bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient phenomena of relaxation from electric-field-induced nematic phase to cholesteric phase
Authors: Kwok S. K. , Liao York
Published: February 2003

In certain mixtures of nematic and cholesteric liquid crystals, it is found that the metastable final state in an electric-field-induced nematic to cholesteric transition depends on the turnoff rate of the applied voltage. Experimental evidence sugests that two processes, i.e., helix winding and Freedericksz transition type molecular reorientation, may be involved. Relaxation times for both are estimated theoretically and compared with experimental results. An overall relaxation process is also proposed phenomenologically and the predictions compare favorably with the temporal data. The prerequisites on the threshold fields and relaxation times for this phenomenon are deduced. It is believed that this new observation may help explain the transient behavior in a nematic-cholesteric phase transition and may promise some practical applications.
Wachtman’s equation and temperature dependence of bulk moduli in solids
Authors: Nandanpawar M. L. , Rajagopalan S.
Published: February 2003

Anderson has derived an equation describing the temperature dependence of bulk moduli of oxide solids using the Mie-Grüneisen equation of state. In this paper, we have shown that this equation can be applied to all solids in general, without restricting the applicablity to oxides alone. In our approach, use has been made of the Mie-Grüneisen equation of state and an assumption that the main change in bulk modulus with temperature arises from the associated volume change and the volume changes encountered are small, which is true in many solids. We have estimated the values of bulk moduli of many nonoxide solids like Au, Ag, Cu, Si, PbSe, Mg2Sn, and MgCu2, which agree well with the experimentally determined values. The Debye characteristic temperature, the Grüneisen parameter, and the Anderson-Grüneisen parameter have been considered to be temperature dependent.
Room-temperature threshold-current dependence of GaAs-AlxGa1−xAs double-heterostructure lasers on x and active-layer thickness
Authors: Casey H. C.
Published: February 2003

The known properties of GaAs and AlxGa1−xAs have been used to calculate the threshold-current density of double-heterostructure (DH) lasers at room temperature without adjustable parameters. In the absence of leakage currents due to unconfined carriers, the room-temperature threshold-current density for broad-area DH lasers may be repesented by Jth (A/cm2) =4.5×103d+(20d/Γ)[αi+(1/L)  ln(1/R)], where d is the active-layer thickness in microns, Γ is the waveguide confinement factor, αi is the internal loss, L is the cavity length, and R is the facet reflectivity. The experimentally observed increase of Jth for x<0.2 given by Rode is shown to be due to the diffusive electron and hole leakage currents, and a best fit to the data was obtained with an electron minority-carrier diffusion length in AlxGa1−xAs (x≲0.3) of ∼1 μm. The above expression for Jth fits Kressel and Ettenberg’s Jth versus active-layer-thickness data at x=0.65, while for x=0.3, the experimental Jth is 300 A/cm2 larger than the calculated Jth at d=0.1 μm. This difference appears to be due to greater scattering loss at x=0.3 than x=0.6.
Sensitive F2 absorption diagnostic
Authors: Spencer Donald J.
Published: February 2003

A sensitive F2 absorption diagnostic technique was developed by which a difference in absorption sensitivity of ΔI/I0=10−4 can be determined. This value corresponds to an F2 pressure–path-length product of 0.215 Torr cm at 300 K. The method was applied to an HF (DF) chemical laser flow and resulted in measured average nozzle-exit values (α) of from 0.4 to 0.5 from a totally dissociated plenum, indicating a large degree of nozzle wall recombination.
A possible explanation for the photovoltaic effect in indium tin oxide on InP solar cells
Authors: Singh R. , Shewchun J.
Published: February 2003

Recently, Sree Harsha and co-workers reported a 14.4% efficient n-indium tin oxide/p-InP solar cell. In principle, it is difficult to visualize a high-efficiency photovoltaic device with this particular structure because of large interfacial defects due to crystal structure and lattice mismatch. However, we propose an explanation for the operation of this solar cell based on the presence of a thin interfacial insulating layer between the indium tin oxide and the InP. The operation is similar to tunnel MIS solar cells where the metal is replaced by a degenerate wide-band-gap oxide (indium tin oxide) semiconductor. Our calculations show that such semiconductor-insulator-semiconductor solar cells can yield efficiencies as high as 26% (AM2) with InP as the base semiconductor.
Pyroelectric effects in thin film
Authors: Zook J. D. , Liu S. T.
Published: February 2003

The pyroelectric effect in a thin film rigidly attached to a thick substrate is discussed and compared to the usual (stress-free) effect. The effects of clamping are negligible for the geometry normally used in pyroelectric detectors in the case of three proper ferroelectric-type pyroelectric materials of practical interest, namely, LiTaO3, Pb5Ge3O11, and Sr0.5Ba0.5Nb2O6. In the case of three wurzite-type (nonferroelectric) pyroelectrics, namely, CdS, CdSe, and ZnO, the pyroelectric effect is drastically reduced by such clamping. Thus the pyroelectric effect in the latter materials appears to be piezoelectric in origin, in contrast to the case of most pyroelectric materials.
Two-photon absorption of neodymium laser radiation in gallium arsenide
Authors: Bosacchi B. , Bessey J. S. , Jain F. C.
Published: February 2003

We have studied the interaction of picosecond pulses from a Nd : glass laser with GaAs. The experimental data at incident powers up to ∼30 GW/cm2 can be satisfactorily explained in terms of two-photon absorption with β=0.015±0.005 cm/MW. The results are discussed in connection with the discrepancies existing in the literature about the experimental values of β. Their implications for the existence of self-induced transparency effects in GaAs are also briefly pointed out.
Flux-flow characteristics of a large Josephson junction
Authors: Yoshida K. , Irie F. , Hamasaki K.
Published: February 2003

In order to study the various aspects associated with flux flow in a large Josephson junction, a new equation which describes a balance of net forces acting on each vortex has been derived by a spatial average of the two-dimensional Josephson equation. This equation reveals the existence of two kinds of driving forces, i.e., a driving force due to density gradients of vortices and that due to a line tension of a vortex, and also the existence of two kinds of counterforces, i.e., a viscous drag force due to a normal current and an inertial force due to a junction capacitance. It is shown by this equation that there exist two propagation modes of envelope waves in a large Josephson junction in a flux-flow state. An analytical expression for flux-flow conductance is also obtained using this equation, which is in reasonable agreement with experimental results.
Electrical properties of lead-zirconate–lead-titanate ferroelectric thin films and their composition analysis by Auger electron spectroscopy
Authors: Okada Akira
Published: February 2003

Lead-zirconate–lead-titanate (PZT) thin films with perovskite and pyrochlore structures were successfully fabricated on several kinds of substrates by rf diode sputtering. Semiquantitative compositional analysis of the deposited thin films were made with Auger electron spectroscopy (AES). The films were deposited from targets consisting of mixed powder oxides. One target had a composition corresponding to 10 mol% PbO-modified PZT 52/48 (Zr to Ti ratio in the PZT, target A), while the other had the composition corresponding to 10 mol% PbO-modified PZT 42/58 (target B). The films in the perovskite structure had ferroelectricity, while the films in pyrochlore had none. The perovskite films deposited from target A had a dielectric constant of 751, a remanent polarization of 20.4 μC/cm2, and a coercive field of 23.3 kV/cm. The films deposited from target B had a dielectric constant of 654, a remanent polarization of 6.37 μC/cm2, and a coercive field of 12.2 kV/cm. The composition of the former film was PZT 60/40 and the latter, PZT 47/53. The difference in the ferroelectric properties is believed to be in the difference in the compositional ratio of Zr/Ti in the film.
An efficient acousto-optic TE?TM mode converter utilizing a doubly confined optical and acoustic waveguide structure
Authors: Hayashi Hideki , Fujii Yoichi
Published: February 2003

Several types of doubly confined optical and acoustic waveguide structure for extremely efficient acousto-optic TE?TM mode conversion are proposed and theoretically analyzed. It is shown that only 1 mW of acoustic power is required for 100% TE10?TM10 mode conversion along the x-axis on Y-cut LiNbO3 with an interaction length of 5 mm and a waveguide width of 30 μm.
Preparation and study of properties of a few alkali antimonide photocathodes
Authors: Ghosh C. , Varma B. P.
Published: February 2003

A new processing technique for a few alkali antimonide photocathodes is described. This technique does not require an initial antimony layer as in the conventional techniques. Electron microscopic examination of the antimony film shows that the antimony film is affected by ambient gases, and the improvement of senistivity which results in this technique is thought to be due to the absence of it. The band gaps of the photocathodes are determined by photoconductivity measurements. The threshold energy and, hence, the electron affinity is calculated from the threshold region photoemission of these photocathodes. The activation energy of the defect levels is determined by the measurement of the electrical conductivity at a low temperature in a specially designed cryostat. Finally, the role of cesium in a multialkali photocathode is discussed, and a model of band bending which assumes a K2CsSb layer at the top is proposed. This gives the threshold energy value observed experimentally.
Solid-liquid equilibria calculations for LPE of AlvGa1−u−vInuAs on InP
Authors: Perea Ernesto H. , Fonstad Clifton G. , Quillec Maurice
Published: February 2003

Detailed phase diagram calculations are presented for the quaternary AlvGa1−u−vInuAs alloys that are lattice matched to InP, and the experimental possibilities of growing AlGaInAs layers on InP by liquid-phase epitaxy are discussed. The calculations indicate that there is a very large distribution coefficient for Al which will make LPE of AlGaInAs difficult.
Infrared fluorescence measurement of equilibrium and vibrational temperatures in laser-irradiated gases
Authors: Kleinman Lawrence I. , Weston Ralph E. , Flynn George W.
Published: February 2003

A calibrated two-color temperature method has been developed for the measurement of time-dependent temperatures in low-pressure gases following laser excitation. Ratios of ir fluorescence signals arising from specific vibrational manifolds are used to determine the magnitude of laser heating, the vibrational temperatures of individual modes, and density fluctuations due to gasdynamic expansion following spatially inhomogeneous excitation. This technique has been applied to a prototype system consisting of SF6, SO2, and CH3F exposed to TEA CO2 laser excitation of the ν3 mode of SF6. Prior to V-T/R relaxation, this system cannot be described by a single vibrational temperature.
Third-harmonic generation by a Gaussian electromagnetic beam in a magnetoplasma
Authors: Sodha M. S. , Umesh G.
Published: February 2003

This paper presents an investigation of nonlinear third-harmonic generation in a weakly collisional magnetoplasma due to simultaneous propagation of both the right and left circularly polarized modes, having a Gaussian intensity distribution; self-focusing has been taken into account. At moderate powers, the self-focusing is seen to enhance the harmonic output by two orders of magnitude; at high powers, propagation occurs in an almost uniform waveguide devoid of plasma, and the harmonic output is, consequently, decreased. In the vicinity (ωc/ω=0.7) of the electron cyclotron resonance, the harmonic output of the extraordinary mode is enhanced by an order of magnitude; the present theory is not applicable at resonance.
Copper acetylacetonate as a source in the 5106-Å neutral copper laser
Authors: Cem Gokay M. , Soltanoalkotabi Mahmood , Cross Lee A.
Published: February 2003

A copper-vapor laser utilizing copper acetylacetonate as a copper atom donor in a flowing gas heated discharge tube has been studied. As in the other metal-vapor laser systems based upon the dissociation of a metal salt, two successive discharges are required to achieve laser action. The output energy of such a system would appear to be comparable to that obtained in the CuCl systems; however, the operating temperature is much lower.
Diffusion coefficient of holes in Ge
Authors: Reggiani L. , Canali C. , Nava F. , Quaranta A. Alberigi
Published: February 2003

The diffusion coefficient of holes in Ge is analyzed as a function of temperature (77⩽T⩽300 K) and electric field (10⩽E⩽104 V/cm). New experiments performed with the time-of-flight technique are presented together with data obtained with the noise-temperature technique, as reported in the literature. The theoretical interpretation makes use of the Monte Carlo procedure in solving the Boltzmann equation and of a band model which accounts for warping and nonparabolic effects of the heavy-hole band. The fact that the theoretical and experimental findings agree satisfactorily suggests that diffusion data may be obtained equally well by either of the two techniques in question (time of flight and noise temperature). Furthermore, warping and nonparabolicity of the hole band are found to be responsible, respectively, for anisotropic effects with the direction of field and for a region of near saturation of the diffusion coefficient at the highest applied fields.
Observation of phosphorus pile-up at the SiO2-Si interface
Authors: Johannessen J. S. , Spicer W. E. , Gibbons J. F. , Plummer J. D. , Taylor N. J.
Published: February 2003

The Si oxidation rate at high temperatures is increased by heavy P doping. Sputter ion-Auger techniques have been used to investigate the oxide thickness and P concentration after 900 °C oxidation with an initial P surface concentration of between 2×1018 and 3.2×1020/cm3. Phosphorus was found to pile up in the Si-SiO2 interface region. The maximum P concentration near the interface was found to depend on doping and was (at certain P concentrations) an order of magnitude larger than that predicted by redistribution theory. A vacancy–P-complex model is presented to explain the observed behavior. A correlation between the selective pile-up of P at the interface and the current gain of planar bipolar transistors is reported.
Application of fracture-mechanics theory to fatigue failure of optical glass fibers
Authors: Ritter J. E. , Sullivan J. M. , Jakus Karl
Published: February 2003

The fatigue behavior of optical glass fibers was determined in air at 23°C and 55% relative humidity by the dynamic-fatigue test technique in which strength is measured as a function of stressing rate. The good correlation found between the fatigue test data and fracture-mechanics theory indicates that failure is controlled by slow crack growth of preexisting flaws and that fracture-mechanics theory can be used in making failure predictions for optical glass fibers.
Ionic conductivity of quenched alkali niobate and tantalate glasses
Authors: Glass A. M. , Nassau K. , Negran T. J.
Published: February 2003

Alkali niobate and tantalate glasses have been prepared by rapid quenching. These glasses exhibit room-temperature ionic conductivities as high as 10−5 (Ω cm)−1 and electronic conductivities less than 10−11(Ω cm)−1. In the case of LiNbO3, the glass conductivity is many orders of magnitude greater than that of the single crystal. These conductivities are sufficiently high for rapidly quenched vitreous oxides to be considered for applications as solid electrolytes.
The understanding and elimination of some suspension instabilities in an electrophoretic display
Authors: Mürau P. , Singer B.
Published: February 2003

The performance and appearance of an electrophoretic display is strongly dependent on the stability of the colloidal suspension in the device. Two primary degradation modes in a suspension have been identified. One is classified as pigment agglomeration which is caused by an insufficient repulsive barrier between particles; the other is classified as pigment clustering which is caused by fluid motion within the cell. Both forms of instabilities are detrimental to the life of the display. The concept of colloid stability will be reviewed briefly and its relation to the image device will be discussed. The mechanism by which the suspension instabilities develop and the methods by which they can be eliminated will be described. Properly stabilized suspensions in a device have survived in excess of 2.5×108 switches (15 600 h) with no serious signs of degradation.
Theoretical considerations on the design of magnetic bubble detectors
Authors: Patel K. , Clegg W. , Pickard R. M.
Published: February 2003

The resistance change experienced in a Permalloy stripe when magnetized by an expanded bubble domain is considered from a theoretical standpoint. A model is developed after consideration of demagnetizing field strengths and thermal and electrical constraints. From this model the output signal level to be expected for any given expansion of the domain may be computed and used as a design aid.
Electron-beam-induced conduction in polyethylene
Authors: Yoshino K. , Kyokane J. , Nishitani T. , Inuishi Y.
Published: February 2003

The electrical conduction in polyethylene induced by the irradiation of the short pulsed electron beam (100-nsec time width) consists of the fast and the slow components. The former is attributed to the carrier transport in the crystalline part and the latter to that in the amorphous part. A logarithmic plot (Scher-Montroll plot) of the slow part of the induced current versus time gives a knee at time Tr, which is thought to be the transit time of the carrier front between electrodes. Simple calculation by the formula μ=L/TrE gives the apparent slow carrier mobility μ of 5.6×10−7 and 3.2×10−7 cm2/V sec for the electron and the hole, respectively, at 343 K under a field E of 1.2 MV/cm for sample thickness L of 12 μm. These apparent slow carrier mobilities are dependent on both the thickness and the field strength. These behaviors are discussed in terms of Scher-Montroll theory on transport in amorphous substances. The activation energy of the mobility is in good agreement with the apparent trap depth obtained from the TSC measurement.
Model of bias sputtering applied to the control of Nb film properties
Authors: Kay Eric , Heim Gunther
Published: February 2003

Niobium films have been prepared by bias sputtering in a conventional sputter system operated in the triode configuration. Gas analysis of the discharge and of the deposited films as well as resistivity and lattice-parameter measurements provide the basis for the interpretation of the deposition process under ion bombardment. The importance of defining the relative rate of arrival of energetic ion versus neutrals in addition to defining the energy of arriving particles is emphasized. The close relationship of bias sputtering to ion implantation is stressed. A model for bias sputtering is developed which is suited for fine-tuning film composition and structure and thereby the resultant thin-film properties.
Dynamic vortex motion in long Josephson junctions
Authors: Nakajima Koji , Ichimura Hideshi , Onodera Yutaka
Published: February 2003

Using long Josephson tunnel junctions, dynamic vortex motion has been observed as the flux-flow voltage across the junction. The flux-flow voltage increases with increasing external magnetic field. The velocities of the flux flow in the junctions can be obtained from the junction-voltage–vs–applied magnetic field characteristics. It is shown that the velocities of the flux flow in the long junctions have the maximum value equal to the phase velocity of the electromagnetic field.
Heat transport in coaxial thermoelectric disks with radial flow of current
Authors: Landecker K.
Published: February 2003

It is shown that in thermocouples consisting of arms in the form of coaxial N and P disks in which the current flow is radial, two regions must be distinguished. If the N and P disks are narrowly spaced, then the temperature difference between the hot and cold junctions tends to infinity. If, on the other hand, the disks are widely spaced, then the maximum temperature difference is the same as that of a linear couple.
Refrigerating thermojunctions with radial flow of current
Authors: Lund T.
Published: February 2003

The operation of a thermocouple of which the arms are coaxial disks of semiconductor so that the current flow is in the radial direction is analyzed for the case when the device is used as a refrigerator. It is found that the maximum temperature difference obtainable and the coefficient of performance obtained at a given temperature difference are the same as for a straight-arm couple made of the same materials. It may, however, be possible to obtain a greater heat pumping rate per unit volume.
Electromagnetic-implosion generation of pulsed high-energy-density plasma
Authors: Baker William L. , Clark Miles C. , Degnan James H. , Kiuttu Gerald F. , McClenahan Charles R. , Reinovsky Robert E.
Published: February 2003

The generation of pulsed high-energy-density plasmas by electromagnetic implosion of cylindrical foils (i.e., imploding liners or hollow Z pinches) has been investigated experimentally and theoretically at the Air Force Weapons Laboratory. The experimental studies involve discharging a 1.3-μsec 1.1-MJ capacitor bank through 7-cm-radius 2-cm-tall 3–30-mg cylindrical foil liners. Typical discharge parameters are 7–12-MA peak current and 1–1.5-μsec current rise time. Current and voltage waveforms indicate strong coupling of the load to the capacitor bank, and analysis of the waveforms indicates good implosion of the current sheath. Optical- and magnetic-probe measurements are consistent with 1–2-cm thickness of the imploding plasma shell and with final implosion velocities ∼15–20 cm/sec. Radiation-diagnostic measurements indicate ultrasoft x-ray yields ∼50–100 kJ with the FWHM of the photon pulse ∼80–100 nsec. The radiation data is consistent with a quasiblackbody spectrum (T∼30–50 eV) comprising most of the energy, with additional higher temperature and optically thin spectral components. Al11+ and Al12+ line and recombination radiation is frequently observed. Comparison of electrical, magnetic, and radiation data with one-dimensional MHD and two-dimensional MHD calculations is presented. The prospects for improving the performance with the present energy source and scaling to larger energy sources are briefly discussed.
Numerical simulation for design of a two-stage acceleration system in a megawatt power ion source
Authors: Ohara Yoshihiro
Published: February 2003

In the design of the neutral-beam injectors for large tokamaks such as JT-60 planned in Japan Atomic Energy Research Institute, the optimum configuration of extraction grids and the operating conditions were studied numerically for a two-stage acceleration in a high-power ion source. Results of the calculations show the feasibility of extracting a proton beam with energy 75 keV and current 15 A of about 0.6° divergence from the 12-cm-diam extraction grids of transparency 40%. Beam divergence in the two-stage configuration depends largely on the field intensity ratio; the optimum ratio that gives a minimum beam divergence is about 0.3–0.5.
Polymorphism and the crystal structures of InSb at elevated temperature and pressure
Authors: Yu Shu-Cheng , Spain Ian L. , Skelton Earl F.
Published: February 2003

Polycrystalline x-ray diffraction data are reported for three high-pressure phases of InSb. InSb-II patterns are indexed on the basis of a body-centered tetragonal lattice with unit cell parameters a=5.810 Å and c=3.136 Å at P∼4.3 GPa and T≳100 °C; a unique space group has not been assigned. Possible space groups and structures have been determined for the other high-pressure phases. Contrary to published results, InSb-III is orthorhombic with a=5.712 Å, b=5.357 Å, c=3.063 Å at 11.5 GPa and room temperature, the space group is either Pmmm or Pmmn, and Z=2. InSb-IV is also orthorhombic with a=2.919 Å, b=5.618 Å, and c=3.066 Å at P=4.4 GPa and room temperature; the space group is Pmm2, and Z=1. Atomic coordinates and appropriate bond angles are also reported.
Radiation damage in neutron transmutation doped silicon: Electrical property studies
Authors: Young R. T. , Cleland J. W. , Wood R. F. , Abraham M. M.
Published: February 2003

Radiation damage in neutron-transmutation-doped (NTD) silicon, irradiated to introduce 5×1013 to 6×1016 phosphorus cm−3, has been studied by electrical property measurements. The experimental results indicate that thermal-neutron-induced (n,γ) recoil-type damage can be annealed at 400 °C. The nature of any remaining lattice defects and their annealing behavior above 400 °C is a function of the fast-neutron fluence. Small defect clusters are present in Si irradiated with a light-to-moderate fast-neutron fluence (?5×1018 n cm−2), and temperature-dependent Hall coefficient measurements indicate that at least two deep acceptor levels and one deep donor level are formed during annealing. One of these acceptor levels anneals at ∼450 °C, and the other two levels anneal at ∼550 °C. A shallow acceptor level near the valence band that anneals at 750 °C is also observed. Larger defect clusters which reduce the electron mobility tremendously and distort the band structure are formed in heavily irradiated Si (5×1018 to 1020 n cm−2). Virtually all of the electrically detectable radiation damage in NTD Si irradiated with a fast-neutron fluence up to 1020 n cm−2 can be removed by annealing at 750 °C for 1/2 h. There is some indication that a minority-carrier-recombination effect remains even after such annealing.
On the analysis of x-ray-diffraction line profiles from small epitaxial binary diffusion couples: Determination of concentration profile and influence of TDS
Authors: Delhez R. , Mittemeijer E. J.
Published: February 2003

The in situ nondestructive determination of the concentration profile in a small epitaxial binary diffusion couple by x-ray-diffraction line-profile analysis is considered. On the basis of the work by Houska and collaborators, a direct method is presented for the determination of the concentration profile from an x-ray intensity band. The method has the advantages that only a single order of the reflection is required and that neither iterative nor trial and error calculations are necessary as compared to previous methods. It is further shown that linear interpolation between both extremeties of the intensity band is a poor approximation to the actual background profile. The background mainly consists of thermal diffuse scattering (TDS) which peaks at the Bragg positions and may contribute significantly to the integrated intensities measured. An iterative method is proposed to calculate the TDS background. Both the direct method for determining the concentration profile and the calculation and subsequent elimination of the TDS background are applied to experiments with Cu/Ni bicrystals where the copper is either electrocrystallized or deposited from the vapor phase onto the 111 nickel substrate.
Reactions of slip dislocations at coherent twin boundaries in face-centered-cubic metals
Authors: Hartley Craig S. , Blachon Dominique L. A.
Published: February 2003

An elastic analysis of dislocations in isotropic media has been applied to study the interaction of dislocations on intersecting {111} planes at a coherent twin boundary in the face-centered-cubic lattice. The nature of energetically favorable barriers formed by such reactions is determined and their equilibrium separations are given, in addition to the equilibrium separations for the barriers found on intersecting {111} planes in the face-centered-cubic structure. The importance of such configurations, and especially the effect of the twin boundary, on work-hardening behavior is discussed.
Mechanisms of the reactive- and chemical-sputter deposition of TiO2 from Ti and TiC targets in mixed Ar+O2 discharges
Authors: Wu L. C. , Greene J. E.
Published: February 2003

Polycrystalline TiO2 films with a rutile crystal structure have been grown on glass substrates at a temperature of 250 °C by rf sputtering from either Ti or TiC targets in mixed Ar+O2 discharges at a total pressure of 15 mTorr (2 Pa) and a peak-to-peak target voltage of −1.9 kV. In the case of the Ti target, film growth occurred by normal reactive sputtering in which oxidation of the target competes with the physical sputtering of titanium. The relative rates of these processes established critical oxygen concentrations fO2 in the discharge of 0.6 and 6 mole%, respectively, at which the film deposition rate began to decrease from that observed for Ti sputtered in pure Ar and reached that of a TiO2 target sputtered in O2. TiO2 films with a (110) preferred orientation were obtained at fO2?6 mole% by the reaction of sputtered titanium with oxygen at the surface of the growing film. TiO2 films were also grown using the TiC target with fO2?7 mole%. Mass-spectrometer sampling of the discharge during film growth showed a large concentration of CO which we believe derived primarily from chemical sputtering of the TiC target by oxygen. In this process the oxygen reacts with the target producing volatile CO, which is desorbed, and a nonvolatile titanium oxide. Ion bombardment from the discharge enhances the evolution of CO and simultaneously removes titanium by physical sputtering. The rate-limiting step in the erosion of the TiC target is the physical sputtering of titanium. The critical value of fO2 necessary to obtain TiO2 films was also the value at which the CO concentration in the discharge saturated at a maximum and the film deposition rate saturated at a minimum. However, the fO2 value at which the TiC-target sputtering rate just began to decrease from that of TiC sputtered in pure Ar towards that of TiO2 sputtered in oxygen was ∼1.3 mole%. This was considerably larger than the equivalent value found with the Ti target since additional oxygen was consumed in the reaction with carbon which occurred preferentially to the titanium oxide formation. In all cases, TiO2 films grown from the TiC target at fO2?7 mole% were found to be identical, as judged by x-ray diffraction, Auger spectroscopy, and tribological measurements, with those grown by pure reactive sputtering from the Ti target.
The plasma oxidation of CF4 in a tubular-alumina fast-flow reactor
Authors: Smolinsky G. , Flamm D. L.
Published: February 2003

Mass-spectrometric analyses were made of the plasma reactions of 50-W CF4 and CF4-O2 discharges as functions of pressure (0.15–0.6 Torr), flow rate (2–80 cm3/min) or the O2 level in the feed. Discharges were investigated both in the presence and absence of single-crystal Si. The products from CF4 alone were F, F2, and C2F6; in the presence of Si the products were SiF4, C2F6, and small amounts of F. The products from CF4-O2 were F, F2, COF2, CO2, and CO; in the presence of Si the products were SiF4, F, F2, COF2, CO2, and CO. The conversion of CF4 to products increased monotonically with residence time in the discharge and the O2 concentration in the feed. It appears that F2 was produced in the plasma zone and that the SiFx (x<4) species reacted with F2 to give SiF4.
Electrochromism in nickel-doped strontium titanate
Authors: Mohapatra Sarat K. , Wagner Sigurd
Published: February 2003

Electrochromism in SrTiO3 : Ni at 200–300°C has been investigated by electrical and optical measurements. (NiTiVO) ′ and Ni′Ti constitute the color centers on the cathode and anode sides, respectively. Oxygen vacancy drift determines the kinetics during the early state of coloration and during the entire process of bleaching. An activation energy of 0.95 eV for oxygen vacancy motion has been obtained from bleaching experiments.
Ion-acceleration mechanisms in vacuum diodes
Authors: Adler R. J. , Nation J. A.
Published: February 2003

A study of proton acceleration in a Luce diode has been carried out. Measurements of beam-neutralization times, electron and ion energy distributions, and induced radioactivity have been made. These measurements show that the effective potential-well depth at the beam head is less than the electron-accelerating voltage. Also, the relative activity of Mylar and copper foils indicates that ion energy increases with mass for Z=1 particles. Both of these observations are consistent with ion acceleration resulting from a moving potential well.
Piezoelectric properties in the composite systems of polymers and PZT ceramics
Authors: Furukawa T. , Ishida K. , Fukada E.
Published: February 2003

Piezoelectric properties have been studied for the composite systems of PZT ceramics and polymers including polyvinylidene fluoride (PVDF), polyethylene (PE), and polyvinyl alcohol (PVA). The values of the piezoelectric constants and their temperature and frequency dependences were discussed on the basis of the theoretical expressions of the piezoelectric constants for a two-phase system with piezoelectric spherical dispersions. The piezoelectric activity of all the composite systems studied was mainly ascribed to the piezoelectricity of PZT ceramics. For the PVDF-PZT system, the piezoelectricity of PVDF was shown to make minor contribution compared to that of PZT ceramics. For the PE-PZT system, the temperature dependence of the d constant due only to elastic relaxation in the PE phase was investigated. For the PVA-PZT system, the retardational and relaxational frequency dependence of the d constant observed above 80 °C were successfully accounted for in terms of the interfacial and electrode polarizations due to the dc conduction in the PVA phase.
Transverse-acoustoelectric-voltage (TAV) spectroscopy of high-resistivity GaAs
Authors: Estrada-Vazquez H. , Webster R. T. , Das P.
Published: February 2003

The space-charge-coupled interaction of surface acoustic waves (SAW) propagating on a piezolectric substrate with a semiconductor surface placed in proximity gives rise to a transverse acoustoelectric voltage. This voltage is developed across the semiconductor and is dependent on the semiconductor surface conductivity. Thus, the spectral response of the acoustoelectric voltage gives information about the interaction of impurity and defect levels of the semiconductors with the conduction and valence bands. Maxima and minima in the photoenhanced acoustoelectric voltage are due to corresponding structures in the photoconductivity. Experimental results on semi-insulating gallium arsenide with no intentional doping, Cr doping, and Cr-Te doping are reported. The results include the dependence of the acoustoelectric voltage on light intensity and on temperature. Peaks in the spectral response are interpreted as impurity levels. Thus, a sharp peak at 0.87 eV is attributed to Cr-level–to–conduction-band transitions and the broad peak centered about 0.72 eV is attributed to oxygen impurities. The absorption threshold determines the Fermi-level location in the energy band and this, in turn, determines the sample resistivity. The experimental temperature dependence of band-gap energy agrees with previously reported results. Photocurrent measurements were also performed and a remarkable correlation between the two spectra was obtained. An important advantage of the TAV technique is the fact that it is contactless, nondestructuve, and requires no special preparation.
Minority-carrier mobility in p-type GaAs
Authors: Walukiewicz W. , Lagowski J. , Jastrzebski L. , Gatos H. C.
Published: February 2003

Theoretical calculations of electron mobility in p-type GaAs were carried out taking into consideration the screening effects and all major scattering processes. Calculated values of mobility are presented as a function of carrier concentration, compensation ratio, and temperature. The basic differences between minority-carrier mobility in p-type GaAs and electron mobility in n-type GaAs are pointed out. A practical procedure is also presented for the evaluation of minority-carrier mobility from available electron-mobility data.
Variation of photovoltaic effect in vertical n/p-junction solar cells
Authors: Yang Yu-Tung
Published: February 2003

Experiments reveal that the power output of an ordinary vertical silicon single-crystal solar cell changes with the local illumination. The dark current is found independent of the location of the local illumination if the illuminated part is only a small porion of the surface area of the vertical solar cell. If the vertical solar cell is fully illuminated, then the dark current may either increase or decrease with the nonhomogeneity or homogeneity of impurity concentration in the single crystal, respectively, and the short-circuit current is always increased. The energy conversion efficiency is different from place to place in a vertical solar cell and the exp(−x/L) law is only approximately followed because the impurity concentration is usually not uniform. The present experiments reveal the minute local variations.
Further results on the aging of silicon Schottky diodes: Influence of the metal
Authors: Ponpon J. P. , Siffert P.
Published: February 2003

In a recently published paper we have emphasized the role of oxygen on the aging process arising in chemically etched silicon Schottky diodes. Complementary results which more accurately show the influence of the behavior of the metal electrodes with respect to oxygen are presented. A qualitative explanation of these observations is proposed.
A necessary condition for magnetic levitation
Authors: Jones T. B.
Published: February 2003

A condition necessary to realize the magnetic levitation of a magnetizable conducting sphere involving frequency, conductivity, and relative permeability is derived. This condition is interpreted in light of the response of magnetic dipoles to curl-free nonuniform magnetic fields.
Derivative surface photovoltage spectroscopy; a new approach to the study of absorption in semiconductors: GaAs
Authors: Lagowski J. , Walukiewicz W. , Slusarczuk M. M. G. , Gatos H. C.
Published: February 2003

Derivative surface photovoltage spectroscopy was achieved with wavelength modulation; it was applied to GaAs and permitted, in a single experiment, the determination of changes in the absorption coefficient over an energy range of 0.5 to 4.3 eV. Photoionization characteristics of deep levels were determined. All known critical-point transitions up to 4.3 eV were clearly obtained from second-derivative spectra. In addition, previously unresolved transitions were observed at about 2.6 eV. Oscillatory photovoltage in high magnetic fields was observed, and it was used to identify the transitions in the vicinity of the energy gap.
On the log-normal distribution of electromigration lifetimes
Authors: Lloyd J. R.
Published: February 2003

It has been shown that a normal temperature distribution within a sample set can produce a log-normal failure rate in electromigration experiments if it is assumed that the equation tf=Aj−n exp(Ef/kT) holds for individual stripe lifetimes. It has also been pointed out that if σ’s determined under accelerated-stress conditions are used to predict failure under normal-use conditions, incorrect failure rates may result. It has also been demonstrated that most of the σ’s observed in accelerated tests can be attributed to variations in temperature.
Laser power variation and time dependence of populations in a burst-mode CuBr laser
Authors: Tenenbaum J. , Smilanski I. , Gabay S. , Levin L. A. , Erez G.
Published: February 2003

The time evolution of ground- and metastable-state copper atom concentrations and the laser energy in a bust-mode CuBr laser were measured as a function of temperature, buffer gas species, and repetition rate within the burst. The concentrations were measured by monitoring the absorption of the 244.2- and 510.6-nm atomic copper lines. The optimum time separations of the electrical pulses within the burst were found to be 80 and 235 μ for helium and argon buffer gases, respectively. A correlation was found between the time dependences of the laser energy and ground-state density within the burst. Accumulation was found to occur in the copper atom ground state but not in the metastable 2D5/2 level.
Twofold joint time interval distribution for chaotic light with Lorentzian spectrum
Authors: Bendjaballah Chérif
Published: February 2003

The correlation structure of the lengths of two disjoint time intervals of the stationary point process obtained by detecting a Gaussian field with Lorentzian spectrum is studied for some special cases.
Initial rate of decomposition of CO2 in volume discharges: An experimental study
Authors: Willis C. , Sarjeant W. J. , Wardlaw D. M.
Published: February 2003

Quantitative data on the plasma and chemical changes in a pulsed glow discharge in CO2 have been obtained using a geometrically stable, chemically inert discharge cell. With resistively-ballasted electrodes it was possible to achieve uniform glow discharges over a relatively large range of pressure and the yield of decomposition products was measured as a function of energy deposited at various initial charging voltages. These experimental results were compared to those predicted by numerical solution of the Boltzmann transport equation by integrating a derived yeild per unit energy, Y (E/N), over the duration of the excitation pulse. Good agreement between experiment and theory was obtained for pressures over 400 Torr but significant deviations were noted at lower pressures.
Prepulse damage to targets and alignment verification
Authors: Benjamin Robert F. , Schappert Gottfried T.
Published: February 2003

We measured the damage threshold of 10.6-μm light incident on glass microballoon laser fusion targets. The threshold is several dozen microjoules, depending on target size and laser pulse width, and the damage mechanism appears to be thermal heating and rupture. Perforating glass microballoons proves to be a useful alignment verification technique.
Analysis of parameteric mixing and harmonic generation of surface acoustic waves
Authors: Normandin R. , Fukui M. , Stegeman G. I.
Published: February 2003

The parametric mixing and harmonic generation of surface acoustic waves (SAW) has been treated by a new formalism in which the nonlinear wave equation and boundary conditions are rigorously satisfied at the sum and difference frequencies. The key features are analytical expressions for the spatial structure of modes which can be synchronously driven by volume forces and surface-boundary conditions. After a propagation distance of a few acoustic wavelengths, the acoustic fields evolve into a linearly growing normal-mode SAW. Equations are derived from which the nonlinear interaction cross sections can be evaluated and numerical results are given for a number of materials. Good agreement was obtained between experiment and theory for y-x and x-y α-quartz in the limit that the piezoelectricity is neglected.
Surface-wave generation by nonlinear mixing of bulk waves
Authors: Normandin R. , Stegeman G. I.
Published: February 2003

The nonlinear interaction between bulk acoustic waves at a surface to produce surface acoustic waves is analyzed theoretically. In this analysis both the nonlinear wave equation and boundary conditions are rigorously satisfied by the total acoustic fields. Shear-wave incidence is treated in detail for isotropic fused quartz and numerical cross sections are evaluated for different angles of incidence. Maximum surface-wave generation is predicted for geometries corresponding to bulk waves, shear or longitudinal, traveling parallel to the surface.
Simultaneous mass and temperature determination using a single quartz wafer: An optimized crystal cut
Authors: van Ballegooijen E. C.
Published: February 2003

Recently we have reported a method to measure mass and temperature simultaneously using a single rotated Y-cut quartz crystal coated with a pair of electrodes and a tab. In this paper we will discuss some modifications by which the performance of the method may be strongly improved. A first improvement is achieved by choosing a particular crystal cut (yxl, −20°<φ<20°), and a second improvement is achieved by the introduction of a small gap between the front electrode and the tab. We will present an analysis of the errors in the determination of mass and temperature, which may result from calibration and experimental errors, as a function of the crystal cut and the thickness of the crystal. The results from this analysis are compared with experimental results for three different crystal cuts (yxl, φ=−15°, 0°, +15°). We found that in the presence of a temperature change of 0.1 °C, a mass change of 5 Å (copper) could be measured with an accuracy of 3%, while in the presence of a mass change of 500 Å (copper) a temperature change of 0.005 °C could be measured within 11.3%. Some suggestions are given to increase the relatively small mass range, i.e., 3000 Å (copper), of the method.
Growth of CuInSe2 on CdS using molecular beam epitaxy
Authors: White F. R. , Clark A. H. , Graf M. C. , Kazmerski L. L.
Published: February 2003

Molecular beam epitaxy has been used to grow CuInSe2 on CdS(0001B). Epitaxial growth, as determined from in situ reflection electron diffraction, was observed at a substrate temperature of 300 °C.
Scattering of an offset two-dimensional Gaussian beam wave by a cylinder
Authors: Kojima Toshitaka , Yanagiuchi Yoichi
Published: February 2003

The scattering of a two-dimensional Gaussian beam wave by a perfectly conducting or dielectric cylinder centered off both the beam axis and the beam waist is treated by the Fourier-series-expansion method. The incident-beam fields are expanded in a Fourier series with respect to the polar angle in a cylindrical coordinate, and the expansion coefficients are numerically evaluated. Several scattering patterns are obtained by the use of these expansion coefficients, and the dependence of the scattering characteristics on the offset of the incident-beam wave is examined.
Dynamics of micromagnetic structures under applied in-plane magnetic fields
Authors: Shir C. C. , Henry G. R.
Published: February 2003

The dynamics of the detailed micromagnetic structure of domain walls in thin films are computed by numerical integration of the Landau-Lifshitz-Gilbert equation. The temporal and spatial variations of wall structure under a suddenly applied in-plane field lying in the plane of the wall are investigated. The structure is substantially changed at in-plane field strengths of only 2% of the anisotropy field, Hk. A critical in-plane field value is reached at about 2.25% of Hk; at this point, the time required for the wall structure to reach equilibrium is a maximum. This settling time is also a function of the damping parameter α. For α≳0.1, the settling time is found to be nearly proportional to α; for α≲0.1, the settling time becomes larger as α decreases due to oscillations of the wall structure. In the language of harmonic oscillators, the micromagnetic structure appears underdamped for α<0.1, critically damped at α?0.1, and overdamped for α≳0.1.