Development of high sensitivity, large frequency bandwidth ZnO-based accelerometers

• A novel method for measuring the acceleration by real-time electrical impedance.
• Electrical impedance correlates with mechanical impedance and thus acceleration.
• The performance of ZnO accelerometer is improved from conventional approach.

ZnO has excellent capability in micromachining process for the fabrication of miniaturized accelerometer but its sensitivity is lower because the piezoelectric effect of ZnO is poor. In this paper, a novel accelerometer was made by ZnO and the real part of electrical impedance of ZnO accelerometer at its electrical port was employed to improve its sensitivity. The proposed method is able to obtain active, time varying real part of electrical impedance which correlates with the measured acceleration, usually experienced at the mechanical port of ZnO accelerometer. By comparing with the conventional approach which relies on the output voltage of ZnO accelerometer, the sensitivity is improved almost double with relatively low linearity error and large full scale output. Furthermore, the frequency bandwidth of ZnO accelerometer is extended up to its resonance frequency because the measurement of acceleration is done at the resonance frequency of ZnO accelerometer. Therefore, it allows the ZnO accelerometer to operate at its full frequency bandwidth since the unity response of ZnO accelerometer is no longer limited by the frequency response function of ZnO accelerometer.