Figure 4: Material characterization using the virtual substrate method.

(a) Top: transmitted spectra for one-, four-, six-, 11- and 14-layer graphene for primary electron energies of 10 keV (dashed lines) and 15 keV (solid lines). Insets show the transmitted spectra at 15 keV without an offset. Bottom: electron transmission spectrum (T_VLEED)²⁵ measured by very-low-energy electron diffraction (VLEED) and transmission data (T_LEEM)²⁶ estimated from the reflectivity spectra (T_LEEM=1−R_LEEM) obtained from low-energy electron microscopy (LEEM). (b) Top: electron energy-loss spectra (EELS) for one-, two-, five- and several-layer graphene showing π and π+σ plasmons²⁷. Bottom: differential surface excitation parameter (DSEP) spectra for the few-layer graphene/gold system. The shaded region is the energy loss below the work function of graphite (ϕ=4.6 eV). For straight comparison, the work function of graphite relative to the cylindrical mirror analyser was determined a priori.