Scanning tunneling spectroscopy of inhomogeneous electronic structure in monolayer and bilayer graphene on SiC

Abstract

We present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface. Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001). STS spectroscopy shows a ~100meV gap-like feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge. Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity. These results are important for potential devices involving electronic transport or tunneling in graphene/SiC.

Origin of the energy bandgap in epitaxial graphene

“…This contradicts our observation of a kink at E D related to electron-plasmon scattering [2], a conclusion supported by doping studies and by theory [3,4]; it also contradicts STM measurements and theory which find no such gap [5,6]. Zhou also asserts that gaps observed in multilayer graphene are dominated by this same substrate effect, and not by the electric field across the film as proposed by Ohta et al [7,8].…”

“…4) as well as by electron microscopy showing an inhomogeneous distribution of small irregular graphene islands. There may also be defects within the graphene islands: our ideal samples have very few defects visible in STM [5] unlike samples studied by Rutter et al [10], suggesting that such defect formation is sensitive to sample preparation.…”

Graphene-Passivated Nickel as an Oxidation-Resistant Electrode for Spintronics

“…3b) due to a vector mismatch: the current in graphene is carried by electron's having non-zero in-plane momentum, , while the distribution of tunneling probabilities through our 1 nm Al 2 O 3 tunneling layer is maximum for = 0 and presents an exponential decay with increasing as shown in STM-tip/graphene measurements. [15][16][17][18][19] This is emphasized in our measurements by the fact that when energies ascribed to out-of-plane acoustic graphene phonon mode at ≈ 60 meV are reached, [15][16][17][18][19] additional inelastic tunneling paths are activated and the current rises. The suppression of the tunneling for small biases and the identification of the phonon-mediated inelastic tunneling channels in the dI/dV spectroscopy further show, in addition to XPS measurements, that the transport occurs as expected in a well-defined Ni/graphene/Al 2 O 3 /Co structure.…”

Configuration-enriched magneto-electronic spectra of AAB-stacked trilayer graphene

“…It includes a few intergroup LL anticrossings at large field strengths (B 0 > 100T). The band structures [73,75,78] and the first LL groups [75] have been experimentally verified for bilayer graphene.…”

“…The band structure and the LLs of monolayer graphene have been verified by a number of experimental methods [59,73,74]. Bilayer graphene, being held together by Van der Waals interactions, can exhibit the highly symmetric AA and AB configurations.…”