Structural properties of TiO2 nanocrystallites condensed in vapor-phase for photocatalyst applications

We have synthesized titanium dioxide (TiO₂) nanocrystallites by pulsed laser ablation (PLA) in oxygen (O₂) background gas for photocatalyst applications. Varying O₂ background gas pressure \( \left( {P_{{{\text{O}}_{ 2} }} } \right) \) or substrate target distance (D _TS), it was possible to change weight fraction of anatase phase in the anatase/rutile mixture from 0.2 to 1.0. Porosity of the deposited TiO₂ films increased with increasing \( \left( {P_{{{\text{O}}_{ 2} }} } \right) \) and D _TS. Relation between the process parameters and the formed crystal phases was explained from the point of cooling process in vapor-phase. Furthermore, rapid thermal annealing (RTA) was performed as post-annealing, suppressing sintering of the nanocrystallites. Photocatalytic activities of the TiO₂ nanocrystallites depended on the RTA temperature and following crystallinity restoring as well as the crystal phase: anatase or rutile.