Ultrahigh Vacuum Optical Spectroscopy of Chemically Functionalized Graphene Nanoribbons

We show that Raman and photoluminescence spectroscopies carried out in an ultrahigh vacuum (UHV) environment are a quick and nondestructive tool for investigating the electronic and vibrational properties of air-sensitive materials. As a showcase of this technique, experimental results of monolayers of chemically functionalized graphene nanoribbons on Au and silicon dioxide surfaces are presented. As functionalization routes we perform ionic and covalent functionalization by alkali metals and hydrogen, respectively. Samples prepared in this way cannot be probed using a standard optical spectroscopy experiment in ambient conditions because of their sensitivity to air and the need for controlled in-situ preparation. UHV optical spectroscopy is able to give valuable information on the orientation, the doping level, the defect concentration, and the luminescent properties of functionalized graphene nanoribbons.