Determination of atomic hydrogen in non-thermal hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry.
Atomic hydrogen plays important roles in chemical vapor deposition of functional materials, plasma etching and new approaches to chemical synthesis of hydrogen-containing compounds. The present work reports experimental determinations of atomic hydrogen near the grounded electrode in medium-pressure dielectric barrier discharge hydrogen plasmas by means of molecular beam threshold ionization mass spectrometry (MB-TIMS). At certain discharge conditions (a.c. frequency of 24 kHz, 28 kV of peak-to-peak voltage), the measured hydrogen dissociation fraction is decreased from approximately 0.83% to approximately 0.14% as the hydrogen pressure increases from 2.0 to 14.0 Torr. A simulation method for extraction of the approximate electron beam energy distribution function in the mass spectrometer ionizer and a semi-quantitative approach to calibrate the mass discrimination effect caused by the supersonic beam formation and the mass spectrometer measurement are reported.
Wang
Wei-Guo
WG
Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian, China.
Xu
Yong
Y
Yang
Xue-Feng
XF
Wang
Wen-Chun
WC
Zhu
Ai-Min
AM