Clean Interface Contact Using a ZnO Interlayer for Low-Contact-Resistance MoS2 Transistors

• Published in: ACS applied materials & interfaces Vol. 12; no. 4; pp. 5031 - 5039
• Main Authors: Jang, Jisu, Kim, Yunseob, Chee, Sang-Soo, Kim, Hanul, Whang, Dongmok, Kim, Gil-Ho, Yun, Sun Jin
• Format: Journal Article
• Language: English
• Published: American Chemical Society 29.01.2020
• Subjects: molybdenum disulfide; contact resistance; Schottky barrier height; metal−interlayer−semiconductor structure; zinc oxide
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.9b18591

Two-dimensional transition metal dichalcogenides (TMDCs) have emerged as promising materials for next-generation electronics due to their excellent semiconducting properties. However, high contact resistance at the metal–TMDC interface plagues the realization of high-performance devices. Here, an effective metal–interlayer–semiconductor (MIS) contact is demonstrated, wherein an ultrathin ZnO interlayer is inserted between the metal electrode and MoS2, providing damage-free and clean interfaces at electrical contacts. Using TEM imaging, we show that the contact interfaces were atomically clean without any apparent damages. Compared to conventional Ti/MoS2 contacts, the MoS2 devices with a Ti/ZnO/MoS2 contact exhibit a very low contact resistance of 0.9 kΩ μm. These improvements are attributed to the following mechanisms: (a) Fermi-level depinning at the metal/MoS2 interface by reducing interface disorder and (b) presence of interface dipole at the metal/ZnO interface, consequently reducing the Schottky barrier and contact resistance. Further, the contact resistivity of a Ti/ZnO/MoS2 contact is insensitive to the variation of ZnO thickness, which facilitates large-scale production. Our work not only elucidates the underlying mechanisms for the operation of the MIS contact but also provides a simple and damage-free strategy for conventional aggressive metal deposition that is potentially useful for the realization of large-scale 2D electronics with low-resistance contacts.