Developing a deeper understanding of doping and defects in metal oxide semiconductors

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Metal oxides (MO) semiconductors play a vital role in number of technology platforms ranging from large area electronics/displays through to applications as diverse as biosensing and photocatalysis. Collectively MOs provide a suite of materials with tuneable electronic properties, including charge carrier mobility and density, high optical transparency and offer access to a plethora of stable nanostructures. Furthermore, the electrical and optical properties of MOs can be further tuned by substitutional doping.Here we propose to investigate several n-type MOs, including In2O3 SnO2, ZnO and WO3 as well as their doped analogues Fabricated by established chemical and physical deposition processes, including atomic layer deposition (ALD), chemical vapour deposition (CVD) and by emerging solution based processes all at temperatures < 450 C. Whilst the different synthetic approaches should result in compositionally similar films, we anticipate significant variation in defect chemistry and correspondingly differences in electrical and optical properties. Using the characterisation tools available in this collaborative research project we aim to address a number of interrelated research questions, namely:- How can stable and controllable free electron concentrations be achieved through substitutional doping?- Can we enhance and/or supress the dual role of defects i.e. reduce defect induced charge carrier recombination but enhance n-type conductivity?- Can we improve our understanding of the interplay between intrinsic and extrinsic dopants on change carrier mobility?- How the major defect types, their concentration and energies vary with processing conditions?