Articles you may be interested inAn investigation on the leakage current and time dependent dielectric breakdown of ferroelectric lead-zirconate-titanate thin film capacitors for memory device applications Pin-hole free ferroelectric ͑Pb,La͒͑Zr 1Ϫx Ti x ͒O 3 thin films with uniform composition have been fabricated using the metallo-organic precursor compounds, which were carefully home synthesized. The structural development, spectroscopic, and dielectric properties of these films have been systematically investigated using atomic force microscopy ͑AFM͒, x-ray diffraction, Fourier transform infrared spectroscopy, Raman scattering, and dielectric measurements. It has been found from our experimental results of PZT 40/60 thin films that the overlapping of (h00) and ͑00l͒ peaks of these films in x-ray diffraction patterns, mainly due to the small grain sizes in films, makes it very difficult to distinguish individual diffraction peaks and to identify the phases. However, Raman measurements undoubtedly reveal the Raman spectra of these films in the tetragonal phase field, demonstrating that Raman spectroscopy is an effective tool to identify structures, especially in the case of thin films having very small grains. AFM results show that the PZT perovskite structure in films may grow radially by rosettes and that microcracks appear in the three-dimensional AFM pictures at grain boundaries, which may be the cause for easy dielectric breakdown. A striking feature of the AFM observation is that three polycrystalline perovskite regions intersect symmetrically at a point with 120°to each other, and a rosette growth model for the perovskite structure in PZT films is thus proposed to explain this new phenomenon. The excellent ferroelectric properties of these films, such as the high fatigue resistance and low leakage current, are attributed to the high quality of the metallo-organic solutions and to reduce the amount of oxygen vacancies in the films by optimizing the annealing conditions and by doping a suitable amount of La ions to minimize the charge blocking of oxygen vacancy at the interface by Pt electrode. It seems that the rhombohedral PZT films with softer hysteresis loops are suitable for nonvolatile random access memory application.

The structural and microwave dielectric properties of Ba 5−x La x Ti x Nb 4−x O 15 (1 ≤ x ≤ 3) was investigated. The single phase with A 5 B 4 O 15 -type cation-deficient hexagonal perovskite structure was obtained over the whole composition range. These ceramics have high dielectric constant up to 56, high quality factors (Q×f ) up to 35,000, and low temperature coefficient of resonant frequencies (t f ) in the range +69 to −3 ppm°C −1 . The dielectric constants and t f of these ceramics gradually decrease parallel to an increase in B-site bond valence with increasing La and Ti content.