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 (XR D). The spectra, in comparison to the single crystal work, show high b ackground in the low frequency region and Raman lines are broader, thu s 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 for ms. This phenomenon is similar to the hydrostatic pressure effect on t he Raman lines of PbTiO3 single crystal. The film, therefore, has grai ns under stress. This stress is caused by nonequilibrium defects and d iffusion at the interface. Measurements at different film positions sh owed variations in the frequency and width of the Raman bands which ar e associated with the stress and grain size inhomogeneities. The measu red shift in the Raman frequencies suggests grain sizes less than or e qual to 1 mu m. XRD indicates grain size of around 22 nm and an averag e stress around 1.3 GPa, which was determined using the measured shift for the c-lattice constant. (C) 1995 American Institute of Physics.