FORMATION OF INTERSTITIAL-VACANCY PAIRS BY ELECTRONIC EXCITATION IN PURE IONIC-CRYSTALS

We review experiments and theories on defect formation induced by electronic excitation. Emphasis is placed on the microscopic mechanism of F-H pair formation in alkali halides and relevant phenomena in other systems such as alkaline earth fluorides, amorphous silicon dioxide and alkali halide surfaces. Dynamic and thermally-activated formation of the F-H pairs are discussed separately and it is pointed out that these two processes involve relaxation on different adiabatic potential surfaces. The mechanism of the temperature dependence is discussed in some detail. The significance of the value of S/D for the defect formation process in alkali halides, where S is the space between the halogen ion and D is the diameter of a halogen atom, is also discussed. Although understanding of the defect formation processes in systems other than alkali halides is not as deep as in alkali halides, the similarities and differences in the processes in alkali halides and other materials are discussed. Defect formation and sputtering of alkali halides are also compared. © 1990.