Volume discharges can also have either planar or coaxial arrangements. In planar electrode arrangements, the two electrodes are parallel to each other, and one or two dielectric barriers are always located either (i) on the powered or the ground electrode, or (ii) on both the electrodes, or (iii) in between the two metal electrodes. The electrodes in DBD can also be arranged in a coaxial manner having one electrode inside the other with at least one or two dielectric barriers located either (i) on the outer side of the inner electrode/on the inner side of the outer electrode, or (ii) on both the electrodes facing each other, or (iii) in between the two cylindrical electrodes. Besides the volume discharges, other designs also exist that use either surface or coplanar discharge geometry. Surface discharge [44] device have a thin and long electrode on a dielectric surface and an extended counter-electrode on the reverse side of the dielectric. In this configuration, the discharge gap is not clearly defined and so the discharge propagates along the dielectric surface. There also exist combinations of both volume and surface discharge configuration such as the coplanar arrangement [45-46] used in plasma display panel. The coplanar discharge device is characterized by pairs of long parallel electrodes with opposite polarity, which are embedded within a dielectric bulk nearby a surface. In addition to these configurations, other variants of DBD [47] are also used in various applications. The typical arrangements of DBD are shown in fig. 6. DBD can exhibit two major discharge modes [48-49], either filamentary mode, which is the common form of discharge composed of many microdischarges that are randomly distributed over the electrode surface; or homogenous glow discharge mode, also known as atmospheric pressure glow discharge mode due to similarity with dc glow discharges