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We have investigated the effect of an Al2O3passivation layer on the performance of few-layer WS2FETs. While the performance of WS2FETs is often limited by a substantial decrease in carrier mobility owing to charged impurities and a Schottky barrier between the WS2and metal electrodes, the introduction of an Al2O3overlayer by atomic layer deposition (ALD) suppressed the influence of charged impurities by high-κdielectric screening effect and reduced the effective Schottky barrier height. We argue that n-doping of WS2, induced by positive fixed charges formed at Al2O3/WS2interface during the ALD process, is responsible for the reduction of the effective Schottky barrier height in the devices. In addition, the Al2O3passivation layer protected the device from oxidation, and maintained stable electrical performance of the WS2FETs over 57 d. Thus, the ALD of Al2O3overlayer provides a facile method to enhance the performance of WS2FETs and to ensure ambient stability.

Many device scientists believe that current Ultra Large Scale Integration (ULSI) technology will face technical and economic difficulties in further miniaturization. It has been proposed that 1-dimensional (1-D) transistors with connecting wires and three-dimensionally stacked structures may replace current field effect transistors with planar integration structures. We propose a new scheme to fabricate and integrate 1-D active devices. As a first step, we show the way to form 1-D wires with spatially variable electronic structures and the way to characterize them.

A graphene nanoribbon (GNR) is an important basic structure to open a bandgap in graphene. The GNR processes reported in the literature are complex, time-consuming, and expensive; moreover, the device yield is relatively low. In this paper, a simple new process to fabricate a long and straight graphene nanoribbon with a high yield has been proposed. This process utilizes CVD graphene substrate and a ZnO nanowire as the hardmask for patterning. 8 µm long and 50‐100 nm wide GNRs were successfully demonstrated in high density without any trimming, and ∼10% device yield was realized with a top-down patterning process. After passivating the surfaces of the GNRs using a low temperature atomic layer deposition (ALD) of Al2O3, high performance GNR MOSFETs with symmetric drain-current‐gate-voltage (Id‐Vg) curves were demonstrated and a field effect mobility up to ∼1200 cm 2 V −1 s −1 was achieved at Vd = 10 mV. (Some figures in this article are in colour only in the electronic version)

The radio-frequency (RF) electrical response of monolayer graphene is reported. From the measured S-parameter in the range of 10 MHz to 50 GHz, a simple equivalent resistor–inductor–capacitor (R–L–C) circuit is established to analyze frequency impedance. The impedance magnitude shows significant frequency dependence only below 10 GHz and this dispersive behavior is originated from the graphene–metal contact. Above 10 GHz, there is no distinctive change in overall characteristic of impedance due to the absence of the skin effect and low intrinsic kinetic inductance of graphene. These results show that graphene could be a promising candidate for high-speed device application.

Evolution of a single graphene layer with disorder generated by remote oxygen plasma irradiation is investigated using atomic force microscopy, Raman spectroscopy and electrical measurement. Gradual changes of surface morphology from planar graphene to isolated granular structure associated with a decrease of transconductance are accounted for by two-dimensional percolative conduction by disorder and the oxygen plasma-induced doping effect. The corresponding evolution of Raman spectra of graphene shows several peculiarities such as a sudden appearance of a saturated D peak followed by a linear decrease in its intensity, a relatively inert characteristic of a D' peak and a monotonic increase of a G peak position as the exposure time to oxygen plasma increases. These are discussed in terms of a disorder-induced change of Raman spectra in the graphite system.