Plasma polymerization: chemical analysis of the plasma gas phase

The polymerization by radiofrquency (RF) plasma of different monomers (methyl methacrylate (MMA), tetraglyme and 2-hydroxyethyl methacrylate (HEMA)) has been carried out. The plasma gas was investigated by optical emission spectroscopy (OES) in the UV-vis wavelength rang. The excited species formed in the plasma were identified for the different monomers. From computer simulations of the ro-vibration bands, the rotational and vibrational temperatures were derived for the molecular bands of different diatomic excited species. In the tetraglyme plasmas, nitrogen impurity was found, where excited radicals CN, N2 , and N2 were observed. The vibrational temperatures derived from the analyses of the different emission bands are close to each other (≈3800K). On the other hand, the XPS surface analysis of deposited thin films did not show any contamination of nitrogen. Correlating information between the plasma gas and the deposited organic thin films is important to understand the physical and chemical processes leading to organic polymer formation by plasma.