Nitrogen controlled iron catalyst phase during carbon nanotube growth

Bernhard C. Bayer, Carsten Baehtz, Piran R. Kidambi, Robert S. Weatherup, Clemens Mangler, Jani Kotakoski, Caroline J. L. Goddard, Sabina Caneva, Andrea Cabrero-Vilatela, Jannik C. Meyer, Stephan Hofmann

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Close control over the active catalyst phase and hence carbon nanotube structure remains challenging in catalytic chemical vapor deposition since multiple competing active catalyst phases typically co-exist under realistic synthesis conditions. Here, using in-situ X-ray diffractometry, we show that the phase of supported iron catalyst particles can be reliably controlled via the addition of NH3 during nanotube synthesis. Unlike polydisperse catalyst phase mixtures during H2 diluted nanotube growth, nitrogen addition controllably leads to phase-pure γ-Fe during pre-treatment and to phase-pure Fe3C during growth. We rationalize these findings in the context of ternary Fe-C-N phase diagram calculations and, thus, highlight the use of pre-treatment- and add-gases as a key parameter towards controlled carbon nanotube growth.
    Original languageEnglish
    JournalApplied Physics Letters
    Volume105
    Issue number14
    DOIs
    Publication statusPublished - 6 Oct 2014

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