Depth profiling the potential in perovskite oxide heterojunctions using photoemission spectroscopy

The authors report on the potential profiling in depth for promising oxide heterojunctions: La _0.6Sr _0.4MnO ₃ (LSMO)/Nb-doped SrTiO ₃ (Nb:STO) having different interfacial terminating layer and SrRuO ₃/Nb:STO heterojunctions. The precise depth-profiling analysis of LSMO/TiO ₂-Nb:STO interfaces with -La _0.6Sr _0.4O/TiO ₂/SrO- structure reveals the existence of a certain thin depletion layer of 1-2 nm with an abrupt potential drop near the interface. In contrast, the ideal depletion layer is formed for other interfaces with a -SrO/TiO ₂/SrO- terminating layer. These results suggest that the adjacency of TiO ₂ layer with La _0.6Sr _0.4O donor layers at the interface is responsible for the formation of the thin depletion layer near the interface.