No abstract

A wafer bending method has been devised to impose biaxial strains on Pb(Zr0.35Ti0.65)O3 (PZT) thin films ranging in thickness from 700 to 4000 Å grown by metal-organic chemical vapor deposition. The ferroelectric and dielectric properties of PZT capacitors were investigated while the film was placed under biaxial tension. It was observed that biaxial strains as small as 0.08% can reversibly reduce the remanent polarization of PZT films by 12 to 14% for all film thicknesses. The small-signal capacitance measured at voltages significantly larger than the switching voltage increased with increasing biaxial tension. These observations present clear evidence of room temperature strain accommodation in PZT thin films by reversible 90° domain wall motion that changes the volume fraction of the film that switches during electrical testing.

No abstract

The structural and electrical properties of metalorganic chemical vapor deposition-grown Pb(Zr0.35Ti0.65)O3 thin films ranging in thickness from 700 to 4000 Å have been investigated. Cross-sectional scanning electron microscopy showed that these films are columnar, with grains extending through the thickness of the film. High-resolution x-ray diffraction showed that while the thickest films are tetragonal, with reflections corresponding to a-type and c-type domains, films thinner than 1500 Å are not. Electron backscatter diffraction and hysteresis loop measurements showed that the thinnest films are ferroelectric and have a rhombohedral crystal structure.

Long-range oxygen motion has been observed in Pt/Pb(Zr,Ti)O3/Ir thin-film structures after electrical fatigue cycling at room temperature. Through an exchange anneal, isotopic O18 was incorporated as a tracer into bare Pb(Zr,Ti)O3 (PZT) films, allowing secondary ion mass spectrometry measurements of the tracer profile evolution as a function of the number of polarization reversals. Observation of O18 tracer redistribution during voltage cycling, which is presumably mediated by oxygen vacancy motion, was found to be strongly dependent upon the thermal history of the film. However, there was no strong correlation between the extent of O18 tracer redistribution and the extent of polarization suppression induced by voltage cycling. Our results suggest that oxygen vacancy motion plays, at most, a secondary role in ferroelectric fatigue of PZT thin films.