Spectroscopic and Microscopic Characterisation of Carbon Nanostructures

Abstract

Currently, carbon nanotubes (CNTs) are produced using a variety of techniques which yield CNT materials with wide ranging levels of chemical purity and structural perfection. Consequently, characterising CNT materials accurately is of utmost importance if potential applications of CNTs are to be realised on a large scale. In this work four commercially available CNT samples are characterised using a number of techniques, namely: scanning electron microscopy (SEM); high resolution transmission microscopy (HRTEM); energy dispersive x-ray analysis (EDX); Auger electron spectroscopy (AES); low-loss electron energy loss spectroscopy (low-loss EELS); ultra-violet photoemission spectroscopy (UPS); x-ray photoemission spectroscopy (XPS) and Raman spectroscopy. The information provided by these techniques is assessed in their ability to characterise different CNT materials. The definition of CNT ‘quality’ is also discussed and the ability of these techniques to determine such a property is considered.
A significant part of ascertaining the ‘quality’ of a CNT sample lies in understanding the nature and number of defects in the walls of these materials. In this work, defects are introduced into the lattice of different CNT species using 1.5 keV Ar+ ions and the effects are monitored using XPS. In particular, the resultant reactivity of irradiated CNTs to ambient atmospheric oxygen is investigated, which is found to be markedly enhanced for CNTs with one wall when compared to those with multiple walls. It is also demonstrated that the type of incident ion and irradiation dose can be used to selectively control the level and nature of the surface composition of oxygen functionalised SWCNTs.
Many applications of fullerenes require detailed understanding of how these molecules interact with surfaces and the perturbations this induces. In this work the interaction of C60 with highly ordered pyrolytic graphite (HOPG) and Ni(110) is studied using scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), XPS and UPS. Investigation focuses on a novel two-dimensional solid-vapour phase in the C60-HOPG system and the C60-induced reconstruction of the Ni(110) surface.