Electron transport through single organic molecules and self-assembled monolayers

Promotie: dhr. E.V. Huisman, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Proefschrift: Electron transport through single organic molecules and self-assembled monolayers

Promotor(s): prof.dr.ir. B.J. van Wees

Faculteit: Wiskunde en Natuurwetenschappen

Contact: Eek Huisman, tel.050-363 8974, e-mail: e.h.huisman@rug.nl

Electron transport through single organic molecules and self-assembled monolayers

A simple molecule is about a billion times (1,000,000,000) smaller than a human being. Small is popular. For example, miniaturization of components has improved computers for many years. In that sense, a molecule is perhaps the ultimate electronic component. However, before being able to build anything sensible, one first needs to know the electronic properties of molecules. To do so you need to connect them to electrodes.

How to put a single molecule in between contacts? This thesis experimentally explores two methods. The first method very gently breaks a thin gold wire. By pulling on the wire, the diameter of the wire gradually decreases, similar to pulling on a piece of chewing gum. Pulling even further will break the wire. The contacts thus formed have very suitable dimensions for contacting a single molecule. The thesis reports on how to get molecules in between these contacts, when you equip them with ‘sticky’ sulfur atoms.

The second method contacts many layers of many molecules at the same time. Although many molecules are involved, the layer is only one molecule thick. More specifically, we investigate molecules which consist of several benzene rings in series. We find that the resistance of these molecules increases with the number of benzene rings. Also, we try to make molecules vibrate using the current.

Models for charge transport through thin layers of insulating oxides have been around for about 50 years. But are molecules really fundamentally different from these systems? This thesis also argues for a new description.