Quantification of the VUV radiation in low pressure hydrogen and nitrogen plasmas

Abstract

Abstract. Hydrogen and nitrogen containing discharges emit intense radiation in a broad wavelength region in the VUV. The measured radiant power of individual molecular transitions and atomic lines between 117 nm and 280 nm are compared to those obtained in the visible spectral range and moreover to the RF power supplied to the ICP discharge. In hydrogen plasmas driven at 540 W of RF power up to 110 W are radiated in the VUV, whereas less than 2 W is emitted in the VIS. In nitrogen plasmas the power level of about 25 W is emitted both in the VUV and in the VIS. In hydrogen-nitrogen mixtures, the NH radiation increases the VUV amount. The analysis of molecular and atomic hydrogen emission supported by a collisional radiative model allowed determining plasma parameters and particle densities and thus particle fluxes. A comparison of the fluxes showed that the photon fluxes determined from the measured emission are similar to the ion fluxes, whereas the atomic hydrogen fluxes are by far dominant. Photon fluxes up to 510 20 m -2 s -1 are obtained, demonstrating that the VUV radiation should not be neglected in surface modifications processes, whereas the radiant power converted to VUV photons is to be considered in power balances. Varying the admixture of nitrogen to hydrogen offers a possibility to tune photon fluxes in the respective wavelength intervals.

Deposition of SiOxCyHz Protective Coatings on Polymer Substrates in an Industrial-Scale PECVD Reactor

“…The transitions to the ground state (which appear in the hard UV range of spectrum) were not visible, but they were much more intense than the transitions to the first excited state. According to Fanz et al [26], the transitions to the ground state are at least an order of magnitude more intensive than those to the first excited state. The radiation arising from the transition from the first H-atom excited state to the ground state appeared at a photon energy just over 10 eV, and such photons were effectively absorbed by the surface film of the polymer, thus breaking bonds.…”

Influence of H2 and D2 plasmas on the work function of caesiated materials

“…Using the given plasma parameters 15 are calculated. Furthermore, radiation of a hydrogen or deuterium plasma has photon energies of up to 15 eV with VUV fluxes of the same order of magnitude as occurring ion fluxes (see e. g. Fantz et al 24 for a detailed discussion on occurring VUV spectra and fluxes in H 2 plasmas). Both these particle and photon energies are 23 ) and moreover exceed the adsorption enthalpies of the contaminants (e. g. around 1 eV for H 2 O on stainless steel 25 ).…”

Hydrogen plasma induced photoelectron emission from low work function cesium covered metal surfaces

“…Nevertheless, the effect of PEs on the plasma sheath structure may be significant for example in Penning type ion sources, 54 where a few kW discharge power is deposited into a small plasma volume (<1 cm 3 ), which can lead to high PE emission density from the walls as a significant part of the injected power is dissipated via photon emission. [9][10][11][12] On the contrary, in neutral beam injection sources the current density can be expected to be smaller, but this does not exclude the PEs effect on the reaction rates.…”

“…9 The theoretical result is supported by experimental evidence showing that low temperature hydrogen plasmas are strong sources of vacuum ultraviolet (VUV) radiation with up to 15%-30% of the discharge power radiated at wavelengths of 120-250 nm in filamentdriven arc discharge, 10 up to 8% of the injected microwave power at 80-250 nm in ECR discharge, 11 and up to 21% of RF power at 117-280 nm in RF discharge. 12 Electrons in the conduction band of a metal follow the Fermi-Dirac distribution which can be used to derive the following relation for the quantum efficiency Y of the PE emission: 13 Y / ðh À /Þ 2 ðU 0 À hÞ 1=2 ; when h ! /;…”