Application of solution chemistry to transparent, conducting thin film formation
Dr. Tim Kemmitt
MacDiarmid Institute for Advanced Materials and Nanotechnology Industry Research Ltd.
Abstract: Al-doped zinc oxide has also been proposed as a cheap and abundant material for the formation of transparent conducting oxide (TCO) thin films. This has the potential to provide a solution to the indium shortage. A number of fabrication techniques have been applied to the synthesis of Al doped ZnO films including magnetron sputtering, chemical vapour deposition, pulsed laser deposition, molecular beam epitaxy etc. It has been proposed that the sol-gel technique provides a cheap and scalable process, and a number of studies have demonstrated the formation of films with appropriate conductivities and transparencies to support the claims. A cursory look at these studies suggests that the efficacy of doping is extremely sensitive to synthesis conditions, and little is actually known about the doping sites within the ZnO crystals. A dopant ion introduced to modify the electronic properties of a material needs to be incorporated into the crystal structure of the host material (either in lattice sites or interstitially). In the case of a ZnO:Al TCO, the Al3+ ion is required to occupy a Zn2+ lattice site in order to provide a free electron (charge carrier). Solid State 27Al NMR is shown to be a powerful tool to track the fate of the Al dopant ions and develop a thermal processing regime to optimize the Al location.
The importance of lateral connectivity in the film is examined, with reference to the film epitaxy using 2-D synchrotron X-ray diffraction studies, and the influence on the resulting electrical resistivity. Thus we have developed a thorough understanding of the processing factors influencing the ZnO crystallisation important in determining conductivity.
Biography: Dr Kemmitt completed his doctorate in inorganic and materials chemistry at Southampton University, UK, in 1989. After his study of one dimensional conductors at Otago University as a post doctorate, he joined the Inorganic Materials Division at the New Zealand Department of Scientific and Industrial Research in 1992. He is currently employed at Industrial Research Ltd. He was appointed as a Principal Investigator at the MacDiarmid Institute for Advanced Materials and Nanotechnology in 2002, based in Wellington New Zealand. His research has focused on the formation of advanced oxide materials, and he has many publications and patents relating to the formation of photocatalyst materials. His recent interest in conducting oxide films has come about through one of his many collaborative research efforts with universities world wide. He is a member of the Materials Research Society (US), the New Zealand Royal Society, the New Zealand Institute of Chemistry, and the New Zealand Association of Scientists, and is involved with the Lower Hutt branch of Café Scientifique. Earlier this year he chaired the organizing committee for AMN-5, the MacDiarmid Institute’s biennial International conference.
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