Electron- and photon-stimulated desorption of epitaxial thin films and bulk
single crystals of alkali halides has been investigated. It has been found
that the widely accepted model based on self-trapped exiton decay and ther
mally activated defect diffusion cannot account for a number of experimenta
l observations. In particular, it cannot explain the stability of the very
thin alkali-halide films against the electron beam, and it fails to interpr
et correctly the yield dependence of the halogen atoms emitted with nonther
mal energies on the film thickness and sample temperature. It is shown that
for satisfactory interpretation of those data one has to take into account
early stages of crystal excitation, i.e., hot carrier formation and transp
ort processes occurring prior to self-trapped exciton phase. Consequently,
a comprehensive description of the observed desorption features is presente
d. [S0163-1829(98)01943-2].