MBE GROWTH AND CHARACTERIZATION OF EPITAXIAL TIO2 AND NB-DOPED TIO2 FILMS

Epitaxial TiO2 and Nb-doped TiO2 thin films have been grown on (110) T iO2 rutile substrates by molecular beam epitaxy using elemental Ti and Nb sources along with an electron cyclotron resonance oxygen plasma s ource. Film composition was measured by X-ray photoelectron spectrosco py. Reflection high-energy electron diffraction and low-energy electro n diffraction patterns reveal excellent long-range crystallographic or der and a rutile structure for both TiO2 and Nb-doped TiO2 films. The high degree of similarity in Ti and Nb core-level X-ray photoelectron diffraction angular distributions establishes that Nb is substitutiona lly incorporated in the rutile lattice. Analysis of the Nb 3d(5/2) cor e-level binding energy suggests an Nb4+ oxidation state.