Oxygen Diffusion in Platinum Electrodes: A Molecular Dynamics Study of the Role of Extended Defects

Abstract

Platinum serves as a model electrode in solid‐state electrochemistry and as the inert electrode in redox‐based resistive random‐access memory (ReRAM) technology. Experimental work has proposed that oxygen may diffuse faster along platinum's extended defects, but quantitative, unambiguous transport data do not exist. In this study, the diffusion of oxygen atoms in crystalline platinum and along its extended defects is studied as a function of temperature by means of molecular dynamics (MD) simulations with the ReaxFF interatomic potentials. The MD simulations indicate that platinum vacancies trap oxygen atoms, inhibiting their diffusion through the platinum lattice and leading to a high activation enthalpy of diffusion of around 3 eV. This picture of trapping is supported by static density‐functional‐theory calculations. MD simulations of selected dislocations and selected grain boundaries indicate that oxygen diffusion is much faster along these extended defects than through the Pt lattice at temperatures below 1400 K, exhibiting a much lower activation enthalpy of ≈0.7 eV for all extended defects examined. Producing specific electrode microstructures with controlled densities and types of extended defects thus offers a new avenue to improve the performance of ReRAM devices and to prevent device failure.

Oxygen vacancy dynamics in Pt/TiOx/TaOy/Pt memristors: exchange with the environment and internal electromigration

“…It is reasonable to assume that the top Pt electrode, with a microstructure of columns and grain boundaries, behaves as a permeable layer that allows oxygen transport between the environment and the oxide bilayer trough grain boundaries, as has been previously suggested in Ref. [34].…”

“…Fast Fourier Transforms (FFT) performed in both oxide layers (not shown here) show the absence of diffraction poles, evidencing their amorphous character. In addition, the top Pt electrode shows the presence of columns and grain boundaries, which could behave eventually as fast paths for oxygen migration in and out of the device [34].…”

Correlation between Electronic Structure, Microstructure, and Switching Mode in Valence Change Mechanism Al2O3/TiOx‐Based Memristive Devices

“…For this mode, a switching mechanism based on an area-dependent interfacial exchange reaction of oxygen near the Pt active electrode combined with ion migration is discussed. [17,[43][44][45] Despite different approaches, a direct comparison of the switching kinetic behavior for the two different modes, namely, the "abrupt, filamentary" and the "gradual, interfacial" is difficult, because often devices of different dimensions and various layer stacks are used for either case. Here, the SET kinetic behavior of identical devices was measured on the same sample and is discussed below.…”

Oxygen vacancy dynamics in Pt/TiOx/TaOy/Pt memristors: exchange with the environment and internal electromigration

“…Fast Fourier transforms (FFT) performed in both oxide layers (displayed in the supplementary information) show the absence of diffraction poles, evidencing their amorphous character. In addition, the top Pt electrode shows the presence of columns and grain boundaries, which could behave eventually as fast paths for oxygen migration in and out of the device [35].…”