bluuebunny/crossref_metadata_2025 huggingface dataset:
Urbach rule behavior in strongly absorbing fine particle solids
Authors: Waring Robert K. , Hsu William Y.
Published: February 2003

The intrinsic absorption spectrum α(E) of fine particles (<0.2 μm) of PbCrO4, BiVO4, CdS, and ZnS, respectively, was measured in the vicinity of the visible absorption edge from 20 to 300 K by diffuse reflectance. In PbCrO4 and in isoelectronic BiVO4, the edge is exponential and steepens, while remaining fixed in energy, as T is reduced. The edge fits the Urbach behavior: σ=dlnα/dE=(2σ0/ℏΩ0) tanh (ℏΩ 0/2 kBT), where σ0 and Ω0 are constants and σ≂80 eV−1 at 300 K. We find ℏΩ0=25×10−3 eV in PbCrO4, nearly coinciding with the 23×10−3 eV vibration observed in natural crocoite. For the exponential edge in single crystal CdS, σ≂80 eV−1 at 300 K and also increases at low T. However, the edge shifts to higher energy at low T. In fine particles of pure CdS, the energy shift was again found, but σ≂20 eV−1, independent of T. This suggests that in pigmentary CdS, σ is controlled by extrinsic factors such as defects. It behaves as a compensated semiconductor in which color arises from a transition between delocalized states. ZnS behaves similarly. The intrinsic nature of edge broadening in fine particle PbCrO4 and BiVO4 may result from the electronically isolated nature of the chromophore in these solids, wherein the color probably results from a charge transfer transition between localized states.
Photoluminescence study of the incorporation of silicon in GaAs grown by molecular beam epitaxy
Authors: Mendez E. E. , Heiblum M. , Fisher R. , Klem J. , Thorne R. E. , Morkoç H.
Published: February 2003

The effect of substrate temperature and As/Ga flux ratio on the incorporation of Si as a dopant in GaAs grown by molecular beam epitaxy has been studied by means of low-temperature photoluminescence (PL) measurements. It is shown that the acceptor character of Si is enhanced as the substrate temperature increases from 590 to 720 °C. The PL results suggest that the amount of Si self-compensation decreases when the atomic flux ratio increases from 2 to 6.
Recombination mechanisms and doping density in silicon
Authors: Passari Luigi , Susi Enrichetta
Published: February 2003

Carrier recombination in silicon is analyzed as a function of doping density. Two mechanisms are identified: one for the low concentration range and one, of the Auger type, for the high concentration range. Disagreements with the theoretical predictions for the Auger process are discussed and empirical laws connecting lifetime to dopant concentration are determined.
Time-dependent response of interface states in indium phosphide metal–insulator–semiconductor capacitors investigated with constant-capacitance deep-level transient spectroscopy
Authors: van Staa P. , Rombach H. , Kassing R.
Published: February 2003

Constant-capacitance deep-level transient spectroscopy measurements performed on InP-SiO2 metal-insulator-semiconductor capacitors are reported for the first time. Two types of samples have been used, one of epitaxial InP with a free-electron concentration n=1.4×1015 cm−3 and covered with an ‘‘undoped’’ SiO2 insulating layer, the other of bulk material with n=1016 cm−3 and covered with an HCl-‘‘doped’’ SiO2 dielectric. Extensive experiments have been performed and a model has been proposed which successfully explains the corresponding results. This model is based on the assumption of a spatial and energetical distribution of interface states within the dielectric. The interaction of these traps with the conduction band takes place via a tunneling process during the capture of electrons and by a tunneling followed by a thermally activated transition during the emission process. The interface state density has been found to be about 1012 cm−2 eV−1 in the energy range between about 0.2 and 0.5 eV below the conduction band and to decrease considerably to the conduction band above about 0.2 eV. Thus accumulation can be reached. The interface state density strongly increases below about 0.6 eV for the undoped sample and about 0.7 eV for the HCl doped one. Thus strong inversion has not been observed. It is shown that the models presented previously are inconsistent with our experimental results while the model proposed in the present paper explains our and most of the experimental results given in the literature.
Compensation temperature in low density polyethylene β and γ relaxations as determined by thermally stimulated depolarization measurements
Authors: Ronarc’h D. , Audren P. , Haridoss S. , Herrou J.
Published: February 2003

A thermally stimulated depolarization current technique has been used to deduce the compensation law in low density polyethylene β and γ relaxations. The linear relationship between the activation energy and the logarithm of the preexponential factor of the relaxation time has been discussed in terms of compensation temperature and variation of the thermal expansion coefficient through the β and γ processes.
Vibrational relaxation and laser extraction in rare gas halide excimers
Authors: Morgan W. L. , Winter N. W. , Kulander K. C.
Published: February 2003

Recent experiments have demonstrated that the finite rate of vibrational relaxation in the formation of KrF affects the saturation characteristics of the KrF(B) state during extraction of laser light. We have assembled a collisional radiative model using calculated Einstein A coefficients for the lowest twenty KrF states and an approximate calculation of the rate of vibrational energy transfer between KrF and a buffer gas. The model describes the flow of excitation through the vibrational levels of KrF, and demonstrates the effects of vibrational relaxation on KrF(B) saturation and spectra. The results of these calculations agree qualitatively with the published experimental results. In addition, we find that, due to the relaxation kinetics of KrF, Kr2F, a major absorber, is not truly saturable.
Gold as a reliable internal pressure calibrant at high temperatures
Authors: Ming L. C. , Manghnani M. H. , Balogh J. , Qadri S. B. , Skelton E. F. , Jamieson J. C.
Published: February 2003

Energy-dispersive x-ray diffraction measurements on a mixture of powdered NaCl and Au were carried out at high temperatures up to 600 °C (at atmospheric pressure) and also at simultaneously high temperatures and high pressures (to 425 °C and 10.2 GPa). A modified diamond-anvil high pressure cell with a mini resistance-wire heater was used in conjunction with the synchrotron radiation at the Stanford Synchrotron Radiation Laboratory. The temperature of the sample was measured directly by a precalibrated Pt-Pt 10% Rh thermocouple adjacent to the sample. The pressure of the sample was determined by measuring the molar volume changes in NaCl and deriving the pressure through an equation of state. The measured thermal expansion from 25 °C up to 600 °C for NaCl and Au at 1 atm can be expressed by second-order polynomials: V/V0(NaCl)=1+(1.08±0.05)×10−4 (T−25)+(7.5±1.1)×10−8 (T−25)2 and V/V0(Au) =1+(4.26±0.85)×10−5 (T−25)+(5.0±20)×10−9 (T−25)2, where T is in °C. These results are in excellent agreement with previously published data. The measured molar volume ratios of Au at simultaneously high temperatures and high pressures have been found to be in good agreement (within 0.2%) with the values based on the calculated isochores from shock wave data. The pressures determined from the compression of Au at high temperature are compatible with those based on the compression of NaCl (within 2.7% at pressures up to 10.2 GPa). These results enhance the reliability and the scope of the use of Au as an internal pressure calibrant at high temperatures.
The effects of ion-implantation damage on the first-order Raman spectra of GaP
Authors: Myers D. R. , Gourley P. L. , Peercy P. S.
Published: February 2003

We have analyzed the effects of ion-implantation-induced damage on the first-order Raman spectra of GaP, and have correlated changes in the Raman spectra with direct measurements of implantation-induced surface stresses. We find that, at low ion fluences, the effects of implantation damage are to produce point defects that remove free carriers from doped material and to produce stresses in the undamaged regions. In this regime, the stress-induced shifts of the Raman lines can be predicted from the known elastic constants of undamaged GaP. At intermediate fluences, implantation damage alters the elastic properties of GaP so that the stress-induced shifts of the Raman lines are less than those predicted from the properties of the undamaged crystal. At higher doses, implantation-induced surface stresses exceed the elastic limit of the damaged material. This plastic deformation of the implanted surface is accompanied by a rapid broadening of the phonon lines in the first-order Raman spectra.
Oxidation enhanced and concentration dependent diffusions of dopants in silicon
Authors: Matsumoto Satoru , Ishikawa Yutaka , Niimi Tatsuya
Published: February 2003

Diffusions of impurities in silicon under oxidizing ambient and under extrinsic conditions have been analyzed by developing the Hu’s model. The general expression of diffusion coefficient, which includes both the vacancy and interstitialcy mechanisms, is used. The temperature dependences of a fraction of interstitialcy mechanism for arsenic fAs, phosphorus fP, and boron fB are obtained from the data of oxidation enhanced diffusion (OED) and oxidation induced stacking faults.  fAs =42 exp(−0.542/kT), fP =156 exp(−0.666/kT), and fB =860 exp(−0.829/kT). Time dependence of OED and the concentration dependence of the diffusion coefficient of arsenic and boron under extrinsic conditions can be explained by this model.
Examination of models for Zn diffusion in GaAs
Authors: van Ommen A. H.
Published: February 2003

Concentration profiles of Zn in GaAs have been calculated for two models: the Frank–Turnbull model involving Schottky defects and the ‘‘kick-out’’ model involving gallium Frenkel defects. Comparison with experimental data shows that the latter model gives a better description. This indicates that Frenkel defects play a predominant role in this diffusion process.
Growth and photoluminescence spectra of high-purity liquid phase epitaxial In0.53Ga0.47As
Authors: Bhattacharya Pallab K. , Rao Mulpuri V. , Tsai Ming-Jong
Published: February 2003

High-purity liquid phase epitaxial In0.53Ga0.47As has been grown on semi-insulating (100) InP:Fe substrates. The electrical characteristics of the layers were determined from Hall measurements. Different melt-baking schemes were used to improve the purity of the grown layers. It was found that the layers with the most desirable transport properties were obtained by a 20–40 h bakeout of the In melt followed by 20–60 h bakeout of In+InAs+GaAs under ultrapure H2 flow. Such layers were n-type with ND and NA∼1014 cm−3 and with μ300 K and μ77 K=9000 and 55 000 cm2/V s, respectively. Some of the as-grown layers were subsequently heat treated with an InAs proximity cap at 670 °C for 20 min under H2 flow. High-resolution photoluminescence measurements were performed with the as-grown and heat-treated layers at temperatures down to 4.4 K. The spectra were correlated with the growth conditions. Measurements at different temperatures and with varying excitation intensity helped to elucidate excitonic and impurity-related transitions. The most intense peaks at the highest energies arise from bound excitons. Carbon is usually not detected in the LPE crystals except those grown after 100 h or longer melt baking. The binding energy EA of carbon acceptors is 13.0±1.0 meV. Other acceptor-related transitions observed in the spectra are Zn with EA=28.0±1.0 meV and Si with EA=33.0±2.0 meV. An LO-phonon replica of the Zn-related transition was consistently observed with ℏwLO=32.0±1.0 meV. From our measurements it transpires that the 0 K band gap of In0.53Ga0.47As is ∼0.822 eV.
End effects of a bifilar magnetic wiggler
Authors: Fajans J.
Published: February 2003

The magnetic field at the entrance of a wiggler magnet in a free-electron laser (FEL) determines the character of the electron orbits and influences the FEL gain. To obtain the desired adiabatic entrance conditions, it is necessary to investigate different methods of connecting leads to the wiggler as well as methods of gradually reducing the wiggler field. The field of a current-driven, finite-length bifilar helical wiggler magnet is derived and is used to investigate the magnetic field end perturbations. For a limited range of wiggler parameters, flaring the wiggler end produces an adiabatic entrance region. Alternatively, gradually terminating the wiggler current at the wiggler entrance is shown to produce an adiabatic entrance for a larger range of parameters.
Reconstruction of inclusions in solids using ultrasonic Born inversion
Authors: Hsu D. K. , Rose J. H. , Thompson D. O.
Published: February 2003

Voids and inclusions in elastic solids are characterized experimentally using scattered ultrasonic waves. The flaws are reconstructed using a one-dimensional elastic wave inverse scattering algorithm based on the Born–Neuman expansion. This method emphasizes the role of low and intermediate frequency longitudinal waves. The utility of the inverse Born approximation is tested for several new circumstances. First the algorithm is tested for pitch-catch (bistatic) geometries. Secondly the effects of resonant excitation of the scatterer on flaw characterization are measured for several spherical flaws. The third and major result shows that the one-dimensional algorithm can be used to determine the size, shape and orientation of nearly ellipsoidal flaws when access angle is limited. The effects of varying access aperture on the reconstruction are reported. Another common experimental limitation in flaw characterization arises from interferences of the flaw signal with nearby surfaces. We briefly report that the same algorithm was successful in inverting several near surface flaws. In particular, we have successfully reconstructed, in the bulk of the sample, an approximately prolate spheroidal inclusion imbedded in plastic, an oblate spheroidal void in titanium, and in the near surface region an approximately prolate spheroidal inclusion.
Accurate determination of the free carrier capture kinetics of deep traps by space-charge methods
Authors: Pons D.
Published: February 2003

A detailed analysis of the pulsed bias techniques used to determine the capture kinetics of free carriers by deep traps in Schottky diodes or asymmetric bipolar junctions is presented. Both exact simulations, involving an exact integration of Poisson’s equation and a self-consistent treatment in the case of large deep trap concentrations and simple analytical approximations are given. The usual depletion approximation for the distribution of free carriers in the Debye tail is demonstrated to yield erroneous results in some occasions and it is shown how to deal simply with the exact distribution. A novel experimental technique is proposed to rigorously extract the exponential capture kinetics in the neutral semiconductor, from the total capture kinetics, getting rid of the capture in the Debye tail; it is also shown how it is possible to obtain a correct estimation of the capture rate from the capture in the Debye tail, when the direct determination by the above mentioned method is impossible.
Some properties of crystallized tantalum pentoxide thin films on silicon
Authors: Oehrlein G. S. , d’Heurle F. M. , Reisman A.
Published: February 2003

Tantalum pentoxide thin films on p-type Si substrates were prepared by thermal oxidation at 525–550 °C of electron-beam deposited Ta. Polycrystalline Ta2O5 films were formed by heat treating the amorphous Ta2O5/Si structures at temperatures of 900–1000 °C for times of up to 2.5 h in Ar or dry O2. The amorphous films crystallized into the low temperature β-Ta2O5 modification. The electrical properties of the polycrystalline Ta2O5 films on Si were studied employing Al/Ta2O5/Si metal-insulator-semiconductor capacitors. Films which were crystallized in Ar show higher leakage for all fields than comparable amorphous films. Heat treatments (900–1000 °C) in dry O2 for times greater than 30 min produce films with similar leakage at fields lower than 0.6 MV/cm, but increased leakage at higher fields. Increasing the temperature or the length of time of the high temperature oxidation step reduces the leakage. After 30 min at 1000 °C in dry O2, a leakage current density of 9.6×10−9 A/cm2 at an applied field of 0.7 MV/cm can be achieved (insulator about 70 nm thick). The conductivity of the dielectric films increases irreversibly (dielectric breakdown) if a current density of 1.93 ×10−4 A/cm2 or higher is forced through the insulator; for a specimen oxidized for 30 min at 1000 °C, this corresponds to a breakdown field of about 1.0 MV/cm. The effective dielectric constant εeff of crystallized Ta2O5 films on Si is higher than that of amorphous Ta2O5 on Si and can be as high as 30. For isochronal oxidations at different temperatures greater than about 900 °C a decrease of εeff is observed, which increases with increasing oxidation temperature. For isothermal oxidations at high temperatures εeff decreases as a function of oxidation time. Auger electron sputter profiles of high-temperature oxidized Ta2O5/Si structures indicate a thin SiO2 layer at the Ta2O5/Si interface. The formation kinetics of this SiO2 layer as a function of oxidation time and temperature enables a consistent explanation of all electrical measurement results.
Titanium silicide formation: Effect of oxygen distribution in the metal film
Authors: Berti M. , Drigo A. V. , Cohen C. , Siejka J. , Bentini G. G. , Nipoti R. , Guerri S.
Published: February 2003

The oxygen behavior and its influence on Ti silicide formation is systematically studied in the TiO2/Si and Ti/TiO2/Si systems using Rutherford backscattering, nuclear reaction analysis, and x-rays diffraction techniques. After annealing in vacuum ( p<5×10−7 Torr), no reaction was observed up to 900 °C in the TiO2/Si system, whereas in the Ti/TiO2/Si system, metallic titanium reacts with the TiO2 film above 400 °C and at 600 °C a uniform oxygen solid solution is formed. The silicide formation starts at 650 °C and up to 750 °C the only phase formed is Ti5Si3. We found that this phase is kinetically favored as long as the Ti is being supplied by the unreacted film. The growth rate kinetics was found to have parabolic behavior and was therefore controlled by Si volume diffusion. Above 750 °C, TiSi2 forms very rapidly, its growth being nucleation controlled. During the growth of the silicide layer, a diffusion of oxgen toward the surface region was observed. When the oxygen concentration in the surface layer exceeded the solubility limit, Ti oxide precipitated and the silicide growth nearly stopped, even if some silicon reached the surface. At a temperature higher than 850 °C, a marked oxygen loss takes place, most probably via SiO sublimation. The sublimation process is favored by the presence of Si in the surface region and prevents the formation of a stable SiO2 diffusion barrier at the TiSi2/TiOx interface.
Deep and shallow levels in n-type indium phosphide irradiated with 200-keV deuterons
Authors: Macrander A. T. , Schwartz B. , Focht M. W.
Published: February 2003

A predominant deep level was found to have been introduced by a fluence of 1012 cm−2 into nominally undoped vapor phase epitaxial material having a carrier concentration of 2×1015 cm−3. The defect was formed up to but not including the end of range and was named a D center. The D-center concentration was ∼1×1016 cm−3, its electron emission activation energy was 0.40 eV, and it was activated at room temperature. In addition, shallow donor levels were formed as a result of the irradiation. An increased electron concentration of ∼1×1016 cm−3 due to these shallow donor levels was measured in the end of range, and we inferred their existence throughout the ion range. Via a Monte Carlo simulation of the ion bombardment, the region in front of the end of range and the end of range itself were found to be differentiated by the amounts of nuclear and electronic energies deposited in them. A model based on the D center being an acceptor can explain the observed results and is also consistent with the compensation known to result from light ion bombardment. We conclude from this model that the entire region between the surface and the end of range can be made highly resistive as a result of deuteron bombardment. Results of capacitance-voltage, capacitance and admittance deep level spectroscopy, and constant-capacitance measurements made on gold Schottky diodes are presented.
Impurity (Si) concentration effects on radiation-induced deep traps in n-InP
Authors: Ando K. , Yamaguchi M. , Uemura C.
Published: February 2003

Impurity concentration effects on radiation defects and minority carrier (hole) diffusion length in 1-MeV electron irradiated n-InP have been studied by deep level transient spectroscopy and the electron beam induced current method. Trap concentrations are found to markedly decrease with an increase in the Si-impurity concentration. It is also indicated that Si-impurity doping more than 1017 cm−3 of concentration shows a strong suppression effect on degradation in minority carrier diffusion length, caused by electron irradiation in n-InP.
Analysis of the electron-beam-induced current of a polycrystalline p-n junction when the diffusion lengths of the material on either side of a grain boundary differ
Authors: von Roos Oldwig , Luke Keung L.
Published: February 2003

The short circuit current generated by the electron beam of a scanning electron microscope in p-n junctions is reduced by enhanced recombination at grain boundaries in polycrystalline material. Frequently, grain boundaries separate the semiconductor into regions possessing different minority carrier life times. This markedly affects the short circuit current ISC as a function of scanning distance from the grain boundary. It will be shown theoretically that (a) the minimum of the ISC in crossing the grain boundary with the scanning electron beam is shifted away from the grain boundary toward the region with smaller life time (shorter diffusion length), (b) the magnitude of the minimum differs markedly from those calculated under the assumption of equal diffusion lengths on either side of the grain boundary, and (c) the minimum disappears altogether for small surface recombination velocities (s<104 cm/s). These effects become however negligible for large recombination velocities s at grain boundaries. For p-type silicon this happens for s≥105 cm/s.
Surface conductivity measurements by a capacitive coupling technique
Authors: Dolgopolov V. , Mazuré C. , Zrenner A. , Koch F.
Published: February 2003

We show how the conductivity of a gate-voltage-induced charge layer in a metal-insulator-semiconductor (MIS/MOS) capacitor structure can be measured quantitatively without the need for source-drain contacts. In this scheme, the interface current is driven by an rf voltage applied across a resistive thin-film gate electrode and coupling capacitively to the conducting interface layer. We give examples that illustrate application possibilities and the sensitivity of the technique.
Light-beam-induced current characterization of grain boundaries
Authors: Marek Jiří
Published: February 2003

A quantitative theory for evaluation of light-beam-induced profiles at grain boundaries is presented. Signals and deduced characteristic values, i.e., the maximum and the half-width, are calculated in a practically important region of the semiconductor parameters. From this numerical simulation the influence of the various parameters on the signal properties is deduced. Light beam experiments are performed with high spatial resolution on semicrystalline solar cells. The light-beam-induced current can be calibrated to give the spatially resolved quantum yield. The experimental data are analyzed using the presented theory. Excellent agreement is obtained between experiment and theory as well as between light-beam-induced current analysis and previous electron-induced experiments.
High-efficiency electroplated heterojunction solar cell
Authors: Basol Bulent M.
Published: February 2003

Over 9% efficiency is demonstrated in electroplated CdS/CdTe thin film solar cells. Processing of the devices is described. A brief heat treatment step first anneals out the deep lifetime killer centers in the material then converts the originally n-type film into solar cell grade p-CdTe.
Some aspects of bonding-solder deterioration observed in long-lived semiconductor lasers: Solder migration and whisker growth
Authors: Mizuishi Ken’ichi
Published: February 2003

This paper reports on catastrophic degradation, called sudden failure (SF), that is observed in both AlGaAs/GaAs and InGaAsP/InP double-heterostructure lasers. The SF observed here is not associated with electrical surge effects and appears unexpectedly in the middle of a long-term, stable operation. It was found that this type of SF can be caused by aging-induced metallurgical deterioration at the interfacial bonding solder layer. Among the metallurgical deteriorations observed were (1) solder migration into the laser crystal due to current-induced local heating near the end mirror of the laser, (2) In whisker growth due to electromigration in In solder, and (3) Sn whisker growth, when using an Au-Sn alloy as solder, due to strain relaxation. All of these effects cause SF. Countermeasures against these deteriorations are described and some successful results are presented.
Ray optics of a planar waveguide with an exponential index profile
Authors: Huang Sun-Yuan , Wang Shou-yin
Published: February 2003

Trajectories of optical rays propagating in planar waveguides with exponential-type refractive index profiles have been solved in an exact analytical closed form. Based on this trajectory idea and the known solutions of E, H fields of such exponential-type waveguides, we have extended the Rayleigh-Tien treatment of a step-function-type waveguide and calculated, using the experimental data of Taylor et al., the attenuation constant of the guided light due to surface roughness scattering. This constant, as obtained from this intuitively clear picture of the trajectory concept, is found to decrease rapidly with increasing mode number, which is just opposite to the modal dependence of attenuation constant of step-function-type waveguides.
Z-pinch instability with distributed current
Authors: Pereira N. R. , Rostoker N. , Pearlman J. S.
Published: February 2003

Sausage and kink growth rates for a Z pinch are computed from ideal magnetohydrodynamic theory for an infinitely thin surface current sheath and for a surface current layer of finite width. The growth rate decreases with increasing layer width. Satisfactory agreement with experiment is obtained for reasonable width estimates based on magnetic field diffusion.
Preparation of devices by liquid phase epitaxy with application to the achievement of a visible laser in GaAlAs
Authors: Vassilieff Georges , Saint-Cricq Beatrice
Published: February 2003

The effect of introducing Sn and Ge doping on the liquidus-solidus curves is studied for the case of epitaxy in GaAlAs. The proposed theory combined with the equations for epitaxial layer deposit kinetics has enabled the SPELLAS (simulation of liquid epitaxy processes for producing lasers) program to be set up. This program helps and completely simulates the production of multilayers by liquid-phase epitaxy according to several technologically important choices. In particular, we shall show the advantage of using a precursor substrate for a first deposition. An example of its application will be described for the preparation of visible lasers in GaAlAs. A laser structure emitting at 706 nm with a threshold current density of 4.3 kA/cm2 and an efficiency of ηD=20% has thus been made.
Transient capacitance study of defects introduced by electron-beam deposition of metals on p-type silicon
Authors: Auret F. D. , Mooney P. M.
Published: February 2003

Defects introduced during electron-beam deposition of Mo, Hf, and Ti on p-type silicon were studied with deep level transient spectroscopy. The most prominent defect observed after deposition was a hole trap, H(0.35), at Ev+0.35 eV. After annealing, H(0.35) migrates deeper into the substrate and several other defects appear. H(0.35) and H(0.38), which were observed after H(0.35) annealed out, exhibit the same annealing behavior as defects with the same thermal activation energies introduced by ion-beam and rf sputtering of Mo and Ti-W on p-type silicon, and also by high-energy (2 MeV) electron irradiation. Annealing at 550 °C for 10 min sufficed to remove all the defects introduced during electron-beam deposition.
Early stages of oxygen segregation and precipitation in silicon
Authors: Bourret A. , Thibault-Desseaux J. , Seidman D. N.
Published: February 2003

The early stages of oxygen segregation at dislocation and precipitation in the bulk have been investigated by high-resolution electron microscopy in Czochralski grown silicon. Two kinds of precipitates are observed: a crystalline silica phase, coesite, and an amorphous phase. Both forms coexist after 650 °C heat treatment: the so-called rodlike defects are in fact long 〈011〉 ribbons of coesite associated with interstitial dipoles. This crystalline form is favored by a high oxygen supersaturation and a low carbon content. Above 870 °C amorphous platelets of silica are formed on the {100} planes, whereas coesite is no longer observed but interstitial dislocation loops are always present. The strain produced by such precipitates is partially relaxed by Si interstitial emission, which explains the internal formation of dislocations. It is suggested that both forms are nucleated on two different species of nuclei. At 〈011〉 dislocation cores it is shown that the coesite phase is stabilized over a wide range of oxygen content or annealing temperature.
On the electron-beam pumped KrF laser
Authors: Witteman W. J. , Kleikamp B. M. H. H.
Published: February 2003

The paper deals with the complex kinetics of excitation, quenching, and absorption in an electron-beam pumped KrF laser. The effect of the pressure dependence of the ionic recombination rates, the role of the metastables, and the formation of ArKr+ are investigated and compared with our experimental results. From the model the maximum power density together with the optimized densities of argon, krypton, and fluorine are calculated as a function of the beam-current-to-outcoupling ratio. Finally, the pressure dependencies of the individual components near the optimized conditions are investigated.
Carrier concentration effects on radiation damage in InP
Authors: Yamaguchi M. , Ando K. , Uemura C.
Published: February 2003

Minority carrier diffusion length and carrier concentration studies have been made on room-temperature 1-MeV electron irradiated liquid-encapsulated Czochralski grown Zn-doped p-InP. The damage rate for the diffusion length and carrier removal rate due to irradiation have been found to strongly decrease with an increase in the carrier concentration in InP. These phenomena suggest that the induced defects interact with impurities in InP. A preliminary study on the annealing behavior has also been performed.
Effect of long-range interaction on diffusion in copper-nickel composition-modulated alloys
Authors: Tsakalakos T. , Hilliard J. E.
Published: February 2003

Vapor deposited Cu–Ni films were produced containing composition modulations with wavelengths between 0.8 to 5.0 nm. The foils, deposited on mica substrates, exhibited a strong 〈111〉 texture and produced satellite peaks in the x-ray diffraction patterns. The interdiffusivities in the range of 375–450 °C, which were measured from the decay rate of the x-ray diffraction satellite intensities, yielded an activation energy of 2.7×105 J/mol. This value is in good agreement with that obtained by tracer diffusivities at high temperatures. The effective diffusion coefficient D̃B at 400 °C [as a function of the dispersion relation B2(h)] showed a minimum at a wavelength of about 1.5 nm in contrast with the linear or monotonic behavior of several other systems. A new formulation of D̃B in a power series of B2 was developed and the first six interaction energies were calculated from short-range order parameters.
Alpha-particle detection with superconductor detectors
Authors: Kurakado M.
Published: February 2003

The Sn-SnOx-Sn tunnel junction of a crossed-film type, cooled down to 0.32 K, is demonstrated as a good energy resolution detector for α particles. Three junctions (A, B: 300×400 μm2×3000 Å and C: 200×300 μm2×3000 Å) have been used to detect 5.3-MeV α particles from 210Po. The present work suggests that reduction of the leakage current enables us to utilize superconducting tunnel junctions with large volumes. Such a device could provide a new means for detection of unclear radiations.
Annealing characteristics of neutron-transmutation-doped germanium
Authors: Palaio N. P. , Pearton S. J. , Haller E. E.
Published: February 2003

The effects of thermal- and injection-enhanced annealing on the electrical properties of initially high-purity (NA−ND =1010 cm−3) neutron-transmutation-doped (NTD) Ge were investigated using capacitance transient spectroscopy and variable temperature Hall effect. Complete recovery of electrical properties was observed after thermal annealing at 400 °C for 6 h, and significant activation of dopants created by the NTD process is seen even in samples left at ambient temperature for eight months after irradiation. Electric field-enhanced emission of trapped holes from deep level, damage-induced states was used to verify their acceptor nature, and a recombination-enhanced annealing mechanism was observed for several deep acceptors. Other high-purity samples irradiated with a lower dose of fast neutrons only (average energy 4.2 MeV) showed many deep hole traps, most of which were tentatively correlated with the amount of hydrogen in the parent crystal. These deep level damage centers were not observed in the more heavily damaged NTD samples.
Measurement of high magnetomechanical coupling factors by resonance techniques
Authors: Hathaway K. B. , Spano M. L.
Published: February 2003

Accurate calculations of the very high magnetomechanical couplings of amorphous magnetic ribbons, as measured by resonance techniques, rest precariously on assumptions of the magnetic boundary conditions in the sample. The limiting cases of uniform magnetic field and uniform induction give very different results when the magnetoelastic coupling factor approaches unity. A data analysis scheme presented here allows interpolation between these two extremes by examination of the location of the first resonance harmonic. Data from 4-in. samples of Metglasa 2605SC, annealed in a transverse field, show very clear harmonic resonances allowing a more precise determination of the coupling constant in these materials than reported previously.
Study of the effect of ferromagnetism on the Kondo state: Ce1−xGdxAl3
Authors: Edelstein A. S. , Koon N. C.
Published: February 2003

Magnetization, magnetostriction, and thermal expansion measurements have been performed on Ce1−xGdxAl3(x=0.05,0.2). The unstable moment Kondo properties of Ce in CeAl3 persist for both values of x, but are modified at the composition x=0.2 at which the system is ferromagnetic. Evidence for this conclusion is that the temperature dependence of the volume magnetostriction and values of the thermal expansion are very small below the Curie temperature.
Influence of crystal orientation distribution on anisotropy of magnetostriction and magnetocrystalline energy in Fe-Si steel
Authors: Szpunar J. A.
Published: February 2003

Crystalline texture is often the cause of the anisotropy of the magnetostriction and the magnetocrystalline energy in polycrystalline materials. Anisotropy of these properties with respect to the specimen reference frame has been described using coefficients of a series expansion of the crystal orientation distribution function and single-crystal constants characterizing magnetocrystalline anisotropy and magnetostriction. Two-dimensional computer drawings can be generated characterizing the anisotropy of the magnetostriction strain in the specimen after the saturation field is applied in any arbitrary direction of the specimen. Average magnetocrystalline energy can be also similarly characterized. The methods have been illustrated by experiments done on Fe-Si steel. Texture has been studied using neutron diffraction and analyzed with the aid of three dimensional orientation distribution functions. Magnetic torque measurements and magnetostriction measurements have been made and the results agree with the prediction of the model.
Spin-wave instability theory for hexagonal ferrites
Authors: Kogekar M. V. , Kabos P. , Patton C. E.
Published: February 2003

The spin-wave instability theory for ferrites with magnetocrystalline anisotropy is extended to include planar anisotropy and second-order processes. General expressions are obtained for first- and second-order processes in planar hexagonal ferrites magnetized in the easy plane and pumped with an arbitrary microwave field configuration. The calculations for second-order processes predict characteristic curves for the critical microwave instability threshold field versus the static magnetic field. These curves, with a minimum at ferromagnetic resonance, are similar to the butterfly curves encountered in the analysis of subsidiary absorption in cubic crystals. The results are applied to previously published experimental data on Zn2Y-type hexagonal ferrite platelets.
Hydrodynamics of thermal self-focusing in laser plasmas
Authors: Craxton R. S. , McCrory R. L.
Published: February 2003

Two-dimensional Eulerian hydrodynamics simulations have been carried out to investigate the thermal self-focusing of laser beams in plasmas with long scale lengths. Realistic modeling of the plasma dynamics and the time dependence of the plasma heating is found to be necessary to follow the fully nonlinear development of self-focusing. The laser propagation is treated using a self-consistent ray-tracing model. The simulations presented illustrate the dependence of thermal self-focusing on beam size, plasma scale length and initial temperature, laser wavelength and intensity, and flux limiter. For the interaction of a finite-sized beam with a preformed long-scale-length plasma, whole-beam self-focusing is found to occur when the beam diameter is smaller than the plasma scale length. For beams with a hot spot imposed on a uniform background, self-focusing occurs only for hot spots of sufficient amplitude (≳a few percent in typical cases). Self-focusing is less likely to occur in an initially hot plasma. Low-density self-focusing channels formed in the underdense plasma by the expulsion of plasma from laser-heated regions may collimate the reflected light back towards the laser. Small-scale self-focusing has also been simulated, along with a subsequent evolution into whole-beam self-focusing.
Study of oxygen transport processes during plasma anodization of Si between room temperature and 600 °C
Authors: Perriere J. , Siejka J. , Chang R. P. H.
Published: February 2003

Studies of oxygen transport mechanisms during plasma anodization of Si have been carried out using a combination of 18O tracing techniques and nuclear microanalysis. A thin 18O-enriched ZrO2 overlay film has been used as a source of oxygen tracers during subsequent plasma anodization of Si. The enhancement effect of the zirconia layer on the kinetics of Si anodization allows one to study the mechanisms of Si anodization between room temperature and 600 °C. Results of the 18O depth distributions show that the order of oxygen atoms is largely preserved in the SiO2 and that oxygen ions migrate during film growth. For the temperature range (25–600 °C) studied the microscopic mechanism of oxygen transport during plasma anodization of Si involves a short-range oxygen ion migration, in contrast to the case of high-temperature thermal oxidation. The contribution of a pure thermal process via the diffusion of neutral oxygen species is negligible compared to the high-field-assisted oxygen ion migration in these plasma anodization experiments.
The exponential optical absorption band tail of Hg1−xCdxTe
Authors: Finkman E. , Schacham S. E.
Published: February 2003

The optical absorption edges of Hg0.71Cd0.29Te and CdTe were measured over the temperature range 80≤T≤300 K. The refractive indices of these materials are determined over a large energy range at T=300 K and their dispersion relation is given. The absorption band tail of Hg1−xCdxTe has an exponential shape. Its slope increases with decreasing temperature. It is suggested that this tail is not caused by permanent lattice disorder but is a material property. An empirical expression for the absorption coefficient as a function of temperature and composition is derived. Using this expression, the zero-intercept cut-on energy of the infrared transmission spectrum at room temperature is used to define the composition for any desired thickness of Hg1−xCdxTe sample.
Bipolar junction transistor models for circuit simulation of cosmic-ray-induced soft errors
Authors: Benumof Reuben , Zoutendyk John
Published: February 2003

This paper examines bipolar junction transistor models suitable for calculating the effects of large excursions of some of the variables determining the operation of a transistor. Both the Ebers–Moll and Gummel–Poon models are studied, and the junction and diffusion capacitances are evaluated on the basis of the latter model. The most interesting result of this analysis is that a bipolar junction transistor when struck by a cosmic particle may cause a single event upset in an electronic circuit if the transistor is operated at a low forward base-emitter bias.
Characterization of CdS/CdTe thin-film solar cells by admittance spectroscopy and deep-level transient spectroscopy
Authors: Isett L. C.
Published: February 2003

Admittance spectroscopy, deep-level transient spectroscopy, and deep-level optical spectroscopy were used to characterize CdS/CdTe thin-film solar cells prepared by close-spaced sublimation. These devices are n+/p-type hetero- (or shallow homo-) junctions, and deep levels in the p-CdTe layer are observed. The energy levels within the band gap can be divided into three groups. The first group consists of the shallow (<0.1 eV from the band edge) acceptors and donors, observed in electrical characterization only as the net carrier concentration. A band of midgap levels with activation energies of 0.6–0.8 eV in deep-level transient spectroscopy is observed. The emission rates and activation energies for these levels agree with deep donor levels found in n-type CdTe. A third band of levels is found with activation energies of 0.28–0.45 eV in admittance spectroscopy. These levels are seen in deep-level optical spectroscopy and also in deep-level transient spectroscopy, provided that a large forward-bias pulse is used to fill the level. The emission rates in the third band agree with donor levels observed in n-CdTe. Estimates of concentrations suggest that the concentration of the group two defects (midgap donors) is ∼0.8 of the net shallow acceptor concentration.
Electrofracture mechanics of dielectric aging
Authors: Zeller H. R. , Schneider W. R.
Published: February 2003

We introduce a fracture mechanics concept of aging in solid dielectrics. The key element is that growth of a damage structure is only possible if the release of electrostatic energy due to growth exceeds the formation energy of the damage structure. Both the electrostatic energy release and the formation energy are calculated for simple examples.
Mechanisms of damage recovery in ion implanted SiO2
Authors: Devine R. A. B.
Published: February 2003

The annealing characteristics of E′1 bridging oxygen vacancy centers in ion implanted SiO2 have been determined using electron spin resonance. For temperatures < 300 °C annealing occurs but the centers can be reactivated using ionizing radiation. For T > 500 °C annealing becomes irreversible and is consistent with the peroxy radical, dangling Si0 linkage, and radiation compaction annealing suggesting overall damage recovery.
Temperature derivatives of elastic stiffness derived from the frequency-temperature behavior of quartz plates
Authors: Lee P. C. Y. , Yong Y. K.
Published: February 2003

Linear field equations for small vibrations superposed on thermally-induced deformations by steady and uniform temperature changes are derived from the nonlinear field equations of thermoelasticity in Lagrangian formulation. From the solutions of these equations for the thickness vibrations, the temperature derivatives of elastic stiffness are related analytically to the known or measured properties such as the second- and third-order elastic stiffnesses, thermal expansion coefficients, and temperature coefficients of frequency of quartz plates. Six values of the first temperature derivative C(1)pq and six values of the effective second temperature derivative C̃(2)pq are calculated from the temperature coefficients of frequency measured by Bechmann, Ballato, and Lukaszek for various doubly-rotated quartz plates. The presently calculated values are compared with the first temperature derivatives obtained by Sinha and Tiersten. In the incremental stress-strain-temperature relations, certain expressions involving the elastic stiffnesses, temperature derivatives, and thermal expansion coefficients can be identified as having similar significance as the temperature coefficients of Cpq defined by Bechmann. Values of these expressions are calculated and compared with the existing values. The loci of the zeros of the first and second order temperature coefficients of frequency for thickness shear (B and C) modes and the frequency-temperature characteristics of the LC cut are studied and compared with experimental values.
Metal hydride photodissociation lasers: Laser operation for Al and In photofragments
Authors: Erlandson Alvin C. , Cool Terrill A.
Published: February 2003

The first metal hydride photodissociation lasers are reported. A room-temperature segmented discharge technique was used for metal hydride production. Laser operation was demonstrated for Al at 3962 Å and for In at 4102 and 4511 Å. A proposed inversion mechanism for these lasers and the prospects for additional metal hydride dissociation lasers are discussed.
Experimental tests of a single-photon calorimeter for x-ray spectroscopy
Authors: McCammon D. , Moseley S. H. , Mather J. C. , Mushotzky R. F.
Published: February 2003

Tests have been made of a nondispersive spectroscopic x-ray detector which operates by measuring the temperature rise following absorption of a single photon. We have observed thermal pulses from 6-keV x-rays, and have resolved the different amplitudes resulting from Mn Kα and K β events. This device was assembled to make quantitative tests of theoretical calculations of the properties of such detectors, and its high heat capacity does not allow it to attain the very high resolution predicted for detectors made by more sophisticated, but still straightforward, techniques. Both the measured resolution of 270-eV full width at half maximum (FWHM) and the absolute amplitude of the response are consistent with predictions. Nonthermal effects in the thermistor limit the precision of this comparison to about 30%.
Epitaxial growth of lattice-matched CaxSr1−xF2 on (100) and (110) GaAs substrates
Authors: Siskos S. , Fontaine C. , Munoz-Yague A.
Published: February 2003

Epitaxial growth of monocrystalline layers of mixed fluorides (CaxSr1−xF2) using molecular beams on GaAs substrates is reported for the first time. Good morphology and crystalline quality of the layers have been obtained. Some possible applications of these structures are considered, and preliminary results are reported concerning the electrical behavior of metal-insulator-semiconductor devices and the use of CaxSr1−xF2 as encapsulant or as masking material for GaAs.