Recent achievements in microelectronics and other high technologies result in the necessity in both improving and further development of copper applications. One of the most actual issues is increasing demand for epitaxially grown Cu films on nonconducting substrates used in integrated circuits, for instance, fabrication of smooth copper films to be served as a growth template for device structures, such as tunneling magnetoresistance devices. MgO substrates in a combination with a Fe/Pt seed layer provide the superior film quality needed. Cu/MgO interface is also of great importance in other technological applications, including catalysis, metal-matrix composites, etc.
To clarify the nature of interfacial bonding in the Cu/MgO(001) interface, we performed DFT calculations for copper adhesion on the perfect magnesia surface with metal coverage varied from 1/4 monolayer (ML), 1/2 ML (with regular net and striped adatom distributions), up to 1 ML substrate coverage. The adhesion associated with polarization and charge redistribution turns out to be the dominant contribution to the bonding on the regular Cu/MgO(001) interface. The most favorable positions for the adsorption of quasi-isolated (1/4 ML) copper atoms are found to be above the surface O^2- ions on the (001) substrate. Due to mismatch between the lattice constants of Cu and MgO crystals the absolute values of bonding energy per adatom for 1 ML and 1/2 (striped) ML (0.33 and 0.37 eV, respectively) are markedly smaller than for 1/4 and 1/2 (net) Cu ML where adatoms may be considered as quasi-isolated (0.62 and 0.65 eV). Because of high mobility of adatoms along a surface (with a low energy barrier), we can predict high probability for the aggregation of Cu atoms into nanoclusters as compared to the mechanism of layer-by-layer film growth on MgO(001) substrate. Qualitatively, our present results are in agreement with earlier experimental and theoretical studies on the Me/MgO interfaces.

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