bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutron depolarization analysis of eddy-current-limited magnetization dynamics in nickel near T
C
Authors: Stüsser N. , Rekveldt M. Th.
Published: July 2002

The magnetization reversal in a polycrystalline nickel ring-shaped specimen has been investigated by neutron depolarization in a temperature range from TC −15 K up to TC (Curie temperature). The time-dependent depolarization is consistent with a reversal process dominated by domain-wall motion, i.e., a shrinkage of an unreversed domain. Additionally the observed depolarization indicates that the local magnetization does not stay parallel or antiparallel to the applied field direction during reversal. Indications for anomalous losses were obtained from both the domain-wall velocity and the heat produced during the reversal process. Time-dependent neutron depolarization studies of the relaxation of the specimen from saturation to remanent magnetization were performed and compared with simple models.
Nondiffusive velocity broadening in ion energy analyzer operation
Authors: Fujita H. , Yagura S. , Rypdal K.
Published: July 2002

Fluctuations in plasma potential bring about an apparent broadening in the ion energy distribution when it is derived from the I-V characteristic of a retarding grid energy analyzer. This effect may have detrimental consequences for the prospects of applying energy analyzers to measure diffusion of the background distribution when electrostatic turbulence is present. The effect is demonstrated by inducing spatially homogeneous oscillations of the plasma potential in a beam-plasma system, applying a directional ion energy analyzer for beam detection. A theoretical analysis is presented, and quantitative agreement with the experimental results is obtained.
Multijunction upper subcell cascade photovoltaics for space applications
Authors: Educato J. L. , Wagner M. , Leburton J. P.
Published: July 2002

A new class of cascade high-efficiency photovoltaics designed for space-based applications is proposed. The design improves upper subcell performance and avoids electrical and optical losses associated with an intercell ohmic contact. Multijunction upper subcells reduce bulk recombination of photogenerated minority carriers by decreasing the average collection distance, yielding improved spectral response and radiation tolerance. A three-terminal design is employed which circumvents the need for a monolithic intercell contact and, thus, the losses associated with such a contact. Problems related to array interconnection of three-terminal devices may be solved by creating a two-terminal cell from complementary pairs (n-p-n and p-n-p) of three-terminal cells. Simulations of lattice-matched AlGaAs-GaAs and lattice-mismatched AlGaAs-InGaAs cascade cells show that one-sun AM0 efficiencies in excess of 26% and 28%, respectively, are possible.
Spin-glass dynamics in Fe2−xTi1+xO5
Authors: Lichti R. L. , Kumar S. , Boekema C.
Published: July 2002

Zero-field muon-spin-relaxation (μSR) and X-band ESR have been used to study the spin-freezing dynamics in single crystals of the Ising spin glass Fe2−x Ti1+x O5 . Parameters obtained for the power-law and Vogel–Fulcher descriptions of the critical slowing are consistent with other methods for x=0 and indicate significantly slower freezing in Ti-rich samples. Interpretation of cluster effects, observed in x=0.25-μSR data, as a Griffiths-like phase yields an estimate of 61±1 K for the Néel temperature in site-ordered Fe2 TiO5 .
Charge fields in Bi12GeO20 and dynamic flat-band potentials
Authors: Braun Christian M. , Fujishima Akira
Published: July 2002

A Bi12GeO20 single crystal was used to construct a photoelectrochemical memory using an aqueous junction. Two kinds of charge fields were observed, the first being of opposed polarity to the applied field in the stable condition, the second situated 0.20 and 0.33 eV above the valence band and in the stable condition with the same polarity as the applied field. The flat-band level at no charge is −250 mV versus SCE at pH=6.9 with −50±5 mV/pH. The presence of charge fields changes the Fermi level in both directions, so that under dynamic conditions a maximum of four different flat-band potentials can be observed. Additional information is given on charge-field processes observed by other authors.
Nonlinear magnetic susceptibility tensors of ferromagnetic films
Authors: Shi Longpei
Published: July 2002

Nonlinear magnetic susceptibility tensors of ferromagnetic films are studied by the method of n+1 time Green functions based upon the Heisenberg model with the surface magnetic anisotropy. It is proved that the ferromagnetic film, which loses translational invariance in one direction, has nonlocal magnetic susceptibility tensors. We derive the second-, third-, and fourth-rank susceptibility tensors in terms of a nonlocal formulation and the relation between the surface magnetic anisotropy of the film and the spin-wave resonance modes excited by the uniform microwave field. A number of nonlinear effects such as second- and third-harmonic generation, frequency mixing, signal amplification, etc., exist in the microwave region. These effects are obviously large near the spin-wave resonance.
Low threshold 1.3-μm InGaAsP/InP lasers prepared by a single-step liquid-phase epitaxy
Authors: Liu Y. Z. , Wang C. C. , Chu M.
Published: July 2002

A novel approach to form low threshold laser structures, similar to existing mass-transported lasers but without the second regrowth step, is described. The laser has comparable performance in threshold current and quantum efficiency to more conventional buried heterostructure lasers made with a two-step process. Because of the simplicity in fabrication and its reduced parasitic capacitance it has the potential to be low cost and to have high modulation bandwidth.
Annealing results on low-energy proton-irradiated GaAs solar cells
Authors: Kachare R. , Anspaugh B. E. , O’Meara L.
Published: July 2002

AlGaAs/GaAs solar cells with an approximately 0.5-μm-thick Al0.85Ga0.15As window layer were irradiated using normal and isotropic incident protons having energies between 50 and 500 keV with fluence up to 1×1012 protons/cm2. The irradiated cells were annealed at temperatures between 150 and 300 °C in nitrogen ambient. The annealing results reveal that significant recovery in spectral response at longer wavelengths occurred. However, the short-wavelength spectral response showed negligible annealing, irrespective of the irradiation energy and annealing conditions. This indicates that the damage produced near the AlGaAs/GaAs interface and the space-charge region anneals differently than damage produced in the bulk. This is explained by using a model in which the as-grown dislocations interact with irradiation-induced point defects to produce thermally stable defects.
Effect of annealing on the Schottky barrier height of Al/n-Si Schottky diodes after Ar+ ion bombardment
Authors: Carr B. A. , Friedland E. , Malherbe J. B.
Published: July 2002

Aluminium Schottky contacts on n-Si were subjected to Ar+ ion bombardment, followed by a thermal anneal at 350 °C. This resulted in a marked improvement in the diode character of the implanted contacts. α-particle channeling analysis showed that very little damage remained after annealing, while AES showed only slight mixing of the Al and Si.
Correlation between electron capture and emission barriers of localized defects in mixed crystals
Authors: Dobaczewski L.
Published: July 2002

A mathematical model and experimental procedure for extraction of the local parameters of localized defects in mixed crystals from alloy fluctuations is proposed. The general procedure is illustrated using isothermal capacitance transient measurements.
Studies on the stability of Cu island films deposited on a softenable substrate
Authors: Pattabi Manjunatha , Sastry M. S.Murali , Sivaramakrishnan V.
Published: July 2002

In this communication, we report the results of the investigations carried out on the stability of discontinuous Cu films deposited on polymethylmethacrylate coated substrate heated to a temperature above the glass transition temperature of the polymer. It was reported that evaporated materials on such substrates form a subsurface particulate structure. It was found that in Cu films post-deposition instability persisted on a softenable substrate similar to the behavior of Cu on glass. On exposure to atmosphere, the resistance increased due to the interaction of atmospheric gases and water vapor. A film deposited at room temperature and and heated also behaved in a similar fashion when exposed to atmosphere.
Liquid-metal flows and power losses in ducts with moving conducting wall and skewed magnetic field
Authors: Walker John S. , Brown Samuel H. , Sondergaard Neal A.
Published: July 2002

Fully developed, laminar liquid-metal flows, currents, and power losses in a rectangular channel in a uniform, skewed high external magnetic field were studied for high Hartmann numbers, high interaction numbers, low magnetic Reynolds numbers, and different aspect ratios. The channel has insulating side walls that are skewed to the external magnetic field. Both the perfectly conducting moving top wall with an external potential and the stationary perfectly conducting bottom wall at zero potential act as electrodes and are also skewed to the external magnetic field. A solution is obtained for high Hartmann numbers by dividing the flow into three core regions, connected by two free-shear regions, and Hartmann layers along all the channel walls. Mathematical solutions are presented in each region in terms of singular perturbation expansions in negative powers of the Hartmann number. The free-shear layers are treated rigorously and in detail with fundamental magnetohydrodynamic theory. Numerical calculations are presented for the total current carried by the core region between top and bottom electrodes, Joulean and viscous power losses, and channel resistance at different skewed external magnetic field angles. With the high external magnetic field, the current through the central core region between the electrodes must be parallel to the external magnetic field lines. The two side core regions carry no current to the zeroth order. The two free-shear layers carry less current than the central core region. The theoretical magnetohydrodynamic model derived here was developed to provide data to help in the design of liquid-metal current collectors.
Determination of grain-boundary parameters of polycrystalline silicon by ac electron-beam-induced current
Authors: Romanowski A. , Wittry D. B.
Published: July 2002

A method for determining local parameters in polycrystalline silicon with ‘‘columnar’’ boundaries is described. The effective recombination velocity at the boundary, the diffusion length, and the lifetime of the minority carriers are determined by measuring the first Fourier harmonic of the short-circuit current generated at a shallow n+p junction by a gated electron beam. In the theoretical analysis diffusion length, lifetime, and effective recombination velocity of the carriers as well as lumped parameters of the junction are taken into account. A simple relation is found for determining the lifetime. The experimental measurement is made on polycrystalline silicon solar cells using an electron probe microanalyzer.
Charge trapping characteristics of multilayer dielectrics in metal-insulator semiconductor structures
Authors: Baunach R. , Spitzer A.
Published: July 2002

An analysis of the charge trapping properties of multilayer dielectrics is important for an understanding of the physics of stacked dielectric films. Quantities of interest are the amount and the centroid of the trapped charge. In this work a new experimental setup is presented that allows the determination of these quantities. In addition, the method itself allows one to check its inherent premises. Its application to oxide/nitride/oxide triple layers reveals that the trapped charge centroid is positioned in the middle of the nitride layer with charge densities up to some 1013 e cm−2 in saturation. The relevance of charge trapping for defect-related breakdown events is pointed out.
Pressure-induced structural changes in boron oxide glass
Authors: Chason Eric , Spaepen Frans
Published: July 2002

Glassy B2O3 samples annealed at 300 °C at 10 and 15 kbar were densified by 9% and 11%, respectively. Relaxation by subsequent annealing at ambient pressure restored the original density. The structure of the pressurized samples was determined with x-ray diffraction. A new method was developed for eliminating the Compton scattering by measuring the entire energy spectrum at each scattering angle and fitting it to a superposition of elastic and inelastic scattering derived from the impulse approximation. The measured pair distribution function was fit to a structural model consisting of BO3 triangles linked to form planar ribbonlike structures. It is proposed that densification occurs by buckling of these ribbons. A simple geometrical model of this process can account quantitatively for the changes in density and in the pair distribution function.
Two-dimensional study of shock breakout at the rear face of laser irradiated metallic targets
Authors: Cottet F. , Marty L. , Hallouin M. , Romain J. P. , Virmont J. , Fabbro R. , Faral B.
Published: July 2002

The two-dimensional propagation dynamics of laser-driven shock waves in solids is studied through the analysis of the shock breakout at the rear face of the target for a set of materials and laser intensities. The laser shock simulations were carried out by means of a two-dimensional hydrodynamics code in which the laser-ablation pressure is replaced by an equivalent pressure pulse. It is shown that the two-dimensional code is a very useful tool to analyze laser-shock experiments where two-dimensional effects arise from a finite laser-spot size or a heterogeneous energy deposition.
Electrical measurement of the dopant segregation profile at the grain boundary in silicon bicrystals
Authors: Broniatowski A.
Published: July 2002

The paper presents a new method of determining the dopant concentration profile at the grain boundaries in polycrystalline semiconductors, based on high-frequency capacitance and dc conductance measurements. The method takes advantage of the electrostatic potential barrier associated with charged grain boundaries, and resembles, in that respect, the well-known junction capacitance technique of dopant profiling in semiconducting single crystals. As an example of application, the doping profile has been determined for the Σ=25 twin boundary in n-type (phosphorus-doped) and p-type (boron-doped) silicon bicrystals. The dopant distribution has been found, in both types of samples, very nearly homogeneous on a range of a few microns about the grain-boundary plane. This has been verified, in the case of the boron-doped bicrystals, by a secondary ion mass spectroscopy measurement of the boron concentration profile at the boundary. Annealing treatments on the n-doped bicrystals induce a slight segregation of phosphorus at the boundary. The form of the doping profile, as given by the electrical measurements, is discussed on the basis of McLean’s model of impurity segregation. The binding energy of phosphorus at the boundary is estimated on the order of 0.6 eV, comparable in order of magnitude to the values obtained by microanalytical studies of the dopant segregation at the boundaries in microcrystalline silicon.
Electrical and thermal properties of a varistor at cryogenic temperatures
Authors: Lawless W. N. , Clark C. F. , Patton B. R. , Khan F. S.
Published: July 2002

A ZnO-based varistor composition has been found whose I-V characteristic is essentially unaffected by temperature (4.2–300 K) or intense magnetic fields at 4.2 K (up to 10 T). Electrical measurements are reported at various temperatures for current densities in the range 10−11–10−3 A/cm2 . Specific-heat and thermal conductivity data are reported at 1.7–300 K. The specific heat below 10 K and above 100 K is dominated by defect modes, and the data can be understood based on simple defect models. The thermal conductivity displays a broad maximum at about 80 K (0.65 W cm−1 K−1 ), and it is concluded that the defect modes do not carry heat. The small temperature dependence of the prebreakdown conductivity is found to be in excellent agreement with a variable-range-hopping model, suggesting that this composition is just above the percolation threshold.
Optical phase conjugation reflectivity and fidelity in CS2 by picosecond pulse four wave mixing
Authors: Van Wonterghem B. , Dutton T. E. , Saltiel S. M. , Rentzepis P. M.
Published: July 2002

We have performed experimental studies designed to elucidate the parameters which limit the efficiency and fidelity of optical phase conjugate reflection of picosecond laser pulses in transparent Kerr media. The experimental data show that at low pulse energies, the reflectivity follows the expected square dependence on the pulse energies. However, it falls below the square at high energies even though, at these high energies, a phase conjugation efficiency of 300% was observed. We observed a rather strong dependence of the reflectivity on the ratio of pump to probe pulse energy. The quality of phase conjugation decreased at very high pump energies, but could under some conditions be improved by focusing the probe beam into the interaction region. Of the several mechanisms responsible for the decrease in efficiency and fidelity, we find that the predominant ones are pump depletion, small scale self-focusing, and dephasing owing to a difference in energy of the two pump pulses.
Increased effective barrier heights in Schottky diodes by molecular-beam epitaxy of CoSi2 and Ga-doped Si on Si(111)
Authors: Fathauer R. W. , Lin T. L. , Grunthaner P. J. , Andersson P. O. , Iannelli J. M. , Jamieson D. N.
Published: July 2002

Increasing the effective Schottky-barrier height of epitaxial CoSi2/Si(111) diodes by the use of thin, highly doped Si layers in close proximity to the metal-semiconductor interface has been studied. Intrinsic Si, Si doped by coevaporation of Ga, and epitaxial CoSi2 layers have all been grown in the same molecular-beam epitaxy system. Current-voltage and photoresponse characterization yield barrier heights ranging from 0.61 eV for a sample with no p+ layer to 0.89 eV for a sample with a 20-nm-thick p+ layer. These results are compared to theoretical values based on a one-dimensional solution of Poisson’s equation under the depletion approximation.
Study on the preparation of 90-K superconductor LaBa2Cu3Oy
Authors: Maeda A. , Noda T. , Matsumoto H. , Wada T. , Izumi M. , Yabe T. , Uchinokura K. , Tanaka S.
Published: July 2002

The high-Tc superconductor LaBa2Cu3Oy has been prepared under various conditions, and characterized by x-ray and neutron powder diffraction techniques, dc and ac magnetic susceptibility measurements, and dc resistivity measurement. It has been found that samples with excellent superconducting characteristics and also with good structural properties are obtained in a reproducible way if the following three procedures are performed: preheat treatment of La2O3 powders, sintering in N2, and low-temperature annealing in dried O2. Long-time annealing in undried O2 was sometimes found to degrade the grain boundaries and to lead to a lower zero-resistance temperature.
Thin-film hermeticity: A quantitative analysis of diamondlike carbon using variable angle spectroscopic ellipsometry
Authors: Orzeszko S. , De Bhola N. , Woollam John A. , Pouch John J. , Alterovitz Samuel A. , Ingram David C.
Published: July 2002

The purpose of this paper is twofold. First, we report on the successful application of variable angle spectroscopic ellipsometry to quantitative thin-film hermeticity evaluation. Secondly, it is shown that under a variety of film preparations and moisture introduction conditions water penetrates only a very thin diamondlike carbon (DLC) top surface-roughness region. Thus DLC is an excellent candidate for use as protective coatings in adverse chemical and aqueous environments.
Experimental evidence for creation of luminescence quenching localized defects by moving dislocations in gallium arsenide
Authors: James T. W. , James J. B. , Harper V. B. , Olsen H.
Published: July 2002

The production of luminescence quenching localized defects by moving dislocations in GaAs plastically deformed at 350 °C has been established by low-temperature (80 K) band-edge cathodoluminescence (CL) and chemical etch-pit studies. Specimens were deformed to two levels, (1) measurable macroscopic plastic deformation, and (2) 20% of the stress applied in (1). It was established by CL and chemical etching that numerous dislocations were generated on the four {111} stressed slip planes of the macroscopically deformed specimen. Uniform bands of reduced CL signal were correlated to bands of enhanced etching in the lightly deformed samples. It was established from the etching and CL images that these bands are not produced by deformation-induced dislocations but must consist of numerous localized luminescence quenching (Refs. 1–3) defects (e.g., point defects and small dislocation loops) created by the passage of dislocations.
Properties of Si-rich SiNx:H films prepared by plasma-enhanced chemical vapor deposition
Authors: Kaya Çetin , Ma Tso-Ping , Chen Tze-Chiang , Barker Richard C.
Published: July 2002

Silicon-rich silicon nitride (designated SiNx:H) films, prepared by the plasma-enhanced chemical vapor deposition technique, have been studied. The films studied contain a wide range of Si contents, which are controlled by the SiH4/NH3 flowrate ratio during the deposition process. Using transmission electron microscopy, coupled with the electron diffraction technique, we have found that the as-deposited films are amorphous. Upon high-temperature (>900 °C) annealing, however, we observe silicon microcrystals in the Si-rich films. The temperature at which the microcrystals start to form decreases with increasing Si richness. Reactions of the SiNx:H film with the gate aluminum as a result of post-metallization annealing treatment (at 400 °C) have been observed, and these reactions cause a drastic reduction of the temperature required for crystallization. Charge separation and current conduction studies made on Al/SiNx:H/Si structures have revealed that electrons are the dominant current carriers for either polarity, and the conduction mechanism in the SiNx:H layer is consistent with the Poole–Frankel type of transport process for moderately Si-rich films.
Optical and electrical properties of sputter-deposited Al films close to the percolation threshold
Authors: Kunz M. , Niklasson G. A. , Granqvist C. G.
Published: July 2002

Thin Al films were deposited onto glass by magnetron sputtering. Spectral transmittance and reflectance were wavelength independent at a thickness tc consistent with the percolation threshold and minimum metallic conductivity. We found tc ≊1 nm, which is much less than for evaporated Al films.
Brillouin scattering study of equation of state of multicomponent liquids: Model oil samples
Authors: Bohidar Himadri B.
Published: July 2002

Brillouin scattering technique has been used to measure the pressure dependence of sound velocity vs(P) in model oil samples (each containing 5-hydrocarbon liquids) at room temperature T=201 °C. Experimental results are reported on two blends of model oil, each containing a mixture of n-heptane, n-tetradecane, cyclo-hexane, benzene, and toluene in different volume fractions. The compositions of these two differed in their cyclohexane and toluene contents. The pressure dependence of vs(P) has been measured up to 815 bars and the results could be least-square fitted to vs(P)=A0+A1P+A2P2 within the limits of experimental error (±1%). The modified Tait’s equation and linear pressure dependence of bulk modulii have been used in consistence with an earlier work to interpret the parabolic pressure dependence of vs(P). This yields the values of Tait parameters (B and C) and hence allows the explicit pressure dependence of density and compressibility of these multicomponent liquids to be evaluated.
High-temperature preservation of InP surface corrugations for distributed feedback lasers
Authors: Knight D. G. , Ingrey S. J. , Benyon W. , Lau W. M.
Published: July 2002

Consistent preservation of 〈01̄1̄〉-oriented grating corrugations with 2850-Å period and 1500-Å height on (100) InP substrates has been achieved during thermal cycling at 660 °C for 60 min in a H2 ambient, using roughened GaAs cover slices. It is found that transport of Ga and As causes the formation of a graded 25-Å-thick InGaAsP alloy on the surface of the gratings, as detected by Auger and x-ray photoelectron spectroscopic analysis. This preservation technique eliminates the need for lower-temperature crystal growth of distributed feedback laser wafers by liquid-phase epitaxy (LPE). Successful growth of distributed feedback laser wafers using conventional high-temperature LPE is demonstrated.
Structural and microstructural characterization of a high-T
c superconducting YBaSrCu3O7−δ compound
Authors: Liang J. M. , Chang L. , Sung H. M. , Wu P. T. , Chen L. J.
Published: July 2002

Transmission electron microscopy (TEM), energy dispersive analysis of x ray (EDS), x-ray diffraction, electrical resistance, and magnetic susceptibility measurements were applied to characterize the structure and microstructures of a high-Tc superconducting YBaSrCu3O7−δ compound. The sintered samples were found to be predominantly of a single phase with a modified perovskite structure. Combined EDS/TEM and high-resolution lattice imaging with computed image simulation data showed that the atomic ratio of Sr and Ba atoms is about unity and Ba sites in YBa2Cu3O7−δ compound were partially substituted by Sr atoms in the three-layer perovskite structure, in agreement with the results of a previous neutron diffraction study. It was also found that the marked contrast difference in high-resolution images along [100] and [010] directions of the high-Tc oxygen-deficient superconducting crystals can be used to advantage to distinguish [100] and [010] directions of the modified perovskite structure in TEM. Lattice defects such as twins and dislocations were observed and analyzed.
Metalorganic chemical vapor deposition of InGaAsP/InP layers and fabrication of 1.3-μm planar buried heterostructure lasers
Authors: Kawabata T. , Ishiguro H. , Koike S.
Published: July 2002

High-quality InGaAsP and InP layers were obtained with good surface morphology by low-pressure metalorgainic chemical vapor deposition (MOCVD). The growth apparatus could be relatively simple using trimethylindium (TMI) as indium source. Abrupt heterointerfaces were also obtained and the compositional grading at the interfaces was estimated to be less than 20–30 Å owing to the low-pressure growth technique. The selective burying growth on several types of mesas was investigated. The growth rate on the {111}B face was found to be smaller than that on the {111}A and the {100} face in MOCVD. As a result, very smooth and flat varying layers were obtained when the rectangular mesas were formed along the 〈110〉 direction. Using these characteristics, low-threshold 1.3-μm InGaAsP/InP lasers with planar buried heterostructures (PBH) were grown entirely by three-stage MOCVD. The threshold current Ith =10 mA and the differential quantum efficiency ηd =60%, which are comparable to lasers grown by liquid-phase epitaxy, were obtained. PBH lasers with multi-quantum-well active layers were also fabricated. Continuous operation with threshold current Ith =35 mA was achieved at room temperature.
Growth, structure, and physical properties of single-phase metastable fcc Cu1−xCrx solid solutions
Authors: McIntyre D. , Sundgren J.-E. , Greene J. E.
Published: July 2002

Single-phase fcc-structure metastable Cu1−xCrx alloys have been grown with Cr concentrations of up to 23 at. %. The films, which were typically 1.5–3 μm thick, were deposited by rf co-sputter deposition onto glass and oxidized-Si substrates at temperature between 55 and 180 °C. The average grain size of alloys grown at 90 °C was ∼100 nm. The lattice parameter of Cu1−xCrx was found to increase linearly with x resulting in an effective fcc Cr radius, in solution, of 0.1332 nm. ∼7% larger than the elemental bcc Cr bonding radius. The room-temperature resistivity of these alloys also increased linearly with x at a rate of 2.8 μΩ cm per at. % Cr. This high differential resistivity was due, in addition to simple alloys scattering, to scattering of conduction electrons into virtual bound states associated with the Cr atoms. Cu0.9Cr0.1 alloys were found to be stable for 24-h anneals at temperatures up to ∼300 °C. From an analysis of x-ray diffraction peak positions and widths as a function of both growth and annealing temperatures, we conclude that the reaction path for the phase transition from the metastable to the equilibrium state involves first the precipitation of coherent fcc Cr particles followed by a transformation to bcc Cr as phase separation continues. The oxidation rate of Cu0.9Cr0.1 was found to be much less that that of pure Cu. At an annealing temperature of 250 °C, the oxide thickness tox on Cu0.9Cr0.1 saturated at J25 nm after 1 h while tox on Cu continued to increase parabolically with time from ∼60 nm at 1 h to 140 nm at 4 h.
InP/InGaAsP lasers with broad area double heterostructure lasers as back-face monitors
Authors: Segner B. P. , Koszi L. A. , Temkin H. , Flynn E. J. , Ketelsen L. J. P. , Napholtz S. G. , Przybylek G. J.
Published: July 2002

An InP/InGaAsP laser-monitor hybrid structure which demonstrates the use of channeled-substrate buried-heterostructure lasers or broad area double heterostructure devices as ‘‘on-board’’ edge-detecting back-face monitors is presented. Devices with and without antireflection facet coatings are used as monitors. A linear relationship between photocurrent and light output from the laser is observed for all monitor types. A photocurrent of 17.6 μA/mW is obtained with a facet-coated, broad area monitor (at a monitor-laser separation of ≊100 μm). The sensitivities obtained are in close agreement with those predicted assuming close to unity quantum efficiency in the junction region. Improved chip placement precision could permit a possible doubling of the monitor sensitivity.
Influence of microstructure on the resistivity of MoSi2 thin films
Authors: van Ommen A. H. , Reader A. H. , de Vries J. W. C.
Published: July 2002

A study of electrical transport properties in MoSi2 thin films revealed a large resistivity difference of 57 vs 157 μΩ cm at room temperature between films formed from a codeposited Mo/Si structure and layers formed by reaction of deposited Mo with Si. The resistivity difference was found to be temperature independent. The Hall effect in the films formed from deposited Mo was a factor of four larger than in films formed from a codeposited alloy. The temperature dependencies of the Hall effect were also found to be different. Analyses of the films by Rutherford backscattering and transmission electron microscopy revealed no significant differences in thickness or grain size of the layers. The only microstructural difference is the stacking fault density, which is very high in the high-ohmic films. The mechanism by which the stacking faults influence the electrical properties of MoSi2 and other refractory metal silicides is discussed, and relations are established between the method of deposition, the microstructure of the films, and the electrical transport properties.
Interface states of Ag/(110)GaAs Schottky diodes without and with interfacial layers
Authors: Platen W. , Schmutzler H.-J. , Kohl D. , Brauchle K.-A. , Wolter K.
Published: July 2002

GaAs(110) faces with different preparations—ultrahigh vacuum (UHV) cleaved, polished and etched, polished and sputtered—are prepared as Schottky diodes by the deposition of Ag. Diodes based on UHV-cleaved faces do show homogeneously distributed EL2 and EL5 states in deep level transient spectroscopy (DLTS). On polished and etched samples an additional interface state (IS) distribution with a density of 9×1011 eV−1 cm−2 at the DLTS maximum appears. These states can be caused by defects at the oxidic interfacial layer. Polishing and sputtering also evokes the IS distribution. The absence of a DLTS signal from metal-induced gap states (MIGS) which pin the Fermi level at 0.49 eV above the valence-band maximum is related to the absence of an interfacial layer in the UHV prepared Schottky diodes. The sputter process increases the electron density in a thin layer below the interface by an As excess. The corresponding smaller extent of the barrier causes an additional electron emission via tunneling processes from the IS distribution. Furthermore, a near-interface state, EL6 (VGa-VAs), shows up. Its concentration at the interface attains NEL6 =2.5×1016 cm−3 comparable to the shallow donor concentration.
Measurement of electron diffusion lengths in ITO/p-InP by surface photocurrents
Authors: Hanak Thomas , Ahrenkiel R. K.
Published: July 2002

The electron diffusion length is deduced in n-indium tin oxide/p-InP heterojunctions by a short-circuit photocurrent technique. The technique involved the nonlinear least-squares fit of the photocurrent and junction capacitance to a simple model. The absorption coefficient of the monochromatic light is also produced by the fit. This produces an electron effective diffusion length in the p-InP which varies from about 1.0 μm for highly absorbed light up to about 8.0 μm for deeply penetrating light.
An internal friction study of neutron-irradiation effects on an amorphous Cu40Ti60 alloy
Authors: Dong Yuanda , Wu Guoan , Xiao Keqin , Li Xiao-Guang , He Yizhen
Published: July 2002

Effects of neutron irradiation on the structure of an amorphous Cu40Ti60 alloy have been studied by internal friction measurements. After irradiation, the position of the first internal friction peak remains almost unchanged and the shoulder position shifts towards a higher temperature by about 5 K, which indicates that the Cu40Ti60 glass becomes more stable. These results are finally discussed based on the concept of changes of chemical short-range ordering and geometrical short-range ordering due to radiation damage.
Explosive crystallization of dilute amorphous Si-Ge alloys
Authors: Aydinli A. , Berti M. , Drigo A. V. , Lotti R. , Merli P. G.
Published: July 2002

Structural characterization of pulsed laser irradiated amorphous alloys of Si(Ge) obtained with heavy dose (Ge) implantation in Si have been carried out using Rutherford backscattering spectrometry/channeling technique and transmission electron microscopy. Comparison of these alloys with self-implanted amorphous Si after irradiation with a ruby laser showed significant reductions in the laser energy densities required for melt propagation, amorphous-crystalline interface penetration, and laser-induced damage formation. Explosive crystallization was found to occur in all samples. Large reductions in melting temperatures and latent heat of melting were found to be necessary to explain the results.
Magnetic properties of crystalline and amorphous Fe-Ni alloy films deposited by sputtering
Authors: Arai Juichiro
Published: July 2002

In order to investigate the peculiar magnetovolume coupling in the Fe-Ni Invar alloy, the relation between the magnetization and the interatomic distance is studied by the Mössbauer effect and x-ray diffraction analysis for the FexNi1−x alloy foils which are obtained by dc sputter deposition. The interatomic distance of the sputter-deposited Fe-Ni alloy foils depends on the sputtering voltage; the sputter deposition at low voltage produces an extended lattice, and further lowering of the sputtering voltage gives rise to an amorphous state. The hyperfine field of the extended lattice in the Invar composition which is produced by sputtering at 2 kV is about 10% larger than that of the bulk alloy and furthermore the extended lattice does not retain the Invar characteristics such as low thermal expansion. The hyperfine field of the amorphous state produced by the lower-voltage sputtering at 1.5 kV doesn’t show the abrupt decrease around the Invar composition range in contrast to that of the crystalline Fe-Ni alloys, where a sharp drop of the hyperfine field is well known. The lack of the Invar characteristics in the sputter-deposited Fe-Ni alloys is discussed on the basis of the change of the 3d band configuration which leads to the disappearance of the weak itinerant ferromagnetic state.
Melting of silicon surfaces by high-power pulsed microwave radiation
Authors: James R. B. , Bolton P. R. , Alvarez R. A. , Christie W. H. , Valiga R. E.
Published: July 2002

We have measured the microwave-induced melting and damage to the near-surface region of arsenic-implanted silicon for 1–2 μs pulses at a frequency of 2.856 GHz and an incident pulse power of up to 9 MW. Rectangular samples were irradiated by single-pass TE10 traveling wave pulses inside a WR-284 waveguide, and time-resolved in situ and post-irradiation studies were performed to characterize the material modifications induced by the microwave pulses. The test chamber where the specimens were irradiated was either evacuated to a pressure of 10−7–10−6 Torr or filled with a 30-psig pressure of Freon-12. Incident, transmitted, and reflected powers were monitored with directional couplers and fast diodes. The results of the time-resolved optical measurements for samples irradiated in vacuum show that melting of the near-surface region occurs for pulse powers exceeding 3 MW, and that the surface melting is accompanied by a large increase in the reflected microwave power. The onset of the enhanced reflectivity is measured at an earlier time as the microwave power is increased, and once the abrupt increase in the reflectivity is observed, it persists throughout the remainder of the pulse. Simultaneous with the onset of surface damage, we observe a large enhancement in the emission of light from the sample. Results are presented for the temporal behavior and spectral components of the fluorescence as a function of the incident microwave power. The gas pressure in the test cell was also monitored, and a large increase in the gas pressure was detected at the same pulse power as the threshold for the sudden increase in the microwave reflectivity. The large increments in the reflected microwave power, light emission, and gas pressure are attributed to the formation of a plasma due to gas breakdown at (or near) the sample surface.

Examination of the irradiated specimens shows that the melting and damage are not homogeneous over the surface, and the degree of energy deposition from the microwave pulses depends on the ambient gas in the test cell. Using secondary ion mass spectrometry, we find that microwave pulses at a power of 8 MW cause melting and vaporization of the near-surface region up to depths that exceed 1 μm.
Electronic defect levels in continuous wave laser annealed silicon metal oxide semiconductor devices
Authors: Cervera M. , Garcia B. J. , Martinez J. , Garrido J. , Piqueras J.
Published: July 2002

The effect of laser treatment on the bulk and interface states of the Si-SiO2 structure has been investigated. The annealing was performed prior to the gate metallization using a continuous wave Ar+ laser. For low laser powers the interface state density seems to decrease slightly in comparison with untreated samples. However, for the highest irradiating laser powers a new bulk level at 0.41 eV above the valence band with concentrations up to 1015 cm−3 arises probably due to the electrical activation of the oxygen diluted in the Czochralski silicon. Later postmetallization annealings reduce the interface state density to values in the 1010 cm−2 eV−1 range but leave the concentration of the 0.41-eV center nearly unchanged.
Temperature-dependent magnetization of canted moments in erbium- iron-manganese-boron
Authors: Pinkerton F. E. , Fuerst C. D. , Meisner G. P.
Published: July 2002

Magnetization as a function of field up to 9 T is reported for Er2Fe14−xMnxB compounds with x=2 and 2.5 at temperatures T between 4 and 120 K. The noncollinear basal plane moment structure which exists among the Er and transition-metal moments within this temperature regime gives rise to an unusual nonsaturating field-dependent magnetization behavior. The magnetization increases linearly with field up to a field H*, where the slope dM/dH abruptly changes. M(H) is again linear above H*, but with a much steeper slope dM/dH∼0.5 μB/formula unit/T. H* increases monotonically with temperature for x=2, until no slope change is observed at experimentally accessible fields when T=120 K. In the x=2.5 sample, H* initially decreases with increasing temperature, and reaches a minimum at 55 K. This behavior appears in a plot of M(T) as a compensation temperature Tcomp, that is, as a minimum in the magnetization near 55 K.
Characterization of the photoresist residue in integrated thermionic devices
Authors: Boland John J. , Segredo Eugenio
Published: July 2002

A study of the thermal decomposition of the Kodak thin-film resist (KTFR) used in the fabrication of integrated thermionic emission devices is presented. In contrast to conventional cathode fabrication schemes which typically employ a nitrocellulose binder, the use of KTFR is shown to produce a carbon residue which persists even at cathode operating temperatures. The degree of residue formation is dependent on the heating rate. Differential thermal analysis and thermal gravimetric analysis studies indicate that the deomposition of the resist occurs at about 450 °C. The presence of the residue is shown to influence the breakdown of the cathode carbonate mixture. X-ray photoelectron spectroscopy analysis of the residue reveals that it is either graphitic- or hydrocarbon-like in nature. In contrast to conventional binders the KTFR residue is not oxidized by CO2 at temperatures below 650 °C. At higher temperatures the time courses of the residue concentration were measured and indicated the presence of residual signal even after the decay appeared complete. The ramifications of the presence of a carbon residue at cathode operating temperatures are discussed.
High-power (2.2 W) cw operation of (111)-oriented GaAs/AlGaAs single-quantum-well lasers prepared by molecular-beam epitaxy
Authors: Hayakawa T. , Suyama T. , Kondo M. , Hosoda M. , Yamamoto S. , Hijikata T.
Published: July 2002

High-power (2.2 W) cw operation has been achieved in a (111)-oriented GaAs/AlGaAs graded-index separate-confinement-heterostructure single-quantum-well laser with the 100-μm wide stripe geometry. High differential quantum efficiency of 81% has been obtained up to ∼1.2 W, and high total power-conversion efficiency of 46% has been achieved at 1.5 W.
Some transport coefficients of multilayer metallic film
Authors: Khater F. , Seoud A.
Published: July 2002

This paper deals with a derivation of some transport coefficients of multilayer metallic film. The derivation is performed on the basis of Fuchs–Sondheimer theory in which the electrical conductivity of thin metallic films is strongly affected by a surface scattering process. The multilayer metallic film consists of alternating layers of two different metals. The scattering of conduction electrons at the interfaces between the layers are described by the Fuchs specularity reflection parameter P and the refractive parameter Q. The latter parameter corresponds to the fraction of conduction electrons refracted at the interfaces. However, the background mechanism of the scattering of conduction electrons in the layers are described by two different relaxation times, which are assumed to be functions of energy. Numerical results are obtained for parameters characteristic of alternating layers of silver and gold.
ac magnetic susceptibility of YBa2Cu3O7−x
Authors: Mei Yu , Luo H. L. , Chen D. X. , Nogues J. , Rao K. V.
Published: July 2002

ac and dc magnetic susceptibilities were studied for relatively dense single-phase YBa2Cu3O7−x samples. The data are discussed in terms of sample defects.
The magnetic properties of a sintered Sm(Co0.83Cu0.1Fe0.07)6.77 permanent magnet
Authors: Jackson S. , McCurrie R. A.
Published: July 2002

The magnetic properties of the sintered permanent magnet Sm(Co0.83Cu0.1Fe0.07)6.77 have been measured as a function of the maximum applied field and the temperature. It has been concluded that the high coercivity is due to general domain-wall pinning at heterogeneous regions within the grains and at the sinter grain boundaries.
The different sets of electrical, mechanical, and electromechanical third-order constants for quartz
Authors: Adam Winfried , Tichý Jan , Kittinger Erwin
Published: July 2002

Any combination of one mechanic, one electric, and one thermal variable may serve as a basis for the phenomenological characterization of piezoelectric crystals by material constants. According to this choice different, but interrelated, sets of constants arise. Based on a proper thermodynamic formulation, relations between the different sets of electrical, mechanical, and electromechanical third-order constants of piezoelectric crystals are given and applied to experimental data on quartz. In this way four complete sets of these constants are obtained.
Phase stability of ferroelectric KNO3 switching devices during polarization aging
Authors: Schaffer W. J. , Mikkola D. E.
Published: July 2002

The persistent observation of polarization aging during repeated room-temperature switching of metastable thin-film ferroelectric potassium nitrate capacitors has led to the conjecture that the observed polarization decay is a direct consequence of a concomitant phase III to phase II structural transformation. Appropriate large area thin-film devices have been fabricated to perform this x-ray diffraction study of the phase stability of ferroelectric KNO3 devices during in situ electrical switching. As the initial remanent polarization of 7.5 μC/cm2 decreases to <0.4 μC/cm2 in <2×106 polarization reversals, the volume fraction of III-KNO3 remains constant, and no reflections from II-KNO3 appear. After complete polarization loss, however, the initial d spacings measured for III-KNO3 have increased an average 0.4%. Examination of the line shapes during aging reveals that the observed shift is not a continuous transition, but a convolution of reflections centered at the initial and final d spacings. This characteristic modification to the original cell, here designated III′-KNO3, occurs throughout the switched volume. The simultaneous loss of polarization and appearance of the expanded unit cell suggest that III′-KNO3 either pins the polarization or is itself nonferroelectric.
Raman investigation of reversible photoinduced effects in semiconducting Ge-S-Ga thin-film glasses
Authors: Raptis C. , Ivanova Z. G.
Published: July 2002

Changes in the optical transparency and local structure, induced by exposure to band-gap light and/or annealing at temperatures below the glass-transition temperature Tg, have been observed in amorphous Ge-S-Ga thin films by measuring their transmission and Raman spectra. Either of the treatments leads to a bleaching effect accompanied by an increase of ordering in the local structure. In the combined treatment, photoexposure of previously annealed films results in (i) a further increase of ordering for annealing temperatures Tan up to a critical temperature Tc about 100 °C below Tg and (ii) a photodarkening effect and decrease of ordering for Tan >Tc . These results raise the possibility of using such films as base materials for the production of both negative and positive photoresists.