In this review, the recent research on local electron transport across the extended, one-dimensional defects in graphene using scanning probe methods is summarized. In particular, substrate steps, wrinkles, stacking faults, monolayer/bilayer-interfaces, collapsed wrinkles and grain boundaries are discussed. While these defects can have a significant influence on the total resistance of a sample, they also help to shed light on the general physics of electron scattering in the defects and the underlying scattering mechanisms.

Recent advances in the syntheses of 1D wires, 2D single layers, and 3D-graphdiyne materials at interfacess and the potential applications of the obtained materials in devices have been summarized.

A method is reviewed to produce graphene employing aromatic self-assembled monolayers as molecular precursors. This method is based on the electron irradiation induced chemical reactions and pyrolysis. As shown by complementary spectroscopic, microscopic and electric transport measurements and theoretical analysis, shape, crystallinity, thickness, optical and electronic properties of the graphene sheets can be flexibly adjusted depending on the production conditions. Novel possibilities of the developed method for nanotechnology are discussed.

The authors review experimental and theoretical studies of photocurrents driven by polarized terahertz radiation in graphene. The phenomenological and microscopic theory of various second order phenomena and the state-of-the-art of the experiments are discussed. They show that nonlinear transport opens up new opportunities for probing helical Dirac electron states, address prospectives of theoretical and experimental studies and discuss the application of structured graphene for fast room temperature detection of THz radiation.

Graphene quantum dots show promis as qubits, but currently still suffer from too much disorder. Using scanning tunneling spectroscopy in ultrahigh vacuum, the authors aim to overcome these problems, e.g., by electrostatically inducing quantum dots into monolayer graphene exploiting the gaps caused by Landau quantization. An extraordinary quality of the charging patterns results, including reliable orbital and valley splittings. The authors review these and other efforts to optimize graphene quantum dots within an ultraclean environment.

The carrier dynamics in graphene is investigated in a joint experiment-theory study, with a particular focus on optical excitations at low energies. The role of carrier-phonon and carrier-carrier scattering is clearly disentangled and a twofold behavior for carrier-carrier scattering is revealed: (i) fast collinear scattering and (ii) comparably slow non-collinear scattering. Furthermore fast ultrabroadband detectors, covering the range from THz to visible, are demonstrated.

A special type of metal substrate has been used to grow monolayer graphene by CVD of hydrocarbons. The substrates consist of 100 to 150 nm thin films of ruthenium, iridium, and nickel, supported on YSZ-buffered Si(111). The films are single-crystalline and available as 4 inch wafers, providing a possibly upscalable route to lattice-oriented graphene.

Twisted bilayer graphene (TBG) consists of a stack of two rotationally misaligned monolayer lattices. This article reviews the current state of the art in preparation, as well as characterization, of TBG. Special focus is directed towards the preparation technique of folding monolayer graphene via Atomic Force Microscope and investigation of the resulting TBG morphology. Different electronic coupling scenarios, as inferred from magnetotransport measurements, are further evaluated under the consideration of superlattice corrugation.

A systematic study of the graphene growth on carbon depleted Cu foils allows to understand the chemical vapor deposition kinetics and to predict the achievable growth velocity of graphene flakes. The experimentally determined thermal equilibrium constant of the reaction agrees with an approximation by thermodynamic data within a factor of two. The identified optimum of the growth parameters allows the growth of high quality graphene.

Graphene nanoribbons (GNRs) show unique properties and may constitute the basic components of the future nanoelectronic systems. In the present work, the state of the art, the merits, and also the drawbacks of the three types of GNR devices – GNR MOSFETs, GNR side-gate FETs, and GNR three terminal junctions (see figure on the left) – are examined, and the potential of these devices for future nanoelectronics is discussed.

The feature article presents a review of the recent theoretical work, providing a microscopic view of the time- and energy-resolved dynamics of optically excited carriers in graphene. The remarkable gapless and linear band structure of graphene opens up new relaxation channels, giving rise to fascinating ultrafast phenomena. In this work, the authors focus on the appearance of technologially relevant carrier multiplication and population inversion.

In the last few years, high was seen interest in hydrodynamic effects in interacting electron systems in ultra-pure materials. This paper reviews the recent advances, both theoretical and experimental, in the hydrodynamic approach to electronic transport in graphene, focusing on viscous phenomena, Coulomb drag, non-local transport measurements, and the possibilities for observing nonlinear effects.

The sublimation growth of epitaxial graphene on silicon carbide in an argon atmosphere is one particular synthesis method that could potentially lead to electronic applications. The paper summarizes the recent work on different aspects of epitaxial graphene growth and interface manipulation by intercalation, which was performed by a combination of low-energy electron microscopy, low-energy electron diffraction, atomic force microscopy and photoelectron spectroscopy.

The authors present an overview of the recent charge carrier transport experiments in both monolayer and bilayer graphene, with emphasis on the phenomena that appear in large-area samples. In the large-area limit classical corrections dominate and shape the magnetoresistance and the tunneling conductance. The discussed phenomena are very general and can, with little modification, be expected in any atomically thin 2D conductor.

This review describes the properties of carbon allotropes from 1D graphene nanoribbons to 2D doped graphene and 3D turbostratic graphene micro-disks. While turbostratic graphene lends itself to spintronic applications resulting from protected graphene layers, where charge carriers are highly mobile, doped graphene and graphene nanoribbons offer the possibility to tailor the electronic properties by introducing heteroatoms and using geometrical confinement.

Recent technological developments allow the fabrication of etched high-quality graphene nanoconstrictions and nanoribbons that exhibit ballistic transport and quantized conductance. The transport through such devices depends crucially on the nature of the edges and the localized edge states. By incorporating local top gates, the influence of the localized edge states can be independently tuned from the transmission of the ballistic channel in such devices (see Figure).

Two-dimensional (2D) materials are being considered ideally suited for ultimately scaled field-effect transistor devices due to their extremely thin thickness and excellent electronic transport properties. The realization of the appropriate contacts and doped source/drain regions is, however, difficult. Multigate substrates are being employed here, that allow generating potential landscapes within 2D field-effect transistor devices, facilitating electronic transport studies, as well as the realization of reconfigurable device functionalities.

In this work, the authors report on the fabrication of edge contacts to large area CVD monolayer graphene using a CMOS compatible metal with a very low contact resistance. The improved contacting scheme enables the realization of high performance graphene devices.

For future graphene electronic devices contacts to the one-atom-thick sheet are of paramount importance. The authors studied the growth of typical seed metals (Co, Pd, and Ti) on epitaxial graphene and found that they do not wet the graphene surface but form three-dimensional islands with a well-defined crystallographic orientation. When the islands are picked up by an STM tip, Co and Pd leave the graphene layer largely undisturbed, while it is often destroyed underneath Ti.

The meanfield or random phase approximations (RPA) are widely used to investigate the symmetry breaking due to the interaction effects in many fermion lattice models, e.g. in models for graphene. While it is known that these approximations overestimate ordering, the quantitative error is rarely estimated. Here, the authors incorporate self-energy effects describing quasiparticle degradation into the RPA analysis. The authors find marked reductions of the temperature scales where the ordering tendencies become strong.

Epitaxial graphene nanoribbons are prepared on lithographically structured Silicon Carbide. The ribbons grow on the facetted mesa side walls in epitaxial relation to the basal-plane graphene. In angle-resolved photoemission spectroscopy (ARPES) the π- electrons from the ribbons display a sharp band and emerge at a distinctly different emission angle compared to the basal-plane graphene.

Bilayer graphene has been suggested as an alternative for obtaining enhanced current saturation in graphene transistors. Large-area CVD grown graphene monolayers are used to prepare scalable artificially stacked bilayers (ASBLG) to study its electronic properties. Transistors based on ASBLG exhibit a reduction in minimum output conductance, resulting in an improved voltage gain compared to monolayer graphene transistors. The plausible reasons behind the present observation are discussed.

The defect-induced Raman modes of lithographically patterned graphene nanoribbons (GNR) are studied as a function of GNR width. The authors discuss the results based on a model that takes into account the partly two-dimensional nature of the scattering process in the GNRs. The authors use the different behaviors of the defect-activated D and D′ Raman modes to propose an all-Raman analysis for GNRs, allowing a simultaneous statement on the quality and the average width of the GNR.