Direct Growth of Al₂O₃ on Black Phosphorus by Plasma-Enhanced Atomic Layer Deposition

Growing high-quality and uniform dielectric on black phosphorus is challenging since it is easy to react with O₂ or H₂O in ambient. In this work, we have directly grown Al₂O₃ on BP using plasma-enhanced atomic layer deposition (PEALD). The surface roughness of BP with covered Al₂O₃ film can reduce significantly, which is due to the removal of oxidized bubble in BP surface by oxygen plasma. It was also found there is an interfacial layer of PO _x in between amorphous Al₂O₃ film and crystallized BP, which is verified by both X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) measurements. By increasing temperature, the PO _x can be converted into fully oxidized P₂O₅.