Structural and Spectroscopic Properties of Hydrothermally Synthesized α-GaO(OH) Structures: Impact of Annealing Temperatures

This work investigated the structural and spectroscopic properties of α -GaO(OH) prepared via a hydrothermal method. The film was heat treated at three different temperatures, which are 350, 450, and 550 °C. The films were characterized by X-ray diffraction, field-emission scanning electron microscopy, UV–vis spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The morphology of the prepared α -Ga 2 O 3 films shows rhombus nanorod structure, which is a favorable morphology for advanced applications. Raman spectroscopy confirmed the rhombus structure of α -Ga 2 O 3 nanocrystals at lower temperatures and indicated adjustments in the lattice vibrations and crystal structure with increasing annealing temperature up to 550 °C. The optical band gap of α -Ga 2 O 3 was estimated using diffused reflectance and Tauc plot analysis. The results showed that the band gap decreased from 5.24 eV to 4.58 eV with increased heat treatment due to reduced defects and improved crystalline structure.