Substrate engineering in stabilizing epitaxial MgO(1 1 1) polar ultrathin films: first-principles calculations

Growing MgO(1 1 1) polar ultrathin films (PUFs) on heterogeneous substrates is technologically challenging. By using first-principles calculations, we show that while the O-termination of the supported PUF can be perfectly passivated by H adatoms, the compensation of the Mg-termination at the interface is the key to the stabilization. Proper charge transfer across the interface is highly required, which is dominated by the work function difference between the two surfaces that form the interface. Taking Ag(1 1 1) as an example, we propose that a thin Pt buffer layer can increase the work function of the substrate,and improve the PUF quality significantly.