Raman tensor elements of $\beta\text{-Ga}_2\text{O}_3$

TL;DR

This study investigates the Raman spectrum and tensor elements of monoclinic $eta$-Ga$_2$O$_3$ through experiments and ab-initio calculations, revealing complex polarization dependencies due to low symmetry and birefringence.

Contribution

It provides the first comprehensive measurement and modeling of Raman tensor elements for $eta$-Ga$_2$O$_3$, accounting for birefringence effects.

Findings

Determined spectral positions of 15 Raman-active phonon modes.

Extracted Raman tensor elements for 13 modes.

Validated experimental results with ab-initio calculations.

Abstract

The Raman spectrum and particularly the Raman scattering intensities of monoclinic $\beta\text{-Ga}_2\text{O}_3$ are investigated by experiment and theory. The low symmetry of $\beta\text{-Ga}_2\text{O}_3$ results in a complex dependence of the Raman intensity for the individual phonon modes on the scattering geometry which is additionally affected by birefringence. We measured the Raman spectra in dependence on the polarization direction for backscattering on three crystallographic planes of $\beta\text{-Ga}_2\text{O}_3$ and modeled these dependencies using a modified Raman tensor formalism which takes birefringence into account. The spectral position of all 15 Raman-active phonon modes and the Raman tensor elements of 13 modes were determined and are compared to results from ab-initio calculations.