Two-step-index ZnMgTe/ZnTe Waveguide Structures with Improved Crystal Quality

MRS Advances ◽  
2016 ◽  
Vol 1 (23) ◽  
pp. 1721-1727
Author(s):  
Wei-Che Sun ◽  
Fukino Kazami ◽  
Jing Wang ◽  
Taizo Nakasu ◽  
Shota Hattori ◽  
...  
Keyword(s):  
Large Scale ◽  
Lattice Mismatch ◽  
Single Step ◽  
Interface Roughness ◽  
Propagation Loss ◽  
Reciprocal Space Mapping ◽  
Step Index ◽  
Cladding Layer ◽  
Plane Lattice ◽  
Waveguide Device

ABSTRACTZnMgTe(Cladding)/ZnTe(Core)/ZnMgTe(Cladding) thin film waveguide had been grown by molecular beam epitaxy (MBE) and presented a great potential to be a high performance Electro-optical (EO) modulator. For a low propagation loss ZnMgTe/ZnTe waveguide, thick cladding layer with high Mg composition (Mg %) is needed. However, the in-plane lattice mismatch of the fabricated device with high Mg % and thick cladding layer was large. It might cause the cladding/core interface roughness and asperities due to the misfit dislocation, and degrade the device performance. Because EO property of waveguide device is primarily influence by the structure thickness, the device efficiency improvement in this study was only considered to reduce the defects asperities that would cause propagation loss without decreasing the Mg % or the total thickness of the cladding layers. Therefore, we introduced a low Mg % layer between the cladding and the core layer to circumvent the effect of large lattice mismatch. The in-plane lattice mismatch of the devices was monitored using reciprocal space mapping, and surface morphologies were also observed using atom force microscope. The two-step index ZnMgTe/ZnTe waveguide had shown to have lower degree of relaxation compared to that of single-step index waveguide device with close Mg % and cladding layer thickness. Therefore, the crystal degradation of the two-step-index waveguide caused by lattice mismatch was successfully suppressed by introduction extra low Mg % layers. The morphologies of the two kinds of waveguide structures have similar surface asperities, which indicated the extra inserted layers did not produce additional large scale asperities at the interfaces that would increase the propagation loss.

TEM study of Cosi2 formation via annealing of Co-Ti bilayers on Si

1995 ◽  
Vol 53 ◽  
pp. 464-465
Author(s):  
N. David Theodore ◽  
Andre Vantomme ◽  
Peter Crazier
Keyword(s):  
Thermal Instability ◽  
Lattice Mismatch ◽  
Field Effect Transistors ◽  
Contact Layer ◽  
Interface Roughness ◽  
Oxide Semiconductor ◽  
Surface Layers ◽  
Silicide Layer ◽  
Small Lattice ◽  
Buried Layers

Contact is typically made to source/drain regions of metal-oxide-semiconductor field-effect transistors (MOSFETs) by use of TiSi2 or CoSi2 layers followed by AI(Cu) metal lines. A silicide layer is used to reduce contact resistance. TiSi2 or CoSi2 are chosen for the contact layer because these silicides have low resistivities (~12-15 μΩ-cm for TiSi2 in the C54 phase, and ~10-15 μΩ-cm for CoSi2). CoSi2 has other desirable properties, such as being thermally stable up to >1000°C for surface layers and >1100°C for buried layers, and having a small lattice mismatch with silicon, -1.2% at room temperature. During CoSi2 growth, Co is the diffusing species. Electrode shorts and voids which can arise if Si is the diffusing species are therefore avoided. However, problems can arise due to silicide-Si interface roughness (leading to nonuniformity in film resistance) and thermal instability of the resistance upon further high temperature annealing. These problems can be avoided if the CoSi2 can be grown epitaxially on silicon.

scholarly journals Long Low-Loss-Litium Niobate on Insulator Waveguides with Sub-Nanometer Surface Roughness

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 910 ◽  
Author(s):  
Rongbo Wu ◽  
Min Wang ◽  
Jian Xu ◽  
Jia Qi ◽  
Wei Chu ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Integrated Circuits ◽  
Large Scale ◽  
Photonic Integrated Circuits ◽  
Surface Patterning ◽  
Propagation Loss ◽  
Direct Writing ◽  
Laser Direct Writing ◽  
Low Loss ◽  
Atomic Force

In this paper, we develop a technique for realizing multi-centimeter-long lithium niobate on insulator (LNOI) waveguides with a propagation loss as low as 0.027 dB/cm. Our technique relies on patterning a chromium thin film coated on the top surface of LNOI into a hard mask with a femtosecond laser followed by chemo-mechanical polishing for structuring the LNOI into the waveguides. The surface roughness on the waveguides was determined with an atomic force microscope to be 0.452 nm. The approach is compatible with other surface patterning technologies, such as optical and electron beam lithographies or laser direct writing, enabling high-throughput manufacturing of large-scale LNOI-based photonic integrated circuits.

scholarly journals Simulation and Analysis of GaN Wafer Bowing on Sapphire Substrate

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Wang Bin ◽  
Qu Yu-xuan ◽  
Hu Shi-gang ◽  
Tang Zhi-jun ◽  
Li Jin ◽  
...  
Keyword(s):  
Sapphire Substrate ◽  
Mass Production ◽  
Large Scale ◽  
Lattice Mismatch ◽  
Wafer Surface ◽  
Heteroepitaxial Growth ◽  
Analysis Software ◽  
Element Analysis ◽  
Modern Mass ◽  
The Mathematical Model

During the process of heteroepitaxial growth, if the lattice constant of the growing film differs from that of the substrate, the wafer surface bows, regardless of whether the lattice mismatch occurs or not. As the growth in large-scale wafers speeds up, bowing effects are becoming more and more important. Wafer bowing has a direct impact on the yield in modern mass-production compound semiconductor industries. By using finite element analysis software, the bowing deformation of the GaN wafer on sapphire substrate can be studied. This paper summarizes the causes of bowing deformation, builds the mathematical model, and deduces the relation equation of the wafer bowing. The results show that epitaxial wafer bowing has a linear relationship with the square of the diameter of the substrate but has little relationship with the thickness of the substrate. Moreover, the relation equation of the wafer bowing is also simplified finally.

Biological Synthesis of Silver Nanoparticles and their Biomedical Activity: A Review

2021 ◽  
Vol 09 ◽  
Author(s):  
Sarvat Zafar ◽  
Aiman Zafar ◽  
Fakhra Jabeen ◽  
Miad Ali Siddiq
Keyword(s):  
Silver Nanoparticles ◽  
Large Scale ◽  
Scale Up ◽  
Cost Effective ◽  
Biological Properties ◽  
Single Step ◽  
Biological Synthesis ◽  
Nanosized Particles ◽  
Environment Friendly ◽  
Physical And Chemical

: Nanotechnology studies the various phenomena of physio-chemical procedures and biological properties for the generation of nanosized particles, and their rising challenges in the various sectors, like medicine, engineering, agriculture, electronic, and environmental studies. The nanosized particles exhibit good anti-microbial, anti-inflammatory, cytotoxic, drug delivery, anti-parasitic, anti-coagulant and catalytic properties because of their unique dimensions with large surface area, chemical stability and higher binding density for the accumulation of various bio-constituents on their surfaces. Biological approaches for the synthesis of silver nanoparticles (AgNPs) have been reviewed because it is an easy and single-step protocol and a viable substitute for the synthetic chemical-based procedures. Physical and chemical approaches for the production of AgNPs are also mentioned herein. Biological synthesis has drawn attention because it is cost-effective, faster, non-pathogenic, environment-friendly, easy to scale-up for large-scale synthesis, and having no demand for usage of high pressure, energy, temperature, or noxious chemical ingredients, and safe for human therapeutic use. Therefore, the collaboration of nanomaterials with bio-green approaches could extend the utilization of biological and cytological properties compatible with AgNPs. In this perspective, there is an immediate need to develop ecofriendly and biocompatible techniques, which strengthen efficacy against microbes and minimize toxicity for human cells. The present study introduces the biological synthesis of silver nanoparticles, and their potential biomedical applications have also been reviewed.

The Dawn of Quantum Information

2020 ◽  
pp. 258-270
Author(s):  
Gershon Kurizki ◽  
Goren Gordon
Keyword(s):  
Quantum Information ◽  
Large Scale ◽  
Quantum Computer ◽  
Quantum Algorithm ◽  
Single Step ◽  
Weather Forecasts ◽  
State Of Mind ◽  
Process Simulations ◽  
Superposition States ◽  
Quantum Revolution

Henry and Eve have finally tested their quantum computer (QC) with resounding success! It may enable much faster and better modelling of complex pharmaceutical designs, long-term weather forecasts or brain process simulations than classical computers. A 1,000-qubit QC can process in a single step 21000 possible superposition states: its speedup is exponential in the number of qubits. Yet this wondrous promise requires overcoming the enormous hurdle of decoherence, which is why progress towards a large-scale QC has been painstakingly slow. To their dismay, their QC is “expropriated for the quantum revolution” in order to share quantum information among all mankind and thus impose a collective entangled state of mind. They set out to foil this totalitarian plan and restore individuality by decohering the quantum information channel. The appendix to this chapter provide a flavor of QC capabilities through a quantum algorithm that can solve problems exponentially faster than classical computers.

scholarly journals Electrochemically derived functionalized graphene for bulk production of hydrogen peroxide

2020 ◽  
Vol 11 ◽  
pp. 432-442 ◽  
Author(s):  
Munaiah Yeddala ◽  
Pallavi Thakur ◽  
Anugraha A ◽  
Tharangattu N Narayanan
Keyword(s):  
Large Scale ◽  
Reduction Reaction ◽  
Single Step ◽  
Scale Production ◽  
Functionalized Graphene ◽  
Large Scale Production ◽  
Production Of Hydrogen ◽  
Electron Reduction ◽  
Bulk Production ◽  
Carbon Based

On-site peroxide generation via electrochemical reduction is gaining tremendous attention due to its importance in many fields, including water treatment technologies. Oxidized graphitic carbon-based materials have been recently proposed as an alternative to metal-based catalysts in the electrochemical oxygen reduction reaction (ORR), and in this work we unravel the role of C=O groups in graphene towards sustainable peroxide formation. We demonstrate a versatile single-step electrochemical exfoliation of graphite to graphene with a controllable degree of oxygen functionalities and thickness, leading to the formation of large quantities of functionalized graphene with tunable rate parameters, such as the rate constant and exchange current density. Higher oxygen-containing exfoliated graphene is known to undergo a two-electron reduction path in ORR having an efficiency of about 80 ± 2% even at high overpotential. Bulk production of H2O2 via electrolysis was also demonstrated at low potential (0.358 mV vs RHE), yielding ≈34 mg/L peroxide with highly functionalized (≈23 atom %) graphene and ≈16 g/L with low functionalized (≈13 atom %) graphene, which is on par with the peroxide production using state-of-the-art precious-metal-based catalysts. Hence this method opens a new scheme for the single-step large-scale production of functionalized carbon-based catalysts (yield ≈45% by weight) that have varying functionalities and can deliver peroxide via the electrochemical ORR process.

scholarly journals Dodecagonal bilayer graphene quasicrystal and its approximants

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Guodong Yu ◽  
Zewen Wu ◽  
Zhen Zhan ◽  
Mikhail I. Katsnelson ◽  
Shengjun Yuan
Keyword(s):  
Large Scale ◽  
Lattice Mismatch ◽  
Tight Binding ◽  
Bilayer Graphene ◽  
Dominant Factor ◽  
Honeycomb Lattice ◽  
Fermi Velocity ◽  
Band Theory ◽  
Incommensurate Structures ◽  
Unfolding Method

AbstractDodecagonal bilayer graphene quasicrystal has 12-fold rotational order but lacks translational symmetry which prevents the application of band theory. In this paper, we study the electronic and optical properties of graphene quasicrystal with large-scale tight-binding calculations involving more than ten million atoms. We propose a series of periodic approximants which reproduce accurately the properties of quasicrystal within a finite unit cell. By utilizing the band-unfolding method on the smallest approximant with only 2702 atoms, the effective band structure of graphene quasicrystal is derived. The features, such as the emergence of new Dirac points (especially the mirrored ones), the band gap at $$M$$M point and the Fermi velocity are all in agreement with recent experiments. The properties of quasicrystal states are identified in the Landau level spectrum and optical excitations. Importantly, our results show that the lattice mismatch is the dominant factor determining the accuracy of layered approximants. The proposed approximants can be used directly for other layered materials in honeycomb lattice, and the design principles can be applied for any quasi-periodic incommensurate structures.

scholarly journals Single-Step Synthesis of Vertically Aligned Carbon Nanotube Forest on Aluminium Foils

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1590 ◽  
Author(s):  
Fabien Nassoy ◽  
Mathieu Pinault ◽  
Jérémie Descarpentries ◽  
Thomas Vignal ◽  
Philippe Banet ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Large Scale ◽  
Chemical Vapour ◽  
Cost Effective ◽  
Liquid Electrolyte ◽  
Single Step ◽  
Synthesis Process ◽  
Catalyst Precursor ◽  
Ionic Liquid Electrolyte ◽  
Vertically Aligned

Vertically aligned carbon nanotube (VACNT) forests are promising for supercapacitor electrodes, but their industrialisation requires a large-scale cost-effective synthesis process suitable to commercial aluminium (Al) foils, namely by operating at a low temperature (<660 °C). We show that Aerosol-Assisted Catalytic Chemical Vapour Deposition (CCVD), a single-step roll-to-roll compatible process, can be optimised to meet this industrial requirement. With ferrocene as a catalyst precursor, acetylene as a carbon source and Ar/H2 as a carrier gas, clean and dense forests of VACNTs of about 10 nm in diameter are obtained at 615 °C with a growth rate up to 5 µm/min. Such novel potentiality of this one-step CCVD process is at the state-of-the-art of the multi-step assisted CCVD processes. To produce thick samples, long synthesis durations are required, but growth saturation occurs that is not associated with a diffusion phenomenon of iron in aluminium substrate. Sequential syntheses show that the saturation trend fits a model of catalytic nanoparticle deactivation that can be limited by decreasing acetylene flow, thus obtaining sample thickness up to 200 µm. Cyclic voltammetry measurements on binder-free VACNT/Al electrodes show that the CNT surface is fully accessible to the ionic liquid electrolyte, even in these dense VACNT forests.

scholarly journals Bio-Based Chemicals from Renewable Biomass for Integrated Biorefineries

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 233 ◽  
Author(s):  
Kirtika Kohli ◽  
Ravindra Prajapati ◽  
Brajendra Sharma
Keyword(s):  
Large Scale ◽  
Large Fraction ◽  
Single Step ◽  
Industrial Chemicals ◽  
Renewable Biomass ◽  
Platform Chemicals ◽  
Multistep Synthesis ◽  
Renewable Feedstock ◽  
Biomass Sugars ◽  
Conversion Technologies

The production of chemicals from biomass, a renewable feedstock, is highly desirable in replacing petrochemicals to make biorefineries more economical. The best approach to compete with fossil-based refineries is the upgradation of biomass in integrated biorefineries. The integrated biorefineries employed various biomass feedstocks and conversion technologies to produce biofuels and bio-based chemicals. Bio-based chemicals can help to replace a large fraction of industrial chemicals and materials from fossil resources. Biomass-derived chemicals, such as 5-hydroxymethylfurfural (5-HMF), levulinic acid, furfurals, sugar alcohols, lactic acid, succinic acid, and phenols, are considered platform chemicals. These platform chemicals can be further used for the production of a variety of important chemicals on an industrial scale. However, current industrial production relies on relatively old and inefficient strategies and low production yields, which have decreased their competitiveness with fossil-based alternatives. The aim of the presented review is to provide a survey of past and current strategies used to achieve a sustainable conversion of biomass to platform chemicals. This review provides an overview of the chemicals obtained, based on the major components of lignocellulosic biomass, sugars, and lignin. First, important platform chemicals derived from the catalytic conversion of biomass were outlined. Later, the targeted chemicals that can be potentially manufactured from the starting or platform materials were discussed in detail. Despite significant advances, however, low yields, complex multistep synthesis processes, difficulties in purification, high costs, and the deactivation of catalysts are still hurdles for large-scale competitive biorefineries. These challenges could be overcome by single-step catalytic conversions using highly efficient and selective catalysts and exploring purification and separation technologies.

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