Simple and Versatile Analytical Method for Monitoring the Deposition of Thin Layers by Optical Measurement and Calculation of Residual Stress

Abstract

This paper develops a simple and versatile analytical method for characterizing residual stress associated with the deposition of thick, thin, single and multilayer coatings. This study is of great importance, since the generation of residual stress can lead to the formation of significant defects in the coating. To illustrate the effectiveness of our analytical method, two different processes were characterized. The coatings formed are intended for anti-corrosion applications. The first is a Physical Vapour Deposition (PVD) involving a High Power Impulsed Magnetron Sputtering (HiPIMS), the second is a sol-gel process. The approach is based on the optical recording of the curvature of a thin substrate, followed by its assessment using a fit of the digitalized image by a parametric model. The results provide experimental data on the development of stress during deposition. Both coatings studied have a low level of residual stress, which explains why they are flawless and which is interesting for the targeted anti-corrosion application. For the PVD coating, it was possible to link the development of the stress to the evolution of the film structure during growth. For the sol-gel process, the study of the stress allowed us to highlight the drying reaction mechanisms involved during the sol-gel transition and their influence on the gel structure.