Figure 4

(a) I-t plots and (b) photocurrent densities of the TiO₂-Au bilayer samples with the TiO₂ thicknesses of 0, 5, 10, 20, 30 and 50 nm, here the sample of 0 nm represents the rough TiO₂ film itself; (c) I-t plots under the irradiation of different monochromatic wavelengths; and (d) action spectra (i.e., photocurrent versus wavelength) of the TiO₂-Au bilayer (red line) and its constituent layers – the bare TiO₂ film (black line) and the bare Au film (blue line), here the TiO₂ film is always 30 nm thick.