| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuM |
| Session: | Contacts and Transport |
| Presenter: | M. Zharnikov, Universität Heidelberg, Germany |
| Authors: | P. Kao, Pennsylvania State University S. Neppl, Technische Universität München, Germany P. Feulner, Technische Universität München, Germany D.L. Allara, Pennsylvania State University M. Zharnikov, Universität Heidelberg, Germany |
| Correspondent: | Click to Email |
Emergence of molecular and organic electronics as frontier fields of modern science and technology require reliable experimental data regarding the charge transport (CT) in individual molecules and their functional units. Whereas static conductance of molecules arranged in self-assembled monolayer (SAM) fashion on a suitable substrate has been extensively studied, little is known about the CT dynamics in these systems. By the example of alkanethiolate films on Au(111), we show that the latter phenomena can be successfully addressed by resonant Auger spectroscopy, using the core hole clock method. The charge transfer pathway was unambiguously defined by resonant excitation of the nitrile tailgroup attached to the alkyl backbone. The length of this backbone was varied to monitor the respective dependence of the CT time. It was found that, similar to the static conductance, this dependence can be coarsely described by an exponential function with an attenuation factor of 0.93 per a methylene unit. As a result, the CT time is quite long even for a relatively short alkyl chain; in particular, it is ca. 100 fs for the chain consisting of only four methylene units. In contrast, the CT time associated with the thiolate headgroup anchor was found to be quite short, viz. 2.3 fs (upper limit), which suggests an efficient interfacial electronic coupling between the aliphatic backbone of the molecules and substrate over the thiolate-gold linkage.