Mechanical Properties Of Annealed Polycrystalline Copper Foils Covered By Graphene

With the rapid development of information technology,higher requirements about the performance of integrated circuits and micro/nano devices have been put forward.Electronic equipment in the service process to withstand mechanical and cyclic fatigue load,mechanical properties are the key to its long-term service reliability.In recent years,graphene has become a research hot spot in materials science due to its excellent electrical,thermal and physical and chemical properties.However,the specific effects of graphene on mechanical properties of the integrated circuit materials have not yet been explored.In this study,annealed polycrystalline copper foils were selected to be an object,and graphene was grown on the surface of pure copper by chemical vapor deposition.Nano-mechanical properties of the pure annealed copper foils and graphene-covered copper foils were studied using nano-indentation.The load-depth curve of pure-Cu sample exhibits multiple displacement bursts.Compared with the annealed pure copper,the Young's modulus and hardness of the pure graphene-covered copper are significantly improved.Graphene has an effect on the deformation recovery of the pure-Cu substrate by nano-indentation tests.Samples of the annealed copper foils and graphene-covered copper were subjected to static tensile testing.The results show that fracture surfaces of the annealed copper foils are rough,while those of the graphene-covered copper are uniform.The yield strength of graphene-covered copper foils is higher than that of the blank copper foils.The tensile strength of the graphene-covered copper foils is significantly higher than that of the annealed copper foils.Graphene grown on the surface of the copper foils can effectively improve the tensile properties of the copper foils.A comparative investigation on fatigue properties of the graphene-covered copper foils and blank annealed copper foils was conducted.The experimental results show that graphene effectively prevented the formation of fatigue extrusions/intrusions in the copper foils,inhibited cyclic strain localization induced by irreversible dislocation slip and thus enhanced fatigue life of the copper foils.Observations and characterization of fatigue damage morphologies and dislocation structures were performed to investigate features of fatigue damage of two kinds of samples.The potential surface strengthening method and the mechanism through graphene coating were discussed.