Initial growth of Pb on Si(0 0 1) at room temperature and low temperature

We have investigated Pb adsorption on Si(0 0 1)-2 × 1 at room temperature (RT) and 78 K, using a low temperature (LT) scanning tunneling microscope. Pb deposition at RT exhibits 1-D chain structures in good agreement with previous works at less than 0.5 ML coverage, however, we find that the buckling of Pb dimers alone cannot explain the configurations such as locally coexisting (2 × 2) and c(2 × 4) phases. At RT and LT, C-type defects existing prior to Pb deposition play an important role as nuclei for the initial adsorption of Pb ad-dimers and determine the buckling direction. For LT deposition, a high density of short Pb units are found, including single Pb monomers. The existence of single Pb adatoms was verified using tip-induced molecular dissociation to split Pb ad-dimers into two single Pb adatoms.