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

Tungsten diselenide (WSe2) possesses extraordinary electronic properties forapplications in electronics, optoelectronics, and emerging exciton physics. Thesynthesis of monolayer WSe2 film is of topmost for device arrays and integratedcircuits. The monolayer WSe2 film has yet been reported by thermal chemicalvapor deposition (CVD) approach, and the nucleation mechanism remainsunclear. Here, we report a pre-seeding strategy for finely regulating the nucleidensity at an early stage and achieving a fully covered film after chemicalvapor deposition growth. The underlying mechanism is heterogeneous nucle-ation from the pre-seeding tungsten oxide nanoparticles. At first, we optimized the precursor concentration for pre-seeding. Besides, we confirmed the superi-ority of the pre-seeding method, compared with three types of substrate pre-treatments, including nontreatment, sonication in an organic solvent, andoxygen plasma. Eventually, the high-quality synthetic WSe2 monolayer filmexhibits excellent device performance in field-effect transistors and photodetec-tors. We extracted thermodynamic activation energy from the nucleation andgrowth data. Our results may shed light on the wafer-scale production ofhomogeneous monolayer films of WSe2, other 2D materials, and their van derWaals heterostructures.