Study of room temperature NO2 sensing performances of ZnO1-x (x=0, 0.05, 0.10)

Zinc oxide nanopowder was made using an auto-combustion method, and oxygen vacancies were formed using a thermally activated procedure under vacuum treatment. The structural and morphological properties of ZnO1-X samples were determined by using X ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electronic microscope (SEM) characterizations. XRD studies revealed that the ZnO1-X samples had a hexagonal wurtzite structure, with nanoparticle sizes ranging from 40 to 47 nm. The growing quantity of oxygen vacancies was confirmed by XPS tests. SEM images showed a spherical nanometric particle with high porosity especially for ZnO0.90. Optical measurements with spectroscopy UV-Visible revealed that oxygen vacancies increase absorption of the material in the visible region. Also, the photoluminescence properties of the prepared samples were investigated by PL and PLE measurement, which indicate a high presence of oxygen vacancies and other defaults in the structure of ZnO0.90 more than pure zinc oxide. The electrical conductivity proportional to the temperature showed that the conduction process was thermally activated and that the carriers had long-distance mobility. Thus, we found that the conductivity of ZnO0.90 was lower than that of ZnO, which can be explained by the introduction of oxygen vacancies which allows the creation of electron trapping centers localized by the presence of the deep-levels. Spraying an aqueous solution of ZnO1-X nanoparticles over alumina substrates with pre-deposited gold interdigitated electrodes resulted in gas sensors. At ambient temperature and under white light illumination, the manufactured sensors showed excellent sensing responses to 0.5 ppm NO2. The presence of oxygen vacancies improves sensor performance, which the sensor based on ZnO0.90 showed a high response of 76.