Reconstruction and dynamics of Ag atoms on Si(1 1 1)-3×3-Ag surface studied by optical second-harmonic generation

In-situ second-harmonic generation (SHG) monitoring of Ag deposition onto Si(1 1 1)-3×3-Ag has been conducted at several sample temperatures ranging from −190 °C to room temperature (RT). The SH signals from Si(1 1 1)-21×21-Ag and Si(1 1 1)- 6 × 6-Ag at a photon energy of 1.17 eV have been identified with the help of low-energy electron diffraction (LEED) observation. The relatively large SH signal from Si(1 1 1)-21×21-Ag is attributed to a resonance related to transitions among surface states. The weak SH signal observed for Si(1 1 1)-6 × 6-Ag results from the absence of the metallic surface state band. A 180° phase shift observed for the SinPout signal at about 3 ML suggests that an additional Ag deposition onto Si(1 1 1)-6 × 6-Ag at −190 °C forms a surface Ag layer in a quasi-layer-by-layer mode.