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Medientyp:
E-Artikel
Titel:
Conventional and non-conventional diagnostics of a stable atmospheric pressure DC normal glow microplasma discharge intended for in situ TEM studies
Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>A simple setup utilizing parallel flat electrodes with a 50–150 <jats:italic>μ</jats:italic>m interelectrode distance divided by a Kapton spacer with a 1 mm diameter whole as discharge region intended for <jats:italic>in situ</jats:italic> transmission electron microscope studies is presented. The rather small setup operated in Ar or He results in an atmospheric pressure DC normal glow discharge and is investigated using various diagnostics. <jats:italic>I</jats:italic>–<jats:italic>V</jats:italic> characteristics show a glow-like behavior of the microplasma. Significant differences due to the working gas, electrode material and electrode distance have been observed. Currents in the range of 0.5–3 mA resulted in electrode potentials of 140–190 V for most experimental conditions. Optical emission spectroscopy and imaging revealed stable plasma operation and enabled the determination of current densities (approx. 16 mA mm<jats:sup>−2</jats:sup> for He, or 28 mA mm<jats:sup>−2</jats:sup> for Ar) independent of the input current as the discharge channel grows in diameter. Sheath thicknesses in the range of a few <jats:italic>μ</jats:italic>m have been calculated by the collision-dominated Child–Langmuir law and trends are confirmed by the optical imaging. Energy flux measurements revealed a pronounced effect of ions on the measurement process and resulted in high energy fluxes locally up to 275 W cm<jats:sup>−2</jats:sup>. Effective secondary electron emission coefficients ranging from 1 to 1.6 depending on the discharge conditions have been determined based on the energy balance at the cathode.</jats:p>