Compositional and gate tuning of the interfacial conductivity in LaAlO3/LaTiO3/SrTiO3 heterostructures

We investigate the effect of LaTiO3 insertion at the interface between LaAlO3 and TiO2 terminated {100} SrTiO3 for a series of LaAlO3 and LaTiO3 thicknesses. A clear increase of the carrier density was observed while the Hall mobility was largely unchanged. In structures with LaAlO3 thickness similar to 3 unit cells, close to the critical thickness for conductivity, as little as 0.25 unit cells of LaTiO3 drives an insulator-to-metal transition. These samples show a strong dependence of the conductivity on voltage with electrostatic back-gating, which can be understood in a two-carrier picture, and dominated by the change in carrier density at the interface. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794410]