Effect of repetition rate on morphology of generated microstructure on silicon surface using low cost N₂ laser in air medium

The systematic investigation has been carried out on the effect of repetition rate on morphology of the Si microstructures generated using an inexpensive Nitrogen (N₂) nanosecond (ns) laser. The wavelength, pulse duration and pulse energy of the used laser are 337nm, ∼3.5ns and 170µJ respectively. The repetition rate of the laser was varied from 5Hz to 20Hz at constant sample scanning velocity of 0.005mm/s. All the experiments were carried out in the air medium. The morphological characterization of the produced microtextured Si were done by an ImageJ software calibrated USB Digital Microscope Endoscope Camera (UDMEC) and Field Emission Scanning Electron Microscope (FESEM). At constant sample velocity with low repetition rate, the periodic gratings like microstructures were observed on Si surface. With the increase of the repetition rate to 10Hz and 12Hz, the channel like groove based microstructures were generated. Further increasing the repetition rate to highest values of 20Hz, we observe the grooved based microstructures. It is also demonstrated that the width of the processed region can be increased with increase of the repetition rate. This significant optimized processing parameters using N₂ ns laser microtextured Si surface is suitable for the generation Black Si in large area for the wide field of applications.