Structure and composition of linear TiOxnanostructures on SrTiO3(001).

High-resolution x-ray photoelectron spectroscopy (XPS) was performed on the surface of 0.7 at.% Nb-doped SrTiO3(00l) decorated with self-assembled linear nanostructures termed dilines, trilines, and tetralines. All three nanoline types share a common side-row feature, while the triline is shown to contain Ti in the 2 + oxidation state as a structural component of the linear backbone. Atomic-resolution scanning tunneling microscopy images and models developed using density functional theory are used to relate the structures to the spectroscopic data, showing that the nanolines consist of a three-layer hill and valley-type structure. Valence band XPS reveals the presence of a well-defined mid-band-gap state at approximately 1 eV, which emerges as a result of nanoline formation. [ABSTRACT FROM AUTHOR]