Anharmonic phonon coupling and phonon confinement in nanocrystalline anatase TiO2

作者：Zhao Jian Hua^*; Chen Bo; Wang De Liang

来源：Acta Physica Sinica, 2008, 57(5): 3077-3084.

• nanocrystalline TiO2
• Raman scattering
• anharmonic coupling
• phonon confinement

A temperature-dependent Raman scattering study of the E-g(1) mode was carried out at 83 to 723 K for nanocrystalline anatase TiO2 with different sizes of 19.4, 8.6 and 5.6 nm. By means of a combined model of anharmonic coupling and phonon confinement, the E,(1) Raman spectra were fitted and calculated. The results show that, the temperature-dependent lattice vibration fundamentals are essentially the same for the three samples. The blue shift of Raman frequencies mainly comes from the contribution of three-phonon processes. In order to get good fittings, both the three- and four-phonon processes need to be considered. With increasing temperature, the four-phonon process becomes more important and counteracts the effect of the three-phonon process. The anharmonic-decay-related phonon lifetime increases as nanocrystalline size decreases, and the smaller nanoparticles have slower anharmonic decay. At low temperatures, the phonon confinement is responsible for a much shorter phonon lifetime for the 5.6-nm nanocrystals. The phonon confinement induces a blue shift of the Eg(,) mode and an asymmetrical broadening at high frequencies. It has a relatively larger effect on the linewidth broadening than on the peak shift.

• 出版日期2008-5
• 单位中国科学技术大学