van der Waals Epitaxy of High-Mobility Polymorphic Structure of MoTe Nanoplates/MoTe Atomic Layers with Low Schottky Barrier Height.

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'-MoTe nanoplates on 2H-MoTe atomic layers by using metal-organic chemical vapor deposition. Importantly, in situ grown 1T'-MoTe nanoplates significantly reduce the contact resistance of the 2H-MoTe atomic layers, providing a record high mobility of 1139 cm/V·s for Pd/1T'-MoTe/2H-MoTe back-gated field-effect transistors, along with a low Schottky barrier height ( qϕ) 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.