R&D: Bipolar Resistive Switching Memory with Bismuth Sulfide Quantum Dots

Journal of Applied Physics has published an article written by Ritu Rohilla, Lalita Goswami, Arti Bisht, Vishal K. Maurya, Ritu Srivastava, and Ajeet Kumar, CSIR—National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India, and Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.

Abstract: “In the era of rapidly advancing integrated electronics, Resistive Random Access Memory (RRAM) devices have garnered significant attention for their vast potential in next-generation data storage. The integration of nanoscale quantum dots (QDs) into RRAM architectures has emerged as a promising approach to address the growing demands for enhanced performance, scalability, and efficiency. This work explores the potential of facile, solution processed, cost effective, non-toxic, and chemically stable semiconducting bismuth sulfide (Bi₂S₃) QDs as a resistive switching layer in Al/Bi₂S₃/ITO RRAM devices. Hot injection method is used for the synthesis of Bi₂S₃ QDs, and a subsequent switching film is produced via the spin coating technique. The device shows electroforming free bipolar nonvolatile resistive switching behavior with high retention time (10⁵ s), good endurance (155 cycles), and an ON/OFF ratio (>40). This device also functions well in the pulse mode using a pulse signal, enabling fast switching. The temporal (cycle-to-cycle) and spatial (device-to-device) variability of the switching characteristics was investigated using 270 cycles across eight devices and found to be reproducible. Ohmic conduction was observed in the low-resistance state while Schottky conduction mechanism dominated in the high-resistance state. The resistive switching behavior in the device is proposed to be governed by the interface-filamentary switching mechanism. This mechanism involves consecutive processes of Schottky barrier alteration at the contact interface and, correspondingly, filament formation within the dielectric. The accumulation and depletion of sulfur vacancies and ions are responsible for the formation and rupture of the conducting filament in response to an external electric field. Furthermore, the observation of discrete quantum conductance states in I–V characteristics enables the realization of multilevel switching, possibly leading to an ultra-high-density storage device. These low-cost, solution-processable Bi₂S₃ QD-based non-volatile RRAM devices hold potential for use in futuristic, large-scale, non-volatile RRAM applications.“