Design of a high-bandwidth tripod scanner for high speed atomic force microscopy

Tip-scanning high-speed atomic force microscopes (HS-AFMs) have several advantages over their sample-scanning counterparts. Firstly, they can be used on samples of almost arbitrary size since the high imaging bandwidth of the system is immune to the added mass of the sample and its holder. Depending on their layouts, they also enable the use of several tip-scanning HS-AFMs in combination. However, the need for tracking the cantilever with the readout laser makes designing tip-scanning HS-AFMs difficult. This often results in a reduced resonance frequency of the HS-AFM scanner, or a complex and large set of precision flexures. Here, we present a compact, simple HS-AFM designed for integrating the self-sensing cantilever into the tip-scanning configuration, so that the difficulty of tracking small cantilever by laser beam is avoided. The position of cantilever is placed to the end of whole structure, hence making the optical viewing of the cantilever possible. As the core component of proposed system, a high bandwidth tripod scanner is designed, with a scan size of 5.8 µm × 5.8 µm and a vertical travel range of 5.9 µm. The hysteresis of the piezoactuators in X- and Y-axes are linearized using input shaping technique. To reduce in-plane crosstalk and vibration-related dynamics, we implement both filters and compensators on a field programmable analog array. Based on these, images with 512 × 256 pixels are successfully obtained at scan rates up to 1024 lines/s, corresponding to a 4 mm/stip velocity.