Reduction in Feedback Bandwidth of the Force-Controlled Atomic Force Microscope Using a Polyimide Cantilever

In this paper we present a method of reducing the bandwidth required in the force-controlled atomic force microscope (AFM) for measuring the force curves. System stability strongly depends on the quality factor of vibration ( Q ) of the cantilever. As polyimide has a low Q , a cantilever fabricated from it reduces the bandwidth required in the feedback system. A polyimide cantilever with dimensions of 540×155×3.4 µm 3 is fabricated to evaluate its Q in vacuum, density and Young's modulus. The measured Q is 50, which is much smaller than those of conventional cantilevers used for AFM. Using the measured mechanical properties of the polyimide, the required frequency response of the feedback system is estimated. Typical force curve measurements are confirmed by some numerical simulations.