Dependence of electronic properties of epitaxial few-layer graphene on the number of layers investigated by photoelectron emission microscopy

Abstract

We used spectroscopic photoemission and low-energy electron microscopy to investigate the electronic properties of epitaxial few-layer graphene grown on 6H-SiC͑0001͒. Photoelectron emission microscopy ͑PEEM͒ images using secondary electrons ͑SEs͒ and C 1s photoelectrons can discriminate areas with different numbers of graphene layers. The SE emission spectra indicate that the work function increases with the number of graphene layers and that unoccupied states in the few-layer graphene promote SE emission. The C 1s PEEM images indicate that the C 1s core level shifts to lower binding energies as the number of graphene layers increases, which is consistent with the reported thickness dependence of the Dirac point energy.

Precise control of epitaxy of graphene by microfabricating SiC substrate

“…This result is consistent with a previous report. 19 In addition, the work function of the finger-like feature is determined to be smaller than that of monolayer graphene, consistent with the electron reflectivity spectra ( Fig. 1(b)).…”

Transparency of graphene for low-energy electrons measured in a vacuum-triode setup

“…According to the literature, Φ ∼ 4.8 eV for gold and ∼4.5 eV for graphene. 19,20 The measured work function for the BaO:W emitter equals ∼2.7 eV. This suggests ∆Φ ∼ 2 eV.…”

Tuning the Graphene Work Function by Electric Field Effect

“…Since the band alignment of two different materials is determined by their respective work functions, control over the graphene work function is the key to reducing the contact barriers of graphene top electrode devices 9,10 . Previous scanning probe based studies [11][12][13] reveal that the work function of graphene is in a similar range to that of graphite, ~4.6 eV 14 , and depends sensitively on the number of layers 15,16 . However, the active controlling of the graphene work function has yet to be demonstrated.…”