Rational design for high-yield monolayer WS₂films in confined space under fast thermal processing

Tungsten Disulfide (WS₂) films, as one of the most attractive members in the family of transition metal dichalcogenides, were synthesized typically on SiO₂/Si substrate by confine-spaced chemical vapor deposition method. The whole process could be controlled efficiently by precursor concentration and fast thermal process. To be priority, the effect of fast heating-up to cooling-down process and source ratio-dependent rule for WS₂structure have been systematically studied, leading to high-yield and fine structure of monolayer WS₂films with standard triangular morphology and average edge length of 92.4μm. The growth time of the samples was regulated within 3 min, and the optimal source ratio of sulfur to tungsten oxide is about 200:3. The whole experimental duration was about 50 min, which is only about quarter in comparison to relevant reports. We assume one type of 'multi-nucleation dynamic process' to provide a potential way for fast synthesis of the samples. Finally, the good performance of as-fabricated field-effect transistor on WS₂film was achieved, which exhibits high electron mobility of 4.62 cm²V^-1s^-1, fast response rate of 42 ms, and remarkable photoresponsivity of 3.7 × 10^-3A W^-1. Our work will provide a promising robust way for rapid synthesis of high-quality monolayer TMDs films and pave the way for the potential applications of TMDCs.