Predicting the Raman spectra of ferroelectric phases in two-dimensional Ga 2 O 3 monolayer.

We investigate the vibrational properties and Raman spectra of the two-dimensional Ga 2 O 3 monolayer, using density functional theory. Two ferroelectric (FE) phases of the Ga 2 O 3 monolayer with wurtzite (WZ) and zinc blende (ZB) structures (FE-WZ and FE-ZB, respectively) are considered. The Raman tensor and angle-dependent Raman intensities of two major Raman peaks (A11 and A21) in both FE-WZ (497, and 779 cm -1 ) and FE-ZB (481, and 772 cm -1 ) Ga 2 O 3 monolayers, are calculated for the polarization of scattered light, parallel and perpendicular to that of the incident light. The characteristics of angle-dependent Raman intensities are analyzed. The average non-resonant Raman spectra of the minor peaks in FE-WZ (E 1 ) and FE-BZ (E 1 and E 2 ) are compared with those of major peaks A11 and A21. These predictions of the Raman spectra of the Ga 2 O 3 monolayer may guide the rational design of two-dimensional optical devices.