Fabrication of ZnO thin film based VOC sensor

Abstract

ZnO thin films devised by RF magnetron sputtering were studied for monitoring volatile organic compounds (VOCs) such as acetone, ammonia and ethanol gases in the concentration range of 50–250 ppm under room temperature. The fabricated films were inspected by X-ray diffractometer (XRD), UV-Vis spectrometer, energy dispersive X-ray spectrometer (EDS) and scanning electron microscope (SEM). The XRD results stipulate that the films having wurtzite structure with (0 0 2) preferential orientation and the grain size of the film were calculated as 12.39 nm using Scherrer’s formula. The UV-Vis spectrum showed that the film having 95 % of the transparency in the visible region. The band gap of the film was calculated from Tauc’s plot and was found to be around 3.2 eV. The EDS spectrum affirms the occupancy of Zn and O elements in the ZnO film. The microscopic structure of the film was examined by SEM and the average grain size was estimated as ~13 nm which is having acceptable harmony with XRD results. The sensor response was appraised by change in electrical resistance of the film under the atmospheric medium of VOC gases at room temperature. The sensor gives a better response (~5.2) towards acetone compared with other vapours.