ROUGHENING AND MELTING OF STEPPED ALUMINUM SURFACES

The energetics and dynamics of the vicinal (113), (115), and (117) sur faces of aluminum have been investigated using a realistic many-body p otential, based upon the effective medium theory, to describe the atom ic interactions. These surfaces are found to show two distinct forms o f thermal disordering. Firstly, above 700 K the surfaces undergo a rou ghening transition, characterized by a disordering of the step edge st ructure, the roughening temperature decreasing with decreasing step de nsity. Secondly, above 900 K the surfaces undergo a melting transition , characterized by a complete disordering of the surface, the melting temperature increasing with decreasing step density. From studies of t he step meandering, the time dependence of fluctuations in the step po sition were found to show a power-law dependence, t(n), where 0.25<n l ess than or equal to 0.5. This is consistent with two-dimensional diff usion on the surfaces, as observed experimentally. For noninteracting steps this corresponds to a time exponent of n=0.5. The reduced time d ependence is then due to the repulsion between the steps.