Role of Graphene in Deformation Behavior of Cu-Graphene Nanolayered Composite

Nanoscale metal-graphene nanolayered composite is known to have ultra high strength due to its ability to effectively block dislocations from penetrating through the metal-graphene interface. The same graphene interface can simultaneously serve as a barrier interface for deflecting the fatigue cracks that are generated under cyclic bendings. Cu-graphene composite with repeat layer spacing of 100 nm was tested for bending fatigue at 1.6% and 3.1% strain up to 1,000,000 cycles that indicated ~5 times enhancement in robustness against fatigue induced damage in comparison to the conventional Cu only thin film. Fatigue induced cracks that are generated within the Cu layer were stopped by the graphene interface, which was confirmed using transmission electron microscopy images acquired ex-situ as well as during in-situ tensile test. Molecular dynamics simulations for uniaxial tension of Cu-graphene showed limited accumulation of dislocations at the film/substrate interface, which makes the fatigue induced crack formation and propagation through thickness of the film difficult in this materials system. Robustness against bending fatigue-induced damage makes this material well-suited for the flexible electrode application, and methods for enhancing the scalability of fabrication will also be discussed.