Coherent consolidation of trillions of nucleations into a coplanar layer for a mono-atom step-level flat surface

Abstract Constructing a mono-atom step-level flat material surface is challenging, especially for thin films, because it is prohibitively difficult for trillions (1012) of clusters nucleated on a 2-inch wafer to coherently merge into a single-orientation thin film. The rough metal surface limits surface–plasmon propagation and acts as a valley for atoms deposited during the growth of the two-dimensional material. Recently, various flat-surface-assisted phenomena have been discovered, including large oxidation resistance of an atomically flat copper (Cu) surface. In this study, we describe in detail the initial growth of Cu(111) thin films with mono-atom step-level flat surfaces. We demonstrated experimentally that the individual deposition of single atoms using atomic sputtering epitaxy induces trillions of islands to coherently merge into a coplanar layer, eventually forming a mono-atom step-level flat surface. Theoretical calculations supported the fact that, when the sputtered particles are single atoms, rapid surface diffusion ensures the formation of highly aligned single-crystal nanodroplets that can be merged into a large domain with a coherent coplanar layer. These findings will open a new avenue in thin-film growth research and represent a watershed in terms of improved efficiency and lifespan of devices in most fields using metal electrodes, as well as metal nanoscience research.