LOCAL DIMER EXCHANGE IN SURFACTANT-MEDIATED EPITAXIAL-GROWTH

While the effectiveness of surfactants in suppressing islanding in Si/Ge heteroepitaxial growth has been demonstrated in previous studies, the atomic scale growth processes have remained unknown. Here we present images of the growing Si(001)/Ge surface obtained with in situ low-energy electron microscopy. From our observations we conclude that surfactant-mediated growth of Ge on Si(001) proceeds by highly local Ge incorporation with minimum surface diffusion. We propose a new two-dimer correlated exchange mechanism to explain this unusual growth mode, as well as the absence of islanding at high Ge coverage.