Ablation and surface structuring of Si₃N₄ ceramics by nanosecond laser pulses

Abstract

The work presents the main characteristics of the process of ablating silicon nitride ceramics by nanosecond laser pulses. Two types of ceramics are considered—tape cast and gas pressure sintered. Laser processing was performed by a Q-switched Nd:YAG laser system at four wavelengths—266 nm, 355 nm, 532 nm, and 1064 nm. The ablation depth dependences on the laser fluence and number of pulses applied at the different wavelengths are presented and discussed. It is found that increasing the laser fluence at a fixed number of pulses leads to a saturation of the ablation depth for all wavelengths used. Further, laser treatment results in a variety of micro- and nanostructures on the surface of the material. Their characteristics are determined as a function of the processing parameters. The ablation process proceeds via decomposition of the ceramic, as traces of silicon and silicon oxide are found in the processed area. The dependences observed are discussed based on a detailed analysis of the morphological and chemical changes estimated by classical analytical methods, namely, SEM, TEM, XRD, XPS, and Raman spectroscopy. The study presented can serve as a basis for the development of a laser-based processing technique for nitride ceramics and fabrication of Si-based composites.