Structural Correlation Study of Pulsed Plasma-Polymerized Fluorocarbon Solids by Two-Dimensional Wide-Line Separation NMR Spectroscopy

Abstract

Two-dimensional wide-line separation (WISE) NMR spectroscopy has been applied to obtain structural correlation in fluorocarbon films deposited via a pulsed plasma enhanced chemical vapor deposition. Films from two pulsed deposition conditions, 10/20 and 10/400 ms on/off times, were analyzed in detail. Onedimensional 19 F and 13 C NMR results agreed well with prior studies of these films using X-ray photoelectron spectroscopy, which showed greater CF 2 fractions with decreasing pulsed deposition duty cycle. 13 C CPMAS studies, in addition, distinguished between unsaturated and saturated fluorocarbon species in these films. However, 19 F-13 C WISE allowed further differentiation of fluorocarbon moieties by the difference in nearestneighbor connectivity. The 10/20 film showed a prevalence of at least two inequivalent CF 3 species. A weak presence of unsaturated )CF-species was also detected. No specific CF 2 moiety was resolved, which was attributed to significant chemical shift dispersion and heterogeneity in CF 2 bonding environment. In contrast, the 10/400 film displayed an increased proportion of CF 2 species, predominantly as -CF 2 CF 2 -and CF 3 CF 2 -groups, and less CF 3 termination, indicative of a structure approaching that of poly(tetrafluoroethylene). These observations support the hypothesis of a less aggressive deposition environment, inducing less cross-links and unsaturation and promoting linear chain propagation, with a longer pulse off-time during deposition. Spinning sideband patterns in the 19 F dimension of NMR spectra did not severely hinder spectral interpretation but instead offered a means of revealing motional differences in the fluorocarbon moieties.

Plasma Polymerization of Thin Films: Correlations between Plasma Chemistry and Thin Film Character

“…Recently, several groups have demonstrated that increased chemical character of the desired polymer functional group is retained if the radio frequency (rf) plasma source is pulsed at frequencies in the hertz to kilohertz range. [7][8][9] Models have predicted that pulsing the discharge may be a unique means to controlling the kinetic processes in the plasma. 10 However, the mechanisms that lead to the plasma deposition of high-quality functional polymers are still poorly understood.…”

“…A great deal of focus has been placed recently on surface functionalization strategies using low-power glow discharges. − Strategies have included direct deposition of the functional group through PECVD methods or activation of the surface by creating reactive groups and derivatizing or by grafting molecules in place. Recently, several groups have demonstrated that increased chemical character of the desired polymer functional group is retained if the radio frequency (rf) plasma source is pulsed at frequencies in the hertz to kilohertz range. − Models have predicted that pulsing the discharge may be a unique means to controlling the kinetic processes in the plasma …”

Probing the Role of Side-Chain Interconnecting Groups in the Structural Hydrophobicity of Comblike Fluorinated Polystyrene by Solid-State NMR Spectroscopy

“…Structures of fluorinated polymers have been widely investigated by a variety of analysis techniques, including wide-angle X-ray diffraction (WXRD), small-angle X-ray scattering (SAXS), grazing-incidence small-angle X-ray scattering (GISAXS), near-edge X-ray absorption fine structure (NEXAFS), and nuclear magnetic resonance (NMR) spectroscopies. ,− Among them, NMR spectroscopy, especially solid-state NMR, is the most effective and useful tool in elucidating the dynamics and structure of the fluorinated polymer because it can ascertain the structural features of the fluorinated polymer from the molecular dynamic (or motional) heterogeneity caused by the structural difference of the fluorinated polymer. − As NMR parameters for investigating molecular motion, the spin–lattice relaxation time in the laboratory frame ( T 1 ) and the spin–lattice relaxation time in the rotating frame ( T 1ρ ) provide accurate insight into the molecular motion of the polymer. T 1 presents the overall motion of the polymer chain on the time scale of the resonance frequency (MHz order), and the local motion of the polymer that occurs in the kHz motional regime can be identified from the decay behavior of the T 1ρ magnetization relaxation.…”

Phase Controlled Class E Amplifier Characteristics for Pulsing Applications

“…This can be achieved using square-wave pulses with periods from 10 to 100 μs [10]- [12]. Furthermore, it has been seen that quality of the deposited thin films is improved and dust particles in the plasma chamber is reduced with the application of RF signal when it is presented in the form of PWM signal instead of continuous signal [13], [14]. The demand to improve the process quality in semiconductor fabrication led to the design and implementation of amplifiers with high-power pulsing capability.…”