(809d) Demonstration of Potential Opportunities in Photo-Initiated Chemical Vapor Deposition (piCVD)

Initiated chemical vapor deposition (iCVD) is an evolving technique that can be used for the gas-phase deposition of different polymers on a variety of substrates [1, 2]. A heated filament is used in the technique to generate radicals from gas-phase species (e.g. tert-butyl peroxide) that act as initiators for the polymerization process. An alternative is to use ultraviolet (UV) light to provide the energy required to generate free radicals for the process [3, 4]. This photo-initiated chemical vapor deposition (piCVD) would enable much lower substrate temperatures to be achieved, thereby enhancing deposition rates for adsorption-controlled processes. The opportunity lies in finding simple, inexpensive chemicals that provide free radicals upon exposure to UV light and that may be used as universal initiators for the polymerization of different monomers.

Polymerization and deposition of hexyl acrylate monomer (HA) on silicon wafers was carried out under UV light. It was observed that HA demonstrated auto-polymerization under a wavelength of 254 nm. Deposition rates were characterized under different operating conditions (e.g. P_m/P_sat ratio, monomer flow rate etc.). Investigation was carried out to see if this property of HA could be harnessed to drive the polymerization and deposition of other monomers (e.g. ethyl acrylate) that are otherwise not auto-polymerizable under UV light of wavelength 254 nm.  

[1] K. K. S. Lau, K. K. Gleason, Macromolecules 2006, 39, 3688

[2] W. E. Tenhaeff, K. K. Gleason, Adv. Funct. Mater. 2008, 18, 979

[3] K. Chan, K. K. Gleason, Langmuir 2005, 21, 11773

[4] T. P. Martin, K. L. Sedransk, K. Chan, S. H. Baxamusa, K. K. Gleason, Macromolecules 2007, 40, 4586