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Title: Molecular thin films and nanostructures for the formation of oxides
Author: Gonzalez Arellano, David
ISNI:       0000 0004 2737 1856
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Metal oxide thin films have a wide range of applications, for example in so-called “plastic electronics” as semiconductors and contacts. However, their synthesis traditionally involves a high temperature step which is not compatible with plastic substrates, and the morphology can be difficult to tailor to different applications. Recently a new method to form oxide films from molecular precursors using only processes close to room temperature has been developed. The procedure relied on irradiating metal phthalocyanines (MPcs) using vacuum ultra-violet (VUV) radiation produced by an excimer lamp (λ =172 nm). In this thesis, we extend the procedure to the fabrication of functional oxides and aim to elucidate the mechanisms of degradation at the nanoscale. The first chapter explores the degradation mechanisms of MPcs. The influence atmosphere is assessed by varying the O concentration and overall pressure in the irradiation process. The existence of O radicals and excited species are found to play a major role in the kinetics of the reaction. An optimized atmosphere for the degradation of the films is obtained. The second chapter explores whether the technique is applicable to new morphologies. Films with flat topography like zinc porphyrin highlight the importance of grain boundaries and the diffusion of reactive species between grains as one of the main reasons to promote film degradation, while nanowires show shape retention. Blends of Zn1- XCoXPc show similar degradation mechanisms to pure films. The CoPc concentration in the blend influences the reaction rate. The final chapter is a study of the elemental composition of irradiated films with energy-dispersive X-ray spectroscopy and secondary ion mass spectrometry. It shows formation of a thin layer of metal oxide as a result of exposure to VUV light on the phthalocyanine thin films.
Supervisor: Huetz, Sandrine ; Ryan, Mary Sponsor: Consejo Nacional de Ciencia y Tecnología (Mexico)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral