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A. Ionin, S. Kudryashov, S. Makarov, A. Levchenko, A. Rudenko, I. Saraeva, D. Zayarny, C. Nathala, W. Husinsky:
"Nanoscale surface boiling in sub-threshold damage and above-threshold spallation of bulk aluminum and gold by single femtosecond laser pulses";
Laser Physics Letters, 13 (2016), 0256031 - 0256038.

The sub and near-threshold topographic signatures of the spallation of nanometer-thick
melt layers during single-shot femtosecond laser ablation of bulk aluminum and gold
were experimentally observed for the first time, using scanning electron microscopy with
high spatial resolution. The novel ablative nanofeatures-sub-threshold boiling nanopits,
the partially detached ultrathin solidified melt layer, and the lamellar surface structure
under the layer along the spallative crater border, as well as the foam-like nanostructure of
the crater bottom-indicate the boiling origin of the spallation threshold, rather than the
thermomechanical rupture of the molten surface layer in a propagating unloading wave. These
ablative surface nanofeatures were also revealed in trenches of single-shot, near-wavelength
normal interference ripples on the aluminum surface, indicating their spallative nature and
being promising for biosensing applications.

aluminum, gold, femtosecond laser ablation, spallation, boiling, plasmonics, biosensing