Manipulating the Band Structure of SrTiO$_{3}$ with Strain*

SrTiO$_{3}$, the hydrogen atom of perovskites, is a very stable photocatalyst for water splitting. In this talk we demonstrate that the bandgap of SrTiO$_{3}$ can be altered by $\pm$ 10{\%} (0.3 eV) using biaxial strain in combination with phase transitions. The strain behavior is predicted and experimentally observed to be significantly different for (100) vs. (111) biaxially strained SrTiO$_{3}$ surfaces. In the absence of phase transitions the bandgap of biaxially strained SrTiO$_{3}$ decreases. In contrast, a strain-induced ferroelectric phase transition results in an increase in the bandgap. The band structure can also be morphed from indirect to direct bandgap through an antiferrodistortive phase transition. Both of these phase transitions can be manipulated using experimentally realizable biaxial strains, providing a new means to accomplish bandgap engineering of SrTiO$_{3}$ and related perovskites.