Study of the Raman spectrum of CeO2 nanometer thin films

The Raman spectra of CeO2 (4.2–20 nm) nanometer thin films deposited by spray pyrolysis are measured at room temperature in various ratios of pulse time to interval time between pulses. The results show that there is a difference from that of single-crystal or polycrystalline CeO2; in the latter, there appear two new characteristic Raman peaks at shifts of 270 and 315 cm−1, whose intensities decrease swiftly with the increase of crystallite sizes. The new peaks can be explained as surface phonon modes of nanometer CeO2. The relationships between the intensities of peaks, crystallite sizes and the ratio of pulse time to interval time are discussed.