Here, we report the characteristics of zero-bias capacitive micromachined ultrasonic transducers (CMUT) in various aspects, considering the transmission and reception sensitivity and evaluation of the long-term stability with AC transmission in immersion. The main idea of the zero-bias CMUT implementation is that the charge is injected by the dielectric charging effects in an insulation layer in the pull-in state. The CMUT was fabricated by a local oxidation of silicon (LOCOS) process, and the insulation layer consists of Si3N4-SiO2 and SiO2, which have been commonly used in previous studies. A study on the charging effects is reported to quantitatively observe the voltage shift by charge transfer with time dependency at different temperatures and collapsing time-dependency. Therefore, we successfully implemented a zero-bias CMUT with a transmission efficiency of 4.62-kPa/V at a center frequency of 7.53 MHz in Si3N4-SiO2 and a transmission efficiency of 6.78 kPa/V at a center frequency of 7.86 MHz in SiO2 immersion.

中文翻译：

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利用介电充电效应比较零偏置CMUT操作的Si3N4-SiO2和SiO2绝缘层。

在这里，我们考虑到发送和接收的灵敏度以及评估交流电在浸没状态下的长期稳定性，在各个方面报告零偏置电容式微加工超声换能器（CMUT）的特性。零偏置CMUT实现的主要思想是，电荷是通过介电电荷效应在拉入状态的绝缘层中注入的。CMUT是通过硅的局部氧化（LOCOS）工艺制造的，绝缘层由先前研究中常用的Si3N4-SiO2和SiO2组成。据报道，对充电效应的研究通过在不同温度下具有时间依赖性和塌陷的时间依赖性的电荷转移来定量观察电压偏移。因此，