bluuebunny/crossref_metadata_2025 huggingface dataset:
A simplified Monte Carlo electron transport algorithm for advanced bremsstrahlung converter design calculations
Authors: Pregenzer Arian , Morel J. E.
Published: July 2002

A fast and simple algorithm is presented for calculating the effects of energy loss and scattering on electrons which pass through a converter foil. This algorithm is designed to be integrated into particle-in-cell codes for electron-beam transport. The results of this algorithm for such quantities as energy and number transmission and reflection coefficients compare very favorably with results obtained from a more sophisticated Monte Carlo transport code for pertinent applications. The savings in time is appreciable: this algorithm is approximately 30 times faster than the more sophisticated code.
Far-infrared, low-loss, cylindrical-Gaussian eigenmodes of a bent rectangular waveguide free electron laser resonator
Authors: Elias Luis , Gallardo Juan , Kimel Isidoro
Published: July 2002

We present approximate analytical solutions of the Helmholtz equation for a slightly bent metallic rectangular waveguide with infinite aperture cylindrical mirrors. The low-order, overmoded, low-losses eigenmodes of the ‘‘cold resonator’’ are naturally expressed as products of cylindrical Gaussian–Hermite and trigonometric functions. In first order in perturbation theory, the correction to the attenuation constant is proportional to the straight waveguide attenuation constant. We show that π modes propagate with negligible losses in the far-infrared region. These results are compatible with preliminary experimental data from the University of California, Santa Barbara Free Electron Laser experiment.
Heat treatment of bulk gallium arsenide using a phosphosilicate glass cap
Authors: Mathur G. , Wheaton M. L. , Borrego J. M. , Ghandhi S. K.
Published: July 2002

n-type bulk GaAs crystals, capped with chemically vapor-deposited phosphosilicate glass, were heat treated at temperatures in the range of 600 to 950 °C. Measurements on Schottky diodes and solar cells fabricated on the heat-treated material, after removal of a damaged surface layer, show an increase in free-carrier concentration, in minority-carrier-diffusion length, and in solar-cell short-circuit current. The observed changes are attributed to a removal of lifetime-reducing acceptorlike impurities, defects, or their complexes.
Isothermal vapor-phase epitaxy of Hg1−xCdxTe on CdTe and Al2O3 substrates
Authors: Shin S. H. , Gertner E. R. , Pasko J. G. , Tennant W. E.
Published: July 2002

The isothermal vapor-phase-epitaxial (ISOVPE) growth of device-quality HgCdTe layers on both CdTe and CdTe/Al2O3 substrates has been demonstrated. The material and device properties on both types of substrates have been studied and compared with reported values for HgCdTe grown by other techniques. The as-grown ISOVPE Hg1−xCdxTe (x≂0.3) epilayers are always p type with carrier concentrations of ∼5×1015 to 3×1016 cm−3 and mobilities of ∼230–260 cm2/V s at 77 K. The temperature and compositional dependence of electrical properties of ISOVPE Hg1−xCdxTe are somewhat different from those of liquid-phase epitaxy (LPE) and bulk HgCdTe. In particular, the acceptor ionization energy, EA =7 meV, is about half that obtained in midwavelength infrared LPE or bulk HgCdTe, and nearly independent of composition x. The R0A product of a representative photodiode (λc ≂4.65 μm, 77 K) is 2×106 and 4 Ω cm2 at 77 and 195 K, respectively, with comparable device qualities seen on both CdTe and CdTe/Al2O3 substrates.
Theory of the high base resistivity n+p
p+ silicon solar cell and its application to radiation damage effects
Authors: Goradia Chandra , Weinberg Irving
Published: July 2002

High-resistivity (84 and 1250 Ω cm) n+pp+ silicon solar cells, with thickness ranging from 56 to 250 μm, were irradiated by 1-MeV electrons and their performance evaluated using a specially developed analytical model. It was found experimentally that, contrary to expectations based on previous performance data for lower resistivity cells, the greatest cell degradation occurred for the present higher-resistivity cell. In addition, the degradation was found to be much greater than that observed for cells with base resistivities typical of those currently used in space. Relevant details of the analytical model are presented. Computer calculations of optically injected minority carrier distributions, and all voltage components at the maximum power point, are used to interpret the experimental results. The analytical model is valid for both low and high injection and includes the effects of band-gap narrowing in the cell’s heavily doped regions. It was concluded that, for the thicker higher-resistivity cell, lack of conductivity modulation, leading to a large ohmic drop in the cell base, was the predominant cause of cell degradation. Although still a significant factor, the magnitude of the ohmic component is less important in the thinner 1250 Ω cm cell. In the thicker 84 Ω cm cell, absence of conductivity modulation becomes comparable to loss in collection efficiency as a loss mechanism while in the 84 Ω cm thinner cell loss in collection efficiency begins to emerge as a dominant loss mechanism. Our results indicate that lack of conductivity modulation is a fundamental roadblock toward achieving increased radiation resistance simply by indefinitely increasing the base resistivity of silicon solar cells.
Thermal conductivity of Tl3AsSe3 (1.5–100 K)
Authors: McCarthy K. A. , Sample H. H. , Gottlieb M. , Kun Z.
Published: July 2002

The thermal conductivity of Tl3AsSe3 in the temperature range 1.5–100 K is reported. The measured thermal conductivity can be fitted using defect scattering only due to isotopes and using normal process scattering.
Epitaxial silicide formation by multi-shot irradiation of Ni thin films on Si with Nd laser
Authors: Harith M. A. , Zhang J. P. , Baeri P. , Rimini E. , Celotti G.
Published: July 2002

Uniform and epitaxial NiSi2 layers were obtained by consecutive irradiation of a Ni thin layer deposited onto Si with Nd-glass laser irradiation, 30-ns pulse duration, using up to 15 shots. The best quality epitaxial NiSi2 layer, for a 50-nm-thick Ni layer deposited on Si(111), was obtained with 10 shots of 1.3 J/cm2 energy density. The normalized minimum yield of the Ni signal amounted to 25%. The stability of the formed compound was investigated by furnace annealing in the 300–800 °C temperature range. After annealing at 300 °C-1 h backscattering and channeling analysis indicated a worsening of the epitaxial quality of the compound. X-ray diffraction patterns showed the presence of the NiSi silicide in addition to the NiSi2 silicide. At 500 °C-1 h annealing the reaction occurred over long distance and a large amount of NiSi was formed at the expense of the NiSi2 and the unreacted Ni. At 800 °C the epitaxial quality of the NiSi2 improved and the Ni minimum yield reached 10%. The NiSi2 was the only silicide present after irradiation and 800 °C-1 h annealing. Channeling analysis established also that the NiSi2 was b type: i.e., the silicide layer was rotated 180° about the surface normal 〈111〉 axis of the Si substrate.
Two-dimensional atomic correlations of epitaxial layers
Authors: Pimbley J. M. , Lu T.-M.
Published: July 2002

We have evaluated the two-dimensional atomic pair correlation function for surfaces containing finite layers of adsorbed atoms and having a random distribution of steps. The step probabilities for the two lateral directions are mutually dependent. We employ a third-rank tensor formalism to describe the two-dimensional array of occupation probability vectors from which we derive the pair correlation function. The two-dimensional electron diffraction angular profile is obtained from this pair correlation function. We have made detailed calculations with the two-layer system as an example and found that the diffraction characteristics describe qualitatively a recent molecular beam epitaxy experiment of Si on Si(111) surface.
Thermo-optic and electro-optic tuning sensitivities of the second-harmonic generation in KH2PO4 crystal measured by diverging beam technique
Authors: Chu Moo Jung , Lee Sang Soo
Published: July 2002

Second-harmonic wave is generated in type-1 and type-2 cuts of KH2PO4 crystal by using a diverging Nd+3–glass laser beam. Angular full width at half-maximum of the conversion efficiencies are measured by recording the diverging output on photographic emulsion. Thermo-optic and electro-optic tuning sensitivities for the two types of crystal cuts are measured accurately from the recorded diverging output beam. The measured thermo-optic tuning sensitivities are 0.005 46±4×10−5 deg/°C for type-1 and 0.0143±4×10−4 deg/°C for type-2, and the measured electro-optic tuning sensitivities are 0.004 37±3×10−5 deg/kV cm for type-1, and zero for type-2.
Permeation of implanted deuterium through Ni near room temperature
Authors: Bo/rgesen P. , Scherzer B. M. U. , Möller W.
Published: July 2002

The permeation of 2–22-keV deuterons implanted into 25-μm-thick cold-rolled Ni foils was studied near room temperature. The results are generally characterized by a time lag τ and a steady-state permeation rate J. The variation of τ with beam intensity and temperature indicates an average relative concentration of ∼4×10−4 of saturable bulk traps of binding energy 0.26±0.01 eV, plus a larger concentration of weaker traps. At the highest energy, J is well described by theory.
Growth temperature dependence of intrinsic and extrinsic acceptor concentration in (Ga,Al)Sb evaluated by C-V characteristics of metal-insulator-semiconductor structures
Authors: Takeda Y. , Noda S. , Sasaki A.
Published: July 2002

Growth temperature (TG) dependence of the acceptor concentrations (NA) in Al0.1Ga0.9Sb grown by liquid phase epitaxy in a very wide growth temperature range (250–500 °C) was investigated. It was found that NA varies with TG down to 350 °C as NA ∝exp(Ea/kBTG) with Ea=0.47 eV and that below 350 °C NA fluctuates depending highly on growth conditions. Acceptors in Al0.1Ga0.9Sb grown above 350 °C were concluded to be intrinsic. These observations were successfully made using the improved extremely low-temperature growth process. The evaluation technique of measuring the impurity concentration in a thin epitaxial layer on the conductive GaSb substrate by C-V characteristics of metal-insulator-semiconductor structures was employed.
Alternative method of preparing high-coercivity neodymium-iron-boron magnets
Authors: Stadelmaier H. H. , ElMasry N. A. , Stallard S. R.
Published: July 2002

Sintered magnets of tetragonal Nd2Fe14B can be prepared not only with powders of the ternary compound itself but also using elemental Nd and Fe in combination with a master alloy of Fe2B. When powders of these materials are compacted and sintered, they react to form Nd2Fe14B. The high coercivity is due to small particle size which results from the reaction and depends critically upon temperature and time. The formation of small particles is constitutional and can only occur in an n-component alloy system where n>2.
Probe-type thin-film head for perpendicular recording using multilayered Fe-Si-Ru films
Authors: Shiroishi Y. , Shiiki K. , Yuitoo I. , Kumasaka N. , Kudo M.
Published: July 2002

The coercivity dependence of read/write and noise characteristics are investigated for the probe-type thin-film head using multilayered Fe-Si-Ru films and Co-Cr/Co-Zr-Mo double-layer media. The D50 recording density of 100 kFCI (flux change per inch) and the output of 0.24 μVpp/μm turn m/s are obtained for the medium with the coercivity of 500 Oe. These characteristics are superior to those for conventional ring head (D50=80 kFCI, E1k=0.12 μVpp/μm turn m/s). Further, thin-film heads have low noise and high overwrite characteristics.
Absorptivity of CePd3 from 5 to 400 meV
Authors: Webb B. C. , Sievers A. J. , Mihalisin T.
Published: July 2002

The far infrared absorptivity of CePd3 has been measured between 4.2 and 300 K over a photon energy range which is an order of magnitude larger than previously reported. These measurements together with previous results map out the entire region of the low-temperature CePd3 absorptivity anomaly, which is larger and extends to larger energies than extrapolation from earlier cavity measurements would suggest. The anomaly is too large to be compatible with simple conduction electron scattering off a resonant level near the Fermi energy. Above 200 meV only a weak temperature dependence is observed although a minimum in the absorptivity at 270 meV, attributed to an f multiplet transition, appears to sharpen at the lowest temperatures.
Capacitance and dielectric constant of Cd1−xMnxTe
Authors: Peek D. , Guerra Vela C. , Sladek R. J.
Published: July 2002

We have measured the electrical impedance of CdTe and Cd0.55Mn0.45Te crystals at temperatures between 82 and 104 K using frequencies between 20 kHz and 2.0 MHz. From the capacitance results we determined that the dielectric constant was only slightly smaller for x=0.45 than for x=0—a result important for the understanding of electromechanical coupling in Cd1−xMnxTe.
Experimental evidence of a multiphase magnetic system in fine particles of ferric hydroxysulfate
Authors: Morais P. C. , Skeff Neto K.
Published: July 2002

Magnetization data obtained by a microvibrating sample magnetometer are presented. These data are obtained at different values of an external field applied to a sample which shows a bimodal particle-size distribution. The bendings in the M3×T plot are taken as an evidence of magnetic reorderings. These magnetic reorderings are discussed extensively.
UV-laser photolysis of trimethylaluminum for Al film growth
Authors: Motooka T. , Gorbatkin S. , Lubben D. , Greene J. E.
Published: July 2002

The photodissociation of dimerized trimethylaluminum, Al2(CH3)6, (TMA) by KrF laser irradiation (248 nm, 5 eV) has been investigated. Optical spectroscopy was used to measure the emission intensities I of excited photofragments as a function of TMA pressure P. The intensities of neutral Al atoms and CH radicals were observed to have quite different pressure dependencies indicating that they were formed by different mechanisms. IAl and ICH initially increased linearly with increasing pressure, however IAl saturated at P≂0.6 Torr (80 Pa) while ICH reached a maximum at P≂0.01 Torr (1.33 Pa) and then decreased with further increases in pressure. Based upon the experimental results and molecular orbital calculations, a model was proposed for the photolysis of TMA. The primary conclusions were that Al atoms were formed directly by a cascade process initiated by a single-photon absorption while CH radicals were generated through a chemical reaction between photofragments. An analysis of the steps involved in the cascade process suggests that it should be possible to grow high-purity, essentially C-free, Al films by photodecomposition of TMA in ultrahigh vacuum in agreement with preliminary experiments.
Field-dependent grain boundary barriers as a cause of carrier drift velocity saturation in organic solids
Authors: Szymański A.
Published: July 2002

The aim of this communication is to present an alternative interpretation of low-field charge carrier drift velocity saturation in polycrystalline organic solids. It is assumed that the above effect is due to grain barriers. In the materials under study, thermal generation of charge carriers is negligible. Therefore the charging of grain barriers is due to the carriers injected, and in the case of electrode injection is dependent on the field applied. The consequences of the above ideas as well as comparison with experiment is presented.
Transmission electron microscopy investigation of laser-induced defects in (Al, Ga) As
Authors: Zysset B. , Salathé R. P. , Martin J. L. , Gotthardt R. , Reinhart F. K.
Published: July 2002

In their luminescence appearance three different defects induced in (Al, Ga) As heterostructures through highly focused cw Kr-ion laser irradiation have been investigated by transmission electron microscopy (TEM). Two of them, a luminescent defect and a nonradiative defect are only revealed by TEM through thickness variations due to the chemical thinning process. They probably consist of point defects or point-defect complexes. A third type of defect consisting of extended dislocation networks was also occasionally found. These networks seem to originate from native defects and are very similar to formerly described dark-line defects.
Characterizations of palladium silicides formed by rapid thermal annealing
Authors: Wei C. S. , Van der Spiegel J. , Santiago J.
Published: July 2002

High intensity quartz-halogen tungsten lamps with power densities of 10, 15, and 25 W/cm2 were used to form palladium silicide films. Metal films of 83–200 nm were evaporated on (100)-oriented single-crystal silicon and subsequently processed in vacuum for time intervals from 5 to 60 s. The electrical characteristics and the microstructure of the silicide films were studied by four-point probe, x-ray diffraction, Auger electron spectroscopy, scanning electron microscopy, and Rutherford backscattering spectroscopy. A nonuniform PdSi film with dendritelike surface topography is formed at 25 W/cm2. A somewhat discontinuous low resistance film of predominantly PdSi is formed at 15 W/cm2. The same power density, for contaminated samples, induces agglomeration upon processing. A uniform Pd2Si film with a resistivity of 27 μΩ cm is obtained at 10 W/cm2. Longer processing times result in nucleation and growth of PdSi from Pd2Si.
Characteristics of velocity overshoot in GaAs under uniform-field conditions
Authors: Vassell M. O. , Lee Johnson
Published: July 2002

The origins of velocity overshoot in homogeneous bulk GaAs under stepped forcing conditions on the electric field are analyzed by phase-portrait methods. The balance equations for particle energy and momentum taken from the uniform-field version of the semiempirical transport equation model are used to define the direction field for charge flow in an energy-velocity phase space. Certain general characteristics of the flow patterns in the nonstationary regime are examined, with emphasis on the classification of possible intrinsic behavior exhibited by the steady states for different applied fields, on the approach to the steady state, and on the role of initial conditions. It is shown that flows describable by such a model have two types of stable generalized dynamical behavior: damped oscillatory behavior under applied fields for which the steady-state energy lies near the intervalley separation energy, and damped aperiodic behavior outside this range of fields. The analysis is illustrated with results deduced from realistic input data on energy and momentum relaxation rates taken from published steady-state Monte Carlo calculations for GaAs at three representative impurity densities.
Transient current response in Pd-SiO2-Si structures during hydrogen absorption and desorption
Authors: D’Amico A. , Fortunato G. , Ruihua W. , Riccó B. , Olivo P.
Published: July 2002

Transient current measurements have been performed on Pd-gate metal-oxide-semiconductor capacitors at zero bias and room temperature, during hydrogen absorption and desorption. It is shown that a simple relationship among transient current, flat-band voltage, and time-dependent capacitance can fit the experimental data. Different possible origins of the transient current phenomenon are considered and discussed and the role played by the Na+ in delaying the transient current response is also illustrated.
Laser optoacoustic measurement of homogeneous linewidth and pump saturation intensity in a CH3I molecule
Authors: Lee Ho Seong , Kong Hong Jin , Lee Sang Soo
Published: July 2002

Optoacoustic measurement of the absorption line shape is carried out for the determination of the homogeneous linewidths and the saturation intensities of a CH3I molecule for a 10-μm P(32) CO2 laser line. By fitting the numerically calculated Voigt function to the experimentally obtained absorption line shape, we find two absorption lines separated by 90 MHz. The measurement of the pressure dependence of the homogeneous linewidth at pressures lower than 0.8 Torr shows that the rate of increase of the homogeneous linewidth is not linear but larger at lower pressure than that at higher pressure. The natural linewidth of 12 MHz is obtained by extrapolating the experimentally obtained linewidth curve toward zero pressure, and also the pump saturation intensities at the line centers of the CH3I absorption line and CO2 laser line are found to be 1.0 and 2.5 W/cm2, respectively.
Ion-beam-mixed iron boron films
Authors: Clemens B. M. , Neumeier J. J.
Published: July 2002

Ion beam mixing of layered iron-boron films with 200-keV Ar ions is investigated by x-ray diffraction, Auger depth profiling, and high-temperature resistivity. Samples consisting of alternating layers of electron beam deposited polycrystalline iron (25 nm thick) and boron (50 nm thick) were irradiated to doses from 5×1015 to 1×1016 ions/cm2, at rates ranging from 0.3 to 3.3 μA cm2. The mixing extends to a depth of 150 nm and increases with dose rate. This dependence is due to beam heating of the sample. The structure of the mixed material is amorphous iron boron.
Studies of the change of a metallic surface microrelief as a result of multiple-pulse action of powerful UV laser pulses
Authors: Ursu I. , Mihăilescu I. N. , Popa Al. , Prokhorov A. M. , Ageev V. P. , Gorbunov A. A. , Konov V. I.
Published: July 2002

The formation of specific structural patterns as a result of the repeated UV laser irradiation on various metallic samples (Ag, Al, Au, bronze, Cu, and Pb) is reported. The physical processes underlying the formation of more or less organized periodical structures in this case are discussed.
An evaluation method for laser diodes
Authors: Nakano Y. , Iwane G.
Published: July 2002

This paper reports a new method for evaluating laser diodes by measuring the variation in driving current of a laser diode operated at a constant light output power against ambient temperature. A close relation was found between the temperature at which the driving current runs away at a given value of light output and degradation in the active region. Selection based on critical temperature is applicable to a simple and effective screening method for long-living laser diodes.
Characteristics of light amplifier of AlGaAs semiconductor diode laser
Authors: Kono Katsuyuki , Sakuda Kyohei
Published: July 2002

This paper reports the experimental and analytical studies of the light amplification of the Fabry–Perot type lasers. Particularly, for high bias current level of the laser amplifier, say more than 90% of the threshold current, the waveform distortion of the amplified output becomes apparent. Considering the following facts that the time division spectra of the input pulse to the amplifier changes from shorter to longer wavelengths due to temperature increase in the active layer after the pulse current is turned on and the peaks of the amplification factors of the Fabry–Perot type amplifiers depend on the wavelength for the different bias current level, we can show that the waveform distortion is caused by the peaks of the spectrum shift of the input and the amplifier. We also observe an important fact that the effective bias current to the amplifier is not the same as the actual bias current, which causes the wavelength shift of the peak gain of the amplifier, because of the reduction of the carrier concentrations in the active layer due to stimulated emission by the input light pulse. Taking into account these facts, the analytical and experimental results are in good agreement with each other.
Hydrogen content of amorphous silicon films deposited in a multipole plasma
Authors: Drevillon B. , Toulemonde M.
Published: July 2002

Hydrogenated amorphous silicon (a-Si:H) samples are prepared in highly controlled conditions in a multipole dc discharge. Hydrogen content of the film is systematically analyzed as a function of deposition parameters such as ion flow, ion bombardment energy Eion, and substrate temperature. Hydrogen atomic concentration and profile are measured by nuclear reaction analysis. The essential role of ion bombardment is emphasized. Increasing deposition temperature and/or decreasing Eion results in a large decrease of the hydrogen content. Hydrogen-enriched surfaces are observed when Eion≲10 eV. It is shown that SinH+m bombardment during film growth produces a dense hydrogen-rich material.
Synthesis of compound thin films by dual ion beam deposition. II. Properties of aluminum-nitrogen films
Authors: Hentzell H. T. G. , Harper J. M. E. , Cuomo J. J.
Published: July 2002

We describe the properties of aluminum-nitrogen films prepared by dual ion beam deposition in which the metal atom flux is supplied by inert ion beam sputtering and the reactive flux is supplied by a low-energy (100–500 eV) ion beam directed at the growing film. This deposition technique and the analysis of film compositions are described in Part I of this two-part paper.The fundamental deposition parameters of arrival rates and ion energy are controlled and directly correlated to the crystallographic structure, microstructure, and morphology of the films, over a range of composition from N/Al=0 to N/Al=1.0. Al sputter deposited in a mixture of Ar and N2 forms an expanded Al lattice with no indications of AlN formation. When the low-energy N+2 beam is turned on, almost all the ionized nitrogen is incorporated in the film forming a mixture of large Al grains and fine grained AlN. In this two-phase cermet region, the resistivity shows a percolation threshold at N/Al=0.45, becoming fully insulating at about N/Al=0.75. Above the arrival rate ratio N/Al=1, excess N is rejected and the films have AlN structure. For stoichiometric AlN films the texture and microstructure depend strongly on the N+2 flux and ion energy. For low ion energies (100 eV) and flux, films are formed with the c axis of the hexagonal AlN structure perpendicular to the film surface, whereas for high ion beam energies (500 eV) the c axis is close to the plane of the film. The AlN grain size also increases with nitrogen ion energy. The relative contributions of chemical driving forces and ion bombardment processes are discussed.
Current noise in sodium β″ alumina ceramic
Authors: Brophy James J. , Smith Steven W.
Published: July 2002

Experimental bulk current noise spectra for Na β″ alumina ceramics are observed over the frequency range f=3×10−3 Hz to 104 Hz and with low contact noise, amalgam electrodes. The noise is proportional to the square of the dc current and varies as f−3/2, suggesting bulk conductivity fluctuations arising from diffusion of the conducting ions. The results indicate that individual grains in the ceramic are not stochastically independent and that only a small fraction of the conducting ions present participate in the diffusion noise process. The number of such ions is thermally activated with an activation energy of 0.75 eV. Chemical and electrochemical contact noise indicates a reaction at the ceramic-amalgam interface characterized by a reaction rate of 6.3×102 sec−1, even for low-noise contacts.
Investigation of the optogalvanic effect in a microwave discharge
Authors: Sekiguchi Hiroshi , Masuyama Akio , Kasuya Takahiro , Suzuki Takanori
Published: July 2002

Laser-induced perturbations of the electron temperature and the electron density are measured by using a Langmuir probe on several electronic transitions in He, Ne, and Ar under a microwave discharge. The electron density either increases or decreases according to the excitation from the nonmetastable or metastable level, respectively. This is consistent with the previous findings in the conventional experiments of the optogalvanic effect. The corresponding electron temperature always decreases with laser excitation showing that the collisional ionization is the dominant process in the discharge. The intensity of the optogalvanic signals is well interpreted in terms of the laser-induced variation of these plasma parameters.
High-energy conversion efficiency amorphous silicon solar cells by photochemical vapor deposition
Authors: Takei H. , Tanaka T. , Kim W. Y. , Konagai M. , Takahashi K.
Published: July 2002

Hydrogenated amorphous silicon solar cells were fabricated by photochemical vapor deposition. A three-separate-chamber system was newly developed to reduce the contamination of the dopant elements as well as oxygen or water originated by the loading and unloading procedure. Wide optical band-gap hydrogenated amorphous silicon carbide was prepared using acetylene (C2H2) for the p layer. The deposition conditions for each layer were optimized and the highest-energy conversion efficiency of 9.64% was obtained. This high conversion efficiency was mainly attributed to the large short-circuit current which indicated that the quality of the i layer is reasonably good.
Reply to ‘‘Comments on ‘Equivalence of the Lorentz and Ampere force laws in magnetostatics [J. Appl. Phys. 5
7, 1743 (1985)]’ ’’
Authors: Ternan J. G.
Published: July 2002

The examples given by Graneau do not contradict the equivalence of the two laws in magnetostatics. Both laws give the same magnetic force per unit volume, which is normal to the current density. The stress in a conductor due to this applied force then follows from the mechanical laws of the conductor and its contraints.
Stimulated emission cross section of Cr-doped GdScGa garnet
Authors: Sekita M. , Miyazawa Y. , Kimura S.
Published: July 2002

The stimulated emission cross section is calculated on the basis of emission spectrum and spontaneous lifetime measurements. The maximum stimulated emission cross section is determined to be 0.69×10−20 cm2. A comparison is made between the calculated stimulated emission cross section and one which has been determined from laser oscillation experiments. Fair agreement between them is obtained within a 20% error at wavelengths from 770 to 810 nm.
Effect of hydrogen dilution of silane on optoelectronic properties in glow-discharged hydrogenated silicon films
Authors: Shirafuji J. , Nagata S. , Kuwagaki M.
Published: July 2002

Electrical and photoelectric properties of glow-discharged hydrogenated silicon films are measured as a function of hydrogen dilution. In the case of films deposited under the condition of highly diluted silane, microcrystalline states are formed accompanying remarkable decreases in the optical gap, the activation energy of the dark conductivity, and the photoluminescence intensity. However, it is significant that the room-temperature photoconductivity is not critically dependent on microcrystalline formation. The temperature dependence of the photoconductivity is drastically different depending on whether the film is in an amorphous or microcrystalline state.
Atomic and microstructural characterization of metal impurities in synthetic diamonds
Authors: Wong J. , Koch E. F. , Hejna C. I. , Garbauskas M. F.
Published: July 2002

The phase and microstructure of Ni, Co, and Fe impurities found in synthetic diamonds have been characterized in some detail using a combination of extended x-ray absorption fine structure (EXAFS) utilizing intense synchrotron radiation as a light source, and conventional transmission electron microscopy (TEM), x-ray diffraction, and fluorescence analyses. In all three cases, the metal impurity exists as an fcc metallic phase dispersed in the diamond matrix. The particles are submicron in size and not facetted. There was no evidence of a metal carbide phase in these systems. Quantitative simulations of the first-shell EXAFS signal showed that the Co and Ni particles contain, respectively, 2.3 and 1.5 at. % of carbon in solution.
Study of spall and recompaction of ceramics using a double-impact technique
Authors: Yaziv D. , Bless S. J. , Rosenberg Z.
Published: July 2002

A new plate impact technique for studying the dynamic properties of shock-damaged materials has been developed. The technique is based on impacting the specimen with two flyer plates which are separated by a small gap. Impact of the first plate causes spall in the target. Impact of the second plate closes the spall. The transmitted shock wave is monitored with a VISAR and/or manganin stress gauge. Analysis of the waves gives the properties of the damaged region. Preliminary results for copper and polycrystalline aluminum oxide have been obtained.
Improvements of electrical and optical properties of InAlAs grown by molecular beam epitaxy
Authors: Kawamura Yuichi , Nakashima Kiichi , Asahi Hajime
Published: July 2002

Great improvement in the electrical and optical properties of molecular-beam-epitaxy-grown InAlAs was obtained by using InP buffer layers and high substrate temperatures of 555 °C. Undoped InAlAs layers are n type and the highest room temperature electron mobility is as high as 5100 cm2/V s with a carrier concentration of 1×1015 cm−3. The room-temperature photoluminescence spectrum has a sharp edge emission with a spectral half-width as narrow as 42 meV.
Improved theory of ultrasonic diffraction at large angles
Authors: Hahn Y. , Gau J. N.
Published: July 2002

A systematic theoretical study of approximations to the Kirchhoff diffraction integral is presented, stressing the improved behavior at large angles. This work was motivated by consideration of diffraction in dual tilted dispersive interdigital transducers for surface acoustic wave generation, but the salient features are applicable to diffraction problems in general. Previous treatments of surface acoustic wave (SAW) propagation were limited to nearly forward directions perpendicular to transducer fingers, where the simple Fresnel diffraction theory was adopted. Improvement of the theory for nonforward angles is obtained in which both the Fraunhofer and Fresnel diffractions are correctly included. The conventional diffraction treatment used in optics (as in the textbook by Born and Wolf) is found inaccurate and a new form is presented.
Intrinsic carrier concentrations in Hg1−xCdxTe with the use of Fermi–Dirac statistics
Authors: Madarasz Frank L. , Szmulowicz Frank
Published: July 2002

The intrinsic carrier concentrations in Hg1−xCdxTe are calculated with the use of the Fermi–Dirac statistics thus expanding on our previous calculation which employed the Boltzmann statistics. The use of Boltzmann statistics for Hg1−xCdxTe is limited to x≥0.20 and is not appropriate for the narrow band gap x<0.20 compositions. Our present treatment improves on existing calculations by using composition and temperature dependent momentum matrix element squared, which is the input to the Kane’s k ⋅ p theory, and by making no approximations to the band structure beyond those inherent to Kane’s theory. We find that our results for x≥0.20 using both statistics are in excellent agreement. We also compare our results with those of Hansen and Schmit. Good agreement is found for the range of 0.15≤x≤0.40.
Al0.2Ga0.8As p+-n junction solar cells grown by molecular beam epitaxy
Authors: Amano Chikara , Shibukawa Atsushi , Yamaguchi Masafumi
Published: July 2002

Al0.2Ga0.8As p+-n junction solar cells were fabricated by molecular beam epitaxy (MBE) and the relationship between cell properties and growth conditions was examined. It was found that growth temperature strongly influenced the minority carrier diffusion length in cell layers. At a growth temperature of 700 °C, minority carrier diffusion length was much improved and a high conversion efficiency of 12.9% (1 sun AM1.5, for an active area) was obtained.
Operating pressure of thallium in a mercury-thallium iodide discharge using the line Tl-5350 Å
Authors: Karabourniotis D. , Couris S. , Karras C.
Published: July 2002

The relationship between the characteristics of the emission contour of the self-reversed line Tl-5350 Å for a path through the arc axis and the operating pressure of Tl has been studied for a Hg–T1I discharge. The estimated pressure of Tl agrees with results from a method involving intensity of the optically thin line Tl-6550 Å and chemical reactions.
Thermally stimulated depolarization current studies of poly(ethylene oxide) and poly(ethylene oxide) complexed with potassium thiocyanate
Authors: Calame J. P. , Fontanella John J. , Wintersgill Mary C. , Andeen Carl G.
Published: July 2002

A digitally controlled thermally stimulated depolarization current facility is described and measurements on poly(ethylene oxide) (PEO) and PEO complexed with potassium thiocyanate (KSCN) are reported. The results complement and extend previous electrical relaxation studies on these materials. In particular, in PEO the presence of a relaxation previously labeled αc is confirmed. The relaxation is assigned to defects in the crystalline phase. In addition, the γ relaxation region is shown to consist of at least two relaxations. Further, a high-temperature family of peaks is obtained which are associated with space charge. For KSCN-complexed PEO three low-temperature relaxations are observed in the γ relaxation region. The relationship between these relaxations and previously reported dielectric relaxation results is established and possible origins of the relaxations are discussed. Finally, differential scanning calorimetry studies were carried out on all of the materials.
Short-term isothermal annealing of polyethylene single crystals
Authors: Grubb David T. , Liu J. Jui-Hsiang
Published: July 2002

Polyethylene single-crystal mats 20 μm thick were heated to the annealing temperatures (120–132 °C) in less than 1 s. The Cornell High Energy Synchrotron Source (CHESS) and a TV detector system were used to obtain wide- and small-angle x-ray scattering patterns from these mats during annealing with a time resolution of 0.3 s. Both whole polymer and a molecular weight fraction showed rapid melting and recrystallization, with a minimum crystallinity at 2–4 s after reaching the annealing temperature. Recrystallization was essentially complete in 60–90 s and most curves could be fitted to the Johnson–Mehl–Avrami equation with exponent n=1. Two-thirds of the material could be molten before there was any loss of the original crystal orientation. The increase in long period was discontinuous at high annealing temperature. The original small-angle long-spacing peak quickly lost intensity as crystallinity fell and a new peak appeared at larger long spacing. This new long spacing increased with time for the whole polymer and was constant for the fractionated material. At lower annealing temperatures the amount melting was small and the small-angle intensity and long period increased continuously.
Influence of a magnetic field on the emission probability of hot electrons from silicon into silicon dioxide
Authors: Garrigues M. , Pavlin A. , Hellouin Y.
Published: July 2002

The influence of a strong magnetic field (up to 12 T), parallel to the Si-SiO2 interface on the injection of hot electrons from Si into SiO2, has been measured in the case where the heating electric field is uniform and normal to the interface. The experimental results show that the influence of the magnetic field can be either an increase or a decrease of the injection probability depending on the type of test device used. These results are compared to a numerical simulation based on the hypothesis that injected electrons are in majority ballistic (‘‘lucky’’) electrons. It is shown that a possible interpretation of the experimental results can be found with this model by taking into account the influence of interface roughness on the escape conditions of hot electrons. Numerical results based on a simple model are given that show for the first time that interface roughness may be an important factor to consider in the study of hot-electron injection physics.
Optical absorption and dangling bonds in damaged silicon
Authors: Seager C. H. , Lenahan P. M.
Published: July 2002

We have examined the optical absorption and spin-resonance signal characteristics of thin layers of silicon damaged by an abrasive process at room temperature. We find an Urbach-like dependence of the subgap absorption and a g=2.0055 isotropic spin-resonance signal characteristic of silicon dangling bonds. Changes in the optical and spin-resonance data caused by thermal anneals in air, or in atomic hydrogen, indicate that direct electronic transitions of the dangling bond defect are not responsible for the observed optical-absorption spectra. The doping level dependence of these spectra is consistent with the hypothesis that electronic transitions arising from disorder-induced band-tail states cause the subgap absorption.
Investigation of the effect of device factors on the traveling wave excitation TE N2 laser
Authors: Chang S. H. , Teii S.
Published: July 2002

The laser output power of a traveling wave excitation TE N2 laser in which the discharge was divided into several sections were calculated theoretically for the spark gap inductance Ls from 20 to 140 nH, the sectional length of the discharge from 5 to 50 cm, and the gas pressure P from 40 to 90 Torr. The experimental confirmation has also been conducted.
High-resolution infrared absorption measurements of Al-doped ZnSe
Authors: Theis W. M. , Talwar D. N. , Vandevyver M. , Spitzer W. G.
Published: July 2002

Infrared absorption measurements of localized vibrational modes (LVM) due to Al in ZnSe performed under high-resolution conditions reveal additional features as compared to previous data. The cluster of bands near 340 cm−1 is resolved into at least six and possibly eight individual absorptions. A Green’s function calculation over various pertinent models best explains most of these LVM as probably arising from a (2 AlZn-ZnSe) antisite complex (or at least an AlZn pair) with other complexes less likely. The linewidth of individual features can be explained in terms of nearest-neighbor Se host lattice isotopes. Finally, features perturbed from the isolated AlZn case are considered as well as the remaining LVM of unknown origin.
Numerical analysis of amorphous silicon solar cells: A detailed investigation of the effects of internal field distribution on cell characteristics
Authors: Ikegaki Tetsuro , Itoh Haruo , Muramatsu Sin’ichi , Matsubara Sunao , Nakamura Nobuo , Shimada Toshikazu , Umeda Jun’ichi , Migitaka Masanobu
Published: July 2002

This paper describes the application of a new iterative method to numerical calculation of the performance of amorphous silicon p-i-n solar cells. Using this method, the effects of gap-state density, dopant impurities (B and P), and various cell parameters (diffusion length, interface recombination velocities, thickness of the i layer, etc.) on cell characteristics are investigated. The calculated results show that a strong electric field advantageously effects cell characteristics (especially through fill factor) in the i-layer where many photocarriers are generated. However, a uniform field isn’t always adequate for high conversion efficiency. The improvement in conversion efficiency provided by boron doping is attributed to stretching of the diffusion length rather than rearrangement of the field distribution.
Josephson 4 K-bit cache memory design for a prototype signal processor. II. Cell array and drivers
Authors: Henkels W. H. , Geppert L. M. , Kadlec J. , Epperlein P. W. , Beha H. , Chang W. H. , Jaeckel H.
Published: July 2002

A detailed optimized design of a 1 K-bit memory cell array with drivers and reset gates has been carried out based upon a set of projections for achievable tolerances in linewidths, resistances, and Josephson critical currents in a 2.5-μm technology employing niobium edge junctions. The cell operating regions were significantly widened relative to a predecessor Pb-alloy design by adjusting gate and cell inductances, adjusting current levels, and by employing a different timing sequence for application of write controls. Much-improved control of array-line current oscillations, without loss of speed, was achieved by employing a distributed filtering scheme using distributed damping. The design employs trimming of currents to accommodate ±8% chip-to-chip differences in the average critical current. The cell size is 63×63 μm. Monte Carlo calculations of threshold curve tolerances and operating current sensitivities and tolerances lead to a design-limited yield of about 95% for 4 K bits.
Existence of deep acceptors in Ga- and B-implanted GaAs after close-contact annealing
Authors: Dansas P.
Published: July 2002

Photoluminescence studies have been carried out on liquid-encapsulated Czochralski GaAs crystals. Two wafers (labeled P1 and P2) originating from the same ingot have been investigated. After close-contact annealing, the presence of a ≂64-meV deep acceptor was observed in P1-type samples only. After gallium implantation at increasing doses and annealing, the presence of the ≂64-meV level is also observed in P2-type samples. Boron implantation at increasing doses also generated the 64-meV level and, in addition, the ≂77-meV acceptor level, often ascribed to GaAs. Using scaling arguments the 64-meV level is tentatively ascribed to the first level of a double-acceptor defect. Owing to the stoichiometric imbalance induced by implantation and annealing and the specific influence of boron implantation, the ≂64- and ≂77-meV levels are tentatively ascribed to GaAs and BAs antisite defects, respectively.
The existence of a new α′-HgI2 phase and its use for growing single crystals of α-HgI2
Authors: Toubektsis S. N. , Polychroniadis E. K. , Economou N. A.
Published: July 2002

The existence of a new red α′-HgI2 phase that occurs in a narrow temperature range prior to melting has been established. This phase allows the growth of single crystals within its stability range, which after quenching retain their monocrystallinity and transform to α-HgI2. The method is used to prepare single crystals of any desired volume either pure or doped.
Uncoupled Helmholtz resonator: An open photoacoustic cell
Authors: Diószeghy T. , Miklós A. , Kelemen A. , Lőrincz A.
Published: July 2002

The results of acoustic and photoacoustic testing of an uncoupled Helmholtz resonator suggest its utilization as an open photoacoustic cell. Although signal levels are lower in our cell than in small closed cells, this type of resonator produces very low coherent noise if light scattering by the sample is negligible. The resonator is free of static pressure fluctuation problems as well.
Supershallow levels in indium-doped silicon
Authors: Cerofolini G. F. , Pignatel G. U. , Mazzega E. , Ottaviani G.
Published: July 2002

Variable temperature Hall-effect measurements on low-concentration Si:In samples show the existence of supershallow levels with an activation energy for ionization of about 18 meV. For high concentration Si:In samples, the levels at 18 meV tend to disappear and transform into levels with energy of about 160 meV.
An analysis of second harmonic generation of surface waves in piezoelectric solids
Authors: Tiersten H. F. , Baumhauer J. C.
Published: July 2002

The solution for the initial spatial rate of growth of the second harmonic surface wave in arbitrarily anisotropic piezoelectric solids is obtained. The solution satisfies the nonlinear electroelastic differential equations and boundary conditions quadratic in the small field variables consistently to second order in the small amplitude of the input wave. The solution is obtained by means of a straightforward iterative procedure without making any ansatz. It turns out that the growing second harmonic surface wave has exactly the same amplitude ratios as the input surface wave. The expression for the initial slope of the second harmonic surface wave is obtained in the general anisotropic case.
Minimization of the noise temperature of the free-electron bolometer mixer
Authors: Moore W. J. , Newman H. S. , Webb D. C.
Published: July 2002

The principal factors which limit the bandwidth and noise temperature of the free-electron bolometer mixer have been calculated. The minimum mixer contribution to the effective noise temperature is found to be 33Tlattice under the conditions of rf match, IF match, and constant current bias. This result is independent of the electron-lattice energy relaxation time, and can be achieved without significantly degrading the information bandwidth. The best experimental values from the literature are found to be near this predicted performance.