Structural and morphological changes on surfaces with multiple phases studied by low-energy electron microscopy

We used low-energy electron microscopy to study structural and morphological changes of Si(1 1 1) on which ‘‘1 1’’ and 7 7 coexist. Because ‘‘1 1’’ and 7 7 have different thermodynamic and kinetic properties, various interesting phenomena unique to the two-phase surface take place. The difference in the surface mass diffusion constant, coupled with the preferential nucleation of 7 7 at the upper step edges, effectively causes a diffusion barrier at the upper side of the step, resulting in the selective slowing down of vacancy island decay and step wandering during homoepitaxial growth. The difference in the surface mass diffusion constant also influences the step motion caused by the difference in the atom density. The 7 7 domains coarsen to reduce the energetic cost of the boundaries consisting of narrow ‘‘1 1’’ regions. We demonstrate that von Neumann’s law governs the coarsening