Nano-structured phases of gallium oxide (GaOOH, α-Ga2O3, β-Ga2O3, γ-Ga2O3, δ-Ga2O3, and ɛ-Ga2O3): fabrication, structural, and electronic structure investigations

Regardless of much curiosity in the synthesis and diversifying properties of the polymorphs of gallium oxide, they are still unrevealed due to their nanoscale size and structural disorders. In this study, convincing methods have been applied to achieve various phases of gallium oxide (i.e., GaOOH, α-Ga₂O₃, β-Ga₂O₃, γ-Ga₂O₃, δ-Ga₂O₃, and ɛ-Ga₂O₃). X-ray diffraction (XRD) along with Rietveld refinement has been employed to investigate the structural parameters of barely reported phases. Transmission electron microscopy (TEM) images reveal the impact of the protocols of chemical synthesis on the morphology/size of the polymorphs of gallium oxide. Mechanistic discussion on the formation of nano-rod morphology in some of the phases (GaOOH and α-Ga₂O₃) and nano-particle morphology in other (β-Ga₂O₃, γ-Ga₂O₃, δ-Ga₂O₃ and ɛ-Ga₂O₃) phases is also provided by considering the experimental parameters. The existence of Ga³⁺ ions and their local hybridization with the oxygen is investigated using the X-ray absorption spectroscopy (XAS) at Ga K-edge and conveyed the phase dependence on the hybridization of frontier orbitals.