bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of deuterium implantation on bubble garnet properties
Authors: Gerard P. , Capra T. , Magnin J.
Published: July 2002

A classical (Y Sm Lu Ca)3 (Fe Ge)5 O12 bubble garnet, supporting 1.8-μm bubbles, has been implanted with 1.5×1016 D+2 cm2 at 60 keV either directly or through a predeposited 100-Å-thick silica layer. Nuclear techniques such as D (3He, α) p nuclear reaction and Rutherford backscattering combined with channeling measurements were used to determine the implant and damage profiles, respectively. Double-crystal x-ray diffraction was used to measure the maximum strain and magnetic properties were obtained from ferromagnetic resonance. The evolution of these parameters has been studied as a function of annealing treatments. It follows that, as compared to hydrogen, deuterium also interacts at damage-level inducing within the garnet new magnetic phenomena. A higher annealing temperature is required for bubble memory applications. The silica overlayer which is useful for increasing the anisotropy field change, somewhat affects the magnetic properties of the implanted layer.
Experimental study of the ion emission from a 0.53-μm laser-produced plasma
Authors: Kieffer J. C. , Quemener Y. , Briand J. , Gomes A. , Adrian V. , Dinguirard J. P. , Armengaud M. , Thoron J. P. , Fournier N. , El Tamer M. , Arnas C. , Poquérusse A.
Published: July 2002

Ion velocity distributions generated in a 0.53-μm laser-produced plasma are studied with a Thomson parabola diagnostic at 5×1013 W/cm2. Ions are observed in a narrow energy range. However, for velocities >4×105 m/s the distribution dN/dV decreases exponentially and the temperatures deduced from these distributions are in good agreement with those given by x-ray emission.
Instability of the heat flux in a laser-produced plasma in the presence of an ion acoustic instability
Authors: Dragila R.
Published: July 2002

We investigate a heat flow instability arising due to transverse perturbation of an initially uniform flow. Its growth rate is shown to be determined by the magnitude of the heat flux. The presence of ion acoustic turbulence driven by the flux itself leads to stabilization of the instability due to a decrease of the transverse heat flow.
Morphological and electrical analysis of micron scale Si lines produced by laser-induced chemical vapor deposition
Authors: Binnie T. D. , Wilson J. I. B. , Colles M. J. , West J. L.
Published: July 2002

We report morphological and electrical differences in micron scale silicon lines deposited by laser-induced chemical vapor deposition, using a range of laser powers and scan rates. We also show how changes in substrate reflectivity can affect and control the deposition reaction.
Electromagnetic wave propagation through an azimuthally perturbed helix
Authors: Basu B. N. , Jha R. K. , Sinha A. K. , Kishore L.
Published: July 2002

A field analysis is developed for the helical slow-wave structure of a traveling-wave tube in the anisotropic sheath helix model considering the effects of the azimuthal harmonics generated due to periodical positioning of the support bars around the helix. A practical relevance is added to the problem by way of considering the effect of an overall metal enclosure; the losses of the structure are, however, ignored. The analytical result justifies the usual heuristic approach of treating the support bars as a continuous dielectric of a suitably interpreted permittivity.
Energy confinement effect on soft x-ray generation in 0.53-μm laser-heated cavity target
Authors: Okada K. , Mochizuki T. , Ikeda N. , Hamada M. , Mineo M. , Kodama R. , Yamanaka C.
Published: July 2002

The first experimental investigation has been made of the time-resolved soft x-ray spectra from an empty high Z cavity target irradiated by 0.53-μm wavelength laser. The soft x-ray emission spectra are compared with those from planar targets with respect to temporal and spectral profiles and brightness temperature. Evidence on the radiation confinement and the plasma confinement in the cavity geometry is discussed in conjunction with the energy dissipation flow.
Factors affecting light-induced excess conductivity in doping-modulated amorphous silicon superlattices
Authors: Su F.-C. , Levine S. , Vanier P. E. , Kampas F. J.
Published: July 2002

Doping-modulated amorphous silicon semiconducting films which exhibit the phenomenon of light-induced excess conductivity (LEC) have been made by silane glow discharge in a single-chamber system. This phenomenon shows a strong dependence on substrate temperature and process gas composition. The LEC effect decreases for very small and very large layer thickness. There also seems to be an optimum defect density for producing large effects.
p-type conduction in ZnSe grown by temperature difference method under controlled vapor pressure
Authors: Nishizawa Jun-ichi , Suzuki Ryoji , Okuno Yasuo
Published: July 2002

Electrical properties of a low-resistive and stable p-type ZnSe crystal grown by the temperature difference method under controlled vapor pressure are reported. The temperature dependence of Hall mobility, carrier (hole) concentration, and conductivity are measured by the van der Pauw method. Hole mobility appears to be about 200 cm2/V s at 100 K and about 50 cm2/V s at 300 K. The activation energy of a shallow acceptor impurity is also determined to be 70–85 meV.
Spectroscopic ellipsometry study of InP, GaInAs, and GaInAs/InP heterostructures
Authors: Erman M. , Andre J. P. , LeBris J.
Published: July 2002

The dielectric functions of high-purity InP and GaInAs layers grown by metal-organic vapor-phase epitaxy (MOVPE) have been measured in the 2.0–3.5-eV energy range using spectroscopic ellipsometry. Analysis of third derivatives computed from these data gives critical-point (E1 and E1+Δ1 transitions) energies, broadening parameters, and phases. The reference dielectric functions of InP and GaInAs are used to analyze GaInAs/InP and InP/GaInAs heterojunctions fabricated in a MOVPE reactor. The sharpest interface as measured by a multilayer modeling is 30 Å of GaInAsP at the interface of InP grown on GaInAs and 9 Å of InAs for GaInAs grown on InP. Dielectric functions of very thin GaInAs and InP layers (<100 Å) have been extracted from the data measured on heterostructures. It is demonstrated that these extracted dielectric functions are extremely sensitive to the interface quality and give further information about the quality of the MOVPE-grown thin layers of GaInAs and InP.
Improved coupling coefficient of laser radiation to aluminum by means of absorptive polymer coatings
Authors: McLachlan A. D.
Published: July 2002

The application of a polymer coating to aluminum is shown to provide a convenient energy-absorbing coating which increases the absorptance of the surface in a theoretically predictable way that is independent of the applied coating thickness. The dynamic absorptance of the coated surface for continuous-wave CO2 laser radiation was measured and found to agree with a theoretical model. Above temperatures of 400–500 °C, the polymer coating was completely removed, leaving a clean aluminum surface. It is shown that up to this temperature the absorptance of the surface was approximately 0.30 and also dependent on the incident laser intensity.
Electron oscillation velocity and electric field in collisionless radio-frequency discharge plasmas
Authors: Popov O. A. , Godyak V. A.
Published: July 2002

It was experimentally shown that in radio-frequency (rf) discharge plasmas excited in mercury vapor at pressures below 10−2 Torr, the electron oscillation velocity and the active component of the rf electric field are substantially smaller than those in direct current (dc) discharges. Results obtained were explained by effects of a noncollisional dissipative process occurring at the oscillating boundaries between rf plasma and rf electrode sheaths.
Primary-ion charge neutralization in secondary ion mass spectrometry analysis of insulators
Authors: Inoue K. , Isogai A.
Published: July 2002

Primary-ion charge neutralization by means of negative ion bombardment, conductive film coating, and conductive layer induced by sputtering has been investigated for the purpose of developing secondary ion mass spectrometry (SIMS) analysis of insulators. It has been found that negative ion bombardment reduces charge accumulation on a specimen, while the conductive film and layer play a subordinate role in charge neutralization. In SIMS analysis of insulators, however, the conductive film is required to provide the extraction field for secondary ions in combination with charge neutralization by negative ion bombardment.
New fast Fourier transform and finite-element approaches to the calculation of multiple-stripe-geometry laser modes
Authors: Yevick David , Hermansson Björn
Published: July 2002

We have developed a new method, based on the split-step fast Fourier transform algorithm, for calculating the modes of a general graded-index active waveguiding structure and demonstrate that the method can be applied to the periodic part of the Bloch function and hence to a strictly periodic multiple-stripe-geometry laser. We also develop a second approach involving the finite-element method.
Dark-current and capacitance analysis of InGaAs/InP photodiodes grown by metalorganic chemical vapor deposition
Authors: Philippe P. , Poulain P. , Kazmierski K. , de Cremoux B.
Published: July 2002

Electron traps have been observed at the InGaAs/InP heterointerface by capacitance voltage measurements in p-i-n photodiodes grown by metalorganic chemical vapor deposition. These traps might be responsible for the sharp increase in dark current which occurred when the space-charge region extended to the InP buffer layer. In addition, the temperature and voltage dependence of dark current has been described using a generation current model which takes into account the thermoionic field emission from an InGaAs midgap trap.
Localized epitaxial growth of MoSi2 on silicon
Authors: Lin W. T. , Chen L. J.
Published: July 2002

Epitaxial tetragonal and hexagonal MoSi2 (t-MoSi2 and h-MoSi2) were grown locally in (001), (111), and (011)Si. Five different epitaxial modes, referring to sets of definite orientation relationships between silicides and the substrate Si, were identified for t-MoSi2, whereas three distinct modes were found for h-MoSi2. Variants of epitaxy, required by the symmetry consideration, were also observed. It is conceived that ample thermal energy was supplied during high-temperature annealings to cause various modes of epitaxy which presumably correspond to low-energy states that occur. The reactive nature of the silicide formation is suggested to facilitate the growth of epitaxial silicides on silicon.
Titanium-tungsten contacts to silicon. II. Stability against aluminum penetration
Authors: Babcock S. E. , Tu K. N.
Published: July 2002

An investigation of the thermal stability and Schottky behavior of Ti-W thin film contacts to n-Si in the presence of an Al overlayer is reported. Rutherford backscattering spectroscopy, glancing-incidence x-ray diffraction, and current-voltage measurements were used to characterize the multilayer contact structures. The low Schottky barrier height, 0.51 eV, of the Al/Ti80W20/n-Si structure was repeatedly measured after 30-min anneals up to 500 °C. This stability was improved to 600 °C when a diffusion barrier layer of Ti30W70 alloy was included. The detection and significance of Al penetration in low Schottky barrier height contacts to Si have been discussed.
Dependence of inductively measured critical temperature on frequency and amplitude of applied field in an i
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i
t
u Nb3Sn superconductor
Authors: Fukumoto M. , Kodaka H. , Okada T. , Yoshida H. , Yasohama K.
Published: July 2002

A superconducting critical temperature Tc has been measured inductively on an in situ-formed Nb3Sn wire. The measurement has been carried out by varying the amplitude and frequency of the applied alternating magnetic field in the range from 0.001 to 100 G and from 0.2 to 100 kHz, respectively. It has been found that the normal to superconducting transition is dependent on the amplitude and slightly dependent on the frequency of the applied field.
Decay of the running state in underdamped Josephson junctions
Authors: Cristiano R. , Silvestrini P.
Published: July 2002

The decay of the running state in the presence of noise is investigated in underdamped Josephson junctions. In order to find an expression for the lifetime of such a state valid also in the region of bias currents near the deterministic switching value Ir, the nonstationary nature of the process is taken into account. Using the classical ‘‘first passage time’’ technique due to Stratonovich, an analytical expression for the lifetime of the V≠0 state is obtained.
Electrical properties of shallow levels in p-type HgCdTe
Authors: Finkman E. , Nemirovsky Y.
Published: July 2002

Electrical measurements of gold-doped and undoped p-type Hg1−xCdxTe with x≂0.22 are reported and two models based on two shallow acceptor levels for the analysis of the Hall data are developed. One model assumes two independent acceptors and the other assumes one divalent acceptor. The models yield ionization energies of 12.5±2 and 2–5 meV. The concentration of the compensating donors is of the order of the hole concentration. Arguments are given in order to assign these levels to established point defects.
Deposition and properties of zinc telluride and cadmium zinc telluride films
Authors: Chu T. L. , Chu Shirley S. , Firszt F. , Herrington Chuck
Published: July 2002

Thin films of ZnTe and Cd1−xZnxTe (x<0.5) have been deposited by the direct combination of the elements on the surface of W/graphite, ceramic, and glass substrates at 550–600 °C in a hydrogen or helium atmosphere. Their microstructure, crystallographic, optical, and electrical properties were studied. Because of the greater stability of ZnTe than CdTe, the Zn/Cd molar ratio in Cd1−xZnxTe films is always less than that in the gas phase. The optical band gap of ZnTe has been determined to be 2.25 eV and that of Cd1−xZnxTe is a linear function of the composition. Preliminary work on Cd1−xZnxTe /CdS heterojunctions has also been carried out.
Uniformity of an embedded stripe large optical-cavity GaAs/GaAlAs double-heterostructure laser grown by metallo-organic chemical vapor deposition
Authors: Fekete D.
Published: July 2002

Large optical-cavity GaAs/GaAlAs double-heterostructure stripe geometry laser with laterally effective step change of the refractive index is described. The stabilization of the transverse mode is achieved by regrowing an embedded stripe selectively on a large optical cavity, using metallo-organic chemical vapor deposition. The near-field and the far-field patterns confirm the index guiding mechanism of the light. No kinks were observed in the light versus current characteristics up to light power of 200 mW/facet. The threshold current uniformity is comparable to those of gain-guided lasers grown by metallo-organic chemical vapor deposition.
An analysis of fivefold symmetry by microtwinning in rapidly solidified Al-Mn alloys
Authors: Carr M. J.
Published: July 2002

The properties of small ensembles of cyclically twinned, rhombohedrally distorted face-centered-cubic crystals are examined and shown to be consistent with reported experimentally determined diffraction patterns and images of rapidly solidified Al-Mn alloys exhibiting icosahedral symmetry. Limitations of previously reported refutations of twinning models are discussed. Proposals are made for definitive tests between microtwinning and quasicrystalline models of these structures.
Growth condition dependence of EL2 concentrations in magnetic field applied liquid-encapsulated Czochralski GaAs crystals
Authors: Terashima Kazutaka , Yahata Akihiro , Fukuda Tsuguo
Published: July 2002

In the magnetic field applied liquid-encapsulated Czochralski (MLEC) GaAs crystals, midgap level EL2 concentrations have been found to be strongly affected by the melt composition and crystal versus crucible rotational conditions. Although the EL2 concentrations only varied from 1 to 4×1016 cm−3 in the conventional LEC GaAs crystals, they ranged from far below 1×1015 cm−3 in Ga-rich melt to 1×1017 cm−3 in As-rich melt for the MLEC GaAs crystals.
Analysis on the gray zone of a Josephson single-flux quantum memory cell
Authors: Hasuo Shinya , Suzuki Hideo
Published: July 2002

In single-flux quantum (SFQ) memory cell operation, a stochastic phenomenon occurs in certain ranges of bias current. These regions, in which the memory cell stochastically switches to the voltage state or to the other vortex mode, are called the gray zone. The gray zone reduces the operating margin of the cell, because the bias current region in the gray zone must be avoided for memory operation. It is very important to investigate the origin of the gray zone for the design of the cell. But the gray zone has not ever been discussed in detail. We have studied memory operation from the viewpoint of the thermal fluctuation of the potential energy of the cell. Our conclusions are as follows. (1) The gray zone originates in bias current fluctuations, caused by the thermal fluctuation of the potential energy of the cell. (2) In the gray zone the probability of transition to the voltage state does not necessarily increase monotonically with the bias current. This is because the transition to the voltage state occurs in several bias current regions, even if there is no thermal fluctuation, for a memory cell with the large McCumber factor.
Flux propagation in thin-film magnetic structures
Authors: Heim D. E.
Published: July 2002

The theoretical basis of the transmission line model (TLM), a model widely used to describe the propagation of flux in thin-film magnetic structures, is examined. The primary prediction of the model is that magnetic flux propagates along the structure exponentially with a characteristic length, simply related to the permeabilities and thicknesses of the films constituting the structure. To examine the validity of the model we analyze the solution of Maxwell’s equations for two canonical thin-film geometries and establish the following results. For the first geometry, infinite in extent, we show how the exponential flux propagation of the TLM emerges directly from the exact solution for the flux, and we derive the range in parameters over which this occurs. For the second geometry, which is of finite extent and thus includes end effects, we show that the TLM is exact in a certain limit. Practical device geometries, for which the TLM was developed (magnetic recording heads), typically approach this limit. Therefore, the solution for the magnetization in these structures will approach the limit solution, i.e., the TLM solution, and may thus, validly, be approximated by it. The physical content of this limit is discussed relative to the range of validity of the TLM. These two results confirm the general soundness of the TLM and provide a theoretical basis for it.
Magnetic behaviors of elongated single-domain particles by chain-of-spheres model
Authors: Ishii Y. , Sato M.
Published: July 2002

We consider the chain of N spheres contacting each other with an area and study the change of the magnetic behaviors of this chain by the contact area. Critical field Hcri for the discontinuous jump of the magnetization and coercive force Hc by both the parallel rotation and fanning mechanisms, and uniaxial magnetic anisotropy constant Ku due to the shape of the chain are found to increase, reach the maximum value, and decrease with an increase in the contact area. The ratios of the maximum value to the value at the point contact for Hcri, Hc, and Ku are also found to increase with an increase in the number of the spheres.
Optical constants of an a-Si1−xCx:H film
Authors: Mui K. , Basa D. K. , Smith F. W.
Published: July 2002

The real and imaginary parts n and k of the index of refraction of a carbon-rich hydrogenated amorphous silicon-carbon alloy film (a-Si1−xCx:H, x∼0.87) have been determined for photon energies between 1.5 and 4.75 eV from measurements of reflectance R and transmittance T. The optical energy gap parameter Eopt has been determined from the energy dependence of ε2=2nk, the imaginary part of the dielectric constant. Depending on assumptions involving the energy dependencies of valence- and conduction-band densities of states and optical matrix elements, values of Eopt ranging from 1.65 to 2.5 eV have been obtained for the as-deposited film (Td=250 °C). Independently of such assumptions, Eopt is observed to decrease to zero as the film is annealed. These results are consistent with enhanced tetrahedral coordination and demonstrate improved thermal stability for this silicon-carbon alloy film as compared to an hydrogenated amorphous carbon film. The density of the film increased from 1.51 to 1.88 g/cm3 with annealing up to 850 °C.
A study of the electronic properties of cleaved InP surfaces induced by oxygen exposure
Authors: Ismail A. , Brahim A. Ben , Lassabatere L. , Lindau I.
Published: July 2002

The modifications of the electronic properties of InP (110) surfaces, induced by oxygen exposures in the 1–103 langmuir (L) range, have been studied by contact potential difference and surface photovoltage measurements. Most of the surface barrier variation has already occurred at exposures lower than 20 L with the Fermi level strongly pinned at about 0.3 eV below the conduction band minimum. A noticeable surface dipole change occurs at 103 L. The results are discussed in terms of a two-state model and surface order modifications.
Simulations of the early period of flux entry into a single-Josephson-junction superconducting loop using the Werthamer theory
Authors: Gayley Robert I.
Published: July 2002

The behavior of a superconducting quantum interference device (SQUID) during the period up to the entry of the first flux quantum has been studied by numerical simulation. The theory of Josephson tunneling due to Werthamer, which includes the time-dependent aspects of the Bardeen–Cooper–Schieffer (BCS) theory, was used. Several interesting qualitative features were observed. One is the discovery of an approximate effective RC time constant (τg+θ), where τg is the RC time constant in units of the gap time and θ is a constant. With this as a scaling factor, the results become approximately independent of RC for the early period of flux entry. A second, related, feature of the results is that the time required for the entry of the first flux quantum accurately follows a simple empirical formula for a wide range of the values of the various parameters of the experiment. In addition, some of the results were compared with those obtained with approximate versions of Josephson’s tunneling equation. In general, these approximations gave poor results.
Perpendicular magnetic ground state of a multilayer film
Authors: Suna A.
Published: July 2002

We evaluate the dipolar energy in a periodic multilayer film consisting of alternating ferromagnetic and nonmagnetic layers, for magnetization perpendicular to the plane of the film, arranged in alternately polarized strip domains. The lowest-energy state for this configuration is calculated for the case of freely mobile domain walls. Within certain limits, the layered film behaves as a uniform medium with an anisotropy arising from the layering. The relevance of the theory to experiments on Pd/Co layered films is discussed.
High-efficiency multikilojoule deuterium fluoride (DF) chemical lasers initiated by intense electron beams
Authors: Inagaki Hirohito , Kannari Fumihiko , Suda Akira , Obara Minoru
Published: July 2002

A multikilojoule deuterium fluoride (DF) chemical laser with a low-pressure mixture of F2/D2/O2/SF6 was developed in which a Lambda-type electron beam initiation scheme was used. The DF laser output obtained from a 27-liter active volume was 2.5 kJ with a pulsewidth of about 500 ns. The corresponding electrical efficiency and chemical efficiency are 128% and 10.5%, respectively.
Current–voltage characteristics through GaAs/AlGaAs/GaAs heterobarriers grown by metalorganic chemical vapor deposition
Authors: Hase I. , Kawai H. , Kaneko K. , Watanabe N.
Published: July 2002

Current–voltage characteristics of GaAs/AlxGa1−xAs /GaAs heterobarriers grown by metalorganic chemical vapor deposition were investigated for x from 0.32 to 0.46. Calculation of the current, which included just two components—a tunneling component and a thermionic component—agreed well with experimental results. The tunneling effective mass used is the same as the Γ point effective mass when x is 0.32; this value allows the calculated results to fit the experimental data. The tunneling effective mass becomes much larger than the Γ point mass as x increases. This fact suggests that the other band edge X participates in the tunneling process, making the effective mass larger as it approaches the Γ point edge. The barrier heights deduced from I–V and I–T relations are in good agreement. The results support a ratio of 60%–65% of AlGaAs/GaAs conduction-band discontinuity to the total band-gap difference.
Kinetics of hydrogen thyratron plasmas during the conduction phase
Authors: Penetrante B. M. , Kunhardt E. E.
Published: July 2002

A study of the conduction-phase characteristics of hydrogen thyratron plasmas is presented. A self-consistent analysis is performed through simultaneous numerical solutions of the Boltzmann equation, the rate equations for the various ionic and neutral particle densities, and the radiative transfer equation. The electron kinetic properties, chemical composition, and radiative properties of the plasma are derived for a wide range of current densities. Moreover, the role of the various collisional processes in shaping the electron energy distribution for various values of E/N (electric field/total gas number density), fractional ionization, and dissociation degree is elucidated. Implications of the obtained plasma properties on the analysis and diagnosis of hydrogen thyratron plasmas are discussed.
Elastic interaction between general parallel screw dislocations and a surface crack
Authors: Juang Ruey-Rong , Lee Sanboh
Published: July 2002

The dislocation-modeling technique and complex variable method are used to analyze the interaction between the general parallel screw dislocations and a surface crack. For the case of one dislocation, the dislocation distribution in the crack, the stress field, the strain energy, the image force, the stress intensity factor, and the crack extension force are obtained. The results are compared with various special cases of other papers. Under the applied stress without the frictional force, there are two metastable points and no stable point in the strain energy diagram. Therefore, the dislocation will move to the free surface, crack surface, or infinity depending on its location. The two-dislocation system or the even dislocation dipole is analyzed. Although this approach gets the same results as the conformal mapping method, the former is superior in analyzing two or more dislocations.
Ionization thresholds of merocyanine dyes in the solid state
Authors: Tang Tong B. , Seki Kazuhiko , Inokuchi Hiroo , Tani Tadaaki
Published: July 2002

The experimental technique of ultraviolet photoelectron spectroscopy has been applied to a number of merocyanine dyes related in chemical structure. Additionally, polarographic and optical measurements were made on these dyes in solution, and Hückel molecular orbital calculations were carried out for isolated dye molecules. The observed photoionization threshold decreases with increasing delocalization of π electrons in the compound. With the use of absorption data, we constructed energy band diagrams for the dyes, assuming that these organic materials exist as molecular solids. Our assumption was supported by the observation that their ionization thresholds correlate well with the polarographic and the computational results. Photoelectron spectroscopy is deemed to provide a powerful method for studying dyes in practical forms.
Formation of a rotating ion layer by normal injection of 90-keV pulsed ion beam
Authors: Ikehata T. , Kawabe T. , Miyoshi S.
Published: July 2002

Cross-field injection of an intense ion beam has been proposed and tested as a method of creating rotating ion layers. Approximately 7% of a proton beam injected (90 keV, 300 A) is found to be trapped in a magnetic field of 5 kG through collective processes and to stay there in the form of a rotating, dilute ion layer for a time several times as long as the ion gyroperiod. The maximum azimuthal current density of trapped ions is 0.3 A/cm2. The trapped ions have a rather wide distribution along the magnetic field because of field-aligned expansion of the injected beam.
Transmission electron microscopy cathodoluminescence investigation of anomalous Sn diffusion in GaAs
Authors: Graham R. J. , Spence J. C. H. , Roedel R. J.
Published: July 2002

Zn-doped GaAs diffused with Sn has been examined in cross section by transmission electron microscopy (TEM) and high-resolution cathodoluminescence (CL) in an attempt to account for the penetration of Sn into this material but the apparent lack of any electricity activity. TEM shows that small Sn-rich precipitates are present in the GaAs near the surface. CL indicates that some of the Sn dopes of GaAs n-type, but additionally that new emissions in the spectra at ∼1.44 and ∼1.455 eV are seen to originate from the diffused region. A possible explanation for the lack of electrical activity of the Sn is discussed in terms of these results and may lie in the formation of a compensating Sn-related complex or an accumulation of Zn in the diffused region.
Anomalous majority-carrier peaks in deep level transient spectroscopy
Authors: Brierley Steven K.
Published: July 2002

An examination of majority-carrier deep level transient spectroscopy (DLTS) spectra for GaAs with filling pulse heights in the vicinity of the flat-band voltage has revealed a subtle anomalous peak with the ‘‘correct’’ sign: one that would normally be associated with emission from a majority-carrier trap. A model is presented which explains the peak as one of a class of peaks due to minority-carrier capture into a minority-carrier trap. Good agreement is found between the experimental and calculated trap signatures (T2τ vs 1/T) assuming the minority-carrier trap to be Fe (a residual impurity which is observed in optical DLTS spectra on the same sample). The importance of using optical DLTS data to assist in properly interpreting the majority-carrier DLTS spectra is stressed.
Resistivity of the solid solutions (Co-Ni)Si2
Authors: d’Heurle F. M. , Tersoff J. , Finstad T. G. , Cros A.
Published: July 2002

Solid solutions of CoSi2 and NiSi2 were prepared from the solid-state reaction of thin films of Ni-Co alloys with their silicon substrates. The room-temperature resistivity of these silicide solid solutions does not increase parabolically, but (within the sensitivity of the measurements) varies linearly with composition. A model is proposed which explains the very weak alloy scattering on the basis that in these disilicides (a) the d bands are pushed below the Fermi level, (b) conduction occurs mostly via s electrons, and (c) there is no s-d scattering.
Photocapacitance of CdZnS/CuInSe2 thin-film heterojunctions
Authors: Ahrenkiel R. K.
Published: July 2002

The photocapacitance of a thin-film CdZnS/CuInSe2 heterojunction was observed under white light excitation. Capacitance increases were observed that were indicative of minority-carrier trapping in the junction. Emission spectroscopy indicated that a distribution of traps produce this signal. Analysis of the data indicate trap distributions ranging from 5×1014 cm−3 to 1.6×1015 cm−3 in the bulk and 3.3×1011 cm−2 at the surface. Photovoltaic efficiency was inversely related to the photocapacitance signal. A model relates deep electron interface states to a decrease in open-circuit voltage.
The effect of He3 on CO2 laser power
Authors: Marcus S. , Stein D. T.
Published: July 2002

Substitution of He3 for normal helium in a sealed-off conventional CO2 laser resulted in power output increases as high as 14%. No such effect was observed in a narrow-bore waveguide laser, indicating that the observed improvements were due to more efficient heat conduction to the tube wall.
Formation of titanium hydrides in (Al, Ga)As double-heterostructure laser contacts and their effect on degradation rate
Authors: Gaw C. A. , Holbrook W. R. , Hakki B. W. , Reynolds C. L. , Nygren S. F. , Lapinsky R. L.
Published: July 2002

A cellular pattern observed in the top surface electron-beam-induced current image of  p-metallized (Al,Ga)As double-heterostructure laser material is investigated and attributed to hydride formation in the grain boundaries of the Ti layer of the TiPt  p metallization. This hydride formation occurs when the TiPt  p metallization is annealed in a forming gas environment and leads to high initial device degradation rates. When the hydride formation in the Ti layer and therefore the presence of the cellular pattern is eliminated by annealing in a N2 environment, low initial device degradation rates are obtained. The initial device degradation rates for material annealed in N2 are equal to or better than those for devices having a weak cellular pattern and 4–5× lower than for devices with a moderate or strong cellular pattern.
Density of gap states in chemical-vapor-deposited hydrogenated amorphous silicon films
Authors: Chu T. L. , Chu Shirley S. , Ang S. T. , Duong A. , Hwuang C. G.
Published: July 2002

The density of gap states in hydrogenated amorphous silicon (a-Si:H) films deposited by the pyrolysis of disilane in a hydrogen atmosphere has been determined by four techniques. The photothermal deflection spectroscopy was used to determine the gap-state density in a-Si:H films on Corning 7059 glass substrates. Schottky barrier structures of the configuration Pd/(i)a-Si:H/( μc)n+-Si/Mo/glass were used for capacitance-temperature, capacitance-frequency, and space-charge-limited current measurements to deduce the density of states. All four techniques have yielded very similar results, (3–5)×1016/cm3 eV for films deposited at 480–500 °C, in agreement with the preliminary result of electron spin resonance measurements.
Current-injection Josephson latch employing a single-flux quantum. II
Authors: Yamada Toshishige , Sone Jun’ichi
Published: July 2002

A novel current-injection Josephson latch with a single-flux quantum memory is experimentally verified. The experimental latch is fabricated by 5-μm Pb-alloy technology and occupies an area of 270×175 μm2, achieving one order of magnitude area reduction compared to magnetically coupled latch. In low-frequency experiments, the proper operation of a single latch under arbitrary input conditions and the proper data transfer from latch to latch are observed. In high-speed experiments, the proper operation of a single latch with cycle time down to 3.7 ns is observed, which is limited by the high-speed restriction of the test instruments at room temperature. These results show the possibility that the complete current injection logic system can be constructed by combining the present latch and current-injection logic gates.
Theory of the vibrating ferromagnetic reed
Authors: Brandt E. H.
Published: July 2002

The complete theory of the magnetomechanical pole effect is given. This effect refers to the change of the resonance frequency of a ferromagnetic reed or bar vibrating in an axial magnetic field, in the absence of intrinsic effects such as the ΔE effect. From the general formulation (arbitrarily shaped reed, reed and field may be inhomogeneous) we derive explicit expressions for the frequency spectrum and vibration modes within the single-pole approximation. This applies to reeds with constant magnetization. The first-order corrections due to nonconstant magnetization are given. The second-order corrections are shown to vanish. The field dependence of the attenuation is derived. With appropriate choice of the field inhomogeneity the pole effect can be strongly enhanced, inverted, or exactly compensated to zero.
Highly controllable pseudoline electron-beam recrystallization of silicon on insulator
Authors: Hamasaki T. , Inoue T. , Higashinakagawa I. , Yoshii T. , Tango H.
Published: July 2002

A new electron-beam annealing technique, an amplitude modulated pseudoline electron beam, has been proposed for recrystallization of large-area silicon layers on insulating materials (SOI). The technique utilizes an amplitude modulated sinusoidal wave for high-frequency beam oscillation. Through computer simulation of the temperature distribution for the sample surface, precise control of the position probability density profile of the line beam proved to be essential in realizing wide and uniform annealing. An optimum oscillation waveform was determined from the simulation. A large-area SOI, 4 mm ⧠, was successfully recrystallized.
Comment on ‘‘Phonon fluctuation model for flicker noise in elemental semiconductors’’ [J. Appl. Phys. 5
2, 2884 (1981)]
Authors: Yevick David , Bardyszewski Witold , Hoenders Bernhard
Published: July 2002

We note several major inconsistencies in the cited paper.
Effects of ion irradiation on conductivity of CrSi2 thin films
Authors: Banwell T. C. , Zhao X.-A. , Nicolet M-A.
Published: July 2002

Electrical resistivity measurements are used to study damage in CrSi2 thin films induced by Ne, Ar, or Xe ion irradiation over a fluence range of 1010–1015 ions cm−2. Irradiation produces a factor of 5–12 increase in film conductivity at the higher fluences. The influence of defect generation and recombination is evident. We speculate that formation of a compound defect is a dominant factor enhancing film conductivity. A temperature dependence at low fluences is reported and tentatively identified.
Electrical behavior of extended twins present in layered GeSe
Authors: Anagnostopoulos A. N. , Kyriakos D. S.
Published: July 2002

Extended twinning bands with their walls oriented parallel to the c axis of layered GeSe crystals seem to influence considerably the electrical conductivity of this material at low temperatures. The ratio σ∥/σ⊥ of the conductivities on the layer plane measured parallel and normal to the twinning bands is thermally activated. This behavior leads to a value for the barrier height h of 18 meV. On the other hand, ac measurements in the same directions clearly show that the conductivity anisotropy vanishes at higher frequencies, thus permitting a rough estimation of the effective thickness of the walls.
Temperature dependence of the Hall-effect electron concentration in n-Al0.28Ga0.72 As/GaAs heterostructures
Authors: Svensson Stefan P. , Swanson Alan W.
Published: July 2002

A precise model for calculation of the spatial distribution of electrons in n-(Al,Ga)As/GaAs heterostructures is described. The model has been used to investigate the spatial distribution of electrons in a n-Al0.28Ga0.72 As/GaAs structure as a function of temperature. The results were compared with Hall-effect experiments on heterostructures as well as thick Al0.28Ga0.72 As films grown by molecular-beam epitaxy (MBE). For both types of samples it was found that it was necessary to use either a conduction-band density of states which is much higher than expected from literature data or to use a temperature-dependent activation energy. The slight increase in concentration of the two-dimensional electron gas observed for lower temperatures could be attributed to a sharpening of the transition region between high- and low-ionization degrees in the depletion layer close to the interface. It thus indicates that the Hall factor changes very little as expected for a degenerate electron system.
Effects of rf bias on the superconducting and structural properties of rf magnetron sputtered NbN
Authors: Carter W. L. , Cukauskas E. J. , Qadri S. B. , Lewis A. S. , Mattauch R. J.
Published: July 2002

The superconducting and structure properties of rf magnetron sputtered NbN films prepared at elevated substrate temperatures were investigated as a function of rf substrate bias. The superconducting transition temperature was observed to be independent of bias up to approximately −60 V after which it decreased and broadened. An increase of up to 60% in deposition rate over the unbiased case was observed. Substrate bias produced little effect on the low-temperature resistivity, resistivity ratio, and the film composition. The major structure change observed was a strong dependence of the preferred crystallite orientation on bias. At low bias the orientation was (200) which changed to (111) as the bias was increased. These materials are of excellent quality for use in all refractory tunnel junctions.
Preparation of remanently ferromagnetic Gd(0001)
Authors: Weller D. , Alvarado S. F.
Published: July 2002

Epitaxial Gd films were prepared in ultrahigh vacuum (UHV) on W(110) substrates. Cleanliness, growth mode, and surface crystallography were analyzed using Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). Stranski–Krastanov growth is established by AES for a substrate temperature Ts =450 °C. The LEED patterns correspond to the hcp(0001) surface. For nominal thicknesses in the range 1≲d̄≲50 Å a typical double diffraction interference pattern occurs. For d̄≳70 Å both the satellite pattern in LEED and the W signal in AES vanish, indicating coherent film surfaces for this thickness range. The films can be remanently magnetized as shown by in situ measurements of the magneto-optical Kerr effect and by spin-polarized low-energy electron diffraction (SPLEED).
Calculation of thickness dependence of magnetization and Curie temperature in (111)-oriented thin Y3Fe5O12 films
Authors: Takeuchi Teruaki , Sugita Yutaka
Published: July 2002

The thickness dependence of the magnetization and the Curie temperature has been calculated for (111)-oriented Y3Fe5O12 films using the molecular field theory to compare with the experimental results. It is found that the sublattice magnetization for a layer, i.e., the local magnetization, changes with depth. The local magnetization changes only four layers from surfaces and is constant for layers inside at room temperature. The average value of the local magnetization with respect to depth, i.e., the magnetization of the film decreases monotonically with decreasing thickness. The Curie temperature is constant down to about 30 Å; below that it decreases. The calculated results explain the experimental thickness dependence of Curie temperature and effective anisotropy field within the error.
cw composite acoustic resonator and some applications in nondestructive testing of materials
Authors: Ivanov D. V. , Burov J. I.
Published: July 2002

A composite acoustic resonator consisting of a buffer and a sample is considered in the present paper. A numerical analysis was accomplished for finding out the resonance conditions. Although complicated expressions were obtained, the composite resonator can be used for nondestructive testing of materials in a relatively simple manner. It is shown that if the acoustic and elasto-optic parameters of the buffer are known, one can find out those of the sample using the diffraction of a laser beam from the acoustic field in the buffer. Good agreement was obtained between the theoretical and the experimental results in the case of a fused quartz-dense flint system. It is shown that attenuation coefficient elasto-optic constants and velocity of propagation can be measured with satisfactory accuracy with the help of the composite acoustic resonator.
Carrier lifetime reduction in silicon by high-energy neutron irradiation
Authors: Mogro-Campero A. , Love R. P. , Jones S. J.
Published: July 2002

Generation lifetime and surface generation velocity were measured by capacitance transient analysis of metal-oxide-semiconductor capacitors to study the effect of high-energy neutron irradiation in the fluence range 1012–1014 cm−2. Thirty-minute isochronal anneals show that the generation lifetime and surface generation velocity recover their preirradiation values at 470 °C, which is close to the temperature for annealing of recombination lifetime decreases produced by electron irradiation. The relatively low value of annealing temperature for the recovery of lifetime after neutron irradiation is in sharp contrast with the improved thermal stability of lifetime effects produced by ion implantation into silicon when compared to the case of electron irradiation.
Photochemical etching during ultraviolet photolytic deposition of metal films on semiconductor surfaces
Authors: Kowalczyk Steven P. , Miller D. L.
Published: July 2002

UV photochemical deposition of Sn films on GaAs (001) surfaces from a variety of tin-containing compounds (tetramethyltin, tetrabutyltin, dibutyltin dibromide, stannic chloride, hexamethylditin, dibutyltin sulfide, and iodotrimethyltin) was studied. X-ray photoelectron spectroscopy showed that during the initial stages of deposition from the halogenated compounds, the GaAs surface was photochemically etched, most likely by a halogen radical species. The photochemical etching resulted in an arsenic deficient surface which was particularly dramatic for the case of SnCl4. These results have important implications for the choice of sources for photochemical deposition when the metal-semiconductor interface is important and for photochemical etching if stoichiometric surfaces are required.
Enhanced electrical conductivity of polydiacetylene crystals by chemical doping and ion implantation
Authors: Sakamoto M. , Wasserman B. , Dresselhaus M. S. , Wnek G. E. , Elman B. S. , Sandman D. J.
Published: July 2002

The conductivity enhancement in polydiacetylene (PDA) crystals due to chemical doping and ion implantation was measured and analyzed in relation to their spin concentration and photocurrent decay based on the structural and optical information obtained through infrared and visible reflectivity spectra. A conductivity jump was observed upon slight increase of the spin concentration at low doping levels of chemically doped PDAs, suggesting the formation of spinless carriers in chemically doped PDAs, as in trans-polyacetylene and poly(p-phenylene). In contrast, in ion-implanted samples, a great difference in the magnitudes (by more than five orders of magnitude) was observed between the conductivity enhancement for two PDAs having different side chain species. Furthermore, the photocurrent decay time measurements reveal different distributions of implantation-induced trap levels between ion-implanted poly [2,4-hexadiyne-1,6-diol-bis-(p-toluene sulfonate)] (PTS) and poly[2,4-hexadiyne-1,6-di(N-carbazolyl)] (DCH). A conduction mechanism which could explain the significant difference in conductivity enhancement between PTS and DCH is suggested. Because the enhanced conductivity by ion-implanted PTS showed no orientational effect associated with the polymer chain direction, a conductive path and network formation by the implantation-induced defects is more plausible for the conduction mechanism than carrier introduction into the backbone chain band from side chain defect levels.
A heat transfer algorithm for the laser-induced melting and recrystallization of thin silicon layers
Authors: Grigoropoulos Costas P. , Buckholz Richard H. , Domoto Gerald A.
Published: July 2002

This paper describes some numerical calculations for the temperature fields associated with laser melting and subsequent recrystallization of a thin silicon film on a conductive (glass) substrate. Particular attention has been paid to the change in the material properties with temperature and to the change in reflectivity which occurs when the silicon undergoes a phase change. Thin film optics have also been incorporated into the solution. Physical arguments and experimental observations suggest the possibility of the coexistence of liquid and solid phases. Here an attempt has been made to simulate this process numerically by using a scheme based on the enthalpy formulation. The numerical algorithm given allows the representation of regions where both the liquid and solid phases coexist. This method of solution has not been applied to cases where the reflectivity changes are considered in the ‘‘slush’’ formation. This is the first numerical simulation to include this effect.