Atomic Layer Deposition of Thin Films Using O2 as Oxygen Source

Atomic layer deposition of TiO 2 films was realized by using alternate pulses of TiI 4 and O 2 . The film growth mechanism was studied by quartz crystal microbalance in the temperature range 200−350 °C. The adsorption of TiI 4 proceeded via partial decomposition of TiI 4, which resulted in an enhanced reactivity by the formation of a TiI x surface layer with x < 3. The reactivity of O 2 toward this layer was sufficient to form TiO 2 at an O 2 pulse duration of 2 s when the substrate temperature was not lower than 235 °C. TiO 2 films were also grown on Si(100) substrates at deposition temperatures between 230 and 460 °C. No residual iodine could be detected in the films grown at temperatures higher than 230 °C. Phase-pure anatase was formed in the whole temperature range except at the highest temperature where rutile was also obtained.