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Title: Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen

Abstract

By using a rf compensated Langmuir probe and optical emission spectroscopy, the effects of driving frequency (13.56-50 MHz) on the electron energy probability function (EEPF), electron density, electron temperature, and the vibrational and rotational temperatures in capacitively coupled nitrogen discharge were investigated. Measurements were performed in the pressure range 60-200 mTorr, and at a fixed voltage of 140 V (peak-to-peak). With increasing the driving frequency, the dissipated power and electron density markedly increased along with the intensity of the optical emission lines belonging to the 2nd positive (337.1 nm) and 1st negative systems (391.4 nm) of N{sub 2}. The EEPF at low pressure 60 mTorr is two-temperature (bi-Maxwellian) distribution, irrespective of the driving frequency, in contrast with argon and helium discharges in the similar conditions. The mechanism forming such bi-Maxwellian shape was explained by two combined effects: one is the collisionless sheath-heating effect enhancing the tail electron population, and the other is the collision-induced reduction of electrons at the energy 2-4 eV where the collision cross-section for the vibrational excitation has a resonantly large peak. The two-temperature EEPF structure was basically retained at moderate pressure 120 mTorr and high pressure 200 mTorr. The vibrational temperature T{sub vib} and rotational temperaturemore » T{sub rot} are measured for the sequence ({Delta}{nu}=-2) of N{sub 2} second positive system (C{sup 3}{Pi}{sub u}{yields}B{sup 3}{Pi}{sub g}) using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. It was found that, both of T{sub vib} and T{sub rot} are a weakly dependent on driving frequency at low pressure 60 mTorr. At higher pressure (120 and 200 mTorr), T{sub vib} rises monotonically with the driving frequency, whereas the T{sub rot} slightly decreases with frequency below 37 MHz, beyond which it relatively increases or saturated.« less

Authors:
 [1];  [2];  [3]
  1. Physics Department, Faculty of Science, Zagazig University, Zagazig 44519 (Egypt)
  2. University of Bucharest, Faculty of Physics, P.O. Box MG11, 077125 Magurele (Romania)
  3. Department of Electronics and Information Engineering, Chubu University, 1200 Matsumoto-cho, Kasugai 487-8501 (Japan)
Publication Date:
OSTI Identifier:
22068926
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 11; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; COLLISIONS; CROSS SECTIONS; ELECTRON DENSITY; ELECTRON TEMPERATURE; EMISSION SPECTROSCOPY; ENERGY SPECTRA; EV RANGE; EXCITATION; HELIUM; HIGH-FREQUENCY DISCHARGES; LANGMUIR PROBE; MHZ RANGE; NITROGEN; PLASMA SHEATH; PRESSURE RANGE MEGA PA 10-100; TAIL ELECTRONS

Citation Formats

Abdel-Fattah, E., Bazavan, M., and Sugai, H. Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen. United States: N. p., 2012. Web. doi:10.1063/1.4766475.
Abdel-Fattah, E., Bazavan, M., & Sugai, H. Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen. United States. doi:10.1063/1.4766475.
Abdel-Fattah, E., Bazavan, M., and Sugai, H. Thu . "Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen". United States. doi:10.1063/1.4766475.
@article{osti_22068926,
title = {Electron energy distribution functions measured by Langmuir probe with optical emission spectroscopy in very high frequency capacitive discharge in nitrogen},
author = {Abdel-Fattah, E. and Bazavan, M. and Sugai, H.},
abstractNote = {By using a rf compensated Langmuir probe and optical emission spectroscopy, the effects of driving frequency (13.56-50 MHz) on the electron energy probability function (EEPF), electron density, electron temperature, and the vibrational and rotational temperatures in capacitively coupled nitrogen discharge were investigated. Measurements were performed in the pressure range 60-200 mTorr, and at a fixed voltage of 140 V (peak-to-peak). With increasing the driving frequency, the dissipated power and electron density markedly increased along with the intensity of the optical emission lines belonging to the 2nd positive (337.1 nm) and 1st negative systems (391.4 nm) of N{sub 2}. The EEPF at low pressure 60 mTorr is two-temperature (bi-Maxwellian) distribution, irrespective of the driving frequency, in contrast with argon and helium discharges in the similar conditions. The mechanism forming such bi-Maxwellian shape was explained by two combined effects: one is the collisionless sheath-heating effect enhancing the tail electron population, and the other is the collision-induced reduction of electrons at the energy 2-4 eV where the collision cross-section for the vibrational excitation has a resonantly large peak. The two-temperature EEPF structure was basically retained at moderate pressure 120 mTorr and high pressure 200 mTorr. The vibrational temperature T{sub vib} and rotational temperature T{sub rot} are measured for the sequence ({Delta}{nu}=-2) of N{sub 2} second positive system (C{sup 3}{Pi}{sub u}{yields}B{sup 3}{Pi}{sub g}) using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. It was found that, both of T{sub vib} and T{sub rot} are a weakly dependent on driving frequency at low pressure 60 mTorr. At higher pressure (120 and 200 mTorr), T{sub vib} rises monotonically with the driving frequency, whereas the T{sub rot} slightly decreases with frequency below 37 MHz, beyond which it relatively increases or saturated.},
doi = {10.1063/1.4766475},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 11,
volume = 19,
place = {United States},
year = {2012},
month = {11}
}