Micro-spectroscopic soft X-ray studies of low-cost epitaxial graphene and adsorbates

Graphene - the remarkable two-dimensional material whose discoverers were awarded a Nobel prize - may revolutionise the electronics industry. This depends on controlling the electronic properties of the material AND on making such material cheaply. In ordinary three-dimensional materials like silicon, control is achieved by introducing impurities into the material ("doping"). It is not possible to dope graphene conventionally without destroying some of the electronic properties that make it so attractive in the first place. An alternative is "transfer doping" where we place certain molecules on top of the graphene sheet and they add or remove electrons without damaging the sheet's superb electrical properties. We will also need to examine the effects of the substrate that the graphene sheet lies on.

In this project we will investigate the electronic structure of graphene on different substrates and with different molecules on top of it. This will be done using a technique called "angle resolved photoemission spectroscopy", or ARPES, in which we knock electrons out of the graphene using soft X-ray photons and calculate their momentum and energy to build up a complete picture of the electronic structure. However, we will be using advanced ARPES systems at major X-ray facilties in France, Italy and elsewhere which are capable of making these measurements on tiny length scales - less than one micrometre. This will enable us to work out changes in the electronic structure of graphene made in a very cheap and simple way in our lab using the same techniques likely to be employed by the electronics industry. Unlike expensive crystalline substrates, our samples are made on cheap metal foils and are not uniform so we need spatial resolution in the ARPES measurement.

A key part of our project is building up collaborations with theoretical physicists who will be able to help us understand and predict the changes of electronic properties of our cheap, industrially relevant graphene. Such a predictive ability will be a big step forward in bringing graphene to real-world applications in areas such as information technology, advanced detectors and energy efficiency.

Graphene has the long-term potential to revolutionise electronics, with a correspondingly broad base of beneficiaries. How could our work contribute to this wide impact? We see a chain of beneficiaries arising from this project. Initially we will contribute to the understanding of the electronic structure of graphene as it is likely to be mass-produced, on cheap metal foil substrates, and of the effects of transfer doping by adsorption or contamination. This fundamental knowledge will benefit scientists in the field and guide further experimental and theoretical work (see "academic beneficiaries"). We will ensure this impact by dissemination, including organising a follow-up meeting to our successful workshop in Warwick, and direct collaboration development during the project. Subsequently, the knowledge developed will feed into more technologically orientated work - for example, by providing more accurate electrical conduction parameters to engineers designing graphene-based devices. The recently announced Graphene Hub, publicity activities organised through the syncrotron facilities and business engagement partners (Science City, Warwick Ventures), and our own outreach work will all help in ensuring effective knowledge transfer beyond academic materials science. During the project we will continue to contribute to our successful schools outreach programme across the Physics and Chemistry departments (outlined in the impact plan).