Crystal structure comparison between conductive SrRuO 3 and CaRuO 3 thin films

Abstract

About 70 nm-thick SrRuO 3 and CaRuO 3 thin films were deposited by metalorganic chemical vapor deposition (MOCVD) on (0 0 1)SrTiO 3 and (0 0 1)[(LaAlO 3) 0.3-(SrAl 0.5Ta 0.5O 3)] 0.7 (LSAT) substrates at 750°C. SrRuO 3 and CaRuO 3 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 SrRuO 3 thin film on (0 0 1)SrTiO 3 substrate was almost the same as that of SrTiO 3, 3.905 Å, and the out-plane lattice parameter was 3.96 Å which was larger than bulk SrRuO 3. On the other hand, in the case of SrRuO 3 thin film on (0 0 1)LSAT substrates, both the in-plane and out-plane lattice parameters of SrRuO 3 film were almost the same as those reported for the bulk. Those of the CaRuO 3 thin film on (0 0 1)SrTiO 3 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. SrRuO 3 film on SrTiO 3 substrate and CaRuO 3 film on LSAT substrate.