THEORETICAL INVESTIGATION ON THE FORMATION PROCESS OF THE STACKING-FAULT TRIANGLE IN THE SI(111)-7X7 STRUCTURE

The formation process of stacking-fault (SF) triangles during the Si(1 11) 1 x 1-->7 x 7 reconstruction has been studied using the quantum ch emical theoretical calculations. On the basis of the propagation and s ubsequent merging mechanism of the SF areas proposed by one of authors (I.O.), several reaction paths to complete a single SF triangle have been examined. The most probable formation process of SF triangles has been determined from the their lowest energy reaction path. A compari son of total energy changes along the SF triangle formation both with and without oxygen atoms indicated a preference of oxygen incorporatio n in the formation of 7 x 7 dimer-stacking-fault (DS) structure, which was compatible with the recent experimental results suggesting the im portant role of oxygen in the 7 x 7 reconstruction. The effect of the step edge has also been discussed. (C) 1997 Elsevier Science B.V.