In situ atomic-scale imaging of the metal/oxide interfacial transformation

Directly probing structure dynamics at metal/oxide interfaces has been a major challenge due to their buried nature. Using environmental transmission electron microscopy, here we report observations of the in-place formation of Cu2O/Cu interfaces via the oxidation of Cu, and subsequently probe the atomic mechanisms by which interfacial transformation and grain rotation occur at the interfaces during reduction in an H2 gas environment. The Cu2O→Cu transformation is observed to occur initially along the Cu2O/Cu interface in a layer-by-layer manner. The accumulation of oxygen vacancies at the Cu2O/Cu interface drives the collapse of the Cu2O lattice near the interface region, which results in a tilted Cu2O/Cu interface with concomitant Cu2O island rotation. These results provide unprecedented microscopic detail regarding the redox reactions of supported oxides, which differs fundamentally from the reduction of bulk or isolated oxides that requires the formation of new interfaces between the parent oxide and the reduced phase.