薄膜厚度对钛酸钡类薄膜传感器敏感特性的影响

利用氩离子束溅射技术,分别在SiO2/Si衬底上淀积了0.5 mm、1 mm和2 mm的Ba1-xLaxNbyTi1–yO3薄膜,并探讨了薄膜厚度对MIS电容湿敏特性的影响以及薄膜厚度对薄膜电阻的光敏和热敏特性的影响。实验结果表明:0.5 mm膜厚的MIS电容传感器具有比2 mm膜厚的MIS电容传感器高9倍的湿敏灵敏度。用孔隙率和孔径分布物理模型分析得出,薄膜越薄,膜的孔隙率越高,器件的湿敏灵敏度越高。反之,薄膜越厚,光吸收越强,薄膜电阻的光敏灵敏度越高;但薄膜厚度对薄膜电阻热敏特性的影响甚微,敏感机理与薄膜的微观结构可解释这些现象。

Effects of Film Thickness on Sensing Properties of Perovskite-type Thin-film Sensors

Using argon ion-beam sputtering technique, Ba1-xLaxNbyTi1-yO3 films of 0.5 mm, 1 mm or 2 mm were deposited on SiO2/Si substrates for metal-insulator-semiconductor (MIS) capacitors. The effect of film thickness on the humidity sensitivity of MIS structure and the effects of film thickness on the photo and thermal sensitivities of the thin film resistor were also investigated. The sensitivity of the sensor with 0.5 mm film was 9 times as hihg as that of the sensors with 2 mm film. The results are explained by the proposed physical model based on the porosity and the pore-volume distribution of the film. The thinner the thin film, the higher is the porosity, and thus the higher is the sensitivity of the device to humidity. On the contrary, the thicker the thin film, the stronger is the light absorption, therefore, the higher is the photo sensitivity. However, the effect of film thickness on the thermal sensitivity of thin film resistor is ignorable. All these are related to the sensing mechanisms and the thin film microstructure.