Coulomb blockade and the Kondo effect in single-atom transistors

Abstract

Using molecules as electronic components is a powerful new direction in the science and technology of nanometre-scale systems. Experiments to date have examined a multitude of molecules conducting in parallel, or, in some cases, transport through single molecules. The latter includes molecules probed in a two-terminal geometry using mechanically controlled break junctions or scanning probes as well as three-terminal single-molecule transistors made from carbon nanotubes, C(60) molecules, and conjugated molecules diluted in a less-conducting molecular layer. The ultimate limit would be a device where electrons hop on to, and off from, a single atom between two contacts. Here we describe transistors incorporating a transition-metal complex designed so that electron transport occurs through well-defined charge states of a single atom. We examine two related molecules containing a Co ion bonded to polypyridyl ligands, attached to insulating tethers of different lengths. Changing the length of the insulating tether alters the coupling of the ion to the electrodes, enabling the fabrication of devices that exhibit either single-electron phenomena, such as Coulomb blockade, or the Kondo effect.

Molecular three-terminal devices: fabrication and measurements

“…[8][9][10][11][12] To be more specific, a surprising feature of the data in Fig. 7 is the absence of degeneracy points along the gate axis for low bias.…”

A Molecular Platinum Cluster Junction: A Single-Molecule Switch

“…Metal atoms have been successfully incorporated into organic frameworks as metal complexes for single-molecule experiments, as well as chains of atoms. [9][10][11][12] Regarding metal clusters, the Mn 12 structure has been investigated as the functional core in single molecule magnets 1 and theoretical studies about its transport properties have been carried out. 13,14 However, despite the vast range of molecular clusters known, only a few have been analyzed in this context.…”

Analytical Challenges in Molecular Electronics

“…Conceptually similar experiments are based on "break junctions" in which a molecule bridges across two nanostructured metal contacts with a gap that can be controlled mechanically or by electron-beam lithography (24, 25; Figure 1b). Several exquisite experiments have been reported on the electronic structure of single molecules as modulated by attachment to the conducting contacts (26,27 ). For example, STM has been used to image the electron density of single molecules of copper phthalocyanine bridging two gold atoms, thus permitting direct investigation of the electronic structure of the molecule as a function of the dimensions of the gap between gold atoms (27 ).…”