High-Performance Sub-Micron 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 transition metal dichalcogenides (TMDCs). However, limited by the registration accuracy and resolution of printing, previously reported printed TMDC field-effect transistors 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 which allows the formation of source/drain metal contacts on TMDC materials with sub-micron channel lengths. This technique involves three steps, including (i) printing gold ink on WSe₂ to form the first electrode, (ii) modifying the surface of the first gold electrode with self-assembled monolayer (SAM) to lower its surface tension, and (iii) printing gold ink close to the SAM-treated first electrode with a certain distance. During the third step, the gold ink would firstly spread toward the first electrode and then get stopped by the hydrophobic SAM coating, forming a sub-micron 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 ~3x10⁵ (average).