(28b) Comparison of the Plasma Polymerization Domains for Deposition of Various Organosilicon Monomers Using Atmospheric Pressure Plasma

Organosilicon thin films are important materials for applications spanning dielectric thin films, corrosion protection, biocompatible coatings, and scratch resistance of polymers.  Low temperature atmospheric plasma polymerization has become increasingly adopted to create films from organosilicon reagents.  This study aims to enhance understanding of the atmospheric plasma deposition process and develop characterization methods that enable prediction of properties and tailoring of the films.  In this investigation, the plasma polymerization behavior of several types of organosilicon reagents was evaluated to elucidate the energy domains of the process.  The organosilicon materials included hexamethyldisiloxane (HMDSO),  decamethylcyclopentasiloxane (D5), tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES),  and bis(trimethoxysilyl)hexane (BTMSH).  A pulsed atmospheric pressure plasma jet was used with air as the plasma gas and with constant frequency, duty, air flow rate, and exposure time.  Energy input to the plasma gas and the monomer flow rates were varied for all monomers.  The normalized energy input parameter that is classically implemented in low pressure plasma polymerization processes was applied in this investigation by dividing the input power by monomer flow rate.  The process and plasma deposited films were characterized using normalized deposition rate, Fourier Transform Infrared (FTIR) spectroscopy, and X-Ray Photoelectron Spectroscopy (XPS).  This analysis revealed the energy-deficient and monomer-deficient domains for the deposition process of each monomer.  The comparison among the monomers revealed groupings of the monomers based on similar resulting trends.   In particular, HMDSO and D5 deposition processes and resulting film properties followed the same trend, although the monomers vary significantly in properties and safety.  Also, TEOS, MTES, and BTMSH were grouped together in a separate trend from HMDSO and D5.  The outcomes and groupings are explained by specific chemical features present in the monomers.