A new dynamic imaging mode for high-resolution and high-bandwidth atomic force microscopy

This paper proposes a new high-bandwidth mode of imaging in an Atomic Force Microscope (AFM). This is achieved by regulating the gap between the sample and the vibrating cantilever tip to an appropriate sinusoidal signal with frequency close to the cantilever resonant frequency. This scheme utilizes the deflection signal of the cantilever instead of its derivatives such as amplitude and phase. We design the regulating controller using H-infinity mixed synthesis. Another major advantage of this approach is that we exploit a structure where sample topography estimation can be accurately done even at frequencies beyond the bandwidth of disturbance rejection resulting from the H-infinity optimal controller. Simulation results show an order of magnitude improvement in bandwidth over conventional tapping mode imaging. Experimental implementation of this new imaging mode is ongoing.