New manufacturable approaches to the deposition and patterning of graphene materials

Graphene, a single layer of carbon atoms held together in a honeycomb array, has a fascinating and exotic range of properties many of which still remain underexplored and that have placed it in the vanguard of modern materials research. With possible applications in high speed electronic devices, solar cells, super capacitors, batteries, thermoelectric devices, super transistors, organic light emitting diodes (OLEDs), sensors, genetic sequencing and hydrogen storage materials, the potential impact of graphene is almost limitless. However, despite the interest in this fascinating material, current graphene synthesis methods, including exfoliation, epitaxial growth, graphite oxidation or chemical vapour deposition (CVD), have significant drawbacks including limits to size of thin film produced, the number of layers of graphene formed, restrictions to the types of surfaces onto which graphene layers are produced, lack of control over multilayer formation, as well as a requirement for high temperature reaction conditions and long time periods to produce high quality graphene; all of which inhibit the long term utility and eventual commercialisation of graphene-based materials. Our goal is therefore to advance and accelerate the commercial exploitation of graphene by developing new routes to the manufacture, patterning and functionalisation of graphene-based materials. Our proposal leverages the very significant existing capabilities of the EPSRC-HEFCE funded Exeter-Bath Centre for Graphene Science (CfGS), comprising over 50 academic and research staff and students working in graphene. Having made great strides in understanding and controlling the fundamental properties of graphene, we will now explore promising routes to manufacturable graphene materials, devices and systems. Specifically we will: (i) develop pioneering, high-throughput atomic layer deposition (ALD) techniques for graphene, suited to industry-compatible production technology on practical substrates, (ii) investigate a 'blue-skies' approach capable of high-speed, high-resolution direct-writing of graphene.

The unique electronic, optical, thermal and mechanical properties of Graphene make it ideal for a wide range of potential applications in sensing/actuation, electronics and photonics. It can address major societal challenges in the energy and healthcare arenas. In the case of the former it is a prime candidate for transparent electrodes for photovoltaic cells, or as an efficient light-absorbing medium inside the cell itself. In addition it is already finding applications in touch screens and for flexible electronic devices and systems. Healthcare applications include graphene biosensing, which is already a very active research field worldwide, as well as the use of functionalised graphene in medical therapy (e.g. photodynamic therapy for treating cancer). In addition graphene has extremely strong potential for new developments in electronics and IT (for example as high-frequency transistors, in flexible electronics applications, for new forms of non-volatile memory, for logic etc etc). The global market for electronics alone is vast, with current estimates for 2011 ranging from $1 to $1.5 trillion. In the specific research areas that we are currently working at the Exeter-Bath Centre for Graphene Science (and that will benefit hugely from the step-change in graphene materials and device fabrication and characterisation capability that this equipment-only proposal will bring), the global market is similarly huge, and growing. For example, the current global market for flexible and printed electronics is estimated to be around $10 billion, but predicted to rise to around $60 billion by 2022. The market for biosensors is also growing rapidly, and expected to be worth ~ $17 billion by 2018. Likewise, the global market for Terahertz radiation systems, though smaller in total, is also burgeoning, growing from around $80 million in 2011 to over $500 million by 2021, with a predicted annual growth rate from 2016 of ~35% . For graphene to make serious impact on such markets, it is clear that industry-compatible and cost-effective routes to the production of graphene and hybrid-graphene materials need to be developed. This is explicitly the goal of our proposal, in which we propose to acquire, install, evaluate and exploit equipment that will enable, for the first time, (i) the use of highly controllable ALD and PE-ALD approaches to fabricate graphene and hybrid-graphene materials for large scale applications, and (ii) the investigation of a highly-novel 'direct-write' method for graphene nanopatterning. Thus, our work will facilitate the timely and cost-effective development of new graphene-based devices and applications, potentially generating a very significant long-term economic impact by increasing the UK share of the above global electronics (and related) market, in addition to a societal impact due to the improvement in the quality of life that will ensue from the new and improved devices and systems ultimately developed (e.g. new biosensors, improved communciations, improved security etc). There will also be a substantial impact in the area of sustainability, since the work we propose will also lead to advances in sustainable manufacturing and sustainable energy production and energy storage devices helping to mitigate the world-wide energy crisis.