Spectroscopic and morphological investigation of laser ablated silicon at various laser fluences

Abstract

The effect of laser fluence by using laser-induced breakdown spectroscopy on the ablation mechanisms of Si (100) has been investigated. For this purpose a Q-switched Nd-YAG laser with the wavelength of 1064 nm, pulse duration of 10 ns was employed. For the very first time by using linearly polarized Nd:YAG laser, the effect of fluence and optical emission spectroscopy has been carried out for various laser fluences ranging from 1.4 × 102 to 11.3 × 102 J/cm2 under the ambient environment of He, Ne and Ar at a constant pressure of 200 torr. Boltzmann plot and Stark broadening method were used to determine the influence of laser fluences on plasma parameters such as electron temperature and number density. Our experimental results suggest that the laser fluence in different ambient environment play a significant role for plasma evolution, ambient gas causes a confinement effect that generation, recombination, and expansion of plasma and consequently affect the excitation temperature as well as electron density of plasma. The morphological analysis of laser irradiated Si was performed by Scanning Electron Microscope (SEM). Various kinds of structures e.g. Laser Induced Periodic Surface Structures (LIPSS) or ripples, droplets and craters have been generated and their density and size are found to be dependent upon the laser fluence and ambient environment. A quantitative analysis of crater depth measured from SEM images showed strong correlation between laser fluence and the growth of micro/nano structures on modified Si surface.