Two-dimensional antimony oxide

Two-dimensional (2D) antimony, so-called antimonene, is one of the promising novel elemental 2D materials. However it can form antimony oxide, when exposed to air. This may even be beneficial for the stability of the material and at the same time result in interesting electronic properties. Here we present different types of 2D antimony single- and few-layer oxide structures, based on density functional theory (DFT) calculations. We show that, depending on stoichiometry and bonding type, these novel antimony oxide layers have different structural stability and electronic properties, ranging from topological insulators to semiconductors with direct and indirect band gaps between 0.8 eV and 4.9 eV. Furthermore, we discuss their vibrational properties and predict Raman spectra, which allow experimental identification of the different structures. Our theoretical results are in good agreement with recent experimental findings. We suggest that oxidized few-layer antimonene forms by itself a heterostructure consisting of semiconducting antimony oxide and semimetallic few-layer antimonene.