Combinatorial Scanning Tunneling Microscopy Study of Cr Deposited on Anatase TiO₂(001) Surface

We have investigated Cr deposited on anatase TiO₂(001) surfaces using a combinatorial approach. Anatase TiO₂(001) thin films covered with Cr metals were prepared on a Nb-doped SrTiO₃(001) substrate by combinatorial laser molecular beam epitaxy and characterized by in situ low-energy electron diffraction and ultrahigh vacuum (UHV) scanning tunneling microscopy (STM). STM images of a clean TiO₂(001) surface showed that one-dimensional structures along the [100] and [010] directions were formed, resulting in a (1 × 4) surface reconstruction. When Cr atoms were deposited on the anatase TiO₂ surface and the films were annealed at 900 K in UHV, the one-dimensional structures became branched and showed short-range disorder. The observed surface structural disordering will be discussed in terms of the lattice strain induced by the Cr atoms diffused into the bulk.