Atmospheric pressure plasmas generate a variety of chemically active species in open air, thus providing the unique ability to treat a variety of materials that do not require or are not compatible with vacuum systems. Producing the plasma-surface interaction that leads to a desired change in the substrate is complicated by the codependency between the plasma and the substrate: while the plasma will modify the surface, the surface will also influence the plasma properties. In this work, a pulsed-DC plasma jet produced in helium and impinging upon glass and metal substrates is studied over a range of applied voltage pulse widths extending from 1 to 10 s. Current–voltage measurements, high speed images, and time-resolved optical emission from three important He and nitrogen excited species are used to examine the evolution of the plasma and its interaction with the surface. At ignition, a streamer is ejected into the open air from the jet exit and eventually collides with the substrate. For a glass substrate, the streamer will hit the surface and form a short-lived plasma across it. This surface plasma is almost completely unaffected by changes in the voltage pulse width. In contrast, when the streamer hits a metal substrate, a surface discharge will form that will last the entirety of the voltage pulse. If the pulse is long enough, a ‘reflected discharge’ will slowly develop that extends from the substrate back towards the outlet of the plasma jet. The emission intensity of the surface discharge closely matches that of the initial streamer, but not the reflected discharge, which suggests different electron kinetics between the two features. The addition of capacitors or resistors between the metal substrate and ground show how differences in substrate electrical properties can account for some of these behaviors. Emission line ratios are used to examine the evolution of electron temperature and the relative importance of Penning processes during the different plasma phases.

大气压等离子体在露天环境中产生各种化学活性物质，因此提供了独特的能力来处理不需要或与真空系统不兼容的各种材料。等离子体和基底之间的相互依赖性使产生导致基底所需变化的等离子体-表面相互作用变得复杂：尽管等离子体将修饰表面，但表面也会影响等离子体性能。在这项工作中，研究了在1至10 s的施加电压脉冲宽度范围内在氦气中产生并撞击玻璃和金属基板的脉冲DC等离子体射流。电流电压测量，高速图像，以及来自三个重要的氦和氮激发物种的时间分辨光发射被用于检查等离子体的演化及其与表面的相互作用。点火时，拖缆从喷嘴出口喷射到室外，并最终与基材碰撞。对于玻璃基板，拖缆将撞击表面并在其上形成短暂的等离子体。该表面等离子体几乎完全不受电压脉冲宽度变化的影响。相反，当拖缆撞击金属基板时，将形成表面放电，该放电将持续整个电压脉冲。如果脉冲足够长，则“反射放电”将慢慢形成，从基材向等离子体射流的出口延伸。表面放电的发射强度与初始拖缆的发射强度非常接近，但没有反射放电，这表明这两个特征之间的电子动力学不同。在金属基板和地面之间添加电容器或电阻器表明，基板电性能的差异如何解释其中的某些行为。发射线比用于检查电子温度的变化以及潘宁过程在不同等离子相期间的相对重要性。