To solve this problem, we introduced hexagonal BN (h-BN) to encapsulate WTe2 thin film so that it is absolutely isolated from oxygen and moisture in atmosphere. Thin film WTe2 encapsulated by h-BN was achieved by a series of dry transfer processes. The process was illustrated in Figure 1. Here, graphene with special shape was selected be used as source/drain electrodes in WTe2 devices. Due to the strong van der Waals interaction among 2D materials, WTe2 was perfectly sealed by BN and graphene and is isolated from ambient environment. Raman spectroscopy on encapsulated WTe2 indicates that the encapsulation interrupts the degradation of WTe2 effectively. Then, e-beam lithography, inductively couple plasma etching, and e-beam evaporation of Ti and Au were used to pattern metal electrodes. As the surface of WTe2 was protected by BN, the transport performance of WTe2 devices was largely enhanced. This dry transfer and encapsulation method also provide a good platform for 2D flexible devices. By transfering the whole encapsulated structure to a flexible substrate, a 2D flexible device with high performance could be envisioned.
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