Ablation-influenced LCVD

As soon as plasma is created, the gas phase is no longer the vapor of the original monomer but becomes a complex mixture of the original monomer, ionized species, excited species of the original monomer, excited species of fragments from the monomer, and gas products that do not participate in polymer formation such as H2 and F2. Perfluorocarbons represent perhaps the most extreme case of ablation competing with polymer formation. The principle found with perfluorocarbons, however, should be applicable to nearly all cases. 

Because solid materials must maintain the vacuum, the reactor wall always exists in an LCVD reactor. The plasma also interacts with wall materials as well as any other materials that exist in the plasma, such as substrate and support. Therefore, polymer-forming intermediates and gaseous by-products may also originate from solid materials with which plasma interacts by virtue of the ablation caused by the luminous gas. In this sense, any material that interacts with plasma becomes a source of monomer for plasma polymerization. 

it is clear that the balance between polymer formation and ablation is dependent not only on the chemical nature of the monomer, the wall material, the substrate, and so on, that come into contact with the luminous gas phase, but also on the discharge conditions, particularly the energy density given by WjFM. 

Engelman, R.A. Yasuda, H.K. J. Appl. Polym. Sci., Appl. Pol . S5mip. 1990, 46, 439. Sun, B.K. Cho, D.L. O Keefe, T.J. Yasuda, H. Chemically graded metalization of nonconducting substrates by glow discharge plasma pol5merization technique. In Metallized Plastics I, Mittal, K.L., Susko, J.R., Eds. Plenum Press New York, 1989 9-27. 

Tibbitt, J.M. Shen, M. Bell, A.T. Thin Solid Films 1975, 29, L43. 

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The creation of reactive species that cause ablation is essentially the same process as that occurs in LCVD, except that the final result is completely opposite, i.e., ablation vs. deposition. In this context, ablation by luminous gas could be described as luminous chemical vapor treatment (LCVT). Therefore, the dependence of ablation on operational parameters in LCVT is very similar to that of LCVD, which is discussed in more detail in Chapter 4. The chemical ablation of polymeric materials by O2 plasma [6] is described here to demonstrate how oxidative ablation is influenced by the operational parameters of discharge. 

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