Development of a hybrid laser-waterjet technology for damage-free surface texturing on 4H-SiC substrates

What we believe to be a novel hybrid femtosecond laser-waterjet technology is proposed for surface texturing on 4H-SiC substrates, in which a high-pressure waterjet removes laser-softened material and mitigates laser thermal effects, enabling the efficient and nearly thermal damage-free fabrication of laser-induced periodic surface structures (LIPSS). Increasing water pressure improves the LIPSS surface quality, but an excessive water pressure (e.g., ≥25 MPa) may distort the micro-texture ridge contours. The number of effective laser pulses is highly correlated to the fabricated LIPSS characteristics, with the transition from low spatial frequency LIPSS (LSFL) to high spatial frequency LIPSS (HSFL) occurring at around 200 effective pulses. Notably, the LSFL period fabricated by the proposed technology is approximately 300 nm, significantly smaller than those from conventional laser processing in air. This reduction arises from the effective shortening of the laser wavelength under aqueous conditions. In contrast, the HSFL period remains nearly identical to that obtained in air. The EDS and Raman spectroscopy results confirm that this technique exerts negligible influence on the intrinsic surface structures of the material. A case study with optimized parameters demonstrates large-area regular nano-textured surfaces with 92-94% light absorption in the 300-1200 nm wavelength range. This study provides a new approach to the efficient and damage-free fabrication of LIPSS for various applications.