Fig. 1. Fabrication process of ZnO-GQDs device

Fig. 2. (a) Top-view SEM images of the as-grown ZnO NWs; (b) High resolution of ZnO NWs; (c) Top-view SEM images of the GQDs-ZnO NWs; (d) High resolution of GQDs-ZnO NWs

Fig. 3. TEM of ZnO NWs and ZnO-GQDs NWs: (a) the single ZnO NW sample for TEM; (b) the observation regions of ZnO NW in red circle; (c) the single ZnO-GQDs NW sample for TEM; (d) the observation regions of ZnO-GQDs NW in red circle

Fig. 4. GQDs’s diameter characterization. (a) the TEM of GQD; (b) the figure of diameter distribution statistics

Fig. 5. I-V characteristics of the ZnO NWs photodetectors (a) and ZnO-GQDs NWs photodetectors (b); I-T characteristics of the ZnO NWs photodetectors (c) and ZnO-GQDs NWs photodetectors (d)

Fig. 6. Photoresponse mechanism of the ZnO-NWs (a)–(b) and ZnO-G QDs (c). The oxygen plasma treatment improves the oxygen CB and VB are the conduction and valence bands, respectively