Color center production and recombination in doped alkali halide thin films were analyzed. It was concluded that the radiation defects in all of the doped systems were spatially distributed close to the dopants; thus implying that the basic radiation defect production reaction, anion exciton decay in the {F,H} pair, took place in the near vicinity of the dopants. The unrelaxed H centers which were produced in this reaction were captured by a dopant ion, within a ps time span, so as to form various dopant hole centers. As a result, the radiation defects were also situated close to the dopant. Photo-stimulated defect recombination also took place, to a limited extent, near to the dopant; with a fast and high yield of energy transfer to the dopant ion. Interaction of the unrelaxed H center with the dopant ion in the excited state did not lead to dopant hole center formation, but this interaction with the electron color center destroyed the latter. There was no difference in the behavior of monocrystalline thin films and single monocrystals. An effect of the surface was apparent only in the case of polycrystalline films. The escape of unrelaxed H atoms from the surface considerably changed the distribution, of F and dopant hole centers, so as to favor the former; thus explaining why temperature-independent F center production was observed. That is, the escape of the unrelaxed H center from the surface of polycrystalline thin films led to the formation of an excess concentration of F centers in the bulk of the grain and made possible the appearance of a temperature-independent photo-stimulated luminescence response.

G.Vâle: Materials Science Forum, 1997, 239-241, 721-4