E. Pallecchi

High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen

We investigate the magneto-transport properties of epitaxial graphene single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in Ar, followed by H2 intercalation. We directly demonstrate the importance of saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve high carrier mobility. Upon successful Si dangling bonds elimination, carrier mobility increases from 3 000 cm2V−1s−1 to >11 000 cm2V−1s−1 at 0.3 K. Additionally, graphene electron concentration tends to decrease from a few 1012 cm−2 to less than 1012 cm−2. For a typical large (30 × 280 μm2) Hall bar, we report the observation of the integer quantum Hall states at 0.3 K with well developed transversal resistance plateaus at Landau level filling factors of ν = 2, 6, 10, 14… 42 and Shubnikov de Haas oscillation of the longitudinal resistivity observed from about 1 T. In such a device, the Hall state quantization at ν = 2, at 19 T and 0.3 K, can be very robust: the dissipation in electronic transport can stay very low, with the longitudinal resistivity lower than 5 mΩ, for measurement currents as high as 250 μA. This is very promising in the view of an application in metrology.

Epitaxial Graphene on 4H-SiC(0001) Grown under Nitrogen Flux: Evidence of Low Nitrogen Doping and High Charge Transfer

Nitrogen doping of graphene is of great interest for both fundamental research to explore the effect of dopants on a 2D electrical conductor and applications such as lithium storage, composites, and nanoelectronic devices. Here, we report on the modifications of the electronic properties of epitaxial graphene thanks to the introduction, during the growth, of nitrogen-atom substitution in the carbon honeycomb lattice. High-resolution transmission microscopy and low-energy electron microscopy investigations indicate that the nitrogen-doped graphene is uniform at large scale. The substitution of nitrogen atoms in the graphene planes was confirmed by high-resolution X-ray photoelectron spectroscopy, which reveals several atomic configurations for the nitrogen atoms: graphitic-like, pyridine-like, and pyrrolic-like. Angle-resolved photoemission measurements show that the N-doped graphene exhibits large n-type carrier concentrations of 2.6 × 10(13) cm(-2), about 4 times more than what is found for pristine graphene, grown under similar pressure conditions. Our experiments demonstrate that a small amount of dopants (<1%) can significantly tune the electronic properties of graphene by shifting the Dirac cone about 0.3 eV toward higher binding energies with respect to the π band of pristine graphene, which is a key feature for envisioning applications in nanoelectronics.

Flower-Shaped Domains and Wrinkles in Trilayer Epitaxial Graphene on Silicon Carbide

Trilayer graphene is of particular interest to the 2D materials community because of its unique tunable electronic structure. However, to date, there is a lack of fundamental understanding of the properties of epitaxial trilayer graphene on silicon carbide. Here, following successful synthesis of large-area uniform trilayer graphene, atomic force microscopy (AFM) showed that the trilayer graphene on 6H-SiC(0001) was uniform over a large scale. Additionally, distinct defects, identified as flower-shaped domains and isolated wrinkle structures, were observed randomly on the surface using scanning tunneling microscopy and spectroscopy (STM/STS). These carbon nanostructures formed during growth, has different structural and electronic properties when compared with the adjacent flat regions of the graphene. Finally, using low temperature STM/STS at 4K, we found that the isolated wrinkles showed an irreversible rotational motion between two 60° configurations at different densities of states.

Observation of the quantum Hall effect in epitaxial graphene on SiC(0001) with oxygen adsorption

In this letter we report on transport measurements of epitaxial graphene on SiC(0001) with oxygen adsorption. In a

Insulating to relativistic quantum Hall transition in disordered graphene

50\times 50 \mu\mathrm{m^2}

Single step fabrication of N-doped graphene/Si3N4/SiC heterostructures

size Hall bar we observe the half-integer quantum Hall effect with a transverse resistance plateau quantized at filling factor around

Graphene FETs With Aluminum Bottom-Gate Electrodes and Its Natural Oxide as Dielectrics

\nu = 2

Epitaxial graphene on step bunching of a 6H-SiC(0001) substrate: Aromatic ring pattern and Van Hove singularities

, an evidence of monolayer graphene. We find low electron concentration of

Contact resistance Study of “edge-contacted” metal-graphene interfaces

9\times 10^{11} \textrm{cm}^{-2}

Disorder-perturbed Landau levels in high-electron-mobility epitaxial graphene

and we show that a doping of