Thermal decay of silicon islands and craters on silicon surfaces by scanning tunneling microscopy

Thermal decomposition processes of isolated silicon islands and filling-up processes of isolated craters on Si(111)7 x 7 surfaces are observed at various temperatures. By Arrhenius plots of rates of these size charges, activation energies for island decomposition and crater filling-up on the Si(111) surface are determined as (1.5 +/- 0.1) and (1.3 +/- 0.2) eV, respectively. Pre-exponential factors are 2.1 x 10(11 +/- 1) and 2.6 x 10(9 +/- 2) s(-1) for the islands and craters on the Si(111) respectively. On the Si(111) surface the rates for island decomposition are five times larger than those of craters filling up. We discuss the results with two-dimensional vapor phase processes and the Schwoebel effect.