Biaxial strain-induced transport property changes in atomically tailored SrTiO3 -based systems

Abstract

Several metallic SrTiO3-based systems, including reduced SrTiO3−δ, Nb-doped SrTiO3, and two-dimensional electron gas at the LaAlO3/SrTiO3(001) interface, have been epitaxially fabricated on various substrates inducing different strain, from −2.98% (compressive) to +0.99% (tensile). For all the SrTiO3-based systems, strain reduces conductivity. Tensile strain, however, is much more effective at reducing conductivity compared to compressive strain. Further, carrier mobility is found to be more sensitive to strain than carrier density. Calculations based on density functional theory show that strain can break the cubic symmetry of TiO6 octahedron, lift the degeneracy of Ti3d orbitals, and reduce the number of available states at the bottom of the conduction band to cause low carrier mobility. Our results show the critical features of strain effect on the conducting SrTiO3-based systems, and shed some light on strain engineering of these functional materials.