STUDIES ON THE PROPERTIES OF RUTILE Ti1-xSnxO2 AND ANATASE Ti1-yTayO2 THIN FILMS

Abstract

High quality single-crystalline rutile Ti1-xSnxO2 films were successfully grown in a layer-by-layer mode. The optically transparent films possessed smooth interfaces and step-terraced surfaces. High solid solubility of up to x = 0.216 has been achieved. Modulation of the bandgap is made possible by varying x due to orbital reconstruction occurring in Ti1-xSnxO2 films. Type II band alignment can be achieved easily by any two Ti1-xSnxO2 thin films. The relationships between ligand field strength, long range band structure and hybridization of different orbitals with respect to x are investigated via X-ray Absorption Spectroscopy. A new exciton peak located at ~6.1 eV is also discovered in anatase TiO2 thin film. Its intensity increases with Ta concentration in the σ1 spectra of 1.8 % and 3.9 % Ta-substituted TiO2, accompanied by significant spectral weight transfer from energies up to 35 eV. These results showed the manifestation of dramatic e-e and e-h correlation effects plays a key role in the observed resonant excitons in Ti1−yTayO2 film system.