Hexagonal boron nitride assisted growth of stoichiometric Al₂O₃ dielectric on graphene for triboelectric nanogenerators

Here we demonstrate the deposition of a high-k dielectric material on graphene using hexagonal boron nitride (h-BN) nanosheets as a buffer layer. The presence of an h-BN layer on top of the graphene facilitated the growth of high-quality Al₂O₃ by atomic layer deposition (ALD). Simulation results also support the experimental observations and provide an explanation for the suitability of h-BN as a buffer layer in terms of mixed ionic-covalent B-N bonding. Additionally, h-BN works as a protective shield to prevent graphene oxidation during ALD of Al₂O₃ for the fabrication of graphene-based devices. Finally, triboelectric nanogenerators (TNGs) based on both Al₂O₃/h-BN/graphene and Al₂O₃/graphene structures are demonstrated for further confirming the importance of h-BN for synthesizing high-quality Al₂O₃ on graphene. It was found that the Al₂O₃/h-BN/graphene-based TNG reveals meaningful electric power generation under a mechanical friction, while no significant electric power output from the Al₂O₃/graphene-based TNG is obtained, indicating high charge storage capacity of the dielectric Al₂O₃ layer on h-BN.