Structural phase transition and erasable optically memorized effect in layered γ-In2Se3 crystals

We have grown In2Se3 layered-type crystals using chemical vapor transport method with ICl3 as the transport agent. The as-grown crystals show two different color groups of black shiny for alpha-phase In2Se3 and red to yellow for c-phase In2Se3. High-resolution transmission electron micro scopy verifies crystalline state and structural polytype of the as-grown In2Se3. The results indicate that the alpha-In2Se3 crystals present more crystalline states than those of the other amorphous gamma-In2Se3. The amorphous effect on the advancing of optoelectronic property of gamma-In2Se3 shows erasable optical-memorized effect in the disordered and polycrystalline gamma-In2Se3 layers. Laser-induced photodarkening and annealed-recovery test verified that a reversible structural-phase transition of gamma ->alpha can occur inside the gamma-In2Se3. Thermoreflectance and Raman scattering measurements are carried out to identify the inter-phase transformation of the gamma-In2Se3 polycrystals using different heat treatments. Direct band gaps and Raman vibration modes for the gamma- and a-In2Se3 crystalline phases are, respectively, characterized and identified. The character of gamma ->alpha a inter-phase transition promotes feasible optical and optoelectronic applications of the gamma-In2Se3 material in optical memory, optics, and solar-energy devices. (C) 2014 AIP Publishing LLC.