Field emission of ZnO nano-structures produced by laser ablation
The thesis describes the development of, and results from, two new laboratory facilities designed to investigate the properties of laser produced plasmas, with in-situ time of flight mass spectrometry, for deposition of ZnO materials for applications as field electron emission sources. The results from the work are concerned with the study of the important physical processes present in a laser ablation zinc oxide plasma plume expanding into vacuum and various ambient gas pressures. The thesis also demonstrated the advantages of combining a linear ToF detector and a mass resolved ReToF spectrometer for clarification of ionisation processes in the pulsed laser ablation regime of solid targets. The outstanding results show that during the ablation process, ZnO atomises into Zn and O. In the vacuum regime we have shown that at long distances from the target multiple charged states of Zn and O are present. While under the same conditions in an ambient gas the multiple charged states are not present, however the ambient gas undergoes an ionisation process. Deposited materials are tested for applications as field electron emission sources, for analysis of field enhancement factors from nano-material ZnO.
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