KINETICS OF ATOMIC-SCALE FLUCTUATIONS OF STEPS ON SI(001) MEASURED WITH VARIABLE-TEMPERATURE STM

Using a variable-temperature scanning tunneling microscope (STM) we me asure the time evolution of the atomic-scale morphology of steps on Si (001) in equilibrium at temperatures up to 350 degrees C. At temperatu res above 230 degrees C, local changes in the atomic arrangement of th e steps are observed between successive STM images. The relative rate at which events occur depends on the local configuration of the step. Rearrangement events are more likely to occur at kink sites than at st raight sections of the step. The relative rates at which the rearrange ment events occur are determined by the configuration energy of the st eps as expected from detailed balance. By measuring the event rate as a function of temperature we determine the effective activation energy barrier for step rearrangement, 1.3 +/- 0.3 eV.