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

Density functional theory (DFT)-based methods are used to understand atomic level interactions and calculate adhesion energies of the Cu2O(111)/ZnO 10 1 ¯ 0 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 ZnO 10 1 ¯ 0 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)/ZnO 10 1 ¯ 0 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 Cu2O band gap.