Mar 1, 2007
Four-probe electrical transport measurements on individual metallic nanowires
As the size of components in electronic devices decreases, it becomes increasingly more difficult and expensive to fabricate them using conventional lithographic techniques. Nanowires provide an interesting “bottom-up” alternative, and can be produced with dimensions far below present lithographic limits. However, if nanowires are to become feasible alternatives to top-down methods, then a thorough electrical characterization is essential.
In our research we use multiple scanning tunnelling microscopes, guided by a high-resolution scanning electron microscope to provide contacts to nanostructures. The advantages of this technique are that any nanostructure drop-cast on a surface can be interrogated and multiple measurements can be taken on the same nanostructure. By using four contacts we can eliminate the effects of contact resistance, which are significant or even dominant at the nanoscale. By varying the separation of the tips along the wires we obtained graphs of resistance against length, allowing the resistivity of the material to be determined.
Currently, work is being undertaken on measuring the transport properties of nanowires composed of semiconducting transition metal oxides and ultrathin virus-templated nanowires. This system is also being used as a novel method for the fabrication of single-walled carbon nanotube devices. In future, we plan to characterize nanowire devices composed of multi-segmented nanowires of both metals and semiconductors.
About the author
Stephen Evans heads the molecular and nanoscale physics group, at the University of Leeds. His interests are in the optical and electronic properties of self-assembled metallic and semiconducting nanostructures.