Investigation on RF styrene plasma by emission spectroscopy

In order to gain an insight into the processes in an RF styrene plasma, gas phase plasmas were investigated by emission spectroscopy. The plasma reactor was a bell-jar-type chamber with two parallel plate electrodes. The measurement of plasma emission spectra was made with axial resolution. The correlations among the emission intensities of CH and C₄H₂⁺ species, the polymer deposition rate and the polymeric structure of the deposited films were studied. The proposed analysis showed that the gas flow pattern in the plasma reactor, and the difference in collisions between styrene monomer molecules and energetic free electrons occurring in the plasma region and RF sheath, made the fragments and ions produced change in the different regions, resulting in a change in polymeric structure and deposition rate of the polymer films. With increasing distance between the substrate position and the lower electrode, the deposition rate and the concentration of phenyl groups both at the polymer surface and in the bulk decreased