Surface Conversion of Single-Crystal Bi2Se3 to β-In2Se3

In this work, we demonstrate that the surface layers of single-crystal layered-2D Bi₂Se₃ can be converted to layered-2D rhombohedral β-In₂Se₃ by annealing under a trimethylindium (TMIn) flux. Samples were prepared in a metalorganic chemical vapor deposition (MOCVD) chamber, then transferred under vacuum to a surface analysis chamber for analysis with low-energy electron diffraction (LEED) and Auger electron spectroscopy. Additional ex situ characterization included x-ray diffraction, transmission-electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS) elemental mapping, and Raman spectroscopy. The resulting single-crystal β-In₂Se₃ adopts the rhombohedral crystal structure (space group R-3m) and orientation of the underlying Bi₂Se₃, and the excess Bi atoms generated by this process create an underlying region of Bi-rich Bi_xSe_y. Due to the difference in bandgap between Bi₂Se₃ and In₂Se₃, this conversion reaction presents a pathway to lateral heterojunctions if only selected regions are converted by masking the surface to spatially define the TMIn exposure. The conversion may also have implications for heteroepitaxy, because the in-plane lattice constants of Bi₂Se₃ and In₂Se₃ (0001) surfaces match those of InP and GaAs (1 1 1), respectively, and the natural cleavage planes of a layered-2D crystal facilitate substrate removal and reuse.