PhD ceremony: H.B. Akkerman, 11.00 uur, Academiegebouw, Broerstraat 5, Groningen
Thesis: Large-area molecular junctions
Promotor(s): prof. B. de Boer, prof. P.W.M. Blom, prof. D.M. de Leeuw
Faculty: Mathematics and Natural Sciences
The main goal of molecular electronics is the fabrication of electronic devices based on the electronic functionality of single molecules or an assembly of molecules. The major challenge, however, is to reliably contact these molecules and fabricate reproducible electronic test beds, since the fabrication of electrodes to molecules leads easily to short circuit formation. This thesis describes a novel approach to overcome this problem of short circuit formation by applying a highly conductive polymer on top of a so-called self-assembled monolayer (SAM), resulting in reliable and reproducible molecular junctions. Although this highly ordered monolayer (the active element) is only a few nanometers thick, the molecules of the conducting polymer are too large to penetrate the SAM and act as a cushion for metal atoms to land on during the evaporation of the final top electrode. Since the fabrication techniques are relatively simple and widely employed by industry, implementation of molecular junctions into existing industrial technology is possible and demonstrated in this thesis.
Alkane(di)thiols, the molecules studied in this thesis, are an ideal benchmark system for any new technology in the field of molecular electronics. Comprising of a linear carbon chain with a sulfur end group, these molecules can self-assemble on gold surfaces into monolayers with a high degree of order. The nature of the electronic transport through these alkane(di)thiols, in combination with the influence of processing conditions on monolayer formation and on electrical characteristics, is investigated. It is shown that the resistance of a molecular junction can be factorized, clearly explaining the apparent discrepancies obtained in literature for the resistance of a single molecule.
See also press release Philips and Dutch University of Groningen demonstrate a breakthrough in fabricating molecular electronics
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