Powder Formation in Gas Phase

The formation of powders in luminous gas phase has significant implications in the processing of LCVD. In an attempt to obtain a uniform nanofilm on a substrate, the powder formation in gas phase ruins the product. On the other hand, the analysis of powder formation as a function of operational parameters provides important information pertinent to the growth mechanism and the deposition mechanism of LCVD, by which growing species deposit on the surface. 

The excessive formation of powders occurs only under limited conditions, although powder formation has been observed in reactors of different designs and types of discharge and with various monomers, particularly in a specific section of a reactor that is related to the flow pattern of gas. Therefore, powder formation provides an excellent opportunity for examining the basic principles of the polymer deposition mechanism. 

A minimal inert gas pressure of 0.6 torr is necessary to form powders exclusively. The upper limit of pressure is due to the reactor, which cannot be operated above 3.0 torr, at which pressure the plasma extinguished. 

Among the monomers investigated, the aromatic hydrocarbons (group I monomers) were most efficient in forming powders. 

Most powders consisted of a large portion of the soluble polymer (as high as 90%) in tetrahydrofuran, which indicates that the kinetic pathlength in powder formation is very short. 

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