2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Nanowires and Nanogaps for Molecular Electronics

F.O. Hadeed, C. Durkan
University of Cambridge, UK

Keywords:
electromigration, nanometer gap, break junction, molecular transistor

Abstract:
By carefully controlling the current stressing conditions of nanowires, the electromigration process can be used to create break-junctions of a controlled gap size. The resultant nanogaps open up the possibility of making novel molecular devices, including molecular transistors, facilitated by the introduction of 1,4-benzene dithiol molecules, other alkanethiols, and porphyrins in various configurations. To date, our electrical characterisation results are for 1µm long Au and Au/Pd nanowires of linewidths 200nm down to 20nm. Our process is an optimisation of conditions capable of repeatedly making nanogaps less than 2nm. Results from electrical characterisation of the nanowires undergoing failure by electromigration are combined with scanning probe microscopy and scanning electron microscopy to image both topographic as well as potential maps of the nanowires and resulting nanogaps. I-V curves exhibiting tunneling behaviour are recorded and used to estimate the size of the formed nanogaps. SEM and AFM corroborate the conclusion that nanogaps are formed by visibly capturing images of the nanogaps as well as measuring a discontinuity in the surface potential along the wire when using a conductive AFM. Current and future challenges include creating more reliable contacts between molecules and electrodes with the aim of reducing contact resistance, reliably placing molecules in nanogaps and measuring the induced changes in the electrical characteristics of the device, and improving the models for both electromigration in metals and conduction through metal-molecule-metal junctions.

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