Verformungsverhalten nanoskaliger Dünnschichten bei AFM-Indentierung

Deformation behaviour of nanoscaled thin films during AFM indentation

by Sönke Wille
Doctoral thesis
Date of Examination:2022-03-04
Date of issue:2023-02-20
Advisor:Prof. Dr. Cynthia A. Volkert
Referee:Prof. Dr. Cynthia A. Volkert
Referee:Prof. Dr. Astrid Pundt
Persistent Address: http://dx.doi.org/10.53846/goediss-9729

 

 

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Abstract

English

Nanoscaled materials differ in their mechanical properties from their bulk counterparts. Reasons therefore are e. g. the different ratio of surface and volume, which leads to different deformation mechanisms. In the case of thin films, the influence of the substrate also plays a role. To examine the influence of the film thickness on the deformation mechanism and the mechanical properties gold thin films of different thickness were deformed using the tip of an atomic force microscope. The same tip was used to image the surface before and after deformation and thus examine the change in topography. From these changes the number and nature of the involved dislocations was determined. In addition, transmission electron microscopy was used for further insight on the defect structure within the deformed films. The sample showed no dependence in the deformation behaviour or morphology from the thickness up to indentation depths far over half the film thickness. The observed defect density was smaller than expected from the amount of deformation. This was explained by cross-slip of dislocations to the surface. Thus the involved volume was close to the indentation tip, which explains why an influence of the film thickness was only seen for very deep indentations.
Keywords: nanoindentation; atomic force microscopy; contact mechanics; deformation behaviour
 
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