Institut Jean Lamour, UMR 7198, Centre National de la Recherche Scientifique (CNRS)–Nancy University, Vandoeuvre-lès-Nancy, France.
IEEE Trans Ultrason Ferroelectr Freq Control. 2012 May;59(5):999-1005. doi: 10.1109/TUFFC.2012.2285.
This paper explores the possibility of using AlN/sapphire piezoelectric bilayer structures for high-temperature SAW applications. To determine the temperature stability of AlN, homemade AlN/sapphire samples are annealed in air atmosphere for 2 to 20 h at temperatures from 700 to 1000°C. Ex situ X-ray diffraction measurements reveal that the microstructure of the thin film is not affected by temperatures below 1000°C. Ellipsometry and secondary ion mass spectroscopy investigations attest that AlN/sapphire is reliable up to 700°C. Beyond this temperature, both methods indicate ongoing surface oxidation of AlN. Additionally, Pt/Ta and Al interdigital transducers are patterned on the surface of the AlN film. The resulting SAW devices are characterized up to 500°C and 300°C, respectively, showing reliable frequency response and a large, quasi-constant temperature sensitivity, with a first-order temperature coefficient of frequency around -75 ppm/°C. Between room temperature and 300°C, both electromechanical coupling coefficient K(2) and propagation losses increase, so the evolution of delay lines' insertion losses with temperature strongly depends on the length of the propagation path.
本文探讨了使用 AlN/蓝宝石压电双层结构进行高温表面声波（SAW）应用的可能性。为了确定 AlN 的温度稳定性，我们将自制的 AlN/蓝宝石样品在空气气氛中于 700 至 1000°C 的温度下退火 2 至 20 小时。原位 X 射线衍射测量表明，薄膜的微结构在 1000°C 以下的温度下不受影响。椭圆光度法和二次离子质谱研究证明 AlN/蓝宝石在 700°C 以下是可靠的。超过这个温度，这两种方法都表明 AlN 表面的氧化仍在继续。此外，Pt/Ta 和 Al 叉指换能器被图案化在 AlN 薄膜的表面上。得到的 SAW 器件在 500°C 和 300°C 下分别进行了表征，分别显示出可靠的频率响应和较大的准恒定温度灵敏度，频率的一阶温度系数约为-75 ppm/°C。在室温到 300°C 之间，机电耦合系数 K(2)和传播损耗都增加，因此延迟线插入损耗随温度的演变强烈取决于传播路径的长度。
