Crystallization of sol-gel derived lead-zirconate-titanate thin films in argon and oxygen atmospheres

Abstract

Electron diffraction and high-resolution electron microscopic techniques are applied to reveal the mechanisms of crystallization of free standing 75-nm-thick thin films of ferroelectric lead-zirconate-titanate (PZT). Sol-gel methods, followed by pyrolysis at 350 °C, were used to provide a common starting point after which a variety of rapid-thermal annealing (RTA) experiments in the temperature range 400–700 °C were made in argon, oxygen, and nitrogen/hydrogen atmospheres. The results are interpreted in terms of a crystal chemical analysis, which points out that partial pressure of oxygen and heating rate are important experimental parameters which must be controlled if ferroelectric perovskite-type Pb2(Zr,Ti)2O6, rather than pyrochlore-type Pb2(Zr,Ti)2O6+X, where 0<X<1 or −1<X<0, is to be obtained after the RTA step. Thus significant improvements in the crystallization of perovskite-type PZT were clearly demonstrated by using argon atmospheres for the RTA step. The results may have significance for the production of high-quality ferroelectric thin films, with improved switching and fatigue characteristics, since even small amounts of the pyrochlore phase may prove detrimental for these properties.