bluuebunny/crossref_metadata_2025 huggingface dataset:
Faraday rotation in alcator tokamaks
Authors: Gomez C. , Lax B.
Published: February 2003

The Faraday effect should provide a direct method for the measurement of the current density profile in a tokamak fusion device. Measuring the angle of rotation of linearly polarized far-infrared beams propagating along several vertical chords in the poloidal plane and then applying proper inversion techniques, will provide information about the current density profile. Assuming the Voigt effect is small, a solution is found using the WKB approximation. Due to the large Ohmic heating currents and plasma densities in Alcator C, sufficiently large angles of rotation are produced with a relatively short wavelength sufficient to make the Voigt and refractive effects negligible. For Alcator A the peak rotation is found to be the order of 4°, for Alcator C it is 12°. These values were calculated assuming a wavelength of 120 μm and ’’typical’’ plasma parameters. In Alcator C, in particular, the large rotation angles should allow measurement of the poloidal field over most of the plasma cross sections.
Theory of the glow transition within a plasma sheath
Authors: Smy P. R. , Clements R. M.
Published: February 2003

The usual model for a sheath formed adjacent to a cathode immersed in a high pressure plasma is modified for ionization and secondary emission effects. It is found at high voltages, when the product of the ionization coefficient within the sheath and the sheath thickness is of order unity, that the sheath can collapse catastrophically with an accompanying decrease in its impedance of many orders of magnitude. The calculations, which are numerical, are particularly well suited to the usual description of the ionization coefficient in terms of two empirical constants, appropriate to a given gas. As a result, it is possible to give a simple curve of sheath breakdown voltage versus the quantity ji0/μiP3 (where ji0 is the ion current density, μi the ion mobility and p the pressure). The breakdown curve for air is given as an example.
Capture-cross-section determination by transient-current trap-filling experiments
Authors: Borsuk Judith A. , Swanson Richard M.
Published: February 2003

A detailed analysis is presented of capture-cross-section determination by transient-current (e.g., current deep-level transient spectroscopy) trap-filling measurements. Data for electron capture by the Au acceptor illustrates the technique. Calculations including spatially dependent capture and the competition of emission with capture are shown to match the experimental data. Results using the parabolic band-bending approximation are compared with those in which Poisson’s equation is solved exactly. The latter is found to fit the data slightly better. By curve fitting this calculation to trap-filling data, the electron capture cross section σn of the Au acceptor is found to be 7.1±0.3×10−17 cm2. The effects obtaining when the trap concentration NT cannot be assumed negligible compared to the shallow-dopant density ND are investigated, and found to be unimportant for the samples studied here (NT/ND≊0.3). It is demonstrated that σn cannot be obtained accurately from the initial slope of a semilog plot of the effective fraction of traps remaining empty at the end of the trap-filling pulse versus filling-pulse width, as is conventionally done for capacitance-transient measurements.
Annealing of phosphorus implanted silicon wafers by multiscanning electron beam: Solar cells application
Authors: Bentini G. G. , Galloni R. , Gabilli E. , Nipoti R. , Olzi E. , Servidori M. , Turisini G. , Zignani F.
Published: February 2003

Silicon wafers (100) and (111) orientation, implanted at 10 KeV energy with 2×1015 P+/cm2 have been annealed with a fixed 20-kV multiscanning electron beam at different current densities. Doping profiles and some transport properties (i.e., carrier diffusion length, mobility, etc.) have been studied to define the parameters for optimal annealing conditions. Analysis of the residual damage, and of the defects induced by the electron beam itself when too high annealing current densities are used, has been made by using Rutherford backscattering, transmission electron microscopy, and x-ray topography. It has been found that very high doping levels up to 1021 at/cm3, exceeding equilibrium solid solubility limits, can be obtained with the scanning electron beam technique working in the current density-time range which involves a solid phase epitaxial regrowth of the damaged layer. Such conditions have been used for fabricating good efficiency solar cells.
The Zr-O-W(100) emitter and coadsorption of zirconium and carbon monoxide on W(100)
Authors: Danielson L. R.
Published: February 2003

The properties of the Zr-O-W(100) emitter and the coadsorption of zirconium and carbon monoxide on W(100) have been studied by Auger electron spectroscopy and work function measurements. The thermionic work function of the Zr-O-W(100) emitter from 1450 to 1800 K is 2.54 eV with a pre-exponential value of 4. The field-emission retarding potential work function is 2.75–2.80 eV. A Zr-O-W(100) emitter free of bulk carbon possesses a longer lifetime than an emitter containing bulk carbon. Heating the emitter in carbon monoxide causes diffusion of zirconium into the bulk, and vacuum annealing restores the zirconium to the surface. The coadsorption of zirconium and carbon monoxide on W(100) followed by vacuum annealing produces a minimum work function of 2.3 eV. The adsorption sequence is important and lower work functions correlate with higher carbon concentrations. The stability of the 2.3 eV surface under background gas adsorption and high-temperature heating is discussed.
Nondestructive analysis of Si3N4/SiO2/Si structures using spectroscopic ellipsometry
Authors: Theeten J. B. , Aspnes D. E. , Simondet F. , Erman M. , Mürau P. C.
Published: February 2003

The electrical properties of Si3N4/SiO2/Si structures, which are currently used in integrated circuits technology, are largely dependent upon the structure and the chemical composition of the interface regions which may be a few Å thick. Such locked-in regions are difficult to analyze by destructive techniques like secondary ion mass spectroscopy (SIMS) or Auger electron spectroscopy (AES) with ion milling. We show that spectroscopic ellipsometry, operating in the 1.5–6 eV range, is capable of nondestructively analyzing the interface region. The method is demonstrated on standard atmospheric pressure chemical vapor deposition (CVD) nitride layers and the results are compared with ion-milling AES data. The effects of O2 annealing and NH3:SiH4 ratios are also investigated.
Dynamics of the DC-SQUID
Authors: Ben-Jacob E. , Imry Y.
Published: February 2003

The dynamics of two inductively-coupled Josephson junctions, driven by a current source and by an external flux were studied. Approximate analytical arguments and numerical simulations were used. The various characteristics times of the DC-SQUID were systematically obtained as functions of the parameters of the junctions and the superconducting loop. We have studied the effects of the external magnetic field and quasiparticle conductance on the structure of the I-V characteristics. The transition times between the various branches of the I-V characteristics were calculated using approximate analytical arguments as well as numerical simulations. The results, both for the I-V characteristics and the transition times, were compared with existing experiments.
Magnetostatic spin-wave modes of a heterogeneous ferromagnetic double layer
Authors: Grünberg P.
Published: February 2003

The theory for the magnetostatic spin-wave modes has previously been presented for homogeneous nonsymmetric double layers [J. Appl. Phys. 51, 4338 (1980)]. It is now extended to the heterogeneous case, where the magnetizations in the two films are allowed to be different. A restriction is still made with respect to inplane magnetization, transverse propagation of the spin waves, and neglect of exchange. Some limiting cases are found to be in agreement with results obtained by other authors. Patterns of the m- and b-fields of some typical modes are also presented.
Influence of the backing substrate on the photoacoustic effect of thermally thin samples
Authors: Parpal J.-L. , Monchalin J.-P. , Bertrand L. , Gagné J.-M.
Published: February 2003

The photoacoustic signal for a thermally thin sample depends, both in magnitude and phase, on the thermal properties of the backing substrate. We have investigated the frequency dependence for such a sample when the backing has: (a) low conductivity and low density (air), and (b) high conductivity and high density (water) with identical heat generation conditions. The data we have obtained verify the unidimensional heat flow theory of Rosencwaig and Gersho and can be explained, in simple terms, by considering the relative magnitude of the heat dissipated in the sample, the gas, and the backing substrate.
Free-electron Čerenkov laser
Authors: Šoln Josip
Published: February 2003

Through the S matrix approach, a model of the free-electron Čerenkov laser is formulated. Here the classical electron current in the field of the wiggler magnet interacts with a quantized radiation field in a refractive medium of finite extent. The S matrix yields the radiated multiphoton distribution function where initially an arbitrary number of photons is present in the interaction volume. From the distribution function, one readily obtains the mean photon multiplicity, which in turn allows us to evaluate the gain at a given frequency. The imposition of the quantum recoil on the calculations affects the gain inasmuch as it now can be evaluated in principle for small and large initial photon densities. The presence of the refractive medium can enhance the calculated gain in most of the radiation frequencies as compared with a vacuum.
A photoluminescence study of beryllium-doped GaAs grown by molecular beam epitaxy
Authors: Scott G. B. , Duggan G. , Dawson P. , Weimann G.
Published: February 2003

The 300-K photoluminescence internal quantum efficiency of beryllium-doped GaAs grown by molecular beam epitaxy at 580 °C from As4 under arsenic stable conditions is limited by nonradiative recombination with τNR = 3.5 to 5.6×10−10 s. τNR remains in this range while 1.3×1015 <  NA−ND  < 8×1017 cm−3. Layers grown at fixed NA−ND = 3×1016 cm−3 and constant thickness exhibited a 140-fold increase in internal efficiency as the growth temperature was raised from 480 to 660 °C. The corresponding internal efficiencies were calculated to be 0.054%,  ⩾ 0.69%, and  ⩾ 7.6%, respectively. The 6.5-K photoluminescence spectra of layers grown at 580, 620, and 660 °C showed no significant differences and exhibited none of the new bound exciton lines reported by Kunzel and Ploog to be present in molecular beam epitaxial GaAs grown from As4 below 610 °C.
High-purity ZnSe obtained by metalorganic chemical vapor deposition epitaxy
Authors: Blanconnier P. , Hogrel J. F. , Jean-Louis A. M. , Sermage B.
Published: February 2003

High-quality homoepitaxial layers of ZnSe have been obtained by the metalorganic method. Optical measurements demonstrate the good purity of these samples. Resonant electronic Raman-scattering experiments have allowed the identification of some residual donors and shown that most of them originate in the substrate. A shallow donor, with an ionization energy of about 30.4 meV, not yet mentioned in the literature, has been observed and is believed to be iodine. Excitation Spectroscopy and Selective Pair Luminescence techniques have shown the existence of a new shallow acceptor associated to a donor-acceptor pair transitions band peaking at 2.75 eV, the ionization energy of which would be about 56 meV. The resonant electronic Raman-scattering technique, used here for the first time to investigate donors, appears much more sensitive than classical luminescence to characterize the semiconductor materials.
Laser implantation of impurity atoms into silicon and gallium-arsenide single crystals
Authors: Damgaard S. , Nevolin V. I. , Petersen J. W. , Weyer G. , Andreasen H.
Published: February 2003

Sn and Fe have been incorporated into the bulk of silicon single crystals by means of an irradiation of thin metallic surface layers of these elements with light pulses from a Nd-glass laser. Analogously, Sn has been implanted into gallium-arsenide single crystals and furthermore, a successful implantation of Sn into GaAs has been achieved by an irradiation from the backside of the sample. Depth profiles of the implants have been determined by Rutherford backscattering analysis. The state of the impurity atoms has been studied by conversion-electron Mössbauer spectroscopy. The surface topography of Sn-implanted silicon was analyzed by scanning electron microscopy. The dependence of the number of implanted impurity atoms and their depth profiles on the laser power density and the thickness of the deposited surface layer has been investigated. The fraction of atoms implanted from the surface layer decreases with increasing layer thickness. For a given layer thickness, the implanted fraction reaches a maximum for a certain laser power density. The impurity atoms can be implanted to a depth of several thousand angstroms with nearly homogeneous depth profiles for suitably chosen conditions. The concentrations exceed the solid solubilities by orders of magnitude. These findings are consistent with a qualitative model for the implantation process assuming a detailed balance between an evaporation of the metallic surface layers and the incorporation of the impurity atoms into the bulk by diffusion in a molten substrate layer. After the recrystallization, as inferred from the Mössbauer spectra, Sn is found on substitutional lattice sites in silicon and on substitutional Ga sites in GaAs, whereas Fe in silicon precipitates in agglomerates. Upon thermal annealing, the depth profiles relax towards more homogeneous distributions. No segregation of Sn from the supersaturated solution is indicated; however, drastic changes in the Fe Mössbauer spectra after annealing indicate that a fraction of these atoms may occupy well-defined lattice sites, whereas the majority remains in agglomerates.
Surface compositions of hexaborides at high temperatures
Authors: Nakazawa M. , Futamoto M. , Usami K. , Kawabe U.
Published: February 2003

The surface compositions of (La,M) B6-type hexaborides are investigated at high temperatures using Auger electron spectroscopy. Above 1000 °C, La atoms become more enriched in the surface layer than in the bulk. Surface composition approaches that of LaB6 above 1400 °C. Above 1400 °C, the hexaboride surface maintains constant composition during long-term operation. The surface layer, in which La is more enriched than other metals, is estimated to be 2 or 3 nm thick. This enrichment may be due to the fact that the metals of higher vapor pressures evaporate faster than lanthanum.
Electron-beam-induced decomposition of ion bombarded calcium fluoride surfaces
Authors: Strecker Charles L. , Moddeman W. E. , Grant J. T.
Published: February 2003

The effects of electron beams on the composition of ion bombarded calcium fluoride surfaces have been studied with Auger electron spectroscopy (AES), electron loss spectroscopy (ELS), and x-ray photoelectron spectroscopy (XPS). It was found with AES that when using typical AES excitation electron-beam parameters (5 keV, 5 μA), the calcium fluoride surface decomposed, resulting in the desorption of fluorine. The ELS and XPS measurements suggest that simultaneous with the desorption of fluorine from the surface, is the accumulation of calcium in a metalliclike state. Threshold measurements for the onset of fluorine desorption showed that AES analysis could be made without significant electron-beam effects by rastering a 2.5-keV, 0.05-μA electron beam over an area of 6×10−4 cm2, corresponding to a current density of 0.082 mA/cm2.
Investigation of the performance of an MoS2‖I−/I2‖C electrochemical solar cell
Authors: Audas R. , Irwin J. C.
Published: February 2003

The performance of an electrochemical solar cell with a single crystal of MoS2 in an I−/I2 electrolyte has been investigated. An efficiency greater than 5% has been obtained by carefully cleaving the crystal to ensure a good quality surface and by optimizing the electrolyte concentration. The cell performance has been compared to the predictions of a phenomenological model, that incorporates a term representing a diffusion overvoltage. Excellent agreement with the experimental results has been obtained with two free parameters, representing the shunt and series resistance of the cell.
Photoelectric quantum efficiencies and filter window absorption coefficients from 20 eV to 10 KeV
Authors: Day R. H. , Lee P. , Saloman E. B. , Nagel D. J.
Published: February 2003

Photodiodes with x-ray sensitive photocathodes are commonly used as broadband x-ray detectors in fusion plasma diagnostics. We have measured the photocathode quantum efficiency between 1–500 Å of common photocathode materials including aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. We have also studied the effects of the experimental environment and long-term cathode aging on the measured quantum efficiencies. In addition, we have measured the x-ray mass-absorption coefficients of x-ray filter windows of Kimfoil, aluminum, polypropylene, and Formvar in energy regions where data were previously unavailable. Measurements between 1–50 Å were performed at the Los Alamos Scientific Laboratory’s low-energy x-ray calibration facility, while the measurements between 50–500 Å were performed at the National Bureau of Standard’s synchrotron ultraviolet radiation facility.
The Schottky barrier height and Auger studies of yttrium and yttrium silicide on silicon
Authors: Campisi G. J. , Bevolo A. J. , Schmidt F. A.
Published: February 2003

Schottky barrier diodes of yttrium and yttrium silicide were fabricated on p-type (111) silicon. The barrier heights of the diodes determined by I-V measurements were correlated with heat treatments and interface conditions as determined by Auger composition depth profiles. The as-deposited Y-Si contact had a barrier height of 0.70 eV. During heat treatment at 300 °C, oxygen diffused into yttrium and formed Y2O3, resulting in a barrier height of 0.65 eV. Yttrium silicide was formed at 410 °C that lead to a Schottky barrier height of 0.60 eV.
Deposition kinetics of SiO2 film
Authors: Maeda Masahiko , Nakamura Hiroaki
Published: February 2003

The deposition mechanism for chemical vapor deposition glassy SiO2 films using SiH4, O2, and N2 mixtures has been studied. With an increasing PO2, the deposition rate increases in the lower PO2 region, while it decreases in the higher PO2 region. The results were analyzed on the basis of the Langmuir-Hinshelwood surface reaction mechanism. A rate equation was derived. It was found that two molecules of adsorbed SiH4 and one atom of dissociatively adsorbed O2 react on the surface. In the increasing region, the rate constant for surface reaction and adsorption coefficients for SiH4 and O2 were obtained by optimizing the parameters in the rate equation. The activation energy of the surface reaction and the heat of adsorption for SiH4 and O2 were obtained as 10±2, 7±1, and 9.5±2 kcal/mol, respectively. In the decreasing region, adsorption coefficients changed away from those in the increasing region, resulting in an abrupt decrease in deposition rate with PO2.
Oxidation kinetics of TiN thin films
Authors: Wittmer M. , Noser J. , Melchior H.
Published: February 2003

We have investigated the oxidation kinetics of TiN thin films in dry O2 in view of a possible application of TiN as material for gate electrodes and interconnections in large-scale integrated circuits. We found that in the temperature range of 500 to 650 °C the oxidation is thermally activated with an activation energy of 2.05±0.05 eV. Thereby the diffusion of oxygen through the oxide is the rate-limiting process. Analysis with x rays indicates that dry oxidation transforms TiN to the rutile form of TiO2. Films of TiO2 formed in such a manner are found to be semi-insulating with resistivities in the order of 106 Ω cm and at higher applied electric fields the injection of space-charge–limited currents is observed.
Laser broadening ratio from the multimode oscillation threshold
Authors: Casperson Lee W.
Published: February 2003

Lasers with mixed line broadening typically oscillate in a single longitudinal mode for excitation levels only slightly above threshold. At high pump levels, less desirable multimode oscillation may sometimes occur. A procedure is described for using the multimode threshold as a sensitive measure of the broadening ratio, and GaAs is mentioned as an example.
Electrical properties of laser annealed AuGe/GaAs ohmic contacts
Authors: Aina O. , Katz W. , Rose K.
Published: February 2003

Contact resistivity measurements of laser annealed AuGe/GaAs ohmic contacts as a function of depth (contact resistivity profiling) has shown a monotonically increasing contact resistivity profile for energy densities lower than 2.12 J/cm2. For energy densities higher than 2.12 J/cm2 a minimum in the profiles was observed at a depth of 1200 Å. This suggests that minima previously observed in the variation of contact resistivity as a function of laser energy density are due to a surface phenomenon. These profiles further show that ohmic contacts can be made to GaAs by deposition of metal films on GaAs surfaces from which laser annealed AuGe films have been removed. Contact resistivities as low as 1×10−6 Ω cm2 were obtained even when metal was deposited on GaAs etched to a depth of 1000 Å. Secondary ion mass spectroscopy profiles are included which allow the redistribution of Ge into GaAs to be compared with these contact resistivity profiles.
New design for an antireflection coating of metal-semiconductor Schottky type Au-CdS solar cell
Authors: Kezuka Hiroshi
Published: February 2003

As an antireflection coating material a Ta2O5 film is deposited onto the surface of Au for Au-CdS solar cells by vacuum evaporation in the presence of O2 at a total gas pressure of about 10−4–10−5 Torr. The reflectance is measured in the spectral region from 330–600 nm. It is found that the optimum thickness of Ta2O5 film for 200 Å of Au thickness is 1220 Å, in which case the minimum reflectance is approximately zero at 480 nm. On both sides of the minimum value the reflectance rises steeply. For a fixed thickness of Ta2O5 the position of wavelength at minimum reflectance has a slight tendancy to move to a longer wavelength with increasing thickness of Au film.
Reply to ’’Comments on nuclear-pumped cw lasing of the 3He-Ne system’’
Authors: Schneider R. T. , Carter B. D. , Rowe M. J.
Published: February 2003

In a recent comment by Prelas and Schlapper, the statement was made that in a paper by Carter, Rowe, and Schneider, the Ne line at 632.8 nm claimed to be observed could not have been observed, since the upper state population of the laser transition could not have possibly have been sufficient to allow lasing. The comment is based on a simple model introduced by Prelas and Schlapper. We show, in this response, that this model is conceptually wrong. In addition, a calculational error was made when they computed the power input to be 4.7 mW/cm3 rather than the correct value of 9.8 mW/cm3.
Magnetostatic energy of a saturating cylinder
Authors: Aharoni Amikam
Published: February 2003

The magnetostatic self-energy is calculated for a finite, ferromagnetic, right-circular cylinder, which has no volume charge, and a constant surface-charge density on the top and bottom ends. For the side of the cylinder, the charge density is assumed to be given by a (finite or infinite) power series in z, except for an adjustable strip in which the magnetization is already saturated so that the charge there vanishes. The result is expressed as a series of functions for which a recurrence relation is given.
Static collapse discrimination of S = 0 bubbles in a garnet film with orthorhombic anisotropy
Authors: Engemann J. , Konishi S. , Heidmann J.
Published: February 2003

Four different types of circular S = 0 bubbles have been identified in a (110)-oriented garnet film with orthorhombic anisotropy, two at a time being large and small at the same bias field. Depending on the magnitude and sign (with respect to the [001] inplane easy axis) of an applied inplane field the S = 0 bubbles show a pronounced difference in their static collapse fields, for example, of up to 12.1 Oe at 50-Oe inplane field. This paper presents the static collapse characteristics of these S = 0 bubbles and a proposal for bubble state discrimination needed in wall state coded devices.
Electron paramagnetic resonance and thermal behavior of NdP5O14 and LaP5O14
Authors: Barthou C. , Blanzat B. , Létoffé J. M.
Published: February 2003

The ferroelastic phase transition of LaP5O14 and NdP5O14 at, respectively, 403 and 428 K was analyzed by electron paramagnetic resonance and differential thermal analysis studies over the temperature range 210–450 K. Near room temperature, another thermal anomaly was clearly identified on both materials by these two methods.
Kinematic theory of piezoelectric hysteresis
Authors: Harper P. G.
Published: February 2003

A biasing voltage applied across a bonded piezoelectric plate causes a transverse deflection. For slowly varying voltages, the displacement shows a characteristic hysteresis. A kinematic model is proposed which relates nonlinearly the displacement and its rate to the applied voltage. The analysis is developed to account quantitatively for the measured quasistatic hysteresis and decay, and to predict resonant dynamical effects.
Nonuniform polarization of vinylidene fluoride-trifluoroethylene copolymer
Authors: Ohwaki Junichi , Yamazaki Hiroki , Kitayama Toyoki
Published: February 2003

Polarization distribution of vinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer is studied. X-ray diffraction spectra and pyroelectric light detecting responses of the films, polarized by dc electric field, suggested extremely nonuniform polarization in the direction of the field. That is, the positively poled surface was well polarized and the negatively poled surface was little polarized. A calculation based on a stepwise polarization distribution model showed that the polarization depth of the 75-μm films was 45% of the film thickness, and that the pyroelectric coefficient of the polarized surface was 9 nC/cm2 K, when the films were polarized by dc 20 kV/mm at 100 °C for 1 h.
Ferroelectric properties of vinylidene fluoride-trifluoroethylene copolymers
Authors: Yamada Takeshi , Kitayama Toyoki
Published: February 2003

The ferroelectric properties of vinylidene fluoride-trifluoroethylene copolymers were studied. According to the x-ray diffraction patterns, the crystalline form of the copolymers with VDF molar content less than 80% was different from that of the copolymer with 82 mole % VDF. The Curie temperature was observed for the copolymers with the molar composition ranging from 37 to 80% in VDF by measuring the dielectric constants and endothermic peaks. The copolymers with low Curie temperature had the crystalline with wide interplanar spacing and small saturation polarization. The copolymer with 55 mole % of VDF showed a typical ferroelectric D-E hysteresis loop at 25 °C and showed a double hysteresis loop at just below the transition temperature.
Preparation, structure, optical, and magnetic properties of lanthanide aluminate single crystals (LnMAl11O19)
Authors: Kahn A. , Lejus A. M. , Madsac M. , Théry J. , Vivien D. , Bernier J. C.
Published: February 2003

Rare-earth aluminates having the general formula LnMAl11O19 with Ln3+ = La, Pr, Nd, Sm, Eu, Gd, and M2+ = Mg, Ni, Co, Mn, Fe have been synthetized. This paper is devoted to mixed compounds of the series La1−xNdx Mg Al11O19 of which large single crystals have been obtained by the flame fusion method. A full refinement of the pure lanthanum compound (x = 0) having a quasimagnetoplumbite structure has been performed (final R = 0.039). Spectroscopic investigations of the (La, Nd) aluminate have allowed the measurement of fluorescence yield and lifetime of Nd3+ in the host lattice as a function of the neodymium content. Additional results have been obtained on the magnetic anisotropy, from susceptibility measurements performed on the Nd3+ aluminate in the temperature range 4–300 K.
Propagation of surface magnetoelastic waves in TmFeO3 at the spin reorientation
Authors: Gorodetsky G. , Shaft S. , Remeika J. P.
Published: February 2003

Experimental and theoretical studies of the propagation of surface magnetoelastic waves at the spin reorientation of TmFeO3 are presented. It was found that surface waves propagating on the (a-b) surface and along the a axis of the orthorhombic crystal, exhibit velocity dips ΔV/V02.5% at the transition temperatures of the spin reorientation. A magnetic field applied in the reorientation plane suppresses and/or shifts the velocity dips. Similar effects were previously observed for shear bulk waves. The observed results are accounted for by using phenomenological magnetic and magnetoelastic expressions in the coupled equations of motion. It is concluded that the surface acoustic wave interacts with the antiferromagnetic modes of the bulk.
The effects of field strength and orientation on magnetostatic wave propagation in an anisotropic ferrimagnetic plate
Authors: Lemons R. A. , Auld B. A.
Published: February 2003

This paper presents a theoretical study of magnetostatic wave propagation as a function of the strength and orientation of an applied magnetic field. The dispersion relation is derived for an isolated ferrimagnetic plate with either cubic or uniaxial magnetic anisotropy. In the crystal symmetry planes where the magnetization is coplanar with the plate normal and the applied field the dispersion relation has a simple analytic form valid for propagation in any direction. The frequency limits for propagation of various modes are readily evaluated from this expression. Selected plots of these frequency bands and the associated dispersion curves are presented to illustrate the effects of field strength and orientation. Particular emphasis is given to applied fields less than the saturation magnetization oriented near the normal to the plate. This case is important for the potential use of magnetostatic waves to detect magnetic bubbles.
On the viscous attenuation and velocity of acoustic surface waves in quartz
Authors: Sinha B. K. , Tiersten H. F.
Published: February 2003

The viscous attenuation of surface waves propagating along various directions in some technologically important orientations of quartz has been obtained from a perturbation procedure which has been successfully employed in calculating the attenuation of such waves due to the finite electrical conductivity of overlaid thin metallic films and air loading. The attenuation and velocity curves show an interesting correlation which has a significant impact on the acoustic quality (Q) factor for such waves. Among other things the computational results indicate that a recently reported orientation (SST-cut) which refers to the propagation direction 23° from the digonal axis of the BT-cut possesses significantly lower viscous attenuation and beam spreading loss than the commonly used ST-cut quartz for surface wave applications. The autocollimation property of surface waves in the new orientation is a consequence of the nature of the slowness curve in the neighborhood of the above mentioned propagation direction. The resulting improvement in the insertion loss for a surface wave delay line using the SST cut over that of the ST-cut quartz has already been established experimentally.
Determination of minority-carrier lifetime in silicon solar cells from laser-transient photovoltaic effect
Authors: Di Giulio M. , Galassini S. , Micocci G. , Tepore A. , Manfredotti C.
Published: February 2003

The minority-carrier lifetime in the base of silicon solar cells has been determined from the transient decay slope of the short-circuit current after pulsed-laser carrier excitation. Two series of solar cells with the same thickness (400 μm) and with base resistivities of 0.1 and 1 Ω cm, respectively, have been analyzed. The values for the lifetime are 2.4/6.0 μs for the 1-Ω cm resistivity cells and of 5.2/19.1 μs for the other ones. The extreme values correspond to back-surface recombination velocity S = 0 or S = ∞. The results are in reasonable agreement with those obtained by other authors with the surface photovoltage method.
Characterization of implanted and annealed vapor phase epitaxial GaAs
Authors: Bhattacharya P. K. , Rhee J. K. , Owen S. J. T. , Yu J. G. , Smith K. K. , Koyama R. Y.
Published: February 2003

The electrical and optical properties of as-grown and implanted and annealed vapor phase epitaxial GaAs have been determined and compared by photoluminescence, transient capacitance spectroscopy, and Hall measurements. The dominant electron trap level with activation energy ΔE = 0.83 eV is observed consistently in the as-grown layers, but is not detected in the implanted layers. A second electron trap level with ΔE = 0.37±0.01 eV is also observed in some as-grown and some implanted layers. A hole trap level with ΔE = 0.86 eV which is detected in some as-grown layers with a low density compared to the carrier concentration and in most of the implanted layers with larger density is attributed to Cr. An electron trap level with ΔE = 0.53 eV detected in some implanted layers and a hole trap level with ΔE = 0.15 eV present in all the implanted layers are believed to be created due to the implant and anneal process. Room-temperature Hall electron mobilities and activated surface carrier concentrations decrease and increase, respectively, with increasing implant dose. The mobility profiles as a function of temperature (80–550 K) are markedly different for the as-grown and implanted layers, the values being lower in the latter. A detailed analysis of the mobility data including the relevant carrier scattering mechanisms indicate that the decreased mobility is due to increased ionized impurity density. Familiar peaks which are ascribed to excitonic transitions and transitions involving C and Cu-VAs complexes have been observed in the photoluminescence spectra of the as-grown crystals. Photoluminescence of implanted and annealed GaAs indicate the formation of Si acceptors.
A highly sensitive chalcogenide photoconductor in a near-infrared wavelength region
Authors: Taniguchi Yoshio , Yamamoto Hideaki , Horigome Shinkichi , Saito Susumu , Maruyama Eiichi
Published: February 2003

A new highly sensitive photoconductor in a near-infrared wavelength region with a low dark decay has been developed for an electrophotographic device. The photoconductor has been created with a multilayered Se-As-Te chalcogenide glass. The structure of the photoconductive layer consists of four parts: (a) Se-rich blocking layer, (b) Te-rich IR-sensitive layer, (c) As-rich space-charge layer, and (d) Se-rich voltage sustaining layer. A Cerium oxide layer is interposed as a carrier blocking layer on the substrate. This photoconductor has shown sensitivity of about 300 m2/J to beams having a wavelength of 750 nm. This sensitivity is as high as that of the amorphous Se photoconductor to light having a wavelength of 442 nm. This photoconductor has favorable characteristics such as a high initial surface potential, low dark decay, low residual surface potential, and long durability in practical use. It is suitable for a photoconductor in a laser beam printer with a diode laser.
Dependence of electrical characteristics on laser power in cw laser processed Al-nSi diodes
Authors: Wu C. M. , Yang E. S. , Sedgwick T. O. , Hodgson R. T.
Published: February 2003

We report here data of the capacitance-voltage and current-voltage measurements on cw laser processed Al-nSi diodes. The range of the laser power is between 12 and 20 W. Significant changes in the ideality factor, reverse saturation current, thermal activation energy, doping concentration, and effective Schottky barrier height have been observed. These results appear to be consistent with the mechanisms of aluminum diffusion and defect generation with high-temperature stress under high-power laser irradiation.
Properties of aluminum epitaxial growth on GaAs
Authors: Petroff P. M. , Feldman L. C. , Cho A. Y. , Williams R. S.
Published: February 2003

The structural perfection and epitaxial growth process of Al films deposited by molecular beam epitaxy (MBE) on (100) GaAs substrates have been analyzed by transmission electron microscopy (TEM) and Rutherford backscattering analysis (RBS). Two epitaxial relationships between the Al film and (100) GaAs are observed. In general, deposition on As-rich surfaces at room temperature and low deposition rates (200–750 Å/h) lead to 〈110〉 oriented Al films. Higher deposition rates at room temperature yield a mixture of 〈110〉 and 〈100〉 oriented films or completely 〈100〉 oriented films at the higher deposition rates. On Ga-rich surfaces, only 〈100〉 oriented Al films are observed. For both epitaxial orientations the misfit elastic strain at the interface is accommodated by misfit dislocations localized in the Al film for film thicknesses of ⩾ 600 Å. Under these conditions the GaAs substrate at the interface is strain free and dislocation free. The presence of surface steps associated with surface reconstruction at the start of the epitaxial process is invoked to account for the existence of 〈110〉 oriented film growth on 〈100〉 substrates.
Determination of the degree of easy axis alignment in uniaxial permanent magnets from remanence measurements
Authors: McCurrie R. A.
Published: February 2003

An expression has been derived for the remanence perpendicular to the preferred direction of magnetization in uniaxial permanent magnet materials and it has been shown that this provides a quick and sensitive method for determining the degree of alignment of the easy axes of the constituent uniaxial particles or grains in the magnet.
Metastable honeycomb model of laser annealing
Authors: Phillips J. C.
Published: February 2003

A model for microstructural double bifurcation following abrupt energy deposition by intense laser pulses to produce epitaxial regrowth of disordered Si surface layers can account for recent observations that indicate local heating far below the bulk melting point. The model also indentifies and explains anomalous functional behavior in k′(v), the crystal impurity segregation coefficient, as a function of regrowth front velocity v.
Electric field enhanced emission from non-Coulombic traps in semiconductors
Authors: Martin P. A. , Streetman B. G. , Hess K.
Published: February 2003

Electric field enhancement of emission from three non-Coulombic traps has been calculated: the shielded Coulombic potential, the polarization potential, and the dipole potential. Both the Poole-Frenkel effect and phonon-assisted tunneling have been included, and both were found to be important. The field effect can be used to distinguish between these potentials on the basis of their long range character. This effect is most important in interpreting the results of capacitance transient studies of deep levels.
An extended and unified solution for the semiconductor surface problem at equilibrium
Authors: Jindal R. P. , Warner R. M.
Published: February 2003

An equilibrium solution is presented for the semiconductor surface in terms of the potential, electric field, charge density, and change in mobile-carrier concentrations throughout the semiconductor as a function of the surface potential and bulk doping. These results are an extension of the work initiated by R. H. Kingston and S. F. Neustadter [J. Appl. Phys. 26, 718 (1955)]; and extended by C. E. Young [J. Appl. Phys. 32, 329 (1961)]. The present results cover a wider range of all the parameters involved in the problem; also, through quantities chosen for normalization and through choice of origin, the present results remove a considerable redundancy existing in the previous data. Finally, the identity of the equilibrium surface problem and the equilibrium step-junction problem is demonstrated and explained.
Mode conversion from Lamb wave to Rayleigh wave via liquid couplant
Authors: Toda Kohji , Hayama Masaru
Published: February 2003

A technique for surface acoustic wave excitation onto nonpiezoelectric materials is described by using a Lamb wave device and a liquid couplant. The optimum angle between two materials is adjustable by the change of frequency because of the dispersive property of the Lamb wave.
Defects in GaAs induced by laser annealing
Authors: Nojima Shunji
Published: February 2003

Laser annealing effects in epitaxially grown n-GaAs and furnace-annealed, Si ion-implanted semi-insulating GaAs were investigated. Carrier concentration, mobility, and photoluminescence intensity were found to be decreased to some degree by laser annealing, indicating a formation of defects. These quantities, however, did not vanish even at a laser energy density (0.79 J cm−2) at which electrical activation fails to occur by laser annealing in low-dose, ion-implanted GaAs. A conclusion was derived from this fact, that these defects thus induced by laser annealing are not the main factors dominating the phenomenon of no carrier generation by laser annealing in low-dose, ion-implanted GaAs.
Surface acoustic wave characteristics of CuCl
Authors: Takeuchi Hiroshi , Yamashita Kunio
Published: February 2003

Surface acoustic wave (SAW1) characteristics of CuCl were calculated. It was found that both the electromechanical coupling factor and delay time temperature coefficient of CuCl fall between those of LiNbO3 and LiTaO3. This crystal was also found to have very low SAW velocities (1040–1500 m/s). It is concluded that CuCl is a potential SAW material for low-frequency filter and delay line applications.
Hexagonal WSi2 in cosputtered (tungsten and silicon) mixture
Authors: Murarka S. P. , Read M. H. , Chang C. C.
Published: February 2003

Hexagonal WSi2 was found to form from nearly amorphous cosputtered (tungsten and silicon) mixtures depostied on oxidized silicon. This form of WSi2 was detected in films sintered at temperatures in the range 400–600 °C. At temperatures of 700 °C or above, only tetragonal WSi2 formed. The hexagonal-to-tetragonal transformation temperature was found to be ∼550 °C. At 600 °C the transformation appears to follow a square root of time dependence.
Application of Penning discharge to the deposition of amorphous silicon
Authors: Hirao T. , Mori K. , Kitagawa M. , Ishihara S. , Ohno M. , Nagata S. , Watanabe M.
Published: February 2003

Hydrogenated amorphous silicon films (a-Si:H) have been successfully prepared by a Penning glow discharge of silane, in which both the electric and magnetic fields are applied. A stable discharge has been observed between electrodes in a wide pressure range (0.005–0.5 Torr). It was found that the plasma was nearly confined between electrodes, thus reducing the quartz tube-plasma interaction. Optical and electrical properties have been studied in correlation with SiH4/SiH4+H2 ratio. The photoconductivity of the a-Si:H films show highest value when the ratio is 0.2. The photoconductivity of the a-Si:H films deposited at 0.07 Torr is as high as 5.2×10−4 (Ω cm)−1 under simulated AM 1 (100 mW/cm2) and the corresponding normalized photoconductivity ημτ is 4.6×10−5 cm2/V under 1.9-eV illumination (3×1014 photons/ sec cm2). The films predominantly show the absorption peak due to Si:H stretch mode at 2000 cm−1. The potential features of this technique over conventional ones are described.
Monte Carlo simulation of 1–10-KeV electron scattering in a gold target
Authors: Kotera Masatoshi , Murata Kenji , Nagami Koichi
Published: February 2003

A new Monte Carlo simulation of electron scattering has been achieved for extension to the low-energy region and to heavy elements such as Au. The Kanaya-Okayama equation, which includes adjustable parameters, is used for the calculation of energy loss instead of the Bethe equation. Further, the Mott equation, which is obtained from a more exact treatment for elastic scattering, is used instead of the screened Rutherford equation for angular scattering. The calculated results are compared with various kinds of experimental results such as the electron range, the backscattering coefficient, and the depth distribution of energy dissipation. The theoretical results are found to be in satisfactory agreement with the experimental results.
Surface damage on stainless steel and molybdenum electrodes caused by electrical breakdown in high vacuum
Authors: Sinha M. K. , Ku Yee-Gee , Johnson Randall P.
Published: February 2003

We have studied the surface damage produced on stainless steel and molybdenum electrodes when electrical breakdown occurs in ultrahigh vacuum. The electrode gap distance was ≊1 mm. In stainless steel, sharp protrusions form on edges of micron-sized pits which are sometimes present on highly polished surfaces. These protrusions may initiate breakdown. Both molybdenum and stainless steel cathodes show surface features similar to the blisters when these metals are irradiated with high doses of hydrogen ions. We propose that the gases dissolved in the electrode material and the high ionic flux produced as a result of outgassing of the electrodes near the breakdown voltage may cause bubble formation and blistering on the cathode surface. These blisters are sites of high-field emission and may burst, leading to crater formation. The craters on the anode surface are formed as a result of field-electron current-induced heating and impact of microparticles originating at the cathode.
Least-squares analysis of x-ray diffraction line shapes with analytic functions
Authors: Houska C. R. , Smith Terence M.
Published: February 2003

This is a second paper of a sequence that provides a useful analytic function which is based upon the Warren-Averbach line shape analysis. Once the Fourier coefficients are interrelated in terms of a minimum number of parameters, the rather lengthy Fourier series can be evaluated by reducing it to a convolution of two known functions. One of these functions includes the particle size distribution, strain, and the Cauchy-like contribution to the instrumental broadening. The second includes another strain parameter and the Gaussian contribution to the instrumental broadening. The resultant convolution integral is readily carried out using a nine-point Gauss-Legendre quadrature. Instrumental parameters are obtained from a separate convolution of Cauchy and Gaussian functions. This procedure reduces the computer time to one-tenth the time required to synthesize the Fourier series and makes it feasible to carry out a least-squares fitting of the profile data. Examples are given for Mo films and for an InSb film.
The response of manganin gauges shock loaded in the 2-D straining mode
Authors: Rosenberg Z. , Partom Y. , Yaziv D.
Published: February 2003

We measured the response of shock loaded manganin gauges in the two-dimensional (2-D) straining mode. This mode, usually achieved by using wire gauges, was obtained for commercial foil-like gauges emplaced in the transverse configuration. In this configuration the plane of the gauge is perpendicular to the shock front. Measurements of gauge response during shock compression as well as in the release phase are compared to data for 1-D straining mode. The two geometries yield significantly different responses which are attributed to the viscoplastic properties of the gauge material.