Tip-enhanced Raman spectroscopy (TERS) is a scanning probe technique that utiHscs a confined, ovanescent field at the tip apex to conduct optical characterisation of a surface at length-scales below the diffraction limit. This thesis details the development of a new TER.S system based upon a shear-force scanning probe microscope (SPM) which sits atop an inverted microscope configured for bottom illumination geometry and coupled to a Raman spectrometer. The system has been optimised for use with solid silver probes and 532 nm illumination. Measurement procedures, automated scripts and data analysis software have been developed that allow reliable alignment of the tip; complex automated mapped measurements; and post processing which produces visual summary sheets to facilitate rapid review of a TERS experiment. Enhanced TERS spectra have been demonstrated on ultra-thin Rhodamine 6G films, self assembled monolayers (SAM) of thiophenole molecules, ultra-thin graphitic films and on multilayered graphene. Improvements in fabrication and alignment procedures have reduced the setup time between fabrication and approach to 20 minutes and improved the reliability of TERS tips with ~ 50% of tips demonstrating TERS activity. Using TERS, heightened defect sensitivity was observed on graphene edges, folds and overlapping regions. The TERS contrast of the defect induced D band was ~ 7.5 times the contrast of the graphene G band. Calculations show that the phonons correlating to the D and G bands interact differently with the enhanced TERS field and that the for certain defect types the D band experiences greater enhancement. Defects play an important role in tailoring the electronic and chemical properties of graphene which is key to the development of graphene based devices. The localised structural and spectral information makes TERS a highly promising tool for the characterisation of defects in graphene. This work demonstrates the potential of TERS for this exciting and important application.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:678488 |
| Date | January 2013 |
| Creators | Rickman, Robert |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://cronfa.swan.ac.uk/Record/cronfa42581 |
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