bluuebunny/crossref_metadata_2025 huggingface dataset:
Memory loss in MNOS capacitors
Authors: Maes Herman E. , Van Overstraeten Roger J.
Published: February 2003

The decay of the flatband voltage in MNOS capacitors has been investigated. Simultaneous determination of charge content in the nitride and the centroid of its distribution indicates both a discharge of the structure and a penetration of charge deep into the nitride. The discharge can be ascribed to back-tunneling, while the charge displacement is due to a redistribution of the remaining charge over the nitride traps.
Spatial distribution of photoexcited electrons in sandwich structures
Authors: Kadlec J. , Gundlach K. H.
Published: February 2003

The spatial distribution of photoexcited electrons along the normal to the film plane of an illuminated metal-insulator-metal sandwich structure has been calculated for various thicknesses of the electrodes using a computer. For very small thicknesses (≲ 100 Å, depending on the optical constants of the electrodes) the number of excited electrons does not follow the commonly used exponential law because of the strong contributions due to the multiple reflections and interference of the light waves within the structure. In some cases the excitation in the not directly illuminated electrode can become even stronger than in the directly illuminated one.
Zero-voltage nondegenerate parametric mode in Josephson tunnel junctions
Authors: Pedersen N. F.
Published: February 2003

A new parametric mode in a Josephson tunnel junction biased in the zero-voltage mode is suggested. It is a nondegenerate parametric excitation where the junction plasma resonance represents the input circuit, and a junction geometrical resonance represents the idler circuit. This nondegenerate mode has been observed in analog experiments. In a real junction the realization of this mode of operation depends on the coupling between the plasma resonance and the geometrical resonance, and it is argued that without an external dc magnetic field the even geometrical resonances are most favorable for such a coupling.
Enhancement effect of magnetostrictive waves by magnetic pulses
Authors: Luponio C. , Porreca F.
Published: February 2003

It is experimentally shown that the response of the magnetization of a ferromagnetic rod to a low-intensity pulsed magnetic field does not consist of an exponential decay alone, but also of a damped oscillation, if the combination of bias and pulsed fields is used. As a matter of fact, magnetoelastic waves propagating in the solid are observed as well as effects of interference.
Analysis of noises in photocurrent time-correlation spectroscopy of scattered light
Authors: Soda Kunitsugu , Nishio Izumi , Wada Akiyoshi
Published: February 2003

A covariance function, VN (τ,σ), is introduced for the analysis of noises in photocurrent time-correlation spectroscopy of scattered light. Its explicit forms under various measuring conditions are given and the characteristics and magnitudes of the noises are investigated. The distortion of a correlation function caused by the truncation of both upper and lower frequency ranges is examined. The reason for the absence of the so-called aliasing error in a Gaussian-photocurrent correlation measurement is given.
Noise in single injection diodes of spherical and cylindrical geometry
Authors: Blasquez G. , van Vliet K. M.
Published: February 2003

Single injection diodes, with injection from a point contact in a sphere or from a line contact at the axis of a cylinder, are studied, using the dc field distribution of Lampert and Mark. From the ac response equation, the transfer impedance tensor is obtained explicitly. Subsequently, the noise is found according to a recently devised procedure (Ref. 1). It is shown that, for sufficiently low frequencies, the noise has the structure of generalized Nyquist noise, SδV(a,b) =4kTn ReZ(a,b)(ω), with a longitudinal noise temperature Tn∥= (14/11) T (sphere), Tn∥= (4/3) T (cylinder), and a transverse noise temperature Tn⊥=T (sphere and cylinder). For higher frequencies the noise temperature decreases, with asymptotic values Tn∥,∞=6/11 (sphere) and Tn∥,∞=2/3 (cylinder). Formulas for contacts with finite radius are also given, as well as the transition to planar geometry.
Tracer self-diffusion and electromigration in thin tin films
Authors: Sun P. H. , Ohring M.
Published: February 2003

A nondestructive tracer-scanning technique was devised to study lateral self-diffusion and electromigration in evaporated thin Sn films. The diffusional spreading and migration of tracer distributions of Sn119m in thin Sn film matrices was recorded over a temperature range 142–213 °C. Determination of the profile shape enabled the diffusivity D to be unfolded, while the profile shift provided values of the migration velocity V. The temperature-dependent results may be summarized as follows: (1) D= (1.8+1.9−0.9) ×10−5 exp(−10 700±700/RT) cm2/sec; (2) V= (1.07+1.10−0.54) ×10−4/T exp(−9800 ±650/RT) cm/sec at a current density of 1×104 A/cm2; and (3) the direction of self-electrotransport is toward the anode at all temperatures. From these data, values of the effective valence Z* and defect resistivity were derived from the Nernst-Einstein and Huntington formulas describing electrotransport. The results are consistent with a bulk-assisted grain-boundary transport mechanism involving a vacancy defect.
CO2-laser–produced plasma columns in a solenoidal magnetic field
Authors: Offenberger A. A. , Cervenan M. R. , Smy P. R.
Published: February 2003

A 1-GW CO2 laser pulse has been used to produce extended column breakdown of hydrogen at low pressure in a 20-cm-long solenoid. Magnetic fields of up to 110 kG were used to inhibit radial losses of the plasma column. A differential pumping scheme was devised to prevent formation of an opaque absorption wave travelling out of the solenoid back toward the focusing lens. Target burns give direct evidence for trapped laser beam propagation along the plasma column.
Development of microwave discharge spots in neon and helium gas by submicrosecond pulses
Authors: Kustom Robert L. , Fuja Raymond E.
Published: February 2003

Microwave discharges were developed in pure neon, pure helium, and 90%-10% neon-helium gas around the trajectory of high-energy charged particles by applying submicrosecond pulses shortly after the passage of the particle. The pulse width and amplitude of the discharge field were varied so that the effect on the discharge spot development could be observed. All measurements were made at room temperature and atmospheric pressure. The discharge chamber is a partially dielectric-loaded waveguide operating in the TEM mode at 1300 MHz so that the discharge fields are uniform over the gas volume.
Ultraviolet photoemission study of cesium oxide films on GaAs
Authors: Gregory Paul E. , Spicer W. E.
Published: February 2003

Ultraviolet photoemission energy distribution curves (EDC’s) have been measured from a GaAs (110) surface covered with Cs oxide layers of varying thickness. There is no evidence of emission from Cs oxide in the EDC’s from GaAs with a surface treatment that produces optimum yield, but structure characteristic of the GaAs is present in the EDC’s. However, EDC’s characteristic of bulk Cs oxide were measured from GaAs with a thick (at least several molecular layers) Cs oxide surface layer, but no structure characteristic of the GaAs was present in the EDC’s. Compared to the GaAs with the optimum surface treatment, this thick Cs oxide film produced yield spectra having a higher photoemission threshold and a lower yield throughout the photon energy range studied (1.4⩽ hν⩽11.6 eV). These measurements indicate that the Cs oxide layer required for activation of GaAs to negative electron affinity is so thin that the Cs oxide layer does not have bulk properties which can be detected by photoemission. Measurements similar to those reported here on narrower-band-gap III-V alloys should determine if the thickness of the Cs oxide layer required for activation increases with decreasing band gap or is independent of band gap.
High-voltage vertical multijunction solar cell
Authors: Soukup R. J.
Published: February 2003

The vertical multijunction solar cell with covering lens is a photovoltaic device which promises efficiencies greater than that predicted under ideal conditions for any other structure. The mathematical analysis presented here illustrates this statement. In addition the structure described here is capable of a high-voltage output for small solar cell dimensions, a feature which makes this device attractive for many applications where other designs are impractical. The analysis predicts the output short-circuit current, open-circuit voltage, maximum power, and an efficiency of 21% for a silicon homojunction solar cell.
Theoretical temperature dependence of thin-film transistors with traps
Authors: Refioglu H. Ilhan , DeMassa Thomas A.
Published: February 2003

The temperature dependence of CdS thin-film transistors with exponentially and uniformly distributed traps in the semiconductor is studied. The theory showed that the logarithm of mobility is linearly dependent upon the reciprocal of temperature. According to the theory, the mobility was gate voltage sensitive—mobility increasing with gate voltage. Also, mobility values were reduced for TFT’s with higher trap densities as expected. These results are consistent with previous experimental observations and results. Additionally, the variation of drain current with temperature was found to be in good agreement with experiment.
Point defects, localized vibrational modes, and free-carrier absorption of Al-doped CdTe
Authors: Dutt B. V. , Al-Delaimi M. , Spitzer W. G.
Published: February 2003

Infrared absorption bands attributable to the localized vibrational modes for several Al-related point defects have been observed for CdTe. The proposed defects, their point-group symmetries, and the vibrational frequencies at 80 °K in cm−1 are as follows: AlCd, Td, 299; AlCd-VCd, Cs, 282,287,326; AlCd-SbTe, C3v, 279,334; AlCd-CuCd, Cs, 291,294, 310; AlCd-AgTe or AlCd-Agi, C3v, 293,314; AlCd-AuTe or AlCd-Aui, C3v, 292,313; and possibly AlCd-AuCd, Cs, 288 (two unresolved bands), 326. The Al and Sb were introduced during crystal gwoth and the Cu, Ag, and Au by saturation diffusions. Annealing of CdTe:Al with [Al]∼1×1019 cm−3 in unsaturated Cd-rich atmospheres produced electron concentrations of 2×1018 and 2×1017 cm−3. Free-carrier absorption measurements at 298 and 80 °K give a nearly temperature-independent absorption coefficient with a frequency dependence of ω−3 after ther higher carrier density anneal with ω−4 for the lower carrier concentration. The free-carrier absorption results are compared with previously reported data and also recent theoretical calculations for CdTe which predict, under appropriate conditions, α∼ω−3 for the polar optical mode scattering and α∼ω−4 for ionized impurity scattering.
Liquid-phase epitaxial growth of thin GaAs layers from supercooled solutions
Authors: Toyoda Nobuyuki , Mihara Minoru , Hara Tohru
Published: February 2003

A technique for the liquid-phase epitaxial growth of thin GaAs layers has been developed. This technique uses supercooled solutions free from GaAs precipitates. With the amount of the initial supercooling in the range of 1–10 °C, very smooth surfaces with a roughness smaller than 0.01 μm are obtained for layers thinner than 1μm. The layer thickness data agree well with the diffusion theory equation by assuming that the diffusion coefficient of As in Ga is 4×10−5 cm2/sec at 800 °C. The thickness uniformity within a wafer is better than ±5%, and the thickness reproducibility among different runs is within ±7%. The carrier concentration is also well controlled.
Diffusion-controlled dissolution of planar, cylindrical, and spherical precipitates
Authors: Brown L. C.
Published: February 2003

The results of a theoretical study of diffusion-controlled dissolution of planar, cylindrical, and spherical precipitates are presented. Graphical relationships between the precipitate size and the dissolution time are developed for a constant diffusion coefficient. The validity of various approximate solutions is considered and it is shown that the invariant-interface treatment provides the best approximation. In this development the composition profile is considered independent of the movement of the phase interface. For concentration-dependent diffusion coefficients, the same dissolution curves can be used, but the time axis must be multiplied by De, an effective diffusion coefficient taken from the plot of diffusion coefficient vs composition. All three precipitate shapes have De equal to the interface value of the diffusion coefficient at very high saturations. At low saturations De is equal to ?, the weighted mean coefficient for spherical precipitates, to ?, the first moment of the diffusion coefficient about the matrix composition for planar precipitates, and to (?+?)/2 for cylindrical precipitates. Procedures for determining De at other values of saturation are discussed.
ac photoresponse of a large-area imaging CdS/CdTe heterojunction
Authors: Fraas L. M. , Bleha W. P. , Grinberg J. , Jacobson A. D.
Published: February 2003

Experimental data are presented for the photosensor-substrate structure presently used with the ac liquid-crystal projection light valve. This structure consists of a thin film (sputter deposited) of n-type CdS on which is evaporated a thin film of p-type CdTe. In an earlier publication, a model was presented which describes the photosensitivity of this structure in terms of the depletion-width photocapacity of the charge-storage diode formed by these two coatings. The experimental data presented here correlate well with this model. Among the data presented are data on light-valve display, photosensor gray scale, and response time. The response-time data are of particular interest because they show that the projection-light-valve photosensor is capable of operation at near-TV rates. The agreement of the experimental data with model and extrapolation from the model imply that large improvements in sensitivity and response time are still quite possible.
Magnetic field effects on the emission law of electron current from cathodes
Authors: Goldstein Shyke A.
Published: February 2003

The Child-Langmuir emission law is corrected to include magnetic field effects. The treatment is performed in local Cartesian coordinates near the cathode surface and all the terms obtained include first-order relativistic effects. The effect of space charge flowing back to the cathode is also considered. The importance of using the corrected emission laws in the simulation of relativistic diodes is discussed.
Space-charged limitation of radiation-induced secondary-electron emission currents in evacuated diodes
Authors: Gianino Peter D. , Costello Thomas M.
Published: February 2003

When a diode is bombarded with high-energy radiation, the current density of low-energy secondary electrons flowing in the interelectrode gap may experience space-charge limitation. In this paper an evacuated planar diode is considered in which the two electrodes may be of dissimilar materials, have different saturation emission current densities, and be subjected to an externally applied potential difference. It is shown in detail how Lindsay and Parker’s analysis pertaining to space-charge effects on thermionic emission in a similar diode configuration can be carried over in its entirety to the present problem with the substitution of just three parameters. Their method is extended so that one can quantitatively specify the threshold conditions at which space-charge effects just begin to occur, the voltage regimes over which they are valid, and their magnitudes throughout this regime. Generalized solutions are presented and graphed showing how the net current through the diode varies as a function of voltage. Heretofore, such quantitative evaluations have not been available for the planar-diode case under such generalized conditions.
Raman scattering from hydrogen and deuterium dissolved in silica as a function of pressure
Authors: Hartwig Charles M.
Published: February 2003

Studies of the Raman scattering from hydrogen and deuterium dissolved in vitreous silica at 90 °C and at pressures from 66 to 849 atm have been performed. The Raman spectra are interpreted to give information about the physics and thermodynamics of dissolution. In particular it is shown that: (1) hydrogen dissolves as a molecule, (2) the dissolved molecules occupy confining interstices and bind only weakly to the silica, and (3) the solubility saturates at higher pressures when the available interstices become filled. The results are explicable using classical thermodynamics and a physical rather than chemical model for dissolution.
Shear-stress trajectories produced by ballistic impact
Authors: Rolsten R. Fred , Lairmore Bill Joe
Published: February 2003

Plastic distribution of stresses in a metal plate under ballistic impact can result in slip lines which can be visibly seen as two orthogonal families of logarithmic spiral trajectories. These spirals can be produced dynamically in oxide surface coatings of steel plate ballistically impacted. The visible spirals in the oxide coating can be described mathematically by assuming a Mohr-Coulomb yield surface with a friction angle of zero. The mutally orthogonal trajectories are continuous lines without breaks, and when the elastic steel body is strained beyond the elastic limit the failure lines follow these trajectories. This is the first time that Lüder bands have been measured under the dynamic conditions described so that not only theories of ideal plasticity are at issue, but large deformation in dynamic plasticity as well.
Free-induction nuclear-magnetic-resonance line shapes of various liquid-sample configurations and the diffusion constant of a liquid crystal by spin echo
Authors: Bossard P. R. , Cicerone V. J. , Karra J. S.
Published: February 2003

Expressions are derived which describe the line shape of magnetization due to the nuclear magnetic moments of a sample placed in a large homogeneous constant magnetic field (H0) with a small magnetic field gradient (G) superimposed on the constant field. The study of the diffusion constant by the spin-echo technique basically involves the superposition of a magnetic field gradient on the constant magnetic field. Therefore, the precise measurement of the magnitude of the magnetic field gradient is required in order to deduce the diffusion constant accurately. The line shape of the free-induction nuclear-resonance signal depends not only on the magnetic field gradient, but also on the shape of the sample holder. Line shapes for spherical, cylindrical, and cubic sample holders were derived and experimentally verified by the free-induction nuclear magnetic resonance of protons in water. Magnitudes of the magnetic field gradients were obtained precisely from the line shape of the free-induction signal. Using the spin-echo technique, the diffusion constant of p-methoxybenzylidene-p′-n-butylaniline (MBBA), a liquid crystal in nematic phase, was measured at room temperature.
Generation lifetime investigation of ion-damage gettered silicon using MOS structure
Authors: Nassibian A. G. , Browne V. A. , Perkins K. D.
Published: February 2003

Gettering of undesirable generation impurities by O and Ar implant damage layer has been investigated by transient response of MOS capacitors. One-half of each Si wafer was masked against the implanting ion beam and comparison was made between the two halves of each wafer by deducing the generation lifetime from the C-t measurements. The implant dosage was 1016 cm−2 and ion energy 200 keV. The gettering anneal at 1070 °C was also the gate oxidation. The generation lifetime from 1–15 μs of the control half was increased to as high as 200 μs after both O and Ar implants. The results with O were more reproducible than with the Ar-implanted Si wafers; however, the largest increase in generation lifetime was observed with the Ar getterered wafer. It is proposed that there are generation centers other than the generation impurity centers that cannot be removed by gettering methods.
Determination of deep levels in Cu-doped GaP using transient-current spectroscopy
Authors: Wessels Bruce W.
Published: February 2003

A method of determining deep levels in semiconductor junctions by observation of the temperature dependence of transient-current decay is described and applied to Cu-doped GaP. It is shown that the important deep-level parameters including trap energy, capture cross section, concentration, and recombination rate can be obtained. For Cu-doped GaP, several trapping levels were observed with energies of 0.50, 0.60, and 0.82 eV. Capture cross sections of these levels were of the order of 1×10−16 cm2.
Amplitude of ferromagnetic spin-wave resonance in thin films
Authors: Wilts C. H. , Ramer O. G.
Published: February 2003

The effect of conductivity on the spin-wave spectrum of thin Permalloy ferromagnetic films has been investigated. If conductivity effects are included and a simple surface anisotropy is assumed, it is known that the calculated mode locations and amplitudes for Permalloy films are in excellent agreement with some experimental data in the range 800–2700 Å in thickness. If conductivity effects are omitted, a much simpler calculation is possible, but the error in mode location and amplitude has been unknown. For both perpendicular and parallel resonance geometries, detailed calculations reported here have shown that mode locations are not significantly affected over the above thickness range, and that the main mode amplitude is in error by only 20% at 800 Å thickness. However, for 2000 Å thickness, the main mode amplitude is in error by a factor of 2.5.
Some remarks on saturation of amplified spontaneous emission
Authors: Coisson R. , Perrone M. R.
Published: February 2003

Analytical (approximate) solution of rate equations for amplified spontaneous emission in a two-level system, in the case of ’’fast’’ pumping, shows the mutual dependence of some parameters characterizing amplification and saturation, such as critical time (or critical length), saturation (or peak) time, and peak power. The spontaneous emission can be accounted for by an equivalent number of initial photons. These results are compared with numerical computer solutions for the N2 laser.
Homogeneous ion combination coefficients in sulphur hexafluoride
Authors: Wilson Derek E. , Quiring Walter J. , Armstrong David A.
Published: February 2003

The homogeneous ion neutralization coefficient in SF6 has values of 1.0±0.1, 1.2±0.1, 1.1±0.1, and 1.2±0.7×10−6 cm3 s−6 respectively at 150, 356, 550, and 603 Torr for ions created by pulses of x rays. The results are compared with calculated three-body neutralization coefficients for monomer and dimer ions.
Electron trapping by radiation-induced charge in MOS devices
Authors: Aitken J. M. , Young D. R.
Published: February 2003

Electron trapping by positive charge centers induced in MOS structures by exposure to x rays has been studied by the avalanche injection technique. Five electron traps with cross sections ranging from 10−13 to 10−19 cm2 have been measured. Two of these account for the majority of positive charge in the SiO2 and the remaining three are associated with positive or neutral centers in the oxide.
Shear strength of metal-sapphire contacts
Authors: Pepper Stephen V.
Published: February 2003

The shear strength of polycrystalline Ag, Cu, Ni, and Fe contacts on clean (0001) sapphire has been studied in ultrahigh vacuum. Both clean metal surfaces and surfaces exposed to O2, Cl2, and C2H4 were used. Auger electron spectroscopy was used to assess both the cleanliness of the surfaces and the approximate coverage of O, Cl, and C after exposure to the gases. The results indicate that there are two sources of strength of Al2O3-metal contacts: an intrinsic one that depends on the particular clean metal in contact with Al2O3 and an additional one due to intermediate films. The shear strength of the clean metal contacts correlated directly with the free energy of oxide formation for the lowest metal oxide, in accord with the hypothesis that a chemical bond is formed between metal cations and oxygen anions in the sapphire surface. Contacts formed by metals exposed to chlorine exhibited uniformly low shear strength indicative of van der Waals bonding between chlorinated metal surfaces and sapphire. Contacts formed by metals exposed to oxygen exhibited enhanced shear strength, in accord with the hypothesis that an intermediate oxide layer increases interfacial strength. It is suggested that the strong oxide-oxide bond is due to the establishment of interfacial bonds associated with complex oxide (spinel structure) formation. It was also found that C2H4 exposures increased the strength of the Fe contact, but had no effect on the other contacts.
Stage-I recovery of prequenched and electron-irradiated pure aluminum and of the alloy Al-15 ppm Ag
Authors: Rizk R. , Loreaux Y. , Vajda P. , Maury F. , Lucasson A. , Lucasson P. , Dimitrov C. , Dimitrov O.
Published: February 2003

High-purity Al and the alloy Al-15 ppm Ag have been irradiated with electrons at liquid-helium temperatures. The influence of various parameters (electron energy and dose, impurity content and the, presence of excess vacancies introduced by prequenching or irradiation doping) upon the annealing spectra of the radiation-induced residual electrical resistivity was determined. Besides the usually observed recovery substages in stage I ( IB, IC, ID, and IE), we have found several supplementary structures labelled IA (at 14–15 K), IC′ (at 26–27 K), ID′ (at 33 K), ID″ (at 39 K), and IF (between 53 and 59 K). The observed characteristics are compatible with the attribution of the substages IA, IB, IC′, and IC to close-pair recombination; ID′, ID, and ID″ to correlated migration of interstitials; IE to the recombination of freely migrating interstitials; and IF to the migration of diinterstitials.
Mobility of arrays of dissociated and superlattice dislocations in an internally stressed solid
Authors: Karihaloo B. L.
Published: February 2003

A study is made of the mobility of planar arrays of dislocations of Burgers vector b that are either separated into their component partials or are of the superlattice type and are contained in an internally stressed solid, the stress being generated by a preexisting coplanar obstacle dislocation of Burgers vector mb. The aim here is to estimate the effect of the internal stress and the fault energy on the separation between the components of the first discrete dislocation since the latter plays an important part in a wide range of physical phenomena. All the mobile complete dislocations except the leader are either smeared into a continuous distribution or are replaced by a superdislocation of appropriate Burgers vector. These two approaches, which lead to lower and upper bounds for the separation distance, are shown to give fairly close results for small m.
Similarity of Hall-conductivity integrals for metals and semiconductors
Authors: Rater L. M. , Mackey H. J.
Published: February 2003

The expressions for the Hall conductivity of a spherical quadratic-band semiconductor for various power-law scattering mechanisms are evaluated numerically as functions of the Fermi energy. Comparison of these results to curves based on the simple constant-τ model shows there is only a slight deviation of geometric form which diminishes as the Fermi energy εF approaches the band edge and vanishes as εf moves deep into the band. This similarity explains the fact that the τ=const. model can be used to determine conductivity mobility and carrier density from σxy curves with surprising accuracy over a wide temperature range. Application is made to n-InSb.
Theory of laser heating of solids: Metals
Authors: Sparks M.
Published: February 2003

Calculations of the transient and steady-state temperature rise T of laser-irradiated metals indicate that values of the intensity (irradiance) If that cause failure change drastically under different experimental conditions, such as the degree of plasma ignition on the surface and the relative magnitudes of the laser-beam diameter, sample thickness l, lateral dimension, and thermal diffusion distance. The dependence of If on material parameters such as thermal conductivity and heat capacity is also quite different, depending on the experimental conditions. The results suggest that the highest of the recently measured copper-damage thresholds of 125–750 J/cm2 for 0.6-μsec pulses at 10.6 μm are likely to be at or at least quite near the intrinsic limit set by the simple process of melting that results from the intrinsic absorption. The theoretical intensity at which the cavity mirrors of recently developed xenon uv lasers fail is in good agreement with the experimental value. The theoretical value of T of metals irradiated for 20 sec with 10.6-μm radiation is two orders of magnitude too small to explain recent experimental results. It is suggested that the discrepancy is related to plasma ignition at the sample surface. The steady-state value of T for metals cooled with a surface-heat-transfer coefficient h is not reduced substantially by increasing the cooling efficiency past a certain point (h≳hl≡K/l). For short time t<τ, where the characteristic time τ depends on both l and h, cooling the metal is not effective is preventing the temperature rise.
Plasma diagnostics using laser-excited coupled and transmission ring resonators
Authors: Haas Roger A.
Published: February 2003

In this paper a simple two-level laser model is used to investigate the frequency response of coupled-cavity laser interferometers. It is found that under certain circumstances, often satisfied by molecular gas lasers, the frequency response exhibits a resonant behavior. This behavior severely complicates the interpretation of coupled-cavity laser interferometer measurements of rapidly varying plasmas. To circumvent this limitation a new type of laser interferometer plasma diagnostic with significantly improved time response was developed. In this interferometer the plasma is located in one arm of a transmission ring resonator cavity that is excited by an externally positioned laser. Thus, the laser is decoupled from the interferometer cavity and the time response of the interferometer is then limited by the Q of the ring resonator cavity. This improved time response is acquired without loss of spatial resolution, but requires a more sensitive signal detector since the laser is no longer used as a detector as it is in conventional coupled-cavity laser interferometers. Thus, the new technique incorporates the speed of the Mach–Zender interferometer and the sensitivity of the coupled-cavity laser interferometer. The basic operating principles of this type of interferometer have been verified using a CO2 laser.
Isotopic analysis by a Raman-spectrometric method
Authors: Kato Daisuke
Published: February 2003

A versatile Raman-spectrometric method for a prompt and reliable isotopic analysis is described. It makes real-time analysis possible if needed. The Raman spectrometric method is applied to the analysis of deuterium in a mixture of D2O and H2O liquid. The Raman-spectrometric determination is found to agree closely with the volumetric one. Sensitivity of Raman spectrometry is confirmed well under 1 mol%.
Determining particle sizes by homodyne spectroscopy of multiply scattered light
Authors: Hochberg A. , Low W.
Published: February 2003

The determination of the excess broadening of the spectrum of multiply scattered light compared with the spectrum of singly scattered light can be used for measurement of the size of the scatterers. The amount of broadening depends on the scattering direction, the concentration of scatterers, and the optical path. At backward scattering, a limiting value of the line width as a function of concentration is reached from which the size of the scattering particles can be determined.
Theory of isothermal dielectric relaxation and direct determination of trap parameters
Authors: Gupta H. M. , Van Overstraeten R. J.
Published: February 2003

A detailed theoretical study is made of the effect of dielectric relaxation on the isothermal I-V characteristics of a metal-insulator-metal structure in which the electrodes make blocking contacts with the insulator, in the ’’growth of cathodic depletion region’’ approach. We developed a method to plot nonsteady-state isothermal characteristics starting from the basic parameters, and we obtain expressions to directly determine the trap density and its space distribution in the insulator region from the experimental I-V characteristic. Finally, we discuss the various non-steady-state methods to determine trap density and the limitations of the methods.
Electroluminescence at high fields in silicon dioxide
Authors: Solomon P. , Klein N.
Published: February 2003

Electroluminescence was observed in thermally grown silicon dioxide films at fields larger than 7 MV/cm. The samples had semitransparent aluminum electrodes. As breakdowns were nonshorting, observations could be extended to fields at which breakdowns occur. The light emission was found to be proportional to the leakage current and the spectrum had a cutoff for energies below 2.5 eV. The quantum efficiency, 10−5–10−4 photon/electron crossing 1000 Å of insulation, was polarity independent. The luminescence does not seem to be connected with breakdown, but perhaps with trapping processes.
Quantitative low-energy x-ray spectroscopy (50–100-Å region)
Authors: Henke Burton L. , Taniguchi Kazuo
Published: February 2003

The quantitative analyis of emission spectra in the 10–100-Å region has become of considerable importance for high-temperature plasma diagnostics (106–107 °K region) and for molecular orbital and solid-state-band analysis. Because measurement intensities are typically low in these applications, achieving an optimum spectrographic measurement is essential. In order to present specific procedures and methods for optimizing and calibrating a low-energy spectrographic measurement, a molecular orbital analysis in the 70–90-Å region (S-LII,III emission spectra) has been carried out quantitatively in energy and intensity using a recently described single-crystal (lead stearate) spectrographic approach with about 1 eV resolution. Radiative yields, Y, for the radiation process being investigated are determined by the relation, Y=Z/(X0RSTQ), where Z is the area (intensity x angle) under the spectrographic line, X0 the excitation function, R (λ) the coefficient of reflection of the analyzer, S (λ) the effective source thickness, T (λ) the window transmission, and Q (λ) the quantum counting efficiency of the detector. The determination of each of these parameters has been considered in detail.
Aberrations due to linear fringe fields in a magnetic spectrometer
Authors: Kosiara Andrew A.
Published: February 2003

Electron trajectories in the median plane of a symmetric magnetic spectrometer are calculated. We consider a uniform-field window-frame magnet, with extended linearly increasing quadrupole fringe fields positioned symmetrically with respect to the magnetic pole boundaries. Relativistic electron equations of motion are solved numerically on a computer to determine aberrations as a function of the width and strength of the fringe fields and the angular divergence of the electron beam. The limit on resolution due to the aberrations is between 2.4×10−5 and 3.2×10−3 eV for the investigated spectrometer geometries at the beam energy of 100 keV.
Measurements on a superconducting X-band structure for linear accelerator application
Authors: Arnolds G. , Heinrichs H. , Hoffmann W. , Mayer R. , Minatti N. , Piel H. , Proch D. , Weingarten W.
Published: February 2003

We report on rf tests of a superconducting disk-loaded waveguide. A three-cell 8-GHz structure, fabricated of two pieces of bulk niobium, has been excited to high-field levels at temperatures below 1.8 °K. The cavity was operated in a π/2 standing-wave mode. Peak electric fields of 37 MV/m, peak magnetic fields of 590 Oe, and effective accelerating fields of 8.0 MV/m were generated at a microwave power level of 8 W/m. The lowest surface resistance that could be obtained was 44 nΩ corresponding to a Q factor of 4×109 at 1.3 °K. These results were achieved using electropolishing and annealing at 1400 °C under moderate vacuum conditions as surface treatments. The fields are limited by fast magnetic thermal breakdown. No electron loading was observed.
Domain walls in bubble films. IV. High-speed wall motion in the presence of an in-plane anisotropy
Authors: Schlömann Ernst
Published: February 2003

The effect of an in-plane anisotropy (such as occurs in orthoferrites due to the orthorhombic crystal structure) on the static and dynamic wall structure has been calculated for walls that are either parallel (ψ=0) or perpendicular (ψ=π/2) to the secondary (i.e., in-plane) anisotropy axis. The results are described in terms of a parameter η=Δ/2πM20, where Δ is the strength of the in-plane anisotropy and M0 the saturation magnetization. For ψ=0, the critical points of the static wall structure move towards the film surface as η increases. For ψ=π/2, they move towards the midplane of the film where they merge for η→1. For ψ=π/2, η≫1, an untwisted wall becomes energetically favored over the twisted wall. The critical velocity at which wall motion becomes unstable is strongly dependent on η. For η<1 the lowest velocity threshold is due to Bloch-line nucleation at a critical point, for ψ=π/2, η<1, it is due to punch-through of the already existing Bloch line. For ψ=0 the critical velocity generally increases with increasing η. For ψ=π/2 the nucleation threshold at first decreases with increasing η and then increases. The punch-through threshold is substantially independent of η. For η≫1 the critical velocities for a film are substantially the same as for an infinite medium.
Improved yields for MOST’s using ion implantation
Authors: Brockman H. E.
Published: February 2003

Conventionally diffused source and drain polysilicon gate MOST’s commonly exhibit one type of fault, namely, that of polysilicon-to-diffusion short circuits. Investigations into the yields of large-area devices fabricated using ion-implanted sources and drains are compared with those of diffused structures. An improved technology for the chemical shaping of the polysilicon gates, which improves the yields for both types of devices, is also described.
Blue-green luminescence in ZnO: Excitation by 20-eV kinetic energy gas-phase positive ions
Authors: Kramer Jerry
Published: February 2003

The characteristic blue-green luminescence of phosphor-grade ZnO has been observed during the interaction of low-kinetic-energy (20–40 eV) gas-phase positive ions with ZnO. The luminescence is attributed to hole formation and injection followed by radiative recombination. The light output has been examined as a function of ion kinetic energy and the ionization potentials of different neutral precursors. The light decays by a first-order process with a 1/e lifetime of 6 μsec. The efficiency of ion excitation is estimated to be about one photon/30 ions for 40-eV kinetic energy He+ ions.
Junction-FET dosimeter
Authors: Tomimasu T. , Yamazaki T.
Published: February 2003

The performance of a new junction-FET dosimeter and its application to the beam profile measurement are presented. One of the two junction FET’s making up an astable multivibrator is used as a small-size (∼0.4×0.4 mm) high-level dose detector. The irradiated dose can be estimated by the amount of the decrease of the oscillator period of the multivibrator. The distinct advantages in its small size and superior resistive property to radiation effect enable us to measure the cross-sectional profile of the electron beam from a linac with high spatial resolution of about 0.4 mm.
Nucleus growth rate of vacuum-deposited thin films
Authors: Lewis B. , Fujiwara S.
Published: February 2003

Doubt has recently been expressed as to the validity of the capture numbers given by surface-diffusion equations when the ratio of capture radius re to diffusion distance X is small. The problem cannot be resolved by growth experiments because of the difficulty of reliable measurements of capture numbers for small nuclei. However, comparison with the results of Monte Carlo simulation of migration over square and hexagonal lattices shows that errors in the surface-diffusion relation are significant only when both re and X are small.
Observation of ghost peaks in GaAs single-heterostructure light-emitting diodes
Authors: Martinez A. Lastras , Konagai M. , Takahashi K.
Published: February 2003

The spectra of GaAs SH LED’s, which are obtained by LPE growth of Zn-doped (GaAl)As on Si-doped n-type GaAs substrates, are reported. The spectra are shown to be composed of two peaks. The relative peak intensity of the two peaks is found to be dependent on both the temperature and the injection level. The intensity of the low-energy peak is found to be almost completely eliminated after covering the sides of the diode in order to avoid edge emission. It is concluded that the low-energy peak is produced by selective absorption of the light traveling in a direction parallel to the junction plane and going out through the edges of the diode. This result is in contradiction with a previous report dealing with the same kind of structure.
Fixed charge in Cr-metallized MOS capacitors
Authors: Lewicki G.
Published: February 2003

Flat-band voltages, surface-state densities, and Fowler-Nordheim tunneling characteristics were measured in MOS capacitor structures with oxide thicknesses ranging from 30 to 400 Å. The oxides were grown in dry oxygen on p-silicon; the metallization was gold on top of chrome. The results show the silicon-silica interface to be independent of oxide thickness down to a value of at most 40 Å. They also suggest the existence of charge not only at the silica-silicon interface but also at the metal-silica interface. The charge near the metal has the characteristic of a double layer. Right next to the interface it is negative and of magnitude 1019 electron charges/cm3. It goes to zero some 75 Å into the oxide and then increases to reach a maximum positive value on the order of −1018 electron charges/cm3. Approximately 150 Å into the oxide it goes to zero. The surface charge at the silicon-silica interface was as in previous investigations found to be positive and, at flat band, on the order of −3×1011 electron charges/cm2.
Hall-effect measurements in Cd-implanted GaAs
Authors: Shin B. K. , Look D. C. , Park Y. S. , Ehret J. E.
Published: February 2003

Cadmium ions were implanted in GaAs crystals at 135 keV to doses ranging from 1012 to 1016 ion/cm2 at room temperature. Sheet-resistivity and Hall-effect measurements were carried out as a function of temperature, 4.2–300°K, after annealings at 700, 800, or 900°C in an Ar ambient. The sample surfaces were protected with pyrolytically deposited Si3N4. Significant p-type conduction was observed when samples with doses ≳1013 cm−2 were annealed at ≳700°C. For doses below 1014 cm−2 nearly complete electrical activity was attained after an 800–900°C anneal. The Cd profiles were determined by differential Hall-effect measurements in conjunction with the acid-etch layer-removal technique. Above about 800°C diffusion becomes important and significantly flattens the implantation profile.
Growth and properties of silicon films on aluminum-nitride films on sapphire
Authors: Wang K. L. , Lakin K. M. , Liu J. K.
Published: February 2003

Epitaxial layers of silicon have been grown on aluminum-nitride films on sapphire by vapor-phase deposition using pyrolysis of silane. The structure of the silicon films is examined by the reflection electron diffraction technique and shown to be a single crystal of orientation (100)Si∥ (112̄0)AlN∥ (011̄2)Al2O3. Lattice matching between Si and AlN along orthogonal axes of [100] Si are 0.78 and 9.0%, respectively. The growth and electrical properties of silicon films are described in some detail. Resistivity and mobility of p-type and n-type silicon films have been measured as functions of temperature. The maximum mobility of 150 cm2/V sec has been obtained for film thickness between 1 and 4 μm. The aluminum autodoping effect upon these films is found to be higher than that of silicon films on sapphire used as control samples.
Effects of electron-beam irradiation on the properties of CVD Si3N4 films in MNOS structures
Authors: Ma T. P. , Yun B. H. , DiMaria D. J. , Scoggan G. A.
Published: February 2003

The influence of energetic electron-beam irradiation on the trap properties of CVD Si3N4 films in MNOS structures has been investigated by means of charge-centroid and conduction measurements. Within the limit of our measurements, the results indicate that electron-beam radiation up to 6.6×10−5 C/cm2 does not affect the trap properties of the nitride, such as the density, capture cross section, and average capture distance, although the charging of these traps may be altered. Furthermore, the effects of radiation in the Si-SiO2 interface properties of MNOS structures have been examined by the C-V method. For an MNOS capacitor with relatively thick oxide, radiation was found to cause a significant increase in the density of surface states, the effective insulator charge, and the slow states. For an MNOS capacitor with very thin oxide, by contrast, the radiation causes a significant change only in the insulator charge—none in the surface states. Since the properties of the nitride have not been affected by the irradiation, the difference in effects must be due to the difference between the oxide films. An explanation based on a broken-bond model is consistent with the results.
Thermal demagnetization and the nonlinear reversible loop
Authors: Feu A.
Published: February 2003

Thermal and cyclic demagnetization produce different magnetic states in polycrystalline ferrites. In subsequent magnetization processes from the initial demagnetized state, the former achieves a nonlinear reversible cycle, while the latter follows the usual Rayleigh behavior. Both Néel’s and Globus’s theories are confirmed in a qualitative way.
Nb-Nb thin-film Josephson junctions
Authors: Hawkins Gilbert , Clarke John
Published: February 2003

We report a simple technique for the construction of thin-film Josephson tunnel junctions in which both electrodes are of sputtered Nb. A thin (8–20 Å) layer of Cu evaporated over the first oxidized Nb film prevents the formation of supershorts between the Nb films. The junctions are extremely rugged, and do not require protection against condensation of water vapor. A number of junctions have been stored at room temperature for six months and cycled to liquid-helium temperatures 50 times without significant deterioration. Critical currents in the range 1 μA<Ic<10 mA may be achieved with an accuracy of ±20%. The dependence of junction characteristics on temperature, oxidation time, and Cu thickness is described. The junctions are particularly suited to the fabrication of practical devices such as SQUID’s.
Optimizing the shape and size of a uniform-current-density magnet to maximize the field at constant power
Authors: Haignere E. B. , Potter W. H.
Published: February 2003

A general method for determining both the shape and size of a uniform-current-density air-core magnet that maximizes the magnetic field at a particular point for a given total power is discussed. This method imposes no restrictions on the cross-sectional shape of the coil or coils, and the method handles any arbitrarily imposed constraints on the shape. As examples of the method we review the optimal solenoid with circular windings and discuss the optimal coils to produce a rotating magnetic field using either two-phase or three-phase power.