Anharmonicity induced faster decay of hot phonons in rutile TiO2nanorods: A Raman spectromicroscopy study

Abstract

Temperature-dependent Raman spectromicroscopy of rutile TiO2 nanorods has been studied here to understand the effect of thermal perturbations on different Raman-active phonon modes. The TiO2 nanorods, characterized using electron microscopy, X-ray diffraction and Raman spectroscopy, were prepared using a hydrothermal method. Raman spectra, recorded at temperatures higher than room temperature, have been analyzed within the theoretical framework developed by considering the anharmonicity of hot phonons. Different temperature-dependent responses were observed for Eg and A1g modes with the latter being immune with respect to the Raman peak position. The experimental results indicated a dominant role of phonon-phonon kinematics on peak shifts and broadenings in the Eg Raman mode, confirming the prevalence of the anharmonic effect. The temperature-dependent redshift in the peak position and broadening of the Raman Eg mode have been explained using three or four phonon decay processes. A consolidated insight, by showing a good agreement between experimental and theoretical frameworks, about the behavior of phonons under the influence of elevated temperatures has been presented. This journal is © The Royal Society of Chemistry.