High-k Ti_xSi_1-xO₂ thin films prepared by co-sputtering method

We report on high-k Ti_xSi_1-xO₂ thin films prepared by RF magnetron co-sputtering using TiO₂ and SiO₂ targets at room temperature. The Ti_xSi_1-xO₂ thin films exhibited an amorphous structure with nanocrystalline grains of 3-30 nm having no interfacial layers. The XPS analyses indicate that stoichiometric TiO₂ phases in the Ti_xSi_1-xO₂ films increased due to stronger Ti-O bond with increasing TiO₂ RF powers. In addition, the electrical properties of the Ti_xSi_1-xO₂ films became better with increasing TiO₂ RF powers, from which the maximum value of the dielectric constant was estimated to be ∼30 for the samples with TiO₂ RF powers of 200 and 250 W. The transmittance of the Ti_xSi_1-xO₂ films was above 95% with optical bandgap energies of 4.1-4.2 eV. These results demonstrate a potential that the Ti_xSi_1-xO₂ thin films were applied to a high-k gate dielectric in transparent thin film transistors as well as metal-oxide-semiconductor field-effect transistors.