Structural analysis of W3O/WO3 and TiO/TiO2 periodic multilayer thin films sputter deposited by the reactive gas pulsing process

DC reactive sputtering was used to deposit titanium and tungsten-based metal/oxide periodic nanometric multilayers using pure metallic targets and Ar+O2 gas mixture as reactive atmosphere. The innovative technique namely, the reactive gas pulsing process allows switching between the metal and oxide to prepare a periodic multilayered structure with various metalloid concentrations and nanometric dimensions. The same pulsing period was used for each deposition to produce metal-oxide periodic alternations close to 10nm. Structure, crystallinity and chemical composition of these films were systematically investigated by Raman spectroscopy, X-ray diffraction and Energy-dispersiveX-ray spectroscopy techniques. The high resolution transmission electron microscopy allowed observing the sharpness of the metal/oxide interfaces and measuring the thickness of each kind of layers. Moreover, the crystalline structure of metal and metal oxide layers was also studied. The difference of reactivity between the two systems leads to periodic β-W3O/a-WO3 and face-centered-cubic-TiO/a-TiO2 multilayers.