Mechanisms for the stability of Al and B adatoms on the Si(111)root 3x root 3R30 degrees surface

The bonding of aluminium and boron adatoms on the Si(111)root 3x root 3R30 degrees surface has been investigated using ab initio density-functional th eory methods in order to understand the difference in stability between dif ferent adatom bonding configurations. It has been found that the greater st ability of the T-4 configurations compared to the H-3 geometries is mainly due to stronger covalent bonding between the adatom and the substrate in th e T-4 structures. The difference in stability between the T-4 and S-5 topol ogies, on the other hand, is determined predominantly by charge redistribut ion. [S0163-1829(99)08503-3].