OICC Press International Nano Letters 2228-5326 15 4 2025 12 30 Structural Tuning of ZnO Nanorods via Seed-Layer Engineering for High Speed n-ZnO/p-Si UV Photodetector 10.57647/inl.2025.1504.14 EN Samaneh Jabbarivand Nanophysics Lab, Faculty of Physics, Kharazmi University, Tehran, Iran Mohammad Hossein Majles Ara Nanophysics Lab, Faculty of Physics, Kharazmi University, Tehran, Iran Soraya Muosavi Nanophysics Lab, Faculty of Physics, Kharazmi University, Tehran, Iran; Department of Physics, Faculty of Physics and Chemistry, Alzahra University, Tehran, Iran Ali Kazempour Nanophysics Lab, Faculty of Physics, Kharazmi University, Tehran, Iran Journal Article 2025 12 30 The effect of seed layer thickness on the optical and electrical properties of ZnO nanorods (NRs) for fast-response UV photodetector applications was investigated. Vertically aligned ZnO NRs were grown via a hydrothermal method using seed layers with various thicknesses ranging from 350 nm to 550 nm. FESEM characterization revealed that the synthesized ZnO NRs had average diameters of 71−175 nm and lengths of 1.3−2 μm. UV-Vis spectra indicated that the sample with the thinnest seed layer (350 nm), which exhibited a higher aspect ratio, showed enhanced absorption in the UV region. p-n heterojunction photodetectors (PDs) based on the synthesized ZnO NRs were fabricated, and their I-V and I-t characteristics were evaluated. The results demonstrated that optimizing the seed layer thickness in accordance with the UV wavelength significantly improves the photodetector’s responsivity, sensitivity, and quantum efficiency, while also achieving remarkably fast response and recovery times. These findings highlight the critical role of structural tuning in enabling high-performance, fast-response UV photodetectors.