AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP10
Stochastic Motion of 7x7 Kinks at Monoatomic Step Edges

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Surface Science Poster Session
Presenter: T. Fukuda, Osaka City University, Japan
Authors: T. Fukuda, Osaka City University, Japan
S. Maeda, Osaka City University, Japan
H. Nakayama, Osaka City University, Japan
Correspondent: Click to Email
Control of steps on the surface have been regarded as one of the promising technique for future electronic devices.@footnote 1@ Synthesis of artificial step arrangement can be achieved by photolithographically patterned substrates followed by thermal treatment. Because an individual step movement is governed by the detail balance between attachment and detachment of surface adatoms at step edges, the study of adatom kinetics is a crucial issue for understanding and controlling of step configuration. Here we propose a method for measuring migrating adatoms and step movements below the 7x7-"1x1" transition temperature.. Microscopically, meandering steps consist of long straight segments with well defined orientations and short segments called kinks. On the Si(111) surface, these kinks are expected to be quantized by the 7x7 reconstruction and their widths and strides are limited within the 7x7 period. Even in thermal equilibrium, these kinks will stochastically fluctuate by attaching or detaching adatoms. So, the individual kink can be regarded as one dimensional "Brownian particle". In this study, we made an in situ measurement of the kink motion by the high-temp. STM and found the kink is really Brownian particle. Because the chemical potential around the kink is uniform in thermal equilibrium, there is no net mass transport between the surface adatoms and the kink site. The Brownian kink, therefore, will not diffuse but restore its position. The kink velocity follows gaussian distribution and its standard deviation is a measure of the diffusion constant of the kink, which is closely connected to the adatom diffusion constant. The temperature dependence of the standard deviation showed an activation type behavior with an energy of ~0.87 eV, compared with the adatom diffusion energy of 0.75±0.2 eV on the Si(111) 7x7 surface.@footnote 2@ @FootnoteText@ @footnote 1@T.Ogino et al., Appl. Surf. Sci. 107 (1996) 1.@footnote 2@Voigtlander et al., Phys. Rev. B51 (1995) 7583.