Effect of Hydrothermal Growth Duration on ZnO Nanorod-Based Photodetectors

In this study, the morphological, structural, and electrical properties of one-dimensional (1D) ZnO nanorod-based photodetectors fabricated via a two-step thin-film growth method were investigated. In the first step, a ZnO seed layer was deposited onto a glass substrate using the dip-coating method. In the second step, ZnO nanorods were hydrothermally grown at 80°C for different durations (3 and 5 h). Structural characterization performed by X-ray diffraction (XRD) confirmed the formation of hexagonal wurtzite ZnO structures with preferential c-axis orientation, while scanning electron microscopy (SEM) analysis revealed homogeneous and vertically aligned nanorod morphologies. The average nanorod diameters were determined to be approximately 53 nm for the Z1 sample and 60 nm for the Z2 sample. Electrical characterization was carried out using current–voltage (I–V) measurements under dark and white-light illumination conditions at different power densities. The fabricated devices exhibited room-temperature resistance values of approximately 102 kΩ for Z1 and 174 kΩ for Z2. Furthermore, periodic light ON/OFF current–time (I–t) measurements demonstrated stable, repeatable, and noise-free dynamic photoresponse behavior. The sensitivity values of the Z1 and Z2 devices were determined as 121% and 61%, respectively. In addition, the maximum photoresponsivity and specific detectivity values were calculated as 3.03×10−2 A/W and 1.28×1010 Jones for the Z1 sample, respectively, whereas the corresponding values for the Z2 sample were 2.48×10−2 A/W 0.84×1010 Jones, respectively. The response/recovery times were calculated as 21/18 s for Z1 and 24/22 s for Z2, respectively. The obtained results indicate that hydrothermal growth duration strongly affects nanorod morphology and photodetection behavior, demonstrating that ZnO nanorod structures fabricated by the proposed method are promising candidates for low-cost photodetector applications with growth-duration-dependent performance.