Strontium titanate is a cubic perovskite, which is insulating in its pristine state but becomes metallic upon electron doping. It is one of the most dilute superconductors and the pairing mechanism is unknown. In addition, SrTiO₃ is a quantum paraelectric, in which zero-point fluctuations prevent the structure from a ferroelectric transition. These fluctuations can be suppressed by ¹⁸O isotope substitution. Combined with the electron doping, this leads to a state in which the superconducting and the ferroelectric order coexist.

The first part of this thesis describes the fabrication of samples with an aim of increasing the rate of the ¹⁸O isotope substitution in SrTiO₃, and the process of the electron doping by oxygen removal, leading to a complete superconducting phase diagram.

The second part of the thesis studies Sr₂TiO₄, a 2D counterpart of SrTiO₃. When a growth of the tetragonal Sr₂TiO₄ is attempted, a high-temperature alpha-phase crystallizes first, and while cooled down a phase transition to the tetragonal phase occurs, which breaks the crystal. The second part of the thesis investigates this phase transition, and presents bulk electronic properties and crystal structure of the new alpha-polymorph, which contains titanium in an unusual tetrahedral coordination.