bluuebunny/crossref_metadata_2025 huggingface dataset:
The magnetization and Curie temperature of compositionally modulated Cu/Ni films
Authors: Zheng J. Q. , Ketterson J. B. , Falco Charles M. , Schuller Ivan K.
Published: February 2003

We report detailed measurements of the magnetization of Cu/Ni composition modulated foils as a function of temperature, magnetic field, composition wavelength, and composition amplitude. We find a Curie temperature that initially increases rapidly with wavelength but quickly saturates. We also find that the Curie temperature is independent of composition amplitude which we ascribe to the existence of disk-like Ni clusters.
Effect of electron beam on the cathodoluminescence from indented MgO in the scanning electron microscope
Authors: Ballesteros C. , Llopis J. , Piqueras J.
Published: February 2003

The effect of an electron beam on the cathodoluminescence from indented MgO single crystals has been studied in the scanning electron microscope. It has been found that the luminescence intensity and spectrum vary with irradiation time. The behavior is attributed to changes in impurities and vacancies defects.
Computer modeling of the temperature rise and carrier concentration induced in silicon by nanosecond laser pulses
Authors: Lietoila A. , Gibbons J. F.
Published: February 2003

A set of simultaneous equations for lattice temperature, carrier concentration, and carrier temperature is numerically solved for typical nanosecond laser pulses. The temperature dependences of the thermal conductivity and lattice absorption are included, as well as the free carrier absorption and reflection. Carrier diffusion and electronic heat conduction are taken into account, and Auger recombination is assumed to be the dominant recombination mechanism. The calculations show that while free carrier absorption plays a major role in annealing with 1.06-μm radiation, only lattice absorption is important at wavelengths corresponding to photon energies well above the band gap. The Auger recombination coefficient is not a sensitive parameter, and the energy relaxation time does not affect the annealing results unless it is comparable to the pulse length. The results of the calculations are consistent with the hypothesis that the observed increase in silicon reflectivity is due to surface melting of the material. When literature values are used for all relevant parameters, the model predicts melt threshold energies which are in agreement with published experimental values.
Chemical sputtering yields of silicon resulting from F+, CFn+ (n = 1,2,3) ion bombardment
Authors: Miyake Kiyoshi , Tachi Shin’ichi , Yagi Kunihiro , Tokuyama Takashi
Published: February 2003

Chemical sputtering yields of crystalline silicon resulting from mass-separated, reactive ion bombardments are measured as a function of ion kinetic energy at room temperature. Ions of F+ and CFn+ (n = 1,2,3) are bombarded independently onto a silicon surface in an ultrahigh vacuum (UHV) environment. Evolution rate of SiF4 molecules resulting from surface chemical reaction: Si+4F→SiF4↑, is measured using a quadrupole mass filter. For F+/Si ion bombardment, yield increases monotonically with ion kinetic energy and saturates at 1 keV giving a value of 0.18. For CFn+/Si ion bombardment, yields show maxima at 1200 eV (CF+), 800 eV (CF2+) and 700 eV (CF3+). At ion energy ranges above 1.5 keV, yields for CFn+/Si are about half that for F+/Si. Carbon deposition and scavenging effects are discussed in detail by relating with fluorocarbon ion bombardment.
Investigations of holes machined by laser beam on Al and Cr thin films
Authors: Yamada Koichi , Watanabe Isao , Kubo Takahiro , Umeno Masataka , Yoshii Kumayasu , Kawabe Hideaki
Published: February 2003

Transmission and scanning electron microscopy studies of holes created by laser irradiation on Al and Cr films were carried out. The results showed that both films have the well-shaped round holes and that the peripheral regions form gentle swells for Al films and steep swells for Cr films. From the measurement of surface shape across the groove made by a laser beam the height of swells was nearly the same as the film thickness. It was also found that the swells are composed of large recrystallized grains, and that the effect of the existence of large grains on the recording characteristics is not so evident. The numerical analysis of temperature rise of the metal films was made using the finite difference method considering the phase transition of the film materials. Comparison of the temperature distributions with the experimental results revealed that the hole initiated by vaporization at the center of the melt expands outwards by the surface tension.
Epitaxial growth of Cd-doped InP from the vapor
Authors: Chevrier J. , Horache E. , Goldstein L. , Linh N. T.
Published: February 2003

Cadmium doping in vapor phase epitaxial growth of InP has been investigated; a partial pressure of cadmium was produced in an open tube system (In/PC13/H2 technique) by heating a cadmium metal source. The characterization of epitaxial layers was carried out over a wide range of doping densities. The distribution coefficient of cadmium was found to be 0.2 for a cadmium partial pressure below 1.5×10−4 atm. Above that pressure, a strong compensation limits NA−ND to a value below 3×1018 at. cm−3, while the growth rate decrease from 8 to 3 μm h−1. The carrier concentration was found to decrease regularly with heat treatment at 300 °C under hydrogen. Photoluminescence measurements have pointed out, in all cases, a broadband emission, centered at 1.3677 eV, corresponding to transition from Cd acceptor levels; however, the near-edge emission lines, peaked at 1.4105, 1.4115, and 1.4126 eV, in heavily doped layers, vanish upon annealing at 300 °C and are replaced by lines characteristic of lightly doped layers (1.413, 1.4145, 1.417, and 1.4182 eV respectively).
Detection of x rays from the anode of a vacuum arc
Authors: Pedrow P. D. , Matthys D. R.
Published: February 2003

A vacuum arc with hollow cylindrical anode can generate an arc voltage in excess of 10 000 V with currents in excess of 1000 A. A model has been developed that describes this high arc voltage as being caused by the conduction of the current through an electron space-charge region near the anode. The detection of x rays emitted from the anode at the time of the high arc voltage has confirmed the model of this vacuum arc. An x-ray pinhole camera gave spatial resolution and showed that the x rays were emitted from the anode. A p-i-n diode x-ray detector gave temporal resolution and showed that the x rays were emitted during the high arc voltage mode. A lithium fluoride crystal spectrometer gave energy resolution and showed that the emitted x rays were characteristic of the copper anode. This experiment confirmed that the major energy dissipation mechanism for this arc during the high voltage mode was the bombardment of the anode by electrons.
Alignment and texture of thin liquid crystal films on solid substrates
Authors: Hochbaum A. , Labes M. M.
Published: February 2003

Thin liquid crystal films in the range from 0.4 to 10 μm were thermally evaporated on solid surfaces. Semistable films were maintained on obliquely evaporated SiO surfaces that induce homeotropic, homogeneous, or tilted alignment. Realignment which violates the boundary conditions was observed in the smectic phase of thin films. The nematic phase of homogeneously aligned films has a peculiar two-domain texture indicative of a spontaneous twist due to conflicting and degenerate boundary conditions.
Sn and Te doping of molecular beam epitaxial GaAs using a SnTe source
Authors: Collins Douglas M. , Miller J. N. , Chai Young G. , Chow Robert
Published: February 2003

Secondary ion mass spectroscopy and free electron concentration measurements have been used to study the incorporation of Sn and Te in MBE GaAs when SnTe is used as the source of these impurities. The probability of incorporation of Sn and Te approaches unity for substrate temperatures (TS )≲550 °C and decreases to less than 0.1 for TS ≳600 °C. This decrease is attributed to desorption of SnTe from the GaAs surface. A SnTe ’’pair’’ incorporation mechanism is proposed which dominates over the entire substrate temperature range studied. However, dissociation of SnTe molecules on the GaAs surface, with subsequent surface accumulation of Sn and Te, becomes non-negligible for TS ≳580 °C. A model is presented which explains these as well as other features of the experimental data.
Experimental study of a new mechanism of magnetic flux cumulation by the propagation of shock-compressed conductive region in silicon
Authors: Nagayama Kunihito , Oka Tadashi , Mashimo Tsutomu
Published: February 2003

A new mechanism of magnetic flux compression proposed by one of the authors has been experimentally proved promising for the generation of ultrahigh pulsed fields. A cylindrical implosion type device is used here, and the thin metal liner normally used is replaced by a solid cylinder of crystalline or powdery silicon. As predicted by the theory, the field compression factor depends strongly on the initial density of the silicon, on the explosive, and on the scale. A typical value of the field multiplication factor is 17.8 for a 45-mm-diam silicon cylinder of density 1.1 g/cm3.
Melting point relations for simple halides, oxides, and chalcides
Authors: Van Uitert L. G.
Published: February 2003

For simple halides, oxides, and chalcides, the measure of crystal cohesion represented by the product of the melting point and the square of the bond length scales with the coordination number of the cation as well as with the ease of reversible transfer of electrons between neighboring atoms. Effects due to changes in the polarizability of inert (s2) pairs and the randomization of cations in crystals with the wurtzite structure are also discussed.
Thermal expansion of poly(vinylidene fluoride) films
Authors: Sao G. D. , Tiwary H. V.
Published: February 2003

Thermal expansion measurement of poly(vinylidene fluoride) is being reported along its film thickness, i.e., the direction of spontaneous polarization. Two-terminal-capacitance method with certain modifications has been adopted to measure the coefficient of linear thermal expansion. So far, the data on values of α along film thickness are not available for PVF2. The temperature variation of α shows anomalous behavior. It has been correlated with conspicuous changes in the related coefficients of piezoelectric, elastic, and electrostrictive properties. The thermal expansion further enhances the pyroelectric property of PVF2 through secondary pyroelectric effect.
Dopant diffusion in tungsten silicide
Authors: Pan Paihung , Hsieh Ning , Geipel Henry J. , Slusser George J.
Published: February 2003

The dopant (B, P, and As) redistribution in a silicide on polycrystalline silicon structure after annealing at 800 and 1000 °C was studied. The distribution of boron was found to be quite different from these of phosphorus and arsenic. At 1000 °C, the distribution coefficient for boron at the WSi2/polycrystalline silicon interface was found to be 2.7. The solubilities of phosphorus and arsenic in WSi2 at 1000 °C were estimated to be 6×1019 and 1.6×1019 atoms/cm3, respectively. At 800 °C, the diffusion coefficient for the dopants was found to be equal to, or greater than 3.3×10−12 cm2/s, which is at least three orders of magnitude larger than in silicon.
Comparison of annealing and ion implantation effects during solid state disilicide formation
Authors: d’Heurle F. M. , Tsai M. Y. , Petersson C. S. , Stritzker B.
Published: February 2003

Arsenic ions were implanted through a molybdenum-tungsten bilayer film into the underlying silicon substrate to a dose of 2×1016 ions/cm2. The implantation causes the formation of two superimposed silicide layers, respectively MoSi2 and WSi2, with the metal atoms showing little tendency to any intermixing. These results are compared with the observations made on similar samples when the silicides were formed through ordinary heat treatment.
Characterization of electron traps in n+ indium tin oxide on p-type InP solar cells
Authors: Lim H. , Sagnes G. , Bastide G. , Gouskov L. , Oemry A.
Published: February 2003

Three electron traps in n+ Indium Tin Oxide on p-type InP solar cells have been analyzed for the first time by Deep Level Transient Spectroscopy technique. These traps are located in the p-InP part of the solar cells. Their thermal signatures are E1 (320 meV, σ∼10−13 cm2), E2 (520 meV, σ∼10−9 cm2) and E3 (475 meV, σ∼10−13 cm3). Comparisons are made with previous data obtained on -type InP.
Theory of the flying light spot experiment to determine ambipolar mobility
Authors: Duggan G. , Lacklison D. E.
Published: February 2003

Theoretical expressions are presented which provide a more general analysis of the flying light spot experiment to determine ambipolar mobility than the standard, one-dimensional, infinite sample theory. We have approximated the semiconductor sample by a semi-infinite bar bounded by a non-ohmic contact. The finite length of the sample traversed by the light spot (the transit length) and the effect of the end contact on the observed carrier distribution have both been considered. The results are illustrated using parameters and device dimensions typical of a prototype Cadmium Mercury Telluride Infra-red detector operating in the 3–5 μm band at 190 K. We show that when contact effects can be neglected that symmetric waveforms are always obtained at the matched condition, regardless of the sample length traversed by the light spot. For short transit lengths the pulses are narrower than the dynamic equilibrium value. A contact with a low interface recombination velocity has an appreciable effect on the observed waveform and results in broadened pulses. When the light spot velocity (VL) and ambipolar velocity (VA) are identical a symmetric waveform is no longer observed. Symmetry occurs when VL<VA. Values of VA deduced using this method, in this situation, would therefore be too low.
Piezoelectric properties of lithium borosilicate glass ceramics
Authors: Halliyal A. , Bhalla A. S. , Newnham R. E. , Cross L. E.
Published: February 2003

Glass ceramics in the system Li2O-SiO2-B2O3 with oriented crystallites were prepared by crystallizing the glasses in a temperature gradient. Piezoelectric and electromechanical properties of the glass ceramics are reported. Some of the compositions exhibit low temperature coefficient of resonance, comparable to LiTaO3 single crystals. Advantages of fabricating glass-ceramic piezoelectric resonators are described and the possibility of using them in surface acoustic wave (SAW) devices is suggested.
Thermal diffusivity determination by cross correlating injected and transmitted heat pulses through a wall
Authors: Kougbeadjo R. A. , Thery P.
Published: February 2003

The method for determining thermal diffusivity described in this paper is an application of a cross correlation method to analysis heat transfer through homogeneous walls. The experimental method consists of switching on and off, in a pseudorandom manner, a thermofoil heater disposed on the front face of a wall to be measured. The resultant heat-flow excursions at the rear face of the wall are then detected by using a large sized and short rise time heat-flow sensor. When the front face of a wall is subjected to a heat pulse, the transmitted heat flow has a maximum value for a delay which is both a function of the heat pulse duration and diffusion time of the wall. The value of this delay can theoretically be used to determine thermal diffusivity. The transit time of the heat through the homogeneous wall can also be measured by cross correlating injected heat pulses and transmitted heat-flow excursions. The cross correlation function between the incident and transmitted heat flow has a maximum value for a cross correlation lag depending also on the injected heat pulse duration and diffusion time of the wall. The principal advantage of the cross correlation method is its capacity to perform thermal diffusivity measurements independently of the exact shape of the incident heat pulse. Another advantage is that cross correlation rejects the effect of spurious noise superimposed on the transmitted signal. It is shown that a pseudorandom injected heat pulse (impulse sequence) having an autocorrelation function similar to that of a single square pulse can be used to determine thermal diffusivity. The thermal diffusivity measurement depends on the employment of a mathematical model which supposes there is no temperature variation at the back face of the wall. The analytical solution forms the basis of a digital computer procedure devised for calculating the thermal diffusivity from experimental measurements. The theoretical developments have been used to outline the construction of a versatile apparatus for thermal diffusivity measurements. This possesses full computational facility for data processing and high precision for determining thermal diffusivity. Examples of materials measured are standard reference materials like plexiglass and other materials used for thermal insulation.
Diffraction of medium and long wavelength horizontally polarized shear waves by edge cracks
Authors: Datta S. K. , Shah A. H. , Fortunko C. M.
Published: February 2003

Scattering of horizontally polarized shear (SH) waves by edge cracks of length l and of different orientations relative to the free surface of the half-space is studied. A combined finite element and analytical technique is presented that is suitable for analyzing scattering by cracks or inhomogeneities in a semi-infinite elastic medium. Attention is focused in the range of wavelengths λ, when the ratio l/λ is ⩽1/2. Numerical results are presented for crack opening displacements and scattered fields on the surface when the medium is homogeneous or when the crack is located in an insert with different material properties. Comparison of the theoretical solution is also made with available experimental results. The experimental results are obtained using electromagnetic-acoustic transducers that can efficiently generate and detect low-frequency SH waves in metals. The results are applicable to sizing and characterization of weld defects. Recent experimental evidence suggests that this can be accomplished when the wavelength is of the order of twice the crack length or longer.
Low-pressure gas flow through a microsize channel
Authors: Kalensher Bernard E. , Perel Julius
Published: February 2003

A theory is developed which predicts the mass flow rate, at low pressure, of an ideal gas through a microsize cylindrical channel. It is assumed that the gas flow is viscous, laminar, and compressible. Experiments are performed in which argon gas at various temperatures is passed through the Capillaritron Ion Source, whose interior geometry is consistent with the theory, and measurements are made of the mass flow rate. The experimental and theoretical flow rates are discussed, and then a comparison is made between these two. It is found that, on the average, the theory predicts the experimental flow rates to within 7.2%.
A kinetic study of the plasma-etching process. I. A model for the etching of Si and SiO2 in CnFm/H2 and CnFm/O2 plasmas
Authors: Kushner M. J.
Published: February 2003

A kinetic model of the plasma-etching process has been developed to describe the etching of Si and SiO2 in CnFm/O2 and CnFm/H2 plasmas (CnFm ≡CF4, C2F6). The model has obtained good agreement with experiment for demonstrating the selective etching of SiO2 in CnFm/H2 plasmas, and the enhancement of the etch rate of Si in CnFm/O2 plasmas. Good agreement is also obtained with mass spectroscopic measurements of neutral species from a CF4/H2 plasma. Results from the model indicate that the adsorption of atomic hydrogen on silicon surfaces from CnFm/H2 plasmas, which then reacts with adsorbed fluorine, can significantly effect the selectivity of etching SiO2 with respect to Si. Similarly, the adsorption of atomic oxygen, which then reacts with adsorbed carbon thereby cleansing the surface, may be responsible for the large etch rates of Si seen in CnFm/O2 plasmas. The selectivity of etching SiO2 in CnFm/H2 plasmas has been found to be a sensitive function of the C/F ratio of the carbon-bearing molecules which desorb from the surface, and a C/F ratio of 0.5 shows best agreement with experiment. Results from the model favor ion drift as a dominant mechanism by which radicals are transported to the surface.
A kinetic study of the plasma-etching process. II. Probe measurements of electron properties in an rf plasma-etching reactor
Authors: Kushner M. J.
Published: February 2003

Electrical probe measurements made in an rf plasma-etching reactor are discussed as a function of gas mix and position in the reactor. Comparisons are made to a kinetic model for the plasma etching process. The electron density as a function of the ratio CF4/H2 and CF4/O2 was found to decrease as the fraction of CF4 decreased, although local extrema in electron density were observed. The electron flux distribution was also found to show extrema as the gas mixture was changed. The spatial variations of electron density and temperature between the electrodes were found to be a function of electrode material.
Study of preheat effects in ND-laser irradiated finite Al disk targets
Authors: Meyer B. , Morin G. , Thiell G.
Published: February 2003

Energy streaming around and through an Al disk target irradiated with a Nd-glass laser delivering a 0.8-ns pulse is discussed as a function of target thickness, disk diameter, and laser irradiance from 5×1012 to 5×1014 W cm−2. Front and rear surface behaviors of the disk are studied by means of frame and streak shadowgraphy, short-time exposure interferometry, ion calorimetry, and charge collectors. Experimental data clearly show that preheat of the rear side of a 500-μm-diam disk is due to plasma encompassing the target and occurs even at laser irradiance as low as 3×1013 W cm−2. Moreover, it is seen on time-resolved photography of double-disk targets, that the second foil expands before being struck by the first disk (irradiated disk) at laser irradiance as low as 1013 W cm−2. This effect is ascribed to preheating by particle bombardment. Numerical simulations do not match the experimentally observed temporal behaviors for the 500-μm-diam disks even with some preheat included in the hydrodynamic code, but they agree quite closely with the experimental results when the irradiated disk diameter is much larger than the characteristic density gradient length.
Repetitive operation of an inductively-driven electron-beam diode
Authors: Fell B. , Commisso R. J. , Scherrer V. E. , Vitkovitsky Ihor
Published: February 2003

Recovery of a pulsed electron beam diode operating in the 50 A/cm2 range has been studied using an inductive storage source producing two∼150 kV pulses with pulse-to-pulse separation ranging from 10–500 μsec. The diode cannot instantaneously support a second voltage pulse because of the short circuit provided by the interelectrode plasma associated with the first pulse. The properties of this plasma, including its effective lifetime, have been studied. The diode is observed to recover for pulse separation times≳100 μsec. The results can be extended to repetitively pulsed electron beam generation as needed in many physics experiments such as those related to beam propagation in gases, opening switches, and laser phenomenon.
High speed response of a GaAs metal-semiconductor field-effect transistor to electron-beam excitation
Authors: Flesner L. D. , Davis N. M. , Wieder H. H.
Published: February 2003

Subnanosecond current gain response of a GaAs power metal-semiconductor field-effect transistor to electron-beam pulses is described. Two distinct gain mechanisms are deduced from the data.
Photocapacitance study of deep levels due to nonstoichiometry in nitrogen-free GaP light-emitting diodes
Authors: Nishizawa J. , Shi Y. J. , Suto K. , Koike M.
Published: February 2003

Photocapacitance spectra of the excitation probability of electrons (or holes) occupied in deep levels have been measured for S- and Te-doped nitrogen-free GaP light-emitting diodes grown by temperature difference method of liquid phase epitaxy under various phosphorus pressures in the vicinity of the optimum pressure (Popt ). A band at 2.00 eV observed for the diodes grown under phosphorus pressures higher than Popt is attributed to interstitial phosphorus atoms. On the other hand, bands at 2.10 and 2.20 eV which were observed, respectively, in the spectra of S- and Te-doped diodes grown under phosphorus pressure lower than Popt are attributed to complex centers of phosphorus vacancies and donors.
High gradient magnetic capture of red blood cells
Authors: Owen Charles S.
Published: February 2003

High gradient magnetic retention of paramagnetic red blood cells was measured under conditions which gave rise to only partial capture of the cells in each sample. The dependence on buffer flow rate, magnetic field, and particle paramagnetic susceptibility was determined and compared with theoretical models. In addition, parallel and transverse geometries (field parallel to, or perpendicular to, flow) were compared and no difference was observed in the probability of capture of weakly paramagnetic cells in a lightly loaded filter bed.
Multitube collimators driven at high pressure for molecular spectroscopy
Authors: Baldacchini G. , Marchetti S. , Montelatici V.
Published: February 2003

Multitube collimators driven at low pressure, usually 1 Torr or less, have been extensively used up to now to produce collimated molecular beams. We have found experimentally that such devices, when driven at high pressure, 1<P0<100 Torr, lose almost completely their collimation properties. However, they produce a sensible cooling of the gas in the beam at a density high enough to make the high-pressure regime attractive for molecular spectroscopy. Moreover, we have observed for the first time an oscillatory behavior of the angular spread of the beam versus the pressure.
Mg+ implantation into AlxGa1−xAs
Authors: Ashigaki Shigeo , Makita Yunosuke , Kanayama Toshihiko , Tsurushima Toshio
Published: February 2003

Ion implantation of Mg into Alx Ga1−xAs was carried out at room temperature. After annealing at 700 °C, GaAs showed nearly 100% electrical activation, however, Al0.60Ga0.40As showed only 15% electrical activation. We explain this result in terms of increasing acceptor energy level and outdiffusion of Mg with increasing alloy composition x.
Thermal study of the Pt-Al reaction and its effects on contact resistance to silicon
Authors: Cohen S. S.
Published: February 2003

The sintering reaction of a thin film of platinum on a silicon substrate followed by a thicker aluminum overlayer has been studied. The metal layers were deposited on 〈100〉 oriented p- and n-type silicon. Aluminum is the major contaminant found in sputtered platinum films. Possible deleterious metallurgical reactions between platinum and several possible metal contaminants during subsequent processing were previously discussed. In the present study the metallization system was exposed to harsh thermal and chemical conditions. The results do not indicate the existence of detrimental effects on the ohmic contact properties due to a platinum-aluminum reaction, following the usual treatment in aqua regia, if a thick enough (∼500 Å) layer of platinum is used. In fact, the formation of a PtAl2 intermetallic compound seems to result in low values for the specific contact resistance.
CO laser annealing of arsenic-implanted silicon
Authors: Delfino M.
Published: February 2003

The annealing behavior of arsenic-implanted silicon using a CO laser is investigated and compared to CO2 laser annealing. The irradiation time dependence of the surface carrier concentration and electron mobility on the laser wavelength and substrate doping density is shown to be a direct consequence of free carrier absorption. The two infrared laser annealing methods are found to result in identical electrical characteristics, which are comparable to that obtained by 30-min furnace anneals at 800 °C.
Minority carrier lifetime in GaP grown by liquid phase epitaxy for high temperature applications
Authors: Gourley P. L. , Dawson L. R.
Published: February 2003

We have measured the minority carrier lifetime τmin in liquid phase epitaxial GaP material grown for high-temperature device applications, as a function of doping concentration, temperature, and epitaxial layer thickness. In p-type GaP doped with Mg, τmin remains constant with increasing carrier concentration until p≊1018 cm−3, where it decreases rapidly. For nominally undoped n-type material we find that τmin increases by nearly one order of magnitude over the temperature range T = 22–600 °C. The apparent lifetimes in these thin-layer materials increase with layer thickness indicating that surface and interface recombination are important.
Magnetostatic volume wave propagation in a ferrimagnetic double layer
Authors: Daniel Michael R. , Emtage P. R.
Published: February 2003

Using the technique of ’’surface permeabilities,’’ an expression is derived for the dispersion of magnetostatic waves propagating in two close proximity ferrimagnetic films. Two modes of propagation for volume waves are identified respectively as the symmetric and antisymmetric modes from the symmetry of the rf magnetization. Useful group delay behavior is shown to result from films of equal thickness. Some measurements are reported using two yttrium iron garnet films sandwiching simple single finger transducers. Difficulties in exciting the symmetric forward volume mode are explained in terms of the coupling coefficients for these double film structures.
High coercivity Co and Co-Ni alloy films
Authors: Maeda H.
Published: February 2003

A high coercivity and a high hysteresis loop squareness pure Co and Co-Ni (up to 50 at %) alloy films have been prepared by a new process. The new process involves the films, including N, being sputter deposited in an atmosphere of Ar-N2 mixture and annealed at temperature above 553 K. Most of the included N diffuses out from the film surface after annealing, and the films have a strong preferred orientation with the c axis parallel to the film plane. In Co70Ni30 alloy films, a high coercivity Hc of 1 kOe (80 kA/m) and a high hysteresis loop squareness S* of 0.95 are achieved. The values of Hc gradually decrease as the Ni/Co concentration ratio of the films departs from 30/70. There is a strong correlation between Hc and the preferred orientation of crystallites; Hc increases as the c axis orientation parallel to the film plane grows.
Magnetization, strain, and anisotropy field of Ne+ and H+ ion-implanted layers in bubble garnet films
Authors: Satoh Y. , Ohashi M. , Miyashita T. , Komenou K.
Published: February 2003

The effects of the implantation dose and annealing on magnetization (4πMs), lattice constant strain (Δd/d), and change in the anisotropy field (ΔHK) of a layer implanted with Ne+ or H+ ions in bubble garnet films have been investigated using a vibrating sample magnetometer (VSM), the double crystal x-ray technique, and ferromagnetic resonance measurements. The magnetic and crystalline properties of Ne+ or H+ ion-implanted layers were quite different. Saturation magnetization of the H+ ion-implanted layer decreased gradually with Δd/d beyond 1%, while that of the Ne+ ion-implanted layer decreased abruptly above 1%. ΔHK of the Ne+ ion-implanted layer was proportional to Δd/d up to a saturation point of about 1%; however, ΔHK of the H+ ion-implanted layer continued to increase after Δd/d passed 1%. The other distinct difference between the H+ and Ne+ ion-implanted specimens was the temperature necessary to obtain annealing effects. In the H+ ion-implanted layer, annealing in the lower (around 200 °C) temperature range had a relatively larger effect on 4πMs and ΔHK than with the Ne+ ion-implanted layer.
Direct evidence for photon recycling in p-(Ga,Al)As:Si with a graded band gap
Authors: Rühle W. , Hoffmann L. , Leibenzeder S.
Published: February 2003

Time resolved photoluminescence experiments show the importance of photon recycling in p-(Ga,Al)As:Si liquid-phase epitaxial layers with a graded band gap. In particular, it is confirmed that the drift of the electrons in the built-in electric field may be neglected. Strong inhomogeneities of the electron lifetime are experimentally demonstrated and explained by the varying compensation of the amphoteric Si doping. The large contribution of photon recycling to the externally observed spectra is shown by ’’front’’ and ’’back’’ excitation of the cw photoluminescence. The internal quantum efficiency at room temperature is probably appreciably above 20%.
Positive secondary-ion emission from Fe-Ni alloys under O+2 bombardment at 45° incidence
Authors: Reuter W. , Yu M. L.
Published: February 2003

Normalized ionization probabilities α+ are reported for binary Fe-Ni alloys under O+2 bombardment at a 45° incidence angle. It is shown that the dependence of α+ on the composition is much smaller than at normal incidence. Photoemission spectroscopy reveals that both nickel and iron remain essentially metallic under oblique-incidence bombardment, whereas almost complete oxidation occurs at normal incidence. This is attributed to our observation that sputter yields under oxygen bombardment increase much faster than cos α−1.
Negative ion formation in magnetically insulated transmission lines
Authors: Stinnett Regan W. , Stanley Tim
Published: February 2003

Negative ion intensities of over 3×105 A/m2 at energies of 2 MeV have been measured in a magnetically insulated transmission line. This negative ion production can affect the power flow in multiterawatt pulsed power devices, and may also have applications in the generation of high-intensity neutral or negative ion beams.
Analysis of the wave forms of breaking arc of electrical contacts in air
Authors: Sato Mitsunori
Published: February 2003

The breaking arc wave forms have been observed by means of an oscilloscope in the range of applied voltages from 20 to 280 V and of amperages from 0.3 to 50 A for both dc and ac circuits of noninductive and inductive loads; the materials of contacts examined are silver, tungsten, and carbon. The equations to give the length, voltage, and current of the breaking arc are derived in terms of the applied voltage and current, minimum voltage and current necessary for a steady arc, breaking phase angle, phase angle between the applied voltage and current, angular velocity, and finally separating speed. The equations are found to be applicable for all materials irrespective of thermionic emission type or field emission (T-F emission) type.
Frequency dependent capacitance studies of the CdS/Cu2S thin-film solar cell
Authors: Hmurcik Lawrence V. , Serway Raymond A.
Published: February 2003

Measurements of the dark capacitance of CdS cells as a function of the frequency of the applied signal voltage have shown that the capacitance varies with frequency according to the relation C−C∞ = (C0−C∞)/(1+ω2τ2), where τ is the time constant associated with interfacial and deep bulk states. Photocapacitance studies show that the CdS cell can be treated according to the frequency dependent model of Schibli and Milnes. Under the influence of light, C∼1/(ω)1/2. Further work demonstrates that the simple planar junction model most often used to describe the CdS cell is accurate at high frequencies.
ZnO varistors for liquid crystal displays
Authors: Levinson Lionel M. , Castleberry Donald E. , Becker Charles A.
Published: February 2003

ZnO varistors are excellent materials for multiplexing dichroic liquid crystal displays. We describe here the development of varistor materials tailored for this application. The varistors are large (∼25 cm diameter), uniform, and have relatively low dielectric constant.
Thermal stability of Pb-alloy Josephson junction electrode materials. VI. Effects of film edges on the strain distribution of Pb-Bi counterelectrodes
Authors: Murakami Masanori
Published: February 2003

Because line-patterned ε-phase Pb-Bi films are used as the counterelectrode materials of Pb-alloy Josephson junction integrated circuits presently under investigation, a study was undertaken on the effects of the film width on the strain distribution and average elastic strain supported by the film at 4.2 K. The study was carried out using an x-ray diffraction technique for 0.6-μm-thick Pb-29% Bi films that were deposited onto oxidized Si wafers at 273 K, and then cooled to 4.2 K. The blanket films supported almost all of the strain elastically at 4.2 K, and symmetric x-ray diffraction peak profiles were observed in the films, indicating that they were uniformly strained. Asymmetric peak profiles due to nonuniform strain distributions in the film were observed when the film width was smaller than ∼40 μm. The measured x-ray diffraction peak profiles were analyzed using a computer simulation technique. The analysis indicated that the strain distribution at the center of the film is close to the one calculated using the energy minimization method developed by Aleck. Average strains supported elastically at 4.2 K by the films were observed to decrease with decreasing the film widths as predicted by the model, and excellent agreement was obtained between the measured and calculated average strains in the films with various film widths. However, the high local strain at the film edges predicted by this model is not observed. The strain is believed to relax during cooling to 4.2 K.
Inhomogeneity size and shape determination from scattering of low-frequency sound waves
Authors: Mountain Raymond D. , Birnbaum George
Published: February 2003

The scattering of sound waves by isolated inhomogeneities in a solid is examined using the Born approximation. A procedure is developed to extract information about the effective volume and shape of the scatterer. The procedure uses data from the long-wavelength region where this approximation is valid. The volume and shape information is in the form of special moments of the volume of the scatterer which depend on the orientation of the scatterer relative to the direction of the difference in the incoming and outgoing wave vectors. A scheme is described which permits the characterization of the scatterer in terms of an equivalent ellipsoid. The scheme provides a second-moment solution of the inverse scattering problem.
Internal friction in intrinsic and n-type germanium and silicon
Authors: Gerk A. P. , Williams Wendell S.
Published: February 2003

The dependence of the high-temperature internal friction of germanium and silicon, both intrinsic and highly n type, was measured as a function of temperature, frequency, dislocation density, and dopant concentration. An acoustoelectric peak in both germanium and silicon was detected and found to agree well with the theory of Weinreich. The high-temperature dislocation-dependent damping in intrinsic germanium and silicon was studied and seen to be consistent with most previous studies. If deformed at high temperature and allowed to anneal, highly doped n-type material behaved intrinsically due to preferential precipitation at dislocations; however, if deformed at moderate temperatures and not allowed to anneal, such crystals exhibited a greatly enhanced dislocation-dependent internal friction which depended on the extrinsic carrier concentration. A theory was developed for dislocation damping in semiconductors and was found to agree well with experimental results. The model is based upon electronic viscous damping of dislocations by excess current carriers whose lifetimes are controlled by Auger recombination processes.
Physical properties of antimony-doped tin oxide thick films
Authors: Kaneko H. , Miyake K.
Published: February 2003

The physical properties of Sb-doped SnO2 thick films, prepared by a repeating chemical spray deposition method, have been investigated. The films 1000–14 000-Å thick were deposited on fused quartz, borosilicate glass, and soda lime glass substrates at 600 °C using an aqueous solution of a mixture of SnCl4 and SbCl3. The films prepared by the method are homogeneous, and the electrical resistivity of the films on fused quartz and borosilicate glass substrates were found to be independent of the film thickness, and are 9.5×10−4 Ω cm, and 8.6×10−4 Ω cm, respectively. The resistivity of the films thicker than 4000 Å on soda lime glass substrates is almost constant, and is 1.8×10−3 Ω cm, although a large increase in the resistivity of the thinner films was observed. The optical band gap of the films on fused quartz and borosilicate glass substrates is also independent of the film thickness, and is almost the same: 3.75 eV. But the band gap of the films on soda lime glass substrates depends on the film thickness, and increases from 2.85 to 3.08 eV with increasing thickness from 2250 to 13 000 Å. The Hall mobility and carrier concentration of the films were also measured. The results of x-ray diffraction analysis and observations by SEM are described.
Electrical and structural properties of Ag-X diffusion couples (X = Te, Se, S, and I)
Authors: Hauser J. J.
Published: February 2003

The deposition of Te on an already deposited Ag film and of Ag on a Te film results in a homogeneous Ag-Te alloy as a result of fast Ag diffusion (4×105 Å2 sec−1 at 300 K). In the case of Ag-Te, when the diffusion proceeds at 200 K, the resulting diffusion couple is amorphous. In situ resistance measurements suggest that the same Ag diffusion mechanism operates when Ag atoms or Ag films are in contact with Se (7.3×104 Å2 sec−1 at 253 K), S, or I. The major difference with the Ag-Te case is that in the latter cases, even when the Ag diffusion proceeds at low temperatures (?200 K), the resulting diffusion couples are always crystalline Ag2Se, Ag2S, or AgI.
Current transport in modulation-doped Ga0.47In0.53As/Al0.48In0.52As heterojunctions at moderate electric fields
Authors: Drummond T. J. , Morkoç H. , Cheng K. Y. , Cho A. Y.
Published: February 2003

Modulation-doped Ga0.47In0.53As/Al0.48In0.52As single period heterostructures were prepared by molecular beam epitaxy. Current versus electrical field characteristics were investigated in a lattice temperature range of 10–300 K. Measurements were performed at electric field strengths as high as 2 kV/cm which is comparable to the field strengths attained in normally-off field effect transistors. Mobilities as high as 8960 cm2/Vs at 300 K, 61 100 cm2/Vs at 75 K, and 93 000 cm2/Vs at 10 K were measured and were found to be proportional to temperature approximately as μ∝T−1.74. Mobility enhancement was observed in the single period Ga0.47In0.53As/Al0.48In0.52As system irrespective of the relative position of the larger band gap Si-doped Al0.48In0.52As.
A study of the high resistivity GaAs surface and the GaAs/oxide interface using two-beam transverse acousticoelectric voltage spectroscopy
Authors: Davari B. , Das P.
Published: February 2003

The presence and the location of a band of acceptor levels at the surface of the high-resistivity GaAs (Cr doped) and the GaAs/oxide interface is studied, using two-beam Transverse Acousticoelectric Voltage (TAV) spectroscopy. This study is not feasible by conventional C-V methods due to the high resistivity of GaAs samples. The band of acceptor levels, centered around 1 eV above the valence band is detected nondestructively. The anodic oxides are grown electrochemically using different current densities (0.1–3 mA/cm2) under constant current regime. The interfacial characteristics of the GaAs/oxide is compared by the two-beam TAV spectroscopy. The results show a lower density of interface states for the oxides grown at lower current densities. To explain the presence of the acceptor band above the midgap in all of the tested samples, the physical models proposed by different authors are presented and compared.
Limitations in determining hole diffusion lengths from photocurrent measurements in gallium arsenide
Authors: Stagg J. P.
Published: February 2003

Photocurrent measurements using sub-band-gap light on low doped n-type gallium arsenide are described. Measurements of photocurrent I as a function of depletion width W and wavelength λ were made to determine minority carrier diffusion lengths L of order 1 μm. For long wavelengths (λ≳0.879 μm) I(W) plots could be used to measure L for carrier concentrations n?2×1015 cm−3. For larger values of n, when W≳L, the method was inapplicable owing to nonlinearities in the plots. The mean change in absorption coefficient, Δα, at λ = 0.8907 μm was determined from the plots as a function of electric field and was in qualitative agreement with calculations of the expected variation due to the Franz–Keldysch effect. It is shown that the measurements of I(λ) may be used to determine L for n<5×1015 cm−3 provided accurate absorption coefficient data are available. A correction for the Franz–Keldysch effect is necessary for 2×1015 <n<5×1015 cm−3. For 5×1015<n<1016 cm−3 the method is inapplicable, when W≳L, owing to nonlinearities caused by the Franz–Keldysch effect.
Electrical conductivity and thermal stability measurements of a mixed perovskite oxide system
Authors: Sukkar Mary H. , Sadoway Donald R.
Published: February 2003

For the mixed perovskite oxide system (Sr0.8125La0.1875 ) (Zr0.75FexRu0.25−x)O3−δ , electrical conductivities were measured in air as a function of temperature and Ru/Fe ratio. Liquidus and solidus temperatures were determined in air by the laser melting point measurement technique. The substitution of Ru for Fe was found to increase the electrical conductivity by over an order of magnitude while decreasing the solidus temperature of the Fe-rich solid solution by less than 10%.
Redistribution of implanted phosphorus after platinum silicide formation and the characteristics of Schottky barrier diodes
Authors: Kikuchi Akira , Sugaki Shojiro
Published: February 2003

Schottky barrier diodes are fabricated on silicon surfaces whose impurity concentrations are controlled by ion implantation techniques. The barriers are produced by PtSi or Al-Si. The forward characteristics of the diodes show that the forward voltages of Schottky barrier diodes made by PtSi are lower than those made by Al-Si for implanted doses of 2×1013 cm−2 and higher. Spreading resistance measurements show that the implanted phosphorus atoms are piled up near the PtSi-Si interface during PtSi formation. This phenomenon causes reduction of the effective barrier height.
Electrical characteristics of heavily arsenic and phosphorus doped polycrystalline silicon
Authors: Murota Junichi , Sawai Takashi
Published: February 2003

The dependence of resistivity, carrier concentration, and grain size upon the impurity concentration and heat-treatment temperature for heavily As- and P-doped chemical-vapor-deposited polycrystalline Si is experimentally investigated, and compared with the resistivity and carrier concentration in single-crystal Si. It is found that the resistivity and carrier concentration in polycrystalline Si are mainly determined by those in crystallite and the grain size which is dependent upon the heat-treatment temperature. Evaluating the segregation of As atoms at grain boundaries from the experimental results of As diffusion into single-crystal Si from polycrystalline Si, it is found that, even when impurity atoms scarcely segregate at grain boundaries, the carrier concentration in polycrystalline Si is lower than that in single-crystal Si. To explain the phenomenon, it is assumed that impurity atoms are electrically inactive in the disordered region near the grain boundaries. Combining the above assumption and the experimental results, the width of the disordered region and carrier trapping density at grain boundaries are estimated to be 110 Å and 4×1012 cm−2, respectively, for the samples heat treated at 1200 °C. It is suggested that As-doped polycrystalline Si has a higher grain boundary barrier resistance than P-doped polycrystalline Si.