Investigating the interactions between a scanning tunneling microscope tip and an Au- coated microcantilever

Algaidi, Hanin (2017) Investigating the interactions between a scanning tunneling microscope tip and an Au- coated microcantilever. Masters thesis, Memorial University of Newfoundland.

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Abstract

In this work we investigated the interactions between a tip used for scanning tunnelling microscopy (STM) and a Au-coated cantilever in ambient conditions. A system was constructed to position an STM tip on a Au-coated cantilever. The van der Waals, electrostatic, and capillary forces were used to model the tip-cantilever interactions. As the piezoelectric scanner adjusted the STM tip on the cantilever surface to maintain the tunnelling current set point, the magnitude of the forces changed, causing the deflection of the cantilever to vary. It was noted that the magnitude of the force was affected by the relative humidity and the tip location on the cantilever. Our experimental results showed that the van der Waals, capillary, and repulsive forces dominated the interactions and affected the stability of the cantilever during the interaction with the STM tip. It was found that an attractive force ranging between 2.4 and 27 nN acted on the cantilever when the STM was approaching toward the cantilever. The magnitudes of these forces were varied as the conditions of the experiments changed. In all cases the theoretical estimated values of the force were calculated to be well within the uncertainties. When the separation distance between the STM tip and the cantilever decreased to within a few angstroms, a repulsive force between 80- 86 nN strong was detected.

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