Charge confinement and doping at LaAlO3/SrTiO3 interfaces.

The thickness and origin of the free charge layer which forms at the LaAlO_{3}/SrTiO_{3} interface is still uncertain. By inserting Mn dopants at different distances from the interface we can locate the position of carriers within the SrTiO3 surface layers. We show that the majority of the carriers in fully-oxygenated samples are confined within 1 unit cell of the interface. This confirms the "polar-catastrophe" mechanism proposed for this system but the low mobility of these carriers demonstrates the need for improved materials for applications and a more complete understanding of the role of the minority of higher mobility carriers identified.