Electrical properties of compacted assembly of copper oxide nanoparticles
TL;DR: In this paper, both dc and ac electrical properties were measured on a compacted nanoparticle assembly and the dc electrical resistivity in the temperature range 140-300K was found to arise due to a variable range hopping conduction mechanism.
Abstract: Cu2O nanoparticles with diameters in the range 6.0-8.6nm were prepared by a chemical method. Both dc and ac electrical properties were measured on a compacted nanoparticle assembly. dc electrical resistivity in the temperature range 140-300K was found to arise due to a variable range hopping conduction mechanism. The ac resistivity variation as a function of frequency (in the range 10kHzto3MHz) and temperature (range 220–320K) was explained on the basis of the power-law exponent in percolating clusters. The interfacial amorphous phase of the nanoparticle assembly appears to control the electrical behavior of the system.
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TL;DR: In this paper, the structural and dielectric properties of CuO nanoparticles have been investigated by extended X-ray powder diffraction and impedance spectroscopy, respectively, and the average crystallite size was calculated to be 18.3 nm from the given line widths using Scherrer's equation.
4 citations
TL;DR: In this article , the effect of deposition temperature on their optoelectronic properties is examined in detail using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) analysis, Raman Spectroscopy, UV-Vis spectroscopy and four-probe sheet resistance measurements.
Abstract: Copper oxide thin films are deposited on quartz substrates by DC magnetron sputtering and the effect of deposition temperature on their optoelectronic properties is examined in detail. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) analysis, Raman spectroscopy, UV-Vis spectroscopy, and four-probe sheet resistance measurements are used to characterize the surface morphology, structural, optical, and electrical properties respectively. Deposition is carried out at room temperature and between 200 and 300 {\deg}C. XRD analysis indicates that the oxide formed is primarily Cu$_2$O and the absorption spectra show the films have a critical absorption edge at around 300 nm. The sheet resistance gradually decreases with increase in deposition temperature thereby increasing the conductivity of these thin films. Also observed is the increase in band gap from 2.20 eV for room temperature deposition to 2.35 eV at 300 {\deg}C. The optical band gap and the variation of sheet resistance with temperature shows that the microstructure plays a vital role in their behavior. These transformation characteristics are of huge technological importance having variety of applications including transparent solar cell fabrication.
3 citations
TL;DR: In this article, the microwave absorbing properties of the Ni/SiO2 core/shell soft magnetic material which was synthesized by the tetraethyl orthosilicate (TEOS) hydrolysis method were reported.
Abstract: In this paper, we report on the microwave absorbing properties of the Ni/SiO2 core/shell soft magnetic material which was synthesized by the tetraethyl orthosilicate (TEOS) hydrolysis method. The SEM patterns were shown that the particles of Ni/SiO2 were more dispersed and homogeneous. Microwave absorbing properties were measured in the range of 0.1–18 GHz. A reflection loss (RL) exceeding −20 dB in the frequency range of 2.6–8.9 GHz was achieved for an absorber thickness of 2.0–5.6 mm, and an optimal RL of −49.5 dB was obtained at 4.4 GHz for the thickness of 3.5 mm. The good microwave absorption properties resulted from a proper impedance match as a consequence of the insulator SiO2 around Ni particles.
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23,110 citations
TL;DR: In this article, a comprehensive survey is given of the experimental a.c. data for two types of amorphous semiconductor, namely chalcogenide and pnictide materials, and it is concluded that the behavior at intermediate to high temperatures is well accounted for by the correlated-barrier-hopping model, whereas the low-temperature behaviour is probably due to atomic tunnelling.
Abstract: The various origins of a frequency-dependent conductivity in amorphous semiconductors are reviewed, stressing particularly recent advances and the influences that factors such as correlation and non-random spatial distributions of electrically active centres can have on the a.c. conductivity. A comprehensive survey is given of the experimental a.c. data for two types of amorphous semiconductor, namely chalcogenide and pnictide materials. It is concluded that the a.c. behaviour at intermediate to high temperatures is well accounted for by the correlated-barrier-hopping model, whereas the low-temperature behaviour is probably due to atomic tunnelling.
1,814 citations
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01 Jan 1963
TL;DR: In this article, the Hartree-Fock Approximation of many-body techniques and the Electron Gas Polarons and Electron-phonon Interaction are discussed.
Abstract: Mathematical Introduction Acoustic Phonons Plasmons, Optical Phonons, and Polarization Waves Magnons Fermion Fields and the Hartree-Fock Approximation Many-body Techniques and the Electron Gas Polarons and the Electron-phonon Interaction Superconductivity Bloch Functions - General Properties Brillouin Zones and Crystal Symmetry Dynamics of Electrons in a Magnetic Field: de Haas-van Alphen Effect and Cyclotron Resonance Magnetoresistance Calculation of Energy Bands and Fermi Surfaces Semiconductor Crystals I: Energy Bands, Cyclotron Resonance, and Impurity States Semiconductor Crystals II: Optical Absorption and Excitons Electrodynamics of Metals Acoustic Attenuation in Metals Theory of Alloys Correlation Functions and Neutron Diffraction by Crystals Recoilless Emission Green's Functions - Application to Solid State Physics Appendix: Perturbation Theory and the Electron Gas Index.
1,132 citations
TL;DR: In this article, the metal-non-metal transition takes place when the volume fraction of the metallic phase approaches the percolation threshold, and it is shown that the static dielectric constant diverges near the threshold.
Abstract: A system consisting of randomly distributed metallic and dielectric regions is considered. The metal-non-metal transition takes place when the volume fraction of the metallic phase approaches the percolation threshold. It is shown that the static dielectric constant diverges near the threshold. Critical indexes are introduced which describe the behaviour of the conductivity and the dielectric constant near the threshold as functions of the volume fraction and frequency. The case of non-zero dc conductivity of dielectric regions is considered also. It is shown that all indexes describing the critical behaviour of complex conductivity can be expressed by two indexes which are known from computer and model experiments. The results of computer calculations of Webman et al. are analysed.
719 citations
TL;DR: In this paper, randomly oriented "nanocrystal" with sizes d below 10 nm, were compacted into a nanocrystalline solid, which consists of crystalline domains and a connective matrix without any short or long range order.
590 citations