Research project P7/34 (Research action P7)
Domain:
The physical chemistry of plasmas – the fourth state of matter – is a field of growing importance that yields both fundamental and industrial challenges. Indeed, highly reactive species generated in plasmas have found applications in surface treatments, material synthesis and/or processing, environmental and bio-medical fields. Although many industrial and large-scale applications have been developed, the understanding of the actual mechanisms in the core of plasmas as well as at the interfaces remains, to a large extent, unknown. It is the role of university research groups to explore, understand and master these mechanisms.
Today, the different disciplines involved in plasma research have reached a status demonstrating that many fundamental phenomena are common among them. An integrating multi-disciplinary approach is necessary to infer cross-fertilization and to make progress.
Such a dynamic as described in the previous lines has been initiated at the Belgian level during the 6th phase of the IAP program. We propose to capitalize on the main outputs of this 6th phase project.
Objectives:
The present project aims at federating Belgian groups involved in research activities on reactive plasmas in order to improve our fundamental understanding of these systems and to develop predictive models. The output of this project, which combines experimental and theoretical activities, is expected to drive technological developments in the area of new materials, new surfaces or new coating processes, and therefore to sustain the economic development of our country. We are developing a multidisciplinary and integrated approach, merging together the expertise of research units specialized in plasma diagnostics (optical, electrical probe, laser induced fluorescence and mass spectrometry techniques), in the fundamental study of the ionized gas phase and its hydrodynamics, in bulk plasma and plasma-surface interaction modeling (molecular dynamics, Monte Carlo) and in (organic and inorganic) material synthesis, functionalization and characterization using state-of-the-art tools.
During the 6th phase of the IAP program we initiated a dynamic based on a global approach of plasmas. Now we want to capitalize on the main outputs of the last five years: (1) development of characterization techniques of the plasmas (arc, HiPIMS, RF, glow, DBD...), (2) building of modeling tools for high and low pressure plasmas, (3) development of a kinetic MonteCarlo code for the nucleation and growth of inorganic films, (4) TiO2 synthesis by using different excitation sources, establishment of a global energy/crystalline phase diagram and (5) deposition of various polymers (polystyrene, polyethyleneglycol, …), and of copolymers. Following the recommendations of the experts, we propose (1) to consolidate the network with new partners specialized in plasma-materials interaction chemistry (extending the research and modeling capabilities), (2) to introduce an activity in ‘plasma catalysis’, which is internationally gaining increasing interest and (3) select the search space which requires combination of expertise of the different consortium partners. Thus, we want to build a larger know-how on the results obtained during the first five years and to understand more complex systems in the framework of plasma-surface interactions. The added complexity lies in the composition (i.e. mixed oxides), the structure (porous materials) and the impact of the solid phase on the gas phase (plasma catalysis). In addition, a special attention will be given to the training of young scientists and to the transfer of know-how through the organization of a virtual PhD school, dedicated workshops and international events.
Methodology:
Based on the respective experience of the partners, the experience acquired during the 6th phase of the IAP program, and a careful analysis of the current international research, we are proposing to structure the project around the type of interactions taking place between the plasma and a solid surface. The distinction between the interactions is especially visible in the experimental part. Nevertheless, similar characterization tools for plasmas and surfaces will be used in the three experimental workpackages.
Workpackages I and III will focus experimentally on the interaction of plasma with an inorganic material. In WP I, the impact of the gas phase composition and particle energy on growing oxide films will be tackled. Metal oxide compounds, namely TiO2 and ZrO2, will be used as standard systems. The main idea in WP I is, based on what we learn in the previous IAP program, to unravel the different energetic contributions during the films growth. Specific experiments will therefore be implemented. Supporting this work, strong plasma diagnostics will be performed by using state-of-the-art techniques (laser induced fluorescence, time-resolved mass spectrometry, …). The implementation of mobile magnetron sputtering and arc chambers will be done in order to access the diagnostic facilities of the different partners. The combination of these data with the thin film features would allow contributing significantly towards the understanding of the key mechanisms defining the material chemical and crystalline properties. WP III on the other hand, will investigate the impact of the solid phase (catalyst) on the composition of the gas phase and on the discharge itself. How the interactions between the catalyst and the discharge can impart selectivity and specificity to the chemical reactions taking place in the gas phase and modify the degradation of molecules (CO2, CH4) will be a key parameter to study and model.
Workpackage II is dedicated to an experimental investigation of the interaction between plasma and organic surfaces. Two topics will be developed in WP II in close collaboration with modeling groups: the growth of plasma polymer films and the functionalization of polymer surfaces. The common experimental strategy is, in addition to a strong plasma diagnostic activity; to evaluate in situ the mechanisms on going at the plasma-surface region. Identification and quantification of surface radicals will be performed by in situ chemical derivatization while a dedicated tool (IRRAS) will be purchased by the network to get a real time in-situ evaluation of the surface chemistry. The systems to be studied in the experimental workpackages are model systems with a limited number of reactants. In such a way it is possible to fully characterize them and to make the link with the numerical simulations.
Workpackages IV and V are dedicated to the modeling of the phenomena taking place in the bulk plasma and at the interface respectively. These two workpackages are highly dependent on each other and an effort of integration through the development of a platform to favor the exchange of data between the various codes will be carried out. The plasma bulk modeling will be mainly based on the PLASIMO code developed by TU/e, as well as on some codes available at UA for plasma chemistry modeling. Creation and losses of plasma species as well as recombination, impact ionization, ion-atom interchange and charge exchange will be taken into consideration. Kinetic aspects will also be investigated. For the modeling of plasma-surface interactions various approaches will be applied: molecular dynamics (MD), hybrid model (MD with Monte Carlo), and quantum chemical studies (for smaller systems). The results of the numerical simulations will be used to understand the phenomena taking place in the experimental set-ups but will also provide inputs to improve them.
The five « research » workpackages are strongly interconnected and will contribute significantly towards our understanding of (i) the fundamental phenomena taking place in the plasma and (ii) the plasma-surface interaction itself.
The last workpackage (VI) is dedicated to training and dissemination. This workpackage is essential to insure the survival and the long-term impact of the project and will include activities directed towards PhD and post-doctoral fellows as well as international dissemination towards the scientific community (conferences, workshops). Common PhD students and mobility of researchers inside the IAP network and the international network developed by the partners will be encouraged.
