Optical, structural and mechanical properties of TiO2 and TiO2-ZrO2 thin films deposited on glass using magnetron sputtering

Abstract

In this study, the structural, optical, and mechanical properties of magnetron sputtered TiO2 and TiO2-ZrO2 mixture transparent thin films along with the effect of heat treatment were investigated. TiO2 and TiO2-ZrO2 thin films were fabricated by magnetron sputtering from ceramic targets at room temperature on both the soda-lime and the borosilicate glass substrates. Structural properties of thin films were studied via X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffractometry (GI-XRD) and scanning electron microscopy (SEM). Optical characterizations were carried out using spectrophotometry and spectroscopic ellipsometry. The hardness and scratch behavior of the samples were investigated using nano-indentation and nano-scratch tests. TiO2 and ZrO2 presence in films was confirmed by XRD and XPS analysis. It was found that TiO2-ZrO2 films show higher hardness values compared to TiO2 thin films. It was also seen that ZrO2 presence in TiO2-ZrO2 thin films prevents the crystallization of TiO2 after annealing compared to TiO2 thin films that resulted in better surface quality and higher thermal stability after annealing. The addition of ZrO2 to TiO2 resulted also in the shifting of the absorption edge to smaller wavelengths while decreasing the sharpness thus providing less absorption in the visible area, especially in the range of 380–500 nm. The refractive index of TiO2-ZrO2 thin film remained relatively unchanged compared to TiO2 after annealing, making it more preferable in terms of optical stability.