20Pm1-E2 Evaluation of Transverse Piezoelectric Coefficient E_<31,f> of PZT Thin Films from Direct/inverse Piezoelectric Effects

We evaluated the transverse piezoelectric coefficient e_<31,f> of Pb(Zr,Ti)O_3 (PZT) thin films from direct and inverse piezoelectric effects using cantilever methods. The PZT/Si unimorph cantilevers (length: 17.8 mm, width: 2.0 mm, thickness: 628 μm) were fabricated by depositing the PZT thin films and the stripe-shaped Pt top electrodes on Pt/Ti/Si substrates by rf-magnetron sputtering. From the e_<31,f> measurement, we confirmed that e_<31,f> largely depended on frequency in both direct and inverse effects. In cases where evaluated from direct piezoelectric effect, e_<31,f> was independent of position and size of electrode and input displacement, and calculated to be -6 C/m^2 above 20 Hz. On the other hand, e_<31,f> evaluated from inverse piezoelectric effect increased with applied voltage, and calculated to be as high as -12 C/m^2 below 500 Hz.