Seeding the growth of femtosecond laser produced microstructures on copper with multi-layered materials

Abstract

Femtosecond lasers can be used to create self-organized micro/nanostructures on the surface of most materials. However, on copper, these structures require significantly higher laser fluence when compared to other metals. We report a method to create self-organized structures on copper by clamping a foil of stainless steel on the copper surface prior to laser processing. All samples reported are processed using a peak fluence of 2.71 J/cm2, which is below the fluence threshold for self-organized micro/nanostructure formation on copper. When stainless steel is layered on copper, structures are created that consist of both stainless steel and copper at pulse counts of 998 and 1,197. With increased pulse count, the thickness of the stainless steel layer decreases. For pulse counts of 1,497 and higher, the permanent structures are completely composed of copper. Using these same parameters, but without the stainless steel foil on the copper, the laser processing formed agglomerations of nanoparticles on the surface regardless of pulse count. The structure morphology and chemistry of the surface features are characterized with surface and subsurface analysis to study the material make-up of the structures and investigate the pulse count necessary to fully remove the stainless steel, leaving a structured copper surface.