Reparative effect of diffusion process on host defects in Cr2+ doped ZnS/ZnSe

Scattering defects, which severely affect the optical quality of materials, have been investigated in polycrystalline ZnSe and ZnS grown by chemical vapor deposition (CVD). Cr ions were introduced into the grown hosts (Cr2+:ZnS/ZnSe) as mid-infrared laser gain media by the post-growth diffusion method. Decrease of the as-grown defects was observed after the diffusion process giving rise to an improvement in optical quality of doped materials. Meantime, the advantages of post treatment (HIP) on CVD hosts became less obvious after the doping process. The reparative effect on internal defects, as we firstly described here, is attributed to the secondary crystallization of host crystals caused by the long period, high temperature diffusion process. Evidences could be found in the microstructure evolutions including the growth of grains, densified grain boundaries and intracrystalline inclusion clusters.