Growth-time-dependent performance of hydrothermally synthesized ZnO nanorods for photodetector applications Rahmat Setiawan Mohar (1,2), Isnaeni (2), and Vivi Fauzia (1*)
1) Study Program of Materials Science, Department of Physics, Universitas Indonesia, Depok, Jawa Barat 16424, Indonesia.
*vivi[at]sci.ui.ac.id
2) Research Center for Photonics, National Research and Innovation Agency (BRIN), Kawasan Sains dan Teknologi B.J. Habibie, Tangerang Selatan, Banten 15314, Indonesia.
Abstract
Zinc oxide (ZnO) is considered a favorable material for ultraviolet (UV) photodetection because of its direct wide band gap and synthesis simplicity. In this work, we prepared photodetectors based on ZnO nanorods (NRs) grown on indium-tin-oxide interdigitated-electrode (ITO-IDE) substrates using a hydrothermal method with different growth times of 2, 4, and 6 hours. The x-ray diffraction (XRD) analysis confirmed that all the ZnO NRs had the wurtzite polycrystalline structure with the predominant orientation of (002). The scanning electron microscopy (SEM) images revealed hexagonal-shaped ZnO NRs, with diameters increasing as growth time prolonged. The optical analysis showed optical band gaps were in the UV region with the value of 3.29, 3.25, and 3.23 eV for growth time of 2, 4, and 6 hours, respectively. The current-voltage (I-V) measurements showed that both dark current and UV photocurrent increased with growth time, hence giving rise the UV photoresponsivity of the photodetectors from 2.92 A/W for the 2-hour sample to 5.41 and 7.32 A/W for the 4-hour and 6-hour samples at 5 V bias, respectively. Furthermore, the growth duration significantly influenced the response time of the photodetectors- the 2-hour sample exhibited the fastest rise and fall times, whereas the 6-hour sample was the slowest. These results demonstrate that optimizing growth time is crucial for balancing photocurrent gain and response speed in ZnO-based UV photodetectors.
Keywords: ZnO- hydrothermal, growth time, photodetectors
