Abstract
Second-harmonic generation (SHG) has been used to monitor the adsorption of Ag on the surface and its successive transformation to in situ at several sample temperatures in the range from to . The decrease of the SH intensity with Ag deposition at elevated temperatures higher than about was found to be a result of destructive interference between the SH signals from and . The temporal dependence of the SH intensity was calculated for a direct transformation model of formation. The calculation using the phase differences and the desorption rates obtained from the SH signal shows a temperature-dependent systematic deviation from the observed data; that is, reduced transformation to in the initial stage of Ag deposition as compared with that in the direct transformation model, which clearly suggests the existence of a critical size of Ag islands for the nucleation of . Once nucleated, the transformation is indicated to be accelerated by the additionally deposited Ag atoms up to a Ag coverage, at which point all the deposited Ag atoms are incorporated into the reconstruction. Moreover, the peak of a polarization-selected SHG signal observed during desorption was found to correspond to a surface fully covered by the structure with a Ag coverage of monolayer.
- Received 7 March 2005
DOI:https://doi.org/10.1103/PhysRevB.72.085308
©2005 American Physical Society