Effect of substrates on covalent surface modification of graphene using photosensitive functional group

Abstract

Abstract Graphene has gained much significance for its potential applications in optics and electronics owing to its unique physical and chemical properties. Nevertheless, its gapless band structure greatly limits its wider application in optoelectronic devices. The present study seeks to explore chemical functionalization as an effective method to tune the properties of graphene. Covalent modification of graphene by aryl diazonium salt of a photosensitive functional group (azobenzene) has been used to achieve this goal. This is based on the fact that graphene is a two-dimensional, atomically thin lattice of sp2-bonded carbon atoms, therefore, its properties can be modulated by modifying the underlying dielectric surface with a self-assembled monolayer resulting in doping control. In the study, a clear difference in the rate of electron-transfer reactions with the photosensitive functional group is shown for monolayer graphene supported on SiO2/Si substrates and organic molecule functionalized SiO2/Si substrates. Graphene supported on SiO2/ Si is more reactive towards functionalization than graphene on organic molecule functionalized surfaces, as shown by Raman spectroscopy. The transport characteristics of functionalized graphene on conventional SiO2/Si substrates as well as substrates modified with organic molecule octadecyltrichlorosilane self-assembled monolayers are also explored and compared.