This paper describes a new technique for reducing the piezoelectric hysteresis in SPM images. Imaging modes such as constant-force AFM require a piezoelectric actuator to vary the probe-sample distance. In such modes, the topography of the sample is reconstructed from the voltage applied to the vertical piezoelectric actuator. However, piezoelectric actuators exhibit significant hysteresis which can produce up to 14% uncertainty in the reproduced topography. To combat this problem, the recent generation of commercial AFM's use capacitive or inductive position sensors to eliminate hysteresis; however, these sensors can be difficult to incorporate into the scanning head and also increase the imaging noise. In this work, an alternative technique is proposed that avoids the use of a vertical position sensor. Instead, a charge amplifier is utilized to linearize the vertical piezoelectric actuator and eliminate imaging hysteresis. Experimental results demonstrate a reduction in non-linearity from from 14% to 0.65%, which is visibly undetectable.
2011 American Control Conference, (ACC 2011). Proceedings of the 2011 American Control Conference (San Francisco, CA 29 June - 1 July, 2011) p. 2861-2866