A mechanism of defect creation in amorphous Ta2O5

Defect creation mechanisms in amorphous (a) Ta2O5 films employed in various microelectronics applications, e.g., resistive switching memories, are still poorly understood. To address this issue, we investigate the role of electron and hole injection in defect creation in a-Ta2O5. Our Density Functional Theory calculations demonstrate that electrons and holes can be trapped in polaron and bipolaron states at structural precursor sites in a-Ta2O5. The bipolaron creation significantly reduces the average energies for the formation of Frenkel pairs (FPs) of oxygen vacancies and interstitial oxygen ions to about 1.4 eV for hole trapping and 3.2 eV for electron trapping. The average diffusion barriers of the O interstitials are 0.3 eV for O2− and 1.4 eV for O0, which forms a bond with a neighboring O ion at the site. Our results predict that hole bipolaron formation provides the lowest energy pathways for FP creation in stoichiometric a-Ta2O5. They can be used in further theoretical simulations of the mechanisms of degradation processes in a-Ta2O5 and to guide experimental studies.