Uniform Amorphization of Crystalline Silicon Surfaces Enabled by Deep Ultraviolet Femtosecond Laser Pulses

Silicon dominates the electronics industry, yet creating amorphous silicon layers on crystalline silicon substrates typically relies on ion implantation or plasma‐based methods. Ultrafast laser pulses offer a promising alternative for localized amorphization, but achieving uniform transformations on large areas by consecutive pulses remains challenging, particularly at near‐infrared wavelengths where the fluence window for amorphization before material damage is relatively narrow. In this work, we investigate the use of deep‐ultraviolet (DUV, 258 nm) femtosecond pulses for producing continuous, uniform amorphous layers on Si(100) and Si(111). Single‐ and multi‐pulse threshold analyses reveal that DUV provides a fluence window for amorphization up to six times larger than at 1030 nm, enabling over 30 successive shots per site without the occurrence of ablation by incubation effects. Using appropriate fluence and overlap conditions, we achieve uniform amorphous lines and areas with thickness of 20–45 nm. Electron microcopy analyses confirm high uniformity and sharp amorphous/crystalline interfaces (<1.5 nm). Time‐resolved reflectivity measurements reveal melting and resolidification dynamics, with melt durations up to 2.5 ns without evidence of a counter‐propagating solidification front. These results establish DUV femtosecond processing as a scalable route for direct writing of ultra‐thin amorphous structures, advancing fabrication techniques for microelectronics and silicon photonics.