Picosecond laser-induced periodic surface structures (LIPSS) on crystalline silicon

In this paper, laser-induced periodic surface structures (LIPSS) are created by a 532 nm picosecond laser with the pulse duration of 8 ps and the pulse repetition rate of 1 kHz on crystalline silicon. The number of the pulse and the fluence of the laser were changed in the experiment. With the same laser fluence, the uniformity of the ripples is improved by increasing the pulse number. With the same pulse number, the period of the ripples is increased by increasing the laser fluence. Morphologies of LIPSS are measured by AFM. Ripples oriented per-pendicular to the polarization of the laser light with two different periods are found in one spot. The period of the LIPSS in the center is 1.38 mu m, while it is 528.5 nm at the periphery of the spot. The height from peak to valley of the LIPSS in the center is 59.82 nm, while it is 33.58 nm at the periphery of the spot. It is found that, the laser-induced surface modifications can be classified into three different categories, including LIPSS molten, LIPSS and LIPSS not appear. The threshold of the laser fluence and pulse numbers for the formation of LIPSS is determined. LIPSS created on the crystalline silicon surface can improve material surface properties, e.g. re-flectivity or wettability. Those properties have a far-reaching significance for potential application in many fields, such as solar energy utilization, specific wavelength absorption, image security, material lubrication and anti-corrosion.