Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures

Raman spectrometry study of phonon anharmonicity of hafnia at elevated temperatures

Raman spectra of monoclinic hafnium oxide HfO2 were measured at temperatures up to 1100 K. Raman peak shifts and broadenings are reported. Phonon dynamics calculations were performed with the shell model to obtain the total and partial phonon density of states, and to identify the individual motions of Hf and O atoms in the Raman modes. Correlating these motions to the thermal peak shifts and b...

Phonon anharmonicity of rutile SnO2 studied by Raman spectrometry and first principles calculations of the kinematics of phonon-phonon interactions

Raman spectra of rutile tin dioxide (SnO2) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths an...

Phonon anharmonicity of rutile TiO2 studied by Raman spectrometry and molecular dynamics simulations

Raman spectra of rutile titanium dioxide (TiO2) were measured at temperatures from 100 to 1150 K. Each Raman mode showed unique changes with temperature. Beyond the volume-dependent quasiharmonicity, the explicit anharmonicity was large. A new method was developed to fit the thermal broadenings and shifts of Raman peaks with a full calculation of the kinematics of three-phonon and four-phonon p...

Surface-enhanced Raman scattering at elevated temperatures.

The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general dec...

Anharmonicity on Raman active phonon modes of LaAlO3