Impact of nitrogen on effective work function of metal/oxide stack: A first-principles study of the Pt/HfO2 interface

Modulating the effective work function (Φeff) of metal electrodes is both crucial and challenging in metal-oxide-semiconductor transistors. The introduction of atomic dopants is shown to be an effective method to modify the interface Φeff. Here we apply the first principles calculations to systematically explore the impact of incorporation of the non-metallic ambient gas element N on the effective work function of a Pt/HfO2 interface. We find that Φeff is very closely related to the doped atomic position and concentration of the incorporated N atoms. The incorporation is favored at the interface near HfO2 side, and it can significantly increase the interface Φeff for the Pt/HfO2 stack (making it more p-type). Also, the Φeff increases with the increase of doped N concentration due to the mitigation effect of doped N on interface dipole moment. Our findings will provide guidance in developing the environment annealing approach to modulation of Φeff of the metal/oxide stack.