Schottky-Barrier-Free Contacts with Two-Dimensional Semiconductors by Surface-Engineered MXenes
Schottky-Barrier-Free Contacts with Two-Dimensional Semiconductors by Surface-Engineered MXenes
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DOI：
10.1021/jacs.6b10834
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发表时间：
2016-12-14
影响因子：
15
通讯作者：
Goddard, William A., III
中科院分区：
文献类型：
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作者：
Liu, Yuanyue;Xiao, Hai;Goddard, William A., III
二维（2D）金属碳化物和氮化物，称为MXenes，在储能等应用中引起了极大的兴趣。我们展示了它们作为二维半导体的肖特基无障碍金属触点的潜力，为二维电子器件中的接触电阻问题提供了解决方案。在第一性原理计算的基础上，我们发现表面化学对MXenes的费米能级有很强的影响：相对于裸露表面的功函数，0终止总是增加，OH总是减少，而F则根据具体的材料表现出两种趋势。这种现象源于表面偶极子的效应，它与弱费米能级钉住一起，使肖特基无障空穴（或电子）通过与一些o端（或所有oh端）MXenes的范德华结注入到二维半导体中。此外，我们提出了基于计算的地层能量来控制地表终止的合成路线。这项研究增强了对二维材料表面化学与电子/输运性质之间关系的理解，并为改进二维电子学提供了预测。
Two-dimensional (2D) metal carbides and nitrides, called MXenes, have attracted great interest for applications such as energy storage. We demonstrate their potential as Schottky-barrier-free metal contacts to 2D semiconductors, providing a solution to the contact resistance problem in 2D electronics. On the basis of first principles calculations, we find that the surface chemistry strongly affects Fermi level of MXenes: 0 termination always increases the work function with respect to that of bare surface, OH always decreases it, whereas F exhibits either trend depending on the specific material. This phenomenon originates from the effect of surface dipoles, which together with the weak Fermi level pinning, enable Schottky-barrier-free hole (or electron) injection into 2D semiconductors through van der Waals junctions with some of the O-terminated (or all the OH-terminated) MXenes. Furthermore, we suggest synthetic routes to control surface terminations based on calculated formation energies. This study enhances understanding of the correlation between surface chemistry and electronic/transport properties of 2D materials, and also gives predictions for improving 2D electronics.