Study of ZrO2 Thin Films Deposited at Glancing Angle by Magnetron Sputtering under Varying Substrate Rotation

TL;DR

This study investigates how substrate rotation during glancing angle magnetron sputtering affects the optical, structural, and morphological properties of ZrO2 thin films, revealing significant changes in refractive index, surface roughness, and residual stress.

Contribution

It provides a detailed analysis of the influence of substrate rotation on the microstructure and properties of ZrO2 films deposited at glancing angles, which was not extensively explored before.

Findings

Refractive index decreases with increasing substrate rotation.

Surface roughness is higher in glancing angle deposited films.

Residual stress switches from compressive to tensile with deposition angle.

Abstract

In the present work, a set of ZrO2 thin films have been deposited at 82 degree angle of deposition at several substrate rotation speeds and at 0 degree. The effect of substrate rotation on optical, structural, morphological properties and residual stress has been studies thoroughly. Refractive index estimated from ellipsometric measurement and suitable modeling depicts an interesting decreasing behavior with substrate rotation and has been explained in the light of varying columnar structure with substrate rotation. Refractive index of GLAD ZrO2 films varies between and 1.901 to 2.011. Normally deposited film exhibits refractive index value of 2.178 which is substantially greater than that of GLAD films. Lowering in refractive index of glancing angle deposited films is the attribute of dominant atomic shadowing at glancing angles. Further, correlation length which is the representative of surface grain size was obtained from suitable modeling of atomic force microscopy data and it exhibits a decreasing trend with substrate rotation. The trend has also been attributed to the varying columnar microstructure with substrate rotation. All the glancing angle deposited ZrO2 films possess root mean square roughness between 4.6 and 5.1 nm whereas normally deposited film depicts 1.0 nm rms roughness. Dominant atomic shadowing is responsible for high roughness of GLAD films. Both glancing angle and normally deposited films exhibit preferential growth of monoclinic phase oriented in different directions. GLAD films also depict a tetragonal peak which has been attributed to the fine nano-crystallite size (~13 nm). Residual stress depicts a great switching from large compressive to small tensile as the deposition angle switches from normal to glancing angle