AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThA

Paper SS3-ThA8
Pb/Si(111) Domain Boundary Fluctuations

Thursday, November 18, 2004, 4:20 pm, Room 213B

Session: Surface Diffusion and Transport
Presenter: D.B. Dougherty, University of Maryland at College Park
Authors: D.B. Dougherty, University of Maryland at College Park
W.G. Cullen, MRSEC
E.D. Williams, MRSEC
Correspondent: Click to Email
The techniques of fluctuation statistics are applied to a common 1D interface on solid surfaces: a domain boundary between two surface phases. We describe variable temperature STM observations of fluctuating boundaries between Si(111)-(1x1)-Pb and Si(111)-@sr@3x@sr@3R30-Pb@footnote 1@. We establish the dominant mass transport mechanism for the fluctuations from the power-law growth in time of the temporal correlation function with an exponent of about 0.5. This behavior implies that fluctuations of the (1x1) boundaries occur via exchange of mass with a 2D adatom gas on the @sr@3x@sr@3 phase. This conclusion is corroborated by the extraction of the persistence probability from the same data, giving a persistence exponent of 0.75. This 2D exchange mechanism allows comparison of the nanoscale fluctuation kinetics with previous macroscopic surface science measurements. The 2D adatom gas has long been established for this system from the observation of zeroth-order desorption kinetics. Previous studies indicate a barrier for this rate-limiting exchange step of 2.3 eV@footnote 2@. Our experimental correlation functions yield an effective activation barrier of about 1.6 eV. This provides a direct physical confirmation of the indirect deduction of 2D exchange of mass at the domain boundary. Finally, the autocorrelation function of the boundary fluctuations can also be determined and used to extract correlation lengths that compare well with the size of (1x1) domains. In addition, these lengths are compared with correlation lengths for fluctuating steps on clean metal surfaces. *Supported by UMD-NSF-MRSEC under DMR-00-80008. @FootnoteText@ @footnote 1@ J. Slezak et al., Surf. Sci. 454 (2000) 584; O. Custance et al., Surf. Sci. 482 (2001) 878.@footnote 2@ M. Saitoh et al., Surf. Sci. 154 (1985) 394.