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A surface study of gold by scanning tunneling microscope

Hindarto, Nathan (1992) A surface study of gold by scanning tunneling microscope. PhD thesis, Murdoch University.

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A tubular Scanning Tunneling Microscope has been constructed and operated in air under ambient conditions. An image with atomic resolution occasionally has been achieved; the performance of the tip determines the resolution.

The tip preparation is carefully controlled, however a good tip with a stable performance and resolution can not be achieved routinely. A sudden improvement or deterioration of the tip during scanning seems to be caused by the transfer of atoms between the tip and the surface. Frequently, a low voltage pulse to the tip can improve its performance.

Using the Scanning Tunneling Microscope, the behaviour of the gold surface under the influence of the tip-surface interaction has been studied through observations of sequential images. The sample used in this work was prepared through deposition of gold vapor onto a preheated mica substrate. This produced films with large flat terraces.

The tip-surface interaction can produce significant effects during scanning and appears to initiate surface changes through disturbing the surface stress. Surface diffusion which leads to a surface smoothing effect, surface modification and the response of the surface to an external disturbance have been studied.

A surface buckling, an alternative model of Au(111) reconstruction suggested by Harten et al [1985], was observed. To my knowledge no one has reported this observation in air, a previous observation having been made under UHV conditions by W611 and co-workers [1989]. The line profile of the surface buckling provides evidence that a STM is sensitive to both surface topography and surface electronic state.

Observing the step movement and growth during the scans, it seems that there were primarily induced by an external force, i.e. the tip-surface interactions, nevertheless the effects of surface contaminants can not be ruled out.

To minimise the influence of the tip-surface interaction, the scan should be made using a low bias and a low tunneling current.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Mathematical and Physical Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Mainsbridge, Bruce
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