Abstract
In order to develop a film electrode for the surface acoustic wave (SAW) devices working in high temperature, harsh environments, novel AlN/Pt/ZnO multilayers were prepared using pulsed laser deposition (PLD) systems on langasite (LGS) substrates. The AlN film was used as a protective layer and the ZnO buffer layer was introduced to improve the crystal quality of Pt films. The results show that the resistances of Pt and AlN/Pt film electrodes violently increase above 600 °C and 800 °C, respectively, while the resistances of AlN/Pt/ZnO electrodes have more stable electrical resistance from room temperature to 1000 °C. The AlN/Pt/ZnO electrode, where the ZnO film was deposited at 600 °C, has the best temperature stability and can steadily work for 4 h at 1000 °C. The mechanism underlying the stable resistance of the AlN/Pt/ZnO electrode at a high temperature was investigated by analyzing the microstructure of the prepared samples. The proposed AlN/Pt/ZnO film electrode has great potential for applications in high temperature SAW sensors.
Highlights
Many efforts in recent years have been focused on surface acoustic wave (SAW) sensors [1,2], mainly due to their excellent wireless, passive, small, multifunctional quality, and their ability to be widely applied to systems sensing temperature [3], pressure [4], and strain [5] et al With the progress of science and technology, these SAW sensors, which work in high temperature, harsh environments, are in high demand [6]
It can be seen that the resistance of the Pt/LGS sample sharply increases above 600 ◦ C, and increases by 22 times when it is heated to 800 ◦ C, from room temperature
It can be seen that the resistance of the AlN/Pt/LGS electrode continues to increase at a remarkable rate, though the AlN capping layer can improve the stability of the Pt film electrode to some extent, by comparing the resistance of Pt/LGS
Summary
Many efforts in recent years have been focused on surface acoustic wave (SAW) sensors [1,2], mainly due to their excellent wireless, passive, small, multifunctional quality, and their ability to be widely applied to systems sensing temperature [3], pressure [4], and strain [5] et al With the progress of science and technology, these SAW sensors, which work in high temperature, harsh environments, are in high demand [6]. The major challenge of SAW sensors operating at high temperatures is to prepare stable high temperature film electrodes, since film electrodes such as Pt [7], Pt-Rh [8], Ir-Rh [9], Ru-Al [10], W/Mo [11], W [12], or Pt-Ni/Pt-Zr [13] film electrodes, always undergo rapid agglomeration and recrystallization above 700 ◦ C, resulting in the discontinuity of film electrodes, an increase in resistance, and a failure of the SAW sensor. The SAW electrode was unable to steadily work above 1000 ◦ C because the recrystallization phenomenon of the electrode film was difficult to prevent
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