Controlled Interfacial Electronic Coupling in Chemical Vapor Deposition-Grown WSe2 Monolayers on Au(111)

We report on the controlled growth and interface engineering of high-quality WSe2 monolayers on Au(111) using ambient-pressure chemical vapor deposition (CVD) combined with comprehensive surface-sensitive characterization in ultrahigh vacuum (UHV). The as-grown films exhibit a selenium buffer layer, which enables the formation of a weakly coupled WSe2 phase at the metal interface, as revealed by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). Annealing in UHV removes the selenium buffer layer and leads to the emergence of a pronounced moiré superstructure and a transition toward a strongly coupled WSe2 phase. Furthermore, this transformation is accompanied by pronounced modifications of the electronic structure, including phase-dependent changes in the valence band structure observed by angle-resolved photoelectron spectroscopy (ARPES), a hybridization-induced metallization measured by scanning tunneling spectroscopy (STS), and a significant decrease in the work function determined by field emission resonance (FER) and ultraviolet photoemission spectroscopy (UPS). Density functional theory (DFT) calculations confirm strong WSe2-Au hybridization and the presence of the mid-gap states for the strongly coupled phase, whereas the Se8 buffer layer weakens the interaction of WSe2 with Au, so that its electronic structure is close to that for the freestanding system. Our results demonstrate that growth-induced interface chemistry provides a powerful handle to tune the electronic coupling in WSe2/Au(111), establishing a direct link between interfacial structure and electronic properties in metal-transition metal dichalcogenide (TMD) interfaces.