Abstract
We present a Raman scattering study of optical phonons in hexagonal BN for temperatures ranging from80 to 600 K. The experiments were performed on high-quality, single-crystalline hexagonal BN platelets. Theobserved temperature dependence of the frequencies and linewidths of both Raman active E2g optical phonons isanalyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light ofdensity-functional theory calculations. With increasing temperature, the Ehigh mode displays strong anharmonic 2ginteractions, with a linewidth increase that indicates an important contribution of four-phonon processes and amarked frequency downshift that can be attributed to a substantial effect of the four-phonon scattering processes(quartic anharmonicity). In contrast, the Elow mode displays a very narrow linewidth and weak anharmonic 2ginteractions, with a frequency downshift that is primarily accounted for by the thermal expansion of the interlayer spacing.