Influence of Buffer Layer Insertion and Annealing Mode upon Microstructures and Ferroelectric Characteristics of Sol-Gel-Derived Pb(Zrx, Ti1-x)O3 Thin Films

As a continuation of our previous work, PZT films with the Zr/Ti ratio varied from 40/60 to 70/30 were prepared by a sol-gel method, and the effects of PZT(120/52/48) buffer layer insertion and the annealing mode were investigated. The results indicate that, irrespective of the annealing mode, unbuffered PZT films with a Zr/Ti ratio of 40/60 to 60/40 exhibit (111)-preferred orientation, whereas buffer layer insertion induces growth with (100) orientation. This is in contrast to the case of PZT(70/30) film in which growth with (100) orientation is discernible even when the buffer layer is not inserted. AFM observations reveal that the PZT films with the buffer layer display slightly smoother surface microstructures than the unbuffered films. This is more clearly displayed in the case the film is subjected to RTA. Although the essential features of P-E hysteresis loops of the films are not significantly affected by the annealing mode, conventional furnace annealing generally leads to slightly larger remanent polarization (Pr) than RTA. Pr vs Zr/Ti ratio curves for PZT films with and without the buffer layer invariably give a peak at Zr/Ti=60/40. Fatigue life does not markedly improve even with an appropriate choice of the process factors in the film synthesis, which influence the microstructures and ferroelectric properties.