Spectroscopic Measurements of Atomic Hydrogen Concentrations in Dielectric Barrier Discharge Hydrogen Plasmas
WANG Wei-guo1, XU Yong1, 2*, LIU Zhong-wei1, ZHU Ai-min1, 2, WANG Wen-chun1, 2
1. Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian 116024, China 2. State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024, China
Abstract：Atomic hydrogen plays important roles in chemical vapor deposition of functional materials, plasma etching，and surface cleaning. The present work introduces the fundamental principle to determine atomic hydrogen density via optical emission spectroscopy using Ar as an actinometer, and also reports the experimental results of atomic hydrogen density in the DBD discharge hydrogen plasmas. The variations of atomic hydrogen density and the hydrogen dissociation fraction as a function of pressure were calculated based on some of the available electron-impact excitation cross section and quenching cross sections in the literatures. In this work, as the pressure increases from 0.32 to 5.1 kPa, the hydrogen dissociation fraction decreases from 5.2% to 0.089%, and the atomic hydrogen density decreases from 4.9×1015 cm-3 to 1.3×1015 cm-3. The variations of H atom Balmer lines and Ar(750.4 nm) emission intensity as functions of gas pressure, discharge voltage, and frequency were also investigated.
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