A study of bismuth sulphoselenide thin films: growth from the solution and properties

Bismuth sulphoselenide [Bi2(S,Se)3] thin films were obtained onto the thoroughly cleaned amorphous glass substrates using a simple chemical growth process. The basic ingredients used were analytical grade and a selenium source was obtained from a reflux action of the sodium sulphite with the metal selenium. Growth kinetics and mechanism of film formation were studied for these films and are explained in brief. The compositional analysis was carried out to determine the actual contents of Bi3+ and Se2− in the films taken out of the bath. The X-ray diffraction analysis showed microcrystalline nature of the samples. It further revealed that the bismuth sulphoselenide is a ternary mixed chalcogenide having a chemical formula [Bi2(S,Se)3]. Optical studies showed direct transitions for these films with a band gap of 1.9 eV for Bi2S3 and 0.97 eV for Bi2Se3. Thermoelectric power measurements were performed on the [Bi2(S,Se)3] films and showed n-type conduction.