Raman studies are reported for the A1 TO , E1 TO , E2 , and A1 LO symmetry phonons of AlN from 20 to 375 K. By applying anharmonic decay theory to the observed temperature dependences of the phonon energies and linewidths, we determine the phonon decay mechanisms of these zone-center vibrations. Thermal expansion is taken into account using published temperature-dependent coefficients. The A1 T...

We report Raman studies of the A1 TO , E1 TO , E2 , A1 LO , and E1 LO symmetry phonons of GaN from 20 to 325 K. By applying anharmonic decay theory to the observed temperature dependences of the phonon energies and linewidths, we determine the phonon decay mechanisms of these zone-center vibrations. Thermal expansion is taken into account using published temperature-dependent coefficients. The ...

Atomic vibrations are partially screened by electrons. In a metal this screening can change rapidly for vibrations associated to certain points of the Brillouin zone, entirely determined by the shape of the Fermi surface. The consequent anomalous behaviour of the phonon dispersion is called Kohn anomaly. Graphite is a semimetal. Nanotubes can be metals or semiconductors. We demonstrate that two...

in this paper, a new model based on kinetic theory of gases and longitude oscillations of metallic nanocluster on single carbon nanotube (cnt) in addition to phononvibrations of cnt on substrate is presented to describe the growth mechanism of ultra-long cnt in chemical vapor deposition (cvd).interaction between cnt and catalyst is investigated by lennard-jones potential. simulations demonstrat...

Fluorescence and phosphorescence phonon sidebands of isotopic mixed hexamethylbenzene crystals at 2°K are presented. The external phonons can be observed separately from the semi-internal (methyl torsion) ones. The nature of the electronic or vibronic state has observable but not drastic effects on the exciton-phonon coupling function. Likewise, the exciton delocalization is of minor importance...

The phonon frequencies of metallic ultrathin films were studied by the resonant acoustic-phonon spectroscopy using femtosecond pump-probe method. We excite and detect the acoustic-phonon resonances in the thin films thinner than 50 nm using the femtosecond light pulses. The pump light causes the phonon vibrations through the thermal expansion at the film surface. For the ultrathin films, the st...

Weak phonon modes at 2032,5; 2040; 2046; and 2 0 5 3 c m 1 in K 3 Cu(CN) 4 have been assigned to originate from 13C = 14N and 12C = 15N vibrations. The assignments have been carried out using measurements at He-temperatures and in aqueous solutions. Furthermore calculations have been used concerning the frequency shifts and relative intensities with respect to the 12C = 14N vibrations. The coup...

Phonons, i.e., quanta of lattice vibrations, manifest themselves practically in all electrical, thermal and optical phenomena in semiconductors and other material systems. Reduction of the size of electronic devices below the acoustic phonon mean free path creates a new situation for phonon propagation and interaction. From one side, it complicates heat removal from the downscaled devices. From...

We study the recently observed orbital excitations, orbitons, and treat electron-electron correlations and lattice dynamics on an equal footing. It is shown that the orbiton energy and dispersion are determined by both correlations and lattice vibrations. The electron-phonon coupling causes satellite structures in the orbiton spectral function and the elementary excitations of the system are mi...

We study theoretically acoustic phonon modes in nanowire superlattices (NWSLs) composed of cubic materials. We classify the acoustic phonon modes in rectangular and square cross-section NWSLs, based on group theory. For NWSLs consisting of GaAs and AlAs, we calculate numerically the dispersion relations of each phonon mode and corresponding displacement fields. We examine the effects of both th...