Investigation on Contact Properties of 2D van der Waals Semimetallic 1T-TiS₂/MoS₂ Heterojunctions

Abstract

Two-dimensional transition metal dichalcogenides (2D TMDCs) are considered promising alternatives to Si as channel materials because of the possibility of retaining their superior electronic transport properties even at atomic body thicknesses. However, the realization of high-performance 2D TMDC field-effect transistors remains a challenge owing to Fermilevel pinning (FLP) caused by gap states and the inherent high Schottky barrier height (SBH) within the metal contact and channel layer. This study demonstrates that high-quality van der Waals (vdW) heterojunction-based contacts can be formed by depositing semimetallic TiS 2 onto monolayer (ML) MoS 2 . After confirming the successful formation of a TiS 2 /ML MoS 2 heterojunction, the contact properties of vdW semimetal TiS 2 were thoroughly investigated. With clean interfaces of the TiS 2 /ML MoS 2 heterojunctions, atomic-layer-deposited TiS 2 can induce gap-state saturation and suppress FLP. Consequently, compared with conventional evaporated metal electrodes, the TiS 2 /ML MoS 2 heterojunctions exhibit a lower SBH of 8.54 meV and better contact properties. This, in turn, substantially improves the overall performance of the device, including its on-current, subthreshold swing, and threshold voltage. Furthermore, we believe that our proposed strategy for vdW-based contact formation will contribute to the development of 2D materials used in next-generation electronics.

Mixed-Dimensional Integration of 3D-on-2D Heterostructures for Advanced Electronics

“…Copyright 2022 Springer Nature. Reprinted with permission from ref . Copyright 2024 American Chemical Society.…”

“…With this approach, near-ideal vdW interfaces were achieved without chemical interaction between the 2D TMDs and 3D metals, resulting in an unpinned Fermi level (Figure c) . More recently, Yoon et al utilized a low-temperature ALD-deposited 2D semimetal as a buffer layer between the electrode and MoS 2 , which effectively improves interface quality and suppresses both MIGS and DIGS. Also, the heterojunctions exhibit a lower Schottky barrier height compared with conventional evaporated metal electrodes, substantially improving their electrical performance.…”