AVS 51st International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA6
Computational Investigation of the Role of Polyatomic Ions in Plasma Polymer Deposition

Tuesday, November 16, 2004, 3:00 pm, Room 213B

Session: Plasma and Polymers
Presenter: S.B. Sinnott, University of Florida
Authors: I. Jang, University of Florida
W.-D. Hsu, University of Florida
S.B. Sinnott, University of Florida
Correspondent: Click to Email
Fluorocarbon plasmas are widely used to chemically modify surfaces and deposit thin films. It is well-accepted that polyatomic ions and neutrals within low-energy plasmas have a significant effect on the surface chemistry induced by the plasma. For this reason, the deposition of mass selected fluorocarbon ions are useful for isolating the effects specific to polyatomic ions. In this study, the detailed chemical modifications that result from the deposition of beams of polyatomic fluorocarbon ions (C@sub 3@F@sub 5@@super +@ and CF@sub 3@@super +@) on polystyrene surfaces at experimental fluxes are identified using classical molecular dynamics simulations with many-body empirical potentials. The ions are deposited at incident energies of 50 or 100 eV/ion. For CF@sub 3@@super +@ deposition, F atoms play the most important role in fluorinating the polystyrene surface, as the majority of F atoms are covalently attached to the polymer chains through replacement of native H atoms or capping the ends of broken chains. CF@sub 2@ fragments are also an important long-lived species. In contrast, F atoms are a minor bi-product and CF@sub 2@ fragments are the most dominant species for C@sub 3@F@sub 5@@super +@ deposition on polystyrene. Thus the simulations explain the experimental finding that C@sub 3@F@sub 5@@super +@ is more efficient at producing fluorocarbon thin films. In particular, many larger fragments produced by C@sub 3@F@sub 5@@super +@ ion deposition contain more than one C atom, may have more than one active site, and readily react to grow polymer-like structures. In contrast, F atoms, the most dominant fragment in CF@sub 3@@super +@ deposition, effectively deactivate potential film nucleation sites when they fluorinate the polymer surface. We compare these findings to results for the deposition of comparable hydrocarbon ions (C@sub 3@H@sub 5@@super +@ and CH@sub 3@@super +@). This work is supported by the National Science Foundation (CHE-0200838).