The Environmental Scanning Electron Microscope (ESEM) has rapidly become established as a new generation of scanning electron microscopes. The sustainability and utilisation of a gaseous atmosphere in these microscopes has opened the way for new electron microscopy studies of insulating, biological and even fully hydrated systems. Recently there has been an increasing drive to push the limits of the technique further to perform more <i>in situ</i> dynamic experiments and extract more quantitative information. However before this potential can be realised, some fundamental groundwork must be done. In this thesis we focus on the interpretation of secondary electron contrast obtained from liquid water droplets, with the aim to make a quantitative interpretation of contact angle. We develop and present two experimental methodologies to explore this parameter: 1) by direct imaging of water droplet profiles on flat insulating substrates and, ii) indirectly by quantitative interpretation of contrast profiles obtained across the surface of water droplets. In developing a procedure to measuring contact angle directly in the ESEM we focus on the practical implications of depositing and stabilising regular droplets and correctly mounting the substrates. We also compare the ESEM contact angle measurements to macroscopic optical measurements performed on the same surfaces to ensure the accuracy of the results. In extracting contact angle from contrast profiles we develop a general model of SE topographic contrast for the ESEM, considering the relative dominance of the different signal contributions that form the final image and how they are processes into an image. We relate the contrast profiles to the geometric shape of the water droplets and find a correlation between the breakdown of the model and the size of the interaction volume of the primary electron beam.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598132 |
| Date | January 2001 |
| Creators | Craven, J. P. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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