CONSIDERATION OF ATOM MOVEMENT DURING SI SURFACE RECONSTRUCTION

Si(111) surface reconstructions are classified into two families, the 2 x 2 family (2 x 2, c2 x 4, c2 x 8 and root 3 x root 3) and n x n DAS family. By in-situ atomic scale observation of Si(111) surface recons truction and by a statistical argument on the nucleation of a daughter phase in Si(lll) matrix, we have found that the 2 x 2 family is a res ult of random motion of adatoms on a Si(lll)-1 x 1 substrate, while th e n x n DAS family can never be formed only by the movement of adatoms but some cooperative movement of substrate Si atoms is necessary.