Defect annealing

Figure 4. Comparison of SRO-kinetics of Ag-23at%Zn for different states of defect atmealing. ( ) as-rolled state A (21% and 65% thickness reduction) (A), (0) isochronal defect annealing to 553K (state C) and 843K (state D), respectively, (A), 3h recrystallization treatment at 843K (state E). For more details see .

In a more general application, thermoluminescence is used to study mechanisms of defect annealing in crystals. Electron holes and traps, crystal defects, and color-centers are generated in crystals by isotope or X-ray irradiation at low temperatures. Thermoluminescent emission during the warmup can be interpreted in terms of the microenvironments around the various radiation induced defects and the dynamics of the annealing process (117-118). ... 

J. Campos-Delgado, Y.A. Kim, T. Hayashi, A. Morelos-Gomez, M. Hofmann, H. Muramatsu, M. Endo, H. Terrones, R.D. Shull, M.S. Dresselhaus, M. Terrones, Thermal stability studies of CVD-grown graphene nanoribbons Defect annealing and loop formation, Chemical Physics Letters, vol. 469, pp. 177-182, 2009. 

As it is known, I centres are the most mobile radiation-induced radiation defects in alkali halides and therefore they play an essential role in low-temperature defect annealing. It is known, in particular, from thermally-stimulated conductivity and thermally-stimulated luminescence measurements, that these centres recombine with the F and F electron centres which results in an electron release from anion vacancy. This electron participates in a number of secondary reactions, e.g., in recombination with hole (H, Vk) centres. Results of the calculations of the correlated annealing of the close pairs of I, F centres are presented in Fig. 3.11. The conclusion could be drawn that even simultaneous annealing of three kinds of pairs (Inn, 2nn and 3nn in equal concentrations) results in the step-structure of concentration decay in complete agreement with the experimental data [82]. 

Figure 2 shows the results of isochronal annealing experiments on ZnO samples treated with a hydrogen plasma at 350 °C. It follows from the figure that the H-I defect anneals out at 500 °C, whereas H-II is more stable and disappears from the spectra at 600 °C. Parallel to the annealing of H-I and H-II, another line at 3191.6 cm grows in the spectra. It represents a stretch LVM of the well-known Cu-H defect. It reaches its maximum intensity at 600 °C, when both H-I and H-II are already gone from the spectra. 

These experiments should become a classic example of the utility of radiation in the understanding of adsorption. The appropriate use of different radiations, physical identification of defects, annealing, and quantitative comparisons succeeded in finding, out of a large number of defects, that type which was responsible for a particular kind of chemisorption. 

It is important to note that such laboratory measurements may not apply under natural conditions. For example, diffusion coefficients are commonly measured at temperatures far higher than are relevant in nature, so large and potentially inaccurate extrapolations are often necessary. Similarly, some minerals undergo chemical or structural transformations and possibly defect annealing during vacuum heating extrapolation of laboratory data from these modified phases to natural conditions may lead to erroneous predictions. 

Ionizing radiation can also cause radiation-enhanced diffusion that leads to defect annealing. Ouchani et al. (1997) demonstrated in a dual-beam irradiation (220 keV Pb and 0.3 to 3.2 MeV He) that the critical amorphization dose increases due to defect annealing caused by electron energy loss processes. Soulet et al. (2001) recently studied... 

Low-temperature irradiation devices are used with increasing frequency, especially to study radiation-induced defects in solids. A liquid-nitrogen irradiation device, which has operated for over 15,000 hours, has been described previously P]. However, certain defects anneal out or are transformed well below 77 °K and their study requires irradiation at lower temperatures. Two liquid-helium [ " ] and one liquid-hydrogen [ ] reactor irradiation devices have been reported in the literature. This paper describes an irradiation device at the temperature of boiling neon, which was installed in the Melusine swimming-pool reactor of the Nuclear Research Center of Grenoble. 

Nadella et al. [204] found that cold-drawing of polypropylene caused voids and a decrease of crystallite size and greatly enhanced lattice strains and defects. Annealing the fibers at 140°C restored a well-formed monoclinic structure and healed the voids. 

The kinetics of surface area changes, mechanisms of defect annealing, pore sintering and the kinetics of morphology changes, in general can be evaluated from DSA results in both isothermal and non-isothermal conditions. 

Ion implantation of SiC is also actively developed. This method is especially important for SiC because of the high temperatures and durations of diffusion annealing. Also diffusion of the most important dopant—nitrogen—is an extremely complicated problem. Now ion implantation is used for doping with nearly all important donor and acceptor dopants. Parameters of ion implantation with different ions are shown in Fig. 11. Radiation defect annealing is carried out by either thermal (1400-1800°C) or laser annealing. 

Point defects are created by neutron-atom collisions Defects anneal out by migration to sinks Migrating defects drag solute to sinks, including grain boundaries... 

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