We report on the microstructural analyses of chemically prepared Pb(Zr0.53Ti0.47)O3 (PZT 53/47) films. Although several techniques were used to analyze films, transmission electron microscopy (TEM) was emphasized. Phase evolution of these films, fabricated using hybrid metallo-organic decomposition (HMD), was determined by processing films at temperatures ranging from 500 °C to 650 °C. Our films, when observed with an optical microscope, appeared to consist of two distinct phases: (1) a featureless matrix and (2) 1–2 μm diameter “rosettes”. PZT films fired at 500 °C consisted of a pyrochlore containing phase (featureless matrix) and contained no perovskite, whereas films fired at 600 °C were ferroelectric and were approximately 90% perovskite (rosettes) by volume. Our TEM analysis showed that the pyrochlore-containing phase consisted of interpenetrating nanocrystalline pyrochlore and amorphous phases, both with dimensions on the order of 5 nm. For PZT films processed at 650 °C, the perovskite phase was observed in two forms: (1) large (≍2 μm) rosette structures containing 30 nm pores and (2) dense equiaxed particles on the order of 100 nm. We propose that phase evolution—with increasing temperature of HMD PZT 53/47 films—consists of the following steps: (1) phase separation, probably occurring in solution, (2) pyrochlore crystallization, (3) heterogeneous nucleation of perovskite PZT, and (4) homogeneous nucleation of perovskite PZT.

We have fabricated highly oriented, chemically prepared thin films of Pb(Zr,,aTio,m)03 (PZT 40/60) on both insulating and conducting substrates. While (100) MgO single crystals were used as the insulating substrates, the conducting substrates were fabricated by RF magnetron sputter deposition of 100-nm-thick (100) Pt films onto (100) MgO substrates. For comparison, we also fabricated PZT 40/60 films that had no significant preferential orientation on platinized MgO substrates. Sputter deposition of an underlying amorphous Pt film was used to fabricate randomly oriented PZT 40/60 films. Highly (001) oriented PZT 40/60 films had higher remanent polarization (61 pC/cm2 compared to 41 pC/cm2) and lower relative dielectric constant (368 compared to 466) than PZT 40160 films that were randomly oriented.

We have determined the effects that orientation and stress have on chemically prepared Pb(Zr,Ti)O, (PZT) film properties. Systematic modification of the underlying substrate technology has permitted us to fabricate suites of films that have various degrees of orientation at a constant stress level, and to also fabricate films that are in different states of stress, but have similar orientation. We have fabricated highly oriented films of the following compositions: PZT 60/40, PZT 40/60 and PZT 20/80. Remanent polarizations ( 4 0 pC/cmZ) greater than the best bulk polycrystalline ferroelectrics were obtained for PZT 40/60 films that were under compression and highly (001) oriented. While we show that systematically varying orientation influences ferroelectric properties, film stress also has a considerable effect.Perhaps the most important concept presented in this paper is that the sign of the film stress at the Curie point controls the type of ferroelectric behavior exhibited by PZT thin films. Further, our stress measurements as a function of thermal history indicate that the coefficient of thermal expansion of the paraelectric state is critical in determining the type of film ferroelectric behavior.

Through systematic variation of film processing temperature and time, we have characterized the pyrochlore to perovskite crystallization process of solution-derived PZT 20/80 thin films. The ≈3000 Å thick films were prepared by spin deposition using <100> single crystal MgO as the film substrate. By controlled rapid thermal processing, films at different stages in the perovskite crystallization process were prepared with the tetragonal PZT 20/80 phase being <100>/<001> oriented relative to the MgO surface. An activation energy for the conversion process of 326 kJ/mole was determined by use of an Arrhenius expression using rate constants found by application of the method of Avrami. The activation energy for formation of the PZT 20/80 perovskite phase of the solution-derived films compared favorably with that calculated from data by Kwok and Desu [1] for sputter-deposited 3500 Å thick PZT 55/45 films. The similarity in activation energies indicates that the energetics of the conversion process is not strongly dependent on the method used for film deposition.

Ferroelectric lead lanthanum titanate (PLT) thin films with composition varying from pure PbTiO(3) to PLT 25/100 (0 to 25 mol.% La) were prepared by spin-casting 0.25M solutions containing metallo-organic precursors of Pb, La, and Ti. The dielectric and ferroelectric properties of the thin (410-nm) films were characterized. The dielectric constants of the films varied from ~80 to ~690 for La contents varying from 0 to 25 mol%, respectively. Dissipation factors varied from ~0.03 to ~0.09 over the same compositional range. The temperature dependence of the dielectric properties was also studied to determine the effects of La content on the Curie point (T(c)). As expected, T(c ) was found to decrease with increasing La concentration. Coercive field and remanent polarization also decreased with increased La concentration.