Morphology and microstructure of Mg-Ti-H films deposited by microwave plasma-assisted co-sputtering
Résumé
Mg-Ti-H films with a Ti content in the range 0 at.% Ti < 20 were obtained in a single-step process using
the microwave reactive plasma-assisted co-sputtering technique. The morphology, crystal structure,
chemical composition and spatial distribution of the elements were investigated by X-ray diffraction,
scanning and transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and
precession electron diffraction. Our results show that the Ti-poor films (0 at.% Ti 0.45) exhibit mainly
the tetragonal beMgH2 phase and have a dense microstructure with discontinuous columnar grains. For
the films with a medium Ti content (2.7 at.% Ti 6.6), the beMgH2, metastable orthorhombic geMgH2
and Mg-Ti phases were found in different proportions, with a typical columnar growth. The abrupt
microstructural changes of the films with a Ti content >10 at.% correlate with the change in crystallinity.
These films exhibit a mainly amorphous/nanocrystalline structure with a granular morphology. We
showed that the Ti content plays a significant role in the formation of structural and microstructural
features of the Mg-Ti-H films, which might be a useful parameter in tuning the functional properties of
magnesium hydride.