Enhancement of ferroelectric and piezoelectric properties in PZT thin films with heterolayered structure

This paper reports the latest experimental results of multilayered, heterolayered, and alternating heterolayered PZT thin films obtained by spin coating on Pt/Ti/SiO2/Si wafers using Zr-rich (P60) and Ti-rich (P40) solutions which were prepared by sol-gel route process. The ferroelectric and piezoelectric properties of the heterolayered and alternating heterolayered P60/P40 thin films were significantly improved when compared to those of multilayered thin films using just P60 or P40 for the same film thickness. The improved properties resulted from the field-induced coupling effect between the rhombohedral (Zr-rich) and tetragonal (Ti-rich) layers which induces domain switching. Namely, the values of the remnant polarization, dielectric constant and piezoelectric coefficient were 18.6 mu C cm(-2), 1040 and 70 pm V-1 respectively, for alternating heterolayered P60/P40 thin films, while the properties for the purely multilayered P60 and P40 thin films were 14.6 mu C cm(-2), 860 and 52 pm V-1, and 17.1 mu C cm(-2), 800 and 50 pm V-1, respectively. The enhancement of the ferroelectric and piezoelectric properties of PZT thin films with increasing film thickness in this case could be explained by the existence of an interfacial layer and substrate clamping. (C) 2013 Elsevier B.V. All rights reserved.