Preparation of SnS₂ thin films by conversion of chemically deposited cubic SnS films into SnS₂

We report the growth of SnS₂ thin films by annealing chemically deposited cubic SnS films under a sulfur atmosphere in a graphite box. The chemically deposited SnS films were annealed in the temperature range of 200–550 °C to understand its influence on the conversion of SnS into SnS₂. In the X-ray diffraction analysis, the as-deposited SnS films annealed in the temperature range of 200–250 °C showed the formation of a minor SnS₂ phase along with the dominant SnS phase. The films annealed at 300 °C contained mixed phases of SnS and SnS₂. Increasing the annealing temperature from 350 to 500 °C led to the formation of only the dominant SnS₂ phase. Further increasing the annealing temperature to 550 °C gave rise to the formation of a highly oriented SnS₂ film with hexagonal structure having (001) as the preferred orientation. The crystallite size of the SnS₂ films was found to increase from 17 nm to 25 nm with increasing annealing temperature from 350 °C to 550 °C. The lattice parameters were found to be a = 0.365 nm and c = 0.592 nm. Raman spectroscopy analysis confirmed the formation of single phase SnS₂ films at annealing temperatures above 350 °C. The morphological studies showed the conversion of the round shaped grains into flake-like ones on annealing at temperatures above 350 °C. These flakes increased in size on increasing the annealing temperature from 350 °C to 500 °C. The direct optical band gap of these SnS₂ films was found to be 2.58 eV.