The ability to modify the electronic structure and properties of graphene is an important step towards the large scale fabrication of electronic devices based on graphene technology.
The research team of Robert C Haddon at the University of California - Riverside (UCR) has successfully attached aryl groups to large epitaxial graphene (EG) substrates. The chemical modification of graphene was achieved via the spontaneous reaction of diazonium salt with the graphene, which resulted in covalent bond formation to the conjugated carbon atoms as illustrated in Figure 1. The transformation of the EG carbon centers from sp2 to sp3 was explored with the goal of introducing a barrier to electron flow, thereby modifying the electronic properties of graphene. The chemical modification of the EG was found to increase the resistance of the devices and the very weak temperature dependence of resistance of pristine EG is substantially increased on NP-functionalization (Figure 2).
The covalent modification of epitaxial graphene was demonstrated by cyclic voltammetry, AFM, FT-IR and XPS measurements.
The results will guide future studies on the chemical modification of epitaxial graphene, which will focus on the control of the degree of functionalization achieved in chemical and electrochemical reactions. Varying the surface coverage of chemically modified graphene offers a wide range of opportunities to modulate the electronic structure and transport properties of graphene from semiconducting to insulating.
This research is collaboration between the researches at UCR and Georgia Tech.