Nonequilibrium free energy and kinetic roughening of steps on the Kossel(001) surface

This paper studies the nonequilibrium energetics of growth steps. It discusses the energy and free energy of a [100] step on a Kossel(001) crystal surface as a function of the driving force in the case that two-dimensional nucleation is not active. Theoretical expressions for these energies are derived and are found to agree with data obtained from Monte Carlo simulations of step flow. The nonequilibrium expressions allow us to propose that the vanishing of the step free energy beyond a critical value of the driving force defines the onset of the kinetic roughening regime. This is found to agree with the earlier phenomenological criteria for this transition.