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Near-Net Shaping Control of Triangular Stacking in Laser Cladding Process
摘要： Fabrication of complex parts with irregular geometric cross-section can be realized through precise control of triangular stacking in laser cladding process. This paper deals with the optimization of overlapping ratio and scanning strategy in order to obtain near-net shaping parts. First, multi-track overlapping surface formation mechanisms and surface flatness evaluation method are described. Then, the effects of overlapping ratio and scanning strategy on surface flatness are investigated and optimized. Afterwards, the formation of triangular stack under the optimized parameters are evaluated in terms of accuracy and metallographic aspects. The results show that the minimum flatness occurred when the overlapping ratio is about 20 %. Changing the scanning sequence from left-to-right to center-to-sides can help reduce the negative effects caused by the accumulated heat during the material deposition process, thereby improving the performance efficiency of the cladding.
关键词： Overlapping,Shaping Control,Triangular Stacking,Laser Cladding,Surface flatness
更新于2025-09-12 10:27:22
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Atomic-scale quantitative analysis of implanted Mg in annealed GaN layers on free-standing GaN substrates
摘要： Achieving efficient p-type conduction in Mg-implanted GaN depends largely on postimplantation annealing conditions. Here, we study the effect of postimplantation annealing on the evolution of defects and their interactions with implanted Mg ions by using scanning transmission electron microscopy and atom probe tomography. We found that Mg clusters start to form by annealing the implanted sample above 1000 °C. In addition to the Mg clusters, stacking faults form at an annealing temperature of 1300 °C. The Mg concentrations of about 2–3 orders of magnitude higher than implanted Mg were segregated at the stacking faults. Nanobeam electron diffraction analysis revealed no distinct phase other than GaN formed at the Mg-enriched defects, suggesting that Mg is substituted for Ga in the GaN lattice at the edge of the stacking faults.
关键词： stacking faults,Mg clusters,postimplantation annealing,scanning transmission electron microscopy,Mg-implanted GaN,atom probe tomography
更新于2025-09-12 10:27:22
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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) - Spin-Layer- and Spin-Valley-Locking Due to Symmetry in Differently-Stacked Tungsten Disulfide Bilayers
摘要： The coupling of the spin and valley degrees of freedom and valley-selective optical selection rules in transition-metal dichalcogenides (TMDCs) monolayers (ML) has been a major research topic in recent years. In contrast, valleytronic properties of TMDC bilayers have not been in the focus so much by now. In our contribution, we study the effect of the relative layer alignment in TMDC homo-bilayer samples on their polarization-dependent optical properties. To this end, CVD-grown WS2 bilayer samples have been prepared that during synthesis favour either the inversion symmetric AA’ or AB stacking without inversion symmetry. For the optical studies, the bilayer samples were transferred either onto a bare SiO2 or a few-layer h-BN buffer. To verify the difference in symmetry for these bilayer configurations, second-harmonic-generation (SHG) raster-scans have been performed, confirming inversion symmetry for the AA’ configuration. Subsequently, a detailed analysis of reflection contrast and photoluminescence (PL) spectra under different polarization conditions has been performed. In photoluminescence, we find a circular and linear dichroism for both stacking configurations that is more pronounced for the AB stacked sample. Furthermore, a lifting of degeneracy and a small shift (~10 meV) of the excitons for different stacks relative to each other is found. Amended theoretical calculations based on our recently developed approach combining density-functional theory (DFT), the gap equations (GE) and the Dirac-Bloch equations (DBE), show that the spin–valley locking is maintained in the AB-stacked WS2 bilayer, whereas the inversion symmetric AA’ bilayer shows a spin–layer-locking instead. Differences in the optical selection rules together with the substrate dependent renormalizations lead to the observed dichroism. Furthermore, the observed lifting of the degeneracy between different stacking configurations is confirmed by theory.
关键词： spin-valley locking,optical properties,transition-metal dichalcogenides,bilayer stacking,spin-layer-locking
更新于2025-09-12 10:27:22
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Stacking Order in Graphite Films Controlled by Van der Waals Technology
摘要： In graphite crystals, layers of graphene reside in three equivalent, but distinct, stacking positions typically referred to as A, B, and C projections. The order in which the layers are stacked defines the electronic structure of the crystal, providing an exciting degree of freedom which can be exploited for designing graphitic materials with unusual properties including predicted high-temperature superconductivity and ferromagnetism. However, the lack of control of the stacking sequence limits most research to the stable ABA form of graphite. Here we demonstrate a strategy to control the stacking order using van der Waals technology. To this end, we first visualise the distribution of stacking domains in graphite films and then perform directional encapsulation of ABC-rich graphite crystallites with hexagonal boron nitride (hBN). We found that hBN-encapsulation which is introduced parallel to the graphite zigzag edges preserves ABC stacking, while encapsulation along the armchair edges transforms the stacking to ABA. The technique presented here should facilitate new research on the important properties of ABC graphite.
关键词： domains,Van der Waals assembly,zigzag,stacking order,rhombohedral graphite
更新于2025-09-11 14:15:04
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A GA-based stacking algorithm for predicting soil organic matter from vis-NIR spectral data
摘要： It has been demonstrated that diffuse reflectance spectroscopy in the visible and near-infrared (vis–NIR) can be exploited to predict chemical and physical soil properties. Immense soil spectral libraries (SSL) are being developed, therefore more elaborate tools that capitalize on contemporary knowledge and techniques need to be established to provide accurate predictions. In this paper, we propose a novel genetic algorithm-based stacking model that makes synergetic use of multiple models developed from different pre-processed spectral sources (termed L1 models). This is a form of ensemble learning where multiple hypotheses are combined to create a more robust and more accurate ensemble hypothesis. The genetic algorithm automatically defines the configuration of the stacked model, by selecting the best cooperating subset of the initial models. Our methodology was tested on the newly developed GEO-CRADLE SSL to predict soil organic matter (SOM). Results showed that the accuracy of prediction of the proposed method ( =0.76, and ratio of performance to inter quartile range RPIQ=2.22) was better than the one attained by the best L1 model ( =0.65, RPIQ=1.93). This approach can thus be effectively utilized to enhance the predictions of soil properties in small and large soil spectral libraries alike.
关键词： model stacking,North Africa,GEO-CRADLE,vis–NIR spectroscopy,soil spectroscopy,Middle East,Balkans
更新于2025-09-10 09:29:36
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Effect of stacking faults and surface roughness on the thermal conductivity of InAs nanowires
摘要： Low thermal conductivity and high power factor are desirable for thermoelectric materials. These properties can be achieved by patterning devices into nano-structures such as nanowires (NWs). The thermal conductivity can be further reduced by altering the NW geometry through the introduction of surface roughness (SR) or stacking faults (SFs). In this paper, relaxation times for scattering of phonons at SFs and SR are developed to accurately compute the impact of both effects on the thermal conductivity of InAs NWs with different diameters. It is found that similar reductions of the thermal conductivity can be obtained with SFs instead of SR. For the shortest possible distance between SFs along a NW, the room temperature thermal conductivity can be reduced to 25% compared to an ideal NW. For a NW with rough surface, a more than 80% decrease of the thermal conductivity is possible for specific roughness profiles. All available experimental data on the lattice thermal conductivity of InAs NWs confirm the theoretical models and simulation results.
关键词： surface roughness,thermal conductivity,phonon scattering,stacking faults,InAs nanowires
更新于2025-09-10 09:29:36
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Inducing defects in 3.3 kV SiC MOSFETs by annealing after ion implantation and evaluating their effect on bipolar degradation of the MOSFETs
摘要： Process-induced basal plane dislocations (BPDs) formed by annealing after aluminum ion implantation were investigated, and their effect on the bipolar degradation of body diodes in 3.3 kV SiC MOSFETs was evaluated. Contact resistance in the p+ region decreases with ion dose but increases with implantation temperature due to the formation of the recrystallized layer at SiC surface and difference of acceptor activation rates in high and low temperature implantation. In the case of high ion dose implantation at room temperature, contact resistance was of 1.3×10?3 Ωcm2. However, process-induced BPDs formed with high ion dose implantation at room temperature, and could be suppressed with low ion dose or high implantation temperature. They were formed after activation annealing, and expanded to form stacking faults (SFs) under both continuous irradiation from a Hg lamp and current stress. Bipolar degradation occurred in the case of MOSFETs fabricated using high ion dose implantation at room temperature, but was not observed in the case of either low ion dose or high implantation temperature. The activation energy for SF expansion velocity in the ?1–100? direction was estimated to be 0.20 eV at a forward current density of 125 A cm?2. Moreover, the results of a long duration current stress test with high current density and high junction temperature indicate that low ion dose or high implantation temperature can suppress the formation of process-induced BPDs. MOSFETs fabricated using optimized ion implantation conditions show high reliability under bipolar operation.
关键词： MOSFET,bipolar degradation,stacking fault,contact resistance,basal plane dislocation,SiC,ion implantation
更新于2025-09-09 09:28:46
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Molybdenum Disulfid: Differentiating Polymorphs in Molybdenum Disulfide via Electron Microscopy (Adv. Mater. 47/2018)
摘要： The presence of rich polymorphs and stacking polytypes in molybdenum disulfide (MoS2) endows it with a diverse range of properties. This has stimulated a lot of interest in the unique properties associated with each polymorph. In article number 1802397, Kian Ping Loh and co-workers discuss the use of electron microscopy for identifying the atomic structures of several important polymorphs in MoS2 and establishing the correlation between structure and properties.
关键词： polymorphs,electron microscopy,stacking polytypes,molybdenum disulfide,MoS2
更新于2025-09-09 09:28:46
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Deciphering the multifarious charge transport behaviour of crystalline propeller-shaped triphenylamine analogues
摘要： A collection of para-substituted propeller-shaped triphenylamine (TPA) derivatives have been computationally investigated for the charge transport characteristics exhibited by the derivatives using the Marcus-Hush formalism. The various substituents chosen in the current work, having features that range from electron withdrawing to electron donating nature, play a key role in defining the reorganization energy and electronic coupling properties of the TPA derivatives. TPA moiety is expected to possess weak electronic coupling on the basis of poor orbital overlap upon aggregation owing to the restriction imposed by the propeller shape of the triphenylamine core. However, the substituent groups attached to the TPA core can significantly dictate the crystal packing motif of the TPA derivatives, wherein the variety of noncovalent intermolecular interactions subsequently generated drive the packing arrangement and influence the electronic coupling between the neighbouring orbitals. The intermolecular interactions in the crystalline architecture of TPA derivatives were probed using Hirshfeld and QTAIM techniques. Furthermore, SAPT analysis of the TPA analogues has revealed that a periodic arrangement of energetically stable dimers having significant electronic coupling is essential in order to contribute a high charge carrier mobility to the overall crystal.
关键词： SAPT,Pi stacking,1-D charge transport pathway,Marcus-Hush formalism,Substituent effect
更新于2025-09-09 09:28:46
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39.3: The LCD Technology Development and Application with an Improved Black Photo Spacer Structure
摘要： A novel Black Photo Spacer (BPS) structure is demonstrated in this present work. The black BPS material supports the substitution of black matix (BM) to realize shading function. Thus the BPS technology can integrate BM into PS process, which saves the material, mask, machine and time cost. In order to improve stability, we use full tone mask design. Different height (ΔH) of Main PS and Sub PS are generated by color filter stacking. Polymer film on array (PFA) is used to reduce the excessive primary height between Main PS and Sub PS. In addition, all the patterns included color filter, BM and PS are on array side, which can effectively avoid the backlight leakage and enhance contrast ratio (CR). More discussions of the designs, process and optical performances about 1-tone BPS such as Data line BM less (DBS) are demonstrated in this paper, and a 28 inch demon with this BPS technology is shown at the end.
关键词： 1-tone mask,BPS,DBS,color stacking,PFA
更新于2025-09-09 09:28:46