Viable Fabrication of Edge-Contacted Monolayer MoS₂ Field-Effect Transistors Enabled by Interfacial Chemical Analysis

Edge contacts offer significant advantage for enhancing the performance of semiconducting transition metal dichalcogenides (TMDCs) devices by interfacing with metallic contact from the lateral side, allowing encapsulation of the whole channel material [1-3]. However, a viable fabrication of electrical edge contact to TMDCs remains a great challenge for high device performance, featuring lack of viable interfacial chemistry characterization by conventional method. The characterization of the interfacial chemistry at the metal–2D semiconductor edge interface represents a major bottleneck owing to negligible cross section in characterizing nominally 1D structure by measuring from top of the edge contact. Here, we present a directional angled etching technique to fabricate slanted edge structure of TMDCs, thereby allowing determining explicit chemical information at the metal–MoS₂ edge interface. The slanted edge structure enables significant cross section for the conventional X-ray photoemission spectroscopy (XPS) to perform element analysis, revealing dominance of pristine MoS₂ layers and an atomically thin, uniform substoichiometric MoS_x interfacial layer, indicating simple chemical environment and clean interface. By optimizing the contact interface, we achieve high-quality slanted edge contact to monolayer MoS₂ transistors encapsulated by hexagonal boron nitride. The transport data of the monolayer MoS₂ device shows efficient charge injection at the edge contact owing to thermionic and tunneling effect, attributed to a clean Au–MoS₂ edge interface and ideal transport characteristics. The demonstrated edge contact method offers a viable approach to fabricate encapsulated 2D material devices which is crucial for both fundamental study of 2D materials and high-performance electronic applications.<br/><br/>Reference<br/>1. Choi, M. S., N. Ali, T. D. Ngo, H. Choi, B. Oh, H. Yang and W. J. Yoo (2022). "Recent Progress in 1D Contacts for 2D-Material-Based Devices." <u>Advanced Materials</u> <b>34</b>(39).<br/>2. Cheng, Z. H., Y. F. Yu, S. Singh, K. Price, S. G. Noyce, Y. C. Lin, L. Y. Cao and A. D. Franklin (2019). "Immunity to Contact Scaling in MoS2 Transistors Using in Situ Edge Contacts." <u>Nano Letters</u> <b>19</b>(8): 5077-5085.<br/>3. Yang, Z., C. Kim, K. Y. Lee, M. Lee, S. Appalakondaiah, C. H. Ra, K. Watanabe, T. Taniguchi, K. Cho, E. Hwang, J. Hone and W. J. Yoo (2019). "A Fermi-Level-Pinning-Free 1D Electrical Contact at the Intrinsic 2D MoS2-Metal Junction." <u>Advanced Materials</u> <b>31</b>(25).