Effect of Oxygen Vacancy*

Surface transfer doping has been explored to be a potential strategy for doping diamond, a material which is known hard to dope traditionally, for applications in high power electronics. Although MoO₃ has been identified as effective surface electron acceptor for hydrogen-terminated diamond, the impact of oxygen vacancies, which are commonly present, still remain elusive. To address this, we conducted reactive molecular dynamics simulations to investigate the deposition of MoO_3-x on hydrogenated diamond (111) surface. As more vacancies are introduced into the material, the local atomic arrangement is observed to become more compact and the Mo-O bonds are found to get stronger. Further we employed first-principles calculations based on density functional theory to investigate the charge transfer and electronic structures. Bader charge calculations further confirm MoO_3-x as effective surface electron acceptors. The change in Bader charge and notable shift of the electronic band alignment upon doping reveal that oxygen vacancy limits the hole-doping capability of MoO_3-x. Spatial distribution of doped holes is characterized after deposition, which demonstrates a widespread distribution of hole density, so-called two-dimensional hole gas, at the interface that can support exceptional transport properties.