Influence of supersaturation on surface structure

Using low-energy electron microscopy, we have investigated the influence of an external flux on the structure of the Si(111) surface during growth and etching at elevated temperatures. We find that varying the adatom supersaturation effectively changes the surface free energies of coexisting 7x7 and '1x1' regions of the surface. In response, the boundaries separating the phases adopt a new steady-state configuration. The measured configuration can be used to quantitatively determine the difference in free energy between the phases, Deltagamma. The change in Deltagamma provides a measure of the local supersaturation at the surface, and can be interpreted as a change in the phase-transition temperature.