Fabrication of ultrathin low-voltage-driven printed organic circuits with anodized gate islands

Abstract

Anodization of gate metals can form thin and robust oxide dielectrics of low-voltage-driven organic thin-film transistors (TFTs) for low-cost, flexible electronics. However, anodic oxide dielectrics have rarely been applied to circuit fabrication with complex layouts because separate gate electrode islands cannot be anodized at the same time. To overcome this limitation, we devise a method to simultaneously anodize multiple aluminum gate islands using removable interconnects. The anodic oxide properties, including dielectric constant, film thickness, and leakage current, were thoroughly investigated by varying anodization voltages from 5 to 50 V and a self-assembled monolayer treatment. By printing p-type polymer ink on top of the pattern-grown anodic oxide dielectrics, p-type organic TFTs were fabricated on a 2-mu m-thick Parylene substrate. The printed TFTs exhibited subthreshold swing of 200 mV.dec(-1), carrier mobility of 0.3 cm(2 )V(-1) S-1, and threshold voltage of 0.17 V on average. Even when the substrate film was crumpled, the TFT characteristics did not substantially changed. Finally, a 3 V differential amplifier with multiple gate islands was successfully demonstrated. These findings suggest that high-quality anodic metal oxide films, when fully incorporated into a low-cost, large-area manufacturing process, can be applied to the fabrication of complex, low-voltage-driven TFT circuits on flexible substrates.