Non-thermal desorption/ablation of molecular solids induced by ultra-short soft x-ray pulses

Opt Express. 2009 Jan 5;17(1):208-17. doi: 10.1364/oe.17.000208.

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 21.7 nm, 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 32 nm. 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Boron Compounds / radiation effects
  • Carbon / radiation effects
  • Electrons
  • Laser Therapy / methods
  • Lasers*
  • Microscopy, Atomic Force
  • Polymethyl Methacrylate
  • Spectrophotometry
  • Surface Properties
  • Ultraviolet Rays
  • X-Rays*

Substances

  • Boron Compounds
  • Carbon
  • Polymethyl Methacrylate