Optical-memory switching and oxygen detection based on the CVT grown γ- and α-phase In2Se3

Layered-type α- and γ-In2Se3 crystals were simultaneously grown by chemical vapor transport (CVT) method using ICl3 as the transport agent. The crystalline state, surface state, and structural polytype of the as-grown In2Se3 were observed by high-resolution transmission electron microscopy (HRTEM). The direct band edges of α- and γ-In2Se3 were evaluated by thermoreflectance (TR) measurements. For α-In2Se3, a surface oxidation layer α-In2Se3−3xO3x (0 ≤ x ≤ 1) can easily form on the crystal face in environmental air by oxygen detection (∼250 nm/day). The surface formation oxide can be easily removed by laser treatment (λ = 266 nm, P = 60 mW) and the oxygen detection can be repeated again. For γ-In2Se3, the HRTEM and Raman measurements reveal amorphous and polycrystalline state existing in the as-grown crystals. The amorphous effect renders erasable optical-memory switching of γ ↔ α inter-phase transition occurred inside the γ-In2Se3 layer with laser heating treatment. The phase transition of In2Se3 is fast and easily by using the laser treatment. The phase transformation of γ ↔ α was verified by Raman and TR measurements. The optical-memory switching and oxygen detection behavior for the as-grown γ- and α-phase In2Se3 are demonstrated herein.