Synthesis and Atomic-Scale Investigation of Phosphorus-Doped Graphene on Copper

Phosphorus doped graphene has potential applications in supercapacitors, lithium ion batteries, fuel cells, and sensors. A phosphorus-containing sole precursor has been used for the synthesis of phosphorus-doped graphene on the Cu(111) surface. The surface morphology, electronic structure of phosphorus dopants, and doping-induced variation of local work function of graphene have been studied on the atomic scale by using scanning tunneling microscopy, dI/dV spectroscopy and dZ/dV spectroscopy. Bias-dependent atomic-resolution STM images of the predominant type of phosphorus dopants have been obtained. dI/dV spectra show the effect of phosphorus doping on the electronic structure of the graphene surface. dZ/dV spectra show that the local work function decreases at the phosphorus dopant site, leading to a downward energy shift of field emission resonances. X-ray photoelectron spectroscopy measurements are also performed to characterize the overall phosphorus doping properties on the sample surface. This work provides atomic-scale experimental insights into the phosphorus dopants in graphene for the first time.