An offset of a straight step, called a kink, was occasionally formed on semiconductor surfaces. The motion of the kink on the Si(111)-7x7 surface in the [¯1¯12] step was studied in detail by high-temperature scanning tunneling microscopy, and thermal fluctuations of the kink displacement along the step edges was observed. The kink displacement did not

diverge with time, suggesting that a restoring force acted on the kink. The displacement, however, could be clearly represented by the Gaussian distribution and it was therefore considered to be a Brownian particle. The temperature dependence of the mean square displacement of the kink position showed that the displacement was a thermal activation process with an apparent activation energy of 1.54eV. From the equation of motion on the kink displacement including an incoming and outgoing flux as a fluctuation source, the phenomenological Langevin equation was derived. The activation energy of the kink displacement was related to the diffusion coefficient of the 2-dimensional adatom gas and the latent heat of the atoms from the kink site to the surface adatom.

Stochastic Motion of 7x7 Kinks at Monoatomic Step Edges on the Si(111) Surface. T.Fukuda, S.Maeda, H.Nakayama: Applied Surface Science, 2003, 216[1-4], 30-4