Doctor of Philosophy
Faculty of Engineering
McKinnon, Jeffery Ronald, The fundamental mechanisms involved in the production of thin films pulsed laser, Doctor of Philosophy thesis, Faculty of Engineering, University of Wollongong, 2003. http://ro.uow.edu.au/theses/1839
The discovery of high-temperature superconductors, coincident with the development short wavelength excimer lasers, made the use of the lasers to produce the thin films the pulsed laser deposition process (PLD) a logical step.
The major thrust of research into high-temperature superconducting thin films has been increase the effective thickness of the film, the area of the film or to produce long of film on a metallic substrate known as coated conductors. With this in mind we set to establish a starting point from which we could address one of these areas.
When we looked at the literature we found that the reported parameters, for the production of Y1Ba2Cu3O7-δ, varied significantly. Most commentators reported reproducibility of film characteristics for their systems but it was apparent that lack of transferability between deposition systems. We believed that this indicated underlying features of the process that were not currently being addressed. It seemed us, that a different approach was warranted.
The aim of this work is the description of these underlying features and the development of a useful model of the PLD process. The model, by making clear the key features of the process, should allow for the determination of the appropriateness of the process for the production of films from specific combinations of elements or the development of reasonable approaches to general processing problems.
To this end, the literature was searched and the data contained therein analysed for characteristics of the process that are universally true. The facts about the process, taken together and restated in consideration of the aim, allowed for a model to be proposed. model is comprised of several hypotheses which describe the fundamental interactions of the laser with the target and of the ejectants firstly with the chamber atmosphere and with the substrate.
The complex nature of the process, the time frames and scales involved and the absence of some suitable instruments made the design of experiments to refute or prove the hypotheses, in any absolute sense, extremely difficult. Nevertheless, several series of experiments were undertaken to assess the validity of the basic hypotheses. Underpinning these experiments were some assumptions, as to what might be inferred from particular target or film characteristics, about the process that created them.
We note that to a large extent the data that allows for the model to be proposed existed within the literature and it is the reappraisal of the data in the knowledge of its variability and in the search for common themes that forms the basis of this work.
We conclude that the model stands on the existing data and that our work serves to support this view.