Combinatorial CVD

This is an application for a Platform for baseline funding to support the joint Carmalt/Parkin research group. Parkin and Carmalt have collaborated extensively in the area of Chemical Vapour Deposition (CVD). Carmalt has focussed on the synthesis of molecular precursors for use in CVD, whereas Parkin has concentrated on the CVD growth and functional characterisation of thin films from these and other precursors. In the course of this research they have, unusually for CVD, discovered a wide number of new phases especially metal nitride, oxide, sulfide and selenide materials that had proven due to kinetic reasons and precursor design, unobtainable by conventional solid-state synthesis. They have also determined how to control preferred growth and orientation of crystallites grown by CVD. This has enabled them to grow materials with improved functional properties for a variety of applications from gas-sensors, through ultraphobic, superhydrophilic surfaces to thermochromic and self-cleaning films. The pinnacle of this work, especially for new phase determination has been their use of combinatorial CVD for the synthesis of new materials. Combinatorial CVD is currently the major focus of the Carmalt and Parkin joint group and is a significant component of all of their current EPSRC funding. This methodology has enabled them, for example, to make a range of new mixed metal oxide photocatalysts and a new series of Ti3O4-xN1 phases (see J. Am. Chem. Soc., 2006, 128, 12147-55; J. Am. Chem. Soc., 2007, 17, 4652-60). The combinatorial CVD process has extraordinary potential. The applicants have shown how, for example, in a single CVD experiment up to 800 different phase compositions can be made. They have also shown how this large phase range can be explored in a robotic fashion using programmed movable X-Y stage Raman, electrical conductivity and X-ray measurements such that the whole phase space can be mapped in overnight experiments. This technique offers the potential to rapidly search for new phases and to explore a systematic range of compositions to determine which combination of materials leads to the best functional properties. They are then able to adjust the synthesis conditions and make the desired phase. The work is primarily focussed at making thin films, however they have shown through a delamination methodology that they can make gram quantities of materials. They wish to take advantage of this unique technique and develop its potential in three main areas;* The preparation of new visible light photocatalysts for water splitting and antimicrobial applications- such materials have potential to revolutionalise energy generation and reduce hospital acquired infections.* The preparation of thin films for use as ultra-sensitive gas sensors- we plan to incorporate such materials to develop a single breath sensor, this could be used routinely in a surgery by a doctor for disease diagnosis (over 30 diseases can be diagnosed from exhaled breath- however current analysis requires shipment to a lab and takes over a week).* The synthesis of new precursors for use as photovoltaic thin films and transparent conducting films. For example; develop low pressure combinatorial CVD to form improved semiconductor materials including indium gallium selenides and related materials, the aim of this subproject is to achieve low processing cost, high throughput and high quality film deposition of these important ternary and higher order materials using combinatorial LPCVD. Thin films of graded composition will be grown by using low pressure chemical vapour deposition with two/three separate precursor gas streams, e.g. one for indium selenide, one for gallium selenide and one for copper selenide. Diffusion of the gas streams allows graded compositions (e.g. CuGaxIn1-xSe2) across the whole plate.