Control of first and higher transverse eigenmodes of active Atomic Force Microscope cantilevers

Abstract

High speed imaging in Atomic Force Microscopy (AFM) tapping mode depends on the cantilever's effective resonance frequency and Q factor. Imaging in higher cantilever eigenmodes implies increased acquisition bandwidths based on the frequency. However, in combination with the corresponding Q factor it leads to a specific time constant of each eigenmode. The detection and control of the higher eigenmodes has become easily available with the development of powerful data acquisition and processing hardware. To achieve a greater flexibility, we apply a control methodology that arbitrary modifies the cantilever dynamics. It results in the modification of both Q factors and resonance frequencies. Using higher eigenmodes in combination with lowered Q factors considerably enhances the image acquisition rate. A 20 times increase in imaging bandwidth is achieved by using the presented methodology. On the other side, the resolution can be enhanced by using increased Q factors. The modification of the resonance frequency (F control) allows imaging at resonances that are not natural to the cantilever. The design of the single eigenmode compensator is outlined and applied as a simple modification to an AFM characterization and imaging environment. The performance is evaluated on different samples in tapping mode in air.