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Colloquium – Seong-Gon Kim – Flat-surface-assisted and self-regulated oxidation resistance of Cu(111)
October 19, 2022 @ 3:30 am - 5:00 pm
Speaker: Seong-Gon Kim (Mississippi State University)
Title: Flat-surface-assisted and self-regulated oxidation resistance of Cu(111)
Oxidation can deteriorate the properties of copper that are critical for its use, particularly in the semiconductor industry and electro-optics applications. This has prompted numerous studies exploring copper oxidation and possible passivation strategies. In situ observations have, for example, shown that oxidation involves stepped surfaces: Cu2O growth occurs on flat surfaces because of Cu adatoms detaching from steps and diffusing across terraces. But even though this mechanism explains why single-crystalline copper is more resistant to oxidation than polycrystalline copper, the fact that a flat copper surfaces can be free of oxidation has not been explored further. Here, we report the fabrication of copper thin films that are semi-permanently oxidation resistant because they consist of flat surfaces with only occasional mono-atomic steps. Our first principles calculations show that mono-atomic step edges are as impervious to oxygen as flat surfaces, and that surface adsorption of O atoms is suppressed once an oxygen fcc surface site coverage of 50% has been reached. These combined effects explain the exceptional oxidation resistance of ultraflat Cu surfaces.
We also introduce colossal oxidation resistance (COR), which not only provides permanent protection against room-temperature oxidation of oxidizable metals but also is robust even against high-temperature oxidation. Our first-principles calculations show that the COR originates from complete blocking of the oxygen entry path into the metal by oxygen atoms themselves and the reconstitution of the metal surface forms an atomically thin barrier impenetrable to oxygen at high temperature. This reliable approach to creating COR will open new directions for research fields and industries hesitating to use oxidizable metals.