Fig. 1. (Color online) (a) SEM diagram of synthesized ultra-large nanobelts which are about 2−3 mm in length. (b) The enlargement of the yellow dotted box of (a). Maximum width of these nanobelts is up to 132 μm. (c) XRD pattern of nanobelt. (d) Electron diffraction patterns of selected regions. (e) Low-resolution TEM image of nanobelt. (f) High resolution TEM image of nanobelt.

Fig. 2. (Color online) (a) Schematic diagram of device structure. (b) Image of the actual fabricated device. (c) Energy band of Schottky-junction under positive bias. W is the width of depletion layer. (d) I−V curves of Schottky-junctions of S₁−O₁ and S₂−O₂, respectively.

Fig. 3. (Color online) (a) Experimental I_S2−V_S2 curve of DSCD in the case of V_S > 0 V. (b) Schematic diagram of energy band of device with grounded S₁. The upper part is the case of V_S = 0 V. The bottom part is the case of V_S > 0 V. (c) Experimental I_S1−V_S1 curve when S₂ is grounded. (d) Band diagram when V_S2 is negative. (e) Experimental I_S2−V_S2 curve in the case of V_S2 < 0 V.

Fig. 4. (Color online) (a) Schematic diagram of energy bands and current generated by photogenerated electrons at V_S2 = 0 V. (b) Experimental I−T curve under UV switching conditions at V_S2 = 0 V, (c) I−V curves of different power densities of 254 nm solar-blind UV light irradiation. (d) Energy band diagram of the device under UV light at V_S > 0 V. (e) Comparison of I_S2O2, I_S1O1 and I_S2 under UV illumination. (f) The relationship of P and I_S2 under different V_S2.

Fig. 5. (Color online) Photoelectric parametes at V_S2 = 10 V under different P. (a) PDCR and R. (b) EQE and D*.

Fig. 6. (Color online) (a) Experimental I−T curves with different V_S2 under 709 μW/cm² UV irradiation. (b) and (c) Rise and decay time curves under conditons of V_S2 > 0 V and V_S2 < 0 V, respectively. (d) Schematic diagram of current of UV light turn-on and turn-off cases. (e) Schematic diagram of recombination process of generated-electrons during turn-off time. (f) Relationships between I_S2 and V_S2 during UV light turn-on and turn-off conditions.