Synthesis of WS₂ flakes via chemical bath deposition technique

Micro-flakes of WS₂ were synthesised by chemical bath deposition technique, using a single source precursor for W and S. Ammonium tetrathiotungstate was used as the source for W and S. The deposition was carried out by chemically reducing the tetrathiotungstate ions to WS₂. Hydrazine hydrate was used as the reducing agent. The films were then annealed at 500°C in inert atmosphere for 30 minutes. The films were then characterized for their stoichiometry and phase. Peaks were observed at ~167 cm^-1, ~320 cm^-1, ~348 cm^-1, 355 cm^-1, and 419 cm^-1, corresponding to LA(M), E_2g(M), 2LA(M), E_2g (and A1_g modes of hexagonal WS₂, respectively. The presence of the non-zone centre modes from the M point of the Brilloiun zone indicates the presence of defects. The 2LA(M) mode is the second overtone of the defect induced LA(M) acoustic mode which appears due to presence of defects. No other peaks of W-sulphides or W-oxides are observed indicating the formation of pure phase WS₂. The W:S ratio of calculated from the peak area is found to be 1:2.03 ≈ 1:2 for pure phase WS₂