Calculated phonon modes, infrared and Raman spectra in orthorhombic $\alpha$-MoO${}_3$ and monolayer MoO${}_3$

Abstract

Orhorhombic $\alpha$-MoO${}_3$ is a layered oxide with various applications and with excellent potential to be exfoliated as a 2D ultrathin film or monolayer. In this paper, we present a first-principles computational study of its vibrational properties. Our focus is on the zone center modes which can be measured by a combination of infared and Raman spectroscopy. The polarization dependent spectra are simulated. Calculations are also performed for a monolayer form in which "double layers" of Mo${}_2$O${}_6$ which are weakly van der Waals bonded in the $\alpha$-structure are isolated. Shift in phonon frequencies are analyzed.

arXiv comment13 pages, 13 figures, 14 tables

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• Ultrathin 2D-oxides: a perspective on fabrication, structure, defect, transport, electron and phonon properties