The realization of ternary, single-layer transition metal dichalcogenides has suggested a promising strategy to develop two-dimensional (2D) materials with alternative features. In this study, we design and investigate Janus aluminum monochalcogenide monolayers, ${\mathrm{Al}}_{2}X{X}^{\prime }$ $(X/X^{\prime }=\mathrm{O},\mathrm{S},\mathrm{Se},\mathrm{Te})$ by using first-principles methods. Starting from binary constituents, the ternary structures are optimized without any constraint and ground-state configurations are obtained. The stability of these systems is tested by performing phonon spectra analysis and ab initio molecular dynamics simulations and all ${\mathrm{Al}}_{2}X{X}^{\prime }$ monolayers other than AlTeO are confirmed to be dynamically stable. Mechanical properties are examined by calculating Young's modulus and Poisson's ratio and subsequently compared with binary counterparts. Monolayers of ${\mathrm{Al}}_{2}X{X}^{\prime }$ have a brittle character but oxygenation makes them less stiff. The electronic structure is also analyzed and variation of the band gap with the type of chalcogen atoms is revealed. It is found that different from their binary counterparts, ${\mathrm{Al}}_{2}X\mathrm{O}$ monolayers are direct band-gap semiconductors. Additionally, modification of the electronic structure in the presence of biaxial compressive or tensile strain is investigated by taking into account possible indirect-direct band-gap transitions. Our results not only predict stable 2D ternary ${\mathrm{Al}}_{2}X{X}^{\prime }$ structures but also point out them as promising materials for optoelectronic applications.

中文翻译：

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二维铝单硫族化物的结构和电子性质的调谐：JanusAl2XX'（X / X'：O，S，Se，Te）单层的预测

三元单层过渡金属二硫代二恶英的实现提出了开发具有替代特征的二维（2D）材料的有前途的策略。在这项研究中，我们设计和研究了Janus单硫属铝化物单层，${铝}_{2}X{X}^{\prime }$ $（X/X^{\prime }=\mathrm{Ø}，\mathrm{小号}，\mathrm{硒}，\mathrm{特}）$通过使用第一原理方法。从二元成分开始，对三元结构进行了优化，而没有任何约束，并且获得了基态配置。这些系统的稳定性通过进行声子光谱分析和从头算分子动力学模拟以及所有${铝}_{2}X{X}^{\prime }$AlTeO以外的其他单层被证实是动态稳定的。通过计算杨氏模量和泊松比来检查机械性能，然后与二元对应物进行比较。单层${铝}_{2}X{X}^{\prime }$具有脆性，但充氧会使它们变硬。还分析了电子结构，并揭示了带隙随硫族元素原子类型的变化。发现与二进制二进制文件不同，${铝}_{2}X\mathrm{Ø}$单层是直接带隙半导体。另外，通过考虑可能的间接-直接带隙跃迁来研究在双轴压缩或拉伸应变存在下电子结构的改变。我们的结果不仅预测稳定的二维三元${铝}_{2}X{X}^{\prime }$ 结构，但也指出它们是光电子应用的有前途的材料。