Interfacial stability and strain-modulated electronic properties in LaAlO3/SrTiO3 (110) heterostructures: A first-principles study

Perovskite oxide interfaces exhibit functional properties that are absent in their bulk counterparts. Compared to the well-studied LaAlO3/SrTiO3 (001) interface, the LaAlO3/SrTiO3 (110) interface remains relatively unexplored. Here, we investigate the interfacial properties of n-type LaAlO3/SrTiO3 (110) heterostructures, including cleavage energy, two-dimensional electron gas (2DEG) formation, and the effects of biaxial strain, using first-principles density functional theory calculations. Our results reveal that the (110) interface has a higher cleavage energy than the (001) interface, indicating stronger interfacial bonding interactions. In addition, we find that a critical LaAlO3 thickness of five unit cells is required to induce 2DEG formation in the (110) heterostructure, compared to four unit cells in the (001) system. Notably, biaxial strain in the (110) heterostructure induces behavior opposite to that observed in the (001) system. Compressive strain reduces the polarization strength in the LaAlO3 film, lowering the critical thickness required for 2DEG formation, whereas tensile strain enhances polarization, increasing the critical thickness for 2DEG formation. This contrasting strain response in the (110) and (001) heterostructures can be explained by their distinct crystallographic orientations at the interface. These findings provide new insights into strain-dependent interfacial phenomena and offer valuable guidance for designing functional perovskite oxide interfaces.