Comparison of Tribological Characteristics of ZnO Coatings Prepared by Sputtering and Sol-gel Methods

In this work the tribological characteristics were compared between ZnO coatings on glass substrate prepared by sputtering and sol-gel methods. In order to assess the effects of processing method on the tribological characteristics, the friction and wear properties of the coatings were measured by using a reciprocating type of micro-tribotester. The sputtered ZnO coatings were prepared on a glass substrate at room temperature, $150^{\circ}$, and $300^{\circ}$. The ZnO coatings prepared by sol-gel method were heat-treated in air atmosphere at $550^{\circ}$ for one hour. The crystal structure and surface morphology of the coatings were measured by X-ray diffraction (XRD) and Atomic Force Microscope (AFM), respectively. The experimental results showed that overall the sputtered coatings exhibited better friction and wear properties than coatings prepared by sol-gel method. The sputtered coating grown at room temperature had a relatively low friction coefficient of 0.14 and superior wear resistance compared with the other coatings. Nevertheless, sol-gel method of coating ZnO on glass is beneficial for economical coating of a large surface area.