Microscopic investigation on surface structures and intrinsic defects of Cu₂O(111)

Copper (I) oxide or cuprous oxide (Cu₂O) is known to be a p-type semiconductor with direct band gap of ~ 2.1 eV. Since most binary oxides exhibit n-type behavior originating from the donor nature of oxygen vacancies, Cu₂O has been considered as a p-type counterpart for oxide-based electronics. Although some theoretical studies reported about the origin of p-type nature in Cu₂O, atomistic experimental study on this issue has not been conducted yet. In this work, we investigate the surface structures and intrinsic defects of Cu₂O(111) via home-built low temperature scanning tunneling microscopy (STM). Thin Cu₂O(111) layer is prepared on top of Cu(111) film by ambient oxidation, and the surface of Cu₂O(111) is cleaned by Ar sputtering and annealing for STM experiments. STM topography reveals the stoichiometric oxygen-terminated surfaces of Cu₂O(111). We also directly observed two types of intrinsic defects which show different contrast in topography depending on bias polarity. These defects are identified by comparison with density functional theory (DFT) simulations. The electronic property of defects will be discussed during the presentation.