Building Principles and Structural Motifs in TiOx Ultrathin Films on a (111) Substrate

The competition between rectangular and hexagonal phases in TiOx ultrathin (monolayer) films grown on a Pt(111) surface is discussed and rationalized on the basis of general building principles for these pseudoepitaxial oxide phases on a (111) metal substrate. A novel hexagonal reduced phase is also presented for the first time, obtained by thermal treatment at high temperature (similar to 1000 K), and its atomistic structure is unveiled through a combination of STM experiments and theoretical simulations. A consistent picture is obtained for a class of structural families for ultrathin oxide phases on close-packed single-crystal metal surfaces.