High-performance electronics and optoelectronics of monolayer tungsten diselenide full film from pre-seeding strategy

Tungsten diselenide (WSe₂) possesses extraordinary electronic properties for applications in electronics, optoelectronics, and emerging exciton physics. The synthesis of monolayer WSe₂ film is of topmost for device arrays and integrated circuits. The monolayer WSe₂ film has yet been reported by thermal chemical vapor deposition (CVD) approach, and the nucleation mechanism remains unclear. Here, we report a pre-seeding strategy for finely regulating the nuclei density at an early stage and achieving a fully covered film after chemical vapor deposition growth. The underlying mechanism is heterogeneous nucleation from the pre-seeding tungsten oxide nanoparticles. At first, we optimized the precursor concentration for pre-seeding. Besides, we confirmed the superiority of the pre-seeding method, compared with three types of substrate pretreatments, including nontreatment, sonication in an organic solvent, and oxygen plasma. Eventually, the high-quality synthetic WSe₂ monolayer film exhibits excellent device performance in field-effect transistors and photodetectors. We extracted thermodynamic activation energy from the nucleation and growth data. Our results may shed light on the wafer-scale production of homogeneous monolayer films of WSe₂, other 2D materials, and their van der Waals heterostructures. (Figure presented.).