Direct measurement of the adhesion energy of monolayer graphene as-grown on metal substrates is important to better understanding its bonding mechanism and control the mechanical release of the graphene from the substrates, but it has not reported yet. The adhesion energy of large area monolayer graphene synthesized on copper by chemical vapor method is reported here. The DCB (Double Cantilever Beam) test was used for a large-area measurement of adhesion energy. The measured adhesion energy between graphene and copper was 0.72 ± 0.07 J m-2. Knowing the directly measured adhesion energy, the etching-free renewable transfer process of graphene was also demonstrated. The process is composed of graphene growth, mechanical delamination and reuse of the metal for graphene regrowth.
The interfacial mechanical reliability of graphene was evaluated by subcritical crack growth
test. The as-grown graphene on copper, wet-transferred monolayer graphene on SiO2, and wettransferred multilayer graphene on SiO2 were tested under various environmental conditions. The crack growth was not affected by humidity in the case of as-grown graphene on copper and wettransferred monolayer graphene on SiO2. The reason for limiting crack propagation was steric hindrance, and it is confirmed by calculation result of crack-flank-opening displacement at each situations. The cohesive fracture was observed in wet-transferred multilayer graphene, and corresponding v-G curve showed significant region II. It is believed that the increased interlayer distance allows fast diffusion of water molecules between graphene surfaces.