Irradiation-Induced Defects

It is known that hydrogen incorporated into Si subsequently exposed to ionizing radiation inhibits the formation of induced secondary point defect (Pearton and Tavendale, 1982a). For example, in both Si and Ge a number of electron or y irradiation induced defect states appear to be vacancy-related, and exposure of the Si or Ge to a hydrogen plasma (or implantation of hydrogen into the sample) prior to irradiation induces a degree of... 

The data also showed evidence that the nature of the BC site changed during warming from 30 K to 550 K. There was no loss of 2H from the sample on warming to 550 K, consistent with other data quoted already (Umezawa et al., 1988b). Of particular interest is a shift in the 2H position, accompanied by a redistribution over different sites, which occurred at 140 K. In interpreting this data, Bech Nielsen assumed that the 2H atom sites were determined by interaction with irradiation-induced defects. In-... 

The third term in Eq. 7, K, is the contribution to the basal plane thermal resistance due to defect scattering. Neutron irradiation causes various types of defects to be produced depending on the irradiation temperature. These defects are very effective in scattering phonons, even at flux levels which would be considered modest for most nuclear applications, and quickly dominate the other terms in Eq. 7. Several types of irradiation-induced defects have been identified in graphite. For irradiation temperatures lower than 650°C, simple point defects in the form of vacancies or interstitials, along with small interstitial clusters, are the predominant defects. Moreover, at an irradiation temperature near 150°C [17] the defect which dominates the thermal resistance is the lattice vacancy. 

Knowledge of the pressure-induced commensurability led to a series of beautiful experiments searching for evidence for a collective electron-phonon or CDW contribution to the low field conductivity in TTF-TCNQ above Tp. Clear evidence was indeed found for a substantial fall in ah between about 150 and 80 K in the narrow commensurability domain, as shown in Fig. 14 [85]. No such dip was found for the transverse conductivity [86], and the dips in ah were also shown to be suppressed by only a 2 x 10 3 molecular fraction of irradiation induced defects [87]. All of this leads to a consistent picture in favor of a collective electron-phonon CDW contribution to ah above Tp of TTF-TCNQ, as discussed in Ref. 2. However, the extra CDW conductivity is not more than 6000 (fl-cm)-1 at 80 K, that is, about one-half of the ambient pressure conductivity of (TMTSF)2PF6 at the same temperature (Fig. 1) and the latter is usually considered to be a single-particle contribution. So until the mechanism... 

Figure 26 Normalized longitudinal resistivity p, of a single crystal of (TMTSF)2C104 at 4.2 K versus concentration of irradiation-induced defects (mole %). Initially, linear behavior is observed, corresponding to Matthiessen s rule, followed by an exponential behavior corresponding to Eqs. (11) and (12) (see the text). (From Ref. 112.)...

Rivera, A., Montilla, I., Alba Garcia, A., Escobar Calindo, R. et al. (2001) "Native and irradiation-induced defects in Si02 Structures studied by positron annihilation techniques , Mater. Sci. Forum 363-365, 64. 

Naturally iron and steel are the materials of particular interest in corrosion research. To get an idea of the action of irradiation-induced defects on the oxide layer of iron, Ashworth et al. made measurements using an electrometric reduction technique which gives the thickness of the oxide layer as well as its composition. 

Rose, M., Balogh, A., Hahn, H. 1997. Instability of irradiation induced defects in nanostructured materials. Nucl. Instrum. Methods Phys. Res. B 127-128 119-122. 

Irradiation-Induced Defects in a Silica-Supported Carbon Nanotube... 

V. Krishnamoorthy and F. Ebrahimi, Effect of alloying elements and annealing on irradiation-induced defects in iron alloys , A/afer. Res. Soc. Proc., 1989,138, 99-104. 

Figure 1.64 Electron beam irradiation-induced defects in a semithin section of gelatin in HEM a focused electron beam can draw patterns in the material ...

H Hanzawa, N Umemura, Y Nisida, H Kanda, M Okada, M Kobayashi. Disorder effecet of nitrogen impurities, irradiation-induced defects, and " C isotope composition on the Raman spectra in synthetic lb diamond. Phys Rev B 54 3793-3799, 1996. 

Journal of Physics, 10, 053021-1-053021-13. Chakraborty, A. K., Woolley, R. A. J., Butenko, Y. V., Dhanak, V. R., Siller, L., Hunt, M. R. C. (2007). A photoelectron spectroscopy study of ion-irradiation induced defects in single-wall carbon nanotubes. Carbon, 45, 2744-2750. Chandra, N., Namilae, S., Shet, C. (2004). Local elastic properties of carbon nanotubes in the presence of Stone-Wales defects. Physical Review B, 69, 094101-1-094101-12. 

Suzuki, S., 8c Kobayashi, Y. (2007). Healing of low-energy irradiation-induced defects in single-walled carbon nanotubes at room temperature. The Journal of Physical Chemistry C, 111,... 

This chapter will discuss the macroscopic and microscopic properties of Generation IV reactor materials, and the advances in characterization of irradiation-induced defects and in mesoscale modeling of irradiation damage. The majority of the examples provided are based on ferritic-martensitic (F-M) steels, even though they might not always be primary candidates for Generation IV reactors, but the reported defects and microstmctural features are typical of other irradiated alloys, and F-M steels are used as an illustrative example. In some cases, comparisons will be made to austenitic steels to illustrate how differences in crystal stmcture and alloy composition can cause large differences in radiation response. 

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