Co-effect of dielectric layer material and driving pulse polarity on the spatial emission intensity distributions of micro dielectric barrier discharge

Abstract

A micro concentric ring device with asymmetric dielectrics (glass and n-silicon) is driven by a bipolar pulse generator with 20 kHz frequency, 1 μs pulse width, 50 ns rising/falling time, and 3.6 kV peak-to-peak voltage, and the spatial emission intensity distributions in the device are investigated. The experiments are operated at 133 mbar pure argon. The spatial-temporal microplasma evolution recorded by intensified charge-coupled device illustrates that ‘edge emission’ arises in the microchannels when the electrode (indium tin oxide) on which the glass dielectric is located acts as the cathode. However, when the electrode (conductive silver paste) adjacent to the n-silicon acts as the cathode, ‘center emission’ is induced. The dielectric materials’ properties (relative permittivity and secondary electron emission coefficient), synergistically with the pulse polarity, which determines the influence of the residual long-living particles generated by previous discharge on the subsequent discharge, are inferred to be responsible for the distinct spatial emission intensity distributions at different pulse polarities. When the n-silicon is situated on the cathode, the high permittivity of n-silicon repels the electric field into plasma, which means that the electrons can obtain more energy in the first half of their journey. Furthermore, the high secondary electron yield of n-silicon makes it possible to provide more seed electrons for microdischarge. This mechanism of electrons dynamics leads to the occurrence of ‘center emission’. When the positive half period of the bipolar pulse arrives at the n-silicon, the residual charged particles generated by the previous discharge will induce a reversed electric field in the channel center to impair the applied electric field and bring about the ‘edge emission’, but this cannot emerge in the microdischarge powered by the unipolar pulse. Investigation of spatial emission intensity distributions of microplasmas is important for the comprehension of devices based on micro-structure techniques.