Defect Formation in Alkali Halide Crystals

An interesting review of lattice defect formation in alkali halides can be organized around the history of events in this field over more than 40 years. It might start from the early demonstrations that ionizing excitation of the crystal can produce Frenkel defects in the form of F-H pairs [6.1,2], proceed through observations that the mere energy of an exciton is sufficient to create lattice defects [6.3–6] and follow subsequent experimental and theoretical turns in the story, up to the present. We will not neglect points of historical interest, but we choose a somewhat different order of presentation here. Recent advances in understanding of STE structure in alkali halides, as discussed in the last chapter, have provided the basis for what we believe is a new level of understanding of the mechanisms of defect formation. Likewise, the defect formation problem has provided clues and confirmation guiding the development of the STE theory. To preserve this sense of connectedness, we now proceed directly to an account of the conversion of STEs to vacancy-interstitial pairs according to recent theoretical and experimental evidence. Several reviews of the status of the defect formation problem have chronicled the development as of 1962 [6.7], 1972 [6.8], 1978 [6.9], 1982 [6.10], 1985 [6.11], and 1988 [6.12], for example.