Self-organization of silicon nanocone array induced by pulsed CO2 laser irradiation

The periodic microfringe structures were induced on the front silicon surface by pulsed CO2 laser irradiation with the existence of a painting or coating layer on the bottom surface of silicon substrate. The microfringes were formed under single pulse irradiation due to the laser induced periodic surface structure (LIPSS) effect. The nanodot were self-organized in chains under cumulative laser pulse irradiation, and located along the microfringe ridges. The silicon surface was patterned with a nanocone array of two different average sizes at even higher laser intensity. The larger cones distributed in rows, and the smaller cones scattered between the two adjacent rows of the larger cones. The far-infrared absorption of silicon is promoted by the increase of free carrier concentration and thermal energy resulting from the laser interaction with the coating/painting materials at the substrate bottom surface.