Near infrared laser beam and silicon water interactions

Abstract

At 1070 nm wavelength, Nanosecond (ns) pulse and Continuous Wavelength (CW) lasers’ ablation of n-type(100) and p-type(111) Si wafer is presented in ambient, water and glycerin environments. Impacts of laser emission mode, pulse energy, pulse number, beam shape and type of environment are investigated by an Optical Microscope, a Scanning Electron Microscope and an Atomic Force Microscope. The integrating sphere measurements of optical reflection and transmission values are used in the calculation of the optical constant of the Si sample. Beam profiles acquired by a beam profiler and a CCD camera are presented before the experimental studies. Ablation zones are analyzed in terms of depth and diameter. Besides, temperature measurement of the samples under illumination by a CW laser at 1070 nm is given. In case of CW laser-induced damage regions, either partial molten or totally molten regions are observed along with the crack areas. After ns laser illumination, both the heataffectedzones(HAZ)andtheablationzonesareobservedinambientenvironment. Furthermore, in the HAZ area, some self-assembled ripple formations and re-solidified regions formed. However, in liquid environment, HAZ formation is observed to have reduced or completely disappeared. Bessel beam’s declining effect on the HAZ area is also investigated after illumination of ns laser irradiation at 1070 nm. In all cases, regardless of medium and beam shape, the ablation diameter increases in line with the increments in pulse emission energies. Finally, through higher number of pulses, ablation craters with different depths are achieved with the same diameter of crater.