Plasma-surface interaction: dynamic evolution of interfacial pattern modes during transformation process from dielectric to metallic substrate

Abstract

Plasma–surface interaction is a complex system involving the codependency between the plasma and the substrate, especially for substrate’s with different permittivities. Therefore, a better understanding of the dynamic evolution of interactions with different substrates is essential for optimizing the required changes of specific substrates. In this work, we report two modes of interfacial pattern formation by a pulsed helium plasma jet interacting with indium tin oxide (ITO) glass and a metal substrate, and we mainly focus on the dynamic evolution process for interfacial pattern modes during a transformation process from ITO glass to metal substrate. Pattern morphology, current–voltage characteristics, intensified charge coupled device images, and reactive species distribution are used to examine the evolution mechanism of the plasma-jet–substrate interaction. Results show that, for the ITO glass substrate, a circular interfacial pattern with plenty of streamer channels is generated while, for the metal substrate, a constricted solid spot interfacial pattern is formed; these two pattern mode transformations are realized from the glass dielectric to the metal substrate. Furthermore, during the transformation process from the dielectric to metal substrate, the pattern area is gradually decreased, while the discharge intensity, emission intensity, and local electric field gradually become stronger. Importantly, by observing the dynamic behavior of the interfacial pattern, the ionization wave on the substrate surface is stopped from spreading toward the metal direction and a bright touch point appears at the interface between the dielectric and the metal, while the surface ionization wave still spreads and has no influence on the other direction besides the metal direction. Additionally, the evolution mechanism of pattern mode transformation is discussed, which may be attributed to the difference in the substrate conductivity leading to the different distribution of the local electric field. This study is beneficial to deep insights into the nature of the plasma–surface interaction.