Texture and interface characterization of iridium thin films grown on MgO substrates with different orientations

Abstract

Iridium thin films are grown by direct-current plasma magnetron sputtering, on MgO single crystal substrates with various surface orientation, i.e. (100), (111) and (110). The surface morphology, the crystalline properties of the films, and the substrate-thin film interface, are investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and high-resolution transmission electron microscopy (HR-TEM), respectively. The results reveal that hetero-epitaxial thin films with different crystallographic orientation and notable atomic scale smooth surface are obtained. From the XRD analysis the following epitaxial relations are obtained: i) (100) Ir || (100) MgO out-of-plane and [001] Ir || [001] MgO in-plane for Ir grown on MgO(100), ii) (110) Ir || (110) MgO out-of-plane and [1-10] Ir || [1-10] MgO in-plane for Ir grown on MgO(110) and iii) (111) Ir || (111) MgO out-of-plane and two variants for in-plane orientation [1-10] Ir || [1-10] MgO and [1-10] Ir || [10-1] MgO , respectively for Ir grown on MgO(111). Because of the large misfit strain (9.7%), the thin films are found to grow in a strain-relaxed state with the formation of geometrical misfit dislocations with a ~2.8 nm spacing, whereas thermal strain is stored upon cooling down from the growth temperature (600 °C). The best structural characteristics are obtained for the (111) oriented films with a mosaicity of 0.3° and vanishingly small lattice distortions. The (100)-and (110)-oriented films exhibit mosaicities of ̴ 1.2° and lattice distortions of ̴ 1% which can be explained by the larger surface energy of these planes as compared to (111).

Structural and electrochemical properties of high quality epitaxial titanium carbide thin films grown by pulsed laser deposition on MgO (111) and Al2O3 (001) substrates

“…This elongation can be due either to a difference in the level of residual strains in the films and/or a different Ti/C molar ratio as compared to the reference material. In the case of epitaxial films, the respective effects of residual strains and composition can be disentangled by using XRD reciprocal space maps (RSMs) following a method previously used to analyse oxide and metallic films [29][30][31].…”