Abstract : We report the first observation of single-shot soft x-ray laser induced desorption occurring below the ablation threshold in a thin layer of poly (methyl methacrylate) - PMMA. Irradiated by the focused beam from the Free-electron LASer in Hamburg (FLASH) at 21.7nm, the samples have been investigated by atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze single-shot imprints in PMMA. An intermediate regime of materials removal has been found, confirming model predictions. We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32nm. Short-time exposure imprints provide sufficient information about transverse beam profile in HOH's tight focus whereas long-time exposed PMMA exhibits radiation-initiated surface ardening making the beam profile measurement infeasible.
https://hal-polytechnique.archives-ouvertes.fr/hal-00508903
Contributor : Thuy Le
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Submitted on : Friday, August 6, 2010 - 6:15:53 PM
Last modification on : Monday, December 16, 2019 - 10:06:12 AM
J. Chalupsky, L. Juha, V. Hájková, J. Cihelka, L. Vyšín, et al.. Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses. Optics Express, Optical Society of America, 2008, 17 (1), pp.208-217. ⟨10.1364/OE.17.000208⟩. ⟨hal-00508903⟩
