纳米晶锐钛矿相TiO2的非简谐效应和声子局域

对晶粒尺寸为194，86和56nm的纳米晶锐钛矿相TiO₂，进行了从83到723K的变温拉曼散射测量，并对E_g(1)模式进行了详细研究.根据非简谐效应和声子局域模型，对E_g(1)拉曼峰进行了拟合与计算.结果表明，以上三种纳米晶粒的晶格振动机理，在本质上是相同的.三声子过程对频率蓝移起主要作用.为了得到很好的拟合，需要同时考虑三声子和四声子过程.随着温度的升高，四声子过程增强，并对三声子过程起抵消作用.与非简谐衰减相关的声子寿命随着晶粒关键词：2')" href="#">纳米晶TiO₂拉曼散射非简谐耦合声子局域

Anharmonic phonon coupling and phonon confinement in nanocrystalline anatase TiO2

A temperature-dependent Raman scattering study of the E_g(1) mode was carried out at 83 to 723K for nanocrystalline anatase TiO₂ with different sizes of 194，86 and 56nm. By means of a combined model of anharmonic coupling and phonon confinement，the E_g(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 E_g(1) mode and an asymmetrical broadening at high frequencies. It has a relatively larger effect on the linewidth broadening than on the peak shift.