Phase relations and optical properties of semiconducting ternary sulfides in the system Cu-Sn-S

The ternary system Cu-Sn-S was re-investigated and the phase diagram Cu2S-SnS2 studied in detail by differential thermal analysis and X-ray diffractometry. Three phases of composition Cu4SnS4, Cu2SnS3 and Cu2Sn3+xS7+2x(0 less than or equal to x less than or equal to 1) were found exhibiting melting points at 833, 856 and 803 degreesC, respectively. Ellipsometric and diffuse reflectance measurements revealed that the latter two sulfides possess a fundamental band gap of 0.93 eV followed by a higher transitions. For the first time it could be demonstrated that Cu2Sn3S7 has semiconducting properties and an absorption coefficients of the order 10(5) cm(-1). (C) 2003 Elsevier Ltd. All rights reserved.