bluuebunny/crossref_metadata_2025 huggingface dataset:
Piezoelectricity and pyroelectricity in vinylidene fluoride/trifluoroethylene copolymers
Authors: Furukawa T. , Wen J. X. , Suzuki K. , Takashina Y. , Date M.
Published: February 2003

Piezoelectric and pyroelectric properties have been investigated in the 52/48, 65/35, and 73/27 mol % copolymers of vinylidene fluoride and trifluoroethylene. The transverse and longitudinal piezoelectric constants as well as the elastic constant were determined for undrawn samples as a function of the remanent polarization Pr created by a room-temperature poling. The elastic constant shows a significant increase with increasing Pr. Thus, the d constant (polarization/stress) tends to saturate at high Pr. On an assumption of elastic isotropy, true e31 and e33 (polarization/strain) were calculated. It is found that e33 is proportional to Pr with a coefficient of −1.2 in three copolymers while e31 is almost zero. The results indicate that the piezoelectric activity in undrawn copolymers primarily arises from macroscopic dimensional changes while molecular dipoles are rigid. The pyroelectric constant p3 and the thermal expansion coefficient α3 were also measured in mechanically-free samples. By the use of e31, e33, and α3, the contribution from the secondary effect was evaluated and found to be smaller than 1/4 of the total activity. The primary effect due probably to disordering of crystalline dipoles seems to play a major role in the pyroelectricity of the copolymers.
Photoacoustic spectroscopy of semiconductor heterostructures by piezoelectric transducers. II. Space-resolved detection of photoacoustic modes
Authors: Kubota K. , Murai H.
Published: February 2003

Photoacoustic spectroscopy was applied to a III-V semiconductor heterostructure layer on a substrate to observe the indirect transition absorption edge. An array of electrodes on a piezoelectric transducer resolved spatially the excited photoacoustic vibration modes in the sample.
Speed of the photorefractive effect in a BaTiO3 single crystal
Authors: Ducharme Stephen , Feinberg Jack
Published: February 2003

We present data on the speed of light-induced refractive index changes in a BaTiO3 single crystal. The light-induced erasure rate of a refractive index grating is shown to depend on optical intensity as I x where x<1. The exponent x depends weakly on temperature and increases from 0.62±0.02 to 0.71±0.02 when the temperature is varied between 12 and 40 °C. The sublinear dependence of rate on intensity implies that higher optical intensity is required to achieve high-speed operation of BaTiO3 devices than previously thought. The dark erasure rate has an anomolously strong temperature dependence; it increases by a factor of 50 over the same temperature range. We have also determined that the number density of photorefractive charge carriers is 6×1016 cm−3 in this crystal.
Nb-H alloys: Model substances for electrothermal resistors
Authors: Welter J.-M.
Published: February 2003

Experiments on electrothermally induced switching phenomena in metal hydrides are reported. They were made with a resistor based on a NbH0.49 alloy. The discontinuous behavior of the resistivity at the structural order-disorder phase transition at 360 K was exploited. Some general results are derived from a heat balance model equation which emphasizes the peculiarities of structural phase transitions in metallic conductors.
Influence of xenon on sealed-off operation of rf-excited CO2 waveguide lasers
Authors: He D. , Hall D. R.
Published: February 2003

The addition of xenon to helium, nitrogen CO2 gas mixtures is shown to increase output power by 24% in sealed-off rf excited waveguide carbon dioxide lasers. Experiments with a range of laser output couplers indicate that this improvement is due to a corresponding increase in small signal gain, with the saturation intensity remaining fairly constant.
Atomic mean excitation energies for stopping powers from local plasma oscillator strengths
Authors: Wilson J. W. , Xu Y. J. , Chang C. K. , Kamaratos E.
Published: February 2003

Mean excitation energies for stopping by isolated atoms are accurately predicted by the plasma absorption spectrum associated with the atomic orbitals when the plasma frequency shift due to individual electron motion proposed by Pines [Phys. Rev. 92, 626 (1953)] is incorporated.
Synchronous mode locking of semiconductor laser diodes by a picosecond optoelectronic switch
Authors: Göbel E. O. , Kuhl J. , Veith G.
Published: February 2003

Synchronous mode locking of a semiconductor diode laser and an acousto-optically mode-locked Ar+-ion laser has been obtained by using a Cr-doped GaAs picosecond optoelectronic switch for synchronous excitation. Synchronously mode-locked pulses with 30-ps duration (full width at half maximum) are generated at a repetition rate of 80.32 MHz with a buried heterostructure GaAs/GaAlAs double heterostructure laser.
Self-detecting light-emitting diode optical sensor
Authors: Johnson Mark , Jokerst Nan Marie
Published: February 2003

A light-emitting diode can be used simultaneously for illumination of a moving object and also for detection of its own reflected light. The result is a novel optical object proximity sensor of very small size and high resolution. Good performance depends on the design of a suitable low-noise electronic preamplifier, on the choice of light-emitting diode material and bias, and on efficient optical design using a mirror or thin-film retroreflector. This optimization is analyzed and implemented.
Presence of doubly-ionized metal ions in rare gas glow discharges
Authors: Hecq M. , Hecq A.
Published: February 2003

The sputtering plasma ions are analyzed from a sampling orifice by a quadrupole mass spectrometer. The doubly-ionized metal species have been searched in a sputtering plasma using several cathodes (Sn, Mo, Ta, Co, Pt, Pd, and Au). Mo2+, Co2+, and Sn2+ ions were measured at several Ar pressures. The IM2+ is found be dependent on the total pressure. A ‘‘hybrid Penning’’ reaction (M+Ar2+→M2++Ar++e) is suggested for the production of the doubly ionized metallic species.
Effect of high stretching rates on the piezoelectric behavior and the structure of polyvinylidene difluoride films
Authors: De Mattei R. C. , Feigelson R. S.
Published: February 2003

It has been shown that both the stretch rate and the ambient temperature during stretching affect the ultimate piezoactivity of the PVF2 film. The highest piezoactivity was obtained for films stretched at an 80–90 °C ambient. The piezoactivity went through a minimum at a stretch rate of 1300 mm/min and then increased. This behavior was also observed in structural changes in the films.
Demonstration of excitation-dependent grain-boundary recombination velocity in polycrystalline silicon
Authors: Sundaresan R. , Fossum J. G. , Burk D. E.
Published: February 2003

The dependence of grain-boundary recombination velocity on the excitation (excess carrier density) at the grain boundary is experimentally demonstrated using electron-beam-induced-current (EBIC) measurements. To facilitate quantitative interpretation of the EBIC measurements, the underlying carrier transport problem in the adjacent grains, subject to the nonlinear boundary condition at the grain boundary, is solved using computer-aided numerical analysis. By comparing the theoretical and experimental EBIC responses, values for the surface-state density at unpassivated and passivated grain boundaries and for the diffusion length in the grains in Wacker (cast) polycrystalline silicon are derived.
Space-charge regions around dipolar grain boundaries
Authors: Duffy D. M. , Tasker P. W.
Published: February 2003

Extended defects in ionic crystals, such as grain boundaries and shear planes, lying along certain crystallographic directions, introduce a potential difference across the defect. The origin of the potential is the dilation between the charged planes on either side of the interface. The energies of charged point defects, are therefore, higher on one side of the crystal than on the other, and this produces space-charge layers in the vicinity of the interface. The resulting charge distribution cancels the boundary potential at some distance from the defect, but a potential barrier remains, similar to the Schottky barrier of semiconductor physics. Such a barrier produces nonlinear electrical characteristics in the crystal which resemble those of a varistor. In addition, the crystal has an inhomogeneous diffusion coefficient which is larger at one side of the boundary than the other.
Segregation of dopants in melt-grown indium selenide crystals
Authors: Chevy A.
Published: February 2003

We report results of doping experiments of indium monoselenide, InSe, by substitution of the metal or of the chalcogen by different foreign atoms. The difficulty of effective doping is related to the method of crystal growing from a nonstoichiometric melt and to the intrinsic properties of lamellar compounds. An estimate of effective distribution coefficients of Sn, Zn, Ga, and S is given.
Diffusivity of 3He atoms in perfect tungsten crystals
Authors: Amano Jun , Seidman David N.
Published: February 2003

The diffusivity of 3He atoms in perfect crystals of tungsten has been studied employing the atom-probe field-ion microscope (FIM) technique. Tungsten FIM specimens were implanted in situ with 300-eV 3He+ ions, to a fluence of 3×1015 ions cm−2, at specimen temperatures which ranged from 60 to 110 K. The 3He+ ion beam was analyzed magnetically and the ion source was connected to the atom probe through a differentially pumped aperture. At an implantation energy of 300 eV no radiation damage was produced by the implanted 3He atoms. Thus, the state of a tungsten specimen after an implantation consisted of 3He atoms with an initial depth distribution that was determined solely by the range profile of the low-energy ions. Isothermal annealing experiments between 90 and 110 K were employed to study the kinetics of recovery of the implanted 3He atoms; at 60 K the 3He atoms are immobile. This data, in combination with a suitable diffusion model, was used to determine—for the first time—the diffusivity [D3He(T)] and the enthalpy change of migration of 3He atoms (Δhm3He ) in tungsten. The quantity D3He (T) is given by the Arrhenius expression: D3He(T)=(5.4±10.63.8) ×10−3 exp(−0.28 eV/kT)cm2 s−1. The value of Δhm3He is approximately the same as for Δhm4He (0.24–0.32 eV). D3He (T) is compared with the diffusivity values of 1H and self-interstitial atoms in tungsten—the self-interstitial atoms are considerably more mobile than 3He or 4He atoms at the same temperature, as are the 1H atoms.
Deep states in GaAs grown by molecular beam epitaxy
Authors: Blood P. , Harris J. J.
Published: February 2003

Using deep level transient capacitance spectroscopy (DLTS) we have investigated the growth parameter dependence and electronic properties of deep level centers in GaAs grown by molecular beam epitaxy (MBE), principally in the temperature range 500–650 °C. In both n- and p-type material we find hole traps ascribed to Fe and Cu and electron traps M1, M3 and M4 unique to MBE layers. Concentrations of the ‘‘M’’ levels depend weakly on As:Ga flux ratio but decrease rapidly with increasing growth temperature. Depth profiles show no evidence for bulk annealing and, by comparison with published secondary ion mass spectrometry data, we suggest these centers are impurity-defect complexes. Capture cross-section (σn) measurements show that two different traps give rise to further DLTS peaks at ∼140 K. One trap with σn >4×10−17 cm2 and (Ec −Et) >0.17 eV (at 140 K), which we associate with M2, is observed at a growth temperature of 650 °C and from the influence of the growth conditions we suggest this is As-vacancy related. The other trap, which we label M2′, has σn =1×10−20 cm2 and (Ec −Et) =0.08 eV (at 140 K) and occurs in material grown at temperatures below 600 °C, with similar growth behavior to M1, M3 and M4. For M3 we measured σn =1.1×10−16 cm2 giving (Ec −Et) =0.236 eV at 173 K. Using measurements of the temperature dependence of σn we have calculated the entropy change on emission or capture of an electron at M2′ and M3 and deduce that these levels are associated with bonding (valence band) states. The capture cross sections of M1 and M4 were too large to be measured (>2×10−16 cm2), but we deduce that σn(M4) >σn (M1). Data are given for the signatures of all the electron traps at low electric fields, and these are compared with data for other traps in GaAs. We do not find convincing evidence for identifying the DLTS peak at 200 K in 300 °C grown material with the E3 center in irradiated GaAs. We suggest that the minority carrier lifetime in p-GaAs will be limited by recombination at M4 and M2 for growth temperatures below and above ∼625 °C, respectively.
X-ray photoemission spectroscopy investigation of Schottky barrier formation in a copolymer of pyrrole and N-methylpyrrole
Authors: Ogama T. , Koezuka H.
Published: February 2003

The contact between indium metal and an electrochemically prepared copolymer having pyrrole and N-methylpyrrole units has been investigated by means of x-ray photoemission spectroscopy (XPS). Changes in binding energies with successive metal depositions have been directly observed. The formation of the extremely thin composite layer has been detected, which is due to the reaction of the deposited metal with the surface layer of the copolymer. But it has also been confirmed that the initial oxidized surface layer on the copolymer formed during the heat treatment has a tendency to protect the evaporated indium metal from the reaction with the dopant ion and stabilizes the diode characteristics. When sufficient indium metal is deposited, energy band bending has occurred within the surface layer of the copolymer. These observations are consistent with the electrical properties of a Schottky barrier-type diode formed with these contacts.
High-density magneto-optical disk storage and the effect of finite beam size in readout
Authors: Mansuripur M.
Published: February 2003

A method of data reconstruction from a digital magneto-optical disk system with diffraction-limited spot size is described. Using a linear filter with high-frequency enhancement we show that significant improvements in the storage capacity can be achieved at a reasonable cost in terms of the signal-to-noise ratio. Performance is evaluated against an optimum but impractical method as well as a technique for the reconstruction of the analog waveforms.
Hydrogen induced drift in palladium gate metal-oxide-semiconductor structures
Authors: Nylander Claes , Armgarth Mårten , Svensson Christer
Published: February 2003

The flat band voltage shift upon hydrogen exposure of palladium gate metal-oxide-semiconductor devices is only partly due to a change in the metal work function. Another effect, here called the hydrogen induced drift (HID), also occurs. The wide distribution of time constants of this effect is a limitation in some applications of the sensors. The effect is characterized and its origin is investigated. It is found that the HID is responsible for a much larger part of the voltage shift than was earlier believed. It is also shown that the effect does not occur at a palladium-alumina interface. The effect of hydrogen on sodium ion drift is examined and it is shown that hydrogen does not give rise to sodium ion drift, but rather increases the image potential barrier for mobile sodium ions at the metal-silicon dioxide interface. A qualitative model for the hydrogen induced drift on the atomic scale is presented and discussed.
Annealing of selenium implanted indium phosphide using a graphite strip heater
Authors: Gill Sukhdev. S. , Sealy Brian J.
Published: February 2003

Both isothermal and isochronal anneals were performed on doses of 1×1013 to 1×1015 cm−2 of 200-keV selenium ions implanted into indium phosphide (InP) at room temperature. A graphite strip heater was used to anneal chemical vapor deposited silicon nitride (CVD-Si3N4) capped samples between 620 and 710 °C for times of 5–180 sec. The electrical properties varied with annealing temperature and time; however, it was found unnecessary to anneal for times in excess of about 40 sec. Also, heat treatment above α 650 °C produced only a small improvement in the electrical properties. Thus only relatively short thermal pulses to temperatures between 650 and 710 °C are required to activate selenium ions implanted into indium phosphide.
An x-ray diffraction study on the microstructures of cold-worked face-centered-cubic Cu-Mn-Zn alloys. III. Role of additions of transitional solute Mn
Authors: Ghosh S. K. , Sen Gupta S. P.
Published: February 2003

In a continuation of our earlier work with Cu-Ni-Zn [J. Appl. Phys. 48, 3560 (1977)] and Cu-1 wt. % Sn-Zn [J. Appl. Phys. 54, 6652 (1983)], the plastically deformed state of ternary Cu-Mn-Zn alloy system (fcc) has been analyzed by x-ray diffraction method using detailed Fourier line profile analyses which take into account peak shift, peak asymmetry, and peak broadening of respective diffraction profiles. Quantitative estimation of intrinsic (α′), extrinsic (α″), and twin fault ( β) probabilities have been made. The results indicate, as in earlier cases, a greater presence of intrinsic stacking faults than the extrinsic type, and a total absence of deformation twins. Other microstructural parameters, namely domain size, rms strain, dislocation density, and stacking fault energy (pure copper) in the alloys have been estimated from analyses of peak broadening as adopted earlier. The results indicate that the addition of transitional solute manganese (1–30 wt. %) fails to produce any significant change in the microstructural parameters for a fixed zinc concentration. However, for a fixed manganese concentration, the parameters vary gradually, similar to a binary system, with the increase of zinc concentration from 10 to 20 wt. %.
Pulsed laser-induced recombination centers in silicon
Authors: Hlávka J. , Jelínková H. , Hamal K. , Prochocký V.
Published: February 2003

Preliminary results which give evidence that recombination centers are produced in silicon (not implanted) when irradiated by pulsed ruby laser are presented. In the experiment, the pulse energy densities ranged from 0.65 to 2.1 J/cm2 and the pulse duration was 10 ns. The thicknesses of the layers of increased recombination ranging from 150 to 5000 Å were found and the estimate gives recombination center density of the order of 1016 cm−3. It is very likely that these recombination centers are connected with structure defects.
Abstract: Interfacial effects on ferromagnetic resonance: MBE iron films
Authors: Vittoria C. , Rachford F. G. , Krebs J. J. , Prinz G. A.
Published: February 2003

Recent studies have implied that the elastic strain and either the magnetization, M or the uniaxial magnetic anisotropy field HA were spatially dependent near the substrate/Fe interface. We now report additional experimental and calculational results which give further evidence for the existence of magnetic parameter variations near the interface. The experimental program consisted of ferromagnetic resonance (FMR) experiments as a function of frequency (9, 16, and 35 GHz), magnetic field direction (parallel and perpendicular to the film plane), and film thickness (t=500–5000 Å). The FMR experiments were complemented with magnetometer measurements. The calculations consisted of determining both volume and surface spin wave dispersions as a function of various assumed variations of magnetic parameters near the interface. This allowed us to predict the excitation of surface modes besides the usual volume spin wave modes. Experimentally, surface modes are excited for t≳1000 Å and are displaced about 500–1000 Oe above the main line. In addition we were able to predict the deviation from quadratic behavior for low order number spin wave excitations as corroborated experimentally. It may now be meaningful to determine intrinsic magnetic properties of both the substrate/Fe and the Fe/air surfaces.
High-resolution measurements of localized vibrational mode infrared absorption of Si-doped GaAs
Authors: Theis W. M. , Spitzer W. G.
Published: February 2003

The infrared absorption due to excitation of localized vibrational modes (LVM) involving Si impurities in GaAs was measured at 80 K under high-resolution conditions for 1×1018 cm−3≤[Si]≤5×1019 cm−3. Electrical compensation by Li diffusion or electron irradiation resulted in no observable differences in peak positions or linewidths for those LVM identified as SiGa, SiAs, and pair absorptions. These modes (including the individual lines composing the SiAs LVM) had intrinsic linewidths of 0.4 cm−1 which broadened as [Si] increased. In electron irradiated materials, an absorption band with major peaks at 366.63, 368.31, 369.53, and 370.7 cm−1 was seen to shift to lower energies by 9.9 cm−1 when 28Si was replaced with 30Si. Arguments are presented to suggest that the 366.63 cm−1 peak may be due to SiAs paired with a nearest-neighbor native defect such as AsGa or a Ga vacancy. In Li compensated material, the isolated 7LiGa LVM was seen for the first time at 449.64 cm−1 as well as several additional unidentified absorptions. The two bands due to 28SiGa-28SiAs have asymmetrically broadened lines which are attributed to various configurations of nearest neighbor Ga isotopes in the host lattice and the observations are compared to model calculations. Finally, the band associated with 28SiGa-30SiAs and 30SiGa-28SiAs pairs was resolved into a doublet with peaks at 455.80 and 457.01 cm−1, respectively.
Optimization of contrast ratio in reversed-polarizer, transmissive-type twisted nematic displays
Authors: Scheffer T. J. , Nehring J.
Published: February 2003

Simple mathematical expressions are presented which describe the transmission of normally-incident light through absorbing, twisted nematic layers. These expressions are used to optimize the contrast ratio in white light of a reversed-polarizer, twisted nematic display with respect to the variables of twist angle, optical path length difference, dye concentration, and polarizer strength. The results are presented in the form of curves showing the optimum contrast and the optimal values of these variables as a function of the on-state brightness of the display. The maximum contrast ratios are compared to optimized twisted layers without dye and conventional 90° twisted layers with and without dye. Also, an explanation is given for the experimental observation reported in the literature that the contrast ratio of twisted layers may assume a maximum value for a certain concentration of dichroic dyes.
Improved characteristics of Nb3Ge tunnel junctions using sputter-deposited amorphous-silicon barrier
Authors: Konishi H. , Kuriki S.
Published: February 2003

We have fabricated Nb3Ge/amorphous-silicon/Pb Josephson tunnel junctions using high Tc(≥20 K) and stoichiometric (25±1 at. %Ge) Nb3Ge films. Good I-V characteristic with large Josephson current Ic and high gap voltage is obtained when the amorphous-silicon barrier is sputter deposited at low rf voltage and high Ar pressure to reduce the damage to the Nb3Ge by the sputtered particles and to obtain good coverage over the Nb3Ge surface. Peculiar I-V characteristics showing the inverse ac Josephson effect and chaotic transition betwen current steps are observed in the response to microwave. The temperature dependence of Ic agrees well with the theoretical calculation when the Ge enrichment at the top surface of the Nb3Ge electrode is reduced.
The origin of interfacial charging in irradiated silicon nitride capacitors
Authors: Hughes R. C.
Published: February 2003

Many experiments show that when metal-silicon nitride-silicon dioxide-silicon (MNOS) devices are irradiated in short circuit, a large interfacial charge builds up near the nitride-SiO2-Si interface. This effect cannot be explained by simple models of radiation-induced conductivity of the nitride, but it is reported here that inclusion of carrier diffusion and recombination in the photoconductivity equations can predict the observed behavior. Numerical solutions on a computer are required, however, when these complications are added. The simulations account for the magnitude and radiation dose dependence of the results, as well as the occurrence of a steady state during the irradiation. The location of the excess trapped charge near the interface is also predicted, along with the large number of new traps which must be introduced to influence the steady-state charge distribution.
Growth and electrical characteristics of palladium silicide contacts on dry-etched silicon surfaces
Authors: Climent A. , Fonash S. J.
Published: February 2003

Damage in silicon induced by dry etching processes is found to affect the kinetics of formation and the current-voltage characteristics of Pd2Si contacts formed in the 225–275 °C range. We show in this work that low-energy ion-beam etching (IBE) with Ar+ ions in the energy range 0.4–1.4 keV modifies the diffusivity controlling the silicide formation process. For the energy range and beam parameters studied, the diffusivity is found to increase approximately linearly with the IBE energy, while the activation energy of the silicide formation process does not change significantly. Although the depth of the damaged layer, prior to silicide formation, is not greater than 200 or 300 Å as detected by the Rutherford backscattering technique, the damage detected by the current-voltage characteristics of the Pd2Si/Si system is not removed by the silicide growth, particularly in the case of n-type silicon. A comparison of current-voltage characteristics for reactive-ion etched silicon and ion-beam etched Si demonstrates that the damage incurred in reactive-ion etching is also not consumed by low-temperature Pd2Si formation.
Electrical properties of semiconducting glasses in the quasi-binary CdGeAs2-CdSiAs2 system
Authors: Bhattacherjee Arya P. , Risbud Subhash H.
Published: February 2003

The electrical properties of melt quenched CdGe1−xSixAs2 glasses and crystallized glasses were investigated. The activation energy for electrical conductivity of glasses followed Vergard’s law in the composition range x=0.5–1.0. Compositions with x<0.5 were inhomogeneous due to amorphous phase separation resulting in significant departures from Vegard’s law. Crystallization of glasses by vacuum heat treatment resulted in reversal in the type of conductivity. Hall measurements suggest greater degeneracy and high conductivity of the x=0.5 glass; this composition also showed the least temperature dependence of the electrical properties. The experimental data on phase stability, electrical and transport properties of the quasi-binary CdGeAs2-CdSiAs2 glasses are discussed in the context of potential device applications.
Interface trap behavior in irradiated metal-oxide-silicon structures
Authors: Jörgensen Christer , Svensson Christer , Ryden Karl-Henrik
Published: February 2003

We have used deep level transient spectroscopy (DLTS) and electron spin resonance (ESR) to investigate the interface states on oxidized silicon. Measurements were performed before and after soft x-ray irradiation. Before irradiation, the ESR Pb peak, corresponding to the DLTS 0.3-eV peak, was observed using both methods. After irradiation, it was unchanged when we used ESR, whereas DLTS showed a general increase in the number of interface states over the band gap. No structure in the DLTS signal was seen in the region where the 0.3-eV peak is situated. We have thus shown that soft x-ray irradiation does not affect the Pb interface trap, but that it gives rise to a broad distribution of non-ESR-active interface traps, instead.
Electrical and optical properties of amorphous hydrogenated silicon prepared by reactive ion beam sputtering
Authors: Singh Jagriti , Budhani R. C. , Chopra K. L.
Published: February 2003

Amorphous hydrogenated silicon (a-Si:H) films have been prepared by a reactive ion beam sputtering technique under different conditions of substrate temperature (300–623 K) and hydrogen to argon flow ratios (0–12/1). Infrared absorption spectra of the films show that monohydride (Si-H) bonding is preferred at low deposition temperatures and increasing temperature leads to the formation of both mono- and dihydride configurations. Electrical and optical properties of the films are sensitively dependent on deposition parameters. Deposition conditions have been optimized to obtain films with low conductivity (≂10−10 Ω−1 cm−1) and high activation energy (0.7 eV) exhibiting extended state transport over a wide temperature range and a large gain in photoconductivity. The optical gap can be varied from 1.4 to 1.9 eV on changing the deposition conditions. A mixed extended state and hopping conduction is observed in high conductivity (≂10−5 Ω−1 cm−1) hydrogen rich (≥20 at. %) films deposited at lower temperatures (≂500 K) and those with less hydrogen (≤4 at. %) deposited at 573 K. These observations are attributed to the large gap state density originating from Si:H complexes in H2 rich films and unsaturated bonds in poorly hydrogenated material.
Haynes–Shockley experiment on n-type HgCdTe
Authors: Shacham-Diamand Y. , Kidron I.
Published: February 2003

The ambipolar drift mobility of holes in n-type HgCdTe with nominal composition of x=0.215 was determined by the Haynes–Shockley experiment. The measurement was performed using a novel device that includes a special photoconductive sensing structure. The output device samples the excess carriers by sensing the conduction modulation in a narrow region. This method enables the measurement of the moving excess carriers packet without the conventional junction that is used traditionally. This way the difficulty to produce a sensing  p-n junction on n-type HgCdTe is eliminated. The mobility of holes at 77 K was measured to be 570 cm2 V−1 s−1 and its temperature dependence is given by  μa=A⋅T−n where n=2.78±0.1 and A=108 in the 77–87 K temperature range.
Direct observation of fine structure in the concentration of the deep donor [EL2] and its correlation with dislocations in undoped, semi-insulating GaAs
Authors: Brozel M. R. , Grant I. , Ware R. M. , Stirland D. J. , Skolnick M. S.
Published: February 2003

Spatial variations in resistivity, dislocation density and [EL2] concentration across {001}, and sometimes {110}, specimens from semi-insulating, undoped, liquid encapsulated Czochralski GaAs ingots have been measured. By using detection methods capable of high spatial resolution (∼100 μm) it has been shown that fine structure in the well known ‘‘M’’- or ‘‘W’’-shaped distributions of dislocation density and [EL2] across 〈110〉 diameters of {001} wafers occurs. A close correlation between complex dislocation substructures, revealed by etching methods, and [EL2] distributions, revealed by infrared (1 μm) absorption microscopy, has been confirmed. The implications both for processes involving dislocation interactions during ingot growth and for the electrical properties of the semi-insulating material are considered.
Matrix determination of the stationary solution of the Boltzmann equation for hot carriers in semiconductors
Authors: Aubert J. P. , Vaissiere J. C. , Nougier J. P.
Published: February 2003

The stationary Boltzmann equation is solved by using a matrix method. This allows determining directly the steady state regime for hot carriers in semiconductors. The main advantages of this new method are: the result does not depend on initial conditions, and the cost is much lower than that of iterative or Monte Carlo techniques, particularly at high electric field.
Crystalline properties of rf-sputtered ZnO film on gold film on fused quartz
Authors: Kushida Keiko , Takeuchi Hiroshi
Published: February 2003

The effect of the crystalline properties of gold film on those of ZnO film was investigated in detail for a ZnO/gold/fused quartz structure. The investigations were done using x-ray diffraction and a rocking curve method. It was found that the crystalline properties of rf-sputtered ZnO films were strongly dependent on those of gold films. Transducer efficiency was also determined for this structure. It was found that the ZnO/gold/fused quartz structure had a high transducer efficiency, if the ZnO film was fabricated on the gold film whose σ for the (111) rocking curve was less than 3°.
Radiative recombination and shallow centers in CuInSe2
Authors: Massé G. , Redjai E.
Published: February 2003

The cathodoluminescence of single crystals of CuInSe2 obtained by melt-grown and iodine chemical transport was studied. As-grown crystals and crystals annealed in Se, In, or in a vacuum were used. We show the emission intensity decreases when the conductivity changes from n to p and then increases due to the decrease of the number of donors created by Se vacancies. We also show that two donor levels (60 and 80 meV) are introduced by the Se vacancy probably associated with impurities, and that the cation (probably Cu) vacancy causes an acceptor level at 40 meV. Another acceptor level is also determined, having a binding energy ≳80 meV.
Cloudlike charged wall in a 1.5-μm bubble-implanted structure
Authors: Suzuki T.
Published: February 2003

A cloudlike charged wall has been observed around a nonimplanted disk by using Ferricolloid and a bubble. The occurrence of this charged cloud is interpreted in terms of A. Hubert’s energy equation. This equation is also used to calculate the stress gradient around a nonimplanted disk. Furthermore, charged clouds around bubble-propagation patterns have been observed experimentally.
Dependence of radiation-induced interface traps on gate Al thickness in metal/SiO2/Si structures
Authors: Zekeriya Viktor , Ma T-P.
Published: February 2003

Generation of interface traps by ionizing radiation at the Si interface of an Al/SiO2/Si structure has been studied for Al thicknesses in the 500–13000 Å range for devices both with and without post-metal-anneal (PMA) treatment. In parallel with that, the interfacial stresses have been determined for the same structures by means of a laser beam reflection technique. The generation of radiation-induced interface traps, as well as the interfacial stresses, depend strongly on Al thickness and PMA treatment. Results suggest that radiation sensitivity and interfacial stresses are closely related. Two mechanisms, both of which depend on the interfacial strained bonds, can explain the results. According to the first one, reformation of bonds broken by radiation depends on the Si surface strain, which in turn is a function of Al thickness and PMA. The second one is based on the bond strain gradient model proposed by F. J. Grunthaner, P. J. Grunthaner, and J. Maserjian [IEEE Trans. Nuc1. Sci. NS-29, 1462 (1982)] in which interface trap generation is a consequence of the propagation of the radiation-induced bonding defects under the bond strain gradient. This process depends on the magnitude of such a gradient, in consistency with the observed dependencies of the radiation sensitivity.
Complete electrical characterization of recombination properties of titanium in silicon
Authors: Wang Alex C. , Sah C. T.
Published: February 2003

Using only purely electrical measurements based on the capacitance transient techniques, for the first time all the four majority and minority carrier capture rates in zero field as well as the two emission rates of the two Ti deep levels have been directly obtained on a single n+/p diode. The data are in good agreement with our results from other n+/p and n-Si and p-Si Schottky barriers and give a reliable picture of the recombination properties of Ti impurity in silicon. The capture rate and level concentration data support the double donor model. The first donor level is found located at EC−271 meV and has electron capture cross section of (2.57±0.17)×10−14 exp[(3.9±0.6) meV/kT] cm2 and hole capture cross section of 1.35×10−15 cm2. The second donor level is located at EV+255 meV and has electron capture cross section of (1.30±0.05)×10−14 (300/T) cm2 and hole capture cross section of (1.09±0.14)×10−16 exp[−(27.0±1.2) meV/kT] cm2.
Simple model for measurements of the photoacoustic signal by a piezoelectric detector in the microwave region
Authors: Tronconi A. L. , Amato M. A. , Morais P. C. , Neto K. Skeff
Published: February 2003

In this paper a piezoelectric detection of the photoacoustic signal in the microwave region using barium titanate as a detector is carried out. The results in the low modulation frequency (below 30 Hz) are fitted very well by White’s theory. For frequencies above 70 Hz a new and simple theory is presented. The effectiveness of this technique is demonstrated in the detection of the ferromagnetic resonance.
Effect of capacitance on I-V characteristics of overdamped Josephson junctions: Classical and quantum limits
Authors: Ovchinnikov Yu. N. , Cristiano R. , Barone A.
Published: February 2003

We have considered the effect of capacitance on the I-V characteristics of a Josephson tunnel junction in the overdamped limit. Both thermal and quantum fluctuations limits have been investigated. In the framework of the washboard-shaped potential the quantum and thermal fluctuations determine the time spent by the particle in and out of a potential well. These characteristic times have been calculated. The results allowed the possibility of obtaining the I-V characteristics of the junctions. It is shown that for current I smaller than the critical Ic, I-V curves with a higher slope correspond to larger capacitance values whereas for I>Ic the curves with smaller capacitance lie above those with larger capacitance.
Interference effects in the photoacoustic spectra of polymer samples with a layered optical structure
Authors: Schneider S. , Möller U. , Alicka M. , Melzig M.
Published: February 2003

It is shown that strongly absorbing layers imbedded into a polymer sample can produce a photoacoustic (PA) response via a thermoelastic effect. The PA spectra of such samples are rather complicated due to the fact that the thermoacoustic signal contribution, which arises from the heat wave through the material to the surface, and the thermoelastic signal contribution, which originates from the coupling of the local heat energy to the vibrational modes of the material itself, add like vectors with large differences in orientation (phase lag). One consequence is the possibility of nearly complete cancellation (zero PA amplitude) despite high optical absorption.
Auger spectra induced by Ne+ and Ar+ impact on Mg, Al, and Si
Authors: Whaley R. , Thomas E. W.
Published: February 2003

Impact of Ne+ and Ar+ at energies of 20–200 keV on targets of Mg, Al, and Si gives rise to an electron spectrum that has sharp atomiclike features superimposed on a continuous background. The continuum is similar to the spectrum observed during electron impact and is generally ascribed to decay of L-shell vacancies in the matrix. We show, however, that this is not completely correct, that the apparent continuum induced by ion impact extends to higher energies than for electron impact and that this is due to the presence of some hitherto unidentified atomiclike lines. We identify the atomiclike transitions as due to particles sputtered with L-shell vacancies. A complete modelling of the spectra is performed which accounts quantitatively for all Auger peaks. We conclude that the major features are due to sputtered neutral atoms with a single inner shell vacancy. The electron configurations and energies are Mg0 2p53s23p (50.6 eV), Al0 2p53s23p2 (73.8 eV), and Si0 2p53s23p3 (101.1 eV). These are states where one electron has been removed from the L shell but an electron added to the 3p shell to maintain neutrality. Other weaker lines are identified as due to sputtered Mg+, Al+, and Si+ with single L-shell vacancies. For the case of silicon we identify an additional feature that we tentatively ascribe to sputtered atoms decaying while still within the field of the surface. A detailed modelling of the spectrum with all these components provides a complete explanation of all features of the spectrum lending confidence to the line identifications. Line intensities provide relative transition probabilities for competing decay processes.
X-cut quartz for improved surface acoustic wave temperature stability
Authors: Webster Richard T.
Published: February 2003

Theoretical and experimental investigations of surface acoustic wave (SAW) propagation on X-cut, 33.44° propagating quartz show that the temperature compensated orientation has better temperature stability (−0.0209 ppm/C2) than ST-cut quartz (−0.0370 ppm/C2). The orientation requires only a single rotation (33.44°) from the crystal axes. This is substantially simpler than previously reported cuts with comparable temperature stability which typically require three rotations. The X-cut orientation has a SAW velocity of 3175 m/sec, an electromechanical coupling (Δv/v) of 4×10−4, and a power flow angle of 2.7°.
Photoacoustic spectra of CdS detected from the unilluminated surface
Authors: Takaue Ryoichi , Matsunaga Morio , Hosokawa Kunisuke
Published: February 2003

The photoacoustic spectra detected from the reverse side of a CdS single crystal have been studied. Photoacoustic amplitude detected from the unilluminated surface is noticeably influenced by the sample absorption, namely the sample thickness, and there is an optimum value of the sample thickness. The phase variations in this method considerably depend on incident light wavelength, compared to the usual photoacoustic spectroscopy (PAS). The Rosencwaig and Gersho theory for the usual PAS has been extended to the reverse side detection of PAS. These theoretical results agree with experimental values, and predict the importance of the phase study in this method.
Vacuum breakdown and surface coating of rf cavities
Authors: Peter William
Published: February 2003

Electrode surface coating may play an important part in overcoming power limitations in rf cavities for voltages far above the electron multipacting limit. In such cases, the prinicpal use of the coating is not to reduce secondary emission but to isolate electrode whiskers from the cavity chamber and to serve as a trap for slow electrons. Restrictions on the layer thickness are derived theoretically, and calculated for conventional accelerator cavities.
Linear and volume compressibilities and isothermal third-order elastic constants
Authors: Powell B. E. , Skove M. J.
Published: February 2003

Bridgman measured the changes in the dimensions or volume of many crystals as a function of hydrostatic pressure P. He expressed the change in volume ΔV from the original volume V as ΔV/V=−a′P+b′P2, where a′ and b′ are elastic constants. Murnaghan’s theory of finite deformations relates the constant b′ to combinations of second- and third-order elastic constants. Bridgman’s experimental work may be compared to values computed from published values of the third-order elastic constants. While the agreement is not close, Bridgman’s work may be useful for materials for which no other experimental values exist.
Effect of static electric fields on phase conjugation in silicon
Authors: Shemwell D. M. , Cantrell C. D.
Published: February 2003

The effect of an electric field applied transversely to a transient grating on the phase-conjugated response of silicon is modeled theoretically. The field is shown to reduce the intensity of the phase-conjugate output, providing a mechanism for modulating optical phase conjugation.
Fluorescence of inversion site Cr3+ ions in alexandrite
Authors: Schepler Kenneth L.
Published: February 2003

A c-axis alexandrite laser rod was longitudinally pumped in the 450–560 nm region with argon ion and dye lasers. In addition to the sharp R lines and broadband phonon-assisted transitions typical of mirror site Cr3+ ions in alexandrite, room temperature fluorescence spectra displayed characteristics in the 690–730 nm region which were maximal when pumped at 496.5 nm but were nearly absent when pumped at 457.9 nm and 560 nm. Time-dependent fluorescence measurements with pulsed excitation yielded two lifetimes, 310 μs and 44 ms. The short lifetime component is mirror site fluorescence. The long lifetime component is typical for Cr3+ ions in inversion symmetry sites and its presence correlates with the pump wavelength dependent features. Inversion site fluorescence consists of magnetic dipole R lines at 690.0 nm and 695.8 nm and phonon-assisted electric dipole transitions at longer wavelengths.
Isolation characteristics for laser diode optical switches
Authors: Ikeda Masahiro
Published: February 2003

The isolation spectra for laser diode optical switches, which are the level difference between the on and off state attenuation, are calculated for n- and p-type GaAlAs and InGaAsP using a Gaussian fit to the Halperin–Lax band tails and Stern’s matrix element model. The measured and calculated isolation spectra for a GaAlAs laser diode are closely coincident with one another. The calculated results show that p-type materials, which contain small background carrier concentrations, are suitable for high isolation laser diode optical switches. Especially, it becomes clear that p-type In0.533Ga0.467As laser diode optical switches, whose operating wavelength is 1.65 μm, give the best isolation characteristics.
The residual streamer channel: Return strokes and secondary streamers
Authors: Sigmond R. S.
Published: February 2003

The streamer and return stroke concepts in positive corona breakdown are reviewed, and examined critically for the case of short (<5 cm) gaps in ambient air. It is shown that return strokes normally should not be observed, but that return streamers may occur in longer or highly overvolted streamer channels. A new physical picture is presented of the secondary streamer, as one or several high field domains formed by Douglas-Hamilton–Mani-type attachment instability of the residual channel created by the passage of the primary streamer. In this way, both the erratic origin and development of the secondary streamer in air are easily explained, as well as the fact that spark breakdown follows if and when the secondary streamer fills the complete residual channel length. Further, it follows that the secondary streamer is not the cause of breakdown, but only a secondary side effect.
Dependence of x-ray intensity scaling on target atomic number in laser produced plasmas
Authors: Gupta P. D. , Naik P. A. , Pant H. C.
Published: February 2003

We have measured the x-ray emission intensity from plasmas created from a number of targets with atomic number (Z) in the range 6≤Z≤73 using a 1-GW, 5-ns neodymium glass laser. The variation of x-ray intensity with laser intensity (Φ) was observed to depend on the target atomic number and showed a scaling of Φα where α varies from 1.9 to 2.8 for different elements. The observed scalings were found to be consistent with a self-regulating model for plasma heating.
Surface flashover of conical insulators in vacuum
Authors: Pillai A. Sivathanu , Hackam Reuben
Published: February 2003

The surface flashover of a Macor glass-ceramic conical insulator in ultrahigh vacuum is investigated using direct current (dc), alternating current (ac at 60 Hz), standard lightning impulse (1.2/50 μs), and combinations of dc+1.2/50 μs and dc+ac. The dc and the 1.2/50-μs flashover voltages are found to be at about the same level when the cone angle θ, which the surface makes with the applied field, is varied from −55° to +55°. At a fixed positive value of θ and a fixed thickness of the insulator, the lightning impulse, and the dc flashover voltages are higher than the ac. The level and the polarity of the dc prestress influence the combined dc+impulse flashover voltage in conical insulators. The ac+dc flashover depends on the dc prestress level and increases with increasing the prestress until a saturation is reached which is at a slightly higher voltage than the dc flashover. The electric field and the potential distributions at the interface of the cone insulator are calculated for different cone angles in the range 5° to 55°.