Organic Electrodes Based on Grafted Oligothiophene Units in Ultrathin, Large-Area Molecular Junctions
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- 作者：Pascal Martin ; Maria Luisa Della Rocca ; Anne Anthore ; Philippe Lafarge ; Jean-Christophe Lacroix
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：January 11, 2012
- 年：2012
- 卷：134
- 期：1
- 页码：154-157
- 全文大小：252K
- 年卷期：v.134,no.1(January 11, 2012)
- ISSN：1520-5126
文摘
Molecular junctions were fabricated with the combined use of electrochemistry and conventional CMOS tools. They consist of a 5鈥?0 nm thick layer of oligo(1-(2-bisthienyl)benzene) between two gold electrodes. The layer was grafted onto the bottom electrode using diazonium electroreduction, which yields a stable and robust gold鈥搊ligomer interface. The top contact was obtained by direct electron-beam evaporation on the molecular layers through masks defined by electron-beam lithography. Transport mechanisms across such easily p-dopable layers were investigated by analysis of current density鈥搗oltage (J鈥?i>V) curves. Application of a tunneling model led to a transport parameter (thickness of 2.4 nm) that was not consistent with the molecular thickness measured using AFM (7 nm). Furthermore, for these layers with thicknesses of 5鈥?0 nm, asymmetric J鈥?i>V curves were observed, with current flowing more easily when the grafted electrode was positively polarized. In addition, J鈥?i>V experiments at two temperatures (4 and 300 K) showed that thermal activation occurs for such polarization but is not observed when the bias is reversed. These results indicate that simple tunneling cannot describe the charge transport in these junctions. Finally, analysis of the experimental results in term of 鈥渙rganic electrode鈥?and redox chemistry in the material is discussed.