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Experimental study of nano-structure and optical properties of polished silicon irradiated by nanosecond Nd:YAG laser beam

In this paper we studied the structure and optical properties of polished silicon irradiated by nanosecond laser beam in ambient air. Under the conditions of the experiment, nano-structure clusters were formed on the surface of silicon after laser irradiation. The cluster structure and its optical properties were evaluated in terms of number of laser pulses (up to 30000) and also different laser fluences up to 8.3 J/cm2. The SEM images of the irradiated region give information on the cluster effective diameter and surface cluster density. The results show that both laser fluence and number of pulses can influence the cluster density. A He-Ne probe beam was also used to evaluate the reflectivity of the irradiated area (by Nd:YAG laser beam). The reflectivity of the irradiated surface shows that the height of clusters grows gradually by increasing the pulse numbers. The data of this experiment is useful for controlling the morphology of polished silicon induced by nanosecond Nd:YAG laser beam.