Mo/W/Al doped tin oxide thin films: exploring optical and mechanical properties for transparent protective coating applications

Abstract

For the last few years research has been intensified in exploring and improving mechanical properties of tin oxide thin films besides the optical and electrical ones that enhances the film's functionality and broadens its application purview. The present investigation reports a comprehensive study on the effect of Mo, W, and Al doping on optoelectronic and mechanical properties of tin oxide thin films. The films exhibited an optical transparency over 350–400 nm with an average transmission of 85–98% at 550 nm and mechanical hardness spanning over 2–8 GPa, and electrically resistivity in the range 900–200 Ωm, based on the dopant used and its content. Compared to bare tin oxide film, the doped films exhibited a decrease in optical transparency with an improvement in the hardness. 10 wt.% Mo doped tin oxide film exhibited good average optical transparency 72% at 550 nm, highest elastic recovery of 70%, highest hardness 8.0 ± 0.5 GPa and reduced-modulus of 89 ± 0.5 GPa of all the films. The investigation demonstrates a simple technique of producing mechanically hard tin oxide thin films useful as transparent protective coatings.