Senior Researcher II, Centre for advanced Laser Processing, National Institute for Laser Plasma and Radiation Physics, Romania.

Speech Title: Vapour-Liquid-Solid Nanowire Grow Using Laser Techniques
Abstract: The continuous progress of the nanotechnologies promote more and more the so called 'Bottom-Up' approach for nanostructure's fabrication and the Vapour-Liquid-Solid (VLS) is one of the most used techniques. In spite of the high productivity of the chemical methods for specific applications, laser techniques are still considered as a better option due to nanostructure structural properties or surface patterning difficulties, contamination problems and so on. The growing mechanism is widely accepted as consisting of few catalyst related elementary processes (adsorption, desorption and deposition) into the liquid droplet but conditioned by some catalyst non-related processes as particle's diffusion and (self) nucleation over the used substrate surface. The knowledge on catalyst related processes are still rather scarce and mostly based on theoretical consideration, making nanostructure fabrication (respectively morphological and structural properties) rather difficult to control in the experimental work. In the present work we are summarizing properties control by liquid catalyst related processes in a gold droplet assisted grow of ZnO nanowires. The investigations are carried out in a PLD system using a high repetition rate (500 kHz) laser. By controlling the ablated particles fluency and respectively plume repetition rate through the ablation process parameters, we analyze their influences over the grown morphologies and structural properties and respectively nanowire-thin film growing competition. Catalyst size influence correlated with particle flux is also presented. Nanowire morphology and surface patterning influences are exemplified for a surface acoustic wave sensor application.