electrons is due to the energy losses of untrapped electrons and/or decrease of the electron hole energy. We stress that taking into account the energy exchange with untrapped electrons increases the lifetime of electron holes in inhomogeneous magnetic field. We illustrate the suggested mechanism for small-amplitude Schamel's [Phys. Scr. T2, 228-237 (1982)] electron holes and show that during propagation along a positive magnetic field gradient their amplitude should grow. Neglect of the energy exchange with untrapped electrons would result in the electron hole dissipation with only modest heating factor of trapped electrons. The suggested mechanism may contribute to generation of suprathermal electron fluxes in the space plasma.

  3. ELECTRON EMISSION REGULATING MEANS

    DOEpatents

    Brenholdt, I.R.

    1957-11-19

    >An electronic regulating system is described for controlling the electron emission of a cathode, for example, the cathode in a mass spectrometer. The system incorporates a transformer having a first secondary winding for the above-mentioned cathode and a second secondary winding for the above-mentioned cathode and a second secondary winding load by grid controlled vacuum tubes. A portion of the electron current emitted by the cathode is passed through a network which develops a feedback signal. The system arrangement is completed by using the feedback signal to control the vacuum tubes in the second secondary winding through a regulator tube. When a change in cathode emission occurs, the feedback signal acts to correct this change by adjusting the load on the transformer.

  4. Electron flow through proteins

    NASA Astrophysics Data System (ADS)

    Gray, Harry B.; Winkler, Jay R.

    2009-11-01

    Electron transfers in photosynthesis and respiration commonly occur between metal-containing cofactors that are separated by large molecular distances. Employing laser flash-quench triggering methods, we have shown that 20-Å, coupling-limited Fe II-Ru III and Cu I-Ru III electron tunneling in Ru-modified cytochromes and blue copper proteins can occur on the microsecond timescale both in solutions and crystals. Redox equivalents can be transferred even longer distances by multistep tunneling, often called hopping, through intervening amino acid side chains. Our work has established that 20-Å hole hopping through an intervening tryptophan is two orders of magnitude faster than single-step electron tunneling in a Re-modified blue copper protein.

  5. Foil Electron Multiplier

    DOEpatents

    Funsten, Herbert O.; Baldonado, Juan R.; Dors, Eric E.; Harper, Ronnie W.; Skoug, Ruth M.

    2006-03-28

    An apparatus for electron multiplication by transmission that is designed with at least one foil having a front side for receiving incident particles and a back side for transmitting secondary electrons that are produced from the incident particles transiting through the foil. The foil thickness enables the incident particles to travel through the foil and continue on to an anode or to a next foil in series with the first foil. The foil, or foils, and anode are contained within a supporting structure that is attached within an evacuated enclosure. An electrical power supply is connected to the foil, or foils, and the anode to provide an electrical field gradient effective to accelerate negatively charged incident particles and the generated secondary electrons through the foil, or foils, to the anode for collection.

  6. Electronic communication. Part III.

    PubMed

    Bergren, M D

    1995-02-01

    This is the concluding article of a three-part series on electronic communication for school nurses. The October 1994 column described electronic communication and the hardware and software required. The December 1994 column examined e-mail, bulletin boards, databases, and file transfers. This column will list many health and nursing resources available on-line. Some of the resources are available only through the Internet. Others are accessible by more than one route: dial-in, telnet, gopher, or world wide web. A few of the services, such as MEDLINE, are only accessed with purchased accounts (Glowniak & Bushway, 1994). The electronic resources of interest to school nurses are so numerous it would be impossible to cite all of them in a column of this length. Selected resources for the school health provider will be listed in alphabetical order. PMID:7767047

  7. Electronic engine controls

    SciTech Connect

    Johanson, C.E.; Owens, T.

    1987-01-01

    This textbook provides competency-based instruction on modern automotive engine electronics. It emphasizes the practical ''need to know'' information on the major American and imported electronic engine controls. Basic theory necessary for a complete understanding of control systems (including background coverage of electricity and electronics) is explained. Designed for students, self-paced instruction, or as a reference for professional automotive technicians, the text utilizes a step-by-step approach that complements factory and shop services manuals. Hands-on applications cover system-specific and component descriptions, significant operational features, and system diagnosis and component replacement. Approximately 500 photographs and illustrations aid in student comprehension. The Instructor's Guide contains outlines, objectives, review questions and tests, discussion topics, solutions to text problems, and suggested instructional methods for competency-based classroom training.

  8. Polarized electron sources

    SciTech Connect

    Clendenin, J.E.

    1995-05-01

    Polarized electron sources for high energy accelerators took a significant step forward with the introduction of a new laser-driven photocathode source for the SLC in 1992. With an electron beam polarization of >80% and with {approximately}99% uptime during continuous operation, this source is a key factor in the success of the current SLC high-energy physics program. The SLC source performance is used to illustrate both the capabilities and the limitations of solid-state sources. The beam requirements for future colliders are similar to that of the SLC with the addition in most cases of multiple-bunch operation. A design for the next generation accelerator source that can improve the operational characteristics and at least minimize some of the inherent limitations of present sources is presented. Finally, the possibilities for producing highly polarized electron beams for high-duty-factor accelerators are discussed.

  9. 4D Electron Tomography

    NASA Astrophysics Data System (ADS)

    Kwon, Oh-Hoon; Zewail, Ahmed H.

    2010-06-01

    Electron tomography provides three-dimensional (3D) imaging of noncrystalline and crystalline equilibrium structures, as well as elemental volume composition, of materials and biological specimens, including those of viruses and cells. We report the development of 4D electron tomography by integrating the fourth dimension (time resolution) with the 3D spatial resolution obtained from a complete tilt series of 2D projections of an object. The different time frames of tomograms constitute a movie of the object in motion, thus enabling studies of nonequilibrium structures and transient processes. The method was demonstrated using carbon nanotubes of a bracelet-like ring structure for which 4D tomograms display different modes of motion, such as breathing and wiggling, with resonance frequencies up to 30 megahertz. Applications can now make use of the full space-time range with the nanometer-femtosecond resolution of ultrafast electron tomography.

  10. Electron launching voltage monitor

    DOEpatents

    Mendel, Clifford W.; Savage, Mark E.

    1992-01-01

    An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors.

  11. Electron launching voltage monitor

    DOEpatents

    Mendel, C.W.; Savage, M.E.

    1992-03-17

    An electron launching voltage monitor measures MITL voltage using a relationship between anode electric field and electron current launched from a cathode-mounted perturbation. An electron launching probe extends through and is spaced from the edge of an opening in a first MITL conductor, one end of the launching probe being in the gap between the MITL conductor, the other end being adjacent a first side of the first conductor away from the second conductor. A housing surrounds the launching probe and electrically connects the first side of the first conductor to the other end of the launching probe. A detector detects the current passing through the housing to the launching probe, the detected current being representative of the voltage between the conductors. 5 figs.

  12. Electronics for Extreme Environments

    NASA Technical Reports Server (NTRS)

    Patel, J. U.; Cressler, J.; Li, Y.; Niu, G.

    2001-01-01

    Most of the NASA missions involve extreme environments comprising radiation and low or high temperatures. Current practice of providing friendly ambient operating environment to electronics costs considerable power and mass (for shielding). Immediate missions such as the Europa orbiter and lander and Mars landers require the electronics to perform reliably in extreme conditions during the most critical part of the mission. Some other missions planned in the future also involve substantial surface activity in terms of measurements, sample collection, penetration through ice and crust and the analysis of samples. Thus it is extremely critical to develop electronics that could reliably operate under extreme space environments. Silicon On Insulator (SOI) technology is an extremely attractive candidate for NASA's future low power and high speed electronic systems because it offers increased transconductance, decreased sub-threshold slope, reduced short channel effects, elimination of kink effect, enhanced low field mobility, and immunity from radiation induced latch-up. A common belief that semiconductor devices function better at low temperatures is generally true for bulk devices but it does not hold true for deep sub-micron SOI CMOS devices with microscopic device features of 0.25 micrometers and smaller. Various temperature sensitive device parameters and device characteristics have recently been reported in the literature. Behavior of state of the art technology devices under such conditions needs to be evaluated in order to determine possible modifications in the device design for better performance and survivability under extreme environments. Here, we present a unique approach of developing electronics for extreme environments to benefit future NASA missions as described above. This will also benefit other long transit/life time missions such as the solar sail and planetary outposts in which electronics is out open in the unshielded space at the ambient space

  13. Relativistic Runaway Electrons

    NASA Astrophysics Data System (ADS)

    Breizman, Boris

    2014-10-01

    This talk covers recent developments in the theory of runaway electrons in a tokamak with an emphasis on highly relativistic electrons produced via the avalanche mechanism. The rapidly growing population of runaway electrons can quickly replace a large part of the initial current carried by the bulk plasma electrons. The magnetic energy associated with this current is typically much greater than the particle kinetic energy. The current of a highly relativistic runaway beam is insensitive to the particle energy, which separates the description of the runaway current evolution from the description of the runaway energy spectrum. A strongly anisotropic distribution of fast electrons is generally prone to high-frequency kinetic instabilities that may cause beneficial enhancement of runaway energy losses. The relevant instabilities are in the frequency range of whistler waves and electron plasma waves. The instability thresholds reported in earlier work have been revised considerably to reflect strong dependence of collisional damping on the wave frequency and the role of plasma non-uniformity, including radial trapping of the excited waves in the plasma. The talk also includes a discussion of enhanced scattering of the runaways as well as the combined effect of enhanced scattering and synchrotron radiation. A noteworthy feature of the avalanche-produced runaway current is a self-sustained regime of marginal criticality: the inductive electric field has to be close to its critical value (representing avalanche threshold) at every location where the runaway current density is finite, and the current density should vanish at any point where the electric field drops below its critical value. This nonlinear Ohm's law enables complete description of the evolving current profile. Work supported by the U.S. Department of Energy Contract No. DEFG02-04ER54742 and by ITER contract ITER-CT-12-4300000273. The views and opinions expressed herein do not necessarily reflect those of

  14. Cylindrical electron beam diode

    DOEpatents

    Bolduc, Paul E.

    1976-01-01

    A diode discharge device may include a tubular anode concentrically encircled by and spaced from a tubular cathode electrode with ends intermediate the ends of said anode electrode, and a metal conductive housing having a tubular wall disposed around the cathode electrode with end walls connected to the anode electrode. High energy electron current coupling is through an opening in the housing tubular wall to a portion of the cathode electrode intermediate its ends. Suitable utilization means may be within the anode electrode at positions to be irradiated by electrons emitted from the cathode electrode and transmitted through the anode walls.

  15. The ATLAS TRT electronics

    NASA Astrophysics Data System (ADS)

    ATLAS TRT Collaboration; Abat, E.; Addy, T. N.; Åkesson, T. P. A.; Alison, J.; Anghinolfi, F.; Arik, E.; Arik, M.; Atoian, G.; Auerbach, B.; Baker, O. K.; Banas, E.; Baron, S.; Bault, C.; Becerici, N.; Beddall, A.; Beddall, A. J.; Bendotti, J.; Benjamin, D. P.; Bertelsen, H.; Bingul, A.; Blampey, H.; Bocci, A.; Bochenek, M.; Bondarenko, V. G.; Bychkov, V.; Callahan, J.; Capeáns Garrido, M.; Cardiel Sas, L.; Catinaccio, A.; Cetin, S. A.; Chandler, T.; Chritin, R.; Cwetanski, P.; Dam, M.; Danielsson, H.; Danilevich, E.; David, E.; Degenhardt, J.; Di Girolamo, B.; Dittus, F.; Dixon, N.; Dogan, O. B.; Dolgoshein, B. A.; Dressnandt, N.; Driouchi, C.; Ebenstein, W. L.; Eerola, P.; Egede, U.; Egorov, K.; Evans, H.; Farthouat, P.; Fedin, O. L.; Fowler, A. J.; Fratina, S.; Froidevaux, D.; Fry, A.; Gagnon, P.; Gavrilenko, I. L.; Gay, C.; Ghodbane, N.; Godlewski, J.; Goulette, M.; Gousakov, I.; Grigalashvili, N.; Grishkevich, Y.; Grognuz, J.; Hajduk, Z.; Hance, M.; Hansen, F.; Hansen, J. B.; Hansen, P. H.; Hare, G. A.; Harvey, A., Jr.; Hauviller, C.; High, A.; Hulsbergen, W.; Huta, W.; Issakov, V.; Istin, S.; Jain, V.; Jarlskog, G.; Jeanty, L.; Kantserov, V. A.; Kaplan, B.; Kapliy, A. S.; Katounin, S.; Kayumov, F.; Keener, P. T.; Kekelidze, G. D.; Khabarova, E.; Khristachev, A.; Kisielewski, B.; Kittelmann, T. H.; Kline, C.; Klinkby, E. B.; Klopov, N. V.; Ko, B. R.; Koffas, T.; Kondratieva, N. V.; Konovalov, S. P.; Koperny, S.; Korsmo, H.; Kovalenko, S.; Kowalski, T. Z.; Krüger, K.; Kramarenko, V.; Kudin, L. G.; LeBihan, A.-C.; LeGeyt, B. C.; Levterov, K.; Lichard, P.; Lindahl, A.; Lisan, V.; Lobastov, S.; Loginov, A.; Loh, C. W.; Lokwitz, S.; Long, M. C.; Lucas, S.; Lucotte, A.; Luehring, F.; Lundberg, B.; Mackeprang, R.; Maleev, V. P.; Manara, A.; Mandl, M.; Martin, A. J.; Martin, F. F.; Mashinistov, R.; Mayers, G. M.; McFarlane, K. W.; Mialkovski, V.; Mills, B. M.; Mindur, B.; Mitsou, V. A.; Mjörnmark, J. U.; Morozov, S. V.; Morris, E.; Mouraviev, S. V.; Muir, A. M.; Munar, A.; Nadtochi, A. V.; Nesterov, S. Y.; Newcomer, F. M.; Nikitin, N.; Novgorodova, O.; Novodvorski, E. G.; Ogren, H.; Oh, S. H.; Oleshko, S. B.; Olivito, D.; Olszowska, J.; Ostrowicz, W.; Passmore, M. S.; Patrichev, S.; Penwell, J.; Perez-Gomez, F.; Peshekhonov, V. D.; Petersen, T. C.; Petti, R.; Placci, A.; Poblaguev, A.; Pons, X.; Price, M. J.; Røhne, O.; Reece, R. D.; Reilly, M. B.; Rembser, C.; Romaniouk, A.; Rousseau, D.; Rust, D.; Ryabov, Y. F.; Ryjov, V.; Söderberg, M.; Savenkov, A.; Saxon, J.; Scandurra, M.; Schegelsky, V. A.; Scherzer, M. I.; Schmidt, M. P.; Schmitt, C.; Sedykh, E.; Seliverstov, D. M.; Shin, T.; Shmeleva, A.; Sivoklokov, S.; Smirnov, S. Yu; Smirnova, L.; Smirnova, O.; Smith, P.; Sosnovtsev, V. V.; Sprachmann, G.; Subramania, S.; Suchkov, S. I.; Sulin, V. V.; Szczygiel, R. R.; Tartarelli, G.; Thomson, E.; Tikhomirov, V. O.; Tipton, P.; Valls Ferrer, J. A.; Van Berg, R.; Vassilakopoulos, V. I.; Vassilieva, L.; Wagner, P.; Wall, R.; Wang, C.; Whittington, D.; Williams, H. H.; Zhelezko, A.; Zhukov, K.

    2008-06-01

    The ATLAS inner detector consists of three sub-systems: the pixel detector spanning the radius range 4cm-20cm, the semiconductor tracker at radii from 30 to 52 cm, and the transition radiation tracker (TRT), tracking from 56 to 107 cm. The TRT provides a combination of continuous tracking with many projective measurements based on individual drift tubes (or straws) and of electron identification based on transition radiation from fibres or foils interleaved between the straws themselves. This paper describes the on and off detector electronics for the TRT as well as the TRT portion of the data acquisition (DAQ) system.

  16. Electronics for better healthcare.

    PubMed

    Wolf, Bernhard; Herzog, Karolin

    2013-06-01

    Microelectronics and microsystem technology have changed our daily lives considerably in the past 50 years. Countless everyday objects contain microelectronic components. In healthcare up to the present, however, it has not been possible to make major alterations in introducing electronics and information technology that would lead to innovative improvements and greater transparency. This paper describes initial steps in diagnostics and oncological therapy including telematic healthcare systems which can, for example, assist patients with cardiovascular diseases and shows, through these areas, how electronics and microsystems technology can contribute to better healthcare.

  17. Precision electron polarimetry

    SciTech Connect

    Chudakov, Eugene A.

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. M{\\o}ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at ~300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100\\%-polarized electron target for M{\\o}ller polarimetry.

  18. Gallium nitride electronics

    NASA Astrophysics Data System (ADS)

    Rajan, Siddharth; Jena, Debdeep

    2013-07-01

    In the past two decades, there has been increasing research and industrial activity in the area of gallium nitride (GaN) electronics, stimulated first by the successful demonstration of GaN LEDs. While the promise of wide band gap semiconductors for power electronics was recognized many years before this by one of the contributors to this issue (J Baliga), the success in the area of LEDs acted as a catalyst. It set the field of GaN electronics in motion, and today the technology is improving the performance of several applications including RF cell phone base stations and military radar. GaN could also play a very important role in reducing worldwide energy consumption by enabling high efficiency compact power converters operating at high voltages and lower frequencies. While GaN electronics is a rapidly evolving area with active research worldwide, this special issue provides an opportunity to capture some of the great advances that have been made in the last 15 years. The issue begins with a section on epitaxy and processing, followed by an overview of high-frequency HEMTs, which have been the most commercially successful application of III-nitride electronics to date. This is followed by review and research articles on power-switching transistors, which are currently of great interest to the III-nitride community. A section of this issue is devoted to the reliability of III-nitride devices, an area that is of increasing significance as the research focus has moved from not just high performance but also production-worthiness and long-term usage of these devices. Finally, a group of papers on new and relatively less studied ideas for III-nitride electronics, such as interband tunneling, heterojunction bipolar transistors, and high-temperature electronics is included. These areas point to new areas of research and technological innovation going beyond the state of the art into the future. We hope that the breadth and quality of articles in this issue will make it

  19. Precision electron polarimetry

    NASA Astrophysics Data System (ADS)

    Chudakov, E.

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. Mo/ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at 300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100%-polarized electron target for Mo/ller polarimetry.

  20. Stretchability of encapsulated electronics

    NASA Astrophysics Data System (ADS)

    Wu, J.; Liu, Z. J.; Song, J.; Huang, Y.; Hwang, K.-C.; Zhang, Y. W.; Rogers, J. A.

    2011-08-01

    Stretchable and flexible electronics offer the performance of conventional wafer-based systems but can be stretched like a rubber band, twisted like a rope, and bent over a pencil. Such a technology offers new application opportunities, in areas of surgical and diagnostic implements that naturally integrate with the human body to provide advanced capabilities, to curvilinear devices such as hemispherical "eyeball" cameras. In practice, stretchable and flexible electronic systems require encapsulation layers to provide mechanical and environmental protection. This paper establishes a simple, analytical model for the optimal design of encapsulation.

  1. Nanotechnology in paper electronics

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Österbacka, Professor Ronald; Han, Jin-Woo, Dr

    2014-03-01

    The ability to put cutting edge technology on paper—not in words but in a working physical form—has been attracting an increasing number of researchers over the past decade. Paper has many advantages that make it attractive for flexible electronics: it is relatively environmentally benign; it is renewable; it can be recycled; it is light weight; production processes for paper are well advanced; and it is inexpensive. This special issue, with guest editors Ronald Österbacka from Åbo Akademi University in Finland and Jin-Woo Han from the NASA AMES Research Center, features some of the latest in paper electronics research, including developments towards applications in displays, sensing and alternative energy sources, as well as fundamental studies to further our understanding of how paper can be most effectively used in electronics. As Andrew Steckl and colleagues in the US point out, 'Cellulose-based paper substrates were implemented as an electronic substrate as early as 1969, with most advancement occurring in the past decade largely due to technology improvements in thin film deposition and organic materials' [1, 2]. They report a detailed comparison between paper, standard liquid crystal display rigid glass and flexible glass for hosting pentacene organic thin film transistors, and obtain promising results for future paper-based devices. As most meaningful electronic devices rely on transistors to function, transistors feature quite prominently in this special issue. Rodrigo Martins and colleagues in France and Portugal study the effect of fibre type, structure and dimension on paper-based transistors and reveal further insights into how paper properties affect device performance [3]. Qing Wan and colleagues in China bring the state of the art in transistor technology to paper substrates [4], fabricating indium-zinc-oxide (IZO)-based protonic/electronic hybrid thin film transistors on paper and showing that they can be used as artificial synapses. Like the

  2. Electronic Structure of Few-Electron Quantum Dot Molecules

    NASA Astrophysics Data System (ADS)

    Popsueva, V.; Hansen, J. P.; Caillat, J.

    2007-12-01

    We present a study of strongly correlated few-electron quantum dots, exploring the spectra of various few-electron quantum dot molecules: a double (diatomic) structure a quadruple two-electron quantum dot, and a three-electron double dot. Electron energy spectra are computed for different values of dot separation. All spectra show clear band structures and can be understood from asymptotical properties of the system.

  3. Japan's electronic packaging technologies

    NASA Technical Reports Server (NTRS)

    Tummala, Rao R.; Pecht, Michael

    1995-01-01

    The JTEC panel found Japan to have significant leadership over the United States in the strategic area of electronic packaging. Many technologies and products once considered the 'heart and soul' of U.S. industry have been lost over the past decades to Japan and other Asian countries. The loss of consumer electronics technologies and products is the most notable of these losses, because electronics is the United States' largest employment sector and is critical for growth businesses in consumer products, computers, automobiles, aerospace, and telecommunications. In the past there was a distinction between consumer and industrial product technologies. While Japan concentrated on the consumer market, the United States dominated the industrial sector. No such distinction is anticipated in the future; the consumer-oriented technologies Japan has dominated are expected to characterize both domains. The future of U.S. competitiveness will, therefore, depend on the ability of the United States to rebuild its technological capabilities in the area of portable electronic packaging.

  4. The electronic stethoscope.

    PubMed

    Leng, Shuang; Tan, Ru San; Chai, Kevin Tshun Chuan; Wang, Chao; Ghista, Dhanjoo; Zhong, Liang

    2015-01-01

    Most heart diseases are associated with and reflected by the sounds that the heart produces. Heart auscultation, defined as listening to the heart sound, has been a very important method for the early diagnosis of cardiac dysfunction. Traditional auscultation requires substantial clinical experience and good listening skills. The emergence of the electronic stethoscope has paved the way for a new field of computer-aided auscultation. This article provides an in-depth study of (1) the electronic stethoscope technology, and (2) the methodology for diagnosis of cardiac disorders based on computer-aided auscultation. The paper is based on a comprehensive review of (1) literature articles, (2) market (state-of-the-art) products, and (3) smartphone stethoscope apps. It covers in depth every key component of the computer-aided system with electronic stethoscope, from sensor design, front-end circuitry, denoising algorithm, heart sound segmentation, to the final machine learning techniques. Our intent is to provide an informative and illustrative presentation of the electronic stethoscope, which is valuable and beneficial to academics, researchers and engineers in the technical field, as well as to medical professionals to facilitate its use clinically. The paper provides the technological and medical basis for the development and commercialization of a real-time integrated heart sound detection, acquisition and quantification system.

  5. Basic Electronics II.

    ERIC Educational Resources Information Center

    Willison, Neal A.; Shelton, James K.

    Designed for use in basic electronics programs, this curriculum guide is comprised of 15 units of instruction. Unit titles are Review of the Nature of Matter and the P-N Junction, Rectifiers, Filters, Special Semiconductor Diodes, Bipolar-Junction Diodes, Bipolar Transistor Circuits, Transistor Amplifiers, Operational Amplifiers, Logic Devices,…

  6. Projectable Basic Electronics Kit.

    ERIC Educational Resources Information Center

    H'ng, John; And Others

    1982-01-01

    Outlines advantages derived from constructing and using a Projectable Basic Electronics Kit and provides: (1) list of components; (2) diagrams of 10 finished components (resistor; capacitor; diode; switch; bulb; transistor; meter; variable capacitor; coil; connecting terminal); and (3) diode and transistor activities. (JN)

  7. Electronically controlled automatic transmission

    SciTech Connect

    Ohkubo, M.; Shiba, H.; Nakamura, K.

    1989-03-28

    This patent describes an electronically controlled automatic transmission having a manual valve working in connection with a manual shift lever, shift valves operated by solenoid valves which are driven by an electronic control circuit previously memorizing shift patterns, and a hydraulic circuit controlled by these manual valve and shift valves for driving brakes and a clutch in order to change speed. Shift patterns of 2-range and L-range, in addition to a shift pattern of D-range, are memorized previously in the electronic control circuit, an operation switch is provided which changes the shift pattern of the electronic control circuit to any shift pattern among those of D-range, 2-range and L-range at time of the manual shift lever being in a D-range position, a releasable lock mechanism is provided which prevents the manual shift lever from entering 2-range and L-range positions, and the hydraulic circuit is set to a third speed mode when the manual shift lever is in the D-range position. The circuit is set to a second speed mode when it is in the 2-range position, and the circuit is set to a first speed mode when it is in the L-range position, respectively, in case where the shift valves are not working.

  8. Selection of Electronic Resources.

    ERIC Educational Resources Information Center

    Weathers, Barbara

    1998-01-01

    Discusses the impact of electronic resources on collection development; selection of CD-ROMs, (platform, speed, video and sound, networking capability, installation and maintenance); selection of laser disks; and Internet evaluation (accuracy of content, authority, objectivity, currency, technical characteristics). Lists Web sites for evaluating…

  9. Electronic Inspection of Beef

    NASA Technical Reports Server (NTRS)

    Anselmo, Victor J.; Gammell, Paul M.; Clark, Jerry

    1987-01-01

    Two proposed methods for grading beef quality based on inspection by electronic equipment: one method uses television camera to generate image of a cut of beef as customer sees it; other uses ultrasonics to inspect live animal or unsliced carcasses. Both methods show promise for automated meat inspection.

  10. Electron beam cutting

    DOEpatents

    Mochel, M.E.; Humphreys, C.J.

    1985-04-02

    A method for the cutting of holes 20 Angstroms in diameter, or lines 20 Angstroms wide in a material having positive ionic conduction by the use of a focused electron probe is described. The holes and lines are stable under ambient conditions. 2 figs.

  11. Electron beam cutting

    DOEpatents

    Mochel, Margaret E.; Humphreys, Colin J.

    1985-04-02

    A method for the cutting of holes 20 Angstroms in diameter, or lines 20 Angstroms wide in a material having positive ionic conduction by the use of a focused electron probe is described. The holes and lines are stable under ambient conditions.

  12. Readily Made Solvated Electrons

    ERIC Educational Resources Information Center

    Ibanez, Jorge G.; Guerra-Millan, Francisco J.; Hugerat, Muhamad; Vazquez-Olavarrieta, Jorge L.; Basheer, Ahmad; Abu-Much, Riam

    2011-01-01

    The existence of solvated electrons has been known for a long time. Key methods for their production (i.e., photoionization of reducing ions, water radiolysis, and the reaction between H[middle dot] and OH[superscript -]) are unsuitable for most school laboratories. We describe a simple experiment to produce liquid ammonia and solvated electrons…

  13. Electronics Book III.

    ERIC Educational Resources Information Center

    Johnson, Dennis; And Others

    This manual, the third of three curriculum guides for an electronics course, is intended for use in a program combining vocational English as a second language (VESL) with bilingual vocational education. Ten units cover AC fundamentals, circuit protection devices, low voltage circuits, communication systems, graphic illustrations, house wiring,…

  14. Shipboard Electronic Equipments.

    ERIC Educational Resources Information Center

    Naval Personnel Program Support Activity, Washington, DC.

    Fundamentals of major electronic equipments on board ships are presented in this text prepared for naval officers in general. Basic radio principles are discussed in connection with various types of transmitters, receivers, antennas, couplers, transfer panels, remote-control units, frequency standard equipments, teletypewriters, and facsimile…

  15. Electronic Scholarly Journal Publishing.

    ERIC Educational Resources Information Center

    Peek, Robin P.; Pomerantz, Jeffrey P.

    1998-01-01

    Reviews the literature that has led to the possible transformation of scholarly publishing through electronic distribution of journals. Discusses the concepts of scholarly communication and computer mediated communication; network delivery experiments; CD-ROM delivery projects; acceptance by the scholarly community; and research and development.…

  16. MEIC electron cooling program

    SciTech Connect

    Derbenev, Yaroslav S.; Zhang, Yuhong

    2014-12-01

    Cooling of proton and ion beams is essential for achieving high luminosities (up to above 1034 cm-2s-1) for MEIC, a Medium energy Electron-Ion Collider envisioned at JLab [1] for advanced nuclear science research. In the present conceptual design, we utilize the conventional election cooling method and adopted a multi-staged cooling scheme for reduction of and maintaining low beam emittances [2,3,4]. Two electron cooling facilities are required to support the scheme: one is a low energy (up to 2 MeV) DC cooler installed in the MEIC ion pre-booster (with the proton kinetic energy up to 3 GeV); the other is a high electron energy (up to 55 MeV) cooler in the collider ring (with the proton kinetic energy from 25 to 100 GeV). The high energy cooler, which is based on the ERL technology and a circulator ring, utilizes a bunched electron beam to cool bunched proton or ion beams. To complete the MEIC cooling concept and a technical design of the ERL cooler as well as to develop supporting technologies, an R&D program has been initiated at Jefferson Lab and significant progresses have been made since then. In this study, we present a brief description of the cooler design and a summary of the progress in this cooling R&D.

  17. ELECTRONIC DIGITAL COMPUTER

    DOEpatents

    Stone, J.J. Jr.; Bettis, E.S.; Mann, E.R.

    1957-10-01

    The electronic digital computer is designed to solve systems involving a plurality of simultaneous linear equations. The computer can solve a system which converges rather rapidly when using Von Seidel's method of approximation and performs the summations required for solving for the unknown terms by a method of successive approximations.

  18. Japan's electronic packaging technologies

    NASA Astrophysics Data System (ADS)

    Tummala, Rao R.; Pecht, Michael

    1995-02-01

    The JTEC panel found Japan to have significant leadership over the United States in the strategic area of electronic packaging. Many technologies and products once considered the 'heart and soul' of U.S. industry have been lost over the past decades to Japan and other Asian countries. The loss of consumer electronics technologies and products is the most notable of these losses, because electronics is the United States' largest employment sector and is critical for growth businesses in consumer products, computers, automobiles, aerospace, and telecommunications. In the past there was a distinction between consumer and industrial product technologies. While Japan concentrated on the consumer market, the United States dominated the industrial sector. No such distinction is anticipated in the future; the consumer-oriented technologies Japan has dominated are expected to characterize both domains. The future of U.S. competitiveness will, therefore, depend on the ability of the United States to rebuild its technological capabilities in the area of portable electronic packaging.

  19. The Electronic Classroom.

    ERIC Educational Resources Information Center

    Mizell, Al P.; Centini, Barry M.

    The role of telecommunications in establishing the electronic classroom in distance education is illustrated. Using a computer-based doctoral program and the UNIX operating system as an example, how a personal computer and modem may be combined with a telephone line for instructional delivery is described. A number of issues must be addressed in…

  20. Electronics Book II.

    ERIC Educational Resources Information Center

    Johnson, Dennis; And Others

    This manual, the second of three curriculum guides for an electronics course, is intended for use in a program combining vocational English as a second language (VESL) with bilingual vocational education. Ten units cover the electrical team, Ohm's law, Watt's law, series resistive circuits, parallel resistive circuits, series parallel circuits,…

  1. Free-Electron Lasers.

    ERIC Educational Resources Information Center

    Brau, Charles A.

    1988-01-01

    Describes the use of free-electron lasers as a source of coherent radiation over a broad range of wavelengths from the far-infrared to the far-ultraviolet regions of the spectrum. Discusses some applications of these lasers, including medicine and strategic defense. (TW)

  2. Designing the Electronic Classroom.

    ERIC Educational Resources Information Center

    Adams, Laural L.

    In an increasingly technological environment, traditional teaching presentation methods such as the podium, overhead, and transparencies are no longer sufficient. This document serves as a guide to designing and planning an electronic classroom for "bidirectional" communication between teacher and student. Topics include: (1) determining whether…

  3. Milestones in electron crystallography.

    PubMed

    Renault, Ludovic; Chou, Hui-Ting; Chiu, Po-Lin; Hill, Rena M; Zeng, Xiangyan; Gipson, Bryant; Zhang, Zi Yan; Cheng, Anchi; Unger, Vinzenz; Stahlberg, Henning

    2006-01-01

    Electron crystallography determines the structure of membrane embedded proteins in the two-dimensionally crystallized state by cryo-transmission electron microscopy imaging and computer structure reconstruction. Milestones on the path to the structure are high-level expression, purification of functional protein, reconstitution into two-dimensional lipid membrane crystals, high-resolution imaging, and structure determination by computer image processing. Here we review the current state of these methods. We also created an Internet information exchange platform for electron crystallography, where guidelines for imaging and data processing method are maintained. The server (http://2dx.org) provides the electron crystallography community with a central information exchange platform, which is structured in blog and Wiki form, allowing visitors to add comments or discussions. It currently offers a detailed step-by-step introduction to image processing with the MRC software program. The server is also a repository for the 2dx software package, a user-friendly image processing system for 2D membrane protein crystals.

  4. Use an Electronic Gradebook.

    ERIC Educational Resources Information Center

    Shalvoy, Mary Lee

    1985-01-01

    Describes range of options and features in gradebook programs and reviews most popular and readily available software for organizing, calculating, and updating grades: Master Grades, EA Gradebook, Gradeaid, Grader, Graphic Gradebook, Classic Plus Gradekeeping System, Records, Gradecalc, Grade Master, Report Card, Electronic Gradebook for…

  5. International Competitiveness in Electronics.

    ERIC Educational Resources Information Center

    Congress of the U.S., Washington, DC. Office of Technology Assessment.

    This assessment continues the Office of Technology Assessment's (OTA) exploration of the meaning of industrial policy in the United States context, while also examining the industrial policies of several U.S. economic rivals. The major focus is on electronics, an area which virtually defines "high technology" of the 1980's. The assessment sets the…

  6. Electronic sleep analyzer

    NASA Technical Reports Server (NTRS)

    Frost, J. D., Jr.

    1970-01-01

    Electronic instrument automatically monitors the stages of sleep of a human subject. The analyzer provides a series of discrete voltage steps with each step corresponding to a clinical assessment of level of consciousness. It is based on the operation of an EEG and requires very little telemetry bandwidth or time.

  7. MEIC electron cooling program

    DOE PAGES

    Derbenev, Yaroslav S.; Zhang, Yuhong

    2014-12-01

    Cooling of proton and ion beams is essential for achieving high luminosities (up to above 1034 cm-2s-1) for MEIC, a Medium energy Electron-Ion Collider envisioned at JLab [1] for advanced nuclear science research. In the present conceptual design, we utilize the conventional election cooling method and adopted a multi-staged cooling scheme for reduction of and maintaining low beam emittances [2,3,4]. Two electron cooling facilities are required to support the scheme: one is a low energy (up to 2 MeV) DC cooler installed in the MEIC ion pre-booster (with the proton kinetic energy up to 3 GeV); the other is amore » high electron energy (up to 55 MeV) cooler in the collider ring (with the proton kinetic energy from 25 to 100 GeV). The high energy cooler, which is based on the ERL technology and a circulator ring, utilizes a bunched electron beam to cool bunched proton or ion beams. To complete the MEIC cooling concept and a technical design of the ERL cooler as well as to develop supporting technologies, an R&D program has been initiated at Jefferson Lab and significant progresses have been made since then. In this study, we present a brief description of the cooler design and a summary of the progress in this cooling R&D.« less

  8. Electronic Component Obsolescence

    SciTech Connect

    Sohns, Carl William; Ward, Christina D

    2010-01-01

    Electronic component obsolescence occurs when parts are no longer available to support the manufacture and/or repair of equipment still in service. Future instrumentation containing complex components WILL face obsolescence issues as technology advances. This paper describes hardware and software obsolescence as well as factors to consider when designing new instrumentation.

  9. Theme: The Electronic Classroom.

    ERIC Educational Resources Information Center

    Herz, Bruce; And Others

    1988-01-01

    Consists of seven articles on the use of electronics in vocational agricultural education. Topics include (1) the Ag Ed Network, (2) computer simulations, (3) video simulation, (4) classroom equipment, (4) online information systems, (5) expert systems, and (6) computer networking in California. (CH)

  10. The Electronic Battle Box

    NASA Astrophysics Data System (ADS)

    Gouin, Denis; Turcotte, Guy; Lebel, Eric; Gilbert, Annie

    2000-08-01

    The Electronic Battle Box is an integrated suite of planning and decision-aid tools specially designed to facilitate Canadian Armed Force Officers during their training and during their tasks of preparing and conducting military operations. It is the result of a collaborative effort between the Defence Research Establishment Valcartier, the Directorate of Army Doctrine (DAD), the Directorate of Land Requirements (DLR), the G4 staff of 1Cdn Div HQ and CGI Information and Management Consultants Inc. Distributed on CD-ROM, the Electronic Battle Box contains efficient and user-friendly tools that significantly reduce the planning time for military operations and ensure staff officers a better focus on significant tasks. Among the tools are an OrBat Browser and an Equipment Browser allowing to view and edit military organizations, a Task Browser providing facilities to prepare plans using Gantt charts, a Logistic Planner allowing to estimate supply requirements applying complex calculations, and Road, Air and Rail Movement Planners. EBB also provides staff officers with a large set of doctrinal documents in an electronic format. This paper provides an overview of the various tools of the Electronic Battle Box.

  11. Electronic document interchange

    NASA Technical Reports Server (NTRS)

    Erwin, Jim

    1993-01-01

    The operational impact of various storage formats related to electronic publishing of documents in the NASA Scientific and Technical Information (STI) Program is discussed. Questions are raised about the development of full text, surrogate, and hybrid storage formats. It appears that the eventual configuration will contain a mix of storage formats based on user demand.

  12. Electron energies in metals

    SciTech Connect

    Mahan, G.D. Tennessee Univ., Knoxville, TN . Dept. of Physics and Astronomy)

    1991-07-10

    The modern era of electron-electron interactions began a decade ago. Plummer's group initiated a program of using angular resolved photoemission to examine the band structure of the simple metals. Beginning with aluminum, and carrying on to sodium and potassium, they always found that the occupied energy bands were much narrower than expected. For example, the compressed energy bands for metallic potassium suggest a band effective mass of m* = 1.33m{sub e}. This should be compared to the band mass found from optical conductivity m*/m{sub e} = 1.01 {plus minus} 0.01. The discrepancy between these results is startling. It was this great difference which started my group doing calculations. Our program was two-fold. On one hand, we reanalyzed the experimental data, in order to see if Plummer's result was an experimental artifact. On the other hand, we completely redid the electron-electron self-energy calculations for simple metals, using the most modern choices of local-field corrections and vertex corrections. Our results will be reported in these lectures. They can be summarized as following: Our calculations give the same effective masses as the older calculations, so the theory is relatively unchanged; Our analysis of the experiments suggests that the recent measurements of band narrowing are an experimental artifact. 38 refs., 9 figs.

  13. The Blacksburg Electronic Village.

    ERIC Educational Resources Information Center

    Wiencko, Joseph A., Jr.

    1993-01-01

    Describes the proposed Blacksburg Electronic Village project, a prototype community telecommunications network which delivers network services to an entire Virginia town. Possible educational, business and professional, civic, and quality of life uses are suggested. The importance of concentrating on applications and user services instead of…

  14. Using Electronic Portfolios

    ERIC Educational Resources Information Center

    Page, Deb

    2012-01-01

    The digitized collections of artifacts known as electronic portfolios are creating solutions to a variety of performance improvement needs in ways that are cost-effective and improve both individual and group learning and performance. When social media functionality is embedded in e-portfolios, the tools support collaboration, social learning,…

  15. Packaging of electronic modules

    NASA Technical Reports Server (NTRS)

    Katzin, L.

    1966-01-01

    Study of design approaches that are taken toward optimizing the packaging of electronic modules with respect to size, shape, component orientation, interconnections, and structural support. The study does not present a solution to specific packaging problems, but rather the factors to be considered to achieve optimum packaging designs.

  16. ELECTRONIC RESEARCH NOTEBOOKS

    EPA Science Inventory

    The paper details the public availability of Electronic notebooks (EN) and an example of a system in use within a research laboratory in the Office of Research and Development. Research notebooks contain intellectual property which must be guarded until it can be disseminated wit...

  17. Inventing the Electronic University

    ERIC Educational Resources Information Center

    Lewis, David W.

    2015-01-01

    Higher education is confronting a fundamental change. The transition from print on paper to digital and electronic technologies is transforming instruction, scholarly communication, and the storage and preservation of knowledge. What is required is not the automation of old systems, but the restructuring of institutions. The drive for autonomy,…

  18. The Electronic Classroom.

    ERIC Educational Resources Information Center

    Mueller, Richard J.

    Current computerized electronic technology is making possible, not only the broad and rapid distribution of information, but also its manipulation, analysis, synthesis, and recombination. The shift from print to a combination of visual and oral expression is being propelled by the mass media, and visual literacy is both a concept and an…

  19. The Electronic Blackboard.

    ERIC Educational Resources Information Center

    Cieri, Marie Corse

    A review discusses the background of the experimental electronic blackboard and its role as an audiovisual aid in instruction. Brief details of several systems are given: the Victor System, Electrowriter Remote Blackboard (VERB); Carbon County Wyoming Project; University of Tennessee Project; the Quebec Project in Canada; New York Institute of…

  20. Evaluating electronic measurement equipment

    SciTech Connect

    Chang, C.K. )

    1990-12-01

    Changes in a utility's rate structure created an urgent need to develop electronic devices to measure transportation gas. The author describes how the company's measurement and test development staff selected proper devices and provided guidelines in quality control, calibration procedure, field maintenance and personnel training.

  1. Forensic Scanning Electron Microscope

    NASA Astrophysics Data System (ADS)

    Keeley, R. H.

    1983-03-01

    The scanning electron microscope equipped with an x-ray spectrometer is a versatile instrument which has many uses in the investigation of crime and preparation of scientific evidence for the courts. Major applications include microscopy and analysis of very small fragments of paint, glass and other materials which may link an individual with a scene of crime, identification of firearms residues and examination of questioned documents. Although simultaneous observation and chemical analysis of the sample is the most important feature of the instrument, other modes of operation such as cathodoluminescence spectrometry, backscattered electron imaging and direct x-ray excitation are also exploited. Marks on two bullets or cartridge cases can be compared directly by sequential scanning with a single beam or electronic linkage of two instruments. Particles of primer residue deposited on the skin and clothing when a gun is fired can be collected on adhesive tape and identified by their morphology and elemental composition. It is also possible to differentiate between the primer residues of different types of ammunition. Bullets may be identified from the small fragments left behind as they pass through the body tissues. In the examination of questioned documents the scanning electron microscope is used to establish the order in which two intersecting ink lines were written and to detect traces of chemical markers added to the security inks on official documents.

  2. Quantitative Electron Nanodiffraction.

    SciTech Connect

    Spence, John

    2015-01-30

    This Final report summarizes progress under this award for the final reporting period 2002 - 2013 in our development of quantitive electron nanodiffraction to materials problems, especially devoted to atomistic processes in semiconductors and electronic oxides such as the new artificial oxide multilayers, where our microdiffraction is complemented with energy-loss spectroscopy (ELNES) and aberration-corrected STEM imaging (9). The method has also been used to map out the chemical bonds in the important GaN semiconductor (1) used for solid state lighting, and to understand the effects of stacking sequence variations and interfaces in digital oxide superlattices (8). Other projects include the development of a laser-beam Zernike phase plate for cryo-electron microscopy (5) (based on the Kapitza-Dirac effect), work on reconstruction of molecular images using the scattering from many identical molecules lying in random orientations (4), a review article on space-group determination for the International Tables on Crystallography (10), the observation of energy-loss spectra with millivolt energy resolution and sub-nanometer spatial resolution from individual point defects in an alkali halide, a review article for the Centenary of X-ray Diffration (17) and the development of a new method of electron-beam lithography (12). We briefly summarize here the work on GaN, on oxide superlattice ELNES, and on lithography by STEM.

  3. Electronic Document Supply Systems.

    ERIC Educational Resources Information Center

    Cawkell, A. E.

    1991-01-01

    Describes electronic document delivery systems used by libraries and document image processing systems used for business purposes. Topics discussed include technical specifications; analogue read-only laser videodiscs; compact discs and CD-ROM; WORM; facsimile; ADONIS (Article Delivery over Network Information System); DOCDEL; and systems at the…

  4. Pulsed Plasma Electron Sources

    NASA Astrophysics Data System (ADS)

    Krasik, Yakov

    2008-11-01

    Pulsed (˜10-7 s) electron beams with high current density (>10^2 A/cm^2) are generated in diodes with electric field of E > 10^6 V/cm. The source of electrons in these diodes is explosive emission plasma, which limits pulse duration; in the case E < 10^5 V/cm this plasma is not uniform and there is a time delay in its formation. Thus, there is a continuous interest in research of electron sources which can be used for generation of uniform electron beams produced at E <= 10^5 V/cm. In the present report, several types of plasma electron source (PES) will be considered. The first type of PES is fiber-based cathodes, with and without CsI coating. The operation of these cathodes is governed by the formation of the flashover plasma which serves as a source of electrons. The second type of PES is the ferroelectric plasma source (FPS). The operation of FPS, characterized by the formation of dense surface flashover plasma is accompanied also by the generation of fast microparticles and energetic neutrals. The latter was explained by Coulomb micro-explosions of the ferroelectric surface due to an large time-varying electric field at the front of the expanding plasma. A short review of recent achievements in the operation of a multi-FPS-assisted hollow anode to generate a large area electron beam will be presented as well. Finally, parameters of the plasma produced by a multi-capillary cathode with FPS and velvet igniters will be discussed. Ya. E. Krasik, J. Z. Gleizer, D. Yarmolich, A. Krokhmal, V. Ts. Gurovich, S.Efimov, J. Felsteiner V. Bernshtam, and Yu. M. Saveliev, J. Appl. Phys. 98, 093308 (2005). Ya. E. Krasik, A. Dunaevsky, and J. Felsteiner, Phys. Plasmas 8, 2466 (2001). D. Yarmolich, V. Vekselman, V. Tz. Gurovich, and Ya. E. Krasik, Phys. Rev. Lett. 100, 075004 (2008). J. Z. Gleizer, Y. Hadas and Ya. E. Krasik, Europhysics Lett. 82, 55001 (2008).

  5. Added Value in Electronic Publications.

    ERIC Educational Resources Information Center

    Bothma, Theo J. D.

    Electronic publications are flooding the market. Some of these publications are created specifically for the electronic environment, but many are conversions of existing material to electronic format. It is not worth the time and effort merely to publish existing material in electronic format if no value is added in the conversion process. The…

  6. Electronic Library: A TERI Experiment.

    ERIC Educational Resources Information Center

    Kar, Debal C.; Deb, Subrata; Kumar, Satish

    2003-01-01

    Discusses the development of Electronic Library at TERI (The Energy and Resources Institute, New Delhi). Highlights include: hardware and software used; the digital library/Virtual Electronic Library; directory of Internet journals; virtual reference resources; electronic collection/Physical Electronic Library; downloaded online full-length…

  7. Electron jet of asymmetric reconnection

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; André, M.; Pritchett, P. L.; Retinò, A.; Phan, T. D.; Ergun, R. E.; Goodrich, K.; Lindqvist, P.-A.; Marklund, G. T.; Le Contel, O.; Plaschke, F.; Magnes, W.; Strangeway, R. J.; Russell, C. T.; Vaith, H.; Argall, M. R.; Kletzing, C. A.; Nakamura, R.; Torbert, R. B.; Paterson, W. R.; Gershman, D. J.; Dorelli, J. C.; Avanov, L. A.; Lavraud, B.; Saito, Y.; Giles, B. L.; Pollock, C. J.; Turner, D. L.; Blake, J. D.; Fennell, J. F.; Jaynes, A.; Mauk, B. H.; Burch, J. L.

    2016-06-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E∥ amplitudes reaching up to 300 mV m-1 and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  8. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2013-10-29

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  9. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2012-04-10

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  10. Imaging coherent electronic motion in atoms by ultrafast electron diffraction

    NASA Astrophysics Data System (ADS)

    Shao, Hua-Chieh; Starace, Anthony F.

    2013-12-01

    Ultrafast electron diffraction from time-varying coherent electronic states of the H atom is analyzed theoretically. This theoretical analysis identifies the conditions necessary to obtain time-resolved measurements. Electron diffraction from coherent electronic states exhibiting breathing and wiggling modes of electronic motion are simulated numerically in order to demonstrate the capability of attosecond electron pulses to image electron dynamics. The scattering patterns and their temporal behaviors are shown to differentiate the two kinds of target electronic motion. Moreover, our simulations show that inelastic processes contribute significantly to the diffraction patterns. Thus, although the diffraction patterns clearly distinguish different modes of target electronic motion, they cannot be easily related to the time-dependent target charge density.

  11. PREFACE: Correlated Electrons (Japan)

    NASA Astrophysics Data System (ADS)

    Miyake, Kazumasa

    2007-03-01

    This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of strongly correlated electron systems under multiple-environment. The physics of strongly correlated electron systems (SCES) has attracted much attention since the discovery of superconductivity in CeCu_2 Si_2 by Steglich and his co-workers a quater-century ago. Its interest has been intensified by the discovery of high-Tc superconductivity in a series of cuprates with layered perovskite structure which are still under active debate. The present issue of Journal of Physics: Condensed Matter present some aspects of SCES physics on the basis of activities of a late project "Centre-Of-Excellence" supported by MEXT (Ministry of Education, Sports, Science, Culture and Technology of the Japanese Government). This project has been performed by a condensed matter physics group in the faculties of science and engineering science of Osaka University. Although this project also covers correlated phenomena in optics and nano-scale systems, we focus here on the issues of SCES related to superconductivity, mainly unconventional. The present issue covers the discussions on a new mechanism of superconductivity with electronic origin (critical valence fluctuation mechanism), interplay and unification of magnetism and superconductivity in SCES based on a systematic study of NQR under pressure, varieties of Fermi surface of Ce- and U-based SCES probed by the de Haas-van Alphen effect, electronic states probed by a bulk sensitive photoemission spectroscopy with soft X-ray, pressure induced superconductivity of heavy electron materials, pressure dependence of superconducting transition temperature based on a first-principle calculation, and new superconductors under very high-pressure. Some papers offer readers' reviews of the relevant fields and/or include new developments of this intriguing research field of SCES. Altogether, the papers within this issue outline some aspects of electronic states

  12. Duskside relativistic electron precipitation

    NASA Astrophysics Data System (ADS)

    Lorentzen, Kirsten Ruth

    1999-10-01

    On August 20, 1996, a balloon-borne X-ray pinhole camera and a high resolution germanium X-ray spectrometer observed an intense X-ray event near Kiruna, Sweden, at 1835 MLT, on an L-shell of 5.8. This X-ray event consisted of seven bursts spaced 100-200 seconds apart, with smaller 10-20 second variations observed within individual bursts. The energy spectra of these bursts show the presence of X-rays with energies greater than 1 MeV, which are best accounted for by atmospheric bremsstrahlung from mono-energetic 1.7 MeV precipitating electrons. The X-ray imager observed no significant motion or small-scale spatial structure in the event, implying that the bursts were temporal in nature. Ultra- violet images from the Polar satellite and energetic particle data from the Los Alamos geosynchronous satellites show a small magnetospheric substorm onset about 24 minutes before the start of the relativistic precipitation event. Since the balloon was south of the auroral oval and there was no associated increase in relativistic electron flux at geosynchronous altitude, the event must be the result of some mechanism selectively precipitating ambient relativistic electrons from the radiation belts. The balloon X-ray observations are analyzed in a magnetospheric context, in order to determine which of several mechanisms for selective precipitation of relativistic electrons can account for the event. Resonance with electromagnetic ion cyclotron mode waves on the equator is the most likely candidate. The drift of substorm-injected warm protons is calculated using input from the geosynchronous satellites. Wave growth in the model is driven by temperature anisotropies in the warm proton population. A numerical solution of the wave dispersion relation shows that electromagnetic ion cyclotron waves can be excited in high-density duskside regions such as the plasmasphere or detached plasma regions. These waves can selectively precipitate relativistic electrons of energy 1.7 MeV in

  13. The effect of electron-electron interaction induced dephasing on electronic transport in graphene nanoribbons

    SciTech Connect

    Kahnoj, Sina Soleimani; Touski, Shoeib Babaee; Pourfath, Mahdi E-mail: pourfath@iue.tuwien.ac.at

    2014-09-08

    The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.

  14. Electron Structure of Francium

    NASA Astrophysics Data System (ADS)

    Koufos, Alexander

    2012-02-01

    This talk presents the first calculations of the electronic structure of francium for the bcc, fcc and hcp structures, using the Augmented Plane Wave (APW) method in its muffin-tin and linearized general potential forms. Both the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA), were used to calculate the electronic structure and total energy of francium (Fr). The GGA and LDA both found the total energy of the hcp structure slightly below that of the fcc and bcc structure, respectively. This is in agreement with similar results for the other alkali metals using the same methodology. The equilibrium lattice constant, bulk modulus and superconductivity parameters were calculated. We found that under pressures, in the range of 1-5 GPa, Fr could be a superconductor at a critical temperature of about 4K.

  15. Pursuing prosthetic electronic skin.

    PubMed

    Chortos, Alex; Liu, Jia; Bao, Zhenan

    2016-09-01

    Skin plays an important role in mediating our interactions with the world. Recreating the properties of skin using electronic devices could have profound implications for prosthetics and medicine. The pursuit of artificial skin has inspired innovations in materials to imitate skin's unique characteristics, including mechanical durability and stretchability, biodegradability, and the ability to measure a diversity of complex sensations over large areas. New materials and fabrication strategies are being developed to make mechanically compliant and multifunctional skin-like electronics, and improve brain/machine interfaces that enable transmission of the skin's signals into the body. This Review will cover materials and devices designed for mimicking the skin's ability to sense and generate biomimetic signals. PMID:27376685

  16. Electron screening in nickel

    SciTech Connect

    Gajevic, Jelena; Lipoglavsek, Matej; Petrovic, Toni; Pelicon, Primoz

    2012-11-20

    In order to further investigate electron screening phenomenon we studied proton induced nuclear reactions over an energy range from 1.35 to 3.08 MeV for different environments: Ni metal and NiO insulator. The measurements were based on observation of the {gamma}-ray yields of {sup 59,61,63,64,65}Cu and {sup 58,60,62}Ni. Also, we have studied the decay of {sup 61}Cu produced in the reaction {sup 60}Ni(p,{gamma}), in order to find a possible decay rate perturbation by atomic electrons and found a small difference in half-life for metallic compared to oxide environment, respectively. The present results clearly show that the metallic environment affects the fusion reactions at low energy and that it might also affect the decay rate.

  17. Double coupled electron shuttle

    NASA Astrophysics Data System (ADS)

    Prada, M.; Platero, G.

    2012-10-01

    A nanoshuttle consisting of two movable islands connected in series and integrated between two contacts is studied. We evaluate the electron transport through the system in the presence of a source-drain voltage with and without an rf excitation. We evaluate the response of the system in terms of the net direct current enhanced by the mechanical motion of the oscillators. An introduction to the charge stability diagram is given in terms of electrochemical potentials and mechanical displacements. The low capacitance of the islands allows the observation of Coulomb blockade even at room temperature. Using radio frequency excitations, the nonlinear dynamics of the system is studied. The oscillators can be tuned to unstable regions where mechanically assisted transfer of electrons can further increase the amplitude of motion, resulting of a net energy being pumped into the system. The resulting amplified response can be exploited to design a mechanical motion detector of nanoscale objects.

  18. Electrons from hydrogen.

    PubMed

    Ogo, Seiji

    2009-06-21

    The growing need for hydrogen-based fuel cells has driven research into hydrogenase (H(2)ase)-a natural enzyme that catalyses the extraction of electrons from H(2) in water under ambient conditions. Unfortunately, the exact mechanism by which H(2)ase achieves this feat has remained a matter of some controversy until now, with many mechanisms being inconsistent with experimental data. Recently, however, we have been able to produce a successful catalytic mimic of H(2)ase that replicates key aspects of it. This paper begins with an overview of the research from many groups that preceded this discovery, followed by a detailed analysis of the key points that set our unique functional model apart-that is to say a proton-like "hydride" species, a surprisingly low-valent Ni(I)Ru(I) complex and the key insight that two molecules of H(2) are required for electron extraction.

  19. Landsat electron beam recorder

    NASA Astrophysics Data System (ADS)

    Grosso, P. F.; Whitley, J. P.

    A minicomputer-controlled electron beam recorder (EBR) presently in use at the Brazilian Government's Institute De Pesquisas Espaclais (INPE) satellite ground station is described. This 5-in.-film-size EBR is used to record both Landsat and SPOT satellite imagery in South America. A brief electron beam recorder technology review is presented. The EBR is capable of recording both vector and text data from computer-aided design, publishing, and line art systems and raster data from image scanners, raster image processors (RIPS), halftone/screen generators, and remote image sensors. A variety of image formats may be recorded on numerous film sizes (16 mm, 35 mm, 70 mm, 105 mm, 5-in, 5.5-in., and 9.5-in.). These recordings are used directly or optically enlarged depending on the final product.

  20. ELECTRON IRRADIATION OF SOLIDS

    DOEpatents

    Damask, A.C.

    1959-11-01

    A method is presented for altering physical properties of certain solids, such as enhancing the usefulness of solids, in which atomic interchange occurs through a vacancy mechanism, electron irradiation, and temperature control. In a centain class of metals, alloys, and semiconductors, diffusion or displacement of atoms occurs through a vacancy mechanism, i.e., an atom can only move when there exists a vacant atomic or lattice site in an adjacent position. In the process of the invention highenergy electron irradiation produces additional vacancies in a solid over those normally occurring at a given temperature and allows diffusion of the component atoms of the solid to proceed at temperatures at which it would not occur under thermal means alone in any reasonable length of time. The invention offers a precise way to increase the number of vacancies and thereby, to a controlled degree, change the physical properties of some materials, such as resistivity or hardness.

  1. Electron hopping through proteins

    PubMed Central

    Warren, Jeffrey J.; Ener, Maraia E.; Vlček, Antonín; Winkler, Jay R.; Gray, Harry B.

    2012-01-01

    Biological redox machines require efficient transfer of electrons and holes for function. Reactions involving multiple tunneling steps, termed “hopping,” often promote charge separation within and between proteins that is essential for energy storage and conversion. Here we show how semiclassical electron transfer theory can be extended to include hopping reactions: graphical representations (called hopping maps) of the dependence of calculated two-step reaction rate constants on driving force are employed to account for flow in a rhenium-labeled azurin mutant as well as in two structurally characterized redox enzymes, DNA photolyase and MauG. Analysis of the 35 Å radical propagation in ribonucleotide reductases using hopping maps shows that all tyrosines and tryptophans on the radical pathway likely are involved in function. We suggest that hopping maps can facilitate the design and construction of artificial photosynthetic systems for the production of fuels and other chemicals. PMID:23420049

  2. Blueprinting macromolecular electronics.

    PubMed

    Palma, Carlos-Andres; Samorì, Paolo

    2011-06-01

    Recently, by mastering either top-down or bottom-up approaches, tailor-made macromolecular nano-objects with semiconducting properties have been fabricated. These engineered nanostructures for organic electronics are based on conjugated systems predominantly made up of sp²-hybridized carbon, such as graphene nanoribbons. Here, we describe developments in a selection of these nanofabrication techniques, which include graphene carving, stimulus-induced synthesis of conjugated polymers and surface-assisted synthesis. We also assess their potential to reproduce chemically and spatially precise molecular arrangements, that is, molecular blueprints. In a broad context, the engineering of a molecular blueprint represents the fabrication of an integrated all-organic macromolecular electronic circuit. In this Perspective, we suggest chemical routes, as well as convergent on-surface synthesis and microfabrication approaches, for the ultimate goal of bringing the field closer to technology.

  3. Dynamic Transmission Electron Microscopy

    SciTech Connect

    Evans, James E.; Jungjohann, K. L.; Browning, Nigel D.

    2012-10-12

    Dynamic transmission electron microscopy (DTEM) combines the benefits of high spatial resolution electron microscopy with the high temporal resolution of ultrafast lasers. The incorporation of these two components into a single instrument provides a perfect platform for in situ observations of material processes. However, previous DTEM applications have focused on observing structural changes occurring in samples exposed to high vacuum. Therefore, in order to expand the pump-probe experimental regime to more natural environmental conditions, in situ gas and liquid chambers must be coupled with Dynamic TEM. This chapter describes the current and future applications of in situ liquid DTEM to permit time-resolved atomic scale observations in an aqueous environment, Although this chapter focuses mostly on in situ liquid imaging, the same research potential exists for in situ gas experiments and the successful integration of these techniques promises new insights for understanding nanoparticle, catalyst and biological protein dynamics with unprecedented spatiotemporal resolution.

  4. Uniform quantized electron gas.

    PubMed

    Høye, Johan S; Lomba, Enrique

    2016-10-19

    In this work we study the correlation energy of the quantized electron gas of uniform density at temperature T  =  0. To do so we utilize methods from classical statistical mechanics. The basis for this is the Feynman path integral for the partition function of quantized systems. With this representation the quantum mechanical problem can be interpreted as, and is equivalent to, a classical polymer problem in four dimensions where the fourth dimension is imaginary time. Thus methods, results, and properties obtained in the statistical mechanics of classical fluids can be utilized. From this viewpoint we recover the well known RPA (random phase approximation). Then to improve it we modify the RPA by requiring the corresponding correlation function to be such that electrons with equal spins can not be on the same position. Numerical evaluations are compared with well known results of a standard parameterization of Monte Carlo correlation energies. PMID:27546166

  5. Pursuing prosthetic electronic skin

    NASA Astrophysics Data System (ADS)

    Chortos, Alex; Liu, Jia; Bao, Zhenan

    2016-09-01

    Skin plays an important role in mediating our interactions with the world. Recreating the properties of skin using electronic devices could have profound implications for prosthetics and medicine. The pursuit of artificial skin has inspired innovations in materials to imitate skin's unique characteristics, including mechanical durability and stretchability, biodegradability, and the ability to measure a diversity of complex sensations over large areas. New materials and fabrication strategies are being developed to make mechanically compliant and multifunctional skin-like electronics, and improve brain/machine interfaces that enable transmission of the skin's signals into the body. This Review will cover materials and devices designed for mimicking the skin's ability to sense and generate biomimetic signals.

  6. ELECTRONIC PHASE CONTROL CIRCUIT

    DOEpatents

    Salisbury, J.D.; Klein, W.W.; Hansen, C.F.

    1959-04-21

    An electronic circuit is described for controlling the phase of radio frequency energy applied to a multicavity linear accelerator. In one application of the circuit two cavities are excited from a single radio frequency source, with one cavity directly coupled to the source and the other cavity coupled through a delay line of special construction. A phase detector provides a bipolar d-c output signal proportional to the difference in phase between the voltage in the two cavities. This d-c signal controls a bias supply which provides a d-c output for varying the capacitnce of voltage sensitive capacitors in the delay line. The over-all operation of the circuit is completely electronic, overcoming the time response limitations of the electromechanical control systems, and the relative phase relationship of the radio frequency voltages in the two caviiies is continuously controlled to effect particle acceleration.

  7. Electronics for Satellite Experiments

    SciTech Connect

    Johnson, Robert P.; /UC, Santa Cruz

    2006-05-16

    The tracking detector for the LAT science instrument on the GLAST mission is an example of a large-scale particle detection system built primarily by particle physicists for space flight within the context of a NASA program. The design and fabrication model in most ways reflected practice and experience from particle physics, but the quality assurance aspects were guided by NASA. Similarly, most of the electronics in the LAT as a whole were designed and built by staff at a particle physics lab. This paper reports on many of the challenges and lessons learned in the experience of designing and building the tracking detector and general LAT electronics for use in the NASA GLAST mission.

  8. Electronic measurement correction devices

    SciTech Connect

    Mahns, R.R.

    1984-04-01

    The electronics semi-conductor revolution has touched every industry and home in the nation. The gas industry is no exception. Sophisticated gas measurement instrumentation has been with us for several decades now, but only in the last 10 years or so has it really begun to boom. First marketed were the flow computers dedicated to orifice meter measurement; but with steadily decreasing manufacturing costs, electronic instrumentation is now moving into the area of base volume, pressure and temperature correction previously handled almost solely by mechanical integrating instruments. This paper takes a brief look at some of the features of the newcomers on the market and how they stack up against the old standby mechanical base volume/pressure/temperature correctors.

  9. Electronic Nose System Sensors

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Jet Propulsion Laboratory has designed and built an electronic nose system -- ENose -- to take on the duty of staying alert for smells that could indicate hazardous conditions in a closed spacecraft environment. Its sensors (shown here) are tailored so they conduct electricity differently when an air stream carries a particular chemical across them. JPL has designed and built a 3-pound flight version. The active parts are 32 sensors, each with a different mix of polymers saturated with carbon. When certain chemicals latch onto a sensor, they change how the sensor conducts electricity. This signal tells how much of a compound is in the air. The electronic nose flown aboard STS-95 in 1998 was capable of successfully detecting 10 toxic compounds.

  10. Electronic Nose System

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Jet Propulsion Laboratory has designed and built an electronic nose system -- ENose -- to take on the duty of staying alert for smells that could indicate hazardous conditions in a closed spacecraft environment. Its sensors are tailored so they conduct electricity differently when an air stream carries a particular chemical across them. JPL has designed and built a 3-pound flight version (shown with palm-size control and data computer). The active parts are 32 sensors, each with a different mix of polymers saturated with carbon. When certain chemicals latch onto a sensor, they change how the sensor conducts electricity. This signal tells how much of a compound is in the air. The electronic nose flown aboard STS-95 in 1998 was capable of successfully detecting 10 toxic compounds.

  11. Uniform quantized electron gas

    NASA Astrophysics Data System (ADS)

    Høye, Johan S.; Lomba, Enrique

    2016-10-01

    In this work we study the correlation energy of the quantized electron gas of uniform density at temperature T  =  0. To do so we utilize methods from classical statistical mechanics. The basis for this is the Feynman path integral for the partition function of quantized systems. With this representation the quantum mechanical problem can be interpreted as, and is equivalent to, a classical polymer problem in four dimensions where the fourth dimension is imaginary time. Thus methods, results, and properties obtained in the statistical mechanics of classical fluids can be utilized. From this viewpoint we recover the well known RPA (random phase approximation). Then to improve it we modify the RPA by requiring the corresponding correlation function to be such that electrons with equal spins can not be on the same position. Numerical evaluations are compared with well known results of a standard parameterization of Monte Carlo correlation energies.

  12. Pulsed electron beam precharger

    SciTech Connect

    Finney, W.C.; Shelton, W.N.

    1991-01-01

    Electron beam precharging of a high resistivity aerosol was successfully demonstrated during this reporting period (Quarters Five and Six). The initial E-beam particle precharging experiments completed this term were designed to confirm and extend some of the work performed under the previous contract. There are several reasons for doing this: (1) to re-establish a baseline performance criterion for comparison to other runs, (2) to test several recently upgraded or repaired subsystems, and (3) to improve upon the collection efficiency of the electron beam precipitator when testing precharging effectiveness with a very high resistivity, moderate-to-high concentration dust load. In addition, these shakedown runs were used to determine a set of suitable operational parameters for the wind tunnel, the electrostatic collecting sections, and the MINACC E-beam accelerator. These parameters will generally be held constant while the precharging parameters are varied to produce an optimum particle charge.

  13. Electronic Packaging Techniques

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A characteristic of aerospace system design is that equipment size and weight must always be kept to a minimum, even in small components such as electronic packages. The dictates of spacecraft design have spawned a number of high-density packaging techniques, among them methods of connecting circuits in printed wiring boards by processes called stitchbond welding and parallel gap welding. These processes help designers compress more components into less space; they also afford weight savings and lower production costs.

  14. Molecular Electronic Shift Registers

    NASA Technical Reports Server (NTRS)

    Beratan, David N.; Onuchic, Jose N.

    1990-01-01

    Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

  15. High-temperature electronics

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Seng, Gary T.

    1990-01-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  16. [Electronic glottography (clinical aspects)].

    PubMed

    Chernobel'skiĭ, S I

    1991-01-01

    In order to study the application of electronic glottography in clinical laryngology, 200 patients with different diseases were examined, using a glottographic unit, computer, oscilloscope, and a recorder. It was found that glottography is an objective method which can be applied to evaluate and detect disorders of vocal folds in different states. This method fails to determine the vibration capacity of an individual fold or diagnose laryngeal lesions without an additional examination.

  17. JPL Electronic Nose

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A.; Homer, Margie L.

    2009-01-01

    The JPL Electronic Nose (ENose) is a full-time, continuously operating event monitor designed to detect air contamination from spills and leaks in the crew habitat in the International Space Station. It fills the long-standing gap between onboard alarms and complex analytical instruments. ENose provides rapid, early identification and quantification of atmospheric changes caused by chemical species to which it has been trained. ENose can also be used to monitor cleanup processes after a leak or a spill.

  18. Chemistry of fast electrons

    PubMed Central

    Maximoff, Sergey N.; Head-Gordon, Martin P.

    2009-01-01

    A chemicurrent is a flux of fast (kinetic energy ≳ 0.5−1.3 eV) metal electrons caused by moderately exothermic (1−3 eV) chemical reactions over high work function (4−6 eV) metal surfaces. In this report, the relation between chemicurrent and surface chemistry is elucidated with a combination of top-down phenomenology and bottom-up atomic-scale modeling. Examination of catalytic CO oxidation, an example which exhibits a chemicurrent, reveals 3 constituents of this relation: The localization of some conduction electrons to the surface via a reduction reaction, 0.5 O2 + δe− → Oδ− (Red); the delocalization of some surface electrons into a conduction band in an oxidation reaction, Oδ− + CO → CO2δ− → CO2 + δe− (Ox); and relaxation without charge transfer (Rel). Juxtaposition of Red, Ox, and Rel produces a daunting variety of metal electronic excitations, but only those that originate from CO2 reactive desorption are long-range and fast enough to dominate the chemicurrent. The chemicurrent yield depends on the universality class of the desorption process and the distribution of the desorption thresholds. This analysis implies a power-law relation with exponent 2.66 between the chemicurrent and the heat of adsorption, which is consistent with experimental findings for a range of systems. This picture also applies to other oxidation-reduction reactions over high work function metal surfaces. PMID:19561296

  19. Computational Electronics and Electromagnetics

    SciTech Connect

    DeFord, J.F.

    1993-03-01

    The Computational Electronics and Electromagnetics thrust area is a focal point for computer modeling activities in electronics and electromagnetics in the Electronics Engineering Department of Lawrence Livermore National Laboratory (LLNL). Traditionally, they have focused their efforts in technical areas of importance to existing and developing LLNL programs, and this continues to form the basis for much of their research. A relatively new and increasingly important emphasis for the thrust area is the formation of partnerships with industry and the application of their simulation technology and expertise to the solution of problems faced by industry. The activities of the thrust area fall into three broad categories: (1) the development of theoretical and computational models of electronic and electromagnetic phenomena, (2) the development of useful and robust software tools based on these models, and (3) the application of these tools to programmatic and industrial problems. In FY-92, they worked on projects in all of the areas outlined above. The object of their work on numerical electromagnetic algorithms continues to be the improvement of time-domain algorithms for electromagnetic simulation on unstructured conforming grids. The thrust area is also investigating various technologies for conforming-grid mesh generation to simplify the application of their advanced field solvers to design problems involving complicated geometries. They are developing a major code suite based on the three-dimensional (3-D), conforming-grid, time-domain code DSI3D. They continue to maintain and distribute the 3-D, finite-difference time-domain (FDTD) code TSAR, which is installed at several dozen university, government, and industry sites.

  20. Electron Calorimeter Experiment

    NASA Technical Reports Server (NTRS)

    Adams, James H.

    2008-01-01

    Boron loaded scintillators are suitable for measuring secondary neutrons produced by high-energy particles: protons & electrons Neutron flux can be used to discriminate hadron and electro-magnetic particles Combined effectiveness of all e/p discriminators techniques employedTBD Only moderate improvement in detection efficiency for B-10 concentrations >few% in thick moderators Bottom scintillator might serve as cascade penetration counter (TBC)