Effect of graphene/4H-SiC(0001) interface on electrostatic properties in graphene

Electrostatic properties, quantum capacitance (C-q) and local density of states (LDOS) are evaluated for graphene on 4H-SiC(0 0 0 1) by measuring the local capacitance with Scanning Capacitance Spectroscopy (SCS). Two distinct samples were used for comparative study, viz., graphene exfoliated and deposited on 4H-SiC(0 0 0 1)-DG, and graphene grown epitaxially on 4H-SiC(0 0 0 1)-EG. We observed a distinctly lower screening length (r(scr)) and C-q while wider variations in the LDOS for EG. Such differences are attributed to the peculiar interface between EG/4H-SiC(0 0 0 1), which is known to be more or less defective having the presence of positive charges.