Laser-induced nanostructuring of dielectric surfaces assited by self-assembling processes of thin metal layers

• Applicant: Dr. Pierre Lorenz
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 249539097

The nanostructuring of dielectrics is a highly topical subject of photonics and has a high application potential. Laser methods enable a fast and flexible surface structuring. Within this project, the laser-induced surface nanostructuring of dielectrics by using self-assembly processes in thin metal layers will be studied. Currently it is known that the laser irradiation of thin metal layers on dielectric substrates at lower laser fluences results in melting of the metal layer and due to the surface tension in the nanostructuring of the metal layer. Thus, this laser-induced forming processes by melting lead for homogeneous laser beam profiles to the formation of randomly distributed nanostructures, it can be expected that periodically modulated intensity distributions preparing metallic nanostructures featuring a periodic super lattice. In preliminary work, it was observed that in addition to the metal nanostructure formation, there is a surface patterning of the dielectric substrate. By suitable choice of the laser fluence was achieved in that first the metal nanostructures can be produced, that are the base of the structure transfer into the dielectric surface by localized ablation at high laser fluences. The metal structures absorb / focus the laser radiation, leading to a surface-localized energy transfer to the dielectric surface, and finally to a localized removal of these. In consequence there is a transfer of the lateral geometry of the metallic structures in the dielectric surface, wherein the transfer conditions depend on the laser parameters. This novel structuring allows the easy production of complex structures, the structural shapes are controlled by the laser and the material parameters. The irradiation of the nanostructured metal layers with high fluence induces an ablation of the metal layers and a partial ablation of the dielectric surface. The metal structures absorb the laser beam and a surface-localized energy transfer into the dielectric surface results in a localized ablation of the dielectric surface. That means, the process allows the transfer of the lateral geometry of the metallic structures into the dielectric surface where the transfer conditions are dependent on the laser parameters. In the first section of the project influences of the laser and the material parameters are examined for the nanostructure formation in the metal layer and the transfer into the surface of the dielectric. To elucidate the physical mechanisms of the patterning process simulation is performed. In the second part of the project, the findings from the first part are used for the production of demonstrators in the field of optics (e.g. antireflection layers), fluidics (e.g. setting of the wetting properties of surfaces for use in lab-on-chip application), and tribology (e.g. adjustment of the surface abrasion properties). The simulation of the process will be used to optimize the production parameters of the demonstrators.

• DFG Programme: Research Grants
• International Connection: Hungary, Switzerland
• Participating Persons: Dr. Béla Hopp; Professor Dr. Patrick Schwaller