SYNTHESIS AND CHARACTERIZATION OF NB-DOPED TIO2(110) SURFACES BY MOLECULAR BEAM EPITAXY

摘要

Epitaxial films of Nb-doped TiO2 rutile were grown on TiO2(110) rutile at 600 degrees C by molecular beam epitaxy. These films grow in a layer-by-layer fashion for doping levels up to 20 at.. In addition, reflection high-energy and low-energy electron diffraction, along with X-ray photoelectron diffraction, reveal that the overlayers possess excellent long- and short-range structure order up to 20 at.. However, strain-induced disorder becomes prevalent for higher doping levels, and the surfaces roughen accordingly. X-ray photoelectron diffraction reveals that Nb atoms substitutionally incorporate at cation sites in the rutile lattice for all doping levels, leading to a mixed rutile NbxTi1-xO2 phase. Analysis of Nb3d and Ti2p core-level binding energies reveal that the oxidation state of both Ti and Nb is 4+. References: 41