Controlling the fabrication of sub-microgrooves on a silicon surface using a femtosecond laser

Abstract

Altering the surface morphology is an approach that is commonly used to enhance desired properties. Femtosecond laser was used to fabricate sub-microgrooves at an average laser power of 31 mW with different scan speeds for a wavelength of 1026 nm. The effect of the laser wavelength on the sub-microstructure fabrication was also studied using 342 and 1026 nm wavelengths using spherical lens f = 40 mm with average powers of 9 mW and 25mW for UV and IR respectively. The sub-microgrooves had the same direction for horizontal, vertical, and diagonal scans. The fabricated sub-microstructures were investigated by a Field Emission Scanning Electron Microscope (FE-SEM) and an Atomic Force Microscope (AFM). At low scan speeds, sub-microgrooves did not appear because the number of pulses was too high. Thus, a high number of pulses per unit length can cause the sub-microgrooves to overlap, owing to the thermal effects. The overlap effects disappeared at scan speeds of 3 mm/s and higher. The sub-microgrooves length decreased as the scan speed increased. Separation distance and width increased with the scan speed. The separation distance reached a maximum value for the samples fabricated at a scan speed of 20 mm/s. At higher speeds, it decreased.