Observation of surface roughening on Cu(1, 1, 5)

We present a detailed analysis of the topography of the Cu(1,1, 5) surface in the temperature range 70 K < T < 670 K. The line-shape analysis of the specular helium beam diffraction peak as a function of temperature is found to be in agreement with a model of roughening previously proposed by Villain et al. The roughening temperature is found to be T R = 380 K. From the anisotropy of peak profiles, the step repulsive energy is deduced and found to be Wn = 120 K per lattice spacing. The experimental procedure is carefully examined and its consequences are discussed. The connection between roughness at small and large scale is indicated.