Structural, Thermal, and Electronic Properties of Two-Dimensional Gallium Oxide (β-Ga2O3) from First-Principles Design

Two-dimensional (2D) materials with exotic electronic, optical and mechanical properties have attracted tremendous attention in the last two decades, due to their potential applications in electronics, energy storage and conversion technologies. However, only a few dozen 2D materials have been successfully synthesized or exfoliated. Motivated by the recent discovery of 2D gallenene, we have explored new 2D allotropes of beta-Ga2O3, an emerging wide-band gap transparent conductive oxide (TCO) with a wide range of semiconducting applications. All the possible 2D allotropes of beta-Ga2O3 with high energetic stability have been predicted using particle swarm optimization, combined with density functional theory calculations. The structural and dynamical stability of the predicted 2D allotropes has been analyzed. Although beta-Ga2O3 is not a van der Waals material, results predict that one or two allotropes of beta-Ga2O3 are stable. In addition, the accurate band structures of these 2D semiconducting oxides have been calculated using both the GGA and LDA-1/2 approach. Remarkably, monolayer Ga2O3(100) has a larger indirect band gap of 4 eV, demonstrating a new avenue for the discovery of 2D beta-Ga2O3 based nano-devices with enhanced electronic properties.