Sulfur vacancy in MoS2 has been found to have an important influence on the performance of optoelectronic devices. Here, we study the effect of sulfur vacancy and O2 adsorption on the electronic and optical properties in the two-dimensional ferroelectric CuInP2S6. It is revealed that a defect state appears at the top of valence band with the presence of sulfur vacancy. However, when O2 is chemisorbed at sulfur vacancy, the defect state disappears. The variation of charge state and charge transfer are calculated and discussed. Although the ferroelectricity is greatly suppressed with the presence of sulfur vacancy, the ferroelectric state can be recovered when the O2 is adsorbed. Within the framework of GW+BSE method, the optical absorption edge of CuInP2S6 monolayer exhibits a red-shift for the presence of sulfur vacancy, and further O2 adsorption gives rise to a blue-shift of the spectrum. Our findings have shown an effective way to improve the functionality of two-dimensional ferroelectrics via defect engineering.

中文翻译：

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硫空位和O ₂吸附对铁电CuInP ₂ S ₆单层电子和光学性质的第一性原理研究

已发现 MoS2 中的硫空位对光电器件的性能有重要影响。在这里，我们研究了硫空位和 O2 吸附对二维铁电 CuInP2S6 中电子和光学性质的影响。结果表明，随着硫空位的存在，价带顶部出现缺陷态。然而，当 O2 在硫空位化学吸附时，缺陷状态消失。计算和讨论了电荷状态和电荷转移的变化。虽然硫空位的存在极大地抑制了铁电性，但当吸附 O2 时可以恢复铁电状态。在 GW+BSE 方法的框架内，CuInP2S6 单层的光吸收边因硫空位的存在而出现红移，进一步的 O2 吸附引起光谱蓝移。我们的研究结果显示了一种通过缺陷工程改善二维铁电体功能的有效方法。