Ir-Rh thin films as high-temperature electrodes for surface acoustic wave sensor applications
Ir-Rh thin films as high-temperature electrodes for surface acoustic wave sensor applications
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DOI：
10.1016/j.sna.2016.03.008
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发表时间：
2016-06-01
影响因子：
4.6
通讯作者：
Talbi, Abdelkrim
中科院分区：
文献类型：
--
作者：
Taguett, Amine;Aubert, Thierry;Talbi, Abdelkrim
实现在高温氧化气氛中稳定的表面声波（SAW）器件需要开发能够承受这种恶劣条件的导电薄膜电极。最近的研究表明，铂基合金、多层膜或纳米复合膜适用于高达800摄氏度的温度。基于新材料和结构的电极仍然必须被开发用于在更高温度下发生的应用。从这个角度来看，基于铱的薄膜可能是关于高熔点的良好候选者，因此这种贵金属的扩散系数低。特别地，Ir-Rh块体合金已经显示出作为火花塞电极的上级性能，火花塞电极必须同时抵抗物理和化学磨损，例如高温SAW电极。因此，本文研究了Ir-Rh薄膜的高温行为。采用单枪电子束蒸发法沉积了铱原子比为10 ~ 50%的铱铑合金和多层膜。通过X射线衍射、扫描和透射电子显微镜、电子能量损失谱和四点探针电阻率测量研究了在空气中在800 ℃下退火4天对薄膜的影响。结果表明，所有的膜在退火期间氧化。退火后的电性能高度依赖于膜的初始组成：膜中的Ir比率越高，退火后的电阻率越低。此外，Rh 2 O3覆盖层，与一些几十纳米的厚度，形成在膜的表面，证实了以前的观察上的Ir-Rh块体合金。在基于Ir 30 Rh 70合金电极的器件上进行的第一SAW测量是非常有希望的，因为SAW信号在4天退火过程之后仍然清晰可见，同时没有观察到团聚现象。(C)© 2016 Elsevier B. V.版权所有。
The achievement of surface acoustic wave (SAW) devices stable in high-temperature oxidizing atmospheres requires the development of conductive thin film electrodes that can withstand such harsh conditions. Recent studies have demonstrated the suitability of Pt-based alloys, multilayers or nanocomposite films for temperatures up to 800 degrees C. Electrodes based on new materials and structures still have to be developed for applications taking place at higher temperatures. In this perspective, thin films based on iridium could be good candidates regarding the high melting point, and thus the low diffusion coefficients of this noble metal. In particular, Ir-Rh bulk alloys have shown superior performance as spark plug electrodes, which have to resist concurrently to physical and chemical wear such as high-temperature SAW electrodes. Consequently, this paper deals with the high-temperature behavior of Ir-Rh thin films. Ir-Rh alloys and multilayers films, with an Ir atomic ratio between 10 and 50%, are deposited by one-gun electron beam evaporation method. The impact on the films of a 4 days annealing treatment at 800 degrees C in air is studied by X-ray diffraction, scanning and transmission electron microscopy, electron energy loss spectroscopy and four-points probe resistivity measurements. It turns out that all the films oxidized during the annealing period. The post-annealing electrical properties are highly dependent of the initial composition of the film: the higher is the Ir rate in the film, the lower is the electrical resistivity after annealing. Moreover, an Rh2O3 overlayer, with a thickness of some tens of nanometers, forms at the surface of the film, confirming previous observations made on Ir-Rh bulk alloys. First SAW measurements made on devices based on Ir30Rh70 alloy electrodes are very promising as a SAW signal is still clearly visible after the 4 days annealing process, while no agglomeration phenomenon can be observed. (C) 2016 Elsevier B.V. All rights reserved.