声表面波ZnO薄膜紫外探测器的响应机制研究

Investigation of Response Mechanism for ZnO Thin Film Based Surface Acoustic Wave Ultraviolet Detector

通过射频磁控溅射法在以128°Y-X LiNbO3为压电衬底的声表面波(SAW)小波器件上沉积了一层ZnO薄膜作为紫外光敏感膜,利用网络分析仪对所制备探测器的紫外光响应特性进行了测试。实验结果表明,在波长365nm、光强210μW/cm2的紫外光照射下,探测器的频移量最大可达到37kHz,且具有良好的可重复性。探测器的紫外光响应过程和暗场恢复过程均包含了一个快过程和一个慢过程,前者决定于ZnO薄膜表面氧气分子的吸附与解吸附过程,而后者则决定于外界氧气分子与ZnO内部本征缺陷间的慢交换过程。最后,结合声电效应和半导体光电导效应分析给出了探测器紫外光响应过程和暗场恢复过程的理论公式。该文对基于ZnO薄膜的高灵敏度SAW紫外探测器响应机制的揭示,为其瞬态特性的改善和实用化提供了思路。

A ZnO thin film as ultraviolet （UV） illumination sensing layer was deposited through radio frequency magnetron sputtering on the surface acoustic wave （SAW） wavelet device,which was fabricated on the 128°Y-X LiNbO3 piezoelectric substrate.The characteristics of UV illumination response of the detector were tested and measured using a network analyzer.The experimental results showed that a maximum frequency shift of 37 kHz could be obtained with a 365 nm 210 μW/cm2 UV illumination and the detector had a good repeatability.Further,the UV response process and the recovery process both contained a fast period and a slow period.The fast period depended on the adsorption and desorption of oxygen molecules at the surface of ZnO thin film,and the slow period depended on the slow exchange process between the outside oxygen molecules and the native defects inside ZnO crystal.At last,the theoretical formulas for the UV response process and the recovery process were derived by combining the acoustoelectric effect and the photoconductivity effect.The investigation of response mechanism of the ZnO thin film based SAW UV detector with high sensitivity provided suggestions for the improvement of transient characteristics and the practicality of the detector.