Abstract
The optical emission spectroscopy technique is used to determine the vibrational temperature of the second positive band system, N_{2} (C,upsilon^{^{prime}} - B,upsilon^{^{primeprime}}) in the wavelength range 367.1–380.5 nm by using the line-ratio and Boltzmann plot methods. The electron temperature is evaluated from the intensity ratio of the selected molecular bands corresponding to N_{2}^{ + } (B,upsilon - X, upsilon^{^{prime}} , 391.44 nm), and, N_{2} (C,upsilon^{^{prime}} - B,upsilon^{^{primeprime}}, 375.4 nm) transitions, respectively. The selected bands have a different threshold of excitation energies and thus serve as a sensitive indicator of the electron energy distribution function (EEDF). The electron density has been determined from the intensity ratio of the molecular transitions corresponding to N_{2}^{ + } (B,upsilon - X, upsilon^{^{prime}} , 391.44 nm), and, N_{2} (C,upsilon^{^{prime}} - B,upsilon^{^{primeprime}}, 380.5 nm) for different levels of pressure and radio frequency power. The results show that the vibrational temperature decreases with increasing nitrogen fill pressure and radio frequency power. However, the electron temperature increases with radio frequency power and reduces with fill pressure. The electron density increases both with nitrogen fill pressure and radio frequency power that attributes to the effective collisional transfer of energy producing electron impact ionization. Plasma parameters show a significant dependence on discharge conditions and can be fine-tuned for specific surface treatments.Article HighlightsSpectrum analysis of RF-driven nitrogen plasma for varying discharge conditionsEvaluation of vibrational temperature using line-ratio and Boltzmann plot methodsComparison of vibrational temperatures for line-ratio and Boltzmann plot methodsEvaluation of electron temperature and density using the intensity-ratio of bandsCorrelation of temperature and density with varying fill pressure and RF power
Highlights
Radio frequency plasma-based surface treatment such as etching, sputtering, and thin-film deposition is the emerging research field aimed at diverse industrial applications [1,2,3]
The results show that the vibrational temperature decreases with increasing nitrogen fill pressure and radio frequency power
It is because the line-ratio method involves only the intensity contribution of two spectral lines while the Boltzmann plot method involves the contribution from several spectral lines
Summary
Radio frequency plasma-based surface treatment such as etching, sputtering, and thin-film deposition is the emerging research field aimed at diverse industrial applications [1,2,3]. The plasma particles go through electron impact excitation and subsequent de-excitation emitting light of a specific wavelength These radiations provide the details of the plasma species and their energies, making OES in the visible range an attractive method for plasma analysis with an manageable experimental setup [6,7,8]. Investigated the effect of gas flow rate, fill pressure and discharge current on the emission intensity of the second positive system of N2, and vibrational temperature. The paper reports the vibrational temperature obtained from the relative intensity of the bands of the second positive system N2(C3Πu → B3Πu ) with sequence (Δ = − 2) for different values of RF power and nitrogen pressure at a fixed frequency of 13.56 MHz. The information of the electron temperature and number density is mandatory to understand the physical properties of the electric discharge. N2(C3Πu → B3Πu ) at 375.4 nm, and 380.5 nm is analyzed for electron temperature and density respectively
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