Surface doping and stabilization of Si(111) with boron

We have investigated the incorporation of boron into the Si(111) (√3×√3)R30° surface from low boron concentration up to (1/3 monolayer, using tunneling microscopy and spectroscopy and first-principles total-energy calculations. Surprisingly, we find that a (√3×√3)R30° structure composed almost entirely of Si adatoms on a Si double layer can be stabilized by boron doping in near surface layers. Moreover, when boron atoms are in the surface layers, the adatom site is unfavorable compared with the site underneath the adatom, unlike other group-III elements adsorbed on the Si(111) surface.