摘要:

The experimental data concerning the pairwise generation of paramagnetic defects (radicals) for irradiation o organic solids are reviewed and discussed. Two main mechanisms of pair formation are shown to be of importance: (1) the disintegration of molecules into heavy fragments remaining inside the ‘cage’ and (2) valence or charge transfer between the nearest molecules following the scheme:. Analysis of EPR signals allows us to calculate the distances separating the radical sites as well as their relative orientations. In the case of mechanism (1) the inter-radical distances are exactly fixed and correspond to that of undamaged molecules, sometimes not only in molecular crystals but even in the frozen solutions. In the case (2) the transfer mechanism permits the generation of a number of pairs differing by distance and orientations, and they are indeed observed, but the radiation yields of different pairs are very much different.

ISSN:0033-7579    

DOI:10.1080/00337576908235564

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Transmission electron microscopy studies of thin films of gallium arsenide have shown that the surface regions become non-crystalline (i.e. amorphous) after bombardment at 21 °C with Ne20ions of energies between 40 and 100 keV. This effect occurs after ion doses of about 1 × 1015ions cm−1and the damaged material recrystallizes onto the underlying single crystal in an apparently epitaxial manner during post-bombardment annealing at temperatures between 270 °C and 300 °C.

ISSN:0033-7579    

DOI:10.1080/00337576908235565

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The atomic displacement process in electron irradiated cadmium has been studied. The experimental data can be fitted using an energetic threshold for Frenkel pair formationTd, = 19 eV. Discussion of the nonlinearity of the resistivity increase per electron versus total electron flux shows that this behaviour may be explained by the existence of a very unstable Frenkel pair specie, the mutual annihilation of which may be initiated either thermally at ∼5.5 °K after the irradiation, or dynamically. In the latter case, the most important events for producing pair annihilation would be elastic interactions of secondary electrons with the atomic nuclei. With regard to the high c/a ratio in cadmium, clues exist showing that these unstable defects are likely to be Frenkel pairs situated in and interacting through densely packed atomic rows in the basal planes.

ISSN:0033-7579    

DOI:10.1080/00337576908235566

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The lattice location of implanted Tl atoms in Si has been studied by means of the channeling technique. A motion from substitutional sites into the tetrahedral interstitial sites along the ⟨111⟩ rows is observed under carbon bombardment at temperatures around 300 °C. It is concluded, that this motion is due to an indirect process associated with the carbon bombardment. We suggest that Si interstitial atoms created during bombardment diffuse to substitutional Tl atoms and displace them into interstitial sites in a Watkins type replacement reaction. A strong temperature dependence is observed, and the process appears to be thermally activated. No effect is detectable (i) for a room temperature bombardment or (ii) for a 340 °C bombardment of a Tl implant that contains a majority of implanted substitutional As dopants.

ISSN:0033-7579    

DOI:10.1080/00337576908235567

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The nature of small defect clusters produced in single crystal gold films by room temperature bombardment with 3 to 40 keV gold ions incident along [001] channeling directions to doses of 109to 1012ions cm−2was investigated using transmission electron microscopy. The number of observed defects per measured incident ion rose from about 0.03 at 3 keV to ∼ 1 defect per ion for ion energies >10 keV. Above 15 keV, closely spaced groups of multiple clusters produced by individual ions were observed in significant numbers. Stereo microscopy showed that essentially all of the defects were produced within about 300 Å of the bombarded surface. Application of the defect contrast analysis of Wilkens and Rühle(5,13)for identifying the nature of small defects revealed that the visible defects were vacancy type over the entire range of ion energies used. Above 15 keV the defects were mainly dislocation loops; below 15 keV they appeared to be centers of dilatation.

ISSN:0033-7579    

DOI:10.1080/00337576908235568

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Further electron microscopy studies were made of the vacancy type defects produced in gold thin films by keV gold ion bombardment along channeling directions at room temperature as described in Part I. It was found that the defect density increased linearly with dose, and that the defect size distribution was independent of dose for a given ion energy. The average defect size increased with increasing ion energy. Measurements of the defect depth distributions below the surface were also made for bombardments along a fixed direction (i.e. [001]) as a function of energy (5–120 keV) and for bombardments of fixed energy (40 keV) as a function of channeling direction (i.e. [111], [001], and [011]). The distributions were all sharply peaked below the surface. It was concluded that serious glissile defect losses to the surface occurred within 100–200 Å of the surface. Considerable evidence in the literature supporting this conclusion was cited. The defect depth distributions in the regions unaffected by surface losses were compared with the corresponding ion penetration data, and reasonably good agreement was found.

ISSN:0033-7579    

DOI:10.1080/00337576908235569

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The geometricai arrangement of visible subcascade defect clusters (i.e. subclusters) formed in large displacement cascades was investigated in single crystal gold films after 120 keV gold ion bombardment at 295 °K along [001] using electron stereomicroscopy. It was concluded that the subclusters were vacancy type defects formedin situat vacancy rich subcascade regions in displacement cascades as described in Parts I and II of the present work. Measurements were made of the sizes and separations of the subclusters in 69 cascade regions, each of which contained either two or three subclusters. The angular directions of the lines constructed between subcluster centers in each cascade were also measured.

ISSN:0033-7579    

DOI:10.1080/00337576908235570

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Irradiation Effects in Nuclear Fuels. J. A. L. Robertson. Monograph Series on Nuclear Energy, Gordon and Breach Science Publishers, Inc., New York, London, Paris, 1969. 309 +x pages $13.00.

ISSN:0033-7579    

DOI:10.1080/00337576908235572

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor