First-principles prediction of a two dimensional electron gas at the BiFeO3/SrTiO3 interface

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The structural and electronic properties of the BiFeO3(BFO)/SrTiO3(STO) heterostructure are studied using supercell approach by ab-initio density functional theory calculations. Our calculations indicate that a two-dimensional electron gas (2DEG) exists at the n-type (BiO)+ and (TiO2)0 interface, due to the fact that electronic reconstruction is expected to avoid the polar catastrophe. Moreover, the large polarization discontinuity between the paraelectric SrTiO3 and ferroelectric BiFeO3 brings about distinguishable 2DEG behaviors to the n-type BiO/TiO2 interfaces, due to the asymmetric screening charge.