Dr John L Pearson -.Participant in the Molecular Interconnect for Nanotechnology (MINT) Project

Project Overview

The aim of the MINT project is to advance the science and technology of fabricating novel nano-devices and their interconnection in circuits. The project is sponsored by the European Commission and involves a collaboration of several universities, Glasgow, Liverpool and Limerick, all co-ordinated by Glasgow University.

As photo-lithography reaches its feature-size limitation, new methods of forming relatively large circuit patterns (>100nm), but incorporating nano-sized features (<10nm), have to be developed. One solution involves using electron beam lithography, but writing (exposing) serially creates job-time issues and even the latest technology would struggle to write such patterns accurately or consistently.

This project aims to address these limitations by invoking the use of long-chain molecules, more specifically natural and synthetic RNA, to form such circuit templates. The physical and chemical nature of RNA lends itself to forming large and varied 2-D lattices, or "circuits", onto planar, electronic substrates. In addition, specific sites along the chains can accommodate or host chemically functionalised, clusters of elemental nano-particles such as gold (mainly the work of Liverpool). With these incorporated, typical circuit elements can be built allowing properties, such as conductivity, to be tailored.

The use of the 2-D lattice templates as lithographic masks will also be investigated in two specific ways. One involves the RNA lattice(s) appropriately positioned on chemically prepared substrates. A polymer coat (self-limiting) is then applied but does not cover the RNA template strands. The strands (~3-4nm) are then ruptured from their substrate attachment and metal is then electro-formed into the gaps, after which the polymer is removed. The other way involves simply bonding the metal (metallation) to the existing lattice(s) using functionalising or electro-chemical means (mainly the work of Limerick).

Most of the above technologies assume the prerequisite that the RNA strands, whether hosting nano-particles or not, can be immobilised onto specific sites on the substrates. This is one of Glasgow's main contributions and involves developing chemical strategies for positioning and attaching RNA to appropriate sites on metal contacts or electrical substrates.

In order to appraise the success or otherwise of the above schemes, ensemble electrical characterisation of the configurations will be necessary (mainly Glasgow). Metal electrodes with gaps down to 20nm will be fabricated on Si/SiO2 substrates. Both the metal and substrate will be chemically prepared to position and immobilise a lattice of RNA, which will bridge the electrodes. Other (gate) electrodes can be added locally to effect if necessary. In order to eliminate the conductive effects of moisture etc on such small bridging systems, measurements may have to be made in a vacuum. Liverpool will also be electrically characterising individual nano-particles in-situ using scanning probe and tunnelling microscopy.