Oct 16, 2012
Model interprets dynamic scanning electron microscopy of vibrating cantilevers
The analysis of cantilever nano-oscillations allows a better understanding of scanning probe microscopy techniques. Currently, there have been only a few direct observations of structures oscillating at the nanoscale. In recent experiments, researchers in Germany have used a scanning electron beam to image a cantilever in oscillation, driven at its first flexural resonance.
In the work, conventional and dynamic SEM imaging is performed simultaneously. The dynamic part is analysed using the fraction of secondary electron signals synchronous to excitation, which is measured by a lock-in amplifier.
As can be seen in the image, the simulated contrasts in the right column correspond well to the experimental data on the left.
The model, which is based on the time-dependent interaction of the electron beam with the vibrating cantilever, provides information about the relationship between the dynamically excited shape and the topological properties of the so obtained images. It allows the team to distinguish between features that are due to the imaging technique and those that carry relevant information, such as those from nonlinear mechanics.
The explicit solution for the image calculation represents another step towards the analysis of nonlinearity in scanning force microscopy experiments. Such nonlinear behaviour of levers appears during intermittent contact imaging or with multi-frequency excitation, which will be explored in future work.
The researchers presented their results in the journal Nanotechnology.
About the author
Dipl. Phys. Maria-Astrid Schröter graduated in theoretical physics at TU Berlin. Currently she works as a PhD candidate at the Federal Institute for Materials Research and Testing (BAM) in Berlin. Her research focuses on nonlinear dynamics of vibrating microcantilevers. Prof. Dr Heinz Sturm has a background in physical chemistry, heads the group “Nanotribology and Nanostructuring” at BAM and lectures at TU Berlin about SFM techniques. Prof. Dr Matthias Holschneider holds the chair of “Applied Mathematics” at the University of Potsdam. He graduated in theoretical physics and mathematics. Currently, he is director of the Potsdam Institute of the Dynamics of Complex Systems (DYCOS). He is a specialist in mathematical modelling, wavelet analysis and nonlinear system theory.