bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy and fluence dependence of the sputtering yield of silicon bombarded with argon and xenon
Authors: Blank P. , Wittmaack K.
Published: February 2003

Using the quartz oscillator technique, we have measured the sputtering yield of silicon bombarded with 10–140-keV argon and 10–540-keV xenon, respectively. Considerable effort has been devoted to achieving high-purity silicon films with smooth surfaces and to calibrating the microbalance. In situ combination of the quartz oscillator technique with Rutherford backscattering allowed a quantitative determination of the fluence dependence of the sputtering yield. Measurements with xenon at 140 and 270 keV showed that the sputtering yield of silicon increases by about 25% due to loading of the target with projectile atoms. A simple estimate indicates that the yield enhancement is caused, to a large extent, by the increase in nuclear-energy deposition resulting from the accumulation of the heavy projectiles in silicon. The measured steady-state sputtering yields are in satisfactory agreement with results achieved by other experimental techniques. Discrepancies with results derived by other authors applying the quartz oscillator microbalance technique can be attributed to surface topography effects. Comparison of the measured energy dependence of the (steady-state) sputtering yield with theory shows good agreement.
Tunable multilayer-film distributed-Bragg-reflector filter
Authors: Kimura Mitsuteru , Okahara Kazuaki , Miyamoto Toshihiko
Published: February 2003

The periodic multilayers of dielectric materials such as polystyrene/collodion or polystyrene/polyvinyl alcohol were fabricated by means of alternately dropping these solutions onto a spinner. As these materials are slightly elastic, a large shift of the center of the Bragg reflection by 650 Å toward shorter wavelength is obtained by the compression of the multilayer. A periodic length Λ is controlled by adjusting both the rotation speed of the spinner and the concentration of the solutions.
Continuum basis for diffusion in regions with multiple diffusivity
Authors: Aifantis Elias C.
Published: February 2003

A continuum model is proposed to consider diffusion situations where distinct types of structural or point defects contribute to the overall diffusivity. With respect to structural defects, the analysis is motivated by diffusion in the presence of a continuous distribution of high-diffusivity paths, such as grain boundaries and dislocations. With respect to point defects, the analysis is motivated by simultaneous diffusion of vacancies and interstitials, or vacancies and substitutionals. As a result of continuum modeling, the analysis is strictly valid in cases where the distribution of defects can be assumed continuous in space-time. The model is illustrated by detailing an example: dislocation-pipe diffusion under steady-state conditions.
Determination of flaw characteristics from ultrasonic scattering data
Authors: Rose J. H. , Krumhansl J. A.
Published: February 2003

We report an approximate technique (and some test results) for determining the characteristics of flaws in elastic media from a knowledge of the ultrasonic scattering amplitudes. The technique is rigorously valid in the weak-scattering limit. Good results have been obtained for strongly scattering spherical flaws such as a void in stainless steel. The technique is insensitive to random noise in the scattering amplitudes.
Frequency dependence of pyroelectric current in poly(vinylidene fluoride) heat sinked at various temperatures
Authors: Hu L. F. , Takahashi K. , Salomon R. E. , Labes M. M.
Published: February 2003

The frequency and temperature dependences of pyroelectric activity in poly(vinylidene fluoride) have been studied from 10 to 369 °K using mechanically chopped and steady-state radiation. From these data, thermal diffusivity and a parameter indicating the polarization inhomogeneity can be deduced and compared with a mathematical model.
Thermally stimulated current and creep in poly(ethylene terephthalate)
Authors: Lacabanne C. , Chatain D. , Monpagens J. C. , Berticat Ph.
Published: February 2003

Two thermal stimulation techniques (thermally stimulated current and creep) have been used to study the dielectric and mechanical retardation modes observed in poly(ethylene terephthalate) between liquid-nitrogen temperature and the glass transition temperature. From the data acquired, the dielectric and mechanical energy losses have been calculated: they are found to be in good agreement with those derived from other dielectric and mechanical techniques. The high resolving power of the thermal stimulation methods has allowed us to distinguish three modes in both bioriented and amorphous PET. In the bioriented sample, the three modes correspond to a discrete distribution of retardation time τ, while in the amorphous sample, they correspond to a continuous distribution of τ. In amorphous PET, the distributions of dielectric and mechanical retardation times are reduced to a single τ—5×10−4 and 7×10−3 sec—for a converging temperature of 233 and 277 K, respectively.
Frequency-stabilized 3.39-μm He-Ne laser with no frequency modulation
Authors: Nakazawa Masataka , Musha Toshimitsu , Tako Toshiharu
Published: February 2003

The frequency of the 3.39-μm He-Ne laser whose output beam does not contain any artificial frequency modulation was newly stabilized in reference to the saturated absorption line of CH4 gas contained in an external cell. Instead of modulating frequency by vibrating the resonator length, the frequency modulation was given by an external vibrating mirror on which the laser beam was reflected. A 3.39-μm low-noise optical amplifier was also used for observing saturated absorption in the external cell. A signal proportional to a frequency deviation from the reference absorption line was fed back to the resonator to control its length such that the frequency deviation was minimized. The short-term stability so achieved under a proportional feedback control was ±1.25×10−12/min, the frequency drift was 2.3×10−10/h, and the long-term stability under an integral feedback control was ±3.5×10−11 over 5 h.
ac losses of bronze-processed (Nb1−xZrx)3Sn between 5 and 16 K
Authors: Bussière J. F. , Kovachev V. T.
Published: February 2003

ac losses of bronze-processed Nb3Sn tapes were measured between 5 and 16 K. Additions of up to 5% Zr to the Nb substrate were found to cause only a slight increase in loss. However, because of the increased Tc of the NbZr substrate as compared to pure Nb, such additions appear advantageous in some ac applications. The lowest losses were obtained for an anodized sample of (Nb–1% Zr)3Sn (e.g., 11 μW/cm2 at 500 rms A/cm and 12 K).
Pulsed-CO2-laser interaction with aluminum in air: Thermal response and plasma characteristics
Authors: McKay J. A. , Bleach R. D. , Nagel D. J. , Schriempf J. T. , Hall R. B. , Pond C. R. , Manlief S. K.
Published: February 2003

Simultaneous target heating, plasma spectral emission, and time-resolved plasma interferometry data were taken for the interaction of CO2 (λ=10.6 μm) laser pulses with aluminum targets in air. The laser spot area on the planar targets was 1.4 cm2, the pulse duration was 1.8 μs, and the maximum peak flux on target was 8×107 W/cm2. The target thermal response is analyzed to provide both the total energy deposited on target and the spatial distribution of the energy. The total energy deposited increases in direct proportion to the laser-pulse energy, with a coupling coefficient of 18% above the plasma ignition threshold. The spatial maximum value of the energy-deposition density, in contrast to the total energy, remains constant as the laser-pulse energy increases, demonstrating that target heating takes place over an area increasing with the laser-pulse energy. Even at the plasma ignition threshold, the area of energy deposition exceeds substantially the laser spot area. The spectroscopic measurements suggest that continuum radiation occurs earlier than and dominates line radiation at wavelengths near 4000 Å. At shorter wavelengths many lines from target elements are observed. Plasma electron temperatures of 12 000 K for aluminum and 16 000 K for nitrogen were derived from LTE calculations. Below the plasma ignition threshold, open-shutter photography shows weak emission at the target surface, while above threshold a bright plasma propagating away from the target is observed. Time-resolved interferometry of the plasma was done using a Q-switched ruby laser in a Mach-Zehnder interferometer. The blast wave propagates with distance nearly proportional to (time)2/3 after the laser pulse, in agreement with theory for one-dimensional propagation. The initial velocity is 1.46×105 cm/s for a pulse energy of 50 J. The plasma refractivity shows that free electrons are an important constituent of the plasma; at the shock front, the electron density is about 1018 cm−3. The target-heating observations, together with the plasma temperature and propagation measurements, are consistent with models of target heating by thermal radiation from the laser-heated plasma. Target heating by thermal radiation alone appears to be insufficient. Enhanced absorption of the laser flux directly, as by a phase transition of the target material, is not consistent with the observation of the increasing area of energy deposition.
High-fluence implantations of silicon: Layer thickness and refractive indices
Authors: Hubler G. K. , Waddell C. N. , Spitzer W. G. , Fredrickson J. E. , Prussin S. , Wilson R. G.
Published: February 2003

Refractive-index measurements are given for amorphous Si produced by ion implantation. Reflection interference measurements in the frequency range 250≲ν≲ 7600 cm−1 were made for several Si samples implanted with P-ion fluences between 1.0×1016 and 10×1016 ions/cm2 and ion energies between 0.20 and 2.7 MeV and for Si implants of 1.0×1016 and 3.0×1016 ions/cm2 and an ion energy of 0.30 MeV. The interference measurements were computer analyzed by using a model in which the damaged layer has a refractive index nD and extinction coefficient kD, and the substrate has a refractive index ns and ks=0. The optical constants of the two regions are smoothly connected by a transition region approximated by a half-Gaussian curve of standard deviation σD. The finite-width transition region is necessary for fitting the data. Excellent fits are obtained for literature values of ns and kD with the chi-square being ?10−5. The value of kD has little effect on the analysis. Within the experimental accuracy a single curve for nD(ν) is obtained for the amorphous region where nD(ν) is independent of the ion type, ion energy, ion fluence, or position in the amorphous layer. The thicknesses of the damaged layers deduced from the infrared data agree well with LSS values for Rp+σp and with channeling results. Visual observations of the thicknesses also agree well for the high-energy implants but not for the lower-energy ones.
Population and temperature shift of TSC peaks of electron-beam-charged Teflon FEP
Authors: Sessler G. M. , West J. E.
Published: February 2003

Teflon FEP films, aluminized on one side, were first charged by monoenergetic electron beams through the nonmetalized surface and then metalized on this surface after a storage period. Thermally-stimulated-current (TSC) experiments on such samples yield two peaks above room temperature. The peak structure was found to be dependent on storage conditions: storage at room temperature does not significantly change the amplitude of the peaks but shifts the positions of the first peak above room temperature to higher tempertures; storage at 100 °C leads to a gradual amplitude decrease of the first peak and an increase of the second peak with a simultaneous shift in position of the first peak. The phenomena are discussed in terms of the time dependence of the radiation-induced conductivity generated by the electron-beam-charging process.
Ohmic contacts on ion-implanted n-type GaAs layers
Authors: Inada Taroh , Kato Shigeki , Hara Tohru , Toyoda Nobuyuki
Published: February 2003

Contact resistance of Ohmic electrodes formed on either Se- or (Se+Ga) -implanted n-type GaAs layers was studied. Experimental results have shown that a low specific-contact resistance of 2.9×10−7 Ω cm2 can be achieved on GaAs layers having a maximum carrier concentration of 1.8×1019 cm−3, which have been formed by a dual-species (4.4×1014 cm−2 Se+ 5.0×1014 cm−2 Ga) implantation in Cr-doped semi-insulating GaAs heated to 400 °C and by subsequent annealing at 950 °C using an oxygen-free CVD Si3N4 layer as an encapsulant.
Polarization reversal and film structure in ferroelectric Bi4Ti3O12 films deposited on silicon
Authors: Wu Shu-Yau
Published: February 2003

A study has been made of the film structure and polarization reversal in ferroelectric bismuth titanate films deposited on silicon. Most films exhibited a fiber-textured c-axis (001) orientation. The structure of the films appeared not to depend on the orientation, resistivity, or conductivity type but on the surface conditions of the silicon substrate. The study on the polarization reversal of the films using the metal-ferroelectric-semiconductor structure yielded spontaneous polarization of 5.7 μC/cm2. The coercive field was about 130 kV/cm. An anomalous kink was observed on some hysteresis loops and the physical mechanism associated with this unusual phenomenon is attributed to the minority carrier of the silicon substrate.
Infrared optical absorption of Hg1−xCdxTe
Authors: Finkman E. , Nemirovsky Y.
Published: February 2003

The absorption near the fundamental absorption edge of Hg1−xCdxTe was measured over the composition range 0.205⩽x⩽0.220 at temperatures from 80 to 300 K. The dispersion of the index of refraction of Hg1−xCdxTe was obtained from the interference pattern. It was found that the absorption tail obeys a modified Urbach’s rule and is expressed by α=α0 exp[σ (E−E0)/(T+T0)] for 20⩽α (cm−1) ⩽1000. The fitting parameters α0, σ, T0, and E0 vary regularly with x. The expression is used to obtain the absorption coefficient and the temperature coefficient of the gap as a function of x and T. Evidence is presented to show that these parameters may be extrapolated to calculate the absorption beyond the measured composition range.
High-pressure crystallization of poly(vinylidene fluoride)
Authors: Scheinbeim J. , Nakafuku C. , Newman B. A. , Pae K. D.
Published: February 2003

The pressure dependence of the melting and crystallization temperatures of poly(vinylidene fluoride) is determined by high-pressure differential thermal analysis (DTA). These results are used in the investigation of the polymorphic crystal form obtained by pressure quenching molten poly(vinylidene fluoride): The resulting crystal form depends on both the initial and final pressures. The pressure-quenching experiments were performed in a high-pressure piston-cylinder system and in a high-pressure DTA system; a comparison is made of the results obtained by both methods.
Giant intrinsic magnetic hardness in SmCo5−xCux
Authors: Oesterreicher H. , Parker F. T. , Misroch M.
Published: February 2003

The system SmCo5−xCux was studied with respect to constitution and magnetic properties, focusing on the mechanism of magnetization. Different modes of preparation result either in single-phase or in multiphase materials as determined by x-ray diffraction. Pseudobinary materials show giant intrinsic magnetic hardness irrespective of mode of preparation. The temperature dependence of coercive force (Hc) is in accordance with a model based on thermally activated domain-wall propagation. Maximum values of Hc extrapolated to absolute zero are the highest for any material so far reported (of order Hc=300 kOe). These values are slightly greater than the maximum in SmCo5−xNix. It is found that a local moment picture predicts relative magnitudes of both magnetic moment and coercivity as a function of composition. Accordingly coercivity is dependent on the number of weakly coupled transition metal atoms.
Electron-beam measurements of minority-carrier lifetime distributions in ion-beam-damaged silicon
Authors: Possin G. E. , Kirkpatrick C. G.
Published: February 2003

An electron-beam technique for the determination of the minority-carrier lifetime distribution in semiconductors is described. Because of the short range of low-energy electrons, it is possible to profile the lifetime distribution in regions considerably less than 1 μ below the semiconductor surface with a depth resolution near the surface better than 0.1 μ. To demonstrate the method, the damage profile due to inert-gas ion implantation in silicon has been measured. The experimental results show that after room-temperature implantation without higher-temperature annealing, some defects have penetrated more than an additional 0.1 μ beyond their generation depth. A possible mechanism for this defect penetration, the diffusion of simple vacancies, is discussed.
Characteristics and contraction of oxygen glow discharge
Authors: Nobata Kanehiro , Kando Masashi
Published: February 2003

The contraction of the positive column of the oxygen glow discharge is observed at pressures higher than about 5 Torr, where the radial variation of the gas temperature in the column becomes large. The distribution of the floating potential in the radial direction is fairly different between oxygen and argon. The reason seems to be a result of the existence of negative ions. The characteristics of the positive column in oxygen are calculated including ionization, diffusion, attachment, recombination, detachment, and thermal conduction. The ratio of negative-ion density to electron density is calculated as a function of the radial position. It is clarified how the positive column contracts. Moreover, the calculated postive-ion density profiles are shown to agree well with the experimental ones.
Constant-capacitance DLTS measurement of defect-density profiles in semiconductors
Authors: Johnson N. M. , Bartelink D. J. , Gold R. B. , Gibbons J. F.
Published: February 2003

An analysis is presented for obtaining spatial depth profiles of electronic defects in semiconductors from deep-level spectroscopic measurements performed in the constant-capacitance mode. Combined with the double-correlation technique proposed by Lefevre and Schulz, the new method offers significant advantages for measuring defect profiles. Deep-level transient spectroscopy (DLTS), performed in either the conventional capacitance-transient mode or the constant-capacitance mode, provides the energy levels of defect states in the semiconductor band gap. The double correlation DLTS technique (DDLTS) is used to define a narrow spatial observation window for defect profiling. However, in the DDLTS analysis of capacitance-transient data, specific approximations are required to deal with the change with time of the semiconductor depletion width during the transient response to a charging pulse. In the constant-capacitance mode, the depletion width is held constant by dynamically varying the applied voltage during the transient response, thus permitting more accurate measurements of defect profiles at high trap densities. Analytical expressions for computing the local trap density are derived, and experimental results are presented for damage profiles in self-implanted silicon.
Enhanced Brillouin scattering of a Gaussian laser beam from a plasma
Authors: Sodha M. S. , Umesh G. , Sharma R. P.
Published: February 2003

Brillouin scattering of a high-power Gaussian laser beam from a hot collisionless plasma has been investigated. The pump (ω0, k0) interacts with a preexcited ion-acoustic wave (ω,k), generating a backscattered wave (ω0−ω, k0−k). The transverse intensity gradient of the pump generates a ponderomotive force, which modifies the plasma-density profile transverse to the beam axis. Consequently, the pump beam is self-focused and it also leads to the focusing of the ion-acoustic and the backscattered electromagnetic waves, provided appropriate conditions are satisfied. It is seen that self-focusing of the waves results in enhanced backscattering.
Changes in internal friction and dislocation charge in sodium chloride crystals following plastic deformation
Authors: Anderson A. R. , Pollard H. F.
Published: February 2003

Measurements of the elastic compliance, the internal friction, and the induced dislocation voltage during deformation recovery indicate that the dislocation damping factor remains constant, while pinning and charging of the dislocation core occur by diffusion. The activation energy for charging by diffusion is 0.45 eV and for the pinning process is 0.65 eV.
Stress effects in two modified lead zirconate titanate ferroelectric ceramics
Authors: Fritz I. J.
Published: February 2003

Mechanical properties of ferroelectric ceramics with compositions Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 and Pb0.97La0.02(Zr0.92Ti0.08)O3 have been studied as functions of both hydrostatic pressure and uniaxial stress. Measurements of ultrasonic velocity and sample strains have been made in order to characterize unpoled samples. Both materials have pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transitions at ∼0.2 GPa of hydrostatic pressure. Under uniaxial-stress conditions two effects are observed: rotation of FE domains and the FE–AFE phase transition. These effects are separately resolved by the measurements, even though they occur in overlapping stress regions. The domain reorientation responses of the two materials appear to be nearly identical, but the FE–AFE transition begins at lower stress levels for the Nb-doped material. This is presumably due to that material transforming into the orthorhombic (PbZrO3) phase, whereas the La-doped material transforms into the tetragonal AFE phase. The phase transition is spread over a broad range of uniaxial stress for each material and is not nearly complete by 0.6 GPa, the highest stress level attainable. Possible implications of the results for shock-wave studies of FE ceramics are briefly discussed.
Full average radiation of electrons and positrons channeled between the planes of a crystal
Authors: Kheifets S. , Knight T.
Published: February 2003

The full average radiation intensity of electrons and positrons channeled between crystal planes is calculated. Comparison of the results of these calculations with calculations using the parabolic approximation for the potential well of a channel is presented. The difference can in extreme cases reach two orders of magnitude. Estimates for the positions of the maxima of the frequency spectra are given. The number of quanta averaged over the angular distribution of the particles in a beam are found.
Metal-rich Pd-silicide formation in thin-film interactions
Authors: Canali C. , Silvestri L. , Celotti G.
Published: February 2003

Phase formation of metal-rich Pd silicides was studied in palladium–amorphous-silicon thin-film interactions by means of 4He+-ion backscattering, Auger spectrometry, electron microprobe, and x-ray diffractometry. In the initial stage of compound formation, where both unreacted Si and Pd layers ar present, the Pd2Si phase has been observed. At increasing annealing temperature in SiO2/Si(a)/Pd systems, where the metal-film thickness was larger than that of amorphous-Si film, phases richer and richer in metal have been detected, following exactly the phase diagram reported in literature. The Pd-richest phase was identified as Pd4Si and is stable up to 650 °C in the presence of unreacted Pd. A crystallographic characterization of this new thin-film end phase was performed on the basis of a triclinic unit cell.
Metal-vapor production by sputtering in a hollow-cathode discharge: Theory and experiment
Authors: Warner B. E. , Persson K. B. , Collins G. J.
Published: February 2003

Laser action in singly ionized metal atoms has been obtained when a rare gas is excited in a metal hollow cathode. The required metal-vapor density is produced by discharge sputtering from the cathode and the excitation of upper levels occurs via a charge-transfer reaction of the type B++M → (M+)+B+ΔE. We present a unified discharge-sputtering theory which describes the metal density created in the hollow cathode, including both the current and spatial dependence. The predictions of this model are then compared to the measured dependence of metal-vapor density with current, spatial position, and buffer-gas pressure. Discharge conditions which support laser oscillation are emphasized. Agreement between theory and experiment is good.
Interaction of moving {110} 90° walls in Fe-Si single crystals with lattice imperfections
Authors: Miltat J. , Kléman M.
Published: February 2003

Observations, by means of X-ray topography and stroboscopy combined, of moving domain walls and wall junctions in Fe–Si single crystals are reported. Instabilities, surface effects and interactions of 90° {110} walls with dislocations have been observed.
Properties of non-crystalline EuIG and DyIG obtained from Mössbauer and magnetization data
Authors: Litterst F. J. , Tejada J. , Kalvius G. M.
Published: February 2003

Non-crystalline (nc) EuIG and DyIG have been prepared by dc-sputtering. Mössbauer data on 57Fe, 151Eu and 161Dy reveal sharp magnetic transitions at 62 K and 70 K for nc EuIG and DyIG, respectively. The 57Fe hyperfine (hf) spectra consist of three superpositioned patterns for Fe3+ in tetrahedral and octahedral and for Fe2+ in tetrahedral oxygen coordination. The saturation hf fields at 4.2 K are reduced compared to the values of the corresponding crystalline materials. The induced hf field at 151Eu is only 1/8 of that for crystalline EuIG.
The effect of mechanical deformation on the magnetic properties of amorphous alloys
Authors: Gibbs M. R. J. , Evetts J. E. , Shah N. J.
Published: February 2003

Amorphous alloys can deform in two distinct modes, one homogeneous and the other inhomogeneous, and it has been known for some time that inhomogeneous deformation produces a severe degradation of soft magnetic properties. We report d.c. measurements on METGLASR 2826, VITROVACR 0040 and VITROVACR 6010 that have been cold rolled up to a 55% thickness reduction. By separately considering the effect of surface roughness on Hc, we are able to give clear evidence for pinning of the domain walls at the bulk shear bands. Measurements on magnetostrictive and non-magnetostrictive materials provide evidence that the major source of pinning after inhomogeneous deformation is associated with localized stress fields in the sample. As a counterpart to our earlier a.c. measurements on homogeneously deformed ribbon, we report d.c. measurements on samples homogeneously deformed at low strains in a creep rig. Hc in this case remains close to that of a ribbon given the same heat treatment but not crept. The results after deformation in both regimes are discussed in terms of the current models of the effects of deformation.
Magnetic hysteresis of CuMn in the spin glass state
Authors: Monod P. , Préjean J. J. , Tissier B.
Published: February 2003

We present a series of measurements of the magnetic hysteresis properties of alloys of CuMn in the concentration range 0.06% at. to 4.7% at. when these are cooled well into the spin glass state i.e. T/Tg<0.3. Previous studies (1) made at higher concentrations have revealed the occurrence of a complete reversal of magnetisation in a narrow range of coercive fields and a shifted hysteresis loop. Quite unexpectedly we find that going to lower Mn concentration increases the cooperative nature of the magnetisation reversal to the point where the hysteresis becomes square and that complete, spontaneous (less than 0.1 second time constant) magnetisation jumps are observed in low magnetic field (typically-150 gauss) together with a shifted square center. We report on the effect on the hysteresis of a number of variables: the magnetisation, the concentration, the temperature, the metallurgy, the time and the application of a static transverse magnetic field. These observations lead to the existence of a well defined anisotropy field in the spin glass state.
Ferromagnetic resonance of spherical particles of α-iron precipitated in fused silica
Authors: Griscom D. L. , Friebele E. J. , Shinn D. B.
Published: February 2003

Ferromagnetic resonance (FMR) spectra were obtained at 9 and 35 GHz for particles of metallic iron precipitated in fused silica containing 1–120 ppm Fe. Accurate g values and anisotropy constants K1, K2 and K3 were extracted by computer simulation of the powder pattern line shapes, assuming negligible shape anisotropy. One sample, melted under a He-H2O atmosphere, exhibited anisotropy constants identical with published values for pure α–iron and a g value of 2.081±0.002. Samples strongly reduced in H2 displayed smaller values of K1, consistent with expectation for alloying of the Fe with up to 20% Si. These K1 values were shown to be statistically distributed and linearly correlated with the g values in the range 5?at.%Si?20. All samples displayed increases ∼ 5–10% in apparent K1 value with increasing frequency, either as-delivered or after aging. It is hypothesized that the latter effects are due to the formation of a magnetic iron oxide layer at the metal-glass interface.
Crystal orientation and its formation process of an anisotropic Mn-Al-C permanent magnet
Authors: Sakamoto Y. , Kojima S. , Kojima K. , Ohtani T. , Kubo T.
Published: February 2003

An easy axis distribution and a crystal texture in a warm extruded anisotropic Mn-Al-C magnet were determined by X-ray diffraction analyses. Resulting values in (001) pole density are treated by introducing a normalization condition in order to determine the quantitative values. The distribution is expressed only as a function of tilt angle φ, and is found to consist of the following Gaussian distribution term and constant. P(φ) = 3.42 exp [−φ2/(2×30.82) ] + 0.11. Magnetically measured Mr/Ms = 0.88 is significantly higher than 0.74, the value calculated from this total distribution when assuming that the magnetization in every grain points in the direction of each easy axis. The crystal texture is approximated by [001] single fiber texture. The inverse pole figure indicates that among twelve {111} 〈112〉 twin systems, four twin systems which preserve CuAu I type superstructure are responsible for the formation of this texture.
Magnetic properties of 3d transition-metal dichalcogenides with the pyrite structure
Authors: Ogawa S.
Published: February 2003

Magnetic properties observed experimentally in the 3d transition-metal dichalcogenides with the pyrite structure are reviewed and compared with properties expected theoretically for the Hubbard model. As characteristics of electrons in a narrow band, the following are discussed: (1) The temperature induced and field induced local moment in Co(S,Se)2 and (Co,Ni)S2. (2) The metal-nonmetal transition in NiS2 and its solid solutions. (3) The paramagnetism and antiferromagnetism in the exchange-enhanced metal Ni(S,Se)2.
Irreversible processes in Bloch wall motion
Authors: Porteseil J. L. , Vergne R.
Published: February 2003

We report experimental results on the motion of a 180° Bloch wall in a Fe-Si single-crystal frame. Below a critical velocity ẋ1, the irreversible wall motion takes place by a large number of small, independant, thermally activated jumps. The onset of large jumps at the critical velocity has the character of an instability. At intermediate velocities, the wall moves by large, reproducible jumps. At a second threshold velocity ẋ2, those jumps begin to break up into smaller and smaller jumps. The evolution of the Barkhausen noise and its power spectrum suggests an analogy with the onset of a turbulent flow. Those phenomena are discussed in terms of thermally activated magnetization processes.
Magnetic moment distribution in bcc Fe-Cu alloys
Authors: Kajzar F. , Parette G.
Published: February 2003

The results of elastic polarized neutron diffuse scattering measurements on two bcc Fe-Cu alloys with 3.89 at % and 6.29 at % of Cu are reported. The magnetic diffuse cross section is strongly peaked at low values of scattering vector k indicating a strong magnetic moment disturbance extended fairly in the space up to about 15Å. Analysis of the data indicates that the iron moment is nearly constant with a slight tendency to increase with impurity concentration. For copper we find a small positive magnetic moment at 6.29 at % of Cu and no moment at 3.89 at % of Cu.
GaInAsP/InP planar stripe lasers prepared by using sputtered SiO2 film as a Zn-diffusion mask
Authors: Oe Kunishige , Ando Seigo , Sugiyama Koichi
Published: February 2003

The dependence of lasing characteristics on stripe width in GaInAsP/InP double-heterostructure planar stripe lasers, prepared by using sputtered SiO2 film as a Zn-diffusion mask, was investigated. The lasers of 10-, 15-, and 20-μm-wide stripes operated in a fundamental-transverse mode with more than 20% differential quantum efficiencies per facet, while the 5-μm-wide stripe lasers operated in a multi-transverse-mode even just above threshold. The threshold current of 5-μm-wide stripe lasers increased greatly, and the lasing wavelengths shifted to shorter than those of stripe lasers with larger stripe widths. The 15-μm-wide stripe lasers showed good mode characteristics to operate in a fundamental-transverse mode up to the output power of 22 mW per facet and in a single longitudinal mode over a wide range of currents. The cause of this dependence of lasing characteristics on stripe width was discussed, and it was assumed that the Zn diffusion into the stripe region using a sputtered SiO2 mask is most responsible for the dependence.
Simulations of the transient photoconductivity in a-SiO2 using a multiple-trap model
Authors: Schaffman M. , Silver M. , Corthell C. , Hughes R. C.
Published: February 2003

Computer simulations for transient photocurrent produced by a uniform excitation in a system with an exponential distribution of traps have been performed, and the results have been compared with recent experimental data of the transient photoconductivity in SiO2 and found to show excellent agreement. The temperature dependence of the parameters of our multiple-trap model are discussed with reference to the experimental results, providing further support for the application of this model to a-SiO2.
The thin-film formation of rhodium silicides
Authors: Petersson S. , Anderson R. , Baglin J. , Dempsey J. , Hammer W. , d’Heurle F. , LaPlaca S.
Published: February 2003

The interaction of rhodium thin films with single-crystal substrates of silicon leads to the formation of four silicides. RhSi forms by diffusion-controlled kinetics at temperatures of about 350 °C with an activation energy of 1.9 eV. For long annealing times one observes the layered formation of Rh2Si at the RhSi-Rh interface. At higher temperatures, in the vicinity of 825 °C, Rh4Si5 forms in the same way as IrSi3: it grows as islands with no measured composition gradient through the thickness of the films. Between 925 and 950 °C Rh4Si5 transforms to Rh3Si4. Oxidation experiments provide useful information about the stability of the Si-rich phases, Rh4Si5 and Rh3Si4, and their mode of formation. The large number of silicides, four, formed in a single metal-silicon system provides the opportunity to examine various modes of thin-film interactions. Some striking differences in behavior in the otherwise similar systems, Ir-Si and Rh-Si, are briefly discussed.
Intense annular relativistic electron beam generation in foilless diodes
Authors: Jones Michael E. , Thode Lester E.
Published: February 2003

The generation of intense annular electron beams in cylindrical foilless diodes is analyzed. A beam equilibrium model is used to determine the diode current. At low voltage the current is very nearly that of the space-charge limited beam. However, at higher voltages the current can be substantially less than the space-charge limit. The analysis is compared to detailed particle-in-cell simulations.
A kinetic study of platinum-mercury contact reaction
Authors: Lahiri S. K. , Gupta D.
Published: February 2003

The reaction between solid Pt and liquid Hg, at temperatures varying from 20 to 153 °C, has been investigated using a combination of gravimetric, x ray, and radioactive tracer techniques in an effort to evaluate the suitability of Pt-Hg contacts for Josephson device packages. The reaction product was identified as Hg4Pt with a lattice parameter of 6.2047 Å±0.02%. No penetration of Hg into Pt lattice or grain boundaries has been detected. The kinetic law governing the amalgam formation has been found to be X (cm)=4.48×10−3t exp(−0.52 eV/kT) where X is Pt thickness consumed in the amalgam, t is time in sec, k is Boltzmann constant, and T is temperature. The results indicate that the rate of amalgam formation is controlled by reaction at the Pt-amalgam interface.
The alignment of polymers during the solvent-coating process
Authors: Prest W. M. , Luca D. J.
Published: February 2003

The solvent-casting process preferentially aligns polymeric chains in the plane of the film. This paper proposes that the mechanism responsible for this behavior is the competition between the relaxation times of the concentrating solution and the time scales associated with the physical collapse of the film. The orientation of molecules has been determined as a function of the coating conditions (film thickness, polymer molecular weight, plasticizer content, casting solvent, and substrate temperature) by measuring the optical anisotropy of the coating with a single-prism film coupler. This orientation is shown to reflect both the stresses supported by the entanglement network and the alignment of localized segments and to be a function of the difference between the casting temperature and the Tg of the film.
Infrared reflectivity and transmissivity of boron-implanted, laser-annealed silicon
Authors: Engstrom Herbert
Published: February 2003

Analysis of the infrared reflectance and transmittance of boron-implanted, laser-annealed silicon shows that the Drude theory of free hole scattering provides a good description of the optical properties of these materials up to the highest doping levels obtainable. It was found that (1) the relaxation time (∼7×10−15 s) was independent of the implant dose, and (2) the boron concentration affecting the optical properties varies essentially linearly with implant dose.
A study of electron penetration in solids using a direct Monte Carlo approach
Authors: Adesida I. , Shimizu R. , Everhart T. E.
Published: February 2003

Fundamental characteristics of electron penetration in solids, such as energy and angular distributions of transmitted electrons, have been theoretically calculated using a Monte Carlo approach. The essential features of the Monte Carlo approach are the inclusion of the random nature of inelastic scattering events, and also the extension of Gryzinski’s semiempirical expression for core electron excitation to valence electron excitation through the use of an appropriate mean binding energy. A detailed comparison of the theoretical results for aluminum and polymethylmethacrylate (PMMA) with experimental results show that the direct Monte Carlo approach describes electron scattering events in solids very well. It is also shown that this approach describes the energy distribution of transmitted electrons through thin films of aluminum and PMMA more realistically than the Monte Carlo approaches utilizing Bethe’s stopping power equation.
Chromium and tellurium redistribution in GaAs and Al0.3Ga0.7As grown by molecular beam epitaxy
Authors: Morkoç Hadis , Hopkins Craig , Evans C. A. , Cho A. Y.
Published: February 2003

Secondary ion mass spectroscopy was used to analyze Cr redistribute in GaAs and AlxGa1−xAs epitaxial layers grown by molecular beam epitaxy (MBE). Results indicate that Cr accumulates at the substrate-epitaxial layer interface, the magnitude of which is dependent on the pregrowth procedure. A larger Cr accumulation layer at the surface (∼1018 cm−3) in comparison to that at the interface was observed in most every sample. A Cr background concentration of ?1016 cm−3 was found in the rest of the epitaxial layers, even when grown on Te-doped substrates. Possible mechanisms responsible for all three Cr regions are suggested. In the case of Cr-doped MBE layers, a surface equilibrium concentration of about 5×1012 cm−2 (∼0.01 monolayer) must be reached before Cr incorporates into the epilayer. For the growth conditions used in this work this delay in incorporation would correspond to about 1000Å epigrowth. In addition, undoped epilayers on Te-doped substrate were used to monitor the Te outdiffusion into the epilayer. Using these data, a diffusion coefficient of 3×10−14 cm2/sec at 580 °C was calculated for Te in GaAs.
Deep levels in ZnSe/GaAs heterojunctions
Authors: Shirakawa Yasuhiro , Kukimoto Hiroshi
Published: February 2003

Deep levels in n-ZnSe/ p-GaAs heterojunction diodes have been studied by deep-level transient-capacitance spectroscopy. As-grown diodes have three well-defined majority-carrier traps of depths 0.30, 0.33, and 0.48 eV. A marked change in the concentration of the first two traps is caused by the Zn treatment of the diodes. They are tentatively identified as the Zn vacancy-interstitial Ga complex and the Se vacancy on the n side of the junction. The third trap of unknown origin is possibly located on the p side of the junction. Discussion is made about the relationship between the behavior of these traps and properties of the devices after the Zn treatment.
Discharge of trapped electrons from MOS structures
Authors: Yamabe K. , Miura Y.
Published: February 2003

It is pointed out that the electron trapping characteristics (ΔVFB-Ninj curve) depend on the pulse frequency and the pulse width of the gate voltage used in avalanche hot electron injection from the Si substrate into the SiO2 film, while the generation of the interface states depends very little on those factors. It is shown that those correlations are mainly due to the discharge of trapped electrons during the zero-bias state between pulses. The experimental results of the discharge of trapped electrons are also described and are explained by means of a modified discharge theory of MNOS structures.
Surface segregation of Ni-Cu alloy in nitrogen and oxygen: An atom-probe field-ion microscope study
Authors: Tsong T. T. , Ng Yee S. , McLane S. B.
Published: February 2003

The energy-focused time-of-flight atom-probe field-ion microscope (FIM) is employed to study surface segregation of a Ni-Cu alloy in nitrogen and oxygen. In nitrogen, in addition to the normal enrichment of Cu to the top surface layer as in the vacuum annealing case, highly Cu-rich regions are formed near plane edges of the top surface layer. In oxygen, no Cu enrichment at the surface is found. Both the composition depth profiles and the spatial distributions of alloy species within an atomic layer can be obtained by the atom-probe (FIM) with depth and spatial resolution of a few angstroms.
Evaluation of defects and degradation in GaAs-GaAlAs wafers using transmission cathodoluminescence
Authors: Chin A. K. , Keramidas V. G. , Johnston W. D. , Mahajan S. , Roccasecca D. D.
Published: February 2003

A large number of GaAs substrates GaAlAs double-heterostructure (DH) wafers, and high-radiance GaAlAs DH light-emitting diodes (LEDS) were evaluated using transmission cathodoluminescence (TCL). We show that only epitaxial wafers with a high defect density as revealed by TCL readily develop dark line defects (DLDs) with current injection, optical excitation, or electron beam excitation. Furthermore, in agreement with the previous work, the electron-beam-induced DLDs originate at dislocations and their growth requires minority-carrier injection. Based on these results, it is inferred that TCL can serve as a nondestructive screening technique for the selection of materials that produces a high yield of reliable LEDs.
Theory of boundary effects on sine-Gordon solitons
Authors: DeLeonardis R. M. , Trullinger S. E. , Wallis R. F.
Published: February 2003

We examine the properties of solutions to the sine-Gordon equation in the presence of various boundary conditions. Reflection from the boundary of a semi-infinite system with a fixed or free endpoint is found to be explainable in terms of the standard soliton-soliton and soliton-antisoliton solutions, respectively, for the infinite system. We also consider both nonlinear standing-wave and solitonic solutions to the sine-Gordon equation on a system of finite length L. Through the use of the application by Costabile et al. of the separation of variables ansatz due to Lamb, analytic expressions in terms of Jacobi elliptic functions are found for these two types of solutions, which assume the forms appropriate to the infinite and semi-infinite system, respectively, as L→∞. Concentrating on the solitonic solution, we examine its symmetry properties, relations among its characteristic parameters, and give plots of its waveform in several cases. The effect of the boundaries on this solution is such that the oscillation of the soliton center closely resembles that of a particle in a symmetric potential, whose shape is determined straightforwardly from the time dependence of the soliton position and of the potential energy of the system.
Composition studies of MBE GaInP alloys by Rutherford scattering and x-ray diffraction
Authors: Blood P. , Bye K. L. , Roberts J. S.
Published: February 2003

Layers of Gax In1−x P (x?0.5) have been grown by molecular-beam epitaxy on GaAs substrates, and their composition measured by both x-ray determination of the lattice parameter and high-energy Rutherford scattering. The x-ray data were corrected for elastic strain due to mismatch and backscattering spectra were analyzed with the aid of computer simulation. Assuming a linear relation between lattice parameter and composition, values of x obtained from these two techniques agreed within experimental error (∼1%). Backscattering results for layer thickness were within 2% of results from ir interference. Small composition variations across the layers were detected by both techniques, and these can be accounted for by the geometry of the cells in the growth chamber. Rutherford scattering has also been used to assess the depth uniformity of composition and analyze GaInP/GaAs/GaInP heterostructures with total thickness ∼2 μm.
Black a-Si solar selective absorber surfaces
Authors: Messier R. , Krishnaswamy S. V. , Gilbert L. R. , Swab P.
Published: February 2003

Amorphous Si films display a unique anisotropic etching phenomenon in which a columnar microstructure results. The alignment of the anisotropic microstructure is related to the average angle of the depositing material. Since cross-sectional spacing of the columns is less than the wavelength of light, a continuous grading of the refractive index occurs and results in a drastic reduction in the total reflectance from 40 to 50% in the as-deposited film to <2% in the etched film. The etchant, HF/HNO3, apparently oxidizes rapidly down aligned void networks followed by an equally rapid dissolution and removal step. Such a semiconductor film on a low ir emmisivity metallic substrate is a potentially efficient photothermal selective absorber surface.
Input noise in the hysteretic rf SQUID: Theory and experiment
Authors: Hollenhorst James N. , Giffard R. P.
Published: February 2003

The spectral density of the low-frequency open-circuit intrinsic input noise of the hysteretic rf-biased SQUID is calculated. The noise level, which affects the optimized power sensitivity of the SQUID, is found to be strongly model dependent and thus also constitutes an interesting probe of device physics. The results of the calculation are significantly different from previous predictions. A direct measurement of the total input noise of a typical rf-biased SQUID system is reported. The results, which are consistent our calculation, correspond to a system noise temperature of 3.1±0.4 mK at a frequency of 1 kHz. This value is consistent with the Manley-Rowe equations and with previous experimentally determined upper limits.