Efficient Ethanol Sensor Based on Vertically Aligned ZnO Nanorods on Radio Frequency Sputtered ZnO/Pt/SiO2/Si Substrate

Abstract

The volatile organic compounds (VOCs) sensing device is developed by using hydrothermally grown vertically aligned 1D ZnO nanorods (ZnO NRs) on radio frequency sputtered ZnO/Pt/SiO2/Si substrate. Before the fabrication of the sensor device, the microstructure, morphology, and temperature stability of the NRs are characterized using x‐ray diffraction, absorption and emission spectrum, field emission scanning electron microscopy, and thermal gravimetric analysis. Observation shows the formation of well‐vertically aligned, temperature‐stable (up to 900 °C) ZnO NRs with a hexagonal wurzite phase. The NRs show enhanced defects, vacancies, and interstitial‐related green emission (503 nm) and red emission (655 nm) with a bandgap of ≈3.74 eV. The observed Raman active E1 and A1 modes are prominent for such NRs. The sensing device exhibits a selective response to ethanol as compared with other VOCs (e.g., methanol, ethanol, and 2‐propanol). The oxygen‐vacancy‐rich ZnO NRs show enhanced ethanol sensing with a speedy response time (87–97 s) and recovery characteristics time (66–169 s). The device shows a lower detection limit for ethanol ≈4.5 ppm. The ethanol sensing mechanism and the advantages of the as‐grown vertically aligned ZnO NRs structure as sensing material are also discussed. The device shows excellent long‐term stability (≈20 weeks) and reproducing capability for ethanol.