Piezoelectric Response to Pressure of Aluminum Nitride Thin Films Prepared on Nickel-Based Superalloy Diaphragms

Aluminum nitride (AlN) thin films were prepared on Inconel 600 superalloy diaphragms by rf magnetron sputtering for the first time to our knowledge. The crystal structure of the AlN films is hexagonal, and the c -axis of the AlN films orients perpendicular to the diaphragm surfaces. The full-width at half-maximum (FWHM) of the X-ray rocking curves of the AlN films is 5.7°, and the piezoelectric constants d 33 and d 31 are 2.0 and 0.7 pC/N, respectively. We have investigated the influence of the diaphragm structure on the piezoelectric response to pressure of the AlN films. The AlN films sensitively generate electric charges to pressure changes, and the generated charges show an excellent linearity with increasing pressure. The AlN films indicate a high sensitivity of 723 pC/N. The sensitivity of the AlN films agrees with the result calculated using a method in which the electroelastic energy is differentiated from the voltage in AlN films for unimorph circular diaphragms.