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

ABSTRACT

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 2003. 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.