InN thin film lattice dynamics by grazing incidence inelastic x-ray scattering.

Achieving comprehensive information on thin film lattice dynamics so far has eluded well established spectroscopic techniques. We demonstrate here the novel application of grazing incidence inelastic x-ray scattering combined with ab initio calculations to determine the complete elastic stiffness tensor, the acoustic and low-energy optic phonon dispersion relations of thin wurtzite indium nitride films. Indium nitride is an especially relevant example, due to the technological interest for optoelectronic and solar cell applications in combination with other group III nitrides.

Electronic excitations in B12As2 and their temperature dependence by vacuum ultraviolet ellipsometry.

The dielectric response function of epitaxial B(12)As(2) films on 4H-SiC was determined at room temperature and at 10 K in the spectral region of 3.6-9.8 eV, i.e., in the vacuum ultraviolet (VUV) spectral region, by synchrotron ellipsometry. The experimental dielectric function was simulated with the critical point parabolic band model. The parameters of the dispersive structures were derived by numerical fitting of the experimental data to the proposed model. New high energy optical transitions are resolved at 5.95, 7.8 and 8.82 eV and their lineshape and origin are discussed. The temperature dependence of the critical point energies and transition strengths was determined, and the excitonic effect is considered.