Voltage Sweep Direction-Dependent Memory Characteristics in an Organic Film

The present work reports the findings of “write once read many” (WORM) characteristics in the thin film of an organic dye, Thiazole Yellow G (TYG), when a positive voltage sweep was applied. For a negative voltage sweep, purely ohmic characteristics were observed. During the positive voltage sweep, electron transport took place, and in the negative sweep, hole transport was observed. These voltage sweep-dependent memory characteristics are explained using density functional theory (DFT) calculations for the dye’s highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy level diagram and other theoretical models. High-temperature studies of the device also supported our explanations. Additionally, the device exhibited impressive data retention time of more than 16 h, a large memory window of the order of 10³, a high success rate in device fabrication (yield), and 2000 write/read cycles (endurance). Overall, this device shows promising features due to its distinct charge transport behaviour depending on the voltage sweep direction, making it a potential candidate for future efficient resistive memory applications.