Residue-free 2D-transfer technology for high-performance field-effect transistors

Beyond-silicon technology demands ultrahigh-performance field-effect transistors (FETs). Transition metal dichalcogenides (TMDs) provide an ideal material platform, but the device performances such as contact resistance, on/off ratio, and mobility are often limited by the presence of interfacial residues caused by transfer procedures. Here, we show an ideal residue-free transfer approach using polypropylene carbonate (PPC) with a negligible residue coverage of ~0.08% for monolayer MoS2 in the centimeter scale. By incorporating bismuth semimetal contact with atomically-clean monolayer MoS2-FET on h-BN substrate, we obtain an ultralow Ohmic contact resistance RC of ~78 Ω-µm, approaching the quantum limit, and a record-high on/off ratio of ~10^11 at 15 K. Such an ultraclean fabrication approach could be the ideal platform for high-performance electrical devices using large-area semiconducting TMDs.