硅基纳米湿敏元件特性、机理研究及其测试仪设计

【作者】 万徽；

【导师】 王兢；

【作者基本信息】 大连理工大学 ， 通信与信息系统， 2004， 硕士

【摘要】 以硅片为衬底制作了纳米钛酸钡（BaTiO₃）膜湿敏元件。用硬脂酸盐法合成纳米钛酸钡材料，丝网印刷法将纳米钛酸钡涂在硅衬底上制成电阻式湿敏元件。测试分析了元件的性能参数，结果表明，元件具有较高的灵敏度。元件阻抗（Z）和电容（C）值随测试频率及相对湿度（RH）而变化，但基本不随测试电压变化。在1V，100Hz条件下，元件阻抗～相对湿度关系曲线的线性最好。 用复阻抗法对硅衬底纳米钛酸钡湿敏元件的感湿机理进行了分析讨论。实验测量得到湿敏元件在不同相对湿度下的复阻抗特性曲线，然后用各种理想等效电路的复阻抗曲线与实际测量的纳米钛酸钡湿敏元件的复阻抗特性曲线进行比较，寻找一组最相近的曲线。结果表明，纳米钛酸钡湿敏元件的感湿特性可以等效为两个电阻—电容并联电路的串联再与另一个电阻串联的等效电路。这个电路在改变电阻与电容参数的情况下，复阻抗特性曲线的变化规律可以很好的与纳米钛酸钡湿敏元件的实验测量的不同湿度下复阻抗特性曲线的变化规律相吻合。分析出相应的等效电路之后，结合等效电路有关参数的变化规律，分析讨论了纳米钛酸钡湿敏元件的感湿机理。低湿时，感湿材料本身颗粒电阻和电容（传导载流子和材料极化）及吸附的少量水分子共同起作用；高湿时，吸附的水分子的电离及水分子引起的电极处的空间电荷极化起主要作用。 纳米钛酸钡感湿芯片是一种电阻式湿度传感器。100Hz交流电压作用下，该感湿芯片的输出电阻值对数与相对湿度之间的线性最好，且在相对湿度11％～98％范围内其阻值变化了4个数量级，感湿灵敏度较高。但是，电阻跨度大成为测湿电路设计的难题。本论文基于单片机AT89C2051，采用程控放大技术，设计了简单化、智能化的湿度测试仪，有效解决了上述难题。更多还原

【Abstract】 The humidity sensor is fabricated with nanometer BaTiO3 film on silicon substrate. The nanometer BaTiO3 is synthesized by stearic acid method and is screen printed on silicon substrate to make the resistive type humidity sensor. The properties of the sensor were measured and analyzed. The results show that the sensor processes high sensitivity. The measurement voltage does not influence the properties of the sensor, while the impedance and the capacitance of the sensor change with the relative humidity (RH) and the measurement frequency. The best linearity of the impedance vs. RH curve is reached under the voltage 1V and the frequency 100Hz.Complex impendence techniques are used to analyze the humidity sensing mechanism of nanometer barium titanate humidity sensors on silicon substrate. The curves of resistance, capacitance and complex impedance of the sensors versus relative humidity (RH) are measured at different frequencies. An equivalent circuit model associated with resistors and capacitors is built. The complex impedance properties of the equivalent circuit changing with parameters of the resistance and the capacitance are coincident with complex impedance properties of BaTiO3 humidity sensor changing with RH in practice. The sensing mechanism of the sensor is discussed. In low RH range, the humidity sensing properties are determined mainly by the crystal grain resistance and the capacitance on the grain interfaces. In high humidity RH range, the polarization and ionization of the absorbed water makes a main contribution to humidity sensing properties.Nanometer barium titanate humidity sensor is a resistive sensor. The resistance changes from 103 to 106 in the RH range of 11%-98%, which shows the high sensitivity of sensor. A simple, intelligent, precision humidity measuring instrument is designed by using singlechip AT89C2051, programmable gain amplifier technology. The difficult design problems of wide resistance changing range are solved.更多还原