LCVD in a Closed Reactor System

In flow system LCVD, the system pressure is continuously adjusted by controlling the opening of a throttle valve connected to the pumping system. Because of fragmentation of the original monomer in the plasma state, the composition of the gas phase changes on the inception of the plasma. The increase in the total number of gas molecules is compensated by the increased pumping rate in a flow system, and 

In the final stage, after 120s, both the silicon-containing and carbon-containing species have been consumed by the LCVD deposition. In the gas phase, only hydrogen is left in the plasma system and no further deposition occurs. Therefore, it is anticipated that there will be no further thickness growth of the TMS plasma coatings after 120 s. 

It was found that the characteristic plasma deposition rate of Si-containing organic compounds is nearly six times than that of hydrocarbons [5]. It is therefore anticipated that Si-containing moieties would deposit faster than C-based moieties leading to an Si-rich depositions from TMS, which contains one Si and three C in the 

Considering the fact that the refractive index continues to increase after most of the polymerizable species are exhausted in the gas phase, DC LCVD of TMS in a closed system contains the aspect of LCVT of once-deposited plasma polymer coating by hydrogen luminous gas phase. In the later stage of closed-system LCVD, oligomeric moieties loosely attached to a three-dimensional network are converted to a more stable form, and significantly improved corrosion protection characteristics (compared to the counterpart in flow system polymerization of TMS) were found, details of which are presented in Part IV. Thus, the merit of closed-system cathodic polymerization is well established. 

Meichsner, J. Arzt, M. Friedrich, M. Rochotzki, R. Kreyssig, E. Surface and Coatings Technology 1993, 59, 365. 

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