The thermal fluctuation of the kinks formed at the monoatomic step edges on the Si(111) 7 x 7 surface was studied by high-temperature scanning tunneling microscopy. The temperature dependence of the mean square displacements of kink positions indicates that the displacements are a thermal activation process with an apparent activation energy of 1.17 + 0.1 eV. Although the direct-current induces surface adatom migration along the current direction, a kink fluctuation anisotropy due to the Ehrlich-Schwobel barrier of the adatom drift across the step was not observed. (C) 2004 Published by Elsevier B.V.