Plasma diagnostic and analysis for the styrene polymerization by low pressure inductively-coupled plasma Z. LI , X. GILLON, M. DIALLO, L. HOUSSIAU, J. -J. PIREAUX University of Namur, FUNDP. Centre de Recherche en Physique de la Matière et du Rayonnement (PMR-LISE) Rue de Bruxelles, 61, B-5000 Namur, Belgium Abstract: Optical emission spectroscopy has been employed to investigate the species formed in the gas phase during styrene plasma polymerization, while Fourier Transform infrared spectroscopy was used to characterize the deposited materials. The optical emission spectrum shows the presence of CH radical and other species in the plasma and the IR spectrum evidences the aromatic and aliphatic CH bands of the deposited polymer. The information from the two spectroscopies is used to investigate the process of pulsed plasma polymerization. Keyword: plasma polymerization, polystyrene, optical emission spectroscopy, Fourier Transform infrared spectroscopy 1 Introduction Pulsed plasma polymerization processes at low temperature are of great interest for many applications, but highly depend on the discharge parameters. The desired surface composition and structure of a plasma deposited polymer requires the control of the monomer flow rate, the duty-cycle and the discharge power among other variable parameters such as the geometry of the system, the reactivity of the starting monomer, the frequency of the excitation signal and the temperature of the substrate. Therefore, pulsed plasma polymerization offers more advantages than other conventional chemical polymerization processes. Plasma is a mixture of free radicals, ions, electrons, excited molecules, metastables, energetic photons and neutral molecules. Radicals generated in a plasma can combine with other reactive species. A fundamental knowledge of the complex reaction processes in a plasma and an effective control of the types and relative ratios of free radicals and the other species are essential for a successful plasma organic synthesis. Diagnostics in a plasma deposition process are relatively difficult because practically all physical parts that are in contact with the plasma, interact with it and get coated. Therefore, it is necessary to develop improved diagnostic methods or instruments to get reliable results. In this paper, the plasma process is studied by optical emission spectroscopy (OES) in order to analyse the light emitted during the process. Specific surface properties of the deposited material, such as polymer chemical composition, hydrophobic or hydrophilic characteristics, roughness, and cross linking are also required. Deposited polymer films were therefore characterized by FTIR (Fourier Ttransform infrared spectroscopy). Hereafter, we present our experimental setup and analyse the optical emission spectra in the plasma and the infrared spectra of the deposited polymer surface. 2 Experimental apparatus 2.1 Plasma reactor The plasma reactor consists of three main parts: the planar source (ICP-P 200, JE PlasmaConsult GmbH, German), the gas injection system and the vacuum chamber (Fig. 1) Fig. 1 Schematic of the apparatus used in this work. The ICP-P 200 generator is an inductively coupled 13.56MHz RF plasma source with a matching unit for the efficient production of a high density, low temperature plasma. By using a planar, multi-turn spiral coil antenna, the RF field is coupled through a dielectric window (quartz) into the plasma chamber. The source can be operated in the 0.25-100Pa pressure range, its power can