In Situ Crystal Surface Reconstructions in Atomic Layer Deposition Thin Films

Atomic layer deposition (ALD) is a thin-film deposition technique renowned for its ability to achieve precise control over film thickness and uniformity. By relying on sequential, self-limiting gas-phase reactions, ALD enables the conformal deposition of thin films with atomic-scale precision. While a wide range of ALD chemistries has been explored, recent research has shown that electrons themselves can act as ALD reactants. They are believed to drive hydrogen desorption, creating dangling bonds that readily adsorb reactants and promote ALD film growth. Building on this understanding of electron-driven reactions, we investigated how high-energy electron probes interact with ALD-grown materials, specifically examining their impact on surface structure and defect formation. In this study, we demonstrate that the crystal surface structure of Wurtzite ZnO undergoes atomic reconstructions when exposed to a high-energy electron probe (200 kV). Sequential imaging of ZnO nanocrystals reveals that electron beam exposure reduces the prevalence of (100) facets, preferentially exposing (001) and (101) surface types. Furthermore, atomic-resolution images of the ZnO lattice show that ALD-grown films contain a variety of inherent defects, particularly those related to oxygen ordering. These findings provide new insights into the role of electron-induced processes in shaping material surfaces during ALD.