Design and control of atomic force microscopes (original) (raw)

Models for two atomic force microscope (AFM) designs were presented, namely, cantilever-on-scanner and sample-an-scanner design. It was found that coupling between scanner's bending and extension motion is present in both designs, making the scanner bending mode observable from the output. As a result, the ultimate feedback bandwidth is limited by the lowerfrequency bending mode in contrast to being ideally limited by the extension mode. Simulation and experimentaldata provided insight into pole-zero flipping and changes in the system dynamics as a function of force set-paint and input amplitude. Closed loop performance under integral and PID control were compared. It was found that PID control offers lower bandwidth over integral control if high-frequency rollloff and step response overshoot constraints were to be met. In addition, integral controller has a single gain compared 3 for PID; which makes it easier for parameter tuning by AFM users.