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We report on magnetotransport in a high-quality graphene device, which is based on monolayer graphene (Gr) encapsulated by hexagonal boron nitride (hBN) layers, i.e., hBN/Gr/hBN stacks. In the vicinity of the Dirac point, a negative magnetoconductance is observed for high temperatures > ~ 40 K, whereas it becomes positive for low temperatures ≤ ~ 40 K, which implies an interplay of quantum interferences in Dirac materials. The elastic scattering mechanism in hBN/Gr/hBN stacks contrasts with that of conventional graphene on SiO2, and our ultra-clean graphene device shows nonzero magnetoconductance for high temperatures of up to 300 K. [ABSTRACT FROM AUTHOR]

A 2D heterostructure consisting of few‐layer direct bandgap ReS2, a thin h‐BN layer, and a monolayer graphene (Gr) for application to various electronic devices is investigated. Metal‐insulator‐semiconductor (MIS)‐type devices with 2D van‐der‐Waals (vdW) heterostructures are recently studied as important components to realize various multifunctional device applications in analogue and digital electronics. The tunnel diodes of ReS2/h‐BN/Gr exhibit light tunable rectifying behaviors with low ideality factors and nearly temperature independent electrical characteristics. The devices behave like conventional MIS‐type tunnel diodes for logic gate applications. Furthermore, similar vertical heterostructures are shown to operate in field‐effect transistors with a low threshold voltage and a memory device with a large memory gate for future multifunctional device applications. [ABSTRACT FROM AUTHOR]

Few‐layer rhenium disulfide (ReS2) field‐effect transistors with a local floating gate (FG) of monolayer graphene separated by a thin hexagonal boron nitride tunnel layer for application to a non‐volatile memory (NVM) device are designed and investigated. FG‐NVM devices based on two‐dimensional van‐der‐Waals heterostructures have been recently studied as important components to realize digital electronics and multifunctional memory applications. Direct bandgap multilayer ReS2 satisfies various requirements as a channel material for electronic devices as well as being a strong light‐absorbing layer, which makes it possible to realize light‐assisted optoelectronic applications. The NVM operation with a high ON/OFF current ratio, a large memory window, good endurance (>1000 cycles), and stable retention (>104 s) are observed. The successive program and erase states using 10 ms gate pulses of +10 V and −10 V are demonstrated, respectively. Laser pulses along with electrostatic gate pulses provide multibit level memory access via opto‐electrostatic coupling. The devices exhibit the dual functionality of a conventional electronic memory and can store laser‐pulse excited signal information for future all‐optical logic and quantum information processing. [ABSTRACT FROM AUTHOR]

This study investigates quantized electron transport in high-mobility quantum point contact (QPC) devices in hBN/graphene/hBN in the quantum Hall regime. This study primarily focuses on the effect of the gap width of split gates on edge-channel manipulations, which defines the QPC structure and its electrostatic potential distribution. The quantized conductance is governed by the dynamics of edge channels passing through or backscattered at the QPC, which is controlled by both the top-gate and back-gate biases. The effects of the split-gate gap width and the filling in the QPC on the edge-channel manipulations are experimentally verified. The experimental results are consistent with the theoretical predictions of open/closed configurations of the edge channels around QPC with different gate gap widths. [ABSTRACT FROM AUTHOR]

We investigate the noise in single layer graphene devices from equilibrium to far-from equilibrium and found that the 1/f noise shows an anomalous dependence on the source-drain bias voltage (VSD). While the Hooge's relation is not the case around the charge neutrality point, we found that it is recovered at very low VSD region. We propose that the depinning of the electron-hole puddles is induced at finite VSD, which may explain this anomalous noise behavior. [ABSTRACT FROM AUTHOR]

We developed dual-gated graphene transistors in which the transistor polarity (n-type or p-type) is electrostatically reversible by the gate bias of one of the top gates. In this device, a channel is defined as the region between a pair of top gates, where graphene is irradiated by an accelerated helium ion beam to form a defect-induced transport gap. This device features not only a large current ON–OFF ratio of four orders of magnitude but also unipolarity of transistors, which would otherwise be ambipolar. We also show how these polarity-reversible transistors can be used in logic circuits. [ABSTRACT FROM PUBLISHER]

We demonstrate the current on-off operation in a novel dual-gated transistor with a He ion irradiated graphene channel in which defect-induced transport gap is formed. The transistor operation was performed by controlling the band configuration of gate-controlled p-i-n junction by independent biasing of top gates. The maximum current on-off ratio of nearly four orders of magnitude was obtained at a temperature of 250 K in the proposed device structure. It was also demonstrated that the transistor polarity can be changed between unipolar and ambipolar just by adjusting the gate bias of one of the dual gates, as expected from the device operation model. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A correction to the article "Parity effect of bipolar quantum Hall edge transport around graphene antidots" that was published in the 2015 issue of the periodical, is presented.

Parity effect, which means that even-odd property of an integer physical parameter results in an essential difference, ubiquitously appears and enables us to grasp its physical essence as the microscopic mechanism is less significant in coarse graining. Here we report a new parity effect of quantum Hall edge transport in graphene antidot devices with pn junctions (PNJs). We found and experimentally verified that the bipolar quantum Hall edge transport is drastically affected by the parity of the number of PNJs. This parity effect is universal in bipolar quantum Hall edge transport of not only graphene but also massless Dirac electron systems. These results offer a promising way to design electron interferometers in graphene. [ABSTRACT FROM AUTHOR]

Unipolar transport is demonstrated in a bilayer graphene with a series of p-n junctions and is controlled by electrostatic biasing by a comb-shaped top gate. The OFF state is induced by multiple barriers in the p-n junctions, where the band gap is generated by applying a perpendicular electric field to the bilayer graphene, and the ON state is induced by the p-p or n-n configurations of the junctions. As the number of the junction increases, current suppression in the OFF state is pronounced. The multiple p-n junctions also realize the saturation of the drain current under relatively high source-drain voltages. [ABSTRACT FROM AUTHOR]

Anderson localization (AL), a major topic in condensed matter physics, has been extensively studied. Since the discovery of graphene, its unique AL in Dirac materials, particularly weak localization (WL), has been studied intensively. Strong localization (SL) has also been investigated in graphene with intentionally introduced defects. The precise control of spacing/strength of defects using conventional methods is challenging; thus, He-ion-irradiation is a promising technology. However, magnetotransport, a sensitive tool to probe AL, has not yet been studied for He-ion-irradiated graphene. Herein, we systematically investigate the magnetotransport of He-ion-irradiated graphene. We observe negative magnetoresistance (MR) due to SL-dominated hopping transport. By systematically tuning the device parameters, negative MR at room temperature is first revealed for graphene field-effect transistor devices. Our study reveals carrier localization via searching in the multidimensional parameter space of Dirac materials, contributing to the development of fundamental AL physics and magnetoelectronic device applications. Image 1 [ABSTRACT FROM AUTHOR]