Nonspecular x-ray reflectivity study of roughness scaling in Si/Mo multilayers

The interfacial roughness and lateral correlation length of a series of Si/Mo multilayers with bilayer period 69 Å and number of bilayers ranging from 5 to 40 have been characterized by diffuse x-ray scattering. Superlattice peaks are preserved in offset radial scans indicating a high degree of conformality in the roughness. The lateral correlation length ξ increases with total film thickness h as ξ∼h0.55; however, the magnitude of the roughness is approximately 2 Å for all film thicknesses, in disagreement with scaling laws for self-affine growing surfaces. This observation suggests that interfaces retard the evolution of high-frequency roughness while replicating longer wavelength roughness from one layer to the next