AVS 45th International Symposium
    Surface Science Division Friday Sessions
       Session SS1-FrM

Paper SS1-FrM5
Low Energy Electron Microscope Measurements of Oxygen-Induced Strain Relief on Si(001)

Friday, November 6, 1998, 9:40 am, Room 308

Session: Surface Structure and Strain
Presenter: G.L. Kellogg, Sandia National Laboratories
Authors: J.B. Hannon, Sandia National Laboratories
B.S. Swartzentruber, Sandia National Laboratories
G.L. Kellogg, Sandia National Laboratories
Correspondent: Click to Email
Real-time observations of step configurations on Si(001) with the low energy electron microscope (LEEM) show a continuous and irreversible change in the populations of the (1x2) and (2x1) domains (i.e., the ratio of adjacent terrace widths) upon exposure to oxygen at elevated temperatures. In the initial configuration, populations of the two domains differ significantly due to an external strain field. Exposure of the surface to ~10@super-8@ Torr oxygen at temperatures between 750-850 C causes the domains to become approximately equal in area. Based on previous LEED and STM measurements,@footnote 1,2@ we conclude that the progression towards equal domain populations results from the removal of the external strain. During equilibration, the potential in which the step moves is determined from the step velocity. The measured exponential time dependence of the equilibration rate is consistent with step motion in the presence of the step-interaction potential proposed by Alerhand et al.@footnote 3@ This agreement implies that strain relief takes place on a time scale of a few seconds. We propose that the mechanism of strain relief is an oxygen-induced change in the shear threshold of Si due to dissolution of oxygen into the bulk. The ability to modify the elastic properties of materials with common adsorbates such as oxygen is important in heteroepitaxy where strain is known to play a key role in defining the properties of the epitaxial film. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000. @FootnoteText@ @footnote 1@F. K. Men, W. E. Packard, and M. B. Webb, Phys. Rev. Lett. 61, 2469 (1988). @footnote 2@B. S. Swartzentruber, Y.-W. Mo, M. B. Webb, and M. G. Lagally, JVST A8, 210 (1990). @footnote 3@O. L. Alerhand, D. Vanderbilt, R. D. Meade, and J. D. Joannopoulos, Phys. Rev. Lett. 61, 1973 (1988).