Selectable growth and electronic structures of two-dimensional layered InSe and In2Se3 films

InSe, as a representative two-dimensional (2D) semiconductor of the III–VI group, possesses numerous advantages and is widely used in 2D electronic and optoelectronic devices. In2Se3, known for its 2D ferroelectricity and high photoelectric response rates, has recently gained widespread attention. Therefore, realizing selectable growth of these two structural phases and studying their electronic structures is important. In this paper, we realized the molecular beam epitaxial growth of InSe and In2Se3 films on bilayer graphene substrates with precisely controlled stoichiometric phases and thickness. Combining the in situ reflection high-energy electron diffraction, scanning tunneling microscopic, and angle-resolved photoemission spectroscopic measurements, we investigated the distinctions in lattice and electronic structures between InSe and In2Se3 films. The InSe film exhibits a hexagonal lattice structure, whereas the In2Se3 film shows a one-dimensional distorted reconstruction. A key finding is that the top valence bands of InSe films display a varying number of splitting branches at the Γ point, which corresponds to the number of layers. In contrast, no splitting of the top valence bands was observed in the In2Se3 films, highlighting a distinct difference in their electronic structure compared to InSe films.