Immunity to Contact Scaling in MoS Transistors Using in Situ Edge Contacts.

Atomically thin two-dimensional (2D) materials are promising candidates for sub-10 nm transistor channels due to their ultrathin body thickness, which results in strong electrostatic gate control. Properly scaling a transistor technology requires reducing both the channel length (distance from source to drain) and the contact length (distance that source and drain interface with semiconducting channel). Contact length scaling remains an unresolved epidemic for transistor scaling, affecting devices from all semiconductors-silicon to 2D materials. Here, we show that clean edge contacts to 2D MoS can provide immunity to the contact-scaling problem, with performance that is independent of contact length down to the 20 nm regime. Using a directional ion beam, in situ edge contacts of various metal-MoS interfaces are studied. Characterization of the intricate edge interface using cross-sectional electron microscopy reveals distinct morphological effects on the MoS depending on its thickness-from monolayer to few-layer films. The in situ edge contacts also exhibit an order of magnitude higher performance compared to the best-reported ex situ metal edge contacts. Our work provides experimental evidence for a solution to contact scaling in transistors, using 2D materials with clean edge contact interfaces, opening a new way of designing devices with 2D materials.