Optical and electronic properties of Ag nanodots on Si(111)

Abstract

Reflectance anisotropy spectroscopy (RAS) has been used, togetherwith scanning tunnelling spectroscopy (STS), to investigate the opticaland electronic properties of nanodots formed by depositing Ag on theSi(111)–3 × 1-Ag surface. One-dimensional (1D) arrays of nanodots were grown on a single-domain(3 × 1)-Ag surface and the anisotropic optical response in the 0.5–5 eV range measuredby RAS. Aligned, elongated Ag islands were also grown on this surface tocompare their properties with those of the nanodots. STS of the Ag islandsshowed distinct metallic behaviour, whereas the nanodots revealed a bandgap of∼0.6 eV, indicating that the surface of the dots has a non-metallic character, similar to that of theSi(111)–3 × 1-Ag surface. RAS also showed substantial differences between the structures, with a largeinfrared anisotropy for the metallic Ag islands consistent with anisotropic Drude-likeintraband transitions, whereas the nanodots gave a negligible response in this spectralregion. The RAS results in the infrared spectral region are consistent with the differencein the metallic character of the nanodots and islands, as determined by STS.