ANISOTROPIC PROFILE DECAY ON PERTURBED AU(111) VICINAL SURFACES

The anisotropy of the surface free energy has a large influence on the decay rate of periodic surface profiles at temperatures below the rou ghening temperature This has been demonstrated by a study of the perio dic surface profiles that were etched into vicinal Au(111) crystals in two orientations: with their wavevector parallel (psi = 0) and perpen dicular (psi = pi/2) to the intrinsic step direction of the vicinal su rface. Due to this modulation, steps become either oscillatory in shap e or remain straight with their average separation modulated. Accordin gly, profile decay is driven primarily by step self-energy (psi = 0) o r step interaction energy (psi = pi/2). The rate of decay was measured under ultra-high vacuum conditions at 750 degrees C using a scanning tunneling microscope for imaging. A large anisotropy of decay was obse rved on two vicinal crystals of 1.5 and 5 degrees miscut, with the psi = 0 decay being much faster than with psi = pi/2. The results are eva luated and discussed in the framework of recent theory.