Substrate-assisted Fermi level shifting of CVD graphene by swift heavy ions

Abstract

The systematic modulation of surface electronic properties of graphene can be achieved through surface and interface engineering using swift heavy ion (SHI) irradiation. The effects of dense electronic excitation on the optical and surface electronic properties of chemical vapor deposited (CVD) graphene sheets are investigated in this work. The spectroscopic and microscopic results indicate that the sputtered substrate atoms are trapped in the graphene sheet during irradiation and alter the Fermi level of graphene. The change in the Fermi level calculated from the Raman spectra is investigated through the surface potential measurement by scanning Kelvin probe microscope (SKPM). The shifting of the Fermi level towards the valence band verifies the hole-doping of the graphene sheet by sputtered substrate atoms. The mechanism of ion interaction and its subsequent effects on the graphene and substrate material are further studied rigorously through Monte Carlo simulations using stopping and range of ions in matter (SRIM) and Surface Sputtering sub-routine of transport of ions in matter (TRIM) packages. This work offers a novel way of analyzing defect-induced modifications in the electronic properties of graphene by Raman spectroscopic features in combination with SKPM.