摘要:

A reflection acoustic microscope may be used to image structural details under the apparent surface of a thick sample. To design such an apparatus, the geometrical parameters of the acoustic lenses must be carefully defined. The acoustic field distribution has been computed in the previous structure for this purpose. Some preliminary experimental results are also reported here.

ISSN:0021-8979    

DOI:10.1063/1.326144

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We have examined the properties of mercury–rare-gas discharges operated at low fields where volume ionization is negligible. The discharge current is due to thermionically produced electrons and is limited by the electron mobility. The mixtures consisted of mercury and either Ar, Kr, or Xe at 30–760 Torr. Temperatures were varied from 50 to 250 °C. uv and visible radiation production, as well as electrical properties, were measured and compared to theoretical calculations. The measured positive volt-ampere characteristics agree well with theory. The calculated efficiency for excitation of Hg3P1in these discharges is greater than 50% over a wide range of conditions. The low measured radiation production efficiency (less than 5%) is consistent with model calculations which include quenching of the3P1by Hg and the rare gas to the3P0state and its subsequent decay by the formation of mercury excimers.

ISSN:0021-8979    

DOI:10.1063/1.326145

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Resonant excitation of an upper hybrid wave by the mixing of two coaxial Gaussian em beams in a collisionless hot magnetoplasma has been investigated; the electric vectors of beams are polarized along a uniform static magnetic field and the beams propagate perpendicular to the magnetic field. The resonant excitation of the upper hybrid wave occurs when the difference frequency of the two em waves and difference of their propagation vectors satisfy the dispersion relation corresponding to the upper hybrid wave. Furthermore, because of the Gaussian intensity distribution of the two beams the electrons are redistributed by the ponderomotive force, cross focusing of the two em beams occurs, and the power of the excited upper hybrid beam (which depends on the background electron concentration, the intensities of the two em beams, and the magnetic field) are correspondingly modified. The present analysis is also applicable to an inhomogeneous magnetoplasma in the WKB approximation.

ISSN:0021-8979    

DOI:10.1063/1.326146

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The elastic interaction energy between a point defect and a stress field is determined for the case in which the point‐defect displacement field has spheroidal symmetry, called the shape interaction. Results are given for the stress field of an edge dislocation, including a term from excluding the elastic interaction arising from the defect and dislocation core regions. With parameters appropriate to an fcc lattice it is then shown that a vacancy will tend to migrate around the dislocation to the compressional side, but that there is an energy barrier in the radial direction between the vacancy and the dislocation on the compressional side.

ISSN:0021-8979    

DOI:10.1063/1.326155

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Experiments are described in which the field‐ion microscope is used to observe the details of grain‐boundary migration in polycrystalline tungsten. Annealing is doneinsituand the specimen is observed prior to and after several heating pulses. Microfacets are formed during the process which after analysis are observed to differ from those expected when the coincidence site lattice model is assumed to be valid.

ISSN:0021-8979    

DOI:10.1063/1.326156

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

We investigate a new technique for the determination of light‐ion stopping powers in metals. The radiation‐damage‐induced resistivity change in thin films is measured as a function of ion energy. As the ion energy is raised, an increasing fraction of the energy passes through the back surface, thereby resulting in decreased damage production. This effect has been analyzed by comparison with predictions based on an Edgeworth expansion of the damage‐distribution function, using the moments tabulated by Winterbon. Results are presented for He, Li, and C irradiations of silver films with thicknesses of 2640 and 3880 A˚. The present results are compared with those of previous work. Other methods for calculation of the damage‐distribution function are compared with the Edgeworth expansion.

ISSN:0021-8979    

DOI:10.1063/1.326157

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The results of attempting to fit the step‐annealing data to an activation energy distribution indicate a dispersion of the frequency factor ranging from 107to 1011sec−1which is explained as arising from diffusion processes. The distribution appears to rise gradually to a peak with the possible existence of a subsidiary peak, then a very sharp drop from the peak. This sharp drop indicates the annealing processes are first order. The beginning of the distribution is in accord with its being the residue from annealing during bombardment, subsequent treatment, and storage. It is hypothesized that the gradual rise is associated with the dispersion of the frequency factor.

ISSN:0021-8979    

DOI:10.1063/1.326158

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The lateral spread of implanted P+ions and the shape of the mask window have been observed simultaneously using the technique of staining the cleaved surface and scanning electron microscopy for the Si samples with the SiO2mask window with a tapered edge. The mask edge with a gradient of 45° or 78° to the Si surface and the implantedn‐type region with a carrier concentration higher than 2×1017/cm3are observed in the same photograph. The observed maximum lateral spread when the gradient of the mask edge is 45° is about 1.6 times larger than that when the gradient is 78°. The calculated results of the lateral spread agree relatively well with the experimental data although the precise analysis based on the definite basis is necessary.

ISSN:0021-8979    

DOI:10.1063/1.326159

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Alkali motion in alkali silicate glass was studied by the method of ionic thermocurrent which was developed as a highly sensitive technique for studying relaxation of polarized impurity‐vacancy dipoles in ionic crystals. Two current peaks were observed in the temperature range −196–100 °C, and were ascribed to orientational depolarization of pseudodipoles composed of localized alkali–nonbridging oxygen and to thermal relaxation of space charges near the cathode. Heterogeneous distribution of alkalis in alkali silicate glass was verified by large differences in ionic thermocurrent and in the evaluated density of localized alkalis from sample to sample taken from even the same glass film, as well as by the distribution in activation energies for dipolar orientation and space‐charge relaxation. It was also concluded that the neutralization process of alkalis in glass was due to tunneling of electrons through the potential barrier in the space‐charge–electrode double layer.

ISSN:0021-8979    

DOI:10.1063/1.326160

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

By using both Auger electron spectroscopy and electron‐stimulated desorption measurement techniques, electron‐beam‐irradiation‐induced oxide reduction has been observed on WO3and Ta2O5. In both cases, the light element (oxygen) is preferentially removed which in turn leaves the specimens’ surface enriched with the metal element. In addition, visible darkening in the beam‐illuminated area provides evidence of beam‐irradiation‐induced oxide reduction and irradiation‐enhanced diffusion effects. Measurements of Auger electron intensities from the composition altered overlayer indicate that the beam‐irradiated overlayer consists of nearly equal parts of metal and oxygen atoms upon extended electron bombardment. The observed changes in the surface composition of contaminated specimens also show additional beam effects like induced out‐diffusion and beam‐induced desorption. A brief comparison with the published results concerning ion irradiation on the corresponding specimens is also included.

ISSN:0021-8979    

DOI:10.1063/1.326161

出版商:AIP    

年代:1979

数据来源: AIP