ZnO thin-film transistors with a polymeric gate insulator built on a polyethersulfone substrate

Zinc oxide (ZnO) thin-film transistors (TFTs) with a cross-linked poly(vinyl alcohol) (c-PVA) insulator are fabricated on a polyethersulfone substrate. The ZnO film, formed by atomic layer deposition, shows a polycrystalline hexagonal structure with a band gap energy of about 3.37 eV. The fabricated ZnO TFT exhibits a field-effect mobility of 0.38 cm2/Vs and a threshold voltage of 0.2 V. The hysteresis of the device is mainly caused by trapped electrons at the c-PVA/ZnO interface, whereas the positive threshold voltage shift occurs as a consequence of constant positive gate bias stress after 5000 s due to an electron injection from the ZnO film into the c-PVA insulator.

► ZnO active layer formed by means of atomic layer deposition.
► Poly(vinyl alcohol) as a solution-processed insulator.
► ZnO transistors built on a flexible polyethersulfone substrate.
► Trapped electrons at the insulator/ZnO interface caused a hysteresis.
► Injected electrons into the insulator caused a positive threshold voltage shift.