Characterization of charge carrier transport in thin organic films used in write once read many resistive memory devices

The study explored the underlying mechanism of resistive switching behaviour in a Write Once Read Many (WORM) memory device using an organic dye, Methylene Blue (MB), as the active layer. The device architecture consisted of two electrodes: Indium Tin Oxide (ITO) as the bottom electrode and gold (Au) as the top electrode. Our experimental observations revealed the intricate interplay of electrons and holes conduction within the MB layer. The crucial role of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of MB have been elucidated in governing charge carriers transport in the active layer of the memory device. The application of positive and negative bias voltages induced a reversible exchange of dominant charge carriers (electrons and holes) within the device. High temperature studies also showed the same WORM characteristics in the device and also confirmed the nature of charge carriers. The fabricated WORM memory device exhibited good performance characteristics. Notably, it demonstrated good data retention capabilities exceeding 5 h. Furthermore, the device showed a substantial memory window having ON–OFF ratio of the order of 10³. The device also exhibited remarkable read endurance, withstanding over 2600 read cycles without significant performance degradation. A high device yield of approximately 74% underscored the robustness and reproducibility of the fabrication process. Moreover, the device maintained excellent stability over an extended period of 150 days, confirming its long-term reliability.