bluuebunny/crossref_metadata_2025 huggingface dataset:
The growth of germanium oxide on thin gold layers on germanium substrates
Authors: Lawson E. M. , Tavendale A. J.
Published: February 2003

Isolated GeO2 centers have been observed to grown on the surface of this (≳200 Å) evaporated Au layers covering Ge single-crystal substrates. This effect is strongly enhanced in the presence of water vapor but depressed if an oxide layer forms on the Ge before the Au evaporation. The effect has been examined for samples activated in air at room temperature, 100 and 200 °C, and for 〈100〉 and 〈111〉 oriented substrates, using optical microscopy, scanning electron microscopy, X-ray diffraction and Rutherford backscattering. The relevance of this work to the long-term storage of high purity Ge nuclear radiation detectors is indicated.
Material parameters of In1−xGaxAsyP1−y and related binaries
Authors: Adachi Sadao
Published: February 2003

Various models for calculation of physical parameters in compound alloys are discussed and the results for In1−x Gax Asy P1−y quaternaries are presented. The model used is based on a linear interpolation scheme, and therefore necessitates known values of the parameters for the related binary and ternary alloys. The material parameters considered in the present study can be classified into the following eleven groups: (1) lattice constant and crystal density, (2) thermal expansion coefficient, (3) electronic-band structure, (4) external perturbation effect on the lowest-direct gap, (5) effective mass, (6) dielectric constant, (7) Fröhlich coupling parameter, (8) elastic properties, (9) piezoelectric properties, (10) deformation potential, and (11) excitonic effect. Of particular interest is the deviation of material parameters from linearity with respect to the alloy composition. It is found that the present model provides generally acceptable parameters, in good agreement with the existing experimental data. A detailed discussion is also given on the acceptability of such interpolated parameters from an aspect of the solid-state physics. Key properties of the material parameters for a variety of In1−x Gax Asy P1−y device applications are also discussed.
Structural relaxation and irreversible changes of electrical resistivity of Fe-Ni-Mo-B amorphous alloys
Authors: Allia P. , Andreone D. , Sato Turtelli R. , Vinai F. , Riontino G.
Published: February 2003

The structural relaxation of Fe-Ni-Mo-B alloys with different Mo content is studied through electrical resistivity measurements between the room temperature and the glass transition temperature Tg. The observed behavior of the resistivity during isothermal annealing treatments gives evidence for the presence of competing processes of compositional and topological short-range ordering, whose nature and role are discussed. The variation of the temperature coefficient of resistivity, α, observed after annealing of ribbons, is related to the variation of the degree of topological short-range order, and interpreted on the basis of the theories describing the electrical resistivity and the structural relaxation of amorphous metals. A simple relation between the variation of α after annealing, and the reduction of the alloys’s free volume, is derived and discussed.
Metastable atom density in helium, neon, and argon glow discharges
Authors: Hardy K. A. , Sheldon J. W.
Published: February 2003

A theoretical model of the positive column of a rare gas glow discharge is used to calculate metastable atom densities in the pressure x radius range from 0.01 to 1.0 Torr cm. Two body quenching is shown to be an important loss process for metastables in neon and argon discharges above 0.1 Torr cm. Measurements of metastable atom flux from an anode slit are reported for the title gases and shown to represent the metastable density in the anode fall region of the discharges.
On the determination of particle concentrations in multitemperature plasmas
Authors: Richley E. , Tuma D. T.
Published: February 2003

The use of the multitemperature Saha equation (MSE) of Prigogine1 and Patapov2 for calculating particle concentrations in plasmas is shown to be an invalid procedure. Errors greater than one order of magnitude in the electron density in high-pressure argon and nitrogen electric arc plasmas can be easily incurred by using the multitemperature Saha equation. The alternative kinetic method for calculating concentrations is shown to be based on firm concepts. Simpliying procedures and computational techniques for calculating concentrations with the kinetic method are illustrated with examples.
Theory of magnetic leakage fields from prolate and oblate spheroidal inclusions
Authors: Sablik M. J. , Beissner R. E.
Published: February 2003

Magnetic leakage fields from nonspherical inclusions in magnetic materials are discussed using classical electromagnetic theory. The model used is that of a prolate or oblate spheroidal inclusion embedded in an infinite medium. Deviations from the leakage field behavior of a spherical inclusion are discussed and procedures are suggested whereby one can test for inclusion shape.
Threshold of a thallium-iodide photodissociation laser operated at low pressure
Authors: Henchoz P.-D. , Lüthy W. , Schmiele R.
Published: February 2003

The emission intensity of the 535-nm line of a thallium-iodide photodissociation laser excited with 193-nm ultraviolet radiation is measured as a function of pump energy and vapor pressure. Pressure was varied between 4×10−5 and 0.13 Torr. No threshold for positive gain has been found experimentally. The measurements and computer simulation indicate a possibility of constructing lasers with extremely low excitation energy.
Deposition of chromium films by multiphoton dissociation of chromium hexacarbonyl
Authors: Mayer T. M. , Fisanick G. J. , Eichelberger IV T. S.
Published: February 2003

Focused, pulsed, tunable dye lasers have been used to deposit chromium films by multiphoton dissociation of Cr(CO)6. The multiphoton dissociation of Cr(CO)6 is strongly wavelength dependent. Large increases in deposition rate occur below 350 nm, where the threshold between initial 1 and 2 photon absorption to the lowest lying dissociative state are reached in Cr(CO)6. Lack of correlation of deposition rate with multiphoton ionization (MPI) resonances, and polarity of a biased electrode in the cell, suggests multiphoton absorption leads to decomposition to Cr atoms followed by ionization. Power dependence of the deposition rates and MPI signals indicate saturation in the focal region for wavelengths 280<λ<340, for pulse energies 0.02–0.2 mJ. Deposition on cell windows not in the focal region also appears saturated at the shorter wavelengths. Films deposited on silicon and quartz substrates appear uniform, with visible evidence of melting and regrowth in the center of the deposits due to heating by subsequent pulses. Isotropic deposition of Cr atoms on the substrate from the gas phase, away from the irradiated spot, was also observed. Auger analysis of films deposited in the focal region suggest that significant quantities of carbon are present in the film. Alloying of the Cr with the underlying Si by laser heating of the substrate is also suggested.
The shape factor of the capacitance of a conductor
Authors: Chow Y. L. , Yovanovich M. M.
Published: February 2003

This paper shows, analytically and numerically, that the capacitance is a slowly changing function of the conductor shape. This slow change can be monitored by a ‘‘shape factor’’ which is independent of the conductor size. Because of this slow change, from the tabulation of the shape factor, the capacitance of many conductors of arbitrary sizes and shapes with both convex and concave surfaces, can be estimated to an error of 5% or less.
New formulas for the electromagnetic field of a vertical electric dipole in a dielectric or conducting half-space near its horizontal interface
Authors: King Ronold W. P.
Published: February 2003

New formulas are derived for the electromagnetic field of a vertical electric dipole in a conducting or dielectric half-space. These continuously approximate in accuracy the general complex integrals over the entire practical range, yet are quite simple. They supplement similar formulas for the horizontal electric dipole with which they are compared, and provide the means for studying the interference patterns between the direct and lateral components of the waves and the reflection and transmission of lateral waves at boundaries.
Relativistic electron-beam transport in curved channels
Authors: Vittitoe Charles N. , Morel J. E. , Wright Thomas P.
Published: February 2003

Collisionless single particle trajectories are modeled for a single plasma channel having one section curved in a circular arc. The magnetic field is developed by superposition of straight and curved channel segments. The plasma density gives charge and beam-current neutralization. High transport efficiencies are found for turning a relativistic electron beam 90° under reasonable conditions of plasma current, beam energy, arc radius, channel radius, and injection distributions in velocity and in position at the channel entrance. Channel exit distributions in velocity and position are found consistent with those for a straight plasma channel of equivalent length. Such transport problems are important in any charged particle-beam application constrained by large diode-to-target distance or by requirements of maximum power deposition in a confined area.
Forbidden line emission from highly ionized atoms in tokamak plasmas
Authors: Feldman U. , Doschek G. A. , Bhatia A. K.
Published: February 2003

Collisional excitation rate coefficients and radiative decay rates are interpolated for ions of elements between calcium and krypton and for levels of the 2s22pk, 2s2pk+1, and 2pk+2 configurations, and for the O I, N I, C I, B I, and Be I isoelectronic sequences. With the use of these interpolated atomic data, level populations and relative line intensities can be calculated for ions of these sequences, for levels of the stated configurations. Relative line intensities for transitions between the 2s22pk ground configurations are considered specifically. These transitions are forbidden, e.g., magnetic dipole transitions, and are strong in XUV spectra of tokamak plasmas. The forbidden lines provide important plasma diagnostic information, such as the ion temperature which can be derived from forbidden line profiles. The relative line intensities are presented graphically, in order that they can be used easily by tokamak researchers. Results are given for three values of electron density: 2.5×1013; 1.6×1014; 1015 cm−3, and two values of electron temperature: the ionization equilibrium temperature and twice this temperature. The behavior of the line intensities along the isoelectronic sequences is discussed and the relative importance of excitations into different intermediate levels for populating the upper level of the forbidden line of the B I sequence by cascade is discussed in detail.
Spectroscopic measurements on discharges along a dielectric surface
Authors: Bordage M. C. , Hartmann G.
Published: February 2003

Spectroscopic measurements have been made on quasilinear surface discharges over dielectric slabs. The first time-resolved spectra in the range 200–800 nm have been obtained; we define the light emitting centers (N2 molecular bands in a first period and atomic lines in a second one) and the dielectric substrate effect. We give the form of the rotational temperature variations and the upper value of the electron temperature (5 eV) in the first period. The spatial dimension of this phase seems to be constant at about 23 mm. In the second period the electron densities calculated from the Stark broadening width of the Hα and Hβ lines vary in 8×10−7 s from 7×1017 to 2×1016 cm−3. In the same period, the temperature which is obtained by Saha’s law using the intensity ratios of ionized atomic and neutral lines (oxygen O+,O) and nitrogen (N+,N) decreases from 24 000 to 15 000 K. Using these results we estimate the cross-sectional area of the discharge to be ≂65 000 μm2.
A high-current magnetically stabilized plasma column for fast current-reversal and penetration studies
Authors: Decoste R. , Lachambre J.-L. , Noël P. , Ouellet G. , Mercure H. , Drouet M. G.
Published: February 2003

A magnetically stabilized He-plasma column with a diameter of about 40 mm is operated in the electron density and temperature range of 1021 m−3 and 5 eV, respectively. The temperature is inferred through spectroscopy from the He line-to-line ratio, and the density profile at a given time is obtained on a single shot from interferometry with a large cross-section Mach-Zehnder. At equilibrium a simple balance between ohmic heating and dominant longitudinal conduction losses predicts a core temperature in relatively good agreement with the measurements. At a given time during the long lasting discharge (milliseconds), the 10-kA current can be completely reversed on a time scale (microseconds) much shorter than the classical time for current penetration toward the center of the column. This plasma device is useful for studying basic energy transport and anomalous current-penetration mechanisms involved in hot and relatively dense plasmas.
Filamentary breakdown of gases in the presence of dielectric surfaces
Authors: Pai S. T. , Marton J. P.
Published: February 2003

The effect of dielectric surfaces on the breakdown voltage of gas spark gaps were investigated both theoretically and experimentally. Experiments have been carried out using N2 and other gases at pressures ranging from one to five atmospheres. Several different dielectric materials were used as substrates, having plain and cylindrical surface geometries. The observed results were interpreted by a physical model which was developed for this purpose. In the model, the major physical processes, i.e., electron production and electron loss due to diffusion, were treated in the presence of the dielectric surface. In addition, electron loss due to electron traps on the dielectric surface has also been taken into consideration. The model yields an analytical expression for the breakdown voltage of a given gas spark gap. For the cases studied, the model predictions fit the observed results reasonably well.
Interfacial properties of (Al,Ga)As/GaAs structures: Effect of substrate temperature during growth by molecular beam epitaxy
Authors: Morkoç H. , Drummond T. J. , Fischer R.
Published: February 2003

Selectively doped (Al,Ga)As/GaAs heterostructures exhibit extremely high electron mobilities, particularly at low temperatures, as a result of electron transfer from doped (Al,Ga)As layer(s) into adjoining GaAs layers. These transferred electrons are confined to within about 100 Å of the interface and the electron mobility is extremely dependent on the structural quality of the heterointerface. By studying low-field mobility of single period (Al,Ga)As/GaAs and inverted GaAs/(Al,Ga)As structures, the quality of each interface can be ascertained. Such single period structures have been prepared by molecular beam epitaxy in a substrate growth temperature range of 600–770 °C to investigate heterointerfaces with GaAs on top of (Al,Ga)As and (Al,Ga)As on top of GaAs. While very good interfaces with (Al,Ga)As on top have been obtained in the growth temperature range of 600–750 °C, the interface quality of the inverted structure has shown a very strong dependence on the substrate temperature. The best interface has been obtained at 700 °C, which is inferior to those with (Al,Ga)As on top. This is attributed to the interface roughness when the binary is grown on top of the ’’rough’’ ternary and perhaps to impurity buildup caused by the Al source. The important impact of this study is that quantum well structures are expected to show the best performance when grown at 700 °C.
Properties of zinc phosphide/zinc oxide heterojunctions
Authors: Nayar P. S.
Published: February 2003

The properties of p-Zn3P2/n-ZnO heterojunctions prepared by sputter deposition of ZnO onto Zn3P2 substrate are investigated. Analysis of the experimental data indicates an interface state density greater than 1012 cm−2 and a capture cross section on the order of 10−13 cm2. Using the experimental data a band diagram for Zn3P2/ZnO heterojunction is proposed. Mechanisms responsible for the low, open-circuit voltage are discussed.
The heteroepitaxy of Ge on Si: A comparison of chemical vapor and vacuum deposited layers
Authors: Mäenpää M. , Kuech T. F. , Nicolet M-A. , Lau S. S. , Sadana D. K.
Published: February 2003

Epitaxial growth of Ge on Si has been investigated by two techniques: vacuum deposition and chemical vapor deposition (CVD). Vacuum-deposited Ge layers (physical vapor deposition, PVD) on heated Si substrates (≲500 °C) have smooth surface morphologies with a surface crystalline quality which improves with Ge layer thickness. Layers prepared by the CVD technique at 500–600 °C are comparable with the PVD prepared layers. Main defects in both PVD and CVD layers are dislocations initiating at the Ge/Si interface. Chemical vapor-deposited Ge layers grown at a substrate temperature of 700–800 °C exhibit poor crystalline quality and often are polycrystalline. Chemical vapor-deposited layers grown at a substrate temperature of 900 °C, again are good quality epitaxial layers. In this case, in addition to dislocations, stacking faults are present. All the studied layers are highly conductive and p-type. The conduction and valence band discontinuities determined from electrical measurements are 0.05±0.04 eV and 0.39±0.04 eV, respectively.
Laser-induced metal deposition on InP
Authors: Karlicek R. F. , Donnelly V. M. , Collins G. J.
Published: February 2003

It has been demonstrated that platinum can be deposited on p-type, n-type, and undoped InP via pulsed laser irradiation of polished substrates immersed in an aqueous solution of chloroplatinic acid. Pulsed laser intensities sufficient to initiate thermal decomposition of the InP surface, yet below the threshold at which gross surface damage occurs, cause elemental platinum to be deposited on the surface. The platinum deposits in the form of rectangular islands on the (100) surface and trigonal structures on the (111) InP surface. Under certain conditions, the islands grow together to form smooth platinum films ∼0.5 μm thick. Failure to form deposits at low laser powers indicates that platinum deposition occurs via a thermal mechanism. Auger electron analysis indicates that the platinum deposits are free of oxygen and chlorine contamination. Preliminary results also indicate that this technique may be used to deposit platinum on GaAs, nickel on InP (using aqueous NiSO4 solutions), and gold on InP (using both aqueous and methanolic HAuCl4 solutions). Platinum and gold deposits on InP exhibit ohmic behavior.
Effect of absorbed water on an indium oxide insulator (BeO⋅SiO2)-p-silicon solar cell
Authors: Ito K. , Nakazawa T.
Published: February 2003

An In2O3/p-Si heterojunction solar cell with an interfacial oxide of beryllium and silicon was investigated. It was found that an efficiency of the heterojunction solar cell was rather low initially but was increased gradually up to 10% after the cell was exposed to an ambient containing water vapor. The effect was qualitatively explained in terms of a trap-assisted tunneling model: Hydroxyl groups absorbed in the interfacial composite oxide layer introduce traps into the oxide band gap which assist selective tunneling of electrons.
Thermally stimulated short-circuited current from plasma-polymerized polyacrylonitrile thin film sandwiched between aluminum electrodes
Authors: Mohanachandran K. , Sathianandan K.
Published: February 2003

An appreciable amount of thermally stimulated short-circuited current is observed during heating and cooling between 30° and 160 °C from unpoled plasma-polymerized polyacrylonitrile thin film sandwiched between aluminum electrodes (Al-PAN-Al). The observed current is attributed to the space charges accumulated at the vicinity of the outer electrode producing a charge gradient towards the inner. The disorientation of dipoles also contributes to the thermally stimulated current. The temperature activation energy of 1.37 eV indicates that the electrons are trapped at the covalent bond of the carbon atoms. A temperature gradient and surface strain, developed in the sandwiched system on heating when the electrode thicknesses are different, give an additional contribution to the thermally stimulated current. Observations are also made by the application of a positive voltage to the outer electrode, and the relative magnitudes of the various components are discussed.
Cr gettering by Ne ion implantation and the correlation with the electrical activation of implanted Si in semi-insulating GaAs
Authors: Yagita H. , Onuma T.
Published: February 2003

Electrical activation of implanted Si in gettered semi-insulating GaAs has been studied. The gettering was performed by Ne implantation and heat treatment. Then, Si ion implantations were performed after removing the surface layer of the gettered substrate to various thicknesses. Higher activation than the native value has been observed when the removed layer thickness is about 1 μm. According to the measurements of Cr concentration profile and the estimation of Cr concentration from the Si activations, the cause of the increased activation has been found to be the Cr decrease in a region deeper than the Ne-implanted region.
Simple estimate of electromigration failure in metallic thin films
Authors: Mogro-Campero A.
Published: February 2003

Electromigration failure in thin metallic films has been studied in detail for aluminum and gold. A simple expression is given here, which can be used to provide rough estimates of median time to failure for thin films of other metals, when experimental information on them is not available.
Electrical conduction at high fields in single-injection, solid-state diodes with traps lying above the Fermi level
Authors: Sharma Y. K.
Published: February 2003

The approximate solutions for the current-voltage characteristic have been given for the single-injection current at high fields in solid-state diodes with a single set of traps lying above the thermal-equilibrium Fermi level. It is shown that there is a large change in current occurring over a restricted change in voltage and pure space-charge regime follows 3/2 power law dependence of the current on voltage.
The variation of residual impurities in ZnSe crystals used in light-emitting diode fabrications
Authors: Kun Zoltan K.
Published: February 2003

Recent reports in the literature suggest that residual impurities, probably interstitial lithium, are responsible for the strong compensation of p-type conductivity in ZnSe. Data presented here support these findings. ZnSe boules that had high Li content, as determined from the pair band of the emission spectra, produced poor light-emitting diodes (LED’s). At the same time LED’s were consistently good when boules that contained less residual Li were used. Ion microprobe measurements showed that one of the processes that takes place during LED fabrication is the reduction of the residual Li content. These two findings together show that low Li content is a prerequisite for good LED formation.
A ruthenium dioxide-semiconductor Schottky barrier photovoltaic device
Authors: McEvoy A. J. , Gissler W.
Published: February 2003

Recent evidence establishes a metallic conduction mechanism in ruthenium dioxide, RuO2. An experimental investigation determined that a Schottky barrier was formed at a ruthenium dioxide/semiconductor interface. A photovoltaic device has been fabricated by rf reactive sputtering of ruthenium dioxide on an etched single-crystal cadmium sulphide, Cds, surface. Its photovoltaic characteristics are reported. The structure may also have applications in photoelectrochemistry.
Comments on the plasma annealing model to explain the dynamics of pulsed laser annealing of ion-implanted silicon
Authors: Bhattacharyya Anjan , Streetman B. G. , Hess K.
Published: February 2003

Experimental problems are discussed associated with optical transmission and Raman spectroscopy measurements during pulsed laser annealing of silicon. In view of these problems, the use of these experiments in support of a plasma annealing model is questioned.
On the current-voltage characteristics of amorphous hydrogenated silicon Schottky diodes
Authors: Chen Inan , Lee Sanboh
Published: February 2003

First principle calculations of amorphous hydrogenated silicon Schottky barrier and p-i-n diodes’ current-voltage characteristics have revealed an interesting relation between the observed quality factor and the composition of the diode current. The diode current consists of two components: (1) The drift/diffusion current, JD, which is virtually independent of carrier recombination mechanism, and (2) the recombination current JR. Each component has a characteristic value of the quality factor, β (inverse slope of semilog J-V plot): β<1.1 for JD and β⩾1.6 for JR. In addition, the relative magnitudes of the two components vary with the device thickness, the density of localized states, and the surface barrier potential. The difference in the quality factors observed in Schottky barriers and in p-i-n diodes can be interpreted as an indication of change in the dominant component from JD to JR, due to a larger surface potential in the latter device.
Second-harmonic generation at resonance absorption and modified plasma density profile
Authors: Dragila R.
Published: February 2003

Efficiency of the second-harmonic generation by a p-polarized electromagnetic wave that is obliquely incident upon an inhomogeneous plasma is analytically investigated considering the steepened plasma density gradients characteristic for the laser-produced plasmas.
Intensity-induced precessional rotation of electromagnetic waves in a plasma
Authors: Bhattacharyya B. , Chakraborty B.
Published: February 2003

Intensity-dependent rotation of the vibration ellipse of strong electromagnetic waves propagating colinearly in a plasma is studied (i) in the resonant case in which the beat frequency of two waves equals the plasma frequency ωp and (ii) in the resonant problem of parametric stimulation of two noise fields by two powerful pump fields when the beat frequency of two of these waves equals ωp in the same plasma.
Kinetics of laser-induced solid phase epitaxy in amorphous silicon films
Authors: Kokorowski S. A. , Olson G. L. , Hess L. D.
Published: February 2003

The kinetics of laser and furnace-induced solid phase epitaxial crystallization of As-implanted amorphous layers (∼0.16 μm) on Si (100) substrates was studied using a time-resolved optical reflectivity technique. Epitaxial rates from 10−10 to 0.2 cm/sec were measured over a temperature range from 750 to 1550 °K at two different As concentrations, ∼2×1019 cm−3 and ∼4×1019 cm−3. Temperatures achieved during cw-laser heating were calculated using a three-dimensional steady-state thermal analysis. The crystal growth rates are accurately described by the Arrhenius equation v = v0e−Ea/kT , with Ea dependent on the dopant concentration; Ea = 2.62 and 2.52 eV for the lower and the higher concentrations, respectively. Additionally, the rate measurements at high temperatures imply that the melt temperature of amorphous Si is greater than 1550 °K.
A photoelectrochemical determination of the position of the conduction and valence band edges of p-type CuO
Authors: Koffyberg F. P. , Benko F. A.
Published: February 2003

Lithium-doped p-type CuO is a low mobility semiconductor with an indirect band gap of 1.35 eV and a flatband potential of +0.55 V, with respect to the saturated calomel electrode (SCE), when in contact with an electrolyte at a pH of 9.4. Its valence band lies 5.42 eV below the vacuum level and is made up mainly from the Cu2+−3d wavefunctions. An oxygen-2p type band is at 7.33 eV, in agreement with a semi-empirical estimate. Its performance as a photoelectrode for the solar photoelectrolysis of water is rather poor, due to the presence of recombination centers in the band gap and its chemical instability. As photoelectrolysis electrodes, oxides with 3d-type valence bands may have advantages over the more common oxides with 2p-type valence bands.
Formation of metastable species in hydrogen thyratrons
Authors: Gundersen Martin , Guha Shekhar
Published: February 2003

Direct spectroscopic evidence is presented for the formation of metastable molecular and atomic species in hydrogen thyratrons. Because these states have long radiative lifetimes and energies greater than 11 and 10 eV, respectively, their behavior may effect thyratron operation.
On the dynamical response of particulate-loaded materials. I. Pressure-shear loading of alumina particles in an epoxy matrix
Authors: Chhabildas L. C. , Swegle J. W.
Published: February 2003

Results of a pressure-shear impact experiment conducted on alumina-filled epoxy are presented. In the pressure-shear experiment the coupled longitudinal and transverse motion generated by the normal impact of Y-cut quartz is transmitted into an alumina-filled epoxy sample. This provides data on the response of the sample material to more general loading conditions than those obtained in the uniaxial strain configuration and allows the development of more complete material models. Experimental results are presented in this paper, and a model for alumina-filled epoxy which incorporates the data is presented in the following paper [J. Appl. Phys. 53, xxxx (1982)].
Deuterium permeation through copper with trapping impurities
Authors: Mitchell D. J. , Harris J. M. , Patrick R. C. , Boespflug E. P. , Beavis L. C.
Published: February 2003

The time dependence of the deuterium permeation rate through impurity-doped copper membranes was measured in the temperature range 300–700 °C. Copper membranes that were doped with Er, Zr, and Ti all exhibited permeabilities that were nearly equal to pure copper, but the apparent diffusivities were smaller than those for pure copper by factors of 10–100 over the experimental temperature range. The permeation characteristics of these alloys appear to be altered from those for pure copper due to trapping of deuterium at sites that are associated with the impurity atoms. It is shown that the deuterium permeation rate through the copper alloys can be expressed in an analytical form that is analogous to that for pure copper, except that the apparent diffusivity takes on a value which depends on the trap concentration and binding energy for deuterium. The binding energies that are calculated for the alloys are used to determine the lag time which is required for deuterium or hydrogen to permeate through initially evacuated membranes. The lag times for copper alloys containing about 1% Er, Zr, or Ti are many orders of magnitude longer than for pure copper at room temperature. Copper alloys containing Cr do not appear to exhibit deuterium trapping. Nuclear reaction and backscattering analyses were used to help determine the effect or surface oxides on the permeation measurements.
Low-temperature formation of polycrystalline silicon films by molecular beam deposition
Authors: Matsui Makoto , Shiraki Yasuhiro , Maruyama Eiichi
Published: February 2003

Textured polycrystalline-silicon films are obtained by molecular beam deposition under ultrahigh vacuum at temperatures between 400 and 700 °C. Thinner films have a 〈110〉 preferred orientation, whereas a 〈100〉 preferred orientation is dominant in films with a thickness of above 1 μm. The deviation of the textured axes decreases from 20° to 10° with raising substrate temperature from 400 to 700 °C. A depth-dependent preferred orientation inside the film is also observed.
Photoluminescence identification of ∼77-meV deep acceptor in GaAs
Authors: Yu Phil Won , Reynolds D. C.
Published: February 2003

A study of the photoluminescence emission band at ∼1.44 eV present in GaAs has been made at temperatures between 2–300 K. Changes in photoluminescence excitation intensity, emission energy, and emission intensity as a function of temperature lead to the identification of a 77±2-meV deep acceptor. The temperature dependence of the emission-peak energy follows Eagles’ model for the free electron-neutral acceptor transition. The origin of the acceptor is discussed on the basis of the presence of a high concentration of arsenic vacancies.
Waveguiding in stripe-geometry diode lasers with power-law profiles
Authors: Olshansky Robert
Published: February 2003

Simple closed-form expressions are derived for the modal propagation constant and field intensity of stripe-geometry double-heterostructure laser diodes with dielectric profiles of the form ε(x) = ε(0)−Δε‖x/w‖α. These expressions are useful for analyzing near-field and far-field data when the parabolic approximation is not sufficiently accurate.
Observation of surface cracks with scanning acoustic microscope
Authors: Yamanaka Kazushi , Enomoto Yuji
Published: February 2003

Surface cracks introduced in soda lime glass and MgO single crystal have been examined with a 200- and 420-MHz scanning acoustic microscope. A fringe pattern was observed around the cracking line on the surface which could not be observed with an optical microscope. A simplified model is proposed in which fringe formation is due to the interference between the leaky surface wave reflected by the crack and the specularly reflected wave at the surface or the leaky surface wave that did not reach the crack. By monitoring these fringes, a Hertzian crack in soda lime glass with a depth as small as 25 μm was detected. The direction of crack orientation relative to the surface normal was also obtained from the asymmetrical contrast distribution of the fringes.
Correlation of electrical carrier and atomic profiles of S implants in GaAs
Authors: Yeo Y. K. , Park Y. S. , Kwor R.
Published: February 2003

A comparative study of secondary ion mass spectrometry (SIMS) atomic profiles and electrical profiles for S-implanted GaAs has been made. For all doses, the electrical profiles are in good agreement with the SIMS profiles in the deep side of the samples, where there is no significant implantation damage. For low dose, the implanted S undergoes substantial redistribution during thermal annealing throughout the entire implanted region while for high dose, S redistributes to a much lesser extent in the implanted peak region. It is suggested that unannealed implantation damage and S precipitation are responsible for the low electrical activation of S implants in GaAs at high dose, and residual surface defects may be a limiting factor at low dose.
Correlation between nitrogen concentration and In content in InxGa1−xP liquid phase epitaxy layers
Authors: Grembowicz J. T. , Pastuszka B. , Kaniewski J. , Mroziewicz B.
Published: February 2003

Photovoltage measurements on InxGa1−xP light-emitting diodes (LED’s) fabricated by double liquid phase epitaxy have shown a definite correlation between N concentration and In content in InxGa1−x P alloys with x≲0.02. The drop of N concentration in the active region of LED’s is followed by marked decrease of the quantum efficiency of the diodes.
Luminescence imaging: A novel approach to surface studies
Authors: Lahav Noam , Horowitz Paul
Published: February 2003

The use of a ’’luminescence microscope’’ is suggested as an imaging system to form two-dimensional pictures of the distribution of light-emitting areas on the surface of a sample undergoing a luminescence reaction. A prototype of this instrument, as well as first results of ’’luminography,’’ is presented.
Etch rates for two material selective etches in the InGaAsP/InP system
Authors: Conway K. L. , Dentai A. G. , Campbell J. C.
Published: February 2003

Two material selective etching solutions have been evaluated for the InGaAsP/InP system. One of these solutions etches the InGaAsP-InGaAs alloys and stops at InP, while the other etches InP and stops on the ternary or quaternary alloys. Room-temperature etch rates were measured for both etches on bulk and liquid phase epitaxial materials.
Nuclear magnetic ordering in solid 3He (invited)
Authors: Osheroff D. D.
Published: February 2003

Solid 3He is the most quantum mechanical of the inert gas solids. In the bcc solid close to the melting pressure, 3He atoms exchange lattice sites with their neighbors millions of times each second, thereby reducing their zero point energy. This atom-atom exchange leads to a spin exchange energy in the solid which is nearly ten thousand times larger than the dipole-dipole energy between neighboring 3He atoms, and as a result, nuclear antiferromagnetism in solid 3He occurs at the unusually high temperature of about 0.001 K. This temperature can be produced directly with modern refrigeration techniques, and recent experimental studies have given us our first detailed picture of the resulting antiferromagnetic states. In magnetic fields below 4 kOe a highly anisotropic sublattice structure with a [100] symmetry is found. Above 4 kOe, a very different structure is observed with apparent cubic symmetry and a nearly field-independent magnetization, which is about 60% of the saturation magnetization. Although the exchange Hamiltonian for this system cannot be determined from first principles, modern multiple exchange theories appear capable of predicting many of the observed features.
Abstract: One-dimensional Heisenberg antiferromagnets with random exchange (invited)
Authors: Clark W. G.
Published: February 2003

In recent years a class of materials has emerged whose low-temperature magnetic properties are those of a random exchange Heisenberg antiferromagnetic chain (REHAC).1 Most of them are based on conducting salts of TCNQ with disorder, which can be intrinsic or induced. The most studied example is quinolinium ditetracyanoquinodimethanide [Qn(TCNQ)2], which at high T has one unpaired spin per formula unit. Several characteristic properties exhibited by this material are discussed. They include the susceptibility χ∝T−α, low-temperature magnetization M∝H1−α, low field H and temperature T specific heat C∝T1−α, exchange narrowed ESR lines,2 two component electron spin relaxation to the exchange reservoir and the bath,2 and the absence of any three-dimensional ordering transition down to T∼1 mK.3 The exponent α shows a quasiuniversal behavior,4 with α≃0.8. Recent models for the thermodynamics of H using renormalization methods are discussed and compared with the experimental results.1 This report is based in part on work supported by NSF Grant DMR 81-03085.      1For a recent review of this subject, see W. G. Clark, Physics in One Dimension, edited by J. Bernasconi and T. Schneider (Springer, Berlin, 1981), p. 289.  2L. C. Tippie and W. G. Clark, Phys. Rev. B 23, 5854 (1981).  3H. M. Bozler, C. M. Gould, and W. G. Clark, Phys. Rev. Lett. 45, 1303 (1980).  4J. Sanny, G. Grüner, and W. G. Clark, Solid State Commun. 35, 657 (1980).
Excitation spectrum of ferromagnetic Heisenberg chains
Authors: Schneider T. , Stoll E.
Published: February 2003

We present a review of the developments leading to our present understanding of the excitation spectrum of planar and uniaxial Heisenberg chains (xxz) as probed by dynamic form factors. Exact zero-temperature results, finite-chain calculations for s = 1/2, and molecular-dynamics results, realistic for s≫1 and T≳0, are discussed, and the role of envelope solitons clarified.
Solitons in magnetic chains: A functional integration approach
Authors: Leung K. M.
Published: February 2003

The free energies and the static spin correlation functions for the 2π- and π-sine-Gordon systems are calculated from a functional integration approach. The free energies for these systems are rather similar but the soliton contributions to the static two-spin correlation functions can be drastically different. The reasons for these behaviors are discussed, and the nature of the T = 0 phase transitions for the π system is briefly analyzed.
The mechanism of photoconductivity in polycrystalline cadmium sulphide layers
Authors: Orton J. W. , Goldsmith B. J. , Chapman J. A. , Powell M. J.
Published: February 2003

The mechanism of photoconductivity in polycrystalline CdS has been studied over the temperature range 100–300 K using Hall-effect and conductivity measurements in the dark and under white light illumination. Samples were prepared in thin film form by spray pyrolysis and as power-binder mixtures. Dark conductivities covered the range 10−9–101 Ω−1 cm−1. Dark conductivity is interpreted in terms of a two-dimensional version of the grain-boundary barrier model developed by Seto for polycrystalline Si. Except at very low carrier densities, Hall mobilities are found to be thermally activated, and intergrain barrier heights φb are derived for spray pyrolysis layers with doping levels covering the range N = 1014–1018 cm−3. A maximum barrier φbmax ≊0.2 Ev is found at a corresponding doping level, Nmax ≊2×1016 cm−3, which represents the situation where the barrier depletion layers just extend through the whole grain. From this we derive a mean grain diameter of 0.3 μm in good agreement with the result of transmission electron microscopy. For samples having N<Nmax the average free carrier density n̄≪N and photoconductivity occurs entirely through an increase in n̄ up to the point where the depletion regions begin to contract away from the center of the grains. For samples having N≳Nmax both μ and n̄ increase. The detailed variations of μ and n̄ are interpreted in terms of the Seto model with the added hypothesis that photogenerated holes are all trapped at grain boundaries. Hall-effect measurements are interpreted on the assumption that the Hall coefficient R measures the average carrier density in the grain, i.e., R = (n̄e)−1, and we note that n̄ may differ significantly from the doping level N, even when N⩾Nmax. Photo-Hall results provide evidence in support of this hypothesis.
Velocity lens model for longitudinal beam dynamics in inductive linear ion accelerators
Authors: Humphries S.
Published: February 2003

Models are presented which facilitate investigation of the longitudinal dynamics of non-relativistic beams in inductive linear accelerators. In the limit that changes in the beam distribution take place during passage through many acceleration gaps, it is shown that the equations governing the response of the beam to the gap voltages are the same as those for the transverse motions of particles passing through an array of thin lenses. The analogy with lenses provides insight into macroscopic beam current profiles, longitudinal emittance growth, beam stability, and velocity bunching.
Polarization sensitive laser calorimetry
Authors: Miles Perry
Published: February 2003

Techniques used currently to determine bulk and surface laser absorption coefficients of highly transparent materials have drawbacks both inherent and practical that limit their accuracy. Conventional bar calorimetry attempts a two-coefficient characterization of nine separate physical absorption sites. Photoacoustic techniques require in situ calibration sensitive to sample geometry and material. This paper proposes a new technique in which a set of conventional ballistic laser calorimetry measurements are made on a single prismatic sample. Systematic changes in the polarization and direction of propagation of the laser beam can lead to an explicit determination of individual surface and bulk absorption coefficients. An equilateral prism sample provides a set of independent measurements sufficient to establish the bulk absorption in each of three internal paths and two absorption components on each of the three surfaces. This geometry can be used, in principle, for materials with refractive indices less than 2; more practically, for indices less than 1.7. For higher indices, a truncated prism is proposed which allows seven independent measures to deduce eight absorption components. As assumption of constant surface anisotropy is proposed to complete the analysis. Design criteria for the prism shape are presented, along with analytical expressions for all relevant absorption experiments, and for the simplest cases of uniform, isotropic high and low index materials.
Controlled operation of a Na2 dimer laser
Authors: Schmiele R. , Lüthy W. , Weber H. P.
Published: February 2003

A Na2 dimer laser which is excited longitudinally by a single-frequency Ar+-ion laser at 488.1 nm exhibits a very narrow gain profile in forward direction of the pump beam. Using linear resonators with lengths ≲2 m, the gain profile can be appreciably narrower than the spacing of adjacent axial resonator modes. Only if a resonator mode coincides with the gain profile, laser oscillation is shown to occur. This leads to a very unstable emission with low efficiency. Possibilities to achieve controlled emission are demonstrated.
Electrical derivative characteristics of InGaAsP buried heterostructure lasers
Authors: Wright P. D. , Joyce W. B. , Craft D. C.
Published: February 2003

Results of a study of the electrical derivative characteristics of InGaAsP buried heterostructure lasers are presented. By considering current-leakage paths and electrical contact nonlinearities, an equivalent circuit model appropriate to the buried heterostructure laser has been developed. Solutions for the theoretical electrical derivatives of series-parallel-reducible networks have been obtained and applied to the equivalent circuit model of the buried heterostructure laser. Comparison of experimentally measured and calculated electrical derivative characteristics provides both qualitative and quantitative information concerning the distribution of current and voltage in buried heterostructure lasers. By combining the techniques of electrical-derivative measurement and equivalent-circuit modelling, an improved understanding of the properties of buried heterostructure lasers has been established.
Optimization of the energy output in pulsed lasers
Authors: Keren Eliezer , Kafri Oded , Band Yehuda B.
Published: February 2003

The time dependence of the reflection of the output mirror for a two-level pulsed laser is determined for an arbitrary time-dependent pumping rate. The result derived using the methods of optimal control theory is given as an explicit function of time. The optimal reflectivity eliminates relaxation oscillation spikes so that the output is a smooth function of time. Moreover, the peak instantaneous intracavity photon density of the optimal solution is significantly reduced relative to the photon density using constant reflectivity, thereby increasing the fluence without reaching the damage threshold. Numerical examples for a Nd+3/YAG system is provided. A practical feedback mechanism for controlling the output mirror reflectivity as a function of time that well approximates the optimal solution is proposed.
The magnetic field due to a number of toroidal conductors
Authors: Caldwell J.
Published: February 2003

This is an extension of the work carried out by Gibson and Caldwell on the optimization of the uniformity of the magnetic field produced in the bore of a toroidal conductor of rectangular cross section. In this paper the work is extended to consider the magnetic field due to a number of conductors. The usefulness of the work is assessed by comparing it to the work of Garrett, and numerical results are given for particular coil parameters.