Cu impurity in insulators and in metal-insulator-metal structures: Implications for resistance-switching random access memories

摘要

We present numerical results from atomistic simulations of Cu in SiO_2 and Al_2O_3, with an emphasis on the thermodynamic, kinetic, and electronic properties. The calculated properties of Cu impurity at various concentrations (9.91 × 10~(20)cm~(-3) and 3.41 × 10~(22)cm~(-3)) in bulk oxides are presented. The metal-insulator interfaces result in up to a ～4 eV reduction in the formation energies relative to the crystalline bulk. Additionally, the importance of Cu-Cu intraction in lowering the chemical potential is introduced. These concepts are then discussed in the context of formation and stability of localized conductive paths in resistance-switching Random Access Memories (RRAM-M). The electronic density of states and non-equilibrium transmission through these localized paths are studied, confirming conduction by showing three orders of magnitude increase in the electron transmission. The dynamic behavior of the conductive paths is investigated with atomistic drift-diffusion calculations. Finally, the paper concludes with a molecular dynamics simulation of a RRAM-M cell that attempts to combine the aforementioned phenomena in one self-consistent model.