First principles study of bonding, adhesion, and electronic structure at the Cu₂O(111)/ZnO 10 1 ̄ 0 interface

Density functional theory (DFT)-based methods are used to understand atomic level interactions and calculate adhesion energies of the Cu ₂O(111)/ZnO101̄0 interface with varying Cu₂O coating thickness. We first establish an accurate model of the ZnO substrate, validating DFT + U against the more accurate hybrid-DFT to calculate properties of bulk wurtzite ZnO and the ZnO101̄0 surface. DFT + U is then used to analyze the structure of the Cu₂O(111) surface, characterizing the formation of surface copper dimers. The Cu₂O(111)/ZnO101̄0 interface is found to be only weakly interacting, with a DFT + U-derived adhesion energy of 0.85 ± 0.07 J/m². Charge density analysis reveals that some interface stabilization occurs because of local ZnO and CuO bonding interactions at the interface. We find that the overall impact of the ZnO substrate on the electronic structure of the Cu₂O overlayer is to reduce the Cu ₂O band gap.