One-Dimensional Defect-Mediated Diffusion of Si Adatoms on the Si(111)-(5x2)-Au Surface

Using scanning tunneling microscopy, we determine that the one-dimensional diffusion of Si adatoms along the Si(111)-(5x2)-Au surface reconstruction occurs by a defect-mediated mechanism. Distinctive diffusion statistics, especially correlations between sequential adatom displacements, imply that the displacements are triggered by an interaction with a defect that is localized to the adatom. The defect is intrinsic and thermally activated. The measured diffusion statistics are modeled accurately by a Monte Carlo simulation. The measured adatom diffusion activation barrier is 1.24 +/- 0.08 eV.