Crystal structure comparison between conductive SrRuO₃ and CaRuO₃ thin films

About 70nm-thick SrRuO₃ and CaRuO₃ thin films were deposited by metalorganic chemical vapor deposition (MOCVD) on (0 0 1)SrTiO₃ and (0 0 1)[(LaAlO₃)_0.3-(SrAl_0.5Ta_0.5O ₃)]_0.7 (LSAT) substrates at 750°C. SrRuO₃ and CaRuO₃ thin films were epitaxially grown on both substrates. All films had very smooth surfaces. The detailed crystal structure was investigated by using high-resolution X-ray reciprocal space mapping. The in-plane lattice parameter of SrRuO₃ thin film on (0 0 1)SrTiO₃ substrate was almost the same as that of SrTiO₃, 3.905 Å, and the out-plane lattice parameter was 3.96 Å which was larger than bulk SrRuO₃. On the other hand, in the case of SrRuO₃ thin film on (0 0 1)LSAT substrates, both the in-plane and out-plane lattice parameters of SrRuO3 film were almost the same as those reported for the bulk. Those of the CaRuO₃ thin film on (0 0 1)SrTiO₃ was almost the same as the reported values for the bulk, while on (0 0 1)LSAT, the in-plane lattice parameter was almost the same as that of LSAT. These results can be explain the strain remained in the thin films due to the smaller lattice mismatch combination between the thin film and the substrate, i.e. SrRuO₃ film on SrTiO₃ substrate and CaRuO₃ film on LSAT substrate.