SOME ELECTRICAL AND OPTICAL STUDIES ON BISMUTH TRISULFIDE THIN-FILMS

An electroless chemical method for the deposition of bismuth trisulphide thin films is presented. For the deposition, the triethanolamine complex of bismuth nitrate was allowed to react with aqueous thiourea solution. The substrates used are glass microslides. Good-quality samples are obtained at 95-degrees-C deposition temperature. The deposition time was 30 min and solution pH was about 9.5. The substrates are kept rotating at a speed of 70 rpm. Layers of Bi2S3, 0.8 to 1.2 mum thick are obtained by this process at the above deposition conditions. The films have n-type conduction with high electrical resistance (10(5) to 10(6) OMEGA cm) compared to single crystals. The activation energies of electrical conduction in low and high temperature regions are 0.16 eV and 0.80 eV, respectively. The films are polycrystalline in nature. Optical absorption studies revealed a high absorption coefficient (10(4) cm-1), with a direct type of transition. The observed bandgap is 1.60 eV.