A mechanical study of W–N/W multilayers

The microstructure of W, W–N single layers and W–N/W multilayers was related to their mechanical properties. For W–N single layer deposition, various nitrogen partial pressures (PN2=10–50%) were investigated. A PN2=50% was chosen to deposit multilayers. The hardness values of the single layers and of the symmetric period multilayers as functions of period thickness (2–80 nm) were studied. Single layers have a hardness close to 14 and 18±1 GPa for W and W2N (with PN2=50%), respectively. For period thickness ranging between 5 and 80 nm, W–N/W multilayer hardness increases as layer spacing decreases. A hardness value 21.5±1.5 GPa was reached for 5 nm of period thickness (Λ). The first experimental results on asymmetric system are presented to determine the influence of W and W–N thickness in the multilayers.