Origins of genuine Ohmic van der Waals contact between indium and MoS2

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The achievement of ultraclean Ohmic van der Waals (vdW) contacts at metal/transition-metal dichalcogenide (TMDC) interfaces would represent a critical step for the development of high-performance electronic and optoelectronic devices based on two-dimensional (2D) semiconductors. Herein, we report the fabrication of ultraclean vdW contacts between indium (In) and molybdenum disulfide (MoS2) and the clarification of the atomistic origins of its Ohmic-like transport properties. Atomically clean In/MoS2 vdW contacts are achieved by evaporating In with a relatively low thermal energy and subsequently cooling the substrate holder down to similar to 100K by liquid nitrogen. We reveal that the high-quality In/MoS2 vdW contacts are characterized by a small interfacial charge transfer and the Ohmic-like transport based on the field-emission mechanism over a wide temperature range from 2.4 to 300K. Accordingly, the contact resistance reaches similar to 600 Omega mu m and similar to 1000 Omega mu m at cryogenic temperatures for the few-layer and monolayer MoS2 cases, respectively. Density functional calculations show that the formation of large in-gap states due to the hybridization between In and MoS2 conduction band edge states is the microscopic origins of the Ohmic charge injection. We suggest that seeking a mechanism to generate strong density of in-gap states while maintaining the pristine contact geometry with marginal interfacial charge transfer could be a general strategy to simultaneously avoid Fermi-level pinning and minimize contact resistance for 2D vdW materials.
Publisher
NATURE PUBLISHING GROUP
Issue Date
2021-01
Language
English
Article Type
Article
Citation

NPJ 2D MATERIALS AND APPLICATIONS, v.5, no.1, pp.9

ISSN
2397-7132
DOI
10.1038/s41699-020-00191-z
URI
http://hdl.handle.net/10203/281035
Appears in Collection
EE-Journal Papers(저널논문)
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