Compositional gradient in and mechanical stability of RF-sputtered and RTA annealed Pb(Zr,Ti)O3 thin films

A previous study made in our laboratory has shown that high sputtering pressure (8 Pa) improved the mechanical stability of RF-sputtered and RTA annealed Pb(Zr,Ti)O-3 (PZT) thin films on Si/SiO2/Ti/Pt substrate. In this work, secondary ion mass spectrometry (SIMS) points out that a Pb-gradient occurs preferentially in the PZT thin films sputtered at low pressure (2 Pa). This experiment allows to exhibit a strong correlation between the mechanical stability of the PZT thin films and the Pb-gradient appearing over their thickness during the sputtering. Furthermore, a pre-annealing of the substrate (400 degrees C during 30 s in Argon at 100 degrees C/s) is found to improve at the same time the mechanical stability and the (111)-orientation of the PZT thin films. The polarizability is also enhanced by multi-sputtering, i.e., by sputtering five identical PZT layers onto the same substrate. However; the ferroelectric properties seem to be very sensitive with the thickness and the Pb-gradient of the PZT thin films. (C) 1999 Elsevier Science S.A. All rights reserved.