Tuning the two-dimensional carrier density at LaAlO3/SrTiO3 interfaces via rare earth doping

The transport properties of LaAlO3/SrTiO3 (LAO/STO) heterostructures with rare earth modified RE0.5Sr0.5TiO3 (RE=La, Nd, Sm, Dy) interlayers are studied. Although it was found that the sheet carrier density of the heterostructure follows the trend of the bulk films, purely extrinsic doping effects are excluded based on observed structural distortions as well as detailed resistance versus temperature analysis. Detailed resistance versus temperature analysis revealed a strong interface confinement of the conduction for a single LSTO unit cell between LAO and STO, which tends toward bulk Fermi-liquid behavior as the LSTO thickness is increased.