Fermi-Level Modulation of Chemical Vapor Deposition-Grown Monolayer Graphene via Nanoparticles to Macromolecular Dopants.

Abstract

It is critical to modulate the Fermi level of graphene for the development of high-performance electronic and optoelectronic devices. Here, we have demonstrated the modulation of the Fermi level of chemical vapor deposition (CVD)-grown monolayer graphene (MLG) via doping with nanoparticles to macromolecules such as titanium dioxide nanoparticles (TiO2 NPs), nitric acid (HNO3), octadecyltrimethoxysilane (OTS) self-assembled monolayer (SAM), and poly(3,4-ethylene-dioxythiophene):polystyrene sulfonate (PEDOT:PSS). The electronic properties of pristine and doped graphene samples were investigated by Raman spectroscopy and electrical transport measurements. The right shifting of G and 2D peaks and reduction in 2D to G peak intensity ratio (I2D/IG) assured that the dopants induced a p-type doping effect. Upon doping, the shifting of the Dirac point towards positive voltage validates the increment of the hole concentration in graphene and thus downward shift of the Fermi level. More importantly, the combination of HNO3/TiO2 NP doping on graphene yields a substantially larger change in the Fermi level of MLG. Our study may be useful for the development of graphene-based high-performance flexible electronic devices.