Kinetic model and spectroscopic measurement of NO (A, B, C) states in low-pressure N₂–O₂microwave discharge

Abstract

A self-consistent kinetic model is developed to study the atomic and molecular processes in the microwave discharge plasma of N 2 -O 2 mixtures. We focus on the NO A 2 Σ + , B 2 Π, and C 2 Π states in the mixture discharge. We find good agreement between the calculated and experimental NO A 2 Σ + densities. On the other hand, the radiation bands from the NO B 2 Π and C 2 Π states are observed only when the oxygen partial pressure is less than 3%. We discuss the de-excitation processes for the NO B 2 Π and C 2 Π states in this low-pressure plasma. We also propose that the de-excitation processes involve collision with O 2 X 3 AE À g for these levels, which can explain the observed spectral disappearance.

Excitation Kinetics of Oxygen O(1D) State in Low-Pressure Oxygen Plasma and the Effect of Electron Energy Distribution Function

“…The governing equations to describe the excitation kinetics in the oxygen plasma consists of two sets of equations: the one is a set of equations to describe the temporal evolution of number densities of excited species in the oxygen plasma, and the other is the Boltzmann equation to find the EEDF in the oxygen plasma [4][5][6]. Concerning the former one, the number densities of the excited species are described as the corresponding rate equations describing the population and depopulation on the basis of chemical kinetics in the plasma, which are simultaneous ordinary differential equations.…”

“…Here, ν w is calculated from the boundary condition, or the deactivation probability γ, on the surface of the discharge tube wall, which can be formulated as follows [4][5][6]9]:…”

“…In the meantime, for the electron impact excitation or de-excitation processes, the rate coefficients k e must be calculated by applying the following integral calculation, because the electrons generally do not obey the Boltzmann distribution [4][5][6][7][8]:…”

“…In these advanced oxidation processes, several papers reported that the O( 1 D) atom, a metastable state of oxygen atom as the first excited state, should play a more essential role than O( 3 P), the ground state oxygen atom, to improve the electronic quality of the gate oxide films [3,4]. Although we also studied the excitation chemical kinetics of nitrogen/oxygen atoms and molecules in the low-pressure discharge nitrogenoxygen mixture plasma [5,6], we did not include the O( 1 D) state in our previous model [4], which should be definitely taken into account to the kinetic modeling for better understanding of the plasma oxidation processes for semiconductors. This is the main objective of the present study.…”

“…However, in the excitation kinetics of the plasma in a state of non-equilibrium, we must always notice the essentiality of the EEDF [7,8], and consequently, we would like to discuss the effect of the EEDF on the number densities of the excited states as well as on the excitation kinetics itself. In other words, in the non-equilibrium plasmas, we should describe the rate equations in terms of the rate coefficients calculated with the EEDF and the corresponding cross sections, and the rate coefficients should not be considered as functions of the electron temperature [1,2,[5][6][7][8].…”