In situ observation of thermal annealing processes of nanoholes on Si(111)7x7

We have studied the thermal annealing characteristics of tip-induced nanoscopic single-layer holes on the Si(111) 7 x 7 surface by high-temperature scanning tunneling microscopy. For most of the holes, a linear size versus time behavior with a constant decay rate is found. A detailed consideration of the rate-limiting nucleation mechanisms and irregular hole configurations reveals that the average number of nucleation sites at edge kinks is constant during the decay. From the temperature 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 attachment energy.