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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 6 (1986), S. 11-25 
    ISSN: 1572-8986
    Keywords: Plasma etching ; CF3 reactions ; CF2 reactions ; F atom reactions ; association reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Reaction rate coefficients have been measured at 295 K for both CF3 and CF2 with atomic and molecular fluorine. The reaction between CF3 and F was studied over a gas number density range of (2.4–23)×1016 cm−3 with helium as the bath gas. The measured rate coefficient increased from (1.1–1.7)×10−11 cm3 s−1 as the gas number density increased over this range. In contrast to this relatively small change in rate coefficient with gas number density, the rate coefficient for CF2+F increased from (0.4–2.3)×10−12 cm3 s−1 as the helium gas number density increased from (3.4–28.4)×1016 cm−3. Even for the highest bath gas number density employed, the rate coefficient was still more than an order of magnitude lower than earlier measurements of this coefficient performed at comparable gas number densities. Both these association reactions are examined from the standpoint of the Gorin model for association of radicals and use is made of unimolecular dissociation theory to examine the expected dependence on gas number density. The calculations reveal that CF3+F can be explained satisfactorily in these terms but CF2+F is not well described by the simple Gorin model for association. CF3 was found to react with molecular fluorine with a rate coefficient of (7±2)×10−14 cm3 s−1 whereas only an upper limit of 2×10−15 cm3 s−1 could be placed on the rate coefficient for the reaction between CF2 and F2. The values obtained for this set of reactions mean that the reaction between CF3 and F will play an important role in plasmas containing CF4. The high rate coefficient will mean that, under certain conditions, this particular reaction will control the amount of CF4 consumed. On the other hand, the much lower rate coefficient for reactions between CF2 and F means that CF2 will attain much higher concentrations than CF3 in plasmas where these combination reactions are dominant.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plasma chemistry and plasma processing 4 (1984), S. 271-283 
    ISSN: 1572-8986
    Keywords: Plasma etching ; CF2 reactions ; F atom production ; CF4-O2 plasmas ; COF reactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Reactions between CF2 and O(3P) have been studied at 295 K in a gas flow reactor sampled by a mass spectrometer. The major reaction for CF2 has been found to be $$CF_2 + O \to COF + F$$ with $$CF_2 + O \to CO + 2F(F_2 )$$ more than a factor of three slower. The rate coefficient for all loss processes for CF2 on reaction with O is (1.8±0.4)×10−11 cm3 s−1. The COF produced in (18) undergoes a fast reaction with O to produce predominantly CO2. $$COF + O \to CO_2 + F$$ It is uncertain from the results whether or not $$COF + O \to CO + FO$$ occurs, but in any event (19) is the major route. The rate coefficient for the loss of COF in this system [i.e., the combined rate coefficients for (19) and (20)] is (9.3±2.1)×10−11 cm3 s−1. Stable product analysis reveals that for each CF2 radical consumed, the following distribution of stable products is obtained: COF2 (0.04±0.02), CO (0.21±0.04), and CO2 (0.75±0.05). Thus COF2, which we assume is produced via $$CF_2 + O \xrightarrow{M} COF_2$$ is a very minor product in this reaction sequence. The measured rate coefficients demonstrate that reactions (18) and (19) are important sources of F atoms in CF4/O2 plasmas.
    Type of Medium: Electronic Resource
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