bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel effects of magnetic field on the silane glow discharge
Authors: Taniguchi M. , Hirose M. , Hamasaki T. , Osaka Y.
Published: February 2003

We have measured the optical-emission spectra of the silane plasma as a function of the external magnetic field, together with the growth rate and vibrational spectra of the resulting a-Si:H films. The optical-emission intensities of the reactive species SiH, H2, and H produced in the plasma are appreciably affected by the magnetic field, and the corresponding change in the hydrogen bonding of the deposited films is interpreted in terms of chemical reaction among the species.
Mechanical properties of heat-treated Czochralski-grown silicon crystals
Authors: Yasutake K. , Umeno M. , Kawabe H.
Published: February 2003

Compression tests were performed on heat-treated silicon crystals. Yield stresses of crystals depended strongly on the size and density of precipitates induced by heat treatments. Transmission electron microscope observation revealed that SiO2 precipitates larger than a few thousand angstroms became the nucleation sites of glide dislocations, causing a decrease in the yield stress, and that microprecipitates of less than several hundred angstroms acted as obstacles to dislocation movement.
Ion channeling in GaAs: Si, S, Se, and Te
Authors: Wilson R. G. , Deline V. R.
Published: February 2003

Atom depth distributions resulting from the implantation of 29Si, 32S, 32Se, and 130Te ions within ∼0.05° of the 〈110〉 and 〈100〉 directions of the GaAs crystal have been measured by secondary-ion mass spectrometry. The two lower-mass ions were implanted at 150 keV and the two higher-mass ions at 300 keV; all were implanted to a fluence of 3.0×1013 cm−2. Well-defined maximum ranges and most probable channeled ranges Rc are observed in the 〈110〉 channeled distributions. The values of R0.1Nmax at Rc, chosen as a measure of the maximum channeled range, are 2.60, 1.60, 3.56, and 4.68 um, respectively, for the four ions. Background-subtracted detection sensitivities for these four atoms in GaAs of l013–3×1014 cm−3 provide up to five orders of magnitude of dynamic range below the maxima in the depth distributions (the peaks in the random components).
CO2 laser excited by preionized transverse discharge through a dielectric
Authors: Cohn D. B.
Published: February 2003

The effect of preionization on a dielectric-electrode discharge in CO2 laser media is described. Compared to previous devices without preionization, specific energy extraction has been increased approximately threefold to 6 J/1 atm and gas pressures for stable operation are increased from below 1 atm to above 2 atm. With preionization, pulse-to-pulse repeatability for a 0.5-Hz repetition rate under static gas conditions is greatly enhanced compared to operation without preionization in the present device. These results compare favorably with those obtained in conventional metallic-electrode discharge transverse electric atmospheric (TEA) lasers.
Optical study of isotopic effects in the sulfur deep level in silicon
Authors: Forman Richard A.
Published: February 2003

The optical absorption spectrum of silicon diffusion doped with sulfur has been studied in the region near 2 μm. Samples containing either 32s or 34s were examined to attempt to detect an isotopic shift of the energy level of the deepest sulfur center. Only a very small shift of 0.14 meV was observed; this is two orders of magnitude smaller than that found for the center studied by deep-level spectroscopy. Analysis of the literature indicates that both measurements are in fact on the same center. The optical spectrum is interpreted as superimposed spectra of a group of slightly differing sulfur centers. If these perturbed centers were formed in different concentrations in different samples, an apparent isotope shift could easily be inferred in the deep-level measurement. The interpretation of multiple centers for the sulfur deepest donor is analogous to the well-known X levels found for several acceptors in silicon. These results may have general applicability toward an understanding of reported differences between various experiments on other deep-level systems.
A backside-illuminated imaging AlGaAs/GaAs charge-coupled device
Authors: Liu Y. Z. , Deyhimy I. , Anderson R. J. , Milano R. A. , Cohen Marshall J. , Harris J. S. , Tomasetta L. R.
Published: February 2003

A glass-supported, backside-illuminated AlGaAs/GaAs heterojunction charge-coupled device (CCD) imager is reported. The CCD structure was grown by liquid phase epitaxy on a GaAs substrate. The top epi-layer was bonded to glass and the GaAs substrate completely removed. A ten-pixel three-phase Schottky gate CCD was fabricated on the glass-supported layer. The CCD was successfully operated as a line imager with the photosignal entering through the support glass.
A model for ion-implantation-induced improvements of photoferroelectric imaging in lead lanthanum zirconate titanate ceramics
Authors: Peercy P. S. , Land C. E.
Published: February 2003

Studies of photoferroelectric image storage in H-, He-, and, more recently, Ar-implanted /(PLZT) lead lanthanum zirconate titanate reveal that the photosensitivity can be significantly increased by ion implantation into the image storage surface. For example, the photosensitivity after implantation with 5×1014 500-keV Ar/cm2 is increased by about three orders of magnitude over that of unimplanted PLZT. The increase in photosensitivity results from a decrease in dark conductivity and changes in the photoconductivity of the implanted layer. We present a phenomenological model which describes the photosensitivity enhancement obtained by ion implantation. This model takes into account both light- and ion- implantation-induced changes in conductivity and gives quantitative agreement with the measured changes in the coercive voltage with near-UV light intensity for ion-implantated PLZT.
High-temperature scanning cw laser-induced diffusion of arsenic and phosphorus in silicon
Authors: Matsumoto S. , Gibbons J. F. , Deline V. , Evans C. A.
Published: February 2003

The diffusion of arsenic and phosphorus in silicon at temperatures near the melting point has been investigated by using a scanned cw laser. The intrinsic diffusion coefficients of arsenic and phosphorus obtained in this work agree well with the extrapolated values of intrinsic diffusion coefficients reported by others. Diffusion coefficients of arsenic under extrinsic conditions at temperatures over 1200 °C are found to depend linearly on the electron concentration. The validity of the analytical model for solid-phase reaction expressed in terms of an effective temperature and an effective time for the laser heat source is shown.
Near-surface regrowth rate effects in high-dose ion-implanted (100) silicon
Authors: Williams J. S. , Elliman R. G.
Published: February 2003

High-resolution Rutherford backscattering and channeling has been employed to investigate regrowth kinetics of amorphous layers in high-dose As- and Pb-implanted (100) silicon. Our results indicate that epitaxial regrowth rates are severely retarded by high concentrations of Pb and As in the silicon lattice and that polycrystalline growth may predominate under such conditions.
The influence of Ti and Zr additions on GaAs liquid phase epitaxial growth
Authors: Stevenson D. A. , Ketrush P. I. , Chang S. C. , Borshchevsky A.
Published: February 2003

Small additions of Zr and Ti to liquid Ga in the liquid phase epitaxial growth of GaAs caused and increased tendency to grow p-type layers and produced high p-type mobilities (200–400 cm2/V sec). The difference in behavior of the two additions was related to the respective oxide stability. The temperature dependence and the high values of the hole mobility suggest that the additions remove donor impurities rather than compensate them.
Surface depletion and inversion in semiconductors with arbitrary dopant profiles
Authors: Bartelink D. J.
Published: February 2003

A general analytical description of the depletion-layer problem in nonuniformly doped semiconductors is a valuable tool because it permits analytical manipulation of critical quantities for the purpose of establishing criteria and relating measurable quantities. A formulation is presented here which retains the dopant profile as an arbitrary function and defines integrals over this profile together with functions of the potential that uniquely specify the problem. An example of a such a criterion, which is presented, is the threshold voltage of a metal-oxide semiconductor field-effect transistor with a highly nonuniform substrate dopant profile.
Backscattering method for the study of blistering with energy-distributed He particles
Authors: Okuda Shuichi , Kuwahara Hideo
Published: February 2003

Helium particles backscattered from the surface of a Nb plate bombarded with 40-keV He+ were used as incident particles for studying the effect of the distribution of incident energies on blistering. After the bombardment, blisters with irregular shapes and sizes were observed on the surface of polycrystalline Mo.
Thermal stabilization of thin-film GaAs solar cells with grain-boundary–edge passivation
Authors: Ghandhi S. K. , Shastry S. K. , Borrego J. M.
Published: February 2003

This letter describes the effect of isochronal anneals on polycrystalline gallium arsenide solar cells, whose grain-boundary edges have been passivated by selective anodization. Both the deterioration of this anodic oxide with temperature, as well as treatments for its full recovery and stabilization, are outlined in this Letter. This treatment consists of a rinse in strong HCl, and is carried out on cells after they are completely fabricated. It is proposed that conversion of the arsenic oxide component to its more stable hydroxide or chloride takes place during this treatment.
Dielectric and hydrodynamic instabilities in certain classes of discotic mesophases
Authors: Dubois J. C. , Hareng M. , Le Berre S. , Perbet J. N. , Torn M.
Published: February 2003

The aim of this letter is to give a short description of some electro-optical effects which are observed in a DF phase of disklike molecules. We point out the existence of dielectric and electrohydrodynamic instabilities. The last one is the experimental evidence of the interesting situation of an anisotropic liquid with εa≳0σa<0 in the homeotropic configuration. These electro-optic effects can be useful in display applications of the discotic phases.
Electron energy distribution in photolytically pumped lasers
Authors: Morgan W. L. , Franklin R. D. , Haas R. A.
Published: February 2003

Calculations of the electron energy distribution function in mixtures of Se(1S), CO, and Xe are presented. The Se(1S) arises from photolysis of OCSe by Xe2 vacuum ultraviolet excimer radiation, and the electrons are due to photoionization of the Se(1S). The calculations show that highly non-Maxwellian electron energy distribution can result from electron heating by super-elastic deexcitation of Se(1S) and cooling by inelastic excitation of CO vibrational levels and Xe electronic states. The kinetic rate constants computed using these distributions differ significantly from those derived from a Maxwellian distribution. It is found that the kinetic rate constants are sensitive to variations in the fractional ionization (α≳10−6), relative CO concentration (nco/nSe(1S)⩾1), CO vibrational temperature (Tv ≳1000 °K), and fractional Xe metastable density (n*/n ≳ 10−5). Adding the molecular buffer, CO, cools electrons and slows multiplication.
Polycrystalline Zn3P2 Schottky barrier solar cells
Authors: Bhushan M. , Catalano A.
Published: February 2003

Energy conversion efficiencies as high as 5.96% are reported on polycrystalline transparent magnesium Zn3P2 diodes, 0.7 cm2 in area, tested under simulated AM1 illumination. The transparent Mg films with low sheet resistivities are obtained by dc sputtering. The effective minority-carrier diffusion length in Zn3P2 is estimated from spectral response measurements and correlates well with the measured short-circuit current. Loss analysis of the present cells shows a practical upper limit of 9% in conversion efficiency.
Characteristics of the metal insulator semiconductor structure:AlN/Si
Authors: Morita M. , Isogai S. , Tsubouchi K. , Mikoshiba N.
Published: February 2003

Single-crystal AlN layers have been grown on Si substrates at ∼1200 °C using metalorganic chemical vapor deposition. The metal/AlN/Si MIS structures have been investigated by the MIS conductance method. It was found that the interface-state density Nss and electron capture cross section σn in the depletion region are of the order of 1011 eV−1 cm−2 and 10−17 cm, respectively.
Optical properties of low-pressure chemically vapor deposited silicon over the energy range 3.0–6.0 eV
Authors: Bagley B. G. , Aspnes D. E. , Adams A. C. , Mogab C. J.
Published: February 2003

The optical properties of undoped and P-doped silicon prepared by low-pressure chemical vapor deposition were measured by spectroscopic ellipsometry over the energy range 3.0–6.0 eV. A marked effect of material microstructure is observed. Approximate values of the density deficit and of the volume fractions of crystalline and amorphous material are estimated as components of the microstructure by comparing measured spectra to those synthesized from constituent spectra in the Bruggeman effective-medium approximation.
Observation of electrochromism in solid-state anodic iridium oxide film cells using fluoride electrolytes
Authors: Rice C. E. , Bridenbaugh P. M.
Published: February 2003

Thin film cells of composition SnO2/AIROF/fluoride/Au have been constructed, where AIROF is anodic iridium oxide film and fluoride is PbF2 on PbSnF4. These devices exhibit reversible electrocoloration and bleaching, with response times as low as 0.1 sec. The behavior of these cells is consistent with the anion insertion mechanism for AIROF electrochromism.
The high-temperature (55–70 °C) device characteristics of cw (AlGa)As double-heterostructure proton-bombarded stripe lasers grown by molecular beam epitaxy
Authors: Tsang W. T. , Holbrook W. R. , Fraley P. E.
Published: February 2003

We present the results of the cw electro-optical characteristics of 5-μm shallow proton-bombarded strip laser fabricated from molecular beam epitaxy (MBE)-grown double-heterostructure (DH) wafers that have Al0.08Ga0.92As active layers at elevated temperatures (55–70 °C), and compare them with those obtained from similar lasers fabricated from liquid phase expitaxy (LPE)-grown DH wafers. It is shown that the MBE lasers maintain their excellent cw device characteristics even at elevated temperatures. The temperature dependence of the cw Ith of MBE lasers is significantly less than that of the LPE lasers. Furthermore, the cw Ith’s of these MBE lasers are at least as good as good LPE lasers. Owing to the very uniform layer thicknesses generated by the MBE process, the resultant slice quality is highly uniform. This results in a significantly increased yield of good lasers per MBE wafer.
Shallow p+ layer in GaAs formed by zinc ion implantation
Authors: Kasahara Jiro , Watanabe Naozo
Published: February 2003

A shallow p+ layer with a steep boundary was obtained by Zn ion implantation and a capless annealing in an arsenic ambient. A capped annealing with a plasma deposited Si3N4 film resulted in a carrier concentration profile broadened by the diffusion enhanced by the interfacial stress between the capping film and the semiconductor. The p+ layer had a peak carrier concentration of 8×1019 cm−3 and a thickness of less than 1000 Å. Arsenic pressure in the annealing ambient also suppressed the enhanced diffuison of Zn in the ion-implanted GaAs.
Glide of dissociated dislocations in III-V compounds
Authors: Carter C. B. , Roberts J. S. , Wood C. E. C.
Published: February 2003

Preliminary observations are presented, which show conclusively that when dissociated dislocations glide in InP, and by direct implication other materials with the zinc blende or diamond cubic crystal lattice, they retain their extended configuration. The observations further indicate that the moving Shockley partial dislocations do tend to lie along certain preferred directions.
Dopant profile analysis of boron in solar grade poly- and single- crystalline silicon
Authors: Jain G. C. , Chakravarty B. C. , Singh S. N.
Published: February 2003

Diffusion of B has been carried out in n-type solar grade poly- and single-crystalline silicon from a paint on source at 1075 °C for 10 min. From the measurements of the sheet conductivity versus depth, the dopant profiles were evaluated. Within the experimental errors the surface concentration is the same for both poly and single crystal, viz., 1.8×1020 atoms cm−3. However, the junction depth is greater by about 850 Å in polycrystalline silicon than in single crystal. The shape of the profile observed in polycrystalline silicon is also quite different and this difference is attributed to fast diffusion through grain boundaries. The particular shape of the profile observed in polycrystalline silicon is more suited to solar cell fabrication than the shape of the profile in single crystal.
Saturation velocity determination for In0.53Ga0.47As field-effect transistors
Authors: Bandy S. , Nishimoto C. , Hyder S. , Hooper C.
Published: February 2003

The fabrication of Schottky-gate field-effect transistors (FET’s) on InGaAs lattice matched to InP is reported. A higher band-gap interface layer is used to lower the gate leakage to acceptable levels. A technique to deduce the effective saturated electron drift velocity is given, which shows over a factor of 2 higher saturated velocity for InGaAs in comparison to GaAs when used as a FET material.
Millimeter-wave generation at 110 GHz by laser modulation of a HgCdTe photodiode
Authors: Taur Y. , Cheung D. T. , Huffman E. H. , SooHoo J. , Gudmundsen R. A.
Published: February 2003

Millimeter-wave power is generated from an n+/p Hg0.74Cd0.26Te photovoltaic diode illuminated by two CO lasers of 5.467- and 5.478-μm wavelengths, respectively. The output frequency is determined by the laser line separation to be 110 GHz. A maximum power of 0.75 μW is observed when the diode is dc biased at 0.5 V in the reverse direction.
Microwave-induced ’’Devil’s Staircase’’ structure and ’’chaotic’’ behavior in current-fed Josephson junctions
Authors: Ben-Jacob E. , Braiman Y. , Shainsky R. , Imry Y.
Published: February 2003

We have obtained the various types of I-V characteristics measured experimentally and in analog simulations, by merely changing the junction and the microwave parameters within the same resistively shunted junction model with purely sinusoidal current-phase relation. It was found that the subharmonic steps do exist in the limit βc→0, though they can have finite rounding without thermal noise. The statistical properties of the ’’chaotic’’ solutions wer e discussed and their effective temperature was defined and calculated.
Optical time domain reflectometer for single-mode fiber at selectable wavelengths
Authors: Kawasaki B. S. , Hill K. O. , Johnson D. C.
Published: February 2003

Optical time domain reflectometry by backscattered light in a single-mode fiber is demonstrated. The experiment employs a novel efficient single-mode/multimode coupling device and also a powerful and versatile multiwavelength mode-locked and pulsed optical source.
Amplified spontaneous-emission quantum beats in flash-pumped H20 vapor
Authors: Lawandy Nabil M. , Robinson D. W.
Published: February 2003

Flashlamp excitation of H2O vapor in the 10–80-mTorr pressure range has produced a population inversion on the (001), g = 3, 954−945 transition. This has resulted in a modulated emission at 115 cm−1. The oscillations on the amplified spontaneous-emission signal are interpreted as quantum beats between magnetic hyperfine levels split by an I⋅J interaction. Analysis of the data results in a splitting of 1.4 MHz and dephasing rates of 7.8 MHz/Torr for H2O-H2O, 0.5 MHz/Torr for He-H2O, and 1.7 MHz/Torr for Ar-H2O mixtures.
Enhanced second-harmonic generation by counter-propagating guided optical waves
Authors: Vella P. J. , Normandin R. , Stegeman G. I.
Published: February 2003

Second-harmonic light generated by mixing oppositely propagating guided waves in LiNbO3 waveguides was enhanced ∼500-fold by varying the refractive index of the medium above the LiNbO3 surface.
LiNbO3 surface-acoustic-wave edge-bonded transducers on ST quartz and 〈001〉 cut GaAs
Authors: Oates D. E. , Becker R. A.
Published: February 2003

LiNbO3 surface-acoustic-wave edge-bonded transducers have been fabricated on ST quartz and 〈001〉 cut GaAs substrates. Efficient transduction has been demonstrated with fractional bandwidths of 50 and 91% for the ST quartz and GaAs substrates, respectively. The devices have a center frequency in the vicinity of 100 MHz. Conversion loss as low as 4 dB has been measured. A model which accurately predicts this transducer performance has been devised.
Penning ionization spectroscopy using the optogalvanic effect
Authors: Ben-Amar A. , Shuker R. , Erez G. , Miron E.
Published: February 2003

The optogalvanic effect is proposed and demonstrated as a new technique for quasiresonant Penning ionization spectroscopy in a discharge plasma of mixtures of rare gases and metal vapors. A calcium and neon mixture is used as a prototype. Neon’s lowest metastable level, 3P2 at 134 034 cm−1, is within kT from the excited state of 2D3/2,5/2 of Ca+. Thus Penning ionization occurs to an excited state of the ion. This process strongly alters the optogalvanic signal and has its own signature. In fact, other energy transfer processes should also change the time dependence of the optogalvanic signal.
Reduction of threading dislocations in iso-epitaxial layers grown on (001) InP substrates by misfit stresses
Authors: Chu S. N. G. , Mahajan S. , Strege K. E. , Johnston W. D. , Ballman A. A.
Published: February 2003

A general reduction of threading dislocations over a large area of a Te-doped InP layer, grown on (001) InP:Fe by vapor phase epitaxy has been observed in the presence of interfacial misfit dislocations. However, near the edge of the epi-layer, the dislocation density increases considerably. These observations have been rationalized in terms of the misfit stress-induced glide of the threading dislocations. The estimated misfit strain is ∼0.2% and evidently results from stoichiometry mismatch between the epi-layer and the substrate.
Intrinsic and deep-level photoacoustic spectroscopy of GaAs (Cr) and of other bulk semiconductors
Authors: Eaves L. , Vargas H. , Williams P. J.
Published: February 2003

Previous work on photoacoustic spectroscopy (PAS) of semiconductors has been restricted to material in powder form. This letter shows that PAS can also be used to study intrinsic and extrinsic (impurity) absorption of semiconductors in bulk, single-crystal form. For GaAs (Cr) the technique can easily detect Cr impurities at 5×1016 cm−3 level. The effects of surface preparation on the spectra are discussed.
Disorder of an AlAs-GaAs superlattice by impurity diffusion
Authors: Laidig W. D. , Holonyak N. , Camras M. D. , Hess K. , Coleman J. J. , Dapkus P. D. , Bardeen J.
Published: February 2003

Data are presented showing that Zn diffusion into an AlAs-GaAs superlattice (41 Lz∼45-Å GaAs layers, 40 LB∼150-Å AlAs layers), or into AlxGa1−xAs-GaAs quantum-well heterostructures, increases the Al-Ga interdiffusion at the heterointerfaces and creates, even at low temperature (<600 °C), uniform compositionally disordered AlxGa1−xAs. For the case of the superlattice, the diffusion-induced disordering causes a change from direct-gap AlAs-GaAs (Eg∼1.61 eV) to indirect-gap AlxGa1−xAs (x∼0.77, EgX∼2.08 eV).
Highly stable, photosensitive evaporated amorphous silicon films
Authors: Tong B. Y. , John P. K. , Wong S. K. , Chik K. P.
Published: February 2003

Vacuum-evaporated pure amorphous silicon films have been successfully hydrogenated in a Theta-pinch plasma source to give high photoconductivity. Unlike films produced by glow discharge of silane gas, these films are highly stable against heat, intense light illumination, moisture, and other atmospheric contamination. Structural change in the bulk Si matrix being absent, a comparison of properties of films before and after plasma treatment can provide valuable information on pure hydrogenation effects.
Transmission electron microscopy study of furnace- and laser-annealed silicon containing implanted carbon and oxygen
Authors: Koyama H. , Kashiwaki T.
Published: February 2003

Microstructures of furnace- and laser-annealed silicon containing implanted oxygen and carbon were studied by transmission electron microscopy. Implanted oxygen atoms tend to cluster resulting in twins at the damaged regions, while dislocation loops and small precipitates were observed throughout in carbon-implanted silicon after furnace annealing. A low density of dislocations was observed in the oxygen-implanted, laser-annealed, and subsequently heat-treated silicon. All the atomic distributions reported in the previous paper were well correlated with the microstructure of the specimens.
Source and elimination of oval defects on GaAs films grown by molecular beam epitaxy
Authors: Chai Young G. , Chow Robert
Published: February 2003

A method to eliminate oval defects from GaAs films grown by molecular beam epitaxy is presented. It appears that gallium oxide in the Ga melt is the major cause for this surface defect. A simple precaution of suppressing oxidation of gallium virtually eliminated oval defects.
Electrical conductivity of Al-implanted films of ZnS
Authors: Thomas C. B. , Reehal H. S. , Warren A. J. , Gallego J. M.
Published: February 2003

Films of ZnS have been deposited by rf sputtering and subsequently implanted with Al. Examination of the conductivities, after annealing, shows that Al is effective in decreasing the film resistivity. At ∼ 300 K the room-temperature conductivity could be reduced to 10−2 Ω−1 cm−1 compared with 10−10 Ω−1 cm−1 in undoped films. The small activation energy of ∼ 0.1 eV of the electrical conductivity and the temperature dependence of the thermoelectric power may possibly be indicative of impurity conduction.
Schottky-barrier profile in a-silicon alloys
Authors: Datta T. , Silver M.
Published: February 2003

A new method to determine the potential profile at a blocking contact to an insulator is presented. We apply this method to a-silicon alloys sandwiched between a metal blocking contact and an injecting contact. The field distribution was found to be approximately Ei(x) = E0 exp (βx), where E0≃1.3×105 V/cm and β−1≃500 Å. The collection width for solar–cell devices is estimated to be approximately 2800 Å. These results agree with previous predictions [M. Shur, W. Czubatyj, and A. Madan, Sol. Energy Mater. 2, 349 (1980)].
Reactive ion etching of LiNbO3
Authors: Jackel J. L. , Howard R. E. , Hu E. L. , Lyman S. P.
Published: February 2003

We describe the reactive ion etching of LiNbO3 in gas mixtures containing CCl2F2, CF4, O2, and Ar. The effects of gas composition and pressure, in the range 1–10-μm total pressure are discussed. Because it is possible to replicate fine features (∼2000 Å) with control of etch profiles, we expect the process to be used for three-dimensional patterning of LiNbO3 for electro-optic and acoustic-optic devices.
Channeling study of coherent Pt precipitates in MgO single crystals
Authors: Turos A. , Meyer O. , Matzke Hj.
Published: February 2003

Channeling experiments have been performed on MgO single crystals implanted with 30-keV Pt ions at room temperature. After annealing at temperatures above 900 °C an angular dependence of the backscattered yield from the Pt atoms was observed with a critical angle substantially larger than that of the host crystal. This result was attributed to the formation of coherent Pt precipitates, and a confirmation was obtained by x-ray diffraction. Reasonable agreement between measured and calculated angular yield curves is reached assuming stacking faults and mosaic spread as predominant defects in the Pt precipitates.
Thermal and structural analysis of the effects of chlorine impurities on pressurized CdS
Authors: Cote P. J. , Capsimalis G. P. , Homan C. G.
Published: February 2003

Anomalous large diamagnetism (χv∼−0.25/4π cgs units) and large positive magnetism (χv∼+10−4 cgs units) have recently been reported in pressure-quenched CdS polycrystalline samples by Homan and MacCrone. These effects were shown to be sample material source dependent, and as a first step toward characterizing these samples, we compared the thermal and structural properties of various CdS samples before and after pressurization. Samples containing up to 6-wt. % Cl were prepared by precipitaion from a chloride containing aqueous bath. We find that (i) Cl impurities are probably present in the form of a complex which can decompose on heating to CdS+CdCl2, (ii) melting of a portion of the samples containing high levels of Cl occurs at 535 °C and is attributed to the eutectic temperature of the CdS+CdCl2 mixture, and (iii) heating beyond 535 °C produces complete volatization of the CdCl2 component. The results on samples prepared by mixing of CdS and CdCl2⋅H20 were examined and found to have similar thermal behavior. The cadmium sulfide used in the previous magnetization study was examined and, based on the similarities in the thermal and structural properties, we conclude that the samples which exhibit the anomalous magnetic effects were also prepared by precipitation. In agreement with earlier studies, metastable phases are observed after various pressurizations to above 4.0 GPa.
Fabrication of planar superconducting-normal-superconducting Josephson microbridges and SQUID’s using shadow evaporations
Authors: Jelks E. C. , Kerber G. L.
Published: February 2003

The technique of ’’shadow evaporation’’ has been used to fabricate superconducting-normal-superconducting Josephson microbridges and SQUID’s with bridge widths of about 0.2 μm and lengths of 0.1 μm or less. The devices consist of vanadium banks and gold bridges and have static current-voltage characteristics that are consistent with the resistively shunted junction model down to at least 0.4 TC. Refined versions of this technique may be useful for batch fabrication of single and multibridge Josephson devices.
Stress effects on superconducting properties of the composite-processed V2(Hf,Zr)
Authors: Inoue K. , Wada H. , Kuroda T. , Tachikawa K.
Published: February 2003

The superconducting critical current Ic (4.2 K) of V2(Hf,Zr) composite tape was measured under tensile load. Ic values of the V2(Hf,Zr) composite tape do not change at all up to a strain level of 0.55%, and then decrease irreversibly with respect to strain, although the stress-strain curves for these tapes exhibit no irreversible behavior. Many cracks were observed in the V2(Hf,Zr) layer of the composite tape strained up to 0.6%. Thermal expansion data indicate that the residual tensile stress may be produced in the V2(Hf,Zr) layer by the large thermal contraction of the layer and may reduce the strain tolerance of the composite tape.
Dynamic behavior of optically induced superconducting weak links
Authors: Vanneste C. , Gilabert A. , Sibillot P. , Ostrowsky D. B.
Published: February 2003

We report experimental measurement of the dynamic response of optically induced superconducting weak links modulated at up to 1 GHz. Increasing the optical modulation depth from 7 to 70% as the frequency varies from low frequency to 30 MHz extinguishes the ac Josephson effect which is consistent with a calculated thermal response time of 150×10−9 sec.
Hydrogen plasma etching of GaAs oxide
Authors: Chang R. P. H. , Darack S.
Published: February 2003

Hydrogen plasma has been used to etch native-grown GaAs oxide on GaAs substrates. It is found that the rate of etching increases with gas pressure (in the range 10–300 μ) and the rf power (in the range 10–400 W) of the discharge. A typical etch rate of ≊20 Å/sec can be easily achieved. The selectivity (determined by scanning electron microscopy) of the oxide etch over the substrate is ≊2. An etch mechanism is proposed, and the use of hydrogen plasma for surface preparation of GaAs and the etching of oxides on other semiconductor materials will be discussed.
Calculation of vibrations of thick piezoceramic disk resonators
Authors: Schwarzenbach H. U. , Lechner H. , Steinle B. , Baltes H. P. , Schwendimann P.
Published: February 2003

Axially symmetrical vibrations of thick circular disk resonators made of polarized piezoelectric ceramic material excited by electrodes on the faces of the disk are calculated from the linear constitutive equations of a piezoelectric solid and the pertinent elastic and electrical boundary conditions using Hamilton’s variational principle and the boundary method of Trefftz. Good agreement with speckle heterodyne interferometric measurements of the waveforms is obtained.
Calculation of the critical cooling rate for amorphous Pd77.5Si16.5Cu6
Authors: Steinberg J. , Tyagi S. , Lord A. E.
Published: February 2003

The viscosity of the molten alloy Pd77.5Si16.5Cu6 has been determined from 744 to 1000 °C using an oscillating cup viscometer. Using this data (together with other pertinent physical data available for this alloy) in existing crystallization theory indicates that it could be made amorphous at cooling rates as low as 5–10 Ks−1. This analysis assumes strictly homogeneous nucleation. Containerless solidification will be one good testing ground for the results of this analysis.
The effect of electron irradiation on the low-temperature emission spectra from Ge-doped Ga0.60Al0.40As grown by liquid phase epitaxy
Authors: Swaminathan V. , Kimerling L. C. , Wagner W. R.
Published: February 2003

The effect of 1-MeV electron irradiation on Ge-doped Ga0.60Al0.40As layers grown by liquid phase epitaxy is investigated by low-temperature photoluminescence. The irradiation is found to decrease the intensities of the pair emissions at 1.91 eV (SiGa-SiAs) and 1.88 eV (SiGa-GeAs) as well as the broad and weak emission at 1.55 eV due to the formation of nonradiative Ge-related complexes of the type GeAs-VAs. The reduction in the intensity of the 1.91-eV band is observed to be greater than that of the 1.88-eV band, and it increases with increasing Ge-doping for both the bands suggesting that the production of the nonradiative defect complexes is a function of the Ge concentration. The recovery of the radiation damage is found to occur for annealing temperatures ⩾200 °C. The photoluminescence intensities of the irradiated and annealed samples are found to be significantly higher than that of the unirradiated and annealed samples. No new bands are observed in the spectral region 1.5–2.0 eV either after irradiation or after annealing.
A new current-injection heterostructure laser: The double-barrier double-heterostructure laser
Authors: Tsang W. T.
Published: February 2003

A new semiconductor current injection heterostructure laser, the double-barrier double-heterostructure (DBDH) laser, is fabricated by incorporating a pair of very thin (250–450 Å) unidirectionally graded barriers of very wide band gaps (≳ 2.00 eV) between the active layer and the uniform cladding layers of the conventional double-heterostructure laser. As a result, the beam divergence of this new heterostructure laser can be independently varied by changing the AlAs composition of the uniform cladding layers without affecting the temperature stability of the threshold Ith, the external differential quantum efficiency ηD, and possibly the reliability of the laser. With these lasers, excellent temperature stability of Ith , ηD spontaneous emission level, and abrupt transition from a light-emitting diode mode to laser mode were achieved and maintained up to temperatures as high as 276 °C. Narrow beam divergence ∼ 26° and low Ith ∼1 kA/cm2 were also obtained simultaneously from the same lasers. The present DBDH laser wafers were grown by molecular beam epitaxy.
Dependence of the structural and optical properties of GaAs-Ga1−xAlxAs multiquantum-well structures on growth temperature
Authors: Weisbuch C. , Dingle R. , Petroff P. M. , Gossard A. C. , Wiegmann W.
Published: February 2003

The structural and optical properties of multiquantum-well (MQW) structures grown by molecular beam epitaxy are strongly dependent on the substrate temperature Ts during the growth. A study of the optimization of MQW structures as a function of Ts is carried out using optical and electron microscopy and photoluminescence characterization. Optimal temperatures in the range 670–730 °C are shown to yield smooth free surfaces and interfaces and high quantum efficiencies.
Absorption and gain measurements in the KrF laser medium at high pump rate
Authors: Edwards C. B. , O’Neill F. , Shaw M. J.
Published: February 2003

Losses have been measured at 257.2 nm in e-beam-pumped, KrF laser mixtures at pump rates up to 4 MW/cm3 and pressures up to 3000 Torr. A maximum absorption of 3.5% cm−1 is observed in a gas mixture of 4-Torr F2, 125-Torr Kr, and 2871-Torr Ar. Losses are reduced in the presence of lasing. The absorption cross section of Kr2F* at 257.2 nm is estimated to be 1.8(±1.1)×10−17 cm2. Net gain has been measured as a function of pump rate in a gas mixture of 4-Torr F2, 125-Torr Kr, and 1371-Torr Ar. A net gain of 22% cm−1 and a gain to nonsaturable loss ratio ∼20 have been observed.
Low-frequency noise characteristics of channel substrate planar GaAlAs laser diodes
Authors: Miles R. O. , Dandridge A. , Tveten A. B. , Giallorenzi T. G. , Taylor H. F.
Published: February 2003

The influence of external feedback on low-frequency noise generation (100 Hz–10 kHz) in single longitudinal and transverse mode channel substrate planar laser diodes is reported. An increase in noise by as much as 60 dB was induced by external feedback as small as 0.04%. The induced intensity variations were observed to be sensitive to both phase and amplitude of the externally reflected light.
Gettering of mobile oxygen and defect stability within back-surface damage regions in Si
Authors: Magee T. J. , Leung C. , Kawayoshi H. , Furman B. K. , Evans C. A.
Published: February 2003

Motion and gettering of oxygen into damage regions created by back-surface mechanical abrasion in Si has been investigated using transmission electron microscopy (TEM), scanning electron microscopy, secondary-ion mass spectrometry profiling and secondary-ion microscopy. Redistribution and gettering of oxygen have been detected along dislocation lines after annealing at 600 °C by both TEM and direct ion imaging. Subsequent annealing at 1050 °C produces additional gettering, SiOx nucleation, and a dramatic increase in dislocation-line density within the initial damage region. Secondary dislocation lines extending to a depth ≃ 40 μm are also generated by the two-stage anneal, resulting in additional gettering sites for oxygen and other impurities. In comparison, single anneals at 1050 °C produce rapid defect annihilation, oxygen outdiffusion, and loss of additional gettering efficiency.
Barriers on n- and p-type germanium
Authors: Rahimi S. , Henisch H. K.
Published: February 2003

When n-type Ge is changed to p-type by neutron bombardment, and back to n-type by subsequent annealing, an original contact barrier is shown to remain substantially unchanged in profile. This is contrary to the widely held belief that the barrier automatically reverses when the conductivity changes type.
Interface and surface structure of epitaxial NiSi2 films
Authors: Chiu K. C. R. , Poate J. M. , Rowe J. E. , Sheng T. T. , Cullis A. G.
Published: February 2003

Epitaxial NiSi2 films have been grown on (100) and (111) Si. Interface and surface structures have been examined by Rutherford backscattering and channeling, transmission electron microscopy, and low-energy electron diffraction. The (111) interface is remarkably flat, whereas the (100) interface has {111} facets. The NiSi2 (111) surface has a bulklike periodicity parallel to the surface, whereas the (100) surface exhibits reconstruction periodicity.
Shape information in microdiffraction patterns of small metallic particles
Authors: Polo G.Vazquez , Romeu D. , Yacaman M. Jose
Published: February 2003

Computer-simulated electron diffraction patterns of small particles are investigated. The patterns show forbidden reflections which are found to be directly correlated with the shape of the particles. Therefore the study of these reflections is suggested as a new possibility for determining shape and crystallography of metal particles using single-particle diffraction techniques.
Deuterium at the Si-SiO2 interface detected by secondary-ion mass spectrometry
Authors: Johnson N. M. , Biegelsen D. K. , Moyer M. D. , Deline V. R. , Evans C. A.
Published: February 2003

Secondary-ion mass spectrometry (SIMS) has been used to measure depth profiles of deuterium in thermally grown films of SiO2 on Si. Deuterium is a readily traceable element which simulates hydrogen chemistry and thereby permits detection of effective changes in the hydrogen content of annealed oxides even in the presence of high background concentrations of hydrogen in the sputtering ambient or oxide layer. For oxidized silicon annealed in atomic deuterium, SIMS profiles clearly reveal an accumulation of deuterium at the Si-SiO2 interface. It is demonstrated that the pile-up of deuterium is not a consequence of ion migration (’’snow plowing’’) during ion sputtering.
Simultaneous bulk and surface microanalyis by electron spectroscopy
Authors: Cazaux J. , Mouze D , Perrin J. , Thomas X.
Published: February 2003

By using an original arrangement it is shown that photoelectron spectroscopy can be used to obtain at the same time the surface and the bulk composition of a sheet, several microns thick. An Al/Mg alloy is chosen to illustrate this new technique and to establish the basic principles quantifying these analyses. 108 Mg surfaces atoms (4.1015 g) have been detected, Mg surface segregation is pointed out and it is shown that oxygen (01s level) is a good converter for the detection of AlKα and MgKα x-ray photons.
Static polarization echoes in metallic powders
Authors: Tsuruoka F. , Kajimura K.
Published: February 2003

Static polarization echoes of metallic powders placed in static magnetic fields are investigated. It is found that the stability of echoes is strongly affected by the atmospheric pressure of helium gas at 4.2 K, and most results are similar in nature to those of piezoelectric powders. These facts indicate that the process involves the macroscopic and mechanical reorientation of individual particles but not the phenomena inside the particles. An echo formation mechanism is proposed in the framework of the torque-rotation model, in which the base axis of rotation is specified by the anisotropic dipole moment caused by the current associated with the mechanical oscillation of particles.
Measurements of ferroelectric switching characteristics in polyvinylidene fluoride
Authors: Furukawa T. , Johnson G. E.
Published: February 2003

The ferroelectric switching characteristics of polyvinylidene fluoride have been investigated by the time domain measurement of electric displacement under a step-function field up to 200 MV/m at temperatures between −100 and 20 °C. Almost complete reversal of polarization is found to occur in a fairly short time if the applied field is sufficiently high. The switching time is 4 μsec at 20 °C under a field of 200 MV/m and increases significantly as either field or temperature decreases. The rate of change of polarization is greater than the rate associated with a single relaxation process. This is an indication of cooperative effects in the switching process of this ferroelectric polymer.
Luminescence properties of GaAs-Ga1−x Alx As double heterostructures and multiquantum-well superlattices grown by molecular beam epitaxy
Authors: Petroff P. M. , Weisbuch C. , Dingle R. , Gossard A. C. , Wiegmann W.
Published: February 2003

Undoped double-heterostructures (DH) and multiquantum-well structures (MQW) grown by molecular beam epitaxy are studied by cathodoluminescence and photoluminescence. Their structural properties are established by scanning transmission electron microscopy. In DH discrete nonradiative centers are observed with densities ∼104–105 cm−2; some of them are correlated with dislocations originating in the substrate. In sharp contrast, MQW show a very uniform luminescence with no nonradiative action at dislocations. These results might explain in part the higher quantum efficiency of MQW grown by molecular beam epitaxy.
A luminescence band associated with the main electron trap in bulk gallium arsenide
Authors: Mircea-Roussel A. , Makram-Ebeid S.
Published: February 2003

The peak energy (0.645 eV) and half-width of a broad photoluminescence band commonly observed in bulk semi-insulating gallium arsenide are shown to agree with those of the main electron trap (EL2) present in this type of material. The bahavior of this photoluminescence band, after thermal annealing, is also found to be compatible with that of EL2.
The effect of lattice mismatch on hole diffusion lengths in liquid phase epitaxial InGaAsP (λg = 1.15 μm)/InP
Authors: Tashima M. M. , Cook L. W. , Tabatabaie N. , Stillman G. E.
Published: February 2003

Hole diffusion lengths Lp were determined as a function of lattice mismatch for n-type InGaAsP (λg = 1.15 μm) layers grown by liquid phase epitaxy on p+ (100)-InP substrates by measuring the variation of the short-circuit photocurrent as a focused laser beam was scanned along a beveled (∼1°) p-n junction. The longest diffusion length (Lp ∼1.5 μm) was obtained when the epitaxial layer was lattice matched to the InP substrate, and as the mismatch increased either positively or negatively (−0.25%<Δa/a<+0.31%) Lp decreased, indicating that the bulk properties of the layer are influenced by the mismatch at the interface.
Low-temperature redistribution of As in Si during Pd2Si formation
Authors: Ohdomari I. , Tu K. N. , Suguro K. , Akiyama M. , Kimura I. , Yoneda K.
Published: February 2003

We have investigated the change in depth compositional profiles of implanted As in Si due to Pd2Si formation by using anodic oxidation and neutron activation analysis. We found that a high concentration (∼1×1021/cm3) of implanted As was snowplowed by the moving silicide-Si interface into the substrate Si during Pd2Si formation at 250 °C. In other words, we have found a very low temperature process of doping As into Si. The amount of snowplowed As was found to be greater in samples which were preannealed at 900 °C—30 min before silicide formation than those without the preannealing.
Selectively emissive refractory metal surfaces
Authors: Craighead H. G. , Howard R. E. , Tennant D. M.
Published: February 2003

In this letter is decribed a spectrally selective tungsten light-emitting surface, employing submicron surface texturing produced by reactive ion etching. The average emissivity of this surface throughout the visible wavelength range of 0.3–0.7 μm is greater than 0.9 compared to ∼0.4 for ordinary tungsten. At longer infrared wavelengths, however, the emissivity of the etched surface approaches that of a smooth tungsten surface. This results in enhanced efficiency in the production of visible light.
Picosecond nonequilibrium carrier transport in GaAs
Authors: Shank C. V. , Fork R. L. , Greene B. I. , Reinhart F. K. , Logan R. A.
Published: February 2003

We report a new picosecond optical technique for observation of nonequilibrium carrier transport. An ’’overshoot’’ electron velocity of 4.4×107 cm/sec is observed at short times in GaAs under appropriate electric field conditions.
Characterization of surface exchange reactions used to grow compound films
Authors: Pessa M. , Mäkelä R. , Suntola T.
Published: February 2003

Sequential surface exchange reations have been provoked by means of an atomic layer epitaxy (ALE) method to grow Ta2O5 and ZnS films from vapor phases of TaCl5 (ZnCl2) and H2O (H2S) reactants. The growth mechanism has been explained. The films were studied by using Auger electron spectroscopy, scanning electron microscopy, and x-ray diffraction.