Mechatronic Demodulation of Self-Sensing Cantilever for DC-bias free AFM Imaging in Liquid

Abstract

This paper presents the application of mechatronic demodulation for performing dynamic mode AFM measurements with self-sensing cantilevers in liquid. In the proposed approach the bridge circuits with the piezoresistive sensing elements are supplied by an ac voltage that corresponds to the cantilever oscillation frequency. In contrast to conventional read-out circuits, no dc voltages are applied to the piezoresistive elements. Therefore, electrochemical effects leading to a deterioration of the self-sensing cantilever are avoided. This is demonstrated by immersing a self-sensing cantilever in water and comparing microscope images for operation with dc and ac voltages. To verify the feasibility of using mechatronic demodulation for dynamic mode AFM imaging in water the topography of a calibration grating is measured.