Applications of dielectric barrier discharges

Abstract

Dielectric barrier discharges (DBDs) in oxygen and air are well established for the production of large quantities of ozone and are more recently being applied to a wider range of plasmachemical processes. As an introduction of this type of gas discharge, the main plasmaphysical features of sinusoidal-driven DBDs (transient, non-thermal plasmas at atmospheric pressure) are described, and plasmachemical reaction pathways for the generation of ozone are briefly discussed. The generation of atomic oxygen for ozone synthesis leads inevitably to the second application of DBDs, the non-thermal oxidation of volatile organic compounds (VOCs) in dry and humid air. Experimental results on the degradation of VOCs (isopropanol, trichloroethylene, carbon tetrachloride) as well as by-product formation will be presented for stand-alone DBD treatment, as well as for simultaneous (V)UV illumination of the discharge. Illumination of the discharge with (V)W can change the plasmachemistry by enhanced formation of certain species of radicals-and thereby can change byproduct formation-but also can change the discharge physics, known as the Joshi effect, Another application of DBDs is the generation of excited dimers and exciplexes for the production of incoherent (V)UV/visible light. As an example, experimental results on a XeBr* excimer UV light source are presented, which LANL has developed to the stage of commercialization. Effects of the total and partial gas pressure of a Xe/Br/sub 2/ system, the gap spacing, and the applied driving frequency on the UV radiant efficiency are presented. The last and latest application of DBDs is the surface processing near atmospheric pressures. As an example, results of photoresist ashing on Si wafers in an oxygen plasma are shown as function of gas pressure, gap spacing, and applied frequency. The surface of the etched photoresist is characterized by profilometry and scanning electron microscopy.