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Sample records for active semiconductor layer

  1. Layered semiconductor neutron detectors

    DOEpatents

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  2. Optical devices featuring textured semiconductor layers

    DOEpatents

    Moustakas, Theodore D.; Cabalu, Jasper S.

    2011-10-11

    A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

  3. Optical devices featuring textured semiconductor layers

    DOEpatents

    Moustakas, Theodore D.; Cabalu, Jasper S.

    2012-08-07

    A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

  4. Semiconductor active plasmonics

    NASA Astrophysics Data System (ADS)

    Mendach, Stefan; Nötzel, Richard

    2013-12-01

    Plasmonics is a research area in nanophotonics attracting increasing interest due to the potential applications in sensing and detecting, sub-wavelength confinement of light, integrated circuits, and many others. In particular, when plasmonic structures such as metal nanostructures or highly doped semiconductor particles are combined with active semiconductor materials and nanostructures, novel exciting physics and applications arise. This special section on semiconductor active plasmonics covers several of the most important and complementary directions in the field. First is the modification of the optical properties of a semiconductor nanostructure due to the close proximity of a metallic film or nanostructure. These arise from the formation hybrid plasmon/exciton states and may lead to enhanced spontaneous emission rates, directional far field emission patterns, strong coupling phenomena, and many more. Second is the realization of sub-wavelength scale nanolasers by coupling a semiconductor gain medium with a plasmonic metallic cavity. Particular emphasis is given on the major technical challenges in the fabrication of these nanolasers, such as device patterning, surface passivation, and metal deposition. While the above topics address mainly active structures and devices operating in the visible or near-infrared wavelength region, in the third, the enhanced THz extinction by periodic arrays of semiconductor particles is discussed. This is based on the build-up of surface plasmon resonances in the doped semiconductor particles which can be resonantly coupled and widely tuned by the carrier density in the semiconductor. We believe these highly diverse aspects give insight into the wide variety of new physics and applications that semiconductor active plasmonics is offering. Finally, we would like to thank the IOP editorial staff, in particular Alice Malhador, for their support, and we would also like to thank the contributors for their efforts and participation

  5. Optical devices featuring nonpolar textured semiconductor layers

    DOEpatents

    Moustakas, Theodore D; Moldawer, Adam; Bhattacharyya, Anirban; Abell, Joshua

    2013-11-26

    A semiconductor emitter, or precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate in a nonpolar orientation. The textured layers enhance light extraction, and the use of nonpolar orientation greatly enhances internal quantum efficiency compared to conventional devices. Both the internal and external quantum efficiencies of emitters of the invention can be 70-80% or higher. The invention provides highly efficient light emitting diodes suitable for solid state lighting.

  6. Method of transferring a thin crystalline semiconductor layer

    DOEpatents

    Nastasi, Michael A.; Shao, Lin; Theodore, N. David

    2006-12-26

    A method for transferring a thin semiconductor layer from one substrate to another substrate involves depositing a thin epitaxial monocrystalline semiconductor layer on a substrate having surface contaminants. An interface that includes the contaminants is formed in between the deposited layer and the substrate. Hydrogen atoms are introduced into the structure and allowed to diffuse to the interface. Afterward, the thin semiconductor layer is bonded to a second substrate and the thin layer is separated away at the interface, which results in transferring the thin epitaxial semiconductor layer from one substrate to the other substrate.

  7. Method for removing semiconductor layers from salt substrates

    DOEpatents

    Shuskus, Alexander J.; Cowher, Melvyn E.

    1985-08-27

    A method is described for removing a CVD semiconductor layer from an alkali halide salt substrate following the deposition of the semiconductor layer. The semiconductor-substrate combination is supported on a material such as tungsten which is readily wet by the molten alkali halide. The temperature of the semiconductor-substrate combination is raised to a temperature greater than the melting temperature of the substrate but less than the temperature of the semiconductor and the substrate is melted and removed from the semiconductor by capillary action of the wettable support.

  8. Conductive layer for biaxially oriented semiconductor film growth

    DOEpatents

    Findikoglu, Alp T.; Matias, Vladimir

    2007-10-30

    A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

  9. Photosensitivity of layered semiconductor propolis heterocontact

    NASA Astrophysics Data System (ADS)

    Drapak, Stepan I.; Orletskii, Volodymyr B.; Bahtinov, Anatolii P.; Kovalyuk, Zakhar D.; Fotiy, Vasyl D.

    2003-03-01

    Room temperature photosensitivity and its spectral distribution are investigated for a hetercontact between a layered semiconductor (p-InSe) and a biological entity (propolis). The obtained heterocontacts has a maximum photosensitivity >= 10^4 V/W. It is shown that the form of spectral sensitivity curve depends on the way of the heterocontact preparation. The long-wave edge of relative quantum efficiency varies from hν =1.2 eV (the energy gap for InSe at T=300 K) to 1.6 eV depending on a state of aggregation of propolis. The maximum photosensitivity in the long-wave spectral range takes place when the propolis layer is under illumination. The obtained peculiarities of the photoelectrical properties cannot be explained in the framework of the classical description of photosensitivity spectral description (the window effect) what follows from the optical absorption measurements for InSe and propolis in the range hν <= 1.2 eV. Impurity states in the energy gap of InSe and states at the heterocontact interface (a classical case of isotype p-p heterojunction) also do not give an appropriate explanation. To interpret the obtained results the complexity of the chemical composition of propolis, a product from honey bee, must be taken into account.

  10. Method for depositing layers of high quality semiconductor material

    DOEpatents

    Guha, Subhendu; Yang, Chi C.

    2001-08-14

    Plasma deposition of substantially amorphous semiconductor materials is carried out under a set of deposition parameters which are selected so that the process operates near the amorphous/microcrystalline threshold. This threshold varies as a function of the thickness of the depositing semiconductor layer; and, deposition parameters, such as diluent gas concentrations, must be adjusted as a function of layer thickness. Also, this threshold varies as a function of the composition of the depositing layer, and in those instances where the layer composition is profiled throughout its thickness, deposition parameters must be adjusted accordingly so as to maintain the amorphous/microcrystalline threshold.

  11. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, Olga B.; Lear, Kevin L.

    1998-01-01

    A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

  12. Method of producing strained-layer semiconductor devices via subsurface-patterning

    DOEpatents

    Dodson, Brian W.

    1993-01-01

    A method is described for patterning subsurface features in a semiconductor device, wherein the semiconductor device includes an internal strained layer. The method comprises creating a pattern of semiconductor material over the semiconductor device, the semiconductor material having a predetermined thickness which stabilizes areas of the strained semiconductor layer that lie beneath the pattern. Subsequently, a heating step is applied to the semiconductor device to cause a relaxation in areas of the strained layer which do not lie beneath the semiconductor material pattern, whereby dislocations result in the relaxed areas and impair electrical transport therethrough.

  13. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  14. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, O.B.; Lear, K.L.

    1998-03-10

    The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

  15. Abrupt Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.

    ERIC Educational Resources Information Center

    Jones, Kenneth

    1979-01-01

    Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the abrupt depletion layer approximation. (Author/GA)

  16. Bandgap Restructuring of the Layered Semiconductor Gallium Telluride in Air.

    PubMed

    Fonseca, Jose J; Tongay, Sefaattin; Topsakal, Mehmet; Chew, Annabel R; Lin, Alan J; Ko, Changhyun; Luce, Alexander V; Salleo, Alberto; Wu, Junqiao; Dubon, Oscar D

    2016-08-01

    A giant bandgap reduction in layered GaTe is demonstrated. Chemisorption of oxygen to the Te-terminated surfaces produces significant restructuring of the conduction band resulting in a bandgap below 0.8 eV, compared to 1.65 eV for pristine GaTe. Localized partial recovery of the pristine gap is achieved by thermal annealing, demonstrating that reversible band engineering in layered semiconductors is accessible through their surfaces. PMID:27171481

  17. Bandgap Restructuring of the Layered Semiconductor Gallium Telluride in Air.

    PubMed

    Fonseca, Jose J; Tongay, Sefaattin; Topsakal, Mehmet; Chew, Annabel R; Lin, Alan J; Ko, Changhyun; Luce, Alexander V; Salleo, Alberto; Wu, Junqiao; Dubon, Oscar D

    2016-08-01

    A giant bandgap reduction in layered GaTe is demonstrated. Chemisorption of oxygen to the Te-terminated surfaces produces significant restructuring of the conduction band resulting in a bandgap below 0.8 eV, compared to 1.65 eV for pristine GaTe. Localized partial recovery of the pristine gap is achieved by thermal annealing, demonstrating that reversible band engineering in layered semiconductors is accessible through their surfaces.

  18. Monolithic 3D CMOS Using Layered Semiconductors.

    PubMed

    Sachid, Angada B; Tosun, Mahmut; Desai, Sujay B; Hsu, Ching-Yi; Lien, Der-Hsien; Madhvapathy, Surabhi R; Chen, Yu-Ze; Hettick, Mark; Kang, Jeong Seuk; Zeng, Yuping; He, Jr-Hau; Chang, Edward Yi; Chueh, Yu-Lun; Javey, Ali; Hu, Chenming

    2016-04-01

    Monolithic 3D integrated circuits using transition metal dichalcogenide materials and low-temperature processing are reported. A variety of digital and analog circuits are implemented on two sequentially integrated layers of devices. Inverter circuit operation at an ultralow supply voltage of 150 mV is achieved, paving the way to high-density, ultralow-voltage, and ultralow-power applications. PMID:26833783

  19. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, John F.; Zolper, John C.

    1997-01-01

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

  20. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, J.F.; Zolper, J.C.

    1997-10-21

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

  1. Prediction of weak topological insulators in layered semiconductors.

    PubMed

    Yan, Binghai; Müchler, Lukas; Felser, Claudia

    2012-09-14

    We report the discovery of weak topological insulators by ab initio calculations in a honeycomb lattice. We propose a structure with an odd number of layers in the primitive unit cell as a prerequisite for forming weak topological insulators. Here, the single-layered KHgSb is the most suitable candidate for its large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Although the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as prototypes to aid in the finding of new weak topological insulators in layered small-gap semiconductors.

  2. Screening method for selecting semiconductor substrates having defects below a predetermined level in an oxide layer

    DOEpatents

    Warren, W.L.; Vanheusden, K.J.R.; Schwank, J.R.; Fleetwood, D.M.; Shaneyfelt, M.R.; Winokur, P.S.; Devine, R.A.B.

    1998-07-28

    A method is disclosed for screening or qualifying semiconductor substrates for integrated circuit fabrication. The method comprises the steps of annealing at least one semiconductor substrate at a first temperature in a defect-activating ambient (e.g. hydrogen, forming gas, or ammonia) for sufficient time for activating any defects within on oxide layer of the substrate; measuring a defect-revealing electrical characteristic of at least a portion of the oxide layer for determining a quantity of activated defects therein; and selecting substrates for which the quantity of activated defects is below a predetermined level. The defect-revealing electrical characteristic may be a capacitance-versus voltage (C-V) characteristic or a current-versus-voltage (I-V) characteristic that is dependent on an electrical charge in the oxide layer generated by the activated defects. Embodiments of the present invention may be applied for screening any type of semiconductor substrate or wafer having an oxide layer formed thereon or therein. This includes silicon-on-insulator substrates formed by a separation by the implantation of oxygen (SIMOX) process or the bond and etch back silicon-on-insulator (BESOI) process, as well as silicon substrates having a thermal oxide layer or a deposited oxide layer. 5 figs.

  3. Screening method for selecting semiconductor substrates having defects below a predetermined level in an oxide layer

    DOEpatents

    Warren, William L.; Vanheusden, Karel J. R.; Schwank, James R.; Fleetwood, Daniel M.; Shaneyfelt, Marty R.; Winokur, Peter S.; Devine, Roderick A. B.

    1998-01-01

    A method for screening or qualifying semiconductor substrates for integrated circuit fabrication. The method comprises the steps of annealing at least one semiconductor substrate at a first temperature in a defect-activating ambient (e.g. hydrogen, forming gas, or ammonia) for sufficient time for activating any defects within on oxide layer of the substrate; measuring a defect-revealing electrical characteristic of at least a portion of the oxide layer for determining a quantity of activated defects therein; and selecting substrates for which the quantity of activated defects is below a predetermined level. The defect-revealing electrical characteristic may be a capacitance-versus-voltage (C-V) characteristic or a current-versus-voltage (I-V) characteristic that is dependent on an electrical charge in the oxide layer generated by the activated defects. Embodiments of the present invention may be applied for screening any type of semiconductor substrate or wafer having an oxide layer formed thereon or therein. This includes silicon-on-insulator substrates formed by a separation by the implantation of oxygen (SIMOX) process or the bond and etch back silicon-on-insulator (BESOI) process, as well as silicon substrates having a thermal oxide layer or a deposited oxide layer.

  4. Methods of producing free-standing semiconductors using sacrificial buffer layers and recyclable substrates

    DOEpatents

    Ptak, Aaron Joseph; Lin, Yong; Norman, Andrew; Alberi, Kirstin

    2015-05-26

    A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a spinel substrate using a sacrificial buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The sacrificial buffer material and semiconductor materials may be deposited using lattice-matching epitaxy or coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The sacrificial buffer layer may be dissolved using an epitaxial liftoff technique in order to separate the semiconductor device from the spinel substrate, and the spinel substrate may be reused in the subsequent fabrication of other semiconductor devices. The low-defect density semiconductor materials produced using this method result in the enhanced performance of the semiconductor devices that incorporate the semiconductor materials.

  5. Overview of atomic layer etching in the semiconductor industry

    SciTech Connect

    Kanarik, Keren J. Lill, Thorsten; Hudson, Eric A.; Sriraman, Saravanapriyan; Tan, Samantha; Marks, Jeffrey; Vahedi, Vahid; Gottscho, Richard A.

    2015-03-15

    Atomic layer etching (ALE) is a technique for removing thin layers of material using sequential reaction steps that are self-limiting. ALE has been studied in the laboratory for more than 25 years. Today, it is being driven by the semiconductor industry as an alternative to continuous etching and is viewed as an essential counterpart to atomic layer deposition. As we enter the era of atomic-scale dimensions, there is need to unify the ALE field through increased effectiveness of collaboration between academia and industry, and to help enable the transition from lab to fab. With this in mind, this article provides defining criteria for ALE, along with clarification of some of the terminology and assumptions of this field. To increase understanding of the process, the mechanistic understanding is described for the silicon ALE case study, including the advantages of plasma-assisted processing. A historical overview spanning more than 25 years is provided for silicon, as well as ALE studies on oxides, III–V compounds, and other materials. Together, these processes encompass a variety of implementations, all following the same ALE principles. While the focus is on directional etching, isotropic ALE is also included. As part of this review, the authors also address the role of power pulsing as a predecessor to ALE and examine the outlook of ALE in the manufacturing of advanced semiconductor devices.

  6. Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions.

    PubMed

    Duan, Xidong; Wang, Chen; Shaw, Jonathan C; Cheng, Rui; Chen, Yu; Li, Honglai; Wu, Xueping; Tang, Ying; Zhang, Qinling; Pan, Anlian; Jiang, Jianhui; Yu, Ruqing; Huang, Yu; Duan, Xiangfeng

    2014-12-01

    Two-dimensional layered semiconductors such as MoS₂ and WSe₂ have attracted considerable interest in recent times. Exploring the full potential of these layered materials requires precise spatial modulation of their chemical composition and electronic properties to create well-defined heterostructures. Here, we report the growth of compositionally modulated MoS₂-MoSe₂ and WS₂-WSe₂ lateral heterostructures by in situ modulation of the vapour-phase reactants during growth of these two-dimensional crystals. Raman and photoluminescence mapping studies demonstrate that the resulting heterostructure nanosheets exhibit clear structural and optical modulation. Transmission electron microscopy and elemental mapping studies reveal a single crystalline structure with opposite modulation of sulphur and selenium distributions across the heterostructure interface. Electrical transport studies demonstrate that the WSe₂-WS₂ heterojunctions form lateral p-n diodes and photodiodes, and can be used to create complementary inverters with high voltage gain. Our study is an important advance in the development of layered semiconductor heterostructures, an essential step towards achieving functional electronics and optoelectronics.

  7. Rhenium Dichalcogenides: Layered Semiconductors with Two Vertical Orientations.

    PubMed

    Hart, Lewis; Dale, Sara; Hoye, Sarah; Webb, James L; Wolverson, Daniel

    2016-02-10

    The rhenium and technetium diselenides and disulfides are van der Waals layered semiconductors in some respects similar to more well-known transition metal dichalcogenides (TMD) such as molybdenum sulfide. However, their symmetry is lower, consisting only of an inversion center, so that turning a layer upside-down (that is, applying a C2 rotation about an in-plane axis) is not a symmetry operation, but reverses the sign of the angle between the two nonequivalent in-plane crystallographic axes. A given layer thus can be placed on a substrate in two symmetrically nonequivalent (but energetically similar) ways. This has consequences for the exploitation of the anisotropic properties of these materials in TMD heterostructures and is expected to lead to a new source of domain structure in large-area layer growth. We produced few-layer ReS2 and ReSe2 samples with controlled "up" or "down" orientations by micromechanical cleavage and we show how polarized Raman microscopy can be used to distinguish these two orientations, thus establishing Raman as an essential tool for the characterization of large-area layers. PMID:26799768

  8. Lattice-Matched Semiconductor Layers on Single Crystalline Sapphire Substrate

    NASA Technical Reports Server (NTRS)

    Choi, Sang; King, Glen; Park, Yeonjoon

    2009-01-01

    SiGe is an important semiconductor alloy for high-speed field effect transistors (FETs), high-temperature thermoelectric devices, photovoltaic solar cells, and photon detectors. The growth of SiGe layer is difficult because SiGe alloys have different lattice constants from those of the common Si wafers, which leads to a high density of defects, including dislocations, micro-twins, cracks, and delaminations. This innovation utilizes newly developed rhombohedral epitaxy of cubic semiconductors on trigonal substrates in order to solve the lattice mismatch problem of SiGe by using trigonal single crystals like sapphire (Al2O3) as substrate to give a unique growth-orientation to the SiGe layer, which is automatically controlled at the interface upon sapphire (0001). This technology is different from previous silicon on insulator (SOI) or SGOI (SiGe on insulator) technologies that use amorphous SiO2 as the growth plane. A cubic semiconductor crystal is a special case of a rhombohedron with the inter-planar angle, alpha = 90 deg. With a mathematical transformation, all rhombohedrons can be described by trigonal crystal lattice structures. Therefore, all cubic lattice constants and crystal planes (hkl) s can be transformed into those of trigonal crystal parameters. These unique alignments enable a new opportunity of perfect lattice matching conditions, which can eliminate misfit dislocations. Previously, these atomic alignments were thought to be impossible or very difficult. With the invention of a new x-ray diffraction measurement method here, growth of cubic semiconductors on trigonal crystals became possible. This epitaxy and lattice-matching condition can be applied not only to SiGe (111)/sapphire (0001) substrate relations, but also to other crystal structures and other materials, including similar crystal structures which have pointgroup rotational symmetries by 120 because the cubic (111) direction has 120 rotational symmetry. The use of slightly miscut (less than

  9. Separating semiconductor devices from substrate by etching graded composition release layer disposed between semiconductor devices and substrate including forming protuberances that reduce stiction

    SciTech Connect

    Tauke-Pedretti, Anna; Nielson, Gregory N; Cederberg, Jeffrey G; Cruz-Campa, Jose Luis

    2015-05-12

    A method includes etching a release layer that is coupled between a plurality of semiconductor devices and a substrate with an etch. The etching includes etching the release layer between the semiconductor devices and the substrate until the semiconductor devices are at least substantially released from the substrate. The etching also includes etching a protuberance in the release layer between each of the semiconductor devices and the substrate. The etch is stopped while the protuberances remain between each of the semiconductor devices and the substrate. The method also includes separating the semiconductor devices from the substrate. Other methods and apparatus are also disclosed.

  10. Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers

    DOEpatents

    Norman, Andrew

    2016-08-23

    A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.

  11. Energy spectrum of layered semiconductors in a magnetic field parallel to the layers: Voigt geometry

    NASA Astrophysics Data System (ADS)

    Yoo, K. H.; Ram-Mohan, L. R.

    2010-11-01

    The electronic band structure of zinc-blende layered semiconductor heterostructures is investigated theoretically in the presence of an in-plane magnetic field, a configuration we label as the Voigt geometry. We use a Lagrangian formulation for modeling the band structure in the individual layers within the kṡP model. This approach has been shown by us to provide the correct ordering of the derivatives appearing in the multiband description of Schrödinger’s equations for the envelope functions through the application of the principle of stationary action. Finite element modeling of the action integral provides a natural and efficient approach to the inclusion of in-plane magnetic fields in the energy-level analysis. Calculations for quantum wells and superlattices are presented, and the complex energy-level structure obtained for the layered structures.

  12. Resonant activation in bistable semiconductor lasers

    SciTech Connect

    Lepri, Stefano; Giacomelli, Giovanni

    2007-08-15

    We theoretically investigate the possibility of observing resonant activation in the hopping dynamics of two-mode semiconductor lasers. We present a series of simulations of a rate-equation model under random and periodic modulation of the bias current. In both cases, for an optimal choice of the modulation time scale, the hopping times between the stable lasing modes attain a minimum. The simulation data are understood by means of an effective one-dimensional Langevin equation with multiplicative fluctuations. Our conclusions apply to both edge-emitting and vertical cavity lasers, thus opening the way to several experimental tests in such optical systems.

  13. Growth of coincident site lattice matched semiconductor layers and devices on crystalline substrates

    DOEpatents

    Norman, Andrew G; Ptak, Aaron J

    2013-08-13

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a substrate having a crystalline surface with a known lattice parameter (a). The method further includes growing a crystalline semiconductor layer on the crystalline substrate surface by coincident site lattice matched epitaxy, without any buffer layer between the crystalline semiconductor layer and the crystalline surface of the substrate. The crystalline semiconductor layer will be prepared to have a lattice parameter (a') that is related to the substrate lattice parameter (a). The lattice parameter (a') maybe related to the lattice parameter (a) by a scaling factor derived from a geometric relationship between the respective crystal lattices.

  14. Point Defects in Two-Dimensional Layered Semiconductors: Physics and Its Applications

    NASA Astrophysics Data System (ADS)

    Suh, Joonki

    Recent advances in material science and semiconductor processing have been achieved largely based on in-depth understanding, efficient management and advanced application of point defects in host semiconductors, thus finding the relevant techniques such as doping and defect engineering as a traditional scientific and technological solution. Meanwhile, two- dimensional (2D) layered semiconductors currently draw tremendous attentions due to industrial needs and their rich physics at the nanoscale; as we approach the end of critical device dimensions in silicon-based technology, ultra-thin semiconductors have the potential as next- generation channel materials, and new physics also emerges at such reduced dimensions where confinement of electrons, phonons, and other quasi-particles is significant. It is therefore rewarding and interesting to understand and redefine the impact of lattice defects by investigating their interactions with energy/charge carriers of the host matter. Potentially, the established understanding will provide unprecedented opportunities for realizing new functionalities and enhancing the performance of energy harvesting and optoelectronic devices. In this thesis, multiple novel 2D layered semiconductors, such as bismuth and transition- metal chalcogenides, are explored. Following an introduction of conventional effects induced by point defects in semiconductors, the related physics of electronically active amphoteric defects is revisited in greater details. This can elucidate the complication of a two-dimensional electron gas coexisting with the topological states on the surface of bismuth chalcogenides, recently suggested as topological insulators. Therefore, native point defects are still one of the keys to understand and exploit topological insulators. In addition to from a fundamental science point of view, the effects of point defects on the integrated thermal-electrical transport, as well as the entropy-transporting process in

  15. Point Defects in Two-Dimensional Layered Semiconductors: Physics and Its Applications

    NASA Astrophysics Data System (ADS)

    Suh, Joonki

    Recent advances in material science and semiconductor processing have been achieved largely based on in-depth understanding, efficient management and advanced application of point defects in host semiconductors, thus finding the relevant techniques such as doping and defect engineering as a traditional scientific and technological solution. Meanwhile, two- dimensional (2D) layered semiconductors currently draw tremendous attentions due to industrial needs and their rich physics at the nanoscale; as we approach the end of critical device dimensions in silicon-based technology, ultra-thin semiconductors have the potential as next- generation channel materials, and new physics also emerges at such reduced dimensions where confinement of electrons, phonons, and other quasi-particles is significant. It is therefore rewarding and interesting to understand and redefine the impact of lattice defects by investigating their interactions with energy/charge carriers of the host matter. Potentially, the established understanding will provide unprecedented opportunities for realizing new functionalities and enhancing the performance of energy harvesting and optoelectronic devices. In this thesis, multiple novel 2D layered semiconductors, such as bismuth and transition- metal chalcogenides, are explored. Following an introduction of conventional effects induced by point defects in semiconductors, the related physics of electronically active amphoteric defects is revisited in greater details. This can elucidate the complication of a two-dimensional electron gas coexisting with the topological states on the surface of bismuth chalcogenides, recently suggested as topological insulators. Therefore, native point defects are still one of the keys to understand and exploit topological insulators. In addition to from a fundamental science point of view, the effects of point defects on the integrated thermal-electrical transport, as well as the entropy-transporting process in

  16. Novel layered two-dimensional semiconductors as the building blocks for nano-electronic/photonic systems

    NASA Astrophysics Data System (ADS)

    Su, Guoxiong; De, Debtanu; Hadjiev, Viktor G.; Peng, Haibing

    2014-06-01

    Layered two-dimensional (2D) semiconductors beyond graphene have been emerging as potential building blocks for the next-generation electronic/photonic applications. Representative metal chalcogenides, including the widely studied MoS2, possess similar layered crystal structures with weak interaction between adjacent layers, thus allowing the formation of stable thin-layer crystals with thickness down to a few or even single atomic layer. Other important chalcogenides, involving earth-abundant and environment-friendly materials desirable for sustainable applications, include SnS2 (band gap: 2.1 eV) and SnS (band gap: 1.1 eV). So far, commonly adopted for research purpose are mechanical and liquid exfoliation methods for creating thin layers of such 2D semiconductors. Most recently, chemical vapor deposition (CVD) was attracting significant attention as a practical method for producing thin films or crystal grains of MoS2. However, critical yet still absent is an effective experimental approach for controlling the positions of thin crystal grains of layered 2D semiconductors during the CVD process. Here we report the controlled CVD synthesis of thin crystal arrays of representative layered semiconductors (including SnS2 and SnS) at designed locations on chip, promising large-scale optoelectronic applications. Our work opens a window for future practical applications of layered 2D semiconductors in integrated nano-electronic/photonic systems.

  17. Quantitative temperature measurement of multi-layered semiconductor devices using spectroscopic thermoreflectance microscopy.

    PubMed

    Kim, Dong Uk; Park, Kwan Seob; Jeong, Chan Bae; Kim, Geon Hee; Chang, Ki Soo

    2016-06-27

    Thermoreflectance microscopy is essential in understanding the unpredictable local heating generation that occurs during microelectronic device operation. However, temperature measurements of multi-layered semiconductor devices represent a challenge because the thermoreflectance coefficient is quite small and is dramatically changed by the optical interference inside transparent layers of the device. Therefore, we propose a spectroscopic thermoreflectance microscopy system using a systematic approach for improving the quantitative temperature measurement of multi-layered semiconductor devices. We demonstrate the quantitative measurement of the temperature profile for physical defects on thin-film polycrystalline silicon resistors via thermoreflectance coefficient calibration and effective coefficient κ estimation.

  18. Quantitative temperature measurement of multi-layered semiconductor devices using spectroscopic thermoreflectance microscopy.

    PubMed

    Kim, Dong Uk; Park, Kwan Seob; Jeong, Chan Bae; Kim, Geon Hee; Chang, Ki Soo

    2016-06-27

    Thermoreflectance microscopy is essential in understanding the unpredictable local heating generation that occurs during microelectronic device operation. However, temperature measurements of multi-layered semiconductor devices represent a challenge because the thermoreflectance coefficient is quite small and is dramatically changed by the optical interference inside transparent layers of the device. Therefore, we propose a spectroscopic thermoreflectance microscopy system using a systematic approach for improving the quantitative temperature measurement of multi-layered semiconductor devices. We demonstrate the quantitative measurement of the temperature profile for physical defects on thin-film polycrystalline silicon resistors via thermoreflectance coefficient calibration and effective coefficient κ estimation. PMID:27410553

  19. Atomic Layer Deposited Thin Films for Dielectrics, Semiconductor Passivation, and Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Xu, Runshen

    Atomic layer deposition (ALD) utilizes sequential precursor gas pulses to deposit one monolayer or sub-monolayer of material per cycle based on its self-limiting surface reaction, which offers advantages, such as precise thickness control, thickness uniformity, and conformality. ALD is a powerful means of fabricating nanoscale features in future nanoelectronics, such as contemporary sub-45 nm metal-oxide-semiconductor field effect transistors, photovoltaic cells, near- and far-infrared detectors, and intermediate temperature solid oxide fuel cells. High dielectric constant, kappa, materials have been recognized to be promising candidates to replace traditional SiO2 and SiON, because they enable good scalability of sub-45 nm MOSFET (metal-oxide-semiconductor field-effect transistor) without inducing additional power consumption and heat dissipation. In addition to high dielectric constant, high-kappa materials must meet a number of other requirements, such as low leakage current, high mobility, good thermal and structure stability with Si to withstand high-temperature source-drain activation annealing. In this thesis, atomic layer deposited Er2O3 doped TiO2 is studied and proposed as a thermally stable amorphous high-kappa dielectric on Si substrate. The stabilization of TiO2 in its amorphous state is found to achieve a high permittivity of 36, a hysteresis voltage of less than 10 mV, and a low leakage current density of 10-8 A/cm-2 at -1 MV/cm. In III-V semiconductors, issues including unsatisfied dangling bonds and native oxides often result in inferior surface quality that yields non-negligible leakage currents and degrades the long-term performance of devices. The traditional means for passivating the surface of III-V semiconductors are based on the use of sulfide solutions; however, that only offers good protection against oxidation for a short-term (i.e., one day). In this work, in order to improve the chemical passivation efficacy of III-V semiconductors

  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. Black Arsenic-Phosphorus: Layered Anisotropic Infrared Semiconductors with Highly Tunable Compositions and Properties

    NASA Astrophysics Data System (ADS)

    Liu, Bilu; Zhou, Chongwu

    2D layered materials with diverse properties have attracted significant interest in the past decade. The layered materials discovered so far have covered a wide, yet discontinuous electromagnetic spectral range from semimetallic graphene, insulating boron nitride, to semiconductors with bandgaps from middle infrared to visible light. Here, we introduce new layered semiconductors, black arsenic-phosphorus (b-AsP), with highly tunable chemical compositions and electronic and optical properties. Transport and infrared absorption studies demonstrate the semiconducting nature of b-AsP with tunable bandgaps, ranging from 0.3 to 0.15 eV. These bandgaps fall into long-wavelength infrared (LWIR) regime and cannot be readily reached by other layered materials. Moreover, polarization-resolved infrared absorption and Raman studies reveal in-plane anisotropic properties of b-AsP. This family of layered b-AsP materials extend the electromagnetic spectra covered by 2D layered materials to the LWIR regime, and may find unique applications for future all 2D layered material based devices. Ref. Liu, B., et al., Black Arsenic-Phosphorus: Layered Anisotropic Infrared Semiconductors with Highly Tunable Compositions and Properties. Adv. Mater., 2015, 27, 4423-4429.

  3. Unitary lens semiconductor device

    DOEpatents

    Lear, K.L.

    1997-05-27

    A unitary lens semiconductor device and method are disclosed. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors. 9 figs.

  4. Unitary lens semiconductor device

    DOEpatents

    Lear, Kevin L.

    1997-01-01

    A unitary lens semiconductor device and method. The unitary lens semiconductor device is provided with at least one semiconductor layer having a composition varying in the growth direction for unitarily forming one or more lenses in the semiconductor layer. Unitary lens semiconductor devices may be formed as light-processing devices such as microlenses, and as light-active devices such as light-emitting diodes, photodetectors, resonant-cavity light-emitting diodes, vertical-cavity surface-emitting lasers, and resonant cavity photodetectors.

  5. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications.

    PubMed

    Zhang, Youwei; Li, Hui; Wang, Haomin; Xie, Hong; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2016-01-01

    Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors. PMID:27403803

  6. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications

    NASA Astrophysics Data System (ADS)

    Zhang, Youwei; Li, Hui; Wang, Haomin; Xie, Hong; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2016-07-01

    Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors.

  7. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications.

    PubMed

    Zhang, Youwei; Li, Hui; Wang, Haomin; Xie, Hong; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2016-01-01

    Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors.

  8. Thickness Considerations of Two-Dimensional Layered Semiconductors for Transistor Applications

    PubMed Central

    Zhang, Youwei; Li, Hui; Wang, Haomin; Xie, Hong; Liu, Ran; Zhang, Shi-Li; Qiu, Zhi-Jun

    2016-01-01

    Layered two-dimensional semiconductors have attracted tremendous attention owing to their demonstrated excellent transistor switching characteristics with a large ratio of on-state to off-state current, Ion/Ioff. However, the depletion-mode nature of the transistors sets a limit on the thickness of the layered semiconductor films primarily determined by a given Ion/Ioff as an acceptable specification. Identifying the optimum thickness range is of significance for material synthesis and device fabrication. Here, we systematically investigate the thickness-dependent switching behavior of transistors with a wide thickness range of multilayer-MoS2 films. A difference in Ion/Ioff by several orders of magnitude is observed when the film thickness, t, approaches a critical depletion width. The decrease in Ion/Ioff is exponential for t between 20 nm and 100 nm, by a factor of 10 for each additional 10 nm. For t larger than 100 nm, Ion/Ioff approaches unity. Simulation using technical computer-aided tools established for silicon technology faithfully reproduces the experimentally determined scaling behavior of Ion/Ioff with t. This excellent agreement confirms that multilayer-MoS2 films can be approximated as a homogeneous semiconductor with high surface conductivity that tends to deteriorate Ion/Ioff. Our findings are helpful in guiding material synthesis and designing advanced field-effect transistors based on the layered semiconductors. PMID:27403803

  9. Low resistance barrier layer for isolating, adhering, and passivating copper metal in semiconductor fabrication

    DOEpatents

    Weihs, Timothy P.; Barbee, Jr., Troy W.

    2002-01-01

    Cubic or metastable cubic refractory metal carbides act as barrier layers to isolate, adhere, and passivate copper in semiconductor fabrication. One or more barrier layers of the metal carbide are deposited in conjunction with copper metallizations to form a multilayer characterized by a cubic crystal structure with a strong (100) texture. Suitable barrier layer materials include refractory transition metal carbides such as vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr.sub.3 C.sub.2), tungsten carbide (WC), and molybdenum carbide (MoC).

  10. Organic light-emitting diode with an emitter based on a planar layer of CdSe semiconductor nanoplatelets

    NASA Astrophysics Data System (ADS)

    Vashchenko, A. A.; Vitukhnovskii, A. G.; Lebedev, V. S.; Selyukov, A. S.; Vasiliev, R. B.; Sokolikova, M. S.

    2014-09-01

    Colloidal CdSe semiconductor nanoplatelets with characteristic longitudinal sizes of 20-70 nm and thicknesses of several atomic layers are synthesized. The spectra and kinetics of the photoluminescence of these quasi-two-dimensional nanostructures (quantum wells) at room and cryogenic temperatures are investigated. A hybrid light-emitting diode with the electron and hole transport layers based on TAZ and TPD organic compounds, respectively, and the active "emissive" element based on a layer of such single-component nanoplatelets is designed. The spectral and electrical characteristics of the fabricated device, emitting at a wavelength of λ = 515 nm, are determined. The use of quasi-two-dimensional nanostructures of this kind (nanoplatelets) is promising for the fabrication of hybrid light-emitting diodes with pure colors.

  11. Few-layer III-VI and IV-VI 2D semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Sucharitakul, Sukrit; Liu, Mei; Kumar, Rajesh; Sankar, Raman; Chou, Fang C.; Chen, Yit-Tsong; Gao, Xuan

    Since the discovery of atomically thin graphene, a large variety of exfoliable 2D materials have been thoroughly explored for their exotic transport behavior and promises in technological breakthroughs. While most attention on 2D materials beyond graphene is focused on transition metal-dichalcogenides, relatively less attention is paid to layered III-VI and IV-VI semiconductors such as InSe, SnSe etc which bear stronger potential as 2D materials with high electron mobility or thermoelectric figure of merit. We will discuss our recent work on few-layer InSe 2D field effect transistors which exhibit carrier mobility approaching 1000 cm2/Vs and ON-OFF ratio exceeding 107 at room temperature. In addition, the fabrication and device performance of transistors made of mechanically exfoliated multilayer IV-VI semiconductor SnSe and SnSe2 will be discussed.

  12. Metal insulator semiconductor solar cell devices based on a Cu{sub 2}O substrate utilizing h-BN as an insulating and passivating layer

    SciTech Connect

    Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex; Regan, William Raymond

    2015-03-09

    We demonstrate cuprous oxide (Cu{sub 2}O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu{sub 2}O layer. The devices are the most efficient of any Cu{sub 2}O based MIS-Schottky solar cells reported to date.

  13. Metal insulator semiconductor solar cell devices based on a Cu2O substrate utilizing h-BN as an insulating and passivating layer

    NASA Astrophysics Data System (ADS)

    Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Regan, William Raymond; Zettl, Alex

    2015-03-01

    We demonstrate cuprous oxide (Cu2O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu2O layer. The devices are the most efficient of any Cu2O based MIS-Schottky solar cells reported to date.

  14. Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers

    SciTech Connect

    Jana, Dipankar Porwal, S.; Sharma, T. K. Oak, S. M.; Kumar, Shailendra

    2014-04-15

    Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.

  15. Strain-induced semiconductor to metal transition in few-layer black phosphorus from first principles

    NASA Astrophysics Data System (ADS)

    Ju, Weiwei; Li, Tongwei; Wang, Hui; Yong, Yongliang; Sun, Jinfeng

    2015-02-01

    Electronic structures of few-layer black phosphorus (BP) with biaxial strain are investigated by using methods based on density functional theory. The compressive strain can result in a semiconductor-metal transition (SMT) for few-layer BP, whereas the tensile strain only affects the band gaps. The critical compressive strain for the SMT is larger in the thinner 2D BP. The band structures and charge densities are calculated in order to provide imperative understanding on SMT. With the compressive strain, the energy of conduction bands moves down, which is induced by the structural change and is essential reason of SMT.

  16. Electrical properties of hybrid (ferromagnetic metal)-(layered semiconductor) Ni/p-GaSe structures

    SciTech Connect

    Bakhtinov, A. P. Vodopyanov, V. N.; Kovalyuk, Z. D.; Netyaga, V. V.; Lytvyn, O. S.

    2010-02-15

    Two-barrier Ni/n-Ga2Se3/p-GaSe structures with nanoscale Ni-alloy grains caused by reactions at the 'metal-layered semiconductor' interface were formed after growing Ni layers on the p-GaSe (0001) surface. Current-voltage and capacitance-voltage characteristics of hybrid structures were studied in the temperature range of 220-350 K. The dependence of the impedance spectra on the bias voltage was studied at various temperatures. The frequency dependences of the impedance at high frequencies (f = 10{sup 6} Hz) are discussed in terms of the phenomena of spin injection and extraction in structures with an ultrathin spin-selective Ni/n-Ga{sub 2}Se{sub 3} barrier and the effects of spin diffusion and relaxation in the semiconductor substrate. The room-temperature phenomena of the Coulomb blockade and negative differential capacitance were detected. These phenomena are explained based on an analysis of transport processes in a narrow region near the 'ferromagnetic metal-semiconductor' interface, where nanoscale grains are arranged.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

  18. Superresolution Structure Optical Disk with Semiconductor-Doped Glass Mask Layer Containing CdSe Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yeh, Tung‑Ti; Wang, Jr‑Hau; Hsieh, Tsung‑Eong; Shieh, Han‑Ping D.

    2006-02-01

    In this work, we demonstrate a distinct superresolution phenomenon and signal properties of an optical disk with a semiconductor-doped glass (SDG) mask layer containing CdSe nanoparticles. It was found that the 69 nm marks could be consistently retrieved at reading power (Pr) = 4 mW with carrier-to-noise ratio (CNR) = 13.56 dB. The signals were clearly resolved with CNRs nearly equal to 40 dB at Pr=4 mW when the recorded marks were larger than 100 nm. The cyclability test indicated that the CdSe-SiO2 SDG layer might serve as a stable and reliable optical mask layer in 105 readout cycles.

  19. Superheating Suppresses Structural Disorder in Layered BiI3 Semiconductors Grown by the Bridgman Method

    SciTech Connect

    Johns, Paul M.; Sulekar, Soumitra; Yeo, Shinyoung; Baciak, James E.; Bliss, Mary; Nino, Juan C.

    2016-01-01

    The susceptibility of layered structures to stacking faults is a problem in some of the more attractive semiconductor materials for ambient-temperature radiation detectors. In the work presented here, Bridgman-grown BiI3 layered single crystals are investigated to understand and eliminate this structural disorder, which reduces radiation detector performance. The use of superheating gradients has been shown to improve crystal quality in non-layered semiconductor crystals; thus the technique was here explored to improve the growth of BiI3. When investigating the homogeneity of non-superheated crystals, highly geometric void defects were found to populate the bulk of the crystals. Applying a superheating gradient to the melt prior to crystal growth improved structural quality and decreased defect density from the order of 4600 voids per cm3 to 300 voids per cm3. Corresponding moderate improvements to electronic properties also resulted from the superheat gradient method of crystal growth. Comparative measurements through infrared microscopy, etch-pit density, x-ray rocking curves, and sheet resistivity readings show that superheat gradients in BiI3 growth led to higher quality crystals.

  20. Electrical Characterization of Metal-Ferroelectric-Insulator- Semiconductor having Double Layered Insulator for Memory Applications

    NASA Astrophysics Data System (ADS)

    Ismail, L. N.; Wahid, M. H.; Habibah, Z.; Herman, S. H.; Rozana, M. D.; Rusop, M.

    2014-08-01

    Metal-ferroelectric-insulator-semiconductor (MFIS) devices were successfully fabricated using poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) and poly (methyl methacrylate): titanium dioxide (PMMA:TiO2) nanocomposite as ferroelectric and insulator films, respectively on n-type silicon (n-Si) substrate. Both ferroelectric and insulator films were prepared by sol-gel spin coating method. The electrical behaviour of metal-ferroelectric-metal (MFM) structure with PVDF-TrFE film and metal-insulator- metal (MIM) structure PMMA:TiO2 film exhibited different current characteristics. The capacitance of the MFIS devices was found to be 0.42 and 0.29 nF at frequency of 1kHz and 1 MHz respectively. Meanwhile, the dielectric loss values are constant (~60 × 10-3) in the frequency range from 100 Hz to 100 kHz. I-V results for MFIS are much higher than MIM and MFM is due to there is a trapped holes/electron located at the semiconductor- insulator interface which contributes to high leakage current in the MFIS device. We conclude, although interposing the PMMA :TiO2 nanocomposite insulator layer between the semiconductor and Al electrodes degrades the MFIS performance, nevertheless, they remain sufficiently good for use in organic electronic devices.

  1. Atomic layer deposition of perovskite oxides and their epitaxial integration with Si, Ge, and other semiconductors

    SciTech Connect

    McDaniel, Martin D.; Ngo, Thong Q.; Hu, Shen; Ekerdt, John G.; Posadas, Agham; Demkov, Alexander A.

    2015-12-15

    Atomic layer deposition (ALD) is a proven technique for the conformal deposition of oxide thin films with nanoscale thickness control. Most successful industrial applications have been with binary oxides, such as Al{sub 2}O{sub 3} and HfO{sub 2}. However, there has been much effort to deposit ternary oxides, such as perovskites (ABO{sub 3}), with desirable properties for advanced thin film applications. Distinct challenges are presented by the deposition of multi-component oxides using ALD. This review is intended to highlight the research of the many groups that have deposited perovskite oxides by ALD methods. Several commonalities between the studies are discussed. Special emphasis is put on precursor selection, deposition temperatures, and specific property performance (high-k, ferroelectric, ferromagnetic, etc.). Finally, the monolithic integration of perovskite oxides with semiconductors by ALD is reviewed. High-quality epitaxial growth of oxide thin films has traditionally been limited to physical vapor deposition techniques (e.g., molecular beam epitaxy). However, recent studies have demonstrated that epitaxial oxide thin films may be deposited on semiconductor substrates using ALD. This presents an exciting opportunity to integrate functional perovskite oxides for advanced semiconductor applications in a process that is economical and scalable.

  2. 78 FR 68814 - Subzone 183B; Authorization of Production Activity; Samsung Austin Semiconductor, LLC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-15

    ... (78 FR 40427, 7-5-2013). The FTZ Board has determined that no further review of the activity is... Foreign-Trade Zones Board Subzone 183B; Authorization of Production Activity; Samsung Austin Semiconductor, LLC (Semiconductors); Austin, Texas On June 26, 2013, Samsung Austin Semiconductor, LLC submitted...

  3. Laser-thinning of MoS₂: on demand generation of a single-layer semiconductor.

    PubMed

    Castellanos-Gomez, A; Barkelid, M; Goossens, A M; Calado, V E; van der Zant, H S J; Steele, G A

    2012-06-13

    Single-layer MoS(2) is an attractive semiconducting analogue of graphene that combines high mechanical flexibility with a large direct bandgap of 1.8 eV. On the other hand, bulk MoS(2) is an indirect bandgap semiconductor similar to silicon, with a gap of 1.2 eV, and therefore deterministic preparation of single MoS(2) layers is a crucial step toward exploiting the large direct bandgap of monolayer MoS(2) in electronic, optoelectronic, and photovoltaic applications. Although mechanical and chemical exfoliation methods can be used to obtain high quality MoS(2) single layers, the lack of control in the thickness, shape, size, and position of the flakes limits their usefulness. Here we present a technique for controllably thinning multilayered MoS(2) down to a single-layer two-dimensional crystal using a laser. We generate single layers in arbitrary shapes and patterns with feature sizes down to 200 nm and show that the resulting two-dimensional crystals have optical and electronic properties comparable to that of pristine exfoliated MoS(2) single layers.

  4. Low Temperature Processed Complementary Metal Oxide Semiconductor (CMOS) Device by Oxidation Effect from Capping Layer

    PubMed Central

    Wang, Zhenwei; Al-Jawhari, Hala A.; Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Wei, Nini; Hedhili, M. N.; Alshareef, H. N.

    2015-01-01

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190°C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field. PMID:25892711

  5. Measurement of residual stress in a multi-layer semiconductor heterostructure by micro-Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Qiu, Wei; Cheng, Cui-Li; Liang, Ren-Rong; Zhao, Chun-Wang; Lei, Zhen-Kun; Zhao, Yu-Cheng; Ma, Lu-Lu; Xu, Jun; Fang, Hua-Jun; Kang, Yi-Lan

    2016-07-01

    Si-based multilayer structures are widely used in current microelectronics. During their preparation, some inhomogeneous residual stress is induced, resulting in competition between interface mismatching and surface energy and even leading to structure failure. This work presents a methodological study on the measurement of residual stress in a multi-layer semiconductor heterostructure. Scanning electron microscopy (SEM), micro-Raman spectroscopy (MRS), and transmission electron microscopy (TEM) were applied to measure the geometric parameters of the multilayer structure. The relationship between the Raman spectrum and the stress/strain on the [100] and [110] crystal orientations was determined to enable surface and cross-section residual stress analyses, respectively. Based on the Raman mapping results, the distribution of residual stress along the depth of the multi-layer heterostructure was successfully obtained.

  6. Low temperature processed complementary metal oxide semiconductor (CMOS) device by oxidation effect from capping layer.

    PubMed

    Wang, Zhenwei; Al-Jawhari, Hala A; Nayak, Pradipta K; Caraveo-Frescas, J A; Wei, Nini; Hedhili, M N; Alshareef, H N

    2015-04-20

    In this report, both p- and n-type tin oxide thin-film transistors (TFTs) were simultaneously achieved using single-step deposition of the tin oxide channel layer. The tuning of charge carrier polarity in the tin oxide channel is achieved by selectively depositing a copper oxide capping layer on top of tin oxide, which serves as an oxygen source, providing additional oxygen to form an n-type tin dioxide phase. The oxidation process can be realized by annealing at temperature as low as 190 °C in air, which is significantly lower than the temperature generally required to form tin dioxide. Based on this approach, CMOS inverters based entirely on tin oxide TFTs were fabricated. Our method provides a solution to lower the process temperature for tin dioxide phase, which facilitates the application of this transparent oxide semiconductor in emerging electronic devices field.

  7. Formation of Ideal Rashba States on Layered Semiconductor Surfaces Steered by Strain Engineering

    SciTech Connect

    Ming, Wenmei; Wang, Z. F.; Zhou, Miao; Yoon, Mina; Liu, Feng

    2015-12-10

    Spin splitting of Rashba states in two-dimensional electron system provides a mechanism of spin manipulation for spintronics applications. However, Rashba states realized experimentally to date are often outnumbered by spin-degenerated substrate states at the same energy range, hindering their practical applications. Here, by density functional theory calculation, we show that Au one monolayer film deposition on a layered semiconductor surface β-InSe(0001) can possess “ideal” Rashba states with large spin splitting, which are completely situated inside the large band gap of the substrate. The position of the Rashba bands can be tuned over a wide range with respect to the substrate band edges by experimentally accessible strain. Furthermore, our nonequilibrium Green’s function transport calculation shows that this system may give rise to the long-sought strong current modulation when made into a device of Datta-Das transistor. Similar systems may be identified with other metal ultrathin films and layered semiconductor substrates to realize ideal Rashba states.

  8. Formation of Ideal Rashba States on Layered Semiconductor Surfaces Steered by Strain Engineering

    DOE PAGES

    Ming, Wenmei; Wang, Z. F.; Zhou, Miao; Yoon, Mina; Liu, Feng

    2015-12-10

    Spin splitting of Rashba states in two-dimensional electron system provides a mechanism of spin manipulation for spintronics applications. However, Rashba states realized experimentally to date are often outnumbered by spin-degenerated substrate states at the same energy range, hindering their practical applications. Here, by density functional theory calculation, we show that Au one monolayer film deposition on a layered semiconductor surface β-InSe(0001) can possess “ideal” Rashba states with large spin splitting, which are completely situated inside the large band gap of the substrate. The position of the Rashba bands can be tuned over a wide range with respect to the substratemore » band edges by experimentally accessible strain. Furthermore, our nonequilibrium Green’s function transport calculation shows that this system may give rise to the long-sought strong current modulation when made into a device of Datta-Das transistor. Similar systems may be identified with other metal ultrathin films and layered semiconductor substrates to realize ideal Rashba states.« less

  9. Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

    NASA Astrophysics Data System (ADS)

    Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

    2015-09-01

    We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10-2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost.

  10. Vacuum-and-solvent-free fabrication of organic semiconductor layers for field-effect transistors

    PubMed Central

    Matsushima, Toshinori; Sandanayaka, Atula S. D.; Esaki, Yu; Adachi, Chihaya

    2015-01-01

    We demonstrate that cold and hot isostatic pressing (CIP and HIP) is a novel, alternative method for organic semiconductor layer fabrication, where organic powder is compressed into a layer shape directly on a substrate with 200 MPa pressure. Spatial gaps between powder particles and the other particles, substrates, or electrodes are crushed after CIP and HIP, making it possible to operate organic field-effect transistors (OFETs) containing the compressed powder as the semiconductor. The CIP-compressed powder of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) had a hole mobility of (1.6 ± 0.4) × 10–2 cm2/Vs. HIP of C8-BTBT powder increased the hole mobility to an amorphous silicon-like value (0.22 ± 0.07 cm2/Vs) because of the growth of the C8-BTBT crystallites and the improved continuity between the powder particles. The vacuum and solution processes are not involved in our CIP and HIP techniques, offering a possibility of manufacturing OFETs at low cost. PMID:26416434

  11. Damaged silicon contact layer removal using atomic layer etching for deep-nanoscale semiconductor devices

    SciTech Connect

    Kim, Jong Kyu; Cho, Sung Il; Lee, Sung Ho; Kim, Chan Kyu; Min, Kyung Suk; Kang, Seung Hyun; Yeom, Geun Young

    2013-11-15

    Silicon atomic layer etching (ALET) using Cl{sub 2} is applied to remove the damaged layer on a 30 nm contact silicon surface formed by high-energy reactive ions during high aspect ratio contact etching, and its effects on the damage removal characteristics are investigated. Compared to a conventional damage removal method, such as the low-power CF{sub 4} plasma treatment technique, ALET produces less secondary damage to the substrate and gives exact etch depth control and extremely high etch selectivity to the contact SiO{sub 2} insulating pattern mold. When ALET is applied after a conventional damage removal technique, the sheet resistance of the damaged contact silicon surface is improved to a level close to that of a clean silicon surface, while exact atomic-scale depth control is maintained without changes in the pattern mold profile.

  12. Tin disulfide-an emerging layered metal dichalcogenide semiconductor: materials properties and device characteristics.

    PubMed

    Huang, Yuan; Sutter, Eli; Sadowski, Jerzy T; Cotlet, Mircea; Monti, Oliver L A; Racke, David A; Neupane, Mahesh R; Wickramaratne, Darshana; Lake, Roger K; Parkinson, Bruce A; Sutter, Peter

    2014-10-28

    Layered metal dichalcogenides have attracted significant interest as a family of single- and few-layer materials that show new physics and are of interest for device applications. Here, we report a comprehensive characterization of the properties of tin disulfide (SnS2), an emerging semiconducting metal dichalcogenide, down to the monolayer limit. Using flakes exfoliated from layered bulk crystals, we establish the characteristics of single- and few-layer SnS2 in optical and atomic force microscopy, Raman spectroscopy and transmission electron microscopy. Band structure measurements in conjunction with ab initio calculations and photoluminescence spectroscopy show that SnS2 is an indirect bandgap semiconductor over the entire thickness range from bulk to single-layer. Field effect transport in SnS2 supported by SiO2/Si suggests predominant scattering by centers at the support interface. Ultrathin transistors show on-off current ratios >10(6), as well as carrier mobilities up to 230 cm(2)/(V s), minimal hysteresis, and near-ideal subthreshold swing for devices screened by a high-k (deionized water) top gate. SnS2 transistors are efficient photodetectors but, similar to other metal dichalcogenides, show a relatively slow response to pulsed irradiation, likely due to adsorbate-induced long-lived extrinsic trap states.

  13. Activation of molecular catalysts using semiconductor quantum dots

    DOEpatents

    Meyer, Thomas J.; Sykora, Milan; Klimov, Victor I.

    2011-10-04

    Photocatalytic materials based on coupling of semiconductor nanocrystalline quantum dots (NQD) and molecular catalysts. These materials have capability to drive or catalyze non-spontaneous chemical reactions in the presence of visible radiation, ultraviolet radiation, or both. The NQD functions in these materials as a light absorber and charge generator. Following light absorption, the NQD activates a molecular catalyst adsorbed on the surface of the NQD via transfer of one or more charges (either electrons or electron-holes) from the NQD to the molecular catalyst. The activated molecular catalyst can then drive a chemical reaction. A photoelectrolytic device that includes such photocatalytic materials is also described.

  14. Active RF Pulse Compression Using An Electrically Controlled Semiconductor Switch

    SciTech Connect

    Guo, Jiquan; Tantawi, Sami; /SLAC

    2007-01-10

    First we review the theory of active pulse compression systems using resonant delay lines. Then we describe the design of an electrically controlled semiconductor active switch. The switch comprises an active window and an overmoded waveguide three-port network. The active window is based on a four-inch silicon wafer which has 960 PIN diodes. These are spatially combined in an overmoded waveguide. We describe the philosophy and design methodology for the three-port network and the active window. We then present the results of using this device to compress 11.4 GHz RF signals with high compression ratios. We show how the system can be used with amplifier like sources, in which one can change the phase of the source by manipulating the input to the source. We also show how the active switch can be used to compress a pulse from an oscillator like sources, which is not possible with passive pulse compression systems.

  15. Nanoscale semiconductor Pb1-xSnxSe (x = 0.2) thin films synthesized by electrochemical atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Lin, Shaoxiong; Zhang, Xin; Shi, Xuezhao; Wei, Jinping; Lu, Daban; Zhang, Yuzhen; Kou, Huanhuan; Wang, Chunming

    2011-04-01

    In this paper the fabrication and characterization of IV-VI semiconductor Pb1-xSnxSe (x = 0.2) thin films on gold substrate by electrochemical atomic layer deposition (EC-ALD) method at room temperature are reported. Cyclic voltammetry (CV) is used to determine approximate deposition potentials for each element. The amperometric I-t technique is used to fabricate the semiconductor alloy. The elements are deposited in the following sequence: (Se/Pb/Se/Pb/Se/Pb/Se/Pb/Se/Sn …), each period is formed using four ALD cycles of PbSe followed by one cycle of SnSe. Then the deposition manner above is cyclic repeated till a satisfactory film with expected thickness of Pb1-xSnxSe is obtained. The morphology of the deposit is observed by field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) pattern is used to study its crystalline structure; X-ray photoelectron spectroscopy (XPS) of the deposit indicates an approximate ratio 1.0:0.8:0.2 of Se, Pb and Sn, as the expected stoichiometry for the deposit. Open-circuit potential (OCP) studies indicate a good p-type property, and the good optical activity makes it suitable for fabricating a photoelectric switch.

  16. Mesoporous layer-by-layer ordered nanohybrids of layered double hydroxide and layered metal oxide: highly active visible light photocatalysts with improved chemical stability.

    PubMed

    Gunjakar, Jayavant L; Kim, Tae Woo; Kim, Hyo Na; Kim, In Young; Hwang, Seong-Ju

    2011-09-28

    Mesoporous layer-by-layer ordered nanohybrids highly active for visible light-induced O(2) generation are synthesized by self-assembly between oppositely charged 2D nanosheets of Zn-Cr-layered double hydroxide (Zn-Cr-LDH) and layered titanium oxide. The layer-by-layer ordering of two kinds of 2D nanosheets is evidenced by powder X-ray diffraction and cross-sectional high resolution-transmission electron microscopy. Upon the interstratification process, the original in-plane atomic arrangements and electronic structures of the component nanosheets remain intact. The obtained heterolayered nanohybrids show a strong absorption of visible light and a remarkably depressed photoluminescence signal, indicating an effective electronic coupling between the two component nanosheets. The self-assembly between 2D inorganic nanosheets leads to the formation of highly porous stacking structure, whose porosity is controllable by changing the ratio of layered titanate/Zn-Cr-LDH. The resultant heterolayered nanohybrids are fairly active for visible light-induced O(2) generation with a rate of ∼1.18 mmol h(-1) g(-1), which is higher than the O(2) production rate (∼0.67 mmol h(-1) g(-1)) by the pristine Zn-Cr-LDH material, that is, one of the most effective visible light photocatalysts for O(2) production, under the same experimental condition. This result highlights an excellent functionality of the Zn-Cr-LDH-layered titanate nanohybrids as efficient visible light active photocatalysts. Of prime interest is that the chemical stability of the Zn-Cr-LDH is significantly improved upon the hybridization, a result of the protection of the LDH lattice by highly stable titanate layer. The present findings clearly demonstrate that the layer-by-layer-ordered assembly between inorganic 2D nanosheets is quite effective not only in improving the photocatalytic activity of the component semiconductors but also in synthesizing novel porous LDH-based hybrid materials with improved chemical

  17. Substrate-emitting semiconductor laser with a trapezoidal active region

    SciTech Connect

    Dikareva, N V; Nekorkin, S M; Karzanova, M V; Zvonkov, B N; Aleshkin, V Ya; Dubinov, A A; Afonenko, A A

    2014-04-28

    Semiconductor lasers with a narrow (∼2°) directional pattern in the planes both parallel and perpendicular to the p–n junction are fabricated. To achieve a low radiation divergence in the p–n junction plane, the active region in this plane was designed in the form of a trapezium. The narrow directional pattern in the plane perpendicular to the p–n junction was ensured by the use of a leaky mode, through which more than 90% of laser power was coupled out. (lasers)

  18. Chemical vapor deposition of thin crystals of layered semiconductor SnS2 for fast photodetection application.

    PubMed

    Su, Guoxiong; Hadjiev, Viktor G; Loya, Phillip E; Zhang, Jing; Lei, Sidong; Maharjan, Surendra; Dong, Pei; M Ajayan, Pulickel; Lou, Jun; Peng, Haibing

    2015-01-14

    Layered two-dimensional (2D) semiconductors, such as MoS(2) and SnS(2), have been receiving intensive attention due to their technological importance for the next-generation electronic/photonic applications. We report a novel approach to the controlled synthesis of thin crystal arrays of SnS(2) at predefined locations on chip by chemical vapor deposition with seed engineering and have demonstrated their application as fast photodetectors with photocurrent response time ∼ 5 μs. This opens a pathway for the large-scale production of layered 2D semiconductor devices, important for applications in integrated nanoelectronic/photonic systems.

  19. Photoprecursor Approach Enables Preparation of Well-Performing Bulk-Heterojunction Layers Comprising a Highly Aggregating Molecular Semiconductor.

    PubMed

    Suzuki, Mitsuharu; Yamaguchi, Yuji; Takahashi, Kohei; Takahira, Katsuya; Koganezawa, Tomoyuki; Masuo, Sadahiro; Nakayama, Ken-ichi; Yamada, Hiroko

    2016-04-01

    Active-layer morphology critically affects the performance of organic photovoltaic cells, and thus its optimization is a key toward the achievement of high-efficiency devices. However, the optimization of active-layer morphology is sometimes challenging because of the intrinsic properties of materials such as strong self-aggregating nature or low miscibility. This study postulates that the "photoprecursor approach" can serve as an effective means to prepare well-performing bulk-heterojunction (BHJ) layers containing highly aggregating molecular semiconductors. In the photoprecursor approach, a photoreactive precursor compound is solution-deposited and then converted in situ to a semiconducting material. This study employs 2,6-di(2-thienyl)anthracene (DTA) and [6,6]-phenyl-C71-butyric acid methyl ester as p- and n-type materials, respectively, in which DTA is generated by the photoprecursor approach from the corresponding α-diketone-type derivative DTADK. When only chloroform is used as a cast solvent, the photovoltaic performance of the resulting BHJ films is severely limited because of unfavorable film morphology. The addition of a high-boiling-point cosolvent, o-dichlorobenzene (o-DCB), to the cast solution leads to significant improvement such that the resulting active layers afford up to approximately 5 times higher power conversion efficiencies. The film structure is investigated by two-dimensional grazing-incident wide-angle X-ray diffraction, atomic force microscopy, and fluorescence microspectroscopy to demonstrate that the use of o-DCB leads to improvement in film crystallinity and increase in charge-carrier generation efficiency. The change in film structure is assumed to originate from dynamic molecular motion enabled by the existence of solvent during the in situ photoreaction. The unique features of the photoprecursor approach will be beneficial in extending the material and processing scopes for the development of organic thin-film devices. PMID

  20. Defect detection in semiconductor layers with built-in electric field with the use of cathodoluminescence

    NASA Astrophysics Data System (ADS)

    Pluska, Mariusz; Czerwinski, Andrzej; Ratajczak, Jacek; Szerling, Anna; Kątcki, Jerzy

    2012-08-01

    Cathodoluminescence (CL) in scanning electron microscopy (SEM) is commonly accepted as revealing local properties of a specimen region illuminated by an electron beam. CL is widely used to visualize defects in semiconductor structures. However, the presence of a strong electric field in, for example, heterojunctions or p-n junctions causes a separation of generated electron-hole (e-h) pairs and suppresses recombination in the specimen region excited by the beam. As a result CL - a radiative recombination - becomes quenched. At the same time, electron beam-induced current (EBIC) flows throughout the structure, which may produce secondary electroluminescence that is registered by the CL detector. Consequently, the CL measurement is distorted and if there are defects in the structure, they remain unrevealed. The current study shows that registration of the CL signal for different values of electron beam current (including high ones) enables true defect detection in semiconductor layers with built-in electric field. Results for a special test structure prepared with focused ion beam on AlGaAs/GaAs laser heterostructures with an 8 nm InGaAs quantum well are presented.

  1. Semiconductor laser diode

    SciTech Connect

    Amann, M.C.

    1982-09-28

    A semiconductor laser diode is disclosed with a connection electrode consisting of a chromium/gold alloy on a highly-doped gallium arsenide layer. The gallium arsenide layer is strip shaped and overlies a further lesser doped layer of gallium aluminum arsenide. The chromium/gold contact has a low-resistance junction only in the region of the more highly doped layer so that a strip shaped restriction of the current path occurs in the semiconductor body. Accordingly, a laser-active zone which is only strip-shaped is achieved.

  2. Size-dependent ligand layer dynamics in semiconductor nanocrystals probed by anisotropy measurements.

    PubMed

    Hadar, Ido; Abir, Tsafrir; Halivni, Shira; Faust, Adam; Banin, Uri

    2015-10-12

    Colloidal semiconductor nanocrystals (NC) have reached a high level of synthetic control allowing the tuning of their properties, and their use in various applications. However, the surface of NCs and in particular their size-dependent capping organic ligand behavior, which play an important role in the NC synthesis, dispersibility, and optoelectronic properties, is still not well understood. We study the size-dependent properties of the ligand shell on the surface of NCs, by embedding surface bound dyes as a probe within the ligand shell. The reorientation times for these dyes show a linear dependence on the NC surface curvature indicating size-dependent change in viscosity, which is related to a change in the density of the ligand layer because of the geometry of the surface, a unique feature of NCs. Understanding the properties of the ligand shell will allow rational design of the surface to achieve the desired properties, providing an additional important knob for tuning their functionality.

  3. 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.

  4. Investigation of the uncertainties of the estimated optical constants and thickness of very thin semiconductor layers

    NASA Astrophysics Data System (ADS)

    Gushterova, P.; Hristov, B.; Sharlandjiev, P.

    2010-04-01

    We recently developed an approach to the estimation of the complex permittivity (epsilon) and thickness (d) of very thin layers using measurements of their transmittance, front-side reflectance and back-side reflectance. The approach is based on a limited expansion of the Abelès characteristic matrix elements and is especially designed for characterization of very thin layers. In this paper we investigate the uncertainties of the estimated real part of epsilon (epsilon1), the imaginary part of epsilon (epsilon2) and d of semiconductor thin layers that are due to the methodological error and the experimental uncertainties in the optical quantities measured. It is shown that the effect of the uncertainties in the measurable quantities is significantly stronger than that of the methodical error and increases considerably with the decrease of the ratio d/λ (λ being the wavelength). An efficient two-step procedure is proposed to reduce this effect. First, we supply a criterion for determination of d with the lowest uncertainty from the ensemble of estimations constructed on a wavelength by wavelength basis. This is crucial for the next step: the estimation of epsilon1 and epsilon2. The approach proposed ensures estimation of epsilon1, epsilon2 and d with the highest accuracy, limited only by the methodological error.

  5. Nitrogen-doped amorphous oxide semiconductor thin film transistors with double-stacked channel layers

    NASA Astrophysics Data System (ADS)

    Xie, Haiting; Wu, Qi; Xu, Ling; Zhang, Lei; Liu, Guochao; Dong, Chengyuan

    2016-11-01

    The amorphous oxide semiconductor (AOS) thin film transistors (TFTs) with the double-stacked channel layers (DSCL) combing the amorphous InZnO (a-IZO) films and the nitrogen-doped amorphous InGaZnO (a-IGZO:N) films were proposed and fabricated, which showed the excellent performance with the field-effect mobility of 49.6 cm2 V-1 s-1 and the subthreshold swing of 0.5 V/dec. More interestingly, very stable properties were observed in the bias stress and light illumination tests for these a-IZO/a-IGZO:N TFTs, as seemed to be the evident improvements over the prior arts. The improved performance and stability might be mainly due to the hetero-junctions in the channel layers and less interface/bulk trap density from the in situ nitrogen doping process in the a-IGZO layers. In addition, the passivation effect of the a-IGZO:N films also made some contributions to the stable properties exhibited in these novel DSCL TFTs.

  6. A metal-oxide-semiconductor radiation dosimeter with a thick and defect-rich oxide layer

    NASA Astrophysics Data System (ADS)

    Liu, Hongrui; Yang, Yuhao; Zhang, Jinwen

    2016-04-01

    Enhancing the density of defects in the oxide layer is the main factor in improving the sensitivity of a metal-oxide-semiconductor (MOS) radiation dosimeter. This paper reports a novel MOS dosimeter with a very thick and defect-rich oxide layer fabricated by MEMS technology. The category of defects in SiO2 and their possible effect on the radiation dose sensing was analyzed. Then, we proposed combining deep-reactive-ion etching, thermal oxidation and low pressure chemical vapor deposition to realize an oxide layer containing multiple and large interfaces which can increase defects significantly. The trench-and-beam structure of silicon was considered in detail. The fabrication process was developed for obtaining a thick and compact MEMS-made SiO2. Our devices were irradiated by γ-rays of 60Co at 2 Gy per minute for 2 h and a thermally stimulated current (TSC) method was used to determine the readout of the dosimeters. Results show that there is a peak current of about 450 nA, indicating a total TSC charge of 158 μC and sensitivity of 1.1 μC mm-3·Gy, which is 40 times the sensitivity of previous MOS dosimeters.

  7. Broadband ultrafast nonlinear absorption and nonlinear refraction of layered molybdenum dichalcogenide semiconductors.

    PubMed

    Wang, Kangpeng; Feng, Yanyan; Chang, Chunxia; Zhan, Jingxin; Wang, Chengwei; Zhao, Quanzhong; Coleman, Jonathan N; Zhang, Long; Blau, Werner J; Wang, Jun

    2014-09-21

    A series of layered molybdenum dichalcogenides, i.e., MoX₂ (X = S, Se and Te), were prepared in cyclohexyl pyrrolidinone by a liquid-phase exfoliation technique. The high quality of the two-dimensional nanostructures was verified by transmission electron microscopy and absorption spectroscopy. Open- and closed-aperture Z-scans were employed to study the nonlinear absorption and nonlinear refraction of the MoX₂ dispersions, respectively. All the three-layered nanostructures exhibit prominent ultrafast saturable absorption (SA) for both femtosecond (fs) and picosecond (ps) laser pulses over a broad wavelength range from the visible to the near infrared. While the dispersions treated with low-speed centrifugation (1500 rpm) have an SA response, and the MoS₂ and MoSe₂ dispersions after higher speed centrifugation (10,000 rpm) possess two-photon absorption for fs pulses at 1030 nm, which is due to the significant reduction of the average thickness of the nanosheets; hence, the broadening of band gap. In addition, all dispersions show obvious nonlinear self-defocusing for ps pulses at both 1064 nm and 532 nm, resulting from the thermally-induced nonlinear refractive index. The versatile ultrafast nonlinear properties imply a huge potential of the layered MoX2 semiconductors in the development of nanophotonic devices, such as mode-lockers, optical limiters, optical switches, etc. PMID:25097043

  8. X-ray photoemission study of manganese thin films deposited on a layered semiconductor

    NASA Astrophysics Data System (ADS)

    Mirabella, F.; Parkinson, B. A.; Ghijsen, J.

    2004-02-01

    Germanium sulphide (GeS) and tin diselenide (SnSe2) present anisotropic properties due to their layered crystal structures. These crystals are composed of atomic layers interacting with each other by van der Waals forces only. Recently these materials have been used to prepare a new diluted magnetic semiconductor (DMS) by substituting some Ge or Sn atoms by manganese in the crystal lattice, forming Ge1-xMnxS and Sn1-xMnxSe2. To compare Mn behaviour within the layered crystals, Mn/GeS and Mn/SnSe2 thin films have been grown and investigated in situ by X-ray induced photoemission. Here is reported the XPS analysis of in situ grown Mn/SnSe2 for coverage ranging from sub-monolayer to thin films. The properties of these films were investigated from the structural and reactivity point of view. XPS measurements suggest that an Mn-Sn alloy is formed at the interface and that Mn atoms first deposit as an atomic netting pattern dictated by the typical structure of the SnSe2 (001) surface.

  9. Analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma

    SciTech Connect

    Shukla, Arun; Jat, K. L.

    2015-07-31

    An analytical study of acoustically perturbed Brillouin active magnetized semiconductor plasma has been reported. In the present analytical investigation, the lattice displacement, acousto-optical polarization, susceptibility, acousto-optical gain constant arising due to the induced nonlinear current density and acousto-optical process are deduced in an acoustically perturbed Brillouin active magnetized semiconductor plasma using the hydrodynamical model of plasma and coupled mode scheme. The influence of wave number and magnetic field has been explored. The analysis has been applied to centrosymmetric crystal. Numerical estimates are made for n-type InSb crystal duly irradiated by a frequency doubled 10.6 µm CO{sub 2} laser. It is found that lattice displacement, susceptibility and acousto-optical gain increase linearly with incident wave number and applied dc magnetic field, while decrease with scattering angle. The gain also increases with electric amplitude of incident laser beam. Results are found to be well in agreement with available literature.

  10. Raman spectra of semiconductor nanoparticles: Disorder-activated phonons

    NASA Astrophysics Data System (ADS)

    Ingale, Alka; Rustagi, K. C.

    1998-09-01

    We present Raman spectra of four semiconductor doped glasses and a single crystal of CdS0.55Se0.45 in the range 30-800 cm-1 in the backscattering geometry. This includes the first-order Raman scattering from the disorder-activated zone-edge phonons and the LO phonons. TO phonon modes are not observed, as in bulk CdS, for the excitation well above the lowest gap. We show that the asymmetric line profile of the LO phonon structure can be understood as a composite of two phonon modes: the zone center and the zone edge phonons. Disorder-activated modes in the (30-130)-cm-1 range and the higher-order Raman spectra are also observed and found to be consistent with this assignment.

  11. Method for sputtering a PIN amorphous silicon semi-conductor device having partially crystallized P and N-layers

    DOEpatents

    Moustakas, Theodore D.; Maruska, H. Paul

    1985-07-09

    A high efficiency amorphous silicon PIN semiconductor device having partially crystallized (microcrystalline) P and N layers is constructed by the sequential sputtering of N, I and P layers and at least one semi-transparent ohmic electrode. The method of construction produces a PIN device, exhibiting enhanced electrical and optical properties, improved physical integrity, and facilitates the preparation in a singular vacuum system and vacuum pump down procedure.

  12. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    PubMed Central

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  13. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors.

    PubMed

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III-V, and II-VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain-low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  14. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Zhang, Yong

    2016-04-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side.

  15. Nucleation and growth of dielectric films on III-V semiconductors during atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Granados Alpizar, Bernal

    In order to continue with metal-oxide-semiconductors (CMOS) transistor scaling and to reduce the power density, the channel should be replaced with a material having a higher electron mobility, such as a III-V semiconductor. However, the integration of III-V's is a challenge because these materials oxidize rapidly when exposed to air and the native oxide produced is characterized by a high density of defects. Deposition of high-k materials on III-V semiconductors using Atomic Layer Deposition (ALD) reduces the thickness of these oxides, improving the semiconductor/oxide interface quality and the transistor electrical characteristics. In this work, ALD is used to deposit two dielectrics, Al 2O3 and TiO2, on two III-V materials, GaAs and InGaAs, and in-situ X-ray photoelectron spectroscopy (XPS) and in-situ thermal programmed desorption (TPD) are used for interface characterization. Hydrofluoric acid (HF) etching of GaAs(100) and brief reoxidation in air produces a 9.0 ±1.6 Å-thick oxide overlayer containing 86% As oxides. The oxides are removed by 1 s pulses of trimethylaluminum (TMA) or TiCl4. TMA removes the oxide overlayer while depositing a 7.5 ± 1.6 Å thick aluminum oxide. The reaction follows a ligand exchange mechanism producing nonvolatile Al-O species that remain on the surface. TiCl4 exposure removes the oxide overlayer in the temperature range 89°C to 300°C, depositing approximately 0.04 monolayer of titanium oxide for deposition temperatures from 89°C to 135°C, but no titanium oxide is present from 170 °C to 230 °C. TiCl4 forms a volatile oxychloride product and removes O from the surface while leaving Cl atoms adsorbed to an elemental As layer, chemically passivating the surface. The native oxide of In0.53Ga0.47As(100) is removed using liquid HF and gas phase HF before deposition of Al2O3 using TMA and H2O at 170 °C. An aluminium oxide film with a thickness of 7.2 ± 1.2 Å and 7.3 ± 1.2 Å is deposited during the first pulse of TMA on

  16. On a chaotic potential at the surface of a compensated semiconductor under conditions of the self-assembly of electrically active defects

    SciTech Connect

    Bondarenko, V. B. Filimonov, A. V.

    2015-09-15

    Natural irregularities of the electric potential on the surface of a semiconductor under conditions of the partial self-assembly of electrically active defects, i.e., on the formation of donor–acceptor pairs in depletion layers, are studied. The amplitude and character of the spatial distribution of the chaotic potential on the surface of a semiconductor in the cases of localized and delocalized states are determined. The dependence of the amplitude of the chaotic potential on the degree of compensation of the semiconductor is obtained.

  17. Interconnected semiconductor devices

    DOEpatents

    Grimmer, Derrick P.; Paulson, Kenneth R.; Gilbert, James R.

    1990-10-23

    Semiconductor layer and conductive layer formed on a flexible substrate, divided into individual devices and interconnected with one another in series by interconnection layers and penetrating terminals.

  18. Semiconductor thin film transfer by wafer bonding and advanced ion implantation layer splitting technologies

    NASA Astrophysics Data System (ADS)

    Lee, Tien-Hsi

    Wafer bonding is an attractive technology for modern semiconductor and microelectronic industry due to its variability in allowing combination of materials. Initially, the bonding of wafers of the same material, such as silicon-silicon wafer bonding has been major interest. In the meantime, research interest has shifted to the bonding of dissimilar materials such as silicon to quartz or to sapphire. Thermal stress coming from the different expansion coefficients usually is a barrier to the success of dissimilar material bonding. Thermal stress may cause debonding, sliding, cracking, thermal misfit dislocations, or film wrinkle to impair the quality of the transferred layer. This dissertation presents several effective approaches to solve the thermal stress problem. These approaches concern bonding processes (low vacuum bonding and storage), thinning (advanced ion implantation layer splitting), and annealing processes (accumulative effect of blister generation) and are combined to design the best heat-treatment cycle. For this propose the concept of hot bonding is used in order to effectively minimize the thermal mismatch of dissimilar material bonding during the bonding and thinning procedures. During the initial bonding and bond strengthening phase, the difference in the temperature between bonding and annealing processes should be decreased as much as possible to avoid excessive thermal stresses. This concept can be realized either by increasing the bonding temperature or by decreasing the annealing temperature. A thinning technique has to employed that can thin the device wafer before debonding occurs due to the thermal stress generated either from the cooling-down process in the first case or by the annealing process itself in the late case. The ion implantation layer splitting method, also known as the Smart-cutsp°ler process, developed by Bruel at LEIT in France is a practical thinning technique which satisfies the above requirement. In the study, an

  19. Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction.

    PubMed

    Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

    2016-01-01

    Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport. PMID:27515115

  20. Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction

    PubMed Central

    Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

    2016-01-01

    Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport. PMID:27515115

  1. 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

  2. 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

  3. Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

    2016-08-01

    Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport.

  4. Infrared reflection-absorption spectroscopy of hyperfine layers on surfaces of semiconductors and dielectrics

    NASA Astrophysics Data System (ADS)

    Gruzinov, S. N.; Tolstoy, V. P.

    1988-02-01

    Infrared reflection-absorption spectroscopy of film son surfaces of transparent or weakly absorbing semiconductor and dielectric substrates is analyzed theoretically, the purpose being to establish the conditions for maximum sensitivity of this method. The absorption factor, namely the relative change of the reflection coefficient upon formation of a film on the substrate surface, is selected as the sensitivity criterion. The analysis is based on exact relations, one for a homogeneous isotopic absorbing film between substrate and ambient medium with plane-parallel boundaries and one for a reflecting layer with the possibility of multiple reflections taken into account. Calculations have been programmed on a computer for up to 60 nm thick SiO2 films on various substrates and infrared radiation within the 8 to 11 gmm waveband. The results indicate that the dependence of the absorption factor on the radiation wavelength and on the film thickness is different with the radiation s-polarized than with the radiation p-polarized. Calculations have also yielded the dispersion of optical constants characterizing a SiO2 film. According to these results, infrared spectroscopy is most sensitive to films on substrates with a small refractive index and when done with p-polarized radiation incident at exactly or approximately the Brewster angle for a determination of their presence and their composition respectively, also when no multiple reflections occur.

  5. Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction.

    PubMed

    Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

    2016-08-12

    Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport.

  6. Interfacial insertion of a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) layer between the poly(3-hexyl thiophene) semiconductor and cross-linked poly(vinyl alcohol) insulator layer in organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Cruz-Cruz, Isidro; Tavares, Ana C. B.; Reyes-Reyes, Marisol; López-Sandoval, Román; Hümmelgen, Ivo A.

    2014-02-01

    The role of a thin layer of conductive poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT : PSS), inserted between the gate dielectric and the active layer in poly(3-hexylthiophene)-based transistors was investigated. The devices were fabricated in the bottom-gate top-contact geometry by using cross-linked poly(vinyl alcohol) as the dielectric, whereas the PEDOT : PSS layer was prepared by using an aged aqueous dispersion with addition of different amounts of dimethyl sulfoxide (DMSO) as a secondary dopant. Under these conditions, both a significant reduction in the number of electrically active traps at the interface with the semiconductor and an improvement in the field-effect mobility were obtained, whereas the low power consumption was preserved. The threshold voltage was also displaced by approximately -1 V.

  7. Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

    SciTech Connect

    Balliou, A.; Douvas, A. M.; Normand, P.; Argitis, P.; Glezos, N.; Tsikritzis, D.; Kennou, S.

    2014-10-14

    In this work we study the utilization of molecular transition metal oxides known as polyoxometalates (POMs), in particular the Keggin structure anions of the formula PW₁₂O₄₀³⁻, as active nodes for potential switching and/or fast writing memory applications. The active molecules are being integrated in hybrid Metal-Insulator/POM molecules-Semiconductor capacitors, which serve as prototypes allowing investigation of critical performance characteristics towards the design of more sophisticated devices. The charging ability as well as the electronic structure of the molecular layer is probed by means of electrical characterization, namely, capacitance-voltage and current-voltage measurements, as well as transient capacitance measurements, C (t), under step voltage polarization. It is argued that the transient current peaks observed are manifestations of dynamic carrier exchange between the gate electrode and specific molecular levels, while the transient C (t) curves under conditions of molecular charging can supply information for the rate of change of the charge that is being trapped and de-trapped within the molecular layer. Structural characterization via surface and cross sectional scanning electron microscopy as well as atomic force microscopy, spectroscopic ellipsometry, UV and Fourier-transform IR spectroscopies, UPS, and XPS contribute to the extraction of accurate electronic structure characteristics and open the path for the design of new devices with on-demand tuning of their interfacial properties via the controlled preparation of the POM layer.

  8. Hydrothermal regimes of the dry active layer

    NASA Astrophysics Data System (ADS)

    Ishikawa, Mamoru; Zhang, Yinsheng; Kadota, Tsutomu; Ohata, Tetsuo

    2006-04-01

    Evaporation and condensation in the soil column clearly influence year-round nonconductive heat transfer dynamics in the dry active layer underlying semiarid permafrost regions. We deduced this from heat flux components quantified using state-of-the-art micrometeorological data sets obtained in dry and moist summers and in winters with various snow cover depths. Vapor moves easily through large pores, some of which connect to the atmosphere, allowing (1) considerable active layer warming driven by pipe-like snowmelt infiltration, and (2) direct vapor linkage between atmosphere and deeper soils. Because of strong adhesive forces, water in the dry active layer evaporates with great difficulty. The fraction of latent heat to total soil heat storage ranged from 26 to 45% in dry and moist summers, respectively. These values are not negligible, despite being smaller than those of arctic wet active layer, in which only freezing and thawing were considered.

  9. Correlation of Photocatalytic Activity with Band Structure of Low-dimensional Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Meng, Fanke

    Photocatalytic hydrogen generation by water splitting is a promising technique to produce clean and renewable solar fuel. The development of effective semiconductor photocatalysts to obtain efficient photocatalytic activity is the key objective. However, two critical reasons prevent wide applications of semiconductor photocatalysts: low light usage efficiency and high rates of charge recombination. In this dissertation, several low-dimensional semiconductors were synthesized with hydrothermal, hydrolysis, and chemical impregnation methods. The band structures of the low-dimensional semiconductor materials were engineered to overcome the above mentioned two shortcomings. In addition, the correlation between the photocatalytic activity of the low-dimensional semiconductor materials and their band structures were studied. First, we studied the effect of oxygen vacancies on the photocatalytic activity of one-dimensional anatase TiO2 nanobelts. Given that the oxygen vacancy plays a significant role in band structure and photocatalytic performance of semiconductors, oxygen vacancies were introduced into the anatase TiO2 nanobelts during reduction in H2 at high temperature. The oxygen vacancies of the TiO2 nanobelts boosted visible-light-responsive photocatalytic activity but weakened ultraviolet-light-responsive photocatalytic activity. As oxygen vacancies are commonly introduced by dopants, these results give insight into why doping is not always beneficial to the overall photocatalytic performance despite increases in absorption. Second, we improved the photocatalytic performance of two-dimensional lanthanum titanate (La2Ti2 O7) nanosheets, which are widely studied as an efficient photocatalyst due to the unique layered crystal structure. Nitrogen was doped into the La2Ti2O7 nanosheets and then Pt nanoparticles were loaded onto the La2Ti2O7 nanosheets. Doping nitrogen narrowed the band gap of the La2Ti 2O7 nanosheets by introducing a continuum of states by the valence

  10. Dopant in Near-Surface Semiconductor Layers of Metal-Insulator-Semiconductor Structures Based on Graded-Gap p-Hg0.78Cd0.22Te Grown by Molecular-Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.

    2016-02-01

    Peculiarities in determining the dopant concentration and dopant distribution profile in the near-surface layer of a semiconductor are investigated by measuring the admittance of metal-insulator-semiconductor structures (MIS structures) based on p-Hg0.78Cd0.22Te grown by molecular beam epitaxy. The dopant concentrations in the near-surface layer of the semiconductor are determined by measuring the admittance of MIS structures in the frequency range of 50 kHz to 1 MHz. It is shown that in this frequency range, the capacitance-voltage characteristics of MIS structures based on p-Hg0.78Cd0.22Te with a near-surface graded gap layer demonstrate a high-frequency behavior with respect to the recharge time of surface states located near the Fermi level for an intrinsic semiconductor. The formation time of the inversion layer is decreased by less than two times, if a near-surface graded-gap layer is created. The dopant distribution profile in the near-surface layer of the semiconductor is found, and it is shown that for structures based on p-Hg0.78Cd0.22Te with a near-surface graded-gap layer, the dopant concentration has a minimum near the interface with the insulator. For MIS structure based on n-Hg0.78Cd0.22Te, the dopant concentration is more uniformly distributed in the near-surface layer of the semiconductor.

  11. Assembly of a high-dielectric constant thin TiOx layer directly on H-terminated semiconductor diamond

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Liu, Jiangwei; Sang, Liwen; Liao, Meiyong; Coathup, David; Imura, Masataka; Shi, Baogui; Gu, Changzhi; Koide, Yasuo; Ye, Haitao

    2016-01-01

    A high-dielectric constant (high-k) TiOx thin layer was fabricated on hydrogen-terminated diamond (H-diamond) surface by low temperature oxidation of a thin titanium layer in ambient air. The metallic titanium layer was deposited by sputter deposition. The dielectric constant of the resultant TiOx was calculated to be around 12. The capacitance density of the metal-oxide-semiconductor (MOS) based on the TiOx/H-diamond was as high as 0.75 μF/cm2 contributed from the high-k value and the very thin thickness of the TiOx layer. The leakage current was lower than 10-13 A at reverse biases and 10-7A at the forward bias of -2 V. The MOS field-effect transistor based on the high-k TiOx/H-diamond was demonstrated. The utilization of the high-k TiOx with a very thin thickness brought forward the features of an ideally low subthreshold swing slope of 65 mV per decade and improved drain current at low gate voltages. The advantages of the utilization high-k dielectric for diamond metal-oxide semiconductor field effect transistors are anticipated.

  12. The effect of the annealing temperature on the transition from conductor to semiconductor behavior in zinc tin oxide deposited atomic layer deposition

    SciTech Connect

    Ahn, Byung Du; Choi, Dong-won Choi, Changhwan; Park, Jin-Seong

    2014-09-01

    We investigated the electrical properties of zinc tin oxide (ZTO) films deposited via atomic layer deposition and compared them to ZnO and SnO{sub 2} films as a function of the annealing temperature. The ZTO and ZnO, except for SnO{sub 2}, films exhibited an electrical transition from a metal to semiconductor characteristics when annealed above 300 °C. The X-ray photoelectron spectroscopy analyses indicate that the relative area of the oxygen vacancy-related peak decreased from 58% to 41% when annealing at temperatures above 400 °C. Thin film transistors incorporating ZTO active layers demonstrated a mobility of 13.2 cm{sup 2}/V s and a negative bias instability of −0.2 V.

  13. Method for making photovoltaic devices using oxygenated semiconductor thin film layers

    SciTech Connect

    Johnson, James Neil; Albin, David Scott; Feldman-Peabody, Scott; Pavol, Mark Jeffrey; Gossman, Robert Dwayne

    2014-12-16

    A method for making a photovoltaic device is presented. The method includes steps of disposing a window layer on a substrate and disposing an absorber layer on the window layer. Disposing the window layer, the absorber layer, or both layers includes introducing a source material into a deposition zone, wherein the source material comprises oxygen and a constituent of the window layer, of the absorber layer or of both layers. The method further includes step of depositing a film that comprises the constituent and oxygen.

  14. Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

    SciTech Connect

    Abbott, Robert; Knox, Hunter Anne; James, Stephanie; Lee, Rebekah; Cole, Chris

    2016-01-01

    We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.

  15. Layer-by-layer nanoencapsulation of camptothecin with improved activity.

    PubMed

    Parekh, Gaurav; Pattekari, Pravin; Joshi, Chaitanya; Shutava, Tatsiana; DeCoster, Mark; Levchenko, Tatyana; Torchilin, Vladimir; Lvov, Yuri

    2014-04-25

    160 nm nanocapsules containing up to 60% of camptothecin in the core and 7-8 polyelectrolyte bilayers in the shell were produced by washless layer-by-layer assembly of heparin and block-copolymer of poly-l-lysine and polyethylene glycol. The outer surface of the nanocapsules was additionally modified with polyethylene glycol of 5 kDa or 20 kDa molecular weight to attain protein resistant properties, colloidal stability in serum and prolonged release of the drug from the capsules. An advantage of the LbL coated capsules is the preservation of camptothecin lactone form with the shell assembly starting at acidic pH and improved chemical stability of encapsulated drug at neutral and basic pH, especially in the presence of albumin that makes such formulation more active than free camptothecin. LbL nanocapsules preserve the camptothecin lactone form at pH 7.4 resulting in triple activity of the drug toward CRL2303 glioblastoma cell. PMID:24508806

  16. Layer-by-layer nanoencapsulation of camptothecin with improved activity

    PubMed Central

    Parekh, Gaurav; Pattekari, Pravin; Joshi, Chaitanya; Shutava, Tatsiana; DeCoster, Mark; Levchenko, Tatyana; Torchilin, Vladimir; Lvov, Yuri

    2014-01-01

    160 nm nanocapsules containing up to 60% of camptothecin in the core and 7–8 polyelectrolyte bilayers in the shell were produced by washless layer-by-layer assembly of heparin and block-copolymer of poly-L-lysine and polyethylene glycol. The outer surface of the nanocapsules was additionally modified with polyethylene glycol of 5 kDa or 20 kDa molecular weight to attain protein resistant properties, colloidal stability in serum and prolonged release of the drug from the capsules. An advantage of the LbL coated capsules is the preservation of camptothecin lactone form with the shell assembly starting at acidic pH and improved chemical stability of encapsulated drug at neutral and basic pH, especially in the presence of albumin that makes such formulation more active than free camptothecin. LbL nanocapsules preserve the camptothecin lactone form at pH 7.4 resulting in triple activity of the drug toward CRL2303 glioblastoma cell. PMID:24508806

  17. Scattering efficiency and near field enhancement of active semiconductor plasmonic antennas at terahertz frequencies.

    PubMed

    Giannini, Vincenzo; Berrier, Audrey; Maier, Stefan A; Sánchez-Gil, José Antonio; Rivas, Jaime Gómez

    2010-02-01

    Terahertz plasmonic resonances in semiconductor (indium antimonide, InSb) dimer antennas are investigated theoretically. The antennas are formed by two rods separated by a small gap. We demonstrate that, with an appropriate choice of the shape and dimension of the semiconductor antennas, it is possible to obtain large electromagnetic field enhancement inside the gap. Unlike metallic antennas, the enhancement around the semiconductor plasmonics antenna can be easily adjusted by varying the concentration of free carriers, which can be achieved by optical or thermal excitation of carriers or electrical carrier injection. Such active plasmonic antennas are interesting structures for THz applications such as modulators and sensors.

  18. Scattering efficiency and near field enhancement of active semiconductor plasmonic antennas at terahertz frequencies.

    PubMed

    Giannini, Vincenzo; Berrier, Audrey; Maier, Stefan A; Sánchez-Gil, José Antonio; Rivas, Jaime Gómez

    2010-02-01

    Terahertz plasmonic resonances in semiconductor (indium antimonide, InSb) dimer antennas are investigated theoretically. The antennas are formed by two rods separated by a small gap. We demonstrate that, with an appropriate choice of the shape and dimension of the semiconductor antennas, it is possible to obtain large electromagnetic field enhancement inside the gap. Unlike metallic antennas, the enhancement around the semiconductor plasmonics antenna can be easily adjusted by varying the concentration of free carriers, which can be achieved by optical or thermal excitation of carriers or electrical carrier injection. Such active plasmonic antennas are interesting structures for THz applications such as modulators and sensors. PMID:20174108

  19. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    NASA Astrophysics Data System (ADS)

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-02-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters.

  20. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current.

    PubMed

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-01-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters. PMID:26842997

  1. Sustained hole inversion layer in a wide-bandgap metal-oxide semiconductor with enhanced tunnel current

    PubMed Central

    Shoute, Gem; Afshar, Amir; Muneshwar, Triratna; Cadien, Kenneth; Barlage, Douglas

    2016-01-01

    Wide-bandgap, metal-oxide thin-film transistors have been limited to low-power, n-type electronic applications because of the unipolar nature of these devices. Variations from the n-type field-effect transistor architecture have not been widely investigated as a result of the lack of available p-type wide-bandgap inorganic semiconductors. Here, we present a wide-bandgap metal-oxide n-type semiconductor that is able to sustain a strong p-type inversion layer using a high-dielectric-constant barrier dielectric when sourced with a heterogeneous p-type material. A demonstration of the utility of the inversion layer was also investigated and utilized as the controlling element in a unique tunnelling junction transistor. The resulting electrical performance of this prototype device exhibited among the highest reported current, power and transconductance densities. Further utilization of the p-type inversion layer is critical to unlocking the previously unexplored capability of metal-oxide thin-film transistors, such applications with next-generation display switches, sensors, radio frequency circuits and power converters. PMID:26842997

  2. Nucleation, Growth, and Strain Relaxation of Lattice-Mismatched III-V Semiconductor Epitaxial Layers

    NASA Technical Reports Server (NTRS)

    Welser, R. E.; Guido, L. J.

    1994-01-01

    We have investigated the early stages of evolution of highly strained 2-D InAs layers and 3-D InAs islands grown by metal-organic chemical vapor deposition (MOCVD) on (100) and (111) B GaAs substrates. The InAs epilayer / GaAs substrate combination has been chosen because the lattice-mismatch is severe (approx. 7.20%), yet these materials are otherwise very similar. By examining InAs-on-GaAs composites Instead of the more common In(x)Ga(1-x)As alloy, we remove an additional degree of freedom (x) and thereby simplify data interpretation. A matrix of experiments is described in which the MOCVD growth parameters -- susceptor temperature, TMIn flux, and AsH3 flux -- have been varied over a wide range. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and electron microprobe analysis have been employed to observe the thin film surface morphology. In the case of 3-D growth, we have extracted activation energies and power-dependent exponents that characterize the nucleation process. As a consequence, optimized growth conditions have been identified for depositing approx. 250 A thick (100) and (111)B oriented InAs layers with relatively smooth surfaces. Together with preliminary data on the strain relaxation of these layers, the above results on the evolution of thin InAs films indicate that the (111)B orientation is particularly promising for yielding lattice-mismatched films that are fully relaxed with only misfit dislocations at the epilayer / substrate interface.

  3. Nucleation, growth, and strain relaxation of lattice-mismatched 3-5 semiconductor epitaxial layers

    NASA Technical Reports Server (NTRS)

    Welser, R. E.; Guido, L. J.

    1994-01-01

    We have investigated the early stages of evolution of highly strained 2-D InAs layers and 3-D InAs islands grown by metal-organic chemical vapor deposition (MOCVD) on (100) and (111)B GaAs substrates. The InAs epilayer/GaAs substrate combination has been chosen because the lattice-mismatch is severe (approximately 7.2 percent), yet these materials are otherwise very similar. By examining InAs-on-GaAs composites instead of the more common In(x)Ga(1-x)As alloy we remove an additional degree of freedom (x) and thereby simplify data interpretation. A matrix of experiments is described in which the MOCVD growth parameters - susceptor temperature, Thin flux, and AsH3 flux - have been varied over a wide range. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and electron microprobe analysis have been employed to observe the thin film surface morphology. In the case of 3-D growth, we have extracted activation energies and power-dependent exponents that characterize the nucleation process. As a consequence, optimized growth conditions have been identified for depositing approximately 250 A thick (100) and (111)B oriented InAs layers with relatively smooth surfaces. Together with preliminary data on the strain relaxation of these layers, the above results on the evolution of thin InAs films indicate that the (111)B orientation is particularly promising for yielding lattice-mismatched films that are fully relaxed with only misfit dislocations at the epilayer/substrate interface.

  4. Method for sputtering a PIN microcrystalline/amorphous silicon semiconductor device with the P and N-layers sputtered from boron and phosphorous heavily doped targets

    DOEpatents

    Moustakas, Theodore D.; Maruska, H. Paul

    1985-04-02

    A silicon PIN microcrystalline/amorphous silicon semiconductor device is constructed by the sputtering of N, and P layers of silicon from silicon doped targets and the I layer from an undoped target, and at least one semi-transparent ohmic electrode.

  5. Interplay of solvent additive concentration and active layer thickness on the performance of small molecule solar cells.

    PubMed

    Love, John A; Collins, Samuel D; Nagao, Ikuhiro; Mukherjee, Subhrangsu; Ade, Harald; Bazan, Guillermo C; Nguyen, Thuc-Quyen

    2014-11-19

    A relationship between solvent additive concentration and active layer thickness in small-molecule solar cells is investigated. Specifically, the additive concentration must scale with the amount of semiconductor material and not as absolute concentration in solution. Devices with a wide range of active layers with thickness up to 200 nm can readily achieve efficiencies close to 6% when the right concentration of additive is used.

  6. Temperature dependence of Raman shifts in layered ReSe{sub 2} and SnSe{sub 2} semiconductor nanosheets

    SciTech Connect

    Taube, A.; Łapińska, A.; Judek, J.; Zdrojek, M.

    2015-07-06

    Transition metal dichalcogenides (TMDCs) are attractive for variety of nanoscale electronics and optoelectronics devices due to their unique properties. Despite growing progress in the research field of TMDCs, many of their properties are still unknown. In this letter, we report measurements of Raman spectra of rhenium diselenide (ReSe{sub 2}) and tin diselenide (SnSe{sub 2}) layered semiconductor nanosheets as a function of temperature (70–400 K). We analyze the temperature dependence of the positions of eight ReSe{sub 2} modes and SnSe{sub 2} A{sub 1g} mode. All observed Raman mode shifts exhibit nonlinear temperature dependence at low temperatures which is explained by optical phonon decay process into two or three acoustics phonons. The first order temperature coefficients (χ), determined for high temperatures, of rhenium diselenide Raman modes are in the range between −0.0033 and −0.0118 cm{sup −1}/K, whereas χ of tin diselenide A{sub 1g} mode was −0.0129 cm{sup −1}/K. Our findings are useful for further analysis of phonon and thermal properties of these dichalcogenide layered semiconductors.

  7. Fabrication and characterization of PbSe nanostructures on van der Waals surfaces of GaSe layered semiconductor crystals

    NASA Astrophysics Data System (ADS)

    Kudrynskyi, Z. R.; Bakhtinov, A. P.; Vodopyanov, V. N.; Kovalyuk, Z. D.; Tovarnitskii, M. V.; Lytvyn, O. S.

    2015-11-01

    The growth morphology, composition and structure of PbSe nanostructures grown on the atomically smooth, clean, nanoporous and oxidized van der Waals (0001) surfaces of GaSe layered crystals were studied by means of atomic force microscopy, x-ray diffractometry, photoelectron spectroscopy and Raman spectroscopy. Semiconductor heterostructures were grown by the hot-wall technique in vacuum. Nanoporous GaSe substrates were fabricated by the thermal annealing of layered crystals in a molecular hydrogen atmosphere. The irradiation of the GaSe(0001) surface by UV radiation was used to fabricate thin Ga2O3 layers with thickness < 2 nm. It was found that the narrow gap semiconductor PbSe shows a tendency to form clusters with a square or rectangular symmetry on the clean low-energy (0001) GaSe surface, and (001)-oriented growth of PbSe thin films takes place on this surface. Using this growth technique it is possible to grow PbSe nanostructures with different morphologies: continuous epitaxial layers with thickness < 10 nm on the uncontaminated p-GaSe(0001) surfaces, homogeneous arrays of quantum dots with a high lateral density (more than 1011 cm-2) on the oxidized van der Waals (0001) surfaces and faceted square pillar-like nanostructures with a low lateral density (˜108 cm-2) on the nanoporous GaSe substrates. We exploit the ‘vapor-liquid-solid’ growth with low-melting metal (Ga) catalyst of PbSe crystalline branched nanostructures via a surface-defect-assisted mechanism.

  8. Insight on a novel layered semiconductors: CuTlS and CuTlSe

    NASA Astrophysics Data System (ADS)

    Aliev, Ziya S.; Zúñiga, Fco. Javier; Koroteev, Yury M.; Breczewski, Tomasz; Babanly, Nizamaddin B.; Amiraslanov, Imamaddin R.; Politano, Antonio; Madariaga, Gotzon; Babanly, Mahammad B.; Chulkov, Evgueni V.

    2016-10-01

    Single crystals of the ternary copper compounds CuTlS and CuTlSe have been successfully grown from stoichiometric melt by using vertical Bridgman-Stockbarger method. The crystal structure of the both compounds has been determined by powder and single crystal X-Ray diffraction. They crystallize in the PbFCl structure type with two formula units in the tetragonal system, space group P4/nmm, a=3.922(2); c=8.123(6); Z=2 and a=4.087(6); c=8.195(19) Å; Z=2, respectively. The band structure of the reported compounds has been analyzed by means of full-potential linearized augmented plane-wave (FLAPW) method based on the density functional theory (DFT). Both compounds have similar band structures and are narrow-gap semiconductors with indirect band gap. The resistivity measurements agree with a semiconductor behavior although anomalies are observed at low temperature.

  9. Rare earth ion implantation and optical activation in nitride semiconductors for multicolor emission

    NASA Astrophysics Data System (ADS)

    Ruterana, Pierre; Chauvat, Marie-Pierre; Lorenz, Katharina

    2015-04-01

    In order to understand the behavior of nitride semiconductors when submitted to ion implantation, we have used 300 keV europium at fluences from 1012 to above 1017 ions cm-2. Subsequently, Rutherford backscattering (RBS), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to investigate the evolution of damage. The optical properties were investigated prior to and after annealing. It was found that the behavior of the three compounds (AlN, GaN InN) under ion implantation is rather different: whereas InN breaks down at very low fluences (˜1012 ions cm-2), the damage formation mechanisms are similar in AlN and GaN. In both compounds, extended defects such as stacking faults play a critical role. However, they exhibit different stability, as a consequence, GaN transforms to nanocrystalline state from the surface at a fluence of around 2.5 × 1015 ions cm-2, whereas AlN undergoes a chemical amorphization starting at the projected range (Rp), when implanted to extremely high Eu fluences >1017 ionscm-2. As for the optical activation, the formation of highly stable extended defects in these compounds constitutes a real challenge for the annealing of heavily doped layers, and it was noticed that for a substantial optical activation, the implantation fluences should be kept low (<1015 Eu at cm-2).

  10. Identification of intrinsic deep level defects responsible for electret behavior in TlGaSe2 layered semiconductor

    NASA Astrophysics Data System (ADS)

    Seyidov, MirHasan Yu.; Mikailzade, Faik A.; Uzun, Talip; Odrinsky, Andrei P.; Yakar, Emin; Aliyeva, Vafa B.; Babayev, Sardar S.; Mammadov, Tofig G.

    2016-02-01

    Unusual behavior of pyroelectric current signal polarity near the Curie point (Tc) was observed for TlGaSe2 a ferroelectric-semiconductor. It has been revealed that the polarity of the spontaneous polarization near Tc depends on the sample poling prehistory. In particular, applying an external electric field only in the temperature range of the paraelectric state during cooling regime in darkness brought to the depolarization current at Tc with the sign opposite to the external field polarity. Otherwise, if the sample was poled in the temperature interval of the incommensurate phase, pyroelectric current exhibits a peak at Tc with the polarity that is the same as for the external poling electric field. These observations indicate that internal electric field is present in the bulk and near-surface layer regions of the electrically poled single crystal TlGaSe2. Possible mechanisms and origins responsible for the internal electric fields in TlGaSe2 are discussed. It is shown that the formation of internal electric fields in TlGaSe2 is due to charging of intrinsic native defects during the poling process. Characteristics of electrically active intrinsic defects in TlGaSe2 were investigated by using of Photo-Induced Current Transient Spectroscopy (PICTS) technique. Six deep defect levels in the band gap of TlGaSe2 were determined, which were localized both in the bulk and on the surface of the sample and could be electrically charged. The correlation between polarization effects and PICTS results has been established. It was shown that native deep defects (A3-A6) localized in the bulk of crystal are responsible for hetero-charge formation and negative sign of the pyroelectric current peak observed around the Curie temperature after poling the sample in the temperature intervals well above Tc. It was also shown that the positive sign pyrocurrent observed near the Curie point is attributed to the homo-charge formed by native A2-trapping centers which are localized near

  11. Electronic structure of MoO3 insertion layer at the interface between organic semiconductor and indium tin oxide (ITO).

    NASA Astrophysics Data System (ADS)

    Ding, Huanjun; Irfan, Irfan; Gao, Yongli; So, Frank

    2009-03-01

    We have investigated the electronic structure of the interfaces formed by inserting thin layer of MoO3 in between indium tin oxide (ITO) and different organic semiconductors, such as aluminium phthalocyanine chloride (AlPcCl) and copper phthalocyanine (CuPc), with photoemission and inverse photoemission spectroscopy (PES and IPES). The presents of MoO3 layer at the interface increases the workfunction dramatically. As a result, the organic HOMO is almost aligned with the Fermi level (Ef) at the AlPc-Cl/MoO3 interface. For thicker AlPc-Cl layers, gradual band bending is observed. However, the recovery of the HOMO is incomplete for AlPc-Cl thickness of 200 å, leading to a great reduction of the hole injection barrier compare to the case without MoO3. Similar situation is found in case of CuPc/MoO3, although the energy levels are almost fully recovered for CuPc film thicker than 200 å. The energy level alignment of these interfaces will be discussed to explain the improvement induced by MoO3 layer in device performance.

  12. Nano-/microstructure improved photocatalytic activities of semiconductors.

    PubMed

    Zhao, Tianyi; Zhao, Yong; Jiang, Lei

    2013-10-13

    Photocatalysis has emerged as a promising technique owing to its valuable applications in environmental purification. With the demand of building effective photocatalyst materials, semiconductor investigation experienced a developing process from simple chemical modification to complicated morphology design. In this review, the general relationship between morphology structures and photocatalytic properties is mainly discussed. Various nano-/microsized structures from zero- to three-dimensional are discussed, and the photocatalytic efficiency correspon- ding to the structures is analysed. The results showed that simple structures can be easily obtained and can facilitate chemical modification, whereas one- or three-dimensional structures can provide structure-enhanced properties such as surface area increase, multiple reflections of UV light, etc. Those principles of structure-related photocatalytic properties will afford basic ideology in designing new photocatalytic materials with more effective catalytic properties.

  13. Possible Deviation from the well-known Threshold Behavior of Field-Effect Doping Phenomenon in Extremely Thin Organic Semiconductor Layer

    NASA Astrophysics Data System (ADS)

    Ikegami, Keiichi

    2004-05-01

    Field-effect doping in a metal/insulator/semiconductor/metal four-layer model indicates that the well-known threshold behavior Q\\propto(VG-Vth), where Q is the induced charge and VG and Vth are the bias voltage and its threshold value, respectively, should be realized even when the thickness of the semiconductor layer (ds) is on the 10 nm scale. At the same time, however, this model suggests that the doping phenomenon deviates from this simple threshold behavior when the density of states is small and ds is on the 1 nm scale.

  14. 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.

  15. Magnetic properties of layered III-VI Diluted Magnetic Semiconductors (DMS)

    NASA Astrophysics Data System (ADS)

    Pekarek, Thomas; Miotkowski, I.; Ramdas, A. K.

    2015-03-01

    The new class of quasi-two-dimensional III-VI Diluted Magnetic Semiconductors (DMS) exhibits a rich collection of magnetic behavior. The Ga1-xMnxS system exhibits a 3-D spin-glass transition, which was unexpected given its four atom thick two dimensional structure. The best scaling fit was found for critical exponents (γ = 4.0, β = 0.8, and δ = 5.5) similar to the three dimensional Zn1-xMnxTe system. Ga1-xFexSe exhibits a prominent magnetic anisotropy over the temperature range from 10 to 400 K. Theoretical models for In1-xMnxSe, In1-xMnxS, and Ga1-xMnxS provide good agreement with experimental results over a wide range of temperatures and fields. The mechanism behind an unusually large thermal hysteresis (ΔT ~ 200 K) in In1-xMnxSe, which extends up to room temperature, is not completely understood at this time. Typically, thermal hysteresis in most materials has a ΔT ~ 20 K occurring well below room temperature. The host III-VI semiconductors themselves are among the best non-linear optical materials. This research was supported by the UNF Terry Presidential Professorship, the Florida Space Grant Consortium, A Purdue U. Academic Reinvestment Program, and by NSF Grant Nos. DMR-07-06593 and DMR-14-29428.

  16. Bandgap narrowing in the layered oxysulfide semiconductor Ba3Fe2O5Cu2S2: Role of FeO2 layer

    NASA Astrophysics Data System (ADS)

    Han, Zhang; Shifeng, Jin; Liwei, Guo; Shijie, Shen; Zhiping, Lin; Xiaolong, Chen

    2016-02-01

    A new layered Cu-based oxychalcogenide Ba3Fe2O5Cu2S2 has been synthesized and its magnetic and electronic properties were revealed. Ba3Fe2O5Cu2S2 is built up by alternatively stacking [Cu2S2]2- layers and iron perovskite oxide [(FeO2)(BaO)(FeO2)]2- layers along the c axis that are separated by barium ions with Fe3+ fivefold coordinated by a square-pyramidal arrangement of oxygen. From the bond valence arguments, we inferred that in layered CuCh-based (Ch = S, Se, Te) compounds the +3 cation in perovskite oxide sheet prefers a square pyramidal site, while the lower valence cation prefers the square planar sites. The studies on susceptibility, transport, and optical reflectivity indicate that Ba3Fe2O5Cu2S2 is an antiferromagnetic semiconductor with a Néel temperature of 121 K and an optical bandgap of 1.03 eV. The measurement of heat capacity from 10 K to room temperature shows no anomaly at 121 K. The Debye temperature is determined to be 113 K. Theoretical calculations indicate that the conduction band minimum is predominantly contributed by O 2p and 3d states of Fe ions that antiferromagnetically arranged in FeO2 layers. The Fe 3d states are located at lower energy and result in a narrow bandgap in comparison with that of the isostructural Sr3Sc2O5Cu2S2. Project supported by the National Natural Science Foundation of China (Grant Nos. 51472266, 51202286, and 91422303), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100) and the ICDD.

  17. Anisotropy of piezoresistance in n-channel inversion layers of metal-oxide-semiconductor transistors on (001)Si

    NASA Astrophysics Data System (ADS)

    Maruyama, T.; Zaima, S.; Koide, Y.; Kanda, Y.; Yasuda, Y.

    1990-12-01

    The crystallographic orientation dependence of piezoresistance of n-channel inversion layers in metal-oxide-semiconductor field-effect transistors on p-type (001)Si has been studied by using a diaphragm at room temperature. The experimental results have been compared with self-consistent calculations based on a surface quantization effect. The main feature of the crystallographic orientation dependence can be explained by an electron repopulation effect induced by applied strain and an effective mass anisotropy. It can be found that the difference between longitudinal and transverse piezoresistance in the devices nearly along the [110] directions is mainly due to an orthorhombic distortion of Si, and the shear deformation coefficients Ξu is determined to be 5.8 eV from comparing the experimental results with the calculated ones. An expression of the shear piezoresistance component π44 is also derived.

  18. Phase Recovery Acceleration of Quantum-Dot Semiconductor Optical Amplifiers by Optical Pumping to Quantum-Well Wetting Layer

    NASA Astrophysics Data System (ADS)

    Kim, Jungho

    2013-11-01

    We theoretically investigate the phase recovery acceleration of quantum-dot (QD) semiconductor optical amplifiers (SOAs) by means of the optical pump injection to the quantum-well (QW) wetting layer (WL). We compare the ultrafast gain and phase recovery responses of QD SOAs in either the electrical or the optical pumping scheme by numerically solving 1088 coupled rate equations. The ultrafast gain recovery responses on the order of sub-picosecond are nearly the same for the two pumping schemes. The ultrafast phase recovery is not significantly accelerated by increasing the electrical current density, but greatly improved by increasing the optical pumping power to the QW WL. Because the phase recovery time of QD SOAs with the optical pumping scheme can be reduced down to several picoseconds, the complete phase recovery can be achieved when consecutive pulse signals with a repetition rate of 100 GHz is injected.

  19. Optical properties of layered III-VI semiconductor γ-InSe:M (M=Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Milutinović, Aleksandra; Lazarević, Zorica Ž.; Jakovljević, Milka; Hadzić, Branka; Petrović, Milica; Gilić, Martina; Dobrowolski, Witold Daniel; Romčević, Nebojša Ž.

    2016-02-01

    Indium selenide belongs to layered III-VI semiconductors with highly anisotropic optical and electronic properties. Energy gap of 1.32 eV makes this material very attractive for solar energy conversion. We investigated the influence of 1% 3-d transition metals M=Mn, Fe, Co, Ni, used as dopants, on energy levels of InSe:M in the range 1.4-6.5 eV and especially in the range of energy gap <1.4 eV by means of ellipsometric measurements. It was concluded that at ambient temperature foregoing dopants, all divalent, with 4s2 valent electrons, in the similar way influenced on blue-shift of energy levels in valent zone, but did not influence on the fundamental energy gap. Photoluminescence measurements confirmed blue-shift of the valent zone energy levels and an existence of deep impurity levels.

  20. ZrO2 on GaN metal oxide semiconductor capacitors via plasma assisted atomic layer deposition

    NASA Astrophysics Data System (ADS)

    von Hauff, P.; Afshar, A.; Foroughi-Abari, A.; Bothe, K.; Cadien, K.; Barlage, D.

    2013-06-01

    ZrO2 has been deposited on GaN by Atomic Layer Deposition. Multiple Metal-Oxide-Semiconductor Capacitors with 4.4 nm, 5.4 nm, and 8.5 nm of ZrO2 oxide were fabricated with Cr electrodes. Capacitance measurements produce capacitance densities as high as 3.8 μF/cm2. Current densities of 0.88 A/cm2 at 1 V for the 4.4 nm oxides and hysteresis values of less than 6 mV were observed for the 5.8 nm oxide, indicating an interfacial Dit not greater than 6.4 × 1010 cm2. Temperature dependent current measurements revealed no signature Poole-Frankel component. Comprehensive assessment of these measurements indicates a low defect density oxide formed on GaN with a low number of interface states.

  1. Atomic layer deposition precursor step repetition and surface plasma pretreatment influence on semiconductor–insulator–semiconductor heterojunction solar cell

    SciTech Connect

    Talkenberg, Florian Illhardt, Stefan; Schmidl, Gabriele; Schleusener, Alexander; Sivakov, Vladimir; Radnóczi, György Zoltán; Pécz, Béla; Dikhanbayev, Kadyrjan; Mussabek, Gauhar; Gudovskikh, Alexander

    2015-07-15

    Semiconductor–insulator–semiconductor heterojunction solar cells were prepared using atomic layer deposition (ALD) technique. The silicon surface was treated with oxygen and hydrogen plasma in different orders before dielectric layer deposition. A plasma-enhanced ALD process was applied to deposit dielectric Al{sub 2}O{sub 3} on the plasma pretreated n-type Si(100) substrate. Aluminum doped zinc oxide (Al:ZnO or AZO) was deposited by thermal ALD and serves as transparent conductive oxide. Based on transmission electron microscopy studies the presence of thin silicon oxide (SiO{sub x}) layer was detected at the Si/Al{sub 2}O{sub 3} interface. The SiO{sub x} formation depends on the initial growth behavior of Al{sub 2}O{sub 3} and has significant influence on solar cell parameters. The authors demonstrate that a hydrogen plasma pretreatment and a precursor dose step repetition of a single precursor improve the initial growth behavior of Al{sub 2}O{sub 3} and avoid the SiO{sub x} generation. Furthermore, it improves the solar cell performance, which indicates a change of the Si/Al{sub 2}O{sub 3} interface states.

  2. Development of Prototype Micro-Lidar using Narrow Linewidth Semiconductor Lasers for Mars Boundary Layer Wind and Dust Opacity Profiles

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.; Cardell, Greg; Chiao, Meng; Esproles, Carlos; Forouhar, Siamak; Hemmati, Hamid; Tratt, David

    1999-01-01

    We have developed a compact Doppler lidar concept which utilizes recent developments in semiconductor diode laser technology in order to be considered suitable for wind and dust opacity profiling in the Mars lower atmosphere from a surface location. The current understanding of the Mars global climate and meteorology is very limited, with only sparse, near-surface data available from the Viking and Mars Pathfinder landers, supplemented by long-range remote sensing of the Martian atmosphere. The in situ measurements from a lander-based Doppler lidar would provide a unique dataset particularly for the boundary layer. The coupling of the radiative properties of the lower atmosphere with the dynamics involves the radiative absorption and scattering effects of the wind-driven dust. Variability in solar irradiance, on diurnal and seasonal time scales, drives vertical mixing and PBL (planetary boundary layer) thickness. The lidar data will also contribute to an understanding of the impact of wind-driven dust on lander and rover operations and lifetime through an improvement in our understanding of Mars climatology. In this paper we discuss the Mars lidar concept, and the development of a laboratory prototype for performance studies, using, local boundary layer and topographic target measurements.

  3. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te)

    PubMed Central

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F. L.; Chantrell, Roy W.; Jeng, Horng-Tay

    2016-01-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics. PMID:27601195

  4. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te)

    NASA Astrophysics Data System (ADS)

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F. L.; Chantrell, Roy W.; Jeng, Horng-Tay

    2016-09-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics.

  5. Newtype single-layer magnetic semiconductor in transition-metal dichalcogenides VX2 (X = S, Se and Te).

    PubMed

    Fuh, Huei-Ru; Chang, Ching-Ray; Wang, Yin-Kuo; Evans, Richard F L; Chantrell, Roy W; Jeng, Horng-Tay

    2016-01-01

    We present a newtype 2-dimensional (2D) magnetic semiconductor based on transition-metal dichalcogenides VX2 (X = S, Se and Te) via first-principles calculations. The obtained indirect band gaps of monolayer VS2, VSe2, and VTe2 given from the generalized gradient approximation (GGA) are respectively 0.05, 0.22, and 0.20 eV, all with integer magnetic moments of 1.0 μB. The GGA plus on-site Coulomb interaction U (GGA + U) enhances the exchange splittings and raises the energy gap up to 0.38~0.65 eV. By adopting the GW approximation, we obtain converged G0W0 gaps of 1.3, 1.2, and 0.7 eV for VS2, VSe2, and VTe2 monolayers, respectively. They agree very well with our calculated HSE gaps of 1.1, 1.2, and 0.6 eV, respectively. The gap sizes as well as the metal-insulator transitions are tunable by applying the in-plane strain and/or changing the number of stacking layers. The Monte Carlo simulations illustrate very high Curie-temperatures of 292, 472, and 553 K for VS2, VSe2, and VTe2 monolayers, respectively. They are nearly or well beyond the room temperature. Combining the semiconducting energy gap, the 100% spin polarized valence and conduction bands, the room temperature TC, and the in-plane magnetic anisotropy together in a single layer VX2, this newtype 2D magnetic semiconductor shows great potential in future spintronics. PMID:27601195

  6. SEMICONDUCTOR DEVICES: Carrier stored trench-gate bipolar transistor with p-floating layer

    NASA Astrophysics Data System (ADS)

    Rongyao, Ma; Zehong, Li; Xin, Hong; Bo, Zhang

    2010-02-01

    A carrier stored trench-gate bipolar transistor (CSTBT) with a p-floating layer (PF-CSTBT) is proposed. Due to the p-floating layer, the thick and highly doped carrier stored layer can be induced, and the conductivity modulation effect will be enhanced near the emitter. The accumulation resistance and the spreading resistance are reduced. The on-state loss will be much lower than in a conventional CSTBT. With the p-floating layer, the distribution of electric fields of the conventional IGBT is reformed, and the breakdown voltage is remarkably improved. The simulation results have shown that the forward voltage drop (VCE-on) of the novel structure is reduced by 20% and 17% respectively, compared with the conventional trench IGBT (TIGBT) and CSTBT under the same conditions. Moreover, an increment of more than 100 V of the breakdown voltage is achieved without sacrificing the SCSOA (short circuit safely operation area) compared with the conventional TIGBT.

  7. Physical layer one-time-pad data encryption through synchronized semiconductor laser networks

    NASA Astrophysics Data System (ADS)

    Argyris, Apostolos; Pikasis, Evangelos; Syvridis, Dimitris

    2016-02-01

    Semiconductor lasers (SL) have been proven to be a key device in the generation of ultrafast true random bit streams. Their potential to emit chaotic signals under conditions with desirable statistics, establish them as a low cost solution to cover various needs, from large volume key generation to real-time encrypted communications. Usually, only undemanding post-processing is needed to convert the acquired analog timeseries to digital sequences that pass all established tests of randomness. A novel architecture that can generate and exploit these true random sequences is through a fiber network in which the nodes are semiconductor lasers that are coupled and synchronized to central hub laser. In this work we show experimentally that laser nodes in such a star network topology can synchronize with each other through complex broadband signals that are the seed to true random bit sequences (TRBS) generated at several Gb/s. The potential for each node to access real-time generated and synchronized with the rest of the nodes random bit streams, through the fiber optic network, allows to implement an one-time-pad encryption protocol that mixes the synchronized true random bit sequence with real data at Gb/s rates. Forward-error correction methods are used to reduce the errors in the TRBS and the final error rate at the data decoding level. An appropriate selection in the sampling methodology and properties, as well as in the physical properties of the chaotic seed signal through which network locks in synchronization, allows an error free performance.

  8. Surface reactions during the atomic layer deposition of high-kappa dielectrics on III-V semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Ye, Liwang

    The quality of the dielectric/semiconductor interface is one of the most critical parameters for the fabrication of high-speed and low-power-consumption III-V semiconductor based metal-oxide-semiconductor field effect transistors (MOSFETs), as it determines the device performance. This dissertation contains investigations of the deposition and interface of binary oxide films on GaAs(100) and InAs(100) surfaces aiming at understanding the removal of the surface native oxides during certain atomic layer deposition (ALD) processes. To accomplish that, two complementary experimental approaches have been used. Initially, films were deposited in a conventional ALD reactor and characterized ex situ using spectroscopic ellipsometry (SE), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The systems examined were Ta2O 5 on GaAs(100) surfaces from pentakis(dimethylamino) tantalum (Ta(N(CH 3)2)5, PDMAT) and TiO2 on GaAs(100) and InAs(100) surfaces from tetrakis(dimethylamino) titanium (Ti(N(CH 3)2)4, TDMAT). For these systems, deposition at the optimal ALD temperature resulted in practically sharp interfaces. Indium oxides were found to diffuse through ~ 6 nm of TiO2 film and accumulate on the topmost film layer. For the ALD of Ta2O5 on GaAs(100) surfaces, native oxide removal was enhanced at deposition temperatures above the ALD window; for ALD of TiO2 on both GaAs(100) and InAs(100) surfaces, native oxide removal was enhanced as the deposition temperatures increased up to 250 A°C, while oxidation of the interface was observed for deposition above 300 A°C due to the formation of noncontinuous films. To elucidate the surface reactions occurring during the deposition, an in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy apparatus was constructed and used to investigate the surface reactions during the ALD of TiO2 and HfO2 on GaAs(100) surfaces. The

  9. SEMICONDUCTOR PHYSICS: Grain boundary layer behavior in ZnO/Si heterostructure

    NASA Astrophysics Data System (ADS)

    Bingce, Liu; Cihui, Liu; Bo, Yi

    2010-03-01

    The grain boundary layer behavior in ZnO/Si heterostucture is investigated. The current-voltage (I-V) curves, deep level transient spectra (DLTS) and capacitance-voltage (C-V) curves are measured. The transport currents of ZnO/Si heterojunction are dominated by grain boundary layer as high densities of interfacial states existed. The interesting phenomenon that the crossing of In I-V curves of ZnO/Si heterojunction at various measurement temperatures and the decrease of its effective barrier height with the decrement of temperature are in contradiction with the ideal heterojunction thermal emission model is observed. The details will be discussed in the following.

  10. Exploration of the new class of layered III-VI Diluted Magnetic Semiconductors (DMS)

    NASA Astrophysics Data System (ADS)

    Pekarek, Thomas; Miotkowski, I.; Ramdas, A. K.

    2014-03-01

    We have explored a new class of quasi-two-dimensional III-VI Diluted Magnetic Semiconductors (DMS) exhibiting a wide range of magnetic behavior. Several are good candidates for potential device applications. In In1-xMnxSe, we found a remarkably large thermal hysteresis (Delta T is approximately 200 K) extending up to room temperature. This is an important material because a typical thermal hysteresis in most materials has a Delta T approximately 20 K occurring well below room temperature. The thermal hysteresis is also seen in transport measurements for In1-xMnxSe. To date, we have found good agreement between experiment and theory for the 1st three III-VI DMS systems (In1-xMnxSe, In1-xMnxS, and Ga1-xMnxS). Ga1-xFexSe is unique amount the III-VI DMS exhibiting substantial magnetic anisotropy. In Ga1-xMnxS, we have found a spin glass transition and critical exponents (γ = 4.0, β = 0.8, and δ = 5.5) that are in agreement with the theory. We surprisingly found that the spin glass transition in the 2-D IIIVI DMS similar to spin glass in 3-D II-VI DMS. [This research was supported by the UNF Terry Presidential Professorship, a Purdue University Academic Reinvestment Program and by the National Science Foundation (NSF) Grant Nos. DMR-07-06593 and DMR-04-05082.

  11. Studies of Large-Area Inversion-Layer Metal-Insulator-Semiconductor (IL/MIS) Solar Cells and Arrays

    NASA Technical Reports Server (NTRS)

    Ho, Fat Duen

    1996-01-01

    Many inversion-layer metal-insulator-semiconductor (IL/MIS) solar cells have been fabricated. There are around eighteen 1 cm(exp 2) IL/MIS solar cells which have efficiencies greater than 7%. There are only about three 19 cm(exp 2) IL/MIS cells which have efficiencies greater than 4%. The more accurate control of the thickness of the thin layer of oxide between aluminum and silicon of the MIS contacts has been achieved. A lot of effort and progress have been made in this area. A comprehensive model for MIS contacts under dark conditions has been developed that covers a wide range of parameters. It has been applied to MIS solar cells. One of the main advantages of these models is the prediction of the range of the thin oxide thickness versus the maximum efficiencies of the MIS solar cells. This is particularly important when the thickness is increased to 25 A. This study is very useful for our investigation of the IL/MIS solar cells. The two-dimensional numerical model for the IL/MIS solar cells has been tried to develop and the results are presented in this report.

  12. High-field electroluminescence in semiconductor tunnel junctions with a Mn-doped GaAs layer

    SciTech Connect

    Hai, Pham Nam; Yatsui, Takashi; Ohtsu, Motoichi; Tanaka, Masaaki

    2014-09-21

    We investigated high-field electroluminescence (EL) in semiconductor tunnel junctions with a Mn-doped GaAs layer (here, referred to as GaAs:Mn). Besides the band-gap emission of GaAs, the EL spectra show visible light emissions with two peaks at 1.94 eV and 2.19 eV, which are caused by d-d transitions of the Mn atoms excited by hot electrons. The threshold voltages for band-gap and visible light EL in the tunnel junctions with a GaAs:Mn electrode are 1.3 V higher than those of GaAs:Mn excited by hot holes in reserve biased p⁺-n junctions, which is consistent with the hot carrier transport in the band profiles of these structures. Our EL results at room temperature show that the electron temperature in GaAs:Mn can be as high as ~700 K for a low input electrical power density of 0.4 W/cm², while the lattice temperature of the GaAs:Mn layer can be kept at 340 K.

  13. Back contact buffer layer for thin-film solar cells

    DOEpatents

    Compaan, Alvin D.; Plotnikov, Victor V.

    2014-09-09

    A photovoltaic cell structure is disclosed that includes a buffer/passivation layer at a CdTe/Back contact interface. The buffer/passivation layer is formed from the same material that forms the n-type semiconductor active layer. In one embodiment, the buffer layer and the n-type semiconductor active layer are formed from cadmium sulfide (CdS). A method of forming a photovoltaic cell includes the step of forming the semiconductor active layers and the buffer/passivation layer within the same deposition chamber and using the same material source.

  14. Field-induced activation of metal oxide semiconductor for low temperature flexible transparent electronic device applications

    NASA Astrophysics Data System (ADS)

    Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony; Haglund, Amada; Ward, Thomas Zac; Mandrus, David; Rack, Philip

    Amorphous metal-oxide semiconductors have been extensively studied as an active channel material in thin film transistors due to their high carrier mobility, and excellent large-area uniformity. Here, we report the athermal activation of amorphous indium gallium zinc oxide semiconductor channels by an electric field-induced oxygen migration via gating through an ionic liquid. Using field-induced activation, a transparent flexible thin film transistor is demonstrated on a polyamide substrate with transistor characteristics having a current ON-OFF ratio exceeding 108, and saturation field effect mobility of 8.32 cm2/(V.s) without a post-deposition thermal treatment. This study demonstrates the potential of field-induced activation as an athermal alternative to traditional post-deposition thermal annealing for metal oxide electronic devices suitable for transparent and flexible polymer substrates. Materials Science and Technology Division, ORBL, Oak Ridge, TN 37831, USA.

  15. Effects of Activation Energy to Transient Response of Semiconductor Gas Sensor

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Ohtani, Tatsuki

    The smell classifiable gas sensor will be desired for many applications such as gas detection alarms, process controls for food production and so on. We have tried to realize the sensor using transient responses of semiconductor gas sensor consisting of tin dioxide and pointed out that the sensor gave us different transient responses for kinds of gas. Results of model calculation showed the activation energy of chemical reaction on the sensor surface strongly depended on the transient response. We tried to estimate the activation energies by molecular orbital calculation with SnO2 Cluster. The results show that there is a liner relationship between the gradient of the transient responses and activation energies for carboxylic and alcoholic gases. Transient response will be predicted from activation energy in the same kind of gas and the smell discrimination by single semiconductor gas sensor will be realized by this relationship.

  16. Cathodoluminescence observation of SiO2 layers in a semiconductor device

    NASA Astrophysics Data System (ADS)

    Koyama, H.

    1980-04-01

    Dispersive cathodoluminescence images from thin films of SiO2 in a Test-Element-Group pattern of a conventional Large Scale Integrated circuit device were observed. Band A (290 nm) and band C (560 nm) of the cathodoluminescence were characteristic of a thermally grown SiO2 covered with chemically vapor-deposited (CVD) SiO2 and may be useful for the study of irradiation induced damages in SiO2. Band B (415 nm) and band D (650 nm) were intense in the surface CVD SiO2 and may provide information on process induced impurities in SiO2 layers. The spatial resolution of a cathodoluminescence image is 2 μm, and it is possible to survey SiO2 layers on a conventional LSI device with this technique.

  17. Misfit accommodation and dislocations in heteroepitaxial semiconductor layers: II-VI compounds on GaAs

    NASA Astrophysics Data System (ADS)

    Patriarche, G.; Rivière, J. P.; Castaing, J.

    1993-06-01

    We suggest a model for the nucleation and expansion of dislocations which accommodate the parameter misfit of an epitaxial layer on a substrate, applied, in this work, to a II-VI compound on GaAs. We examine in particular the dislocations threading through the layer, which must be kept as low as possible in density. Nous proposons un mécanisme de germination et de développement des dislocations permettant de compenser l'écart de paramètres d'une couche épitaxiée sur un substrat, par exemple dans notre cas, un composé II-VI sur GaAs. On porte une attention particulière aux dislocations résiduelles dans la couche dont on cherche à minimiser la densité.

  18. Fused Methoxynaphthyl Phenanthrimidazole Semiconductors as Functional Layer in High Efficient OLEDs.

    PubMed

    Jayabharathi, Jayaraman; Ramanathan, Periyasamy; Karunakaran, Chockalingam; Thanikachalam, Venugopal

    2016-01-01

    Efficient hole transport materials based on novel fused methoxynaphthyl phenanthrimidazole core structure were synthesised and characterized. Their device performances in phosphorescent organic light emitting diodes were investigated. The high thermal stability in combination with the reversible oxidation process made promising candidates as hole-transporting materials for organic light-emitting devices. Highly efficient Alq3-based organic light emitting devices have been developed using phenanthrimidazoles as functional layers between NPB [4,4-bis(N-(1-naphthyl)-N-phenylamino)biphenyl] and Alq3 [tris(8-hydroxyquinoline)aluminium] layers. Using the device of ITO/NPB/4/Alq3/LiF/Al, a maximum luminous efficiency of 5.99 cd A(-1) was obtained with a maximum brightness of 40,623 cd m(-2) and a power efficiency of 5.25 lm W(-1). PMID:26585347

  19. Far-infrared magnetospectroscopy on epitaxial zero-gap and wide-gap semiconductor layer systems

    NASA Astrophysics Data System (ADS)

    Kempf, P.; von Ortenberg, M.; Bicknell-Tassius, R.; Waag, A.

    1992-02-01

    Far-infrared magnetotransmission measurements have been performed on MBE-grown HgTe and CdTe epilayers. The results on the HgTe samples can be understood by the standard Pidgeon-Brown model for bulk HgTe. For the CdTe layers, transitions were only observed under illumination by visible light. The spectra are dominated by the 1 s→2 p transition of the shallow hydrogen-like impurity. These transitions are persistent with a life time of the order of magnitude of one second.

  20. Ionic Liquid Activation of Amorphous Metal-Oxide Semiconductors for Flexible Transparent Electronic Devices

    DOE PAGES

    Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony T.; Ovchinnikova, Olga S.; Haglund, Amanda V.; Dai, Sheng; Ward, Thomas Zac; Mandrus, David; Rack, Philip D.

    2016-02-09

    To begin this abstract, amorphous metal-oxide semiconductors offer the high carrier mobilities and excellent large-area uniformity required for high performance, transparent, flexible electronic devices; however, a critical bottleneck to their widespread implementation is the need to activate these materials at high temperatures which are not compatible with flexible polymer substrates. The highly controllable activation of amorphous indium gallium zinc oxide semiconductor channels using ionic liquid gating at room temperature is reported. Activation is controlled by electric field-induced oxygen migration across the ionic liquid-semiconductor interface. In addition to activation of unannealed devices, it is shown that threshold voltages of a transistormore » can be linearly tuned between the enhancement and depletion modes. Finally, the first ever example of transparent flexible thin film metal oxide transistor on a polyamide substrate created using this simple technique is demonstrated. Finally, this study demonstrates the potential of field-induced activation as a promising alternative to traditional postdeposition thermal annealing which opens the door to wide scale implementation into flexible electronic applications.« less

  1. Profiling of semiconductor surface layers by heavy ion TOF-E-ERD

    NASA Astrophysics Data System (ADS)

    Arai, E.; Zounek, A.; Saito, K.

    1993-06-01

    We have adapted the elastic recoil detection (ERD) technique to analyse passivation layers of Si xN yO 1- x- y grown on Si substrates in low pressure CVD process. Sample targets were bombarded by 9.87 MeV 35Cl ions to recoil Si, O, N and C atoms incorporated in the sample film. The atomic species of recoils have been identified through eventwise registration of flight time (TOF) and kinetic energy ( E). Using an unfolding program developed by Bachmann the depth profile for each element has been calculated from the TOF energy spectrum. The unfolding program is based on an iterative algorithm that takes into account the interplay between the stopping of projectiles as well as recoils and the stoichiometry of the sample. The chemical composition as a function of depth is discussed in the context of sample preparation conditions.

  2. Detection of deep-subwavelength dielectric layers at terahertz frequencies using semiconductor plasmonic resonators.

    PubMed

    Berrier, Audrey; Albella, Pablo; Poyli, M Ameen; Ulbricht, Ronald; Bonn, Mischa; Aizpurua, Javier; Rivas, Jaime Gómez

    2012-02-27

    Plasmonic bowtie antennas made of doped silicon can operate as plasmonic resonators at terahertz (THz) frequencies and provide large field enhancement close to their gap. We demonstrate both experimentally and theoretically that the field confinement close to the surface of the antenna enables the detection of ultrathin (100 nm) inorganic films, about 3750 times thinner than the free space wavelength. Based on model calculations, we conclude that the detection sensitivity and its variation with the thickness of the deposited layer are related to both the decay of the local THz field profile around the antenna and the local field enhancement in the gap of the bowtie antenna. This large field enhancement has the potential to improve the detection limits of plasmon-based biological and chemical sensors. PMID:22418310

  3. Metal oxide semiconductor gas sensors utilizing a Cr-zeolite catalytic layer for improved selectivity

    NASA Astrophysics Data System (ADS)

    Mann, D. P.; Paraskeva, T.; Pratt, K. F. E.; Parkin, I. P.; Williams, D. E.

    2005-05-01

    A novel method of improving the selectivity of metal oxide sensors has been developed. The addition of zeolites, catalytically modified with chromium, results in controlled selectivity to alkanes based on shape and size effects. The cracking patterns of n-alkanes over Cr-zeolite Y and Cr-zeolite β between 200 °C and 400 °C have been ascertained using a novel system involving a heated zeolite bed, thermal desorber and GC/MS. The findings correlate with discrimination shown when the respective zeolites are incorporated as a catalytic layer on chromium titanium oxide (CTO) gas sensors used in a proprietary sensor array system to ascertain their suitability for inclusion into an electronic nose.

  4. Biosynthesis and Antimicrobial Activity of Semiconductor Nanoparticles against Oral Pathogens

    PubMed Central

    Malarkodi, C.; Rajeshkumar, S.; Paulkumar, K.; Vanaja, M.; Gnanajobitha, G.; Annadurai, G.

    2014-01-01

    Dental care is an essential phenomenon in human health. Oral pathogens can cause severe break which may show the way to serious issues in human disease like blood circulation and coronary disease. In the current study, we demonstrated the synthesis and antimicrobial activity of cadmium sulphide and zinc sulphide nanoparticles against oral pathogens. The process for the synthesis of cadmium sulphide (CdS) and zinc sulphide (ZnS) nanoparticles is fast, novel, and ecofriendly. Formation of cadmium sulphide (CdS) and zinc sulphide (ZnS) nanoparticles was confirmed by surface plasmon spectra using UV-Vis spectrophotometer. The morphology of crystalline phase of nanoparticles was determined from transmission electron microscopy (TEM) and X-ray diffraction (XRD) spectra. The average size of cadmium sulphide (CdS) and zinc sulphide (ZnS) nanoparticles was in the range of 10 nm to 25 nm and 65 nm, respectively, and the observed morphology was spherical. The results indicated that the proteins, which contain amine groups, played a reducing and controlling responsibility during the formation of cadmium sulphide (CdS) and zinc sulphide (ZnS) nanoparticles in the colloidal solution. The antimicrobial activity was assessed against oral pathogens such as Streptococcus sp. Staphylococcus sp. Lactobacillus sp., and Candida albicans and these results confirmed that the sulphide nanoparticles are exhibiting good bactericidal activity. PMID:24860280

  5. Screening of inorganic wide-bandgap p-type semiconductors for high performance hole transport layers in organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Ginley, David; Zakutayev, Andriy; Garcia, Andreas; Widjonarko, Nicodemus; Ndione, Paul; Sigdel, Ajaya; Parilla, Phillip; Olson, Dana; Perkins, John; Berry, Joseph

    2011-03-01

    We will report on the development of novel inorganic hole transport layers (HTL) for organic photovoltaics (OPV). All the studied materials belong to the general class of wide-bandgap p-type oxide semiconductors. Potential candidates suitable for HTL applications include SnO, NiO, Cu2O (and related CuAlO2, CuCrO2, SrCu2O4 etc) and Co3O4 (and related ZnCo2O4, NiCo2O4, MgCo2O4 etc.). Materials have been optimized by high-throughput combinatorial approaches. The thin films were deposited by RF sputtering and pulsed laser deposition at ambient and elevated temperatures. Performance of the inorganic HTLs and that of the reference organic PEDOT:PSS HTL were compared by measuring the power conversion efficiencies and spectral responses of the P3HT/PCBM- and PCDTBT/PCBM-based OPV devices. Preliminary results indicate that Co3O4-based HTLs have performance comparable to that of our previously reported NiOs and PEDOT:PSS HTLs, leading to a power conversion efficiency of about 4 percent. The effect of composition and work function of the ternary materials on their performance in OPV devices is under investigation.

  6. Possible unified model for the Hooge parameter in inversion-layer-channel metal-oxide-semiconductor field-effect transistors

    NASA Astrophysics Data System (ADS)

    Omura, Yasuhisa

    2013-06-01

    This paper proposes a possible unified model for the Hooge parameter by considering the impact of transport dimensionality on the Hooge parameter behavior of various inversion-layer-channel metal-oxide-semiconductor field-effect transistors. Past experiments show that the Hooge parameter has a couple of peculiar behaviors. Based on a phenomenological consideration, the original mobility-based model for the Hooge parameter is shown to provide only a partial understanding of the results. It is also observed that, in contrast to past models, the interpretation of some aspects of the Hooge parameter strongly depends on how the two fluctuation modes, the carrier-density fluctuation and the mobility fluctuation, correlate. The phenomenological model proposed here gives a fundamental physical basis that allows important aspects of the Hooge parameter to be interpreted; the model also introduces three basic parameters (the Hooge parameter elements for the carrier-density fluctuation, the mobility fluctuation, and the cross-correlation component). Theoretical expressions for the three basic Hooge parameters are given by merging the fundamental Hooge model, Handel's theory, statistical physics, and quantum-mechanical transport physics. The gate voltage dependence of the Hooge parameter can be explained reasonably well by stating that the screening length rules the dielectric function and that the mobility fluctuation and carrier density fluctuation are correlated. Finally, the theoretical models are examined against the results of past experiments.

  7. Semiconductor device PN junction fabrication using optical processing of amorphous semiconductor material

    SciTech Connect

    Sopori, Bhushan; Rangappan, Anikara

    2014-11-25

    Systems and methods for semiconductor device PN junction fabrication are provided. In one embodiment, a method for fabricating an electrical device having a P-N junction comprises: depositing a layer of amorphous semiconductor material onto a crystalline semiconductor base, wherein the crystalline semiconductor base comprises a crystalline phase of a same semiconductor as the amorphous layer; and growing the layer of amorphous semiconductor material into a layer of crystalline semiconductor material that is epitaxially matched to the lattice structure of the crystalline semiconductor base by applying an optical energy that penetrates at least the amorphous semiconductor material.

  8. Surface properties and photocatalytic activity of KTaO3, CdS, MoS2 semiconductors and their binary and ternary semiconductor composites.

    PubMed

    Bajorowicz, Beata; Cybula, Anna; Winiarski, Michał J; Klimczuk, Tomasz; Zaleska, Adriana

    2014-09-24

    Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  9. Polarization Control via He-Ion Beam Induced Nanofabrication in Layered Ferroelectric Semiconductors

    DOE PAGES

    Belianinov, Alex; Iberi, Vighter; Tselev, Alexander; Susner, Michael A.; McGuire, Michael A.; Joy, David; Jesse, Stephen; Rondinone, Adam J.; Kalinin, Sergei V.; Ovchinnikova, Olga S.

    2016-02-23

    Rapid advanced in nanoscience rely on continuous improvements of matter manipulation at near atomic scales. Currently, well characterized, robust, resist-based lithography carries the brunt of the nanofabrication process. However, use of local electron, ion and physical probe methods is also expanding, driven largely by their ability to fabricate without the multi-step preparation processes that can result in contamination from resists and solvents. Furthermore, probe based methods extend beyond nanofabrication to nanomanipulation and imaging, vital ingredients to rapid transition to prototyping and testing of layered 2D heterostructured devices. In this work we demonstrate that helium ion interaction, in a Helium Ionmore » Microscope (HIM), with the surface of bulk copper indium thiophosphate CuMIIIP2X6 (M = Cr, In; X= S, Se), (CITP) results in the control of ferroelectric domains, and growth of cylindrical nanostructures with enhanced conductivity; with material volumes scaling with the dosage of the beam. The nanostructures are oxygen rich, sulfur poor, and with the copper concentration virtually unchanged as confirmed by Energy Dispersive X-ray (EDX). Scanning Electron Microscopy (SEM) imaging contrast as well as Scanning Microwave Microscopy (SMM) measurements suggest enhanced conductivity in the formed particle, whereas Atomic Force Microscopy (AFM) measurements indicate that the produced structures have lower dissipation and a lower Young s modulus.« less

  10. Polarization Control via He-Ion Beam Induced Nanofabrication in Layered Ferroelectric Semiconductors.

    PubMed

    Belianinov, Alex; Iberi, Vighter; Tselev, Alexander; Susner, Michael A; McGuire, Michael A; Joy, David; Jesse, Stephen; Rondinone, Adam J; Kalinin, Sergei V; Ovchinnikova, Olga S

    2016-03-23

    Rapid advances in nanoscience rely on continuous improvements of material manipulation at near-atomic scales. Currently, the workhorse of nanofabrication is resist-based lithography and its various derivatives. However, the use of local electron, ion, and physical probe methods is expanding, driven largely by the need for fabrication without the multistep preparation processes that can result in contamination from resists and solvents. Furthermore, probe-based methods extend beyond nanofabrication to nanomanipulation and to imaging which are all vital for a rapid transition to the prototyping and testing of devices. In this work we study helium ion interactions with the surface of bulk copper indium thiophosphate CuM(III)P2X6 (M = Cr, In; X= S, Se), a novel layered 2D material, with a Helium Ion Microscope (HIM). Using this technique, we are able to control ferrielectric domains and grow conical nanostructures with enhanced conductivity whose material volumes scale with the beam dosage. Compared to the copper indium thiophosphate (CITP) from which they grow, the nanostructures are oxygen rich, sulfur poor, and with virtually unchanged copper concentration as confirmed by energy-dispersive X-ray spectroscopy (EDX). Scanning electron microscopy (SEM) imaging contrast as well as scanning microwave microscopy (SMM) measurements suggest enhanced conductivity in the formed particles, whereas atomic force microscopy (AFM) measurements indicate that the produced structures have lower dissipation and are softer as compared to the CITP.

  11. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-01

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells.

  12. Hybrid pn-junction solar cells based on layers of inorganic nanocrystals and organic semiconductors: optimization of layer thickness by considering the width of the depletion region.

    PubMed

    Saha, Sudip K; Guchhait, Asim; Pal, Amlan J

    2014-03-01

    We report the formation and characterization of hybrid pn-junction solar cells based on a layer of copper diffused silver indium disulfide (AgInS2@Cu) nanoparticles and another layer of copper phthalocyanine (CuPc) molecules. With copper diffusion in the nanocrystals, their optical absorption and hence the activity of the hybrid pn-junction solar cells was extended towards the near-IR region. To decrease the particle-to-particle separation for improved carrier transport through the inorganic layer, we replaced the long-chain ligands of copper-diffused nanocrystals in each monolayer with short-ones. Under illumination, the hybrid pn-junctions yielded a higher short-circuit current as compared to the combined contribution of the Schottky junctions based on the components. A wider depletion region at the interface between the two active layers in the pn-junction device as compared to that of the Schottky junctions has been considered to analyze the results. Capacitance-voltage characteristics under a dark condition supported such a hypothesis. We also determined the width of the depletion region in the two layers separately so that a pn-junction could be formed with a tailored thickness of the two materials. Such a "fully-depleted" device resulted in an improved photovoltaic performance, primarily due to lessening of the internal resistance of the hybrid pn-junction solar cells. PMID:24452695

  13. Melanin as an active layer in biosensors

    SciTech Connect

    Piacenti da Silva, Marina Congiu, Mirko Oliveira Graeff, Carlos Frederico de; Fernandes, Jéssica Colnaghi Biziak de Figueiredo, Natália Mulato, Marcelo

    2014-03-15

    The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12. EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.

  14. Carbon Doping of Compound Semiconductor Epitaxial Layers Grown by Metalorganic Chemical Vapor Deposition Using Carbon Tetrachloride.

    NASA Astrophysics Data System (ADS)

    Cunningham, Brian Thomas

    1990-01-01

    A dilute mixture of CCl_4 in high purity H_2 has been used as a carbon dopant source for rm Al_ {x}Ga_{1-x}As grown by low pressure metalorganic chemical vapor deposition (MOCVD). To understand the mechanism for carbon incorporation from CCl_4 doping and to provide experimental parameters for the growth of carbon doped device structures, the effects of various crystal growth parameters on CCl _4 doping have been studied, including growth temperature, growth rate, V/III ratio, Al composition, and CCl_4 flow rate. Although CCl _4 is an effective p-type dopant for MOCVD rm Al_{x}Ga_ {1-x}As, injection of CCl_4 into the reactor during growth of InP resulted in no change in the carrier concentration or carbon concentration. Abrupt, heavy carbon doping spikes in GaAs have been obtained using CCl_4 without a dopant memory effect. By annealing samples with carbon doping spikes grown within undoped, n-type, and p-type GaAs, the carbon diffusion coefficient in GaAs at 825 ^circC has been estimated and has been found to depend strongly on the GaAs background doping. Heavily carbon doped rm Al_{x}Ga _{1-x}As/GaAs superlattices have been found to be more stable against impurity induced layer disordering (IILD) than Mg or Zn doped superlattices, indicating that the low carbon diffusion coefficient limits the IILD process. Carbon doping has been used in the base region on an Npn AlGaAs/GaAs heterojunction bipolar transistor (HBT). Transistors with 3 x 10 μm self-aligned emitter fingers have been fabricated which exhibit a current gain cutoff frequency of f_ {rm t} = 26 GHz.

  15. Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

    SciTech Connect

    Chang-Hwan Kim

    2003-12-12

    Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.

  16. Synthesis, optical properties and ultrafast electronic relaxation of layered semiconductor nanoparticles: Lead iodide, bismuth iodide, bismuth sulfide

    NASA Astrophysics Data System (ADS)

    Sengupta, Archita

    nanoparticle system. The dynamics observed were somewhat dependent on the probe wavelength and independent of the excitation intensity. These results suggest that the surface plays a major role in the electronic relaxation processes of colloidal solutions of layered semiconductor nanoparticles, such as, PbI2, BiI3 and Bi2S3.

  17. The role of ultra-thin SiO2 layers in metal-insulator-semiconductor (MIS) photoelectrochemical devices (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Esposito, Daniel V.

    2015-08-01

    Solid-state junctions based on a metal-insulator-semiconductor (MIS) architecture are of great interest for a number of optoelectronic applications such as photovoltaics, photoelectrochemical cells, and photodetection. One major advantage of the MIS junction compared to the closely related metal-semiconductor junction, or Schottky junction, is that the thin insulating layer (1-3 nm thick) that separates the metal and semiconductor can significantly reduce the density of undesirable interfacial mid-gap states. The reduction in mid-gap states helps "un-pin" the junction, allowing for significantly higher built-in-voltages to be achieved. A second major advantage of the MIS junction is that the thin insulating layer can also protect the underlying semiconductor from corrosion in an electrochemical environment, making the MIS architecture well-suited for application in (photo)electrochemical applications. In this presentation, discontinuous Si-based MIS junctions immersed in electrolyte are explored for use as i.) photoelectrodes for solar-water splitting in photoelectrochemical cells (PECs) and ii.) position-sensitive photodetectors. The development and optimization of MIS photoelectrodes for both of these applications relies heavily on understanding how processing of the thin SiO2 layer impacts the properties of nano- and micro-scale MIS junctions, as well as the interactions of the insulating layer with the electrolyte. In this work, we systematically explore the effects of insulator thickness, synthesis method, and chemical treatment on the photoelectrochemical and electrochemical properties of these MIS devices. It is shown that electrolyte-induced inversion plays a critical role in determining the charge carrier dynamics within the MIS photoelectrodes for both applications.

  18. Dynamics of active layer in wooded palsas of northern Quebec

    NASA Astrophysics Data System (ADS)

    Jean, Mélanie; Payette, Serge

    2014-02-01

    Palsas are organic or mineral soil mounds having a permafrost core. Palsas are widespread in the circumpolar discontinuous permafrost zone. The annual dynamics and evolution of the active layer, which is the uppermost layer over the permafrost table and subjected to the annual freeze-thaw cycle, are influenced by organic layer thickness, snow depth, vegetation type, topography and exposure. This study examines the influence of vegetation types, with an emphasis on forest cover, on active layer dynamics of palsas in the Boniface River watershed (57°45‧ N, 76°00‧ W). In this area, palsas are often colonized by black spruce trees (Picea mariana (Mill.) B.S.P.). Thaw depth and active layer thickness were monitored on 11 wooded or non-wooded mineral and organic palsas in 2009, 2010 and 2011. Snow depth, organic layer thickness, and vegetation types were assessed. The mapping of a palsa covered by various vegetation types and a large range of organic layer thickness were used to identify the factors influencing the spatial patterns of thaw depth and active layer. The active layer was thinner and the thaw rate slower in wooded palsas, whereas it was the opposite in more exposed sites such as forest openings, shrubs and bare ground. Thicker organic layers were associated with thinner active layers and slower thaw rates. Snow depth was not an important factor influencing active layer dynamics. The topography of the mapped palsa was uneven, and the environmental factors such as organic layer, snow depth, and vegetation types were heterogeneously distributed. These factors explain a part of the spatial variation of the active layer. Over the 3-year long study, the area of one studied palsa decreased by 70%. In a context of widespread permafrost decay, increasing our understanding of factors that influence the dynamics of wooded and non-wooded palsas and understanding of the role of vegetation cover will help to define the response of discontinuous permafrost landforms

  19. p-Type semiconducting nickel oxide as an efficiency-enhancing anodal interfacial layer in bulk heterojunction solar cells

    SciTech Connect

    Irwin, Michael D; Buchholz, Donald B; Marks, Tobin J; Chang, Robert P. H.

    2014-11-25

    The present invention, in one aspect, relates to a solar cell. In one embodiment, the solar cell includes an anode, a p-type semiconductor layer formed on the anode, and an active organic layer formed on the p-type semiconductor layer, where the active organic layer has an electron-donating organic material and an electron-accepting organic material.

  20. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1995-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  1. Monolithic in-based III-V compound semiconductor focal plane array cell with single stage CCD output

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R. (Inventor); Cunningham, Thomas J. (Inventor); Krabach, Timothy N. (Inventor); Staller, Craig O. (Inventor)

    1994-01-01

    A monolithic semiconductor imager includes an indium-based III-V compound semiconductor monolithic active layer of a first conductivity type, an array of plural focal plane cells on the active layer, each of the focal plane cells including a photogate over a top surface of the active layer, a readout circuit dedicated to the focal plane cell including plural transistors formed monolithically with the monolithic active layer and a single-stage charge coupled device formed monolithically with the active layer between the photogate and the readout circuit for transferring photo-generated charge accumulated beneath the photogate during an integration period to the readout circuit. The photogate includes thin epitaxial semiconductor layer of a second conductivity type overlying the active layer and an aperture electrode overlying a peripheral portion of the thin epitaxial semiconductor layer, the aperture electrode being connectable to a photogate bias voltage.

  2. Crystallinity Modulation of Layered Carbon Nitride for Enhanced Photocatalytic Activities.

    PubMed

    Wang, Jianhai; Shen, Yanfei; Li, Ying; Liu, Songqin; Zhang, Yuanjian

    2016-08-22

    As an emerging metal-free semiconductor, covalently bonded carbon nitride (CN) has attracted much attention in photocatalysis. However, drawbacks such as a high recombination rate of excited electrons and holes hinder its potential applications. Tailoring the crystallinity of semiconductors is an important way to suppress unwanted charge recombination, but has rarely been applied to CN so far. Herein, a simple method to synthesize CN of high crystallinity by protonation of specific intermediate species during conventional polymerization is reported. Interestingly, the as-obtained CN exhibited improved photocatalytic activities of up to seven times those of the conventional bulk CN. This approach, with only a slight change to the conventional method, provides a facile way to effectively regulate the crystallinity of bulk CN to improve its photocatalytic activities and sheds light on large-scale industrial applications of CN with high efficiency for sustainable energy. PMID:27436164

  3. Crystallinity Modulation of Layered Carbon Nitride for Enhanced Photocatalytic Activities.

    PubMed

    Wang, Jianhai; Shen, Yanfei; Li, Ying; Liu, Songqin; Zhang, Yuanjian

    2016-08-22

    As an emerging metal-free semiconductor, covalently bonded carbon nitride (CN) has attracted much attention in photocatalysis. However, drawbacks such as a high recombination rate of excited electrons and holes hinder its potential applications. Tailoring the crystallinity of semiconductors is an important way to suppress unwanted charge recombination, but has rarely been applied to CN so far. Herein, a simple method to synthesize CN of high crystallinity by protonation of specific intermediate species during conventional polymerization is reported. Interestingly, the as-obtained CN exhibited improved photocatalytic activities of up to seven times those of the conventional bulk CN. This approach, with only a slight change to the conventional method, provides a facile way to effectively regulate the crystallinity of bulk CN to improve its photocatalytic activities and sheds light on large-scale industrial applications of CN with high efficiency for sustainable energy.

  4. Anomalous output characteristic shift for the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer

    SciTech Connect

    Liu, Siyang; Zhang, Chunwei; Sun, Weifeng; Su, Wei; Wang, Shaorong; Ma, Shulang; Huang, Yu

    2014-04-14

    Anomalous output characteristic shift of the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer is investigated. It shows that the linear drain current has obvious decrease when the output characteristic of fresh device is measured for two consecutive times. The charge pumping experiments demonstrate that the decrease is not from hot-carrier degradation. The reduction of cross section area for the current flowing, which results from the squeezing of the depletion region surrounding the P-top layer, is responsible for the shift. Consequently, the current capability of this special device should be evaluated by the second measured output characteristic.

  5. Flexography-Printed In2 O3 Semiconductor Layers for High-Mobility Thin-Film Transistors on Flexible Plastic Substrate.

    PubMed

    Leppäniemi, Jaakko; Huttunen, Olli-Heikki; Majumdar, Himadri; Alastalo, Ari

    2015-11-25

    Industrially scalable and roll-to-roll-compatible fabrication methods are utilized to fabricate high-mobility (≈8 cm(2) V(-1) s(-1) ) nanocrystalline In2 O3 thin-film transistors (TFTs) on an flexible plastic substrate. Flexographic printing of multiple thin In2 O3 semiconductor layers from precursor-solution is performed on a Al2 O3 gate dielectric obtained via atomic layer deposition. A low-temperature post-contact-annealing step allows control of the TFT device turn-on voltage to ≈0 V for enhancement-mode operation.

  6. Magnetic properties of the layered III-VI diluted magnetic semiconductor Ga1-xFexTe

    NASA Astrophysics Data System (ADS)

    Pekarek, T. M.; Edwards, P. S.; Olejniczak, T. L.; Lampropoulos, C.; Miotkowski, I.; Ramdas, A. K.

    2016-05-01

    Magnetic properties of single crystalline Ga1-xFexTe (x = 0.05) have been measured. GaTe and related layered III-VI semiconductors exhibit a rich collection of important properties for THz generation and detection. The magnetization versus field for an x = 0.05 sample deviates from the linear response seen previously in Ga1-xMnxSe and Ga1-xMnxS and reaches a maximum of 0.68 emu/g at 2 K in 7 T. The magnetization of Ga1-xFexTe saturates rapidly even at room temperature where the magnetization reaches 50% of saturation in a field of only 0.2 T. In 0.1 T at temperatures between 50 and 400 K, the magnetization drops to a roughly constant 0.22 emu/g. In 0 T, the magnetization drops to zero with no hysteresis present. The data is consistent with Van-Vleck paramagnetism combined with a pronounced crystalline anisotropy, which is similar to that observed for Ga1-xFexSe. Neither the broad thermal hysteresis observed from 100-300 K in In1-xMnxSe nor the spin-glass behavior observed around 10.9 K in Ga1-xMnxS are observed in Ga1-xFexTe. Single crystal x-ray diffraction data yield a rhombohedral space group bearing hexagonal axes, namely R3c. The unit cell dimensions were a = 5.01 Å, b = 5.01 Å, and c = 17.02 Å, with α = 90°, β = 90°, and γ = 120° giving a unit cell volume of 369 Å3.

  7. Semiconductor devices incorporating multilayer interference regions

    DOEpatents

    Biefeld, R.M.; Drummond, T.J.; Gourley, P.L.; Zipperian, T.E.

    1987-08-31

    A semiconductor high reflector comprising a number of thin alternating layers of semiconductor materials is electrically tunable and may be used as a temperature insensitive semiconductor laser in a Fabry-Perot configuration. 8 figs.

  8. Semiconductor devices incorporating multilayer interference regions

    DOEpatents

    Biefeld, Robert M.; Drummond, Timothy J.; Gourley, Paul L.; Zipperian, Thomas E.

    1990-01-01

    A semiconductor high reflector comprising a number of thin alternating layers of semiconductor materials is electrically tunable and may be used as a temperature insensitive semiconductor laser in a Fabry-Perot configuration.

  9. Physics of Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Brütting, Wolfgang

    2004-05-01

    Organic semiconductors are of steadily growing interest as active components in electronics and optoelectronics. Due to their flexibility, low cost and ease-of-production they represent a valid alternative to conventional inorganic semiconductor technology in a number of applications, such as flat panel displays and illumination, plastic integrated circuits or solar energy conversion. Although first commercial applications of this technology are being realized nowadays, there is still the need for a deeper scientific understanding in order to achieve optimum device performance.This special issue of physica status solidi (a) tries to give an overview of our present-day knowledge of the physics behind organic semiconductor devices. Contributions from 17 international research groups cover various aspects of this field ranging from the growth of organic layers and crystals, their electronic properties at interfaces, their photophysics and electrical transport properties to the application of these materials in different devices like organic field-effect transistors, photovoltaic cells and organic light-emitting diodes.Putting together such a special issue one soon realizes that it is simply impossible to fully cover the whole area of organic semiconductors. Nevertheless, we hope that the reader will find the collection of topics in this issue useful for getting an up-to-date review of a field which is still developing very dynamically.

  10. Thin-Layer Chromatography: Four Simple Activities for Undergraduate Students.

    ERIC Educational Resources Information Center

    Anwar, Jamil; And Others

    1996-01-01

    Presents activities that can be used to introduce thin-layer chromatography at the undergraduate level in relatively less developed countries and that can be performed with very simple and commonly available apparati in high schools and colleges. Activities include thin-layer chromatography with a test-tube, capillary feeder, burette, and rotating…

  11. Sporadic E-Layers and Meteor Activity

    NASA Astrophysics Data System (ADS)

    Alimov, Obid

    2016-07-01

    In average width it is difficult to explain variety of particularities of the behavior sporadic layer Es ionospheres without attraction long-lived metallic ion of the meteoric origin. Mass spectrometric measurements of ion composition using rockets indicate the presence of metal ions Fe+, Mg+, Si+, Na+, Ca+, K+, Al+ and others in the E-region of the ionosphere. The most common are the ions Fe+, Mg+, Si+, which are primarily concentrated in the narrow sporadic layers of the ionosphere at altitudes of 90-130 km. The entry of meteoric matter into the Earth's atmosphere is a source of meteor atoms (M) and ions (M +) that later, together with wind shear, produce midlatitude sporadic Es layer of the ionosphere. To establish the link between sporadic Es layer and meteoroid streams, we proceeded from the dependence of the ionization coefficient of meteors b on the velocity of meteor particles in different meteoroid streams. We investigated the dependence of the critical frequency f0Es of sporadic E on the particle velocity V of meteor streams and associations. It was established that the average values of f0Es are directly proportional to the velocity V of meteor streams and associations, with the correlation coefficient of 0.53 < R < 0.74. Thus, the critical frequency of the sporadic layer Es increases with the increase of particle velocity V in meteor streams, which indicates the direct influence of meteor particles on ionization of the lower ionosphere and formation of long-lived metal atoms M and ions M+ of meteoric origin.

  12. Activity Coefficients of Electrons and Holes in Degenerate Semiconductors with Nonuniform Composition

    NASA Astrophysics Data System (ADS)

    Chang, Kow-Ming; Yeh, Ta-Hsun; Wang, Shih-Wei; Lee, Chi-Hung

    1994-03-01

    A new simple, general and rigorous analytic expression for the equilibrium activity coefficients of electrons and holes in degenerate semiconductors with nonuniform composition is presented. These activity coefficients are functions of the carrier degeneracy (Fermi-Dirac statistics), the band gap, the electron affinity and the density of states which vary with position. The calculation of carrier activity coefficients requires the selection of chemical potential and electrostatic potential references. The choice of these reference states is addressed. The relationships between purely thermodynamic quantities and parameters of the band theory are also presented. Emphasis is also placed on formulating an equation in a simple, Boltzmann-like form in which the nonideal behavior is described by two parameters, the effective band-gap shrinkage, ΔE g, and the effective asymmetry factor, A. In this form the working equations for the carrier densities and activity coefficients are convenient for use in computer-aided analysis and design. The approach presented here allows convenient treatment of nonuniform degenerate semiconductors in a manner that is consistent with thermodynamics as well as with the Poisson-Boltzmann equation for the electrostatic potential.

  13. Amorphous semiconductor solar cell

    DOEpatents

    Dalal, Vikram L.

    1981-01-01

    A solar cell comprising a back electrical contact, amorphous silicon semiconductor base and junction layers and a top electrical contact includes in its manufacture the step of heat treating the physical junction between the base layer and junction layer to diffuse the dopant species at the physical junction into the base layer.

  14. Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal–oxide–semiconductor devices

    NASA Astrophysics Data System (ADS)

    Jia, Yifan; Lv, Hongliang; Niu, Yingxi; Li, Ling; Song, Qingwen; Tang, Xiaoyan; Li, Chengzhan; Zhao, Yanli; Xiao, Li; Wang, Liangyong; Tang, Guangming; Zhang, Yimen; Zhang, Yuming

    2016-09-01

    The effect of nitric oxide (NO) annealing on charge traps in the oxide insulator and transition layer in n-type 4H–SiC metal–oxide–semiconductor (MOS) devices has been investigated using the time-dependent bias stress (TDBS), capacitance–voltage (C–V), and secondary ion mass spectroscopy (SIMS). It is revealed that two main categories of charge traps, near interface oxide traps (Nniot) and oxide traps (Not), have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples. The Nniot are mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics, which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor. However, Not is mainly responsible for the TDBS induced C–V shifts. Electrons tunneling into the Not are hardly released quickly when suffering TDBS, resulting in the problem of the threshold voltage stability. Compared with the Ar-annealed sample, Nniot can be significantly suppressed by the NO annealing, but there is little improvement of Not. SIMS results demonstrate that the Nniot are distributed within the transition layer, which correlated with the existence of the excess silicon. During the NO annealing process, the excess Si atoms incorporate into nitrogen in the transition layer, allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot. Project supported by the National Natural Science Foundation of China (Grant Nos. 61404098 and 61274079), the Doctoral Fund of Ministry of Education of China (Grant No. 20130203120017), the National Key Basic Research Program of China (Grant No. 2015CB759600), the National Grid Science & Technology Project, China (Grant No. SGRI-WD-71-14-018), and the Key Specific Project in the National Science & Technology Program, China (Grant Nos. 2013ZX02305002-002 and 2015CB759600).

  15. Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal-oxide-semiconductor devices

    NASA Astrophysics Data System (ADS)

    Jia, Yifan; Lv, Hongliang; Niu, Yingxi; Li, Ling; Song, Qingwen; Tang, Xiaoyan; Li, Chengzhan; Zhao, Yanli; Xiao, Li; Wang, Liangyong; Tang, Guangming; Zhang, Yimen; Zhang, Yuming

    2016-09-01

    The effect of nitric oxide (NO) annealing on charge traps in the oxide insulator and transition layer in n-type 4H-SiC metal-oxide-semiconductor (MOS) devices has been investigated using the time-dependent bias stress (TDBS), capacitance-voltage (C-V), and secondary ion mass spectroscopy (SIMS). It is revealed that two main categories of charge traps, near interface oxide traps (Nniot) and oxide traps (Not), have different responses to the TDBS and C-V characteristics in NO-annealed and Ar-annealed samples. The Nniot are mainly responsible for the hysteresis occurring in the bidirectional C-V characteristics, which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor. However, Not is mainly responsible for the TDBS induced C-V shifts. Electrons tunneling into the Not are hardly released quickly when suffering TDBS, resulting in the problem of the threshold voltage stability. Compared with the Ar-annealed sample, Nniot can be significantly suppressed by the NO annealing, but there is little improvement of Not. SIMS results demonstrate that the Nniot are distributed within the transition layer, which correlated with the existence of the excess silicon. During the NO annealing process, the excess Si atoms incorporate into nitrogen in the transition layer, allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot. Project supported by the National Natural Science Foundation of China (Grant Nos. 61404098 and 61274079), the Doctoral Fund of Ministry of Education of China (Grant No. 20130203120017), the National Key Basic Research Program of China (Grant No. 2015CB759600), the National Grid Science & Technology Project, China (Grant No. SGRI-WD-71-14-018), and the Key Specific Project in the National Science & Technology Program, China (Grant Nos. 2013ZX02305002-002 and 2015CB759600).

  16. Magnetic anisotropy induced by crystal distortion in Ge{sub 1−x}Mn{sub x}Te/PbTe//KCl (001) ferromagnetic semiconductor layers

    SciTech Connect

    Knoff, W. Łusakowski, A.; Domagała, J. Z.; Minikayev, R.; Taliashvili, B.; Łusakowska, E.; Pieniążek, A.; Szczerbakow, A.; Story, T.

    2015-09-21

    Ferromagnetic resonance (FMR) study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor Ge{sub 1−x}Mn{sub x}Te with x = 0.14 grown by molecular beam epitaxy on KCl (001) substrate with a thin PbTe buffer. Analysis of the angular dependence of the FMR resonant field reveals that an easy magnetization axis is located near to the normal to the layer plane and is controlled by two crystal distortions present in these rhombohedral Ge{sub 1−x}Mn{sub x}Te layers: the ferroelectric distortion with the relative shift of cation and anion sub-lattices along the [111] crystal direction and the biaxial in-plane, compressive strain due to thermal mismatch.

  17. Atomic layer deposition of ZrO2 as gate dielectrics for AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors on silicon

    NASA Astrophysics Data System (ADS)

    Ye, G.; Wang, H.; Arulkumaran, S.; Ng, G. I.; Hofstetter, R.; Li, Y.; Anand, M. J.; Ang, K. S.; Maung, Y. K. T.; Foo, S. C.

    2013-09-01

    In this Letter, the device performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) on silicon substrate using 10-nm-thick atomic-layer-deposited ZrO2 as gate dielectrics is reported. The ZrO2 AlGaN/GaN MISHEMTs showed improved maximum drain current density (Idmax) with high peak transconductance (gmmax) as comparison to Schottky-barrier-gate HEMTs (SB-HEMTs). Also compared to SB-HEMTs, reverse gate leakage current was four orders of magnitude lower and forward gate bias extended to +7.4 V. At energy from -0.29 eV to -0.36 eV, low interface trap state density evaluated by AC conductance and "Hi-Lo frequency" methods indicates good quality of atomic-layer-deposited ZrO2 dielectric layer.

  18. Superior Photostability and Photocatalytic Activity of ZnO Nanoparticles Coated with Ultrathin TiO2 Layers through Atomic-Layer Deposition.

    PubMed

    Sridharan, Kishore; Jang, Eunyong; Park, Young Min; Park, Tae Joo

    2015-12-21

    Atomic-layer deposition (ALD) is a thin-film growth technology that allows for conformal growth of thin films with atomic-level control over their thickness. Although ALD is successful in the semiconductor manufacturing industry, its feasibility for nanoparticle coating has been less explored. Herein, the ALD coating of TiO2 layers on ZnO nanoparticles by employing a specialized rotary reactor is demonstrated. The photocatalytic activity and photostability of ZnO nanoparticles coated with TiO2 layers by ALD and chemical methods were examined by the photodegradation of Rhodamine B dye under UV irradiation. Even though the photocatalytic activity of the presynthesized ZnO nanoparticles is higher than that of commercial P25 TiO2 nanoparticles, their activity tends to decline due to severe photocorrosion. The chemically synthesized TiO2 coating layer on ZnO resulted in severely declined photoactivity despite the improved photostability. However, ultrathin and conformal ALD TiO2 coatings (≈ 0.75-1.5 nm) on ZnO improved its photostability without degradation of photocatalytic activity. Surprisingly, the photostability is comparable to that of pure TiO2, and the photocatalytic activity to that of pure ZnO.

  19. Active unjamming of confluent cell layers

    NASA Astrophysics Data System (ADS)

    Marchetti, M. Cristina

    Cell motion inside dense tissues governs many biological processes, including embryonic development and cancer metastasis, and recent experiments suggest that these tissues exhibit collective glassy behavior. Motivated by these observations, we have studied a model of dense tissues that combines self-propelled particle models and vertex models of confluent cell layers. In this model, referred to as self-propelled Voronoi (SPV), cells are described as polygons in a Voronoi tessellation with directed noisy cell motility and interactions governed by a shape energy that incorporates the effects of cell volume incompressibility, contractility and cell-cell adhesion. Using this model, we have demonstrated a new density-independent solid-liquid transition in confluent tissues controlled by cell motility and a cell-shape parameter measuring the interplay of cortical tension and cell-cell adhesion. An important insight of this work is that the rigidity and dynamics of cell layers depends sensitively on cell shape. We have also used the SPV model to test a new method developed by our group to determine cellular forces and tissue stresses from experimentally accessible cell shapes and traction forces, hence providing the spatio-temporal distribution of stresses in motile dense tissues. This work was done with Dapeng Bi, Lisa Manning and Xingbo Yang. MCM was supported by NSF-DMR-1305184 and by the Simons Foundation.

  20. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES; HJALMARSON,HAROLD P.; BACA,ALBERT G.; THORNTON,R.L.; DONALDSON,R.D.

    1999-12-17

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer that is very effective in the suppression of filament formation, alleviating current crowding. Damage-free operation is now possible with virtually infinite expected lifetime at much higher current levels than before. The inherent damage-free current capacity of the bulk GaAs itself depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approx}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs, unlike a switch with conventional contacts. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  1. Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

    SciTech Connect

    Baca, A.G.; Brown, D.J.; Donaldson, R.D.; Helgeson, W.D.; Hjalmarson, H.P.; Loubriel, G.M.; Mar, A.; O'Malley, M.W.; Thornton, R.L.; Zutavern, F.J.

    1999-08-05

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 50 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer beneath the PCSS contacts which is very effective in the suppression of filament formation and alleviating current crowding to improve the longevity of PCSS. Virtually indefinite, damage-free operation is now possible at much higher current levels than before. The inherent damage-free current capacity of the switch depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approximately}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.

  2. Thermally robust semiconductor optical amplifiers and laser diodes

    DOEpatents

    Dijaili, Sol P.; Patterson, Frank G.; Walker, Jeffrey D.; Deri, Robert J.; Petersen, Holly; Goward, William

    2002-01-01

    A highly heat conductive layer is combined with or placed in the vicinity of the optical waveguide region of active semiconductor components. The thermally conductive layer enhances the conduction of heat away from the active region, which is where the heat is generated in active semiconductor components. This layer is placed so close to the optical region that it must also function as a waveguide and causes the active region to be nearly the same temperature as the ambient or heat sink. However, the semiconductor material itself should be as temperature insensitive as possible and therefore the invention combines a highly thermally conductive dielectric layer with improved semiconductor materials to achieve an overall package that offers improved thermal performance. The highly thermally conductive layer serves two basic functions. First, it provides a lower index material than the semiconductor device so that certain kinds of optical waveguides may be formed, e.g., a ridge waveguide. The second and most important function, as it relates to this invention, is that it provides a significantly higher thermal conductivity than the semiconductor material, which is the principal material in the fabrication of various optoelectronic devices.

  3. Kinetics of Ion Transport in Perovskite Active Layers and Its Implications for Active Layer Stability.

    PubMed

    Bag, Monojit; Renna, Lawrence A; Adhikari, Ramesh Y; Karak, Supravat; Liu, Feng; Lahti, Paul M; Russell, Thomas P; Tuominen, Mark T; Venkataraman, D

    2015-10-14

    Solar cells fabricated using alkyl ammonium metal halides as light absorbers have the right combination of high power conversion efficiency and ease of fabrication to realize inexpensive but efficient thin film solar cells. However, they degrade under prolonged exposure to sunlight. Herein, we show that this degradation is quasi-reversible, and that it can be greatly lessened by simple modifications of the solar cell operating conditions. We studied perovskite devices using electrochemical impedance spectroscopy (EIS) with methylammonium (MA)-, formamidinium (FA)-, and MA(x)FA(1-x) lead triiodide as active layers. From variable temperature EIS studies, we found that the diffusion coefficient using MA ions was greater than when using FA ions. Structural studies using powder X-ray diffraction (PXRD) show that for MAPbI3 a structural change and lattice expansion occurs at device operating temperatures. On the basis of EIS and PXRD studies, we postulate that in MAPbI3 the predominant mechanism of accelerated device degradation under sunlight involves thermally activated fast ion transport coupled with a lattice-expanding phase transition, both of which are facilitated by absorption of the infrared component of the solar spectrum. Using these findings, we show that the devices show greatly improved operation lifetimes and stability under white-light emitting diodes, or under a solar simulator with an infrared cutoff filter or with cooling. PMID:26414066

  4. Low-background instrumental neutron activation analysis of silicon semiconductor materials

    SciTech Connect

    Smith, A.R.; McDonald, R.J.; Manini, H.; Hurley, D.L.; Norman, E.B.; Vella, M.C.; Odom, R.W.

    1996-01-01

    Samples of silicon wafers, some implanted with zinc, some with memory circuits fabricated on them, and some with oxide coatings were activated with neutrons and analyzed for trace element impurities with low-background germanium gamma-ray spectrometers. Results are presented for these samples as well as for a reference material. Because the silicon matrix activation is so small, reduced spectrometer system background permits the detection of significantly lower impurity concentrations than would otherwise be possible. For the highest efficiency and lowest background system, limits on the lowest levels of trace element concentrations have been measured for wafer sized (1 to 10 g) samples and inferred for bulk sized (365 g) samples. For wafer-sized samples, part-per-trillion detection capabilities are demonstrated for a variety of elemental contaminants important in semiconductor fabrication.

  5. Epitaxial Gd2O3 on strained Si1-xGex layers for next generation complementary metal oxide semiconductor device application

    NASA Astrophysics Data System (ADS)

    Ghosh, Kankat; Das, Sudipta; Fissel, A.; Osten, H. J.; Laha, Apurba

    2013-10-01

    Strained Si1-xGex (x = 0.1-0.4) layers were grown on Si(111) and Si(001) substrates using molecular beam epitaxy followed by the growth of epitaxial Gd2O3 thin films on Si1-xGex layers using same technique. Pt/Gd2O3/Si1-xGex/Si stacks fabricated by several in situ process steps exhibit excellent electrical properties. Surface and microstructural analysis of both Si1-xGex and Gd2O3 layers carried out by different in situ and ex situ tools reveal a relaxed epi-Gd2O3 layer on a strained Si1-xGex layer on both Si(111) and Si(001) substrates with sharp interfaces between the oxide and the SiGe layer. Standard electrical measurements, such as capacitance-voltage and leakage current analysis, demonstrate promising electrical properties for such metal oxide semiconductor capacitors. A capacitance equivalent thickness as low as 1.20 nm with associated leakage current density of 2.0 mA/cm2 was obtained for devices with 4.5 nm thin oxide films where the density of interface trap (Dit) was only ˜1011 cm-2 eV-1.

  6. Improving the catalytic activity of semiconductor nanocrystals through selective domain etching.

    PubMed

    Khon, Elena; Lambright, Kelly; Khnayzer, Rony S; Moroz, Pavel; Perera, Dimuthu; Butaeva, Evgeniia; Lambright, Scott; Castellano, Felix N; Zamkov, Mikhail

    2013-05-01

    Colloidal chemistry offers an assortment of synthetic tools for tuning the shape of semiconductor nanocrystals. While many nanocrystal architectures can be obtained directly via colloidal growth, other nanoparticle morphologies require alternative processing strategies. Here, we show that chemical etching of colloidal nanoparticles can facilitate the realization of nanocrystal shapes that are topologically inaccessible by hot-injection techniques alone. The present methodology is demonstrated by synthesizing a two-component CdSe/CdS nanoparticle dimer, constructed in a way that both CdSe and CdS semiconductor domains are exposed to the external environment. This structural morphology is highly desirable for catalytic applications as it enables both reductive and oxidative reactions to occur simultaneously on dissimilar nanoparticle surfaces. Hydrogen production tests confirmed the improved catalytic activity of CdSe/CdS dimers, which was enhanced 3-4 times upon etching treatment. We expect that the demonstrated application of etching to shaping of colloidal heteronanocrystals can become a common methodology in the synthesis of charge-separating nanocrystals, leading to advanced nanoparticles architectures for applications in areas of photocatalysis, photovoltaics, and light detection.

  7. Active photonic devices based on colloidal semiconductor nanocrystals and organometallic halide perovskites

    NASA Astrophysics Data System (ADS)

    Suárez Alvarez, Isaac

    2016-10-01

    Semiconductor nanocrystals have arisen as outstanding materials to develop a new generation of optoelectronic devices. Their fabrication under simple and low cost colloidal chemistry methods results in cheap nanostructures able to provide a wide range of optical functionalities. Their attractive optical properties include a high absorption cross section below the band gap, a high quantum yield emission at room temperature, or the capability of tuning the band-gap with the size or the base material. In addition, their solution process nature enables an easy integration on several substrates and photonic structures. As a consequence, these nanoparticles have been extensively proposed to develop several photonic applications, such as detection of light, optical gain, generation of light or sensing. This manuscript reviews the great effort undertaken by the scientific community to construct active photonic devices based on these nanoparticles. The conditions to demonstrate stimulated emission are carefully studied by comparing the dependence of the optical properties of the nanocrystals with their size, shape and composition. In addition, this paper describes the design of different photonic architectures (waveguides and cavities) to enhance the generation of photoluminescence, and hence to reduce the threshold of optical gain. Finally, semiconductor nanocrystals are compared to organometallic halide perovskites, as this novel material has emerged as an alternative to colloidal nanoparticles.

  8. Semiconductor nanocrystal-based phagokinetic tracking

    DOEpatents

    Alivisatos, A Paul; Larabell, Carolyn A; Parak, Wolfgang J; Le Gros, Mark; Boudreau, Rosanne

    2014-11-18

    Methods for determining metabolic properties of living cells through the uptake of semiconductor nanocrystals by cells. Generally the methods require a layer of neutral or hydrophilic semiconductor nanocrystals and a layer of cells seeded onto a culture surface and changes in the layer of semiconductor nanocrystals are detected. The observed changes made to the layer of semiconductor nanocrystals can be correlated to such metabolic properties as metastatic potential, cell motility or migration.

  9. Activity recognition from video using layered approach

    NASA Astrophysics Data System (ADS)

    McPherson, Charles A.; Irvine, John M.; Young, Mon; Stefanidis, Anthony

    2012-01-01

    The adversary in current threat situations can no longer be identified by what they are, but by what they are doing. This has lead to a large increase in the use of video surveillance systems for security and defense applications. With the quantity of video surveillance at the disposal of organizations responsible for protecting military and civilian lives comes issues regarding the storage and screening the data for events and activities of interest. Activity recognition from video for such applications seeks to develop automated screening of video based upon the recognition of activities of interest rather than merely the presence of specific persons or vehicle classes developed for the Cold War problem of "Find the T72 Tank". This paper explores numerous approaches to activity recognition, all of which examine heuristic, semantic, and syntactic methods based upon tokens derived from the video. The proposed architecture discussed herein uses a multi-level approach that divides the problem into three or more tiers of recognition, each employing different techniques according to their appropriateness to strengths at each tier using heuristics, syntactic recognition, and HMM's of token strings to form higher level interpretations.

  10. Sporadic Layer es and Siesmic Activity

    NASA Astrophysics Data System (ADS)

    Alimov, Obid; Blokhin, Alexandr; Kalashnikova, Tatyana

    2016-07-01

    To determine the influence of seismogenic disturbances on the calm state of the iono-sphere and assess the impact of turbulence development in sporadic-E during earthquake prepa-ration period we calculated the variation in the range of semitransparency ∆fES = f0ES - fbES. The study was based primarily on the ionograms obtained by vertical sounding of the ionosphere at Dushanbe at nighttime station from 15 to 29 August 1986. In this time period four successive earthquakes took place, which serves the purpose of this study of the impact of seis-mogenic processes on the intensity of the continuous generation of ionospheric turbulence. Analysis of the results obtained for seismic-ionospheric effects of 1986 earthquakes at station Dushanbe has shown that disturbance of ionospheric parameters during earthquake prepa-ration period displays a pronounced maximum with a duration of t = 1-6 hours. Ionospheric effects associated with the processes of earthquake preparation emerge quite predictably, which verifies seismogenic disturbances in the ionosphere. During the preparation of strong earthquakes, ionograms of vertical sounding produced at station Dushanbe - near the epicenter area - often shown the phenomenon of spreading traces of sporadic Es. It is assumed that the duration of manifestation of seismic ionospheric precursors in Du-shanbe τ = 1 - 6 hours may be associated with deformation processes in the Earth's crust and var-ious faults, as well as dissimilar properties of the environment of the epicentral area. It has been shown that for earthquakes with 4.5 ≤ M ≤ 5.5 1-2 days prior to the event iono-spheric perturbations in the parameters of the sporadic layer Es and an increase in the value of the range of semitransparency Es - ΔfEs were observed, which could lead to turbulence at altitudes of 100-130 km.

  11. HfO2-based InP n-channel metal-oxide-semiconductor field-effect transistors and metal-oxide-semiconductor capacitors using a germanium interfacial passivation layer

    NASA Astrophysics Data System (ADS)

    Kim, Hyoung-Sub; Ok, I.; Zhang, M.; Zhu, F.; Park, S.; Yum, J.; Zhao, H.; Lee, Jack C.; Majhi, Prashant

    2008-09-01

    In this letter, we present our experimental results of HfO2-based n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) and metal-oxide-semiconductor capacitors (MOSCAPs) on indium phosphide (InP) substrates using a thin germanium (Ge) interfacial passivation layer (IPL). We found that MOSCAPs on n-InP substrates showed good C-V characteristics such as a small capacitance equivalent thickness (14Å ), a small frequency dispersion (<10% and <200mV), and a low dielectric leakage current (˜5×10-4A/cm2 at Vg=1.5V), whereas MOSCAPs on p-InP exhibited poor characteristics, implying severe Fermi level pinning. It was also found that InP was more vulnerable to a high temperature process such that C-V curves showed a characteristic "bump" and inversion capacitance at relatively high frequencies. From n-channel MOSFETs on a semi-insulating InP substrate using Ge IPL, HfO2, and TaN gate electrodes, excellent electrical characteristics such as a large transconductance (9.3mS /mm) and large drain currents (12.3mA/mm at Vd=2V and Vg=Vth+2V) were achieved, which are comparable to other works.

  12. Semiconductor films on flexible iridium substrates

    DOEpatents

    Goyal, Amit

    2005-03-29

    A laminate semiconductor article includes a flexible substrate, an optional biaxially textured oxide buffer system on the flexible substrate, a biaxially textured Ir-based buffer layer on the substrate or the buffer system, and an epitaxial layer of a semiconductor. Ir can serve as a substrate with an epitaxial layer of a semiconductor thereon.

  13. Electrical properties of germanium-based insulator-semiconductor structures with an insulating layer of polynucleotides, and their monomer components on the surface

    SciTech Connect

    Yafyasov, A. M. Bakulev, V. M.; Konorov, P. P.; Bogevolnov, V. V.

    2011-12-15

    It is shown that adsorption of nucleic acid molecules and their monomeric components, i.e., nitrogenous bases, from aqueous solutions results in the formation of an insulating layer on the germanium surface. Comparatively small values of the insulator charge and the surface-state density point to promising applications of nucleotides for both the formation of germanium-based insulator-semiconductor structures with nanoscale insulating layers and low surface-state densities at the phase interface, and for germanium surface passivation. Changes in the electronic properties of the space-charge region of germanium during nucleotide adsorption on its surface can be used as a method for determining the nucleotide molecule concentration in aqueous solutions.

  14. Re-evaluation of Galileo Energetic Particle Detector data - a correction model and comparison to semiconductor detector dead-layer sensitivity losses using SRIM

    NASA Astrophysics Data System (ADS)

    Lee-Payne, Zoe Hannah

    2016-10-01

    The Energetic Particle Detector launched in 1989 on the Galileo satellite took data on the Jovian Particle environment for 8 years before its demise. Over the course of the mission the detectors in the Composition Measurement System (CMS) have visibly decayed with higher mass particles, specifically oxygen and sulphur, reading far lower energies at later epochs. By considering the non-steady accumulation of damage in the detector, as well as the operation of the priority channel data recording system in place on the EPD, an evolving correction can be made. The recalibration significance can be validated using a model of dead layer build-up in semiconductor detectors, based on SRIM results. The final aim is to assign an estimation dead-layer depth during the mission data recordings.

  15. Investigation of p-side contact layers for II-VI compound semiconductor optical devices fabricated on InP substrates by MBE

    NASA Astrophysics Data System (ADS)

    Takamatsu, Shingo; Nomura, Ichirou; Shiraishi, Tomohiro; Kishino, Katsumi

    2015-09-01

    N-doped p-type ZnTe and ZnSeTe contact layers were investigated to evaluate which is more suitable for use in II-VI compound semiconductor optical devices on InP substrates. Contact resistances (Rc) between the contact layers and several electrode materials (Pd/Pt/Au, Pd/Au, and Au) were measured by the circular transmission line model (c-TLM) method using p-n diode samples grown on InP substrates by molecular beam epitaxy (MBE). The lowest Rc (6.5×10-5 Ω cm2) was obtained in the case of the ZnTe contact and Pd/Pt/Au electrode combination, which proves that the combination is suitable for obtaining low Rc. Yellow light-emitting diode devices with a ZnTe and ZnSeTe p-contact layer were fabricated by MBE to investigate the effect of different contact layers. The devices were characterized under direct current injections at room temperature. Yellow emission at around 600 nm was observed for each device. Higher emission intensity and lower slope resistance were obtained for the device with the ZnTe contact layer and Pd/Pt/Au electrode compared with other devices. These device performances are ascribed to the low Rc of the ZnTe contact and Pd/Pt/Au electrode combination.

  16. A Novel Method for Measuring the Temperature in the Active Region of Semiconductor Modules

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Feng, Shi-Wei; Zhang, Guang-Chen; Zhu, Hui; Guo, Chun-Sheng; Qiao, Yan-Bin; Li, Jing-Wan

    2012-04-01

    The temperature in the active region of semiconductor modules can be measured by a vacuum system method. The test device is positioned on a vacuum test platform and heated in two ways, from the chip and from the case, to identify the required heat to establish stable temperature gradients for the two processes, respectively. A complementary relationship between the temperatures under the two heating methods is found. By injecting the total heat into the device, the resulting uniform temperature can be derived from the temperature curves of the chip and case. It is demonstrated that the temperature obtained from this vacuum system method is equivalent to the normal operating temperature of the device in the atmosphere. Further comparison of our result with that of the electrical method also shows good agreement.

  17. Semiconductor structure

    NASA Technical Reports Server (NTRS)

    Hovel, Harold J. (Inventor); Woodall, Jerry M. (Inventor)

    1979-01-01

    A technique for fabricating a semiconductor heterostructure by growth of a ternary semiconductor on a binary semiconductor substrate from a melt of the ternary semiconductor containing less than saturation of at least one common ingredient of both the binary and ternary semiconductors wherein in a single temperature step the binary semiconductor substrate is etched, a p-n junction with specific device characteristics is produced in the binary semiconductor substrate by diffusion of a dopant from the melt and a region of the ternary semiconductor of precise conductivity type and thickness is grown by virtue of a change in the melt characteristics when the etched binary semiconductor enters the melt.

  18. Structural complexities in the active layers of organic electronics.

    PubMed

    Lee, Stephanie S; Loo, Yueh-Lin

    2010-01-01

    The field of organic electronics has progressed rapidly in recent years. However, understanding the direct structure-function relationships between the morphology in electrically active layers and the performance of devices composed of these materials has proven difficult. The morphology of active layers in organic electronics is inherently complex, with heterogeneities existing across multiple length scales, from subnanometer to micron and millimeter range. A major challenge still facing the organic electronics community is understanding how the morphology across all of the length scales in active layers collectively determines the device performance of organic electronics. In this review we highlight experiments that have contributed to the elucidation of structure-function relationships in organic electronics and also point to areas in which knowledge of such relationships is still lacking. Such knowledge will lead to the ability to select active materials on the basis of their inherent properties for the fabrication of devices with prespecified characteristics.

  19. Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

    NASA Astrophysics Data System (ADS)

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-03-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  20. Photo-catalytic Activities of Plant Hormones on Semiconductor Nanoparticles by Laser-Activated Electron Tunneling and Emitting

    PubMed Central

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-01-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO2), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated. PMID:25749635

  1. Photo-catalytic activities of plant hormones on semiconductor nanoparticles by laser-activated electron tunneling and emitting.

    PubMed

    Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Jiang, Ruowei; Zhong, Hongying

    2015-01-01

    Understanding of the dynamic process of laser-induced ultrafast electron tunneling is still very limited. It has been thought that the photo-catalytic reaction of adsorbents on the surface is either dependent on the number of resultant electron-hole pairs where excess energy is lost to the lattice through coupling with phonon modes, or dependent on irradiation photon wavelength. We used UV (355 nm) laser pulses to excite electrons from the valence band to the conduction band of titanium dioxide (TiO₂), zinc oxide (ZnO) and bismuth cobalt zinc oxide (Bi₂O₃)₀.₀₇(CoO)₀.₀₃(ZnO)₀.₉ semiconductor nanoparticles with different photo catalytic properties. Photoelectrons are extracted, accelerated in a static electric field and eventually captured by charge deficient atoms of adsorbed organic molecules. A time-of-flight mass spectrometer was used to detect negative molecules and fragment ions generated by un-paired electron directed bond cleavages. We show that the probability of electron tunneling is determined by the strength of the static electric field and intrinsic electron mobility of semiconductors. Photo-catalytic dissociation or polymerization reactions of adsorbents are highly dependent on the kinetic energy of tunneling electrons as well as the strength of laser influx. By using this approach, photo-activities of phytohormones have been investigated.

  2. Controlling the interface charge density in GaN-based metal-oxide-semiconductor heterostructures by plasma oxidation of metal layers

    SciTech Connect

    Hahn, Herwig Kalisch, Holger; Vescan, Andrei; Pécz, Béla; Kovács, András; Heuken, Michael

    2015-06-07

    In recent years, investigating and engineering the oxide-semiconductor interface in GaN-based devices has come into focus. This has been driven by a large effort to increase the gate robustness and to obtain enhancement mode transistors. Since it has been shown that deep interface states act as fixed interface charge in the typical transistor operating regime, it appears desirable to intentionally incorporate negative interface charge, and thus, to allow for a positive shift in threshold voltage of transistors to realise enhancement mode behaviour. A rather new approach to obtain such negative charge is the plasma-oxidation of thin metal layers. In this study, we present transmission electron microscopy and energy dispersive X-ray spectroscopy analysis as well as electrical data for Al-, Ti-, and Zr-based thin oxide films on a GaN-based heterostructure. It is shown that the plasma-oxidised layers have a polycrystalline morphology. An interfacial amorphous oxide layer is only detectable in the case of Zr. In addition, all films exhibit net negative charge with varying densities. The Zr layer is providing a negative interface charge density of more than 1 × 10{sup 13 }cm{sup –2} allowing to considerably shift the threshold voltage to more positive values.

  3. Two-dimensional inorganic–organic hybrid semiconductors composed of double-layered ZnS and monoamines with aromatic and heterocyclic aliphatic rings: Syntheses, structures, and properties

    SciTech Connect

    Wang, Sujing; Li, Jing

    2015-04-15

    As an addition to the II–VI based inorganic–organic hybrid semiconductor family, five new two-dimensional (2D) double-layered structures have been synthesized employing monoamines with different aromatic or heterocyclic aliphatic rings. Zn{sub 2}S{sub 2}(bza) (1), Zn{sub 2}S{sub 2}(mbza) (2), Zn{sub 2}S{sub 2}(fbza) (3), Zn{sub 2}S{sub 2}(pca) (4), and Zn{sub 2}S{sub 2}(thfa) (5) (bza=benzylamine, mbza=4-methoxybenzylamine, fbza=4-flurobenzylamine, pca=3-picolylamine, and thfa=tetrahydrofurfurylamine) are prepared by solvothermal reactions and characterized by different analytical methods, including powder X-ray diffraction, optical diffuse reflection, thermogravimetric analysis and photoluminescence spectroscopy. The powder X-ray diffraction patterns show that all five compounds adopt 2D double-layered structures. Optical diffuse reflectance spectra of these compounds suggest that they have notably lower band gaps than those of the similar compounds composed of aliphatic alkyl amines. Their photoluminescence properties and thermal stability are also analyzed. - Graphical abstract: Five new members of two-dimensional double-layered 2D-Zn{sub 2}S{sub 2}(L) (L=Ligand) structures employing monoamines with different aromatic or heterocyclic aliphatic rings have been designed, synthesized, and characterized. - Highlights: • A new sub-family of II-VI based hybrid semiconductors are designed, synthesized, and structurally characterized using amines with aromatic or aliphatic cyclic rings. • These compounds have notably lower band gaps than those made of aliphatic alkyl amines, greatly broadening the range of band gaps of this material family. • They emit strongly with systematically tunable emission intensity and energy.

  4. On the charge neutrality level and the electronic properties of interphase boundaries in the layered ε-GaSe semiconductor

    SciTech Connect

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

    2015-10-15

    The height of the (Au, Pd, Pt, Cu, Ag, Sn, In, Al, Mg, Ca, Li, Cs)/GaSe(0001) Schottky barrier as a function of the metal work function and the energy-band offsets in InSe(0001)/GaSe(0001) and GaSe(0001)/Si(111) heteropairs are analyzed within the context of the concept of the charge neutrality level, CNL{sub vb}(GaSe) = E{sub v} + 0.83 eV, with consideration for partial screening of the interface electrostatic dipole by metal- or semiconductor-induced tunneling states at the GaSe(0001) surface.

  5. Enhanced excitonic photoconductivity due to built-in internal electric field in TlGaSe{sub 2} layered semiconductor

    SciTech Connect

    Seyidov, MirHasan Yu. Suleymanov, Rauf A.; Şale, Yasin; Balaban, Ertan

    2014-12-07

    The strong enhancement, by several orders of magnitude, of the excitonic peak within the photoconductivity spectrum of TlGaSe{sub 2} semiconductor was observed. The samples were polarized in external dc electric field, which was applied prior to the measurements. Due to the accumulation of charges near the surface, an internal electric field was formed. Electron-hole pairs that were created after the absorption of light are fallen in and then separated by the built-in electric field, which prevents radiative recombination process.

  6. Fabricating metal-oxide-semiconductor field-effect transistors on a polyethylene terephthalate substrate by applying low-temperature layer transfer of a single-crystalline silicon layer by meniscus force

    NASA Astrophysics Data System (ADS)

    Sakaike, Kohei; Akazawa, Muneki; Nakamura, Shogo; Higashi, Seiichiro

    2013-12-01

    A low-temperature local-layer technique for transferring a single-crystalline silicon (c-Si) film by using a meniscus force was proposed, and an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) was fabricated on polyethylene terephthalate (PET) substrate. It was demonstrated that it is possible to transfer and form c-Si films in the required shape at the required position on PET substrates at extremely low temperatures by utilizing a meniscus force. The proposed technique for layer transfer was applied for fabricating high-performance c-Si MOSFETs on a PET substrate. The fabricated MOSFET showed a high on/off ratio of more than 108 and a high field-effect mobility of 609 cm2 V-1 s-1.

  7. Fabricating metal-oxide-semiconductor field-effect transistors on a polyethylene terephthalate substrate by applying low-temperature layer transfer of a single-crystalline silicon layer by meniscus force

    SciTech Connect

    Sakaike, Kohei; Akazawa, Muneki; Nakamura, Shogo; Higashi, Seiichiro

    2013-12-02

    A low-temperature local-layer technique for transferring a single-crystalline silicon (c-Si) film by using a meniscus force was proposed, and an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) was fabricated on polyethylene terephthalate (PET) substrate. It was demonstrated that it is possible to transfer and form c-Si films in the required shape at the required position on PET substrates at extremely low temperatures by utilizing a meniscus force. The proposed technique for layer transfer was applied for fabricating high-performance c-Si MOSFETs on a PET substrate. The fabricated MOSFET showed a high on/off ratio of more than 10{sup 8} and a high field-effect mobility of 609 cm{sup 2} V{sup −1} s{sup −1}.

  8. Silicon dioxide with a silicon interfacial layer as an insulating gate for highly stable indium phosphide metal-insulator-semiconductor field effect transistors

    NASA Technical Reports Server (NTRS)

    Kapoor, V. J.; Shokrani, M.

    1991-01-01

    A novel gate insulator consisting of silicon dioxide (SiO2) with a thin silicon (Si) interfacial layer has been investigated for high-power microwave indium phosphide (InP) metal-insulator-semiconductor field effect transistors (MISFETs). The role of the silicon interfacial layer on the chemical nature of the SiO2/Si/InP interface was studied by high-resolution X-ray photoelectron spectroscopy. The results indicated that the silicon interfacial layer reacted with the native oxide at the InP surface, thus producing silicon dioxide, while reducing the native oxide which has been shown to be responsible for the instabilities in InP MISFETs. While a 1.2-V hysteresis was present in the capacitance-voltage (C-V) curve of the MIS capacitors with silicon dioxide, less than 0.1 V hysteresis was observed in the C-V curve of the capacitors with the silicon interfacial layer incorporated in the insulator. InP MISFETs fabricated with the silicon dioxide in combination with the silicon interfacial layer exhibited excellent stability with drain current drift of less than 3 percent in 10,000 sec, as compared to 15-18 percent drift in 10,000 sec for devices without the silicon interfacial layer. High-power microwave InP MISFETs with Si/SiO2 gate insulators resulted in an output power density of 1.75 W/mm gate width at 9.7 GHz, with an associated power gain of 2.5 dB and 24 percent power added efficiency.

  9. Temperature-activated layer-breathing vibrations in few-layer graphene.

    PubMed

    Lui, Chun Hung; Ye, Zhipeng; Keiser, Courtney; Xiao, Xun; He, Rui

    2014-08-13

    We investigated the low-frequency Raman spectra of freestanding few-layer graphene (FLG) at varying temperatures (400-900 K) controlled by laser heating. At high temperature, we observed the fundamental Raman mode for the lowest-frequency branch of rigid-plane layer-breathing mode (LBM) vibration. The mode frequency redshifts dramatically from 81 cm(-1) for bilayer to 23 cm(-1) for 8-layer. The thickness dependence is well described by a simple model of coupled oscillators. Notably, the LBM Raman response is unobservable at room temperature, and it is turned on at higher temperature (>600 K) with a steep increase of Raman intensity. The observation suggests that the LBM vibration is strongly suppressed by molecules adsorbed on the graphene surface but is activated as desorption occurs at high temperature.

  10. Passive and active control of boundary layer transition

    NASA Astrophysics Data System (ADS)

    Nosenchuck, Daniel Mark

    It is well known that laminar-turbulent boundary layer transition is initiated by the formation of Tollmien-Schlichting laminar instability waves. The amplification rates of these waves are strongly dependent on the shape of the boundary layer velocity profile. Consequently, the transition process can be controlled by modifying the velocity profile. This can be accomplished by controlling the pressure gradient (dp/dx), using boundary layer suction, installing surface roughness elements, or by surface heating or cooling. Methods used to modify the transition process through changes in the mean velocity profile are called "passive" in this paper. There exists a large set of experiments and theory on the application of passive methods for boundary layer control. In the present work only surface heating will be addressed.Transition measurements were made on a heated flat plate in water. Results are presented for several plate wall temperature distributions. An increase by a factor of 2.5 in transition Reynolds number was observed for a 5°C isothermal wall overheat. Buoyancy effects on transition were minimal due to the small Richardson and Grashof numbers encountered in the experiments.The amplification of laminar instability waves is comparatively to process, taking place over many boundary layer thicknesses. After the slow amplification of the laminar instability waves, transition occurs by a strong three dimensional dynamic instability. It appears possible to attenuate (or reinforce) the instability waves by introducing amplitude-and phase-controlled perturbations into the laminar boundary layer using feedback control system. This method is called "active" control and forms the larger part of the research reported in this thesis.A combination of sensors, activators and feedback control electronics is required for active control. The sensors used in the experiments are flush-mounted hot film wall shear robes. A new type of activator was developed using thin, flush

  11. High-gain complementary metal-oxide-semiconductor inverter based on multi-layer WSe2 field effect transistors without doping

    NASA Astrophysics Data System (ADS)

    Kang, Won-Mook; Cho, In-Tak; Roh, Jeongkyun; Lee, Changhee; Lee, Jong-Ho

    2016-10-01

    A high-gain complementary metal-oxide-semiconductor (CMOS) logic inverter was implemented by fabricating p- and n-type field effect transistors (FETs) based on multi-layer WSe2 on the same wafer. Au as a high work-function metal is contacted to WSe2 for the source/drain of the p-type FET. The n-type FET has an Al electrode contacted to WSe2 for the source/drain. Both FETs were designed to have similar on-current densities (>10-7 A μm-1) and high on/off current ratios (>106). The inverter shows excellent switching characteristics including relatively high voltage gains (>25) and high noise margins (>0.9) in the range of supply voltage from 2 V to 8 V. This work has a great significance in the realization of a CMOS logic gate based on WSe2 without an additional doping scheme.

  12. Monte Carlo simulation of the influence of pressure and target-substrate distance on the sputtering process for metal and semiconductor layers

    NASA Astrophysics Data System (ADS)

    Bouazza, Abdelkader; Settaouti, Abderrahmane

    2016-07-01

    The energy and the number of particles arriving at the substrate during physical vapor deposition (PVD) are in close relation with divers parameters. In this work, we present the influence of the distance between the target and substrate and the gas pressure in the sputtering process of deposited layers of metals (Cu, Al and Ag) and semiconductors (Ge, Te and Si) for substrate diameter of 40 cm and target diameter of 5 cm. The nascent sputter flux, the flux of the atoms and their energy arriving at the substrate have been simulated by Monte Carlo codes. A good agreement between previous works of other groups and our simulations for sputter pressures (0.3-1 Pa) and target-substrate distances (8-20 cm) is obtained.

  13. Effect of wetting-layer density of states on the gain and phase recovery dynamics of quantum-dot semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Kim, Jungho; Yu, Bong-Ahn

    2015-03-01

    We numerically investigate the effect of the wetting-layer (WL) density of states on the gain and phase recovery dynamics of quantum-dot semiconductor optical amplifiers in both electrical and optical pumping schemes by solving 1088 coupled rate equations. The temporal variations of the ultrafast gain and phase recovery responses at the ground state (GS) are calculated as a function of the WL density of states. The ultrafast gain recovery responses do not significantly depend on the WL density of states in the electrical pumping scheme and the three optical pumping schemes such as the optical pumping to the WL, the optical pumping to the excited state ensemble, and the optical pumping to the GS ensemble. The ultrafast phase recovery responses are also not significantly affected by the WL density of states except the optical pumping to the WL, where the phase recovery component caused by the WL becomes slowed down as the WL density of states increases.

  14. Monte Carlo simulation of the influence of pressure and target-substrate distance on the sputtering process for metal and semiconductor layers

    NASA Astrophysics Data System (ADS)

    Bouazza, Abdelkader; Settaouti, Abderrahmane

    2016-07-01

    The energy and the number of particles arriving at the substrate during physical vapor deposition (PVD) are in close relation with divers parameters. In this work, we present the influence of the distance between the target and substrate and the gas pressure in the sputtering process of deposited layers of metals (Cu, Al and Ag) and semiconductors (Ge, Te and Si) for substrate diameter of 40 cm and target diameter of 5 cm. The nascent sputter flux, the flux of the atoms and their energy arriving at the substrate have been simulated by Monte Carlo codes. A good agreement between previous works of other groups and our simulations for sputter pressures (0.3-1 Pa) and target-substrate distances (8-20 cm) is obtained.

  15. Estimating Active Layer Thickness from Remotely Sensed Surface Deformation

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K. M.; Zhang, T.; Wahr, J. M.

    2010-12-01

    We estimate active layer thickness (ALT) from remotely sensed surface subsidence during thawing seasons derived from interferometric synthetic aperture radar (InSAR) measurements. Ground ice takes up more volume than ground water, so as the soil thaws in summer and the active layer deepens, the ground subsides. The volume of melted ground water during the summer thaw determines seasonal subsidence. ALT is defined as the maximum thaw depth at the end of a thawing season. By using InSAR to measure surface subsidence between the start and end of summer season, one can estimate the depth of thaw over a large area (typically 100 km by 100 km). We developed an ALT retrieval algorithm integrating InSAR-derived surface subsidence, observed soil texture, organic matter content, and moisture content. We validated this algorithm in the continuous permafrost area on the North Slope of Alaska. Based on InSAR measurements using ERS-1/2 SAR data, our estimated values match in situ measurements of ALT within 1--10 cm at Circumpolar Active Layer Monitoring (CALM) sites within the study area. The active layer plays a key role in land surface processes in cold regions. Current measurements of ALT using mechanical probing, frost/thaw tubes, or inferred from temperature measurements are of high quality, but limited in spatial coverage. Using InSAR to estimate ALT greatly expands the spatial coverage of ALT observations.

  16. 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.

  17. Method for fabricating an interconnected array of semiconductor devices

    DOEpatents

    Grimmer, Derrick P.; Paulson, Kenneth R.; Gilbert, James R.

    1989-10-10

    Semiconductor layer and conductive layer formed on a flexible substrate, divided into individual devices and interconnected with one another in series by interconnection layers and penetrating terminals.

  18. Variable temperature semiconductor film deposition

    DOEpatents

    Li, Xiaonan; Sheldon, Peter

    1998-01-01

    A method of depositing a semiconductor material on a substrate. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  19. Variable temperature semiconductor film deposition

    DOEpatents

    Li, X.; Sheldon, P.

    1998-01-27

    A method of depositing a semiconductor material on a substrate is disclosed. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  20. Overview of the recent activities of the RD50 collaboration on radiation hardening of semiconductor detectors for the sLHC

    NASA Astrophysics Data System (ADS)

    Casse, Gianluigi

    2009-01-01

    The RD50 collaboration has been exploring the development of radiation hard semiconductor devices for very high-luminosity colliders since 2002. The target fluence to qualify detectors set by the anticipated dose for the innermost tracking layers of the future upgrade of the CERN large hadron collider (LHC) is 10 16 1 MeV neutron equivalent (n eq) cm -2. This is about an order of magnitude higher than the maximum dose for the most exposed silicon detectors in the current machine. RD50 investigates the radiation hardening of silicon sensors from many angles: improvement of the intrinsic tolerance of the substrate material, optimisation of the readout geometry and study of novel design of detectors. A review of some of the recent activities within RD50 is here presented.

  1. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  2. Active microwave remote sensing of an anisotropic random medium layer

    NASA Technical Reports Server (NTRS)

    Lee, J. K.; Kong, J. A.

    1985-01-01

    A two-layer anisotropic random medium model has been developed to study the active remote sensing of the earth. The dyadic Green's function for a two-layer anisotropic medium is developed and used in conjunction with the first-order Born approximation to calculate the backscattering coefficients. It is shown that strong cross-polarization occurs in the single scattering process and is indispensable in the interpretation of radar measurements of sea ice at different frequencies, polarizations, and viewing angles. The effects of anisotropy on the angular responses of backscattering coefficients are also illustrated.

  3. Multiphysics modeling of non-linear laser-matter interactions for optically active semiconductors

    NASA Astrophysics Data System (ADS)

    Kraczek, Brent; Kanp, Jaroslaw

    Development of photonic devices for sensors and communications devices has been significantly enhanced by computational modeling. We present a new computational method for modelling laser propagation in optically-active semiconductors within the paraxial wave approximation (PWA). Light propagation is modeled using the Streamline-upwind/Petrov-Galerkin finite element method (FEM). Material response enters through the non-linear polarization, which serves as the right-hand side of the FEM calculation. Maxwell's equations for classical light propagation within the PWA can be written solely in terms of the electric field, producing a wave equation that is a form of the advection-diffusion-reaction equations (ADREs). This allows adaptation of the computational machinery developed for solving ADREs in fluid dynamics to light-propagation modeling. The non-linear polarization is incorporated using a flexible framework to enable the use of multiple methods for carrier-carrier interactions (e.g. relaxation-time-based or Monte Carlo) to enter through the non-linear polarization, as appropriate to the material type. We demonstrate using a simple carrier-carrier model approximating the response of GaN. Supported by ARL Materials Enterprise.

  4. A Unified Understanding of the Thickness-Dependent Bandgap Transition in Hexagonal Two-Dimensional Semiconductors.

    PubMed

    Kang, Joongoo; Zhang, Lijun; Wei, Su-Huai

    2016-02-18

    Many important layered semiconductors, such as hexagonal boron nitride (hBN) and transition-metal dichalcogenides (TMDs), are derived from a hexagonal lattice. A single layer of such hexagonal semiconductors generally has a direct bandgap at the high-symmetry point K, whereas it becomes an indirect, optically inactive semiconductor as the number of layers increases to two or more. Here, taking hBN and MoS2 as examples, we reveal the microscopic origin of the direct-to-indirect bandgap transition of hexagonal layered materials. Our symmetry analysis and first-principles calculations show that the bandgap transition arises from the lack of the interlayer orbital couplings for the band-edge states at K, which are inherently weak because of the crystal symmetries of hexagonal layered materials. Therefore, it is necessary to judiciously break the underlying crystal symmetries to design more optically active, multilayered semiconductors from hBN or TMDs.

  5. Electrical properties of GaAs metal-oxide-semiconductor structure comprising Al2O3 gate oxide and AlN passivation layer fabricated in situ using a metal-organic vapor deposition/atomic layer deposition hybrid system

    NASA Astrophysics Data System (ADS)

    Aoki, Takeshi; Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-01

    This paper presents a compressive study on the fabrication and optimization of GaAs metal-oxide-semiconductor (MOS) structures comprising a Al2O3 gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal-organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al2O3 in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al2O3 layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance-voltage (C-V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (Dit) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce Dit to below 2 × 1012 cm-2 eV-1. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  6. Complex-envelope alternating-direction-implicit FDTD method for simulating active photonic devices with semiconductor/solid-state media.

    PubMed

    Singh, Gurpreet; Ravi, Koustuban; Wang, Qian; Ho, Seng-Tiong

    2012-06-15

    A complex-envelope (CE) alternating-direction-implicit (ADI) finite-difference time-domain (FDTD) approach to treat light-matter interaction self-consistently with electromagnetic field evolution for efficient simulations of active photonic devices is presented for the first time (to our best knowledge). The active medium (AM) is modeled using an efficient multilevel system of carrier rate equations to yield the correct carrier distributions, suitable for modeling semiconductor/solid-state media accurately. To include the AM in the CE-ADI-FDTD method, a first-order differential system involving CE fields in the AM is first set up. The system matrix that includes AM parameters is then split into two time-dependent submatrices that are then used in an efficient ADI splitting formula. The proposed CE-ADI-FDTD approach with AM takes 22% of the time as the approach of the corresponding explicit FDTD, as validated by semiconductor microdisk laser simulations.

  7. Method and structure for passivating semiconductor material

    DOEpatents

    Pankove, Jacques I.

    1981-01-01

    A structure for passivating semiconductor material comprises a substrate of crystalline semiconductor material, a relatively thin film of carbon disposed on a surface of the crystalline material, and a layer of hydrogenated amorphous silicon deposited on the carbon film.

  8. III-V semiconductor nanoresonators-a new strategy for passive, active, and nonlinear all-dielectric metamaterials

    DOE PAGES

    Liu, Sheng; Keeler, Gordon A.; Reno, John L.; Sinclair, Michael B.; Brener, Igal

    2016-06-10

    We demonstrate 2D and multilayer dielectric metamaterials made from III–V semiconductors using a monolithic fabrication process. The resulting structures could be used to recompress chirped femtosecond optical pulses and in a variety of other optical applications requiring low loss. Moreover, these III–V all-dielectric metamaterials could enable novel active applications such as efficient nonlinear frequency converters, light emitters, detectors, and modulators.

  9. A melt clusterization within the interfacial boundary layer and its hydrodynamics modelling at the microgravity semiconductor single crystal growth

    NASA Astrophysics Data System (ADS)

    Ginkin, Vladimir; Kartavykh, Andrey; Zabudko, Mikhail

    2004-10-01

    The paper gives a brief analysis of current concepts on the process of melt ordering and structural self-organization at the temperature close to melting point, including that within the interface area when growing semiconductor single crystals. The experimental data presented confirm the existence of ordered multi-atomic growth units (clusters) in the melt under the conditions close to undisturbed equilibrium crystallization. The conclusion is justified on the prospects of studying the clustering processes within a melt in microgravity. A mathematical model of convective mass transfer is proposed as an independent investigation tool. This model includes the equations of hydrodynamics, impurity transfer and convective flow within the interface transient area. Materials properties and the temperature are presented as a single-value function of enthalpy. For the first time the melt structural model near the crystallization front considers the availability of clusters formation (CF) that cause resistance to the melt flow. This resistance of medium is described by means of specific double-phase coefficient introduction depending on the enthalpy value in each assigned mesh micro-volume under calculation. Basing onto our previous space growth experiments aboard the Photon series satellites (J. Crystal Growth 205 (1999) 497; 223 (2001) 29), the necessary empirical model parameters are evaluated. The results of CF-model testing are demonstrated, including the description of real orbital and ground-based GaSb:In crystallization experiments.

  10. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

    PubMed

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-12-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT. PMID:27129687

  11. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors.

    PubMed

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-12-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade(-1) and 3.62 × 10(11) eV(-1) cm(-2), respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

  12. Three-Dimensional Flexible Complementary Metal-Oxide-Semiconductor Logic Circuits Based On Two-Layer Stacks of Single-Walled Carbon Nanotube Networks.

    PubMed

    Zhao, Yudan; Li, Qunqing; Xiao, Xiaoyang; Li, Guanhong; Jin, Yuanhao; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan

    2016-02-23

    We have proposed and fabricated stable and repeatable, flexible, single-walled carbon nanotube (SWCNT) thin film transistor (TFT) complementary metal-oxide-semiconductor (CMOS) integrated circuits based on a three-dimensional (3D) structure. Two layers of SWCNT-TFT devices were stacked, where one layer served as n-type devices and the other one served as p-type devices. On the basis of this method, it is able to save at least half of the area required to construct an inverter and make large-scale and high-density integrated CMOS circuits easier to design and manufacture. The 3D flexible CMOS inverter gain can be as high as 40, and the total noise margin is more than 95%. Moreover, the input and output voltage of the inverter are exactly matched for cascading. 3D flexible CMOS NOR, NAND logic gates, and 15-stage ring oscillators were fabricated on PI substrates with high performance as well. Stable electrical properties of these circuits can be obtained with bending radii as small as 3.16 mm, which shows that such a 3D structure is a reliable architecture and suitable for carbon nanotube electrical applications in complex flexible and wearable electronic devices. PMID:26768020

  13. Impact of an ultra-thin ZrTiO4 buffer layer for long retention characteristics of metal–ferroelectric–insulator–semiconductor capacitor

    NASA Astrophysics Data System (ADS)

    Hyo Park, Jae; Joo, Seung Ki

    2016-05-01

    In most ferroelectric field-effect transistors (FeFETs), a thin interfacial layer is inserted between the ferroelectric and semiconductor in order to avoid the interdiffusion of metallic impurities. In this work, we have used ZrTiO4 (ZTO) as an interfacial layer to improve the interface of Pb(Zr,Ti)O3 (PZT)/Si and prevent the diffusion of metallic impurities of PZT. It was found that optimizing the thickness of ZTO strongly influences the FeFET retention characteristics. Gate leakage current and Pb metallic interdiffusion were effectively suppressed when the ZTO thickness was thicker than 5 nm. However, a self-depolarization field was generated by the charge compensation loss in PZT, caused by the thick ZTO. On the other hand, our sample showed a large gate leakage current and Pb metallic interdiffusion when ZTO was thinner than 2 nm. It was found that 2 nm thick ZTO is the optimum thickness for long retention characteristics in FeFETs.

  14. High-pressure melt growth and transport properties of SiP, SiAs, GeP, and GeAs 2D layered semiconductors

    NASA Astrophysics Data System (ADS)

    Barreteau, C.; Michon, B.; Besnard, C.; Giannini, E.

    2016-06-01

    Silicon and Germanium monopnictides SiP, SiAs, GeP and GeAs form a family of 2D layered semiconductors. We have succeeded in growing bulk single crystals of these compounds by melt-growth under high pressure (0.5-1 GPa) in a cubic anvil hot press. Large (mm-size), shiny, micaceous crystals of GeP, GeAs and SiAs were obtained, and could be exfoliated into 2D flakes. Small and brittle crystals of SiP were yielded by this method. High-pressure sintered polycrystalline SiP and GeAs have also been successfully used as a precursor in the Chemical Vapor Transport growth of these crystals in the presence of I2 as a transport agent. All compounds are found to crystallize in the expected layered structure and do not undergo any structural transition at low temperature, as shown by Raman spectroscopy down to T=5 K. All materials exhibit a semiconducting behavior. The electrical resistivity of GeP, GeAs and SiAs is found to depend on temperature following a 2D-Variable Range Hopping conduction mechanism. The availability of bulk crystals of these compounds opens new perspectives in the field of 2D semiconducting materials for device applications.

  15. Atomic Layer Deposition of Gallium Oxide Films as Gate Dielectrics in AlGaN/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistors

    NASA Astrophysics Data System (ADS)

    Shih, Huan-Yu; Chu, Fu-Chuan; Das, Atanu; Lee, Chia-Yu; Chen, Ming-Jang; Lin, Ray-Ming

    2016-04-01

    In this study, films of gallium oxide (Ga2O3) were prepared through remote plasma atomic layer deposition (RP-ALD) using triethylgallium and oxygen plasma. The chemical composition and optical properties of the Ga2O3 thin films were investigated; the saturation growth displayed a linear dependence with respect to the number of ALD cycles. These uniform ALD films exhibited excellent uniformity and smooth Ga2O3-GaN interfaces. An ALD Ga2O3 film was then used as the gate dielectric and surface passivation layer in a metal-oxide-semiconductor high-electron-mobility transistor (MOS-HEMT), which exhibited device performance superior to that of a corresponding conventional Schottky gate HEMT. Under similar bias conditions, the gate leakage currents of the MOS-HEMT were two orders of magnitude lower than those of the conventional HEMT, with the power-added efficiency enhanced by up to 9 %. The subthreshold swing and effective interfacial state density of the MOS-HEMT were 78 mV decade-1 and 3.62 × 1011 eV-1 cm-2, respectively. The direct-current and radio-frequency performances of the MOS-HEMT device were greater than those of the conventional HEMT. In addition, the flicker noise of the MOS-HEMT was lower than that of the conventional HEMT.

  16. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Kane, D.L.

    1986-01-01

    In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. During the ablation period, runoff dominates the hydrologic cycle. Some meltwater goes to rewetting the organic soils in the active layer. The remainder is lost primarily because of evaporation, since transpiration is not a very active process at this time. Following the snowmelt period, evapotranspiration becomes the dominate process, with base flow contributing the other watershed losses. It is important to note that the water initally lost by evapotranspiration entered the organic layer during melt. This water from the snowpack ensures that each year the various plant communities will have sufficient water to start a new summer of growth.

  17. Layered shielding design for an active neutron interrogation system

    NASA Astrophysics Data System (ADS)

    Whetstone, Zachary D.; Kearfott, Kimberlee J.

    2016-08-01

    The use of source and detector shields in active neutron interrogation can improve detector signal. In simulations, a shielded detector with a source rotated π/3 rad relative to the opening decreased neutron flux roughly three orders of magnitude. Several realistic source and detector shield configurations were simulated. A layered design reduced neutron and secondary photon flux in the detector by approximately one order of magnitude for a deuterium-tritium source. The shield arrangement can be adapted for a portable, modular design.

  18. Electrically pumped edge-emitting photonic bandgap semiconductor laser

    DOEpatents

    Lin, Shawn-Yu; Zubrzycki, Walter J.

    2004-01-06

    A highly efficient, electrically pumped edge-emitting semiconductor laser based on a one- or two-dimensional photonic bandgap (PBG) structure is described. The laser optical cavity is formed using a pair of PBG mirrors operating in the photonic band gap regime. Transverse confinement is achieved by surrounding an active semiconductor layer of high refractive index with lower-index cladding layers. The cladding layers can be electrically insulating in the passive PBG mirror and waveguide regions with a small conducting aperture for efficient channeling of the injection pump current into the active region. The active layer can comprise a quantum well structure. The quantum well structure can be relaxed in the passive regions to provide efficient extraction of laser light from the active region.

  19. Active terahertz beam steering by photo-generated graded index gratings in thin semiconductor films.

    PubMed

    Steinbusch, T P; Tyagi, H K; Schaafsma, M C; Georgiou, G; Gómez Rivas, J

    2014-11-01

    We demonstrate active beam steering of terahertz radiation using a photo-excited thin layer of gallium arsenide. A constant gradient of phase discontinuity along the interface is introduced by an spatially inhomogeneous density of free charge carriers that are photo-generated in the GaAs with an optical pump. The optical pump has been spatially modulated to form the shape of a planar blazed grating. The phase gradient leads to an asymmetry between the +1 and -1 transmission diffracted orders of more than a factor two. Optimization of the grating structure can lead to an asymmetry of more than one order of magnitude. Similar to metasurfaces made of plasmonic antennas, the photo-generated grating is a planar structure that can achieve large beam steering efficiency. Moreover, the photo-generation of such structures provides a platform for active THz beam steering. PMID:25401807

  20. Surface activation of CNT Webs towards layer by layer assembly of biosensors.

    PubMed

    Musameh, Mustafa; Huynh, Chi P; Hickey, Mark; Kyratzis, Ilias Louis

    2016-04-25

    Several surface activation methods such as chemical, electrochemical and plasma have been used for enhancing the electrochemical performance of carbon based electrodes for various applications. However, some of these surface activation methods may not be useful depending on the chemical and physical properties of the activated surface. Herein we investigate the surface activation of carbon nanotube (CNT) webs by electrochemical and plasma techniques to enhance their electrochemical performance and enable the fabrication of a biosensor using the layer-by-layer (LBL) approach. The pretreated CNT webs were characterized by SEM, TEM, Raman, XPS and electrochemical methods. TEM images and Raman analysis showed an increase in the level of surface defects upon pretreatment with higher number of defects after electrochemical pretreatment. XPS analysis showed an increase in the level of oxygen functional groups after pretreatment (4 to 5 times increase) which resulted in enhanced water wettability especially for plasma pretreated CNT webs. The pretreated CNT web electrodes also showed an enhanced electrochemical activity towards the oxidation and reduction of different redox probes with higher sensitivity for the electrochemically pretreated CNT web electrode that was accompanied by a higher level of noise in amperometric measurements. A highly linear response was obtained for the untreated and the electrochemically pretreated CNT web electrodes towards the amperometric detection of NADH (R(2) of 0.9996 and 0.9986 respectively) while a non-linear response was observed for the plasma pretreated CNT web electrode (R(2) of 0.8538). The pretreated CNT web electrodes enabled the fabrication of a LBL biosensor for alcohol detection with highest operational stability obtained for the plasma pretreated CNT web surface.

  1. Semiconductor structure and devices

    NASA Technical Reports Server (NTRS)

    Dinkel, Nancy A. (Inventor); Goldstein, Bernard (Inventor); Ettenberg, Michael (Inventor)

    1987-01-01

    Semiconductor devices such as lasers which include a substrate with a channel therein with a clad layer overlying the substrate and filling the channel exhibit irregularities such as terraces in the surface of the clad layer which are detrimental to device performance. These irregularities are substantially eliminated by forming the channel in a surface of a buffer layer greater than about 4 micrometers thick on the substrate and forming the clad layer over the buffer layer and the channel. CW lasers incorporating the principles of the invention exhibit the highest output power in a single spatial mode and maximum output power which have been observed to date.

  2. Observation of power gain in an inductive pulsed power system with an optically activated semiconductor closing and opening switch

    NASA Astrophysics Data System (ADS)

    Kung, Chun C.; Funk, Eric E.; Chauchard, Eve A.; Rhee, M. J.; Lee, Chi H.; Yan, Li

    1991-03-01

    Peak power gain greater than 15 was obtained with a current charged transmission line and an optically activated semiconductor opening switch. The optical pulse used for activating the switch is generated by a Nd:glass laser emitting at 1. 054 pm. It has a slow rise-time (''--''2OO uS) and a fast fall-time (s1O uS). In the experiment a 2 kV output voltage pulse was achieved with a 5 mm cube GaAs p-i-n diode sitch at 500 V charging voltage.

  3. Monolayer-Mediated Growth of Organic Semiconductor Films with Improved Device Performance.

    PubMed

    Huang, Lizhen; Hu, Xiaorong; Chi, Lifeng

    2015-09-15

    Increased interest in wearable and smart electronics is driving numerous research works on organic electronics. The control of film growth and patterning is of great importance when targeting high-performance organic semiconductor devices. In this Feature Article, we summarize our recent work focusing on the growth, crystallization, and device operation of organic semiconductors intermediated by ultrathin organic films (in most cases, only a monolayer). The site-selective growth, modified crystallization and morphology, and improved device performance of organic semiconductor films are demonstrated with the help of the inducing layers, including patterned and uniform Langmuir-Blodgett monolayers, crystalline ultrathin organic films, and self-assembled polymer brush films. The introduction of the inducing layers could dramatically change the diffusion of the organic semiconductors on the surface and the interactions between the active layer with the inducing layer, leading to improved aggregation/crystallization behavior and device performance. PMID:25992464

  4. Experiments on the active control of transitional boundary layers

    NASA Astrophysics Data System (ADS)

    Nelson, P. A.; Rioual, J.-L.; Fisher, M. J.

    Experimental results are presented which demonstrate that the streamwise position of the transition region of a flat plate boundary layer can be actively controlled. The means of control is through the application of suction through the surface of the plate, a progressive increase in suction rate being capable of producing transition at progressively larger distances downstream from the plate leading edge. A simple digital feedback regulator based on an integral control law is shown to be most effective in regulating the position of transition, an error signal being derived from measurements of pressure fluctuations on the surface of the plate.

  5. Peculiarities of Determining the Dopant Concentration in the Near-Surface Layer of a Semiconductor by Measuring the Admittance of MIS Structures Based on P-Hg0.78Cd0.22Te Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.

    2016-06-01

    Peculiarities of determining the concentration and distribution profile of dopant in the near-surface layer of a semiconductor by measuring the admittance of MIS structures based on p-Hg0.78Cd0.22Te grown by molecular beam epitaxy are studied. A technique is proposed for the determining the concentration of dopant based on the measurement of the admittance of MIS structures in the frequency range of 50 kHz - 1 MHz. It is shown that in this frequency range, the capacitance-voltage characteristics of MIS structures based on p-Hg0.78Cd0.22Te with a near-surface graded-gap layer have a high- frequency behavior with respect to the recharge time of surface states located near the Fermi level of intrinsic semiconductor. The distribution profile of dopant in the nearsurface layer of the semiconductor is calculated. It is shown that in p-Hg0.78Cd0.22Te with a near-surface graded-gap layer, the dopant concentration has the lowest value near the interface with the insulator.

  6. Effects of the Cu off-stoichiometry on transport properties of wide gap p-type semiconductor, layered oxysulfide LaCuSO

    SciTech Connect

    Goto, Yosuke Tanaki, Mai; Okusa, Yuki; Matoba, Masanori; Kamihara, Yoichi; Shibuya, Taizo; Yasuoka, Kenji

    2014-07-14

    Layered oxysulfide LaCu{sub 1−x}SO (x = 0–0.03) was prepared to elucidate the effect of Cu off-stoichiometry on their electrical and thermal transport properties. Electrical resistivity drastically decreases down from ∼10{sup 5} Ω·cm to ∼10{sup −1} Ω·cm as a result of Cu deficiency (x = 0.01) at 300 K. Thermal conductivity of the samples at 300 K, which is dominated by lattice components, is estimated to be 2.3(3) Wm{sup −1}K{sup −1}. Stoichiometric LaCuSO has an optical band gap of 3.1 eV, while broad optical absorption at photon energies of approximately 2.1 eV was observed for Cu-deficient samples. Density functional theory calculation suggests that these broad absorption structures probably originate from the in-gap states generated by the sulfur vacancies created to compensate the charge imbalance due to Cu off-stoichiometry. These results clearly demonstrate that Cu deficiency plays a crucial role in determining the electrical transport properties of Cu-based p-type transparent semiconductors.

  7. SEMICONDUCTOR DEVICES: Analytical charge control model for AlGaN/GaN MIS-HFETs including an undepleted barrier layer

    NASA Astrophysics Data System (ADS)

    Shenghui, Lu; Jiangfeng, Du; Qian, Luo; Qi, Yu; Wei, Zhou; Jianxin, Xia; Mohua, Yang

    2010-09-01

    An analytical charge control model considering the insulator/AlGaN interface charge and undepleted Al-GaN barrier layer is presented for AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors (MIS-HFETs) over the entire operation range of gate voltage. The whole process of charge control is analyzed in detail and partitioned into four regions: I—full depletion, II—partial depletion, III—neutral region and IV—electron accumulation at the insulator/AlGaN interface. The results show that two-dimensional electron gas (2DEG) saturates at the boundary of region II/III and the gate voltage should not exceed the 2DEG saturation voltage in order to keep the channel in control. In addition, the span of region II accounts for about 50% of the range of gate voltage before 2DEG saturates. The good agreement of the calculated transfer characteristic with the measured data confirms the validity of the proposed model.

  8. Ultra-low specific on-resistance high-voltage vertical double diffusion metal-oxide-semiconductor field-effect transistor with continuous electron accumulation layer

    NASA Astrophysics Data System (ADS)

    Da, Ma; Xiao-Rong, Luo; Jie, Wei; Qiao, Tan; Kun, Zhou; Jun-Feng, Wu

    2016-04-01

    A new ultra-low specific on-resistance (R on,sp) vertical double diffusion metal-oxide-semiconductor field-effect transistor (VDMOS) with continuous electron accumulation (CEA) layer, denoted as CEA-VDMOS, is proposed and its new current transport mechanism is investigated. It features a trench gate directly extended to the drain, which includes two PN junctions. In on-state, the electron accumulation layers are formed along the sides of the extended gate and introduce two continuous low-resistance current paths from the source to the drain in a cell pitch. This mechanism not only dramatically reduces the R on,sp but also makes the R on,sp almost independent of the n-pillar doping concentration (N n). In off-state, the depletion between the n-pillar and p-pillar within the extended trench gate increases the N n, and further reduces the R on,sp. Especially, the two PN junctions within the trench gate support a high gate-drain voltage in the off-state and on-state, respectively. However, the extended gate increases the gate capacitance and thus weakens the dynamic performance to some extent. Therefore, the CEA-VDMOS is more suitable for low and medium frequencies application. Simulation indicates that the CEA-VDMOS reduces the R on,sp by 80% compared with the conventional super-junction VDMOS (CSJ-VDMOS) at the same high breakdown voltage (BV). Project supported by the National Natural Science Foundation of China (Grant Nos. 61176069 and 61376079) and the Fundamental Research Funds for the Central Universities, China (Grant No. ZYGX2014Z006).

  9. Ultra-low specific on-resistance high-voltage vertical double diffusion metal–oxide–semiconductor field-effect transistor with continuous electron accumulation layer

    NASA Astrophysics Data System (ADS)

    Da, Ma; Xiao-Rong, Luo; Jie, Wei; Qiao, Tan; Kun, Zhou; Jun-Feng, Wu

    2016-04-01

    A new ultra-low specific on-resistance (R on,sp) vertical double diffusion metal–oxide–semiconductor field-effect transistor (VDMOS) with continuous electron accumulation (CEA) layer, denoted as CEA-VDMOS, is proposed and its new current transport mechanism is investigated. It features a trench gate directly extended to the drain, which includes two PN junctions. In on-state, the electron accumulation layers are formed along the sides of the extended gate and introduce two continuous low-resistance current paths from the source to the drain in a cell pitch. This mechanism not only dramatically reduces the R on,sp but also makes the R on,sp almost independent of the n-pillar doping concentration (N n). In off-state, the depletion between the n-pillar and p-pillar within the extended trench gate increases the N n, and further reduces the R on,sp. Especially, the two PN junctions within the trench gate support a high gate–drain voltage in the off-state and on-state, respectively. However, the extended gate increases the gate capacitance and thus weakens the dynamic performance to some extent. Therefore, the CEA-VDMOS is more suitable for low and medium frequencies application. Simulation indicates that the CEA-VDMOS reduces the R on,sp by 80% compared with the conventional super-junction VDMOS (CSJ-VDMOS) at the same high breakdown voltage (BV). Project supported by the National Natural Science Foundation of China (Grant Nos. 61176069 and 61376079) and the Fundamental Research Funds for the Central Universities, China (Grant No. ZYGX2014Z006).

  10. SEMICONDUCTOR DEVICES: A Ga-doped ZnO transparent conduct layer for GaN-based LEDs

    NASA Astrophysics Data System (ADS)

    Zhen, Liu; Xiaofeng, Wang; Hua, Yang; Yao, Duan; Yiping, Zeng

    2010-09-01

    An 8 μm thick Ga-doped ZnO (GZO) film grown by metal-source vapor phase epitaxy was deposited on a GaN-based light-emitting diode (LED) to substitute for the conventional ITO as a transparent conduct layer (TCL). Electroluminescence spectra exhibited that the intensity value of LED emission with a GZO TCL is markedly improved by 23.6% as compared to an LED with an ITO TCL at 20 mA. In addition, the forward voltage of the LED with a GZO TCL at 20 mA is higher than that of the conventional LED. To investigate the reason for the increase of the forward voltage, X-ray photoelectron spectroscopy was performed to analyze the interface properties of the GZO/p-GaN heterojunction. The large valence band offset (2:24 ± 0:21 eV) resulting from the formation of Ga2O3 in the GZO/p-GaN interface was attributed to the increase of the forward voltage.

  11. Optical activity of transparent polymer layers characterized by spectral means

    NASA Astrophysics Data System (ADS)

    Cosutchi, Andreea Irina; Dimitriu, Dan Gheorghe; Zelinschi, Carmen Beatrice; Breaban, Iuliana; Dorohoi, Dana Ortansa

    2015-06-01

    The method based on the channeled spectrum, validated for inorganic optical active layers, is used now to determine the optical activity of some transparent polymer solutions in different solvents. The circular birefringence, the dispersion parameter and the specific rotation were estimated in the visible range by using the measurements of wavelengths in the channeled spectra of Hydroxypropyl cellulose in water, methanol and acetic acid. The experiments showed the specific rotation dependence on the polymer concentration and also on the solvent nature. The decrease of the specific rotation in the visible range with the increase in wavelength was evidenced. The method has some advantages as the rapidity of the experiments and the large spectral range in which it can be applied. One disadvantage is the fact that the channeled spectrum does not allow to establish the rotation sense of the electric field intensity.

  12. Method of passivating semiconductor surfaces

    DOEpatents

    Wanlass, Mark W.

    1990-01-01

    A method of passivating Group III-V or II-VI semiconductor compound surfaces. The method includes selecting a passivating material having a lattice constant substantially mismatched to the lattice constant of the semiconductor compound. The passivating material is then grown as an ultrathin layer of passivating material on the surface of the Group III-V or II-VI semiconductor compound. The passivating material is grown to a thickness sufficient to maintain a coherent interface between the ultrathin passivating material and the semiconductor compound. In addition, a device formed from such method is also disclosed.

  13. Method of passivating semiconductor surfaces

    DOEpatents

    Wanlass, M.W.

    1990-06-19

    A method is described for passivating Group III-V or II-VI semiconductor compound surfaces. The method includes selecting a passivating material having a lattice constant substantially mismatched to the lattice constant of the semiconductor compound. The passivating material is then grown as an ultrathin layer of passivating material on the surface of the Group III-V or II-VI semiconductor compound. The passivating material is grown to a thickness sufficient to maintain a coherent interface between the ultrathin passivating material and the semiconductor compound. In addition, a device formed from such method is also disclosed.

  14. Determination of thorium and uranium at the nanogram per gram level in semiconductor potting plastics by neutron activation analysis

    SciTech Connect

    Dyer, F.F.; Emery, J.F.; Bate, L.C.

    1985-01-01

    A method was developed to determine thorium and uranium in semiconductor potting plastics. The method is based on neutron activation and subsequent radiochemical separation to isolate and permit measurement of the induced /sup 233/Pa and /sup 239/Np. These plastics typically contain macro amounts of silicon, bromine and antimony and nanogram per gram amounts of thorium and uranium. The radiochemical method provides the necessary sensitivity and makes it possible to easily attain adequate decontamination of the tiny amounts of /sup 233/Pa and /sup 239/Np from the high levels of radioactive bromine and antimony. 8 refs.

  15. Semiconductors for high temperature active devices: silicon, GaAs, and GaP. [For use in geothermal wells

    SciTech Connect

    Coquat, J.A.

    1980-01-01

    This paper reviews developments during the past three years in the area of high-temperature active semiconductor devices for use at 275/sup 0/C in instrumentation needed to characterize geothermal resources. Surveys of silicon bipolar, MOS, and JFET devices operated at high temperature and development work on high temperature silicon CMOS logic and DI analog circuits are reviewed. The initial results of developmental work on GaAs and GaP diodes are discussed. These efforts have identified several promising devices for high temperature applications; however, further development is required to resolve such problems as excessive leakage currents, metallization degradation, device stability, and long term aging.

  16. Kansas Advanced Semiconductor Project

    SciTech Connect

    Baringer, P.; Bean, A.; Bolton, T.; Horton-Smith, G.; Maravin, Y.; Ratra, B.; Stanton, N.; von Toerne, E.; Wilson, G.

    2007-09-21

    KASP (Kansas Advanced Semiconductor Project) completed the new Layer 0 upgrade for D0, assumed key electronics projects for the US CMS project, finished important new physics measurements with the D0 experiment at Fermilab, made substantial contributions to detector studies for the proposed e+e- international linear collider (ILC), and advanced key initiatives in non-accelerator-based neutrino physics.

  17. Isotopically engineered semiconductors

    NASA Astrophysics Data System (ADS)

    Haller, E. E.

    1995-04-01

    Scientific interest, technological promise, and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This review of mostly recent activities begins with an introduction to some past classical experiments which have been performed on isotopically controlled semiconductors. A review of the natural isotopic composition of the relevant elements follows. Some materials aspects resulting in part from the high costs of enriched isotopes are discussed next. Raman spectroscopy studies with a number of isotopically pure and deliberately mixed Ge bulk crystals show that the Brillouin-zone-center optical phonons are not localized. Their lifetime is almost independent of isotopic disorder, leading to homogeneous Raman line broadening. Studies with short period isotope superlattices consisting of alternating layers of n atomic planes of 70Ge and 74Ge reveal a host of zone-center phonons due to Brillouin-zone folding. At n≳40 one observes two phonon lines at frequencies corresponding to the bulk values of the two isotopes. In natural diamond, isotope scattering of the low-energy phonons, which are responsible for the thermal conductivity, is very strongly affected by small isotope disorder. Isotopically pure 12C diamond crystals exhibit thermal conductivities as high as 410 W cm-1 K-1 at 104 K, leading to projected values of over 2000 W cm-1 K-1 near 80 K. The changes in phonon properties with isotopic composition also weakly affect the electronic band structures and the lattice constants. The latter isotope dependence is most relevant for future standards of length based on crystal lattice constants. Capture of thermal neutrons by isotope nuclei followed by nuclear decay produces new elements, resulting in a very large number of possibilities for isotope selective doping of semiconductors. This neutron transmutation of isotope nuclei, already used

  18. Active Flow Control on a Boundary-Layer-Ingesting Inlet

    NASA Technical Reports Server (NTRS)

    Gorton, Susan Althoff; Owens, Lewis R.; Jenkins, Luther N.; Allan, Brian G.; Schuster, Ernest P.

    2004-01-01

    Boundary layer ingestion (BLI) is explored as means to improve overall system performance for Blended Wing Body configuration. The benefits of BLI for vehicle system performance benefit are assessed with a process derived from first principles suitable for highly-integrated propulsion systems. This performance evaluation process provides framework within which to assess the benefits of an integrated BLI inlet and lays the groundwork for higher-fidelity systems studies. The results of the system study show that BLI provides a significant improvement in vehicle performance if the inlet distortion can be controlled, thus encouraging the pursuit of active flow control (AFC) as a BLI enabling technology. The effectiveness of active flow control in reducing engine inlet distortion was assessed using a 6% scale model of a 30% BLI offset, diffusing inlet. The experiment was conducted in the NASA Langley Basic Aerodynamics Research Tunnel with a model inlet designed specifically for this type of testing. High mass flow pulsing actuators provided the active flow control. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion was determined by 120 total pressure measurements located at the aerodynamic interface plane. The test matrix was limited to a maximum freestream Mach number of 0.15 with scaled mass flows through the inlet for that condition. The data show that the pulsed actuation can reduce distortion from 29% to 4.6% as measured by the circumferential distortion descriptor DC60 using less than 1% of inlet mass flow. Closed loop control of the actuation was also demonstrated using a sidewall surface static pressure as the response sensor.

  19. Strained-bond semiconductors

    NASA Astrophysics Data System (ADS)

    Dow, John D.

    1994-05-01

    Theories of strained-bond semiconductors and superconductors have been developed that promise to have significant impact on future electronic devices of interest to the Air Force. These include: (1) development of a theory of high-temperature superconductivity based on the idea of strained-layer superlattices, (2) elucidation of the physics of doping in Type-2 semiconductor superlattices, which is now central to the development of high-speed field-effect transistors, (3) a theory of dimerization and reconstruction on (001) semiconductor surfaces, (4) theory of Mobius transforms as applied to physics and remote sensing, (5) new understanding of how defects affect the vibrational properties of semiconductors, (6) new methods of efficiently computing the trajectories of atoms in semiconductors by a priori molecular dynamics, (7) elucidation of the criteria affecting quantum-well luminescence from Si, (8) models of the effects of vacancies in large-gap Al(x)Ga(1-x)N alloys, (9) physics of rare-earth-doped silicon, (10) models of Co adsorption to silicon surfaces, (11) theories of how defects affect the properties of large band-gap superlattices, and (12) models of the effects of electronic structure on the properties of semiconductors.

  20. Back-side readout semiconductor photomultiplier

    DOEpatents

    Choong, Woon-Seng; Holland, Stephen E

    2014-05-20

    This disclosure provides systems, methods, and apparatus related to semiconductor photomultipliers. In one aspect, a device includes a p-type semiconductor substrate, the p-type semiconductor substrate having a first side and a second side, the first side of the p-type semiconductor substrate defining a recess, and the second side of the p-type semiconductor substrate being doped with n-type ions. A conductive material is disposed in the recess. A p-type epitaxial layer is disposed on the second side of the p-type semiconductor substrate. The p-type epitaxial layer includes a first region proximate the p-type semiconductor substrate, the first region being implanted with p-type ions at a higher doping level than the p-type epitaxial layer, and a second region disposed on the first region, the second region being doped with p-type ions at a higher doping level than the first region.

  1. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, Jr., Richard P.; Crawford, Mary H.

    1996-01-01

    A visible semiconductor laser. The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1.lambda.) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%.

  2. Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth

    DOEpatents

    Fan, John C. C.; Tsaur, Bor-Yeu; Gale, Ronald P.; Davis, Frances M.

    1986-12-30

    Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

  3. Reducing dislocations in semiconductors utilizing repeated thermal cycling during multistage epitaxial growth

    DOEpatents

    Fan, John C. C.; Tsaur, Bor-Yeu; Gale, Ronald P.; Davis, Frances M.

    1992-02-25

    Dislocation densities are reduced in growing semiconductors from the vapor phase by employing a technique of interrupting growth, cooling the layer so far deposited, and then repeating the process until a high quality active top layer is achieved. The method of interrupted growth, coupled with thermal cycling, permits dislocations to be trapped in the initial stages of epitaxial growth.

  4. The Impacts of Contact Etch Stop Layer Thickness and Gate Height on Channel Stress in Strained N-Metal Oxide Semiconductor Field Effect Transistors.

    PubMed

    Lin, K C; Twu, M J; Deng, R H; Liu, C H

    2015-04-01

    The stress induced by strain in the channel of metal oxide semiconductor field effect transistors (MOSFET) is an effective method to boost the device performance. The geometric dimensions of spacer, gate height, and the contact etch stop layer (CESL) are important factors among the feasible booster. This study utilized the mismatch of the thermal expansion coefficients of stressors to simulate the process-induced stress in the N-MOSFET. Different temperatures are applied to different region of the device to generate the required strain. The analysis was performed by well-developed finite element package. The composite spacers with variant width of inserted silicon nitride (SiO2/SiN/SiO2, ONO) were proposed and their impacts on channel stress were compared. Two aspects of the impacts of those factors on the channel stress in the longitudinal direction for N-MOSFET with variant channel length were investigated. Firstly, the channel stresses of device without CESL for different gate heights were studied. Secondly, with stress applied to CESL and ONO spacers, the induced stresses in the channel were analyzed for long/short gate length. Two conclusions were drawn from the results of simulation. The N-MOSFET device without CESL shows that the stressed spacer alone generates compressive stress and the magnitude increases along with higher gate height. The channel stress becomes tensile for device with CESL and increases when the thickness of CESL and the height of gate increase, especially for device with shorter gate length. The gate height plays more significant role in inducing channel stress compared with the thickness of CESL. The channel stress can be used to quantify the mobility of electron/hole for strained MOSFET device. Therefore, with the guideline disclosed in this study, better device performance can be expected for N-MOSFET. PMID:26353480

  5. Characterization of cathode keeper wear by surface layer activation

    NASA Technical Reports Server (NTRS)

    Polk, James E.

    2003-01-01

    In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

  6. Semiconductor laser devices having lateral refractive index tailoring

    DOEpatents

    Ashby, Carol I. H.; Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

    1990-01-01

    A broad-area semiconductor laser diode includes an active lasing region interposed between an upper and a lower cladding layer, the laser diode further comprising structure for controllably varying a lateral refractive index profile of the diode to substantially compensate for an effect of junction heating during operation. In embodiments disclosed the controlling structure comprises resistive heating strips or non-radiative linear junctions disposed parallel to the active region. Another embodiment discloses a multi-layered upper cladding region selectively disordered by implanted or diffused dopant impurities. Still another embodiment discloses an upper cladding layer of variable thickness that is convex in shape and symmetrically disposed about a central axis of the active region. The teaching of the invention is also shown to be applicable to arrays of semiconductor laser diodes.

  7. Improving the photocatalytic activity and anti-photocorrosion of semiconductor ZnO by coupling with versatile carbon.

    PubMed

    Han, Chuang; Yang, Min-Quan; Weng, Bo; Xu, Yi-Jun

    2014-08-28

    Coupling ZnO with carbon materials using a suitable integration method to form ZnO-carbon composites has been established as a promising strategy to ameliorate the photocatalytic performance of semiconductor ZnO. In this perspective article, we describe the recent advances and current status of enhancing the photocatalytic activity and anti-photocorrosion of semiconductor ZnO by coupling with versatile carbon materials, e.g., C60, carbon nanotube, graphene and other carbon materials. The primary roles of carbon materials in boosting the photoactivity and photostability of ZnO have been outlined and illustrated with some selected typical examples. In particular, the three main kinds of mechanisms with regard to anti-photocorrosion of ZnO by coupling with carbon have been demonstrated. Finally, we give a concise perspective on this important research area and specifically propose further research opportunities in optimizing the photocatalytic performance of ZnO-carbon composites and widening the scope of their potential photocatalytic applications.

  8. Fabrication and characterization of 6,13-bis(triisopropylsilylethynyl)-pentacene active semiconductor thin films prepared by flow-coating method

    SciTech Connect

    Mohamad, Khairul Anuar; Rusnan, Fara Naila; Seria, Dzulfahmi Mohd Husin; Saad, Ismail; Alias, Afishah; Katsuhiro, Uesugi; Hisashi, Fukuda

    2015-08-28

    Investigation on the physical characterization and comparison of organic thin film based on a soluble 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene is reported. Oriented thin-films of pentacene have been successfully deposited by flow-coating method, in which the chloroform solution is sandwiched between a transparent substrate and a slide glass, followed by slow-drawing of the substrate with respect to the slide glass. Molecular orientation of flow-coated TIPS-pentacene is comparable to that of the thermal-evaporated pentacene thin film by the X-ray diffraction (XRD) results. XRD results showed that the morphology of flow-coated soluble pentacene is similar to that of the thermal-evaporated pentacene thin films in series of (00l) diffraction peaks where the (001) diffraction peaks are strongest in the nominally out-of-plane intensity and interplanar spacing located at approximately 2θ = 5.33° (d-spacing, d{sub 001} = 16 Å). Following that, ITO/p-TIPS-pentacene/n-ZnO/Au vertical diode was fabricated. The diode exhibited almost linear characteristics at low voltage with nonlinear characteristics at higher voltage which similar to a pn junction behavior. The results indicated that the TIPS-pentacene semiconductor active thin films can be used as a hole injection layer for fabrication of a vertical organic transistor.

  9. Fabrication and characterization of 6,13-bis(triisopropylsilylethynyl)-pentacene active semiconductor thin films prepared by flow-coating method

    NASA Astrophysics Data System (ADS)

    Mohamad, Khairul Anuar; Rusnan, Fara Naila; Seria, Dzulfahmi Mohd Husin; Saad, Ismail; Alias, Afishah; Katsuhiro, Uesugi; Hisashi, Fukuda

    2015-08-01

    Investigation on the physical characterization and comparison of organic thin film based on a soluble 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene is reported. Oriented thin-films of pentacene have been successfully deposited by flow-coating method, in which the chloroform solution is sandwiched between a transparent substrate and a slide glass, followed by slow-drawing of the substrate with respect to the slide glass. Molecular orientation of flow-coated TIPS-pentacene is comparable to that of the thermal-evaporated pentacene thin film by the X-ray diffraction (XRD) results. XRD results showed that the morphology of flow-coated soluble pentacene is similar to that of the thermal-evaporated pentacene thin films in series of (00l) diffraction peaks where the (001) diffraction peaks are strongest in the nominally out-of-plane intensity and interplanar spacing located at approximately 2θ = 5.33° (d-spacing, d001 = 16 Å). Following that, ITO/p-TIPS-pentacene/n-ZnO/Au vertical diode was fabricated. The diode exhibited almost linear characteristics at low voltage with nonlinear characteristics at higher voltage which similar to a pn junction behavior. The results indicated that the TIPS-pentacene semiconductor active thin films can be used as a hole injection layer for fabrication of a vertical organic transistor.

  10. Semiconductor sensors

    NASA Technical Reports Server (NTRS)

    Gatos, Harry C. (Inventor); Lagowski, Jacek (Inventor)

    1977-01-01

    A semiconductor sensor adapted to detect with a high degree of sensitivity small magnitudes of a mechanical force, presence of traces of a gas or light. The sensor includes a high energy gap (i.e., .about. 1.0 electron volts) semiconductor wafer. Mechanical force is measured by employing a non-centrosymmetric material for the semiconductor. Distortion of the semiconductor by the force creates a contact potential difference (cpd) at the semiconductor surface, and this cpd is determined to give a measure of the force. When such a semiconductor is subjected to illumination with an energy less than the energy gap of the semiconductors, such illumination also creates a cpd at the surface. Detection of this cpd is employed to sense the illumination itself or, in a variation of the system, to detect a gas. When either a gas or light is to be detected and a crystal of a non-centrosymmetric material is employed, the presence of gas or light, in appropriate circumstances, results in a strain within the crystal which distorts the same and the distortion provides a mechanism for qualitative and quantitative evaluation of the gas or the light, as the case may be.

  11. Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS{sub 2} layered semiconductor

    SciTech Connect

    Seyidov, MirHasan Yu. Suleymanov, Rauf A.; Mikailzade, Faik A.; Kargın, Elif Orhan; Odrinsky, Andrei P.

    2015-06-14

    Lanthanum-doped high quality TlInS{sub 2} (TlInS{sub 2}:La) ferroelectric-semiconductor was characterized by photo-induced current transient spectroscopy (PICTS). Different impurity centers are resolved and identified. Analyses of the experimental data were performed in order to determine the characteristic parameters of the extrinsic and intrinsic defects. The energies and capturing cross section of deep traps were obtained by using the heating rate method. The observed changes in the Thermally Stimulated Depolarization Currents (TSDC) near the phase transition points in TlInS{sub 2}:La ferroelectric-semiconductor are interpreted as a result of self-polarization of the crystal due to the internal electric field caused by charged defects. The TSDC spectra show the depolarization peaks, which are attributed to defects of dipolar origin. These peaks provide important information on the defect structure and localized energy states in TlInS{sub 2}:La. Thermal treatments of TlInS{sub 2}:La under an external electric field, which was applied at different temperatures, allowed us to identify a peak in TSDC which was originated from La-dopant. It was established that deep energy level trap BTE43, which are active at low temperature (T ≤ 156 K) and have activation energy 0.29 eV and the capture cross section 2.2 × 10{sup −14} cm{sup 2}, corresponds to the La dopant. According to the PICTS results, the deep level trap center B5 is activated in the temperature region of incommensurate (IC) phases of TlInS{sub 2}:La, having the giant static dielectric constant due to the structural disorders. From the PICTS simulation results for B5, native deep level trap having an activation energy of 0.3 eV and the capture cross section of 1.8 × 10{sup −16} cm{sup 2} were established. A substantial amount of residual space charges is trapped by the deep level localized energy states of B5 in IC-phase. While the external electric field is applied, permanent dipoles

  12. Towards NOAA Forecasts of Permafrost Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Livezey, M. M.; Jonassen, R. G.; Horsfall, F. M. C.; Jafarov, E. E.; Schaefer, K. M.

    2014-12-01

    NOAA's implementation of its 2014 Arctic Action Plan (AAP) lacks services related to permafrost change yet the Interagency Working Group on Coordination of Domestic Energy Development and Permitting in Alaska noted that warming permafrost challenges land-based development and calls for agencies to provide focused information needed by decision-makers. To address this we propose to link NOAA's existing seasonal forecasts of temperature and precipitation with a high-resolution model of the thermal state of permafrost (Jafarov et al., 2012) to provide near-term (one year ahead) forecasts of active layer thickness (ALT). Such forecasts would be an official NOAA statement of the expected thermal state of permafrost ALT in Alaska and would require: (1) long-term climate outlooks, (2) a permafrost model, (3) detailed specification of local spatial and vertical controls upon soil thermal state, (4) high-resolution vertical measurements of that thermal state, and (5) demonstration of forecast skill in pilot studies. Pilot efforts should focus on oil pipelines where the cost can be justified. With skillful forecasts, engineers could reduce costs of monitoring and repair as well as ecosystem damage by positioning equipment to more rapidly respond to predicted disruptions.

  13. Active Layer Soil Carbon and Nutrient Mineralization, Barrow, Alaska, 2012

    DOE Data Explorer

    Stan D. Wullschleger; Holly M. Vander Stel; Colleen Iversen; Victoria L. Sloan; Richard J. Norby; Mallory P. Ladd; Jason K. Keller; Ariane Jong; Joanne Childs; Deanne J. Brice

    2015-10-29

    This data set consists of bulk soil characteristics as well as carbon and nutrient mineralization rates of active layer soils manually collected from the field in August, 2012, frozen, and then thawed and incubated across a range of temperatures in the laboratory for 28 day periods in 2013-2015. The soils were collected from four replicate polygons in each of the four Areas (A, B, C, and D) of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska. Soil samples were coincident with the established Vegetation Plots that are located in center, edge, and trough microtopography in each polygon. Data included are 1) bulk soil characteristics including carbon, nitrogen, gravimetric water content, bulk density, and pH in 5-cm depth increments and also by soil horizon, 2) carbon, nitrogen, and phosphorus mineralization rates for soil horizons incubated aerobically (and in one case both aerobically and anaerobically) for 28 days at temperatures that included 2, 4, 8, and 12 degrees C. Additional soil and incubation data are forthcoming. They will be available when published as part of another paper that includes additional replicate analyses.

  14. Active millimeter wave detection of concealed layers of dielectric material

    NASA Astrophysics Data System (ADS)

    Bowring, N. J.; Baker, J. G.; Rezgui, N. D.; Southgate, M.; Alder, J. F.

    2007-04-01

    Extensive work has been published on millimetre wave active and passive detection and imaging of metallic objects concealed under clothing. We propose and demonstrate a technique for revealing the depth as well as the outline of partially transparent objects, which is especially suited to imaging layer materials such as explosives and drugs. The technique uses a focussed and scanned FMCW source, swept through many GHz to reveal this structure. The principle involved is that a parallel sided dielectric slab produces reflections at both its upper and lower surfaces, acting as a Fabry-Perot interferometer. This produces a pattern of alternating reflected peaks and troughs in frequency space. Fourier or Burg transforming this pattern into z-space generates a peak at the thickness of the irradiated sample. It could be argued that though such a technique may work for single uniform slabs of dielectric material, it will give results of little or no significance when the sample both scatters the incident radiation and gives erratic reflectivities due to its non-uniform thickness and permittivity . We show results for a variety of materials such as explosive simulants, powder and drugs, both alone and concealed under clothing or in a rucksack, which display strongly directional reflectivities at millimeter wavelengths, and whose location is well displayed by a varying thickness parameter as the millimetre beam is scanned across the target. With this system we find that samples can easily be detected at standoff distances of at least 4.6m.

  15. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Hinzman, L.D.; Kane, D.L.

    1987-04-01

    The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events in a small watershed scale,but these events are rapidly attenuated outside the basin. Data collection began in August 1984. We have continuously monitored the hydrologic, the meteorologic, and the soil`s physical conditions. Information was collected through implementation of four snowmelt runoff plots and measurements of essential microclimate parameters. Soil moisture and temperature profiles were measured adjacent to each snowmelt runoff plot, and heat flux is collected adjacent to one of these plots. Meteorological parameters were measured locally. The water content of the snowpack prior to snowmelt was measured throughout the watershed and measured daily adjacent to each plot during snowmelt. The stream draining the basin was measured regularly during the spring melt event to provide information on watershed runoff rates and the volume of snowmelt.

  16. Active layer hydrology for Imnavait Creek, Toolik, Alaska

    SciTech Connect

    Hinzman, L.D.; Kane, D.L.

    1987-04-01

    The hydrology of the active layer of a watershed is described. In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. Significant runoff events are few. Convective storms covering relatively small areas on the North Slope of Alaska can produce significant small-scale events in a small watershed scale,but these events are rapidly attenuated outside the basin. Data collection began in August 1984. We have continuously monitored the hydrologic, the meteorologic, and the soil's physical conditions. Information was collected through implementation of four snowmelt runoff plots and measurements of essential microclimate parameters. Soil moisture and temperature profiles were measured adjacent to each snowmelt runoff plot, and heat flux is collected adjacent to one of these plots. Meteorological parameters were measured locally. The water content of the snowpack prior to snowmelt was measured throughout the watershed and measured daily adjacent to each plot during snowmelt. The stream draining the basin was measured regularly during the spring melt event to provide information on watershed runoff rates and the volume of snowmelt.

  17. Effects of Soil Property Uncertainty on Projected Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Harp, D. R.; Atchley, A. L.; Coon, E.; Painter, S. L.; Wilson, C. J.; Romanovsky, V. E.; Liljedahl, A.

    2014-12-01

    Uncertainty in future climate is often assumed to contribute the largest uncertainty to active layer thickness (ALT) projections. However, the impact of soil property uncertainty on these projections may be significant. In this research, we evaluate the contribution of soil property uncertainty on ALT projections at the Barrow Environmental Observatory, Alaska. The effect of variations in porosity, thermal conductivity, saturation, and water retention properties of peat and mineral soil are evaluated. The micro-topography of ice wedge polygons present at the site is included in the analysis using three 1D column models to represent polygon center, rim and trough features. The Arctic Terrestrial Simulator (ATS) is used to model multiphase thermal and hydrological processes in the subsurface. We apply the Null-Space Monte Carlo (NSMC) algorithm to identify an ensemble of soil property combinations that produce simulated temperature profiles that are consistent with temperature measurements available from the site. ALT is simulated for the ensemble of soil property combinations for four climate scenarios. The uncertainty in ALT due to soil properties within and across climate scenarios is evaluated. This work was supported by LANL Laboratory Directed Research and Development Project LDRD201200068DR and by the The Next-Generation Ecosystem Experiments (NGEE Arctic) project. NGEE-Arctic is supported by the Office of Biological and Environmental Research in the DOE Office of Science.

  18. Lattice matched semiconductor growth on crystalline metallic substrates

    SciTech Connect

    Norman, Andrew G; Ptak, Aaron J; McMahon, William E

    2013-11-05

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a metal or metal alloy substrate having a crystalline surface with a known lattice parameter (a). The methods further include growing a crystalline semiconductor alloy layer on the crystalline substrate surface by coincident site lattice matched epitaxy. The semiconductor layer may be grown without any buffer layer between the alloy and the crystalline surface of the substrate. The semiconductor alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter (a). The semiconductor alloy may further be prepared to have a selected band gap.

  19. Longevity improvement of optically activated, high gain GaAs photoconductive semiconductor switches

    SciTech Connect

    MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES; HJALMARSON,HAROLD P.; BACA,ALBERT G.

    2000-03-02

    The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses at 23A, and over 100 pulses at 1kA. This is achieved by improving the ohmic contacts by doping the semi-insulating GaAs underneath the metal, and by achieving a more uniform distribution of contact wear across the entire switch by distributing the trigger light to form multiple filaments. This paper will compare various approaches to doping the contacts, including ion implantation, thermal diffusion, and epitaxial growth. The device characterization also includes examination of the filament behavior using open-shutter, infra-red imaging during high gain switching. These techniques provide information on the filament carrier densities as well as the influence that the different contact structures and trigger light distributions have on the distribution of the current in the devices. This information is guiding the continuing refinement of contact structures and geometries for further improvements in switch longevity.

  20. One dimensional semiconductor nanostructures: An effective active-material for terahertz detection

    SciTech Connect

    Vitiello, Miriam S. Viti, Leonardo; Ercolani, Daniele; Sorba, Lucia; Coquillat, Dominique; Knap, Wojciech

    2015-02-01

    One-dimensional (1D) nanostructure devices are at the frontline of studies on future electronics, although issues like massive parallelization, doping control, surface effects, and compatibility with silicon industrial requirements are still open challenges. The recent progresses in atomic to nanometer scale control of materials morphology, size, and composition including the growth of axial, radial, and branched nanowire (NW)-based heterostructures make the NW an ideal building block for implementing rectifying diodes or detectors that could be well operated into the Terahertz (THz), thanks to their typical achievable attofarad-order capacitance. Here, we report on our recent progresses in the development of 1D InAs or InAs/InSb NW-based field effect transistors exploiting novel morphologies and/or material combinations effective for addressing the goal of a semiconductor plasma-wave THz detector array technology. Through a critical review of material-related parameters (NW doping concentration, geometry, and/or material choice) and antenna-related issues, here we underline the crucial aspects that can affect detection performance across the THz frequency region.

  1. Controlled Chemical Doping of Semiconductor Nanocrystals Using Redox Buffers

    SciTech Connect

    Engel, Jesse H.; Surendranath, Yogesh; Alivisatos, Paul

    2013-07-20

    Semiconductor nanocrystal solids are attractive materials for active layers in next-generation optoelectronic devices; however, their efficient implementation has been impeded by the lack of precise control over dopant concentrations. Herein we demonstrate a chemical strategy for the controlled doping of nanocrystal solids under equilibrium conditions. Exposing lead selenide nanocrystal thin films to solutions containing varying proportions of decamethylferrocene and decamethylferrocenium incrementally and reversibly increased the carrier concentration in the solid by 2 orders of magnitude from their native values. This application of redox buffers for controlled doping provides a new method for the precise control of the majority carrier concentration in porous semiconductor thin films.

  2. Wavelength-tunable actively mode-locked erbium-doped fiber ring laser using a distributed feedback semiconductor laser as mode locker and tunable filter

    NASA Astrophysics Data System (ADS)

    Li, Shenping; Chan, K. T.

    1999-07-01

    A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a distributed feedback semiconductor laser as an intensity mode locker and a tunable optical filter. Very stable optical pulse trains at gigabit repetition rates were generated using harmonica mode locking. The supermode noise was suppressed to 60 dB below the signal level and the root-mean-square timing jitter (0.45 kHz-1 MHz) was found to be about 1% of the pulse duration. A continuous wavelength tuning range of 1.8 nm was achieved by changing the semiconductor laser temperature from 11.4 to 30 °C.

  3. Near-Unity Absorption in van der Waals Semiconductors for Ultrathin Optoelectronics.

    PubMed

    Jariwala, Deep; Davoyan, Artur R; Tagliabue, Giulia; Sherrott, Michelle C; Wong, Joeson; Atwater, Harry A

    2016-09-14

    We demonstrate near-unity, broadband absorbing optoelectronic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) of molybdenum and tungsten as van der Waals semiconductor active layers. Specifically, we report that near-unity light absorption is possible in extremely thin (<15 nm) van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We further fabricate Schottky junction devices using these highly absorbing heterostructures and characterize their optoelectronic performance. Our work addresses one of the key criteria to enable TMDCs as potential candidates to achieve high optoelectronic efficiency. PMID:27563733

  4. Near-Unity Absorption in van der Waals Semiconductors for Ultrathin Optoelectronics.

    PubMed

    Jariwala, Deep; Davoyan, Artur R; Tagliabue, Giulia; Sherrott, Michelle C; Wong, Joeson; Atwater, Harry A

    2016-09-14

    We demonstrate near-unity, broadband absorbing optoelectronic devices using sub-15 nm thick transition metal dichalcogenides (TMDCs) of molybdenum and tungsten as van der Waals semiconductor active layers. Specifically, we report that near-unity light absorption is possible in extremely thin (<15 nm) van der Waals semiconductor structures by coupling to strongly damped optical modes of semiconductor/metal heterostructures. We further fabricate Schottky junction devices using these highly absorbing heterostructures and characterize their optoelectronic performance. Our work addresses one of the key criteria to enable TMDCs as potential candidates to achieve high optoelectronic efficiency.

  5. Layers

    NASA Astrophysics Data System (ADS)

    Hong, K. J.; Jeong, T. S.; Youn, C. J.

    2014-09-01

    The temperature-dependent photoresponse characteristics of MnAl2S4 layers have been investigated, for the first time, by use of photocurrent (PC) spectroscopy. Three peaks were observed at all temperatures. The electronic origin of these peaks was associated with band-to-band transitions from the valence-band states Γ4( z), Γ5( x), and Γ5( y) to the conduction-band state Γ1( s). On the basis of the relationship between PC-peak energy and temperature, the optical band gap could be well expressed by the expression E g( T) = E g(0) - 2.80 × 10-4 T 2/(287 + T), where E g(0) was estimated to be 3.7920 eV, 3.7955 eV, and 3.8354 eV for the valence-band states Γ4( z), Γ5( x), and Γ5( y), respectively. Results from PC spectroscopy revealed the crystal-field and spin-orbit splitting were 3.5 meV and 39.9 meV. The gradual decrease of PC intensity with decreasing temperature can be explained on the basis of trapping centers associated with native defects in the MnAl2S4 layers. Plots of log J ph, the PC current density, against 1/ T, revealed a dominant trap level in the high-temperature region. By comparing PC and the Hall effect results, we confirmed that this trap level is a shallow donor 18.9 meV below the conduction band.

  6. Excellent sun-light-driven photocatalytic activity by aurivillius layered perovskites, Bi₅-xLaxTi₃FeO₁₅ (x = 1, 2).

    PubMed

    Naresh, Gollapally; Mandal, Tapas Kumar

    2014-12-10

    Aurivillius phase layered perovskites, Bi5-xLaxTi3FeO15 (x = 1, 2) are synthesized by solid-state reaction. The compounds are characterized by powder X-ray diffraction (PXD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis diffuse reflectance (UV-vis DRS), and photoluminescence (PL) spectroscopy. UV-vis DRS data revealed that the compounds are visible light absorbing semiconductors with band gaps ranging from ∼2.0-2.7 eV. Photocatalytic activity studies by Rhodamine B (RhB) degradation under sun-light irradiation showed that these layered oxides are very efficient photocatalysts in mild acidic medium. Scavenger test studies demonstrated that the photogenerated holes and superoxide radicals (O2(•-)) are the active species responsible for RhB degradation over the Aurivillius layered perovskites. Comparison of PL intensity, dye adsorption and ζ-potential suggested that a slow e(-)-h(+) recombination and effective dye adsorption are crucial for the degradation process over these photocatalysts. Moreover, relative positioning of the valence and conduction band edges of the semiconductors, O2/O2(•-), (•)OH/H2O potential and HOMO-LUMO levels of RhB appears to be responsible for making the degradation hole-specific. Photocatalytic cycle tests indicated high stability of the catalysts in the reaction medium without any observable loss of activity. This work shows great potential in developing novel photocatalysts with layered structures for sun-light-driven oxidation and degradation processes largely driven by holes and without any intervention of hydroxyl radicals, which is one of the most common reactive oxygen species (ROS) in many advanced oxidation processes.

  7. Grain sorting in the morphological active layer of a braided river physical model

    NASA Astrophysics Data System (ADS)

    Leduc, P.; Ashmore, P.; Gardner, J. T.

    2015-07-01

    A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morpho-dynamics and for measuring and predicting bed load transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to re-work the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three-dimensions. Normalizing active layer thickness and dividing into 10 sub-layers we show that all grain sizes occur with almost equal frequency in all sub-layers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bed load prediction a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.

  8. Effects of spatial variation of skull and cerebrospinal fluid layers on optical mapping of brain activities

    NASA Astrophysics Data System (ADS)

    Wang, Shuping; Shibahara, Nanae; Kuramashi, Daishi; Okawa, Shinpei; Kakuta, Naoto; Okada, Eiji; Maki, Atsushi; Yamada, Yukio

    2010-07-01

    In order to investigate the effects of anatomical variation in human heads on the optical mapping of brain activity, we perform simulations of optical mapping by solving the photon diffusion equation for layered-models simulating human heads using the finite element method (FEM). Particularly, the effects of the spatial variations in the thicknesses of the skull and cerebrospinal fluid (CSF) layers on mapping images are investigated. Mapping images of single active regions in the gray matter layer are affected by the spatial variations in the skull and CSF layer thicknesses, although the effects are smaller than those of the positions of the active region relative to the data points. The increase in the skull thickness decreases the sensitivity of the images to active regions, while the increase in the CSF layer thickness increases the sensitivity in general. The images of multiple active regions are also influenced by their positions relative to the data points and by their depths from the skin surface.

  9. The first 25 years of semiconductor muonics at ISIS, modelling the electrical activity of hydrogen in inorganic semiconductors and high-κ dielectrics

    NASA Astrophysics Data System (ADS)

    Cox, S. F. J.; Lichti, R. L.; Lord, J. S.; Davis, E. A.; Vilão, R. C.; Gil, J. M.; Veal, T. D.; Celebi, Y. G.

    2013-12-01

    Early muonium studies provided the very first atomistic pictures of interstitial hydrogen in semiconductors. By the time ISIS muons came on line, the main crystallographic sites, and the electronic structures for the neutral centres, were established in archetypal materials such as Si and GaAs. The results were quite unanticipated, and raised awareness of this deceptively simple defect system. This paper marks contributions to the subject made using ISIS muon beams, in the first 25 years of their operation since 1987. By this time, hydrogen was understood to be a significant and unavoidable impurity in all electronic grade material, and attention was turning to the interaction with charge carriers, revealing an equally unanticipated interplay of site and charge state. In particular, muonium spectroscopy now provides a model for hydrogen in dozens of materials where hydrogen itself is difficult or impossible to study directly, and is able to predict its effect on the electronic properties of new materials, such as those envisaged for optoeletronic or dielectric applications. Donor, acceptor and so-called pinning levels are known in a good many of these materials, revealing intriguing systematics and providing severe tests and challenges to current theory. Progress and prospects are summarized in this report, addressing the obvious questions such as ‘why, how and what next?’

  10. Layer-by-layer engineered nanocapsules of curcumin with improved cell activity.

    PubMed

    Kittitheeranun, Paveenuch; Sajomsang, Warayuth; Phanpee, Sarunya; Treetong, Alongkot; Wutikhun, Tuksadon; Suktham, Kunat; Puttipipatkhachorn, Satit; Ruktanonchai, Uracha Rungsardthong

    2015-08-15

    Nanocarriers based on electrostatic Layer-by-layer (LbL) assembly of CaCO3 nanoparticles (CaCO3 NPs) was investigated. These inorganic nanoparticles was used as templates to construct nanocapsules made from films based on two oppositely charged polyelectrolytes, poly(diallyldimethylammonium chloride), and poly (sodium 4-styrene-sulfonate sodium salt), followed by core dissolution. The naked CaCO3 NPs, CaCO3 NPs coated with the polyelectrolytes and hollow nanocapsules were found with hexagonal shape with average sizes of 350-400 nm. A reversal of the surface charge between positive to negative zeta potential values was found, confirming the adsorption of polyelectrolytes. The loading efficiency and release of curcumin were controlled by the hydrophobic interactions between the drug and the polyelectrolyte matrix of the hollow nanocapsules. The quantity of curcumin released from hollow nanocapsules was found to increase under acidic environments, which is a desirable for anti-cancer drug delivery. The hollow nanocapsules were found to localize in the cytoplasm and nucleus compartment of Hela cancer cells after 24 h of incubation. Hollow nanocapsules were non-toxic to human fibroblast cells. Furthermore, curcumin loaded hollow nanocapsules exhibited higher in vitro cell inhibition against Hela cells than that of free curcumin, suggesting that polyelectrolyte based-hollow nanocapsules can be utilized as new carriers for drug delivery. PMID:26143232

  11. Electroless silver plating of the surface of organic semiconductors.

    PubMed

    Campione, Marcello; Parravicini, Matteo; Moret, Massimo; Papagni, Antonio; Schröter, Bernd; Fritz, Torsten

    2011-10-01

    The integration of nanoscale processes and devices demands fabrication routes involving rapid, cost-effective steps, preferably carried out under ambient conditions. The realization of the metal/organic semiconductor interface is one of the most demanding steps of device fabrication, since it requires mechanical and/or thermal treatments which increment costs and are often harmful in respect to the active layer. Here, we provide a microscopic analysis of a room temperature, electroless process aimed at the deposition of a nanostructured metallic silver layer with controlled coverage atop the surface of single crystals and thin films of organic semiconductors. This process relies on the reaction of aqueous AgF solutions with the nonwettable crystalline surface of donor-type organic semiconductors. It is observed that the formation of a uniform layer of silver nanoparticles can be accomplished within 20 min contact time. The electrical characterization of two-terminal devices performed before and after the aforementioned treatment shows that the metal deposition process is associated with a redox reaction causing the p-doping of the semiconductor.

  12. Monolayer and Few-Layer All-Inorganic Perovskites as a New Family of Two-Dimensional Semiconductors for Printable Optoelectronic Devices.

    PubMed

    Song, Jizhong; Xu, Leimeng; Li, Jianhai; Xue, Jie; Dong, Yuhui; Li, Xiaoming; Zeng, Haibo

    2016-06-01

    Printed flexible photodetectors based on 2D inorganic perovskites with atomic thickness show excellent photosensing with fast rise and decay response times. As-synthesized nanosheets can easily be dispersed in various solvents, leading to large-area, crack-free, low-roughness, flexible films after printing. This study demonstrates that all-inorganic perovskite CsPbX3 nanosheets as a new class of 2D semiconductors have huge potential for flexible optoelectronic applications. PMID:27110705

  13. Silver ions/ovalbumin films layer-by-layer self-assembled polyacrylonitrile nanofibrous mats and their antibacterial activity.

    PubMed

    Song, Rukun; Yan, Jinjiao; Xu, Shasha; Wang, Yuntao; Ye, Ting; Chang, Jing; Deng, Hongbing; Li, Bin

    2013-08-01

    The CN groups of polyacrylonitrile (PAN) can strongly adsorb silver ions. The possibility of using this attraction as a layer-by-layer (LBL) self-assembly driving force was investigated. Firstly, the surface of the PAN nanofibrous mats was modified by silver ions to make sure it was positively charged. Then oppositely charged ovalbumin (OVA) and silver ions in aqueous media were alternatively deposited onto the surface of the obtained composite mats by layer-by-layer self-assembly technique. The morphology of the LBL films coating mats was observed by field emission scanning electron microscope (FE-SEM). The deposition of silver ions and OVA was confirmed by X-ray photoelectron spectroscopy (XPS) and wide-angle X-ray diffraction (XRD). The thermal degradation properties were investigated by thermo-gravimetric analysis (TGA). Besides these, the cytotoxicity and antibacterial activity of the prepared mats were studied via flow cytometry (FCM) and inhibition zone test, respectively. The results showed that the composite mats after LBL self-assembly processing exhibited improved thermal stability, slightly decreased cytotoxicity, and excellent antibacterial activity against Escherichia coil and Staphylococcus aureus. PMID:23563300

  14. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

    Schneider, R.P. Jr.; Crawford, M.H.

    1996-09-17

    The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1{lambda}) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%. 5 figs.

  15. Semiconductor electrode with improved photostability characteristics

    DOEpatents

    Frank, Arthur J.

    1987-01-01

    An electrode is disclosed for use in photoelectrochemical cells having an electrolyte which includes an aqueous constituent. The electrode includes a semiconductor and a hydrophobic film disposed between the semiconductor and the aqueous constituent. The hydrophobic film is adapted to permit charges to pass therethrough while substantially decreasing the activity of the aqueous constituent at the semiconductor surface thereby decreasing the photodegradation of the semiconductor electrode.

  16. Semiconductor electrode with improved photostability characteristics

    DOEpatents

    Frank, A.J.

    1985-02-19

    An electrode is described for use in photoelectrochemical cells having an electrolyte which includes an aqueous constituent. The electrode consists of a semiconductor and a hydrophobic film disposed between the semiconductor and the aqueous constituent. The hydrophobic film is adapted to permit charges to pass therethrough while substantially decreasing the activity of the aqueous constituent at the semiconductor surface thereby decreasing the photodegradation of the semiconductor electrode.

  17. Efficient semiconductor light-emitting device and method

    DOEpatents

    Choquette, K.D.; Lear, K.L.; Schneider, R.P. Jr.

    1996-02-20

    A semiconductor light-emitting device and method are disclosed. The semiconductor light-emitting device is provided with at least one control layer or control region which includes an annular oxidized portion thereof to channel an injection current into the active region, and to provide a lateral refractive index profile for index guiding the light generated within the device. A periodic composition grading of at least one of the mirror stacks in the device provides a reduced operating voltage of the device. The semiconductor light-emitting device has a high efficiency for light generation, and may be formed either as a resonant-cavity light-emitting diode (RCLED) or as a vertical-cavity surface-emitting laser (VCSEL). 12 figs.

  18. Efficient semiconductor light-emitting device and method

    DOEpatents

    Choquette, Kent D.; Lear, Kevin L.; Schneider, Jr., Richard P.

    1996-01-01

    A semiconductor light-emitting device and method. The semiconductor light-emitting device is provided with at least one control layer or control region which includes an annular oxidized portion thereof to channel an injection current into the active region, and to provide a lateral refractive index profile for index guiding the light generated within the device. A periodic composition grading of at least one of the mirror stacks in the device provides a reduced operating voltage of the device. The semiconductor light-emitting device has a high efficiency for light generation, and may be formed either as a resonant-cavity light-emitting diode (RCLED) or as a vertical-cavity surface-emitting laser (VCSEL).

  19. Physical Modeling of Activation Energy in Organic Semiconductor Devices based on Energy and Momentum Conservations.

    PubMed

    Mao, Ling-Feng; Ning, H; Hu, Changjun; Lu, Zhaolin; Wang, Gaofeng

    2016-04-22

    Field effect mobility in an organic device is determined by the activation energy. A new physical model of the activation energy is proposed by virtue of the energy and momentum conservation equations. The dependencies of the activation energy on the gate voltage and the drain voltage, which were observed in the experiments in the previous independent literature, can be well explained using the proposed model. Moreover, the expression in the proposed model, which has clear physical meanings in all parameters, can have the same mathematical form as the well-known Meyer-Neldel relation, which lacks of clear physical meanings in some of its parameters since it is a phenomenological model. Thus it not only describes a physical mechanism but also offers a possibility to design the next generation of high-performance optoelectronics and integrated flexible circuits by optimizing device physical parameter.

  20. Physical Modeling of Activation Energy in Organic Semiconductor Devices based on Energy and Momentum Conservations

    PubMed Central

    Mao, Ling-Feng; Ning, H.; Hu, Changjun; Lu, Zhaolin; Wang, Gaofeng

    2016-01-01

    Field effect mobility in an organic device is determined by the activation energy. A new physical model of the activation energy is proposed by virtue of the energy and momentum conservation equations. The dependencies of the activation energy on the gate voltage and the drain voltage, which were observed in the experiments in the previous independent literature, can be well explained using the proposed model. Moreover, the expression in the proposed model, which has clear physical meanings in all parameters, can have the same mathematical form as the well-known Meyer-Neldel relation, which lacks of clear physical meanings in some of its parameters since it is a phenomenological model. Thus it not only describes a physical mechanism but also offers a possibility to design the next generation of high-performance optoelectronics and integrated flexible circuits by optimizing device physical parameter. PMID:27103586

  1. Physical Modeling of Activation Energy in Organic Semiconductor Devices based on Energy and Momentum Conservations

    NASA Astrophysics Data System (ADS)

    Mao, Ling-Feng; Ning, H.; Hu, Changjun; Lu, Zhaolin; Wang, Gaofeng

    2016-04-01

    Field effect mobility in an organic device is determined by the activation energy. A new physical model of the activation energy is proposed by virtue of the energy and momentum conservation equations. The dependencies of the activation energy on the gate voltage and the drain voltage, which were observed in the experiments in the previous independent literature, can be well explained using the proposed model. Moreover, the expression in the proposed model, which has clear physical meanings in all parameters, can have the same mathematical form as the well-known Meyer-Neldel relation, which lacks of clear physical meanings in some of its parameters since it is a phenomenological model. Thus it not only describes a physical mechanism but also offers a possibility to design the next generation of high-performance optoelectronics and integrated flexible circuits by optimizing device physical parameter.

  2. Soft, conformable electrical contacts for organic semiconductors: high-resolution plastic circuits by lamination.

    PubMed

    Loo, Yueh-Lin; Someya, Takao; Baldwin, Kirk W; Bao, Zhenan; Ho, Peter; Dodabalapur, Ananth; Katz, Howard E; Rogers, John A

    2002-08-01

    Soft, conformable electrical contacts provide efficient, noninvasive probes for the transport properties of chemically and mechanically fragile, ultrathin organic semiconducting films. When combined with high-resolution printing and lamination techniques, these soft contacts also form the basis of a powerful technique for fabricating flexible plastic circuits. In this approach, a thin elastomeric film on a plastic substrate supports the electrodes and interconnections; laminating this substrate against another plastic substrate that supports the gate, dielectric and semiconductor levels establishes effective electrical contacts and completes the circuits. In addition to eliminating many of the problems associated with traditional layer-by-layer fabrication strategies, this lamination scheme possesses other attractive features: the transistors and circuit elements are naturally and efficiently encapsulated, and the active organic semiconductor layer is placed near the neutral mechanical plane. We demonstrate the features of soft, laminated contacts by fabricating large arrays of high-performance thin film transistors on plastic substrates by using a wide variety of organic semiconductors.

  3. Activities of Combined TiO2 Semiconductor Nanocatalysts Under Solar Light on the Reduction of CO2.

    PubMed

    Liu, Hongfang; Dao, Anh Quang; Fu, Chaoyang

    2016-04-01

    The materials based on TiO2 semiconductors are a promising option for electro-photocatalytic systems working as solar energy low-carbon fuels exchanger. These materials' structures are modified by doping metals and metal oxides, by metal sulfides sensitization, or by graphene supported membrane, enhancing their catalytic activity. The basic phenomenon of CO2 reduction to CH4 on Pd modified TiO2 under UV irradiation could be enhanced by Pd, or RuO2 co-doped TiO2. Sensitization with metal sulfide QDs is effective by moving of photo-excited electron from QDs to TiO2 particles. Based on characteristics of the catalysts various combinations of catalysts are proposed in order to creat catalyst systems with good CO2 reduction efficiency. From this critical review of the CO2 reduction to organic compounds by converting solar light and CO2 to storable fuels it is clear that more studies are still attractive and needed. PMID:27451648

  4. Complex Förster energy transfer interactions between semiconductor quantum dots and a redox-active osmium assembly.

    PubMed

    Stewart, Michael H; Huston, Alan L; Scott, Amy M; Efros, Alexander L; Melinger, Joseph S; Gemmill, Kelly Boeneman; Trammell, Scott A; Blanco-Canosa, Juan B; Dawson, Philip E; Medintz, Igor L

    2012-06-26

    The ability of luminescent semiconductor quantum dots (QDs) to engage in diverse energy transfer processes with organic dyes, light-harvesting proteins, metal complexes, and redox-active labels continues to stimulate interest in developing them for biosensing and light-harvesting applications. Within biosensing configurations, changes in the rate of energy transfer between the QD and the proximal donor, or acceptor, based upon some external (biological) event form the principle basis for signal transduction. However, designing QD sensors to function optimally is predicated on a full understanding of all relevant energy transfer mechanisms. In this report, we examine energy transfer between a range of CdSe-ZnS core-shell QDs and a redox-active osmium(II) polypyridyl complex. To facilitate this, the Os complex was synthesized as a reactive isothiocyanate and used to label a hexahistidine-terminated peptide. The Os-labeled peptide was ratiometrically self-assembled to the QDs via metal affinity coordination, bringing the Os complex into close proximity of the nanocrystal surface. QDs displaying different emission maxima were assembled with increasing ratios of Os-peptide complex and subjected to detailed steady-state, ultrafast transient absorption, and luminescence lifetime decay analyses. Although the possibility exists for charge transfer quenching interactions, we find that the QD donors engage in relatively efficient Förster resonance energy transfer with the Os complex acceptor despite relatively low overall spectral overlap. These results are in contrast to other similar QD donor-redox-active acceptor systems with similar separation distances, but displaying far higher spectral overlap, where charge transfer processes were reported to be the dominant QD quenching mechanism.

  5. Semiconductor eutectic solar cell

    NASA Astrophysics Data System (ADS)

    Yue, A. S.; Yu, J. G.

    1986-12-01

    Two-phase semiconducting eutectics are potential device-materials. Of these, the SnSe-SnSe2 eutectic was chosen for studies in detail because it consists of multi-p/n-layers of SnSe and SnSe2 semiconductors. Since plasma frequency has not been detected in its infrared reflectance spectrum up to 40 micrometers of wavelength, it suggests that the SnSe-SnSe2 eutectic is a nondegenerate semiconductor. As-grown SnSe2 single crystals have hexagonal crystallographic structure and show n-type conductivity. Polycrystalline SnSe and SnSe2 films have been successfully prepared in vacuum using a close-space-vapor transport technique.

  6. High temperature microbial activity in upper soil layers.

    PubMed

    Santana, M M; Gonzalez, J M

    2015-11-01

    Biomineralization at high temperatures in upper soil layers has been largely ignored, although desertification and global warming have led to increasing areas of soils exposed to high temperatures. Recent publications evidenced thermophilic bacteria ubiquity in soils as viable cells, and their role in nutrient cycling and seedling development. High temperature events, frequently observed at medium and low latitudes, locate temporal niches for thermophiles to grow in soils. There, at temperatures inhibitory for common mesophiles, thermophilic bacteria could perform biogeochemical reactions important to the soil food web. Nutrient cycling analyses in soils at medium and low latitudes would benefit from considering the potential role of thermophiles.

  7. Grain sorting in the morphological active layer of a braided river physical model

    NASA Astrophysics Data System (ADS)

    Leduc, P.; Ashmore, P.; Gardner, J. T.

    2015-12-01

    A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morphodynamics, and for measuring and predicting bedload transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to rework the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs (digital elevation models) of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three dimensions. By normalizing active layer thickness and dividing into 10 sublayers, we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bedload prediction, a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.

  8. Continuous Monitoring of Electrical Activity of Pancreatic β-Cells Using Semiconductor-Based Biosensing Devices

    NASA Astrophysics Data System (ADS)

    Sakata, Toshiya; Sugimoto, Haruyo

    2011-02-01

    The electrical activity of rat pancreatic β-cells caused by introduction of glucose was directly and noninvasively detected using a cell-based field-effect transistor (FET). Rat pancreatic β-cells were adhered to the gate sensing surface of the cell-based FET. The principle of cell-based FETs is based on the detection of charge density changes such as pH variation at the interface between the cell membrane and the gate surface. The gate surface potential of pancreatic β-cell-based FET increased continuously after introduction of glucose at a high concentration of 10 mg/ml. This result indicates that the electrical activity of β-cells was successfully monitored on the basis of pH changes, i.e., increase in the concentration of hydrogen ions, at the cell/gate interface using the pancreatic β-cell-based FET. We assume that the pH variation based on hydrogen ion accumulation at the cell/gate interface was induced by activation of respiration accompanied by insulin secretion process following glucose addition. The platform based on the field-effect devices is suitable for application in a real-time, noninvasive, and label-free detection system for cell functional analyses.

  9. Density Functional Theory Calculations of Activation Energies for Carrier Capture by Defects in Semiconductors

    NASA Astrophysics Data System (ADS)

    Modine, N. A.; Wright, A. F.; Lee, S. R.

    The rate of defect-induced carrier recombination is determined by both defect levels and carrier capture cross-sections. Density functional theory (DFT) has been widely and successfully used to predict defect levels, but only recently has work begun to focus on using DFT to determine carrier capture cross-sections. Lang and Henry developed the theory of carrier-capture by multiphonon emission in the 1970s and showed that carrier-capture cross-sections differ between defects primarily due to differences in their carrier capture activation energies. We present an approach to using DFT to calculate carrier capture activation energies that does not depend on an assumed configuration coordinate and that fully accounts for anharmonic effects, which can substantially modify carrier activation energies. We demonstrate our approach for intrinisic defects in GaAs and GaN and discuss how our results depend on the choice of exchange-correlation functional and the treatment of spin polarization. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  10. Strained layer Fabry-Perot device

    DOEpatents

    Brennan, Thomas M.; Fritz, Ian J.; Hammons, Burrell E.

    1994-01-01

    An asymmetric Fabry-Perot reflectance modulator (AFPM) consists of an active region between top and bottom mirrors, the bottom mirror being affixed to a substrate by a buffer layer. The active region comprises a strained-layer region having a bandgap and thickness chosen for resonance at the Fabry-Perot frequency. The mirrors are lattice matched to the active region, and the buffer layer is lattice matched to the mirror at the interface. The device operates at wavelengths of commercially available semiconductor lasers.

  11. Semiconductor technology program. Progress briefs

    NASA Technical Reports Server (NTRS)

    Bullis, W. M.

    1980-01-01

    Measurement technology for semiconductor materials, process control, and devices is reviewed. Activities include: optical linewidth and thermal resistance measurements; device modeling; dopant density profiles; resonance ionization spectroscopy; and deep level measurements. Standardized oxide charge terminology is also described.

  12. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    PubMed

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials. PMID:27607941

  13. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Zhang, Ting-Jun; Li, Shu-Sun

    2003-01-01

    The objective of this project is to map the spatial variation of the active layer over the arctic permafrost in terms of two parameters: (i) timing and duration of thaw period and (ii) differential frost heave and thaw settlement of the active layer. To achieve this goal, remote sensing, numerical modeling, and related field measurements are required. Tasks for the University of Colorado team are to: (i) determine the timing of snow disappearance in spring through changes in surface albedo (ii) simulate the freezing and thawing processes of the active layer and (iii) simulate the impact of snow cover on permafrost presence.

  14. Semiconductor laser having a non-absorbing passive region with beam guiding

    NASA Technical Reports Server (NTRS)

    Botez, Dan (Inventor)

    1986-01-01

    A laser comprises a semiconductor body having a pair of end faces and including an active region comprising adjacent active and guide layers which is spaced a distance from the end face and a passive region comprising adjacent non-absorbing guide and mode control layers which extends between the active region and the end face. The combination of the guide and mode control layers provides a weak positive index waveguide in the lateral direction thereby providing lateral mode control in the passive region between the active region and the end face.

  15. Orexin-dependent activation of layer VIb enhances cortical network activity and integration of non-specific thalamocortical inputs.

    PubMed

    Hay, Y Audrey; Andjelic, Sofija; Badr, Sammy; Lambolez, Bertrand

    2015-11-01

    Neocortical layer VI is critically involved in thalamocortical activity changes during the sleep/wake cycle. It receives dense projections from thalamic nuclei sensitive to the wake-promoting neuropeptides orexins, and its deepest part, layer VIb, is the only cortical lamina reactive to orexins. This convergence of wake-promoting inputs prompted us to investigate how layer VIb can modulate cortical arousal, using patch-clamp recordings and optogenetics in rat brain slices. We found that the majority of layer VIb neurons were excited by nicotinic agonists and orexin through the activation of nicotinic receptors containing α4-α5-β2 subunits and OX2 receptor, respectively. Specific effects of orexin on layer VIb neurons were potentiated by low nicotine concentrations and we used this paradigm to explore their intracortical projections. Co-application of nicotine and orexin increased the frequency of excitatory post-synaptic currents in the ipsilateral cortex, with maximal effect in infragranular layers and minimal effect in layer IV, as well as in the contralateral cortex. The ability of layer VIb to relay thalamocortical inputs was tested using photostimulation of channelrhodopsin-expressing fibers from the orexin-sensitive rhomboid nucleus in the parietal cortex. Photostimulation induced robust excitatory currents in layer VIa neurons that were not pre-synaptically modulated by orexin, but exhibited a delayed, orexin-dependent, component. Activation of layer VIb by orexin enhanced the reliability and spike-timing precision of layer VIa responses to rhomboid inputs. These results indicate that layer VIb acts as an orexin-gated excitatory feedforward loop that potentiates thalamocortical arousal.

  16. Structural properties and sensing performance of high-k Nd2TiO5 thin layer-based electrolyte-insulator-semiconductor for pH detection and urea biosensing.

    PubMed

    Pan, Tung-Ming; Lin, Jian-Chi; Wu, Min-Hsien; Lai, Chao-Sung

    2009-05-15

    For high sensitive pH sensing, an electrolyte-insulator-semiconductor (EIS) device with Nd(2)TiO(5) thin layers fabricated on Si substrates by means of reactive sputtering and the subsequent post-deposition annealing (PDA) treatment was proposed. In this work, the effect of thermal annealing (600, 700, 800, and 900 degrees C) on the structural characteristics of Nd(2)TiO(5) thin layer was investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy. The observed structural properties were then correlated with the resulting pH sensing performances. For enzymatic field-effect-transistors-based urea biosensing, a hybrid configuration of the proposed Nd(2)TiO(5) thin layer with urease-immobilized alginate film attached was established. Within the experimental conditions investigated, the EIS device with the Nd(2)TiO(5) thin layer annealed at 800 degrees C exhibited a higher pH detection sensitivity of 57.2 mV/pH, a lower hysteresis voltage of 2.33 mV, and a lower drift rate of 1.80 mV/h compared to those at other annealing temperatures. These results are attributed to the formation of a thinner low-k interfacial layer at the oxide/Si interface and the higher surface roughness occurred at this annealing temperature. Furthermore, the presented urea biosensor was also proved to be able to detect urea with good linearity (R(2)=0.99) and reasonable sensitivity of 9.52 mV/mM in the urea concentration range of 3-40 mM. As a whole, the present work has provided some fundamental data for the use of Nd(2)TiO(5) thin layer for EIS-based pH detection and the extended application for biosensing.

  17. 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.

  18. Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions

    DOE PAGES

    Dissanayake, D. M. N. M.; Ashraf, A.; Dwyer, D.; Kisslinger, K.; Zhang, L.; Pang, Y.; Efstathiadis, H.; Eisaman, M. D.

    2016-02-12

    Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 1012 e/cm2 or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene’s properties. Here we demonstrate strong (1.33 × 1013 e/cm2), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-doping reaches 2.11 × 1013more » e/cm2 when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. As a result, the ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors.« less

  19. Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions.

    PubMed

    Dissanayake, D M N M; Ashraf, A; Dwyer, D; Kisslinger, K; Zhang, L; Pang, Y; Efstathiadis, H; Eisaman, M D

    2016-01-01

    Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 10(12) e/cm(2) or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene's properties. Here we demonstrate strong (1.33 × 10(13) e/cm(2)), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-doping reaches 2.11 × 10(13) e/cm(2) when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. The ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors.

  20. Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions.

    PubMed

    Dissanayake, D M N M; Ashraf, A; Dwyer, D; Kisslinger, K; Zhang, L; Pang, Y; Efstathiadis, H; Eisaman, M D

    2016-01-01

    Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 10(12) e/cm(2) or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene's properties. Here we demonstrate strong (1.33 × 10(13) e/cm(2)), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-doping reaches 2.11 × 10(13) e/cm(2) when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. The ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors. PMID:26867673

  1. Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions

    PubMed Central

    Dissanayake, D. M. N. M.; Ashraf, A.; Dwyer, D.; Kisslinger, K.; Zhang, L.; Pang, Y.; Efstathiadis, H.; Eisaman, M. D.

    2016-01-01

    Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 1012 e/cm2 or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene’s properties. Here we demonstrate strong (1.33 × 1013 e/cm2), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-doping reaches 2.11 × 1013 e/cm2 when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. The ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors. PMID:26867673

  2. Spontaneous and strong multi-layer graphene n-doping on soda-lime glass and its application in graphene-semiconductor junctions

    NASA Astrophysics Data System (ADS)

    Dissanayake, D. M. N. M.; Ashraf, A.; Dwyer, D.; Kisslinger, K.; Zhang, L.; Pang, Y.; Efstathiadis, H.; Eisaman, M. D.

    2016-02-01

    Scalable and low-cost doping of graphene could improve technologies in a wide range of fields such as microelectronics, optoelectronics, and energy storage. While achieving strong p-doping is relatively straightforward, non-electrostatic approaches to n-dope graphene, such as chemical doping, have yielded electron densities of 9.5 × 1012 e/cm2 or below. Furthermore, chemical doping is susceptible to degradation and can adversely affect intrinsic graphene’s properties. Here we demonstrate strong (1.33 × 1013 e/cm2), robust, and spontaneous graphene n-doping on a soda-lime-glass substrate via surface-transfer doping from Na without any external chemical, high-temperature, or vacuum processes. Remarkably, the n-doping reaches 2.11 × 1013 e/cm2 when graphene is transferred onto a p-type copper indium gallium diselenide (CIGS) semiconductor that itself has been deposited onto soda-lime-glass, via surface-transfer doping from Na atoms that diffuse to the CIGS surface. Using this effect, we demonstrate an n-graphene/p-semiconductor Schottky junction with ideality factor of 1.21 and strong photo-response. The ability to achieve strong and persistent graphene n-doping on low-cost, industry-standard materials paves the way toward an entirely new class of graphene-based devices such as photodetectors, photovoltaics, sensors, batteries, and supercapacitors.

  3. Photovoltaic healing of non-uniformities in semiconductor devices

    DOEpatents

    Karpov, Victor G.; Roussillon, Yann; Shvydka, Diana; Compaan, Alvin D.; Giolando, Dean M.

    2006-08-29

    A method of making a photovoltaic device using light energy and a solution to normalize electric potential variations in the device. A semiconductor layer having nonuniformities comprising areas of aberrant electric potential deviating from the electric potential of the top surface of the semiconductor is deposited onto a substrate layer. A solution containing an electrolyte, at least one bonding material, and positive and negative ions is applied over the top surface of the semiconductor. Light energy is applied to generate photovoltage in the semiconductor, causing a redistribution of the ions and the bonding material to the areas of aberrant electric potential. The bonding material selectively bonds to the nonuniformities in a manner such that the electric potential of the nonuniformities is normalized relative to the electric potential of the top surface of the semiconductor layer. A conductive electrode layer is then deposited over the top surface of the semiconductor layer.

  4. Characterization study of an intensified complementary metal-oxide-semiconductor active pixel sensor

    NASA Astrophysics Data System (ADS)

    Griffiths, J. A.; Chen, D.; Turchetta, R.; Royle, G. J.

    2011-03-01

    An intensified CMOS active pixel sensor (APS) has been constructed for operation in low-light-level applications: a high-gain, fast-light decay image intensifier has been coupled via a fiber optic stud to a prototype "VANILLA" APS, developed by the UK based MI3 consortium. The sensor is capable of high frame rates and sparse readout. This paper presents a study of the performance parameters of the intensified VANILLA APS system over a range of image intensifier gain levels when uniformly illuminated with 520 nm green light. Mean-variance analysis shows the APS saturating around 3050 Digital Units (DU), with the maximum variance increasing with increasing image intensifier gain. The system's quantum efficiency varies in an exponential manner from 260 at an intensifier gain of 7.45 × 103 to 1.6 at a gain of 3.93 × 101. The usable dynamic range of the system is 60 dB for intensifier gains below 1.8 × 103, dropping to around 40 dB at high gains. The conclusion is that the system shows suitability for the desired application.

  5. Antineoplastic Activity Comparison of Bovine Serum Albumin--Conjugated Sulfides Semiconductor Nanomaterials.

    PubMed

    Wang, Hua-Jie; Huang, Jing-Chun; Wu, Sha-Sha; Wang, Cai-Feng; Yu, Xue-Hong; Cao, Ying

    2015-04-01

    Although tumor is one of the most frequently occurring diseases and a leading cause of death, nanotechnology, one of the frontier sciences, is exhibiting its great potential to tumor treatments. The aim of this study was to design a facile and environmentally-friendly method to prepare bovine serum albumin-conjugated heavy metal sulfides nano-materials, including Ag2S, PbS and CdS. Here, bovine serum albumin was introduced in order to direct the synthesis of nano-materials by using its template effect and supply more sites for further modification in future. The crystal structure and morphology were analyzed by XRD and TEM, respectively. Additionally, the antineoplastic activity of nano-materials was compared by cell viability analysis, optical and electron microscopy observation after exposure of the human hepatoma cell line. The results showed that the inhibition effect of heavy metal sulfides on tumor cells was in the order of nano-PbS > bulk CdS > nano-Ag2S > nano-CdS > bulk PbS > bulk Ag2S. It could be concluded that heavy metal sulfides had significantly negative impact on human hepatoma cells growth but it could not be obviously generalized that nano-particles were always more effective to kill tumor cells than bulk materials. The size and surface reactivity might be the important factors causing the difference.

  6. Semiconductor-based optical refrigerator

    DOEpatents

    Epstein, Richard I.; Edwards, Bradley C.; Sheik-Bahae, Mansoor

    2002-01-01

    Optical refrigerators using semiconductor material as a cooling medium, with layers of material in close proximity to the cooling medium that carries away heat from the cooling material and preventing radiation trapping. In addition to the use of semiconducting material, the invention can be used with ytterbium-doped glass optical refrigerators.

  7. Mechanical scriber for semiconductor devices

    DOEpatents

    Lin, P.T.

    1985-03-05

    A mechanical scriber using a scribing tip, such as a diamond, provides controlled scriber forces with a spring-loaded compound lever arrangement. The scribing force and range of scribing depth are adjusted by a pair of adjustable micrometer heads. A semiconductor device, such as a multilayer solar cell, can be formed into scribed strips at each layer. 5 figs.

  8. Mechanical scriber for semiconductor devices

    DOEpatents

    Lin, Peter T.

    1985-01-01

    A mechanical scriber using a scribing tip, such as a diamond, provides controlled scriber forces with a spring-loaded compound lever arrangement. The scribing force and range of scribing depth are adjusted by a pair of adjustable micrometer heads. A semiconductor device, such as a multilayer solar cell, can be formed into scribed strips at each layer.

  9. The Role of Organic Capping Layers of Platinum Nanoparticles in Catalytic Activity of CO Oxidation

    SciTech Connect

    Park, Jeong Y.; Aliaga, Cesar; Renzas, J. Russell; Lee, Hyunjoo; Somorjai, Gabor A.

    2008-12-17

    We report the catalytic activity of colloid platinum nanoparticles synthesized with different organic capping layers. On the molecular scale, the porous organic layers have open spaces that permit the reactant and product molecules to reach the metal surface. We carried out CO oxidation on several platinum nanoparticle systems capped with various organic molecules to investigate the role of the capping agent on catalytic activity. Platinum colloid nanoparticles with four types of capping layer have been used: TTAB (Tetradecyltrimethylammonium Bromide), HDA (hexadecylamine), HDT (hexadecylthiol), and PVP (poly(vinylpyrrolidone)). The reactivity of the Pt nanoparticles varied by 30%, with higher activity on TTAB coated nanoparticles and lower activity on HDT, while the activation energy remained between 27-28 kcal/mol. In separate experiments, the organic capping layers were partially removed using ultraviolet light-ozone generation techniques, which resulted in increased catalytic activity due to the removal of some of the organic layers. These results indicate that the nature of chemical bonding between organic capping layers and nanoparticle surfaces plays a role in determining the catalytic activity of platinum colloid nanoparticles for carbon monoxide oxidation.

  10. Application of Satellite SAR Imagery in Mapping the Active Layer of Arctic Permafrost

    NASA Technical Reports Server (NTRS)

    Li, Shu-Sun; Romanovsky, V.; Lovick, Joe; Wang, Z.; Peterson, Rorik

    2003-01-01

    A method of mapping the active layer of Arctic permafrost using a combination of conventional synthetic aperture radar (SAR) backscatter and more sophisticated interferometric SAR (INSAR) techniques is proposed. The proposed research is based on the sensitivity of radar backscatter to the freeze and thaw status of the surface soil, and the sensitivity of INSAR techniques to centimeter- to sub-centimeter-level surface differential deformation. The former capability of SAR is investigated for deriving the timing and duration of the thaw period for surface soil of the active layer over permafrost. The latter is investigated for the feasibility of quantitative measurement of frost heaving and thaw settlement of the active layer during the freezing and thawing processes. The resulting knowledge contributes to remote sensing mapping of the active layer dynamics and Arctic land surface hydrology.

  11. Dynamics of the Thermal State of Active Layer at the Alaska North Slope and Northern Yakutia

    NASA Astrophysics Data System (ADS)

    Kholodov, A. L.; Romanovsky, V. E.; Marchenko, S.; Shiklomanov, N. I.; Fedorov-Davydov, D.

    2010-12-01

    Dynamics of the active layer is one of the most important indexes, reflecting permafrost response to the modern climate changes. Monitoring of active layer thickness dynamics is the main goal of CALM (Circumpolar Active Layer Monitoring) project. But, from different points of view, it is very important to know not only maximal depth of seasonal thawing but also dynamics of thermal field of active layer and duration of its staying in the unfrozen state. Current research was aimed on the analyzing data of temperature measurements have been done during the more then 10 years at the North Slope of Brooks Range (Alaska) and 2 years at the selected sites at the Northern Yakutia (Russia) and its comparison with the 17 to 10 years records of active layer thickness dynamics at the corresponding sites (http://www.udel.edu/Geography/calm/data/north.html). The area of investigation characterized by the typical tundra landscape and different kinds of micro topography. Reported observation sites located at the latitudinal range from 68.5 to 70.3N in Alaska and 70.5 to 71.75N in the Northern Yakutia. Observation have been done using the 1 meter long MRC probe with 11 sensors (every 10 cm) and single Campbell SCI A107 sensors in Alaska and 2-channel HOBO U23 data loggers with TMC-HD thermistors in the Northern Yakutia. Analyses of CALM data show what most observation sites in Alaska (except located near the Brooks Range and at the Arctic Ocean coast) do not subjected to the significant sustainable changes of active layer thickness over the last 10 years. At the same time active layer thickness at the Yakutian sites was increasing. Temperature observations show decreasing of the mean annual temperature at the average depth of active layer bottom at the Alaskan sites. But, because of general trend to increasing of period of thawing it does not lead to the decreasing of active layer thickness. Recent equipment deployment at the Tiksi and Allaikha sites (Northern Yakutia) does not

  12. Improving ice nucleation activity of zein film through layer-by-layer deposition of extracellular ice nucleators.

    PubMed

    Shi, Ke; Yu, Hailong; Lee, Tung-Ching; Huang, Qingrong

    2013-11-13

    Zein protein has been of scientific interest in the development of biodegradable functional food packaging. This study aimed at developing a novel zein-based biopolymer film with ice nucleation activity through layer-by-layer deposition of biogenic ice nucleators, that is, extracellular ice nucleators (ECINs) isolated from Erwinia herbicola , onto zein film surface. The adsorption behaviors and mechanisms were investigated using quartz crystal microbalance with dissipation monitoring (QCM-D). On unmodified zein surface, the highest ECINs adsorption occurred at pH 5.0; on UV/ozone treated zein surface followed by deposition of poly(diallyldimethylammonium chloride) (PDADMAC) layer, the optimum condition for ECINs adsorption occurred at pH 7.0 and I 0.05 M, where the amount of ECINs adsorbed was also higher than that on unmodified zein surface. QCM-D analyses further revealed a two-step adsorption process on unmodified zein surfaces, compared to a one-step adsorption process on PDADMAC-modified zein surface. Also, significantly, in order to quantify the ice nucleation activity of ECINs-coated zein films, an empirical method was developed to correlate the number of ice nucleators with the ice nucleation temperature measured by differential scanning calorimetry. Calculated using this empirical method, the highest ice nucleation activity of ECINs on ECINs-modified zein film reached 64.1 units/mm(2), which was able to elevate the ice nucleation temperature of distilled water from -15.5 °C to -7.3 °C.

  13. Performance enhancement of n-channel inversion type In{sub x}Ga{sub 1-x}As metal-oxide-semiconductor field effect transistor using ex situ deposited thin amorphous silicon layer

    SciTech Connect

    Sonnet, A. M.; Hinkle, C. L.; Jivani, M. N.; Chapman, R. A.; Pollack, G. P.; Wallace, R. M.; Vogel, E. M.

    2008-09-22

    Significant enhancement in metal-oxide-semiconductor field effect transistor (MOSFET) transport characteristics is achieved with In{sub x}Ga{sub 1-x}As (x=0.53, x=0.20) channel material using ex situ plasma enhanced chemical vapor deposited amorphous Si layer. In{sub x}Ga{sub 1-x}As MOSFETs (L=2 {mu}m, V{sub gs}-V{sub t}=2.0 V) with Si interlayer show a maximum drain current of 290 mA/mm (x=0.53) and 2 {mu}A/mm (x=0.20), which are much higher compared to devices without a Si interlayer. However, charge pumping measurements show a lower average interface state density near the intrinsic Fermi level for devices without the silicon interlayer indicating that a reduction in the midgap interface state density is not responsible for the improved transport characteristics.

  14. Depth heterogeneity of fully aromatic polyamide active layers in reverse osmosis and nanofiltration membranes.

    PubMed

    Coronell, Orlando; Mariñas, Benito J; Cahill, David G

    2011-05-15

    We studied the depth heterogeneity of fully aromatic polyamide (PA) active layers in commercial reverse osmosis (RO) and nanofiltration (NF) membranes by quantifying near-surface (i.e., top 6 nm) and volume-averaged properties of the active layers using X-ray photoelectron spectrometry (XPS) and Rutherford backscattering spectrometry (RBS), respectively. Some membranes (e.g., ESPA3 RO) had active layers that were depth homogeneous with respect to the concentration and pK(a) distribution of carboxylic groups, degree of polymer cross-linking, concentration of barium ion probe that associated with ionized carboxylic groups, and steric effects experienced by barium ion. Other membranes (e.g., NF90 NF) had active layers that were depth heterogeneous with respect to the same properties. Our results therefore support the existence of both depth-homogeneous and depth-heterogeneous active layers. It remains to be assessed whether the depth heterogeneity consists of gradually changing properties throughout the active layer depth or of distinct sublayers with different properties.

  15. Interface/border trap characterization of Al{sub 2}O{sub 3}/AlN/GaN metal-oxide-semiconductor structures with an AlN interfacial layer

    SciTech Connect

    Liu, Shenghou; Yang, Shu; Tang, Zhikai; Jiang, Qimeng; Liu, Cheng; Chen, Kevin J.; Wang, Maojun; Shen, Bo

    2015-02-02

    We report the interface characterization of Al{sub 2}O{sub 3}/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al{sub 2}O{sub 3}/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density D{sub it} in MOS structures, D{sub it} in the device with AlN was determined to be in the range of 10{sup 11}–10{sup 12 }eV{sup −1 }cm{sup −2}, showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well.

  16. Activity of lactoperoxidase when adsorbed on protein layers.

    PubMed

    Haberska, Karolina; Svensson, Olof; Shleev, Sergey; Lindh, Liselott; Arnebrant, Thomas; Ruzgas, Tautgirdas

    2008-09-15

    Lactoperoxidase (LPO) is an enzyme, which is used as an antimicrobial agent in a number of applications, e.g., food technology. In the majority of applications LPO is added to a homogeneous product phase or immobilised on product surface. In the latter case, however, the measurements of LPO activity are seldom reported. In this paper we have assessed LPO enzymatic activity on bare and protein modified gold surfaces by means of electrochemistry. It was found that LPO rapidly adsorbs to bare gold surfaces resulting in an amount of LPO adsorbed of 2.9mg/m(2). A lower amount of adsorbed LPO is obtained if the gold surface is exposed to bovine serum albumin, bovine or human mucin prior to LPO adsorption. The enzymatic activity of the adsorbed enzyme is in general preserved at the experimental conditions and varies only moderately when comparing bare gold and gold surface pretreated with the selected proteins. The measurement of LPO specific activity, however, indicate that it is about 1.5 times higher if LPO is adsorbed on gold surfaces containing a small amount of preadsorbed mucin in comparison to the LPO directly adsorbed on bare gold.

  17. 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.

  18. Quantum size effects in layered VX{sub 2} (X = S, Se) materials: Manifestation of metal to semimetal or semiconductor transition

    SciTech Connect

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

    2015-02-14

    Most of the two dimensional (2D) transition metal dichalcogenides (TMDC) are nonmagnetic in pristine form. However, 2D pristine VX{sub 2} (X = S, Se, Te) materials are found to be ferromagnetic. Using spin polarized density functional theory (DFT) calculations, we have studied the electronic, magnetic, and surface properties of this class of materials in both trigonal prismatic H- and octahedral T-phase. Our calculations reveal that they exhibit materially different properties in those two polymorphs. Most importantly, detailed investigation of electronic structure explored the quantum size effect in H-phase of these materials thereby leading to metal to semimetal (H-VS{sub 2}) or semiconductor (H-VSe{sub 2}) transition when downsizing from bilayer to corresponding monolayer.

  19. Leakage Current Mechanism of InN-Based Metal-Insulator-Semiconductor Structures with Al2O3 as Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zhang, G. Z.; Xu, Y.; Gan, X. W.; Chen, C.; Wang, Z.; Wang, Y.; Wang, J. L.; Wang, T.; Wu, H.; Liu, C.

    2016-01-01

    InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10-9 A/cm2 at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors.

  20. Semiconductor P-I-N detector

    DOEpatents

    Sudharsanan, Rengarajan; Karam, Nasser H.

    2001-01-01

    A semiconductor P-I-N detector including an intrinsic wafer, a P-doped layer, an N-doped layer, and a boundary layer for reducing the diffusion of dopants into the intrinsic wafer. The boundary layer is positioned between one of the doped regions and the intrinsic wafer. The intrinsic wafer can be composed of CdZnTe or CdTe, the P-doped layer can be composed of ZnTe doped with copper, and the N-doped layer can be composed of CdS doped with indium. The boundary layers is formed of an undoped semiconductor material. The boundary layer can be deposited onto the underlying intrinsic wafer. The doped regions are then typically formed by a deposition process or by doping a section of the deposited boundary layer.

  1. Contribution of S-Layer Proteins to the Mosquitocidal Activity of Lysinibacillus sphaericus

    PubMed Central

    Allievi, Mariana Claudia; Palomino, María Mercedes; Prado Acosta, Mariano; Lanati, Leonardo; Ruzal, Sandra Mónica; Sánchez-Rivas, Carmen

    2014-01-01

    Lysinibacillus sphaericus strains belonging the antigenic group H5a5b produce spores with larvicidal activity against larvae of Culex mosquitoes. C7, a new isolated strain, which presents similar biochemical characteristics and Bin toxins in their spores as the reference strain 2362, was, however, more active against larvae of Culex mosquitoes. The contribution of the surface layer protein (S-layer) to this behaviour was envisaged since this envelope protein has been implicated in the pathogenicity of several bacilli, and we had previously reported its association to spores. Microscopic observation by immunofluorescence detection with anti S-layer antibody in the spores confirms their attachment. S-layers and BinA and BinB toxins formed high molecular weight multimers in spores as shown by SDS-PAGE and western blot detection. Purified S-layer from both L. sphaericus C7 and 2362 strain cultures was by itself toxic against Culex sp larvae, however, that from C7 strain was also toxic against Aedes aegypti. Synergistic effect between purified S-layer and spore-crystal preparations was observed against Culex sp. and Aedes aegypti larvae. This effect was more evident with the C7 strain. In silico analyses of the S-layer sequence suggest the presence of chitin-binding and hemolytic domains. Both biochemical characteristics were detected for both S-layers strains that must justify their contribution to pathogenicity. PMID:25354162

  2. Wide band gap semiconductor templates

    DOEpatents

    Arendt, Paul N.; Stan, Liliana; Jia, Quanxi; DePaula, Raymond F.; Usov, Igor O.

    2010-12-14

    The present invention relates to a thin film structure based on an epitaxial (111)-oriented rare earth-Group IVB oxide on the cubic (001) MgO terminated surface and the ion-beam-assisted deposition ("IBAD") techniques that are amendable to be over coated by semiconductors with hexagonal crystal structures. The IBAD magnesium oxide ("MgO") technology, in conjunction with certain template materials, is used to fabricate the desired thin film array. Similarly, IBAD MgO with appropriate template layers can be used for semiconductors with cubic type crystal structures.

  3. Nanofibrous mats layer-by-layer assembled by HTCC/layered silicate composites with in vitro antitumor activity against SMMC-7721 cells.

    PubMed

    Huang, Rong; Zhou, Xue; Liu, Xinqin; Zhang, Qi; Jin, Huan'guang; Shi, Xiaowen; Luo, Wenjing; Deng, Hongbing

    2014-03-01

    Organic rectorite (OREC) was used to prepare the intercalated nanocomposites with N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC), and then the immobilization of the positively charged HTCC-OREC nanocomposites and the negatively charged sodium alginate (ALG) on cellulose nanofibrous mats was performed through layer-by-layer (LBL) technique. Fiber diameter distribution results from Field Emission Scanning Electron Microscopy (FE-SEM) images showed that the average fiber diameter of (HTCC-OREC/ALG)(n) films coating obviously increased from 433 to 608 nm. Moreover, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results further confirmed the interaction between HTCC and OREC and their successful immobilization on cellulose template. MTT assay indicated that the prepared nanofibrous mats exhibited strong inhibitory activity against human hepatocellular carcinoma cells (SMMC-7721) but a little cytotoxic effect on human Chang liver (CCL-13) cells. Furthermore, the experimental results from FE-SEM and Inverted Fluorescence Microscope of SMMC-7721 cells cultured on LBL structured nanofibrous mats demonstrated the significant antitumor activity of prepared samples. The developed approach to immobilize nanocomposites onto polymer nanofibers with controllable thickness may also be utilized to tumor therapy. PMID:24730244

  4. SEMICONDUCTOR DEVICES: Conductivity modulation enhanced lateral IGBT with SiO2 shielded layer anode by SIMOX technology on SOI substrate

    NASA Astrophysics Data System (ADS)

    Wensuo, Chen; Bo, Zhang; Zhaoji, Li; Jian, Fang; Xu, Guan

    2010-06-01

    A new lateral insulated-gate bipolar transistor (LIGBT) with a SiO2 shielded layer anode on SOI substrate is proposed and discussed. Compared to the conventional LIGBT, the proposed device offers an enhanced conductivity modulation effect due to the SiO2 shielded layer anode structure which can be formed by SIMOX technology. Simulation results show that, for the proposed LIGBT, during the conducting state, the electron-hole plasma concentrations in the n-drift region are several times larger than those of the conventional LIGBT; the conducting current is up to 37% larger than that of the conventional one. The enhanced conductivity modulation effect by SiO2 shielded layer anode does not sacrifice other characteristics of the device, such as breakdown and switching, but is compatible with other optimized technologies.

  5. Method for depositing high-quality microcrystalline semiconductor materials

    DOEpatents

    Guha, Subhendu; Yang, Chi C.; Yan, Baojie

    2011-03-08

    A process for the plasma deposition of a layer of a microcrystalline semiconductor material is carried out by energizing a process gas which includes a precursor of the semiconductor material and a diluent with electromagnetic energy so as to create a plasma therefrom. The plasma deposits a layer of the microcrystalline semiconductor material onto the substrate. The concentration of the diluent in the process gas is varied as a function of the thickness of the layer of microcrystalline semiconductor material which has been deposited. Also disclosed is the use of the process for the preparation of an N-I-P type photovoltaic device.

  6. Permafrost and Active Layer Monitoring in the Maritime Antarctic: A Contribution to TSP and ANTPAS projects

    NASA Astrophysics Data System (ADS)

    Vieira, G.; Ramos, M.; Batista, V.; Caselli, A.; Correia, A.; Fragoso, M.; Gruber, S.; Hauck, C.; Kenderova, R.; Lopez-Martinez, J.; Melo, R.; Mendes-Victor, L. A.; Miranda, P.; Mora, C.; Neves, M.; Pimpirev, C.; Rocha, M.; Santos, F.; Blanco, J. J.; Serrano, E.; Trigo, I.; Tome, D.; Trindade, A.

    2008-12-01

    Permafrost and active layer monitoring in the Maritime Antarctic (PERMANTAR) is a Portuguese funded International Project that, in cooperation with the Spanish project PERMAMODEL, will assure the installation and the maintenance of a network of boreholes and active layer monitoring sites, in order to characterize the spatial distribution of the physical and thermal properties of permafrost, as well as the periglacial processes in Livingston and Deception Islands (South Shetlands). The project is part of the International Permafrost Association IPY projects Thermal State of Permafrost (TSP) and Antarctic and Sub-Antarctic Permafrost, Soils and Periglacial Environments (ANTPAS). It contributes to GTN-P and CALM-S networks. The PERMANTAR-PERMAMODEL permafrost and active layer monitoring network includes several boreholes: Reina Sofia hill (since 2000, 1.1m), Incinerador (2000, 2.3m), Ohridski 1 (2008, 5m), Ohridski 2 (2008, 6m), Gulbenkian-Permamodel 1 (2008, 25m) and Gulbenkian- Permamodel 2 (2008, 15m). For active layer monitoring, several CALM-S sites have been installed: Crater Lake (2006), Collado Ramos (2007), Reina Sofia (2007) and Ohridski (2007). The monitoring activities are accompanied by detailed geomorphological mapping in order to identify and map the geomorphic processes related to permafrost or active layer dynamics. Sites will be installed in early 2009 for monitoring rates of geomorphological activity in relation to climate change (e.g. solifluction, rockglaciers, thermokarst). In order to analyse the spatial distribution of permafrost and its ice content, electrical resistivity tomography (ERT), and seismic refraction surveys have been performed and, in early 2009, continuous ERT surveying instrumentation will be installed for monitoring active layer evolution. The paper presents a synthesis of the activities, as well as the results obtained up to the present, mainly relating to ground temperature monitoring and from permafrost characteristics and

  7. Controlled growth of semiconductor crystals

    DOEpatents

    Bourret-Courchesne, E.D.

    1992-07-21

    A method is disclosed for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B[sub x]O[sub y] are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T[sub m1] of the oxide of boron (T[sub m1]=723 K for boron oxide B[sub 2]O[sub 3]), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T[sub m2] of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm[sup 2]. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 [mu]m. 7 figs.

  8. Controlled growth of semiconductor crystals

    DOEpatents

    Bourret-Courchesne, Edith D.

    1992-01-01

    A method for growth of III-V, II-VI and related semiconductor single crystals that suppresses random nucleation and sticking of the semiconductor melt at the crucible walls. Small pieces of an oxide of boron B.sub.x O.sub.y are dispersed throughout the comminuted solid semiconductor charge in the crucible, with the oxide of boron preferably having water content of at least 600 ppm. The crucible temperature is first raised to a temperature greater than the melt temperature T.sub.m1 of the oxide of boron (T.sub.m1 =723.degree. K. for boron oxide B.sub.2 O.sub.3), and the oxide of boron is allowed to melt and form a reasonably uniform liquid layer between the crucible walls and bottom surfaces and the still-solid semiconductor charge. The temperature is then raised to approximately the melt temperature T.sub.m2 of the semiconductor charge material, and crystal growth proceeds by a liquid encapsulated, vertical gradient freeze process. About half of the crystals grown have a dislocation density of less than 1000/cm.sup.2. If the oxide of boron has water content less than 600 ppm, the crucible material should include boron nitride, a layer of the inner surface of the crucible should be oxidized before the oxide of boron in the crucible charge is melted, and the sum of thicknesses of the solid boron oxide layer and liquid boron oxide layer should be at least 50 .mu.m.

  9. Group I-III-VI.sub.2 semiconductor films for solar cell application

    DOEpatents

    Basol, Bulent M.; Kapur, Vijay K.

    1991-01-01

    This invention relates to an improved thin film solar cell with excellent electrical and mechanical integrity. The device comprises a substrate, a Group I-III-VI.sub.2 semiconductor absorber layer and a transparent window layer. The mechanical bond between the substrate and the Group I-III-VI.sub.2 semiconductor layer is enhanced by an intermediate layer between the substrate and the Group I-III-VI.sub.2 semiconductor film being grown. The intermediate layer contains tellurium or substitutes therefor, such as Se, Sn, or Pb. The intermediate layer improves the morphology and electrical characteristics of the Group I-III-VI.sub.2 semiconductor layer.

  10. Passivation of oxide traps and interface states in GaAs metal-oxide-semiconductor capacitor by LaTaON passivation layer and fluorine incorporation

    SciTech Connect

    Liu, L. N.; Choi, H. W.; Lai, P. T.; Xu, J. P.

    2015-11-23

    GaAs metal-oxide-semiconductor capacitor with TaYON/LaTaON gate-oxide stack and fluorine-plasma treatment is fabricated and compared with its counterparts without the LaTaON passivation interlayer or the fluorine treatment. Experimental results show that the sample exhibits better characteristics: low interface-state density (8 × 10{sup 11 }cm{sup −2}/eV), small flatband voltage (0.69 V), good capacitance-voltage behavior, small frequency dispersion, and small gate leakage current (6.35 × 10{sup −6} A/cm{sup 2} at V{sub fb} + 1 V). These should be attributed to the suppressed growth of unstable Ga and As oxides on the GaAs surface during gate-oxide annealing by the LaTaON interlayer and fluorine incorporation, and the passivating effects of fluorine atoms on the acceptor-like interface and near-interface traps.

  11. Layer-by-layer carbon nanotube bio-templates for in situ monitoring of the metabolic activity of nitrifying bacteria

    NASA Astrophysics Data System (ADS)

    Loh, Kenneth J.; Guest, Jeremy S.; Ho, Genevieve; Lynch, Jerome P.; Love, Nancy G.

    2009-03-01

    Despite the wide variety of effective disinfection and wastewater treatment techniques for removing organic and inorganic wastes, pollutants such as nitrogen remain in wastewater effluents. If left untreated, these nitrogenous wastes can adversely impact the environment by promoting the overgrowth of aquatic plants, depleting dissolved oxygen, and causing eutrophication. Although nitrification/denitrification processes are employed during advanced wastewater treatment, effective and efficient operation of these facilities require information of the pH, dissolved oxygen content, among many other parameters, of the wastewater effluent. In this preliminary study, a biocompatible CNT-based nanocomposite is proposed and validated for monitoring the biological metabolic activity of nitrifying bacteria in wastewater effluent environments (i.e., to monitor the nitrification process). Using carbon nanotubes and a pH-sensitive conductive polymer (i.e., poly(aniline) emeraldine base), a layer-by-layer fabrication technique is employed to fabricate a novel thin film pH sensor that changes its electrical properties in response to variations in ambient pH environments. Laboratory studies are conducted to evaluate the proposed nanocomposite's biocompatibility with wastewater effluent environments and its pH sensing performance.

  12. Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

    PubMed

    Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

    2016-11-15

    Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering. PMID:27494632

  13. Transfection activity of layer-by-layer plasmid DNA/poly(ethylenimine) films deposited on PLGA microparticles

    PubMed Central

    Kakade, Sandeep; Manickam, Devika Soundara; Handa, Hitesh; Mao, Guangzhao; Oupický, David

    2009-01-01

    Layer-by-layer (LbL) assemblies of DNA and polycations on the surface of colloidal templates can be used for gene delivery. Plasmid DNA encoding for secreted alkaline phosphatase (SEAP) was used to deposit LbL films with poly(ethylenimine) (PEI) on the surface of polystyrene and poly(lactide-co-glycolide) microparticles. The formation of LBL films was confirmed by zeta potential analysis and fluorescence and atomic force microscopy techniques. The LbL particles were rapidly internalized in a dose-dependent manner by J774.1 murine macrophages. Transfection activity of the LbL particles was evaluated in J774.1 cells using three different doses (5, 10, 25 particle per cell). The levels of SEAP expression increased with increasing dose but were lower than transfection levels mediated by control PEI/DNA polyplexes at corresponding DNA doses. The LbL particles reported here present a promising platform for delivery of DNA to phagocytic cells. PMID:18786622

  14. Rapid electrostatics-assisted layer-by-layer assembly of near-infrared-active colloidal photonic crystals.

    PubMed

    Askar, Khalid; Leo, Sin-Yen; Xu, Can; Liu, Danielle; Jiang, Peng

    2016-11-15

    Here we report a rapid and scalable bottom-up technique for layer-by-layer (LBL) assembling near-infrared-active colloidal photonic crystals consisting of large (⩾1μm) silica microspheres. By combining a new electrostatics-assisted colloidal transferring approach with spontaneous colloidal crystallization at an air/water interface, we have demonstrated that the crystal transfer speed of traditional Langmuir-Blodgett-based colloidal assembly technologies can be enhanced by nearly 2 orders of magnitude. Importantly, the crystalline quality of the resultant photonic crystals is not compromised by this rapid colloidal assembly approach. They exhibit thickness-dependent near-infrared stop bands and well-defined Fabry-Perot fringes in the specular transmission and reflection spectra, which match well with the theoretical calculations using a scalar-wave approximation model and Fabry-Perot analysis. This simple yet scalable bottom-up technology can significantly improve the throughput in assembling large-area, multilayer colloidal crystals, which are of great technological importance in a variety of optical and non-optical applications ranging from all-optical integrated circuits to tissue engineering.

  15. Carbon nanotubes supported cerium dioxide and platinum nanohybrids: Layer-by-layer synthesis and enhanced electrocatalytic activity for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Lou, Xinyuan; Chen, Jiayi; Wang, Mengdi; Gu, Jialei; Wu, Ping; Sun, Dongmei; Tang, Yawen

    2015-08-01

    We successfully synthesize carbon nanotubes (CNTs) supported cerium dioxide and platinum (Pt/CeO2/CNTs) nanohybrids via layer-by-layer assembly. The composition, morphology and structure of the as-prepared Pt/CeO2/CNTs nanohybrids are characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometer (EDX), selected-area electron diffraction (SAED), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectrometry (ICP-AES). By comparison of the electrocatalytic properties of the Pt/CeO2/CNTs with the Pt/CNTs, we systematically investigate the promotion effect of CeO2 on the Pt/CeO2/CNTs catalysts towards methanol oxidation. It is found that the introduction of CeO2 not only enhances the electrocatalytic activity and stability of the Pt/CeO2/CNTs catalyst for methanol oxidation but also minimizes the CO poisoning, probably accounting for the good oxygen carrying capacity of CeO2 and its high stability in acidic solution.

  16. O3-sourced atomic layer deposition of high quality Al2O3 gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Huang, Sen; Liu, Xinyu; Wei, Ke; Liu, Guoguo; Wang, Xinhua; Sun, Bing; Yang, Xuelin; Shen, Bo; Liu, Cheng; Liu, Shenghou; Hua, Mengyuan; Yang, Shu; Chen, Kevin J.

    2015-01-01

    High quality Al2O3 film grown by atomic layer deposition (ALD), with ozone (O3) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al-O-H and Al-Al bonds in ALD-Al2O3 has been realized by substituting conventional H2O source with O3. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O3-Al2O3 and 2-nm H2O-Al2O3 interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 1012 cm-2, contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance RON,sp of 0.49 mΩ cm2.

  17. Enhanced photocurrent density in graphene/Si based solar cell (GSSC) by optimizing active layer thickness

    SciTech Connect

    Rosikhin, Ahmad Hidayat, Aulia Fikri; Syuhada, Ibnu; Winata, Toto

    2015-12-29

    Thickness dependent photocurrent density in active layer of graphene/Si based solar cell has been investigated via analytical – simulation study. This report is a preliminary comparison of experimental and analytical investigation of graphene/Si based solar cell. Graphene sheet was interfaced with Si thin film forming heterojunction solar cell that was treated as a device model for photocurrent generator. Such current can be enhanced by optimizing active layer thickness and involving metal oxide as supporting layer to shift photons absorption. In this case there are two type of devices model with and without TiO{sub 2} in which the silicon thickness varied at 20 – 100 nm. All of them have examined and also compared with each other to obtain an optimum value. From this calculation it found that generated currents almost linear with thickness but there are saturated conditions that no more enhancements will be achieved. Furthermore TiO{sub 2} layer is effectively increases photon absorption but reducing device stability, maximum current is fluctuates enough. This may caused by the disturbance of excitons diffusion and resistivity inside each layer. Finally by controlling active layer thickness, it is quite useful to estimate optimization in order to develop the next solar cell devices.

  18. Organic Semiconductors and its Applications

    NASA Astrophysics Data System (ADS)

    Kamalasanan, M. N.

    2011-10-01

    Organic semiconductors in the form of evaporated or spin coated thin films have many optoelectronic applications in the present electronic industry. They are frequently used in many type of displays, photo detectors, photoconductors for photocopiers and photovoltaic cells. But many p-conjugated molecules and polymer based devices do not provide satisfactory device performance and operational stability. Most of these problems are related to the interfaces they make with other organic materials and electrodes and the low conductivity of the organic layers. The study of organic-metal and organic—organic interfaces as well as electrical doping of organic semiconductors are very important areas of research at present. In this talk, I will be discussing some of the recent advances in this field as well as some of our own results in the area of interface modification and electrical doping of organic semiconductors.

  19. Semiconductor radiation detector

    DOEpatents

    Patt, Bradley E.; Iwanczyk, Jan S.; Tull, Carolyn R.; Vilkelis, Gintas

    2002-01-01

    A semiconductor radiation detector is provided to detect x-ray and light photons. The entrance electrode is segmented by using variable doping concentrations. Further, the entrance electrode is physically segmented by inserting n+ regions between p+ regions. The p+ regions and the n+ regions are individually biased. The detector elements can be used in an array, and the p+ regions and the n+ regions can be biased by applying potential at a single point. The back side of the semiconductor radiation detector has an n+ anode for collecting created charges and a number of p+ cathodes. Biased n+ inserts can be placed between the p+ cathodes, and an internal resistor divider can be used to bias the n+ inserts as well as the p+ cathodes. A polysilicon spiral guard can be implemented surrounding the active area of the entrance electrode or surrounding an array of entrance electrodes.

  20. Discrete-Layer Piezoelectric Plate and Shell Models for Active Tip-Clearance Control

    NASA Technical Reports Server (NTRS)

    Heyliger, P. R.; Ramirez, G.; Pei, K. C.

    1994-01-01

    The objectives of this work were to develop computational tools for the analysis of active-sensory composite structures with added or embedded piezoelectric layers. The targeted application for this class of smart composite laminates and the analytical development is the accomplishment of active tip-clearance control in turbomachinery components. Two distinct theories and analytical models were developed and explored under this contract: (1) a discrete-layer plate theory and corresponding computational models, and (2) a three dimensional general discrete-layer element generated in curvilinear coordinates for modeling laminated composite piezoelectric shells. Both models were developed from the complete electromechanical constitutive relations of piezoelectric materials, and incorporate both displacements and potentials as state variables. This report describes the development and results of these models. The discrete-layer theories imply that the displacement field and electrostatic potential through-the-thickness of the laminate are described over an individual layer rather than as a smeared function over the thickness of the entire plate or shell thickness. This is especially crucial for composites with embedded piezoelectric layers, as the actuating and sensing elements within these layers are poorly represented by effective or smeared properties. Linear Lagrange interpolation polynomials were used to describe the through-thickness laminate behavior. Both analytic and finite element approximations were used in the plane or surface of the structure. In this context, theoretical developments are presented for the discrete-layer plate theory, the discrete-layer shell theory, and the formulation of an exact solution for simply-supported piezoelectric plates. Finally, evaluations and results from a number of separate examples are presented for the static and dynamic analysis of the plate geometry. Comparisons between the different approaches are provided when

  1. High-resolution three-dimensional scanning transmission electron microscopy characterization of oxide-nitride-oxide layer interfaces in Si-based semiconductors using computed tomography.

    PubMed

    Sadayama, Shoji; Sekiguchi, Hiromi; Bright, Alexander; Suzuki, Naohisa; Yamada, Kazuhiro; Kaneko, Kenji

    2011-01-01

    Oxide-nitride-oxide (ONO) layer structures are widely used for charge storage in flash memory devices. The ONO layer interfaces should be as flat as possible, so measurement of the nanoscale roughness of those interfaces is needed. In this study, quantification of an ONO film from a commercially available flash memory device was carried out with a pillar-shaped specimen using scanning transmission electron microscopy (STEM) and computed tomography. The ONO area contained only low Z- and low STEM-contrast materials, which makes high-quality reconstruction difficult. The optimum three-dimensional reconstruction was achieved with an STEM annular dark-field detector inner collection angle of 32 mrad, a sample tilt range from -78° to +78° and 25 iterations for the simultaneous iterative reconstruction technique.

  2. Study of the influence of semiconductor material parameters on acoustic wave propagation modes in GaSb/AlSb bi-layered structures by Legendre polynomial method

    NASA Astrophysics Data System (ADS)

    Othmani, Cherif; Takali, Farid; Njeh, Anouar; Ben Ghozlen, Mohamed Hédi

    2016-09-01

    The propagation of Rayleigh-Lamb waves in bi-layered structures is studied. For this purpose, an extension of the Legendre polynomial (LP) method is proposed to formulate the acoustic wave equation in the bi-layered structures induced by thin film Gallium Antimonide (GaSb) and with Aluminum Antimonide (AlSb) substrate in moderate thickness. Acoustic modes propagating along a bi-layer plate are shown to be quite different than classical Lamb modes, contrary to most of the multilayered structures. The validation of the LP method is illustrated by a comparison between the associated numerical results and those obtained using the ordinary differential equation (ODE) method. The convergency of the LP method is discussed through a numerical example. Moreover, the influences of thin film GaSb parameters on the characteristics Rayleigh-Lamb waves propagation has been studied in detail. Finally, the advantages of the Legendre polynomial (LP) method to analyze the multilayered structures are described. All the developments performed in this work were implemented in Matlab software.

  3. Active/Passive Control of Sound Radiation from Panels using Constrained Layer Damping

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2003-01-01

    A hybrid passive/active noise control system utilizing constrained layer damping and model predictive feedback control is presented. This system is used to control the sound radiation of panels due to broadband disturbances. To facilitate the hybrid system design, a methodology for placement of constrained layer damping which targets selected modes based on their relative radiated sound power is developed. The placement methodology is utilized to determine two constrained layer damping configurations for experimental evaluation of a hybrid system. The first configuration targets the (4,1) panel mode which is not controllable by the piezoelectric control actuator, and the (2,3) and (5,2) panel modes. The second configuration targets the (1,1) and (3,1) modes. The experimental results demonstrate the improved reduction of radiated sound power using the hybrid passive/active control system as compared to the active control system alone.

  4. Active layer thermal monitoring at Fildes Peninsula, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, R. F. M.; Schaefer, C. E. G. R.; Simas, F. N. B.; Francelino M., R.; Fernandes-Filho, E. I.; Lyra, G. B.; Bockheim, J. G.

    2014-07-01

    International attention to the climate change phenomena has grown in the last decade; the active layer and permafrost are of great importance in understanding processes and future trends due to their role in energy flux regulation. The objective of the this paper is to present active layer temperature data for one CALM-S site located at Fildes Peninsula, King George Island, Maritime Antarctica over an fifth seven month period (2008-2012). The monitoring site was installed during the summer of 2008 and consists of thermistors (accuracy of ± 0.2 °C), arranged vertically with probes at different depths, recording data at hourly intervals in a~high capacity data logger. A series of statistical analysis were performed to describe the soil temperature time series, including a linear fit in order to identify global trend and a series of autoregressive integrated moving average (ARIMA) models were tested in order to define the best fit for the data. The controls of weather on the thermal regime of the active layer have been identified, providing insights about the influence of climate chance over the permafrost. The active layer thermal regime in the studied period was typical of periglacial environment, with extreme variation at the surface during summer resulting in frequent freeze and thaw cycles. The active layer thickness (ALT) over the studied period showed variability related to different annual weather conditions, reaching a maximum of 117.5 cm in 2009. The ARIMA model was considered appropriate to treat the dataset, enabling more conclusive analysis and predictions when longer data sets are available. Despite the variability when comparing temperature readings and active layer thickness over the studied period, no warming trend was detected.

  5. Active-layer thermal monitoring on the Fildes Peninsula, King George Island, maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, R. F. M.; Schaefer, C. E. G. R.; Simas, F. M. B.; Francelino, M. R.; Fernandes-Filho, E. I.; Lyra, G. B.; Bockheim, J. G.

    2014-12-01

    International attention to climate change phenomena has grown in the last decade; the active layer and permafrost are of great importance in understanding processes and future trends due to their role in energy flux regulation. The objective of this paper is to present active-layer temperature data for one Circumpolar Active Layer Monitoring South hemisphere (CALM-S) site located on the Fildes Peninsula, King George Island, maritime Antarctica over an 57-month period (2008-2012). The monitoring site was installed during the summer of 2008 and consists of thermistors (accuracy of ±0.2 °C), arranged vertically with probes at different depths, recording data at hourly intervals in a high-capacity data logger. A series of statistical analyses was performed to describe the soil temperature time series, including a linear fit in order to identify global trends, and a series of autoregressive integrated moving average (ARIMA) models was tested in order to define the best fit for the data. The affects of weather on the thermal regime of the active layer have been identified, providing insights into the influence of climate change on permafrost. The active-layer thermal regime in the studied period was typical of periglacial environments, with extreme variation in surface during the summer resulting in frequent freeze and thaw cycles. The active-layer thickness (ALT) over the studied period shows a degree of variability related to different annual weather conditions, reaching a maximum of 117.5 cm in 2009. The ARIMA model could describe the data adequately and is an important tool for more conclusive analysis and predictions when longer data sets are available. Despite the variability when comparing temperature readings and ACT over the studied period, no trend can be identified.

  6. Activation Layer Stabilization of High Polarization Photocathodes in Sub-Optimal RF Gun Environments

    SciTech Connect

    Gregory A. Mulhollan

    2010-11-16

    Specific activation recipes for bulk, 100 nm thick MBE grown and high polarization III-V photocathode material have been developed which mitigate the effects of exposure to background gasses. Lifetime data using four representative gasses were acquired for bulk GaAs, 100 nm unstrained GaAs and strained superlattice GaAs/GaAsP, all activated both with Cs and then Cs and Li (bi-alkali). Each photoemitter showed marked resilience improvement when activated using the bi-alkali recipe compared to the standard single alkali recipe. A dual alkali activation system at SLAC was constructed, baked and commissioned with the purpose of performing spin-polarization measurements on electrons emitted from the bi-alkali activated surfaces. An end station at SSRL was configured with the required sources for energy resolved photoemission measurements on the bi-alkali activated and CO2 dosed surfaces. The bi-alkali recipes were successfully implemented at SLAC/SSRL. Measurements at SLAC of the photoelectron spin-polarization from the modified activation surface showed no sign of a change in value compared to the standard activated material, i.e., no ill effects. Analysis of photoemission data indicates that the addition of Li to the activation layer results in a multi-layer structure. The presence of Li in the activation layer also acts as an inhibitor to CO2 absorption, hence better lifetimes in worse vacuum were achieved. The bi-alkali activation has been tested on O2 activated GaAs for comparison with NF3 activated surfaces. Comparable resilience to CO2 exposure was achieved for the O2 activated surface. An RF PECVD amorphous silicon growth system was modified to allow high temperature heat cleaning of GaAs substrates prior to film deposition. Growth versus thickness data were collected. Very thin amorphous silicon germanium layers were optimized to exhibit good behavior as an electron emitter. Growth of the amorphous silicon germanium films on the above substrates was fine tuned

  7. Electron gas grid semiconductor radiation detectors

    DOEpatents

    Lee, Edwin Y.; James, Ralph B.

    2002-01-01

    An electron gas grid semiconductor radiation detector (EGGSRAD) useful for gamma-ray and x-ray spectrometers and imaging systems is described. The radiation detector employs doping of the semiconductor and variation of the semiconductor detector material to form a two-dimensional electron gas, and to allow transistor action within the detector. This radiation detector provides superior energy resolution and radiation detection sensitivity over the conventional semiconductor radiation detector and the "electron-only" semiconductor radiation detectors which utilize a grid electrode near the anode. In a first embodiment, the EGGSRAD incorporates delta-doped layers adjacent the anode which produce an internal free electron grid well to which an external grid electrode can be attached. In a second embodiment, a quantum well is formed between two of the delta-doped layers, and the quantum well forms the internal free electron gas grid to which an external grid electrode can be attached. Two other embodiments which are similar to the first and second embodiment involve a graded bandgap formed by changing the composition of the semiconductor material near the first and last of the delta-doped layers to increase or decrease the conduction band energy adjacent to the delta-doped layers.

  8. MAPLE prepared heterostructures with arylene based polymer active layer for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Stanculescu, F.; Rasoga, O.; Catargiu, A. M.; Vacareanu, L.; Socol, M.; Breazu, C.; Preda, N.; Socol, G.; Stanculescu, A.

    2015-05-01

    This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of heterostructures with single layer of arylene based polymer, poly[N-(2-ethylhexyl)2.7-carbazolyl vinylene]/AMC16 and poly[N-(2-ethylhexyl)2.7-carbazolyl 1.4-phenylene ethynylene]/AMC22, and with layers of these polymers mixed with Buckminsterfullerene/C60 in the weight ratio of 1:2 (AMC16:C60) and 1:3 (AMC22:C60). The deposited layers have been characterized by spectroscopic (UV-Vis-NIR, PL, FTIR) and microscopic (SEM, AFM) methods. The effect of the polymer particularities on the optical and electrical properties of the structures based on polymer and polymer:C60 mixed layer has been analyzed. The study of the electrical properties has revealed typical solar cell behavior for the heterostructure prepared by MAPLE on glass/ITO/PEDOT-PSS with AMC16, AMC22 and AMC22:C60 layer, confirming that this method is adequate for the preparation of polymeric and mixed active layers for solar cells applications. The highest photovoltaic effect was shown by the solar cell structure realized with single layer of AMC16 polymer: glass/ITO/PEDOT-PSS/AMC16/Al.

  9. Efficacy of different final irrigant activation protocols on smear layer removal by EDTA and citric acid.

    PubMed

    Herrera, Daniel R; Santos, Zarina T; Tay, Lidia Y; Silva, Emmanuel J; Loguercio, Alessandro D; Gomes, Brenda P F A

    2013-04-01

    The aim of this study was to evaluate the influence of different activation protocols for chelating agents used after chemo-mechanical preparation (CMP), for smear layer (SL) removal. Forty-five single-rooted human premolars with straight canals and fully formed apex were selected. The specimens were randomly divided into three groups depending on the chelating agent used for smear layer removal: distilled water (DW, control group); 17% ethylenediaminetetraacetic acid (EDTA); and 10% citric acid (CA). Each group was further divided into three subgroups according to the activation protocol used: no-activation (NA), manual dynamic activation (MDA), or sonic activation (SA). After CMP, all specimens were sectioned and processed for observation of the apical thirds by using scanning electron microscopy (SEM). Two calibrated evaluators attributed scores to each specimen. The differences between activation protocols were analyzed with Kruskal-Wallis and Mann-Whitney U tests. Friedman and Wilcoxon signed rank tests were used for comparison between each root canal third. When chelating agents were activated, either by MDA or SA, it was obtained the best cleaning results with no significant difference between EDTA and CA (P > 0.05). Sonic activation showed the best results when root canal thirds were analyzed, in comparison to MDA and NA groups (P < 0.05). The activation of chelating agents, independent of the protocol used, benefits smear layer removal from root canals.

  10. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

    PubMed Central

    Ciobanu, C. S.; Groza, A.; Iconaru, S. L.; Popa, C. L.; Chapon, P.; Chifiriuc, M. C.; Hristu, R.; Stanciu, G. A.; Negrila, C. C.; Ghita, R. V.; Ganciu, M.; Predoi, D.

    2015-01-01

    The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC—American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells. PMID:26504849

  11. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer.

    PubMed

    Ciobanu, C S; Groza, A; Iconaru, S L; Popa, C L; Chapon, P; Chifiriuc, M C; Hristu, R; Stanciu, G A; Negrila, C C; Ghita, R V; Ganciu, M; Predoi, D

    2015-01-01

    The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells. PMID:26504849

  12. Modeling the gain and bandwidth of submicron active layer n+-i-p+ avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Majumder, Kanishka; Das, N. R.

    2012-10-01

    The electron initiated avalanche gain and bandwidth are calculated for thin submicron GaAs n+-i-p+ avalanche photodiode. A model is used to estimate the avalanche build-up of carriers in the active multiplication layer considering the dead-space effect. In the model, the carriers are identified both by their energy and position in the multiplication region. The excess energy of the carriers above threshold is assumed to be equally distributed among the carriers generated after impact ionization. The gain versus bias and bandwidth versus gain characteristics of the device are also demonstrated for different active layer thicknesses of the APD.

  13. L{sub g} = 100 nm In{sub 0.7}Ga{sub 0.3}As quantum well metal-oxide semiconductor field-effect transistors with atomic layer deposited beryllium oxide as interfacial layer

    SciTech Connect

    Koh, D. E-mail: Taewoo.Kim@sematech.org; Kwon, H. M.; Kim, T.-W. E-mail: Taewoo.Kim@sematech.org; Veksler, D.; Gilmer, D.; Kirsch, P. D.; Kim, D.-H.; Hudnall, Todd W.; Bielawski, Christopher W.; Maszara, W.; Banerjee, S. K.

    2014-04-21

    In this study, we have fabricated nanometer-scale channel length quantum-well (QW) metal-oxide-semiconductor field effect transistors (MOSFETs) incorporating beryllium oxide (BeO) as an interfacial layer. BeO has high thermal stability, excellent electrical insulating characteristics, and a large band-gap, which make it an attractive candidate for use as a gate dielectric in making MOSFETs. BeO can also act as a good diffusion barrier to oxygen owing to its small atomic bonding length. In this work, we have fabricated In{sub 0.53}Ga{sub 0.47}As MOS capacitors with BeO and Al{sub 2}O{sub 3} and compared their electrical characteristics. As interface passivation layer, BeO/HfO{sub 2} bilayer gate stack presented effective oxide thickness less 1 nm. Furthermore, we have demonstrated In{sub 0.7}Ga{sub 0.3}As QW MOSFETs with a BeO/HfO{sub 2} dielectric, showing a sub-threshold slope of 100 mV/dec, and a transconductance (g{sub m,max}) of 1.1 mS/μm, while displaying low values of gate leakage current. These results highlight the potential of atomic layer deposited BeO for use as a gate dielectric or interface passivation layer for III–V MOSFETs at the 7 nm technology node and/or beyond.

  14. Electrical and photoelectric characteristics of structures based on InSe and GaSe layered semiconductors irradiated with 12.5-MeV electrons

    SciTech Connect

    Kovalyuk, Z. D. Politanska, O. A.; Sydor, O. N.; Maslyuk, V. T.

    2008-11-15

    The effect of irradiation with 12.5-MeV electrons on the electrical and photoelectric parameters of layered photoconverters based on p-InSe-n-InSe and p-GaSe-n-InSe structures is studied. The observed variations in the current-voltage characteristics, photoresponse spectra, open-circuit voltage, and short-circuit current are caused by the formation of point defects. The absence of pronounced changes in the characteristics of the homojunctions and heterojunctions even after irradiation at the highest dose makes it possible to recommend these junctions for use in the fabrication of radiation-resistant photodetectors.

  15. Microbial diversity of active layer and permafrost in an acidic wetland from the Canadian High Arctic.

    PubMed

    Wilhelm, Roland C; Niederberger, Thomas D; Greer, Charles; Whyte, Lyle G

    2011-04-01

    The abundance and structure of archaeal and bacterial communities from the active layer and the associated permafrost of a moderately acidic (pH < 5.0) High Arctic wetland (Axel Heiberg Island, Nunavut, Canada) were investigated using culture- and molecular-based methods. Aerobic viable cell counts from the active layer were ∼100-fold greater than those from the permafrost (2.5 × 10(5) CFU·(g soil dry mass)(-1)); however, a greater diversity of isolates were cultured from permafrost, as determined by 16S rRNA gene sequencing. Isolates from both layers demonstrated growth characteristics of a psychrotolerant, halotolerant, and acidotolerant community. Archaea constituted 0.1% of the total 16S rRNA gene copy number and, in the 16S rRNA gene clone library, predominantly (71% and 95%) consisted of Crenarchaeota related to Group I. 1b. In contrast, bacterial communities were diverse (Shannon's diversity index, H = ∼4), with Acidobacteria constituting the largest division of active layer clones (30%) and Actinobacteria most abundant in permafrost (28%). Direct comparisons of 16S rRNA gene sequence data highlighted significant differences between the bacterial communities of each layer, with the greatest differences occurring within Actinobacteria. Comparisons of 16S rRNA gene sequences with those from other Arctic permafrost and cold-temperature wetlands revealed commonly occurring taxa within the phyla Chloroflexi, Acidobacteria, and Actinobacteria (families Intrasporangiaceae and Rubrobacteraceae). PMID:21491982

  16. Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Luong, G. V.; Wirths, S.; Stefanov, S.; Holländer, B.; Schubert, J.; Conde, J. C.; Stoica, T.; Breuer, U.; Chiussi, S.; Goryll, M.; Buca, D.; Mantl, S.

    2013-05-01

    Excimer Laser Annealing (ELA) with a wavelength of 248 nm is used to study doping of biaxialy compressively strained Si1-xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1 × 1015 As+/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650 Ω/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62 Ω/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods.

  17. Electrospun nanofiber layers with incorporated photoluminescence indicator for chromatography and detection of ultraviolet-active compounds.

    PubMed

    Kampalanonwat, Pimolpun; Supaphol, Pitt; Morlock, Gertrud E

    2013-07-19

    For the first time, electrospun nanofiber phases were fabricated with manganese-activated zinc silicate as photoluminescent indicator (UV254) to transfer and enlarge its application to the field of UV-active compounds. By integration of such an indicator, UV-active compounds got visible on the chromatogram. The separation of 7 preservatives and a beverage sample were studied on the novel luminescent polyacrylonitrile layers. The mat thickness and mean fiber diameters were calculated for additions of different UV254 indicator concentrations. The separation efficiency on the photoluminescent layers was characterized by comparison to HPTLC layers and calculation of the plate numbers and resolutions. Some benefits were the reduction in migration distance (3cm), migration time (12min), analyte (10-nL volumes) and mobile phase volumes (1mL). As ultrathin stationary phase, such layers are suited for their integration into the Office Chromatography concept. For the first time, electrospun nanofiber layers were hyphenated with mass spectrometry and the confirmation of compounds was successfully performed using the elution-head based TLC-MS Interface.

  18. Survey of cryogenic semiconductor devices

    SciTech Connect

    Talarico, L.J.; McKeever, J.W.

    1996-04-01

    Improved reliability and electronic performance can be achieved in a system operated at cryogenic temperatures because of the reduction in mechanical insult and in disruptive effects of thermal energy on electronic devices. Continuing discoveries of new superconductors with ever increasing values of T{sub c} above that of liquid nitrogen temperature (LNT) have provided incentive for developing semiconductor electronic systems that may also operate in the superconductor`s liquid nitrogen bath. Because of the interest in high-temperature superconductor (HTS) devices, liquid nitrogen is the cryogen of choice and LNT is the temperature on which this review is focused. The purpose of this survey is to locate and assemble published information comparing the room temperature (298 K), performance of commercially available conventional and hybrid semiconductor device with their performance at LNT (77K), to help establish their candidacy as cryogenic electronic devices specifically for use at LNT. The approach to gathering information for this survey included the following activities. Periodicals and proceedings were searched for information on the behavior of semiconductor devices at LNT. Telephone calls were made to representatives of semiconductor industries, to semiconductor subcontractors, to university faculty members prominent for their research in the area of cryogenic semiconductors, and to representatives of the National Aeronautics and Space Administration (NASA) and NASA subcontractors. The sources and contacts are listed with their responses in the introduction, and a list of references appears at the end of the survey.

  19. Estimation of semiconductor-like pigment concentrations in paint mixtures and their differentiation from paint layers using first-derivative reflectance spectra.

    PubMed

    Pallipurath, Anuradha R; Skelton, Jonathan M; Ricciardi, Paola; Elliott, Stephen R

    2016-07-01

    Identification of the techniques employed by artists, e.g. mixing and layering of paints, if used together with information about their colour palette and style, can help to attribute works of art with more confidence. In this study, we show how the pigment composition in binary paint mixtures can be quantified using optical-reflectance spectroscopy, by analysis of the peak features corresponding to colour-transition edges in the first-derivative spectra. This technique is found to be more robust than a number of other spectral-analysis methods, which can suffer due to shifts in the transition edges in mixed paints compared to those observed in spectra of pure ones. Our method also provides a means of distinguishing paint mixtures from layering in some cases. The spectroscopy also shows the presence of multiple electronic transitions, accessible within a narrow energy range, to be a common feature of many coloured pigments, which electronic-structure calculations attribute to shallow band edges. We also demonstrate the successful application of the reflectance-analysis technique to painted areas on a selection of medieval illuminated manuscripts.

  20. Estimation of semiconductor-like pigment concentrations in paint mixtures and their differentiation from paint layers using first-derivative reflectance spectra.

    PubMed

    Pallipurath, Anuradha R; Skelton, Jonathan M; Ricciardi, Paola; Elliott, Stephen R

    2016-07-01

    Identification of the techniques employed by artists, e.g. mixing and layering of paints, if used together with information about their colour palette and style, can help to attribute works of art with more confidence. In this study, we show how the pigment composition in binary paint mixtures can be quantified using optical-reflectance spectroscopy, by analysis of the peak features corresponding to colour-transition edges in the first-derivative spectra. This technique is found to be more robust than a number of other spectral-analysis methods, which can suffer due to shifts in the transition edges in mixed paints compared to those observed in spectra of pure ones. Our method also provides a means of distinguishing paint mixtures from layering in some cases. The spectroscopy also shows the presence of multiple electronic transitions, accessible within a narrow energy range, to be a common feature of many coloured pigments, which electronic-structure calculations attribute to shallow band edges. We also demonstrate the successful application of the reflectance-analysis technique to painted areas on a selection of medieval illuminated manuscripts. PMID:27154649

  1. Microbial Activity in Active and Upper Permafrost Layers in Axel Heiberg Island

    NASA Astrophysics Data System (ADS)

    Vishnivetskaya, T. A.; Allan, J.; Cheng, K.; Chourey, K.; Hettich, R. L.; Layton, A.; Liu, X.; Murphy, J.; Mykytczuk, N. C.; Phelps, T. J.; Pfiffner, S. M.; Saarunya, G.; Stackhouse, B. T.; Whyte, L.; Onstott, T. C.

    2011-12-01

    Data on microbial communities and their metabolic activity in Arctic wetlands and underlying permafrost sediments is lacking. Samples were collected from different depths of a cryosol (D1, D2) and upper permafrost (D3) at the Axel Heiberg Island in July 2009. Upper cryosol has lower H2O but higher C and N content when compared to deeper horizons including upper permafrost layer. Deep cryosol and upper permafrost contained SO42- (155 and 132 ppm) and NO3- (0.12 and 0.10 ppm), respectively. The phylogenetic analyses of the environmental 16S rRNA genes showed the putative SRB were more abundant in permafrost (8%) than in cryosols, D1 (0.2%) and D2 (1.1%). Putative denitrifying bacteria varied along depth with near 0.1% in D1 and a significant increase in D2 (2.7%) and D3 (2.2%). Methanogens were not detected; methanotrophs were present at low levels in D3 (1%). Two sets of microcosms were set up. Firstly, anaerobic microcosms, amended with 10 mM glucose, sulfate or nitrate, were cultivated at varying temperatures (15o, 6o, and 0o C) for 10 months. Metabolic activity was monitored by measuring CO2 and CH4 every 3 months. A total of 89.5% of the D3-originated microcosms showed higher activity in comparison to cryosols in first 3 months. CH4 was not detected in these microcosms, whereas CO2 production was higher at 15o C or with glucose. Metaproteomics analyses of microcosms with higher levels of CO2 production indicated the presence of stress responsive proteins (e.g. DnaK, GroEL) and proteins essential for energy production and survival under carbon starvation (e.g. F0F1 ATP synthase, acyl-CoA dehydrogenase). These proteins have been previously shown to be up-regulated at low temperatures by permafrost bacteria. Metaproteomics data based on the draft sequences indicated the presence of proteins from the genera Bradyrhizobium, Sphingomonas, Lysinibacillus and Methylophilaceae and these bacteria were also detected by pyrosequencing. Secondly, a duplicate set of anaerobic

  2. Photocatalytic activity of layered perovskite-like oxides in practically valuable chemical reactions

    NASA Astrophysics Data System (ADS)

    Rodionov, I. A.; Zvereva, I. A.

    2016-03-01

    The photocatalytic properties of layered perovskite-like oxides corresponding to the Ruddlesen–Popper, Dion–Jacobson and Aurivillius phases are considered. Of the photocatalytic reactions, the focus is on the reactions of water splitting, hydrogen evolution from aqueous solutions of organic substances and degradation of model organic pollutants. Possibilities to conduct these reactions under UV and visible light in the presence of layered perovskite-like oxides and composite photocatalysts based on them are shown. The specific surface area, band gap energy, particle morphology, cation and anion doping and surface modification are considered as factors that affect the photocatalytic activity. Special attention is paid to the possibilities to enhance the photocatalytic activity by intercalation, ion exchange and exfoliation, which are inherent in this class of compounds. Conclusions are made about the prospects for the use of layered perovskite-like oxides in photocatalysis. The bibliography includes 253 references.

  3. Photocatalytic activity of layered perovskite-like oxides in practically valuable chemical reactions

    NASA Astrophysics Data System (ADS)

    Rodionov, I. A.; Zvereva, I. A.

    2016-03-01

    The photocatalytic properties of layered perovskite-like oxides corresponding to the Ruddlesen-Popper, Dion-Jacobson and Aurivillius phases are considered. Of the photocatalytic reactions, the focus is on the reactions of water splitting, hydrogen evolution from aqueous solutions of organic substances and degradation of model organic pollutants. Possibilities to conduct these reactions under UV and visible light in the presence of layered perovskite-like oxides and composite photocatalysts based on them are shown. The specific surface area, band gap energy, particle morphology, cation and anion doping and surface modification are considered as factors that affect the photocatalytic activity. Special attention is paid to the possibilities to enhance the photocatalytic activity by intercalation, ion exchange and exfoliation, which are inherent in this class of compounds. Conclusions are made about the prospects for the use of layered perovskite-like oxides in photocatalysis. The bibliography includes 253 references.

  4. Activity induces traveling waves, vortices and spatiotemporal chaos in a model actomyosin layer

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Rajesh; Jülicher, Frank

    2016-02-01

    Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics.

  5. Activity induces traveling waves, vortices and spatiotemporal chaos in a model actomyosin layer

    PubMed Central

    Ramaswamy, Rajesh; Jülicher, Frank

    2016-01-01

    Inspired by the actomyosin cortex in biological cells, we investigate the spatiotemporal dynamics of a model describing a contractile active polar fluid sandwiched between two external media. The external media impose frictional forces at the interface with the active fluid. The fluid is driven by a spatially-homogeneous activity measuring the strength of the active stress that is generated by processes consuming a chemical fuel. We observe that as the activity is increased over two orders of magnitude the active polar fluid first shows spontaneous flow transition followed by transition to oscillatory dynamics with traveling waves and traveling vortices in the flow field. In the flow-tumbling regime, the active polar fluid also shows transition to spatiotemporal chaos at sufficiently large activities. These results demonstrate that level of activity alone can be used to tune the operating point of actomyosin layers with qualitatively different spatiotemporal dynamics. PMID:26877263

  6. Electrical properties of GaAs metal–oxide–semiconductor structure comprising Al{sub 2}O{sub 3} gate oxide and AlN passivation layer fabricated in situ using a metal–organic vapor deposition/atomic layer deposition hybrid system

    SciTech Connect

    Aoki, Takeshi Fukuhara, Noboru; Osada, Takenori; Sazawa, Hiroyuki; Hata, Masahiko; Inoue, Takayuki

    2015-08-15

    This paper presents a compressive study on the fabrication and optimization of GaAs metal–oxide–semiconductor (MOS) structures comprising a Al{sub 2}O{sub 3} gate oxide, deposited via atomic layer deposition (ALD), with an AlN interfacial passivation layer prepared in situ via metal–organic chemical vapor deposition (MOCVD). The established protocol afforded self-limiting growth of Al{sub 2}O{sub 3} in the atmospheric MOCVD reactor. Consequently, this enabled successive growth of MOCVD-formed AlN and ALD-formed Al{sub 2}O{sub 3} layers on the GaAs substrate. The effects of AlN thickness, post-deposition anneal (PDA) conditions, and crystal orientation of the GaAs substrate on the electrical properties of the resulting MOS capacitors were investigated. Thin AlN passivation layers afforded incorporation of optimum amounts of nitrogen, leading to good capacitance–voltage (C–V) characteristics with reduced frequency dispersion. In contrast, excessively thick AlN passivation layers degraded the interface, thereby increasing the interfacial density of states (D{sub it}) near the midgap and reducing the conduction band offset. To further improve the interface with the thin AlN passivation layers, the PDA conditions were optimized. Using wet nitrogen at 600 °C was effective to reduce D{sub it} to below 2 × 10{sup 12} cm{sup −2} eV{sup −1}. Using a (111)A substrate was also effective in reducing the frequency dispersion of accumulation capacitance, thus suggesting the suppression of traps in GaAs located near the dielectric/GaAs interface. The current findings suggest that using an atmosphere ALD process with in situ AlN passivation using the current MOCVD system could be an efficient solution to improving GaAs MOS interfaces.

  7. Reliability Assessment and Activation Energy Study of Au and Pd-Coated Cu Wires Post High Temperature Aging in Nanoscale Semiconductor Packaging.

    PubMed

    Gan, C L; Hashim, U

    2013-06-01

    Wearout reliability and high temperature storage life (HTSL) activation energy of Au and Pd-coated Cu (PdCu) ball bonds are useful technical information for Cu wire deployment in nanoscale semiconductor device packaging. This paper discusses the influence of wire type on the wearout reliability performance of Au and PdCu wire used in fine pitch BGA package after HTSL stress at various aging temperatures. Failure analysis has been conducted to identify the failure mechanism after HTSL wearout conditions for Au and PdCu ball bonds. Apparent activation energies (Eaa) of both wire types are investigated after HTSL test at 150 °C, 175 °C and 200 °C aging temperatures. Arrhenius plot has been plotted for each ball bond types and the calculated Eaa of PdCu ball bond is 0.85 eV and 1.10 eV for Au ball bond in 110 nm semiconductor device. Obviously Au ball bond is identified with faster IMC formation rate with IMC Kirkendall voiding while PdCu wire exhibits equivalent wearout and or better wearout reliability margin compare to conventional Au wirebond. Lognormal plots have been established and its mean to failure (t50) have been discussed in this paper.

  8. [Effects of human engineering activities on permafrost active layer and its environment in northern Qinghai-Tibetan plateau].

    PubMed

    Guo, Zhenggang; Wu, Qingbo; Niu, Fujun

    2006-11-01

    With disturbed and undisturbed belts during the construction of Qinghai-Tibet highway as test objectives, this paper studied the effects of human engineering activities on the permafrost ecosystem in northern Qinghai-Tibetan plateau. The results showed that the thickness of permafrost active layer was smaller in disturbed than in undisturbed belt, and decreased with increasing altitude in undisturbed belt while no definite pattern was observed in disturbed belt. Different vegetation types had different effects on the thickness of permafrost active layer, being decreased in the order of steppe > shrub > meadow. In the two belts, altitude was the main factor affecting the vertical distribution of soil moisture, but vegetation type was also an important affecting factor if the altitude was similar. Due to the human engineering activities, soil temperature in summer was lower in disturbed than in undisturbed belt.

  9. Effect of atomic layer deposition growth temperature on the interfacial characteristics of HfO{sub 2}/p-GaAs metal-oxide-semiconductor capacitors

    SciTech Connect

    Liu, C.; Zhang, Y. M.; Zhang, Y. M.; Lv, H. L.

    2014-12-14

    The effect of atomic layer deposition (ALD) growth temperature on the interfacial characteristics of p-GaAs MOS capacitors with ALD HfO{sub 2} high-k dielectric using tetrakis(ethylmethyl)amino halfnium precursor is investigated in this study. Using the combination of capacitance-voltage (C-V) and X-ray photoelectron spectroscopy (XPS) measurements, ALD growth temperature is found to play a large role in controlling the reaction between interfacial oxides and precursor and ultimately determining the interface properties. The reduction of surface oxides is observed to be insignificant for ALD at 200 °C, while markedly pronounced for growth at 300 °C. The corresponding C-V characteristics are also shown to be ALD temperature dependent and match well with the XPS results. Thus, proper ALD process is crucial in optimizing the interface quality.

  10. Low interface defect density of atomic layer deposition BeO with self-cleaning reaction for InGaAs metal oxide semiconductor field effect transistors

    SciTech Connect

    Shin, H. S.; Yum, J. H.; Johnson, D. W.; Harris, H. R.; Hudnall, Todd W.; Oh, J.; Kirsch, P.; Wang, W.-E.; Bielawski, C. W.; Banerjee, S. K.; Lee, J. C.; Lee, H. D.

    2013-11-25

    In this paper, we discuss atomic configuration of atomic layer deposition (ALD) beryllium oxide (BeO) using the quantum chemistry to understand the theoretical origin. BeO has shorter bond length, higher reaction enthalpy, and larger bandgap energy compared with those of ALD aluminum oxide. It is shown that the excellent material properties of ALD BeO can reduce interface defect density due to the self-cleaning reaction and this contributes to the improvement of device performance of InGaAs MOSFETs. The low interface defect density and low leakage current of InGaAs MOSFET were demonstrated using X-ray photoelectron spectroscopy and the corresponding electrical results.

  11. Toward Efficient Thick Active PTB7 Photovoltaic Layers Using Diphenyl Ether as a Solvent Additive.

    PubMed

    Zheng, Yifan; Goh, Tenghooi; Fan, Pu; Shi, Wei; Yu, Junsheng; Taylor, André D

    2016-06-22

    The development of thick organic photovoltaics (OPV) could increase absorption in the active layer and ease manufacturing constraints in large-scale solar panel production. However, the efficiencies of most low-bandgap OPVs decrease substantially when the active layers exceed ∼100 nm in thickness (because of low crystallinity and a short exciton diffusion length). Herein, we report the use of solvent additive diphenyl ether (DPE) that facilitates the fabrication of thick (180 nm) active layers and triples the power conversion efficiency (PCE) of conventional thienothiophene-co-benzodithiophene polymer (PTB7)-based OPVs from 1.75 to 6.19%. These results demonstrate a PCE 20% higher than those of conventional (PTB7)-based OPV devices using 1,8-diiodooctane. Morphology studies reveal that DPE promotes the formation of nanofibrillar networks and ordered packing of PTB7 in the active layer that facilitate charge transport over longer distances. We further demonstrate that DPE improves the fill factor and photocurrent collection by enhancing the overall optical absorption, reducing the series resistance, and suppressing bimolecular recombination.

  12. Diversity of aerobic methanotrophic bacteria in a permafrost active layer soil of the Lena Delta, Siberia.

    PubMed

    Liebner, Susanne; Rublack, Katja; Stuehrmann, Torben; Wagner, Dirk

    2009-01-01

    With this study, we present first data on the diversity of aerobic methanotrophic bacteria (MOB) in an Arctic permafrost active layer soil of the Lena Delta, Siberia. Applying denaturing gradient gel electrophoresis and cloning of 16S ribosomal ribonucleic acid (rRNA) and pmoA gene fragments of active layer samples, we found a general restriction of the methanotrophic diversity to sequences closely related to the genera Methylobacter and Methylosarcina, both type I MOB. In contrast, we revealed a distinct species-level diversity. Based on phylogenetic analysis of the 16S rRNA gene, two new clusters of MOB specific for the permafrost active layer soil of this study were found. In total, 8 out of 13 operational taxonomic units detected belong to these clusters. Members of these clusters were closely related to Methylobacter psychrophilus and Methylobacter tundripaludum, both isolated from Arctic environments. A dominance of MOB closely related to M. psychrophilus and M. tundripaludum was confirmed by an additional pmoA gene analysis. We used diversity indices such as the Shannon diversity index or the Chao1 richness estimator in order to compare the MOB community near the surface and near the permafrost table. We determined a similar diversity of the MOB community in both depths and suggest that it is not influenced by the extreme physical and geochemical gradients in the active layer. PMID:18592300

  13. Active Layer and Moisture Measurements for Intensive Site 0 and 1, Barrow, Alaska

    DOE Data Explorer

    John Peterson

    2015-04-17

    These are measurements of Active Layer Thickness collected along several lines beginning in September, 2011 to the present. The data were collected at several time periods along the Site0 L2 Line, the Site1 AB Line, and an ERT Monitoring Line near Area A in Site1.

  14. Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients

    EPA Science Inventory

    Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

  15. Groundwater hydrochemistry in the active layer of the proglacial zone, Finsterwalderbreen, Svalbard

    USGS Publications Warehouse

    Cooper, R.J.; Wadham, J.L.; Tranter, M.; Hodgkins, R.; Peters, N.E.

    2002-01-01

    Glacial bulk meltwaters and active-layer groundwaters were sampled from the proglacial zone of Finsterwalderbreen during a single melt season in 1999, in order to determine the geochemical processes that maintain high chemical weathering rates in the proglacial zone of this glacier. Results demonstrate that the principle means of solute acquisition is the weathering of highly reactive moraine and fluvial active-layer sediments by supra-permafrost groundwaters. Active-layer groundwater derives from the thaw of the proglacial snowpack, buried ice and glacial bulk meltwaters. Groundwater evolves by sulphide oxidation and carbonate dissolution. Evaporation- and freeze-concentration of groundwater in summer and winter, respectively produce Mg-Ca-sulphate salts on the proglacial surface. Re-dissolution of these salts in early summer produces groundwaters that are supersaturated with respect to calcite. There is a pronounced spatial pattern to the geochemical evolution of groundwater. Close to the main proglacial channel, active layer sediments are flushed diurnally by bulk meltwaters. Here, Mg-Ca-sulphate deposits become exhausted in the early season and geochemical evolution proceeds by a combination of sulphide oxidation and carbonate dissolution. At greater distances from the channel, the dissolution of Mg-Ca-sulphate salts is a major influence and dilution by the bulk meltwaters is relatively minor. The influence of sulphate salt dissolution decreases during the sampling season, as these salts are exhausted and waters become increasingly routed by subsurface flowpaths. ?? 2002 Elsevier Science B.V. All rights reserved.

  16. Toward Efficient Thick Active PTB7 Photovoltaic Layers Using Diphenyl Ether as a Solvent Additive.

    PubMed

    Zheng, Yifan; Goh, Tenghooi; Fan, Pu; Shi, Wei; Yu, Junsheng; Taylor, André D

    2016-06-22

    The development of thick organic photovoltaics (OPV) could increase absorption in the active layer and ease manufacturing constraints in large-scale solar panel production. However, the efficiencies of most low-bandgap OPVs decrease substantially when the active layers exceed ∼100 nm in thickness (because of low crystallinity and a short exciton diffusion length). Herein, we report the use of solvent additive diphenyl ether (DPE) that facilitates the fabrication of thick (180 nm) active layers and triples the power conversion efficiency (PCE) of conventional thienothiophene-co-benzodithiophene polymer (PTB7)-based OPVs from 1.75 to 6.19%. These results demonstrate a PCE 20% higher than those of conventional (PTB7)-based OPV devices using 1,8-diiodooctane. Morphology studies reveal that DPE promotes the formation of nanofibrillar networks and ordered packing of PTB7 in the active layer that facilitate charge transport over longer distances. We further demonstrate that DPE improves the fill factor and photocurrent collection by enhancing the overall optical absorption, reducing the series resistance, and suppressing bimolecular recombination. PMID:27253271

  17. Investigation of semiconductor clad optical waveguides

    NASA Technical Reports Server (NTRS)

    Batchman, T. E.; Carson, R. F.

    1985-01-01

    A variety of techniques have been proposed for fabricating integrated optical devices using semiconductors, lithium niobate, and glasses as waveguides and substrates. The use of glass waveguides and their interaction with thin semiconductor cladding layers was studied. Though the interactions of these multilayer waveguide structures have been analyzed here using glass, they may be applicable to other types of materials as well. The primary reason for using glass is that it provides a simple, inexpensive way to construct waveguides and devices.

  18. Radiation hardening of metal-oxide semi-conductor (MOS) devices by boron

    NASA Technical Reports Server (NTRS)

    Danchenko, V.

    1974-01-01

    Technique using boron effectively protects metal-oxide semiconductor devices from ionizing radiation without using shielding materials. Boron is introduced into insulating gate oxide layer at semiconductor-insulator interface.

  19. Activation of ethylenediaminetetraacetic acid by a 940 nm diode laser for enhanced removal of smear layer.

    PubMed

    Lagemann, Manfred; George, Roy; Chai, Lei; Walsh, Laurence J

    2014-08-01

    Laser enhancement of ethylenediaminetetraacetic acid with cetrimide (EDTAC) has previously been shown to increase removal of smear layer, for middle-infrared erbium lasers. This study evaluated the efficiency of EDTAC activation using a near-infrared-pulsed 940 nm laser delivered by plain fibre tips into 15% EDTAC or 3% hydrogen peroxide. Root canals in 4 groups of 10 single roots were prepared using rotary files, with controls for the presence and absence of smear layer. After laser treatment (80 mJ pulse(-1) , 50 Hz, 6 cycles of 10 s), roots were split and the apical, middle and coronal thirds of the canal were examined using scanning electron microscopy, with the area of dentine tubules determined by a validated quantitative image analysis method. Lasing EDTAC considerably improved smear layer removal, while lasing into peroxide gave minimal smear layer removal. The laser protocol used was more effective for smear layer removal than the 'gold standard' protocol using EDTAC with sodium hypochlorite (NaOCl). In addition, lasers may also provide a benefit through photothermal disinfection. Further research is needed to optimise irrigant activation protocols using near-infrared diode lasers of other wavelengths.

  20. A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes

    PubMed Central

    He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

    2016-01-01

    Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them. PMID:27561546

  1. A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes

    NASA Astrophysics Data System (ADS)

    He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

    2016-08-01

    Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them.

  2. A Novel Surface Structure Consisting of Contact-active Antibacterial Upper-layer and Antifouling Sub-layer Derived from Gemini Quaternary Ammonium Salt Polyurethanes.

    PubMed

    He, Wei; Zhang, Yi; Li, Jiehua; Gao, Yunlong; Luo, Feng; Tan, Hong; Wang, Kunjie; Fu, Qiang

    2016-01-01

    Contact-active antibacterial surfaces play a vital role in preventing bacterial contamination of artificial surfaces. In the past, numerous researches have been focused on antibacterial surfaces comprising of antifouling upper-layer and antibacterial sub-layer. In this work, we demonstrate a reversed surface structure which integrate antibacterial upper-layer and antifouling sub-layer. These surfaces are prepared by simply casting gemini quaternary ammonium salt waterborne polyurethanes (GWPU) and their blends. Due to the high interfacial energy of gemini quaternary ammonium salt (GQAS), chain segments containing GQAS can accumulate at polymer/air interface to form an antibacterial upper-layer spontaneously during the film formation. Meanwhile, the soft segments composed of polyethylene glycol (PEG) formed the antifouling sub-layer. Our findings indicate that the combination of antibacterial upper-layer and antifouling sub-layer endow these surfaces strong, long-lasting antifouling and contact-active antibacterial properties, with a more than 99.99% killing efficiency against both gram-positive and gram-negative bacteria attached to them. PMID:27561546

  3. Stable surface passivation process for compound semiconductors

    DOEpatents

    Ashby, Carol I. H.

    2001-01-01

    A passivation process for a previously sulfided, selenided or tellurated III-V compound semiconductor surface. The concentration of undesired mid-gap surface states on a compound semiconductor surface is reduced by the formation of a near-monolayer of metal-(sulfur and/or selenium and/or tellurium)-semiconductor that is effective for long term passivation of the underlying semiconductor surface. Starting with the III-V compound semiconductor surface, any oxidation present thereon is substantially removed and the surface is then treated with sulfur, selenium or tellurium to form a near-monolayer of chalcogen-semiconductor of the surface in an oxygen-free atmosphere. This chalcogenated surface is then contacted with a solution of a metal that will form a low solubility chalcogenide to form a near-monolayer of metal-chalcogen-semiconductor. The resulting passivating layer provides long term protection for the underlying surface at or above the level achieved by a freshly chalcogenated compound semiconductor surface in an oxygen free atmosphere.

  4. Nitride passivation reduces interfacial traps in atomic-layer-deposited Al{sub 2}O{sub 3}/GaAs (001) metal-oxide-semiconductor capacitors using atmospheric metal-organic chemical vapor deposition

    SciTech Connect

    Aoki, T. Fukuhara, N.; Osada, T.; Sazawa, H.; Hata, M.; Inoue, T.

    2014-07-21

    Using an atmospheric metal-organic chemical vapor deposition system, we passivated GaAs with AlN prior to atomic layer deposition of Al{sub 2}O{sub 3}. This AlN passivation incorporated nitrogen at the Al{sub 2}O{sub 3}/GaAs interface, improving the capacitance-voltage (C–V) characteristics of the resultant metal-oxide-semiconductor capacitors (MOSCAPs). The C–V curves of these devices showed a remarkable reduction in the frequency dispersion of the accumulation capacitance. Using the conductance method at various temperatures, we extracted the interfacial density of states (D{sub it}). The D{sub it} was reduced over the entire GaAs band gap. In particular, these devices exhibited D{sub it} around the midgap of less than 4 × 10{sup 12} cm{sup −2}eV{sup −1}, showing that AlN passivation effectively reduced interfacial traps in the MOS structure.

  5. O{sub 3}-sourced atomic layer deposition of high quality Al{sub 2}O{sub 3} gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors

    SciTech Connect

    Huang, Sen; Liu, Xinyu Wei, Ke; Liu, Guoguo; Wang, Xinhua; Sun, Bing; Yang, Xuelin; Shen, Bo; Liu, Cheng; Liu, Shenghou; Hua, Mengyuan; Yang, Shu; Chen, Kevin J.

    2015-01-19

    High quality Al{sub 2}O{sub 3} film grown by atomic layer deposition (ALD), with ozone (O{sub 3}) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al–O–H and Al–Al bonds in ALD-Al{sub 2}O{sub 3} has been realized by substituting conventional H{sub 2}O source with O{sub 3}. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O{sub 3}-Al{sub 2}O{sub 3} and 2-nm H{sub 2}O-Al{sub 2}O{sub 3} interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 × 10{sup 12 }cm{sup −2}, contributing to the realization of normally-off operation with a high threshold voltage of +1.6 V and a low specific ON-resistance R{sub ON,sp} of 0.49 mΩ cm{sup 2}.

  6. Method of transferring strained semiconductor structure

    DOEpatents

    Nastasi, Michael A.; Shao, Lin

    2009-12-29

    The transfer of strained semiconductor layers from one substrate to another substrate involves depositing a multilayer structure on a substrate having surface contaminants. An interface that includes the contaminants is formed in between the deposited layer and the substrate. Hydrogen atoms are introduced into the structure and allowed to diffuse to the interface. Afterward, the deposited multilayer structure is bonded to a second substrate and is separated away at the interface, which results in transferring a multilayer structure from one substrate to the other substrate. The multilayer structure includes at least one strained semiconductor layer and at least one strain-induced seed layer. The strain-induced seed layer can be optionally etched away after the layer transfer.

  7. Electrical and mechanical characterization of nanoscale-layered cellulose-based electro-active paper.

    PubMed

    Yun, Gyu-Young; Yun, Ki-Ju; Kim, Joo-Hyung; Kim, Jaehwan

    2011-01-01

    In order to understand the electro-mechanical behavior of piezoelectric electro active paper (EAPap), the converse and direct piezoelectric characterization of cellulose EAPap was studied and compared. A delay between the electrical field and the induced strain of EAPap was observed due to the inner nano-voids or the localized amorphous regions in layer-by-layered structure to capture or hold the electrical charges and remnant ions. The linear relation between electric field and induced strain is also observed. The electro-mechanical performance of EAPap is discussed in detail in this paper.

  8. Thermal regime of active layer at two lithologically contrasting sites on James Ross Island, Antarctic Peninsula.

    NASA Astrophysics Data System (ADS)

    Hrbáček, Filip; Nývlt, Daniel; Láska, Kamil

    2016-04-01

    Antarctic Peninsula region (AP) represents one of the most rapidly warming parts of our planet in the last 50 years. Despite increasing research activities along both western and eastern sides of AP in last decades, there is still a lot of gaps in our knowledge relating to permafrost, active layer and its thermal and physical properties. This study brings new results of active layer monitoring on James Ross Island, which is the largest island in northern AP. Its northern part, Ulu Peninsula, is the largest ice-free area (more than 200 km2) in the region. Due its large area, we focused this study on sites located in different lithologies, which would affect local thermal regime of active layer. Study site (1) at Abernethy Flats area (41 m a.s.l.) lies ~7 km from northern coast. Lithologically is formed by disintegrated Cretaceous calcareous sandstones and siltstones of the Santa Marta Formation. Study site (2) is located at the northern slopes of Berry Hill (56 m a.s.l.), about 0.4 km from northern coastline. Lithology is composed of muddy to intermediate diamictites, tuffaceous siltstones to fine grained sandstones of the Mendel Formation. Data of air temperature at 2 meters above ground and the active layer temperatures at 75 cm deep profiles were obtained from both sites in period 1 January 2012 to 31 December 2014. Small differences were found when comparing mean air temperatures and active temperatures at 5 and 75 cm depth in the period 2012-2014. While the mean air temperatures varied between -7.7 °C and -7.0 °C, the mean ground temperatures fluctuated between -6.6 °C and -6.1 °C at 5 cm and -6.9 °C and -6.0 °C at 75 cm at Abernethy Flats and Berry Hill slopes respectively. Even though ground temperature differences along the profiles weren't pronounced during thawing seasons, the maximum active layer thickness was significantly larger at Berry Hill slopes (80 to 82 cm) than at Abernethy Flats (52 to 64 cm). We assume this differences are affected by

  9. Work function tuning of plasma-enhanced atomic layer deposited WC{sub x}N{sub y} electrodes for metal/oxide/semiconductor devices

    SciTech Connect

    Zonensain, Oren; Fadida, Sivan; Eizenberg, Moshe; Fisher, Ilanit; Gao, Juwen; Chattopadhyay, Kaushik; Harm, Greg; Mountsier, Tom; Danek, Michal

    2015-02-23

    One of the main challenges facing the integration of metals as gate electrodes in advanced MOS devices is control over the Fermi level position at the metal/dielectric interface. In this study, we demonstrate the ability to tune the effective work function (EWF) of W-based electrodes by process modifications of the atomic layer deposited (ALD) films. Tungsten carbo-nitrides (WC{sub x}N{sub y}) films were deposited via plasma-enhanced and/or thermal ALD processes using organometallic precursors. The process modifications enabled us to control the stoichiometry of the WC{sub x}N{sub y} films. Deposition in hydrogen plasma (without nitrogen based reactant) resulted in a stoichiometry of WC{sub 0.4} with primarily W-C chemical bonding, as determined by x-ray photoelectron spectroscopy. These films yielded a relatively low EWF of 4.2 ± 0.1 eV. The introduction of nitrogen based reactant to the plasma or the thermal ALD deposition resulted in a stoichiometry of WC{sub 0.1}N{sub 0.6–0.8} with predominantly W-N chemical bonding. These films produced a high EWF of 4.7 ± 0.1 eV.

  10. Semiconductor switch geometry with electric field shaping

    DOEpatents

    Booth, R.; Pocha, M.D.

    1994-08-23

    An optoelectric switch is disclosed that utilizes a cylindrically shaped and contoured GaAs medium or other optically active semiconductor medium to couple two cylindrically shaped metal conductors with flat and flared termination points each having an ovoid prominence centrally extending there from. Coupling the truncated ovoid prominence of each conductor with the cylindrically shaped optically active semiconductor causes the semiconductor to cylindrically taper to a triple junction circular line at the base of each prominence where the metal conductor conjoins with the semiconductor and a third medium such as epoxy or air. Tapering the semiconductor at the triple junction inhibits carrier formation and injection at the triple junction and thereby enables greater current carrying capacity through and greater sensitivity of the bulk area of the optically active medium. 10 figs.

  11. Semiconductor switch geometry with electric field shaping

    DOEpatents

    Booth, Rex; Pocha, Michael D.

    1994-01-01

    An optoelectric switch is disclosed that utilizes a cylindrically shaped and contoured GaAs medium or other optically active semiconductor medium to couple two cylindrically shaped metal conductors with flat and flared termination points each having an ovoid prominence centrally extending there from. Coupling the truncated ovoid prominence of each conductor with the cylindrically shaped optically active semiconductor causes the semiconductor to cylindrically taper to a triple junction circular line at the base of each prominence where the metal conductor conjoins with the semiconductor and a third medium such as epoxy or air. Tapering the semiconductor at the triple junction inhibits carrier formation and injection at the triple junction and thereby enables greater current carrying capacity through and greater sensitivity of the bulk area of the optically active medium.

  12. Active layer temperature in two Cryosols from King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, Roberto F. M.; Schaefer, Carlos Ernesto G. R.; Poelking, Everton L.; Simas, Felipe N. B.; Fernandes Filho, Elpidio I.; Bockheim, James G.

    2012-06-01

    This study presents soil temperature and moisture regimes from March 2008 to January 2009 for two active layer monitoring (CALM-S) sites at King George Island, Maritime Antarctica. The monitoring sites were installed during the summer of 2008 and consist of thermistors (accuracy of ± 0.2 °C), arranged vertically with probes at different depths and one soil moisture probe placed at the bottommost layer at each site (accuracy of ± 2.5%), recording data at hourly intervals in a high capacity datalogger. The active layer thermal regime in the studied period for both soils was typical of periglacial environments, with extreme variation in surface temperature during summer resulting in frequent freeze and thaw cycles. The great majority of the soil temperature readings during the eleven month period was close to 0 °C, resulting in low values of freezing and thawing degree days. Both soils have poor thermal apparent diffusivity but values were higher for the soil from Fildes Peninsula. The different moisture regimes for the studied soils were attributed to soil texture, with the coarser soil presenting much lower water content during all seasons. Differences in water and ice contents may explain the contrasting patterns of freezing of the studied soils, being two-sided for the coarser soil and one-sided for the loamy soil. The temperature profile of the studied soils during the eleven month period indicates that the active layer reached a maximum depth of approximately 92 cm at Potter and 89 cm at Fildes. Longer data sets are needed for more conclusive analysis on active layer behaviour in this part of Antarctica.

  13. Influences and interactions of inundation, peat, and snow on active layer thickness

    NASA Astrophysics Data System (ADS)

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-01

    Active layer thickness (ALT), the uppermost layer of soil that thaws on an annual basis, is a direct control on the amount of organic carbon potentially available for decomposition and release to the atmosphere as carbon-rich Arctic permafrost soils thaw in a warming climate. We investigate how key site characteristics affect ALT using an integrated surface/subsurface permafrost thermal hydrology model. ALT is most sensitive to organic layer thickness followed by snow depth but is relatively insensitive to the amount of water on the landscape with other conditions held fixed. The weak ALT sensitivity to subsurface saturation suggests that changes in Arctic landscape hydrology may only have a minor effect on future ALT. However, surface inundation amplifies the sensitivities to the other parameters and under large snowpacks can trigger the formation of near-surface taliks.

  14. Influences and interactions of inundation, peat, and snow on active layer thickness

    DOE PAGES

    Atchley, Adam L.; Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R.; Wilson, Cathy J.

    2016-05-18

    The effect of three environmental conditions: 1) thickness of organic soil, 2) snow depth, and 3) soil moisture content or water table height above and below the soil surface, on active layer thickness (ALT) are investigated using an ensemble of 1D thermal hydrology models. Sensitivity analyses of the ensemble exposed the isolated influence of each environmental condition on ALT and their multivariate interactions. The primary and interactive influences are illustrated in the form of color maps of ALT change. Results show that organic layer acts as a strong insulator, and its thickness is the dominant control of ALT, but themore » strength of the effect of organic layer thickness is dependent on the saturation state. Snow depth, subsurface saturation, and ponded water depth are strongly codependent and positively correlated to ALT.« less

  15. Realizing the full potential of Remotely Sensed Active Layer Thickness (ReSALT) Products

    NASA Astrophysics Data System (ADS)

    Schaefer, K. M.; Chen, A.; Liu, L.; Parsekian, A.; Jafarov, E. E.; Panda, S. K.; Zebker, H. A.

    2015-12-01

    The Remotely Sensed Active Layer Thickness (ReSALT) product uses the Interferometric Synthetic Aperture Radar (InSAR) technique to measure ground subsidence, active layer thickness (ALT), and thermokarst activity in permafrost regions. ReSALT supports research for the Arctic-Boreal Vulnerability Experiment (ABoVE) field campaign in Alaska and northwest Canada and is a precursor for a potential Nasa-Isro Synthetic Aperture Radar (NISAR) product. ALT is a critical parameter for monitoring the status of permafrost and thermokarst activity is one of the key drivers of change in permafrost regions. The ReSALT product currently includes 1) long-term subsidence trends resulting from the melting and subsequent drainage of excess ground ice in permafrost-affected soils, 2) seasonal subsidence resulting from the expansion of soil water into ice as the active layer freezes and thaws, and 3) ALT estimated from the seasonal subsidence assuming a vertical profile of water within the soil column. ReSALT includes uncertainties for all parameters and is validated against in situ measurements from the Circumpolar Active Layer Monitoring (CALM) network, Ground Penetrating Radar and mechanical probe measurements. We present high resolution ReSALT products on the North Slope of Alaska: Prudhoe Bay, Barrow, Toolik Lake, Happy Valley, and the Anaktuvuk fire zone. We believe that the ReSALT product could be expanded to include maps of individual thermokarst features identified as spatial anomalies in the subsidence trends, with quantified expansion rates. We illustrate the technique with multiple examples of thermokarst features on the North Slope of Alaska. Knowing the locations and expansion rates for individual features allows us to evaluate risks to human infrastructure. Our results highlight the untapped potential of the InSAR technique to remotely sense ALT and thermokarst dynamics over large areas of the Arctic.

  16. Piezo activated mode tracking system for widely tunable mode-hop-free external cavity mid-IR semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Wysocki, Gerard (Inventor); Tittel, Frank K. (Inventor); Curl, Robert F. (Inventor)

    2010-01-01

    A widely tunable, mode-hop-free semiconductor laser operating in the mid-IR comprises a QCL laser chip having an effective QCL cavity length, a diffraction grating defining a grating angle and an external cavity length with respect to said chip, and means for controlling the QCL cavity length, the external cavity length, and the grating angle. The laser of claim 1 wherein said chip may be tuned over a range of frequencies even in the absence of an anti-reflective coating. The diffraction grating is controllably pivotable and translatable relative to said chip and the effective QCL cavity length can be adjusted by varying the injection current to the chip. The laser can be used for high resolution spectroscopic applications and multi species trace-gas detection. Mode-hopping is avoided by controlling the effective QCL cavity length, the external cavity length, and the grating angle so as to replicate a virtual pivot point.

  17. Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microeletronic [corrected] devices.

    PubMed

    Bretos, Iñigo; Jiménez, Ricardo; Tomczyk, Monika; Rodríguez-Castellón, Enrique; Vilarinho, Paula M; Calzada, M Lourdes

    2016-01-01

    Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound--morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT)--are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm(-2) is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics.

  18. Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

    NASA Astrophysics Data System (ADS)

    Bretos, Iñigo; Jiménez, Ricardo; Tomczyk, Monika; Rodríguez-Castellón, Enrique; Vilarinho, Paula M.; Calzada, M. Lourdes

    2016-02-01

    Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound - morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) - are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm-2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics.

  19. Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microelecronic devices

    PubMed Central

    Bretos, Iñigo; Jiménez, Ricardo; Tomczyk, Monika; Rodríguez-Castellón, Enrique; Vilarinho, Paula M.; Calzada, M. Lourdes

    2016-01-01

    Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound ─ morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT) ─ are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm−2 is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics. PMID:26837240

  20. Active layers of high-performance lead zirconate titanate at temperatures compatible with silicon nano- and microeletronic [corrected] devices.

    PubMed

    Bretos, Iñigo; Jiménez, Ricardo; Tomczyk, Monika; Rodríguez-Castellón, Enrique; Vilarinho, Paula M; Calzada, M Lourdes

    2016-01-01

    Applications of ferroelectric materials in modern microelectronics will be greatly encouraged if the thermal incompatibility between inorganic ferroelectrics and semiconductor devices is overcome. Here, solution-processable layers of the most commercial ferroelectric compound--morphotrophic phase boundary lead zirconate titanate, namely Pb(Zr0.52Ti0.48)O3 (PZT)--are grown on silicon substrates at temperatures well below the standard CMOS process of semiconductor technology. The method, potentially transferable to a broader range of Zr:Ti ratios, is based on the addition of crystalline nanoseeds to photosensitive solutions of PZT resulting in perovskite crystallization from only 350 °C after the enhanced decomposition of metal precursors in the films by UV irradiation. A remanent polarization of 10.0 μC cm(-2) is obtained for these films that is in the order of the switching charge densities demanded for FeRAM devices. Also, a dielectric constant of ~90 is measured at zero voltage which exceeds that of current single-oxide candidates for capacitance applications. The multifunctionality of the films is additionally demonstrated by their pyroelectric and piezoelectric performance. The potential integration of PZT layers at such low fabrication temperatures may redefine the concept design of classical microelectronic devices, besides allowing inorganic ferroelectrics to enter the scene of the emerging large-area, flexible electronics. PMID:26837240

  1. Coupling with a narrow-band-gap semiconductor for the enhancement of visible-light photocatalytic activity: preparation of Bi2OxS3-x/Nb6O17 and application to the degradation of methyl orange.

    PubMed

    Yan, Gang; Shi, Hongfei; Tan, Huaqiao; Zhu, Wanbin; Wang, Yonghui; Zang, Hongying; Li, Yangguang

    2016-09-21

    A series of 2D sheet Bi2OxS3-x/Nb6O17 (Bi/Nb) heterostructure photocatalysts were synthesized through a facile hydrothermal vulcanization method between Bi(3+) exchanged K4Nb6O17 and thiourea (NH2CSNH2). XRD results confirm that the heterostructures were composed of Bi2OxS3-x and Nb6O17. HRTEM indicates that Bi2OxS3-x was successfully intercalated into layers of K4Nb6O17. Such large interfacial contacts can be beneficial to the transfer and separation of photogenerated charge carriers. Thus the composites exhibit good photocatalytic performance for the degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm), which is superior to that of both precursors, pure Bi2S3 and K4Nb6O17. Radical capture tests reveal that photogenerated holes h(+) and ˙O2(-) play important roles in the photodegradation of MO. And based on the UV-visible diffuse reflectance spectra (DRS) and the band gap of the semiconductors, the mechanism of the enhanced visible light photocatalytic activity of these composites has been proposed. PMID:27526958

  2. Coupling with a narrow-band-gap semiconductor for the enhancement of visible-light photocatalytic activity: preparation of Bi2OxS3-x/Nb6O17 and application to the degradation of methyl orange.

    PubMed

    Yan, Gang; Shi, Hongfei; Tan, Huaqiao; Zhu, Wanbin; Wang, Yonghui; Zang, Hongying; Li, Yangguang

    2016-09-21

    A series of 2D sheet Bi2OxS3-x/Nb6O17 (Bi/Nb) heterostructure photocatalysts were synthesized through a facile hydrothermal vulcanization method between Bi(3+) exchanged K4Nb6O17 and thiourea (NH2CSNH2). XRD results confirm that the heterostructures were composed of Bi2OxS3-x and Nb6O17. HRTEM indicates that Bi2OxS3-x was successfully intercalated into layers of K4Nb6O17. Such large interfacial contacts can be beneficial to the transfer and separation of photogenerated charge carriers. Thus the composites exhibit good photocatalytic performance for the degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm), which is superior to that of both precursors, pure Bi2S3 and K4Nb6O17. Radical capture tests reveal that photogenerated holes h(+) and ˙O2(-) play important roles in the photodegradation of MO. And based on the UV-visible diffuse reflectance spectra (DRS) and the band gap of the semiconductors, the mechanism of the enhanced visible light photocatalytic activity of these composites has been proposed.

  3. Air-coupled piezoelectric transducers with active polypropylene foam matching layers.

    PubMed

    Gómez Alvarez-Arenas, Tomás E

    2013-05-10

    This work presents the design, construction and characterization of air-coupled piezoelectric transducers using 1-3 connectivity piezocomposite disks with a stack of matching layers being the outer one an active quarter wavelength layer made of polypropylene foam ferroelectret film. This kind of material has shown a stable piezoelectric response together with a very low acoustic impedance (<0.1 MRayl). These features make them a suitable candidate for the dual use or function proposed here: impedance matching layer and active material for air-coupled transduction. The transducer centre frequency is determined by the l/4 resonance of the polypropylene foam ferroelectret film (0.35 MHz), then, the rest of the transducer components (piezocomposite disk and passive intermediate matching layers) are all tuned to this frequency. The transducer has been tested in several working modes including pulse-echo and pitch-catch as well as wide and narrow band excitation. The performance of the proposed novel transducer is compared with that of a conventional air-coupled transducers operating in a similar frequency range.

  4. Activation of Extrasynaptic NMDARs at Individual Parallel Fiber–Molecular Layer Interneuron Synapses in Cerebellum

    PubMed Central

    Nahir, Ben

    2013-01-01

    NMDA receptors (NMDARs) expressed by cerebellar molecular layer interneurons (MLIs) are not activated by single exocytotic events but can respond to glutamate spillover following coactivation of adjacent parallel fibers (PFs), indicating that NMDARs are perisynaptic. Several types of synaptic plasticity rely on these receptors but whether they are activated at isolated synapses is not known. Using a combination of electrophysiological and optical recording techniques in acute slices of rat cerebellum, along with modeling, we find that repetitive activation of single PF–MLI synapses can activate NMDARs in MLIs. High-frequency stimulation, multivesicular release (MVR), or asynchronous release can each activate NMDARs. Frequency facilitation was found at all PF–MLI synapses but, while some showed robust MVR with increased release probability, most were limited to univesicular release. Together, these results reveal a functional diversity of PF synapses, which use different mechanisms to activate NMDARs. PMID:24107963

  5. Influence of the Halogen Activation on the Ozone Layer in XXIst Century

    NASA Astrophysics Data System (ADS)

    Larin, Igor; Aloyan, Artash; Yermakov, Alexandr

    2016-04-01

    The aim of the work is to evaluate a possible effect of heterophase chemical reactions (HCR) with participation of reservoir gases (ClONO2, HCl) and sulfate particles of the Junge layer on the ozone layer at mid-latitudes in the XXI century, which could be relevant for more accurate predicting a recovery of the ozone layer, taking into account that just these processes were the main cause of the ozone depletion at the end of XXth century. Required for calculating the dynamics of GHR data on the specific volume/surface of the sulfate aerosols in the lower stratosphere were taken from the data of field experiments. Their physico-chemical properties (chemical composition, density, water activity and free protons activity et al.) have been obtained with help of thermodynamic calculations (Atmospheric Inorganic Model, AIM). Altitude concentration profiles of individual gas components, as well as temperature and relative humidity (RH) at a given geographic location and season have been calculated using a two-dimensional model SOCRATES. The calculations have been made for the conditions of June 1995, 2040 and 2080 at 15 km altitude and 50° N latitude. It has been shown that the rate of ozone depletion as a result of processes involving halogen activation for the given conditions in 2040, 2080 is about 35% lower than a corresponding value in 1995 (a year of maximum effect of halogen activation). From this we can conclude that in the XXI century, despite the natural decline of ozone-depleting chlorofluorocarbons. processes of halogen activation of the ozone depletion with participation of sulfate aerosols should be taken into account in the calculations of the recovery of the ozone layer at mid-latitudes.

  6. Activity retention after nisin entrapment in a polyethylene oxide brush layer.

    PubMed

    Auxier, Julie A; Schilke, Karl F; McGuire, Joseph

    2014-09-01

    The cationic, amphiphilic peptide nisin is an effective inhibitor of gram-positive bacteria whose mode of action does not encourage pathogenic resistance, and its proper incorporation into food packaging could enhance food stability, safety, and quality in a number of circumstances. Sufficiently small peptides have been shown to integrate into otherwise nonfouling polyethylene oxide (PEO) brush layers in accordance with their amphiphilicity and ordered structure, including nisin, and we have recently shown that nisin entrapment within a PEO layer does not compromise the nonfouling character of that layer. In this work we test the hypothesis that surface-bound, pendant PEO chains will inhibit displacement of entrapped nisin by competing proteins and, in this way, prolong retention of nisin activity at the interface. For this purpose, the antimicrobial activity of nisinloaded, PEO-coated surfaces was evaluated against the gram-positive indicator strain, Pediococcus pentosaceous. The retained antimicrobial activity of nisin layers was evaluated on uncoated and PEO-coated surfaces after incubation in the presence of bovine serum albumin for contact periods up to 1 week. Nisin-loaded, uncoated and PEO-coated samples were withdrawn at selected times and were incubated on plates inoculated with P. pentosaceous to quantify nisin activity by determination of kill zone radii. Our results indicate that nisin activity is retained at a higher level for a longer period of time after entrapment within PEO than after direct adsorption in the absence of PEO, owing to inhibition of nisin exchange with dissolved protein afforded by the pendant PEO chains.

  7. A brief history of ... semiconductors

    NASA Astrophysics Data System (ADS)

    Jenkins, Tudor

    2005-09-01

    The development of studies in semiconductor materials is traced from its beginnings with Michael Faraday in 1833 to the production of the first silicon transistor in 1954, which heralded the age of silicon electronics and microelectronics. Prior to the advent of band theory, work was patchy and driven by needs of technology. However, the arrival of this successful quantum theory of solids, together with a concentration on the growth of pure silicon and germanium and an understanding of their properties, saw an explosion in activity in semiconductor studies that has continued to this day.

  8. Dry etching method for compound semiconductors

    DOEpatents

    Shul, Randy J.; Constantine, Christopher

    1997-01-01

    A dry etching method. According to the present invention, a gaseous plasma comprising, at least in part, boron trichloride, methane, and hydrogen may be used for dry etching of a compound semiconductor material containing layers including aluminum, or indium, or both. Material layers of a compound semiconductor alloy such as AlGaInP or the like may be anisotropically etched for forming electronic devices including field-effect transistors and heterojunction bipolar transistors and for forming photonic devices including vertical-cavity surface-emitting lasers, edge-emitting lasers, and reflectance modulators.

  9. Dry etching method for compound semiconductors

    DOEpatents

    Shul, R.J.; Constantine, C.

    1997-04-29

    A dry etching method is disclosed. According to the present invention, a gaseous plasma comprising, at least in part, boron trichloride, methane, and hydrogen may be used for dry etching of a compound semiconductor material containing layers including aluminum, or indium, or both. Material layers of a compound semiconductor alloy such as AlGaInP or the like may be anisotropically etched for forming electronic devices including field-effect transistors and heterojunction bipolar transistors and for forming photonic devices including vertical-cavity surface-emitting lasers, edge-emitting lasers, and reflectance modulators. 1 fig.

  10. Deposition method for producing silicon carbide high-temperature semiconductors

    DOEpatents

    Hsu, George C.; Rohatgi, Naresh K.

    1987-01-01

    An improved deposition method for producing silicon carbide high-temperature semiconductor material comprising placing a semiconductor substrate composed of silicon carbide in a fluidized bed silicon carbide deposition reactor, fluidizing the bed particles by hydrogen gas in a mildly bubbling mode through a gas distributor and heating the substrate at temperatures around 1200.degree.-1500.degree. C. thereby depositing a layer of silicon carbide on the semiconductor substrate.

  11. Active layer hydrology for Imnavait Creek, Toolik, Alaska. Annual progress report, July 1984--January 1986

    SciTech Connect

    Kane, D.L.

    1986-12-31

    In the annual hydrologic cycle, snowmelt is the most significant event at Imnavait Creek located near Toolik Lake, Alaska. Precipitation that has accumulated for more than 6 months on the surface melts in a relatively short period of 7 to 10 days once sustained melting occurs. During the ablation period, runoff dominates the hydrologic cycle. Some meltwater goes to rewetting the organic soils in the active layer. The remainder is lost primarily because of evaporation, since transpiration is not a very active process at this time. Following the snowmelt period, evapotranspiration becomes the dominate process, with base flow contributing the other watershed losses. It is important to note that the water initally lost by evapotranspiration entered the organic layer during melt. This water from the snowpack ensures that each year the various plant communities will have sufficient water to start a new summer of growth.

  12. Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

    SciTech Connect

    Newman, Brent D.; Throckmorton, Heather M.; Graham, David E.; Gu, Baohua; Hubbard, Susan S.; Liang, Liyuan; Wu, Yuxin; Heikoop, J. M.; Herndon, Elizabeth M.; Phelps, Tommy J.; Wilson, Cathy; Wullschleger, Stan D.

    2015-03-24

    Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) for analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.

  13. Dual Gate Thin Film Transistors Based on Indium Oxide Active Layers

    SciTech Connect

    Kekuda, Dhananjaya; Rao, K. Mohan; Tolpadi, Amita; Chu, C. W.

    2011-07-15

    Polycrystalline Indium Oxide (In{sub 2}O{sub 3}) thin films were employed as an active channel layer for the fabrication of bottom and top gate thin film transistors. While conventional SiO{sub 2} served as a bottom gate dielectric, cross-linked poly-4-vinylphenol (PVP) was used a top gate dielectric. These nano-crystalline TFTs exhibited n-channel behavior with their transport behavior highly dependent on the thickness of the channel. The correlation between the thickness of the active layer and TFT parameters such as on/off ratio, field-effect mobility, threshold voltage were carried out. The optical spectra revealed a high transmittance in the entire visible region, thus making them promising candidates for the display technology.

  14. Microtopographic and depth controls on active layer chemistry in Arctic polygonal ground

    NASA Astrophysics Data System (ADS)

    Newman, B. D.; Throckmorton, H. M.; Graham, D. E.; Gu, B.; Hubbard, S. S.; Liang, L.; Wu, Y.; Heikoop, J. M.; Herndon, E. M.; Phelps, T. J.; Wilson, C. J.; Wullschleger, S. D.

    2015-03-01

    Polygonal ground is a signature characteristic of Arctic lowlands, and carbon release from permafrost thaw can alter feedbacks to Arctic ecosystems and climate. This study describes the first comprehensive spatial examination of active layer biogeochemistry that extends across high- and low-centered, ice wedge polygons, their features, and with depth. Water chemistry measurements of 54 analytes were made on surface and active layer pore waters collected near Barrow, Alaska, USA. Significant differences were observed between high- and low-centered polygons suggesting that polygon types may be useful for landscape-scale geochemical classification. However, differences were found for polygon features (centers and troughs) for analytes that were not significant for polygon type, suggesting that finer-scale features affect biogeochemistry differently from polygon types. Depth variations were also significant, demonstrating important multidimensional aspects of polygonal ground biogeochemistry. These results have major implications for understanding how polygonal ground ecosystems function, and how they may respond to future change.

  15. Influence of active layer and support layer surface structures on organic fouling propensity of thin-film composite forward osmosis membranes.

    PubMed

    Lu, Xinglin; Arias Chavez, Laura H; Romero-Vargas Castrillón, Santiago; Ma, Jun; Elimelech, Menachem

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes.

  16. Influence of active layer and support layer surface structures on organic fouling propensity of thin-film composite forward osmosis membranes.

    PubMed

    Lu, Xinglin; Arias Chavez, Laura H; Romero-Vargas Castrillón, Santiago; Ma, Jun; Elimelech, Menachem

    2015-02-01

    In this study, we investigate the influence of surface structure on the fouling propensity of thin-film composite (TFC) forward osmosis (FO) membranes. Specifically, we compare membranes fabricated through identical procedures except for the use of different solvents (dimethylformamide, DMF and N-methyl-2-pyrrolidinone, NMP) during phase separation. FO fouling experiments were carried out with a feed solution containing a model organic foulant. The TFC membranes fabricated using NMP (NMP-TFC) had significantly less flux decline (7.47 ± 0.15%) when compared to the membranes fabricated using DMF (DMF-TFC, 12.70 ± 2.62% flux decline). Water flux was also more easily recovered through physical cleaning for the NMP-TFC membrane. To determine the fundamental cause of these differences in fouling propensity, the active and support layers of the membranes were extensively characterized for physical and chemical characteristics relevant to fouling behavior. Polyamide surface roughness was found to dominate all other investigated factors in determining the fouling propensities of our membranes relative to each other. The high roughness polyamide surface of the DMF-TFC membrane was also rich in larger leaf-like structures, whereas the lower roughness NMP-TFC membrane polyamide layer contained more nodular and smaller features. The support layers of the two membrane types were also characterized for their morphological properties, and the relation between support layer surface structure and polyamide active layer formation was discussed. Taken together, our findings indicate that support layer structure has a significant impact on the fouling propensity of the active layer, and this impact should be considered in the design of support layer structures for TFC membranes. PMID:25564877

  17. Features of high-frequency measurements of the impedance of metal-insulator-semiconductor structures with an ultrathin oxide

    SciTech Connect

    Goldman, E. I.; Levashova, A. I.; Levashov, S. A.; Chucheva, G. V.

    2015-04-15

    The possibilities of using the data of high-frequency measurements of the impedance of metal-oxide-semiconductor structures with an ultrathin insulating layer for determining the parameters of the semiconductor and the tunneling characteristics of the insulator are considered. If the accuracy of the experiment makes it possible to record both the active and reactive impedance components, the thickness of the surface depletion layer, the resistance of the semiconductor base portion, the differential tunnel conductivity of the insulating layer, and the differential tunneling-stimulated current of the generation of electron-hole pairs are calculated using the values of the capacitance and conduction of the structure measured at two frequencies. In the case, where the values of the active component of the impedance is beyond the accuracy of measurements, analysis of the parameters is possible upon four-frequency organization of the experiment from the values of only the capacitances with an increased accuracy of their measurements. A test for the necessary accuracy of data of such an experiment is formulated. If the test fails, it is possible to determine only the capacitance of the surface depletion layer in the semiconductor and, in this case, it is sufficient to implement only the single-frequency experiment.

  18. Semiconductor technology program: Progress briefs

    NASA Technical Reports Server (NTRS)

    Galloway, K. F.; Scace, R. I.; Walters, E. J.

    1981-01-01

    Measurement technology for semiconductor materials, process control, and devices, is discussed. Silicon and silicon based devices are emphasized. Highlighted activities include semiinsulating GaAs characterization, an automatic scanning spectroscopic ellipsometer, linewidth measurement and coherence, bandgap narrowing effects in silicon, the evaluation of electrical linewidth uniformity, and arsenicomplanted profiles in silicon.

  19. Fabrication of optically reflecting ohmic contacts for semiconductor devices

    DOEpatents

    Sopori, B.L.

    1995-07-04

    A method is provided to produce a low-resistivity ohmic contact having high optical reflectivity on one side of a semiconductor device. The contact is formed by coating the semiconductor substrate with a thin metal film on the back reflecting side and then optically processing the wafer by illuminating it with electromagnetic radiation of a predetermined wavelength and energy level through the front side of the wafer for a predetermined period of time. This method produces a thin epitaxial alloy layer between the semiconductor substrate and the metal layer when a crystalline substrate is used. The alloy layer provides both a low-resistivity ohmic contact and high optical reflectance. 5 figs.

  20. Fabrication of optically reflecting ohmic contacts for semiconductor devices

    DOEpatents

    Sopori, Bhushan L.

    1995-01-01

    A method is provided to produce a low-resistivity ohmic contact having high optical reflectivity on one side of a semiconductor device. The contact is formed by coating the semiconductor substrate with a thin metal film on the back reflecting side and then optically processing the wafer by illuminating it with electromagnetic radiation of a predetermined wavelength and energy level through the front side of the wafer for a predetermined period of time. This method produces a thin epitaxial alloy layer between the semiconductor substrate and the metal layer when a crystalline substrate is used. The alloy layer provides both a low-resistivity ohmic contact and high optical reflectance.

  1. A Comparison of Active and Passive Methods for Control of Hypersonic Boundary Layers on Airbreathing Configurations

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Nowak, Robert J.

    2003-01-01

    Active and passive methods for control of hypersonic boundary layers have been experimentally examined in NASA Langley Research Center wind tunnels on a Hyper-X model. Several configurations for forcing transition using passive discrete roughness elements and active mass addition, or blowing, methods were compared in two hypersonic facilities, the 20-Inch Mach 6 Air and the 31-Inch Mach 10 Air tunnels. Heat transfer distributions, obtained via phosphor thermography, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. The comparisons between the active and passive methods for boundary layer control were conducted at test conditions that nearly match the nominal Mach 7 flight trajectory of an angle-of-attack of 2-deg and length Reynolds number of 5.6 million. For the passive roughness examination, the primary parametric variation was a range of trip heights within the calculated boundary layer thickness for several trip concepts. The prior passive roughness study resulted in a swept ramp configuration being selected for the Mach 7 flight vehicle that was scaled to be roughly 0.6 of the calculated boundary layer thickness. For the active jet blowing study, the blowing manifold pressure was systematically varied for each configuration, while monitoring the mass flow, to determine the jet penetration height with schlieren and transition movement with the phosphor system for comparison to the passive results. All the blowing concepts tested were adequate for providing transition onset near the trip location with manifold stagnation pressures on the order of 40 times the model static pressure or higher.

  2. Proximity charge sensing for semiconductor detectors

    SciTech Connect

    Luke, Paul N; Tindall, Craig S; Amman, Mark

    2013-10-08

    A non-contact charge sensor includes a semiconductor detector having a first surface and an opposing second surface. The detector includes a high resistivity electrode layer on the first surface and a low resistivity electrode on the high resistivity electrode layer. A portion of the low resistivity first surface electrode is deleted to expose the high resistivity electrode layer in a portion of the area. A low resistivity electrode layer is disposed on the second surface of the semiconductor detector. A voltage applied between the first surface low resistivity electrode and the second surface low resistivity electrode causes a free charge to drift toward the first or second surface according to a polarity of the free charge and the voltage. A charge sensitive preamplifier coupled to a non-contact electrode disposed at a distance from the exposed high resistivity electrode layer outputs a signal in response to movement of free charge within the detector.

  3. Acoustic radiation from the submerged circular cylindrical shell treated with active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Yuan, Li-Yun; Xiang, Yu; Lu, Jing; Jiang, Hong-Hua

    2015-12-01

    Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping (i.e., ACLD), combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic. Project supported by the National Natural Science Foundation of China (Grant Nos. 11162001, 11502056, and 51105083), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2012GXNSFAA053207), the Doctor Foundation of Guangxi

  4. Depletion effect of oxide semiconductor analyzed by Hall effects.

    PubMed

    Oh, Teresa

    2014-12-01

    This letter discusses the tunneling behavior of amorphous indium-gallium-zinc-oxide (a-IGZO) analyzed through the observation of its Hall effects. The properties of the a-IGZO changed from those of a majority carrier to those of a minority carrier after the annealing process as a result of the electron-hole recombination due to the thermal activation energy and the formation of a depletion layer with a high-potential Schottky barrier. Therefore, the diffusion current of these minority charge carriers caused ambipolar transfer characteristics, a tunneling behavior, in the metal-oxide semiconductor (MOS) transistor. PMID:25971008

  5. Self-assembly Columnar Structure in Active Layer of Bulk Heterojunction Solar Cell

    NASA Astrophysics Data System (ADS)

    Pan, Cheng; Segui, Jennifer; Yu, Yingjie; Li, Hongfei; Akgun, Bulent; Satijia, Sushil. K.; Gersappe, Dilip; Nam, Chang-Yong; Rafailovich, Miriam

    2012-02-01

    Bulk Heterojunction (BHJ) polymer solar cells are an area of intense interest due to their flexibility and relatively low cost. However, due to the disordered inner structure in active layer, the power conversion efficiency of BHJ solar cell is relatively low. Our research provides the method to produce ordered self-assembly columnar structure within active layer of bulk heterojunction (BHJ) solar cell by introducing polystyrene (PS) into the active layer. The blend thin film of polystyrene, poly (3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) at different ratio are spin coated on substrate and annealed in vacuum oven for certain time. Atomic force microscopy (AFM) images show uniform phase segregation on the surface of polymer blend thin film and highly ordered columnar structure is then proven by etching the film with ion sputtering. TEM cross-section technology is also used to investigate the column structure. Neutron reflectometry was taken to establish the confinement of PCBM at the interface of PS and P3HT. The different morphological structures formed via phase segregation will be correlated with the performance of the PEV cells to be fabricated at the BNL-CFN.

  6. Origin of photogenerated carrier recombination at the metal-active layer interface in polymer solar cells.

    PubMed

    Kumar, Mukesh; Dubey, Ashish; Reza, Khan Mamun; Adhikari, Nirmal; Qiao, Qiquan; Bommisetty, Venkat

    2015-11-01

    The role of the metal-active layer interface in photogenerated recombination has been investigated using nanoscale current sensing atomic force microscopy (CS-AFM) and intensity modulated photocurrent spectroscopy (IMPS) in as-deposited, pre-annealed and post-annealed bulk heterojunction (BHJ) solar cells. Aluminum (Al) confined post-annealed BHJ solar cells exhibited a significantly improved device efficiency compared to pre-annealed BHJ solar cells having similar photocarrier harvesting ability in the active layer. The nanoscale topography and CS-AFM results indicate a uniform PCBM rich phase at the metal-active layer interface in the post-annealed cells, but PCBM segregation in the pre-annealed cells. These two different annealing processes showed different carrier dynamics revealed using IMPS under various light intensities. The IMPS results suggest reduced photo generated carrier recombination in uniform PCBM rich post-annealed BHJ solar cells. This study reveals the importance of the metal-bend interface in BHJ solar cells in order to obtain efficient charge carrier extraction for high efficiency. PMID:26431263

  7. Architectural evolution of the Nojima fault and identification of the activated slip layer by Kobe earthquake

    NASA Astrophysics Data System (ADS)

    Tanaka, Hidemi; Omura, Kentaro; Matsuda, Tatsuo; Ikeda, Ryuji; Kobayashi, Kenta; Murakami, Masaki; Shimada, Koji

    2007-07-01

    Evolutionary history of Nojima Fault zone is clarified by comprehensive examinations of petrological, geophysical, and geochemical characterizations on a fault zone in deep-drilled core penetrating the Nojima Fault. On the basis of the results, we reconstruct a whole depth profile of the architecture of the Nojima Fault and identify the primal slip layer activated by 1995 Kobe earthquake. The deepest part (8- to 12-km depth) of the fault zone is composed of thin slip layers of pseudotachylite (5 to 10 mm thick each, 10 cm in total). Middle depth (4- to 8-km depth) of the fault zone is composed of fault core (6 to 10 m thick), surrounded by thick (100 m thick) damage zone, characterized by zeolite precipitation. The shallow part of the fault zone (1- to 4-km depth) is composed of distributed narrow shear zones, which are characterized by combination of thin (0.5 cm thick each, 10 cm in total) ultracataclasite layers at the core of shear zones, surrounded by thicker (1 to 3 m thick) damage zones associated with carbonate precipitation. An extremely thin ultracataclasite layer (7 mm thick), activated by the 1995 Kobe earthquake, is clearly identified from numerous past slip layers, overprinting one of the shear zones, as evidenced by conspicuous geological and geophysical anomalies. The Nojima Fault zone was 10 to 100 times thicker at middle depth than that of shallower and deeper depths. The thickening would be explained as a combination of physical and chemical effects as follows. (1) Thickening of "fault core" at middle depth would be attributed to normal stress dependence on thickness of the shear zone and (2) an extreme thickening of "damage zone" in middle depth of the crust would result from the weakening of the fault zone due to super hydrostatic fluid pressure at middle depths. The high fluid pressure would result from faster sealing with low-temperature carbonate at the shallower fault zone.

  8. Bioavailable Carbon and the Relative Degradation State of Organic Matter in Active Layer and Permafrost Soils

    NASA Astrophysics Data System (ADS)

    Jastrow, J. D.; Burke, V. J.; Vugteveen, T. W.; Fan, Z.; Hofmann, S. M.; Lederhouse, J. S.; Matamala, R.; Michaelson, G. J.; Mishra, U.; Ping, C. L.

    2015-12-01

    The decomposability of soil organic carbon (SOC) in permafrost regions is a key uncertainty in efforts to predict carbon release from thawing permafrost and its impacts. The cold and often wet environment is the dominant factor limiting decomposer activity, and soil organic matter is often preserved in a relatively undecomposed and uncomplexed state. Thus, the impacts of soil warming and permafrost thaw are likely to depend at least initially on the genesis and past history of organic matter degradation before its stabilization in permafrost. We compared the bioavailability and relative degradation state of SOC in active layer and permafrost soils from Arctic tundra in Alaska. To assess readily bioavailable SOC, we quantified salt (0.5 M K2SO4) extractable organic matter (SEOM), which correlates well with carbon mineralization rates in short-term soil incubations. To assess the relative degradation state of SOC, we used particle size fractionation to isolate fibric (coarse) from more degraded (fine) particulate organic matter (POM) and separated mineral-associated organic matter into silt- and clay-sized fractions. On average, bulk SOC concentrations in permafrost were lower than in comparable active layer horizons. Although SEOM represented a very small proportion of the bulk SOC, this proportion was greater in permafrost than in comparable active layer soils. A large proportion of bulk SOC was found in POM for all horizons. Even for mineral soils, about 40% of bulk SOC was in POM pools, indicating that organic matter in both active layer and permafrost mineral soils was relatively undecomposed compared to typical temperate soils. Not surprisingly, organic soils had a greater proportion of POM and mineral soils had greater silt- and clay-sized carbon pools, while cryoturbated soils were intermediate. For organic horizons, permafrost organic matter was generally more degraded than in comparable active layer horizons. However, in mineral and cryoturbated horizons

  9. Energy resolution in semiconductor gamma radiation detectors using heterojunctions and methods of use and preparation thereof

    DOEpatents

    Nikolic, Rebecca J.; Conway, Adam M.; Nelson, Art J.; Payne, Stephen A.

    2012-09-04

    In one embodiment, a system comprises a semiconductor gamma detector material and a hole blocking layer adjacent the gamma detector material, the hole blocking layer resisting passage of holes therethrough. In another embodiment, a system comprises a semiconductor gamma detector material, and an electron blocking layer adjacent the gamma detector material, the electron blocking layer resisting passage of electrons therethrough, wherein the electron blocking layer comprises undoped HgCdTe. In another embodiment, a method comprises forming a hole blocking layer adjacent a semiconductor gamma detector material, the hole blocking layer resisting passage of holes therethrough. Additional systems and methods are also presented.

  10. Microwave assisted synthesis and characterisation of a zinc oxide/tobacco mosaic virus hybrid material. An active hybrid semiconductor in a field-effect transistor device.

    PubMed

    Sanctis, Shawn; Hoffmann, Rudolf C; Eiben, Sabine; Schneider, Jörg J

    2015-01-01

    Tobacco mosaic virus (TMV) has been employed as a robust functional template for the fabrication of a TMV/zinc oxide field effect transistor (FET). A microwave based approach, under mild conditions was employed to synthesize stable zinc oxide (ZnO) nanoparticles, employing a molecular precursor. Insightful studies of the decomposition of the precursor were done using NMR spectroscopy and material characterization of the hybrid material derived from the decomposition was achieved using dynamic light scattering (DLS), transmission electron microscopy (TEM), grazing incidence X-ray diffractometry (GI-XRD) and atomic force microscopy (AFM). TEM and DLS data confirm the formation of crystalline ZnO nanoparticles tethered on top of the virus template. GI-XRD investigations exhibit an orientated nature of the deposited ZnO film along the c-axis. FET devices fabricated using the zinc oxide mineralized virus template material demonstrates an operational transistor performance which was achieved without any high-temperature post-processing steps. Moreover, a further improvement in FET performance was observed by adjusting an optimal layer thickness of the deposited ZnO on top of the TMV. Such a bio-inorganic nanocomposite semiconductor material accessible using a mild and straightforward microwave processing technique could open up new future avenues within the field of bio-electronics.

  11. PwrSoC (integration of micro-magnetic inductors/transformers with active semiconductors) for more than Moore technologies

    NASA Astrophysics Data System (ADS)

    Mathuna, Cian Ó.; Wang, Ningning; Kulkarni, Santosh; Roy, Saibal

    2013-07-01

    This paper introduces the concept of power supply on chip (PwrSoC) which will enable the development of next-generation, functionally integrated, power management platforms with applications in dc-dc conversion, gate drives, isolated power transmission and ultimately, high granularity, on-chip, power management for mixed-signal, SOC chips. PwrSoC will integrate power passives with the power management IC, in a 3D stacked or monolithic form factor, thereby delivering the performance of a highefficiency dc-dc converter within the footprint of a low-efficiency linear regulator. A central element of the PwrSoC concept is the fabrication of power micro-magnetics on silicon to deliver micro-inductors and micro-transformers. The paper details the magnetics on silicon process which combines thin film magnetic core technology with electroplated copper conductors. Measured data for micro-inductors show inductance operation up to 20 MHz, footprints down to 0.5 mm2, efficiencies up to 93% and dc current carrying capability up to 600 mA. Measurements on micro-transformers show voltage gain of approximately - 1 dB at between 10 MHz and 30 MHz. Contribution to the Topical Issue “International Semiconductor Conference Dresden-Grenoble - ISCDG 2012”, Edited by Gérard Ghibaudo, Francis Balestra and Simon Deleonibus.

  12. Material degradation of liquid organic semiconductors analyzed by nuclear magnetic resonance spectroscopy

    SciTech Connect

    Fukushima, Tatsuya; Yamamoto, Junichi; Fukuchi, Masashi; Kaji, Hironori; Hirata, Shuzo; Jung, Heo Hyo; Adachi, Chihaya; Hirata, Osamu; Shibano, Yuki

    2015-08-15

    Liquid organic light-emitting diodes (liquid OLEDs) are unique devices consisting only of liquid organic semiconductors in the active layer, and the device performances have been investigated recently. However, the device degradation, especially, the origin has been unknown. In this study, we show that material degradation occurs in liquid OLEDs, whose active layer is composed of carbazole with an ethylene glycol chain. Nuclear magnetic resonance (NMR) experiments clearly exhibit that the dimerization reaction of carbazole moiety occurs in the liquid OLEDs during driving the devices. In contrast, cleavages of the ethylene glycol chain are not detected within experimental error. The dimerization reaction is considered to be related to the device degradation.

  13. Real-time monitoring of enzyme activity in a mesoporous silicon double layer

    NASA Astrophysics Data System (ADS)

    Orosco, Manuel M.; Pacholski, Claudia; Sailor, Michael J.

    2009-04-01

    The activity of certain proteolytic enzymes is often an indicator of disease states such as cancer, stroke and neurodegeneracy, so there is a need for rapid assays that can characterize the kinetics and substrate specificity of enzymatic reactions. Nanostructured membranes can efficiently separate biomolecules, but coupling a sensitive detection method to such a membrane remains difficult. Here, we demonstrate a single mesoporous nanoreactor that can isolate and quantify in real time the reaction products of proteases. The reactor consists of two layers of porous films electrochemically prepared from crystalline silicon. The upper layer, with large pore sizes (~100 nm in diameter), traps the protease and acts as the reactor. The lower layer, with smaller pore sizes (~6 nm), excludes the proteases and other large proteins and captures the reaction products. Infiltration of the digested fragments into the lower layer produces a measurable change in optical reflectivity, and this allows label-free quantification of enzyme kinetics in real time within a volume of ~5 nl.

  14. On the two dimensional effective electron mass in quantum wells, inversion layers and NIPI superlattices of Kane type semiconductors in the presence of strong light waves: Simplified theory and relative comparison

    NASA Astrophysics Data System (ADS)

    Bhattacharya, S.; De, D.; Adhikari, S. M.; Ghatak, K. P.

    2012-02-01

    An attempt is made to study the two dimensional (2D) effective electron mass (EEM) in quantum wells (Qws), inversion layers (ILs) and NIPI superlattices of Kane type semiconductors in the presence of strong external photoexcitation on the basis of a newly formulated electron dispersion laws within the framework of k.p. formalism. It has been found, taking InAs and InSb as examples, that the EEM in Qws, ILs and superlattices increases with increasing concentration, light intensity and wavelength of the incident light waves, respectively and the numerical magnitudes in each case is band structure dependent. The EEM in ILs is quantum number dependent exhibiting quantum jumps for specified values of the surface electric field and in NIPI superlattices; the same is the function of Fermi energy and the subband index characterizing such 2D structures. The appearance of the humps of the respective curves is due to the redistribution of the electrons among the quantized energy levels when the quantum numbers corresponding to the highest occupied level changes from one fixed value to the others. Although the EEM varies in various manners with all the variables as evident from all the curves, the rates of variations totally depend on the specific dispersion relation of the particular 2D structure. Under certain limiting conditions, all the results as derived in this paper get transformed into well known formulas of the EEM and the electron statistics in the absence of external photo-excitation and thus confirming the compatibility test. The results of this paper find three applications in the field of microstructures.

  15. High-performance self-aligned inversion-channel In{sub 0.53}Ga{sub 0.47}As metal-oxide-semiconductor field-effect-transistors by in-situ atomic-layer-deposited HfO{sub 2}

    SciTech Connect

    Lin, T. D.; Chang, W. H.; Chang, Y. C.; Hong, M. E-mail: mhong@phys.ntu.edu.tw; Chu, R. L.; Chang, Y. H.; Lee, M. Y.; Hong, P. F.; Chen, Min-Cheng; Kwo, J. E-mail: mhong@phys.ntu.edu.tw

    2013-12-16

    Self-aligned inversion-channel In{sub 0.53}Ga{sub 0.47}As metal-oxide-semiconductor field-effect-transistors (MOSFETs) have been fabricated using the gate dielectrics of in-situ directly atomic-layer-deposited (ALD) HfO{sub 2} followed by ALD-Al{sub 2}O{sub 3}. There were no surface pretreatments and no interfacial passivation/barrier layers prior to the ALD. TiN/Al{sub 2}O{sub 3} (4 nm)/HfO{sub 2} (1 nm)/In{sub 0.53}Ga{sub 0.47}As/InP MOS capacitors exhibited well-behaved capacitance-voltage characteristics with true inversion behavior, low leakage current densities of ∼10{sup −8} A/cm{sup 2} at ±1 MV/cm, and thermodynamic stability at high temperatures. Al{sub 2}O{sub 3} (3 nm)/HfO{sub 2} (1 nm)/In{sub 0.53}Ga{sub 0.47}As MOSFETs of 1 μm gate length, with 700 °C–800 °C rapid thermal annealing in source/drain activation, have exhibited high extrinsic drain current (I{sub D}) of 1.5 mA/μm, transconductance (G{sub m}) of 0.84 mS/μm, I{sub ON}/I{sub OFF} of ∼10{sup 4}, low sub-threshold swing of 103 mV/decade, and field-effect electron mobility of 1100 cm{sup 2}/V · s. The devices have also achieved very high intrinsic I{sub D} and G{sub m} of 2 mA/μm and 1.2 mS/μm, respectively.

  16. Microbial activities at the benthic boundary layer in the Aegean Sea

    NASA Astrophysics Data System (ADS)

    Bianchi, A.; Tholosan, O.; Garcin, J.; Polychronaki, T.; Tselepides, A.; Buscail, R.; Duineveld, G.

    2003-05-01

    During the Aegean Sea component of the EU MTP-MATER project, benthic samples were acquired along a depth gradient from two continental margins in the Aegean Sea. Sampling was undertaken during spring and summer 1997 and the microbial metabolic activities measured (Vmax for aminopeptidase activity, 14C-glutamate respiration and assimilation) displayed seasonal variability even in deep-sea conditions. The metabolic rates encountered in the North Aegean (average depth 566±234 m), were approximately five-fold higher than in the deeper (1336±140 m) Southern part of the Aegean. The aminopeptidase rates, however, were the exception with higher values recorded in the more oligotrophic sediments of the Southern stations (1383±152 vs. 766±297 nmol MCA cm -2 h -1). A discrepancy in bacterial metabolism also appeared in the near bottom waters. In the Southern stations, 80% of the glutamate uptake was used for energy yielding processes and only 20% devoted to biomass production, while in the North Aegean, most of the used glutamate was incorporated into bacterial cells. During the early burial stages, bacterial mineralization rates estimated from 14C-glutamate respiration decreased drastically compared to the rates of biopolymer hydrolysis estimated by aminopeptidase assays. Thus, at the 2-cm depth layer, these rates were only 32 and up to 77% of the corresponding average values, respectively, in the superficial layer. Such a discrepancy between the evolution of these two metabolic activities is possibly due to the rapid removal of readily utilizable monomers in the surface deposits. The correlation between bacterial respiration and total organic carbon, or total organic nitrogen, is higher in the surficial sediment (0-2 and 2-4 cm) than in the underlying layer. Conversely, it is only at 4-cm depth layer that the hydrolysis rates appear correlated with organic carbon and nitrogen concentrations. This pattern confirms the drastic degradation of organic matter during the

  17. Active layer thermal regime at different vegetation covers at Lions Rump, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Almeida, Ivan C. C.; Schaefer, Carlos Ernesto G. R.; Fernandes, Raphael B. A.; Pereira, Thiago T. C.; Nieuwendam, Alexandre; Pereira, Antônio Batista

    2014-11-01

    Climate change impacts the biotic and abiotic components of polar ecosystems, affecting the stability of permafrost, active layer thickness, vegetation, and soil. This paper describes the active layer thermal regimes of two adjacent shallow boreholes, under the same soil but with two different vegetations. The study is location in Lions Rump, at King George Island, Maritime Antarctic, one of the most sensitive regions to climate change, located near the climatic limit of Antarctic permafrost. Both sites are a Turbic Cambic Cryosol formed on andesitic basalt, one under moss vegetation (Andreaea gainii, at 85 m a.s.l.) and another under lichen (Usnea sp., at 86 m a.s.l.), located 10 m apart. Ground temperature at same depths (10, 30 and 80 cm), water content at 80 cm depth and air temperature were recorded hourly between March 2009 and February 2011. The two sites showed significant differences in mean annual ground temperature for all depths. The lichen site showed a higher soil temperature amplitude compared to the moss site, with ground surface (10 cm) showing the highest daily temperature in January 2011 (7.3 °C) and the lowest daily temperature in August (- 16.5 °C). The soil temperature at the lichen site closely followed the air temperature trend. The moss site showed a higher water content at the bottommost layer, consistent with the water-saturated, low landscape position. The observed thermal buffering effect under mosses is primarily associated with higher moisture onsite, but a longer duration of the snowpack (not monitored) may also have influenced the results. Active layer thickness was approximately 150 cm at low-lying moss site, and 120 cm at well-drained lichen site. This allows to classify these soils as Cryosols (WRB) or Gelisols (Soil Taxonomy), with evident turbic features.

  18. Active but inoperable thrombin is accumulated in a plasma protein layer surrounding Streptococcus pyogenes.

    PubMed

    Naudin, Clément; Hurley, Sinead M; Malmström, Erik; Plug, Tom; Shannon, Oonagh; Meijers, Joost C M; Mörgelin, Matthias; Björck, Lars; Herwald, Heiko

    2015-10-01

    Activation of thrombin is a critical determinant in many physiological and pathological processes including haemostasis and inflammation. Under physiological conditions many of these functions are involved in wound healing or eradication of an invading pathogen. However, when activated systemically, thrombin can contribute to severe and life-threatening conditions by causing complications such as multiple multi-organ failure and disseminated intravascular coagulation. In the present study we investigated how the activity of thrombin is modulated when it is bound to the surface of Streptococcus pyogenes. Our data show that S. pyogenes bacteria become covered with a proteinaceous layer when incubated with human plasma, and that thrombin is a constituent of this layer. Though the coagulation factor is found attached to the bacteria with a functional active site, thrombin has lost its capacity to interact with its natural substrates and inhibitors. Thus, the interaction of bacteria with human plasma renders thrombin completely inoperable at the streptococcal surface. This could represent a host defense mechanism to avoid systemic activation of coagulation which could be otherwise induced when bacteria enter the circulation and cause systemic infection.

  19. Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Darányi, Mária; Csesznok, Tamás; Kukovecz, Ákos; Kónya, Zoltán; Kiricsi, Imre; Ajayan, Pulickel M.; Vajtai, Robert

    2011-05-01

    We report on the layer-by-layer (LbL) formation of TiO2-MWNT-TiO2 coatings on quartz with either trititanate derived TiO2 nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h - 1 range over a 2.5 × 2.5 cm2 film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO2 nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.

  20. Metal Insulator Semiconductor Structures on Gallium Arsenide.

    NASA Astrophysics Data System (ADS)

    Connor, Sean Denis

    Available from UMI in association with The British Library. The compound semiconductor gallium arsenide and its associated aluminium alloys have been the subject of intensive research in recent years. These materials offer the advantage of high electron mobilities coupled with the ability to be 'barrier engineered' leading to high injection efficiencies in bipolar devices. From a technological viewpoint however these materials are difficult to work with and device realisation is a major problem. Both thermal and anodic oxidation of these materials fail to produce a dielectric of sufficient quality for device applications and as a result devices tend to be complex non planar, mesa structures. A technique is proposed whereby the electrical interface is separated from the dielectric by means of a thin layer of AlGaAs, carrier confinement in the active GaAs region being maintained by the potential barriers to holes and electrons formed by the GaAs-AlGaAs junction. The integrity of these barriers is maintained by the provision of a suitable 'capping' dielectric. The electrical characteristics of various dielectric systems on GaAs have been investigated by means of current -voltage, capacitance-voltage and electronic breakdown measurements. Transport mechanisms for leakage current through these systems are identified and the interface properties (viz Fermi level pinning etc.) assessed by means of a direct comparison between experimental capacitance-voltage curves and theoretical data obtained from classical theory. As a technique for producing a convenient, in house 'capping' dielectric with good electrical and mechanical properties, the plasma anodisation of deposited aluminium films has been investigated. The anodisation parameters have been optimised for oxidation of these films in a microwave sustained oxygen plasma to give alumina films of around 500 A. A qualitative model for the anodisation process, involving linear and parabolic growth kinetics is proposed and

  1. 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.

  2. Study on Na layer response to geomagnetic activities based on Odin/OSIRIS Na density data

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo; Nakamura, Takuji; Hedin, Jonas; Gumbel, Jorg; Hosokawa, Keisuke; Ejiri, Mitsumu K.; Nishiyama, Takanori; Takahashi, Toru

    2016-07-01

    The Na layer is normally distributed from 80 to 110 km, and the height range is corresponding to the ionospheric D and E region. In the polar region, the energetic particles precipitating from the magnetosphere can often penetrate into the E region and even into the D region. Thus, the influence of the energetic particles to the Na layer is one of interests in the aspect of the atmospheric composition change accompanied with the auroral activity. There are several previous studies in this issue. For example, recently, we have reported an initial result on a clear relationship between the electron density increase (due to the energetic particles) and the Na density decrease from observational data sets obtained by Na lidar, EISCAT VHF radar, and optical instruments at Tromsoe, Norway on 24-25 January 2012. However, all of the previous studies had been carried out based on case studies by ground-based lidar observations. In this study, we have performed, for the first time, statistical analysis using Na density data from 2004 to 2009 obtained with the Optical Spectrograph and InfraRed Imager System (OSIRIS) onboard Odin satellite. In the presentation, we will show relationship between the Na density and geomagnetic activities, and its latitudinal variation. Based on these results, the Na layer response to the energetic particles will be discussed.

  3. Enhancing the performance of nanofiltration membranes by modifying the active layer with aramide dendrimers.

    PubMed

    de Jubera, Ana M Saenz; Gao, Yuan; Moore, Jeffrey S; Cahill, David G; Mariñas, Benito J

    2012-09-01

    The fully aromatic polyamide active layer of a commercial nanofiltration membrane was modified with three generations (G1, G2, and G3) of aramide dendrimers, all with oligoethylene glycol chains on their peripheries. Permeation experiments revealed that the rejection of Rhodamine WT, used as a surrogate for organic contaminants, improved 1-2 orders of magnitude for membranes modified with G2 and G3 dendrimers at loadings of 0.7-3.5 μg/cm(2) (dendrimer layer thicknesses of ~1-6 nm) compared to the performance of unmodified membranes. In contrast, the corresponding water permeability of dendrimer-modified membranes decreased by only ~30%. Although an enhancement in the rejection of H(3)AsO(3), NaCl, and BaCl(2) was also observed for dendritic membranes, the effect was less pronounced than that for rhodamine WT. Characterization of membranes modified with 3.5 μg/cm(2) dendrimers G2 and G3 by Rutherford backscattering spectrometry with the aid of heavy ion probes (Ag(+) and Ba(2+)) revealed that accessibility of the larger Ba(2+) probe to carboxylate groups on the active layer decreased for the membranes modified with dendrimers.

  4. Statistical analysis on Na layer response to geomagnetic activities using Odin/OSIRIS data

    NASA Astrophysics Data System (ADS)

    Tsuda, Takuo T.; Nakamura, Takuji; Ejiri, Mitsumu K.; Nishiyama, Takanori; Hosokawa, Keisuke; Takahashi, Toru; Gumbel, Jörg; Hedin, Jonas

    2016-04-01

    The Na layer is normally distributed from 80 to 110 km, and the height range is corresponding to the ionospheric D and E region. In the polar region, the energetic particles precipitating from the magnetosphere can often penetrate into the E region and even into the D region. Thus, the influence of the energetic particles to the Na layer is one of interests in the aspect of the atmospheric composition change accompanied with the auroral activity. There are several previous studies in this issue. For example, recently, we have reported an initial result on a clear relationship between the electron density increase (due to the energetic particles) and the Na density decrease from observational dataset obtained by Na lidar, EISCAT VHF radar, and optical instruments at Tromsoe, Norway on 24-25 January 2012. However, all of the previous studies had been carried out based on case studies by ground-based lidar observations. In this study, we have performed, for the first time, statistical analysis using Na density data from 2004 to 2009 obtained with the Optical Spectrograph and InfraRed Imager System (OSIRIS) onboard Odin satellite. In the presentation, we will show relationship between the Na density and geomagnetic activities, and its latitudinal variation. Based on these results, the Na layer response to the energetic particles will be discussed.

  5. Design method of the layered active magnetic regenerator (AMR) for hydrogen liquefaction by numerical simulation

    NASA Astrophysics Data System (ADS)

    Park, Inmyong; Kim, Youngkwon; Park, Jiho; Jeong, Sangkwon

    2015-09-01

    The design procedure of an active magnetic regenerator (AMR) operating between liquid nitrogen temperature and liquid hydrogen temperature is discussed with the selected magnetic refrigerants. Selected magnetic refrigerants (GdNi2, Dy0.85Er0.15Al2, Dy0.5Er0.5Al2, and Gd0.1Dy0.9Ni2) that have different transition temperatures are layered in an AMR to widen the temperature span. The optimum volume fraction of the layered refrigerants for the maximum COP with minimum volume is designed in a two-stage active magnetic regenerative refrigerator (AMRR) using one dimensional numerical simulation. The entropy generation in each stage of the AMR is calculated by the numerical simulation to optimize the proposed design. The main sources of the entropy generation in the AMR are pressure drop, convection and conduction heat transfers in the AMR. However, the entropy generation by the convective heat transfer is mostly dominant in the optimized cases. In this paper, the design parameters and the operating conditions such as the distribution of the selected refrigerants in the layered AMR, the intermediate temperature between two stages and the mass flow rate of heat transfer fluid are specifically determined to maximize the performance of the AMR. The proposed design method will facilitate the construction of AMR systems with various magnetic refrigerants and conditions such as AMR size, operating temperature range, and magnetic field variation.

  6. Low temperature production of large-grain polycrystalline semiconductors

    DOEpatents

    Naseem, Hameed A.; Albarghouti, Marwan

    2007-04-10

    An oxide or nitride layer is provided on an amorphous semiconductor layer prior to performing metal-induced crystallization of the semiconductor layer. The oxide or nitride layer facilitates conversion of the amorphous material into large grain polycrystalline material. Hence, a native silicon dioxide layer provided on hydrogenated amorphous silicon (a-Si:H), followed by deposited Al permits induced crystallization at temperatures far below the solid phase crystallization temperature of a-Si. Solar cells and thin film transistors can be prepared using this method.

  7. Layer V Perirhinal Cortical Ensemble Activity during Object Exploration: A Comparison between Young and Aged Rats

    PubMed Central

    Burke, S.N.; Hartzell, A.L.; Lister, J.P.; Hoang, L.T.; Barnes, C.A.

    2012-01-01

    Object recognition memory requires the perirhinal cortex (PRC) and this cognitive function declines during normal aging. Recent electrophysiological recordings from young rats have shown that neurons in layer V of the PRC are activated by 3-dimensional objects. Thus, it is possible that age-related object recognition deficits result from alterations in PRC neuron activity in older animals. To examine this, the present study used cellular compartment analysis of temporal activity by fluorescence in situ hybridization (catFISH) with confocal microscopy to monitor cellular distributions of activity-induced Arc RNA in layer V of the PRC. Activity was monitored during two distinct epochs of object exploration. In one group of rats (6 young/6 aged) animals were placed in a familiar testing arena and allowed to explore five different 3-dimensional objects for two 5-min sessions separated by a 20-min rest (AA). The second group of animals (6 young/6 aged) also explored the same objects for two 5-min sessions, but the environment was changed between the first and the second epoch (AB). Behavioral data showed that both age groups spent less time exploring objects during the second epoch, even when the environment changed, indicating successful recognition. Although the proportion of active neurons between epochs did not change in the AA group, in the AB group more neurons were active during epoch 2 of object exploration. This recruitment of neurons into the active neural ensemble could serve to signal that familiar stimuli are being encountered in a new context. When numbers of Arc positive neurons were compared between age groups, the old rats had significantly lower proportions of Arc-positive PRC neurons in both the AA and AB behavioral conditions. These data support the hypothesis that age-associated functional alterations in the PRC contribute to declines in stimulus recognition over the lifespan. PMID:22987683

  8. Layer V perirhinal cortical ensemble activity during object exploration: a comparison between young and aged rats.

    PubMed

    Burke, S N; Hartzell, A L; Lister, J P; Hoang, L T; Barnes, C A

    2012-10-01

    Object recognition memory requires the perirhinal cortex (PRC) and this cognitive function declines during normal aging. Recent electrophysiological recordings from young rats have shown that neurons in Layer V of the PRC are activated by three-dimensional objects. Thus, it is possible that age-related object recognition deficits result from alterations in PRC neuron activity in older animals. To examine this, the present study used cellular compartment analysis of temporal activity by fluorescence in situ hybridization (catFISH) with confocal microscopy to monitor cellular distributions of activity-induced Arc RNA in layer V of the PRC. Activity was monitored during two distinct epochs of object exploration. In one group of rats (6 young/6 aged) animals were placed in a familiar testing arena and allowed to explore five different three-dimensional objects for two 5-min sessions separated by a 20-min rest (AA). The second group of animals (6 young/6 aged) also explored the same objects for two 5-min sessions, but the environment was changed between the first and the second epoch (AB). Behavioral data showed that both age groups spent less time exploring objects during the second epoch, even when the environment changed, indicating successful recognition. Although the proportion of active neurons between epochs did not change in the AA group, in the AB group more neurons were active during epoch 2 of object exploration. This recruitment of neurons into the active neural ensemble could serve to signal that familiar stimuli are being encountered in a new context. When numbers of Arc positive neurons were compared between age groups, the old rats had significantly lower proportions of Arc-positive PRC neurons in both the AA and AB behavioral conditions. These data support the hypothesis that age-associated functional alterations in the PRC contribute to declines in stimulus recognition over the lifespan.

  9. Phonon-assisted stimulated emission and ultra-thin active layers in cleaved-cavity and vertical-cavity surface emitting lasers

    SciTech Connect

    Benjamin, S.D.

    1991-01-01

    Unique lasing processes in III-V semiconductor lasers are examined. The dynamics of stimulated photon emissions in thin AlGaAs/GaAs single quantum well lasers are observed experimentally and modeled by rate equations describing the electron and photon densities. Agreement between experiment and theory are achieved when the transition probability matrix, calculated with the spreading out of electron and hole wave functions taken into account, is used. The phonon assisted stimulated photon emission observed in this work is delayed with respect to the unassisted emission. This observation is modeled by using a weaker matrix element for the unassisted process which is expected from theory and thus supports the author' claim that this emission is phonon assisted. Rate equations developed to simulate doubly stimulated emission of photons and phonons do not describe the experimental data so the possibility of stimulated phonon emission is ruled out for the samples studied in this work. Vertical Cavity Surface Emitting Lasers are also studied since they can be designed to support unique lasing processes. The design and growth of vertical cavity surface emitting lasers are discussed and these concepts are applied to the realization of a vertical cavity surface emitting laser with the thinnest active layer of any laser yet reported. Stimulated emission supported across the sub-monolayer thick InAs single quantum well active region can be understood by considering the spreading of the electron and hole wavefunctions beyond the confines of the quantum well to increase the length of the effective gain region.

  10. Low-noise encoding of active touch by layer 4 in the somatosensory cortex.

    PubMed

    Hires, Samuel Andrew; Gutnisky, Diego A; Yu, Jianing; O'Connor, Daniel H; Svoboda, Karel

    2015-08-06

    Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.

  11. Phosphorus doping a semiconductor particle

    DOEpatents

    Stevens, G.D.; Reynolds, J.S.

    1999-07-20

    A method of phosphorus doping a semiconductor particle using ammonium phosphate is disclosed. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried with the phosphorus then being diffused into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement. 1 fig.

  12. Phosphorous doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don; Reynolds, Jeffrey Scott

    1999-07-20

    A method (10) of phosphorus doping a semiconductor particle using ammonium phosphate. A p-doped silicon sphere is mixed with a diluted solution of ammonium phosphate having a predetermined concentration. These spheres are dried (16, 18), with the phosphorus then being diffused (20) into the sphere to create either a shallow or deep p-n junction. A good PSG glass layer is formed on the surface of the sphere during the diffusion process. A subsequent segregation anneal process is utilized to strip metal impurities from near the p-n junction into the glass layer. A subsequent HF strip procedure is then utilized to removed the PSG layer. Ammonium phosphate is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirement.

  13. Atomic layer deposition encapsulated activated carbon electrodes for high voltage stable supercapacitors.

    PubMed

    Hong, Kijoo; Cho, Moonkyu; Kim, Sang Ouk

    2015-01-28

    Operating voltage enhancement is an effective route for high energy density supercapacitors. Unfortunately, widely used activated carbon electrode generally suffers from poor electrochemical stability over 2.5 V. Here we present atomic layer deposition (ALD) encapsulation of activated carbons for high voltage stable supercapacitors. Two-nanometer-thick Al2O3 dielectric layers are conformally coated at activated carbon surface by ALD, well-maintaining microporous morphology. Resultant electrodes exhibit excellent stability at 3 V operation with 39% energy density enhancement from 2.5 V operation. Because of the protection of surface functional groups and reduction of electrolyte degradation, 74% of initial voltage was maintained 50 h after full charge, and 88% of capacitance was retained after 5000 cycles at 70 °C accelerated test, which correspond to 31 and 17% improvements from bare activated carbon, respectively. This ALD-based surface modification offers a general method to enhance electrochemical stability of carbon materials for diverse energy and environmental applications.

  14. On Active Layer Environments and Processes in Western Dronning Maud Land, Antarctica

    NASA Astrophysics Data System (ADS)

    Hansen, C. D.; Meiklejohn, I.; Nel, W.

    2012-12-01

    The current understanding of Antarctic permafrost is poor, particularly regarding its evolution, the current thermal characteristics, and relationships with pedogenesis, hydrology, geomorphic, dynamics, biotic activity and response to global changes. Results from borehole temperature measurements over a four-year period in Western Dronning Maud Land suggest that the active layer depth is dependent on the substrate, latitude, altitude and the volume of ground exposed; the latter alludes to the potential impact of surrounding ice on the ground thermal regime. The active layer depths at the monitoring sites, varied between 16 cm at Vesleskarvet, a small nunatak at 850 masl to 28 cm in granitic till at Jutulsessen (1 270 masl). The mean near surface (1.5 cm depth) ground temperatures from 2009 to 2012 in the region have a narrow range from -16.4°C at 850m to -17.5°C at 1270 masl. Permafrost temperatures for the same locations vary between -16.3°C and -18.3°C. While little variability exists between the mean temperatures at the study locations, each site is distinct and seasonal and shorter-term frost cycles have produced landforms that are characteristic of both permafrost and diurnal frost environments. One of the key aspects of investigation is the control that the active layer has on autochthonous blockfield development in the region. The, thus far, exploratory research is being used to understand controls on the landscape and the relationship between distribution and abundance of biota. Given the rapidly changing climates in the region, improving knowledge of what drives patterns of biodiversity at a local and regional scale is vital to assess consequences of environmental change.

  15. Engineering optical properties of semiconductor metafilm superabsorbers

    NASA Astrophysics Data System (ADS)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2016-04-01

    Light absorption in ultrathin layer of semiconductor has been considerable interests for many years due to its potential applications in various optical devices. In particular, there have been great efforts to engineer the optical properties of the film for the control of absorption spectrums. Whereas the isotropic thin films have intrinsic optical properties that are fixed by materials' properties, metafilm that are composed by deep subwavelength nano-building blocks provides significant flexibilities in controlling the optical properties of the designed effective layers. Here, we present the ultrathin semiconductor metafilm absorbers by arranging germanium (Ge) nanobeams in deep subwavelength scale. Resonant properties of high index semiconductor nanobeams play a key role in designing effective optical properties of the film. We demonstrate this in theory and experimental measurements to build a designing rule of efficient, controllable metafilm absorbers. The proposed strategy of engineering optical properties could open up wide range of applications from ultrathin photodetection and solar energy harvesting to the diverse flexible optoelectronics.

  16. Active layer thermal monitoring at Fildes Peninsula, King George Island, Maritime Antarctica

    NASA Astrophysics Data System (ADS)

    Michel, Roberto; Schaefer, Carlos; Simas, Felipe; Pregesbauer, Michael; Bockheim, James

    2013-04-01

    International attention on the climate change phenomena has grown in the last decade, intense modelling of climate scenarios were carried out by scientific investigations searching the sources and trends of these changes. The cryosphere and its energy flux became the focus of many investigations, being recognised as a key element for the understanding of future trends. The active layer and permafrost are key components of the terrestrial cryosphere due to their role in energy flux regulation and high sensitivity to climate change (Kane et al., 2001; Smith and Brown, 2009). Compared with other regions of the globe, our understanding of Antarctic permafrost is poor, especially in relation to its thermal state and evolution, its physical properties, links to pedogenesis, hydrology, geomorphic dynamics and response to global change (Bockheim, 1995, Bockheim et al., 2008). The active layer monitoring site was installed in the summer of 2008, and consist of thermistors (accuracy ± 0.2 °C) arranged in a vertical array (Turbic Eutric Cryosol 600 m asl, 10.5 cm, 32.5 cm, 67.5 cm and 83.5 cm). King George Island experiences a cold moist maritime climate characterized by mean annual air temperatures of -2°C and mean summer air temperatures above 0°C for up to four months (Rakusa-Suszczewski et al., 1993, Wen et al., 1994). Ferron et al., (2004) found great variability when analysing data from 1947 to1995 and identified cycles of 5.3 years of colder conditions followed by 9.6 years of warmer conditions. All probes were connected to a Campbell Scientific CR 1000 data logger recording data at hourly intervals from March 1st 2008 until November 30th 2012. Meteorological data for Fildes was obtained from the near by stations. We calculated the thawing days, freezing days; thawing degree days and freezing degree days; all according to Guglielmin et al. (2008). The active lawyer thickness was calculated as the 0 °C depth by extrapolating the thermal gradient from the two

  17. Determination of active doping in highly resistive boron doped silicon nanocrystals embedded in SiO2 by capacitance voltage measurement on inverted metal oxide semiconductor structure

    NASA Astrophysics Data System (ADS)

    Zhang, Tian; Puthen-Veettil, Binesh; Wu, Lingfeng; Jia, Xuguang; Lin, Ziyun; Yang, Terry Chien-Jen; Conibeer, Gavin; Perez-Wurfl, Ivan

    2015-10-01

    We investigate the Capacitance-Voltage (CV) measurement to study the electrically active boron doping in Si nanocrystals (ncSi) embedded in SiO2. The ncSi thin films with high resistivity (200-400 Ω cm) can be measured by using an inverted metal oxide semiconductor (MOS) structure (Al/ncSi (B)/SiO2/Si). This device structure eliminates the complications from the effects of lateral current flow and the high sheet resistance in standard lateral MOS structures. The characteristic MOS CV curves observed are consistent with the effective p-type doping. The CV modeling method is presented and used to evaluate the electrically active doping concentration. We find that the highly boron doped ncSi films have electrically active doping of 1018-1019 cm-3 despite their high resistivity. The saturation of doping at about 1.4 × 1019 cm-3 and the low doping efficiency less than 5% are observed and discussed. The calculated effective mobility is in the order of 10-3 cm2/V s, indicating strong impurity/defect scattering effect that hinders carriers transport.

  18. Determination of active doping in highly resistive boron doped silicon nanocrystals embedded in SiO{sub 2} by capacitance voltage measurement on inverted metal oxide semiconductor structure

    SciTech Connect

    Zhang, Tian Puthen-Veettil, Binesh; Wu, Lingfeng; Jia, Xuguang; Lin, Ziyun; Yang, Terry Chien-Jen; Conibeer, Gavin; Perez-Wurfl, Ivan

    2015-10-21

    We investigate the Capacitance-Voltage (CV) measurement to study the electrically active boron doping in Si nanocrystals (ncSi) embedded in SiO{sub 2}. The ncSi thin films with high resistivity (200–400 Ω cm) can be measured by using an inverted metal oxide semiconductor (MOS) structure (Al/ncSi (B)/SiO{sub 2}/Si). This device structure eliminates the complications from the effects of lateral current flow and the high sheet resistance in standard lateral MOS structures. The characteristic MOS CV curves observed are consistent with the effective p-type doping. The CV modeling method is presented and used to evaluate the electrically active doping concentration. We find that the highly boron doped ncSi films have electrically active doping of 10{sup 18}–10{sup 19 }cm{sup −3} despite their high resistivity. The saturation of doping at about 1.4 × 10{sup 19 }cm{sup −3} and the low doping efficiency less than 5% are observed and discussed. The calculated effective mobility is in the order of 10{sup −3} cm{sup 2}/V s, indicating strong impurity/defect scattering effect that hinders carriers transport.

  19. Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer

    NASA Astrophysics Data System (ADS)

    Sarkar, Niladri; Basu, Abhik

    2015-11-01

    We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ . Being controlled by Γ , our model provides a unified framework to describe the long-wavelength behavior of a variety of thin polar-ordered systems, ranging from wet to dry active matter and free-standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system that can depend sensitively on Γ . Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems.

  20. Spin-dependent shot noise in diluted magnetic semiconductor/semiconductor heterostructures with a nonmagnetic barrier

    NASA Astrophysics Data System (ADS)

    Wu, Shuang; Guo, Yong

    2014-05-01

    We investigate quantum size effect on the spin-dependent shot noise in the diluted magnetic semiconductor (DMS)/semiconductor heterostructure with a nonmagnetic semiconductor (NMS) barrier in the presence of external magnetic and electric fields. The results demonstrate that the NMS barrier plays a quite different role from the DMS layer in the electron transport process. It is found that spin-down shot noise shows relatively regular oscillations as the width of DMS layer increases, while the spin-up shot noise deceases monotonically. However, as the width of NMS layer increases, the spin-down shot noise displays irregular oscillations at first and then decreases while the spin-up shot noise decreases at a quite different rate. The results indicate that the shot noise can be used as a sensitive probe in detecting material type and its size.