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Effective masses and electronic structure of diamond including electron correlation effects in first principles calculations using the GW-approximation
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
2011 (Engelska)Ingår i: AIP Advances, ISSN 2158-3226, Vol. 1, nr 3, s. 032139-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present calculated interband transitions and effective masses for diamond from first principles including electron correlation effects via the GW-approximation. Our findings are in agreement with experiments, already the first iteration of the GW-scheme gives a direct gap at the gamma-point of 7.38 eV and a indirect gap of 5.75 eV close to experimental values. For deeper bands a quasiparticle self-consistent method is necessary to accurately reproduce the valence band width to 23.1 eV. We also obtain effective hole masses along different symmetry axes and electron conduction masses, ml = 1.1m0 and mt = 0.22m0

Ort, förlag, år, upplaga, sidor
New York: AIP , 2011. Vol. 1, nr 3, s. 032139-
Nyckelord [en]
ab initio calculations, diamond, effective mass, electron correlations, valence bands
Nationell ämneskategori
Den kondenserade materiens fysik Teknik och teknologier
Forskningsämne
Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik; Teknisk fysik med inriktning mot elektricitetslära
Identifikatorer
URN: urn:nbn:se:uu:diva-157835DOI: 10.1063/1.3630932ISI: 000302139600039OAI: oai:DiVA.org:uu-157835DiVA, id: diva2:436452
Tillgänglig från: 2011-08-23 Skapad: 2011-08-23 Senast uppdaterad: 2013-11-08Bibliografiskt granskad
Ingår i avhandling
1. Computational Studies of Electron Transport in Nanoscale Devices
Öppna denna publikation i ny flik eller fönster >>Computational Studies of Electron Transport in Nanoscale Devices
2013 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

In this thesis, a combination of density functional theory (DFT) based calculations and nonequilibrium Green’s functions are employed to investigate electron transport in molecular switches, molecular cords and nanoscale devices.

  Molecular electronic devices have been proposed as an approach to complement today’s silicon based electronic devices. However, engineering of such miniature devices and design of functional molecular components still present significant challenges.

  First, the way to connect a molecule to conductive electrodes has to be controlled. We study, in a nanoelectrode-nanoparticle platform, how structural changes affect the measured conductance and how current fluctuations due to these structural changes can be decreased. We find that, for reproducible measurements, it is important to have the molecules chemically bonded to the surfaces of adjacent nanoparticles. Furthermore, we show by a combination of DFT and theoretical modeling that we can identify signals from single-molecules in inelastic electron spectroscopy measurements on these devices.

  Second, active elements based on molecules, some examples being switches, rectifiers or memory devices, have to be designed. We study molecular conductance switches that can be operated by light and/or temperature. By tuning the substituents on the molecules, we can optimize the shift of the most conducting molecular orbital and increase the effective coupling between the molecule and the electrodes when going from the OFF to the ON-state of the switches, giving high switching ratio (up to three orders of magnitude). We also study so called mechanoswitches that are activated by a mechanical force elongating the molecules, which means that these switches could operate as sensors.

  Furthermore, we have studied two different classes of compounds that may function either as rigid molecular spacers with a well-defined conductance or as molecular cords. In both cases, we find that it is of great importance to match the conjugation of the anchoring groups with the molecular backbone for high conductance.

  The last part of the thesis is devoted to another interesting semiconductor material, diamond. We have accurately calculated the band structure and effective masses for this material. Furthermore, these results have been used to calculate the Hall coefficient, the resistivity and the Seebeck coefficient.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2013. s. i-x, 89
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1090
Nyckelord
Density functional theory, Molecular electronics, Organosilicon chemistry, Diamond, Molecular switches, Nanoelectrode bridge platform, Molecular cords
Nationell ämneskategori
Den kondenserade materiens fysik Fysikalisk kemi
Forskningsämne
Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik
Identifikatorer
urn:nbn:se:uu:diva-209261 (URN)978-91-554-8781-2 (ISBN)
Disputation
2013-11-29, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2013-11-08 Skapad: 2013-10-16 Senast uppdaterad: 2014-01-23

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