bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations of low emittance-neutralized alkali ion beams from a large-area multistage injector
Authors: Phelps D. A. , Wharton C. B.
Published: February 2003

Experiments are reported on the operation of a three-stage accel-decel ion injector that is driven by a 500-kV–200-ns pulse line at a power density of ≳100 kW/cm2—previously unobserved for injectors with no simultaneous electron breakdown. Stable thermionic emission of sodium ions from an array of sixteen 3-mm×10-cm scintered zeolite strips is demonstrated. Observations of over 500 mA/cm2 beams are noted and attributed to uniform space-charge–limited extraction in the first stage and 3:1 electrostatic focusing in the second stage of the injector. After passing through the third stage, 500-V decel potential (to retard electron flow), 70% charge neutralization is achieved with a reflex triode electron source. A mean angular divergence of less than 5 mrad is deduced from profile data of the sodium ion beam and reported.
Backscatter of CO2 laser light from an overdense Z-pinch plasma
Authors: Walsh C. J. , Meyer J. , Hilko B.
Published: February 2003

A mode-locked train of CO2 laser pulses, 2.5-nsec wide with 14.6 nsec between pulses, has been focused into an overdense Z-pinch plasma at vacuum intensities up to 2×1012 W cm−2. Backscatter through the f/5 lens has been observed to grow from a large noise level which is not present in the absence of the laser, and saturate at a value ∼ 4%.
Acoustoelectric measurement of low carrier mobilities in highly resistive films
Authors: Adler R. , Janes D. , Hunsinger B. J. , Datta S.
Published: February 2003

The acoustoelectric method of determining carrier mobility μ in semiconductor films has been modified to permit its application to high-resistance, low-mobility films. The conventional method requires knowledge of the acoustic loss caused by the mobile carriers; in high-resistance films this loss becomes too small to be measured. We show that the required information may be derived from knowledge of the acoustic power and the device geometry. Our samples were amorphous hydrogenated Si and Si0.6Ge0.4 films on nonpiezoelectric substrates, separated by a convenient air gap (12.5 μm) from a LiNb03 slab carrying surface acoustic waves. One sample had 108 Ω/⧠ and μ=0.08 cm2/V sec, another sample 1010 Ω/⧠ and μ=0.5 cm2/V sec.
Alteration of Ni silicide formation by N implantation
Authors: Wieluński L. , Scott D. M. , Nicolet M.-A. , von Seefeld H.
Published: February 2003

The possibility of controlling the growth of nickel silicide by implanting N into thin Ni films evaporated on Si substrates has been studied using 4He backscattering spectrometry. The reaction between Ni and Si is completely halted below annealing temperatures of ∼375 °C by implanted doses of 5×1016 N/cm2. At higher annealing temperatures, localized intermixing takes place. For low doses ≲0.5×1016 N/cm2, the reaction between Ni and Si is that observed for unimplanted samples both in the phase formed (Ni2Si) and in rate of growth. For intermediate doses ∼0.9×1016 N/cm2, the first phase formed corresponds to NiSi, and the growth rate is greatly reduced. These results are explained in terms of a silicon nitride barrier to Ni diffusion forming at the Ni/Si interface.
New method of magnetic flux compression by means of the propagation of shock-induced metallic transition in semiconductors
Authors: Nagayama Kunihito
Published: February 2003

A new procedure of generating ultrahigh pulsed magnetic field was described. The method is based on the fact that semiconducting materials undergo shock-induced metallic transition at very high pressures. An approximate numerical analysis using the magnetohydrodynamics equations was carried out for silicon with normal and low initial densities. It is shown that flux concentration may become efficient for low-impedance materaials.
Merocyanine-dye photovoltaic cell on a plastic film
Authors: Moriizumi T. , Kudo K.
Published: February 2003

A flexible photovoltaic cell was produced by depositing a merocyanine-dye layer on a transparent electro-conducting film, which is a polyester film coated with ITO (indium-tin oxide). Two kinds of the layered structures on the films were examined; i.e., Al/merocyanine/ITO and Ag/merocyanine/ZnO/ITO structures. It was found that the latter structure was more promising for a solar cell because of a considerably better output stability and a higher conversion effiency.
Uncertainty principle limit to the energy sensitivity of SQUID’s and other linear amplifiers
Authors: Voss Richard F.
Published: February 2003

SQUID’s (Superconducting quantum interference devices) and other amplifiers are modeled by ideal noiseless linear amplifiers with current in and voltage en noise sources in their input circuits. For independent sources at frequency v the uncertainty principle requires that (e2ni2n)1/2 ≳2hv, where h is Planck’s constant. This limits the intrinsic energy sensitivity ε=Φ2n/2L of a SQUID of inductance L and effective flux noise power Φ2n to ε≳εmin=(e2ni2n)1/2 /2πν=h/π. Correlation of the noise sources or mismatch of the SQUID inductance is shown to degrade εmin.
Shock-compression temperature rise in polymethyl methacrylate determined from resistivity of embedded copper foils
Authors: Bloomquist D. D. , Sheffield S. A.
Published: February 2003

The temperature rise induced by shock compression of polymethyl methacrylate(PMMA) was determined from measurements of the electrical resistivity of embedded copper foils. The temperature of the copper was determined from the observed foil resistance and known values of the change in copper resistivity with temperature and shock compression. It was inferred, from equilibration evident on the records, that the copper and PMMA were at the same temperature. Observed values for the temperature rise in PMMA were 44 and 409 K for compressions of 14.0% and 22.4%, respectively; these values are in good agreement with those reported previously on the basis of thermocouple measurements.
Explosive crystallization of amorphous germanium
Authors: Leamy H. J. , Brown W. L. , Celler G. K. , Foti G. , Gilmer G. H. , Fan J. C. C.
Published: February 2003

We have obtained experimental confirmation of the prediction that explosive crystallization of amorphous germanium proceeds via an intermediate melting step.
Microcrystalline structure in glow-discharge-produced silicon films
Authors: Nagata Yujiro , Kunioka Akio , Yamazaki Shumpei
Published: February 2003

Semiamorphous silicon films have been prepared by rf glow discharge in silane diluted with helium gas at low substrate temperatures. The films have many fine clusters (about 500 Å) overlapped with each other and have a crystalline structure.
Diffusion of gold in silicon: A new model
Authors: Gösele U. , Morehead F. , Frank W. , Seeger A.
Published: February 2003

Experimental results from the diffusion of Au in Si, which could not be explained before, in terms of the Frank-Turnbull mechanism involving vacancies, can be quantitatively understood with the assumption that the equilibrium between interstitial and substitutional Au is established via Si self-interstitials. The results suggest that these defects dominate diffusion in Si.
Reactivity and interface chemistry during Schottky-barrier formations: Metals on thin native oxides of GaAs investigated by x-ray photoelectron spectroscopy
Authors: Kowalczyk Steven P. , Waldrop J. R. , Grant R. W.
Published: February 2003

The room-temperature interfacial chemical reactions of overlayers of several diverse metals (Au, Cu, Al, Mg, Cr, and Ti) with thin native oxide films (∼10 Å) on GaAs (100) surfaces were investigated with x-ray photoelectron spectroscopy (XPS). The reactivity of these metals with the native oxides of GaAs ranged from inert to complete reduction for the oxides and is well predicted by bulk thermodynamic free energies of formation. Variations in band bending during Schottky-barrier formation were monitored by XPS. The implication of the observed interface chemistry for Schottky-barrier modeling is discussed.
Modulation of two-dimensional conductivity in a molecular beam epitaxially grown GaAs bulk space-charge system
Authors: Künzel H. , Döhler G. H. , Fischer A. , Ploog K.
Published: February 2003

The electron channel conductivity σ(2)nn in a molecular beam epitaxially grown structure consisting of an ultrathin n-doped GaAs layer sandwiched between two thicker p-type layers has been studied in detail. The free carrier concentration n(2) in the channel can be varied continuously over a wide range by an external potential difference betweeen the active n layer and the p-type material. The observed characteristics demonstrate that this three-layer pnp doping structure in GaAs represents a special version of the junction field effect transistor and is an ideal system for studying the two-dimensional conduction near the mobility edge.
Solid-phase heteroepitaxy of Ge on 〈100〉Si
Authors: Tsaur B. Y. , Fan John C. C. , Gale R. P.
Published: February 2003

Heteroepitaxial Ge films have been obtained by solid-phase crystallization of amorphous Ge deposited on single-crystal 〈100〉Si substrates. The substrates were chemically cleaned by conventional procedures without any attempt to achieve atomically clean surfaces. The as-crystallized Ge films contain dislocations and twins. Reduction in twin density has been achieved by using an ion implantation and reannealing treatment. Epitaxial GaAs layers of good crystal quality have been grown by chemical vapor deposition on heteroepitaxial Ge films subjected to this treatment.
Continuous room-temperature photopumped laser operation of modulation-doped AlxGa1−xAs/GaAs superlattices
Authors: Dapkus P. D. , Coleman J. J. , Laidig W. D. , Holonyak N. , Vojak B. A. , Hess K.
Published: February 2003

The low-threshold continuous room-temperature laser operation of a photopumped metalorganic chemical vapor deposition AlxGa1−x As-GaAs superlattice is described. The superlattice, a bare superlattice without cladding or confining layers, consists of 25 140-Å AlxGa1−x As (x∼0.3) coupling barriers doped to a level nd ∼7×1017/cm3 and 25 alternating undoped 140-Å GaAs quantum wells. Low-temperature data (77 K) are presented indicating that the threshold for phonon-assisted recombination occurs near the excitation level at which the excess carrier density approaches the built-in carrier density ∼7×1017/cm3 of the superlattice.
11.5% solar conversion efficiency in the photocathodically protected p-InP/V3+-V2+-HCI/C semiconductor liquid junction cell
Authors: Heller Adam , Miller Barry , Thiel F. A.
Published: February 2003

Oxidation of the surface of p-InP with alkaline peroxide and treatment with dilute potassium cyanide increase the efficiency of the p-InP/V2+−V3+ -HCl/C cell to 11.5%. The open circuit voltage of the cell follows the redox potential of the solution over a 0.5 V range. The lack of voltage pinning is consistent with photoemission studies of Spicer et al., showing that adsorption of oxygen on p-InP raises the surface fermi level from a position near the valence band maximum to noe near the conduction band minimum.
Electron suppression in a multicusp negative ion source
Authors: Ehlers K. W. , Leung K. N.
Published: February 2003

Three different techniques for reducing the background electron density at the exit region of a multicusp negative ion source are described.
Optically detected photothermal imaging
Authors: Murphy J. C. , Aamodt L. C.
Published: February 2003

A method of photothermal imaging is described, which uses optical detection with no contact between specimen and detector.
Shock-tube CO2 gas-dynamic laser operating on the (0310)⇄(10°0) transition at 18.4 μm
Authors: Vedeneev A. A. , Volkov A. Yu. , Demin A. I. , Kudriavtsev E. M. , Stanco J. , Milewski J. , Brunné M.
Published: February 2003

Laser action at 18.4 μm has been obtained between the (0310) and (1000) levels in a shock-tube-driven CO2/Ar gas-dynamic laser. The pulse duration was equal to about 4 ms, giving the output power up to 2 W extracted from a 10-cm3 volume cavity mounted within a nozzle of 60° divergence angle and 0.5-mm throat height 67-mm downstream of the nozzle throat.
Possibility of lasing at the 1083-nm He line in a He-Hg mixture
Authors: Ninomiya H.
Published: February 2003

In a He-Hg pulsed discharge, the temporal behavior of the population densities of He(2 3S) and He(2 3P) atoms has been studied experimentally using the Hook method. The possibility of the lasing at 1083 nm line (2 3S—2 3P) is discussed on the basis of the experimental fact that, when the partial pressure of Hg is adequate, the population inversion occurs transiently between these two states.
Seeded and limited seeding regrowth of Si over SiO2 by cw laser annealing
Authors: Magee T. J. , Palkuti L. J. , Ormond R. , Leung C. , Graham S.
Published: February 2003

Single-crystal Si sheets (0.2 μm in thickness) of (100) orientation and of maximum dimensions, 100×10 000 μm, have been recrystallized by cw laser annealing of poly crystalline Si films deposited over parallel 3-μm-wide SiO2 bars adjacent to 3-μm Si (100) substrate openings. The recrystallized films are free of cracks, mosaic structure, stacking faults, or excessive mass flow at the oxide edges. In a correlated series of experiments we have shown that the Si can be recrystallized over the SiO2 with only limited or relaxed requirements for vertical seeding from the substrate window.
Perfection of homoepitaxial layers grown on (001) InP substrates
Authors: Mahajan S. , Keramidas V. G. , Chin A. K. , Bonner W. A. , Ballman A. A.
Published: February 2003

The perfection of homoepitaxial layers grown on highly S-, Zn- and Sn-doped InP substrates by liquid phase epitaxy has been evaluated by etch pitting and transmission cathodoluminescence. It is shown that high-quality layers, which are macroscopically dislocation free over large areas, can be grown on the S-doped substrates. The situation regarding the epitaxial layers deposited on the Zn-doped substrates is complex. The transmission cathodoluminescence study reveals, in addition to dislocations, areas with poor luminescence within the epitaxial layers. Furthermore, the quality of thin layers (∼2 μm thick) grown on the Zn- and Sn-doped substrates is better than that of the thick layers (∼10 μm).
Metal-insulator semiconductor Schottky-barrier solar cells fabricated on InP
Authors: Kamimura K. , Suzuki T. , Kunioka A.
Published: February 2003

High-efficiency Schottky-barrier solar cells with a metal-insulator semiconductor structure have been fabricated on p-type InP. The open-circuit voltage and the energy conversion efficiency can be increased by introducing a thin oxide layer between the metal and the semiconductor. The open-circuit voltage and the energy conversion efficiency are 0.78 V and 14.5% under AM2 conditions.
Gettering of crystalline defects in Si by bending
Authors: Sawada R. , Karaki T. , Watanabe J.
Published: February 2003

Suppression of oxidation-induced stacking faults and microdefects in a Si wafer, subjected to bending during thermal oxidation, was studied. Straight dislocations were introduced only at the neutral plane in Si bulk, during bending in a furnace and retained as sinks through all subsequent high-temperature processings, thereby continuing to suppress the formation of oxidation-induced stacking faults and microdefects. Gettering while applying bending stress to the wafer is described, including the formation mechanism for dislocations at the neutral region.
Light-flash induced metallic silicides from titanium films on silicon
Authors: Lue Juh Tzeng , Liu Yuen Chung , Shen Wei Jiun
Published: February 2003

Reaction of thin titanium films on silicon has been observed in forming polyphase silicides by flash irradiations with full width at half-maximum of 100 ms. Ion back scattering and optical micrographic studies show that the metallization occurs only when the temperature of the metal surface reaches the melting point. The experimental threshold irradiation energy density for the metal surface to reach the melting point is 17.6 J/cm2, which is close to the theoretical value of 20.4 J/cm2, based on the strong-thermal-diffusion-limit approach.
Damage and reordering of ion-implanted layers of InP
Authors: Kennedy E. F.
Published: February 2003

Si ion-implantation damage in InP was studied by channeling measurements with 1-MeV4 He ions. 200-keV Si ions were implanted at fluences ranging from 1013 to 5×1014/cm2. A fluence of about 1014/cm2 was sufficient to produce an amorphous layer. Epitaxial annealing of amorphous layers takes place at temperatures below 250°C but leaves a high level of residual damage. Annealing at 450°C removes most of the lattice damage. Some annealing of lower fluence damage takes place at room temperature. Most lattice damage can be avoided by implanting with the substrate at an elevated temeperature (∼180°C).
Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser
Authors: AuYeung John
Published: February 2003

We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.
Corrosion resistant alloys Mo-Ru-X (X = Fe, Co, and Ni)
Authors: Meng R. L. , Huang S. Z. , Chu C. W.
Published: February 2003

We found that some Mo-Ru-X (X = Fe, Co, and Ni) alloys could be made with exceptional corrosion resistance and variable magnetic and mechanical strengths both in bulk and thin-films forms. Crystal structure did not seem to play an important role in these unusual and useful properties.
Generation of picosecond pulses of amplified spontaneous emission by two-photon excitation in GaAs
Authors: Cao Wei-Lou , Vaucher Aileen M. , Lee Chi H.
Published: February 2003

A strong and uniform picosecond amplified-spontaneous-emission (ASE) pulse train was produced by two-photon excitation in GaAs without a resonant cavity. The frequency bandwidth and the power of the ASE were found to depend upon the pumping power density and the length of the GaAs crystal that was pumped.
Preparation of low-resistivity n-type ZnSe by organometallic chemical vapor deposition
Authors: Stutius W.
Published: February 2003

Low-resistivity n-type ZnSe with p<0.05 W cm and n≳1017 cm−3 has been grown epitaxially on (100) GaAs substrates by a low-pressure low-temperature organometallic chemical vapor deposition process. Triethylaluminum is used as a dopant. The as-grown layers show a strong near-band-gap photoluminescence peak. The much weaker photoluminescence intensity at longer wavelength indicates that the concentration of deep centers is lower than in doped ZnSe prepared by other methods.
Donor-acceptor pairs in GaP and GaAs involving the deep nickel acceptor
Authors: Ennen H. , Kaufmann U. , Schneider J.
Published: February 2003

Seven new, sharply structured bands in the 2-mm region have been observed in absorption and emission from n-type GaP and GaAs diffused with nickel. Each of these bands is both Ni and donor type specific. They are assigned to intra d-shell transitions of Ni acceptor-shallow donor near-neighbor associates, namely Ni-S and Ni-Ge in GaP and Ni-S, Ni-Se, Ni-Te, Ni-Si, and Ni-Sn in GaAs. Uniaxial stress measurements, performed on the Ni-S band in GaP, demonstrate that the corresponding center has trigonal symmetry, thus confirming that a nearest-neighbor pair is involved. This is the first definite optical identification of a donor-acceptor pair containing a deep 3d-metal acceptor. It is concluded that Ni has a strong tendency to form such pairs, especially with sulphur.
Fully ion-implanted p+-n germanium avalanche photodiodes
Authors: Kagawa S. , Kaneda T. , Mikawa T. , Banba Y. , Toyama Y. , Mikami O.
Published: February 2003

Germanium avalanche photodiodes with a shallow p+-n junction have been fabricated using full ion implantation, together with a low temperature (650 °C), single-stage annealing process. This procedure yielded high-performance germanium avalanche photodiodes with a high rate of reproducibility. About 80% of the diodes obtained showed a dark current of 150–250 nA at 0.9 VB. At a multiplication factor of 10, low excess noise resulted (F≊6.5 at 1.55 mm and F = 8–9 at 1.3 mm), and deterioration of the response at 500 MHz was limited to 0.5–1 dB.
Sub-20-nm-wide metal lines by electron-beam exposure of thin poly(methyl methacrylate) films and liftoff
Authors: Beaumont S. P. , Bower P. G. , Tamamura T. , Wilkinson C. D. W.
Published: February 2003

Platinum/palladium lines (17 nm wide) have been defined by the electron-beam exposure of a film of poly(methyl methacrylate) 60 nm thick supported on a 30-nm-thick carbon-film substrate followed by liftoff of overcoated metal. Line pitch may be reduced to 50 nm before liftoff fails. An 8-nm-diam 50-kV electron beam is used for exposure. A combination of finite source diameter, molecular size effects, and secondary electron exposure are believed to be responsible for the observed resolution limit. It is shown that pattern-size accuracies of a few nanometers can be achieved.
Direct observation of I2 collisional dissociation by O2(b1Σ+g)
Authors: Muller D. F. , Young R. H. , Houston P. L. , Wiesenfeld J. R.
Published: February 2003

Collisional dissociation of I2 by O2(1𝒥) has been directly observed by monitoring the appearance rate and amplitude of transient I(5 2P3/2) absorption on the 6 2P3/2-5 2P3/2 resonance line at 178 nm. A pulsed, Raman-shifted dye laser was used to excite a single rotational line of O2(1𝒥, v′ = 0) near 763 nm. Radiation at this wavelength also dissociated some I2 via absorption to the continuum region of the I2(A 3R1u) state. The variation in the appearance rate of the iodine atom signal with I2 pressure leads to a rate constant for total deactivation of O2(1𝒥) by I2 of k = 7×10−11 cm3 molecules−1 sec−1. Comparison of the amplitude of the I-atom absorption signal induced by O2(1𝒥) dissociation of I2 to that resulting from direct I2 photodissociation leads to the conclusion that the branching ratio for O2(1𝒥)+I2→O2+2 I versus all other pathways is less than 0.2.
Damage and lattice location studies in high-temperature ion-implanted diamond
Authors: Braunstein G. , Kalish R.
Published: February 2003

The results of implantation of various ions (Li,C,P,Ge, and Sb) into heated diamond (∼1000 °C) are studied by channeling techniques. The residual damage and the locations in the lattice, which the implants occupy, are determined. It is shown that by implanting into heated diamond (i) graphitization can be avoided and (ii) an appreciable fraction of Li ions can be driven into interstitial sites where they are expected to be electrically active donors.
Defect photoluminescence from pulsed-laser-annealed ion-implanted Si
Authors: Skolnick M. S. , Cullis A. G. , Webber H.C.
Published: February 2003

Low-temperature photoluminescence studies of pulsed-laser annealed self-ion-implanted Si are reported. Two sharp damage luminescence peaks W and G are found. The main peak W is strongest at a laser energy of 1.5 J/cm2 even though this gives good recrystallization of the amorphous surface region. Most of the W centers are created by solid-phase annealing of ion-implantation damage in a band beyond the laser-melted region. The G centers are present in the channeling tail of the implant before laser annealing.
Resistance standard using quantization of the Hall resistance of GaAs-AlxGa1−xAs heterostructures
Authors: Tsui D. C. , Gossard A. C.
Published: February 2003

Quantization of the Hall resistance of the two-dimensional electron gas in GaAs-AlxGa1−xAs heterostructures is observed at 4.2 K and at magnetic fields as low as 4.2 T. This demonstrates its practical use as a primary resistance standard.
Electric charge in GaAs native oxides: Annealing characteristics
Authors: Siejka J. , Morawski A. , Lagowski J. , Gatos H. C.
Published: February 2003

Electric charge in the GaAs native oxide formed by anodic oxidation and by plasma oxidation was successfully characterized utilizing contact potential difference measurements. Negative electric charge as high as 1012 q/cm2 was found in all oxide layers independent of their thickness. At room temperature this charge can be effectively screened out by absorption of polar molecules (organic solvents) which thermally desorb at 70 °C. Higher temperature annealing (70–180 °C) irreversibly reduces the charge in oxide by over an order of magnitude. It is shown that the oxide charge reflects the internal electric polarization created during the oxidation process.
Masked and selective thermal oxidation of GaAs-Ga1−xAlxAs multilayer structures
Authors: Liu Hong-du , Zhang Bei , Wang De-huang , Chen Wei-xi
Published: February 2003

The masked thermal oxidation of GaAs was carried out successfully with stripe Cr-Au metal film as a mask. The oxidation rate of Ga1−xAlxAs was found to be much smaller than that of GaAs; this fact means that the thermal oxidation process is selective for the GaAs-Ga1−xAlxAs multilayer structure. By means of this masked and selective thermal oxidation (MSTO) technique, the stripe optical waveguides of GaAs and stripe GaAs-Ga1−xAlxAs double-heterostructure (DH) lasers were fabricated. A demonstration of the stripe guide and some performance of stripe DH lasers are presented.
Josephson effects in ultrashort mean-free-path superconductors
Authors: Lee T. W. , Falco Charles M.
Published: February 2003

We show that it is possible to observe Josephson effects at temperatures up to 17 K in a superconductor with intrinsic mean free path <20 Å, contrary to what is generally thought possible. The temperature dependence of the critical current in Nb3Sn microbridges near Tc is consistent with predictions of the one-dimensional Ginzburg-Landau (ODGL) theory, while microwave-induced steps in the current-voltage characteristics are in excellent agreement with the resistively shunted junction (RSJ) model.
Laser photodeposition of refractory metals
Authors: Solanki R. , Boyer P. K. , Mahan J. E. , Collins G. J.
Published: February 2003

We report the deposition of the refractory metals chromium, molybdenum, and tungsten through the laser-induced gas-phase photolysis of their respective hexacarbonyls. A copper, hollow cathode laser was used at ultraviolet wavelengths matched to peaks in the absorption spectra of the carbonyl molecules. Localized room-temperature metal deposition was achieved by focusing the beam into a cell containing the carbonyl gas and helium as a buffer. No major differences were noted for deposition on a polished silicon wafer, a thermally oxidized silicon wafer, and a quartz flat.
Visible-light spectroscopy by photothermal radiometry using an incoherent source
Authors: Nordal Per-Erik , Kanstad Svein Otto
Published: February 2003

Photothermal radiometry (PTR) is shown to yield optical absorption spectra in the visible region of untreated and strongly scattering material, using Nd2O3 powder, blood, and a green leaf as test samples. A conventional high pressure Xe lamp/monochromator combination was employed for illumination at power levels below 1 mW, with a PbSnTe infrared detector for recording the thermal reradiation. Calculated PTR signals and signal-to-noise ratios are found to compare well with those observed.
Gain and transient absorption profiles for the iodine monofluoride 490-nm and iodine monochloride 430-nm bands under discharge excitation
Authors: Dlabal M. L. , Eden J. G.
Published: February 2003

The optical gain and transient absorption spectra for the IF 490-nm and ICl 430-nm bands have been measured in discharge-excited He, CF3I and NF3 or CCl4 gas mixtures using a flashlamp–-pumped, tunable dye laser. For the IF blue-green band, gain in excess of 1.0% cm−1 was observed over the entire 479–498-nm wavelength interval. Peak optical gain coefficients of ∼3.0% cm−1 and 1.3% cm−1 were observed for IF at 490.7 nm and ICl at 431.3 nm, respectively. For both molecules, strong absorption in the vicinity of the wavelength of maximum gain was identified as being due to the He (2p1P1) excited species. The addition of Ne or Ar to the gas mixture was found to substantially reduce the He (1P1) density, thereby improving the IF small-signal gain-to-absorption ratio as well as the temporal width of the gain pulse.
Bistable reflectivity of phase-conjugated signal through intracavity degenerate four-wave mixing
Authors: Agrawal G.P. , Flytzanis C. , Frey R. , Pradère F.
Published: February 2003

Through intracavity degenerate four-wave interaction the reflectivity of the phase-conjugated signal is shown to exhibit bistability and hysteresis when the driving pump field is varied in a continuous matter. The nonlinear medium inside the Fabry-Perot cavity may be in one- or two-photon resonance with the pump. We suggest suitable materials and discuss possible applications of the bistable response of the reflectivity.
Picosecond injection mode-locking of the XeCl laser
Authors: Reksten G. , Varghese T. , Bradley D. J.
Published: February 2003

Ultrashort pulse generation has been achieved in a UV-preionized transverse discharge XeCl laser by injection mode-locking using the second harmonic of a passively mode-locked Rh 6G dye laser tuned to the XeCl gain bandwidth. Temporal measurements using a Photochron II streak camera showed pulse durations ∼7 ps with single-pulse peak power of ∼150 MW.
Multiple layer spalling in single-crystal Al during He ion implantation
Authors: Greggi J. , Choyke W. J. , Tzeng C. F. , Chamberlain C. L. , Doyle N. J. , Matuza D. M.
Published: February 2003

Al single crystals were implanted with 150-keV He+ ions at room temperature to fluences high enough to produce several layers of exfoliation. Each exfoliated layer occurs by spalling of the entire bombarded crystal surface, and step height measurements show that the spalling occurs at a depth less than the calculated projected range of the He ions. Preliminary evidence from aligned backscattered (channeling) spectra of exfoliated crystals indicates that the He remaining in the crystal after spalling is in the form of bubbles.
Observation of stepwise variations of the lattice parameter on GaxIn1−xAsyP1−y layers grown by liquid phase epitaxy on (100) InP
Authors: Burgeat J. , Quillec M. , Primot J. , Le Roux G. , Launois H.
Published: February 2003

Epitaxial GaxIn1−xAsyP1−y layers several microns thick have been grown on (100) InP substrates by ramp cooling. Using high-resolution double x-ray diffractometry, the profiles obtained from such layers could be resolved into several peaks. Chemical thinning of the layers allowed these peaks to be attributed to successive sublayers having slightly different perpendicular lattice parameters, the lattice parameter within each sublayer being constant.
Buried convex waveguide structure (GaAl) As injection lasers
Authors: Shima K. , Hanamitsu K. , Fujiwara T. , Takusagawa M.
Published: February 2003

A new channeled substrate (GaAl)As double-heterostructure laser with mode control as well as internal current confinement is described. The narrow active region (3–3.5 mm) surrounded by GaAlAs is buried in the etched channel, around which a reverse-biased heterojunction is formed. The threshold current is as low as 20 mA cw, and highly stable fundamental-mode lasing is observed.
Self-aligned GaAs/GaAIAs semiconductor laser with lateral spatial variation in thickness grown by metalorganic-chemical vapor deposition
Authors: Fekete D. , Burnham R. D. , Scifres D. R. , Streifer W. , Yingling R. D.
Published: February 2003

A self-aligned masking technique for growing diode lasers with lateral spatial variations in the active and/or cladding regions by metalorganic-chemical vapor deposition is described. These lasers inherently have both lateral current confinement and lateral real refractive index waveguidance. Threshold currents of 40 mA and differential quantum efficiencies of 30% are measured reproducibly over a wafer.
Influence of cw laser scan speed in solid-phase crystallization of amorphous Si film on Si3N4/glass substrate
Authors: Auvert G. , Bensahel D. , Georges A. , Nguyen V. T. , Henoc P. , Morin F. , Coissard P.
Published: February 2003

Using optical transmission and transmission electron microscopies, structural features of scanned laser crystallized amorphous Si films on Si3N4/glass substrates have been investigated as a function of the laser scan speed. We have found the existence of a critical speed VSC≃30 cm/sec below which only the solid-phase furnace crystallization mechanism occurs yielding fine-grained Si films. For laser scan speeds higher than VSC, the crystallization mechanism is one of coherent and rapid crystallization, which has yielded Si films containing crystallites of dimensions up to 1×1 mm. For this regime, the velocity of the crystallization front is estimated to be as high as 1000 cm/sec.
Effect of lithium on the electrical properties of grain boundaries in silicon
Authors: Young R. T. , Lu M. C. , Westbrook R. D. , Jellison G. E.
Published: February 2003

The effect of lithium on the electrical properties of polycrystalline silicon has been studied using scanning light spot and Hall-effect measurements. It was found that the addition of lithium to polycrystalline silicon significantly improved the majority-carrier mobility and reduced the minority-carrier recombination at the grain boundaries. A possible mechanism for the interaction of Li with grain boundaries is discussed.
Identification of electron traps in thermal silicon dioxide films
Authors: Hartstein A. , Young D. R.
Published: February 2003

The infrared absorption of thermal SiO2 has been measured using the attenuated total reflectance technique. The samples were subjected to various water diffusion and annealing treatments. Electron trapping was also measured in similar samples. The infrared measurements show the presence of SiH, SiOH, and H2O groups in the SiO2 films, particularly after H2O diffusion. Examination of both the infrared absorption results and the electron trapping results show that the electron trap with a cross section of 1×10−17 cm2 is associated with SiOH groups, and that the electron trap with a cross section of 2×10−18 cm2 is associated with H2O.
Infrared photoconductivity of indium (1-x) thallium (x) telluride
Authors: Gaw C. A. , Kannewurf C. R.
Published: February 2003

For selected compositions of the variable band-gap alloy semiconductor In1−xTlxTe the photoconductive response has been observed over the special range from 0.6 to 12.2 mm. The band-gap energy was found to decrease linearly as a function of composition from 0.72 eV at x = 0.48 to a zero band-gap at x≃0.06. All compositions in this range were found to be p type.
Laser-induced waveguide propagation concept
Authors: Newman Leon A. , Smith David C.
Published: February 2003

A laser propagation concept is described, which can be used to eliminate or reduce laser beam spreading due to thermal blooming and diffraction. The concept involves establishing a guiding channel with a laser operating in the TEM01* mode, through which the main laser beam is propagated. A feasibility demonstration of the concept is presented using CO2 lasers.
Subnanosecond electrical modulation of light with hydrogenated amorphous silicon
Authors: Phelan R. J. , Larson D. R. , Werner P. E.
Published: February 2003

A silicon thin-film interferometer structure is used to demonstrate subnanosecond electrical modulation of light. Both thermally and electrically induced modulations are reported. An electrically induced change in refractive index of 4.7×10−4 is observed.
Growth interface breakdown during laser recrystallization from the melt
Authors: Cullis A.G. , Hurle D. T. J. , Webber H. C. , Chew N. G. , Poate J. M. , Baeri P. , Foti G.
Published: February 2003

Morphological instability occurring during high-velocity Si crystal growth from an impurity containing melt is examined in detail. The experimental conditions are achieved by annealing an ion-implanted Si layer with pulsed laser radiation. Computer modeling is employed to understand the heat flow and impurity diffusion behavior that occurs. The stability and size of impurity segregation cells observed to occur under particular conditions are related to the predictions of morphological stability theory.
Monocrystalline aluminium ohmic contact to n-GaAs by H2S adsorption
Authors: Massies J. , Chaplart J. , Laviron M. , Linh N. T.
Published: February 2003

700-K H2S adsorption in the monolayer range onto the GaAs (100) surface induces profound modifications of surface properties. Al in situ epitaxially deposited near room temperature by molecular beam epitaxy (MBE) on a H2S adsorbed semiconductor surface exhibits low-effective Schottky-barrier height. It is shown that this Schottky-barrier lowering can be used to obtain monocrystalline nonalloyed ohmic contacts with low specific-contact resistances.
Laser generation as a standard acoustic source in metals
Authors: Hutchins D.A. , Dewhurst R.J. , Palmer S.B. , Scruby C.B.
Published: February 2003

Absolute acoustic waveforms, generated by laser irradiation of aluminium and mild steel samples, have been detected at epicenter with a wide-band capacitance transducer. Comparison has been made with theoretical waveforms, utilizing theory for wave propagation within a plate and assuming certain source characteristics. Results have shown that laser generation is able to produce three types of standard acoustic source, namely a horizontal force dipole and a normal force monopole, each with step-function time dependence, and a normal force monopole with δ-function time dependence. Underlying generation mechanisms are discussed.
Electrical and optical properties of tellurium-doped silicon
Authors: Lin Alice L. , Crouse Allen G. , Wendt Jerry , Campbell Albert G. , Newman Roger
Published: February 2003

Te-doped Si single crystals were successfully grown by the float zone technique with a doping concentration as high as 7×1016/cm3. The tellurium ionization level in silicon was investigated by both the temperature dependence of the Hall effect and by infrared absoprtion spectral measurements. Close agreement was found between these two techniques. The former shows a thermal activation energy for Si:Te of 0.20 eV, and the latter shows an optical activation energy of 0.1988 eV. The spacings and shapes of the excitation spectra for neutral Te donors in Si exhibits a close resemblance to that of other hydrogenic donor impurities in Si. The maximum absorption cross section for the Te ground-state—continuum transition is σmax = 1.4×1016 cm2 at hν = 0.27 eV.
Si-doped GaAs by SiCl4-AsCl3 liquid solution in AsCl3/GaAs-Ga/H2 chemical vapor deposition system
Authors: Feng M. , Eu V. , Zielinski T. , Kim H. B. , Whelan J. M.
Published: February 2003

We have used SiC14/AsC13 liquid solutions for Si doping of GaAs epitaxial layers grown using the AsC13/GaAs-Ga/H2 chemical vapor deposition system. These solutions can be readily prepared with reproducible compositions and can provide excellent doping control. Fine adjustments in the doping level can be achieved by adjusting the H2 flow rate and by varying the temperature of the SiC14/AsC13 doping solution. The epitaxial layers doped using this technique have excellent room-temperature and liquid-nitrogen mobilities for electron concentrations between 1×1016 and 8×1018 cm−3. This doping method is particularly useful for the growth as GaAs epitaxial layers for field effect transistor devices.
Hydrogenated amorphous silicon films prepared by an ion-beam-sputtering technique
Authors: Kobayashi Michiya , Saraie Junji , Matsunami Hiroyuki
Published: February 2003

Hydrogenated amorphous silicon films were obtained by an ion-beam-sputtering technique. Hydrogen content in the films increases with the increasing flow rate of hydrogen into the sputtering chamber. The optical energy gap increases from 1.4 to 1.62 eV and the electrical conductivity at room-temperature decreases from 10−5 to 5×10−9 Ω/cm with increasing hydrogen content in the films from 0 to 9.2 at.%, respectively.
On the use of AsH3 in the molecular beam epitaxial growth of GaAs
Authors: Calawa A. R.
Published: February 2003

High-quality epitaxial layers of GaAs have been grown in a molecular beam epitaxial system using AsH3 as the arsenic source. Peak electron mobilities of over 130 000 cm2/V sec and 77-K mobilities as high as 110 000 cm2/V sec have been observed in a 5-μm-thick GaAs layer with a carrier concentration of 2.4×1014 cm−3. These layers were grown on Cr-doped semi-insulating GaAs substrates. Initial results indicate that As1 may be the preferred specie for the growth of high-purity GaAs.
Photoluminescence in spray-pyrolyzed CdTe
Authors: Feldman Bernard J. , Boone J. L. , Van Doren T.
Published: February 2003

We report very intense photoluminescence in spray-pyrolyzed CdTe at 77 K. We also notice striking similarities in the luminescence spectra, decay, and temperature dependence between CdTe and other thin-film semiconductors, which we interpret in terms of recombination at defect sites in intergranular regions.
Epitaxial regrowth of thin amorphous GaAs layers
Authors: Grimaldi M. G. , Paine B. M. , Mäenpää M. , Nicolet M.-A. , Sadana D. K.
Published: February 2003

Channeling and transmission electron microscopy have been used to investigate the parameters that govern the crystal quality following capless funace annealing at low temperature (∼ 400 °C) in ion-implanted GaAs. From the results obtained, we concluded that the crystal quality after annealing depends strongly on the thickness of the amorphous layer generated by ion implantation and the number of residual defects increases linearly with the thickness of the implanted layer. Single-crystal regrowth free of defects detectable by megaelectron volt He+ channeling was achieved for a very thin amorphous layer (≲ 400 Å).
Growth kinetics of oxidation-induced stacking faults in silicon: A new concept
Authors: Tan T. Y. , Gösele U.
Published: February 2003

It is reasonable to assume that the volume increase of about 120% associated with the formation of a SiO2 molecule from a Si atom during thermal oxidation of Si is facilitated by viscoelastic flow of the newly formed SiO2 layer at the SiO2-Si interface. This flow is driven by a compressive plane stress. We propose that it is this stress which gives rise to a supersaturation of Si self-interstitials in the Si crystal, and that consequently the growth kinetics of oxidation-induced stacking faults is determined by the kinetics of the viscoelastic flow of the SiO2.
C-V characteristics of SiC metal-oxide-semiconductor diode with a thermally grown SiO2 layer
Authors: Suzuki Akira , Mameno Kazunobu , Furui Nobuyuki , Matsunami Hiroyuki
Published: February 2003

C-V characteristics of Al-SiO2-SiC metal-oxide-semiconductor structures have been measured at low and high frequencies in the dark and under illumination. The oxide layer (432 Å thick) is prepared by thermal oxidation of liquid phase expitaxially grown n-type 6H-SiC using wet oxygen at 1000 °C. The accumulation, depletion, and inversion regions are clearly observed in the C-V characteristics under illumination. In the dark the inversion does not occur, probably owing to the absence of minority carriers due to the large band gap (3.0 eV) of 6H-SiC. The experimental results are briefly discussed and compared with theoretical curves.
A stable hydrogen-sensitive Pd gate metal-oxide semiconductor capacitor
Authors: Armgarth M. , Nylander C.
Published: February 2003

A palladium gate metal-oxide semiconductor device has serious hydrogen-induced drift problems. We have shown that this drift can be eliminated through the introduction of a thin alumina layer between the metal and the silicon dioxide. This makes it possible to use Pd metal-oxide semiconductor devices as stable and accurate sensors for hydrogen.
IR-red GaAs-AlAs superlattice laser monolithically integrated in a yellow-gap cavity
Authors: Holonyak N. , Laidig W. D. , Camras M. D. , Coleman J. J. , Dapkus P. D.
Published: February 2003

Disk-shaped IR-red (Eg ∼1.61 eV) GaAs-AlAs superlattice lasers (41 Lz ∼45-Å GaAs layers, 40 LB ∼150-Å AlAs layers) are demonstrated (cw 300 K) that are monolithically integrated into rectangular yellow-gap AlxGa1−xAs [x∼LB/(Lz+LB), EgX∼2.08 eV] cavities. The yellow-gap AlxGa1−xAs (x∼0.77) is generated by low-temperature Zn diffusion (575 °C, 30 min), which disorders selected portions of the superlattice [portions complementary to regions (disks) masked by Si3N4].
Internal dynamics of long Josephson junction oscillators
Authors: Christiansen P. L. , Lomdahl P. S. , Scott A. C. , Soerensen O. H. , Eilbeck J. C.
Published: February 2003

Numerical computations on a sine-Gordon model of the Josephson junction fluxon oscillator are compared with experimental measurements. Good agreement is found for the voltage current characteristic, oscillator power output, and range of current bias over which oscillation is observed. Our numerical results imply a ’’bunched-fluxon’’ mode of oscillation at larger values of bias current.
New transitions in the photoluminescence of GaAs quantum wells
Authors: Miller R. C. , Kleinman D. A. , Munteanu O. , Tsang W. T.
Published: February 2003

When GaAs quantum wells are optically excited with intensities ≳10 kW/cm2 new peaks appear in the photoluminescence spectrum at low temperatures. The excitation spectra are used to demonstrate that the new peaks correspond to the recombination of electrons in excited well states, n≳1, with holes in n = 1 states. These parity-forbidden transitions, Δn odd, derive their strength from three body interactions that occur at high excitation levels.
Graded-index Pt-Al2O3 composite solar absorbers
Authors: Craighead H. G. , Howard R. E. , Sweeney J. E. , Buhrman R. A.
Published: February 2003

The solar absorption properties of thin composite films of coevaporated Pt and Al2O3, formed with a graded composition-depth profile, are compared to those of an identical film overcoated with a microscopically textured layer of SiOx. The composition grade of the metal-dielectric composite and the surface texturing of the SiOx produces a film with a refractive index slowly varying to unity at the front surface. This results in a very low reflectance of the film. The solar absorptivity of this graded refractive index surface is shown to be a high as 0.98. The production and structure of these surfaces are described as well as a general method of absorptivity enhancement using a microscopically textured surface formed by reactive ion etching.
Pair transitions in Zn3P2
Authors: Briones Fernando , Wang Faa-Ching , Bube Richard H.
Published: February 2003

Laser-excited photoluminescence emission has been measured from 2.5 to 100 °K for single crystals of Zn3P2 grown either by sublimation or by iodine chemical transport. Sublimation-grown crystals show two main peaks at 1.361 and 1.354 eV at 2.5 °K, each of which has a phonon replica displaced by 43 meV, and a third much smaller peak observable only above 20 °K at 1.367 eV. Iodine-transport grown crystals show a broad peak at 2.5 °K at 1.320 eV and its phonon replica displaced by 42 meV. The photon energy for peak emission shifts with excitation intensity as is typical of pair transitions, for the major bands seen at 2.5 °K. Temperature dependence measurements identify the donor and acceptor ionization energies corresponding to each of these bands.
The effect of electroabsorption on the determination of ionization coefficients
Authors: Bulman G. E. , Cook L. W. , Stillman G. E.
Published: February 2003

It has been shown through attempts to obtain pure carrier injection for the determination of electron and hole impact ionization rates (α and β) that electroabsorption of recombination radiation can result in significant contamination of the injected currents in direct band-gap semiconductors. The influence of this contamination on the values determined for α and β and the requirements on the device structure to minimize this contamination are discussed.