Electronic properties calculation of MgO thin films adsorbed on semi-infinite Ag(001)

We report a theoretical investigation of the electronic structure of ultrathin MgO films on Ag(001). Such a study has been motivated by recent experiments in which a peculiar behavior was observed when the film thickness is less than a few layers, suggesting that the interface properties may play a crucial role. We tried to verify such a statement by a comparative analysis between the clean surfaces of Ag and MgO, and the 1-, 2-, and 3-monolayer (ML) adsorbed systems. To perform these calculations we applied the embedding method {proposed by Inglesfield [J. E. Inglesfield, J. Phys. C 14, 3795 (1981)]} which allows us to consider a semi-infinite substrate and is therefore one of the state-of-the-art methods for the theoretical treatment of surfaces. We find evidences of a weak interaction between the silver substrate and the MgO overlayers and we show how, as the film thickness exceeds the 2 ML width, the electronic properties converge on those of a clean MgO surface. In the last part of the work we also suggest a possible interpretation of the ultraviolet photoelectron spectroscopy data obtained on these systems.