Energetics of Native Defects in Al2O3 and SiO2

Abstract

Formation energies of various defects in Al₂O₃ and SiO₂ are calculated by using the plane-wave pseudopotential method. Also, the formation energies of Schottky defects and Frenkel defects are evaluated on the basis of these calculations. It is shown that formation energies of these defects are higher in SiO₂ than in Al₂O₃. In other words, less defects are formed in SiO₂ than in Al₂O₃. It is also found that the principal defect is the cation Frenkel defect in Al₂O₃ but the anion Frenkel defect in SiO₂. These results agree with the experimental results that Al ions diffuse preferably in Al₂O₃ but oxygen ions diffuse in SiO₂ at high temperatures.