As thin film technology moves into the truly nano-scale region (<10 nm), many conventional methods of growth and analysis of thin films and multilayers break down due to large levels of interfacial roughness and diffusion, or incompatability of the analyzing probe for such small length measurements. Our group has developed facilities to grow thin films and multilayers, with reproducible layer thicknesses as thin as 1 nm and interfacial roughness as small as 0.2 nm, using dual ion-beam assisted deposition (DIBAD). Grazing incidence x-ray scattering (GIXS) measurements of these structures and subsequent modelling of the x-ray behavior yield simple characterization with a minimum number of modelling parameters. One immediate result is the ability to produce high quality x-ray multilayer mirrors.
Recent developments in our modelling facility have focused on investigation
of the diffuse scattering (scattering away from specular reflection). Modelling
of the specular reflection yields accurate layer thicknesses, while diffuse
scatter is highly sensitive to both interfacial diffusion and roughness.
We have seen that even interfacial roughness which is replicated at each
interface from the substrate up (conformal roughness) can be separated from
the inherent roughness in each interface (non-conformal roughness). Our
ability to model the layer thicknesses, densities and all three types of
interfacial roughness provides a complete characterization of multilayer
structures.