SURFACE RECONSTRUCTIONS IN THE AG/SI(001) SYSTEM

Scanning tunneling, microscopy and low-energy electron diffraction have been used to study the surface reconstructions of Ag on Si(001) as a function of the Ag coverage up to one monolayer (ML), and annealing temperatures above 450-degrees-C. Ag grows in the Stranski-Krastanov mode. An ordered 2 X 3 structure is observed in the first two-dimensional (2D) layer grown, and the 2D 2 X 3 layer is completed at 0.5 ML of Ag. Atomic-resolution images of this ordered surface structure are presented. Above 0.5-ML saturation coverage, an unusual growth transition from 2D to 3D is seen, which results from the subsurface accommodation of Ag accompanied by rearrangement of substrate Si.