Current Applied Physics, Vol.15, No.11, 1453-1462, 2015
Quantitative evaluation of the densities of active species of N-2 in the afterglow of Ar-embedded N-2 RF plasma
The N-2 and Ar-20%N-2 RF plasmas and afterglows have been generated in a quartz tube under a flowing condition maintained at 6-8 Torr and a flow rate of 0.5-0.6 slm. The detailed emission characteristics of active species have been analyzed by emission spectroscopy. Under such conditions, the plasma rotational temperature increases from 400 to 800 K with increasing RF powers from 50 to 130 W, while the characteristic vibrational temperature remains at about 104 K. The densities of active species (N, N-2(A), N-2(X, v > 13) and N-2(+)) in the afterglow are measured to be in the order of similar to 10(15), similar to 10(11), similar to 10(14) and similar to 10(10) cm(-3), respectively. In addition, the following characteristics of the afterglows are noted: First, the same densities of the active species can be obtained at lower RF powers (20-50 W) for Ar-20%N-2 than for pure N-2 which requires higher RF powers (50-100 W). Second, the ionization degree of N-2(+) = N-2 in the plasma increases readily to a saturation value at a lower RF power of 50 W for Ar-20%N-2, whereas in the afterglow, the absolute density of N-2(+) is further reduced below 109 cm(-3). (C) 2015 Elsevier B.V. All rights reserved.