The Schottky-barrier heights for the Ni and ZrO2 interfaces have been determined using the x-ray photoemission method. Depending on the surface treatment of ZrO2, the variation of Schottky-barrier heights at Ni∕ZrO2 interfaces was found as large as 0.76±0.10eV. The p-type Schottky-barrier height for the oxygen-rich (oxygen-deficient) interface was measured to be 2.60eV (3.36eV). First-principles calculations provide a microscopic explanation of such variation, which was attributed to the different interface dipole formed by interfacial Ni–O, Ni–Zr bonds, or oxygen vacancies.
The energy-band alignments for LaAlO3 films on p-Ge(001) with and without GeOxNy interfacial layer have been studied using photoemission spectroscopy. The valence-band offsets at LaAlO3∕GeOxNy∕Ge and LaAlO3∕Ge interfaces were measured to be 2.70 and 3.06eV, respectively. The effect of interfacial GeOxNy layer on the band alignments is attributed to the modification of interface dipoles. The conduction-band offsets at LaAlO3∕Si(001) and LaAlO3∕Ge interfaces are found to have the same value of 2.25±0.05eV, where the shift of valence-band top accounts for the difference in the energy-band alignment at two interfaces.
The evolution of Schottky barrier heights ͑SBHs͒ at Ni/ HfO 2 / n-Si stacks was studied by in situ x-ray photoemission. It was found that the n-SBH ͑or the effective work function͒ increases with thickness of the Ni overlayer and approaches 2.4 eV ͑or 4.9 eV͒ 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 HfO 2 was found different from that in vacuum by 0.3 eV. The interface dipole was induced by the weak interaction of Ni thin film and HfO 2 dielectric.
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