Energy Technology Data Exchange (ETDEWEB)

Photocurrent and capacitance measurements of semiconductor passive films formed on metals and alloys can be used to study the electronic properties and reveal indirect information about structure and composition. The current work used these techniques to investigate the electronic properties of the passive films formed on three austenitic stainless steels, types 304L, 316L and 254SMO, in borate. Evidence was found for the existence of a large number of localised mid bandgap states, consistent with amorphous oxides. However, the flat-band potentials of the austenitic stainless steel passive films were found to be independent of both composition and measuring frequency. The most credible explanation for the bandgap values determined from photocurrent measurements is that the passive films are formed as dual layers, iron oxide outer layer and chromium oxide inner layer. This model does not need to evoke ...

International Nuclear Information System (INIS)

This thesis is devoted to the study and development of Heterojunction Bipolar Transistors (HBTs) designed for high voltage operation. The work concentrates on the use of wide bandgap III-V semiconductor materials as the collector material and their associated properties influencing breakdown, such as impact ionisation coefficients. The work deals with issues related to incorporating a wide bandgap collector into double heterojunction structures such as conduction band discontinuities at the base-collector junction and results are presented which detail, a number of methods designed to eliminate the effects of such discontinuities. In particular the use of AlGaAs as the base material has been successful in eliminating the conduction band spike at this interface. A method of electrically injecting electrons into the collector has been employed to investigate impact ionisation in GaAs, GaInP and AlInP ...

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The effect of molybdenum on the electronic structure of the passive films formed on ferritic (Fe-Cr and Fe-Cr-Mo) stainless steels is examined by capacitance and photoelectrochemical measurements. The capacitance study is supported by a mathematical analysis of the Schottky barrier developed at the semiconductor-electrolyte interface in the case of a semiconductor with multiple bulk electronic states in the bandgap. The numerical simulations, based on the more general Mott-Schottky relation proposed, are in good agreement with the experimental results. It can be concluded that the capacitance behavior of the passive films is related to the contributions of a shallow donor level very close to the conduction band and a deep donor level at about 0.4 eV below the conduction band. The addition of molybdenum decreases the donor density of the deep level. Photoeffects observed for subbandgap photon energies ...

Energy Technology Data Exchange (ETDEWEB)

Quaternary semiconductor compounds are ideal candidates for use in monolithic cascade solar cells because the lattice constant and the bandgap of such compounds can be independently varied. The quaternary semiconductor compound Ga[sub 0.83]In[sub 0.17]As[sub 0.67]P[sub 0.33] not only is lattice matched to GaAs and Ge but also provides a current matched top cell for the GaInAsP/Ge monolithic cascade solar cell. Under concentration of 100 suns, the projected efficiency for such a cell is about 34%. The growth of Ga[sub 0.83]In[sub 0.17]As[sub 0.67]P[sub 0.33] lattice matched to GaAs and Ge has been demonstrated. GaInAsP solar cells have been grown on both GaAs and Ge substrates. A GaInAsP on GaAs solar cell with an active area efficiency of 23.2% for 1 sun, AM 1.5 direct illumination has been prepared. A proposed structure for the GaInAsP/Ge cascade cell is also given.

Science.gov (United States)

An estimate of the undercounted electrostatic energy terms in local-density-functional total-energy calculations for nonmetallic systems with separated electron-hole pairs is used to derive a simplified correction to density-functional - theory band gaps. The correction is evaluated for Ne, Ar, Kr, LiF, NaCl, CsCl, MgO, CaS, BaS, C, AlP, and Si. The band-gap errors are reduced from 40-50% to 10-15% for most of the systems studied. Conduction-band corrections are shown to be nearly as large as valence-band corrections in free-electron-like semiconductors. 28 references, 1 figure.

Science.gov (United States)

The specification describes a semiconductor solar cell and fabrication process therefor wherein a thin N-type gallium arsenide layer is deposited on a larger P-type substrate layer which is selected from the group of III-V ternary compounds consisting of aluminum phosphide antimonide, AlPSb, and aluminum indium phosphide, AlInP. P-type impurities are diffused from the substrate layer into a portion of the thin N-type gallium arsenide layer to form P-type region wherein which defines a PN junction in the thin gallium arsenide layer. Thus, the quantity of gallium arsenide required to provide this PN photovoltaic junction layer in the cell is minimized, and th P-type substrate serves as a high bandgap window layer for the cell. Such high bandgap of this window material is especially well suited for efficiently transmitting the blue spectrum of sunlight to the PN junction, thus enhancing the power conversion efficiency of the ...

British Library Electronic Table of Contents (United Kingdom)

In the present study the optical properties of co-evaporated indium sulfide thin films are investigated. Before being optically characterized, the composition as well as the crystalline properties of the film have been checked with the help of energy dispersive spectroscopy (EDX) and X-Ray diffraction (XRD) analyses. The optical absorption coefficient ? of this indium sulfide film has been deduced from reflectivity R(?) and transmission T(?) measurements. The fit of the curve representing ?(h?) suggests that the ?-In2S3 has an indirect bandgap of 2.01?eV. Density functional theory (DFT) calculations are performed on this indium sulfide compound, using TB-LMTO code. Through these band structure investigations, an indirect bandgap is predicted as observed experimentally. The top of the valen...

Energy Technology Data Exchange (ETDEWEB)

III-V semiconductors, GaAs and in particular InGaP, are used in many different electronic applications, such as high power and high frequency devices, laser diodes and high brightness LED. Their direct bandgap and high reliability make them ideal candidates for the realisation of high efficiency solar cells: in the past years they have been successfully used as power sources for satellites in space, where they are able to produce electricity from sunlight with an overall efficiency of around 30%. Nowadays, the use of arsenides and phosphides as photovoltaic (PV) devices is confined only to space applications since their price is much higher than conventional Si flat panel modules, the leading PV market technology. But with the introduction of multijunction solar cells capable of operating in high concentration solar light, the area and, therefore, the cost of these cells can be reduced and will eventually find an application and market also on ...

International Nuclear Information System (INIS)

In this work passive films formed in AISI 304 stainless steel were envisaged as semiconductors and studied by means of photoelectrochemistry and Mott-Schottky plots. The passive films were potentiostatically formed at different potentials (0.2-0.8V) in a basic borate/boric acid solution without and with addition of NaCl (0.5 and 1g/l) and at various temperatures in the range 8-60"oC. The influence of these parameters on the photocurrent, quantum efficiency, bandgap energy and density of charge carriers was determined. The results show that the experimental conditions at which the films are formed influence the semiconductive properties of the film, which seem to be related to the higher or lower stability of the film. An Arrhenius type of relationship was also found between the density of charge carriers and temperature, leading to the determination of an activation energy. (author) 13 refs., 7 figs.

Energy Technology Data Exchange (ETDEWEB)

The principle of conservation and transferability of chemical bonds explains the recent discovery by extended x-ray absorption fine-structure measurements of two unequal anion-cation bond lengths R/sub A/C and R/sub B/C in A/sub x/B/sub 1-x/C zinc-blende semiconductor alloys despite the close adherence of the lattice constant to the average value (Vegard rule). This bond alternation, manifested as a structural distortion to a local chalcopyrite coordination around the anions, explains also most of the observed optical bowing in semiconductor alloys.

International Nuclear Information System (INIS)

To calculate the energy band structures in semiconductors using the relativistic augmented plane wave method, atomic potential and charge density are needed, which are calculated by self-consistent method. Wave function for one electron is determined by solving the Dirac equation with the Hartree-Fock equation based on the slater's exchange potential. The results of calculation for Cu"+"1 are given. (Author).

Science.gov (United States)

The metal-semiconductor solar cell is a potential candidate for converting solar energy to electrical energy for space and terrestrial application. In this paper, a method for obtaining parameters of practical antireflection (AR) coatings for the metal-semiconductor solar cells is given. This method utilizes the measured equivalent index of refraction obtained from ellipsometry, since the surface to be AR coated has a multilayer structure. Both the experimental results and theoretical calculations of optical parameters for Ta/sub 2/O/sub 5/ AR coatings on Au-GaAs and Au-GaAs/sub 0.78/P/sub 0.22/ solar cells are presented for comparison. (AIP)

Science.gov (United States)

A film of GaSb grown epitaxially on a Si substrate is a direct transition semiconductor useful for application as a light source in Si photonics and channel material in next-generation field effect transistors because its energy bandgap is close to the optical fibre communication wavelength and it possesses high carrier mobility. Here, we report a novel method for heteroepitaxial growth of high-quality GaSb/Si films, despite having a lattice mismatch as large as ? 12%, using elastically strain-relaxed GaSb nanodots with ultrahigh density as seed crystals for film growth. The nanodot seed crystals were grown epitaxially by restricted contact with the Si substrate through nanowindows in an ultrathin SiO(2) film on the Si substrate. A light-emitting diode containing GaSb/Si films with a thickness of ? 90 nm fabricated by this method operated at room temperature. The growth method was also used to fabricate AlGaSb films of high quality. Our method ...

UK PubMed Central (United Kingdom)

Electronic and structural properties of antiphase boundaries in group III-V semiconductor compounds have been receiving increased attention due to the potential to integration of optically-active III-V...Full Text Available

International Nuclear Information System (INIS)

Semiconductor properties of passive films formed on the Fe-18Cr alloy in a borate buffer solution (pH = 8.4) and 0.1 M H_2SO_4 solution were examined using a photoelectrochemical spectroscopy and an electrochemical impedance spectroscopy. Photo current reveals two photo action spectra that derived from outer hydroxide and inner oxide layers. A typical n-type semiconductor behaviour is observed by both photo current and impedance for the passive films formed in the borate buffer solution. On the other hand, a negative photo current generated, the absolute value of which decreased as applied potential increased in the sulfuric acid solution. This indicates that the passive film behaves as a p-type semiconductor. However, Mott-Schottky plot revealed the typical n-type semiconductor property. It is concluded that the passive film on the Fe-18Cr alloy formed in the borate buffer solution is composed of both ...

Science.gov (United States)

The authors present electric-field dependent electroreflectance and photocurrent spectra of visible-bandgap In{sub x}(Al{sub y}Ga{sub 1{minus}y}){sub 1{minus}x}P/In{sub x{prime}}(Al{sub y{prime}}Ga{sub 1{minus}y{prime}}){sub 1{minus}x{prime}}P multiple-quantum-well (MQW) structures. These structures, grown by metal-organic vapor phase epitaxy on 6{degrees}-misoriented (100) GaAs substrates, have undoped MQWs sandwiched between doped In{sub 0.5}Al{sub 0.5}P layers, forming p-i-n diodes. Quantum-well compositions in the range 0.46{le}x{le}0.52 and 0{le}y{le}0.4, corresponding to bandgaps in the red to yellow-green range, were used. The Stark shifts in these various samples were measured and found to depend on the details of the Mg p-type doping profile, confirming important diffusion effects, in agreement with secondary ion mass spectrometry and capacitance-voltage data. The results show that these new ...

International Nuclear Information System (INIS)

The electronic structures of platinum group elements (Ru, Os, Rh, Ir, Pd, and Pt) silicides have been calculated. Ir_3Si_5 is a semiconductor with the direct gap of 1.14 eV. Among monosilicides, RuSi and OsSi with the FeSi-type structure are semiconductors with the gap values of 0.21 and 0.41 eV but RhSi, IrSi, PdSi, and PtSi with the MnP-type structure are metals. No semiconducting compounds can be found in other platinum group elements silicides other than known Ru_2Si_3, Os_2Si_3, and OsSi_2.

International Nuclear Information System (INIS)

The excess energy of several III-V and II-VI strained-layer semiconductor superlattices (AC)_p(BC)_p is studied as a function of the repeat period p and orientation G=[001], [110], [111], and [201], using first-principles calculations. We discover a number of universal features, including the predicted instability for nearly all p's and G's with respect to bulk disproportionation, the identification of chalcopyrite as a metastable ordered structure, and the stability of all thin epitaxial [110] and [201] and most common-anion [001] superlattices relative to coherent phase separation.

International Nuclear Information System (INIS)

Crystalline and non-crystalline iron oxide (#alpha#-Fe_2O_3) thin films were obtained by spray pyrolysis onto glass substrate at different temperatures. The results of X-ray diffraction showed that with increasing the deposition time, the film structure changed from non-crystalline to crystalline at the same substrate temperature. At different substrate temperatures and low deposition times (5 min), iron oxide appears almost in non-crystalline form. With rising the substrate temperature and deposition time, the crystallinity was improved. The effect of substrate temperature as well as deposition time on the optical features (absorption coefficient and bandgap) and optical constants of these films has been investigated. Optical constants of the films were determined from spectrophotometric measurement of reflectance and transmittance. Analysis of the results showed that, for non-crystalline iron oxide films of different thicknesses (76-118 nm) ...

Science.gov (United States)

The use of Auger electron spectroscopy (AES) combined with in situ sputter etching for revealing the metallurgy of the metal-semiconductor interface is presented. The physical basis, measurement techniques, and data interpretation for Auger analysis of thin-film structures are briefly reviewed. Results of a detailed study of an alloyed multilayered contact (Ni/Au-Ge) on n-type epitaxial GaAs are summarized to illustrate how electrical and metallurgical contact properties can be correlated using AES. In addition, the results of a study of the growth kinetics and chemical phase identification of palladium silicide on single-crystal Si is given, as well as the initial results of a study of aluminum-palladium silicide interaction at elevated temperature. (auth)

Science.gov (United States)

By using a model dielectric matrix in electron self-energy evaluations the computational effort of a quasiparticle band-structure calculation for a semiconductor is greatly reduced. Applications to various systems with or without inversion symmetry, having narrow or wide band gaps, and semiconductor alloys demonstrate the reliability and accuracy of the method. Calculations have been performed for thirteen semiconducting or insulating materials: Si, LiCl, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, and the Al{sub 0.5}Ga{sub 0.5}As and In{sub 0.53}Ga{sub 0.47}As alloys. Excellent agreement with experimental results is obtained for the quasiparticle energies for these materials. The only three exceptions, {ital E}({Gamma}{sub 1{ital c}}) of AlP, {ital E}({ital L}{sub 1{ital c}}) of AlAs, and {ital E}({ital L}{sub 1{ital c}}) of AlSb are discussed and attributed to various experimental uncertainties. Several other ...

International Nuclear Information System (INIS)

The composite wave variational version of the APW (augmented plane wave) method is used to obtain the electronic band structure of the compounds boron phosphide and boron arsenide at the high symmetry points #GAMMA#, X, and L. The tight binding interpolation scheme of Slater and Koster is used to calculate the rest of the band structure. The results show that both these materials are indirect band gap semiconductors. The density of states, and the imaginary part of the dielectric constant is also calculated. The theoretical results are compared with the reported experimental and theoretical data. (author).

International Nuclear Information System (INIS)

Reflectance anisotropy spectroscopy (RAS) has been used, together with scanning tunnelling spectroscopy (STS), to investigate the optical and electronic properties of nanodots formed by depositing Ag on the Si(111)-3 x 1-Ag surface. One-dimensional (1D) arrays of nanodots were grown on a single-domain (3 x 1)-Ag surface and the anisotropic optical response in the 0.5-5 eV range measured by RAS. Aligned, elongated Ag islands were also grown on this surface to compare their properties with those of the nanodots. STS of the Ag islands showed distinct metallic behaviour, whereas the nanodots revealed a bandgap of #approx#0.6 eV, indicating that the surface of the dots has a non-metallic character, similar to that of the Si(111)-3 x 1-Ag surface. RAS also showed substantial differences between the structures, with a large infrared anisotropy for the metallic Ag islands consistent with anisotropic Drude-like intraband transitions, whereas the ...

Energy Technology Data Exchange (ETDEWEB)

The formation and breakdown of the passive films on stainless steels are mainly controlled by ionic and electronic transport processes. Both these processes are in part controlled by the electronic properties of the oxide film. Consequently, it is vital to gain a detailed perception of the electronic properties of the passive films together with structural and compositional information for a comprehensive understanding of mechanisms behind passivity and localised corrosion. As a step towards this goal the passive films formed on two main austenitic stainless steels AISI 316L and AISI 304L in borate solution were characterised by in situ Raman spectroscopy and photocurrent spectroscopy coupled with electrochemical measurements. This revealed the formation of an Fe-Cr spinel as the dominant constituent in the passive films with more Cr enrichment in the oxide film on 316L than that of 304L. Bandgap readings and semiconductivities of the two ...

Energy Technology Data Exchange (ETDEWEB)

The electrochemical behaviour of passive films formed on one austenitic stainless steel (AISI 304) and one ferritic stainless steel (AISI 446) in solutions with pH between 0.6 and 8.4 was studied by capacitance measurements and photocurrent spectroscopy. Compositional characterization of the passive films was done by X-ray photoelectron spectroscopy. The capacitance increases with decreasing pH. Doping densities evaluated from Mott-Schottky plots are in the range 2-6 x 10{sup 20} cm{sup -3} and increased with the pH in the neutral/alkaline range while in pH 0.6, values above 10{sup 21} cm{sup -3} were found. The bandgap energy indicates two transitions, at 2.5-2.8 and 3.2 eV. The analytical data reveal that, as the pH increased, the films become enriched in Fe(II) and Fe(III), whereas the Cr(III) gradually decreases. The films formed at very low pH had a behaviour that contrasts with that of the films formed in the neutral/alkaline media. The films are described by ...

Energy Technology Data Exchange (ETDEWEB)

A p[sup +]-Al[sub 0.3]Ga[sub 0.7]As/n[sup +]-GaAs heterojunction tunnel diode was fabricated using Atomic Layer Epitaxy (ALE) growth technique. Background carbon doping of [similar to]10[sup 20] cm[sup [minus]3] was achieved in the p-side of the diode by optimizing growth conditions such as V/III ratio, exposure times to reactant gases, and growth temperature. In the n-side of the diode GaAs was doped with silane and doping concentrations as high as 7[times]10[sup 18] cm[sup [minus]3] were also achieved. The dopants are chosen to satisfy the high levels and low diffusion requirements. The diode can be used to interconnect the high and low band-gap cells in the AlGaAs/GaAs cascade solar cell structure. The reactor used in this investigation is a commercial MOCVD system which has been specially modified for dual operation of ALE and MOCVD growth modes.

International Nuclear Information System (INIS)

The wavelength dependence of the threshold in an InGaP-InAlGaP vertical cavity surface emitting laser is investigated using a microscopic theory of the semiconductor gain medium. Good agreement is found between experiment and theory for the minimum threshold lasing wavelength for a range of laser structures.

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In this work it is made a study of the structure and electric properties of chlorate polyethylene (PE-CI) with double and simple bonds obtained by continuous plasma with resistive coupling to 13.5 MHz. The synthesis conditions are power between 10 and 14 W and pressure of (6-7) x 10{sup -2} Torr. The synthesized PE-Cl in that way is soluble in acetone what indicates that probably is formed of short chains and not it shows the generalized inter crossing that is presented in some syntheses by plasma and that it can degrade the electric properties of these polymers. The IR and XPS analysis show the vibration of the C-C, C=C and C-CI bonds. The morphology of the polymer after being dissolved shows a compact and flat configuration. The electric conductivity has an approximately lineal behavior in an interval of 35 to 90% of relative humidity. (Author)

Science.gov (United States)

The excess energy of several III-V and II-VI strained-layer semiconductor superlattices ({ital AC}){sub {ital p}}(BC){sub p} is studied as a function of the repeat period {ital p} and orientation {bold G}=(001), (110), (111), and (201), using first-principles calculations. We discover a number of universal features, including the predicted instability for nearly all {ital p}'s and {bold G}'s with respect to {ital bulk} disproportionation, the identification of chalcopyrite as a metastable ordered structure, and the stability of all thin {ital epitaxial} (110) and (201) and most common-anion (001) superlattices relative to coherent phase separation.

International Nuclear Information System (INIS)

Focused ion beam (FIB) micromachining has been used to produce inclined planes on semiconductor surfaces. A 10 keV FIB system, utilising a Ga"+ liquid metal ion source (LMIS), was employed. The ramped surfaces were prepared by digitally deflecting the ion beam in a serpentine fashion over a rectangular area and incrementing the time the beam spends at a pixel, dwell time, line by line. For the conditions used, control in micromachining the inclination of the ramps to the starting horizontal surface is of the order of 1 arc s per scan of the FIB over the area of interest. The possibility of using such surfaces prepared by FIB, along with vacuum growth techniques such as molecular beam epitaxy (MBE), for application to strain relief structures and lateral device production is discussed. (author).

Science.gov (United States)

... Tunable semiconductor lasers are essential components for links employing optical frequency modulation (OFM) for enhanced dynamic range or ...

Science.gov (United States)

The zinc-blende (ZB) and wurtzite (W) structures are the most common crystal forms of binary octet semiconductors. In this work we have developed a simple scaling that systematizes the {ital T}=0 energy difference {Delta}{ital E}{sub W{minus}ZB} between W and ZB for all simple binary semiconductors. We have first calculated the energy difference {Delta}{ital E}{sub W{minus}ZB}{sup LDF}({ital AB}) for AlN, GaN, InN, AlP, AlAs, GaP, GaAs, ZnS, ZnSe, ZnTe, CdS, C, and Si using a numerically precise implementation of the first-principles local-density formalism (LDF), including structural relaxations. We then find a {ital linear} scaling between {Delta}{ital E}{sub W{minus}ZB}{sup LDF}({ital AB}) and an atomistic orbital-radii coordinate {ital {tilde R}}({ital A},{ital B}) that depends only on the properties of the free atoms {ital A} and {ital B} making up the binary compound {ital AB}. Unlike classical ...

Energy Technology Data Exchange (ETDEWEB)

We present the results of a comprehensive study of the temperature dependences of the quantum efficiency for ultraviolet detectors based on GaAs, GaP and 4H--SiC Schottky structures, and on Si, GaAs p-n structures. For ultraviolet detectors based on Schottky structures, the quantum efficiency increases with increasing temperature for all photon energies, even including the semiconductor intrinsic absorption region. On the other hand, for ultraviolet detectors based on p-n structures, the quantum efficiency is practically temperature independent in the semiconductor intrinsic absorption region. The change in the quantum efficiency for the GaAs and Si detectors is less than 0.01% per degree. To explain the measurements, a variable trap occupancy model is presented. Subsurface imperfections of the semiconductor cause fluctuations in the profile ...

Energy Technology Data Exchange (ETDEWEB)

In situ scanning tunneling microscopy has been used to study the nucleation and growth mechanisms and the structure of passive films formed on Cu(111) surfaces in 0.1 M borate buffer solution (pH 9.3). A surface topography characterized by terraces with monoatomic steps is obtained after potentiodynamic reduction down to {minus}1.12 V/standard hydrogen electrode (SHE), of the electropolished surface exposed to air. The formation of a single Cu{sub 2}O passive layer at 0.03 V/SHE proceeds first by a roughening of the steps assigned to a locally blocked step flow process due to a competition between dissolution and preferential nucleation of the oxide at the steps. The observed oxide nuclei are 2--3 nm wide and about one atomic plane high. This process leads to the complete coverage of the terraces by a grain-like structure of the oxide film. The initial terrace topography is completely altered. Thickening of this oxide layer leads to unstable ...

International Nuclear Information System (INIS)

Neutron semiconductor detectors for neutron counting and neutron radiography have an increasing importance. Simple silicon neutron detectors are combination of a planar diode with a layer of an appropriate neutron converter such as 6LiF. These devices have limited detection efficiency of not more than 5%. The detection efficiency can be increased by creating a 3D microstructure of dips, trenches or pores in the detector and filling it with a neutron converter. The first results related to the development of such devices are presented. Silicon detectors were fabricated with pyramidal dips on the surface covered with 6LiF and then irradiated by thermal neutrons. Pulse height spectra of the energy deposited in the sensitive volume were compared with simulations. The detection efficiency of these devices was about 6.3%. Samples with different column sizes were fabricated to study the electrical properties of 3D structures. Charge collection ...

Energy Technology Data Exchange (ETDEWEB)

By ab-initio calculation we show that the (Ga,Fe)N ground state may be changed from anti-ferromagnetic to ferromagnetic by acceptor defect like Ga vacancies. The electronic structures are calculated by using the Korringa-Kohn-Rostoker (KKR) method combined with coherent potential approximation (CPA). We show that we can increase the magnetic moment of Fe in p-type GaN by oxygen co-doping. Mechanism of exchange interactions between magnetic ions in p-type (Ga,Fe)N is also studied. The effect of external magnetic field on the electronic structure of (Ga, Fe)N and p-type (Ga, Fe)N is investigated.

International Nuclear Information System (INIS)

Within about 10 years, microelectronic devices will be made with more than a billion (10"9) electronic components per chip. To implement such a sophisticated technology it will be essential to have a fundamental understanding of the solid state interaction between the different materials in thin film semiconductor structures. This is the main purpose of this research program. Characterization and analysis is carried out mainly by Rutherford backscattering spectrometry and channelling using accelerated nuclear particles from the Van de Graaff accelerator, while radioactive isotopes provide information about interaction mechanisms. 6 figs., 1 ref.

International Nuclear Information System (INIS)

AlN nanocrystalline layers and superstructures are used in the modern optoelectronic technology as reflecting mirrors in semiconductor layers. In the present work the properties of AlN films prepared by sputtering methods from an AlN target in reactive Ar + N plasma were investigated. The characterization was performed with HRTEM, SEM, glancing angle XRD and RBS methods. The present measurements confirmed the polycrystalline structure of AlN layers and enabled the evaluation of their grain size. The roughness and thickness of the layers were additionally determined by ellipsometric and profilometric measurements. (author)

Science.gov (United States)

Continuous wave lasing operation with the shortest wavelength for semiconductor lasers was obtained from AlGaInP double heterostructure lasers at 77 K. The structure was grown by metalorganic vapor phase epitaxy. Lasing wavelength was 583.6 nm (yellow). Threshold current was 43 mA (1.9 kA/cm/sup 2/). Magnesium was adopted as a p-type dopant, and was proved to be preferable for a high aluminum composition AlGaInP cladding layer.

International Nuclear Information System (INIS)

A systematic study for the materials design of III-V and II-VI compound-based ferromagnetic diluted magnetic semiconductors is given based on ab initio calculations within the local spin density approximation. The electronic structures of 3d-transition-metal-atom-doped GaN and Mn-doped InN, InP, InAs, InSb, GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs and AlSb were calculated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation. It is found that the ferromagnetic ground states are readily achievable in V-, Cr- or Mn-doped GaN without any additional carrier doping treatments, and that InN is the most promising candidate for high-T_C ferromagnet. A simple explanation of the systematic behavior of the magnetic states in III-V and II-VI compound-based diluted magnetic semiconductors is also given. It is also shown that V or Cr-doped ZnS, ZnSe, and ZnTe are ferromagnetic without p- or n-type doping ...

International Nuclear Information System (INIS)

At room pressure and temperature the system EuOsub(1-x)Nsub(x) has two solid-solubility ranges, each with the NaCl structure: for 0 =< x =< 0.30 the system is ferromagnetic and semiconducting above the Curie temperature; for 0.92 =< x <1 it is metallic. Conductivity and Seebeck voltages indicate intrinsic behaviour above 310 K with an energy gap that decreases with increasing x for 0 =< x =< 0.30. Magnetic susceptibilities are consistent with 4f"6 configurations at x europium ions per molecule and a ferromagnetic Curie temperature Tsub(C) that increases with x. Low-temperature transport measurements were made only for 0.20 =< x =< 0.30: a minimum in the electrical conductivity, approximately 30 K above Tsub(C) correlates well with the onset of an anomalous low-temperature crystal contraction and with deviations from a Curie-Weiss law typical of short-range magnetic order. Below Tsub(C) there is a metal-to-semiconductor ...

Science.gov (United States)

Cadmium telluride single crystals were grown heavily doped with chloride by the THM method. The resulting crystals were n-type with free carrier concentrations of the order of 10('12)/cm at room temperature. Hall effect studies revealed room temperature mobilities between 30 and 350 cm('2)/v-sec and resistivites between 2 x 10('3) and 10('4) ohm-cm. Studies were made of the gamma and alpha counting characteristics of these crystals with metal, metal-semiconductor, and metal-insulator electrodes. It was found that the MIS and MSS structures resulted in significant improvement over the MS structures in counting, signal-to-noise and energy resolution.

Energy Technology Data Exchange (ETDEWEB)

A specific radiochemical procedure for indium determination in semiconductor-grade silicon, using an inorganic ion exchanger (cerium oxalate) is proposed.

Energy Technology Data Exchange (ETDEWEB)

Classical semiconductor physics has been continuously improving electronic components such as diodes, light-emitting diodes, solar cells and transistors based on highly purified inorganic crystals over the past decades. Organic semiconductors, notably polymeric, are a comparatively young field of research, the first light-emitting diode based on conjugated polymers having been demonstrated in 1990. Polymeric semiconductors are of tremendous interest for high-volume, low-cost manufacturing (''printed electronics''). Due to their rather simple device structure mostly comprising only one or two functional layers, polymeric diodes are much more difficult to optimize compared to small-molecular organic devices. Usually, functions such as charge injection and transport are handled by the same material which thus needs to be highly optimized. The present work contributes to ...

International Science & Technology Center (ISTC)

Elaboration of Electrochemical Solar Energy Converter Incorporating Cadmium Selenide Semiconductor Developed Electrochemically

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(Watkins and. Corbett,. 1964) which is a phosphorous-vacancy complex, i.e., ...... Grover. 1965. Semiconductor. Surfaces. ...

International Nuclear Information System (INIS)

Single-crystalline PbTe nanowires were synthesized using the chemical vapor transport method. They consisted of rock-salt structure PbTe nanocrystals uniformly grown in the [100] direction. We fabricated field-effect transistors using a single PbTe nanowire, providing evidence for its intrinsic n-type semiconductor characteristics. The values of the carrier mobility and concentration were estimated to be 0.83 cm"2 V"-"1 s"-"1 and 8.8 x 10"1"7 cm"-"3, respectively. The Seebeck coefficients (-72 ?V K"-"1) of individual nanowires were measured to show their n-type carrier-dominated thermoelectric transport properties.

Energy Technology Data Exchange (ETDEWEB)

A first-principles quasiparticle approach to the electronic excitation energies in crystals and at surfaces is described. The quasiparticle energies are calculated within the GW approximation for comparison with photoemission and other spectroscopic experiments. Applications of the method to bulk semiconductors and the Si(111)2[times]l, Ge(111)2[times]l. and H/Si(III) surfaces are presented. In both cases, significant self-energy corrections arising from many-electron effects to the excitation energies are found. Using atomic positions from total energy minimization, the calculated excitation energies explain quantitatively the experimental spectra. This approach thus provides an ab initio means for analyzing and predicting results from spectroscopic probes.

International Nuclear Information System (INIS)

In this Letter, we study the structural, elastic and electronic properties of perovskite semiconductor SrTiO_3 using two different methods: the full-potential linearized augmented plane wave (FP-LAPW) method and the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA). We have evaluated the ground state quantities such as lattice parameter, bulk modulus and its pressure derivative as well as the elastic constants. Also, we have presented the results of the band structure, densities of states and charge densities. These results were in favourable agreement with previous theoretical works and the existing experimental data. To complete the fundamental characteristics of this compound we have analyzed the thermodynamic properties such as thermal expansion coefficient, and specific heats in the whole pressure range from 0 to 20 GPa and temperature range from 0 to 1200 K.

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There has been considerable interest in producing and studying nanoparticle materials because of the effect of size on their structure, physical and chemical structure. Most studied nanoparticle semiconductors belong to the II-VI group, as they are relatively easy to synthesize and are generally prepared as particulates or in thin film form. Among II-VI compounds, CdS is one of the most studied materials. There are different ways to synthesize CdS nanoparticles such as colloidal particles, chemical decomposition, sol-gel, gas evaporation, magnetron sputtering, electrostatic deposition, and etc. {gamma}-irradiation is one of the effective methods for synthesis of nanomaterials. These nonomaterials have been extensively used in the preparation of nanocrystalline metals, metal oxides, and metal-polymer composites. However, The preparation of CdS nanoparticle and CdS/ polyacrylonitrile nanocomposite by {gamma}-irradiation ...

International Nuclear Information System (INIS)

The possibility to compress and to split laser pulses at their nonlinear optical transmission through semiconductor films was investigated

International Nuclear Information System (INIS)

Czech May 1979. p. 32-33. Czechoslovakia Benada, J. Spacek, B. Ustav

Science.gov (United States)

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

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Motivation is given for a technique to more thoroughly test semiconductor equipment control systems. A description is given of a simulator-based control system testing technique. Potential benefits that could be realized by using this technique in the semiconductor industry as well as benefits documented by using this technique in other industries are described. Specific requirements for using the technique in the semiconductor industry are outlined. A summary of a survey of nine commercial simulation systems is given. Finally, the outcome of the survey is compared with the requirements for using the technique.

International Nuclear Information System (INIS)

The effects of hydrostatic pressure on the electronic band structure of the semiconductor mineral iron pyrite FeS_2 have been investigated theoretically by an ab initio full-potential linearized-augmented plane wave (FPLAPW) method within a local approximation (LDA/GGA) to the density functional theory. The calculations predict that at a pressure of 94.1 GPa the indirect band gap of pyrite FeS_2 vanishes and the material becomes a metal. This is due to the presence of the S-S and Fe-S bonds, which provide novel energy band distortions in the process of attaining the metallic state. Analysis indicates that, under increasing high pressure, the conduction bands (3p_z of sulfur and 3d_x_"2_-_y_"2+3d_x_y of iron) intrude downwards into the valence bands, which are predominantly 3d in nature. At normal pressure, the lattice constant, the bulk modulus, sulfur position parameter u, S-S bond length, and the indirect band gap of pyrite FeS_2 are ...

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Dose dependences of conductivity at a temperature of 78 K for InSb and InAs single crystals under reactor fast neutron, 50 MeV proton and 80 MeV alpha particle irradiation up to fluence of 10{sup 17} cm{sup -2} are considered. Special attention is given to non-trivial, but little known semi-conductor characteristics in terms of {sigma}(F) dependence at large fluences, and also to the versatility of such dependence for all semiconductors. The behaviour of semiconductor materials conductivity dependence on fluence presented here may be used for semiconductor dosemeters characterisitic variation forecasting under large fluence measurements and in radiation emergency dosimetry. (author).

British Library Electronic Table of Contents (United Kingdom)

The pentenary compound semiconductor Cu(In,Ga)(Se,S)2 is one of the most attractive materials for high-efficiency solar cells due to its tunable band gap to match well the solar spectrum. In this study, semiconducting Cu(In,Ga)(Se,S)2 thin films were prepared by a classical two-step growth process, which involves the selenization and/or sulfurization of In/Cu?Ga precursor. During the precursor formation step metallic In/Cu?Ga alloys were deposited onto the Mo-coated soda-lime glass substrates by DC magnetron sputter process. The respective precursors were subsequently reacted with H2Se and/or H2S gasses, at elevated temperatures. By optimizing the selenization parameters, such as the gas concentrations, reaction time, reaction temperature, and the flow of H2Se and H2S, high quality, single...

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Properties of photoconductive ultraviolet detectors fabricated on ZnO films were presented. Highly c-axis oriented ZnO films were grown on glass substrates by pulsed laser deposition. Ultraviolet photodetectors were fabricated based on metal-semiconductor-metal planar structures. The photoresponsivity and the quantum efficiency are much higher in the ultraviolet range than in the visible range, and the peak values are around 360 nm. Photocurrent transients show that the detector has a large photocurrent with the peak value of 2.8 mA, and a slow photoresponse with a rise time of 5 min and a decay time of 7 min. The response curve of the detector is fitted well with exponential curve. The large photocurrent should result from the both effects of the accumulation of conduction electrons and the decrease of the barrier height between crystallites. The relaxation time constant {tau} obtained from the curve fitting represents the time accumulation ...

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Composite ZnO/Ag nanoparticles have been formed via the photocatalytic reduction of silver nitrate over the ZnO nanocrystals, their optical, electrophysical and photochemical properties have been investigated. Mie theory has been applied to analyze the structure of the absorption spectra of ZnO/Ag nanocomposite. The irradiation effects upon the optical properties of ZnO/Ag nanostructure have been investigated. It has been found that the irradiation of ZnO/Ag nanoparticles results in electrons accumulation by both the semiconductor and the metallic components of the nanocomposite. It has been found that silver nitrate can be photochemically deposited onto the surface of ZnO nanoparticles under the illumination with the visible light in the presence of the sensitizer - methylene blue. Kinetics of the sensitized Ag(I) photoredution has been studied. It has been concluded that the key stage of this process is the electron injection from ...

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The following work deals with the realization, characterization and modeling of GaInP / AlGaInP high power semiconductor laser diodes in the visible wavelength range. In addition to the exploration and optimization of efficiency, temperature stability and maximum output power of multi-mode lasers especially methods for longitudinal and lateral mode stabilization of high power laser diodes have been investigated. Although often the focus of optimization is on the threshold current density, in this work the performance of the laser diode for an operation point around 1 Watt under continous wave operation is regarded as the figure of merit. It turns out that low carrier densities are key for an efficient reduction of the heterobarrier leakage currents. In addition, large optical cavity structures with low internal losses enable high external quantum efficiencies even for long cavities. Finally high laser effiency as well as an efficient cooling ...

International Nuclear Information System (INIS)

Focused Ion Beams are an important approach for nanostructure fabrication in the semiconductor industry and material sciences. Applications in sputtering and ion induced deposition of materials are investigated. The IMSA FIB system equipped with the high resolution Orsay Physics CANION M31plus ion column with current densities up to 10 A/cm"2 including a gas injection system is applied. In this work the ion beam induced chemical vapour deposition of tungsten, wherefore tungsten hexacarbonyl as precursor gas is used for a first investigation. Conductive tungsten-nanowires with smallest cross-section upon a substrate of Si and SiO_2 are produced. The ion beam parameters of this focused ion beam system are optimized for the metal deposition. A short insight in the theory of layer nucleation and growth induced by the ion beam during the metal deposition is given. The layer quality is determined by Auger electron analysis which shows the components in atomic percent ...

Science.gov (United States)

This report summarizes the results obtained under a contract from 1974 to 1977, focusing on silicide formation of thin metal films on a Si substrate. The main thrust of the effort was directed at: (1) Development of the data base on thin-film silicide formation, and the investigation of the influence of the Si substrate on the silicide formation. When taken in context with results of other studies, the data obtained exhibit a clear pattern of behavior among the various metal films, but the detailed picture appears to be complex; (2) Development of marker experiments by ion-implanted Ar or Xe markers; (3) Clarification of the role played by oxygen contamination in silicide formation; (4) Stability of silicide layers; (5) Reaction of metal layers with SiO/sub 2/; (6) Electrical characteristics of Pd/sub 2/Si; and (7) A computer program was written to synthesize backscattering spectra for thin-film samples composed of successive layers of uniform thickness and composition.

International Nuclear Information System (INIS)

We present FIB-lithography methods for rapid and cost-effective prototyping of metal structures covering the deep-submicron- to the millimeter-range in a single lithography cycle. Focused ion beam (FIB) systems are widely used in semiconductor industry and research facilities for both analytical testing and prototyping. A typical application is to apply electrical contact to micron-sized sensors/particles by FIB induced metal deposition. However, as for E-beam lithography, patterning times for large area bonding pads are unacceptably long, resulting in cost-intensive prototyping. In this work, we optimized FIB lithography processing for negative and positive imaging mode to form metallic structures for large-areas down do the sub-100 nm range. For negative lithography features are defined by implanting Ga"+-ions into a commercial photo resist, without affecting the underlying structures by impinging ...

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Photocurrent measurements for stainless steel type 304 in the as-received condition after dc and AV (alternating voltage) passivation have confirmed that significant changes of the passive film properties occur due to AV passivation. The photocurrents were the highest for the sample treated by the AV passivation process (AVPP). The bandgap energy increased from about 2.8 to about 3.05 eV for this treatment. Very similar results have been obtained for pure chromium, which suggests that the AVPP produces a thicker passive film with a less defective nature due to a partial dehydration of the chromium oxide phase in the film.

Science.gov (United States)

The liquid-phase synthesis of metal oxide nanoparticles in organic solvents under exclusion of water is nowadays a well-established alternative to aqueous sol-gel chemistry. In this article, we highlight some of the advantages of these routes based on selected examples. The first part reviews some recent developments in the synthesis of ternary metal oxide nanoparticles by surfactant-free nonaqueous sol-gel routes, followed by the discussion of the morphology-controlled synthesis of lanthanum hydroxide nanoparticles, and the presentation of structural peculiarities of manganese oxide nanoparticles with an ordered Mn vacancy superstructure. These examples show that nonaqueous systems, on the one hand, allow the preparation of compositionally complex oxides, and, on the other hand, make use of the organic components (initially present or formed in situ) in the reaction mixture to tailor the morphology. Furthermore, obviously even the crystal ...

Science.gov (United States)

Nonparabolicity of the heavy hole band in diamond-like semiconductors, which occurs within the framework of the three band model with the perturbation from the other bands taken into account according to the Loewdin procedure, is studied. A direct dependence of nonparabolicity on the band anisotropy (caused by the different effect of Gamma/sub 15c/ and Gamma/sub 12c/ bands) and the inverse dependence on the magnitude of the spin-orbit splittiing is established. A connection between the effective mass of heavy holes and their energy is obtained, which is valid for the majority of diamond-like semiconductors, except for materials with a very strong nonparabolicity of the band of silicon type

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The object of this work is to develop and optimize a new type of light-emitting diode (LED) with a wire-shaped, cylindrical geometry.

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The formation of palladium silicides near the interface may decrease hydrogen solubility at the effective metal/semiconductor ...

International Nuclear Information System (INIS)

2009 p. 77-78 Ukraine Lepikh, Ya.I. Fedchuk, AP Odesa National University,

International Nuclear Information System (INIS)

Russian 1977. p. 582. USSR Antropov, AE Fedoseeva, OP Milovanov,

Energy Technology Data Exchange (ETDEWEB)

For InAs-GaAs based quantum dot lasers emitting at 1300 nm, digital modulation showing an open eye pattern up to 12 Gb s{sup -1} at room temperature is demonstrated, at 10 Gb s{sup -1} the bit error rate is below 10{sup -12} at -2 dB m receiver power. Cut-off frequencies up to 20 GHz are realised for lasers emitting at 1.1 {mu}m. Passively mode-locked QD lasers generate optical pulses with repetition frequencies between 5 and 50 GHz, with a minimum Fourier limited pulse length of 3 ps. The uncorrelated jitter is below 1 ps. We use here deeply etched narrow ridge waveguide structures which show excellent performance similar to shallow mesa structures, but a circular far field at a ridge width of 1 {mu}m, improving coupling efficiency into fibres. No beam filamentation of the fundamental mode, low a-factors and strongly reduced sensitivity to optical feedback are observed. QD lasers are thus superior to QW lasers for any system or network. ...

International Nuclear Information System (INIS)

The purpose of this work was to investigate the optical properties of several high T/sub c/ compounds in the form of sputtered films. The measurements are used toward this end: optical absorptance (using a calorimetric technique near 4.2K), which yields (after Kramers-Kronig analysis) the complex dielectric function, and thermoreflectance (which measures the change in reflectance in the optical range when a 1 to 10_0K temperature wave is applied), performed at two ambient temperatures (80 and 300_0K), yielding the differential dielectric function. The sputtered films included Nb"3Ge, Nb"3Al, V"3Ga and Nb"3Ir. It is noted that Nb"3Ir is not a high T/sub c/ superconductor. The thermoreflectance on the bulk samples V"3Si, V"3Ge and single crystal Cr"3Si were not performed because the samples were not in the form of thin films. The thermomodulation studies are correlated with the absorptance measurements in comparison to band structure calculations. When ...

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Described herein is an optical probe (120) for use in characterizing surface defects in wafers, such as semiconductor wafers. The optical probe (120) detects laser light reflected from the surface (124) of the wafer (106) within various ranges of angles. Characteristics of defects in the surface (124) of the wafer (106) are determined based on the amount of reflected laser light detected in each of the ranges of angles. Additionally, a wafer characterization system (100) is described that includes the described optical probe (120).

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Thermophotovoltaic (TPV) converters were developed and tested at the heat source operating temperature of 1,700 K. Rare-earth-doped yttrium aluminum garnet (YAG) and lutetium yttrium aluminum garnet (Lu, YAG) selective emitters, as well as a blackbody emitter, were coupled to InGaAs/InP photovoltaic (PV) cells and bandpass/infrared (IR) reflector filters. YAG-based selective emitters were adopted with Ho, Tm, and Er. PV cells had bandgaps of 0.51, 0.57, and 0.69 eV. Converter energy conversion efficiencies approaching 30%, as well as electrical output power densities near 2 W/cm{sup 2} were demonstrated. The overall performance of the filtered blackbody-based converter was found to be superior to the selective emitter YAG-based converters. The details of the measurements performed on the above converters and their individual components are presented.

Science.gov (United States)

We report the first visible (657 nm) vertical-cavity surface-emitting laser. The photopumped undoped structure was grown using low-pressure metalorganic vapor-phase epitaxy in a single-growth sequence on misoriented GaAs substrates. The optical cavity consists of an In{sub 0.54}Ga{sub 0.46}P/In{sub 0.48}(Al{sub 0.7}Ga{sub 0.3}){sub 0.52} P strained quantum-well active region and a lattice-matched In{sub 0.48}(Al{sub {ital y}}Ga{sub 1{minus}{ital y}}){sub 0.52} P (0.7{le}{ital y}{le}1.0) graded spacer region, while the distributed Bragg reflectors are composed of Al{sub 0.5}Ga{sub 0.5}As/AlAs quarter-wave stacks. Room-temperature optically pumped lasing was achieved with a very low-threshold power, clearly demonstrating the viability of this new technology. These results provide the foundation for visible semiconductor laser-diode arrays for a number of applications including laser projection displays, holographic memories, and plastic fiber ...

International Nuclear Information System (INIS)

In this work, a focused ion beam (FIB) milling process has been developed to fabricate 50 nm Bi nanowire and transistor structures using FEI-200 dual beam FIB system. For the fabrication, 50 nm bismuth film was thermally evaporated through EBL patterned PMMA windows onto SiO_2 substrates with pre-defined contact pads. Bi nanowire widths ranging from 30 nm to 100 nm have been successfully fabricated by milling out unwanted areas using 30 KeV Ga+ ion beam. A single-pixel-line ion beam blanking technique has been utilised to fabricate Bi nanowire as small as 30 nm in diameter and few micrometers long. In order to form good ohmic contacts for sub 50 nm bismuth nanowires, a drill-and-fill process has been developed using FIB to sputter away the surface oxide of bismuth after the in-situ platinum nanowire contacts deposition. To our knowledge, this is the first time a focused ion beam process has been used to fabricate bismuth nanowire. The fabricated Bi nanowires were ...

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Alloy 600 is used as a material for steam generator tubing in pressurized water reactors(PWR) due to its high corrosion resistance under PWR environment. In spite of its corrosion resistance, stress corrosion cracking(SCC) has occurred on the primary side as well as the secondary side of the tubing. Oxide on steel surfaces in aqueous solution above 100 .deg. C is composed of duplex film structure. Inner layer of the oxide is dense and less porous, which is formed by growth of oxide layer on metal surface. Outer layer of the oxide is loose adhesive, which is formed by dissolution precipitation mechanism. Growth processes occur at the metal/oxide and oxide/electrolyte interfaces and are controlled by transport of the layer forming species through the layer, i.e. by the inward diffusion of oxygen including electrolyte species and the outward diffusion of metal cations. Understanding of basic electrochemical behaviors about anodic dissolution and passivation of bare ...

International Nuclear Information System (INIS)

We have studied in detail the gamma radiation induced changes in the electrical properties of the (TeO_2)_0_._9 (In_2O_3)_0 _._1 thin films of different thicknesses, prepared by thermal evaporation in vacuum. The current-voltage characteristics for the as-deposited and exposed thin films were analysed to obtain current versus dose plots at different applied voltages. These plots clearly show that the current increases quite linearly with the radiation dose over a wide range and that the range of doses is higher for the thicker films. Beyond certain dose (a quantity dependent on the film thickness), however, the current has been observed to decrease. In order to understand the dose dependence of the current, we analysed the optical absorption spectra for the as-deposited and exposed thin films to obtain the dose dependences of the optical bandgap and energy width of band tails of the localized states. The increase of the current with the gamma radiation dose may be ...

Science.gov (United States)

Beta silicon carbide is an excellent candidate semiconductor material for demanding applications in high power and high temperature electronic devices due to its high breakdown voltage, relatively large band gap, high thermal conductivity and high melting...

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A theory has been developed for the mechano-catalytic water-splitting, which is the system of simultaneous H{sub 2} and O{sub 2} evolution by stirring the powder of an oxide semiconductor in pure water under the condition that the stirring rod must be kept in contact with the surface of the glass vessel. The kinetic equations and the coupling strength of the frictional energy conversion between mechanical and electrical systems are calculated . The total system composed of the formation of the dangling bonds on the glass surface, the trapping of the semiconductor particles at the microcrevice of the glass surface, the strong field inside the fine particles due to the frictional electricity, the mechanism of charge transfer from the semiconductor to the stirring rod, the hopping conduction of positive hole, the electric current density injected into water from the semiconductors, and the tunnel chemical ...

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A comparitive analysis is made of the principal characteristics of narrow-band and conventional semiconductor light amplifiers. It is shown that quasi-distributed filtering of the spontaneous radiation ensures a high gain and a low level of the spontaneous noise at the amplifier output.

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This course is based upon lectures in physics given by Professor Feynman at the California institute of technology during 1961 and 1962. This volume is dedicated to quantum physics, semiconductors, symmetry and advanced principles of physics.

International Nuclear Information System (INIS)

In this work, the effects of the focus ion beam (FIB) milling process on the optical properties of semiconductor nanostructures were investigated. With this aim, a sensitive materials system based on InGaAs/GaAs quantum dots with well known and excellent optical properties was selected for the FIB treatment. The FIB technique was used to locally remove a metallic mask deposited on top of the quantum dot sample. The photoluminescence (PL) signal, collected from the circular openings, was used to infer the possible damage effects of the ion beam on the properties of the dots.

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The bibliography contains citations concerning plasma immersion ion implantation (PIII) and equipment. PIII is a new technique to implant plasma ions into materials for surface modification and treatment. Topics include plasma nitriding, semiconductor doping, ion energy distribution, ion dose, pulsed plasma, metal plasma, and defect passivation. References also review applications in semiconductor device and integrated circuit manufacture, silicon material fabrication, aerospace bearings, carbon coatings on metals, and ceramic coatings. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

Science.gov (United States)

Nanosized particles are important because of their unique properties, different from the bulk, which leads to their enhanced catalytic, photocatalytic and electronic properties. This work has dealt with three different nanoparticle systems in the context of three different aspects of nanoparticle properties: (a) photocatalytis (TiO2/metal) system, (b) luminescence (CdSe) (c) alloying (Pt-Ag and Pd-Ag). The initial photocatalytic enhancement obtained by adding noble metal on semiconductor nanoparticles, degrades as fast as in 15 minutes and questions their long-term performance. XANES measurements on such irradiated systems like TiO2/Au, TiO2/Pt, TiO2/Ir indicates a positive oxidation state of these noble metals which renders them as recombination centers for photo-excited electrons and explains the decreased photocurrent. The oxidation is caused by holes. The EXAFS results also indicate a change of the interfacial structure under the effect of ...

International Nuclear Information System (INIS)

The series of cubic pyrochlore structure compounds, R_2Mo_2O_7 (R = Nd-Yb, Y; R not= Eu), were prepared as single phase materials by solid state reaction between R_2O_3 and MoO_2 at 1400 "0C in a CO/CO_2 = 1 buffer gas atmosphere. Lattice constants obtained from X-ray powder data compare well with results from previous studies. Magnetic susceptibility and magnetization data were obtained for all samples between 300 K and 4.2 K (700 K for R = Gd) and a range of applied fields. For R = Nd, Sm, and Gd magnetic ordering is observed at 97 K, 93 K and 83 K respectively which is assigned to ferromagnetism on the Mo(IV) sublattice. The Mo(IV) moment in the ordered state is about 1 #mu#/sub B/. At low temperatures, the Gd(III) and Mo(IV) moments are apparently coupled feromagnetically in Gd_2Mo_2O_7 yet the high temperature susceptibility data seem to indicate a ferrimagnetic (antiparallel) Gd(III)-Mo(IV) coupling. The low-temperature magnetic properties of Nd_2Mo_2O_7 and ...

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Using a coplanar, end-mounted antenna as a baseline, various configuration trades were performed to select a preferred solid state concept. The increase in efficiency that could be realized by use of multi bandgap solar cells, either with klystron or solid state antenna was evaluated. Satellite configurations were developed to exploit the sandwich antenna concept wherein solar cells are located on one side of the antenna panel and solid state dc/RF converters on the other side. These concepts entailed various primary and secondary reflector arrangements for directing solar energy to the solar cell side of the antenna with higher concentration ratios than used on the coplanar configurations. Operations analysis included development of a satellite construction scenario, a concept for the SCB, a top-level satellite construction operation, construction operation, construction timelines and crew sizes, mass flows to orbit, and a satellite maintenance scenario. The list ...

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New rare earth oxide emitters show greater efficiency than previous emitters. As a result, based on a simple model the efficiency of these emitters was calculated. Results indicate that the emission band of the selective emitter must be at relatively low energy (less than or equal to .52 eV) to obtain maximum efficiency at moderate emitter temperatures (less than or equal to 1500 K). Thus low bandgap energy PV materials are required to obtain an efficient thermophotovoltaic (TPV) system. Of the 4 specific rare earths (Nd, Ho, Er, Yb) studied Ho has the largest efficiency at moderate temperatures (72 percent at 1500 K). A comparison was made between a selective emitter TPV system and a TPV system that uses a thermal emitter plus a band pass filter to make the thermal emitter behave like a selective emitter. Results of the comparison indicate that only for very optimistic filter and thermal emitter properties will the filter TPV system have a greater efficiency than ...

CERN Document Server

The behavior of silver and lead azides (scaly and threadlike crystals, and compacted powders) in initiation of explosive decomposition by laser pulsed radiation has been investigated. Initiation energy thresholds in irradiation at wavelengths of 1064 nm, 532 nm, 354.7 nm, 266 nm corresponding to four laser radiation harmonics have been measured. Samples both uncovered and covered with a transparent dielectric (a quartz plate) with the compressive force of up to 0.5GPa were initiated. In the transparent spectral region (the first and second laser harmonics) of the heavy metal azide matrix the effect of covering the sample surface with a plate on initiation energy threshold was insignificant, whereas, in the region of bandgap absorption (the fourth harmonic) strong dependence of the initiation threshold on whether the surface under irradiation is uncovered or covered. The results obtained have been considered with the account of the influence of the transparent plate ...

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

International Nuclear Information System (INIS)

In a vacuum insulator, the narrow electron beam emitted from the cathode impinges on the anode and raises its temperature and also may produce high thermal stress. This high thermal stress, in conjuction with the surface electrostatic pressure may rupture the surface and detach particles from it. In this thesis, the interaction of high energy electron and laser beams with metals and semiconductors is investigated. The differential equations governing the physical processes involved in the interaction are solved by the finite element method. Effects of beam penetration into the material, variable beam reflectance at the surface, finite beam size and dependence of material properties on temperature are accounted for. The two-phase moving boundary problem, also known as the Stefan problem, is solved by an enthalpy formulation of the heat equation. Material deformation by thermal stresses caused by high temperature gradients and electrostatic forces induced by space ...

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A device for detecting neutrons includes a semi-insulated bulk semiconductor substrate having opposed polished surfaces. A blocking Schottky contact comprised of a series of metals such as Ti, Pt, Au, Ge, Pd, and Ni is formed on a first polished surface of the semiconductor substrate, while a low resistivity ("ohmic") contact comprised of metals such as Au, Ge, and Ni is formed on a second, opposed polished surface of the substrate. In one embodiment, n-type low resistivity pinout contacts comprised of an Au/Ge based eutectic alloy or multi-layered Pd/Ge/Ti/Au are also formed on the opposed polished surfaces and in contact with the Schottky and ohmic contacts. Disposed on the Schottky contact is a neutron reactive film, or coating, for detecting neutrons. The coating is comprised of a hydrogen rich polymer, such as a polyolefin or paraffin; lithium or lithium fluoride; or a heavy metal fissionable material. By varying the coating thickness and ...

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This dissertation deals with both the theoretical and the technological aspects of monolithic tunable lasers, and the experimental techniques for opto-electronic integration. In the theoretical part, the principles and limitations of wavelength tuning and spectral linewidth reduction in monolithic semiconductor lasers are described, with coupled distributed feedback-Fabry Perot (DFB-FP) lasers and long DFB lasers as examples. Stepwise tuning of wavelength over tens of nanometers and continuous tuning over the range of a mode spacing are shown to be possible. Spatial hole burning is found to affect the spectral linewidth of lasers involving strong active gratings. On the technological side, one of the major issues is the fabrication of flexible gratings. Direct-writing techniques, such as focused ion beam (FIB) implantation and e-beam lithography, provide the resolution, flexibility and accuracy that conventional holographic lithography lacks. The parasitic ...

International Nuclear Information System (INIS)

An overview on neutron scattering studies of ferromagnetic and antiferromagnetic all-semiconductor superlattices is presented. Diffraction experiments on MnTe/CdTe, MnTe/ZnTe and EuTe/PbTe superlattices show pronounced correlations between the MnTe and EuTe layers across the non-magnetic spaces, even though these layers are antiferromagnetic and the systems are nearly-insulating. Current theory status of these systems is discussed. Diffractometry and reflectometry data from EuS/PbS superlattices reveal pronounced antiferromagnetic coupling between the ferromagnetic EuS block. First polarized neutron reflectometry data from superlattices prepared of a novel ferromagnetic 'spintronics' material, Ga(Mn)As are also presented. (author)

International Nuclear Information System (INIS)

The RD50 collaboration has been exploring the development of radiation hard semiconductor devices for very high-luminosity colliders since 2002. The target fluence to qualify detectors set by the anticipated dose for the innermost tracking layers of the future upgrade of the CERN large hadron collider (LHC) is 1016 1 MeV neutron equivalent (neq) cm-2. This is about an order of magnitude higher than the maximum dose for the most exposed silicon detectors in the current machine. RD50 investigates the radiation hardening of silicon sensors from many angles: improvement of the intrinsic tolerance of the substrate material, optimisation of the readout geometry and study of novel design of detectors. A review of some of the recent activities within RD50 is here presented.

International Nuclear Information System (INIS)

The highest equilibrium free-carrier doping concentration possible in a given material is limited by the ''pinning energy'' which shows a remarkable universal alignment in each class of semiconductors. Our first-principles total energy calculations reveal that equilibrium n -type doping is ultimately limited by the spontaneous formation of close-shell acceptor defects: the 3- -charged cation vacancy in AlN, GaN, InP, and GaAs and the 1- -charged DX center in AlAs, AlP, and GaP. This explains the alignment of the pinning energies and predicts the maximum equilibrium doping levels in different materials. (c) 2000 The American Physical Society

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The mass and charge distributions in an unseparated mix of fission product nuclei from thermal-neutron fission of /sup 242m/Am were studied through semiconductor gamma-ray spectrometry. Samples of the fissionable material under study were irradiated in a vertical irradiation tube of the MIFI IRT research reactor. Following irradiation, measurements were made on aperture-calibrated semiconductor detectors. For broader identification of fission fragment nuclides three experiments were conducted that differed substantially in irradiation duration. The spectrum of gamma radiation from the mix of fission products and the time dependences of count rate at total absorption peaks were analyzed on SM-4 and Iskra-226 computers. The values of yields obtained were compared with data of investigations conducted earlier with other experimental methods, and also with the results of calculations.

International Nuclear Information System (INIS)

The radionuclide X-ray fluorescence analyzer consists of a source changer and a sample changer. "5"5Fe, "1"0"9Cd and "2"4"1Am are used as excitation sources. The radiation is detected with a semiconductor Si(Li) detector. The complete assembly of the apparatus consists of an imagine unit, a keyboard, a floppy disc drive, a printer, a console and a rack with analog and digital electronics. Its multichannel amplitude analyzer consists of power supplies, a high voltage supply, a linear amplifier, an analog-to-digital converter and a computer. The technical specifications are given. The control and data processing system is controlled with an MHB 8080A microprocessor. Software for semiconductor gamma spectrometry and for quantitative gamma spectrometry will be supplied with the equipment. (E.S.). 3 figs., 4 refs.

International Nuclear Information System (INIS)

The authors discuss several aspects of defect formation in epitax heterostructures based on solid solutions of A"3B"5 semiconductor compounds; these heterstructures were prepared by liquid phase epitaxy by cooling suitable high-temperature solutions from the initial growth temperature. An analysis shows that the regions near heterojunctions are regions of increased defect density even in compositions based on Al /SUB x/ Ga /SUB 1-x/ As-GaAs, Al /SUB x/ Ga /SUB 1-x/ P-GaP, Al /SUB x/ Ga /SUB 1-x/ Sb-GaSb, where the differences in lattice parameters of the contacting materials are a minimum.

Energy Technology Data Exchange (ETDEWEB)

Using carbon-paste-CuFeS{sub 2} electrodes and a cyclic voltammetric technique, it was found that a large number of intermediate electrochemical oxidation reactions were associated with the dissolution of chalcopyrite in presence and absence of bacteria. The effects of concentrations of copper, ferrous and ferric ions, as well as of agitation on the peaks of cyclic voltammograms were measured. It was established that chalcopyrite oxidation was solid-state controlled as suggested by the data of chronopotentiometric and chronoamperometric measurements. The activation energy of solid state diffusion of chalcopyrite leaching was determined by the Sand's method to be {triangle}E{sub a} = 20.5 kJ. The leaching mechanism is discussed in terms of solid-state properties (energy bonding) of the n-type semiconductor chalcopyrite and energy density states of redox systems of acidic bacterial leach media. A generalized model for the mechanism of chalcopyrite leaching ...

Science.gov (United States)

A general model for the analysis of metal-semiconductor solar cells is presented. The model takes into account the cell optical properties, carrier recombination effects, semiconductor minority-carrier properties, series resistance, cell thickness, and active surface area. Numerical methods are used to solve the appropriate continuity equations and hence compute the photocurrent density under AMO conditions. The operation of the model is demonstrated using p- and n-type Si and GaAs with Au being taken as the barrier metal. Calculations are presented showing the effect on solar energy conversion efficiency of surface recombination velocity, barrier height, minority-carrier lifetime, barrier metal thickness, collecting grid configuration, and cell thickness. A comparison of practical and computed data for the Au/n-GaAs system yields good agreement. (AIP)

International Nuclear Information System (INIS)

Recent progress with the (Al_xGa_1_-_x)_0_._5In_0_._5P alloy system has resulted in laser diodes which operate at room temperature at wavelengths below 640 nm. OMVPE is used to grow the multi-quantum-well devices in a graded-index separate-confinement configuration. Laser threshold currents as low as 75 mA have been achieved.

International Nuclear Information System (INIS)

An investigation of the Ll x-#gamma# angular correlations following the decay of "2"0"7Bi is done by using a Si(Li) semiconductor counter as L x-ray detector. Coincidence measurements at five different angles were made between the 570-keV #gamma# ray (gated in the movable counter) and the Ll x spectrum (displayed in a multichannel analyzer).

CERN Document Server

A self-organizing particle swarm is presented. It works in dissipative state by employing the small inertia weight, according to experimental analysis on a simplified model, which with fast convergence. Then by recognizing and replacing inactive particles according to the process deviation information of device parameters, the fluctuation is introduced so as to driving the irreversible evolution process with better fitness. The testing on benchmark functions and an application example for device optimization with designed fitness function indicates it improves the performance effectively.

International Nuclear Information System (INIS)

This study mainly concerns medical explorations by radioisotopes. Detectors with medical exams and applications are described. Ionisation chambers, semiconductor detectors and scintillation counters are also presented. Uses of radioisotopes in medicine in vivo and in vitro techniques are explained. Examples of scintiscanning are given like: angiography, nuclear cardiography and thyroid scintiscanning. The importance of the study is to present a panorama of nuclear medicine laboratories -at the time- in hospitals in Lebanon.

International Nuclear Information System (INIS)

X-ray scattering methods suitable for the investigation of the morphology and chemical composition of self-organized quantum dots and quantum wires are reviewed. Their application is demonstrated in experimental examples showing that a combination of small angle X-ray scattering with high-resolution X-ray diffraction can reveal both the shape and the chemical composition of the self-organized objects. (author)

International Nuclear Information System (INIS)

Elements Ti, Mn, Fe, Ni, Cu, Zn, Pb, Br, Rb and Sr were determined by the method of radionuclide X-ray fluorescence analysis with semiconductor detection in samples of Taraxacum officinale from various localities of Bratislava. The dependence of their content on the source and the degree of the air pollution was found out. (author).

International Nuclear Information System (INIS)

Radionuclide X-ray fluorescence method with a Si/Li semiconductor detector and "2"3"8Pu exciting source was used in the determination of Cr, Fe, Ni, Cu, and Zn content in industrial wastewaters. Simultaneously, the effects of the wastewaters on activated sludge biocenose were evaluated. (author) 6 refs.; 1 fig.; 1 tab.

International Nuclear Information System (INIS)

Radionuclide X-ray fluorescence method with Si/Li semiconductor detector and "2"3"8Pu exciting source was used for the determination of Cu, Ni, Zn and Pb in plant samples (Taraxacum officinale) from various localities near the highway D-61 Bratislava-Trnava (SR). (author) 2 refs.; 1 fig.; 1 tab.

Energy Technology Data Exchange (ETDEWEB)

Extensive research into the treatment and control of Volatile Organic Compounds (VOCs) from semiconductor industry manufacturing processes has identified the need for alternatives to existing combustion devices. Specifically, semiconductor manufacturing design is moving toward exploiting effective, small-scale, abatement control technologies for specific point-of-use (POU) waste streams associated with a particular component or manufacturing tool. The Silent Discharge Plasma (SDP) developed at Los Alamos National Laboratory is a nonthermal plasma technology created by a dielectric-ballasted electrical discharge. Influent gas-phase pollutants are destroyed in the reactor by the free radicals or electrons generated by the plasma. This paper examines the potential for SDP to be used in niche circumstances for POU control of VOC exhaust streams specific to the semiconductor industry. A sensitivity analysis is presented, showing ...

Science.gov (United States)

"Precision manufacture of ceramic parts with CNC machining capability for aerospace, lasers, semiconductors and other industries. Materials include alumina, zirconia, glass, ferrites, silicon carbide, silicon nitride, sapphire, cordierite, mullite and others. A.C.T. has seen the number of applications and demand for high-realiability ceramics (aluminum oxide, zirconia, glass, ferrites, silicon carbide, silicon nitride, sapphire, cordierite, mullite, etc...) increase continually within the aerospace, computer and the industrial markets."

Wastenet

The structure of the creative industries is changing 15

Energy Technology Data Exchange (ETDEWEB)

Since information has been regarded os a physical entity, the field of quantum information theory has blossomed. This brings novel applications, such as quantum computation. This field has attracted the attention of numerous researchers with backgrounds ranging from computer science, mathematics and engineering, to the physical sciences. Thus, we now have an interdisciplinary field where great efforts are being made in order to build devices that should allow for the processing of information at a quantum level, and also in the understanding of the complex structure of some physical processes at a more basic level. This thesis is devoted to the theoretical study of structures at the nanometer-scale, 'nanostructures', through physical processes that mainly involve the solid-state and quantum optics, in order to propose reliable schemes for the processing of quantum information. Initially, the main results of quantum information ...

Science.gov (United States)

Surface scientists argue about the fundamental nature of Schottky barriers, or more precisely what determines the location of the Fermi level at semiconductor surfaces and interfaces. Electrical and materials engineers worry about how to make Schottky barrier diodes and gates to field effect transistors and the control of barrier heights. There is some interesting middle ground in which the location of the surface and interface Fermi level can, for example, determine semiconductor doping characteristics during crystal growth. The authors will discuss several interesting and well known examples of doping characteristics which are still somewhat mysterious. Specifically, they address the following question: (1) why is Ge doped GaAs p type when grown from Ga melts but n type when grown from Au melts (2) why is low resistivity p type ZnSe, AlAs, and AlGaInP hard to make, and more importantly, how can the problem be fixed. In addition they describe ...

Energy Technology Data Exchange (ETDEWEB)

A system of equations describing transient enhanced diffusion of beryllium in InGaAs due to kick-out mechanism or due to formation, migration, and dissociation of the pairs ''beryllium atom-group III self-interstitial'' is proposed and analyzed. Simulation of coupled diffusion of beryllium atoms and self-interstitials in InGaAs during rapid thermal annealing was done for the case of dual implantation. For the experiment under consideration the first ion implantation of phosphorus atoms produced the region of extended defects that led to ''uphill'' diffusion of implanted Be in the defect region and in the vicinity of the surface. The suggested reason of ''uphill'' diffusion could be related to the nonuniform distribution of group III self-interstitials that was formed due to the absorption of point defects on the extended defects and on the surface of a ...

Energy Technology Data Exchange (ETDEWEB)

Neutron transmutation doping(NTD) for producing ntype silicon semiconductor is based on the conversion of the Si-30 isotope into phosphorus atom by neutron absorption reaction. By using this method, silicon semiconductors with extremely uniform n-type dopant distributions can be produced, and this is the dominant advantage of NTD compared with the conventional chemical doping. HANARO has two vertical holes for NTD, and the commercial NTD service for 5 and 6 inch silicon ingots has been going on at the NTD2 hole. Generally, NTD method is applied to the initially n-type silicon material. But, an initially p-type silicon material can also be used for the production of uniformly doped n-type silicon by using NTD method. Therefore, in this work, we investigated the relationship between the irradiation neutron fluence and the final resistivity of the initially p-type silicon material. Thereafter, we established the methodology for the neutron ...

Science.gov (United States)

Data are presented on the insulating properties and capacitance-voltage (CV) characteristics of metal-oxide-semiconductor (MOS) device-thickness (below approx. 100 nm) native oxides formed by wet thermal oxidation of thin InAlP epilayers lattice matched to GaAs. Low leakage current densities of J=1.4 x 10-9 A/cm2 and J=8.7 x 10-11 A/cm2 are observed at an applied field of 1 MV/cm for MOS capacitors fabricated with 17 nm and 48 nm oxides, respectively. TEM images show that the In-rich interfacial particles which exist in 110 nm oxides are absent in 17 nm oxide films. Quasi-static capacitance-voltage measurements of MOS capacitors fabricated on both n-type and p-type GaAs show that the InAlP oxide-GaAs interface is sufficiently free of traps to support inversion, indicating an unpinned Fermi level. These data suggest that InAlP native oxides may be a viable insulator for GaAs MOS device applications.

Energy Technology Data Exchange (ETDEWEB)

As semiconductor device dimensions continue to shrink, the drive beyond 250 nm is creating significant problems for the device processor. In particular, trends toward shallower-junctions, lower thermal budgets and simplified processing steps present severe challenges to ion implantation. In parallel with greater control of the implant process goes the need for a better understanding of the physical processes involved during implantation and subsequent activation annealing. For instance, the need for an understanding of dopant-defect interaction is paramount as defects mediate a number of technologically important phenomena such as transient enhanced diffusion and impurity gettering. This paper will outline the current trends in the ion implantation and some of the challenges it faces in the next decade, as described in the semiconductor roadmap. It will highlight some recent positron annihilation work that has made a contribution to addressing ...

Energy Technology Data Exchange (ETDEWEB)

The research on the therapy of brain tumors and others by the thermal neutron irradiation using research reactors is to kill tumor cells by accumulating boron at a tumor part, and using {alpha} particles and {sup 7}Li generated by {sup 10}B(n, {alpha}){sup 7}Li reaction of thermal neutrons, which is known as boron neutron capture therapy (BNCT). In Japan Atomic Energy Research Institute, the medical irradiation facility was installed in the thermal neutron column of the JRR-2, and as of March, 1994, 22 cases of irradiation have been carried out. In order to monitor the variation of thermal neutron flux during irradiation, the real time measurement using a simultaneous monitor is carried out, but there is the variation of measured values in the Si semiconductor, p-n junction detector possibly due to its direction dependence. The experiment was carried out to quantity the direction dependence of the detector by using the neutron radiography facility at the JRR-3M. Si ...

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the progress of the Solid State Photovoltaic Research Branch of the Solar Energy Research Institute (SERI) from October 1, 1988, through September 30,l 1989. Six technical sections of the report cover these main areas of SERIs in-house research: Semiconductor Crystal Growth, Amorphous Silicon Research, Polycrystalline Thin Films, III-V High-Efficiency Photovoltaic Cells, Solid-State Theory, and Laser Raman and Luminescence Spectroscopy. Sections have been indexed separately for inclusion on the data base.

International Nuclear Information System (INIS)

This chapter is an overview of total-ionizing-dose and single-event hardening techniques and should be used as a guide to a range of research publications. It should be stressed that there is no clear and simple route to a radiation-tolerant silicon integrated circuit. What works for one fabrication process may not work for another, and there are many complex interactions within individual processes and designs. The authors have attempted to highlight the most important factors and those process changes which should bring improved hardness. The main point is that radiation-hardening as a procedure must be approached in a methodical fashion and with a good understanding of the response mechanisms involved.

International Nuclear Information System (INIS)

Radionuclide X-ray fluorescence analysis for nondestructive determination of Fe, Zn, Pb, and Br in air samples collected on nitrocellulose membrane filter Synpor 4 is described. A "2"3"8Pu source for the excitation and a semiconductor Si/Li detector for the detection of characteristic and L-fluorescent radiation of the above elements were used. A correction method based upon the measurements of simple or multiple Compton scattering for compensation of varying mass per unit area values in sample deposits was theoretically proposed and experimentally tested. The results obtained both with and without the correction were compared and good agreement with those given by atomic absorption spectrometry was observed. (author).

International Nuclear Information System (INIS)

The present work gives preliminary results of analysis of drug mixtures (NEPHROSAL tea bag) and its water infusion. In a sample of dried drugs the elements K, Ca, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Pb were identified, whereas in their water infusion only Ca, Mn, Zn and Sr were found. The method applied was radionuclide X-ray fluorescence analysis using a radionuclide source "1"0"9Cd, a Si/Li semiconductor detector and a multichannel analyzer Canberra 8100. (author) 6 refs.; 3 figs.

Energy Technology Data Exchange (ETDEWEB)

The physics of microcavities have been a subject of intense study over the past 25 years. This work stimulated a large body of experimental and theoretical work on the optimization of the light extraction properties of light-emitting diodes. Not only has this led to the current high efficiency microcavity LEDs but also to the high brightness LEDs based on other approaches, which are presently available on the market. An overview of the state of the art of planar semiconductor microcavity LEDs will be presented. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

International Nuclear Information System (INIS)

Radionuclide X-ray fluorescence method with a Si/Li semiconductor detector and "2"3"8Pu exciting source was used in the study of Mn, Fe, Cu, Zn, and Pb content of solid emissions, raw and final materials of a brick factory. From the point of view of metal content, the working environment if the brick factory is safe for workers. (author) 2 refs.; 2 figs.; 1 tab.

International Nuclear Information System (INIS)

The aim of this thesis is the study of new systems devoted to the real time neutron spectrometry and dosimetry. The microelectronics technologies have been used to research a micro system integrating sensor and data processing in real time. The multi range sensor is based on many pair of semiconductor diodes placed face to face and covered by lithium fluoride. The sensor has been designed and its behavior has been simulated. Its operating in reference neutrons beams has been analyzed. (A.L.B.)

International Nuclear Information System (INIS)

The physical foundations are described of radionuclide X-ray fluorescence analysis (RXFA) and the table shows the values of K- and L-absorption thresholds and the K- and L-line energies of elements. The calculation of the intensity of characteristic radiation during RXFA proceeds from relations derived for conventional X-ray fluorescence analysis. The choice of the radionuclide source is ruled by the nature of the analysed substance and the used detection technique. The diagram shows the areas of radionuclide sources and the energy of the fluorescence radiation of elements. The table shows the spectra of radionuclide sources suitable for the purposes of RXFA measured by semiconductor Si(Li) and Ge(Li) detectors. (ES).

Science.gov (United States)

Another difference lies in the speed of star evolution. 2. Computation of Stellar Structure and Their Evolution. The structure of stars at certain instants ...

KoreaScience (Korea)

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J-STORE (Japan)

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UK PubMed Central (United Kingdom)

Approximately 65% of PSI structures report some type of ligand(s) that is bound in the crystal structure. Here, a description is given of how such ligands are handled and analyzed at the JCSG and a...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

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Energy Technology Data Exchange (ETDEWEB)

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KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

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International Science & Technology Center (ISTC)

Fundamental Research of Materials Structure and Properties Changes Resulted from Irradiation by Means of Complex of Modern Physical Methods

Energy Technology Data Exchange (ETDEWEB)

Techniques for studying nuclear structure are reviewed. Examples are given of charge density determinations by electron and proton inelastic scattering. (AIP)

Energy Technology Data Exchange (ETDEWEB)

We summarize the Hopf algebra structure on Feynman diagrams and emphasize the interest in further algebraic structures hidden in Feynman graphs.

British Library Electronic Table of Contents (United Kingdom)

Two analytical methods were proposed in this research, coupled electro-thermal finite element (FE) analysis and thermal-mechanical FE analysis, to analyze the mechanical behavior of bonding wire of power module under cyclic power loads, and the International Electrotechnical Commission standard is adopted in conducting a power cycling test. The exterior temperature distribution was measured by an infrared thermometer. Moreover, the junction temperature is calculated from the given thermal impedance of the semiconductor chip, chip power loss, and case temperature. Subsequently, the simulated temperature distribution via electro-thermal FE analysis is compared with experimental results to validate the methodology used in the aforementioned analysis. The analysis shows compressive stress at t...

International Nuclear Information System (INIS)

The importance of point defects in semiconductor and function materials has been studied in detail, but effective means for detecting point defects has not been available for a long time. The end of range defects in Si, produced by 140 keV Ge"+ implantation, were investigated as detectors for measuring the interstitial concentration created by 42 keV B"+ implantation. The concentration of interstitial resulting from the B"+ implantation and the behavior of the interstitial flux under different annealing condition were given. The enhanced diffusion in the boron doped EPI marker, resulting from mobile non-equilibrium interstitials was demonstrated to be transient. Interstitial fluxes arising from processing can be detected by transient enhanced diffusion (TED) of doped marker layers as well

International Nuclear Information System (INIS)

Reactions of reducing species from acetonitrile media with silver iodide particles (#approx#25-angstrom diameter) have been investigated by pulse radiolysis techniques. Injection of electrons into these ultrasmall particles leads to transient bleaching of the adsorption of AgI at wavelengths close to the onset of absorption (#approx#400 nm) with the concomitant reduction of AgI to metallic silver. The reduction of Ag"+ ions and formation of silver atoms and/or dimeric Ag_2 molecules on three different size AgI particles (#approx#100, 35, and #approx#25 angstrom) have also been examined by picosecond laser spectroscopy.

International Nuclear Information System (INIS)

A novel system for real-time radiation monitoring in reactor or accelerator facilities has been studied using an imaging plate. The authors made a feasibility study on a new neutron detection system using both photostimulated luminescence (PSL) and prompt luminescence (PL) generated in a neutron imaging plate (NIP) when the NIP is irradiated by neutrons. A readout system consisting of a semiconductor laser and a photomultiplier tube was fabricated for the purpose. It was confirmed that the system can measure both PSL and PL, where Am-Li was used as a neutron source. It may be possible to establish a new wide-range neutron monitoring system using the developed system as a PL mode normally, and as a PSL mode in case of intense neutron dose that cannot be measured in a PL mode because of saturation of the detection system. (author)

Energy Technology Data Exchange (ETDEWEB)

Pilot-plant irradiation began in Hungary in 1969 with the construction of a high-activity multi-purpose /sup 60/Co facility. Technologies for radiation sterilization, food handling, plastics irradiation as well as chemical dosimetry, semiconductor instrumental dosimetry, computer-based construction and control methods have been developed. Our chlorobenzene dose-meter system is used in Hungary and abroad; as a result of an IAEA-organized dosimetric intercomparison the system was adopted as a reference system. The institute has developed into a basic institute for the reconstruction and re-load of old ..gamma..-facilities as well as it serves for the planning, construction and launching of new ones in Hungary.

Energy Technology Data Exchange (ETDEWEB)

As thin films become increasingly popular (for solar cells, LEDs, microelectronics, batteries), quantitative morphological information is needed to predict and optimize the film's electronic, optical and mechanical properties. This quantification can be obtained quickly and easily with X-ray diffraction using an area detector and synchrotron radiation in two simple geometries. In this paper, we describe a methodology for constructing complete pole figures for thin films with fiber texture (isotropic in-plane orientation). We demonstrate this technique on semicrystalline polymer films, self-assembled nanoparticle semiconductor films, and randomly-packed metallic nanoparticle films. This method can be immediately implemented to help understand the relationship between film processing and microstructure, enabling the development of better and less expensive electronic and optoelectronic devices.

Energy Technology Data Exchange (ETDEWEB)

The photocatalyzed degradation of pyridine in the gas phase was investigated using titanium dioxide semiconductor supported on mordenite. The complete mineralization was found to occur over a catalyst containing 75 wt% TiO{sub 2} and 25 wt% mordenite in about 180 min in the presence of saturated water vapor at O{degrees}C (4.6 Torr). Low water vapor pressure of 0.096 Torr was found to be sufficient to achieve a reasonably high percentage and rate of degradation. Diffusion of pyridine within the catalyst adversely affects the activity when the thickness of the catalyst coating exceeds the penetration depth of illumination. The activity of the zeolite-supported catalysts was higher than that of TiO{sub 2}. The photonic efficiency for the complete mineralization of pyridine to CO{sub 2} was determined to be 0.48. 29 refs., 6 refs., 1 tab.

Energy Technology Data Exchange (ETDEWEB)

This report describes progress during the first year of a three-year project. The objective of the research is to examine new design approaches for achieving very high conversion efficiencies. The program is divided into two areas. The first centers on exploring new thin-film approaches specifically designed for III-V semiconductors. The second area centers on exploring design approaches for achieving high conversion efficiencies without requiring extremely high quality material. Research activities consisted of an experimental study of minority carrier recombination in n-type, metal-organic chemical vapor deposition (MOCVD)-deposited GaAs, an assessment of the minority carrier lifetimes in n-GaAs grown by molecular beam epitaxy, and developing a high-efficiency cell fabrication process.

Energy Technology Data Exchange (ETDEWEB)

An all solid-state kicker pulser for a proton radiography system has been designed. Multiple solid-state modulators stacked in an inductive-adder configuration are utilized in this kicker pulser design. Each modulator is comprised of multiple metal-oxide-semiconductor field-effect transistors (MOSFETs) which quickly switch the energy storage capacitors across a magnetic induction core. Metglas is used as the core material to minimize loss. Voltage from each modulator is inductively added by a voltage summing stalk. A circuit model of a prototype inductive adder kicker pulser modulator has been developed to predict the performance of the pulser modulator. The modeling results are compared with experimental data.

International Nuclear Information System (INIS)

Efficient, low-temperature conversion of infrared light into visible light (red, orange, green) is reported at single heterojunctions and undoped quantum wells of GaAs and ordered Al_xGa_1_-_xInP_2; an increase in photon energy of 700 meV is obtained. The signal originates from the high-band-gap layers and disappears only if the excitation energy is tuned below the GaAs band gap. The intensity of the up-converted photoluminescence (PL) is found to decrease significantly slower with increasing temperature than that of the regular PL and it remains observable up to 200 K. Interface-induced cold Auger processes along with the presence of trapped states for both electrons and holes in these ordered alloys account for this nonlinear mechanism. A colinear double-beam experiment confirms this. copyright 1996 The American Physical Society.

Energy Technology Data Exchange (ETDEWEB)

The difference between the two nonclassical lights, i.e., the squeezed state and number-phase minimum uncertainty state (NUS) is discussed. The four different generation principles for NUS are described. They are: unitary evolution using self-phase modulation; nonunitary state reduction by the first kind measurement; controlled state reduction by quantum correlation measurement-feedback, and high saturated laser oscillation with suppressed-pump-noise. The constant current-driven semiconductor laser based on the last principle generated the NUS with photon number noise reduced below the standard quantum limit by 40 percent in the entire frequency region from dc to 1.1 GHz. Several applications of NUS including quantum communication, quantum mechanical computers and interferometric gravitational detection are discussed briefly. This presentation is represented by viewgraphs only.

Energy Technology Data Exchange (ETDEWEB)

A focused ion beam (FIB) system produces a final beam spot size down to 0.1 .mu.m or less and an ion beam output current on the order of microamps. The FIB system increases ion source brightness by properly configuring the first (plasma) and second (extraction) electrodes. The first electrode is configured to have a high aperture diameter to electrode thickness aspect ratio. Additional accelerator and focusing electrodes are used to produce the final beam. As few as five electrodes can be used, providing a very compact FIB system with a length down to only 20 mm. Multibeamlet arrangements with a single ion source can be produced to increase throughput. The FIB system can be used for nanolithography and doping applications for fabrication of semiconductor devices with minimum feature sizes of 0.1 .mu.m or less.

International Nuclear Information System (INIS)

The excitation functions of the reactions "9"8Mo(d,p)"9"9Mo and "1"0"0Mo(d,p)"1"0"1Mo have been determined by irradiation of stacked foils with deuterons of energies less than 13 MeV and non-destructive determination of the absolute activity of the Mo radioisotopes by semiconductor #gamma#-ray spectrometry. From the excitation functions, the thick-target yields and the saturation production rates of "9"9Mo and "1"0"1Mo for deuteron energies of 13.0 MeV and 11.7 MeV have been calculated. Implications for the production of "9"9Mo for generators of sup(99m)Tc are discussed. (author).

International Nuclear Information System (INIS)

Off-axis electron holography is used to characterize a linear array of transistors, which was prepared for examination in cross-sectional geometry in the transmission electron microscope (TEM) using focused ion beam (FIB) milling from the substrate side of the semiconductor device. The measured electrostatic potential is compared with results obtained from TEM specimens prepared using the more conventional 'trench' FIB geometry. The use of carbon coating to remove specimen charging effects, which result in electrostatic fringing fields outside 'trench' specimens, is demonstrated. Such fringing fields are not observed after milling from the substrate side of the device. Analysis of the measured holographic phase images suggests that the electrically inactive layer on the surface of each FIB-milled specimen typically has a thickness of 100 nm.

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the progress of the Basic Sciences Branch of the National Renewable Energy Laboratory (NREL) from October 1, 1989, through September 30, 1990. Six technical sections of the report cover these main areas of NREL's in-house research: Semiconductor Crystal Growth, Amorphous Silicon Research, Polycrystalline Thin Films, III-V High-Efficiency Photovoltaic Cells, Solid-State Theory, and Solid-State Spectroscopy. Each section of the report was written by the group leader principally in charge of the work. The task in each case was to explain the purpose and major accomplishments of the work in the context of the US Department of Energy's National Photovoltaic Research Program plans.

Energy Technology Data Exchange (ETDEWEB)

An apparatus capable of producing current or voltage controlled positive and negative ion beams in 1-atm oxidizing and nonoxidizing ambients between 25/sup 0/ and 950 /sup 0/C is presented. The apparatus utilizes a point-to-plane corona discharge in the gas phase. Room-temperature experiments revealed that the small differences in ion beam shape between the two polarities is primarily due to the difference in applied voltage required to produce the same current for the two polarities. Due to increased ion mobility and decreased threshold voltage at higher temperatures, a slight broadening of the ion beam current-density profiles for both positive and negative ions is predicted.

Energy Technology Data Exchange (ETDEWEB)

For charged particle irradiations, the response of an imaging plate (IP) changes around the Bragg peak. Therefore, an appropriate compensation is necessary for the evaluation of dose distribution formed by charged particles such as protons. In this paper, the response of IPs to clinical proton beams is investigated. An experimentally-obtained depth-dose distribution (an ordinary Bragg curve) by a silicon semiconductor detector (SSD) is employed to evaluate the compensation factors as a function of proton penetrating depth, i.e. residual range. A typical dose distribution in a water phantom formed by an L-shaped bolus is measured by IPs and corrected by using the information of those compensation factors; the residual proton range is successfully calculated by the pencil beam algorithm at an arbitrary point. The results show a good agreement with the measurements by the SSD within the rms error of 3.0%.

Energy Technology Data Exchange (ETDEWEB)

The availability of polysilicon feedstock has become a major issue for the photovoltaic (PV) industry in recent years. Most of the current polysilicon feedstock is derived from rejected material from the semiconductor industry. However, the reject material can become scarce and more expensive during periods of expansion in the integrated-circuit industry. Continued rapid expansion of the PV crystalline-silicon industry will eventually require a dedicated supply of polysilicon feedstock to produce solar cells at lower costs. The photovoltaic industry can accept a lower purity polysilicon feedstock (solar-grade) compared to the semiconductor industry. The purity requirements and potential production techniques for solar-grade polysilicon have been reviewed. One interesting process from previous research involves reactive gas blowing of the molten silicon charge. As an example, Dosaj et all reported a reduction of metal and boron impurities from ...

Energy Technology Data Exchange (ETDEWEB)

The effect of various window layers for InP solar cells are studied. Window materials that have type 1 and type 2 alignment in the window/emitter interface are compared. All window materials that form a type 2 alignment with InP, such as Al{sub 0.20}In{sub 0.80}P, Ga{sub 0.20}In{sub 0.80}P, Al{sub 0.55}In{sub 0.45}As and Al{sub 0.60}In{sub 0.40}P, cause a high interface recombination velocity, which deteriorates the carrier collection. This recombination takes place due to the spatially indirect quantum well transition between the triangular quantum wells formed in the interface. ZnSe as a window layer material with type 1 alignment does not have this problem, but still decreased response in the short wavelength region is observed due to misfit dislocation induced trap sites. Future prospects for the window layer development for InP are discussed. The discussion is extended also to other III-V semiconductor based solar cell materials, such as Ga{sub 0.5}In{sub ...

Energy Technology Data Exchange (ETDEWEB)

Analyses of process system properties were continued for important chemical materials involved in the several processes under consideration for semiconductor and solar cell grade silicon production. Major activities were devoted to physical, thermodynamic and transport property data for silicon. Property data are reported for vapor pressure heat of vaporization, heat of sublimation, liquid heat capacity and solid heat capacity as a function of temperature to permit rapid usage in engineering. Chemical engineering analysis of the HSC process (Hemlock Semiconductor Corporation) for production of silicon was initiated. The process is based on hydrogen reduction of dichlorosilane (DCS) to produce the polysilicon. The chemical vapor deposition reaction for DCS is faster in rate than the conventional process route which utilizes trichlorosilane (TCS) as the silicon raw material. Status and progress are reported for primary activities of base case ...

Energy Technology Data Exchange (ETDEWEB)

The novel optical, electronic, and/or magnetic properties of metal and semiconductor nanoparticles have resulted in extensive research on new methods for their preparation. An ideal preparation method would allow the particle size, size distribution, crystallinity, and particle shape to be easily controlled, and would be applicable to a wide variety of material systems. Numerous preparation methods have been reported, each with its inherent advantages and disadvantages; however, an ideal method has yet to emerge. The most widely applied methods for nanoparticle preparation include the sonochemical reduction of organometallic reagents,(1&2) the solvothermal method of Alivisatos,(3) reactions in microemulsions,(4-6) the polyol method (reduction by alcohols),(7-9) and the use of polymer and solgel materials as hosts.(10-13) In addition to these methods, there are a variety of methods that take advantage of the unique properties of a supercritical fluid.(14&15) ...

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An overview of the understanding of correlation between valence electron and the optical properties of binary (A{sup N}B{sup 8-N}) and ternary (A{sup N}B{sup 2+N}C{sub 2}{sup 7-N}) tetrahedral semiconductors is presented here. We have presented two expressions relating the dielectric constant and electronic polarizability for the transition metal chalcogenides and pnictides (A{sup II}B{sup VI} and A{sup III}B{sup V}) and chalcopyrites (A{sup I}B{sup III}C{sub 2}{sup VI} and A{sup II}B{sup IV}C{sub 2}{sup V}) with the product of valence electrons and nearest neighbour distance d (A). The dielectric constant and electronic polarizability of these solids exhibit a linear relationship when plotted on a log-log scale against the nearest neighbour distance d (A), but fall on different straight lines according to the valence electron product of the compounds. We have applied the proposed relation on these solids and found a better agreement with the experimental data as ...

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In order to perform the structural analysis and stress evaluation for frame structures in the nuclear power plants, ADAMS (AIJ Design Analysis and Modules System) has been developed by the addition of the following functions to the ICES-STRUDL system. 1. Load combination and stress evaluation on the basis of specifications for designing steel structure (issued by the Architecture Institute of Japan). 2. Combination of load and stress evaluation of piping support on the basis of the regulations of Ministry of International Trade and Industry. 3. Addition of other functions than that described above. ADAMS enables structural analysis and stress evaluation exactly and efficiently not only for a large scale structure such as the pipe whip protection structure installed inside of the primary containment vessel for many loading cases but also for a large number of ...

International Nuclear Information System (INIS)

The aim of the paper is to define and study algebraic operations closely related to the group structure on the homotopy groups of topological spaces. These are certain many-place operations on the homotopy groups. The family of these operations induces an algebraic structure on the homotopy groups, which is called an A?-group structure by analogy with the A?-structures introduced by Stasheff.

International Nuclear Information System (INIS)

It is shown that the available data on x, Q"2, and A dependence of nuclear structure functions and for their ratios (EMS effect) can be described in terms of the flucton model with rescaling of parton distributions in nuclei. The x, Q"2 and A dependence of nuclear structure functions in the cumulative range (x >1) is predicted.

UK PubMed Central (United Kingdom)

Emphasis was put on the comparative quantitative structure-activity approaches to the exploration of action mechanisms of structurally different classes of compounds showing the same type of activity...Full Text Available

UK PubMed Central (United Kingdom)

AbstractX-ray diffraction analysis of pressure-induced structural changes in the Aequorea yellow fluorescent protein Citrine reveals the structural basis for the continuous...Full Text Available

UK PubMed Central (United Kingdom)

BackgroundStructured noncoding RNAs perform many functions that are essential for protein synthesis, RNA processing, and gene regulation. Structured RNAs can be detected by comparative...Full Text Available

British Library Electronic Table of Contents (United Kingdom)

The present paper considers the evaluation of timber structures with the focus on robustness due to connection ductility. The robustness analysis is based on the structural reliability framework applied to a simplified mechanical system. The structural timber system is depicted as a parallel system. An evaluation method of the ductile behaviour is introduced. For different ductile behaviours, the system reliability is estimated based on Monte Carlo simulation. A correlation between the strength of the structural elements is introduced. The results indicate that the reliability of a structural timber system can be significantly increased due to the ductile behavior.

British Library Electronic Table of Contents (United Kingdom)

Major similarities between robustness assessment and seismic design exist, and significant information can be brought from seismic design to robustness design. As will be discussed, although some methods and limitations considered in seismic design can improve robustness, the capacity of the structure to sustain limited damage without disproportionate effects is significantly more complex. In fact, seismic design can either improve or reduce the resistance of structures to unforeseeable events, depending on the structural type, triggering event, structural material, among others. Based on a case study, the influence of redundancy and ductility on the seismic behavior and robustness of a long-span timber structure is assessed.

UK PubMed Central (United Kingdom)

This paper examines theoretically the effects that restraints on the tertiary structure of a superhelical DNA domain exert on the energetics of linking and the onset of conformational transitions. The...Full Text Available

Science.gov (United States)

The synthesis and structural characterization of a novel In(III) complex is described. The reaction

International Nuclear Information System (INIS)

1974. 20 p. United States Anon. American Society of Mechanical

UK PubMed Central (United Kingdom)

Structural analysis of an acetylcholine receptor from Torpedo californica leads to a three-dimensional model in which a "monomeric" receptor is shown to contain subunits arranged around a central ionophoretic...Full Text Available

Science.gov (United States)

... Composite sandwich panels with fiber reinforced plastic (FRP) faces and low 3 density foam cores are fast becoming the structural material of ...

International Nuclear Information System (INIS)

In the past decade, considerable progress has been made on reducing the seismic response of structures through seismic isolation. Application of seismic-isolation techniques to nuclear power facilities is currently being investigated. This paper presents an analysis of the effect of long period motions on a seismic-isolated nuclear structure. Preliminary analysis indicates that long-period earthquake motions increase structural accelerations and relative displacements between the upper and lower mats. Relative displacement between the mats can be represented by spectral displacement at the frequency of the structure, and can be effectively reduced by increasing viscous damping in the isolator. The isolated structure behaves as a system with one degree of freedom. Future analysis of seismic effects on seismic-isolated structures should include the linear and ...

Science.gov (United States)

Development efforts have been undertaken to improve the processing and structural efficiencies of

International Nuclear Information System (INIS)

... functions intermediate structure isobaric analogs level widths mev range

Science.gov (United States)

star evolution, globular cluster structure and evolution, massive stars, supernova remnants, reflection nebulae, interstellar dust, structure of the ISM, ...

Science.gov (United States)

... CI Appendix D: Conference Attendees ..... D1 Appendix E: Structural Steel Connection Design on Federal Projects ..... El iv ...

CERN Document Server

A conceptual design for the module design and disc support structure for the ATLAS forward SCT tracker

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An x-ray zone plate was fabricated using the novel approach of focused ion beam (FIB) milling. The FIB technique was developed in recent years, it has been successfully used for transmission electron microscopy (TEM) sample preparation, lithographic mask repair, and failure analysis of semiconductor devices. During FIB milling, material is removed by the physical sputtering action of ion bombardment. The sputter yield is high enough to remove a substantial amount of material, therefore FIB can perform a direct patterning with submicron accuracy. The authors succeeded in fabricating an x-ray phase zone plate using the Micrion 9500HT FIB station, which has a 50 kV Ga{sup +} column. Circular Fresnel zones were milled in a 1.0-{micro}m-thick TaSiN film deposited on a silicon wafer. The outermost zone width of the zone plate is 170 nm at a radius of 60 {micro}m. An achieved aspect ratio was 6:1.

International Nuclear Information System (INIS)

Semiconductor quantum dots (QDs) are a promising approach to realize a single-photon source. To avoid bulky and expensive laser systems for future applications, electrical excitation is desirable. InP QDs are especially suited, as they emit in the red spectral range and therefore in the optimal range of commercial detectors. Additionally, they have been shown to be capable of emitting single photons up to 80 K. Thus, we embedded InP QDs in the intrinsic region of a p-i-n diode. To form single devices, 100 #mu#m mesas were etched and supplied with electrical contacts. We investigated the electroluminescence from single QDs and performed second-order auto correlation measurements to verify single-photon emission. To prevent expensive helium cooling and reach operation above 80 K, we investigated the influence of elevated temperature on the performance of our device. Since triggered single-photon emission is required for most applications, sub-nanosecond pulses were ...

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Mott-Schottky (M-S) analysis is an effective approach to investigate the electronic property of passive films of metals, and it is well suitable for the passive film with single space charge capacitance. But there is no proper method to analyze the C{sub sc}{sup -2} vs. V{sub m} plots of passive films with several space charge capacitances in series connection, such as bipolar passive films. In this paper, the relationship between the space charge capacitance of the bipolar passive film and the applied potential was deduced and the features of corresponding plots were given out simultaneously. Accordingly, a non-linear fitting method was presented to analyze the C{sub sc}{sup -2} vs. V{sub m} plots of bipolar passive films. Then the method was used to study the semiconductor characteristics of bipolar passive films formed on the surface of Nickel base alloy after being corroded in the environments with high temperatures and high partial pressures of H{sub ...

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The influence of small amounts of alloying elements (0.36% Cu and 0.47% Cr) on the semiconducting properties of passive films formed on weathering steels was investigated either in tetraborate/boric acid buffer solution (pH 9.2) or artificial atmospheric environment (SO{sub 2}-containing environment). The electrochemical behaviour was assessed by potentiodynamic polarisation, capacitance measurements and photoelectrochemistry. The chemical characterisation of the films was carried by Auger electron spectroscopy. The polarization results obtained in the buffer solution show that the addition of chromium decreases the passive current density. The capacitance results show that the films behave as an n-type semiconductor with shallow and deep donor levels situated in the forbidden gap. The presence of copper seems to affect the density of the shallow and of the deep donor levels in the forbidden gap, and as chromium, it also decreases the doping density in the case of ...

International Nuclear Information System (INIS)

The profile imaging technique is used to study the oxidation of ZnTe and InP surfaces induced by in situ reaction due to the electron beam of the microscope and by ex situ heating in air. For both materials, in situ reaction with the electron beam resulted in desorption of the anion species and the formation of the metal oxide. The observation of In metal particles, and the fact that the rate of formation of In_2O_3 was substantially reduced by an improvement of the vacuum near the specimen region, suggested that the presence of oxygen is not involved in the desorption process. The ex situ heating of ZnTe up to 260 degrees C in air resulted in crystals of ZnO and Te metal, generally in a layered surface region with the sequence of ZnTe/Te/ZnO. The large Te crystals usually had an epitaxial relationship with the bulk ZnTe but the small ZnO crystals had random orientations. The ex situ heating of InP to 380 degrees C in air only gave rise to small crystals of In_2O_3 in random ...

Science.gov (United States)

The strain dependence of Si-Ge interdiffusion in epitaxial Si/Si{sub 1-y}Ge{sub y}/Si heterostructures on relaxed Si{sub 1-x}Ge{sub x} substrates has been studied using secondary ion mass spectrometry, Raman spectroscopy, and simulations. At 800 and 880 deg. C, significantly enhanced Si-Ge interdiffusion is observed in Si/Si{sub 1-y}Ge{sub y}/Si heterostructures (y=0.56, 0.45, and 0.3) with Si{sub 1-y}Ge{sub y} layers under compressive strain of -1%, compared to those under no strain. In contrast, tensile strain of 1% in Si{sub 0.70}Ge{sub 0.30} layer has no observable effect on interdiffusion in Si/Si{sub 0.70}Ge{sub 0.30}/Si heterostructures. These results are relevant to the device and process design of high mobility dual channel and heterostructure-on-insulator metal oxide semiconductor field effect transistors.

International Nuclear Information System (INIS)

A set of equations describing a stress-mediated evolution of the nonequilibrium dopant-defect system has been derived and analyzed. Together with coupled diffusion of dopant atoms and point defects, we consider the drift of all mobile species in different charge states, namely vacancies, self-interstitials, and pairs 'dopant atom-point defect', in the field of stress. It has been shown that stresses may affect the diffusion of dopant atoms mainly in two ways: (1) directly, due to the drift of the pairs in the field of stress; (2) indirectly, by the formation of nonuniform defect distribution due to the drift of point defects. On this basis, various features of doping processes, such as phenomena of 'uphill' impurity diffusion near the surface (within the framework of the first or second mechanisms) and the peculiarities of high concentration phosphorus diffusion (due to the second mechanism), can be explained. Numerical computations of high concentration phosphorus diffusion in silicon ...

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This report contains the document control information and abstracts for Solar Energy Research Institute (SERI) Photovoltaic (PV) Program publications resulting from SERI's subcontracted PV research. The information is presented for reports published or distributed from August 1 through December 31, 1990. In the past, copies of the subcontractor reports were distributed to a broad spectrum of researchers in the field of photovoltaics at a considerable cost to the program. In an attempt to reduce costs and ensure that all researchers receive those current publications that are of specific interest to them, this report will outline these publications, organized by technology, on a regular basis. A list of additional publications and sources is included herein to provide the photovoltaic community with other sources of information. All of the documents represented here are available from the National Technical Information Service (NTIS) and can be purchased using the NTIS order ...

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By using this doping method, silicon semiconductors with extremely uniform dopant distributions can be produced, and this is the dominant advantage of NTD compared with a conventional chemical doping. Good uniformity of a dopant concentration is usually required for high power applications such as thyristor (SCR), IGBT, IGCT and GTO and for special sensors. Achieving an accurate neutron fluence corresponding to a target resistivity as well as a uniform irradiation is the prime target of a neutron irradiation for NTD. Generally, in order to reach an accurate neutron fluence, a real time neutron flux is monitored by a neutron detector such as a Self-powered Neutron Detector(SPND). And, after an irradiation, the total irradiation fluence is confirmed by measuring the absolute activity of a neutron activation sample that has been irradiated with a silicon ingot, and thus the SPND can be properly calibrated. Excellent irradiation uniformity and a high accuracy for a ...

Energy Technology Data Exchange (ETDEWEB)

Neutron scattering experiments on the mixed-valence (MV) compounds SmB{sub 6} are reported. The inelastic magnetic response of SmB{sub 6} at T = 2 K, measured on a double-isotope single crystal,displays a strongly damped peak at 35 meV corresponding to the inter multiplet transition of Sm{sup 2+}. At lower energies ( h.{omega} {approx_equal} 14 meV), a narrow magnetic excitation is observed, with remarkable scattering-vector and temperature dependences of its intensity. This novel feature is discussed in terms of recent theoretical works describing the formation of an anisotropic local bound state in semiconducting MV materials. If the average samarium valence is decreased by substituting La for Sm, a peak is found to appear at high energies. The elastic magnetic form factor of SmB{sub 6} was determined using polarised neutrons and no significant difference is observed in its Q-dependence with respect to that of pure divalent samarium. This surprising behaviour is constant with ...

International Nuclear Information System (INIS)

Several configurations of moderating and shielding materials have been designed and measured on the LVR-15 reactor for boron neutron capture therapy (BNCT) purposes. To determine the neutron and gamma ray space-energy distributions in the cylindrical geometry, the two-dimensional code DOT with the coupled neutron-gamma data library DLC-36 was used. The experimental verification of the beam parameters was performed in the LVR-15 reactor thermal column empty space with layers of graphite, aluminium, alumina, lead and bismuth. Attention was paid to establishing techniques and instrumentation for monitoring the neutron and gamma ray dose and beam quality. The thermal and epithermal flux densities were measured by activation foils, the neutron spectrum was determined with a Bonner spectrometer and gamma ray background with a scintillation spectrometer. The distribution of thermal neutrons in the human head phantom was mapped with a small semiconductor detector (Si"6Li). ...

International Nuclear Information System (INIS)

A combination of measuring instruments, consisting of a Beta-Sedimeter and a radionuclide X-ray fluorescence instrument, is described. With the Beta-Sedimeter the C-14-radiation is measured. Through direct irradiation with photons of a Pu238-source in an ancillary irradiation chamber and energy dispersing measurement of the K- and L-radiation resp. of the excited heavy metals with the aid of a Si(Li)-semiconductor detector and a 4-channel analyzer the heavy metal concentrations of the heavy metals Zn, Cr, Ni and Pb are determined. For the determination of cadmium the indirect excitation with Am-241 and Dy-targets is described. The system produces records and operates fully automatically in a step-by-step mode with a testing cycle of 45 minutes. In connection with the process monitoring of the wastewater from a zinc plating plant during a period of 8 months the concentration of the solid material and of the metals Cr and Zn, which were considered to be ...