Dependence of Ablation Thresholds for Silicon on Laser Incident Angle

This study investigated the dependence of ablation thresholds for Si on the incident angle of a P- or S- polarized XeCl excimer laser (0°, 15°, 30°, 45°, and 60°). As the incident angle increased, the ablation threshold decreased for the P-polarized laser and increased for the S-polarized laser. It was found that the dependence of the ablation threshold on laser incident angle was related to the incidence angle dependence of the reflectance for P-polarized or S-polarized laser light. Based on observed laser incident angle dependence of the ablation threshold for Si, periodic nanostructures of several hundreds of nanometers were formed over the entire surface of a pyramid structure when silicon solar cells were irradiated with linearly polarized laser pulses rotated 90° at a laser fluence of 0.5 J/cm2.