The scanning tunneling microscopy atom-tracking technique is used to follow the individual diffusive hops of single H and D atoms on the Si(001) surface in ultrahigh vacuum. Attempt frequencies and activation energies for diffusion along the dimer row (intrarow) and between the atoms of a single Si dimer (intradimer) are extracted. For intrarow H diffusion, an activation energy of 1.75±0.10 eV and an attempt frequency of ${10}^{14.5\pm 0.8}\mathrm{Hz}$ are found. For intradimer H diffusion, an activation energy of 1.01±0.05 eV and a low attempt frequency of ${10}^{10.3\pm 0.5}\mathrm{Hz}$ are found. The ratios of H to D attempt frequencies for intradimer and intrarow diffusion are also determined.

• Received 8 July 1999

DOI:https://doi.org/10.1103/PhysRevB.60.15896