Confirmation of charge carriers’ types based on HOMO-LUMO positions in the active layer of a WORM memory device

In this communication, we have tried to explain the experimental observation of the flow of opposite charge carriers (electrons and holes) in a Write Once Read Many times (WORM) type memory device’s resistive switching phenomena. A thiazine dye namely Toluidine Blue O (TBO) was used as the active layer. Bottom and top electrodes were taken as ITO and Au, respectively. The positions of HOMO and LUMO levels in TBO have been shown to play a crucial role in the flow of charge carriers upon applying a bias voltage. Depending on the positive and negative sweep voltages, the charge carriers have been exchanged. This confirmation was made on the basis of theoretical model, Density functional theory (DFT), and temperature-dependent studies. The devices also showed excellent retention capacity for more than 6 h. Memory window was having of the order of 10³ and read endurance of greater than 3300 cycles. The device yield showed almost 80% and an excellent device stability of 90 days.