The authors present a novel closed loop electromagnetic actuator for fine position control. In this, six NdBFe permanent magnets are attached to a linear flexure mechanism. These are, in turn, surrounded by solenoid actuation coils. Feedback is provided by a sensor having sub-nanometre capability. Initial results are presented of a system in which two such springs have been combined to form a tunnelling profilometer. This has been used to profile 35 nm of the surface of a silicon wafer that has been coated with a 20 nm thick gold film. Results indicate nanometre-level resolution and a thermal drift in the probe axis of better than 0.02 nm s-1.
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Smith et al. (1992) studied this question.
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