Oxidation Mechanisms in Copper Surfaces

Copper surfaces undergo complex chemical transformations upon exposure to oxygen, governing processes from corrosion control to catalyst performance. Initial stages involve adsorption of oxygen molecules and their dissociation into atomic oxygen, followed by diffusion across terraces and nucleation at defect sites such as step edges, grain boundaries and vacancies. On atomically flat regions, copper adatoms detach from steps and migrate to form islands of cuprous oxide, often in a layer‐by‐layer fashion, whereas high‐energy sites promote three‐dimensional oxide growth. Surface crystallography dictates the relative resistance of different facets, with close‐packed (111) planes exhibiting distinct oxidation kinetics compared with more open (100) or stepped orientations. As oxide islands expand, continued oxygen incorporation and vacancy migration define the transition from self‐limited passivation layers to thicker, polycrystalline oxide films. Defects such as mono‐atomic steps or twin boundaries can either accelerate local oxidation by acting as oxygen traps or retard growth by forming impervious barriers once a critical coverage of oxygen is reached. Temperature, oxygen partial pressure and surface preparation further modulate the balance between oxidation, reduction and restructuring, yielding oscillatory redox behaviour under reactive conditions. An integrated understanding of these mechanistic elements underpins advances in electrical interconnect stability, corrosion protection and copper‐based heterogeneous catalysis.

Research from Nature Portfolio

Recent studies have demonstrated that ultraflat copper films comprising large terraces with minimal mono‐atomic steps exhibit exceptional resistance to oxidation. First‐principles calculations reveal that once half of the face‐centred cubic adsorption sites are occupied by oxygen, further adsorption is energetically unfavourable, effectively passivating the surface. Separately, in situ environmental transmission electron microscopy coupled with theoretical modelling has shown that epitaxial cuprous‐oxide islands grow strictly one monolayer at a time on copper substrates, following Frank–van der Merwe kinetics for individual layers and Stranski–Krastanov behaviour for island formation. Growth rates display a cubic time dependence, reflecting the dynamic interplay between step‐edge sources and bulk diffusion. These findings reconcile classical corrosion theories with atomic‐scale observations and highlight strategies for nanoscale oxidation control.

Oxidation Mechanisms in Copper Surfaces publication trend

The graph below shows the total number of articles in oxidation mechanisms in copper surfaces across all publications each year (not limited to Nature Index journals).

Technical terms

Passivation: Formation of a thin, protective oxide layer that slows further oxidation.

Epitaxy: Oriented growth of one crystalline material on the surface of another.

Grain boundary: Interface between crystals of different orientations within a polycrystalline material.

Chemisorption: Strong adsorption involving chemical bond formation between adsorbate and surface atoms.

Adatom: An atom that resides on a crystalline surface, capable of diffusing across terraces.

References

1. Flat-surface-assisted and self-regulated oxidation resistance of Cu(111). Nature (2022).
2. Unusual layer-by-layer growth of epitaxial oxide islands during Cu oxidation. Nature Communications (2021).
3. In situ observation of oscillatory redox dynamics of copper. Nature Communications (2020).
4. The Role of Grain Boundary Sites for the Oxidation of Copper Catalysts during the CO Oxidation Reaction. ACS Nano (2023).
5. Ambient pressure X-ray photoelectron spectroscopy study of room-temperature oxygen adsorption on Cu(100) and Cu(111). Applied Surface Science (2022).