How the surface-processing conditions affect the intrinsic luminescence of CsI crystals

Abstract

It is shown that luminescence of CsI crystals with wavelength em=305 nm is observed at room temperature when it is excited in the long-wavelength exciton-absorption band at ex=220 nm. To excite this luminescence close to the surface, two factors need to be taken into account when fabricating the samples. First, the temporal character of the relaxation of the damaged layer; second, the penetration of quenching impurities into the near-surface layer during the diffusion escape of surplus vacancies onto the free surface. The intrinsic photoluminescence of CsI crystals was observed earlier only in the two-photon absorption regime, when the crystal was transparent to the exciting light. To minimize the number of defects in the near-surface layer, chemical polishing of the surface is proposed, carried out after the damaged layer relaxes.