OH-terminated two-dimensional transition metal carbides and nitrides as ultralow work function materials
OH-terminated two-dimensional transition metal carbides and nitrides as ultralow work function materials
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DOI：
10.1103/physrevb.92.075411
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发表时间：
2015-08-10
影响因子：
3.7
通讯作者：
Yunoki, Seiji
中科院分区：
文献类型：
--
作者：
Khazaei, Mohammad;Arai, Masao;Yunoki, Seiji
MXene是一组二维过渡金属碳化物和氮化物，在能量存储和电子器件中提供许多潜在的应用。作为设计新电子器件的重要参数，我们使用第一性原理计算研究了裸MXene及其具有F，OH和O化学基团的功能化MXene的功函数。根据我们的计算，OH封端的MXene获得了1.6至2.8 eV的超低功函数。此外，取决于过渡金属的类型，F或O官能化影响功函数的增加或减少。我们发现，功能化后的功函数的变化与表面偶极矩的变化呈线性相关。结果表明，F-或O-封端的MXene的功函数由两个因素控制：由F/O和衬底之间的电荷转移引起的诱导偶极矩，以及由表面弛豫引起的总表面偶极矩的变化。然而，在OH封端的MXene的情况下，除了这两个因素之外，OH基团的固有偶极矩在确定总偶极矩中起重要作用，因此证明其超低功函数是合理的。
MXenes are a set of two-dimensional transition metal carbides and nitrides that offer many potential applications in energy storage and electronic devices. As an important parameter to design new electronic devices, we investigate the work functions of bare MXenes and their functionalized ones with F, OH, and O chemical groups using first-principles calculations. From our calculations, it turns out that the OH-terminated MXenes attain ultralow work functions between 1.6 and 2.8 eV. Moreover, depending on the type of the transition metal, the F or O functionalization affects increasing or decreasing the work functions. We show that the changes in the work functions upon functionalizations are linearly correlated with the changes in the surface dipole moments. It is shown that the work functions of the F- or O-terminated MXenes are controlled by two factors: the induced dipole moments by the charge transfers between F/O and the substrate, and the changes in the total surface dipole moments caused by surface relaxation upon the functionalization. However, in the cases of the OH-terminated MXenes, in addition to these two factors, the intrinsic dipole moments of the OH groups play an important role in determining the total dipole moments and consequently justify their ultralow work functions.