Nano-roughness in gold revealed from X-ray signature

We present a new method for investigating roughness for surface structure and internal inhomogeneity down to the nano-scale for thin, nano-structured and opaque materials. The method uses careful measurements of the X-ray mass-attenuation coefficient and is applied to measure the magnitude of the roughness of gold foils. The technique is unique, providing insight into both surface and internal roughness. We show that moments of the distribution function of surface and internal structure can be investigated using this method, and discuss observable signatures. The approach is non-destructive and very sensitive as a local in situ measurement and as a diagnostic for accurate characterisation.