Synthesis of WSe2 by Chemical Vapor Deposition and Influence of Hydrogen on Morphology

Two-dimensional transition metal dichalcogenides have recently attracted much attention owing to their potential applications in flexible, low power electronics and optoelectronic devices. This paper investigated the growth of WSe
₂
films by atmospheric pressure chemical vapor deposition (CVD). The introduction of hydrogen in the reaction chamber helps to activate the selenization of WO
₃
, where large-size WSe
₂
monolayer and few-layer films can be successfully grown. By this method, WSe
₂
flakes with different shapes were deposited on the SiO
₂
/Si substrates, and the maximum side length of dozens of microns. The mono- and few-layered WSe
₂
films were characterized by optical microscopy, atomic force microscope (AFM) and Raman spectra. We attribute the evolution of morphology to the result of the growth rate of terminations under two different growth conditions. Our results provide a foundation for the controlled synthesis of WSe
₂
and reveal the morphological evolution of WSe
₂
grown by CVD.