Growth and Optical Property of 2D-Layered In2Se3 Crystals
Ching-Hwa Ho / 何清華1*
1Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan
* presenting author:何清華,
In2Se3 layered-type crystals have been grown by chemical vapor transport method using ICl3 as a transport agent. The as-grown crystals show two different color groups of black shiny for α-phase In2Se3 (hexagonal) and red to yellow for γ-phase In2Se3 (defect Wurtzite). High-resolution transmission electron miscopy (HRTEM) confirmed crystalline phases of the as-grown In2Se3, which indicated that the α-In2Se3 crystals present more crystalline states than those of the other amorphous γ-In2Se3. For α-In2Se3, experimental results of TEM, X-ray photoemission spectroscopy, surface photovoltage, photoluminescence, and surface photoconductive response measurements show that a surface oxidation layer α-In2Se3-3xO3x (0≦x≦1) has formed on the crystal face of α-In2Se3 in environmental air with the inner layer content close to In2Se3 but outmost layer content approaching In2O3. The surface oxide layer facilitates photoelectric conversion of ultraviolet to visible range while the native defects (Se and In vacancies) sustain photoconductivity in the near infrared region. On the other hand, the amorphous effect on advancing optoelectronic property of γ-In2Se3 shows thickness dependent absorption-edge change and erasable optical-memorized effect in the disordered layers. Laser-induced photodarkening and annealed-recovery test verified reversible structural-phase transition of γ↔α occurred inside the γ-In2Se3. All the experimental results promote feasible optical and optoelectronic properties of α- and γ-In2Se3 that are suitable for application in photodetector, optical memory, optics, and solar-cell devices.

Keywords: III-VI Layers, Defect semiconductor, Optical memory switching, In2O3/In2Se3 heterostructure, Optical properties