Abstract
The realization of a c-axis oriented aluminum nitride thick film on aluminum substrates is a promising step in the development of transducers for applications with a working temperature up to about 600 °C. The present paper deals with the realization of AlN thick films by means of reactive magnetron sputtering with a pulsed DC power supply, operating in continuous mode for 50 h. Two values (0.4 and 0.8) of nitrogen concentration were used; operative pressure and power were set at 0.3 Pa and 150 W, respectively. The thickness of the obtained aluminum nitride films on the aluminum substrate, assessed with a profilometer, varied from 20 to 30 µm. The preferential orientation of AlN crystals was verified by X-ray diffraction. Finally, as the main focus of the investigation, the films underwent electrical characterization by means of an LCR-meter used on a parallel plate capacitor set-up and a test system based on a cantilever beam configuration. AlN conductivity and ε33 permittivity were derived in the 100 Hz–300 kHz frequency range. Magnetron sputtering operation with nitrogen concentration equal to 0.4 resulted in the preferred operative condition, leading to a d31 piezoelectric coefficient, in magnitude, of 0.52 × 10−12 C/N.
Highlights
Accepted: 10 March 2022In situ process monitoring of materials working at high temperatures by means of piezoelectric transducers is an important issue in many applications of different fields, for example, aerospace or automotive [1,2]
Aluminum nitride (AlN) may offer a promising alternative for high-temperature applications, and AlN thin film sputtered on aluminum (Al) substrate is proposed for nondestructive testing applications with a working temperature up to about 600 ◦ C [2]
With increasing nitrogen concentration, typically, three operation modes of magnetron sputtering can be identified according to the coverage of the aluminum target by aluminum nitride
Summary
In situ process monitoring of materials working at high temperatures by means of piezoelectric transducers is an important issue in many applications of different fields, for example, aerospace or automotive [1,2]. Aluminum nitride (AlN) may offer a promising alternative for high-temperature applications, and AlN thin film sputtered on aluminum (Al) substrate is proposed for nondestructive testing applications with a working temperature up to about 600 ◦ C [2]. The good adhesion of AlN films on Al substrates, in our opinion, can be the basis for the development of transducers with a working temperature up to about 600 ◦ C. With this in mind, with tests performed just at room temperature, the electrical properties of magnetron sputtered
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