Variations in Cross-link Density with Deposition Pressure in Ultrathin Plasma Polymerized Benzene and Octafluorocyclobutane Films
Someswara R. Peri, Brian Habersberger, Bulent Akgun, Hao Jiang, Jesse Enlow, Timothy J. Bunning, Charles Majkrzak, Mark D. Foster
For ultrathin, plasma polymerized (PP) films, variations in structure with depth near the substrate and near the surface are much more readily apparent than in thick films. Neutron reflectometry (NR) measurements of ultrathin PP-films from octafluorocyclobutane (OFCB) and benzene (B) precursors deposited using Plasma Enhanced Chemical Vapor Deposition (PECVD) at two pressures (0.6 and 0.05 torr) reveal that under both deposition conditions there is a 70 Å-thick surface layer, which has structure different than that deeper in the film. A transition region next to the substrate in which the structure varies markedly, over a very small depth, is also observed for both precursors at both pressures. The observation of both, not seen previously in much thicker films of each , is attributed to the ultrathin nature of the PP-films and an increase in deposition power from 30 to 45 W used to fabricate the films. NR measurements of films swollen with solvent reveal that the density of cross-linking next to the substrate is lower than that in the middle of the film or the region adjacent to the surface of the film for both precursors. Variations in the cross-link density with processing pressure are much stronger for PP-B films than for PP-OFCB films. Sensitively resolving the internal structure variations that come with changes in process conditions is crucial for tailoring plasma polymerization for the creation of waveguides, passive filters and capacitors.
, Habersberger, B.
, Akgun, B.
, Jiang, H.
, Enlow, J.
, Bunning, T.
, Majkrzak, C.
and Foster, M.
Variations in Cross-link Density with Deposition Pressure in Ultrathin Plasma Polymerized Benzene and Octafluorocyclobutane Films, Polymer, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=904809
(Accessed March 1, 2024)