Evolution of Schottky barrier heights at Ni∕HfO2 interfaces

The evolution of Schottky barrier heights (SBHs) at Ni∕HfO2∕n-Si stacks was studied by in situ x-ray photoemission. It was found that the n-SBH (or the effective work function) increases with thickness of the Ni overlayer and approaches 2.4eV (or 4.9eV) when metallic behavior of Ni overlayer is recovered. This is in good agreement with results of first-principles calculations. The effective work function of Ni in contact with HfO2 was found different from that in vacuum by 0.3eV. The interface dipole was induced by the weak interaction of Ni thin film and HfO2 dielectric.