摘要:

A new technique to determine the depth distribution of energy loss, the so‐called depth‐dose function, is described for electrons whose energies ranged from 15 to 30 keV at normal and 45° incident angles. This method is based on a series of measurements of currents induced by the penetration of energetic electrons through a metal‐oxide‐semiconductor‐structure (Al&sngbnd;SiO2&sngbnd;Si) specimen whose metal electrode is formed by an aluminum layer deposited in a stepwise manner. The experimental depth‐dose function and range‐energy relation are compared with other experimental and theoretical results. A particular interest was taken in the comparison of the experimental results with those predicted by our Monte Carlo calculations to confirm the good agreement between them. Furthermore, the ratio of the product of mobility and lifetime to the mean electron excitation energy in SiO2was also determined to be &mgr;&tgr;/EA= 0.10 × 10−11cm/V2, which may be ranked between the values reported by Everhart and Hoff and by Goodman. The effects of space charge in SiO2are also discussed.

ISSN:0021-8979    

DOI:10.1063/1.1663311

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A piston‐cylinder apparatus was developed in which ultrasonic waves were transmitted into a high‐pressure sample through the unsupported area of a Bridgman seal. The sound‐wave transmission could be divided so that one portion returned from a fixed reflector in the sample, giving sound‐velocity measurements, and the other portion returned from the piston itself, giving the relative volume of the sample. In this way, adiabatic and isothermal compressibilities could be measured simultaneously. Relative volumes were also determined from the piston travel, observed externally. A calibrated manganin gauge allowed pressures to be compared with those calculated from the ram force and hysteresis curve of the advancing and retreating piston. Data are reported for argon at room temperature up to about 13 kbar where it solidifies.

ISSN:0021-8979    

DOI:10.1063/1.1663312

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The impact of drops with target liquids has been investigated. A description of the cavity growth after the impact of a single droplet is presented and a theoretical model has been derived which gives the time dependency of the cavity depth. Experimental verification with water shows good agreement between theory and experiment.

ISSN:0021-8979    

DOI:10.1063/1.1663313

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An analysis is performed to investigate free and forced oscillation of a gas bubble and cavitation in viscoelastic liquids of a three‐parameter Oldroyd model. The first‐order perturbation method for small amplitudes has been employed to obtain periodic solutions to the bubble dynamics equation. Consideration is given to the influence of surface tension, vapor pressure, and thermodynamic behavior of the gas inside the bubble. It is disclosed that transient behavior of the bubble in viscoelastic liquids is governed by five dimensionless parameters. Conditions for stable bubbles are obtained. Free oscillation consists of a decaying exponential component and a damped sinusoidal oscillation associated with the natural frequency of the bubble‐liquid system. The effects of the five governing parameters on the natural frequency are determined. The radial motion of the bubble in an oscillating pressure field includes a sinusoidal oscillation associated with the forcing frequency, a decaying exponential component, and a damped sinusoidal oscillation associated with the natural frequency. Criteria for the onset of incipient cavitation are determined when a bubble is suddenly released into the liquid or is situated in an oscillating pressure field.

ISSN:0021-8979    

DOI:10.1063/1.1663314

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The stability and classification of steady‐profile plane shocks in liquids are studied by hydrodynamic equations which include the relaxational properties of momentum and heat fluxes. The thermodynamic behavior during shock deformation is shown to be equivalent to the dissipative motion of a particle described by a generalized Lie´nard equation. The stability condition produces relations for the relaxation times for momentum and heat fluxes. These relations are in agreement with acoustic data and other theoretical calculations which produce the relaxation times of 10−13−10−14sec.

ISSN:0021-8979    

DOI:10.1063/1.1663315

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Surface acoustic waves have been used successfully in the present work to study the mechanical properties of ion‐exchanged glass surfaces. The surface wave velocity was measured as a function of frequency on an alkali‐aluminosilicate glass before and after sodium for lithium ion exchange. The exchange was carried out at temperatures both above and below the transformation range of the glass and for various treatment times. The surface wave dispersion is explained in terms of depth‐dependent changes in the density and modulus resulting from the concentration gradient caused by the ion exchange. An independent measurement of the density change has allowed a quantitative measurement of shear modulus change in the ion‐exchanged layer. The experimentally determined dispersion curve agrees well with theoretical calculations at frequencies for which the latter are available. The presence of surface stresses has been detected by means of these measurements which has allowed a determination of their time dependence.

ISSN:0021-8979    

DOI:10.1063/1.1663316

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper presents the results of an investigation conducted on the switching behavior of copper oxide. The filamentary nature of the current and also the formation of a copper channel have been observed to be associated with the process of switching. The experiments and the analysis carried out by the authors show that the formation of copper channel is due only to a secondary process and is not responsible for the actual switching of the device to the low‐voltage mode. The switching, as is clear from the analysis, seems to be the result of a purely electrothermal process. The effect of the dimensions of the device on theV‐Icharacteristics is also discussed. It has further been shown that it is possible to prevent the formation of copper channel to obtain a monoshot type of switching transition.

ISSN:0021-8979    

DOI:10.1063/1.1663317

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Simplified models of collision processes are introduced which make possible closed‐form analyses of electron distributions in molecular gases. In particular, models are considered that approximate the collision processes in a diatomic gas and in a gas mixture resembling the He : N2: CO2laser. Expressions are obtained for the rates of excitation of the vibrational modes which include the effect of superelastic collisions. The results are illustrated by evaluating theV‐Icharacteristic and the efficiency of anE‐beam CO2laser.

ISSN:0021-8979    

DOI:10.1063/1.1663318

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

This paper presents an analysis of lifetime versus excess density or photoconductivity versus excitation intensity for a semiconductor when two or more trapping levels are present. As an example, data for ap‐type (boron‐doped vacuum‐float‐zone grown) silicon sample which had been irradiated with Co60&ggr; rays are considered. Measurements covered seven orders of magnitude in photoconductivity, and the lowest excess electron concentration was ∼ 10−8times the equilibrium hole concentration. Two trap levels were identified atEc−(0.56±0.01) eV andEc−(0.71±0.02) eV. Introduction rates for these levels were ∼ 10−6and ∼ 10−8(photon cm)−1, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1663319

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The behavior of the Zn acceptor in conjunction with the N isoelectronic trap in GaAs1−xPxis studied. The photoluminescence spectra of GaAs1−xPx: N : Zn, dopedptype by dilute Zn diffusion, are shifted to lower energy by an amountEZn≃30 meV (x<xc≃0.46, 77°K) for recombination transitions involving the &Ggr; band edge, theAline, or NN pairs. For transitions involving theAline or NN pairs and crystal composition beyond the direct‐indirect transition (x>xc), the spectral shift due to the Zn acceptor weakens with increasingx, which is in accord with the relative weakening ofk= 0 recombination components asE&Ggr;increases relative toE&khgr;. Photopumped laser operation of GaAs1−xPx: N : Zn (x< 0.46) platelets is demonstrated on Zn&sngbnd;N transitions. No effect is observed attributable to Zn&sngbnd;N complexes.

ISSN:0021-8979    

DOI:10.1063/1.1663320

出版商:AIP    

年代:1974

数据来源: AIP