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oe1(光电查) - 科学论文

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出版时间
  • 2019
研究主题
  • solar cell
  • thin film
  • sputtering
  • Tungsten di sulfide (WS2)
应用领域
  • Optoelectronic Information Materials and Devices
机构单位
  • Universiti Kebangsaan Malaysia
  • German Malaysian Institute
  • Universiti Tenaga Nasional
143 条数据
?? 中文（中国） ▾

  • Novel Spark Method for Deposition of Metal Oxide Thin Films: Deposition of Hexagonal Tungsten Oxide

    摘要： Hexagonal tungsten trioxide (WO3) layers are grown on indium tin oxide (ITO) substrates using a novel spark deposition system. The effects of deposition time, substrate temperature, and oxygen (O2) flow rate through the chamber on the structural and morphological characteristics as well as the electrochemical response of the layers are examined. It is found that a deposition temperature of 400 °C and O2 flow rate at 60 mL min?1 through the chamber can result in hexagonal WO3 with improved crystallinity and quite effective electrochemical/electrochromic response.

    关键词： tungsten trioxide,spark method deposition,electrochemical response

    更新于2025-09-23 15:23:52

  • Spatial Separation of Carrier Spin by the Valley Hall Effect in Monolayer WSe <sub/>2</sub> Transistors

    摘要： We investigate the valley Hall effect (VHE) in monolayer WSe2 field-effect transistors using optical Kerr rotation measurements at 20 K. While studies of the VHE have so far focused on n-doped MoS2, we observe the VHE in WSe2 in both the n- and p-doping regimes. Hole doping enables access to the large spin-splitting of the valence band of this material. The Kerr rotation measurements probe the spatial distribution of the valley carrier imbalance induced by the VHE. Under current flow, we observe distinct spin-valley polarization along the edges of the transistor channel. From analysis of the magnitude of the Kerr rotation, we infer a spin-valley density of 44 spins/μm, integrated over the edge region in the p-doped regime. Assuming a spin diffusion length less than 0.1 μm, this corresponds to a spin-valley polarization of the holes exceeding 1%.

    关键词： magneto-optical Kerr effect,Tungsten diselenide,valleytronics,spintronics

    更新于2025-09-23 15:23:52

  • Two-dimensional amorphous heterostructures of Ag/a-WO3- for high-efficiency photocatalytic performance

    摘要： Synergistic photocatalysis is an important concept for designing the high-efficiency catalysis for fundamental research and technical applications. In this study a well-defined synergistic photocatalysis system is realized by the 2D amorphous heterostructures (2DAHs) Ag/a-WO3-x, which are constructed by Ag nanoparticles on 2D amorphous tungsten oxide (a-WO3-x) fabricated via supercritical CO2 method. We demonstrate theoretically that the oxygen evolution reactions (OER), characterized by photocurrent response, have been dramatically improved in Ag/a-WO3-x than those of both single a-WO3-x and Ag/WO3 systems. Such an enhanced photoelectrochemical performance attributes to the superposition effect of amorphous effect catalysis and local surface plasmon resonances (LSPR) catalysis. More interestingly, the ab initio density-functional theory calculations reveal that the amorphous effect catalysis ascribes to the unique d-d tail states coupling of both Ag and W atoms in the 2DAHs. Overall, our findings not only propose the prototype of synergistic photocatalysis, but also provide a new methodology to the design of novel catalyst.

    关键词： 2D amorphous tungsten oxide,amorphous effect catalysis,synergistic photocatalysis,d-d tail states coupling,2D amorphous heterostructures Ag/a-WO3-x

    更新于2025-09-23 15:23:52

  • Stoichiometric and non-stoichiometric tungsten doping effect in bismuth vanadate based photoactive material for photoelectrochemical water splitting

    摘要： In photoelectrochemical (PEC) water splitting, BiVO4 has attracted attention due to its favorable band gap but it suffers low PEC performance due to poor conductivity. The vast majority of publications on this system has examined doping of stoichiometric composition of tungsten (W) on this system to increase bulk and interfacial conductivity while managing the contaminant generation of crystallographic defects and recombination sites. In this paper, a deep investigation was carried out to examine the effect of non-stoichiometric W doping in BiVO4 system. Stoichiometric and non-stoichiometric W-doped monoclinic BiVO4 (i.e. Bi1-(xtd)V1-xWxtdO4; BiV1-xWxtdO4 and BiV1-yWyO4; x ? 0.008; y ? 0.03 and d ? 0.005) were prepared using a facile dip coating technique. The stoichiometric composition contains charge balanced Bi, V and W atoms whereas non-stoichiometric compositions contain excess Bi and excess Bi and W. The non-stoichiometric composition BiV1-xWxtdO4 has shown better photoelectrochemical water splitting performance with respect to other compositions at 1.23 V vs RHE, under one sun illumination of electrode. The XRD and XPS results shows that non-stoichiometric doping with excess Bi or with excess Bi and W can possibly create an environment where V5t ions are substitutional replaced by W6t ions without generating other defects. But there was no signi?cant difference in band gap of different compositional samples observed. Further electrochemical impedance technique was used to analyze change in bulk and surface charge mobility with W-doping in BiVO4. The electrochemical impedance analysis showed the presence of low interfacial resistance, lower charge transfer resistance and high charge donor/surface state density for non-stoichiometric composition BiV1-xWxtdO4 electrode. It is evident from and cyclic voltammetry that the addition of excess Bi and W from its stoichiometric quantity ef?ciently suppressed the formation of hole-electron pair recombination sites. The electrochemical analytical results lead us to believe that the particular non-stoichiometric composition of BiV1-xWxtdO4 can signi?cantly lower trap sites and enhances kinetics of charge transfer, leading to the better photoelectrochemical water splitting performance.

    关键词： Oxygen evolution,Photoelectrochemical cell,Water splitting,Bismuth vanadate,Tungsten doping

    更新于2025-09-23 15:23:52

  • The design of a polyaniline-decorated three dimensional W18O49 composite for full solar spectrum light driven photocatalytic removal of aqueous nitrite with high N2 selectivity

    摘要： Photocatalysis using solar energy is the most promising green technology for nitrite removal. However, effective photocatalytic performance is often challenged by the limited light absorption, utilization of expensive noble metals and undesired products (nitrate and ammonium). Here, we report for the first time that a full solar light response polyaniline-decorated three dimensional W18O49 composite (PANI@W18O49), a noble metal-free photocatalyst, possesses excellent photocatalytic activity for aqueous nitrite removal with high N2 selectivity. The prepared sample was thoroughly identified via XRD, Raman, FTIR, SEM, TEM, UV–vis DRS and PL. The catalytic results demonstrated that over 80% N2 selectivity (initial concentration 1.0 mM) was achieved through the PANI@W18O49 without sacrificial agent under 300 W Xe lamp irradiation for 60 min. Such advantages were attributed to the built-in junction between n-type W18O49 and p-type PANI, offering suitable redox levels of electron-hole pairs for NO2? reaction. The modification of PANI also benefited the light harvesting ability and activated carriers migration, the calculated rate constant of PANI@W18O49 is about four times as high as that of W18O49. The current study not only prepared a promising photocatalyst, but also provides new insights into improving the photocatalytic activity and N2 selectivity for nitrite treatment.

    关键词： Nitrite,Polyaniline,Tungsten oxide,Full solar spectrum light driven,Photocatalysis

    更新于2025-09-23 15:23:52

  • A novel approach to synthesize nanostructured WO3 and graphene/WO3 nanocomposites: Structural and morphological investigations

    摘要： Nanostructured metal oxide based nanocomposites have attracted considerable attention due to their promising and remarkable properties. In the present study, a novel method is developed for the preparation of Graphene oxide (GO)/tungsten oxide WO3 nanocomposites by using tungsten carbide (WC) and graphite as precursors. (GO)/WO3 nanocomposites are prepared via in situ and ex situ chemical approaches followed by subsequent thermal treatment at 500 °C. The obtained samples were characterized by di?erent techniques to con?rm the transformation of WC to WO3 nanostructures and the formation of their nanocomposites with carbon nanostructures. X-ray di?raction (XRD) analysis indicates that the WO3 nanoparticles were ?ne crystallized with a monoclinic phase even after interaction with GO for the ex situ prepared GO/WO3 and di?erent phases of WO3 appeared during their growth in situ in the presence of graphite. Scanning electron microscopy (SEM) images reveal the rods-like shape of WO3 nanostructures with uniform distribution onto the RGO nanosheets. Fourier transform infrared (FTIR) spectroscopy con?rms the interaction and charge transfer between the components. The experimental results reveal the e?ciency of the proposed approach that opens up a promising route to prepare G/WO3 nanocomposites for many applications.

    关键词： Graphene,Hybrid nanocomposite,Tungsten oxide

    更新于2025-09-23 15:23:52

  • Synthesis of Tungsten Oxide Nanowires onto ITO Glass Using T-CVD

    摘要： Tungsten oxide is an n-type semiconductor with interesting physical and chemical properties that make it suitable for various technological applications. Tungsten oxide nanowires were synthesized not only at low temperature but also without the use of any catalysts. The tungsten oxide nanowires were synthesized at 550 °C with tungsten layers onto the ITO glass using thermal chemical vapor deposition (T-CVD). The SEM image shows that the tungsten oxide nanowires are effectively grown with the 200 nm tungsten film. The Raman spectra shoulder at ~690 cm-1 proves the synthesized of tungsten oxide nanowires.

    关键词： ITO glass,thermal chemical vapor deposition,Tungsten oxide nanowires

    更新于2025-09-23 15:22:29

  • Gate-Tunable Thermal Metal–Insulator Transition in VO <sub/>2</sub> Monolithically Integrated into a WSe <sub/>2</sub> Field-Effect Transistor

    摘要： Vanadium dioxide (VO2) shows promise as a building block of switching and sensing devices because it undergoes an abrupt metal-insulator transition (MIT) near room temperature, where the electrical resistivity changes by orders of magnitude. A challenge for versatile applications of VO2 is to control the MIT by gating in the field-effect device geometry. Here, we demonstrate a gate-tunable abrupt switching device based on a VO2 microwire that is monolithically integrated with a two-dimensional (2D) tungsten diselenide (WSe2) semiconductor by van der Waals stacking. We fabricated the WSe2 transistor using the VO2 wire as the drain contact, titanium as the source contact, and hexagonal boron nitride as the gate dielectric. The WSe2 transistor was observed to show ambipolar transport, with higher conductivity in the electron branch. The electron current increases continuously with gate voltage below the critical temperature of the MIT of VO2. Near the critical temperature, the current shows an abrupt and discontinuous jump at a given gate voltage, indicating that the MIT in the contacting VO2 is thermally induced by gate-mediated self-heating. Our results have paved the way for the development of VO2-based gate-tunable devices by the van der Waals stacking of 2D semiconductors, with great potential for electronic and photonic applications.

    关键词： 2D materials,field-effect transistor,tungsten diselenide,phase-change materials,vanadium dioxide,metal-insulator transition,van der Waals heterostructures

    更新于2025-09-23 15:22:29

  • Quantum Calligraphy: Writing Single-Photon Emitters in a Two-Dimensional Materials Platform

    摘要： We present a paradigm for encoding strain into two dimensional materials (2DM) to create and deterministically place single photon emitters (SPEs) in arbitrary locations with nanometer-scale precision. Our material platform consists of a 2DM placed on top of a deformable polymer film. Upon application of sufficient mechanical stress using an atomic force microscope tip, the 2DM/polymer composite deforms, resulting in formation of highly localized strain fields with excellent control and repeatability. We show that SPEs are created and localized at these nanoindents, and exhibit single photon emission up to 60K, the highest temperature reported in these materials. This quantum calligraphy allows deterministic placement and real time design of arbitrary patterns of SPEs for facile coupling with photonic waveguides, cavities and plasmonic structures. In addition to enabling versatile placement of SPEs, these results present a general methodology for imparting strain into 2DM with nanometer-scale precision, providing an invaluable tool for further investigations and future applications of strain engineering of 2DM and 2DM devices.

    关键词： tungsten disulfide,atomic force microscopy,two-dimensional materials,single photon emitter,strain engineering

    更新于2025-09-23 15:22:29

  • A promising CuOx/WO3 p-n heterojunction thin-film photocathode fabricated by magnetron reactive sputtering

    摘要： A CuOx/WO3 thin-film based on p-n heterojunction proposed as a highly performance and stable photocathode. The CuOx/WO3 thin-film was deposited by magnetron reactive sputtering layer by layer, followed with slow rate annealing in O2 ambient. This is an excellent method for high-quality and uniform composite thin-film deposition with large areas at a high growth rate. The optimized CuOx/WO3 thin-film photocathode after slow rate annealing at 500 °C in O2 provides an obviously enhanced photoinduced current density of -3.8 mA cm-2 at a bias potential of -0.5 V (vs. Ag/AgCl), which value is 1.5 times higher than that of bared CuOx thin-film. This highly enhanced photoelectrochemical performance is attributed to p-n heterojunction, which accelerates the photogenerated electrons and holes transfer to n-WO3 and p-CuOx, thereby accelerate the separation of photogenerated carries. In addition, WO3 layer covered on the surface of CuOx thin film can improve the stability of Cu2O in electrolytes.

    关键词： p-n heterojunction,Tungsten oxide,Photoelectrochemical,Copper oxide,Magnetron reactive sputtering

    更新于2025-09-23 15:22:29