Multi-mode resonant control of a microcantilever for atomic force microscopy

When operating the Atomic Force Microscope in tapping mode it is possible to decrease the quality factor of the microcantilever to enhance scan speed. A new field of Atomic Force Microscopy is evolving, which makes use of multiple frequency excitation and detection of the cantilever modes making it necessary to be able to control these modes and their response to excitation. This work proposes a multi-mode Q control approach utilizing positive position feedback, offering full control over the first two flexural modes of the cantilever. By completely damping the first mode and adjusting the quality factor of the second mode, it is possible to scan and obtain images at the second resonance frequency which improves image quality at high scan speeds due to the increased bandwidth of the z-axis feedback loop.