bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulated backscattering of electromagnetic waves from electrostatic waves in a magnetized plasma
Authors: Willett Joseph E. , Bilikmen Sinan
Published: February 2003

An analysis of the parametric decay of an intense electromagnetic wave into an electrostatic wave and a backscattered electromagnetic wave is presented. A generalized dispersion relation is derived which describes stimulated backscattering from four types of electrostatic waves propagating at an arbitrary angle with respect to a uniform static magnetic field. In the subsequent analysis of the absolute backscatter instability in homogeneous and inhomogeneous, bounded and unbounded plasma, approximations which permit independent treatment of the high-frequency electron modes and the low-frequency ion modes are invoked where appropriate. A numerical study of a laser beam with its direction of propagation making an angle ϑ equal to 5°, 45°, and 85° with the static magnetic field is discussed. Effects of the magnetic field on the growth rate γ0 in an unbounded plasma, the growth rate γ in a bounded plasma, the basic gain length l0, and the inhomogeneity parameter λ are illustrated.
The thermally enhanced diffusion of point defects near dislocations during device operation
Authors: Basson J. H. , Booyens H. , Ball C. A. B.
Published: February 2003

The effect of thermal expansion on the temperature distributions around dislocations in III-V crystals during conduction parallel to their lines is considered. It is found that the thermal expansion has little effect on the temperature distribution close to the core of the dislocation. It is further shown that these temperature variations give rise to lateral variations in the diffusion constants of point defects and may hence play an important role in device degradation due to the climb of threading dislocations.
Radiation damage in silicon dioxide films exposed to reactive ion etching
Authors: DiMaria D. J. , Ephrath L. M. , Young D. R.
Published: February 2003

The enhanced electron-trapping characteristics and the location of this trapped charge in an SiO2 layer exposed to either CF4, O2, or Ar plasmas in a reactive ion etching (RIE) system are reported. Capacitance-voltage (C-V) and photocurrent-voltage (photo I-V) techniques were used to monitor charge trapping and location after the samples were incorporated in metal-oxide-semiconductor (MOS) capacitors. Using a CF4 plasma which etches SiO2, trapping sites caused by penetrating radiation were observed. These traps were removed by annealing at temperatures ?600 °C for 30 min in N2 prior to metallization. These bulk SiO2 trapping sites showed no strong dependence on whether the samples were placed on the anode or cathode in the RIE chamber, implying no preferred directionality in the photons which are believed to generate them. With an O2 or an Ar plasma which does not etch SiO2, an additional trapping layer within about 100 Å of the exposed SiO2 surface caused by penetration of energetic ions (?400 eV) was detected. Trapping in this layer was greatly reduced by a 1000 °C anneal in N2 for 30 min, and almost entirely removed by a buffered HF dip which etched about 100 Å of SiO2. Samples placed on the anode (ground plane) of the RIE system which would see energetic secondary electrons, but only relatively low-energy ions (approximately 35 eV), also had electron-trapping sites near the exposed surface; however, the trapping in this layer was greatly reduced compared with samples placed on the cathode.
Solid-state electrochromic device consisting of amorphous WO3 and Cr2O3
Authors: Shimizu Isamu , Shizukuishi Makoto , Inoue Eiich
Published: February 2003

The electrochromic (EC) characteristics were investigated on a solid-state EC device In2O3/a-WO3//Cr2O3/Au which was prepared by vacuum deposition. Besides the color change caused by passage of current in the WO3 layer, the color of the Cr2O3 layer was also changed as a result of electrochemical reaction at the interface. In the open-circuit condition after the coloration, rapid spontaneous discoloration was found due to bimolecular recombination of the colored species in both layers at the interface. The existence of adsorbed water molecules in the respective layers is essential for the solid-state ECD. The ECD in this study was scarcely affected by the ambient condition and was able to operate in the high vacuum (e.g., 10—6 Torr) since the Cr2O3 layer adsorbed water tightly. Positive polarization of the Cr2O3 layer in an electrolyte solution (Na2SO4 aqueous solution) caused change in the color as a result of electrochemical reaction, whereas the coloration of a-WO3 was taken place by negative polarization of the a-WO3. We have confirmed that this ECD could be operated without any conspicuous deterioration after the reversible switching cycles more than 5×106 times.
Elastic and piezoelectric constants of trigonal selenium and tellurium crystals
Authors: Royer D. , Dieulesaint E.
Published: February 2003

The elastic and piezoelectric constants of trigonal crystals of selenium and tellurium have been determined. Their values were deduced from measurements of ultrasonic phase velocities at room temperature. The stiffnesses cEαβ in units of 1010 N/m2 and the piezoelectric constants eiα in C/m2 for selenium are found to be cE11=1.98±0.02, cE12=0.66±0.04, cE13=2.02±0.06, ‖cE14‖=0.69±0.03, cE33=8.36±0.03, cE44=1.83±0.01, cE66=0.66±0.01, e11=0.32±0.02, ‖e14‖=0.10±0.1; for tellurium cE11=3.257±0.01, cE12=0.845±0.015, cE13=2.57±0.05, ‖cE14‖=1.238±0.014, cE33=7.17±0.01, cE44=3.094±0.01, cE66=1.206±0.005.
Temperature dependence of Akhieser loss in indium antimonide
Authors: Nandanpawar Manik , Rajagopalan S.
Published: February 2003

According to the Mason-Bateman theory, the nonlinearity constant, which governs the Akhieser attenuation in solids, can be estimated provided the second- and third-order moduli are known. Some values of the nonlinearity parameter D of InSb have been reported in the literature at room temperature only and these fail to agree with one another and with experimental values. In the present work, attenuation and D values have been estimated in indium antimonide for longitudinal-wave propagation along the 〈111〉 direction and for shear-wave propagation along the 〈110〉 direction at 300 and 80 K. Our results indicate fairly good agreement with experimental values.
Growth initiation and cathodoluminescence irregularities in LPE AlGaAs layers
Authors: Ladany I. , Levin E. R.
Published: February 2003

In a previous publication, we described the occurrence of a patchy contrast in cathodoluminescence (CL) images of thin LPE layers of AlGaAs grown on Cr-doped GaAs substrates. The present paper, a continuation of that work, reports on CL observations of LPE AlGaAs layers grown on Si-doped GaAs substrates and on freshly grown Sn-doped LPE layers; in addition, we have examined changes in the CL intensity distribution with layer thickness. It is concluded that the ’’patches’’ are confined to a region near the GaAs-AlGaAs interface, and that their appearance is associated with the initiation of the AlGaAs epilayer growth.
Detection of SiO2 at the indium tin oxide/Si solar cell interface
Authors: Wager J. F. , Wilmsen C. W.
Published: February 2003

Auger analysis has been used to detect thin SiO2 layers at the interface of the ITO/Si solar cell. The energy shift and line-shape changes of the Si LVV line were used to determine the chemical bonding state of the interfacial Si. An exact determination of the SiO2 thickness was not possible, but it is estimated that the SiO2 layer of the best cell is in the range 12–20 Å. The interfacial SiO2 layers of cells fabricated at 373 °C appear thicker and more completely developed than that of cells fabricated at room temperature.
A distribution function for ion track lengths in rectangular volumes
Authors: Bradford John N.
Published: February 2003

A distribution function for the chord lengths through a rectangular body is developed. Since the trajectories of high-energy massive particles are straight lines, the chord-length distribution function describes the path-length distribution on an object exposed to the cosmic-ray flux. The formalism has application to the energy deposited in satellite-borne microelectronic circuitry by cosmic rays.
Observation of infrared-microwave double resonance for the far-infrared laser pumping transition of CH3OH coincident with the 10.4 R (38) CO2 laser line
Authors: Young C. , Lees R. M. , Van der Linde J. , Oliver B. A.
Published: February 2003

An infrared-microwave double-resonance experiment has been performed on the CH3OH infrared transition pumped by the 10.4 R (38) CO2 laser line. The effect of the laser pumping was investigated on the intensities of the JK=264←255A± ground-state microwave absorption lines, which were monitored in a standard microwave Stark cell. The intensity of the A+ microwave probe transition increased by about 5% with laser pumping, while that of the A− transition did not change. This supports the reported assignment of the infrared CH3OH far-infrared laser pumping transition as the QP4(26) A+ transition.
Effect of gain saturation on injection laser switching
Authors: Channin D. J.
Published: February 2003

Gain saturation is introduced into the laser-coupled rate equations. Numerical and analytical solutions show considerable damping of relaxation oscillations for small amounts of saturation.
Gain conditions for electron-beam-excited Ar-N2 laser lines at 337.1, 357.7, and 380.5 nm
Authors: Ernst W. E. , Tittel F. K. , Wilson W. L. , Marowsky G.
Published: February 2003

Simultaneous laser action of argon-nitrogen mixtures excited by an electron beam has been observed at 337.1, 357.7, and 380.5 nm. Spectrally resolved gain and laser output were measured for these three lines. Different gas mixtures and resonator configurations were studied and the best conditions for each line were established.
Energy absorption in plasmas produced by intense 10-μm laser radiation
Authors: Villeneuv D. M. , Enright F G. D. , Richardson M. C. , Isenor N. R.
Published: February 2003

Results are presented of measurements made of the fractional absorption of short (∼1 ns) intense (2×1014 W cm−2) 10.6-μm laser radiation by plasmas produced from massive plane targets. Two complementary techniques were used: infrared light accounting and plasma calorimetry. The methods are shown to provide consistent results, demonstrating peak absorptions of up to 50%. The beam-polarization and irradiance-angle dependence of the absorption is consistent with a resonance absorption model. Plasma calorimetry also yields a detailed spatial distribution of the particle emission, while infrared calorimetry shows that the scattered laser light distribution is strongly dependent on the polarization of the incident laser beam.
Long self-magnetically insulated power transport experiments
Authors: VanDevender J. P.
Published: February 2003

Energy and power transport in a self-magnetically insulated triplate transmission line are examined. The experiments are done on the MITE accelerator (2 MV, 0.4 MA, 40 ns), which is one module of the electron beam fusion accelerator, EBFA I. The transport efficiency is very sensitive to the injection geometry. An abrupt transition at the beginning of the line causes ∼40% power losses through an apparent instability. The growth length of the instability is ∼53 cm in a line with a vacuum wave impedance Z0=7.6 Ω. A second loss mechanism is associated with an azimuthal asymmetry in the self-magnetic field near the injection region. Both loss mechanisms were avoided by properly shaping the input to the transmission line and 90% energy transport and ∼100% power transport were achieved.
The structure of the Cu2S layer of Cu2S/CdS thin-film solar cells
Authors: Shirland F. A.
Published: February 2003

Techniques have been developed for separating the Cu2S layer from Cu2S/CdS thin-film solar cells by slowly dissolving away the CdS. Free-standing Cu2S layers, cemented-down Cu2S layers, Cu2S layers exposed after potting and cross sectioning, and replicas of Cu2S layers have been prepared and examined in the scanning electron microscope. The Cu2S morphology so disclosed is a complex composite of a conformal coating of the upper surface of the texture-etched CdS film and more or less vertical penetrations into the CdS film along grain boundaries. The texture etch of the CdS film opens deep [about (10–15) ×10−4 cm] etch pits from which a substantial portion of the Cu2S penetration into grain boundaries occurs. The thickness of the Cu2S layer of conventional CdS thin-film solar cells is about 1000 Å, though the thickness of some of the deeper penetrations may be less than 500 Å.
Thermal properties of natural rubber versus temperature and pressure
Authors: Sandberg O. , Bäckström G.
Published: February 2003

The thermal conductivity λ and the heat capacity per unit volume ρcp were determined by the transient hot-wire method at pressures up to 1.0 GPa and in the temperature range 130–340 K. Specimens were cold-pressed pure rubber and hot-pressed rubber containing 3.7% sulphur. The vulcanized variety was found to have a higher glass transition temperature Tg at all pressures. Our value of Tg at atmospheric pressure is higher by 23 K than the previously reported values from quasistatic experiments, which can be accounted for by the relaxation time of the excitation mode. The derivative of the transition temperature ∂Tg/∂P was found to decrease with increasing pressure for both samples, as predicted by a recent theory. The thermal-expansion coefficient was determined under pressure from the temperature response to adiabatic pressurization using the heat-capacity data.
The drag force on a moving dislocation. II. Nonzero temperature (thermal drag force)
Authors: Partom Y.
Published: February 2003

In this part of the paper we consider the effect of the thermal motion of the atoms on the dynamics of a moving dislocation in the linear chain model. We express the effect in terms of a thermal drag force averaged over a lattice step. We compute this drag force for a range of dislocation velocities through computer simulation single-step runs. In each of such runs we compute the change of dislocation velocity caused by a fluctuation of velocity or displacement in one of the atoms. We then add up the overall effect according to thermal equilibrium statistics. We employ a first-order approximation in the sense that we take the thermal drag force to be proportional to the temperature. Our analysis is thus limited to the low-temperature range. For a range of dislocation velocities we obtain a negative thermal drag force (as anticipated by Weiner from a normal-mode analysis). The magnitude of the thermal effect is such that it causes a 10−4 change in dislocation velocity along a single lattice step per degree Kelvin (at low temperature levels).
Analysis of chrome-black solar-absorber surfaces
Authors: Clark G. J. , Switkowski Z. E. , Petty R. J. , Heggie J. C. P.
Published: February 2003

The 52Cr(p,γ) 53Mn resonance reaction and the 16O(p,γ) 17F direct-capture reaction have been used to determine quantitatively the chromium and oxygen depth distributions in a series of electroplated chrome-black solar absorbers. In conjunction with SEM investigations, the chemical and structural composition of the films have been studied as a function of plating time. Two stages of deposition were identified. The commencement of the second stage correlated well with the reported minimum in the thermal emittance of the films. The unusual oxide compositions are consistent with the absorbers being Cr/Cr2O3 cermet films.
Effects of the growth conditions on the incorporation of deep levels in vapor-grown GaAs
Authors: Ozeki Masashi , Komeno Junji , Shibatomi Akihiro , Ohkawa Shinji
Published: February 2003

The effects of various conditions on the incorporation of deep levels in VPE GaAs were studied by capacitance spectroscopy. Three kinds of electron traps (Ec−0.86 eV, Ec−0.84 eV, and Ec−0.77 eV) and two kinds of hole traps (EV+0.60 eV and EV+0.44 eV) were measured. Trap concentrations increased strongly with increasing growth rate, but were found to be independent of n-doping level, type of dopants used (S, Se, Si, Ge, Sn), and growth atmosphere (H2 or N2). These experimental results indicate that the centers responsible for these levels are not due to simple substitutional chemical impurities, but are related to native defects or to complexes involving native defects.
NbO2 devices for subnanosecond transient protection
Authors: Philipp H. R. , Levinson Lionel M.
Published: February 2003

The feasibility of using ∼10-μm-thick polycrystalline NbOx layers on NbO and ∼25-μm-thick single-crystal NbOx (x∼2.0) chips as fast-response-time low-capacitance nonpermanent switching devices has been investigated. A packaging configuration with evaporated small-area contacts exhibiting low insertion loss in high-frequency applications has been developed. Both polycrystalline and single-crystal NbOx materials exhibit switching at an electric field of ∼25 V/μm for a 3-ns-wide pulse with a delay time of less than 1 ns. For polycrystalline NbOx layers, device degradation (increased insertion loss) with repeated pulsing is observed for 3-ns pulse widths and degradation is markedly accelerated for longer pulse width. Device stability in the thicker single-crystal chips is greatly improved compared to the polycrystalline material. Switching and associated sparking phenomena in single-crystal chips were investigated in air, Freon, helium, and vacuum environments, and only minor behavioral differences were observed. We have related this sparking to a volatilization of material from the NbOx upon pulsing and correlate it with the formation of pits ∼25 μm in diameter and ∼20 μm deep on the crystal surface around the periphery of the contact.
Bound-exciton luminescence associated with cobalt acceptors in vapor-grown GaAs
Authors: Ozeki M. , Shibatomi A. , Ohkawa S.
Published: February 2003

A new emission line due to a recombination of an exciton bound to a cobalt acceptor has been observed at 1.489 eV in vapor-grown GaAs. Detailed Zeeman analysis of the emission revealed that the corresponding center has a tetrahedral symmetry in the crystal. Relevant splitting factors are ge=−0.47(electron), K=0.61(hole), and L=−0.05(hole).
Electrical response of a bimetallic junction to shock compression
Authors: Bloomquist D. D. , Duvall G. E. , Dick J. J.
Published: February 2003

The electrical response of a copper-Constantan junction to shock compression has been studied over a pressure range 14.5–36.0 GPa. Four possible sources of anomalous response were found: electrical noise due to circuit closure at impact, shock demagnetization of a ferromagnetic material, high local temperature at the junction interface due to shock compression of a surface damage layer, and two-dimensional flow in the pressurized region due to pressure relief from the edges. Using a diffusion-welded junction in uniaxial strain the emf measured is within 20% of the predicted emf based on normal thermocouple response to shock-compression temperatures. In a geometry in which a guard ring was used to prevent lateral flow behind the shock front, the observed voltage-time profile was a step with constant plateau. In a similar configuration where radial pressure relief was allowed behind the shock front, the initial step (which compares directly in amplitude to the above results) is followed by a marked positive ramping. This ramping was directly correlated with the two-dimensional flow due to radial pressure relief. The results indicate that any fundamental anomaly which exists for one-dimensional strain is less than 10–20% of the observed signals in the pressure range studied.
A barrier model for ZnO varistors
Authors: Hower P. L. , Gupta T. K.
Published: February 2003

A model of current transport in ZnO varistors is proposed. The model is a modification of an earlier one suggested by Levine, with the major difference being the inclusion of a thin (?10 Å) ’’disordered’’ layer which separates the single-crystal ZnO grains. The proposed model is shown to be consistent with electrical and microstructural observations and can satisfactorily account for α’s in excess of 60. A technique for extracting the surface-state density Ns(E) and doping profiles from C-V and I-V data is described. It is also shown from the theory that the maximum α is approximately proportional to the grain voltage, a result that is in agreement with measurements on varistors made under a wide range of processing conditions. By calculating the I-V characteristic for different Ns(E) profiles, it is shown that Ns(E) largely determines this characteristic and that certain profiles are to be favored over others when processing conditions are considered.
Properties of chalcogenide-glass/n-GaAs heterojunctions
Authors: Frye Robert C. , Adler David , Shaw Melvin P.
Published: February 2003

Heterojunctions of threshold-type chalcogenide glasses deposited onto crystalline n-GaAs have been fabricated and studied. Once the glass is switched into the on-state, very asymmetric behavior is observed. Under forward bias, the devices exhibit low resistance, but strong current saturation occurs under reverse bias. No microwave gains or losses have been detected. The properties are explained by a consideration of the expected results when an N-type negative-differential-resistance device is placed in series with an S-type negative-differential-resistance device. A band diagram for the heterojunctions has been determined. The investigation of these heterojunctions has led to the conclusion that a high field near the anode exists in the on-state of the glass.
Neutralization of mobile ions in the SiO2 film of MOS structures
Authors: Hino Taro , Yamashita Ken
Published: February 2003

Space-charge polarization of sodium ions in the SiO2 layer of MOS structures is observed by comparing thermally stimulated currents with capacitance-voltage characteristics. The results cannot be interpreted by only a space-charge polarization of a constant excess charge. Charge exchange at the interface is suggested and this idea is supported by the results of thermally stimulated surface potentials. Further, estimation of some parameters of ions are discussed for the case when neutralization of ions occurs at the interface.
Resolution of NMR images from the sensitive line method
Authors: Meiere F. T. , Thatcher F. C.
Published: February 2003

The mathematical solution for the NMR signal produced by a series of pulses in the presence of time-dependent gradients is derived for the first time. This is used to discuss the localization properties of the sensitive line method of imaging and the resolution is expressed in terms of the experimental parameters. It is pointed out that an upper limit of sample size to resolution exists.
Negative surface ionization: Intense halogen-ion source
Authors: Pelletier J. , Pomot C. , Cocagne J.
Published: February 2003

A surface negative-ionization source was created in order to produce intense negative-ion beams. The advantages of an ionizer functioning in transmission were shown, which led to the theoretical determination of ionizer-pore useful dimensions. It was thus shown that, contrary to the case with positive ions, the pore diameter necessary for a satisfactory transmission-ionization efficiency is highly dependent on the electron affinity of the element to be ionized. A lanthanum hexaboride ionizer was then chosen since it gives a good ionization of halogens and especially of iodine. Experimental study showed that the maximum densities of the extracted-ion current are comparable to those obtained by the same process for positive Cs+ ions ionized on tungsten. Finally, the influence of the ionizer-pore diameter on ion-current characteristics according to temperature and flow was highlighted. These characteristics confirm the hypothesis established for the working of transmission ionizers.
Matrix methods in potential theory and electromagnetic scattering
Authors: Waterman P. C.
Published: February 2003

Employing a conserved-flux concept, the T-matrix equations describing boundary-value problems of potential theory and electromagnetic scattering are obtained without recourse to the Huygens principle or physically fictitious fields. For scattering by dielectric objects, tangential electric and magnetic fields on the surface are both represented in a single expansion, cutting the computation in half. In the low-frequency limit the dynamical equations are shown to reduce to the static case, and numerical computations then indicate that in comparison with other approaches, the present method can achieve as much as an order of magnitude reduction in the number of equations and unknowns needed for a given accuracy. New exact relations are found between the electrostatic and magnetostatic problems, and analytical results are also obtained from the equations, with and without truncation.
Ferroelectric domain inversion in Ti-diffused LiNbO3 optical waveguide
Authors: Miyazawa Shintaro
Published: February 2003

The ferroelectric domain in Ti-diffused c-plate LiNbO3 optical waveguides were examined by chemical etching. In the Ti-diffused +c layer, a domain-inversion layer was formed where the spontaneous polarization is opposite to that of the substrate. The formation is dependent upon diffusion conditions. On the other hand, no domain inversion appeared in the diffused −c layer. It is concluded that the −c face is quite favorable for fabricating Ti-diffused c-plate optical waveguide for application in electro-optic devices. A plausible explanation for the domain inversion is considered.
Study of intensity pulsations in proton-bombarded stripe-geometry double-heterostructure AlxGa1−xAs lasers
Authors: van der Ziel J. P. , Merz J. L. , Paoli T. L.
Published: February 2003

The pulsations in the laser emission from several lasers have been studied as a function of temperature, cavity length, external mirror illumination, and effect of mirror etching. Selected DH lasers with 12-μm-wide stripes delineated by proton bombardment and 380-μm-long cavities were used. The modulation depth of the pulsations at 300 °K increases approximately linearly with current above a threshold value and becomes fully modulated at high output powers. At intermediate temperatures, the modulation exhibits a similar initial slope but is not complete at the highest measured output. At low temperatures, well-developed pulsations are not observed; the modulation reaches a maximum at a low amplitude level and then decreases. The frequency dependence of the pulsations indicates that when the modulation level is increasing, the frequency f is relatively constant, and above the maximum moduation f 2 increases approximately linearly with output power. The dependence on cavity length was studied using a series of 380-μm-long unbonded chips which showed strong pulsations under pulsed operation and were then cleaved into ∼125-μm-long sections. Of the short devices which lased, both center and end segments showed pulsations, indicating that unpumped end regions are not acting as saturable absorbers, resulting in the pulsations. The effects of illuminating the mirrors with 4880- and 6328-Å laser radiation and injecting 1.06-μm radiation into the active region were studied. Illuminating the mirrors increased the threshold and decreased the external differential quantum efficiency. The pulsations had the same light power threshold and had qualitatively the same dependence on output power. The possibility that an oxide layer over the facet is associated with the pulsations was studied by stripping the oxide with a dilute NH4OH solution. Up to four 5-sec strippings did not appreciably affect the pulsations. Hence, oxide layers and related nonradiative centers at the mirrors are not responsible for pulsations. Most lasers had kinks in the L-I characteristic. The pulsations were quenched if the lasers were operated in a region near the kink. The models used previously to describe the pulsations do not appear to apply to the lasers studied here. Much of the pulsation behavior can be explained by a simple nonlinear-gain model in the electron-photon density equations of the laser. Such a nonlinear gain can result from spatial nonlinearities in the gain within the stripe.
A simple representation of the Pugh, Eichelberger, and Rostoker solution to the shaped charge jet formation problem
Authors: Hirsch Eitan
Published: February 2003

A mathematical manipulation of the solution to the shaped charge jet formation problem of Pugh, Eichelberger, and Rostoker gives a simple formula which lends itself to easy clear interpretation. This helps to explain some of the facts known to shaped-charge designers by experience, without the need of a computer code.
General plasma characteristics of a Berkeley multifilament ion source
Authors: Schoenberg Kurt F. , Kunkel Wulf B.
Published: February 2003

The general plasma characteristics of a Berkeley Multifilament Ion Source are presented. The measurements are obtained via a pulsed electrostatic-probe data-acquisition system, and in part conclude: (a) The electron distribution function consists of a bulk component of thermal electrons (kTe∼3–5 eV) comprising 90–97% of the total electron population (depending on operating conditions), plus a nonthermal high-energy tail, which is a monotonically decreasing function of energy, and contains a small but experimentally significant electron population at energy values 10–15 eV above maximum cathode fall. (b) Overall source performance, i.e., the spatial distribution of plasma potential, plasma density, and ion current density, approximately follows steady-state low-pressure discharge theory assuming spatially uniform ion production.
Influence of turbulence on a diffuse electrical gas discharge under moderate pressures
Authors: Khait Y. , Biblarz O.
Published: February 2003

Aspects of a corona discharge under the influence of a turbulent flow are considered. This problem represents an extension of the already complicated situation of discharges in very nonuniform electric fields but in nonmoving gases. Our approach is restricted to providing a qualitative and semiquantitative description of some important phenomena occurring in plasmas formed in a turbulent gas which flows through the strong nonuniform electric field present in the small corona region. These phenomena lead to interesting experimentally observable effects; in particular, they allow a substantial increase of current and power consumption in the diffuse discharge which is associated with a sharp enhancement of transport coefficients in the hydrodynamically turbulent plasma. Estimates of the relative current increase and power consumption (turbulent-to-laminar) can be made with the information presented. These estimates are in agreement with observations.
Reply to ’’Comment on ’Transverse 1/f noise in InSb thin films and the signal-to-noise ratio of related Hall elements’ ’’
Authors: Kotera Nobuo , Nakashima Muneyasu , Shigeta Junji , Oi Tetsu , Sato Kikuji
Published: February 2003

Noise formula describing the 1/f noise in InSb films is pointed out. The noise-intensity coefficient K is introduced as a variable depending on film-preparation methods. Experimentally, K2 changes by two orders of magnitude. However, existing noise calculations show that K2 should remain constant except for a dimension factor. Therefore, the experimental results cannot be explained by the existing theory.
Carrier concentration and mobility of PbTe and Pb1−xSnxTe LPE thin layers
Authors: Zemel A. , Tamari N. , Eger D. , Yaniv O.
Published: February 2003

Galvanomagnetic measurements were made on n-type PbTe and p-type Pb0.79Sn0.21Te layers, 5 to 20 μm thick, grown by liquid-phase epitaxy (LPE) on highly conductive PbTe or Pb1−xSnxTe substrates. PbSnTe-PbTe heterostructure diodes were formed in order to isolate the measured layer from the underlying substrate (or LPE layer). The dependence of carrier concentration and mobility on LPE growth temperature in the range 470–650 °C was studied. The carrier concentration of the epilayers was found to be strongly influenced by the underlying layer or substrate, possibly due to interdiffusion of native defects during the LPE growth process. Bulklike mobilities were measured between 4.2 and 77 K.
Static and dynamic pyroelectric coefficients of polyvinylidene fluoride over a 90–370 K temperature range
Authors: Lang Sidney B.
Published: February 2003

The static and the real and imaginary components of the dynamic pyroelectric coefficients were measured on a film of polyvinylidene fluoride (PVF2) over a 90–370 K temperature range. These are the first pyroelectric coefficients of PVF2 measured at extremely low temperatures, and the first complex dynamic pyroelectric coefficients reported in the literature. The static coefficient was small and constant below the glass transition temperature Tg, but increased very rapidly above Tg. The real dynamic coefficient was in good qualitative agreement with the static value. The imaginary dynamic coefficient had a complicated frequency dependence which can be used to examine elastic and piezoelectric relaxation processes.
Electron paramagnetic resonance in powdered semiconductors and semimetals
Authors: Sansonetti J. E. , Mullin D. P. , Dixon J. R. , Furdyna J. K.
Published: February 2003

The problem of electron paramagnetic resonance (EPR) in powders of highly conducting semiconductors and semimetals is examined. Attention is focused on the fact that the observed EPR signal can be strongly influenced by the conductivity of the powder grains, and particularly by the high degree of anisotropy (gyrotropy) of the conductivity which arises in these materials when a dc magnetic field is present. The interaction of a single powder grain with an electromagnetic wave is analyzed in terms of the recently developed theory of Ford and Werner for electromagnetic excitations of a gyrotropic sphere. Although the general form of this theory can only be handled numerically, we show that in the case of powder grains, which are typically small compared to the outside wavelength, closed analytic expressions can be obtained for the magnetic and electric polarizabilities of the particles. Using these polarizabilities as a point of departure, the description of the powder as a whole is then obtained in the form of an effective powder as a whole is then obtained in the form of an effective powder permeability and permittivity. A detailed analysis of these general results in specific parameter ranges shows that both the EPR line shape and its intensity depend strongly on the value of the particle conductivity, on its tensorial character, and on the particle size. It is demonstrated that when the powder particles are small compared to the skin-depth and internal wavelength, the EPR absorption line shape is Lorentzian, predicted by the imaginary (dissipative) part of the magnetic susceptibility χ. When particles are large compared to the skin depth, the EPR absorption line shape is determined by a mixture of the dispersive and dissipative components of χ, depending on the behavior of the elements of the magnetoconductivity tensor. Specific limiting cases of the electrical parameters are discussed and the effect of particle-size distribution on EPR in powders is also considered. Where available, experimental data are used to illustrate the behavior predicted by the analysis.
Properties of ambient-enhanced photoluminescence from InP and GaAs surfaces
Authors: Nagai Haruo , Tohno Shunichi , Mizushima Yoshihiko
Published: February 2003

Photoluminescent properties due to ambient gas are investigated. Photoluminescence (PL) as a function of gas pressure indicates a molecular adsorption. Curious gas-flow effect on PL intensity from InP and GaAs surface is observed. Gas-feeding condition on the sample crystal surface affects the PL intensity in all of the examined gases (N2, Ar, H2, and O2). Various factors which are assumed to be the cause of this phenomenon were discussed, and the molecular adsorption is found to be the possible mechanism.
Photoluminescence at dislocations in GaAs and InP
Authors: Böhm K. , Fischer B.
Published: February 2003

The influence of dislocations on the radiative recombination of electron-hole pairs in GaAs and InP is investigated by spatially resolved photoluminescence measurements. The shape of the spectra is unchanged at individual dislocations, while the overall intensity is lowered by about 30% in a region of 5–10 μm around the dislocations. This relative change of intensity is temperature independent in the investigated range 10–300 K. Deformation-induced dislocations, prepared by plastic deformation at 600 °C, behave similarly to as-grown dislocations. These statements hold for 60° dislocations and screw dislocations in both n-type and p-type material. Search for dislocation-induced electronic levels in the band gap by deep-level transient spectroscopy, optical absorption, and photoluminescence of GaAs samples with very high dislocation density gives no evidence for such levels. Our findings suggest that the quenching of the radiative recombination near dislocations is caused by an enhancement of the nonradiative bulk mechanisms, rather than by an additional mechanism at dislocations. Possible reasons for this enhancement are discussed. Under special circumstances precipitation or segregation of impurity atoms at dislocations is observed; in these cases the spectrum at dislocations is changed compared to the bulk.
On a general treatment of acousto-optic interactions in linear anisotropic crystals
Authors: Rouvaen J. M. , Ghazaleh M. G. , Bridoux E. , Torguet R.
Published: February 2003

In arbitrary anisotropic crystals exhibiting optical activity, the normal modes of light propagation are elliptically polarized. These modes are studied using a new gyration pseudotensor affecting the relative dielectric impermeability tensor, defined here for convenience. The propagation of light inside a first-order acoustically perturbated medium is then considered. The equations are solved by using a normal-mode expansion of the electric-displacement vector, assuming a stationary regime of diffraction and slowly spatially varying amplitudes. A coupled first-order partial derivative set is so obtained, which describes the acousto-optic interactions. The case of acoustic plane bulk wave modulation is finally emphasized and all the classical approximate results, deduced from theories with more restricted areas of applications, are retrieved using suitable assumptions in our general equations.
Fracture of ceramics by single-pulse 10.6-μm irradiation
Authors: Mecholsky J. J.
Published: February 2003

A model has been developed to predict fracture of ceramic materials exposed to single-pulse irradiation. In this model based on a modification of the theory for metal-plate rupture by single-pulse irradiation, the impulse required for fracture is directly proportional to the thickness of the sample and the average fracture stres. This model correctly predicts fracture of fused-silica glass irradiated with a single pulse (?28 MW/cm2) on a 300-J pulsed laser (AVCO–Everett). This result suggests that pressures of 50–150 bars, when delivered in short times (∼12 μs), are sufficient to fracture brittle materials such as fused silica.
A statistical model of sputtering
Authors: Schwarz S. A. , Helms C. R.
Published: February 2003

An elementary statistical model of sputtering based on simple geometrical considerations is described. A useful equation for relative sputtering yields is derived which accurately predicts variations with ion energy, mass, and incident angle over a broad range of these parameters. An empirical relation for the absolute sputtering yields is also deduced. Several comparisons are made to experimental and theoretical work in the literature.
Ultrafine nickel particles for photothermal conversion of solar energy
Authors: Niklasson G. A. , Granqvist C. G.
Published: February 2003

Ni particles with mean diameters ≲10 nm were produced by inert-gas evaporation onto KBr plates. Heating in air to 400 °C for a few minutes led to the electrical decoupling of the grains by formation of NiO pellicles. Transmittance measurements in the interval 0.3–30 μm showed excellent spectral selectivity with high absorption over the solar spectrum and low absorption in the thermal infrared range. Heat treatments up to 600 °C in air did not affect the selectivity significantly. These properties prove that coatings with Ni grains are very useful for the photothermal conversion of solar energy. A theoretical analysis of the optical properties of aggregated spherical particles with dielectric shells was carried out by use of an extended effective-medium theory founded on the Maxwell Garnett approach. We obtained satisfactory agreement between computations and experiments.
Shear properties of polarized PVF2 film studied by the piezoelectric resonance method
Authors: Auld B. A. , Gagnepain J. J.
Published: February 2003

Observations have been made of thickness shear resonances in commercially available stretched and poled PVF2 film. The resonances were observed by direct coupling through the piezoelectric properties of the film, using an electrode configuration that applies the rf electric field in the plane of the film. Observations were made from ambient temperature to liquid-helium temperature and values of resonant frequencies, piezoelectric coupling constants, and mechanical quality factors were deduced from input-impedance–vs–frequency curves for thickness shear resonances with vibration polarized parallel and perpendicular to the stretch direction.
Comment on ’’The significance of the distribution of hot spots on the interpretation of laser-produced plasma experiments’’
Authors: Goel S. K. , Gupta P. D. , Bhatnagar R.
Published: February 2003

It is shown that the estimation of the scaling laws relating plasma parameters to laser intensity obtained by a least-squares fit for logarithmically transformed variables implicitly takes into account the effect of laser hot-spot distributions.
Morphologic discussion of the transition mechanism from corona to glow discharge
Authors: Fujii Kan-ichi , Oikawa Toshio , Kuwana Hisashi , Tajiri Tetsuo
Published: February 2003

The transition mechanism from the initiation of a corona discharge to a glow discharge is morphologically shown in the atmosphere with 1-mm narrow-gap spacing. The anode glow spreads out widely on the anode surface, similar to that of a low-pressure glow discharge, and changes into a positive column after spark-over. A dc component of the discharge current appears when the anode glow occurs.
Reply to ’’Comments on the spectroscopic analysis of a high-density plasma’’
Authors: Neufeld C. R.
Published: February 2003

The alternative interpretation of previously reported data is critically examined, and several inherent weaknesses of such an interpretation are discussed. The difficulties raised are real, however, and their recognition has recently led to a revised interpretation of the experimental data, the essential elements of which are presented here.
Investigation of an m=0 mode instability in a cold-cathode Penning discharge
Authors: Guharay S. K. , SenGupta S. N.
Published: February 2003

In the high-pressure mode of a cold-cathode Penning discharge, an extensive study of the behavior of a rotationally symmetric wave, excited by a positive radial electron-temperature gradient, is made by utilizing a simple analog correlator. Several important experimental results, concerning the influence of the discharge parameters on the coherence and the frequency of the excited waves, are obtained and these are found to agree well with the theoretical predictions. The mechanism of the low-frequency waves in the high-pressure mode is also ascertained in this report.
Compositional and structural properties of amorphous SixC1−x : H alloys prepared by reactive sputtering
Authors: Shimada T. , Katayama Y. , Komatsubara K. F.
Published: February 2003

Amorphous SixC1−x : H alloys are prepared by simultaneous rf reactive sputtering of silicon and graphite in a H2-Ar gas mixture. Silicon, carbon, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford-backscattering method, and thermal evolution of hydrogen. Evolution temperature dependence of the number of evolved hydrogen atoms is measured. The hydrogen-evolution behavior and the optical gap are x dependent. These phenomena are discussed in the light of chemical-bonding states.
Laser annealing of silicon on sapphire
Authors: Roulet M. E. , Schwob P. , Affolter K. , Lüthy W. , von Allmen M. , Fallavier M. , Mackowski J. M. , Nicolet M. A. , Thomas J. P.
Published: February 2003

Silicon-implanted silicon-on-sapphire wafers have been annealed by 50-ns pulses from a Q-switched Nd : YAG laser. The samples have been analyzed by channeling and by ω-scan x-ray double diffraction. After irradiation with pulses of a fluence of about 5 J cm−2 the crystalline quality of the silicon layer is found to be better than in the as-grown state.
Acoustic determination of depletion depth in metal-semiconductor contacts
Authors: Fossheim K. , Holt R. M. , Raaen A. M.
Published: February 2003

The discovery of highly efficient acoustic-surface-wave and acoustic-volume-wave generation in nonpiezoelectric crystals has previously been explained by the properties of metal-semiconductor contacts (surface-barrier model). In the present paper we demonstrate that measurements of the frequency-dependent efficiency of the volume-wave transducer provides an accurate method for the determination of the depletion depth of a metal-semiconductor contact. It is concluded that the surface-barrier transducer model accounts for observations on acoustic-volume-wave generation and detection in nonpiezoelectric dielectrics.
Interrupted neutron-irradiation experiments involving dislocations in sodium chloride
Authors: Anderson A. R. , Pollard H. F.
Published: February 2003

Ultrasonic and electric charge experiments near room temperature yield information on dislocation pinning, damping, and charging during interruptions to high-energy neutron irradiation. Small changes in the pinning point density during interruption provide evidence for a dfifusion pinning process in the core region. Changes in the decrement are found to be not wholly dependent on the fourth power of the average loop length. Changes of 10–20% are found in the damping factor B during interruptions that depend only on the concentration of point defects in the regions surrounding the dislocations and not on the state of the core region. Experiments below room temperature indicate negligible changes in dislocation charge q during interruption. There is no evidence for any direct relationship between B and q.
Magnetoelastic waves in a ferromagnetic film on a nonmagnetic substrate
Authors: Camley R. E.
Published: February 2003

We present a theoretical study of the propagation of magnetoelastic waves in a ferromagnetic film bonded to a nonmagnetic substrate. We find magnetoelastic waves which correspond to both Rayleigh waves and Love waves modified by the magnetoelastic interaction. Deviations from the elastic-wave characteristics are found in the frequency region where bulk and surface spin waves propagate. Most particularly, a rich, strongly frequency dependent, and highly nonreciprocal attenuation rate is found for these modes. The anomalies associated with the surface spin waves are very sensitive to spin pinning conditions.