A Review of Recombination Coefficients of Neutral Oxygen Atoms for Various Materials

Abstract

Relevant data on heterogeneous surface recombination of neutral oxygen atoms available in the scientific literature are reviewed and discussed for various materials. The coefficients are determined by placing the samples either in non-equilibrium oxygen plasma or its afterglow. The experimental methods used to determine the coefficients are examined and categorized into calorimetry, actinometry, NO titration, laser-induced fluorescence, and various other methods and their combinations. Some numerical models for recombination coefficient determination are also examined. Correlations are drawn between the experimental parameters and the reported coefficients. Different materials are examined and categorized according to reported recombination coefficients into catalytic, semi-catalytic, and inert materials. Measurements from the literature of the recombination coefficients for some materials are compiled and compared, along with the possible system pressure and material surface temperature dependence of the materials’ recombination coefficient. A large scattering of results reported by different authors is discussed, and possible explanations are provided.

Plasma-induced reversible surface modification and its impact on oxygen heterogeneous recombination

“…Then, the surface recombination probability γ O has been obtained from ν loss O , using the relationship γ O = ν loss O 2R/v th , where v th is the known thermal velocity of atomic oxygen in the plasma near the wall [15]. The experimentally obtained γ O , ranging between 2 × 10 −4 and 2 × 10 −3 , is in agreement with literature on recombination probability in Pyrex [30].…”

“…The probability for this latter process is highly dependent on the type of surface and on working conditions of pressure, current and wall temperature. Hence, atomic oxygen surface recombination is highly relevant and widely studied in plasma reactors for different conditions and surfaces [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

Recent Progress in Cellulose Hydrophobization by Gaseous Plasma Treatments

“…Namely, all surface reactions upon treatment of solid materials with non-equilibrium gaseous plasma are exothermic, so a cellulose sample will likely be heated upon plasma treatment. The list of highly exothermic surface reactions includes the weak bombardment by positively charged ions, which accelerate in the sheath between the unperturbed plasma and the sample, the neutralization of charged particles, the oxidation of cellulose materials upon chemical interaction with radicals of high oxidation potential (F, O, OH), and surface association of atoms to parent molecules (often referred as heterogeneous surface recombination [ 48 ]). Unfortunately, the authors of the review paper did not report the temperature of cellulose samples upon treatment with gaseous plasma.…”

Surface recombination in Pyrex in oxygen DC glow discharges: mesoscopic modelling and comparison with experiments

“…Hence, atomic oxygen surface recombination is a very complex process and has been widely studied in plasma reactors for different conditions and surfaces. These studies are listed and compared in the recent review by Paul et al (2023). The recombination is very effective (above 10%) on metallic and catalytic surfaces (Morgan and Schiff 1964, Mozetic and Cvelbar 2007, Mozetic et al 2015, less effective on crystals and semi-catalytic surfaces and even less (below 1%) on inert materials like silica-based or glass-based materials such as Pyrex and quartz.…”