Applied Physics A

, Volume 69, Supplement 1, pp S887–S894

Time-resolved plasma diagnostics and mass removal during single-pulse laser ablation

  • R.E. Russo
  • X.L. Mao
  • H.C. Liu
  • J.H. Yoo
  • S.S. Mao

DOI: 10.1007/s003390051553

Cite this article as:
Russo, R., Mao, X., Liu, H. et al. Appl Phys A (1999) 69: S887. doi:10.1007/s003390051553
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Abstract.

Laser ablation processes occurring over several orders of magnitude in time were investigated by using time-resolved spectroscopy, shadowgraphs and interferograms. A picosecond ablation plasma was measured with an electron density on the order of 1020 cm-3 originating from the breakdown of air. The longitudinal expansion of this plasma was suppressed due to the development of a strong space-charge field. At post-pulse times, the lateral (radial) expansion of the plasma was found to follow the relation, r∼t1/2, consistent with the expansion from an instantaneous line source of energy.

The electron number density and temperature were deduced by measuring spectroscopic emission-line broadening during the early phase (30–300 ns) of a mass (atomic/ionic) plasma. These properties were measured as a function of the delay time and irradiance. Possible mechanisms such as inverse bremsstrahlung and self-regulation were used to describe the data before an explosion threshold of 20 GW/cm2. The laser self-focusing and critical temperature are discussed to explain dramatic changes in these properties after the irradiance threshold.

On the microsecond time scale, the surface explodes and large (>μm) particles are ejected. Mass removed from single-crystal silicon by high power (109–1011 W/cm2) single-pulse laser ablation is studied by measuring the crater morphology. Time-resolved shadowgraph images show that the rapid increase in the crater depth at the threshold corresponds to large-size droplets leaving the surface. This rapid growth of the crater volume is attributed to explosive boiling.

PACS: 79.20.-m

Copyright information

© Springer-Verlag 1999

Authors and Affiliations

  • R.E. Russo
    • 1
  • X.L. Mao
    • 1
  • H.C. Liu
    • 2
  • J.H. Yoo
    • 1
  • S.S. Mao
    • 1
  1. 1.Lawrence Berkeley National Laboratory, Berkeley, CA-94720, USAUS
  2. 2.Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, P.R. ChinaCN