TiO epitaxial film growth on MgO(001) and its surface structural analysis

The metallic TiO single crystal film formed epitaxially on MgO is reported. It was found that the simultaneous supply of Ti vapor and O2 gas on the MgO(001) surface resulted in the TiO(001) film formation. The surface structure of the TiO(001) film was investigated using Li+ impact-collision ion scattering spectroscopy and reflection high energy electron diffraction. The surface of TiO formed on MgO was very close to an ideal truncation of the TiO bulk structure, while the O vacancies, whose concentration was estimated to be 28%, exist on the outermost surface. When the TiO film was exposed to the O2 atmosphere of 1×10−8 Torr partial pressure with maintaining the substrate temperature at 1070 K, the TiO-2×2-O superstructure was found to be formed. In the 2×2-O structure, the adsorbed O atoms were located on the top sites of Ti of the outermost TiO surface, where the distance between O and Ti was equal to that in the bulk, which was 2.09 Å.