Elucidating the growth mechanism of two-dimensional tungsten diselenide via chemical vapor deposition using molten salt precursor

초록

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have gained significant attention as promising materials for electronic and optoelectronic devices due to their high electron mobility and tunable bandgap. Chemical vapor deposition (CVD) is a widely used technique for synthesizing large-area monolayer TMDs. However, given the rich elemental libraries of currently synthesizable 2D TMDs, it is crucial to optimize the growth variables, including precursor types and CVD conditions. In particular, the challenge of growing 2D TMDs with high melting point precursors has led to the development of salt-based precursors, which are yet to be optimized for the growth of uniform and large-area domains. In this study, we systematically investigate the effect of various process variables on the CVD growth of 2D WSe2 monolayers using salt-based precursors, such as Na2WO4 and Na2SeO3. Specifically, we analyze the domain morphology and substrate coverage of WSe2 as a function of substrate pre-annealing time, substrate temperature, substrate orientation, and co-carrier gas flow (H2). Our results provide insights into the growth mechanism of salt-based CVD of 2D TMDs and the fabrication of large-area and uniform monolayers for potential electronic and optoelectronic applications.