Raman, FT-IR and dielectric studies of PZT 40/60 films deposited by MOD technology

Abstract

Ferroelectric Pb(Zr_0.4Ti_0.6) O₃ (PZT 40/60) thin films with uniform composition have been fabricated using the metallo-organic precursor compounds lead di-ethylhexanoate Pb(C₇H₁₅COO)₂, titanium di-methoxy-di-neodecanoate Ti(OCH₃)₂(C₉H₁₉COO)₂ and zirconium octoate Zr(C₇H₁₅COO)₄. These metallo-organic precursors were stored for more than four years and are very stable in ambient conditions, compared to sol-gel solutions. The structural development of these films under different annealing temperatures was systematically studied using X-ray diffraction, FT-IR spectroscopy and Raman scattering. The results show that the overlapping of (h 0 0) and (0 0 I) peaks of the PZT 40/60 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. In FT-IR measurements, the intensity of Zr/TiO₆ metal-oxygen octahedral vibrational modes becomes stronger with increasing annealing temperatures, while the FT-IR spectral peaks of vibrations of the residual carbon ligands (COO⁻) finally disappear at high temperatures, showing that FT-IR spectroscopy is a good way to monitor the growth of the perovskite phase in PZT 40/60 films. Raman measurements undoubtedly reveal the Raman spectra of these PZT 40/60 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 small grains. The values of high dielectric constant and the total remanent polarization obtained by ferroelectric pulse measurements show that the PZT film is a suitable material for non-volatile random access memory and dynamic random access memory applications.