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Impact of Al2O3 stress liner on two-dimensional SnS2 nanosheet for photodetector application
摘要： Layered tin disulfide (SnS2) nanosheets are gradually coming into people’s vision as an emerging two-dimensional material for the potential application majority in optoelectronic field. We investigate a sample of ultra-thin SnS2 nanosheets (~5 nm) on SiO2/Si substrates and the photodetectors performance based on it with and without high-k ALD-Al2O3 stress liner. By means of temperature-dependent Raman spectroscopy, both a red-shift of Raman frequency from 313.1 cm-1 to 311.2 cm-1 as well as a reduction of the first order temperature coefficient from -0.01232 cm-1/K to -0.00895 cm-1/K are measured. For device, compared to SnS2 photodetector, Al2O3/SnS2 photodetector shows enhancement with 7-times light current, 10-times responsivity, 25%-off rising time and 70%-off falling time under 365 nm illumination. The phenomena can be rationalized by factors that the SnS2 sample suffers a tensile strain and passivation effect exerted by capped Al2O3 layer. Meanwhile, the first principle calculations assist the study from an angle of verification. The analogue stress treatment operated in this work improves the properties of SnS2 and enhances the performances of SnS2-based photodetectors, aiming at expanding the thin-film materials applications in optoelectronic devices.
关键词： Al2O3 stress liner,Photodetector,SnS2,Raman spectroscopy
更新于2025-09-23 15:19:57
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The effect of spot overlap ratio on femtosecond laser planarization processing of SiC ceramics
摘要： Silicon carbide ceramics are widely used in many fields owing to their excellent mechanical properties such as good wear resistance, thermal stability, and chemical corrosion resistance. The laser planarization processing can effectively achieve the functional, practical, and engineering process, satisfying the demands of the assembly precision. Therefore, different spot overlap ratios were utilized to investigate the effect of femtosecond laser planarization processing on silicon carbide ceramic samples. Various scanning speeds and laser repetition frequencies were matched to achieve different spot overlap ratios under the premise of fixed laser incident angle and single pulse energy. Under different parameters, the ablation depth, surface roughness, surface morphology, oxidation, and residual stress were compared. The result showed that at the same spot overlap ratio, the ablation depth and surface roughness are basically maintained at a stable value despite the difference in the scanning speed and repetition rate. The surface oxidation phenomenon remarkably decreased at the spot overlap ratio less than 90%. The decrease in the overlap ratio leads to the transition of the low frequency nano-ripple and the high frequency nano-ripple, and the surface residual stress converted from tensile stress to compressive stress. Combining processing requirements with ablation quality, the parameters are divided into three parts to fit three processes based on the spot overlap ratios. The variation in the spot overlap ratios as the guidelines had good potential in guiding the parameter range selection.
关键词： Residual stress,Spot overlap ratios,Femtosecond laser,Silicon carbide ceramics,Planarization processing
更新于2025-09-23 15:19:57
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Transformation of a liquid electrolyte to a gel inside dye sensitized solar cells for better stability and performance
摘要： A gel electrolyte based on a metal-organic framework (MOF), comprised of Al3+ and trimesic acid, was used in dye-sensitized solar cells. The electrolyte was gelated inside the solar cell to ensure the best interfacial connection between the TiO2 photoanode and electrolyte ingredients. The photovoltaic performance of the solar cells showed that the gel has a good ability to preserve the function of liquid electrolytes. By optimizing the ratio of MOF and liquid electrolyte, the current density was improved, which was due to the increase in the redox couple I-/I3- content in the gel electrolyte. The open-circuit voltage was affected because of the change in the conduction band of TiO2 by the introduction of Al3+ ions and also because of electron recombination. Thus, a slightly higher efficiency was achieved using the gel electrolyte compared to the liquid electrolyte based cells. A superior stability was achieved with the MOF gel electrolyte under thermal stress at 60 °C for 250 h, while the efficiency of cells with liquid electrolyte deteriorated continuously under the same conditions. The drop in efficiency in the liquid electrolyte cells, was 24%, compared to only a 6% drop in the MOF gel electrolyte cells.
关键词： Stability,Metal organic framework,Dye sensitized solar cells,Thermal stress,Gel electrolyte
更新于2025-09-23 15:19:57
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[IEEE 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Bhopal, India (2019.12.19-2019.12.21)] 2019 Sixteenth International Conference on Wireless and Optical Communication Networks (WOCN) - Palm print Recognition Using Neighboring Direction Indicator
摘要： An electroless plating of Co–Ni–P was applied to a grain-oriented electrical steel substrate, resulting in a power loss improvement of ～9%–11%. The mean thickness of the coating was found to be 2.15 ± 0.15 μm from environmental scanning electron microscopy images. Shifts of the magnetostriction stress sensitivity curves showed that stress was acting on the substrate and was corroborated by a shift in X-ray diffraction (XRD) peaks and narrowing of the domains after the samples were coated. The magnetic property measurement system results con?rmed the magnetic nature of the coating and XRD results showed peaks of α-iron in the uncoated sample, α-iron-cobalt and α-iron in the Co-Ni-P-coated sample. The Talysurf pro?lometer showed a decrease in surface roughness values after coating the sample, which reduced the hysteresis loss.
关键词： magnetic coating,power loss,grain-oriented electrical steel,stress,Electroless coating,magnetostriction
更新于2025-09-23 15:19:57
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633-nm InGaN-based red LEDs grown on thick underlying GaN layers with reduced in-plane residual stress
摘要： This work investigates the in?uence of residual stress on the performance of InGaN-based red light-emitting diodes (LEDs) by changing the thickness of the underlying n-GaN layers. The residual in-plane stress in the LED structure depends on the thickness of the underlying layer. Decreased residual in-plane stress resulting from the increased thickness of the underlying n-GaN layers improves the crystalline quality of the InGaN active region by allowing for a higher growth temperature. The electroluminescence intensity of the InGaN-based red LEDs is increased by a factor of 1.3 when the thickness of the underlying n-GaN layer is increased from 2 to 8 lm. Using 8-lm-thick underlying n-GaN layers, 633-nm-wavelength red LEDs are realized with a light-output power of 0.64 mW and an external quantum ef?ciency of 1.6% at 20 mA. The improved external quantum ef?ciency of the LEDs can be attributed to the lower residual in-plane stress in the underlying GaN layers.
关键词： InGaN,n-GaN layers,residual stress,red LEDs,electroluminescence
更新于2025-09-23 15:19:57
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Numerical analysis of the effect of the scan strategy on the residual stress in the multi-laser selective laser melting
摘要： The inevitably formed residual stress in the Selective Laser Melting (SLM) process leads to distortion, crack and even delamination of the workpiece. Single laser is commonly applied during SLM processing. However, its productivity is much lower than multiple lasers. In addition, the research of residual stress with multi-laser condition currently is limited in the open documents. In this paper, a three-dimensional (3D) thermo-mechanical model, with considerations of temperature dependent properties of Ti-6Al-4V, phase change and convective flow, is developed at first. Then, the numerical results of maximum temperature and dimensions of the molten pool are validated by available experimental data. Furthermore, a parametric study in regards to a series of scan strategies is investigated. According to the simulation results, the residual stress increases significantly when the laser number reaches four. The “two-zone technique” scan strategy decreases the equivalent residual stress by 10.6% compared to the successive scan strategy. With a shortening scan length, the residual stress first increases slightly, then decreases dramatically and attains the minimum when it is a quarter. Furthermore, for the multi-laser SLM process, carefully planning the scanning sequence and the sweeping direction to decrease heat concentration is beneficial in controlling the residual stress.
关键词： Scan strategy,Thermo-mechanical model,Residual stress,Selective laser melting,Multi-laser
更新于2025-09-23 15:19:57
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On the application of laser shock peening for retardation of surface fatigue cracks in laser beam-welded AA6056
摘要： The present study aims to investigate the extent to which the fatigue behaviour of laser beam-welded AA6056-T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as-welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as-welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing.
关键词： fatigue crack,aluminium alloys,laser beam welding,ultrasonic crack tip diffraction,residual stress,laser shock peening
更新于2025-09-23 15:19:57
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Fatigue Life of Materials Strengthened by Laser Shock Processing
摘要： The influence of the thickness of 03Х22Н6М2 stainless steel samples strengthened by laser shock processing on their fatigue life is investigated by finite-element modeling. This technology is found to increase the fatigue life of thin (2 mm) samples more than threefold.
关键词： finite-element modeling,fatigue life,residual stress,laser shock processing
更新于2025-09-23 15:19:57
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Coupling characteristics of the spun optical fiber with multiple stress elements
摘要： Possible coupling between fundamental modes and higher order modes in a spun optical ?ber with multiple stress elements is analyzed. It shows that only the higher order HEmn mode with the opposite circular polarization state can be coupled with the fundamental HE11 mode. The coupling between the fundamental HE11 mode and the TE, TM or EH modes can never be occurred. In the possible coupling between HEmn mode and HE11 mode, m should be equal to N-1, where N is the number of the stress elements. As a comparison, the coupling property in a spun optical ?ber with single stress element is also demonstrated. In this case, the fundamental HE11 mode can not only be coupled with the higher orderHE2n mode but also can be coupled with the higher order TE mode.
关键词： Coupling characteristics,Polarization,Stress elements,Spun optical fiber,Optical fiber
更新于2025-09-23 15:19:57
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Dimensional Deviation Management for Selective Laser Melted Ti6Al4V Alloy Blade
摘要： This article presents a systematically study through experimental and theoretical methods to better understand the mechanism of the geometric deformation produced during selective laser melting (SLM) treatment of the Ti6Al4V blade. Ti6Al4V blade was prepared by SLM. Microstructure, dimensional deviation and residual stress were investigated. The microstructure observation illustrates that the acicular α(cid:48) martensite formed in prior β grain, in addition, the smaller the grain size, the larger the dimensional deviation. The geometric deviation demonstrates that the directions of dimensional deviation at the leading and trailing edges of the blade are opposite to those in the middle. The distribution of dimensional deviation exhibits a parabolic change at the trailing edge of blade. The thermal stresses along the edges are much larger than that of the blade body, which cause the severe deformation of the edges toward the suction side of the blade. This conclusion is further veri?ed by the XRD method. The residual stress distribution measured through X-ray diffraction is consistent with the simulation results.
关键词： microstructure,dimensional deviation,residual stress,thermal elasto-plastic theory,selective laser melting
更新于2025-09-23 15:19:57