摘要:

This article surveys the present state of the experimental investigations dealing with photostimulated desorption from the solid surface upon excitation by laser radiation. Emphasis is put on Russian research of the laser desorption from semiconductor surfaces. The time-of-flight technique for the analysis of desorbed particles with respect to masses and initial energies is described. The principal regularities of the photodesorption from the semiconductor surfaces characterized by the different degrees of ionicity are considered. Qualitative physical models of the laser induced from electronic and molecular surface processes leading to the desorption are discussed.

ISSN:1042-0150    

DOI:10.1080/10420159108220573

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Luminescence characteristics of stable Fe3+and metastable (Fe2+)+ions in silicate glasses are reported. Infrared emission of (Fe2+)+ions has been observed. From the luminescent data it has been concluded that Fe3+ions are in a tetrahedral coordination with respect to the oxygen ions and Fe2+ions are in an octahedral one. The near environment of recharged ions is not changed under irradiation.

ISSN:1042-0150    

DOI:10.1080/10420159108220574

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Reflection of 30 keV molecular ions N2+from a copper single crystal was studied experimentally in a series of experiments performed at the Moscow State University in 1982–1987. A good correspondence between maxima (minima) of probability of nondissociative reflection and presence of surface semichannels (infinite deeps) on the crystal face is found. In the paper present state of the theory of molecular ion interaction with solids as well as relevance of the orientation dependence regularities to the molecular ion focusing effects and to experiments with polycrystalline targets are also discussed.

ISSN:1042-0150    

DOI:10.1080/10420159108220575

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The results of studying the angular and spectral characteristics of X-rays produced by passage of 10 GeV electrons through sufficiently thick Si (0.8 and 3.0 mm) and Ge (0.5 mm) single crystals at small angles to the ⟨111⟩ crystallographic axis are presented. Information have been obtained on the excess of the spectralangular characteristics of radiation in the crystal over respective values for an amorphous target.

ISSN:1042-0150    

DOI:10.1080/10420159108220576

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The thickness of ice (H2O) layers accreted on a cold finger has been measured by detecting the interference pattern of a He-Ne laser beam (632.8 nm) reflected from the ice surface and from the underlying substrate.

ISSN:1042-0150    

DOI:10.1080/10420159108220577

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Surface compositional modifications due to room temperature ion bombardment were investigated in thirteen Cr-Mo alloys using Auger Electron Spectroscopy (AES). Preferential sputtering of Cr was observed across the entire composition range. A phenomenological model of the sputtering process was adopted and the results yielded a component sputter rate constant ratioK(=kCr/kMo) = 1.73 ± 0.04, insensitive to alloy composition. This value is in good agreement with the enhancement ratio calculated according to Sigmund theory of 1.66 ⩽YCr/YMo⩽ 1.73 and the elemental sputter yield ratioYCr/YMo= 2.22 ± 0.74. The homogeneity of the altered layer was investigated using elemental Auger transitions of various sampling depths in the range 20–600 eV. The altered layer was found to be essentially uniform in composition over the sampled depth. The small inhomogeneity suggested by the data was quantified using layer calculations and various profile models. The calculations showed that the inhomogeneity was small in comparison to the overall compositional modifications due to the sputtering process. The experimental results indicate that in the room-temperature sputtering of such refractory alloys, the athermal “ballistic” processes play the dominant role in establishing the steady-state surface composition and its profile. Preferential sputtering determines the compositional perturbation of the surface, and collisional mixing, i.e., displacement mixing and possibly recoil implantation, maintains an essentially uniform composition over the “altered layer” depth. The thermally activated processes of Gibbsian segregation, radiation-induced segregation (RIS) and radiation-enhanced diffusion (RED) appear to play a negligible role.

ISSN:1042-0150    

DOI:10.1080/10420159108220578

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Dislocation free Si crystals implanted with 16 MeV/n U-ions using the Darmstadt accelerator have been investigated by X-ray diffraction methods. X-ray section topography showed that the induced damage range is a little larger than the theoretically calculated U-ion range. The created defects cause the volume increase in the implanted part of the crystals. For the dose 1.9·1012i/cm2the increase of lattice constant is 1.4·10−5±5·10−6Å and for the dose 4.4·1012i/cm22.4·10−5± 5·10−6Å.

ISSN:1042-0150    

DOI:10.1080/10420159108220579

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The effects of self-radiation damage due to alpha decay was studied as a function of cumulative decay events in synthetic zircon doped with238Pu. The density of the Pu-doped zircon decreased exponentially with dose to a value corresponding to a density change of 14.2% at saturation. The initially crystalline material became fully X-ray amorphous at a dose of 6.7 × 1018alpha decays/g. Isochronal annealing indicated that recovery associated with recrystallization of amorphous zircon occurs in two stages, with estimated activation energies of 5.1 ± 0.2 and 6.6 ± 0.3 eV. These results are in good agreement with behavior observed in studies of self-radiation damage over geologic time in natural zircons.

ISSN:1042-0150    

DOI:10.1080/10420159108220580

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

To study the different populations of defects existing in Ba1-xGdxF2+xsolid solutions forxranging from 0.0001 to 0.1, comparative Ionic Thermal Currents (ITC) and Electron Paramagnetic Resonance (EPR) experiments have been performed. In the as-grown crystals weak trigonal centers assigned to the nnn Gd3+-Fi−dipoles coexist at all concentrations with Gd3+in cubic sites. The variation of the number of these nnn dipoles as a function ofxfound with the two series of experiments is a strong indication of the existence of larger clusters in the crystals. The appearance of new relaxation peaks in the low temperature zone of the ITC spectra is correlated to the formation of these aggregates together with the observed variation in the number of cubic sites. An association energy of 0.41 eV of the nnn dipole is calculated from the equilibrium of associated and free defects. The less doped crystals were treated thermally at 1223 K and variable amounts of O2−ions diffused into the samples creating Gd3+and O2−centers in which the oxygen to gadolinium ratio varies. It is shown that the trigonal T2center is the first step in the oxidation process and at least one new O2−center is shown to exist in an annealed crystal where no trigonal or cubic Gd3+centers exist. The structure proposed for this center is consistent with the appearance of a new relaxation peak in the ITC spectrum obtained after the annealing. The Monte Carlo procedure for fitting the effective spin Hamiltonian parameters is used for identifying the weak trigonal, the cubic and the T2Gd3+centers.

ISSN:1042-0150    

DOI:10.1080/10420159108220581

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor