Film-thickness and composition dependence of epitaxial thin-film PZT-based mass-sensors

The transverse piezoelectric coefficient e(31,f) and mass-sensitivity were measured on piezoelectric cantilevers based on epitaxial PZT thin-films with film-thicknesses ranging from 100 to 2000 nm. The highest values of e(31,f) and mass-sensitivity were observed at a film thickness of 500-750 nm, while the observed remnant polarization P-r and longitudinal piezoelectric coefficient d(33,f) values become saturated with a film thickness of 750-1000 nm. To obtain high performance by making use of its optimal film thickness, PZT thin films with various Zr/Ti ratios from 20/80 to 80/20 were studied. The experimental results indicated that the ferroelectric property reached a highest remnant polarization P-r at a Zr/Ti ratio of 20/80, while the longitudinal piezoelectric coefficient d(33,f) increased with increasing Zr content and reaches a maximum at a Zr/Ti ratio of 52/48. The findings suggest that the optimal composition for mass-sensitivity and transverse piezoelectric coefficient e(31,f) was shifted to the tetragonal part of the phase diagram with the Zr/Ti ratios of 45/55 and 40/60, respectively. (C) 2013 Elsevier B.V. All rights reserved.