Optical and electronic properties of quasi-1D gold nanowires on Si(553) surfaces

The structures of many 1D metallic nanowire systems have not yet been sufficiently clarified, such as gold nanowires on vicinal Si surfaces. Such structures are intrinsically anisotropic and can be investigated by Reflectance Anisotropy Spectroscopy (RAS), which is a powerful non-invasive optical technique for probing electronic states of surfaces and buried interfaces. The optical response of the clean Si(553), Si(553)-Au and hydrogenated Si(553)-Au surfaces are measured with RAS and compared with density functional theory simulations. Good agreement between experiment and theory is obtained. Local structural elements such as the Si honeycomb chains and the gold atomic wires, yield distinctive features in the optical spectra. By comparing the optical response of the freshly prepared and hydrogenated Si(553)-Au surfaces, the spectral features can be directly attributed to particular structural elements on the surface. Hydrogen adsorption attenuates the anisotropic response at spectral regions associated with the honeycomb chains at the Si step edges. This combination of experiment and theory is very useful in identifying specific structural sites on the surface, which generate distinctive features in the optical response.