ToF-SIMS of femtosecond laser irradiated muscovite with topography: Evidence of Na and K enrichment near the surface

ToF-SIMS is a sensitive technique for interrogating chemical composition at or near the surface of a material, with an emphasis on detecting elements present in extremely low quantities. Here, it was utilized to determine changes in element distribution at a muscovite surface caused by a single 150 fs laser pulse at 800 nm. Muscovite is a mineral with the standard chemical formula KAl₂ (Si₃Al) O₁₀(OH)₂. As a natural mineral, the composition varies. Several ions were studied including aluminium (Al), potassium (K), sodium (Na), and silicon (Si). The laser-irradiated surface area is microscopic - a few microns in diameter. To achieve spatial resolution of the ions within the laser treated region, a ∼100 nm wide ion beam is used. The laser material interaction produces a non-flat surface morphology that changes as the laser pulse fluence increases. Thus, ToF-SIMS is influenced by the ion beam shadowing effect. After the implications of artefacts linked to this are taken into account, there is a finding of net enrichment of sodium and potassium due to the laser irradiation. ToF-SIMS also shows differences in the elemental makeup of nanoparticulates ejected from the laser treated region and redeposited on the surrounding surface. With careful consideration of surface morphological changes, this study shows that ToF-SIMS can be employed in laser materials processing studies to investigate changes in elemental distribution.