Sub-3 V ZnO Electrolyte-Gated Transistors and Circuits with Screen-Printed and Photo-Crosslinked Ion Gel Gate Dielectrics: New Routes to Improved Performance

A facile, high-resolution patterning process is introduced for fabrication of electrolyte-gated transistors (EGTs) and circuits using a photo-crosslinkable ion gel and stencil-based screen printing. The photo-crosslinkable gel is based on a triblock copolymer incorporating UV-sensitive terminal azide functionality and a common ionic liquid. Using this material in conjunction with conventional photolithography and stenciling techniques, well-defined 0.5–1 μm thick ion gel films are patterned on semiconductor channels as narrow as 10 μm. The resulting n-type ZnO EGTs display high electron mobility (>2 cm² Vs⁻¹) and on/off current ratios (>10⁵). Further, EGT-based inverters exhibit static gains >23 at supply voltages below 3 V, and five-stage EGT ring oscillator circuits display dynamic propagation delays of 50 μs per stage. In general, the screen printing and photo-crosslinking strategy provides a clean room-compatible method to fabricate EGT circuits with improved sensitivity (gain) and computational power (gain × oscillating frequency). Detailed device analysis indicates that significantly shorter delay times, of order 1 μs, can be obtained by improving the ion gel conductance.