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First Principles Study of Molecular Electronic Devices
KTH, School of Biotechnology (BIO).
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Molecular electronics is an active research area for the future information technology. The fabrication of basic electronic elements with molecules as the core-operators has been made experimentally in the laboratory in recent years. However, the underlying electron or charge transport mechanisms for most devices are still under debate, Theoretical modelling based on the first-principles methods are expected to play an important role in this field.

A generalized quantum chemical approach based on Green's function scattering theory has been developed and applied to two- and three-terminal molecular devices. It allows to study both elastic and inelastic electron scattering at hybrid density functional theory levels. It can treat molecular devices where the metal electrodes and the molecule are either chemically or physically bonded on equal footing. As one of the applications, we have studied the length dependence of electron transport in gold-oligophenylene-gold junctions. We have shown that the experimental results for molecular junctions of oligophenylene with di erent lengths can be well reproduced by hybrid density functional theory calculations. It is also found that the current-voltage characteristics of the junctions depend strongly on the metal-molecule bonding distances. With the help of the calculations, the possible gold-molecule bonding distances in the experimental devices are identi ed.

The central focus of this thesis is to study the three-terminal molecular devices, namely the eld e ect transistor (FET). An extension of our quantum chemical approach to FET devices has been made and successfully applied to different FET devices constructed with polymer, small and middle sized conjugated molecules. The experimentally observed conductance oscillation in polymer FET and three orders of magnitude enhancement of the current in electrochemical gated molecular FET have been verified by the calculations. The electron transport mechanisms of these devices are revealed.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , 46 p.
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-3882ISBN: 91-7178-290-7 (print)OAI: oai:DiVA.org:kth-3882DiVA: diva2:9856
Presentation
2006-03-24, Sal FD41, AlbaNova, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101129Available from: 2006-03-15 Created: 2006-03-15 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Quantum chemical study of coherent electron transport in oligophenylene molecular junctions of different lengths
Open this publication in new window or tab >>Quantum chemical study of coherent electron transport in oligophenylene molecular junctions of different lengths
2005 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 412, no 4-6, 406-410 p.Article in journal (Refereed) Published
Abstract [en]

The coherent electron transportation properties of the gold-oligophenylene-gold junctions of different lengths have been studied by means of a generalized quantum chemical approach. The experimentally measured length dependence of current flow in the junctions has been well reproduced by the hybrid density functional theory calculations. It is found that the current-voltage characteristics of the junctions depend strongly on the metal-molecule bonding distances. With the help of the calculations, the possible gold-molecule bonding distances in the experimental devices are identified.

Keyword
self-assembled monolayers, atomic-force microscopy, wires, conductance, dependence, scattering, metal
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-15016 (URN)10.1016/j.cplett.2005.07.021 (DOI)000231660800032 ()2-s2.0-23944509693 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Understanding the Performance of a Single Molecular Field Effect Transistor by First Principles Modeling
Open this publication in new window or tab >>Understanding the Performance of a Single Molecular Field Effect Transistor by First Principles Modeling
2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Other academic) Submitted
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:kth:diva-26915 (URN)
Note
QS 20120316Available from: 2010-11-29 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
3. A generalized quantum chemical approach for modeling of single molecular field effect transistors
Open this publication in new window or tab >>A generalized quantum chemical approach for modeling of single molecular field effect transistors
2005 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Article in journal (Other academic) Submitted
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-26916 (URN)
Note
QS 20120316Available from: 2010-11-29 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved

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Citation style
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