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Systematic assessment of a nanoparticle bridge platform for molecular electronics measurements
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. (Elektronmikroskopi och Nanoteknologi)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. (Elektronmikroskopi och Nanoteknologi)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. (Nanoteknologi och Funktionella Material)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. (Elektronmikroskopi och Nanoteknologi)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A combination of electron beam lithography, photolithography and focused ion beam milling was used to create a nanogap platform, which was bridged by gold nanoparticles (AuNPs) in order to make electrical measurements and assess the platform under ambient conditions. Initially bare electrodes were tested to determine the response of the platform and it was found that creating devices in ambient conditions requires careful cleaning processes and awareness of the contributions contaminants may make to measurements. Both octanethiol (OT) and Biphenyldithiol (BPDT) molecules were also tested by functionalizing the nanoelectrodes with the molecules prior to bridging the nanogap with the nanoparticles. Measurements on OT show that it is possible to make measurements on relatively small numbers of molecules, but that a large variation in response can be expected when one of the metal-molecule junctions is physisorbed, which was partially explained by attachment of OT molecules to different sites on the surface of the Au electrode using a density function theory calculation. On the other hand, when dealing with BPDT, high yields for device creation are very difficult to achieve when preparing the devices in ambient conditions. Significant hysteresis, or conductance switching, in the I-V curves of BPDT was also observed, which we attribute primarily to voltage induced changes at the interface between the molecule and the metal.

National Category
Nano Technology
Identifiers
URN: urn:nbn:se:uu:diva-122931OAI: oai:DiVA.org:uu-122931DiVA: diva2:311410
Available from: 2010-04-21 Created: 2010-04-21 Last updated: 2012-12-07
In thesis
1. Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
Open this publication in new window or tab >>Fabrication and Applications of a Focused Ion Beam Based Nanocontact Platform for Electrical Characterization of Molecules and Particles
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of new materials with novel properties plays an important role in improving our lives and welfare. Research in Nanotechnology can provide e.g. cheaper and smarter materials in applications such as energy storage and sensors. In order for this development to proceed, we need to be able to characterize the material properties at the nano-, and even the atomic scale. The ultimate goal is to be able to tailor them according to our needs.

One of the great challenges concerning the characterization of nano-sized objects is how to achieve the physical contact to them. This thesis is focused on the contacting of nanoobjects with the aim of electrically characterizing them and subsequently understanding their electrical properties. The analyzed nanoobjects are carbon nanosheets, nanotetrapods, nanoparticles and molecular systems.

Two contacting strategies were employed in this thesis. The first strategy involved the development of a focused ion beam (FIB) based nanocontact platform. The platform consists of gold nanoelectrodes, having nanogaps of 10-30 nm, on top of an insulating substrate. Gold nanoparticles, double-stranded DNA and cadmium telluride nanotetrapods have been trapped in the gaps by using dielectrophoresis. In certain studies, the gold electrodes have also been coated with conducting or non-conducting molecules, prior to the trapping of gold nanoparticles, in order to form molecular junctions. These junctions were subsequently electrically characterized to evaluate the conduction properties of these molecular systems. For the purpose of better controlling the attachment of molecules to the nanoelectrodes, a novel route to synthesize alkanedithiol coated gold nanoparticles was developed. The second contacting strategy was based on the versatility of the FIB instrument as a platform for in-situ manipulation and electrical characterization of non-functionalized and functionalized carbon nanosheets, where it was found that the functionalized samples had an increased conductivity by more than one order of magnitude.

Both contacting strategies proved to be valuable for building knowledge around contacting and electrical characterization of nanoobjects

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 88 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 745
Keyword
Focused Ion Beam, FIB, Scanning Electron Microscopy, SEM, Nanogap electrodes, Nanostructuring, Nanofabrication, Electron Beam Lithography, Electrical characterization, Dielectrophoresis
Identifiers
urn:nbn:se:uu:diva-122940 (URN)978-91-554-7809-4 (ISBN)
Public defence
2010-06-07, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, 75121, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2010-05-17 Created: 2010-04-21 Last updated: 2010-05-18Bibliographically approved

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Jafri, HassanBlom, Tobias

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