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

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 x 10(-5) mbar. The properties of as-deposited 1000 Angstrom thick films on silicon substrates have been studied in the growth temperature interval 100-680 degrees C. X-ray diffractometry demonstrated a phase evolution as a function of growth temperature, from amorphous (100 degrees C) to anatase (300 degrees C) and eventually rutile (680 degrees 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/cm(2) at 0.3 MV/cm). With increasing amount of rutile phase, the leakage current decreased resulting in a leakage current density of 70 nA/cm(2) at an electrical field of 0.3 MV/cm for; rutile films grown at 680 degrees C. High-frequency C-V measurements on rutile films resulted in typical metal-insulator semiconductor behavior with a measured static dielectric constant of 39. (C) 1998 American Vacuum Society. [S0734-2101(98)05204-X]..