Controllable CVD Synthesis and Sulfur-Vacancy-Mediated Phase Transition of SnS2 and Sn2S3 Nanostructures

Abstract Tin-based sulfides have attracted considerable interest because of their distinctive electronic structures and promising optoelectronic, photovoltaic, electrochemical, and photocatalytic properties. However, the phase-controlled synthesis of tin sulfides remains challenging because competing Sn−S phases can readily form during growth. In addition, the thermodynamic and kinetic factors governing phase evolution among tin sulfides are still not fully understood, which limits rational phase engineering and device-oriented optimization. Here, we report a facile chemical vapor deposition strategy using fluorine-doped tin oxide as an in situ tin source for the controllable growth of large-area SnS2 nanosheet arrays and Sn2S3 nanostructures. By tuning the growth temperature, sulfur precursor dosage, and reaction duration, SnS2 nanosheets can be transformed into Sn2S3 under sulfur-deficient, high-temperature conditions. The optimized window for pure Sn2S3 formation is 525 °C, 50 mg sulfur precursor, and 10 min growth duration, under sulfur-deficient Ar/H2 atmosphere. Comprehensive structural and chemical characterizations, together with Gibbs free-energy analysis and density functional theory calculations, suggest that sulfur vacancies play a key role in weakening Sn−S bonding and promoting lattice reconstruction. These results provide an experimentally accessible route for the phase-controlled synthesis of tin sulfides and offer mechanistic insight into vacancy-mediated phase transformation in two-dimensional metal chalcogenides.