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Title: Electrodeposition of zinc oxide nanostructured films
Author: Illy, Benoit
ISNI:       0000 0004 2681 968X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2010
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ZnO nanostructures have great promise in a wide range of applications such as sensors, optoelectronics, piezoelectronics, healthcare. Preparation of oxide films by electrodeposition from aqueous solution presents several advantages over other techniques such as controlling the rate and morphology through several well-defined parameters (electrode potential, current, temperature, pH, etc.), the fact that electrolytic processing is a well-established technology and readily scalable for production, and the non-equilibrium nature of the electrochemical interface often gives rise to morphologies and compositions not attainable through other, usually high-temperature, routes. Despite a large amount of research in this area the detailed mechanism of nucleation and growth is still controversial. Only a good understanding of it will allow the expected industrial applications to be achieved. One of the main difficulties to overcome is that tiny amounts of material are involved and the required in-situ measurements are thus very delicate. The ability of synchrotron radiation to probe material structure during deposition makes it the ideal tool for the study of nucleation and growth of these materials as a function of the processing parameters. Here we will present two synchrotron-based approaches involving both X-ray absorption and scattering. The first method, together with ex-situ characterisation, provides detailed information about how the kinetics of the growth and/or dissolution is influenced by the electrochemical parameters. The effect of time, potential, zinc ions concentration, oxygen precursor, temperature and electrolyte composition have been studied. Following this understanding of the influence of the parameters, films of desired structure can be synthesised and new structures have been made. Beside the electrochemical parameters, the growth of the film is influenced by the interaction with substrate in the early stage of nucleation. The second synchrotron technique allows the direct observation of the development of the crystal orientation of the films during the deposition. It gives promising results to study how the substrate influences the growth and thus the properties of the films.
Supervisor: Ryan, Mary ; Shollock, Barbara Sponsor: Foundation for Research, Science and Technology
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral