Orientation effects on polarization and pyroelectric properties of ferroelectric thin films on Si

Oriented ferroelectric thin films (less than or equal to 1 pm) of PZT (90/10), Bi4Ti3O12, and La-modified Bi4Ti3O12, on Pt(111)/Ti/SiO2/Si(100) substrates were fabricated using (MOD) technique. Film orientation was controlled through heat treatment, composition and layer structure, and correlated to structural changes using XRD, SEM and RAMAN techniques. Measured properties included P-E hysteresis loop, static pyroelectric and fatigue behavior. Temperature stable (25-90 degreesC) polarization with 2P(r) values of 6-24 muC/cm(2) and low switching fields E-c = 10-40 kV/cm were determined. For L-BIT films, low E-c values are attributed to easier domain wall mobility with La ions on the different Bi sites, resulting in improved fatigue behavior, comparable to SBT films, at much lower switching fields (Scott, J. F., High-dielectric constant thin films for dynamic random access memories (DRAM). Ann. Rev. Mater. Sci., 1998, 28, 79-100; Joshi, P. C. and Krupanidhi, S. B., Switching, fatigue, and retention in ferroelectric Bi4Ti3O12 thin films. Appl. Phys. Lett., 1993, 62, 1928-1930; Dimos, D., Al-Schareef, N. H., Warren, W. L. and Tuttle, B. A., Photoinduced changes in the fatigue behavior of SrBi2Ta2O9 and Pb(Zr,Ti)O-3 thin films. J. Appl. Phys., 1996, 80, 1682-1687). High pyroelectric coefficients similar to 10-60 nC/cm(2) K were also determined for the different films, up to similar to 100 degreesC. (C) 2001 Elsevier Science Ltd. All rights reserved.