Structure analysis of the HF-treated Si(111): H surface with medium-energy ion scattering

Medium-energy ion scattering (MEIS) measurements have been performed on the Si(111) surface which was terminated with hydrogen by means of immersion in a diluted HF solution. The measurements and the fit of Monte Carlo simulations to the experimental data show that the structure of the Si(111):H surface is close to that of a truncated bulk Si lattice. The relaxation of the distance between the top and the second layer, d_l2, and that between the second and the third layer, d₂₃, are as small as 0.00 + 0.04 Å (0.0 + 5.1%) and - 0.04 + 0.04 Å (—1.7 + 1.7%), respectively. The measurements further reveal that the average one-dimensional root-mean-square thermal displacement of the two outermost atomic layers is enhanced from the bulk value of 0.075 Å to 0.11+ 0.01 Å.