$Q$ Control of an Atomic Force Microscope Microcantilever: A Sensorless Approach

The scan rate and image resolution of the atomic force microscope (AFM) operating in tapping-mode may be im proved by modifying the quality (Q) factor of the AFM micro cantilever according to the sample type and imaging environment. Piezoelectric shunt control is a new method of controlling the Q factor of a piezoelectric self-actuating AFM microcantilever. The mechanical damping of the microcantilever is controlled by an electrical impedance placed in series with the tip oscillation circuit. A synthetic impedance was designed to allow easy modification of the control parameters which may vary with environmental conditions. The proposed techniques are experimentally demonstrated to reduce the Q factor of an AFM microcantilever from 297.6 to 35.5. AFM images obtained using this method show significant improvement in both scan rate and image quality.