Expanding atomic force microscopy beyond a steady-state approach
Expanding atomic force microscopy beyond a steady-state approach lead image
With atomic force microscopy (AFM), scientists can observe the microscopic ridges and troughs that make up the surface of any object. Along with topographic information, this microscopic technique also can gather magnetic, electrostatic and near-field optic information about the sample. While previous studies have examined the effect of external forces of motion at the AFM tip in specific detection schemes, a general theory for the stead-state operation has only been developed recently.
The new paper by Wagner extends the theoretical description of AFM beyond the steady-state including a detailed analysis of the transient cantilever movement, which was neglected in previous studies.
“A description of transients is indispensable when new experimental methods are designed, which often involve modulations of the tip-sample force,” Wagner said. “My work improves our understanding of how the system reacts to external forces, resulting in faster and more accurate force measurements and imaging.”
In the paper, Wagner used the transient behavior outside steady-state to derive baseband dynamics at the tip to understand the amplitude, phase, and frequency response of the cantilever in the transient dynamic regime. The approach allows for the correct tuning of feedback loops and signal-to noise-analysis. This holistic approach reveals the inner-connection and similarities of dynamic AFM techniques used today and potentially in the future.
“For me, the most exciting outcome is the unified theory that explains the steady-state and transient dynamics of an AFM cantilever, given a minimal set of assumptions,” Wagner said. “Such a compact description in a single source is not only easier to understand but also reveals that all AFM modes operate on the same foundation.”
Source: “Steady-state and transient behavior in dynamic atomic force microscopy,” by Tino Wagner, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5078954 .
