Equilibrium fluctuations and decay of step bumps on vicinal Cu(111) surfaces

Using scanning tunneling microscopy we have investigated the time dependence of equilibrium step fluctuations and the time dependence of the decay of bumps in (100) steps on Cu (111) vicinal surfaces. From the analysis of the equilibrium fluctuations we find that the dominant mass transport is along the step edges with an activation energy for diffusion along a kinked step of 0.37 eV. Using this result we estimate an upper limit for the hopping barrier along (100) steps to be 0.24 eV. Non-equilibrium bumps in steps occur when wandering monatomic islands attach to a step edge. We have analyzed the time dependence of the decay of these bumps. From the Fourier representation of the bump decay we find that the dependence of the time constant on the wave number q is that of a q(-4) law. This result is consistent with the analysis of the equilibrium fluctuations. (C) 1998 Elsevier Science B.V. All rights reserved.