Electrical transport properties of BaTiO$_{3}$/LaAlO$_{3}$/SrTiO$_{3}$ heterostructure

Strongly correlated materials with incompletely filled d- of f-electron shells exhibit unusual electronic and magnetic properties, which cannot be effectively explained in terms of non-interacting electron model, and hence hold the promise of novel electronic applications. Here we report the tunneling measurement across BaTiO$_{3}$/LaAlO$_{3}$/SrTiO$_{3}$ heterostructure revealing the metal-insulator transition (MIT), at low temperatures, modulated by varying BaTiO$_{3}$ (BTO) layer thickness. Accordingly, we observed an Ohmic behavior at temperatures $>$ 200 K for all BTO thicknesses, this can be understood with thermoionic emission mechanism, and a clear rectification at low temperatures. The direct tunneling lends a good explanation for the structures with thin BTO layer ($<$ 8 unit cells) and the critical thickness for Zener tunneling contribution is 20 unit cells of BTO. The MIT was clearly observed in the structure with 18 unit cells of BTO.