1：Experimental Design and Method Selection:

The experiment involved focusing single femtosecond extreme ultraviolet pulses from the SACLA free-electron laser onto silicon substrates to create craters. The methodology included theoretical modeling with the XTANT code to understand the physical mechanisms of damage creation.

2：Sample Selection and Data Sources:

Single crystalline silicon substrates (p-doped, orientation (100), specific resistivity 0.02 ～ 30 Ω cm) were used. The surface modifications were analyzed using differential interference contrast microscope (DIC), laser scanning microscope (LSM), and atomic force microscope (AFM).

3：02 ～ 30 Ω cm) were used. The surface modifications were analyzed using differential interference contrast microscope (DIC), laser scanning microscope (LSM), and atomic force microscope (AFM). List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: SACLA free-electron laser, Kirkpatrick–Baez (K–B) mirror, thin-film filters of zirconium and silicon, X-ray charge-coupled device (CCD) camera, gas intensity monitor (GIM), atomic force microscope (AFM).

4：Experimental Procedures and Operational Workflow:

The laser spot was focused onto the silicon substrate, with pulse energy regulated by thin-film filters. The pulse energy was monitored on a shot-to-shot basis. The produced craters were investigated using microscopy techniques.

5：Data Analysis Methods:

The crater depth as a function of the laser fluence was analyzed and compared to simulations from the XTANT code to understand the damage mechanisms.