Epitaxial growth of MoSe₂ and MoTe₂ monolayer on GaAs by molecular beam epitaxy

Molybdenum diselenide (MoSe₂) and molybdenum ditelluride (MoTe₂) are promising transition metal dichalcogenides (TMDs) that have attracted great interests in recent years because of their unique electrical and optical properties. In this work, we fabricate crystallographically aligned MoSe₂ and MoTe₂ monolayers on gallium arsenide (GaAs) (111) surface by MBE as revealed by low energy electron diffraction (LEED) measurements. Unlike TMDs growth on van der Waals (vdW) substrates such as the highly oriented pyrolytic graphite (HOPG) and graphene, the interface interactions between GaAs and the epitaxial TMD films are electronically stabilized surface as suggested by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Ultraviolet photoelectron spectroscopy (UPS) measurements are also performed to provide additional evidence and results.