Displacement Measurement by a Microfabricated Tunneling Unit

Abstract

A microfabricated tunneling unit (LTU: lateral tunneling unit) was successfully applied to minute displacement detection. An LTU has a tunneling tip protruding from the chip edge and can be moved back and forth by a microactuator. The tip end was positioned close to a planar electrode attached to a PZT actuator. When the PZT actuator moved, the gap between the tip and the opposing electrode was kept constant by moving the tip so that the tunneling current flows through the gap should be constant. The displacement of the planar electrode was determined from the change in the microactuator's driving voltage.