WorldWideScience

Sample records for temperature semiconductor x

  1. Temperature controller of semiconductor laser

    Czech Academy of Sciences Publication Activity Database

    Matoušek, Vít; Číp, Ondřej

    2003-01-01

    Roč. 73, č. 3 (2003), s. 10 - 12 ISSN 0928-5008 Institutional research plan: CEZ:AV0Z2065902 Keywords : temperature controller * semiconductor laser * laser diode Subject RIV: BH - Optics, Masers, Lasers

  2. Semiconductor X-ray spectrometers

    International Nuclear Information System (INIS)

    Muggleton, A.H.F.

    1978-02-01

    An outline is given of recent developments in particle and photon induced x-ray fluorescence (XRF) analysis. Following a brief description of the basic mechanism of semiconductor detector operation a comparison is made between semiconductor detectors, scintillators and gas filled proportional devices. Detector fabrication and cryostat design are described in more detail and the effects of various device parameters on system performance, such as energy resolution, count rate capability, efficiency, microphony, etc. are discussed. The main applications of these detectors in x-ray fluorescence analysis, electron microprobe analysis, medical and pollution studies are reviewed

  3. Semiconductor X-ray detectors

    CERN Document Server

    Lowe, Barrie Glyn

    2014-01-01

    Identifying and measuring the elemental x-rays released when materials are examined with particles (electrons, protons, alpha particles, etc.) or photons (x-rays and gamma rays) is still considered to be the primary analytical technique for routine and non-destructive materials analysis. The Lithium Drifted Silicon (Si(Li)) X-Ray Detector, with its good resolution and peak to background, pioneered this type of analysis on electron microscopes, x-ray fluorescence instruments, and radioactive source- and accelerator-based excitation systems. Although rapid progress in Silicon Drift Detectors (SDDs), Charge Coupled Devices (CCDs), and Compound Semiconductor Detectors, including renewed interest in alternative materials such as CdZnTe and diamond, has made the Si(Li) X-Ray Detector nearly obsolete, the device serves as a useful benchmark and still is used in special instances where its large, sensitive depth is essential. Semiconductor X-Ray Detectors focuses on the history and development of Si(Li) X-Ray Detect...

  4. Novel room temperature ferromagnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Amita [KTH Royal Inst. of Technology, Stockholm (Sweden)

    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

  5. Room-temperature semiconductors and scintillators for planetary instruments

    CERN Document Server

    Schweitzer, J S

    1999-01-01

    Room temperature semiconductors introduce some exciting potential for use in instruments designed for planetary measurements. It is important, however, to consider carefully the different types of measurement environments. In some cases room temperature semiconductors provide significant advantages over scintillators, while in some cases scintillators still have advantages over room temperature semiconductors. A number of instrumentation applications for detecting X-rays and gamma rays are considered. By focusing on the physical properties of both types of detectors, it is possible to better understand how each type of detector can best be used for measurements from satellites and directly on planetary bodies.

  6. Influence of high energy lead irradiation on the low and high temperature metal-semiconductor transitions in (V 1 - xCr x) 2O 3 ceramics

    Science.gov (United States)

    Kokabi, H. R.; Studer, F.

    1997-04-01

    Ceramic samples of chromium doped vanadium sesquioxide [(V 1 - xCr x) 2O 3] have been irradiated using high energy lead ions (208Pb : 6.032 GeV) with various fluences (4 to 50 × 10 11 ions/cm 2). Irradiations have been carried out under vacuum and at different temperatures. Irradiated samples have been characterized by electrical resistivity measurements as a function of temperature for low and high temperature transitions in the (V 1 - xCr x) 2O 3 system. As the low and high temperature (LT and HT) phase transitions in this system correspond to different enthalpy variations, both transitions do not exhibit the same sensitivity to irradiation with heavy ions. Because of internal stress formation, lead ions irradiation induced shifts of the HT and LT transition temperatures and broadening of these transitions. Besides, stabilization of a fraction of the microcrystals in the sample in the metallic state led to the reduction of the PTC (Positive Temperature Coefficient)-like effect. The effects of the doping amounts ( x = 0.003 and 0.007) and the irradiation temperature (77 K and 300 K) on the modification of electrical properties of the irradiated materials have been studied using resistivity measurements. Irradiations with a smaller doping rate and at 77 K lead to more significant changes in the thermal variations of the electrical resistivity. Large differences in electrical characteristics have been observed between samples irradiated either in the metallic (300 K) or the semiconducting state (77 K) which showed that the sensitivity of (V 1 - xCr x) 2O 3 ceramics to heavy ion irradiation is dependent on the phase state and on its physical properties.

  7. Fibre-Optic Semiconductor Temperature Gage

    Science.gov (United States)

    Sharma, M.

    1982-01-01

    "Safe" temperature gage for explosive liquids is based on optical transmission. Semiconductor crystal inserted between input and output optical fibers is temperature-sensing element in a new approach to measuring temperature of cryogens. Since no electrical components are immersed in liquid, new sensor minimizes danger of electrically ignited explosions in hazardous cryogens such as oxygen and hydrogen. Gage also useful for handling noncryogenic liquids in aircraft, automobiles, boats and water tanks.

  8. Temperature dependent electronic conduction in semiconductors

    International Nuclear Information System (INIS)

    Roberts, G.G.; Munn, R.W.

    1980-01-01

    This review describes the temperature dependence of bulk-controlled electronic currents in semiconductors. The scope of the article is wide in that it contrasts conduction mechanisms in inorganic and organic solids and also single crystal and disordered semiconductors. In many experimental situations it is the metal-semiconductor contact or the interface between two dissimilar semiconductors that governs the temperature dependence of the conductivity. However, in order to keep the length of the review within reasonable bounds, these topics have been largely avoided and emphasis is therefore placed on bulk-limited currents. A central feature of electronic conduction in semiconductors is the concentrations of mobile electrons and holes that contribute to the conductivity. Various statistical approaches may be used to calculate these densities which are normally strongly temperature dependent. Section 1 emphasizes the relationship between the position of the Fermi level, the distribution of quantum states, the total number of electrons available and the absolute temperature of the system. The inclusion of experimental data for several materials is designed to assist the experimentalist in his interpretation of activation energy curves. Sections 2 and 3 refer to electronic conduction in disordered solids and molecular crystals, respectively. In these cases alternative approaches to the conventional band theory approach must be considered. For example, the velocities of the charge carriers are usually substantially lower than those in conventional inorganic single crystal semiconductors, thus introducing the possibility of an activated mobility. Some general electronic properties of these materials are given in the introduction to each of these sections and these help to set the conduction mechanisms in context. (orig.)

  9. New developments in CdZnTe semiconductors for X and Gamma-ray detection

    OpenAIRE

    Zambelli, Nicola

    2014-01-01

    Semiconductor ionizing radiation detectors have experienced a rather rapid development in the last years. Recently, a substantial international effort has been invested in developing a range of compound semiconductors with wide band gap and high atomic number for X-ray and Gamma ray detectors. Among the compound semiconductors Cadmium Zinc Telluride (CZT) is the most promising material for radiation detectors with good energy resolution, high detection efficiency and room temperature operatio...

  10. Chromium and nickel ion irradiation effects on the low- and high-temperature metal-semiconductor transitions in (V1 - xCrx)2O3 ceramics

    Science.gov (United States)

    Kokabi, H. R.; Studer, F.

    1996-11-01

    Chromium doped vanadium sesquioxide [(V1-xCrx)2O3] ceramic samples have been irradiated using medium energy chromium and nickel ions (52Cr:572 MeV, 64Ni:640 MeV) at various fluences (4×1011-1.1×1014 ions/cm2) and doping rates (x=0.3, 0.6, and 0.7). Irradiation has been carried out under vacuum and at room temperature. Irradiated samples have been characterized by electrical resistivity measurements as a function of temperature for the low- and the high-temperature transitions in the (V1-xCrx)2O3 system. Irradiation by chromium and nickel ions creates bilayered samples as the ions mean projected range were smaller than the sample thickness. The bilayer structure is characterized by two transitions at low temperature. Dealing with the high temperature positive temperature coefficient transition, the negative temperature coefficient behavior above this transition has been considerably attenuated due to the bilayered structure. In situ measurements on an irradiated sample have shown that after annealing the electrical characteristics for the low- and the high-temperature transitions tend to be close to those of an unirradiated sample. However, even an annealing at 380 °C does not eliminate all the irradiation effects.

  11. Photoelectrochemical cell including Ga(Sb.sub.x)N.sub.1-x semiconductor electrode

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Madhu; Sheetz, Michael; Sunkara, Mahendra Kumar; Pendyala, Chandrashekhar; Sunkara, Swathi; Jasinski, Jacek B.

    2017-09-05

    The composition of matter comprising Ga(Sb.sub.x)N.sub.1-x where x=0.01 to 0.06 is characterized by a band gap between 2.4 and 1.7 eV. A semiconductor device includes a semiconductor layer of that composition. A photoelectric cell includes that semiconductor device.

  12. Development of electron holes across the temperature-induced semiconductor-metal transition in Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-δ)(x, y = 0.2-0.8): a soft x-ray absorption spectroscopy study.

    Science.gov (United States)

    Harvey, A S; Yang, Z; Infortuna, A; Beckel, D; Purton, J A; Gauckler, L J

    2009-01-07

    The x-ray absorption spectra of Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-δ) (BSCF) powders quenched in air from 623 and 1173 K were measured at the oxygen K and transition metal L(II,III) edges. All the samples show a predominantly Fe high spin ground state of 3d(5)L character, while the 3d(6)L Co ions are intermediate spin at 623 K and high spin at 1173 K. Further changes in the metal L(II,III) peaks caused by higher temperature quenching are attributed to changes in symmetry around the cations associated with oxygen loss. The oxygen K spectra show the development of unoccupied states just above the Fermi level for samples quenched from 1173 K. At 1173 K, Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-δ) shows metallic conductivity, while at 623 K it is a semiconductor; the states developed at high temperature with strong oxygen character are pathways for hole conductivity. Splitting of the transition metal 3d energy levels by the ligand field was observed in the oxygen K spectra, and the range for 10Dq is 1.6-1.8 eV, while the 3d bandwidth is 1.1-1.4 eV in samples quenched from 623 K. On the basis of the soft x-ray absorption results, the classification of Ba(1-x)Sr(x)Co(1-y)Fe(y)O(3-δ) as a material with a negative charge-transfer energy is proposed.

  13. Development of electron holes across the temperature-induced semiconductor-metal transition in Ba{sub 1-x}Sr{sub x}Co{sub 1-y}Fe{sub y}O{sub 3-{delta}}(x, y = 0.2-0.8): a soft x-ray absorption spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, A S; Yang, Z; Infortuna, A; Beckel, D; Gauckler, L J [Nonmetallic Inorganic Materials, Department of Materials, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich (Switzerland); Purton, J A [Science and Technology Facilities Council, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)], E-mail: ashley.harvey@mat.ethz.ch

    2009-01-07

    The x-ray absorption spectra of Ba{sub 1-x}Sr{sub x}Co{sub 1-y}Fe{sub y}O{sub 3-{delta}} (BSCF) powders quenched in air from 623 and 1173 K were measured at the oxygen K and transition metal L{sub II,III} edges. All the samples show a predominantly Fe high spin ground state of 3d{sup 5}L character, while the 3d{sup 6}L Co ions are intermediate spin at 623 K and high spin at 1173 K. Further changes in the metal L{sub II,III} peaks caused by higher temperature quenching are attributed to changes in symmetry around the cations associated with oxygen loss. The oxygen K spectra show the development of unoccupied states just above the Fermi level for samples quenched from 1173 K. At 1173 K, Ba{sub 1-x}Sr{sub x}Co{sub 1-y}Fe{sub y}O{sub 3-{delta}} shows metallic conductivity, while at 623 K it is a semiconductor; the states developed at high temperature with strong oxygen character are pathways for hole conductivity. Splitting of the transition metal 3d energy levels by the ligand field was observed in the oxygen K spectra, and the range for 10Dq is 1.6-1.8 eV, while the 3d bandwidth is 1.1-1.4 eV in samples quenched from 623 K. On the basis of the soft x-ray absorption results, the classification of Ba{sub 1-x}Sr{sub x}Co{sub 1-y}Fe{sub y}O{sub 3-{delta}} as a material with a negative charge-transfer energy is proposed.

  14. High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb

    International Nuclear Information System (INIS)

    Tu, Nguyen Thanh; Hai, Pham Nam; Anh, Le Duc; Tanaka, Masaaki

    2016-01-01

    We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga 1−x ,Fe x )Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.

  15. High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Nguyen Thanh [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physics, Ho Chi Minh City University of Pedagogy, 280, An Duong Vuong Street, District 5, Ho Chi Minh City 748242 (Viet Nam); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Anh, Le Duc [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-05-09

    We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.

  16. Metal-semiconductor interface in extreme temperature conditions

    International Nuclear Information System (INIS)

    Bulat, L.P.; Erofeeva, I.A.; Vorobiev, Yu.V.; Gonzalez-Hernandez, J.

    2008-01-01

    We present an investigation of electrons' and phonons' temperatures in the volume of a semiconductor (or metal) sample and at the interface between metal and semiconductor. Two types of mismatch between electrons' and phonons' temperatures take place: at metal-semiconductor interfaces and in the volume of the sample. The temperature mismatch leads to nonlinear terms in expressions for heat and electricity transport. The nonlinear effects should be taken into consideration in the study of electrical and heat transport in composites and in electronic chips

  17. Neutron scattering studies of a dilute magnetic semiconductor: Cd1-xMnxTe

    DEFF Research Database (Denmark)

    Steigenberger, Ursula; Lebech, Bente; Galazka, Robert R.

    1986-01-01

    The development of the magnetic ordering in the magnetic semiconductor Cd1-xMnxTe was investigated by elastic neutron scattering. A detailed study of the correlation length and the intensity as a function of temperature, direction in reciprocal space and concentration of the magnetic ions has been...

  18. Magnetoresistance and Curie temperature of GaAs semiconductor doped with Mn ions

    International Nuclear Information System (INIS)

    Yalishev, V.Sh.

    2006-02-01

    Key words: diluted magnetic semiconductors, magnetoresistance, ferromagnetism, ionic implantation, molecular-beam epitaxy, magnetic clusters, Curie temperature. Subjects of the inquiry: Diluted magnetic semiconductor GaAs:Mn. Aim of the inquiry: determination of the possibility of the increase of Curie temperature in diluted magnetic semiconductors based on GaAs doped with Mn magnetic impurity. Method of inquiry: superconducting quantum interference device (SQUID), Hall effect, magnetoresistance, atomic and magnetic force microscopes. The results achieved and their novelty: 1. The effect of the additional doping of Ga 0,965 Mn 0,035 As magnetic epitaxial layers by nonmagnetic impurity of Be on on the Curie temperature was revealed. 2. The exchange interaction energy in the investigated Ga 0,965 Mn 0,035 As materials was determined by the means of the magnetic impurity dispersion model from the temperature dependence of the resistivity measurements. 3. The effect of magnetic clusters dimensions and illumination on the magnetoresistance of GaAs materials containing nano-dimensional magnetic clusters was studied for the first time. Practical value: Calculated energy of the exchange interaction between local electrons of magnetic ions and free holes in Ga 1-x Mn x As magnetic semiconductors permitted to evaluate the theoretical meaning of Curie temperature depending on concentration of free holes and to compare it with experimental data. Sphere of usage: micro- and nano-electronics, solid state physics, physics of semiconductors, magnetic materials physics, spin-polarized current sources. (author)

  19. Room temperature electrodeposition of aluminum antimonide compound semiconductor

    International Nuclear Information System (INIS)

    Gandhi, T.; Raja, K.S.; Misra, M.

    2008-01-01

    AlSb is a group III-V compound semiconductor material that is conventionally grown by high temperature processes such as Czochralski and Bridgman methods. Development of a method to synthesize AlSb at room temperature will be more economical to help modulate the electronic properties. In this investigation, a pulsed potential electrodeposition method using a room temperature molten salt system (aluminum trichloride, AlCl 3 /1-methyl-3-ethylimidazolium chloride, EMIC) with an addition of SbCl 3 is discussed. The potential pulse parameters were established by carrying out cyclic voltammetry at different concentrations of SbCl 3 and with varying molar ratios of AlCl 3 /EMIC. Stoichiometric AlSb deposits were obtained from an acidic AlCl 3 /EMIC (1.5:1 molar ratio) melt containing 4 x 10 -3 mol/l of SbCl 3 onto an ordered TiO 2 nanotubular template. The AlSb compound was predominantly amorphous in as-deposited condition and annealing at 350 deg. C for 2 h in argon transformed into crystalline phase. The AlSb deposit showed a high resistivity in the order of 10 9 Ω-cm and a defect concentration of 10 16 cm -3 which was attributed to presence of carbon. The deposits obtained from a basic melt (0.67:1 molar ratio of AlCl 3 /EMIC) were enriched with antimony

  20. Semiconductors for room temperature nuclear detector applications

    CERN Document Server

    James, Ralph B

    1995-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The""Willardson and Beer""Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series.

  1. Development of electron holes across the temperature-induced semiconductor-metal transition in Ba1-xSrxCo1-yFeyO3-δ(x, y = 0.2-0.8): a soft x-ray absorption spectroscopy study

    Science.gov (United States)

    Harvey, A. S.; Yang, Z.; Infortuna, A.; Beckel, D.; Purton, J. A.; Gauckler, L. J.

    2009-01-01

    The x-ray absorption spectra of Ba1-xSrxCo1-yFeyO3-δ (BSCF) powders quenched in air from 623 and 1173 K were measured at the oxygen K and transition metal LII,III edges. All the samples show a predominantly Fe high spin ground state of 3d5L character, while the 3d6L Co ions are intermediate spin at 623 K and high spin at 1173 K. Further changes in the metal LII,III peaks caused by higher temperature quenching are attributed to changes in symmetry around the cations associated with oxygen loss. The oxygen K spectra show the development of unoccupied states just above the Fermi level for samples quenched from 1173 K. At 1173 K, Ba1-xSrxCo1-yFeyO3-δ shows metallic conductivity, while at 623 K it is a semiconductor; the states developed at high temperature with strong oxygen character are pathways for hole conductivity. Splitting of the transition metal 3d energy levels by the ligand field was observed in the oxygen K spectra, and the range for 10Dq is 1.6-1.8 eV, while the 3d bandwidth is 1.1-1.4 eV in samples quenched from 623 K. On the basis of the soft x-ray absorption results, the classification of Ba1-xSrxCo1-yFeyO3-δ as a material with a negative charge-transfer energy is proposed.

  2. Low temperature production of large-grain polycrystalline semiconductors

    Science.gov (United States)

    Naseem, Hameed A [Fayetteville, AR; Albarghouti, Marwan [Loudonville, NY

    2007-04-10

    An oxide or nitride layer is provided on an amorphous semiconductor layer prior to performing metal-induced crystallization of the semiconductor layer. The oxide or nitride layer facilitates conversion of the amorphous material into large grain polycrystalline material. Hence, a native silicon dioxide layer provided on hydrogenated amorphous silicon (a-Si:H), followed by deposited Al permits induced crystallization at temperatures far below the solid phase crystallization temperature of a-Si. Solar cells and thin film transistors can be prepared using this method.

  3. High-Temperature, Wirebondless, Ultracompact Wide Bandgap Power Semiconductor Modules

    Science.gov (United States)

    Elmes, John

    2015-01-01

    Silicon carbide (SiC) and other wide bandgap semiconductors offer great promise of high power rating, high operating temperature, simple thermal management, and ultrahigh power density for both space and commercial power electronic systems. However, this great potential is seriously limited by the lack of reliable high-temperature device packaging technology. This Phase II project developed an ultracompact hybrid power module packaging technology based on the use of double lead frames and direct lead frame-to-chip transient liquid phase (TLP) bonding that allows device operation up to 450 degC. The new power module will have a very small form factor with 3-5X reduction in size and weight from the prior art, and it will be capable of operating from 450 degC to -125 degC. This technology will have a profound impact on power electronics and energy conversion technologies and help to conserve energy and the environment as well as reduce the nation's dependence on fossil fuels.

  4. Faraday effect in Cd1-xMnxTe semimagnetic semiconductor

    International Nuclear Information System (INIS)

    Vatamanyuk, P.P.; Savitskij, A.V.; Savchuk, A.I.; Ul'yanitskij, K.S.

    1988-01-01

    The Faraday effect is investigated in the semimagnetic semiconductor Cd 1-x Mn x Te (0≥x≤0.3) in the spectral range from 0.6 to 1.8 eV at temperatures between 4.2 and 350 K and in magnetic fields up to 250 kOe. Some peculiarities in the dispersion of the Faraday rotation (FR) are observed which are connected with a change in the direction of rotation depending on the composition and temperature. The results are analyzed by assuming the FR to consist of three components: an interband, exciton and intracentral contribution. The deviation of FR from saturation in strong magnetic fields is interpreted within the framework of antiferromagnetic exchange interaction between the Mn 2+ ions. On the basis of an analysis of the FR temperature dependence it is suggested that the spontaneous Faraday effect is characteristic of semimagnetic semiconductors in spin glass phase

  5. New magnetic semiconductors CuCr1.5+xSb0.5-xS4 (0<=x<=0.3)

    Science.gov (United States)

    Saifullaeva, Dilaram; Solieva, Shahlo; Muminov, Asamat

    2002-11-01

    New compounds with spinel structure CuCr1.5+xSb0.5-xS4(0semiconductores. The compounds (0<=x<=0.1) were found to have the magnetic properties characteristic for antiferromagnets. Compounds (0.2<=x<=0.3) have a spontaneous magnetization, with the Curie point of the compound with x=0.3, Tc = 334 K, being higher than room temperature. The re-entrant spin glass transition is observed in the compounds with x=0.17;0.2)

  6. Room temperature electrodeposition of aluminum antimonide compound semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Gandhi, T.; Raja, K.S. [Metallurgical and Materials Engineering, University of Nevada, Mail Stop 388, Reno, NV 89557 (United States); Misra, M. [Metallurgical and Materials Engineering, University of Nevada, Mail Stop 388, Reno, NV 89557 (United States)], E-mail: misra@unr.edu

    2008-10-15

    AlSb is a group III-V compound semiconductor material that is conventionally grown by high temperature processes such as Czochralski and Bridgman methods. Development of a method to synthesize AlSb at room temperature will be more economical to help modulate the electronic properties. In this investigation, a pulsed potential electrodeposition method using a room temperature molten salt system (aluminum trichloride, AlCl{sub 3}/1-methyl-3-ethylimidazolium chloride, EMIC) with an addition of SbCl{sub 3} is discussed. The potential pulse parameters were established by carrying out cyclic voltammetry at different concentrations of SbCl{sub 3} and with varying molar ratios of AlCl{sub 3}/EMIC. Stoichiometric AlSb deposits were obtained from an acidic AlCl{sub 3}/EMIC (1.5:1 molar ratio) melt containing 4 x 10{sup -3} mol/l of SbCl{sub 3} onto an ordered TiO{sub 2} nanotubular template. The AlSb compound was predominantly amorphous in as-deposited condition and annealing at 350 deg. C for 2 h in argon transformed into crystalline phase. The AlSb deposit showed a high resistivity in the order of 10{sup 9} {omega}-cm and a defect concentration of 10{sup 16} cm{sup -3} which was attributed to presence of carbon. The deposits obtained from a basic melt (0.67:1 molar ratio of AlCl{sub 3}/EMIC) were enriched with antimony.

  7. Electronic paramagnetic resonance in the Mn In X (X:Te,S) diluted magnetic semiconductor system

    International Nuclear Information System (INIS)

    Vincent, Bernardo; Betancourt, Luis; Sagredo, Vicente; Alcala, Rafael

    1996-01-01

    Semiconductor compounds wit the II-III-VI stoichiometry are very interesting materials since they present very good semiconducting characteristics and, along with strong magnetic properties, these II Mn In VI compounds have a great potential as opt and magneto-electronic devices. Among the possible magnetic properties of the materials is the presence of the spin-glass phase. Electron paramagnetic resonance is one of the techniques used to confirm this phase. The chosen crystals were chosen by chemical vapor transport. The absorption lines of these two families with 0.1 x 1 were all Lorentzian in shape and centred at g=2. A large broadening of the resonance line width was observed when lowering the temperature to below 80 K. This behaviour was fitted to the known existing models, and good values of the calculated parameters were obtained (author)

  8. New electroluminescent-semiconductor X-Ray detector

    International Nuclear Information System (INIS)

    Vlasenko, N.A.; Kononets, Y.F.; Veligura, L.I.; Braylovsky, E.Y.; Berdnichenko, P.E.; Berdnichenko, S.V.; Kuts, V.I.; Tsyrkunov, Y.A.

    1999-01-01

    X-ray detectors capable of visualization of the spatial distribution of the radiation field are interesting for many applications, especially in medicine. In 50's the attention of researchers has been attracted to the detectors based on a powder electroluminescent (EL) phosphor (e.g. ZnS:Cu) connected in series with a semiconductors (S) sensitive to X-ray (e.g. thick-film CdS) [1,2]. Impedance of the two chosen so that the voltage drop on the EL layer is insufficient to excite electroluminescence in darkness (without X-rays). Under action of X-rays the S-layer resistance is decreased and, as consequence, the voltage on the phosphor increases and EL emission with the intensity dependent on X-ray dose rate arises. However, these 'EL-S' detectors did not of use due to the slow response (several seconds), instability, and low picture contrast. To improve these characteristics, a new variant of the EL-S detector has been studied in this paper. The novelty consists in the use of a thin-film electroluminescent structure (TFELS) and a semiconductor wafer instead of a powder and thick-film layers used earlier. (authors)

  9. X-ray image intensifier camera tubes and semiconductor targets

    International Nuclear Information System (INIS)

    1979-01-01

    A semiconductor target for use in an image intensifier camera tube and a camera using the target are described. The semiconductor wafer for converting an electron image onto electrical signal consists mainly of a collector region, preferably n-type silicon. It has one side for receiving the electron image and an opposite side for storing charge carriers generated in the collector region by high energy electrons forming a charge image. The first side comprises a highly doped surface layer covered with a metal buffer layer permeable to the incident electrons and thick enough to dissipate some of the incident electron energy thereby improving the signal-to-noise ratio. This layer comprises beryllium on niobium on the highly doped silicon surface zone. Low energy Kα X-ray radiation is generated in the first layer, the radiation generated in the second layer (mainly Lα radiation) is strongly absorbed in the silicon layer. A camera tube using such a target with a photocathode for converting an X-ray image into an electron image, means to project this image onto the first side of the semiconductor wafer and means to read out the charge pattern on the second side are also described. (U.K.)

  10. Peculiarities of semiconductor detector performance at low temperatures

    International Nuclear Information System (INIS)

    Afanas'eva, N.P.; Eremin, V.K.; Strokan, N.B.; Shamagdiev, A.Sh.

    1982-01-01

    Temperature dependence of Ge and Si detector signal amplitude is investigated in the temperature range of 180-4.2 K. Main processes conditioning temperature dependence of charging signal amplitude and semiconductor detector resolution are analyzed. Expressions for the evaluation of temperature values corresponding to the most considerable changes in the detector signals are obtained. Amplitude spectra of alpha particles emitted by 238 Pu (Esub(α)=5.495 MeV) recorded by optimazed Si detector at temperatures of 77 and 4.2 K are given. Analysis of the spectra obtained shows that the detector possesses good resolution equal to 29 keV at 77 K and 38 keV at helium temperature. It is concluded that spectrometric properties of Si detectors do not change at helium temperatures [ru

  11. Theory of temperature dependent photoemission spectrum of heavy fermion semiconductors

    International Nuclear Information System (INIS)

    Riseborough, P.S.

    1998-01-01

    The heavy fermion semiconductors are a class of strongly correlated materials, that at high temperatures show properties similar to those of heavy fermion materials, but at low temperatures show a cross-over into a semi-conducting state. The low temperature insulating state is characterized by an anomalously small energy gap, varying between 10 and 100 K. The smallness of the gap is attributed to the result of a many-body renormalization, and is temperature dependent. The temperature dependence of the electronic spectral density of states is calculated, using the Anderson lattice model at half filling. The spectrum is calculated to second order in 1/N, where N is the degeneracy of the 'f' orbitals, using a slave boson technique. The system is an indirect gap semi-conductor, with an extremely temperature dependent electronic spectral density A(k, ω). The indirect gap is subject to a temperature dependent many-body renormalization, and leads to a sharp temperature dependent structure in the angle resolved photo-emission spectrum at the indirect threshold. The theoretical predictions are compared with experimental observations on FeSi. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)

  12. Phonon emission in a degenerate semiconductor at low lattice temperatures

    International Nuclear Information System (INIS)

    Midday, S.; Nag, S.; Bhattacharya, D.P.

    2015-01-01

    The characteristics of phonon growth in a degenerate semiconductor at low lattice temperatures have been studied for inelastic interaction of non-equilibrium electrons with the intravalley acoustic phonons. The energy of the phonon and the full form of the phonon distribution are taken into account. The results reveal significant changes in the growth characteristics compared to the same for a non-degenerate material

  13. A room-temperature magnetic semiconductor from a ferromagnetic metallic glass

    OpenAIRE

    Liu, Wenjian; Zhang, Hongxia; Shi, Jin-an; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V.; Chen, Mingwei; Yao, Kefu; Chen, Na

    2016-01-01

    Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III?V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make dilu...

  14. Stable room-temperature thallium bromide semiconductor radiation detectors

    Science.gov (United States)

    Datta, A.; Fiala, J.; Becla, P.; Motakef, Shariar

    2017-10-01

    Thallium bromide (TlBr) is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br- species, with an estimated electro-diffusion velocity of 10-8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br- ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation) for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

  15. Stable room-temperature thallium bromide semiconductor radiation detectors

    Directory of Open Access Journals (Sweden)

    A. Datta

    2017-10-01

    Full Text Available Thallium bromide (TlBr is a highly efficient ionic semiconductor with excellent radiation detection properties. However, at room temperature, TlBr devices polarize under an applied electric field. This phenomenon not only degrades the charge collection efficiency of the detectors but also promotes chemical reaction of the metal electrodes with bromine, resulting in an unstable electric field and premature failure of the device. This drawback has been crippling the TlBr semiconductor radiation detector technology over the past few decades. In this exhaustive study, this polarization phenomenon has been counteracted using innovative bias polarity switching schemes. Here the highly mobile Br− species, with an estimated electro-diffusion velocity of 10−8 cm/s, face opposing electro-migration forces during every polarity switch. This minimizes the device polarization and availability of Br− ions near the metal electrode. Our results indicate that it is possible to achieve longer device lifetimes spanning more than 17 000 h (five years of 8 × 7 operation for planar and pixelated radiation detectors using this technique. On the other hand, at constant bias, 2500 h is the longest reported lifetime with most devices less than 1000 h. After testing several biasing switching schemes, it is concluded that the critical bias switching frequency at an applied bias of 1000 V/cm is about 17 μHz. Using this groundbreaking result, it will now be possible to deploy this highly efficient room temperature semiconductor material for field applications in homeland security, medical imaging, and physics research.

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

    Science.gov (United States)

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

    2017-08-01

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

  17. Dual-Energy Semiconductor Detector of X-rays and Gamma Radiation

    Directory of Open Access Journals (Sweden)

    Brodyn, M.S.

    2014-03-01

    Full Text Available Analysis of the major types of ionizing radiation detectors, their advantages and disadvantages are presented. Application of ZnSe-based semiconductor detector in high temperature environment is substantiated. Different forms of ZnSe-based detector samples and double-crystal scheme for registration of X- and gamma rays in a broad energy range were used . Based on the manufactured simulator device, the study sustains the feasibility of the gamma quanta recording by a high-resistance ZnSe-based detector operating in a perpulse mode.

  18. An investigation of performance characteristics of a pixellated room-temperature semiconductor detector for medical imaging

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, P; Santos, A [Centro de Investigacion Biomedica de Bioningenieria, Biomateriales y Nanomedicina, CEEI-Modulo 3, C/ Maria de Luna, 11, 50018 Zaragoza (United States); Darambara, D G, E-mail: pguerra@ciber-bbn.e [Joint Department of Physics, Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Fulham Road, London SW3 6JJ (United Kingdom)

    2009-09-07

    The operation of any semiconductor detector depends on the movement of the charge carriers, which are created within the material when radiation passes through, as a result of energy deposition. The carrier movement in the bulk semiconductor induces charges on the metal electrodes, and therefore a current on the electrodes and the external circuit. The induced charge strongly depends on the material transport parameters as well as the geometrical dimensions of a pixellated semiconductor detector. This work focuses on the performance optimization in terms of energy resolution, detection efficiency and intrinsic spatial resolution of a room-temperature semiconductor pixellated detector based on CdTe/CdZnTe. It analyses and inter-relates these performance figures for various dimensions of CdTe and CdZnTe detectors and for an energy range spanning from x-ray (25 keV) to PET (511 keV) imaging. Monte Carlo simulations, which integrate a detailed and accurate noise model, are carried out to investigate several CdTe/CdZnTe configurations and to determine possible design specifications. Under the considered conditions, the simulations demonstrate the superiority of the CdZnTe over the CdTe in terms of energy resolution and sensitivity in the photopeak. Further, according to the results, the spatial resolution is maximized at high energies and the energy resolution at low energies, while a reasonable detection efficiency is achieved at high energies, with a 1 x 1 x 6 mm{sup 3} CdZnTe pixellated detector.

  19. An investigation of performance characteristics of a pixellated room-temperature semiconductor detector for medical imaging

    International Nuclear Information System (INIS)

    Guerra, P; Santos, A; Darambara, D G

    2009-01-01

    The operation of any semiconductor detector depends on the movement of the charge carriers, which are created within the material when radiation passes through, as a result of energy deposition. The carrier movement in the bulk semiconductor induces charges on the metal electrodes, and therefore a current on the electrodes and the external circuit. The induced charge strongly depends on the material transport parameters as well as the geometrical dimensions of a pixellated semiconductor detector. This work focuses on the performance optimization in terms of energy resolution, detection efficiency and intrinsic spatial resolution of a room-temperature semiconductor pixellated detector based on CdTe/CdZnTe. It analyses and inter-relates these performance figures for various dimensions of CdTe and CdZnTe detectors and for an energy range spanning from x-ray (25 keV) to PET (511 keV) imaging. Monte Carlo simulations, which integrate a detailed and accurate noise model, are carried out to investigate several CdTe/CdZnTe configurations and to determine possible design specifications. Under the considered conditions, the simulations demonstrate the superiority of the CdZnTe over the CdTe in terms of energy resolution and sensitivity in the photopeak. Further, according to the results, the spatial resolution is maximized at high energies and the energy resolution at low energies, while a reasonable detection efficiency is achieved at high energies, with a 1 x 1 x 6 mm 3 CdZnTe pixellated detector.

  20. Optical, Electrical and Photocatalytic Properties of the Ternary Semiconductors ZnxCd1-xS, CuxCd1-xS and CuxZn1-xS

    Directory of Open Access Journals (Sweden)

    Sandra Andrea Mayén-Hernández

    2014-01-01

    Full Text Available The effects of vacuum annealing at different temperatures on the optical, electrical and photocatalytic properties of polycrystalline and amorphous thin films of the ternary semiconductor alloys ZnxCd1-xS, CuxCd1-xS and CuxZn1-xS were investigated in stacks of binary semiconductors obtained by chemical bath deposition. The electrical properties were measured at room temperature using a four-contact probe in the Van der Pauw configuration. The energy band gap of the films varied from 2.30 to 2.85 eV. The photocatalytic activity of the semiconductor thin films was evaluated by the degradation of an aqueous methylene blue solution. The thin film of ZnxCd1-xS annealed under vacuum at 300°C exhibited the highest photocatalytic activity.

  1. Nanoscale semiconductor Pb{sub 1-x}Sn{sub x}Se (x = 0.2) thin films synthesized by electrochemical atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Lin Shaoxiong; Zhang Xin; Shi Xuezhao; Wei Jinping; Lu Daban; Zhang Yuzhen; Kou Huanhuan [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Wang Chunming, E-mail: wangcm@lzu.edu.cn [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-04-15

    In this paper the fabrication and characterization of IV-VI semiconductor Pb{sub 1-x}Sn{sub x}Se (x = 0.2) thin films on gold substrate by electrochemical atomic layer deposition (EC-ALD) method at room temperature are reported. Cyclic voltammetry (CV) is used to determine approximate deposition potentials for each element. The amperometric I-t technique is used to fabricate the semiconductor alloy. The elements are deposited in the following sequence: (Se/Pb/Se/Pb/Se/Pb/Se/Pb/Se/Sn ...), each period is formed using four ALD cycles of PbSe followed by one cycle of SnSe. Then the deposition manner above is cyclic repeated till a satisfactory film with expected thickness of Pb{sub 1-x}Sn{sub x}Se is obtained. The morphology of the deposit is observed by field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) pattern is used to study its crystalline structure; X-ray photoelectron spectroscopy (XPS) of the deposit indicates an approximate ratio 1.0:0.8:0.2 of Se, Pb and Sn, as the expected stoichiometry for the deposit. Open-circuit potential (OCP) studies indicate a good p-type property, and the good optical activity makes it suitable for fabricating a photoelectric switch.

  2. Low temperature properties of the magnetic semiconductor TmTe

    International Nuclear Information System (INIS)

    Matsumura, Takeshi; Nakamura, Shintaro; Goto, Terutaka; Amitsuka, Hiroshi; Matsuhira, Kazuyuki; Sakakibara; Toshiro; Suzuki, Takashi

    1998-01-01

    The magnetic susceptibility, elastic constant, specific heat and magnetization of the magnetic semiconductor TmTe have been measured in detail. A phase transition which is likely to be an antiferro quadrupolar ordering was found to occur at 1.8 K. The specific heat measurements under magnetic fields along the three main crystal axes revealed the unusual characters of this phase transition. The (H-T) phase diagram below 5 T is very similar to that of the antiferro quadrupolar ordering in CeB 6 . Above 5 T, however, the phase line for H parallels (100) begins to close toward T = 0 K. The physical properties in the paramagnetic region at high temperatures are discussed in the mean field approximation. The theoretical fitting of the elastic softening indicates the antiferro inter-ionic quadrupolar interactions. However, the mean field theory can not explain the specific heat results. (author). 50 refs

  3. Wide Bandgap Semiconductor Detector Optimization for Flash X-Ray Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Roecker, Caleb Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schirato, Richard C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-17

    Charge trapping, resulting in a decreased and spatially dependent electric field, has long been a concern for wide bandgap semiconductor detectors. While significant work has been performed to characterize this degradation at varying temperatures and radiation environments, this work concentrates upon examining the event-to-event response in a flash X-ray environment. The following work investigates if charge trapping is a problem for CZT detectors, with particular emphasis on flash X-ray radiation fields at cold temperatures. Results are compared to a non-flash radiation field, using an Am-241 alpha source and similar temperature transitions. Our ability to determine if a response change occurred was hampered by the repeatability of our flash X-ray systems; a small response change was observed with the Am-241 source. Due to contrast of these results, we are in the process of revisiting the Am-241 measurements in the presence of a high radiation environment. If the response change is more pronounced in the high radiation environment, a similar test will be performed in the flash X-ray environment.

  4. InSb:Mn - A high temperature ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Laehderanta, E.; Lashkul, A.V. [Lappeenranta University of Technology (Finland); Kochura, A.V. [Lappeenranta University of Technology (Finland); South-West State University, Kursk (Russian Federation); Lisunov, K.G. [Lappeenranta University of Technology (Finland); Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev (Moldova, Republic of); Aronzon, B.A. [Lappeenranta University of Technology (Finland); RRC ' ' Kurchatov Institute' ' , Moscow (Russian Federation); Shakhov, M.A. [Lappeenranta University of Technology (Finland); A.F. Ioffe Physico-Technical Institute, St. Petersburg (Russian Federation)

    2014-05-15

    Diluted magnetic semiconductor InSb:Mn exhibits a ferromagnetic behavior up to T ∝ 600 K due to presence of nanosize MnSb precipitates [Kochura et al., J. Appl. Phys. 113, 083905 (2013)]. Transport properties of InSb:Mn, including the resistivity, the magnetoresistance (MR), and the Hall effect, are investigated between T ∝ 1.6 and 300 K in magnetic fields B up to 15 T. The resistivity, ρ(T), displays an upturn with lowering the temperature below T ∝ 10-20 K attributable to the Kondo effect, where the universal Kondo behavior is observed. The Hall resistivity, ρ{sub H}, demonstrates a nonlinear dependence on B up to T ∝ 300 K, suggesting an anomalous contribution due to the effect of the MnSb nanoprecipitates. The relative MR, Δρ(B)/ρ(0), is positive (pMR) above T ∝ 10 K and transforms into a negative one (nMR) with lowering temperature. The Hall effect and pMR are interpreted simultaneously with the two-band model, addressed to presence of the two types of holes with quite different concentrations and mobilities. The dependences of nMR on B and T follow those of the Khosla-Fischer model, taking into account damping of the spin-dependent scattering of charge carriers in magnetic field. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Equation of states and melting temperatures of diamond cubic and zincblende semiconductors: pressure dependence

    Energy Technology Data Exchange (ETDEWEB)

    Hung, V V; Hanh, P T M [Hanoi National Pedagogic University, Km8 Hanoi-Sontay Highway, Hanoi (Viet Nam); Masuda-Jindo, K [Department of Material Science and Engineering, Tokyo Institute of Technology, Nagasuta, Midori-ku, Yokohama 226-8503 (Japan); Hai, N T [Hanoi University of Technology, 01 Dai Co Viet Road, Hanoi (Viet Nam)], E-mail: kmjindo@issp.u-tokyo.ac.jp

    2008-02-15

    The pressure dependence of the melting temperatures of tetrahedrally coordinated semiconductors are studied using the equation of states derived from the statistical moment method, in comparison with those of the normal metals. Using the general expressions of the limiting temperatures T{sub m}, we calculate the 'melting' temperatures of the semiconductor crystals and normal metals as a function of the hydrostatic pressure. The physical origins for the inverse pressure dependence of T{sub m} observed for tetrahedrally coordinated semiconductors are also discussed.

  6. Tunability of room-temperature ferromagnetism in spintronic semiconductors through nonmagnetic atoms

    Science.gov (United States)

    Leedahl, Brett; Abooalizadeh, Zahra; LeBlanc, Kyle; Moewes, Alexander

    2017-07-01

    The implementation and control of room-temperature ferromagnetism (RTFM) by adding magnetic atoms to a semiconductor's lattice has been one of the most important problems in solid-state physics in the last decade. Herein we report on the mechanism that allows RTFM to be tuned by the inclusion of nonmagnetic aluminum in nickel ferrite. This material, NiFe2 -xAlxO4 (x =0 ,0.5 ,1.5 ), has already shown much promise for magnetic semiconductor technologies, and we are able to add to its versatility technological viability with our results. The site occupancies and valencies of Fe atoms (Fe3 +Td , Fe2 +Oh , and Fe3 +Oh ) can be methodically controlled by including aluminum. Using the fact that aluminum strongly prefers a 3+ octahedral environment, we can selectively fill iron sites with aluminum atoms, and hence specifically tune the magnetic contributions for each of the iron sites, and therefore the bulk material as well. Interestingly, the influence of the aluminum is weak on the electronic structure, allowing one to retain the desirable electronic properties while achieving desirable magnetic properties.

  7. Effect of Temperature on Photonic Band Gaps in Semiconductor-Based One-Dimensional Photonic Crystal

    Directory of Open Access Journals (Sweden)

    J. V. Malik

    2013-01-01

    Full Text Available The effect of the temperature and angle of incidence on the photonic band gap (PBG for semiconductor-based photonic crystals has been investigated. The refractive index of semiconductor layers is taken as a function of temperature and wavelength. Three structures have been analyzed by choosing a semiconductor material for one of the two materials in a bilayer structure. The semiconductor material is taken to be ZnS, Si, and Ge with air in first, second, and third structures respectively. The shifting of band gaps with temperature is more pronounced in the third structure than in the first two structures because the change in the refractive index of Ge layers with temperature is more than the change of refractive index of both ZnS and Si layers with temperature. The propagation characteristics of the proposed structures are analyzed by transfer matrix method.

  8. Semiconductor terahertz technology devices and systems at room temperature operation

    CERN Document Server

    Carpintero, G; Hartnagel, H; Preu, S; Raisanen, A

    2015-01-01

    Key advances in Semiconductor Terahertz (THz) Technology now promises important new applications enabling scientists and engineers to overcome the challenges of accessing the so-called "terahertz gap".  This pioneering reference explains the fundamental methods and surveys innovative techniques in the generation, detection and processing of THz waves with solid-state devices, as well as illustrating their potential applications in security and telecommunications, among other fields. With contributions from leading experts, Semiconductor Terahertz Technology: Devices and Systems at Room Tempe

  9. Room Temperature Hard Radiation Detectors Based on Solid State Compound Semiconductors: An Overview

    Science.gov (United States)

    Mirzaei, Ali; Huh, Jeung-Soo; Kim, Sang Sub; Kim, Hyoun Woo

    2018-03-01

    Si and Ge single crystals are the most common semiconductor radiation detectors. However, they need to work at cryogenic temperatures to decrease their noise levels. In contrast, compound semiconductors can be operated at room temperature due to their ability to grow compound materials with tunable densities, band gaps and atomic numbers. Highly efficient room temperature hard radiation detectors can be utilized in biomedical diagnostics, nuclear safety and homeland security applications. In this review, we discuss room temperature compound semiconductors. Since the field of radiation detection is broad and a discussion of all compound materials for radiation sensing is impossible, we discuss the most important materials for the detection of hard radiation with a focus on binary heavy metal semiconductors and ternary and quaternary chalcogenide compounds.

  10. Particle detection with semiconductor thermistors at low temperatures

    International Nuclear Information System (INIS)

    Wang, N.; Beeman, J.; Cleland, A.N.

    1988-11-01

    We have studied the use of neutron transmutation doped (NTD) Ge thermistors as phonon sensors at dilution refrigerator temperatures. In addition to measuring their thermal and electrical properties, we have observed pulses generated by X-rays incident on a thermistor thermally well-clamped to a heat sink. We find that during these pulses the lattice temperature of the thermistor apparently does not change. This surprising result is interpreted as evidence of a strong coupling between the high energy phonons generated by the interaction and the charge carriers in the thermistor. Additionally, these phonons appear to be absorbed within a fraction of a millimeter. We conclude that these thermistors have several desirable properties for a good high energy phonon sensor. It remains to be seen, however, if a composite detector consisting of a large crystal and attached phonon sensors can be developed. 15 refs., 9 figs

  11. Particle detection with semiconductor thermistors at low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, N.; Beeman, J.; Cleland, A.N.; Cummings, A.; Lange, A.; Ross, R.; Sadoulet, B.; Steiner, H.; Shutt, T.; Wellstood, F.C.

    1988-11-01

    We have studied the use of neutron transmutation doped (NTD) Ge thermistors as phonon sensors at dilution refrigerator temperatures. In addition to measuring their thermal and electrical properties, we have observed pulses generated by X-rays incident on a thermistor thermally well-clamped to a heat sink. We find that during these pulses the lattice temperature of the thermistor apparently does not change. This surprising result is interpreted as evidence of a strong coupling between the high energy phonons generated by the interaction and the charge carriers in the thermistor. Additionally, these phonons appear to be absorbed within a fraction of a millimeter. We conclude that these thermistors have several desirable properties for a good high energy phonon sensor. It remains to be seen, however, if a composite detector consisting of a large crystal and attached phonon sensors can be developed. 15 refs., 9 figs.

  12. Hard x-ray emission spectroscopy: a powerful tool for the characterization of magnetic semiconductors

    OpenAIRE

    Rovezzi, Mauro; Glatzel, Pieter

    2013-01-01

    This review aims to introduce the x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS) techniques to the materials scientist working with magnetic semiconductors (e.g. semiconductors doped with 3d transition metals) for applications in the field of spin-electronics. We focus our attention on the hard part of the x-ray spectrum (above 3 keV) in order to demonstrate a powerful element- and orbital-selective characterization tool in the study of bulk electronic struct...

  13. Ferrimagnetic resonance study on photo-induced magnetism in hybrid magnetic semiconductor V(TCNE)x, x ˜2 film

    Science.gov (United States)

    Yoo, Jung-Woo; Shima Edelstein, R.; Lincoln, D. M.; Epstein, A. J.

    2007-03-01

    The V(TCNE)x, x˜2 is a fully spin-polarized magnetic semiconductor, whose magnetic order exceeds room temperature (Tc > 350 K), and electronic transport follows hopping mechanism through the Coulomb energy split &*circ; subband. In addition, it was determined that this material has thermally reversible persistent change in both magnetism and conductivity driven by the optical excitation [1]. Here, we report detailed investigation on photo-induced magnetism in V(TCNE)x by employing ferrimagnetic resonance (PIFMR) study with an in-situ light illumination. Upon optical excitation (λ˜ 457.9 nm), the FMR spectra display substantial change in their linewidth and resonance field. Angular dependence analyses of line shift indicate the increase of unixial anisotropy field in the film caused by the light irradiation. The results demonstrated that the change in overall magnetic anisotropy by the illumination plays an important role in inducing photo- induced magnetism in (TCNE) class magnet. [1] J.-W. Yoo, et al. to be published in Phys. Rev. Lett.

  14. Temperature-dependent resonance energy transfer from semiconductor quantum wells to graphene.

    Science.gov (United States)

    Yu, Young-Jun; Kim, Keun Soo; Nam, Jungtae; Kwon, Se Ra; Byun, Hyeryoung; Lee, Kwanjae; Ryou, Jae-Hyun; Dupuis, Russell D; Kim, Jeomoh; Ahn, Gwanghyun; Ryu, Sunmin; Ryu, Mee-Yi; Kim, Jin Soo

    2015-02-11

    Resonance energy transfer (RET) has been employed for interpreting the energy interaction of graphene combined with semiconductor materials such as nanoparticles and quantum-well (QW) heterostructures. Especially, for the application of graphene as a transparent electrode for semiconductor light emitting diodes, the mechanism of exciton recombination processes such as RET in graphene-semiconductor QW heterojunctions should be understood clearly. Here, we characterized the temperature-dependent RET behaviors in graphene/semiconductor QW heterostructures. We then observed the tuning of the RET efficiency from 5% to 30% in graphene/QW heterostructures with ∼60 nm dipole-dipole coupled distance at temperatures of 300 to 10 K. This survey allows us to identify the roles of localized and free excitons in the RET process from the QWs to graphene as a function of temperature.

  15. High Temperature Superconductor/Semiconductor Hybrid Microwave Devices and Circuits

    Science.gov (United States)

    Romanofsky, Robert R.; Miranda, Felix A.

    1999-01-01

    Contents include following: film deposition technique; laser ablation; magnetron sputtering; sequential evaporation; microwave substrates; film characterization at microwave frequencies; complex conductivity; magnetic penetration depth; surface impedance; planar single-mode filters; small antennas; antenna arrays phase noise; tunable oscillations; hybrid superconductor/semiconductor receiver front ends; and noise modeling.

  16. Searching Room Temperature Ferromagnetism in Wide Gap Semiconductors Fe-doped Strontium Titanate and Zinc Oxide

    CERN Document Server

    Pereira, LMC; Wahl, U

    Scientific findings in the very beginning of the millennium are taking us a step further in the new paradigm of technology: spintronics. Upgrading charge-based electronics with the additional degree of freedom of the carriers spin-state, spintronics opens a path to the birth of a new generation of devices with the potential advantages of non-volatility and higher processing speed, integration densities and power efficiency. A decisive step towards this new age lies on the attribution of magnetic properties to semiconductors, the building block of today's electronics, that is, the realization of ferromagnetic semiconductors (FS) with critical temperatures above room temperature. Unfruitful search for intrinsic RT FS lead to the concept of Dilute(d) Magnetic Semiconductors (DMS): ordinary semiconductor materials where 3 d transition metals randomly substitute a few percent of the matrix cations and, by some long-range mechanism, order ferromagnetically. The times are of intense research activity and the last fe...

  17. Hybrid High-Temperature-Superconductor–Semiconductor Tunnel Diode

    Directory of Open Access Journals (Sweden)

    Alex Hayat

    2012-12-01

    Full Text Available We report the demonstration of hybrid high-T_{c}-superconductor–semiconductor tunnel junctions, enabling new interdisciplinary directions in condensed matter research. The devices are fabricated by our newly developed mechanical-bonding technique, resulting in high-T_{c}-superconductor–semiconductor tunnel diodes. Tunneling-spectra characterization of the hybrid junctions of Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} combined with bulk GaAs, or a GaAs/AlGaAs quantum well, exhibits excess voltage and nonlinearity, similarly to spectra obtained in scanning-tunneling microscopy, and is in good agreement with theoretical predictions for a d-wave-superconductor–normal-material junction. Additional junctions are demonstrated using Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} combined with graphite or Bi_{2}Te_{3}. Our results pave the way for new methods in unconventional superconductivity studies, novel materials, and quantum technology applications.

  18. Donor type semiconductor at low temperature as maser active medium

    OpenAIRE

    Kornyushin, Yuri

    2007-01-01

    In some semiconductors donor impurity atoms can attract additional electrons, forming negative donor impurity ions. Thus we have 3 energy levels for electrons: zero energy levels at the bottom of the conductivity band, negative energy levels of the bounded electrons of the negative donor impurity ions, and deeper negative energy levels of the outer electrons of the neutral donor impurity atoms. So the donor impurity atoms could serve as active centres for a maser. The maximum achievable relat...

  19. Temperature dependence of muon-decay positron channeling in semiconductors

    International Nuclear Information System (INIS)

    Simmler, H.; Eschle, P.; Keller, H.; Kuendig, W.; Odermatt, W.; Patterson, B.D.; Puempin, B.; Savic, I.M.; Schneider, J.W.; Straumann, U.; Truoel, P.

    1991-01-01

    Planar channeling data of μ + -decay positrons in various semiconductors are reported. Together with the extensive spectroscopic data supplied by transverse μSR, the location of the different states of the hydrogen pseudo-isotope μ + e - (muonium) can be identified by means of planar simulations. In high purity silicon as well as in gallium arsenide a thermally activated site transition is observed which can be assigned to a transition between different muonium states. (orig.)

  20. Origin and control of high-temperature ferromagnetism in semiconductors

    Science.gov (United States)

    Kuroda, Shinji; Nishizawa, Nozomi; Takita, Kôki; Mitome, Masanori; Bando, Yoshio; Osuch, Krzysztof; Dietl, Tomasz

    2007-06-01

    The extensive experimental and computational search for multifunctional materials has resulted in the development of semiconductor and oxide systems, such as (Ga,Mn)N, (Zn,Cr)Te and HfO2, which exhibit surprisingly stable ferromagnetic signatures despite having a small or nominally zero concentration of magnetic elements. Here, we show that the ferromagnetism of (Zn,Cr)Te, and the associated magnetooptical and magnetotransport functionalities, are dominated by the formation of Cr-rich (Zn,Cr)Te metallic nanocrystals embedded in the Cr-poor (Zn,Cr)Te matrix. Importantly, the formation of these nanocrystals can be controlled by manipulating the charge state of the Cr ions during the epitaxy. The findings provide insight into the origin of ferromagnetism in a broad range of semiconductors and oxides, and indicate possible functionalities of these composite systems. Furthermore, they demonstrate a bottom-up method for self-organized nanostructure fabrication that is applicable to any system in which the charge state of a constituent depends on the Fermi-level position in the host semiconductor.

  1. In situ X-ray synchrotron study of organic semiconductor ultra-thin films growth

    International Nuclear Information System (INIS)

    Moulin, J.-F.; Dinelli, F.; Massi, M.; Albonetti, C.; Kshirsagar, R.; Biscarini, F.

    2006-01-01

    In this work we present an X-ray diffraction study of the early stages of growth of an organic semiconductor (sexithiophene, T 6 ) thin film prepared by high vacuum sublimation. Specular reflectometry and grazing incidence X-ray diffraction were used to monitor the formation of T 6 films on silicon oxide. Our results show that T 6 grows as a crystalline layer from the beginning of the evaporation. The reflectometry analysis suggests that, in the range of rates and temperatures studied, the growth is never layer by layer but rather 3D in nature. In-plane GIXD has allowed us to observe for the first time a thin film phase of T 6 formed of molecules standing normal to the substrate and arranged in a compressed unit cell with respect to the bulk, i.e. the unit cell parameters b and c are relatively smaller. We have followed the dynamics of formation of this new phase and identified the threshold of appearance of the bulk phase, which occurs above ∼5-6 monolayers. These results are relevant to the problem of organic thin film transistors, for which we have previously demonstrated experimentally that only the first two monolayers of T 6 films are involved in the electrical transport. The layers above the second one do not effectively contribute to charge mobility, either because they are more 'disordered' or because of a screening of the gate field

  2. Distinction of gases with a semiconductor sensor depending on the scanning profile of a cyclic temperature.

    Science.gov (United States)

    Nakata, Satoshi; Okunishi, Hirokazu; Nakashima, Yusuke

    2006-01-01

    A gas-sensing system based on a dynamic nonlinear response is reported to improve the selectivity in the sensor response toward sample gases. A cyclic temperature composed of fundamental and second harmonics was applied to a SnO(2) semiconductor gas sensor and the resulting conductance of the sensor was analyzed by fast Fourier transformation (FFT). The dynamic nonlinear responses to the gas species were further characterized depending on the scanning profile of the temperature. These characteristic sensor responses under the application of second-harmonic perturbation were theoretically considered based on a reaction-diffusion model for the semiconductor surface.

  3. Study of semiconductor detectors applied to diagnostic X-ray

    International Nuclear Information System (INIS)

    Salgado, Cesar Marques

    2003-08-01

    This work aims an evaluation of procedures for photons spectrum determination, produced by a X ray tube, normally used for medical diagnoses which operation voltage ranges from 20 to 150 kVp, to allow more precise characterization of the photon beam. The use of spectrum analysis will contribute to reduce the uncertainty in the ionization camera calibrations. For this purpose, two kind of detectors were selected, a Cadmium Zinc Telluride (CZT) and a planar HPGe detector. The X ray interaction with the detector's crystal produces, by electronic processes, a pulse high distribution as an output, which is no the true photon spectrum, due to the presence of K shell escape peaks, Compton scattering and to the fact that the detectors efficiency diminish rapidly with the increase of the photon energy. A detailed analysis of the contributing factors to distortions in the spectrum is necessary and was performed by Monte Carlo calculation with the MCNP 4B computer code. In order to determine the actual photon spectrum for a X ray tube a spectra stripping procedure is described for the HPGe detector. The detector's response curves, determined by the Monte Carlo calculation, were compared to the experimental ones, for isotropic point sources. For the methodology validation, stripped spectra were compared to the theoretical ones, for the same X ray tube's settings, for a qualitative evaluation. The air kerma rate calculated with the photon spectra were compared to the direct measurement using an ionization chamber, for a quantitative evaluation. (author)

  4. Ultrahigh sensitive temperature sensor based on graphene-semiconductor metamaterial

    Science.gov (United States)

    Keshavarz, A.; Zakery, A.

    2017-12-01

    In this paper, we theoretically describe a nanoscale THz metamaterial, consisting of a graphene H-shaped that is located on an indium antimonide (InSb) substrate. This metamaterial in its simulated transmission spectrum exhibits a filtering effect and at a specific frequency, the percentage of light passing through the metamaterial is greatly reduced. Since the optical properties of graphene and InSb strongly depend on temperature, as the temperature changes, the frequency of resonance is also shifted. Thus we can expect our structure is suitable for ultrahigh sensitive temperature sensors. The temperature sensor presented is very sensitive with a sensitivity of 1814 nm/{°C} which is very high compared to other designed structures. This THz temperature sensor can play an important role for high-accurate temperature measurements.

  5. Magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bihler, Christoph

    2009-04-15

    In this thesis we investigated in detail the properties of Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P, and Ga{sub 1-x}Mn{sub x}N dilute magnetic semiconductor thin films with a focus on the magnetic anisotropy and the changes of their properties upon hydrogenation. We applied two complementary spectroscopic techniques to address the position of H in magnetic semiconductors: (i) Electron paramagnetic resonance, which provides direct information on the symmetry of the crystal field of the Mn{sup 2+} atoms and (ii) x-ray absorption fine structure analysis which allows to probe the local crystallographic neighborhood of the absorbing Mn atom via analysing the fine structure at the Mn K absorption edge. Finally, we discussed the obstacles that have to be overcome to achieve Curie temperatures above the current maximum in Ga{sub 1-x}Mn{sub x}As of 185 K. Here, we outlined in detail the generic problem of the formation of precipitates at the example of Ge:MN. (orig.)

  6. X-ray measurement with Pin type semiconductor detectors

    International Nuclear Information System (INIS)

    Ramirez J, F.J.

    1999-01-01

    Here are presented the experimental results of the applications of Pin type radiation detectors developed in a National Institute of Nuclear Research (ININ) project, in the measurement of low energy gamma and X-rays. The applications were oriented mainly toward the Medical Physics area. It is planned other applications which are in process of implementation inside the National Institute of Nuclear Research in Mexico. (Author)

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

    Directory of Open Access Journals (Sweden)

    T. M. Pekarek

    2016-05-01

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

  8. High-temperature MEMS Heater Platforms: Long-term Performance of Metal and Semiconductor Heater Materials

    Directory of Open Access Journals (Sweden)

    Theodor Doll

    2006-04-01

    Full Text Available Micromachined thermal heater platforms offer low electrical power consumptionand high modulation speed, i.e. properties which are advantageous for realizing non-dispersive infrared (NDIR gas- and liquid monitoring systems. In this paper, we report oninvestigations on silicon-on-insulator (SOI based infrared (IR emitter devices heated byemploying different kinds of metallic and semiconductor heater materials. Our resultsclearly reveal the superior high-temperature performance of semiconductor over metallicheater materials. Long-term stable emitter operation in the vicinity of 1300 K could beattained using heavily antimony-doped tin dioxide (SnO2:Sb heater elements.

  9. A Two-Temperature Photothermal Interaction in a Semiconductor Medium Containing a Cylindrical Hole

    Science.gov (United States)

    Abbas, Ibrahim A.; Hobiny, Aatef

    2018-01-01

    Photothermoelastic interactions in an infinite semiconductor medium containing a cylindrical hole with two temperatures are studied using mathematical method under the purview of the coupled theory of thermal, plasma and elastic waves. The internal surface of the hole is constrained and the carrier density is photogenerated by bound heat flux with an exponentially decaying pulse. Based on Laplace transform and the eigenvalue approach methodology, the solutions of all variables have been obtained analytically. The numerical computations for silicon-like semiconductor material have been obtained. The results further show that the analytical scheme can overcome mathematical problems to analyze these problems.

  10. First principles investigation of half-metallicity and spin gapless semiconductor in CH3NH3Cr x Pb1- x I3 mixed perovskites

    Science.gov (United States)

    Huang, H. M.; Zhu, Z. W.; Zhang, C. K.; He, Z. D.; Luo, S. J.

    2018-04-01

    The structural, electronic and magnetic properties of organic-inorganic hybrid mixed perovskites CH3NH3Cr x Pb1- x I3 ( x = 0.25, 0.50, 0.75, 1.00) in cubic, tetragonal and orthorhombic phases have been investigated by first-principles calculation. The results indicate that the tetragonal CH3NH3Cr0.75Pb0.25I3 is a spin gapless semiconductor with Curie temperature of 663 K estimated using mean field approximation. All other CH3NH3Cr x Pb1- x I3 mixed perovskites are half-metallic ferromagnets together with 100% spin polarization, and their total magnetic moment are 4.00, 8.00, 12.00 and 16.00 µB per unit cell for x = 0.25, 0.50, 0.75 and 1.00, respectively. The effect of , and orientation of organic cation CH3NH3 + on the electronic properties of CH3NH3Cr0.50Pb0.50I3 was investigated. The results show that the CH3NH3 + in different orientations have a slight effect on the lattice constants, the energy gap in minority-spin states, half-metallic gap, local magnetic moment, and Curie temperature.

  11. X-ray measurement with Pin type semiconductor detectors; Medicion de rayos X con detectores de semiconductor tipo PIN

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez J, F.J. [Instituto Nacional de Investigaciones Nucleares, Departamento de Electronica, C.P. 52045 Salazar, Estado de Mexico (Mexico)

    2000-07-01

    Here are presented the experimental results of the applications of Pin type radiation detectors developed in a National Institute of Nuclear Research (ININ) project, in the measurement of low energy gamma and X-rays. The applications were oriented mainly toward the Medical Physics area. It is planned other applications which are in process of implementation inside the National Institute of Nuclear Research in Mexico. (Author)

  12. The simulation of charge sharing in semiconductor X-ray pixel detectors

    International Nuclear Information System (INIS)

    Mathieson, K.; Bates, R.; O'Shea, V.; Passmore, M.S.; Rahman, M.; Smith, K.M.; Watt, J.; Whitehill, C.

    2002-01-01

    Two simulation packages were used to model the sharing of charge, due to the scattering and diffusion of carriers, between adjacent pixel elements in semiconductors X-ray detectors. The X-ray interaction and the consequent multiple scattering was modelled with the aid of the Monte Carlo package, MCNP. The resultant deposited charge distribution was then used to create the charge cloud profile in the finite element semiconductor simulation code MEDICI. The analysis of the current pulses induced on pixel electrodes for varying photon energies was performed for a GaAs pixel detector. For a pixel pitch of 25 μm, the charge lost to a neighbouring pixel was observed to be constant, at 0.6%, through the energies simulated. Ultimately, a fundamental limit on the pixel element size for imaging and spectroscopic devices may be set due to these key physical principles

  13. The simulation of charge sharing in semiconductor X-ray pixel detectors

    CERN Document Server

    Mathieson, K; O'Shea, V; Passmore, M S; Rahman, M; Smith, K M; Watt, J; Whitehill, C

    2002-01-01

    Two simulation packages were used to model the sharing of charge, due to the scattering and diffusion of carriers, between adjacent pixel elements in semiconductors X-ray detectors. The X-ray interaction and the consequent multiple scattering was modelled with the aid of the Monte Carlo package, MCNP. The resultant deposited charge distribution was then used to create the charge cloud profile in the finite element semiconductor simulation code MEDICI. The analysis of the current pulses induced on pixel electrodes for varying photon energies was performed for a GaAs pixel detector. For a pixel pitch of 25 mu m, the charge lost to a neighbouring pixel was observed to be constant, at 0.6%, through the energies simulated. Ultimately, a fundamental limit on the pixel element size for imaging and spectroscopic devices may be set due to these key physical principles.

  14. Temperature and Dilatation Estimation for Modern Semiconductor Devices

    Directory of Open Access Journals (Sweden)

    Eric JOUBERT

    2015-01-01

    Full Text Available This paper presents a new approach for measuring physical variables on micro- electronic components. An optical system is used to simultaneously quantify the surface temperature of a component and its expansion. This double acquisition is realized by a Michelson interferometer coupled with a Charge Coupled Device (CCD line device. To validate this method, the temperature measurements were directly compared with the results obtained by an infrared camera and by a measurement of variation of I (V. The displacement measurements were compared with those obtained by a laser 3D vibrometer, whose physical principle is completely different. Consistent results were obtained regarding the different techniques.

  15. A note on anomalous band-gap variations in semiconductors with temperature

    Science.gov (United States)

    Chakraborty, P. K.; Mondal, B. N.

    2018-03-01

    An attempt is made to theoretically study the band-gap variations (ΔEg) in semiconductors with temperature following the works, did by Fan and O'Donnell et al. based on thermodynamic functions. The semiconductor band-gap reflects the bonding energy. An increase in temperature changes the chemical bondings, and electrons are promoted from valence band to conduction band. In their analyses, they made several approximations with respect to temperature and other fitting parameters leading to real values of band-gap variations with linear temperature dependences. In the present communication, we have tried to re-analyse the works, specially did by Fan, and derived an analytical model for ΔEg(T). Because, it was based on the second-order perturbation technique of thermodynamic functions. Our analyses are made without any approximations with respect to temperatures and other fitting parameters mentioned in the text, leading to a complex functions followed by an oscillating nature of the variations of ΔEg. In support of the existence of the oscillating energy band-gap variations with temperature in a semiconductor, possible physical explanations are provided to justify the experimental observation for various materials.

  16. High-temperature complementary metal oxide semiconductors (CMOS)

    International Nuclear Information System (INIS)

    McBrayer, J.D.

    1979-10-01

    Silicon CMOS devices were studied, tested, and evaluated at high temperatures to determine processing, geometric, operating characteristics, and stability parameters. After more than 1000 hours at 300 0 C, most devices showed good stability, reliability, and operating characteristics. Processing and geometric parameters were evaluated and optimization steps discussed

  17. High-temperature complementary metal oxide semiconductors (CMOS)

    Energy Technology Data Exchange (ETDEWEB)

    McBrayer, J.D.

    1979-10-01

    Silicon CMOS devices were studied, tested, and evaluated at high temperatures to determine processing, geometric, operating characteristics, and stability parameters. After more than 1000 hours at 300/sup 0/C, most devices showed good stability, reliability, and operating characteristics. Processing and geometric parameters were evaluated and optimization steps discussed.

  18. Radiation damage measurements in room-temperature semiconductor radiation detectors

    CERN Document Server

    Franks, L A; Olsen, R W; Walsh, D S; Vizkelethy, G; Trombka, J I; Doyle, B L; James, R B

    1999-01-01

    The literature of radiation damage measurements on cadmium zinc telluride (CZT), cadmium telluride (CT), and mercuric iodide (HgI sub 2) is reviewed and in the case of CZT supplemented by new alpha particle data. CZT strip detectors exposed to intermediate energy (1.3 MeV) proton fluences exhibit increased interstrip leakage after 10 sup 1 sup 0 p/cm sup 2 and significant bulk leakage after 10 sup 1 sup 2 p/cm sup 2. CZT exposed to 200 MeV protons shows a two-fold loss in energy resolution after a fluence of 5x10 sup 9 p/cm sup 2 in thick (3 mm) planar devices but little effect in 2 mm devices. No energy resolution effects were noted from a moderated fission spectrum of neutrons after fluences up to 10 sup 1 sup 0 n/cm sup 2 , although activation was evident. Exposures of CZT to 5 MeV alpha particles at fluences up to 1.5x10 sup 1 sup 0 alpha/cm sup 2 produced a near linear decrease in peak position with fluence and increases in FWHM beginning at about 7.5x10 sup 9 alpha/cm sup 2. CT detectors show resolution...

  19. Temperature effects in contacts between a metal and a semiconductor nanowire near the degenerate doping

    Science.gov (United States)

    Sun, Zhuting; Burgess, Tim; Tan, H. H.; Jagadish, Chennupati; Kogan, Andrei

    2018-04-01

    We have investigated the nonlinear conductance in diffusion-doped Si:GaAs nanowires contacted by patterned metal films in a wide range of temperatures T. The wire resistance R W and the zero bias resistance R C, dominated by the contacts, exhibit very different responses to temperature changes. While R W shows almost no dependence on T, R C varies by several orders of magnitude as the devices are cooled from room temperature to T = 5 K. We develop a model that employs a sharp donor level very low in the GaAs conduction band and show that our observations are consistent with the model predictions. We then demonstrate that such measurements can be used to estimate carrier properties in nanostructured semiconductors and obtain an estimate for N D, the doping density in our samples. We also discuss the effects of surface states and dielectric confinement on carrier density in semiconductor nanowires.

  20. Indium tin oxide films prepared by atmospheric plasma annealing and their semiconductor-metal conductivity transition around room temperature

    International Nuclear Information System (INIS)

    Li Yali; Li Chunyang; He Deyan; Li Junshuai

    2009-01-01

    We report the synthesis of indium tin oxide (ITO) films using the atmospheric plasma annealing (APA) technique combined with the spin-coating method. The ITO film with a low resistivity of ∼4.6 x 10 -4 Ω cm and a high visible light transmittance, above 85%, was achieved. Hall measurement indicates that compared with the optimized ITO films deposited by magnetron sputtering, the above-mentioned ITO film has a higher carrier concentration of ∼1.21 x 10 21 cm -3 and a lower mobility of ∼11.4 cm 2 V -1 s -1 . More interestingly, these electrical characteristics result in the semiconductor-metal conductivity transition around room temperature for the ITO films prepared by APA.

  1. Heat-Electric Power Conversion Without Temperature Difference Using Only n-Type Ba8Au x Si46-x Clathrate with Au Compositional Gradient

    Science.gov (United States)

    Osakabe, Yuki; Tatsumi, Shota; Kotsubo, Yuichi; Iwanaga, Junpei; Yamasoto, Keita; Munetoh, Shinji; Furukimi, Osamu; Nakashima, Kunihiko

    2018-02-01

    Thermoelectric power generation is typically based on the Seebeck effect under a temperature gradient. However, the heat flux generated by the temperature difference results in low conversion efficiency. Recently, we developed a heat-electric power conversion mechanism using a material consisting of a wide-bandgap n-type semiconductor, a narrow-bandgap intrinsic semiconductor, and a wide-bandgap p-type semiconductor. In this paper, we propose a heat-electric power conversion mechanism in the absence of a temperature difference using only n-type Ba8Au x Si46-x clathrate. Single-crystal Ba8Au x Si46-x clathrate with a Au compositional gradient was synthesized by Czochralski method. Based on the results of wavelength-dispersive x-ray spectroscopy and Seebeck coefficient measurements, the presence of a Au compositional gradient in the sample was confirmed. It also observed that the electrical properties changed gradually from wide-bandgap n-type to narrow-bandgap n-type. When the sample was heated in the absence of a temperature difference, the voltage generated was approximately 0.28 mV at 500°C. These results suggest that only an n-type semiconductor with a controlled bandgap can generate electric power in the absence of a temperature difference.

  2. High-z semiconductor nuclear radiation detectors for room-temperature gamma-ray spectrometry

    International Nuclear Information System (INIS)

    Bornand, Bernard; Friant, Alain.

    1978-09-01

    A bibliographical review (182 articles of periodicals, conferences, reports, thesis and french patents) is presented, as addendum of the report CEA-BIB-210 (1974) on high-Z semiconductor compounds used as materials for the gamma and X-ray detection and spectrometry. This publication reviews issues from 1974 to 1977. References and summaries (in french) are incorporated into 182 bibliograhical notices. Index for authors, corporate authors, documents and periodicals, and subjects is included [fr

  3. Performance analysis of Arithmetic Mean method in determining peak junction temperature of semiconductor device

    Directory of Open Access Journals (Sweden)

    Mohana Sundaram Muthuvalu

    2015-12-01

    Full Text Available High reliability users of microelectronic devices have been derating junction temperature and other critical stress parameters to improve device reliability and extend operating life. The reliability of a semiconductor is determined by junction temperature. This paper gives a useful analysis on mathematical approach which can be implemented to predict temperature of a silicon die. The problem could be modeled as heat conduction equation. In this study, numerical approach based on implicit scheme and Arithmetic Mean (AM iterative method will be applied to solve the governing heat conduction equation. Numerical results are also included in order to assert the effectiveness of the proposed technique.

  4. Femtosecond differential transmission measurements on low temperature GaAs metal-semiconductor-metal structures

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Hvam, Jørn Märcher; Tautz, S.

    1997-01-01

    We report on differential transmission measurements on low temperature grown (LT)-GaAs with and without applied electrical fields at different wavelengths. Electrical fields up to 100 kV/cm can be applied via an interdigitated contact structure to our LT GaAs samples which have been removed from....... The response time of a biased metal-semiconductor-metal detector, therefore, exceeds the carrier life time of the substrate material. (C) 1997 American Institute of Physics....

  5. High-temperature MEMS Heater Platforms: Long-term Performance of Metal and Semiconductor Heater Materials

    OpenAIRE

    Spannhake, Jan; Schulz, Olaf; Helwig, Andreas; Krenkow, Angelika; M?ller, Gerhard; Doll, Theodor

    2006-01-01

    Micromachined thermal heater platforms offer low electrical power consumption and high modulation speed, i.e. properties which are advantageous for realizing non-dispersive infrared (NDIR) gas- and liquid monitoring systems. In this paper, we report on investigations on silicon-on-insulator (SOI) based infrared (IR) emitter devices heated by employing different kinds of metallic and semiconductor heater materials. Our results clearly reveal the superior high-temperature performance of semicon...

  6. Curie temperature and exchange interactions in diluted group-IV magnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    Kudrnovský, Josef; Turek, Ilja; Drchal, Václav; Bruno, P.

    272-276, - (2004), s. 1995-1996 ISSN 0304-8853 R&D Projects: GA AV ČR IAA1010203; GA AV ČR IAA1010214; GA ČR GA106/02/0943 Institutional research plan: CEZ:AV0Z1010914 Keywords : magnetic semiconductors * Curie temperature * exchange interactions * first principles Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.031, year: 2004

  7. The effects of Mn concentration on structural and magnetic properties of Ge{sub 1-x}Mn{sub x} diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Le, T-G; Dau, M-T; Thanh, V Le; Michez, L; Derrien, J [Centre Interdisciplinaire de Nanoscience de Marseille (CINaM-CNRS), Aix-Marseille Universite, Campus de Luminy, case 913, 13288 Marseille (France); Nam, D N H [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Road, Charlottesville, VA 22904 (United States); Luong, T K P; Khiem, N V, E-mail: lethanh@cinam.univ-mrs.fr [Department of Engineering and Technology, Hong Duc University, 307 Le Lai Street, Thanh Hoa City (Viet Nam)

    2011-04-01

    Reflexion high-energy electron diffraction (RHEED), transmission electron microscopy (TEM) along with physical property measurement system (PPMS) were used to investigate the growth kinetics of Ge{sub 1-x}Mn{sub x} diluted magnetic semiconductors (DMS) grown on Ge(001) by means of molecular beam epitaxy (MBE). At a given intermediate growth temperature of 130 deg. C, we have identified the formation of successive heterogeneous phases when increasing the Mn concentration from 1 to 14 %: DMS phase containing nanosized Mn-rich clusters for x below 2%, DMS phase containing high Curie temperature (T{sub C}) nanocolumns for x ranging from 5 to 6 %, DMS phase in which GeMn nanocolumns and Mn{sub 5}Ge{sub 3} clusters coexist and then finally DMS containing mainly Mn{sub 5}Ge{sub 3} clusters at Mn concentration higher than 12%. Our results confirm that the low solubility of Mn in Ge is the main origin of the formation of heterogeneous phases and provide evidence that it is extremely difficult to form a homogenous GeMn DMS even for Mn concentrations being below 2%. We also demonstrate that high-T{sub C} nanocolumns and Mn{sub 5}Ge{sub 3} clusters are competing processes and the process window corresponding to the stabilisation of high-T{sub C} nanocolumns remains extremely tight.

  8. Effects of nuclear fusion produced neutrons on silicon semiconductor plasma X-ray detectors

    CERN Document Server

    Kohagura, J; Hirata, M; Numakura, T; Minami, R; Watanabe, H; Sasuga, T; Nishizawa, Y; Yoshida, M; Nagashima, S; Tamano, T; Yatsu, K; Miyoshi, S; Hirano, K; Maezawa, H

    2002-01-01

    The effects of nuclear fusion produced neutrons on the X-ray energy responses of semiconductor detectors are characterized. The degradation of the response of position-sensitive X-ray tomography detectors in the Joint European Torus (JET) tokamak is found after neutron exposure produced by deuterium-deuterium and deuterium-tritium plasma fusion experiments. For the purpose of further detailed characterization of the neutron degradation effects, an azimuthally varying-field (AVF) cyclotron accelerator is employed using well-calibrated neutron fluence. These neutron effects on the detector responses are characterized using synchrotron radiation from a 2.5 GeV positron storage ring at the Photon Factory (KEK). The effects of neutrons on X-ray sensitive semiconductor depletion thicknesses are also investigated using an impedance analyser. Novel findings of (i) the dependence of the response degradation on X-ray energies as well as (ii) the recovery of the degraded detector response due to the detector bias applic...

  9. Alpha-ray spectrometry at high temperature by using a compound semiconductor detector.

    Science.gov (United States)

    Ha, Jang Ho; Kim, Han Soo

    2013-11-01

    The use of conventional radiation detectors in harsh environments is limited by radiation damage to detector materials and by temperature constraints. We fabricated a wide-band gap semiconductor radiation detector based on silicon carbide. All the detector components were considered for an application in a high temperature environment like a nuclear reactor core. The radiation response, especially to alpha particles, was measured using an (241)Am source at variable operating voltages at room temperature in the air. The temperature on detector was controlled from 30°C to 250°C. The alpha-particle spectra were measured at zero bias operation. Even though the detector is operated at high temperature, the energy resolution as a function of temperature is almost constant within 3.5% deviation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  10. High-Temperature, Wirebondless, Ultra-Compact Wide Bandgap Power Semiconductor Modules for Space Power Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Silicon carbide (SiC) and other wide band-gap semiconductors offer great promise of high power rating, high operating temperature, simple thermal management, and...

  11. High-Temperature, Wirebondless, Ultra-Compact Wide Bandgap Power Semiconductor Modules for Space Power Systems, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Silicon carbide (SiC) and other wide band-gap semiconductors offer great promise of high power rating, high operating temperature, simple thermal management, and...

  12. Determination of chlorine concentration using single temperature modulated semiconductor gas sensor

    Science.gov (United States)

    Woźniak, Ł.; Kalinowski, P.; Jasiński, G.; Jasiński, P.

    2016-11-01

    A periodic temperature modulation using sinusoidal heater voltage was applied to a commercial SnO2 semiconductor gas sensor. Resulting resistance response of the sensor was analyzed using a feature extraction method based on Fast Fourier Transformation (FFT). The amplitudes of the higher harmonics of the FFT from the dynamic nonlinear responses of measured gas were further utilized as an input for Artificial Neuron Network (ANN). Determination of the concentration of chlorine was performed. Moreover, this work evaluates the sensor performance upon sinusoidal temperature modulation.

  13. Current applications of semiconductor x-ray detectors in chemical analysis

    International Nuclear Information System (INIS)

    Whitehead, N.E.

    1975-07-01

    In the last few years, semiconductor detectors have been used as X-ray detectors with great success, and the routine rapid accumulation of X-ray spectra is now possible. This review surveys the historical development of the detectors, the utilisation, and relative merits of various means of exciting the X-radiation from the elements in the sample, and compares the technique with other methods claiming to offer the capability of simultaneous multi-element analysis. It is concluded that it is of average sensitivity, but offers some advantages from its non-destructive nature, and in some cases its ability to offer information about the spatial distribution of elements in a sample. Other types of analysis may also be possible simultaneously. Sample preparation techniques are reviewed, especially techniques of manufacturing thin samples. An appendix contains details of the very wide variety of samples which have been analysed. More than 350 references are included. (auth.)

  14. X-ray and photoelectron spectroscopy of the structure, reactivity, and electronic structure of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hamad, Kimberly Sue [Univ. of California, Berkeley, CA (United States)

    2000-01-01

    Semiconductor nanocrystals are a system which has been the focus of interest due to their size dependent properties and their possible use in technological applications. Many chemical and physical properties vary systematically with the size of the nanocrystal and thus their study enables the investigation of scaling laws. Due to the increasing surface to volume ratio as size is decreased, the surfaces of nanocrystals are expected to have a large influence on their electronic, thermodynamic, and chemical behavior. In spite of their importance, nanocrystal surfaces are still relatively uncharacterized in terms of their structure, electronic properties, bonding, and reactivity. Investigation of nanocrystal surfaces is currently limited by what techniques to use, and which methods are suitable for nanocrystals is still being determined. This work presents experiments using x-ray and electronic spectroscopies to explore the structure, reactivity, and electronic properties of semiconductor (CdSe, InAs) nanocrystals and how they vary with size. Specifically, x-ray absorption near edge spectroscopy (XANES) in conjunction with multiple scattering simulations affords information about the structural disorder present at the surface of the nanocrystal. X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS) probe the electronic structure in terms of hole screening, and also give information about band lineups when the nanocrystal is placed in electric contact with a substrate. XPS of the core levels of the nanocrystal as a function of photo-oxidation time yields kinetic data on the oxidation reaction occurring at the surface of the nanocrystal.

  15. Temperature dependence of the in intensity of diffraction maxima in roentgenograms of semiconductor compounds GaAs, InAs, InP in the 7-310 K temperature range

    International Nuclear Information System (INIS)

    Sirota, N.N.; Sidorov, A.A.

    1985-01-01

    Systematic investigation into temperature dependence of reflexes intensity of the Bragg coherent X-ray scattering with A 3 B 5 semiconductor compounds - gallium and indium arsenides and indium phosphides in a wide temperature range from helium to room temperatures is performed. It is shown that data on the temperature dependence of the coherent scattering reflex intensity permit to obtain comprehensive information on peculiarities of lattice dynamics of the objects investigated and their elastic properties. Measurement of reflex intensities near absolute zero enables direct experimental estimation of absolute values of root-mean-square atom dynamic shifts

  16. Resonant inelastic scattering in dilute magnetic semiconductors by x-ray fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lawniczak-Jablonska, K. [Lawrence Berkeley National Lab., CA (United States)]|[Institute of Physics, Warsaw (Poland); Jia, J.J.; Underwood, J.H. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    As modern, technologically important materials have become more complex, element specific techniques have become invaluable in studying the electronic structure of individual components from the system. Soft x-ray fluorescence (SXF) and absorption (SXA) spectroscopies provide a unique means of measuring element and angular momentum density of electron states, respectively, for the valence and conducting bands in complex materials. X-ray absorption and the decay through x-ray emission are generally assumed to be two independent one-photon processes. Recent studies, however have demonstrated that SXF excited near the absorption threshold generate an array of spectral features that depend on nature of materials, particularly on the localization of excited states in s and d-band solids and that these two processes can no be longer treated as independent. Resonant SXF offers thus the new way to study the dynamics of the distribution of electronic valence states in the presence of a hole which is bound to the electron low lying in the conduction band. This process can simulate the interaction between hole-electron pair in wide gap semiconductors. Therefore such studies can help in understanding of transport and optics phenomena in the wide gap semiconductors. The authors report the result of Mn and S L-resonant emission in Zn{sub 1{minus}x}Mn{sub x}S (with x=0.2 and 0.3) and MnS as the energy of exciting radiation is tuned across the Mn and S L{sub 3,2} absorption edge, along with the resonant excited spectra from elemental Mn as a reference.

  17. An Assessment of Critical Dimension Small Angle X-ray Scattering Metrology for Advanced Semiconductor Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Settens, Charles M. [State Univ. of New York (SUNY), Albany, NY (United States)

    2015-01-01

    Simultaneous migration of planar transistors to FinFET architectures, the introduction of a plurality of materials to ensure suitable electrical characteristics, and the establishment of reliable multiple patterning lithography schemes to pattern sub-10 nm feature sizes imposes formidable challenges to current in-line dimensional metrologies. Because the shape of a FinFET channel cross-section immediately influences the electrical characteristics, the evaluation of 3D device structures requires measurement of parameters beyond traditional critical dimension (CD), including their sidewall angles, top corner rounding and footing, roughness, recesses and undercuts at single nanometer dimensions; thus, metrologies require sub-nm and approaching atomic level measurement uncertainty. Synchrotron critical dimension small angle X-ray scattering (CD-SAXS) has unique capabilities to non-destructively monitor the cross-section shape of surface structures with single nanometer uncertainty and can perform overlay metrology to sub-nm uncertainty. In this dissertation, we perform a systematic experimental investigation using CD-SAXS metrology on a hierarchy of semiconductor 3D device architectures including, high-aspect-ratio contact holes, H2 annealed Si fins, and a series of grating type samples at multiple points along a FinFET fabrication process increasing in structural intricacy and ending with fully fabricated FinFET. Comparative studies between CD-SAXS metrology and other relevant semiconductor dimensional metrologies, particularly CDSEM, CD-AFM and TEM are used to determine physical limits of CD-SAXS approach for advanced semiconductor samples. CD-SAXS experimental tradeoffs, advice for model-dependent analysis and thoughts on the compatibility with a semiconductor manufacturing environment are discussed.

  18. Photosensitive srtuctures on the basis of Pb1-xMnxTe semimagnetic semiconductors thin films

    International Nuclear Information System (INIS)

    Mehrabova, M.A.; Kerimova, T.I.; Memishova, R.M.; Nuriyev, I.R.; Ismayilov, T.G.

    2010-01-01

    Full text : Narrow-band semimagnetic semiconductors (SMS) Pb 1 -xMn x Te are unique materials for infrared optoelectronics. The investigation of Faraday effect in Pb 1 -xMn x Te thin films of SMS is of a special interest. So it can be used at the construction of optic isolators, amplifiers, IR detectors and other equipments. In the given work Pb 1 -xMn x Te thin films (SMS) have been produced, the interband Faraday effect in these semiconductors has been theoretically and experimentally studied. Opportunities of making IR detectors have been studied. Pb 1 -xMn x Te thin films have been grown at BaF 2 substrates by the method of molecular beam condensation. The optimal conditions of producing thin films with high crystallic perfection, electrophysical and optical parameters have been determined. The energy spectrum and wave functions have been theoretically calculated for quantum-sized films of Pb 1 -xMn x Te SMS in the case when the surface of the film is perpendicular to the axis X and the spin-spin exchange interaction occurs between the electrons in the conductivity band (valence band) and the electrons of half-filled d-shells of manganese ions as well as taking into account electron spins and the band nonparabolicity. For the calculation of the spectra and wave functions double-band Kane model has been used. On the basis of the found formulae an analytical equation has been found out for interband Faraday rotation (IFR) depending on the energy of the incident photon, band gap and the film thickness. It has been shown that by the decrease in the band gap the value of the IFR angle increases too. The formula of parabolic approximation has been also obtained. The dependence of IFR angle on photon energy, band gap and the film thickness has been built. It has been specified that the decrease of the film thickness leads to a strong increase of IFR angle. The contribution of nonparabolicity into IFR angle has been established, so taking into consideration the band

  19. Ab-initio calculations of Co-based diluted magnetic semiconductors Cd 1-xCoxX (X=S, Se, Te)

    KAUST Repository

    Saeed, Yasir

    2010-10-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic semiconductors composed of IIVI compounds Cd1-xCoxX (X=S, Se, Te) at x=0.25. From the calculated results of band structure and density of states, the half-metallic character and stability of ferromagnetic state for Cd1-xCoxS, Cd1-xCoxSe and Cd 1-xCoxTe alloys are determined. It is found that the tetrahedral crystal field gives rise to triple degeneracy t2g and double degeneracy eg. Furthermore, we predict the values of spin-exchange splitting energies Δx(d) and Δ x(p-d) and exchange constants N0α and N 0β produced by the Co 3d states. Calculated total magnetic moments and the robustness of half-metallicity of Cd1-xCo xX (X=S, Se, Te) with respect to the variation in lattice parameters are also discussed. We also extend our calculations to x=0.50, 0.75 for S compounds in order to observe the change due to increase in Co. © 2010 Elsevier B.V.

  20. Reference-free total reflection X-ray fluorescence analysis of semiconductor surfaces with synchrotron radiation.

    Science.gov (United States)

    Beckhoff, Burkhard; Fliegauf, Rolf; Kolbe, Michael; Müller, Matthias; Weser, Jan; Ulm, Gerhard

    2007-10-15

    Total reflection X-ray fluorescence (TXRF) analysis is a well-established method to monitor lowest level contamination on semiconductor surfaces. Even light elements on a wafer surface can be excited effectively when using high-flux synchrotron radiation in the soft X-ray range. To meet current industrial requirements in nondestructive semiconductor analysis, the Physikalisch-Technische Bundesanstalt (PTB) operates dedicated instrumentation for analyzing light element contamination on wafer pieces as well as on 200- and 300-mm silicon wafer surfaces. This instrumentation is also suited for grazing incidence X-ray fluorescence analysis and conventional energy-dispersive X-ray fluorescence analysis of buried and surface nanolayered structures, respectively. The most prominent features are a high-vacuum load-lock combined with an equipment front end module and a UHV irradiation chamber with an electrostatic chuck mounted on an eight-axis manipulator. Here, the entire surface of a 200- or a 300-mm wafer can be scanned by monochromatized radiation provided by the plane grating monochromator beamline for undulator radiation in the PTB laboratory at the electron storage ring BESSY II. This beamline provides high spectral purity and high photon flux in the range of 0.078-1.86 keV. In addition, absolutely calibrated photodiodes and Si(Li) detectors are used to monitor the exciting radiant power respectively the fluorescence radiation. Furthermore, the footprint of the excitation radiation at the wafer surface is well-known due to beam profile recordings by a CCD during special operation conditions at BESSY II that allow for drastically reduced electron beam currents. Thus, all the requirements of completely reference-free quantitation of TXRF analysis are fulfilled and are to be presented in the present work. The perspectives to arrange for reference-free quantitation using X-ray tube-based, table-top TXRF analysis are also addressed.

  1. X-ray radiometric transducer with Si semiconductor detector cooling by means of thermoelectric refrigerator

    International Nuclear Information System (INIS)

    Vajgachev, A.A.; Kokhov, E.D.; Mamikonyan, S.V.; Mel'ttser, L.V.; Pan'kin, V.V.; Shchekin, K.I.

    1975-01-01

    The cooling is considered of the silicon-lithium detectors with the use of the thermoelectric cooler. The operation of the thermoelectric cooler is based on Peltje's effect. A temperature differential of up to 50-60 deg C may be obtained on one-stage thermopile. For obtaining lower temperatures, several stages of the thermopiles are employed. The suggested thermal electric cooler is actually a five-stage thermopile consisting of 70-80 semiconductors and ensuring cooling of the detector in the vacuum of 10 -5 torr down to a temperature of -100 deg C. There has been designed, constructed and tested a roentgen-radiometric transducer with a silicon-lithium detector. The energy resolution of the detector amounts to 1.3 keV in the Ag, Ka line

  2. Temperature controlled infrared broadband cloaking with the bilayer coatings of semiconductor and superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaohua [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); Liu, Youwen, E-mail: ywliu@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Feng, Yuncai [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2015-06-15

    Highlights: • We first propose that the cloak is composed of the bilayer of semiconductor and superconductor. • We realize the infrared broadband cloaking based on the scattering cancellation method. • The cloaking frequency can be tuned by external temperature. - Abstract: The infrared broadband tunable cloaking have been proposed and investigated with the bilayer coating materials of semiconductor (n-Ge) and high-temperature superconductor (YBa{sub 2}Cu{sub 3}O{sub 7}), whose cloaking frequency can be controlled by external temperature. The analytical solution is derived based on the scattering cancellation cloaking technique from the Mie scattering theory, and the full-wave numerical simulation is performed by the finite element method. The calculated and simulated results have demonstrated that this invisibility cloak may reduce the total scattering cross section of the composite structure of 90% over a broad frequency band of nearly 20 THz, and the infrared cloaking frequency can be tuned by the external temperature. It can provide a feasible way to design a broadband tunable cloak.

  3. Improved x-ray spectroscopy with room temperature CZT detectors.

    Science.gov (United States)

    Fritz, Shannon G; Shikhaliev, Polad M; Matthews, Kenneth L

    2011-09-07

    Compact, room temperature x-ray spectroscopy detectors are of interest in many areas including diagnostic x-ray imaging, radiation protection and dosimetry. Room temperature cadmium zinc telluride (CZT) semiconductor detectors are promising candidates for these applications. One of the major problems for CZT detectors is low-energy tailing of the energy spectrum due to hole trapping. Spectral post-correction methods to correct the tailing effect do not work well for a number of reasons; thus it is advisable to eliminate the hole trapping effect in CZT using physical methods rather than correcting an already deteriorated energy spectrum. One method is using a CZT detector with an electrode configuration which modifies the electric field in the CZT volume to decrease low-energy tailing. Another method is to irradiate the CZT surface at a tilted angle, which modifies depth of interaction to decrease low-energy tailing. Neither method alone, however, eliminates the tailing effect. In this work, we have investigated the combination of modified electric field and tilted angle irradiation in a single detector to further decrease spectral tailing. A planar CZT detector with 10 × 10 × 3 mm³ size and CZT detector with 5 × 5 × 5 mm³ size and cap-shaped electrode were used in this study. The cap-shaped electrode (referred to as CAPture technology) modifies the electric field distribution in the CZT volume and decreases the spectral tailing effect. The detectors were investigated at 90° (normal) and 30° (tilted angle) irradiation modes. Two isotope sources with 59.6 and 122 keV photon energies were used for gamma-ray spectroscopy experiments. X-ray spectroscopy was performed using collimated beams at 60, 80 and 120 kVp tube voltages, in both normal and tilted angle irradiation. Measured x-ray spectra were corrected for K x-ray escape fractions that were calculated using Monte Carlo methods. The x-ray spectra measured with tilted angle CAPture detector at 60, 80 and 120

  4. The structure of liquid semiconductors, superionic conductors and glasses by neutron scattering, X-ray diffraction and extended X-ray absorption fine structure

    International Nuclear Information System (INIS)

    Buchanan, P.

    2001-09-01

    A study of the applicability of modern X-ray and neutron scattering techniques to the study of the structure of liquid semiconductors and glasses has been made. The results demonstrate how neutron scattering with isotopic substitution (NDIS), anomalous X-ray scattering and Extended X-ray Absorption Fine Structure (EXAFS) can be successfully used to elucidate the structure of materials that cannot be studied by NDIS alone. The local coordination structure of Ag 2 Se in its room temperature, superionic and liquid phases has been determined using the EXAFS technique. This EXAFS data have been combined with previously available neutron diffraction data to provide a refinement of the structure obtained through neutron diffraction alone. The structure of GeO 2 has been determined to the full partial structure factor level using a combination of anomalous X-ray scattering and neutron diffraction measurements. The data are in good agreement with previously obtained results. The partial structure factors of P 40 Se 60 and P 50 Se 50 have been determined to the first order difference level using the anomalous X-ray diffraction technique. The structure of liquid Ga 2 Te 3 has been determined to the partial structure factor level using combined neutron diffraction with isotopic substitution (NDIS) and anomalous X-ray diffraction. The structure of liquid FeSe 2 has been determined to the first order difference level using the NDIS technique alone. The structure of liquid FeTe 2 was determined at the total structure factor level using neutron diffraction in order to estimate the effect of chalcogenide ion size on the structure. The results demonstrate the feasibility of the additional structural determination techniques for disordered materials made possible through the development of third generation X-ray synchrotron sources. (author)

  5. A novel theoretical model for the temperature dependence of band gap energy in semiconductors

    Science.gov (United States)

    Geng, Peiji; Li, Weiguo; Zhang, Xianhe; Zhang, Xuyao; Deng, Yong; Kou, Haibo

    2017-10-01

    We report a novel theoretical model without any fitting parameters for the temperature dependence of band gap energy in semiconductors. This model relates the band gap energy at the elevated temperature to that at the arbitrary reference temperature. As examples, the band gap energies of Si, Ge, AlN, GaN, InP, InAs, ZnO, ZnS, ZnSe and GaAs at temperatures below 400 K are calculated and are in good agreement with the experimental results. Meanwhile, the band gap energies at high temperatures (T  >  400 K) are predicted, which are greater than the experimental results, and the reasonable analysis is carried out as well. Under low temperatures, the effect of lattice expansion on the band gap energy is very small, but it has much influence on the band gap energy at high temperatures. Therefore, it is necessary to consider the effect of lattice expansion at high temperatures, and the method considering the effect of lattice expansion has also been given. The model has distinct advantages compared with the widely quoted Varshni’s semi-empirical equation from the aspect of modeling, physical meaning and application. The study provides a convenient method to determine the band gap energy under different temperatures.

  6. Synthesis and Optical Properties of Zn1-xMnxS Dilute Magnetic Semiconductors

    Directory of Open Access Journals (Sweden)

    WU Mei-rong

    2017-07-01

    Full Text Available Diluted magnetic semiconductors Zn1-xMnxS with different consistency (x=0.00, 0.02, 0.05, 0.07 were synthesized by hydrothermal method, and the effects of doping concentration Mn2+ on the microstructure and optical properties of ZnS nanorods were investigated. The crystal microstructure,morphology and optical properties of the products were characterized by X-ray diffraction (XRD, high-resolution transmission electron microscopy (HRTEM, corresponding selected-area electron diffraction (SAED, X-ray energy dispersive spectrometry (XEDS and ultraviolet-visible spectrophotometer(UV-vis.The results show that all samples synthesized by this method possess wurtzite structure with good crystallization, no other impurity phase appears and generates single-phase Zn1-xMnxS nanocrystalline. The morphology of the samples is nanorods and well disperses. The doping element of Mn enters into the ZnS nanocrystals, Mn2+ replaces Zn2+, and the lattice constant decreases with the increase of Mn content. Meanwhile, the optical band gap increases and the blue shift occurs for the sample in the UV-vis spectra.

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

    KAUST Repository

    Wang, Zhenwei

    2015-04-20

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

  8. Polarization Pyrometry of Layered Semiconductor Structures under Conditions of Low-Temperature Technological Processes

    Science.gov (United States)

    Azarov, I. A.; Shvets, V. A.; Dulin, S. A.; Mikhailov, N. N.; Dvoretskii, S. A.; Ikusov, D. G.; Uzhakov, I. N.; Rykhlitskii, S. V.

    2017-11-01

    Principal issues of using pyrometry for temperature monitoring in low-temperature processes in the technology of production of semiconductor structures are considered by an example of growing mercury-cadmium-telluride (MCT) layers on the GaAs substrate by the method of molecular beam epitaxy. Optical and thermophysical models are proposed to describe the processes of radiant heat transfer in a vacuum chamber. Based on these models, it is demonstrated that radiation from the heater and the signal reflected from the chamber walls, which are comparable in magnitude with the measured radiation emitted by the sample, should be taken into account in interpreting data measured by a pyrometer. Methods of useful signal identification are found. Experiments on temperature measurement by a pyrometer mounted on the MCT growth chamber are performed. Results of these experiments are in good agreement with theoretical predictions.

  9. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  10. Effect of temperature-dependent energy-level shifts on a semiconductor's Peltier heat

    International Nuclear Information System (INIS)

    Emin, D.

    1984-01-01

    The Peltier heat of a charge carrier in a semiconductor is calculated for the situation in which the electronic energy levels are temperature dependent. The temperature dependences of the electronic energy levels, generally observed optically, arise from their dependences on the vibrational energy of the lattice (e.g., as caused by thermal expansion). It has been suggested that these temperature dependences will typically have a major effect on the Peltier heat. The Peltier heat associated with a given energy level is a thermodynamic quantity; it is the product of the temperature and the change of the entropy of the system when a carrier is added in that level. As such, the energy levels cannot be treated as explicitly temperature dependent. The electron-lattice interaction causing the temperature dependence must be expressly considered. It is found that the carrier's interaction with the atomic vibrations lowers its electronic energy. However, the interaction of the carrier with the atomic vibrations also causes an infinitesimal lowering (approx.1/N) of each of the N vibrational frequencies. As a result, there is a finite carrier-induced increase in the average vibrational energy. Above the Debye temperature, this cancels the lowering of the carrier's electronic energy. Thus, the standard Peltier-heat formula, whose derivation generally ignores the temperature dependence of the electronic energy levels, is regained. This explains the apparent success of the standard formula in numerous analyses of electronic transport experiments

  11. PHOTOSENSITIVE STRUCTURES ON THE BASIS OF THIN FILMS OF SEMIMAGNETIC SEMICONDUCTORS Pb1-x Mnx Te

    International Nuclear Information System (INIS)

    Mehrabova, M.A; Nuriyev, I.R; Ismayilov, T.G; Kerimova, T.I; Mamishova, R.M

    2011-01-01

    Full text: Narrow-band semimagnetic semiconductors (SMS) Pb1-xMnxTe are unique materials for infrared (IR) optoelectronics.The investigation of Faraday effect in Pb1-xMnxTe thin films of SMS is of a special interest. So it can be used at the construction of optic isolators, amplifiers, IR detectors and other equipments.In the given work Pb1-xMnxTe thin films (SMS) have been produced, the interband Faraday effect in these semiconductors has been theoretically and experimentally studied. Opportunities of making IR detectors have been studied. Pb1-xMnxTe (x=0.005 0.06) thin films have been grown at BaF2 substrates by the method of molecular beam condensation. The optimal conditions of producing thin films with high crystallic perfection, electrophysical and optical parameters have been determined [1]. The energy spectrum and wave functions have been theoretically calculated for quantum-sized films of Pb1-xMnxTe SMS in the case when the surface of the film is perpendicular to the axis X and the spin-spin exchange interaction occurs between the electrons in the conductivity band (valence band) and the electrons of half-filled d-shells of manganese ions as well as taking into account electron spins and the band nonparabolicity. For the calculation of the spectra and wave functions double-band Kane model has been used. On the basis of the found formulae an analytical equation has been found out for interband Faraday rotation (IFR) depending on the energy of the incident photon, band gap and the film thickness. It has been shown that by the decrease in the band gap the value of the IFR angle increases too [2]. The formula of parabolic approximation has been also obtained. The dependence of IFR angle on photon energy, band gap and the film thickness has been built. It has been specified that the decrease of the film thickness leads to a strong increase of IFR angle. The contribution of nonparabolicity into IFR angle has been established, so taking into consideration the

  12. Improvements in investigation methods by X-ray topography. Applications to studies of semiconductor technology problems

    International Nuclear Information System (INIS)

    Rolland, Guy

    1973-01-01

    The electrical performances of semiconductor electronic devices are liable to depend on the structural faults which exist in the starting material, or which are introduced into it by electronic devices fabrication technology. The present work shows some applications of X-ray topography to elucidate these structural defects in silicon. The examination method by X-ray topography is briefly discussed and the experimental set-up described. Results are presented in an analysis of the different types of faults created in silicon during integrated circuits fabrication steps: faults due to material growth, faults due to diffusions and thermal treatments. It will be shown that X-ray topography alone often is not sufficient to give a clear picture of formation and development of several types of faults, but must be assisted by other methods of characterization (chemical revelation, electron transmission microscopy). Finally the advantages of a double crystal diffraction method will be discussed. An apparatus using this method is presently being set up in the laboratory to complete classical X-ray topography. (author) [fr

  13. Semiconductor detectors. Recent evolution

    International Nuclear Information System (INIS)

    Siffert, P.

    1977-01-01

    The recent evolution as well as the problems appearing in the use of semiconductor counters in both X and γ-ray as well as heavy ions spectroscopy are reviewed. For the photon counters the discussion is limited to cadmium telluride and mercuric iodide room temperature diodes, whereas for heavy ions, identification by means of thin ΔE/Δx counters and some problems related to the pulse amplitude in E detectors are considered [fr

  14. Inelastic X-ray scattering experiments at extreme conditions: high temperatures and high pressures

    Directory of Open Access Journals (Sweden)

    S.Hosokawa

    2008-03-01

    Full Text Available In this article, we review the present status of experimental techniques under extreme conditions of high temperature and high pressure used for inelastic X-ray scattering (IXS experiments of liquid metals, semiconductors, molten salts, molecular liquids, and supercritical water and methanol. For high temperature experiments, some types of single-crystal sapphire cells were designed depending on the temperature of interest and the sample thickness for the X-ray transmission. Single-crystal diamond X-ray windows attached to the externally heated high-pressure vessel were used for the IXS experiment of supercritical water and methanol. Some typical experimental results are also given, and the perspective of IXS technique under extreme conditions is discussed.

  15. Development of UItra-Low Temperature Motor Controllers: Ultra Low Temperatures Evaluation and Characterization of Semiconductor Technologies For The Next Generation Space Telescope

    Science.gov (United States)

    Elbuluk, Malik E.

    2003-01-01

    Electronics designed for low temperature operation will result in more efficient systems than room temperature. This improvement is a result of better electronic, electrical, and thermal properties of materials at low temperatures. In particular, the performance of certain semiconductor devices improves with decreasing temperature down to ultra-low temperature (-273 'C). The Low Temperature Electronics Program at the NASA Glenn Research Center focuses on research and development of electrical components and systems suitable for applications in deep space missions. Research is being conducted on devices and systems for use down to liquid helium temperatures (-273 'C). Some of the components that are being characterized include semiconductor switching devices, resistors, magnetics, and capacitors. The work performed this summer has focused on the evaluation of silicon-, silicon-germanium- and gallium-Arsenide-based (GaAs) bipolar, MOS and CMOS discrete components and integrated circuits (ICs), from room temperature (23 'C) down to ultra low temperatures (-263 'C).

  16. Raman Scattering Studies in Dilute Magnetic Semiconductor Zn(1-x)Co(x)O

    Science.gov (United States)

    Samanta, K.; Bhattacharya, P.; Katiyar, R. S.; Iwamoto, W.; Pagiluso, P. G.; Rettori, C.

    2006-01-01

    Raman spectra of ZnO and Co substituted Zn1-xCoxO (ZCO) were carried out using the Raman microprobe system with an p.,+ ion laser source of 514.5 nm wavelength. The shift towards the lower frequency side of the nonpolar E210w mode and the broadening due to Co substitution in ZnO were analyzed using the phonon confinement model. The magnetic measurements showed ferromagnetic behavior with the maximum saturation magnetization (1.2micron Beta/ErCo) for 10% Co substitution, which decreased wi th at further increase in Co concentrations. The intensities of E1(LO) at 584 cm-1 and multiphonon modes at 540 cm-1 were increased with an increase in Co substitution. The additional Raman modes in ceramic targets of ZCO spectra for higher concentration of Co substitution (x=15%-20%) were identified to be due to the spinel ZnCo2O4 secondary phase.

  17. Biaxial stress driven tetragonal symmetry breaking and high-temperature ferromagnetic semiconductor from half-metallic CrO2

    Science.gov (United States)

    Xiao, Xiang-Bo; Liu, Bang-Gui

    2018-03-01

    It is highly desirable to combine the full spin polarization of carriers with modern semiconductor technology for spintronic applications. For this purpose, one needs good crystalline ferromagnetic (or ferrimagnetic) semiconductors with high Curie temperatures. Rutile CrO2 is a half-metallic spintronic material with Curie temperature 394 K and can have nearly full spin polarization at room temperature. Here, we find through first-principles investigation that when a biaxial compressive stress is applied on rutile CrO2, the density of states at the Fermi level decreases with the in-plane compressive strain, there is a structural phase transition to an orthorhombic phase at the strain of -5.6 % , and then appears an electronic phase transition to a semiconductor phase at -6.1 % . Further analysis shows that this structural transition, accompanying the tetragonal symmetry breaking, is induced by the stress-driven distortion and rotation of the oxygen octahedron of Cr, and the half-metal-semiconductor transition originates from the enhancement of the crystal field splitting due to the structural change. Importantly, our systematic total-energy comparison indicates the ferromagnetic Curie temperature remains almost independent of the strain, near 400 K. This biaxial stress can be realized by applying biaxial pressure or growing the CrO2 epitaxially on appropriate substrates. These results should be useful for realizing full (100%) spin polarization of controllable carriers as one uses in modern semiconductor technology.

  18. X-ray photoemission electron microscopy for the study of semiconductor materials

    International Nuclear Information System (INIS)

    Anders, Simone; Stammler, Thomas; Padmore, Howard A.; Terminello, Louis J.; Jankowski, Alan F.; Stoehr, Joachim; Diaz, Javier; Cossy-Favre, Aline; Singh, Sangeet

    1998-01-01

    Photoemission Electron Microscopy using X-rays (X-PEEM) is a novel combination of two established materials analysis techniques--PEEM using UV light, and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. This combination allows the study of elemental composition and bonding structure of the sample by NEXAFS spectroscopy with a high spatial resolution given by the microscope. A simple, two lens, 10 kV operation voltage PEEM has been used at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (ALS) in Berkeley to study various problems including materials of interest for the semiconductor industry. In the present paper we give a short overview over the method and the instrument which was used, and describe in detail a number of applications. These applications include the study of the different phases of titanium disilicide, various phases of boron nitride, and the analysis of small particles. A brief outlook is given on possible new fields of application of the PEEM technique, and the development of new PEEM instruments

  19. X-ray photoemission electron microscopy for the study of semiconductor materials

    Energy Technology Data Exchange (ETDEWEB)

    Anders, S.; Stammler, T.; Padmore, H.A. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720 (United States); Terminello, L.J.; Jankowski, A.F. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, California 94550 (United States); Stoehr, J. [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Diaz, J. [Departamento de Fisic, Facultad de Ciencias, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo, 33007 (Spain); Cossy-Favre, A. [EMPA, Duebendorf, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Singh, S. [Center for X-ray Lithography, University of Wisconsin-Madison, Stoughton, Wisconsin 53589 (United States)

    1998-11-01

    Photoemission Electron Microscopy using X-rays (X-PEEM) is a novel combination of two established materials analysis techniques{emdash}PEEM using UV light, and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. This combination allows the study of elemental composition and bonding structure of the sample by NEXAFS spectroscopy with a high spatial resolution given by the microscope. A simple, two lens, 10 kV operation voltage PEEM has been used at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (ALS) in Berkeley to study various problems including materials of interest for the semiconductor industry. In the present paper we give a short overview over the method and the instrument which was used, and describe in detail a number of applications. These applications include the study of the different phases of titanium disilicide, various phases of boron nitride, and the analysis of small particles. A brief outlook is given on possible new fields of application of the PEEM technique, and the development of new PEEM instruments. {copyright} {ital 1998 American Institute of Physics.}

  20. Microscopic Foundation and Simulation of Coupled Carrier-Temperature Diffusions in Semiconductor Lasers

    Science.gov (United States)

    Li, J.; Ning, Cun-Zheng; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    A typical semiconductor-based optoelectronic device, such as a diode laser, consists of three subsystems: an optical field, an electron-hole plasma (EHP), and a host crystal lattice. The physics of such a device involves the interplay of optical, electrical and thermal processes. A proper description of such a device requires that all three processes are treated on equal footing and in a self-consistent fashion. Furthermore, since a semiconductor laser has intrinsic spatial inhomogeneity, such a self-consistency naturally leads to a set of partial differential equations in space and time. There is a significant lacking of research interest and results on the transport aspects of optical devices in the literature with only a few exceptions. Even the most important carrier diffusion coefficient has not been properly derived and studied so far for optically excited plasma, while most of the work adopted results from electronics community where heavily doped semiconductors with mainly one type of carriers are dealt with. The corresponding transport equation for plasma energy or temperature has received even less attention. In this talk we describe our recent results on such a self-consistent derivation of temperature and carrier-density diffusion equations coupled with the lasing process. Starting from the microscopic semiconductor Bloch equations (SBEs) including the Boltzmann transport terms in the distribution function equations for electrons and holes, we derived a closed set of diffusion equations for carrier densities and temperatures with self-consistent coupling to Maxwell's equation and to an effective optical polarization equation. The coherent many-body effects are included within the screened Hartree-Fock approximation, while scatterings are treated within the second Born approximation including both the in- and out-scatterings. Microscopic expressions for electron-hole (e-h) and carrier-LO (c-LO) phonon scatterings are directly used to derive the momentum

  1. Colossal change in thermopower with temperature-driven p-n-type conduction switching in La x Sr2-x TiFeO6 double perovskites

    Science.gov (United States)

    Roy, Pinku; Maiti, Tanmoy

    2018-02-01

    Double perovskite materials have been studied in detail by many researchers, as their magnetic and electronic properties can be controlled by the substitution of alkaline earth metals or lanthanides in the A site and transition metals in the B site. Here we report the temperature-driven, p-n-type conduction switching assisted, large change in thermopower in La3+-doped Sr2TiFeO6-based double perovskites. Stoichiometric compositions of La x Sr2-x TiFeO6 (LSTF) with 0  ⩽  x  ⩽  0.25 were synthesized by the solid-state reaction method. Rietveld refinement of room-temperature XRD data confirmed a single-phase solid solution with cubic crystal structure and Pm\\bar{3}m space group. From temperature-dependent electrical conductivity and Seebeck coefficient (S) studies it is evident that all the compositions underwent an intermediate semiconductor-to-metal transition before the semiconductor phase reappeared at higher temperature. In the process of semiconductor-metal-semiconductor transition, LSTF compositions demonstrated temperature-driven p-n-type conduction switching behavior. The electronic restructuring which occurs due to the intermediate metallic phase between semiconductor phases leads to the colossal change in S for LSTF oxides. The maximum drop in thermopower (ΔS ~ 2516 µV K-1) was observed for LSTF with x  =  0.1 composition. Owing to their enormous change in thermopower of the order of millivolts per kelvin, integrated with p-n-type resistance switching, these double perovskites can be used for various high-temperature multifunctional device applications such as diodes, sensors, switches, thermistors, thyristors, thermal runaway monitors etc. Furthermore, the conduction mechanisms of these oxides were explained by the small polaron hopping model.

  2. Temperature Dependence of Charge Localization in High-Mobility, Solution-Crystallized Small Molecule Semiconductors Studied by Charge Modulation Spectroscopy

    DEFF Research Database (Denmark)

    Meneau, Aurélie Y. B.; Olivier, Yoann; Backlund, Tomas

    2016-01-01

    In solution-processable small molecule semiconductors, the extent of charge carrier wavefunction localization induced by dynamic disorder can be probed spectroscopically as a function of temperature using charge modulation spectroscopy (CMS). Here, it is shown based on combined fi eld-effect tran......In solution-processable small molecule semiconductors, the extent of charge carrier wavefunction localization induced by dynamic disorder can be probed spectroscopically as a function of temperature using charge modulation spectroscopy (CMS). Here, it is shown based on combined fi eld...

  3. Effects of x-ray irradiation on AC characteristics of pyrolyzed polyacrylonitrile semiconductor

    International Nuclear Information System (INIS)

    Ito, Seiichi; Matsumura, Yasuo; Koshita, Itsuro; Imazaki, Kazuo.

    1975-01-01

    Polyacrylonitrile was turned into two kinds of semiconductors by different processes of pyrolysis up to 500 0 C. Then they were irradiated with X-rays in the air, and variations of their impedance after cessation of irradiation were measured. The variation of impedance is closely connected with scission and recombination of the conjugated double bond chain, with enlargement and narrowing of space between two chains and also with generation and recombination of ions and electrons. And these variations of structure cause a variation of resistance at any place and that of capacitance in the neighborhood of the electrode. Two kinds of processes of impedance variation appear after cessation of irradiation; one of them disappears within about 30 minutes, and the other persists for more than 2 hours. And both processes occur extensively at the part where the chemical bond is imperfectly conjugated. Generally speaking, it seems that the main reaction which is caused by X-rays irradiation is the scission of the conjugated double bond. (auth.)

  4. X-ray photoemission electron microscopy for the study of semiconductor materials

    Energy Technology Data Exchange (ETDEWEB)

    Anders, S.; Stammler, T.; Padmore, H. [Lawrence Berkeley National Lab., CA (United States). Advanced Light Source Div.; Terminello, L.J.; Jankowski, A.F. [Lawrence Livermore National Lab., CA (United States); Stohr, J. [IBM Almaden Research Center, San Jose, CA (United States); Diaz, J. [Univ. de Oviedo (Spain). Dept. de Fisica; Cossy-Gantner, A. [EMPA, Duebendorf (Germany)

    1998-03-01

    Photoemission Electron Microscopy (PEEM) using X-rays is a novel combination of two established materials analysis techniques--PEEM using UV light, and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. This combination allows the study of elemental composition and bonding structure of the sample by NEXAFS spectroscopy with a high spatial resolution given by the microscope. A simple, two lens, 10 kV operation voltage PEEM has been used at the Stanford Synchrotron Radiation Laboratory and at the Advanced Light Source (ALS) in Berkeley to study various problems including materials of interest for the semiconductor industry. In the present paper the authors give a short overview over the method and the instrument which was used, and describe in detail a number of applications. These applications include the study of the different phases of titanium disilicide, various phases of boron nitride, and the analysis of small particles. A brief outlook is given on possible new fields of application of the PEEM technique, and the development of new PEEM instruments.

  5. Temperature and concentration dependence af energy gap and refrective index in certain mixed crystals and semiconductors

    Science.gov (United States)

    Reddy, R. R.; Kumar, M. Ravi; Rao, T. V. R.

    1993-02-01

    Variations of energy gap ( Eg) and refractive index ( n) with the concentration have been studied through a set of simple empirical equations proposed in the case of certain mixed crystals of technological importance. Similarly, another set of equations has been proposed to explain the temperature dependence of the energy gap in semiconductors such as GaS, GaSe, GaTe, SnS 2 and SnSe 2. The results obtained in both cases are found to be in excellent agreement with the experimental values. The proposed equations are proved to be simple and advantageous over others in the sense that less computational work is involved in the calculations of Eg and n.

  6. Effect of p–d hybridization, structural distortion and cation electronegativity on electronic properties of ZnSnX2 (X=P, As, Sb) chalcopyrite semiconductors

    International Nuclear Information System (INIS)

    Mishra, S.; Ganguli, B.

    2013-01-01

    Significant effects of p–d hybridization, structural distortion and cation-electro-negativity are found on band gap in ZnSnX 2 (X=P, As, Sb). Our study suggests these compounds to be direct band gap semiconductors with band gaps of 1.23, 0.68 and 0.19 eV respectively. Lattice constants, tetragonal distortion (η), anion displacement, bond lengths and bulk moduli are calculated by Density Functional Theory based on Tight binding Linear Muffin-Tin orbital method. Our result of structural properties is in good agreement with the available experimental and other theoretical results. Calculated band gaps also agree well with the experimental works within LDA limitation. Unlike other semiconductors in the group II–IV–V 2 , there is a reduction in the band gap of 0.22, 0.20 and 0.24 eV respectively in ZnSnX 2 (X=P, As, Sb) due to p–d hybridization. Structural distortion decreases band gap by 0.20, 0.12 and 0.10 eV respectively. We find that cation electronegativity effect is responsible for increasing the band gap relative to their binary analogs GaInP 2 , InGaAs 2 and GaInSb 2 respectively and increment are 0.13, 0.04 and 0.13 eV respectively. - Graphical abstract: One unit cell of ZnSnX 2 (X=P, As, Sb) chalcopyrite semiconductor. Semiconductors ZnSnX 2 (X=P, As, Sb) are found to be direct band gap semiconductors with band gaps 1.23, 0.68 and 0.19 eV respectively. The quantitative estimate of effects of p–d hybridization, structural distortion and cation electronegativity shows band gaps change significantly due to these effects. Highlights: ► ZnSnX 2 (X=P, As, Sb) are direct band gap semiconductors. ► These have band gaps of 1.23 eV, 0.68 eV and 0.19 eV respectively. ► The band gap reduction due to p–d hybridization is 13.41%, 18.51% and 40% respectively. ► Band gap reduction due to structural distortion is 12.12%, 11.11% and 16.66% respectively. ► Band gap increases 8.38%, 3.70% and 21.31% respectively due to cation electronegativity

  7. Room temperature ferromagnetism in Zn1‑x Ni x O nanostructures synthesized by chemical precipitation method

    Science.gov (United States)

    Chacko, Levna; Shafeeq, K. M.; Anjana, R.; Jayaraj, M. K.; Aneesh, P. M.

    2017-10-01

    ZnO nanomaterials have drawn considerable research interest as a multifunctional semiconductor material due to its unique thermal, electrical, optical and optoelectronic properties and also a suitable candidate for the transparent conducting oxide (TCO) layer in optoelectronic devices. The present work deals with the co-precipitation synthesis of ZnO nanostructures with Ni dopants. The structure and phase identification, morphology, optical and magnetic response of the prepared Zn1‑x Ni x O nanostructures have been investigated by employing x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscopy (EDAX), Raman analysis, UV–Vis–NIR and fluorescence spectrophotometer and vibrating sample magnetometer (VSM) measurements. Structural studies reveal the hexagonal wurtzite structure of ZnO nanostructures with a slight decrease in the particle size with Ni doping. The incorporation Ni in the ZnO host lattice is confirmed by EDAX measurements. Optical studies confirm the observance of blue shift and violet photoluminescence emission for Zn1‑x Ni x O nanostructures. Vibrating sample magnetometer (VSM) measurements of Zn1‑x Ni x O nanostructures shows hysteresis loop at room temperature confirming the ferromagnetic behaviour of the samples.

  8. Permittivity and soft mode in narrow-gap Pbsub(1-x)Snsub(x)Te(x<0.35) semiconductors

    International Nuclear Information System (INIS)

    Antkiv, Z.P.; Baginskij, V.M.; Tovstyuk, K.D.

    1979-01-01

    Presented are the results of theoretical studies of the effect of carrier concentration and composition X on static dielectric function and the frequency of transverse optical phonon in solid Pbsub(1-x)Snsub(x)Te solutions. It is shown that to calculate the dependence of the frequency of transverse phonon mode and the width of forbidden zone on solid solution composition and concentration it is sufficient to limit oneself to the simplest approximation for polarization operator, optical deformation potential being chosen as an adjusting parameter. The results of calculations are compared with available experimental data

  9. A novel semiconductor pixel device and system for X-ray and gamma ray imaging

    International Nuclear Information System (INIS)

    Allison, D.; Myers, M.; Sanghera, B.

    1996-01-01

    We are presenting clinical images and data from a novel X-ray imaging device and system. The device comprises a pixel semiconductor detector flip-chip joined to an ASIC circuit. CdZnTe and Si pixel detectors with dimensions of the order of 1 cm 2 have been implemented with a pixel pitch of 35 μm. Individual detectors comprise, therefore, tens of thousands of pixels. A novel ASIC accumulates charge created from directly absorbed X-rays impinging on the detector. Each circuit on the ASIC, corresponding to a detector pixel, is capable of accumulating thousands of X-rays in the energy spectrum from a few to hundreds of keV with high efficiency (CdZnTe). Image (X-ray) accumulation times are user controlled and range from just a few to hundreds of ms. Image frame updates are also user controlled and can be provided as fast as every 20 ms, thus offering the possibility of real time imaging. The total thickness of an individual imaging tile including the mounting support does not exceed 4 mm. Individual imaging tiles are combined in a mosaic providing an imaging system with any desired shape and useful active area. The mosaic allows for cost effective replacement of individual tiles. A scanning system, allows for elimination, in the final image, of any inactive space between the imaging tiles without use of software interpolation techniques. The Si version of our system has an MTF of 20% at 14 lp/mm and the CdZnTe version an MTF of 15% at 10 lp/mm. Our digital imaging devices and systems are intended for use in X-ray and gamma-ray imaging for medical diagnosis in a variety of applications ranging from conventional projection X-ray imaging and mammography to fluoroscopy and CT scanning. Similarly, the technology is intended for use in non destructive testing, product quality control and real time on-line monitoring

  10. Cobalt nanoparticles doped emaraldine salt of polyaniline: A promising room temperature magnetic semiconductor

    Science.gov (United States)

    Hatamie, Shadie; Kulkarni, M. V.; Kulkarni, S. D.; Ningthoujam, R. S.; Vatsa, R. K.; Kale, S. N.

    2010-12-01

    Incorporation of magnetic nanoparticles in polymers with organic functional groups working as semiconducting substrate is of immense interest in the field of dilute magnetic semiconductors (DMS) and spintronics. In this article we report on synthesis and evaluation of dilutely doped (0-10 wt%) cobalt nanoparticles in emaraldine salt (ES) of polyaniline in the presence of dodecyl benzene sulfonic acid (DBSA) and p-toluene sulfonic acid (p-TSA) using a sonochemical-assisted-reduction approach as a possible DMS candidate. The X-ray diffraction pattern and high resolution transmission electron microscopy (HRTEM) image show the ES to be polycrystalline, in which 10 nm sized Co nanoparticles get embedded in its FCC structural form. From Fourier transform infrared (FT-IR) and UV-visible (UV-vis) spectroscopy studies, it is predicted that cobalt particles get electrostatically bound to the specific SO3- ion sites of ES, thereby modifying torsional degrees of freedom of the system. The applied field dependent magnetization study shows that the sample exhibits hysteresis loop with a minimal doping of 3 wt% of Co nanoparticles and increases with the amount of Co nanoparticles in ES due to dipolar interaction. The electron transport data show that with increase in Co wt% there is a gradual shift from ohmic to non-ohmic response to the sample bias, accompanied by opening of electrical hysteresis and an increased resistance. The non-linear response of higher doped systems has been attributed to the combination of direct and Fowler-Nordheim tunneling phenomena in these systems. Persistence of optical and transport properties of the polymer, with an introduction of magnetic moment in the system, envisages the system to be a fine magnetic semiconductor.

  11. The dependence of magnetic ordering temperature in amorphous semiconductors on paramagnetic centre concentration

    International Nuclear Information System (INIS)

    Khokhlov, A.F.; Mashin, A.I.; Satanin, A.M.

    1981-01-01

    In silicon amorphized by ion implantation (a-Si) the dependence of magnetic ordering temperature (theta) on localized spin concentration (Nsub(s)) is studied by EPR method. Nsub(s) changes by varying the Ne + ion dose from 6x10 14 to 2x10 17 cm -2 and sample annealing. From the comparison of the data obtained with literature ones conclusions are made about the existence of two critical values of Nsub(s) in a-Si (approximately 10 19 and approximately 2x10 20 cm -3 ), when a transition occurs from paramagnetism to antiferromagnetism (at T < theta) and from antiferromagnetism to ferromagnetism, respectively. (author)

  12. Dielectric Properties of Cd1-xZnxSe Thin Film Semiconductors

    International Nuclear Information System (INIS)

    Wahab, L.A.; Farrag, A.A.; Zayed, H.A.

    2012-01-01

    Cd 1-x Zn x Se (x=0, 0.5 and 1) thin films of thickness 300 nm have been deposited on highly cleaned glass substrates (Soda-lime glass) by thermal evaporation technique under pressure 10-5 Torr. The crystal structure, lattice parameters and grain size were determined from X-ray diffraction patterns of these films. The dielectric response and ac conductivity of the films are investigated in the frequency range from 80 Hz to 5 MHz and temperature range from 300 K to 420 K. AC conductivity increases linearly with the frequency according to the power relation σ a c (ψ)=A (ψ) s . The dielectric constant and loss show low values at high frequencies. The relaxation time t, resistance R and capacitance C were calculated from Nyquist diagram. The behavior can be modeled by an equivalent parallel RC circuit.

  13. First-Principles Calculations of Structural, Electronic and Optical Properties of Ternary Semiconductor Alloys ZAs x Sb1- x ( Z = B, Al, Ga, In)

    Science.gov (United States)

    Bounab, S.; Bentabet, A.; Bouhadda, Y.; Belgoumri, Gh.; Fenineche, N.

    2017-08-01

    We have investigated the structural and electronic properties of the BAs x Sb 1- x , AlAs x Sb 1- x , GaAs x Sb 1- x and InAs x Sb 1- x semiconductor alloys using first-principles calculations under the virtual crystal approximation within both the density functional perturbation theory and the pseudopotential approach. In addition the optical properties have been calculated by using empirical methods. The ground state properties such as lattice constants, both bulk modulus and derivative of bulk modulus, energy gap, refractive index and optical dielectric constant have been calculated and discussed. The obtained results are in reasonable agreement with numerous experimental and theoretical data. The compositional dependence of the lattice constant, bulk modulus, energy gap and effective mass of electrons for ternary alloys show deviations from Vegard's law where our results are in agreement with the available data in the literature.

  14. Temperature stimulates charge carriers in Ce0.90Fe0.1O2 for semiconductor to metal phase

    Science.gov (United States)

    Parveen, Mubeena; Saravanan, G.; Asvini, V.; Ravichandran, K.; Kalaiselvi, D.

    2018-04-01

    Ce0.90Fe0.1O2, cubic structure exhibits interesting electrical property-due to the effects of oxygen vacancies. Electrical response of nanocrystalline Ce0.90Fe0.1O2 material as a function of temperature was investigated using impedance spectroscopy. A change was observed in Nyquist plot for the temperature 903k, which has been analysed in terms of localized and delocalized electrons. An interesting behaviour of temperature stimulate semiconductor to metal like transition was observed in frequency dependent dielectric constant (ɛ') and frequency dependent dielectric loss(tan δ). Frequency dependence on the real and imaginary part of impedence with respect to temperature aids the presences of semiconductor to metal like transition in Ce0.90Fe0.1O2.

  15. High-temperature stability of electron transport in semiconductors with strong spin-orbital interaction

    Science.gov (United States)

    Tomaka, G.; Grendysa, J.; ŚliŻ, P.; Becker, C. R.; Polit, J.; Wojnarowska, R.; Stadler, A.; Sheregii, E. M.

    2016-05-01

    Experimental results of the magnetotransport measurements (longitudinal magnetoresistance Rx x and the Hall resistance Rx y) are presented over a wide interval of temperatures for several samples of Hg1 -xCdxTe (x ≈0.13 -0.15 ) grown by MBE—thin layers (thickness about 100 nm) strained and not strained and thick ones with thickness about 1 μ m . An amazing temperature stability of the SdH-oscillation period and amplitude is observed in the entire temperature interval of measurements up to 50 K. Moreover, the quantum Hall effect (QHE) behavior of the Hall resistance is registered in the same temperature interval. These peculiarities of the Rx x and Rx y for strained thin layers are interpreted using quantum Hall conductivity (QHC) on topologically protected surface states (TPSS) [C. Brüne et al., Phys. Rev. Lett. 106, 126803 (2011), 10.1103/PhysRevLett.106.126803]. In the case of not strained layers it is assumed that the QHC on the TPSS (or on the resonant interface states) contributes also to the conductance of the bulk samples.

  16. Effect of temperature and magnetic field on disorder in semiconductor structures

    Energy Technology Data Exchange (ETDEWEB)

    Agrinskaya, N. V., E-mail: nina.agrins@mail.ioffe.ru; Kozub, V. I. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2017-02-15

    We present the results of consistent theoretical analysis of various factors that may lead to influence of temperature and external magnetic field on disorder in semiconductor structures. Main attention is paid to quantum well (QW) structures in which only QWs or both QW and barriers are doped (the doping level is assumed to be close to the value corresponding to the metal–insulator transition). The above factors include (i) ionization of localized states to the region of delocalized states above the mobility edge, which is presumed to exist in the impurity band; (ii) the coexistence in the upper and lower Hubbard bands (upon doping of QWs as well as barriers); in this case, in particular, the external magnetic field determines the relative contribution of the upper Hubbard band due to spin correlations at doubly filled sites; and (iii) the contribution of the exchange interaction at pairs of sites, in which the external magnetic field can affect the relation between ferromagnetic and antiferromagnetic configurations. All these factors, which affect the structure and degree of disorder, lead to specific features in the temperature dependence of resistivity and determine specific features of the magnetoresistance. Our conclusions are compared with available experimental data.

  17. Bound magnetic polaron driven low-temperature ferromagnetism in Cu1-xMnxO compounds

    Science.gov (United States)

    Cai, J. Z.; Li, L.; Wang, S.; Zou, W. Q.; Wu, X. S.; Zhang, F. M.

    2013-09-01

    Partial Mn atoms have been confirmed to enter the CuO lattice and form the Cu1-xMnxO compounds in the case of doping with 0≤x≤0.2 by the sol-gel method. With increasing Mn content, magnetism is observed. The magnetic critical transition temperature increases with enhanced magnetism, which obeys the bound magnetic polaron theory. The electronic transportation shows an insulating behavior as the band-gap decreases. Our results may indicate that CuO may be used as a candidate of magnetic semiconductor.

  18. Parallel of semi-empirical results simulated by MCNP of X-ray spectra with a semiconductor

    International Nuclear Information System (INIS)

    Santos, L.R.; Vivolo, V.; Potiens, M.P.A.; Navarro, M.V.T.; Santos, W.S.

    2016-01-01

    The aim of this study was to use the MCNPX radiation transport code to simulate X-ray spectra generated by a constant voltage system in a CdTe semiconductor detector. As part of the validation process, we obtained a series of experimental spectra. Comparatively, in all cases there is a good correlation between the two spectra. There were no statistically significant differences between the experimental results with the simulated. (author)

  19. Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopy

    OpenAIRE

    Acbas, G.; Kim, M. -H.; Cukr, M.; Novak, V.; Scarpulla, M. A.; Dubon, O. D.; Jungwirth, T.; Sinova, Jairo; Cerne, J.

    2009-01-01

    We employ Faraday and Kerr effect spectroscopy in the infrared range to investigate the electronic structure of Ga1-xMnxAs near the Fermi energy. The band structure of this archetypical dilute-moment ferromagnetic semiconductor has been a matter of controversy, fueled partly by previous measurements of the unpolarized infrared absorption and their phenomenological impurity-band interpretation. The infrared magneto-optical effects we study arise directly from the spin-splitting of the carrier ...

  20. Preparation of Si sub 1 sub - sub x sub - sub y Ge sub x C sub y semiconductor films on Si by ion implantation and solid phase epitaxy

    CERN Document Server

    Liu Xue Qin; Zhen Cong Mian; Zhang Jing; Yang Yi; Guo Yong

    2002-01-01

    Si sub 1 sub - sub x sub - sub y Ge sub x C sub y ternary alloy semiconductor films were prepared on Si(100) substrates by C ion implanting SiGe films and subsequent solid phase epitaxy (SPE). Two-step annealing technique was employed in the SPE processing. The properties of the alloy films were determined using Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and High-resolution x-ray diffraction (HRXRD) measurements. It is shown that C atoms are located at substitutional sites and the incorporation of C relieves the compressive strain in the SiGe layer

  1. Energy loss in degenerate semiconductors due to inelastic interaction with acoustic and piezoelectric phonons at low lattice temperatures

    International Nuclear Information System (INIS)

    Midday, S; Bhattacharya, D P

    2011-01-01

    The energy loss rate of an electron in a degenerate semiconductor because of inelastic interaction with deformation potential and piezoelectric acoustic phonons is calculated in the case when the lattice temperature is low, so that the approximations of the well-known traditional theory are not valid. Compared to the traditional results and those for non-degenerate semiconductors, the theory here reveals a more complex and altogether different dependence of the loss rate on the carrier energy and the lattice temperature. The numerical results obtained here for Si and GaAs show how significantly the degeneracy level, the true phonon distribution or the inelasticity of the interaction affects the loss characteristics at low temperatures.

  2. Application of the high-pressure thermoelectric technique for characterization of semiconductor microsamples: PbX-based compounds

    International Nuclear Information System (INIS)

    Ovsyannikov, Sergey V; Shchennikov, Vladimir V; Ponosov, Yuri S; Gudina, Svetlana V; Guk, Vera G; Skipetrov, Eugenii P; Mogilenskikh, Viktor E

    2004-01-01

    In this paper the technique of thermoelectric measurements at high pressure was applied for characterization of semiconductor microsamples based on lead chalcogenide compounds (p-PbSe, n-Pb 1-x Sn x Se). The Raman scattering technique at ambient pressure was used as an alternative tool for testing of the samples. Raman measurements have revealed broad peaks at 135 and 265 cm -1 for PbSe and Pb 1-x Sn x Se. Analogous spectra were obtained for PbS, and PbTe-based ternary compounds at higher and lower frequencies, respectively. The peaks have been attributed to the first- and second-order Raman modes. From resistivity and thermoelectric power data the linear decrease in the pressure of the NaCl → GeS structural phase transition with increasing Sn content has been established and the thermopower of high-pressure GeS phases have been determined. Thermoelectric properties of the samples at high pressure have shown high sensitivity to a small variation in the composition of the ternary Pb 1-x Sn x Se compounds, which makes it possible to distinguish semiconductor microsamples whose compositions are very similar

  3. A novel high temperature scanning tunneling microscope for investigating semiconductor surfaces

    Science.gov (United States)

    Lamb, Mark Alan

    2001-11-01

    The issues concerning the description of structural and dynamic features at the nanometer scale has become an active field of research in surface science. The development of the scanning tunneling microscope (STM) has begun only recently to contribute substantially in this effort. For this dissertation project, the author has designed, constructed, and utilized a high temperature ultra high vacuum STM (HT-UHV-STM) for investigating semiconducting surfaces from room temperature to 790°C. In order to isolate the instrument from external noise, the author has developed and demonstrated a novel method of approaching decoupled passive magnetic levitation for vibration isolation. Using advanced magnet technology currently available, this isolation method could achieve resonance frequencies as low as 10-3 Hz for levitation pressures as high as several MPa in a single stage. The instrument has been used to study the clean Si(111) surface at high temperatures. The electromigration phenomenon has been utilized to modify the surface steps and produce metastable reconstruction zones of the "1 x 1" phase and 5 x 5 islands. The growth of the thermodynamically favored 7 x 7 reconstruction has been observed at high temperatures within these metastable phases. The production of nanostructures on the surface by the tip of the STM has been achieved and their thermal relaxation observed and analyzed. Several new observations include the appearance of periodic oscillations in the number of Si atoms constituting each of a pair of 5 x 5 magic islands, imaging of local melting and apparent sputtering of the surface by the tip, and the spontaneous formation of clusters by heat treatment.

  4. Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors.

    Science.gov (United States)

    Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Eickhoff, Martin

    2015-09-23

    In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO₂ and NH₃, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high.

  5. Bound magnetic polaron driven low-temperature ferromagnetism in Cu{sub 1−x}Mn{sub x}O compounds

    Energy Technology Data Exchange (ETDEWEB)

    Cai, J.Z.; Li, L.; Wang, S.; Zou, W.Q.; Wu, X.S., E-mail: xswu@nju.edu.cn; Zhang, F.M., E-mail: fmzhang@nju.edu.cn

    2013-09-01

    Partial Mn atoms have been confirmed to enter the CuO lattice and form the Cu{sub 1−x}Mn{sub x}O compounds in the case of doping with 0≤x≤0.2 by the sol–gel method. With increasing Mn content, magnetism is observed. The magnetic critical transition temperature increases with enhanced magnetism, which obeys the bound magnetic polaron theory. The electronic transportation shows an insulating behavior as the band-gap decreases. Our results may indicate that CuO may be used as a candidate of magnetic semiconductor.

  6. Impact of process temperature on GaSb metal-oxide-semiconductor interface properties fabricated by ex-situ process

    Science.gov (United States)

    Yokoyama, Masafumi; Asakura, Yuji; Yokoyama, Haruki; Takenaka, Mitsuru; Takagi, Shinichi

    2014-06-01

    We have studied the impact of process temperature on interface properties of GaSb metal-oxide-semiconductor (MOS) structures fabricated by an ex-situ atomic-layer-deposition (ALD) process. We have found that the ALD temperature strongly affects the Al2O3/GaSb MOS interface properties. The Al2O3/GaSb MOS interfaces fabricated at the low ALD temperature of 150 °C have the minimum interface-trap density (Dit) of ˜4.5 × 1013 cm-2 eV-1. We have also found that the post-metalization annealing at temperature higher than 200 °C degrades the Al2O3/GaSb MOS interface properties. The low-temperature process is preferable in fabricating GaSb MOS interfaces in the ex-situ ALD process to avoid the high-temperature-induced degradations.

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

    Science.gov (United States)

    Suja, Mohammad Zahir Uddin

    Room temperature excitonic lasing is demonstrated and developed by utilizing metal-semiconductor-metal devices based on ZnO and MgZnO materials. At first, Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films and the best conductivity is achieved with a high hole concentration of 1.54x1018 cm-3, a low resistivity of 0.6 O cm and a moderate mobility of 6.65 cm2 V -1 s-1 at room temperature. Metal oxide semiconductor (MOS) capacitor devices have been fabricated on the Cu-doped ZnO films and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as XRD, XPS, Raman and absorption are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO. To overcome the stability issue of p-type ZnO film, alternate devices other than p-n junction has been developed. Electrically driven plasmon-exciton coupled random lasing is demonstrated by incorporating Ag nanoparticles on Cu-doped ZnO metal-semiconductor-metal (MSM) devices. Both photoluminescence and electroluminescence studies show that emission efficiencies have been enhanced significantly due to coupling between ZnO excitons and Ag surface plasmons. With the incorporation of Ag nanoparticles on ZnO MSM structures, internal quantum

  8. Semiconductor-to-metallic flipping in a ZnFe2O4–graphene based smart nano-system: Temperature/microwave magneto-dielectric spectroscopy

    International Nuclear Information System (INIS)

    Ameer, Shahid; Gul, Iftikhar Hussain; Mahmood, Nasir; Mujahid, Muhammad

    2015-01-01

    Zn-(FeO 2 ) 2 –graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis with different percentages of graphene. The structure of the nanocomposite was confirmed through X-ray diffraction, micro-Raman scattering spectroscopy, Ultraviolet–Visible spectroscopy, and Fourier transform infrared spectroscopy. The structural growth and morphological aspects were analyzed using scanning/transmission electron microscopy, revealing marvelous micro-structural features of the assembled nano-system resembling a maple leaf. To determine the composition, energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used. Microwave magneto-dielectric spectroscopy revealed the improved dielectric properties of the nano-composite compared to those of the parent functional nanocrystals. Temperature gradient dielectric spectroscopy was used over the spectral range from 100 Hz to 5 MHz to reveal the phenomenological effect that the nanosystem flips from its usual semiconductor nature to a metallic nature with sensing temperature. Electrical conductivity and dielectric analysis indicated that the dielectric loss and the dielectric permittivity increased at room temperature. This extraordinary switching capability of the functionalized graphene nanosystem opens up a new dimension for engineering advanced and efficient smart composite materials. - Graphical abstract: Display Omitted - Highlights: • Zn-(FeO 2 ) 2 –graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis. • The synthesized nano-system exhibits marvelous leaf like microstructure. • These nano-composites show improved magneto dielectric response. • This engineered smart nano-system shows phenomenological flipping from semiconductor like nature to metallic behavior

  9. The role of hydrostatic pressure and temperature on bound polaron in semiconductor quantum dot

    International Nuclear Information System (INIS)

    El Moussaouy, A.; Ouchani, N.

    2014-01-01

    We studied theoretically the effects of hydrostatic pressure and temperature on the binding energy of shallow hydrogenic impurity in a cylindrical quantum dot (QD) using a variational approach within the effective mass approximation. The hydrostatic stress was applied along the QD growth axis. The interactions between the charge carriers and confined longitudinal optical (LO) phonon modes are taken into account. The numerical computation for GaAs/Ga 1−x Al x As QD has shown that the binding energy with and without the polaronic correction depends on the location of the impurity and the pressure effect and it is more pronounced for impurities in the QD center. Both the binding energy and the polaronic contribution increase linearly with increasing stress. For each pressure value, these energies are also found to decrease as the temperature increases. The results obtained show that in experimental studies of optical and electronic properties of QDs, the effects of pressure, temperature and polaronic correction on donor impurity binding energy should be taken into consideration

  10. Low Power Operation of Temperature-Modulated Metal Oxide Semiconductor Gas Sensors.

    Science.gov (United States)

    Burgués, Javier; Marco, Santiago

    2018-01-25

    Mobile applications based on gas sensing present new opportunities for low-cost air quality monitoring, safety, and healthcare. Metal oxide semiconductor (MOX) gas sensors represent the most prominent technology for integration into portable devices, such as smartphones and wearables. Traditionally, MOX sensors have been continuously powered to increase the stability of the sensing layer. However, continuous power is not feasible in many battery-operated applications due to power consumption limitations or the intended intermittent device operation. This work benchmarks two low-power, duty-cycling, and on-demand modes against the continuous power one. The duty-cycling mode periodically turns the sensors on and off and represents a trade-off between power consumption and stability. On-demand operation achieves the lowest power consumption by powering the sensors only while taking a measurement. Twelve thermally modulated SB-500-12 (FIS Inc. Jacksonville, FL, USA) sensors were exposed to low concentrations of carbon monoxide (0-9 ppm) with environmental conditions, such as ambient humidity (15-75% relative humidity) and temperature (21-27 °C), varying within the indicated ranges. Partial Least Squares (PLS) models were built using calibration data, and the prediction error in external validation samples was evaluated during the two weeks following calibration. We found that on-demand operation produced a deformation of the sensor conductance patterns, which led to an increase in the prediction error by almost a factor of 5 as compared to continuous operation (2.2 versus 0.45 ppm). Applying a 10% duty-cycling operation of 10-min periods reduced this prediction error to a factor of 2 (0.9 versus 0.45 ppm). The proposed duty-cycling powering scheme saved up to 90% energy as compared to the continuous operating mode. This low-power mode may be advantageous for applications that do not require continuous and periodic measurements, and which can tolerate slightly higher

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

    Energy Technology Data Exchange (ETDEWEB)

    Taube, A.; Łapińska, A.; Judek, J.; Zdrojek, M., E-mail: zdrojek@if.pw.edu.pl [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland)

    2015-07-06

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

  12. In situ X-ray investigations of oxygen precipitation in semiconductor silicon; In-situ-Roentgenuntersuchungen der Sauerstoffpraezipitation in Halbleitersilizium

    Energy Technology Data Exchange (ETDEWEB)

    Grillenberger, Hannes

    2011-03-04

    The precipitation of oxygen in Czochralski grown semiconductor silicon is investigated in situ during thermal treatments up to 1000 C with high energy X-rays. All investigations are performed with a focusing Laue diffractometer. The parameters of the diffraction curve are the relative full width at half maximum (rFHWM) and the enhancement of the integral intensity (EII). A readout software has been developed to extract these automatically from the detector image for the measured 220, -220 and 040 Bragg peaks. The sample thickness is set to 15 mm as this enhances the sensitivity of the method and the samples are processed after the strain-field diffraction (SFD) experiments to wafers for an ex situ characterization demanding wafers. Three experimental series with a total of 21 in situ SFD experiments with different thermal treatments have been performed. The slope of the initial temperature ramp is set to 1 K/min in the first and the third series to generate a high precipitate (Bulk Micro Defect, BMD) density. In the second series the slope is chosen as 10 K/min to generate a lower density in the same silicon material. It is shown with all experiments and with preliminary works that the built up of strain during the heat treatment is caused by BMDs during the high temperature period of the treatment. The detection limit of series 1 is found at 7 nm at a density of 10{sup 13}/cm{sup 3}, of series 2 at 40 nm at a density of 2 x 10{sup 8}/cm{sup 3}, and at 8 nm at a density of 4.8 x 10{sup 12}/cm{sup 3} for series 3. The local maximum of the EII at 450 C, which emerges coincident with a local minimum of the rFWHM in series 2 may be caused by thermal donors (TD). With the experiments is shown that SFD operates in the infrared-laser scattering tomography detection range, but also reaches in a region covered only by transmission electron microscopy (TEM) so far. In contrast to these methods SFD is not limited to low temperatures and in situ experiments can be done. Thus

  13. Measurement of minute local strain in semiconductor materials and electronic devices by using a highly parallel X-ray microbeam

    CERN Document Server

    Matsui, J; Yokoyama, K; Takeda, S; Katou, M; Kurihara, H; Watanabe, K; Kagoshima, Y; Kimura, S

    2003-01-01

    We have developed an X-ray microbeam with a small angular divergence by adopting X-ray optics with successive use of asymmetric Bragg reflection from silicon crystals for the both polarizations of the synchrotron X-rays. The microbeam actually obtained is several microns in size and possesses an angular divergence of less than 2 arcsec which enables us to measure the strain of 10 sup - sup 5 -10 sup - sup 6. By scanning the sample against the microbeam, distribution of the minute local strain in various regions of semiconductor crystals for electronic devices, e.g., the strain around the SiO sub 2 /Si film edge in silicon devices, the strain in an InGaAsP/InP stripe laser were measured.

  14. Development of high power X-band semiconductor microwave switch for pulse compression systems of future linear colliders

    Directory of Open Access Journals (Sweden)

    Fumihiko Tamura

    2002-06-01

    Full Text Available We describe concepts for high power semiconductor rf switches, designed to handle signals at X-band with power level near 100 MW. We describe an abstract design methodology and derive a general scaling law for these switches. We also present a design and experimental work of a switch operating at the TE_{01} mode in overmoded circular waveguides. The switch is composed of an array of tee junction elements that have a p-i-n diode array window in the third arm.

  15. Growth and characterization of monocrystals from HgI2 semiconductor compound for using in X and gamma spectroscopy

    International Nuclear Information System (INIS)

    Faria, L.O. de.

    1987-09-01

    Mercury Iodide (HgI 2 ) platelets were grown from the vapor phase in the presence of polymers. These platelets are convenient to be used as room temperature operating semiconductor radiation detectors. Experiments demonstrate that the growth of platelets depends on a two-stage mass transport instead of depending on just one, as it has been thought. HgI 2 platelets 30 mm 2 large and 90 μm thick were obtained in a sealed evacuated fused quartz tube and were characterized by etch pit density measurements. (author)

  16. Monocrystal growth and characterization of HgI2 semiconductor compound for using in X and gamma spectrometries

    International Nuclear Information System (INIS)

    Faria, L.O.

    1987-01-01

    Mercury Iodide (HgI 2 ) platelets were grown from the vapor phase in the presence of polymers. These platelets are convenient to be used as room temperature operating semiconductor radiation detectors. Experiments demonstrate that the growth of platelets depends on a two-stage mass transport instead of depending on just one, as it has been thought. HgI 2 platelets 30 mm 2 large and 90 μm thick were obtained in a sealed evacuated fused quartz tube and were characterized by etch pit density measurements. (author) [pt

  17. Carrier concentration induced ferromagnetism in semiconductors

    International Nuclear Information System (INIS)

    Story, T.

    2007-01-01

    In semiconductor spintronics the key materials issue concerns ferromagnetic semiconductors that would, in particular, permit an integration (in a single multilayer heterostructure) of standard electronic functions of semiconductors with magnetic memory function. Although classical semiconductor materials, such as Si or GaAs, are nonmagnetic, upon substitutional incorporation of magnetic ions (typically of a few atomic percents of Mn 2+ ions) and very heavy doping with conducting carriers (at the level of 10 20 - 10 21 cm -3 ) a ferromagnetic transition can be induced in such diluted magnetic semiconductors (also known as semimagnetic semiconductors). In the lecture the spectacular experimental observations of carrier concentration induced ferromagnetism will be discussed for three model semiconductor crystals. p - Ga 1-x Mn x As currently the most actively studied and most perspective ferromagnetic semiconductor of III-V group, in which ferromagnetism appears due to Mn ions providing both local magnetic moments and acting as acceptor centers. p - Sn 1-x Mn x Te and p - Ge 1-x Mn x Te classical diluted magnetic semiconductors of IV-VI group, in which paramagnet-ferromagnet and ferromagnet-spin glass transitions are found for very high hole concentration. n - Eu 1-x Gd x Te mixed magnetic crystals, in which the substitution of Gd 3+ ions for Eu 2+ ions creates very high electron concentration and transforms antiferromagnetic EuTe (insulating compound) into ferromagnetic n-type semiconductor alloy. For each of these materials systems the key physical features will be discussed concerning: local magnetic moments formation, magnetic phase diagram as a function of magnetic ions and carrier concentration as well as Curie temperature and magnetic anisotropy engineering. Various theoretical models proposed to explain the effect of carrier concentration induced ferromagnetism in semiconductors will be briefly discussed involving mean field approaches based on Zener and RKKY

  18. Prospects and fundamental limitations of room temperature, non-avalanche, semiconductor photon-counting sensors (Conference Presentation)

    Science.gov (United States)

    Ma, Jiaju; Zhang, Yang; Wang, Xiaoxin; Ying, Lei; Masoodian, Saleh; Wang, Zhiyuan; Starkey, Dakota A.; Deng, Wei; Kumar, Rahul; Wu, Yang; Ghetmiri, Seyed Amir; Yu, Zongfu; Yu, Shui-Qing; Salamo, Gregory J.; Fossum, Eric R.; Liu, Jifeng

    2017-05-01

    This research investigates the fundamental limits and trade-space of quantum semiconductor photodetectors using the Schrödinger equation and the laws of thermodynamics.We envision that, to optimize the metrics of single photon detection, it is critical to maximize the optical absorption in the minimal volume and minimize the carrier transit process simultaneously. Integration of photon management with quantum charge transport/redistribution upon optical excitation can be engineered to maximize the quantum efficiency (QE) and data rate and minimize timing jitter at the same time. Due to the ultra-low capacitance of these quantum devices, even a single photoelectron transfer can induce a notable change in the voltage, enabling non-avalanche single photon detection at room temperature as has been recently demonstrated in Si quanta image sensors (QIS). In this research, uniform III-V quantum dots (QDs) and Si QIS are used as model systems to test the theory experimentally. Based on the fundamental understanding, we also propose proof-of-concept, photon-managed quantum capacitance photodetectors. Built upon the concepts of QIS and single electron transistor (SET), this novel device structure provides a model system to synergistically test the fundamental limits and tradespace predicted by the theory for semiconductor detectors. This project is sponsored under DARPA/ARO's DETECT Program: Fundamental Limits of Quantum Semiconductor Photodetectors.

  19. Computational Search for Two-Dimensional MX2 Semiconductors with Possible High Electron Mobility at Room Temperature

    Directory of Open Access Journals (Sweden)

    Zhishuo Huang

    2016-08-01

    Full Text Available Neither of the two typical two-dimensional materials, graphene and single layer MoS 2 , are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX 2 , where M (=Mo, W, Sn, Hf, Zr and Pt are transition metals, and Xs are S, Se and Te. We approximated the electron phonon scattering matrix by deformation potentials, within which long wave longitudinal acoustical and optical phonon scatterings were included. Piezoelectric scattering in the compounds without inversion symmetry is also taken into account. We found that out of the 14 compounds, WS 2 , PtS 2 and PtSe 2 are promising for logical devices regarding the possible high electron mobility and finite band gap. Especially, the phonon limited electron mobility in PtSe 2 reaches about 4000 cm 2 ·V - 1 ·s - 1 at room temperature, which is the highest among the compounds with an indirect bandgap of about 1.25 eV under the local density approximation. Our results can be the first guide for experiments to synthesize better two-dimensional materials for future semiconductor devices.

  20. X-ray magnetic dichroism in (Zn,Mn)O diluted magnetic semiconductors: First-principles calculations

    Science.gov (United States)

    Antonov, V. N.; Bekenov, L. V.; Mazur, D. V.; Germash, L. P.

    2012-06-01

    The electronic structure of (Zn,Mn)O diluted magnetic semiconductors was investigated theoretically from first principles by using the fully-relativistic Dirac linear muffin-tin orbital band structure method with the local spin-density approximation (LSDA) and the LSDA+ U approach. The X-ray magnetic circular dichroism (XMCD) spectra at the Mn, Zn, and O K and Mn L 2,3 edges were investigated theoretically from first principles. The origin of the XMCD spectra in these compounds was examined. The effect of oxygen vacancy atoms was found to be crucial for the X-ray magnetic dichroism at the Mn L 2,3 edges. The calculated results are compared with available experimental data.

  1. Development of High Power X-Band Semiconductor RF Switch for Pulse Compression Systems of Future Linear Colliders

    International Nuclear Information System (INIS)

    Tantawi, Sami

    2000-01-01

    We describe development of semiconductor X-band high-power RF switches. The target applications are high-power RF pulse compression systems for future linear colliders. We describe the design methodology of the architecture of the whole switch systems. We present the scaling law that governs the relation between power handling capability and number of elements. We designed and built several active waveguide windows for the active element. The waveguide window is a silicon wafer with an array of four hundred PIN/NIP diodes covering the surface of the window. This waveguide window is located in an over-moded TE01 circular waveguide. The results of high power RF measurements of the active waveguide window are presented. The experiment is performed at power levels of a few megawatts at X-band

  2. Room temperature transparent conducting magnetic oxide (TCMO properties in heavy ion doped oxide semiconductor

    Directory of Open Access Journals (Sweden)

    Juwon Lee

    2017-08-01

    Full Text Available Bismuth doped ZnO (ZnBi0.03O0.97 thin films are grown using pulsed laser deposition. The existence of positively charged Bi, absence of metallic zinc and the Zn-O bond formation in Bi doped ZnO are confirmed using X-ray Photoelectron Spectroscopy (XPS. Temperature dependent resistivity and UV-visible absorption spectra show lowest resistivity with 8.44 × 10-4 Ω cm at 300 K and average transmittance of 93 % in the visible region respectively. The robust ferromagnetic signature is observed at 350 K (7.156 × 10-4 emu/g. This study suggests that Bi doped ZnO films should be a potential candidate for spin based optoelectronic applications.

  3. Structural characterization of the high-temperature modification of the Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor compound

    Energy Technology Data Exchange (ETDEWEB)

    Nieves, L.; Marcano, G.; Power, C.; Rincon, C. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Lopez-Rivera, S.A. [Grupo de Fisica Aplicada, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of)

    2016-06-15

    A combined study of the X-ray powder diffraction, differential thermal analysis, optical absorption, and Raman spectroscopy of the high-temperature modification of Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor, obtained by fast quenching from 820 K to ice water temperature, has been done. It has been found that this phase crystallizes in a tetragonal kesterite-type structure. From the analysis of the absorption coefficient spectra, the band gap energy of this material at room temperature has been found to be 1.49 eV. An optical transition from defect acceptor states to the conduction band is also observed below the fundamental absorption edge. Three strongest Raman lines observed at 116, 119, and 139 cm{sup -1} have been assigned to the A-symmetry modes. Also, lines at 81, 89, 97, and 263 cm{sup -1} tentatively ascribed as B or E-symmetry modes have been detected from the spectrum. The presence in this high-temperature modification of ZnTe and Cu{sub 2}GeTe{sub 3} secondary phases has been detected by both XRD and Raman spectroscopy. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Semiconductor annealing

    International Nuclear Information System (INIS)

    Young, J.M.; Scovell, P.D.

    1982-01-01

    A process for annealing crystal damage in ion implanted semiconductor devices in which the device is rapidly heated to a temperature between 450 and 900 0 C and allowed to cool. It has been found that such heating of the device to these relatively low temperatures results in rapid annealing. In one application the device may be heated on a graphite element mounted between electrodes in an inert atmosphere in a chamber. (author)

  5. Improvement of thermal characteristics by radiation catalyst. 2. Leidenfrost temperature on surface of semiconductor-coated material

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Yasuyuki; Takamasa, Tomoji [Tokyo Univ. of Mercantile Marine, Tokyo (Japan); Okamoto, Koji [Tokyo Univ., Tokai, Ibaraki (Japan); Ogawa, Norihiro [Tokyo Univ., Tokyo (Japan); Mishima, Kaichiro [Kyoto Univ., Kumatori, Osaka (Japan); Uematsu, Susumu [Ship Research Institute, Mitaka, Tokyo (Japan)

    2001-07-01

    An experimental study to investigate Leidenfrost temperature was performed by use of oxide semiconductor-coated materials under {gamma} ray radiation environment. The purpose of the experiment was to clarify the thermal properties of the materials irradiated by {gamma} ray, to improve the critical heat flux. Two {sup 60}Co {gamma} ray facilities in University of Tokyo and in Kyoto University were used in the experiment. Leidenfrost temperature or lifetime of water droplet on the heated material surface was measured by use of a lead-bismuth pot and a CCD video camera. The results revealed that Leidenfrost temperature on the surface of oxide-titanium increased about 20-50degC after {gamma} ray irradiation. This effect of radiation catalyst was lost after the end of the irradiation. (author)

  6. Synthesis of diluted magnetic semiconductor Bi{sub 2−x}Mn{sub x}Te{sub 3} nanocrystals in a host glass matrix

    Energy Technology Data Exchange (ETDEWEB)

    Silva, R.S. [Instituto de Ciências Exatas, Naturais e Educação (ICENE), Departamento de Física, Universidade Federal do Triângulo Mineiro, 38025-180 Uberaba, Minas Gerais (Brazil); Mikhail, H.D., E-mail: ricardosilva@fisica.uftm.edu.br [Instituto de Ciências Tecnológicas e Exatas (ICTE), Departamento de Engenharia Mecânica, Universidade Federal do Triângulo Mineiro, 38064-200 Uberaba, Minas Gerais (Brazil); Pavani, R. [Instituto de Ciências Exatas, Naturais e Educação (ICENE), Departamento de Física, Universidade Federal do Triângulo Mineiro, 38025-180 Uberaba, Minas Gerais (Brazil); Cano, N.F. [Departamento de Ciências do Mar, Universidade Federal de São Paulo, 11030-400 Santos, São Paulo (Brazil); Silva, A.C.A.; Dantas, N.O. [Instituto de Física, Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Universidade Federal de Uberlândia, 38400-902 Uberlândia, Minas Gerais (Brazil)

    2015-11-05

    Diluted magnetic semiconductors of manganese doped in bismuth-telluride nanocrystals (Bi{sub 2−x}Mn{sub x}Te{sub 3} NCs) were grown in a glass matrix and investigated by Transmission Electron Microscopy, X-Ray Diffraction, Atomic Force Microscopy/Magnetic Force Microscopy, and Electron Paramagnetic Resonance. TEM images showed that the nanocrystals formed within the glass matrix were nearly spherical, with average sizes between 4 and 5 nm, and d{sub 015}-spacing of approximately 0.322 nm, which corresponds to the (015) interplanar distance in Bi{sub 2}Te{sub 3} bulk. The diffraction patterns showed that the diffraction peak associated with the (015) plane of the Bi{sub 2−x}Mn{sub x}Te{sub 3} nanocrystals shifts to larger diffraction angles as manganese (Mn) concentration increases, suggesting that the Mn{sup 2+} ions are substitutional defects occupying Bi sites (Mn{sub Bi}). AFM and MFM measurements showed magnetic phase contrast patterns, providing further evidence of Mn{sup 2+} ion incorporation in the nanocrystal structure. EPR signal of manganese ion incorporation and valence states in the crystalline structure of the Bi{sub 2}Te{sub 3} nanocrystals confirmed the presence of the Mn{sup 2+} state. - Highlights: • Bi{sub 2−x}Mn{sub x}Te{sub 3} NCs were synthesized in a glass matrix by fusion method. • Transmission Electronic Microscopy shows the formation of Bi{sub 2−x}Mn{sub x}Te{sub 3} NCs. • The sp-d exchange interaction in DMS NCs can be evidenced by X Ray-Diffraction and Magnetic Force Microscopy. • Electron Paramagnetic Resonance spectra confirmed that Mn{sup 2+} ions are located in two distinct Bi{sub 2}Te{sub 3} NCs sites.

  7. Colloidal Nanocrystals of Wurtzite Zn1-xCoxO (0 ≤ x ≤ 1): Models of Spinodal Decomposition in an Oxide Diluted Magnetic Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    White, Michael A.; Ochsenbein, Stefan T.; Gamelin, Daniel R.

    2008-11-25

    Magnetic-ion-rich nanoscale inclusions formed by spinodal decomposition have been observed in many diluted magnetic semiconductors and have recently been implicated in the ferromagnetic ordering observed in some of these materials. In this study, colloidal nanocrystals of the ternary alloy wurtzite Zn1-xCoxO, with x ranging from 0.0 (w-ZnO) to 1.0 (w-CoO), have been synthesized as model systems for the proposed spinodal decomposition nanostrucures of ferromagnetic Zn1-xCoxO thin films and powders. As freestanding nanocrystals, these phases do not show any signs of ferromagnetism or superparamagnetism at any value of x. Changes in the electronic absorption and magnetic circular dichroism (MCD) spectra with x are described that should allow optical identification of spinodal decomposition in other Zn1-xCoxO samples. Optical and magneto-optical spectroscopic results are presented for the end member of this series (w-CoO), apparently for the first time, and show this binary oxide to be an indirect gap chargetransfer insulator with Eg ≈ 2.3 eV.

  8. Colloidal Nanocrystals of Wurtzite Zn 1-xCox0 (0 ≤ x ≥ 1) Models of Spinodal Decomposition in an Oxide Diluted Magnetic Semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    White, Michael A.; Ochsenbein, Stefan T.; Gamelin, Daniel R.

    2008-11-25

    Magnetic-ion-rich nanoscale inclusions formed by spinodal decomposition have been observed in many diluted magnetic semiconductors and have recently been implicated in the ferromagnetic ordering observed in some of these materials. In this study, colloidal nanocrystals of the ternary alloy wurtzite Zn1-xCoxO, with x ranging from 0.0 (w-ZnO) to 1.0 (w-CoO), have been synthesized as model systems for the proposed spinodal decomposition nanostrucures of ferromagnetic Zn1-xCoxO thin films and powders. As freestanding nanocrystals, these phases do not show any signs of ferromagnetism or superparamagnetism at any value of x. Changes in the electronic absorption and magnetic circular dichroism (MCD) spectra with x are described that should allow optical identification of spinodal decomposition in other Zn1-xCoxO samples. Optical and magneto-optical spectroscopic results are presented for the end member of this series (w-CoO), apparently for the first time, and show this binary oxide to be an indirect gap chargetransfer insulator with Eg ≈ 2.3 eV.

  9. Multiphonon resonant Raman scattering in the semimagnetic semiconductor Cd sub 1 sub - sub x Mn sub x Te: Froehlich and deformation potential exciton-phonon interaction

    CERN Document Server

    Riera, R; Marin, J L; Bergues, J M; Campoy, G

    2003-01-01

    A theory describing multiphonon resonant Raman scattering (MPRRS) processes in wide-gap diluted magnetic semiconductors is presented, with Cd sub 1 sub - sub x Mn sub x Te as an example. The incident radiation frequency omega sub l is taken above the fundamental absorption region. The photoexcited electron and hole make real transitions through the LO phonon, when one considers Froehlich (F) and deformation potential (DP) interactions. The strong exchange interaction, typical of these materials, leads to a large spin splitting of the exciton states in the magnetic field. Neglecting Landau quantization, this Zeeman splitting gives rise to the formation of eight bands (two conduction and six valence ones) and ten different exciton states according to the polarization of the incident light. Explicit expressions for the MPRRS intensity of second and third order, the indirect creation and annihilation probabilities, the exciton lifetime, and the probabilities of transition between different exciton states and diff...

  10. Low temperature magnetic characterization of EuO1-x

    Science.gov (United States)

    Rimal, Gaurab; Tang, Jinke

    EuO is a widely studied magnetic semiconductor. It is an ideal case of a Heisenberg ferromagnet as well as a model magnetic polaron system. The interesting aspect of this material is the existance of magnetic polarons in the low temperature region. We study the properties of oxygen deficient EuO prepared by pulsed laser deposition. Besides normal ferromagnetic transitions near 70K and 140K, we observe a different transition at 16K. We also observe a shift in the coercivity for field cooling versus zero field cooling. Possible mechanisms driving these behaviors will be discussed. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (DEFG02-10ER46728) and by the School of Energy Resources of the University of Wyoming.

  11. Study of the modifications induced in AlxGa1-xN semiconductors under swift heavy ion irradiation

    International Nuclear Information System (INIS)

    Moisy, Florent

    2016-01-01

    Nitride semiconductors are attractive materials for optoelectronic applications. They can be subjected to heavy ions in a wide range of energy during their elaboration (improvement of their properties by ionic implantation) or during their potential use in extreme environments (outer space). This thesis focuses on the study of AlxGa1-xN alloys under heavy ion irradiation from GANIL. In GaN, the formation of Ga vacancies has been highlighted, these latter coming from elastic collisions between atoms in the material and the projectiles. On the other hand, it is possible to observe the formation of disordered ion tracks for projectiles with high electronic stopping power (Se). These tracks induce strong surface modifications, a closing of the optical bandgap, but also an extension strain along the direction parallel to the ion direction and biaxial stresses of some GPa. Concerning AlxGa1-xN alloys with x from 0.3 to 1, the points defects are more complex, and a synergy between electronic excitations and nuclear collisions is responsible of their formation. Nevertheless, the increase of the Al molar fraction (x), tends to improve the resistance to ion tracks formation in these materials. (author) [fr

  12. Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors

    Directory of Open Access Journals (Sweden)

    Konrad Maier

    2015-09-01

    Full Text Available In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO2 and NH3, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high.

  13. Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors

    Science.gov (United States)

    Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Eickhoff, Martin

    2015-01-01

    In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO2 and NH3, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high. PMID:28793583

  14. Room-temperature semiconductor detectors for in vivo monitoring of internal contamination.

    Science.gov (United States)

    Genicot, J L

    1997-01-01

    In vivo monitoring of low-energy X-ray and gamma-ray emitters has always been a difficult task, primarily because of lack of accuracy and the high detection limits of classical techniques. Various types of PIN diodes (diodes with a large intrinsic zone) were tested in the Radiation Protection Department of the Studie Centrum voor Kernenergie, Centre d'étude de l'Energie Nucléaire (Mol, Belgium) in the measurement of radioactive body burden by direct methods. Current research is oriented toward the use of room-temperature diodes for the detection of low-energy photons escaping the body. In this paper, a new counting technique that involves a portable jacket containing the diodes is described. The system uses silicon diodes and is used out of shielding room in order to be near the contamination. With this method rapid analysis and long counting times are possible, stress is reduced, and medical treatment can be optimized. CdZnTe detectors were also evaluated for this measurement technique but this type of detector is better adapted for counting inside a shielding room. The improvement of the accuracy of the measurement, taking into account the effect of the ribs, is described here, as well the associated electronics necessary for this type of counting. Images Figure 1. PMID:9467055

  15. Impact of process temperature on GaSb metal-oxide-semiconductor interface properties fabricated by ex-situ process

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, Masafumi, E-mail: yokoyama@mosfet.t.u-tokyo.ac.jp; Takenaka, Mitsuru; Takagi, Shinichi [Department of Electrical Engineering and Information Systems, The University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); JST-CREST, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); Asakura, Yuji [Department of Electrical Engineering and Information Systems, The University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032 (Japan); Yokoyama, Haruki [NTT Photonics Laboratories, NTT Corporation, Atsugi 243-0198 (Japan)

    2014-06-30

    We have studied the impact of process temperature on interface properties of GaSb metal-oxide-semiconductor (MOS) structures fabricated by an ex-situ atomic-layer-deposition (ALD) process. We have found that the ALD temperature strongly affects the Al{sub 2}O{sub 3}/GaSb MOS interface properties. The Al{sub 2}O{sub 3}/GaSb MOS interfaces fabricated at the low ALD temperature of 150 °C have the minimum interface-trap density (D{sub it}) of ∼4.5 × 10{sup 13 }cm{sup −2} eV{sup −1}. We have also found that the post-metalization annealing at temperature higher than 200 °C degrades the Al{sub 2}O{sub 3}/GaSb MOS interface properties. The low-temperature process is preferable in fabricating GaSb MOS interfaces in the ex-situ ALD process to avoid the high-temperature-induced degradations.

  16. Charge Carriers Modulate the Bonding of Semiconductor Nanoparticle Dopants As Revealed by Time-Resolved X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Asra; Zhang, Xiaoyi; Liu, Xiaohan; Rowland, Clare E. [Department; Jawaid, Ali M.; Chattopadhyay, Soma; Gulec, Ahmet; Shamirian, Armen; Zuo, Xiaobing; Klie, Robert F.; Schaller, Richard D. [Department; Snee, Preston T.

    2017-08-31

    Understanding the electronic structure of doped semiconductors is essential to realize advancements in electronics and in the rational design of nanoscale devices. Reported here are the results of time-resolved X-ray absorption studies on copper-doped cadmium sulfide nanoparticles that provide an explicit description of the electronic dynamics of the dopants. The interaction of a dopant ion and an excess charge carrier is unambiguously observed via monitoring the oxidation state. The experimental data combined with DFT calculations demonstrate that dopant bonding to the host matrix is modulated by its interaction with charge carriers. Furthermore, the transient photoluminescence and the kinetics of dopant oxidation reveal the presence of two types of surface-bound ions that create mid-gap states.

  17. Urbach Tail and Optical Absorption in Layered Semiconductor TlGaSe2(1-x)S2x Single Crystals

    Science.gov (United States)

    Duman, S.; Gürbulak, B.

    2005-01-01

    TlGaSe2(1 - x)S2x single crystals were grown by the modified Bridgman-Stockbarger method. None of the grown crystals had cracks and voids on the surface. The freshly cleaved crystals had mirror-like surfaces and there was no need for mechanical or chemical polishing treatments. The measurements were performed in steps of 10 K if changes were small, and with steps of 3 and 5 K if changes were large in the direct and indirect band gaps energies. The direct and indirect band gaps for TlGaSe2(1 - x)S2x (x = 0, 0.2, 0.4, 0.6, 0.8, 1) samples were calculated as a function of temperature. There is an abrupt change in the energy spectrum of TlGaSe2(1 - x)S2x in the temperature ranges 90 100, 100, 100 120, 160 180, 220 240, and 240 250 K. The values obtained from the energy peak change may be phase transition temperatures. It is the first time that Urbach's rule and steepness parameters of TlGaSe2(1 - x)S2x samples have been investigated. The steepness parameters and Urbach energies for TlGaSe2(1 - x)S2x samples increased with increasing sample temperature in the range 10 320 K. We have concluded that the compositions x are determined without using the other techniques during crystal growth considering band gaps energies.

  18. Low temperature transport and thermodynamic properties of the Zintl compound Yb11AlSb9: A new Kondo lattice semiconductor

    International Nuclear Information System (INIS)

    Magnavita, E.T.; Rettori, C.; Osorio-Guillén, J.M.; Ferreira, F.F.; Mendonça-Ferreira, L.; Avila, M.A.; Ribeiro, R.A.

    2016-01-01

    A thorough transport and thermodynamic investigation of flux-grown single crystals of the ternary Zintl phase Yb 11 AlSb 9 , combined with first-principles density functional theory calculations, shows that this compound is a metal above T ≈ 100 K and a semiconductor with small hybridization gap at low-T. The general behavior resembles those of Kondo lattice semiconductors, although some of the measured properties are strongly sample dependent, as often seen in hybridized f-electron materials. We thus suggest that Yb 11 AlSb 9 can be considered as a new Yb-based Kondo lattice semiconductor joining the family of strongly correlated electron systems. - Highlights: • First characterization at low temperatures of Yb 11 AlSb 9 . • Yb 11 AlSb 9 has a small, field dependent hybridization gap at low-T. • Yb 11 AlSb 9 can be considered as a new Kondo lattice semiconductor.

  19. TlHgInS 3 : An Indirect-Band-Gap Semiconductor with X-ray Photoconductivity Response

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hao; Malliakas, Christos D.; Han, Fei; Chung, Duck Young; Kanatzidis, Mercouri G.

    2015-08-11

    The quaternary compound TlHgInS3 crystallizes in a new structure type of space group, C2/c, with cell parameters a = 13.916(3) angstrom, b = 3.9132(8) angstrom, c = 21.403(4) angstrom, beta = 104.16(3)degrees, V = 1130.1(8) angstrom(3), and rho = 7.241 g/cm(3). The structure is a unique three-dimensional framework with parallel tunnels, which is formed by (1)(infinity)[InS33-] infinite chains bridged by linearly coordinated Hg2+ ions. TlHgInS3 is a semiconductor with a band gap of 1.74 eV and a resistivity of similar to 4.32 G Omega cm. TlHgInS3 single crystals exhibit photocurrent response when exposed to Ag X-rays. The mobility-lifetime product (mu tau) of the electrons and holes estimated from the photocurrent measurements are (mu tau)(e) approximate to 3.6 x 10(-4) cm(2)/V and (mu tau)(h) approximate to 2.0 x 10(-4) cm(2)/V. Electronic structure calculations at the density functional theory level indicate an indirect band gap and a relatively small effective mass for both electrons and holes. Based on the photoconductivity data, TlHgInS3 is a potential material for radiation detection applications.

  20. Colossal X-Ray-Induced Persistent Photoconductivity in Current-Perpendicular-to-Plane Ferroelectric/Semiconductor Junctions

    KAUST Repository

    Hu, Weijin

    2017-12-07

    Persistent photoconductivity (PPC) is an intriguing physical phenomenon, where electric conduction is retained after the termination of electromagnetic radiation, which makes it appealing for applications in a wide range of optoelectronic devices. So far, PPC has been observed in bulk materials and thin-film structures, where the current flows in the plane, limiting the magnitude of the effect. Here using epitaxial Nb:SrTiO3/Sm0.1Bi0.9FeO3/Pt junctions with a current-perpendicular-to-plane geometry, a colossal X-ray-induced PPC (XPPC) is achieved with a magnitude of six orders. This PPC persists for days with negligible decay. Furthermore, the pristine insulating state could be fully recovered by thermal annealing for a few minutes. Based on the electric transport and microstructure analysis, this colossal XPPC effect is attributed to the X-ray-induced formation and ionization of oxygen vacancies, which drives nonvolatile modification of atomic configurations and results in the reduction of interfacial Schottky barriers. This mechanism differs from the conventional mechanism of photon-enhanced carrier density/mobility in the current-in-plane structures. With their persistent nature, such ferroelectric/semiconductor heterojunctions open a new route toward X-ray sensing and imaging applications.

  1. Metastable Cu(I)-niobate semiconductor with a low-temperature, nanoparticle-mediated synthesis.

    Science.gov (United States)

    Choi, Jonglak; King, Nacole; Maggard, Paul A

    2013-02-26

    A nanoparticle synthetic strategy for the preparation of a new metastable Cu(I)-niobate is described, and that involves multipored Li₃NbO₄ nanoparticles as a precursor. A hydrothermal reaction of HNbO₃ and LiOH·H₂O in PEG200 and water at ∼180 °C yields ∼15-40 nm Li₃NbO₄ particles. These particles are subsequently used in a solvothermal copper(I)-exchange reaction with excess CuCl at 150 °C. Heating these products within the used CuCl flux (mp = 430 °C) to 450 °C for 30 min yields ∼4-12 nm Cu₂Nb₈O₂₁ crystalline nanoparticles, and for a heating time of 24 h yields μm-sized, rod-shaped crystals. The new structure was characterized by single-crystal X-ray diffraction to have a condensed network consisting of NbO₇ polyhedra and chains of elongated CuO₄ tetrahedra. The compound thermally decomposes starting at ∼250 °C and higher temperatures, depending on the particle sizes, owing to the loss of the weakly coordinated Cu(I) cations from the structure and a concurrent disproportionation reaction at its surfaces. Thus, conventional solid-state reactions involving higher temperatures and bulk reagents have proven unsatisfactory for its synthesis. The measured bandgap size is ∼1.43-1.65 eV (indirect) and shows a dependence on the particle sizes. Electronic structure calculations based on density functional theory show that the bandgap transition results from the excitation of electrons at the band edges between filled Cu(I) 3d¹⁰-orbitals and empty Nb(V) 4d⁰-orbitals, respectively. The p-type nature of the Cu₂Nb₈O₂₁ particles was confirmed in photoelectrochemical measurements on polycrystalline films that show a strong photocathodic current under visible-light irradiation in aqueous solutions. These results demonstrate the general utility of reactive nanoscale precursors in the synthetic discovery of new Cu(I)-based semiconducting oxides and which also show promise for use in solar energy conversion applications.

  2. X3 expansion tube driver gas spectroscopy and temperature measurements

    Science.gov (United States)

    Parekh, V.; Gildfind, D.; Lewis, S.; James, C.

    2017-11-01

    The University of Queensland's X3 facility is a large, free-piston driven expansion tube used for super-orbital and high Mach number scramjet aerothermodynamic studies. During recent development of new scramjet test flow conditions, experimentally measured shock speeds were found to be significantly lower than that predicted by initial driver performance calculations. These calculations were based on ideal, isentropic compression of the driver gas and indicated that loss mechanisms, not accounted for in the preliminary analysis, were significant. The critical determinant of shock speed is peak driver gas sound speed, which for a given gas composition depends on the peak driver gas temperature. This temperature may be inaccurately estimated if an incorrect fill temperature is assumed, or if heat losses during driver gas compression are significant but not accounted for. For this study, the ideal predicted peak temperature was 3750 K, without accounting for losses. However, a much lower driver temperature of 2400 K is suggested based on measured experimental shock speeds. This study aimed to measure initial and peak driver gas temperatures for a representative X3 operating condition. Examination of the transient temperatures of the driver gas and compression tube steel wall during the initial fill process showed that once the filling process was complete, the steady-state driver gas temperature closely matched the tube wall temperature. Therefore, while assuming the gas is initially at the ambient laboratory temperature is not a significant source of error, it can be entirely mitigated by simply monitoring tube wall temperature. Optical emission spectroscopy was used to determine the driver gas spectra after diaphragm rupture; the driver gas emission spectrum exhibited a significant continuum radiation component, with prominent spectral lines attributed to contamination of the gas. A graybody approximation of the continuum suggested a peak driver gas temperature of

  3. P2X(3) receptor gating near normal body temperature

    Czech Academy of Sciences Publication Activity Database

    Kmyhz, V.; Maximyuk, O.; Teslenko, V.; Verkhratsky, Alexei; Krishtal, O.

    2008-01-01

    Roč. 456, č. 12 (2008), s. 339-347 ISSN 0031-6768 Institutional research plan: CEZ:AV0Z50390703 Keywords : P2X3 receptors * Temperature-sensitivity * Gating Subject RIV: FH - Neurology Impact factor: 3.526, year: 2008

  4. Study of hard X-ray dose enhancement effects for some kinds of semiconductor devices

    CERN Document Server

    Guo Hong Xia; Chen Yu Sheng; Zhou Hui; He Chao Hui; Xie Ya Ning; Huang Yu Ying; He Wei; Hu Tian Dou

    2002-01-01

    Experimental results of X-ray dose enhancement effects are given for CMOS4069 and floating gate ROMs irradiated in Beijing Synchrotron Radiation Facility and in cobalt source. Shift of threshold voltage vs. total dose for CMOS4069 and the errors vs. total dose for 28f256 and 29c256 have been tested on line and the equivalent relation of total dose damage under the same accumulated dose is provided comparing the response of devices irradiated by X-ray and gamma-ray source. These results can be provided for X-ray radiation hardening technology as an effective evaluation data

  5. Controlled growth of semiconductor crystals

    Science.gov (United States)

    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. High Efficiency Semiconductor Arrays for Hard X-Ray Imaging, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The next generation of wide-field survey instruments with improved angular and energy resolution for research into astrophysical transient X-ray phenomena is...

  7. Microbeam high-resolution diffraction and x-ray standing wave methods applied to semiconductor structures

    International Nuclear Information System (INIS)

    Kazimirov, A; Bilderback, D H; Huang, R; Sirenko, A; Ougazzaden, A

    2004-01-01

    A new approach to conditioning x-ray microbeams for high angular resolution x-ray diffraction and scattering techniques is introduced. We combined focusing optics (one-bounce imaging capillary) and post-focusing collimating optics (miniature Si(004) channel-cut crystal) to generate an x-ray microbeam with a size of 10 μm and ultimate angular resolution of 14 μrad. The microbeam was used to analyse the strain in sub-micron thick InGaAsP epitaxial layers grown on an InP(100) substrate by the selective area growth technique in narrow openings between the oxide stripes. For the structures for which the diffraction peaks from the substrate and the film overlap, the x-ray standing wave technique was applied for precise measurements of the strain with a Δd/d resolution of better than 10 -4 . (rapid communication)

  8. Room temperature X- and gamma-ray detectors using thallium bromide crystals

    CERN Document Server

    Hitomi, K; Shoji, T; Suehiro, T; Hiratate, Y

    1999-01-01

    Thallium bromide (TlBr) is a compound semiconductor with wide band gap (2.68 eV) and high X- and gamma-ray stopping power. The TlBr crystals were grown by the horizontal travelling molten zone (TMZ) method using purified material. Two types of room temperature X- and gamma-ray detectors were fabricated from the TlBr crystals: TlBr detectors with high detection efficiency for positron annihilation gamma-ray (511 keV) detection and TlBr detectors with high-energy resolution for low-energy X-ray detection. The detector of the former type demonstrated energy resolution of 56 keV FWHM (11%) for 511 keV gamma-rays. Energy resolution of 1.81 keV FWHM for 5.9 keV was obtained from the detector of the latter type. In order to analyze noise characteristics of the detector-preamplifier assembly, the equivalent noise charge (ENC) was measured as a function of the amplifier shaping time for the high-resolution detector. This analysis shows that parallel white noise and 1/f noise were dominant noise sources in the detector...

  9. Structural, electronic, magnetic and optical properties of semiconductor Zn1-xMoxTe compound

    Science.gov (United States)

    Feng, Zhong-Ying; Zhang, Jian-Min

    2018-03-01

    The structural, electronic, magnetic and optical properties of the Zn1-xMoxTe (x = 0.00, 0.25, 0.50, 0.75, 1.00) have been investigated by the spin-polarized first-principles calculations. The Zn0.50Mo0.50Te has tetragonal structure while the Zn1-xMoxTe (x = 0.00, 0.25, 0.75, 1.00) crystallize in cubic structures. For Zn1-xMoxTe (x = 0.25, 0.50, 0.75, 1.00) alloys, the lattice constant and the volume are found larger than those of pure ZnTe alloy. The Zn1-xMoxTe (x = 0.25, 0.50, 0.75, 1.00) is magnetic and the Mo element is found dominant in the bands crossing the Fermi level in the spin-up channel. The Zn0.75Mo0.25Te and MoTe have half-metallic (HM) behavior. In spin-down channel of the Zn0.75Mo0.25Te, the Zn atom mainly contributed to the conduction band minimum (CBM), while the valence band maximum (VBM) appears mainly due to contribution of Te element. A positive spin splitting and crystal field splitting of d-states of Mo atom has been observed for Zn0.75Mo0.25Te alloy. The maximum values of the absorption coefficients αMAX(ω) of the Zn0.50Mo0.50Te alloy along a or b axes are smaller than the absorption coefficient along c axis. The first absorption peak appearing in the energy range of 0.000-1.000 eV for Zn1-xMoxTe (x = 0.25, 0.50, 0.75 or 1.00) alloys is the new peak which is not observed in ZnTe.

  10. Temperature Modulation with Specified Detection Point on Metal Oxide Semiconductor Gas Sensors for E-Nose Application

    Directory of Open Access Journals (Sweden)

    Arief SUDARMAJI

    2015-03-01

    Full Text Available Temperature modulation technique, some called dynamic measurement mode, on Metal-Oxide Semiconductor (MOS/MOX gas sensor has been widely observed and employed in many fields. We present its development, a Specified Detection Point (SDP on modulated sensing element of MOS sensor is applied which associated to its temperature modulation, temperature modulation-SDP so-named. We configured the rectangular modulation signal for MOS gas sensors (TGSs and FISs using PSOC CY8C28445-24PVXI (Programmable System on Chip which also functioned as acquisition unit and interface to a computer. Initial responses and selectivity evaluations were performed using statistical tool and Principal Component Analysis (PCA to differ sample gases (Toluene, Ethanol and Ammonia on dynamic chamber measurement under various frequencies (0.25 Hz, 1 Hz, 4 Hz and duty-cycles (25 %, 50 %, 75 %. We found that at lower frequency the response waveform of the sensors becomes more sloping and distinct, and selected modulations successfully increased the selectivity either on singular or array sensors rather than static temperature measurement.

  11. A facile and green preparation of high-quality CdTe semiconductor nanocrystals at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Liu Yan [Jilin Province Research Center for Engineering and Technology of Spectral Analytical Instruments, Jilin University, Changchun 130023 (China); Shen Qihui; Shi Weiguang; Li Jixue; Liu Xiaoyang [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Yu Dongdong [1st Hopstail affiliated to Jilin University, Jilin University, Changchun 130023 (China); Zhou Jianguang [Research Center for Analytical Instrumentation, Zhejiang University, Hangzhou 310058 (China)], E-mail: liuxy@jlu.edu.cn, E-mail: jgzhou70@126.com

    2008-06-18

    One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

  12. Semiconductor ultraviolet photodetectors based on ZnO and MgxZn1−xO

    International Nuclear Information System (INIS)

    Hou, Yaonan; Mei, Zengxia; Du, Xiaolong

    2014-01-01

    It is indispensable to develop wide-band-gap based ultraviolet (UV) photodetectors (PDs), which are one of the basic building blocks of solid state UV optoelectronic devices. In the last two decades, we have witnessed the renaissance of ZnO as a wide-band-gap semiconductor and an enormous development of ZnO-based UV PDs as a result of its superb optical and electronic properties. Since the first demonstration, a great variety of UV PDs based on ZnO and its related materials have been proposed and demonstrated. These PDs, with diverse device geometries, exhibit either high performance or multiple functions, reflecting a state-of-the-art technology of UV optoelectronics. In this review, we study the latest progress of UV PDs made on ZnO and Mg x Zn 1−x O, which is a representative alloy of ZnO for band-gap engineering techniques. The discussion focuses on the device performance and the behind device physics according to the architecture of UV PDs. (topical review)

  13. Active silicon x-ray for measuring electron temperature

    International Nuclear Information System (INIS)

    Snider, R.T.

    1994-07-01

    Silicon diodes are commonly used for x-ray measurements in the soft x-ray region between a few hundred ev and 20 keV. Recent work by Cho has shown that the charge collecting region in an underbiased silicon detector is the depletion depth plus some contribution from a region near the depleted region due to charge-diffusion. The depletion depth can be fully characterized as a function of the applied bias voltage and is roughly proportional to the squart root of the bias voltage. We propose a technique to exploit this effect to use the silicon within the detector as an actively controlled x-ray filter. With reasonable silicon manufacturing methods, a silicon diode detector can be constructed in which the sensitivity of the collected charge to the impinging photon energy spectrum can be changed dynamically in the visible to above the 20 keV range. This type of detector could be used to measure the electron temperature in, for example, a tokamak plasma by sweeping the applied bias voltage during a plasma discharge. The detector samples different parts of the energy spectrum during the bias sweep, and the data collected contains enough information to determine the electron temperature. Benefits and limitations of this technique will be discussed along with comparisons to similar methods for measuring electron temperature and other applications of an active silicon x-ray filter

  14. Semiconductor annealing

    International Nuclear Information System (INIS)

    Young, J.M.; Scovell, P.D.

    1981-01-01

    A process for annealing crystal damage in ion implanted semiconductor devices is described in which the device is rapidly heated to a temperature between 450 and 600 0 C and allowed to cool. It has been found that such heating of the device to these relatively low temperatures results in rapid annealing. In one application the device may be heated on a graphite element mounted between electrodes in an inert atmosphere in a chamber. The process may be enhanced by the application of optical radiation from a Xenon lamp. (author)

  15. (TMTSF)2X materials and structural implications for low-dimensional polymeric and disordered molecular semiconductors

    DEFF Research Database (Denmark)

    Bechgaard, Klaus; Nielsen, Martin Meedom; Krebs, Frederik C

    2000-01-01

    The structural characteristics and the relation to the electronic properties of three types of molecular materials are discussed. In TMTSF2X salts a triclinic unit cell it suggested to be important in avoiding a 2k(F) Peierls distortion. In polythiophenes appropriate ordering of microcrystallites...

  16. High-pressure-low-temperature x-ray power diffractometer.

    Science.gov (United States)

    Syassen, K; Holzapfel, W B

    1978-08-01

    A high-pressure technique for x-ray diffraction studies at low temperatures is described. The system consists of a Bridgman anvil type high-pressure device with either tungsten carbide or boron carbide anvils, a liquid He cryostat, and x-ray diffractometer operating in Debye-Scherrer geometry. The newly developed boron carbide anvil cell is capable of containing a liquid pressure transmitting medium. The precision of the lattice parameter determination is discussed and the effect of nonisostatic stress components on the diffraction pattern is examined.

  17. Preparation of lead-tin telluride Pbsub(1-x)Snsub(x)Te at low temperature

    International Nuclear Information System (INIS)

    Gafni, G.

    1977-01-01

    A new method for the preparation of Pbsub(1-x)Snsub(x)Te at low temperature is described. The experiments were carried out in the concentration range 0.1 2 as solvent. The alloy obtained was a polycrystallized powder of 20-100 *mm. The material prepared in this way can be used as a source for the growth of single crystals for the manufacture of electro-optical devices. (B.G.)

  18. Thermoelectrically cooled semiconductor detectors for non-destructive analysis of works of art by means of energy dispersive X-ray fluorescence

    International Nuclear Information System (INIS)

    Cesareo, Roberto; Ettore Gigante, Giovanni; Castellano, Alfredo

    1999-01-01

    Thermoelectrically cooled semiconductor detectors, such as Si-PIN, Si-drift, Cd 1-x Zn x Te and HgI 2 , coupled to miniaturized low-power X-ray tubes, are well suited in portable systems for energy-dispersive X-ray fluorescence (EDXRF), analysis of archaeological samples. The Si-PIN detector is characterized by a thickness of about 300 μm, an area of about 2x3 mm 2 , an energy resolution of about 200-250 eV at 5.9 keV and an entrance window of 25-75 μm. The Si-drift detector has approximately the same area and thickness, but an energy resolution of 155 eV at 5.9 keV. The efficiency of these detectors is around 100% from 4 to 10 keV, and then decreases versus energy, reaching ∼9% at 30 keV. Coupled to a miniaturized 10 kV, 0.1 mA, Ca-anode or to a miniaturized 30 kV, 0.1 mA, W-anode X-ray tubes, portable systems can be constructed, which are able to analyse K-lines of elements up to about silver, and L-lines of heavy elements. The Cd 1-x Zn x Te detector has an area of 4 mm 2 and a thickness of 3 mm. It has an energy resolution of about 300 eV at 5.9 keV, and an efficiency of 100% over the whole range of X-rays. Finally the HgI 2 detector has an efficiency of about 100% in the whole range of X-rays, and an energy resolution of about 200 eV at 5.9 keV. Coupled to a small 50-60 kV, 1 mA, W-anode X-ray tube, portable systems can be constructed, for the analysis of practically all elements. These systems were applied to analysis in the field of archaeometry and in all applications for which portable systems are needed or at least useful (for example X-ray transmission measurements, X-ray microtomography and so on). Results of in-field use of these detectors and a comparison among these room temperature detectors in relation to concrete applications are presented. More specifically, concerning EDXRF analysis, ancient gold samples were analysed in Rome, in Mexico City and in Milan, ancient bronzes in Sassari, in Bologna, in Chieti and in Naples, and sulfur (due to

  19. Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: A review

    Science.gov (United States)

    Casady, J. B.; Johnson, R. W.

    1996-10-01

    Silicon carbide (SiC), a material long known with potential for high-temperature, high-power, high-frequency, and radiation hardened applications, has emerged as the most mature of the wide-bandgap (2.0 eV ≲ Eg ≲ 7.0 eV) semiconductors since the release of commercial 6HSiC bulk substrates in 1991 and 4HSiC substrates in 1994. Following a brief introduction to SiC material properties, the status of SiC in terms of bulk crystal growth, unit device fabrication processes, device performance, circuits and sensors is discussed. Emphasis is placed upon demonstrated high-temperature applications, such as power transistors and rectifiers, turbine engine combustion monitoring, temperature sensors, analog and digital circuitry, flame detectors, and accelerometers. While individual device performances have been impressive (e.g. 4HSiC MESFETs with fmax of 42 GHz and over 2.8 W mm -1 power density; 4HSiC static induction transistors with 225 W power output at 600 MHz, 47% power added efficiency (PAE), and 200 V forward blocking voltage), material defects in SiC, in particular micropipe defects, remain the primary impediment to wide-spread application in commercial markets. Micropipe defect densities have been reduced from near the 1000 cm -2 order of magnitude in 1992 to 3.5 cm -2 at the research level in 1995.

  20. A Very Low Dark Current Temperature-Resistant, Wide Dynamic Range, Complementary Metal Oxide Semiconductor Image Sensor

    Science.gov (United States)

    Mizobuchi, Koichi; Adachi, Satoru; Tejada, Jose; Oshikubo, Hiromichi; Akahane, Nana; Sugawa, Shigetoshi

    2008-07-01

    A very low dark current (VLDC) temperature-resistant approach which best suits a wide dynamic range (WDR) complementary metal oxide semiconductor (CMOS) image sensor with a lateral over-flow integration capacitor (LOFIC) has been developed. By implementing a low electric field photodiode without a trade-off of full well-capacity, reduced plasma damage, re-crystallization, and termination of silicon-silicon dioxide interface states in the front end of line and back end of line (FEOL and BEOL) in a 0.18 µm, two polycrystalline silicon, three metal (2P3M) process, the dark current is reduced to 11 e-/s/pixel (0.35 e-/s/µm2: pixel area normalized) at 60 °C, which is the lowest value ever reported. For further robustness at low and high temperatures, 1/3-in., 5.6-µm pitch, 800×600 pixel sensor chips with low noise readout circuits designed for a signal and noise hold circuit and a programmable gain amplifier (PGA) have also been deposited with an inorganic cap layer on a micro-lens and covered with a metal hermetically sealed package assembly. Image sensing performance results in 2.4 e-rms temporal noise and 100 dB dynamic range (DR) with 237 ke- full well-capacity. The operating temperature range is extended from -40 to 85 °C while retaining good image quality.

  1. Multielement X-ray radiometric analysis with application of semiconductor detectors and automatic processing of the results of measurements

    International Nuclear Information System (INIS)

    Berezkin, V.V.; Mamikonyan, S.V.; Shchekin, K.I.

    1979-01-01

    Problems of complex extraction of useful components from the ores with compound composition demand to ensure multielement analysis having the accuracy which is sufficient for practical purposes. Great possibilities has the X-ray-radiometric analysis with application of semiconductor detectors (SD) and with processing the results of measurements by means of mini- or micro-computers. Present state in the detection and computation techniques permits to introduce the said instruments into the practical use in the analytical laboratories of the mining enterprises. On the base of discussion of the practical tasks in analysis of different types of ores, in the paper basic principles of the multielement X-ray-radiometric analysis for industrial purposes have been formulated. First of all it is an installation with few channels. The main requirement in creation of such installations is to ensure high relaibility and stability of their performance. A variant is given of such analyzer, constructed with use of SiLi or Ge detecting blocks. Possibility for quick change of the excitation sources made of the set of iron-55, cadmium-109, americium-241 or cobalt-57 ensures effective excitation of elements in the range from calcium to uranium. Some practical methods of analysis have been discussed in the paper. They are based both on the methods of passive and active experiments at the calibration stages. Accuracy of these methods is enough for change of ordinary chemical analysis by the radiometric one. Problems are discussed of application of mini- and micro-computers, permitting processing of information according to the metods of analysis having been developed. Some examples are given of practical realization of the multielement X-ray-radiometric analysis of the lead-zinc, cppper-molybdenum, lead-barite and some other types of ores and also of the products of processing of ores [ru

  2. Calorimetric low-temperature detectors on semiconductor base for the energy-resolving detection of heavy ions

    International Nuclear Information System (INIS)

    Kienlin, A. von.

    1994-01-01

    In the framework of this thesis for the first time calorimetric low-temperature detectors for the energy-resolving detection of heavy ions were developed and successfully applied. Constructed were two different detector types, which work both with a semiconductor thermistor. The temperature increasement effected by a particle incidence is read out. In the first detector type the thermistor was simutaneously used as absorber. The thickness of the germanium crystals was sufficient in order to stop the studied heavy ions completely. In the second type, a composed calorimeter, a sapphire crystal, which was glued on a germanium thermistor, served as absorber for the incident heavy ions. The working point of the calorimeter lies in the temperature range (1.2-4.2 K), which is reachable with a pumped 4 He cryostat. The temperatur increasement of the calorimeter amounts after the incidence of a single α particle about 20-30 μK and that after a heavy ion incidence up to some mK. An absolute energy resolution of 400-500 keV was reached. In nine beam times the calorimeters were irradiated by heavy ions ( 20 Ne, 40 Ar, 136 Xe, 208 Pb, 209 Bi) of different energies (3.6 MeV/nucleon< E<12.5 MeV/nucleon) elastically scattered from gold foils. In the pulse height spectra of the first detector type relatively broad, complex-structurated line shapes were observed. By systematic measurements dependences of the complex line structures on operational parameters of the detector, the detector temperature, and the position of the incident particle could be detected. Together with the results of further experiments a possible interpretation of these phenomena is presented. Contrarily to the complex line structures of the pure germanium thermistor the line shapes in the pulse height spectra, which were taken up in a composite germanium/sapphire calorimeter, are narrow and Gauss-shaped

  3. Single Ion transient-IBIC analyses of semiconductor devices using a cryogenic temperature stage

    International Nuclear Information System (INIS)

    Laird, J.S.; Bardos, R.; Legge, G.J.F.; Jagadish, C.

    1998-01-01

    A new Transient - IBIC data acquisition and analysis system at MARC is described. A discussion on the need for single ion control and temperature control is also given. The recorded signal is used as the trigger for beam pulsing. The new cryostatic temperature control stage is introduced. Data is presented on line profiles across the edge of a Au-Si junction collected over the temperature range of 25-300K using a developed C-V and I-V variable temperature stage incorporating a liquid helium cryostat. It demonstrates the potential improvements in spatial resolution in materials of long lifetime by mapping on timing windows around the prompt charge component in the charge transient

  4. Single Ion transient-IBIC analyses of semiconductor devices using a cryogenic temperature stage

    Energy Technology Data Exchange (ETDEWEB)

    Laird, J.S.; Bardos, R.; Legge, G.J.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Jagadish, C. [Australian National Univ., Canberra, ACT (Australia). School of Physics, Electronic Materials Engineering

    1998-06-01

    A new Transient - IBIC data acquisition and analysis system at MARC is described. A discussion on the need for single ion control and temperature control is also given. The recorded signal is used as the trigger for beam pulsing. The new cryostatic temperature control stage is introduced. Data is presented on line profiles across the edge of a Au-Si junction collected over the temperature range of 25-300K using a developed C-V and I-V variable temperature stage incorporating a liquid helium cryostat. It demonstrates the potential improvements in spatial resolution in materials of long lifetime by mapping on timing windows around the prompt charge component in the charge transient. 2 figs.

  5. Whole-surface analysis of semiconductor wafers by accumulating short-time mapping data of total-reflection X-ray fluorescence spectrometry.

    Science.gov (United States)

    Mori, Yoshihiro; Uemura, Kenichi; Lizuka, Yoshinori

    2002-03-01

    Total-reflection X-ray fluorescence (TXRF) spectrometry with no chemical preconcentration, often called "straight-TXRF", is now widely used in the semiconductor industry. The small detection area of TXRF enablesmapping measurement of contamination of the semiconductor surface, which is very useful in process characterization. However, the small detection area had been believed to limit rapid whole-surface analysis. Contrary to this general understanding, in this study we demonstrated that a new method, called "sweeping-TXRF", which is essentially short-time multipoint mapping by straight-TXRF, can rapidly provide an average concentration. A considerable problem of this method is the contribution of errors in glancing angle and areal element distribution to the fluorescence. Using statistics, we examined the errors and demonstrated that most of them are canceled and are not significant in actual semiconductor applications. The results of an experiment that measured localized 6 x 10(10) atoms cm(-2) nickel contamination supported the above conclusion. Applying sweeping-TXRF to existing TXRF instruments is easy-the only requirement is a small software modification. We believe that sweeping-TXRF will be utilized for rapid whole-surface analysis in many fields, especially in the semiconductor industry.

  6. Gate-control efficiency and interface state density evaluated from capacitance-frequency-temperature mapping for GaN-based metal-insulator-semiconductor devices

    International Nuclear Information System (INIS)

    Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu

    2014-01-01

    We present an analysis method for GaN-based metal-insulator-semiconductor (MIS) devices by using capacitance-frequency-temperature (C-f-T) mapping to evaluate the gate-control efficiency and the interface state density, both exhibiting correlations with the linear-region intrinsic transconductance. The effectiveness of the method was exemplified by application to AlN/AlGaN/GaN MIS devices to elucidate the properties of AlN-AlGaN interfaces depending on their formation processes. Using the C-f-T mapping, we extract the gate-bias-dependent activation energy with its derivative giving the gate-control efficiency, from which we evaluate the AlN-AlGaN interface state density through the Lehovec equivalent circuit in the DC limit. It is shown that the gate-control efficiency and the interface state density have correlations with the linear-region intrinsic transconductance, all depending on the interface formation processes. In addition, we give characterization of the AlN-AlGaN interfaces by using X-ray photoelectron spectroscopy, in relation with the results of the analysis

  7. Temperature dependence of the photoluminescence polarization of ordered III-V semiconductor alloys

    International Nuclear Information System (INIS)

    Prutskij, T.; Makarov, N.; Attolini, G.

    2016-01-01

    We studied the linear polarization of the photoluminescence (PL) emission of atomically ordered GaInAsP and GaInP alloys with different ordering parameters in the temperature range from 10 to 300 K. The epitaxial layers of these alloys were grown on GaAs and Ge (001) substrates by metal organic vapor phase epitaxy. The polarization of the PL emission propagating along different crystallographic axes depends on the value of biaxial strain in the layer and changes with temperature. We calculated the PL polarization patterns for different propagation directions as a function of biaxial strain using an existing model developed for ternary atomically ordered III-V alloys. Comparing the calculated PL polarization patterns with those obtained experimentally, we separated the variation of the PL polarization due to change of biaxial strain with temperature.

  8. Relaxation dynamics of femtosecond-laser-induced temperature modulation on the surfaces of metals and semiconductors

    Czech Academy of Sciences Publication Activity Database

    Levy, Yoann; Derrien, Thibault; Bulgakova, Nadezhda M.; Gurevich, E.L.; Mocek, Tomáš

    2016-01-01

    Roč. 374, Jun (2016), s. 157-164 ISSN 0169-4332 R&D Projects: GA MŠk ED2.1.00/01.0027 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : LIPSS * modulated temperature relaxation * two-temperature model * nano-melting Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.387, year: 2016

  9. Zero thermal expansion and ferromagnetism in cubic Sc(1-x)M(x)F3 (M = Ga, Fe) over a wide temperature range.

    Science.gov (United States)

    Hu, Lei; Chen, Jun; Fan, Longlong; Ren, Yang; Rong, Yangchun; Pan, Zhao; Deng, Jinxia; Yu, Ranbo; Xing, Xianran

    2014-10-01

    The rare physical property of zero thermal expansion (ZTE) is intriguing because neither expansion nor contraction occurs with temperature fluctuations. Most ZTE, however, occurs below room temperature. It is a great challenge to achieve isotropic ZTE at high temperatures. Here we report the unconventional isotropic ZTE in the cubic (Sc1-xMx)F3 (M = Ga, Fe) over a wide temperature range (linear coefficient of thermal expansion (CTE), αl = 2.34 × 10(-7) K(-1), 300-900 K). Such a broad temperature range with a considerably negligible CTE has rarely been documented. The present ZTE property has been designed using the introduction of local distortions in the macroscopic cubic lattice by heterogeneous cation substitution for the Sc site. Even though the macroscopic crystallographic structure of (Sc0.85Ga0.05Fe0.1)F3 adheres to the cubic system (Pm3̅m) according to the results of X-ray diffraction, the local structure exhibits a slight rhombohedral distortion. This is confirmed by pair distribution function analysis of synchrotron radiation X-ray total scattering. This local distortion may weaken the contribution from the transverse thermal vibration of fluorine atoms to negative thermal expansion, and thus may presumably be responsible for the ZTE. In addition, the present ZTE compounds of (Sc1-xMx)F3 can be functionalized to exhibit high-Tc ferromagnetism and a narrow-gap semiconductor feature. The present study shows the possibility of obtaining ZTE materials with multifunctionality in future work.

  10. Simulation of photon and charge transport in X-ray imaging semiconductor sensors

    CERN Document Server

    Nilsson, H E; Hjelm, M; Bertilsson, K

    2002-01-01

    A fully stochastic model for the imaging properties of X-ray silicon pixel detectors is presented. Both integrating and photon counting configurations have been considered, as well as scintillator-coated structures. The model is based on three levels of Monte Carlo simulations; photon transport and absorption using MCNP, full band Monte Carlo simulation of charge transport and system level Monte Carlo simulation of the imaging performance of the detector system. In the case of scintillator-coated detectors, the light scattering in the detector layers has been simulated using a Monte Carlo method. The image resolution was found to be much lower in scintillator-coated systems due to large light spread in thick scintillator layers. A comparison between integrating and photon counting readout methods shows that the image resolution can be slightly enhanced using a photon-counting readout. In addition, the proposed model has been used to study charge-sharing effects on the energy resolution in photon counting dete...

  11. X-ray analysis of spintronic semiconductor and half metal thin film systems; Roentgenstrukturuntersuchungen an spintronischen Halbleiter- und Halbmetall-Duennschichtsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, Andreas

    2010-07-01

    In this work the structural properties of spintronic semiconductor and halfmetalic thin-film systems were investigated. The layer thicknesses and interface roughnesses of the multi-layer systems were estimated by X-ray reflectivity measurements. The fits were performed using the software Fewlay which uses the Parratt formalism to calculate the reflectivities. The relaxation of the films was analyzed by reciprocal space mapping on preferably highly indexed Bragg reflexes. (orig.)

  12. Electron energy loss spectroscopy of excitons in two-dimensional-semiconductors as a function of temperature

    Energy Technology Data Exchange (ETDEWEB)

    Tizei, Luiz H. G., E-mail: luiz.galvao-tizei@u-psud.fr [Laboratoire de Physique des Solides, Université Paris-Sud, CNRS-UMR 8502, Orsay 91405 (France); Lin, Yung-Chang; Suenaga, Kazu, E-mail: suenaga-kazu@aist.go.jp [Nanotube Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565 (Japan); Lu, Ang-Yu; Li, Lain-Jong [Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2016-04-18

    We have explored the benefits of performing monochromated Electron Energy Loss Spectroscopy (EELS) in samples at cryogenic temperatures. As an example, we have observed the excitonic absorption peaks in single layer Transition Metal Dichalcogenides. These peaks appear separated by small energies due to spin orbit coupling. We have been able to distinguish the split for MoS{sub 2} below 300 K and for MoSe{sub 2} below 220 K. However, the distinction between peaks is only clear at 150 K. We have measured the change in absorption threshold between 150 K and 770 K for MoS{sub 2} and MoSe{sub 2}. We discuss the effect of carbon and ice contamination in EELS spectra. The increased spectral resolution available made possible with modern monochromators in electron microscopes will require the development of stable sample holders which reaches temperatures far below that of liquid nitrogen.

  13. Temperature Dependence of Oxide Semiconductor and Channel Effect of Thin Film Transistor.

    Science.gov (United States)

    Oh, Teresa

    2018-03-01

    ZTO was prepared on SiOC/ITO glass and the electrical characteristics were analyzed in accordance with the annealing temperature to research the temperature dependence and an amorphous structure. SiOC annealed at 150 °C as a gate insulator became an amorphous structure. The ZTO annealed at 150 °C had the capacitance without any variation. However, the capacitance of ZTO on SiOC annealed at 150 °C was increased due to the reduction of energy loss. ZTO/SiOC transistor was observed the ambipolar transfer characteristics with high stability and mobility in accordance with the decrement of drain voltages as a result of tunneling effect. Therefore it was obtained that the SiOC annealed at 150 °C means the highest Schottky barrier (SB) at the interface of ZTO/SiOC as the optimization parameter.

  14. Electron energy loss spectroscopy of excitons in two-dimensional-semiconductors as a function of temperature

    KAUST Repository

    Tizei, Luiz H. G.

    2016-04-21

    We have explored the benefits of performing monochromated Electron Energy Loss Spectroscopy(EELS) in samples at cryogenic temperatures. As an example, we have observed the excitonic absorption peaks in single layer Transition Metal Dichalcogenides. These peaks appear separated by small energies due to spin orbit coupling. We have been able to distinguish the split for MoS2 below 300 K and for MoSe2 below 220 K. However, the distinction between peaks is only clear at 150 K. We have measured the change in absorption threshold between 150 K and 770 K for MoS2 and MoSe2. We discuss the effect of carbon and ice contamination in EELSspectra. The increased spectral resolution available made possible with modern monochromators in electron microscopes will require the development of stable sample holders which reaches temperatures far below that of liquid nitrogen.

  15. Temperature-induced delocalization of charge carriers and semiconductor to metal-like phase in SrFeO{sub 3-δ}

    Energy Technology Data Exchange (ETDEWEB)

    Manimuthu, P.; Venkateswaran, C. [University of Madras, Department of Nuclear Physics, Guindy Campus, Chennai (India); Murugaraj, R. [Anna University, Department of Physics, MIT Campus, Chennai (India)

    2015-04-01

    Perovskite SrFeO{sub 3-δ}, a Ruddlesden-Popper class of system exhibits interesting electronic and magnetic properties. Influence of oxygen vacancies on the electrical response of nanocrystalline SrFeO{sub 2.91} as a function of temperature is investigated using impedance spectroscopy technique. A change observed in the Nyquist plot at 383 K has been analyzed in terms of localized and delocalized e{sub g} electrons. An unusual and interesting temperature-induced semiconductor to metal-like transition is observed in the frequency-dependent real part of dielectric permittivity. Dependence of frequency on the real and imaginary parts of impedance with respect to temperature supports the presence of semiconductor to metal-like transition in SrFeO{sub 2.91}. (orig.)

  16. High temperature x-ray micro-tomography

    Energy Technology Data Exchange (ETDEWEB)

    MacDowell, Alastair A., E-mail: aamacdowell@lbl.gov; Barnard, Harold; Parkinson, Dilworth Y.; Gludovatz, Bernd [Lawrence Berkeley National Lab., Berkeley, CA 94720 (United States); Haboub, Abdel [Lawrence Berkeley National Lab., Berkeley, CA 94720 (United States); current –Lincoln Univ., Jefferson City, Missouri, 65101 (United States); Larson, Natalie; Zok, Frank [University California Santa Barbara, Santa Barbara CA 93106 (United States); Panerai, Francesco; Mansour, Nagi N. [NASA Ames Research Centre, Moffett Field, CA, 94035 (United States); Bale, Hrishikesh [University California Berkeley, Berkeley, CA 94720 (United States); current - Carl Zeiss X-ray Microscopy, 4385 Hopyard Rd #100, Pleasanton, CA 94588 (United States); Acevedo, Claire [Lawrence Berkeley National Lab., Berkeley, CA 94720 (United States); University California San Francisco, San Francisco, CA 94143 (United States); Liu, Dong [University of Bristol, Bristol BS8 1TH (United Kingdom); Ritchie, Robert O. [Lawrence Berkeley National Lab., Berkeley, CA 94720 (United States); University California Berkeley, Berkeley, CA 94720 (United States)

    2016-07-27

    There is increasing demand for 3D micro-scale time-resolved imaging of samples in realistic - and in many cases extreme environments. The data is used to understand material response, validate and refine computational models which, in turn, can be used to reduce development time for new materials and processes. Here we present the results of high temperature experiments carried out at the x-ray micro-tomography beamline 8.3.2 at the Advanced Light Source. The themes involve material failure and processing at temperatures up to 1750°C. The experimental configurations required to achieve the requisite conditions for imaging are described, with examples of ceramic matrix composites, spacecraft ablative heat shields and nuclear reactor core Gilsocarbon graphite.

  17. High-Temperature Ferromagnetism in Transition Metal Implanted Wide-Bandgap Semiconductors

    Science.gov (United States)

    2005-07-01

    R., R. Doradziński, J. Garczyński, L. Sierzputowski, J. M. Bara- nowski, and M. Kamińska. “AMMONO method of GaN and AlN production,” Diamond and...implanted ZnO nanorods ,” Journal of Vacuum Science and Technology B , 21 (4):1476–1481 (July/August 2003). 47. Jin, Z., T. Fukumura, M. Kawasaki, K. Ando...R. Gamelin. “High-Temperature Ferromagnetism in Ni2+-Doped ZnO Aggregates Prepared from Colloidal Diluted Magnetic Semi- conductor Quantum Dots

  18. High temperature semiconductor diode laser pumps for high energy laser applications

    Science.gov (United States)

    Campbell, Jenna; Semenic, Tadej; Guinn, Keith; Leisher, Paul O.; Bhunia, Avijit; Mashanovitch, Milan; Renner, Daniel

    2018-02-01

    Existing thermal management technologies for diode laser pumps place a significant load on the size, weight and power consumption of High Power Solid State and Fiber Laser systems, thus making current laser systems very large, heavy, and inefficient in many important practical applications. To mitigate this thermal management burden, it is desirable for diode pumps to operate efficiently at high heat sink temperatures. In this work, we have developed a scalable cooling architecture, based on jet-impingement technology with industrial coolant, for efficient cooling of diode laser bars. We have demonstrated 60% electrical-to-optical efficiency from a 9xx nm two-bar laser stack operating with propylene-glycolwater coolant, at 50 °C coolant temperature. To our knowledge, this is the highest efficiency achieved from a diode stack using 50 °C industrial fluid coolant. The output power is greater than 100 W per bar. Stacks with additional laser bars are currently in development, as this cooler architecture is scalable to a 1 kW system. This work will enable compact and robust fiber-coupled diode pump modules for high energy laser applications.

  19. Thermal ionization induced metal-semiconductor transition and room temperature ferromagnetism in trivalent doped ZnO codoped with lithium

    Energy Technology Data Exchange (ETDEWEB)

    Sivagamasundari, A.; Chandrasekar, S.; Pugaze, R.; Kannan, R., E-mail: kannan@pec.edu [Department of Physics, Pondicherry Engineering College, Puducherry 605 014 (India); Rajagopan, S. [Department of Chemistry, Pondicherry Engineering College, Puducherry 605 014 (India)

    2014-03-07

    Thermal ionization induced metallic to semiconductor (MST) transition occurring at 460 K for Zn{sub 0.97}Al{sub 0.03}O, 463 K for Zn{sub 0.94}Al{sub 0.03}Li{sub 0.03}O, and 503 K for Zn{sub 0.91}Al{sub 0.03}Li{sub 0.03}Mn{sub 0.03}O has been found in the sol-gel synthesized (using hexamethylenetetramine), trivalent doped (Al, Mn) ZnO codoped with lithium. Increase in the thermally ionized carrier concentration due to Al doping is responsible for near band edge (NBE) peak shift causing Fermi level to move into conduction band making it metallic consistent with resistivity results. Free carrier (thermally activated) neutralization with ionized donor is responsible for semiconducting nature, which is supported from the free carrier screening produced energy shift in the NBE of photoluminescence peak. Furthermore, independently band gap shrinkage is also obtained from UV-Visible studies confirming localization induced MST. An anti-correlation is found between defect density (DLE) and room temperature ferromagnetism (RTFM) indicating intrinsic defects are not directly responsible for RTFM.

  20. Preparation and characterization of semiconductor thin film cells of n-CdSe and CdSel-x Tex. Application in solar cells of liquid union

    International Nuclear Information System (INIS)

    Gutierrez, M.A.

    1987-01-01

    The development of the new energy sources, constitutes one of the most active and changing investigation areas of nowday. Within this frame, the conservation of photovoltaic solar energy, has taken a particular importance, as these systems become directly the photovoltaic solar energy, which incises on a semiconductor, in electric energy. In spite of this advantage, the use of photovoltaic systems is limited, being the main reason for this, the still high cost of the devices. One of the objectives of this Memory is to contribute to the reduction of these photovoltaic devices by using available methods for the preparation of photosensitive material, and for the union formation. The chosen preparation method is the electrochemical one and the electric field is made up in the interphase semiconductor/electrolyte, dipping the semiconductor in a convenient electrolyte. Summarizing, it can be said that the Memory's objetive presented is to discover the experiences realized in the electrochemical preparation of the n-CdSel-x Tex and its characterization by chemical analysis, X-rays difraction, electronic microscope of swept, optical techniques and photoelectrochemical methods. From the data obtained with these techniques, a study of the physical parameters evolution which determine the photovoltaic properties of the semiconductor, is made, as: the concentration of minoritary carriers, ND, and the diffusion length of these carriers, LP. Finally, taking into account the results obtained by the characterization of n-CdSe and CdSel-x Tex, is made from the construction of the photoelectrochemical cell, using two kinds of electrolyte: sulfide- polysulfide ands ferro-ferricyanide. (Author)

  1. Molecular-beam epitaxy growth and structural characterization of semiconductor-ferromagnet heterostructures by grazing incidence X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Satapathy, D.K.

    2005-12-19

    The present work is devoted to the growth of the ferromagnetic metal MnAs on the semiconductor GaAs by molecular-beam epitaxy (MBE). The MnAs thin films are deposited on GaAs by molecular-beam epitaxy (MBE). Grazing incidence diffraction (GID) and reflection high-energy electron diffraction (RHEED) are used in situ to investigate the nucleation, evolution of strain, morphology and interfacial structure during the MBE growth. Four stages of the nucleation process during growth of MnAs on GaAs(001) are revealed by RHEED azimuthal scans. GID shows that further growth of MnAs films proceed via the formation of relaxed islands at a nominal thickness of 2.5 ML which increase in size and finally coalesce to form a continuous film. Early on, an ordered array of misfit dislocations forms at the interface releasing the misfit strain even before complete coalescence occurs. The fascinating complex nucleation process of MnAs on GaAs(0 0 1) contains elements of both Volmer-Weber and Stranski-Krastanov growth. A nonuniform strain amounting to 0.66%, along the [1 -1 0] direction and 0.54%, along the [1 1 0] direction is demonstrated from x-ray line profile analysis. A high correlation between the defects is found along the GaAs[1 1 0] direction. An extremely periodic array of misfit dislocations with a period of 4.95{+-}0.05 nm is formed at the interface along the [1 1 0] direction which releases the 7.5% of misfit. The inhomogeneous strain due to the periodic dislocations is confined at the interface within a layer of 1.6 nm thickness. The misfit along the [1 -1 0] direction is released by the formation of a coincidence site lattice. (orig.)

  2. Lattice location of impurities in semiconductors: a RBS/channeling and proton-induced x-ray emission study

    Energy Technology Data Exchange (ETDEWEB)

    Kringhoj, P. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences

    1993-12-31

    Rutherford backscattering spectrometry (RBS)/channeling and proton-induced x-ray emission (PIXE) are two well established and characterised techniques. Over the last three decades RBS/channeling measurements has been performed to extract the substitutional fraction of impurities in both elemental and compound semiconductors. However, due to the limitation of RBS, only elements heavier than the host crystal can be examined (except for a few elements, where a nuclear reaction or a resonance can be used). In silicon this limitation is acceptable, due to the low mass of Si, but in the III-V compounds (e.g. InP), the technique is limited to a few elements of hardly no technological or fundamental interest. One can overcome this by combining RBS/channeling with PIXE, where PIXE is applied to detect elements with a mass lower than the host crystal. In the present work, the lattice location of Ge in InP has been studied and compared to the group-III impurity Ga, and the group-VI impurity Se which is known to be a donor. The (RBS)/channeling technique has been used to detect not only the substitutional fraction, but also the relative population of the two sublattices. The half-width is approximately equal to the characteristic angle, {psi}{sub 1}. The channeling data obtained indicate that all three dopants are located exclusively on substitutional sites and that Ga is occuping the In position, Se theP position and that Ge is distributed equally between both sublattices. 6 refs., 1 tab., 3 figs.

  3. State of the art in semiconductor detectors

    International Nuclear Information System (INIS)

    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

  4. X-Ray diffraction analysis of thermally evaporated copper tin selenide thin films at different annealing temperature

    International Nuclear Information System (INIS)

    Mohd Amirul Syafiq Mohd Yunos; Zainal Abidin Talib; Wan Mahmood Mat Yunus; Josephine Liew Ying Chyi; Wilfred Sylvester Paulus

    2010-01-01

    Semiconductor thin films Copper Tin Selenide, Cu 2 SnSe 3 , a potential compound for semiconductor radiation detector or solar cell applications were prepared by thermal evaporation method onto well-cleaned glass substrates. The as-deposited films were annealed in flowing purified nitrogen, N 2 , for 2 hours in the temperature range from 100 to 500 degree Celsius. The structure of as-deposited and annealed films has been studied by X-ray diffraction technique. The semi-quantitative analysis indicated from the Reitveld refinement show that the samples composed of Cu 2 SnSe 3 and SnSe. These studies revealed that the films were structured in mixed phase between cubic space group F-43 m (no. 216) and orthorhombic space group P n m a (no. 62). The crystallite size and lattice strain were determined from Scherrer calculation method. The results show that increasing in annealing temperature resulted in direct increase in crystallite size and decrease in lattice strain. (author)

  5. Determination of band-structure parameters of Pbsub(1-x)Snsub(x)Te narrow-gap semiconductor from infrared Faraday rotation

    International Nuclear Information System (INIS)

    Sizov, F.F.; Lashkarev, G.V.; Martynchuk, E.K.

    1977-01-01

    The temeprature dependences of Faraday rotation in Pbsub(1-x)Snsub(x)Te of p type with the hole density 3x10 16 -2.2x10 18 cm -3 are studied in the range 40-370 K and in the spectral interval 4-16 μm. The analysis of interband Faraday rotation confirms a conclusion made by the authors earlier that the g factor for the c band (gsub(c)) is positive, for the v band (gsub(v))-negative and that [gsub(c)] > [gsub(v)]. The temperature dependences of carrier effective masses are investigated on the basis of the two-band model. It is demonstrated that for T < 200 K the Faraday effective mass of holes near the ceiling of the valency band varies in direct proportion to the width of the forbidden band. The temperature increase of the Faraday effective mass of current carriers, which is faster than that of the effective electron mass, is discovered, and this is related to the effect of the heavy hole band

  6. Development of a scanning nearfield optical microscope for low-temperature investigations of semiconductor nanostructures

    International Nuclear Information System (INIS)

    Hodeck, Kai Friedrich

    2009-01-01

    In the present work the electronic structure of MOCVD-grown InGaAs/GaAs and InAs/GaAs quantum dots which are characterized by a particularly low ground state transition energy, was investigated using Scanning Nearfield Optical Microscopy (SNOM). The pivotal question of the presented investigations is, which influence the interaction of the confined carriers has on the energy states of the biexcitons and the multiexcitons in a quantum dot. Therefore, photoluminescence spectra of single quantum dots were investigated under varying excitation intensity at different temperatures between 5 K and 300 K. The construction of a novel scanning nearfield microscope especially for low temperatures allowed the investigation of single quantum dots. Due to significant improvements of the positioning technology and the shear-force distance control between the sample and the nearfield probe a stable scanning of the quantum dot samples at 5 K could be demonstrated, showing a lateral optical resolution of 200 nm. This way, in the photoluminescence spectroscopy of single quantum dots the thermal linewidth broadening of the detected light was reduced down to a value of less than 1 meV, which allowed the identification of the transitions of biexcitons and multiexcitons. On the basis of the performed measurements, for the InGaAs/GaAs quantum dots a biexciton state was identified, with variable binding energies of 2-7 meV. Furthermore, a positively charged trion state with a binding energy of 11 meV was observed, showing high emission intensity, which can be assigned to the sample doping. Accordingly, for the positively charged biexciton state a binding energy of 11 meV can be announced. For the investigated InAs/GaAs quantum dots a biexciton state with binding energies of 3-4 meV was found. Some of the investigated InAs/GaAs quantum dots showed the formation of positively charged states, in particular of a trion state with a binding energy of 3 meV, and of the positively charged

  7. Development of a scanning nearfield optical microscope for low-temperature investigations of semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Hodeck, Kai Friedrich

    2009-02-19

    In the present work the electronic structure of MOCVD-grown InGaAs/GaAs and InAs/GaAs quantum dots which are characterized by a particularly low ground state transition energy, was investigated using Scanning Nearfield Optical Microscopy (SNOM). The pivotal question of the presented investigations is, which influence the interaction of the confined carriers has on the energy states of the biexcitons and the multiexcitons in a quantum dot. Therefore, photoluminescence spectra of single quantum dots were investigated under varying excitation intensity at different temperatures between 5 K and 300 K. The construction of a novel scanning nearfield microscope especially for low temperatures allowed the investigation of single quantum dots. Due to significant improvements of the positioning technology and the shear-force distance control between the sample and the nearfield probe a stable scanning of the quantum dot samples at 5 K could be demonstrated, showing a lateral optical resolution of 200 nm. This way, in the photoluminescence spectroscopy of single quantum dots the thermal linewidth broadening of the detected light was reduced down to a value of less than 1 meV, which allowed the identification of the transitions of biexcitons and multiexcitons. On the basis of the performed measurements, for the InGaAs/GaAs quantum dots a biexciton state was identified, with variable binding energies of 2-7 meV. Furthermore, a positively charged trion state with a binding energy of 11 meV was observed, showing high emission intensity, which can be assigned to the sample doping. Accordingly, for the positively charged biexciton state a binding energy of 11 meV can be announced. For the investigated InAs/GaAs quantum dots a biexciton state with binding energies of 3-4 meV was found. Some of the investigated InAs/GaAs quantum dots showed the formation of positively charged states, in particular of a trion state with a binding energy of 3 meV, and of the positively charged

  8. Compound Semiconductor Radiation Detectors

    CERN Document Server

    Owens, Alan

    2012-01-01

    Although elemental semiconductors such as silicon and germanium are standard for energy dispersive spectroscopy in the laboratory, their use for an increasing range of applications is becoming marginalized by their physical limitations, namely the need for ancillary cooling, their modest stopping powers, and radiation intolerance. Compound semiconductors, on the other hand, encompass such a wide range of physical and electronic properties that they have become viable competitors in a number of applications. Compound Semiconductor Radiation Detectors is a consolidated source of information on all aspects of the use of compound semiconductors for radiation detection and measurement. Serious Competitors to Germanium and Silicon Radiation Detectors Wide-gap compound semiconductors offer the ability to operate in a range of hostile thermal and radiation environments while still maintaining sub-keV spectral resolution at X-ray wavelengths. Narrow-gap materials offer the potential of exceeding the spectral resolutio...

  9. Low temperature transport and thermodynamic properties of the Zintl compound Yb{sub 11}AlSb{sub 9}: A new Kondo lattice semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Magnavita, E.T. [CCNH, Universidade Federal do ABC (UFABC), Santo André, SP, 09210-580 (Brazil); Rettori, C. [CCNH, Universidade Federal do ABC (UFABC), Santo André, SP, 09210-580 (Brazil); Instituto de Física “Gleb Wataghin”, UNICAMP, Campinas, SP, 13083-970 (Brazil); Osorio-Guillén, J.M. [Instituto de Física, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín (Colombia); Ferreira, F.F.; Mendonça-Ferreira, L.; Avila, M.A.; Ribeiro, R.A. [CCNH, Universidade Federal do ABC (UFABC), Santo André, SP, 09210-580 (Brazil)

    2016-06-05

    A thorough transport and thermodynamic investigation of flux-grown single crystals of the ternary Zintl phase Yb{sub 11} AlSb{sub 9}, combined with first-principles density functional theory calculations, shows that this compound is a metal above T ≈ 100 K and a semiconductor with small hybridization gap at low-T. The general behavior resembles those of Kondo lattice semiconductors, although some of the measured properties are strongly sample dependent, as often seen in hybridized f-electron materials. We thus suggest that Yb{sub 11} AlSb{sub 9} can be considered as a new Yb-based Kondo lattice semiconductor joining the family of strongly correlated electron systems. - Highlights: • First characterization at low temperatures of Yb{sub 11}AlSb{sub 9}. • Yb{sub 11}AlSb{sub 9} has a small, field dependent hybridization gap at low-T. • Yb{sub 11}AlSb{sub 9} can be considered as a new Kondo lattice semiconductor.

  10. Effect of temperature on terahertz photonic and omnidirectional band gaps in one-dimensional quasi-periodic photonic crystals composed of semiconductor InSb.

    Science.gov (United States)

    Singh, Bipin K; Pandey, Praveen C

    2016-07-20

    Engineering of thermally tunable terahertz photonic and omnidirectional bandgaps has been demonstrated theoretically in one-dimensional quasi-periodic photonic crystals (PCs) containing semiconductor and dielectric materials. The considered quasi-periodic structures are taken in the form of Fibonacci, Thue-Morse, and double periodic sequences. We have shown that the photonic and omnidirectional bandgaps in the quasi-periodic structures with semiconductor constituents are strongly depend on the temperature, thickness of the constituted semiconductor and dielectric material layers, and generations of the quasi-periodic sequences. It has been found that the number of photonic bandgaps increases with layer thickness and generation of the quasi-periodic sequences. Omnidirectional bandgaps in the structures have also been obtained. Results show that the bandwidths of photonic and omnidirectional bandgaps are tunable by changing the temperature and lattice parameters of the structures. The generation of quasi-periodic sequences can also change the properties of photonic and omnidirectional bandgaps remarkably. The frequency range of the photonic and omnidirectional bandgaps can be tuned by the change of temperature and layer thickness of the considered quasi-periodic structures. This work will be useful to design tunable terahertz PC devices.

  11. Soft-X-ray electron temperature measurements on TORTUR

    International Nuclear Information System (INIS)

    Lopes Cardozo, N.J.

    1984-02-01

    During June and July 1982, some 250 discharges were produced in the TORTUR tokamak. The discharges can be characterized roughly by the predischarge current peak of 40 to 45 kA at 2 ms, followed by a current plateau of 30 to 40 kA which lasted 20 to 30 ms. At 5 ms, Thomson scattering indicated a central Tsub(e) of about 900 eV which fell to a lasting temperature of 600 to 400 eV in discharges that were stigmatized 'mildly turbulent' for their high ohmic dissipation. Soft-X-ray measurements of Tsub(e) were carried out with PLATO, a 4-channel X-ray detector, in which two surface barrier diodes and two channeltrons were mounted. Tsub(e) was determined by means of the absorber foil technique. To that end four exchangeable Be absorber foils ranging in thickness from 30 to 100 micron were mounted in each channel. Every single discharge yielded 3 independent, time-resolved (resolution 100 μs) measurements of Tsub(e). (Auth.)

  12. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  13. Parallel of semi-empirical results simulated by MCNP of X-ray spectra with a semiconductor; Paralelo de resultado semi- empiricos simulados por MCNPX de espectros de raios-X com um semicondutor

    Energy Technology Data Exchange (ETDEWEB)

    Santos, L.R.; Vivolo, V.; Potiens, M.P.A., E-mail: dossantos.lucasrodrigues@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Navarro, M.V.T.; Santos, W.S. [Universidade Federal de Uberlandia (INFIS/UFU), MG (Brazil). Instituto de Fisica

    2016-07-01

    The aim of this study was to use the MCNPX radiation transport code to simulate X-ray spectra generated by a constant voltage system in a CdTe semiconductor detector. As part of the validation process, we obtained a series of experimental spectra. Comparatively, in all cases there is a good correlation between the two spectra. There were no statistically significant differences between the experimental results with the simulated. (author)

  14. SOME PHYSICOCHEMICAL PROPERTIES OF OCTYLPHENOL ETHOXYLATE NONIONICS (TRITON X-100, TRITON X-114 AND TRITON X-405 AND THE TEMPERATURE EFFECT ON THIS PROPERTIES

    Directory of Open Access Journals (Sweden)

    Taliha Sidim

    2016-11-01

    Full Text Available Surface tensions and condutvities of aqueous solutions of nonionic surfactants at various concentrations were measured at diffferent temperatures.The critical micelle concentration (CMC of aqueous solutions of three different octylphenol ethoxylate nonionics(Triton X-114, Triton X-100 and Triton X-405 are determined at different temperatures.The effect of the ethylene oxide chain length and temperature on the CMC is also determined.

  15. Semiconductor physics

    CERN Document Server

    Böer, Karl W

    2018-01-01

    This handbook gives a complete survey of the important topics and results in semiconductor physics. It addresses every fundamental principle and most research topics and areas of application in the field of semiconductor physics. Comprehensive information is provided on crystalline bulk and low-dimensional as well as amporphous semiconductors, including optical, transport, and dynamic properties.

  16. Thermoelectrically cooled semiconductor detectors for non-destructive analysis of works of art by means of energy dispersive X-ray fluorescence

    CERN Document Server

    Cesareo, R; Castellano, A

    1999-01-01

    Thermoelectrically cooled semiconductor detectors, such as Si-PIN, Si-drift, Cd sub 1 sub - sub x Zn sub x Te and HgI sub 2 , coupled to miniaturized low-power X-ray tubes, are well suited in portable systems for energy-dispersive X-ray fluorescence (EDXRF), analysis of archaeological samples. The Si-PIN detector is characterized by a thickness of about 300 mu m, an area of about 2x3 mm sup 2 , an energy resolution of about 200-250 eV at 5.9 keV and an entrance window of 25-75 mu m. The Si-drift detector has approximately the same area and thickness, but an energy resolution of 155 eV at 5.9 keV. The efficiency of these detectors is around 100% from 4 to 10 keV, and then decreases versus energy, reaching approx 9% at 30 keV. Coupled to a miniaturized 10 kV, 0.1 mA, Ca-anode or to a miniaturized 30 kV, 0.1 mA, W-anode X-ray tubes, portable systems can be constructed, which are able to analyse K-lines of elements up to about silver, and L-lines of heavy elements. The Cd sub 1 sub - sub x Zn sub x Te detector ha...

  17. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  18. Calculation of the thermal mode in semiconductor devices in conditions of their operation in semiconductor apparatuses

    OpenAIRE

    Сосков, Анатолій Георгійович; Глєбова, Марина Леонідівна; Сабалаєва, Наталія Олегівна; Форкун, Яна Борисівна

    2014-01-01

    The study of the temperature field of power semiconductor devices, operating in semiconductor apparatuses, either non-contact or hybrid was carried out in the paper.It was also shown that the main mode of the current load of power semiconductor devices, operating in semiconductor apparatuses is a pulse mode.Analytical method for calculating the values of the temperature rise in the structure of power semiconductor devices when subjected to a current pulse of arbitrary shape based on a model t...

  19. Hard-X and gamma-ray imaging detector for astrophysics based on pixelated CdTe semiconductors

    Science.gov (United States)

    Gálvez, J.-L.; Hernanz, M.; Álvarez, L.; Artigues, B.; Ullán, M.; Lozano, M.; Pellegrini, G.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2016-01-01

    Stellar explosions are astrophysical phenomena of great importance and interest. Instruments with high sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators. In order to achieve the needed performance, a hard-X and gamma-ray imaging detector with mm spatial resolution and large enough efficiency is required. We present a detector module which consists of a single CdTe crystal of 12.5 × 12.5mm 2 and 2mm thick with a planar cathode and with the anode segmented in an 11x11 pixel array with a pixel pitch of 1 mm attached to the readout chip. Two possible detector module configurations are considered: the so-called Planar Transverse Field (PTF) and the Parallel Planar Field (PPF). The combination of several modules in PTF or PPF configuration will achieve the desired performance of the imaging detector. The sum energy resolution of all pixels of the CdTe module measured at 122 keV and 356 keV is 3.8% and 2% respectively, in the following operating conditions: PPF irradiation, bias voltage -500 V and temperature -10̂ C.

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

    Science.gov (United States)

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

    2017-05-01

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

  1. Low temperature X-ray imaging of magnetic flux patterns in high temperature superconductors

    Science.gov (United States)

    Stahl, Claudia; Ruoß, Stephen; Weigand, Markus; Bechtel, Michael; Schütz, Gisela; Albrecht, Joachim

    2015-05-01

    We present X-ray magnetic circular dichroism (XMCD) microscopy results obtained at liquid nitrogen temperatures on the high-Tc superconductor YBCO (YBa2Cu3O7-δ). The magnetic flux distribution arising from electric currents in the superconductor is detected and visualized using soft-magnetic Co40Fe40B20 (CoFeB) as sensor layer and XMCD as contrast mechanism. It has been shown that the XMCD contrast in the sensor layer directly corresponds to magnetic flux distribution of the superconductor and hence can be used to image magnetic structures in superconductors [Stahl et al., Phys. Rev. B 90, 104515 (2014)]. The existing scanning UHV X-ray microscopy setup MAXYMUS at the synchrotron BESSY II in Berlin has been upgraded for that purpose: we use a nitrogen based MMR Micro Miniature Joule-Thompson Cryostat with temperature range from 75 K to 580 K. The capability of the method is demonstrated on two different superconducting samples, an optimally doped thin film and a melt-textured block.

  2. Evidence of Room Temperature Ferromagnetism Due to Oxygen Vacancies in (In1- x Fe x )2O3 Thin Films

    Science.gov (United States)

    Chakraborty, Deepannita; Munuswamy, Kuppan; Shaik, Kaleemulla; Nasina, Madhusudhana Rao; Dugasani, Sreekantha Reddy; Inturu, Omkaram

    2018-03-01

    Iron substituted indium oxide (In1- x Fe x )2O3 thin films at x = 0.00, 0.03, 0.05 and 0.07 were coated onto Corning 7059 glass substrates using the electron beam evaporation technique followed by annealing at different temperatures. The prepared thin films were subjected to different characterization techniques to study their structural, optical and magnetic properties. The structural properties of the thin films were studied using x-ray diffractometry (XRD). From the XRD results it was found that the films were crystallized in cubic structure, and no change in crystal structure was observed with annealing temperature. No secondary phases related to iron were observed from the XRD profiles. The chemical composition and surface morphology of the films were examined by field emission scanning electron microscope (FE-SEM) attached with energy dispersive analysis of x-ray (EDAX). The valence state of the elements were studied by x-ray photoelectron spectroscopy (XPS) and found that the indium, iron and oxygen were in In+3, Fe+3 and O-2 states. From the data, the band gap of the (In1- x Fe x )2O3 thin films were calculated and it increased with increase of annealing temperature. The magnetic properties of the films were studied at room temperature by vibrating sample magnetometer (VSM). The films exhibited ferromagnetism at room temperature.

  3. Low-temperature activation and deactivation of high-Curie-temperature ferromagnetism in a new diluted magnetic semiconductor: Ni2+-Doped SnO2.

    Science.gov (United States)

    Archer, Paul I; Radovanovic, Pavle V; Heald, Steve M; Gamelin, Daniel R

    2005-10-19

    We report the synthesis of colloidal Ni(2+)-doped SnO(2) (Ni(2+):SnO(2)) nanocrystals and their characterization by electronic absorption, magnetic circular dichroism, X-ray absorption, magnetic susceptibility, scanning electron microscopy, and X-ray diffraction measurements. The Ni(2+) dopants are found to occupy pseudooctahedral Sn(4+) cation sites of rutile SnO(2) without local charge compensation. The paramagnetic nanocrystals exhibit robust high-Curie-temperature (T(C)) ferromagnetism (M(s)(300 K) = 0.8 mu(B)/Ni(2+), T(C) > 300 K) when spin-coated into films, attributed to the formation of interfacial fusion defects. Facile reversibility of the paramagnetic-ferromagnetic phase transition is also observed. This magnetic phase transition is studied as a function of temperature, time, and atmospheric composition, from which the barrier to ferromagnetic activation (E(a)) is estimated to be 1200 cm(-1). This energy is associated with ligand mobility on the surfaces of the Ni(2+):SnO(2) nanocrystals. The phase transition is reversed under air but not under N(2), from which the microscopic identity of the activating defect is proposed to be interfacial oxygen vacancies.

  4. Low temperature magnetization and anomalous high temperature dielectric behaviour of (1-x) YMnO3/xZnFe2O4 composites

    Science.gov (United States)

    Kumar, Virendra; Gaur, Anurag

    2018-04-01

    We synthesized YMnO3 and ZnFe2O4 composites, (1-x)YMnO3/x(ZnFe2O4) with x = 0, 0.05, 0.10, and 0.15 by high temperature sintering. X-ray diffraction (XRD) patterns indicate the successful formation of composites. Weak ferromagnetism is manifested below Néel temperature (TN) for pristine YMnO3, according to (M-H) study performed at 10 K. For (1-x)YMnO3/xZnFe2O4 (x = 0.05, 0.10, 0.15) a thin coercivity is observed in all compositions, due to short range magnetic ordering at low temperature after the insertion of ZnFe2O4. For pristine YMnO3 explicit divarication between FC-ZFC curves is observed, with crimps observed in both FC and ZFC curves at 75 K, which is the TN of YMnO3. For 1-x(YMnO3)/x ZnFe2O4 composites (x = 0.05, 0.10, 0.15) crimps are perceived only in ZFC curves at slightly varying values of 39.8, 42.32 and 45.63 K respectively. Anomalous peaks are observed in high temperature dielectric curves above 400 K for 1-x(YMnO3)/xZnFe2O4 (x = 0, 0.05, 0.10, 0.15) composites due to Maxwell-Wagner relaxation effect.

  5. Rabi oscillations and self-induced transparency in InAs/InP quantum dot semiconductor optical amplifier operating at room temperature.

    Science.gov (United States)

    Karni, Ouri; Capua, Amir; Eisenstein, Gadi; Sichkovskyi, Vitalii; Ivanov, Vitalii; Reithmaier, Johann Peter

    2013-11-04

    We report direct observations of Rabi oscillations and self-induced transparency in a quantum dot optical amplifier operating at room temperature. The experiments make use of pulses whose durations are shorter than the coherence time which are characterized using Cross-Frequency-Resolved Optical Gating. A numerical model which solves the Maxwell and Schrödinger equations and accounts for the inhomogeneously broadened nature of the quantum dot gain medium confirms the experimental results. The model is also used to explain the relationship between the observability of Rabi oscillations, the pulse duration and the homogeneous and inhomogeneous spectral widths of the semiconductor.

  6. Bulk Crystal Growth, and High-Resolution X-ray Diffraction Results of LiZnAs Semiconductor Material

    Science.gov (United States)

    Montag, Benjamin W.; Reichenberger, Michael A.; Sunder, Madhana; Ugorowski, Philip B.; Nelson, Kyle A.; Henson, Luke C.; McGregor, Douglas S.

    2017-08-01

    LiZnAs is being explored as a candidate for solid-state neutron detectors. The compact form, solid-state device would have greater efficiency than present day gas-filled 3He and 10BF3 detectors. Devices fabricated from LiZnAs having either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. The 6Li( n, t)4He reaction yields a total Q-value of 4.78 MeV, an energy larger than that of the 10B reaction, which can easily be identified above background radiations. LiZnAs material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10-6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace (Montag et al. in J Cryst Growth 412:103, 2015). The raw synthesized LiZnAs was purified by a static vacuum sublimation in quartz (Montag et al. in J Cryst Growth 438:99, 2016). Bulk crystalline LiZnAs ingots were grown from the purified material with a high-temperature Bridgman-style growth process described here. One of the largest LiZnAs ingots harvested was 9.6 mm in diameter and 4.2 mm in length. Samples were harvested from the ingot and were characterized for crystallinity using a Bruker AXS Inc. D8 AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS Inc. D8 DISCOVER, high-resolution x-ray diffractometer equipped with molybdenum radiation, Gobel mirror, four bounce germanium monochromator and a scintillation detector. The primary beam divergence was determined to be 0.004°, using a single crystal Si standard. The x-ray based characterization revealed that the samples nucleated in the (110) direction and a high-resolution open detector rocking curve recorded on the (220) LiZnAs yielded a full width at half maximum (FWHM) of 0.235°. Sectional pole figures using off-axis reflections of the (211) LiZnAs confirmed in-plane ordering, and also indicated the presence of multiple

  7. The experimental and theoretical investigation of vibration spectra in ferroelectric semiconductor SbSBrxI1-x crystals

    International Nuclear Information System (INIS)

    Audzijonis, A.; Zigas, L.; Kvedaravicius, A.; Zaltauskas, R.

    2009-01-01

    The vapor grown SbSBr x I 1-x (x=0.1; 0.5; 0.9) crystals with clear mirror surfaces have been used for infrared reflection measurements with Fourier spectrometer. The vibration frequencies along c(z)-axis have been derived from Kramers-Kroning and optical parameters fitting analysis of the experimental reflectivity spectra at T=300 K. The theoretical vibration spectra of SbSBr x S 1-x (x=0.1; 0.5; 0.9) crystals in paraelectric phase (T=300 K) along c(z)-axis have been determined in quasiharmonic approximation by diagonalization of dynamical matrix. The theoretical vibration spectra of these crystals in a-b(x-y) plane have been determined in harmonic approximation. In this work we discuss the nature of anharmonism in SbSBr x I 1-x crystals along the c(z)-axis.

  8. X-ray emission from high temperature plasmas

    Science.gov (United States)

    Harries, W. L.

    1974-01-01

    X-rays from a 25-hJ plasma focus apparatus were observed with pinhole cameras. The cameras consist of 0.4 mm diameter pinholes in 2 cm thick lead housing enclosing an X-ray intensifying screen at the image plane. Pictures recorded through thin aluminum foils or plastic sheets for X-ray energies sub gamma smaller than 15 keV show distributed X-ray emissions from the focussed plasma and from the anode surface. However, when thick absorbers are used, radial filamentary structure in the X-ray emission from the anode surface is revealed. Occasionally larger structures are observed in addition to the filaments. Possible mechanisms for the filamentary structure are discussed.

  9. Semiconductor Gas Sensors Based on Pd/SnO2 Nanomaterials for Methane Detection in Air

    Science.gov (United States)

    Fedorenko, George; Oleksenko, Ludmila; Maksymovych, Nelly; Skolyar, Galina; Ripko, Oleksandr

    2017-05-01

    Semiconductor sensors based on nanosized Pd-containing tin dioxide have been obtained by a sol-gel technique. Semiconductor gas-sensitive materials were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. Influence of Pd additives on sensitivity of the sensors to methane has been studied. Temperature dependences of electrical resistance in air and sensor response to methane on palladium content for the sensors based on nanosized materials Pd/SnO2 have been investigated.

  10. Structural characterization of Al xGa1-xSb films grown at low temperatures by liquid phase epitaxy

    International Nuclear Information System (INIS)

    Rosendo, E.; Diaz, T.; Martinez, J.; Juarez, H.; Juarez, G.

    2005-01-01

    High resolution X-ray diffraction (HRXRD) and far-infrared reflectivity techniques were applied to characterize Al x Ga 1-x Sb alloys. Layers of Al x Ga 1-x Sb grown by the liquid phase epitaxy technique and deposited on GaSb (100) substrates were obtained in the temperature range of 250 to 450 deg. C. From the HRXRD measurements it can be inferred that the films have good structural characteristics, this is because the lattice mismatch values were no bigger than 0.02% and from the rocking curves the Al concentration was ranged from 0.04 to 0.058. The presence of the ternary alloy in the films was confirmed by reflectivity. A change of the conductivity type in the film was observed for films grown at temperatures lower than 350 deg. C

  11. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  12. Semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Marstein Erik Stensrud

    2003-07-01

    This thesis presents a study of two material systems containing semiconductor nanocrystals, namely porous silicon (PSi) films and germanium (Ge) nanocrystals embedded in silicon dioxide (SiO2) films. The PSi films were made by anodic etching of silicon (Si) substrates in an electrolyte containing hydrofluoric acid. The PSi films were doped with erbium (Er) using two different doping methods. electrochemical doping and doping by immersing the PSi films in a solution containing Er. The resulting Er concentration profiles were investigated using scanning electron microscopy (SEN1) combined with energy dispersive X-ray analysis (EDS). The main subject of the work on PSi presented in this thesis was investigating and comparing these two doping methods. Ge nanocrystals were made by implanting Ge ions into Si02 films that were subsequently annealed. However. nanocrystal formation occurred only for certain sets of processing parameters. The dependence of the microstructure of the Ge implanted Si02 films on the processing parameters were therefore investigated. A range of methods were employed for these investigations, including transmission electron microscopy (TEM) combined with EDS, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The observed structures, ranging from Ge nanocrystals to voids with diameters of several tens of nanometers and Ge rich Si02 films without any nanocrystals is described. A model explaining the void formation is also presented. For certain sets of processing parameters. An accumulation of Ge at the Si-Si02 interface was observed. The effect of this accumulation on the electrical properties of MOS structures made from Ge implanted SiO2 films was investigated using CV-measurements. (Author)

  13. High Resolution X-ray Diffraction Characterization of III-Nitride Semiconductors: Bulk Crystals and Thin Films

    Science.gov (United States)

    Bobea, Milena Rebeca

    m-plane AlN single crystals by metalorganic chemical vapor deposition. The films were deposited under identical growth conditions, within a temperature range between 1150°C and 1550°C. XRCs exhibited full-width at half maximum values ranging between 12 to 35 arcsec, confirming the high crystallinity of the epitaxial films. Absolute lattice parameter measurements indicated that the films were strain-free. However, differences among the film surfaces were identified, corresponding to a transition from a heavily faceted step morphology to monolayer steps as the growth temperature was increased. To examine the presence of extended defects, defect-selective RSM analysis was performed using (h0h¯0) maps taken parallel to the [0001]. For all films, no characteristic broadening from basal plane stacking faults was observed. Additionally, for a two-layer AlN homoepitaxial structure, transmission electron microscopy under different diffraction conditions did not exhibit defect imaging contrast. These results evidence the ability to use HRXRD RSMs to characterize highly perfect non-polar m-plane AlN films. The strain state and composition of AlxGa1-xN alloy epitaxial films deposited on (0001) AlN single crystals by MOCVD was studied using several HRXRD methods, including relative lattice parameter measurements (zone-axis techniques) and RSMs. Within the investigated compositional range, all alloy films were revealed to be pseudomorphic to the AlN substrate. However, crystallographic tilting was observed for several cases, which led to large errors in extracted biaxial stress relaxation values. To eliminate measurement error and further explore film tilting as a potential in-plane stress relaxation mechanism, alloy films were grown on 0.2°-4.0° off-cut substrates and examined using HRXRD RSMs, taken both parallel and perpendicular to the measured tilt direction. Results revealed a linear dependence of film tilt with substrate offcut, following the Nagai tilt model

  14. Temperature Dependent Electrical Transport in Al/Poly(4-vinyl phenol/p-GaAs Metal-Oxide-Semiconductor by Sol-Gel Spin Coating Method

    Directory of Open Access Journals (Sweden)

    Şadan Özden

    2016-01-01

    Full Text Available Deposition of poly(4-vinyl phenol insulator layer is carried out by applying the spin coating technique onto p-type GaAs substrate so as to create Al/poly(4-vinyl phenol/p-GaAs metal-oxide-semiconductor (MOS structure. Temperature was set to 80–320 K while the current-voltage (I-V characteristics of the structure were examined in the study. Ideality factor (n and barrier height (ϕb values found in the experiment ranged from 3.13 and 0.616 eV (320 K to 11.56 and 0.147 eV (80 K. Comparing the thermionic field emission theory and thermionic emission theory, the temperature dependent ideality factor behavior displayed that thermionic field emission theory is more valid than the latter. The calculated tunneling energy was 96 meV.

  15. Single carrier trapping and de-trapping in scaled silicon complementary metal-oxide-semiconductor field-effect transistors at low temperatures

    Science.gov (United States)

    Li, Zuo; Khaled Husain, Muhammad; Yoshimoto, Hiroyuki; Tani, Kazuki; Sasago, Yoshitaka; Hisamoto, Digh; Fletcher, Jonathan David; Kataoka, Masaya; Tsuchiya, Yoshishige; Saito, Shinichi

    2017-07-01

    The scaling of Silicon (Si) technology is approaching the physical limit, where various quantum effects such as direct tunnelling and quantum confinement are observed, even at room temperatures. We have measured standard complementary metal-oxide-semiconductor field-effect-transistors (CMOSFETs) with wide and short channels at low temperatures to observe single electron/hole characteristics due to local structural disturbances such as roughness and defects. In fact, we observed Coulomb blockades in sub-threshold regimes of both p-type and n-type Si CMOSFETs, showing the presence of quantum dots in the channels. The stability diagrams for the Coulomb blockade were explained by the potential minima due to poly-Si grains. We have also observed sharp current peaks at narrow bias windows at the edges of the Coulomb diamonds, showing resonant tunnelling of single carriers through charge traps.

  16. Theoretical investigations of electronic, optical and mechanical properties for GaSb and AlSb semiconductors under the influence of temperature.

    Science.gov (United States)

    Elkenany, Elkenany B

    2015-11-05

    In this paper we explore the effects of temperature on the electronic and mechanical properties of GaSb and AlSb semiconductors by using the local empirical pseudo-potential method. Our results show that the band gaps, refractive index, optical dielectric constant, elastic constants (C11, C12, C44), bulk modulus, shear modulus and Young modulus of these compounds vary with the change in temperature. The comparison of some of our results with the available experimental data confirms the accurateness of our theoretical approach, which also infers the reliability of our other theoretical results. As, for some of the present calculations a little experimental data is available for comparison, therefore these results can be used as a reference work in the future studies. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Temperature dependence of electromechanical properties of PLZT x ...

    Indian Academy of Sciences (India)

    Administrator

    temperature much lower than the ferroelectric to paraelectric phase transition of the material. The same behaviour is observed for the overtones also. However, the piezoelectric response of the overtones disappears at a lower temperature than the fundamental mode. The quantity, Δfps, depends on the electromechanical.

  18. Temperature dependence of electromechanical properties of PLZT x ...

    Indian Academy of Sciences (India)

    ... broad peak at a temperature higher than mt. The voltage constant 31 decreases and the planar coupling coefficient p remains constant up to half of the mt and then falls sharply with . Half of the mt can, therefore, be used for specifying the working temperature limit of the piezoceramics for the device applications.

  19. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic......Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  20. Temperature-dependent elastic properties of Ti{sub 1−x}Al{sub x}N alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shulumba, Nina [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Functional Materials, Saarland University, D-66123 Saarbrücken (Germany); Hellman, Olle [Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125 (United States); Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Odén, Magnus [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Abrikosov, Igor A. [Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Materials Modeling and Development Laboratory, NUST “MISIS,” 119049 Moscow (Russian Federation); LACOMAS Laboratory, Tomsk State University, 634050 Tomsk (Russian Federation)

    2015-12-07

    Ti{sub 1−x}Al{sub x}N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C{sub 11} decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy.

  1. Electronic properties of semiconductor surfaces and metal/semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tallarida, M.

    2005-05-15

    This thesis reports investigations of the electronic properties of a semiconductor surface (silicon carbide), a reactive metal/semiconductor interface (manganese/silicon) and a non-reactive metal/semiconductor interface (aluminum-magnesium alloy/silicon). The (2 x 1) reconstruction of the 6H-SiC(0001) surface has been obtained by cleaving the sample along the (0001) direction. This reconstruction has not been observed up to now for this compound, and has been compared with those of similar elemental semiconductors of the fourth group of the periodic table. This comparison has been carried out by making use of photoemission spectroscopy, analyzing the core level shifts of both Si 2p and C 1s core levels in terms of charge transfer between atoms of both elements and in different chemical environments. From this comparison, a difference between the reconstruction on the Si-terminated and the C-terminated surface was established, due to the ionic nature of the Si-C bond. The growth of manganese films on Si(111) in the 1-5 ML thickness range has been studied by means of LEED, STM and photoemission spectroscopy. By the complementary use of these surface science techniques, two different phases have been observed for two thickness regimes (<1 ML and >1 ML), which exhibit a different electronic character. The two reconstructions, the (1 x 1)-phase and the ({radical}3 x {radical}3)R30 -phase, are due to silicide formation, as observed in core level spectroscopy. The growth proceeds via island formation in the monolayer regime, while the thicker films show flat layers interrupted by deep holes. On the basis of STM investigations, this growth mode has been attributed to strain due to lattice mismatch between the substrate and the silicide. Co-deposition of Al and Mg onto a Si(111) substrate at low temperature (100K) resulted in the formation of thin alloy films. By varying the relative content of both elements, the thin films exhibited different electronic properties

  2. Elliptically Bent X-Ray Mirrors with Active Temperature Stabilization

    International Nuclear Information System (INIS)

    Yuan, S.; Church, M.; Yashchuk, V.V.; Celestre, R.S.; McKinney, W.R.; Morrison, G.; Warwick, T.; Padmore, H.A.; Goldberg, K.A.; Kirschman, J.; Noll, T.

    2010-01-01

    We present details of design of elliptically bent Kirkpatrick-Baez mirrors developed and successfully used at the advanced light source for submicron focusing. A distinctive feature of the mirror design is an active temperature stabilization based on a Peltier element attached directly to the mirror body. The design and materials have been carefully optimized to provide high heat conductance between the mirror body and substrate. We describe the experimental procedures used when assembling and precisely shaping the mirrors, with special attention paid to laboratory testing of the mirror-temperature stabilization. For this purpose, the temperature dependence of the surface slope profile of a specially fabricated test mirror placed inside a temperature-controlled container was measured. We demonstrate that with active mirror-temperature stabilization, a change of the surrounding temperature by more than 3 K does not noticeably affect the mirror figure. Without temperature stabilization, the rms slope error is changed by approximately 1.5 μrad (primarily defocus) under the same conditions

  3. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai

    2012-01-01

    Semiconductor Spintronics, as an emerging research discipline and an important advanced field in physics, has developed quickly and obtained fruitful results in recent decades. This volume is the first monograph summarizing the physical foundation and the experimental results obtained in this field. With the culmination of the authors' extensive working experiences, this book presents the developing history of semiconductor spintronics, its basic concepts and theories, experimental results, and the prospected future development. This unique book intends to provide a systematic and modern foundation for semiconductor spintronics aimed at researchers, professors, post-doctorates, and graduate students, and to help them master the overall knowledge of spintronics.

  4. Temperature-dependent thermal and thermoelectric properties of n -type and p -type S c1 -xM gxN

    Science.gov (United States)

    Saha, Bivas; Perez-Taborda, Jaime Andres; Bahk, Je-Hyeong; Koh, Yee Rui; Shakouri, Ali; Martin-Gonzalez, Marisol; Sands, Timothy D.

    2018-02-01

    Scandium Nitride (ScN) is an emerging rocksalt semiconductor with octahedral coordination and an indirect bandgap. ScN has attracted significant attention in recent years for its potential thermoelectric applications, as a component material in epitaxial metal/semiconductor superlattices, and as a substrate for defect-free GaN growth. Sputter-deposited ScN thin films are highly degenerate n -type semiconductors and exhibit a large thermoelectric power factor of ˜3.5 ×10-3W /m -K2 at 600-800 K. Since practical thermoelectric devices require both n- and p-type materials with high thermoelectric figures-of-merit, development and demonstration of highly efficient p-type ScN is extremely important. Recently, the authors have demonstrated p-type S c1 -xM gxN thin film alloys with low M gxNy mole-fractions within the ScN matrix. In this article, we demonstrate temperature dependent thermal and thermoelectric transport properties, including large thermoelectric power factors in both n- and p-type S c1 -xM gxN thin film alloys at high temperatures (up to 850 K). Employing a combination of temperature-dependent Seebeck coefficient, electrical conductivity, and thermal conductivity measurements, as well as detailed Boltzmann transport-based modeling analyses of the transport properties, we demonstrate that p-type S c1 -xM gxN thin film alloys exhibit a maximum thermoelectric power factor of ˜0.8 ×10-3W /m -K2 at 850 K. The thermoelectric properties are tunable by adjusting the M gxNy mole-fraction inside the ScN matrix, thereby shifting the Fermi energy in the alloy films from inside the conduction band in case of undoped n -type ScN to inside the valence band in highly hole-doped p -type S c1 -xM gxN thin film alloys. The thermal conductivities of both the n- and p-type films were found to be undesirably large for thermoelectric applications. Thus, future work should address strategies to reduce the thermal conductivity of S c1 -xM gxN thin-film alloys, without affecting

  5. Temperature dependence of magnetoelastic properties of Fe100−xSix (5 < x < 20)

    Energy Technology Data Exchange (ETDEWEB)

    Petculescu, G.; Lambert, P.K.; Clark, A.E.; Hathaway, K.B.; Xing, Qingfeng; Lograsso, Tom; Restorff, J.B.; Wun-Fogle, M.

    2012-02-29

    Tetragonal magnetostriction (λγ,2) and elastic constants (c′, c44, and c11) for Fe100−xSix were measured as a function of temperature (T). Compositions corresponding to the disordered A2 (x = 5), ordered D03 (x = 19.8), and mixed (x = 11.6) phases, were investigated. The magnetoelastic coupling (−b1) was determined for 77 < T < 300 K and compared with those of Fe-Ga, Fe-Ge, and Fe-Al. Both λγ,2(T) and −b1(T) of Fe-Si behave similarly to those of Fe-Ge, while other notable differences exist between the measured properties of Fe-Si and those of the other three alloys. Due to the early establishment of short range order, Fe-Si exhibits a positive, although small, slope in λγ,2(T) at 5 at. % Si, and a remarkable drop in −b1 before the solubility limit. The weaker softening of the tetragonal shear modulus with the addition of Si and the lack of strong anharmonic effects in the Fe-Si lattice inferred from the weak T-dependence of all the moduli suggest that Fe-Si exhibits more structural stability than the other three alloys. The distinctive behavior is likely due to the smaller size of Si compared to the sizes of Ga, Ge and Al, and therefore to the effect of the larger size difference between Fe and Si in the Fe-Si lattice.

  6. The effects of annealing temperature on the structural properties and optical constants of a novel DPEA-MR-Zn organic crystalline semiconductor nanostructure thin films

    Science.gov (United States)

    Al-Hossainy, A. Farouk; Ibrahim, A.

    2017-11-01

    The dependence of structural properties and optical constants on annealing temperature of a 2-((1,2-bis (diphenylphosphino)ethyl)amino) acetic acid-methyl red-monochloro zinc dihydride (DPEA-MR-Zn) as a novel organic semiconductor thin film was studied. The DPEA-MR-Zn thin film was deposited on silicon substrates using the spin coating technique. The as-deposited film was annealed in air for 1 h at 150, 175 and 205 °C. The XRD study of DPEA-MR-Zn in its powder form showed that this complex is mere a triclinic crystal structure with a space group P-1. In addition, the XRD patterns showed that the as-deposited thin films were crystallized according to the preferential orientation [(214), (121), (0 2 bar 6), (3 bar 02), (122) and (11 4 bar)]. Moreover, two additional peaks (2 bar 2 bar 1 and 2 4 bar 7) were shown at 2θ nearly 30°, and 69°, where, the more annealing temperature, the more the intensity of the two peaks. In addition, it was noticed that the grain size had a remarkable change with an annealing temperature of the DPEA-MR-Zn thin films. The optical measurements showed that the thin film has a relatively high absorption region where the photon energy ranges from 2 to 3.25 eV. Both of Wemple-DiDomenico and single Sellmeier oscillator models were applied on the DPEA-MR-Zn to analyze the dispersion of the refractive index and the optical and dielectric constants. The outcome of the study of the structural and optical properties reported here of the DPEA-MR-Zn organic semiconductor crystalline nanostructure thin film had shown various applications in many advanced technologies such as photovoltaic solar cells.

  7. Metal-semiconductor, composite radiation detectors

    International Nuclear Information System (INIS)

    Orvis, W.J.; Yee, J.H.; Fuess, D.

    1992-12-01

    In 1989, Naruse and Hatayama of Toshiba published a design for an increased efficiency x-ray detector. The design increased the efficiency of a semiconductor detector by interspersing layers of high-z metal within it. Semiconductors such as silicon make good, high-resolution radiation detectors, but they have low efficiency because they are low-z materials (z = 14). High-z metals, on the other hand, are good absorbers of high-energy photons. By interspersing high-z metal layers with semiconductor layers, Naruse and Hatayama combined the high absorption efficiency of the high-z metals with the good detection capabilities of a semiconductor. This project is an attempt to use the same design to produce a high-efficiency, room temperature gamma ray detector. By their nature, gamma rays require thicker metal layers to efficiently absorb them. These thicker layers change the behavior of the detector by reducing the resolution, compared to a solid state detector, and shifting the photopeak by a predictable amount. During the last year, the authors have procured and tested a commercial device with operating characteristics similar to those of a single layer of the composite device. They have modeled the radiation transport in a multi-layered device, to verify the initial calculations of layer thickness and composition. They have modeled the electrostatic field in different device designs to locate and remove high-field regions that can cause device breakdown. They have fabricated 14 single layer prototypes

  8. Magnetic properties and magnetocaloric effect at room temperature of Ni50- x Ag x Mn37Sn13 alloys

    Science.gov (United States)

    Thanh, Tran Dang; Mai, Nguyen Thi; Dan, Nguyen Huy; Phan, The-Long; Yu, Seong-Cho

    2014-11-01

    In this work, we present a detailed study of the magnetic properties and the magnetocaloric effect at room temperature of Ni50- x Ag x Mn37Sn13 alloys with x = 1, 2, and 4, which were prepared by using an arc-melting method. Experimental results reveal that a partial replacement of Ag for Ni leads to a decrease in the anti-FM phase in the alloys. In addition, the martensitic-austenitic phase transition shifts towards lower temperature and is broaded. The Curie temperature ( T C A ) for the austenitic phase also shifts toward to lower temperature, but not by much. The Curie temperature was found to be 308, 305, and 298 K for x = 1, 2, and 4, respectively. The magnetic entropy change (Δ S m ) of the samples was calculated by using isothermal magnetization data. Under an applied magnetic field change of 10 kOe, the maximum value of Δ S m (|Δ S max |) was achieved at around room temperature and did not change much (~0.8 J·kg-1·K-1) with increasing Ag-doping concentration. Particularly, the M 2 vs. H/ M curves prove that all the samples exhibited a second-order magnetic phase transition. Based on Landau's phase-transition theory and careful analyses of the magnetic data around the T C A , we have determined the critical parameters β, γ, δ, and T C . The results show that the β values are located between those expected for the 3D-Heisenberg model ( β = 0.365) and mean-field theory ( β = 0.5). Such a result proves the coexistence of short-range and long-range ferromagnetic interactions in Ni50- x Ag x Mn37Sn13 alloys. The nature of the changes in the critical parameters and the |Δ S max | is thoroughly discussed by means of structural analyses.

  9. Evaluation of the occupational X-rays dose of the medical staff in a cardiac catheterization laboratory using an acrylic phantom and semiconductor dosimeter.

    Science.gov (United States)

    Pan, Lung Fa; Kittipayak, Samrit; Yen, Shan Lin; Pan, Lung Kwang; Lin, Cheng Hsun

    2016-01-01

    The occupational X-rays doses of medical staff in a cardiac catheterization laboratory were evaluated. Four customized acrylic phantoms were used to simulate a patient, medical doctor, assistant, and radiologist to evaluate the in-situ X-rays exposure dose using semiconductor dosimeters. The exposure dose was measured under three scenarios that were preset to imply: no shielding, moderate shielding and complete shielding for the medical staff in the laboratory. The doses were applied by changing the dose area product (DAP) from 11,000 to 500,000mGy·cm(2) in 14 increments. The estimated annual occupational doses for doctors, assistants and radiologists in scenarios I, II, and III were: I) 35.03, 7.78, 1.95; II) 1.95, 0.78, 0.06; and III) 0.19, 0.10, 0.05cSv, respectively. The derived linear regression line of the exposure dose with respect to the DAP were extrapolated to obtain the minimum detectable level (MDL) of DAP for triggering the staff dosimeters. Accordingly, the minimum annual dose was estimated as 0.05cSv. Additional shielding provided measurable protection to the staff. The protective clothing used in scenarios II and III can reduce the original dose from scenario I to ∼3% (scenario II) and ∼0.5% (scenario III). The annual occupational dose also changed with the various X-rays energy settings. The annual dose increased to 126% when the preset X-rays energy was changed from 70 to 100kVp. The semiconductor dosimeter proved to be an adequate tool for measuring low doses and low dose rates under these circumstances. The dose can be reduce of I) 35.03, 7.78, 1.95; to II) 1.95, 0.78, 0.06 (∼3%); or III) 0.19, 0.10, 0.05 (∼0.5%)cSv, respectively according to different protective scenarios.

  10. Macroporous Semiconductors

    Directory of Open Access Journals (Sweden)

    Helmut Föll

    2010-05-01

    Full Text Available Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed.

  11. Label-free detection of rheumatoid factor using YbY{sub x}O{sub y} electrolyte–insulator–semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Tung-Ming, E-mail: tmpan@mail.cgu.edu.tw [Department of Electronics Engineering, Chang Gung University, Taoyuan 33302, Taiwan (China); Lin, Ting-Wei [School of Medicine, Chang Gung University, Taoyuan 33302, Taiwan (China); Chen, Ching-Yi [Department of Electronics Engineering, Chang Gung University, Taoyuan 33302, Taiwan (China)

    2015-09-03

    In this study, we investigated the effect of yttrium content on the structural properties and sensing characteristics of YbY{sub x}O{sub y} sensing membranes for electrolyte–insulator–semiconductor (EIS) sensors to detect the rheumatoid factor (RF). The YbY{sub x}O{sub y} EIS device prepared at the 60 W plasma condition exhibited a higher sensitivity of 65.77 mV/pH, a lower hysteresis voltage of ∼1 mV, and a smaller drift rate of 0.14 mV/h than did those prepared at the other conditions. We attribute this behavior to the optimal yttrium content in the YbY{sub x}O{sub y} film forming a smooth surface. Furthermore, we used a novel YbTi{sub x}O{sub y} EIS biosensor to measure the RF antigen in human serum because of its rapid and label-free detection. Two different techniques were used for the immobilization of RF antibody onto the surface of an YbTi{sub x}O{sub y} EIS sensor. The RF antibody was directly immobilized on the EIS surface modified with 3-aminopropyltriethoxysilane (APTES) followed by glutaraldehyde (GA). In contrast, a mixture of 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) solution was used to functionalize the carboxyl groups at the tail of RF antibodies. RF antibodies functionalized with the active NHS esters were covalently immobilized on the APTES-modified YbTi{sub x}O{sub y} surface. The immobilized RF antibodies on the EIS that are functionalized with the EDC and NHS exhibit higher (41.11 mV/pC{sub RF}) for detection of serum RF antigen in the range 10{sup −7} to 10{sup −3} M, compared to traditional antibody immobilization technique via APTES and GA linkage. The YbTi{sub x}O{sub y} EIS biosensor is a promising analytical tool for RF antigen monitoring due to its good sensitivity, stability and repeatability. - Highlights: • Effect of yttrium content on the structural and sensing properties of YbY{sub x}O{sub y} sensing membrane was explored. • YbY{sub x}O{sub y} EIS device prepared at the

  12. Semiconductor heterojunctions

    CERN Document Server

    Sharma, B L

    1974-01-01

    Semiconductor Heterojunctions investigates various aspects of semiconductor heterojunctions. Topics covered include the theory of heterojunctions and their energy band profiles, electrical and optoelectronic properties, and methods of preparation. A number of heterojunction devices are also considered, from photovoltaic converters to photodiodes, transistors, and injection lasers.Comprised of eight chapters, this volume begins with an overview of the theory of heterojunctions and a discussion on abrupt isotype and anisotype heterojunctions, along with graded heterojunctions. The reader is then

  13. Introductory semiconductor device physics

    CERN Document Server

    Parker, Greg

    2004-01-01

    ATOMS AND BONDINGThe Periodic TableIonic BondingCovalent BondingMetallic bondingvan der Waals BondingStart a DatabaseENERGY BANDS AND EFFECTIVE MASSSemiconductors, Insulators and MetalsSemiconductorsInsulatorsMetalsThe Concept of Effective MassCARRIER CONCENTRATIONS IN SEMICONDUCTORSDonors and AcceptorsFermi-LevelCarrier Concentration EquationsDonors and Acceptors Both PresentCONDUCTION IN SEMICONDUCTORSCarrier DriftCarrier MobilitySaturated Drift VelocityMobility Variation with TemperatureA Derivation of Ohm's LawDrift Current EquationsSemiconductor Band Diagrams with an Electric Field Presen

  14. Temperature dependence of ferromagnetic resonance spectra of permalloy on (Bi1‑ x Sb x )2Te3

    Science.gov (United States)

    Gupta, Sachin; Kanai, Shun; Matsukura, Fumihiro; Ohno, Hideo

    2018-02-01

    We investigate the temperature dependence of ferromagnetic resonance spectra of permalloy (Py: Ni0.80Fe0.20) on (Bi1‑ x Sb x )2Te3 with x = 0–1. Smaller resonance fields and broader linewidths are observed for Py/(Bi,Sb)2Te3 than those for Py/substrate below ∼40 K. The result indicates the presence of the coupling as well as spin pumping at the interface between Py and (Bi,Sb)2Te3.

  15. New Icosahedral Boron Carbide Semiconductors

    Science.gov (United States)

    Echeverria Mora, Elena Maria

    Novel semiconductor boron carbide films and boron carbide films doped with aromatic compounds have been investigated and characterized. Most of these semiconductors were formed by plasma enhanced chemical vapor deposition. The aromatic compound additives used, in this thesis, were pyridine (Py), aniline, and diaminobenzene (DAB). As one of the key parameters for semiconducting device functionality is the metal contact and, therefore, the chemical interactions or band bending that may occur at the metal/semiconductor interface, X-ray photoemission spectroscopy has been used to investigate the interaction of gold (Au) with these novel boron carbide-based semiconductors. Both n- and p-type films have been tested and pure boron carbide devices are compared to those containing aromatic compounds. The results show that boron carbide seems to behave differently from other semiconductors, opening a way for new analysis and approaches in device's functionality. By studying the electrical and optical properties of these films, it has been found that samples containing the aromatic compound exhibit an improvement in the electron-hole separation and charge extraction, as well as a decrease in the band gap. The hole carrier lifetimes for each sample were extracted from the capacitance-voltage, C(V), and current-voltage, I(V), curves. Additionally, devices, with boron carbide with the addition of pyridine, exhibited better collection of neutron capture generated pulses at ZERO applied bias, compared to the pure boron carbide samples. This is consistent with the longer carrier lifetimes estimated for these films. The I-V curves, as a function of external magnetic field, of the pure boron carbide films and films containing DAB demonstrate that significant room temperature negative magneto-resistance (> 100% for pure samples, and > 50% for samples containing DAB) is possible in the resulting dielectric thin films. Inclusion of DAB is not essential for significant negative magneto

  16. High vacuum high temperature x-ray camera (1961)

    International Nuclear Information System (INIS)

    Baron, J.L.

    1961-01-01

    - This camera makes it possible to carry out X-ray studies on highly oxidisable materials, up to about 900 deg. C. Most of the existing models do not provide sufficient protection against the formation of surface oxide or carbide films on the sample. The present arrangement makes it possible to operate at very low pressures: 5 x 10 -8 to 10 -7 torr, thanks to an entirely metallic apparatus. The radiation heating system consists of an incandescent lamp, outside the evacuated portion, and a reflector which concentrates the energetic flux into the sample through a silica window. The heated parts have thus only a small thermal inertia. With the apparatus it has been possible to determine the phase parameters of uranium-α up to 650 deg. C with a precision of ± 0.0015 A. A similar study has been carried out on a uranium-chromium alloy in the β-phase up to 740 deg. C. (author) [fr

  17. Temperature dependence of electromechanical properties of PLZT x ...

    Indian Academy of Sciences (India)

    Administrator

    behaviour is observed for the overtones also. However, the piezoelectric response of the overtones disappears at a lower temperature than the fundamental mode. The quantity, Δfps, depends on the electromechanical coupling coefficient as well as geometry of the piezo- ceramic material (Jaffe et al 1971). The behaviour of ...

  18. Low resistivity WxV1-xO2-based multilayer structure with high temperature coefficient of resistance for microbolometer applications

    Science.gov (United States)

    Émond, Nicolas; Hendaoui, Ali; Chaker, Mohamed

    2015-10-01

    Materials that exhibit semiconductor-to-metal phase transition (SMT) are commonly used as sensing layers for the fabrication of uncooled microbolometers. The development of highly responsive microbolometers would benefit from using a sensing material that possesses a large thermal coefficient of resistance (TCR) close to room temperature and a resistivity low enough to compromise between noise reduction and high TCR, while it should also satisfies the requirements of current CMOS technology. Moreover, a TCR that remains constant when the IR camera surrounding temperature varies would contribute to achieve reliable temperature measurements without additional corrections steps for TCR temperature dependence. In this paper, the characteristics of the SMT occurring in undoped and tungsten-doped vanadium dioxide thin films deposited on LaAlO3 (100) substrates are investigated. They are further exploited to fabricate a WxV1-xO2 (0 ≤ x ≤ 2.5) multilayer structure exhibiting a bottom-up gradient of tungsten content. This MLS displays a combination of properties that is promising for application to uncooled microbolometer, such as a large TCR of -10.4%/ °C and low resistivity values ranging from 0.012 to 0.10 Ω-cm over the temperature range 22 °C-42 °C.

  19. Enhancement of Photon Absorption on BaxSr1-xTiO3 Thin-Film Semiconductor Using Photonic Crystal

    Directory of Open Access Journals (Sweden)

    Abd. Wahidin Nuayi

    2014-01-01

    Full Text Available Enhancement of photon absorption on barium strontium titanate (BaxSr1-xTiO3 thin-film semiconductor for mole fraction x=0.25, 0.35, 0.45, and 0.55 using one-dimensional photonic crystal with defect was investigated experimentally. The thin film was grown on transparent conductive oxide (TCO substrate using chemical solution deposition method and annealed at 500°C for 15 hours with increasing rate of 1.6°C/min. From optical characterization in visible spectrum it was found that the average absorption percentages are 92.04%, 83.55%, 91.16%, and 80.12%, respectively. The BST thin film with embedded photonic crystal exhibited a relatively significant enhancement on photon absorption, with increasing value of 3.96%, 7.07%, 3.04%, and 13.33% for the respective mole fraction and demonstrating absorbance characteristic with flat feature. In addition, we also discuss the thin-film properties of attenuation constant and electrical conductivity.

  20. Temperature dependence of the electrical resistivity of R6(Fesub(1-x)Mnsub(x))23 compounds in the temperature range 4.2 to 300 K

    International Nuclear Information System (INIS)

    Gratz, E.; Kirchmayr, H.R.

    1976-01-01

    The temperature dependence of the electrical resistivity rho of binary R 6 Mn 23 , R 6 Fe 23 (R=Y,Dy,Ho,Er,Tm) and pseudobinary R 6 (Fesub(1-x)Mnsub(x)) 23 (R=Y,Er,Ho) compounds has been determined by a four-probe measuring technique in the temperature range 4 to 300 K. The binary compounds exhibit a rho prop. T 2 dependence at low temperatures, while above 100 K a negative curvature of the rho-T-curves is observed. These experimental results are discussed on the basis of electron-spin wave scattering in the low temperature range and on the basis of s-d scattering in the high temperature range, taking explicitly into account the temperature dependence of the chemical potentials. The pseudobinary compounds generally exhibit a decreasing resistivity with increasing temperature, combined with a high residual resistivity. These facts are explained by the so-called strong scattering mechanism and the appearance of 'quasilocalized' states. (Auth.)

  1. In situ X-ray ptychography imaging of high-temperature CO2 acceptor particle agglomerates

    DEFF Research Database (Denmark)

    Høydalsvik, Kristin; Fløystad, Jostein Bø; Zhao, Tiejun

    2014-01-01

    Imaging nanoparticles under relevant reaction conditions of high temperature and gas pressure is difficult because conventional imaging techniques, like transmission electron microscopy, cannot be used. Here we demonstrate that the coherent diffractive imaging technique of X-ray ptychography can ...

  2. Band gap calculations of the semiconductor BNxP1−x using modified Becke–Johnson approximation

    International Nuclear Information System (INIS)

    Benkraouda, M.; Amrane, N.

    2013-01-01

    Highlights: ► The Modified Becke–Johnson scheme gives a very accurate band gap. ► We have shown the invalidity of Vegard’s linear rule for BN x P 1−x . ► The band gap changes with alloy concentration are important in band gap engineering. - Abstract: In this work, the electronic properties of BN, BP and BN x P 1−x compounds have been investigated by means of first-principles density-functional total-energy calculation using the all-electron full potential linear augmented plane-wave method (FP-LAPW). The (FP-LAPW) method was used within the density functional theory (DFT) along with the Engel–Vosko and Becke–Johnson exchange correlation potential. The energy bands along high symmetry directions, the density of states and bowing distributions are calculated. The results have been discussed in terms of previously existing experimental and theoretical data, and comparisons with similar compounds have been made. Analysis of band structure suggests direct and pseudo-direct band gaps for both compounds.

  3. Semiconductor composition containing iron, dysprosium, and terbium

    Science.gov (United States)

    Pooser, Raphael C.; Lawrie, Benjamin J.; Baddorf, Arthur P.; Malasi, Abhinav; Taz, Humaira; Farah, Annettee E.; Kalyanaraman, Ramakrishnan; Duscher, Gerd Josef Mansfred; Patel, Maulik K.

    2017-09-26

    An amorphous semiconductor composition includes 1 to 70 atomic percent iron, 15 to 65 atomic percent dysprosium, 15 to 35 atomic percent terbium, balance X, wherein X is at least one of an oxidizing element and a reducing element. The composition has an essentially amorphous microstructure, an optical transmittance of at least 50% in at least the visible spectrum and semiconductor electrical properties.

  4. Microstructure and mechanical properties of Al-xMg alloys processed by room temperature ECAP

    OpenAIRE

    Chen, Yongjun; Chai, YC; Roven, Hans Jørgen; Subbarayan, Sapthagireesh; Yu, Yingda; Hjelen, Jarle

    2012-01-01

    Microstructure development and mechanical properties of Al–xMg alloys (x = 0, 1, 5–10 wt%), processed by ECAP at room temperature, have been investigated. The results show that the microstructures of Al–xMg alloys are refined by the interaction of shear bands and their increase in number during ECAP. The addition of magnesium to aluminum promotes the grain refinement. Misorientation increase induced by particles along grain boundaries is observed by using high resolution EBSD. As ECAP strain ...

  5. Faraday effect in semimagnetic semiconductors

    International Nuclear Information System (INIS)

    Nikitin, P.I.; Savchuk, A.I.

    1990-01-01

    Experimental and theoretical studies of the Faraday effect in a new class of materials -semimagnetic semiconductors (SS) have been received. Mechanisms of the giant Faraday effect in SS based on s, p-d exchange interaction of excitons, electrons and holes with magnetic ions have been discussed. Faraday rotation as a function of a radiation wavelength, magnetic component concentration, temperature, magnetic field intensity for crystals A 2 B 6 (Mn)A 2 x -1Mn xB 6 : and other SS (GaAs(Mn), CdP 2 (Mn),Pb 1-X2 )Mn x J 2 have been considered. We have attended to use FR for the study of a paramagnetic-spin glass transmission for determining the role of the relaxation effects with a participation of magnetic Mn 2+ ions, exitons, polarons in the direct and inverse Faraday effects. In addition the features of FR in thin films of SS and in spin superlattices have been discussed. Finally, we have analysed possibilities of applying the SS Faraday effect for developing magnetooptic devices (optical isolators and fibre optic sensors of magnetic fields)

  6. Survey of cryogenic semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Low Temperature Synthesis, Chemical and Electrochemical Characterization of LiNi(x)Co(1-x)O2 (0 less than x less than 1)

    Science.gov (United States)

    Nanjundaswamy, K. S.; Standlee, D.; Kelly, C. O.; Whiteley, R. V., Jr.

    1997-01-01

    A new method of synthesis for the solid solution cathode materials LiNi(x)Co(1-x)O2 (0 less than x less than 1) involving enhanced reactions at temperatures less than or equal to 700 deg. C, between metal oxy-hydroxide precursors MOOH (M = Ni, Co) and Li-salts (Li2CO3, LiOH, and LiNO3) has been investigated. The effects of synthesis conditions and sources of Li, on phase purity, microstructure, and theoretical electrochemical capacity (total M(3+) content) are characterized by powder X-ray diffraction analysis, scanning electron microscopy, chemical analysis and room temperature magnetic susceptibility. An attempt has been made to correlate the electrochemical properties with the synthesis conditions and microstructure.

  8. Energy gaps, effective masses and ionicity of AlxGa1-xSb ternary semiconductor alloys

    Science.gov (United States)

    Bouarissa, N.; Boucenna, M.; Saib, S.; Siddiqui, S. A.

    2017-12-01

    A pseudopotential calculation of the electronic structure of AlxGa1-xSb ternary alloys in the zinc-blende structure has been performed. The compositional dependence of energy gaps, electron and heavy hole effective masses and ionicity of the material system of interest have been examined and discussed. Special attention has been given to the effect of the alloy disorder on the direct (Γ-Γ) bandgap energy. It is found that all features of interest vary monotonically with increasing the Al concentration x. Besides, bandgap bowing parameters and extent of the direct-to-indirect bandgap transition have been determined. Our findings agree generally well with the data reported in the literature. Trends in ionicity are found to be consistent with the Phillips ionicity scale.

  9. Semiconductor electrochemistry

    CERN Document Server

    Memming, Rüdiger

    2015-01-01

    Providing both an introduction and an up-to-date survey of the entire field, this text captivates the reader with its clear style and inspiring, yet solid presentation. The significantly expanded second edition of this milestone work is supplemented by a completely new chapter on the hot topic of nanoparticles and includes the latest insights into the deposition of dye layers on semiconductor electrodes. In his monograph, the acknowledged expert Professor Memming primarily addresses physical and electrochemists, but materials scientists, physicists, and engineers dealing with semiconductor technology and its applications will also benefit greatly from the contents.

  10. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1962-01-01

    Semiconductor Statistics presents statistics aimed at complementing existing books on the relationships between carrier densities and transport effects. The book is divided into two parts. Part I provides introductory material on the electron theory of solids, and then discusses carrier statistics for semiconductors in thermal equilibrium. Of course a solid cannot be in true thermodynamic equilibrium if any electrical current is passed; but when currents are reasonably small the distribution function is but little perturbed, and the carrier distribution for such a """"quasi-equilibrium"""" co

  11. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati

    2013-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scient

  12. X-Aerogels for Structural Components and High Temperature Applications

    Science.gov (United States)

    2005-01-01

    Future NASA missions and space explorations rely on the use of materials that are strong ultra lightweight and able to withstand extreme temperatures. Aerogels are low density (0.01-0.5 g/cu cm) high porosity materials that contain a glass like structure formed through standard sol-gel chemistry. As a result of these structural properties, aerogels are excellent thermal insulators and are able to withstand temperatures in excess of l,000 C. The open structure of aerogels, however, renders these materials extremely fragile (fracturing at stress forces less than 0.5 N/sq cm). The goal of NASA Glenn Research Center is to increase the strength of these materials by templating polymers and metals onto the surface of an aerogel network facilitating the use of this material for practical applications such as structural components of space vehicles used in exploration. The work this past year focused on two areas; (1) the research and development of new templated aerogels materials and (2) process development for future manufacturing of structural components. Research and development occurred on the production and characterization of new templating materials onto the standard silica aerogel. Materials examined included polymers such as polyimides, fluorinated isocyanates and epoxies, and, metals such as silver, gold and platinum. The final properties indicated that the density of the material formed using an isocyanate is around 0.50 g/cc with a strength greater than that of steel and has low thermal conductivity. The process used to construct these materials is extremely time consuming and labor intensive. One aspect of the project involved investigating the feasibility of shortening the process time by preparing the aerogels in the templating solvent. Traditionally the polymerization used THF as the solvent and after several washes to remove any residual monomers and water, the solvent around the aerogels was changed to acetonitrile for the templating step. This process

  13. Ferromagnetic semiconductor-metal transition in europium monoxide

    International Nuclear Information System (INIS)

    Arnold, M.

    2007-10-01

    We present a microscopical model to describe the simultaneous para-to-ferromagnetic and semiconductor-to-metal transition in electron-doped EuO. The physical properties of the model are systematically studied, whereas the main remark is on the interplay between magnetic order and the transport properties. The theory correctly describes detailed experimental features of the conductivity and of the magnetization, obtained for EuO 1-x or Gd-doped Gd x Eu 1-x 0. In particular the doping dependence of the Curie temperature is reproduced The existence of correlation-induced local moments on the impurity sites is essential for this description. (orig.)

  14. Images through semiconductors

    International Nuclear Information System (INIS)

    Anon.

    1986-01-01

    Improved image processing techniques are constantly being developed for television and for scanners using X-rays or other radiation for industrial or medical applications, etc. As Erik Heijne of CERN explains here, particle physics too has its own special requirements for image processing. The increasing use of semiconductor techniques for handling measurements down to the level of a few microns provides another example of the close interplay between scientific research and technological development. (orig.).

  15. Energy gaps, electronic structures, and x-ray spectroscopies of finite semiconductor single-walled carbon nanotubes.

    Science.gov (United States)

    Gao, Bin; Jiang, Jun; Wu, ZiYu; Luo, Yi

    2008-02-28

    We report hybrid density functional theory calculations for electronic structures of hydrogen-terminated finite single-walled carbon nanotubes (6,5) and (8,3) up to 100 nm in length. Gap states that are mainly arisen from the hydrogen-terminated edges have been found in (8,3) tubes, but their contributions to the density of states become invisible when the tube is longer than 10 nm. The electronic structures of (6,5) and (8,3) tubes are found to be converged around 20 nm. The calculated band-gap energies of 100 nm long nanotubes are in good agreement with experimental results. The valence band structures of (6,5), (8,3), as well as (5,5) tubes are also investigated by means of ultraviolet photoelectron spectra (UPS), x-ray emission spectroscopy (XES), and the resonant inelastic x-ray scattering (RIXS) spectra theoretically. The UPS, XES and RIXS spectra become converged already at 10 nm. The length-dependent oscillation behavior is found in the RIXS spectra of (5,5) tubes, indicating that the RIXS spectra may be used to determine the size and length of metallic nanotubes. Furthermore, the chiral dependence observed in the simulated RIXS spectra suggests that RIXS spectra could be a useful technique for the determination of chirality of carbon nanotubes.

  16. Low Temperature Reactivities of Ultra-High Temperature Ceramics (Hf-X System)

    National Research Council Canada - National Science Library

    Blum, Yigal

    2006-01-01

    ..., because of their high thermal and oxidation resistance stability. Unfortunately, these composites are currently formed by an expensive, size and shape limited hot-press operation at a temperature range of 1900 to 2200 degrees C...

  17. Analysis of AlN/AlGaN/GaN metal-insulator-semiconductor structure by using capacitance-frequency-temperature mapping

    International Nuclear Information System (INIS)

    Shih, Hong-An; Kudo, Masahiro; Suzuki, Toshi-kazu

    2012-01-01

    AlN/AlGaN/GaN metal-insulator-semiconductor (MIS) structure is analyzed by using capacitance-frequency-temperature (C-f-T) mapping. Applying sputtering-deposited AlN, we attained AlN/AlGaN/GaN MIS heterostructure field-effect transistors with much suppressed gate leakage currents, but exhibiting frequency dispersion in C-V characteristics owing to high-density AlN/AlGaN interface states. In order to investigate the interface states deteriorating the device performance, we measured temperature-dependent frequency dispersion in the C-V characteristics. As a result, we obtained C-f-T mapping, whose analysis gives the activation energies of electron trapping, namely the interface state energy levels, for a wide range of the gate biases. This analysis method is auxiliary to the conventional conductance method, serving as a valuable tool for characterization of wide-bandgap devices with deep interface states. From the analysis, we can directly evaluate the gate-control efficiency of the devices.

  18. Ab initio Assessment of Bi1-xRExCuOS (RE=La, Gd, Y, Lu) Solid Solution as Semiconductor for Photochemical Water Splitting

    KAUST Repository

    Lardhi, Sheikha F.

    2017-04-12

    The investigation of BiCuOCh (Ch = S, Se and Te) semiconductors family for thermoelectric or photovoltaic materials is an increasing topic of research. These materials can also be considered for photochemical water splitting if one representative having a bandgap, Eg, around 2 eV can be developed. With this aim, we simulated the solid solution Bi1-xRExCuOS (RE = Y, La, Gd and Lu) from pure BiCuOS (Eg~1.1 eV) to pure RECuOS compositions (Eg~2.9 eV) by DFT calculations based on the HSE06 range-separated hybrid functional with inclusion of spin-orbit coupling. Starting from the thermodynamic stability of the solid solution, a large variety of properties were computed for each system including bandgap, dielectric constants, effective masses and exciton binding energies. We discussed the variation of these properties based on the relative organization of Bi and RE atoms in their common sublattice to offer a physical understanding of the influence of the RE doping of BiCuOS. Some compositions were found to give appropriate properties for water splitting application. Furthermore, we found that at low RE fractions the transport properties of BiCuOS are improved that can find applications beyond water splitting.

  19. Elastic Properties and the Band Gap of AlNxP1-x Semiconductor Alloy: A Comparative Study of Various Ab Initio Approaches

    Directory of Open Access Journals (Sweden)

    M. P. Polak

    2016-01-01

    Full Text Available Structural and elastic properties of AlNxP1-x, a novel semiconductor alloy, are studied from the first principles in both zinc-blende and wurtzite structures. Performances of the finite difference (FD method and the density functional perturbation theory (DFPT are tested and compared. Both of these methods are applied to two different approaches of alloy simulation, a supercell of 16 and 32 atoms (for zinc-blende and wurtzite structures, resp. and the alchemical mixing (AM method, where the pseudopotentials are mixed in an appropriate way to form an alloy. All elastic properties, including the elastic tensors, elastic moduli, Poisson’s ratio, B/G, and relaxation coefficient, as well as lattice parameters are calculated using all said methods. Conclusions about the use of the approaches investigated in this paper and about their performance are drawn. In addition, in both crystal structures, the band gap is studied in the whole composition range using the MBJLDA functional. The band gap bowings are unusually high, which confirms earlier reports.

  20. Room temperature magneto-electric coupling in La-Zn doped Ba1- x La x Fe12- x Zn x O19 ( x = 0.0-0.4) hexaferrite

    Science.gov (United States)

    Kumar, Pawan; Gaur, Anurag

    2017-12-01

    Barium hexaferrite powder samples with substitution of La+3 at Ba+2 and Zn+2 at Fe+3 site, according to the series formula Ba1- x La x Fe12- x Zn x O19 ( x = 0.0, 0.1, 0.2, 0.3, 0.4) have been prepared by the co-precipitation method. These samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy, Polarization versus electric field loop tracer and vibrating sample magnetometer techniques. XRD patterns and Rietveld refinement indicate the single-phase formation of the magneto-plumbite barium hexaferrite for all the samples. Significant changes in dielectric properties are obtained by the different doping concentration of La and Zn. Ferroelectric loop for all the samples shows the lossy ferroelectric behaviour. Large spontaneous polarization is observed for x = 0.2 sample at room temperature. With increasing La and Zn doping content, the value of saturation magnetization and retentivity increases, and reaches a maximum value of 40.0 emu/gm and 24.0 emu/gm, respectively, for x = 0.2 sample and then decreases. To confirm the magneto-electric coupling, the second-order magneto-electric coupling coefficient β is measured through the dynamic method with the maximum value of 1.69 × 10- 6 mV/cm.Oe2 for x = 0.2 sample at room temperature. The observations of room temperature magneto-electric coupling in these samples are useful for evolution of new multifunctional devices.

  1. Valence Band Structure of InAs1-xBix and InSb1-xBix Alloy Semiconductors Calculated Using Valence Band Anticrossing Model

    Directory of Open Access Journals (Sweden)

    D. P. Samajdar

    2014-01-01

    Full Text Available The valence band anticrossing model has been used to calculate the heavy/light hole and spin-orbit split-off energies in InAs1-xBix and InSb1-xBix alloy systems. It is found that both the heavy/light hole, and spin-orbit split E+ levels move upwards in energy with an increase in Bi content in the alloy, whereas the split E− energy for the holes shows a reverse trend. The model is also used to calculate the reduction of band gap energy with an increase in Bi mole fraction. The calculated values of band gap variation agree well with the available experimental data.

  2. Temperature-dependent elastic properties of Ti1−xAlxN alloys

    International Nuclear Information System (INIS)

    Shulumba, Nina; Hellman, Olle; Rogström, Lina; Raza, Zamaan; Tasnádi, Ferenc; Odén, Magnus; Abrikosov, Igor A.

    2015-01-01

    Ti 1−x Al x N is a technologically important alloy that undergoes a process of high temperature age-hardening that is strongly influenced by its elastic properties. We have performed first principles calculations of the elastic constants and anisotropy using the symmetry imposed force constant temperature dependent effective potential method, which include lattice vibrations and therefore the effects of temperature, including thermal expansion and intrinsic anharmonicity. These are compared with in situ high temperature x-ray diffraction measurements of the lattice parameter. We show that anharmonic effects are crucial to the recovery of finite temperature elasticity. The effects of thermal expansion and intrinsic anharmonicity on the elastic constants are of the same order, and cannot be considered separately. Furthermore, the effect of thermal expansion on elastic constants is such that the volume change induced by zero point motion has a significant effect. For TiAlN, the elastic constants soften non-uniformly with temperature: C 11 decreases substantially when the temperature increases for all compositions, resulting in an increased anisotropy. These findings suggest that an increased Al content and annealing at higher temperatures will result in a harder alloy

  3. Fractal properties of nanostructured semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhanabaev, Z.Zh. [Al-Farabi Khazakh National University, Tole bi Street, 96, Almaty 050012 (Kazakhstan); Grevtseva, T.Yu. [Al-Farabi Khazakh National University, Tole bi Street, 96, Almaty 050012 (Kazakhstan)]. E-mail: kenwp@mail.ru

    2007-03-15

    A theory for the temperature and time dependence of current carrier concentration in semiconductors with different non-equilibrium nanocluster structure has been developed. It was shown that the scale-invariant fractal self-similar and self-affine laws can exist near by the transition point to the equilibrium state. Results of the theory have been compared to the experimental data from electrical properties of semiconductor films with nanoclusters.

  4. Muonium states in semiconductors

    International Nuclear Information System (INIS)

    Patterson, B.D.

    1987-01-01

    There is a brief summary of what is known about the muonium states isotropic, anisotropic and diamagnetic in diamond and zincblende semiconductors. The report deals with muonium spectroscopy, including the formation probabilities, hyperfine parameters and electronic g-factors of the states. The dynamics of the states is treated including a discussion of the transition from isotropic Mu to anisotropic Mu in diamond, temperature-dependent linewidthes in silicon and germanium and effects of daping and radiation damage

  5. Semiconductor Detectors; Detectores de Semiconductores

    Energy Technology Data Exchange (ETDEWEB)

    Cortina, E.

    2007-07-01

    Particle detectors based on semiconductor materials are among the few devices used for particle detection that are available to the public at large. In fact we are surrounded by them in our daily lives: they are used in photoelectric cells for opening doors, in digital photographic and video camera, and in bar code readers at supermarket cash registers. (Author)

  6. Electron temperature from x-ray continuum measurements on the NIF

    Science.gov (United States)

    Jarrott, Leonard; Bachmann, Benjamin; Benedetti, Robin; Izumi, Nobuhiko; Khan, Shahab; Landen, Otto; Ma, Tammy; Nagel, Sabrina; Pak, Arthur; Patel, Prav; Schneider, Marilyn; Springer, Paul; LLNL Collaboration

    2017-10-01

    We report on measurements of the electron temperature within the hot spot of inertially confined, layered implosions on the NIF using a titanium differential filtering x-ray diagnostic. The electron temperature from x-ray emission is insensitive to non-thermal velocity flows as is the case with ion temperature measurements and is thus a critical parameter in interpreting stagnated hot spot conditions. Here we discuss measurements using titanium filters ranging from 10 μm to 1mm in thickness with a sensitivity band of 10-30keV coupled with penumbral pinholes. The use of larger pinhole diameters increases x-ray fluence improving sensitivity of photon energies with minimal attenuation from the compressed fuel/shell. This diagnostic has been fielded on a series of cryogenic shots with DT ion temperatures ranging from 2-5keV. Analysis of the measurement will be presented along with a comparison against simulated electron temperatures and x-ray spectra as well as a comparison to DT ion temperature measurements. This work was performed under the auspices of U.S. DoE by LLNL under Contract No. DE-AC52-07NA27344.

  7. Effect of P-anion codoping on the Curie temperature of GaMnAs diluted magnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    Bouzerar, R.; Máca, František; Kudrnovský, Josef; Bergqvist, L.

    2010-01-01

    Roč. 82, č. 3 (2010), 035207/1-035207/6 ISSN 1098-0121 R&D Projects: GA ČR GA202/09/0775; GA ČR(CZ) GC202/07/J047 Institutional research plan: CEZ:AV0Z10100520 Keywords : GaMnAs * calculations * Curie temperature * defects Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010

  8. Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1 -xMnxAs and Ga1 -xMnxP by means of fluctuation spectroscopy

    Science.gov (United States)

    Lonsky, Martin; Teschabai-Oglu, Jan; Pierz, Klaus; Sievers, Sibylle; Schumacher, Hans Werner; Yuan, Ye; Böttger, Roman; Zhou, Shengqiang; Müller, Jens

    2018-02-01

    We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga1 -xMnxAs epitaxial thin films covering a large parameter space in terms of the Mn content x and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with x >2 % do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature TC, we find indications for an electronic phase separation in films with x power spectral density. These results are compared with noise measurements on an insulating Ga1 -xMnxP reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation-induced disorder on the electronic properties of Ga1 -xMnxAs films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials.

  9. Visible photoassisted room-temperature oxidizing gas-sensing behavior of Sn2S3 semiconductor sheets through facile thermal annealing

    Science.gov (United States)

    Liang, Yuan-Chang; Lung, Tsai-Wen; Wang, Chein-Chung

    2016-11-01

    Well-crystallized Sn2S3 semiconductor thin films with a highly (111)-crystallographic orientation were grown using RF sputtering. The surface morphology of the Sn2S3 thin films exhibited a sheet-like feature. The Sn2S3 crystallites with a sheet-like surface had a sharp periphery with a thickness in a nanoscale size, and the crystallite size ranged from approximately 150 to 300 nm. Postannealing the as-synthesized Sn2S3 thin films further in ambient air at 400 °C engendered roughened and oxidized surfaces on the Sn2S3 thin films. Transmission electron microscopy analysis revealed that the surfaces of the Sn2S3 thin films transformed into a SnO2 phase, and well-layered Sn2S3-SnO2 heterostructure thin films were thus formed. The Sn2S3-SnO2 heterostructure thin film exhibited a visible photoassisted room-temperature gas-sensing behavior toward low concentrations of NO2 gases (0.2-2.5 ppm). By contrast, the pure Sn2S3 thin film exhibited an unapparent room-temperature NO2 gas-sensing behavior under illumination. The suitable band alignment at the interface of the Sn2S3-SnO2 heterostructure thin film and rough surface features might explain the visible photoassisted room-temperature NO2 gas-sensing responses of the heterostructure thin film on exposure to NO2 gas at low concentrations in this work.

  10. Effects of Temperature and X-rays on Plastic Scintillating Fiber and Infrared Optical Fiber.

    Science.gov (United States)

    Lee, Bongsoo; Shin, Sang Hun; Jang, Kyoung Won; Yoo, Wook Jae

    2015-05-11

    In this study, we have studied the effects of temperature and X-ray energy variations on the light output signals from two different fiber-optic sensors, a fiber-optic dosimeter (FOD) based on a BCF-12 as a plastic scintillating fiber (PSF) and a fiber-optic thermometer (FOT) using a silver halide optical fiber as an infrared optical fiber (IR fiber). During X-ray beam irradiation, the scintillating light and IR signals were measured simultaneously using a dosimeter probe of the FOD and a thermometer probe of the FOT. The probes were placed in a beaker with water on the center of a hotplate, under variation of the tube potential of a digital radiography system or the temperature of the water in the beaker. From the experimental results, in the case of the PSF, the scintillator light output at the given tube potential decreased as the temperature increased in the temperature range from 25 to 60 °C. We demonstrated that commonly used BCF-12 has a significant temperature dependence of -0.263 ± 0.028%/°C in the clinical temperature range. Next, in the case of the IR fiber, the intensity of the IR signal was almost uniform at each temperature regardless of the tube potential range from 50 to 150 kVp. Therefore, we also demonstrated that the X-ray beam with an energy range used in diagnostic radiology does not affect the IR signals transmitted via a silver halide optical fiber.

  11. Semiconductor Optics

    CERN Document Server

    Klingshirn, Claus F

    2012-01-01

    This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto and electrooptics, high-excitation effects and laser processes, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. Significantly updated chapters add coverage of current topics such as electron hole plasma, Bose condensation of excitons and meta materials. Over 120 problems, chapter introductions and a detailed index make it the key textbook for graduate students in physics. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered ...

  12. Semiconductor sensors

    International Nuclear Information System (INIS)

    Hartmann, Frank

    2011-01-01

    Semiconductor sensors have been around since the 1950s and today, every high energy physics experiment has one in its repertoire. In Lepton as well as Hadron colliders, silicon vertex and tracking detectors led to the most amazing physics and will continue doing so in the future. This contribution tries to depict the history of these devices exemplarily without being able to honor all important developments and installations. The current understanding of radiation damage mechanisms and recent R and D topics demonstrating the future challenges and possible technical solutions for the SLHC detectors are presented. Consequently semiconductor sensor candidates for an LHC upgrade and a future linear collider are also briefly introduced. The work presented here is a collage of the work of many individual silicon experts spread over several collaborations across the world.

  13. Temperature dependence of the propagation vector in Ni3-xCoxV2O8 with x=0.1 and 0.5

    Science.gov (United States)

    Lee, Seongsu; Lee, Heeju; Choi, Yong Nam; Semkin, M. A.; Teplykh, A. E.; Skryabin, Yu. N.; Li, Wen-Hsien; Pirogov, A. N.

    2016-01-01

    We present the susceptibility and neutron diffraction data on multiferroic Ni3-xCoxV2O8 with x=0.1 and 0.5. The temperature dependence of the susceptibility indicates that the magnetic order-disorder transition occurs at THTI=8.5 K in both samples. Below THTI, the high-temperature incommensurate magnetic structure is realized, which undergoes a transition to the low-temperature incommensurate phase when the sample is cooled. The temperature evolution of the propagation vector k for x=0.1 is very weak, which confirms previous studies showing that substitution of 3.5% Ni ions by Co ions suppresses the explicit temperature dependence of k that is observed in the parent compound. On the other hand, we found that the vector k for x=0.5 exhibits a definite temperature dependence, which differs from the case of the undoped sample (x=0).

  14. EDITORIAL: Oxide semiconductors

    Science.gov (United States)

    Kawasaki, M.; Makino, T.

    2005-04-01

    Blue or ultraviolet semiconducting light-emitting diodes have the potential to revolutionize illumination systems in the near-future. Such industrial need has propelled the investigation of several wide-gap semiconducting materials in recent years. Commercial applications include blue lasers for DVD memory and laser printers, while military applications are also expected. Most of the material development has so far been focused on GaN (band gap 3.5 eV at 2 K), and ZnSe (2.9 eV) because these two representative direct transition semiconductors are known to be bright emitting sources. GaN and GaN-based alloys are emerging as the winners in this field because ZnSe is subject to defect formation under high current drive. On the other hand, another II-VI compound, ZnO, has also excited substantial interest in the optoelectronics-oriented research communities because it is the brightest emitter of all, owing to the fact that its excitons have a 60 meV binding energy. This is compared with 26 meV for GaN and 20 meV for ZnSe. The stable excitons could lead to laser action based on their recombination even at temperatures well above room temperature. ZnO has additional major properties that are more advantageous than other wide-gap materials: availability of large area substrates, higher energy radiation stability, environmentally-friendly ingredients, and amenability to wet chemical etching. However, ZnO is not new to the semiconductor field as exemplified by several studies made during the 1960s on structural, vibrational, optical and electrical properties (Mollwo E 1982 Landolt-Boernstein New Series vol 17 (Berlin: Springer) p 35). In terms of devices, the luminescence from light-emitting diode structures was demonstrated in which Cu2O was used as the p-type material (Drapak I T 1968 Semiconductors 2 624). The main obstacle to the development of ZnO has been the lack of reproducible p-type ZnO. The possibility of achieving epitaxial p-type layers with the aid of thermal

  15. Ultrasonic acoustic levitation for fast frame rate X-ray protein crystallography at room temperature

    OpenAIRE

    Tsujino, Soichiro; Tomizaki, Takashi

    2016-01-01

    Increasing the data acquisition rate of X-ray diffraction images for macromolecular crystals at room temperature at synchrotrons has the potential to significantly accelerate both structural analysis of biomolecules and structure-based drug developments. Using lysozyme model crystals, we demonstrated the rapid acquisition of X-ray diffraction datasets by combining a high frame rate pixel array detector with ultrasonic acoustic levitation of protein crystals in liquid droplets. The rapid spinn...

  16. A planar Al-Si Schottky barrier metal–oxide–semiconductor field effect transistor operated at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Purches, W. E. [School of Physics, UNSW, Sydney 2052 (Australia); Rossi, A.; Zhao, R. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Kafanov, S.; Duty, T. L. [School of Physics, UNSW, Sydney 2052 (Australia); Centre for Engineered Quantum Systems (EQuS), School of Physics, UNSW, Sydney 2052 (Australia); Dzurak, A. S. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia); Rogge, S.; Tettamanzi, G. C., E-mail: g.tettamanzi@unsw.edu.au [School of Physics, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia)

    2015-08-10

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  17. Electrical resistivity at high temperatures of Heusler alloys of the Cu2MnAl sub(1-x) Sn sub (x)

    International Nuclear Information System (INIS)

    Grandi, T.A.

    1978-01-01

    The structural fase L2 1 of the Heusler alloys Cu 2 MnAl sub (1-x) Sn sub(x), with x varying between 0 and 1, was studied. X-ray diffraction, metallography and diferential termoanalysis techniques were employed. For the alloys with x = 0; 0,05; 0,10 and 0,15 the electrical resistivity measurements were performed in the temperature range 300 K [pt

  18. An X- and Q-band Fe3+ EPR study of nanoparticles of magnetic semiconductor Zn1−xFexO

    International Nuclear Information System (INIS)

    Misra, Sushil K.; Andronenko, S.I.; Thurber, A.; Punnoose, A.; Nalepa, A.

    2014-01-01

    EPR studies on two types of nanoparticles of Fe 3+ doped, 0.1–10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (∼9.5 GHz) at 77 K and at Q-band (∼34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe 3+ ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles. - Highlights: • X and Q band EPR studies on NL and QJ nanoparticles of Fe 3+ doped ZnO at 10, 80, and 295 K. • Fe ions are present at different magnetically active sites in these samples. • NL samples consist of paramagnetic Fe 3+ ions, and ferromagnetically coupled Fe ions. • QJ samples exhibit only intense ferromagnetic lines, different from QJ. • Spectra vary strongly with the surface morphology of nanoparticles

  19. Thermal expansion studies on Inconel-600[reg] by high temperature X-ray diffraction

    International Nuclear Information System (INIS)

    Raju, S.; Sivasubramanian, K.; Divakar, R.; Panneerselvam, G.; Banerjee, A.; Mohandas, E.; Antony, M.P.

    2004-01-01

    The lattice thermal expansion characteristics of Inconel-600[reg] have been studied by high temperature X-ray diffraction (HT-XRD) technique in the temperature range 298-1200 K. Altogether four experimental runs were conducted on thin foils of about 75-100 μm thickness. The diffraction profiles have been accurately calibrated to offset the shift in 2θ values introduced by sample buckling at elevated temperatures. The corrected lattice parameter data have been used to estimate the instantaneous and mean linear thermal expansion coefficients as a function of temperature. The thermal expansion values estimated in the present study show a fair degree of agreement with other existing dilatometer based bulk thermal expansion estimates. The lattice parameter for this alloy at 300 K is found to be 0.3549(1) nm. The mean linear thermal expansivity is found to be 11.4 x 10 -6 K -1

  20. Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor

    International Nuclear Information System (INIS)

    Yan-Rong, Cao; Xiao-Hua, Ma; Yue, Hao; Shi-Gang, Hu

    2010-01-01

    This paper studies the effect of drain bias on ultra-short p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) degradation during negative bias temperature (NBT) stress. When a relatively large gate voltage is applied, the degradation magnitude is much more than the drain voltage which is the same as the gate voltage supplied, and the time exponent gets larger than that of the NBT instability (NBTI). With decreasing drain voltage, the degradation magnitude and the time exponent all get smaller. At some values of the drain voltage, the degradation magnitude is even smaller than that of NBTI, and when the drain voltage gets small enough, the exhibition of degradation becomes very similar to the NBTI degradation. When a relatively large drain voltage is applied, with decreasing gate voltage, the degradation magnitude gets smaller. However, the time exponent becomes larger. With the help of electric field simulation, this paper concludes that the degradation magnitude is determined by the vertical electric field of the oxide, the amount of hot holes generated by the strong channel lateral electric field at the gate/drain overlap region, and the time exponent is mainly controlled by localized damage caused by the lateral electric field of the oxide in the gate/drain overlap region where hot carriers are produced. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  1. Temperature dependence of AlGaAs soft X-ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, A.M., E-mail: amb67@le.ac.u [Space Research Centre, Department of Physics and Astronomy, Michael Atiyah Building, University of Leicester, Leicester LE1 7RH (United Kingdom); Bassford, D.J.; Lees, J.E. [Space Research Centre, Department of Physics and Astronomy, Michael Atiyah Building, University of Leicester, Leicester LE1 7RH (United Kingdom); Ng, J.S.; Tan, C.H.; David, J.P.R. [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2010-09-21

    We have fabricated and characterised unpassivated 200 {mu}m diameter circular mesa Al{sub 0.8}Ga{sub 0.2}As p{sup +}-i-n{sup +} diodes as soft X-ray photon counting detectors. The spectroscopic performance, as measured by the FWHM of the 5.9 keV X-ray line from an {sup 55}Fe radioisotope, shows that these detectors can be used for X-ray photon counting spectroscopy with promising energy resolution (0.9-2.5 keV) over a -30 to +90 {sup o}C temperature range.

  2. Study of dielectric liquids at room temperature for high energy x ray Tomography

    International Nuclear Information System (INIS)

    Lepert, S.

    1989-09-01

    The detection of X rays by means of a dielectric liquid detector system, at room temperature, is discussed. The physico-chemical properties of a dielectric liquid, the construction of a cleaning device and of two electrode configurations, and the utilization of different amplifier models are studied. The results allowed the analysis and characterization of the behavior of the dielectric liquid under X ray irradiation. Data obtained is confirmed by computerized simulation. The choice of Tetramethyl-germanium for the X ray tomography, applied in nondestructive analysis, is explained. The investigation of the system parameters allowed the setting of the basis of a prototype project for a multi-detector [fr

  3. Temperature-dependent properties of semiconductor quantum dots in coherent regime; Temperaturabhaengige Eigenschaften einzelner Halbleiter-Quantenpunkte im Kohaerenten Regime

    Energy Technology Data Exchange (ETDEWEB)

    Huebner, Marc C.

    2009-10-15

    Recently, the public has become aware of keywords like ''Quantum computer'' or ''Quantum cryptography''. Regarding their potential application in solid state based quantum information processing and their overall benefit in fundamental research quantum dots have gained more and more public interest. In this context, quantum dots are often referred to as ''artificial atoms'', a term subsuming their physical properties quite nicely and emphasizing the huge potential for further investigations. The basic mechanism to be considered is the theoretical model of a two-level system. A quantum dot itself represents this kind of system quite nicely, provided that only the presence or absence of a single exciton in the ground state of that structure is regarded. This concept can also be expanded to the presence of two excitons (bi-exciton). Transitions between the relevant levels can be induced by optical stimulation. When integrating quantum dots in diode like structures measurements of this phenomena can be accomplished regarding photo currents. This means of detection is highly sensitive and allows for tuning of the energy levels with respect to the energy of an exciting laser utilizing the Stark effect (via an external electric field). The photo current then shows narrow resonances representing those transitions. By this, the system can be used as a highly sensitive nano-spectrometer. The examination of coherent interactions between quantum dots and an electromagnetic field uses laser pulses that are much shorter than the dephasing time of the system (2 ps). The basic study to be done on two level systems is the measurement of Rabi oscillations allowing for the selection of an arbitrary superposition of states. In this work, the existing setup was improved regarding the possibility to control the temperature of the sample. Up to now, only investigations at 4,2 K have been possible. Even at 70 K Rabi oscillations

  4. High temperature X-ray and neutron diffraction studies on zirconium oxide systems

    International Nuclear Information System (INIS)

    Turner, D.R.

    1980-04-01

    High and room temperature X-ray powder diffraction studies have been made on the monoclinic and tetragonal forms of zirconium dioxide (zirconia). The formation of low temperature tetragonal zirconia from pure and doped zirconium hydroxides has been studied as has the formation of high temperature tetragonal zirconia from monoclinic zirconia. The thermal expansions of monoclinic and high temperature tetragonal zirconia have been measured at temperatures up to 1100 deg C for monoclinic and 1300 deg C for tetragonal zirconia. Neutron powder diffraction profile analysis has been performed on monoclinic zirconia using the PANDA diffractometer at AERE Harwell. Data were collected at liquid helium temperature, room temperature and at up to 800 deg C. The results confirm the thermal expansion results from the X-ray study. In addition, the changes with temperature in fractional atomic coordinates and cell parameters have been used to compute the changes in relative atomic positions and interpreted in accordance with a proposed mechanism for the monoclinic to tetragonal transformation. The major movement is that of the Osub(II) (3-coordinate) oxygen atom. (author)

  5. Substrate temperature influence on W/WCN{sub x} bilayers grown by pulsed vacuum arc discharge

    Energy Technology Data Exchange (ETDEWEB)

    Ospina, R.; Escobar, D. [Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia); Arango, P.J.; Jurado, J.F. [Universidad Nacional de Colombia Sede Manizales, Km. 9 via al Magdalena, Manizales (Colombia)

    2012-04-01

    W/WCN{sub x} coatings were produced by using a repetitive pulsed vacuum arc discharge on stainless-steel 304 substrates, varying the substrate temperature from room temperature to 200 Degree-Sign C. Energy dispersive spectroscopy (EDS) was used for determining W, C and N concentrations dependence on the substrate temperature. A competition between C and N can be observed. Atomic force microscopy was employed for obtaining the thickness and grain size that present similar tendencies as a function of the temperature. X-ray diffraction characterization showed phases of W and {alpha}-WCN (hexagonal). Raman spectra for all substrate temperatures were obtained, presenting two peaks corresponding to D (disorder) and G (graphite) bands in the region of 1100-1700 cm{sup -1} due to the amorphous carbon. As an important conclusion, it was stated that substrate temperature has strong influence on the structure, chemical composition and morphology of W/WCN{sub x} bilayers, caused by the competition between carbon and nitrogen.

  6. Electrodeposited semiconductors at room temperature: an X-ray Absorption Spectroscopy study of Cu-, Zn-, S-bearing thin films

    International Nuclear Information System (INIS)

    Di Benedetto, Francesco; Cinotti, Serena; D’Acapito, Francesco; Vizza, Francesco; Foresti, Maria Luisa; Guerri, Annalisa; Lavacchi, Alessandro; Montegrossi, Giordano; Romanelli, Maurizio; Cioffi, Nicola; Innocenti, Massimo

    2015-01-01

    A SEM, DRS and XAS study was carried out on ultra-thin films with chemical composition belonging to the Cu-Zn-S ternary system, related to the kesterite-type materials, in the light of their potential application to thin film photovoltaic technology. The films, realized through the layer-by-layer E-ALD electrochemical technique, reveal variable phase composition as a function of the applied E-ALD sequence. In particular, by increasing the Zn cycles per Cu cycle from 1:1 to 9:1, the number of detected phases changes from 3 to 2. In all samples, Cu mainly crystallize in a Cu 2 S type phase, whereas Zn occurs as ZnS. In the 1:1 sample, additional ZnO is detected. The variable phase composition parallels apparent changes in the sample morphology. In all samples, a sulphide thin film is covered by a net of elongated nanostructures, the length of which decreases with increasing the number of Zn cycles per Cu cycle. All these evidences are interpreted as due to the operating electrochemical route during the synthesis and confirm the lack of miscibility between Cu 2 S and ZnS, thermodynamically relevant after the E-ALD has stopped. The band gap values exhibited by the three films, modulated by changing the copper:zinc ratio, progressively approach a value useful for solar energy conversion, thus strongly proposing these new sulfide nanomaterials for photovoltaics and photochemical applications.

  7. An X- and Q-band Fe3+ EPR study of nanoparticles of magnetic semiconductor Zn1-xFexO

    Science.gov (United States)

    Misra, Sushil K.; Andronenko, S. I.; Thurber, A.; Punnoose, A.; Nalepa, A.

    2014-08-01

    EPR studies on two types of nanoparticles of Fe3+ doped, 0.1-10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (~9.5 GHz) at 77 K and at Q-band (~34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe3+ ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles.

  8. Spectrally-resolved Soft X-ray Observations and the Temperature Structure of the Solar Corona

    Science.gov (United States)

    Caspi, Amir; Warren, Harry; McTiernan, James; Woods, Thomas N.

    2015-04-01

    Solar X-ray observations provide important diagnostics of plasma heating and particle acceleration, during solar flares and quiescent periods. How the corona is heated to its ~1-3 MK nominal temperature remains one of the fundamental unanswered questions of solar physics; heating of plasma to tens of MK during solar flares -- particularly to the hottest observed temperatures of up to ~50 MK -- is also still poorly understood. Soft X-ray emission (~0.1-10 keV; or ~0.1-10 nm) is particularly sensitive to hot coronal plasma and serves as a probe of the thermal processes driving coronal plasma heating. Spectrally- and temporally-resolved measurements are crucial for understanding these energetic processes, but there have historically been very few such observations. We present new solar soft X-ray spectra from the Amptek X123-SDD, measuring quiescent solar X-ray emission from ~0.5 to ~30 keV with ~0.15 keV FWHM resolution from two SDO/EVE calibration sounding rocket underflights in 2012 and 2013. Combined with observations from RHESSI, GOES/XRS, SDO/EVE, and SDO/AIA, the temperature distribution derived from these data suggest significant hot (5-10 MK) emission from active regions, and the 2013 spectra suggest a low-FIP enhancement of only ~1.6 relative to the photosphere, 40% of the usually-observed value from quiescent coronal plasma. We explore the implications of these findings on coronal heating. We discuss future missions for spectrally-resolved soft X-ray observations using the X123-SDD, including the upcoming MinXSS 3U CubeSat using the X123-SDD and scheduled for deployment in mid-2015, and the CubIXSS 6U CubeSat mission concept.

  9. Boron Arsenide and Boron Phosphide for High Temperature and Luminescent Devices. [semiconductor devices - crystal growth/crystal structure

    Science.gov (United States)

    Chu, T. L.

    1975-01-01

    The crystal growth of boron arsenide and boron phosphide in the form of bulk crystals and epitaxial layers on suitable substrates is discussed. The physical, chemical, and electrical properties of the crystals and epitaxial layers are examined. Bulk crystals of boron arsenide were prepared by the chemical transport technique, and their carrier concentration and Hall mobility were measured. The growth of boron arsenide crystals from high temperature solutions was attempted without success. Bulk crystals of boron phosphide were also prepared by chemical transport and solution growth techniques. Techniques required for the fabrication of boron phosphide devices such as junction shaping, diffusion, and contact formation were investigated. Alloying techniques were developed for the formation of low-resistance ohmic contacts to boron phosphide. Four types of boron phosphide devices were fabricated: (1) metal-insulator-boron phosphide structures, (2) Schottky barriers; (3) boron phosphide-silicon carbide heterojunctions; and (4) p-n homojunctions. Easily visible red electroluminescence was observed from both epitaxial and solution grown p-n junctions.

  10. Interface state density of SiO2/p-type 4H-SiC ( 0001 ), ( 11 2 ¯ 0 ), ( 1 1 ¯ 00 ) metal-oxide-semiconductor structures characterized by low-temperature subthreshold slopes

    Science.gov (United States)

    Kobayashi, Takuma; Nakazawa, Seiya; Okuda, Takafumi; Suda, Jun; Kimoto, Tsunenobu

    2016-04-01

    Interface properties of heavily Al-doped 4H-SiC ( 0001 ) (Si-face), ( 11 2 ¯ 0 ) (a-face), and ( 1 1 ¯ 00 ) (m-face) metal-oxide-semiconductor (MOS) structures were characterized from the low-temperature gate characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs). From low-temperature subthreshold slopes, interface state density (Dit) at very shallow energy levels (ET) near the conduction band edge (Ec) was evaluated. We discovered that the Dit near Ec (Ec - 0.01 eV MOS structures with higher Al doping density for every crystal face (Si-, a-, and m-face). Linear correlation is observed between the channel mobility and Dit near Ec, and we concluded that the mobility drop observed in heavily doped MOSFETs is mainly caused by the increase of Dit near Ec.

  11. Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

    Science.gov (United States)

    Willa, K.; Diao, Z.; Campanini, D.; Welp, U.; Divan, R.; Hudl, M.; Islam, Z.; Kwok, W.-K.; Rydh, A.

    2017-12-01

    Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-δ crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

  12. Opening of cut Iris x hollandica flowers as affected by temperature, dry storage, and light

    NARCIS (Netherlands)

    Doorn, van W.G.; Dole, I.; Celikel, F.G.; Harkema, H.

    2014-01-01

    Flower opening in Iris (Iris x hollandica) depends on elongation of the pedicel + ovary. This elongation lifts the bud above the point where the sheath leaves no longer mechanically inhibit lateral tepal movement. We here report on the effects on flower opening of storage at various temperatures, of

  13. Characterization of polymorphic solid-state changes using variable temperature X-ray powder diffraction

    DEFF Research Database (Denmark)

    Karjalainen, Milja; Airaksinen, Sari; Rantanen, Jukka

    2005-01-01

    The aim of this study was to use variable temperature X-ray powder diffraction (VT-XRPD) to understand the solid-state changes in the pharmaceutical materials during heating. The model compounds studied were sulfathiazole, theophylline and nitrofurantoin. This study showed that the polymorph form...... of sulfathiazole SUTHAZ01 was very stable and SUTHAZ02 changed as a function of temperature to SUTHAZ01. Theophylline monohydrate changed via its metastable form to its anhydrous form during heating and nitrofurantoin monohydrate changed via amorphous form to its anhydrous form during heating. The crystallinity...... of SUTHAZ01, SUTHAZ02 and theophylline monohydrate were very high and stable. Nitrofurantoin monohydrate was also very crystalline at room temperature but during heating at lower temperatures the crystallinity decreased and started to increase strongly at the temperature where the sample had changed...

  14. Room temperature femtosecond X-ray diffraction of photosystem II microcrystals

    Science.gov (United States)

    Kern, Jan; Alonso-Mori, Roberto; Hellmich, Julia; Tran, Rosalie; Hattne, Johan; Laksmono, Hartawan; Glöckner, Carina; Echols, Nathaniel; Sierra, Raymond G.; Sellberg, Jonas; Lassalle-Kaiser, Benedikt; Gildea, Richard J.; Glatzel, Pieter; Grosse-Kunstleve, Ralf W.; Latimer, Matthew J.; McQueen, Trevor A.; DiFiore, Dörte; Fry, Alan R.; Messerschmidt, Marc; Miahnahri, Alan; Schafer, Donald W.; Seibert, M. Marvin; Sokaras, Dimosthenis; Weng, Tsu-Chien; Zwart, Petrus H.; White, William E.; Adams, Paul D.; Bogan, Michael J.; Boutet, Sébastien; Williams, Garth J.; Messinger, Johannes; Sauter, Nicholas K.; Zouni, Athina; Bergmann, Uwe; Yano, Junko; Yachandra, Vittal K.

    2012-01-01

    Most of the dioxygen on earth is generated by the oxidation of water by photosystem II (PS II) using light from the sun. This light-driven, four-photon reaction is catalyzed by the Mn4CaO5 cluster located at the lumenal side of PS II. Various X-ray studies have been carried out at cryogenic temperatures to understand the intermediate steps involved in the water oxidation mechanism. However, the necessity for collecting data at room temperature, especially for studying the transient steps during the O–O bond formation, requires the development of new methodologies. In this paper we report room temperature X-ray diffraction data of PS II microcrystals obtained using ultrashort (< 50 fs) 9 keV X-ray pulses from a hard X-ray free electron laser, namely the Linac Coherent Light Source. The results presented here demonstrate that the ”probe before destroy” approach using an X-ray free electron laser works even for the highly-sensitive Mn4CaO5 cluster in PS II at room temperature. We show that these data are comparable to those obtained in synchrotron radiation studies as seen by the similarities in the overall structure of the helices, the protein subunits and the location of the various cofactors. This work is, therefore, an important step toward future studies for resolving the structure of the Mn4CaO5 cluster without any damage at room temperature, and of the reaction intermediates of PS II during O–O bond formation. PMID:22665786

  15. temperature

    Directory of Open Access Journals (Sweden)

    G. Polt

    2015-10-01

    Full Text Available In-situ X-ray diffraction was applied to isotactic polypropylene with a high volume fraction of α-phase (α-iPP while it has been compressed at temperatures below and above its glass transition temperature Tg. The diffraction patterns were evaluated by the Multi-reflection X-ray Profile Analysis (MXPA method, revealing microstructural parameters such as the density of dislocations and the size of coherently scattering domains (CSD-size. A significant difference in the development of the dislocation density was found compared to compression at temperatures above Tg, pointing at a different plastic deformation mechanism at these temperatures. Based on the individual evolutions of the dislocation density and CSD-size observed as a function of compressive strain, suggestions for the deformation mechanisms occurring below and above Tg are made.

  16. Structural, magnetic and optical properties of a dilute magnetic semiconductor based on Ce{sub 1−x}Co{sub x}O{sub 2} thin film grown on LaAlO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoud, Waleed E., E-mail: w_e_mahmoud@yahoo.com [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Suez Canal University, Faculty of Science, Department of Physics, Ismailia (Egypt); Al-Ghamdi, A.A. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Al-Agel, F.A. [Hail University, College of Science, Department of Physics, Hail (Saudi Arabia); Al-Arfaj, E. [Umm Alqura University, Department of Physics, Makkah (Saudi Arabia); Qassim University, College of Science, Physics Department, Buraidah 5145 (Saudi Arabia); Shokr, F.S. [King Abdulaziz University, Faculty of Science & Arts, Department of Physics, Rabigh (Saudi Arabia); Al-Gahtany, S.A. [King Abdulaziz University, Faculty of Science for Girls, Department of Physics, Jeddah (Saudi Arabia); Alshahrie, Ahmed [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Jalled, Ouissem [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Laboratory of Applied Mineral Chemistry, Department of Chemistry, University Tunis ElManar, Faculty of Sciences, Campus 2092, Tunis (Tunisia); Bronstein, L.M. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Texas State University-San Marcos, Department of Chemistry and Biochemistry, 601 University Dr., San Marcos, TX 78666 (United States); Beall, Gary W. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Indiana University, Department of Chemistry, Bloomington, IN 47405 (United States)

    2015-12-15

    Highlights: • Co doped CeO{sub 2} was grown on LaAlO{sub 3} (0 0 1) via a modified sol–gel spin-coating technique. • The concentration of the Co ions was varied from 1 to 15 at.%. • The incorporation of 5 at.% of Mn ions was found to provide formation of exceptionally magnetic moment. • This amount demonstrated a giant magnetic moment of 1.09 μ{sub B}/Co. • This amount reduced the optical band gap and enhanced the optical performance. - Abstract: The enhancement of the room temperature ferromagnetism and optical properties of the dilute magnetic metal oxides is a crucial clue to construct spin-based optoelectronic devices. In this work, Ce{sub 1−x}Co{sub x}O{sub 2} (0.01 ≤ x ≤0.15) thin films were prepared via ethylene glycol modified sol–gel spin coating technique on the LaAlO{sub 3} (0 0 1) substrate to enhance their room temperature ferromagnetism and optical properties. The structures, magnetic and optical properties of the prepared films were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, SQUID magnetometer, X-ray photoelectron spectroscopy and UV–vis spectrophotometer. The results demonstrated that a single phase cubic structure was formed, implying the substitution of Co ions into the Ce ions sites. The prepared films showed room temperature ferromagnetism with saturation magnetic moment of 1.09 μ{sub B}/Co was achieved for 5 at.% Co-doped CeO{sub 2}. This film exhibited high optical transparency of 85% and low optical band energy gap of 3.39 eV. The improved magnetic and optical properties are argued to the increase of the density of the oxygen vacancies into the cerium oxide crystal structure due to the incorporation of Co ions.

  17. Power semiconductors

    CERN Document Server

    Kubát, M

    1984-01-01

    The book contains a summary of our knowledge of power semiconductor structures. It presents first a short historic introduction (Chap. I) as well as a brief selection of facts from solid state physics, in particular those related to power semiconductors (Chap. 2). The book deals with diode structures in Chap. 3. In addition to fundamental facts in pn-junction theory, the book covers mainly the important processes of power structures. It describes the emitter efficiency and function of microleaks (shunts). the p +p and n + n junctions, and in particular the recent theory of the pin, pvn and p1tn junctions, whose role appears to be decisive for the forward mode not only of diode structures but also of more complex ones. For power diode structures the reverse mode is the decisive factor in pn-junction breakdown theory. The presentation given here uses engineering features (the multiplication factor M and the experimentally detected laws for the volume and surface of crystals), which condenses the presentation an...

  18. Semiconductors with structurally determined vacancies PAC studies

    CERN Document Server

    Dietrich, M; Kortus, J; Unterricker, S; Deicher, M; Burchard, A; Magerle, R

    1999-01-01

    Ternary semiconductors of type Square Operator A/sup II/B/sub 2//sup III/C/sub 4//sup VI/ with an ordered array of vacancies were investigated by PAC. Thereby the six probes /sup 111m/Cd, /sup 117/Cd (/sup 117/In), /sup 111/In(/sup 111/Cd), /sup 111/Ag(/sup 111/Cd), /sup 77/Br(/sup 77/Se) and /sup 77/Kr(/sup 77/Br) were applied. The positions of the different probes are determined and the corresponding electric field gradients by the WIEN 95 code calculated. By /sup 111/Ag(/sup 111/Cd)-probes the vacancies could be substituted. The electronic charge density distributions are discussed. At elevated temperatures the substances show order- disorder transitions. As compared to the X-ray diffraction patterns the beginning of disorder is observed by PAC at distinctly lower temperatures. (7 refs).

  19. High-resolution calorimetry: limitations of doped semiconductor thermometers

    CERN Document Server

    McCammon, D; Apodaca, E; Deiker, S; Galeazzi, M; Han, S I; Lesser, A; Sanders, W; Kelley, R L; Moseley, S H; Porter, F S; Stahle, C K; Szymkowiak, A E

    1999-01-01

    Small thermal calorimeters operating at cryogenic temperatures have achieved an energy resolution for single X-ray photons that is a factor of 20 better than the theoretical limit for a silicon ionization detector. To determine the potential for further improvements and decide on likely routes for achieving them, we discuss detector design optimization, first for an ideal calorimeter, and then for the case where components exhibit non-ideal behavior. Two serious non-ideal properties of doped semiconductor thermometers are electron-phonon decoupling and excess noise. These have been characterized over a range of sensitivity and operating temperature, and their effects on design optimization and ultimate performance can be evaluated.

  20. Semiconductor Laser Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Laser Measurements Laboratory is equipped to investigate and characterize the lasing properties of semiconductor diode lasers. Lasing features such...

  1. Effects of Temperature and X-rays on Plastic Scintillating Fiber and Infrared Optical Fiber

    Directory of Open Access Journals (Sweden)

    Bongsoo Lee

    2015-05-01

    Full Text Available In this study, we have studied the effects of temperature and X-ray energy variations on the light output signals from two different fiber-optic sensors, a fiber-optic dosimeter (FOD based on a BCF-12 as a plastic scintillating fiber (PSF and a fiber-optic thermometer (FOT using a silver halide optical fiber as an infrared optical fiber (IR fiber. During X-ray beam irradiation, the scintillating light and IR signals were measured simultaneously using a dosimeter probe of the FOD and a thermometer probe of the FOT. The probes were placed in a beaker with water on the center of a hotplate, under variation of the tube potential of a digital radiography system or the temperature of the water in the beaker. From the experimental results, in the case of the PSF, the scintillator light output at the given tube potential decreased as the temperature increased in the temperature range from 25 to 60 °C. We demonstrated that commonly used BCF-12 has a significant temperature dependence of −0.263 ± 0.028%/°C in the clinical temperature range. Next, in the case of the IR fiber, the intensity of the IR signal was almost uniform at each temperature regardless of the tube potential range from 50 to 150 kVp. Therefore, we also demonstrated that the X-ray beam with an energy range used in diagnostic radiology does not affect the IR signals transmitted via a silver halide optical fiber.

  2. Modulation spectroscopy characterization of MOCVD semiconductors and semiconductors structures

    Science.gov (United States)

    Pollak, Fred H.; Shen, H.

    1989-11-01

    This paper reviews recent developments in the use of contactless modulation spectroscopy to yield important information about MOCVD growth as well as the properties of MOCVD fabricated semiconductors and semiconductor microstructures. The method of reflectance difference spectroscopy can be used to gain significant insights into chemical and structural parameters during actual growth conditions. The electromodulation technique of photoreflectance (PR) probes the electronic states of the material. It has many applications for in-situ post-growth characterization of crystal quality, very thin Ga 1-xAl xAs/GaAs epitaxial layers, Ga 1-xAl xAs alloy composition, deep trap states, surface electric fields and carrier concentrations, lattice-mismatch strain, etc, as well as the determination of relevant parameters of heterojunction structures. In addition, recent PR experiments at 600°C on GaAs and Ga 0.82Al 0.18As show potential for in-situ monitoring during growth.

  3. Semiconductor characterization for optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Miner, C.J. [Bell Northern Research Ltd., Ottawa, ON (Canada)

    1996-03-01

    Scanning reflectance spectroscopy, scanning photoluminescence, and double crystal x-ray diffraction mapping are all specialized non-destructive characterization tools which monitor the advanced materials used in the development of high speed optoelectronics. Each technology was described and their application in the assessment of III-V semiconductor composition, layer thickness and defect density was demonstrated. The new techniques have been optimized for speed, to make high spatial resolution mapping practical. Since the tests are non-destructive, frequent monitoring is possible. 11 refs., 7 figs.

  4. Temperature dependence of the EPR spectra for the Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    P, Silva; W, Braemer; F, Torres [Institute Venezolano de Investigaciones Cientificas, Centro de Fisica, Carretera Panamericana Km. 11, Aptdo. 20632 (Venezuela, Bolivarian Republic of); V, Sagredo; E, Perez, E-mail: silva@ivic.v [Universidad de Los Andes, Departamento de Fisica, Laboratorio de Magnetismo, Merida (Venezuela, Bolivarian Republic of)

    2010-01-01

    Electron Paramagnetic Resonance (EPR) was used to study, the temperature dependence, of the magnetic behavior of Ni{sub 1-x}Co{sub x}Fe{sub 2}O{sub 4} with 0.0 < x < 0.5, in the temperature range 80 < T < 700 K. Nanoparticles of sizes between 30 and 40 nm were obtained using the sol-gel method. The results show that the resonance field (H{sub R}) decrease while the linewidth (AH{sub PP}) increase, in the temperature range studied, when x is increased. The H{sub R} values for x = 0 are in agreement with a superparamagnetic phase in the temperature range studied, while for x = 0.2, H{sub R} and {Delta}H{sub PP} are in accordance with a ferri to superparamagnetic transition at T{approx}350 K, where T is related to the EPR blocking temperature of these samples. For sample with x = 0.5 this temperature is T{approx}470 K. These results are in good agreement with the magnetization and MOKE results. MOKE measurements as a function of temperature were made to corroborate EPR results.

  5. Semiconductor radiation detectors: device physics

    National Research Council Canada - National Science Library

    Lutz, Gerhard

    1999-01-01

    ..., including nuclear physics, elementary particle physics, optical and x-ray astronomy, medicine, and materials testing - and the number of applications is growing continually. Closely related, and initiated by the application of semiconductors, is the development of low-noise low-power integrated electronics for signal readout. The success of semicond...

  6. Study about uranium oxides at high temperature by X-ray diffraction

    International Nuclear Information System (INIS)

    Costa, M.I.

    1978-01-01

    In this work a technique to study the lattice parameters in the crystalline substances at hight temperature by X-rays diffraction is developed. The results obtained agree very well with the experimental data found in the literature. The crystalline structure of uranium oxide at different temperature is studied in detail by this technique. At the range of the temperature investigated, i.e., 20 0 C to 640 0 C, the following forms for uranium oxide: U 3 O 8 in its hexagonal modification, cubic UO 2 , cubic U 4 O 9 and tetragonal U 3 O 7 is observed. The appearance of two hexagonal units observed in this work is identified by Milne. A good reproducibillity is observed for measurements at the same temperature [pt

  7. The spectral resolution of high temperature GaAs photon counting soft X-ray photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, A.M., E-mail: amb67@le.ac.uk [Space Research Centre, Department of Physics and Astronomy, Michael Atiyah Building, University of Leicester, Leicester LE1 7RH (United Kingdom); Lees, J.E.; Bassford, D.J. [Space Research Centre, Department of Physics and Astronomy, Michael Atiyah Building, University of Leicester, Leicester LE1 7RH (United Kingdom); Ng, J.S.; Tan, C.H.; Babazadeh, N.; Gomes, R.B. [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2011-10-21

    Circular mesa GaAs p{sup +}-i-n{sup +} diodes for photon counting soft X-ray spectroscopy have been fabricated and characterised over a temperature range of +80 to -30 {sup o}C. The spectroscopic performance of the diodes, as measured by the FWHM of the Mn K{sub {alpha}} X-ray line from an {sup 55}Fe radioisotope, is reported. In addition, we compare the GaAs diodes with previously fabricated and characterised Al{sub 0.8}Ga{sub 0.2}As p{sup +}-i-n{sup +} diodes of similar geometry.

  8. Development of a new growth method of the semiconductor material CdTe, for obtaining imagers of X and gamma-ray

    International Nuclear Information System (INIS)

    Dierre, Fabrice

    2007-01-01

    This thesis aims at obtaining large dimension CdTe crystals, suited to X and γ-rays detection, by a new method of growth using the evaporation of the solvent tellurium as the driving force for crystallization, from a tellurium-rich solution of cadmium and tellurium. This method is called Process By Solvent Evaporation (PBSE) or in French, Methode par Evaporation de Solvant. Two essential points characterize it: it is carried out in an open tube, which allows its extension to large diameters, and the growth proceeds at constant temperature, which must ensure a better uniformity of the properties of the elaborated material. The results obtained by this PBSE method show that the wafers can be classified in three categories (under-evaporated, ideal, over-evaporated) depending on the imposed 'temperature/time of growth' couple. It appears that only the wafers elaborated under the ideal conditions have properties required by the X and γ-ray detection. The characterization of several detectors extracted from various wafers made it possible to evaluate the potential of this material as detector for X and γ-rays: the material shows characteristics comparable to those indicated for various detectors in the scientific literature or present on the commercial market (in term of resolution and μτ product). The study of the chlorine incorporation by SIMS analysis shows that the chlorine profiles in the thickness of the various detectors are increasing from the beginning of growth face to the end of growth face according to an hyperbolic law. A simple and unidimensional model is developed to describe what occurs during a PBSE experiment. This model, based on the method of finished volumes, discretizes the liquid phase into several layers. According to the laws and numerical values assigned to the physical phenomena involved in the process, the model predicts the existence of three possible situations, which were encountered experimentally. (O.M.)

  9. SOFT X-RAY TEMPERATURE TIDAL DISRUPTION EVENTS FROM STARS ON DEEP PLUNGING ORBITS

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Lixin; McKinney, Jonathan C.; Miller, M. Coleman, E-mail: cosimo@umd.edu [Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States)

    2015-10-20

    One of the puzzles associated with tidal disruption event candidates (TDEs) is that there is a dichotomy between the color temperatures of a few × 10{sup 4} K for TDEs discovered with optical and UV telescopes and the color temperatures of a few × 10{sup 5}–10{sup 6} K for TDEs discovered with X-ray satellites. Here, we propose that high-temperature TDEs are produced when the tidal debris of a disrupted star self-intersects relatively close to the supermassive black hole, in contrast to the more distant self-intersection that leads to lower color temperatures. In particular, we note from simple ballistic considerations that greater apsidal precession in an orbit is the key to closer self-intersection. Thus, larger values of β, the ratio of the tidal radius to the pericenter distance of the initial orbit, are more likely to lead to higher temperatures of more compact disks that are super-Eddington and geometrically and optically thick. For a given star and β, apsidal precession also increases for larger black hole masses, but larger black hole masses imply a lower temperature at the Eddington luminosity. Thus, the expected dependence of the temperature on the mass of the black hole is non-monotonic. We find that in order to produce a soft X-ray temperature TDE, a deep plunging stellar orbit with β > 3 is needed and a black hole mass of ≲5 × 10{sup 6}M{sub ⊙} is favored. Although observations of TDEs are comparatively scarce and are likely dominated by selection effects, it is encouraging that both expectations are consistent with current data.

  10. Temperature dependence of the minimum V/III ratio for the growth of In[sub x]Ga[sub 1-x]As

    Energy Technology Data Exchange (ETDEWEB)

    Riechert, H. (Siemens Corporate Research and Development, Muenchen (Germany)); Averbeck, R. (Siemens Corporate Research and Development, Muenchen (Germany)); Bernklau, D. (Siemens Corporate Research and Development, Muenchen (Germany))

    1993-02-01

    We have quantitatively determined the minimum V/III ratios for the growth of In[sub x]Ga[sub 1-x]As(x=0, 0.1, 0.2 and 0.53) on GaAs and InP. Minimum As[sub 4] fluxes were measured for a wide range of growth temperatures using a transition of the surface reconstruction. Their temperature dependence can be fitted very well by the typical curve for thermally activated behavior. We find In[sub x]Ga[sub 1-x]As and GaAs are found to be similar (1.9 and 2.1 eV, respectively) but the rates of As-desorption are much higher for In[sub x]Ga[sub 1-x]As. This may be seen as evidence for a less effective dissociative reaction of As[sub 4] with In than with Ga. (orig.)

  11. Temperature-dependent evolution of RbBSi2O6 glass into crystalline Rb-boroleucite according to X-ray diffraction data

    International Nuclear Information System (INIS)

    Levin, Aleksandr A.; Filatov, Stanislav K.; Krzhizhanovskaya, Maria G.; Paufler, Peter; Bubnova, Rimma S.; Russian Academy of Sciences, St. Petersburg; Meyer, Dirk C.; Technische Univ. Bergakademie Freiberg

    2013-01-01

    The temperature-dependent evolution of the glass into a crystalline phase is studied for a rubidium borosilicate glass of composition 16.7 Rb 2 O . 16.7 B 2 O 3 . 66.6 SiO 2 employing X-ray diffraction (XRD) data. A glass sample was prepared by melt quenching from 1500 within 0.5 hour. The glass sample was step-wise annealed at 13 distinct temperatures from 300 C up to 900 C for 1 h at every annealing step. To investigate changes in the glass structure, angle-dispersive XRD was applied by using an energy-resolving semiconductor detector. The radial distribution functions (RDFs) were calculated at every stage. For polycrystalline states the crystal structure of the samples with different thermal history was refined using the Rietveld method. Comparing correlation distances estimated from RDFs of glass and polycrystalline samples and mean interatomic distances calculated for polycrystalline samples by using atomic coordinates after Rietveld refinement, it is concluded that the borosilicate glass under study is converted into the crystalline state in the temperature range of 625-750 C (i.e. in the temperature range close to the glass transition range 620-695 C as determined by differential scanning calorimetry by using of heating rate of 20 K/min) at an average heating rate of about 0.35 K/min. When the heating rate is increased up to 10 or 20 K/min, the crystallisation temperature shifts sharply up to 831-900 C and 878-951 C, respectively. XRD data give evidence that distinctive traces of cubic RbBSi 2 O 6 appear from glass at about 625 C and a two-phase range exists up to 750 C. After annealing at higher temperatures (800-900 C) the crystal structure practically does not change any more. (orig.)

  12. Interior Temperature Measurement Using Curved Mercury Capillary Sensor Based on X-ray Radiography

    Science.gov (United States)

    Chen, Shuyue; Jiang, Xing; Lu, Guirong

    2017-07-01

    A method was presented for measuring the interior temperature of objects using a curved mercury capillary sensor based on X-ray radiography. The sensor is composed of a mercury bubble, a capillary and a fixed support. X-ray digital radiography was employed to capture image of the mercury column in the capillary, and a temperature control system was designed for the sensor calibration. We adopted livewire algorithms and mathematical morphology to calculate the mercury length. A measurement model relating mercury length to temperature was established, and the measurement uncertainty associated with the mercury column length and the linear model fitted by least-square method were analyzed. To verify the system, the interior temperature measurement of an autoclave, which is totally closed, was taken from 29.53°C to 67.34°C. The experiment results show that the response of the system is approximately linear with an uncertainty of maximum 0.79°C. This technique provides a new approach to measure interior temperature of objects.

  13. Fabrication and properties of YBa2Cu3O7- x ceramics at different sintering temperatures

    Science.gov (United States)

    Prayoonphokkharat, Poom; Jiansirisomboon, Sukanda; Watcharapasorn, Anucha

    2013-07-01

    The influence of sintering temperatures on the fabrication of YBCO ceramics under normal air atmosphere was investigated in this study. YBCO ceramics were prepared by mixing starting compounds of Y2O3, BaCO3 and CuO powders, which were calcined at 850°C for 12 h. The powder was pelletized and sintered at different temperatures, from 930°C-1050°C, for 12 h. Phase identification was carried out by x-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study microstructure and chemical composition. In addition, density, Vickers hardness properties, the change of resistance and dielectric properties with temperature above T c were investigated. It was found that, at 950°C-1000°C, high-purity YBCO ceramic could be obtained. Outside this temperature range, either impurity phases were present or melting occurred. SEM images showed that grain size, which ranged from 1.5-2.5 µm, and hardness were related to density and liquid phase present in the sample. Furthermore, the sintering temperature affected oxygen content which, in turn, determined the conductive or semi-conductive behavior observed by electrical property measurement.

  14. Nonlinear Gyrokinetic Simulations of Ion-Temperature-Gradient Turbulence for the Optimized Wendelstein 7-X Stellarator

    Science.gov (United States)

    Xanthopoulos, P.; Merz, F.; Görler, T.; Jenko, F.

    2007-07-01

    Ion-temperature-gradient turbulence constitutes a possibly dominant transport mechanism for optimized stellarators, in view of the effective suppression of neoclassical losses characterizing these devices. Nonlinear gyrokinetic simulation results for the Wendelstein 7-X stellarator [G. Grieger , in Proceedings of the IAEA Conference on Plasma Physics and Controlled Nuclear Fusion Research, 1990 (IAEA, Vienna, 1991) Vol. 3, p. 525]—assuming an adiabatic electron response—are presented. Several fundamental features are discussed, including the role of zonal flows for turbulence saturation, the resulting flux-gradient relationship, and the coexistence of ion-temperature-gradient modes with trapped ion modes in the saturated state.

  15. Oxidation of X20 in Water Vapour: The Effect of Temperature and Oxygen Partial Pressure

    DEFF Research Database (Denmark)

    Hansson, Anette Nørgaard; Montgomery, Melanie; Somers, Marcel A. J.

    2009-01-01

    The oxidation behaviour of X20 in various mixtures of water, oxygen and hydrogen was investigated at temperatures between 500 C and 700 C (time: 336 h). The samples were characterised using reflected light microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy....... Double-layered oxides developed during oxidation under all conditions. The morphology of the oxide layers was strongly influenced by temperature, whereas the influence of the oxidising environment appeared to be less pronounced, as long as it contained water vapour. The inner layer consisted of converted...... are discussed based on the various hypotheses of the accelerating effect of water vapour that have been put forth in the literature....

  16. The Effect of Growth Temperature and V/III Flux Ratio of MOCVD Antimony Based Semiconductors on Growth Rate and Surface Morphology

    Directory of Open Access Journals (Sweden)

    Ramelan Ari Handono

    2017-01-01

    Full Text Available Epitaxial Alx Ga1-x Sb layers on GaSb and GaAs substrates have been grown by atmospheric pressure metalorganic chemical vapor deposition using TMAl, TMGa and TMSb. Nomarski microscope and a profiler were employed to examine the surface morphology and growth rate of the samples. We report the effect of growth temperature and V/III flux ratio on growth rate and surface morphology. Growth temperatures in the range of 520°C and 680°C and V/III ratios from 1 to 5 have been investigated. A growth rate activation energy of 0.73 eV was found. At low growth temperatures between 520 and 540°C, the surface morphology is poor due to antimonide precipitates associated with incomplete decomposition of the TMSb. For layers grown on GaAs at 580°C and 600°C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580°C with a V/III flux ratio of 3 at the rate of 3.5 μm/hour shows p-type conductivity with smooth surface morphology

  17. Layered semiconductor neutron detectors

    Science.gov (United States)

    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.

  18. Temperature dependence of resonant x-ray magnetic scattering in holmium

    International Nuclear Information System (INIS)

    Helgesen, G.; Hill, J.P.; Thurston, T.R.; Gibbs, D.; Kwo, J.; Hong, M.

    1994-01-01

    We report the results of resonant x-ray magnetic scattering experiments on bulk and thin-film single crystals of holmium. The scattering at the principal magnetic reflection has been characterized as a function of the temperature in the spiral phases near and below their respective Neel temperatures. The integrated intensity of the principal magnetic peak in both samples shows power-law behavior versus reduced temperature with nearly equal exponents. The exponents for the scattering at the resonant second and third harmonics in the bulk sample are not simple integer multiples of the first, and motivate the consideration of simple scaling corrections to mean-field theory. We also present and compare the results of high-resolution measurements of the temperature dependence of the magnetic wave vectors, c-axis lattice constants, and correlation lengths of the magnetic scattering of the two samples in their spiral phases. Although the qualitative behavior is similar, systematic differences are found, including uniformly larger magnetic wave vectors and the suppression of the 1/6 phase in the film. The spiral magnetic structure of the film forms a domain state at all temperatures in the ordered phase. The magnetic correlation lengths of both samples are greatest near the Neel temperature, where that of the film appears to exceed the translational correlation lengths of the lattice. As the temperature decreases, the magnetic correlation lengths also decrease. These results are discussed in terms of the strain present in the samples

  19. Crystallographic and oxidation kinetic study of uranium dioxide by high temperature X-ray diffractometry

    International Nuclear Information System (INIS)

    Teixeira, S.R.

    1981-01-01

    The structural behavior of UO 2 sintered plates was studied as a function of temperature by X-ray diffractometry. All the experiments were carried out under an inert atmosphere with low oxygen content (approximated 140 ppm). The thermal expansion coefficient of UO 2 05 was found to be 10,5 x 10 - 6 0 C - 1 for temperatures above 165 0 C. Structural transformations during oxidation were observed at 170,235 and 275 0 C. The isothermal oxidation of UO 2 to U 3 O 7 follows a parabolic form and the diffusion of oxygen through the product layer U 4 O 9 is the mechanism controlling the oxidation rate. The phases observed were UO 2 (cubic) - U 4 O 9 (cubic) - U 3 O 7 (tetragonal). Activation energies of oxidation were found for different crystallographic planes (hkl). From this one can conclude that there is a preferential occupation of interstitial oxygen within the UO 2 structure. (Author) [pt

  20. Power X-ray diffraction under extreme conditions of pressure and temperature

    International Nuclear Information System (INIS)

    Fiquet, G.; Andrault, D.

    1999-01-01

    An important work has been carried out in the field of X-ray diffraction in obtaining accurate structure information from materials at extreme conditions of pressure and temperature. An experimental set-up combining a diamond-anvil high-pressure cell and a laser-heating technique has been installed at the high-pressure beamline ID30 at the ESRF (Grenoble) to study two major constituents of the Earth's deep interior: MgSiO 3 perovskite and iron. Experiments carried out on MgSiO 3 perovskite up to 86 GPa and over 2000 K yielded detailed structural information on this compound under these conditions and thus important constraints for the lower mantle mineralogical model, favouring a mixture of perovskite and magnesiowuestite. X-ray diffraction patterns recorded on imaging plates with micro-focused monochromatic radiation revealed a new high-temperature structure of iron above 40 GPa. (au)

  1. Low-temperature magnetic properties of NiCrxFe2-xO4 ferrites

    Science.gov (United States)

    Bushkova, V. S.

    2017-12-01

    Nickel-chrome ferrites of general formula NiCrxFe2-xO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) were produced using low-temperature sol-gel self-combustion technique. Magnetic hysteresis loop of the samples showed that due to a low coercive field Hc, in the range of 2484-4283 A/m at 77 K, the ferrites are soft magnetic materials. The residual induction Br of the magnetic field decreases with increasing the concentration of Cr3+ ions due to a weakening of the interaction between the tetrahedral and octahedral sublattices of the ferrite with the spinel structure. The specific saturation magnetization σs of NiFe2O4 ferrite is 33.9 A m2/kg. The blocking temperature Tb was determined; its average value was found to be 157 K.

  2. Heavy metal ternary halides for room-temperature x-ray and gamma-ray detection

    Science.gov (United States)

    Liu, Zhifu; Peters, John A.; Stoumpos, Constantinos C.; Sebastian, Maria; Wessels, Bruce W.; Im, Jino; Freeman, Arthur J.; Kanatzidis, Mercouri G.

    2013-09-01

    We report our recent progress on wide bandgap ternary halide compounds CsPbBr3 and CsPbCl3 for room temperature x-ray and gamma-ray detectors. Their bandgaps are measured to be 2.24 eV and 2.86 eV, respectively. The measured mobility-lifetime products of CsPbBr3 are 1.7×10-3, 1.3×10-3 cm2/V, for electron and hole carriers, respectively, comparable to those of CdTe. We measured the room temperature spectral response of CsPbBr3 sample to Ag x-ray radiation. It has a well-resolved spectral response to the 22.4 keV Kα radiation peak and detector efficiency comparable to that of CdZnTe detector at 295 K.

  3. Miniature thermoelectric coolers for semiconductor lasers

    International Nuclear Information System (INIS)

    Semenyuk, V.A.; Pilipenko, T.V.; Albright, G.C.; Ioffe, L.A.; Rolls, W.H.

    1994-01-01

    The problem of matching thermoelectric coolers and semiconductor lasers with respect to heat flow densities and electrical currents is discussed. It is shown that the solution of this problem is accomplished by the reduction of thermoelement dimensions to the submillimeter level. Assembled with extruded thermoelectric materials, miniature coolers with a thermoelement length as short as 0.1 mm and a cross section of 0.2x0.2 mm 2 are demonstrated. Using 0.5 mm thick aluminum ceramic plates, the overall height of these miniature coolers can be as low as 1.1 mm. The devices are designed for cooling and thermally stabilizing miniature optoelectronic elements, especially semiconductor lasers. The results of device testing over a wide range of temperature and heat loads are given. This novel approach in thermoelectric cooler design represents a new step in miniaturization and reduced current requirements, with little or no loss in maximum attainable temperature difference. A ΔT max of 68 K is demonstrated with input current of 200 mA. Due to the small thermoelement length, extremely large heat flow densities at cold junctions are practical (up to 100 W/cm 2 at ΔT=0), making these devices ideal for heat intensive local sources such as injection laser diodes. Due to the extremely small sizes, these coolers have a high speed of response where a ΔT of 35 K in specimens with the thermoelement length of 0.1 mm is approximately 150 milliseconds. These micro coolers are ideal for use within the semiconductor device housing and under conditions where limitations of power, size, and electrical current predominate. copyright 1995 American Institute of Physics

  4. Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect microscope for the investigation of electron spin dynamics in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution.

    Science.gov (United States)

    Henn, T; Kiessling, T; Ossau, W; Molenkamp, L W; Biermann, K; Santos, P V

    2013-12-01

    We describe a two-color pump-probe scanning magneto-optical Kerr effect microscope which we have developed to investigate electron spin phenomena in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution. The key innovation of our microscope is the usage of an ultrafast "white light" supercontinuum fiber-laser source which provides access to the whole visible and near-infrared spectral range. Our Kerr microscope allows for the independent selection of the excitation and detection energy while avoiding the necessity to synchronize the pulse trains of two separate picosecond laser systems. The ability to independently tune the pump and probe wavelength enables the investigation of the influence of excitation energy on the optically induced electron spin dynamics in semiconductors. We demonstrate picosecond real-space imaging of the diffusive expansion of optically excited electron spin packets in a (110) GaAs quantum well sample to illustrate the capabilities of the instrument.

  5. Neutron scattering studies of Cd1−xMnxTe

    DEFF Research Database (Denmark)

    Giebultowicz, T.; Lebech, Bente; Buras, B

    1984-01-01

    The diluted magnetic (‘‘semimagnetic’’) semiconductor Cd1–xMnxTe reveals intriguing spin glass properties. In this paper, the results of neutron scattering studies of Cd1–xMnxTe are presented. The low‐temperature spin correlations have been studied for several single crystal samples in the compos......The diluted magnetic (‘‘semimagnetic’’) semiconductor Cd1–xMnxTe reveals intriguing spin glass properties. In this paper, the results of neutron scattering studies of Cd1–xMnxTe are presented. The low‐temperature spin correlations have been studied for several single crystal samples...

  6. Low temperature synthesis of nanosized Mn1–xZnxFe2O4 ferrites ...

    Indian Academy of Sciences (India)

    Nanosized Mn1–ZnFe2O4 ( = 0, 0.1, 0.3, 0.5, 0.6, 0.7, 0.9) mixed ferrite samples of particle size < 12 nm were prepared using the co-precipitation technique by doping the Zn2+ ion impurities. Autoclave was employed to maintain constant temperature of 80°C and a constant pressure. The X-ray analysis and the IR ...

  7. Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature

    Science.gov (United States)

    Kern, Jan; Alonso-Mori, Roberto; Tran, Rosalie; Hattne, Johan; Gildea, Richard J.; Echols, Nathaniel; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G.; Lassalle-Kaiser, Benedikt; Koroidov, Sergey; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R.; Miahnahri, Alan; Schafer, Donald W.; Messerschmidt, Marc; Seibert, M. Marvin; Koglin, Jason E.; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J.; Grosse-Kunstleve, Ralf W.; Zwart, Petrus H.; White, William E.; Glatzel, Pieter; Adams, Paul D.; Bogan, Michael J.; Williams, Garth J.; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Sauter, Nicholas K.; Yachandra, Vittal K.; Bergmann, Uwe; Yano, Junko

    2013-01-01

    Intense femtosecond X-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous X-ray diffraction (XRD) and X-ray emission spectroscopy (XES) of microcrystals of Photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD/XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies. PMID:23413188

  8. Giant magnetoresistance and superparamagnetism in Dy{sub x}Fe{sub 100-x} nanogranular magnetic thin films at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Mekala, Laxman, E-mail: mailstolaxman@gmail.com; Shameem, Muhammed P.V.; Singh, Dushyanth; Kumar, M. Senthil, E-mail: senthil@iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2016-05-06

    In this article, Dy{sub x}Fe{sub 100-x} nanogranular (15 ≤ x ≤ 25) thin films have been prepared at ambient temperature by dc magnetron sputtering. The correlation between the microstructure, magneto transport and magnetization properties is discussed. The grain size of Dy (Dysprosium) and Fe (Iron) was measured to be about 2 to 3 nm, respectively and the distribution of grains was homogenous throughout the sample. The magnetoresistance is sensitive to microstructural changes (particle size as well as Dy concentration). At the room temperature, the magnetoresistance [MR %] increased from 0.2 to 2.2 with increase in atomic concentration of Dy from x = 15 to 25 and we obtained maximum 2.2 MR [%] for x = 25 in this series of samples. The magnetization studies have revealed that all the samples are superparamagnetic (SPM) at room temperature.

  9. Ultrafast Spectroscopy of Semiconductor Devices

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Hvam, Jørn Marcher

    1999-01-01

    In this work we present an experimental technique for investigating ultrafast carrier dynamics in semiconductor optical amplifiers at room temperature. These dynamics, influenced by carrier heating, spectral hole-burning and two-photon absorption, are very important for device applications in inf...

  10. Performance of room temperature mercuric iodide (HgI2) detectors in the ultra low energy x-ray region

    International Nuclear Information System (INIS)

    Dabrowski, A.J.; Iwanczyk, J.S.; Barton, J.B.; Huth, G.C.; Whited, R.; Ortale, C.; Economou, T.E.; Turkevich, A.L.

    1980-01-01

    Performance of room temperature mercuric iodide x-ray spectrometers has been recently improved through new fabrication techniques and further development of low noise associated electronic systems. This progress has extended the range of measurements to the ultra low energy x-ray region at room temperature. This paper reports the study of the effect of contact material on the performance of HgI 2 detectors in the low energy x-ray region

  11. Induced Charge Fluctuations in Semiconductor Detectors with a Cylindrical Geometry

    Science.gov (United States)

    Samedov, Victor V.

    2018-01-01

    Now, compound semiconductors are very appealing for hard X-ray room-temperature detectors for medical and astrophysical applications. Despite the attractive properties of compound semiconductors, such as high atomic number, high density, wide band gap, low chemical reactivity and long-term stability, poor hole and electron mobility-lifetime products degrade the energy resolution of these detectors. The main objective of the present study is in development of a mathematical model of the process of the charge induction in a cylindrical geometry with accounting for the charge carrier trapping. The formulae for the moments of the distribution function of the induced charge and the formulae for the mean amplitude and the variance of the signal at the output of the semiconductor detector with a cylindrical geometry were derived. It was shown that the power series expansions of the detector amplitude and the variance in terms of the inverse bias voltage allow determining the Fano factor, electron mobility lifetime product, and the nonuniformity level of the trap density of the semiconductor material.

  12. Unstable ion-temperature-gradient modes in the Wendelstein 7-X stellarator configuration

    Science.gov (United States)

    Rafiq, T.; Kleiber, R.; Nadeem, M.; Persson, M.

    2002-12-01

    The linear stability of the ion-temperature-gradient modes (ITG) in the electrostatic limit is examined in the short wavelength region by using a two fluid reactive model in fully three-dimensional Wendelstein 7-X (W7-X) stellarator [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525] geometry. The spectrum of stable and unstable modes and their real frequencies and eigenfunctions are calculated. The effects of density gradients, temperature gradients, temperature ratios, wavevector, ballooning angle, curvature and local magnetic shear on the ITG mode are also investigated. The frequency and growth rate of the most unstable ITG mode is calculated and visualized for a specific magnetic flux surface. For the equilibrium under investigation both localized and extended eigenmodes are found. The effect of small and large temperature ratios, small and large density gradients as well as large local magnetic shear are all found to be stabilizing. The highest growth rates are found at the outer part of the surface where the local magnetic shear is small and normal curvature is unfavorable.

  13. Soft X-ray and cathodoluminescence measurement, optimisation and analysis at liquid nitrogen temperatures

    Science.gov (United States)

    MacRae, C. M.; Wilson, N. C.; Torpy, A.; Delle Piane, C.

    2018-01-01

    Advances in field emission gun electron microprobes have led to significant gains in the beam power density and when analysis at high resolution is required then low voltages are often selected. The resulting beam power can lead to damage and this can be minimised by cooling the sample down to cryogenic temperatures allowing sub-micrometre imaging using a variety of spectrometers. Recent advances in soft X-ray emission spectrometers (SXES) offer a spectral tool to measure both chemistry and bonding and when combined with spectral cathodoluminescence the complementary techniques enable new knowledge to be gained from both mineral and materials. Magnesium and aluminium metals have been examined at both room and liquid nitrogen temperatures by SXES and the L-emission Fermi-edge has been observed to sharpen at the lower temperatures directly confirming thermal broadening of the X-ray spectra. Gains in emission intensity and resolution have been observed in cathodoluminescence for liquid nitrogen cooled quartz grains compared to ambient temperature quartz. This has enabled subtle growth features at quartz to quartz-cement boundaries to be imaged for the first time.

  14. Observation on Surface Change of Fragile Glass: Temperature - Time Dependence Studied by X-Ray Reflectivity

    International Nuclear Information System (INIS)

    Kikkawa, Hiroyuki; Kitahara, Amane; Takahashi, Isao

    2004-01-01

    The structural change of a fragile glass surface close to the glass transition temperature Tg is studied by using X-ray reflectivity. Measurements were performed on surfaces of maltitol, which is a typical polyalcohol fragile glass with Tg = 320K. Upon both heating and cooling, we find the following features which are also noticed in silicate glass surfaces: (i) On heating, the surface morphology indicates a variation at temperatures below Tg; (ii) A drastic increase in surface roughness occurs at a temperature about 333K on heating, which is 13K higher than Tg; (iii) During the cooling of the sample, formation of a low-density surface layer (3nm at 293K) is observed. Prior to the crystallization, nm - μm sized domains were grown at the surface, which might not be reported for other glasses

  15. High temperature x-ray diffraction in transmission under controlled environment

    International Nuclear Information System (INIS)

    Margulies, L.; Kramer, M.J.; Williams, J.J.; Deters, E.M.; McCallum, R.W.; Goldman, A.I.; Haeffner, D.R.; Lang, J.C.; Kycia, S.

    1998-01-01

    A compact tube furnace has been developed for high temperature X-ray diffraction studies using high energy synchrotron radiation. The furnace design has a low absorption path in transmission yet allows for a high degree of control of the sample atmosphere and a minimal temperature gradient across the sample. The design allows for a maximum temperature of 1,500 C with a variety of atmospheres including inert, reducing, and oxidizing. Preliminary results obtained at the SRI-CAT 1-ID undulator line (60 keV) at the APS facility and the A2 24 pole wiggler line (45 keV) at CHESS on the Ti 5 Si 3 Z .5 (Z = C, N, O) system will be presented to demonstrate the feasibility of this approach

  16. Selenium semiconductor core optical fibers

    Directory of Open Access Journals (Sweden)

    G. W. Tang

    2015-02-01

    Full Text Available 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.

  17. On the structural properties and superconductivity of room-temperature chemically oxidized La2-xBaxCuO4+y (0<=x<=0.15)

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario-Franco, M.A.

    1996-01-01

    The insertion of oxygen within the structure of La2-xBaxCuO4+y (x less than or equal to 0.15), by means of room-temperature chemical oxidation, modifies both the physical and the structural features of these materials, Concerning the superconducting properties, the extra oxygen gives rise...

  18. High count-rate study of two TES x-ray microcalorimeters with different transition temperatures

    Science.gov (United States)

    Lee, Sang-Jun; Adams, Joseph S.; Bandler, Simon R.; Betancourt-Martinez, Gabriele L.; Chervenak, James A.; Eckart, Megan E.; Finkbeiner, Fred M.; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.; Smith, Stephen J.; Wassell, Edward J.

    2017-10-01

    We have developed transition-edge sensor (TES) microcalorimeter arrays with high count-rate capability and high energy resolution to carry out x-ray imaging spectroscopy observations of various astronomical sources and the Sun. We have studied the dependence of the energy resolution and throughput (fraction of processed pulses) on the count rate for such microcalorimeters with two different transition temperatures (T c). Devices with both transition temperatures were fabricated within a single microcalorimeter array directly on top of a solid substrate where the thermal conductance of the microcalorimeter is dependent upon the thermal boundary resistance between the TES sensor and the dielectric substrate beneath. Because the thermal boundary resistance is highly temperature dependent, the two types of device with different T cs had very different thermal decay times, approximately one order of magnitude different. In our earlier report, we achieved energy resolutions of 1.6 and 2.3 eV at 6 keV from lower and higher T c devices, respectively, using a standard analysis method based on optimal filtering in the low flux limit. We have now measured the same devices at elevated x-ray fluxes ranging from 50 Hz to 1000 Hz per pixel. In the high flux limit, however, the standard optimal filtering scheme nearly breaks down because of x-ray pile-up. To achieve the highest possible energy resolution for a fixed throughput, we have developed an analysis scheme based on the so-called event grade method. Using the new analysis scheme, we achieved 5.0 eV FWHM with 96% throughput for 6 keV x-rays of 1025 Hz per pixel with the higher T c (faster) device, and 5.8 eV FWHM with 97% throughput with the lower T c (slower) device at 722 Hz.

  19. Solvent vapor annealing of an insoluble molecular semiconductor

    KAUST Repository

    Amassian, Aram

    2010-01-01

    Solvent vapor annealing has been proposed as a low-cost, highly versatile, and room-temperature alternative to thermal annealing of organic semiconductors and devices. In this article, we investigate the solvent vapor annealing process of a model insoluble molecular semiconductor thin film - pentacene on SiO 2 exposed to acetone vapor - using a combination of optical reflectance and two-dimensional grazing incidence X-ray diffraction measurements performed in situ, during processing. These measurements provide valuable and new insight into the solvent vapor annealing process; they demonstrate that solvent molecules interact mainly with the surface of the film to induce a solid-solid transition without noticeable swelling, dissolving or melting of the molecular material. © 2010 The Royal Society of Chemistry.

  20. Electrical transport in La1−xCaxMnO3 thin films at low temperatures

    Indian Academy of Sciences (India)

    Electrical transport in La1−xCaxMnO3 thin films at low temperatures. S ANGAPPANE, K SETHUPATHI and G RANGARAJAN. Physics Department, Low Temperature Laboratory, Indian Institute of Technology,. Chennai 600 036, India. Abstract. We report here the low-temperature resistivity of the chemical solution deposited.

  1. Growth and characterization of insulating ferromagnetic semiconductor (Al,Fe)Sb

    Energy Technology Data Exchange (ETDEWEB)

    Anh, Le Duc, E-mail: anh@cryst.t.u-tokyo.ac.jp; Kaneko, Daiki; Tanaka, Masaaki, E-mail: masaaki@ee.t.u-tokyo.ac.jp [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hai, Pham Nam [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan)

    2015-12-07

    We investigate the crystal structure, transport, and magnetic properties of Fe-doped ferromagnetic semiconductor (Al{sub 1−x},Fe{sub x})Sb thin films up to x = 14% grown by molecular beam epitaxy. All the samples show p-type conduction at room temperature and insulating behavior at low temperature. The (Al{sub 1−x},Fe{sub x})Sb thin films with x ≤ 10% maintain the zinc blende crystal structure of the host material AlSb. The (Al{sub 1−x},Fe{sub x})Sb thin film with x = 10% shows intrinsic ferromagnetism with a Curie temperature (T{sub C}) of 40 K. In the (Al{sub 1−x},Fe{sub x})Sb thin film with x = 14%, a sudden drop of the hole mobility and T{sub C} was observed, which may be due to the microscopic phase separation. The observation of ferromagnetism in (Al,Fe)Sb paves the way to realize a spin-filtering tunnel barrier that is compatible with well-established III-V semiconductor devices.

  2. Inference of the electron temperature in ICF implosions from the hard X-ray spectral continuum

    Science.gov (United States)

    Kagan, Grigory; Landen, O. L.; Svyatsky, D.; Sio, H.; Kabadi, N. V.; Simpson, R. A.; Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Shah, R. C.; Joshi, T. R.; Hakel, P.; Weber, T. E.; Rinderknecht, H. G.; Thorn, D.; Schneider, M.; Bradley, D.; Kilkenny, J.

    2017-10-01

    The NIF Continuum Spectrometer, scheduled to be first deployed in Fall of 2017, will infer the imploded core electron temperature from the free-free continuum self-emission spectra of photons with energies of 20 to 30 keV. However, this hard X-ray radiation is emitted by the tail of the electron distribution, which likely deviates from Maxwellian and thus obscures interpretation of the data. We investigate resulting modifications to the X-ray spectra. The logarithmic slope of the spectrum from the more realistic, non-thermal tail of the electron distribution is found to decrease more rapidly at higher photon energies, as compared to the perfectly Maxwellian case. Interpreting the spectrum with assumption of Maxwellian electrons enforced is shown to give an electron temperature that is lower than the actual one. Conversely, due to its connection with the non-thermal features in the electron distribution, hard X-ray emission can provide unprecedented information about kinetic processes in the hot DT core. This work was performed under the auspices of the U.S. Dept. of Energy by the Los Alamos National Security, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396.

  3. Ultrasonic acoustic levitation for fast frame rate X-ray protein crystallography at room temperature

    Science.gov (United States)

    Tsujino, Soichiro; Tomizaki, Takashi

    2016-05-01

    Increasing the data acquisition rate of X-ray diffraction images for macromolecular crystals at room temperature at synchrotrons has the potential to significantly accelerate both structural analysis of biomolecules and structure-based drug developments. Using lysozyme model crystals, we demonstrated the rapid acquisition of X-ray diffraction datasets by combining a high frame rate pixel array detector with ultrasonic acoustic levitation of protein crystals in liquid droplets. The rapid spinning of the crystal within a levitating droplet ensured an efficient sampling of the reciprocal space. The datasets were processed with a program suite developed for serial femtosecond crystallography (SFX). The structure, which was solved by molecular replacement, was found to be identical to the structure obtained by the conventional oscillation method for up to a 1.8-Å resolution limit. In particular, the absence of protein crystal damage resulting from the acoustic levitation was carefully established. These results represent a key step towards a fully automated sample handling and measurement pipeline, which has promising prospects for a high acquisition rate and high sample efficiency for room temperature X-ray crystallography.

  4. Fabrication and electrical properties of metal-oxide semiconductor capacitors based on polycrystalline p-Cu{sub x}O and HfO{sub 2}/SiO{sub 2} high-{kappa} stack gate dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Zou Xiao [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Department of Electromachine Engineering, Jianghan University, Wuhan, 430056 (China); Fang Guojia, E-mail: gjfang@whu.edu.c [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Yuan Longyan; Liu Nishuang; Long Hao; Zhao Xingzhong [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China)

    2010-05-31

    Polycrystalline p-type Cu{sub x}O films were deposited after the growth of HfO{sub 2} dielectric on Si substrate by pulsed laser deposition, and Cu{sub x}O metal-oxide-semiconductor (MOS) capacitors with HfO{sub 2}/SiO{sub 2} stack gate dielectric were primarily fabricated and investigated. X-ray diffraction and X-ray photoelectron spectroscopy were applied to analyze crystalline structure and Cu{sup +}/Cu{sup 2+} ratios of Cu{sub x}O films respectively. SiO{sub 2} interlayer formed between the high-{kappa} dielectric and substrate was estimated by the transmission electron microscope. Results of electrical characteristic measurement indicate that the permittivity of HfO{sub 2} is about 22, and the gate leakage current density of MOS capacitor with 11.3 nm HfO{sub 2}/SiO{sub 2} stack dielectrics is {approx} 10{sup -4} A/cm{sup 2}. Results also show that the annealing in N{sub 2} can improve the quality of Cu{sub x}O/HfO{sub 2} interface and thus reduce the gate leakage density.

  5. High-Temperature Thermoelectric Properties of Perovskite-Type Pr0.9Sr0.1Mn1- x Fe x O3 (0 ≤ x ≤ 1)

    Science.gov (United States)

    Nakatsugawa, H.; Saito, M.; Okamoto, Y.

    2017-05-01

    Polycrystalline samples of Pr0.9Sr0.1Mn1- x Fe x O3 (0 ≤ x ≤ 1) have been synthesized using a conventional solid-state reaction method, and the crystal structure studied at room temperature. The magnetic susceptibility was measured from 5 K to 350 K. The electrical resistivity, Seebeck coefficient, and thermal conductivity were investigated as functions of temperature below 850 K. For all samples, the perovskite structure at room temperature exhibited orthorhombic Pbnm phase. While the Pr0.9Sr0.1MnO3 ( x = 0) sample exhibited ferromagnetic-like ground state below T C = 145 K (Curie temperature), the ferromagnetic transition temperature T C decreased with increasing x. The Seebeck coefficient of the samples with 0 ≤ x ≤ 0.8 decreased with increasing temperature because of double-exchange interaction of Mn ions. In fact, the carrier type for x = 0 changed from hole-like to electron-like behavior above 800 K. On the other hand, the samples with x ≥ 0.9 showed large positive Seebeck coefficient over the entire temperature range, indicating that the low-spin state of Fe ions dominated the electronic structure for this x range. In particular, the sample with x = 1 exhibited p-type thermoelectric properties with relatively high Seebeck coefficient, moderate electrical resistivity, and low thermal conductivity. Thus, the sample with x = 1 showed power factor of 20 μW m-1 K-2 at 850 K leading to ZT of 0.024 at this temperature, indicating that hole-doped perovskite-type iron oxide is a good candidate high-temperature thermoelectric p-type oxide.

  6. Serial femtosecond X-ray diffraction of 30S ribosomal subunit microcrystals in liquid suspension at ambient temperature using an X-ray free-electron laser

    International Nuclear Information System (INIS)

    Demirci, Hasan; Sierra, Raymond G.; Laksmono, Hartawan; Shoeman, Robert L.; Botha, Sabine; Barends, Thomas R. M.; Nass, Karol; Schlichting, Ilme; Doak, R. Bruce; Gati, Cornelius; Williams, Garth J.; Boutet, Sébastien; Messerschmidt, Marc; Jogl, Gerwald; Dahlberg, Albert E.; Gregory, Steven T.; Bogan, Michael J.

    2013-01-01

    Serial femtosecond X-ray (SFX) diffraction extending beyond 6 Å resolution using T. thermophilus 30S ribosomal subunit crystals is reported. High-resolution ribosome structures determined by X-ray crystallography have provided important insights into the mechanism of translation. Such studies have thus far relied on large ribosome crystals kept at cryogenic temperatures to reduce radiation damage. Here, the application of serial femtosecond X-ray crystallography (SFX) using an X-ray free-electron laser (XFEL) to obtain diffraction data from ribosome microcrystals in liquid suspension at ambient temperature is described. 30S ribosomal subunit microcrystals diffracted to beyond 6 Å resolution, demonstrating the feasibility of using SFX for ribosome structural studies. The ability to collect diffraction data at near-physiological temperatures promises to provide fundamental insights into the structural dynamics of the ribosome and its functional complexes

  7. Magnetic properties of Mn3-xFexSn compounds with tuneable Curie temperature by Fe content for thermomagnetic motors

    Science.gov (United States)

    Felez, Marissol R.; Coelho, Adelino A.; Gama, Sergio

    2017-12-01

    Mn3-xFexSn system (0.00 ≤ x ≤ 3.00 with Δx = 0.25) alloys present the Curie temperature (TC) or transition temperature (TT) tuneable by the Fe content. A piece-wise linear profile for TC,T as a function of x is observed in a two wide temperature ranges, between 155 K up to 759 K and 259 K up to 155 K. Their equations are TC,T = (59 ± 15) + (240 ± 7)·x and TC,T = (257 ± 1) - (206 ± 4)·x, respectively. The alloys are low cost and easy manufacturing, rare earth free, with second order magnetic transition (SOMT), and have good magnetic properties. These features suggest an immediate application of the material in cascade thermomagnetic motors that operate with a large temperature range between hot and cold sources. Furthermore, SOMT Mn-Fe-Sn system materials are also reported with advantages that could make alloys of the Mn3-xFexSn system, (0.88 ≤ x ≤ 1.20), promising candidate for magnetic refrigeration. The typical ferromagnetic behaviour is achieved only by samples with x ≥ 1. The samples with x between 0.00 and 0.75 do not show the saturation magnetization even using fields up to 13 T.

  8. Development of Large Cryogenic Semiconductor Detectors

    International Nuclear Information System (INIS)

    Mandic, Vuk

    2016-01-01

    This project aims at developing large cryogenic semiconductor detectors for applications in particle physics and more broadly. We have developed a 150 mm diameter, 43 mm thick, Si-based detector that measures ionization released in an interaction of a particle inside the silicon crystal of high purity, operated at 30 mK temperature. We demonstrated that such a detector can be used to measure recoil energies on the keV scale, and that its stable operation can be maintained indefinitely. Detectors of this type could therefore be used in the fields of direct dark matter searches, coherent neutrino scattering measurements, X-ray observations, as well as in broader applications such as homeland security.

  9. X-ray absorption spectroscopy on high-temperature superconductors and related compounds

    International Nuclear Information System (INIS)

    Pellegrin, E.J.H.A.

    1995-07-01

    The electronic structure of the cuprate high-temperature superconductors La 2-x Sr x CuO 4+δ , Tl 2 Ba 2 CaCu 2 O 8 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 has been investigated using polarization-dependent near-edge X-ray absorption fine structure spectroscopy (NEXAFS). In addition, La 2-x Sr x NiO 4+δ has been included in the actual study as an isostructural analogue to the La 2-x Sr x CuO 4+δ system. It appears that the electronic structure of these compounds corresponds to that of a p-type doped charge-transfer insulator including electron-electron interactions on the Cu(Ni) sites and a strong hybridization between Cu(Ni) and O atoms. It is concluded that the low-energy excitations in these compounds can be described on the basis of an effective one-band Mott-Hubbard model. The polarization-dependence of the above spectra gives evidence for the strong in-plane character of the intrinsic and the doped holes. The small amount and the doping-dependence of the out-of-plane character of these charge carriers rule out models for a microscopic mechanism of superconductivity based on a large amount of hole states in the corresponding Apex-O2p z /Cu3d 3z 2 -r 2 orbitals. On the other hand, the reduction of this anisotropy in the overdoped compounds together with similar findings in the macroscopic properties seems to indicate a detrimental influence of non-planar orbitals on the superconducting properties. The differences in the energetic ordering and atomic character of the states close to the Fermi level between the undoped compounds La 2 CuO 4+δ , La 2 NiO 4+δ , and NiO have been determined from the NEXAFS data. It is found that these differences can be explained by the different size of the tetragonal crystal field splitting E Z compared to that of the Hund's rule interaction J H in these systems. This gives evidence for the high-spin d 8 ground state of the undoped nickelates (i.e. J H >E Z ). It is suggested that the polarons in La 2-x Sr x NiO 4+δ can be seen as non

  10. Characterization of heterojunctions via x-ray and uv photoemission spectroscopy: energy level implications for single and mixed monolayer SAMs, cadmium selenide nanoparticle films, and organic semiconductor depositions

    Science.gov (United States)

    Graham, Amy L.

    This work has centered on the interface dipoles arising at heterojunctions between metals, semiconductor nanoparticles, self-assembled monolayers, and organic semiconductor materials. Alkanethiol self-assembled monolayers, CdSe nanocrystals, and the organic semiconductors zinc phthalocyanine (ZnPc) and Buckminster fullerene (C60) were the basis of these investigations. UV photoemission spectroscopy has proven to be an invaluable tool to observe the vacuum level shifts for these analyses while using XPS to corroborate surface structure. With a full evaluation of these surfaces, the shifts in the vacuum level, valence ionizations, and core ionizations, the impact of these interfaces, as well as their influence on the subsequent deposition of organic semiconductor layers is established. Alkanethiols possessing varying dipole moments were examined on gold and silver substrates. The viability of these alkanethiols was demonstrated to predictively adjust the work function of these metals as a function of their intrinsic dipole moments projected to surface normal, and established differences between Ag---S and Au---S bonds. The capability of the SAMs to modify the work function of gold provided an opportunity for mixed monolayers of the alkanethiols to produce a precise range of work functions by minimal adjustments of solution concentration, which were examined with a simple point dipole model. Photoemission spectroscopy offers a thorough analysis of CdSe nanoparticle films. Despite a plethora of research on these nanocrystals, there still is controversy on the magnitude of the shift in the valence band with diameter. In our research we found the majority of the valence band shift could be attributed to the interface dipole, ignored previously. Meanwhile, the valence band tethered films was obscured by the sulfur of the thiol tether. Finally, organic semiconductor layers deposited on SAMs on gold exhibited various interface dipole effects at these heterojunctions. Charge

  11. Analysis for positions of Sn atoms in epitaxial Ge{sub 1−x}Sn{sub x} film in low temperature depositions

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, Eiji, E-mail: ejkamiyama@aol.com [Dept. of Comm. Eng., Okayama Pref. Univ., 111 Kuboki, Soja, Okayama 719-1197 (Japan); Sueoka, Koji [Dept. of Comm. Eng., Okayama Pref. Univ., 111 Kuboki, Soja, Okayama 719-1197 (Japan); Nakatsuka, Osamu; Taoka, Noriyuki; Zaima, Shigeaki [Dept. of Cryst. Mat. Sci., Grad. School of Eng., Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Izunome, Koji; Kashima, Kazuhiko [Technology, GlobalWafers Japan Corp. Ltd, 6-861-5 Higashiko, Seiro, Niigata 957-0197 (Japan)

    2014-04-30

    We investigated the position of Sn atoms in Ge{sub 1−x}Sn{sub x} film grown at a low temperature by using the Extended X-ray Absorption Fine Structure (EXAFS) method. Vacancies had been expected to be introduced near the growing surface vicinity of a Sn atom and located at a split-vacancy position due to the binding nature between a Sn atom and a vacancy, which was predicted by the calculation for a bulk model in the literature. However, the EXAFS showed that almost all Sn atoms were located at the substitutional position and did not form a split-vacancy. - Highlights: • Extended X-ray Absorption Fine Structure (EXAFS) study of epitaxial Ge{sub 1−x}Snx film • EXAFS shows that almost all Sn atoms are located at substitutional positions. • The amount of vacancies introduced in low-temperature epitaxial growth is small.

  12. Temperature and X-ray Illumination Effects in Oxygen Doped La2CuO4

    Science.gov (United States)

    Campi, G.; di Castro, D.; Dell'omo, C.; Agrestini, S.; Saini, N. L.; Bianconi, A.; Bianconi, G.; Barba, L.; Colapietro, M.

    We have investigated charge ordering in an oxygen doped La2CuO4.1 crystal by high resolution x-ray diffraction using synchrotron radiation. Thanks to the high brilliance synchrotron radiation it has been possible to record a large number of weak superstructure spots due to charge ordering around the main peaks of the average structure. A study of the charge modulations with stage 3.5, and their behaviour as a function of the temperature and the intensity of the x-ray incident flux is reported. We are able to distinguish a microscopic decomposition in; 1) a stable domain, due to charges self trapped into a crystal of static ordered strings of finite length (~ 145 Å) and; 2) bubbles of `superstripes' showing, as a function of photon dose, a decreasing coherence length at T = 220 K.

  13. Ab initio study of the magnetic ordering in the semiconductors Mn{sub x}Ti{sub 1-x}O{sub 2}, Co{sub x}Ti{sub 1-x}O{sub 2} and Fe{sub x}Ti{sub 1-x}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Errico, L.A. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900, La Plata (Argentina)]. E-mail: errico@fisica.unlp.edu.ar; Weissmann, M. [Departamento de Fisica, Comision Nacional de Energia Atomica, Avda. del Libertador 8250, 1429 Buenos Aires (Argentina); Renteria, M. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900, La Plata (Argentina)

    2004-12-31

    In this work we present a set of density-functional-theory calculations in the systems Mn{sub x}Ti{sub 1-x}O{sub 2}, Fe{sub x}Ti{sub 1-x}O{sub 2}, and Co{sub x}Ti{sub 1-x}O{sub 2}. The calculations were performed with the full-potential linearized augmented plane wave method, assuming that the magnetic impurities substitutionally replace the Ti ions and considering different distributions of them in the host lattice. Our results show that the system Co{sub x}Ti{sub 1-x}O{sub 2} is ferromagnetic, while Mn{sub x}Ti{sub 1-x}O{sub 2} is antiferromagnetic. In both cases, this is independent of the distribution of the impurities in the TiO{sub 2} lattice. First results obtained in the system Fe{sub x}Ti{sub 1-x}O{sub 2} are also presented.

  14. Thin Al1?x Ga x As0.56Sb0.44 diodes with extremely weak temperature dependence of?avalanche breakdown

    OpenAIRE

    Zhou, Xinxin; Tan, Chee Hing; Zhang, Shiyong; Moreno, Manuel; Xie, Shiyu; Abdullah, Salman; Ng, Jo Shien

    2017-01-01

    When using avalanche photodiodes (APDs) in applications, temperature dependence of avalanche breakdown voltage is one of the performance parameters to be considered. Hence, novel materials developed for APDs require dedicated experimental studies. We have carried out such a study on thin Al1?x Ga x As0.56Sb0.44 p?i?n diode wafers (Ga composition from 0 to 0.15), plus measurements of avalanche gain and dark current. Based on data obtained from 77 to 297?K, the alloys Al1?x Ga x As0.56Sb0.44 ex...

  15. Measurement of core plasma temperature and rotation on W7-X made available by the x-ray imaging crystal spectrometer (XICS)

    Energy Technology Data Exchange (ETDEWEB)

    Pablant, N A; Bitter, M; Burhenn, R; Delgado-Aparicio, L; Ellis, R; Gates, D; Goto, M; Hill, K W; Langenberg, A; Lazerson, S; Mardenfeld, M; Morita, S; Neilson, G H; Oishi, T; Pedersen, T S

    2014-07-01

    A new x-ray imaging crystal spectrometer diagnostic (XICS) is currently being built for installation on W7-X. This diagnostic will contribute to the study of ion and electron thermal transport and the evolution of the radial electric field by providing high resolution temperature and rotation measurements under many plasma conditions, including ECH heated plasmas. Installation is expected before the first experimental campaign (OP1.1), making an important set of measurements available for the first W7-X plasmas. This diagnostic will also work in concert with the HR-XCS diagnostic to provide an excellent diagnostic set for core impurity transport on W7-X.

  16. Fundamentals of semiconductor devices

    CERN Document Server

    Lindmayer, Joseph

    1965-01-01

    Semiconductor properties ; semiconductor junctions or diodes ; transistor fundamentals ; inhomogeneous impurity distributions, drift or graded-base transistors ; high-frequency properties of transistors ; band structure of semiconductors ; high current densities and mechanisms of carrier transport ; transistor transient response and recombination processes ; surfaces, field-effect transistors, and composite junctions ; additional semiconductor characteristics ; additional semiconductor devices and microcircuits ; more metal, insulator, and semiconductor combinations for devices ; four-pole parameters and configuration rotation ; four-poles of combined networks and devices ; equivalent circuits ; the error function and its properties ; Fermi-Dirac statistics ; useful physical constants.

  17. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    OpenAIRE

    Oswald, Benjamin B.; Schuren, Jay C.; Pagan, Darren C.; Miller, Matthew P.

    2013-01-01

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic pro...

  18. Crystallographic and oxidation kinetic study of uranium dioxide by high temperature X-ray diffractometry

    International Nuclear Information System (INIS)

    Teixeira, S.R.

    The structural transformation of UO 2 sintered plates is studied as a function of temperature using X-ray diffractometry. The thermal expansion coefficient of UO sub(2.05) is determined and the structural transformation during isothermal oxidation is observed. The results favored a oxidation mechanism in which the rate-controling process is the diffusion of oxigen through the product layer of the new phase. Activation energies for the oxidation of UO 2 to UO sub(2.25) are found for different crystallographic planes (h,k,l). From this one can conclude that there is a preferential occupation of interstitial oxygen atoms within the UO 2 structure. (Author) [pt

  19. Room temperature stable CO x -free H2production from methanol with magnesium oxide nanophotocatalysts.

    Science.gov (United States)

    Liu, Zhengqing; Yin, Zongyou; Cox, Casandra; Bosman, Michel; Qian, Xiaofeng; Li, Na; Zhao, Hongyang; Du, Yaping; Li, Ju; Nocera, Daniel G

    2016-09-01

    Methanol, which contains 12.6 weight percent hydrogen, is a good hydrogen storage medium because it is a liquid at room temperature. However, by releasing the hydrogen, undesirable CO and/or CO 2 byproducts are formed during catalytic fuel reforming. We show that alkaline earth metal oxides, in our case MgO nanocrystals, exhibit stable photocatalytic activity for CO/CO 2 -free H 2 production from liquid methanol at room temperature. The performance of MgO nanocrystals toward methanol dehydrogenation increases with time and approaches ~320 μmol g -1 hour -1 after a 2-day photocatalytic reaction. The CO x -free H 2 production is attributed to methanol photodecomposition to formaldehyde, photocatalyzed by surface electronic states of unique monodispersed, porous MgO nanocrystals, which were synthesized with a novel facile colloidal chemical strategy. An oxygen plasma treatment allows for the removal of organic surfactants, producing MgO nanocrystals that are well dispersible in methanol.

  20. Transmission in situ and operando high temperature X-ray powder diffraction in variable gaseous environments

    Science.gov (United States)

    Schlicker, Lukas; Doran, Andrew; Schneppmüller, Peter; Gili, Albert; Czasny, Mathias; Penner, Simon; Gurlo, Aleksander

    2018-03-01

    This work describes a device for time-resolved synchrotron-based in situ and operando X-ray powder diffraction measurements at elevated temperatures under controllable gaseous environments. The respective gaseous sample environment is realized via a gas-tight capillary-in-capillary design, where the gas flow is achieved through an open-end 0.5 mm capillary located inside a 0.7 mm capillary filled with a sample powder. Thermal mass flow controllers provide appropriate gas flows and computer-controlled on-the-fly gas mixing capabilities. The capillary system is centered inside an infrared heated, proportional integral differential-controlled capillary furnace allowing access to temperatures up to 1000 °C.

  1. Liquid structure of trihexyltetradecylphosphonium chloride at ambient temperature: an X-ray scattering and simulation study.

    Science.gov (United States)

    Gontrani, Lorenzo; Russina, Olga; Celso, Fabrizio Lo; Caminiti, Ruggero; Annat, Gary; Triolo, Alessandro

    2009-07-09

    We report on an experimental and simulation study done on a representative room temperature ionic liquid, namely tetradecyltrihexylphosphonium chloride, at ambient conditions. The study was conducted using small and wide angle X-ray scattering and molecular dynamics simulations. Both approaches converge in indicating that this material is characterized by the existence of strong P-Cl interactions (with characteristic distances between 3.5 and 5.0 A) and by the occurrence of nanoscale segregation, despite the symmetric nature of the cation and similarly to other room temperature ionic liquids. A good agreement is found between the structure factor and pair correlation functions obtained from MD simulations and the corresponding experimental observables, thus strongly validating the interaction potential used in the simulations.

  2. Ge1−xSix on Ge-based n-type metal–oxide semiconductor field-effect transistors by device simulation combined with high-order stress–piezoresistive relationships

    International Nuclear Information System (INIS)

    Lee, Chang-Chun; Hsieh, Chia-Ping; Huang, Pei-Chen; Cheng, Sen-Wen; Liao, Ming-Han

    2016-01-01

    The considerably high carrier mobility of Ge makes Ge-based channels a promising candidate for enhancing the performance of next-generation devices. The n-type metal–oxide semiconductor field-effect transistor (nMOSFET) is fabricated by introducing the epitaxial growth of high-quality Ge-rich Ge 1−x Si x alloys in source/drain (S/D) regions. However, the short channel effect is rarely considered in the performance analysis of Ge-based devices. In this study, the gate-width dependence of a 20 nm Ge-based nMOSFET on electron mobility is investigated. This investigation uses simulated fabrication procedures combined with the relationship of the interaction between stress components and piezoresistive coefficients at high-order terms. Ge 1−x Si x alloys, namely, Ge 0.96 Si 0.04 , Ge 0.93 Si 0.07 , and Ge 0.86 Si 0.14 , are individually tested and embedded into the S/D region of the proposed device layout and are used in the model of stress estimation. Moreover, a 1.0 GPa tensile contact etching stop layer (CESL) is induced to explore the effect of bi-axial stress on device geometry and subsequent mobility variation. Gate widths ranging from 30 nm to 4 μm are examined. Results show a significant change in stress when the width is < 300 nm. This phenomenon becomes notable when the Si in the Ge 1−x Si x alloy is increased. The stress contours of the Ge channel confirm the high stress components induced by the Ge 0.86 Si 0.14 stressor within the device channel. Furthermore, the stresses (S yy ) of the channel in the transverse direction become tensile when CESL is introduced. Furthermore, when pure S/D Ge 1−x Si x alloys are used, a maximum mobility gain of 28.6% occurs with an ~ 70 nm gate width. A 58.4% increase in mobility gain is obtained when a 1.0 GPa CESL is loaded. However, results indicate that gate width is extended to 200 nm at this point. - Highlights: • A 20 nm Ge-based n-channel metal–oxide semiconductor field-effect transistor is investigated

  3. Temperature dependence of the minimum V/III ratio for the growth of In xGa 1-xAs

    Science.gov (United States)

    Riechert, H.; Averbeck, R.; Bernklau, D.

    1993-02-01

    We have quantitatively determined the minimum V/III ratios for the growth of In xGa 1- xAs ( x = 0, 0.1, 0.2 and 0.53) on GaAs and InP. Minimum As 4 fluxes were measured for a wide range of growth temperatures using a transition of the surface reconstruction. Their temperature dependence can be fitted very well by thetypical curve for thermally activated behavior. We find that the basic reaction kinetics of As 4 with In xGa 1- xAs are the same as with GaAs. The activation energies for As desorption from In xGa 1- xAs and GaAs are found to be similar (1.9 and 2.1 eV, respectively) but the rates of As- In xGa 1- xAs. This may be seen as evidence for a less effective dissociative reaction of As 4 with In than with Ga.

  4. Thermodynamic properties and low-temperature X-ray diffraction of vitamin B{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Knyazev, A.V., E-mail: knyazevav@gmail.com; Smirnova, N.N.; Shipilova, A.S.; Shushunov, A.N.; Gusarova, E.V; Knyazeva, S.S.

    2015-03-20

    Highlights: • Temperature dependence of heat capacity of vitamin B{sub 3} has been measured by precision adiabatic vacuum calorimetry. • The thermodynamic functions of the vitamin B{sub 3} have been determined for the range from T → 0 to 346 K. • The thermodynamic analysis of reactions involving nicotinic acid was made. • The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion. - Abstract: In the present work temperature dependence of heat capacity of vitamin B{sub 3} (nicotinic acid) has been measured for the first time in the range from 5 to 346 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the vitamin B{sub 3}, namely, the heat capacity, enthalpy H°(T) – H°(0), entropy S°(T) – S°(0) and Gibbs function G°(T) – H°(0) have been determined for the range from T → 0 to 343 K. The value of the fractal dimension D in the function of multifractal generalization of Debye’s theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. The thermodynamic parameters Δ{sub f}S°, Δ{sub f}G° at T = 298.15 K and p = 0.1 MPa have been calculated. The thermodynamic analysis of reactions involving nicotinic acid was made. The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.

  5. Substitution effect of pentavalent bismuth ions on the electronic structure and physicochemical properties of perovskite-structured Ba(In0.5Ta0.5-xBix)O3 semiconductors

    International Nuclear Information System (INIS)

    Kim, Tae Woo; Hur, Su Gil; Hwang, Seong-Ju; Park, Hyunwoong; Park, Yiseul; Choi, Wonyong; Choy, Jin-Ho

    2007-01-01

    We have investigated the substitution effect of pentavalent bismuth ions on the electronic structure and physicochemical properties of barium indium tantalate. X-ray diffraction, X-ray absorption spectroscopic, and energy dispersive spectroscopic microprobe analyses reveal that, under oxygen atmosphere of 1 atm, pentavalent Bi ions are successfully stabilized in the octahedral site of the perovskite tantalate lattice. According to diffuse reflectance UV-vis spectroscopic analysis, the Bi substitution gives rise to the significant narrowing of band gap of barium indium tantalate even at a low Bi content of ∼5%, underscoring a high efficiency of Bi substitution in the band gap engineering. Such an effective narrowing of the band gap upon the Bi substitution would be attributable to the lowering of conduction band position due to the high electronegativity of Bi V substituent. As a result of band gap engineering, the Ba(In 0.5 Ta 0.5-x Bi x )O 3 compounds with x ≥ 0.03 can generate photocurrents under visible light irradiation (λ > 420 nm). Based on the present experimental findings, it becomes clear that the substitution of highly electronegative p-block element like Bi V ion can provide a very powerful tool for tailoring the electronic structure and physicochemical properties of wide band gap semiconductors

  6. Numerical evaluation of multipass welding temperature field in API 5L X80 steel welded joints

    Directory of Open Access Journals (Sweden)

    J Nóbrega

    2016-10-01

    Full Text Available Many are the metallurgical changes suffered by materials when subjected to welding thermal cycle, promoting a considerable influence on the welded structures thermo mechanical properties. In project phase, one alternative for evaluating the welding cycle variable, would be the employment of computational methods through simulation. So, this paper presents an evaluation of the temperature field in a multipass welding of API 5L X80 steel used for oil and gas transportation, using the ABAQUS ® software, based on Finite Elements Method (FEM. During the simulation complex phenomena are considerable including: Variation in physical and mechanical properties of materials as a function of temperature, welding speed and the different mechanisms of heat exchange with the environment (convection and radiation were used. These considerations allow a more robust mathematical modeling for the welding process. An analytical heat source proposed by Goldak, to model the heat input in order to characterize the multipass welding through the GTAW (Gas Tungsten Arc Welding process on root and the SMAW (Shielded Metal Arc Welding process for the filling passes were used. So, it was possible to evaluate the effect of each welding pass on the welded joint temperature field, through the temperature peaks and cooling rates values during the welding process.

  7. Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

    Science.gov (United States)

    Lee, Jonathan A.

    2009-01-01

    In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

  8. Temperature-dependent photoemission and x-ray absorption studies of the metal-insulator transition in Bi1-xLaxNiO3

    Science.gov (United States)

    Wadati, Hiroki; Tanaka, Kiyohisa; Fujimori, Atsushi; Mizokawa, Takashi; Kumigashira, Hiroshi; Oshima, Masaharu; Ishiwata, Shintaro; Azuma, Masaki; Takano, Mikio

    2007-11-01

    Perovskite-type BiNiO3 is an insulating antiferromagnet in which a charge disproportionation occurs at the Bi site. La substitution for Bi suppresses the charge disproportionation and makes the system metallic, and for 0.05≤x≤0.1 a broad metal-insulator transition (MIT) occurs as a function of temperature. We have measured the temperature dependence of the photoemission and x-ray absorption (XAS) spectra of Bi1-xLaxNiO3 to investigate how the electronic structure changes across the MIT. From the Ni2p XAS spectra of x=0.05 , we found almost no change in the valence of Ni across the MIT. In the valence-band photoemission spectra, the Fermi cutoff disappeared for x=0.05 at a low temperature, whereas for x=0.1 and 0.2, it remained at all temperatures but the intensity at the Fermi level decreased gradually with decreasing temperature. Our experimental results suggest that the MIT is caused by the localization of holes in the O2p band and that the “insulating” phase below the MIT is indeed a mixture of insulating and metallic regions.

  9. Josephson oscillations and noise temperatures in YBa2Cu3O7-x grain-boundary junctions

    DEFF Research Database (Denmark)

    Yu, Ya. Divin; Mygind, Jesper; Pedersen, Niels Falsig

    1992-01-01

    The ac Josephson effect was studied in YBa2Cu3O7−x grain-boundary junctions (GBJ) in the temperature range from 4 to 90 K. The temperature dependence of the linewidth of millimeter-wave Josephson oscillations was measured and it is shown that the derived effective noise temperatures may be as low...... as the physical temperature in the temperature range investigated. In the millimeter-wave range, linewidths as low as 380 MHz were found at liquid-nitrogen temperatures. Applied Physics Letters is copyrighted by The American Institute of Physics....

  10. Platform development of x-ray absorption-based temperature measurements above 100-eV on the OMEGA laser

    Science.gov (United States)

    Workman, Jonathan; Keiter, P.; Tierney, T.; Tierney, H.; Belle, K.; Magelssen, G.; Peterson, R.; Fryer, C.; Comley, A.; Taylor, M.

    2007-11-01

    Experiments were performed on the OMEGA laser system at the University of Rochester to measure radiation temperature in hohlraum-heated foams. Using x-ray absorption spectroscopy in the 3-6-keV x-ray range allows temperature determination in the range of 50-200-eV. Uranium, bismuth and gold M-shell x-ray emission were used as broadband backlighters. Backlighter absorption through heated chlorinated foam and scandium tracers were used to determine temperatures. The development of this technique in the temperature range of 100-200-eV will be used for platform development of future NIF experiments. We will present time-integrated and time-resolved measurements of x-ray emission from the backlighter materials as well as absorption measurements trough the heated tracer materials. We will also present future directions in the development of this platform.

  11. Semiconductor testing method

    International Nuclear Information System (INIS)

    Brown, Stephen.

    1992-01-01

    In a method of avoiding use of nuclear radiation, eg gamma rays, X-rays, electron beams, for testing semiconductor components for resistance to hard radiation, which hard radiation causes data corruption in some memory devices and 'latch-up' in others, similar fault effects can be achieved using a xenon or other 'light' flash gun even though the penetration of light is significantly less than that of gamma rays. The method involves treating a device with gamma radiation, measuring a particular fault current at the onset of a fault event, repeating the test with light to confirm the occurrence of the fault event at the same measured fault current, and using the fault current value as a reference for future tests using light on similar devices. (author)

  12. Semiconductor/High-Tc-Superconductor Hybrid ICs

    Science.gov (United States)

    Burns, Michael J.

    1995-01-01

    Hybrid integrated circuits (ICs) containing both Si-based semiconducting and YBa(2)Cu(3)O(7-x) superconducting circuit elements on sapphire substrates developed. Help to prevent diffusion of Cu from superconductors into semiconductors. These hybrid ICs combine superconducting and semiconducting features unavailable in superconducting or semiconducting circuitry alone. For example, complementary metal oxide/semiconductor (CMOS) readout and memory devices integrated with fast-switching Josephson-junction super-conducting logic devices and zero-resistance interconnections.

  13. FY06 Annual Report: Amorphous Semiconductors for Gamma Radiation Detection (ASGRAD)

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Bradley R.; Riley, Brian J.; Crum, Jarrod V.; Sundaram, S. K.; Henager, Charles H.; Zhang, Yanwen; Shutthanandan, V.

    2007-01-01

    We describe progress in the development of new materials for portable, room-temperature, gamma-radiation detection at Pacific Northwest National Laboratory at the Hanford Site in Washington State. High Z, high resistivity, amorphous semiconductors are being designed for use as solid-state detectors at near ambient temperatures; principles of operation are analogous to single-crystal semiconducting detectors. Amorphous semiconductors have both advantages and disadvantages compared to single crystals, and this project is developing methods to mitigate technical problems and design optimized material for gamma detection. Several issues involved in the fabrication of amorphous semiconductors are described, including reaction thermodynamics and kinetics, the development of pyrolytic coating, and the synthesis of ingots. The characterization of amorphous semiconductors is described, including sectioning and polishing protocols, optical microscopy, X-ray diffraction, scanning electron microscopy, optical spectroscopy, particle-induced X-ram emission, Rutherford backscattering, and electrical testing. Then collaboration with the University of Illinois at Urbana-Champaign is discussed in the areas of Hall-effect measurements and current voltage data. Finally, we discuss the strategy for continuing the program.

  14. Characterization of gallium arsenide X-ray mesa p-i-n photodiodes at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lioliou, G. [Semiconductor Materials and Devices Laboratory, Department Engineering and Design, Sch. of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom); Meng, X.; Ng, J.S. [Department of Electronic & Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Barnett, A.M. [Semiconductor Materials and Devices Laboratory, Department Engineering and Design, Sch. of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom)

    2016-03-21

    Two GaAs mesa p{sup +}-i-n{sup +} photodiodes intended for photon counting X-ray spectroscopy, having an i layer thickness of 7 μm and diameter of 200 μm, have been characterized electrically, for their responsivity at the wavelength range 580 nm to 980 nm and one of them for its performance at detection of soft X-rays, at room temperature. Dark current and capacitance measurements as a function of applied forward and reverse bias are presented. The results show low leakage current densities, in the range of nA/cm{sup 2} at the maximum internal electric field (22 kV/cm). The unintentional doping concentration of the i layer, calculated from capacitance measurements, was found to be <10{sup 14} cm{sup −3}. Photocurrent measurements were performed under visible and near infrared light illumination for both diodes. The analysis of these measurements suggests the presence of a non-active (dead) layer (0.16 μm thickness) at the p{sup +} side top contact interface, where the photogenerated carriers do not contribute to the photocurrent, possibly due to recombination. One of the diodes, D1, was also characterized as detector for room temperature photon counting X-ray spectroscopy; the best energy resolution achieved (FWHM) at 5.9 keV was 745 eV. The noise analysis of the system, based on spectra obtained at different shaping times and applied reverse biases, showed that the dominant source of noise is the dielectric noise. It was also calculated that there was at least (165±24) eV charge trapping noise at 0 V.

  15. Development of a high temperature unicam camera and application to X-ray diffraction on powdered uranium

    International Nuclear Information System (INIS)

    Laugier, J.; Blum, P.L.; Debrenne, P.

    1964-01-01

    A high temperature commercial X-ray camera (UNICAM S150), modified in order to improve some of its performances, is adapted to the uranium powder problem. The strong uranium reactivity for oxygen and silica, the sintering and the grain growth in β-phase are avoided. X-ray photographs are thus possible even in the γ-phase. (authors) [fr

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

    International Nuclear Information System (INIS)

    Walukiewicz, W.

    1988-02-01

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

  17. Defects in semiconductor nanostructures

    Indian Academy of Sciences (India)

    Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow impurities in semiconductors. Although work in semiconductor nanostructures ...

  18. Solid spectroscopy: semiconductors

    International Nuclear Information System (INIS)

    Silva, C.E.T.G. da

    1983-01-01

    Photoemission as technique of study of the semiconductor electronic structure is shortly discussed. Homogeneous and heterogeneous semiconductors, where volume and surface electronic structure, core levels and O and H chemisorption in GaAs, Schottky barrier are treated, respectively. Amorphous semiconductors are also discussed. (L.C.) [pt

  19. Neural-based pile-up correction and ballistic deficit correction of X-ray semiconductor detectors using the Monte Carlo simulation and the Ramo theorem

    Science.gov (United States)

    Kafaee, Mahdi; Moussavi Zarandi, Ali; Taheri, Ali

    2016-03-01

    Pile-up distortion is a common problem in many nuclear radiation detection systems, especially in high count rates. It can be solved by hardware-based pile-up rejections, but there is no complete pile-up elimination in this way. Additionally, the methods can lead to poor quantitative results. Generally, time characteristics of semiconductor detector pulses are different from Scintillator detector pulses due to ballistic deficit. Hence, pulse processing-based pile-up correction in the detectors should consider this specification. In this paper, the artificial neural network pile-up correction method is applied for silicon detector piled-up pulses. For this purpose, the interaction of photons with a silicon detector is simulated by the MCNP4c code and the pulse current is calculated by Ramo's theorem. In this approach, we use a sub-Nyquist frequency sampling. The results show that the proposed method is reliable for pile-up correction and ballistic deficit in semiconductor detectors. The technique is remarkable for commercial considerations and high-speed, real-time calculations.

  20. Electrical conductivity of ion irradiated Ge{sub 20}Se{sub 80-x}Bi{sub x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Pratibha; Vashistha, Manvendra; Jain, I.P.I.P. E-mail: ipjain46@sify.com

    2003-06-01

    Amorphous chalcogenide semiconductor Ge{sub 20}Se{sub 80-x}Bi{sub x} thin films have been bombarded with 75 MeV Ni ions at room temperature. The ion irradiation induced effects on the electronic properties have been monitored by DC conductivity measurements over a temperature range of 77-476 K. The electrical conductivity and conduction activation energy changes on irradiation.

  1. Hydrogen in anion vacancies of semiconductors

    Science.gov (United States)

    Du, Mao-Hua; Singh, David

    2009-03-01

    Hydrogen typically terminates the dangling bonds around vacancies in semiconductors, thereby, partially or completely passivating the vacancies. However, it has been shown recently that hydrogen in anion vacancies of many semiconductors, such as ZnO, MgO, InN, SnO2, and GaN, takes multi-coordinated structures and acts as shallow donors, providing n-type conductivity to the materials. We study the hydrogen in the anion vacancies of a series of II-VI and III-V semiconductors using density functional calculations. The results on these materials show that, in the anion vacancies of polar II-VI semiconductors, the hydrogen is usually anionic and is coordinated with more than one cation atoms as a result of the relatively high ionicity of the host materials. The hydrogen coordination number depends on the host anion size. On the other hand, in more covalent semiconductors such as some III-V semiconductors, the single cation-H bonding configuration may become most stable. In the anion vacancies of ZnX and CdX where X represents anions, hydrogen is typically amphoteric except for oxides, in which the small anion size prohibits the formation of the cation-cation bond that is required for the acceptor configuration.

  2. Evidence of interstitial oxygen in room temperature oxidized La2-xSrxCuO4+y (0-LESS-THAN-X-LESS-THAN-0.1)

    DEFF Research Database (Denmark)

    Rial, C.; Amador, U.; Morán, E.

    1994-01-01

    of interstitial oxygen located at (1/4, y, 3/4; y almost-equal-to 1/4), as previously observed in oxygen-rich La2CuO4+y, is proposed from neutron diffraction data at different temperatures. This is supported by the excess of mass loss detected by TG for the oxidized materials relative to the starting ones......The crystal structure, superconducting properties and oxygen stoichiometry of room temperature chemically oxidized La2-xSrxCuO4+y (x = 0.05, 0.09) have been studied by means of powder neutron diffraction, magnetic susceptibility and thermogravimetric analysis. The presence in these materials...

  3. Application of the high temperature series expansions method Green’s function theory to the spinel systems: AxA’1-xB2X4

    Science.gov (United States)

    El Grini, A.; Salmi, S.; Marzouk, A.; Benzakour, N.; Bouslykhane, K.; Hourmatallah, A.

    2017-03-01

    The magnetic properties of Mn-Cu ferrites MnxCu1-xFe2O4, have been studied using the many-body Green’s function theory (GFT) and high temperature series expansion theory (HTSE). The thermal magnetization and the magnetic susceptibility are given for different values of magnetic field and dilution x. The transition temperature TC is calculated as a function of Mn concentration. The obtained results are in good agreement with experimental results. The critical exponents associated with the magnetic susceptibility (γ) and the correlation lengths (ν) have been deduced. The obtained values are comparable to those of 3D Heisenberg model.

  4. Multi-Energy Soft X-ray Measurements of the Electron Temperature Profile

    Science.gov (United States)

    Tritz, K.; Clayton, D. J.; Stutman, D.; Bell, R. E.; Diallo, A.; Leblanc, B. P.; Podesta, M.; Sabbagh, S.; NSTX Team

    2013-10-01

    A novel analysis method using a neural network algorithm has been used to reconstruct the electron temperature profile for high power NSTX discharges with fast time resolution (> 10 kHz) using multi-energy soft X-ray (ME-SXR) arrays both alone and in combination with low time-resolution space-resolved spectroscopy and a single chord of line-integrated density. This fast profile reconstruction uses the measured electron temperature profile from the 60 Hz multipoint Thomson scattering (MPTS) diagnostic to train the neural network with the high time resolution ME-SXR data. Comparisons using cross-validation between the neural network reconstruction and the measured Te profiles from MPTS show agreement within 5% over the profile radius. The accuracy of the neural network reconstruction demonstrates the ability to use ME-SXR diagnostics for high time resolution electron temperature measurements, and will be available on both EAST and NSTX-U for studies of electron heat transport as well as other general studies including impurity/particle transport, ELM profile dynamics, and MHD. Work supported by DoE grant no. DE-FG02-09ER55012.

  5. Large refrigeration capacities near room temperature in Ni{sub 2}Mn{sub 1−x}Cr{sub x}In

    Energy Technology Data Exchange (ETDEWEB)

    Brock, Jeffrey; Khan, Mahmud, E-mail: khanm2@miamioh.edu

    2017-03-01

    We report on the observation of large refrigeration capacities near room temperature in Ni{sub 2}Mn{sub 1−x}Cr{sub x}In Heusler alloys. The alloys exhibit the L2{sub 1} cubic crystal structure and undergo a second order ferromagnetic to paramagnetic phase transition. The respective Curie temperatures vary with Cr concentration from 315 K to 290 K. Net refrigerant capacities of up to 60 J/kg and 168 J/kg are observed in the alloys for applied magnetic fields of 20 kOe and 50 kOe, respectively. Due to the second order phase transition, the materials do not exhibit any hysteresis loss or other problems usually associated with materials exhibiting first order phase transitions. The observed refrigeration capacities in Ni{sub 2}Mn{sub 1−x}Cr{sub x}In are higher than those observed in many Heusler alloys with first order magnetic transitions. - Highlights: • The magnetic and magnetocaloric properties of Ni{sub 2}Mn{sub 1−x}Cr{sub x}In have been investigated. • The materials exhibit ferromagnetic transitions and associated magnetocaloric effects near room temperature. • The materials exhibit refrigeration capacities that are superior to those of Heusler alloys with first order phase transition.

  6. Temperature dependent nanoscale atomic correlations in Ir1-xPtxTe2 (x = 0.0, 0.03 and 0.04) system

    Science.gov (United States)

    Joseph, B.; Paris, E.; Mulato-Gómez, D. F.; Simonelli, L.; Bendele, M.; Maugeri, L.; Iadecola, A.; Pyon, S.; Kudo, K.; Nohara, M.; Mustre de Leon, J.; Mizokawa, T.; Saini, N. L.

    2014-09-01

    X-ray absorption near-edge structure (XANES) spectroscopy has been used to investigate the unoccupied electronic states and local geometry of Ir1-xPtxTe2(x = 0.0, 0.03 and 0.04) as a function of temperature. The Ir L3-edge absorption white line, as well as high energy XANES features due to the photoelectron multiple scatterings with near neighbours, reveal clear changes in the unoccupied 5d-electronic states and the local geometry with Pt substitution. We find an anomalous spectral weight transfer across the known first-order structural phase transition from the trigonal to monoclinic phase in IrTe2, which characterizes the reduced atomic structure symmetry below the transition temperature. No such changes with temperature are seen in the Pt substituted superconducting samples. In addition, a gradual increase of the spectral weight transfer is observed in IrTe2 with a further decrease in temperature below the transition, indicating that the low temperature phase is likely to have a symmetry lower than the monoclinic one. The results suggest that the interplay between inter-layer and intra-layer atomic correlations should have a significant role in the properties of an Ir1-xPtxTe2 system.

  7. Effect of La-CO substitution on the crystal structure and magnetic properties of low temperature sintered Sr1-xLaxFe12-xCoxO19 (x=0-0.5) ferrites

    Science.gov (United States)

    Peng, Long; Li, Lezhong; Wang, Rui; Hu, Yun; Tu, Xiaoqiang; Zhong, Xiaoxi

    2015-11-01

    The La-Co substituted Sr1-xLaxFe12-xCoxO19 (x=0-0.5) ferrites with appropriate Bi2O3 additive were prepared at a low sintering temperature of 890 °C compatible with LTCC (low temperature co-fired ceramics) systems, and the effect of La-Co substitution on their crystal structure and magnetic properties was investigated. The results show that the pure M-type phase is successfully obtained when the La-Co substitution amount x does not exceed 0.3. However, the single M-type phase structure transforms to multiphase structure with further increased x, where the α-Fe2O3 phase and La2O3 phase coexist with the M-type phase. Moreover, the saturation magnetization Ms, magnetic anisotropy field Ha, intrinsic coercivity Hci, and Curie temperature TC of the ferrites depend on the La-Co substitution amount strongly, which are suggested to be determined by the partially substitution of La3+-Co2+ ions for Sr2+-Fe3+ ions with x not higher than 0.3. It is found that the obtained Sr1-xLaxFe12-xCoxO19 (x=0.2 and 0.3) ferrites can provide improved magnetic properties (Ms>62 emu/g, Ha>1400 kA/m, and Hci>320 kA/m) as low temperature sintered M-type hexaferrites for microwave LTCC applications.

  8. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  9. Temperature dependent characterization of gallium arsenide X-ray mesa p-i-n photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Lioliou, G., E-mail: G.Lioliou@sussex.ac.uk; Barnett, A. M. [Semiconductor Materials and Devices Laboratory, Department Engineering and Design, School of Engineering and Informatics, University of Sussex, Falmer, Brighton BN1 9QT (United Kingdom); Meng, X.; Ng, J. S. [Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2016-03-28

    Electrical characterization of two GaAs p{sup +}-i-n{sup +} mesa X-ray photodiodes over the temperature range 0 °C to 120 °C together with characterization of one of the diodes as an X-ray detector over the temperature range 0 °C to 60 °C is reported as part of the development of photon counting X-ray spectroscopic systems for harsh environments. The randomly selected diodes were fully etched and unpassivated. The diodes were 200 μm in diameter and had 7 μm thick i layers. The leakage current density was found to increase from (3 ± 1) nA/cm{sup −2} at 0 °C to (24.36 ± 0.05) μA/cm{sup −2} at 120 °C for D1 and from a current density smaller than the uncertainty (0.2 ± 1.2) nA/cm{sup −2} at 0 °C to (9.39 ± 0.02) μA/cm{sup −2} at 120 °C for D2 at the maximum investigated reverse bias (15 V). The best energy resolution (FWHM at 5.9 keV) was achieved at 5 V reverse bias, at each temperature; 730 eV at 0 °C, 750 eV at 20 °C, 770 eV at 40 °C, and 840 eV at 60 °C. It was found that the parallel white noise was the main source of the photopeak broadening only when the detector operated at 60 °C, at 5 V, 10 V, and 15 V reverse bias and at long shaping times (>5 μs), whereas the sum of the dielectric noise and charge trapping noise was the dominant source of noise for all the other spectra.

  10. Influence of Concentration and Temperature on Tunneling and Rotational Dynamics of Ammonium in $Rb_{1-x}(NH_{4})_{x}$ Mixed Crystals

    CERN Document Server

    Natkaniec, I; Martínez-Sarrion, M L; Mestres, L; Herraiz, M; Smirnov, L S; Shuvalov, L A

    2001-01-01

    The Rb_{1-x}(NH_{4})_{x} mixed crystals are studied by inelastic incoherent neutron scattering using time-of-flight spectrometers in the concentration region of the x-T phase diagram 0.01\\lq x \\lq 0.66 at 5\\lq T \\lq 150 K, where dynamic and static orientational disorder phases are generally found. It is shown that at 5 K rotational tunneling levels for ammonium concentrations x=0.01,0.02 and 0.06 are similar. Additional tunneling levels are observed for x=0.16 which can be explained as the result of T-states splitting for annount of NH_{4}-NH_{4} interaction. Tunneling levels are not observed for 0.40 as the result of forming orientational glass state. The elastic incoherent structure factors for concentrations 0.01\\lq x \\lq 0.16 (dynamic orientational disordered \\alpha-phase), x=0.40 (orientational glass state) and 0.50\\lq x \\lq 0.66 (orientational ordered state) have different temperature dependences.

  11. Method of physical vapor deposition of metal oxides on semiconductors

    Science.gov (United States)

    Norton, David P.

    2001-01-01

    A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

  12. Numerical simulation of temperature field in multiple-wire submerged arc welding of X80 pipeline steel

    Science.gov (United States)

    Yan, Chunyan; Jiang, Han; Wu, Lichao; Kan, Chenxia; Yu, Wen

    2018-01-01

    Three dimensional (3D) finite element (FE) simulation was implemented to predict the temperature distribution during multiple-wire submerged arc welding (SAW) throughout the welded joint of X80 pipeline steel. A moving heat source model based on Goldak’s double-ellipsoid heat flux distribution was applied in the simulation to capture the heating effect of the welding arc. Effects of welding speed, wire spacing and leading wire current on temperature distribution were further investigated. The simulation results show that both welding speed and wire spacing have significant effects on welding temperature distribution in X80 pipeline steel welded joint.

  13. Amorphous Semiconductors: From Photocatalyst to Computer Memory

    Science.gov (United States)

    Sundararajan, Mayur

    encouraging but inconclusive. Then the method was successfully demonstrated on mesoporous TiO2SiO 2 by showing a shift in its optical bandgap. One of the special class of amorphous semiconductors is chalcogenide glasses, which exhibit high ionic conductivity even at room temperature. When metal doped chalcogenide glasses are under an electric field, they become electronically conductive. These properties are exploited in the computer memory storage application of Conductive Bridging Random Access Memory (CBRAM). CBRAM is a non-volatile memory that is a strong contender to replace conventional volatile RAMs such as DRAM, SRAM, etc. This technology has already been commercialized, but the working mechanism is still not clearly understood especially the nature of the conductive bridge filament. In this project, the CBRAM memory cells are fabricated by thermal evaporation method with Agx(GeSe 2)1-x as the solid electrolyte layer, Ag as the active electrode and Au as the inert electrode. By careful use of cyclic voltammetry, the conductive filaments were grown on the surface and the bulk of the solid electrolyte. The comparison between the two filaments revealed major differences leading to contradiction with the existing working mechanism. After compiling all the results, a modified working mechanism is proposed. SAXS is a powerful tool to characterize nanostructure of glasses. The analysis of the SAXS data to get useful information are usually performed by different programs. In this project, Irena and GIFT programs were compared by performing the analysis of the SAXS data of glass and glass ceramics samples. Irena was shown to be not suitable for the analysis of SAXS data that has a significant contribution from interparticle interactions. GIFT was demonstrated to be better suited for such analysis. Additionally, the results obtained by programs for samples with low interparticle interactions were shown to be consistent.

  14. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Directory of Open Access Journals (Sweden)

    Hiroyuki Hara

    2017-08-01

    Full Text Available The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5–7.5 × 1013 cm−3. The UTA spectral structure was due to emission from 4d–4f transitions in highly charged ions with average charge states of q = 20–40. A numerical simulation successfully reproduced the observed spectral behavior.

  15. Trapping of hydrogen atoms in X-irradiated salts at room temperature and the decay kinetics

    Science.gov (United States)

    May, C. E.; Philipp, W. H.; Marsik, S. J.

    1974-01-01

    The salts (hypophosphites, formates, a phosphite, a phosphate, and an oxalate) were X-irradiated, whereby hydrogen formed chemically by a radiolytic process becomes trapped in the solid. By room temperature vacuum extraction, the kinetics for the evolution of this trapped hydrogen was studied mass spectrometrically. All salts except two exhibited second-order kinetics. The two exceptions (NaH2PO2(H2O) and K2HPO4) showed first-order kinetics. Based on experimental results, the escape of hydrogen involves three steps: the diffusion of hydrogen atoms from the bulk to the surface, association of these atoms on the surface (rate controlling step for second-order hydrogen evolution), and the desorption of molecular hydrogen from the surface. The hydrogen does not escape if the irradiated salt is stored in air, apparently because adsorbed air molecules occupy surface sites required in the escape mechanism.

  16. Spectral evolution of soft x-ray emission from optically thin, high electron temperature platinum plasmas

    Science.gov (United States)

    Hara, Hiroyuki; Ohashi, Hayato; Li, Bowen; Dunne, Padraig; O'Sullivan, Gerry; Sasaki, Akira; Suzuki, Chihiro; Tamura, Naoki; Sakaue, Hiroyuki A.; Kato, Daiji; Murakami, Izumi; Higashiguchi, Takeshi; LHD Experiment Group

    2017-08-01

    The soft x-ray spectra of heavy element plasmas are frequently dominated by unresolved transition array (UTA) emission. We describe the spectral evolution of an intense UTA under optically thin conditions in platinum plasmas. The UTA was observed to have a peak wavelength around 4.6 nm at line-of-sight averaged electron temperatures less than 1.4 keV at electron densities of (2.5-7.5) × 1013 cm-3. The UTA spectral structure was due to emission from 4d-4f transitions in highly charged ions with average charge states of q = 20-40. A numerical simulation successfully reproduced the observed spectral behavior.

  17. Phase transitions and doping in semiconductor nanocrystals

    Science.gov (United States)

    Sahu, Ayaskanta

    impurities (or doping) allows further control over the electrical and optical properties of nanocrystals. However, while impurity doping in bulk semiconductors is now routine, doping of nanocrystals remains challenging. In particular, evidence for electronic doping, in which additional electrical carriers are introduced into the nanocrystals, has been very limited. Here, we adopt a new approach to electronic doping of nanocrystals. We utilize a partial cation exchange to introduce silver impurities into cadmium selenide (CdSe) and lead selenide (PbSe) nanocrystals. Results indicate that the silver-doped CdSe nanocrystals show a significant increase in fluorescence intensity, as compared to pure CdSe nanocrystals. We also observe a switching from n- to p-type doping in the silver-doped CdSe nanocrystals with increased silver amounts. Moreover, the silver-doping results in a change in the conductance of both PbSe and CdSe nanocrystals and the magnitude of this change depends on the amount of silver incorporated into the nanocrystals. In the bulk, silver chalcogenides (Ag2E, E=S, Se, and Te) possess a wide array of intriguing properties, including superionic conductivity. In addition, they undergo a reversible temperature-dependent phase transition which induces significant changes in their electronic and ionic properties. While most of these properties have been examined extensively in bulk, very few studies have been conducted at the nanoscale. We have recently developed a versatile synthesis that yields colloidal silver chalcogenide nanocrystals. Here, we study the size dependence of their phase-transition temperatures. We utilize differential scanning calorimetry and in-situ X-ray diffraction analyses to observe the phase transition in nanocrystal assemblies. We observe a significant deviation from the bulk alpha (low-temperature) to beta (high-temperature) phase-transition temperature when we reduce their size to a few nanometers. Hence, these nanocrystals provide great

  18. Effect of heat treatment conditions on stress corrosion cracking resistance of alloy X-750 in high temperature water

    International Nuclear Information System (INIS)

    Yonezawa, Toshio; Onimura, Kichiro; Sakamoto, Naruo; Sasaguri, Nobuya; Susukida, Hiroshi; Nakata, Hidenori.

    1984-01-01

    In order to improve the resistance of the Alloy X-750 in high temperature and high purity water, the authors investigated the influence of heat treatment condition on the stress corrosion cracking resistance of the alloy. This paper describes results of the stress corrosion cracking test and some discussion on the mechanism of the stress corrosion cracking of Alloy X-750 in deaerated high temperature water. The following results were obtained. (1) The stress corrosion cracking resistance of Alloy X-750 in deaerated high temperature water remarkably depended upon the heat treatment condition. The materials solution heat treated and aged within temperature ranges from 1065 to 1100 0 C and from 704 to 732 0 C, respectively, have a good resistance to the stress corrosion cracking in deaerated high temperature water. Especially, water cooling after the solution heat treatment gives an excellent resistance to the stress corrosion cracking in deaerated high temperature water. (2) Any correlations were not observed between the stress corrosion cracking susceptibility of Alloy X-750 in deaerated high temperature water and grain boundary chromium depleted zones, precipitate free zones and the grain boundary segregation of impurity elements and so on. It appears that there are good correlations between the stress corrosion cracking resistance of the alloy in the environment and the kinds, morphology and coherency of precipitates along the grain boundaries. (author)

  19. Effect of AlN growth temperature on trap densities of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors

    Directory of Open Access Journals (Sweden)

    Joseph J. Freedsman

    2012-06-01

    Full Text Available The trapping properties of in-situ metal-organic chemical vapor deposition (MOCVD grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructure field-effect transistors (MIS-HFETs with AlN layers grown at 600 and 700 °C has been quantitatively analyzed by frequency dependent parallel conductance technique. Both the devices exhibited two kinds of traps densities, due to AlN (DT-AlN and AlGaN layers (DT-AlGaN respectively. The MIS-HFET grown at 600 °C showed a minimum DT-AlN and DT-AlGaN of 1.1 x 1011 and 1.2 x 1010 cm-2eV-1 at energy levels (ET -0.47 and -0.36 eV. Further, the gate-lag measurements on these devices revealed less degradation ∼ ≤ 5% in drain current density (Ids-max. Meanwhile, MIS-HFET grown at 700 °C had more degradation in Ids-max ∼26 %, due to high DT-AlN and DT-AlGaN of 3.4 x 1012 and 5 x 1011 cm-2eV-1 positioned around similar ET. The results shows MIS-HFET grown at 600 °C had better device characteristics with trap densities one order of magnitude lower than MIS-HFET grown at 700 °C.

  20. Applications of X-ray absorption spectroscopy and low temperature XMCD to metalloproteins

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, J.H. [Univ. of California, Davis, CA (United States). Dept. of Applied Science]|[Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.

    1996-01-01

    The author has used the extended X-ray absorption fine structure (EXAFS) and ultra-low temperature X-ray magnetic circular dichroism (XMCD) to study the environments of the metal sites in metalloproteins. EXAFS has been used to study the Zn site in spinach carbonic anhydrase. The EXAFS, in parallel with site directed mutagenesis studies, indicate that the active site Zn is in a cys-cys-his-H{sub 2}O environment, very different from the mammalian carbonic anhydrase active site. Nitrogenase, the primary enzyme in biological nitrogen fixation, contains two complex metal clusters of unique structure. EXAFS studies at the Fe and Mo K-edges of nitrogenase solutions and crystals yielded information about the various metal-metal distances in these two clusters. The author assigned 4 Fe and 3 Mo interactions >4 {angstrom}. Single crystal Mo K-edge EXAFS then found a very long Fe-Fe distance of {approximately}5.1 {angstrom}. These distances were then used to further refine the proposed crystallographic models to their highest accuracy yet. Studies were carried further by examining nitrogenas in oxidized and reduced forms--states for which there is no crystallographic information. Small structural changes were observed and an EXAFS model was put forth that attempts to deconvolute the EXAFS distances of the two metal clusters. Nitrogenase Apo I, a genetic mutant of nitrogenase which is though to contain only one of the two different metal clusters, was also examined using EXAFS. These studies showed results consistent with current models, yet the metal clusters were very disordered. Finally, ultra-low temperature methods were used to further the development of XMCD as a technique for studying biological systems. Experiments were performed on the copper in plastocyanin. Data was collected that definitively proves that the sample surface was at 0.55 {+-} 0.05 K. This result opens the door to further study of more complex biological metal clusters.

  1. The crystal structure of benzoic acid: a redetermination with X-rays at room temperature

    International Nuclear Information System (INIS)

    Feld, R.; Lehmann, M.S.; Muir, K.W.; Speakman, J.C.

    1981-01-01

    The crystal structure of benzoic acid, C 6 H 5 CO 2 H, has been redetermined by X-ray diffraction at room temperature. Extensive neutron-diffraction measurements have also been made; by single-crystal methods at room temperature and 130 K; and, at 130 K and 5 K, by powder-profile analysis on C 6 D 5 CO 2 H. The structure consists of centrosymmetric dimers, in which two molecules are linked by a pair of hydrogen bonds between their carboxyl groups. Better precision attaches to the X-ray results. Full-matrix refinement, on 1011 independent reflexions, converged at R = 3.7%. This refinement was indeed based on a model that was formally ordered, so far as concerns all atoms except the acidic hydrogen. However the structural results implied an averaged molecule, with the C - O distances 1.258, 1.268(2)Angstroem and the C - C - O angles 118.7, 117.8(1) 0 ; and the acidic hydrogen appeared as two half atoms on the hydrogen bond, 0.9 Angstroem from each oxygen atom. These findings are most simply interpreted as due to disorder; the two configurations, A and B (of Fig. 1), occur randomly and in nearly equal proportions. Owing to difficulties inherent in the crystal texture of benzoic acid, the neutron results were less satisfactory. Large single crystals were affected by twinning. Though the powder method avoids this difficulty, the structure, further confused by modulation, is rather too complicated for profile refinement. At 5 K however, the structure may be ordered, consisting wholly of dimers in the A-configuration. (orig.)

  2. Rare earth doped III-nitride semiconductors for spintronic and optoelectronic applications (Conference Presentation)

    Science.gov (United States)

    Palai, Ratnakar

    2016-10-01

    Since last four decades the information and communication technologies are relying on the semiconductor materials. Currently a great deal of attention is being focused on adding spin degree-of-freedom into semiconductor to create a new area of solid-state electronics, called spintronics. In spintronics not only the current but also its spin state is controlled. Such materials need to be good semiconductors for easy integration in typical integrated circuits with high sensitivity to the spin orientation, especially room temperature ferromagnetism being an important desirable property. GaN is considered to be the most important semiconductor after silicon. It is widely used for the production of green, blue, UV, and white LEDs in full color displays, traffic lights, automotive lightings, and general room lighting using white LEDs. GaN-based systems also show promise for microwave and high power electronics intended for radar, satellite, wireless base stations and spintronic applications. Rare earth (Yb, Eu, Er, and Tm) doped GaN shows many interesting optoelectronic and magnetoptic properties e. g. sharp emission from UV through visible to IR, radiation hardness, and ferromagnetism. The talk will be focused on fabrication, optoelectronic (photoluminescence, cathodeluminescence, magnetic, and x-ray photoelectron spectroscopy) properties of some rare earth doped GaN and InGaN semiconductor nanostructures grown by plasma assisted molecular beam epitaxy (MBE) and future applications.

  3. InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors. Growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Lien

    2011-04-13

    host material InSb during growth. I have investigated the properties of the samples with a range of low Mn content (x<1%). Mn decreases the lattice constant as well as the degree of relaxation of (In,Mn)Sb films. Mn also distributes itself to result in two different and distinct magnetic materials: the diluted magnetic semiconductor (In,Mn)Sb and clusters of ferromagnetic MnSb. The MnSb clusters dominate only on the surface as indicated by the structural characterization. The measured values of Curie temperature T{sub c} for these two materials are found to be highly dependent on Mn concentration. For the DMS alloy (In,Mn)Sb, the Curie temperature appears to be smaller than 50 K, whereas it is greater than 300 K for the MnSb clusters. The occurrence of the high T{sub c} and and MnSb clusters on the surface suggest the possibility to obtain higher T{sub c} by adding more Mn into the host material and etching the samples down to several ten nanometers from the surface to eliminate the MnSb clusters as well as annealing at low temperature to remove the Mn interstitial sites. (orig.)

  4. Comprehensive analysis of structure and temperature, frequency and concentration-dependent dielectric properties of lithium-substituted cobalt ferrites (Li x Co1- x Fe2O4)

    Science.gov (United States)

    Anjum, Safia; Nisa, Mehru; Sabah, Aneeqa; Rafique, M. S.; Zia, Rehana

    2017-08-01

    This paper has been dedicated to the synthesis and characterization of a series of lithium-substituted cobalt ferrites Li x Co1- x Fe2O4 ( x = 0, 0.2, 0.4, 0.6, 0.8, 1). These samples have been prepared using simple ball milling machine through powder metallurgy route. The structural analysis is carried out using X-ray diffractometer and their 3D vitalization is simulated using diamond software. The frequency and temperature-dependent dielectric properties of prepared samples have been measured using inductor capacitor resistor (LCR) meter. The structural analysis confirms that all the prepared samples have inverse cubic spinel structure. It is also revealed that the crystallite size and lattice parameter decrease with the increasing concentration of lithium (Li+1) ions, it is due to the smaller ionic radii of lithium ions. The comprehensive analysis of frequency, concentration and temperature-dependent dielectric properties of prepared samples is described in this paper. It is observed that the dielectric constant and tangent loss have decreased and conductivity increased as the frequency increases. It is also revealed that the dielectric constant, tangent loss and AC conductivity increase as the concentration of lithium increases due to its lower electronegativity value. Temperature plays a vital role in enhancing the dielectric constant, tangent loss and AC conductivity because the mobility of ions increases as the temperature increases.

  5. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    Science.gov (United States)

    Oswald, Benjamin B.; Schuren, Jay C.; Pagan, Darren C.; Miller, Matthew P.

    2013-03-01

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.

  6. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    International Nuclear Information System (INIS)

    Oswald, Benjamin B.; Pagan, Darren C.; Miller, Matthew P.; Schuren, Jay C.

    2013-01-01

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 °C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.

  7. An experimental system for high temperature X-ray diffraction studies with in situ mechanical loading

    Energy Technology Data Exchange (ETDEWEB)

    Oswald, Benjamin B.; Pagan, Darren C.; Miller, Matthew P. [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853 (United States); Schuren, Jay C. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States)

    2013-03-15

    An experimental system with in situ thermomechanical loading has been developed to enable high energy synchrotron x-ray diffraction studies of crystalline materials. The system applies and maintains loads of up to 2250 N in uniaxial tension or compression at a frequency of up to 100 Hz. The furnace heats the specimen uniformly up to a maximum temperature of 1200 Degree-Sign C in a variety of atmospheres (oxidizing, inert, reducing) that, combined with in situ mechanical loading, can be used to mimic processing and operating conditions of engineering components. The loaded specimen is reoriented with respect to the incident beam of x-rays using two rotational axes to increase the number of crystal orientations interrogated. The system was used at the Cornell High Energy Synchrotron Source to conduct experiments on single crystal silicon and polycrystalline Low Solvus High Refractory nickel-based superalloy. The data from these experiments provide new insights into how stresses evolve at the crystal scale during thermomechanical loading and complement the development of high-fidelity material models.

  8. In-situ X-ray structure measurements on aerodynamically levitated high temperature liquids

    International Nuclear Information System (INIS)

    Weber, Richard; Benmore, Christopher; Mei Qiang; Wilding, Martin

    2009-01-01

    High energy, high flux X-ray sources enable new measurements of liquid and amorphous materials in extreme conditions. Aerodynamic levitation in combination with laser beam heating can be used to access high purity and non-equilibrium liquids at temperatures up to 3000 K. In this work, a small aerodynamic levitator was integrated with high energy beamline 11 ID-C at the Advanced Photon Source. Scattered X-rays were detected with a Mar345 image plate. The experiments investigated a series of binary in the CaO-Al 2 O 3 , MgO-SiO 2 , SiO 2 -Al 2 O 3 metal oxide compositions and pure SiO 2 . The results show that the liquids exhibit large changes in structure when the predominant network former is diluted. Measurements on glasses with the same compositions as the liquids suggest that significant structural rearrangement consistent with a fragile-strong transition occurs in these reluctant glass forming liquids as they vitrify.

  9. Determination of equilibrium humidities using temperature and humidity controlled X-ray diffraction (RH-XRD)

    International Nuclear Information System (INIS)

    Linnow, Kirsten; Steiger, Michael

    2007-01-01

    Confined growth of crystals in porous building materials is generally considered to be a major cause of damage. We report on the use of X-ray diffraction under controlled conditions of temperature and relative humidity (RH-XRD) for the investigation of potentially deleterious phase transition reactions. An improved procedure based on rate measurements is used for the accurate and reproducible determination of equilibrium humidities of deliquescence and hydration reactions. The deliquescence humidities of NaCl (75.4 ± 0.5% RH) and Ca(NO 3 ) 2 .4H 2 O (50.8 ± 0.7% RH) at 25 deg. C determined with this improved RH-XRD technique are in excellent agreement with available literature data. Measurement of the hydration of anhydrous Ca(NO 3 ) 2 to form Ca(NO 3 ) 2 .2H 2 O revealed an equilibrium humidity of 10.2 ± 0.3%, which is also in reasonable agreement with available data. In conclusion, dynamic X-ray diffraction measurements are an appropriate method for the accurate and precise determination of equilibrium humidities with a number of interesting future applications

  10. Study of conductivity of K41X chromia forming alloy in high temperature electrolysis environment

    International Nuclear Information System (INIS)

    Guillou, S.; Desgranges, C.; Chevalier, S.

    2013-01-01

    Alloy K41X has been proposed as interconnect material for high temperature vapor electrolysis (HTVE) devices. This chromia forming alloy (alloy K41X) was oxidized at 800 C in a thermo balance in oxidizing (synthetic air) and reducing (Ar-1%H 2 -9%H 2 O) environments for 250 h. The evolution of the contact resistance was evaluated using a dedicated device under the same conditions. There were higher oxidation kinetics rate in air than in Ar-1%H 2 -9%H 2 O but surprisingly, the corresponding area specific resistance (ASR) values were 20 times higher in Ar-1%H 2 -9%H 2 O mixture than in air. Additional tests and analyses (exposure in Ar-D 2 -H 2 O environment, GD-OES and SIMS analyses) clearly showed that the higher ASR value can be attributed to the presence of hydrogen in the oxide scale when exposed in Ar-H 2 -H 2 O mixture. In situ changes of atmosphere during ASR measurement showed the rapid kinetics for hydrogen desorption. (authors)

  11. Ion implantation for semiconductors

    International Nuclear Information System (INIS)

    Grey-Morgan, T.

    1995-01-01

    Full text: Over the past two decades, thousands of particle accelerators have been used to implant foreign atoms like boron, phosphorus and arsenic into silicon crystal wafers to produce special embedded layers for manufacturing semiconductor devices. Depending on the device required, the atomic species, the depth of implant and doping levels are the main parameters for the implantation process; the selection and parameter control is totally automated. The depth of the implant, usually less than 1 micron, is determined by the ion energy, which can be varied between 2 and 600 keV. The ion beam is extracted from a Freeman or Bernas type ion source and accelerated to 60 keV before mass analysis. For higher beam energies postacceleration is applied up to 200 keV and even higher energies can be achieved by mass selecting multiplycharged ions, but with a corresponding reduction in beam output. Depending on the device to be manufactured, doping levels can range from 10 10 to 10 15 atoms/cm 2 and are controlled by implanter beam currents in the range up to 30mA; continuous process monitoring ensures uniformity across the wafer of better than 1 % . As semiconductor devices get smaller, additional sophistication is required in the design of the implanter. The silicon wafers charge electrically during implantation and this charge must be dissipated continuously to reduce the electrical stress in the device and avoid destructive electrical breakdown. Electron flood guns produce low energy electrons (below 10 electronvolts) to neutralize positive charge buildup and implanter design must ensure minimum contamination by other isotopic species and ensure low internal sputter rates. The pace of technology in the semiconductor industry is such that implanters are being built now for 256 Megabit circuits but which are only likely to be widely available five years from now. Several specialist companies manufacture implanter systems, each costing around US$5 million, depending on the

  12. Effect of the annealing temperature on the structure and optical properties of Cd{sub 1-x} Mn{sub x}Te thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gad, S.A., E-mail: samiagad2000@yahoo.co [Solid State Physics Department, National Research Centre, El-Bohoos str., 12311 Dokki, Giza (Egypt); Boshta, M.; Abo El-Soud, A.M. [Solid State Physics Department, National Research Centre, El-Bohoos str., 12311 Dokki, Giza (Egypt); El-Gendy, Y.A. [Physics Department, Faculty of Science, Helwan, Cairo (Egypt)

    2010-11-15

    Ternary systems of Cd{sub 1-x}Mn{sub x}Te were synthesized by the direct fusion technique. Thin films of these compounds were prepared by an electron beam gun under a vacuum of 10{sup -5} Torr. Structural properties of these compounds in thin film forms were investigated by X-ray diffraction. It was found that these materials crystallize in the zinc-blende form. The optical constants (absorption coefficient and band gap) of the thin films were determined by measuring their reflectance and transmittance in the wavelength region from 500 to 2500 nm. Analysis of the optical absorption spectra revealed the existence of one direct energy gap. The energy gap increases as the Mn concentration increases and with decreasing annealing temperatures. The electrical conductivity {sigma} was measured at room temperature and was found to decrease with increasing Mn content.

  13. Ultrawide band gap amorphous oxide semiconductor, Ga–Zn–O

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Junghwan, E-mail: JH.KIM@lucid.msl.titech.ac.jp [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Miyokawa, Norihiko; Sekiya, Takumi; Ide, Keisuke [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Toda, Yoshitake [Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio [Materials and Structures Laboratory, Tokyo Institute of Technology, Mailbox R3-4, 4259 Nagatsuta, Midori-ku, Yokohama (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, Mailbox SE-6, 4259 Nagatsuta, Midori-ku, Yokohama (Japan)

    2016-09-01

    We fabricated amorphous oxide semiconductor films, a-(Ga{sub 1–x}Zn{sub x})O{sub y}, at room temperature on glass, which have widely tunable band gaps (E{sub g}) ranging from 3.47–4.12 eV. The highest electron Hall mobility ~ 7 cm{sup 2} V{sup −1} s{sup −1} was obtained for E{sub g} = ~ 3.8 eV. Ultraviolet photoemission spectroscopy revealed that the increase in E{sub g} with increasing the Ga content comes mostly from the deepening of the valence band maximum level while the conduction band minimum level remains almost unchanged. These characteristics are explained by their electronic structures. As these films can be fabricated at room temperature on plastic, this achievement extends the applications of flexible electronics to opto-electronic integrated circuits associated with deep ultraviolet region. - Highlights: • Incorporation of H/H{sub 2}O stabilizes the amorphous phase. • Ultrawide band gap (~ 3.8 eV) amorphous oxide semiconductor was fabricated. • The increase in band gap comes mostly from the deepening of the valence band maximum level. • Donor level is more likely aligned to the valence band maximum level.

  14. Influence of oxygen stoichiometry on the structure and superconducting transition temperature of YBa 2Cu 3O x

    Science.gov (United States)

    Farneth, W. E.; Bordia, R. K.; McCarron, E. M.; Crawford, M. K.; Flippen, R. B.

    1988-06-01

    A detailed study of the superconducting properties and the crystal symmetry of YBa 2Cu 3O x as a function of oxygen content (x) is presented. We correlate the oxygen content, structure and superconducting transition temperature for YBa 2Cu 3O x (6topotactic intercalation/deintercalation of oxygen. It is shown that the orthorhombic to tetragonal phase transition coincides with a loss in superconductivity for samples prepared both by quenching from high temperature and samples prepared by deoxygenation at low temperature. For the orthorhombic phase, T c monotonically decreases as x goes from 7.0 to 6.4 along with a complementary decrease in the extent of orthorhombic distortion. The decrease in T c, however, is not uniform. For quenched samples it shows a plateau for x ˜ 6.75 to 6.55 and then a rather abrupt drop around x ˜ 6.5. Comparison of our data with the literature indicates that the dependence of superconducting properties and crystal structure on the oxygen content can be a complex function of sample processing history. Samples with the same oxygen content but prepared in different ways may have x-ray powder patterns that are indistinguishable, but significantly different electrical properties.

  15. Soft x-ray scattering using FEL radiation for probing near-solid density plasmas at few electronvolt temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Toleikis, S; Faustlin, R R; Cao, L; Doppner, T; Dusterer, S; Forster, E; Fortmann, C; Glenzer, S H; Gode, S; Gregori, G; Irsig, R; Laarmann, T; Lee, H J; Li, B; Meiwes-Broer, K; Przystawik, A; Radcliffe, P; Redmer, R; Tavella, F; Thiele, R; Tiggesbaumker, J; Truong, N X; Uschmann, I; Zastrau, U; Tschentscher, T

    2009-03-03

    We report on soft x-ray scattering experiments on cryogenic hydrogen and simple metal targets. As a source of intense and ultrashort soft x-ray pulses we have used free-electron laser radiation at 92 eV photon energy from FLASH at DESY, Hamburg. X-ray pulses with energies up to 100 {micro}J and durations below 50 fs provide interaction with the target leading simultaneously to plasma formation and scattering. Experiments exploiting both of these interactions have been carried out, using the same experimental setup. Firstly, recording of soft x-ray inelastic scattering from near-solid density hydrogen plasmas at few electronvolt temperatures confirms the feasibility of this diagnostics technique. Secondly, the soft x-ray excitation of few electronvolt solid-density plasmas in simple metals could be studied by recording soft x-ray line and continuum emission integrated over emission times from fs to ns.

  16. Reduction of the Curie temperature in the multiferroic Bi5Fe1+xTi3−xO15 solid solution

    International Nuclear Information System (INIS)

    Salazar-Kuri, U; Mendoza, M E; Silva, R; Siqueiros, J M; Gervacio-Arciniega, J J

    2014-01-01

    In this work, the phase diagram of the system Bi 4 Ti 3 O 12 -BiFeO 3 in the region of the solid solution Bi 5 Fe 1+x Ti 3−x O 15 was refined. The limit of solubility was determined to be at x = 0.1. The Curie temperature (T C ) of the ferroelectric phase transition was determined by dielectric permittivity measurements at 100 kHz for the phase Bi 5 FeTi 3 O 15 as well as for the solid solution. A decrease in T C from 750 °C to 742 °C (solid solution at x = 0.1) was found. These results can be explained in terms of the perturbation of the oxygen octahedral perovskite layers resulting from the substitution of Ti 4+ by Fe 3+ ions. (paper)

  17. Some properties of Ga-As-Alsub(x)Gasub(1-x)As heterojunction grown by low temperature liquid phase epitaxy

    International Nuclear Information System (INIS)

    Yu Lisheng; Liu Hongxun; Zhang Bei; Wang Shumin

    1986-03-01

    GaAs-Alsub(x)Gasub(1-x)As heterojunction was grown by liquid phase epitaxy at low growth temperature 650-700 deg. C. The series resistance of heterojunction with DH laser structure was measured. Doping properties of Mg in GaAs and Alsub(x)Gasub(1-x)As were investigated. It is found that impurity concentration of Mg as high as 10 18 cm -3 can be doped easily. The Shubnikov-de-Haas oscillation was observed in GaAs-N Alsub(0.35)Gasub(0.65)As heterointerface. It is demonstrated that in these heterointerfaces there exists 2DEG with some contribution from 3D electron of N-AlGaAs layer. (author)

  18. Transient photoconductivity in amorphous semiconductors

    International Nuclear Information System (INIS)

    Mpawenayo, P.

    1997-07-01

    Localized states in amorphous semiconductors are divided in disorder induced shallow trap levels and dangling bonds deep states. Dangling bonds are assumed here to be either neutral or charged and their energy distribution is a single gaussian. Here, it is shown analytically that transient photocurrent in amorphous semiconductors is fully controlled by charge carriers transitions between localized states for one part and tunneling hopping carriers on the other. Localized dangling bonds deep states act as non radiative recombination centres, while hopping tunnelling is assisted by the Coulomb interaction between defects sites. The half-width of defects distribution is the disorder parameter that determines the carrier hopping time between defects sites. The macroscopic time that explains the long decay response times observed will all types of amorphous semiconductors is duly thought to be temperature dependent. Basic equations developed by Longeaud and Kleider are solved for the general case of a semiconductor after photo-generation. It turns out that the transient photoconductivity decay has two components; one with short response times from carriers trap-release transitions between shallow levels and extended states and a hopping component made of inter-dependent exponentials whose time constants span in larger ranges depending on disorder. The photoconductivity hopping component appears as an additional term to be added to photocurrents derived from existing models. The results of the present study explain and complete the power law decay derived in the multiple trapping models developed 20 years ago only in the approximation of the short response time regime. The long response time regime is described by the hopping macroscopic time. The present model is verified for all samples of amorphous semiconductors known so far. Finally, it is proposed to improved the modulated photoconductivity calculation techniques by including the long-lasting hopping dark documents

  19. Semiconductor Physical Electronics

    CERN Document Server

    Li, Sheng

    2006-01-01

    Semiconductor Physical Electronics, Second Edition, provides comprehensive coverage of fundamental semiconductor physics that is essential to an understanding of the physical and operational principles of a wide variety of semiconductor electronic and optoelectronic devices. This text presents a unified and balanced treatment of the physics, characterization, and applications of semiconductor materials and devices for physicists and material scientists who need further exposure to semiconductor and photonic devices, and for device engineers who need additional background on the underlying physical principles. This updated and revised second edition reflects advances in semicondutor technologies over the past decade, including many new semiconductor devices that have emerged and entered into the marketplace. It is suitable for graduate students in electrical engineering, materials science, physics, and chemical engineering, and as a general reference for processing and device engineers working in the semicondi...

  20. Synthesis of nanocrystalline SnO(x) (x = 1-2) thin film using a chemical bath deposition method with improved deposition time, temperature and pH.

    Science.gov (United States)

    Ebrahimiasl, Saeideh; Yunus, Wan Md Zin Wan; Kassim, Anuar; Zainal, Zulkarnain

    2011-01-01

    Nanocrystalline SnO(x) (x = 1-2) thin films were prepared on glass substrates by a simple chemical bath deposition method. Triethanolamine was used as complexing agent to decrease time and temperature of deposition and shift the pH of the solution to the noncorrosive region. The films were characterized for composition, surface morphology, structure and optical properties. X-ray diffraction analysis confirms that SnO(x) thin films consist of a polycrystalline structure with an average grain size of 36 nm. Atomic force microscopy studies show a uniform grain distribution without pinholes. The elemental composition was evaluated by energy dispersive X-ray spectroscopy. The average O/Sn atomic percentage ratio is 1.72. Band gap energy and optical transition were determined from optical absorbance data. The film was found to exhibit direct and indirect transitions in the visible spectrum with band gap values of about 3.9 and 3.7 eV, respectively. The optical transmittance in the visible region is 82%. The SnO(x) nanocrystals exhibit an ultraviolet emission band centered at 392 nm in the vicinity of the band edge, which is attributed to the well-known exciton transition in SnO(x). Photosensitivity was detected in the positive region under illumination with white light.

  1. Semiconductor Modeling Techniques

    CERN Document Server

    Xavier, Marie

    2012-01-01

    This book describes the key theoretical techniques for semiconductor research to quantitatively calculate and simulate the properties. It presents particular techniques to study novel semiconductor materials, such as 2D heterostructures, quantum wires, quantum dots and nitrogen containing III-V alloys. The book is aimed primarily at newcomers working in the field of semiconductor physics to give guidance in theory and experiment. The theoretical techniques for electronic and optoelectronic devices are explained in detail.

  2. Contacts to semiconductors

    International Nuclear Information System (INIS)

    Tove, P.A.

    1975-08-01

    Contacts to semiconductors play an important role in most semiconductor devices. These devices range from microelectronics to power components, from high-sensitivity light or radiation detectors to light-emitting of microwave-generating components. Silicon is the dominating material but compound semiconductors are increasing in importance. The following survey is an attempt to classify contact properties and the physical mechanisms involved, as well as fabrication methods and methods of investigation. The main interest is in metal-semiconductor type contacts where a few basic concepts are dealt with in some detail. (Auth.)

  3. Semiconductor Electrical Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Electrical Measurements Laboratory is a research laboratory which complements the Optical Measurements Laboratory. The laboratory provides for Hall...

  4. Semiconductor laser using multimode interference principle

    Science.gov (United States)

    Gong, Zisu; Yin, Rui; Ji, Wei; Wu, Chonghao

    2018-01-01

    Multimode interference (MMI) structure is introduced in semiconductor laser used in optical communication system to realize higher power and better temperature tolerance. Using beam propagation method (BPM), Multimode interference laser diode (MMI-LD) is designed and fabricated in InGaAsP/InP based material. As a comparison, conventional semiconductor laser using straight single-mode waveguide is also fabricated in the same wafer. With a low injection current (about 230 mA), the output power of the implemented MMI-LD is up to 2.296 mW which is about four times higher than the output power of the conventional semiconductor laser. The implemented MMI-LD exhibits stable output operating at the wavelength of 1.52 μm and better temperature tolerance when the temperature varies from 283.15 K to 293.15 K.

  5. Evidence for modified transport due to sheared E x B flows in high-temperature plasmas

    International Nuclear Information System (INIS)

    Groebner, R.J.; Burrell, K.H.; Austin, M.E.

    1994-11-01

    Sheared mass flows are generated in many fluids and are often important for the dynamics of instabilities in these fluids. Similarly, large values of the E x B velocity have been observed in magnetic confinement machines and there is theoretical and experimental evidence that sufficiently large shear in this velocity may stabilize important instabilities. Two examples of this phenomenon have been observed in the DIII-D tokamak. In the first example, sufficient heating power can lead to the L-H transition, a rapid improvement in confinement in the boundary layer of the plasma. For discharges with heating power close to the threshold required to get the transition, changes in the edge radial electric field are observed to occur prior to the transition itself. In the second example, certain classes of discharges with toroidal momentum input from neutral beam injection exhibit a further improvement of confinement in the plasma core leading to a regime called the VH-mode. In both examples, the region of improved confinement is characterized by an increase of shear in the radial electric field E r , reduced levels of turbulence and increases in gradients of temperatures and densities. These observations are consistent with the hypothesis that the improved confinement is caused by an increase in shear of the E x B velocity which leads to a reduction of turbulence. For the VH-mode, the dominant term controlling E r is the toroidal rotation v φ , indicating that the E r profile is controlled by the source and transport of toroidal momentum

  6. X-ray absorption near edge spectroscopy at the Mn K-edge in highly homogeneous GaMnN diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A. [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Martinez-Criado, G.; Salome, M.; Susini, J. [ESRF, Polygone Scientifique Louis Neel, 6 rue Jules Horowitz, 38000 Grenoble (France); Olguin, D. [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D.F. (Mexico); Dhar, S.; Ploog, K. [Paul Drude Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

    2006-06-15

    We have studied by X-ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga{sub 1-x}Mn{sub x}N (0.06<x<0.14) thin epilayers grown by molecular beam epitaxy on [0001] SiC substrates. The measurements were performed in fluorescence mode around the Ga and Mn K-edges. In this report, we focus our attention to the X-ray absorption near edge spectroscopy (XANES) results. The comparison of the XANES spectra corresponding to the Ga and Mn edges indicates that Mn is substitutional to Ga in all samples studied. The XANES spectra measured at the Mn absorption edge shows in the near-edge region a double peak and a shoulder below the absorption edge and the main absorption peak after the edge, separated around 15 eV above the pre-edge structure. We have compared the position of the edge with that of MnO (Mn{sup 2+}) and Mn{sub 2}O{sub 3} (Mn{sup 3+}). All samples studied present the same Mn oxidation state, 2{sup +}. In order to interprete the near-edge structure, we have performed ab initio calculations with a 2 x 2 x 1supercell ({proportional_to}6% Mn) using the full potential linear augmented plane wave method as implemented in the Wien2k code. The calculations show the appearance of Mn anti-bonding t{sub 2g} bands, which are responsible for the pre-edge absorption. The shoulder and main absorption peaks are due to transitions from the valence band 1s-states of Mn to the p-contributions of the conduction bands. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Method for fabricating semiconductor devices

    Science.gov (United States)

    Kaiser, William J. (Inventor); Grunthaner, Frank J. (Inventor); Hecht, Michael H. (Inventor); Bell, Lloyd D. (Inventor)

    1995-01-01

    A process for fabricating gold/gallium arsenide structures, in situ, on molecular beam epitaxially grown gallium arsenide. The resulting interface proves to be Ohmic, an unexpected result which is interpreted in terms of increased electrode interdiffusion. More importantly, the present invention surprisingly permits the fabrication of Ohmic contacts in a III-V semiconductor material at room temperature. Although it may be desireable to heat the Ohmic contact to a temperature of, for example, 200 degrees Centigrade if one wishes to further decrease the resistance of the contact, such low temperature annealing is much less likely to have any deleterious affect on the underlying substrate. The use of the term in situ herein, contemplates continuously maintaining an ultra-high vacuum, that is a vacuum which is at least 10.sup.-8 Torr, until after the metallization has been completed. An alternative embodiment of the present invention comprising an additional step, namely the termination of the gallium arsenide by a two monolayer thickness of epitaxial aluminum arsenide as a diffusion barrier, enables the recovery of Schottky barrier behavior, namely a rectified I-V characteristic. The present invention provides a significant breakthrough in the fabrication of III-V semiconductor devices wherein excellent Ohmic contact and Schottky barrier interfaces to such devices can be achieved simply and inexpensively and without requiring the high temperature processing of the prior art and also without requiring the use of exotic high temperature refractory materials as substitutes for those preferred contact metals such as gold, aluminum and the like.

  8. Effect of Finish Rolling Temperature on the Microstructure and Tensile Properties of Nb–Ti Microalloyed X90 Pipeline Steel

    Directory of Open Access Journals (Sweden)

    Bin Guo

    2016-12-01

    Full Text Available The relationship between microstructure and tensile properties of an Nb–Ti microalloyed X90 pipeline steel was studied as a function of finish rolling temperature using a Gleeble 3500 simulator, an optical and scanning electron microscope, electron back scattered diffraction (EBSD, a transmission electron microscope (TEM and X-ray diffraction. The results indicate that the microstructure is primarily composed of non-equiaxed ferrite with martensite/austenite (M/A constituent dispersed at grain boundaries for the specimens with different finish rolling temperatures. With a decrease in the finish rolling temperature, the yield strength increases, following a significant increase in the grain refinement strengthening contribution and dislocation strengthening contribution, although the precipitation strengthening contribution decreases. The increasing yield ratio (YR shows that the strain hardening capacity declines as a result of the microstructure evolution when decreasing the finish rolling temperature.

  9. Measurement of irradiation temperature and study of local overheating of claddings of austenitic steel, by X-ray diffraction

    International Nuclear Information System (INIS)

    Rousset, P.; Cadalbert, R.

    1983-01-01

    The development of fuel elements of fast neutron reactors makes the CEA effectuate numerous irradiations of steel in the RAPSODIE and PHENIX reactor. Detailed knowledge and control of the irradiation temperature pose an important problem both for experimental claddings and for fuel claddings used in these reactors. The authors utilize the relation that exists between the irradiation temperature and the failure density present in the austenitic steels, for measuring irradiation temperatures and for studying local overheating of the claddings by means of X-ray diffraction. In effect, the line widths of X-ray diffraction is a measure of the degree of lattice distortion. Quantitative analysis of this failure density enables to study the thermal profiles of the claddings in the assembly; to study local overheating (hot spots); and to measure the irradiation temperature in capsules. (Auth.)

  10. Neutron diffraction study of zoisite at 15 K and X-ray study at room temperature

    International Nuclear Information System (INIS)

    Smith, J.V.; Pluth, J.J.; Richardson, J.W. Jr.; Kvick, A.

    1987-01-01

    The crystal structure of zoisite, Ca 2 Al 3 Si 3 O 12 OH; Pnma, Z=4, was determined for crystals of the tanzanite gem variety at 15 K (neutron diffraction, a = 16.218(3), b = 5.5406(14), c = 10.033(3) A) and room temperature, ≅ 295 K (X-ray diffraction, a = 16.1909(15), b = 5.5466(5), c = 10.0323(6) A). Only one proton position was located with positional coordinates 0.2690(1), 0.25, 0.9753(2) and population factor 0.98(1) at 15 K. It forms a hydroxyl group with O(10) at 0.986(2) A and a hydrogen bond with O(4) at 1.757(2) A. There is no diffraction evidence of a second proton position to explain the weak infrared absorption at 2160 cm -1 at room temperature for both natural and synthetic zoisites; however, the detection level of 0.01 atom at the 2 σ level might be insufficient. The possibility of hydrogen bonding to two O(2) at 2.96 A from O(10) is discussed. Because the displacement ellipsoid of the proton at 15 K is oblate and smaller than the ones in staurolite, it is concluded that there is only a single center of motion of the proton. The wide ranges of Ca-O, Al-O and Si-O distances are consistent with valence balancing in which short distances go to oxygen atoms with low values of formal bond strength. The displacement ellipsoids at 295 K can be explained qualitatively by anisotropic thermal motion constrained by the bonding to the nearest neighbors. There is an additional overall anisotropy at 15 K which is unexplained. However, values of B iso are consistent with zero-point motion, and there is no evidence for positional disorder. (orig.)

  11. Study of temperature dependent local structure by polarized Cu K-edge EXAFS measurements on La sub 2 sub - sub x Sr sub x CuO sub 4 (x=0.105, 0.13, 0.20)

    CERN Document Server

    Saini, N L; Bianconi, A; Oyanagi, H; Ito, T; Oka, K

    2003-01-01

    We have studied temperature dependent local structure of superconducting La sub 2 sub - sub x Sr sub x CuO sub 4 (0.105, 0.13, 0.20) single crystals by Cu K-edge extended x-ray absorption fine structure (EXAFS) measurements with polarization parallel to the in-plane Cu-O bonds. We find that, while underdoped crystals (x=0.105, 0.13) show anomalous temperature dependence, similar to the case of optimally doped system (x=0.15), overdoped crystal (x=0.20) does not reveal such anomaly. Correlated Debye-Waller factor (DWF) of the Cu-O bonds (distance broadening) has been used as an order parameter to determine characteristic local displacements in the CuO sub 2 plane. The amplitude of temperature dependent step-like increase in the DWF at low temperature decreases with increasing doping. It has been discussed that decreasing electron-lattice interaction with increasing doping, shown by angle resolved photoemission measurements, is closely related to the evolving anomalous local CuO sub 2 distortion and charge inho...

  12. Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks

    International Nuclear Information System (INIS)

    Sesnic, S.; Diesso, M.; Hill, K.; Holland, A.; Pohl, F.

    1988-01-01

    Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron temperature, the Be filter thickness, and the electronic parameters of the acquisition system are known. PG 1810,1812 ID 131801CON N X-ray diagnostics TT Profile correction to electron temperature and enhancement factor in soft-x-ray pulse-height-analysis measurements in tokamaks AU S. Sesnic, M. Diesso, K. Hill, and A. Holland LO Princeton University, Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 AU F. Pohl LO Max-Planck Institut fuer Plasmaphysik, 8046-Garching, Federal Republic of Germany SD (Presented on 16 March 1988) AB Because soft-x-ray pulse-height-analysis spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. The correction factors for the electron temperature and the enhancement factor as a function of the temperature and density profile parameters and the energy are obtained. The spectrum distortion due to pulse pileup effects is also evaluated. A set of curves is given from which the distortion of the spectrum can be obtained if the electron tempe

  13. Activation parameters of low-temperatures peak of internal friction in YBa2Cu3O7-x ceramics

    International Nuclear Information System (INIS)

    Natsik, V.D.; Pal'-Val', P.P.; Ehngert, J.; Kaufmann, Kh.J.

    1989-01-01

    Temperature dependences of velocity and absorption coefficient of longitudinal ultrasound with two frequencies f 1 =1x25x10 5 s -1 and F 2 =75x10 5 s -1 are measured between 6 and 300 K. Hysteresis of sound velocity under thermal cycling and series of absorption peaks are recorded. The sound frequency-dependent behaviour of the peak localized in the hysteresis region is analysed. An assumption is made on the relation of this peak to a thermally asctivated structural process, and the activation parameters of such a process are estimated

  14. Property of a CZT semiconductor detector for radionuclide identification

    International Nuclear Information System (INIS)

    Chun, Sung-Dae; Park, Se-Hwan; Ha, Jang Ho; Kang, Sang Mook; Lee, Dong Hoon; Kim, Yong Kyun; Cho, Yun Ho; Kim, Jong Kyung; Hong, Duk-Geun

    2008-01-01

    Compound semiconductors of high Z value material have been studied intensively for X-ray and γ-ray spectroscopy at room temperature. CdZnTe has wide band gap energy as 1.6 eV and can provide high quantum efficiency with reasonably good energy resolution at room temperature. This study is aimed at determining radionuclide analysis ability by measuring energy resolution of CZT detector which will be applied at nuclear material identification purpose. For experiment we used a CZT detector (5 x 5 x 5 mm 3 ) which is manufactured by eV Products. We have performed our measurement at varied temperatures similar to the outdoor environment for the investigation about temperature dependence of energy resolution and peak centroid fluctuation of CZT detector by using gas cooling and Peltier cooling methods. In order to test radionuclide identification we used various radionuclide samples; plutonium, europium and other standard sources. Pulse height spectra were obtained by standard electronics which consists of a preamplifier, a shaping amplifier, and a multi-channel analyzer. (author)

  15. Accurate solid solution range of BiMnxFe3-xO6 and low temperature magnetism

    Science.gov (United States)

    Jiang, Pengfei; Yue, Mufei; Cong, Rihong; Gao, Wenliang; Yang, Tao

    2017-11-01

    BiMnxFe3-xO6 (x = 1) represents a new type of oxide structure containing Bi3+ and competing magnetic super-exchanges. In literature, multiple magnetic states were realized at low temperatures in BiMnFe2O6, and the hypothetical parent compounds (BiMn3O6, BiFe3O6) were predicted to be different in magnetism. Herein, we performed a careful study on the syntheses of BiMnxFe3-xO6 at ambient pressure, and the solid solution range was determined to be 0.9 ≤ x ≤ 1.3 by Rietveld refinements on high-quality powder X-ray diffraction data. Due to the very similar cationic size of Mn3+ and Fe3+, and possibly the structural rigidity, there was no significant structure change in the whole range of solid solution. The magnetic behavior of BiMnxFe3-xO6 (x = 1.2, 1.22, 1.26, 1.28 and 1.3) was generally similar to BiMnFe2O6, while the relative higher concentration of Mn3+ led to the decreasing of the antiferromagnetic ordering temperature.

  16. Anisotropy of the galaxy cluster X-ray luminosity-temperature relation

    Science.gov (United States)

    Migkas, Konstantinos; Reiprich, Thomas H.

    2018-03-01

    We introduce a new test to study the cosmological principle with galaxy clusters. Galaxy clusters exhibit a tight correlation between the luminosity and temperature of the X-ray-emitting intracluster medium. While the luminosity measurement depends on cosmological parameters through the luminosity distance, the temperature determination is cosmology-independent. We exploit this property to test the isotropy of the luminosity distance over the full extragalactic sky, through the normalization a of the LX-T scaling relation and the cosmological parameters Ωm and H0. To this end, we use two almost independent galaxy cluster samples: the ASCA Cluster Catalog (ACC) and the XMM Cluster Survey (XCS-DR1). Interestingly enough, these two samples appear to have the same pattern for a with respect to the Galactic longitude. More specifically, we identify one sky region within l (-15°, 90°) (Group A) that shares very different best-fit values for the normalization of the LX-T relation for both ACC and XCS-DR1 samples. We use the Bootstrap and Jackknife methods to assess the statistical significance of these results. We find the deviation of Group A, compared to the rest of the sky in terms of a, to be 2.7σ for ACC and 3.1σ for XCS-DR1. This tension is not significantly relieved after excluding possible outliers and is not attributed to different redshift (z), temperature (T), or distributions of observable uncertainties. Moreover, a redshift conversion to the cosmic microwave background (CMB) frame does not have an important impact on our results. Using also the HIFLUGCS sample, we show that a possible excess of cool-core clusters in this region, is not able to explain the obtained deviations. Furthermore, we tested for a dependence of the results on supercluster environment, where the fraction of disturbed clusters might be enhanced, possibly affecting the LX-T relation. We indeed find a trend in the XCS-DR1 sample for supercluster members to be underluminous compared to

  17. Recent advances in Tl Br, Cd Te and CdZnTe semiconductor radiation detectors: a review

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Icimone B. [Universidade Bandeirante (UNIBAN), Sao Paulo, SP (Brazil)

    2011-07-01

    The success in the development of radiation spectrometers operating at room temperature is based on many years of effort on the part of large numbers of workers around the world. These individuals have contributed to the understanding of the fundamental materials issues associated with the growth of semiconductors for this application, the development of device fabrication and processing technology, and advances in low noise electronics and pulse processing. Progress in this field continues at an accelerated pace, as in evidenced by the improvements in detector performance and by the growing number of commercial products. Thus, the last years have been seen continued effort in the development of room temperature compound semiconductors devices. High-Z compound semiconductor detectors has been explored for high energy resolution, high detection efficiency and are of low cost. Compound semiconductors detectors are well suited for addressing needs of demanding applications such as bore hole logging where high operating temperature are encountered. In this work recent developments in semiconductors detectors were reviewed. This review concentrated on thallium bromide (TlBr), cadmium zinc telluride (CdZnTe) and cadmium telluride (CdTe) crystals detectors. TlBr has higher stopping power compared to common semiconductor materials because it has the higher photoelectric and total attenuation coefficients over wide energy range from 100 keV to 1 MeV. CdTe and CdZnTe detectors have several attractive features for detecting X-ray and low energy gamma ray. Their relatively large band gaps lead to a relatively low leakage current and offer an excellent energy resolution at room temperature. A literature survey and bibliography was also included. (author)

  18. Formation of color centers in ammonium perchlorate by x-ray irradiation at room temperature

    International Nuclear Information System (INIS)

    Levy, P.W.; Goldberg, M.; Herley, P.J.

    1978-01-01

    Radiation induced color center formation has been studied in single crystal ammonium perchlorate. Large, high purity, water clear single crystals were uniformly irradiated normal to the c or 001 face with filtered 60 kV x-rays at room temperature. The radiation induced coloring, measured through the c face, can be resolved into four Gaussian shaped absorption bands whose peak energies and full widths are 6.72, 1.62; 4.81, 0.88; 3.91, 1.12; and 2.47, 0.72 eV. The 6.72 band lies at the 'band-gap' or 'edge' and could represent either a shift in the edge or the superposition of one or more bands on the edge. The other bands are, most likely, defect related color centers or trapped molecular species. The coloring contains a small unstable component, at most 10%, consisting of these bands and an additional one at 5.78 eV, width 0.35 eV, which has a negligible effect on coloring kinetic determinations. The color-centers vs. dose curves for the bands at 6.72 and 2.47 eV are linear. The curves for the 4.81 and 3.91 eV bands contain a linear and one saturating exponential component. The linear components appear to be related to a linear dose induced process observed in the thermal decomposition of irradiated ammonium perchlorate. (author)

  19. Creep strength of hastelloy X TIG-welded cylinder under internal pressure at elevated temperature

    International Nuclear Information System (INIS)

    Udoguchi, Teruyoshi; Indo, Hirosato; Isomura, Kazuyuki; Kobatake, Kiyokazu; Nakanishi, Tsuneo.

    1981-01-01

    Creep tests on circumferentially TIG-welded Hastelloy x cylinders were carried out under internal pressure for the investigation of structural behavior of welded components in high temperature environment. The creep rupture strength of TIG-welded cylinders was much lower than that of non-welded cylinders, while such reduction was not found in uniaxial creep tests on TIG-welded bars. It was deduced that the reduction was due to the low ductility (ranging from 1 to 5%) of the weld metal to which enhanced creep was induced by the adjacent base metal whose creep strain rate was much higher than that of the weld metal. Therefore, uniaxial creep tests on bar specimens is not sufficient for proper assessment of the creep rupture strength of welded components. Both creep strain rate and creep ductility should be concerned for the assessment. Creep tests by using components such as cylinder under internal pressure are recommendable for the confirmation of creep strength of welded structures and components. (author)

  20. Lead iodide X-ray and gamma-ray spectrometers for room and high temperature operation

    Energy Technology Data Exchange (ETDEWEB)

    Hermon, H.; James, R.B.; Cross, E. [and others

    1997-02-01

    In this study, we report on the results of the investigation of lead iodide material properties. The effectiveness of zone refining purification methods on the material purity is determined by ICP-MS and ICP-OES and correlated to the electrical and physical material properties. We show that this zone refining method is very efficient in removing impurities from lead iodide and we also determine the segregation coefficient for some of these impurities. Triple axis x- ray diffraction (TAD) analysis has been used to determine the crystalline perfection of the lead iodide after applying various cutting, etching, and fabrication methods. The soft lead iodide crystal was found to be damaged when cleaved by a razor blade, but by using a diamond wheel saw, followed by etching, the crystallinity of the material was improved, as observed by TAD. Low temperature photoluminescence also indicates an improvement in the material properties of the purified lead iodide. Electrical properties of lead iodide such as carrier mobility, were calculated based on carrier- phonon scattering. The results for the electrical properties were in good agreement with the experimental data.

  1. Room temperature photoluminescence from In{sub x}Al{sub (1−x)}N films deposited by plasma-assisted molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Kong, W., E-mail: wei.kong@duke.edu; Jiao, W. Y.; Kim, T. H.; Brown, A. S. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Mohanta, A. [Oak Ridge Institute for Science and Education, Research Participation Program, U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC), Redstone Arsenal, Alabama 35898 (United States); Roberts, A. T. [Charles Bowden Research Lab, Army Aviation and Missile RD and E Center, Redstone Arsenal, Alabama 35898 (United States); Fournelle, J. [Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706 (United States); Losurdo, M. [Plasma Chemistry Research Center-CNR, via Orabona, 4-70126 Bari (Italy); Everitt, H. O. [Charles Bowden Research Lab, Army Aviation and Missile RD and E Center, Redstone Arsenal, Alabama 35898 (United States); Department of Physics, Duke University, Durham, North Carolina 27708 (United States)

    2014-09-29

    InAlN films deposited by plasma-assisted molecular beam epitaxy exhibited a lateral composition modulation characterized by 10–12 nm diameter, honeycomb-shaped, columnar domains with Al-rich cores and In-rich boundaries. To ascertain the effect of this microstructure on its optical properties, room temperature absorption and photoluminescence characteristics of In{sub x}Al{sub (1−x)}N were comparatively investigated for indium compositions ranging from x = 0.092 to 0.235, including x = 0.166 lattice matched to GaN. The Stokes shift of the emission was significantly greater than reported for films grown by metalorganic chemical vapor deposition, possibly due to the phase separation in these nanocolumnar domains. The room temperature photoluminescence also provided evidence of carrier transfer from the InAlN film to the GaN template.

  2. X-ray diffraction study of a semiconductor/electrolyte interface: n-GaAs(001)/H2SO4(:Cu)

    DEFF Research Database (Denmark)

    Zegenhagen, J.; Kazimirov, A.; Scherb, G.

    1996-01-01

    We used X-ray diffraction to investigate the n-GaAs(001)/0.5M H2SO4 interface in-situ under potential control in a three-electrode, thin-layer electrochemical cell. The intensity of crystal truncation rods as a function of the electrode potential was recorded. A pronounced increase in surface rou...

  3. Foreword: Focus on Superconductivity in Semiconductors

    Directory of Open Access Journals (Sweden)

    Yoshihiko Takano

    2008-01-01

    Full Text Available Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm−3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.This focus issue features a variety of topics on superconductivity in semiconductors selected from the 2nd International Workshop on Superconductivity in Diamond and Related Materials (IWSDRM2008, which was held at the National Institute for Materials Science (NIMS, Tsukuba, Japan in July 2008. The 1st workshop was held in 2005 and was published as a special issue in Science and Technology of Advanced Materials (STAM in 2006 (Takano 2006 Sci. Technol. Adv. Mater. 7 S1.The selection of papers describe many important experimental and theoretical studies on superconductivity in semiconductors. Topics on boron-doped diamond include isotope effects (Ekimov et al and the detailed structure of boron sites, and the relation between superconductivity and disorder induced by boron doping. Regarding other semiconductors, the superconducting properties of silicon and SiC (Kriener et al, Muranaka et al and Yanase et al are discussed, and In2O3 (Makise et al is presented as a new superconducting semiconductor. Iron-based superconductors are presented as a new series of high

  4. Low temperature synthesis of Ba1–xSrxSnO3 (x= 0–1) from molten ...

    Indian Academy of Sciences (India)

    ... Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 33; Issue 1. Low temperature synthesis of Ba1–SrSnO3 ( = 0–1) from molten alkali hydroxide flux. B Ramdas R Vijayaraghavan. Electrical Properties Volume 33 Issue 1 February 2010 pp 75- ...

  5. Low temperature synthesis of Ba1–xSrxSnO3 (x = 0–1) from molten ...

    Indian Academy of Sciences (India)

    Administrator

    The morphology of the particles of BaSnO3 and SrSnO3 is spherical and rod shaped, respectively. Effect of soaking periods on the grain growth is observed clearly in SrSnO3. Ba0⋅5Sr0⋅5SnO3 (BSS5) crystallizes in flake like morphology. Keywords. Perovskite; stannates; molten salt synthesis; X-ray diffraction; scanning ...

  6. Semiconductor Research Experimental Techniques

    CERN Document Server

    Balkan, Naci

    2012-01-01

    The book describes the fundamentals, latest developments and use of key experimental techniques for semiconductor research. It explains the application potential of various analytical methods and discusses the opportunities to apply particular analytical techniques to study novel semiconductor compounds, such as dilute nitride alloys. The emphasis is on the technique rather than on the particular system studied.

  7. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias

    2013-01-01

    In this proceedings we describe our recent results on semiconductor nonlinear optics, investigated using single-cycle THz pulses. We demonstrate the nonlinear absorption and self-phase modulation of strong-field THz pulses in doped semiconductors, using n-GaAs as a model system. The THz nonlinear...

  8. Semiconductors data handbook

    CERN Document Server

    Madelung, Otfried

    2004-01-01

    This volume Semiconductors: Data Handbook contains frequently used data from the corresponding larger Landolt-Börnstein handbooks in a low price book for the individual scientist working in the laboratory. The Handbook contain important information about a large number of semiconductors

  9. Semiconductor radiation detection systems

    CERN Document Server

    2010-01-01

    Covers research in semiconductor detector and integrated circuit design in the context of medical imaging using ionizing radiation. This book explores other applications of semiconductor radiation detection systems in security applications such as luggage scanning, dirty bomb detection and border control.

  10. Soft x-ray continuum radiation transmitted through metallic filters: An analytical approach to fast electron temperature measurements

    International Nuclear Information System (INIS)

    Delgado-Aparicio, L.; Hill, K.; Bitter, M.; Tritz, K.; Kramer, T.; Stutman, D.; Finkenthal, M.

    2010-01-01

    A new set of analytic formulas describes the transmission of soft x-ray continuum radiation through a metallic foil for its application to fast electron temperature measurements in fusion plasmas. This novel approach shows good agreement with numerical calculations over a wide range of plasma temperatures in contrast with the solutions obtained when using a transmission approximated by a single-Heaviside function [S. von Goeler et al., Rev. Sci. Instrum. 70, 599 (1999)]. The new analytic formulas can improve the interpretation of the experimental results and thus contribute in obtaining fast temperature measurements in between intermittent Thomson scattering data.

  11. Efficient and stable CH3NH3PbI3-x(SCN)x planar perovskite solar cells fabricated in ambient air with low-temperature process

    Science.gov (United States)

    Zhang, Zongbao; Zhou, Yang; Cai, Yangyang; Liu, Hui; Qin, Qiqi; Lu, Xubing; Gao, Xingsen; Shui, Lingling; Wu, Sujuan; Liu, Jun-Ming

    2018-02-01

    Planar perovskite solar cells (PSCs) based on CH3NH3PbI3-x(SCN)x (SCN: thiocyanate) active layer and low-temperature processed TiO2 films are fabricated by a sequential two-step method in ambient air. Here, alkali thiocyanates (NaSCN, KSCN) are added into Pb(SCN)2 precursor to improve the microstructure of CH3NH3PbI3-x(SCN)x perovskite layers and performance of the as-prepared PSCs. At the optimum concentrations of alkali thiocyanates as additives, the as-prepared NaSCN-modified and KSCN-modified PSCs demonstrate the efficiencies of 16.59% and 15.63% respectively, being much higher than 12.73% of the reference PSCs without additives. This improvement is primarily ascribed to the enhanced electron transport, reduced recombination rates and much improved microstructures with large grain size and low defect density at grain boundaries. Importantly, it is revealed that the modified PSCs at the optimized concentrations of alkali thiocyanates additives exhibit remarkably improved stability than the reference PSCs against humid circumstance, and a continuous exposure to humid air without encapsulation over 45 days only records about 5% degradation of the efficiency. These findings provide a facile approach to fabricate efficient and stable PSCs by low processing temperature in ambient air, both of which are highly preferred for future practical applications of PSCs.

  12. Effect of Temperature on the Corrosion Behavior of API X120 Pipeline Steel in H2S Environment

    Science.gov (United States)

    Okonkwo, Paul C.; Sliem, Mostafa H.; Shakoor, R. A.; Mohamed, A. M. A.; Abdullah, Aboubakr M.

    2017-08-01

    The corrosion behavior of newly developed API X120 C-steel that is commenced to be used for oil pipelines was studied in a H2S saturated 3.5 wt.% NaCl solution between 20 and 60 °C using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The corrosion products formed on the surface of the alloy were characterized using x-ray diffraction and scanning electron microscopy. It has been noticed that the formation of corrosion product layer takes place at both lower and higher temperatures which is mainly comprised of iron oxides and sulfides. The electrochemical results confirmed that the corrosion rate decreases with increasing temperature up to 60 °C. This decrease in corrosion rate with increasing temperature can be attributed to the formation of a protective layer of mackinawite layer. However, cracking in the formed mackinawite layer may not be responsible for the increase in the corrosion rate. More specifically, developed pourbaix diagrams at different temperatures showed that the formed protective layer belongs to mackinawite (FeS), a group of classified polymorphous iron sulfide, which is in good agreement with the experimental results. It is also noticed that the thickness of corrosion products layer increases significantly with decrease in the corrosion rate of API X120 steel exposed to H2S environment. These findings indicate that API X120 C-steel is susceptible to sour corrosion under the above stated experimental conditions.

  13. Multichord time-resolved electron temperature measurements by the x-ray absorber-foil method on TFTR

    International Nuclear Information System (INIS)

    Kiraly, J.; Bitter, M.; Efthimion, P.

    1985-09-01

    Absorber foils have been installed in the TFTR X-Ray Imaging System to permit measurement of the electron temperature along 10 to 30 chords spaced at 5-12.5 cm with a time resolution of less than 100 μs. The technique uses the ratio of x-ray fluxes transmitted through two different foils. The ratio depends mainly on electron temperature. Simulations show that strong impurity line radiation can distort this ratio. To correct for these effects, special beryllium-scandium filters are employed to select the line-free region between 2 and 4.5 keV. Other filter pairs allow corrections for Fe L and Ni L line radiation as well as Ti K and Ni K emission. Good accuracy is also obtained with simple beryllium filters, provided that impurity corrections are incorporated in the analysis, taking line intensities from the x-ray pulse-height analysis diagnostic. A description of modeling calculations and a comparison of temperature values from this diagnostic with data from the x-ray pulse height analysis, the electron cyclotron emission, and the Thomson scattering diagnostics are presented. Several applications of the absorber foil electron temperature diagnostic on TFTR are discussed

  14. Determination of rotational temperature of AlO from the B2Σ+–X2Σ+ ...

    Indian Academy of Sciences (India)

    pp. 597–600. Determination of rotational temperature of AlO from the B2Σ+–X2Σ+ system. M M CHAUDHARI1, C T LONDHE2 and S H BEHERE2. 1Maharashtra Mahavidyalaya, Nilanga 413 521, Dist. Latur, India. 2Department of Physics, Dr Babasaheb Ambedkar Marathwada University,. Aurangabad 431 004, India.

  15. Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Willa, K. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Diao, Z. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Laboratory of Mathematics, Physics and Electrical Engineering, Halmstad University, P.O. Box 823, SE-301 18 Halmstad, Sweden; Campanini, D. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Welp, U. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Divan, R. [Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Hudl, M. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden; Islam, Z. [X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Kwok, W. -K. [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA; Rydh, A. [Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden

    2017-12-01

    Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-delta crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

  16. High temperature X-ray diffraction studies on HfO2-Gd2O3 system

    International Nuclear Information System (INIS)

    Panneerselvam, G.; Antony, M.P.; Ananthasivan, K.; Joseph, M.

    2016-01-01

    High temperature X-ray diffraction (HTXRD) technique is an important experimental tool for measuring thermal expansion of materials of interest. A series of solid solutions containing GdO 1.5 in HfO 2 ,Hf 1-y Gd y )O 2 (y = 0.15, 0.2, 0.3, 0.41 and 0.505) were prepared by solid state method. Structural characterization and computation of lattice parameter was carried out by using room temperature X-ray diffraction measurements. The room temperature lattice parameter estimated for (Hf 1-y Gd y )O 2 (y=0.15, 0.2, 0.3, 0.41 and 0.505) are 0.51714 nm, 0.51929 nm, 0.52359nm, 0.52789nm and 0.53241 nm, respectively. Thermal expansion coefficients and percentage linear thermal expansion of the HfO 2 -Gd 2 O 3 solid solutions containing 20 and 41 mol% GdO 1.5 were determined using HTXRD in the temperature range 298 to 1673K. The mean linear thermal expansion coefficients of the solid solutions containing 20 and 41 mol. %Gd are 11.65 x 10 -6 K -1 and 12.07 x 10 -6 K -1 , respectively. (author)

  17. Organic semiconductor crystals.

    Science.gov (United States)

    Wang, Chengliang; Dong, Huanli; Jiang, Lang; Hu, Wenping

    2018-01-22

    Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

  18. Investigation on Transmission Properties of Terahertz Wave Through Semiconductor Aperture

    International Nuclear Information System (INIS)

    He Xiaoyong; Cao Juncheng

    2008-01-01

    The transmission properties of terahertz (THz) wave passing through semiconductor aperture have been investigated. The dispersion relationship for surface plasmon polariton (SPP) at different temperatures has been numerically calculated. The results show that the dispersion relationship increases with the increasing of frequency and the decreasing of temperature, the thickness of slab has to be taken into consideration because of the large skin depth for semiconductor slab. In addition, the propagation constant increases with the increasing of frequency and the decreasing of temperature.

  19. Nuclear relaxation in semiconductors doped with magnetic impurities

    International Nuclear Information System (INIS)

    Mel'nichuk, S.V.; Tovstyuk, N.K.

    1984-01-01

    The temperature and concentration dependences are investigated of the nuclear spin-lattice relaxation time with account of spin diffusion for degenerated and non-degenerated semicon- ductors doped with magnetic impurities. In case of the non-degenerated semiconductor the time is shown to grow with temperature, while in case of degenerated semiconductor it is practically independent of temperature. The impurity concentration growth results in decreasing the spin-lattice relaxation time

  20. Ultra-low power high temperature and radiation hard complementary metal-oxide-semiconductor (CMOS) silicon-on-insulator (SOI) voltage reference.

    Science.gov (United States)

    Boufouss, El Hafed; Francis, Laurent A; Kilchytska, Valeriya; Gérard, Pierre; Simon, Pascal; Flandre, Denis

    2013-12-13

    This paper presents an ultra-low power CMOS voltage reference circuit which is robust under biomedical extreme conditions, such as high temperature and high total ionized dose (TID) radiation. To achieve such performances, the voltage reference is designed in a suitable 130 nm Silicon-on-Insulator (SOI) industrial technology and is optimized to work in the subthreshold regime of the transistors. The design simulations have been performed over the temperature range of -40-200 °C and for different process corners. Robustness to radiation was simulated using custom model parameters including TID effects, such as mobilities and threshold voltages degradation. The proposed circuit has been tested up to high total radiation dose, i.e., 1 Mrad (Si) performed at three different temperatures (room temperature, 100 °C and 200 °C). The maximum drift of the reference voltage V(REF) depends on the considered temperature and on radiation dose; however, it remains lower than 10% of the mean value of 1.5 V. The typical power dissipation at 2.5 V supply voltage is about 20 μW at room temperature and only 75 μW at a high temperature of 200 °C. To understand the effects caused by the combination of high total ionizing dose and temperature on such voltage reference, the threshold voltages of the used SOI MOSFETs were extracted under different conditions. The evolution of V(REF) and power consumption with temperature and radiation dose can then be explained in terms of the different balance between fixed oxide charge and interface states build-up. The total occupied area including pad-ring is less than 0.09 mm2.