June

Picture of the Month - June 2018

Here you see current insights into the research of the LaMa groups. A collection of the former pictures can be found in the Gallery.

Friction force microscopy as a new tool to analyze phase transitions

In recent years, a number of papers from the Institute of Applied Physics of the Justus-Liebig University Giessen have shown that friction force microscopy comprises a highly sensitive tool to explore internal relaxation modes for materials like polymers or self-assembled monolayers. Now, this experimental approach could be transferred to the general analysis of phase transitions. More specifically, phase transitions, which are usually accompanied by mechanical anomalies, can be pinpointed by detecting the resulting frictional changes. On contrary to previous approaches, experiments are not performed as a series of fixed temperature measurements, but instead the lateral forces are constantly monitored during a continuous change of the sample temperature (see Fig.).

As a model system, the layered charge density wave material 1T-TaS2 was analyzed and it was found, that e.g. the first order phase transition between the NC-CDW and the C-CDW phase was accompanied by distinct friction peaks. This behavior can be explained by a theoretical model, where small mechanical perturbations by the AFM tip are assumed to preemptively trigger the spinodal transformation, if the free energy barrier preventing this transformation becomes small enough. This new experimental technique thereby opens up fascinating perspectives to probe phase transitions, while at the same time mechanically interacting with the materials.

Publication: Panizon et al., New Journal of Physics 20, 023033 (2018), doi: https://doi.org/10.1088/1367-2630/aaac00

This picture was submitted by Dr. Dirk Dietzel, group of Prof. Schirmeisen.