A high-temperature resistant polyimide gate insulator surface-modified with a YOx interlayer for high-performance, solution-processed Li-doped ZnO thin-film transistors

We report here a fully aromatic polyimide film with excellent electrical insulating properties and thermal stability. To use the polyimide as a gate insulator for high-performance solution-processed metal oxide thin-film transistors, the surface of a 350 nm thick polyimide film was modified with a 25 nm thick yttrium oxide interlayer. The YOx/polyimide gate insulator showed excellent gate insulating properties with a dielectric constant of 3.2 at 10 kHz and a leakage current density of 3.3 x 10(-10) A cm(-2) at 2 MV cm(-1) after the 300 degrees C annealing process. We prepared solution-processed Li-doped ZnO thin-film transistors with the prepared gate insulators. After the surface modification with the interlayer, the field-effect mobility of the 300 degrees C annealed Li-doped ZnO thin-film transistor increased from 0.1 cm(2) V-1 s(-1) to 4.9 cm(2) V-1 s(-1).