Tuning of Graphene Work Function by Alkyl Chain Length in Amine-Based Compounds

Abstract

In this study, the effect of alkyl chain length in amine-based compounds on the work function of graphene was investigated. The graphene was synthesized by the chemical vapor deposition method. The graphene layers were functionalized by amine-based groups using a simple spin-coating method. The amine-based compounds were composed of phenyl amine and methyl-, ethyl-, propyl-, n/t-butyl-, and octyl-phenyl amine groups. Materials were confirmed by X-ray photoelectron spectroscopy to show the C and N bonding. The work function of the doped graphene layers decreased because of the effect of the doping agents. Among the doped graphene samples, t-butyl-phenyl amine functionalized graphene achieved the lowest work function of 3.89 eV (compared with 4.43 eV for pristine graphene). Further, the sheet resistance of n-doped graphene increased, confirming the high concentration of n-doping agents on the graphene layers. These results suggest the best alkyl chain is the t-butyl group to reduce the work function of graphene, and promise the use of these materials as cathodes for opto-electronic applications.