DIFFUSION AND DIMER EXCHANGE IN SURFACTANT-MEDIATED EPITAXIAL-GROWTH

We propose a new dimer-exchange mechanism for surfactant-mediated epit axial growth of Ge on Si(001) surfaces based on first-principles total -energy calculations. We find that, on Si(001) covered by As surfactan ts, Ge dimers are formed not on As dimers but between As-dimer rows, a nd then substitute for the As atoms at subsurface sites. This exchange process leads to As-capped needlelike growth of Ge along {110BAR} dir ection which prevents islanding at high Ge coverage.