bluuebunny/crossref_metadata_2025 huggingface dataset:
CdS Thin-Film Formation by the Method of Co-evaporation
Authors: Pizzarello F. A.
Published: April 2005

The technique of double evaporation of CdS and S was investigated. A significant increase of resistivity to 107 Ω·cm, and the onset of space-charge-limited current were observed in films made by this technique. It is hypothesized that the improvement noted compared with films from a single source evaporation of CdS is due to the reduction in number of sulfur vacancies.
Temperature Dependence of Light Scattering in some Alkali Halides
Authors: Plint C. A. , Breig M. L.
Published: April 2005

Measurements of the scattering by crystals of NaCl, KCl, and KBr, containing ≈10−6 divalent impurity concentration, at λ4358 Å are reported for the temperature range 200°–1000°K. The results for equilibrium heat treatments are entirely reversible, but not for quench treatments. The equilibrium results are consistent with the predictions of the theory of charged dislocations and scattering theory for defect clouds associated with the dislocations. Formation energies for anion and cation vacancies are obtained, viz.: NaCl, g+=0.6, g−=1.4; KCl, g+=0.65, g−=1.75; KBr, g+=0.80, g−=1.40, energies in eV. Precipitation of impurities at dislocations occurs at T=273°, 213°, 223°K for NaCl, KCl, and KBr, respectively.
Switching Properties of Single-Crystal Ni–Fe Films
Authors: Yelon A. , Voegeli O. , Pugh E. W.
Published: April 2005

Single-crystal films of Ni–Fe prepared by vapor deposition onto (100) planes of heated rocksalt substrates exhibit high-speed and quasistatic magnetization switching behavior which is characteristic of biaxial elements and is not found in uniaxial or isotropic films. The biaxial critical curve for coherent-rotational switching can be combined with partial switching and labyrinth-switching concepts, adapted from observations in uniaxial films, to provide a semiquantitative explanation for observations in single-crystal films. Direct verification of switching models here inferred from electronic measurements, and limited Bitter studies, will require Lorentz microscopy or detailed Bitter studies of walls formed during the switching process.
Heat Capacity of Glycerol Glass Between 1.5° and 4°K. Use of Glycerol as a Heat Exchange Medium in Low-Temperature Calorimetry
Authors: Craig R. S. , Massena C. W. , Mallya R. M.
Published: April 2005

The heat capacity of glycerol glass was measured between 1.5° and 4°K. Below 2°K the heat capacity is in excess of that expected from theoretical considerations for an isotropic solid. The use of glycerol as a heat exchange medium is discussed and described.
Angular Variation of Coercivity in Orthoferrite Single Crystals
Authors: Reich S. , Shtrikman S. , Treves D.
Published: April 2005

The coercive force Hc as a function of the angle between the easy axis of magnetization and the external field has been studied in orthoferrite single crystals using the vibrating sample technique. The experimental results are in good agreement with the Kondorsky 180° wall motion model which predicts the relation Hc(0)/Hc(θ)=cosθ.
Effect of Cesium Vapor on the Emission Characteristics of Uranium Carbide at Elevated Pressures
Authors: Kidd Philip W.
Published: April 2005

The saturated emission currents from uranium carbide in cesium vapor were measured for four different bath temperatures T: 167°, 197°, 227°, and 250°C (the cesium arival rates μa, in 1019 atoms/cm2, were 0.3, 1, 3, and 6, respectively). The measurements were made with a ``plasma anode'' tube at constant temperature. The plot of logμa vs 1000/T was used to extrapolate the electron emission ``S'' curves to arrival rates that differed by a factor of ten. Since calculations based on the assumption of a homogeneous surface yields unexpectedly high binding energies and surface coverages, it seems likely that some surface patchiness exists.
Polarity Effects in InSb Alloyed p-n Junctions
Authors: Barber H. D. , Heasell E. L.
Published: April 2005

The shape dependence of the profiles of alloy junctions formed on {111} and {1̄1̄1̄} surfaces of InSb has been studied as a function of alloying conditions. Polarity-dependent effects are found which may be attributed to different dissolution rates for {111} and {1̄1̄1̄} surfaces. Direct evidence of this difference is presented. By proper choice of alloying conditions it is possible to obtain planar junctions on both types of surface. The rectification ratios of such junctions prepared on either surface range from 107 to 2×108, at 250 mV. The polar differences in the current-voltage characteristics of these junctions are small and tentatively attributed to polarity-dependent surface effects.
Avalanche-Induced Negative Resistance in Thin Oxide Films
Authors: Chopra K. L.
Published: April 2005

A current-controlled negative resistance phenomenon, similar to that exhibited by a gas discharge tube, has been observed in suitably prepared thin oxide films of Nb, Ta, and Ti, sandwiched between thin-film metal electrodes, at frequencies up to 1 Mc/sec. The voltage required to sustain the negative resistance in both directions of current is independent of the electrode materials, apparent area and thickness (up to 500 Å) of the oxide film, and is about 0.4, 1.3, and 3.5 V for Ti, Nb, and Ta oxide films, respectively. The corresponding electric fields are approximately 0.8×106, 3×106, 9×106 V/cm. These values increase slightly with decrease of temperature. Experimental evidence supports the interpretation of the phenomenon in terms of avalanche multiplication of carriers in a thin region of the oxide film attended by space-charge-limited flow conditions.
Hot Electron Emission from Silicon Surfaces
Authors: Waldner M.
Published: April 2005

The decrease of the emission efficiency of hot electrons from a reverse-biased silicon junction has been measured as a function of time after etching. The decrease is largely due to a change in the surface potential of the silicon emitter. A density of surface states of 8×1012/cm2 has been determined from the effective attenuation distance of the hot electrons in the growing surface oxide layer, and from the characteristic energy of the emitted electrons. Changes in emission efficiency due to interface and oxide layer scattering have been determined from the emission efficiency for the more energetic electrons. A linear growth rate of the surface oxide induced by continuous charging of the surface states has been found.
Faraday Rotation in Artificial Dielectrics
Authors: Nag B. R. , Engineer M. H.
Published: April 2005

It is shown from an analysis of the propagation characteristics of a plane polarized wave in an artificial dielectric that Faraday rotation would be produced. Numerical results for n-type InSb indicate that the rotation should be experimentally observable. Some practical applications of the phenomenon are suggested.
Thermoelectric Properties of Liquid Semiconductor Solutions of Thallium and Tellurium
Authors: Cutler M. , Mallon C. E.
Published: April 2005

Experimental techniques have been developed for measuring the Seebeck coefficient S and electrical resistivity ρ of liquid semiconductors at high temperatures. Data have been obtained for S(T) and ρ(T) in a temperature range of 200° to 800°C and a composition range of 31 to 68 at.% of thallium. The liquids are n type for compositions with more than 66% thallium, and p type for lower thallium concentrations. At several compositions where thermal conductivity data are available, evaluation of the thermoelectric figure of merit γ(=ZT) shows ranges of relatively large values of γ(0.1 to 0.85).
Solubility Interactions in Compensated, Heavily Doped Germanium
Authors: McCaldin J. O.
Published: April 2005

The solubility of the two donors, arsenic and antimony, in Ge at 870°C was enhanced by the acceptor dopant Ga at concentrations ≥1019 cm−3. The observed enhancement is in agreement with theory of the dopant-carrier ionization equilibrium in the Boltzmann approximation and confirms the requirement of the theory that the solubility enhancement depend only on the net carrier concentration and not on the chemical identity of the donor. A contrary result would have been likely, if donor-acceptor complexes played an important role in these solubility effects. The experimentally determined intrinsic carrier concentration at 870°C is ni=1.8×1019 cm−3 compared to the extrapolated Hall value of ni∼1.3×1019 cm−3. The indicated extrinsic behavior implies that p-n junctions persist in very heavily doped germanium to the melting point.
Dislocation Contribution to the Second Harmonic Generation of Ultrasonic Waves
Authors: Hikata Akira , Chick Bruce B. , Elbaum Charles
Published: April 2005

The experimental evidence and the associated theory are presented for the dislocation contribution to the generation of the second harmonic of an ultrasonic wave in solids. The contribution is measured through the changes, as a function of static bias stress, in the amplitude of the second harmonic of a fundamental wave (10 Mc/sec compressional wave) propagating in the specimen.

In aluminum single crystals the amplitude of the second harmonic, for a given amplitude of the fundamental, changes markedly with static bias stresses ranging from 0 to 106 dyn/cm2. In alloys, there are essentially no changes of the amplitude of the second harmonic even for bias stresses up to 107 dyn/cm2. These observations are consistent with the predicted dependence of the amplitude on dislocation loop length and on the static stress. The effects of small amounts of plastic deformation were consistent with the proposed model.
Thin Films Deposited by Bias Sputtering
Authors: Maissel L. I. , Schaible P. M.
Published: April 2005

The application of a suitable negative bias to a film that is being deposited by dc sputtering produces a film of substantially lower resistivity (than without bias). The action of the bias is shown to result from positive ion bombardment of the film during deposition, leading to the selective removal of adsorbed impurities. An analytical expression describing the process is derived and found to give good agreement for tantalum films sputtered in argon containing oxygen as a contaminant. The effect of bias on contaminants originating both at the cathode and in the gas is compared. Comparison of bias sputtering and asymmetric ac sputtering in terms of an ion bombardment model shows that bias sputtering leads to purer films because ion clean-up is in operation during the entire deposition time only for the case of bias sputtering. Good adhesion of bias-sputtered Ta films to glass substrates is obtained by initially applying a small positive bias to the substrate.
Migration of a Liquid Zone Through a Solid. Part III
Authors: Tiller W. A.
Published: April 2005

In the present paper, the author extends his theoretical analysis of this topic to include nonconservative systems where atoms are exchanged between the liquid zone and the environment. It applies to both evaporation and condensation of either the solute or the solvent species. When the vapor exchange is such as to increase or decrease the liquidus temperature of the zone, the zone migration velocity increases or decreases, respectively, in a linear manner with zone size. For certain conditions it is possible to produce a zone of constitutionally supercooled liquid ahead of the freezing interface. The migration rates of gallium alloy zones through GaAs are quantitatively consistent with this treatment.
Synthesis of Beryl under High Pressure and Temperature
Authors: Wilson Wayne
Published: April 2005

Clear single crystals of beryl have been obtained at pressures of 10 000 atm and above by melting beryl powder and allowing it to crystallize under the high pressure. The difficulties associated with this method of crystal synthesis are discussed in detail.
Epitaxial Growth on MgO of Niobium Films Investigated by Electron Microscopy
Authors: Hutchinson T. E.
Published: April 2005

Niobium films deposited in vacuum (<5×10−6 Torr) on a (100) face of cleaved MgO were found by electron microscopy to have two types of epitaxial growth, independent of the deposition rate (2 to 120 Å/min). Although the epitaxial films have a very high dislocation density for substrate temperatures below about 500°C, thin films (<250 Å) grown between 500° and 600°C have no crystalline defects observable either by direct electron microscopy or in overlapping Moiré fringe patterns. Perfect (001) epitaxy with [100]Nb// [100]MgO occurred in these thin films for substrate temperatures from 25° to 600°C. Thicker films (>400 Å), have regions of a new orientation which enlarge as the films thicken, until only the new orientation is observed at 1000 Å and thicker. These nuclei are oriented with a {110} plane parallel to the substrate surface and a 〈110〉 direction along a 〈100〉 direction in the substrate. These nuclei grow more rapidly along their 〈110〉 directions. Nucleation of the new structure is discussed briefly. Calculation of the lattice misfits shows that neither of the observed orientations minimizes misfit.
Structure in Textured Gold Films
Authors: Davey John E. , Deiter R. H.
Published: April 2005

The structural properties of gold films vacuum-deposited on neutral substrates have been studied over a deposition temperature range of from 35° to 750°C by means of both reflection electron diffraction (RED) and x-ray diffraction. For deposition temperatures between about 350° and 500°C, extra reflections are observed in RED and are indexed as belonging to an hcp phase; these lines have previously been reported for beaten gold foils and single-crystal gold films. In addition, we have observed a weak extra reflection which we have tentatively identified as the forbidden (110). In no case were these extra lines observable by x-ray diffraction. In the case of cold deposited-annealed films, significant Bragg line shift is observed in the x-ray data; these shifts are attributed to the formation of large vacancy complexes which can only be annealed out by heating to the melting point. An argument is presented, from a comparison of the direction and magnitude of the Bragg line shift with resistivity increases, that the extra lines in RED indicate the existence of a hexagonal phase in these films as the source of the extra reflections, as opposed to a double diffraction process.
Excitation of Hypersonic Vibrations by Means of Photoelastic Coupling of High-Intensity Light Waves to Elastic Waves
Authors: Kroll Norman M.
Published: April 2005

A theory of the excitation of elastic waves arising from photoelastic coupling with light is presented. It is similar in character to the theory of optical parametric amplification in spatially extended media. Special attention is given to the self-excited transient case. A novel form for the space—time development of the instability appears for the case in which the spatial dimensions of the interaction region are large compared to the distance traveled by an elastic wave during the illumination time. The predicted effects should be readily observable with existing giant pulse lasers.
Giant Pulses from a Laser: Optimum Conditions
Authors: Menat M.
Published: April 2005

The conditions for maximized peak power extraction from a giant pulse laser are examined. In order to formulate an appropriate mathematical framework relating the various significant magnitudes, some simplifying assumptions and approximations have been used. The critical coupling conditions and the value of the resulting optimum peak power as a function of a characteristic loss factor have been determined. A distinction is made between maximum peak power and maximum energetic yield since the conditions for the achievement of both are slightly different.
Focal Properties of Isotope Separators using Azimuthally Invariant Magnetic Fields
Authors: Whitehead T. W
Published: April 2005

The ion optical properties of an azimuthally invariant magnetic field which are important in the electro-magnetic separation of isotopes are considered. The solutions are limited to the case where the object and image are within the field. A method based on the principle of least action is used to find general expressions for the values of the coefficients in the field expansion that will produce midplane focus at any angle. The three-dimensional motion of ions is considered with regard to isotope separations, and the general focal properties of inhomogeneous magnetic fields that satisfy the midplane image requirements are described.
Application of Electron and Optical Microscopy in Studying Laser-Irradiated Metal Surfaces
Authors: Vogel K. , Backlund P.
Published: April 2005

Electron and optical microscopy were applied in studying laser-irradiated metal surfaces. The preparation of carbon replica films of irradiated surfaces is described. A summary of observations from irradiated Ag, Al, Be, Cu, Pb, and low-carbon steel is given. Microcraters of less than 10 μ diam were found to be an early stage in the development of radiation damage on laser-irradiated metal surfaces. The observed surface structure is assumed to be of interest when interpreting experiments on the interaction of laser beams with metal surfaces.
Surface Dependence of Magnetostatic-Mode Linewidths in Yttrium Iron Garnet
Authors: Jones G. R.
Published: April 2005

The observed linewidths of the magnetostatic modes of roughened spheres of yttrium iron garnet do not follow the expected simple dependence on the density of degenerate spinwave states. A theoretical explanation is presented of the apparently erratic differences between the linewidths of the low-order magnetostatic modes. Semiclassical spinwave theory is used to calculate the coupling between the resonant mode and the degenerate spinwaves. Linewidths dependent on surface condition are calculated on the basis of typical values for the parameters to describe rough surfaces, and fit to experimental linewdiths. The calculated and observed linewidths are presented; the agreement between them is very good. The results are consistent with the general assumptions of the previous treatments, but in addition it is shown that it is necessary to include the field configuration of the magnetostatic modes in the calculation of surface-dependent linewidths.
Pulse Propagation in Anisotropic, Randomly Inhomogeneous Media
Authors: Knollman G. C.
Published: April 2005

A theoretical study is conducted of plane-harmonic narrow-band pulse propagation in a statistically uniform but anisotropic transmission medium of weak, stationary refractive-index fluctuation. Large-scale inhomogeneities of arbitrary ellipsoidal shape are treated, with transmitter-to-receiver ranges taken as large compared with the longitudinal correlation length. Of interest is the influence of range, transmitter frequency, and degree of anisotropy on the pulse shape and intensity. Comparison is made between pulse transmission in isotropic and anisotropic random media, and special attention is given the low- and high-frequency limits of the theory as well as certain extreme conditions of anisotropy. The general formulation is applied to the analysis of both an initially Gaussian and an initially rectangular pulse.
Measurement of Hot Carrier Diffusion Constant in Semiconductors
Authors: Okamoto K. , Nishizawa J. , Takahashi K.
Published: April 2005

Measurements of the electric field dependence of the hole diffusion constant in n-type germanium were made up to 2000 V/cm at temperatures of 297°, 195°, and 77°K. A distinctive feature of our experiments was the attenuation-rate measurements of sinusoidally modulated hole wave drifting along a filamentary specimen by the electric field supplied from a high-voltage pulser. The resistivity of the specimen was 5.3 Ω· cm and the hole diffusion constant was obtained which increased nearly in proportion to the two-thirds power of the electric field above 50 V/cm at 297°K and increased more rapidly at lower temperatures. For example, the result was Dp=900 cm2/sec when the electric field intensity was 1000 V/cm at 297°K.
Afterglow Studies in Noble-Gas-Hydrogen Mixtures
Authors: Oskam H. J. , Mittelstadt V. R.
Published: April 2005

The time dependence of the electron density during the afterglow period of plasma produced in helium-hydrogen, neon-hydrogen, and argon-hydrogen mixtures was measured by means of the microwave cavity method. The time dependence was found to be exponential during the later part of the afterglow period for pressures up to about 25 Torr. The relevant time constant depended on the plasma excitation condition at all values of pressure in helium-hydrogen mixtures, while this dependence was not observed in neon-hydrogen mixtures at pressure above 12 Torr and was absent in argon-hydrogen mixtures. The ion mobility values calculated from the measured ambipolar diffusion coefficients are 38±4 cm2/V·sec for helium-hydrogen, 17±1.0 cm2/V·sec for neon-hydrogen and 6.3±0.5 cm2/V·sec for argon-hydrogen mixtures.
Experimental Study of Gold-Gallium Arsenide Schottky Barriers
Authors: Padovani F. A. , Sumner G. G.
Published: April 2005

Departures from the theoretical behavior of a Schottky barrier are reported in the case of gold on gallium arsenide. It is shown that the empirical introduction of a single temperature-independent parameter takes care of all the observed departures.
On the Refractory Dust Method
Authors: Anderson Wallace L. , Rosen Gerald
Published: April 2005

Detailed theory is developed for the effective absorption of free electrons in a plasma by dust (micron-size) particles of a chemically inert refractory material. The analysis reveals a sharply defined regime of practical applicability for this ``refractory dust method.''
Injection-Stimulated Vacancy Reordering in p-Type Silicon at 76°K
Authors: Gregory B. L.
Published: April 2005

Electron injection into p-type silicon at 76°K has been observed to reduce the lifetime degradation rate due to 60Co gamma irradiation at 76°K. By comparing isochronal annealing data between 76° and 300°K with similar data obtained by Watkins in EPR studies, the lifetime degradation at 76°K is seen to be due primarily to recombination through vacancies. Since the activation energy of motion of silicon vacancies is known to depend strongly on charge state, the injection-stimulated reduction in degradation rate at 76°K has been related to vacancy reordering which occurs when the injected electron density is sufficiently large to modify the vacancy charge state from neutral (mobile above 160°K) to negative (mobile above 60°K). Quantitative estimates of the vacancy-reordering rate in the presence of excess electrons show this model to be consistent with the observed phenomena.
Electrical Properties of Carrier Generation-Recombination Centers in Silicon p-n Junctions
Authors: Sato Shuichi , Kawaji Shinji , Kobayashi Akio
Published: April 2005

The energy levels, the effective capture cross section for holes, and the concentration of the deep traps in the space-charge layer of ordinary p-n+ junctions and p-n+ junctions which contain gold atoms diffused throughout the specimen have been studied by the pulsed-field technique. The temperature dependence of the current-voltage characteristics of both types of silicon p-n junctions has also been studied. That the deep traps studied by the pulsed-field technique are the Shockley-Read-type carrier generation-recombination centers in the space-charge layer of the silicon p-n junctions has been confirmed for both kinds of silicon p-n junctions by comparing the pulsed-field data and the activation energy for the reverse current of the diodes. The energy levels and the charge character of the centers as well as the hole lifetime τpo for the ordinary silicon p-n+ junctions are in good agreement with the data of Sah, Noyce, and Shockley determined from their analysis of the diode characteristics.
Quantum Descriptions of an Infinite Lossless Transmission Line
Authors: She C. Y.
Published: April 2005

An infinite lossless transmission line is quantized by standard canonical procedures. The total Hamiltonian of the system is found to consist of two parts: the unperturbed Hamiltonian of the line H0 which describes the system when there is no signal applied, and the interaction Hamiltonian HI which describes the interaction of the input current i0(t) with the transmission line which governs the signal propagation in a quantum mechanical manner. The density operator ρ(t) of the transmission line is derived and the system is found to be in a state of ``signal plus noise.'' The statistics of a field observation is discussed with the aid of its characteristic function and it is statistically Gaussian. The average value of the local field (voltage or current) which describes the signal as propagating in two opposite directions with the speed of light agrees with the classical result. In the fluctuations of the field, a term due to noncommutativity of field operators (quantum noise) is found to be additive to the thermal noise. A narrow-band detector with bandwidth B located far away from the sender sees signal, thermal noise, and quantum noise which is equivalent to noise quanta of the carrier frequency arriving at a rate B/2.
Soft X-Ray Photoelectric Yield Formulas
Authors: Ogier W. T. , Ellis Darwin V.
Published: April 2005

Thick target x-ray photoelectric yield formulas are derived assuming a simple range for photoelectrons in the target. The predictions are compared with available experimental results for Cu Kα x rays impinging on Al, Cr, and Sn targets at an angle of 70°. Agreement is within a factor of 2 for Al and within 10% for Cr and Sn.
Magnetic Bubble Trapping in Liquids
Authors: Crozier M. H.
Published: April 2005

In a high magnetic field a liquid is subject to forces due to its para- or diamagnetism which contribute to the hydrostatic pressure at each point. It is shown that this contribution may give rise to a local pressure minimum at which bubbles in the liquid will accumulate. This effect is often produced in commercial liquid nitrogen with a standard laboratory electromagnet, because of the paramagnetism caused by a small oxygen content, and can cause experimental problems. The corresponding effect caused by diamagnetism has now been observed in water with a high-field solenoid operated in the range 165–205 kG, and it is predicted that a bubble trap will likewise occur in liquid helium when a magnet of this design is operated at slightly higher fields. Such an effect can produce irregularities in the results of low-temperature experiments in high magnetic fields unless bubbles are prevented from forming.
Rapid Method for Determining Ternary-Alloy Phase Diagrams
Authors: Kennedy Kurt , Stefansky Tibor , Davy Gordon , Zackay Victor F. , Parker Earl R.
Published: April 2005

A rapid method for determining isothermal sections of ternary-alloy diagrams has been developed. Three elements are evaporated simultaneously onto a heated substrate in such a way that the composition of the deposit varies from point to point as it does in a ternary-phase diagram. An isothermal section of the Fe–Cr–Ni system prepared by the new technique is compared with one reported in the literature. The applicability of this technique to the preparation of ternary phase diagrams is discussed.
Study of Defect Structures in BeO Single Crystals by X-Ray Diffraction Topography
Authors: Austerman S. B. , Newkirk J. B. , Smith D. K.
Published: April 2005

X-ray diffraction topography methods and supplementary optical microscopy were used to examine pyramidal and prismatic BeO crystals grown from lithium molybdate flux. The crystals appeared to have a high degree of perfection in that few dislocation lines were observed. Several specific types of defect structures were observed, however, in most of the crystals studied. The inversion-twin core structure was visible by image contrast effects from the twin boundary as well as by unequal image contrast on either side of the boundary. A screw dislocation line, possibly a group of many dislocations, commonly was present in the core and ran the full length of the crystal. Growth strata parallel to the active growth surfaces were also present. The topographs also revealed that considerable surface damage can be inflicted by intercrystal abrasion, much of which is removed by thermal annealing.
Surface-State and Interface Effects in Schottky Barriers at n-Type Silicon Surfaces
Authors: Crowell C. R. , Shore H. B. , LaBate E. E.
Published: April 2005

In an attempt to develop a Schottky barrier sufficiently low to be Ohmic at high current densities, Ca and Mg have been evaporated on freshly cleaved Si surfaces and on cleaved surfaces given controlled exposure to oxygen and water vapor. The results are explained in terms of the metal work function, the density of semiconductor surface (or interface) states and the thickness of the interface layer between metal and semiconductor. For clean metal-Si interfaces, measurements of barrier height as a function of the metal work function and as a function of the electric field in the Si are shown to determine an upper limit of 0.9 Å for the (thickness)/(dielectric constant) of the interface layer, and a lower limit of 2×1014 states/cm2/eV for the surface-state density. The Thomas-Fermi shielding length (≈0.5 Å for most metals) is proposed as the width of the interface layer. The resulting surface-state density is in good agreement with that for a free Si surface. This relationship appears to be a fairly general pattern for a wide variety of metal-semiconductor contacts. When a monolayer of oxygen separates the metal and the Si, the surface-state density relative to that of clean Si decreases appreciably, but the thickness of the interface layer also increases. With a given metal, the resulting dipole moment associated with the interface layer is only slightly changed. Thus only a small decrease in barrier height occurs. In both clean contacts and contacts with an interface composed of approximately one monolayer of oxygen, approximately ¼ of any change in the metal-Si contact potential is effective in changing the Schottky barrier height. The surface-state density and barrier height are very greatly reduced if the silicon surface is exposed to water vapor before deposition of the metal, but the resulting barrier is not stable in time.
Measurement of Space-Charge-Limited Current Characteristics in High-Resistivity Materials
Authors: Harnik E.
Published: April 2005

A method is proposed for the measurement of space-charge-limited current characteristics in high-resistivity materials which overcomes the difficulty of ensuring thermal equilibrium conditions throughout the measurements. Measurements carried out on high-resistivity single crystals of CdS, using this method, show the well-known characteristics of space-charge-limited current. It is shown that if proper care is not taken to ensure thermal equilibrium, the measured I-V characteristics depend strongly on the history of the sample and their interpretation on the basis of space-charge-limited current theories is unjustified and meaningless.
Diffusion of Copper in Nickel and Aluminum
Authors: Anand M. S. , Murarka S. P. , Agarwala R. P.
Published: April 2005

Diffusion of copper in nickel and aluminum has been studied by the residual activity technique in the temperature ranges of 850° to 1050°C, and 350° to 630°C, respectively. Diffusivities (cm2/sec) are expressed as DCu/NiCu/Ni=0.724 exp[−(61 000/RT)]DCu/AlCu/Al=0.150 exp[−(30 200/RT)].

Results have been compared with those calculated from the theories of diffusion based on charge and size difference between the impurity and the solvent atoms.
Three-Fluid Analysis of a Hydromagnetic Waveguide
Authors: Willett Joseph E. , Sodek Benard A.
Published: April 2005

A three-fluid method is developed for analyzing the modes of propagation in a waveguide filled with a partially ionized magnetoplasma. The method of approach involves the derivation of an effective Ohm's law from the three-fluid equations of motion. Dispersion relations are obtained for hydromagnetic and acoustic waves. The effects of neutral particles are shown explicitly for two limiting cases; namely, weak coupling and strong coupling between the neutral-particle gas and the electron-ion gas. The effects of Hall current, pressure, and resistivity are shown in the limit of negligible coupling.
Electromagnetic Scattering by Finite Dense Plasmas
Authors: Wyatt Philip J.
Published: April 2005

The often used hypothesis that a large overdense plasma medium may be treated as a perfect reflector is critically examined using a large homogeneous plasma sphere for particular emphasis as a simple scattering volume. This hypothesis is found to be in substantial error for densities between about four and κa/2 times the critical density where κ is the vacuum propagation constant of the incident field and a is the radius of the scatterer. The ``anomalous'' scattering in this restricted density range arises because of interference effects between the backscattered wave and tightly bound surface waves. These surface waves are of considerable importance for even very large (κa∼700) scatterers. The effects of absorption and inhomogeneity are also discussed. In general, it appears that deductions based on radar and other backscatter measurements are of questionable validity for a rather broad range of ionized scattering media.
Optical Properties of Cuprous Sulfide
Authors: Marshall R. , Mitra S. S.
Published: April 2005

Measurements of transmission and reflection over the ranges 400–10 500 cm−1 and 300–4000 cm−1, respectively, in Cu2S are reported. The bandgap changes from 1.21 eV at 300°K to 1.26 eV at 80°K. The minimum gap is apparently indirect with an effective phonon of frequency ∼280 cm−1 participating. In the region 700–8000 cm−1 the reflection and absorption is characteristic of free carriers. Lattice vibrational bands were observed in the region 400–700 cm−1, arising probably through excitation of the fundamentals and combinations of the zone-edge frequencies.
Nonideal Behavior of Inhomogeneous Superconducting Alloys
Authors: Joiner W. C. H.
Published: April 2005

An investigation of nonideal superconducting properties of inhomogeneous tin alloys reveals that the behavior of such samples represents a diverse set of phenomena intimately related to the nature of the inhomogeneities. Resistive temperature and field transitions are presented along with critical field data, magnetization curves, and remnant moment measurements. Several inhomogeneous samples are shown to possess very unstable magnetization curves and to show flux penetration at fields less than the bulk critical value. Annealing can make the magnetization more or less ideal, or produce very little change, depending on the nature of the inhomogeneity and the way it is altered in the process. Annealing sharpens the resistive transition temperature curve when more impurity goes into solution. It also can produce a large change in the apparent transition temperature. Samples examined represent both positive and negative surface energy materials containing either predominantly normal state or superconducting state inhomogeneities, or a combination of both. Although negative surface energy materials show more hysteresis than positive surface energy materials under equivalent conditions, the nature of the inhomogeneity and its role in flux retention is more important than the simple difference between positive and negative surface energy. A detailed description of the behavior of each sample and speculations as to the origins of features not heretofore reported are included.
Phase Locking of Modes in Lasers
Authors: Statz H. , Tang C. L.
Published: April 2005

An investigation is made of the phase-locking effects in lasers. It is shown that the phases of the simultaneously oscillating modes of lasers are not independent variables as sometimes thought. The calculations have been limited to three modes and homogeneously broadened lines. It is found that the sum of the phases of the low- and high-frequency modes as measured relative to the phase of the center mode assumes a definite value, which depends in turn upon the location of the active medium within the cavity. This phase relationship has a profound effect on experiments conducted with multimode lasers. For example, it is found that there should be essentially no fundamental-frequency beat note as observed by a square-law detector when a small laser crystal is placed in the center of an optical cavity.
Photoelectronic Analysis of Imperfections in Grown Stannic Oxide Single Crystals
Authors: Houston Jack E. , Kohnke E. E.
Published: April 2005

A study of the imperfection properties of grown stannic oxide single crystals was made using photoelectronic techniques. The primary objective has been to propose an energy level scheme for defects in these samples based on the results of measurements of spectral response, thermally stimulated currents, thermal quenching, and dark conductivity as a function of temperature. Measurements of thermally stimulated current indicated the existence of three trapping levels with average activation energies of 0.21, 0.52, and 0.60 eV. Comparison with dark conductivity data implied the 0.60-eV trap to be associated with the compensated portion of those donor states responsible for the normal n-type conductivity. Extrinsic thermal quenching results established that these levels were all trapping states for electrons, with the two shallow ones completely compensated and the deeper one only partially compensated. The results of intrinsic thermal quenching measurements indicated the existence of a compensated acceptor level lying 0.33 eV above the valence band and acting under certain conditions as a sensitizing center. The ratio of hole to electron capture cross sections for this level was found to be 7×102. Also found were more-or-less discrete levels having optical activation energies of approximately 1.0, 1.3, and 1.8 eV. These levels were determined from spectral response measurements which, in addition, show the existence of other unresolved levels lying further from the conduction band than 2.0 eV and a fundamental absorption edge at 4.0 eV.
Electron Density Measurements in the Magnetically Confined Arc
Authors: McLane C. K. , Takeda S. , Thomas W. E. , Thompson R. C.
Published: April 2005

Three methods were used to obtain electron density as a function of radius in a magnetically confined, low-pressure argon arc. The first utilized the phase shift of a reflected 35-kMc/sec microwave, and the second determined density from the ion saturation current to a Langmuir probe. The third determination utilized the broadening of the H β line emitted by a small quantity of added hydrogen. Agreement among the three methods is satisfactory; the electron density at the axis of this discharge is of order 1014 cm−3, in agreement with results obtained by others for discharges of similar type.
Gas Velocity Probe for Moving Ionized Gases
Authors: Cason Charles
Published: April 2005

A direct electrical method for measuring the velocity of a flowing plasma is based upon the polarization voltage induced when a plasma flows transversely to an applied magnetic field. A method has been developed to allow the estimation of certain background signals and the determination of allowable measurement currents arising from plasma and probe properties. Applications for this technique of ionized gas velocity measurements are indicated.

It was found that an ac magnetic field of the order of 5 G would give a sufficient signal to determine the gas velocity of a plasma jet as compared to a dc field of the order of 100 G. Gas stream velocities produced by a low-power argon plasma jet were found to vary from 1000 to 3000 m/sec depending slightly on the mass flow rate and predominantly on the ambient pressure.
Edge-Effect Limitations on the Critical Currents of Thin Films of Tin
Authors: Hagedorn F. B.
Published: April 2005

The edges of planar thin-film strips of tin are shown to limit the supercurrent carrying capacity of the films in some cases. This edge effect is demonstrated by means of a special structure which provides two current flow-paths through the same film. The film strip edges are included in only one of these two paths. Detailed results are given for a 4400-Å film of tin in which dc critical currents near the Silsbee limit are observed when the edges are excluded. Including the edges reduces the critical current for this film by more than 30%. It is suggested that an evaporation process can probably be developed which leads to films which will not exhibit this edge effect. The special structure would provide a useful tool for this process development, and it can also be adapted to serve as an improved gate for thin-film cryotrons.
Secondary Electron Yield from Fission Fragments
Authors: Jamerson F. E. , Leffert C. B. , Rees D. B.
Published: April 2005

The secondary electron yield from fission fragments has been measured directly using an ultrahigh-vacuum diode containing uranium which was operated in a nuclear reactor. The current measured in this diode consisted of contributions from the positively charged fission fragments, secondary electron emission induced by fission fragments, and photoelectrons generated by gamma radiation. The secondary electron yield Δ was determined from the secondary electron current and the computed fission fragment emission rate. For a thick (>one range) uranium-nickel (5.7 wt. % nickel) alloy the value of Δ is 207±10.
Constricted Discharges in the Rare Gases. I. Spectroscopic and Electrical Measurements
Authors: Massey J. T. , Cannon S. M.
Published: April 2005

A description of the visual characteristics of some constricted discharges in the rare gases using dc, rf, and microwave excitation is given. These discharges require power inputs of from 20 to greater than 100 W/cc. The results of a series of spectroscopic and electrical measurements made on these discharges indicate the range of plasma parameters encountered. Gas temperatures were measured using the intensity distribution of the spectra of several diatomic molecules. The gas temperature falls in the range from 2000° to 3000°K, but atomic excitation levels are not in equilibrium at this temperature. The charge density is around 1014/cc from continuum intensity, line broadening, and electrical measurements. The electron energy distribution is Maxwellian with an average electron energy which falls between 1 and 2 eV. Thus, these plasmas lie between ``thermal'' and ``cold'' plasmas in their properties. The recombination process probably has contributions from both dissociative recombination and dielectronic recombination with an over-all recombination coefficient of about 2×10−11 cm3/sec.
Characteristics of the ``Synchrotron Light'' from the NBS 180-MeV Machine
Authors: Codling K. , Madden R. P.
Published: April 2005

The characteristics of the ``synchrotron light'' emitted by electrons in the NBS 180-MeV electron synchrotron were studied in detail. The electron beam cross section was approximately 1×2 mm. The angular distribution and polarization properties were determined for the visible radiation; photoelectric techniques resulted in a more critical comparison of the experimental results to the theoretical predictions than heretofore possible. Doubts raised by previous work regarding the symmetry of the radiation with respect to the orbital plane have been allayed. Characteristics of the radiation in the extreme ultraviolet are calculated for the NBS machine, and applications of this source for physical experiments are discussed.
Stopping Cross Section of Low Atomic Number Materials for He+, 65–180 keV
Authors: Moorhead R. Dale
Published: April 2005

Stopping cross sections were measured for H1+ in carbon and for He+ in carbon, aluminum, and chromium over the energy range of 65 to 180 keV. Layers of the stopping materials were evaporated in vacuo onto a gold-plated quartz crystal and their areal densities were computed from the shift in the resonant frequency of the crystal. The energy lost by the ions in the stopping material was determined by measuring the energy of the scattered ions. Experimental results show a divergence from available theory above 80 keV.
Temperature Dependence of the Multimode Behavior of GaAs Lasers
Authors: Lavine J. M. , Iannini A. A.
Published: April 2005

In GaAs lasers with a homogeneously broadened spontaneous emission line, spatial inhomogeneity of the inverted population can lead to multimode oscillation. In this paper the behavior of higher-order axial modes of Fabry-Perot GaAs lasers at 4.2° and 77°K is shown to be in good agreement with the theory of Statz and Tang, strongly supporting the model of spatial inhomogeneity. Since diffusion plays a prominent role in smoothing out these spatial inhomogeneities, the theory calls for, and the experiment verifies, that GaAs lasers must be pumped harder at higher temperature to produce oscillations in a given number of modes.
Improved Thermionic Emitter: Thorium on Grain-Oriented Polycrystalline Tungsten
Authors: Weissman Ira
Published: April 2005

A grain-oriented polycrystalline thoriated tungsten emitter is described which demonstrates vastly improved emission characteristics over ordinary emitters of the same type.

The factor of four improvement in electron emission in high vacuum is almost entirely the result of an increase in A value from four to seventeen. The Richardson work function φ of the improved emitter is essentially the same as that of the ordinary one.

A comparison is made of the efficiencies of two cesium-neutralized thermionic converters, identical in every respect except that one contains the improved emitter and the other an ordinary one. The measured improved factor of three in conversion efficiency is in close agreement with the predicted factor based on the difference in A values.
Precision Measurement of the Microwave Dielectric Constant of Liquids
Authors: Fatuzzo E. , Mason P. R.
Published: April 2005

A method utilizing reflection measurements on a liquid-filled line section terminated in a short circuit is described. Its chief feature is the use of line lengths such that the impedance at the liquid surface is real, which simplifies the calculation ofε* from the measurements. Additionally it reduces systematic errors due to the window used to constrain the liquid surface, and the nonzero impedance of the sliding plunger used to adjust the length. These factors give errors inε′ about an order of magnitude below those inε″. This makes the method particularly suitable for determination of the dielectric relaxation time of solutions of polar in nonpolar liquids. Limits on the window and plunger parameters to give an accuracy of about 5% inε″ and 0.5% inε′ are derived. Results of measurements with equipment satisfying these requirements are given, and it is seen that relaxation times can be found to about 5% accuracy for solutions 1–10 Molar % nitro-benzene in benzene.
Probe Measurements through a Double Layer
Authors: Medicus G.
Published: April 2005

Probe curves and their second derivatives are automatically plotted for a small spherical probe going through a double layer (DL) at the opening of a hollow hot oxide cathode in a discharge in pure Ne of about 1 Torr. The cathode emission electrons are accelerated toward the DL in its fringe fields. Between cathode surface and DL, the electrons behave approximately according to the ``accelerated half-Maxwellian''; in the DL they are accelerated to energies equivalent to the metastable Ne levels near 16.5 V. A region of strong excitation and ionization (``ball of fire'') forms just outside the cathode opening. The cathode emission electrons enter the ball of fire as a ``fast group,'' superimposed on the approximately Maxwellian slow group of the ball of fire plasma. The development of potential, density, and e spectrum is discussed.