RAMAN-SPECTROSCOPY AND X-RAY-DIFFRACTION OF PBTIO3 THIN-FILM

A PbTiO3 thin film prepared on silicon substrate by sol-gel technique has been studied by micro-Raman spectroscopy and x-ray diffraction (XRD). The spectra, in comparison to the single crystal work, show high background in the low frequency region and Raman lines are broader, thus revealing the polycrystalline nature of the film. The frequencies of the Raman bands in the film are clearly shifted to lower frequencies compared to the corresponding ones in the single crystal or powder forms. This phenomenon is similar to the hydrostatic pressure effect on the Raman lines of PbTiO3 single crystal. The film, therefore, has grains under stress. This stress is caused by nonequilibrium defects and diffusion at the interface. Measurements at different film positions showed variations in the frequency and width of the Raman bands which are associated with the stress and grain size inhomogeneities. The measured shift in the Raman frequencies suggests grain sizes less than or equal to 1 mu m. XRD indicates grain size of around 22 nm and an average stress around 1.3 GPa, which was determined using the measured shift for the c-lattice constant. (C) 1995 American Institute of Physics.