The microstructure and magnetic property of TiO₂-terminated SrTiO₃ substrate selected growth cubic phase CaRuO₃ film

CaRuO₃ thin films with various thicknesses were synthesized by pulsed laser deposition respectively on SrTiO₃ substrates with SrO- and TiO₂-termination. The microstructure of these films was studied by transmission electron microscopy. The results demonstrate that the CaRuO ₃ thin films grown on TiO₂-terminated substrates show quite uniform morphology, whilst they do the facet morphology when the substrates are SrO-terminated. In addition, there is a 5∼7 unit-cell-thickness cubic CaRuO₃ layer in the films grown on TiO ₂-terminated substrates. The measured ferromagnetic hysteresis loop is attributed to the cubic CaRuO₃ layer, which is supported by a first-principles calculations. On the contrary, there is free of cubic CaRuO₃ layer in samples grown on SrO-terminated substrates. The crystallographic domains, the orientation relationship between domains and substrates and crystal defects in these films were studied as well. The different growth mechanism of CaRuO₃ on SrO- and TiO ₂-terminated SrTiO₃ substrates may be correlated with the selective nucleation and growth. CaRuO₃ thin films with various thicknesses were synthesized on SrO- and TiO₂-terminated SrTiO ₃ substrates. The results further confirm that cubic CaRuO ₃ was selectively grown on TiO₂ terminated substrate and that this cubic phase is in response to the ferromagnetism showing in the film.