Coulomb-blockade transport in single-crystal organic thin-film transistors

• Published in: Nature (London) 2000-04, Vol.404 (6781), p.977-980
• Main Authors: Schoonveld, W. A, Wildeman, J, Fichou, D, Bobbert, P. A, van Wees, B. J, Klapwijk, T. M
• Format: Article
• Language: English
• Subjects: Applied sciences; Arrays; Blocking; Charging; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Coulomb friction; Crystals; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in interface structures; Electronics; Electrons; Energy; Exact sciences and technology; Humanities and Social Sciences; letter; Low temperature; Miscellaneous; multidisciplinary; Physics; Science; Science (multidisciplinary); Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Semiconductor-device characterization, design, and modeling; Thin films; Transistors; Transport; Tunnels (transportation)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/35010073

Coulomb-blockade transport-whereby the Coulomb interaction between electrons can prohibit their transport around a circuit-occurs in systems in which both the tunnel resistance, RT, between neighbouring sites is large (>h/e2) and the charging energy, EC (EC = e2/2C, where C is the capacitance of the site), of an excess electron on a site is large compared to kT. (Here e is the charge of an electron, k is Boltzmann's constant, and h is Planck's constant.) The nature of the individual sites-metallic, superconducting, semiconducting or quantum dot-is to first order irrelevant for this phenomenon to be observed. Coulomb blockade has also been observed in two-dimensional arrays of normal-metal tunnel junctions, but the relatively large capacitances of these micrometre-sized metal islands results in a small charging energy, and so the effect can be seen only at extremely low temperatures. Here we demonstrate that organic thin-film transistors based on highly ordered molecular materials can, to first order, also be considered as an array of sites separated by tunnel resistances. And as a result of the sub-nanometre sizes of the sites (the individual molecules), and hence their small capacitances, the charging energy dominates at room temperature. Conductivity measurements as a function of both gate bias and temperature reveal the presence of thermally activated transport, consistent with the conventional model of Coulomb blockade.