Micro-spikes formed on mesoporous silicon by UV picosecond laser irradiation

Abstract

Conical spikes with sizes ranging between 0.2 and 5 µm were formed on a mesoporous silicon surface under ultraviolet picosecond laser irradiation in ambient air. Scanning electron microscopy was employed to visualize the successive steps in the formation of the spikes. On increasing the number of shots (up to 1000) at a fluence of 400 mJ/cm², an increase in the size and an enhancement in the distribution of spikes were observed. The experimental observations revealed that the formation and the growth of these structures were mainly due to material ablation and removal mechanisms. FTIR analysis on several large (5X 5 mm2) irradiated zones showed an enhancement in the absorption coefficient mainly in the IR range from 1 to 8 µm versus the size of the microstructures.

Nano-Squares and Regular Lipss on Ysz Coating by Picosecond Uv Laser Beam: Thin Film Mediated and Direct Texturing

“…This confirms that the key parameter for LIPSS formation is the applied energy density (F) (Figure 7 In the case of a number of pulses N = 20000 at the same laser fluence (F = 310 mJ/cm 2 ), elongated nano-spikes structures appear on top of the LSFL already formed on the YSZ surface, both of which are perpendicular to the polarization of the E laser beam, as shown in the figure 8. Based on SEM images, the size of these Nano-Spikes is found to vary between 0.8 and 1 µm (Figure 8.a), while the approximate spatial period of LSFLs is about 240 nm (Figure 8.b) [42].…”