Interfacial local strain analysis in [Cu/W]_n multilayers produced by sequential RF sputtering

[Cu/W]_n multilayers are candidates to reduce W embrittlement in plasma facing components. However, its performance for stopping He⁺ ions is determined by their mechanical properties, which are influenced by the density and lattice mismatch at the Cu/W interfaces. In this work, Cu/W multilayers with nominal thickness of individual layers of 2, 5, 10, 20 and 50 nm and 300 nm of total film thickness, were deposited by sequential RF sputtering. From AFM images a Stranski-Krastanov growth mode of the top layer was deduced. From HR-TEM, a geometric phase analysis was performed, where the strain fields parallel with the Cu/W interfaces show different strain concentrations (tensile and compressive) as the layer thickness increases, which determines the hardness of the multilayers. The results indicate the dependence of mechanical behavior with interfacial local strain and element intermixing in as-manufactured multilayers, and the importance of fully under standing this relation for interface engineering design.