Quantitative measurements of thermal relaxation of isolated silicon hillocks and craters on the Si(111)-(7x7) surface by scanning tunneling microscopy

Thermal decomposition rates of silicon hillocks and filling-up rates of craters are, for the first time, measured at various substrate temperatures of 400 to 600 degrees C. Effects of the probe tip on the rates are measured, and the reduced rates are determined without the tip effects. Activation energies for hillock decomposition and crater filling up are determined as 1.5 +/- 0.1 and 1.3 +/- 0.2 eV, respectively. Preexponential factors are 2 x 10(11+/-1) s(-1) for hillocks and 3 x 10(9+/-2) s(-1) for craters. We discuss the results in terms of two-dimensional vapor phase processes and the Schwoebel effect.