Effective work function of metals interfaced with dielectrics: A first-principles study of the Pt-HfO2 interface

A parameter-free methodology to determine the effective work function, defined as the work function of the metal on the dielectric side of a metal-dielectric interface, is presented. This method relies on the direct determination of the effective work function through the interfacial dipole moment from standard density functional theory calculations devoid of scaling the band gap and band offset. For the case of a Pt-HfO2 interface, this strategy is combined with statistical thermodynamic principles to predict the most probable effective work function at given combinations of temperature and O-2 pressure (through determination of the most favored interfacial O coverage). The predicted results are in excellent agreement with observations.