A new insight for ohmic contacts to MoS2: by tuning MoS2 affinity energies but not metal work-functions,Physical Chemistry Chemical Physics

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A new insight for ohmic contacts to MoS2: by tuning MoS2 affinity energies but not metal work-functions
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2017-09-05 00:00:00 , DOI: 10.1039/c7cp05109c
Qian Wang _{1,

2,

3,

4,

5} , Bei Deng _{3,

4,

5,

6} , Xingqiang Shi _{3,

4,

5,

6}

Affiliation

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have recently attracted tremendous interest for fundamental studies and applications. High contact resistances between the metal electrodes and the 2D TMDCs, usually composed of a tunneling barrier (TB) and a Schottky barrier (SB), are the key bottleneck to the realization of high performance devices based on such systems. Here, from van der Waals density functional theory calculations, we demonstrate that strain can provide a feasible means to reduce the contact resistances between, for example, 2D semiconductor MoS₂ and metal surfaces, in both strong and weak coupling regimes. Both the SB and TB are lowered significantly with the increasing tensile strain in both the coupling regimes. Especially, the SB can reduce to zero in all configurations considered, with tensile strain increasing to ∼4% or above. The mechanism of SB reduction under tensile strain is attributed to the increase of the MoS₂ affinity energy since the monolayer MoS₂ conduction band minimum (CBm) is derived from anti-bonding states. Thus, the SB in other semiconducting TMDCs with an anti-bonding CBm (for n-type contact) could also be reduced to zero by tensile strain. Our discoveries thus shed a new and general light on minimizing the contact resistance of semiconducting TMDCs–metal based contacts and this can also prove applicable to other 2D semiconductors, e.g. phosphorene.

中文翻译：

MoS ₂欧姆接触的新见解：通过调整MoS ₂亲和能而不是金属功函数

二维（2D）过渡金属二硫化碳（TMDC）最近引起了基础研究和应用的极大兴趣。金属电极与通常由隧道势垒（TB）和肖特基势垒（SB）组成的2D TMDC之间的高接触电阻是实现基于此类系统的高性能器件的关键瓶颈。在此，根据范德华力密度泛函理论计算，我们证明了应变可以提供一种可行的方法来降低例如2D半导体MoS ₂之间的接触电阻和金属表面，无论是强耦合还是弱耦合。在两种耦合方式下，随着拉伸应变的增加，SB和TB均显着降低。尤其是，在所有考虑的配置中，SB都可以减小到零，而拉伸应变增加到〜4％或更高。拉伸应变下SB还原的机制归因于MOS的增加₂由于单层的MoS亲和力能量₂导带最小值（CBm）由反键态得出。因此，具有抗粘结CBm（用于n型接触）的其他半导体TMDC中的SB也可以通过拉伸应变而减小到零。因此，我们的发现为最小化半导体TMDC-基于金属的触点的接触电阻提供了新的常规方法，这也可以证明适用于其他2D半导体，例如磷光体。

更新日期：2017-09-20

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