Low-Dimensional Electronic Device Fabrication at Low Cost over Large Areas

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There is a general rule of thumb that the cost of manufacturing doubles every time the precision is improved by a factor of ten. Crudely, this is why it costs billions of pounds to set up a fabrication plant to manufacture microprocessors, where the physical size of the transistors being manufactured is on the length scale of a few nanometre, compared with the cost of setting up a facility to manufacture printed circuit boards which sufficiently cheap to be widely available, but features are on the scale of hundreds of micrometers.There are cases of where this rule can be broken. One is in the use of low-dimensional materials which naturally form on a nanometre length scale. An example of this is graphene, which has received a lot of attention in recent years. It naturally forms in a two-dimensional sheet of carbon atoms, and so does not need to be 'machined' to achieve a nanometre-scale thickness. Such 'bottom-up' processes achieve high resolution at very low cost, which is one reason for the interest. However, they still require electrical contacts to be made to the materials to define a complete device. Ideally, we would like to use only a small quantity of these materials, for example by patterning two metal electrodes separated by only a few nanometre with the low-dimensional material (e.g. graphene) inside the nanogap. As the patterning of the metal one this length scale requires a high resolution process, the cost becomes prohibitive again.This project aims to tackle this manufacturing problem directly by combining an emerging technique called 'adhesion lithography' with the growth of low-dimensional materials to create the structures required to make real electronic devices using these materials. Adhesion lithography uses self-assembled monolayers (SAM) to control how well different materials can stick to each other. This allows one metal to be deposited onto a low-cost substrate, like plastic, and patterned using a low cost, low resolution process and a second to be deposited everywhere over the top. Using the SAM, it is possible to ensure that the second metal does not stick to the first. This allows the second metal to be peeled away from the first, uncovering it in the process and leaving a nanogap all around the edge of the first metal. A nanometre scale structure hastherefore been manufactured, but without the associated cost.The peeling process has been shown to be critical to make this work. Therefore, this project aims to design and build a low cost tool to carry out this peeling process on a 10x10 cm length scale, but with a clear route to scaling up to large areas (e.g. an A3 sheet). In addition, we will show that the nanogap can be incorporated with the deposition of a low-dimensional material to create a genuine electronic nanoscale device, but with the cost of a much larger device. We expect the this will allow entirely new devices to be developed for a whole range of applications, from logic to memories to sensors.