Figure 3.

Supplementary theoretical calculations. (a) Influence of the TiO₂ thickness on the reflectivity of a titanium surface. (b) Theoretical reflectivity of clean titanium (for the p-, s-, and unpolarized light) and theoretical reflectivity for the oxidized titanium (d_ox = 25 nm) as a function of the incidence angle; measurements from ref.¹ are shown as black triangles. (c) Reflectivity of titanium covered by a TiO₂ layer and water as a function of the water-layer thickness; results for three different oxide thicknesses d_ox are shown and the dashed curves present the average reflectivity. (d) Reflectivity as a function of the oxide layer thickness for a dry sample (only oxide is present on a titanium surface, the black curve) and for a wet sample (the oxide is additionally covered by water, the red curve). The green curve shows the ratio between the red and the black curves. Unless explicitly stated otherwise, calculations are made for λ = 532 nm and for normal incidence (θ_i = 0°) of unpolarized light.