Effect of porosity on the ferroelectric properties of sol-gel prepared lead zirconate titanate thin films

Pb(Zr0.3Ti0.7)O-3 (PZT) thin films are of major interest in micro-electro-mechanical systems for their ability to provide electro-mechanical coupling and pyroelectric coupling. In this work, dense, crack-free PZT thin films have been obtained on silicon substrates up to a thickness of 3 mu m. Piezoelectric coefficients d(33,f) and e(31,f) of sol-gel processed films were investigated as a function of film thickness. Both d(33,f) (-50 similar to-90 pC/N) and e(31,f)(2.5 similar to 4 C/m(2)) values have been obtained in the whole thickness range of 1-3 mu m. Increasing the thickness of a single layer introduced pores into the films. Up to 700 nm porous, crack-free single layers could be obtained. It was found that the introduction of pores into the thin films decreased the dielectric constant. Therefore, it helps increase the pyroelectric performance. A dense PZT thin film (700 nm) has dielectric constant, F-d and F-v of 372, 1.02 x 10(-5) Pa-0.5 and 0.022 m(2)/C, respectively, while a porous thin film (700 nm) with porosity of 3% has dielectric constant, F-d and F-v of 210, 1.32 x 10(-5) Pa-0.5 and 0.031 m(2)/C, respectively. (c) 2005 Elsevier B.V. All rights reserved.