Femtosecond laser application in materials science

In material science focused ion beam (FIB) milling has become a standard tool for material removal at the microscale. Due to the small removal rates the FIB technique poses a bottleneck for micro-mechanical sample preparation and limits the possible sample dimensions. Furthermore, FIB damage and gallium implantation lead to a reduction in the sample quality [1].

By employing a laser for material ablation, the removal rates are orders of magnitude higher [2]. While continuous and short pulse laser lead to an extended heat affected zone, ultrashort pulse laser (< picosecond) exert no thermal influence on the surrounding material [3]. Especially for the processing of micromechanical samples this is of utmost importance. Therefore, a femtosecond laser offers an ideal tool for micrometer-sized sample preparation and pre-preparation.

In addition to the micromachining capability Echlin et al. [2] demonstrated the possibility to fabricate EBSD compatible surfaces using an ultrashort pulse laser. This allows for the preparation of samples for crystallographic investigations of large areas.

We develop a prototype on the basis of the Zeiss Auriga Laser platform combining the FIB/SEM Crossbeam with a femtosecond laser. The advantage of this platform is the separation of the laser processing chamber from the main chamber containing the FIB/SEM column. Thus, severe contamination of the main chamber due to laser ablation is prevented and processing at non-vacuum conditions or under inert gas atmosphere is possible.

The project focuses especially on the influence of laser processing on the microstructure. Additionally the laser parameters for different materials and various sample geometries are investigated and optimized. Finally, workflows for the preparation of samples employing the laser system are established.

Recent works to demonstrate the capabilities of the FIB/fs-laser combination are listed below, while documents for academic purpose only can be found at the bottom of the page.

 

References:

[1] D. Kiener, C. Motz, M. Rester, M. Jenko, G. Dehm - Materials Science and Engineering: A, 2007, 459, 1, pp 262-272

[2] B.N. Chichkov, C. Momma, S. Nolte, F. von Alvensleben, A. Tünnermann – Appl. Phys. A, 1996, 63, 2, pp 109-115

[3] M.P. Echlin, M. Straw, S. Randolph, J. Filevich, T.M. Pollock - Mater. Charact., 2015, 100, pp 1-12