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Threshold Level Laser Ablation of Yba2Cu3Ox+6 at 351 nm, 248 nm, and 193 nm: Ejected Product Population and Kinetic Energy Distributions

Published online by Cambridge University Press:  16 February 2011

L. Wiedeman
Affiliation:
Laser Chemistry & Spectroscopy Department, The Aerospace Corporation, P. O. Box 92957, Los Angeles, California 90009.
H. Helvajian*
Affiliation:
Laser Chemistry & Spectroscopy Department, The Aerospace Corporation, P. O. Box 92957, Los Angeles, California 90009.
*
*Project funded by DARPA (ARPA 6814) and Aerospace Sponsored Research. Person to whom correspondence should be addressed.
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Abstract

Using a sintered Yba2Cu3Ox+6 wafer in high vacuum, we have measured the photo-ejected products and kinetic energies at selected UV laser wavelengths (351 nm, 248 nm, and 193 nm) where the laser fluence is maintained near product formation threshold. At these fluences, we are well below the above surface plasma formation threshold and do not detect; any evidence for surface melting. Our results show that, for a specific laser wavelength, both the ion and the neutral mass spectrum agree. The measured spectrum shows that the photablated products consist only of atomic and diatomic species. In addition, the oxygen is bound only to the yttrium and barium. Our measurements further show that, for a specific ejected species, the yield is dependent on both the laser fluence and wavelength. However, the measured KE distribution is independent of the laser fluence for fluences near threshold. The species are ejected with mean KE between 6–9 eV and no species has kinetic energy in excess of 13 eV Our results imply that for UV laser threshold fluence ablation, the excitation/desorption process is nonthermal.

Type
Research Article
Copyright
Copyright © Materials Research Society 1990

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References

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