Al2O3保护层对高温下Pt/ZnO/Al2O3电极导电稳定性的影响

本工作研究了Al₂O₃保护层的厚度对高温下声表面波器件电极导电稳定性的影响, 采用激光分子束外延方法在Pt/ZnO/Al₂O₃电极上制备了不同厚度的Al₂O₃保护层。通过测量样品高温环境中的实时电阻, 发现Al₂O₃缓冲层的厚度对电极在高温下的导电稳定性的影响非常大。结果表明, 没有Al₂O₃保护层时, Pt/ZnO/Al₂O₃电极的电阻升温至800 ℃时开始急剧地增加。当包覆40 nm的Al₂O₃保护层时, 电极在升温至900 ℃以上才出现电阻值剧烈增加的现象。而随着Al₂O₃保护层厚度的增加, 电极的电阻在高温下的导电性能也更加稳定。SEM测试结果表明, 经过1000 ℃、1 h的高温测试后, Al₂O₃保护层越薄的Pt/ZnO/Al₂O₃电极, 结块形成的Pt颗粒越大与不连续的Pt空洞更多。这些结果为制备高温下稳定工作的声表面波器件提供了一条新的思路。

Al2O3 Coating Layer on the High Temperature Conductive Stability of Pt/ZnO/Al2O3 Film Electrode

To investigate the effects of Al₂O₃ coating layers on the conductive stability of surface acoustic wave electrodes working at high temperature, laser molecular beam epitaxy was carried out to deposit a series of Al₂O₃/Pt/ZnO/Al₂O₃ multilayer electrodes coated with Al₂O₃ layers of different thicknesses. The real-time resistance measurements of these samples were performed in the heat treatment. It can be found that the conductive stabilities of Al₂O₃/Pt/ZnO/Al₂O₃ samples were significantly related to the thickness of the Al₂O₃ coating layers. For the sample without Al₂O₃ coating layer, its resistance began to increase when the temperature rose up to 800 ℃. However, its resistances began to increase at 900, 1100 and 1150 ℃, at the thickness of Al₂O₃ coating layers of 40, 80 and 120 nm respectively. For the samples with 160 nm and 200 nm Al₂O₃ coating layers, the resistances almost remained stable during the whole heating process. According to the surface topographies of these samples, it found that the sample without Al₂O₃ coating layer formed isolated Pt grains after high-temperature measurement. As a comparison, the samples with Al₂O₃ coating layers did not form isolated Pt grains after high-temperature resistance measurement. After high-temperature measurement, the less discontinuous Pt voids appeared at the surface of the sample with a relative thicker Al₂O₃ coating layer. XRD tests of theses samples, performed before and after high-temperature measurement, showed that Pt recrystallization at high temperature can be inhibited by the Al₂O₃ coating layer, and the thicker layer could inhibit its recrystallization more effectively. These results provide a new way to prepare SAW devices which can work stably at high temperature.