Artificially controlled synthesis of graphene intramolecular heterojunctions for phonon engineering

Because phonons are the main carriers for graphene heat transfer, modifying the dynamic properties of the crystal lattice by isotopes modulates the phonon behavior and alters the thermal properties. Here we demonstrate an artificially controlled texture synthesis of 12C-graphene/13C-graphene heterostructures via chemical vapor deposition and an O2 plasma etching. The electrical and thermal properties of the graphene across the heterojunction show that 12C-graphene and 13C- graphene are electronically connected as resistors in series, while the thermal conductivity across the junction is dramatically reduced due to the suppressed phonon propagation, which causes the conductivity across the junction to be lower than that of graphene sheets with randomly mixed isotopes. These findings should help realize novel two-dimensional graphene thermoelectric devices where phonon modulation controls the electrons and heat transport independently. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)