Role of Crack Deflection on Rate Dependent Mechanical Transfer of Multilayer Graphene and Its Application to Transparent Electrodes

The rate dependence in the thin-film delamination process has been widely studied to develop advanced transfer technologies, such as selective mechanical transfer and kinetically controlled transfer printing. However, so far there has been no consideration of crack deflection in transfer processes, although the fracture behavior at an interface depends on the deflection of a crack. Here, we demonstrate the role of crack deflection on rate dependent mechanical transfer of synthesized multilayer graphene. We used double cantilever beam fracture mechanics testing to investigate the crack deflection in an adhesive-multilayer graphene-donor substrate sandwiched structure. The experimental results show that transfer yield of multilayer graphene increases as a higher loading rate is applied, and the mechanism is attributed to the degree of crack deflection. The high loading rate mitigates the elastic modulus mismatch between the adhesive and the donor substrate due to the viscoelasticity of the adhesive. Mitigation of the elastic modulus mismatch reduces crack deflection and consequently increases transfer yield. The suggested mechanism is verified by finite element analysis. Moreover, the rate effect is adopted for a selective mechanical transfer process for transparent electronics. We believe this study provides a new insight on understanding the underlying physics of the rate dependence.