In situ growth of evaporated TiO2 thin films using oxygen radicals: Effect of deposition temperature

Publisher Website
Google Scholar
Abstract
The growth and characterization of TiO2 thin films deposited by electron-beam evaporation of TiO2 have been studied. The growing film was exposed to a flux of atomic oxygen supplied from an oxygen radical beam source at a total deposition pressure of 1×10−5 mbar. The properties of as-deposited 1000 Å thick films on silicon substrates have been studied in the growth temperature interval 100–680 °C. X-ray diffractometry demonstrated a phase evolution as a function of growth temperature, from amorphous (100 °C) to anatase (300 °C) and eventually rutile (680 °C). While the amorphous film surface had a smooth film surface as evidenced by atomic force microscopy, the anatase and rutile specimens exhibited a grain-like morphology. No apparent difference in surface roughness was observed between the anatase and rutile phase. Secondary ion mass spectrometry indicated that silicon diffused into the rutile film grown at the highest temperature. Ellipsometry measurements revealed that the crystallized films exhibited significantly larger refractive index and absorption than the amorphous film. Current–voltage (C–V) measurements demonstrated that the leakage was very high in the amorphous and anatase films (3–5 A/cm2 at 0.3 MV/cm). With increasing amount of rutile phase, the leakage current decreased resulting in a leakage current density of 70 nA/cm2 at an electrical field of 0.3 MV/cm for rutile films grown at 680 °C. High-frequency C–V measurements on rutile films resulted in typical metal-insulator- semiconductor behavior with a measured static dielectric constant of 39.