Defect creation in amorphous HfO2 facilitated by hole and electron injection

Abstract

Using Density Functional Theory (DFT) calculations we modeled the mechanisms of formation of oxygen vacancies and interstitial ions in amorphous HfO2 under electron and hole injection conditions. The results demonstrate that injected electrons and holes can create strongly localised bipolaron states at intrinsic trapping sites in amorphous structure. These bipolarons decompose into stable and mobile O vacancies and interstitial ions upon thermal activation. These mechanisms can contribute to dielectric breakdown of gate oxide films and electro-forming in RRAM cells based on amorphous HfO2.