Optical reflectance anisotropy studies of Fe nanostructures grown on vicinal W(110)

A vicinal W(110) substrate, offcut by 1.4 degrees in the [110] direction, has been used as a template to grow Fe nanostructures under UHW conditions. For sub-monolayer coverages, deposition of Fe on the substrate at room temperature, followed by annealing, forms continuous Fe stripes aligned with the step edges, which run along [001]. In situ reflection anisotropy spectroscopy (RAS) between 1.5 eV and 5.0 eV shows the damping of the W(110) surface state with increased Fe coverage. Broad and featureless step and Fe nanostructure contributions are identified in the 4 eV to 5 eV spectral region, but no strong signature of the aligned nanostructures or steps is found, in contrast to recent RAS studies of vicinal Cu(111). Capping by Ag for ex situ characterization was investigated by using an eclipsing mask to produce a checkerboard pattern of 0 to 3 ML Fe coverage in 0.25 ML steps, followed by deposition of 18 ML of Ag at room temperature. RAS of the capped structure is dominated by the response of the Ag interfaces. The W(110)/Ag interface shows a distinctive feature at 3.4 eV, which diminishes rapidly with increasing Fe coverage and may be related to the sharp peak observed at 3.9 eV on clean Ag(110) surfaces. The absence of other significant RAS features in this spectral region that can be clearly associated with the aligned Fe nanostructures indicates that characterization of capped structures by other epioptic techniques, such as optical second-harmonic generation, needs to be explored. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.