Plasma parameters and electric field fluctuations in a cold micro-plasma jet interacting with a substrate

Interaction of a cold atmospheric pressure micro-plasma jet with different types of substrates having a range of electrical permittivity (epsilon(r)), such as conductor (copper), semiconductor (p-type silicon), insulator (Teflon and quartz), and biological (goat skin), is carried out experimentally. The electric field fluctuations, cross-phase analysis, plasma parameters [electron excitation temperature (T-exc) and electron density (n(e))], average propagation velocity of the plasma bullet, gas temperature (T-g), power dissipated on the substrates, and substrate temperature are investigated during the interaction. Cross phase analysis and plasma bullet velocity support the return stroke phenomenon for high epsilon(r) samples, such as copper and silicon, and a surface ionization wave is generated in the case of low epsilon(r) samples, such as Teflon, quartz, and biological tissue. The highest substrate current (I-S) is observed for copper due to its high conductivity. T-g and n(e) are affected by the interaction; however, T-exc is observed to change only slightly. n(e) is comparatively higher for high epsilon(r) samples, and for all samples, it increases initially and, thereafter, decreases as we get closer to the sample's surface. T-g is comparatively higher for low epsilon(r) samples and increases axially downward from the orifice of the jet, it is lower and almost constant for copper and silicon. The electric field fluctuation (E-Z and E phi components) frequencies lie up to similar to 8 kHz with a peak amplitude at similar to 1 kHz, which is found to be comparatively higher for low epsilon(r) samples.

Automated summary

The interaction between a cold atmospheric pressure micro-plasma jet and different types of substrates with varying electrical permittivity is experimentally investigated. The results show that high permittivity substrates exhibit a return stroke phenomenon, while low permittivity substrates generate a surface ionization wave. The conductivity of the substrate affects the substrate current. The interaction also affects the gas temperature and electron density, but has minimal impact on the electron excitation temperature. The frequency of electric field fluctuations is higher for low permittivity substrates.