Diffusion Monte Carlo study of defects in Hafnia

Recent years have seen an increased interest in understanding the electronic properties of Hafnia (HfO2) for its industrial applications in optical coating, high-k dielectrics, as well as potential applications in resistive random access memories (RRAMs). A fundamental problem affecting HfO2 transistors performance is the leakage current near the gate dielectric. This is understood to be related to defects, such as oxygen vacancies, in hafnia. Oxygen vacancies are also understood to profoundly affect resistive switching characteristics of hafnia. In order to elucidate the role of defects, we used Density Functional Theory (DFT) and Diffusion Monte Carlo (DMC) to study the energetics of vacancy/defect creation in cubic hafnia and their effect on the band structure gap of the material.