Neuromorphic Synaptic Devices Utilizing Flexible SWCNT-TFTs Fabricated via Roll-to-Roll Gravure Printing Process

Neuromorphic systems, which mimic the brain, achieve superior power efficiency, leading to significant energy savings compared to conventional von Neumann architectures. The roll-to-roll (R2R) gravure printing process offers significant potential for enabling large-area, cost-effective printed electronics, and in this study, it was utilized to print neuromorphic synaptic devices. The R2R printed SWCNT-TFT can be used as a charge trap memory, where the threshold voltage changes due to the storage of electrons in the dielectric layer induced by the voltage pulses applied to the gate. The threshold voltage shifts by approximately 25 V when a gate voltage sweep from -35 V to 35 V is applied. Additionally, the retention measurement over 30 minutes demonstrated good stability. When the voltage pulses were applied repeatedly, the current level increased, and when a negative voltage was applied, the current level decreased, exhibiting the characteristics of Long-Term Potentiation (LTP) and Long-Term Depression (LTD) respectively, indicating its potential as a synaptic device. Furthermore, through epoxy encapsulation, the device's response became more linear. Ultimately, flexible printed neuromorphic chips with 100 synapses will be demonstrated based on the R2R printed SWCNT-TFT.