Charge drives for scanning probe microscope positioning stages

Due to hysteresis exhibited by piezoelectric actuators, positioning stages in scanning probe microscopes require sensor-based closed-loop control. Although closed-loop control is effective at eliminating non-linearity at low scan speeds, the bandwidth compared to open loop is severely reduced. In addition, sensor noise significantly degrades achievable resolution in closed loop. In this work, charge drives are evaluated as a simple positioning alternative when feedback control cannot be applied or provides inadequate performance. These situations arise in high-speed imaging, where position sensor noise can be large or where no feedback sensors are present. Charge drives can reduce the error caused by hysteresis to less than 1% of the scan range. We review the design of charge drives and compare them to voltage amplifiers for driving lateral SPM scanners. The first experimental images using charge drive are presented.