Development of Highly Sensitive and Selective Ethanol Sensors Based on RF Sputtered ZnO Nanoplates

This paper reports highly sensitive and selective ethanol sensing performance of ZnO thin films in a resistive configuration. ZnO thin films were grown by RF sputtering on a Si substrate at room temperature under a controlled environment. The grown film was characterized by x-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy. XRD analysis reveals a crystalline size of ∼ 73 nm with preferential (002) plane growth along the c-axis, and FESEM confirms a uniform film with nanoplate like structures. Ethanol sensing performance of the ZnO based device with Al as contacts were carried out in the temperature range of 50–200°C for concentrations of 1–400 ppm. The highest response magnitude of ∼ 95% was obtained at 200°C with fast response and recovery time of ∼ 27 s and ∼ 25 s, respectively. Sensor responses of other similar volatile organic compounds confirms the high selectivity of ZnO nanoplates towards ethanol sensing. The ethanol sensing mechanism of the ZnO thin film is discussed considering adsorption–desorption kinetics under different ambient conditions and defect states.