Structural evolution of SnO2-TiO2 nanocrystalline films for gas sensors

Thin films (50-200 nm) of SnO2-TiO2 were deposited on SiO2/(001)Si substrat es by RF-sputtering and by molecular beam before they were annealed in vacu um at 200-900 degrees C. In-situ TEM, XRD, SEM, Raman and IR-spectroscopy w ere used to analyze the structure transformations in the SnO2-TiO2 films. I n the as-deposited state, the films are amorphous. They crystallize at high er temperatures (starting at about 500 degrees C) forming nanosized grains. The problem of the spinodal decomposition in the SnO2-TiO2 system observed earlier at high temperatures is discussed also for low-temperature process ing. The stoichiometry of the films of both groups (reactive ion sputtered and high-vacuum e-gun sputtered) is being compared. (C) 2000 Elsevier Scien ce S.A. All rights reserved.