Mechanical buckling induced periodic kinking/stripe microstructures in mechanically peeled graphite flakes from HOPG

Mechanical exfoliation is a widely used method to isolate high quality graphene layers from bulk graphite. In our recent experiments, some ordered microstructures, consisting of a periodic alternation of kinks and stripes, were observed in thin graphite flakes that were mechanically peeled from highly oriented pyrolytic graphite. In this paper, a theoretical model is presented to attribute the formation of such ordered structures to the alternation of two mechanical processes during the exfoliation: (1) peeling of a graphite flake and (2) mechanical buckling of the flake being subjected to bending. In this model, the width of the stripes L is determined by thickness h of the flakes, surface energy (Formula presented.), and critical buckling strain (Formula presented.). Using some appropriate values of (Formula presented.) and (Formula presented.) that are within the ranges determined by other independent experiments and simulations, the predicted relations between the stripe width and the flake thickness agree reasonably well with our experimental measurements. Conversely, measuring the L–h relations of the periodic microstructures in thin graphite flakes could help determine the critical mechanical buckling strain (Formula presented.) and the interface energy (Formula presented.).