Electrochemical dynamics of nanoscale metallic inclusions in dielectrics

Abstract

Nanoscale metal inclusions in or on solid-state dielectrics are an integral part of modern electrocatalysis, optoelectronics, capacitors, metamaterials and memory devices. The properties of these composite systems strongly depend on the size, dispersion of the inclusions and their chemical stability, and are usually considered constant. Here we demonstrate that nanoscale inclusions (for example, clusters) in dielectrics dynamically change their shape, size and position upon applied electric field. Through systematic in situ transmission electron microscopy studies, we show that fundamental electrochemical processes can lead to universally observed nucleation and growth of metal clusters, even for inert metals like platinum. The clusters exhibit diverse dynamic behaviours governed by kinetic factors including ion mobility and redox rates, leading to different filament growth modes and structures in memristive devices. These findings reveal the microscopic origin behind resistive switching, and also provide general guidance for the design of novel devices involving electronics and ionics.

Memristors with diffusive dynamics as synaptic emulators for neuromorphic computing

“…Up to this point, the behaviour of Ag nanoparticles in SiO x N y is similar to previous observations, which have been interpreted as electrochemical reactions at effectively bipolar electrodes [21][22][23][24][25][26] . We next turned off the power at 5.0s to observe the spontaneous relaxation, which is critical for understanding the dynamics of these devices, but has not been previously reported to the best of our knowledge.…”

“…S1-S2). These devices are similar to electrochemical metallization memory (ECM) [21][22][23][24][25][26] cells in terms of utilizing mobile species of noble metals, but they differ substantially in terms of the structural symmetry and operating voltage polarities, metal concentration and profile, and transient switching behaviour. An applied voltage above an apparent threshold abruptly switched the device to a conductance state limited by an external compliance current (Fig. 1b).…”

“…This model links electrical, nano-mechanical and thermal degrees of freedom (Methods). The model results here did not include redox reactions, although they can be added in order to more closely resemble the electrochemical models proposed previously [21][22][23][24][25][26] .…”

Reliable current changes with selectivity ratio above 109 observed in lightly doped zinc oxide films

“…This phenomenon has similarly been observed when devices are scaled down to o40 nm. 42 The limited metal source of electrolytes may be a reason for the gap between the filament and the electrode. In addition, the electric-field has an important effect on filament instability.…”

Kinetic simulation of filament growth dynamics in memristive electrochemical metallization devices

“…[30] It has been worked out recently by Yang et al that such a specific growth mode functionally relies on the particular microstructure and kinetic factors of the material system. [31] By investigating metal clusters inside a dielectric layer they have argued that these metal clusters can be treated as bipolar electrodes influencing the growth mode significantly. Moreover, they have shown evidence that the filament growth is guided by mainly two kinetic factors, i.e.…”