2023 journal article

Effect of dielectric target properties on plasma surface ionization wave propagation

Journal of Physics D: Applied Physics.

By: J. Morsell n, N. Bhatt, C. Dechant & S. Shannon

Source: ORCID
Added: March 1, 2023

Abstract Surface ionization waves (SIWs) propagating along dielectric covered, grounded surfaces have been studied for various dielectric bulk and surface conditions; a dependence on the propagation velocity with respect to dielectric electrical thickness and near surface permittivity profiles are observed. SIWs generated by an atmospheric pressure plasma source are imaged interacting with planar dielectric surface. Surface wave velocity is obtained by tracking emission intensity as a function of time. Target dielectric thickness is varied from <?CDATA $d = 0.15-10$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>d</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.15</mml:mn> <mml:mo>−</mml:mo> <mml:mn>10</mml:mn> </mml:math> mm and dielectric constant is varied from <?CDATA $\epsilon_r = 6.21 - 9.4$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>ϵ</mml:mi> <mml:mi>r</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>6.21</mml:mn> <mml:mo>−</mml:mo> <mml:mn>9.4</mml:mn> </mml:math> . The propagation of SIWs can be generally predicted by relating their velocity to the RC time constant of the circuit generated between the plasma and the dielectric surface, but it is found that this approximation breaks down for dielectric substrates of sufficient thickness and wave velocity becomes constant. The results show that wave velocity is stable and predictable for target thicknesses beyond a certain point determined by the permittivity of the target material. It is also shown that SIW propagation is strongly driven by the dielectric material near to the surface of the target in addition to the bulk material. The possible mechanisms driving these thickness dependent behaviors is discussed.