Formation of dense nanostructures on femtosecond laser-processed silicon carbide surfaces

Femtosecond (fs) laser has been proved to be a reliable tool for high-quality micromachining on silicon carbide (SiC) surfaces. In this work, we studied the formation of dense nanostructures on fs laser-processed SiC surfaces. These nanostructures are composed of lots of amorphous silicon dioxide (SiO2) nanoparticles with diameters ranging from 5 nm to 30 nm. The distribution and morphology of the formed nanostructures are primarily affected by the laser pulse energy, the laser scanning velocity, and the laser repetition rate. Under specific parameters, the width of the nanostructure area is more than five times wider than the width of the prepared microgrooves. We also observe the expansion of plasma plumes produced upon single-pulse laser ablation by a microscopic imaging system equipped with an intensified charge-coupled device (ICCD) camera to explain the formation mechanisms. We propose that the dense nanostructures are formed due to the high-temperature decomposition, assembling, and oxidation of the laser ablation products. The effective accumulation of laser-ablated products above the laser-irradiated areas is the key to their formation.