Optical and morphological evolution of black TiOx synthesized in water by Nd:YAG laser

Optical and morphological properties of nanostructured TiO film formed by 532 nm nanosecond pulsed laser irradiation in water is analysed. We observe three different surface features: blackening, surface pits and sub-surface bubbles. The appearance of these features is allowed once an irradiation fluence of 0.9 J cm is used. Nevertheless, blackening, formation of pits and bubble are delayed until an accumulated fluence threshold of 7.5, 23 and 24 J cm is achieved respectively. A fully evolved complex nano-porous structure is obtained at an accumulated fluence of 100 J cm. A possible mechanism of formation of these features was inferred.