A micro resonant electrometer with 9-electron charge resolution in room temperature

This paper reports a mode-localized resonant electrometer with 9-electron charge resolution in room temperature. To the best knowledge of the authors, it is the highest resolution level for MEMS resonant electrometers. It uses a 3 degree-of-freedom (DoF) weakly coupled resonators (WCRs) as sensing element, then input charge causes stiffness perturbation to one resonator and leads to a drastic change of the mode shape owing to the mode localization phenomenon. Under the closed-loop test, the relative sensitivity based on the amplitude ratios (2280858ppm) is -900 times higher than that of the frequency (2539ppm) with the input charge of 380/C. The resolution of the electrometer is 9.21 e/√Hz. Compared to the state-of-the-art MEMS resonant electrometer (5250e/√Hz) [1], the resolution is improved by nearly three orders of magnitude.