Fig. 2: Neutral epigraphene characterization.
From: An epitaxial graphene platform for zero-energy edge state nanoelectronics
a SEM micrograph of trapezoidal graphene islands that form early in the growth and ultimately coalesce to produce a uniform graphene layer. (Inset) STM image of the epigraphene showing the characteristic hexagonal lattice of graphene at T = 12.5 K. b Raman spectroscopy. Measured spectrum (red) and SiC subtracted spectrum (blue). The 2D peak is typical of a graphene monolayer. c ARPES (beam energy = 200 eV, EF = 197.4 eV) taken at room temperature along K-M-K’ showing characteristic graphene Dirac cones with vF = 1.06 × 106 m/s, with an apex at E = 0 confirming charge neutrality and no detectable anisotropy. d Infrared magneto-spectroscopy. The transitions follow the expected characteristic graphene \(\sqrt{B}\) dispersion (indicated by the red lines) confirming its monolayer character. e Typical scanning tunneling spectrum (T = 4.4 K, Iset = 400 pA at Vbias = 500 mV), showing the characteristic graphene density of states. A linear fit (dashed lines) indicates a doping level |EF – ED| < 6 meV, showing that the graphene is charge neutral. f STS image at a graphene island edge (T = 12.5 K, Iset = 250 pA at Vbias = 2 V) taken at various distances from the edge from SiC to inside the ribbon with a lateral resolution of about 2 nm (traces are displaced vertically for clarity). Note the 0-DoS peak at the edge, similar to that observed in sidewall ribbons43.
