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.

Micromachines for nanoscale science and technology

“…Micromachined tunnelling units [8] and STMs [9,10] have already been reported. Among these devices, the lateral tunnelling unit (LTU) has many advantages, such as a simple fabrication process that allows us to integrate many kinds of different microstructures, such AFM tips, or a proof mass as for accelerometer applications [11]. The electrostatic actuator has a large operating range and is easy to control.…”