Progressive evolution of silicon surface microstructures via femtosecond laser irradiation in ambient air

Using 800-nm femtosecond laser irradiation, progressive evolution of the silicon surface microstructures has been demonstrated. Via the variation of laser irradiation parameters, four kinds of microstructures, such as: well-defined and clean nano-ripples, obscured nano-ripples with nano-protrusions and nano-holes, micro-spikes with nano-holes, and separated micro-spikes, have been produced. The morphology and chemical compositions of these microstructures have been characterized by a scanning electronic microscopy equipped with an energy dispersive x-ray spectroscopy. The formation and evolution mechanism of these microstructures have been systematically discussed. Meanwhile, the incorporation mechanism of foreign oxygen species into silicon materials has also been discussed on the basis of the femtosecond laser induced trapping effect of the dangling bonds.