Mechanically Robust and Highly Flexible Nonvolatile Charge-Trap Memory Transistors Using Conducting-Polymer Electrodes and Oxide Semiconductors on Ultrathin Polyimide Film Substrates

Flexible charge-trap memory thin-film transistors (CTM-TFTs) are fabricated and characterized for next-generation highly functional consumer electronics. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and 1.2-µm-thick polyimide (PI) films are introduced as source/drain electrodes and plastic substrates, respectively, to realize highly flexible CTM-TFTs with conducting polymers. A uniquely structured sacrificial layer is suggested for the lithography-compatible transfer and patterning processes of PEDOT:PSS on inorganic Al₂O₃ barrier layers are prepared on the PI substrates. The CTM-TFTs show significantly improved device performance compared with those of the previous proto-type devices, including a memory window (MW) of 16.8 V and program speed of 100 µs at a program pulse amplitude of ±20 V. Furthermore, the MWs and on/off current ratio do not shown remarkable degradation, and total variations within a range of less than 7.5% are observed even under harsh bending strains with a curvature radius of 1 mm. Additionally, the mechanical robustness of the fabricated CTM-TFTs is quantitatively discussed based on the contributions of the conducting polymer electrode and the ultrathin PI film to further improve device performance of the flexible CTM-TFTs.