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1 Jun 1984

Volume 55, Issue 11, pp. 3907-4137

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Vapor coating of electrostatically dispersed powders

S. G. Szirmai, D. H. Morton, and P. L. Kelly

J. Appl. Phys. 55, 4088 (1984); http://dx.doi.org/10.1063/1.332999 (7 pages)

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The deposition of vapors on electrostatically suspended dust has been studied through the construction of a laboratory‐scale coating unit suitable for depositing coatings of high‐melting point vapors (up to 1600 °C) on dispersed metal powders in a vacuum. Following a brief discussion of electrodispersion, the physical effect by which electrostatic suspensions may be generated, the construction and use of a laboratory coating unit is described. The equipment, which is housed in a vacuum enclosure at <10−5 Torr, consists partly of systems for maintaining the powder in a state of continuous suspension and flux and partly of others responsible for generating vapors. Our laboratory equipment, which relies on the indirect electron‐beam heating of the evaporant, has a nominal capacity of 0.5‐Kg coated metal powder per day and was successfully used for the production of powders treated with zinc, silver, tin, gold, and palladium. In discussing the potential for industrial scale use, it is shown that the process parameters of such a unit may be calculated with relative ease and it is concluded that a scale up to industrial size is feasible.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation

Thermal oxidation of silicon: Chemisorption and linear rate constant

S. M. Hu

J. Appl. Phys. 55, 4095 (1984); http://dx.doi.org/10.1063/1.333000 (11 pages) | Cited 22 times

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This is the first of a series of three papers which, by introducing new concepts and new formulations that are consistent with experimental observations, attempt to treat a number of topics related to the kinetics and the mechanisms of the thermal oxidation of silicon. The present paper deals with the surface reaction aspect of oxidation. A new oxide growth law has been formulated to be consistent with the observed power‐law pressure dependence of interface reaction kinetics. Then the subject of chemisorption, proposed here as an intermediate step of the thermal oxidation of silicon, is treated at length. It is shown, from a first‐principles analysis, that the energy of chemisorption should vary approximately logarithmically with the amount of chemisorption, that this leads to an adsorption isotherm which is related to the oxygen pressure by a power law, and that the exponent of the power law should vary linearly with temperature within a reasonable span. The effects of substrate doping and of substrate damage are also analyzed.
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81.65.-b Surface treatments
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Theory of the retarding potential method of cathode temperature measurement

E. A. Adler and R. T. Longo

J. Appl. Phys. 55, 4106 (1984); http://dx.doi.org/10.1063/1.332963 (7 pages)

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Retarding potential measurements can be used to determine the temperature of the cathode in a traveling wave tube. General expressions are derived for the current in a thermionic diode as a function of cathode temperature and applied voltage. An enumeration is made of the conditions under which such expressions can be reduced to a form that enables application of the retarding potential method of temperature measurement. An integral form is given for the factor needed to generalize the Richardson equation to more general geometry, and it is evaluated for a special case. Finally, there is a discussion of the case when, because of surface or other effects, the distribution function of emitted electrons is not given by the Fermi–Dirac distribution.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
79.40.+z Thermionic emission

High power blue‐green laser by hypocycloidal‐pinch plasmas

K. S. Han, S. H. Nam, and J. H. Lee

J. Appl. Phys. 55, 4113 (1984); http://dx.doi.org/10.1063/1.332964 (3 pages) | Cited 3 times

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A high power blue‐green laser has been pumped with an array of multiple‐stage hypocycloidal‐pinch plasmas. The maximum untuned laser power obtained with LD‐490 dye exceeded 230 kW with a pulse width of 1.0 μs (FWHM). The characteristics of the new pumping source and optical coupling configuration indicate that the system can be developed for repetitive and high average power operation.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems
33.80.Be Level crossing and optical pumping
52.75.-d Plasma devices

Spatial frequencies generation in an optical nonlinear medium

A. Adolf, D. Chatrefou, D. Euzenne, and B. Morbieu

J. Appl. Phys. 55, 4116 (1984); http://dx.doi.org/10.1063/1.332965 (4 pages) | Cited 1 time

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We present an experiment which shows the generation of spatial harmonic frequencies due to the refractive index nonlinearity in CS2. This experiment allows to test the validity of the formalism using the break‐up integral and can lead to a new measurement method of the nonlinear index in optical materials.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.25.Gy Edge and boundary effects; reflection and refraction
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Discharge striations in rf excited waveguide lasers

D. He, C. J. Baker, and D. R. Hall

J. Appl. Phys. 55, 4120 (1984); http://dx.doi.org/10.1063/1.332966 (3 pages) | Cited 11 times

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The existence of transverse striations in radio‐frequency discharge excited waveguide carbon dioxide lasers is reported. A simple model indicates how these effects can be explained in terms of internal space‐charge fields. An additional effect of the space‐charge regions on the discharge capacitance is described.
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52.80.Pi High-frequency and RF discharges
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Internal friction changes in NaCl at 77 K

G. A. Bielig

J. Appl. Phys. 55, 4123 (1984); http://dx.doi.org/10.1063/1.332967 (2 pages)

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The behavior of B/B0, the fractional change in the dislocation damping coefficient, has been studied at 77 K for continuous and interrupted radiation experiments using λ rays. Preliminary results indicate that B shows similar increases as observed at room temperature, but there appears to be a decreasing component of B/B0 when the radiation is first switched on. Illumination with laser light (λ=633 nm) tends to ‘‘erase’’ previous B/B0 changes as well as unpinning dislocations.
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61.80.Ed γ-ray effects
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Measurements of laser shock pressure and estimate of energy lost at 1.05‐μm wavelength

F. Cottet, J. P. Romain, R. Fabbro, and B. Faral

J. Appl. Phys. 55, 4125 (1984); http://dx.doi.org/10.1063/1.332968 (3 pages) | Cited 10 times

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Laser‐driven shock pressures at 1.05‐μm wavelength have been evaluated from measurements of shock transit time through aluminum foils by streak camera records of shock luminosity at the back face of the foil. An ablation pressure of 0.3 TPa is obtained for 1.2×1014 W/cm2 laser pulses focused on 300‐μm spot diameter and 0.55 TPa for 3.5×1015 W/cm2 laser pulses focused on 60‐μm spot diameter. These results, compared with theoretical values, show an important loss of energy, attributed to two‐dimensional effects. The ratio of effective energy for compression to incident energy is estimated to be 12% for 1.2×1014 W/cm2 experiments and only 1% for 3.5×1015 W/cm2 experiments.
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62.50.-p High-pressure effects in solids and liquids
79.20.Ds Laser-beam impact phenomena

Xerographic measurements in compensated hydrogenated amorphous silicon

F. Jansen, J. Mort, S. Grammatica, and M. Morgan

J. Appl. Phys. 55, 4128 (1984); http://dx.doi.org/10.1063/1.332969 (2 pages)

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Xerographic discharge measurements are reported on 10‐μm‐thick compensated hydrogenated amorphous silicon samples for doping levels as high as 5000 ppm by weight. Excellent xerographic characteristics including photosensitivity, charge acceptance, and hole range are maintained up to doping levels ∼ 100 ppm by weight. Beyond this both charge acceptance and hole range degrade due to associated increases in mid‐gap‐state densities.
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72.40.+w Photoconduction and photovoltaic effects
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
61.72.U- Doping and impurity implantation

dc conduction and dielectric absorption in PVF2

Roberto M. Faria, Bernhard Gross, and G. F. Leal Ferreira

J. Appl. Phys. 55, 4130 (1984); http://dx.doi.org/10.1063/1.332970 (2 pages) | Cited 18 times

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Charging and discharging currents in PVF2 are found to depend on the nature of the gas (argon or air) in which the samples are kept during measuring and on the pressure and humidity of the air.
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77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
66.30.Dn Theory of diffusion and ionic conduction in solids

Optical properties of diffusion‐produced AuSn

S. Neel, E. T. Arakawa, and T. Inagaki

J. Appl. Phys. 55, 4132 (1984); http://dx.doi.org/10.1063/1.332971 (2 pages) | Cited 1 time

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Optical properties of the intermetallic compound AuSn were determined for photon energies between 0.6 and 2.9 eV by ellipsometry. The samples were made by interdiffusion in evaporated Au/Sn thin films at room temperature. The results obtained agree well with the results previously obtained for AuSn made by direct evaporation of a stoichiometric mixture of gold and tin.
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78.66.Bz Metals and metallic alloys

A new approach of the dose‐rate measurements in thermoluminescence dating

Ch. Michael, P. Andronikos, and D. Haikalis

J. Appl. Phys. 55, 4134 (1984); http://dx.doi.org/10.1063/1.332972 (3 pages)

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A method is described in which the dose rates of β and γ irradiation that are due to radioactivity in both the pottery and its environment are measured simultaneously. The main advantage of this method is that the CaF2 grains are irradiated under conditions similar to those existing during the irradiation of the quartz grains of the pottery, while buried in the soil. The calculations for the determination of the annual dose and subsequently of the pottery’s archaeological age, considering that the natural dose is known, are also described.
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89.90.+n Other topics in areas of applied and interdisciplinary physics (restricted to new topics in section 89)
78.60.Kn Thermoluminescence
FREE

Erratum: Second‐harmonic emission from laser‐plasma interactions [J. Appl. Phys. 54, 4902 (1983)]

Xu Zhizhan, Xu Yuguang, Yin Guangyu, Zhang Yanzhen, Yu Jiajin, and P. H. Y. Lee

J. Appl. Phys. 55, 4137 (1984); http://dx.doi.org/10.1063/1.333391 (1 page)

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Abstract Unavailable
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
99.10.Cd Errata
FREE

Erratum: Simple model to explain inhomogeneous structures in shocked solids [J. Appl. Phys. 54, 7198 (1983)]

G. H. Vineyard

J. Appl. Phys. 55, 4137 (1984); http://dx.doi.org/10.1063/1.332973 (1 page)

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Abstract Unavailable
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62.50.-p High-pressure effects in solids and liquids
46.40.Cd Mechanical wave propagation (including diffraction, scattering, and dispersion)
46.40.Jj Aeroelasticity and hydroelasticity
81.40.-z Treatment of materials and its effects on microstructure, nanostructure, and properties
99.10.Cd Errata
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