Combining Anisotropic Etching and PDMS Casting for Three-Dimensional Analysis of Laser Ablation Processes

Area of Science:

• Materials Science and Engineering
• Analytical Chemistry
• Surface Science

Background:

• Laser ablation (LA) techniques like LA-ICP-MS, LIBS, and LIMS enable high-resolution chemical analysis of solids.
• Precise determination of LA crater volume is essential for accurate correlation of chemical data with sample location.
• Current methods for characterizing micro- and nanometer-scale LA craters require refinement for quantitative analysis.

Purpose of the Study:

• To develop and demonstrate novel approaches for quantitative analysis of laser ablation craters.
• To investigate crater evolution by systematically varying laser parameters (shot number, pulse energy).
• To accurately determine the 3D structure and volume of femtosecond-LA craters in silicon and copper.

Main Methods:

• Parametric studies involving systematic variation of laser shots and pulse energy to create crater matrices.
• For silicon (Si): Combination of lithography and deep reactive-ion etching (DRIE) followed by high-resolution scanning electron microscopy (HR-SEM).
• For copper (Cu): Polydimethylsiloxane (PDMS) casting to create 3D replicas of craters, analyzed by HR-SEM.

Main Results:

• Both methods successfully characterized laser ablation craters with depths ranging from 1 to 70 μm.
• Craters exhibited a cone-like shape in both single-crystalline Si(100) and polycrystalline Cu.
• Copper demonstrated a significantly larger ablation depth compared to silicon, approximately a factor of three.

Conclusions:

• The developed methods provide improved quantitative analysis of laser ablation craters at the micrometer level.
• Understanding crater geometry is vital for accurate depth-profiling and chemical analysis using LA techniques.
• Material-dependent ablation behavior, as observed between Si and Cu, is critical for optimizing LA processes.