Intrinsic origin of the two-dimensional electron gas at polar oxide interfaces

Source: arXiv


The predictions of the polar catastrophe scenario to explain the occurrence
of a metallic interface in heterostructures of the solid
solution(LaAlO$_3$)$_{x}$(SrTiO$_3$)$_{1-x}$ (LASTO:x) grown on (001) SrTiO$_3$
were investigated as a function of film thickness and $x$. The films are
insulating for the thinnest layers, but above a critical thickness, $t_c$, the
interface exhibits a constant finite conductivity which depends in a
predictable manner on $x$. It is shown that $t_c$ scales with the strength of
the built-in electric field of the polar material, and is immediately
understandable in terms of an electronic reconstruction at the nonpolar-polar
interface. These results thus conclusively identify the polar-catastrophe model
as the intrinsic origin of the doping at this polar oxide interface.

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