Indirect band gap investigation of orthorhombic single crystals of sulfur

Abstract

Single crystals of pure and selenium doped orthorhombic sulfur crystal were prepared from carbon disulphide solution. They were investigated at two temperatures (6°C and 85°C) in an optical absorption apparatus. The optical absorption increased with temperature and it was found to be higher for Se doped crystals within the same range of temperatures. The indirect allowed band gap transitions and assisting phonons were observed. Their values were found to shift toward lower energy with increasing temperatures. They are also lower for doped samples. At 6°C, the indirect allowed band gaps are 2.61 eV and 2.56 eV for pure and selenium-doped crystals, respectively. At 85°C, they are 2.44 eV and 2.40 eV for pure and doped crystals, respectively. The phonons associated with the optical transitions could be attributed to the stretching band of S 8 rings.