PHONON EXCITATIONS AND RELATED THERMAL-PROPERTIES OF ALUMINUM NITRIDE

The phonon density of states of aluminum nitride was determined by tim e-of-flight neutron spectroscopy using a polycrystalline sample. The o bserved phonon excitation spectrum consists of a broadband centered at about 35 meV, a small gap in the 75-80 meV region, and two sharp band s at approximately 85 and 92 meV. A rigid-ion model was applied to the interpretation of the data. After optimization, the model provided a satisfactory description of the neutron results as well as the Raman a nd IR data, sound-velocity measurements, and the lattice specific heat reported in the literature. The partial and total DOS and the phonon- dispersion curves along major symmetry directions of the Brillouin zon e were calculated, and the contribution of phonons to the Debye behavi or of the low-temperature thermal conductivity was discussed. [S0163-1 829(98)00618-3].