Wide-bandwidth electromechanical actuators for tunneling displacement transducers

Abstract

A series of displacement transducers have been demonstrated which are based on the detection of electrons that quantum-mechanically tunnel across a narrow gap between electrodes. These transducers have important applications due to the sensitivity of the tunneling mechanism to su~A variations in the electrode gap. In this paper, we describe the recent development of wide-bandwidth electro-mechanical actuators and'simple feedback circuitry which have been adapted for use in tunneling displacement transducers.

Displacement Measurement by a Microfabricated Tunneling Unit

“…However, the voltage-displacement conversion factor (Ke/K) can be known by measuring the static transfer characteristic from the driving voltage to the displacement. The relationship between the distance of a vacuum gap and a tunneling current that passes across the gap is already shown in equations (1) and (2). Since the work function of metal ranges from 4 to 6eV, the tunneling current increases approximately 10 times with 0.1nm decrease of the gap.…”

“…The tunneling current which flows across the gap between the tip and the opposing electrode can be controlled by moving the tip and adjusting the gap distance. We call the device a lateral tunneling unit (LTU) because its tip moves lateral to the substrate, while most of micromechanical tunneling devices reported so far have vertical tips [2][3][4].…”

Historical Perspective of Accelerometer Technologies

“…Although this is just a simple example, it shows that the preamplifier noise is lower than the contributions of other noise sources. Therefore, researchers at JPL and Stanford University working with tunnelling sensors use simple opamp-based electronics, and do not focus on noise optimisation of the amplifiers (30). Until now, the work from the researchers at JPL and Stanford University on accelerometers was primarily focused on devices with a limited frequency range (100Hz), but with a Research on electron tunnelling accelerometers started only a few years ago, and electron tunnelling based sensors are not yet on the market.…”

Design, Fabrication and Operation of a Micromachined Tunneling Control Unit.

“…Micromachined tunneling units [2] and STM's [3,4] have been previously reported. Some of them require assembly [2] and coarse adjustment of the opposing surface [3,4].…”

“…Some of them require assembly [2] and coarse adjustment of the opposing surface [3,4]. In all these cases, the coarse positioner was not made by micromachining.…”