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Electron-phonon anharmonicity and low thermal conductivity in phosphorous chalcogenide ferroelectrics
摘要： The dependence of thermal conductivity with temperature has been studied for Sn(Pb)2P2S(Se)6 ferroelectrics-semiconductors, showing an ultra-low (0.5 W/m K) thermal conductivity above 250 K and the possibility to tune it at lower temperatures playing with the dopant concentration. This behavior has been explained taking into account the combination of different physical mechanisms: hopping heat conductivity in a lattice with strong electron-phonon anharmonicity linked to the stereoactivity of tin and lead cations electron lone pairs together with valence fluctuations in P2S(Se)6 groups. Besides, the presence of an incommensurate phase in the more covalent compounds, the location of tricritical points near 250 K and the peculiarities of the chemical bonding have all been correlated with the experimental behavior observed.
关键词： Ferroelectricity,Bonding,Thermal Conductivity,Structure–Property Relationship,Temperature Dependence
更新于2025-09-09 09:28:46
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Physical Properties, Ligand Field and Judd-Ofelt Intensity Parameters of Bio-silicate Borotellurite Glass System Doped with Erbium Oxide
摘要： A glass series containing bio-silicate borotellurite (BSBT) doped with erbium oxide with composition of {[(TeO2)0.8 (B2O3)0.2]0.8 (SiO2)0.2}1-y (Er2O3)y, y= 0.01, 0.02, 0.03, 0.04, 0.05 mol fraction were fabricated using the melt quenching technique. In this glass composition, the bio-silicate was extracted from the rice husk. The X-ray fluorescence (XRF), X-ray diffraction (XRD), molar volume, density, optical absorption and luminescence properties and excitation of the glass sample were investigated. Result of x-ray diffraction (XRD) confirmed the amorphous nature of the glass. The X-ray fluorescence (XRF) verified the achievement of 98.6% of silicate from rice husk. The density is found to be increasing from 3.845 g/cm3 to 4.142 g/cm3 with the increase in the concentration of Er3+. The molar volume is also found to be increasing with concentration of Er3+, but later decreases at 0.04 and 0.05 mol fraction of erbium. The decrease may be due to the tightly packed atom giving rise to a denser glass. The obtained values of the Racah parameters are derived from the absorption spectra region with higher energy. The bonding parameters are found to increase with the increase in the concentration of Er3+ from 0.002789 to 0.002835 while the Racah parameters and nephelauxetic ratio decreased. The increase in crystal field strength also shows a strong field sites. The Judd-Ofelt (J-O) intensity parameters are derived from the UV-Vis spectra and the results showed ?2>?4>?6 trend with the exception of Erbium at 0.04 mol fraction which showed ?2>?6>?4 trend. The appearance of higher values of ?2 and ?6 indicate the presence of a stronger covalency and lower symmetry around Er3+ ions. MacCumber theory was used to determine the stimulated emission cross section from the calculated absorption cross section for 4I13/2 to 4I15/2 transition. The glass displayed intense green and a week red emission under 380 nm excitation. The width of the gain is found to shift towards the shorter wavelength which proves that this glass system is a good material for photonics and laser applications.
关键词： Bio-silicate,Bonding parameters,Judd-Ofelt,emission cross section,Luminescence
更新于2025-09-09 09:28:46
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Evidence of Pure Spin-Current Generated by Spin Pumping in Interface Localized States in Hybrid Metal-Silicon-Metal Vertical Structures
摘要： Due to the difficulty to grow high quality semiconductors on ferromagnetic metals, the study of spin diffusion transport in Si was only limited to lateral geometry devices. In this work, by using ultra-high vacuum wafer-bonding technique, we have successfully fabricated metal-semiconductor-metal CoFeB/MgO/Si/Pt vertical structures. We hereby demonstrate pure spin-current injection and transport in the perpendicular current flow geometry over a distance larger than 2μm in n-type Si at room temperature. In those experiments, a pure propagating spin-current is generated via ferromagnetic resonance spin-pumping and converted into a measurable voltage by using the inverse spin-Hall effect occurring in the top Pt layer. A systematic study by varying both Si and MgO thicknesses reveals the important role played by the localized states at the MgO/Si interface for the spin-current generation. Proximity effects involving indirect exchange interactions between the ferromagnet and the MgO/Si interface states appears to be a prerequisite to establish the necessary out-of-equilibrium spin-population in Si under the spin-pumping action.
关键词： localized electronic states,wafer-bonding,inverse spin Hall effect,spin-current,spin pumping
更新于2025-09-09 09:28:46
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Research on the Effects of Process Parameters on Surface Roughness in Wet-Activated Silicon Direct Bonding Base on Orthogonal Experiments
摘要： Surface roughness is a very important index in silicon direct bonding and it is affected by processing parameters in the wet-activated process. These parameters include the concentration of activation solution, holding time and treatment temperature. The effects of these parameters were investigated by means of orthogonal experiments. In order to analyze the wafer roughness more accurately, the bear ratio of the surface was used as the evaluation index. From the results of the experiments, it could be concluded that the concentration of the activation solution affected the roughness directly and the higher the concentration, the lower the roughness. Holding time did not affect the roughness as acutely as that of the concentration, but a reduced activation time decreased the roughness perceptibly. It was also discovered that the treatment temperature had a weak correlation with the surface roughness. Based on these conclusions, the parameters of concentration, temperature and holding time were optimized respectively as NH4OH:H2O2=1:1 (without water), 70 °C and 5 min. The results of bonding experiments proved the validity of the conclusions of orthogonal experiments.
关键词： wet activation,process optimization,wafer bonding,surface hydrophilicity
更新于2025-09-09 09:28:46
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Sensitive X-ray Absorption Near Edge Structure Analysis on the Bonding Properties of Au <sub/>30</sub> (SR) <sub/>18</sub> Nanoclusters
摘要： Au nanoclusters (NCs) with organothiolate protecting ligands are a field of great interest and X-ray absorption spectroscopy is a useful tool for the structure and property studies of these Au NCs. However, the Au NCs normally show broad and low-intensity features in the gold X-ray absorption near-edge structure (XANES) region, lowering the sensitivity of the technique and making it difficult to use for the analysis of Au NCs. In this work we report a sensitive gold L3-edge XANES study on the bonding properties of the newly discovered Au30(SR)18 NCs utilizing a combined approach of the first derivative XANES spectra and quantum simulations. First derivative XANES spectra are compared with the well-studied Au25(SR)18 with the aim of determining the unique features of Au30(SR)18. It is found that the early XANES region of the Au NCs is significantly influenced by the gold?gold bonding environment in the surface sites, as the varying surface Au?Au bond lengths in Au25(SR)18 and Au30(SR)18 result in pronounced difference in the first derivative XANES. These findings can be consistently explained using site-selective quantum simulations of the XANES spectra based on the Au NC structural models. The XANES method presented in this work offers a useful tool for the sensitive analysis on structure and bonding properties of Au NCs.
关键词： Au nanoclusters,bonding properties,quantum simulations,XANES,X-ray absorption spectroscopy
更新于2025-09-09 09:28:46
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Electronic, bonding and optical properties of the LiGaGe2X6 (X?=?S, Se, and Te) compounds: An ab initio study
摘要： In order to gain an insight into the bonding and to characterize linear and nonlinear optical properties of three infrared LiGaGe2S6, LiGaGe2Se6, and LiGaGe2Te6 compounds, we performed an ab initio calculation based on density functional theory. The calculations determined lattice parameters, band gaps, dipole moments, and second harmonic components that commonly agreed well with the available experimental data. We show in this article, through a large body of calculations, the trend in the row of participating anions, S ? Se ? Te, enhances the polarization effect and the coordination structure distortions in the polyhedra groups forming the bonding pattern of the cell. This one also affects both the electronic and the optical properties, making the compounds more propitious for device-based optical applications.
关键词： Ab initio calculation,Bonding analysis,Optical properties,Electronic population
更新于2025-09-09 09:28:46
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Determination of interfacial fracture energy for 'pop-in' delaminations in a glass-epoxy system using the indentation method
摘要： The adhesion of coatings often controls the performance of the substrate-coating system. Certain engineering applications require an epoxy coating on a brittle substrate to protect and improve the performance of the substrate. Interfacial adhesion measurements of such systems provide a quantitative metric of that performance. Indentation experiments were performed to induce interfacial delaminations in a glass substrate-epoxy coating system. Delamination loads and radii were measured and applied to an analytical solution originally developed by Rosenfeld et al. (1990) to estimate the interfacial fracture energy of the substrate-coating adhesive bond. Results suggest an interfacial bond strength far exceeding that of similar previously studied glass-epoxy systems.
关键词： bonding,indentation,glass,coatings,epoxy,interfaces,fracture energy,adhesion
更新于2025-09-09 09:28:46
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The Nature of Si-O-Si Bonding via Molecular Orbital Calculations
摘要： the nature of Si-o bonding and Si-o-Si bridging is discussed using molecular orbital calculations. we found the equilibrium geometries for two pyrosilisic acid molecules (C2V and 60° torsion) using m?ller-Plesset perturbation theory and 6-311G (d,p) split valence basis set. The bent configuration of the Si-O-Si angle in equilibrium geometries can be explained by the balance of Coulombic repulsion between Sio4 tetrahedra and the energy of lone pair orbitals belonging to bridging oxygen atom without concerning the contribution of d-p π-bonding from the results of natural bonding orbital analysis. the energy surfaces of two pyrosilisic acid molecules with varying Si-o length to the bridging oxygen and Si-o-Si angle were calculated and we found the relationship between Si-o length to the bridging and Si-o-Si bridging angle. the Si-o bonding strengthens with increasing Si-o-Si angle because of stabilization in energy of Si-O bonding orbital with decreasing the hybridization index λ in spλ orbital of bridging oxygen and increase of Coulombic interaction between Si and bridging oxygen atom.
关键词： Natural Bonding orbital analysis,Silicates,molecular orbital Calculation,Siloxanes
更新于2025-09-09 09:28:46
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15.1: <i>Invited Paper:</i> Bonding Spacer Technologies for Future Foldable LCDs using Ultra-Thin Polyimide Substrates
摘要： We have developed foldable LCD using ultra-thin polyimide substrates and bonding polymer spacer and successfully achieved small curvature of radius less than 2mm. We discuss the bonding spacer can suppress the deformation of plastic substrate and achieve high image quality in bending state.
关键词： Polyimide substrate,Small radius of curvature,Foldable LCD,Bending stress,Bonding spacer,Liquid crystal display
更新于2025-09-09 09:28:46
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Flip-Chip Bonding Fabrication Technique
摘要： Military systems, outer space exploration and even in medical diagnosis and treatment used magnetic field detection. Low magnetic field detection is particularly important in tracking of magnetic. Traditional magnetometer tends to be bulky that hinders its inclusion into micro-scaled environment. This concern has brought the magnetometer into the trend of device miniaturization. Miniaturized magnetometer is usually fabricated using conventional microfabrication method particularly surface micromachining in which micro structures are built level by level starting from the surface of substrates upwards until completion of final structure. Although the miniaturization of magnetometer has been widely researched and studied, the process however is not. Thus, the process governing the fabrication technique is studied in this paper. Conventional method of fabrication is known as surface micromachining. Besides time consuming, this method requires many consecutive steps in fabrication process and careful alignment of patterns on every layer which increase the complexity. Hence, studies are done to improve time consuming and reliability of the microfabrication process. The objective of this research includes designing micro scale magnetometer and complete device fabrication processes. A micro-scale search coil magnetometer of 15 windings with 600μm thickness of wire and 300μm distance between each wire has been designed.
关键词： Surface Micromachining,Fabrication Technique,Micro magnetometer,Flip-Chip Bonding
更新于2025-09-09 09:28:46