Defect Chemistry and Size Effects in SrRuO₃

The metal-insulator transition in strontium ruthenate (SrRuO₃) is an unsolved issue of great relevance.
SrRuO₃, one of the oxides with the highest conductivity, is widely used in applications such as electrodes of capacitors. In addition, it is ferromagnetic, has low intrinsic disorder and its epitaxial growth is well understood. It is thus a good candidate for spintronics where a two-dimensional spin-polarized conducting system is a long-standing goal. Investigations in ultrathin SrRuO₃, however, have revealed an insulating state for film thicknesses below three unit cells¹. These findings are however not unanimous, and single-layer conductive SRO might be experimentally possible².
We investigate by means of DFT+U structural phenomena which could occur in the crystal deposition of SrRuO₃ and lead to an insulating state. In particular, we focus on single point defects and defect dipoles on the electronic structure of an SrRuO₃ thin film. Moreover, we investigate changes in octahedral distortions and lattice tetragonality as a function of film thickness.
1 J. Xia, W. Siemons et al., Phys. Rev. B 79, 140407(R) (2009)
2 C.R. Hughes, T. Harada et al. https://arxiv.org/pdf/1609.08901