bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical characterization of deep O implants in GaAs
Authors: Monemar B. , Blum J. M.
Published: February 2003

Optical methods for characterization of deep implants in semiconductors are evaluated, notably optical absorption below band-gap energies, and photoluminescence. Results from such measurements on 2–3-MeV O implants in GaAs are presented, and discussed with emphasis on possible physical interpretations of defect properties. The spectral shape of optical absorption from doses ?1014 cm−2 indicates that a description of initial damage as amorphous regions is not appropriate. It seems possible to qualitatively explain this spectral behavior before anneal as mainly due to the electronic states caused by disrupted bonds along the ion track. Photoluminescence (PL) spectra of implanted material (before as well as after anneal) can give specific information on the various defect complexes created by the treatment. Furthermore, the intensity reduction of PL due to residual recombination centers is by far the most sensitive way of detecting residual damage in the material, and thus offers several applications for evaluation of, e.g., annealing efficiency or, for low doses, annealing during implantation. Such measurements also show that there is an apparent orientation dependence on the level of damage introduced, so that 〈110〉 is most favorable, while 〈100〉 and especially 〈111〉 orientation of the GaAs surface resulted in higher damage. A characteristic annealing temperature of 460±30 °C for PL efficiency was found in n-type as well as p-type material, indicating annealing of important nonradiative recombination centers at this temperature. The ultimate result of annealing is critically dependent on the encapsulation technique, and we found that neither Al2O3 nor Si3N4 prepared by sputtering at 400 °C are satisfactory as capping material on n-GaAs, although they caused a slight reduction on the rate of Ga outdiffusion during anneal. Results from PL-profiling experiments are also discussed.
Contact resistance studies of sintering using ultra clean copper surfaces in ultrahigh vacuum
Authors: Massachi Manouchehr
Published: February 2003

The mechanism of mass transport during sintering of copper was determined by measuring the contact resistance as a function of neck growth. The decrease in resistance, due to the growth of a neck between two tips of copper rods in contact, was observed as a function of time and temperature in the range 147–947 °C. At temperatures between 515 and 947 °C, the neck growth proceeded according to a (1/7) -power law, consistent with a surface diffusion model.
Optical characteristics of twisted nematic liquid crystals: Application to the improvement of the scanning capability in matrix displays
Authors: Goscianski Michel
Published: February 2003

The scanning limitations of a liquid-crystal matrix display due to the lack of sharpness of the transmission characteristic can be extended in the case of the twisted nematic configuration. Indeed, the output polarization from an electrically excited cell, generally elliptic, can be made linear when the linear input polarization is rotated from the molecular alignment at the entrance of the cell. Thus it is possible to decrease the transmission of the nonselected dots while keeping a suitable transmission for the selected dots. A theoretical treatment of the output polarization versus the input polarization and the π/2-twisted nematic parameter u=2dΔn/λ shows the existence of linear output polarizations. Experiments made on a 64×64-dot matrix display agree with the predictions. With a duty cycle equal to 1/128, the contrast ratio is 20 : 1, while the response time is 100 ms at 20 °C; the address and the data pulses, applied to the rows and to the columns, respectively, are V1=12.4 V and V2=±1.1 V.
Frequency dependence of photoacoustic spectroscopy: Surface- and bulk-absorption coefficients
Authors: Bennett Herbert S. , Forman Richard A.
Published: February 2003

Researchers seek improved ways to measure separately the surface- and bulk-absorption coefficients of highly transparent materials. The case in which a laser beam modulated at angular frequency ω passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived. An intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies as ω−1 and has a 90 ° phase shift relative to the modulated laser beam and for which the acoustic stress due to bulk absorption varies as ω−3/2 and has a 45 ° phase shift. In addition, expressions for the acoustic stress and phase shift which are valid for all frequencies are given. These expressions enable one to develop numerical procedures by which the surface- and bulk-absorption coefficients may be determined separately. Numerical examples for a representative laser glass and air (nitrogen) are given.
Piezoelectric method of determining mechanical properties of a small sandwich specimen at 30 to 200 kHz
Authors: Devine S. D. , Robinson W. H.
Published: February 2003

The piezoelectric composite oscillator vibrating either in the longitudinal or torsional mode enables the mechanical damping, strain amplitude, elastic modulus, and piezoelectric modulus of a specimen to be determined rapidly and accurately. Previously the technique has been developed for specimens of a length equal to a mutliple of half-wavelengths requiring a specimen size of ∼80×3×3 mm for 40 kHz. In this paper we develop the theory of the longitudinal technique for sandwich specimens of ∼1 to 10×3×3 mm which are cemented between two fused quartz rods to form a one-half-wavelength unit. We demonstrate the sandwich specimen technique by determining the compliance (S1111) of a 〈100〉 KCl single crystal without using its density and find that this value is in agreement with the published result. The equations for the ideal transformer ratio and strain amplitude for the sandwich specimen are confirmed experimentally by measuring the voltage from an α quartz specimen cemented between rods of α quartz, 〈110〉 CaF2, and 〈100〉 CaF2, respectively.
The reflection coefficient in stimulated parmetric backscattering
Authors: Yu Chung , Hsu Hsiung
Published: February 2003

The step-function approximation of the anomalous reflection coefficient in laser-induced parametric backscattering currently used in the theory of nonlinear laser plasma interactions is improved using a simple exponential derived from elliptic functions. The validity of the single-reflection analysis is reaffirmed.
cw laser oscillators in MeNdP4O12 (Me=Li,Na,K) at 1.32 μm
Authors: Otsuka Kenju , Miyazawa Shintaro , Yamada Tomoaki , Iwasaki Hiroshi , Nakano Jun’ichi
Published: February 2003

Room-temperature cw laser oscillation near 1.3 μm has been obtained in neodymium tetraphosphate lasers such as LiNdP4O12, NaNdP4O12, and KNdP4O12 using argon laser pumping. It was found that the LiNdP4O12 laser showed the smallest threshold pump power among them. cw laser oscillation properties, an effective emission cross section, and a resonant absorption of LiNdP4O12 at 1.32 μm were examined in comparison with those at 1.048 μm.
Selective epitaxial growth of single-crystal anthracene
Authors: Ono Takashi , Kimura Mitsuteru , Miyamoto Toshihiko
Published: February 2003

New techniques are described for preparation of a thin film of single-crystal anthracene and selective epitaxial growth on it. The anthracene substrate, several thousand Å in thickness, is grown from solution on a Pyrex glass plate by a new spinner technique. Epitaxial growth on the substrate occurs at a residual gas pressure of 1×10−3 Torr and at substrate temperature and crystal growth rate in the ranges 0–10 °C and 500–1000 Å/min, respectively. Epitaxial growth of anthracene does not occur on an Au substrate under similar conditions. An optical waveguide is demonstrated as an application of this selective epitaxial growth technique.
The influence of stripe width on the threshold current of double-heterojunction lasers
Authors: Ladany I.
Published: February 2003

Experimental measurements of the threshold current of oxide-isolated stripe lasers as a function of stripe width and p-layer resistivity are presented. A calculation of the influence of carrier outdiffusion has been made, including the effect of current leakage beyond the stripe edges. The calculated threshold increase is in substantial agreement with experiment for stripe widths down to about 10 μm. The data also yield an effective diffusion length of ∼7 μm for the lasers studied. Deviations between experimental and calculated thresholds occurring at stripe widths of 4–6 μm are represented by an empirical curve which is compared with previously published calculations of threshold gain.
Some optical properties of high-resistivity zinc sulfide
Authors: Joseph James Dean , Neville Richard C.
Published: February 2003

Measurements were made of the optical transmission properties of pure high-resistivity (≳1010Ω cm) zinc sulfide single crystals. Transmission measurements were made as a function of crystal thermal processing history. From the data, relative imperfection concentrations were calculated. In particular, the data exhibit a marked increase in the zinc vacancy concentration with temperature. This provides independent confirmation of evidence acquired in studies of Ohmic contacts and Schottky barriers on zinc sulfide.
Interaction of a CO2 laser beam with a shock-tube plasma
Authors: Box S. J. C. , John P. K. , Byszewski W. W.
Published: February 2003

The results of experimental investigations of the interaction of a CO2 laser beam with plasma produced in an electromagnetic shock tube are presented. The interaction was investigated in two different configurations: with the laser beam perpendicular to the direction of propagation of the shock wave and with the laser beam parallel to the direction of the shock wave. The laser energy was 0.3 J in a 180-nsec pulse. The plasma density was in the range 1017–1018 cm−3 and temperature was around 2 eV. Spectroscopic methods were used in the measurement of density and temperature. Direct observation of the path of the laser beam through the plasma was made by an image-convertor camera in conjunction with a narrow-band interference filter. The propagation of the laser through the plasma and energy absorption are discussed. The observed maximum increase in electron temperature due to the laser in the first configuration was 0.4 eV and the estimated temperature increase in the second configuration was about 2 eV.
Electron impact excitation cross sections and rates for hydrogen-like ions
Authors: Perez J. D.
Published: February 2003

A simple expression for the excitation cross sections and excitation rates of hydrogen-like ions is presented. A combination of Coulomb-Born and Born approximation calculations have been parameterized. The expression for the excitation cross section is continued below threshold in order to estimate electron capture cross sections.
Pulse velocity, power, and mode phase in a self-locked He-Ne laser
Authors: Chow C. N. Y. , Willenbring G. R. , Carruthers J. A.
Published: February 2003

Changes in pulse velocity and output power when a He-Ne 6328-Å self-locked laser becomes partially unlocked have been measured. The pulse velocity is greater by about 9 parts in 106, and the power is higher by about 0.5% for the locked laser. Measurements on mode phase in the self-locked laser show that the phase angles are not zero, and in a particular case one mode is lagging others by almost 60°. The experimental observations are in general agreement with analytical results for self-pulsing in a unidirectional ring laser.
Electrical compensation in semi-insulating GaAs
Authors: Zucca R.
Published: February 2003

Identification of the deep levels responsible for the electrical compensation of Cr-doped semi-insulating GaAs has been lacking in spite of the increasing importance of this material. Transport measurements on bulk-grown semi-insulating GaAs single crystals with three different Cr concentrations are presented to shed light on this problem. Alternative models for the electrical compensation are discussed. A detailed analysis of the temperature dependence of the resistivity shows that the ’’conventional’’ model in which deep Cr acceptors compensate residual shallow donors is incorrect. A more elaborate model which includes both a deep acceptor and a deep donor is proposed to properly interpret the experimental data. The deep donor level, located between 0.64 and 0.72 eV from the conduction band, is assigned to oxygen.
The photoelectrolysis of water using iron titanate anodes
Authors: Ginley D. S. , Butler M. A.
Published: February 2003

Single-crystal and polycrystalline samples of the iron titanates FeTiO3, Fe2TiO4, and Fe2TiO5 have been studied as anodes for the photoelectrolysis of water. Band gaps and flatbands for the various compositions have been determined and aging studies have been conducted which indicate electrochemical leaching of iron atoms from the surface.
Magnetostriction of single-crystal SmCo5 and of liquid-phase sintered SmCo5 permanent magnet material
Authors: Doane D. A.
Published: February 2003

This paper reports measurements of the magnetostriction in both single-crystal SmCo5 and in the liquid-phase sintered (LPS) SmCo5 permanent magnet material at fields up to μoH=21 T. By using a strain-gauge technique the changes in length in different crystallographic directions were measured as a function of the field applied perpendicular to the c axis. Extrapolation of one of the measurements shows that there would be a contraction perpendicular to the c axis of almost 10−3 cm/cm at saturation along the same direction. The magnetostriction had the expected field dependence in SmCo5 except for the measurement containing a contribution from shear. In demagnetized LPS material, the field dependence of the magnetostriction was altered in some cases from that in the single crystal. In one case, the field dependence changed dramatically following magnetization of the LPS material parallel to the c axis.
The tensile strength of di-ethyl ether using Briggs’s method
Authors: Apfel Robert E. , Smith Milton P.
Published: February 2003

We have used the centrifugal method for measuring the tensile strength of liquids in measuring the strength of di-ethyl ether. Modifications of Briggs’s method include an air turbine spinner, after Beams and Pickels, and a prepressurization scheme for assuring that the liquid wets all solid surfaces. The greatest tensile strength measured was 176 atm, which is within 10% of the predictions of homogeneous nucleation theory.
Seebeck measurements of rf sputtered nickel-chromium films
Authors: Wilhelm Ralph V. , Roland James P.
Published: February 2003

Thin films of nickel-chromium alloys (10% chromium) were produced by the radio-frequency (rf) sputtering technique. The Seebeck coefficient of these films was measured with a constant 10 °C differential up to 360 °C versus bulk Alumel wires. At higher sputtering power (400 w) with a water-cooled anode, the seebeck coefficient approached the bulk response to within 2-1/2%. At lower sputtering powers, oxygen was incorporated into the lower density films, causing a decrease in thermal emf. Depositions made at elevated anode temperatures also showed a degradation in thermal emf, probably due to increased film oxidation with temperature.
Electromigration of carbon in α-iron
Authors: Nakajima Hideo , Hirano Ken-ichi
Published: February 2003

Electromigration of carbon in α-iron has been investigated by the steady-state method to determine the effective charge number Z* of carbon as functions of the electric current density and the temperature in the ranges 97–867 A/cm2 and 550–850 °C, respectively. It has been found that the drift velocity of carbon is proportional to the electric current density, that is, Z* is independent of the electric current density, and Z* decreases from +12.2 to +3.6 with increasing temperature from 550 to 850 °C, showing larger temperature dependence in the ferromagnetic α-iron. This is explained in terms of the spin-disorder scattering model. Z* estimated from the electrical resistivity data depends on temperature in a way similar to that determined from the electromigration. From the dependence of Z* on the resistivity increment in α-iron due to solution of carbon, the true charge number of carbon has been determined to be about zero. Thus, it is concluded that the carbon ion is subjected not to the electrostatic force but to the drag force from the current carriers during electromigration.
A mechanism for liquid-phase epitaxial growth of nonequilibrium compositions producing a coherent interface
Authors: Hirth J. P. , Stringfellow G. B.
Published: February 2003

A model is presented for growth by so-called composition pulling, wherein an epitaxial deposit grows coherently but with a composition different from that which would be in bulk equilibrium with the liquid phase from which growth occurs. The breakdown of coherent growth occurs when a dislocation nucleates at a ledge at the growing solid-liquid interface. An expression for the critical condition for breakdown is presented.
Arsenic implantation into polycrystalline silicon and diffusion to silicon substrate
Authors: Tsukamoto Katsuhiro , Akasaka Youichi , Horie Kazuo
Published: February 2003

Arsenic implantation into polycrystalline silicon and drive-in diffusion to silicon substrate have been investigated by MeV He+ backscattering analysis and also by electrical measurements. The range distributions of arsenic implanted into polycrystalline silicon are well fitted to Gaussian distributions over the energy range 60–350 keV. The measured values of RP and ΔRP are about 10 and 20% larger than the theoretical predictions, respectively. The effective diffusion coefficient of arsenic implanted into polycrystalline silicon is expressed as D=0.63 exp[(−3.22 eV/kT)] and is independent of the arsenic concentration. The drive-in diffusion of arsenic from the implanted polycrystalline silicon layer into the silicon substrate is significantly affected by the diffusion atmosphere. In the N2 atmosphere, a considerable amount of arsenic atoms diffuses outward to the ambient. The outdiffusion can be suppressed by encapsulation with Si3N4. In the oxidizing atmosphere, arsenic atoms are driven inward by growing SiO2 due to the segregation between SiO2 and polycrystalline silicon, and consequently the drive-in diffusion of arsenic is enhanced. At the interface between the polycrystalline silicon layer and the silicon substrate, arsenic atoms are likely to segregate at the polycrystalline silicon side.
0.1–10-keV x-ray-induced electron emissions from solids—Models and secondary electron measurements
Authors: Henke Burton L. , Smith Jerel A. , Attwood David T.
Published: February 2003

Analytical models are presented describing the x-ray-excited emission of ’’no-loss’’ photoelectrons and Auger electrons and the energy distribution of emitted secondary electrons. The secondary electron energy distribution is given in terms of the electron kinetic energy EK, work function W, photon energy Eo, and mass photoionization coefficient μ (Eo), as proportional to Eoμ (Eo) EK(EK+W)−4. Techniques of electron spectral measurements utilizing uniform field preacceleration and limited acceptance angle spectrometers are discussed. Secondary electron energy distributions are measured at about 10−8 Torr from thick evaporated films of gold and aluminum at photon energies 277, 1487, and 8050 eV. The shapes of these distributions do not depend significantly upon photon energy. The full width at half-maximum (FWHM) of these distributions are 3.9, 6.7, and 4.4 eV for Au and ion-cleaned Au and Al photocathodes, respectively. The data agree well with the model predictions.
Use of stimulated scattering for ion temperature measurement
Authors: Pietrzyk Z. A. , Massey R.
Published: February 2003

The use of stimulated Brillouin and Compton scattering is proposed for measurements of ion temperature in a plasma. Experimental spectra are compared with existing theories. Possible applications are discussed. The advantages and disadvantages of this method over Thomson scattering are discussed.
Antenna-coupled infrared detectors
Authors: Schwarz S. E. , Ulrich B. T.
Published: February 2003

A theoretical study has been made of the use of antennas to couple radiation to infrared detectors. It is shown in general that for any detector characterized by a specific detectivity D, noise-equivalent power (NEP) can be reduced until the background blackbody fluctuation limit is reached. The reduction in NEP is expected to be on the order of b/λ, where b2 is the area of the detector. In the case of far-infrared bolometers away from the blackbody limit, significant reductions of NEP appear to be possible. Alternatively the antenna may be used to increase the temperature at which the bolometer can be operated or to reduce its response time. The possible use of antennas with various other infrared detectors is also considered, and some criteria for suitability are described.
Thickness evaluation of Si/SiO2 interfaces by He-backscattering experiments
Authors: Offermann Peter
Published: February 2003

The thickness (δ) of the transition region of the Si/SiO2 system was derived from backscattering measurements with 600-kev He ions. Random spectra were interpreted, giving an upper limit δ?50 Å, whereas the aligned spectra indicated some disorder in the interface. This was correlated with concentration gradients of Si and O resulting in a new definition of δ and values from 15 to 50 Å. The number of disordered atoms is about a factor of 2 less for oxides grown on (100) surfaces as compared to substrates with a 〈111〉 orientation.
Neutron damage in GaP : Zn,O light-emitting diodes
Authors: Barnes C. E.
Published: February 2003

Electrical and optical measurements have been carried out at 300 K to ascertain the effects of neutron irradiation on the properties of red-emitting GaP : Zn,O light-emitting diodes. Capacitance measurements at 300 K indicate that majority-carrier removal is insignificant below a neutron fluence Φ of 1015 n/cm2. Above this value, a removal rate of 6.5 cm−1 is found. Current-voltage data show that the total current increases with Φ at constant voltage and that the neutron-added current is due to space-charge recombination. The rate of increase in current with Φ leads to a lifetime–damage-constant product τK of (3.0±0.9) ×10−14 cm2. A similar analysis of the degradation of the light output, which is due to a diffusion current at 300 K, results in τK= (2.4±0.4) ×10−14 cm2. This analysis also reveals that near the junction in the p region the concentration of Zn-O pairs is linearly graded as is the Zn profile according to the capacitance data. Curves of efficiency versus current measured at 300 K possess maxima which decrease in magnitude and shift to higher current densities with increasing Φ. These results are indicative of saturation of the Zn-O centers at high injection levels. The rate of decrease of the maxima with Φ leads to a τK value of (2.0±0.6) ×10−14 cm2 and suggests that the Zn-O profile is also linearly graded a few diffusion lengths from the junction. The agreement between the various τK values tends to support the damage model employed in which neutron irradiation results in the introduction of nonradiative recombination centers in both the depletion and neutral regions.
Optical determination of impurity compensation in n-type gallium arsenide
Authors: Kamiya Takeshi , Wagner Elmar
Published: February 2003

A new method is developed for the determination of the impurity compensation in n-GaAs on the basis of line-shape analysis of impurity photoluminescence spectra. The observation of these spectra under weak excitation conditions together with a room-temperature free-carrier-concentration measurement enables us to determine the impurity compensation. This method is applied to undoped LPE GaAs crystals with carrier concentrations ranging from 1013 to 5×1015 cm−3. Our method reveals significantly smaller values of the compensation than a conventional mobility analysis. This discrepancy is mainly due to inhomogeneous dopant concentrations in epitaxial layers and the higher spatial resolution of this optical method, provided by the small values of light penetration depth and charge-carrier-diffusion length.
Perpendicular magnetic anisotropy in evaporated amorphous GdCo films
Authors: Brunsch A. , Schneider J.
Published: February 2003

Amorphous GdCo films with strong perpendicular magnetic anisotropy were vacuum deposited by thermal evaporation of the constituents in an oxygen atmosphere of at least 3×10−8 Torr. In this paper the fabrication technique and the magnetic properties of the resulting GdCo films will be reported.
Transverse flux constraint for excitation of electron plasma waves in a magnetic field
Authors: Willett Joseph E. , Maraghechi Behrooz
Published: February 2003

The analog of the conservation law for photon number is derived for a three-wave interaction involving two circularly polarized electromagnetic waves and an electron plasma wave propagating along a uniform static magnetic field.
Spectral response of photocurrents in the MOST and the dependence on gate and substrate bias
Authors: Card H. C. , Fang F. F.
Published: February 2003

An experimental study has been made of the spectral response of photocurrents in the n-channel Si MOS transistor, including the effects of temperature and applied voltages. It is found that the photoresponse may be enhanced over the entire spectral range by the application of a gate or substrate bias voltage. Of particular interest, however, is that the response at short wavelengths (λ≲0.6 μ) undergoes a considerably greater relative increase than that over the remainder of the spectrum. This tendency is most pronounced in the case of an applied substrate bias.
Theory of hologram formation in photorefractive media
Authors: Blo/tekjaer K.
Published: February 2003

A theory for the formation of phase holograms in lithium niobate and similiar materials is presented. The experimental situation considered is that of an open-circuited crystal with no applied voltage. The present theory differs from previous theories in that the electric field is treated self-consistently in agreement with basic electrostatic laws. It is found to be important to account for the dark conductivity of the crystal. Several new results are obtained: The dependence of stationary-state diffraction efficiency on light intensity is predicted. The influence of previous illumination of the crystal is investigated. It is shown that the phase shift between the interference pattern and the refractive-index pattern changes during hologram recording. Nonlinear effects occurring at high modulation indices are evaluated. The effect of piezoelectricity on hologram recording is discussed.
Measurement of the gain profile of high-pressure Kr/O2 mixtures near 5577 Å
Authors: Woodworth Joseph R. , Rice James K.
Published: February 2003

An intense relativistic electron beam (1.8 MeV, 100 ns, 4 kJ) was used to transversely excite a 50-cm-long laser cell containing 5200 Torr krypton and 10 Torr O2. Optical gain in the medium in the afterglow of the e-beam pulse was determined by measuring the decay of a 5-ns-long pulse from a carefully wavelength-tuned (±0.1 Å) narrow-band (0.04 Å FWHM) dye laser which was trapped in the test cell by two highly reflecting mirrors. The peak gain occurs at 5578.4±0.2 Å, 1.1 Å on the red side of the O(21S→21D) transition. The half-width of the gain profile is ?1.5 Å and the profile is completely dominated by KrO quasimolecules.
Thermochemical generation of CS and S for CO chemical lasers
Authors: Richardson R. J. , Buonadonna V. R.
Published: February 2003

A thermochemical equilibrium calculation is compared with the experimental results of active mass spectrometric sampling of a high-temperature NF3-CH4-H2-CS2 flame. The predicted flow rate of the products HF, CS, N2, and CS2 is found to agree with the experimental data. The presence of S among the product species is inferred from a second experiment, in which the flux from the high-temperature combustor was extracted through a supersonic nozzle and mixed with a second supersonic stream containing He and O2. The flow rate of the reaction product CO determined during the latter experiment is compared with the flow rate predicted by a kinetics model of the chain reaction between CS and O2 initiated by small amounts of S. It is suggested that such a CS and S generator coupled with a supersonic mixing nozzle could be utilized to construct a completely chemical CO laser of any desired output power.
A nitrogen laser employing an electron seeding technique
Authors: Ma Ing-Jiunn , Wang Tieh Chu , Wang Yuh Shuh
Published: February 2003

Electron-beam injection was utilized in this nitrogen laser to preionize the lasing gas. Data taken from the same laser operated with and without electron seeding are compared under the same condition. It is demonstrated that electron seeding can (a) increase the laser power because the optimum lasing pressure is shifted to a higher value, (b) extend the laser action to a much higher gas pressure, (c) reduce the output power fluctuation, and (d) extend the range of validity of a linear gas-pressure–laser-power scaling law.
Expansion of the spontaneous magnetic field in a plasma produced on a copper target by a CO2 laser
Authors: Drouet M. G. , Bolton R. , Kieffer P. , Saint-Hilaire G. , Szili Z. , Pépin H. , Grek B.
Published: February 2003

Measurements are presented for the magnetic field B and the uv radiation generated by a plasma produced by irradiation of a copper target by a 4-J 1.7-ns CO2 laser. The dependences of the uv and B intensities on the N2 or the helium background pressure are found to be comparable. There are two phases in the field expansion: diffusion within the photoionized background followed by convection with the laser plasma.
Band and hopping conduction in high-resistivity ZnO
Authors: Schoenes J. , Kanazawa K. , Kay E.
Published: February 2003

We have measured the complex dielectric function of sputtered ZnO films over a wide frequency range (10−2–107 Hz) and over a temperature range extending from −60 to 100 °C. A detailed examination of these results reveals the contributions of band conduction and hopping conduction to the dielectric dispersion. In certain cases, contact polarization effects gave an additional contribution at the lowest frequencies. A microscopic model for the conduction is proposed in which singly charged oxygen-vacancy sites are in communication with one another by way of the conduction band. Quantitative evaluation of the data are in support of this model.
Dielectric effects in the optically stimulated electron spin resonance in silicon
Authors: Shiota Ikuo , Miyamoto Nobuo , Nishizawa Jun-ichi
Published: February 2003

The appearance of the photoinduced ESR lines is directly responsible for the dielectric effect caused by a change in spin-dependent photoconductivity at resonance point. This appearance mechanism proposed in the optically stimulated ESR method is quite different from that of an ordinary ESR absorption line based on the paramagnetic absorption loss. A simple calculation to justify this model is made and typical features of the photoinduced ESR lines are explained in connection with the appearance mechanism.
Temperature dependence of electrical properties in Be-implanted semi-insulating GaAs
Authors: Hutchby J. A. , Vaidyanathan K. V.
Published: February 2003

The Hall coefficient and sheet resistivity have been measured as functions of temperature for Cr-doped semi-insulating GaAs implanted with 100-keV Be ions at fluences between 1×1013 and 5×1015 cm−2. Impurity conduction influences or dominates hole transport processes at all temperatures for fluences of 1×1014, 4×1014, and 5×1015 cm−2, but is evident only for T <80 °K for lower fluence implants of 1×1013 and 4×1013 cm−2. Analysis of higher-temperature sheet-hole concentration data for these lower-fluence implants indicates the implanted layers are heavily doped and compensated, and the activation energy Ea decreases with increasing ionized acceptor concentration Nai. These results, along with an earlier result for a much lower concentration of implanted Be acceptors, can be represented by Ea=28.4 meV −(1.77×10−5) N1/3ai. In addition, measurement of electrical properties as a function of room-temperature sample-storage time indicates slow activation of compensating donors for the 4×1013-cm−2 implant. This effect is not observed for 4×1014- and 5×1015-cm−2 implants.
Propagation along azimuthally magnetized ferrite-loaded circular waveguides
Authors: Mueller R. S. , Rosenbaum F. J.
Published: February 2003

The azimuthally symmetric modal spectrum for the azimuthally magnetized ferrite-loaded coaxial transmission line and the ferrite-loaded wire are presented on normalized ω-β diagrams. Practical considerations of magnetic biasing are discussed.
Effect of in-plane magnetic field on bubble collapse field in ion-implanted garnet films
Authors: Uchishiba H. , Obokata T. , Asama K.
Published: February 2003

Bubble collapse fields in several kinds of garnet films ion implanted for hard-bubble suppression were measured in the presence of an in-plane magnetic field and were found to vary according to the direction of the in-plane field. That is, bubble collapse fields exhibit a threefold symmetry in response to the threefold symmetry of crystallographic axes. The appearance of this threefold symmetry was explained by the response of closure domains associated with bubbles to in-plane fields. This phenomenon is shown to be dependent on the properties of garnet films and implantation conditions, i.e., dose, energy, and ion species used: H, Ne, and Ar.
Coupled electron photon collisional transport in externally applied electromagnetic fields
Authors: Halbleib J. A. , Vandevender W. H.
Published: February 2003

The model presented describes the time-independent production and transport of the electron/photon cascade in two-dimensional cylindrical material/void configurations in the presence of static electromagnetic fields of arbitrary spatial dependence. The range of phenomena that can be studied with the model is carefully delineated. The underlying assumptions required for coupling condensed-history collisional Monte Carlo with macroscopic field transport are set forth in detail. The method is applied to specific problems in electron-beam-excited high-pressure gas laser research, high-intensity flash x-ray source development, and electron-beam-fusion research. Results are compared with the predictions of earlier theoretical models and with experimental data. Comparisons between the theoretical models clearly demonstrate the importance of the additional capabilities achieved in the model described here. Because of the complexity of the experiments, comparisons between the theoretical predictions and the experimental data are not especially definitive; where comparisons are possible, however, there appears to be at least qualitative agreement.
Electron-beam transport for inertial fusion
Authors: Benford James
Published: February 2003

Two methods for transporting electron beams from the diode to a pellet are analyzed. First, pinched beams can propagate along a Z pinch with current density Jb≲ν/γJp, where Jp is the pinch current density. Heavy high-density (∼1018cm−3) gas is required in order to (1) reduce plasma turbulence that could prevent total current neutralization and (2) prevent expansion of the pinch by transverse beam pressure. Second, compression in a magnetic mirror with multiple reflections between diode and mirror is considered. Reflex diode current density enhancements ≳100 above Child’s law are required for this approach to succeed.
Radiative energy losses from a high-current air-blast arc
Authors: Strachan D. C. , Lidgate D. , Jones G. R.
Published: February 2003

The importance of total radiation losses from high-current arcs burning in highly accelerated air flows representative of conditions existing in commercial gas-blast switchgear has been investigated. Such losses have been measured both in the high-pressure region upstream of a shaped orifice, where gas velocities are low, and in the region downstream where velocities become supersonic and pressure conditions approach ambient. The dominance of upstream electrode vapor as the source of plasma radiation losses is demonstrated and the importance of radiated losses within the arc energy balance is examined using measured values of axial electric field. For upstream electrodes of elkonite (sintered copper/tungsten) as used in high-power gas-blast circuit breakers, it is shown that some 30–40% of the electrical energy input upstream of the orifice is lost as radiation, while downstream this figure becomes 10–20%. The effect of reservoir pressure on arc electric fields is examined and the contribution to this effect of radiation losses is quantified.
Investigation of quasi-steady-state high-current arcs in an orifice air flow
Authors: Malghan V. R. , Fang M. T. C. , Jones G. R.
Published: February 2003

A detailed analysis of the experimental results from an orifice flow arc during the quasisteady period following a peak current of 3 kA is presented. The velocity profile of the gas flow has been derived from the experimentally measured temperature profile and the axial and radial pressure distributions. It is shown that the total electric power dissipated in the arc column can be adequately taken into account without necessarily introducing the possible effects of turbulence. The analysis also yields an indication of the local energy balance. A simplified arc model, based on the integral method of arc analysis but including kinetic energy transport, total radiation loss, and compressibility effect has been established. The radiation is taken into account using an empirical relation derived from the experimental data of Strachan et al. Arc scaling parameters are introduced and experimental results obtained during the quasi-steady-state agree well with those predicted by the present arc model.
Modification of the double cantilever beam method for the direct measurement of the fracture energy of glasses and brittle materials
Authors: Hamert J. -M. , Robino P. , Dinh P. Nguyen , Eberhart J. -P.
Published: February 2003

A method for the direct measurement of the fracture energy γF of brittle materials is presented. The samples used are of the double cantilever beam (DCB) type and have a groove to guide the crack to a hole where it is entrapped; thus, the elastic energy stored in the specimen will be released by the returning of the crosshead of the testing instrument. The energy of fracture is then measured directly by the ratio of the area of the ’’load-vs-displacement’’ cycle to the surface of the fracture measured on a photographic enlargement. Results obtained from microscope slides are the following: 3.5 J/m2 in air and 5 J/m2 in dry nitrogen. This method allows for good control of the fracture speed and is well designed to determine γF in opaque brittle materials where the length of the crack is difficult to measure.
Measurements with double probes in organic vapor for understanding the glow-discharge polymerization processes
Authors: Yamaguchi Shinji , Sawa Goro , Ieda Masayuki
Published: February 2003

Effects of contamination on the double-probe characteristics in nitrogen glow discharge are studied by using defined films polymerized in styrene glow discharge. As the contamination of the film is increased in thickness, the current-voltage (Id-Vd) curve of the probe shifts along the Vd axis and all the parameters employed for estimating electron temperature are varied. An equivalent circuit of the film allows one to interpret neither of these parameters but the shift of curve. The limit of the film thickness is also determined within which the probe characteristic is scarcely affected. On the assumption that this limit can be applied to the organic vapor, the electron temperature in the positive column of glow discharge in styrene vapor at 1 Torr is estimated at 22 000 °K by a quick performance of the double-probe measurement.
Thermodynamic relations for shock waves in materials with a linear relation between shock-wave and particle velocities
Authors: Rodean Howard C.
Published: February 2003

The Rankine-Hugoniot relations for shock waves and the empirical linear relation between the shock-wave and particle velocities define an incomplete thermodynamic description of the states along the Hugoniot curve. This incomplete description defines the following along the Hugoniot: (1) internal energy and pressure as functions of specific volume, (2) the ratio of enthalpy to internal energy, (3) the ratio of the changes in enthalpy and internal energy across a shock wave, and (4) the relation between the Grüneisen coefficient and the effective isentropic exponent. We use the Dugdale-MacDonald relation for the Grüneisen coefficient at low pressure, an assumed constant value for the specific heat at constant volume, and reasonable physical assumptions for extremely strong shock waves together with the incomplete thermodynamic state description to define the following along the Hugoniot: (5) the Grüneisen coefficient, (6) the effective isentropic exponent, (7) the ratio of specific heats, and (8) thermal and elastic components of pressure, temperature, and entropy. We present representative numerical values of these parameters as functions of reduced volumetric compression. We show how the solutions for these parameters define tangent planes to the surfaces of the incomplete E,P, and V and P,V, and T equations of state at each point along the Hugoniot curve.
Surface pressures from laser-supported detonations
Authors: Holmes Bayard S. , Erlich David C.
Published: February 2003

The surface pressures directly behind a Laser-Supported Detonation (LSD) were measured with a system of carbon piezoresistive gauges. A quartz piezoelectric gauge was also used to measure surface pressures far away from the laser spot. The small size of the carbon gauges, relative to the laser beam diameter, permitted simultaneous resolution of the surface pressure history at several locations within the laser spot. A comparison of the experimental data with recent theories indicates that the theories predict peak pressures close to those measured but overestimate the impulse intensity at the target surface.
Electron tunneling through fatty-acid monolayers
Authors: Polymeropoulos Epaminondas E.
Published: February 2003

The exponential dependence of the tunneling conductivity on the thickness of the insulating material has been studied by varying the length of fatty-acid monolayers in metal/fatty-acid-monolayer/metal junctions. By varying the temperature between 20 and −100 °C it is shown that the tunneling current remains relatively constant, while the decrease in capacitance observed can be attributed to the influence of the Al2O3 layer in our junctions.
Semiconducting oxide anodes in photoassisted electrolysis of water
Authors: Kung H. H. , Jarrett H. S. , Sleight A. W. , Ferretti A.
Published: February 2003

The electrochemical properties of semiconducting anodes of TiO2, SrTiO3, BaTiO3, Fe2O3, CdO, CdFe2O4, WO3, PbFe12O19, Pb2Ti1.5W0.5O6.5, Hg2Ta2O7, and Hg2Nb2O7 in photoassisted electrolysis of water were determined. All of these oxides formed a rectifying junction with the electrolyte and anodic photocurrents were generated only with larger-than-band-gap illumination. For Fe2O3, the optical absorption spectrum was different from the photoelectrochemical spectrum due to crystal field transitions. These oxides were found to be stable over certain range of pH. In a given electrolyte, the flatband potential Vfb varied linearly with the band gap. A good correlation was obtained between Vfb and the heat of formation of the oxide per metal atom per metal-oxygen bond, but not between Vfb and the calculated Fermi energy of the oxide. This suggests that a semiconductor-electrolyte interface may be approximated by a semiconductor-metal junction where the barrier height is determined by the heat of formation of the metal-semiconductor compound. The practical aspect of using a photoassisted electrolysis cell for solar energy conversion is discussed.
Electroluminescence of anthracene with powdered graphite electrodes and ambient gas effects on the electrodes
Authors: Gu Jyongsil , Kawabe Mitsuo , Masuda Kohzoh , Namba Susumu
Published: February 2003

Double-injection electroluminescence of anthracene with a special electrode has been studied. The electrode was efficiently capable of injecting both electrons and holes into anthracene. Both current and electroluminescence intensity were markedly enhanced by a factor of about 30 when the ambient gas of the cathode was changed from air to nitrogen. The emitted light which peaked at 4440 Å was generated with an external quantum efficiency ranging from 4 to 6%.
Excess vacancy generation by E-center dissociation in the case of phosphorus diffusion in silicon
Authors: Yoshida Masayuki
Published: February 2003

Phosphorus diffusion equations in silicon are proposed taking into account the following: Phosphorus diffuses as E centers; an E center is formed by pairing a negatively ionized vacancy with a positively ionized phosphorus atom; with increasing phosphorus concentration, the equilibrium concentration of negatively ionized vacancies increases and the ionization rate of phosphorus decreases. The equations are solved numerically under the boundary conditions of constant surface concentrations of total phosphorus atoms and negatively ionized vacancies. The phosphorus diffusion coefficient depends not only on the vacancy concentration but also on its gradient. The excess vacancies are generated by the E-center dissociation. The concentration and the distribution of the excess vacancies are good enough to explain qualitatively the anomalous diffusion of phosphorus, except the kink in the phosphorus concentration profile.
Efficient bulk-wave excitation by interdigital transducers in layered media
Authors: Nalamwar A. L. , Wagers R. S. , Epstein M.
Published: February 2003

Shear bulk waves multiply reflected from polished surfaces of a nonpiezoelectric substrate are efficiently excited by thin-film ZnO interdigital transducers. Analytical results obtained using digital computations of a boundary-value problem in a two-layer system compare well with experimental measurements. The effect of the ZnO thin film and the shear-bulk-wave propagation are described.
Piezoresistive effects in ytterbium stress transducers
Authors: Grady D. E. , Ginsberg M. J.
Published: February 2003

Ytterbium has been successfully used as the piezoresistive element in stress transducers for in situ measurements of stress amplitudes associated with wave propagation in rocks and soils and for laboratory studies of high-rate loading effects in solids and liquids. Ytterbium has been calibrated over its useful range and it can be seen that consideration of the tensor aspects of the piezoresistance become important below 10 kbar. We have used static tensile and hydrostatic data to determine the piezoresistivity tensor coefficients and estimate the shock-wave piezoresistance coefficient, which compares well with experiment. In addition, we offer an explanation of the difference observed between hydrostatic and shock-wave data in the region where plastic deformation becomes important during dynamic compression.