Studies on the thermoelectric effect in semiconducting MnO2 thin films

Islam, A. Z. M. Touhidul; Islam, Riyajul; Khan, K. A.

doi:10.1007/s10854-005-0766-1

Cited by 35 publications

(35 citation statements)

References 12 publications

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“…The empirical Hubbard U correction opens up a small band gap close to the experimental value (PBE+U : 0.20 eV, PBEsol+U : 0.28 eV, Expt. : 0.27 eV [54,55]), which could be expected as, by construction, the Hubbard U leads to the localization of carriers, flattening of d bands, and opening of band gaps [24]. HSE in turn converges to a much larger band gap (1.7 eV), while SCAN gives a gap (0.43 eV) that is close to the +U and experimental results.…”

supporting

confidence: 78%

Energetics ofMnO2polymorphs in density functional theory

et al. 2016

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We report the energetics and properties of the β, α, R, γ , λ, and δ polymorphs of MnO 2 within density functional theory, comparing the performance of the recently introduced SCAN functional with that of conventional exchange-correlation functionals and experiment. We find that SCAN uniquely yields accurate formation energies and properties across all MnO 2 polymorphs. We explain the superior performance of SCAN based on its satisfaction of all known constraints appropriate to a semilocal exchange-correlation functional and its accurate representation of all types of orbital overlap. DOI: 10.1103/PhysRevB.93.045132 First-principles thermodynamics has over the last decades matured into a reliable method for accessing the energetics of phase transitions and reactions in condensed matter systems. At the heart of this method lies Kohn-Sham density functional theory (DFT) [1], with its standard approximations to the exchange-correlation energy providing a reasonably accurate picture of electronic structure. One of the most basic results that can be derived from a set of DFT calculations is the ground-state structure of a given compound under some set of conditions, usually set as zero temperature and pressure. However, despite the importance of accurate first-principles structure determination for both materials and property analysis [2][3][4][5] this determination is often extremely difficult as the total energy differences between competing phases can be on the order of only a few meV per formula unit [6]. As a result, ground state structure selection is an attractive benchmark for verifying the adequacy of the physical model underlying a given approximation to the exchange-correlation energy.One particularly interesting system for investigating structure-transition energetics within DFT is the set of manganese oxides. The Mn-O system contains a diverse set of relatively well characterized structures both across a range of stoichiometries (MnO, Mn 3 O 4 , Mn 2 O 3 , and MnO 2 ), and within a single stoichiometry (pyrolusite β, ramsdellite R, hollandite α, intergrowth γ , spinel λ, layered δ MnO 2 ), as shown in Fig. 1. All the MnO 2 polymorphs share a common basic atomic structure-small Mn 4+ ions in a spin-polarized 3d 3 configuration and large, highly polarizable O 2-ions in a spin-unpolarized 2p 6 configuration, arranged in corner-and edge-sharing MnO 6 octahedra. The different packings of these octahedra form a variety of polymorphic structures, many of which have been studied extensively for applications in energy storage, catalysis, pigmentation, etc. [7][8][9][10][11][12][13][14][15]. * Corresponding author: gceder@berkeley.edu Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.The relative stability of the various oxidation states of Mn-O has been previously investigated within the PerdewBurke-Erzenhof (PBE) and...

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confidence: 78%

Energetics ofMnO2polymorphs in density functional theory

et al. 2016

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“…where S represents the Seebeck coefficient, kB denotes the Boltzmann constant, T is the absolute temperature, e is the electronic charge, EF is the Fermi energy and r is the scattering parameter. From the TEP data, r has been calculated to be 3 2 indicating ionized impurity scattering is dominant in the films [51] . Using the estimated value of S at 305K, the abovementioned equation provides Fermi energy, EF≈4.4eV.…”

Section: Thermoelectric Propertiesmentioning

confidence: 99%

Unveiling the electrical and thermoelectric properties of highly degenerate indium selenide thin films: indication of In₃Se₄ phase

Hossain

Julkarnain

Mondal

et al. 2019

Mater. Res. Express

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The effects of annealing and variation of temperature on the electrical and thermoelectric properties of e-beam evaporated InSe thin films has been investigated in details. The XRD study demonstrates that the as-deposited InSe thin films are amorphous while they become polycrystalline with the presence of In3Se4 phase after annealing. The SEM micrographs reveal that the surfaces of as-deposited films are smooth whereas they become non-uniform due to annealing. The heating and cooling cycles of the as-deposited films exhibit that the resistivity of the films shows an irreversible phase-transition and become stable after 3-4 successive heattreatment operations in air. The electrical conductivity of annealed InSe thin films shows a highly degenerate semiconducting (metallic) behavior. The thermopower of the annealed films indicates that InSe thin film is a highly degenerate n-type semiconductor i.e. metallic.Thickness dependence thermopower obeys the Fuchs-Sondheimer theory. The optical band gap of the annealed films increases as compared to the as-deposited films. These results indicate that InSe thin films encounter a phase-transformation from In2Se3 to a new In3Se4 metallic phase with an optical band gap of ~1.8 eV due to heat-treatment.

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“…their TE properties have not been widely investigated, and only a limited number of studies exist. It has been reported that bulk and thin film β-MnO2 exhibit S of approximately -300 μV/K and σ of 10 3 S/m, resulting in a TPF of μW/m.K 2[147].Recently, Song et al reported extremely high Seebeck coefficients in β-MnO2nanopowder[142]. The S and σ of the MnO2 thin films have been shown to increase dramatically with temperature[9].…”

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confidence: 99%

Transition metal oxides – Thermoelectric properties

Walia

Balendhran

Nili

et al. 2013

Progress in Materials Science

312

199

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Transition metal oxides (TMOs) are a fascinating class of materials due to their wide ranging electronic, chemical and mechanical properties. Additionally, they are gaining increasing attention for their thermoelectric (TE) properties due to their high temperature stability, tunable electronic and phonon transport properties and well established synthesis techniques. In this article, we review TE TMOs at cryogenic, ambient and high temperatures. An overview of strategies used for morphological, composting and stoichiometric tuning of their key TE parameters is presented. This article also provides an outlook on the current and future prospects of implementing TMOs for a wide range of TE applications.

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Studies on the thermoelectric effect in semiconducting MnO2 thin films

Cited by 35 publications

References 12 publications

Energetics ofMnO2polymorphs in density functional theory

Energetics ofMnO2polymorphs in density functional theory

Unveiling the electrical and thermoelectric properties of highly degenerate indium selenide thin films: indication of In₃Se₄ phase

Transition metal oxides – Thermoelectric properties

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Studies on the thermoelectric effect in semiconducting MnO2 thin films

Cited by 35 publications

References 12 publications

Energetics ofMnO2polymorphs in density functional theory

Energetics ofMnO2polymorphs in density functional theory

Unveiling the electrical and thermoelectric properties of highly degenerate indium selenide thin films: indication of In3Se4 phase

Transition metal oxides – Thermoelectric properties

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Unveiling the electrical and thermoelectric properties of highly degenerate indium selenide thin films: indication of In₃Se₄ phase