van der Waals Epitaxy of High-Mobility Polymorphic Structure of Mo<sub>6</sub>Te<sub>6</sub> Nanoplates/MoTe<sub>2</sub> Atomic Layers with Low Schottky Barrier Height.

Lee, Rochelle S; Kim, Donghwan; Pawar, Sachin A; Kim, TaeWan; Shin, Jae Cheol; Kang, Sang-Woo · ACS Nano · 2019

basic_science · Level V

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Abstract

High contact resistance between two-dimensional (2D) transition metal dichalcogenides (TMDs) and metal electrodes is a practical barrier for applications of 2D TMDs to conventional devices. A promising solution to this is polymorphic integration of 1T'-phase semimetallic and 2H-phase semiconducting TMD crystals, which can lower the Schottky barrier of the TMDs. Here, we demonstrate the van der Waals epitaxy of density-controlled single isolated 1T'-Mo<sub>6</sub>Te<sub>6</sub> nanoplates on 2H-MoTe<sub>2</sub> atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T'-Mo<sub>6</sub>Te<sub>6</sub> nanoplates significantly reduce the contact resistance of the 2H-MoTe<sub>2</sub> atomic layers, providing a record high mobility of 1139 cm<sup>2</sup>/V·s for Pd/1T'-Mo<sub>6</sub>Te<sub>6</sub>/2H-MoTe<sub>2</sub> back-gated field-effect transistors, along with a low Schottky barrier height ( qϕ<sub>b</sub>) of 8.7 meV. These results lead to the possibility of ameliorating the high contact resistance faced by other TMDs and, furthermore, offer polymorphic structures for realizing higher-mobility TMD devices.