Topography-Driven UVC Detection: ZnO Nanoflowers on Etched Silicon Inverted Pyramids

In this study, a high-sensitivity UVC photodetector was developed by integrating hydrothermally synthesized ZnO nanoflowers with microstructured silicon substrates featuring inverted pyramid arrays. The silicon substrates were fabricated via wet etching using a copper-assisted method to form anisotropic inverted pyramid cavities that significantly enhance surface-to-volume ratio and light-trapping capabilities. Among different etching durations, the 10-minute treatment produced well-defined and uniformly distributed pyramid structures, which served as an ideal scaffold for ZnO nanoflower growth. The ZnO nanoflowers exhibited a hierarchical structure composed of radially aligned nanorods, as confirmed by SEM, XRD, EDS, and PL analyses. The combination of high-surface-area nanoflowers with the three-dimensional silicon architecture greatly improved the UV light absorption and carrier generation efficiency. Photodetection measurements under 365 nm (UVA) and 254 nm (UVC) illumination revealed that the hybrid ZnO NFs/inverted Si device achieved superior performance compared to planar and partially structured counterparts. A maximum response of 128% under UVC and 50% under UVA was observed at a reverse bias of 5 V, along with fast response and recovery times. The synergistic integration of nanoscale ZnO morphology and microscale substrate engineering offers a promising route for the next generation of high-performance UV photodetectors.