Creep in piezoelectric scanners of atomic force microscopes

Piezoelectric actuators exhibit creep during open loop operation. Two models for creep, namely, a logarithmic and a LTI model, were presented and discussed. The LTI model was found to be more appropriate in predicting creep. A 3rd order LTI filter was used to compensate for creep in an AFM piezoelectric scanner. The performance of the filter was tested by imaging 530 and 1590 nm steps. With compensation, the creep response was reduced to 2.6%, compared to 9.6% without compensation, for images taken over 6.67 minutes. Closed loop operation can offer better creep compensation but is a more expensive option. Moreover, it reduces image resolution for small scans/sample features due to limited dynamic range of sensors at high bandwidth.