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We present a lattice-dynamics study of rocksalt cadmium oxide (CdO). We use Raman scattering to investigate a series of high-quality CdO epilayers grown on sapphire substrates by means of metal-organic vapor phase epitaxy. Two main features are found to dominate the Raman spectra of CdO: a sharp peak at ∼265 cm−1 and a broad feature at ∼390 cm−1. To assign these and other weaker second-order features that appear in the Raman spectra, we have carried out an ab initio calculation of the phonon dispersion in CdO. From the calculated two-phonon density of states (PDOS) we tentatively assign the peak at 265 cm−1 to a 2TA(L) mode. The broadband centered at ∼390 cm−1 seems to reflect the high two-PDOS in the 300–450 cm−1 spectral region.

The lattice dynamical properties of the corundum-like a-phase of Ga 2 O 3 are investigated by means of Raman scattering experiments and ab-initio calculations. A high-quality, single-crystal thick epilayer was grown on sapphire by the mist-chemical vapor deposition method. The phonon frequencies at the Brillouin zone center of all the Raman-active modes are determined by polarized Raman scattering measurements on an a-Ga 2 O 3 single crystal. By performing backscattering measurements from (0001) and ð10 10Þ faces, all Raman active modes are unambiguously identified. Density functional perturbation theory calculations were carried out to determine the symmetry and the frequency of the a-Ga 2 O 3 lattice modes. We find a good agreement between the theoretical predictions and the Raman spectra. The relative intensity of the different modes and their polarizability are discussed. The Raman spectrum is dominated by a narrow A 1g peak which indicates the high crystalline quality of the layers grown by the mist chemical vapor deposition method. V C 2015 AIP Publishing LLC. [http://dx