Journal ArticleDOI

# Electrical properties of compacted assembly of copper oxide nanoparticles

A. Bose
05 Oct 2005-Journal of Applied Physics (American Institute of Physics)-Vol. 98, Iss: 7, pp 074307

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.

AbstractCu2O 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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, Kai Xi1
TL;DR: This article provides a comprehensive review on traditional and recently emergent p-TCOs, including Cu(+)-based delafossites, layered oxychalcogenides, nd (6) spinel oxides, Cr(3+-based oxides), and post-transition metal oxides with lone pair state (ns (2).
Abstract: Transparent conducting oxides constitute a unique class of materials combining properties of electrical conductivity and optical transparency in a single material. They are needed for a wide range of applications including solar cells, flat panel displays, touch screens, light emitting diodes and transparent electronics. Most of the commercially available TCOs are n-type, such as Sn doped In2O3, Al doped ZnO, and F doped SnO2. However, the development of efficient p-type TCOs remains an outstanding challenge. This challenge is thought to be due to the localized nature of the O 2p derived valence band which leads to difficulty in introducing shallow acceptors and large hole effective masses. In 1997 Hosono and co-workers (1997 Nature 389 939) proposed the concept of 'chemical modulation of the valence band' to mitigate this problem using hybridization of O 2p orbitals with close-shell Cu 3d (10) orbitals. This work has sparked tremendous interest in designing p-TCO materials together with deep understanding the underlying materials physics. In this article, we will provide a comprehensive review on traditional and recently emergent p-TCOs, including Cu(+)-based delafossites, layered oxychalcogenides, nd (6) spinel oxides, Cr(3+)-based oxides (3d (3)) and post-transition metal oxides with lone pair state (ns (2)). We will focus our discussions on the basic materials physics of these materials in terms of electronic structures, doping and defect properties for p-type conductivity and optical properties. Device applications based on p-TCOs for transparent p-n junctions will also be briefly discussed.

244 citations

Journal ArticleDOI
TL;DR: In this paper, the formation of $p$-type defects in transparent conducting oxides was investigated, giving rise to singleparticle levels that are deep in the band gap, consistent with experimentally observed activated, polaronic conduction.
Abstract: Understanding conduction in ${\mathrm{Cu}}_{2}\mathrm{O}$ is vital to the optimization of Cu-based $p$-type transparent conducting oxides. Using a screened hybrid--density-functional approach we have investigated the formation of $p$-type defects in ${\mathrm{Cu}}_{2}\mathrm{O}$ giving rise to single-particle levels that are deep in the band gap, consistent with experimentally observed activated, polaronic conduction. Our calculated transition levels for simple and split copper vacancies explain the source of the two distinct hole states seen in DLTS experiments. The necessity of techniques that go beyond the present generalized-gradient- and local-density-approximation techniques for accurately describing $p$-type defects in Cu(I)-based oxides is discussed.

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Journal ArticleDOI
TL;DR: In this article, the authors examined the electronic structure, thermodynamic stability and the p-type defect chemistry of CuCrO2 using density functional theory with three different approaches to the exchange and correlation.
Abstract: CuCrO2 is the most promising Cu-based delafossite for p-type optoelectronic devices. Despite this, little is known about the p-type conduction mechanism of this material, with both CuI/CuII and CrIII/CrIV hole mechanisms being proposed. In this article we examine the electronic structure, thermodynamic stability and the p-type defect chemistry of this ternary compound using density functional theory with three different approaches to the exchange and correlation; the generalized-gradient-approximation of Perdew, Burke and Ernzerhof (PBE), PBE with an additional correction for on-site Coulombic interactions (PBE + U) and the nonlocal, screened-exchange hybrid functional HSE06. The fundamental band gap of CuCrO2 is demonstrated to be indirect in nature. Under all growth conditions, the dominant intrinsic p-type defect will be the Cu vacancy, with hole formation centered solely on the Cu sublattice. Mg doping is found to be significantly lower in energy than intrinsic defect formation, explaining the large increases in conductivity seen experimentally. Cu-rich/Cr-poor growth conditions are found to be optimal for both intrinsic and extrinsic (Mg doping) defect formation, and should be adopted to maximize performance.

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Journal ArticleDOI
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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.

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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.
Abstract: Randomly oriented “nanocrystal” with sizes d below 10 nm, were compacted into a nanocrystalline solid. Studies by X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements suggest a novel type of solid structure which consists of crystalline domains and a connective matrix without any short or long range order, corresponding structurally to a “gas-like solid”.

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