Room-Temperature Sensing of Single Electrons Using Vibrating-Reed Electrometer in Silicon-on-Glass Technology

In the commonly used existing siliconon-insulator microelectromechanical systems (MEMS) process, a silicon-oxide-silicon sandwich structure in the sensor device creates parasitic capacitance, which reduces the charge sensitivity. In this letter, for the first time, we demonstrate a vibrating-reed-based electrometry system with high sensitivity and resolution in the silicon-onglass (SOG) MEMS process. In this letter, we utilize a glass substrate instead of silicon to ameliorate charge sensitivity by reducing the parasitic capacitance. An improved preamplifier circuit topology incorporating with the proposed sensor shows a sensitivity of 1.43 × 10¹¹ V/C, which is the highest in the literature. In addition, the best charge resolution of 1.03 e/√Hz@5.7 kHz has achieved at room temperature and atmospheric pressure. This result provides strong evidence for the validity of our SOG-based MEMS device as a charge sensor for detecting even a single electron.

I. Introduction

The sensing of charge with high resolution plays an important role widening the use of electrometers or charge sensors in many diverse applications, such as surface charge analysis, mass spectrometry, tunneling microscopy, powder technology and aerosol science, bimolecular charge detection and ionization current measurement in ionization chambers [1]. The commercial transistor based electrometer, such as, the Keithley 6517A has a minimum charge resolution of 10 fC (~63k electrons) [2]. However, for bespoke scientific applications where charge noise of less than 1 fC is required, Keithley 6517A’s resolution is insufficient to meet the scientific needs. Recently, both resonator type and vibrating-reed (VR) type microelectromechanical systems (MEMS) electrometers exhibit significant improvement on charge sensing [1]. Nevertheless, the resonant MEMS sensors operated at room temperature suffer a poor charge resolution due to high phase noise. Thus, a vacuum environment is vital to achieve high quality factor (Q factor) for overcoming phase noise issue to improve the device performance [3]–[8]. On the other hand, compared to the existing commercial macro-scale and resonator type MEMS charge sensors, the vibrating-reed based MEMS charge sensors exhibit superior charge resolution at room temperature, and vacuum environment is not required [9]–[13].