Synthesis of elemental phosphorus and arsenic nanostructures
Author(s)
Winchester, Richard
Type
Thesis
Abstract
The experimental work described in this thesis concerns the synthesis of elemental nanorods consisting of phosphorus and arsenic. Growth of such nanostructures was achieved via the vapour-liquid-solid (VLS) mechanism in which a liquid metal catalyst nanoparticle acts as a medium for crystallisation from a vapour phase feedstock. The size of the metal droplet restricts lateral dimensions of the growing solid to the nanoscale. The aim of this research was to synthesise phosphorus and arsenic nanorods in a controllable manner and to characterise the resulting product. Methods are described for producing two distinct forms of phosphorus nanorods using a simple, ampoule-based technique. Relatively high aspect ratio phosphorus nanorods, which have a polycrystalline structure, were produced via VLS growth from a nanoscale bismuth catalyst formed in-situ on the silicon substrate surface. Faceted, single crystal phosphorus nanorods were produced without a catalyst via anisotropic crystallisation from the vapour. Control of the dimension of these products was obtained by modifying the synthesis temperature. The synthesis of 400-1700 nm diameter arsenic rods, via VLS growth from a lead catalyst, is described using a similar ampoule based technique. Investigations into the mechanism of formation of the active lead catalyst particles during ampoule synthesis are also presented. Experiments using pre-formed gold nanoparticles as a catalyst source show that arsenic rods with nanoscale dimensions can also be produced in good yield. The design, assembly and preliminary experiments with a custom built chemical vapour deposition (CVD) apparatus are also described. This apparatus represents a potentially more versatile approach to nanorod synthesis than the ampoule-based syntheses described elsewhere in this thesis. Preliminary experiments are presented which investigate the formation of phosphorus nanorods from bismuth and lead catalysts.
Date Issued
2010
Date Awarded
2010
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Shaffer, Prof. Milo
Whitby, Dr. Max
Sponsor
EPSRC and RGB Research Ltd.
Publisher Department
Department of Chemistry
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)