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 C$_{60}$ on Ag(111) at room temperature. The distribution of C$_{60}$ at step edges exhibits a step orientation dependence: low-symmetry step edges are more favorable for C$_{60}$ binding. The temporal correlation functions of step segments between C$_{60}$-covered step regions scale as a power law, with an average exponent of 0.23$\pm $0.02, indicating that fluctuations of these ``confined'' steps are consistent with step-edge diffusion limited fluctuations. Parameters extracted from temporal correlation and autocorrelation analysis consistently indicate that close-packed steps have smaller fluctuation magnitude and higher step mobility than low-symmetry steps. The measured system sizes of step segments with different lengths show at most a weak step-length dependence. Fluctuation features thus yield the surprising conclusion that C$_{60}$ molecules are not acting as pinning points that constrain mass transport along the step edges.