Tunneling transport in a few monolayer-thick WS_2/graphene heterojunction

摘要

This paper demonstrates the high-quality tunnel barrier characteristics and layer number controlled tunnel resistance of a transition metal dichalcogenide (TMD) measuring just a few monolayers in thickness. Investigation of vertical transport in WS_2 and MoS_2 TMDs in graphene/TMD/metal heterostructures revealed that WS_2 exhibits tunnel barrier characteristics when its thickness is between 2 and 5 monolayers, whereas MoS_2 experiences a transition from tunneling to thermionic emission transport with increasing thickness within the same range. Tunnel resistance in a graphene/WS_2/metal heterostructure therefore increases exponentially with the number of WS_2 layers, revealing the tunnel barrier height of WS_2 to be 0.37 eV.