Assigning Physical Significance to the Diffuse Interface Between Terraces In Phase-Field Modeling of Steps on Crystal Surfaces

We apply a modified phase field modeling approach to the analysis of steps on a crystalline surface. Specifically we are interested in capturing phenomena associated with non-mass transport related interaction between steps. To this end we assign a physical significance to the form of the interfacial region between terraces (i.e. steps), inherent in the phase field approach, by tuning the double well potential to produce long range interaction energies varying as 1/L^2,, where L is half the distance between steps. Resultant repulsive interactions between adjacent steps of the same sign are shown to affect step-flow kinetics in a manner consistent with Gibbs-Thomson related supersaturation. This phenomenon is further demonstrated to cause dislocation-driven (spiral) crystal growth kinetics to deviate, for large supersaturation values, from the classical quadratic growth law. Attractive interactions between adjacent steps of opposite sign, also resulting from the finite interfacial width, are briefly explored particularly with respect to their possible impact on two-dimensional nucleation