Novel sensors for scanning force microscopy based on carbon nanotube mechanical resonators

Dynamic mode scanning force microscopy is a versatile method for studying forces and force-related properties close to a sample's surface with sub-nanometer resolution. The measurement principle of this method is based on mechanically exciting a force sensor consisting of a cantilever beam with a sharp interaction tip at its free end to oscillations close to or at its resonance frequency. Interactions between the sample and the tip alter the resonance frequency of the cantilever beam and the corresponding changes in its oscillatory state can be used to reconstruct sample properties. In this book a new bidirectional sensor concept is explored that allows for the measurement of perpendicular and lateral force components or their derivatives, respectively. The experiments with these novel force sensors focus on magnetostatic interactions by using special interaction tips consisting of iron-filled carbon nanotubes. It is shown that by calculating the mechanical properties of the cantilever beams and the magnetic behavior of the interaction tips quantitative evaluation of data measured with the bidirectional sensor is possible. Furthermore, a new co-resonant sensor concept is introduced to enhance the bidirectional scanning force microscopy sensors. This concept can be used to combine the ease-of-detection of micromechanical oscillators with the superior interaction sensing capabilities of nanoscaled mechanical resonator systems such as carbon nanotubes. The corresponding validation experiments demonstrate scanning force microscopy based on the resonant oscillations of a carbon nanotube.