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Surface improvement investigation of sol–gel SiO <sub/>2</sub> cladding for waveguide device passivation
摘要： The sol–gel method is a well-known process for SiO2 formation on top of a semiconductor-based waveguide. This method does not require expensive equipment or SiH4 gas. However, it may result in difficulty with wet-etching, which prevents proper current injection into the semiconductor layer. We have investigated the surface condition of sol–gel SiO2 on top of Si, and have confirmed that the main causes of the anti-etching property might be due to the formation of a polymer layer after the curing process. To improve the surface condition, plasma ashing, in addition to 700 °C curing, is proposed. Regular wet etching of SiO2 layer on Si with a ratio of 1800 nm min?1 has been successfully confirmed.
关键词： SiO2,waveguide passivation,plasma ashing,sol–gel method,polymer layer,wet etching
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Saturable Absorption with CNT Coupled WGM and Fabrication of Er-Doped Microresonator for on-Chip Mode-Locked Laser
摘要： Mode-locked (ML) fiber lasers are becoming key components in industry, because they provide high performance while being relatively inexpensive. The generation of high-repetition rate pulses is gaining interest but it remains a challenge to achieve a GHz repetition rate with fiber lasers. On the other hand, whispering-gallery-mode (WGM) microresonators allow the strong confinement of light and miniaturizing an ML laser into a WGM microresonator will enable us to achieve a high pulse repetition rate, a small footprint and on-chip integrability. In this work, we explore the possibility of a passive ML laser with the system shown in Fig. 1(a). There are two key technologies involved; one is saturable absorption (SA) and the other is laser gain in a microresonator. First, we verified numerically that we could realize an ML laser with our proposed carbon nanotube (CNT) coupled erbium (Er) doped microresonator, and the result is shown in Fig. 1(b). We modelled our system with a nonlinear Schr?dinger equation, where we took gain and SA (also loss (Q), Kerr effect, and dispersion) into account [2]. The result shows that a self-starting ML is possible with microresonator parameters. Next, encouraged by the numerical result, we experimentally demonstrated SA in a microtoroid. We grew CNTs selectively on a silica microtoroid by chemical vapor deposition and investigated the SA behavior (Fig. 1(c)). By performing a pump-probe like experiment we successfully characterized the SA behavior in a microresonator system. This is the first demonstration of SA in a WGM microcavity system [1]. We then fabricated an Er-doped active microtoroid by using the sol-gel method. The sol-gel method is one way of forming silica from a metal alkoxide precursor. Although sol-gel has been widely used, it is still a challenge to fabricate high-quality defect-free film on a Si wafer that allows us to fabricate an ultrahigh-Q WGM microresonator. Figure 1(d)-(f) shows the fabricated films. We found optimum parameters and obtained a clean film as shown in Fig. 1(g). By using this film, we fabricated an Er-doped WGM microresonator, where the Q was 1.2×106 at 1480 nm (Fig. 1(h)). We obtained clear up-conversion luminescence when we pumped the cavity at 1480 nm, which constitutes the first step towards ML lasing in such a WGM microresonator. In summary, these results provide a promising approach for realizing an on-chip high repetition rate ML WGM microresonator.
关键词： saturable absorption,sol-gel method,carbon nanotube,whispering-gallery-mode microresonators,erbium-doped microresonator,Mode-locked fiber lasers
更新于2025-09-11 14:15:04
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Multi-mode optical coded patterns enabled by upconversion nanoparticles and photonic crystals
摘要： The Al-Zr-ZnO films was deposited on the surface of n-Si (111) by sol-gel method. The results showed that the average grain size of Al-Zr-ZnO films decreases due to ion doping concentration. Based on XPS analysis, the surface defect oxygen of Al-Zr-ZnO films decreases. As for graphene/ Al-Zr-ZnO Schottky contact, barrier height increased and ideality factor decreased with the increasing of Al ion or Zr ion doping, indicating that the rectifying characteristics of graphene/Al-Zr-ZnO Schottky contacts was enhanced due to ion co-doping. It can be explained that oxygen vacancies of Al-Zr-ZnO films decreases due to the ion doping and weakens Fermi level pinning.
关键词： sol-gel method,Ion doping,Al-Zr-ZnO films,electrical properties,graphene
更新于2025-09-11 14:15:04
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CuZnSn(SxSe1-x)4 Solar Cell Prepared by the Sol-Gel Method Following a Modified Three-Step Selenization Process
摘要： In current work, Cu2ZnSn(S,Se)4 thin films have been prepared by the sol-gel method based on dimethyl sulfoxide solution followed by a modified three-step selenization process. The key process of this method is to divide the Se evaporation and annealing into two different stages: employ a thermal cracking Se source in the Se evaporation stage and an above-atmospheric pressure in the annealing process. The morphological, structural, elemental distributional, and photovoltaic properties of Cu2ZnSn(S,Se)4 thin films prepared with the three-step selenization process were systematically investigated. It was found that through this modified selenization process, the formations of secondary phases (ZnSe, CuSnSe3) and a fine-grain bottom layer, which usually exists in the traditional one-step selenization process, were effectively suppressed. These improvements could further reduce the carrier recombination and improve the solar cell performance. The best solar cell is obtained with a short-circuit current density of 28.16 mA/cm2, open-circuit voltage of 404.91 mV, fill factor of 62.91%, and a power conversion efficiency of 7.17% under air mass 1.5 (100 mW/cm2) illumination.
关键词： selenization,thermal cracking Se,CZTSSe solar cell,secondary phases,sol-gel method,above-atmospheric pressure
更新于2025-09-11 14:15:04
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Surface Treatment on Nickel Oxide to Enhance the Efficiency of Inverted Perovskite Solar Cells
摘要： The organic-inorganic hybrid perovskites such as CH3NH3PbI3 have been considered as one of the most promising candidates for the next-generation photovoltaic materials due to its high absorption coefficient, low exciton binding energy, and long diffusion length. Herein, we have chosen NiOx as the hole transport material because metal oxides exhibit robust properties in air. We synthesized the NiOx film by a common sol-gel method. It is found that high-temperature annealing (500°C) is required to ensure the perovskite solar cell (PSC) with an efficiency over 15%. Low-temperature annealing (100°C) cannot convert the precursor materials to fully covered NiOx film, while the PSC based on mediate-temperature annealing (300°C) NiOx has larger resistance and thus lower efficiency. Fortunately, we have found that UV-ozone treatment on the NiOx film can reduce the resistance of the device based on 300°C annealed NiOx. The champion device can reach 16% efficiency with UV-ozone-treated 300°C annealed NiOx. This work has made it possible to reduce the annealing temperature of the sol-gel NiOx for high-efficiency PSCs, and it is believed that this simple surface treatment can be further employed in other metal oxide-based optoelectronic devices.
关键词： perovskite solar cells,NiOx,annealing temperature,sol-gel method,UV-ozone treatment
更新于2025-09-11 14:15:04
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Preparation and Photocatalytic Properties of Sr2-xAxFeMoO6 (X = 0, 0.1; A = Li, Na, K)
摘要： In this paper, the sol-gel method is used to synthesize a series of double perovskite oxides Sr2FeMoO6 and Sr1.9A0.1FeMoO6 (A = Li, Na, K). The crystal structure was investigated by X-ray powder diffraction. The results show that all the as-synthesized samples have tetragonal crystal structure, small amount of substitution has little effect to the structure of Sr2FeMoO6 and they can keep double perovskite structure. Their photocatalytic activities were evaluated by degradation of dye acid black 10 B. The effects of the dosage of photocatalyst, irradiation time, irradiation source, initial concentration of dye solutions and alkali metal ions doping on the photocatalytic activity of samples were investigated. The results show that all the samples present high photocatalytic activities. In the dye concentration range of 20-150 mg/L, the decolorizing rate of acid black 10 B can reach above 95 % when the dosage of photocatalyst Sr2FeMoO6 is 100 mg under UV irradiation for 40 min. Moreover, the photocatalytic activity of Li-doped sample is lower than that of the un-doped sample, but the photocatalytic activity of the Na- or K-doped samples are much better than the un-doped sample and the decolorizing rate is nearly 100 %.
关键词： Photocatalytic performance,Sr2FeMoO6,Alkali metal doping,Sol-gel method,Decolorizing rate
更新于2025-09-11 14:15:04
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Effect of Annealing on Optical Properties of Zinc Oxide Thin Films Prepared by Homemade Spin Coater
摘要： Zinc oxide (ZnO) thin films were deposited on the ordinary glass substrates by spin coating method. The precursor solution was prepared by mixing zinc acetate dihydrate in appropriate proportions with ethanol and diethanolamine (DEA). The obtained thin films were dried at 200oC for 15 minutes in hot air oven. Crystalline ZnO thin films were achieved following annealing process at temperatures 300o, 400o and 500oC for 2 hours. Thin films as- prepared were studied by X-ray diffraction and UV-visible spectroscopy. The films were transparent from near ultraviolet to infrared region. Optical band gap energy of ZnO was obtained 3.22 eV at 300oC. On annealing at 400o and 500oC, band gap energy was shifted at 3.14 eV and 3.05 eV respectively.
关键词： annealing,absorption spectra,sol-gel method,zinc oxide,band gap energy
更新于2025-09-11 14:15:04
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Fabrication of Luminescent Antireflective Coatings with CaMoO4:Eu3+/Ag Composite Structure
摘要： Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an aluminum source in coating solutions, the sol–gel-derived films underwent a remarkable microstructural change during the hot water treatment due to the reaction between an amorphous alumina phase and water. This change brought both an antireflective effect (suppression of Fresnel reflection) and luminescence enhancement (suppression of total internal reflection) to the films. The introduction of Ag nanoparticles into the films further increased luminescence intensity without losing the antireflective effect.
关键词： calcium molybdate,silver nanoparticles,antireflective coatings,europium,nanocomposite,sol–gel method,photoluminescence
更新于2025-09-11 14:12:44
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Synthesis of Mesoporous TiO2/Boron-Doped Diamond Photocatalyst and Its Photocatalytic Activity under Deep UV Light (λ = 222 nm) Irradiation
摘要： There is a need for highly efficient photocatalysts, particularly for water purification. In this study, we fabricated a mesoporous TiO2 thin film on a boron-doped diamond (BDD) layer by a surfactant-assisted sol-gel method, in which self-assembled amphiphilic surfactant micelles were used as an organic template. Scanning electron microscopy revealed uniform mesopores, approximately 20 nm in diameter, that were hexagonally packed in the TiO2 thin film. Wide-angle X-ray diffraction and Raman spectroscopy clarified that the framework crystallized in the anatase phase. Current–voltage (I–V) measurements showed rectification features at the TiO2/BDD heterojunction, confirming that a p–n hetero-interface formed. The as-synthesized mesoporous TiO2/BDD worked well as a photocatalyst, even with a small volume of TiO2 (15 mm × 15 mm × c.a. 1.5 μm in thickness). The use of deep UV light (λ = 222 nm) as a light source was necessary to enhance photocatalytic activity, due to photo-excitation occurring in both BDD and TiO2.
关键词： photocatalyst,water purification,thin film,surfactant-assisted sol-gel method,p-n heterojunction,deep UV light,mesoporous metal oxide
更新于2025-09-10 09:29:36
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Preparation of core–shell nanostructured black nano-TiO <sub/>2</sub> by sol–gel method combined with Mg reduction
摘要： Black nano-TiO2 samples with core–shell nanostructure were successfully prepared by sol–gel method combined with Mg reduction using butyl titanate as titanium source and calcining at 500°C in air atmosphere and at 400–600°C in nitrogen atmosphere. The prepared black TiO2 samples were characterized by X-ray diffraction, high resolution transmission electron microscopy, Raman spectra, photoluminescence emission spectra, N2 adsorption–desorption, and ultraviolet–visible spectroscopy. The results show that the black TiO2 exhibits a crystalline core–disordered shell structure composed of disordered surface and oxygen vacancies, and the thickness of the disordered layer is about 2–3 nm. The optical absorption properties of black nano-TiO2 samples have been remarkably enhanced in visible light region. Compared with the white TiO2, the reduced black TiO2 samples exhibit enhanced photocatalytic hydrogen production under the full solar wavelength range of light, and the sample prepared with the Mg and TiO2 ratio of 9:1 calcined at 500 °C has the maximum hydrogen production rate.
关键词： core–shell nanostructure,Black nano-TiO2,photocatalytic hydrogen production,sol–gel method,Mg reduction
更新于2025-09-10 09:29:36