Studies on gold atom chains and lead nanowires on silicon vicinal surfaces

The Si(557) vicinal surface is produced from Si(111) by cutting the crystal at a small angle of 9.45 deg. along the [1-bar 1-bar 2] direction. By a special cleaning process performed under ultra-high vacuum conditions, Si(557) displays a perfect grating structure consisting of parallel narrow terraces, each of them composes of a silicon plane with half unit cell of the Si(111)-7x7 reconstruction and a silicon row. Such an atomic grating makes it possible to get self-assembled atomic wires by decorating the surface with an optimal amount of 0.2 monolayer (ML) of Au. In the first step of the study, Si(557) is used as a template for fabricating of Pb nanowires by self-assembling in which the steps on the Si(557) surface provide the high-oriented diffusion channels for Pb wires growth. By means of polarized infrared spectroscopy the optical response of the Pb nanowires is investigated. As a major consequence of the interaction between infrared light and nanostructures, an antenna-like resonance appears. We found the shift of the antenna resonance frequency to lower wavenumbers due to the development of the nanowires in length under parallel excitation, whereas there is no significant change due to perpendicular excitation observed.