This dissertation describes the development of atomic force microscope cantilevers as surface stress sensors for monitoring surface processes at the solid-liquid interface. Micromechanical bending-beams are highly sensitive stress sensors; stress changes as small as 10<SUP>-4</SUP>Nm<SUP>-1</SUP> can be detected using this type of bending-beam, whereas typical stress changes associated with monolayer processes are 0.1-1Nm<SUP>-1</SUP>. As well as offering high sensitivity, micromechanical cantilevers have a fast response time (0.5ms in liquids) which means they are ideally suited for fast stress measurements. Textured (111) surfaces were prepared by thermal evaporation of Au onto one face of the Si<SUB>3</SUB>N<SUB>4</SUB> cantilevers. These cantilevers were used as electrodes to monitor the stress changes associated with electrochemical processes, in conjunction with electrochemical measurements such as cyclic voltammetry and chronoamperometry. The potential-dependent adsorption of C1<SUP>-</SUP> and I<SUP>-</SUP> anions gave rise to stress changes of 0.5-1Nm<SUP>-1</SUP>, and in both cases, adsorption of the anion was associated with an increase in compressive surface stress. Underpotential deposition (UPD) of Pb and Ag on Au(111) has been studied in detail. For Pb UPD on Au(111) a compressive stress change of 1Nm<SUP>-1</SUP> was measured on deposition of one monolayer. More detailed features in the surface stress-potential curve have been directly related to features in the cyclic voltammogram and known structural processes such as the potential-dependent compression of the Pb monolayer. The measured stress changes for Ag UPD on Au(111) were also 1Nm<SUP>-1</SUP> and did not display a strong dependence on the nature of the anion present in the electrolyte.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:597031 |
| Date | January 1997 |
| Creators | Brunt, T. A. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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