Abstract It is well known that the optoelectronic properties of two-dimensional (2D) materials may vary considerably by changing the layers number as well as the stacking order. In this work, the structural, electronic and optical properties of Cadmium oxide (CdO) monolayer and bilayers with different stacking orders are explored using first principles calculations. Simulations assert that the CdO single layer is a direct gap semiconductor with energy gap of 0.811 (1.883) eV as predicted by PBE(HSE06) functional. The bilayer formation leads to the considerable reduction of this parameter, however the direct nature is retained. Results show that the bilayers band gap depends strongly on the stacking order. The charge density maps are indicative of either chemical or physical interlayers interaction of the CdO bilayers. Our optical properties calculations show that the bilayers are more sensitive to the incident light than the monolayer, where the in-plane polarized light can excite more effectively the electronic transitions from the valence band to the conduction band. Additionally, the prospective optoelectronic applicability of the CdO 2D materials studied here is also demonstrated through the capability of absorbing a wide range of electromagnetic radiation with large absorption coefficient. Results reported here are useful covering the lack of knowledge on the optoelectronic properties of the CdO nanomaterials, and may be good guidance for the design of practical applications.

中文翻译：

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CdO 单层和双层的结构、电子和光学特性：堆叠效应研究

摘要 众所周知，二维 (2D) 材料的光电特性可能会随着层数和堆叠顺序的改变而发生很大变化。在这项工作中，使用第一性原理计算探索了具有不同堆叠顺序的氧化镉 (CdO) 单层和双层的结构、电子和光学特性。模拟断言 CdO 单层是直接带隙半导体，其能隙为 0.811 (1.883) eV，如 PBE(HSE06) 函数预测的那样。双层的形成导致该参数显着降低，但保留了直接性质。结果表明双层带隙强烈依赖于堆叠顺序。电荷密度图表示 CdO 双层的化学或物理层间相互作用。我们的光学性质计算表明，双层比单层对入射光更敏感，其中面内偏振光可以更有效地激发从价带到导带的电子跃迁。此外，这里研究的 CdO 2D 材料的前瞻性光电适用性也通过吸收大范围吸收系数的大范围电磁辐射的能力得到证明。此处报告的结果有助于弥补对 CdO 纳米材料的光电特性缺乏了解，并且可能对实际应用的设计有很好的指导。其中面内偏振光可以更有效地激发从价带到导带的电子跃迁。此外，这里研究的 CdO 2D 材料的前瞻性光电适用性也通过吸收大范围吸收系数的大范围电磁辐射的能力得到证明。此处报告的结果有助于弥补对 CdO 纳米材料的光电特性缺乏了解，并且可能对实际应用的设计有很好的指导。其中面内偏振光可以更有效地激发从价带到导带的电子跃迁。此外，这里研究的 CdO 2D 材料的前瞻性光电适用性也通过吸收大范围吸收系数的大范围电磁辐射的能力得到证明。此处报告的结果有助于弥补对 CdO 纳米材料的光电特性缺乏了解，并且可能对实际应用的设计有很好的指导。