Enhancement of the adhesion energy between monolayer graphene and SiO2 by thermal annealing

Because graphene is placed on a rigid or flexible substrate for future applications such as transparent or flexible electronic devices, the interfacial characteristics between graphene and the underlying substrate are of great importance for developing mechanically and electrically reliable devices. In this work, the interaction strength of large-area monolayer graphene transferred on SiO2/Si was adjusted by thermal treatments, and its adhesion energy was measured by mode I fracture tests using a double cantilever beam (DCB) configuration with a laminated composite (Si/SiO2/graphene/epoxy/SiO2/Si). Mechanical delamination of monolayer graphene from SiO2 showed an adhesion energy of 1.5 ± 0.15 J/m2. It was found that thermal annealing of graphene on SiO2 at 300 and 450 °C increased the adhesion energy to 2.2 ± 0.20 and 4.6 ± 0.31 J/m2, respectively. Characterization of graphene on SiO2 using atomic force microscopy and Raman spectroscopy revealed that the enhanced adhesion energy was attributed to the improved conformal contacts of monolayer graphene with corrugated SiO2 surfaces.