Structural characterization of nanoparticles-assembled titanium dioxide films produced by ultrafast laser ablation and deposition in background oxygen

Ultrafast laser ablation of titanium dioxide and deposition of nanoparticles-assembled films in oxygen ambient gas at pressures going from high-vacuum up to several mbar is investigated. We identify various regimes of the plumes propagation into the background gas as well as of the material deposition rate. These reflect on the structural characteristics of the nanoparticles-assembled films: the film morphology changes from a structure with glue-like nanoparticulates, at low pressure, to a highly porous assembly of individual nanoparticles, at larger pressure. Our findings indicate that background gas pressure provides an interesting key for additional control on the structural characteristics of oxide nanostructures produced by femtosecond laser deposition.