Frequency response separation scheme for non-contact type atomic force microscope

Abstract

We propose the simple structure of non-contact type atomic force microscope (AFM) with frequency response separation (FRS) scheme. In conventional non-contact AFM, two actuators have been used: one actuator is used for controlling the gap between the cantilever tip and the sample surface. Another is for vibrating the tip at its fundamental mode to measure the tip–sample distance. However, with the FRS scheme, only one actuator is enough for non-contact AFM measurement. Based on the FRS scheme, the multiplex signals of the gap control command signal and the gap measuring vibrating signal are applied to the only one actuator. So, this ‘single’ actuator plays two roles: tip–sample gap control and cantilever vibrating. In this paper, block PZT and bimorph PZT are used as ‘single’ actuators, respectively. And, a piezo-resistive cantilever is used for an easy detection of cantilever deflection with simple structure. Frequency responses of each actuator and the cantilever were experimented to confirm the effect of the FRS scheme. And, a 10 μm standard grid sample was imaged with the proposed structure to verify feasibility.