Effect of Oxygen Plasma Treatment on the Performance of GQDs-Modulated InGaZnO Thin-Film Transistors

This study investigates the effect of oxygen plasma treatment on the surface morphology, electrical properties, and stability of amorphous graphene quantum dots (GQDs)-modulated InGaZnO (IGZO) thin-film transistors (TFTs) prepared by all-solution method. The weak threshold voltage shifts ( $\Delta \textit{V}_{\text{TH}}\text{)}$ of the oxygen plasma-treated GQDs-IGZO TFTs under positive bias stress (PBS), negative bias stress (NBS), positive bias illumination stress (PBIS), and negative bias illumination stress (NBIS) show a significant improvement of the bias-induced instability. Based on the energy band diagrams, this work demonstrates that O $_{\text{2}}^{-}$ and H $_{\text{2}}$ O $^{+}$ are formed in the back channel under PBS and NBS conditions in addition to ionized oxygen vacancy (V $_{\text{o}}\text{)}$ defects at the GQDs–IGZO/ZrO $_{\textit{x}}$ interface, leading to the gate bias instability, which can be effectively suppressed by the oxygen plasma treatment to improve the stability of the device. From the experimental results, it can be seen that the electrical properties, such as field effect mobility ( $\mu _{\text{FE}}\text{)}$ , on-/off-current ratio ( $\textit{I}_{\text{on}}$ / $\textit{I}_{\text{off}}\text{)}$ , and subthreshold fluctuations, are significantly improved by the passivation of interfacial trap density and bulk trap defects by oxygen plasma treatment. To confirm the potential applications of IGZO-TFTs in logic circuits, inverter based on GQDs-IGZO/ZrO $_{\textit{x}}$ has been integrated, demonstrating good dynamic response characteristics and narrow transition width. Low-frequency noise (LFN) analyses of TFTs have revealed that mobility fluctuations are the main source of noise. As a result, it can be concluded that the facile oxygen plasma treatment strategy is a promising technique to optimize device performance and has demonstrated potential applications in preparing GQDs-IGZO TFTs with high performance.