Science.gov

Sample records for engineered semiconductors ii

  1. Engineering the cell-semiconductor interface: a materials modification approach using II-VI and III-V semiconductor materials.

    PubMed

    Bain, Lauren E; Ivanisevic, Albena

    2015-02-18

    Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function.

  2. 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

  3. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  4. 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.

  5. Mod II engine performance

    NASA Technical Reports Server (NTRS)

    Richey, Albert E.; Huang, Shyan-Cherng

    1987-01-01

    The testing of a prototype of an automotive Stirling engine, the Mod II, is discussed. The Mod II is a one-piece cast block with a V-4 single-crankshaft configuration and an annular regenerator/cooler design. The initial testing of Mod II concentrated on the basic engine, with auxiliaries driven by power sources external to the engine. The performance of the engine was tested at 720 C set temperature and 820 C tube temperature. At 720 C, it is observed that the power deficiency is speed dependent and linear, with a weak pressure dependency, and at 820 C, the power deficiency is speed and pressure dependent. The effects of buoyancy and nozzle spray pattern on the heater temperature spread are investigated. The characterization of the oil pump and the operating cycle and temperature spread tests are proposed for further evaluation of the engine.

  6. Taming excitons in II-VI semiconductor nanowires and nanobelts

    NASA Astrophysics Data System (ADS)

    Xu, Xinlong; Zhang, Qing; Zhang, Jun; Zhou, Yixuan; Xiong, Qihua

    2014-10-01

    Excitons are one of the most important fundamental quasi-particles, and are involved in a variety of processes forming the basis of a wide range of opto-electronic and photonic devices based on II-VI semiconductor nanowires and nanobelts, such as light-emitting diodes, photovoltaic cells, photodetectors and nanolasers. A clear understanding of their properties and unveiling the potential engineering for excitons is of particular importance for the design and optimization of nanoscale opto-electronic and photonic devices. Herein, we present a comprehensive review on discussing the fundamental behaviours of the excitons in one-dimensional (1D) II-VI semiconductor nanomaterials (nanowires and nanobelts). We will start with a focus on the unique properties (origin, generation, etc) and dynamics of excitons and exciton complexes in the II-VI semiconductor nanowires and nanobelts. Then we move to the recent progress on the excitonic response in 1D nanomaterials and focus on the tailoring and engineering of excitonic properties through rational controlling of the physical parameters and conditions, intrinsically and extrinsically. These include (1) exciton-exciton interaction, which is important for 1D nanomaterial nanolasing; (2) exciton-phonon interaction, which has interesting applications for laser cooling; and (3) exciton-plasmon interaction, which is the cornerstone towards the realization of plasmonic lasers. The potential of electric field, morphology and size control for excitonic properties is also discussed. Unveiling and controlling excitonic properties in II-VI semiconductor nanowires and nanobelts would promote the development of 1D nanoscience and nanotechnology.

  7. Band structure engineering in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A.; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-01

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

  8. Band structure engineering in organic semiconductors.

    PubMed

    Schwarze, Martin; Tress, Wolfgang; Beyer, Beatrice; Gao, Feng; Scholz, Reinhard; Poelking, Carl; Ortstein, Katrin; Günther, Alrun A; Kasemann, Daniel; Andrienko, Denis; Leo, Karl

    2016-06-17

    A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors. PMID:27313043

  9. Mod II Stirling engine overviews

    NASA Technical Reports Server (NTRS)

    Farrell, Roger A.

    1988-01-01

    The Mod II engine is a second-generation automotive Stirling engine (ASE) optimized for part-power operation. It has been designed specifically to meet the fuel economy and exhaust emissions objectives of the ASE development program. The design, test experience, performance, and comparison of data to analytical performance estimates of the Mod II engine to date are reviewed. Estimates of Mod II performance in its final configuration are also given.

  10. Aircraft engines. II

    SciTech Connect

    Smith, M.G. Jr.

    1988-01-01

    An account is given of the design features and prospective performance gains of ultrahigh bypass subsonic propulsion configurations and various candidate supersonic commercial aircraft powerplants. The supersonic types, whose enhanced thermodynamic cycle efficiency is considered critical to the economic viability of a second-generation SST, are the variable-cycle engine, the variable stream control engine, the turbine-bypass engine, and the supersonic-throughflow fan. Also noted is the turboramjet concept, which will be applicable to hypersonic aircraft whose airframe structure materials can withstand the severe aerothermodynamic conditions of this flight regime.

  11. Semiconductor Chemical Reactor Engineering and Photovoltaic Unit Operations.

    ERIC Educational Resources Information Center

    Russell, T. W. F.

    1985-01-01

    Discusses the nature of semiconductor chemical reactor engineering, illustrating the application of this engineering with research in physical vapor deposition of cadmium sulfide at both the laboratory and unit operations scale and chemical vapor deposition of amorphous silicon at the laboratory scale. (JN)

  12. Electronic Structure of II-Vi Semiconductors and Their Alloys

    NASA Astrophysics Data System (ADS)

    Wei, Su-Huai

    The II-VI semiconductors ZnXVI, CdXVI, and HgXVI are known to have a metal d band inside the main valence band. Using all-electron self-consistent electronic structure techniques, we study their effects on valence properties. For II-VI semiconductors, we find that p-d repulsion and hybridization (i) lower the band gaps, (ii) alter the sign of the crystal-field splitting, (iii) reduce the spin-orbit splitting, (iv) change the valence band offset between common-anion semiconductors, and (v) increase the equilibrium lattice parameters, p-d repulsion is also shown to be responsible for the anomalously small band gaps in chalcopyrites, and for the negative exchange splitting in MnTe. We also study the electronic structure of ordered and random II-VI substitutional alloys and identify the mechanism for their band gap narrowing. The random {A_{1-x}^{II}B_{x}^{II}C^{VI}} alloys are represented by the "special quasirandom structures." We show how chemical and structural perturbations lead to (i) distinct A-like and B-like features in the density of states and (ii) different C-like features associated with fluctuations in the local environments around the common sublattice.

  13. Semiconductor/dielectric interface engineering and characterization

    NASA Astrophysics Data System (ADS)

    Lucero, Antonio T.

    The focus of this dissertation is the application and characterization of several, novel interface passivation techniques for III-V semiconductors, and the development of an in-situ electrical characterization. Two different interface passivation techniques were evaluated. The first is interface nitridation using a nitrogen radical plasma source. The nitrogen radical plasma generator is a unique system which is capable of producing a large flux of N-radicals free of energetic ions. This was applied to Si and the surface was studied using x-ray photoelectron spectroscopy (XPS). Ultra-thin nitride layers could be formed from 200-400° C. Metal-oxide-semiconductor capacitors (MOSCAPs) were fabricated using this passivation technique. Interface nitridation was able to reduce leakage current and improve the equivalent oxide thickness of the devices. The second passivation technique studied is the atomic layer deposition (ALD) diethylzinc (DEZ)/water treatment of sulfur treated InGaAs and GaSb. On InGaAs this passivation technique is able to chemically reduce higher oxidation states on the surface, and the process results in the deposition of a ZnS/ZnO interface passivation layer, as determined by XPS. Capacitance-voltage (C-V) measurements of MOSCAPs made on p-InGaAs reveal a large reduction in accumulation dispersion and a reduction in the density of interfacial traps. The same technique was applied to GaSb and the process was studied in an in-situ half-cycle XPS experiment. DEZ/H2O is able to remove all Sb-S from the surface, forming a stable ZnS passivation layer. This passivation layer is resistant to further reoxidation during dielectric deposition. The final part of this dissertation is the design and construction of an ultra-high vacuum cluster tool for in-situ electrical characterization. The system consists of three deposition chambers coupled to an electrical probe station. With this setup, devices can be processed and subsequently electrically characterized

  14. Electrical transport engineering of semiconductor superlattice structures

    NASA Astrophysics Data System (ADS)

    Shokri, Aliasghar

    2014-04-01

    We investigate the influence of doping concentration on band structures of electrons and electrical transmission in a typical aperiodic semiconductor superlattice consisting of quantum well and barrier layers, theoretically. For this purpose, we assume that each unit cell of the superlattice contains alternately two types of material GaAs (as a well) and GaAlAs (as a barrier) with six sublayers of two materials. Our calculations are based on the generalized Kronig-Penny (KP) model and the transfer matrix method within the framework of the parabolic conductance band effective mass approximation in the coherent regime. This model reduces the numerical calculation time and enables us to use the transfer matrix method to investigate transport in the superlattices. We show that by varying the doping concentration and geometrical parameters, one can easily block the transmission of the electrons. The numerical results may be useful in designing of nanoenergy filter devices.

  15. Electron Paramagnetic Resonance in II-Vi Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Gui-Lin

    This dissertation is devoted to investigation of the electron paramagnetic resonance (EPR) of Mn ^{++} ions in II-VI semiconductor heterostructures, in order to determine how EPR is affected by this layered environment and what new information can be extracted by this technique. We first introduce the concept of the effective spin, and we review the theoretical background of the spin Hamiltonian, for describing the ground state of a paramagnetic ion in a solid. The physical origin of the constituent terms in the spin Hamiltonion are discussed, and their characteristics described, for use at later stages in the thesis. We then analyze the effect on EPR of the potential exchange interaction between the localized d-electrons of the Mn^{++} ions and the band electrons. We predict that such exchange interaction can lead to significant changes in the g-factors of Mn ^{++} ions due to the spin polarization of band electrons, resulting in line shifts of EPR spectra. Although such shifts would be too small to be observed for Mn^{++} ions introduced into bulk semiconductors, we show that the shifts can be significantly larger for Mn^ {++} ions in quantum wells, superlattices, and similar heterostructures, due to the electron confinement effect. This effect of the potential exchange interaction on the EPR spectra of Mn^{++} ions leads us to propose to use the Mn ^{++} ions as built-in localized probes for mapping the wave functions of electronic states in II-VI semiconductor quantum wells and superlattices. We then consider the influence of internal strain on the EPR transitions of Mn^{++} in II-VI semiconductor heterostructures. Our analysis of the changes of the Mn^{++} fine structure indicates that EPR can be used to detect even minute amounts of strain (e.g., strain resulting from as little as 0.01% lattice mismatch can readily be measured). Accordingly, we demonstrate EPR to be an ultrasensitive and probably unique tool for small strain measurements in II

  16. Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

  17. Synthesis and characterization of II-IV-V(2) semiconductors

    NASA Astrophysics Data System (ADS)

    Wen, Yuan-Chung

    1998-11-01

    The II-IV-V2 chalcopyrite semiconductors are isostructural and isoelectronic analogues of the III-V semiconductors. Like the III-V materials the compounds have potential applications in nonlinear optics, optoelectronics and solar energy conversion. The naturally abundant elements and high absorption coefficients in many of the II-IV-V2's make these materials more attractive for large scale applications. Our study focused on the investigation of the basic electrical and optical properties of a number of II-IV- V2 materials by photoelectrochemical methods and photoluminescence. A variety of single crystals in II-IV- V2 family such as ZnSiAs2, CdSiAs2, CdSiP2, ZnSiP2, CdGeP2, ZnGeP2, and ZnSnP2 have been synthesized by chemical vapor transport (CVT) and Bridgman growth techniques. Intentional doping with S, Se, Al, Ga and In of the crystals resulted in complex behavior. In some systems compensation with intrinsic acceptors was observed and in other systems the change of doping type and controllable doping levels were observed. The bandgap, doping level, band position, quantum yield and current voltage behavior in various electrolytes for many of the II-IV-V2 semiconductors have been determined using photoelectrochemical methods. Hall effect measurements of doping density have been used to compare with values obtained from Mott-Schottky analysis. Frequency and pH dependence of the Mott-Schottky plots were observed. The minority diffusion length of II-IV-V2 calculated from quantum yield and absorption coefficient data at the onset of photocurrent matches well to the prediction from the Gartner Model. Polarization dependent photoluminescence has been used for the study of interband transitions and optical anisotropy in CdSiAs2 and CdSiP2 crystals. The electrode surfaces of CdSiAs2 crystals treated by wet chemical etchants were investigated and characterized by XPS. 31P solid state MAS NMR studies of the II-IV- P2 compounds gave very sharp 31P resonances and revealed

  18. Band-Gap Engineering at a Semiconductor-Crystalline Oxide Interface

    SciTech Connect

    Moghadam, Mohammadreza J.; Ahmadi-Majlan, K.; Shen, Xuan; Droubay, Timothy C.; Bowden, Mark E.; Chrysler, M.; Su, Dong; Chambers, Scott A.; Ngai, Joseph

    2015-02-09

    The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to electrically coupling crystalline oxides with semiconductors to realize functional behavior is controlling the manner in which their bands align at interfaces. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZrxTi1-xO3 and Ge, in which the band gap of the former is enhanced with Zr content x. We present structural, electrical and photoemission characterization of SrZrxTi1-xO33-Ge heterojunctions for x = 0.2 to 0.75 and demonstrate the band offset can be tuned from type-II to type-I. The type-I band offset provides a platform to integrate the dielectric, ferroelectric and ferromagnetic functionalities of oxides with semiconducting devices.

  19. Semiconductor nanomembranes: a platform for new properties via strain engineering

    PubMed Central

    2012-01-01

    New phenomena arise in single-crystal semiconductors when these are fabricated in very thin sheets, with thickness at the nanometer scale. We review recent research on Si and Ge nanomembranes, including the use of elastic strain sharing, layer release, and transfer, that demonstrate new science and enable the fabrication of materials with unique properties. Strain engineering produces new strained forms of Si or Ge not possible in nature, new layered structures, defect-free SiGe sheets, and new electronic band structure and photonic properties. Through-membrane elastic interactions cause the double-sided ordering of epitaxially grown nanostressors on Si nanomembranes, resulting in a spatially and periodically varying strain field in the thin crystalline semiconductor sheet. The inherent influence of strain on the band structure creates band gap modulation, thereby creating effectively a single-element electronic superlattice. Conversely, large-enough externally applied strain can make Ge a direct-band gap semiconductor, giving promise for Group IV element light sources. PMID:23153167

  20. Method of manufacturing semiconductor having group II-group VI compounds doped with nitrogen

    DOEpatents

    Compaan, Alvin D.; Price, Kent J.; Ma, Xianda; Makhratchev, Konstantin

    2005-02-08

    A method of making a semiconductor comprises depositing a group II-group VI compound onto a substrate in the presence of nitrogen using sputtering to produce a nitrogen-doped semiconductor. This method can be used for making a photovoltaic cell using sputtering to apply a back contact layer of group II-group VI compound to a substrate in the presence of nitrogen, the back coating layer being doped with nitrogen. A semiconductor comprising a group II-group VI compound doped with nitrogen, and a photovoltaic cell comprising a substrate on which is deposited a layer of a group II-group VI compound doped with nitrogen, are also included.

  1. Monolayer II-VI semiconductors: A first-principles prediction

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Li, Xian-Bin; Chen, Nian-Ke; Xie, Sheng-Yi; Tian, Wei Quan; Chen, Yuanping; Xia, Hong; Zhang, S. B.; Sun, Hong-Bo

    2015-09-01

    A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. While none of the two-dimensional (2D) structures can be energetically stable, it appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability. The stability of the five oxides is consistent with the work published by Zhuang et al. [Appl. Phys. Lett. 103, 212102 (2013), 10.1063/1.4831972]. The rest of the compounds in the form of honeycomb are dynamically unstable, revealed by phonon calculations. In addition, according to the molecular dynamic (MD) simulation evolution from these unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS [P 4 /n m m (129 ) ] and orthorhombic HgS [P 21/m (11 ) ] . The honeycomb monolayers exist in the form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has recently been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC) [J. Li et al., arXiv:1412.2528]. Some II-VI partners with less than 5 % lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics.

  2. Novel engineered compound semiconductor heterostructures for advanced electronics applications

    NASA Astrophysics Data System (ADS)

    Stillman, Gregory E.; Holonyak, Nick, Jr.; Coleman, James J.

    1992-06-01

    To provide the technology base that will enable SDIO capitalization on the performance advantages offered through novel engineered multiple-lavered compound semiconductor structures, this project has focussed on three specific areas: (1) carbon doping of AlGaAs/GaAs and InP/InGaAs materials for reliable high frequency heterojunction bipolar transistors; (2) impurity induced layer disordering and the environmental degradation of AlxGal-xAs-GaAs quantum-well heterostructures and the native oxide stabilization of AlxGal-xAs-GaAs quantum well heterostructure lasers; and (3) non-planar and strained-layer quantum well heterostructure lasers and laser arrays. The accomplishments in this three year research are reported in fifty-six publications and the abstracts included in this report.

  3. II-VI wide band gap semiconductors under hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Baquero, R.; Decoss, R.; Olguin, D.

    1993-08-01

    We set an analytical expression for the gap as a function of hydrostatic deformation, E(sub g)(epsilon), by diagonalizing in Gamma the corresponding empirical tight-binding Hamiltonian (ETBH). In the ETBH we use the well known d(exp -2) Harrison scaling law (HSL) to adjust the TB parameter (TBP) to the changes in interatomic distances. We do not consider cation-anion charge transfer. We calculate E(sub g)(epsilon) for wide band gap II-VI semiconductors with zincblende crystal structure for deformations under pressure up to -5 percent. Results are in good agreement with experiment for the compounds of lower ionicity but deviate as the ionicity of the compound increases. This is due to the neglect of charge transfer which should be included self-consistently. Within the approximation we always find a positive second derivative of E(sub g)(epsilon) with respect to epsilon, independent of the material. Furthermore, the inclusion of deviations from HSL appear to be unimportant to this problem.

  4. Band-Gap Engineering at a Semiconductor-Crystalline Oxide Interface

    SciTech Connect

    Jahangir-Moghadam, Mohammadreza; Ahmadi-Majlan, Kamyar; Shen, Xuan; Droubay, Timothy; Bowden, Mark; Chrysler, Matthew; Su, Dong; Chambers, Scott A.; Ngai, Joseph H.

    2015-02-09

    The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to integrating the functionalities of oxides onto semiconductors is controlling the band alignment at interfaces between the two materials. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZrxTi1-xO₃ and Ge, in which the band gap of the former is enhanced with Zr content x. We present structural and electrical characterization of SrZrxTi1-xO₃-Ge heterojunctions and demonstrate a type-I band offset can be achieved. These results demonstrate that band gap engineering can be exploited to realize functional semiconductor crystalline oxide heterojunctions.

  5. Band-Gap Engineering at a Semiconductor-Crystalline Oxide Interface

    DOE PAGES

    Jahangir-Moghadam, Mohammadreza; Ahmadi-Majlan, Kamyar; Shen, Xuan; Droubay, Timothy; Bowden, Mark; Chrysler, Matthew; Su, Dong; Chambers, Scott A.; Ngai, Joseph H.

    2015-02-09

    The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to integrating the functionalities of oxides onto semiconductors is controlling the band alignment at interfaces between the two materials. Here we apply principles of band gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZrxTi1-xO₃ and Ge, in which the band gap of the former is enhanced with Zr content x. We presentmore » structural and electrical characterization of SrZrxTi1-xO₃-Ge heterojunctions and demonstrate a type-I band offset can be achieved. These results demonstrate that band gap engineering can be exploited to realize functional semiconductor crystalline oxide heterojunctions.« less

  6. Hybrid bandgap engineering for super-hetero-epitaxial semiconductor materials, and products thereof

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2012-01-01

    "Super-hetero-epitaxial" combinations comprise epitaxial growth of one material on a different material with different crystal structure. Compatible crystal structures may be identified using a "Tri-Unity" system. New bandgap engineering diagrams are provided for each class of combination, based on determination of hybrid lattice constants for the constituent materials in accordance with lattice-matching equations. Using known bandgap figures for previously tested materials, new materials with lattice constants that match desired substrates and have the desired bandgap properties may be formulated by reference to the diagrams and lattice matching equations. In one embodiment, this analysis makes it possible to formulate new super-hetero-epitaxial semiconductor systems, such as systems based on group IV alloys on c-plane LaF.sub.3; group IV alloys on c-plane langasite; Group III-V alloys on c-plane langasite; and group II-VI alloys on c-plane sapphire.

  7. Nanophase Engineering of Organic Semiconductor-based Solar Cells

    SciTech Connect

    Shao, Ming; Keum, Jong Kahk; Geohegan, David B; Xiao, Kai

    2015-01-01

    Organic photovoltaics are promising low-cost, easily-processable energy sources of the future, and are the subject of current academic and industrial interest. In order to achieve the envisioned device efficiencies to surpass commercialization target values, several challenges must be met: (1) to design and synthesize conjugated molecules with low optical bandgaps and optimized electronic energy levels, (2) optimization the morphology of donor/acceptor interpenetrating networks by controlling nanoscale phase separation and self-assembly, and (3) precise tuning of the active layer/electrode interfaces and donor/acceptor interfaces for optimized charge transfer. Here, we focus on recent advances in: (i) synthetic strategies for low-bandgap conjugated polymers and novel fullerene acceptors, (ii) processing to tune film morphologies by solvent annealing, thermal annealing, and the use of solvent additives and compatibilizers, and (iii) engineering of active layer/electrode interfaces and donor/acceptor interfaces with self-assembled monolayer dipoles.

  8. PREFACE: Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II (Symposium K, E-MRS 2009 Spring Meeting)

    NASA Astrophysics Data System (ADS)

    Nötzel, Richard

    2009-07-01

    This volume of IOP Conference Series: Materials Science and Engineering contains papers that were presented at the special symposium K at the EMRS 2009 Spring Meeting held 8-12 June in Strasbourg, France, which was entitled 'Semiconductor Nanostructures towards Electronic and Optoelectronic Device Applications II'. Thanks to the broad interest a large variety of quantum dots and quantum wires and related nanostructures and their application in devices could be covered. There was significant progress in the epitaxial growth of semiconductor quantum dots seen in the operation of high-power, as well as mode locked laser diodes and the lateral positioning of quantum dots on patterned substrates or by selective area growth for future single quantum dot based optoelectronic and electronic devices. In the field of semiconductor nanowires high quality, almost twin free structures are now available together with a new degree of freedom for band structure engineering based on alternation of the crystal structure. In the search for Si based light emitting structures, nanocrystals and miniband-related near infrared luminescence of Si/Ge quantum dot superlattices with high quantum efficiency were reported. These highlights, among others, and the engaged discussions of the scientists, engineers and students brought together at the symposium emphasize how active the field of semiconductor nanostructures and their applications in devices is, so that we can look forward to the progress to come. Guest Editor Richard Nötzel COBRA Research Institute Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven The Netherlands Tel.: +31 40 247 2047; fax: +31 40 246 1339 E-mail address: r.noetzel@tue.nl

  9. Photophysical Properties of II-VI Semiconductor Nanocrystals

    NASA Astrophysics Data System (ADS)

    Gong, Ke

    As it is well known, semiconductor nanocrystals (also called quantum dots, QDs) are being actively pursued for use in many different types of luminescent optical materials. These materials include the active media for luminescence downconversion in artificial lighting, lasers, luminescent solar concentrators and many other applications. Chapter 1 gives general introduction of QDs, which describe the basic physical properties and optical properties. Based on the experimental spectroscopic study, a semiquantitative method-effective mass model is employed to give theoretical prediction and guide. The following chapters will talks about several topics respectively. A predictive understanding of the radiative lifetimes is therefore a starting point for the understanding of the use of QDs for these applications. Absorption intensities and radiative lifetimes are fundamental properties of any luminescent material. Meantime, achievement of high efficiency with high working temperature and heterostructure fabrication with manipulation of lattice strain are not easy and need systematic investigation. To make accurate connections between extinction coefficients and radiative recombination rates, chapter 2 will consider three closely related aspects of the size dependent spectroscopy of II-VI QDs. First, it will consider the existing literature on cadmium selenide (CdSe) QD absorption spectra and extinction coefficients. From these results and fine structure considerations Boltzmann weighted radiative lifetimes are calculated. These lifetimes are compared to values measured on very high quality CdSe and CdSe coated with zinc selenide (ZnSe) shells. Second, analogous literature data are analyzed for cadmium telluride (CdTe) nanocrystals and compared to lifetimes measured for very high quality QDs. Furthermore, studies of the absorption and excitation spectra and measured radiative lifetimes for CdTe/CdSe Type-II core/shell QDs are reported. These results are also analyzed in

  10. The Impedance Response of Semiconductors: An Electrochemical Engineering Perspective.

    ERIC Educational Resources Information Center

    Orazem, Mark E.

    1990-01-01

    Shows that the principles learned in the study of mass transport, thermodynamics, and kinetics associated with electrochemical systems can be applied to the transport and reaction processes taking place within a semiconductor. Describes impedance techniques and provides several graphs illustrating impedance data for diverse circuit systems. (YP)

  11. Microwave-assisted synthesis of II-VI semiconductor micro-and nanoparticles towards sensor applications

    NASA Astrophysics Data System (ADS)

    Majithia, Ravish Yogesh

    Engineering particles at the nanoscale demands a high degree of control over process parameters during synthesis. For nanocrystal synthesis, solution-based techniques typically include application of external convective heat. This process often leads to slow heating and allows decomposition of reagents or products over time. Microwave-assisted heating provides faster, localized heating at the molecular level with near instantaneous control over reaction parameters. In this work, microwave-assisted heating has been applied for the synthesis of II-VI semiconductor nanocrystals namely, ZnO nanopods and CdX (X = Se, Te) quantum dots (QDs). Based on factors such as size, surface functionality and charge, optical properties of such nanomaterials can be tuned for application as sensors. ZnO is a direct bandgap semiconductor (3.37 eV) with a large exciton binding energy (60 meV) leading to photoluminescence (PL) at room temperature. A microwave-assisted hydrothermal approach allows the use of sub-5 nm ZnO zero-dimensional nanoparticles as seeds for generation of multi-legged quasi one-dimensional nanopods via heterogeneous nucleation. ZnO nanopods, having individual leg diameters of 13-15 nm and growing along the [0001] direction, can be synthesized in as little as 20 minutes. ZnO nanopods exhibit a broad defect-related PL spanning the visible range with a peak at ~615 nm. Optical sensing based on changes in intensity of the defect PL in response to external environment (e.g., humidity) is demonstrated in this work. Microwave-assisted synthesis was also used for organometallic synthesis of CdX(ZnS) (X = Se, Te) core(shell) QDs. Optical emission of these QDs can be altered based on their size and can be tailored to specific wavelengths. Further, QDs were incorporated in Enhanced Green-Fluorescent Protein -- Ultrabithorax (EGFP-Ubx) fusion protein for the generation of macroscale composite protein fibers via hierarchal self-assembly. Variations in EGFP- Ubx˙QD composite

  12. Surface Bonding Effects in Compound Semiconductor Nanoparticles: II

    SciTech Connect

    Helen H. Farrell

    2008-07-01

    Small nanoparticles have a large proportion of their atoms either at or near the surface, and those in clusters are essentially all on the surface. As a consequence, the details of the surface structure are of paramount importance in governing the overall stability of the particle. Just as with bulk materials, factors that determine this stability include “bulk” structure, surface reconstruction, charge balance and hybridization, ionicity, strain, stoichiometry, and the presence of adsorbates. Needless to say, many of these factors, such as charge balance, hybridization and strain, are interdependent. These factors all contribute to the overall binding energy of clusters and small nanoparticles and play a role in determining the deviations from an inverse size dependence that we have previously reported for compound semiconductor materials. Using first-principles density functional theory calculations, we have explored how these factors influence particle stability under a variety of conditions.

  13. Diluted II-VI oxide semiconductors with multiple band gaps.

    PubMed

    Yu, K M; Walukiewicz, W; Wu, J; Shan, W; Beeman, J W; Scarpulla, M A; Dubon, O D; Becla, P

    2003-12-12

    We report the realization of a new mult-band-gap semiconductor. Zn(1-y)Mn(y)OxTe1-x alloys have been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of extended states located within the band gap of the Zn(1-y)Mn(y)Te host. When only 1.3% of Te atoms are replaced with oxygen in a Zn0.88Mn0.12Te crystal the resulting band structure consists of two direct band gaps with interband transitions at approximately 1.77 and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model. With multiple band gaps that fall within the solar energy spectrum, Zn(1-y)Mn(y)OxTe1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.

  14. Achieving Optimal Self-Adaptivity for Dynamic Tuning of Organic Semiconductors through Resonance Engineering.

    PubMed

    Tao, Ye; Xu, Lijia; Zhang, Zhen; Chen, Runfeng; Li, Huanhuan; Xu, Hui; Zheng, Chao; Huang, Wei

    2016-08-01

    Current static-state explorations of organic semiconductors for optimal material properties and device performance are hindered by limited insights into the dynamically changed molecular states and charge transport and energy transfer processes upon device operation. Here, we propose a simple yet successful strategy, resonance variation-based dynamic adaptation (RVDA), to realize optimized self-adaptive properties in donor-resonance-acceptor molecules by engineering the resonance variation for dynamic tuning of organic semiconductors. Organic light-emitting diodes hosted by these RVDA materials exhibit remarkably high performance, with external quantum efficiencies up to 21.7% and favorable device stability. Our approach, which supports simultaneous realization of dynamically adapted and selectively enhanced properties via resonance engineering, illustrates a feasible design map for the preparation of smart organic semiconductors capable of dynamic structure and property modulations, promoting the studies of organic electronics from static to dynamic. PMID:27403886

  15. Ballistic transport in II-VI semiconductor compounds and alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Krishnamurthy, S.; Sher, A.; Chen, A.-B.

    1988-01-01

    Realistic band structures are used in calculating the group velocity and scattering rates for electrons with injection energies up to 1 eV in ZnTe, CdTe, and the low-effective-mass alloy Hg(0.7)Cd(0.3)Te. Scattering from longitudinal optical phonons, ionized impurities, and alloy disorder have been included in the full band-structure calculation, which automatically includes both intra- and intervalley scattering. Of the II-VI materials considered, at 77 K HgCdTe is superior for low injection energies (up to 0.25 eV) while CdTe is superior at higher injection energies (1 eV) at room temperature. The attainable mean free paths (equal to or greater than 1000 A) and group velocities (equal to or greater than 10 to the 8th cm/s) for both systems are comparable to values found in III-V systems.

  16. Engineered semiconductor nanocrystals with enhanced carrier multiplication yields

    NASA Astrophysics Data System (ADS)

    Klimov, Victor

    2014-03-01

    Carrier multiplication (CM) is a process whereby absorption of a single photon results in multiple electron-hole pairs (excitons). This process could benefit a number of solar-energy conversion technologies, most notably photocatalysis and photovoltaics. This presentation overviews recent progress in understanding the CM process in semiconductor nanocrystals, motivated by an outstanding challenge in this field - the lack of capability to predict the CM performance of nanocrystals based on their known photophysical properties or documented parameters of parental bulk solids. Here, we present a possible solution to this problem by showing that, using biexciton Auger lifetimes and intraband relaxation rates inferred from ultrafast spectroscopic studies, we can rationalize relative changes in CM yields as a function of nanocrystal composition, size and shape. Further, guided by this model, we demonstrate a two-fold enhancement in multiexciton yields in PbSe nanorods vs. quantum dots attributed to enhanced Coulomb interactions. We also explore the control of competing intra-band cooling for increasing multiexciton production. Specifically, we design a new type of hetero-structured PbSe/CdSe quantum dots with reduced rates of intra-band relaxation and demonstrate a four-fold boost in the multiexciton yield. These studies provide useful guidelines for future efforts to achieve the ultimate, energy-conservation-defined CM efficiencies.

  17. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon

    PubMed Central

    Averyanov, Dmitry V.; Karateeva, Christina G.; Karateev, Igor A.; Tokmachev, Andrey M.; Vasiliev, Alexander L.; Zolotarev, Sergey I.; Likhachev, Igor A.; Storchak, Vyacheslav G.

    2016-01-01

    Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics. PMID:26957146

  18. Atomic-Scale Engineering of Abrupt Interface for Direct Spin Contact of Ferromagnetic Semiconductor with Silicon

    NASA Astrophysics Data System (ADS)

    Averyanov, Dmitry V.; Karateeva, Christina G.; Karateev, Igor A.; Tokmachev, Andrey M.; Vasiliev, Alexander L.; Zolotarev, Sergey I.; Likhachev, Igor A.; Storchak, Vyacheslav G.

    2016-03-01

    Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics.

  19. Tailoring the Spectroscopic Properties of Semiconductor Nanowires via Surface-Plasmon-Based Optical Engineering

    PubMed Central

    2014-01-01

    Semiconductor nanowires, due to their unique electronic, optical, and chemical properties, are firmly placed at the forefront of nanotechnology research. The rich physics of semiconductor nanowire optics arises due to the enhanced light–matter interactions at the nanoscale and coupling of optical modes to electronic resonances. Furthermore, confinement of light can be taken to new extremes via coupling to the surface plasmon modes of metal nanostructures integrated with nanowires, leading to interesting physical phenomena. This Perspective will examine how the optical properties of semiconductor nanowires can be altered via their integration with highly confined plasmonic nanocavities that have resulted in properties such as orders of magnitude faster and more efficient light emission and lasing. The use of plasmonic nanocavities for tailored optical absorption will also be discussed in order to understand and engineer fundamental optical properties of these hybrid systems along with their potential for novel applications, which may not be possible with purely dielectric cavities. PMID:25396030

  20. Charge transport and mobility engineering in two-dimensional transition metal chalcogenide semiconductors.

    PubMed

    Li, Song-Lin; Tsukagoshi, Kazuhito; Orgiu, Emanuele; Samorì, Paolo

    2016-01-01

    Two-dimensional (2D) van der Waals semiconductors represent the thinnest, air stable semiconducting materials known. Their unique optical, electronic and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. However, the charge transport behavior in 2D semiconductors is more susceptible to external surroundings (e.g. gaseous adsorbates from air and trapped charges in substrates) and their electronic performance is generally lower than corresponding bulk materials due to the fact that the surface and bulk coincide. In this article, we review recent progress on the charge transport properties and carrier mobility engineering of 2D transition metal chalcogenides, with a particular focus on the markedly high dependence of carrier mobility on thickness. We unveil the origin of this unique thickness dependence and elaborate the devised strategies to master it for carrier mobility optimization. Specifically, physical and chemical methods towards the optimization of the major factors influencing the extrinsic transport such as electrode/semiconductor contacts, interfacial Coulomb impurities and atomic defects are discussed. In particular, the use of ad hoc molecules makes it possible to engineer the interface with the dielectric and heal the vacancies in such materials. By casting fresh light on the theoretical and experimental studies, we provide a guide for improving the electronic performance of 2D semiconductors, with the ultimate goal of achieving technologically viable atomically thin (opto)electronics.

  1. Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Sha, Yi-Gao

    1995-01-01

    The studies on the crystal growth and characterization of II-VI wide band gap compound semiconductors, such as ZnTe, CdS, ZnSe and ZnS, have been conducted over the past three decades. The research was not quite as extensive as that on Si, III-V, or even narrow band gap II-VI semiconductors because of the high melting temperatures as well as the specialized applications associated with these wide band gap semiconductors. In the past several years, major advances in the thin film technology such as Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) have demonstrated the applications of these materials for the important devices such as light-emitting diode, laser and ultraviolet detectors and the tunability of energy band gap by employing ternary or even quaternary systems of these compounds. At the same time, the development in the crystal growth of bulk materials has not advanced far enough to provide low price, high quality substrates needed for the thin film growth technology.

  2. Microscopic Modeling of Intersubband Optical Processes in Type II Semiconductor Quantum Wells: Linear Absorption

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Kolokolov, Kanstantin I.; Ning, Cun-Zheng

    2003-01-01

    Linear absorption spectra arising from intersubband transitions in semiconductor quantum well heterostructures are analyzed using quantum kinetic theory by treating correlations to the first order within Hartree-Fock approximation. The resulting intersubband semiconductor Bloch equations take into account extrinsic dephasing contributions, carrier-longitudinal optical phonon interaction and carrier-interface roughness interaction which is considered with Ando s theory. As input for resonance lineshape calculation, a spurious-states-free 8-band kp Hamiltonian is used, in conjunction with the envelop function approximation, to compute self-consistently the energy subband structure of electrons in type II InAs/AlSb single quantum well structures. We demonstrate the interplay of nonparabolicity and many-body effects in the mid-infrared frequency range for such heterostructures.

  3. Degree of circular polarization in II-VI diluted magnetic semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Rana, Shivani; Sen, Pratima; Sen, Pranay Kumar

    2012-07-01

    Degree of circular polarization (DCP) in II-VI diluted magnetic semiconductor quantum dots (QDs) has been studied analytically. Energy levels have been calculated using Luttinger-Kohn Hamiltonian and effective mass approximation. Effects due to application of externa magnetic field have been investigated, followed by calculation of transition dipole moment and DCP. Numerical estimates made for Mn-doped CdSe/ZnSe QDs show that DCP in undoped QDs is negligible while transition metal ion doping yields substantial polarization rotation (≈-2.20%) even at moderate magnetic fields (≈0.5T).

  4. Engineering of chimeric class II polyhydroxyalkanoate synthases.

    PubMed

    Niamsiri, Nuttawee; Delamarre, Soazig C; Kim, Young-Rok; Batt, Carl A

    2004-11-01

    PHA synthase is a key enzyme involved in the biosynthesis of polyhydroxyalkanoates (PHAs). Using a combinatorial genetic strategy to create unique chimeric class II PHA synthases, we have obtained a number of novel chimeras which display improved catalytic properties. To engineer the chimeric PHA synthases, we constructed a synthetic phaC gene from Pseudomonas oleovorans (phaC1Po) that was devoid of an internal 540-bp fragment. Randomly amplified PCR products (created with primers based on conserved phaC sequences flanking the deleted internal fragment) were generated using genomic DNA isolated from soil and were substituted for the 540-bp internal region. The chimeric genes were expressed in a PHA-negative strain of Ralstonia eutropha, PHB(-)4 (DSM 541). Out of 1,478 recombinant clones screened for PHA production, we obtained five different chimeric phaC1Po genes that produced more PHA than the native phaC1Po. Chimeras S1-71, S4-8, S5-58, S3-69, and S3-44 exhibited 1.3-, 1.4-, 2.0-, 2.1-, and 3.0-fold-increased levels of in vivo activity, respectively. All of the mutants mediated the synthesis of PHAs with a slightly increased molar fraction of 3-hydroxyoctanoate; however, the weight-average molecular weights (Mw) of the PHAs in all cases remained almost the same. Based upon DNA sequence analyses, the various phaC fragments appear to have originated from Pseudomonas fluorescens and Pseudomonas aureofaciens. The amino acid sequence analyses showed that the chimeric proteins had 17 to 20 amino acid differences from the wild-type phaC1Po, and these differences were clustered in the same positions in the five chimeric clones. A threading model of PhaC1Po, developed based on homology of the enzyme to the Burkholderia glumae lipase, suggested that the amino acid substitutions found in the active chimeras were located mostly on the protein model surface. Thus, our combinatorial genetic engineering strategy proved to be broadly useful for improving the catalytic

  5. Lattice dynamics of II-VI mixed semiconductor ZnS 1- xSe x

    NASA Astrophysics Data System (ADS)

    Kushwaha, A. K.

    2008-09-01

    Lattice dynamical properties of II-VI compounds having zinc-blende structure have been calculated by three-body shell model. This model incorporates the effect of the short-range repulsive interactions up to and including the second nearest neighbours, in addition to the long-range Coulombic interactions in the frame work of the rigid-shell model with both the ions are polarizable. The model involves in total eleven disposable parameters. Using the above proposed model the phonon dispersion relations for mixed II-VI semiconductor ZnS 1- xSe x are plotted. We find an overall good agreement with the experimental results. The application of the present model has been made to calculate the phonon dispersion relations of ZnS, ZnSe and mixed semiconductor ZnS 1- xSe x. The comparison of the theoretical results with the available experimental has been made along high symmetry directions. A reasonably good agreement is observed between theory and experiments.

  6. Surface engineering of ZnO nanostructures for semiconductor-sensitized solar cells.

    PubMed

    Xu, Jun; Chen, Zhenhua; Zapien, Juan Antonio; Lee, Chun-Sing; Zhang, Wenjun

    2014-08-20

    Semiconductor-sensitized solar cells (SSCs) are emerging as promising devices for achieving efficient and low-cost solar-energy conversion. The recent progress in the development of ZnO-nanostructure-based SSCs is reviewed here, and the key issues for their efficiency improvement, such as enhancing light harvesting and increasing carrier generation, separation, and collection, are highlighted from aspects of surface-engineering techniques. The impact of other factors such as electrolyte and counter electrodes on the photovoltaic performance is also addressed. The current challenges and perspectives for the further advance of ZnO-based SSCs are discussed.

  7. Enhanced thermoelectric performance in the Rashba semiconductor BiTeI through band gap engineering.

    PubMed

    Wu, Lihua; Yang, Jiong; Zhang, Tiansong; Wang, Shanyu; Wei, Ping; Zhang, Wenqing; Chen, Lidong; Yang, Jihui

    2016-03-01

    Rashba semiconductors are of great interest in spintronics, superconducting electronics and thermoelectrics. Bulk BiTeI is a new Rashba system with a giant spin-split band structure. 2D-like thermoelectric response has been found in BiTeI. However, as optimizing the carrier concentration, the bipolar effect occurs at elevated temperature and deteriorates the thermoelectric performance of BiTeI. In this paper, band gap engineering in Rashba semiconductor BiTeI through Br-substitution successfully reduces the bipolar effect and improves the thermoelectric properties. By utilizing the optical absorption and Burstein-Moss-effect analysis, we find that the band gap in Rashba semiconductor BiTeI increases upon bromine substitution, which is consistent with theoretical predictions. Bipolar transport is mitigated due to the larger band gap, as the thermally-activated minority carriers diminish. Consequently, the Seebeck coefficient keeps increasing with a corresponding rise in temperature, and thermoelectric performance can thus be enhanced with a ZT  =  0.5 at 570 K for BiTeI0.88Br0.12.

  8. Enhanced thermoelectric performance in the Rashba semiconductor BiTeI through band gap engineering.

    PubMed

    Wu, Lihua; Yang, Jiong; Zhang, Tiansong; Wang, Shanyu; Wei, Ping; Zhang, Wenqing; Chen, Lidong; Yang, Jihui

    2016-03-01

    Rashba semiconductors are of great interest in spintronics, superconducting electronics and thermoelectrics. Bulk BiTeI is a new Rashba system with a giant spin-split band structure. 2D-like thermoelectric response has been found in BiTeI. However, as optimizing the carrier concentration, the bipolar effect occurs at elevated temperature and deteriorates the thermoelectric performance of BiTeI. In this paper, band gap engineering in Rashba semiconductor BiTeI through Br-substitution successfully reduces the bipolar effect and improves the thermoelectric properties. By utilizing the optical absorption and Burstein-Moss-effect analysis, we find that the band gap in Rashba semiconductor BiTeI increases upon bromine substitution, which is consistent with theoretical predictions. Bipolar transport is mitigated due to the larger band gap, as the thermally-activated minority carriers diminish. Consequently, the Seebeck coefficient keeps increasing with a corresponding rise in temperature, and thermoelectric performance can thus be enhanced with a ZT  =  0.5 at 570 K for BiTeI0.88Br0.12. PMID:26829207

  9. Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in Transition-Metal Dichalcogenides.

    PubMed

    Huang, Bing; Yoon, Mina; Sumpter, Bobby G; Wei, Su-Huai; Liu, Feng

    2015-09-18

    Developing practical approaches to effectively reduce the amount of deep defect levels in semiconductors is critical for their use in electronic and optoelectronic devices, but this still remains a very challenging task. In this Letter, we propose that specific alloying can provide an effective means to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties. Specifically, we demonstrate that for transition-metal dichalcogenides, such as MoSe_{2} and WSe_{2}, where anion vacancies are the most abundant defects that can induce deep levels, the deep levels can be effectively suppressed in Mo_{1-x}W_{x}Se_{2} alloys at low W concentrations. This surprising phenomenon is associated with the fact that the band edge energies can be substantially tuned by the global alloy concentration, whereas the defect level is controlled locally by the preferred locations of Se vacancies around W atoms. Our findings illustrate a concept of alloy engineering and provide a promising approach to control the defect properties of semiconductors.

  10. Vapor transport epitaxy: an advanced growth process for III-V and II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Gurary, Alexander; Tompa, Gary S.; Nelson, Craig R.; Stall, Richard A.; Lu, Yicheng; Liang, Shaohua

    1992-09-01

    The Vapor Transport Epitaxy (VTE) thin film deposition technique for the deposition of III - V and II - VI compound semiconductors and material results are reviewed. The motivation for development of the VTE technique is the elimination of several problems common to molecular beam epitaxy/chemical beam epitaxy and metalorganic chemical vapor deposition systems. In VTE, vapors from sources feed through throttling valves into a common manifold which is located directly below the inverted wafer. A high degree of film uniformity is achieved by controlling the flux distribution from the common manifold. The technique operates in the 10-4 - 10-6 Torr range using elemental, metalorganic or gaseous precursors. The system is configurated for 2 inch diameter wafers but the geometry may easily be scaled for larger diameters. Using elemental sources, we have demonstrated oval defect free growth of GaAs on GaAs (100) and (111) 2 degree(s) off substrates, through several microns of thickness at growth rates up to ten microns per hour. GaAs films which were grown without the manifold exhibit classic oval defects. The deposition rate of ZnSe films as a function of elemental flux, VI/II ratio, and growth temperature are described. The ZnSe films exhibited smooth surface morphologies on GaAs (100) 2 degree(s) off substrates. X- ray analysis shows that III - V and II - VI films exhibited crystallinities comparable to films produced by molecular beam epitaxy and metalorganic chemical vapor deposition techniques.

  11. Biochemical Engineering. Part II: Process Design

    ERIC Educational Resources Information Center

    Atkinson, B.

    1972-01-01

    Describes types of industrial techniques involving biochemical products, specifying the advantages and disadvantages of batch and continuous processes, and contrasting biochemical and chemical engineering. See SE 506 318 for Part I. (AL)

  12. Multi-band Bloch equations and gain spectra of highly excited II-VI semiconductor quantum wells

    SciTech Connect

    Girndt, A.; Jahnke, F.; Knorr, A.; Koch, S.W.; Chow, W.W.

    1997-04-21

    Quasi-equilibrium excitation dependent optical probe spectra of II-VI semiconductor quantum wells at room temperature are investigated within the framework of multi-band semiconductor Bloch equations. The calculations include correlation effects beyond the Hartree-Fock level which describe dephasing, interband Coulomb correlations and band-gap renormalization in second Born approximation. In addition to the carrier-Coulomb interaction, the influence of carrier-phonon scattering and inhomogeneous broadening is considered. The explicit calculation of single particle properties like band structure and dipole matrix elements using k {center_dot} p theory makes it possible to investigate various II-VI material combinations. Numerical results are presented for CdZnSe/ZnSe and CdZnSe/MnZnSSe semiconductor quantum-well systems.

  13. Characterization of convection related defects in II-VI compound semiconductors

    NASA Technical Reports Server (NTRS)

    Witt, August F.

    1993-01-01

    The research carried out under NAG8-913, 'Characterization of Convection Related Defects in II-VI Compound Semiconductors', was aimed at exploration of the potential of axial magnetic fields for melt stabilization when applied in Bridgman geometry to the growth of HgMnTe. The thrust of the work was directed at the experimental establishment of the limits of magnetic melt stabilization during crystal growth and at the analytical verification of the effects of stabilization on critical materials properties. The data obtained indicate noticeable stabilization effects, particularly as far as the formation of microscopic compositional inhomogeneities is concerned. The effects of magnetic fields on precipitate formation are found to be minor. Magnetic field effects were investigated for both 'Bridgman' and 'travelling heater' geometries. The research was conducted during the period from May 22 to September 30, 1992.

  14. Theoretical and experimental studies of stressed nanoparticles of II-VI semiconductors.

    PubMed

    Ferreira, D Lourençoni; Silva, F Oliveira; Viol, L Cristina de Souza; Licínio, P; Schiavon, M Antônio; Alves, J Luiz Aarestrup

    2010-01-01

    A theoretical and experimental study of isolated nanoparticles of II-VI semiconductor materials has been done. Using the framework of the effective mass model, the optical absorption spectrum of distributions of spherical quantum dots, freestanding, and under compressive or tensile stress, has been examined theoretically. The theoretical results allow one to foresee the absorption spectra of quantum dots made of a series of materials and having any size. The syntheses of colloidal quantum dots of CdS and CdSe has also been performed through wet chemical routes and characterized by means of optical techniques. The values of the strains in the synthesized quantum dots were inferred from a correlation established between the theoretical and the experimental results. PMID:20078149

  15. Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers

    NASA Astrophysics Data System (ADS)

    Gunnarsson, D.; Richardson-Bullock, J. S.; Prest, M. J.; Nguyen, H. Q.; Timofeev, A. V.; Shah, V. A.; Whall, T. E.; Parker, E. H. C.; Leadley, D. R.; Myronov, M.; Prunnila, M.

    2015-12-01

    The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour.

  16. Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers.

    PubMed

    Gunnarsson, D; Richardson-Bullock, J S; Prest, M J; Nguyen, H Q; Timofeev, A V; Shah, V A; Whall, T E; Parker, E H C; Leadley, D R; Myronov, M; Prunnila, M

    2015-01-01

    The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour.

  17. All-vapor processing of P-type tellurium-containing II-VI semiconductor and ohmic contacts thereof

    SciTech Connect

    McCandless, Brian E.

    2000-03-01

    An all dry method for producing solar cells is provided comprising first heat-annealing a II-VI semiconductor; enhancing the conductivity and grain size of the annealed layer; modifying the surface and depositing a tellurium layer onto the enhanced layer; and then depositing copper onto the tellurium layer so as to produce a copper tellurium compound on the layer.

  18. All-vapor processing of p-type tellurium-containing II-VI semiconductor and ohmic contacts thereof

    DOEpatents

    McCandless, Brian E.

    2001-06-26

    An all dry method for producing solar cells is provided comprising first heat-annealing a II-VI semiconductor; enhancing the conductivity and grain size of the annealed layer; modifying the surface and depositing a tellurium layer onto the enhanced layer; and then depositing copper onto the tellurium layer so as to produce a copper tellurium compound on the layer.

  19. The Effect of World War II on Women in Engineering

    NASA Astrophysics Data System (ADS)

    Barker, Anne M.

    The field of engineering has been one of the most difficult for women to enter. Even with an increase in the proportion of women in the engineering workforce from 0.3% before the 1970s to 9.5% in 1999, women are still seriously underrepresented. This article examines the history of women in engineering in the United States during World War II. Women were actively recruited as engineering aides by the federal government, which saw them as a temporary substitute for men who were in the military. Yet this crisis did not break down the barriers to and prejudices against women in engineering, nor did it give them a real opportunity to become professional engineers equal to men. After the war, calls for a return to normalcy were used to reestablish social norms, which kept women at home and reserved desirable places in the workforce, including in engineering, for men.

  20. Bulk Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    1997-01-01

    The mechanism of physical vapor transport of II-VI semiconducting compounds was studied both theoretically, using a one-dimensional diffusion model, as well as experimentally. It was found that the vapor phase stoichiometry is critical in determining the vapor transport rate. The experimental heat treatment methods to control the vapor composition over the starting materials were investigated and the effectiveness of the heat treatments was confirmed by partial pressure measurements using an optical absorption technique. The effect of residual (foreign) gas on the transport rate was also studies theoretically by the diffusion model and confirmed experimentally by the measurements of total pressure and compositions of the residual gas. An in-situ dynamic technique for the transport rate measurements and a further extension of the technique that simultaneously measured the partial pressures and transport rates were performed and, for the first time, the experimentally determined mass fluxes were compared with those calculated, without any adjustable parameters, from the diffusion model. Using the information obtained from the experimental transport rate measurements as guideline high quality bulk crystal of wide band gap II-VI semiconductor were grown from the source materials which undergone the same heat treatment methods. The grown crystals were then extensively characterized with emphasis on the analysis of the crystalline structural defects.

  1. Vibrational signatures of isotopic impurities and complexes in II-VI compound semiconductors

    NASA Astrophysics Data System (ADS)

    Talwar, Devki N.; Feng, Zhe Chuan; Yang, Tzuen-Rong

    2012-05-01

    In II-VI compound semiconductors, we have used a comprehensive Green's function theory to study the vibrational properties of isotopic defects and to ascertain the microstructure of complex centers involving dopants and intrinsic impurities. The phonons generated by a realistic lattice-dynamical model for the host materials are integrated in simulating the Green's functions to help explicate the observed localized vibrational modes (LVMs) for various defect centers. Contrary to the distinct force constants required for isolated defects, the isotopic shift of LVMs has offered strong revelations for inflexible ‘impurity-host’ interactions in each isotopic defect. In compound semiconductors a unique force variation correlation with bond covalency is proposed providing corrections to the nearest-neighbor (NN) force constants for the closest mass isoelectronic and impurities carrying static charges. The articulation is extremely useful for defining perturbations and for analyzing the infrared absorption data on LVMs of complex defect centers. In corroboration with experiments, the Green's functions theory of impurity modes in Li-doped CdTe:Al (ZnSe:Al) has established second NN LiCd(Zn)-AlCd(Zn) pairs indicating the passivation of group-I acceptors via interaction with group-III elements as donors. The proposal of an antisite complex model AlZn-ZnSe-AlZn for the X center is consistent with the existing absorption results on impurity modes and is equally justified by theoretical considerations—making it the more likely identity for the native defect compensating neighboring AlZn donors in ZnSe.

  2. Crystal engineering of dual channel p/n organic semiconductors by complementary hydrogen bonding.

    PubMed

    Black, Hayden T; Perepichka, Dmitrii F

    2014-02-17

    The supramolecular arrangement of organic semiconductors in the solid state is as critical for their device properties as the molecular structure, but is much more difficult to control. To enable supramolecular design of semiconducting materials, we introduced dipyrrolopyridine as a new donor semiconductor capable of complementary hydogen bonding with naphthalenediimide acceptors. Through a combination of solution, crystallographic, and device studies, we show that the self-assembly driven by H bonding a) modulates the charge-transfer interactions between the donor and acceptor, b) allows for precise control over the solid-state packing, and c) leads to a combination of the charge-transport properties of the individual components. The predictive power of this approach was demonstrated in the synthesis of three new coassembled materials which show both hole and electron transport in single-crystal field-effect transistors. These studies provide a foundation for advanced solid-state engineering in organic electronics, capitalizing on the complementary H bonding. PMID:24500891

  3. Room Temperature Semiconductor-Metal Transition of MoTe2 Thin Films Engineered by Strain.

    PubMed

    Song, Seunghyun; Keum, Dong Hoon; Cho, Suyeon; Perello, David; Kim, Yunseok; Lee, Young Hee

    2016-01-13

    We demonstrate a room temperature semiconductor-metal transition in thin film MoTe2 engineered by strain. Reduction of the 2H-1T' phase transition temperature of MoTe2 to room temperature was realized by introducing a tensile strain of 0.2%. The observed first-order SM transition improved conductance ∼10 000 times and was made possible by an unusually large temperature-stress coefficient, which results from a large volume change and small latent heat. The demonstrated strain-modulation of the phase transition temperature is expected to be compatible with other TMDs enabling the 2D electronics utilizing polymorphism of TMDs along with the established materials. PMID:26713902

  4. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    NASA Astrophysics Data System (ADS)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  5. Epitaxial growth and characterization of II-VI-semiconductor, one-dimensional nanostructures and thin films

    NASA Astrophysics Data System (ADS)

    Zhu, Zuoming

    In this thesis, I present the results of three material science studies on II-VI semiconductor nanostructures and thin films: (1) epitaxial growth and characterization of one-dimensional ZnO nanostructures, (2) crystal structure and self-assembly of ultrathin ZnO nanorods, and (3) investigations of surface chemistry for atomic layer epitaxy of ZnS thin film on silicon with chemical precursors. First, in Chapter 3, I present a comparative study of metal-surface-catalyzed growth of ZnO nanowires using four different metal catalysts and using substrates of differing materials and crystal orientation. Multiple material diagnostics were employed to compare the material, structural, and optical properties of the nanowires grown using these different surface systems. My study showed that the growth modes of nanowires are dependent on the choice of surface catalysts. Further, the study revealed that these differences in growth modes are also closely related to the differences in materials properties of these wires including the degree of nanowire alignment on substrates, and the atomic composition ratio of Zn/O, as well as the relative intensity of the oxygen vacancy-related emission in photoluminescence spectra. Second, in Chapter 4, I investigated the growth and self-assembly of ultrathin ZnO nanorods using a combination of small-angle and wide-angle synchrotron X-ray diffraction (SAXRD and WAXRD), and TEM. SAXRD and TEM were used to investigate nanorod self-assembly and the influence of surfactant/precursor ratio on self-assembly; WAXRD were used to study the effects of growth chemistry and physical parameters on the nanorod size and lattice constants. These measurements revealed that these rods self-assemble into periodic superstructures and that the surfactant ligands are important in controlling self-assembly. WAXRD results suggest that surface-dependent changes, such as the binding of surface ligands or other adsorbed species may dominate the changes in nanorod

  6. X-34 40K Fastrac II Engine Test

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This is a photo of an X-34 40K Fastrac II duration test performed at the Marshall Space Flight Center test stand 116 (TS116) in June 1997. Engine ignition is started with Tea-Gas which makes the start burn green. The X-34 program was cancelled in 2001.

  7. Ultrafast spin dynamics in II-VI diluted magnetic semiconductors with spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Ungar, F.; Cygorek, M.; Tamborenea, P. I.; Axt, V. M.

    2015-05-01

    We study theoretically the ultrafast spin dynamics of II-VI diluted magnetic semiconductors in the presence of spin-orbit interaction. Our goal is to explore the interplay or competition between the exchange sd coupling and the spin-orbit interaction in both bulk and quantum-well systems. For bulk materials we concentrate on Zn1 -xMnxSe and take into account the Dresselhaus interaction, while for quantum wells we examine Hg1 -x -yMnxCdyTe systems with a strong Rashba coupling. Our calculations were performed with a recently developed formalism which incorporates electronic correlations beyond mean-field theory originating from the exchange sd coupling. For both bulk and quasi-two-dimensional systems we find that, by varying the system parameters within realistic ranges, either of the two interactions can be chosen to play a dominant role or they can compete on an equal footing with each other. The most notable effect of the spin-orbit interaction in both types of system is the appearance of strong oscillations where the exchange sd coupling by itself causes only an exponential decay of the mean electronic spin components. The mean-field approximation is also studied and an analytical interpretation is given as to why it shows a strong suppression of the spin-orbit-induced dephasing of the spin component parallel to the Mn magnetic field.

  8. Temperature Dependence of Density, Viscosity and Electrical Conductivity for Hg-Based II-VI Semiconductor Melts

    NASA Technical Reports Server (NTRS)

    Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The relaxation phenomenon of semiconductor melts, or the change of melt structure with time, impacts the crystal growth process and the eventual quality of the crystal. The thermophysical properties of the melt are good indicators of such changes in melt structure. Also, thermophysical properties are essential to the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the Hg-based II-VI semiconductor melts are scarce. This paper reports the results on the temperature dependence of melt density, viscosity and electrical conductivity of Hg-based II-VI compounds. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. Results were compared with available published data and showed good agreement. The implication of the structural changes at different temperature ranges was also studied and discussed.

  9. Band structure engineering of semiconductors for enhanced photoelectrochemical water splitting: The case of TiO2

    NASA Astrophysics Data System (ADS)

    Yin, Wan-Jian; Tang, Houwen; Wei, Su-Huai; Al-Jassim, Mowafak M.; Turner, John; Yan, Yanfa

    2010-07-01

    Here, we propose general strategies for the rational design of semiconductors to simultaneously meet all of the requirements for a high-efficiency, solar-driven photoelectrochemical (PEC) water-splitting device. As a case study, we apply our strategies for engineering the popular semiconductor, anatase TiO2 . Previous attempts to modify known semiconductors such as TiO2 have often focused on a particular individual criterion such as band gap, neglecting the possible detrimental consequence to other important criteria. Density-functional theory calculations reveal that with appropriate donor-acceptor coincorporation alloys with anatase TiO2 hold great potential to satisfy all of the criteria for a viable PEC device. We predict that (Mo, 2N) and (W, 2N) are the best donor-acceptor combinations in the low-alloy concentration regime whereas (Nb, N) and (Ta, N) are the best choice of donor-acceptor pairs in the high-alloy concentration regime.

  10. Multinary I-III-VI2 and I2-II-IV-VI4 Semiconductor Nanostructures for Photocatalytic Applications.

    PubMed

    Regulacio, Michelle D; Han, Ming-Yong

    2016-03-15

    are the multinary chalcogenide semiconductors (MCSs), which include the ternary I-III-VI2 semiconductors (e.g., AgGaS2, CuInS2, and CuInSe2) and the quaternary I2-II-IV-VI4 semiconductors (e.g., Cu2ZnGeS4, Cu2ZnSnS4, and Ag2ZnSnS4). These inorganic compounds consist of environmentally benign elemental components, exhibit excellent light-harvesting properties, and possess band gap energies that are well-suited for solar photon absorption. Moreover, the band structures of these materials can be conveniently modified through alloying to boost their ability to harvest visible photons. In this Account, we provide a summary of recent research on the use of ternary I-III-VI2 and quaternary I2-II-IV-VI4 semiconductor nanostructures for light-induced photocatalytic applications, with focus on hydrogen production and organic dye degradation. We include a review of the solution-based methods that have been employed to prepare multinary chalcogenide semiconductor nanostructures of varying compositions, sizes, shapes, and crystal structures, which are factors that are known to have significant influence on the photocatalytic activity of semiconductor photocatalysts. The enhancement of photocatalytic performance through creation of hybrid nanoscale architectures is also presented. Lastly, views on the current challenges and future directions are discussed in the concluding section. PMID:26864703

  11. Multinary I-III-VI2 and I2-II-IV-VI4 Semiconductor Nanostructures for Photocatalytic Applications.

    PubMed

    Regulacio, Michelle D; Han, Ming-Yong

    2016-03-15

    are the multinary chalcogenide semiconductors (MCSs), which include the ternary I-III-VI2 semiconductors (e.g., AgGaS2, CuInS2, and CuInSe2) and the quaternary I2-II-IV-VI4 semiconductors (e.g., Cu2ZnGeS4, Cu2ZnSnS4, and Ag2ZnSnS4). These inorganic compounds consist of environmentally benign elemental components, exhibit excellent light-harvesting properties, and possess band gap energies that are well-suited for solar photon absorption. Moreover, the band structures of these materials can be conveniently modified through alloying to boost their ability to harvest visible photons. In this Account, we provide a summary of recent research on the use of ternary I-III-VI2 and quaternary I2-II-IV-VI4 semiconductor nanostructures for light-induced photocatalytic applications, with focus on hydrogen production and organic dye degradation. We include a review of the solution-based methods that have been employed to prepare multinary chalcogenide semiconductor nanostructures of varying compositions, sizes, shapes, and crystal structures, which are factors that are known to have significant influence on the photocatalytic activity of semiconductor photocatalysts. The enhancement of photocatalytic performance through creation of hybrid nanoscale architectures is also presented. Lastly, views on the current challenges and future directions are discussed in the concluding section.

  12. Exposure assessment and risk management of engineered nanoparticles: Investigation in semiconductor wafer processing

    NASA Astrophysics Data System (ADS)

    Shepard, Michele N.

    Engineered nanomaterials (ENMs) are currently used in hundreds of commercial products and industrial processes, with more applications being investigated. Nanomaterials have unique properties that differ from bulk materials. While these properties may enable technological advancements, the potential risks of ENMs to people and the environment are not yet fully understood. Certain low solubility nanoparticles are more toxic than their bulk material, such that existing occupational exposure limits may not be sufficiently protective for workers. Risk assessments are currently challenging due to gaps in data on the numerous emerging materials and applications as well as method uncertainties and limitations. Chemical mechanical planarization (CMP) processes with engineered nanoparticle abrasives are used for research and commercial manufacturing applications in the semiconductor and related industries. Despite growing use, no published studies addressed occupational exposures to nanoparticles associated with CMP or risk assessment and management practices for these scenarios. Additional studies are needed to evaluate potential sources of workplace exposure or emission, as well as to help test and refine assessment methods. This research was conducted to: identify the lifecycle stages and potential exposure sources for ENMs in CMP processes; characterize worker exposure; determine recommended engineering controls and compare risk assessment models. The study included workplace air and surface sampling and an evaluation of qualitative risk banding approaches. Exposure assessment results indicated the potential for worker contact with ENMs on workplace surfaces but did not identify nanoparticles readily dispersed in air during work tasks. Some increases in respirable particle concentrations were identified, but not consistently. Measured aerosol concentrations by number and mass were well below current reference values for poorly soluble low toxicity nanoparticles. From

  13. Defect chemistry and defect engineering of TiO2-based semiconductors for solar energy conversion.

    PubMed

    Nowotny, Janusz; Alim, Mohammad Abdul; Bak, Tadeusz; Idris, Mohammad Asri; Ionescu, Mihail; Prince, Kathryn; Sahdan, Mohd Zainizan; Sopian, Kamaruzzaman; Mat Teridi, Mohd Asri; Sigmund, Wolfgang

    2015-12-01

    This tutorial review considers defect chemistry of TiO2 and its solid solutions as well as defect-related properties associated with solar-to-chemical energy conversion, such as Fermi level, bandgap, charge transport and surface active sites. Defect disorder is discussed in terms of defect reactions and the related charge compensation. Defect equilibria are used in derivation of defect diagrams showing the effect of oxygen activity and temperature on the concentration of both ionic and electronic defects. These defect diagrams may be used for imposition of desired semiconducting properties that are needed to maximize the performance of TiO2-based photoelectrodes for the generation of solar hydrogen fuel using photo electrochemical cells (PECs) and photocatalysts for water purification. The performance of the TiO2-based semiconductors is considered in terms of the key performance-related properties (KPPs) that are defect related. It is shown that defect engineering may be applied for optimization of the KPPs in order to achieve optimum performance. PMID:26446476

  14. Fabrication and characterization of II-VI semiconductor nanoparticles decorated electrospun polyacrylonitrile nanofibers.

    PubMed

    Nirmala, R; Jeon, Kyungsoo; Navamathavan, R; Kim, Byoung-Suhk; Khil, Myung-Seob; Kim, Hak Yong

    2013-05-01

    Semiconductor nanoparticles incorporated highly aligned electrospun polyacrylonitrile (PAN) composite nanofibers were obtained via a simple, scalable and low-cost dip coating technique at room temperature. The resultant PAN nanofibers exhibited good incorporation of CdS, ZnS and CoS semiconductor nanoparticles. The detailed characterizations of these composite nanofibers were investigated. The incorporation of semiconductor nanoparticles on the surfaces of PAN nanofibers were confirmed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction analysis. The current-voltage (I-V) characteristics revealed that the electrical conductivity of these composite nanofibers were higher than that of the pristine PAN nanofibers. Overall, the feasibility of obtaining uniformly dispersed semiconductor nanoparticles on PAN nanofibers can be utilized for the realization of various nanotechnological device applications. PMID:23453708

  15. Evolving biomolecular control and peptide specificity for the synthesis and assembly of II-VI semiconductor nanomaterials

    NASA Astrophysics Data System (ADS)

    Flynn, Christine Elizabeth

    Peptides were selected using an evolutionary screening process utilizing engineered virus libraries to isolated peptides that recognized, nucleated and controlled II-VI semiconductor materials. Specifically, materials screened for this project included polycrystalline and single crystal surfaces of ZnS, CdS, PbS, and ZnSe. Once a positive peptide recognition sequence was isolated using phage display screening, the population of peptides found for ZnS or CdS were successfully tested to decipher relative binding affinities, results that further verified the consensus motifs identified. The peptides selected were then used to nucleate nanocrystals, specifically controlling nanoparticle sizes and directing crystal phases of ZnS and CdS. The ZnS-specific A7 and Z8 peptides were isolated from virus screenings of ZnS and tested for ZnS nucleation ability. Upon HRTEM analysis of the resultant nanocrystals, two different phases of ZnS were grown in the presence of A7 and Z8. A7 directed the wurtzite structure crystal phase of ZnS while Z8 directed the sphalerite crystal phase of ZnS. Two CdS-specific peptides, J140 and J182, were isolated from virus screenings of CdS and were further tested, not only for their CdS recognition ability, but for their CdS nucleating ability. Upon HRTEM analysis of the resultant nanocrystals, two different phases of CdS were grown in the presence of J140 and J182, a trend parallel to that seen with ZnS specific phage grown nanocrystals. J140 directed the wurtzite structure crystal phase while J182 directed the zinc blende crystal phase. Further, orientation of the materials using display of the specific peptides as fusions on the viral protein coat indicated that relative order of nanocrystals over several hundred nanometers could be achieved, while maintaining the crystal phase and size selectivity that was seen on the smaller scale.

  16. Ground-based research of crystal growth of II-VI compound semiconductors by physical vapor transport

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Gillies, D. C.; Szofran, F. R.; Lehoczky, S. L.; Su, Ching-Hua; Sha, Yi-Gao; Zhou, W.; Dudley, M.; Liu, Hao-Chieh; Brebrick, R. F.; Wang, J. C.

    1994-01-01

    Ground-based investigation of the crystal growth of II-VI semiconductor compounds, including CdTe, CdS, ZnTe, and ZnSe, by physical vapor transport in closed ampoules was performed. The crystal growth experimental process and supporting activities--preparation and heat treatment of starting materials, vapor partial pressure measurements, and transport rate measurements are reported. The results of crystal characterization, including microscopy, microstructure, optical transmission photoluminescence, synchrotron radiation topography, and chemical analysis by spark source mass spectrography, are also discussed.

  17. Three-Dimensional Topological Insulators in I-III-VI2 and II-IV-V2 Chalcopyrite Semiconductors

    SciTech Connect

    Feng, wanxiang; Ding, Jun; Yao, yugui

    2011-01-01

    The recent discovery of topological insulators with exotic metallic surface states has garnered great interest in the fields of condensed matter physics and materials science.1 A number of spectacular quantum phenomena have been predicted when the surface states are under the influence of magnetism and superconductivity,2 5 which could open up new opportunities for technological applications in spintronics and quantum computing. To achieve this goal, material realization of topological insulators with desired physical properties is of crucial importance. Based on first-principles calculations, here we show that a large number of ternary chalcopyrite compounds of composition I-III-VI2 and II-IV-V2 can realize the topological insulating phase in their native states. The crystal structure of chalcopyrites is derived from the frequently used zinc-blende structure, and many of them possess a close lattice match to important mainstream semiconductors, which is essential for a smooth integration into current semiconductor technology. The diverse optical, electrical and structural properties of chalcopyrite semiconductors,6 and particularly their ability to host room-temperature ferromagnetism,7 9 make them appealing candidates for novel spintronic devices.

  18. Quantum spintronics: engineering and manipulating atom-like spins in semiconductors.

    PubMed

    Awschalom, David D; Bassett, Lee C; Dzurak, Andrew S; Hu, Evelyn L; Petta, Jason R

    2013-03-01

    The past decade has seen remarkable progress in isolating and controlling quantum coherence using charges and spins in semiconductors. Quantum control has been established at room temperature, and electron spin coherence times now exceed several seconds, a nine-order-of-magnitude increase in coherence compared with the first semiconductor qubits. These coherence times rival those traditionally found only in atomic systems, ushering in a new era of ultracoherent spintronics. We review recent advances in quantum measurements, coherent control, and the generation of entangled states and describe some of the challenges that remain for processing quantum information with spins in semiconductors.

  19. Biosphere II: engineering of manned, closed ecological systems.

    PubMed

    Dempster, W F

    1991-01-01

    Space Biospheres and Ventures, a private, for-profit firm, has undertaken a major research and development project in the study of biospheres, with the objective of creating and producing biospheres. Biosphere II-scheduled for completion in March 1991-will be essentially isolated from the existing biosphere by a closed structure, composed of components derived from the existing biosphere. Like the biosphere of the Earth, Biosphere II will be essentially closed to exchanges of material or living organisms with the surrounding environment and open to energy and information exchanges. Also, like the biosphere of the Earth, Biosphere II will contain five kingdoms of life, a variety of ecosystems, plus humankind, culture, and technics. The system is designed to be complex, stable and evolving throughout its intended 100-year lifespan, rather than static. Biosphere II will cover approximately 1.3 hectare and contain 200,000 m3 in volume, with seven major biomes: tropical rainforest, tropical savannah, marsh, marine, desert, intensive agriculture, and human habitat. An interdisciplinary team of leading scientific, ecological, management, architectural, and engineering consultants have been contracted by Space Biospheres Ventures for the project. Potential applications for biospheric systems include scientific and ecological management research, refuges for endangered species, and life habitats for manned stations on spacecraft or other planets.

  20. Thermophysical analysis of II-VI semiconductors by PPE calorimetry and lock-in thermography

    SciTech Connect

    Streza, M.; Dadarlat, D.; Strzałkowski, K.

    2013-11-13

    An accurate determination of thermophysical properties such as thermal diffusivity, thermal effusivity and thermal conductivity is extremely important for characterization and quality assurance of semiconductors. Thermal diffusivity and effusivity of some binary semiconductors have been investigated. Two experimental techniques were used: a contact technique (PPE calorimetry) and a non contact technique (lock-in thermography). When working with PPE, in the back (BPPE) configuration and in the thermally thick regim of the pyroelectric sensor, we can get the thermal diffusivity of the sample by performing a scanning of the excitation frequency of radiation. Thermal effusivity is obtained in front configuration (sensor directly irradiated and sample in back position) by performing a thickness scan of a coupling fluid. By using the lock-in thermography technique, the thermal diffusivity of the sample is obtained from the phase image. The results obtained by the two techniques are in good agreement. Nevertheless, for the determination of thermal diffusivity, lock-in thermography is preferred.

  1. Cobalt (II) oxide and nickel (II) oxide alloys as potential intermediate-band semiconductors: A theoretical study

    NASA Astrophysics Data System (ADS)

    Alidoust, Nima; Lessio, Martina; Carter, Emily A.

    2016-01-01

    Solar cells based on single pn junctions, employing single-gap semiconductors can ideally achieve efficiencies as high as 34%. Developing solar cells based on intermediate-band semiconductors (IBSCs), which can absorb light across multiple band gaps, is a possible way to defy this theoretical limit and achieve efficiencies as high as 60%. Here, we use first principles quantum mechanics methods and introduce CoO and Co0.25Ni0.75O as possible IBSCs. We show that the conduction band in both of these materials is divided into two distinct bands separated by a band gap. We further show that the lower conduction band (i.e., the intermediate band) is wider in Co0.25Ni0.75O compared with CoO. This should enhance light absorption from the valence band edge to the intermediate band, making Co0.25Ni0.75O more appropriate for use as an IBSC. Our findings provide the basis for future attempts to partially populate the intermediate band and to reduce the lower band gap in Co0.25Ni0.75O in order to enhance the potential of this material for use in IBSC solar cell technologies. Furthermore, with proper identification of heterojunctions and dopants, CoO and Co0.25Ni0.75O could be used in multi-color light emitting diode and laser technologies.

  2. Alloy Engineering of Defect Properties in Semiconductors: Suppression of Deep Levels in 2D Transition-metal Dichalcogenides

    DOE PAGES

    Huang, Bing; Yoon, Mina; Sumpter, Bobby G; Wei, Su-Huai; Liu, Feng

    2015-09-18

    Developing practical approaches to effectively reduce the deep defect levels in semiconductors is critical for their use in electronic and optoelectronic devices, but this is still a very challenging task. In this Letter, we propose that specific alloying can provide an effective means to suppress the deep defect levels in semiconductors while maintaining their basic electronic properties. Specifically, we demonstrate that for such 2D transition-metal dichalcogenides as MoSe2 and WSe2, in which the most abundant defects that can induce deep levels are anion vacancies, the deep levels can be effectively suppressed in Mo1-xWxSe2 alloys at low W concentrations. This surprisingmore » phenomenon is associated with the fact that the global alloy concentration can substantially tune the band edge energies, whereas the preferred locations of Se vacancies around W atoms control the defect level locally. Our findings illustrate a new concept of alloy engineering and provide a promising approach to control the defect properties of semiconductors.« less

  3. Self-Interaction Corrections to the Electronic Structure of II-VI and III-V Nitride Semiconductors

    NASA Astrophysics Data System (ADS)

    Pollmann, J.

    1998-03-01

    II-VI and group-III nitride semiconductors have paramount technological potential for applications in micro- and optoelectronics. A most accurate description of their bulk electronic structure as a basis for studying defect properties, band-edge properties in respective ternary or quaternary alloys and electronic properties of their surfaces and interfaces is of major importance, therefore. Standard LDA band-structure calculations for these wide-band-gap compounds using nonlocal normconserving pseudopotentials yield gap energies and semicore d-band positions that are largely at variance with experimental data. Actually, InN even turns out to be a semimetal with a negative gap of about --0.4 eV in standard LDA, in contrast to the experimental gap of 1.9 eV. To improve the theoretical basis for the above mentioned studies, we have developed self-interaction- and relaxation-corrected pseudopotentials (SIRC-PPs) which are very efficient and physically well-founded. The properties of the constituent atoms are incorporated in these SIRC-PPs as accurately as possible from the start by taking atomic SIC contributions and electronic relaxation in the atoms fully into account. By this construction, we arrive at very useful pseudopotentials and effective one-particle Hamiltonians for the solids that can readily be employed in ab-initio LDA codes. This approach is computationally not more involved than any LDA calculation and, nevertheless, overcomes to a large extent the above mentioned shortcomings of standard LDA calculations employing 'state-of-the-art' pseudopotentials. Applications of our approach to II-VI and group-III nitride semiconductors have shown very gratifying results. The approach has also proven very useful for Hg-chalcogenides, as well as, for Ag- and Cu-halides. The calculations yield band structures, d-band positions, gap energies, densities of states, lattice constants, bulk moduli and effective masses in very good agreement with experiment. Due to the

  4. Photoinduced electron donor/acceptor processes in colloidal II-VI semiconductor quantum dots and nitroxide free radicals

    NASA Astrophysics Data System (ADS)

    Dutta, Poulami

    Electron transfer (ET) processes are one of the most researched topics for applications ranging from energy conversion to catalysis. An exciting variation is utilizing colloidal semiconductor nanostructures to explore such processes. Semiconductor quantum dots (QDs) are emerging as a novel class of light harvesting, emitting and charge-separation materials for applications such as solar energy conversion. Detailed knowledge of the quantitative dissociation of the photogenerated excitons and the interfacial charge- (electron/hole) transfer is essential for optimization of the overall efficiency of many such applications. Organic free radicals are the attractive counterparts for studying ET to/from QDs because these undergo single-electron transfer steps in reversible fashion. Nitroxides are an exciting class of stable organic free radicals, which have recently been demonstrated to be efficient as redox mediators in dye-sensitized solar cells, making them even more interesting for the aforementioned studies. This dissertation investigates the interaction between nitroxide free radicals TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), 4-amino-TEMPO (4-amino- 2,2,6,6-tetramethylpiperidine-1-oxyl) and II-VI semiconductor (CdSe and CdTe) QDs. The nature of interaction in these hybrids has been examined through ground-state UV-Vis absorbance, steady state and time-resolved photoluminescence (PL) spectroscopy, transient absorbance, upconversion photoluminescence spectroscopy and electron paramagnetic resonance (EPR). The detailed analysis of the PL quenching indicates that the intrinsic charge transfer is ultrafast however, the overall quenching is still limited by the lower binding capacities and slower diffusion related kinetics. Careful analysis of the time resolved PL decay kinetics reveal that the decay rate constants are distributed and that the trap states are involved in the overall quenching process. The ultrafast hole transfer from CdSe QDs to 4-Amino TEMPO observed

  5. Selection of stirling engine parameter and modes of joint operation with the Topaz II

    SciTech Connect

    Kirillov, E.Y.; Ogloblin, B.G.; Shalaev, A.I.

    1996-03-01

    In addition to a high-temperature thermionic conversion cycle, application of a low-temperature machine cycle, such as the Stirling engine, is being considered. To select the optimum mode for joint operation of the Topaz II system and Stirling engine, output electric parameters are obtained as a function of thermal power released in the TFE fuel cores. The hydraulic diagram used for joint operation of the Topaz II and the Stirling engine is considered. Requirements to hydraulic characteristics of the Stirling engine heat exchanges are formulated. Scope of necessary modifications to mount the Stirling Engine on the Topaz II is estimated. {copyright} {ital 1996 American Institute of Physics.}

  6. Application of the transition semiconductor to semimetal in type II nanostructure superlattice for mid-infrared optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Boutramine, Abderrazak; Nafidi, Abdelhakim; Barkissy, Driss; Hannour, Abdelkrim; Elanique, Abdellatif; Gouti, Thami El

    2016-04-01

    The present work is devoted to the study of band structure and band gap in symmetric InAs (d 1 = 25 Å)/GaSb (d 2 = 25 Å) type II superlattice. Our calculations were performed in the envelope function formalism with the valence band offset Λ = 570 meV. We discussed the semiconductor to semimetal transition and the evolutions of the fundamental band gap, E g (Γ), as a function of d 1, Λ and the temperature. This study suggests that a wide range of wavelength can be reached by adjusting d 1. In addition, E g (Γ, T) decreases from 288.7 to 230 meV in the range of 4.2-300 K, corresponding to the cutoff wavelength ranging from 4.3 to 5.4 µm. These latter results explain the recent experimental ones realized by C. Cervera et al. for our Λ = 588 meV.

  7. Superdiffusive heat conduction in semiconductor alloys. II. Truncated Lévy formalism for experimental analysis

    NASA Astrophysics Data System (ADS)

    Vermeersch, Bjorn; Mohammed, Amr M. S.; Pernot, Gilles; Koh, Yee Rui; Shakouri, Ali

    2015-02-01

    Nearly all experimental observations of quasiballistic heat flow are interpreted using Fourier theory with modified thermal conductivity. Detailed Boltzmann transport equation (BTE) analysis, however, reveals that the quasi-ballistic motion of thermal energy in semiconductor alloys is no longer Brownian but instead exhibits Lévy dynamics with fractal dimension α <2 . Here, we present a framework that enables full three-dimensional experimental analysis by retaining all essential physics of the quasiballistic BTE dynamics phenomenologically. A stochastic process with just two fitting parameters describes the transition from pure Lévy superdiffusion as short length and time scales to regular Fourier diffusion. The model provides accurate fits to time domain thermoreflectance raw experimental data over the full modulation frequency range without requiring any "effective" thermal parameters and without any a priori knowledge of microscopic phonon scattering mechanisms. Identified α values for InGaAs and SiGe match ab initio BTE predictions within a few percent. Our results provide experimental evidence of fractal Lévy heat conduction in semiconductor alloys. The formalism additionally indicates that the transient temperature inside the material differs significantly from Fourier theory and can lead to improved thermal characterization of nanoscale devices and material interfaces.

  8. Design of I2-II-IV-VI4 Semiconductors through Element-substitution: the Thermodynamic Stability Limit and Chemical Trend

    NASA Astrophysics Data System (ADS)

    Chen, Shiyou; Wang, Congcong; Xiang, Hongjun; Gong, Xin-Gao; Walsh, Aron; Wei, Su-Huai

    2015-03-01

    Through element substitution in kesterite Cu2ZnSnS4orCu2ZnSnSe4, a class of I2-II-IV-VI4 semiconductors can be designed as novel functional materials. Using the first-principles calculations, we show that this element-substitution design is thermodynamically limited, i.e., although I2-II-IV-VI4 with I =Cu, Ag, II =Zn, Cd, Hg, IV =Si, Ge, Sn and VI =S, Se, Te are stable quaternary compounds, those with II =Mg, Ca, Sr, Ba, IV =Ti, Zr, Hf, and VI =O are unstable against the phase-separation into the competing binary and ternary compounds. Three main phase-separation pathways are revealed. In general, we show that if the secondary II-VI or I2-IV-VI3 phases prefer to have non-tetrahedral structures, then the I2-II-IV-VI4 semiconductors tend to phase separate. This finding can be used as a guideline for future design of new quaternary semiconductors.

  9. Chemistry and the Internal Combustion Engine II: Pollution Problems.

    ERIC Educational Resources Information Center

    Hunt, C. B.

    1979-01-01

    Discusses pollution problems which arise from the use of internal combustion (IC) engines in the United Kingdom (UK). The IC engine exhaust emissions, controlling IC engine pollution in the UK, and some future developments are also included. (HM)

  10. Hetero-engineering infrared detectors with type-II superlattices

    NASA Astrophysics Data System (ADS)

    Tian, Z.-B.; DeCuir, E. A.; Gautam, N.; Krishna, S.; Wijewarnasuriya, P. S.; Pattison, J. W.; Dhar, N.; Welser, R. E.; Sood, A. K.

    2013-09-01

    InAs/GaSb type-II superlattices (T2-SLs) are of great interest as they provide a lot of band engineering flexibility. A wide variety of unipolar barrier structures have been investigated with this material system. In this report, we will present our recent work on the development of low noise long-wave infrared (LWIR) InAs/GaSb T2-SLs photodetectors. By adopting a so-called pBiBn design, the dark current of LWIR photodetectors is greatly suppressed. The LWIR pBiBn device has demonstrated a dark current density as low as 1.42×10-5 A/cm2 at -60 mV, and R0A of 5365 Ωcm2 at 76 K. A peak detectivity at 7.8 μm of 7.7×1011 cmHz1/2W-1 is obtained at 76 K. Further effort to reduce the operating bias is also reported. By refining the energy-band alignment, a 2-μm-thick LWIR pBiBn device has demonstrated a single pass (no AR coating) quantum efficiency of 20% at 10 μm under zero-bias at 77 K. We have recently extended our efforts to further reduce the dark current by using an interband cascade (IC) photodetector structure. Some further details about the device operation and results will be discussed.

  11. Learning Activity Packets for Auto Mechanics II. Section A--Engine Rebuilding.

    ERIC Educational Resources Information Center

    Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    Eight learning activity packets (LAPs) are provided for the instructional area of engine rebuilding in the auto mechanics II program. They accompany an instructor's guide available separately. The LAPs outline the study activities and performance tasks for these eight units: (1) engine condition evaluation; (2) engine removal; (3) engine…

  12. Advances in graphene-based semiconductor photocatalysts for solar energy conversion: fundamentals and materials engineering.

    PubMed

    Xie, Xiuqiang; Kretschmer, Katja; Wang, Guoxiu

    2015-08-28

    Graphene-based semiconductor photocatalysis has been regarded as a promising technology for solar energy storage and conversion. In this review, we summarized recent developments of graphene-based photocatalysts, including preparation of graphene-based photocatalysts, typical key advances in the understanding of graphene functions for photocatalytic activity enhancement and methodologies to regulate the electron transfer efficiency in graphene-based composite photocatalysts, by which we hope to offer enriched information to harvest the utmost fascinating properties of graphene as a platform to construct efficient graphene-based composite photocatalysts for solar-to-energy conversion.

  13. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors

    NASA Astrophysics Data System (ADS)

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-06-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 107 A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38-65 μA) and response speed (40-60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications.

  14. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors.

    PubMed

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-01-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 10(7) A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38-65 μA) and response speed (40-60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications. PMID:27349692

  15. Luminescence properties of II/VI semiconductor colloidal nanocrystals at collective and single scales

    NASA Astrophysics Data System (ADS)

    Vion, Céline; Barthou, Carlos; Coolen, Laurent; Bennaloul, Paul; Chinh, Vu Duc; Thuy Linh, Pham; Thi Bich, Vu; Thu Nga, Pham; Maître, Agnès

    2009-09-01

    Colloidal nanocrystals are crystalline spheres of semiconductors of a few nanometers, obtained by chemical synthesis. At this size scale, lower than Bohr radius of the exciton, emission properties are dominated by quantum confinement effects and depend crucially on the nanocrystal radius, which can be controlled by adjusting the synthesis parameters. Nanocrystals present high photostability and good quantum efficiency, even at room temperature. Their emission wavelength can be tuned over the whole visible range, making them very attractive solid state light sources which are already used in optoelectronic devices or for biological labeling. The luminescence properties of CdSe colloidal nanocrystals synthesized at the Institute of Materials Science in Hanoi are presented. At collective scale, the emission properties reveal the synthesis quality. Temperature effects from ambient to 4 K on spectra and decay rates will be presented and analyzed in terms of emitting level fine structure. The study of CdSe colloidal quantum dots at the single emitter scale is of great interest as it reveals properties which are hidden by collective studies, such as luminescence "blinking", a random switching from a fluorescent to a non fluorescent state, which is closely related to the crystalline defects of a nanocrystal and its interaction with its environment. We will present the blinking properties of the prepared nanocrystals, and relate them to the nanocrystals synthesis quality and shell quality.

  16. High Resolution Triple Axis X-Ray Diffraction Analysis of II-VI Semiconductor Crystals

    NASA Technical Reports Server (NTRS)

    Volz, H. M.; Matyi, R. J.

    1999-01-01

    The objective of this research program is to develop methods of structural analysis based on high resolution triple axis X-ray diffractometry (HRTXD) and to carry out detailed studies of defect distributions in crystals grown in both microgravity and ground-based environments. HRTXD represents a modification of the widely used double axis X-ray rocking curve method for the characterization of grown-in defects in nearly perfect crystals. In a double axis rocking curve experiment, the sample is illuminated by a monochromatic X-ray beam and the diffracted intensity is recorded by a fixed, wide-open detector. The intensity diffracted by the sample is then monitored as the sample is rotated through the Bragg reflection condition. The breadth of the peak, which is often reported as the full angular width at half the maximum intensity (FWHM), is used as an indicator of the amount of defects in the sample. This work has shown that high resolution triple axis X-ray diffraction is an effective tool for characterizing the defect structure in semiconductor crystals, particularly at high defect densities. Additionally, the technique is complimentary to X-ray topography for defect characterization in crystals.

  17. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors

    PubMed Central

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-01-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 107 A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38–65 μA) and response speed (40–60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications. PMID:27349692

  18. 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.

  19. 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.

  20. 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

  1. Prediction of reduced thermal conductivity in nano-engineered rough semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Martin, Pierre N.; Aksamija, Zlatan; Pop, Eric; Ravaioli, Umberto

    2009-11-01

    We explore phonon decay processes necessary to the design of efficient rough semiconductor nanowire (NW) thermoelectric devices. A novel approach to surface roughness-limited thermal conductivity of Si, Ge, and GaAs NW with diameter D < 500 nm is presented. In particular, a frequency-dependent phonon scattering rate is computed from perturbation theory and related to a description of the surface through the root-mean-square roughness height Δ and autocovariance length L. Using a full phonon dispersion relation, the thermal conductivity varies quadratically with diameter and roughness as (D/Δ)2. Computed results are in agreement with experimental data, and predict remarkably low thermal conductivity below 1 W/m/K in rough-etched 56 nm Ge and GaAs NW at room temperature.

  2. Synthesis, functionalization, and biological tagging applications of II-VI semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Jun

    Fluorescent labeling of biological molecules is a technique that is used widely for analytical purposes in biotechnology and bioengineering. It typically involves the use of an organic dye molecule linked to a moiety that selectively bonds a particular biological molecule, allowing the detection of the latter by the fluorescence of the dye molecule. Semiconductor nanocrystals or quantum dots have emerged as a new class of fluorescent markers with distinct advantages over the traditional organic dyes. Their attractive properties include narrow, symmetric, and bright emission, continuous excitation by any wavelength smaller than the emission wavelength, broad absorption spectrum, long lifetime, resistance to photobleaching, as well as excellent optical and chemical stability that allows their use in lengthy experiments. The focus of this thesis is the synthesis and surface functionalization of ZnSe quantum dots and (ZnSe)ZnS core-shell nanostructures, and their biological conjugation with DNA and protein. The ability to synthesize different populations of quantum dots with narrow emission spectra permits multiplexing, a property that is very important for simultaneous detection of several analytes, which would be very tedious and expensive if done sequentially. Highly luminescent ZnSe nanocrystals have been synthesized using a hot-injection colloidal method. The synthesis was performed in a stirred batch reactor containing liquid hexadecylamine at 310°C. The precursors were diethylzinc diluted in heptane and selenium powder mixed with trioctylphosphine. The mixture of reactants was injected into the batch reactor and the time of reaction was used to control the size and luminescence emission wavelength of the quantum dots. In order to optimize the process various parameters that can influence the photoluminescence property of quantum dots obtained were investigated, such as surfactant addition, temperature, precursor ratio, and mixing conditions. Capping of the Zn

  3. Turnable Semiconductor Laser Spectroscopy in Hollow Optical Waveguides, Phase II SBIR

    SciTech Connect

    Gregory J. Fetzer, Ph.D.

    2001-12-24

    In this study a novel optical trace gas sensor based on a perforated hollow waveguide (PHW) was proposed. The sensor has been given the acronym ESHOW for Environmental Sensor using Hollow Optical Waveguides. Realizations of the sensor have demonstrated rapid response time (<2s), low minimum detection limits (typically around 3 x 10-5 absorbance). Operation of the PHW technology has been demonstrated in the near-infrared (NIR) and mid0infrared (MIR) regions of the spectrum. Simulation of sensor performance provided in depth understanding of the signals and signal processing required to provide high sensitivity yet retain rapid response to gas changes. A dedicated sensor electronics and software foundation were developed during the course of the Phase II effort. Commercial applications of the sensor are ambient air and continuous emissions monitoring, industrial process control and hazardous waste site monitoring. There are numerous other applications for such a sensor including medical diagnosis and treatment, breath analysis for legal purposes, water quality assessment, combustion diagnostics, and chemical process control. The successful completion of Phase II resulted in additional funding of instrument development by the Nations Institute of Heath through a Phase I SBIR grant and a strategic teaming relationship with a commercial manufacture of medical instrumentation. The purpose of the NIH grant and teaming relationship is to further develop the sensor to monitor NO in exhaled breath for the purposes of asthma diagnosis.

  4. Materials and device design with III-V and II-VI compound-based diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Katayama-Yoshida, Hiroshi; Sato, Kazunori

    2002-03-01

    Since the discovery of the carrier induced ferromagnetism in (In, Mn)As and (Ga, Mn)As, diluted magnetic semiconductors (DMS) have been of much interest from the industrial viewpoint because of their potentiality as a new functional material (spintronics). In this paper, the magnetism in DMS is investigated based on the first principles calculations, and materials and device design with the DMS is proposed toward the spintronics. The electronic structure is calculated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation based on the local spin density approximation. We calculate the electronic structure of ferromagnetic and spin-glass DMS, and total energy difference between them is calculated to estimate whether the ferromagnetic state is stable or not. It is shown that V-, Cr- and Mn-doped III-V compounds, V- and Cr-doped II-VI compounds and Fe-, Co- and Ni-doped ZnO are promising candidates for a high-Curie temperature ferromagnet. A chemical trend in the ferromagnetism is well understood based on the double exchange mechanism [1]. Based upon this material design, some prototypes of the spintronics devices, such as a spin-FET, a photo-induced-magnetic memory and a coherent-spin-infection device, are proposed. [1] K. Sato and H. Katayama-Yoshida, Jpn. J. Appl. Phys. 39 (2000) L555, 40 (2001) L334, L485 and L651.

  5. Small Engines Care, Operation, Maintenance and Repair. Volume II.

    ERIC Educational Resources Information Center

    Turner, J. Howard

    Developed by teacher educators and agricultural engineers, this teacher and student reference is for use in a course in small engine operation and maintenance. Content includes: (1) Principles of Good Workmanship, (2) Repairing Starters, (3) Maintaining and Repairing Ignition Systems, (4) Repairing Fuel Systems, (5) Repairing Governors, (6)…

  6. Electrochemical photovoltaic cells stabilization and optimization of II-VI semiconductors. Third technical progress report, 1 October 1980 to 31 December 1980

    SciTech Connect

    Noufi, R.; Tench, D.; Warren, L.

    1981-01-20

    A program to provide the basis for designing a practical electrochemical solar cell based on the II-VI compound semiconductors is described. Emphasis is on developing new electrolyte redox systems and electrode surface modifications which will stabilize the II-VI compounds against photodissolution without seriously degrading the long-term solar response. Work on redox couple stabilization of n-CdX photoanodes has focused on fast metal-based one-electron couples in various nonaqueous solvents which represent an extension of work with the methanol/ferro-ferricyanide system, which, although stabilizing for n-CdSe photoanodes, has been found to be photolytically unstable. Very promising results which were obtained for the FeCl/sub 4//sup 1-/2-/ couple in acetonitrile suggest that related chloro-couples should be considered, including the colorless two-electron tin (II, IV) and antimony (III, V) systems. Conducting polymer films of polyrrole photoelectrochemically deposited onto n-type semiconductors were previously shown to protect these electrode materials from photodecomposition while permitting electron exchange with the electrolyte, but poor adhesion has remained a key problem. Recently, improved adhesion has been attained for roughened semiconductor surfaces. It now appears that polypyrrole films are to some extent permeable to solvent/solute species since the film stability depends on the nature of the redox electrolyte, and semiconductor decomposition products seem to form underneath the film in some cases. One possibility for circumventing this problem is to incorporate larger species, e.g., phthalocyanine dyes, within the film matrix.

  7. Low-dimensional transport and large thermoelectric power factors in bulk semiconductors by band engineering of highly directional electronic states.

    PubMed

    Bilc, Daniel I; Hautier, Geoffroy; Waroquiers, David; Rignanese, Gian-Marco; Ghosez, Philippe

    2015-04-01

    Thermoelectrics are promising for addressing energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but less by maximizing the power factor. The latter imposes apparently conflicting requirements on the band structure: a narrow energy distribution and a low effective mass. Quantum confinement in nanostructures and the introduction of resonant states were suggested as possible solutions to this paradox, but with limited success. Here, we propose an original approach to fulfill both requirements in bulk semiconductors. It exploits the highly directional character of some orbitals to engineer the band structure and produce a type of low-dimensional transport similar to that targeted in nanostructures, while retaining isotropic properties. Using first-principle calculations, the theoretical concept is demonstrated in Fe2YZ Heusler compounds, yielding power factors 4 to 5 times larger than in classical thermoelectrics at room temperature. Our findings are totally generic and rationalize the search of alternative compounds with similar behavior. Beyond thermoelectricity, these might be relevant also in the context of electronic, superconducting, or photovoltaic applications. PMID:25884131

  8. Low-dimensional transport and large thermoelectric power factors in bulk semiconductors by band engineering of highly directional electronic states.

    PubMed

    Bilc, Daniel I; Hautier, Geoffroy; Waroquiers, David; Rignanese, Gian-Marco; Ghosez, Philippe

    2015-04-01

    Thermoelectrics are promising for addressing energy issues but their exploitation is still hampered by low efficiencies. So far, much improvement has been achieved by reducing the thermal conductivity but less by maximizing the power factor. The latter imposes apparently conflicting requirements on the band structure: a narrow energy distribution and a low effective mass. Quantum confinement in nanostructures and the introduction of resonant states were suggested as possible solutions to this paradox, but with limited success. Here, we propose an original approach to fulfill both requirements in bulk semiconductors. It exploits the highly directional character of some orbitals to engineer the band structure and produce a type of low-dimensional transport similar to that targeted in nanostructures, while retaining isotropic properties. Using first-principle calculations, the theoretical concept is demonstrated in Fe2YZ Heusler compounds, yielding power factors 4 to 5 times larger than in classical thermoelectrics at room temperature. Our findings are totally generic and rationalize the search of alternative compounds with similar behavior. Beyond thermoelectricity, these might be relevant also in the context of electronic, superconducting, or photovoltaic applications.

  9. Usage of the SYSCAP II circuit analysis program to determine semiconductor failure threshold levels caused by lightning/EMP transients

    NASA Astrophysics Data System (ADS)

    Rusher, D. L.; Kleiner, C. T.

    1983-06-01

    An improved technique for calculating semiconductor junction heating resulting from arbitrary time-varying source terms is described. A FORTRAN subroutine is developed which permits solution of the convolution integral in the SYSCAP circuit analysis program which will simulate the thermal transient for each semiconductor of interest in a circuit subject to lightning/electromagnetic pulses disturbances. An example circuit is used to demonstrate the techniques; the results compare favorably with laboratory test data.

  10. 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.

  11. Introduction to Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Brennan, Kevin F.

    2005-03-01

    This volume offers a solid foundation for understanding the most important devices used in the hottest areas of electronic engineering today, from semiconductor fundamentals to state-of-the-art semiconductor devices in the telecommunications and computing industries. Kevin Brennan describes future approaches to computing hardware and RF power amplifiers, and explains how emerging trends and system demands of computing and telecommunications systems influence the choice, design and operation of semiconductor devices. In addition, he covers MODFETs and MOSFETs, short channel effects, and the challenges faced by continuing miniaturization. His book is both an excellent senior/graduate text and a valuable reference for practicing engineers and researchers.

  12. High-throughput engineering and analysis of peptide binding to class II MHC.

    PubMed

    Jiang, Wei; Boder, Eric T

    2010-07-27

    Class II major histocompatibility complex (MHC-II) proteins govern stimulation of adaptive immunity by presenting antigenic peptides to CD4+ T lymphocytes. Many allelic variants of MHC-II exist with implications in peptide presentation and immunity; thus, high-throughput experimental tools for rapid and quantitative analysis of peptide binding to MHC-II are needed. Here, we present an expression system wherein peptide and MHC-II are codisplayed on the surface of yeast in an intracellular association-dependent manner and assayed by flow cytometry. Accordingly, the relative binding of different peptides and/or MHC-II variants can be assayed by genetically manipulating either partner, enabling the application of directed evolution approaches for high-throughput characterization or engineering. We demonstrate the application of this tool to map the side-chain preference for peptides binding to HLA-DR1 and to evolve novel HLA-DR1 mutants with altered peptide-binding specificity.

  13. Testing of bellows for engineering systems. Part II

    SciTech Connect

    McCoy, H.E. Jr.; McNabb, B.

    1981-04-01

    Techniques were developed for performing elastic, creep, fatigue, and squirm tests on several specific geometries of Hastelloy X and type 347 stainless steel bellows. The fatigue cycle studies was complex and included time, temperature strain, and internal pressure as variables. A programmable calculator was used to control the test and record data. Fatigue failures occurred by typical high-temperature deformation modes, and observed lifetimes were close to those predicted by the designer. In creep tests where bellows length was restrained, individual convolutions widened while the gaps between convolutions contracted. Deformation during creep was often very inhomogeneous. Nevertheless, this test program showed that bellows can be designed and characterized for engineering service.

  14. Safety-I, Safety-II and Resilience Engineering.

    PubMed

    Patterson, Mary; Deutsch, Ellen S

    2015-12-01

    In the quest to continually improve the health care delivered to patients, it is important to understand "what went wrong," also known as Safety-I, when there are undesired outcomes, but it is also important to understand, and optimize "what went right," also known as Safety-II. The difference between Safety-I and Safety-II are philosophical as well as pragmatic. Improving health care delivery involves understanding that health care delivery is a complex adaptive system; components of that system impact, and are impacted by, the actions of other components of the system. Challenges to optimal care include regular, irregular and unexampled threats. This article addresses the dangers of brittleness and miscalibration, as well as the value of adaptive capacity and margin. These qualities can, respectively, detract from or contribute to the emergence of organizational resilience. Resilience is characterized by the ability to monitor, react, anticipate, and learn. Finally, this article celebrates the importance of humans, who make use of system capabilities and proactively mitigate the effects of system limitations to contribute to successful outcomes. PMID:26549146

  15. 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.

  16. 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.

  17. Blooms' separation of the final exam of Engineering Mathematics II: Item reliability using Rasch measurement model

    NASA Astrophysics Data System (ADS)

    Fuaad, Norain Farhana Ahmad; Nopiah, Zulkifli Mohd; Tawil, Norgainy Mohd; Othman, Haliza; Asshaari, Izamarlina; Osman, Mohd Hanif; Ismail, Nur Arzilah

    2014-06-01

    In engineering studies and researches, Mathematics is one of the main elements which express physical, chemical and engineering laws. Therefore, it is essential for engineering students to have a strong knowledge in the fundamental of mathematics in order to apply the knowledge to real life issues. However, based on the previous results of Mathematics Pre-Test, it shows that the engineering students lack the fundamental knowledge in certain topics in mathematics. Due to this, apart from making improvements in the methods of teaching and learning, studies on the construction of questions (items) should also be emphasized. The purpose of this study is to assist lecturers in the process of item development and to monitor the separation of items based on Blooms' Taxonomy and to measure the reliability of the items itself usingRasch Measurement Model as a tool. By using Rasch Measurement Model, the final exam questions of Engineering Mathematics II (Linear Algebra) for semester 2 sessions 2012/2013 were analysed and the results will provide the details onthe extent to which the content of the item providesuseful information about students' ability. This study reveals that the items used in Engineering Mathematics II (Linear Algebra) final exam are well constructed but the separation of the items raises concern as it is argued that it needs further attention, as there is abig gap between items at several levels of Blooms' cognitive skill.

  18. Guidelines for clinical engineering programs--Part I: guidelines for electrical isolation; Part II: performance evaluation of clinical engineering programs.

    PubMed

    Ridgway, M

    1980-01-01

    This series presents guidelines for: electrically isolated inputs and outputs; measuring the performance of hospital biomedical engineering programs; evaluating the risk of electric shock in hospitals; and for isolated power in anesthetizing locations. In Part I, specific recommendations are given for the use of insulated approach, battery-powered monitors in surgery, and for isolation requirements for devices connected to cardiac leads. In Part II, checklists are provided for the self-evaluation of an in-house, biomedical engineering staff. Parts III and IV, in future issues of this Journal, will include discussion of the theoretical electrical hazard potential in reference to the use of isolated power systems. The question of whether isolated power should be required in all anesthetizing locations will be discussed in Part IV.

  19. Effect of dissolved organic matter on Fe(II) oxidation in natural and engineered waters.

    PubMed

    Lee, Ying Ping; Fujii, Manabu; Terao, Koumei; Kikuchi, Tetsuro; Yoshimura, Chihiro

    2016-10-15

    Fe(II) oxidation was investigated in samples from the Sagami River basin (Japan) with particular emphasis on the effect of dissolved organic matter (DOM) in an urban river system. Collected samples consisted of main stream and tributary waters impacted to a moderate and minor extent by anthropogenic activities, respectively, and treated effluents from adjacent municipal wastewater treatment plants (MWWTPs: as representative anthropogenic point source). Nanomolar Fe(II) oxidation was measured in air-saturated waters using luminol chemiluminescence in the dark at 25 °C. Second-order rate constant for Fe(II) oxidation (with respect to Fe(II) and O2 concentrations) showed spatial and temporal variation. Annual average of the rate constant was highest for MWWTP effluents, followed by reservoir and river waters, with tributary waters showing the lowest oxidation rate. Manipulation experiments indicated that, in addition to pH (7.8-8.4), DOM characteristics are important explanatory variable for the Fe(II) oxidation. For example, the addition of MWWTP-derived humic-type DOM to anthropogenically less-influenced tributary water resulted in substantial increase in the oxidation rate. Significant negative correlation observed between the specific UV absorbance (SUVA254) and Fe(II) oxidation rate constant (pH 8.0) suggests a potential effect of humic-type DOM with low SUVA254 (high aliphatic content) on Fe(II) oxidation in natural and engineered waters.

  20. Effect of dissolved organic matter on Fe(II) oxidation in natural and engineered waters.

    PubMed

    Lee, Ying Ping; Fujii, Manabu; Terao, Koumei; Kikuchi, Tetsuro; Yoshimura, Chihiro

    2016-10-15

    Fe(II) oxidation was investigated in samples from the Sagami River basin (Japan) with particular emphasis on the effect of dissolved organic matter (DOM) in an urban river system. Collected samples consisted of main stream and tributary waters impacted to a moderate and minor extent by anthropogenic activities, respectively, and treated effluents from adjacent municipal wastewater treatment plants (MWWTPs: as representative anthropogenic point source). Nanomolar Fe(II) oxidation was measured in air-saturated waters using luminol chemiluminescence in the dark at 25 °C. Second-order rate constant for Fe(II) oxidation (with respect to Fe(II) and O2 concentrations) showed spatial and temporal variation. Annual average of the rate constant was highest for MWWTP effluents, followed by reservoir and river waters, with tributary waters showing the lowest oxidation rate. Manipulation experiments indicated that, in addition to pH (7.8-8.4), DOM characteristics are important explanatory variable for the Fe(II) oxidation. For example, the addition of MWWTP-derived humic-type DOM to anthropogenically less-influenced tributary water resulted in substantial increase in the oxidation rate. Significant negative correlation observed between the specific UV absorbance (SUVA254) and Fe(II) oxidation rate constant (pH 8.0) suggests a potential effect of humic-type DOM with low SUVA254 (high aliphatic content) on Fe(II) oxidation in natural and engineered waters. PMID:27450354

  1. Isocrystalline core/shell synthesis of high quality II-VI diluted magnetic semiconductor quantum dots: ligand-field spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Radovanovic, Pavle V.; Gamelin, Daniel R.

    2002-11-01

    Ligand field electronic absorption spectroscopy has been applied as a direct probe of Co2+ dopant ions in II-VI based diluted magnetic semiconductor quantum dots. Synthesis of Co2+-doped CdS (Co2+:CdS) quantum dots by simple coprecipitation in inverted micelle solutions has been found to yield predominantly surface bound dopant ions, which are unstable with respect to solvation in a coordinating solvent (pyridine). The solvation kinetics are biphasic, involving two transient intermediates. In contrast, Co2+ ions are doped much more isotropically in ZnS QDs, and this difference is attributed to the similar ionic radii of Co2+ and Zn2+ ions (0.74 Å), as opposed to Cd2+ ions (0.97 Å). We have developed an isocrystalline core/shell synthetic methodology that enables us to synthesize high quality internally doped Co2+:CdS quantum dots. The effect of Co2+ binding on the surface energies of CdS and ZnS quantum dots is discussed and related to the growth mechanism of diluted magnetic semiconductor quantum dots.

  2. Systematic defect donor levels in III-V and II-VI semiconductors revealed by hybrid functional density-functional theory

    NASA Astrophysics Data System (ADS)

    Petretto, Guido; Bruneval, Fabien

    2015-12-01

    The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.

  3. Engineering-scale destruction of organics at Savannah River Site using the silver(II) ion

    SciTech Connect

    Fleischman, S.D.; Pierce, R.A.

    1991-09-04

    Electrochemical destruction of organics to carbon dioxide, water, and inorganic salts using the silver(II) ion as an oxidizer has been demonstrated at the Savannah River Site (SRS) on a laboratory scale. An engineering-scale facility has been constructed at SRS for a process demonstration of the technology using benzene. Organic destruction rates, cell efficiencies and off gas generation will be related to key process variables. Electrocell design, peripheral support equipment, engineering considerations, safety issues, and operating parameters will be discussed. Future test plans and the impact of early results on the direction of the organics destruction program at SRS will also be addressed.

  4. Nature-Inspired, Highly Durable CO2 Reduction System Consisting of a Binuclear Ruthenium(II) Complex and an Organic Semiconductor Using Visible Light.

    PubMed

    Kuriki, Ryo; Matsunaga, Hironori; Nakashima, Takuya; Wada, Keisuke; Yamakata, Akira; Ishitani, Osamu; Maeda, Kazuhiko

    2016-04-20

    A metal-free organic semiconductor of mesoporous graphitic carbon nitride (C3N4) coupled with a Ru(II) binuclear complex (RuRu') containing photosensitizer and catalytic units selectively reduced CO2 into HCOOH under visible light (λ > 400 nm) in the presence of a suitable electron donor with high durability, even in aqueous solution. Modification of C3N4 with Ag nanoparticles resulted in a RuRu'/Ag/C3N4 photocatalyst that exhibited a very high turnover number (>33000 with respect to the amount of RuRu'), while maintaining high selectivity for HCOOH production (87-99%). This turnover number was 30 times greater than that reported previously using C3N4 modified with a mononuclear Ru(II) complex, and by far the highest among the metal-complex/semiconductor hybrid systems reported to date. The results of photocatalytic reactions, emission decay measurements, and time-resolved infrared spectroscopy indicated that Ag nanoparticles on C3N4 collected electrons having lifetimes of several milliseconds from the conduction band of C3N4, which were transferred to the excited state of RuRu', thereby promoting photocatalytic CO2 reduction driven by two-step photoexcitation of C3N4 and RuRu'. This study also revealed that the RuRu'/Ag/C3N4 hybrid photocatalyst worked efficiently in water containing a proper electron donor, despite the intrinsic hydrophobic nature of C3N4 and low solubility of CO2 in an aqueous environment.

  5. High-throughput engineering and analysis of peptide binding to class II MHC

    PubMed Central

    Jiang, Wei; Boder, Eric T.

    2010-01-01

    Class II major histocompatibility complex (MHC-II) proteins govern stimulation of adaptive immunity by presenting antigenic peptides to CD4+ T lymphocytes. Many allelic variants of MHC-II exist with implications in peptide presentation and immunity; thus, high-throughput experimental tools for rapid and quantitative analysis of peptide binding to MHC-II are needed. Here, we present an expression system wherein peptide and MHC-II are codisplayed on the surface of yeast in an intracellular association-dependent manner and assayed by flow cytometry. Accordingly, the relative binding of different peptides and/or MHC-II variants can be assayed by genetically manipulating either partner, enabling the application of directed evolution approaches for high-throughput characterization or engineering. We demonstrate the application of this tool to map the side-chain preference for peptides binding to HLA-DR1 and to evolve novel HLA-DR1 mutants with altered peptide-binding specificity. PMID:20622157

  6. Beyond modulation doping: Engineering a semiconductor to be ambipolar, or making an ON-OFF-ON transistor

    SciTech Connect

    Gupta, K. Das; Croxall, A. F.; Zheng, B.; Sfigakis, F.; Farrer, I.; Nicoll, C. A.; Beere, H. E.; Ritchie, D. A.

    2014-04-24

    Semiconductors are traditionaly either p-type or n-type, meaning that the mobile charge carriers in them are either 'holes' in the valence band or electrons in the conduction band. Ambipolar conduction implies that the experimenter should be able to populate the same channel with either electrons or holes in a controlled manner. This has been shown to be possible in newer materials like Graphene and some organic semiconductors. 'Ambipolarity' can open up new device possibilities as well as new ways to study fundamental scattering mechanisms in semiconductors. However, achieving this in a conventional high mobility structure like a GaAs-AlGaAs heterostructure/quantum well requires new thinking. It was realized, that to do this modulation doping must be given up and techniques to make an undoped heterostructure conduct, must be developed first. Such structures have been developed by only a few groups worldwide. They are of great interest to low temperature physicists working with Quantum Hall states and mesoscopic/nano structures in the ballistic regime. We discuss the reason behind this interest and the analysis of scattering mechanisms in such structures. Finally very recent experimental success in developing fully gate controlled ambipolar structures where both electron and hole mobilites exceed 1 million cm{sup 2}/Vs at low temperatures (T∼1Kelvin) are discussed. Such gated ambipolar structures can be used to analyse scattering mechanisms in ultra-high mobility 2dimensional electron and hole gases in a way that is not possible using other techniques.

  7. Electron-beam-enhanced oxidation processes in II-VI compound semiconductors observed by high-resolution electron microscopy

    SciTech Connect

    Thangaraj, N.; Wessels, B.W.

    1990-02-01

    Enhanced oxidation of ZnS and ZnSe semiconductor surfaces has been observed in situ during electron irradiation in a high-resolution electron microscope. The phase present at the surface region has been identified as ZnO by optical diffractogram and selected area electron diffraction techniques. For ZnS oxidation, both hexagonal ZnO having a random orientation and cubic ZnO in perfect epitaxial relationship with the bulk ZnS were observed. Enhanced oxidation of ZnSe to ZnO has also been observed under electron beam irradiation. However, only the hexagonal form was observed. The oxidation rates for both ZnS and ZnSe depended on electron flux but was independent of orientation. A model in which the oxidation process is limited by diffusion through the oxide film is proposed. By electron irradiation the diffusion rate is enhanced presumably by a nonthermal process.

  8. Engineering English and the High-Tech Industry: A Case Study of an English Needs Analysis of Process Integration Engineers at a Semiconductor Manufacturing Company in Taiwan

    ERIC Educational Resources Information Center

    Spence, Paul; Liu, Gi-Zen

    2013-01-01

    The global high-tech industry is characterized by extreme competitiveness, innovation, and widespread use of English. Consequently, Taiwanese high-tech companies require engineers that are talented in both their engineering and English abilities. In response to the lack of knowledge regarding the English skills needed by engineers in Taiwan's…

  9. Metabolic engineering of Pichia pastoris for the production of dammarenediol-II.

    PubMed

    Liu, Xin-Bin; Liu, Min; Tao, Xin-Yi; Zhang, Zhong-Xi; Wang, Feng-Qing; Wei, Dong-Zhi

    2015-12-20

    Dammarenediol-II is the nucleus of dammarane-type ginsenosides, which are a group of active triterpenoids exhibiting various pharmacological activities. Based on the native triterpene synthetic pathway, a dammarenediol-II synthetic pathway was established in Pichia pastoris by introducing a dammarenediol-II synthase gene (PgDDS) from Panax ginseng, which is responsible for the cyclization of 2,3-oxidosqualene to dammarenediol-II in this study. To enhance productivity, a strategy of "increasing supply and reducing competitive consumption of 2,3-oxidosqualene" was used. To increase the supply of 2,3-oxidosqualene, we augmented expression of the ERG1 gene, which is responsible for 2,3-oxidosqualene synthesis. This significantly improved the yield of dammarenediol-II over 6.7-fold, from 0.030mg/g dry cell weight (DCW) to 0.203mg/g DCW. Subsequently, to reduce competition for 2,3-oxidosqualene from ergosterol biosynthesis without affecting the normal growth of P. pastoris, we targeted the ERG7gene, which is responsible for conversion of 2,3-oxidosqualene to lanosterol. This gene was downregulated by replacing its native promoter with a thiamine-repressible promoter, using a marker-recycling and gene-targeting Cre- lox71/66 system developed for P. pastoris herein. The yield of dammarenediol-II was further increased more than 3.6-fold, to 0.736mg/g DCW. Furthermore, the direct addition of 0.5g/L squalene into the culture medium further enhanced the yield of dammarenediol-II to 1.073mg/g DCW, which was 37.5-fold higher than the yield from the strain with the PgDDS gene introduction only. The P. pastoris strains engineered in this study constitute a good platform for further production of ginsenosides in Pichia species. PMID:26467715

  10. Analysis of type II diabetes mellitus adipose-derived stem cells for tissue engineering applications

    PubMed Central

    Minteer, Danielle Marie; Young, Matthew T; Lin, Yen-Chih; Over, Patrick J; Rubin, J Peter; Gerlach, Jorg C

    2015-01-01

    To address the functionality of diabetic adipose-derived stem cells in tissue engineering applications, adipose-derived stem cells isolated from patients with and without type II diabetes mellitus were cultured in bioreactor culture systems. The adipose-derived stem cells were differentiated into adipocytes and maintained as functional adipocytes. The bioreactor system utilizes a hollow fiber–based technology for three-dimensional perfusion of tissues in vitro, creating a model in which long-term culture of adipocytes is feasible, and providing a potential tool useful for drug discovery. Daily metabolic activity of the adipose-derived stem cells was analyzed within the medium recirculating throughout the bioreactor system. At experiment termination, tissues were extracted from bioreactors for immunohistological analyses in addition to gene and protein expression. Type II diabetic adipose-derived stem cells did not exhibit significantly different glucose consumption compared to adipose-derived stem cells from patients without type II diabetes (p > 0.05, N = 3). Expression of mature adipocyte genes was not significantly different between diabetic/non-diabetic groups (p > 0.05, N = 3). Protein expression of adipose tissue grown within all bioreactors was verified by Western blotting.The results from this small-scale study reveal adipose-derived stem cells from patients with type II diabetes when removed from diabetic environments behave metabolically similar to the same cells of non-diabetic patients when cultured in a three-dimensional perfusion bioreactor, suggesting that glucose transport across the adipocyte cell membrane, the hindrance of which being characteristic of type II diabetes, is dependent on environment. The presented observation describes a tissue-engineered tool for long-term cell culture and, following future adjustments to the culture environment and increased sample sizes, potentially for anti-diabetic drug testing. PMID:26090087

  11. Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe).

    PubMed

    Ramos-Ruiz, Adriana; Zeng, Chao; Sierra-Alvarez, Reyes; Teixeira, Luiz H; Field, Jim A

    2016-11-01

    This work investigated the microbial toxicity of soluble species that can potentially be leached from the II-VI semiconductor materials, cadmium telluride and cadmium selenide. The soluble ions tested included: cadmium, selenite, selenate, tellurite, and tellurate. Their toxicity towards the acetoclastic and hydrogen-consuming trophic groups in a methanogenic consortium as well as towards a bioluminescent marine bacterium, Aliivibrio fischeri (Microtox(®) test), was assessed. The acetoclastic methanogenic activity was the most affected as evidenced by the low 50% inhibiting concentrations (IC50) values obtained of 8.6 mg L(-1) for both cadmium and tellurite, 10.2 mg L(-1) for tellurate, and 24.1 mg L(-1) for selenite. Both tellurium oxyanions caused a strong inhibition of acetoclastic methanogenesis at low concentrations, each additional increment in concentration provided progressively less inhibition increase. In the case of the hydrogenotrophic methanogenesis, cadmium followed by selenite caused the greatest inhibition with IC50 values of 2.9 and 18.0 mg L(-1), respectively. Tellurite caused a moderate effect as evidenced by a 36.8% inhibition of the methanogenic activity at the highest concentration tested, and a very mild effect of tellurate was observed. Microtox(®) analyses showed a noteworthy inhibition of cadmium, selenite, and tellurite with 50% loss in bioluminescence after 30 min of exposure of 5.5, 171.1, and 458.6 mg L(-1), respectively. These results suggest that the leaching of cadmium, tellurium and selenium ions from semiconductor materials can potentially cause microbial toxicity. PMID:27494313

  12. Carrier-impurity spin transfer dynamics in paramagnetic II-VI diluted magnetic semiconductors in the presence of a wave-vector-dependent magnetic field

    NASA Astrophysics Data System (ADS)

    Cygorek, M.; Tamborenea, P. I.; Axt, V. M.

    2016-05-01

    Quantum kinetic equations of motion for carrier and impurity spins in paramagnetic II-VI diluted magnetic semiconductors in a k -dependent effective magnetic field are derived, where the carrier-impurity correlations are taken into account. In the Markov limit, rates for the electron-impurity spin transfer can be derived for electron spins parallel and perpendicular to the impurity spins corresponding to measurable decay rates in Kerr experiments in Faraday and Voigt geometry. Our rigorous microscopic quantum kinetic treatment automatically accounts for the fact that, in an individual spin flip-flop scattering process, a spin flip of an electron is necessarily accompanied by a flop of an impurity spin in the opposite direction and the corresponding change of the impurity Zeeman energy influences the final energy of the electron after the scattering event. This shift in the electron energies after a spin flip-flop scattering process, which usually has been overlooked in the literature, turns out to be especially important in the case of extremely diluted magnetic semiconductors in an external magnetic field. As a specific example for a k -dependent effective magnetic field the effects of a Rashba field on the dynamics of the carrier-impurity correlations in a Hg1 -x -yCdyMnxTe quantum well are described. It is found that, although accounting for the Rashba interaction in the dynamics of the correlations leads to a modified k -space dynamics, the time evolution of the total carrier spin is not significantly influenced. Furthermore, a connection between the present theory and the description of collective carrier-impurity precession modes is presented.

  13. Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe).

    PubMed

    Ramos-Ruiz, Adriana; Zeng, Chao; Sierra-Alvarez, Reyes; Teixeira, Luiz H; Field, Jim A

    2016-11-01

    This work investigated the microbial toxicity of soluble species that can potentially be leached from the II-VI semiconductor materials, cadmium telluride and cadmium selenide. The soluble ions tested included: cadmium, selenite, selenate, tellurite, and tellurate. Their toxicity towards the acetoclastic and hydrogen-consuming trophic groups in a methanogenic consortium as well as towards a bioluminescent marine bacterium, Aliivibrio fischeri (Microtox(®) test), was assessed. The acetoclastic methanogenic activity was the most affected as evidenced by the low 50% inhibiting concentrations (IC50) values obtained of 8.6 mg L(-1) for both cadmium and tellurite, 10.2 mg L(-1) for tellurate, and 24.1 mg L(-1) for selenite. Both tellurium oxyanions caused a strong inhibition of acetoclastic methanogenesis at low concentrations, each additional increment in concentration provided progressively less inhibition increase. In the case of the hydrogenotrophic methanogenesis, cadmium followed by selenite caused the greatest inhibition with IC50 values of 2.9 and 18.0 mg L(-1), respectively. Tellurite caused a moderate effect as evidenced by a 36.8% inhibition of the methanogenic activity at the highest concentration tested, and a very mild effect of tellurate was observed. Microtox(®) analyses showed a noteworthy inhibition of cadmium, selenite, and tellurite with 50% loss in bioluminescence after 30 min of exposure of 5.5, 171.1, and 458.6 mg L(-1), respectively. These results suggest that the leaching of cadmium, tellurium and selenium ions from semiconductor materials can potentially cause microbial toxicity.

  14. Applications of ion chromatography in the semiconductor industry. II. Determination of basic airborne contaminants in a cleanroom.

    PubMed

    Lue, S J; Huang, C

    1999-07-30

    Since the geometry of semiconductors and integrated circuits has been shrunk to well below sub-micron dimensions, there is a great demand for precise and reliable analytical techniques to measure and monitor the contaminants in all areas related to the fabrication process. Special concerns about the air cleanliness in a Fab lead to the necessity for developing analytical techniques to perform this task. In this research, basic airborne contaminants in a cleanroom were adsorbed onto a collection tube, subsequently extracted with deionized water and analyzed by ion chromatography. Such a method is capable of simultaneously measuring the concentrations of ammonia and cations (e.g., sodium, potassium, calcium, magnesium, etc.) present in the cleanroom air samples. The optimal sample preparation method was determined and the analyte concentrations at various locations in the cleanroom were measured. The results showed significant variations from one location to another. The long-term fluctuations in the contaminant levels were also significant. Data obtained using this method compared well with data from inductively coupled plasma analysis of the same materials.

  15. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    SciTech Connect

    Yin, Wan-Jian; Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Wei, Su-Huai; Yan, Yanfa

    2015-10-05

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  16. Molecular beam epitaxial growth and characterization of Bi{sub 2}Se{sub 3}/II-VI semiconductor heterostructures

    SciTech Connect

    Chen, Zhiyi Zhao, Lukas; Krusin-Elbaum, Lia; Garcia, Thor Axtmann; Tamargo, Maria C.; Hernandez-Mainet, Luis C.; Deng, Haiming

    2014-12-15

    Surfaces of three-dimensional topological insulators (TIs) have been proposed to host quantum phases at the interfaces with other types of materials, provided that the topological properties of interfacial regions remain unperturbed. Here, we report on the molecular beam epitaxy growth of II-VI semiconductor–TI heterostructures using c-plane sapphire substrates. Our studies demonstrate that Zn{sub 0.49}Cd{sub 0.51}Se and Zn{sub 0.23}Cd{sub 0.25}Mg{sub 0.52}Se layers have improved quality relative to ZnSe. The structures exhibit a large relative upward shift of the TI bulk quantum levels when the TI layers are very thin (∼6nm), consistent with quantum confinement imposed by the wide bandgap II-VI layers. Our transport measurements show that the characteristic topological signatures of the Bi{sub 2}Se{sub 3} layers are preserved.

  17. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Yin, Wan-Jian; Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Yan, Yanfa; Wei, Su-Huai

    2015-10-01

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  18. Influence of the exchange-correlation functional on the quasi-harmonic lattice dynamics of II-VI semiconductors.

    PubMed

    Skelton, Jonathan M; Tiana, Davide; Parker, Stephen C; Togo, Atsushi; Tanaka, Isao; Walsh, Aron

    2015-08-14

    We perform a systematic comparison of the finite-temperature structure and properties of four bulk semiconductors (PbS, PbTe, ZnS, and ZnTe) predicted by eight popular exchange-correlation functionals from quasi-harmonic lattice-dynamics calculations. The performance of the functionals in reproducing the temperature dependence of a number of material properties, including lattice parameters, thermal-expansion coefficients, bulk moduli, heat capacities, and phonon frequencies, is evaluated quantitatively against available experimental data. We find that the phenomenological over- and under-binding characteristics of the local-density approximation and the PW91 and Perdew-Burke-Enzerhof (PBE) generalised-gradient approximation (GGA) functionals, respectively, are exaggerated at finite temperature, whereas the PBEsol GGA shows good general performance across all four systems. The Tao-Perdew-Staroverov-Scuseria (TPSS) and revTPSS meta-GGAs provide relatively small improvements over PBE, with the latter being better suited to calculating structural and dynamical properties, but both are considerably more computationally demanding than the simpler GGAs. The dispersion-corrected PBE-D2 and PBE-D3 functionals perform well in describing the lattice dynamics of the zinc chalcogenides, whereas the lead chalcogenides appear to be challenging for these functionals. These findings show that quasi-harmonic calculations with a suitable functional can predict finite-temperature structure and properties with useful accuracy, and that this technique can serve as a means of evaluating the performance of new functionals in the future. PMID:26277159

  19. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis

    PubMed Central

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-01-01

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts. PMID:27650485

  20. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis.

    PubMed

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-09-21

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts.

  1. Engineering surface atomic structure of single-crystal cobalt (II) oxide nanorods for superior electrocatalysis.

    PubMed

    Ling, Tao; Yan, Dong-Yang; Jiao, Yan; Wang, Hui; Zheng, Yao; Zheng, Xueli; Mao, Jing; Du, Xi-Wen; Hu, Zhenpeng; Jaroniec, Mietek; Qiao, Shi-Zhang

    2016-01-01

    Engineering the surface structure at the atomic level can be used to precisely and effectively manipulate the reactivity and durability of catalysts. Here we report tuning of the atomic structure of one-dimensional single-crystal cobalt (II) oxide (CoO) nanorods by creating oxygen vacancies on pyramidal nanofacets. These CoO nanorods exhibit superior catalytic activity and durability towards oxygen reduction/evolution reactions. The combined experimental studies, microscopic and spectroscopic characterization, and density functional theory calculations reveal that the origins of the electrochemical activity of single-crystal CoO nanorods are in the oxygen vacancies that can be readily created on the oxygen-terminated {111} nanofacets, which favourably affect the electronic structure of CoO, assuring a rapid charge transfer and optimal adsorption energies for intermediates of oxygen reduction/evolution reactions. These results show that the surface atomic structure engineering is important for the fabrication of efficient and durable electrocatalysts. PMID:27650485

  2. Los Alamos Controlled Air Incinerator for radioactive waste. Volume II. Engineering design reference manual

    SciTech Connect

    Koenig, R.A.; Draper, W.E.; Newmyer, J.M.; Warner, C.L.

    1982-10-01

    This two-volume report is a detailed design and operating documentation of the Los Alamos National Laboratory Controlled Air Incinerator (CAI) and is an aid to technology transfer to other Department of Energy contractor sites and the commercial sector. Volume I describes the CAI process, equipment, and performance, and it recommends modifications based on Los Alamos experience. It provides the necessary information for conceptual design and feasibility studies. Volume II provides descriptive engineering information such as drawings, specifications, calculations, and costs. It aids duplication of the process at other facilities.

  3. Cutaneous exposure scenarios for engineered nanoparticles used in semiconductor fabrication: a preliminary investigation of workplace surface contamination

    PubMed Central

    Shepard, Michele; Brenner, Sara

    2014-01-01

    Background: Numerous studies are ongoing in the fields of nanotoxicology and exposure science; however, gaps remain in identifying and evaluating potential exposures from skin contact with engineered nanoparticles in occupational settings. Objectives: The aim of this study was to identify potential cutaneous exposure scenarios at a workplace using engineered nanoparticles (alumina, ceria, amorphous silica) and evaluate the presence of these materials on workplace surfaces. Methods: Process review, workplace observations, and preliminary surface sampling were conducted using microvacuum and wipe sample collection methods and transmission electron microscopy with elemental analysis. Results: Exposure scenarios were identified with potential for incidental contact. Nanoparticles of silica or silica and/or alumina agglomerates (or aggregates) were identified in surface samples from work areas where engineered nanoparticles were used or handled. Conclusions: Additional data are needed to evaluate occupational exposures from skin contact with engineered nanoparticles; precautionary measures should be used to minimize potential cutaneous exposures in the workplace. PMID:25000112

  4. Bulk anisotropic excitons in type-II semiconductors built with 1D and 2D low-dimensional structures

    NASA Astrophysics Data System (ADS)

    Coyotecatl, H. A.; Del Castillo-Mussot, M.; Reyes, J. A.; Vazquez, G. J.; Montemayor-Aldrete, J. A.; Reyes-Esqueda, J. A.; Cocoletzi, G. H.

    2005-08-01

    We used a simple variational approach to account for the difference in the electron and hole effective masses in Wannier-Mott excitons in type-II semiconducting heterostructures in which the electron is constrained in an one-dimensional quantum wire (1DQW) and the hole is in a two-dimensional quantum layer (2DQL) perpendicular to the wire or viceversa. The resulting Schrodinger equation is similar to that of a 3D bulk exciton because the number of free (nonconfined) variables is three; two coming from the 2DQL and one from the 1DQW. In this system the effective electron-hole interaction depends on the confinement potentials.

  5. Chemical trends of the luminescence in wide band gap II 1-xMn xVI semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Benecke, C.; Busse, W.; Gumlich, H.-E.

    1990-04-01

    Time resolved emission and excitation spectroscopy is used to investigate the Mn correlated luminescence in wide band gap II-VI compounds, i.e. Zn 1-xMn xS, Cd 1-xMn xSe, Zn 1-xMn xTe and Cd 1-xMn xTe. Additional Information has been obtained with CdxZnyMnzTe( x+ y+ z=1) in checking the luminescence by variation of the ratio of the cations Cd and Zn. Generally speaking, at least two distinct emissions bands can be observed for each II 1- xMn xVI compound. One emissions band is attributed to the internal transition 4T 1(G)→ 6A 1(S) of the 3d 5 electron of the Mn 2+ on regular metal sites with energies of about ≈2 eV. The other emission band is found to occur in the near infrared range of about ≈1.3 eV. This emission band is tentatively interpreted as a transition of Mn 2+ ions on interstitial sites or in small Mn chalcogenide clusters, both interpretations assuming cubic symmetry. This model is supported by the existence of low energy excitation bands and by the great similarity of the shape of the two emission bands which lead to comparable Huang-Rhys factors and effective phonon energies. Also the established trend in the experimental data of the II-VI compounds under consideration confirm this interpretation. For both the IR and the yellow Mn 2+ center, the Racah parameters B and C and the crystal field parameter Dq are determined on the basis of experimental data. As a result, the energy of both the emission and the excitation bands is predominantly determined by the sorrounding anions. These bands shift to higher energies when the anions are changed in the fixed order: Te→Se→S. Regularly, there is also a spectral shift when Zn is replaced by Cd, which is smaller than the shift due to the variation of onions.

  6. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    PubMed

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  7. 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.

  8. Effect of Residual Accelerations on the Crystal Growth of II-VI Semiconductors in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Su, C.-H.; Szofran, F. R.; Scripa, R. N.; Cobb, S. D.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The paper compares and summarizes the effects of residual acceleration during crystal growth on the compositional variation of two II-VI solid solution binary alloys (Hg(0.8)Cd(0.2)Te and Hg(0.84)Zn(0.16)Te). The crystals were grown by directional solidification on the second United States Microgravity Payload (USMP-2) and the first United States Microgravity Laboratory (USML-1) missions, respectively. For both alloys, changes in the direction and magnitude of the quasisteady acceleration vector (approximately 0.4- 1 mu g) caused large changes in the radial compositional distribution that demonstrates the importance of residual accelerations, even in the submicrogravity range, for large density gradients in the melt and slow solidification rates. The observed compositional variations will be correlated to changes in the radial flow velocities ahead of the solidification interface.

  9. Covalent Attachment to GaP(110) - Engineering the Chemical Functionalization of a III-V Semiconductor

    NASA Astrophysics Data System (ADS)

    Bradley, A. J.; Ugeda, M. M.; Liu, Wenjun; Yu, Min; Tilley, T. Don; Pérez, Rubén; Neaton, Jeffrey B.; Crommie, M. F.

    2014-03-01

    With its 2.3 eV bulk bandgap, relatively high conduction band edge, and low chemical reactivity, the (110) surface of GaP is an excellent candidate for many UV and visible light applications, such as photo-catalysis and light-induced chemical reduction. However, the reconstruction and resulting charge transfer of the surface makes it difficult to covalently attach the required molecules. Indeed, very little work has been done to understand either covalent functionalization or passivation of this surface. Here we report on a Staudinger-type, thermally-driven covalent attachment of perfluorophenyl azide (pfpa) to GaP(110). We have studied the adsorption of pfpa molecules by means of high-resolution scanning tunneling microscopy and spectroscopy in combination with first principles calculations. We show a progression from a physisorbed state at room temperature to a covalently attached state after exposure to slightly higher temperatures (~ 50°C). The developed approach is expected to be valid for various other functional groups attached to the azide, as well as other III-V semiconductors.

  10. Nano-engineered electron–hole exchange interaction controls exciton dynamics in core–shell semiconductor nanocrystals

    PubMed Central

    Brovelli, S.; Schaller, R.D.; Crooker, S.A.; García-Santamaría, F.; Chen, Y.; Viswanatha, R.; Hollingsworth, J.A.; Htoon, H.; Klimov, V.I.

    2011-01-01

    A strong electron–hole exchange interaction (EI) in semiconductor nanocrystals (NCs) gives rise to a large (up to tens of meV) splitting between optically active ('bright') and optically passive ('dark') excitons. This dark–bright splitting has a significant effect on the optical properties of band-edge excitons and leads to a pronounced temperature and magnetic field dependence of radiative decay. Here we demonstrate a nanoengineering-based approach that provides control over EI while maintaining nearly constant emission energy. We show that the dark–bright splitting can be widely tuned by controlling the electron–hole spatial overlap in core–shell CdSe/CdS NCs with a variable shell width. In thick-shell samples, the EI energy reduces to <250 μeV, which yields a material that emits with a nearly constant rate over temperatures from 1.5 to 300 K and magnetic fields up to 7 T. The EI-manipulation strategies demonstrated here are general and can be applied to other nanostructures with variable electron–hole overlap. PMID:21505436

  11. 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.

  12. Analysis of Performance of Jet Engine from Characteristics of Components II : Interaction of Components as Determined from Engine Operation

    NASA Technical Reports Server (NTRS)

    Goldstein, Arthur W; Alpert, Sumner; Beede, William; Kovach, Karl

    1949-01-01

    In order to understand the operation and the interaction of jet-engine components during engine operation and to determine how component characteristics may be used to compute engine performance, a method to analyze and to estimate performance of such engines was devised and applied to the study of the characteristics of a research turbojet engine built for this investigation. An attempt was made to correlate turbine performance obtained from engine experiments with that obtained by the simpler procedure of separately calibrating the turbine with cold air as a driving fluid in order to investigate the applicability of component calibration. The system of analysis was also applied to prediction of the engine and component performance with assumed modifications of the burner and bearing characteristics, to prediction of component and engine operation during engine acceleration, and to estimates of the performance of the engine and the components when the exhaust gas was used to drive a power turbine.

  13. Metalorganic vapor phase epitaxy of wide-gap II VI semiconductors for optoelectronic applications: current status and future trends

    NASA Astrophysics Data System (ADS)

    Heuken, Michael

    1995-01-01

    The current status and future trends to overcome the major problems of wide-gap II-VI compounds grown by metalorganic vapor phase epitaxy (MOVPE) which are p-type doping and the understanding of interface properties of {ZnSSe}/{ZnSe-based} heterostructures will be discussed. Since a low growth temperature is required to reduce defects and impurities and to increase the sticking coefficient of dopant atoms, a matched precursor combination of zinc and selenium compounds or an additional growth assistance (e.g. plasma stimulation) must be employed. The optical and electrical properties of ZnSe doped with nitrogen will be discussed. Emphasis will be put on the fact that most of the MOVPE grown ZnSe:N layers remain highly resistive or that they show only low free hole concentrations. Occurring compensation mechanisms such as parasitic compensating donors associated with nitrogen or compensating nitrogen-hydrogen complexes may be the reason. The ability of MOVPE to handle high vapor pressure elements such as sulphur favours this technology for the growth of sophisticated quantum wells and superlattices to achieve electrical and optical confinement in laser structures and to push the emission wavelength further into the blue. Scanning transmission electron microscope, photoluminescence (PL) and X-ray measurements were used for the analysis of the interface properties. Growth optimization of {ZnSSe}/{ZnSe} interfaces results in monolayer fluctuations at the interfaces. High excitation PL experiments show that room temperature stimulated emission is possible with this kind of structures. To realize high bit rate data transmission in the blue spectral range at 2.7 eV the physical properties of optoelectronic modulators based on {ZnSSe}/{ZnSe} superlattices were examined.

  14. Defect engineering of complex semiconductor alloys: Cu2-2xMxO1-yXy

    NASA Astrophysics Data System (ADS)

    Lany, Stephan; Stevanovic, Vladan

    2013-03-01

    The electrical properties of semiconductors are generally controlled via doping, i.e., the incorporation of dilute concentrations of aliovalent impurity atoms, whereas the band structure properties (gap, effective masses, optical properties) are manipulated by alloying, i.e., the incorporation of much larger amounts of isovalent elements. Theoretical approaches usually address either doping or alloying, but rarely both problems at the same time. By combining defect supercell calculations, GW quasi-particle energy calculation, and thermodynamic modeling, we study the range of electrical and band structure properties accessible by alloying aliovalent cations (M = Mg, Zn, Cd) and isovalent anions (X = S, Se) in Cu2O. In order to extend dilute defect models to higher concentrations, we take into account the association/dissociation of defect pairs and complexes, as well as the composition dependence of the band gap and the band edge energies. Considering a composition window for the Cu2-2xMxO1-yXy alloys of 0 <= (x,y) <= 0.2, we predict a wide range of possible band gaps from 1.7 to 2.6 eV, and net doping concentrations between p = 1019 cm-3 and n = 1017cm-3, notably achieving type conversion from p- to n-type at Zn or Cd compositions around x = 0.1. This work is supported as part of the SunShot initiative by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy under Contract No. DE-AC36-08GO28308 to NREL.

  15. AUTOMOTIVE DIESEL MAINTENANCE L. UNIT XII, PART I--MAINTAINING THE FUEL SYSTEM (PART II), CUMMINS DIESEL ENGINE, PART II--UNIT INSTALLATION (ENGINE).

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL SYSTEM AND THE PROCEDURES FOR DIESEL ENGINE INSTALLATION. TOPICS ARE FUEL FLOW CHARACTERISTICS, PTG FUEL PUMP, PREPARATION FOR INSTALLATION, AND INSTALLING ENGINE. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL BRANCH…

  16. Repository Planning, Design, and Engineering: Part II-Equipment and Costing.

    PubMed

    Baird, Phillip M; Gunter, Elaine W

    2016-08-01

    Part II of this article discusses and provides guidance on the equipment and systems necessary to operate a repository. The various types of storage equipment and monitoring and support systems are presented in detail. While the material focuses on the large repository, the requirements for a small-scale startup are also presented. Cost estimates and a cost model for establishing a repository are presented. The cost model presents an expected range of acquisition costs for the large capital items in developing a repository. A range of 5,000-7,000 ft(2) constructed has been assumed, with 50 frozen storage units, to reflect a successful operation with growth potential. No design or engineering costs, permit or regulatory costs, or smaller items such as the computers, software, furniture, phones, and barcode readers required for operations have been included. PMID:26886768

  17. Intriguing electronic properties of two-dimensional MoS2/TM2CO2 (TM = Ti, Zr, or Hf) hetero-bilayers: type-II semiconductors with tunable band gaps.

    PubMed

    Li, Xinru; Dai, Ying; Ma, Yandong; Liu, Qunqun; Huang, Baibiao

    2015-03-27

    Two-dimensional (2D) transition metal compound (TMC) monolayers, as well as their van der Waals heterostructures with unique properties, are fundamentally and technologically intriguing. Here, heterostructures consisting of a MoS2 monolayer and TM2CO2 (TM = Ti, Zr or Hf) monolayers are systematically researched by means of the density functional theory (DFT). Different from semiconductor/metal contacts, MoS2 and TM2CO2 monolayers are all semiconductors with band gaps ranging from 0.25-1.67 eV. According to rigorous screening of stacking patterns, MoS2/Zr2CO2 is shown to be an indirect type-II semiconductor with the maximum valence and minimum conduction bands spatially separated on opposite monolayers. Simultaneously, the interface charges transfer from Zr2CO2 to MoS2 results in a built-in field that separates the electrons and holes efficiently. Also, the smaller effective masses of electrons and the holes of band edges indicate the higher carrier mobility. Moreover, strain regulation can make the hetero-bilayer's character a semiconductor-semimetal-metal transition. The physical insights pave the way for the good performance of MoS2/TM2CO2 in next-generation electronic devices and photocatalysts.

  18. Intriguing electronic properties of two-dimensional MoS2/TM2CO2 (TM = Ti, Zr, or Hf) hetero-bilayers: type-II semiconductors with tunable band gaps

    NASA Astrophysics Data System (ADS)

    Li, Xinru; Dai, Ying; Ma, Yandong; Liu, Qunqun; Huang, Baibiao

    2015-03-01

    Two-dimensional (2D) transition metal compound (TMC) monolayers, as well as their van der Waals heterostructures with unique properties, are fundamentally and technologically intriguing. Here, heterostructures consisting of a MoS2 monolayer and TM2CO2 (TM = Ti, Zr or Hf) monolayers are systematically researched by means of the density functional theory (DFT). Different from semiconductor/metal contacts, MoS2 and TM2CO2 monolayers are all semiconductors with band gaps ranging from 0.25-1.67 eV. According to rigorous screening of stacking patterns, MoS2/Zr2CO2 is shown to be an indirect type-II semiconductor with the maximum valence and minimum conduction bands spatially separated on opposite monolayers. Simultaneously, the interface charges transfer from Zr2CO2 to MoS2 results in a built-in field that separates the electrons and holes efficiently. Also, the smaller effective masses of electrons and the holes of band edges indicate the higher carrier mobility. Moreover, strain regulation can make the hetero-bilayer’s character a semiconductor-semimetal-metal transition. The physical insights pave the way for the good performance of MoS2/TM2CO2 in next-generation electronic devices and photocatalysts.

  19. Preparation and characterization of a novel hybrid magnetic semiconductor containing rare, one-dimensional mixed-iodide/chloride anion of lead(II)

    SciTech Connect

    Fan Leqing Wu Jihuai Huang Yunfang

    2007-12-15

    A new hybrid inorganic-organic magnetic semiconductor [Ni(bipy){sub 3}Pb{sub 2}I{sub 4.84}Cl{sub 1.16}.DMF]{sub n} (bipy=2,2'-bipyridine) containing novel one-dimensional mixed-halide anion of lead(II) was synthesized by reactions of PbI{sub 2}, NaI, NiCl{sub 2} and bipy in DMF solution, and structurally characterized by single-crystal X-ray diffraction. It crystallizes in the space group C2/c with a=29.260(8) A, b=15.602(4) A, c=23.695(6) A, {beta}=126.815({sup o}), Z=8, V=8660(4) A{sup 3} and consists of a magnetic cation [Ni(bipy){sub 3}]{sup 2+} in addition to one-dimensional mixed-halide anion, which is built up of face-sharing [PbX{sub 6}] octahedra. Of the seven crystallographically independent halide sites in this anion, one and five are occupied by Cl and I, respectively, the remaining one has mixed-iodide and -chloride occupancy. The title yellow compound has an optical bandgap of 2.59 eV, and the variable-temperature magnetic susceptibility measurement indicates paramagnetic behavior. - Graphical abstract: Based upon magnetic metal-organic complex as template, a novel one-dimensional haloplumbate containing mixed-halide anion has been successfully synthesized. Its structural characteristics, optical bandgap, magnetic and thermal properties are reported.

  20. Genetically engineered plants and foods: a scientist's analysis of the issues (part II).

    PubMed

    Lemaux, Peggy G

    2009-01-01

    Genetic engineering provides a means to introduce genes into plants via mechanisms that are different in some respects from classical breeding. A number of commercialized, genetically engineered (GE) varieties, most notably canola, cotton, maize and soybean, were created using this technology, and at present the traits introduced are herbicide and/or pest tolerance. In 2007 these GE crops were planted in developed and developing countries on more than 280 million acres (113 million hectares) worldwide, representing nearly 10% of rainfed cropland. Although the United States leads the world in acres planted with GE crops, the majority of this planting is on large acreage farms. In developing countries, adopters are mostly small and resource-poor farmers. For farmers and many consumers worldwide, planting and eating GE crops and products made from them are acceptable and even welcomed; for others GE crops raise food and environmental safety questions, as well as economic and social issues. In Part I of this review, some general and food issues related to GE crops and foods were discussed. In Part II, issues related to certain environmental and socioeconomic aspects of GE crops and foods are addressed, with responses linked to the scientific literature.

  1. Molecular beam epitaxy engineered III-V semiconductor structures for low-power optically addressed spatial light modulators

    NASA Technical Reports Server (NTRS)

    Larsson, Anders G.; Maserjian, Joseph

    1992-01-01

    Device approaches are investigated for optically addressed SLMs based on molecular-beam epitaxy (MBE) engineered III-V materials and structures. Strong photooptic effects can be achieved in periodically delta-doped multiple-quantum-well structures, but are still insufficient for high-contrast modulation with only single- or double-pass absorption through active layers of practical thickness. The asymmetric Fabry-Perot cavity approach is employed to permit extinction of light due to interference of light reflected from the front and back surfaces of the cavity. This approach is realized with an all-MBE-grown structure consisting of GaAs/AlAs quarter-wave stack reflector grown over the GaAs substrate as the high reflectance mirror and the GaAs surface as the low reflectance mirror. High-contrast modulation is achieved using a low-power InGaAs/GaAs quantum well laser for the control signal.

  2. The thermodynamics and gas dynamics of internal-combustion engines. Volume II

    SciTech Connect

    Horlock, J.H.; Winterbone, D.E.

    1986-01-01

    This book is composed of chapters covering methods of analyzing engine air and gas flows, combustion and heat transfer in the engine cylinder, and the application and integration of these analytical tools into a tool for complete engine performance prediction.

  3. Optimization of SiGe selective epitaxy for source/drain engineering in 22 nm node complementary metal-oxide semiconductor (CMOS)

    NASA Astrophysics Data System (ADS)

    Wang, G. L.; Moeen, M.; Abedin, A.; Kolahdouz, M.; Luo, J.; Qin, C. L.; Zhu, H. L.; Yan, J.; Yin, H. Z.; Li, J. F.; Zhao, C.; Radamson, H. H.

    2013-09-01

    SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobility. In this study, selective Si1-xGex growth (0.25 ≤ x ≤ 0.35) with boron concentration of 1-3 × 1020 cm-3 in the process for 22 nm node complementary metal-oxide semiconductor (CMOS) has been investigated and optimized. The growth parameters were carefully tuned to achieve deposition of high quality and highly strained material. The thermal budget was decreased to 800 °C to suppress dopant diffusion, to minimize Si loss in S/D recesses, and to preserve the S/D recess shape. Two layers of Si1-xGex were deposited: a bottom layer with high Ge content (x = 0.35) which filled the recess and a cap layer with low Ge content (x = 0.25) which was elevated in the S/D regions. The elevated SiGe cap layer was intended to be consumed during the Ni-silicidation process in order to avoid strain reduction in the channel region arising from strain relaxation in SiGe S/D. In this study, a kinetic gas model was also applied to predict the pattern dependency of the growth and to determine the epi-profile in different transistor arrays. The input parameters include growth temperature, partial pressures of reactant gases, and chip layout. By using this model, the number of test wafers for epitaxy experiments can be decreased significantly. When the epitaxy process parameters can be readily predicted by the model for epi-profile control in an advanced chip design, fast and cost-effective process development can be achieved.

  4. Engineered Photosystem II reaction centers optimize photochemistry versus photoprotection at different solar intensities.

    PubMed

    Vinyard, David J; Gimpel, Javier; Ananyev, Gennady M; Mayfield, Stephen P; Dismukes, G Charles

    2014-03-12

    The D1 protein of Photosystem II (PSII) provides most of the ligating amino acid residues for the Mn4CaO5 water-oxidizing complex (WOC) and half of the reaction center cofactors, and it is present as two isoforms in the cyanobacterium Synechococcus elongatus PCC 7942. These isoforms, D1:1 and D1:2, confer functional advantages for photosynthetic growth at low and high light intensities, respectively. D1:1, D1:2, and seven point mutations in the D1:2 background that are native to D1:1 were expressed in the green alga Chlamydomonas reinhardtii. We used these nine strains to show that those strains that confer a higher yield of PSII charge separation under light-limiting conditions (where charge recombination is significant) have less efficient photochemical turnover, measured in terms of both a lower WOC turnover probability and a longer WOC cycle period. Conversely, these same strains under light saturation (where charge recombination does not compete) confer a correspondingly faster O2 evolution rate and greater protection against photoinhibition. Taken together, the data clearly establish that PSII primary charge separation is a trade-off between photochemical productivity (water oxidation and plastoquinone reduction) and charge recombination (photoprotection). These trade-offs add up to a significant growth advantage for the two natural isoforms. These insights provide fundamental design principles for engineering of PSII reaction centers with optimal photochemical efficiencies for growth at low versus high light intensities.

  5. Semiconductor devices: solar cells. January 1975-May 1981 (citations from the International Information Service for the Physics and Engineering Communities Data Base). Report for Jan 75-May 81

    SciTech Connect

    Not Available

    1981-05-01

    The applications of semiconductor devices to solar cells and arrays are presented. Emphasis is placed on manufacturing processes, cell design, and performance. (Contains 235 citations fully indexed and including a title list.)

  6. A stepwise increase in pristinamycin II biosynthesis by Streptomyces pristinaespiralis through combinatorial metabolic engineering.

    PubMed

    Li, Lei; Zhao, Yawei; Ruan, Lijun; Yang, Sheng; Ge, Mei; Jiang, Weihong; Lu, Yinhua

    2015-05-01

    Pristinamycin, which is a streptogramin antibiotic produced by Streptomyces pristinaespiralis, contains two chemically unrelated compounds, pristinamycin I (PI) and pristinamycin II (PII). Semi-synthetic derivatives of PI and PII have been approved for use in human medicine to treat a broad range of drug-resistant pathogens. In this study, we design and implement a combinatorial metabolic engineering strategy for improving PII production. First, an extra copy of the PII biosynthetic gene cluster, which was assembled using a modified Gibson assembly method for cloning large DNA fragments with high GC contents, was introduced into a high-producing strain S. pristinaespiralis HCCB10218. This duplication of the PII biosynthetic gene cluster resulted in a maximum increase in PII titer by 45%. Second, all seven cluster-situated regulatory genes (from papR1 to papR6 and spbR) were systematically manipulated. Higher PII titers were achieved by deleting either one of the two repressor genes papR3 or papR5 in combination with overexpression of both activator genes papR4 and papR6, and the resulting strains ∆papR3+R4R6 and ∆papR5+R4R6 showed maximum increases in PII production by 99% and 75%, respectively. A combination of the above two different approaches was employed. Integration of the assembled PII gene cluster (BAC-F1F15) into ∆papR5+R4R6 led to the highest PII titer improvement, which was approximately 1.5-fold higher than the parental strain. By adding the macroreticular resin, which can separate pristinamycin in situ and thereby lessen end-product feedback inhibition and toxic effects, PII titers of the final engineered strain ∆papR5+R4R6/BAC-F1F15 reached 1.13 and 1.16g/L in the Erlenmeyer flask and 5-L bioreactor, respectively, with 5.13- and 5.26-fold improvements over the parental strain. Taken together, this combinatorial strategy is an efficient method to optimize PII biosynthesis of S. pristinaespiralis and may be extended to other industrially used

  7. Engineering semiconductor hybrids for sensing

    NASA Astrophysics Data System (ADS)

    Gumbs, Godfrey; Iurov, Andrii; Huang, Danhong

    2016-06-01

    The effect of screening of the coulomb interaction between two layers of two-dimensional electrons, such as in graphene, by a highly doped semiconducting substrate is investigated. We employ the random-phase approximation to calculate the dispersion equation of this hybrid structure in order to determine the plasmon excitation spectrum. When an electric current is passed through a layer, the low-frequency plasmons in the layer may bifurcate into separate streams due to the current-driving effect. At a critical wave vector, determined by the separation between layers and their distance from the surface, their phase velocities may be in opposite directions and a surface plasmon instability leads to the emission of radiation. Applications to detectors and other electromagnetic devices exploiting nano-plasmonics are discussed.

  8. 76 FR 24872 - California State Nonroad Engine and Vehicle Pollution Control Standards; Authorization of Tier II...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-03

    ... applicable part: Construction equipment or vehicle means any internal combustion engine-powered machine... any internal combustion engine- powered machine primarily used in the commercial production and/or... AGENCY California State Nonroad Engine and Vehicle Pollution Control Standards; Authorization of Tier...

  9. Handbook of Semiconductor Technology, 2 Volume Set

    NASA Astrophysics Data System (ADS)

    Jackson, Kenneth A.; Schröter, Wolfgang

    2000-09-01

    Semiconductor technology is the basis of today's microelectronics industry with its many impacts on our modern life, i.e. computer and communication technology. This two-volume handbook covers the basics of semiconductor processing technology, which are as essential for the design of new microelectronic devices as the fundamental physics. Volume 1 'Electronic Structure and Properties' covers the structure and properties of semiconductors, with particular emphasis on concepts relevant to semiconductor technology. Volume 2 'Processing of Semiconductors' deals with the enabling materials technology for the electronics industry. World-renowned authors have contributed to this unique treatment of the processing of semiconductors and related technologies. Of interest to physicists and engineers in research and in the electronics industry, this is a valuable reference source and state-of-the-art review by the world's top authors.

  10. Molecularly Engineered Ru(II) Sensitizers Compatible with Cobalt(II/III) Redox Mediators for Dye-Sensitized Solar Cells.

    PubMed

    Wu, Kuan-Lin; Huckaba, Aron J; Clifford, John N; Yang, Ya-Wen; Yella, Aswani; Palomares, Emilio; Grätzel, Michael; Chi, Yun; Nazeeruddin, Mohammad Khaja

    2016-08-01

    Thiocyanate-free isoquinazolylpyrazolate Ru(II) complexes were synthesized and applied as sensitizers in dye-sensitized solar cells (DSCs). Unlike most other successful Ru sensitizers, Co-based electrolytes were used, and resulting record efficiency of 9.53% was obtained under simulated sunlight with an intensity of 100 mW cm(-2). Specifically, dye 51-57dht.1 and an electrolyte based on Co(phen)3 led to measurement of a JSC of 13.89 mA cm(-2), VOC of 900 mV, and FF of 0.762 to yield 9.53% efficiency. The improved device performances were achieved by the inclusion of 2-hexylthiophene units onto the isoquinoline subunits, in addition to lengthening the perfluoroalkyl chain on the pyrazolate chelating group, which worked to increase light absorption and decrease recombination effects when using the Co-based electrolyte. As this study shows, Ru(II) sensitizers bearing sterically demanding ligands can allow successful utilization of important Co electrolytes and high performance. PMID:27420188

  11. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  12. The discrimination of type I and type II collagen and the label-free imaging of engineered cartilage tissue.

    PubMed

    Su, Ping-Jung; Chen, Wei-Liang; Li, Tsung-Hsien; Chou, Chen-Kuan; Chen, Te-Hsuen; Ho, Yi-Yun; Huang, Chi-Hsiu; Chang, Shwu-Jen; Huang, Yi-You; Lee, Hsuan-Shu; Dong, Chen-Yuan

    2010-12-01

    Using excitation polarization-resolved second harmonic generation (SHG) microscopy, we measured SHG intensity as a function of the excitation polarization angle for type I and type II collagens. We determined the second order susceptibility (χ((2))) tensor ratios of type I and II collagens at each pixel, and displayed the results as images. We found that the χ((2)) tensor ratios can be used to distinguish the two types of collagen. In particular, we obtained χ(zzz)/χ(zxx) = 1.40 ± 0.04 and χ(xzx)/χ(zxx) = 0.53 ± 0.10 for type I collagen from rat tail tendon, and χ(zzz)/χ(zxx) = 1.14 ± 0.09 and χ(xzx)/χ(zxx) = 0.29 ± 0.11 for type II collagen from rat trachea cartilage. We also applied this methodology on the label-free imaging of engineered cartilage tissue which produces type I and II collagen simultaneously. By displaying the χ((2)) tensor ratios in the image format, the variation in the χ((2)) tensor ratios can be used as a contrast mechanism for distinguishing type I and II collagens. PMID:20875682

  13. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2009-05-19

    Disclosed herein is a graded core/shell semiconductor nanorod having at least a first segment of a core of a Group II-VI, Group III-V or a Group IV semiconductor, a graded shell overlying the core, wherein the graded shell comprises at least two monolayers, wherein the at least two monolayers each independently comprise a Group II-VI, Group III-V or a Group IV semiconductor.

  14. III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers

    NASA Astrophysics Data System (ADS)

    Chiu, YenTing

    This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further

  15. Recent Development of the Two-Stroke Engine. II - Design Features. 2; Design Features

    NASA Technical Reports Server (NTRS)

    Zeman, J.

    1945-01-01

    Completing the first paper dealing with charging methods and arrangements, the present paper discusses the design forms of two-stroke engines. Features which largely influence piston running are: (a) The shape and surface condition of the sliding parts. (b) The cylinder and piston materials. (c) Heat conditions in the piston, and lubrication. There is little essential difference between four-stroke and two-stroke engines with ordinary pistons. In large engines, for example, are always found separately cast or welded frames in which the stresses are taken up by tie rods. Twin piston and timing piston engines often differ from this design. Examples can be found in many engines of German or foreign make. Their methods of operation will be dealt with in the third part of the present paper, which also includes the bibliography. The development of two-stroke engine design is, of course, mainly concerned with such features as are inherently difficult to master; that is, the piston barrel and the design of the gudgeon pin bearing. Designers of four-stroke engines now-a-days experience approximately the same difficulties, since heat stresses have increased to the point of influencing conditions in the piston barrel. Features which notably affect this are: (a) The material. (b) Prevailing heat conditions.

  16. Raman spectra of Cu{sub 2}B{sup II}C{sup IV}X{sub 4}{sup VI} magnetic quaternary semiconductor compounds with tetragonal stannite type structure

    SciTech Connect

    Rincón, C. Quintero, M.; Power, Ch.; Moreno, E.; Quintero, E.; Morocoima, M.; Henao, J. A.; Macías, M. A.

    2015-05-28

    A comparative study of the Raman spectra of Cu{sub 2}B{sup II}C{sup IV}S{sub 4}{sup VI} and Cu{sub 2}B{sup II}C{sup IV}Se{sub 4}{sup VI}(where B = Mn or Fe) magnetic quaternary semiconductor compounds with stannite-type structure (I4{sup ¯}2m) has been done. Most of the fourteen Raman lines expected for these materials were observed in the spectra. The two strongest lines observed have been assigned to the IR inactive A{sub 1}{sup 1} and A{sub 1}{sup 2} stannite modes that originated from the motion of the S or Se anion around the Cu and C{sup IV} cations remaining at rest. The shift in the frequency of these two lines of about 150 cm{sup −1} to lower energies observed in Cu{sub 2}B{sup II}C{sup IV}Se{sub 4}{sup VI} compounds as compared to those in Cu{sub 2}B{sup II}C{sup IV}S{sub 4}{sup VI} ones, can then be explained as due to the anion mass effect. Based on the fact that values of these frequencies depend mainly on anion mass and bond-stretching forces between nearest-neighbor atoms, the vibrational frequencies v{sup ¯}(A{sub 1}{sup 2}) and v{sup ¯}(A{sub 1}{sup 2}) of both modes for several Cu{sub 2}B{sup II}C{sup IV}X{sub 4}{sup VI} stannite compounds (where X = S, Se, or Te) very close to the experimental data reported for these materials were calculated from a simple model that relates these stretching forces to the anion-cation bond-distances.

  17. Three-dimensional modeling of diesel engine intake flow, combustion and emissions-II

    SciTech Connect

    Reitz, R.D.; Rutland, C.J.

    1993-09-01

    A three-dimensional computer code, KIVA, is being modified to include state-of-the-art submodels for diesel engine flow and combustion. Improved and/or new submodels which have already been implemented and previously reported are: Wall heat transfer with unsteadiness and compressibility, laminar-turbulent characteristic time combustion with unburned HC and Zeldo`vich NO{sub x}, and spray/wall impingement with rebounding and sliding drops. Progress on the implementation of improved spray drop drag and drop breakup models, the formulation and testing of a multistep kinetics ignition model and preliminary soot modeling results are described in this report. In addition, the use of a block structured version of KIVA to model the intake flow process is described. A grid generation scheme has been developed for modeling realistic (complex) engine geometries, and computations have been made of intake flow in the ports and combustion chamber of a two-intake-valve engine. The research also involves the use of the code to assess the effects of subprocesses on diesel engine performance. The accuracy of the predictions is being tested by comparisons with engine experiments. To date, comparisons have been made with measured engine cylinder pressure, temperature and heat flux data, and the model results are in good agreement with the experiments. Work is in progress that will allow validation of in-cylinder flow and soot formation predictions. An engine test facility is described that is being used to provide the needed validation data. Test results have been obtained showing the effect of injection rate and split injections on engine performance and emissions.

  18. Part I: Synthesis and study of nonacene derivatives; Part II: Optoelectronic properties of metal-semiconductor nanocomposites in strongly coupled regime

    NASA Astrophysics Data System (ADS)

    Khon, Dmitriy

    Acenes are polycyclic aromatic hydrocarbons (PAHs) consisting of linearly fused benzene rings. In the recent past, acenes have been of interest from fundamental and applied perspectives. Smaller acenes such as benzene, naphthalene, and anthracene are among the most studied organic compounds and their properties are well explored. Pentacene has received considerable attention as the most promising active semiconductor for use in organic thin film transistors (TFT) because of its high charge-carrier mobility; however, poor environmental stability is one of the problems limiting its practical application. As the number of rings increases, the members of the acene family become increasingly reactive. The successful synthesis of heptacene developed by Mondal et al. used the Strating-Zwanenberg photodecarbonylation reaction. The lesser stability of the tetracene moieties in the nonacene photoprecursor compared to the anthracene moieties of the heptacene process make its synthesis more challenging. The latter scheme requires 2,3-dibromoanthracene as one of the starting materials. Besides the poor solubility of 2,3-dibromoanthracene, failure was also due to insufficient formation of anthracyne upon treatment of 2,3-dibromoanthracene with n-BuLi. Although the initial idea didn't work we used the same scheme replacing 2,3-dibromoanthracene with 7,8-dibromo-1,4-dihydroanthracene. The reaction of the latter with 5,6,7,8-tetramethylenebicyclo[2.2.2]oct-2-ene gave 1,4,7,8,9,12,15,18,19,20-octadecahydro-8,19-diethenononacene albeit in low yield. Multiple attempts to dehydrogenate the non-aromatic rings using DDQ and other reagents under various conditions failed to produce the desired compound. Recently Miller reported the synthesis of relatively stable heptacene derivatives having a combination of arylthio and o-dialkylphenyl substituents. Miller's scheme used 1,2,4,5-tetrakis(bromomethyl)-3,6-bis(4'- t-butylthiophenyl)benzene as the core precursor. Another synthetic approach

  19. TIBER II/ETR final design report: Volume 1, 1. 0 Introduction; 2. 0 plasma engineering

    SciTech Connect

    Lee, J.D.

    1987-09-01

    This paper discusses the design of the TIBER II tokamak test reactor. Specific topics discussed are the physics objectives for Tiber, magnetics, baseline operating point, pulsed inductive operation, edge physics and impurity control, fueling, disruption control, vertical stability and impurity flow reversal. (LSP)

  20. Biomedical Engineering at the Indian Institute of Technology, (Madras)-II.

    PubMed

    Ghista, D N

    1980-01-01

    The Biomedical Engineering Division of the Indian Institute of Technology in Madras engages in a program of research, development and teaching. A visitor to our institution would, at any time, find a considerable variety of projects and courses being followed as well as active consultation with industry and the medical profession.

  1. Designing Preclinical Instruction for Psychomotor Skills (II)--Instructional Engineering: Task Analysis.

    ERIC Educational Resources Information Center

    Knight, G. William; And Others

    1994-01-01

    The first step in engineering the instruction of dental psychomotor skills, task analysis, is explained. A chart details the procedural, cognitive, desired-criteria, and desired-performance analysis of a single task, occlusal preparation for amalgam restoration with carious lesion. (MSE)

  2. Shaping the Future. Volume II: Perspectives on Undergraduate Education in Science, Mathematics, Engineering, and Technology.

    ERIC Educational Resources Information Center

    National Science Foundation, Washington, DC. Directorate for Education and Human Resources.

    This is a companion study to "Shaping the Future: New Expectations for Undergraduate Education in Science, Math, Engineering, and Technology (SMET)" (NSF 96-139). Both the original report and Volume 2 focus on a collaborative approach to developing and implementing strategies to improve undergraduate SMET education. The reports, compiled by the…

  3. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT II, MAINTAINING THE AIR SYSTEM--DETROIT DIESEL ENGINES.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE AIR SYSTEM. TOPICS ARE (1) OPERATION AND FUNCTION, (2) AIR CLEANER, (3) AIR SHUT-DOWN HOUSING, (4) EXHAUST SYSTEM, (5) BLOWER, (6) TURBOCHARGER, AND (7) TROUBLE-SHOOTING TIPS ON THE AIR SYSTEM. THE MODULE CONSISTS OF A…

  4. 40 CFR Appendix II to Part 1045 - Duty Cycles for Propulsion Marine Engines

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Speed terms are defined in 40 CFR part 1065. Percent speed values are relative to maximum test speed. 2... 40 CFR part 1065. Percent speed values are relative to maximum test speed. 2 Advance from one mode to...) The following duty cycle applies for ramped-modal testing: RMC Mode Time in mode(seconds) Engine...

  5. Chemical Science and Technology II. A Study Guide of the Science and Engineering Technician Curriculum.

    ERIC Educational Resources Information Center

    Ballinger, Jack T.; Wolf, Lawrence J.

    This study guide is part of a program of studies entitled the Science and Engineering Technician (SET) Curriculum developed to provide a framework for training technicians in the use of electronic instruments and their applications. This interdisciplinary course of study integrates elements from the disciplines of chemistry, physics, mathematics,…

  6. Enhanced carrier multiplication in engineered quasi-type-II quantum dots.

    PubMed

    Cirloganu, Claudiu M; Padilha, Lazaro A; Lin, Qianglu; Makarov, Nikolay S; Velizhanin, Kirill A; Luo, Hongmei; Robel, Istvan; Pietryga, Jeffrey M; Klimov, Victor I

    2014-01-01

    One process limiting the performance of solar cells is rapid cooling (thermalization) of hot carriers generated by higher-energy solar photons. In principle, the thermalization losses can be reduced by converting the kinetic energy of energetic carriers into additional electron-hole pairs via carrier multiplication (CM). While being inefficient in bulk semiconductors this process is enhanced in quantum dots, although not sufficiently high to considerably boost the power output of practical devices. Here we demonstrate that thick-shell PbSe/CdSe nanostructures can show almost a fourfold increase in the CM yield over conventional PbSe quantum dots, accompanied by a considerable reduction of the CM threshold. These structures enhance a valence-band CM channel due to effective capture of energetic holes into long-lived shell-localized states. The attainment of the regime of slowed cooling responsible for CM enhancement is indicated by the development of shell-related emission in the visible observed simultaneously with infrared emission from the core. PMID:24938462

  7. Enhanced carrier multiplication in engineered quasi-type-II quantum dots

    PubMed Central

    Cirloganu, Claudiu M.; Padilha, Lazaro A.; Lin, Qianglu; Makarov, Nikolay S.; Velizhanin, Kirill A.; Luo, Hongmei; Robel, Istvan; Pietryga, Jeffrey M.; Klimov, Victor I.

    2014-01-01

    One process limiting the performance of solar cells is rapid cooling (thermalization) of hot carriers generated by higher-energy solar photons. In principle, the thermalization losses can be reduced by converting the kinetic energy of energetic carriers into additional electron-hole pairs via carrier multiplication (CM). While being inefficient in bulk semiconductors this process is enhanced in quantum dots, although not sufficiently high to considerably boost the power output of practical devices. Here we demonstrate that thick-shell PbSe/CdSe nanostructures can show almost a fourfold increase in the CM yield over conventional PbSe quantum dots, accompanied by a considerable reduction of the CM threshold. These structures enhance a valence-band CM channel due to effective capture of energetic holes into long-lived shell-localized states. The attainment of the regime of slowed cooling responsible for CM enhancement is indicated by the development of shell-related emission in the visible observed simultaneously with infrared emission from the core. PMID:24938462

  8. Engineering an intracellular pathway for major histocompatibility complex class II presentation of antigens.

    PubMed Central

    Wu, T C; Guarnieri, F G; Staveley-O'Carroll, K F; Viscidi, R P; Levitsky, H I; Hedrick, L; Cho, K R; August, J T; Pardoll, D M

    1995-01-01

    The presentation of antigenic peptides by major histocompatibility complex (MHC) class II molecules to CD4+ T cells is critical to the function of the immune system. In this study, we have utilized the sorting signal of the lysosomal-associated membrane protein LAMP-1 to target a model antigen, human papillomavirus 16 E7 (HPV-16 E7), into the endosomal and lysosomal compartments. The LAMP-1 sorting signal reroutes the antigen into the MHC class II processing pathway, resulting in enhanced presentation to CD4+ cells in vitro. In vivo immunization experiments in mice demonstrated that vaccinia containing the chimeric E7/LAMP-1 gene generated greater E7-specific lymphoproliferative activity, antibody titers, and cytotoxic T-lymphocyte activities than vaccinia containing the wild-type HPV-16 E7 gene. These results suggest that specific targeting of an antigen to the endosomal and lysosomal compartments enhances MHC class II presentation and vaccine potency. Images Fig. 2 Fig. 3 PMID:8524826

  9. Altitude-chamber Performance of British Roll-royce Nene II Engine IV : Effect of Operational Variables on Temperature Distribution at Combustion-chamber Outlets

    NASA Technical Reports Server (NTRS)

    Huntley, Sidney C

    1950-01-01

    Temperature surveys were made at the combustion-chamber outlets of a British Rolls-Royce Nene II engine. The highest mean nozzle-vane and mean gas temperatures were found to occur at a radius approximately 75% of the nozzle-vane length from the inner ring of the nozzle-vane assembly. Variations in engine speed, jet-nozzle area, simulated altitude, and simulated flight speed altered the temperature level but did not materially affect the pattern of radial temperature distribution.

  10. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2013-03-26

    Graded core/shell semiconductor nanorods and shapped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  11. Graded core/shell semiconductor nanorods and nanorod barcodes

    DOEpatents

    Alivisatos, A. Paul; Scher, Erik C.; Manna, Liberato

    2010-12-14

    Graded core/shell semiconductor nanorods and shaped nanorods are disclosed comprising Group II-VI, Group III-V and Group IV semiconductors and methods of making the same. Also disclosed are nanorod barcodes using core/shell nanorods where the core is a semiconductor or metal material, and with or without a shell. Methods of labeling analytes using the nanorod barcodes are also disclosed.

  12. Tuning and synthesis of semiconductor nanostructures by mechanical compression

    DOEpatents

    Fan, Hongyou; Li, Binsong

    2015-11-17

    A mechanical compression method can be used to tune semiconductor nanoparticle lattice structure and synthesize new semiconductor nanostructures including nanorods, nanowires, nanosheets, and other three-dimensional interconnected structures. II-VI or IV-VI compound semiconductor nanoparticle assemblies can be used as starting materials, including CdSe, CdTe, ZnSe, ZnS, PbSe, and PbS.

  13. Ice Protection of Turbojet Engines by Inertia Separation of Water II : Single-offset-duct System

    NASA Technical Reports Server (NTRS)

    Von Glahn, Uwe

    1948-01-01

    Investigation of a single-offset-duct system designed to prevent entrance of water into a turbojet engine was conducted on a half-scale nacelle model. An investigation was made to determine ram-pressure recovery and radial velocity profiles at the compressor section and icing characteristics of such a duct system. At a design inlet velocity of 0.77, the maximum ram-pressure recovery attained with effective water-separating inlet was 77 percent, which is considerably less than attainable with a direct-ram inlet. Continuous heating of the accessory-housing surface would be required for inlets that have a small ice storage space.

  14. Near-Infrared Photoluminescence Enhancement in Ge/CdS and Ge/ZnS Core/Shell Nanocrystals: Utilizing IV/II-VI Semiconductor Epitaxy

    SciTech Connect

    Guo, Yijun; Rowland, Clare E; Schaller, Richard D; Vela, Javier

    2014-08-26

    Ge nanocrystals have a large Bohr radius and a small, size-tunable band gap that may engender direct character via strain or doping. Colloidal Ge nanocrystals are particularly interesting in the development of near-infrared materials for applications in bioimaging, telecommunications and energy conversion. Epitaxial growth of a passivating shell is a common strategy employed in the synthesis of highly luminescent II–VI, III–V and IV–VI semiconductor quantum dots. Here, we use relatively unexplored IV/II–VI epitaxy as a way to enhance the photoluminescence and improve the optical stability of colloidal Ge nanocrystals. Selected on the basis of their relatively small lattice mismatch compared with crystalline Ge, we explore the growth of epitaxial CdS and ZnS shells using the successive ion layer adsorption and reaction method. Powder X-ray diffraction and electron microscopy techniques, including energy dispersive X-ray spectroscopy and selected area electron diffraction, clearly show the controllable growth of as many as 20 epitaxial monolayers of CdS atop Ge cores. In contrast, Ge etching and/or replacement by ZnS result in relatively small Ge/ZnS nanocrystals. The presence of an epitaxial II–VI shell greatly enhances the near-infrared photoluminescence and improves the photoluminescence stability of Ge. Ge/II–VI nanocrystals are reproducibly 1–3 orders of magnitude brighter than the brightest Ge cores. Ge/4.9CdS core/shells show the highest photoluminescence quantum yield and longest radiative recombination lifetime. Thiol ligand exchange easily results in near-infrared active, water-soluble Ge/II–VI nanocrystals. We expect this synthetic IV/II–VI epitaxial approach will lead to further studies into the optoelectronic behavior and practical applications of Si and Ge-based nanomaterials.

  15. Engineered Mononuclear Variants in Bacillus cereus Metallo-β-lactamase BcII Are Inactive†

    PubMed Central

    Abriata, Luciano A.; González, Lisandro J.; Llarrull, Leticia I.; Tomatis, Pablo E.; Myers, William K.; Costello, Alison L.; Tierney, David L.; Vila, Alejandro J.

    2008-01-01

    Metallo-β-lactamases (MβLs) are zinc enzymes able to hydrolyze almost all β-lactam antibiotics, rendering them inactive, at the same time endowing bacteria high levels of resistance. The design of inhibitors active against all classes of MβLs has been hampered by their structural diversity and by the heterogeneity in metal content in enzymes from different sources. BcII is the metallo-β-lactamase from Bacillus cereus, which is found in both the mononuclear and dinuclear forms. Despite extensive studies, there is still controversy about the nature of the active BcII species. Here we have designed two mutant enzymes in which each one of the metal binding sites was selectively removed. Both mutants were almost inactive, despite preserving most of the structural features of each metal site. These results reveal that neither site isolated in the MβL scaffold is sufficient to render a fully active enzyme. This suggests that only the dinuclear species is active or that the mononuclear variants can be active only if aided by other residues that would be metal ligands in the dinuclear species. PMID:18652482

  16. Class II-restricted T cell receptor engineered in vitro for higher affinity retains peptide specificity and function

    PubMed Central

    Weber, K. Scott; Donermeyer, David L.; Allen, Paul M.; Kranz, David M.

    2005-01-01

    The T cell receptor (TCR) αβ heterodimer determines the peptide and MHC specificity of a T cell. It has been proposed that in vivo selection processes maintain low TCR affinities because T cells with higher-affinity TCRs would (i) have reduced functional capacity or (ii) cross-react with self-peptides resulting in clonal deletion. We used the class II-restricted T cell clone 3.L2, specific for murine hemoglobin (Hb/I-Ek), to explore these possibilities by engineering higher-affinity TCR mutants. A 3.L2 single-chain TCR (Vβ-linker-Vα) was mutagenized and selected for thermal stability and surface expression in a yeast display system. Stabilized mutants were used to generate a library with CDR3 mutations that were selected with Hb/I-Ek to isolate a panel of affinity mutants with KD values as low as 25 nM. Kinetic analysis of soluble single-chain TCRs showed that increased affinities were the result of both faster on-rates and slower off-rates. T cells transfected with the mutant TCRs and wild-type TCR responded to similar concentrations of peptide, indicating that the increased affinity was not detrimental to T cell activation. T cell transfectants maintained exquisite hemoglobin peptide specificity, but an altered peptide ligand that acted as an antagonist for the wild-type TCR was converted to a strong agonist with higher-affinity TCRs. These results show that T cells with high-affinity class II reactive TCRs are functional, but there is an affinity threshold above which an increase in affinity does not result in significant enhancement of T cell activation. PMID:16365315

  17. Preparing Climate Engineering Responses to Climate Emergencies II: Impact Detection/Attribution and Field Testing

    NASA Astrophysics Data System (ADS)

    Blackstock, J. J.; Battisti, D.; Caldeira, K.; Eardley, D. M.; Katz, J. I.; Keith, D. W.; Koonin, S. E.; Patrinos, A. A.; Schrag, D. P.; Socolow, R. H.

    2008-12-01

    Through a one-week intensive study, the authors of this abstract explored the question: What program of comprehensive technical research over the next decade would maximally reduce the uncertainties associated with climate engineering responses to climate emergencies? The motivations underlying this question, our group's focus on climate engineering concepts for manipulating incident short-wave solar radiation, and our in-depth consideration of stratospheric aerosol interventions as a case example are all described in a previous presentation (Keith et al. in this session). This second of two presentations on our study group's findings concentrates specifically on our technical evaluation of the issues associated with climate impact detection and attribution. Our analyses begin by examining the natural variability (noise) and equilibration timescales (temporal response) of a number of specific climate parameters (e.g. surface radiative flux, surface temperature, atmospheric ozone concentrations, etc.) at both the global and regional scales. First, using the assumption of immediate response for all climate parameters, order-of-magnitude signal-to-noise ratio calculations are used to estimate the minimum intervention durations and amplitudes needed for climate impacts of predicted magnitude to be attributably detected. Next, a number of relevant processes (physical, chemical and biological) within the climate system are evaluated to provide order-of-magnitude estimates for the actual temporal response of these climate parameters (e.g. delay in global temperature response due to ocean heat capacity). Cumulatively, these first-order quantitative estimates reveal a number of basic limits to the timescale over which equilibrium climatic parameter impacts of a climate engineering intervention could be detected. Building from these basic results, we examine current climate monitoring capabilities across four broad categories of climate parameters: (1) radiative; (2

  18. Engineering functional artificial hybrid proteins between poplar peroxiredoxin II and glutaredoxin or thioredoxin

    SciTech Connect

    Rouhier, Nicolas . E-mail: nrouhier@scbiol.uhp-nancy.fr; Gama, Filipe; Wingsle, Gunnar; Gelhaye, Eric; Gans, Pierre; Jacquot, Jean-Pierre

    2006-03-24

    The existence of natural peroxiredoxin-glutaredoxin hybrid enzymes in several bacteria is in line with previous findings indicating that poplar peroxiredoxin II can use glutaredoxin as an electron donor. This peroxiredoxin remains however unique since it also uses thioredoxin with a quite good efficiency. Based on the existing fusions, we have created artificial enzymes containing a poplar peroxiredoxin module linked to glutaredoxin or thioredoxin modules. The recombinant fusion enzymes folded properly into non-covalently bound homodimers or homotetramers. Two of the three protein constructs exhibit peroxidase activity, a reaction where the two modules need to function together, but they also display enzymatic activities specific of each module. In addition, mass spectrometry analyses indicate that the Prx module can be both glutathiolated or overoxidized in vitro. This is discussed in the light of the Prx reactivity.

  19. Molecular Engineering, Photophysical and Electrochemical Characterizations of Novel Ru(II) and BODIPY Sensitizers for Mesoporous TiO2 Solar Cells

    NASA Astrophysics Data System (ADS)

    Cheema, Hammad Arshad

    To realize the dream of a low carbon society and ensure the wide spread application of renewable energy sources such as solar energy, photovoltaic devices should be highly efficient, cost-effective and stable for at least 20 years. Dye sensitized solar cells (DSCs) are photovoltaic cells that mimic the natural photosynthesis. In a DSC, the dye absorbs photons from incident light and converts those photons to electric charges, which are then extracted to the outer circuit through semiconductor TiO2, whereas the mediator regenerates the oxidized dye. A sensitizer is the pivotal component in the device in terms of determining the spectral response, color, photocurrent density, long term stability, and thickness of a DSC. The breakthrough report by O'Regan and Gratzel in 1991 has garnered more than 18,673 citations (as of October 9, 2014), which indicates the immense scientific interest to better understand and improve the fundamental science of this technology. With the aforementioned in mind, this study has focused on the molecular engineering of novel sensitizers to provide a better understanding of structure-property relationships of novel sensitizers for DSCs. The characterization of sensitizers (HD-1-mono, HD-2-mono and HD-2) for photovoltaic applications showed that the photocurrent response of DSCs can be increased by using mono-ancillary ligand instead of bis-ancillary ligands, which is of great commercial value considering the difference in the molecular weights of both dyes. The results of this work were published in Journal of Materials Chemistry A (doi:10.1039/c4ta01942c) and ACS Applied Materials and Interfaces (doi: 10.1021/am502400b). Furthermore, structure-property relationships were investigated in Ru (II) sensitizers HL-41 and HL-42 in order to elucidate the steric effects of electron donating ancillary ligands on photocurrent and photovoltage, as discussed in Chapter 4. It was found that the electron donating group (ethoxy) ortho to the CH=CH spacer

  20. Seals/Secondary Fluid Flows Workshop 1997; Volume II: HSR Engine Special Session

    NASA Technical Reports Server (NTRS)

    Hendricks, Robert C. (Editor)

    2006-01-01

    The High Speed Civil Transport (HSCT) will be the largest engine ever built and operated at maximum conditions for long periods of time. It is being developed collaboratively with NASA, FAA, Boeing-McDonnell Douglas, Pratt & Whitney, and General Electric. This document provides an initial step toward defining high speed research (HSR) sealing needs. The overview for HSR seals includes defining objectives, summarizing sealing and material requirements, presenting relevant seal cross-sections, and identifying technology needs. Overview presentations are given for the inlet, turbomachinery, combustor and nozzle. The HSCT and HSR seal issues center on durability and efficiency of rotating equipment seals, structural seals and high speed bearing and sump seals. Tighter clearances, propulsion system size and thermal requirements challenge component designers.

  1. Characterization of optoelectronic properties of mercury cadmium telluride and zinc oxide II-VI semiconductors for infrared and ultraviolet detector applications

    NASA Astrophysics Data System (ADS)

    Moazzami, Kaveh

    Infrared (IR) and Ultraviolet (UV) light detectors have numerous applications including thermal imaging and chemical and biological spectroscopy. In this work, key aspects of HgCdTe and ZnO semiconductor materials are studied in accordance to their importance to state of the art IR and UV detector technologies. The leading material technology for IR detectors today is the lattice matched HgCdTe alloy. The model for optical absorption in this material has not been reexamined after major improvements in HgCdTe material growth technology. Access to an accurate model for absorption coefficient of this material is important for understanding of detector behavior, where the degree of accuracy required continues to grow as detector structures continue to add complexity. In this work, the optical absorption coefficient of HgCdTe is studied in detail using theoretical bandstructure calculations, temperature dependent optical spectroscopy, and infrared spectroscopic ellipsometry. A new model for the optical absorption coefficient of this material as a function of composition and temperature is presented based on a proposed empirical relationship. A significant improvement in the prediction of photovoltaic detector spectral response is observed based on this proposed model. ZnO is emerging as an important material for short wavelength optoelectronic devices, and may have a major impact on high-performance UV detectors. In this work, the steady-state and time-resolved response of ZnO photoconductors are studied. A sharp turn on is observed in the UV for these photodetectors, corresponding to the bandgap energy of 3.4eV for the ZnO material. Photoconductive decay transients show a fast (nanoseconds) and slow (milliseconds) time constant that are attributed to minority carrier relaxation and trapping processes, respectively. Persistent photoconductivity was observed, with time constant on the order of minutes, in response to both visible and UV excitation and is attributed to

  2. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XIX, I--ENGINE TUNE-UP--CUMMINS DIESEL ENGINE, II--FRONT END SUSPENSION AND AXLES.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF DIESEL ENGINE TUNE-UP PROCEDURES AND THE DESIGN OF FRONT END SUSPENSION AND AXLES USED ON DIESEL ENGINE EQUIPMENT. TOPICS ARE (1) PRE-TUNE-UP CHECKS, (2) TIMING THE ENGINE, (3) INJECTOR PLUNGER AND VALVE ADJUSTMENTS, (4) FUEL PUMP ADJUSTMENTS ON THE ENGINE (PTR AND PTG),…

  3. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XI, PART I--MAINTAINING THE FUEL SYSTEM (PART I), CUMMINS DIESEL ENGINES, PART II--UNIT REPLACEMENT (ENGINE).

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF DIFFERENCES BETWEEN TWO AND FOUR CYCLE ENGINES, THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL SYSTEM, AND THE PROCEDURES FOR DIESEL ENGINE REMOVAL. TOPICS ARE (1) REVIEW OF TWO CYCLE AND FOUR CYCLE CONCEPT, (2) SOME BASIC CHARACTERISTICS OF FOUR CYCLE ENGINES,…

  4. 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.

  5. 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.

  6. Strain engineering of magnetic anisotropy: The epitaxial growth of cobalt-manganese-gallium Heusler alloy films on III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Carr, David Michael

    This research is the first step towards manipulating thin film magnetic anisotropy through control of uniform epitaxial strain. Pseudomorphic Co 2MnGa films with thicknesses of 300 A have been grown on several III-V semiconductors to generate coherently-strained epitaxial films. Growth of Co2MnGa films at 200°C both directly on GaAs substrates and on thermodynamically stable Sc0.3Er0.7As interlayers resulted in similar physical and magnetic properties. The epitaxial strain generated an induced perpendicular anisotropy and magnetic stripe domains. This resulted in a reduced in-plane remnant magnetization, high coercivity, and a relatively low saturation field for the out-of-plane magnetization. For higher temperature growths, the interlayer was required to minimize interfacial reactions and maintain the magnetic properties of the films. When the growth temperature on the Sc0.3Er0.7As interlayers was increased from 0 to 400°C, the subsequent films had improved L21 atomic ordering, decreased out-of-plane lattice parameters, and enhanced strain-induced perpendicular anisotropy. Dramatic variations in the magnetic anisotropy were observed for films grown on different III-V semiconductors due to controlled strain-induced perpendicular anisotropy. For Co2MnGa films grown under tension on InP, the magnetization barely saturated out-of-plane with a field of 1.75 Tesla. These films displayed clear in-plane anisotropy and low coercivity switching. For films grown under compression on GaAs, the magnetization easily saturated out-of-plane with a field of a few thousand Oe. These films displayed no in-plane anisotropy in the hysteresis loops and had large coercivities. For comparison, bulk-like unstrained Co2MnGa films were grown on relaxed ErAs interlayers on InAs. These films displayed properties intermediate between films grown on GaAs and InP. Finally, growth of films on GaP resulted in partial relaxation, thereby reducing the induced perpendicular anisotropy and verifying

  7. Effectiveness of Cooperative Learning (Jigsaw II) Method in Teaching English as a Foreign Language to Engineering Students (Case of Firat University, Turkey)

    ERIC Educational Resources Information Center

    Gomleksiz, M. N.

    2007-01-01

    The present study compares the effects of the cooperative jigsaw II method and traditional teacher-centred teaching method on improving vocabulary knowledge and active-passive voice in English as a foreign language for engineering students and the students' attitudes towards learning English. Jigsaw is a cooperative learning model that involves…

  8. 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.

  9. 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.

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

    SciTech Connect

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

    2007-11-15

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

  11. Polymorph engineering of CuMO2 (M = Al, Ga, Sc, Y) semiconductors for solar energy applications: from delafossite to wurtzite.

    PubMed

    Scanlon, David O; Walsh, Aron

    2015-12-01

    The cuprous oxide based ternary delafossite semiconductors have been well studied in the context of p-type transparent conducting oxides. CuAlO2, CuGaO2 and CuInO2 represent a homologous series where the electronic properties can be tuned over a large range. The optical transparency of these materials has been associated with dipole forbidden transitions, which are related to the linear O-Cu-O coordination motif. The recent demonstration that these materials can be synthesized in tetrahedral structures (wurtzite analogues of the chalcopyrite lattice) opens up a new vista of applications. We investigate the underlying structure-property relationships (for Group 3 and 13 metals), from the perspective of first-principles materials modelling, towards developing earth-abundant photoactive metal oxides. All materials studied possess indirect fundamental band gaps ranging from 1 to 2 eV, which are smaller than their delafossite counterparts, although in all cases the difference between direct and indirect band gaps is less than 0.03 eV.

  12. Polymorph engineering of CuMO2 (M = Al, Ga, Sc, Y) semiconductors for solar energy applications: from delafossite to wurtzite.

    PubMed

    Scanlon, David O; Walsh, Aron

    2015-12-01

    The cuprous oxide based ternary delafossite semiconductors have been well studied in the context of p-type transparent conducting oxides. CuAlO2, CuGaO2 and CuInO2 represent a homologous series where the electronic properties can be tuned over a large range. The optical transparency of these materials has been associated with dipole forbidden transitions, which are related to the linear O-Cu-O coordination motif. The recent demonstration that these materials can be synthesized in tetrahedral structures (wurtzite analogues of the chalcopyrite lattice) opens up a new vista of applications. We investigate the underlying structure-property relationships (for Group 3 and 13 metals), from the perspective of first-principles materials modelling, towards developing earth-abundant photoactive metal oxides. All materials studied possess indirect fundamental band gaps ranging from 1 to 2 eV, which are smaller than their delafossite counterparts, although in all cases the difference between direct and indirect band gaps is less than 0.03 eV. PMID:26634726

  13. Polymorph engineering of CuMO2 (M = Al, Ga, Sc, Y) semiconductors for solar energy applications: from delafossite to wurtzite

    PubMed Central

    Scanlon, David O.; Walsh, Aron

    2015-01-01

    The cuprous oxide based ternary delafossite semiconductors have been well studied in the context of p-type transparent conducting oxides. CuAlO2, CuGaO2 and CuInO2 represent a homologous series where the electronic properties can be tuned over a large range. The optical transparency of these materials has been associated with dipole forbidden transitions, which are related to the linear O—Cu—O coordination motif. The recent demonstration that these materials can be synthesized in tetrahedral structures (wurtzite analogues of the chalcopyrite lattice) opens up a new vista of applications. We investigate the underlying structure–property relationships (for Group 3 and 13 metals), from the perspective of first-principles materials modelling, towards developing earth-abundant photoactive metal oxides. All materials studied possess indirect fundamental band gaps ranging from 1 to 2 eV, which are smaller than their delafossite counterparts, although in all cases the difference between direct and indirect band gaps is less than 0.03 eV. PMID:26634726

  14. Mid-IR semiconductor lasers for chemical sensing

    NASA Technical Reports Server (NTRS)

    Hill, C. J.; Yang, R. Q.

    2003-01-01

    The development of mid-IR semiconductor diode lasers based on type-II interband cascade structures is presented. How these diode lasers can be developed to meet the requirements in chemical sensing applications is discussed.

  15. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1999-04-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%, NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) coal providing {ge} 65% of heat input, all solid wastes benign, and cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAC Combustors; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  16. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1998-07-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%, NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard), coal providing {ge} 65% of heat input, all solid wastes benign cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAF Combustor; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  17. The use of the TOPAZ II systems with different conversion and engine systems

    NASA Astrophysics Data System (ADS)

    Ponomarev-Stepnoi, Nikolai N., Dr.; Ogloblin, Boris; Kirillov, E. Y.; Thome, Frank V.

    1995-01-01

    Increase of output electric power and use of heat released in nuclear fuel for thermal jet propulsion is promising for the future development of a bimodal reactor and use of the Topaz-2 Thermionic Space Nuclear Power System (TI-SNPS). In addition to the high-temperature thermionic conversion cycle, the application of low-temperature cycles, such as a machine-type cycle using the Stirling engine and a thermoelectric cycle, is being considered. The possibility of using the Topaz-2 system as a power source for thermal jet propulsion in bimodal operation is also being examined. For low-temperature cycles, the following data are obtained: output electric parameters, geometrical and weight characteristics as a function of thermal power released in the TFE fuel cores, and the relationship of generated total electric power to the total Topaz-2 system weight. The results obtained from this data make it possible to evaluate energy potentials when applying the high-temperature and low-temperature cycles Conference on alternative powere from space; Conference to the Topaz-2 system. The most likely values of specific impulse and propulsion force in relation to hydrogen flow rate in bimodal operation are shown.

  18. Engineering development of coal-fired high performance power systems, Phase II and III

    SciTech Connect

    1999-01-01

    The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: thermal efficiency (HHV) {ge} 47%; NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) coal providing {ge} 65% of heat input; all solid wastes benign; cost of electricity {le} 90% of present plants. Phase 1, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase 1 also included preliminary R and D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. This phase, Phase 2, involves the development and testing of plant subsystems, refinement and updating of the HIPPS commercial plant design, and the site selection and engineering design of a HIPPS prototype plant. Work reported herein is from: Task 2.1 HITAC Combustors; Task 2.2 HITAF Air Heaters; Task 6 HIPPS Commercial Plant Design Update.

  19. Proceedings of the third U. S. national conference on earthquake engineering. Volume II

    SciTech Connect

    Not Available

    1986-01-01

    During the past quarter century the North American continent has experienced a number of damaging earthquakes, among which were the 1964 Alaska earthquake, the 1971 San Fernando, California, earthquake, and most recently the 1985 Mexico City earthquake. A large number of smaller earthquakes have occurred during this period, all of which, along with large earthquakes that have occurred in other parts of the world, serve to remind one that the earthquake hazard is real. In view of potential loss of life and the economic losses that could result from large earthquakes, it is important that the United States continue its vigorous efforts towards mitigating the hazards of earthquakes including developing and implementing safe and economic methods of earthquake-resistant design and construction. In the light of the foregoing observations it it fitting that this Third U.S. National Conference on Earthquake Engineering be held in 1986 at Charleston, South Carolina, on the one-hundred-year anniversary of the 1886 Charleston earthquake. Although intended primarily for participation by U.S. practitioners and researchers, participants from many other parts of the world are also present. From the more than 300 papers offered for publication and presentation, over 200 papers are published in the three volumes of Proceedings and the single volume of Post-Conference Proceedings.

  20. Workshop report and presentations from the Semiconductor Research Corporation-DOE Semiconductor Task Force Workshop

    NASA Astrophysics Data System (ADS)

    The Semiconductor Research Corporation-DOE Semiconductor Task Force Workshop was held in Oak ridge, Tennessee, on November 2-3, 1987. It was to provide a forum for representatives of the national laboratories, DOE, and the semiconductor industry in which to discuss capabilities of the national laboratories which could contribute to the future competitiveness of the US semiconductor industry, to identify specific large and small projects at the national laboratories which would be of direct benefit to the semiconductor industry, and to find ways of implementing these projects. Numerous small projects were identified which would utilize unique capabilities of the national laboratories in advanced ion implantation, plasma processing (including electron cyclotron resonance plasmas), ion and cluster beam deposition, materials characterization, electronic packaging, and laser processing and deposition. Five large-scale candidate projects were identified in synchrotron x-ray lithography, silicon process integration, advanced materials processing science, process analysis and diagnostics, and ultra clean room engineering. The major obstacle to implementing these projects if the lack of appropriate funds to initiate and stimulate interactions between the national laboratories and the semiconductor industry. SEMATECH and the federal government are potential sources of seed funds for these projects. The Semiconductor Research Corporation is ideally suited to interface the semiconductor industry and the national laboratories for many of these interactions.

  1. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXVIII, I--CATERPILLAR STARTING (PONEY) ENGINE (PART II), II--UNDERSTANDING MORE ABOUT STARTING DEVICES.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF DIESEL ENGINE STARTING ENGINES. TOPICS ARE (1) STARTING ENGINE MAGNETO (WICO), (2) MAGNETO MAINTENANCE, (3) SPARK PLUGS, (4) GENERAL DESCRIPTION (STARTING DEVICES), (5) OPERATING (STARTING DEVICES), (6) LUBRICATION (STARTING DEVICES), (7)…

  2. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXVII, I--CATERPILLAR STARTING (PONEY) ENGINE (PART I), II--LEARNING ABOUT BRAKES (PART II).

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE CONSTRUCTION AND OPERATION OF DIESEL ENGINE STARTING ENGINES AND BRAKE SYSTEMS USED ON DIESEL POWERED VEHICLES. TOPICS ARE (1) GENERAL DESCRIPTION, (2) OPERATION, (3) COMBUSTION SPACE AND VALVE ARRANGEMENT (STARTING ENGINES), (4) TYPES OF BRAKES, AND (5) DOUBLE…

  3. SEMICONDUCTOR PHYSICS: Stability and vibrational properties of the hydrogen atom for p-type AlN doped with group-II: a first-principles study

    NASA Astrophysics Data System (ADS)

    Jianmin, Zhang; Guigui, Xu; Qingyun, Wu; Zhigao, Chen; Zhigao, Huang

    2010-06-01

    The stability and local vibrational mode (LVM) of hydrogen related p-type AlN have been studied by first-principles calculations based on density functional theory. The stable and metastable microscopic geometries of group-II (Be, Mg, Ca, Sr, Ba)-H complexes have been investigated. The calculated results indicate that BC|| is the most stable configuration for isolated interstitial H+ and Be-H complexes, while it is ABN,⊥ for Mg-H, Ca-H, Sr-H and Ba-H complexes. Moreover, the vibrational frequencies and the values of k and |α| for the H atom with LVM are calculated. Here, the values of k and |α| are used to describe the parameters of the harmonic and anharmonic contributions, respectively. The calculated results indicate that the larger the size of the doped ion is, the shorter the N-H bond length is, and the larger the potential energy, the vibrational frequencies, the values of k and |α| are. This implies that the size of the doped ion has an important influence on the vibrational properties of H.

  4. Electronic structures and magnetic properties of a II-II-V based diluted magnetic semiconductor Ba 1‑x K x (Cd 1‑y Mn y )2 As 2 with decoupled charge and spin doping

    NASA Astrophysics Data System (ADS)

    Yang, Juntao; Luo, Shijun; Cheng, ZhenXiang; Wang, Xiaotian; Xiong, Yongchen; Amel, Laref

    2016-10-01

    By using the density functional theory within Perdew–Burke–Ernzerh of generalized gradient approximation, the electronic structures and magnetic properties of {{Ba}}1-x{K}x{({{Cd}}1-y{{Mn}}y)}2{{As}}2 system were investigated. Undoped compound {{BaCd}}2{{As}}2 is a semiconductor crystallized with a hexagonal {{CaAl}}2{{Si}}2‑type structure. After local moments doping via isovalent (Cd2+, Mn2+) substitutions, {Ba}{({{Cd}}1-y{{Mn}}y)}2{{As}}2 is antiferromagnetic system, which is attributed to the superexchange interactions between the Mn2+ ions in the high spin state. With itinerant holes introduced via off-stoichiometry (Ba2+, {{{K}}}+) substitutions, {{Ba}}1-x{K}x{({{Cd}}1-y{{Mn}}y)}2{{As}}2 system (except for the system doped with the most nearest neighbor Mn-Mn pair) changes from antiferromagnetic to ferromagnetic, resulted from the indirect exchange interactions based on p ‑ d exchange coupling between As 4p and Mn 3d orbitals. Moreover, hypothetical supercells {{Ba}}10{K}2{{Cd}}22{{Mn}}2{{As}}24 with different lattice parameters under mechanical compression and expansion were calculated to study the effect of itinerant holes on the Curie temperature. Our results reveal that the {{Ba}}1-x{K}x{({{Cd}}1-y{{Mn}}y)}2{{As}}2 system with small lattice has more holes amount and better holes mobility, leading to a higher Curie temperature for the {{CaAl}}2{{Si}}2-type structure DMSs.

  5. Engine

    SciTech Connect

    Shin, H.B.

    1984-02-28

    An internal combustion engine has a piston rack depending from each piston. This rack is connected to a power output shaft through a mechanical rectifier so that the power output shaft rotates in only one direction. A connecting rod is pivotally connected at one end to the rack and at the other end to the crank of a reduced function crankshaft so that the crankshaft rotates at the same angular velocity as the power output shaft and at the same frequency as the pistons. The crankshaft has a size, weight and shape sufficient to return the pistons back into the cylinders in position for the next power stroke.

  6. Semiconductor ohmic contact

    NASA Technical Reports Server (NTRS)

    Hawrylo, Frank Zygmunt (Inventor); Kressel, Henry (Inventor)

    1977-01-01

    A semiconductor device has one surface of P type conductivity material having a wide energy bandgap and a large crystal lattice parameter. Applied to the P type surface of the semiconductor device is a degenerate region of semiconductor material, preferably a group III-V semiconductor material, having a narrower energy bandgap. The degenerate region is doped with tin to increase the crystal lattice of the region to more closely approximate the crystal lattice of the one surface of the semiconductor device. The degenerate region is compensatingly doped with a P type conductivity modifier. An electrical contact is applied to one surface of the degenerate region forming an ohmic contact with the semiconductor device.

  7. Semiconductor bridge (SCB) detonator

    DOEpatents

    Bickes, Jr., Robert W.; Grubelich, Mark C.

    1999-01-01

    The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length.

  8. Semiconductor bridge (SCB) detonator

    DOEpatents

    Bickes, R.W. Jr.; Grubelich, M.C.

    1999-01-19

    The present invention is a low-energy detonator for high-density secondary-explosive materials initiated by a semiconductor bridge (SCB) igniter that comprises a pair of electrically conductive lands connected by a semiconductor bridge. The semiconductor bridge is in operational or direct contact with the explosive material, whereby current flowing through the semiconductor bridge causes initiation of the explosive material. Header wires connected to the electrically-conductive lands and electrical feed-throughs of the header posts of explosive devices, are substantially coaxial to the direction of current flow through the SCB, i.e., substantially coaxial to the SCB length. 3 figs.

  9. 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.

  10. Program plan for the DOE Office of Fusion Energy First Wall/Blanket/Shield Engineering Technology Program. Volume II. Detailed technical plan. Revision 2

    SciTech Connect

    Not Available

    1982-08-01

    The four sections which comprise Part II describe in detail the technical basis for each of the four Program Elements (PE's) of the FWBS Engineering Technology Program (ETP). Each PE is planned to be executed in a number of phases. The purpose of the DTP's is to delineate detailed near-term research, development, and testing required to establish a FWBS engineering data base. Optimum testing strategies and construction of test facilities where needed are identified. The DTP's are based on guidelines given by Argonne National Laboratory which included the basic programmatic goals and the requirements for the types of tests and test conditions.

  11. Textured semiconductors for enhanced photoconductive terahertz emission

    NASA Astrophysics Data System (ADS)

    Collier, Christopher M.; Krupa, Jeffrey D. A.; Hristovski, Ilija R.; Stirling, Trevor J.; Bergen, Mark H.; Holzman, Jonathan F.

    2016-02-01

    There are severe limitations that photoconductive (PC) terahertz (THz) antennas experience due to Joule heating and ohmic losses, which cause premature device breakdown through thermal runaway. In response, this work introduces PC THz antennas utilizing textured InP semiconductors. These textured InP semiconductors exhibit high surface recombination properties and have shortened carrier lifetimes which limit residual photocurrents in the picoseconds following THz pulse emission—ultimately reducing Joule heating and ohmic losses. Fine- and coarse-textured InP semiconductors are studied and compared to a smooth-textured InP semiconductor, which provides a baseline. The surface area ratio (measuring roughness) of the smooth-, fine-, and coarse-textured InP semiconductors is resolved through a computational analysis of SEM images and found as 1.0 +/- 0.1, 2.9 +/- 0.4, and 4.3 +/- 0.6, respectively. The carrier lifetimes of the smooth-, fine-, and coarse-textured InP semiconductors are found as respective values of 200 +/- 6, 100 +/- 10, and 20 +/- 3 ps when measured with a pump-probe experimental system. The emitted THz electric fields and corresponding consumption of photocurrent are measured with a THz experimental setup. The temporal and spectral responses of PC THz antennas made with each of the textured InP semiconductors are found to be similar; however, the consumption of photocurrent (relating to Joule heating and ohmic losses) is greatly diminished for the semiconductors that are textured. The findings of this work can assist in engineering of small-scale PC THz antennas for high-power operation, where they are extremely vulnerable to premature device breakdown through thermal runaway.

  12. Synthesis of semiconductor nanoparticles.

    PubMed

    Chen, Xianfeng; Dobson, Peter J

    2012-01-01

    Here, we describe typical methods and provide detailed experimental protocols for synthesizing and processing various semiconductor nanoparticles which have potential application in biology and medicine. These include synthesis of binary semiconductor nanoparticles; core@shell nanoparticles and alloyed nanoparticles; size-selective precipitation to obtain monodisperse nanoparticles; and strategies for phase transfer of nanoparticles from organic solution to aqueous media. PMID:22791427

  13. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXX, I--CATERPILLAR DIESEL ENGINE MAINTENANCE SUMMARY, II--REIEWING FACTS ABOUT ALTERNATORS.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO PROVIDE A SUMMARY OF DIESEL ENGINE MAINTENANCE FACTORS AND A REVIEW OF DIESEL ENGINE ALTERNATOR OPERATION. THE SEVEN SECTIONS COVER DIESEL ENGINE TROUBLESHOOTING AND THE OPERATION, TESTING, AND ADJUSTING OF ALTERNATORS. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL BRANCH PROGRAMED TRAINING FILM…

  14. Explicit Finite Element Modeling of Multilayer Composite Fabric for Gas Turbine Engine Containment Systems, Phase II. Part 3; Material Model Development and Simulation of Experiments

    NASA Technical Reports Server (NTRS)

    Simmons, J.; Erlich, D.; Shockey, D.

    2009-01-01

    A team consisting of Arizona State University, Honeywell Engines, Systems & Services, the National Aeronautics and Space Administration Glenn Research Center, and SRI International collaborated to develop computational models and verification testing for designing and evaluating turbine engine fan blade fabric containment structures. This research was conducted under the Federal Aviation Administration Airworthiness Assurance Center of Excellence and was sponsored by the Aircraft Catastrophic Failure Prevention Program. The research was directed toward improving the modeling of a turbine engine fabric containment structure for an engine blade-out containment demonstration test required for certification of aircraft engines. The research conducted in Phase II began a new level of capability to design and develop fan blade containment systems for turbine engines. Significant progress was made in three areas: (1) further development of the ballistic fabric model to increase confidence and robustness in the material models for the Kevlar(TradeName) and Zylon(TradeName) material models developed in Phase I, (2) the capability was improved for finite element modeling of multiple layers of fabric using multiple layers of shell elements, and (3) large-scale simulations were performed. This report concentrates on the material model development and simulations of the impact tests.

  15. Semimetal/Semiconductor Nanocomposites for Thermoelectrics

    SciTech Connect

    Lu, Hong; Burke, Peter G.; Gossard, Arthur C.; Zeng, Gehong; Ramu, Ashok T.; Bahk, Je-Hyeong; Bowers, John E.

    2011-04-15

    In this work, we present research on semimetal-semiconductor nanocomposites grown by molecular beam epitaxy (MBE) for thermoelectric applications. We study several different III-V semiconductors embedded with semimetallic rare earth-group V (RE-V) compounds, but focus is given here to ErSb:InxGa1-xSb as a promising p-type thermoelectric material. Nano­structures of RE-V compounds are formed and embedded within the III-V semiconductor matrix. By codoping the nanocomposites with the appropriate dopants, both n-type and p-type materials have been made for thermoelectric applications. The thermoelectric properties have been engineered for enhanced thermoelectric device performance. Segmented thermoelectric power generator modules using 50 μm thick Er-containing nanocomposites have been fabricated and measured. Research on different rare earth elements for thermoelectrics is discussed.

  16. International Semiconductor Device Research Symposium (ISDRS-91)

    NASA Astrophysics Data System (ADS)

    Shur, Michael; Money, John M.

    1992-03-01

    The First International Semiconductor Device Research Symposium took place in Charlottesville, VA, on 4-6 Dec. 1991 for the purpose of providing a convenient forum for the exchange of information and new ideas for researchers from industry, university, and government laboratories with leading researchers from the US, Canada, Europe, Asia, and the former Soviet Union. As the first international conference of its kind to take place after the Aug. 1991 coup attempt in the Soviet Union, it was unique with the presence of an unusually large contingent of Russian scientists. The emphasis of the program was on advanced semiconductor technologies still in their infancy whose tangible technological outcomes are not expected for another five to ten years. Some of the technologies discussed at the symposium included bandgap engineering, large area semiconductor electronics, new millimeter wave and optoelectronic technologies, and silicon carbide and diamond devices.

  17. International Semiconductor Device Research Symposium (ISDRS-91)

    NASA Astrophysics Data System (ADS)

    Shur, Michael

    1992-03-01

    The First International Semiconductor Device Research Symposium (ISDRS-91) took place in Charlottesville, Va on December 4-6, 1991 for the purpose of providing a convenient forum for the exchange of information and new ideas for researchers from industry, university, and government laboratories with leading researchers from the United States, Canada, Europe, Asia, and the former Soviet Union. As the first international conference of its kind to take place after the August 1991 coup attempt in the Soviet Union, it was unique with the presence of an unusually large contingent of Russian scientists. The emphasis of the program was on novel ideas such as advanced semiconductor technologies still in their infancy whose tangible technological outcomes are not expected for another five to ten years. Some of the technologies discussed at the symposium included bandgap engineering, large area semiconductor electronics, new millimeter wave and opto-electronics technologies, and silicon carbide and diamond devices.

  18. Product engineering guide

    SciTech Connect

    McCarty, C.E.

    1989-12-01

    The semiconductor product engineers job requires knowledge and expertise related to many different subjects. This report provides guidance for newcomers to product engineering and is a consise reference for all others involved in product engineering. Subjects addressed are Customer/Supplier interactions, component development sequence, production schedule support, component characterization, product specifications, test equipment requirements, product qualification, characterization and development reports, preferred parts list, standard packaging, and finally, classification and security considerations. This guide is intended to help standardize and simplify the component development sequence presently used in the semiconductor product engineering department. 3 figs., 2 tabs.

  19. 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

  20. Hightower Engineering Academy Prepares High School Students for the Engineering Professions - A Program by the Fort Bend Independent School District - II

    NASA Astrophysics Data System (ADS)

    Cain, Lee; Verret, Doug; Griffin, Richard

    1998-10-01

    Hightower Engineering Academy, a project of the Fort Bend Independent School District, near Houston Texas, introduces high school students to the engineering professions. It has a college preparatory curriculum in which students are first grounded in the fundamentals of science and mathematics. Then more specific courses help them develop an appreciation for, and many of the skills of, the engineering profession. The Academy will implement a consistent teaching philosophy using a diverse array of innovative technology. The Academy is unique in the degree of partnership with local industry and state universities. It is committed to using the best known science pedagogy in combination with proven teaching art, experienced science educators and state-of-the art facilities all aimed at providing future engineers with complete mastery of the foundation knowledge of the profession. Hightower is committed to a "constructivist" teaching philosophy, the synergy of teamwork, and an appreciation of personal and professional ethics To the greatest extent possible, Hightower will have working engineers present the profession to students. There will be guest lecturers, field trips, and mentorships. Students will participate in engineering-specific organizations and competitions. Students will build a portfolio of their accomplishments at Hightower. They will experience project-based learning, culminating in a senior project that will encompass college-level research, experimentation, data analysis, and technical writing.

  1. Pioneering a learning partnership: the University of Texas, SPIE, and the federal government together extend a hand to semiconductor manufacturers

    NASA Astrophysics Data System (ADS)

    Karakekes, Meg; Chen, Ray T.

    1995-10-01

    Semiconductors (the process of making computer chips) is the most competitive component of the electronics industry. To stay competitive, semiconductor manufacturers need employees who continually learn. In an industry in which the knowledge base turns over every three years, keeping engineering professionals on the cutting edge is a challenge. This paper specifically examines the first year activity and outcomes of a regionally based pilot program serving the continuing eduction needs of semiconductor manufacturing engineers. The experimental program's success depends on effective partnering among The University of Texas, The International Society for Optical Engineering (SPIE), the Federal Government, organizations representing displaced engineers, and semiconductor manufacturers in the Southwest.

  2. Assessing Conceptual Knowledge for the Physics of Semiconductors

    ERIC Educational Resources Information Center

    Ene, Emanuela

    2013-01-01

    Following the trend in science and engineering education generated by the visible impact created by the Force Concept Inventory (FCI), the investigator developed a Physics of Semiconductors Concept Inventory (PSCI). PSCI fills the need of standardized concept tests for undergraduate education in photonics and electrical engineering. The structure…

  3. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXIII, I--MAINTAINING THE FUEL SYSTEM, PART II--CATERPILLAR DIESEL ENGINE, II--UNDERSTANDING STEERING SYSTEMS.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL INJECTION SYSTEM AND THE STEERING SYSTEM OF DIESEL POWERED VEHICLES. TOPICS ARE FUEL INJECTION SECTION, AND DESCRIPTION OF THE STEERING SYSTEM. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL BRANCH PROGRAMED TRAINING…

  4. Isotopically controlled semiconductors

    SciTech Connect

    Haller, E.E.

    2004-11-15

    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  5. SLM based semiconductor maskwriter

    NASA Astrophysics Data System (ADS)

    Diez, Steffen; Jehle, Achim

    2015-09-01

    The high-end semiconductor mask fabrication is dominated by e-beam technology. But still more than 50% of all semiconductor masks are produced by laser writers. The current laser writers are based on the same technology that was used 25 years ago. They are reliable and fast but not very economical. Heidelberg Instruments has developed a new economical and fast laser writer based on the latest technologies.

  6. Artificial Photosynthesis with Semiconductor-Liquid Junctions.

    PubMed

    Guijarro, Néstor; Formal, Florian Le; Sivula, Kevin

    2015-01-01

    Given the urgent need to develop a sustainable, carbon neutral energy storage system on a global scale, intense efforts are currently underway to advance the field of artificial photosynthesis: i.e. solar fuel engineering. In this review we give an overview of the field of artificial photosynthesis using a semiconductor-electrolyte interface employed in a photoelectrochemical device or as a heterogeneous photocatalyst. First we present a basic description of the operation principles of a semiconductor-liquid junction based device. The role of nanotechnology in the recent advances in the field is highlighted and common material systems under current study are briefly reviewed. The importance of the material surfaces are further scrutinized by presenting recent advances in interfacial engineering. Technical challenges and an outlook towards industrialization of the technology are given.

  7. 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.

  8. Construction Mechanic, Engine Tune-Up II (Diesel), 8-8. Military Curriculum Materials for Vocational and Technical Education.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. National Center for Research in Vocational Education.

    This course, adapted from military curriculum materials for vocational and technical education, teaches students to restore diesel engine performance to the manufacturer's specifications through troubleshooting and analyzing diesel engine fuel systems and to make minor and major adjustments to those components that directly affect engine…

  9. Wide-Bandgap Semiconductors

    SciTech Connect

    Chinthavali, M.S.

    2005-11-22

    With the increase in demand for more efficient, higher-power, and higher-temperature operation of power converters, design engineers face the challenge of increasing the efficiency and power density of converters [1, 2]. Development in power semiconductors is vital for achieving the design goals set by the industry. Silicon (Si) power devices have reached their theoretical limits in terms of higher-temperature and higher-power operation by virtue of the physical properties of the material. To overcome these limitations, research has focused on wide-bandgap materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond because of their superior material advantages such as large bandgap, high thermal conductivity, and high critical breakdown field strength. Diamond is the ultimate material for power devices because of its greater than tenfold improvement in electrical properties compared with silicon; however, it is more suited for higher-voltage (grid level) higher-power applications based on the intrinsic properties of the material [3]. GaN and SiC power devices have similar performance improvements over Si power devices. GaN performs only slightly better than SiC. Both SiC and GaN have processing issues that need to be resolved before they can seriously challenge Si power devices; however, SiC is at a more technically advanced stage than GaN. SiC is considered to be the best transition material for future power devices before high-power diamond device technology matures. Since SiC power devices have lower losses than Si devices, SiC-based power converters are more efficient. With the high-temperature operation capability of SiC, thermal management requirements are reduced; therefore, a smaller heat sink would be sufficient. In addition, since SiC power devices can be switched at higher frequencies, smaller passive components are required in power converters. Smaller heat sinks and passive components result in higher-power-density power converters

  10. The Beginning of Semiconductor Research in Cuba

    NASA Astrophysics Data System (ADS)

    Veltfort, Theodore

    I was invited to Cuba in 1962 to initiate some efforts in semiconductor development. I had been a physicist and senior research engineer with various electronic companies of the "Silicon Valley" of California, south of San Francisco. I had heard of the efforts made by the new revolutionary government of Cuba to advance the level of science and technology, and I was anxious to see what I could do to help.

  11. EDITORIAL The 23rd Nordic Semiconductor Meeting The 23rd Nordic Semiconductor Meeting

    NASA Astrophysics Data System (ADS)

    Ólafsson, Sveinn; Sveinbjörnsson, Einar

    2010-12-01

    A Nordic Semiconductor Meeting is held every other year with the venue rotating amongst the Nordic countries of Denmark, Finland, Iceland, Norway and Sweden. The focus of these meetings remains 'original research and science being carried out on semiconductor materials, devices and systems'. Reports on industrial activity have usually featured. The topics have ranged from fundamental research on point defects in a semiconductor to system architecture of semiconductor electronic devices. Proceedings from these events are regularly published as a topical issue of Physica Scripta. All of the papers in this topical issue have undergone critical peer review and we wish to thank the reviewers and the authors for their cooperation, which has been instrumental in meeting the high scientific standards and quality of the series. This meeting of the 23rd Nordic Semiconductor community, NSM 2009, was held at Háskólatorg at the campus of the University of Iceland, Reykjavik, Iceland, 14-17 June 2009. Support was provided by the University of Iceland. Almost 50 participants presented a broad range of topics covering semiconductor materials and devices as well as related material science interests. The conference provided a forum for Nordic and international scientists to present and discuss new results and ideas concerning the fundamentals and applications of semiconductor materials. The meeting aim was to advance the progress of Nordic science and thus aid in future worldwide technological advances concerning technology, education, energy and the environment. Topics Theory and fundamental physics of semiconductors Emerging semiconductor technologies (for example III-V integration on Si, novel Si devices, graphene) Energy and semiconductors Optical phenomena and optical devices MEMS and sensors Program 14 June Registration 13:00-17:00 15 June Meeting program 09:30-17:00 and Poster Session I 16 June Meeting program 09:30-17:00 and Poster Session II 17 June Excursion and dinner

  12. 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

  13. Investigating the effect of flexible ligands on the crystal engineering of the iron(II) coordination compounds

    NASA Astrophysics Data System (ADS)

    Beheshti, Azizolla; Lalegani, Arash; Bruno, Giuseppe; Amiri Rudbari, Hadi

    2013-11-01

    Iron(II) coordination compounds [Fe(bib)2(NCS)2]n(1) and [Fe(bpp)(NCS)2] (2) were synthesized by using the neutral flexible bidentate N-donor ligands 1,4-bis(imidazolyl)butane (bib) and 1,3-bis(3,5-dimethylpyrazolyl)propane (bpp), mono-anionic NCS- ligand and appropriate iron(II) salts. In the CdSO4 network structure of 1, the iron(II) ion lies on an inversion center and exhibits an FeN6 octahedral arrangement while, in the monomeric structure of 2, the iron(II) ion adopts an FeN4 tetrahedral geometry. In the complex 1, each μ2-bib acts as bridging ligand connecting two adjacent iron(II) ions while in the complex 2, the bpp ligand is coordinated to an iron(II) ion in a cyclic-bidentate fashion forming an eight-membered metallocyclic ring. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analyses and single-crystal X-ray diffraction. Thermal analysis of polymer 1 was also studied. An attempt to synthesize [Fe(bbd)(NCS)2] (3) (bbd = 1,4-bis(3,5-dimethylpyrazolyl)butane) with the reaction of bbd, Fe(NH4)2(SO4)2·6H2O and KNCS was failed.

  14. Reactive codoping of GaAlInP compound semiconductors

    DOEpatents

    Hanna, Mark Cooper; Reedy, Robert

    2008-02-12

    A GaAlInP compound semiconductor and a method of producing a GaAlInP compound semiconductor are provided. The apparatus and method comprises a GaAs crystal substrate in a metal organic vapor deposition reactor. Al, Ga, In vapors are prepared by thermally decomposing organometallic compounds. P vapors are prepared by thermally decomposing phospine gas, group II vapors are prepared by thermally decomposing an organometallic group IIA or IIB compound. Group VIB vapors are prepared by thermally decomposing a gaseous compound of group VIB. The Al, Ga, In, P, group II, and group VIB vapors grow a GaAlInP crystal doped with group IIA or IIB and group VIB elements on the substrate wherein the group IIA or IIB and a group VIB vapors produced a codoped GaAlInP compound semiconductor with a group IIA or IIB element serving as a p-type dopant having low group II atomic diffusion.

  15. An Investigation of the Ranger V-770-8 Engine Installation for the Edo XOSE-1 Airplane II : Aerodynamics

    NASA Technical Reports Server (NTRS)

    Dennard, John S.

    1945-01-01

    Investigations were made to determine the cowling and cooling characteristics of the Ranger V-770-8 engine installation in an observation seaplane. Final cowl configurations possessed ample engine and oil-cooler pressure drops for cooling in the critical normal-power climb condition with any of the three baffle configurations tested. The indicated critical Mach number of the cowling was found to be 0.70 as determined by the pressure on the lower lip of the inlet.

  16. Cooling Characteristics of the V-1650-7 Engine. II - Effect of Coolant Conditions on Cylinder Temperatures and Heat Rejection at Several Engine Powers

    NASA Technical Reports Server (NTRS)

    Povolny, John H.; Bogdan, Louis J.; Chelko, Louis J.

    1947-01-01

    An investigation has been conducted on a V-1650-7 engine to determine the cylinder temperatures and the coolant and oil heat rejections over a range of coolant flows (50 to 200 gal/min) and oil inlet temperatures (160 to 2150 F) for two values of coolant outlet temperature (250 deg and 275 F) at each of four power conditions ranging from approximately 1100 to 2000 brake horsepower. Data were obtained for several values of block-outlet pressure at each of the two coolant outlet temperatures. A mixture of 30 percent by volume of ethylene glycol and 70-percent water was used as the coolant. The effect of varying coolant flow, coolant outlet temperature, and coolant outlet pressure over the ranges investigated on cylinder-head temperatures was small (0 deg to 25 F) whereas the effect of increasing the engine power condition from ll00 to 2000 brake horsepower was large (maximum head-temperature increase, 110 F).

  17. Characterization of archaeal group II chaperonin-ADP-metal fluoride complexes: implications that group II chaperonins operate as a "two-stroke engine".

    PubMed

    Iizuka, Ryo; Yoshida, Takao; Ishii, Noriyuki; Zako, Tamotsu; Takahashi, Kazunobu; Maki, Kosuke; Inobe, Tomonao; Kuwajima, Kunihiro; Yohda, Masafumi

    2005-12-01

    Group II chaperonins, found in Archaea and in the eukaryotic cytosol, act independently of a cofactor corresponding to GroES of group I chaperonins. Instead, the helical protrusion at the tip of the apical domain forms a built-in lid of the central cavity. Although many studies on the lid's conformation have been carried out, the conformation in each step of the ATPase cycle remains obscure. To clarify this issue, we examined the effects of ADP-aluminum fluoride (AlFx) and ADP-beryllium fluoride (BeFx) complexes on alpha-chaperonin from the hyperthermophilic archaeum, Thermococcus sp. strain KS-1. Biochemical assays, electron microscopic observations, and small angle x-ray scattering measurements demonstrate that alpha-chaperonin incubated with ADP and BeFx exists in an asymmetric conformation; one ring is open, and the other is closed. The result indicates that alpha-chaperonin also shares the inherent functional asymmetry of bacterial and eukaryotic cytosolic chaperonins. Most interestingly, addition of ADP and BeFx induced alpha-chaperonin to encapsulate unfolded proteins in the closed ring but did not trigger their folding. Moreover, alpha-chaperonin incubated with ATP and AlFx or BeFx adopted a symmetric closed conformation, and its functional turnover was inhibited. These forms are supposed to be intermediates during the reaction cycle of group II chaperonins.

  18. Method of doping a semiconductor

    DOEpatents

    Yang, Chiang Y.; Rapp, Robert A.

    1983-01-01

    A method for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient.

  19. Continuous adsorption of Pb(II) and methylene blue by engineered graphite oxide coated sand in fixed-bed column

    NASA Astrophysics Data System (ADS)

    Gong, Ji-Lai; Zhang, Yong-Liang; Jiang, Yan; Zeng, Guang-Ming; Cui, Zhi-Hui; Liu, Ke; Deng, Can-Hui; Niu, Qiu-Ya; Deng, Jiu-Hua; Huan, Shuang-Yan

    2015-03-01

    The mixture of several effluents, caused by the improper handling and management of effluents, generated multi-component wastewater containing both metals and dyes, leading to the complicated treatment process. In this study, a continuous adsorption of Pb(II) and methylene blue (MB) has been studied in single and binary solutions by using graphite oxide coated sand (GO-sand) as an adsorbent in a fixed-bed column. GO-sand was analyzed by X-ray photoelectron spectroscopy before and after analyte adsorption. Compared with sand filter, adsorption quantity and capacity for Pb(II) and MB by GO-sand filter were greatly increased. In Pb(II) and MB single solutions, the experimental parameters were investigated in detail including initial concentration, flow rate, bed depth and pH. Exhaustion time decreased with increasing initial concentration and flow rate, and increased with increasing bed depth and pH. In the Pb(II)-MB binary solution, exhaustion time significantly decreased for Pb(II) adsorption, but increased for MB adsorption. The reason was explained that the more favorable adsorption for MB onto the surface of GO-sand than that for Pb(II), which was derived from π-π interaction between MB and GO on sand surface in packed filter. The Yoon-Nelson model was applied at different concentration of Pb(II) and MB to predict the breakthrough curves. The experimental data were well fit with the model indicating that it was suitable for this column design.

  20. Search for WW and WZ production in lepton, neutrino plus jets final states at CDF Run II and Silicon module production and detector control system for the ATLAS SemiConductor Tracker

    SciTech Connect

    Sfyrla, Anna

    2008-03-10

    In the first part of this work, we present a search for WW and WZ production in charged lepton, neutrino plus jets final states produced in p$\\bar{p}$ collisions with √s = 1.96 TeV at the Fermilab Tevatron, using 1.2 fb-1 of data accumulated with the CDF II detector. This channel is yet to be observed in hadron colliders due to the large singleWplus jets background. However, this decay mode has a much larger branching fraction than the cleaner fully leptonic mode making it more sensitive to anomalous triple gauge couplings that manifest themselves at higher transverse W momentum. Because the final state is topologically similar to associated production of a Higgs boson with a W, the techniques developed in this analysis are also applicable in that search. An Artificial Neural Network has been used for the event selection optimization. The theoretical prediction for the cross section is σWW/WZtheory x Br(W → ℓv; W/Z → jj) = 2.09 ± 0.14 pb. They measured NSignal = 410 ± 212(stat) ± 102(sys) signal events that correspond to a cross section σWW/WZ x Br(W → ℓv; W/Z → jj) = 1.47 ± 0.77(stat) ± 0.38(sys) pb. The 95% CL upper limit to the cross section is estimated to be σ x Br(W → ℓv; W/Z → jj) < 2.88 pb. The second part of the present work is technical and concerns the ATLAS SemiConductor Tracker (SCT) assembly phase. Although technical, the work in the SCT assembly phase is of prime importance for the good performance of the detector during data taking. The production at the University of Geneva of approximately one third of the silicon microstrip end-cap modules is presented. This collaborative effort of the university of Geneva group that lasted two years, resulted in 655 produced modules, 97% of which were good modules, constructed within the mechanical and electrical specifications and delivered in the SCT collaboration for assembly on the end-cap disks. The SCT end-caps and barrels

  1. Photoinduced superconductivity in semiconductors

    NASA Astrophysics Data System (ADS)

    Goldstein, Garry; Aron, Camille; Chamon, Claudio

    2015-02-01

    We show that optically pumped semiconductors can exhibit superconductivity. We illustrate this phenomenon in the case of a two-band semiconductor tunnel-coupled to broad-band reservoirs and driven by a continuous wave laser. More realistically, we also show that superconductivity can be induced in a two-band semiconductor interacting with a broad-spectrum light source. We furthermore discuss the case of a three-band model in which the middle band replaces the broad-band reservoirs as the source of dissipation. In all three cases, we derive the simple conditions on the band structure, electron-electron interaction, and hybridization to the reservoirs that enable superconductivity. We compute the finite superconducting pairing and argue that the mechanism can be induced through both attractive and repulsive interactions and is robust to high temperatures.

  2. Superconductivity in doped semiconductors

    NASA Astrophysics Data System (ADS)

    Bustarret, E.

    2015-07-01

    A historical survey of the main normal and superconducting state properties of several semiconductors doped into superconductivity is proposed. This class of materials includes selenides, tellurides, oxides and column-IV semiconductors. Most of the experimental data point to a weak coupling pairing mechanism, probably phonon-mediated in the case of diamond, but probably not in the case of strontium titanate, these being the most intensively studied materials over the last decade. Despite promising theoretical predictions based on a conventional mechanism, the occurrence of critical temperatures significantly higher than 10 K has not been yet verified. However, the class provides an enticing playground for testing theories and devices alike.

  3. 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)

  4. 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.

  5. Semiconductor surface protection material

    NASA Technical Reports Server (NTRS)

    Packard, R. D. (Inventor)

    1973-01-01

    A method and a product for protecting semiconductor surfaces is disclosed. The protective coating material is prepared by heating a suitable protective resin with an organic solvent which is solid at room temperature and converting the resulting solution into sheets by a conventional casting operation. Pieces of such sheets of suitable shape and thickness are placed on the semiconductor areas to be coated and heat and vacuum are then applied to melt the sheet and to drive off the solvent and cure the resin. A uniform adherent coating, free of bubbles and other defects, is thus obtained exactly where it is desired.

  6. Special Issue featuring invited articles arising from UK Semiconductors 2012

    NASA Astrophysics Data System (ADS)

    Clarke, Edmund; Wada, Osamu

    2013-07-01

    Semiconductor research has formed the basis of many technological advances over the past 50 years, and the field is still highly active, as new material systems and device concepts are developed to address new applications or operating conditions. In addition to the development of traditional semiconductor devices, the wealth of experience with these materials also allows their use as an ideal environment for testing new physics, leading to new classes of devices exploiting quantum mechanical effects that can also benefit from the advantages of existing semiconductor technology in scalability, compactness and ease of mass production. This special issue features papers arising from the UK Semiconductors 2012 Conference, held at the University of Sheffield. The annual conference covers all aspects of semiconductor research, from crystal growth, through investigations of the physics of semiconductor structures to realization of semiconductor devices and their application in emerging technologies. The 2012 conference featured over 150 presentations, including plenary sessions on interband cascade lasers for the 3-6 µm spectral band, efficient single photon sources based on InAs quantum dots embedded in GaAs photonic nanowires, nitride-based quantum dot visible lasers and single photon sources, and engineering of organic light-emitting diodes. The seven papers collected here highlight current research advances, taken from across the scope of the conference. The papers feature growth of novel nitride-antimonide material systems for mid-infrared sources and detectors, use of semiconductor nanostructures for charge-based memory and visible lasers, optimization of device structures either to reduce losses in solar cells or achieve low noise amplification in transistors, design considerations for surface-emitting lasers incorporating photonic crystals and an assessment of laser power convertors for power transfer. The editors of this special issue and the conference

  7. Regulated and Unregulated Exhaust Emissions Comparison for Three Tier II Non-Road Diesel Engines Operating on Ethanol-Diesel Blends

    SciTech Connect

    Merritt, P. M.; Ulmet, V.; McCormick, R. L.; Mitchell, W. E.; Baumgard, K. J.

    2005-11-01

    Regulated and unregulated emissions (individual hydrocarbons, ethanol, aldehydes and ketones, polynuclear aromatic hydrocarbons (PAH), nitro-PAH, and soluble organic fraction of particulate matter) were characterized in engines utilizing duplicate ISO 8178-C1 eight-mode tests and FTP smoke tests. Certification No. 2 diesel (400 ppm sulfur) and three ethanol/diesel blends, containing 7.7 percent, 10 percent, and 15 percent ethanol, respectively, were used. The three, Tier II, off-road engines were 6.8-L, 8.1-L, and 12.5-L in displacement and each had differing fuel injection system designs. It was found that smoke and particulate matter emissions decreased with increasing ethanol content. Changes to the emissions of carbon monoxide and oxides of nitrogen varied with engine design, with some increases and some decreases. As expected, increasing ethanol concentration led to higher emissions of acetaldehyde (increases ranging from 27 to 139 percent). Benzene emissions were reduced by up to 50 percent with the ethanol-blended fuels. Emissions of 1,3-butadiene were also substantially decreased, with reductions ranging from 24 to 82 percent. Isolated trends were noted for certain PAHs. There was a decrease in 1-nitropyrene with use of ethanol in all cases. Particulate phase 1-nitropyrene was reduced from 18 to 62 percent. There was also a general increase in the proportion of heavy PAHs in the particulate phase with ethanol use, and although less pronounced, a general decrease in light PAHs in the particulate phase.

  8. A Comprehensive and Systematic Model of User Evaluation of Web Search Engines: II. An Evaluation by Undergraduates.

    ERIC Educational Resources Information Center

    Su, Louise T.

    2003-01-01

    Presents an application of a model of user evaluation of four major Web search engines (Alta Vista, Excite, Infoseek, and Lycos) by undergraduates. Evaluation was based on 16 performance measures representing five evaluation criteria-relevance, efficiency, utility, user satisfaction, and connectivity. Content analysis of verbal data identified a…

  9. CRITERIA POLLUTANT EMISSIONS FROM INTERNAL COMBUSTION ENGINES IN THE NATURAL GAS INDUSTRY VOLUME II. APPENDICES A-I

    EPA Science Inventory

    The report summarizes emission factors for criteria pollutants (NOx, CO, CH4, C2H6, THC, NMHC, and NMEHC) from stationary internal combustion engines and gas turbines used in the natural gas industry. The emission factors were calculated from test results from five test campaigns...

  10. 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.

  11. Chemically Derivatized Semiconductor Photoelectrodes.

    ERIC Educational Resources Information Center

    Wrighton, Mark S.

    1983-01-01

    Deliberate modification of semiconductor photoelectrodes to improve durability and enhance rate of desirable interfacial redox processes is discussed for a variety of systems. Modification with molecular-based systems or with metals/metal oxides yields results indicating an important role for surface modification in devices for fundamental study…

  12. 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.

  13. 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.

  14. Instantaneous amplitude and frequency dynamics of coherent wave mixing in semiconductor quantum wells

    SciTech Connect

    Chemla, D.S.

    1993-06-30

    This article reviews recent investigations of nonlinear optical processes in semiconductors. Section II discusses theory of coherent wave mixing in semiconductors, with emphasis on resonant excitation with only one exciton state. Section III reviews recent experimental investigations of amplitude and phase of coherent wave-mixing resonant with quasi-2d excitons in GaAs quantum wells.

  15. Proceedings of the 6th International Conference on Narrow Gap Semiconductors

    NASA Astrophysics Data System (ADS)

    Stradling, R. A.; Mullin, J. B.

    1992-07-01

    This proceedings includes papers in the following areas: novel growth and structures; dilute magnetic semiconductors; II-VI electronics, optics, and growth; III-V devices; magnetism and magneto-optics; dots and novel confinement; linear and nonlinear optics; and material properties of IV-VI semiconductors.

  16. Optical and electronic properties of some semiconductors from energy gaps

    NASA Astrophysics Data System (ADS)

    Tripathy, Sunil K.; Pattanaik, Anup

    2016-03-01

    II-VI and III-V tetrahedral semiconductors have significant potential for novel optoelectronic applications. In the present work, some of the optical and electronic properties of these groups of semiconductors have been studied using a recently proposed empirical relationship for refractive index from energy gap. The calculated values of these properties are also compared with those calculated from some well known relationships. From an analysis of the calculated electronic polarisability of these tetrahedral binary semiconductors from different formulations, we have proposed an empirical relation for its calculation. The predicted values of electronic polarisability of these semiconductors agree fairly well with the known values over a wide range of energy gap. The proposed empirical relation has also been used to calculate the electronic polarisability of some ternary compounds.

  17. Reflection and Transmission of Acoustic Waves at Semiconductor - Liquid Interface

    NASA Astrophysics Data System (ADS)

    Sharma, J. N.; Sharma, A.

    2011-09-01

    The study of reflection and transmission characteristics of acoustic waves at the interface of a semiconductor halfspace underlying an inviscid liquid has been carried out. The reflection and transmission coefficients of reflected and transmitted waves have been obtained for quasi-longitudinal (qP) wave incident at the interface from fluid to semiconductor. The numerical computations of reflection and transmission coefficients have been carried out with the help of Gauss elimination method by using MATLAB programming for silicon (Si), germanium (Ge) and silicon nitride (Si3N4) semiconductors. In order to interpret and compare, the computer simulated results are plotted graphically. The study may be useful in semiconductors, seismology and surface acoustic wave (SAW) devices in addition to engines of the space shuttles.

  18. Semiconductor Thermoelectric Converters of Alternating Current Signals

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Bodnaruk, V. I.; Taschuk, D. D.

    2011-05-01

    Measuring converters have been developed based on Bi2Te3 solid solutions optimized for temperature and temporal stability of the basic thermoelectric parameters (thermal conductivity, electrical conductivity, and the Seebeck coefficient). Semiconductor material was grown by the vertical zone melting method. High efficiency of the optimized semiconductor materials made it possible to reduce the operating temperature considerably, as well as facilitating selection of structural materials and the converter fabrication technique. The influence of the Peltier and Thomson effects on the accuracy of direct current conversion has been reduced, and the operating frequency range of measurements has been expanded. Thermoelectric converters with sensitivity up to 30 V W-1 have been created without evacuation of the working space, which is filled with an inert gas mixture. The engineered converters offer the advantages of high sensitivity and a wide operating frequency range (up to 30 MHz).

  19. A Physics of Semiconductors Concept Inventory

    NASA Astrophysics Data System (ADS)

    Ene, Emanuela; Bruce J. Ackerson Collaboration; Alan Cheville Collaboration

    2011-03-01

    Following the trend in science and engineering education generated by the visible impact that the Force Concept Inventory (FCI) has created, a Physics of Semiconductors Concept Inventory (PSCI) has been developed. Whereas most classroom tests measure how many facts students can remember, or if they can manipulate equations, PSCI measures how well students interpret concepts and how well they can infer new knowledge from already learned knowledge. Operationalized in accordance with the revised Bloom's taxonomy, the multiple--choice items of the PSCI address the ``understand'', ``apply'', ``analyze'' and ``evaluate'' levels of cognition. Once standardized, PSCI may be used as a predictor for students' academic performance in the field of semiconductors and as an assessment instrument for instructional strategies.

  20. DOE Backup Power Working Group Best Practices Handbook for Maintenance and Operation of Engine Generators, Volume II

    SciTech Connect

    Gross, R.E.

    1998-10-30

    The lubricating oil system provides a means to introduce a lubricant in the form of a film to reduce friction and wear between surfaces that bear against each other as they move.1 The oil film which is established also cools the parts by carrying generated heat away from hot surfaces, cleans and carries dirt or metal wear particles to the filter media, and helps seal the piston to the cylinder during combustion. Most systems are pressure lubricated and distribute oil under pressure to bearings, gears, and power assemblies. Lubricating oil usually reaches main, connecting rod, and camshaft bearings through drilled passages in the cylinder block and crankshaft or through piping and common manifolds.Many parts rely on oil for cooling, so if the lube oil system fails to perform its function the engine will overheat. Metal to metal surfaces not separated by a thin film of oil rapidly build up frictional heat. As the metals reach their melting point, they tend to weld together in spots or streaks. Lube oil system failures can cause significant damage to an engine in a short period of time. Proper maintenance and operation of the lubricating oil system is essential if your engine is to accomplish its mission.

  1. Altitude-chamber performance of British Rolls-Royce Nene II engine III : 18.00-inch-diameter jet nozzle

    NASA Technical Reports Server (NTRS)

    Grey, Ralph E; Brightwell, Virginia L; Barson, Zelmar; NACA

    1950-01-01

    An altitude-chamber investigation of British Rolls-Royce Nene II turbojet engine was conducted over range of altitudes from sea level to 65,000 feet and ram pressure ratios from 1.10 to 3.50, using an 18.00-inch-diameter jet nozzle. The 18.00-inch-diameter jet nozzle gave slightly lower values of net-thrust specific fuel consumption than either the 18.41- or the standard 18.75-inch-diameter jet nozzles at high flight speeds. At low flight speeds, the 18.41-inch-diameter jet nozzle gave the lowest value of net-thrust specific fuel consumption.

  2. Effects of sudden density changes in disordered superconductors and semiconductors

    NASA Astrophysics Data System (ADS)

    Assi, Hiba; Chaturvedi, Harshwardhan; Pleimling, Michel; Täuber, Uwe

    Vortices in type-II superconductors in the presence of extended, linear defects display the strongly pinned Bose glass phase at low temperatures. This disorder-dominated thermodynamic state is characterized by suppressed lateral flux line fluctuations and very slow structural relaxation kinetics: The vortices migrate between different columnar pinning centers to minimize the mutual repulsive interactions and eventually optimize the system's pinning configuration. To monitor the flux lines' late-time structural relaxations, we employ a mapping between an effectively two-dimensional Bose glass system and a modified Coulomb glass model, originally developed to describe disordered semiconductors at low temperatures. By means of Monte Carlo simulations, we investigate the effects of the introduction of random bare site energies and sudden changes in the vortex or charge carrier density on the soft Coulomb gap that appears in the density of states due to the emerging spatial anticorrelations. The non-equilibrium relaxation properties of the Bose and Coulomb glass states and the ensuing aging kinetics are studied through the two-time density autocorrelation function and its various scaling forms. Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-09ER46613.

  3. 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.

  4. 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.

  5. Light amplification using semiconductors

    SciTech Connect

    Dupuis, R.D.

    1987-06-01

    During the summer of 1953, John von Neumann discussed his ideas concerning light amplification using semiconductors with Edward Teller. In September of that year, von Neumann sent a manuscript containing his ideas and calculations on this subject to Teller for his comments. To the best of our knowledge, von Neumann did not take time to work further on these ideas, and the manuscript remained unpublished. These previously unpublished writings of John von Neumann on the subject of light amplification in semiconductors are printed as a service to the laser community. While von Neumann's original manuscript and his letter to Teller are available to anyone who visits the Library of Congress, it is much more convenient to have this paper appear in an archival journal.

  6. Biotechnology and genetic engineering in the new drug development. Part II. Monoclonal antibodies, modern vaccines and gene therapy.

    PubMed

    Stryjewska, Agnieszka; Kiepura, Katarzyna; Librowski, Tadeusz; Lochyński, Stanisław

    2013-01-01

    Monoclonal antibodies, modern vaccines and gene therapy have become a major field in modern biotechnology, especially in the area of human health and fascinating developments achieved in the past decades are impressive examples of an interdisciplinary interplay between medicine, biology and engineering. Among the classical products from cells one can find viral vaccines, monoclonal antibodies, and interferons, as well as recombinant therapeutic proteins. Gene therapy opens up challenging new areas. In this review, a definitions of these processes are given and fields of application and products, as well as the future prospects, are discussed.

  7. Tunable semiconductor lasers

    NASA Technical Reports Server (NTRS)

    Taghavi-Larigani, Shervin (Inventor); Vanzyl, Jakob J. (Inventor); Yariv, Amnon (Inventor)

    2006-01-01

    Tunable semiconductor lasers are disclosed requiring minimized coupling regions. Multiple laser embodiments employ ring resonators or ring resonator pairs using only a single coupling region with the gain medium are detailed. Tuning can be performed by changing the phase of the coupling coefficient between the gain medium and a ring resonator of the laser. Another embodiment provides a tunable laser including two Mach-Zehnder interferometers in series and a reflector coupled to a gain medium.

  8. Semiconductor Ion Implanters

    NASA Astrophysics Data System (ADS)

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at 7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at 6.2 billion! Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing `only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around 2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  9. Semiconductor Ion Implanters

    SciTech Connect

    MacKinnon, Barry A.; Ruffell, John P.

    2011-06-01

    In 1953 the Raytheon CK722 transistor was priced at $7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at $6.2 billion. Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing 'only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around $2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  10. Synchronous semiconductor memory device

    SciTech Connect

    Onno, C.; Hirata, M.

    1989-11-21

    This patent describes a synchronous semiconductor memory device. It comprises: first latch means for latching a write command in synchronism with clock signal; second latch means for latching a write data in synchronism with the clock signal and for outputting two write process signals based on the write data latched thereby; pulse generating means for generating an internal write pulse signal based on the write command latched by the first latch means. The internal write pulse signal having a semiconductor memory device; write control means supplied with the internal write pulse signal and the write process signals for controlling write and read operations of the synchronous semiconductor memory device; memory means for storing the write data latched by the second latch means; and noise preventing means coupled to the second latch means and the write control means for supplying the write process signals to the write control means only in the write mode responsive to the internal write pulse signal and for setting the write process signals to fixed potentials during a time other than the write mode.

  11. Quantum jumps in the PEMFC science and technology from the 1960s to the year 2000. Part II. Engineering, technology development and application aspects

    NASA Astrophysics Data System (ADS)

    Costamagna, Paola; Srinivasan, Supramaniam

    The technology of proton exchange membrane fuel cells (PEMFCs) has now reached the test-phase, and engineering development and optimization are vital in order to achieve to the next step of the evolution, i.e. the realization of commercial units. This paper highlights the most important technological progresses in the areas of (i) water and thermal management, (ii) scale-up from single cells to cell stacks, (iii) bipolar plates and flow fields, and (iv) fuel processing. Modeling is another aspect of the technological development, since modeling studies have significantly contributed to the understanding of the physico-chemical phenomena occurring in a fuel cell, and also have provided a valuable tool for the optimization of structure, geometry and operating conditions of fuel cells and stacks. The 'quantum jumps' in this field are reviewed, starting from the studies at the electrode level up to the stack and system size, with particular emphasis on (i) the 'cluster-network' model of perfluorosulfonic membranes, and the percolative dependence of the membrane proton conductivity on its water content, (ii) the models of charge and mass transport coupled to electrochemical reaction in the electrodes, and (iii) the models of water transport trough the membrane, which have been usefully applied for the optimization of water management of PEMFCs. The evolution of PEMFC applications is discussed as well, starting from the NASA's Gemini Space Flights to the latest developments of fuel cell vehicles, including the evolutions in the areas of portable power sources and residential and building applications.

  12. A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing, Part II: Additive Manufacturing and Characterization of Polymer Composites

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Grady, Joseph E.; Arnold, Steven M.; Draper, Robert D.; Shin, Eugene; Patterson, Clark; Santelle, Tom; Lao, Chao; Rhein, Morgan; Mehl, Jeremy

    2015-01-01

    This publication is the second part of the three part report of the project entitled "A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing" funded by NASA Aeronautics Research Institute (NARI). The objective of this project was to conduct additive manufacturing to produce aircraft engine components by Fused Deposition Modeling (FDM), using commercially available polyetherimides-Ultem 9085 and experimental Ultem 1000 mixed with 10% chopped carbon fiber. A property comparison between FDM-printed and injection molded coupons for Ultem 9085, Ultem 1000 resin and the fiber-filled composite Ultem 1000 was carried out. Furthermore, an acoustic liner was printed from Ultem 9085 simulating conventional honeycomb structured liners and tested in a wind tunnel. Composite compressor inlet guide vanes were also printed using fiber-filled Ultem 1000 filaments and tested in a cascade rig. The fiber-filled Ultem 1000 filaments and composite vanes were characterized by scanning electron microscope (SEM) and acid digestion to determine the porosity of FDM-printed articles which ranged from 25 to 31%. Coupons of Ultem 9085, experimental Ultem 1000 composites and XH6050 resin were tested at room temperature and 400F to evaluate their corresponding mechanical properties. A preliminary modeling was also initiated to predict the mechanical properties of FDM-printed Ultem 9085 coupons in relation to varied raster angles and void contents, using the GRC-developed MAC/GMC program.

  13. Drag and Cooling with Various Forms of Cowling for a "Whirlwind" Radial Air-cooled Engine II

    NASA Technical Reports Server (NTRS)

    Weick, Fred E

    1930-01-01

    This report gives the results of the second portion of an investigation in the twenty-foot Propeller Research Tunnel of the National Advisory Committee for Aeronautics, on the cowling and cooling of a "Whirlwind" J-5 radial air-cooled engine. The first portion pertains to tests with a cabin fuselage. This report covers tests with several forms of cowling, including conventional types, individual fairings behind the cylinders, individual hoods over the over the cylinders, and the new N. A. C. A. complete cowling, all on an open cockpit fuselage. Drag tests were also made with a conventional engine nacelle, and with a nacelle having the new complete cowling. In the second part of the investigation the results found in the first part were substantiated. It was also found that the reduction in drag with the complete cowling over that with conventional cowling is greater with the smaller bodies than with the cabin fuselage; in fact, the gain in the case of the completely cowled nacelle is over twice that with the cabin fuselage. The individual fairings and hoods did not prove effective in reducing the drag. The results of flight tests on AT-5A airplane has been analyzed and found to agree very well with the results of the wind tunnel tests. (author)

  14. The application of multiple biophysical cues to engineer functional neocartilage for treatment of osteoarthritis. Part II: signal transduction.

    PubMed

    Brady, Mariea A; Waldman, Stephen D; Ethier, C Ross

    2015-02-01

    The unique mechanoelectrochemical environment of cartilage has motivated researchers to investigate the effect of multiple biophysical cues, including mechanical, magnetic, and electrical stimulation, on chondrocyte biology. It is well established that biophysical stimuli promote chondrocyte proliferation, differentiation, and maturation within "biological windows" of defined dose parameters, including mode, frequency, magnitude, and duration of stimuli (see companion review Part I: Cellular Response). However, the underlying molecular mechanisms and signal transduction pathways activated in response to multiple biophysical stimuli remain to be elucidated. Understanding the mechanisms of biophysical signal transduction will deepen knowledge of tissue organogenesis, remodeling, and regeneration and aiding in the treatment of pathologies such as osteoarthritis. Further, this knowledge will provide the tissue engineer with a potent toolset to manipulate and control cell fate and subsequently develop functional replacement cartilage. The aim of this article is to review chondrocyte signal transduction pathways in response to mechanical, magnetic, and electrical cues. Signal transduction does not occur along a single pathway; rather a number of parallel pathways appear to be activated, with calcium signaling apparently common to all three types of stimuli, though there are different modes of activation. Current tissue engineering strategies, such as the development of "smart" functionalized biomaterials that enable the delivery of growth factors or integration of conjugated nanoparticles, may further benefit from targeting known signal transduction pathways in combination with external biophysical cues. PMID:25065615

  15. Automotive Stirling engine development program

    NASA Technical Reports Server (NTRS)

    Farrell, R.; Hindes, C.; Battista, R.; Connelly, M.; Cronin, M.; Howarth, R.; Donahue, A.; Slate, E.; Stotts, R.; Lacy, R.

    1988-01-01

    The study of high power kinematic Stirling engines for transportation use, testing of Mod I and Mod II Stirling engines, and component development activities are summarized. Mod II development testing was performed to complete the development of the basic engine and begin characterization of performance. Mod I engines were used for Mod II component development and to obtain independent party (U.S. Air Force) evaluation of Stirling engine vehicle performance.

  16. Multi-objective optimization of combustion, performance and emission parameters in a jatropha biodiesel engine using Non-dominated sorting genetic algorithm-II

    NASA Astrophysics Data System (ADS)

    Dhingra, Sunil; Bhushan, Gian; Dubey, Kashyap Kumar

    2014-03-01

    The present work studies and identifies the different variables that affect the output parameters involved in a single cylinder direct injection compression ignition (CI) engine using jatropha biodiesel. Response surface methodology based on Central composite design (CCD) is used to design the experiments. Mathematical models are developed for combustion parameters (Brake specific fuel consumption (BSFC) and peak cylinder pressure (Pmax)), performance parameter brake thermal efficiency (BTE) and emission parameters (CO, NO x , unburnt HC and smoke) using regression techniques. These regression equations are further utilized for simultaneous optimization of combustion (BSFC, Pmax), performance (BTE) and emission (CO, NO x , HC, smoke) parameters. As the objective is to maximize BTE and minimize BSFC, Pmax, CO, NO x , HC, smoke, a multiobjective optimization problem is formulated. Nondominated sorting genetic algorithm-II is used in predicting the Pareto optimal sets of solution. Experiments are performed at suitable optimal solutions for predicting the combustion, performance and emission parameters to check the adequacy of the proposed model. The Pareto optimal sets of solution can be used as guidelines for the end users to select optimal combination of engine output and emission parameters depending upon their own requirements.

  17. Development of improved processing and evaluation methods for high reliability structural ceramics for advanced heat engine applications Phase II. Final report

    SciTech Connect

    Pujari, V.J.; Tracey, D.M.; Foley, M.R.

    1996-02-01

    The research program had as goals the development and demonstration of significant improvements in processing methods, process controls, and nondestructive evaluation (NDE) which can be commercially implemented to produce high reliability silicon nitride components for advanced heat engine applications at temperatures to 1370{degrees}C. In Phase I of the program a process was developed that resulted in a silicon nitride - 4 w% yttria HIP`ed material (NCX 5102) that displayed unprecedented strength and reliability. An average tensile strength of 1 GPa and a strength distribution following a 3-parameter Weibull distribution were demonstrated by testing several hundred buttonhead tensile specimens. The Phase II program focused on the development of methodology for colloidal consolidation producing green microstructure which minimizes downstream process problems such as drying, shrinkage, cracking, and part distortion during densification. Furthermore, the program focused on the extension of the process to gas pressure sinterable (GPS) compositions. Excellent results were obtained for the HIP composition processed for minimal density gradients, both with respect to room-temperature strength and high-temperature creep resistance. Complex component fabricability of this material was demonstrated by producing engine-vane prototypes. Strength data for the GPS material (NCX-5400) suggest that it ranks very high relative to other silicon nitride materials in terms of tensile/flexure strength ratio, a measure of volume quality. This high quality was derived from the closed-loop colloidal process employed in the program.

  18. Indistinguishable Photons from Independent Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Sanaka, Kaoru; Pawlis, Alexander; Ladd, Thaddeus D.; Lischka, Klaus; Yamamoto, Yoshihisa

    2009-07-01

    We demonstrate quantum interference between photons generated by the radiative decay processes of excitons that are bound to isolated fluorine donor impurities in ZnSe/ZnMgSe quantum-well nanostructures. The ability to generate single photons from these devices is confirmed by autocorrelation experiments, and the indistinguishability of photons emitted from two independent nanostructures is confirmed via a Hong-Ou-Mandel dip. These results indicate that donor impurities in appropriately engineered semiconductor structures can portray atomlike homogeneity and coherence properties, potentially enabling scalable technologies for future large-scale optical quantum computers and quantum communication networks.

  19. Nonlinear behavior of acoustic waves in combustion chambers. I, II. [stability in solid propellant rocket engine and T burner

    NASA Technical Reports Server (NTRS)

    Culick, F. E. C.

    1976-01-01

    The general problem of the nonlinear growth and limiting amplitude of acoustic waves in a combustion chamber is treated in three parts: (1) the general conservation equations are expanded in two small parameters, and then combined to yield a nonlinear inhomogeneous wave equation, (2) the unsteady pressure and velocity fields are expressed as a synthesis of the normal modes of the chamber, but with unknown time-varying amplitudes, and (3) the system of nonlinear equations is treated by the method of averaging to produce a set of coupled nonlinear first order differential equations for the amplitudes and phases of the modes. This approximate analysis is applied to the investigation of the unstable motions in a solid propellant rocket engine and in a T burner.

  20. Assessment of existing roadside swales with engineered filter soil: II. Treatment efficiency and in situ mobilization in soil columns.

    PubMed

    Ingvertsen, Simon T; Cederkvist, Karin; Jensen, Marina B; Magid, Jakob

    2012-01-01

    Use of roadside infiltration systems using engineered filter soil for optimized treatment has been common practice in Germany for decades, but little documentation is available regarding their long-term treatment performance. Here we present the results of laboratory leaching experiments with intact soil columns (15 cm i.d., 25-30 cm length) collected from two German roadside infiltration swales constructed in 1997. The columns were irrigated with synthetic solutions of unpolluted or polluted (dissolved heavy metals and fine suspended solids) road runoff, as well as a soluble nonreactive tracer (bromide) and a dye (brilliant blue). The experiments were performed at two irrigation rates corresponding to catchment rainfall intensities of approximately 5.1 and 34 mm/h. The bromide curves indicated that preferential flow was more pronounced at high irrigation rates, which was supported by the flow patterns revealed in the dye tracing experiment. Nonetheless, the soils seemed to be capable of retaining most of the dissolved heavy metals from the polluted road runoff at both low and high irrigation rates, except for Cr, which appears to pass through the soil as chromate. Fluorescent microspheres (diameter = 5 μm) used as surrogates for fine suspended solids were efficiently retained by the soils (>99%). However, despite promising treatment abilities, internal mobilization of heavy metals and P from the soil was observed, resulting in potentially critical effluent concentrations of Cu, Zn, and Pb. This is mainly ascribed to high concentrations of in situ mobilized dissolved organic carbon (DOC). Suggestions are provided for possible improvements and further research to minimize DOC mobilization in engineered filter soils. PMID:23128754

  1. Fuzzy Logic Connectivity in Semiconductor Defect Clustering

    SciTech Connect

    Gleason, S.S.; Kamowski, T.P.; Tobin, K.W.

    1999-01-24

    In joining defects on semiconductor wafer maps into clusters, it is common for defects caused by different sources to overlap. Simple morphological image processing tends to either join too many unrelated defects together or not enough together. Expert semiconductor fabrication engineers have demonstrated that they can easily group clusters of defects from a common manufacturing problem source into a single signature. Capturing this thought process is ideally suited for fuzzy logic. A system of rules was developed to join disconnected clusters based on properties such as elongation, orientation, and distance. The clusters are evaluated on a pair-wise basis using the fuzzy rules and are joined or not joined based on a defuzzification and threshold. The system continuously re-evaluates the clusters under consideration as their fuzzy memberships change with each joining action. The fuzzy membership functions for each pair-wise feature, the techniques used to measure the features, and methods for improving the speed of the system are all developed. Examples of the process are shown using real-world semiconductor wafer maps obtained from chip manufacturers. The algorithm is utilized in the Spatial Signature Analyzer (SSA) software, a joint development project between Oak Ridge National Lab (ORNL) and SEMATECH.

  2. New developments in power semiconductors

    NASA Technical Reports Server (NTRS)

    Sundberg, G. R.

    1983-01-01

    This paper represents an overview of some recent power semiconductor developments and spotlights new technologies that may have significant impact for aircraft electric secondary power. Primary emphasis will be on NASA-Lewis-supported developments in transistors, diodes, a new family of semiconductors, and solid-state remote power controllers. Several semiconductor companies that are moving into the power arena with devices rated at 400 V and 50 A and above are listed, with a brief look at a few devices.

  3. Thermodynamic Stability of Semiconductors for Photocatalytic Water Splitting

    NASA Astrophysics Data System (ADS)

    Chen, Shiyou; Wang, Lin-Wang

    2012-02-01

    Band structure engineering design of the light-absorbing semiconductors for water splitting has attracted wide attention recently. One of such design is to use the Z-scheme where a photocathode is connected with photoanode to reduce (generate H2) and oxidize (generate O2) water respectively. This requires the conduction band of photocathode and valence band of photoanode to straddle the redox levels of water. However, equally important in this design is the thermodynamic stability of the semiconductors in the aqueous solution upon illumination, i.e., the semiconductors may be oxidized (or reduced) before the water is oxidized (or reduced), causing the corrosion of the photoanode (photocathode). We will present our theoretical study on the thermodynamic stability of a series of photocatalytic semiconductors, including metal oxides, sulfides and nitrides, through the combination of phenomenological models for the semiconductor corrosion and the first-principles total energy and band alignment calculations. We find that almost all sulfides and nitrides are unstable as photoanode, while most of oxides are stable. This limits the choice of the photoanode materials for oxygen evolution. In contrast, for photocathode, most of the considered semiconductors are stable and resistant to reduction, indicating a much wider choice of the photocathode materials for hydrogen evolution.

  4. Integrated devices including cleaved semiconductor lasers

    SciTech Connect

    Chen, C.Y.

    1987-11-17

    A process for fabricating a semiconductor device is described comprising semiconductor laser on a semiconductor substrate in which prior to cleaving the semiconductor substrate to form a facet of the semiconductor laser a hole is made in the substrate along the cleave plane so as to produce a stop cleave facet.

  5. Inductively Coupled Plasma Etching of III-V Semiconductors in BCl(3)-Based Chemistries: Part II: InP, InGaAs, InGaAsP, InAs and AllnAs

    SciTech Connect

    Abernathy, C.R.; Han, J.; Hobson, W.S.; Hong, J.; Lambers, E.S.; Lee, J.W.; Maeda, T.; Pearton, S.J.; Shul, R.J

    1998-12-02

    A parametric study of etch rates and surface morphologies of In-containing compound semiconductors (InP, InGaAs, InGaAsP, InAs and AlInAs) obtained by BClj-based Inductively Coupled Plasmas is reported. Etch rates in the range 1,500-3,000 &min. are obtained for all the materials at moderate source powers (500 W), with the rates being a strong function of discharge composition, rf chuck power and pressure. Typical root-mean-square surface roughness of-5 nm were obtained for InP, which is worse than the values obtained for Ga-based materials under the same conditions (-1 run). The near surface of etched samples is typically slightly deficient in the group V element, but the depth of this deficiency is small (a few tens of angstroms).

  6. Advanced Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Shur, Michael S.; Maki, Paul A.; Kolodzey, James

    2007-06-01

    I. Wide band gap devices. Wide-Bandgap Semiconductor devices for automotive applications / M. Sugimoto ... [et al.]. A GaN on SiC HFET device technology for wireless infrastructure applications / B. Green ... [et al.]. Drift velocity limitation in GaN HEMT channels / A. Matulionis. Simulations of field-plated and recessed gate gallium nitride-based heterojunction field-effect transistors / V. O. Turin, M. S. Shur and D. B. Veksler. Low temperature electroluminescence of green and deep green GaInN/GaN light emitting diodes / Y. Li ... [et al.]. Spatial spectral analysis in high brightness GaInN/GaN light emitting diodes / T. Detchprohm ... [et al.]. Self-induced surface texturing of Al2O3 by means of inductively coupled plasma reactive ion etching in Cl2 chemistry / P. Batoni ... [et al.]. Field and termionic field transport in aluminium gallium arsenide heterojunction barriers / D. V. Morgan and A. Porch. Electrical characteristics and carrier lifetime measurements in high voltage 4H-SiC PiN diodes / P. A. Losee ... [et al.]. Geometry and short channel effects on enhancement-mode n-Channel GaN MOSFETs on p and n- GaN/sapphire substrates / W. Huang, T. Khan and T. P. Chow. 4H-SiC Vertical RESURF Schottky Rectifiers and MOSFETs / Y. Wang, P. A. Losee and T. P. Chow. Present status and future Directions of SiGe HBT technology / M. H. Khater ... [et al.]Optical properties of GaInN/GaN multi-quantum Wells structure and light emitting diode grown by metalorganic chemical vapor phase epitaxy / J. Senawiratne ... [et al.]. Electrical comparison of Ta/Ti/Al/Mo/Au and Ti/Al/Mo/Au Ohmic contacts on undoped GaN HEMTs structure with AlN interlayer / Y. Sun and L. F. Eastman. Above 2 A/mm drain current density of GaN HEMTs grown on sapphire / F. Medjdoub ... [et al.]. Focused thermal beam direct patterning on InGaN during molecular beam epitaxy / X. Chen, W. J. Schaff and L. F. Eastman -- II. Terahertz and millimeter wave devices. Temperature-dependent microwave performance of

  7. 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.

  8. Semiconductor superlattice photodetectors

    NASA Technical Reports Server (NTRS)

    Chuang, S. L.; Hess, K.; Coleman, J. J.; Leburton, J. P.

    1984-01-01

    A superlattice photomultiplier and a photodetector based on the real space transfer mechanism were studied. The wavelength for the first device is of the order of a micron or flexible corresponding to the bandgap absorption in a semiconductor. The wavelength for the second device is in the micron range (about 2 to 12 microns) corresponding to the energy of the conduction band edge discontinuity between an Al/(sub x)Ga(sub 1-x)As and GaAs interface. Both devices are described.

  9. Deep levels in semiconductors

    NASA Astrophysics Data System (ADS)

    Watkins, George D.

    1983-03-01

    The 3d transition element ion impurities in silicon are reviewed for the broad insight they provide in understanding deep levels in semiconductors. As interstitials, their interaction with the host tends to confine the d-levels to the forbidden gap, providing many deep states. The interaction at the substitutional site is best considered as an interaction with the lattice vacancy, into which the impurity is placed. This interaction tends to repel deep a1 and t2 levels from the gap. When the levels are present, they are mostly vacancy-like and the defect is likely to display the large lattice relaxations characteristic of the vacancy.

  10. 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.

  11. Isotopically controlled semiconductors

    SciTech Connect

    Haller, Eugene E.

    2001-12-21

    Semiconductor bulk crystals and multilayer structures with controlled isotopic composition have attracted much scientific and technical interest in the past few years. Isotopic composition affects a large number of physical properties, including phonon energies and lifetimes, bandgaps, the thermal conductivity and expansion coefficient and spin-related effects. Isotope superlattices are ideal media for self-diffusion studies. In combination with neutron transmutation doping, isotope control offers a novel approach to metal-insulator transition studies. Spintronics, quantum computing and nanoparticle science are emerging fields using isotope control.

  12. Semiconductor nanorod liquid crystals

    SciTech Connect

    Li, Liang-shi; Walda, Joost; Manna, Liberato; Alivisatos, A. Paul

    2002-01-28

    Rodlike molecules form liquid crystalline phases with orientational order and positional disorder. The great majority of materials in which liquid crystalline phases have been observed are comprised of organic molecules or polymers, even though there has been continuing and growing interest in inorganic liquid crystals. Recent advances in the control of the sizes and shapes of inorganic nanocrystals allow for the formation of a broad class of new inorganic liquid crystals. Here we show the formation of liquid crystalline phases of CdSe semiconductor nanorods. These new liquid crystalline phases may have great importance for both application and fundamental study.

  13. Multilayers of zinc-blende half-metals with semiconductors

    NASA Astrophysics Data System (ADS)

    Mavropoulos, Ph; Galanakis, I.; Dederichs, P. H.

    2004-06-01

    We report on first-principles calculations for multilayers of zinc-blende half-metallic ferromagnets CrAs and CrSb with III-V and II-VI semiconductors, in the [001] orientation. We examine the ideal and tetragonalized structures, as well as the case of an intermixed interface. We find that, as a rule, half-metallicity can be conserved throughout the heterostructures, provided that the character of the local coordination and bonding is not disturbed. We describe a mechanism operative at the interfaces with semiconductors that can also give a non-integer spin moment per interface transition atom, and derive a simple rule for evaluating it.

  14. Multi-spectral Infrared Photodetectors and Focal Plane Arrays based on Band-engineered Type-II Indium-Arsenic / Gallium-Antimony Superlattices and its Variants

    NASA Astrophysics Data System (ADS)

    Huang, Edward Kwei-wei

    Type-II InAs/GaSb superlattices (T2SLs) is a quantum system that has recently garnered much attention for high performance infrared applications. Superlattices can be considered as an artificial bulk material with alternating heterojunctions at the atomic scale where electrons and holes are spatially separated into the InAs and GaSb wells respectively. The effective bandgaps are tailorable from 40meV to 400meV, making it highly suitable for imaging multiple wavebands in the infrared. With a high electron effective mass and energy bands that can also be optimized for the suppression of Auger recombination, T2SLs has drawn considerable interest in recent years and proves to be a prime candidate for third generation imaging. The general principles presented here are powerful and illustrate the flexibility of the T2SL system. The trends seen in the LWIR have also been applied to the MWIR regime resulting in impressive electrical performances at high operating temperatures. Combined with high quantum efficiencies typical of the T2SL material system, both the MWIR and LWIR detectors have reached 300K background-limited performances as demonstrated in this work. The bulk material improvements witnessed, however, make the manufacturability of the T2SL system more challenging, particularly in the aspect of mesa delineation. As the bulk material resistance is elevated, the delineated surface can become the path of least resistance and the result can be detrimental as semiconductor surfaces have been known to be a source of excess noise that could ultimately limit the detector's signal resolution. The difficulty of the problem is compounded by the fact that plasma etched diodes, where high energy ions are driven by an electric field toward the semiconductor to create anisotropic profiles, have been empirically evidenced to generate surface traps. Inductively coupled plasma etching techniques have been investigated in this work. This investigation found that the superlattice

  15. 14 CFR 23.67 - Climb: One engine inoperative.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... engine inoperative and its propeller in the minimum drag position; (ii) Remaining engine(s) at not more... minimum drag position; (ii) Remaining engine(s) at not more than maximum continuous power; (iii) Landing... the— (i) Critical engine inoperative and its propeller in the minimum drag position; (ii)...

  16. Semiconductors: A pillar of pure and applied physics

    NASA Astrophysics Data System (ADS)

    Chelikowsky, James R.; Cohen, Marvin L.

    2015-03-01

    We give an overview of the central role semiconductor research that has played in basic, applied, and computational science. Our focus is on basic science. However, we will make general comments about applications, such as the transistor, integrated circuits, solar devices, and lasers, which evolved from basic research, and about simulations using computational science, which has enormously benefited from semiconductor research. We will make reference to links with other branches of physics and more generally other areas of science and fields like electrical engineering, computer science, material science, medical science, and chemistry that have made significant contributions to our everyday life.

  17. 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.

  18. 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.

  19. Silicon carbide, an emerging high temperature semiconductor

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Powell, J. Anthony

    1991-01-01

    In recent years, the aerospace propulsion and space power communities have expressed a growing need for electronic devices that are capable of sustained high temperature operation. Applications for high temperature electronic devices include development instrumentation within engines, engine control, and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Other earth-based applications include deep-well drilling instrumentation, nuclear reactor instrumentation and control, and automotive sensors. To meet the needs of these applications, the High Temperature Electronics Program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. Research is focussed on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of silicon carbide electronic devices and integrated sensors. The progress made in developing silicon carbide is presented, and the challenges that lie ahead are discussed.

  20. Aqueous Based Semiconductor Nanocrystals.

    PubMed

    Jing, Lihong; Kershaw, Stephen V; Li, Yilin; Huang, Xiaodan; Li, Yingying; Rogach, Andrey L; Gao, Mingyuan

    2016-09-28

    This review summarizes traditional and recent nonconventional, bioinspired, methods for the aqueous synthesis of colloidal semiconductor quantum dots (QDs). The basic chemistry concepts are critically emphasized at the very beginning as these are strongly correlated with the selection of ligands and the optimal formation of aqueous QDs and their more sophisticated structures. The synergies of biomimetic and biosynthetic methods that can combine biospecific reactivity with the robust and strong optical responses of QDs have also resulted in new approaches to the synthesis of the nanoparticles themselves. A related new avenue is the recent extension of QD synthesis to form nanoparticles endowed with chiral optical properties. The optical characteristics of QD materials and their advanced forms such as core/shell heterostructures, alloys, and doped QDs are discussed: from the design considerations of optical band gap tuning, the control and reduction of the impact of surface traps, the consideration of charge carrier processes that affect emission and energy and charge transfer, to the impact and influence of lattice strain. We also describe the considerable progress in some selected QD applications such as in bioimaging and theranostics. The review concludes with future strategies and identification of key challenges that still need to be resolved in reaching very attractive, scalable, yet versatile aqueous syntheses that may widen the scope of commercial applications for semiconductor nanocrystals. PMID:27586892

  1. Progress in semiconductor drift detectors

    SciTech Connect

    Rehak, P.; Walton, J.; Gatti, E.; Longoni, A.; Sanpietro, M.; Kemmer, J.; Dietl, H.; Holl, P.; Klanner, R.; Lutz, G.

    1985-01-01

    Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.

  2. 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.

  3. 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.

  4. Fibre ring cavity semiconductor laser

    SciTech Connect

    Duraev, V P; Medvedev, S V

    2013-10-31

    This paper presents a study of semiconductor lasers having a polarisation maintaining fibre ring cavity. We examine the operating principle and report main characteristics of a semiconductor ring laser, in particular in single- and multiple-frequency regimes, and discuss its application areas. (lasers)

  5. Stripline mount for semiconductor lasers

    SciTech Connect

    Dietrich, N.R.; Holbrook, W.R.; Johnson, A.F. Jr.; Zacharias, A.

    1988-08-02

    An arrangement for coupling a semiconductor optical device to a signal source, is described, the arrangement comprising a stripline transmission path having a predetermined characteristic impedance Z/sub 0/; and resistance means connected in series with the stripline transmission path, chosen to provide impedance matching between the stripline transmission path and an associated semiconductor optical device.

  6. Physics with isotopically controlled semiconductors

    SciTech Connect

    Haller, E. E.

    2010-07-15

    This paper is based on a tutorial presentation at the International Conference on Defects in Semiconductors (ICDS-25) held in Saint Petersburg, Russia in July 2009. The tutorial focused on a review of recent research involving isotopically controlled semiconductors. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, is the most prominent effect for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples.

  7. Fueling the central engine of radio galaxies. II. The footprints of AGN feedback on the ISM of 3C 236

    NASA Astrophysics Data System (ADS)

    Labiano, A.; García-Burillo, S.; Combes, F.; Usero, A.; Soria-Ruiz, R.; Tremblay, G.; Neri, R.; Fuente, A.; Morganti, R.; Oosterloo, T.

    2013-01-01

    Context. There is growing observational evidence of active galactic nuclei (AGN) feedback on the interstellar medium (ISM) of radio-quiet and radio-loud galaxies. While AGN feedback is expected to be more common at high-redshift objects, studying local universe galaxies helps to better characterize the different manifestations of AGN feedback. Aims: Molecular line observations can be used to quantify the mass and energy budget of the gas affected by AGN feedback. We study the emission of molecular gas in 3C 236, a Faranoff-Riley type 2 (FR II) radio source at z ~ 0.1, and search for the footprints of AGN feedback. The source 3C 236 shows signs of a reactivation of its AGN triggered by a recent minor merger episode. Observations have also previously identified an extreme H i outflow in this source. Methods: The IRAM Plateau de Bure interferometer (PdBI) was used to study the distribution and kinematics of molecular gas in 3C 236 by imaging with high spatial resolution (0.6″) the emission of the 2-1 line of 12CO in the nucleus of the galaxy. We searched for outflow signatures in the CO map. We also derived the star-formation rate (SFR) in 3C 236 using data available from the literature at UV, optical, and IR wavelengths, to determine the star-formation efficiency (SFE) of molecular gas. Results: The CO emission in 3C 236 comes from a spatially resolved ~1.4″(2.6 kpc-) diameter disk characterized by a regular rotating pattern. Within the limits imposed by the sensitivity and velocity coverage of the CO data, we do not detect any outflow signatures in the cold molecular gas. The disk has a cold gas mass M(H2) ~ 2.1 × 109 M⊙. Based on CO we determine a new value for the redshift of the source zCO = 0.09927 ± 0.0002. The similarity between the CO and H i profiles indicates that the deep H i absorption in 3C 236 can be accounted for by a rotating H i structure. This restricts the evidence of H i outflow to only the most extreme velocities. In the light of the new

  8. Evolving Biomolecular Control and Assembly of Semiconductor and Magnetic Nanostructures

    NASA Astrophysics Data System (ADS)

    Belcher, Angela

    2003-03-01

    We are investigating the principles of natural biological molecular recognition in materials and developing new methods to pattern useful non-biological electronic and magnetic materials on new length scales. A peptide combinatorial approach has been employed to identify proteins that select for and specifically bind to inorganic structures such as semiconductor wafers and semiconductor and magnetic nanoparticles. This approach utilizes the inherent self-organizing, highly selective properties of biologically derived molecules. We are currently investigating peptide recognition and interaction with III-V and II-VI semiconductor materials and magnetic materials. These peptides are being used to grow nanoparticles and nanowires of specific crystallographic structure and orientation. Using these molecular interactions and specific nanoparticles, we are organizing organic/inorganic hybrid materials into supramolecular architectures.

  9. Diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Anderson, James R.

    1990-03-01

    Growth and physical properties of diluted magnetic semiconductors (DMS) were investigated. Growth included Bridgman, solid state recrystallization, and liquid phase epitaxy of Mercury(1-x)Manganese(x)Telluride and Mercury(1-x-y)Manganese(x)Cadmium(y)Telluride. Very uniform crystals were produced by solid state recrystallization. Physical properties studied included magnetization, optical response, and magnetotransport. From magnetization, the exchange interactions among magnetic ions have been deduced. Modulated spectroscopy gave details of the electronic structure of DMS and the quality of the material was indicated by the line widths. Magnetotransport, carried out in some cases to 30 T, showed a large negative magnetoresistance and subsequent increase. The Hg(1-x-y)Mn(x)Cd(y)Te has considerable promise for avalanche photodiodes between 1.2 and 1.8 micrometers.

  10. Semiconductor nanowire lasers

    NASA Astrophysics Data System (ADS)

    Eaton, Samuel W.; Fu, Anthony; Wong, Andrew B.; Ning, Cun-Zheng; Yang, Peidong

    2016-06-01

    The discovery and continued development of the laser has revolutionized both science and industry. The advent of miniaturized, semiconductor lasers has made this technology an integral part of everyday life. Exciting research continues with a new focus on nanowire lasers because of their great potential in the field of optoelectronics. In this Review, we explore the latest advancements in the development of nanowire lasers and offer our perspective on future improvements and trends. We discuss fundamental material considerations and the latest, most effective materials for nanowire lasers. A discussion of novel cavity designs and amplification methods is followed by some of the latest work on surface plasmon polariton nanowire lasers. Finally, exciting new reports of electrically pumped nanowire lasers with the potential for integrated optoelectronic applications are described.

  11. Zintl Concepts for Interface Engineering

    NASA Astrophysics Data System (ADS)

    Demkov, Alex

    2006-03-01

    Crystalline epitaxial oxides on semiconductors (COS) could very well extend the Complimentary Metal Oxide Semiconductor (CMOS) technology from Si to other semiconductors and thus give new lease on life to the paradigm responsible for the outstanding success of the semiconductor electronics. Another tantalizing possibility is the growth of functional oxide structures utilizing ferroelectricity, superconductivity, magnetism, and other such properties not normally accessible in conventional semiconductors in monolithic integration with Si. There also may be applications of COS at the end of the Si Roadmap. Two dimensional (2D) crystal growth of ionic oxides on covalent semiconductors and visa versa is essential for these approach to work. In this talk I will discuss how concepts developed by Edward Zintl more than seventy years ago can be used for interface engineering. I will use ab-initio density functional theory to demonstrate how the bonding character at the oxide/semiconductor interface is manipulated through charge transfer in the engineered intermetallic contact layer. This transition layer lowers the energy of the interface and results in 2D growth, and high quality epitaxial films.

  12. Efficient and stable near infrared emitters using band gap engineered quantum dots for biomedical applications

    NASA Astrophysics Data System (ADS)

    Blackman, Bridgette Renee

    Synthetic chemistry of colloidal semiconductor nanocrystals has been a major area for materials chemistry and this field has advanced dramatically. Emphasis in terms of materials development has gradually shifted from simple composition with regular dot-shape to complex composition/morphologies. One of the present frontiers is "band gap engineering in solution". Band gap engineering refers to the control of the behavior of the photo-generated carriers, both electrons and holes, by means of epitaxial growth of various semiconductors with different band structures, often referred to as complex heterostructures. Potential uses for these complex heterostructures exist as emitters for biomedical labeling, quantum dot (QD)-based lasers, light emitting diodes (LEDs), electroluminescent devices, and solar cells. To date, band gap engineering in solution is much less developed. This direction is expected to yield nanocrystals with properties otherwise not available from the corresponding individual materials. By using what is known about monomer activities, ligand effects, noncoordinating solvents, and SILAR growth methods, it is now possible to controllably synthesize high quality complex semiconductor nanocrystals. In this research, we modified a solution-based epitaxial growth method to synthesize nanomaterials with unusual type II band offsets. More specifically, novel SILAR synthesis of CdSe/CdTe type II core/shell, CdS/CdSe/CdTe type II quantum well, and water soluble CdSe/CdTe/ZnSe nanocrystals are described. In all systems, a new concept of "thermal cycling" of the reaction temperature was incorporated to control the size and size/shape distribution of the nanocrystals. In addition, a controlled etching methodology was developed for use as an analytical tool to determine information about the surface chemistry and structure. Details on the syntheses, optical properties, and stability, of these complex materials will be described.

  13. Semiconductor Nanocrystals for Biological Imaging

    SciTech Connect

    Fu, Aihua; Gu, Weiwei; Larabell, Carolyn; Alivisatos, A. Paul

    2005-06-28

    Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission feature. Semiconductor nanocrystals, on the other hand, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

  14. Assessing conceptual knowledge for the physics of semiconductors

    NASA Astrophysics Data System (ADS)

    Ene, Emanuela

    Following the trend in science and engineering education generated by the visible impact created by the Force Concept Inventory (FCI), the investigator developed a Physics of Semiconductors Concept Inventory (PSCI). PSCI fills the need of standardized concept tests for undergraduate education in photonics and electrical engineering. The structure of the PSCI test followed a concept map reflecting the input from a panel of experts from different universities and from a survey of textbooks currently used in engineering schools in the United States. Based on the statistical analysis of the scores and response patterns, the test was calibrated as an instrument to measure participants' cognitive ability independent of items' difficulty. The models employed were the Rasch Model and the Rasch Partial Credit Model. The estimation procedure employed was Conditional Maximum Likelihood. The analysis was carried on using algorithms written in the open-source language R. The current PSCI BETA test contains eighteen calibrated items covering six concepts of the physics of semiconductors. PSCI BETA may be used for three purposes: individual student diagnostic if applied at the beginning of a physics of semiconductors course; predictor for students' academic performance in the field of semiconductors if applied at the end of instruction; assessment instrument for instructional strategies if applied both for pre- and post-instruction. The PSCI BETA instrument can be applied in any English speaking college setting. The main results of the PSCI research are: ranking persons' ability related to the physics of semiconductors on an objective linear scale, building a diagnose matrix that may be utilized by instructors for choosing an optimal teaching approach and by students for remediation, and demonstrating a calibration method for small sample size.

  15. 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.

  16. State of the art in semiconductor detectors

    SciTech Connect

    Rehak, P. ); Gatti, E. )

    1989-01-01

    The state of the art in semiconductor detectors for elementary particle physics and x-ray astronomy is briefly reviewed. Semiconductor detectors are divided into two groups; classical semiconductor diode detectors; and semiconductor memory detectors. Principles of signal formation for both groups of detectors are described and their performance is compared. New developments of silicon detectors are reported here. 13 refs., 8 figs.

  17. Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors

    DOE PAGES

    Fluegel., Brian; Mialitsin, Aleksej V.; Beaton, Daniel A.; Reno, John L.; Mascarenhas, Angelo

    2015-05-28

    Semiconductor strain engineering has become a critical feature of high-performance electronics because of the significant device performance enhancements that it enables. These improvements, which emerge from strain-induced modifications to the electronic band structure, necessitate new ultra-sensitive tools to probe the strain in semiconductors. Here, we demonstrate that minute amounts of strain in thin semiconductor epilayers can be measured using electronic Raman scattering. We also applied this strain measurement technique to two different semiconductor alloy systems using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10-4. Thus, comparing our strain sensitivity and signal strength inmore » AlxGa 1-x As with those obtained using the industry-standard technique of phonon Raman scattering, we found that there was a sensitivity improvement of 200-fold and a signal enhancement of 4 × 103, thus obviating key constraints in semiconductor strain metrology.« less

  18. Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors

    PubMed Central

    Fluegel, Brian; Mialitsin, Aleksej V.; Beaton, Daniel A.; Reno, John L.; Mascarenhas, Angelo

    2015-01-01

    Semiconductor strain engineering has become a critical feature of high-performance electronics because of the significant device performance enhancements that it enables. These improvements, which emerge from strain-induced modifications to the electronic band structure, necessitate new ultra-sensitive tools to probe the strain in semiconductors. Here, we demonstrate that minute amounts of strain in thin semiconductor epilayers can be measured using electronic Raman scattering. We applied this strain measurement technique to two different semiconductor alloy systems using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10−4. Comparing our strain sensitivity and signal strength in AlxGa1−xAs with those obtained using the industry-standard technique of phonon Raman scattering, we found that there was a sensitivity improvement of 200-fold and a signal enhancement of 4 × 103, thus obviating key constraints in semiconductor strain metrology. PMID:26017853

  19. Engineering topological superconductors using surface atomic-layer/molecule hybrid materials.

    PubMed

    Uchihashi, Takashi

    2015-08-28

    Surface atomic-layer (SAL) superconductors consisting of epitaxially grown metal adatoms on a clean semiconductor surface have been recently established. Compared to conventional metal thin films, they have two important features: (i) space-inversion symmetry-breaking throughout the system and (ii) high sensitivity to surface adsorption of foreign species. These potentially lead to manifestation of the Rashba effect and a Zeeman field exerted by adsorbed magnetic organic molecules. After introduction of the archetypical SAL superconductor Si(111)-(√7 × √3)-In, we describe how these features are utilized to engineer a topological superconductor with Majorana fermions and discuss its promises and expected challenges. PMID:26234824

  20. Hydrogen local vibrational modes in semiconductors

    SciTech Connect

    McCluskey, M D

    1997-06-01

    Following, a review of experimental techniques, theory, and previous work, the results of local vibrational mode (LVM) spectroscopy on hydrogen-related complexes in several different semiconductors are discussed. Hydrogen is introduced either by annealing in a hydrogen ambient. exposure to a hydrogen plasma, or during growth. The hydrogen passivates donors and acceptors in semiconductors, forming neutral complexes. When deuterium is substituted for hydrogen. the frequency of the LVM decreases by approximately the square root of two. By varying the temperature and pressure of the samples, the microscopic structures of hydrogen-related complexes are determined. For group II acceptor-hydrogen complexes in GaAs, InP, and GaP, hydrogen binds to the host anion in a bond-centered orientation, along the [111] direction, adjacent to the acceptor. The temperature dependent shift of the LVMs are proportional to the lattice thermal energy U(T), a consequence of anharmonic coupling between the LVM and acoustical phonons. In the wide band gap semiconductor ZnSe, epilayers grown by metalorganic chemical vapor phase epitaxy (MOCVD) and doped with As form As-H complexes. The hydrogen assumes a bond-centered orientation, adjacent to a host Zn. In AlSb, the DX centers Se and Te are passivated by hydrogen. The second, third, and fourth harmonics of the wag modes are observed. Although the Se-D complex has only one stretch mode, the Se-H stretch mode splits into three peaks. The anomalous splitting is explained by a new interaction between the stretch LVM and multi-phonon modes of the lattice. As the temperature or pressure is varied, and anti-crossing is observed between LVM and phonon modes.

  1. Signal processing for semiconductor detectors

    SciTech Connect

    Goulding, F.S.; Landis, D.A.

    1982-02-01

    A balanced perspective is provided on the processing of signals produced by semiconductor detectors. The general problems of pulse shaping to optimize resolution with constraints imposed by noise, counting rate and rise time fluctuations are discussed.

  2. Artificial atoms on semiconductor surfaces

    PubMed Central

    Tisdale, W. A.; Zhu, X.-Y.

    2011-01-01

    Semiconductor nanocrystals are called artificial atoms because of their atom-like discrete electronic structure resulting from quantum confinement. Artificial atoms can also be assembled into artificial molecules or solids, thus, extending the toolbox for material design. We address the interaction of artificial atoms with bulk semiconductor surfaces. These interfaces are model systems for understanding the coupling between localized and delocalized electronic structures. In many perceived applications, such as nanoelectronics, optoelectronics, and solar energy conversion, interfacing semiconductor nanocrystals to bulk materials is a key ingredient. Here, we apply the well established theories of chemisorption and interfacial electron transfer as conceptual frameworks for understanding the adsorption of semiconductor nanocrystals on surfaces, paying particular attention to instances when the nonadiabatic Marcus picture breaks down. We illustrate these issues using recent examples from our laboratory. PMID:21097704

  3. Metal-Insulator-Semiconductor Photodetectors

    PubMed Central

    Lin, Chu-Hsuan; Liu, Chee Wee

    2010-01-01

    The major radiation of the Sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III–V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows. PMID:22163382

  4. 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.

  5. Medical applications of semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Mancha, Sylvia D.; Keipert, Andreas; Prairie, Michael W.

    1994-06-01

    The High Power Semiconductor Laser Technology (HPSLT) program is currently developing, in-house, a belt pack medical laser. This compact semiconductor laser device provides the field paramedic or physician a unique portable laser capability. The pack consists of a completely self-contained laser system that fits inside a belt pack. Several other medical applications being investigated by the HPSLT program include urological applications, photodynamic therapy, and ophthalmic applications.

  6. Dye Sensitization of Semiconductor Particles

    SciTech Connect

    Hartland, G. V.

    2003-01-13

    In this project electron transfer at semiconductor liquid interfaces was examined by ultrafast time-resolved and steady-state optical techniques. The experiments primarily yielded information about the electron transfer from titanium dioxide semiconductor particles to absorbed molecules. The results show that the rate of electron transfer depends on the structure of the molecule, and the crystalline phase of the particle. These results can be qualitatively explained by Marcus theory for electron transfer.

  7. Semiconductor crystal high resolution imager

    NASA Technical Reports Server (NTRS)

    Levin, Craig S. (Inventor); Matteson, James (Inventor)

    2011-01-01

    A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

  8. Method for making graded I-III-VI.sub.2 semiconductors and solar cell obtained thereby

    DOEpatents

    Devaney, Walter E.

    1987-08-04

    Improved cell photovoltaic conversion efficiencies are obtained by the simultaneous elemental reactive evaporation process of Mickelsen and Chen for making semiconductors by closer control of the evaporation rates and substrate temperature during formation of the near contact, bulk, and near junction regions of a graded I-III-VI.sub.2, thin film, semiconductor, such as CuInSe.sub.2 /(Zn,Cd)S or another I-III-VI.sub.2 /II-VI heterojunction.

  9. 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.

  10. Donor level of interstitial hydrogen in semiconductors: Deep level transient spectroscopy

    NASA Astrophysics Data System (ADS)

    Kolkovsky, Vl.; Dobaczewski, L.; Nielsen, K. Bonde; Kolkovsky, V.; Larsen, A. Nylandsted; Weber, J.

    2009-12-01

    The behaviour of hydrogen in crystalline semiconductors has attracted considerable interest during several decades. Due to its high diffusion rate and ability to react with a wide variety of lattice imperfections such as intrinsic point defects, impurities, interfaces and surfaces, hydrogen is an impurity of fundamental importance in semiconductor materials. It has been already evidenced in previous investigations that the most fundamental hydrogen-related defects in-group IV semiconductors are interstitial hydrogen atoms occupying the bond-centre site ( BC) or the interstitial tetrahedral site ( T). Using first-principles calculations Van de Walle predicted similar properties of isolated hydrogen in other II-VI and III-V semiconductors. Another interesting prediction shown in that work was the existence of a universal alignment for the hydrogen electronic (-/+) level. Until now there is no direct experimental information regarding the individual isolated hydrogen states in compound semiconductors and most reported properties have been inferred indirectly. In the present work in-situ conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques are used to analyse hydrogen-related levels after low-temperature proton implantation in different II-VI and III-V semiconductors including GaAs, ZnO and CdTe. From these experimental observations the donor level of isolated hydrogen is found to keep almost a constant value in the absolute energy scale taking into account different band-offsets calculated for the whole group of semiconductors.

  11. Simulating nanoscale semiconductor devices.

    SciTech Connect

    Salinger, Andrew Gerhard; Zhao, P.; Woolard, D. L.; Kelley, C. Tim; Lasater, Matthew S.

    2005-03-01

    The next generation of electronic devices will be developed at the nanoscale and molecular level, where quantum mechanical effects are observed. These effects must be accounted for in the design process for such small devices. One prototypical nanoscale semiconductor device under investigation is a resonant tunneling diode (RTD). Scientists are hopeful the quantum tunneling effects present in an RTD can be exploited to induce and sustain THz frequency current oscillations. To simulate the electron transport within the RTD, the Wigner-Poisson equations are used. These equations describe the time evolution of the electrons distribution within the device. In this paper, this model and a parameter study using this model will be presented. The parameter study involves calculating the steady-state current output from the RTD as a function of an applied voltage drop across the RTD and also calculating the stability of that solution. To implement the parameter study, the computational model was connected to LOCA (Library of Continuation Algorithms), a part of Sandia National Laboratories parallel solver project, Trilinos. Numerical results will be presented.

  12. Impurity gettering in semiconductors

    DOEpatents

    Sopori, B.L.

    1995-06-20

    A process for impurity gettering in a semiconductor substrate or device such as a silicon substrate or device is disclosed. The process comprises hydrogenating the substrate or device at the back side thereof with sufficient intensity and for a time period sufficient to produce a damaged back side. Thereafter, the substrate or device is illuminated with electromagnetic radiation at an intensity and for a time period sufficient to cause the impurities to diffuse to the back side and alloy with a metal there present to form a contact and capture the impurities. The impurity gettering process also can function to simultaneously passivate defects within the substrate or device, with the defects likewise diffusing to the back side for simultaneous passivation. Simultaneously, substantially all hydrogen-induced damage on the back side of the substrate or device is likewise annihilated. Also taught is an alternate process comprising thermal treatment after hydrogenation of the substrate or device at a temperature of from about 500 C to about 700 C for a time period sufficient to cause the impurities to diffuse to the damaged back side thereof for subsequent capture by an alloying metal. 1 fig.

  13. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XVIII, I--UNDERSTAND ENGINE GEARS AND GEARING PRINCIPLES, II--MACK INTER-AXLE POWER DIVIDER.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF DIESEL ENGINE GEARS AND GEARING PRINCIPLES AND THE OPERATING PRINCIPLES AND MAINTENANCE OF POWER DIVIDERS (GEAR BOXES) USED IN DIESEL ENGINE POWER TRANSMISSION. TOPICS ARE (1) THE PURPOSE OF THE ENGINE GEARS, (2) INSPECTING FOR GEAR FAILURES, (3) INSPECTING FOR SHAFT…

  14. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XVII, I--MAINTAINING THE LUBRICATION SYSTEM--CUMMINS DIESEL ENGINE, II--UNIT INSTALLATION AND REMOVAL--DRIVE LINES.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE DIESEL ENGINE LUBRICATION SYSTEM AND THE PROCEDURES FOR REMOVAL AND INSTALLATION OF THE DRIVE LINE USED IN DIESEL ENGINE POWER DISTRIBUTION. TOPICS ARE (1) PROLONGING ENGINE LIFE, (2) FUNCTIONS OF THE LUBRICATING SYSTEM, (3) TRACING THE LUBRICANT FLOW, (4) DETERMINING…

  15. 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

  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.

  17. Electron states in semiconductor quantum dots

    SciTech Connect

    Dhayal, Suman S.; Ramaniah, Lavanya M.; Ruda, Harry E.; Nair, Selvakumar V.

    2014-11-28

    In this work, the electronic structures of quantum dots (QDs) of nine direct band gap semiconductor materials belonging to the group II-VI and III-V families are investigated, within the empirical tight-binding framework, in the effective bond orbital model. This methodology is shown to accurately describe these systems, yielding, at the same time, qualitative insights into their electronic properties. Various features of the bulk band structure such as band-gaps, band curvature, and band widths around symmetry points affect the quantum confinement of electrons and holes. These effects are identified and quantified. A comparison with experimental data yields good agreement with the calculations. These theoretical results would help quantify the optical response of QDs of these materials and provide useful input for applications.

  18. Approaches toward a blue semiconductor laser

    NASA Technical Reports Server (NTRS)

    Ladany, I.

    1989-01-01

    Possible approaches for obtaining semiconductor diode laser action in the blue region of the spectrum are surveyed. A discussion of diode lasers is included along with a review of the current status of visible emitters, presently limited to 670 nm. Methods are discussed for shifting laser emission toward shorter wavelengths, including the use of II-IV materials, the increase in the bandgap of III-V materials by addition of nitrogen, and changing the bandstructure from indirect to direct by incorporating interstitial atoms or by constructing superlattices. Non-pn-junction injection methods are surveyed, including avalanche breakdown, Langmuir-Blodgett diodes, heterostructures, carrier accumulation, and Berglund diodes. Prospects of inventing new multinary semiconducting materials are discussed, and a number of novel materials described in the literature are tabulated. New approaches available through the development of quantum wells and superlattices are described, including resonant tunneling and the synthesis of arbitrary bandgap materials through multiple quantum wells.

  19. Delta II Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Final preparations for lift off of the DELTA II Mars Pathfinder Rocket are shown. Activities include loading the liquid oxygen, completing the construction of the Rover, and placing the Rover into the Lander. After the countdown, important visual events include the launch of the Delta Rocket, burnout and separation of the three Solid Rocket Boosters, and the main engine cutoff. The cutoff of the main engine marks the beginning of the second stage engine. After the completion of the second stage, the third stage engine ignites and then cuts off. Once the third stage engine cuts off spacecraft separation occurs.

  20. Multistability, chaos, and random signal generation in semiconductor superlattices.

    PubMed

    Ying, Lei; Huang, Danhong; Lai, Ying-Cheng

    2016-06-01

    Historically, semiconductor superlattices, artificial periodic structures of different semiconductor materials, were invented with the purpose of engineering or manipulating the electronic properties of semiconductor devices. A key application lies in generating radiation sources, amplifiers, and detectors in the "unusual" spectral range of subterahertz and terahertz (0.1-10 THz), which cannot be readily realized using conventional radiation sources, the so-called THz gap. Efforts in the past three decades have demonstrated various nonlinear dynamical behaviors including chaos, suggesting the potential to exploit chaos in semiconductor superlattices as random signal sources (e.g., random number generators) in the THz frequency range. We consider a realistic model of hot electrons in semiconductor superlattice, taking into account the induced space charge field. Through a systematic exploration of the phase space we find that, when the system is subject to an external electrical driving of a single frequency, chaos is typically associated with the occurrence of multistability. That is, for a given parameter setting, while there are initial conditions that lead to chaotic trajectories, simultaneously there are other initial conditions that lead to regular motions. Transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt. Multistability thus presents an obstacle to utilizing the superlattice system as a reliable and robust random signal source. However, we demonstrate that, when an additional driving field of incommensurate frequency is applied, multistability can be eliminated, with chaos representing the only possible asymptotic behavior of the system. In such a case, a random initial condition will lead to a trajectory landing in a chaotic attractor with probability 1, making quasiperiodically driven semiconductor superlattices potentially as a reliable

  1. Multistability, chaos, and random signal generation in semiconductor superlattices.

    PubMed

    Ying, Lei; Huang, Danhong; Lai, Ying-Cheng

    2016-06-01

    Historically, semiconductor superlattices, artificial periodic structures of different semiconductor materials, were invented with the purpose of engineering or manipulating the electronic properties of semiconductor devices. A key application lies in generating radiation sources, amplifiers, and detectors in the "unusual" spectral range of subterahertz and terahertz (0.1-10 THz), which cannot be readily realized using conventional radiation sources, the so-called THz gap. Efforts in the past three decades have demonstrated various nonlinear dynamical behaviors including chaos, suggesting the potential to exploit chaos in semiconductor superlattices as random signal sources (e.g., random number generators) in the THz frequency range. We consider a realistic model of hot electrons in semiconductor superlattice, taking into account the induced space charge field. Through a systematic exploration of the phase space we find that, when the system is subject to an external electrical driving of a single frequency, chaos is typically associated with the occurrence of multistability. That is, for a given parameter setting, while there are initial conditions that lead to chaotic trajectories, simultaneously there are other initial conditions that lead to regular motions. Transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt. Multistability thus presents an obstacle to utilizing the superlattice system as a reliable and robust random signal source. However, we demonstrate that, when an additional driving field of incommensurate frequency is applied, multistability can be eliminated, with chaos representing the only possible asymptotic behavior of the system. In such a case, a random initial condition will lead to a trajectory landing in a chaotic attractor with probability 1, making quasiperiodically driven semiconductor superlattices potentially as a reliable

  2. Multistability, chaos, and random signal generation in semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Ying, Lei; Huang, Danhong; Lai, Ying-Cheng

    2016-06-01

    Historically, semiconductor superlattices, artificial periodic structures of different semiconductor materials, were invented with the purpose of engineering or manipulating the electronic properties of semiconductor devices. A key application lies in generating radiation sources, amplifiers, and detectors in the "unusual" spectral range of subterahertz and terahertz (0.1-10 THz), which cannot be readily realized using conventional radiation sources, the so-called THz gap. Efforts in the past three decades have demonstrated various nonlinear dynamical behaviors including chaos, suggesting the potential to exploit chaos in semiconductor superlattices as random signal sources (e.g., random number generators) in the THz frequency range. We consider a realistic model of hot electrons in semiconductor superlattice, taking into account the induced space charge field. Through a systematic exploration of the phase space we find that, when the system is subject to an external electrical driving of a single frequency, chaos is typically associated with the occurrence of multistability. That is, for a given parameter setting, while there are initial conditions that lead to chaotic trajectories, simultaneously there are other initial conditions that lead to regular motions. Transition to multistability, i.e., the emergence of multistability with chaos as a system parameter passes through a critical point, is found and argued to be abrupt. Multistability thus presents an obstacle to utilizing the superlattice system as a reliable and robust random signal source. However, we demonstrate that, when an additional driving field of incommensurate frequency is applied, multistability can be eliminated, with chaos representing the only possible asymptotic behavior of the system. In such a case, a random initial condition will lead to a trajectory landing in a chaotic attractor with probability 1, making quasiperiodically driven semiconductor superlattices potentially as a reliable

  3. Deployable Engine Air Brake

    NASA Technical Reports Server (NTRS)

    2014-01-01

    On approach, next-generation aircraft are likely to have airframe noise levels that are comparable to or in excess of engine noise. ATA Engineering, Inc. (ATA) is developing a novel quiet engine air brake (EAB), a device that generates "equivalent drag" within the engine through stream thrust reduction by creating a swirling outflow in the turbofan exhaust nozzle. Two Phase II projects were conducted to mature this technology: (1) a concept development program (CDP) and (2) a system development program (SDP).

  4. PREFACE: 3rd Workshop on Theory, Modelling and Computational Methods for Semiconductors (TMCSIII)

    NASA Astrophysics Data System (ADS)

    Califano, Marco; Migliorato, Max; Probert, Matt

    2012-05-01

    These conference proceedings contain the written papers of the contributions presented at the 3rd International Conference on Theory, Modelling and Computational Methods for Semiconductor materials and nanostructures. The conference was held at the School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK on 18-20 January 2012. The previous conferences in this series took place in 2010 at St William's College, York and in 2008 at the University of Manchester, UK. The development of high-speed computer architectures is finally allowing the routine use of accurate methods for calculating the structural, thermodynamic, vibrational, optical and electronic properties of semiconductors and their hetero- and nano-structures. The scope of this conference embraces modelling, theory and the use of sophisticated computational tools in semiconductor science and technology, where there is substantial potential for time-saving in R&D. Theoretical approaches represented in this meeting included: Density Functional Theory, Tight Binding, Semiempirical Pseudopotential Methods, Effective Mass Models, Empirical Potential Methods and Multiscale Approaches. Topics included, but were not limited to: Optical and Transport Properties of Quantum Nanostructures including Colloids and Nanotubes, Plasmonics, Magnetic Semiconductors, Graphene, Lasers, Photonic Structures, Photovoltaic and Electronic Devices. This workshop ran for three days, with the objective of bringing together UK and international leading experts in the theoretical modelling of Group IV, III-V and II-VI semiconductors, as well as students, postdocs and early-career researchers. The first day focused on providing an introduction and overview of this vast field, aimed particularly at students, with several lectures given by recognised experts in various theoretical approaches. The following two days showcased some of the best theoretical research carried out in the UK in this field, with several

  5. Closing photoconductive semiconductor switches

    SciTech Connect

    Loubriel, G.M.; Zutavern, F.J.; Hjalmarson, H.P.; O'Malley, M.W.

    1989-01-01

    One of the most important limitations of Photoconductive Semiconductor Switches (PCSS) for pulsed power applications is the high laser powers required to activate the switches. In this paper, we discuss recent developments on two different aspects of GaAs PCSS that result in reductions in laser power by a factor of nearly 1000. The advantages of using GaAs over Si are many. First of all, the resistivity of GaAs can be orders of magnitude higher than that of the highest resistivity Si material, thus allowing GaAs switches to withstand dc voltages without thermal runaway. Secondly, GaAs has a higher carrier mobility than Si and, thus, is more efficient (per carrier). Finally, GaAs switches can have naturally fast (ns) opening times at room temperature and low fields, microsecond opening times at liquid nitrogen temperature of 77 K, or, on demand, closing and opening at high fields and room temperature by a mechanism called lock-on (see Ref. 1). By contrast, Si switches typically opening times of milliseconds. The amount of laser light required to trigger GaAs for lock-on, or at 77 K, is about three orders of magnitude lower than at room temperature. In this paper we describe the study of lock-on in GaAs and InP, as well as switching of GaAs at 77 K. We shall show that when GaAs is switched at 77 K, the carrier lifetime is about three orders of magnitude longer than it is at room temperature. We shall explain the change in lifetime in terms of the change in electron capture cross section of the deep levels in GaAs (these are defect or impurity levels in the band gap). In the second section, we describe the lock-on effect, now seen in GaAs and InP, and at fields as high as 70 kV/cm. We show how lock-on can be tailored by changing the GaAs temperature or by neutron bombardment. In the third section, we discuss possible lock-on mechanisms. 5 refs., 5 figs.

  6. High mobility emissive organic semiconductor

    PubMed Central

    Liu, Jie; Zhang, Hantang; Dong, Huanli; Meng, Lingqiang; Jiang, Longfeng; Jiang, Lang; Wang, Ying; Yu, Junsheng; Sun, Yanming; Hu, Wenping; Heeger, Alan J.

    2015-01-01

    The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm2 V−1 s−1. Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m−2 and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics. PMID:26620323

  7. High mobility emissive organic semiconductor

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Zhang, Hantang; Dong, Huanli; Meng, Lingqiang; Jiang, Longfeng; Jiang, Lang; Wang, Ying; Yu, Junsheng; Sun, Yanming; Hu, Wenping; Heeger, Alan J.

    2015-12-01

    The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm2 V-1 s-1. Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m-2 and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics.

  8. High mobility emissive organic semiconductor.

    PubMed

    Liu, Jie; Zhang, Hantang; Dong, Huanli; Meng, Lingqiang; Jiang, Longfeng; Jiang, Lang; Wang, Ying; Yu, Junsheng; Sun, Yanming; Hu, Wenping; Heeger, Alan J

    2015-01-01

    The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm(2) V(-1) s(-1). Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m(-2) and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics.

  9. 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.

  10. Selenium semiconductor core optical fibers

    SciTech Connect

    Tang, G. W.; Qian, Q. Peng, K. L.; Wen, X.; Zhou, G. X.; Sun, M.; Chen, X. D.; Yang, Z. M.

    2015-02-15

    Phosphate glass-clad optical fibers containing selenium (Se) semiconductor core were fabricated using a molten core method. The cores were found to be amorphous as evidenced by X-ray diffraction and corroborated by Micro-Raman spectrum. Elemental analysis across the core/clad interface suggests that there is some diffusion of about 3 wt % oxygen in the core region. Phosphate glass-clad crystalline selenium core optical fibers were obtained by a postdrawing annealing process. A two-cm-long crystalline selenium semiconductor core optical fibers, electrically contacted to external circuitry through the fiber end facets, exhibit a three times change in conductivity between dark and illuminated states. Such crystalline selenium semiconductor core optical fibers have promising utility in optical switch and photoconductivity of optical fiber array.

  11. Voltage-controlled quantum light from an atomically thin semiconductor

    NASA Astrophysics Data System (ADS)

    Chakraborty, Chitraleema; Kinnischtzke, Laura; Goodfellow, Kenneth M.; Beams, Ryan; Vamivakas, A. Nick

    2015-06-01

    Although semiconductor defects can often be detrimental to device performance, they are also responsible for the breadth of functionality exhibited by modern optoelectronic devices. Artificially engineered defects (so-called quantum dots) or naturally occurring defects in solids are currently being investigated for applications ranging from quantum information science and optoelectronics to high-resolution metrology. In parallel, the quantum confinement exhibited by atomically thin materials (semi-metals, semiconductors and insulators) has ushered in an era of flatland optoelectronics whose full potential is still being articulated. In this Letter we demonstrate the possibility of leveraging the atomically thin semiconductor tungsten diselenide (WSe2) as a host for quantum dot-like defects. We report that this previously unexplored solid-state quantum emitter in WSe2 generates single photons with emission properties that can be controlled via the application of external d.c. electric and magnetic fields. These new optically active quantum dots exhibit excited-state lifetimes on the order of 1 ns and remarkably large excitonic g-factors of 10. It is anticipated that WSe2 quantum dots will provide a novel platform for integrated solid-state quantum photonics and quantum information processing, as well as a rich condensed-matter physics playground with which to explore the coupling of quantum dots and atomically thin semiconductors.

  12. Voltage-controlled quantum light from an atomically thin semiconductor.

    PubMed

    Chakraborty, Chitraleema; Kinnischtzke, Laura; Goodfellow, Kenneth M; Beams, Ryan; Vamivakas, A Nick

    2015-06-01

    Although semiconductor defects can often be detrimental to device performance, they are also responsible for the breadth of functionality exhibited by modern optoelectronic devices. Artificially engineered defects (so-called quantum dots) or naturally occurring defects in solids are currently being investigated for applications ranging from quantum information science and optoelectronics to high-resolution metrology. In parallel, the quantum confinement exhibited by atomically thin materials (semi-metals, semiconductors and insulators) has ushered in an era of flatland optoelectronics whose full potential is still being articulated. In this Letter we demonstrate the possibility of leveraging the atomically thin semiconductor tungsten diselenide (WSe2) as a host for quantum dot-like defects. We report that this previously unexplored solid-state quantum emitter in WSe2 generates single photons with emission properties that can be controlled via the application of external d.c. electric and magnetic fields. These new optically active quantum dots exhibit excited-state lifetimes on the order of 1 ns and remarkably large excitonic g-factors of 10. It is anticipated that WSe2 quantum dots will provide a novel platform for integrated solid-state quantum photonics and quantum information processing, as well as a rich condensed-matter physics playground with which to explore the coupling of quantum dots and atomically thin semiconductors.

  13. 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.

  14. 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.

  15. The processing of semiconductor materials

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Five experiments involving the processing of semiconductor materials were performed during the Skylab mission. After discussions on semiconductors and their unique electronic properties, and techniques of crystal growth, these five experiments are presented. Four melt growth experiments were attempted: (1) steady state growth and segregation under zero gravity (InSb); (2) seeded, containerless solidification of InSb; (3) influence of gravity-free solidification on microsegregation; and (4) directional solidification of InSb-GaSb alloys. One vapor growth experiment, crystal growth by vapor transport, was attempted.

  16. Building a Community of Scholars: One University's Story of Students Engaged in Learning Science, Mathematics, and Engineering through a NSF S-STEM Grant--Part II

    ERIC Educational Resources Information Center

    Kalevitch, Maria; Maurer, Cheryl; Badger, Paul; Holdan, Greg; Sirinterlikci, Arif

    2015-01-01

    The School of Engineering, Mathematics, and Science (SEMS) at Robert Morris University (RMU) was awarded a five-year grant from the National Science Foundation (NSF) to fund scholarships to 21 academically talented but financially challenged students majoring in the disciplines of science, technology, engineering, and mathematics (STEM). Each…

  17. Method of preparing nitrogen containing semiconductor material

    DOEpatents

    Barber, Greg D.; Kurtz, Sarah R.

    2004-09-07

    A method of combining group III elements with group V elements that incorporates at least nitrogen from a nitrogen halide for use in semiconductors and in particular semiconductors in photovoltaic cells.

  18. 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.

  19. Semiconductor Reliability--Another Field for Physicists.

    ERIC Educational Resources Information Center

    Derman, Samuel; Anderson, Wallace T.

    1994-01-01

    Stresses that an important industrial area is product reliability, especially for semiconductors. Suggests that physics students would benefit from training in semiconductors: the many modes of failure, radiation effects, and electrical contact problems. (MVL)

  20. Glass-clad semiconductor core optical fibers

    NASA Astrophysics Data System (ADS)

    Morris, Stephanie Lynn

    Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. As research into these fibers has progressed, it has become evident that excessive losses are limiting performance and so greater understanding of the underlying materials science, coupled with advances in fiber processing, is needed. More specifically, the semiconductor core fibers possess three performance-limiting characteristics that need to be addressed: (a) thermal expansion mismatches between crystalline core and glass cladding that lead to cracks, (b) the precipitation of oxide species in the core upon fiber cooling, which results from partial dissolution of the cladding glass by the core melt, and (c) polycrystallinity; all of which lead to scattering and increased transmission losses. This dissertation systematically studies each of these effects and develops both a fundamental scientific understanding of and practical engineering methods for reducing their impact. With respect to the thermal expansion mismatch and, in part, the dissolution of oxides, for the first time to our knowledge, oxide and non-oxide glass compositions are developed for a series of semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding to minimize cracking and (2) matching the viscosity-temperature dependences, such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor in order to minimize dissolution and improve the fiber draw process. The x[Na 2O:Al2O3] + (100 - 2x)SiO2 glass compositional family was selected due to the ability to tailor the glass properties to match the aforementioned targets through slight variations in composition and adjusting the ratios of bridging and non-bridging oxygen

  1. 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.

  2. 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.

  3. Semiconductor devices having a recessed electrode structure

    DOEpatents

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2015-05-26

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  4. 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.

  5. Diode having trenches in a semiconductor region

    DOEpatents

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2016-03-22

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  6. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2001-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  7. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2002-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  8. 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.

  9. A Brief History of ... Semiconductors

    ERIC Educational Resources Information Center

    Jenkins, Tudor

    2005-01-01

    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…

  10. Hydroplane polishing of semiconductor crystals

    NASA Astrophysics Data System (ADS)

    Gormley, J. V.; Manfra, M. J.; Calawa, A. R.

    1981-08-01

    A new technique for obtaining optically flat, damage-free surfaces on semiconductor crystals has been developed. The polishing is very fast, being capable of removing over 30 μm of materials per minute in the case of GaAs and InP. Initial results indicate that the technique can also be used in the polishing of HgCdTe.

  11. 2010 Defects in Semiconductors GRC

    SciTech Connect

    Shengbai Zhang

    2011-01-06

    Continuing its tradition of excellence, this Gordon Conference will focus on research at the forefront of the field of defects in semiconductors. The conference will have a strong emphasis on the control of defects during growth and processing, as well as an emphasis on the development of novel defect detection methods and first-principles defect theories. Electronic, magnetic, and optical properties of bulk, thin film, and nanoscale semiconductors will be discussed in detail. In contrast to many conferences, which tend to focus on specific semiconductors, this conference will deal with point and extended defects in a broad range of electronic materials. This approach has proved to be extremely fruitful for advancing fundamental understanding in emerging materials such as wide-band-gap semiconductors, oxides, sp{sup 2} carbon based-materials, and photovoltaic/solar cell materials, and in understanding important defect phenomena such as doping bottleneck in nanostructures and the diffusion of defects and impurities. The program consists of about twenty invited talks and a number of contributed poster sessions. The emphasis should be on work which has yet to be published. The large amount of discussion time provides an ideal forum for dealing with topics that are new and/or controversial.

  12. 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.

  13. 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.

  14. 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.

  15. Semiconductor ac static power switch

    NASA Technical Reports Server (NTRS)

    Vrancik, J.

    1968-01-01

    Semiconductor ac static power switch has long life and high reliability, contains no moving parts, and operates satisfactorily in severe environments, including high vibration and shock conditions. Due to their resistance to shock and vibration, static switches are used where accidental switching caused by mechanical vibration or shock cannot be tolerated.

  16. (Magnetic properties of doped semiconductors)

    SciTech Connect

    Not Available

    1990-01-01

    Research continued on the transport behavior of doped semiconductors on both sides of the metal-insulator transition, and the approach to the transition from both the insulating and the metallic side. Work is described on magneto resistance of a series of metallic Si:B samples and CdSe. (CBS)

  17. Electronic spectra of semiconductor nanocrystals

    SciTech Connect

    Alivisatos, A.P.

    1993-12-31

    Semiconductor nanocrystals smaller than the bulk exciton show substantial quantum confinement effects. Recent experiments including Stark effect, resonance Raman, valence band photoemission, and near edge X-ray adsorption will be used to put together a picture of the nanocrystal electronic states.

  18. Electron beam pumped semiconductor laser

    NASA Technical Reports Server (NTRS)

    Hug, William F. (Inventor); Reid, Ray D. (Inventor)

    2009-01-01

    Electron-beam-pumped semiconductor ultra-violet optical sources (ESUVOSs) are disclosed that use ballistic electron pumped wide bandgap semiconductor materials. The sources may produce incoherent radiation and take the form of electron-beam-pumped light emitting triodes (ELETs). The sources may produce coherent radiation and take the form of electron-beam-pumped laser triodes (ELTs). The ELTs may take the form of electron-beam-pumped vertical cavity surface emitting lasers (EVCSEL) or edge emitting electron-beam-pumped lasers (EEELs). The semiconductor medium may take the form of an aluminum gallium nitride alloy that has a mole fraction of aluminum selected to give a desired emission wavelength, diamond, or diamond-like carbon (DLC). The sources may be produced from discrete components that are assembled after their individual formation or they may be produced using batch MEMS-type or semiconductor-type processing techniques to build them up in a whole or partial monolithic manner, or combination thereof.

  19. High-speed semiconductor devices

    NASA Astrophysics Data System (ADS)

    Sze, S. M.

    An introduction to the physical principles and operational characteristics of high-speed semiconductor devices is presented. Consideration is given to materials and technologies for high-speed devices, device building blocks, the submicron MOSFET, homogeneous field-effect transistors, and heterostructure field-effect transistors. Also considered are quantum-effect devices, microwave diodes, and high-speed photonic devices.

  20. 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.

  1. Optical bistability in semiconductor microcavities

    SciTech Connect

    Baas, A.; Karr, J.Ph.; Giacobino, E.; Eleuch, H.

    2004-02-01

    We report the observation of polaritonic bistability in semiconductor microcavities in the strong-coupling regime. The origin of bistability is the polariton-polariton interaction, which gives rise to a Kerr-like nonlinearity. The experimental results are in good agreement with a simple model taking transverse effects into account.

  2. First principles exploration of crystal structures and physical properties of silicon hydrides KSiH3 and K2SiH6, alkali and alkaline earth metal carbides, and II-V semiconductors ZnSb and ZnAs

    NASA Astrophysics Data System (ADS)

    Benson, Daryn Eugene

    This dissertation is focused on material property exploration and analysis using computational quantum mechanics methods. Theoretical calculations were performed on the recently discovered hexahydride materials A2SiH 6 (A=Rb, K) to calculate the lattice dynamics of the systems in order to check for structural stability, verify the experimental Raman and infrared spectroscopy results, and obtain the theoretical free energies of formation. The electronic structure of the systems was calculated and the bonding and ionic properties of the systems were analyzed. The novel hexahydrides were compared to the important hydrogen storage material KSiH3. This showed that the hypervalent nature of the SiH2-6 ions reduced the Si-H bonding strength considerably. These hydrogen rich compounds could have promising energy applications as they link to alternative hydrogen fuel technology. The carbide systems Li-C (A=Li, Ca, Mg) were studied using ab initio and evolutionary algorithms at high pressures. At ambient pressure Li2C2 and CaC2 are known to contain C2-2 dumbbell anions and CaC2 is polymorphic. At elevated pressure both CaC2 and Li2C2 display polymorphism. At ambient pressure the Mg-C system contains several experimentally known phases, however, all known phases are shown to be metastable with respect to the pure elements Mg and C. First principle investigation of the configurational space of these compounds via evolutionary algorithms results in a variety of metastable and unique structures. The binary compounds ZnSb and ZnAs are II-V electron-poor semiconductors with interesting thermoelectric properties. They contain rhomboid rings composed of Zn2Sb2 (Zn2As2) with multi-centered covalent bonds which are in turn covalently bonded to other rings via two-centered, two-electron bonds. Ionicity was explored via Bader charge analysis and it appears that the low ionicity that these materials display is a necessary condition of their multicentered bonding. Both compounds were

  3. PREFACE: Theory, Modelling and Computational methods for Semiconductors

    NASA Astrophysics Data System (ADS)

    Migliorato, Max; Probert, Matt

    2010-04-01

    These conference proceedings contain the written papers of the contributions presented at the 2nd International Conference on: Theory, Modelling and Computational methods for Semiconductors. The conference was held at the St Williams College, York, UK on 13th-15th Jan 2010. The previous conference in this series took place in 2008 at the University of Manchester, UK. The scope of this conference embraces modelling, theory and the use of sophisticated computational tools in Semiconductor science and technology, where there is a substantial potential for time saving in R&D. The development of high speed computer architectures is finally allowing the routine use of accurate methods for calculating the structural, thermodynamic, vibrational and electronic properties of semiconductors and their heterostructures. This workshop ran for three days, with the objective of bringing together UK and international leading experts in the field of theory of group IV, III-V and II-VI semiconductors together with postdocs and students in the early stages of their careers. The first day focused on providing an introduction and overview of this vast field, aimed particularly at students at this influential point in their careers. We would like to thank all participants for their contribution to the conference programme and these proceedings. We would also like to acknowledge the financial support from the Institute of Physics (Computational Physics group and Semiconductor Physics group), the UK Car-Parrinello Consortium, Accelrys (distributors of Materials Studio) and Quantumwise (distributors of Atomistix). The Editors Acknowledgements Conference Organising Committee: Dr Matt Probert (University of York) and Dr Max Migliorato (University of Manchester) Programme Committee: Dr Marco Califano (University of Leeds), Dr Jacob Gavartin (Accelrys Ltd, Cambridge), Dr Stanko Tomic (STFC Daresbury Laboratory), Dr Gabi Slavcheva (Imperial College London) Proceedings edited and compiled by Dr

  4. PHOTOOXIDATION OF ORGANIC WASTES USING SEMICONDUCTOR NANOCLUSTERS

    SciTech Connect

    Wilcoxon, Jess P.

    2000-12-31

    It would be a major boon to have a visible light absorbing semiconductor catalytic material available, which is also photostable and non-toxic. Such a photocatalyst would make it possible to exploit sunlight as the sole energy source required for detoxification. To this end we have employed our expertise in nanocluster synthesis and processing to make and purify nanoparticles of MoS2. The band-gap and absorbance edges of these nanoparticles can be adjusted by particle size based upon the quantum confinement of the electron-hole pair. In a recent paper we demonstrated the use of these new photocatalysts to destroy phenol, and demonstrated a strong effect of size or band-gap on the rate of photo-oxidation.5 In this research we investigate the photooxidation kinetics and products formed for a standard material, Degussa P-25 TiO2, as compared to nanosize TiO2, SnO2, and MoS2. We examined the light intensity dependence for nanosize SnO2 compared to TiO2 (Degussa), and the effect o f size on photooxidation kinetics for both SnO2 and MoS2. We studied photooxidation in aqueous systems and, for the first time, a system consisting almost entirely of a polar organic, acetonitrile. Our primary objective was to develop an entirely new class of material: nanosize semiconductors with visible bandgaps and to engineer these material's properties to allow us to photooxidize toxic organic compounds in water on a reasonable time scale ({approx}8 hrs). A second objective was to study how certain material properties such as size, surface treatment, and material type affect the efficiency of the photocatalytic process as well as optimizing these features.

  5. Performance simulation of a combustion engine charged by a variable geometry turbocharger. I - Prerequirements, boundary conditions and model development. II - Simulation algorithm, computed results

    NASA Astrophysics Data System (ADS)

    Malobabic, M.; Buttschardt, W.; Rautenberg, M.

    The paper presents a theoretical derivation of the relationship between a variable geometry turbocharger and the combustion engine, using simplified boundary conditions and model restraints and taking into account the combustion process itself as well as the nonadiabatic operating conditions for the turbine and the compressor. The simulation algorithm is described, and the results computed using this algorithm are compared with measurements performed on a test engine in combination with a controllable turbocharger with adjustable turbine inlet guide vanes. In addition, the results of theoretical parameter studies are presented, which include the simulation of a given turbocharger with variable geometry in combination with different sized combustion engines and the simulation of different sized variable-geometry turbochargers in combination with a given combustion engine.

  6. General Methodology Combining Engineering Optimization of Primary HVAC and R Plants with Decision Analysis Methods--Part II: Uncertainty and Decision Analysis

    SciTech Connect

    Jiang, Wei; Reddy, T. A.; Gurian, Patrick

    2007-01-31

    A companion paper to Jiang and Reddy that presents a general and computationally efficient methodology for dyanmic scheduling and optimal control of complex primary HVAC&R plants using a deterministic engineering optimization approach.

  7. Semiconductor Quantum Rods as Single Molecule FluorescentBiological Labels

    SciTech Connect

    Fu, Aihua; Gu, Weiwei; Boussert, Benjamine; Koski, Kristie; Gerion, Daniele; Manna, Liberato; Le Gros, Mark; Larabell, Carolyn; Alivisatos, A. Paul

    2006-05-29

    In recent years, semiconductor quantum dots have beenapplied with great advantage in a wide range of biological imagingapplications. The continuing developments in the synthesis of nanoscalematerials and specifically in the area of colloidal semiconductornanocrystals have created an opportunity to generate a next generation ofbiological labels with complementary or in some cases enhanced propertiescompared to colloidal quantum dots. In this paper, we report thedevelopment of rod shaped semiconductor nanocrystals (quantum rods) asnew fluorescent biological labels. We have engineered biocompatiblequantum rods by surface silanization and have applied them fornon-specific cell tracking as well as specific cellular targeting. Theproperties of quantum rods as demonstrated here are enhanced sensitivityand greater resistance for degradation as compared to quantum dots.Quantum rods have many potential applications as biological labels insituations where their properties offer advantages over quantumdots.

  8. 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

  9. Local electronic properties of organic semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Blumenfeld, Michael L.

    Understanding organic semiconductor interfaces is critical to developing organic photovoltaics (OPV). OPV interfaces are disordered due to weak intermolecular interactions, resulting in diverse charge transfer micro-environments. I present experimental data isolating high-order intermolecular interactions controlling interfacial energy level alignment and describe new instrumental capabilities providing access to the local electronic and kinetic landscape at organic semiconductor interfaces. Interface formation between vanadyl naphthalocyanine (VONc) and highly ordered pyrolytic graphite (HOPG) is investigated. Ultraviolet photoemission spectroscopy (UPS) shows that the VONc binding energy (BE) decouples from the work function, shifting in an opposite direction and contradicting the standard interface dipole model. This effect is quantitatively described using an electrostatic depolarization model and confirmed by simulations which show an inhomogeneous potential at the interface. New data and literature values suggest orthogonality between polarizability and molecular dipole in polar porphyrazines. Their potential for interface engineering is discussed. The electron-rich Au(111)/VONc interface is investigated. The organic layer induces a large interface dipole in Au(111) which can be fit to a depolarization model. Ionization potential and depolarization data suggest that the second VONc layer on Au(111) adopts a tilted geometry. Electrostatic differences between Au(111)/VONc and HOPG/VONc are discussed, demonstrating that interface dipole contributions are not interchangeable. The surface states of the Au(111)/VONc interface are characterized by angle resolved 2-photon photoemission to determine the magnitude of the perturbation. The measured free-electron-like effective mass and BE destabilization of the Shockley state is attributed to step edges caused by lifting the Au(111) (22x 3 ) reconstruction. The Shockley state is accessible primarily through resonance

  10. Semiconductor Laser Multi-Spectral Sensing and Imaging

    PubMed Central

    Le, Han Q.; Wang, Yang

    2010-01-01

    Multi-spectral laser imaging is a technique that can offer a combination of the laser capability of accurate spectral sensing with the desirable features of passive multispectral imaging. The technique can be used for detection, discrimination, and identification of objects by their spectral signature. This article describes and reviews the development and evaluation of semiconductor multi-spectral laser imaging systems. Although the method is certainly not specific to any laser technology, the use of semiconductor lasers is significant with respect to practicality and affordability. More relevantly, semiconductor lasers have their own characteristics; they offer excellent wavelength diversity but usually with modest power. Thus, system design and engineering issues are analyzed for approaches and trade-offs that can make the best use of semiconductor laser capabilities in multispectral imaging. A few systems were developed and the technique was tested and evaluated on a variety of natural and man-made objects. It was shown capable of high spectral resolution imaging which, unlike non-imaging point sensing, allows detecting and discriminating objects of interest even without a priori spectroscopic knowledge of the targets. Examples include material and chemical discrimination. It was also shown capable of dealing with the complexity of interpreting diffuse scattered spectral images and produced results that could otherwise be ambiguous with conventional imaging. Examples with glucose and spectral imaging of drug pills were discussed. Lastly, the technique was shown with conventional laser spectroscopy such as wavelength modulation spectroscopy to image a gas (CO). These results suggest the versatility and power of multi-spectral laser imaging, which can be practical with the use of semiconductor lasers. PMID:22315555

  11. Semiconductor detectors in nuclear and particle physics

    SciTech Connect

    Rehak, P.; Gatti, E.

    1992-12-31

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups: Classical semiconductor diode detectors and semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported.

  12. 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.

  13. Geometry strategy for engineering the recombination possibility of excitons in nanowires.

    PubMed

    Wang, Youwei; Zhang, Yubo; Zhu, Haiming; Liu, Jianjun; Lian, Tianquan; Zhang, Wenqing

    2016-04-01

    We proposed a geometry strategy to engineer the radiative recombination possibility and thus the lifetime of excitons in nanowires of some photovoltaic semiconductors by using theoretical analysis and first-principles calculations. We demonstrated that the shape can engineer the symmetry of the wave-functions of band-edge states and influence the radiative recombination possibility. The nanowires need to satisfy the following requirements to forbid the radiative recombination possibility of band-edge excitons: (i) wurtzite structure; (ii) pxy-characterized wave-function of VBM state and (iii) C3v-symmetry shape. The geometrical symmetry results in the pxy-characterized C3v-symmetry wave-function of VBM state and leads to forbidden radiative recombination of band-edge excitons. The geometry strategy offers a flexible proposal to prolong the exciton lifetime, leaving optical absorption impregnable. PMID:26980541

  14. Geometry strategy for engineering the recombination possibility of excitons in nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Youwei; Zhang, Yubo; Zhu, Haiming; Liu, Jianjun; Lian, Tianquan; Zhang, Wenqing

    2016-03-01

    We proposed a geometry strategy to engineer the radiative recombination possibility and thus the lifetime of excitons in nanowires of some photovoltaic semiconductors by using theoretical analysis and first-principles calculations. We demonstrated that the shape can engineer the symmetry of the wave-functions of band-edge states and influence the radiative recombination possibility. The nanowires need to satisfy the following requirements to forbid the radiative recombination possibility of band-edge excitons: (i) wurtzite structure; (ii) pxy-characterized wave-function of VBM state and (iii) C3v-symmetry shape. The geometrical symmetry results in the pxy-characterized C3v-symmetry wave-function of VBM state and leads to forbidden radiative recombination of band-edge excitons. The geometry strategy offers a flexible proposal to prolong the exciton lifetime, leaving optical absorption impregnable.

  15. Compact, High Power, Multi-Spectral Mid-Infrared Semiconductor Laser Package

    NASA Astrophysics Data System (ADS)

    Guo, Bujin; Hwang, Wen-Yen; Lin, Chich-Hsiang

    2001-10-01

    Through a vertically integrated effort involving atomic level material engineering, advanced device processing development, state-of-the-art optomechanical packaging, and thermal management, Applied Optoelectronics, Inc. (AOI), University of Houston (U H), and Physical Science, Inc. (PSI) have made progress in both Sb-based type-II semiconductor material and in P-based type-I laser device development. We have achieved record performance on inP based quantum cascade continuous wave (CW) laser (with more than 5 mW CW power at 210 K). Grating-coupled external-cavity quantum cascade lasers were studied for temperatures from 20 to 230 K. A tuning range of 88 nm has been obtained at 80 K. The technology can be made commercially available and represents a significant milestone with regard to the Dual Use Science and Technology (DUST) intention of fostering dual use commercial technology for defense need. AOI is the first commercial company to ship products of this licensed technology.

  16. Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting

    NASA Astrophysics Data System (ADS)

    Zhou, Shengqiang

    2015-07-01

    Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III-V compound semiconductors have been regarded as the prototype of DFS from both experimental and theoretic investigations. The magnetic properties of III-V:Mn can be controlled by manipulating free carriers via electrical gating, as for controlling the electrical properties in conventional semiconductors. However, the preparation of DFS presents a big challenge due to the low solubility of Mn in semiconductors. Ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LT-MBE) approach. Both ion implantation and pulsed-laser melting occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants and the subsequent laser pulse deposit energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Here, we review the experimental study on preparation of III-V:Mn using II-PLM. We start with a brief description about the development of DFS and the physics behind II-PLM. Then we show that ferromagnetic GaMnAs and InMnAs films can be prepared by II-PLM and they show the same characteristics of LT-MBE grown samples. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III-V:Mn DFS. Both GaMnP and InMnP films show the signature of DFS and an insulating behavior. At the end, we summarize the work done for Ge:Mn and Si:Mn using II-PLM and present suggestions for future investigations. The remarkable advantage of II-PLM approach is its versatility. In general, II-PLM can be utilized to prepare supersaturated alloys with mismatched components.

  17. Electron-hole correlations in semiconductor quantum dots with tight-binding wave fuctions

    NASA Technical Reports Server (NTRS)

    Seungwon, L.; Jonsson, L.; Wilkins, J.; Bryant, G.; Klimeck, G.

    2001-01-01

    The electron-hole states of semiconductor quantum dots are investigated within the framework of empirical tight-binding descriptions for Si, as an example of an indirect-gap material, and InAs and CdSe as examples of typical III-V and II-VI direct-gap materials.

  18. Dimensional crossover in semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    McDonald, Matthew P.; Chatterjee, Rusha; Si, Jixin; Jankó, Boldizsár; Kuno, Masaru

    2016-08-01

    Recent advances in semiconductor nanostructure syntheses provide unprecedented control over electronic quantum confinement and have led to extensive investigations of their size- and shape-dependent optical/electrical properties. Notably, spectroscopic measurements show that optical bandgaps of one-dimensional CdSe nanowires are substantially (approximately 100 meV) lower than their zero-dimensional counterparts for equivalent diameters spanning 5-10 nm. But what, exactly, dictates the dimensional crossover of a semiconductor's electronic structure? Here we probe the one-dimensional to zero-dimensional transition of CdSe using single nanowire/nanorod absorption spectroscopy. We find that carrier electrostatic interactions play a fundamental role in establishing dimensional crossover. Moreover, the critical length at which this transition occurs is governed by the aspect ratio-dependent interplay between carrier confinement and dielectric contrast/confinement energies.

  19. Dimensional crossover in semiconductor nanostructures

    PubMed Central

    McDonald, Matthew P.; Chatterjee, Rusha; Si, Jixin; Jankó, Boldizsár; Kuno, Masaru

    2016-01-01

    Recent advances in semiconductor nanostructure syntheses provide unprecedented control over electronic quantum confinement and have led to extensive investigations of their size- and shape-dependent optical/electrical properties. Notably, spectroscopic measurements show that optical bandgaps of one-dimensional CdSe nanowires are substantially (approximately 100 meV) lower than their zero-dimensional counterparts for equivalent diameters spanning 5–10 nm. But what, exactly, dictates the dimensional crossover of a semiconductor's electronic structure? Here we probe the one-dimensional to zero-dimensional transition of CdSe using single nanowire/nanorod absorption spectroscopy. We find that carrier electrostatic interactions play a fundamental role in establishing dimensional crossover. Moreover, the critical length at which this transition occurs is governed by the aspect ratio-dependent interplay between carrier confinement and dielectric contrast/confinement energies. PMID:27577091

  20. Hypersonic modes in nanophononic semiconductors.

    PubMed

    Hepplestone, S P; Srivastava, G P

    2008-09-01

    Frequency gaps and negative group velocities of hypersonic phonon modes in periodically arranged composite semiconductors are presented. Trends and criteria for phononic gaps are discussed using a variety of atomic-level theoretical approaches. From our calculations, the possibility of achieving semiconductor-based one-dimensional phononic structures is established. We present results of the location and size of gaps, as well as negative group velocities of phonon modes in such structures. In addition to reproducing the results of recent measurements of the locations of the band gaps in the nanosized Si/Si{0.4}Ge{0.6} superlattice, we show that such a system is a true one-dimensional hypersonic phononic crystal.

  1. Radiation Effects on Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Liu, Guangyu

    In order to observe and analyze the behavior of semiconductor devices under radiation exposure, a real time measurement system has been built so that investigations can be carried out before, during, and after radiation exposure. The system consists of an IBM personal computer with IEEE488 I/O interface board and various Hewlett-Packard instruments. Real time measurement and device parameter characterization programs have been written to accommodate the study. Such a system provides the ability to do not only direct and dynamic measurements, but also comprehensive parameter analyses for semiconductor devices. It is well known that MOS devices are vulnerable to radiation produced ionization. Many MOS device parameters are radiation sensitive. Based on real time measurement results and the mathematical model of a CMOS inverter, a radiation hardening design method has been developed. With the example of noise margin optimization, the concept of desensitizing device parameters is expected to minimize radiation damage to MOS integrated circuits.

  2. Dimensional crossover in semiconductor nanostructures.

    PubMed

    McDonald, Matthew P; Chatterjee, Rusha; Si, Jixin; Jankó, Boldizsár; Kuno, Masaru

    2016-01-01

    Recent advances in semiconductor nanostructure syntheses provide unprecedented control over electronic quantum confinement and have led to extensive investigations of their size- and shape-dependent optical/electrical properties. Notably, spectroscopic measurements show that optical bandgaps of one-dimensional CdSe nanowires are substantially (approximately 100 meV) lower than their zero-dimensional counterparts for equivalent diameters spanning 5-10 nm. But what, exactly, dictates the dimensional crossover of a semiconductor's electronic structure? Here we probe the one-dimensional to zero-dimensional transition of CdSe using single nanowire/nanorod absorption spectroscopy. We find that carrier electrostatic interactions play a fundamental role in establishing dimensional crossover. Moreover, the critical length at which this transition occurs is governed by the aspect ratio-dependent interplay between carrier confinement and dielectric contrast/confinement energies. PMID:27577091

  3. Property prediction of new semiconductors by computer modeling and simulation

    NASA Astrophysics Data System (ADS)

    Wu, Ping; Lin, Guo Q.; Zeng, Yingzhi

    2002-11-01

    A new methodology of systematic design of new materials for various applications is presented in this paper. In particular, a large number of candidate compounds that are formed by all possible combinations of the targeted elements in the periodic table are first screened and shortlisted by artificial neural network techniques. Then the quantum mechanics computation is employed to evaluate the promising candidates selected from the first step. Finally experiments are performed to further examine the computation results. In the present work, we apply this methodology to the study of semiconductors of binary (III-V and II-VI) and ternary (I-III-VI2 and II-IV-V2) compounds. Firstly, we systematically study all possible binary and ternary compounds by using pattern recognition and perform prediction of two important properties, namely band gap energy and lattice constant, with the artificial neural network model. Candidate semiconductors are then selected. On the basis of the above study, we perform first principles quantum mechanics computation for some promising II-VI binary candidates. The first principles study of the ternary candidates will be conducted in the near future, and the experiment study of the binary compounds is ongoing. The model predicted new compounds as well as the developed design methodology may be of interest to general materials scientists including these of smart materials research.

  4. Automotive Stirling engine development program

    NASA Technical Reports Server (NTRS)

    Ernst, W.; Richey, A.; Farrell, R.; Riecke, G.; Smith, G.; Howarth, R.; Cronin, M.; Simetkosky, M.; Meacher, J.

    1986-01-01

    The major accomplishments were the completion of the Basic Stirling Engine (BSE) and the Stirling Engine System (SES) designs on schedule, the approval and acceptance of those designs by NASA, and the initiation of manufacture of BSE components. The performance predictions indicate the Mod II engine design will meet or exceed the original program goals of 30% improvement in fuel economy over a conventional Internal Combustion (IC) powered vehicle, while providing acceptable emissions. This was accomplished while simultaneously reducing Mod II engine weight to a level comparable with IC engine power density, and packaging the Mod II in a 1985 Celebrity with no external sheet metal changes. The projected mileage of the Mod II Celebrity for the combined urban and highway CVS cycle is 40.9 mpg which is a 32% improvement over the IC Celebrity. If additional potential improvements are verified and incorporated in the Mod II, the mileage could increase to 42.7 mpg.

  5. Compound semiconductor optical waveguide switch

    DOEpatents

    Spahn, Olga B.; Sullivan, Charles T.; Garcia, Ernest J.

    2003-06-10

    An optical waveguide switch is disclosed which is formed from III-V compound semiconductors and which has a moveable optical waveguide with a cantilevered portion that can be bent laterally by an integral electrostatic actuator to route an optical signal (i.e. light) between the moveable optical waveguide and one of a plurality of fixed optical waveguides. A plurality of optical waveguide switches can be formed on a common substrate and interconnected to form an optical switching network.

  6. Selective Etching of Semiconductor Glassivation

    NASA Technical Reports Server (NTRS)

    Casper, N.

    1982-01-01

    Selective etching technique removes portions of glassivation on a semi-conductor die for failure analysis or repairs. A periodontal needle attached to a plastic syringe is moved by a microprobe. Syringe is filled with a glass etch. A drop of hexane and vacuum pump oil is placed on microcircuit die and hexane is allowed to evaporate leaving a thin film of oil. Microprobe brings needle into contact with area of die to be etched.

  7. Acoustoelectric effect in semiconductor superlattice

    NASA Astrophysics Data System (ADS)

    Mensah, S. Y.; Allotey, F. K. A.; Adjepong, S. K.

    1993-10-01

    Acoustoelectric effect in semiconductor superlattice has been studied for acoustic wave whose wavelength lambda = 2pi/q is smaller than the mean free path of the electrons l (where ql approaches 1). Unlike the homogeneous bulk material where Weinreich relation is independent of the wave number q in the superlattice we observe a dependence on q i.e. spatial dispersion. In the presence of applied constant field E a threshold value was obtained where the acoustoelectric current changes direction.

  8. Cooling and mounting power semiconductors

    NASA Astrophysics Data System (ADS)

    Wetzel, P.

    1980-04-01

    The article examines the process of heat dissipation from power semiconductors. It is shown that for the relationship between temperature loading and dissipation it is possible to take an 'Ohm's law of heat abduction' to define the thermal impedance. The computation of the optimal size for a heatsink is demonstrated in detail. Discussion covers the types of heat dissipation such as heat radiation, heat conduction, and convection. Finally, some factors to consider during installation are examined.

  9. Technology Roadmaps for Compound Semiconductors

    PubMed Central

    Bennett, Herbert S.

    2000-01-01

    The roles cited for compound semiconductors in public versions of existing technology roadmaps from the National Electronics Manufacturing Initiative, Inc., Optoelectronics Industry Development Association, Microelectronics Advanced Research Initiative on Optoelectronic Interconnects, and Optoelectronics Industry and Technology Development Association (OITDA) are discussed and compared within the context of trends in the Si CMOS industry. In particular, the extent to which these technology roadmaps treat compound semiconductors at the materials processing and device levels will be presented for specific applications. For example, OITDA’s Optical Communications Technology Roadmap directly connects the information demand of delivering 100 Mbit/s to the home to the requirement of producing 200 GHz heterojunction bipolar transistors with 30 nm bases and InP high electron mobility transistors with 100 nm gates. Some general actions for progress towards the proposed International Technology Roadmap for Compound Semiconductors (ITRCS) and methods for determining the value of an ITRCS will be suggested. But, in the final analysis, the value added by an ITRCS will depend on how industry leaders respond. The technical challenges and economic opportunities of delivering high quality digital video to consumers provide concrete examples of where the above actions and methods could be applied. PMID:27551615

  10. Tests of Nacelle-Propeller Combinations in Various Positions with Reference to Wings II : Thick Wing - Various Radial-Engine Cowlings - Tractor Propeller

    NASA Technical Reports Server (NTRS)

    Wood, Donald H

    1932-01-01

    This report is the second of a series giving the results obtained in the 20-foot wind tunnel of the National Advisory Committee for Aeronautics on the interference drag and propulsive efficiency of nacelle-propeller-wing combinations. The first report gave the results of the test of a N.A.C.A. cowled air-cooled engine nacelle located in 21 positions with reference to a thick wing. The present report gives results of tests of a normal engine nacelle with several types of cowling and fairings in four of the positions with reference to the same wing. (author)

  11. Mesoscopic spin Hall effect in semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Zarbo, Liviu

    The spin Hall effect (SHE) is a name given to a collection of diverse phenomena which share two principal features: (i) longitudinal electric current flowing through a paramagnetic semiconductor or metallic sample leads to transverse spin current and spin accumulation of opposite sign at opposing lateral edges; (ii) SHE does not require externally applied magnetic field or magnetic ordering in the equilibrium state of the sample, instead it relies on the presence of spin-orbit (SO) couplings within the sample. This thesis elaborates on a new type of phenomenon within the SHE family, predicted in our recent studies [Phys. Rev. B 72, 075361 (2005); Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 72, 075335 (2005); Phys. Rev. B 73 , 075303 (2006); and Europhys. Lett. 77, 47004 (2007)], where pure spin current flows through the transverse electrodes attached to a clean finitesize two-dimensional electron gas (2DEG) due to unpolarized charge current injected through its longitudinal leads. If transverse leads are removed, the effect manifests as nonequilibrium spin Hall accumulation at the lateral edges of 2DEG wires. The SO coupling driving this SHE effect is of the Rashba type, which arises due to structural inversion asymmetry of semiconductor heterostructure hosting the 2DEG. We term the effect "mesoscopic" because the spin Hall currents and accumulations reach optimal value in samples of the size of the spin precession length---the distance over which the spin of an electron precesses by an angle pi. In strongly SO-coupled structures this scale is of the order of ˜100 nm, and, therefore, mesoscopic in the sense of being much larger than the characteristic microscopic scales (such as the Fermi wavelength, screening length, or the mean free path in disordered systems), but still much smaller than the macroscopic ones. Although the first theoretical proposal for SHE, driven by asymmetry in SO-dependent scattering of spin-up and spin-down electrons off impurities

  12. Vacancy formation and extraction energies in semiconductor compounds and alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.

    1990-01-01

    A model for calculating the extraction energies and vacancy-formation energies in diamond-cubic and zinc-blende semiconductors is developed on the basis of Harrison's (1980, 1983) tight-binding theory. The extraction energies provide a reference from which other final states of the removed atoms can be calculated. The results of calculations show that, in a given compound, the calculated extraction energies are larger for the anion than for the cation, with the difference between the cation and the anion being larger in the II-VI than in the III-V compounds. This is in agreement with experimental results.

  13. Tunneling versus thermionic emission in one-dimensional semiconductors.

    PubMed

    Appenzeller, J; Radosavljević, M; Knoch, J; Avouris, Ph

    2004-01-30

    This Letter focuses on the role of contacts and the influence of Schottky barriers on the switching in nanotransistors. Specifically, we discuss (i) the mechanism for injection from a three-dimensional metal into a low-dimensional semiconductor, i.e., the competition between thermionic emission and thermally assisted tunneling, (ii) the factors that affect tunneling probability with emphasis on the importance of the effective mass for transistor applications, and (iii) a novel approach that enables determination of barrier presence and its actual height.

  14. III-V semiconductor solid solution single crystal growth

    NASA Technical Reports Server (NTRS)

    Gertner, E. R.

    1982-01-01

    The feasibility and desirability of space growth of bulk IR semiconductor crystals for use as substrates for epitaxial IR detector material were researched. A III-V ternary compound (GaInSb) and a II-VI binary compound were considered. Vapor epitaxy and quaternary epitaxy techniques were found to be sufficient to permit the use of ground based binary III-V crystals for all major device applications. Float zoning of CdTe was found to be a potentially successful approach to obtaining high quality substrate material, but further experiments were required.

  15. Altitude-Wind-Tunnel Investigation of the 19B-2, 19B-8, and 19XB-1 Jet-Propulsion Engines. II - Analysis of Turbine Performance of the 19B-8 Engine

    NASA Technical Reports Server (NTRS)

    Krebs, Richard P.; Suozzi, Frank L.

    1947-01-01

    Performance characteristics of the turbine in the 19B-8 jet propulsion engine were determined from an investigation of the complete engine in the Cleveland altitude wind tunnel. The investigation covered a range of simulated altitudes from 5000 to 30,000 feet and flight Mach numbers from 0.05 to 0.46 for various tail-cone positions over the entire operable range of engine speeds. The characteristics of the turbine are presented as functions of the total-pressure ratio across the turbine and the turbine speed and the gas flow corrected to NACA standard atmospheric conditions at sea level. The effect of changes in altitude, flight Mach number, and tail-cone position on turbine performance is discussed. The turbine efficiency with the tail cone in varied from a maximum of 80.5 percent to minimum of 75 percent over a range of engine speeds from 7500 to 17,500 rpm at a flight Mach number of 0.055. Turbine efficiency was unaffected by changes in altitude up to 15,000 feet but was a function of tail-cone position and flight Mach number. Decreasing the tail-pipe-nozzle outlet area 21 percent reduced the turbine efficiency between 2 and 4.5 percent. The turbine efficiency increased between 1.5 and 3 percent as the flight Mach number changed from 0.055 to 0.297.

  16. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXV, I--CATERPILLAR DIESEL ENGINE COOLING SYSTEM D-8 AND 824 MODELS, II--TIRES AND TIRE HARDWARE.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE COOLING SYSTEM AND TO PROVIDE A DESCRIPTION OF HEAVY TIRES AND WHEELS USED ON DIESEL POWERED VEHICLES. TOPICS ARE (1) THEORY OF THE COOLING SYSTEM, (2) COOLING SYSTEM COMPONENTS, (3) MAINTENANCE TIPS (COOLING SYSTEM), (4)…

  17. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXI, I--MAINTAINING THE AIR SYSTEM--CATERPILLAR DIESEL ENGINE, II--UNDERSTANDING REAR END SUSPENSION.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE AIR SYSTEM AND REAR AXLE SUSPENSION USED ON DIESEL POWERED VEHICLES. TOPICS ARE (1) AIR INDUCTION AND EXHAUST SYSTEM, (2) VALVE MECHANISM, (3) TROUBLESHOOTING THE AIR SYSTEM, (4) PURPOSE OF VEHICLE SUSPENSION, (5) TANDEM…

  18. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXIV, I--MAINTAINING THE FUEL SYSTEM PART III--CATERPILLAR DIESEL ENGINE, II--UNDERSTANDING THE VOLTAGE REGULATOR/ALTERNATOR.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATION AND MAINTENANCE OF THE DIESEL ENGINE FUEL AND BATTERY CHARGING SYSTEM. TOPICS ARE (1) INJECTION TIMING CONTROLS, (2) GOVERNOR, (3) FUEL SYSTEM MAINTENANCE TIPS, (4) THE CHARGING SYSTEM, (5) REGULATING THE GENERATOR/ALTERNATOR, AND (6) CHARGING SYSTEM SERVICE…

  19. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XXII, I--MAINTAINING THE FUEL SYSTEM (PART I)--CUMMINS DIESEL ENGINE, II--UNDERSTANDING THE DIFFERENTIAL.

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE FUNCTION AND MAINTENANCE OF THE DIESEL ENGINE FUEL SYSTEM AND DIFFERENTIAL DRIVE UNITS USED IN DIESEL POWERED VEHICLES. TOPICS ARE (1) FUEL SYSTEM COMPARISONS, (2) FUEL SYSTEM SUPPLY COMPONENTS, (3) FUEL SUPPLY SECTION MAINTENANCE, (4) FUNCTION OF THE DIFFERENTIAL,…

  20. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XIV, I--MAINTAINING THE AIR SYSTEM, CUMMINS DIESEL ENGINE, II--UNIT REMOVAL--TRANSMISSION.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES AND MAINTENANCE OF THE DIESEL ENGINE AIR SYSTEM AND THE PROCEDURES FOR TRANSMISSION REMOVAL. TOPICS ARE (1) DEFINITION OF TERMS RELATED TO THE DIESEL AIR SYSTEM, (2) PRNCIPLES OF DIESEL AIR COMPRESSORS, (3) PRINCIPLES OF AIR STARTING MOTORS, (4)…

  1. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT XIII, I--MAINTAINING THE FUEL SYSTEM (PART III), CUMMINS DIESEL ENGINES, II--RADIATOR SHUTTER SYSTEM.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE CONSTRUCTION, OPERATION, AND MAINTENANCE OF THE DIESEL ENGINE FUEL AND RADIATOR SHUTTER SYSTEMS. TOPICS ARE (1) MORE ABOUT THE CUMMINS FUEL SYSTEM, (2) CALIBRATING THE PT FUEL PUMP, (3) CALIBRATING THE FUEL INJECTORS, (4) UNDERSTANDING THE SHUTTER SYSTEM, (5) THE…

  2. Engineering nanomaterials with a combined electrochemical and molecular biomimetic approach

    NASA Astrophysics Data System (ADS)

    Dai, Haixia

    Biocomposite materials, such as bones, teeth, and shells, are created using mild aqueous solution-based processes near room temperature. Proteins add flexibility to these processes by facilitating the nucleation, growth, and ordering of specific inorganic materials into hierarchical structures. We aim to develop a biomimetic strategy for engineering technologically relevant inorganic materials with controlled compositions and structures, as Nature does, using proteins to orchestrate material formation and assembly. This approach involves three basic steps: (i) preparation of inorganic substrates compatible with combinatorial polypeptide screening; (ii) identification of inorganic-binding polypeptides and their engineering into inorganic-binding proteins; and (iii) protein-mediated inorganic nucleation and organization. Cuprous oxide (Cu2O), a p-type semiconductor, has been used to demonstrate all three steps. Zinc oxide (ZnO), an n-type semiconductor, has been used to show the generality of selected steps. Step (i), preparation of high quality inorganic substrates to select inorganic-binding polypeptides, was accomplished using electrochemical microfabrication to grow and pattern Cu2O and ZnO. Raman spectroscopy and x-ray photoelectron spectroscopy were used to verify phase purity and compositional stability of these surfaces during polypeptide screening. Step (ii), accomplished in collaboration with personnel in Prof Baneyx' lab at the University of Washington, involved incubating the inorganic substrates with the FliTrx(TM) random peptide library to identify cysteine-constrained dodecapeptides that bind the targeted inorganic. Insertion of a Cu2O-binding dodecapeptide into the DNA-binding protein TraI endowed the engineered TraI with strong affinity for Cu2O (Kd ≈ 10 -8 M). Finally, step (iii) involved nonequilibrium synthesis and organization of Cu2O nanoparticles, taking advantage of the inorganic and DNA recognition properties of the engineered TraI. The

  3. Demonstration of a home projector based on RGB semiconductor lasers.

    PubMed

    Zhang, Yunfang; Dong, Hui; Wang, Rui; Duan, Jingyuan; Shi, Ancun; Fang, Qing; Liu, Yuliang

    2012-06-01

    In this paper, we demonstrate a high-definition 3-liquid-crystal-on-silicon (3-LCOS) home cinema projection system based on RGB laser source modules. Both red and blue laser modules are composed of an array of laser diodes, and the green laser is based on an optically pumped semiconductor laser. The illumination engine is designed to realize high energy efficiency, uniform illumination, and suppression of speckle noise. The presented laser projection system producing 1362 lm D65 light has a volume of about 450×360×160  mm3.

  4. Demonstration of a home projector based on RGB semiconductor lasers.

    PubMed

    Zhang, Yunfang; Dong, Hui; Wang, Rui; Duan, Jingyuan; Shi, Ancun; Fang, Qing; Liu, Yuliang

    2012-06-01

    In this paper, we demonstrate a high-definition 3-liquid-crystal-on-silicon (3-LCOS) home cinema projection system based on RGB laser source modules. Both red and blue laser modules are composed of an array of laser diodes, and the green laser is based on an optically pumped semiconductor laser. The illumination engine is designed to realize high energy efficiency, uniform illumination, and suppression of speckle noise. The presented laser projection system producing 1362 lm D65 light has a volume of about 450×360×160  mm3. PMID:22695597

  5. Spinodal nanodecomposition in semiconductors doped with transition metals

    NASA Astrophysics Data System (ADS)

    Dietl, T.; Sato, K.; Fukushima, T.; Bonanni, A.; Jamet, M.; Barski, A.; Kuroda, S.; Tanaka, M.; Hai, Pham Nam; Katayama-Yoshida, H.

    2015-10-01

    This review presents the recent progress in computational materials design, experimental realization, and control methods of spinodal nanodecomposition under three- and two-dimensional crystal-growth conditions in spintronic materials, such as magnetically doped semiconductors. The computational description of nanodecomposition, performed by combining first-principles calculations with kinetic Monte Carlo simulations, is discussed together with extensive electron microscopy, synchrotron radiation, scanning probe, and ion beam methods that have been employed to visualize binodal and spinodal nanodecomposition (chemical phase separation) as well as nanoprecipitation (crystallographic phase separation) in a range of semiconductor compounds with a concentration of transition metal (TM) impurities beyond the solubility limit. The role of growth conditions, codoping by shallow impurities, kinetic barriers, and surface reactions in controlling the aggregation of magnetic cations is highlighted. According to theoretical simulations and experimental results the TM-rich regions appear in the form of either nanodots (the dairiseki phase) or nanocolumns (the konbu phase) buried in the host semiconductor. Particular attention is paid to Mn-doped group III arsenides and antimonides, TM-doped group III nitrides, Mn- and Fe-doped Ge, and Cr-doped group II chalcogenides, in which ferromagnetic features persisting up to above room temperature correlate with the presence of nanodecomposition and account for the application-relevant magneto-optical and magnetotransport properties of these compounds. Finally, it is pointed out that spinodal nanodecomposition can be viewed as a new class of bottom-up approach to nanofabrication.

  6. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

    NASA Astrophysics Data System (ADS)

    Chambers, Scott A.; Gallagher, Bryan

    2008-05-01

    -orbit coupling. They have also led to the demonstration of a wide range of novel phenomena including some, like tunneling anisotropic magnetoresistance, which have subsequently been achieved in metal ferromagnetic systems. However despite considerable effort over many years the maximum Curie point achieved in (Ga,Mn)As is still less than 200 K. So unless some major new breakthrough is achieved these materials are unlikely to be of use for practical spin electronics technologies. In 2000, Dietl et al [1] published a seminal paper in which mean field theory was used to predict which of the common diamagnetic semiconductors would exhibit a Curie point above ambient if doped with 5 at.% Mn and a hole concentration of 3.5 × 1020 cm-3. Of the many host semiconductors simulated, only ZnO and GaN were predicted to exhibit a critical temperature in excess of 300 K. Since 2000, high-Tc DMS research has proliferated in both experimental and theoretical arenas. Many papers have been published containing claims of new DMS materials based largely on limited film growth, powder diffraction, and magnetometry. In these papers, a film which exhibits a hysteretic SQUID or VSM loop at 300 K and phase purity with only the host semiconductor detected by XRD are often claimed to be true ferromagnetic DMSs. Many of these papers are flawed because the criteria for a well-defined DMS are much more extensive. These include: (i) a random dopant distribution, (ii) a well-known and preferably unique charge state and preferentially a unique local structural environment for the dopant, (iii) a demonstrated coupling of the dopant spin to the host band structure, leading to spin polarization of the majority carriers, and (iv) a rational dependence of the saturation magnetization and Curie point on the magnetic dopant and carrier concentrations. Implicit in this list is that trivial causes of ferromagnetism, such as magnetic contamination and magnetic secondary phase formation, are eliminated. Yet, in many

  7. Moving liquids with light: Photoelectrowetting on semiconductors

    NASA Astrophysics Data System (ADS)

    Arscott, Steve

    2011-12-01

    By linking semiconductor physics and wetting phenomena a brand new effect termed ``photoelectrowetting-on-semiconductors'' is demonstrated here for a conducting droplet resting on an insulator-semiconductor stack. Optical generation of carriers in the space-charge region of the underlying semiconductor alters the capacitance of the liquid-insulator-semiconductor stack; the result of this is a modification of the wetting contact angle of the droplet upon illumination using above band gap light. The effect is demonstrated using commercial silicon wafers, both n- and p-type having a doping range spanning four orders of magnitude (6×1014-8×1018 cm-3), coated with a commercial amorphous fluoropolymer insulating film (Teflon®). Impedance measurements confirm that the observations are semiconductor space-charge related effects. The impact of the work could lead to new silicon-based technologies in areas such as Laboratory-on-a-Chip, Microfluidics and Optofluidics.

  8. Semiconductor device modeling on a workstation

    SciTech Connect

    Diegert, C.

    1985-09-01

    We choose to move from large mainframe computers to workstations to gain the interactive graphics we need to prepare and to analyze semiconductor device modeling problems. Given this much on a workstation, it is convenient to attempt to solve the entire problem there. We find that a top-of-the-line Apollo 660 workstation, with bit-slice processor, pipelined arithmetic processor, and 4 megabytes of real memory, is surprisingly effective in finding solutions when running the Pisces II device modeling code. In our experiment we find where the workstation bogs down when running these problems. We both analyze the Pisces CPU time log and we sample the executing program to accumulate a histogram of execution time as distributed over the source code. Results suggest how Pisces could be adapted to solve somewhat larger problems entirely on the workstation. Evolution of a trusted derivative of Pisces, to be used on supercomputers without interactivity, is suggested to complement our success with Pisces on workstations. 4 refs.

  9. Strategies for Radiation Hardness Testing of Power Semiconductor Devices

    NASA Technical Reports Server (NTRS)

    Soltis, James V. (Technical Monitor); Patton, Martin O.; Harris, Richard D.; Rohal, Robert G.; Blue, Thomas E.; Kauffman, Andrew C.; Frasca, Albert J.

    2005-01-01

    Plans on the drawing board for future space missions call for much larger power systems than have been flown in the past. These systems would employ much higher voltages and currents to enable more powerful electric propulsion engines and other improvements on what will also be much larger spacecraft. Long term human outposts on the moon and planets would also require high voltage, high current and long life power sources. Only hundreds of watts are produced and controlled on a typical robotic exploration spacecraft today. Megawatt systems are required for tomorrow. Semiconductor devices used to control and convert electrical energy in large space power systems will be exposed to electromagnetic and particle radiation of many types, depending on the trajectory and duration of the mission and on the power source. It is necessary to understand the often very different effects of the radiations on the control and conversion systems. Power semiconductor test strategies that we have developed and employed will be presented, along with selected results. The early results that we have obtained in testing large power semiconductor devices give a good indication of the degradation in electrical performance that can be expected in response to a given dose. We are also able to highlight differences in radiation hardness that may be device or material specific.

  10. Semiconductor quantum wells: old technology or new device functionalities

    NASA Astrophysics Data System (ADS)

    Kolbas, R. M.; Lo, Y. C.; Hsieh, K. Y.; Lee, J. H.; Reed, F. E.; Zhang, D.; Zhang, T.

    2009-08-01

    The introduction of semiconductor quantum wells in the 1970s created a revolution in optoelectronic devices. A large fraction of today's lasers and light emitting diodes are based on quantum wells. It has been more than 30 years but novel ideas and new device functions have recently been demonstrated using quantum well heterostructures. This paper provides a brief overview of the subject and then focuses on the physics of quantum wells that the lead author believes holds the key to new device functionalities. The data and figures contained within are not new. They have been assembled from 30 years of work. They are presented to convey the story of why quantum wells continue to fuel the engine that drives the semiconductor optoelectronic business. My apologies in advance to my students and co-workers that contributed so much that could not be covered in such a short manuscript. The explanations provided are based on the simplest models possible rather than the very sophisticated mathematical models that have evolved over many years. The intended readers are those involved with semiconductor optoelectronic devices and are interested in new device possibilities.

  11. A Statistical Process Control Method for Semiconductor Manufacturing

    NASA Astrophysics Data System (ADS)

    Kubo, Tomoaki; Ino, Tomomi; Minami, Kazuhiro; Minami, Masateru; Homma, Tetsuya

    To maintain stable operation of semiconductor fabrication lines, statistical process control (SPC) methods are recognized to be effective. However, in semiconductor fabrication lines, there exist a huge number of process state signals to be monitored, and these signals contain both normally and non-normally distributed data. Therefore, if we try to apply SPC methods to those signals, we need one which satisfies three requirements: 1) It can deal with both normally distributed data, and non-normally distributed data, 2) It can be set up automatically, 3) It can be easily understood by engineers and technicians. In this paper, we propose a new SPC method which satisfies these three requirements at the same time. This method uses similar rules to the Shewhart chart, but can deal with non-normally distributed data by introducing “effective standard deviations”. Usefulness of this method is demonstrated by comparing false alarm ratios to that of the Shewhart chart method. In the demonstration, we use various kinds of artificially generated data, and real data observed in a chemical vapor deposition (CVD) process tool in a semiconductor fabrication line.

  12. 75 FR 49526 - Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-13

    ... Register on November 17, 2009 (74 FR 59249). At the request of the petitioners, the Department reviewed the... Employment and Training Administration Freescale Semiconductor, Inc., Technical Information Center, Tempe, AZ; Freescale Semiconductor, Inc., Technical Information Center, Woburn, MA; Amended Certification...

  13. Stretchable semiconductor elements and stretchable electrical circuits

    DOEpatents

    Rogers, John A.; Khang, Dahl-Young; Menard, Etienne

    2009-07-07

    The invention provides methods and devices for fabricating printable semiconductor elements and assembling printable semiconductor elements onto substrate surfaces. Methods, devices and device components of the present invention are capable of generating a wide range of flexible electronic and optoelectronic devices and arrays of devices on substrates comprising polymeric materials. The present invention also provides stretchable semiconductor structures and stretchable electronic devices capable of good performance in stretched configurations.

  14. 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.

  15. 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.

  16. Spectroscopic characterization of iron-doped II-VI compounds for laser applications

    NASA Astrophysics Data System (ADS)

    Martinez, Alan

    The middle Infrared (mid-IR) region of the electromagnetic spectrum between 2 and 15 ?m has many features which are of interest to a variety of fields such as molecular spectroscopy, biomedical applications, industrial process control, oil prospecting, free-space communication and defense-related applications. Because of this, there is a demand for broadly tunable, laser sources operating over this spectral region which can be easily and inexpensively produced. II-VI semiconductor materials doped with transition metals (TM) such as Co 2+, Cr2+, or Fe2+ exhibit highly favorable spectroscopic characteristics for mid-IR laser applications. Among these TM dopants, Fe2+ has absorption and emission which extend the farthest into the longer wavelength portion of the mid-IR. Fe2+:II-VI crystals have been utilized as gain elements in laser systems broadly tunable over the 3-5.5 microm range [1] and as saturable absorbers to Q -switch [2] and mode-lock [3] laser cavities operating over the 2.7-3 microm. TM:II-VI laser gain elements can be fabricated inexpensively by means of post-growth thermal diffusion with large homogeneous dopant concentration and good optical quality[4,5]. The work outlined in this dissertation will focus on the spectroscopic characterization of TM-doped II-VI semiconductors. This work can be categorized into three major thrusts: 1) the development of novel laser materials, 2) improving and extending applications of TM:II-VI crystals as saturable absorbers, and 3) fabrication of laser active bulk crystals. Because current laser sources based on TM:II-VI materials do not cover the entire mid-IR spectral region, it is necessary to explore novel laser sources to extend available emissions toward longer wavelengths. The first objective of this dissertation is the spectroscopic characterization of novel ternary host crystals doped with Fe2+ ions. Using crystal field engineering, laser materials can be prepared with emissions placed in spectral regions not

  17. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates.

    PubMed

    Wu, Xue-Jun; Chen, Junze; Tan, Chaoliang; Zhu, Yihan; Han, Yu; Zhang, Hua

    2016-05-01

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures. PMID:27102681

  18. Controlled growth of high-density CdS and CdSe nanorod arrays on selective facets of two-dimensional semiconductor nanoplates

    NASA Astrophysics Data System (ADS)

    Wu, Xue-Jun; Chen, Junze; Tan, Chaoliang; Zhu, Yihan; Han, Yu; Zhang, Hua

    2016-05-01

    The rational synthesis of hierarchical three-dimensional nanostructures with specific compositions, morphologies and functionalities is important for applications in a variety of fields ranging from energy conversion and electronics to biotechnology. Here, we report a seeded growth approach for the controlled epitaxial growth of three types of hierarchical one-dimensional (1D)/two-dimensional (2D) nanostructures, where nanorod arrays of II-VI semiconductor CdS or CdSe are grown on the selective facets of hexagonal-shaped nanoplates, either on the two basal facets of the nanoplate, or on one basal facet, or on the two basal facets and six side facets. The seed engineering of 2D hexagonal-shaped nanoplates is the key factor for growth of the three resulting types of 1D/2D nanostructures. The wurtzite- and zinc-blende-type polymorphs of semiconductors are used to determine the facet-selective epitaxial growth of 1D nanorod arrays, resulting in the formation of different hierarchical three-dimensional (3D) nanostructures.

  19. Toward Ultrafast Spin Dynamics in Low Dimensional Semiconductors

    NASA Astrophysics Data System (ADS)

    Chiu, Yi-Hsin

    Since the discovery of long spin relaxation times of itinerant electrons up to 100 nanoseconds and spin diffusion lengths over 100 mum in GaAs, extraordinary advances in semiconductor spintronics have been made in the past one and half decades. Incorporating spins in semiconductors requires the following essential capabilities: (i) injection of spins into semiconductors, (ii) manipulation of spins, and (iii) sensitive detection of spin coherence. The solutions to these challenges lie in a deeper understanding of spin interactions and spin relaxation in semiconductors as well as appropriate tools to probe spin dynamics. In particular, recent experiments have suggested the important role of dimensionality in spin dynamics. For example, spin-orbit interaction, the dominant source of spin relaxation in most II-VI and III-V semiconductors, has been shown to be significantly suppressed in reduced dimensions. Low-dimensional semiconductors are therefore appealing candidates for exploring spin physics and device applications. This dissertation aims at exploring spin dynamics in low dimensional semiconductor systems using time-resolved optical techniques. The time resolution allows for a direct measurement of the equilibrium and non-equilibrium carrier spins and various spin interactions in the time domain. Optical approaches are also a natural fit for probing optically active nanostructures where electric approaches can often encounter challenges. For instance, fabricating electric contacts with nanostructures is a proven challenge because of their reduced size and modified electronic structure. This dissertation is divided into three sections targeting an ultimate goal of employing optical methods to explore spin dynamics in low dimensional semiconductors. First, the time-resolved Kerr rotation technique is employed to study spin relaxation in Fe/MgO/GaAs heterostructures. The results reveal rich interactions between the GaAs electron spins, nuclear spins, and the

  20. Wafer-fused semiconductor radiation detector

    DOEpatents

    Lee, Edwin Y.; James, Ralph B.

    2002-01-01

    Wafer-fused semiconductor radiation detector useful for gamma-ray and x-ray spectrometers and imaging systems. The detector is fabricated using wafer fusion to insert an electrically conductive grid, typically comprising a metal, between two solid semiconductor pieces, one having a cathode (negative electrode) and the other having an anode (positive electrode). The wafer fused semiconductor radiation detector functions like the commonly used Frisch grid radiation detector, in which an electrically conductive grid is inserted in high vacuum between the cathode and the anode. The wafer-fused semiconductor radiation detector can be fabricated using the same or two different semiconductor materials of different sizes and of the same or different thicknesses; and it may utilize a wide range of metals, or other electrically conducting materials, to form the grid, to optimize the detector performance, without being constrained by structural dissimilarity of the individual parts. The wafer-fused detector is basically formed, for example, by etching spaced grooves across one end of one of two pieces of semiconductor materials, partially filling the grooves with a selected electrical conductor which forms a grid electrode, and then fusing the grooved end of the one semiconductor piece to an end of the other semiconductor piece with a cathode and an anode being formed on opposite ends of the semiconductor pieces.

  1. Reflection technique for thermal mapping of semiconductors

    DOEpatents

    Walter, Martin J.

    1989-06-20

    Semiconductors may be optically tested for their temperatures by illuminating them with tunable monochromatic electromagnetic radiation and observing the light reflected off of them. A transition point will occur when the wavelength of the light corresponds with the actual band gap energy of the semiconductor. At the transition point, the image of the semiconductor will appreciably darken as the light is transmitted through it, rather than being reflected off of it. The wavelength of the light at the transition point corresponds to the actual band gap energy and the actual temperature of the semiconductor.

  2. Visible light water splitting using dye-sensitized oxide semiconductors.

    PubMed

    Youngblood, W Justin; Lee, Seung-Hyun Anna; Maeda, Kazuhiko; Mallouk, Thomas E

    2009-12-21

    Researchers are intensively investigating photochemical water splitting as a means of converting solar to chemical energy in the form of fuels. Hydrogen is a key solar fuel because it can be used directly in combustion engines or fuel cells, or combined catalytically with CO(2) to make carbon containing fuels. Different approaches to solar water splitting include semiconductor particles as photocatalysts and photoelectrodes, molecular donor-acceptor systems linked to catalysts for hydrogen and oxygen evolution, and photovoltaic cells coupled directly or indirectly to electrocatalysts. Despite several decades of research, solar hydrogen generation is efficient only in systems that use expensive photovoltaic cells to power water electrolysis. Direct photocatalytic water splitting is a challenging problem because the reaction is thermodynamically uphill. Light absorption results in the formation of energetic charge-separated states in both molecular donor-acceptor systems and semiconductor particles. Unfortunately, energetically favorable charge recombination reactions tend to be much faster than the slow multielectron processes of water oxidation and reduction. Consequently, visible light water splitting has only recently been achieved in semiconductor-based photocatalytic systems and remains an inefficient process. This Account describes our approach to two problems in solar water splitting: the organization of molecules into assemblies that promote long-lived charge separation, and catalysis of the electrolysis reactions, in particular the four-electron oxidation of water. The building blocks of our artificial photosynthetic systems are wide band gap semiconductor particles, photosensitizer and electron relay molecules, and nanoparticle catalysts. We intercalate layered metal oxide semiconductors with metal nanoparticles. These intercalation compounds, when sensitized with [Ru(bpy)(3)](2+) derivatives, catalyze the photoproduction of hydrogen from sacrificial

  3. Quantum theory of the electronic and optical properties of low-dimensional semiconductor systems

    NASA Astrophysics Data System (ADS)

    Lau, Wayne Heung

    This thesis examines the electronic and optical properties of low-dimensional semiconductor systems. A theory is developed to study the electron-hole generation-recombination process of type-II semimetallic semiconductor heterojunctions based on a 3 x 3 k·p matrix Hamiltonian (three-band model) and an 8 x 8 k·p matrix Hamiltonian (eight-band model). A novel electron-hole generation and recombination process, which is called activationless generation-recombination process, is predicted. It is demonstrated that the current through the type-II semimetallic semiconductor heterojunctions is governed by the activationless electron-hole generation-recombination process at the heterointerfaces, and that the current-voltage characteristics are essentially linear. A qualitative agreement between theory and experiments is observed. The numerical results of the eight-band model are compared with those of the threeband model. Based on a lattice gas model, a theory is developed to study the influence of a random potential on the ionization equilibrium conditions for bound electron-hole pairs (excitons) in III--V semiconductor heterostructures. It is demonstrated that ionization equilibrium conditions for bound electron-hole pairs change drastically in the presence of strong disorder. It is predicted that strong disorder promotes dissociation of excitons in III--V semiconductor heterostructures. A theory of polariton (photon dressed by phonon) spontaneous emission in a III--V semiconductor doped with semiconductor quantum dots (QDs) or quantum wells (QWs) is developed. For the first time, superradiant and subradiant polariton spontaneous emission phenomena in a polariton-QD (QW) coupled system are predicted when the resonance energies of the two identical QDs (QWs) lie outside the polaritonic energy gap. It is also predicted that when the resonance energies of the two identical QDs (QWs) lie inside the polaritonic energy gap, spontaneous emission of polariton in the polariton

  4. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    SciTech Connect

    Zhu, Xiaoyang

    2014-12-10

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering. Organic semiconductors are emerging as viable materials for low-cost electronics and optoelectronics, such as organic photovoltaics (OPV), organic field effect transistors (OFETs), and organic light emitting diodes (OLEDs). Despite extensive studies spanning many decades, a clear understanding of the nature of charge carriers in organic semiconductors is still lacking. It is generally appreciated that polaron formation and charge carrier trapping are two hallmarks associated with electrical transport in organic semiconductors; the former results from the low dielectric constants and weak intermolecular electronic overlap while the latter can be attributed to the prevalence of structural disorder. These properties have lead to the common observation of low charge carrier mobilities, e.g., in the range of 10-5 - 10-3 cm2/Vs, particularly at low carrier concentrations. However, there is also growing evidence that charge carrier mobility approaching those of inorganic semiconductors and metals can exist in some crystalline organic semiconductors, such as pentacene, tetracene and rubrene. A particularly striking example is single crystal rubrene (Figure 1), in which hole mobilities well above 10 cm2/Vs have been observed in OFETs operating at room temperature. Temperature dependent transport and spectroscopic measurements both revealed evidence of free carriers in rubrene. Outstanding questions are: what are the structural features and physical properties that make rubrene so unique? How do we establish fundamental design principles for the development of other organic semiconductors of high mobility? These questions are critically important but not comprehensive, as the nature of

  5. Semiconductor technology program. Progress briefs

    NASA Technical Reports Server (NTRS)

    Bullis, W. M. (Editor)

    1979-01-01

    The current status of NBS work on measurement technology for semiconductor materials, process control, and devices is reported. Results of both in-house and contract research are covered. Highlighted activities include modeling of diffusion processes, analysis of model spreading resistance data, and studies of resonance ionization spectroscopy, resistivity-dopant density relationships in p-type silicon, deep level measurements, photoresist sensitometry, random fault measurements, power MOSFET thermal characteristics, power transistor switching characteristics, and gross leak testing. New and selected on-going projects are described. Compilations of recent publications and publications in press are included.

  6. HERO resistant semiconductor bridge igniter

    NASA Astrophysics Data System (ADS)

    Bickes, R. W., Jr.; Greenway, D.; Grubelich, M. C.; Meyer, W. J.; Hartman, J. K.; McCampbell, C. B.

    1992-10-01

    The problem of accidental ignition of explosive components when exposed to radio frequency (RF) environments or radiation from other electromagnetic sources is commonly referred to as Hazards of Electromagnetic Radiation to Ordnance (HERO). One illustration of such a HERO problem is the MK 149 Phalanx ammunition, which is sensitive to RF energy over a broad range of frequencies. We have demonstrated that a potential solution to the Phalanx HERO problem consists of a semiconductor bridge (SCB) igniter that incorporates microcircuitry to protect the SCB from the RF environment. Direct RF injection and ground plane tests have demonstrated the resistance of our designs to severe RF environments.

  7. High gain photoconductive semiconductor switching

    SciTech Connect

    Zutavern, F.J.; Loubriel, G.M.; O'Malley, M.W.; Helgeson, W.D.; McLaughlin, D.L.

    1991-01-01

    Switching properties are reported for high gain photoconductive semiconductor switches (PCSS). A 200 ps pulse width laser was used in tests to examine the relations between electric field, rise time, delay, and minimum optical trigger energy for switches which reached 80 kV in a 50 {Omega} transmission line with rise times as short as 600 ps. Infrared photoluminescence was imaged during high gain switching providing direct evidence for current filamentation. Implications of these measurements for the theoretical understanding and practical development of these switches are discussed. 16 refs., 10 figs.

  8. Processing of insulators and semiconductors

    SciTech Connect

    Quick, Nathaniel R.; Joshi, Pooran C.; Duty, Chad Edward; Jellison, Jr., Gerald Earle; Angelini, Joseph Attilio

    2015-06-16

    A method is disclosed for processing an insulator material or a semiconductor material. The method includes pulsing a plasma lamp onto the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a large area region of the material. The method may further include pulsing a laser onto a selected region of the material to diffuse a doping substance into the material, to activate the doping substance in the material or to metallize a selected region of the material.

  9. Tunable catalytic alloying eliminates stacking faults in compound semiconductor nanowires.

    PubMed

    Heo, Hoseok; Kang, Kibum; Lee, Donghun; Jin, Li-Hua; Back, Hyeon-Jun; Hwang, Inchan; Kim, Miseong; Lee, Hyun-Seung; Lee, Byeong-Joo; Yi, Gyu-Chul; Cho, Yong-Hoon; Jo, Moon-Ho

    2012-02-01

    Planar defects in compound (III-V and II-VI) semiconductor nanowires (NWs), such as twin and stacking faults, are universally formed during the catalytic NW growth, and they detrimentally act as static disorders against coherent electron transport and light emissions. Here we report a simple synthetic route for planar-defect free II-VI NWs by tunable alloying, i.e. Cd(1-x)Zn(x)Te NWs (0 ≤ x ≤ 1). It is discovered that the eutectic alloying of Cd and Zn in Au catalysts immediately alleviates interfacial instability during the catalytic growth by the surface energy minimization and forms homogeneous zinc blende crystals as opposed to unwanted zinc blende/wurtzite mixtures. As a direct consequence of the tunable alloying, we demonstrated that intrinsic energy band gap modulation in Cd(1-x)Zn(x)Te NWs can exploit the tunable spectral and temporal responses in light detection and emission in the full visible range.

  10. Engineering Encounters: Engineering Adaptations

    ERIC Educational Resources Information Center

    Gatling, Anne; Vaughn, Meredith Houle

    2015-01-01

    Engineering is not a subject that has historically been taught in elementary schools, but with the emphasis on engineering in the "Next Generation Science Standards," curricula are being developed to explicitly teach engineering content and design. However, many of the scientific investigations already conducted with students have…

  11. A Program in Semiconductor Processing.

    ERIC Educational Resources Information Center

    McConica, Carol M.

    1984-01-01

    A graduate program at Colorado State University which focuses on integrated circuit processing is described. The program utilizes courses from several departments while allowing students to apply chemical engineering techniques to an integrated circuit fabrication research topic. Information on employment of chemical engineers by electronics…

  12. Charge-controlled magnetism in colloidal doped semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Gamelin, Daniel

    2010-03-01

    Electrical control over the magnetic states of doped semiconductor nanostructures could enable new spin-based information processing technologies, but the relatively weak interactions between dopants and charge carriers have so far suggested that such gated magnetism will be limited to cryogenic temperatures. This talk will describe the observation of a large, reversible, room-temperature magnetic response to charge injection in free-standing colloidal ZnO nanocrystals doped with Mn(II) ions. Injected electrons are found to delocalize throughout the entire nanocrystal, and to activate new ferromagnetic Mn(II)-Mn(II) exchange interactions that are strong enough to overcome antiferromagnetic coupling between nearest-neighbor Mn(II) ions, making the full magnetic moments of all dopants observable upon charging. Removal of the electron causes the system to revert to its original form, allowing reversible charge-controlled manipulation of room-temperature nanocrystal magnetism. The physical properties of these charged, doped nanocrystals are directly analogous to those of bound magnetic poltroons (BMPs) postulated to underlie high-temperature ferromagnetic ordering in the bulk forms of this and related diluted magnetic oxides. This discovery of charge-controlled magnetism in free-standing colloidal nanocrystals that is large, reversible, and stable at room temperature presents new opportunities for fundamental studies and raises interesting possibilities for the development of spin-based information processing technologies from solution-processable semiconductor nanostructures. Related references: Ochsenbein, S. T.; Feng, Y.; Whitaker, K. M.; Badaeva, E.; Liu, W. K.; Li, X.; Gamelin, D. R., Nature Nanotechnology, 4, 681 (2009); Liu, W. K.; Whitaker, K. M.; Kittilstved, K. R.; Gamelin, D. R., J. Am. Chem. Soc., 128, 3910 (2006).

  13. Lattice thermal expansion for normal tetrahedral compound semiconductors

    SciTech Connect

    Omar, M.S. . E-mail: dr_m_s_omar@yahoo.com

    2007-02-15

    The cubic root of the deviation of the lattice thermal expansion from that of the expected value of diamond for group IV semiconductors, binary compounds of III-V and II-VI, as well as several ternary compounds from groups I-III-VI{sub 2}, II-IV-V{sub 2} and I-IV{sub 2}V{sub 3} semiconductors versus their bonding length are given straight lines. Their slopes were found to be 0.0256, 0.0210, 0.0170, 0.0259, 0.0196, and 0.02840 for the groups above, respectively. Depending on the valence electrons of the elements forming these groups, a formula was found to correlate all the values of the slopes mentioned above to that of group IV. This new formula which depends on the melting point and the bonding length as well as the number of valence electrons for the elements forming the compounds, will gives best calculated values for lattice thermal expansion for all compounds forming the groups mentioned above. An empirical relation is also found between the mean ionicity of the compounds forming the groups and their slopes mentioned above and that gave the mean ionicity for the compound CuGe{sub 2}P{sub 3} in the range of 0.442.

  14. Spin-glass behaviors in carrier polarity controlled Fe3-xTixO4 semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Yamahara, H.; Seki, M.; Adachi, M.; Takahashi, M.; Nasu, H.; Horiba, K.; Kumigashira, H.; Tabata, H.

    2015-08-01

    Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe3-xTixO4 thin films have been obtained on spinel MgAl2O4 substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6-0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe3-xTixO4 films (x = 0.6-0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe2.2Ti0.8O4 film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe2.2Ti0.8O4 film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.

  15. Directional charge separation in isolated organic semiconductor crystalline nanowires

    NASA Astrophysics Data System (ADS)

    Labastide, J. A.; Thompson, H. B.; Marques, S. R.; Colella, N. S.; Briseno, A. L.; Barnes, M. D.

    2016-02-01

    One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry.

  16. Directional charge separation in isolated organic semiconductor crystalline nanowires.

    PubMed

    Labastide, J A; Thompson, H B; Marques, S R; Colella, N S; Briseno, A L; Barnes, M D

    2016-01-01

    One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry. PMID:26912040

  17. Directional charge separation in isolated organic semiconductor crystalline nanowires

    PubMed Central

    Labastide, J. A.; Thompson, H. B.; Marques, S. R.; Colella, N. S.; Briseno, A. L.; Barnes, M. D.

    2016-01-01

    One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry. PMID:26912040

  18. Development of silicon carbide semiconductor devices for high temperature applications

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Powell, J. Anthony; Petit, Jeremy B.

    1991-01-01

    The semiconducting properties of electronic grade silicon carbide crystals, such as wide energy bandgap, make it particularly attractive for high temperature applications. Applications for high temperature electronic devices include instrumentation for engines under development, engine control and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Discrete prototype SiC devices were fabricated and tested at elevated temperatures. Grown p-n junction diodes demonstrated very good rectification characteristics at 870 K. A depletion-mode metal-oxide-semiconductor field-effect transistor was also successfully fabricated and tested at 770 K. While optimization of SiC fabrication processes remain, it is believed that SiC is an enabling high temperature electronic technology.

  19. Semiconductor foundry, lithography, and partners

    NASA Astrophysics Data System (ADS)

    Lin, Burn J.

    2002-07-01

    The semiconductor foundry took off in 1990 with an annual capacity of less than 0.1M 8-inch-equivalent wafers at the 2-mm node. In 2000, the annual capacity rose to more than 10M. Initially, the technology practiced at foundries was 1 to 2 generations behind that at integrated device manufacturers (IDMs). Presently, the progress in 0.13-mm manufacturing goes hand-in-hand with any of the IDMs. There is a two-order of magnitude rise in output and the progress of technology development outpaces IDMs. What are the reasons of the success? Is it possible to sustain the pace? This paper shows the quick rise of foundries in capacity, sales, and market share. It discusses the their uniqueness which gives rise to advantages in conjunction with challenges. It also shows the role foundries take with their customer partners and supplier partners, their mutual dependencies, as well as expectations. What role then does lithography play in the foundries? What are the lithographic challenges to sustain the pace of technology? The experience of technology development and transfer, at one of the major foundries, is used to illustrate the difficulties and progresses made. Looking into the future, as semiconductor manufacturing will become even more expensive and capital investment more prohibitive, we will make an attempt to suggest possible solutions.

  20. Performance of Axial-Flow Supersonic Compressor of XJ55-FF-1 Turbojet Engine. II - Performance of Inlet Guide Vanes as Separate Component

    NASA Technical Reports Server (NTRS)

    Graham, Robert C.; Tysl, Edward R.

    1949-01-01

    The inlet wide vanes for the supersonic compressor of the XJ55-FF-1 engine were studied as a separate component in order to determine the performance prior to installation in the compressor test rig. Turning angles approached design values, and increased approximately to through the inlet Mach number range from 0.30 to choke. A sharp break in turning angle was experienced when the choke condition was reached. The total-pressure loss through the guide vanes was approximately 1 percent for the unchoked conditions and from 5 to 6 percent when choked.

  1. Novel room temperature ferromagnetic semiconductors

    SciTech Connect

    Gupta, Amita

    2004-06-01

    Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will be higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous distribution of Mn substituting

  2. Hybrid anode for semiconductor radiation detectors

    DOEpatents

    Yang, Ge; Bolotnikov, Aleksey E; Camarda, Guiseppe; Cui, Yonggang; Hossain, Anwar; Kim, Ki Hyun; James, Ralph B

    2013-11-19

    The present invention relates to a novel hybrid anode configuration for a radiation detector that effectively reduces the edge effect of surface defects on the internal electric field in compound semiconductor detectors by focusing the internal electric field of the detector and redirecting drifting carriers away from the side surfaces of the semiconductor toward the collection electrode(s).

  3. Apparatus for edge etching of semiconductor wafers

    NASA Technical Reports Server (NTRS)

    Casajus, A.

    1986-01-01

    A device for use in the production of semiconductors, characterized by etching in a rapidly rotating etching bath is described. The fast rotation causes the surface of the etching bath to assume the form of a paraboloid of revolution, so that the semiconductor wafer adjusted at a given height above the resting bath surface is only attacked by etchant at the edges.

  4. Energetics of the Semiconductor-Electrolyte Interface.

    ERIC Educational Resources Information Center

    Turner, John A.

    1983-01-01

    The use of semiconductors as electrodes for electrochemistry requires an understanding of both solid-state physics and electrochemistry, since phenomena associated with both disciplines are seen in semiconductor/electrolyte systems. The interfacial energetics of these systems are discussed. (JN)

  5. Preparation of a semiconductor thin film

    DOEpatents

    Pehnt, M.; Schulz, D.L.; Curtis, C.J.; Ginley, D.S.

    1998-01-27

    A process is disclosed for the preparation of a semiconductor film. The process comprises depositing nanoparticles of a semiconductor material onto a substrate whose surface temperature during nanoparticle deposition thereon is sufficient to cause substantially simultaneous fusion of the nanoparticles to thereby coalesce with each other and effectuate film growth.

  6. Preparation of a semiconductor thin film

    DOEpatents

    Pehnt, Martin; Schulz, Douglas L.; Curtis, Calvin J.; Ginley, David S.

    1998-01-01

    A process for the preparation of a semiconductor film. The process comprises depositing nanoparticles of a semiconductor material onto a substrate whose surface temperature during nanoparticle deposition thereon is sufficient to cause substantially simultaneous fusion of the nanoparticles to thereby coalesce with each other and effectuate film growth.

  7. Silicon carbide, a high temperature semiconductor

    NASA Technical Reports Server (NTRS)

    Powell, J. A.

    1983-01-01

    Electronic applications are described that would benefit from the availability of high temperature semiconductor devices. Comparisons are made among potential materials for these devices and the problems of each are discussed. Recent progress in developing silicon carbide as a high temperature semiconductor is described.

  8. 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.

  9. Photoelectroconversion by Semiconductors: A Physical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Fan, Qinbai; And Others

    1995-01-01

    Presents an experiment designed to give students some experience with photochemistry, electrochemistry, and basic theories about semiconductors. Uses a liquid-junction solar cell and illustrates some fundamental physical and chemical principles related to light and electricity interconversion as well as the properties of semiconductors. (JRH)

  10. The Effect of Compression Ratio on Knock Limits of High-Performance Fuels in a CFR Engine II : Blends of 2,2,3-Trimethylpentane with 28-R

    NASA Technical Reports Server (NTRS)

    Tower, Leonard K

    1945-01-01

    The knock-limited performance of blends of 0,50; and 100 percent by volume of 2,2,3-trimethylpentane in 28-R fuel determined with a modified F-4 engine at three sets of conditions varying from severe to mild at each of three compression ratios (6.0, 8.0, and 10.0). A comparison of the knock-limited performance of 2,2,3-trimethylpentane with that of triptane (2,2,3-trimethylbutane) is included. The knock-Limited performance of 2,2,3-trimethylpontane was usually more sensitive to either compression ratio or inlet-air temperature than 28-R fuel, but the ratio of the knock-limited indicated mean effective pressure of a given blend containing 2,2,3-trimethypentane and 28-R to the indicated mean effective pressure of 28-R alone was not greatly affected by compression ratio if the engine operating conditions were mild. Although 2,2,3-trimethylpentane in general had a lower knock-limited performance than triptane, the characteristics of the two fuels were somewhat similar.

  11. Construction of collagen II/hyaluronate/chondroitin-6-sulfate tri-copolymer scaffold for nucleus pulposus tissue engineering and preliminary analysis of its physico-chemical properties and biocompatibility.

    PubMed

    Li, Chang-Qing; Huang, Bo; Luo, Gang; Zhang, Chuan-Zhi; Zhuang, Ying; Zhou, Yue

    2010-02-01

    To construct a novel scaffold for nucleus pulposus (NP) tissue engineering, The porous type II collagen (CII)/hyaluronate (HyA)-chondroitin-6-sulfate (6-CS) scaffold was prepared using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) cross-linking system. The physico-chemical properties and biocompatibility of CII/HyA-CS scaffolds were evaluated. The results suggested CII/HyA-CS scaffolds have a highly porous structure (porosity: 94.8 +/- 1.5%), high water-binding capacity (79.2 +/- 2.8%) and significantly improved mechanical stability by EDC/NHS crosslinking (denaturation temperature: 74.6 +/- 1.8 and 58.1 +/- 2.6 degrees C, respectively, for the crosslinked scaffolds and the non-crosslinked; collagenase degradation rate: 39.5 +/- 3.4 and 63.5 +/- 2.0%, respectively, for the crosslinked scaffolds and the non-crosslinked). The CII/HyA-CS scaffolds also showed satisfactory cytocompatibility and histocompatibility as well as low immunogenicity. These results indicate CII/HyA-CS scaffolds may be an alternative material for NP tissue engineering due to the similarity of its composition and physico-chemical properties to those of the extracellular matrices (ECM) of native NP.

  12. Automotive Stirling Engine Development Program

    NASA Technical Reports Server (NTRS)

    Nightingale, N.; Richey, A.; Farrell, R.; Riecke, G.; Ernst, W.; Howarth, R.; Cronin, M.; Simetkosky, M.; Smith, G.; Meacher, J.

    1985-01-01

    Development test activities on Mod I engines directed toward evaluating technologies for potential inclusion in the Mod II engine are summarized. Activities covered include: test of a 12-tube combustion gas recirculation combustor; manufacture and flow-distribution test of a two-manifold annular heater head; piston rod/piston base joint; single-solid piston rings; and a digital air/fuel concept. Also summarized are results of a formal assessment of candidate technologies for the Mod II engine, and preliminary design work for the Mod II. The overall program philosophy weight is outlined, and data and test results are presented.

  13. Moving liquids with light: Photoelectrowetting on semiconductors

    PubMed Central

    Arscott, Steve

    2011-01-01

    By linking semiconductor physics and wetting phenomena a brand new effect termed “photoelectrowetting-on-semiconductors” is demonstrated here for a conducting droplet resting on an insulator-semiconductor stack. Optical generation of carriers in the space-charge region of the underlying semiconductor alters the capacitance of the liquid-insulator-semiconductor stack; the result of this is a modification of the wetting contact angle of the droplet upon illumination using above band gap light. The effect is demonstrated using commercial silicon wafers, both n- and p-type having a doping range spanning four orders of magnitude (6×1014−8×1018 cm−3), coated with a commercial amorphous fluoropolymer insulating film (Teflon®). Impedance measurements confirm that the observations are semiconductor space-charge related effects. The impact of the work could lead to new silicon-based technologies in areas such as Laboratory-on-a-Chip, Microfluidics and Optofluidics. PMID:22355699

  14. Semiconductor Laser Low Frequency Noise Characterization

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Logan, Ronald T.

    1996-01-01

    This work summarizes the efforts in identifying the fundamental noise limit in semiconductor optical sources (lasers) to determine the source of 1/F noise and it's associated behavior. In addition, the study also addresses the effects of this 1/F noise on RF phased arrays. The study showed that the 1/F noise in semiconductor lasers has an ultimate physical limit based upon similar factors to fundamental noise generated in other semiconductor and solid state devices. The study also showed that both additive and multiplicative noise can be a significant detriment to the performance of RF phased arrays especially in regard to very low sidelobe performance and ultimate beam steering accuracy. The final result is that a noise power related term must be included in a complete analysis of the noise spectrum of any semiconductor device including semiconductor lasers.

  15. 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.

  16. 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.

  17. Creating semiconductor metafilms with designer absorption spectra.

    PubMed

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  18. Creating semiconductor metafilms with designer absorption spectra

    PubMed Central

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  19. Semiconductor technology trend and requirements for masks

    NASA Astrophysics Data System (ADS)

    Komiya, Hiroyoshi

    1999-08-01

    The fabrication cost of the semiconductor device is increasing because the fabrication cost per wafer unit area and the mask cost are increasing rapidly with the design rule decreased. The rapid increase in the mask cost will influence the semiconductor industry growth. The progress in the lithography, including the mask, is the key issue for the progress in the entire semiconductor technology beyond 180 nm design rule, because the mask is indispensable for any types of lithography, and is regarded as one of the most critical technologies, both in resolution and productivity. To continue the progress in the entire semiconductor technology and the growth of the semiconductor business, it is indispensable to make challenges in the low cost and high precision mask technology under the cooperation with related industries and academia. It is especially important to develop the cost optimum solution for the total lithography technology including masks.

  20. Manipulating semiconductor colloidal stability through doping.

    PubMed

    Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

    2014-10-10

    The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.