DIRECT CURRENT PLASMA POLYMERIZATION REACTOR FOR THIN DUROMER FILM DEPOSITION B. BUTOI 1 , C. BEREZOVSKI 1 , D. STAICU 1 , R. BEREZOVSKI 1 , A. M. MARIN 2 and E.S. BARNA 1* 1 University of Bucharest, Faculty of Physics, PO Box Mg-11, 077125, Bucharest, Romania 2 University of Medicine and Pharmacy “Carol Davila”, No. 8 Eroilor Sanitari Blvd., Bucharest, Romania * corresponding author (email: barna_emil@yahoo.com) Abstract: Plasma polymerization is a technique for obtaining thin polymer films on a substrate surface from organic monomers by means of plasma discharge. In glow discharge polymerization the monomer structure is not retained, yet the original monomer molecules serve as a source of elements for the formation of larger molecules. Here we present a new model of variable geometry Direct Current (DC) plasma polymerization discharge reactor, demonstrating some clear advantages over the already existing devices. The way our reactor is built allows for dynamically changing all of the most important discharge parameters for the polymer deposition. By carefully adjusting these main quantities, one can obtain countless duromer thin film structural morphologies exhibiting interesting chemical and physical features. Key words: direct current plasma reactor, plasma polymerization, monomer, charged particles, surface properties 1. Introduction Human produced plasma is commonly used in various areas, due to its important role in the processing of industrial materials, such as: engraving, removal, pulverization, thin film developing etc. In its true meaning, plasma may be defined as a cvasineutral electric system formed of particles which are charged and neutral, having collective behaviour, photons, and electromagnetic fields. Positive charged particles are atomic or molecular ions and the negative ones are, usually, electrons, or, in particular cases, they are both electrons and negative ions. The neutral particles are those atoms or molecules which may be found in a fundamental state or in different excited states [1-3]. Plasma contains a mix of particles with different masses and electrical charges. At first sight, by thermal point of view, plasma may be considered to be made up of two subsystems, one of electrons and one of the heavy particles (molecules, neutral atoms and ions), each of them being in thermal equilibrium. This is why ions and electrons can be characterized by their own temperatures: the ion temperature (Ti) and the electron temperature (Te). In particular cases, other temperatures can characterize the particles in plasma. At the same time, the heavy particles in the plasma can be characterized by the temperature of the gas (Tg), the temperature of the excitation (Tex), the temperature of the ionization (Tion), the temperature of dissociation (Td) and the temperature of radiation (Tr). [4-6] The thermodynamic equilibrium in plasma is reached only if: Tg = Tex = Tion = Td = Tr = Te (1) The thermodynamic equilibrium cannot be reached since Tr at the external limits of the plasma is never equal to the value of Tr for the core region. Nevertheless, in certain conditions, a local thermodynamic equilibrium (LTE) can be achieved. Generally, in the low pressure plasmas, the stabilization condition of LTE is not fulfilled. For these types of plasma, the temperature of the electrons is the most important parameter [2-4,7,8]. Plasma polymerization technique makes use of plasma sources to generate a discharging gas that supplies the energy to activate or fragment a liquid or gas monomer (often containing a formation of vinyl) in order to start the polymerization process. Generally, the resulting polymers are very ramified, reticular and adhere very well to solid surfaces, unlike the usual polymers created by means of classical methods. Some of the main properties of the ramified polymers are considered elsewhere [9]. The greatest advantage offered by plasma polymerization is that polymers can be directly attached to the desired surface, while the chains are growing, reducing the number of steps necessary for other processes for covering (i.e. grafting). This is an important phase for covering surfaces from 1000 pm, to a thickness of hundreds of microns, with otherwise insoluble polymers [10]. The mechanism of