Comparing properties of femtosecond and nanosecond laser-structured silicon

Sharp microcones form on crystalline silicon surfaces upon irradiation with either femtosecond or nanosecond laser pulses in a sulfur hexafluoride environment. While the general shape and aspect ratio of femtosecond and nanosecond laser cones are similar, several features (such as size and position relative to the original surface) suggest that different mechanisms may be involved in the formation of these structures. The microscopic structure and optoelectronic properties of surfaces covered with nanosecond or femtosecond laser cones could therefore differ as well. We compare the optical properties (reflectance, transmittance, and absorptance), chemical composition, and crystallinity of femtosecond and nanosecond laser cones. We also report the dependence of these properties on processing parameters.