Systematic study of structural, electronic, and optical properties of atomic-scale defects in the two-dimensional transition metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te)
Systematic study of structural, electronic, and optical properties of atomic-scale defects in the two-dimensional transition metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te)
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DOI：
10.1103/physrevb.92.235408
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发表时间：
2015-12-07
影响因子：
3.7
通讯作者：
Sanyal, Biplab
中科院分区：
文献类型：
--
作者：
Haldar, Soumyajyoti;Vovusha, Hakkim;Sanyal, Biplab
二维过渡金属二硫属化物MX2（M = Mo和W; X = S、Se和Te）中的缺陷。各种类型的缺陷，例如，X空位、X间隙空位、M空位、M间隙空位以及MX和XX双空位。已经发现，X间隙具有最低的形成能（类似于1 eV）的所有系统在富X的条件下，而对于富M的条件下，X空位具有最低的形成能除了MTe 2系统。这两种缺陷在文献报道的生长温度（1000-1200 K）下具有非常高的平衡缺陷浓度。一对缺陷，例如，两个X空位或一个M和一个X空位倾向于占据最近的可能距离。对于所考虑的任何一种缺陷，都没有发现磁性的痕迹。除了X间隙，所有其他缺陷都有缺陷态出现在带隙中，这会极大地影响原始系统的电子和光学性质。我们计算的光学性质表明，缺陷态引起的光学跃迁在类似于1.0 eV，这可能是有益的发光器件。我们的系统研究的结果，预计将指导实验纳米工程的缺陷，以实现适当的性能相关的带隙修改和缺陷指纹的表征，通过光学吸收测量。
defects in 2D transition metal dichalcogenides MX2 (M = Mo and W; X = S, Se, and Te) by density functional theory. Various types of defects, e.g., X vacancy, X interstitial, M vacancy, M interstitial, and MX and XX double vacancies, have been considered. It has been found that the X interstitial has the lowest formation energy (similar to 1 eV) for all the systems in the X-rich condition, whereas for the M-rich condition, X vacancy has the lowest formation energy except for MTe2 systems. Both these defects have very high equilibrium defect concentrations at growth temperatures (1000-1200 K) reported in literature. A pair of defects, e.g., two X vacancies or one M and one X vacancies, tend to occupy the nearest possible distance. No trace of magnetism has been found for any one of the defects considered. Apart from X interstitial, all other defects have defect states appearing in the band gap, which can greatly affect the electronic and optical properties of the pristine systems. Our calculated optical properties show that the defect states cause optical transitions at similar to 1.0 eV, which can be beneficial for light emitting devices. The results of our systematic study are expected to guide the experimental nanoengineering of defects to achieve suitable properties related to band gap modifications and characterization of defect fingerprints via optical absorption measurements.