Cleaning properties of atomic oxygen excited to metastable state 2 s 2 2 p 4 ( S 1 )

Abstract

A possibility to treat surfaces of various materials by bombardment with neutral atomic oxygen excited to the metastable state 2s22p4(S10), (4.1891 V from the ground) is described. The oxygen dissociation and excitation was developed in plasmas generated in reactors of capacitively coupled dielectric barrier discharge configurations comprised of a quartz or ceramic tube passing throughout two annular electrodes and containing a gas mixture of ∼98% Ar with ∼2% O2 ionized at the atmospheric pressure by the radio frequency discharge at 13.56 MHz and flowing at about 6 m/s. As shown in the experiments, the transition 2s22p4(S10)−2s22p4(D12) with a high degree of probability is responsible for the yellow color of afterglow products, and the lifetime of the metastable state can be as long as 5.4 ms in certain cases, allowing one to separate the excited atomic medium from plasma that it produced. It has been shown that the cleaning process included significant Van der Waals bonds liberation to the depth of several hundred angstroms of surfaces treated, which drastically reduced the percentage of carbon-containing contaminants and changed, to some degree, the chemical structure of surfaces containing chemically bonded oxygen.

Treatment surfaces with atomic oxygen excited in dielectric barrier discharge plasma of O2 admixed to N2

“…Note that additional experimental data for several materials can be found in Ref. 5. Section V discusses briefly some of important results obtained in the present work.…”

“…(24)) with a relaxation time τ br ≈ 10. 5 ± 0.16 ms that is almost seven times longer than the relaxation time τ br ≈ 1.6 ms of the excited oxygen (state 2s 2 2 p 4 ( 1 S 0 )) admixed with Ar-gas and flowing in ambient air, 5 see Fig. 2(a).…”

“…Note that the expected lifetime of the undisturbed state 2s 2 Note that there was hypothesis 19 suggesting to consider the emissive line found in Ref. 5 as the Lewis-Rayleigh afterglow chemoluminiscence. However direct comparison of this line form with a shape of the spectra of most recently obtained experimentally Lewis-Rayleigh afterglow 20 showed sufficient and unavoidable their differences.…”

“…Experiments on treatment surfaces of various materials with excited gas composition generated in plasma of DBD in N 2 admixed with O 2 demonstrated in some cases a higher rate of surface treatment compared to the gas composition generated in plasma of RF discharge in mixture of argon and oxygen. 5 Taking into account the fact that excited gases produced by DBD in N 2 were released in ambient air before interaction with the surface treated, one can make the natural assumption (in the light of results of the previous section, see Figs. 18(b) and 20(b)), that the atomic oxygen excited to the state 2s 2 2 p 4 ( 1 S 0 ) is responsible for surface treatment in the case considered.…”

“…[5][6][7] It has been shown recently 8 that a small addition of oxygen (∼1%) to operating Ar-gas enables one to obtain in gas-discharge plasma and its afterglow components a significant quantity of neutral excited atomic oxygen 9 capable of cleaning and improving the adhesion of surfaces of various materials. It is understood that application of nitrogen for the same purpose could significantly reduce the cost of industrial processes requiring a large amount of operating gas.…”