Complex Nanostructures by Supercritical Fluid Electrodeposition

Have you ever wondered why water vapour can pass out through your Gortex(TM) waterproof jacket but the rain can't get in? It is because Gortex(TM) contains very small pores which vapours can penetrate but liquids cannot. Similarly, electroplating (also known as electrodeposition) of materials into pores with diameters smaller than a few tens of atoms is very difficult if not impossible from liquids. However, using the extreme penetrating power of supercritical fluids (substances at a temperature and pressure above their critical points which behave like gases) enables electroplating into these extremely small structures. This is a really exciting development since the nanomaterials that are produced have properties which cannot be found in existing (larger scale) materials. This is the primary objective of this project - to develop supercritical fluid electrodeposition as a technology to enable spatially selective electrodeposition of high quality metals, semiconductors and other materials inside two and three dimensional nanostructured templates. Within this project we will tackle 4 major research targets that will transform supercritical fluid electrodeposition into a really exciting new and industrially viable deposition technology: (i) exploit the unique pore penetrating ability of supercritical fluids to demonstrate deposition of a range of materials inside extreme nano-scale (< 2 nm) pores and establish the effect of reducing pore size on the properties of the deposited materials;(ii) allow the full exploitation of the large electrochemical windows available with supercritical fluids to enable the deposition of extremely reactive materials, such as silicon and lanthanide metals (rare earths);(iii) take supercritical fluid electrodeposition to much higher temperatures and realise hybrid thermo-electrochemical deposition as an entirely novel materials deposition method - enabling production of luminescent quality compound semiconductors e.g. for electronic devices;(iv) achieve epitaxial growth - the growth of a material deposited in a specific orientation, using supercritical electrodeposition, producing atomically sharp hetero-junctions contained inside the nanopores. Success with any one of these targets will represent a significant breakthrough beyond existing deposition technologies, will enhance the likelihood of success in the other target areas, and will have a major impact on many applications requiring materials deposition on a nano-scale. Less complex nanomaterials are already used in self-cleaning glass and as chemical catalysts for the petrochemical industry. This project will develop supercritical fluid electrodeposition so that it can be used to produce more complex nanomaterials for use in ultrahigh density memory for computers, micro thursters for satellites, ultra-efficient micro machines capable of harvesting sound energy to produce electronic gadgets for embedding in the human body which require no external power source and a huge range of other applications which no-one has yet dreamt of.To achieve these ambitious targets requires a multidisciplinary approach involving several key contributions - electrochemistry; supercritical fluid science; synthetic chemistry; materials characterisation. Our distinctive team of investigators brings together the necessary complementary and unique set of skills and expertise to realise these very ambitious targets.

The deposition of functional materials in a structured and patterned form underpins all of modern technology and has a profound societal impact. It is the basis of the fabrication of every computer chip, data storage device, solid state laser, physical and chemical sensor and microfabricated device which we use everyday. New deposition methods, such as supercritical fluid deposition, offer new opportunities in the materials that can be deposited, the 3-dimensional complexity of the structures that can be formed and the spatial resolution that can be achieved. They enable new devices and technologies across the widest range of applications from the digital economy to healthcare, from energy conversion to environmental monitoring - therefore having a potentially profound impact across a broad cross section of high tech materials industries. The need for new deposition technologies with unique capabilities is clearly recognised in the EUMAT Roadmap for Advanced Engineering Materials and Technologies where it says that Advanced materials technology is a vital technology for European industry and even larger opportunities are expected in the case of artefacts with active thin films . The aim of this project is to develop SCFED so that its unique combination of capabilities will find technological applications and thus benefit many different groups of people. First, and most immediately, academic researchers in the areas of chemistry, materials physics and microscopy will directly benefit from the increased understanding and fundamental underpinning science generated in the project. In addition, scientists and technologists working in the adjacent fields of electronics, metamaterials, and optoelectronics will benefit directly from the new fabrication methods for metal and semiconductor nanostructures allowing them to fabricate and study new structures and devices of significantly smaller size and greater complexity than currently possible. Second, in the medium term, high technology industries will benefit from the research through the development of new ways to make complex nanoscale structures and devices enabling new types of sensor, data storage, optoelectronic device, MEMS structure, etc., which will, in turn, create new commercial opportunities. Third, in the longer term, the general public will benefit from access to this new range of nanoscale structures and devices with applications in computing, communications, data storage and retrieval, sensing, energy conversion, and medical diagnostics. In addition the young researchers (PhD and postdoctoral) working on the project will benefit through the training provided in a cutting edge project with a truly interdisciplinary approach to nanomaterials research (and in so doing directly address one of the recommendations of the 2009 EPSRC International Review of UK Chemistry to encourage multidisciplinary training in the area of materials). In turn the UK will benefit from this output of talented and highly motivated researchers