# Current Filaments in Asymmetric Surface Dielectric Barrier Discharge
## 2 Recent Works on SDBD Microdischarges  
The study of the SDBD microdischarges is an active field of research which has drawn a great deal of interest in recent years, both in applied and basic plasma physics communities. We briefly review some of the works relevant for our present study.  
In [41], the authors studied an extension of SDBD to a volume-surface dielectric barrier discharge for the ozone production and benzene degradation. Concerning the discharge characterization, they found that both SDBD and V-SDBD configurations worked in a filamentary discharge mode, which produced current pulses superimposed to the capacitive current, resulting in an increasing number and amplitude of current pulses with the applied voltage. In a typical SDBD configuration, the charges are transferred along a thin layer on the dielectric surface, and the accumulation of charges on the dielectric surface finally leads to a reduction in the transfer, and therefore to the extinction of the electric discharge. Compared to conventional SDBD, the hybrid volume-surface DBD (V-SDBD) apparently enhances the discharge current, widening the spatial distribution of discharge plasma, which can be explained by the enhanced spatial electric field due to the added ground electrode over SDBD configuration.  
In [42], the inactivation of _Bacillus subtilis_ spores using coplanar surface dielectric barrier discharge (CSDBD) is studied. As in any other plasma-chemical application, the efficacy of the treatment depends on various discharge operating conditions, such as discharge electrode geometry, mean dissipated power, and feed gas flow and composition, all of which influence the chemical and physical processes of the discharge. For that reason, the authors studied the plasma properties using a photomultiplier and ICCD camera to record the optical emission waveforms and the spectra collected from the whole surface of the CSDBD electrode. The production of micro-discharges occurs with a certain distribution along the rising slope of a positive half-period with a typical pulse-to-pulse separation of a few microseconds. A similar trend can be observed during any negative halfcycle. The characteristic distribution of micro-discharges during both the positive and negative half-cycles captured by the photomultiplier tube (PMT) waveforms for a (peak-to-peak) HV amplitude of 22 kV, has been acquired by averaging over 1024 samples. The highest probability of micro-discharge onset occurs for positive AC voltages between 6.6 and 7 kV, while for negative AC voltages, the best conditions occur between \(-8.5\) and \(-9.5\) kV. Further insight can be obtained by analysing the voltage, current and PMT waveforms for micro-discharges onset at a defined HV amplitude.  
In [43], the effects of optical characteristics, electrical performances and mechanical properties of SDBD carrying a composite dielectric glass/polyimide film were investigated. The current, discharge plasma morphology, electrical power consumption, and induced airflow velocity were analyzed at an applied voltage of 17-23 kV with a working frequency of 9.15 kHz. The SDBD physical process of discharge is complicated, of which discharge characteristics are influenced by many factors, including the applied power, electrode parameters, dielectric properties, environmental conditions and so on. The discharge intensity at the positive half cycle is higher than the negative one, corresponding to a large number of intense pulses with noticeable amplitude difference, and the maximum pulse current peak is about 17 mA. The changes in current are relatively low, having an average value of about 4 mA during the negative half cycle.