scholarly journals 2D Bi2Se3 van der Waals Epitaxy on Mica for Optoelectronics Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1653
Author(s):  
Shifeng Wang ◽  
Yong Li ◽  
Annie Ng ◽  
Qing Hu ◽  
Qianyu Zhou ◽  
...  
Keyword(s):  
Coincidence Site Lattice ◽  
Van Der Waals ◽  
Mica Substrate ◽  
Promising Candidate ◽  
Rocking Curve ◽  
Rhombohedral Crystal Structure ◽  
Covalently Bonded ◽  
Wide Range ◽  
Lattice Unit ◽  
Rhombohedral Crystal

Bi2Se3 possesses a two-dimensional layered rhombohedral crystal structure, where the quintuple layers (QLs) are covalently bonded within the layers but weakly held together by van der Waals forces between the adjacent QLs. It is also pointed out that Bi2Se3 is a topological insulator, making it a promising candidate for a wide range of electronic and optoelectronic applications. In this study, we investigate the growth of high-quality Bi2Se3 thin films on mica by the molecular beam epitaxy technique. The films exhibited a layered structure and highly c-axis-preferred growth orientation with an XRD rocking curve full-width at half-maximum (FWHM) of 0.088°, clearly demonstrating excellent crystallinity for the Bi2Se3 deposited on the mica substrate. The growth mechanism was studied by using an interface model associated with the coincidence site lattice unit (CSLU) developed for van der Waals epitaxies. This high (001) texture favors electron transport in the material. Hall measurements revealed a mobility of 726 cm2/(Vs) at room temperature and up to 1469 cm2/(Vs) at 12 K. The results illustrate excellent electron mobility arising from the superior crystallinity of the films with significant implications for applications in conducting electrodes in optoelectronic devices on flexible substrates.

Efficient Prediction of Structural and Electronic Properties of Hybrid 2D Materials Using DFT and Machine Learning

2018 ◽  
Author(s):  
Sherif Tawfik ◽  
Olexandr Isayev ◽  
Catherine Stampfl ◽  
Joseph Shapter ◽  
David Winkler ◽  
...  
Keyword(s):  
Machine Learning ◽  
Band Gap ◽  
Density Functional ◽  
2D Materials ◽  
Van Der Waals ◽  
Building Blocks ◽  
Machine Learning Techniques ◽  
Interlayer Distance ◽  
Computational Screening ◽  
Wide Range

Materials constructed from different van der Waals two-dimensional (2D) heterostructures offer a wide range of benefits, but these systems have been little studied because of their experimental and computational complextiy, and because of the very large number of possible combinations of 2D building blocks. The simulation of the interface between two different 2D materials is computationally challenging due to the lattice mismatch problem, which sometimes necessitates the creation of very large simulation cells for performing density-functional theory (DFT) calculations. Here we use a combination of DFT, linear regression and machine learning techniques in order to rapidly determine the interlayer distance between two different 2D heterostructures that are stacked in a bilayer heterostructure, as well as the band gap of the bilayer. Our work provides an excellent proof of concept by quickly and accurately predicting a structural property (the interlayer distance) and an electronic property (the band gap) for a large number of hybrid 2D materials. This work paves the way for rapid computational screening of the vast parameter space of van der Waals heterostructures to identify new hybrid materials with useful and interesting properties.

van der Waals Epitaxial Growth of Borophene on a Mica Substrate toward a High-Performance Photodetector

2021 ◽  
Author(s):  
Zenghui Wu ◽  
Guoan Tai ◽  
Runsheng Liu ◽  
Chuang Hou ◽  
Wei Shao ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
High Performance ◽  
Van Der Waals ◽  
Mica Substrate

Microwave-Assisted Solution Combustion Synthesis and Characterization of Thermoelectric Ca3Co2O6 Powders

2013 ◽  
Vol 802 ◽  
pp. 84-88
Author(s):  
Sagulthai Kahatta ◽  
Nopsiri Chaiyo ◽  
Chesta Ruttanapun ◽  
Wicharn Techitdheera ◽  
Wisanu Pecharapa ◽  
...  
Keyword(s):  
Combustion Synthesis ◽  
Solution Combustion Synthesis ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
X Ray ◽  
Microwave Assisted ◽  
Product Characterization ◽  
Rhombohedral Crystal Structure ◽  
Rhombohedral Crystal

The microwave-assisted solution combustion synthesis was applied to the initial synthesizing of Ca3Co2O6powder using glycine as a fuel and nitrate as an oxidant. The as-synthesized powders were calcined at 700-1,000ºC for 4h. Product characterization was performed using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Scanning electron microscope (SEM). The fuel-to-oxidizer molar ratio was found to affect the combustion reaction and character of the powder obtained. The phase composition of powder after calcination at various temperatures has shown that the formation of Ca3Co2O6occurs directly. The calcined powder possesses a rhombohedral crystal structure with an X-ray diffraction pattern that could be matched with the Ca3Co2O6JCPDS: 89-0629. This method is a simple way of synthesizing fine Ca3Co2O6powder with a low calcination temperature.

scholarly journals Recent Progress in the Study of Thermal Properties and Tribological Behaviors of Hexagonal Boron Nitride-Reinforced Composites

2020 ◽  
Vol 4 (3) ◽  
pp. 116
Author(s):  
Maryam Khalaj ◽  
Sanaz Zarabi Golkhatmi ◽  
Sayed Ali Ahmad Alem ◽  
Kahila Baghchesaraee ◽  
Mahdi Hasanzadeh Azar ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Boron Nitride ◽  
Recent Progress ◽  
Phonon Scattering ◽  
Hexagonal Boron Nitride ◽  
High Thermal Conductivity ◽  
Promising Candidate ◽  
Reinforced Composite ◽  
Low Thermal Expansion ◽  
Wide Range

Ever-increasing significance of composite materials with high thermal conductivity, low thermal expansion coefficient and high optical bandgap over the last decade, have proved their indispensable roles in a wide range of applications. Hexagonal boron nitride (h-BN), a layered material having a high thermal conductivity along the planes and the band gap of 5.9 eV, has always been a promising candidate to provide superior heat transfer with minimal phonon scattering through the system. Hence, extensive researches have been devoted to improving the thermal conductivity of different matrices by using h-BN fillers. Apart from that, lubrication property of h-BN has also been extensively researched, demonstrating the effectivity of this layered structure in reduction of friction coefficient, increasing wear resistance and cost-effectivity of the process. Herein, an in-depth discussion of thermal and tribological properties of the reinforced composite by h-BN will be provided, focusing on the recent progress and future trends.

Preparation and Characterization of Dysprosium (Dy) Ultrafine Nanocrystalline Structures

2008 ◽  
Vol 8 (2) ◽  
pp. 961-966
Author(s):  
Nianduan Lu ◽  
Xiaoyan Song ◽  
Jiuxing Zhang ◽  
Xiangquan Yan ◽  
Markus Rettenmayr
Keyword(s):  
Elastic Modulus ◽  
Nanocrystalline Structure ◽  
Physical And Mechanical Properties ◽  
Gas Condensation ◽  
Rhombohedral Crystal Structure ◽  
Nanocrystalline Structures ◽  
Metallic Nanomaterials ◽  
Efficient Route ◽  
Rhombohedral Crystal

By combining the inert-gas condensation with the SPS technology in an entirely closed system with the oxygen concentration below 0.5 ppm, the pure Dy bulk with the ultrafine nanocrystalline structure has been prepared. Thus a novel and efficient route of preparing nano rare-earth metals, as well as metallic nanomaterials that are highly reactive in the air, is proposed. The thermal, physical and mechanical properties of the prepared ultrafine nanocrystalline Dy bulk have been characterized and compared with those of the conventional raw polycrystalline bulk. It is found that in the nanocrystalline Dy bulk, the starting temperature of phase transformation from hexagonal to rhombohedral crystal structure is reduced by 70 °C in comparison with that of the raw polycrystalline bulk. The electrical resistivity of the ultrafine nanocrystalline bulk is slightly increased by a few percent as compared with that of the polycrystalline bulk, while the thermal conductivity is reduced by 28–35%. The microhardness and the elastic modulus of the ultrafine nanocrystalline Dy bulk are found to be remarkably improved as compared with those of the raw polycrystalline bulk, e.g., the microhardness and the elastic modulus are approximately 2.4 and 2.0 times as high as those of the raw polycrystalline bulk, respectively.

scholarly journals Gold Nanoparticles Promote Oxidant-Mediated Activation of NF-κB and 53BP1 Recruitment-Based Adaptive Response in Human Astrocytes

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Jennifer Mytych ◽  
Anna Lewinska ◽  
Jacek Zebrowski ◽  
Maciej Wnuk
Keyword(s):  
Oxidative Stress ◽  
Cell Cycle ◽  
Gold Nanoparticles ◽  
Adaptive Response ◽  
Inverse Correlation ◽  
Galactosidase Activity ◽  
Promising Candidate ◽  
Human Astrocytes ◽  
Wide Range

Nanogold-based materials are promising candidate tools for nanobased medicine. Nevertheless, no conclusive information on their cytotoxicity is available. In the present study, we investigated the effects of gold nanoparticles (AuNPs) on human astrocytesin vitro. Nanogold treatment in a wide range of concentrations did not result in cytotoxicity. In contrast, nanogold provoked changes in the astrocyte cell cycle and induced senescence-associatedβ-galactosidase activity. AuNPs promoted oxidative stress and caused activation of NF-κB pathway. After nanogold treatment, an inverse correlation between the formation of 53BP1 foci and micronuclei generation was observed. The robust 53BP1 recruitment resulted in reduced micronuclei production. Thus, nanogold treatment stimulated an adaptive response in a human astrocyte cell.

TOWARDS A MOLECULAR THEORY FOR THE VAN DER WAALS–MAXWELL DESCRIPTION OF FLUID PHASE TRANSITIONS

2002 ◽  
Vol 01 (02) ◽  
pp. 381-406 ◽  
Author(s):  
ANDRIY KOVALENKO ◽  
FUMIO HIRATA
Keyword(s):  
Hydrogen Bonding ◽  
Phase Transitions ◽  
Phase Diagrams ◽  
Equations Of State ◽  
Van Der Waals ◽  
Fluid Phase ◽  
Carbon Aerogel ◽  
Molecular Fluids ◽  
Wide Range ◽  
Realistic Interaction

We briefly review developments of theories for phase transitions of molecular fluids and mixtures, from semi-phenomenological approaches providing equations of state with adjustable parameters to first-principles microscopic methods qualitatively correct for a variety of molecular models with realistic interaction potentials. We further present the generalization of the van der Waals–Maxwell description of fluid phase diagrams to account for chemical specificities of polar molecular fluids, such as hydrogen bonding. Our theory uses the reference interaction site model (RISM) integral equation approach complemented with the new closure we have proposed (KH approximation), successful over a wide range of density from gas to liquid. The RISM/KH theory is applied to the known three-site models of water, methanol, and hydrogen fluoride. It qualitatively reproduces their vapor-liquid phase diagrams and the structure in the gas as well as liquid phases, including hydrogen bonding. Furthermore, phase transitions of water and methanol sorbed in nanoporous carbon aerogel are described by means of the replica generalization of the RISM approach we have developed. The changes as compared to the bulk fluids are in agreement with simulations and experiment. The RISM/KH theory is promising for description of phase transitions in various associating fluids, in particular, electrolyte as well as non-electrolyte solutions and ionic liquids.

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