A Dual-functional Superoxide Precursor to Improve the Electrical Characteristics of Oxide Thin Film Transistors.

We investigated a method to simultaneously improve the mobility and reliability of solution-processed zinc tin oxide thin film transistors (ZTO TFTs) using a dual-functional potassium superoxide precursor. Potassium cations in the potassium superoxide (KO2) precursor act as carrier suppliers in the ZTO thin film to improve the carrier (electron) concentration, which allows the potassium-doped ZTO TFT to exhibit high mobility. The anions in the precursor exist as superoxide radicals that reduce oxygen vacancies during the formation of thin oxide film. Consequently, the KO2-treated ZTO TFTs exhibited improved mobility and reliability compared with pristine ZTO TFTs, with an increase in field effect mobility from 5.57 to 8.74 cm2/Vs and a decrease in the threshold voltage shift from 7.18 to 3.85 V, after a positive bias temperature stress test conducted over 5000 sec.