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Threshold Fluence UV Laser Ablation of Single Crystal Bi2Sr2Ca1Cu2O8: Product Population and Kinetic Energy Distributions of Ejected Ionic Species

Published online by Cambridge University Press:  26 February 2011

Lawrence Wiedeman ,
Hyun Sook Kim  and
Henry Helvajian
Lawrence Wiedeman
Affiliation:
Laser Chemistry & Spectroscopy Department, Aerophysics Laboratory, The Aerospace Corporation, P.O. Box 92957, Los Angeles, California 90009
Hyun Sook Kim
Affiliation:
Laser Chemistry & Spectroscopy Department, Aerophysics Laboratory, The Aerospace Corporation, P.O. Box 92957, Los Angeles, California 90009
Henry Helvajian*
Affiliation:
Laser Chemistry & Spectroscopy Department, Aerophysics Laboratory, The Aerospace Corporation, P.O. Box 92957, Los Angeles, California 90009
*
Person to whom correspondence should be addressed.
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Abstract

We have conducted an experiment which measures the product population and kinetic energy (KE) distributions from the UV laser induced decomposition of crystalline Bi2Sr2Ca1Cu2O8. We have measured these distributions at two laser wavelengths 248, 351. At a third wavelength (355 nm) we have measured the photoejected mass spectra from both a single crystal Bi2Sr2Ca1Cu2O8 sample and a polycrystalline Bi2Sr2Ca2Cu3O10 sample. For all the experiments, the laser fluence is maintained near the threshold for ion formation. The laser fluences are well below the level for instigating a laser induced above surface plasma. Our results show that the ejected products are not the consequence of a laser surface evaporation process. We measure a wavelength dependence in the ejected species population distribution and the ejected kinetic energy distribution (< KE > = 5 ± 1 eV.2eV FWHM) is indicative of an electronic excitation process. The measured ion mass spectra show atomic, diatomic (e.g. Sr2+), and oxide (e.g. SrO+, CaO+) species with lesser quantities of the complex oxides (e.g. S2O+). Distinctly absent from the mass spectra are the oxide compounds BiO+, CuO+, and the atomic species O+. Furthermore, the mass spectrum shows that at 248 nm laser excitation, the Bi+ species is the abundant photopro-duct. However, for both the 351 nm and 355 nm excitations, the Sr+ and SrO+ ions are measured as more abundant. Also, comparing the 355 nm laser excitation of the single and polycrystalline samples, there is very little difference in the photoejected species mass spectrum.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 201: Symposium A – Surface Chemistry and Beam-Solid Interactions , 1990 , 575
Copyright
Copyright © Materials Research Society 1991

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Footnotes

*

National Academy of Science (NRC) Post Doctoral Fellow.

References

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