Optical response of Ag‐induced reconstructions on vicinal Si(111)

Abstract

The optical response of the Si(111)-(3 × 1) -Ag surface has been studied for the first time with reflectance anisotropy spectroscopy (RAS). A single domain surface was obtained by depositing <1 ML of Ag onto a vicinal Si(111) substrate at 870 K. A significant optical anisotropy develops around 2.2 eV which is related to the formation of the 3 × 1 structure. This surface was then used as a template to grow onedimensional (1D) arrays of Ag nanodots, and also 3D Ag islands, by depositing 0.5 ML, and higher, coverages of Ag at room temperature. RAS of these structures showed a different response in the 2.2 eV region, with a broadened and reduced anisotropy. By extending the RA spectra into the infra-red region (0.5 -1.5 eV), substantial differences between the structures were observed below 1 eV, which may be linked to a difference in the metallic character of the nanodots and islands.

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 We have also shown that one particular surface state, state S 4 in Figs. 3 and 4, is the key vacant state for sub-band-gap optical transitions in this system.…”

“…Furthermore, the onset for sub-band-gap optical absorption occurs at a higher energy than in the Ag system. RA spectra for the Si(111)-(3 × 1)Ag surface from experiment 16 and for both (3 × 1)Ag and (3 × 1)Li systems calculated using these dielectric functions are also shown in Fig. 5.…”

“…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.…”

Structure of Si(111)-In Nanowires Determined from the Midinfrared Optical Response

“…Vicinal, wedged n-type Si(111) samples offcut by 1 towards the ½ " 1 " 1 2 direction were cleaned by heat treatment under ultrahigh vacuum (UHV), and a predominantly single domain Sið111Þ-ð4 Â 1Þ-In structure was grown by depositing In on the clean Si surface at 670 K. The surface order and the phase transition were monitored in situ with RAS, which has been shown to be very useful in monitoring the surface reconstructions of Si(111) [27]. The RAS measurements indicated that the dominant domain occupied about 80% of the surface.…”