Fig. 1. (Color online) (a) A schematic diagram of the SnO₂ microbelt-based UV PD. (b) Optical image of the as prepared SnO₂ microbelt and (c) SnO₂ microbelt based UV PD.

Fig. 2. (Color online) Morphology and structure of SnO₂ microbelts. (a)−(c) SEM images at different magnifications of SnO₂ microbelts (Inset in Fig. 1(a) is the optical image of as-prepared SnO₂ samples). (d) XRD pattern of a single SnO₂ microbelt.

Fig. 3. (Color online) XPS and UV−vis spectra of SnO₂ microbelts. (a) The survey spectrum, high-resolution X-ray photoelectron spectra for (b) Sn 3d core level, (c) O 1s core level. (d) The UV−vis absorption spectrum. The inset in (d) is a plot of (αhν)² versus hν for the SnO₂ microbelts, with E_g representing the optical band gap.

Fig. 4. (Color online) Photoelectrical performances of the single SnO₂ microbelt based photodetector. (a) The I−V curves under dark, and under illumination with 500 and 300 nm in ambient air, (b) I−t curve under 3 V and 300 nm (0.311 mW∙cm⁻²), (c) instant photo response and (d) spectral photo response ranging 250 to 500 nm (Inset: a semi-log plot showing the responsivity as a function of wavelength).

Fig. 5. (Color online) Photoelectrical performances of the self-powered p-Si/n-SnO₂ UV PD. (a) Illumination area of single SnO₂ microbelt and p-Si/n-SnO₂ based UV PD. (b) I−V curves under dark conditions and under exposure to 500 and 300 nm UV light in ambient conditions, (c) I−t curve at 300 nm and 3 V, (d) instant photo response and (e) spectral photo response from 250 to 500 nm at a basis of 3 V.

Fig. 6. (Color online) Self-powered performances of the SnO₂−p-Si UV PD. (a) I−t curve at 300 nm and 0 V, (b) spectral photo response from 250 to 700 nm at a basis of 0 V (Inset: a plausible response mechanism for the p-Si/n-SnO₂ heterojunction device).