SYSTEMATIC STUDY ON STRUCTURAL AND DIELECTRIC-PROPERTIES OF LEAD ZIRCONATE TITANATE (PB,LA)(ZR(1-X)TI(X))O-3 THIN-FILMS DEPOSITED BY METALLOORGANIC DECOMPOSITION TECHNOLOGY/

Pin-hole free ferroelectric (Pb,La)(Zr1-xTix)O-3 thin films with unifo rm composition have been fabricated using the metallo-organic precurso r compounds, which were carefully home synthesized. The structural dev elopment, spectroscopic, and dielectric properties of these films have been systematically investigated using atomic force microscopy (AFM), x-ray diffraction, Fourier transform infrared spectroscopy, Raman sca ttering, and dielectric measurements. It has been found from our exper imental results of PZT 40/60 thin films that the overlapping of (h00) and (00l) peaks of these films in x-ray diffraction patterns, mainly d ue to the small grain sizes in films, makes it very difficult to disti nguish individual diffraction peaks and to identify the phases. Howeve r, Raman measurements undoubtedly reveal the Raman spectra of these fi lms in the tetragonal phase field, demonstrating that Raman spectrosco py 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 boun daries, which may be the cause for easy dielectric breakdown. A striki ng feature of the AFM observation is that three polycrystalline perovs kite regions intersect symmetrically at a point with 120 degrees to ea ch other, and a rosette growth model for the perovskite structure in P ZT films is thus proposed to explain this new phenomenon. The excellen t ferroelectric properties of these films, such as the high fatigue re sistance and low leakage current, are attributed to the high quality o f the metallo-organic solutions and to reduce the amount of oxygen vac ancies in the films by optimizing the annealing conditions and by dopi ng a suitable amount of La ions to minimize the charge blocking of oxy gen vacancy at the interface by Pt electrode. It seems that the rhombo hedral PZT films with softer hysteresis loops are suitable for nonvola tile random access memory application. (C) 1996 American Institute of Physics.