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Title: Nanofabrication techniques for nickel and cobalt nanostructures
Author: Gnanavel, Thirunavukkarasu
ISNI:       0000 0004 2724 8137
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2010
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The aim of this work is to explore novel ways of nanofabrication for nickel and cobalt nanostructures. This has been achieved using conventional as well as new methods. Novel electron beam sculpting by ablation of atoms is utilised for two-dimensional (2D) thin film nanostructuring and three-dimensional (3D) nanostructuring as well. Electron beam lithography (EBL) is explored mainly for thin film nanostructuring for nanojunction formation. Electron beam induced phase transformation or electron beam fabrication of nanoparticles and nanobeads are shown to be innovative and successful methods for fabrication of nanopartic1e assemblies. An electron beam sculpting method was successfully tested to produce nanostructures such as nanohole arrays, nanolines, nanoelectrodes and nanojunctions on a cross-sectional transmission electron microscopy (XTEM) specimen. A novel 3D nanofabrication method (tomographic nanofabrication) has been introduced using a high-tilt tomographic holder with example on an electrochemically etched nickel nanotip sharpening. The EBL produced nanojunctions were found to be better to realise sub-25 nm sized structures while electron beam sculpting has been shown to be superior to realise sub-5 nm dimensional structures. Further, a combination of EBL and electron beam sculpting techniques is worked out for realising sub-5 nm structures. A new nanoparticle or nanobead synthesis method has been introduced using transition metal fluorides (NiF2 and CoF2) as the starting material. An electron beam of a TEM depletes tluorine from the transition metal fluoride fragment quickly compared to the metal depletion, which results in the metal end product. Depending on the beam condition (acceleration voltage, intensity of the beam and beam focusing techniques) it was possible to tune the final end product into a singular or a few nanobead(s) or a distribution of nanoparticles. The produced nanobeads of 100-1000 nm size showed stacking faults and grain boundaries. In most of the cases, these nanobeads consist of multiply twined-nanograins. On the other hand, the achieved nanopartic1es mostly consist of metallic Ni or Co nanocrystals of 1-100 nm in size. This simplest, non-hazardous, oxide-free fabrication method offers great potential for laboratory-scale research.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available