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Effects of Hydrogen Bonding on Current−Voltage Characteristics of Molecular Junctions
KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences.
KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.ORCID-id: 0000-0003-0007-0394
2006 (Engelska)Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, nr 19, s. 194703-1-194703-7Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present a first-principles study of hydrogen bonding effect on current-voltage characteristics of molecular junctions. Three model charge-transfer molecules, 2'-amino-4,4'-di(ethynylphenyl)-1-benzenethiolate (DEPBT-D), 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate (DEPBT-A), and 2'-amino-4,4'-di(ethynylphenyl)-5'-nitro-1-benzenethiolate (DEPBT-DA), have been examined and compared with the corresponding hydrogen bonded complexes formed with different water molecules. Large differences in current-voltage characteristics are observed for DEPBT-D and DEPBT-A molecules with or without hydrogen bonded waters, while relatively small differences are found for DEPBT-DA. It is predicted that the presence of water clusters can drastically reduce the conductivities of the charge-transfer molecules. The underlying microscopic mechanism has been discussed.

Ort, förlag, år, upplaga, sidor
2006. Vol. 125, nr 19, s. 194703-1-194703-7
Nyckelord [en]
Charge transfer, Current voltage characteristics, Electric conductivity, Hydrogen bonds;, Mathematical models, Water, Charge transfer molecules, Molecular junctions, Aromatic compounds
Nationell ämneskategori
Teoretisk kemi
Identifikatorer
URN: urn:nbn:se:kth:diva-7524DOI: 10.1063/1.2364494ISI: 000242181800066PubMedID: 17129146Scopus ID: 2-s2.0-33845301692OAI: oai:DiVA.org:kth-7524DiVA, id: diva2:12574
Anmärkning
QC 20100804Tillgänglig från: 2007-09-28 Skapad: 2007-09-28 Senast uppdaterad: 2022-06-26Bibliografiskt granskad
Ingår i avhandling
1. Understanding Electron Transport Properties of Molecular Electronic Devices
Öppna denna publikation i ny flik eller fönster >>Understanding Electron Transport Properties of Molecular Electronic Devices
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2007. s. 54
Nationell ämneskategori
Teoretisk kemi
Identifikatorer
urn:nbn:se:kth:diva-4500 (URN)978-91-7178-768-2 (ISBN)
Disputation
2007-10-18, FB52, AlbaNova Universitetscentrum, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100804. Ändrat titeln från: "Understanding Electron Transport Properties in Molecular Devices" 20100804.Tillgänglig från: 2007-09-28 Skapad: 2007-09-28 Senast uppdaterad: 2022-06-26Bibliografiskt granskad
2. Elastic and Inelastic Electron Tunneling in Molecular Devices
Öppna denna publikation i ny flik eller fönster >>Elastic and Inelastic Electron Tunneling in Molecular Devices
2006 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: Bioteknologi, 2006. s. 46
Nyckelord
molecular electronics, inelastic electron tunneling spectroscopy, IETS, Green's function, scattering
Nationell ämneskategori
Teoretisk kemi
Identifikatorer
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
Handledare
Anmärkning
QC 20101118Tillgänglig från: 2006-05-11 Skapad: 2006-05-11 Senast uppdaterad: 2022-06-27Bibliografiskt granskad
3. A generalized quantum chemical approach for nano- and bio-electronics
Öppna denna publikation i ny flik eller fönster >>A generalized quantum chemical approach for nano- and bio-electronics
2005 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

A generalized quantum chemical approach for electron transport in molecular devices is developed. It allows to treat the devices where the metal electrodes and the molecule are either chemically or physically bonded on equal footing. Effects of molecular length and hydrogen bonding on the current-voltage (I-V) characteristics of molecular devices are discussed. An extension to include the vibration motions of the molecule has been derived and implemented. It provides the inelastic electron tunneling spectroscopy (IETS) of molecular devices with unprecedented accuracy, and reveals important information about the molecular structures that are not accessible in the experiment. The IETS is shown to be a powerful characterization tool for molecular devices.

An effective elongation method has been developed to study the electron transport in nanoand bio-electronic devices at hybrid density functional theory level. It enables to study electronic structures and transportation properties of a 40 nm long self-assembled conjugated polymer junction, a 21 nm long single-walled carbon nanotubes (SWCNT), and a 60 basepairs DNA molecule. It is the first time that systems consisting of more than 10,000 electrons have been described at such a sophisticated level. The calculations have shown that the electron transport in sub-22 nm long SWCNT and short DNA molecules is dominated by the coherent scattering through the delocalized unoccupied states. The derived length dependence of coherent electron transport in these nanostructured systems will be useful for the future experiments. Moreover, some unexpected behaviors of these devices have been discovered.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2005. s. 48
Nyckelord
Biotechnology, Bioteknik
Nationell ämneskategori
Industriell bioteknik
Identifikatorer
urn:nbn:se:kth:diva-286 (URN)91-7178-022-X (ISBN)
Presentation
2005-05-24, Sal FB53, AlbaNova, 10:00
Opponent
Handledare
Anmärkning
QC 20101203Tillgänglig från: 2005-07-06 Skapad: 2005-07-06 Senast uppdaterad: 2022-06-23Bibliografiskt granskad

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