Fig. 1. Optical image and SEM images of TiO₂NF and Se/TiO₂NF. (a) Optical image of TiO₂NF; (b) SEM image of TiO₂NF; (c) SEM image of Se/TiO₂NF

Fig. 2. XRD patterns and Raman spectra of TiO₂NF, Se, and Se/TiO₂NF. (a) XRD pattern; (b) Raman sepctra

Fig. 3. I-V characteristics of TiO₂NF and Se/TiO₂NF. (a) I-V characteristics of TiO₂NF device at dark and 350 nm; (b) I-V characteristics of Se/TiO₂NF device at dark, 350 nm, 450 nm, and 610 nm light illumination, respectively

Fig. 4. I-t curves of TiO₂NF and Se/TiO₂NF.(a) I-t curves of TiO₂NF device under 350 nm at bias voltage of 5 V; (b) I-t curves of Se/TiO₂NF device under 350 nm, 450 nm, and 610 nm light illumination without bias voltage, respectively

Fig. 5. Spectral response and schematic illustration of energy band for Se/TiO₂NF. (a) Spectral response of Se/TiO₂NF device without bias voltage; (b) schematic illustration of Se/TiO₂NF type II band aligned heterojunction