Modified phonon confinement model for Raman spectroscopy of nanostructured materials

Abstract

This work describes further development of the confinement theory used for fitting of the Raman-spectroscopy signal obtained from nanostructured materials. We present a simple algebraic method for the incorporation of an anisotropic phonon-dispersion function into the phonon confinement model. The anisotropy is shown to have particular effects on low-dimensional systems, of sizes below $\ensuremath{\sim}15\text{ }\text{nm}$, even for systems with low anisotropy such as Ge. Experimental verification of the model is provided by fitting the Raman signal from Ge nanowires grown on quartz substrates. The interplay between the temperature change due to Raman laser heating and the size of the nanostructures is discussed.