MORPHOSURF - Research project

Recently, femtosecond laser irradiations on Ni (100) revealed the appearance of hexagonal nanostructures (nanoholes) with a diameter & depth of ~25nm, and a periodicity of ~60nm. The objective of this project is to enlarge the understanding of the physical mechanisms leading to the formation of different nanostructures, in order to be able to predict their appearance according to the irradiation parameters. The main idea is to widen the field of experimental investigation from the point of view of materials, and the spatio-temporal formation of the energy deposition. In particular, experiments in circular and cross polarization will be carried out. The goal is to be able to obtain this type of nanostructuring on surfaces from the order of a few mm² to a few cm² in order to be able to study their physical properties, and to consider them possible for industrial applications.
 

The self-organization of periodic patterns is a spectacular phenomenon, omnipresent in nature, and regularly reported at the microscale in laser-surface interaction, referred as "LIPSS". Our work demonstrates the potential of ultrafast laser for the fabrication of unconventional patterns (uniform periodic nanopatterns with a sub-100nm periodicity). In an elegant way, the control of fluid flows on the nanoscale by laser irradiation is demonstrated by tuning laser parameters.
We’ve reported the formation of unconventional self-organized patterns on the 100 nm scale generated by focused ultrafast light. Irradiated surface turns to a forest of nanopeaks with the highest aspect ratio reported in the literature at the nanoscale (height 100 nm: width 20 nm with a sub-100nm periodicity). Laser beam polarization is timely controlled to prevent anisotropic energy absorption and to synchronize the laser energy delivery rate with the material dynamic response. This strategy upgrades the energy coupling and the structure growth explained by a state-of-the-art Maxwell-hydrodynamic simulation. Initiated by convective instabilities at the nanoscale, we demonstrate that the crossed pulses polarization cancels the individual response of each nano-relief due to near-field optical enhancement and enables a collective response of the dissipative structure. The uniformity of the patterns results finally from the regulation between growth and local ablation process. Extreme thermomechanical conditions are supported by both simulations and high-resolution structural measurements owing to HR-TEM microscopy.
The exploited nanostructuring strategy, relying on a timely-controlled polarization feedback, paves the way for the production of homogeneous high-aspect ratio structures for nanoengineering metamaterials. Nanostructuring of high aspect ratio regular and densely packed nanostructures, open up new avenues for improving bactericidal properties and high adhesive forces, antiphase and polarization state manipulation, localized surface plasmon resonance excitation, and extreme light confinement at the nanoscale, significantly improving surface nonlinear optical response.