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Contribution à l'étude des contacts atomiques et moléculaires ponctuels

Abstract : Molecular electronics tends to use a single molecule as a component of an electronic device. Such realization would merge the potential of chemistry potential with the most developed nanotechnologies. But there is still a long way to go before the electronics transport properties of a single molecule can be completely understood. Experimental realizations are difficult as they require contact of nanometer size electrodes. Our work is devoted to the development of this type of experimental technique which concerns not only molecular electronics but also electronic transport at nanometric scale. In the first part of the manuscript the experimental techniques are described. We use a modified scanning tunneling microscope to form nanosized electrodes (break junction technique). This approach combine two research domain namely charge transport in molecules and atomic point contact. More precisely, the formation and the electronic transport in atomic point contact are particularly studied. Afterwards we present our result on atomic point contact (Au-Au junction) and on molecular contact (Au-molecule-Au junction). Conductance quantization and ballistic transport are displayed. Our research shows that the electrical signature of a single molecule can be distinguished. But despite the progresses in single molecule conductance determination brought by theses experimental techniques, there is still a large disparities on reported results. At the end of the first part we concentrate on the importance of statistical studies on a large population of experimental data. The Au-Au junction is used in this study. In the second part we describe the specific statistical analysis tools which allow the extraction of the needed parameters (for example the lifetime) from each Au-Au junction conductance measurement. The statistical analyses of these parameters in different experimental conditions are discussed. They provide information on the mechanic of these nanosystems (i.e. on the breaking mechanism of the nanowire). The developed tools allow observing the subtle effects. It is shown that a little fraction of electron is not ballistic. Finally we show the existence of bistable fluctuations and discuss their effect on ballistic transport and their link with atomic movement.
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https://tel.archives-ouvertes.fr/tel-00412904
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Submitted on : Wednesday, September 2, 2009 - 4:18:17 PM
Last modification on : Tuesday, November 16, 2021 - 4:06:02 PM
Long-term archiving on: : Tuesday, June 15, 2010 - 8:24:37 PM

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  • HAL Id : tel-00412904, version 1

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Thomas Leoni. Contribution à l'étude des contacts atomiques et moléculaires ponctuels. Matière Condensée [cond-mat]. Université de la Méditerranée - Aix-Marseille II, 2009. Français. ⟨tel-00412904⟩

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