Zinc oxide is a wurtzite semiconductor with a band gap of 3.4 eV that has stimulated renewed interest in its properties for optoelectronic applications in the ultraviolet energy range. To this aim, knowledge of the thermal properties and heat transport of ZnO is essential. The latter are mostly dominated by the lattice dynamics, which can be investigated by measurements and theoretical calculations of the phonon dispersion relations along high symmetry directions in the Brillouin zone. Unfortunately, until now little information is available in this respect, obtained mainly from Raman and infrared spectroscopy. The phonon dispersion of ZnO has 12 branches from which only some quasi-acoustic phonons have been reported in the literature [1].

We present here the phonon dispersion relations of ZnO obtained by inelastic neutron scattering measurements. The results are compared with ab-initio lattice dynamical calculations that have shown an excellent agreement with empirical data obtained under pressure and temperature. They also account for the observed dependence on isotopic mass [2]. The calculations reproduce very well the experimental dispersion along all investigated symmetry directions. The main deviations occur for the lower E₂ modes, which require an increased accuracy in the calculated interatomic forces, and for the longitudinal optic modes.

[1] A. W. Hewat, Solid State Commun. 8, 187 (1970); K. Thoma et al., Solid State Commun. 15, 1111 (1974).

[2] J. Serrano et al., Phys. Rev. Lett. 90, 055510 (2003); Phys. Status Solidi B 235, 260 (2003); Phys. Rev. B 69, 094306 (2004).

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