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Connecting Diffraction-Based Strain with Macroscopic Stresses in Laser Powder Bed Fused Ti-6Al-4V
摘要： The laser powder bed fusion (LPBF) production process often results in large residual stress (RS) in the parts. Nondestructive techniques to determine RS are badly needed. However, a reliable quantification of macro-RS (i.e., stress at the component level) by means of diffraction-based techniques is still a great challenge, because the link between diffraction-based strain and macro-RS is not trivial. In this study, we experimentally determine (by means of in-situ synchrotron radiation diffraction) this link for LPBF Ti-6Al-4V. We compare our results with commonly used models to determine the so-called diffraction elastic constants (DECs). We show that LPBF materials possess different DECs than wrought alloys, simply because their microstructural and mechanical properties are different. We also show that the existing models can be used to calculate DECs only if high accuracy of the RS values is not required. If the peculiarities of the microstructure have to be taken into account (as is the case of additively manufactured materials), a radically new approach is desirable.
关键词： synchrotron radiation diffraction,Laser powder bed fusion,residual stress,Ti-6Al-4V,diffraction elastic constants
更新于2025-09-23 15:21:01
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Growth of high purity zone-refined Boron Carbide single crystals by Laser Diode Floating Zone method
摘要： We report the growth of 4 mm diameter x 50 mm long Boron Carbide (B4C) with large single crystal regions using a Laser Diode Floating Zone (LDFZ) method at varying growth rates of 5-20 mm/hr. These materials were grown using polycrystalline B4C as a seed. Microstructural characterization shows the presence of a significant number of twinning-boundaries along the growth direction ([001]h) oriented in the (1210)h plane. At faster growth rates >10 mm/hr, the crystal orientation was reproducible, suggesting a twin-plane mediated growth mechanism. On the contrary, at slower growth rates <10 mm/hr the crystal orientation was not reproducible, suggesting a critical rate for twin-plane mediated growth to dominate. Zone refinement of these crystals led to a significant reduction of trace impurities to better than 99.999 wt % purity, at the expense of increased twinning. Powder x-ray diffraction confirms that the bulk is rhombohedral B4C, consistent with the microstructural analysis. The X-ray reciprocal space maps reveal the growth direction to be close to the [001]h direction, and the corresponding ω-rocking curve width is ~530arcsec. The rocking curve consisted of 3 distinct peaks, indicating in-plane mosaicism, consistent with the twinning observed. Berkovich nano-indentation of the key (001)h plane showed 41 ± 1 GPa hardness, with a Young’s modulus of 520 ± 14 GPa, comparable to literature reports.
关键词： A2. Single crystal growth,A1. Defects,A1. X-ray diffraction,A1. Characterization,A2. Growth from melt
更新于2025-09-23 15:21:01
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Self-assembled indium nanostructures formation on InSe (0001) surface
摘要： The surfaces of 2D layered crystals are one among most perspective templates for self-assembling of metal nanostructures due to the dewetting. The initial InSe (0001) surface as topological template was characterized by means of scanning tunneling microscopy/spectroscopy (STM/STS) and low electron energy diffraction. InSe (0001) surface used in the process of formation of nanostructures found to be a template covered with array of triangular-shaped cites. The results of STM/STS studies on the formation of indium nanostructures on (0001) surface of InSe layered semiconductor crystal are presented. Indium was thermally deposited on structurally perfect InSe crystal cleavages obtained in situ. Geometrically heterogeneous (in height) initial (0001) InSe surface is used to activate the dewetting phenomenon in a manner that leads to the formation of 0D triangular-shaped nucleus of deposited indium nanostructures. STS acquired spatially averaged I–V curves changes their dependence from semiconductor one to almost metallic due to dewetting process. Moreover, the spatial arrangement of formed indium nanostructures is powered by hexagonal lattice symmetry of InSe surface on macroscale.
关键词： Hetero nanostructures,Nanostructures template-directed assembly,Layered crystals,Scanning tunneling microscopy/spectroscopy,Indium selenide,Low energy electron diffraction
更新于2025-09-23 15:21:01
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Growth and investigation on novel single crystal of ?2-cyclodextrin 2, 4-dinitrophenylhydrazine for optical sensors applications
摘要： Nonlinear optical (NLO) 2, 4-Dinitrophenylhydrazine (DNPH) single crystal was grown by slow evaporation solution growth method at ambient temperature. The characterization of Powder X – Ray diffraction peaks was con?rmed the new crystalline system. Fourier transform infrared spectroscopic analysis (FTIR) was used to the identi?cation of various functional groups present in the grown crystal. The range of optical transmittance exhibited by the grown bCD-DNPH crystal was investigated by UV Visible – NIR spectral analysis. The lower cut off wavelength of the grown crystal is observed at 270 nm. The SEM ?gures are recorded in different magni?cation. It is clear that the surface of the grown crystal appears very smooth although it has pots and microcrystal on the surface. The grain boundaries are clearly seen which shows the perfect growth of the crystal. The weight percentage (wt %) of C, N and O as obtained from EDAX analysis is in concurrent with the theoretical values. The SHG ef?ciency of the grown crystal was determined.
关键词： Optical properties,X-ray diffraction,Crystal growth
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Method of Controlling the Micro-and Nanoscale Displacements Based on Optical Correlation
摘要： The formation of a complex ?eld in an optical correlator consisting of a set of phase gratings separated by layers of space is investigated. We found conditions when the redistribution of intensities in the output diffraction orders in such a correlator is very sensitive to a small transverse shift of the input interference pattern of light. Registration of changes in the angular spectrum can be used as an effective sensor to monitor small displacements, including the nanoscale range.
关键词： phase gratings,angular spectrum,optical correlator,sensor of small displacements,intensity control in diffraction orders
更新于2025-09-23 15:21:01
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Microstructure characteristics of non-monodisperse quantum dots: On the potential of transmission electron microscopy combined with X-ray diffraction
摘要： Although the concept of quantum confinement was introduced more than thirty years ago, a wide application of the quantum dots is still limited by the fact that monodisperse quantum dots with controlled optoelectronic properties are typically synthesized on a relatively small scale. Larger scale synthesis techniques are usually not able to produce monodisperse nanoparticles yet. In this contribution, we illustrate the capability of the combination of transmission electron microscopy and X-ray diffraction to reveal detailed and scale-bridging information about the complex microstructure of non-monodisperse quantum dots, which is the first step towards a further upscalling of the techniques for production of quantum dots with controlled properties. As a model system, CdSe quantum dots synthesized using an automated robotic hot-injection method at different temperatures were chosen. The combined microstructure analytics revealed the size and shape of the CdSe nanocrystals and the kind, density and arrangement of planar defects. The role of the planar defects in the particle coarsening by oriented attachment and the effect of the planar fault arrangement on the phase constitution, on the crystallographic coherence of the counterparts and on the optoelectronic properties are discussed.
关键词： microstructure,optoelectronic properties,planar defects,transmission electron microscopy,X-ray diffraction,quantum dots,oriented attachment,CdSe
更新于2025-09-23 15:21:01
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High Responsivity Visible Blind Pd/Al2O3/MoS2/ITO MISM UV Photodetector
摘要： In the present paper, Pd/Al2O3/MoS2/ITO MISM UV photodetector structure is proposed and analyzed. For the proposed photodetector, responsivity is 488 A/W, detectivity is 8.22×1013Jones and external quantum efficiency (EQE) is 1.9×105%, at wavelength 308nm, 1V bias and light intensity 13.6μW/cm2. Thus, proposed MISM photodetector device gives significant performance improvement over other UV photodetectors.
关键词： Molybdenum di-sulphide (MoS2),Responsivity,Photodetector,X-ray diffraction (XRD)
更新于2025-09-23 15:21:01
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CMOS Nanophotonic Sensor with Integrated Readout System
摘要： The measurement of nanophotonic sensors currently requires the use of external measuring equipment for their read-out such as an optical spectrum analyzer, spectrophotometer, or detectors. This requirement of external laboratory-based measuring equipment creates a 'chip-in-a-lab' dilemma and hinders the use of nanophotonic sensors in practical applications. Making nanophotonic sensors usable in everyday life requires miniaturization of not only the sensor chip itself but also the equipment used for its measurement. In this paper, we have removed the need of external measuring equipment by monolithically integrating 1-D grating structures with a complementary metal-oxide-semiconductor (CMOS) integrated circuit having an array of photodiodes. By doing so, we get a direct electrical read-out of the refractive index changes induced when applying different analytes to grating structures. The gratings are made of CMOS compatible silicon nitride. Employing a nanophotonic sensor made of CMOS compatible material allows fabrication of the integrated sensor chip in a commercial CMOS foundry, enabling mass production for commercialization with low cost. Our results present a significant step toward transforming present laboratory-based nanophotonic sensors into practical portable devices to enable applications away from the analytical laboratory. We anticipate the work will have a major impact on technology for personalized medicine, environmental, and industrial sensing.
关键词： Diffraction gratings,nanophotonics,photodetectors,optoelectronics,sensors
更新于2025-09-23 15:21:01
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Effect of Surface Plasmon Resonance on the Anomalous Result of Young’s Double-Slit Experiment with a Metal Screen
摘要： An abnormal result of Young’s classic experiment with two slits in a metal screen is discussed, in which the appearance of a light spot behind a screen located centrally between the images of the slits is unusual. It is shown that the anomaly is caused by plasmon resonance in the metal–dielectric structure. The intensity of the diffraction pattern is calculated. Under resonance conditions, it overcomes the diffraction limit.
关键词： Young’s double-slit experiment,metal screen,diffraction limit,plasmon resonance
更新于2025-09-23 15:21:01
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Determination of Phonon Deformation Potentials in Carbon-Doped Silicon
摘要： Carbon-doped silicon (Si:C) is used as a stressor to the channel of n-type metal oxide semiconductor field-effect-transistor (MOSFET). In this study, we determined PDPs, phonon deformation potentials, (p and q) of Si:C to realize evaluation of anisotropic biaxial stress by using water-immersion Raman spectroscopy. Raman peak shift in longitudinal and transverse optical (LO and TO) phonon modes were measured by water-immersion Raman spectroscopy. Furthermore, in-plane and out-of-plane strain were measured by X-ray diffraction (XRD). Based on the Raman shift and the in-plane strain, p and q in each sample were derived. As a result, it took a different value from pure-Si, and the PDPs tended to increase as the C concentration increased.
关键词： phonon deformation potentials,strain evaluation,Carbon-doped silicon,X-ray diffraction,water-immersion Raman spectroscopy
更新于2025-09-23 15:21:01