Potential profiling of the nanometer-scale charge-depletion layer in $n$-ZnO/$p$-NiO junction using photoemission spectroscopy

We have performed a depth-profile analysis of an all-oxide $p-n$ junction $n$-ZnO/$p$-NiO [1] using photoemission spectroscopy combined with Ar-ion sputtering, and investigated the potential profile of the space-charge region embedded at the interface [2]. Systematic core-level shifts were observed during the gradual removal of the ZnO overlayer, and were interpreted using a model based on charge conservation. Spatial profile of the potential around the interface was deduced, including the charge-depletion width of 2.3 nm extending on the ZnO side and the built-in potential of 0.54 eV. [1] H. Ohta, \textit{et al}., APL \textbf{83}, 1029 (2003). [2] Y. Ishida, \textit{et al}., APL \textbf{89}, 153502 (2006).