Study On Resistive Switching Memory Based On Amorphous Carbon

Abstract:The memory device is toward high-storage density, long-time date retention, miniaturization, low-power consumption and rapid writing/reading speed and so on. Resistive random access memory (RRAM) has attracted great attention for its potential application in next generation nonvolatile memory due to its simple structure and compatibility with the CMOS process. Explorating new storage materials and revealing the mechanism of the resistance transformation are the key projects for development of RRAM. For the simple component and good stability, amorphous carbon thin film is one of the promising materials for RRAM application.The electrical properties of amorphous carbon film and N-doped amorphous carbon film, which were prepared by DC magnetron sputtering in high-purity Ar and N2, respectively, have been comparatively studied. The research found that the N-doped amorphous carbon film showes resistive switching characteristics, while the undoped amorphous carbon film could not. The best memory device could steadily circulate more than10times and the ROFF/RON was slightly more than10, although the device yield was only50%.An amorphous carbon thin film, consisting of penetrated-pores with dozens of nanometers in diameter, has been synthesized by annealing the magnetron sputtered nitrogen-doped carbon thin films in an inert atmosphere. Based on this nanoporous carbon film, the present work first found the forming-free resistive switching feature in a two terminal device, which shows good endurance and retention performance, containing ready-made metal nanofilaments. The novel memory device could circulate more than103times stably and the devices are kept stable upon heat treatment at120℃in Ar ambient for at least seven days or close to84days at the room temperature. Our work also investigated the relationship between the metal electrode (Cu, Ag or Pt) and the performance of these devices. The results showed that the devices with Cu as top electrode show the best switching performance, while the ones with Pt as top electrode does not have resistive switching characteristics. Finally, microstructure and performance of the carbon films and devices were investigated by using XPS, AFM, CAFM, TEM and PPMS. The results confirmed that the "cone" shaped conductive metal filaments present in the carbon film, and the switching mechanism of RRAM device follows the conductive metal filament model. The SET and RESET of the device are carried out by the electrochemical dissolution of these conductive Cu filaments.