Polarization effects on the interfacial conductivity in LaAlO₃/SrTiO₃heterostructures: a first-principles study

Abstract

We studied the influence of uniaxial [100] strain (-1% to +1%) on the electron transport properties of a two-dimensional electron gas (2DEG) at the n-type interface of the LaAlO3/SrTiO3(LAO/STO) heterostructure (HS)-based slab system from the perspective of polarization effects via first-principles density functional theory calculations. We first analyzed the unstrained system, and found that the induced polarization toward the vacuum in the LAO film leads to a small charge carrier density on the order of 10(13) cm(-2) (less than the theoretical value of 3.3 × 10(14) cm(-2) from the superlattice-model-based polar catastrophe mechanism), which is in excellent agreement with the experimental values of oxygen-annealed LAO/STO HS samples. Upon applying [100] tensile strain on the STO substrate, we found a significant reduction of the induced polarization in the LAO film. This reduction weakens the driving force against charge transfer from LAO to STO, causing an increase in the interfacial charge carrier density. The uniaxial strain also leads to a decrease of the effective mass of interfacial mobile electrons, resulting in a higher electron mobility. These findings suggest that applying uniaxial [100] tensile strain on the STO substrate can significantly enhance the interfacial conductivity of the LAO/STO HS system, which gives a comprehensive explanation for experimental observations. In contrast, compressively strained LAO/STO systems show stronger LAO film polarization than the unstrained system, which reduces the interfacial charge carrier density and increases the electron effective mass, thus suppressing the interfacial conductivity.

Correlated Lattice Instability and Emergent Charged Domain Walls at Oxide Heterointerfaces

“…Both the δ B and δ OII change sign when crossing the LAO/STO interface. Furthermore, the off‐center‐displacement‐induced polarization can be calculated by , where Z i is the Born effective charge of different ions . δ i is the ion displacement (δ B , δ OII , and δ OI ) relative to centrosymmetric position of A cation position, and V is the unit cell volume.…”

High-mobility two-dimensional electron gas in SrGeO3- and BaSnO3-based perovskite oxide heterostructures: an ab initio study

“…It is worth mentioning that the superlattice model could exhibit different materials properties from the HS-based slab model in which both the film and the substrate have a surface. 40,41 The difference is mainly caused by the surface effects in the HS-based slab mode in which the film and the substrate both have a surface. For instance, for the well-known LaAlO 3 /SrTiO 3 system, prior computational studies indicate that only a HS-based slab model can well depict the polarization behavior in the LaAlO 3 film though both models can reproduce the interfacial electron reconstruction phenomenon.…”

Oxygen vacancy formation in the SrTiO3 Σ5 [001] twist grain boundary from first‐principles

“…Strontium titanate (SrTiO 3 ) is a versatile, low-cost material whose favorable bulk properties enable wide usage as a varistor, 1 thermistor, 2 and dielectric. 3 SrTiO 3 also finds diverse applications as a substrate in perovskite heterostructures for forming 2-dimensional-electron-gas, [4][5][6][7][8] and as a photocatalyst. 9 While the properties of bulk SrTiO 3 are quite well understood, many grain boundary (GB) properties are less clear.…”