bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of photoelectrochemical cells with a chemically sprayed photoanode
Authors: Liu Chin-Hsin Jason , Wang Jui H.
Published: February 2003

Chemically sprayed CdSe thin films were used as photoanodes in photoelectrochemical solar cells. The power characteristics of the cell ITO/CdSe/Na2S-S-NaOH/Pt was measured. The energy conversion efficiency of this cell was 7.8% at 340 nm and 5.2% under 50-mW/cm2 white light.
Carbon films with relatively high conductivity
Authors: Kaplan Martin L. , Schmidt Paul H. , Chen Cheng-Hsuan , Walsh Walter M.
Published: February 2003

The pyrolysis of organic dianhydrides (e.g., 3,4,9,10-perylenetetracarboxylic dianhydride) in an evacuated system results in the loss of hydrogen, CO, and CO2 and the deposition of a chemically inert, metallic-appearing mirrolike film. The films are highly conducting (σRT250 Ω−1 cm−1) and can evidence either metallic or semiconducting behavior, depending on the preparation temperature. Superconducting films are obtained when niobium is used as a dopant. Preparation of films on doped silicon semiconductor chips results in the formation of p-n junctions. ESR spectra exhibit a moderately strong line at g=2.0025. The resonance intensity remains almost constant to 20 °K, characteristic of a highly delocalized spin system.
Surface acoustic wave characteristics of (Ba2−xSrx)TiSi2O8 crystals
Authors: Ito Yukio , Nagatsuma Kazuyuki , Ashida Sakichi
Published: February 2003

The surface acoustic wave characteristics of fresnoite (Ba2TiSi2O8) crystals are improved. The temperature coefficients of delay time are greatly lowered, with almost no change in the electromechanical coupling factor, as the result of partial substitution of Sr for Ba, particularly in (Ba2−xSrx)TiSi2O8 crystals. These crystals have temperature coefficients of delay comparable to LiTaO3, while their electromechanical coupling factors are twice as large.
Submicrosecond bistable electro-optic switching in liquid crystals
Authors: Clark Noel A. , Lagerwall Sven T.
Published: February 2003

Ferroelectric smectic C (FSC) liquid crystals are used in a simple new geometry that allows the spontaneous formation of either of two surface-stabilized smectic C monodomains of opposite ferroelectric polarization. These domains are separated by well-defined walls which may be manipulated with an applied electric field. The resulting electro-optic effects exhibit a unique combination of properties: microsecond dynamics, threshold behavior, symmetric bistability, and a large electro-optic response.
Transient absorption in electron-beam-excited rare gases at XeF laser wavelengths
Authors: Chang R. S. F. , Champagne L. F.
Published: February 2003

Transient absorption experiments in pure and mixed rare gases were performed at the XeF laser wavelength using a broadband probe technique. The major absorbing species in this region are identified. There is a strong broadband absorption in electron-beam-excited argon which is due to Ar+2. In neon plasmas the broadband absorption is much weaker. However, there are a number of strong line absorptions due to Ne(3s-4p) transitions, one of which coincides with the 351-nm emission band of the XeF laser. Addition of xenon reduces Ne* absorption. The amount of xenon used is limited by the formation of Xe+2, which is also a strong absorber in the 350-nm region.
Close-contact annealing of ion-implanted GaAs and InP
Authors: Molnar B.
Published: February 2003

Both n- and p-type ion-implanted GaAs and InP have been annealed at temperatures up to 880 and 760 °C, respectively, using a ’’close-contact’’ capless annealing technique. In this annealing process the flat, implanted surface of the semiconductor is placed in close contact with another flat surface, usually a Si3N4 encapsulated identical semiconductor. Samples annealed in such a proximity manner show no detectable sign of decomposition and exhibit state of the art electrical performance. This is the first report of successful capless annealing of InP.
Exploding-pusher-tamper areal density measurement by neutron activation
Authors: Campbell E. Michael , Ploeger William M. , Lee Peter H. , Lane Stephen M.
Published: February 2003

Neutron activation of 28Si nuclei was used to measure the areal density ρΔR of a silicate-glass tamper of a laser-driven exploding-pusher target. The values found were in good agreement with complex computer codes and an empirically based scaling model. This is the first demonstration of a technique that will be used in diagnosing the compression of high-density inertial confinement fusion targets.
Theoretical study of formation rates of rare-gas halide trimers
Authors: Shui Ven H. , Duzy Carolyn
Published: February 2003

A scarcity of information on the rare-gas halide trimers makes detailed calculations of their formation rates from the excited rare-gas halides impossible. However, we have developed an approximate method/model for determining these rate constants. Rate constants for reactions of possible interest for the KrF* and XeF* laser systems are calculated. These reactions are (1) KrF*+Rg+Rg′→KrRgF*+Rg′ and (2) XeF*+Rg+Rg′→XeRgF*+Rg′, where Rg, Rg′=Ar, Kr in Eq. (1) and Ne, Ar, Xe in Eq. (2). Results are compared with available experimental data.
Cohesion of solids under laser irradiation
Authors: Wautelet M. , Laude L. D.
Published: February 2003

The effects of laser irradiation on the cohesion of diamondlike solids are investigated. It is shown that the melting temperature decreases under laser irradiation, due to the increase of the vibrational energy induced by bond-charge effects and of the electronic contribution to the total energy of the solid.
High specific power long-pulse supersonic flow XeCl laser at 308 nm
Authors: Fontaine B. , Forestier B.
Published: February 2003

Quasi cw laser action has been achieved at several wavelengths near 308 nm in an electron-beam excited supersonic flow at very low temperature and high density. The 0–1, 0–2, and 0–3 XeCl laser emissions have been obtained when Ne/Xe/HCl mixtures aerodynamically cooled to 120 K and at a density up to 1.7 amagat were excited by an electron beam of medium intensity (jeb≃10 A cm−2, 600 ns). Up to 15 mj of laser energy (≃1 J/l) was extracted in 500-ns pulses from the 16-cm long and 1-cm-diam useful volume of this laser. The highest intrinsic efficiency (laser energy out / e-beam energy deposited in the active medium) observed was over 2.5%.
Implementation of a novel procedure to optimize electron optical systems through the use of orthogonal functions
Authors: van der Merwe J. P.
Published: February 2003

It is shown how Fourier-Bessel series solutions published recently, representing the electric potential in various electrostatic electron optical configurations with rotational symmetry, can be used in a constrained optimization procedure through which local minima of an aberration function A=A (B1, B2, ...) can be found by direct search or by descent methods. The variables Bi are Fourier coefficients. As a simple illustration, a Bessel Box with a coaxial annular aperture is obtained, which produces a tangential ray image of low field curvature and distortion. Optimization with respect to both paraxial and zonal focal properties can be carried out, because the method is not restricted by the use of the paraxial ray equation. The procedure can be applied to one-foil, and open systems.
Observation of a second bulk compressional wave in a porous medium at ultrasonic frequencies
Authors: Plona Thomas J.
Published: February 2003

A second bulk compressional wave has been observed in a water-saturated porous solid composed of sintered glass spheres using an ultrasonic mode conversion technique. The speed of this second compressional wave was measured to be 1040 m/sec in a sample with 18.5% porosity. The theory of Biot, which predicts two bulk compressional waves in porous media, provides a qualitative explanation of the observations. To the author’s knowledge, this type of bulk wave has not been observed at ultrasonic frequencies.
Destruction of ground state XeCl molecules by HCl and rare gas collisions
Authors: Waynant R. W. , Eden J. G.
Published: February 2003

Rate constants for quenching of several XeCl (X) vibrational levels by the rare gases and HCl have been measured. The temporally resolved decay of the population densities of the XeCl (X, v″=0–2) levels was monitored using a frequency-doubled tunable dye laser. Within experimental error, the measured rate constants did not vary with vibrational number, and the temperature dependence of the rates over the range 300⩽T⩽375 °K was found to be consistent with the previously measured XeCl (X) dissociation energy (∼250 cm−1). The rate constants for the destruction of XeCl (X, v″=0) state molecules by HCl, Xe, Ar and Ne at 300 °K were determined to be (2.20.5) ×10−11, (5.60.8) ×10−12, (0.60.06) ×10−13, and (1.00.15) ×10−13 cm3 sec−1, respectively.
Stability study of laser irradiation of silicon diffused with arsenic
Authors: Chu Wei-Kan
Published: February 2003

The stability of a metastable state produced by laser irradiation on arsenic-diffused Si is studied by measurement of the sheet resistance as a function of postlaser heat treatment between 300 and 900 °C. The good conductivity produced by laser irradiation decays at as low as 400 °C within 1 h. This preempts the advantage of good conductivity produced by transient annealing and sets a severe restriction on the application of transient processing.
Scintillation study of ZnWO4 single crystals
Authors: Oi Tetsu , Takagi Kazumasa , Fukazawa Tokuumi
Published: February 2003

Scintillation characteristics of the Czochralski-grown ZnWO4 single crystal were studied. This crystal, with light red-brown color, exhibits a maximum luminescence wavelength of 480 nm under excitation at 254 nm. The total luminescence output under x-ray excitation at 254 nm. The total luminescence output under x-ray excitation was found to be 2.3 times larger than that of the best Bi4Ge3O12 at room temperature with small afterglow.
Substrate temperature related degradation mechanisms in molecular beam epitaxial InP
Authors: Norris M. T.
Published: February 2003

The deleterious effects of structural changes on the quality of (001) oriented InP grown by MBE at low substrate temperatures has been investigated. For deposition below Ts=300 °C, concomitant with the loss of reconstruction in the reflection high energy electron diffraction (RHEED) pattern, the electrical properties of the epilayers begin to degrade, culminating in their total collapse at Ts =145 °C, associated with the onset of twinned growth.
Frequency-modulated shot noise limited stimulated Raman gain spectroscopy
Authors: Levine B. F. , Bethea C. G.
Published: February 2003

We demonstrate for the first time an electro-optic frequency-modulated stimulated Raman gain laser system which achieves shot noise limited detection. The frequency modulation technique reduces the otherwise large thermal background produced by absorbing substrates by a factor of 104–105, thereby permitting the full use of the ultrahigh sensitivity which is sufficeint to observe the vibrational spectroscopy of monolayers.
Homogeneous nucleation of oxide precipitates in Czochralski-grown silicon
Authors: Ōsaka Jiro , Inoue Naohisa , Wada Kazumi
Published: February 2003

The nucleation rate of oxide precipitates in silicon at 750 °C was determined by two-step annealing and through transmission electron microscopy. The density of oxide precipitates was found to increase by annealing in proportion to annealing time. The precipitates were of two kinds: (a) grown from microprecipitates which existed in as-grown crystals, and (b) grown nuclei which nucleated during the annealing. The nucleation rate was obtained by discriminating (b) from (a) to be about 107 cm−3 sec−1 for an oxygen content of 11×1017 atoms cm−3. Using this result and classical nucleation theory, homogeneous nucleation mechanism of oxygen precipitation is discussed.
Transmission electron microscope observation of dark-spot defects in InGaAsP/InP double-heterostructure light-emitting diodes aged at high temperature
Authors: Ueda Osamu , Yamakoshi Shigenobu , Komiya Satoshi , Akita Kenzo , Yamaoka Toyoshi
Published: February 2003

Dark-spot defects revealed in the electroluminescence patterns of degraded InGaAsP/InP double-heterostructure light-emitting diodes that are operated at the current density of 8.0 kA/cm2 at 200 °C were investigated using transmission electron microscopy. Bar-shaped defects lying in the direction of 〈100〉 or 〈110〉 were observed corresponding to the dark defects. These defects were precipitates of a certain kind of metal or compound and not ’’dislocationlike’’ ones.
Thomson scattering from a tokamak plasma with a repetitively Q-switched ruby laser
Authors: Behn R. , Röhr H. , Steuer K.-H. , Meisel D.
Published: February 2003

A ruby laser sytem in periodically Q-switched operation was used for Thomson scattering from a tokamak plasma. The laser delivers about 25 equidistant pulses of more than 10 MW peak power during the 1-ms flashlamp discharge. Electron density and temperature of the plasma were recorded as a function of time during the pulse sequence. The repetitively Q-switched system has been used to measure temperature and density development during a disruptive instability.
Self-imaging in a planar x-ray waveguide
Authors: Fischer B. , Ulrich R.
Published: February 2003

Single and multiple self-imaging with soft x rays (λ=4.48 nm) in a waveguide has been achieved for the first time. Images of a 2-μm-wide slit were produced by a hollow planar waveguide, consisting of two parallel gold surfaces of W≃10 μm separation and L=90 mm length. These dimensions satisfy the imaging condition Lλ=4W2 for a single ivnerted image in a homogeneous waveguide.
TiN and TaN as diffusion barriers in metallizations to silicon semiconductor devices
Authors: Wittmer Marc
Published: February 2003

The role of diffusion barriers in the contact metallurgy of silicon semiconductor devices is to prevent silicon diffusion into the top layer of the metallization. It is shown that TiN and TaN are good diffusion barriers in metallization schemes which consist of a silicide layer for contact to the silicon and a top layer of nickel for soldering purposes. With these diffusion barriers, the contacts are stable under annealing up to 600 °C.
n-channel insulated-gate field-effect transistors in Hg1−xCdxTe with x=0.215
Authors: Nemirovsky Y. , Margalit S. , Kidron I.
Published: February 2003

The characteristics of n-channel insulated-gate field-effect transistors in Hg1−xCdxTe with x=0.215, channel length of 4 μm, and 0.2-μm ZnS as an insulator are presented and analyzed. The transistors exhibit at 77 K a threshold voltage of −0.1 V and an effective inversion layer electron mobility of (1–2) ×104 cm2 V−1 sec−1. A strong dependence of the surface mobility upon surface electric field is measured. The transistors may be used as switching and amplifying elements for monolithic structures in HgCdTe.
Optimization of optoacoustic cell for depth profiling studies of semiconductor surfaces
Authors: Tam A. C. , Wong Y. H.
Published: February 2003

The authors present a simple theory to explain how optoacoustic depth profiling studies of an opaque solid surface dimension and coupling gas. An experimental cell suitable for such studies for a Si surface is constructed and experimental results taken at large and small gas column lengths lg (compared to gas thermal diffusion length) supported theoretical predictions. At large (small) lg, signal strength for He is about 3.2 (1.1) times that for N2 as the coupling gas used, in agreement with theory.
Observation of electromigration in heavily doped polycrystalline silicon thin films
Authors: Lloyd J. R. , Polcari M. R. , MacKenzie G. A.
Published: February 2003

Heavily doped P- and N-type polycrystalline silicon conductor stripes were subjected to a high direct current density stress of ∼1×106 A/cm2. It was found that all of the N-type stripes failed near the cathode, whereas all of the P–type stripes failed near the anode, thus pointing out the importance of the sign of the effective mass of the charge carriers in the momentum exchange that leads to electromigration. A model where migration of the dopant is responsible for the observed failures is suggested.
A tunable, ultrahigh spectral brightness KrF* excimer laser source
Authors: Hawkins R. T. , Egger H. , Bokor J. , Rhodes C. K.
Published: February 2003

An extremely high spectral brightness KrF* (248 nm) excimer source is described. This instrument combines the property of continuous tunability over the full gain profile with the following output pulse characteristics: pulse energy ∼60 mJ, pulse duration ∼10 nsec, spectral width 15030 MHz, absolute frequency control to within 300 MHz, and beam divergence ∼50 μrad. Within the uncertainty of measurement, the spectral width of the output radiation is Fourier transform limited, and the beam divergence corresponds to the diffraction of the radiating aperture.
Dissociative excitation of HgBr2 by rare-gas metastable atoms and N2(A 3σ+u)
Authors: Chang R. S. F. , Burnham R.
Published: February 2003

The dissociative excitation of HgBr2 by rare-gas metastable atoms and N2(A3𝒥+u) has been studied in a flowing afterglow apparatus. Reaction of HgBr2 with the lighter rare gas (He, Ne, and Ar) metastable atoms gave strong Hg* line emissions. Intense HgBr (B2𝒥+→X2𝒥+) emission (300–513 nm) from Xe(3P2) and N2(A) reactions was observed. The rate constants for HgBr* (B) formation from HgBr2 excitation by Xe(3P2) and N2(A) were determined as (5.31.5) ×10−10 cm3 sec−1 and ⩽1×10−10 cm3 sec−1 at 350 °K, respectively. Also, the formation rate constant for HgBr* (C) from HgBr2+Xe(3P2) was determined to be (1.10.3) ×10−10 cm3 sec−1.
Doping effect of annealed GaAs surfaces on vacuum-epitaxy-Ge/〈100〉 GaAs
Authors: Tseng W. F. , Davey J. E. , Christou A. , Wilkins B. R.
Published: February 2003

In this letter it is shown that both p- and n-type Ge vacuum-deposited films can be obtained on the same GaAs substrate during the same pump-down. p-type films are generally obtained if films are deposited immediately on the substrate at temperature ⩾300 °C, cooled down from outgas temperature 575 °C. n-type films are obtained consistently if the same substrate is then held below 300 °C for about 100 min before deposition. The low electron mobility observed for n-type Ge films leads to the conclusion that the properties of the films are determined by As compensation of p-type defects inherent in the films.
A heat-resisting new amorphous silicon
Authors: Matsumura Hideki , Nakagome Yoshinobu , Furukawa Seijiro
Published: February 2003

By using the sputtering method in a mixture of Ar and SiF4 gases, a purely fluorinated amorphous-silicon (a-Si : F) has been deposited, which does not contain hydrogen, and whose dangling bonds are terminated only by fluorine. Fluorine content, infrared absorption, and temperature dependence of conductivity, and also their variation due to the annealing process, are experimentally studied for this a-Si : F. It is found that all these are kept unchanged even after an annealing process at 600 °C, and that this new a-Si : F is heat resistant.
Ohmic contacts to p-type InP using Be-Au metallization
Authors: Temkin H. , McCoy R. J. , Keramidas V. G. , Bonner W. A.
Published: February 2003

A new contact to p-InP is reported with beryllium as the acceptor. The contact consists of a thin layer of 3 wt.% Be in Au alloy and a Au overlay sequentially deposited by e-gun evaporation. Alloying at 420 °C yields Ohmic contacts with low specific contact resistance rc⩽8×10−5 Ω cm2 for InP with NA−ND ≲1×1018 cm−3. To minimize the tendency of InP for thermal dissociation, the alloying temperature can be reduced to 375 °C by adding a thin Pd layer at the semiconductor metallization interface. This is achieved at the expense of a slight increase in resistance.
Semiconducting properties of ZnO–grain-boundary–ZnO junctions in ceramic varistors
Authors: Lou L. F.
Published: February 2003

The capacitance-voltage (C-V) curves and their frequency dependence are measured for ZnO varistors. Within the band picture of ZnO–grain-boundary–ZnO junctions, the prebreakdown portion of the C-V curves is calculated self-consistently to 1%. The strong frequency dependence of the capacitance at higher bias is shown to be consistent with the formation of an inversion layer near the grain boundary.
Directional reactive ion etching at oblique angles
Authors: Boyd G. D. , Coldren L. A. , Storz F. G.
Published: February 2003

Directional reactive ion etching (RIE) at oblique angles is possible using a simple grid-covered structure (Faraday cage) in conventional parallel-plate sputter etching equipment. Oblique-angle etching, as is possible in any ion-beam system, has been demonstrated using the etchant ions from CHF3 gas on a fused-silica substrate. The first detailed measurements of the angular etch dependence of RIE show a strong similarity to those of an ion-beam system (no chemical etching).
Influence of surface morphology on the angular distribution and total yield of copper sputtered by energetic argon ions
Authors: Whitton J. L. , Hofer W. O. , Littmark U. , Braun M. , Emmoth B.
Published: February 2003

The angular distribution of 40-keV-argon-sputtered copper has been measured by collecting the copper on a semicircular superpure aluminum foil and later analyzing by 1.8-MeV-He backscattering. Comparison has been made of the distributions from a flat surface of (11 3 1) copper and a pyramid-covered surface of the same orientation. The overall yield from the pyramid-covered surface is ∼50% greater than from the flat. This result is in contradiction to earlier reports of sputtering yields from flat and rough surfaces. Directional effects of sputtering are observed from both flat and pyramid-covered surfaces with enhancement by a factor of ∼4 in the latter case.
Efficient XeCl(B) formation in an electron-beam assisted Xe/HCl laser discharge
Authors: Nighan William L. , Brown Robert T.
Published: February 2003

XeCl(B) formation processes are examined for conditions typical of a discharge-excited laser using HCl as the chlorine donor. It is shown that vibrational excitation of HCl followed by dissociative attachment is a primary step in the reaction sequence resulting in Cl− . XeCl(B) formation is the result of a three-body Xe+ -CL− recombination reaction. Experimental results are presented which demonstrate efficient (∼2%) XeCl laser operation in an e-beam assisted discharge in which over 75% of the energy was deposited by the discharge.
Effect of inhomogeneous bonding on output of injection lasers
Authors: Lynch R. T.
Published: February 2003

Experimental and theoretical evidence is presented which demonstrates the large effect on cw lasing properties of inhomogeneities in the thermal resistance seen by the lasing cavity of semiconductor injection lasers.
n-type molybdenum-diselenide-based liquid-junction solar cells: A nonaqueous electrolyte system employing the chlorine/chloride couple
Authors: Schneemeyer Lynn F. , Wrighton Mark S. , Stacy Angelica , Sienko Michell J.
Published: February 2003

Single-crystal, n-type MoSe2 (Eg=1.4 eV) is shown to serve as a stable photoanode in an electrochemical cell employing a nonaqueous (CH3CN) solution of Cl2/Cl− as the redox active material. At 90 mW/cm2 input, 632.8-nm light can be converted to electricity with an efficiency of 5.9–7.5%. The photoanode reaction is 2Cl−→Cl2 and the cathode reaction is Cl2→2Cl−. The MoSe2 is qualitatively better than MoS2 (∼0.5% efficiency) which has a larger band gap (1.7 eV), but both materials are rugged in the nonaqueous solution, while both photocorrode in aqueous Cl− solutions. In H2O, the I3−/I− couple is excellent but in CH3CN it yields lower efficiency than the Cl2/Cl− couple. The stable Cl2/Cl− system provides evidence that a transparent, reversible, non-O2-sensitive redox couple can be useful in n-type semiconductor-based liquid-junction cells employing a direct band gap material having optimum solar response.
Nucleation and growth of high-T
c Nb3Ge coevaporated films
Authors: Krevet B. , Schauer W. , Wüchner F. , Schulze K.
Published: February 2003

Results from coevaporation of Nb3Ge using ultrahigh-purity niobium indicate that high-Tc A15 nucleation starts from an initial strongly disordered NbGe layer if the formation of Nb precipitates and other phases is suppressed by adding oxygen, directly during initial growth or via substrate precoating with oxidized surface layers. The influence of oxygen (or other suitable impurities) is assumed to reduce the mobility of the constituents, thus preventing their arrangement in stable formations of Nb or Nb5Ge3. Reduced mobility is supposed to be the condition required for formation of the initial disordered structure from which the high-Tc A15 phase grows.
Hemispherical emittance of rough metal surfaces
Authors: Löfving Sten
Published: February 2003

In this letter it is shown that surface roughness causes a pronounced increase in emittance for metal substrates. This is very important for solar-selective surfaces. With the help of laser absorptance measurements at wavelengths around 10 μm we show that it is plausible that coupling between thermally excited surface plasmons and free propagating waves at rough metal surfaces causes thermal radiation.
Photoacoustic effect with thermally thin solids
Authors: Crowley Thomas P. , Faxvog Frederick R. , Roessler David M.
Published: February 2003

Photoacoustic signals from opaque thermally thin solids (Ni, Al, and SiC) with a gas backing have an ω−3/2 frequency dependence. This first experimental observation of such a dependence from thin solids is in excellent agreement with the Rosencwaig-Gersho theory when a low-conductivity backing material is considered, but in disagreement with predictions based on the theory of Cesar et al. Surface heat conductance is determined by molecular collisions with the surface and not by blackbody radiative transfer.
New radiative deep states in epitaxial Ga1−xAlxAs
Authors: Bhattacharya P. K. , Owen S. J. T. , Marrs J.
Published: February 2003

Photoluminescence measurements performed at 6–7 K on intentionally undoped n-type liquid-phase epitaxy Ga1−xAlxAs (0.19⩽x⩽0.78) reveal transitions involving energies significantly lower than the band gap for crystals with x⩾0.47. Analysis of the luminescence data as a function of excitation intensity shows the presence of deep-level acceptors which participate in radiative transitions, and binding energies of 0.52, 0.48, and 0.56 eV are obtained for x=0.47, 0.50, and 0.61, respectively. These values are strikingly similar to the activation energies of hole traps which are present in crystals with x=0.50, 0.61, and 0.78 and strongly suggests that the radiative acceptors and the hole traps are either identical or related states. Electron trap levels which are also present in the same crystal are found to be nonradiative.
Arsenic segregation in polycrystalline silicon
Authors: Mandurah M. M. , Saraswat K. C. , Kamins T. I.
Published: February 2003

Dopant segregation at grain boundaries in polycrystalline silicon has been investigated. Arsenic was ion implanted into low-pressure, chemically vapor-deposited polycrystalline-silicon films. All films were then annealed at 1000 °C for 1 h, and some were subsequently further annealed at 800, 850, or 900 °C for 64, 24, or 12 h, respectively. The room-temperature resistivity of the films and the carrier Hall mobility were found to be higher after annealing at lower temperatures. By successively annealing the same sample at lower and higher temperatures, the resistivity would repeatedly increase and decrease, indicating dopant segregation. The heat of segregation was calculated to be 10.2 kcal/mol.
The excitation by light pulses of mechanical vibrations in solids
Authors: Hodby J. W. , Lewis A. V. , Alexandrou C. , Schwab C. , Boatner L. A.
Published: February 2003

Pulsed light is found to excite the intrinsic mechanical vibration modes of absorbing solid materials. The effect has been studied in seven piezoelectric solids using electrical detection of the vibrations. Arguments are given for a thermal mechanism, and transfer efficiencies of ∼10−9 are found for the conversion of visible energy into the mechanical energy of vibration. If the proposed mechanism is confirmed by further studies, the process should occur in all partially absorbing solid optical components.
Derivation of surface-atom polarizability from field-ion energy deficits
Authors: Forbes Richard G.
Published: February 2003

The field dependence of the difference in standarized energy between helium ions produced from the field-adsorbed position and from the critical surface has recently been interpreted in terms of field penetration into a jellium surface. A model that takes the atomic structure of the real surface into account interprets these results in terms of the proper polarizability of emitter surface atoms. Values obtained for tungsten are 2.01 and 2.07 meV V−2 nm2.
Chromium as a hole trap in GaP and GaAs
Authors: Kaufmann U. , Schneider J.
Published: February 2003

A characteristic electron spin resonance signal at g=1.986 has been observed in p-type Cr-doped GaP. It is assigned to a hole trap state of isolated chromium, presumably the A+ state Cr4+(3d2). Evidence for the existence of this state in GaAs is also presented.
dc bias dependence of W-Ni and W-Co point-contact diodes as harmonic generators and mixers at 9.4 μm
Authors: Kurosawa Tomizo , Sakurai Toshio , Tanaka Keiichi
Published: February 2003

The S/N ratios of the rf beat notes between harmonics of an x-band microwave source and the mixed output of two CO2 lasers at different frequencies are studied by means of the W-Ni and W-Co point-contact diodes at various mixing orders and various conditions of dc bias voltage. By applying the appropriate dc bias voltage to the W-Co diode in the even mixing orders, improvements on the S/N ratios by 5–10 dB are obtained.
On the (110) orientation as the preferred orientation for the molecular beam epitaxial growth of GaAs on Ge, GaP on Si, and similar zincblende-on-diamond systems
Authors: Kroemer Herbert , Polasko Kenneth J. , Wright Steve C.
Published: February 2003

Recent successful (110) growth of GaAs on Ge has prompted a reevaluation of the (110) orientation for the MBE growth of zincblende-on-diamond–type heterostructures. It is argued that the atomic geometry at a (110) interface should be particularly favorable for defect-free heteroepitaxy in such systems, for two reasons: (a) Recent work by Harrison et al. has shown that interfaces other than (110) interfaces in such systems must reconstruct. Such reconstruction will be incomplete, leaving behind hard-to-control interface charges. (b) The free-surface reconstruction of the diamond-structure (110) surface is such that it should favor subsequent growth of zincblende structures without antiphase domain boundaries.
Fast-moving laser focus
Authors: Felber F. S.
Published: February 2003

If a laser pulse is passed through a nonlinear medium, its focus can move rapidly. The paraxial-ray approximation is used to calculate analytically the position and radius of a moving laser focus as a function of time-dependent laser power and properties of the nonlinear medium.
High-resolution photoacoustic thermal-wave microscopy
Authors: Rosencwaig Allan , Busse G.
Published: February 2003

Experiments on photoacoustic thermal-wave microscopy are presented, for the first time, at high resolution. Using piezoelectric detection and a modulation frequency of 185 kHz, we obtain a thermal-wave resolution of ∼7 μm. We show that the photoacoustic phase signal provides true thermal-wave imaging even in the presence of surface features with strong optical contrast.
A new vacuum-etched high-transmittance (antireflection) film
Authors: Horwitz Chris M.
Published: February 2003

Films of high optical transmittance have been formed by the reactive sputter etching of quartz slides. With a globular metal masking layer, conical structures are formed in the quartz which form a gradient-index film. To date films have been produced which have less than half the loss of an uncoated quartz surface over a 2:1 wavelength range. Film scattering limits the short-wavelength performance and is shown to depend on the film structure’s average period.
Observation of phase coherence among multiple Josephson oscillators
Authors: Jain A. K. , Mankiewich P. , Lukens J. E.
Published: February 2003

A method is described for obtaining coherent in-phase oscillation in a large array of Josephson oscillators. This coherence has been demonstrated in a ten-junction array through the observation of strong voltage locking between sections of the array in the range of frequencies from 5 to 35 GHz. It has been demonstrated that this coherent in-phase oscillation in a ten-junction array gives 100 times (i.e., N2) the power of a similar single junction into the same load.
Low-temperature epitaxial regrowth of ion-implanted amorphous GaAs
Authors: Williams J. S. , Austin M. W.
Published: February 2003

Glancing-angle Rutherford backscattering and channeling techniques have been used to investigate the regrowth of Ar+-ion-implanted amorphous layers on (100) GaAs. Under carefully controlled implant conditions, amorphous GaAs layers can be recrystallized epitaxially at temperatures below 250 °C. However, the regrowth process is complex, with the crystalline quality and regrowth rate most dependent on implant dose.
Raman spectroscopy of surface oxides at elevated temperatures
Authors: Farrow R. L. , Nagelberg A. S.
Published: February 2003

Backscattering Raman spectroscopy is demonstrated to be a useful technique for in situ characterization of oxide films on metals at high temperatures. Data obtained during oxidation at temperatures between 300 and 850 °C are presented for two different iron-based alloys. The sensitivity and specificity of the technique were sufficient to detect the formation of iron oxide films (Fe2O3 and Fe3O4) less than 150 Å in thickness at temperatures below 350 °C. Above 600 °C, the predominant oxide was Cr2O3; however, the presence of a few weight percent Mn in a commercial alloy produced a mixed spinel oxide in addition to Cr2O3.
Oxidized amorphous-silicon superconducting tunnel junction barriers
Authors: Rudman D. A , Beasley M. R.
Published: February 2003

A systematic study of the behavior of oxidized amorphous silicon layers as tunneling barriers in transition-metal-based superconducting tunnel junctions is reported. These barriers are found to work universally well, provided the native oxide of the base electrode has a sufficiently low conductance to block pinholes. For silicon layers larger than ∼2 nm the properties of the barriers are found to be independent of the base electrode and lead to a simple model of the barrier which should be useful for further applications.
Uphill diffusion mechanism in proton-irradiated silicon
Authors: Morikawa Yasumitsu , Yamamoto Keiichi , Nagami Koichi
Published: February 2003

Uphill diffusion of boron or phosphorus in silicon due to high-temperature proton irradiation is explained by a proposed model in which a vancancy mechanism is assumed. The results calculated from the model show good agreement with the experimentally measured profiles, and some physical parameters can be estimated. A significant feature of the proposed model is that Fick’s law is included as a special case.
Quantum-mechanical estimates of the speed of field ionization of shallow impurity levels
Authors: Chaudhuri Siddheswar , Coon Darryl D. , Derkits Gustav E.
Published: February 2003

Using a Kohn-Luttinger approach to shallow impurity levels in semiconductors, we estimate the speed of charge release associated with field ionization. At sufficiently low temperatures, this is predominantly a quantum-mechanical process. It is found that charge release times in the picosecond regime may be achievable in prebreakdown fields in semiconductors. In GaAs, one picosecond release times correspond to fields of 0.2 V/μ and field energy densities of 2×10−18 J/μ3. In the picosecond regime, our estimates rely on published, mutually consistent Stark width results obtained by various techniques including dispersion relations and Weyl’s complex-eigenvalue method.
Regenerative compression of laser pulses
Authors: Murray J. E. , Kuizenga D. J.
Published: February 2003

We report stable temporal compression of mode-locked laser pulses using a saturable dye in a regenerative amplifier. We have demonstrated compression at 1.06 μm from 120 to 15 ps with energy stability better than ±5%, and we have demonstrated synchronization of the compressed pulse to pulses as long as 1000 ps.
A theory for the radiation pattern of a narrow-strip acoustic transducer
Authors: Selfridge A. R. , Kino G. S. , Khuri-Yakub B. T.
Published: February 2003

An important criterion in the design of transducer array elements for acoustic imaging is the angular response, or the far-field radiation pattern, of a single element. In this letter, we show that the widely accepted formula for the angular response function is inadequate and must be multiplied by cosϑ. Good agreement with experiment is then obtained.
Nonlinear optical amplification in a nematic liquid crystal above the Frederiks transition
Authors: Khoo I. C. , Zhuang Shu-Lu
Published: February 2003

We have observed a new nonlinear light amplification process in a nematic liquid crystal, p-methoxybenzylidene-p-n-butylaniline, maintained above the Frederiks transition by a magnetic field. Substantial probe-beam gain (10% or more) was observed for a moderate same-frequency pump beam of intensity on the order of W/cm2, and is attributed to the molecular anisotropy associated with the director axis reorientation. The observed gain and nonlinear intensity dependence are in excellent quantitative agreement with theoretical predictions. An analogous effect is also observed for the case when the Fredericks transition is caused by a dc electric field.
High-energy Fe-Cr-Co permanent magnets with (B
H)max ≃8–10 MG Oe
Authors: Homma M. , Horikoshi E. , Minowa T. , Okada M.
Published: February 2003

A series of new high-energy Fe-Cr-Co magnet alloys with (BH)max≃8–10 MG Oe have been developed. An Fe-22Cr-15Co alloy with equiaxed grain structure achieves (BH)max=8.3 MG Oe utilizing the abnormal shape of the miscibility gap of the system. The addition of Mo to the alloys enhances the anisotropic decomposition and the development of <100≳ columnar grains further improves the magnetic properties up to (BH)max=9.5 MG Oe.
Fabrication of 300-Å metal lines with substrate-step techniques
Authors: Prober D. E. , Feuer M. D. , Giordano N.
Published: February 2003

Metal lines as narrow as 30 nm and as long as 0.5 mm have been fabricated by new techniques based on substrates with surface-relief steps. Substrate steps with a square profile are formed by ion-beam etching. Metal wires of triangular cross section are produced by ion-etching a metal-coated substrate at an angle, so that the wire is formed in the shadow of the step. An alternative process, direct evaporation onto the step edge, is used to produce lines of very high aspect ratio of height to width.
Au and Al interface reactions with SiO2
Authors: Bauer R. S. , Bachrach R. Z. , Brillson L. J.
Published: February 2003

The chemical bonding, extent, and evolution of metal-oxide semiconductor interface regions have been probed with soft-x-ray photoemission spectroscopy following room-temperature, in situ metallization. We identify strong atomic rearrangement and charge transfer at metal-SiO2 interfaces. The quantitatively different processes found for Au and Al suggest new structural models. For Al-SiO2, Al first clusters about each surface O and then grows Al2O3 by reducing SiOx (X < 2) and leaving excess Si at the interface. In contrast, Au forms islands on SiO2 with evidence of Au–Si bonding, causing an SiOx layer beneath the contact.
Comparative structural and electrical characterization of scanning-electron- and pulsed-laser-annealed silicon
Authors: McMahon R. A. , Ahmed H. , Cullis A. G.
Published: February 2003

Silicon implanted with As+, P+, or B+ ions has been annealed by the multiple-scan electron beam method and by use of pulsed radiation from a Q-switched ruby laser. Electron microscope examination of specimen cross section gives direct comparison of the initial implantation damage with the structures produced by the different annealing methods. Sample electric conductivities after annealing are also compared. This work highlights the differences between the liquid- and solid-phase annealing mechanisms of the pulsed-laser and scanned-electron-beam methods, respectively.
Precipitation and redistribution of oxygen in Czochralski-grown silicon
Authors: Shimura Fumio , Tsuya Hideki , Kawamura Tsutomu
Published: February 2003

Thermally induced oxygen precipitation and redistribution phenomena in Czochralski-grown silicon crystals are investigated by means of transmission electron microscopy and differential-infrared absorption (DIR). In order to investigate the role of thermal history and the oxygen supersaturated condition for oxygen precipitation, a two-step annealing process is adopted. Evident existence of SiO2 (crystobalite) is observed in as-grown crystals by DIR at 1225 cm−1. As a result, it is ascertained that oxygen precipitation does not occur by homogeneous nucleation depending on the ratio of supersaturated oxygen but occurs by heterogeneous nucleation. A model of a grown-in nucleus for oxygen precipitation by heat treatment is also proposed.
Fundamental-mode VHF/UHF minature acoustic resonators and filters on silicon
Authors: Grudkowski T. W. , Black J. F. , Reeder T. M. , Cullen D. E. , Wagner R. A.
Published: February 2003

Novel bulk acoustic-wave high-Q resonators and acoustically coupled resonator filters have been fabricated and operated at their fundamental half-wavelength mode in the 200-500-MHz frequency range. These structures are fabricated on thin ZnO/silicon diaphragms with dimensions small enough to be incorporated within integrated circuits. Resonator Q’s near 2600 at the fundamental mode have been obtained and strong inter-resonator acoustic coupling has been achieved yielding filters having insertion loss (untuned) as low as 5.5 dB.
Controlled fabrication of multilayer soft-x-ray mirrors
Authors: Spiller Eberhard , Segmüller Armin , Rife Jack , Haelbich Rolf-Peter
Published: February 2003

Multilayer mirrors have been fabricated for various angles of incidence throughout the wavelength range λ=1.5–160 Å. Reflectivity increases by more than a factor 103 over the best single-film reflectors have been obtained. Measured reflectivities are around 10% near normal incidence in the λ=45–160-Å wavelength region and above 50% near grazing incidence (grazing angle 1°–2°) for λ=1.54 Å. The required thickness control has been achieved by monitoring the reflectivity of the films in situ during the deposition.
Temperature dependence of electrochromic processes in iridium oxide displays
Authors: Hackwood S. , Beni G. , Dautremont-Smith W. C. , Schiavone L. M , Shay J. L.
Published: February 2003

We report measurements of the temperature dependence of coloration and bleaching times of electrochromic iridium oxide films in the range +20 to −43 °C. The intrinsic response times increase gradually with decreasing temperature according to an activation energy of ∼0.25 eV. For a contrast ratio of ∼4:1, suitable for a practical device, we find that the response times remain below ∼0.25 sec for T⩾−10 °C and below 1 sec for T⩾−25 °C. We have also found that the temperature variation of the response times is independent of pH, so that an optimized electrolyte can be chosen for a practical device. Moreover, its independence of pH suggests that the electrochromism of iridium oxide is due to insertion and fast-ion diffusion of the same ion species in either basic or acidic aqueous electrolytes.
Evidence of p/n homojunction formation in Zn3P2
Authors: Catalano A. , Bhushan M.
Published: February 2003

Heating of magnesium/p-Zn3P2 contacts at 100 °C results in a ∼ 102 lower reverse saturation current than found for the unheated metal-semiconductor diode. Spectral response and electron-beam-induced current (EBIC) measurements show the formation of a buried junction upon heating, and the latter method has been used to obtain values of junction depth and minority carrier diffusion length. A model expressing the collection efficiency of an n-on-p homojunction shows good agreement with experiment when the minority carrier diffusion lengths and junction depth determined by EBIC measurements are used. This is the first evidence that p/n homojunctions may be formed in Zn3P2.
Ambient effects on the diffusion of Cr and Si in thin Pt films
Authors: Chang Chin-An , Chu W.-K.
Published: February 2003

We have studied the ambient effects on the low-temperature diffusion of Cr and Si in thin Pt films. The surface-potential model proposed earlier predicts that, contrary to the case in gold, oxygen should suppress the diffusion of Cr and Si in Pt. We have observed a reduced out-diffusion of Cr and a reduced rate of Pt2Si formation in the prseence of O2. The technological significance of this effect is also discussed.
High-quality transparent conductive indium oxide films prepared by thermal evaporation
Authors: Pan C. A. , Ma T. P.
Published: February 2003

Highly transparent (over 90% transmission in the visible range) and highly conductive (resistivity ≃2×10−4 Ω cm) indium oxide (undoped) films have been produced by thermal evaporation from an In+In2O3 source in a vacuum chamber containing low pressures of O2. These properties are comparable or superior to the best tin-doped indium oxide films ever reported, and excellent reproducibility has been achieved. Hall effect measurements have revealed that the observed low resistivity is primarily a result of the excellent electron mobility (≃70 cm2/V sec), although the electron concentration is also rather high (⩾4×1020/cm3). X-ray diffraction measurements show distinctly polycrystalline In2O3 structure with a lattice constant ranging from 10.07 to 10.11 Å. Electrolytic electroreflectance spectra exhibit at least four critical transitions, from which we have determined the direct and indirect optical band gaps (≃3.56 and 2.69 eV, respectively). Burstein shifts due to the population of electrons in the conduction band are also observed. These and other results along with a discussion of the processing details are reported.
A monolithic integration of GaAs/GaAlAs bipolar transistor and heterostructure laser
Authors: Katz J. , Bar-Chaim N. , Chen P. C. , Margalit S. , Ury I. , Wilt D. , Yust M. , Yariv A.
Published: February 2003

A GaAlAs double-heterostructure laser has been monolithically integrated with a heterojunction bipolar transistor on a GaAs substrate. Integration is achieved by means of a mutually compatible structure formed by Be ion implantation. Typical pulsed threshold currents for the laser are 60 mA, and the transistors have a typical common-emitter current gain of 900.
Effects of grain boundaries in polycrystalline solar cells
Authors: Zook J. David
Published: February 2003

In polycrystalline solar cells, the short-circuit current is reduced (compared to single-crystal cells) due to recombination of minority carriers at the grain boundaries. The magnitude of this reduction is calculated for the case of a monochromatic beam of light, assuming that both the light beam and the grain boundaries are perpendicular to a p-n junction. The photoresponse of the junction is calculated in terms of the absorption coefficient of the light, the minority-carrier diffusion length, the surface recombination velocity at the grain boundary and the distance of the light beam from the grain boundary. The analysis gives an expression for an effective grain boundary width which depends on wavelength. This width determines the reduction in short-circuit current of solar cells made from material with columnar-type grains.