Strain effects on the electronic properties in [delta]-doped oxide superlattices

Strain effects on the electronic properties of (LaTiO sub(3)) sub(1)/(SrTiO sub(3))N superlattices were investigated using density functional theory. Under biaxial in-plane strain within the range of -5% [< or =] [epsilon]// [< or =] 5%, the d sub(xy), orbital electrons are highly localized at the interfaces whereas the d sub(yz) and d sub(xz) orbital electrons are more distributed in the SrTiO sub(3) (STO) spacer layers. For STO thickness N > or = 3 unit cells (u.c.), the d sub(xy) orbital electrons form two-dimensional (2D) electron gases (2DEGs). The quantized energy levels of the 2DEG are insensitive to the STO spacer thickness, but are strongly dependent on the applied biaxial in-plane strain. As the in-plane strain changes from compressive to tensile, the quantized energy levels of the d sub(xy) orbitals decrease thereby creating more states with 2D character. In contrast to the d sub(xy) orbital, the d sub(yz) and d sub(xz) orbitals always have three-dimensional (3D) transport characteristics and their energy levels increase as the strain changes from compressive to tensile. Since the charge densities in the d sub(xy) orbital and the d sub(yz) and d sub(xz) orbitals respond to biaxial in-plane strain in an opposite way, the transport dimensionality of the majority carriers can be controlled between 2D and 3D by applying biaxial in-plane strain.