Unusual Growth Behavior of Atomic Layer Deposited PbTiO3 Thin Films Using Water and Ozone As Oxygen Sources and Their Combination

PbTiO3 thin films were deposited on Si and Ru substrates by atomic layer deposition at a substrate temperature of 200 degrees C using H2O and O-3 as oxygen sources and lead(II) bis(3-N,N-dimethylamino-2-methyl-2-propoxide) and titanium(IV) isopropoxide as the Pb and Ti precursors, respectively. When H2O was used as the oxygen source for both Pb and Ti precursors, film growth was most effective under the conditions where a stoichiometric PTO film was achieved (Pb/Ti concentration ratio similar to 1). On the other hand, the PTO growth per cycle increased with increasing the PbOx/TiO2 subcycle ratio when O-3 was used as the oxygen source for the Ti precursor, even when Pb-rich PTO films were deposited. These unexpected results were explained by the different reactions occurring according to the oxygen source used, in particular, by a reaction mechanism involving the direct condensation between surface formate species and alkoxy species in the case of ozone.