Stability of the Ga sqrt 3 x sqrt 3 and B sqrt 3 x sqrt 3 Superstructure on Si(111) During MBE Deposition of alpha-Si

We report a striking difference between the behavior of the Si(111)/Ga sqrt 3 x sqrt 3 structure and the Si(111)/B sqrt 3 x sqrt 3 structure with respect to the subsequent deposition of additional Si adatoms. LEED observations at 0-1ML Si coverage during room temperature deposition on the Ga covered surface show that the sqrt 3 x sqrt 3 structure changes to an apparent 1x1 at submonolayer Si coverage indicating that the two dimensional Ga superlattice is disordered.