bluuebunny/crossref_metadata_2025 huggingface dataset:
A new space-charge-limited-current diode theory with analysis of CuxS/CdS data
Authors: Partain Larry D.
Published: February 2003

A new theory for trap controlled, space-charge-limited-current (SCLI) diode behavior has been derived. Standard approaches have been modified so that only the drift component of current transport is considered along with the asymmetric boundary conditions required for rectification. Simple analytical expressions for the current-voltage properties were obtained for the single-trapping level case. A straightforward, numerical integration scheme was developed for the multiple trapping level situation. Application of the results to CuxS/CdS current-voltage data provides the first SCLI explanation for rectification in these devices. Electron trapping levels at 0.60, 0.44, and 0.20 eV below the conduction band edge with respective concentrations of 3(1015), 6(1014), and 3.1(1017) cm−3 were identified. These parameters compare well to electron traps reported in the literature for CuxS/CdS and gold/CdS diodes measured by deep-level-transient spectroscopy (DLTS), admittance spectroscopy, and by SCLI analysis.
Semiconducting behavior of Ag2Te thin films and the dependence of band gap on thickness
Authors: Das V. Damodara , Karunakaran D.
Published: February 2003

Thin films of Ag2Te of various thicknesses in the range 500–1500 Å have been prepared by thermal evaporation of the compound under vacuum on clean glass substrates held at room temperature. The electrical resistance of the films has been measured as a function of temperature during heating, which was carried out immediately after the film formation. The observed exponential decrease of resistance with temperature up to the transition point points to the semiconducting nature of the low temperature polymorph of Ag2Te. The band gap of the low temperature phase is calculated for various thicknesses of the films and it is found that the band gap is a function of film thickness, increasing with decreasing thickness. The increase in the band gap, which was found to be inversely proportional to the square of the film thickness, is attributed to quantization of electron momentum component normal to film plane.
Electron trapping/detrapping within thin SiO2 films in the high field tunneling regime
Authors: Olivo P. , Riccó B. , Sangiorgi E.
Published: February 2003

The work presents the essential features of a model for the electrical behavior of thin SiO2 films in the high field tunneling regime. In particular the carrier trapping/detrapping phenomena, taking place within the insulator and responsible for the current time dependence at constant applied voltages, are considered: the suggestion is proposed that all the oxide Si–O bonds take active part in such processes and explanations are consequently derived for some aspects of previous works not yet convincingly interpreted. The results of a computer program implementing the model are also presented and shown to be in satisfactory agreement with experimental curves which can be fit with a single variable parameter.
Solder bump height dependence of Josephson chip-to-card interconnection inductance using flip-chip bonding technique
Authors: Temmyo Jiro , Aoki Katsuhiko , Yoshikiyo Haruo , Tsurumi Shigeyuki , Takeuchi Yoshiaki
Published: February 2003

Inductance measurements of solder bump flip-chip interconnection for a Josephson chip bonding are carried out by employing direct-coupled two-junction interferometers. For detailed chip bonding design, interconnection inductances are studied experimentally, as functions of solder bump heights, niobium pad shapes with moat structures, and pad positions from the chip ground plane edge. It is found that the ground plane inductance contribution is dominant; the bump height dependence of the interconnection inductance is not a simple linear function, because ground plane image current is modulated by the existence of pads and the moat structure.
Use of electric probes in silane radio frequency discharges
Authors: Mosburg Earl R. , Kerns Ralph C. , Abelson John R.
Published: February 2003

The use of electrostatic probe techniques for measurement of the electron temperature kTe and the electron density ne in pure and BF3 doped silane radio frequency (13.56 MHz) discharges is demonstrated to be feasible even though amorphous silicon is being deposited on the probe surfaces. The required conductivity of such deposited silicon surface layers is examined and compared with the measured photoconductivity and thermally induced conductivity of amorphous silicon. An equation is derived for the double probe current–voltage (I–V) curve which includes the first order effect of ac fields and can be used to determine the electron density. During typical depositions of thin films of amorphous silicon from such discharges, values of kTe =2–2.5 eV and ne =(1–1.5)×109 cm−3 were obtained. These values are consistent with those obtained by other workers using microwave and optical techniques. In BF3 doped silane an abrupt step is observed in the Langmuir I–V curves which indicates the presence of a group of fast, anisotropic electrons. In diborane doped silane, probe measurements become unstable and irreproducible. For this reason we investigate a rf probe technique. The advantages and constraints inherent in using this method in our rf discharges are examined and analyzed.
Generalized theory of first Townsend ionization coefficient in strong electric fields
Authors: Friedland L. , Kagan Ju. M.
Published: February 2003

A one dimensional model of electron multiplication in a gas in strong electric fields is considered by using the Laplace transform technique. An approximate expression for the first Townsend ionization coefficient is derived and found to be in a good agreement with the experimental data for a variety of atomic and molecular gases.
Ionization mechanism in a nitrogen glow discharge
Authors: Brunet H. , Vincent P. , Rocca Serra J.
Published: February 2003

The electron distribution function has been calculated in nitrogen taking into account collisions of electrons with vibrationally excited molecules. Transport coefficients, vibrational excitation rates, excitation rates for the lowest-lying electronic states, and direct ionization rates are presented as a function of E/N (electric field to gas density ratio) for different values of the vibrational temperature. At low E/N values, a very large increase of the direct ionization rate is observed due to the rise of the tail of the electron distribution in presence of large vibrational populations. Ionization processes occuring in the collision of metastable molecules have also been investigated. It is concluded that in most glow discharge, ionization occurs mainly from associative ionization produced by collision between two metastable molecules in the a′∑−u state. Ionization due to collisions of electrons with metastable molecules was found to be unimportant because of the low concentration of metastable molecules in glow discharges.
Computer simulation of a nematic guest-host display
Authors: Gharadjedaghi F.
Published: February 2003

The steady state electro-optical behavior of a dichroic type of display cell using a nematic mixture with positive dielectric anisotropy is considered. This study makes use of a mathematical simulation method. Numerical results obtained from this method are in very good agreement with experiment. The effect of physical and technological parameters of the system on the form of the transmission-voltage characteristic is studied and in particular the slope of this characteristic in the neighborhood of the threshold voltage. The role played by the twist angle is especially considered.
Crystal site location of dopants in semiconductors using a 100-keV electron probe
Authors: Tafto/ J. , Spence J. C. H. , Fejes P.
Published: February 2003

The channeling effect on electron induced characteristic x-ray emission has been used to study the site occupancy of As in submicron regions of Si (3×1019 As atoms cm−3). We report here the first absolute intensity measurements of the crystallographic orientation dependence of characteristic x-ray production by kilovolt electrons in order to determine quantitatively the crystal site occupancy of an impurity.
Radiation-induced mobility of lithium and sodium in alpha-quartz
Authors: Hitt K. B. , Martin J. J.
Published: February 2003

The radiation-induced release of the charge compensating ions Li+ and Na+ from the substitutional aluminum impurity in α-quartz has been investigated by measuring the growth of the infrared active Al–OH− center as a function of sample temperature during irradiation. It was found that Li+ is released 10–15 K lower in temperature than Na+.
Anisotropic elastic limits and phase transitions of rutile phase TiO2 under shock compression
Authors: Mashimo Tsutomu , Nagayama Kunihito , Sawaoka Akira
Published: February 2003

Anisotropic elastic limits and phase transitions of the rutile phase TiO2 under shock compression are studied, on the basis of the measurements of particle-velocity histories and free-surface motions along the [100], [110], and [001] axis directions in the stress range up to 38.6 GPa. The stresses of Hugoniot elastic limit (HEL) along the [100] and [001] axis directions are determined to be 7.8±0.5 and 4.1±0.3 GPa, respectively. These different HEL stresses are reasonably analyzed by an inherent yield stress of 3.0±0.3 GPa. A Hugoniot kink at 12.2±0.6 or 17.0±0.7 GPa along the [100] or [110] axis direction, respectively, and two kinks at 10.6±0.5 and 33.7±1.3 GPa along the [001] axis direction are observed. Considering the volume changes and the recovery experiments of α-PbO2 phase, two former ones and the last one are suggested to correspond to the beginning of phase transitions to a α-PbO2 phase and a hexagonal phase, respectively. These anisotropic behaviors clearly show the typical evidences of the uniaxial strain effects of shock wave metamorphism of crystals.
Stress in chemical-vapor-deposited SiO2 and plasma-SiNx films on GaAs and Si
Authors: Blaauw C.
Published: February 2003

Stress was measured in films of chemical-vapor-deposited SiO2 and plasma-deposited SiNx on GaAs, in the temperature range 20–300 °C, using the laser beam deflection method to measure curvature of the substrate. Film thickness was in the range 1000–7500 Å. SiO2 films with and without P doping were deposited at 425 °C in a silox reactor. Stress in these films is independent of film thickness. The intrinsic stress σi is tensile with σi=5.1×109 dyne/cm2 and dσ/dT =12.6×106 dyne/cm2 °C for undoped films. P doping decreases the value of each of these parameters. Films of SiNx were deposited at 500 °C in a plasma-reactor. Both σi and dσ/dT decrease with film thickness, with values on the order of 5–15×109 dyne/cm2 and 15–35×106 dyne/cm2 °C, respectively. Annealing of films, deposited on Si, at temperatures in the range 500–700 °C does not affect stress in SiNx. However, stress relief is observed in both undoped and P-doped films of SiO2.
Ablative optical recording using organic dye-in-polymer thin films: Some mechanistic aspects
Authors: Law Kock-Yee , Johnson Gordon E.
Published: February 2003

The influence of a number of materials properties and device structure variations on the energy threshold for laser marking of organic dye-in-polymer films has been investigated. Our results indicate that the write-sensitivity of these organic dye-in-polymer optical recording media is strongly dependent on the absorption efficiency of the recording film, the quantum efficiency of generation of thermal energy by the dye and the recording film thickness for films >100 nm. The write-sensitivity is however, not dependent on the glass transition temperature, the surface tension or the melt viscosity of the polymer binder. This independence is attributed to the very rapid nature of the mark formation process. The technological implications of the present work are discussed.
Fading properties of a NaF:F+2* color center laser
Authors: Eisele H. , Paus H. J. , Wagner J. , Leduc M.
Published: February 2003

An investigation of the temporal stability of a color center laser based on F+2* centers in NaF is presented. It is found that the fading of the output power strongly depends on pump power, intracavity power, pump wavelength, and temperature. Optimum conditions for operation were thus derived to improve the temporal stability of this tunable laser.
Effects of gaps on long range surface plasmon polaritons
Authors: Stegeman G. I. , Burke James J.
Published: February 2003

We show that air gaps of 50 Å and less in a symmetric dielectric-metal film-dielectric structure lead to mode cutoff for long range surface plasmons. High index liquids are discussed as a solution to this problem for most cases.
Two-dimensional simulation of a plasma KrF pulse compressor
Authors: Marchand R. , Capjack C. E. , James C. R.
Published: February 2003

Results from a two-dimensional simulation of a KrF laser pulse compression to parameters relevant to laser-driven fusion are presented. The amplifying medium consists of a fully ionized hydrogen plasma cylinder. The plasma density can be adjusted so as to radially confine the laser beams and thus, alleviate the constraints on the input beam divergences. Energy transfer efficiencies of order 50% are possible for experimentally feasible laser and plasma parameters.
Stress dependence of magnetically induced ultrasonic shear wave velocity change in polycrystalline A-36 steel
Authors: Kwun H. , Teller C. M.
Published: February 2003

Magnetically induced changes in the velocity of 4.5-MHz ultrasonic shear waves were investigated in polycrystalline A-36 steel as a funtion of both uniaxial tensile and compressive stresses. The velocity changes induced by the applied magnetic field exhibit distinctly different stress effects depending on the relative orientations between the shear wave polarization, the magnetic field, and the external stress axis as well as on the magnitude and sign, i.e., tensile or compressive, of the stress. The magnetically induced velocity changes and their stress dependence were found to be insensitive to the elastic anisotropy associated with the preferred orientation (rolling texture). Based on the magnetoelastic coupling in the material, a phenomenological account for the distinctly different stress effects on the magnetically induced velocity changes is given. Good semiquantitative agreement was found between the observed characteristic stress dependence of the magnetically induced velocity changes and the phenomenological explanation presented. The characteristic stress dependence of the magnetically induced velocity change together with its lack of sensitivity to the elastic anisotropy of the material offers a new means of nondestructively determining the magnitude, the direction, as well as the sign of an unknown stress in ferromagnetic materials.
Analysis of radial distribution of plasma parameters in a coaxial-line microwave discharge tube
Authors: Kato Isamu , Hara Shinji , Wakana Shin-ichi
Published: February 2003

The discharge mechanism in a coaxial-line microwave discharge tube that makes uniform plasma along the circumference of the tube has been analyzed. The analysis includes the skin effect of microwave penetration into the plasma and the equilibrium between generation and losses of the charged particles. It is shown that the radial distributions of electron density and electron temperature can calculated from measured values of the radial distribution of light intensity. The electron density is about 1012 cm−3 near the center axis of the plasma column and is close to trapezoidal in shape. The electron temperature is about 4×104 K near the tube wall and decreases monotonically toward the center of the plasma column.
Theory of gyrotron amplifier in a tape helix loaded waveguide
Authors: Uhm Han S. , Choe Joon Y.
Published: February 2003

Stability properties of the cyclotron maser instability in an annular electron beam propagating through a cylindrical waveguide loaded with a tape helix are investigated, in connection with applications on the gyrotron amplifier. Closed form of the dispersion relation for the cyclotron maser instability is obtained, including influence of the tape helix in stability behavior. It is shown that the bandwidth of the gyrotron amplifier for a tape helix is narrow in comparison with results for a sheath helix. However, the growth rate of the tape helix gyrotron is comparable to that of the sheath helix gyrotron.
Second-harmonic emission from laser-plasma interactions
Authors: Zhizhan Xu , Yuguang Xu , Guangyu Yin , Yanzhen Zhang , Jiajin Yu , Lee P. H. Y.
Published: February 2003

We have systematically investigated the second-harmonic (2ω) emission spectrum from 1.06-μm laser-plasma interactions. Experimental data on the dependence of 2ω spectrum, especially its broadness and complexity, on laser irradiation intensity, incidence angle, and prepulse are presented. A theoretical model using linear mode conversion and parametric decay instability processes can qualitatively explain the experimental results.
The laser irradiated gas jet: A spectroscopic experimental and theoretical study
Authors: Lee Richard W. , Matthews D. L. , Koppel L. , Busch G. E. , Charatis G. , Dunning M. J. , Mayer F. J.
Published: February 2003

We present x-ray spectroscopic measurements of the longitudinal electron density profile and the longitudinal and transverse electron temperature profiles for a laser irradiated gas jet. We attempt to verify our spectroscopic method by laser interferometry and by comparison of inferred quantities to those determined from laser plasma interaction simulations. Because temperature profiles were time dependent, we used a theoretical time dependent radiation transport code to analyze the data.
The investigation of image formation in a large-area solid state x-ray receptor with electrophoretic display
Authors: Yang K. H.
Published: February 2003

The image formation and the resolution of a self-contained electrophoretic x-ray imager have been investigated. The electrophoretic suspension contained pigments and counterions, ionic surfactants, and extraneous charges. Rate equations have been formulated to describe the transport properties of the ionic surfactants from the low to high field regions. The electrical transport properties of the electrophoretical suspension were investigated in relation to x-ray image formation using three different modes of operation: the pulse, the biased-pulse, and the universal modes. The reflectance versus charge curves of the x-ray images were qualitatively explained. Both negative- and positive-mode x-ray images of 22×22 cm2 have been demonstrated with two different electrophoretic suspensions. The imager can achieve x-ray images of high resolution and large area at the same time.
Optimization of a permanent magnet undulator for free electron laser studies on the ACO storage ring
Authors: Ortega J. M. , Bazin C. , Deacon D. A. G.
Published: February 2003

We describe the magnetic design problems involved in the realization of the permanent magnet undulator ‘‘Nouvel Onduleur pour l’Etude du Laser (NOEL)’’currently being used for the free electron laser experiments on the storage ring ACO. The undulator has been compensated for the magnetic imperfections of the magnet elements used for its construction. Each pole piece was made from two elements so that we could cancel out the transverse field errors. Each undulator pole was selected from a two-dimensional magnet distribution graph which was drawn with the results of a set of Hall-probe measurements. Magnetic measurements of the assembled undulator as well as the first experiments on the ACO storage ring indicate that the method has been successful.
Distribution of indium ions in indium substituted Mn-Zn ferrites
Authors: Rao K. H. , Mendiratta R. G.
Published: February 2003

The variations in dc resistivity and Mossbauer line intensities for various dopant concentrations of indium in a manganese-zinc ferrite have been investigated to analyze the site occupancy of indium ions. The indium ions are observed to occupy both tetrahedral and octahedral sites throughout the whole range of concentration studied. The picture proposed on the basis of resistivity measurements has been confirmed by Mossbauer data.
How well does 4He backscattering from low-Z nuclei obey the Rutherford formula?
Authors: MacDonald Jack R. , Davies J. A. , Jackman T. E. , Feldman L. C.
Published: February 2003

A study of 4He backscattering (150°) cross sections for O, Al, and Si atoms in the energy range 0.6–2.3 MeV has been completed. We conclude that the 4He backscattering cross section for these elements follows the E−2 energy dependence of Rutherford backscattering to 1%–2% over this energy range. These results have significant implications for the use of 4He backscattering as a materials analysis tool for low-Z elements.
Strain scattering of electrons in piezoelectric semiconductors
Authors: Fedders Peter A.
Published: February 2003

Static strains in piezoelectric semiconductors give rise to an electric field or potential which can have an effect on the electrical properties of the material. We have calculated the electric potential due to the strain field arising from a random distribution of point defects. This potential contributes a term to the mobility that is proportioned to T1/2 and a Hall factor of 1.10. Crude estimates of strain strengths indicate that this scattering mechanism may contribute significantly to the mobility of electrically rather pure III-V semiconductors below room temperature when neutral impurity concentrations are greater than 1018 cm−3. The mechanism may also constitute a dominant one in the mobility of some III-V alloys at fairly low temperatures. The existence of strain induced electric potentials also provides at least a possible mechanism whereby different donors can have different line shapes as measured in photoconductivity experiments.
Lattice thermal resistivity of III–V compound alloys
Authors: Adachi Sadao
Published: February 2003

Lattice thermal resistivities of III–V compound alloys have been analyzed with a theoretical prediction based on a simplified model of the alloy-disorder scattering. The theoretical prediction shows a quite good agreement with the experimental data on various III–V ternary compounds. This model has also been applied to obtain the thermal resistivity of In1−x Gax Asy  P1−y lattice-matched to InP for the composition range of 0≤y≤1.0. The result indicates that the thermal resistivity increases markedly with alloying and exhibits a maximum value of about 24 W−1 deg cm at an alloying composition of y≂0.75.
Interface effects in the formation of silicon oxide on metal silicide layers over silicon substrates
Authors: Baglin J. E. E. , d’Heurle F. M. , Petersson C. S.
Published: February 2003

Samples of several metal silicides grown over silicon substrates and samples of pure silicon were oxidized at the same time in an atmosphere of wet oxygen. The rates of silicon oxide growth were analyzed in terms of both linear and parabolic coefficients. The biggest difference is seen between the linear coefficients for metallic silicides on the one hand and pure silicon on the other, with a semiconducting silicide occupying an intermediate position. While the question of why metallic oxides are not always generated simultaneously with SiO2 remains a mystery, the results suggest a possible interpretation.
Intense relativistic electron beam injector system for tokamak current drive
Authors: Bailey Vernon L. , Creedon John M. , Ecker Bruce M. , Helava Heikki I.
Published: February 2003

We report experimental and theoretical studies of an intense relativistic electron beam (REB) injection system designed for tokamak current drive experiments. The injection system uses a standard high-voltage pulsed REB generator and a magnetically insulated transmission line (MITL) to drive an REB-accelerating diode in plasma. A series of preliminary experiments has been carried out to test the system by injecting REBs into a test chamber with preformed plasma and applied magnetic field. REBs were accelerated from two types of diodes: a conventional vacuum diode with foil anode, and a plasma diode, i.e., an REB cathode immersed in the plasma. REB current was in the range of 50 to 100 kA and REB particle energy ranged from 0.1 to 1.0 MeV. MITL power density exceeded 10 GW/cm2. Performance of the injection system and REB transport properties is documented for plasma densities from 5×1012 to 2×1014 cm−3. Injection system data are compared with numerical calculations of the performance of the coupled system consisting of the generator, MITL, and diode.
Enhanced stopping of relativistic electron beams using applied magnetic fields
Authors: Maron Y. , Blaugrund A. E.
Published: February 2003

A high-current-density relativistic electron beam is extracted through a thin anode window from the pinch region of a diode. An externally applied azimuthal magnetic field forces the electrons to make multiple passes through the anode window or through adjacent metal or insulator foils, thus causing enhanced energy deposition and x-ray emission. Enhancement factors of 2 to 4 have been observed.
Helical-flow CO2 laser
Authors: Yessik M. , Macken J. A.
Published: February 2003

A CO2 laser based on a helical gas-flow design has been developed. The major features of this device are as follows: (1) an integral heat exchanger plasmatube with much lower gas flow rates than other convection-cooled lasers, (2) a multiply segmented plasmatube for high-voltage standoff, (3) coaxial beam and electric discharge with small diameter-to-length ratio resulting in high beam quality and high discharge stability, and, (4) a magnetically stabilized discharge position. Gain profile measurements show that the gain distribution highly favors low-order modes, as desired. Temperature profile measurements of the gas in the plasmatube verify the efficiency of the integral heat exchanger concept. Specific laser configurations based on this design concept, intended for industrial material-processing applications, and with output powers of 400–500 W/m, are described.
Energy transport velocity of surface elastic waves
Authors: Seshadri S. R.
Published: February 2003

For the Love wave and the Rayleigh wave the power flux and the energies are evaluated, and, therefrom, the group velocity is determined by the dynamic method and is verified to be identical to that obtained by the kinematic method. A proof based on a variation theorem is also provided to show in a general way that the kinematic and the dynamic methods yield identical results for the group velocity of the surface elastic waves.
Ultrasonic attenuation and nonlinearity constant in silicon in the temperature range 73–293 K
Authors: Rajagopalan S. , Joharapurkar D. N. , Shende P. R.
Published: February 2003

The temperature dependence of the nonlinearity constant in silicon has been studied for longitudinal waves along 〈111〉 axis and for shear waves along 〈100〉 axis in the temperature range 73–293 K. The temperature dependence of the nonlinearity constant estimated from second-order elastic constant and third-order elastic constants has been further used to evaluate the ultrasonic attenuation at 480 MHz along 〈111〉 axis for (i) silicon with 1018 oxygen atoms per cubic centimeter, (ii) silicon with less than 1015 oxygen atoms per cubic centimeter and also at 495 MHz along 〈100〉 axis for shear waves. The estimated values of attenuation have been compared with the measured values available in the literature. The estimated temperature dependence of the nonlinearity constant has been further compared with that obtained for the measured values of attenuation. The estimated nonlinearity constant increases with temperature for longitudinal waves, whereas it shows a negative temperature coefficient for shear waves. The results are similar to those obtained for Ge and Cu.
Dispersion characteristics of a free electron laser with a linearly polarized wiggler and axial guide field
Authors: Yin Y. Z. , Bekefi G.
Published: February 2003

Calculations of the dispersion characteristics of a free electron laser with a linearly polarized wiggler magnetic field and an axial guide magnetic field have been carried out in the collective (Raman) regime for a cold, relativistic electron beam passing through a parallel-plate waveguide. The linear growth rate and efficiency of the transverse electric (TE) and transverse electromagnetic (TEM) waveguide modes have been computed for radiation in the centimeter and millimeter wavelength ranges.
Reflection acoustic microscopy for thick specimens
Authors: Wang J. K. , Tsai C. S.
Published: February 2003

This paper presents a theoretical modeling and experimental verification on the V(Z) characteristics of a three-media system in small numerical aperture reflection acoustic microscopy. The three-media system consists of either water-specimen-water or water-specimen-defect and is used as a model for a one-dimensional discontinuity or defect in a thick specimen. The following factors are treated in detail: acoustic attenuations in water and specimen, aberrations in specimen, and nonuniformity of lens pupil function. Measurements were carried out using a 150-MHz reflection scanning acoustic microscope and thick specimens such as silicon wafers and aluminum and steel plates. The findings are the following: (1) The acoustic attenuation in water causes the V(z) curve to deviate significantly from the ideal sinc function. Also, an absolute maximum in the V(z) curve is created when the focus is brought upon the second boundary of a thick but moderately attenuating specimen (e.g., silicon wafer). (2) The acoustic attenuations in water and in specimen degrade the system sensitivity. (3) The nonuniformity of the generalized pupil function smoothes out the periodic nature of the previously mentioned sinc function. (4) The aberrations in the specimen result in an increased axial movement of the specimen for a given plane to be focused. (5) The acoustic lenses with the aperture angle between 7° and longitudinal critical angle are desirable for imaging the defects in most commonly used solid materials, especially for those located at a few acoustic wavelengths beneath the host medium. Utilization of the model for defect characterization is also illustrated through measurement of the V(Z) curve and recording of the acoustic images of a solder bond which is located at 20 mil beneath the silicon wafer of a thick flip-chip microelectronic module. Finally, it is also suggested that the model can be generalized to treat multiple-media systems involving more than three media and an acoustic lens with large numerical aperture.
A new doping method using metalorganics in chemical vapor deposition of 6H–SiC
Authors: Yoshida S. , Sakuma E. , Misawa S. , Gonda S.
Published: February 2003

Aluminum doping was performed using triethylaluminum as the dopant in chemical vapor deposition of 6H–silicon carbide (SiC). Measurements on the electrical and cathodoluminescent properties of the epilayers indicate that the doping concentration of aluminum can be easily controlled by the flow rate of metalorganics. Electroluminescence was also observed for the pn junctions prepared by the successive growth of a nondoped n layer and a p layer doped with aluminum using metalorganics.
Thermoelectric drift of thermocouples due to inhomogeneous changes in composition
Authors: Ternan J. G.
Published: February 2003

A cylindrical thermoelement which has an axial temperature gradient undergoes both lateral and axial changes in chemical composition. The thermoelectric field is directed along the axis, but currents will circulate within the thermoelement if the composition change causes any lateral variation in the field. Such a field is nonconservative. It is shown that, if the temperature gradient is not too large, the electromotive force (emf) of the element is approximately the integral over temperature of the weighted average of the Seebeck coefficient, where the average is taken at each cross section of the cylinder, and the weighting factor is the normalized electrical conductivity. The thermoelectric drift is given by a similar expression that uses the change in Seebeck coefficient. A general method is given for correcting the approximations for the effect of the temperature gradient. If the conductivity is uniform, the approximations become exact and apply for all gradients. The theory is illustrated on a hypothetical Ni-Cr thermoelement which has a concentration gradient in Cr. The net composition of the element is calculated by Goodman’s approximation. The drift is proportional to the square root of time and inversely proportional to the diameter of the element. Conditions are given under which these relations are true for thermoelements of other compositions. The drift problem of the Ni-Cr thermoelement is also solved by a numerical finite-difference network. The results, and also the analysis, show that temperature gradients of less than 103 K cm−1 change the drift by less than 1%. This suggests that the drift approximation is virtually exact and will be useful for all thermoelements in practical temperature gradients.
Photovoltaic effect in Pb2CrO5 ceramic
Authors: Toda Kohji , Morita Shinichi
Published: February 2003

The existence of the photovoltaic effect has been observed in Pb2CrO5 ceramic. A typical photosensitive device has one pair of surface electrodes on one surface of a ceramic disk. The illumination response of the photovoltage in the device is described with the measured relation between the photovoltage and the illuminated area. The spectral photovoltaic response of the device has a peak sensitivity around 5700 Å in the visible region.
Collection efficiency of thin-film metal-insulator-semiconductor solar cells
Authors: So S. M. , Hwang W. , Meyers P. V. , Liu C. H.
Published: February 2003

A theory is proposed to quantify the collection efficiency of a thin-film metal-insulator-semiconductor (MIS) solar cell with back-surface field. The model incorporates two loss mechanisms: first, the image force effect producing an electron potential maximum located at xm near the surface within which all photogenerated electrons as well as holes are collected and thus do not contribute to the photocurrent, and second, the collection of the majority carriers, photogenerated in the depletion region, which diffuse against the electric field to xm and thus reduce the photocurrent. In addition to being affected by doping density, majority carrier mobility, minority carrier diffusion length, and effective surface collection velocity, the collection efficiency is shown to be thickness dependent when the semiconductor is fully depleted. Calculations are included for the specific case of electrodeposited n-type CdTe MIS solar cells. Methods to improve the collection efficiency include: designing a high-low doping profile; reducing the surface collection velocity; and optimizing the thickness and doping for the semiconductor.
Study of the radiation from an undulator: Near field formulation
Authors: Hirai Yasuharu , Luccio Alfredo , Yu Li-hua
Published: February 2003

The spectrum of undulator radiation has been formulated analytically for the near field case and compared with that of the far field case. For an undulator built for the free electron laser experiment in the vacuum ultraviolet storage ring at the National Synchrotron Light Source, it has been calculated that prominent near field effects of the fundamental component could be detected by setting a narrow slit at a specific position on the observation plane off the undulator axis, and the near field effects might disappear within an error of 1% on the undulator axis.
Enhanced energy deposition in a thin anode relativistic electron beam diode determined by Kα emission
Authors: Nardi E. , Zinamon Z.
Published: February 2003

The reflexing motion of electrons in the pinch region of a relativistic electron beam diode is studied using Kα x-ray emission from the anode as a diagnostic. In reference experiments reflexing is suppressed by using multilayered targets and Monte Carlo simulations are used to correct for backscattering. An enhancement factor of about 1.7 in the energy deposition relative to the single-pass case is found in the particular diode studied.
Thermal stability of the aluminum/titanium carbide/silicon contact system
Authors: Eizenberg M. , Brener R. , Murarka S. P.
Published: February 2003

The thermal stability of Al thin films on titanium carbide (TixC, where x defines the atomic ratio Ti/C) films reactively sputter deposited on Si substrate has been studied using Auger electron spectroscopy and x-ray diffraction. The stability of the deposited structure increases with increasing carbon content in the TixC films. However, an enhanced stability is obtained for a Ti3.1C film that is preannealed at 750 °C for 30 min to induce a phase separation to a titanium silicide inner layer and a TixC outer layer prior to Al deposition. Such a film with an Al top layer maintains its structure even following 550 °C-30 min heat treatment. The lower temperature (500 °C) failure observed in other cases results from severe intermixing of layers and the formation of the ternary compound Ti7Al5Si12, whereas failures observed at 600 °C result from similar intermixing and formation of the compound Al4C3, indicating the decomposition of TiC.
Mechanism of non-Shockley conduction in almost ideal silicon junction diodes
Authors: Cerofolini G. F. , Polignano M. L.
Published: February 2003

Well-gettered diodes behave as ideal Shockley diodes for forward bias. For reverse bias their characteristics may deviate from the Shockley theory according to the preparation precedure. A model for this behavior is presented; it ascribes the deviation to a generation current produced at donor-acceptor shallow levels in the depletion layer.
Metastable (InP)1−xGe2x alloys as potential materials with band gap ≂10 μm
Authors: Jenkins David W. , Newman Kathie E. , Dow John D.
Published: February 2003

Based on the idea of a zincblende-diamond structural phase transition, we predict that metastable, crystalline, substitutional alloys of (InP)1−xGe2x should exhibit significantly smaller fundamental band gaps than has been expected for random alloys of InP and Ge, and hence may be candidates for materials with gaps ≂10 μm.
Electrical characteristics of amorphous molybdenum-nickel contacts to silicon
Authors: Kung K. T-Y. , Suni I. , Nicolet M-A.
Published: February 2003

The electrical characteristics of sputtered, amorphous Mo-Ni contacts have been measured on both p- and n-type Si, as functions of composition (30, 54, and 58 at. % Mo). The contact resistivity on both p+ and n+ Si is in the 10−6 Ω cm2 range. The barrier height for as-deposited samples varies between φbp=0.47–0.42 V on p-type Si and between φbn=0.63–0.68 V on n-type Si, as the composition of the amorphous layer goes from Ni-rich to Mo-rich. The sum φbp+φbn always equals 1.12 V, within experimental error. After thermal treatment at 500 °C for 1/2 h, the contact resistivity changes by a factor of two or less, while the barrier height changes by at most ∼0.05 V. In light of these results, the amorphous Mo-Ni film makes good ohmic contacts to silicon.
Resistivity anisotropy of pyrrhotite
Authors: Krontiras Chr. , Pomoni K. , Theodossiou A.
Published: February 2003

Resistivity measurements are reported on pyrrhotite from room temperature and beyond its Néel point. Anisotropy of resistivity was found for the cases of applying electric field parallel and perpendicular to the c axis.
Peripheral electron-beam induced current response of a shallow p-n junction
Authors: Holloway H.
Published: February 2003

A theory is given for the response of a shallow p-n junction to a small spot of light or electrons that impinges near its periphery. This gives a basis for numerical analyses of a number of situations that are of practical interest. In particular, the results provide a method for determining minority-carrier diffusion lengths by scanning electron microscopy of the surfaces of devices. It is shown that the response of a shallow junction is quite different from that of the deep junction that has been considered in previous treatments. The response is influenced by reduction of the semiconductor thickness or of the junction dimensions to values less than the minority-carrier diffusion length and also by competition with adjacent junctions and by surface recombination. All of these effects are considered.
Hydrogenation effects in sputtered polycrystalline cadmium telluride
Authors: Wang Francis , Reinhard D. K.
Published: February 2003

The hydrogenation of rf sputtered thin film polycrystalline CdTe is reported. Hydrogenation is achieved by reactive sputtering in an argon and hydrogen mixture. Results include an order of magnitude decrease in conductivity, an increase and sign change in band bending for Au-CdTe junctions, and a significant increase in the anomalous photovoltaic effect (APE). APE coplanar voltages increase from approximately 10 V/cm without hydrogen to a maximum of 350 V/cm with hydrogenation. The results are interpreted in terms of increased band bending at crystallite surfaces and interfaces due to hydrogenation. These results support a previously proposed mechanism for the APE due to surface photovoltages in inclined crystallites.
Heat treatment of semi-insulating InP:Fe with phosphosilicate glass encapsulation
Authors: Kamijoh T. , Takano H. , Sakuta M.
Published: February 2003

Photoluminescence and Raman scattering characterization measurements were performed on semi-insulating InP:Fe (100) samples heat treated with phosphosilicate glass (PSG) protective layers. Photoluminescence spectra of PSG encapsulated InP samples indicated that native phosphorus vacancies were reduced in these samples following heat treatment. The presence of a TO phonon line in Raman spectra, which is related to a modification of structual bonding, was observed in InP samples heat treated with an SiO2 layer, while the absence of this TO phonon line was observed in InP heat treated with the PSG layer. Activation of Si implanted into the InP:Fe samples increased with increasing phosphorus concentration in the PSG layers which were used as protective layers for the post ion-implantation annealing.
Composition dependence of photoluminescence of AlxGa1−xAs grown by molecular beam epitaxy
Authors: Mihara M. , Nomura Y. , Mannoh M. , Yamanaka K. , Naritsuka S. , Shinozaki K. , Yuasa T. , Ishii M.
Published: February 2003

Low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs grown by molecular beam epitaxy has been studied. The defect-related emissions, due to the defect exciton (d, X) and the defect complex (d), have been identified. The peak energies of these emissions, which are 1.505 eV (d, X) and 1.474 eV (d) for GaAs, have been determined as a function of the mole fraction x ( x<0.45). The energy difference between the donor–bound-exciton (BE) peak and the defect-exciton peak is almost constant (∼9 meV). In contrast, the energy difference of the BE peak and the defect-complex peak increases from 40 meV at x=0 to about 70 meV at x∼0.4. In addition, the ionization energies of carbon and silicon acceptors in AlxGa1−xAs have been determined as a function of x and compared with theoretical calculations.
Defect-related emissions in photoluminescence spectra of AlxGa1−xAs grown by molecular beam epitaxy
Authors: Mihara M. , Nomura Y. , Mannoh M. , Yamanaka K. , Naritsuka S. , Shinozaki K. , Yuasa T. , Ishii M.
Published: February 2003

We have studied defect-related emissions in low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs (x<0.45) grown by molecular beam epitaxy. The relative intensities of the defect exciton (d,X) and defect complex (d) emissions depend on the mole fraction x; the (d,X) emission becomes dominant for x>0.27. This suggests different origins for the (d,X) and (d) emissions. The (d,X) and (d) emissions are tentatively associated with oxygen and carbon, respectively.
Electrical and optical properties of Mg-, Ca-, and Zn-doped InP crystals grown by the synthesis, solute diffusion technique
Authors: Kubota Eishi , Ohmori Yutaka , Sugii Kiyomasa
Published: February 2003

p-type InP crystals doped with Mg, Ca, and Zn have been grown by the synthesis, solute diffusion (SSD) technique. Distribution coefficients for the Mg and Ca in the SSD-grown InP were determined to be 0.20 and 0.025, respectively. 4.2 K photoluminescence emission peaks have also been investigated for Mg-, Ca-, and Zn-doped samples. The binding energy is determined to be EA (Mg)=40 meV, EA (Ca)=43 meV, and EA (Zn)=47 meV. Comparison of the emission peak energies between impurity-doped and nominally-undoped InP shows that Mg and Ca as well as Zn are incorporated as residual shallow acceptors in the high-purity SSD-grown InP (ND−NA ≤1015 cm−3 at 300 K).
Inclined pileup of screw dislocations at the crack tip without a dislocation-free zone
Authors: Chang S.-J. , Ohr S. M.
Published: February 2003

A linear array of screw dislocations in front of a mode 3 crack lying on a plane inclined to the crack is studied. The problem is formulated in terms of an integral equation describing the equilibrium condition between the dislocations and the crack under an externally applied shear stress. The distribution function for dislocations is derived from a solution of the integral equation by applying the Wiener–Hopf technique. The condition of finite stress at the end of the pileup, or the Bilby, Cottrell, and Swindeman (BCS) condition and the crack opening displacement (COD) are obtained in simple analytical forms as a function of the angle of inclination. Numerical results show that, for a given applied stress, the distribution function, the length of the plastic zone, and the COD decrease only slightly as the angle of inclination increases from 0 to π/2. The quantity of σf COD , where σf is the friction stress, is shown to be equal to the radial component of the complex J integral and, hence, is the total force on the dislocations along the direction of the pileup. A method to estimate results under mode 1 condition involving an inclined pileup of edge dislocations is considered.
Structure and growth kinetics of RhSi on single crystal, polycrystalline, and amorphous silicon substrates
Authors: Psaras P. A. , Thompson R. D. , Herd S. R. , Tu K. N.
Published: February 2003

Growth kinetics of rhodium silicide in the temperature range of 375–450 °C have been studied on three different silicon substrates: single crystal, polycrystalline, and amorphous. The methods of analysis and specimen characterization utilized in this study are Rutherford backscattering spectroscopy (RBS), Seemann–Bohlin x-ray diffraction, cross-sectional transmission electron microscopy (TEM), sheet resistivity via four-point probe, and Schottky barrier height measurements obtained from the current-voltage relationship. Our results conclude that all three silicon substrates form an identical rhodium silicide compound, RhSi, indicating that the crystallinity of the substrate has no effect on the resulting rhodium silicide. The growth of RhSi was determined to be diffusion-limited and the activation energy of growth was similar for single crystal (1.88±0.04 eV) and amorphous silicon (1.86±0.07 eV), yet it was slightly lower (1.71±0.08 eV) for polycrystalline silicon. The difference can be attributed to the rhodium silicide compound having a smaller grain size in the polycrystalline silicon case. The layer formation and the thickness of rhodium silicide between unreacted rhodium and the three different silicon structures was examined by cross-sectional TEM and compared to those measured by RBS.