Gao Kai, Chen Yan-Jin, Ou Yang, Zeng Jin-Ming, Hou Chunju, Yang Yi
College of Rare Earths and Faculty of Materials, Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou, 341000, China.
School of Science, Jiangxi University of Science and Technology, Ganzhou, 341000, China.
Phys Chem Chem Phys. 2024 Dec 18;27(1):112-118. doi: 10.1039/d4cp03683b.
Bismuth oxychalcogenides (BiOX, X = S, Se, Te), a family of non-van der Waals (non-vdW) two-dimensional (2D) semiconductors, are attracting significant attention due to their outstanding semiconducting properties and huge potential in various applications of electronic and optoelectronic devices. Surface imperfections (, surface vacancies) and surface reconstructions are more likely to appear and may cause intriguing physical properties and novel phenomena in the non-vdW 2D materials than the vdW cases. Here, we explore the impacts of surface vacancies and surface reconstructions on the properties of the surfaces and 2D structures of BiOX by using the first-principles method. We find that the dimerization of surface X-vacancies occurs in BiOS and BiOTe (001) surfaces, like that happening in BiOSe. Unexpectedly, the electronic structures of BiOX (001) surfaces show strong tolerance to the order of surface X-vacancies. Furthermore, we find a phenomenon of thickness-dependent surface reconstructions for non-vdW BiOX ultrathin films. For a monolayer, the zipper-surface is more stable, while the dimer-surface is generally more stable for thicker films. Calculated exfoliation energies of the BiOX monolayer and multi-layers are close to those of common vdW 2D materials, indicating that 2D BiOX belong to easily fabricated 2D materials, even though the inter-layer binding interaction is of the non-vdW type. Our results suggest that non-vdW 2D materials can possess intriguing properties because of surface imperfections and reconstructions in comparison with vdW 2D materials.
氧族铋化物（BiOX，X = S、Se、Te）是一类非范德华（non-vdW）二维（2D）半导体，由于其出色的半导体性能以及在电子和光电器件的各种应用中具有巨大潜力而备受关注。与范德华情况相比，表面缺陷（如表面空位）和表面重构在非范德华二维材料中更易出现，并且可能导致引人入胜的物理性质和新现象。在此，我们使用第一性原理方法探究表面空位和表面重构对BiOX表面和二维结构性质的影响。我们发现，BiOS和BiOTe（001）表面会发生表面X空位的二聚化，这与BiOSe中发生的情况类似。出乎意料的是，BiOX（001）表面的电子结构对表面X空位的排列表现出很强的耐受性。此外，我们发现了非范德华BiOX超薄膜的厚度依赖性表面重构现象。对于单层膜，拉链状表面更稳定，而对于较厚的膜，二聚体表面通常更稳定。计算得到的BiOX单层和多层膜的剥离能与常见范德华二维材料的剥离能相近，这表明二维BiOX属于易于制备的二维材料，尽管层间结合相互作用是非范德华类型的。我们的结果表明，与范德华二维材料相比，非范德华二维材料由于表面缺陷和重构可能具有引人入胜的性质。
