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Nat Mater. 2008 Aug;7(8):621-5. doi: 10.1038/nmat2223. Epub 2008 Jun 29.

Mapping the spatial distribution of charge carriers in LaAlO3/SrTiO3 heterostructures.

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Unité Mixte de Physique CNRS/Thales, Associée à l'Université Paris-Sud, Route départementale 128, 91767 Palaiseau Cedex, France.


At the interface between complex insulating oxides, novel phases with interesting properties may occur, such as the metallic state reported in the LaAlO(3)/SrTiO(3) system . Although this state has been predicted and reported to be confined at the interface, some studies indicate a much broader spatial extension, thereby questioning its origin. Here, we provide for the first time a direct determination of the carrier density profile of this system through resistance profile mappings collected in cross-section LaAlO(3)/SrTiO(3) samples with a conducting-tip atomic force microscope (CT-AFM). We find that, depending on specific growth protocols, the spatial extension of the high-mobility electron gas can be varied from hundreds of micrometres into SrTiO(3) to a few nanometres next to the LaAlO(3)/SrTiO(3) interface. Our results emphasize the potential of CT-AFM as a novel tool to characterize complex oxide interfaces and provide us with a definitive and conclusive way to reconcile the body of experimental data in this system.


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