The roughening of metal surfaces

We address the problem of the departure of a crystal surface from a perfectly ordered crystal plane. We discuss the energetics of the surface defects and their statistical mechanics which lead to the so-called “roughening transition”. The theory of this transition is outlined and a special emphasis is put on the experimental aspects: roughening measurement techniques and critical review of the available data. We pay special attention to the case of vicinal surfaces. Apart from the equilibrium situation there is an increasing interest in the dynamical roughening of crystal surfaces during MBE growth or ion-bombardment etching, or in the reverse problem: the annealing of a non-equilibrium roughness. We review the present state of this field by recalling relevant models which lead to the concept of dynamical scaling and we discuss some recent data. The present review is restricted to the case of metal surfaces; however, most of the concepts which are presented have a much larger generality.