Influence of doping at the nanoscale at LaAlO3/SrTiO3 interfaces

The origin of the free charge layer which forms at the LaAlO3/SrTiO3 interface is still uncertain. By varying the doping concentration and the nature of the dopant in SrTiO3 at the LaAlO3/SrTiO3 interface, we show the extreme sensitivity of the system and confirm that the underlying phenomenon accounting for the conduction is most likely an electronic reconstruction. We explain that although doping these interfaces might be useful to induce additional properties such as ferromagnetism or useful to probe the electronic reconstruction, undoped interfaces provide the highest carrier density.