Spectroscopic measurements of the electron temperature in low pressure radiofrequency Ar/H₂/C₂H₂and Ar/H₂/CH₄plasmas used for the synthesis of nanocarbon structures

Abstract

This paper deals with optical emission spectroscopy studies of low pressure (0.1-0.5 Torr) capacitively coupled radiofrequency hydrocarbon/argon-rich plasmas used for the synthesis of nanocarbon structures. The main goal of this paper is to obtain the electron temperature of such far-from-equilibrium plasmas as a function of the pressure, the excitation power and the argon content. In doing so, we have found that the argon upper energy levels used for electron temperature estimation remain close to corona balance. The latter has allowed us to use a modified Boltzmann plot technique to derive the electron temperature. It was found that, for the plasmas investigated, an increase of the argon population density (from 10% to 95%) leads to a pronounced decrease of the electron temperature while an increase of the processing pressure produces a moderate increase of the electron temperature. Additionally, the increase of the power from 50 to 300 W produces a very slight growth of the electron temperature.

Low‐Pressure PECVD of Nanoparticles in Carbon Thin Films from Ar/H2/C2H2 Plasmas: Synthesis of Films and Analysis of the Electron Energy Distribution Function

“…2a)). It is worth mentioning that, in reasonable agreement with measurements of T e with increasing C 2 H 2 , the values of the T e associated with the Maxwellian fits (better for 20 % C 2 H 2 ) are roughly around 1.75 eV (for 1 % C 2 H 2 ) and the more realistic 1.15 eV (for 20 % C 2 H 2 ), exhibiting a decreasing trend with growing C 2 H 2 that is probably connected with an increase of the non-uniformly distributed [25,29] dust concentration in the discharge due to the fast polymerization of C 2 H 2 in the plasma. We can see in Figures 2 and 3 that the assumption of a Maxwellian shape for the EEDF is, in general, better justified as the relative concentration of C 2 H 2 grows so that the measured T e s are closer to the calculated ones when using 20 % C 2 H 2 .…”

“…The latter is only a useful approach since, under the conditions of this work (0.1 Torr, 300 W with an excitation frequency of 13.56 MHz), stochastic heating can also be important. [25] Therefore, although our approach of solving a homogeneous Boltzmann equation does not completely fit to the real physical situation of the problem, we believe that it is still valid and can give valuable information on the approximate behavior of the EEDF and mean electron energy in our dusty RF plasma. Moreover, recent results by Denysenko et al [31] have shown that, for relatively high dust density (∼5 × 10 7 cm -3 ) and/or dust radius (∼100 nm), the results of the homogeneous Boltzmann are reasonable in describing the effect of plasma nonuniformity on the EEDF.…”

“…Using a technique that we have developed in a previous work, [25] the present OES data are used to evaluate the electron temperature of the plasma as a function of the content of C 2 H 2 . The temperatures obtained are 1.37 ± 0.27 eV (1 % C 2 H 2 ), 1.33 ± 0.26 eV (5 % C 2 H 2 ), 1.34 ± 0.26 eV (10 % C 2 H 2 ), and 1.35 ± 0.26 eV (20 % C 2 H 2 ), that is, T e remains fairly constant (within experimental error) when the concentration of C 2 H 2 increases.…”

“…[10] In a previous paper [25] we related the formation of nanostructured carbon films with changes in the parameters of hydrocarbon/argon plasmas produced in capacitively coupled RF discharges. There we pointed out a decrease in the electron temperature as spherical particles were detected in the deposited coatings.…”

Measurement of plasma electron temperature and density by using different applied voltages and working pressures in a magnetron sputtering system

“…The temperature of electron and the density of electron, etc.. By using the information from optical emission spectroscopy [13 -16]. The temperature of electron and the density of electron obtained by the following equation respectively: Reported by F.J. Vazquez et al the density of electron increasing and the temperature of electron decrease with increasing gas pressure , while electron temperature increase with increasing the power .Althought several studies have indicated to electrical characteristics of plasma , little attention has been paid to spectrum characteristics of plasma [17]. The aim of this research is to study the effect of changing applied voltage and working pressure on electron temperature , electron density and intensity of the spectral lines in argon plasma discharges to determine the optimum condition of produced plasma.…”