Growth of bismuth- and antimony-based chalcohalide single crystals by the physical vapor transport method

AVBVICVII ternary compounds with a special structure show strong anisotropy, which can be attributed to the double chains along the b axis. The crystals have attracted widespread interest because of their unique photoelectricity and piezoelectricity properties. However, the AVBVICVII crystals are limited by the difficulty to obtain large-sized single phase specimens. Herein, an alternative way to grow large AVBVICVII crystals using the physical vapor transport (PVT) method was reported. By tailoring the temperature gradient and growth temperature, centimeter-sized BiSeI, SbSeI and BiSeBr single crystals with a needle-like morphology were obtained and their optical and electrical properties were investigated. The as-grown BiSeBr and BiSeI crystals exhibited band gaps of 1.41 eV and 1.31 eV and resistivities of 0.25 and 28.30 Ω cm, respectively, and they can be classified as optoelectronic materials with low bulk resistivity and suitable band gaps. Additionally, a wider band gap of 1.66 eV was revealed for SbSeI, owing to the p-orbital of Sb contributing to the conduction band edge states, as well as large resistivity of 2.53 × 106 Ω cm. These results indicated that PVT can be considered as an effective method for growing large-sized AVBVICVII single crystals, which can be further used to explore the unique properties of AVBVICVII compounds and meet the basic demands of their applications.