Enhancing the electric charge output in LiNbO₃-based piezoelectric pressure sensors

Lithium niobate (LiNbO₃) single crystals are a kind of ferroelectric material with a high piezoelectric coefficient and Curie temperature, which is suitable for the preparation of piezoelectric pressure sensors. However, there is little research reporting on the use of LiNbO₃ single crystals to prepare piezoelectric pressure sensors. Therefore, in this paper, LiNbO₃ was used to prepare piezoelectric pressure sensors to study the feasibility of using LiNbO₃ single crystals as a sensitive material for piezoelectric pressure sensors. In addition, chemical mechanical polishing (CMP) technology was used to prepare LiNbO₃ crystals with different thicknesses to study the influence of these LiNbO₃ crystals on the electric charge output of the sensors. The results showed that the sensitivity of a 300 μm sample (0.218 mV kPa^-1) was about 1.23 times that of a 500 μm sample (0.160 mV kPa^-1). Low-temperature polymer heterogeneous integration and oxygen plasma activation technologies were used to realize the heterogeneous integration of LiNbO₃ and silicon to prepare piezoelectric pressure sensors, which could significantly improve the sensitivity of the sensor by approximately 16.06 times (2.569 mV kPa^-1) that of the original sample (0.160 mV kPa^-1) due to an appropriate residual stress that did not shatter LiNbO₃ or silicon, thus providing a possible method for integrating piezoelectric pressure sensors and integrated circuits.