bluuebunny/crossref_metadata_2025 huggingface dataset:
Fast-neutron sputtering of niobium
Authors: Harling O. K. , Thomas M. T. , Brodzinski R. L. , Rancitelli L. A.
Published: February 2003

Neutron sputtering yield measurements of niobium are reported for 14.8-MeV (d,t) neutrons and for fast neutrons in the forward direction produced by 40-MeV deuteron bombardment of a thick Be target. Six irradiations were performed with 23 niobium targets with a range of 1.7×1015 to 6.1×1016 (d,t) neutrons. One irradiation was performed with five niobium targets irradiated with a range of 4.7×1016 to 4.5×1017 (d,Be) neutrons. Sputtering targets included single crystals and annealed and cold-worked material with various surface preparations. Target preparation overlapped or was identical, in several cases, to that used by another research group which has reported the observation of fast-neutron-induced ’’chunk’’ or micrometer particle emission. Several cm2 of collector which faced Nb targets irradiated to fluences of (0.4–1.1) ×1016 (d,t) neutrons/cm2 were carefully examined by scanning electron microscopy, but no evidence for neutron-produced chunk emission ?0.5 μm was found. Thermal neutron activation analysis was used to determine absolute yield on most of the silicon collectors which faced the front and back surfaces of the Nb targets. These determinations indicate that the yield in atoms/neutron for a wide variety of Nb target preparations, including those which are reputed to be high-probability chunk emitters, are likely to be less than several times 10−5. The experimental procedures are presented in detail. The present results for fast-neutron sputtering yields are discussed in relation to other recent results for niobium and theoretical estimates. Limitations in our experiments and others are also discussed. The present results, as well as other recent results for niobium, indicate that neutron sputtering will not be a significant factor in the erosion of the first wall or in plasma contamination in future fusion reactors.
Interactions of water vapor and oxygen with Si(111) surfaces studied by low-energy electron-loss spectroscopy
Authors: Fujiwara K. , Ogata H.
Published: February 2003

Low-energy electron-loss spectroscopy (ELS) has been applied for the studies of interactions of water vapor and oxygen with Si(111) 7×7 surfaces. It has been shown that ELS, due to its high surface sensitivity, is capable of observing the microscopic changes of the surfaces after adsorption, decomposition, desorption, and oxidation. The primary electron energy dependence of the loss spectra has shown a qualitative difference between oxygen-covered Si(111) and SiO2 surfaces. For SiO2 surfaces, the breakdown of the opticlike selection rule has been observed in the one-electron transitions at the low primary electron energies.
Evaluation of the CdS/CdTe heterojunction solar cell
Authors: Mitchell Kim W. , Fahrenbruch Alan L. , Bube Richard H.
Published: February 2003

A variety of CdS/CdTe heterojunction solar cells have been prepared by the vacuum evaporation of n-CdS films onto single-crystal p-CdTe substrates. Comparisons have been made between cells prepared using different substrate resistivities, substrate surface preparations, and CdS film resistivities. The mechanisms controlling the dark junction current, photocarrier collection, and photovoltaic properties with junction interface states present are modeled. A solar efficiency of 7.9% under 85 mW/cm2 of solar simulator illumination was measured on a cell with an indium-tin-oxide coating and a glycerol antireflection coating.
Enthalpy of mixing of poly(2,6-dimethyl phenylene oxide) and polystyrene
Authors: Weeks N. E. , Karasz F. E. , MacKnight W. J.
Published: February 2003

Various compatibility criteria for polymer-polymer blends are considered and their shortcomings discussed. An unambiguous thermodynamic criteria of compatibility, the enthalpy of mixing ΔHm, is obtained by application of Hess’s law to heat-of-solution data for blends and their components. The enthalpy of mixing for PPO/PS blends is determined by utilizing the Hess’s-law approach. Consideration is given to the excess glass enthalpy contribution to ΔHm. Consistent with the known compatibility of PPO/PS blends, a small negative ΔHm is found for all blend compositions.
Thermodynamics of the glassy state with multiple order parameters
Authors: Roe Ryong-Joon
Published: February 2003

Experimental data, both old and more recent, indicate the need for more than a single order parameter for adequate description of glassy materials. The thermodynamics of the glassy state with multiple order parameters, previously discussed by others, has been examined and developed further systematically. The result shows that the Prigogine-Defay ratio can be defined at every point on the (T,p) plane near the glass transition line and is generally greater than unity. One has to define a number of glass transition lines (Tg versus p), depending on which of the order parameters are assumed frozen-in at the glass transition. Even for a definition of the glass transition line operationally in terms of the relaxation time, one has to specify not only the time scale of the experiment but also the particular property observed and the mode by which the system is disturbed from equilibrium. A one-dimensional lattice gas model is utilized to obtain an expression for the Gibbs free energy as a function of T, p, and two order parameters, and this is then used to illustrate and test out the concepts and the thermodynamic relations derived here.
A selective surface degradation study of polysiloxane homopolymers and random-block copolymers with hydrofluoric acid solution
Authors: Okui N. , Magill J. H. , Gardner K. H.
Published: February 2003

Solution-grown crystals of homopolymer fractions of poly(tetramethyl-p-silphenylene siloxane) (pTMPS) and block copolymers of tetramethyl-p-silphenylene siloxane (TMPS) and dimethyl siloxane (DMS) have been selectively degraded using 48% HF solution at 30 °C. The HF preferentially attacks the Si-O bonds on the crystal surfaces. Changes in the degradation kinetics were monitored primarily by following the change in sample weight with etching time. Observation on changes in molecular weight, molecular distribution (by GPC), small-angle x-ray spacing, heat of fusion (by DSC), and degree of crystallinity were all employed to probe changes in crystal morphology with etching time within these polymeric systems. In the case of the homopolymer the correlated experimental results favored a chain-grown folded-crystal model for the TMPS homopolymer solution crystals and a substantially disordered surface topography in the crystals of the TMPS-DMS block copolymers. The size of the disordered interface expanded as the weight fraction of noncrystallizable DMS component was increased. In the copolymer series the dimension of the crystalline core in the chain direction exhibited a constant thickness on selective chemical etching, irrespective of the weight percent of DMS present in the TMPS-DMS system.
Fracture toughness of polycarbonate structural foams
Authors: Hobbs S. Y.
Published: February 2003

This paper describes some preliminary studies of the crack-induced fracture of structural foams molded from LexanR resin. Single edge-notch (SEN), double-cantilever beam (DCB), and compact tension specimens of various sizes were evaluated independently. A rapid rise in the nominal crack tip stress with decreasing sample size in the SEN and compact tension specimens was found to introduce significant errors in the strain-energy release rate (G) values calculated from data on small samples. Minimum sample size constraints were established from plots of G against σnom/σF. The concept of plane strain failure in these materials appears to be complicated by significant microscopic crazing and shear yielding in the thin bubble walls resulting in G values which are somewhat higher than those reported for the solid resin. This localized deformation, which is not readily discerned from the shape of the load/elongation curves or the macroscopic appearance of the fracture surfaces, results in an overestimation in the inherent flaw size for these materials.
A combined normal- and transverse-displacement interferometer with an application to impact of y-cut quartz
Authors: Kim Kyung-Suk , Clifton Rodney J. , Kumar Prashant
Published: February 2003

A new transverse-displacement inteferometer (TDI) is described. This interferometer makes use of intensity variations of a beam obtained by superposition of two beams diffracted symmetrically from a diffraction grating copied onto a plane surface. The TDI is used to monitor the transverse motion of the rear surface of a y-cut quartz target plate in a plate-impact experiment. For this application, a 200-line/mm grating is copied onto the rear surface of the target plate. The normal motion of the rear surface is monitored by means of a standard Michelson interferometer in which the zeroth-order diffracted beam is used as the beam reflected from the moving mirror. The transverse motion is monitored simultaneously by means of a TDI employing the two fourth-order diffracted beams, with a resulting sensitivity of 0.625 μm per fringe. The recorded motion confirms the predicted features of two coupled elastic waves, each involving both normal and transverse motion.
Volume-averaged rate equations for planar and disk-cavity lasers
Authors: Moreno J. B.
Published: February 2003

Volume-averaged rate equations are formulated for both planar and disk-cavity lasers. These equations involve not only volume averages of the photon and population number densities, but also volume averages of products of these quantities, and the average over the reflecting surfaces of the incident photon flux. Closure relations for this open set are derived using exact solutions obtained from spatially dependent laser rate equations. The results show that over a wide range of conditions, above threshold, with reflectivities greater than 0.2, the usual spatially uniform rate equations are adequate for symmetric planar cavities. Falling below threshold, or towards smaller values of reflectivity, these equations are shown to be increasingly less accurate. Ultimately, simple closure relations do not suffice. For disk cavities, the exact solutions as well as the volume-averaged rate equation formulations are new. Radial gain profiles, and directional-intensity distributions at the mirror, are presented. Closure conditions for specular and diffuse-reflectivity models are given. As in the planar case, simple closure relations eventually fail to give an adequate description as reflectivities tend towards zero or operation falls below threshold.
The measurement of the antisymmetric components of nonlinear optical susceptibilities of TeO2 crystal
Authors: Okada Masakatsu , Takizawa Kuniharu , Ieiri Shogo
Published: February 2003

The antisymmetric components of the second-order nonlinear optical susceptibility of TeO2 crystal have been measured by the process of sum-frequency mixing between the laser beams at the wavelengths of 1.064 and 0.532 μm. The experimental results were χ123/ (χ123+χ132) =0.59, χ132/(χ123 +χ132) =0.41, and χ312/(χ123+χ132) =−χ321/(χ123+χ132) =−0.18, which imply that χ123 and χ132 are slightly asymmetric and χ312 and χ321 are antisymmetric in the second and third suffices. It is thus concluded that the contribution of the antisymmetric component to the signal at the sum frequency may be comparable with that of the symmetric one forbidden by the Kleinman symmetry relation. Moreover, the symmetric and antisymmetric components of the nonlinear optical polarizabilities of the bond Te-O have been estimated in terms of the scheme of bond additivity by assuming a bond symmetry ∞.
Operational characteristics of a light amplifier
Authors: Urisu T. , Kajiyama K. , Mizushima Y.
Published: February 2003

A general operation diagram of a traveling unidirectional light amplifier is proposed by theoretical analysis, wherein different regimes are specified by a noise condition and the several threshold conditions of gain. The effects of hole burning and cross relaxation on the amplified spontaneous-emission (AES) noise and the gain saturation threshold were formulated. The transient operation diagram was determined by a numerical calculation of the rate equations in dye-laser amplifier with a rhodamine 6G methanol solution system. The numerically calculated diagram agreed well with the general analytical results.
Pressure dependence of the thermodynamical Grüneisen parameter of fluids
Authors: Boehler Reinhard , Kennedy George C.
Published: February 2003

Temperature changes associated with adiabatic pressure changes have been measured for water, mercury, pentane, isopentane, ethanol, methanol, and ether. For the first four fluids mentioned, the pressure dependence of the adiabatic bulk modulus, Ks, is known from ultrasonic measurements, and the Grüneisen parameter can be calculated using the thermodynamic relationship γth= (Ks/T)(ℓT/ℓP)s. For all fluids except water a large decrease of ΔT/ΔP with pressure is observed and the ΔT/ΔP curves converge at about 2.5 °C/kbar before freezing occurs. A considerable increase of γth with pressure is observed.
Investigation of tunable stimulated Raman scattering by light mixing in liquid N2
Authors: Sinnott T. , Meyer J. , Mennicke H.
Published: February 2003

High-order tunable anti-Stokes Raman scattering is produced by mixing the radiation of a Q-switched ruby laser and that of a dye laser in liquid nitrogen. All investigated orders of both ruby laser and dye laser anti-Stokes radiation are found to have the same ruby laser power threshold of about 0.5 MW. The intensities of the anti-Stokes radiation are found to increase linearly with ruby laser power once threshold has been surpassed appreciably. The dye laser anti-Stokes radiation does not exhibit a dye laser threshold power. The results can be explained by a simple theoretical model which treats the ruby laser as a pump for coherent molecular oscillations.
cw laser oscillation on transitions of Cd+ and Zn+ He–Cd halide and He–Zn halide discharges
Authors: Piper J. A. , Brandt M.
Published: February 2003

Continuous-wave laser oscillation has been obtained on transitions of Cd+ in hollow-cathode He–CdI2, He–CdCl2, and He–CdBr2 discharges, and on transitions of Zn+ in hollow-cathode He–ZnI2, He–ZnCl2, and He–ZnBr2 discharges. Excitation of upper laser levels is attributed to thermal energy charge transfer or Penning reactions between helium ions or neutral metastables and neutral metal atoms generated in the discharge volume by electron collisional dissociation of the metal-halide molecules. The operating characteristics of each system are discussed and compared with those of hollow-cathode He–Cd and He–Zn lasers. The results of these experiments suggest that operation of cw metal-ion lasers at lower temperatures than are required for the elemental metal can be achieved by use of a volatile metal compound in place of the elemental metal.
Narrowband operation of a pulsed dye laser without intracavity beam expansion
Authors: Shoshan I. , Danon N. N. , Oppenheim U. P.
Published: February 2003

A new simple cavity design for nitrogen-laser-pumped dye lasers is presented. Narrowband operation is achieved with a single dispersive element and without any intracavity beam expansion. The dispersive element is a diffraction grating used near grazing incidence with an additional mirror, instead of the usual Littrow arrangement. The large angular dispersion obtained results in a linewidth of 0.08 cm−1. The typical peak power obtained is 4 kW with 50 kW in the pump beam. Calculations of linewidth based on single-pass estimates are presented and are found to be in good agreement with experimental results.
Relativistic electron-beam-focusing experiments employing axial loads
Authors: Genuario R. D. , Triebes K. , Spence P. , Kishi H.
Published: February 2003

The self-focusing of intense relativistic electron beams in vacuum diodes relies upon beam-anode interactions to govern the time required to pinch the beam. Experiments performed at various laboratories have yielded sweep-in velocities of ∼1–2 mm/nsec. These low velocities result in the loss of a large fraction of the energy of the REB outside the pinch region.. As a means of increasing the sweep-in velocity and also improving beam centering and reproducibility, experiments were performed utilizing axial loads, either resistively or inductively isolated from the main low-impedance cathode. These experiments were carried out on various high-power generators, and average sweep-in velocities of up to ∼6 mm/nsec have been recorded for modest amounts of current on axis (≲10% of the generator current).
Ablation rates of polystyrene microspheres in a ϑ-pinch plasma
Authors: Smith D. L. , Kristiansen M. , Hagler M. O.
Published: February 2003

The ablation rates of stationary solid polystyrene spheres of 50–150-μm radii exposed to a dense (ne∼5×1022 m−3) hot (Te<Ti∼120 eV) plasma of 2-μs duration have been measured. Qualitative agreement with recent theoretical scaling laws was obtained. Comparison of the ionization intensities in the ablating neutral pellet material through the first four carbon lines indicate temperatures in the range of 5 eV. Focusing a Q-switched ruby laser on the cloud produces a marked increase in the ionization intensities. The pellet surfaces acquire a fine polish when exposed to a plasma as shown by electron microscopy.
Solving potential field problems in composite media with complicated geometries
Authors: Yeh Hsu-Chieh
Published: February 2003

Recently, Yeh developed a method of solving potential field problems for complicated geometries and theorems of piecewise continuous eigenfunctions which can be used to solve boundary-value problems in composite media by the separation of variables. This paper shows that by a proper arrangement of matching conditions and boundary conditions, this method and these theorems can be applied simultaneously so that the problems in composite media with complicated geometries can be solved. To illustrate this, a heat-conduction problem in a composite cylinder with an abrupt change in cross-section area is solved. Also presented in this paper are the method of handling the nonhomogeneous boundary conditions for composite media and the extension of one of the above-mentioned theorems to include imperfect contact on material boundaries.
Time-resolved double-probe study in a He-Hg afterglow plasma
Authors: Shay T. , Kano H. , Hattori S. , Collins G. J.
Published: February 2003

A double-probe technique is described and a simplified model presented which together allow for the direct measurement of the time rate of change of the He+ ion density in a He-Hg afterglow plasma. Using this double-probe method we have obtained direct experimental evidence that the dominant excitation mechanism in the He-Hg+ laser is a charge-transfer collision of the form He++Hg→ (Hg+) **+He+ΔE.
Experimental and theoretical study of the spatial variation of junction voltage and current distribution in narrow stripe injection lasers
Authors: Sommers H. S. , North D. O.
Published: February 2003

The spatial variation of the junction voltage and current distribution are deduced from measured profiles of the intensity of high-frequency light across the emitting facet of stripe lasers. The dependence of voltage on current follows closely the current dependence deduced from study of the external beam. Below, threshold, the shape of the voltage profile is found to be practically independent of current. The change at threshold in the differential conductance of the junction has only a minor effect on the profile, although its effect is observable over the entire front of the coherent waves. However, there is no apparent modification of the profile connected with the structure of the coherent illumination of the facet. A new theory is developed of the current spreading in a layered structure which successfully describes the features of the measured distributions. Using only material parameters of the layers of the laser, it predicts to good approximation the observed current spreading. The modifications to the voltage profile on transit of threshold are treated as perturbations, which introduce a new parameter related to an effective total impedance of the junction. A single-parameter fit of the theory at each power gives a good account of the corresponding profile. In principle, the parameter can be calculated, but the necessary model of the lasing modes is lacking.
Effect of space charge on F centers near the stopping region of monoenergetic protons
Authors: Dreschhoff Gisela , Zeller Edward J.
Published: February 2003

Single crystals of sodium chloride were bombarded with 1–2-MeV protons from a Van de Graaff accelerator at low temperature (77 K) and at room temperature. In the case of low temperature, a layered structure was found to be developed within the irradiated part of the crystal. This was indicated by the color-center formation. The color-center distribution in the irradiated area along the particles’ trajectories was studied using thin sections under a petrographic microscope and etched crystal surfaces in a scanning electron microscope. Three zones are visible: (1) strong color-center development in the upper region, followed by (2) a colorless layer, and (3) the end of the particles’ path is marked by a deeply colored zone caused mainly by severe lattice damage. The relative degree of lattice damage throughout the irradiated region is clearly visible in scanning electron microscope photographs. During the irradiation, the terminal layer constitutes a region of positive charge. This space charge gives rise to a second-order Stark effect resulting in the annihilation of F centers immediately above this zone and is, therefore, responsible for the observed decoloration.
Incremental charge/mass characterization of powders
Authors: Collins Leland F.
Published: February 2003

The triboelectric charging characteristics of a powder/bead mixture have been experimentally investigated by incrementally dislodging powder contained within a Faraday cage. It is shown that incremental charge-to-mass can be exponentially dependent solely on the areal coverage of the bead surface. The interpretation parallels earlier work on the charging characteristics of belts passing over rollers, spheres rolling on planes, and sand sliding down chutes.
Gallium arsenide films on recrystallized germanium films
Authors: Chu Shirley S. , Chu T. L. , Monroe S. , Wang C. P. , Yang H. T.
Published: February 2003

Germanium films deposited on tungsten/graphite substrates have been recrystallized by a unidirectional solidification technique. Gallium arsenide films deposited on recrystallized germanium have elogated grains with a strong {111} preferred orientation and are epitaxial with respect to the substrate. The deposited films have a room-temperature Hall mobility of 600–700 cm2/V sec and electron concentration of (1–3) ×1017 cm−3.
A star-shaped flyer for plate-impact recovery experiments
Authors: Kumar P. , Clifton R. J.
Published: February 2003

An eight-pointed star flyer is shown to cause release waves from lateral boundaries to be confined largely to the outer regions of the target. Analysis and experiment indicate that a central octagonal region is relatively unaffected by lateral release waves. Use of the star flyer in conjunction with a longitudinal-momentum trap allows the target to be recovered without the central octagonal region undergoing appreciable further inelastic deformation following the passage of the initial plane pulse.
A simple measurement of absolute solar-cell efficiency
Authors: Shay J. L. , Wagner Sigurd , Epworth R. W. , Bachmann K. J. , Buehler E.
Published: February 2003

We describe a simple technique for measuring absolute solar-cell efficiencies. Widespread adoption of this technique would permit meaningful comparisons of the various approaches to terrestrial photovoltaics.
GaP negative-electron-affinity cold cathodes: A demonstration and appraisal
Authors: Stupp E. , Pelissier A. , Kidder M. , Milch A.
Published: February 2003

Negative-electron-affinity GaP p-n junction cold cathodes have been demonstrated. The emitted currents from these devices are of the expected order of magnitude based on the limiting material and geometric factors. Emission currents suitable for vidicon-type tubes should be readily achievable. Theoretical analyses of the energy distributions of the emitted electrons show significant heating due to electron-phonon scattering. To obtain lower beam temperatures would require a significant advance in material technology.
Influence of secondary-electron emission from MgO surfaces on voltage-breakdown curves in Penning mixtures for insulated-electrode discharges
Authors: Aboelfotoh M. O. , Lorenzen J. A.
Published: February 2003

Voltage-breakdown curves in a Ne+0.1% Ar Penning mixture for insulated-electrode discharges are strongly influenced by changes in the surface properties of a deposited MgO cathode. A model has been developed to calculate an effective secondary-electron-emission coefficient γ in Penning mixtures as a function of the insulator-energy-band parameters. Incorporation of the calculated γ into the breakdown criterion results in good agreement between calculated and measured voltage-breakdown curves for differently prepared MgO cathode surfaces. The calculated results show that the value of γ for argon ions depends on the state of the MgO surface, and this occurs through a change in the width of the band gap of MgO. The results also show that a nonzero value of γ (Ar+) significantly lowers the breakdown voltages and changes the shape of the breakdown curves at higher values of P0d.
Limits on the yield of photochemical solar energy conversion
Authors: Ross Robert T. , Hsiao Ta-Lee
Published: February 2003

Entropy and unavoidable irreversibility place a limit on the efficiency of photochemical solar energy conversion which is substantially lower than that placed by the first law of thermodynamics alone. Shockley and Queisser’s ’’detailed balance limit’’ on the efficiency of p-n-junction photovoltaic devices is a special case of this general thermodynamic limit on the efficiency of all quantum-utilizing solar energy converters. For a single photochemical system operating at 20 °C in sunlight not attenuated by the atmosphere, this efficiency cannot exceed 29%. Under the same conditions, the efficiency of a solar converter composed of two photochemical systems can reach 41%.
Upconversion of radiation in LaCl3 : Nd
Authors: Hacskaylo Michael
Published: February 2003

A mechanism for the upconversion of 1.06-μm radiation to 0.873 μm in LaCl3 : Nd is described. The 1.06-μm radiation is absorbed by 4I13/2→4F7/2, 2S3/2 transitions and 0.873-μm radiation is emitted by 2S3/2, 4F7/2→4I11/2 transitions of the Nd3+ ions. The temperature dependence of the intensity response is a function of (a) the population density of the 4I13/2 level at high temperatures, (b) the trap density of the 4I11/2 level at low temperatures, and (c) the quantum efficiency of radiative transitions from the A level. The multiphonon transitions from the populated A level reduce the radiative transitions to zero at approximately 365 °K, whereas the multiphonon transitions do not appreciably affect the radiative transitions at lower temperatures. By postulating that electrons are thermally present in the ground state of the Nd3+ ions of the LaCl3 : Nd prepared by vapor chemical deposition, the model is in agreement with experimental data.
Determination of electron density and electron collision frequency in a nonuniform plasma column by rf coil probe
Authors: Basu J. , Hore K.
Published: February 2003

A nonimmersive-coil-probe method is presented for determining the electron density and electron collision frequency for momentum transfer in a cylindrical plasma column with a Bessel-type density distribution along the radius, the plasma being either isotropic or embedded in an axial static magnetic field. The method is based on the relation between the plasma parameters and the impedance of an rf coil placed coaxially around the plasma. Simplified expressions relating the parameters to the coil impedance are found to be valid under suitable conditions in the isotropic case.
Determination of the thermal conductivity of barium sodium niobate
Authors: Burkhart G. H. , Rice R. R.
Published: February 2003

An optical method of determining thermal conductivity has been devised for birefringent optical materials based on optically counting phase retardation fringes. The thermal conductivity of barium sodium niobate was found to be 0.059 W/cm °C, independent of sample orientation. The thermal conductivity of lithium niobate was found to be 0.082 and 0.087 W/cm °C parallel and normal to the c axis.
Photoelectromagnetic effect in CuInSe2
Authors: Mora S. , Romeo N.
Published: February 2003

The photoelectromagnetic effect is studied in single crystals of CuInSe2. A region of light excitation is found in which the dependence of iPEM on light intensity is linear. From the experimental data, a lifetime of the minority carriers τn=0.6×10−9 sec and a surface recombination velocity s=3×105 cm/sec are determined.
A cw-bulk silicon air-gap amplifier
Authors: Girard P.
Published: February 2003

In this paper, we report experimental results on an air-gap device using high-resistivity bulk silicon (ρ=1400 Ω cm, μd?1300 cm2/V s) on YZ LiNbO3 in cw operation. Experimentally at 120 MHz with a 1-cm interaction length, we obtain a 3.5-dB net gain with 260 mW of dissipated power.
Effect of hydrostatic pressure on the magnetic properties of certain metallic glasses
Authors: Anderson III P. M. , Lord A. E.
Published: February 2003

Measurements have been made of hydrostatic pressure dependence (up to 4 kbar) of the ’’saturation’’ magnetization and Curie temperatures of some commercially available Fe-Ni-based metallic glass materials. The magnetizations decrease by a few tenths of a percent per kbar in the amorphous state and increase by about 1% per kbar in the crystalline form of the same material. The Curie temperatures of the amorphous materials decrease by a few tenths of a degree per kbar. From this work, it is possible to derive the forced volume magnetostriction, the volume dependence of the ’’saturation’’ moment at 0 °K, and the volume dependence of the effective exchange energy.
Electromechanical coupling of surface acoustic waves in the vicinity of the phase transition in triglycine sulfate
Authors: Sader E. , Harnik E.
Published: February 2003

The temperature dependences of an effective piezoelectric constant have been determined in the vicinity of the Curie temperature in the presence of externally applied electric fields from simultaneous measurements of the temperature variations of the electromechanical coupling constant of surface acoustic waves and of the dielectric constant. It is shown that the experimental results can be explained on the assumption that piezoelectricity in triglycine sulfate is of an ’’induced’’ and not an ’’intrinsic’’ nature.
A study of deep impurity levels in GaAs due to Cr and O by ac photoconductivity
Authors: Stocker H. J.
Published: February 2003

ac photoconductivity measurements at T?20 K allow accurate determination of the energy levels of GaAs : O at Ec 753 meV and of GaAs : Cr at Ec−838 meV. O gives a clearly defined sharp threshold, while Cr shows a peak at 860–870 meV of varying width. These levels have been observed in boat-grown and in n- and p-type LPE material. Oscillatory photoconductivity is observed in conjunction with the O level.
Velocity-field characteristics of GaAs with Γc6-L
c6-X
c6 conduction-band ordering
Authors: Littlejohn M. A. , Hauser J. R. , Glisson T. H.
Published: February 2003

This paper describes Monte Carlo calculations of velocity-field characteristics for GaAs using the recent experimental conduction-band ordering of Aspnes, which places the Lc6(111) conduction-band minima lower in energy than the Xc6(100) minima. These calculations use intervalley deformation potentials which give the best fit to recent high-field drift velocity measurements, and at the same time give good agreement with accepted peak velocity and threshold field values.
Magnetic properties of MnBi particles
Authors: Kishimoto Mikio , Wakai Kunio
Published: February 2003

Platelet-shaped MnBi particles with diameter smaller than 0.5 μm were prepared by grinding sintered MnBi in a ball mill. The MnBi particles were dispersed and oriented in a polymer binder. The oriented MnBi particles were demagnetized in cooling to 85 °K, at which the coercivity was about 300 Oe. The applied magnetic-field dependence of coercivity was measured at 300 °K on the demagnetized MnBi particles. The coercivity remarkably increased with increasing strength of magnetic field, and in a magnetic field strength of 16 kOe, the maximum coercivity of 16 kOe was attained. It is suggested that ’’nuclei’’ from which magnetization reversal occurs exist in particles in the demagnetized state, and disappear by applying a strong magnetic field.
Magnetic properties and hydrogen absorption in rare-earth intermetallics of the type RMn2 and R6Mn23
Authors: Buschow K. H. J. , Sherwood R. C.
Published: February 2003

Magnetic properties of the compounds RMn2 and RMn23 (R=Y, Lu, Gd, and Th) were studied before and after hydrogen absorption. Hydrogen-induced transitions from Pauli paramagnetism to ferromagnetism were observed in YMn2, LuMn2, and Th6Mn23. The reverse effect, i.e., changes from ferromagnetism to Pauli paramagnetism, was observed in Y6Mn23. Gradual changes in magnetic properties were found in ThMn2, GdMn2, Lu6Mn23, and Gd6Mn23. It was established by means of x-ray diffraction that the lattice parameters increase considerably upon hydrogen absorption and the crystal structure remains preserved. Attempts have been made to correlate the changes in magnetic properties with the existence of a critical Mn-Mn nearest-neighbor separation.
Elliptical distortion and bias compensation in the gradient propagation of bubble domains
Authors: DeLuca J. C. , Malozemoff A. P. , Maekawa S.
Published: February 2003

Using high-speed photography in a pulsed gradient field experiment we have studied the elliptical and radial distortion of bubble domains during propagation as a function of bias compensation, pulse width, and drive. We propose a theory which relates the gyrotropic forces exerted by the Bloch-line pairs to the elliptical and radial distortion. As a function of bias compensation a peak appears in both the distortion and ballistic overshoot data at a point which closely coincides with the proper calculated value of bias compensation. The elliptical distortion and radial expansion at the peak are found to agree quite closely with theory at short pulse widths and low drives. At values of bias compensation different from the proper calculated value significant deviations from theory occur. In these cases the bubble losses its closely elliptical shape, becoming slightly asymmetrical, suggesting unequal generation of Bloch lines on its front and rear wall sections.
The anisotropy dependence of ferromagnetic domain-wall widths in crystalline and amorphous metals
Authors: Marti J. , Paul D. I.
Published: February 2003

We have used the techniques of Lorentz electron microscopy to study the behavior of ferromagnetic domain-wall widths as a function of the magnetic anisotropy constant K and the foil thickness D. This was done by varying the temperature T in crystalline iron and in amorphous Fe75P15C10 for various D’s. Our results are compared with existing theories. We observed an increase in wall width with temperature in crystalline iron and explained this by assuming the width of the wall to be an explicit function of both the anisotropy constant K (T) and the temperature T. After removing the explicit temperature dependence, the experimental results yielded an expression for the wall width of the form 2.5D/K1/6 within the range of ∼1000 Å foil thickness. An increase in wall width with temperature was also observed for walls in amorphous Fe75P15C10. From the measured wall structures we obtained a value of ∼104 erg/cm3 for the effective anisotropy constant of this amorphous alloy.
Injection-level dependence, frequency response, and thermal quenching of the 1.39-eV luminescence in Sn-doped LPE GaAs
Authors: Norris C. B.
Published: February 2003

We have investigated the injection-level dependence, frequency response, and thermal-quenching characteristics of the extrinsic 1.39-eV bands in Sn-doped LPE GaAs. In lightly doped material, both the peak energy and band shape are insensitive to injection level. Frequency-response measurements show that the dynamic response of the 1.39-eV band is slow, with characteristic times of μsec. Thermal-quenching data show a relatively large activation energy which rules out the participation of normal shallow levels in the luminescence. In heavily doped material, the 1.39-eV band is very similar in shape to that in the lightly doped material. However, the band in heavily doped material shows an anomalous injection-level dependence and a lower thermal-quenching activation energy than the band in lightly doped material. Our data indicate that normal donor-acceptor pair transitions are not involved in the 1.39-eV luminescence; rather, the 1.39-eV luminescence results either from intracenter transitions in compact complexes or from partially forbidden transitions between the conduction band and a deep acceptor level associated with a complex.
The work function of the elements and its periodicity
Authors: Michaelson Herbert B.
Published: February 2003

A new compilation, based on a literature search for the period 1969–1976, is made of experimental data on the work function. For these 44 elements, preferred values are selected on the basis of valid experimental conditions. Older values, which are widely accepted, are given for 19 other elements on which there is no recent literature, and are so identified. In the data for the 63 elements, trends that occur simultaneously in both the columns and the rows of the periodic table are shown to be useful in predicting correct values and also for identifying questionable data. Several illustrative examples are given, including verifications of predictions published in 1950.
Nonresonant detection of Josephson radiation from thin-film microbridges
Authors: Soerensen O. H. , Mygind J. , Pedersen N. F. , Gubankov V. N. , Levinsen M. T. , Lindelof P. E.
Published: February 2003

Measurements are reported of the Josephson radiation from microbridges coupled to an X-band receiver via a nonresonant microwave transformer. Although closely coupled to the bridge, the transformer does not modify the bridge properties. We find that near the transition temperature the radiation linewidth is proportional to the square of the dynamic resistance, which is also predicted by the resistively shunted junction model. The effective noise temperature determined by the linewidth is 19±3 K and the measured maximum integral power is 5×10−12 W.
Matteucci effect in nickel tubular samples
Authors: Cecchi G. C. , Ronconi F.
Published: February 2003

An equation deduced from classical electromagnetic theory relates the electromotive force arising at the ends of twisted tubular magnetostrictive samples (Matteucci effect) to the circular magnetization induced by a longitudinal magnetic field. This equation is verified for nickel samples along a magnetization curve.
Cathodoluminescence study of a silicon dioxide layer on silicon with the aid of Auger electron spectroscopy
Authors: Koyama H. , Matsubara K. , Mouri M.
Published: February 2003

Silicon dioxide layers were investigated for analyzing irradiation effects by a new technique of cathodoluminescence (CL) with accelerating voltages from 2.5 to 10 kV. The irradiation-dependent 280- and 530-nm CL peaks were characteristic in dry-grown oxides and reduced in wet-grown or P2O5-doped oxides. The AES (Auger electron spectroscopy) study of the dissociation of SiO2 and phosphosilicate glass (PSG) was helpful in analyzing the luminescence centers. The CL study may enable the in situ analysis of the electron-beam-irradiation effects in oxide-silicon structures.
On the measurement of high densities of dislocations in NaCl crystals
Authors: de Wainer Lelia S. , Miguez Victoria
Published: February 2003

A chemical etchant was developed to measure dislocation densities in zones of cleavage surfaces of NaCl crystals which show severe plastic deformation. Replicas of etched surfaces were observed in the electron microscope. Densities of approximately 109 dislocations/cm2 were measured in zones where a cleavage crack had been stopped.
An x-ray diffraction study of lattice imperfections in cold-worked fcc alloys. III. Silver germanium (α phase)
Authors: Halder S. K. , Sen Gupta S. P.
Published: February 2003

Detailed x-ray Fourier line profile analysis has been performed on five compositions of cold-worked α-phase Ag-Ge alloys containing 1.48, 3.06, 4.51, 5.89, and 7.53 at.% of solute germanium. X-ray diffraction profiles from 111, 200, 220, 311, 222, and 400 reflections have been recorded in a Geiger-counter diffractometer with nickel-filtered copper radiation, and microstructural parameters have been evaluated from the line-shift, line-asymmetry, and line-shape analyses in an identical manner as done earlier in Papers I and II with Ag-Ga and Cu-Ga alloys, respectively. Quantitative estimations of intrinsic (α′), extrinsic (α″), and twin (β) stacking-fault probabilities have been made, and these have shown an increased presence of an intrinsic fault over the extrinsic fault and a total absence of deformation twin faults. The values of the dislocation density ρ have been evaluated, and from the parameter γ/μ (γ: stacking fault energy; μ: shear modulus), the stacking-fault energy of pure silver γ0 has been estimated (∼16–21 mJ/m2), which is found to be well within the general range of fault energy values observed for silver.
Radiation conductance of apodized ID transducers in wedges
Authors: Datta Supriyo , Hunsinger Bill J.
Published: February 2003

The radiation conductance of an apodized ID transducer for acoustic waves in wedges is derived from normal-mode theory. Using the analytical expressions for the field distribution developed in an earlier paper, the radiation conductance is calculated for an ID transducer on a 40° LiNbO3 wedge. The calculated values are in good agreement with published experimental results.
Determination of the saturation parameter of a cw CO2 gasdynamic laser
Authors: Hara Hiroshi
Published: February 2003

The saturation parameter of a cw CO2 gasdynamic laser was calculated from consecutive measurements of output power and small-signal gain performed at the same experimental conditions. The measurement of small-signal gain was made as a function of the of the H2O concentration in the laser gas; measurements of output power were done as a function of the H2O concentration in the laser gas and as a function of laser-cavity diffraction loss which was varied by changing the diameter of an aperture placed in the laser cavity. Saturation parameters obtained by both methods coincide with each other, Is=3.0 kW/cm2. This value is insensitive to the H2O concentration and this behavior is qualitatively explained by a two-level model.
p-type conductive alloys in the Zn-Ga-P-S quaternary system
Authors: Kun Zoltan K. , Robinson Robert J. , Catano Aurelio
Published: February 2003

It was reported in the literature that high electrical conductivities, either n or p type, cannot be obtained in the GaP-ZnS system at higher than 5 mol% ZnS. This behavior is similar to that of the other (II-VI)x(III-V)1−x pseudobinary alloys. It is reported in this paper that degenerate p-type conductivity can be achieved in those Zn-Ga-P-S quaternary alloys which slightly deviate from the pseudobinary composition. The required conversion treatment is high-temperature annealing in zinc vapor. A comparison of the crystal growth technique with those of other researchers suggests that the deviation from the pseudobinary composition originated from the large excess of Ga in the closed system. This effect was enhanced by precipitating the crystals from the Ga solvent by cooling over a wide temperature interval. The significance of finding the high p-type conductivity was that it led to our present technique of p-type doping of ZnSe and ZnSxSe1−x.
Interface-state effects in irradiated MOS structures
Authors: Hughes Gary W.
Published: February 2003

The effect that ionizing radiation has on Si-SiO2 MOS devices is to create trapped holes and interface states at the Si-SiO2 interface. Several recent publications claim that it is possible to distinguish donor or acceptor interface states by analyzing C-V curves. It is shown here that in the presence of interface states it is not possible, in general, to determine either interface-state type or the quantity of fixed oxide charge from C-V measurements. Furthermore, observed differences between flatband voltage shifts on p- and n-type MOS devices are shown to be independent of whether interface states are donors or acceptors.
Design of a Josephson-junction picosecond pulser
Authors: McDonald D. G. , Peterson R. L. , Bender B. K.
Published: February 2003

Calculations are described which show that a Josephson junction, when driven by a microwave source, will produce a continuous train of picosecond-wide pulses. Detailed circuit designs, incorporating the microscopic theory of the junction, indicate that it is probably practical to build such pulsers. Furthermore, the theory indicates that picosecond pulses can be produced by circuits with submicron linewidth lithography, if desired. Thus, the possibility of both extremely fast and extremely high-density integrated circuits is supported by these calculations.
Nonequilibrium morphology of liquid inclusions migrating in solids
Authors: Cline H. E. , Anthony T. R.
Published: February 2003

The nonequilibrium shape of a liquid droplet migrating in a thermal gradient in a solid depends on both anisotropic surface energy and its anisotropic interface kinetics. In contrast, in equilibrium, the droplet shape is simply a surface of minimal total interfacial energy. From the surface energy and interface kinetic anisotropy the shape of brine droplets migrating in KCl is calculated for different migrating rates, droplet volumes, and orientations of the thermal gradient. As the migration rate increases, the droplet flattens by having its dissolving facets grow and the solidifying facets shrink in size. A gradient in the curvature of the interface is generated by the nonequilibrium composition gradient in the liquid. The shape of molten-metal wires used to dope semiconductors by thermomigration is also discussed.
Identification of deep centers in ZnSe
Authors: Grimmeiss H. G. , Ovrén C. , Ludwig W. , Mach R.
Published: February 2003

Cu-doped, Mn-doped, and nominally undoped ZnSe crystals were prepared by vapor transport or sublimation. The presence of the dopants was established by photoluminescence EPR, atomic absorption, and radiotracer techniques, and their associated energy levels studied by photoluminescence. From measurements of photocurrent and photocapacitance, it was shown that Cu doping introduces an energy level at about 0.68 eV above the valence band. From the good agreement between the optical cross sections obtained from the measurement of photocapacitance and optical quenching of photoluminescence, it was concluded that this center is responsible for the red Cu-emission in photoluminescence. This conclusion was supported by the observation that the absolute concentration of this level agrees with the reduction of the free-carrier concentration caused by Cu doping. Owing, presumably, to residual copper contamination, the 0.68-eV center was sometimes detected in nonintentionally doped and Mn-doped material. Evidence is given that this center is identical to the M center reported previously in Mn-doped ZnSe is identical with the 0.68-eV energy level. Independent of dopant, another level at about 0.58 eV above the valence band was observed.