Ultraclean van der Waals contacts

FETs using 2D semiconductors as the channel material offer excellent gate electrostatics, which allows mitigation of short channel effects. However, in short channel devices, the transport through the semiconductor is ballistic and virtually all of the power is dissipated at the contacts. Thus, optimizing the contacts between 2D semiconductors and metal electrodes is an important technological challenge. Fundamentally, ultraclean vdW contacts between 3D metals and single layer 2D semiconductors have yet to be realized.

We have successfully demonstrated ultraclean contacts by evaporating indium and gold onto single layer 2D semiconductors. We provide direct evidence using atomic resolution imaging and chemical analysis that the interface between the metal and single layer MoS2 is atomically clean with no chemical interaction between semiconductor and the metal. This allows the 2D semiconductor to remain pristine and thus lowering the contact resistance to record levels.

Figure caption: Low-pass filtered annular dark field scanning transmission electron microscopy image showing In/Au alloy on monolayer MoS₂. Scale bar = 5Å.