Dewei Chu

Formation and Photocatalytic Application of ZnO Nanotubes Using Aqueous Solution

Vertically aligned ZnO nanotubes were prepared by etching ZnO rod arrays in aqueous solution, which were previously developed by chemical bath deposition method. The morphological, structural, photoluminescence, as well as photocatalytic properties of the ZnO nanotubes were examined with respect to the pH values of chemical bath solution. The morphology of the products was found to be sensitive to the pH values and chemical bath temperatures. The nanotubes synthesized at a low pH value (5.82) exhibited a strong UV emission and a weak defect-related visible emission. The highest photocatalytic efficiency was also observed at pH = 5.82. The possible mechanism for the difference of photocatalytic efficiency was discussed.

Recent developments in black phosphorus transistors

The discovery of graphene has inspired great research interest in two-dimensional (2D) layered nanomaterials during the past decade. As one of the newest members in the 2D layered nanomaterial family, black phosphorus (BP), with puckered structure similar to graphene, has shown great potential in novel nanoelectronics owing to its thickness-dependent bandgap. Especially, the unique in-plane anisotropy and high carrier mobility enable BP to be a promising candidate for field-effect transistor (FET) applications. In addition, monolayer or few-layer BP can be combined into van der Waals heterostructures and this opens up a pathway for overcoming existing problems such as impurity scattering and surface degradation or achieving functionalities. In this article, we will review the typical physical and chemical properties of BP and provide an overview of the recent developments in BP-based transistors. In this review, we also discuss the current challenges in BP transistors and future research directions.

Oxygen level: the dominant of resistive switching characteristics in cerium oxide thin films

Currently, resistive switching mechanisms in metal oxide thin films are not clearly understood due to lack of solid evidence. In this work, the switching behaviour of the Au/CeO2/conductive glass structure was analysed, where reproducible and pronounced resistive switching characteristics were obtained. The role of oxygen vacancies in switching characteristics was investigated. The concentration of oxygen vacancies in the CeO2 thin films was controlled by post-annealing and monitored by x-ray photon spectroscopy. The reduction in the switching ratio and the intensity of the peak associated with oxygen concentration O 1s level after annealing treatment confirmed the dominating role of oxygen vacancies in switching behaviour.

Direct growth of TiO2 nanotubes on transparent substrates and their resistive switching characteristics

In this work, TiO2 nanotubes were directly grown by one-step electrochemical deposition process, in the absence of any templates or metal Ti substrates. The Au/TiO2 nanotube/fluorine-doped tin oxide glass capacitor exhibits stable bipolar resistive switching behaviour. The resistive switching behaviour may be related to the oxygen vacancies, giving rise to the formation of straight and extensible conducting filaments along the wall of each vertically aligned TiO2 nanotube. Superior stability in resistive switching characteristics was also observed, indicating that TiO2 nanotubes are one of the potential materials for next-generation nonvolatile memory applications.

Reversible Hydrophobic to Hydrophilic Transition in Graphene via Water Splitting Induced by UV Irradiation

Although the reversible wettability transition between hydrophobic and hydrophilic graphene under ultraviolet (UV) irradiation has been observed, the mechanism for this phenomenon remains unclear. In this work, experimental and theoretical investigations demonstrate that the H2O molecules are split into hydrogen and hydroxyl radicals, which are then captured by the graphene surface through chemical binding in an ambient environment under UV irradiation. The dissociative adsorption of H2O molecules induces the wettability transition in graphene from hydrophobic to hydrophilic. Our discovery may hold promise for the potential application of graphene in water splitting.

Electric double-layer transistors: a review of recent progress

With the miniaturization of electronic devices, it is essential to achieve higher carrier density and lower operation voltage in field-effect transistors (FETs). However, this is a great challenge in conventional FETs owing to the low capacitance and electric breakdown of gate dielectrics. Recently, electric double-layer technology with ultra-high charge-carrier accumulation at the semiconductor channel/electrolyte interface has been creatively introduced into transistors to overcome this problem. Some interesting electrical transport characteristics such as superconductivity, metal–insulator transition, and tunable thermoelectric behavior have been modulated both theoretically and experimentally in electric double-layer transistors (EDLTs) with various semiconductor channel layers and electrolyte materials. The present article is a review of the recent progress in the EDLTs and the impacts of EDLT technology on modulating the charge transportation of various electronics.

Tuning the phase and morphology of In2O3 nanocrystals via simple solution routes

By decomposing In(OH)3 under different reaction conditions, In2O3 nanocrystals with controllable phases and morphologies were synthesized. Metastable hexagonal In2O3 nanocrystals were obtained by an alcoholysis process in ethanol, and followed by decomposition in air. The well-defined cubic In2O3 nanocubes can be fabricated by treating In(OH)3 in methanol at 250??C for 25?h, whereas the replacement of the solvent by ethanol yields nanorods. The results indicated that the solvent, dopants, pressure, and reaction temperature are responsible for the variations of phases and morphologies. In addition, the photoluminescence properties of the products are strongly dependent on their phases, crystallinity, and morphologies.

Shape-Controlled Growth of In(OH)3/In2O3 Nanostructures by Electrodeposition

In(OH)(3) nanostructures with controllable shapes were successfully synthesized using indium nitrate as an indium source by one-step electrodeposition process. The influences of the reaction temperature, time, indium nitrate concentration, and the applied potential on the morphology of the obtained products were discussed in detail. The results revealed that the growth behavior of In(OH)(3) was mainly determined by the indium nitrate concentration and applied potential, and well-defined ellipsoids, cubes, and rods could be prepared under suitable conditions. Their possible growth mechanisms as well as photocatalytic applications were addressed. Furthermore, In(2)O(3) nanostructures were obtained from In(OH)(3) upon heating, while size and morphology can be maintained during this process.

High-performance nanocomposite based memristor with controlled quantum dots as charge traps.

We report a novel approach to improve the resistive switching performance of semiconductor nanorod (NR) arrays, by introducing ceria (CeO2) quantum dots (QDs) as surface charge trappers. The vertically aligned zinc oxide (ZnO) (NR) arrays were grown on transparent conductive glass by electrochemical deposition while CeO2 QDs were prepared by a solvothermal method. Subsequently, the as-prepared CeO2 QDs were embedded into a ZnO NR array by dip coating to obtain a CeO2-ZnO nanocomposite. Interestingly, such a device exhibits excellent resistive switching properties with much higher ON/OFF ratios, better uniformity, and stability over the pure ZnO and CeO2 nanostructures. The origin of resistive switching was studied and the role of heterointerface was discussed.

Interface-Engineered Resistive Switching: CeO2 Nanocubes as High-Performance Memory Cells

We reported a novel and facile approach to fabricate self-assembled CeO2 nanocube-based resistive-switching memory device. The device was found to exhibit excellent bipolar resistive-switching characteristics with a high resistance state (HRS/OFF) to low resistance state (LRS/ON) ratio of 10(4), better uniformity, and stability up to 480 K. The presence of oxygen vacancies and their role was discussed to explain the resistive-switching phenomenon in the fabricated devices. Further, the effect of the film thickness on carrier concentrations and estimated electric field strength with the switching (OFF/ON) ratio were also discussed.