Rapid thermal annealing induced modification in structural and electronic structure properties of Ti0.95Co0.05O2-delta thin films

Abstract

Thin film of Ti0.95Co0.0O2-delta was deposited on Si (100) using PLD method and annealed in O-2 and N-2 environment. Raman spectra confirm that all the films have rutile structure. Surface morphology indicates that the surface roughness and grain size increase with annealing. The electronic structure studied by NEXAFS spectroscopy at O K, Ti L-3,L-2 and Co L-3,L-2-edges revealed that peak intensities decrease significantly for the film annealed N2 environment. The ligand-field splitting estimated from the energy difference between the t(2g) and e(g) features in O K-edge spectra were 2.71 eV for as-deposited and O-2 annealed film, whereas reduced more than double (similar to 1.32 eV) for the film annealed in N-2. Atomic multiplet calculations and experimentally observed NEXAFS spectra at Co L-3,L-2-edge and Ti L-3,L-2-edge confirm that Co present in 2+ and Ti in +4 valence state, whereas the multiplet structures of O-2 annealed film looks similar to Co metal. (C) 2016 Elsevier Ltd. All rights reserved.