Titanium oxide (titania) nanoparticles/thin films were deposited on a non-heated substrate by the ablation of a rutile TiO2 target in Ar atmosphere using an ArF excimer laser under off-axis configuration. The ambient pressure was changed to evaluate its influence on the morphology and crystal structure of the deposited titanium oxide. The ablated species tend to form thin film or nanoparticles embedded in the thin film at low growth pressure while moderate pressure favors the formation of monodispersed nanoparticles. Transmission electron microscopic (TEM) results showed that an increase of Ar pressure from 13.3 to 133 Pa leads to an increase in mean diameter of the primary nanoparticle from 5.9 to 32 nm and reached a maximum. The further increase of the growth pressure leads to a decrease in mean diameter of the primary nanoparticles. The selected area electron diffraction (SAED) rings and X-ray diffraction (XRD) peaks were observed for the titania prepared in the Ar pressure range of 133 Pa and 1.06 kPa at room temperature. Under the pressure range higher than 1.06 kPa or lower than 133 Pa the products were less-oxidized amorphous phase, TiO2-x. (C) 2002 Elsevier Science B.V. All rights reserved.