  First-principles calculation was used to study the structural and electronic
features of the low dimensional oxide structure,
SrTiO_{3}/Sr_{1-x}La_{x}TiO_{3} (x=0.25) superlattices, constructed by
submonolayer low dimensional La doping into SrTiO_{3}. We demonstrate a
dimensionality crossover from three-dimensional to two-dimensional (3D \to 2D)
electronic behavior in the system. Two types of carriers, one confined to 2D
and the other extended, exhibit distinct tunable (3D \to 2D) transport
characteristics that will enable the study of many properties (e.g.,
superconductivity) through this change in dimensionality.
