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

Abstract

Reflectance anisotropy spectroscopy (RAS) has been used, together with scanning tunnelling spectroscopy (STS), to investigate the optical and electronic properties of nanodots formed by depositing Ag on the Si(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 measured by RAS. Aligned, elongated Ag islands were also grown on this surface to compare their properties with those of the nanodots. STS of the Ag islands showed 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 the Si(111)–3 × 1-Ag surface. RAS also showed substantial differences between the structures, with a large infrared anisotropy for the metallic Ag islands consistent with anisotropic Drude-like intraband transitions, whereas the nanodots gave a negligible response in this spectral region. The RAS results in the infrared spectral region are consistent with the difference in the metallic character of the nanodots and islands, as determined by STS.

Reflectance anisotropy spectroscopy of Si(111)-(3×1)Li and Ag surfaces

“…The computed RA spectrum for the (3 × 1)Ag surface is in good agreement with previously reported experimental RA data for this surface; 16,17 the RA spectrum for the (3 × 1)Li surface has not been reported in the literature, however, strong similarities in the surface electronic structures of the Ag and Li systems and their surface dielectric functions result in similar predicted RA spectra. The origins of the features of the RA spectra below the bulk band gap are identified in terms of transitions between surface states associated with the HCC and chains of Li or Ag atoms.…”

“…16,17 A plot of the modulus squared of the transition matrix element in Eq. (5), p α nn k , between the occupied and vacant states with transition energies of 1.50 ± 0.05 eV with the electric vector of the radiation aligned parallel or perpendicular to Ag chains, is shown in Fig.…”

In situcharacterization of one-dimensional plasmonic Ag nanocluster arrays

“…34,35 In contrast, the separation between individual nanocluster rows is much greater here, and the measured anisotropy is 1 or 2 orders of magnitude larger. Despite the similar low coverages, the islands are large enough to show metallic behavior, which is not the case for smaller islands of Ag on Si(111) (Ref.…”

“…There have been numerous discussions on the optical response of LPR 1 and reports of RAS measurements of anisotropic arrangements of metal islands. 30,[33][34][35] However, none of the theoretical models described there can be directly applied to our structures.…”

In-situ characterization of metal clusters supported on a birefringent substrate using reflectance difference spectroscopy

“…Due to the normal incidence of light, in the case of two-dimensional cluster layers, RDS is sensitive to the anisotropy of the in-plane (1, 1) plasmon modes, only. The reflectance-difference (RD) signal contains contributions related to (1) a screening effect, which describes the absorption of the layer grown on an anisotropic substrate [17,18], and (2) one or more intrinsic effects, which correspond to the lifting of the degeneracy of the in-plane modes caused by the ellipsoidal shape of the particle [19][20][21], the anisotropic interaction between particles arranged in a low symmetric array [22][23][24][25], or by anisotropic images forming in the birefringent substrate [17]. The screening contribution is proportional to the planar component of the surface susceptibility γ , whereas the intrinsic effects give rise to a differential-like line shape ∝ dγ /dE.…”