Dissociative electron attachment to C2F5 radicals

Abstract

Dissociative electron attachment to the reactive C 2 F 5 molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F − is formed close to zero electron energy in dissociative electron attachment to C 2 F 5 . The afterglow measurements also show that F − is formed in collisions between electrons and C 2 F 5 molecules with rate constants of 3.7 × 10 −9 cm 3 s −1 to 4.7 × 10 −9 cm 3 s −1 at temperatures of 300-600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

A novel technique for measurement of thermal rate constants and temperature dependences of dissociative recombination: CO2+, CF3+, N2O+, C7H8+, C7H7+, C6H6+, C6H5+, C5H6+, C4H4+, and C3H3+

“…The technique, dubbed variable electron and neutral density attachment mass spectrometry (VENDAMS), 11 has been applied to measure rate constants and product distributions of mutual neutralization [12][13][14][15][16] and electron attachment to short-lived species such as radicals. 11,17,18 Here, a variation of the technique is used to determine thermal DR rate constants. Unlike other VENDAMS applications, the method does not involve electron attachment; however, for consistency the acronym is retained.…”

Electron attachment to CF3 and CF3Br at temperatures up to 890 K: Experimental test of the kinetic modeling approach

“…25 In particular, no data on thermal electron attachment to fluorocarbon radicals existed; these data are particularly important because they are needed for predictive modeling of plasma etching of semiconductor material, a vital industrial process involved in the fabrication of microelectronics. We have previously reported rate constants and product branching for most small fluorocarbon radicals (CF 2 , CF 3 , C 2 F 3 , C 2 F 5 , 1-C 3 F 7 , 2-C 3 F 7 , 3-C 3 F 5 ) from 300 to 600 K. 11,18,19 In concert, a separate beam experiment provided relative cross sections of attachment to CF 2 10 and C 2 F 5 18 as a function of electron energy up to 10 eV. Kinetic modeling was used to extrapolate these data to conditions most relevant to plasma etching, namely gas temperatures around 300 K and electron temperatures up to 10 000 K. The CF 3 system is particularly intriguing because, due to a mild endothermicity for dissociative attachment, electron attachment (1) proceeds via a competition between associative attachment (2a), dissociative attachment yielding F − (2b), and autodetachment (2c),…”

Characterization of Neutral Radicals from a Dissociative Electron Attachment Process

“…Considering electron interaction with radicals in the gas phase, to our knowledge, only those with fluorocarbon radicals have been investigated to date, including measurements of absolute elastic cross sections for CF 2 CF 3 [26,27] and DEA processes for CF 2 and C 2 F 5 [28,29]. In the latter experiments, the target radical beam has been obtained by either pyrolysis or microwave discharge.…”