Plasma polymers formed in radio frequency sustained nonequilibrium plasma

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Plasma polymers formed in radio frequency
sustained non-equilibrium plasma

• Morgan Alexander

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Plasma
A fluorescent lamp is a gas-discharge lamp that
uses electricity to excite mercury vapor in argon
or neon gas, resulting in a plasma that produces
short-wave ultraviolet light. This light then
causes a phosphor to fluoresce, producing visible
light.0
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Radio frequency sustained non-equilibrium plasma
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Plasma components

• Electrons
• Monomer
• Radical monomer molecules and molecular and
  atomic fragments
• Positive molecules
• Negative molecules
• Radiation, including visible and vacuum UV
• Substrate-sheath

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Examples of reactions which can occur in the
plasma phase of a di-atomic gas

• Reactions of electrons
• Ionization
• e- X-X ? X-X 2 e-
• e- X ? X 2 e-
• Dissociative ionization
• e- X-X ? X X 2 e-
• Dissociation
• e- X-X ? 2X e-
• Dissociative attachment
• e- X-X ? X- X
• X- X e-
• Attachment
• e- X-X ? X-X-
• e- X ? X-
• Recombination
• e- X ? X
• e- X-X ? X-X

• Reactions of ions
• Charge transfer
• X X-X ? X-X X
• X-X X ? X-X X
• X- X-X ? X-X- X
• X-X- X ? X-X X-
• Detachment
• X- X ? X-X e-
• X- X-X ? X-X X e-
• X-X- X ? XX X-X e-
• X-X- X-X ? 2 X-X e-
• Ion-ion recombination
• X- X ? X-X
• X- X-X ? X-XX
• X-X- X ? X-X X
• X-X- X-X ? 2 X-X
• Atom recombination
• 2 X ? X-X

A.T. Bell, Chapter 1 in Techniques and
Applications of Plasma Chemistry, Eds. J.R.
Hollahan and A.T. Bell, Johan Wiley, New York,
(1974).
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Yasuda (1985)
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A new positive ion mechanism
O'Toole, L. Beck, A. J. Ameen, A. P. Jones, F.
R. Short, R. D., Radiofrequency-Induced Plasma
Polymerization of Propenoic Acid and Propanoic
Acid. Journal of the Chemical Society-Faraday
Transactions 1995, 91, (21), 3907-3912.
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More positive ion mechanisms
Alexander, M. R. Jones, F. R. Short, R. D.,
Mass spectral investigation of the
radio-frequency plasma deposition of
hexamethyldisiloxane. Journal of Physical
Chemistry B 1997, 101, (18), 3614-3619.
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Surface MS (ToF SIMS)
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Experimental setup required to detect negative
ions
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Peculiarities of PPs
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Summary

• A large range of reactions are possible in
  plasma.
• Initial plasma polymerisation mechanisms were
  speculative based on conventional chemistry.
• Much subsequent work has sought to measure the
  species in organic plasmas, revealing other
  potential mechanisms.
• Plasma polymers are often unstable due to a high
  concentration of trapped free radicals. T
  Gengenback