Optical reflectance anisotropy of buried Fe nanostructures on vicinal W(110).

The optical anisotropy of Au protected Fe layers grown on a vicinal W(110) surface has been investigated using reflectance anisotropy spectroscopy (RAS). Iron nanostripes formed at submonolayer coverage, as well as Fe layers up to 3 ML coverage, were protected by 12 and 16 nm gold caps and measured ex situ under ambient conditions. The RAS is dominated by structures originating in the interfacial W(110) region, modified by the absorption in the Au cap and possibly by uniaxial strain in the Au cap itself. The Fe nanostructures themselves do not produce a significant RAS signature but, nevertheless, differences with Fe coverage were identified and explained in terms of a simple isotropic Fe absorbing layer, together with strain relief in the W/Fe/Au interfacial region.