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Probing molecule-metal bonding in molecular junctions by inelastic electron tunneling spectroscopy
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0003-0007-0394
2006 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 6, no 8, 1693-1698 p.Article in journal (Refereed) Published
Abstract [en]

We present first-principles calculations for the inelastic electron tunneling spectra ( IETS) of three molecules, 1-undecane thiol (C11), alpha, omega-bis(thioacetyl)oligophenylenethynylene (OPE), and alpha,omega-bis(thioacetyl) oligophenylenevinylene (OPV), sandwiched between two gold electrodes. We have demonstrated that IETS is very sensitive to the bonding between the molecule and electrodes. In comparison with experiment of Kushmerick et al. (Nano Lett. 2004, 4, 639), it has been concluded that the C11 forms a strong chemical bond, while the bonding of the OPE and OPV systems are slightly weaker. All experimental spectral features have been correctly assigned.

Place, publisher, year, edition, pages
2006. Vol. 6, no 8, 1693-1698 p.
Keyword [en]
Chemical bonds; Electrodes; Electron tunneling; Organic compounds; First principles calculations; Inelastic electron tunneling spectra (IETS); Molecular junctions; Molecule-metal bonding; article; binding site; chemical model; chemical structure; chemistry; computer simulation; elasticity; electron transport; energy filtered transmission electron microscopy; methodology; microelectrode; scanning tunneling microscopy; Binding Sites; Computer Simulation; Elasticity; Electron Transport; Metals; Microelectrodes; Microscopy, Energy-Filtering Transmission Electron; Microscopy, Scanning Tunneling; Models, Chemical; Models, Molecular; Nanostructures; Polymers
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-6989DOI: 10.1021/nl060951wISI: 000239623900021Scopus ID: 2-s2.0-33748329697OAI: oai:DiVA.org:kth-6989DiVA: diva2:11856
Note
QC 20100730Available from: 2007-04-17 Created: 2007-04-17 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Elastic and Inelastic Electron Tunneling in Molecular Devices
Open this publication in new window or tab >>Elastic and Inelastic Electron Tunneling in Molecular Devices
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

A theoretical framework for calculating electron transport through molecular junctions is presented. It is based on scattering theory using a Green's function formalism. The model can take both elastic and inelastic scattering into account and treats chemical and physical bonds on equal footing. It is shown that it is quite reliable with respect to the choice of functional and basis set. Applications concerning both elastic and inelastic transport are presented, though the emphasis is on the inelastic transport properties. The elastic scattering application part is divided in two part. The first part demonstrates how the current magnitude is strongly related to the junction width, which provides an explanation why experimentalists get two orders of magnitude differences when performing measurements on the same type of system. The second part is devoted to a study of how hydrogenbonding affects the current-voltage (I-V) characteristics. It is shown that for a conjugated molecule with functional groups, the effects can be quite dramatic. This shows the importance of taking possible intermolecular interactions into account when evaluating and comparing experimental data. The inelastic scattering part is devoted to get accurate predictions of inelastic electron tunneling spectroscopy (IETS) experiments. The emphasis has been on elucidating the importance of various bonding conditions for the IETS. It is shown that the IETS is very sensitive to the shape of the electrodes and it can also be used to discriminate between different intramolecular conformations. Temperature dependence is nicely reproduced. The junction width is shown to be of importance and comparisons between experiment as well as other theoretical predictions are made.

Place, publisher, year, edition, pages
Stockholm: Bioteknologi, 2006. 46 p.
Keyword
molecular electronics, inelastic electron tunneling spectroscopy, IETS, Green's function, scattering
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-3958 (URN)91-7178-362-8 (ISBN)
Presentation
2006-05-31, FB52, AlbaNova Main Building, Roslagstullsbacken 21, SE-106 91, Stockholm, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101118Available from: 2006-05-11 Created: 2006-05-11 Last updated: 2010-11-18Bibliographically approved
2. Understanding Electron Transport Properties of Molecular Electronic Devices
Open this publication in new window or tab >>Understanding Electron Transport Properties of Molecular Electronic Devices
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

his thesis has been devoted to the study of underlying mechanisms for electron transport in molecular electronic devices. Not only has focus been on describing the elastic and inelastic electron transport processes with a Green's function based scattering theory approach, but also on how to construct computational models that are relevant to experimental systems. The thesis is essentially divided into two parts. While the rst part covers basic assumptions and the elastic transport properties, the second part covers the inelastic transport properties and its applications.

It is discussed how di erent experimental approaches may give rise to di erent junction widths and thereby di erences in coupling strength between the bridging molecules and the contacts. This di erence in coupling strength is then directly related to the magnitude of the current that passes through the molecule and may thus explain observed di erences between di erent experiments. Another focus is the role of intermolecular interactions on the current-voltage (I-V) characteristics, where water molecules interacting with functional groups in a set of conjugated molecules are considered. This is interesting from several aspects; many experiments are performed under ambient conditions, which means that water molecules will be present and may interfere with the experiment. Another point is that many measurement are done on self-assembled monolayers, which raises the question of how such a measurement relates to that of a single molecule. By looking at the perturbations caused by the water molecules, one may get an understanding of what impact a neighboring molecule may have. The theoretical predictions show that intermolecular e ects may play a crucial role and is related to the functional groups, which has to be taken into consideration when looking at experimental data.

In the second part, the inelastic contribution to the total current is shown to be quite small and its real importance lies in probing the device geometry. Several molecules are studied for which experimental data is available for comparison. It is demonstrated that the IETS is very sensitive to the molecular conformation, contact geometry and junction width. It is also found that some of the spectral features that appear in experiment cannot be attributed to the molecular device, but to the background contributions, which shows how theory may be used to complement experiment. This part concludes with a study of the temperature dependence of the inelastic transport. This is very important not only from a theoretical point of view, but also for the experiments since it gives experimentalists a sense of which temperature ranges they can operate for measuring IETS.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 54 p.
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-4500 (URN)978-91-7178-768-2 (ISBN)
Public defence
2007-10-18, FB52, AlbaNova Universitetscentrum, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100804. Ändrat titeln från: "Understanding Electron Transport Properties in Molecular Devices" 20100804.Available from: 2007-09-28 Created: 2007-09-28 Last updated: 2010-08-04Bibliographically approved
3. A Quantum Chemical View of Molecular and Nano-Electronics
Open this publication in new window or tab >>A Quantum Chemical View of Molecular and Nano-Electronics
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This dissertation presents a generalized quantum chemical approach for electron transport in molecular electronic devices based on Green's function scattering theory. It allows to describe both elastic and inelastic electron transport processes at first principles levels of theory, and to treat devices with metal electrodes either chemically or physically bonded to the molecules on equal footing. Special attention has been paid to understand the molecular length dependence of current-voltage characteristics of molecular junctions. Effects of external electric fields have been taken into account non-perturbatively, allowing to treat electrochemical gate-controlled single molecular field effect transistors for the first time. Inelastic electron tunneling spectroscopy of molecular junctions has been simulated by including electron-vibration couplings. The calculated spectra are often in excellent agreement with experiment, revealing detailed structure information about the molecule and the bonding between molecule and metal electrodes that are not accessible in the experiment.

An effective central insertion scheme (CIS) has been introduced to study electronic structures of nanomaterials at first principles levels. It takes advantage of the partial periodicity of a system and uses the fact that long range interaction in a big system dies out quickly. CIS method can save significant computational time without loss of accuracy and has been successfully applied to calculate electronic structures of one- , two- , and three-dimensional nanomaterials, such as sub-116 nm long conjugated polymers, sub-200nm long single-walled carbon nanotubes, sub-60 base pairs DNA segments, nanodiamondoids of sub-7.3nm in diameter and Si-nanoparticles of sub-6.5nm in diameter at the hybrid density functional theory level. The largest system under investigation consists of 100,000 electrons. The formation of energy bands and quantum confinement effects in these nanostructures have been revealed. Electron transport properties of polymers, SWCNTs and DNA have also been calculated.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 70 p.
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:kth:diva-4335 (URN)978-91-7178-618-0 (ISBN)
Public defence
2007-04-24, FA32, AlbaNova, Roslagstullsbacken, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100729. Ändrat felaktig titel "Theoretical Chemistry, Molecular and Nano-electronics" 20100729.Available from: 2007-04-17 Created: 2007-04-17 Last updated: 2010-07-30Bibliographically approved

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