Amorphous effect on the advancing of wide-range absorption and structural-phase transition in γ-In₂Se₃ polycrystalline layers

摘要

The exploitation of potential functions in material is crucial in materials research. In this study, we demonstrate a III-VI chalcogenide, polycrystalline γ-In₂Se₃, which simultaneously possesses the capabilities of thickness-dependent optical gaps and wide-energy-range absorption existed in the polycrystalline layers of γ-In₂Se₃. Transmission electron microscopy and Raman measurement show a lot of γ-phase nanocrystals contained in the disordered and polycrystalline state of the chalcogenide with medium-range order (MRO). The MRO effects on the γ-In₂Se₃ layers show thickness-dependent absorption-edge shift and thickness-dependent resistivities. The amorphous effect of MRO also renders a structural-phase transition of γ → α occurred inside the γ-In₂Se₃ layer with a heat treatment of about 700°C. Photo-voltage-current (Photo V-I) measurements of different-thickness γ-In₂Se₃ layers propose a wide-energy-range photoelectric conversion unit ranging from visible to ultraviolet (UV) may be achieved by stacking γ-In₂Se₃ layers in a staircase form containing dissimilar optical gaps.