Doping of graphene via adlayer formation of electrochemically reduced dibenzyl viologen

Abstract

In this contribution we demonstrate doping of graphene by uncharged dibenzyl viologen (DBV⁰). Deposited electrochemically on chemical vapor deposited (CVD) graphene on SiO₂, DBV⁰ forms a water-insoluble self-assembled molecular network, in contrast to water-soluble monocationic DBV˙⁺. The phase formation at the molecular scale is revealed by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). The doping efficiency is characterized by a combination of Raman spectroscopy and Kelvin probe force microscopy (KPFM). The Raman mapping of the G-band of the DBV⁰ adlayer on top of CVD graphene on SiO₂ shows an apparent red shift compared to the unmodified analogue indicating an n-doping effect. This observation is in line with the KPFM results of which the measured contact potential difference (CPD) displays a positive shift compared to that of the pristine graphene.