Electronic Structures of Molecular Beam Epitaxially Grown SnSe2 Thin Films on 3×3-Sn Reconstructed Si(111) Surface

SnSe2, as a prominent member of the post-transition metal dichalcogenides, exhibits many intriguing physical phenomena and excellent thermoelectric properties, calling for both fundamental study and potential application in two-dimensional (2D) devices. In this article, we realized the molecular beam epitaxial growth of SnSe2 films on a 3×3-Sn reconstructed Si(111) surface. The analysis of reflection high-energy electron diffraction reveals the in-plane lattice orientation as SnSe2[110]//3-Sn [112]//Si [110]. In addition, the flat morphology of SnSe2 film was identified by scanning tunneling microscopy (STM), implying the relatively strong adsorption effect of 3-Sn/Si(111) substrate to the SnSe2 adsorbates. Subsequently, the interfacial charge transfer was observed by X-ray photoemission spectroscopy. Afterwards, the direct characterization of electronic structures was obtained via angle-resolved photoemission spectroscopy. In addition to proving the presence of interfacial charge transfer again, a new relatively flat in-gap band was found in monolayer and few-layer SnSe2, which disappeared in multi-layer SnSe2. The interface strain-induced partial structural phase transition of thin SnSe2 films is presumed to be the reason. Our results provide important information on the characterization and effective modulation of electronic structures of SnSe2 grown on 3-Sn/Si(111), paving the way for the further study and application of SnSe2 in 2D electronic devices.