Nucleation promoted synthesis of large-area ReS₂ film for high-speed photodetectors

Rhenium disulfide (ReS₂) is a transition metal dichalcogenide with a layer-independent direct bandgap. Notably, the weak interlayer coupling owing to its T-phase structure enables multi-layer ReS₂ to behave similarly to decoupled monolayers. This inherent characteristic makes continuous multilayer ReS₂ film a unique platform for large-area electronic applications. To date, the bulk of work on ReS₂ has been conducted using mechanically exfoliated samples or small size flakes (<1 mm²) with no potential for large-scale electronics. A chemical vapor deposition (CVD) synthesis of a large area, continuous ReS₂ film directly on a SiO₂ substrate is also known to be more challenging compared with that of other 2D materials, such as MoS₂ and WS₂. This is partly due to its tendency to grow into discrete dendritic structures. In this study, a large-area (>1 cm²), continuous multilayer ReS₂ film is directly synthesized on a SiO₂ substrate without any transfer process. The polycrystalline ReS₂ film synthesized by this method exhibits one of the fastest photoresponse speeds (0.03 s rise time and 0.025 s decay time) among the reported CVD films. The photoresponsivity R _λ was also the highest among large-area CVD films. The synthesis method for a continuous multilayer ReS₂ film is amenable to large-scale integration and will pave the way for practical optoelectronic applications based on 2D layered materials.