Ultrasensitive mode-localized micromechanical electrometer

We report a highly sensitive prototype micromechanical electrometer that employs the phenomena of mode-localization and curve veering for monitoring minute charge fluctuations across an input capacitor. The device consists of a pair of weakly coupled, nearly identical single crystal silicon, double-ended tuning fork (DETF) resonators. An addition of charge across an input capacitor on one of the coupled resonators induces a differential axial strain on that resonator relative to the other consequently perturbing the structural symmetry of the nearly periodic system. The resulting shifts in the eigenstates for the same magnitudes of charge input are theoretically and experimentally demonstrated to be nearly three orders of magnitude greater than corresponding resonant frequency variations. The topology chosen may also be adapted for force or strain monitoring thereby widening the relevance of the results reported here to precision inertial sensing as well.

I. Introduction

Electrometers, devices that are used to measure precise quantities of charge, have been a focus of research for over a hundred years. A wide variety of concepts have been proposed and demonstrated for accurately monitoring charge fluctuations across an input capacitor [1]–[5]. At present, however, the cryogenically cooled single electron transistor (SET) electrometers that utilize the phenomenon of quantum tunneling for charge detection, are seen as the benchmark for high sensitivity charge sensing, with demonstrated resolutions down to [2]. While these solid-state electrometers offer excellent charge resolutions, they suffer from the inherent disadvantages of limited operational bandwidth and their need for operation at sub-Kelvin temperatures (in order to reduce thermal noise effects [2]).