Effect of post-growth annealing on the optical properties of LiGaS-2nonlinear crystals

摘要

High chalcogen volatility and Li interaction with the container walls result in variation of crystal composition and presence of both extended and point defects in as-grown LiGaS-2 nonlinear crystals. Annealing in appropriate conditions is used to correct the composition and improve the optical quality. We annealed LiGaS-2 in vacuum, in the presence of Li-2S, Ga-2S-3, and S, and studied changes in transmission, photoluminescence and photo-induced absorption. OH groups, S-H and S-S complexes, sulfur vacancies and cation antisite defects (Ga-(Li)) are most important. Photo-induced absorption is reversible: It appears after illumination with UV/blue light and disappears after illumination with IR light or by heating the sample.