Suppression of conductivity by 1 uc buffer layer at LAO/STO interface

The conducting properties of oxide heterointerface can be significantly affected by buffer layers, gate voltage, capping layer, etc.; sometimes, a monolayer is enough to show a drastic change in these properties. Herein, we report that the insertion of one unit-cell (uc) of CaMnO3 material as a buffer layer at conducting LaAlO3/SrTiO3 interface turns it into an insulator. The presence of MnO2-layer in CaMnO3 uc at the interface blocks the charge transfer to SrTiO3 which makes the interface conducting as explained by the polar catastrophe model. The study may help to resolve the puzzle of the origin of conductivity at oxide heterostructure interfaces.