High-mobility semiconductive ultrathin films of bismuth oxyselenide (Bi₂O₂Se) have attracted great interest due to their potential applications in advanced electronic and photoelectronic devices. Enthusiasm aside, future success of such applications hinges upon the fundamental understanding of two dimensional (2D) Bi₂O₂Se, which is far from mature. In particular, unlike many other 2D materials with a van der Waals gap, 2D Bi₂O₂Se features a weak electrostatic stacking interaction, which gives rise to a significantly different mechanical response. The unique mechanical response of 2D Bi₂O₂Se has a strong influence on its band gap, a critical property toward its device applications. Here, using ab initio calculations, we investigate the mechanical and electronic responses of both bulk and monolayer Bi₂O₂Se under uniaxial and biaxial tension as well as those of monolayer Bi₂O₂Se under in-plane shearing. The distinct mechanical responses of bulk and monolayer Bi₂O₂Se under different mechanical deformation are explained by the associated study of the evolution of electron localization function and charge density analysis. We reveal that the band gap of both bulk and monolayer Bi₂O₂Se decreases as the applied tensile strain increases. The critical uniaxial and biaxial tensile strains, above which bulk and monolayer Bi₂O₂Se transform from being semiconductive to being metallic, are determined. These findings suggest fertile yet largely unexplored opportunities of strain engineering of 2D Bi₂O₂Se toward new device applications.

氧化硒铋 (Bi ₂ O ₂ Se) 的高迁移率半导体超薄膜因其在先进电子和光电子器件中的潜在应用而引起了极大的兴趣。抛开热情不谈，此类应用未来的成功取决于对二维 (2D) Bi ₂ O ₂ Se的基本理解，这还远未成熟。特别是，与许多其他具有范德华间隙的 2D 材料不同，2D Bi ₂ O ₂ Se 具有弱静电堆叠相互作用，这会产生显着不同的机械响应。2D Bi ₂ O ₂独特的机械响应Se 对其带隙有很大影响，这是其器件应用的关键特性。在这里，我们使用ab initio计算，研究了单层和双轴拉伸下本体和单层 Bi ₂ O ₂ Se的机械和电子响应，以及面内剪切下单层 Bi ₂ O ₂ Se的机械和电子响应。大块和单层 Bi ₂ O ₂ Se 在不同机械变形下的不同机械响应可以通过对电子定域函数演化和电荷密度分析的相关研究来解释。我们揭示了块状和单层 Bi ₂ O ₂的带隙Se随着施加的拉伸应变增加而减少。确定了临界单轴和双轴拉伸应变，高于该拉伸应变，块体和单层 Bi ₂ O ₂ Se 从半导体转变为金属。这些发现表明 2D Bi ₂ O ₂ Se应变工程向新设备应用提供了丰富但很大程度上尚未开发的机会。