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 CaRuO₃ 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 TiO₂‐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 TiO₂‐terminated SrTiO₃ substrates may be correlated with the selective nucleation and growth.