# Stability Prediction of 2H–MoO2 Monolayer as a Platform for Photonic Devices: from Thermodynamics to the Excitonic Effects through First-Principles Calculations

## TL;DR

This study explores the stability and optical properties of a 2H–MoO2 monolayer for potential use in photonic devices.

## Contribution

The paper provides a comprehensive first-principles analysis of the structural, electronic, and excitonic properties of 2H–MoO2 monolayer.

## Key findings

- 2H–MoO2 monolayer is dynamically, thermodynamically, and mechanically stable.
- It has a direct band gap of 2.50 eV with weak spin–orbit coupling.
- Excitonic effects are significant with a binding energy of 0.38 eV.

## Abstract

The conception, study,
and development of two-dimensional (2D)
materials have expanded the frontiers of next-generation optoelectronic
devices. Representative of this class, the MoO2 monolayer
in its 2H phase was investigated here with respect to its structural,
electronic, optical, and excitonic properties, through the PBE level
for structural and electronic properties, being the electronic band
gap correct at the HSE06 level, the optical and excitonic properties
were obtained by solving the Bethe-Salpeter equation. The structural
stability was also investigated at the dynamical (phonons), thermodynamic
(AIMD), and mechanical (elastic constants) levels, ensuring the stability
of this monolayer at all levels. This 2D transition-metal dioxide
exhibits semiconducting behavior with a HSE06 direct band gap of 2.50
eV, where spin–orbit coupling is weak. We also observe spin
degeneracy breaking in the valence bands close to the Fermi level
in the vicinity of the K and K′ valleys and along the connecting
path between them. Excitonic band-structure analysis revealed a binding
energy of 0.38 eV, which gives rise to significant excitonic effects
in the linear optical response. The response is isotropic across the
infrared and visible ranges, extending to the onset of the ultraviolet
spectrum.