Site preference of cation vacancies in Mn-doped Ga₂O₃ with defective spinel structure

A strong site preference of intrinsic cation vacancies in Mn-doped Ga ₂O₃ with a defective spinel structure is revealed using a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and first-principles calculations. The intensity profile analysis of HAADF-STEM images clearly indicates that the cation vacancies prefer the octahedral sites. Systematic first-principles calculations for 698 atomic configurations suggest that the Mn ions and cation vacancies are energetically favorable at the tetrahedral and octahedral sites, respectively. The site preference of the cation vacancies is found to correlate with the electrostatic energy.