Zero residual stress determination of iridium/carbon bilayer and multilayers coatings by utilizing chromium

Abstract

NewAthena (New Advanced Telescope for High-Energy Astrophysics) has been endorsed by the European Space Agency in November 2023 and the mission is entering a pre-industrialization phase prior to the foreseen adoption early 2027.A key aspect of the thin film coating development for the NewATHENA X-ray optics, is to determine the adhesion efficiency and the residual stress limitation of the coatings on silicon substrates. To do so, we magnetron sputtered different layer thicknesses of chromium layers underneath iridium/carbon bilayer and linear graded multilayer coatings. The samples were characterized using X-ray Reflectometry (XRR) to derive the thickness and micro-roughness. The residual stress was assessed by profilometry using a Dektak 150 stylus profilometer. The curvature of the samples before and after coating, along with the total film thickness derived from XRR, was used to evaluate the residual stress.