Mechanical strain of chemically functionalized chemical vapor deposition grown graphene

Chemical functionalization and mechanical strain of graphene are both important for the optimization of flexible electronic devices as both can alter the electronic structure of graphene. Here, we investigate the combined effects of covalent aryl diazonium functionalization and mechanical strain on graphene by Raman spectroscopy. Raman spectroscopy provides a wealth of information regarding the electronic structure of graphene and can be easily applied to flexible device architectures. The use of chemical vapor deposition (CVD) grown polycrystalline graphene is found to exhibit increased reactivity toward diazonium functionalization. This is attributed to the increased reactivity of defects predominantly present along domain boundaries. Functionalization with nitrobenzene diazonium molecules causes p-type doping to occur in the CVD graphene. The combined effects of mechanical strain and chemical functionalization on the graphene are also investigated. The Raman peak width is affected because of phonon splitting when under strain as well as an increase in frequency because of doping. Interestingly, we also observe a decrease in the I_D/I_G ratio when strain is applied to the chemically functionalized graphene indicating a possible morphological change to the surface.