Figure 1.

(a) Schematics of the working principle for X-ray reflectivity analyses on a gig-lox TiO₂ sample deposited on a glass substrate. The presence of lead in the gig-lox films causes an increase of the critical angle θ_c. (b) X-ray reflectivity curves from TiO₂ films (340 nm-thick) before and after soaking into an aqueous solution containing 2.2 ppm of Pb. The black line represents the TiO₂ sample before soaking and the red line represents the same sample after soaking, with its critical angle shifted rightwards.