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Title: Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma

Abstract

A microplasma suitable for material processing at atmospheric pressure in argon and argon-oxygen mixtures is being studied here. The microplasma is ignited by a high voltage dc pulse and sustained by low power (1-5 W) at 450 MHz. the mechanisms responsible for sustaining the microplasma require a more detailed analysis, which will be the subject of further study. Here it is shown that the microplasma is in nonequilibrium and appears to be in glow mode. The effect of power and oxygen content is also analyzed in terms of gas temperature and electron temperature. Both the gas temperature and the electron temperature have been determined by spectral emission and for the latter a very simple method has been used based on a collisional-radiative model. It is observed that power coupling is affected by a combination of factors and that prediction and control of the energy flow are not always straightforward even for simple argon plasmas. Varying gas content concentration has shown that oxygen creates a preferential energy channel towards increasing the gas temperature. Overall the results have shown that combined multiple diagnostics are necessary to understand plasma characteristics and that spectral emission can represent a valuable tool for tailoring microplasma tomore » specific processing requirements.« less

Authors:
; ; ;  [1]
  1. Nanoarchtectonics Research Center (NARC), National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 (Japan)
Publication Date:
OSTI Identifier:
20884963
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 1; Other Information: DOI: 10.1063/1.2409318; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ARGON; ATMOSPHERIC PRESSURE; ELECTRIC POTENTIAL; ELECTRON TEMPERATURE; EMISSION SPECTROSCOPY; GLOW DISCHARGES; MHZ RANGE 100-1000; MIXTURES; OXYGEN; PHOTON EMISSION; PLASMA; PLASMA DIAGNOSTICS

Citation Formats

Mariotti, Davide, Shimizu, Yoshiki, Sasaki, Takeshi, and Koshizaki, Naoto. Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma. United States: N. p., 2007. Web. doi:10.1063/1.2409318.
Mariotti, Davide, Shimizu, Yoshiki, Sasaki, Takeshi, & Koshizaki, Naoto. Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma. United States. doi:10.1063/1.2409318.
Mariotti, Davide, Shimizu, Yoshiki, Sasaki, Takeshi, and Koshizaki, Naoto. Mon . "Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma". United States. doi:10.1063/1.2409318.
@article{osti_20884963,
title = {Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma},
author = {Mariotti, Davide and Shimizu, Yoshiki and Sasaki, Takeshi and Koshizaki, Naoto},
abstractNote = {A microplasma suitable for material processing at atmospheric pressure in argon and argon-oxygen mixtures is being studied here. The microplasma is ignited by a high voltage dc pulse and sustained by low power (1-5 W) at 450 MHz. the mechanisms responsible for sustaining the microplasma require a more detailed analysis, which will be the subject of further study. Here it is shown that the microplasma is in nonequilibrium and appears to be in glow mode. The effect of power and oxygen content is also analyzed in terms of gas temperature and electron temperature. Both the gas temperature and the electron temperature have been determined by spectral emission and for the latter a very simple method has been used based on a collisional-radiative model. It is observed that power coupling is affected by a combination of factors and that prediction and control of the energy flow are not always straightforward even for simple argon plasmas. Varying gas content concentration has shown that oxygen creates a preferential energy channel towards increasing the gas temperature. Overall the results have shown that combined multiple diagnostics are necessary to understand plasma characteristics and that spectral emission can represent a valuable tool for tailoring microplasma to specific processing requirements.},
doi = {10.1063/1.2409318},
journal = {Journal of Applied Physics},
number = 1,
volume = 101,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The collisional electron spectroscopy (CES) method, which lays the ground for a new field for analytical detection of gas impurities at high pressures, has been verified. The CES method enables the identification of gas impurities in the collisional mode of electron movement, where the advantages of nonlocal formation of the electron energy distribution function (EEDF) are fulfilled. Important features of dc negative glow microplasma and probe method for plasma diagnostics are applied. A new microplasma gas analyzer design is proposed. Admixtures of 0.2% Ar, 0.6% Kr, 0.1% N{sub 2}, and 0.05% CO{sub 2} are used as examples of atomic andmore » molecular impurities to prove the possibility for detecting and identifying their presence in high pressure He plasma (50–250 Torr). The identification of the particles under analysis is made from the measurements of the high energy part of the EEDF, where maxima appear, resulting from the characteristic electrons released in Penning reactions of He metastable atoms with impurity particles. Considerable progress in the development of a novel miniature gas analyzer for chemical sensing in gas phase environments has been made.« less
  • The measurement of the electron mean kinetic energy by identifying the electron temperature and the excitation temperature obtained by optical emission spectroscopy is theoretically studied for two temperature argon plasmas at atmospheric pressure. Using a 32-level collisional radiative model in which both electron impact and argon-impact inelastic collisions are taken into account, it has been found that under certain conditions the argon inelastic collisions may cause a decrease of the argon excitation temperature so that the relation T{sub e}>T{sub exc}>T{sub 0} is satisfied. This inequality also appears when electron losses due to diffusion are important and the electron density ismore » lower than its equilibrium value.« less
  • An atmospheric pressure plasma jet generated in Ar/water vapor mixtures has been investigated and the effect of water content on plasma properties has been studied. Plasma generated in Ar/water (0.05%) mixture shows higher intensity of OH radicals in emission spectra than pure argon alone. Plasma density has been estimated from current measurement and is in order of 1.5x10{sup 13} cm{sup -3}. Electron temperature has been estimated as 0.97 eV in pure Ar and it decreases with an increase in water content in plasma. The gas temperature has been determined by fitting of the experimental spectra and using the Boltzmann plotmore » method. The gas temperature increases with the addition of water to feed gas from 620 K in pure Ar up to 1130 K for 0.76%H{sub 2}O.« less
  • A novel spectroscopic method is proposed for the measurement of electron density and temperature in atmospheric pressure dielectric barrier discharges using nitrogen gas. Simplified collisional-radiative models for the electronic and the vibrational states yield two separate continuity equations as a function of the electron density and the temperature with the coefficients expressed in terms of rotational temperature, vibrational temperature, and emission intensity ratio between the first positive system and the second positive system of nitrogen molecules. The electron density and the temperature in nonequilibrium atmospheric pressure plasmas can be determined by solving the continuity equations with the coefficients estimated frommore » the spectroscopic measurements. It was confirmed by applying to a high power dielectric barrier discharge, where the measured plasma parameters were in good agreement with the estimation by using the electron conductivity of the discharge.« less
  • An atmospheric pressure microplasma jet was employed as a deposition tool to fabricate silicon oxycarbide films from tetraethoxysilane-argon (Ar) mixture gas at room temperature. Resultant films exhibit intense visible emission under a 325 nm excitation which appears white to naked eyes in the range from {approx}1.75 to {approx}3.5 eV at room temperature. The origin of photoluminescence is attributed to the electron-hole pair recombination through neutral oxygen vacancies (NOVs) in the film. The density of NOV defects was found in the range from 3.48x10{sup 15} to 2.23x10{sup 16} cm{sup -3}. The photoluminescence quantum efficiencies were estimated to be 1.48%-4.15%. Present experimentmore » results demonstrate that the silicon oxycarbide films prepared by using atmospheric pressure microplasma jet would be a competitive candidate for the development of white light emission devices.« less