Switching Enhancement in Copper Oxide Thin-Film Transistors via Molybdenum Trioxide Buffering and Nitrogen Doping

Switching characteristics of copper oxide (Cu₂O) thin-film transistors (TFTs) were enhanced by buffering both sides of the channel with a thin layer of sputtered molybdenum trioxide (MoO₃). On the top side, the thin MoO₃ layer was capable of controlling the back-channel phase by forming a high-resistance surface-path and hence reducing the drain off-current. While on the bottom side, the MoO₃ film worked as a passivation layer at the (semiconductor/dielectric) interface which helped in reducing the interfacial states density D_it by one order of magnitude. By optimizing the nitrogen doping conditions and harnessing the bilayer channel scheme, switching characteristics were enhanced even more. Our best double-buffered bilayer TFT achieved a subthreshold swing of 0.14 V dec⁻¹, an on/off current ratio (I_on/I_off) of 2.7 × 10⁶, and a field-effect mobility (μ_FE) of 0.11 cm² V⁻¹ s⁻¹, a considerable enhancement in performance compared to that of non-doped non-buffered Cu₂O TFTs.