Electrical contact design for stable and reliable measurement of electromechanical properties in graphene on flexible substrates

• We developed a novel method to accurately measure the electromechanical properties of graphene. • The method eliminates stress concentrations at the graphene-electrical contact junction, ensuring precise results. • Graphene/polyethylene terephthalate films show the highest stretchability: 20% for monolayer, 57% for bilayer. • Conventional methods distort results by causing stress concentrations at the graphene-electrical contact junction. • An Au/Ti interlayer enhances adhesion, improving measurement stability and accuracy. Accurate measurement of the electromechanical properties of graphene (Gr) on polymeric substrates is crucial for graphene-based flexible electronics. However, the atomically thin nature of Gr and its fragility present challenges in determining its intrinsic electromechanical properties, leading to considerable variation in results across testing methods. This paper highlights the importance of electrical contact (EC) design in electromechanical testing of Gr on polymeric substrates. Our results from in-situ scanning electron microscope observations and finite element analysis show that when ECs are positioned in regions undergoing deformation, mechanical stiffness mismatches between the ECs, Gr, and substrate cause high stress concentrations (∼1.7) at the Gr-EC junctions, resulting in premature cracks and increased contact resistance. This leads to an underestimation of the intrinsic electromechanical properties. To address this, we propose a novel testing method where polymer-supported Gr is affixed to the tester grips using adhesive, and ECs are positioned where deformation is minimal, preventing damage at the Gr-EC junctions during testing. We validate the method by measuring the electromechanical properties of monolayer and bilayer Gr films and examining the Gr degradation mechanism. The highest stretchability values of 20 % for monolayer Gr and 57 % for bilayer Gr − previously unreported − demonstrate the effectiveness of the proposed method.