Measurement of Graphene-substrates adhesion energy using nano-scratch study

S. Das, D. Lahiri, D-Y Lee, A. Agarwal, W. Choi
University of North Texas, US

Keywords: graphene, nanoscratch, adhesion, bonding, density functional theory

Summary:

The adhesion energy of graphene was evaluated for both the as grown graphene as well as the transferred graphene on different substrates. Nano-scratch method was performed at the graphene-substrate interface in order to measure the de-bonding energy. The adhesion energy of graphene with the metal substrates were calculated and found to be 12.8 J.m-2 and 72.7 J.m-2 on the Cu and Ni respectively. Density functional Theory (DFT) calculations show that the graphene/Ni interface exhibit more covalent bonding than graphene/Cu which is partially ionic, hence this justifies for the higher adhesion energy for graphene/Ni. Furthermore, we transferred the graphene on a SiOx/Si substrate using a chemical transfer method and we adopted the different annealing protocols, namely rapid thermal annealing (RTA) and vacuum annealing (VA) for different time in order to enhance the bonding between graphene and SiOx/Si substrate. We found that the adhesion energy of as transferred graphene on SiOx/Si substrate is ~ 2.978 Jm-2. By applying different annealing protocols of RTA and VA, the adhesion energy of graphene-SiOx/Si is increased to 10.09 and 20.64 Jm-2, respectively. The increase in adhesion energy is owing to the formation of chemical bonds between the graphene and SiOx at high temperature.