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Quantum transport in photoswitching molecules: An investigation based on ab initio calculations and Non Equilibrium Green Function theory
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Molecular electronics is envisioned as a possible next step in device miniaturization. It is usually taken to mean the design and manufacturing of electronic devices and applications where organic molecules work as the fundamental functioning unit. It involves the easurement and manipulation of electronic response and transport in molecules attached to conducting leads. Organic molecules have the advantages over conventional solid state electronics of inherent small sizes, endless chemical diversity and ambient temperature low cost manufacturing.

In this thesis we investigate the switching and conducting properties of photochromic dithienylethene derivatives. Such molecules change their conformation in solution when acted upon by light. Photochromic molecules are attractive candidates for use in molecular electronics because of the switching between different states with different conducting properties. The possibility of optically controlling the conductance of the molecule attached to leads may lead to new device implementations.

The switching reaction is investigated with potential energy calculations for different values of the reaction coordinate between the closed and the open isomer. The electronic and atomic structure calculations are performed with density functional theory (DFT). It is concluded that there is a large potential energy barrier separating the open and closed isomer and that switching between open and closed forms must involve excited states.

The conducting properties of the molecule inserted between gold leads is calculated within the Non Equilibrium Green Function theory. The transmission function is calculated for the two isomers with different basis sizes for the gold contacts, as well as the electrostatic potential, for finite applied bias voltages. We conclude that a Au 6s basis give qualitatively the same result as a Au spd basis close to the Fermi level. The transmission coefficient at the Fermi energy is around 10 times larger in the closed molecule compared to the open. This will result in a large difference in conductivity. It is also found that the large difference in conductivity will remain for small applied bias voltages. The results are consistent with earlier work.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , v, 35 p.
Keyword [en]
molecular electronics, electron transport, electron structure, density functional theory, non equilibrium green function theory
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-4790ISBN: 978-91-7415-020-9 (print)OAI: oai:DiVA.org:kth-4790DiVA: diva2:13974
Presentation
2008-06-13, K408, Materialvetenskap, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-11-19Bibliographically approved
List of papers
1. Ab Initio Study of Switching Properties of Photochromic Dithienylethene Molecules
Open this publication in new window or tab >>Ab Initio Study of Switching Properties of Photochromic Dithienylethene Molecules
2006 (English)In: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 965, 296-300 p.Article in journal (Refereed) Published
Abstract [en]

We report an ab initio study of a photochromic dithienylethene derivative. The mechanisms for switching between open and closed conformations are investigated based on total energy calculations for the ground and first excited state. An explanation for the central ring closure based on relaxation of the excited state is presented.

Keyword
Derivatives, Excited states, Molecular structure, Dithienylethene molecules, Switching properties
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8604 (URN)2-s2.0-40949126958 (Scopus ID)
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2017-12-14Bibliographically approved
2. Ab initio study of the electron transport in dithienylethene photochromic molecules attached to gold leads
Open this publication in new window or tab >>Ab initio study of the electron transport in dithienylethene photochromic molecules attached to gold leads
2008 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 100, no 5, 052061- p.Article in journal (Refereed) Published
Abstract [en]

We report a theoretical study of single molecule conduction in open and closed conformations of photochromic dithienylethene molecules attached to metallic leads. Photochromic molecules are attractive candidates for use in molecular electronics because of the switching between different states with different conducting behavior. We also investigate the switching behavior of the molecule based on total energy calculations for intermediate conformations along the reaction path. The results are compared to earlier work.

Keyword
Ab initio study, Conducting behavior, Dithienylethene, Electron transport, Intermediate conformation, Metallic leads, Photochromic molecules, Reaction paths, Single molecule, Switching behaviors, Theoretical study, Total energy calculation, Molecular electronics, Molecules, Photochromism, Reaction intermediates
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8605 (URN)10.1088/1742-6596/100/5/052061 (DOI)000275655200157 ()2-s2.0-77954319826 (Scopus ID)
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2017-12-14Bibliographically approved
3. Investigation of conducting properties of a photochromic dithienylethene molecule using different lead atomic basis sets
Open this publication in new window or tab >>Investigation of conducting properties of a photochromic dithienylethene molecule using different lead atomic basis sets
(English)Manuscript (Other academic)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8606 (URN)
Note
QC 20101119Available from: 2008-06-02 Created: 2008-06-02 Last updated: 2010-11-19Bibliographically approved

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Citation style
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