Investigation of mechanisms for plasma polymerization of organic thin films

An inductively-coupled continuous wave (CW) rf plasma was used to study the effects of hydrogen addition (0–97.5%) on thin films deposited from saturated fluorocarbon (CF₄ and C₂F₆) plasmas. Bulk and surface properties of the deposited films were determined using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Deposition rates and contact angles are determined for all films. These analyses indicate a strong dependence of the bulk and surface chemical structure on the hydrogen content of the feed for both C₂F₆ and CF₄ plasmas. In addition, the use of a variable duty cycle, pulsed rf plasmas was employed for comparison to the CW results. Significantly different film chemistry and deposition rates are observed in contrasting CW with equivalent power pulsed plasmas. The use of a variable duty cycle pulsed rf plasma results in a high CF₂ content fluoropolymer with unique properties.; Pulsed plasma polymerization is used to produce aromatic thin films from benzene, 1,2,4-trifluorobenzene and hexafluorobenzene plasmas. The effects of aromatic monomer fluorination and duty cycle variation on the resulting films' properties were examined. Systematic changes in film chemistry are observed with the lowest duty cycles producing films containing substituted aromatic rings.; Pulsed plasma polymerization of benzaldehyde was used to produce thin films containing aldehyde functional groups. The effects of pulse peak power, pulse on time, duty cycle, and monomer pressure on film composition, especially aldehyde functional groups, and surface polarity were examined. Surface and bulk analyses show retention of the aromatic structure occurs with the longest off times and smallest duty cycles while retention of the aldehyde group occurs only under plasma conditions that result in fragmentation of the aromatic ring, higher peak pulse power and a relatively large duty cycle (20%).; The imaging of radicals interacting with surfaces (IRIS) technique was used to collect spatially-resolved lasr-induced fluorescence (LIF) images of CF2 radicals from 100% C2F6 and 50/50 C2F6/H2 plasmas interacting with a variety of organic and inorganic substrates. Simulation of LIF cross-sectional data shows high scattering coefficients for CF2 radicals using 100% C2F6 plasmas. These extremely large scattering coefficients (>1.0) indicate CF₂ molecules are generated through plasma interactions with the substrate. In contrast, scattering coefficients for CF2 radicals using a 50/50 C2F6/H2 plasma are <1.0 and a fluorocarbon film is deposited. Fluorocarbon film formation and CF₂ surface generation mechanisms are discussed, with consideration of CF and ion bombardment contributions to the generation of CF₂ and the creation of active sites for deposition.