Abstract
•ZnO nanostructures have been grown by rf-magnetron sputtering.•Argon sputtering pressure considerably alters the morphology of ZnO nanostructures.•Oxygen vacancies increase with the argon sputtering pressure.•ZnO nanostructures exhibit excellent NH3 gas sensitivity.
In this report, the NH3 gas sensing properties of ZnO nanostructures fabricated by radio frequency magnetron sputtering under various argon sputtering pressures have been investigated under various temperatures. The morphological transitions occur from vertical standing nanorods to inclined and tapered nanostructures with increasing the argon sputtering pressure. The dominant green emission at around 2.28eV in the photoluminescence spectra signifies the presence of oxygen vacancies in the ZnO nanostructures which increases as a function of argon sputtering pressure. Despite low surface area, the nanostructures grown under higher argon sputtering pressure of 10Pa exhibit excellent NH3 gas response magnitude since it is exhibiting more oxygen vacancies as compared to other counterparts. For 25ppm NH3 gas at room temperature, a response time of 49s and a fast recovery time of 19s are attributed to the modification in the intermediate defect states induced by the oxygen vacancies through the adsorption and desorption of gas molecules on the surface of ZnO nanostructures.