Kink distance and binding energy of colloidal crystals

Particle interaction is a critical parameter for growth kinetics of colloidal crystals. The equilibrium concentration and step free energy are strongly dependent on the particle interaction. The growth mechanism of the attractive system of colloidal crystals is similar to that of vapor or solution growth, where crystals grow by incorporating diffusing ad-particles on the terrace into kinks of steps (Terrace-Step-Kink model). Here, we have applied the theory of crystal growth to experimentally determine the binding energy that originates from the particle interaction. We focus on the relationship between kink distance and bond energy, which is described by BCF (Burton-Cabrera-Frank) theory. The value of the step free energy determined by the kink distance measurement agrees well with the values obtained from other measurements, including nucleation rate and critical radius. The obtained value also accounts well for the change in step velocity of two-dimensional islands, which is due to the Gibbs-Thomson effect. The measurement of binding energy contributes significantly to the fundamental study of colloidal science as well as to technology for growing high quality colloidal crystals.