Time dependency of the laser-induced nanostructuring process of chromium layers with different thicknesses on fused silica

- The ns laser-induced melting effect of thin Cr layers on fused silica was studied.
- The molten layer was analyzed by study of the time-dependent optical properties.
- The liquid phase lifetime ΔtLF depends on the metal thickness and the fluence.
- The ΔtLF dependency can be well described by an analytic function.
- The comparison of the results with FEM simulation yields to a moderate agreement.

Nanostructures exhibit a raised importance in manifold application fields like electronics and optics. The laser irradiation of thin metal layers allows the fabrication of metal nanostructures induced by a melting and deformation process where the resultant structures are dependent on the laser and metal layer parameters. However, for an optimization of this process a detailed physical understanding is necessary. Therefore, the dynamics of the metal layer deformation process was measured by time-dependent reflection and transmission as well as shadow graph measurements at different KrF excimer laser parameters (laser fluence and number of laser pulses) and metal layer thicknesses were used. Magnetron-sputtered thin chromium films with a thickness from 10 to 100 nm on fused silica substrates were studied. Based on the optical measurements the liquid phase lifetime of the metal was estimated and compared with the calculated lifetime using a simple thermodynamic model.