HOW THE DOWN STEP EDGES INFLUENCE FORMATION OF THE 7X7 STRUCTURE OF SI(111)

A surface that has wide terraces was fabricated by utilizing the step bunching phenomenon to study the effect of the down step edges on the formation of the 7x7 reconstruction. The surface with wide terraces wa s quenched through the 1x1-7x7 phase transition, freezing the formatio n process of the 7x7 reconstruction. On this surface, it became possib le to investigate the influence of the down step edges on the formatio n of the 7x7 reconstruction because the influence of the upper step ed ge, which is located at the other side of the terrace, did not reach t o the down step edge. A considerable decrease in the existence probabi lity of the 7x7 reconstruction was observed near the down step edges. This decrease cannot explained by electromigration and steps advanceme nt caused by the difference in adatom density between the 7x7 and diso rdered structure. Instead, we propose that the decrease in existence p robability at down step edges is well explained by a simple topographi c model assuming corner holes as the growth nuclei of the 7x7 domains.