Unveiling the Dynamic Oxidative Etching Mechanisms of Nanostructured Metals/Metallic Oxides in Liquid Media Through In Situ Transmission Electron Microscopy

Abstract

Oxidative etching in nanostructured metals and metallic oxides plays a fundamental role in numerous areas of chemical synthesis and materials processing for the semiconductor industry. An in-depth understanding of the oxidative etching mechanisms is of great significance to design various fascinating nanomaterials for practical application. In situ liquid cell transmission electron microscopy (TEM) has the merits of high temporal and spatial resolutions in real-time, and thus it can provide solid evidence directly for the dynamic evaluation of oxidative etching in nanostructured materials that occur in solution. Herein, the recent progress of oxidative etching in nanostructured metals and metallic oxides is overviewed. First, the advancements in liquid cells designs are briefly introduced for in situ TEM observation. Subsequently, in situ liquid cell TEM/STEM advances for the oxide etching mechanisms in different surface chemistry surroundings are systematically described. In addition, both the galvanic replacement and electrochemical etching reactions are also discussed. Finally, the challenges and opportunities in utilizing the in situ liquid cell TEM technique to visualize a specific dynamic oxidative etching process are proposed. This review will provide deep insights into dynamic changes in oxidative etching processes of nanostructured materials and assist in formulating design rules for developing high-end advanced devices.

In situ TEM investigation of nucleation and crystallization of hybrid bismuth nanodiamonds

“…39 Moreover, the boundary atoms with fewer coordination numbers exhibit lower binding energies and are more likely to break away from the binding behavior when the boundary atoms absorb external energy, which also provides possible insights into useful electronic etching applications. 66 Reversible melting and freezing processes are difficult for large particles (the small nanodroplet and big nanodiamond in Fig. 4a).…”

Etching Strategy for Photocatalysis: The Evolution of Structures and Properties

“…[ 67 ] This information is vital for understanding the etching mechanisms, optimizing the process, and ultimately enhancing the performance and application of the etched materials. [ 68 ] For example, Tan et al used in situ TEM to study the morphology evolution of Ag nanocubes during the etching process. [ 69 ] Time‐lapse TEM enables the visualization of the real‐time dynamics of the reaction.…”

Observing the Evolution of Metal Oxides in Liquids

“…[131,132] The in situ liquid-phase TEM/STEM technology for etching metal oxide nanostructures in diverse surface chemical environments has been depictive. [133][134][135][136][137][138][139] In neutral water environments, CeO 2 nanocubes are transformed into polyhedron nanoparticles in the context of electron beam irradiation, within a liquid cell. [140] The etching rate is ≈0.27 ± 0.03 nm 2 s −1 .…”

“…A high electron beam dose rate changes the solution chemistry and produces positive charges on the SiN x surface. [120,139,174] Thus, control experiments with different dose rates or liquid cells are essential in distinguishing these artifacts. [175] The low-dose-optimized TEM technique also reduces the accumulated electron dose and optimizes the imaging conditions.…”