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Start Over Descriptor "semiconductor-metal transition" Publisher elsevier
3 results on '"semiconductor-metal transition"'

1. Pressure-dependent semiconductor–metal transition and elastic, electronic, optical, and thermophysical properties of orthorhombic SnS binary chalcogenide

Author

Ayesha Tasnim, Md. Mahamudujjaman, Md. Asif Afzal, R.S. Islam, and S.H. Naqib

Subjects
Density functional theory, Semiconductor-metal transition, Elastic properties, Optoelectronic properties, Physics, QC1-999
Abstract

Pressure dependent physical properties of binary SnS compound have been studied using the density functional theory based methodology. The computed elastic constants reveal that SnS is stable mechanically and is brittle under ambient conditions. With increasing pressure, the compound becomes ductile. The Poisson’s ratio and Cauchy pressure also indicate brittle-ductile transition when pressure increases. The hardness of SnS increases significantly with pressure. The compound possesses elastic anisotropy. The ground state electronic band structure is semiconducting with a small band gap. The band structure becomes metallic under pressure. The bands crossing the Fermi level become more and more dispersive with the increase in pressure while the electronic correlations decrease as pressure is raised. Both the Debye temperature and the phonon thermal conductivity of SnS increase sharply with pressure. The melting temperature of the compound is low. Mixed bonding characteristics are found with ionic and moderate covalent contributions. SnS is a good absorber of ultraviolet light. The reflectivity of the material increases with the increase in the pressure. The reflectivity is nonselective over a wide spectral range. The low energy refractive index is high. The low band gap energy under ambient conditions makes SnS suitable for photovoltaic applications. Non-selective and high reflectivity of SnS indicates that this compound can be used as a coating material to reduce solar heating. Unlike structural anisotropy, the optical anisotropy of SnS is low.

Published
2023
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2. Light modulation in phase change disordered metamaterial - A smart cermet concept

Author

Naoufal Bahlawane, Sunil Kumar, Francis Maury, Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Luxembourg Institute of Science and Technology - LIST (LUXEMBOURG), Institut National Polytechnique de Toulouse - INPT (FRANCE), Centre interuniversitaire de recherche et d'ingenierie des matériaux (CIRIMAT), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC), and Luxembourg Institute of Science and Technology (LIST)

Subjects
Materials science, Physics and Astronomy (miscellaneous), Semiconductor-metal transition, 02 engineering and technology, Dielectric, 01 natural sciences, 7. Clean energy, Science des matériaux, Low emissivity, Metamaterial, Phase (matter), 0103 physical sciences, Emissivity control, Emissivity, General Materials Science, [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, 010306 general physics, Total internal reflection, business.industry, Cermet, 021001 nanoscience & nanotechnology, Smart cermet, Hysteresis, Micro et nanotechnologies/Microélectronique, Vanadium oxide, MOCVD, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, business, Solar selective coatings, human activities, Energy (miscellaneous)
Abstract

International audience; Cermet coatings are popular solar selective absorbers as they allow capturing most of the solar energywhile minimising radiative losses. Embedded metallic nanoparticles in dielectric matrices promotemultiple internal reflection of light and provide an overall low emissivity. VO2 in the metamaterial stateis regarded in this study as a responsive mixed phase comprising metallic rutile VO2 inclusions insemiconducting monoclinic VO2 phase mimicking cermet. The smart cermet responds to thermal stimuliby modulating the size of the metallic inclusions and thereby enabling the manipulation of theirinteraction with light. The highly reliable and reproducible response of the smart cermet corroborateswith the observed ramp reversal memory effect in VO2. We demonstrate a thermally controlled 85%emissivity switch taking advantage of the narrow hysteresis and tuning abilities of the disorderedmetamaterial.

Published
2017
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3. Synchrotron X-ray absorption of LaCoO3 perovskite

Author

R.P.W.J Struis, Otto Haas, and J.M McBreen

Subjects
Absorption spectroscopy, Analytical chemistry, Electronic-Structure, Inorganic Chemistry, LaCoO3, Fine-Structure, Materials Chemistry, La0.6Ca0.4Coo3, Cathode Materials, Physical and Theoretical Chemistry, Absorption (electromagnetic radiation), Perovskite (structure), X-ray absorption spectroscopy, Extended X-ray absorption fine structure, Chemistry, Temperature, Semiconductor-Metal Transition, Condensed Matter Physics, electronic structure, XANES, Electronic, Optical and Magnetic Materials, Cobalt Oxides, Crystallography, Ceramics and Composites, Spin-State Transition, Debye–Waller factor, Fuel-Cells, FEFF8 simulation, Core-Hole, Monoclinic crystal system
Abstract

LaCoO3 perovskite was prepared at 700degreesC using citrate precursors. The product was then characterized with X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The powder XRD pattern indicates rhomboliedral (R (3) over barc) or its monoclinic I2/a subgroup symmetry. The electronic configuration and the short-range atomic structure of the LaCoO3 perovskite at room temperature were investigated using synchrotron near-edge X-ray absorption spectroscopy (XANES) and extended X-ray absorption spectroscopy (EXAFS). From the XANES region of the XAS we conclude that Co(III) is at least partly in its intermediate- or high-spin state, which is in accordance with most of the published literature on LaCoO3 perovskite. The EXAFS region of the LaCoO3 perovskite spectrum, which up to now was almost not investigated, was simulated satisfactorily for the first two radial structure peaks in terms of the dominant scattering contributions generated with the FEFF8 code and the structural information available from crystallographic data. The best simulation results were obtained with I2/a symmetry. The obtained amplitude reduction factor, zero-energy shift and Debye-Waller factors are useful reference values for data analyses of similar compounds like partly substituted LaCoO3 perovskite, such as La1-xCaxCoO3 or La1-xSrxCoO3, which are materials of technical interest in catalyst and other applications. (C) 2003 Elsevier Inc. All rights reserved.

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