Phonon anharmonicity in α-In2O3: A Raman scattering study of the A1 modes

We present a temperature dependent Raman scattering study of the A 1 g modes of α -In 2 O 3 . The temperature behavior of the frequency and linewidth of the high and low frequency A 1 g Raman peaks is analyzed using a perturbation theory model of anharmonic decay including 3- and 4-phonon processes. Possible decay channels are identified in the light of density functional perturbation theory calculations of the phonon dispersion. A very different anharmonic behavior of the two A 1 g modes is observed. The low-frequency mode shows an unusually small linewidth because of the dominance of upconversion channels due to the lack of lower-energy optical modes for anharmonic decay. In contrast, 3-phonon decay into lower energy optical modes dominates the high frequency mode, which shows a linear increase in linewidth with temperature. The anharmonic decay model fitted to the Raman data gives an excellent agreement with the experiment and allows the relative strength of 3- and 4-phonon channels to be assessed. • The low- and high-frequency A 1 g phonons of α -In 2 O 3 display very different anharmonic behavior. • The low-frequency A 1 g phonon of α -In 2 O 3 exhibits an unusually long lifetime. • The high-frequency A 1 g phonon decays via 3-phonon processes while the low-frequency A 1 g phonon anharmonicity is well accounted for by 3- and 4-phonon upconversion processes.