Figure 6.

Hot electron dynamics in the surface oxide of TiON 25%. (a) Differential reflectivity measurements of Au/TiO₂, TiON 10%, and TiON 25% over the first 1.75 ps. TiON 25% exhibits an additional ultrafast peak (shaded region) attributed to hot electrons in the TiO_2–x relaxing to the conduction band minimum. (b) Decomposition of the TiON 25% signal into conduction band electron occupation (blue dashed line) and hot electron population (red-dashed line). The lifetime of the hot electron distribution (τ_CB) describes the electron–phonon scattering time in the TiO_2–x. It is described by the fitted full width at half-maximum (FWHM) of the signal showed by the red arrow. (c) Power dependence of τ_CB, showing a slower relaxation with increasing power (and thus increased electron temperature) characteristic of a hot electron population. Error bars denote standard deviation of the fitted data.