Scientists and engineers have studied zinc oxide (ZnO) nanomaterials for a great variety of applications. Specifically, ZnO nanomaterials with oxygen vacancies have attracted attention due to improved performance in some of these applications compared to pristine ZnO. For instance, ZnO with oxygen vacancies exhibits ferromagnetic behavior at room temperature, suitable for spintronics applications. Also, for visible light photocatalysis, ZnO with oxygen vacancies shows better absorption of visible light than pristine ZnO. Furthermore, an improvement in the ZnO gas sensing capabilities results from oxygen-deficient oxides. These properties are mainly due to the changes in the carrier's density and band structure of ZnO due to oxygen vacancies. Furthermore, in the sputtering deposition technique, it is known that the plasma processing parameters influence the ZnO properties. Therefore, in this seminar, we discuss the effects of the oxygen to argon sputtering gas ratio on the oxygen vacancies in ZnO thin films and hence, the gas sensing properties for environmental monitoring applications.