Orientation Dependence of Shear Mode Piezoelectric Properties of Epitaxial Pb(Zrx,Ti1-x)O3 Thin Films

Abstract

The orientation dependence of shear mode piezoelectric properties has been investigated for epitaxial Pb(Zr,Ti)O3 (PZT) thin films with composition near the morphotropic phase boundary. (101)- and (111)-oriented PZT films were epitaxially grown on SrTiO3 (STO) substrates by rf magnetron sputtering and microfabricated into rectangular-shaped specimens to apply a horizontal electric field using lateral electrodes. The application of a sinusoidal input voltage of 100 kHz generated in-plane shear vibration, which was measured using a laser Doppler vibrometer. In-plane displacement proportionally increased with applied voltage for each PZT film. When a horizontal electric field was applied to (101)PZT along the directions parallel and perpendicular to [110]STO, the shear piezoelectric coefficient d15 was calculated to be 110 and 305 pm/V, respectively. On the other hand, d15 of (111)PZT under the electric field parallel to [110]STO was calculated to be 160 pm/V. These results indicate that the shear mode piezoelectric coefficients of the epitaxial PZT films not only show large values compatible with bulk ceramics, but also strongly depend on the crystallographic orientation and the direction of the electric field.