Large-scale Mesoscopic Transport in Nanostructured Graphene

Dinescu

Physica E: Low-dimensional Systems and Nanostructures

2018

Tens of graphene transistors with nanoperforated channels and different channel lengths were fabricated at the wafer scale. The nanoholes have a central diameter of 20 nm and a period of 100 nm, the lengths of the channel being of 1, 2, 4 or 8 m. We have found that the mobility in these 2 m-wide transistors varies from about 10400 cm 2 /Vs for a channel length of 1 m to about 550 cm 2 /Vs for a channel length of 8 m. Irrespective of the mobility value, in all transistors the onoff ratio is in the range 10 3 -10 4 at drain and gate voltages less than 2 V. The channel lengthdependent mobility and conductance values indicate the onset of strong localization of charge carriers, whereas the high on-off ratio is due to bandgap opening by nanoperforations.

Section: Fabrication and Characterization Of Nanopatterned Gfetsmentioning

confidence: 79%

Solving the graphene electronics conundrum: High mobility and high on-off ratio in graphene nanopatterned transistors

Dinescu

Physica E: Low-dimensional Systems and Nanostructures

2018

“…To open a gap, one can fabricate a narrow graphene nanoribbon [15][16][17][18] or make a periodic array of holes, known as antidot graphene [19,20]. The band structure [19][20][21][22][23][24][25][26] and transport properties [27][28][29][30][31][32][33][34] of antidot graphene were extensively investigated; however, the topological properties, such as Berry curvature [35], are unknown. One might expect its Berry curvature to be zero since creating holes does not break either sublattice symmetry (inversion symmetry) or time-reversal symmetry.…”

Section: Creating Sublattice Asymmetry Is Not the Only Way To Open A mentioning

confidence: 99%

Berry Curvature and Nonlocal Transport Characteristics of Antidot Graphene

Pan

Zhang

et al. 2017

Phys. Rev. X

Self Cite

Antidot graphene denotes a monolayer of graphene structured by a periodic array of holes. Its energy dispersion is known to display a gap at the Dirac point. However, since the degeneracy between the A and B sites is preserved, antidot graphene cannot be described by the 2D massive Dirac equation, which is suitable for systems with an inherent A=B asymmetry. From inversion and time-reversal-symmetry considerations, antidot graphene should therefore have zero Berry curvature. In this work, we derive the effective Hamiltonian of antidot graphene from its tight-binding wave functions. The resulting Hamiltonian is a 4 × 4 matrix with a nonzero intervalley scattering term, which is responsible for the gap at the Dirac point. Furthermore, nonzero Berry curvature is obtained from the effective Hamiltonian, owing to the double degeneracy of the eigenfunctions. The topological manifestation is shown to be robust against randomness perturbations. Since the Berry curvature is expected to induce a transverse conductance, we have experimentally verified this feature through nonlocal transport measurements, by fabricating three antidot graphene samples with a triangular array of holes, a fixed periodicity of 150 nm, and hole diameters of 100, 80, and 60 nm. All three samples display topological nonlocal conductance, with excellent agreement with the theory predictions.

“…. Denoting the halfwidth of the Coulomb gap as Δ, one can conclude, therefore, that at T << Δ, ES law has to be observed, while in the opposite case (T >> Δ), the Mott law should dominate.There are a number of reports about observation of either Mott or ES laws in different disordered graphene based materials[35][36][37][38]. We show that in samples 3 and 4, both VRH laws are observable at different temperatures.…”

mentioning

confidence: 59%

Irradiation-induced metal-insulator transition in monolayer graphene

et al. 2019

A brief review of experiments directed to study a gradual localization of charge carriers and metal-insulator transition in samples of disordered monolayer graphene is presented. Disorder was induced by irradiation with different doses of heavy and light ions. Degree of disorder was controlled by measurements of the Raman scattering spectra. The temperature dependences of conductivity and magnetoresistance (MR) showed that at low disorder, conductivity is governed by the weak localization and antilocalization regime. Further increase of disorder leads to strong localization of charge carriers, when the conductivity is described by the variable-range-hopping (VRH) mechanism. It was observed that MR in the VRH regime is negative in perpendicular fields and is positive in parallel magnetic fields which allowed to reveal different mechanisms of hopping MR. Theoretical analysis is in a good agreement with experimental data.