Characterization of Argon Plasma by Use of Optical Emission Spectroscopy and Langmuir Probe Measurements

Abstract

Spectroscopic and Langmuir probe measurements are presented to characterize the argon glow discharge plasma generated by a cost-effective 50 Hz AC power source. Optical emission spectra (400-700 nm) are recorded for different gas flow rates and filling pressures at constant power level. The plasma parameters (electron temperature and density) are deduced from the relative intensities of Ar-I and Ar-II lines. The variation in the intensity ratio of the selected emission lines, electron temperature and density is studied as a function of gas flow rate and filling pressure. Slight increase in the intensity ratio I 2 (426.62 nm)/I 1 (404.44 nm) of the emission lines is observed whereas the electron temperature and density are found to decrease with increase in gas flow rate and filling pressure.

Langmuir probe characterization of nitrogen plasma for surface nitriding of AISI-4140 steel

“…Probe current is measured for DC bias voltages ranging from −100 to +100 V. The probe I-V characteristics are recorded for different pressures (2-5 mbar) at constant power. The electron temperature is determined in electron volt (eV) from the slope of the ln(I)-V curve of the probe in the transition region between floating potential and plasma potential by the following equation (Qayyum et al, 2003;Nisha et al, 2006):…”

“…The electron number density (cm −3 ) is obtained from the electron saturation current (I se ) using the following equation (Grill, 1993;Qayyum et al, 2003): …”

“…The reduction of electron temperature with filling pressure may be explained as follows: when the pressure of nitrogen gas in the chamber increases, it causes an increase in the number of collisions between the electrons and the plasma species. The resulting energy transfer from electrons to gas particles increases the gas temperature while lowering the electron temperature (Qayyum et al, 2003). The electron density is determined from the electron current saturation region of the I-V characteristic recorded for different filling pressures to investigate the dependence of electron density on the filling pressure.…”

“…It is found that the electron density decreases with increase in filling pressure, which may be explained as follows: when the filling pressure in the chamber increases, the high-energy tail of the electron energy distribution function contracts to the lower energies. Therefore the ionization, which results from the energetic electron's impact with gas particles, is reduced causing a decrease in ionization process and consequently the electron density (Qayyum et al, 2003). …”

Diagnostics of nitrogen plasma by trace rare-gas–optical emission spectroscopy

“…This method requires a pair of lines emitted by the same species with a large difference in excited states' energy. 11,12 In this paper, we report the measurement of relative population density of reactive species ͑N, N 2 , N 2 +* , and N 2 * ͒ and electron temperature ͑kT e ͒ as a function of discharge a͒ Electronic mails: mzakaullah@qau.edu.pk and zaka_qau_pk@yahoo.com parameters such as input electrical power and filling pressure. The emission intensities of the first negative bandhead ͑0-0͒ and second positive bandhead ͑0-0͒ are used to obtain the knowledge of the excited-state population densities ͑N 2 +* and N 2 * ͒.…”