Polarity and surface structural evolution of iron oxide films

Abstract

Various ordered Fe oxide films were prepared in an ultrahigh vacuum system, and their surface and electronic structure were studied in situ by low-energy electron diffraction and photoelectron spectroscopy. We obtain Fe₂O₃(0001) films with oxygen termination (O–Fe₂O₃(0001)), a polar surface, via FeO(111) films. The O–Fe₂O₃(0001) films can be transformed to a non-polar surface of iron-terminated Fe₂O₃(0001) (Fe–Fe₂O₃(0001)) films. Fe₃O₄(111) films are formed after annealing O–Fe₂O₃(0001) films. A co-existed phase of Fe–Fe₂O₃(0001) and Fe₃O₄(111) is observed via annealing Fe–Fe₂O₃(0001) films. These Fe oxide films with different surface structures and properties can be designedly used as model plates for further studies in surface physics and chemistry.