Well-ordered ultrathin titanium oxide layers were grown on reconstructed Au (111) surfaces by Ti evaporation at room temperature and post-deposition oxidation at a pressure of 10-6 Pa O2 and a temperature of around 600 °C. Depending on the amount of Ti deposited, three different structures were observed. The structures were characterized by scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

 

With Ti coverage below one monolayer (ML), an epitaxial oxide honeycomb structure is created. The herringbone reconstruction of the Au (111) substrate is lifted underneath the titanium oxide monolayer. STM reveals that the contrast between the honeycomb monolayer and the gold reconstruction is influenced by both tip termination and imaging bias. The measured periodicity and crystallographic alignment of the honeycomb structure indicates a (2 × 2) reconstruction on Au (111). XPS and AES data show the deposited titanium is fully oxidised to TiO2. Increasing the Ti dose up to 2 MLs gives rise to a pinwheel structure that coexists with the honeycomb on the surface. The spokes of the pinwheels are parallel to the three close-packed directions of the honeycomb structure. Triangular islands start to grow and coalesce with higher Ti coverage. It is difficult to resolve the structure on the islands, but after 1.5 hours annealing of the thicker films, a row-like structure can be observed with a periodicity of 0.95 nm across the rows. XPS and AES indicate the presence of the Ti2+ oxidation state.