Novel AlN/Pt/ZnO Electrode for High Temperature SAW Sensors

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.

Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure

“…In the last years, Aluminum Nitride (AlN) became a hot topic material for many sensing applications. This is due to its good piezoelectric properties, large bandgap (6.2 eV), high temperature stability (up to 1000 °C), chemical inertness, compatibility with the process technology, that makes AlN a very interesting material for realization of various types of sensors [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. For instance, piezoelectric AlN thin films were successfully integrated in pressure sensors capable to operate in high temperature or in harsh environments conditions (e.g., combustion pressure sensors for cars) [ 8 ] or for measuring pressure fluctuations in rotating machinery such as compressors and turbines [ 9 ].…”

Improvement of High-Temperature Stability of Al2O3/Pt/ZnO/Al2O3 Film Electrode for SAW Devices by Using Al2O3 Barrier Layer

“…From Figure 4a, we can see that only the Pt (111) peaks appear in these two samples. No ZnO peaks can be observed in these patterns because this this ZnO film was too thin to be detected [12]. The intensity of the Pt (111) peak is much lower for Al 2 O 3 /Pt/ZnO/LGS than Al 2 O 3 /Pt/ZnO/Al 2 O 3 /LGS.…”

“…The large FWHM of the Pt peak of Al 2 O 3 /Pt/ZnO/LGS is due to the low temperature of deposition of the ZnO buffer layer, which results in the poor crystalline qualities of both ZnO and Pt. The crystalline qualities these films are typically improved by increasing the deposition temperature to 600 °C [12]. However, we have found that by inserting an Al 2 O 3 barrier layer we can improve the crystalline quality of the ZnO buffer layer deposited at low temperatures; this was possible because of their similar crystal structures [16,17].…”

“…Pereira da Cunha [11] investigated a Pt-Ni/Pt-Zr electrode containing an Al 2 O 3 interfacial layer that was used to reduce the degradation of the electrode layer by inhibiting the interdiffusion and interfacial reactions. In our previous work [12], we prepared a AlN/Pt/ZnO multilayered electrode on Langasite (LGS, La 3 Ga 5 SiO 14 ) substrate and found that the ZnO buffer layer improved the crystalline quality of Pt by inhibiting the recrystallization of Pt film at 1000 °C, showing that the crystalline quality is an important factor in determining the stability of film electrodes at high temperature. However, the abovementioned AlN/Pt/ZnO film electrode was unable to work steadily above 1100 °C because both agglomeration and the interdiffusion (of the Ga, Si, and La atoms) were difficult to control at such high temperatures.…”

2D-Modeling for the temperature-composition dependent thermal-conductivity of AlmNn compounded semiconductor materials

“…Here, m is the Al mole fraction in the composite alloy and mn. For example, AlN based semiconductor materials play a significant potential applications in opto-electrics operating at deep ultraviolet since these materials' high thermal conductivity properties [3][4][5][6] and [7]. However, so far its knowledge is very limited in the field of the quantitative description of thermal conductivities with respect to Al mole fraction m and temperature T in composite semiconductor of Al m N n .…”