Atomic and Electronic Properties of Molecular Beam Epitaxy Grown Monoclinic Ag₂Se Thin Film

Silver chalcogenides have attracted a lot of interest as promising candidates for novel topological properties. Using scanning tunneling microscopy/spectroscopy (STM/S), we characterized the atomic structure and electronic properties of monoclinic Ag₂Se thin film grown on SrTiO₃ (STO)(001) substrate by molecular beam epitaxy (MBE) for the first time. Three kinds of atomic terminations of Ag₂Se are observed on the surface: (i) homogeneous hexagonal-like, (ii) rough mixed and (iii) flat zigzag striped structures. The structural analysis indicates that the different atomic terminations are from different growth directions which can be attributed to the lattice mismatch between substrate and Ag₂Se film. The STS of these atomic terminations exhibit different features near the Fermi level, indicating constituent- and direction-dependent electronic properties. Our findings provide a convenient method to produce the Ag₂Se thin film and a deeper understanding of the physical properties of this compound.