EFFECT OF REPETITIVE PULSED LASER IRRADIATION ON PLASMA PLUME EMISSION INTENSITY AND SURFACE MORPHOLOGY OF 15 MeV ELECTRON-DEFECTED SILICON

Abstract

In this work, laser induced plasma plume intensity and surface morphology of electron-defected silicon have been studied. For this purpose, the silicon (1 1 1) was irradiated with 15 MeV electrons at different doses (2000–10,000 cGy). The electron-defected silicon samples were analyzed by XRD and SEM, showing increase in number of defects (incubation or absorption centers) by increasing electron dose. Afterward, repetitive Nd:YAG laser pulses were applied to electron-defected silicon. The plasma plume due to each laser pulse was photographed by computer controlled image capture system. From the images, the integrated intensity of plasma plume was calculated by image processing software and plotted as a function of number of laser pulses. The plasma plume intensity was found to increase linearly with increasing pulse number for all silicon samples. The integrated intensity of plasma plume also increases for those silicon samples which were irradiated at higher electron doses. The surface morphology of laser-ablated electron-defected samples was examined through SEM showing different phenomena, like thermal, electronic and hydrodynamic sputtering processes along with the formation of cone, craters, re-deposition of material, heat affected zone (HAZ) and debris formation.