Titanium oxide nanostructured films by reactive pulsed laser deposition

Nanostructured titanium oxide thin films have been grown by nanosecond UV pulsed laser deposition (PLD) performed in a reactive background atmosphere. We exploited laser ablation of a Ti target at different pressures of pure oxygen and Ar:O2 mixtures to show that film growth can be tuned at the nanoscale from compact and dense to columnar and to porous, leading to different morphology, density and structure (oxidized fraction and degree of crystallinity). We observed that the position of the substrate relative to the time integrated visible plume front is fundamental in the determination of film structure and morphology. Film growth and film properties can be related to a non-dimensional parameter L which is the ratio between the target-to-substrate distance and the visible plume length. In particular, surface morphology and degree of structural order are strictly related to L irrespective of the oxygen content, while the latter mainly affects the oxidized fraction in the film.