X-ray diffuse-scattering study of interfacial morphology and conformal roughness in metallic multilayers

The nature of the interfacial roughness in ${\mathrm{Ni}}_{0.81}$ ${\mathrm{Fe}}_{0.19}$/Au multilayers was studied using x-ray diffuse scattering. Using an image-plate detector this scattering could be observed to an extended momentum transfer. The roughness exponent and the cutoff length of the interfacial height-height self-correlation function could thereby be determined using a model of conformal roughness, for which the interfaces are smooth within the cutoff length. We also show that while the roughness is not conformal for short length scales, a transition to conformal behavior occurs from ∼25 to 100 Å.