Temperature dependent Raman scattering in polycrystalline Bi4Ti3O12 thin films

Polycrystalline Bi₄Ti₃O₁₂ thin films were prepared on quartz substrates by pulsed laser deposition. The films were crystallized in the orthorhombic layer perovskite structure confirmed by X-ray diffraction and Raman spectroscopy. The Raman spectra are strongly dependent on temperature. A subtle phase transition in the temperature range 473-573 K exists in polycrystalline BTO thin films, which is evidenced by the disappearance of the Raman band at 116 cm⁻¹ and appearance of a new Raman band at 151 cm⁻¹. The two broad Raman bands centered at the 57 and 93 cm⁻¹ at 300 K break up into clusters of several sharp Raman peaks at 77 K, due to monoclinic distortion of orthorhombic structure at low temperature in the as-prepared Bi₄Ti₃O₁₂ thin films.