High-Performance Sub-Micrometer Channel WSe2 Field-Effect Transistors Prepared Using a Flood-Dike Printing Method.

Printing technology has potential to offer a cost-effective and scalable way to fabricate electronic devices based on two-dimensional (2D) transition metal dichalcogenides (TMDCs). However, limited by the registration accuracy and resolution of printing, the previously reported printed TMDC field-effect transistors (FETs) have relatively long channel lengths (13-200 µm), thus suffering low current-driving capabilities (≤0.02 µA/µm). Here, we report a "flood-dike" self-aligned printing technique that allows the formation of source/drain metal contacts on TMDC materials with sub-micrometer channel lengths in a reliable way. This self-aligned printing technique involves three steps: (i) printing of gold ink on a WSe2 flake to form the first gold electrode, (ii) modifying the surface of the first gold electrode with a self-assembled monolayer (SAM) to lower the surface tension and render the surface hydrophobic, and (iii) printing of gold ink close to the SAM-treated first electrode at a certain distance. During the third step, the gold ink would first spread toward the edge of the first electrode and then get stopped by the hydrophobic SAM coating, ending up forming a sub-micrometer channel. With this printing technique, we have successfully downscaled the channel length to ∼750 nm and achieved enhanced on-state current densities of ∼0.64 µA/µm (average) and high on/off current ratios of ∼3 × 105 (average). Furthermore, with our high-performance printed WSe2 FETs, driving capabilities for quantum-dot light-emitting diodes (LEDs), inorganic LEDs, and organic LEDs have been demonstrated, which reveals the potential of using printed TMDC electronics for display backplane applications.