| Summary: | 碩士 === 國立中興大學 === 物理學系所 === 105 === Resistive Random Access Memories (ReRAMs) are promising candidates for non-volatile memory in the future. The underlying mechanism involves resistive switching in high-k dielectric layers, the changes of the resistance due to various mechanisms are caused by the evolution of the defect structures triggered by the electric and thermal effects. For the memory purpose in ReRAM, one can impose the electric field to adjust the resistance of the resistance material to store information. In this work, non-equilibrium molecular dynamics (MD) simulations with a charge equilibration method is employed to study the electrochemical reactions of ReRAMs. Three ReRAM models, include Cu/SiO2/Si, Si/SiO2/Si, and Cu/TiO2/Ti heterojunction structures, are considered to investigate the resistive switching properties on the electrical, thermal, and structural of three models. Dielectric layers with grain boundary of bicrystal structure is composed of silica nanoparticles and titanium dioxide nanoparticles (thickness is approximately 4 nm). The results reveal that switching behavior depends not only on the material properties and electrical characteristics of switching layers, but also on the metal electrodes and the interfacial structure of grains in dielectric materials.
In addition, the Joule heating effect, defect formation, and charge transfer affected by different grain boundaries under a strong electric field are also examine. Our results demonstrate that an applied external electric field on grain boundaries is a key issue in resistive switching. This simulation work provides the detail mechanism of resistance switching, including the variation of atomic structure and electronic properties, at atomistic length scale and picosecond time scale, which suggest a useful reference for the future development and optimization of material for this technology.
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