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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） ▾

  • Optimization of Residual Stresses in Laser-Mixed WC(Co, Ni) Coatings

    摘要： A ternary mixture of tungsten carbide (WC), cobalt (Co), and nickel (Ni) powders is prepared to form ceramic-metal composite coatings employed for laser cladding of 40Cr steel. This coating is investigated using the mixture design to evaluate the influence of its ratios on the residual stresses in the clads. The WC/Co/Ni ternary mixture exhibits higher residual stresses than those of the Co/Ni or WC/Ni binary mixtures, except for the WC/Co one. Single WC, Co, or Ni designs illustrate a high sensitivity of residual stresses, cracks pass through the interior of WC particles rather than around them, and the cracks mostly propagate along the eutectic phases at 50%Co–50%WC. A reduced special quartic model in the mixture design exhibits excellent fit, predicted and experimental values of residual stresses for these laser clads are in good agreement.

    关键词： residual stress optimization,mixture,reduced special quartic model,tungsten carbide

    更新于2025-11-28 14:24:20

  • Tunable passively Q-switched ytterbium-doped fiber laser using MoWS2/rGO nanocomposite saturable absorber

    摘要： We demonstrated a tunable Q-switched ytterbium-doped fiber laser (YDFL) using MoWS2/rGO nanocomposite as passive saturable absorber. Further, the Mo1?xWxS2/rGO nanosheets, with x proportion of 0.2, are synthesized using hydrothermal exfoliation technique. The proposed nanocomposite-PVA based thin film is fabricated by mixing the MoWS2/rGO nanosheets with polyvinyl alcohol (PVA). The fabricated thin film is sandwiched between two fiber ferrules to realize the proposed saturable absorber (SA). Further, the proposed MoWS2/rGO-PVA based thin film SA exhibits a fast relaxation time and a high damage threshold which are suitable to realize a Q-switched pulsed laser with a tunable wavelength range of 10 nm that extends from 1028 nm to 1038 nm. For the highest pump power of 267.4 mW, the generated Q-switched pulses exhibit a narrow pulse width of 1.22 μs, the pulse repetition rate of 90.4 kHz, the highest pulse energy of 2.13 nJ and its corresponding average power of 0.193 mW. To the best of author’s knowledge, this is the first realization of a tunable Q-switching fiber laser in a 1 μm wavelength using MoWS2/rGO nanocomposite saturable absorber.

    关键词： Saturable absorber,Molybdenum,Tungsten disulfide,Q-switched fiber laser,Transition metal dichalcogenides

    更新于2025-11-28 14:24:03

  • Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor

    摘要： In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.

    关键词： tungsten disulfide (WS2),side-polished fiber (SPF),molybdenum disulfide (MoS2)

    更新于2025-11-28 14:23:57

  • Electrochromic device with Magnetron sputtered Tungsten Oxide (WO<sub>3</sub>) and nafion membrane: performance with varying Tungsten Oxide thickness- A report

    摘要： Electrochromics is the emerging technology for energy conservation and indoor climatic control through smart windows. In this study we are reporting four layer electrochromic device: ITO (400nm)/ commercially procured Nafion (183μm) / WO3 (44nm to 200nm)/ ITO (400nm). The active area (A) of the electrochromic devices are 3cm2. The tungsten oxide (WO3) and ITO thin films have been deposited at room temperature (300 K) by reactive DC Magnetron sputtering. The sheet resistance of ITO is 20 ?/□. The “as deposited” WO3 films are amorphous and have high optical transmission (75%- 85%) in the visible spectrum. The optical band gap decreases with increasing thickness of WO3 thin films. The coloration efficiency (CE) of the electrochromic device increases with increasing thickness of the WO3 layer. The CE for the device with WO3 thickness 200 nm is 184 cm2/C: the highest reported so far for a hybrid electrochromic device. The increase in the CE with thickness has been explained (for the first time) by replacing the surface charge density (Q/A) with the volume charge density (Q/A*t) in the coloration efficiency formula derived from the Beer Lambert’s law.

    关键词： coloration efficiency,electrochromism,nafion and Magnetron sputtering.,Tungsten oxide

    更新于2025-11-19 16:56:35

  • Dual functionality of K0.3WO3/Ag2O nanocomposites for smart window: Energy saving and visible photocatalytic self-cleaning performance

    摘要： Series of novel K0.3WO3/Ag2O nanocomposites were successfully prepared by simple two steps method. An exciting fact that near-infrared light shielding and visible photocatalytic self-cleaning effects are integrated into the K0.3WO3/Ag2O film (weight ratio of K0.3WO3 to Ag2O = 30) could offer significant potential applications in smart windows. Furthermore, the optical properties and photocatalytic activity of the composites could be tuned by adjusting the weight ratio of K0.3WO3 to Ag2O. The obtained K0.3WO3/Ag2O films presented enhanced photocatalytic self-cleaning performance compared with pure K0.3WO3 under visible light irradiation. The improved self-cleaning performance of the K0.3WO3/Ag2O composites was ascribed to a combined contribution of the matched energy band structures and boosted separation efficiency of photo-generated carriers. An approximately 2.3°C-3.4 °C decrease in inner temperature was obtained for the heat box covered with K0.3WO3/Ag2O coated glass. Therefore, the proposed K0.3WO3/Ag2O (weight ratio of K0.3WO3 to Ag2O = 30) smart coating is a promising material for self-cleaning energy-saving windows.

    关键词： Self-cleaning,Visible photocatalytic,Ag2O,KxWO3,Tungsten bronze,NIR shielding

    更新于2025-11-19 16:56:35

  • Visible-Light Overall Water Splitting by CdS/WO <sub/>3</sub> /CdWO <sub/>4</sub> Tricomposite Photocatalyst Suppressing Photocorrosion

    摘要： Photocatalytic water splitting under visible light has attracted attention as a possible solution to the energy exhaustion problem. Hitherto, water splitting has been generally achieved using several oxynitrides, oxysul?des, and nitrides, and only a few studies report water splitting using cadmium sul?de (CdS) as a photocatalyst. A major reason for this is that CdS undergoes photocorrosion. In this study, we achieved an overall water splitting under visible light using a CdS/WO3/CdWO4 tricomposite photocatalyst. In the process, photocorrosion of CdS was suppressed by covering it with WO3 and CdWO4, and the oxidation reaction progressed in WO3 by the Z-scheme type photocatalytic reaction.

    关键词： cadmium tungstate,tungsten oxide,photocorrosion,water splitting,cadmium sul?de,Z-scheme

    更新于2025-11-19 16:51:07

  • Bismuth vanadate single crystal particles modified with tungsten for efficient photoeletrochemical water oxidation

    摘要： Highly efficient water oxidation utilizing visible light is a crucial step in water splitting. Bismuth vanadate (BiVO4) single crystal particles have attracted much attention in water oxidation recently, owing to their outstanding physicochemical properties and exposed active facets. The performance of BiVO4 single crystal particles is generally hindered by their poor conductivity and worse charge separation. Doping BiVO4 single crystal particles with other metal elements has been considered as an efficient way to improve their conductivity, charge separation and performance. However, there are few successful reports, because structure and morphology of BiVO4 single crystal particles are easily changed by addition of impurities. Here, we present that W doped BiVO4 crystal particles were successfully achieved by developing a simple impregnation method following with a high temperature annealing process. The obtained W-BiVO4 single crystal particles exhibited improved conductivity, carrier density and thereby enhanced activity for water oxidation. The solar energy conversion of the W-BiVO4 electrode was doubled compared with the pristine one. Thus, this work opens an avenue for developing efficient single crystal particle photocatalysts.

    关键词： BiVO4,Tungsten,Single crystal particles,Water oxidation

    更新于2025-11-19 16:51:07

  • A Comparative Study of Gas Sensing Properties of Tungsten Oxide, Tin Oxide and Tin-Doped Tungsten Oxide Thin Films for Acetone Gas Detection

    摘要： Nowadays, various metal oxide thin films have been used for the purpose of gas sensing. This research depicts a comparison of gas sensing properties among four different metal oxide thin films, namely, tungsten dioxide (WO2), tungsten trioxide (WO3), tin oxide (SnO2) and tin doped tungsten trioxide (Sn-doped WO3), for detecting acetone gas. Each metal oxide thin film was subjected to acetone gas flow of various concentrations and the corresponding changes in resistance were calculated. Characterizations such as x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and gas sensing characterization for recording resistance changes have been performed. Each film was annealed at different temperatures for 1 h (WO2 and WO3 at 500°C, SnO2 at 300°C and Sn-doped WO3 at 400°C) so as to achieve an optimum grain size for sensing. The XRD patterns reveal formation of an orthorhombic phase of WO2, hexagonal phase of WO3 and orthorhombic phase of SnO2. AFM and SEM depict clear images of grain boundaries on the film. SnO2 has been found to be the best thin film for sensing acetone gas. Operational optimum temperature for sensing acetone gas has been calculated for each thin film (260°C for WO2, 220°C for WO3, 360°C for SnO2 and 300°C for Sn-doped WO3). It can detect a very low concentration of 1.5 ppm acetone gas with a good resistance response change of 30%. Various concentrations of acetone gas, namely, 1.5 ppm, 3 ppm, 5 ppm, 7 ppm, 10 ppm, 15 ppm and 20 ppm, have been detected using these metal oxide thin films, and thus the comparison has been made. The response time for SnO2 is approximately 3 min and recovery time is approximately 4 min.

    关键词： tungsten oxide,acetone gas detection,topography,tin oxide,Metal oxide thin films,surface metrology,gas sensing,tin-doped tungsten oxide

    更新于2025-09-23 15:23:52

  • 2D Material-Based Vertical Double Heterojunction Bipolar Transistors with High Current Amplification

    摘要： The heterojunction bipolar transistor (HBT) differs from the classical homojunction bipolar junction transistor in that each emitter-base-collector layer is composed of a different semiconductor material. 2D material (2DM)-based heterojunctions have attracted attention because of their wide range of fundamental physical and electrical properties. Moreover, strain-free heterostructures formed by van der Waals interaction allows true bandgap engineering regardless of the lattice constant mismatch. These characteristics make it possible to fabricate high-performance heterojunction devices such as HBTs, which have been difficult to implement in conventional epitaxy. Herein, NPN double HBTs (DHBTs) are constructed from vertically stacked 2DMs (n-MoS2/p-WSe2/n-MoS2) using dry transfer technique. The formation of the two P–N junctions, base-emitter, and base-collector junctions, in DHBTs, was experimentally observed. These NPN DHBTs composed of 2DMs showed excellent electrical characteristics with highly amplified current modulation. These results are expected to extend the application field of heterojunction electronic devices based on various 2DMs.

    关键词： 2D materials,tungsten diselenide,P–N junction,heterojunction bipolar transistor,molybdenum disulfide

    更新于2025-09-23 15:23:52

  • The <i>h</i> -Sb <sub/>x</sub> WO <sub/> 3+2 <i>x</i> </sub> Oxygen Excess Antimony Tungsten Bronze

    摘要： The previously unreported oxygen excess hexagonal antimony tungsten bronze is reported, with a composition of Sb0.5W3O10, in the following denoted as h-SbxWO3 + 2x with x = 0.167, to demonstrate its analogy to classical AxWO3 tungsten bronzes. This compound forms in a relatively narrow temperature range between 580 8C < T < 620 8C. It was obtained as a dark-blue polycrystalline powder, and as thin, needle-shaped, blue single crystals. h-SbxWO3 + 2x crystallizes in the hexagonal space group P6/mmm with the cell parameters a = 7.4369(4) (cid:2) and c = 3.7800(2) (cid:2). The antimony and excess oxygen occupy the hexagonal channels within the network of corner-sharing WO6 octahedra. h-SbxWO3 + 2x has a resistivity of 1300 K (cid:2) 1.28 mW cm at room temperature, with little if any temperature-dependence on cooling. DFT calculations on a simplified model for this compound find a metallic-like electronic structure with the Fermi level falling within rather flat bands, especially around the G point.

    关键词： hexagonal bipyramids,metallic oxide,tungsten,antimony,bronze

    更新于2025-09-23 15:23:52