Growth and electrical properties of SnS1-xSex (0 <= x <= 1) single crystals grown using the temperature gradient method

Abstract

Tin selenide (SnSe) has attracted much attention due to its record ZT value in both pristine and doped crystals. This issue has renewed interest in the single-crystal form of tin-based chalcogenide compounds which possess the same layered structure as SnSe such as tin sulfide (SnS). Due to their natural abundances and low toxicities, SnSe and SnS can be alloyed at reduced the processing cost while maintaining the favorable electrical properties of SnSe. In this research, using the temperature gradient method, we successfully fabricated single crystals of SnS1-xSex with 0 <= x <= 1. High-quality crystals were obtained, and the electrical properties of those crystals were investigated. The results showed that the p-type crystals have layered structures with lattice constants changing gradually according to Vegard's law. The value of the band gap monotonically decreased with increasing Se amount (x). The substitution of Se into S sites results in not only a large increase in the electrical conductivity but also a decrease in the Seebeck coefficient; i.e., the electrical conductivity at room temperature increased from 5 x 10(-4) (x = 0) to 5.24 S.cm(-1) (x = 0.8). The Seebeck coefficient decreased from 1069 in SnS to 525 mu VK-1 in SnS0.2Se0.8 and to 481 mu VK-1 in SnSe at room temperature. This work provides positive information for the growth of large-size SnS-SnSe single crystals.