Solution-based flexible indium oxide thin-film transistors with high mobility and stability by selective surface modification

Abstract

Improved performances of solution-based flexible indium oxide (In2O3) thin-film transistors (TFTs) was achieved by introducing clear-cut edges of the active areas on substrate surfaces. Patterned areas for the In2O3 active regions were converted to hydrophilic by oxygen plasma treatment whereas the remaining areas between the active region patterns were converted to hydrophobic by transferring oligomer molecules from a partially cured polydimethylsiloxane (PDMS) mask. This way, In2O3 precursor could be settled only on the intended patterns for the active regions and therefore the active regions were formed with distinct edges and regular shapes. A model TFT prepared via this method exhibited significantly improved performances over a reference device prepared without the selective surface treatment in terms of threshold voltage (Vth), subthreshold swing (SS), saturation mobility (μsat), off-state current (Ioff), and bias-stress stability. Furthermore, the TFT exhibited good electrical stability under a bias stress and sustainable mechanical stability even at 10,000 cycles of bending tests at a radius of curvature of 5 mm. Such improvements were attributed to decreased trap state density at the channel/dielectric interface due to clear distinction of the active region edges and good interface properties, which also helped improving the mechanical stability under prolonged cyclic bending.