IN-SITU OBSERVATION OF THERMAL ANNEALING PROCESSES OF NANOHOLES ON SI(111)7X7

We have studied the thermal annealing characteristics of tip-induced n anoscopic single-layer holes on the Si(111) 7 x 7 surface by high-temp erature scanning tunneling microscopy. For most of the holes, a linear size versus time behavior with a constant decay rate is found. A deta iled consideration of the rate-limiting nucleation mechanisms and irre gular hole configurations reveals that the average number of nucleatio n sites at edge kinks is constant during the decay. From the temperatu re dependence of the decay rates, an activation energy of 1.6 +/- 0.2 eV has been determined, which may be connected with the step edge atta chment energy.