Investigation of the NiO surface reduction induced by Nd overlayers

The interface between the oxide and metal plays an important role in modern technologies like microelectronics, solar cells, magnetic storage media, and sensors. NiO is an important oxide material with potential application in several technologies. In this regard, the understanding of the interface between metals and NiO is an important research topic. Here we study the change in interface electronic properties of Nd-deposited NiO thin films utilizing X-ray photoelectron spectroscopy (XPS) and ultra-violet photoelectron spectroscopy (UPS). We observed oxidation of deposited Nd by reacting with NiO lattice oxygen at the interface resulting in the reduction of a fraction of NiO to metallic Ni. The thickness of the interface metallic Ni layer increases linearly to 3.0 Å when the Nd overlayer thickness reaches 13.8 Å. An additional increase in Nd thickness has no further effect on interface Ni metal thickness indicating termination of the oxidation/reduction process. Such interface redox reactions could be used in special interface structures.