Study on oxygen vacancies in gallium oxide nanostructures

Monoclinic-oriented gallium oxide (β-Ga₂O₃) has diverse applications in optoelectronic devices due to its wide bandgap and stable thermal properties. Moreover, nanostructured β-Ga₂O₃ exhibits high sensitivity in gas detection because oxygen vacancies in β-Ga₂O₃ transfer electrons with absorbed gas molecules, such as O₂, CO, and CH₄. However, gas sensors based on gallium oxide nanomaterials still face significant challenges in realizing high sensitivity and working at room temperature. This paper reported the growth of nanostructured β-Ga₂O₃ on sapphire substrates using chemical vapor deposition with gold as catalyst. Stoichiometry radio in β-Ga₂O₃ showed the absence of oxygen according to the energy dispersive spectrum result, which is consistent with the photoluminescence analysis. The excitation wavelength was 261.0 nm. Photoluminescence spectrum showed broad emission with a 467.1 nm wavelength peak associated with oxygen vacancies. The sensors were coated with β-Ga₂O₃ nanostructures on the interdigitated electrodes, making them sensitive to oxygen at room temperature and responsive to light. The sensing mechanism revealed the photogenerated electrons and holes transferred between oxygen vacancies in β-Ga₂O₃ and adsorbed gas.