Step fluctuations on Ag „ 111 ... surfaces with C 60

STM has been used to characterize fluctuation properties of segments of step edges partly covered by C60 on Ag 111 at room temperature. The distribution of C60 at step edges exhibits a step orientation dependence: Low-symmetry step edges are more favorable for C60 binding. The temporal correlation functions of step segments between C60-covered step regions scale as a power law, with an average exponent of 0.23±0.02, indicating that fluctuations of these “confined” steps are consistent with step-edge diffusion limited fluctuations. Parameters extracted from temporal correlation and autocorrelation analysis consistently indicate that close-packed steps have smaller fluctuation magnitude and higher step mobility than low-symmetry steps. The measured effective system sizes of step segments with different lengths show at most a weak step-length dependence. Fluctuation features thus yield the surprising conclusion that C60 molecules are not acting as pinning points that constrain mass transport along the step edges.