Interface-controlled materials and 3-D surface nano-patterning

Prof. Gerhard Wilde and Prof. Yong Lei

University of Muenster, Institute of Materials Physics and CeNTech, Muenster, Germany

       Nanocrystalline and nanostructured materials offer particular promise for new and potentially very useful products, since they can have very different - and often superior properties that crucially depend on the atomistic details of interior or exterior interfaces. As nanocrystalline materials are structures far away from thermodynamic equilibrium and since they have short transport pathways, fast diffusion and rapid transformation kinetics often lead to coarsening and to the deterioration of the microstructure and the associated properties. Thus, ensuring the stability of the nanoscale structures, e.g. by utilizing a composite approach, is a key issue. This approach, however, imposes additional constraints on processing-related issues as well as on the stability of phases and phase mixtures and on phase transformations within the nanoscale structural units due to size confinement and due to the presence of heterophase interfaces with excess free energy contributions. While the entire field of nanocrystalline composite materials is far too vast to be addressed in a single overview, recent developments concerning synthesis, phase stability, phase transformationa and materials properties of nanocrystalline materials as followed at the Institute of Materials Physics of the University of Muenster will be highlighted.

      Multifunctional surface nano-patterns are the foundation of semiconductor nano-devices. There is a major shortcoming of the existing surface nano-patterning techniques - in fact almost all synthesized surface patterns are two-dimensional (2-D) planar structures with low aspect ratio. Thus one of the most attractive advantages of nanomaterials, an extremely large surface area, is missing in the existing 2-D surface nano-patterns. Using an emerging UTAM surface nano-patterning technique, 3-D surface nano-patterning could be realized. The UTAM surface patterning approach possesses advantageous features such as tunable structural parameters, large pattern area, and general applicability in fabricating surface structures within nano- and quantum-sized range. The realization of the 3-D surface nano-patterning will not only retain the most attractive feature of the conventional 2-D surface nano-patterning, but also will bring back one of the basic advantages of nanomaterials, i.e. an extremely large surface area. Using an innovative addressing system, it is possible to analyze the properties of an individual unit within a regular nanostructure array and the coupling interaction between the adjacent units. By integrating these data, the properties of the whole ensembles could be obtained. This ‘bottom-up’ property investigation might pave the way to a complete property tuning based on the structure design of surface nanostructures.