Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors
Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors
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DOI：
10.1038/s41586-019-1052-3
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发表时间：
2019-04-04
期刊：
影响因子：
64.8
通讯作者：
Chhowalla, Manish
中科院分区：
文献类型：
--
作者：
Wang, Yan;Kim, Jong Chan;Chhowalla, Manish
随场效应晶体管中半导体沟道尺寸的减小，金属-半导体界面在源极和漏极的接触电阻增加，从而决定了器件的性能(1-3)。二硫化钼(MoS_2)等二维过渡金属二卤化物(MoS_2)已被证明是制作超薄场效应晶体管(4，5)的优良半导体。然而，在金属和2D过渡金属二卤化物(3，5-9)之间的界面上观察到了异常高的接触电阻。最近的研究表明，转移的石墨烯(10，11)和金属(12)在少层过渡金属二卤化物上形成的van der Waals接触具有良好的接触性能。然而，三维金属和单层2D过渡金属二卤化物之间的范德华接触还没有得到证实。在这里，我们报道了用100纳米厚的金电极覆盖的10纳米厚的金属铟与单层MoS_2之间的超清洁范德华接触的实现。扫描电子显微镜成像表明，经过200℃的热处理，铟和金层形成了固溶体，金覆盖的铟和MoS_2之间的界面原子上很尖锐，金属和2D过渡金属二卤化物之间没有可检测到的化学作用，这表明金覆盖的铟和单层MoS_2之间存在范德华类型的成键。对于单层MoS2，铟/金电极的接触电阻为3000+/-300欧姆微米，对于少层MoS2，其接触电阻为800+/-200欧姆微米。这些值是蒸发到MoS2上的三维金属电极观察到的最低值之一，使高性能场效应管的迁移率达到167+/-20平方厘米/伏/秒。我们还发现超薄NbS_2(NbS_2)具有220+/-50欧姆的低接触电阻，与铟合金接触的二硫化钨(WS_2)和二硒化钨(WSe_2)具有接近理想的能带偏移量，表明界面无缺陷。我们的工作提供了一种使用标准实验室技术在单层2D半导体上制造超清洁范德华触点的简单方法。
As the dimensions of the semiconducting channels in fieldeffect transistors decrease, the contact resistance of the metalsemiconductor interface at the source and drain electrodes increases, dominating the performance of devices(1-3). Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS2) have been demonstrated to be excellent semiconductors for ultrathin field-effect transistors(4,5). However, unusually high contact resistance has been observed across the interface between the metal and the 2D transition-metal dichalcogenide(3,5-9). Recent studies have shown that van der Waals contacts formed by transferred graphene(10,11) and metals(12) on few-layered transitionmetal dichalcogenides produce good contact properties. However, van der Waals contacts between a three-dimensional metal and a monolayer 2D transition-metal dichalcogenide have yet to be demonstrated. Here we report the realization of ultraclean van der Waals contacts between 10-nanometre-thick indium metal capped with 100-nanometre-thick gold electrodes and monolayer MoS2. Using scanning transmission electron microscopy imaging, we show that the indium and gold layers form a solid solution after annealing at 200 degrees Celsius and that the interface between the gold-capped indium and the MoS2 is atomically sharp with no detectable chemical interaction between the metal and the 2D transition-metal dichalcogenide, suggesting van-der-Waals-type bonding between the gold-capped indium and monolayer MoS2. The contact resistance of the indium/gold electrodes is 3,000 +/- 300 ohm micrometres for monolayer MoS2 and 800 +/- 200 ohm micrometres for few-layered MoS2. These values are among the lowest observed for three-dimensional metal electrodes evaporated onto MoS2, enabling high-performance field-effect transistors with a mobility of 167 +/- 20 square centimetres per volt per second. We also demonstrate a low contact resistance of 220 +/- 50 ohm micrometres on ultrathin niobium disulfide (NbS2) and near-ideal band offsets, indicative of defect-free interfaces, in tungsten disulfide (WS2) and tungsten diselenide (WSe2) contacted with indium alloy. Our work provides a simple method of making ultraclean van der Waals contacts using standard laboratory technology on monolayer 2D semiconductors.