Highly-ordered growth of solution-processable ZnO for thin film transistors

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Buckley, Darragh
McNulty, David
Zubialevich, Vitaly Z.
Parbrook, Peter J.
O'Dwyer, Colm
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We demonstrate that crystalline, epitaxial-like and highly ordered ZnO thin films and quasi-superlattice structures can be achieved from a precursor liquid at relatively low temperature via spin-coating. The synthesised films are smooth, stoichiometric ZnO with controllable thickness. An iterative layer-by-layer coating schematic is employed to demonstrate the effects of film thickness on structure, morphology as well as the surface and internal defects. Characterisation of the crystallinity, morphology, O-vacancy formation, stoichiometry, surface roughness and thickness variation was determined through X-ray diffraction, scanning and transmission electron and atomic force microscopy, X-ray photoelectron and photoluminescence spectroscopy. We demonstrate that iterative spin-coating of deposited ZnO films results in a transition in crystal texture with increasing thickness (number of layers) from the [ ] m-plane to the [ ] c-plane. The films attain a c-axis preferential orientation, with no other crystalline peaks present. Results show that the film’s surface morphology was very smooth, with average rms roughness <0.15 nm. Examination of these films also shows the consistency of the surface composition and defect level while highlighting the effect of temperature and cumulative annealing condition on the internal defect concentration.
Thin films , Annealing condition , Effect of temperature , Preferential orientation , Solution processable , Super-lattice structures , Thickness variation , Transmission electron , X-ray photoelectrons , Atomic force microscopy , Coatings , Crystalline materials , Film growth , Metallic films , Morphology , Photoluminescence spectroscopy , Surface defects , Surface roughness , Temperature , Thin film circuits , X ray diffraction , Zinc oxide
Buckley, D., McNulty, D., Zubialevich, V. Z., Parbrook, P. J. and O'Dwyer, C. (2017) 'Highly-Ordered Growth of Solution-Processable ZnO for Thin Film Transistors', ECS Transactions, 77(4), pp. 99-107. doi: 10.1149/07704.0099ecs
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