Atomic-resolution study on the interface in multilayer hard coatings

Wider research context Multilayer coating resulting from the stabilization of non-equilibrium (metastable) phase exhibit exceptional properties such as extremely high strength and high corrosion resistance, optical, and magnetic properties as compared to single-layer counterparts. Here, interfaces play a significant role in the mechanical property of multilayer. The interface structures are thus determining factors for controlling the behaviour of the materials. To date, due to the complexity of multilayers, detailed interfacial atomic and electronic structure information on multilayer is missing, and the atomic-scale mechanism of epitaxial stabilization and its effect on hardness enhancement in multilayer are unclear. The atomic-level understanding of these phenomena is very important since insight into the atomic details is expected to lead to the likely creation of a new class of multilayer coatings. Research questions what is the atomic-scale mechanism of epitaxial stabilization? How does the interfaces and N defect affect the structure and property of multilayer? Approach/methods This experimental project aims to develop our atomic-resolution understanding on the interface with an emphasis on some key issues, e.g., interface atomic and electronic structure related to metastable phase, the mechanism of epitaxial stabilization, and its effects on the superhardness of the multilayer. To achieve these goals, atomic-scale structural investigations, quantitative structural and chemical composition measurements, and electronic structure characterization at the interface, supported by theoretical calculations, will be performed on the immiscible non-isostructural systems such as TiN/TaN. The experimental methods to be used include atomic-resolution CS-corrected TEM imaging, atomic-resolution spectroscopy analysis, in-situ experiments, and X-ray diffraction. The installed powerful TEMs and a new capability for insitu TEM at Erich Schmid Institute (ESI) will be utilized. Together with high-quality film growth at University of Leoben (MLU), the study realized by this unique combination is of great importance to exploit the fundamental issues at the multilayer films at the atomic level, and technologically provide the guidelines for design a new class of multilayers with novel functionalities for industrial applications. Level of originality The proposed research will provide in-depth knowledge of the interface of multilayer coatings. It will result in the following important new insights: i) atomic and electronic structure of the interface and metastable phase in multilayer; ii) the physical mechanism of epitaxial stabilization and its effect on the property; iii) the defect effect on the structure and property, and the atomic-scale origin of thermal stability in multilayer. Primary researchers involved The main researcher to be responsible for the project is Priv.-Doz. Dr. Zaoli Zhang at ESI, and Professor Christian Mitterer at MLU.