Waveguiding and correlated roughness effects in layered nanocomposite thin films studied by grazing-incidence small-angle x-ray scattering

Long-range interface correlations in C/Au/C and Ag/Si3N4 layered films consisting of metal nanoparticles embedded in amorphous matrices are investigated by atomic force microscopy, high-angle annular dark-field scanning transmission electron microscopy, x-ray reflectivity, and grazing-incidence small-angle x-ray scattering (GISAXS). We demonstrate that the GISAXS intensity of such systems is modulated by waveguiding and correlated roughness effects, which involve the use of a dynamical scattering theory to analyze the experimental data and to distinguish between both effects. Direct imaging methods and GISAXS experiments combined with quantitative analysis within the distorted wave-Born approximation thus provide complementary information. While no roughness correlation is observed in the C/Au/C trilayers, the surface roughness of the Si3N4 capping layers in the Ag/Si3N4 bilayers replicate the topography of the Ag nanoparticles resulting in a partial correlation, which decreases as the Si3N4 thickness increases.