Controlling of the Dirac band states of Pb-deposited graphene by using work function difference

We have performed scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES) in Pb-deposited bilayer graphene (BLG) on the SiC(0001) substrate to investigate the dependence of the electronic structures on the Pb-deposition amount. We have observed that the Pb atoms form islands by STM and the pi bands of the BLG shift toward the Fermi level by ARPES. This hole-doping-like energy shift is enhanced as the amount of Pb is increased, and we were able to tune the Dirac gap to the Fermi level by 4 ML deposition. Considering the band dispersion, we suggest that the hole-doping-like effect is related to the difference between the work functions of Pb islands and BLG/SiC; the work function of BLG/SiC is lower than that of Pb. Our results propose an easy way of band tuning for graphene with an appropriate selection of both the substrate and deposited material.