Self-assembled epitaxy of Ga2Se3 on the oxidized GaSe surface and atomic imaging of the Ga2Se3/GaSe heterostructure

Gallium selenides (GaSe and Ga2Se3) and their heterostructures have been widely concerned owing to their attractive properties and potential applications in the field of photoelectric and photocatalysis. In this work, we develop an unprecedented Ga2Se3/GaSe self-assembled heterostructure through thermal oxidation of GaSe. The crystal structure and defects of GaSe and Ga2Se3/GaSe heterostructure have been studied by advanced Cs-STEM imaging. The present bulk GaSe possesses ε-polytype as the dominant phase along with γ-GaSe inclusions and structural defects, i.e., stacking faults, twins, and antisites. The Ga2Se3 layer, generated on the GaSe oxidized surface, exhibits a defective zincblende-like cubic structure where vacancies locally ordered on the {1 1 1} planes, which even results in superstructure domains. Furthermore, atomically van der Waals epitaxy and orientation relationships between Ga2Se3 and GaSe were revealed. Finally, the optical properties of Ga2Se3/GaSe heterostructures were preliminary studied and future directions for the structural development and property investigation of Ga2Se3/GaSe heterostructures were also discussed. These findings are insightful for recognizing the microscopic structure of GaSe and Ga2Se3/GaSe heterostructures and provide a valuable route for the generation of self-assembled heterostructures in other related layered semiconductors.