Na_1.88Bi_1.88S₄ and Na_1.36Ca_1.28Bi_1.36S₄ Single Crystals: Growth, Structure and Optical Property

Na 1.88 Bi 1.88 S4 and Na 1.36 Ca 1.28 Bi 1.36 S 4 single crystals of high quality were successfully synthesized by solid-state reaction method using NaI as flux. Both compounds crystallize in the rocksalt structure type of a cubic Fm-3m space group. The preferred orientation growth of lattice face (111) were observed in both two compounds. The optical absorption measurements show that the band gap of Na 1.88 Bi 1.88 S 4 and Na 1.36 Ca 1.28 Bi 1.36 S 4 compounds are 1.29 eV and 1.45 eV, respectively. Two compounds were fabricated into devices that exhibit notable photoelectric behavior, suggesting their potential for applications as photoelectric switches.