Work Function Tuning in Ferric Chloride Intercalated Few-layer Epitaxial Graphene

Ferric chloride (FeCl₃) is a p-type dopant for few-layer graphene. We studied the electronic density of states of FeCl₃intercalated between single-layer (stage 1) and tri-layer (stage 3) graphene with applied electric bias. The work function of these layers as a function of the electric bias was analyzed using ultraviolet photoemission spectroscopy. The results showed that the work function of graphene could be tuned in FeCl₃ intercalated few-layer graphene by up to 2.5 eV by the action of the resulting electric field. Further, we compared the density of states obtained by ultraviolet photoemission spectroscopy with that calculated using density functional theory. The inherently high 6.2 eV work function of the intercalated graphene due to charge transfer from FeCl₃to graphene appears to be compensated with increasing negative bias. The wide range of control over the work function of graphene demonstrated here suggests that these systems are excellent for electronic and optoelectronic applications.