The Possibility of Layered Non-Van Der Waals Boron Group Oxides: A First-Principles Perspective

Two-dimensional (2D) metal oxides have broad prospective applications in the fields of catalysis, electronic devices, sensors, and detectors. However, non-van der Waals 2D metal oxides have rarely been studied because they are hard to peel off or synthesize. In this work, taking alumina (Al₂O₃) as a typical representative of 2D boron group oxides, the structural stability and electrical properties of 2D Al₂O₃ are investigated through first-principles calculations. The thinnest Al₂O₃ structure is a bilayer, and the band gap of Al₂O₃ is found to decrease with decreasing layer thickness because of the giant surface reconstruction. The band gap of bilayer X₂O₃ (X = Al, Ga, and In) decreases with increasing atomic radius. Our findings provide theoretical support for the preparation of non-van der Waals 2D boron group oxide semiconductors.