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A DFT Study on the Direct CF2 Fragmentation Mechanisms of 1,3-C4F6 and 1,3-C4F6+ in Plasma

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Abstract

Elucidation of the CF2 generation mechanism in 1,3-C4F6 gas plasma has been one of the important issues for experimental and theoretical researchers because of the importance of the CF2 radical in plasma etching processes. To determine the direct CF2 fragmentation mechanisms of 1,3-C4F6 in the S0, T1, and cationic D0 states, the reaction geometry, electron transfer, and molecular orbital transformation were investigated by applying the DFT(ɷB97X-D/aVTZ) method. The direct CF2 (S0) formation by C–C double bond rupture of 1,3-C4F6 (S0) proceeds while maintaining the trans-bent structure by dative bonding interaction between CF2 and its counterpart. 1,3-C4F6 (T1) preferentially produces the CFCFCF2 (T1) and CF2 (S0) fragments following a linear reaction course. This process can be explained using a stepwise electron-sharing interaction model. 1,3-C4F6+ (D0) generates a CF2 (S0) radical rather than CF2 (T1) and CF2+ (D0). The CF2 fragmentation process in D0 is also described using the electron-sharing interaction model but proceeds along the trans-rocking pathway, featuring electron oscillations between the CFCFCF2 and CF2 moieties in the C–C distance range of 1.8–2.6 Å. These findings provide insight into CF2 generation of CF2-containing perfluoro-olefins as potential alternatives to c-C4F8 and valuable information to establish the high-reliable 1,3-C4F6 plasma chemistry database essential to plasma simulations.

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Acknowledgements

This research was supported by a National Research Council of Science & Technology (NST) grant by the Korea government (MSIP) (No. CAP-17-02-NFRI) and was also supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20202010100020). H.Choi thanks Prof. K.K.Baeck (GWNU) for helpful discussions during the preparation of this paper.

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  1. Institute of Plasma Technology, Korea Institute of Fusion Energy, Gunsan, Jeollabuk-do, 54004, Republic of Korea

    Heechol Choi, Young Choon Park, Deuk-Chul Kwon & Sang-Young Chung

  2. School of Semiconductor and Chemical Engineering, Jeonbuk National University, Jeonju, Jeollabuk-do, 54896, Republic of Korea

    Yeon-Ho Im

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Choi, H., Park, Y.C., Im, YH. et al. A DFT Study on the Direct CF2 Fragmentation Mechanisms of 1,3-C4F6 and 1,3-C4F6+ in Plasma. Plasma Chem Plasma Process 43, 47–66 (2023). https://doi.org/10.1007/s11090-022-10288-6

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