Photo-Chemical Tuning of the Dirac Point in CVD-Grown Graphene

Graphene, a two-dimensional sp² hybridized carbon lattice, has attracted significant interest due to its distinctive electrical and mechanical properties including its nearly linear energy dispersion relation that results in electric field induced generation of electrons and holes which travel as massless Dirac fermions with high velocities giving rise to its high charge carrier mobility.

These electrical properties have spurred research directed at modifying graphene for use in a variety of electronic, optoelectronic, and sensor technologies. In order to fully utilize its potentials, it is critical to manipulate its electronic properties while maintaining its pristine state. Intentional doping of graphene is such an effective method to modify the electrical properties of graphene, while preserving its electronic properties.

Here we demonstrated the use of TPS-F and NBC as photo-chemical dopants respectively. The neutrality point of graphene field effect transistors (GFET) was tuned significantly by controlling the light exposure time. Furthermore, the charge transfer between both molecules and graphene was analyzed via Raman Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS) and Ultraviolet Electron Spectroscopy (UPS).