Energy Conversion Efficiency in Plasma Polymerization – A Comparison of Low‐ and Atmospheric‐Pressure Processes

Abstract

In the plasma polymerization literature, there has been an interest since at least the 1970s to correlate the structure of plasma polymer (PP) deposits with plasma parameters during deposition, most particularly with the energy input per monomer molecule, E m . In our two laboratories, we have developed methods for measuring E m (or somewhat equivalent, E a ) in low-(LP) and atmospheric-pressure (AP) discharge plasmas. In this article we propose a new parameter, the so-called energy conversion efficiency, ECE, which permits direct comparison of LP and AP experiments. This is done for the case of three model monomer compounds, ethane, acetylene, and acrylic acid (AAc). ''Critical'' energy values that demarcate ECE regimes separating different fragmentation/reaction mechanisms agree remarkably well for all three monomers examined; resulting E m (or E a ) values are correlated with specific mechanisms, and the numerical results are convincingly supported by data from the chemical literature. Figure 6. FTIR spectra of (a) LP PP-AAc, and of (b) AP PP-AAc thin film deposits. Numbers in brackets represent values of energy per monomer molecule (in eV). Also shown are spectral assignments of the various observed absorption bands. Energy Conversion Efficiency in Plasma Polymerization.

DBD‐based plasma polymerization from monomer‐argon mixtures: Analytical model of monomer reactions with excited argon species

“…The decrease in wall flux (Figure b (right)) at low y is accompanied by the appearance of a straight segment in the j P ( y , h ) curve which flattens and expands towards larger y values as k rij are increased. Eventually a horizontal j P ( y , h ) curve is formed, as observed experimentally for plasma polymerization of TMS and hexenal, respectively . Remarkably, not only the experimental growth profile shape but also the absolute total flux are reproduced by the model calculation without further adaption of input data if k r has a value between 10 −11 and 10 −10 cm 3 s −1 , in good agreement with a literature value of k r 11 .…”

“…We also want to emphasize that the model outlined by Park and Kim and extensively used by Hegemann and coauthors (see references and papers cited in these publications) is inherently a “macroscopic kinetic” model in the sense that it considers an integrated or average deposition rate. Therefore, it results in a linear proportionality between mass deposition rate and monomer flow rate in the monomer‐deficient region.…”

Impact of hexamethyldisiloxane admixtures on the discharge characteristics of a dielectric barrier discharge in argon for thin film deposition

“…When following the concept of Hegemann et al and Watson et al and using as the energy uptake by the monomer molecules, the corresponding energy efficiency for HMDSO destruction reads as and it is also displayed in Figure . The increase of with increasing HMDSO fraction is much more pronounced than that of η , and exceeds 100% for x > 150 ppm.…”

“…It increases up to about 19% with increasing HMDSO fraction x in the parameter range considered. When following the concept of Hegemann et al [7,40] and Watson et al [39] and usingẼ m (27) as the energy uptake by the monomer molecules, the corresponding energy efficiencỹfor HMDSO destruction reads as…”

Energetics of reactions in a dielectric barrier discharge with argon carrier gas: VI PEG‐like coatings

“…Some of the present authors have recently shown that dielectric barrier discharge (DBD) plasmas with Ar as carrier gas can be used to deposit PP coatings from a wide variety of monomers, with precise knowledge of the energy per precursor molecule, , absorbed from the plasma's “energy reservoir.” In recent joint communications with D. Hegemann, this approach was even shown to permit comparisons between AP and LP PP processes, based on a new “energy conversion efficiency” (ECE) parameter reminiscent of the “Yasuda parameter— W/FM ” concept from the 1970s and 80s …”