MORPHOLOGY OF PERIODIC SURFACE PROFILES ON AU SINGLE-CRYSTALS AND THE ANISOTROPY OF THE SURFACE FREE-ENERGY OF AU

The shapes of periodic surface profiles on Au(111), Au(100) and Au(110) crystals were studied by laser diffraction, interference microscopy and secondary electron microscopy. By simulating the surface-diffusion-controlled annealing of these profiles at elevated temperature, including the effect of anisotropic surface free energy, the shape of experimental profiles was matched by calculated profiles. From this match, the relative anisotropy of the surface free energy, DELTA-gamma(THETA,T)/gamma(THETA,T), was derived at several temperatures for a limited range of the [112] zone near (111) and the [110] zone near (100). The maximum anisotropies were evaluated at these temperatures and compared to previous data for Au as well as expected anisotropies at T = 0 K. Interpolation of all measured data between T = 0 K and the melting temperature by gamma(T) = E - TS(T), with S either as a constant or a T-dependent surface entropy, yields a description of the relative temperature dependence of DELTA-gamma/gamma(T). The total anisotropy DELTA-gamma/gamma at T = 0 K depends on the choice of S(T) and ranges between 14 and 23% for the {111}[112] zone and between 2.7 and 3.9% for the {100}[110] zone.