Growth of ultra-thin titanium oxide on Cu(100), Fe/Cu(100) and ordered ultra-thin iron oxide studied by low-energy electron diffraction and X-ray photoelectron spectroscopy

Abstract

The growth, structure and chemical state of ultra-thin titanium oxide prepared on Cu(100), Fe/Cu(100) and on ultra-thin iron oxide have been investigated using X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED). The titanium oxide on Cu(100) was prepared by evaporating titanium atoms on the oxygen chemisorbed substrate, followed by heating at 623 K in 1×10 −5 Pa O 2. Up to one layer coverage the titanium oxide showed a chemical shift of the Ti 2p 3/2 peak corresponding to Ti 4+ and a LEED pattern of a hexagonal structure with two domains rotated 90° with respect to each other. The oxide has been proposed to consist of oxygen–titanium–oxygen trilayers with the stoichiometry of TiO 2. The surface structure was unstable at higher coverage. The same structure of titanium oxide overlayer was prepared by evaporating titanium atoms on 1.7 ML Fe/Cu(100), followed by oxidation under the condition to give the FeO(111) underlayers consisting of two iron–oxygen bilayers. The ordered titanium oxide on FeO(111)/Cu(100) was prepared also by evaporating titanium atoms on an ordered Fe 3O 4/Cu(100) surface, followed by heating at 623 K in vacuum. The ordered structure of the titanium oxide was not stable on the iron oxide at higher oxidation state.