Raman spectra have been investigated in PbTiO 3 thin films grown on Si by metalorganic chemical vapor deposition. A large grazing-angle scattering technique was taken to measure the temperature dependence of Raman spectra below room temperature. All Raman modes in the thin films are assigned and compared with those in the bulk single crystal, a new A 1 (TO) soft mode at 104 cm~1 was recorded wh...