EXAFS study of PZT ferroelectric thin films of different crystallinities

Lead zirconate titanate (PbZrxTi1-xO3, PZT) thin films were deposited on Pt/TiOx/SiO2/Si substrate by RF-magnetron sputtering with a Pb1.2Zr0.3Ti0.7O3 target at room temperature. The Zr K-edge of PZT thin films of different crystallinities were studied by extended x-ray absorption fine structure (EXAFS) spectrum. Scans were made in fluorescence mode to monitor the structural differences between the amorphous thin films and the crystalline thin films. It was found that the local structure of the amorphous thin films was quite different from that of the crystalline thin films from the analyses of the EXAFS spectra. In the amorphous PZT thin films only one oxygen coordination shell can be found. By contrast, in the crystalline PZT thin films, the EXAFS spectrum was fitted with three shells and Zr-Pb bond was found. The oxygen coordination numbers of the amorphous and crystalline PZT thin films were same. The Zr-O bond distance of the amorphous samples were bigger than the crystalline samples. Thus, the influences of the phase transformation on the ferroelectric properties of PZT thin films were interpreted from the angle of the local chemical structures.