Low-dimensional electron transport observed along complex oxide heterointerfaces has attracted enormous attention in recent years. While the formation of these 2-dimensional electron gases is generally attributed to electronic charge transfer triggered by a built-in electric field, the ionic defect structure at these interfaces is still being discussed controversially.
Here, we address the thermodynamic processes associated with built-in electric fields and derive ionic defect concentration profiles established at polar/non-polar oxide interfaces.  As we discuss, the specific ionic-electronic defect structure stabilized within such interfacial space charge layers strongly depends on ambient oxygen partial pressure applied during sample fabrication and on the strength of the built-in electric field.
As we ground states obtained for various oxide heterostructure systems  and discuss resulting implications for important measures characterizing the electron gas, such as electron mobility  as well as its magnetic signature , both controllable by thermodynamic means. The thermodynamic model obtained for oxide heterointerfaces is furthermore linked to kinetic space charge formation occurring at complex oxide surfaces [5, 6].
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