The Atomic Force Microscope (AFM) is an invention that has enabled a significant number of studies and discoveries in the field of nanotechnology. It is well-known that the resolution of AFM-based applications is critically dependent on the tip bluntness of the probe utilised. Numerous researchers have proposed different approaches to assess the condition of AFM probe tips. In spite of these efforts, further advances are still needed for the express analysis of the bluntness of such tips. In this context, the overall aim of the research work presented in this Thesis was to investigate a novel in-situ technique for assessing the apex condition of AFM tips. In particular, this technique relies on the analysis of depth-sensing data obtained from the nanoindentation of the probe tip into a soft elastic sample. Nanoindentation is a process that is readily implemented on AFM devices. For this reason, the proposed technique could be a fast an efficient approach for deciding when AFM probes should be replaced. The theoretical argument on which the technique is based is that the current shape of the tip apex in its working position within an AFM device can be approximated as a power-law function and that the exponent of this function can be used as a quantitative measure of the tip bluntness. Based on this approximation and the use of the self-similar (scaling) approach to depth-sensing indentation, it is possible to extract this bluntness parameter, herein also referred to as the degree of tip bluntness, from AFM nanoindentation data. The practical implementation of this technique was realised using a commercial AFM device and commercial probes. The actual geometry of the apex of these probe was also studied in details using additional experimental methods via the use of Scanning Electron Microscopy and also via the so-called “reverse imaging” method to obtain two- and three-dimensional data about the tip apex of these probes. Among the different iv contributions made from the work carried out in this research, the most important conclusion is that a good agreement was found between values of the bluntness parameter evaluated by the proposed technique and the effective bluntness obtained from analysing the actual three dimensional geometry of the AFM tips. Thus, it can be argued that the technique put forward in this work for the express analysis of the bluntness of AFM probe tips using depth-sensing nanoindentation can be considered as a valid method when assessing the condition of AFM probes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:723602 |
| Date | January 2017 |
| Creators | Alraziqi, Zaynab |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/104912/ |
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