Caractérisation de décharges à barrières diélectriques atmosphériques et sub-atmosphériques et application à la déposition de couches d'oxyde de silicium

Dielectric Barrier Discharges (DBD) have been used for more than a century, especially for ozone production. Research conducted within the last twenty years has investigated the discharge mechanisms involved and the different discharge regimes observable (filamentary, glow, Townsned and multi-peaks). These studies highlight the fundamental role of metastable species to establish and maintain a homogeneous discharge. These recent improvements in understanding the physics of DBD's open perspectives for new applications and new interests in atmospheric pressure surface treatment. Working at atmospheric pressure for silicon oxide deposition is of great interest : the possibility of continuous process, no vacuum component costs and maintenance, no loading/unloading time. However, in comparison with a classical plasma enhanced chemical vapor deposition (PECVD) process, the high pressure and thus the high gas density may result in a gas phase chemistry and a larger formation of dust particles. Exploring a new pressure range from 10 to 1000 mbar could be an alternative for this process. In the first part of this work the effect of the pressure on a DBD in non-reactive gases (helium, argon and nitrogen), then in neutral gas/oxygen mixture has been investigated with electrical measurements (discharge current and applied voltage), with high-speed imaging and with time-resolved optical emission spectroscopy. The second part of this work is dedicated to SiOx barrier coating characterization (FTIR-ATR, XPS, AFM and SEM) as a function of pressure in oxygen/hexamethyldisiloxane (HMDSO) gas mixture highly diluted in nitrogen. The exploration of discharge regimes as a function of pressure shows, in nitrogen, a progressive transition from Townsend to multi-peaks regime between 320 and 160 mbar. A detailed study of this regime in helium and nitrogen with high-speed imaging shows that each multi-peak corresponds to a new spatially homogeneous discharge. However, the discharge is not completely extinguished between each pulse and the remaining light emission reveals the metastable activity (excitation transfer or Penning effect). Paschen's curves obtained from electrical characterization of the discharge show an inversion (compared to standard cuves) of argon and helium cuves. This inversion shows the importance of metastable energies and capabilities to ionize almost all impurities, in the case of helium. This explains why in helium a breakdown under a lower electric field than in argon is possible. A detailed study of a glow discharge in helium as a function of pressure and impurities with time-resolved spectroscopy showed the metastables evolution within a discharge and the role of impurities in quenching or creation rate of metastables. This study also shows a 4 minutes time for thermal stabilization of the discharge (electrode heating and thermosdesorption). In helium and nitrogen, the very first microseconds of discharge are filamentary and change after 2-3 peri