Juergen Reif, Olga Varlamova, Mourad Bounhalli, Tzanimir Arguirov, Martin Schade, Hartmut S. Leipner
Long-time feedback in self-organized nanostructures formation upon multi-pulse femtosecond laser ablation.
Proc SPIE 7586 (2010), 75860H
Self-organized nanostructures (ripples) on the target surface after multi-pulse femtosecond laser ablation exhibit, obviously, a positive multi-pulse feedback in the self-organization process. Experiments on different targets (CaF2, Si) investigate this feedback in more detail, in particular its dynamics. The influence of pulse number and time separation be- tween successive pulses on both the size and the complexity of the nanostructures as well as the size of the modified surface area is studied. In addition to a dependence on the coupled dose, confirming incubation effects previously observed on ablation efficiency, both modified area as well as pattern feature size and complexity decrease with increasing pulse-to-pulse delay between 1 ms and 1 s, indicating an unexpectedly long lifetime of the feedback. Further, for silicon, a persisting modification of the crystalline structure is found well beyond the ablation spot, though no apparent change in surface morphology can be seen. Mapping the band-to-band photoluminescence displays a spatially modulated dramatic increase of non-radiative recombination compared to unaffected material.
Keywords: patterning, irradiation, nano, silicon, ionic crystals, photoluminescence, nonradiative recombination, EELS, transmission electron microscopy
© SPIE 2010