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Effects of nitrogen-dopant bonding states on liquid-flow-induced electricity generation of graphene: A comparative study
摘要： We fabricate, measure and compare the effects of the bonding states of dopant nitrogen atoms in graphene devices, specifically on the liquid-flow-induced electricity by these devices. We find that nitrogen doping enhances the voltage induced by liquid flow regardless of the nitrogen bonding state. However, different nitrogen bonding states affect graphene’s conductivity differently: while graphitic nitrogen is suitable for electricity-generation applications, pyridinic nitrogen is hopeless for this purpose, due to the formation of symmetry-breaking defects of the latter.
关键词： Water-graphene interface,Nitrogen doped graphene,Flow-induced electricity generation
更新于2025-09-23 15:22:29
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Single-mode large-mode-area Er–Yb fibers with core based on phosphorosilicate glass highly doped with fluorine
摘要： Single-mode Er–Yb fibers with the core based on a phosphorosilicate glass matrix (up to 6.5 mol.% P2O5) highly doped with fluorine (up to 0.9 wt.%) were fabricated using an all-gas-phase modified chemical vapor deposition method. The core numerical aperture was in the range of 0.07–0.08 relative to the pure silica, which allowed us to increase the single-mode core diameter up to 20 μm. The slope efficiency in lasers based on the fabricated fibers reached 34% relative to the launched pump power.
关键词： fiber lasers,optical fibers,erbium–ytterbium fibers,erbium-doped fiber amplifiers
更新于2025-09-23 15:22:29
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The influence of yttrium-ions on the optical and electrical behavior of PVA polymeric films
摘要： The polyvinyl alcohol (PVA) films doped with various wt% of yttrium nitrate salt were synthesized by standard solution casting technique in order to examine the functional electrical and optical properties. The degree of the crystalline structure that evaluated in the films were investigated by x-ray diffraction and Fourier transform infrared spectroscopy measurements. In addition, the surface images have been obtained via scanning electron microscopy (SEM). The optical parameters have been calculated from UV–visible-NIR transmittance spectroscopy. Also, the dielectric constant measurement and the DC resistance that are arisen in the PVA films with different wt% of Y3+ have been done. All the samples show semi-crystalline phases. The average size, of the cluster Y3+ in the SEM images, increase to 1.63 μm for PVA/37 wt% Y3+ sample. Therefore, the optical absorption of this sample is higher than the others. The value of the energy gap decrease from 5.11 eV to 4.47 eV for PVA/0.037 wt% Y3+ and PVA/37 wt% Y3+ samples, respectively. The nonlinear current—voltage behavior, at high applied voltage, of the polymeric films, is observed with different values of slope, which is a characteristic of the varistor materials. So, these films could be used in different applications like optoelectronic and varistor devices.
关键词： Varistor,Dielectric,XRD/FTIR,SEM,Optical energy gap,Y3+-doped PVA
更新于2025-09-23 15:22:29
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Tuning electronic and optical properties of TiO<sub>2</sub> with Pt/Ag doping to a prospective photocatalyst: a first principles DFT study
摘要： Using first-principles density functional theory, the modulated electronic and optical properties of TiO2 with Pt/Ag substitutional dopants with varying concentration are investigated. Our calculations reveal the significant decreasing trend in the band gap of TiO2 while increasing the Pt (direct band gap) and Ag (indirect band gap) impurity concentration from 4.17% to 8.33% to 12.5%. The spin-polarized density of states reveal strong hybridization between the impurity bands with Ti-(3d) and O-(2p) bands near the Fermi level. The charge transfer mechanism depicts the delocalized electron cloud forming a strong bonding between the dopants (Pt/Ag) and oxygen of TiO2. Moreover, the absorption spectra of the Pt doped TiO2 structures have a broad peak at the visible range of energy spectrum with maximum absorption up to 0.7×10?5cm?1. The calculated reflectivity, energy loss function and extinction coefficient shows the enhanced optical properties of doped TiO2 compared to its pristine form. The obtained results predict the way to tailor the optical properties of Pt/Ag-doped TiO2 as an efficient photocatalyst in the visible region.
关键词： Pt,Optical properties,Electronic structure,Photocatalyst,Ag doped TiO2
更新于2025-09-23 15:22:29
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou, China (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - All-fibre acoustic sensor for the sound source localization
摘要： The large size and electromagnetic interference of microphones array are long standing challenges for sound source localization. Here an all-fibre vector acoustic sensor based on crossed microfiber Bragg gratings (micro-FBGs) has been proposed and experimentally demonstrated that enables the two-dimension sound source localization with a size less than 1.5mm. Two micro-FBGs inscribed in the Co2+-doped fibre are fabricated through a hydrofluoric acid solution, which are placed parallel to each other to form a micro-FBG pair. Based on the self-heating and asymmetric temperature distribution of two Co2+-doped fibres, the crossed micro-FBGs provide a direct two-dimensional measurement of the acoustic particle velocity. The experimental results show that an orientation sensitivity of 1.57 mV/deg for the micro-FBGs is achieved with a figure-of-eight response of the acoustic source direction. Meanwhile, the direction responses of two crossed pairs of micro-FBGs are exactly orthogonal to each other, which could detect the sound source localization. The all-fibre vector acoustic sensor is immune to electromagnetic interference, which appears to have a variety of potential applications, including research in acoustic communication, pipeline monitoring and navigation, etc.
关键词： Co2+-doped fibre,sound source localization,micro-FBG
更新于2025-09-23 15:22:29
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High Channel Conductivity, Breakdown Field Strength, and Low Current Collapse in AlGaN/GaN/Si δ -Doped AlGaN/GaN:C HEMTs
摘要： This paper reports the AlGaN/GaN/Si δ-doped AlGaN/GaN:C HEMT device on silicon with high channel conductivity, high breakdown ?eld (E-?eld) strength, and low current collapse by using the Si-doped AlGaN back barriers. The Si δ-doped AlGaN back barrier was used to compensate for the reduction of channel conductivity as a result of a carbon-doped semiinsulating GaN buffer layer. The maximum drain current increases from 412 to 720 mA/mm, and peak extrinsic transconductance is improved from 103 to 210 mS/mm. Due to the reduction of electric ?eld between the gate and drain along the GaN channel by inserting the Si δ-doped AlGaN back barrier layer, it can effectively suppress the capture of electrons in channel by carbon-induced accepted traps in the GaN:C buffer. Combined with the high conductivity of Si δ-doped AlGaN back barrier and high resistance of GaN:C buffer, the device showed the high breakdown E-?eld strength and the low speci?c on-resistance. Our proposed device is observed to hold a gate–drain voltage of 769 V at 10 μA/mm (7-μm gate–drain spacing) and 0.53 mΩ · cm2 and the gate-to-drain electric ?eld corresponds to 1.1 MV/cm.
关键词： high channel conductivity,high-voltage device,Si δ-doped AlGaN back barrier,GaN,Current collapse (CC)
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - Chennai (2018.3.22-2018.3.24)] 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - An Efficient Photonic-based Millimeter Wavelength Switching Techniques Towards 5G
摘要： Millimeter Waves (MMWs) operating at 30–300 GHz band, is very encouraging to the next-generation 5G wireless communication systems, supporting data rates of multiple Gbps per user. By using the Four Wave Mixing (FWM), Self-Phase Modulation (SPM) and Cross Phase Modulation (XPM) effects in the Semiconductor Optical Amplifier (SOA) and Erbium Doped Fiber Amplifier (EDFA), the photonic millimeter switching is realized. These effects can reduce the switching crosstalk since the Optical Single Sideband (OSSB) signal occupies the least optical bandwidth. The best operating conditions improve the Sideband Suppression Ratio (SSR) and at the same time reduce the intensity of unintended sideband signal. This leads to a dispersion-free transmission in the optical fiber and improves the data rate as required in 5G communication. In this paper, the wavelength switching of a 9 Gbps QPSK signal carried on the 30 GHz over a spacing of 1.6 nm as a function of probe wavelength of 1548.515 nm and pump wavelength of 1550.115 nm is achieved.
关键词： Millimeter Waves,Four Wave Mixing,Self Phase Modulation,Cross Phase Modulation,Erbium Doped Fiber Amplifier
更新于2025-09-23 15:22:29
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Polarity Control in Growing Highly Ga-doped ZnO Nanowires with Vapor-liquid-solid Process
摘要： Surface behavior modification by forming surface transparent conductive nanowires (NWs) is an important technique for many applications, particularly when the polarities of the NWs can be controlled. The polarities of Ga-doped ZnO (GaZnO) NWs grown on templates of different polarities under different growth conditions are studied for exploring a polarity control growth technique. The NWs are formed on Ga- and N-face GaN through the vapor-liquid-solid (VLS) process using Ag nanoparticles as growth catalyst. The NWs grown on templates of different polarities under the Zn- (O-) rich condition are always Zn (O) polar. During the early stage of NW growth, because the lattice sizes among different nucleation islands formed at the triple-phase line are quite different, high-density planar defects are produced when lateral growths from multiple nucleation islands form a GaZnO double-bilayer. In this situation, frequent domain inversions occur and GaZnO polarity is unstable. Under the Zn- (O-) rich condition, because the lateral growth rate of GaZnO in the Zn- (O-) polar structure is higher due to more available dangling bonds, the growth of Zn- (O-) polar structure dominates NW formation such that the NW eventually becomes Zn (O) polar irrespective of the polarity of growth template. Therefore, the polarity of a doped-ZnO NW can be controlled simply by the relative supply rates of Zn and O during VLS growth.
关键词： catalyst,Ga-doped ZnO nanowire,vapor-liquid-solid growth,triple-phase line,polarity
更新于2025-09-23 15:21:21
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Ferromagnetic Order in Substitutional Fe-doped In2O3 Powder
摘要： We report an experimental investigation of the room-temperature ferromagnetism of an Fe-doped In2O3 system. (In1?xFex)2O3(x = 0.00, 0.02, 0.06,0.10,0.14 or 0.18) powders were prepared by a standard solid-state reaction method followed by sintering in air at 1200 °C for 48h. The influence of Fe-doping concentration on the structural and magnetic properties of the In2O3 samples was studied. X-ray diffraction analysis reveals that Fe ions are incorporated into the In3+ sites of the In2O3 lattice without altering the cubic bixbyite structure. Magnetic characterization shows ferromagnetic behavior at room temperature for all the Fe-doped In2O3 samples. The observed ferromagnetism is attributed to the oxygen vacancies induced by substitution of Fe into In3+ sites and vacuum annealing. A model of ferromagnetic exchange interactions was proposed to explain the ferromagnetism in this system.
关键词： DMS,RTFM,Fe doped In2O3,Defects,Ferromagnetism
更新于2025-09-23 15:21:21
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Single Nickel Atoms Anchored on Nitrogen-Doped Graphene as a Highly Active Co-Catalyst for Photocatalytic H2 Evolution
摘要： Earth abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanoparticles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. In this research, we report single nickel atoms anchored on nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We have demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt.% of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst is 3.4 times greater than that of NG/CdS. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal based cocatalysts reported in literature. Photoluminescence spectral analyses and electrochemical examinations have indicated that Ni-NG coupled to CdS can serve not only as an electron storage medium to suppress electron-hole recombination, but also as an active catalyst for proton reduction reaction. Density functional theory calculation shows that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the activation energy barrier of the hydrogen evolution reaction. This approach may be valuable for developing robust and highly active noble-metal free cocatalysts for solar hydrogen production.
关键词： Non-noble Metal Cocatalyst,CdS,Photocatalytic Hydrogen Evolution,Nitrogen-Doped Graphene,Single Ni Atom Catalysts
更新于2025-09-23 15:21:21