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

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 Fermi-level 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 TiS₂ onto monolayer (ML) MoS₂. After confirming the successful formation of a TiS₂/ML MoS₂ heterojunction, the contact properties of vdW semimetal TiS₂ were thoroughly investigated. With clean interfaces of the TiS₂/ML MoS₂ heterojunctions, atomic-layer-deposited TiS₂ can induce gap-state saturation and suppress FLP. Consequently, compared with conventional evaporated metal electrodes, the TiS₂/ML MoS₂ 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.