Manipulating Oxygen Vacancies in γ-Ga₂O₃ Nanocrystals: Correlation between Defect Location, Charge State, and Photophysical Properties

Recent advancements in colloidal synthesis have enabled precise control of extrinsic dopants in semiconductor nanocrystals (NCs), enriching our understanding of dopant-exciton interactions and opening new avenues for controlling NC properties. However, the manipulation of intrinsic defects in colloidal NCs remains challenging. Here, we demonstrate regulation of oxygen vacancy concentration and location in γ-Ga₂O₃ NCs, significantly altering their photoluminescent properties. Spectroscopic analysis and density functional theory calculations reveal that bulk oxygen vacancies are mostly neutral and lead to the formation of a deep donor band that contributes to the UV emission. Conversely, surface-proximate oxygen vacancies, influenced by the band bending effect, exhibit a tendency toward double ionization, giving rise to the characteristic donor-acceptor pair emission. This work highlights the correlation between the oxygen vacancy location and charge states, leading to diverse defective states and distinct photophysical processes. Precise defect manipulation offers new insights into structure-property relationships and the design of functional nanomaterials.