Formation of iron oxide nanoparticles by pulsed laser ablation

Femtosecond and nanosecond lasers are used to produce oxide nanoparticles by laser ablation of steel. The deposition of those particles on the surface strongly modifies its properties. The aim of this study is the understanding of the nanoparticle formation. The dynamics of the plume expansion and of the nanoparticle deposition processes are investigated by means of in-situ time resolved optical analysis. Scanning electron microscopy and atomic force microscopy are used to characterise the particle film morphology deposited on the surface. The influence of laser parameters such as pulse duration (ns, fs), wavelength (UV, visible, IR) and background gas pressure (10 mbar-1 bar) on the processes of nanoparticle formation is studied. It is shown that a high density plasma favours the particle formation, and that the high temperature of the plume obtained with nanosecond IR irradiation impedes the nanoclusters nucleation and prevents an efficient nanoparticle formation.