Atomic layer deposition of thin films using O2 as oxygen source

Atomic layer deposition of TiO2 films was realized by using alternate pulses of TiI4 and O-2. The film growth mechanism was studied by quartz crystal microbalance in the temperature range 200-350 degreesC. The adsorption of TiI4 proceeded via partial decomposition of TiI4, which resulted in an enhanced reactivity by the formation of a TiIx surface layer with x < 3. The reactivity of O-2 toward this layer was sufficient to form TiO2 at an O-2 pulse duration of 2 s when the substrate temperature was not lower than 235 degreesC. TiO2 films were also grown on Si(100) substrates at deposition temperatures between 230 and 460 degreesC. No residual iodine could be detected in the films grown at temperatures higher than 230 degreesC. Phase-pure anatase was formed in the whole temperature range except at the highest temperature where rutile was also obtained.