| Step dynamics on vicinal surfaces is an active research field, both for the sake of “pure” science and in the interest of a better understanding of more application driven problems. Experimental probes that can measure equilibrium surface dynamics over wide ranges of parameters like length scale, temperature regime, coverage, etc., are rare. We propose the analysis of low energy electron diffraction (LEED) fluctuations to obtain near-equilibrium kinetics information. We call this technique temporal LEED spectroscopy (TLS). In particular, we developed the analysis techniques to gain important diffusion parameters by the reciprocal space measurement of surface step fluctuations. As an example, we studied equilibrium step fluctuations on vicinal Si(001). We determined the rate limiting dynamics and measured activation energies for step dynamics on this surface in the temperature range 950K ≤ T ≤ 1,130K. We have found some rather surprising results on this supposedly well understood system: While previous studies determined the evaporation and condensation of atoms and dimers as the rate limiting process at both higher and lower temperatures than covered by our measurements, we can exclude this process as rate limiting in the temperature regime 950K ≤ T ≤ 1,130K. A detailed account of all the experimental factors can reconcile this difference. As a result, we must conclude that the dynamics of steps on Si(001) are quite complicated. It is therefore essential to cover wide ranges of experimental parameters, a task for which we believe TLS will be an important tool. |
