Proton Irradiation-Induced Electrostatic Modulation in ZnO Nanowire Field-Effect Transistors With Bilayer Gate Dielectric

We report an efficient method to predictably control the conductance and operation voltage of ZnO nanowire field-effect transistors (FETs) with bilayer polyimide (PI)-SiO₂ gate dielectric by selectively generating oxide-trapped charges via proton beam irradiation. The bilayer gate dielectrics was made by polyimide and thermally grown SiO₂ , which prevents negatively charged interface states between the gate dielectric and the ZnO nanowire after proton irradiation. The proton beam-induced charges trapped in the SiO₂ dielectric layer can effectively enhance the electric field toward the n-channel ZnO nanowire, which allows for more accumulation of electrons in the conduction channel of the ZnO nanowire. As a result, the conductance increased and the threshold voltages shifted toward the negative gate bias direction after irradiation. Furthermore, selective modulation of the electrostatic characteristics of the ZnO nanowire FETs was possible by varying the proton irradiation time, which is important for practical application of these devices.