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Unveiling the multilevel structure of midgap states in Sb-dopedMoX2(X=S,Se,Te)monolayers
Physical Review B ( IF 3.2 ) Pub Date : 2021-09-27 , DOI: 10.1103/physrevb.104.125438
Marcos G. Menezes 1 , Saif Ullah 2
Affiliation  

In this study, we use first-principles calculations to investigate the electronic and structural properties of MoX2 (X=S, Se, Te) monolayers doped with substitutional Sb atoms, with a central focus on the Sb(Mo) substitution. In MoS2, we observe that this substitution is energetically favored under S-rich conditions, where the S2 gaseous phase is likely to be present. This result is compatible with a recent experimental observation in Sb-doped MoS2 nanosheets grown by chemical vapor deposition. A similar behavior is found in MoSe2, but in MoTe2 the Sb(Mo) substitution is less likely to occur due to the possible absence of gaseous Te phases in experimental setups. In all cases, several impurity-induced states are found inside the band gap, with energies that span the entire gap. The Fermi energy is pinned a few tenths of eV above the top of the valence band, suggesting a predominant p-type behavior, and gap energies are slightly increased in comparison to the pristine systems. The orbital nature of these states is further investigated with projected and local density of states calculations, which reveal similarities to defect states induced by single Mo vacancies as well as their rehybridization with the 5s orbital from Sb. Additionally, we find that the band gap of the doped systems is increased in comparison with the pristine materials, in contrast with a previous calculation in Sb-doped MoS2 that predicts a gap reduction with a different assignment of valence band and impurity levels. We discuss the similarities, discrepancies, and the limitations of both calculations. We also speculate possible reasons for the experimentally observed redshifts of the A and B excitons in the presence of the Sb dopants in MoS2. We hope that these results spark future investigations on other aspects of the problem, particularly those concerning the effects of disorder and electron-hole interaction, and continue to reveal the potential of doped transition-metal dichalcogenides for applications in optoelectronic devices.

中文翻译:

揭示 Sb 掺杂的 MoX2(X=S,Se,Te) 单层中带隙态的多级结构

在这项研究中,我们使用第一性原理计算来研究电子和结构特性 X2 (X=, , )掺杂有替代 Sb 原子的单层,重点放在 Sb(Mo) 替代上。在硫化钼2,我们观察到这种替代在富含 S 的条件下受到大力支持,其中 2很可能存在气相。该结果与最近在 Sb 掺杂中的实验观察一致硫化钼2通过化学气相沉积生长的纳米片。类似的行为在2, 但在 莫特2由于实验装置中可能不存在气态 Te 相,因此 Sb(Mo) 取代不太可能发生。在所有情况下,在带隙内都发现了几种杂质诱导态,能量跨越整个带隙。费米能量被固定在价带顶部上方十分之几 eV 处,表明主要是型行为,与原始系统相比,间隙能量略有增加。通过投影和局部状态密度计算进一步研究了这些状态的轨道性质,这揭示了与由单个 Mo 空位引起的缺陷状态的相似性以及它们与5来自 Sb 的轨道。此外,我们发现与原始材料相比,掺杂系统的带隙增加了,这与之前在 Sb 掺杂中的计算相反硫化钼2这预测了具有不同价带和杂质水平分配的间隙减少。我们讨论了两种计算的相似性、差异和局限性。我们还推测了实验观察到的红移的可能原因一种 存在 Sb 掺杂剂时的激子 硫化钼2. 我们希望这些结果激发未来对该问题其他方面的研究,特别是那些有关无序和电子-空穴相互作用的研究,并继续揭示掺杂过渡金属二硫属化物在光电器件中的应用潜力。
更新日期:2021-09-28
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