Near-field Strong Plasmonic Resonances in Bi1.5Sb0.5Te1.8Se1.2 Topological Insulator Film

Topological insulators are a new class of quantum materials with metallic (edge) surface states and insulating bulk states. They exhibit various novel electronic and optical properties that make them highly promising electronic, spintronic, and optoelectronic materials. Our report confirms that the topological insulator Bi 1.5 Sb 0.5 Te 1.8 Se 1.2 (BSTS) is also an effective plasmonic material in the visible and near-infrared range. A BSTS film can effectively control transmission and reflection characteristics by changing the period of the hole array. This study determined that a strong resonant surface plasmonic mode at the resonance peak can confine approximately 80% of the electromagnetic field energy is demonstrated. Higher-order (second- and third-order) resonance peaks were also found, which is critical for controlling electromagnetic waves and research into new optoelectronic devices.

Gate induced quantum wires in GaAs/AlGaAs heterostructures by cleaved edge deposition

Electric conductors with dimensions reduced to the nanometer scale are the prerequisite of the quantum devices upon which the future advanced electronics is expected to be based. In the past, the fabrication of one-dimensional (1D) wires has been a particular challenge because they have to be defect-free over their whole length, which can be several tens µm. Excellent 1D wires have been produced by cleaving semiconductors (GaAs, AlGaAs) in ultra high vacuum and overgrowing the pristine edge surface by molecular beam epitaxy (MBE)1,2. Unfortunately, this cleaved edge overgrowth (CEO) technique did not find wide-spread use because it requires a series of elaborate steps that are difficult to accomplish. In this Letter, we present a greatly simplified variation of this technique where the cleaving takes place in ambient air and the MBE overgrowth is replaced by a standard deposition process. Wires produced by this cleaved edge deposition (CED) technique have properties that are as least as good as the traditional CEO ones. Due to its simplicity, the CED technique offers a generally accessible way to produce 1D devices.

The Effect of Wafer Edge Cu Contamination on FinFET Devices

The effect of copper (Cu) contamination inside the Si substrate from the wafer edge to the nearby devices has been investigated. After the Cu seed layer deposition, Cu contacted directly with Si at wafer edge where dielectric isolation layer was removed. Under the routine BEOL metallization and after the capping SiON/Si2O layers, SEM and AES analysis located a strip of islets of Cu contaminants. TEM analysis revealed that the seed Cu had interacted with Si substrate to form a stable ?-Cu3Si intermetallic compound that appeared to be planted into the Si substrate at the surface. SIMS analysis from the wafer backside, opposite to this strip of ?-Cu3Si islets at front, showed no Cu detection even after the majority of the backside Si was removed by grinding. Electrical nano-probing did not discern any parametric drift for the nanometer FinFET devices on chips near the edge surface of massive ?-Cu3Si islets in comparison with a reference chip from an uncontaminated wafer center. These results indicate that the formation of ?-Cu3Si, with a well-defined crystalline structure and a relatively stable stoichiometry, immobilizes Cu diffusion inside the Si substrate. In other word, the impact of Cu diffusion in Si has no effect on device performances as long as ?-Cu3Si is not directly formed in the FinFET channel or presents to short any structures within the chip.

Aeroacustic and aerodynamic investigating of a new airfoil trailing-edge noise-suppressing design

In this work, a new noise suppressing airfoil trailing-edge design, termed "finned serrations", is presented and numerically evaluated. This brand-new approach consists of the superposition of two different noise suppressing morphological features inspired by the wings of the owl. Embedded Large Eddy Simulations are employed in tandem with the Ffowcs WilliamsHawkings model to predict and analyze the design aerodynamics and aeroacoustics and compare the obtained output to that of a flat trailing-edge airfoil. Finned serrations are shown to combine the effects of having finlets and serrations. Because of the bluntness of the serration roots, the airfoil is subject to vortex shedding, while the flow is generally decorrelated in the spanwise direction, thanks to the channeling effect of the finlets. The turbulent kinetic energy distribution close to the airfoil trailing-edge surface is also significantly altered, as the more energetic eddies are convected away from the airfoil surface. Lastly, mixing across the airfoil surface is improved, and the average size of the turbulent coherent structures near the airfoil trailing-edge is reduced. The presented results suggest that the coupling of different noise-suppressing mechanisms is a promising path to explore, with the goal of coming up with new, quieter trailing-edge configurations.

Adsorption Characteristics and Mechanism of Calcium Ions on Different Molybdenite Surfaces via Experiments and DFT Simulations

Calcium ions are common in flotation process water, and have a significant effect on the molybdenite floatability, making separation of molybdenite from other minerals more difficult. Therefore, to improve the separation selectivity, the research of how calcium ions affect the molybdenite surface properties is of great significance. In this study, various methods including flotation tests, contact angle measurements, batch adsorption tests and Density Functional Theory (DFT) simulations were carried out to understand the adsorption characteristics and mechanism. Results of the contact angle measurements showed that the inhibition effects of calcium ions on molybdenite flotation kinetics were mostly attributed to the decrease of the edge surface hydrophobicity, as the contact angle of the edge surface decreased more than the face surface after treatment with calcium ions. While fitting the results of batch adsorption tests with adsorption kinetics and isotherm models, it was found that the Lagergen pseudo-first-order equation and the Freundlich isotherm model nicely follow the experimental trend. Moreover, DFT calculation results indicated that both Ca2+ and CaOH+ preferentially adsorb on the molybdenite (100) surface, particularly the edge surface, which was consistent with the contact angle results. Ca2+ adsorbed on the Mo-top site on the S-(100) surface by forming Ca-S bonds, transferring electrons from Ca 3d orbitals to S 3p orbitals. CaOH+ adsorbed on the S-top site of Mo-(100) surface by forming a strong covalent Mo-O bond and S-Ca bond. The results provide a basis for understanding and improving the separation effect of molybdenite from other minerals in the presence of calcium ions.

Post-tensioning of glass beams: Analytical determination of the allowable pre-load

The effectiveness of post-tensioning in enhancing the fracture resistance of glass beams depends on the level of compressive pre-stress introduced at the glass edge surface that will in service be exposed to tensile stresses induced by bending. Maximum pre-load that can be applied in a post-tensioned glass beam system, yielding maximum compressive pre-stress, is limited by various failure mechanisms which might occur during post-tensioning. In this paper, failure mechanisms are identified for a post-tensioned glass beam system with a flat stainless steel tendon adhesively bonded at the bottom glass edge, including the rupture of the tendon, glass failure in tension and adhesive/glass failure in the load introduction zone. Special attention is given to the load introduction failure given that the transparent nature of glass limits the use of vertical confinement usually applied in concrete. An analytical model for determination of the allowable pre-load in post-tensioned glass beams is proposed, based on the model applied for externally post-tensioned concrete beams. The model is verified with the results of a numerical model, showing good correlation, and applied in a parametric study to determine the influence of various beam parameters on the effectiveness of post-tensioning glass beams.

Edge surface supercurrent and transport anomalies in Hall effect measurements in Nb

We report an experimental study of the edge surface superconductivity and the Hall effect in a Nb thin film Hall device. We show that the previously reported anomalous sign reversal of the Hall resistance across the superconducting-normal transition is due to the edge supercurrent. Large anomalous oscillations between the transverse voltage probes are observed in the field range between Hc2 and Hc3, in both the anti-symmetric (Hall) and symmetric (resistive) channels. These oscillations are extremely sensitive to a small tilting of the edge surface relative to the external magnetic field. We suggest that these oscillations may arise from the Aharonov-Bohm interference of the edge supercurrents.

Experimental analysis of process parameters in drilling nimonic C263 alloy under nano fluid mixed MQL environment

Nimonic C263 is a super alloy and it is difficult to cut. As this alloy possess high proportion of chromium, cobalt, and molybdenum, which fortify the material by solution hardening, which inhibits the dislocation movement, resulting in higher plastic deformation. In this research, an attempt has been made to model, analysis and investigate the machining characteristics such as thrust force, temperature at drill cutting edge, flank wear and surface finish during drilling of this alloy using silver nano fluid mixed Minimum Quantity Lubrication (MQL) environment. Residual stress at various combinations of process parameters was also observed and discussed. RSM based empirical models of the process parameters and optimization of multi response was developed. Thrust force, Temperature at drill cutting edge, surface roughness and tool wear affected by feed rate (percentage of contribution-60%), spindle speed (percentage of contribution-88.63%), spindle speed (percentage of contribution-71.42%) and feed rate (percentage of contribution-67.76%) respectively followed by other parameters.