摘要:

Doped hydrogenated amorphous‐microcrystalline mixed‐phase silicon (&mgr;c‐Si:H) films were prepared by the mercury photosensitized decomposition of a disilane‐hydrogen gas mixture, by adding phosphine and diborane fornandptype, respectively. The maximum dark conductivity and optical band gap of the films were, respectively, 20 S cm−1and ∼2.0 eV forntype, and 1 S cm−1and 2.3 eV forptype. It is most significant that the gaseous ratio of hydrogen to disilane should be enhanced up to 70 forntype, and even 300 forptype, to obtain such a highly conductive and wide gap film. The crystallinity of the photodeposited &mgr;c‐Si films appeared to be improved in comparison with that of films by conventional plasma glow discharge technique.

ISSN:0021-8979    

DOI:10.1063/1.336071

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A calculation is presented of the incoherent radiation emitted by an electron beam of finite radius passing through a linearly polarized magnetic undulator in a rectangular waveguide with perfect conducting walls. This analysis is based on the Fourier component of the Lienard–Wiechert fields. The metallic boundary conditions are exactly incorporated in the formalism by means of the ‘‘image currents’’ method. In the Fresnel approximation, we show that the double infinite sum over ‘‘images’’ is transformed into one over ‘‘vertical modes,’’ consisting of trigonometric functions. The discrete frequency spectrum and angular distribution of the radiation are studied for several energy spread and electron beam radius cases. The predicted radiation patterns provide useful diagnostics to determine the electron beam properties (trajectories, energy and angular spread, betatron oscillation). The amount of relative power emitted on each mode is a gaussian function exp(−an2).

ISSN:0021-8979    

DOI:10.1063/1.336072

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The pump and probe variant of the stimulated Raman gain technique permits the measurement of picosecond dephasing times with low‐power, continuous‐wave mode‐locked lasers, but it suffers by its susceptibility to inevitable randomly induced fluctuations in the relative phases of the interacting laser fields. The resulting severe requirements on optical stability can be circumvented through application of a double‐modulation–detection scheme that we have developed. It is based on rms detection of theT2signal as generated through application of a low‐frequency phase modulation of precise amplitude, additional to the commonly applied rf modulation with corresponding lock‐in detection. A detailed description of the method and its experimental realization is presented.T2measurements on the 656 cm−1vibration of liquid CS2illustrate its performance. In comparison with previous techniques, precision is improved by about a factor of 4. But more important is the fact that the technique permits to make a continuous recording of theT2signal, while achieving at the same time a reduction in measurement time by an order of magnitude. Furthermore, optimization of the optical setup is possible, through direct monitoring of the dephasing signal at any delay. Automating the data taking and processing should be straightforward.

ISSN:0021-8979    

DOI:10.1063/1.336073

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The interaction of light with Lamb waves propagating in transparent plates has been investigated. The analytical study has been done by considering a three‐step interaction, at the limiting surfaces and within the propagation medium. Experimental data are given, relative to isotropic crystal plates in the MHz frequency regions and compared with theory.

ISSN:0021-8979    

DOI:10.1063/1.336074

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The wave equation in which the source term is coupled with the thermal energy migration was analyzed, and the physical meaning of the phase of photoacoustic signals generated in turbid solutions was clarified. These theoretical results, partially verified by experiments, showed the possibility for novel thermal characterizations and size measurement methods of microparticles. The theoretical limitation of the size measurement was 102A˚ for samples with nonradiative relaxation times of 1 nsec.

ISSN:0021-8979    

DOI:10.1063/1.336075

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown in this paper that a high‐voltage gap exhibits a nonlinear capacitance behavior in the presence of large space‐charge fields. The existence of this nonlinear capacitor is quasi dc in nature and does not result from transit time effects, i.e., high‐frequency effects. This nonlinear behavior can be used to tailor the shape of bunched intense relativistic electron beams.

ISSN:0021-8979    

DOI:10.1063/1.336076

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Activation or enhanced arc durations due to the presence of minute quantities of organic contaminants in low‐current arcing atmospheres is becoming a problem in the reliability of the new generation of miniature relays sealed in plastic or metal containers. This article describes arc duration reduction by the addition of the electronegative gases, SF6and C2Cl3F3to the arcing atmosphere when part‐per‐million hydrocarbon impurities were present. The effects of hydrogen on the arc durations is also examined.

ISSN:0021-8979    

DOI:10.1063/1.336077

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Experimental measurements of the cation vacancy formation energies (Ef) of Hg1−xCdxTe were carried out by Hg‐annealing and rapid quenching to room temperature, followed by Hall measurements at 77 K. Our observations show that one charge state vacancy is dominant, so that the fractional numbernof cation vacancies at temperatureTis related exponentially to the energyEfrequired to create one vacancy,n=A exp(−Ef/kT). No appreciable temperature dependence ofEfdue to temperature variation of the ionization levels and the self‐consistent Fermi level is seen. Our measured value for the activation energy is found to beEf=0.9±0.1 eV, for Hg1−xCdxTe withx=0.21, 0.3, and 0.43. This value is found to be nearly independent of Cd compositionx. Theoretical calculations of thep‐type carrier concentrations due to cation vacancies in Hg0.8Cd0.2Te yield results which are in good agreement with experimental data. These modeling calculations predict the cation vacancies to be predominantly doubly ionized species at 77 K.

ISSN:0021-8979    

DOI:10.1063/1.336078

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Changes in the sizes of second‐phase precipitates in nickel‐ and cobalt‐doped MgO single crystals have been examined in samples which were subjected to progressive thermal anneals at temperatures ranging from 600 to 1500 °C. Precipitate sizes and spatial locations were measured by means of light scattering before and after anneals in flowing argon. Absolute light scattering angular distribution measurements were used to obtain size distributions from a Mie theory deconvolution procedure. Comparison of the Ostwald ripening theory with the annealing time evolution of these precipitates indicates that the predominant growth can be described by a dislocation or grain boundary diffusion ripening mechanism. This mechanism is also consistent with ultramicroscope measurements taken before and after each anneal. The depletion region surrounding these ripening particles has been observed by means of backscattering in the measured angular distributions. Our results for diffusion within boundary regions areD’=(1.19±0.8×10−6cm2/s)exp(−1.72 eV/kT) for nickel ions andD’=(1.60±0.9×10−7cm2/s)exp(−1.36 eV/kT) for cobalt ions in MgO. These equations are in agreement with previous diffusion‐couple measurements of nonenhanced diffusion in grain‐boundary regions in these materials.

ISSN:0021-8979    

DOI:10.1063/1.336079

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

This paper presents a transient analysis of electron‐beam induced current in a semi‐infinite semiconductor containing an individual pointlike defect. A focused electron beam positioned in the vicinity of the defect is cut off and the resulting current versus time decay is calculated. It is shown that the time constant of this decay is a complex function of geometrical aspects of the system, bulk properties of the material, and strength of the defect. Computational results are given for a dislocation line parallel to the charge collection plane.

ISSN:0021-8979    

DOI:10.1063/1.336080

出版商:AIP    

年代:1985

数据来源: AIP