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appears at lower wavenumber. The well-resolved peak has been assigned to the crystalline phase, and the broader one to the amorphous phase. The integrated intensity ratios of these two peaks versus fluence are in good agreement with the damage fractions determined by X-ray diffraction (XRD). Fits of the amorphous fraction versus fluence show that the amorphization mechanismsisdominatedbyasingle-impactprocessforiodineionsandbyadouble-impactprocessforkryptonionsinthecase of single crystals and sinters. For both irradiations, complete amorphization could not be obtained. The amorphous fraction saturatesatamaximumvalueof88%forsintersand72%forsinglecrystals.Thisisattributedtoarecrystallizationeffectwhich is more important in single crystals than in sinters. For both types of samples, the crystalline peak shifts slightly to a lower wavenumber with fluence, and then shifts back to its initial value for an amorphous fraction larger than 60%. This feature is attributedtoastressrelaxation,asshownintheXRDdata,whichisaccompaniedbyadecreaseofthecrystallinepeakfull-width at half-maximum. Copyright c � 2011 John Wiley & Sons, Ltd. |
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