Advanced Bipolar Resistive Switching Behaviors by Nitrogen-doped and Cu Layer Stacked Amorphous Carbon Oxide

Abstract

Recent advances in resistive switching devices have garnered considerable interest as a potential alternative for next-generation non-volatile memories, owing to their ultralow power consumption, fast operation, and outstanding scalability. Among various active media, amorphous carbon oxide (α-COx) has shown promising device performance, primarily due to the transition between carbon sp2-sp3 complexes under bias. However, its widespread application is hindered by two significant challenges: high forming voltage and insufficient stability. This study addresses these issues by first introducing a simple method to stack a Cu layer at the α-COx layer/W interface in Pt/α-COx/W structures, aiming to enhance the resistive switching characteristics. A precisely controlled Cu layer (2.5 nm thick) demonstrated forming-free behavior, reliable switching, and notably stable features compared to a single α-COx active medium. We attribute our experimental findings to the oxygen ion drift-driven transition between sp2 and sp3 bonds at the intermixed regions of α-COx/Cu interfaces under bias, as systematically confirmed through structural observations. Secondly, we explored the use of an oxynitride amorphous carbon (α-COxNy) active medium, carefully controlled for nitrogen content during growth, to achieve high electrical stability. This resulted in distinct pulse endurance of over 107 cycles, a high retention time of 105 seconds at 85°C, and improved uniformity in SET/RESET distribution, maintaining thermally robust resistive switching stability even at high annealing temperatures of 400°C. These improvements are likely due to the sp2-sp3 conversion nature facilitated by the presence of pyridinic N or pyrrolic N, acting through a substitution reaction mechanism.