Probing Electronic Doping in CVD Graphene Crystals Treated by HNO3 Vapors

In this work, we present a comprehensive protocol for achieving hole doping in graphene through exposure to nitric acid (HNO3) vapors. We demonstrate gradual p-type surface doping of CVD-grown graphene on a Si/SiO2 substrate by thermally depositing nitric acid molecules to form self-assembled charge transfer complexes. Detailed analysis of charge carrier concentration and Fermi energy shifts was conducted using Raman, X-ray and ultraviolet photoelectron spectroscopies (XPS/UPS). Our methodology, including a novel PMMA coating step, ensures stability and efficiency of the doping process, highlighting its effectiveness in inducing permanent hole doping while maintaining the structural integrity of the graphene.